JP2004044504A - Fuel supply system for liquefied gas internal combustion engine - Google Patents

Abstract

An object of the present invention is to provide a fuel supply device for a liquefied gas internal combustion engine capable of maintaining a state of a fuel tank in a state where external fuel supply is possible.
The fuel supply device sends a liquid fuel stored in a fuel tank in a saturated state under pressure by a fuel pump. The fuel in the delivery pipe 35 is returned to the fuel tank 31 via the return path Rd2 while being supplied by injection. Further, the fuel supply pressure, which is the pressure of the fuel that is pressurized and replenished from the fuel tank of the refueling station to the fuel tank 31, is calculated based on the saturated vapor characteristics of the fuel in the fuel tank 31, the outside air temperature, and the like. When the pressure of the fuel in the fuel tank 31 becomes equal to or higher than the refueling pressure, the gaseous fuel in the fuel tank 31 is supplied to the internal combustion engine by the gaseous fuel injector GIN.
[Selection diagram] FIG.

Description

に適用して、図５に示すようにプロパン比率Ｒに対応したＬＰＧの飽和蒸気圧曲線を決定する（ステップＳ１０３）。なお、上記飽和蒸気圧計算式［１］において、「Ｐ」はＬＰＧの飽和蒸気圧力（ｋｇ／ｃｍ^２）、「Ｔ」はＬＰＧの温度、「Ｒ」はＬＰＧ中のプロパン比率を示している。
【００７５】
次に、上記算出された飽和蒸気圧曲線及び外気温度ＴＨａｔｍから、当該内燃機関１を搭載する車両をはじめとしたＬＰＧを燃料とする車両に対して燃料の補給を行う給油スタンドの燃料タンク（スタンド燃料タンク）内に貯留されている燃料の飽和蒸気圧力（スタンド飽和蒸気圧力Ｐｓｖｓｔ）を推定する（ステップＳ１０４）。そして、給油スタンドにおいてスタンド燃料タンクから車両の燃料タンク（燃料タンク３１）へ燃料を補給する際にスタンド燃料タンクの燃料に加えられる所定の圧力である給油時加圧力Ｐｃａ（補給時加圧力）を上記スタンド飽和蒸気圧力Ｐｓｖｓｔに加算して、上記所定の圧力が加えられた燃料の圧力（燃料タンク３１へ補給される燃料の圧力）であるスタンド給油圧力Ｐｓｔ（補給圧力）を算出する（ステップＳ１０５）。即ち、図６に示すように、プロパン比率Ｒの飽和蒸気圧曲線及び外気温度ＴＨａｔｍを通じてスタンド飽和蒸気圧力Ｐｓｖｓｔが推定されるとともに、次式
Ｐｓｔ←Ｐｓｖｓｔ＋Ｐｃａ　　　　　　　　　　　　　　　…［２］
からスタンド給油圧力Ｐｓｔが算出される。
【００７６】
そして、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）が上記算出されたスタンド給油圧力Ｐｓｔ以上であるか否かを判定する（ステップＳ１０６）。燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ１０６：Ｙｅｓ）、気相燃料インジェクタＧＩＮによる気相燃料の供給を行い（ステップＳ１０７）、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないときは液相燃料のみの供給を継続して行う（ステップＳ１０６：Ｎｏ）。
【００７７】
このように、上記気相燃料インジェクタの駆動処理によれば、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき、即ち給油スタンドにおいて燃料タンク３１へ燃料を補給することができない状態にあるとき、気相燃料インジェクタＧＩＮによる気相燃料の供給が行われる。
【００７８】
ところで、本実施の形態の燃料供給装置３のように、燃料ポンプ３２により圧送された燃料を燃料噴射機構３４を介して燃料タンク３１に還流させるフューエルリターン式の燃料循環方式にあっては、デリバリパイプ３５（燃料噴射機構３４）内の燃料が燃焼室１７等からの熱を受け高温となって燃料タンク３１に還流されるため、同燃料タンク３１内の燃料の温度上昇にともなって圧力も上昇する傾向を示す。そして、この燃料の圧力が給油スタンドにおいて上記燃料タンク３１に補給される燃料の圧力（燃料タンク３１に補給される際に所定の圧力が加えられた燃料の圧力）以上である場合には、同燃料タンク３１に燃料を補給することができなくなる。
【００７９】
そこで、本実施の形態においては、燃料タンク圧力Ｐｔｋを監視するとともに同圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるとき、燃料タンク３１内の気相燃料を消費することで、同燃料タンク３１において液相燃料の気化を促進させるようにしている。これにより、液相燃料が気化する際の気化熱を通じて燃料タンク３１内の燃料の温度とともに同燃料の圧力が低下するようになる。
【００８０】
次に、図７を参照して、気相燃料インジェクタの駆動処理（図３）による気相燃料の供給態様の一例を説明する。
例えば、時刻ｔ７１において燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上である旨検出されたとすると、気相燃料インジェクタＧＩＮによる気相燃料の供給が行われるようになる（図７（ａ），（ｂ））。これにより、気相燃料の供給が行われなかった場合には、例えば一点鎖線で示す態様をもって上昇すると推定される燃料タンク圧力Ｐｔｋが、実線にて示すように下降するようになる（図７（ａ））。そして、時刻ｔ７２において燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ未満となった旨検出されたとすると、気相燃料の供給が停止される（図７（ａ），（ｂ））。
【００８１】
以上詳述したように、この第１の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、以下に列記するような優れた効果が得られるようになる。
（１）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、同燃料タンク３１内の気相燃料を内燃機関１に供給することで、燃料タンク圧力Ｐｔｋが減圧されるようにしている。これにより、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【００８２】
（２）本実施の形態では、スタンド給油圧力Ｐｓｔの算出を以下の態様をもって行うようにしている。即ち、
・燃料タンク３１内の燃料の飽和蒸気圧曲線及び外気温度ＴＨａｔｍから給油スタンドの燃料タンク（スタンド燃料タンク）内に貯留されている燃料の飽和蒸気圧力（スタンド飽和蒸気圧力Ｐｓｖｓｔ）を推定する。
・スタンド飽和蒸気圧力Ｐｓｖｓｔと給油時にスタンド燃料タンクの燃料へ加えられる所定の圧力（給油時加圧力Ｐｃａ）とを加算してスタンド給油圧力Ｐｓｔを算出する。
といった態様をもってスタンド給油圧力Ｐｓｔの算出を行うようにしている。ちなみに、燃料タンク３１内の燃料とスタンド燃料タンク内の燃料とは、一般にほぼ同じ飽和蒸気特性を示し、同スタンド燃料タンク内に貯留されている燃料の温度は、基本的には外気温度に依存する傾向にある。一方で、スタンド燃料タンクから燃料タンク３１へ加圧されて補給される燃料の圧力（スタンド給油圧力ｐｓｔ）は、基本的にはスタンド飽和蒸気圧力Ｐｓｖｓｔに対して給油時にスタンド燃料タンクの燃料に加えられる所定の圧力（給油時加圧力Ｐｃａ）を加算した値となる。そこで、上記態様をもってスタンド給油圧力Ｐｓｔを算出することで、燃料タンク３１内の燃料の圧力とスタンド給油圧力Ｐｓｔとの関係をより適切に把握することができるようになるとともに、燃料タンク３１の状態を給油スタンドにおいて燃料補給が可能な状態により好適に維持することができるようになる。
【００８３】
（３）本実施の形態では、燃料タンク３１内の燃料の温度（燃料タンク温度ＴＨｔｋ）及び圧力（燃料タンク圧力Ｐｔｋ）から同燃料の組成（プロパン比率Ｒ）を推定し、この推定される燃料の組成から同燃料の飽和蒸気圧計算式（飽和蒸気圧曲線）を算出するようにしている。ちなみに、燃料（ＬＰＧ）の組成は季節等に応じて変更されることがあり、また、燃料の飽和蒸気特性（飽和蒸気圧曲線）は燃料の組成に応じて異なる傾向を示す。そこで、上記態様をもって算出される飽和蒸気圧曲線に基づいてスタンド燃料タンク内の燃料の飽和蒸気圧力（スタンド飽和蒸気圧力Ｐｓｖｓｔ）を推定することで、スタンド給油圧力Ｐｓｔを適切に算出することができるようになる。これにより、燃料の組成が変更されるようなことがあっても、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【００８４】
（４）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上であるときにのみ、同燃料タンク３１内の気相燃料を内燃機関１に供給することで、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ未満に維持されるようにしている。ここで、燃料タンク圧力Ｐｔｋをスタンド給油圧力Ｐｓｔ未満に維持するために、例えば内燃機関１の運転中、常に気相燃料を同内燃機関１に供給するといった対策も考えられるが、この場合には次のようなことが懸念される。即ち、気相燃料は液相燃料に比べて密度が小さい燃料であるため、気相燃料を内燃機関１に供給するときには、混合気中に占める気相燃料の割合が大きくなることにより吸入空気量が不足することが考えられる。そして、こうした吸入空気量の不足が生じた場合には、必要とされる出力が得られず内燃機関１の出力性能の低下などをまねくことになる。この点、本実施の形態においては、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるときにのみ気相燃料の供給を行うようにしているため、気相燃料が供給されることに起因する内燃機関１の出力性能の低下を好適に抑制することができるようになる。
【００８５】
（５）本実施の形態では、燃料タンク３１内の気相燃料を内燃機関１に供給することで、燃料タンク温度ＴＨｔｋとともに燃料タンク圧力Ｐｔｋを低下させるようにしている。ちなみに、燃料タンク３１内の燃料の温度上昇にともなう同燃料の圧力上昇は、基本的には燃料噴射機構３４内にて受熱した燃料が燃料タンク３１に還流されるといったことに起因するが、他に例えば次のような要因も挙げられる。即ち、一般にＬＰＧ機関を搭載した車両にあっては燃料タンクが同車両のトランクルーム内に設けられているため、外気温度の上昇によりトランクルーム内が高温となるような場合には、このトランクルーム内の温度上昇に応じて燃料タンク内の燃料の温度及び圧力が上昇する傾向を示す。そして、こうした燃料タンク内の燃料の圧力上昇によっても、給油スタンドにおいて燃料タンクに燃料を補給することができなくなることも考えられる。そこで、このトランクルーム内の温度上昇に起因する上記懸念を解消するための対策として、例えば燃料タンクを車両のトランクルーム以外の高温となりにくい場所に設けることで、同燃料タンク内の燃料の温度上昇及び圧力上昇を抑制するといったことも考えられる。しかし、この場合、燃料タンクの配置場所を変更する等の作業が必要となり、既存のＬＰＧ機関の燃料供給装置に対して大幅な改良を加えなければならなくなる。この点、本実施の形態においては、気相燃料を供給することで燃料タンク内の燃料の温度及び圧力が下げられるようにしているため、燃料タンクの配置場所を変更するといった対策を講じなくとも、上記トランクルーム内の温度上昇に起因する懸念を解消することができるようになる。このように、本実施の形態にあっては、既存のＬＰＧ機関の燃料供給装置を有効に利用しつつも燃料タンクを給油スタンドにおいて燃料供給が可能な状態に維持することができるため、実用性の高いＬＰＧ機関の燃料供給装置を提供することができるようになる。
【００８６】
なお、上記第１の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第１の実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、液相燃料インジェクタＬＩＮにあわせて気相燃料インジェクタＧＩＮによる燃料の供給を行う構成としたが、例えば次のような構成とすることも可能である。即ち、上記条件が満たされるとき、気相燃料インジェクタＧＩＮによる気相燃料の供給のみを行う構成とすることもできる。
【００８７】
（第２の実施の形態）
本発明を具体化した第２の実施の形態について、図８及び図９を参照して説明する。
【００８８】
本実施の形態において、内燃機関をはじめとした装置全体の基本的な構成は先の第１の実施の形態と同様であるが、気相燃料インジェクタの駆動処理（図３）の一部が図８に示す処理に変更されている。
【００８９】
ここで、本実施の形態における気相燃料インジェクタの駆動処理の説明に先立って、その概要を説明する。
本実施の形態の処理も前記第１の実施の形態の処理（図３）と同様に、内燃機関１に対する気相燃料の供給態様を制御することで、燃料タンク３１内の燃料の圧力の減圧を図るものとなっている。そして、前記第１の実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上であることを気相燃料の供給を行うための条件としているのに対して、本実施の形態では、以下に説明する条件に基づいて気相燃料の供給を行うようにしている。
【００９０】
図８に示すように、本実施の形態の気相燃料インジェクタの駆動処理では、まず前記第１の実施の形態に準じた態様をもって先のステップＳ１０５までの処理（図３）を行う。そして、燃料タンク３１内の燃料の飽和蒸気圧曲線にスタンド給油圧力Ｐｓｔを適用することで、気相燃料インジェクタＧＩＮによる気相燃料の供給を行うか否かを決定するための判定値である給油時飽和蒸気温度ＴＨｓｔを算出する（ステップＳ１０５ａ）。即ち、図９に示すように、給油スタンドにおいて所定の圧力（給油時加圧力Ｐｃａ）が加えられて車両の燃料タンク（燃料タンク３１）に供給される燃料の圧力（スタンド給油圧力Ｐｓｔ）に対応した飽和蒸気温度（給油時飽和蒸気温度ＴＨｓｔ）の算出が行われる。
【００９１】
そして、燃料タンク３１内の燃料の温度（燃料タンク温度ＴＨｔｋ）が上記算出された給油時飽和蒸気圧力ＴＨｓｔ以上であるか否かを判定する（ステップＳ１０６ａ）。燃料タンク温度ＴＨｔｋが給油時飽和蒸気圧力ＴＨｓｔ以上のとき（ステップＳ１０６ａ：Ｙｅｓ）、気相燃料インジェクタＧＩＮによる気相燃料の供給を行い（ステップＳ１０７）、燃料タンク温度ＴＨｔｋが給油時飽和蒸気温度ＴＨｓｔ以上でないときは液相燃料のみの供給を継続して行う（ステップＳ１０６ａ：Ｎｏ）。
【００９２】
このように、上記気相燃料インジェクタの駆動処理によれば、燃料タンク温度ＴＨｔｋが給油時飽和蒸気圧力ＴＨｓｔ以上であるか否かに基づいて気相燃料インジェクタＧＩＮの駆動態様が決定される。
【００９３】
ちなみに、燃料タンク３１内の燃料（ＬＰＧ）は飽和状態にあるため、同燃料の温度及び圧力は、基本的には同燃料の飽和蒸気圧曲線に沿って変動する傾向を示す。従って、図９に示すように、燃料タンク圧力Ｐｔｋが圧力Ｐｔｋａからスタンド給油圧力Ｐｓｔよりも高い圧力Ｐｔｋｂまで上昇したとき、燃料タンク温度ＴＨｔｋは温度ＴＨｔｋａから給油時飽和蒸気温度ＴＨｓｔよりも高い温度ＴＨｔｋｂまで上昇していることになる。
【００９４】
そこで、本実施の形態のように、燃料タンク温度ＴＨｔｋが給油時飽和蒸気圧力ＴＨｓｔ以上であるときに気相燃料の供給を行うようにすることによっても、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるときに気相燃料の供給を行うことと同様の効果が得られるようになる。
【００９５】
以上詳述したように、この第２の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第１の実施の形態における前記（１）〜（５）の効果に準じた効果が得られるようになる。
【００９６】
（第３の実施の形態）
本発明を具体化した第３の実施の形態について、図１０を参照して説明する。本実施の形態において、装置全体の基本的な構成は前記第１の実施の形態（図１）と同様であるが、図２に示される燃料供給装置３の構成が図１０に示す構成に変更されている（なお、この変更にともなって図１に示される気相燃料インジェクタＧＩＮは除外されるものとする）。ちなみに、その構成は同図１０の破線内にて示されるように、前記第１の実施の形態における燃料供給装置３（図２）に対して次のような変更を加えたものとなっている。
【００９７】
即ち、本実施の形態の気相燃料供給系統３Ｇは、燃料タンク３１内に滞留している気相燃料をサージタンク２３に供給するための気相燃料供給経路Ｒｄ３と、同経路Ｒｄ３を選択的に開閉する気相制御弁Ｅｖｇと、同経路Ｒｄ３を流通する気相燃料の流量を規制する絞り機構３７とを備えて構成される。そして、ＥＣＵ５からの信号に応じて気相制御弁Ｅｖｇが開弁されることにより、燃料タンク３１内の気相燃料が吸気負圧によりサージタンク２３内に吸引されるようになる。なお、気相制御弁Ｅｖｇとして、常時閉弁、即ち非通電時には閉弁されておりＥＣＵ５からの通電によって開弁される電磁弁が採用されるものとする。
【００９８】
そして、本実施の形態において、気相制御弁Ｅｖｇは前記第１の実施の形態における気相燃料インジェクタの駆動処理（図３）に準じた態様をもって開閉制御される。即ち、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上であるとき、気相制御弁Ｅｖｇが開弁されることにより内燃機関１に対する気相燃料の供給が行われるようになる。
【００９９】
以上詳述したように、この第３の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第１の実施の形態における前記（１）〜（５）の効果に準じた効果に加えて、さらに以下に示すような効果が得られるようになる。
【０１００】
（６）本実施の形態では、気相燃料供給経路Ｒｄ３に設けられる気相制御弁Ｅｖｇを開閉操作することによって、内燃機関１へ燃料タンク３１内の気相燃料を供給することができるようにしている。このように、気相燃料インジェクタを用いることなく気相燃料を供給することができるようにしているため、より簡易な構成の燃料供給装置を提供することができるようになる。
【０１０１】
なお、上記第３の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第３の実施の形態では、気相燃料供給経路Ｒｄ３に絞り機構３７を備える構成としたが、例えば次のような構成とすることも可能である。即ち、絞り機構３７を備えない構成、あるいは同絞り機構３７に代えて、絞り径を可変とすることができる可変絞り機構を備える構成とすることもできる。
【０１０２】
（第４の実施の形態）
本発明を具体化した第４の実施の形態について、図１１〜図１５を参照して説明する。
【０１０３】
本実施の形態において、装置全体の基本的な構成は前記第１の実施の形態（図１）と同様であるが、図２に示される燃料供給装置３の構成が図１１に示す構成に変更されている（なお、この変更にともなって図１に示される気相燃料インジェクタＧＩＮは除外されるものとする）。
【０１０４】
ここで、本実施の形態における燃料供給装置の説明に先立って、その概要を説明する。
本実施の形態も、前記第１の実施の形態と同様に、燃料タンク３１内の燃料の圧力を減圧するための機能を備えるものとなっている。そして、前記第１の実施の形態では、内燃機関１への気相燃料の供給を通じて上記機能を実現しているのに対して、本実施の形態では、ＥＣＵ５による燃料ポンプ３２の仕事量の調整を通じて上記機能が実現されるようにしている。なお、本実施の形態において、ＥＣＵ５は燃料ポンプ３２に供給する電流量を調整することで、同燃料ポンプ３２の液相燃料の吐出量（燃料吐出量）を低流量及び高流量の２段階に変更する。そして、燃料ポンプ３２は内燃機関１の運転中、基本的には高流量で駆動されるものとする。以下、図１１を参照して本実施の形態の燃料供給装置について説明する。
【０１０５】
同図１１に示されるように、本実施の形態の燃料供給装置３は、前記第１の実施の形態の燃料供給装置３（図２）から気相燃料供給系統３Ｇを除外して、デリバリパイプ３５に破線内にて示される各センサを追加した構成となっている。即ち、本実施の形態の燃料供給装置３にあって、検出系６は、前記各センサ６１〜６３にあわせ、さらに噴射機構温度センサ６４及び噴射機構圧力センサ６５を備えて構成される。ちなみに、噴射機構温度センサ６４はデリバリパイプ３５（燃料噴射機構３４）内における燃料の温度（噴射機構温度ＴＨｄｖ）を、噴射機構圧力センサ６５はデリバリパイプ３５（燃料噴射機構３４）内における燃料の圧力（噴射機構圧力Ｐｄｖ）をそれぞれ検出する。そして、上記各センサ６１〜６５により検出されたデータはＥＣＵ５に入力され、ＥＣＵ５はこの入力された各検出データに基づいて以下に示す燃料ポンプの吐出量変更処理を行う。
【０１０６】
次に、前記第１の実施の形態における気相燃料インジェクタの駆動処理（図３）に代えて行われる燃料ポンプの吐出量変更処理を、図１２〜図１４を参照して説明する。なお、本処理は所定の時間を周期として繰り返し実行される。
【０１０７】
図１２に示すように、この処理では、まず各センサ６１〜６５により検出されたデータ（外気温度ＴＨａｔｍ、燃料タンク温度ＴＨｔｋ、燃料タンク圧力Ｐｔｋ、噴射機構温度ＴＨｄｖ、噴射機構圧力Ｐｄｖ）を読み込む（ステップＳ３０１）。次に、燃料タンク温度ＴＨｔｋ及び燃料タンク圧力Ｐｔｋをプロパン比率のマップ（図４）に適用して燃料タンク３１内に貯留されている燃料（ＬＰＧ）中のプロパン比率Ｒを推定する（ステップＳ３０２）。そして、この推定されたプロパン比率Ｒを前記飽和蒸気圧計算式

に適用して、プロパン比率Ｒに対応したＬＰＧの飽和蒸気圧曲線を決定する（ステップＳ３０３）。
【０１０８】
次に、噴射機構温度ＴＨｄｖを上記決定された飽和蒸気圧曲線に適用して、デリバリパイプ３５（燃料噴射機構３４）内の燃料の飽和蒸気圧力（噴射機構飽和蒸気圧力Ｐｓｖｄｖ）を推定する（ステップＳ３０４）。そして、予め設定されている所定値（見込み圧力Ｐｃｂ）を上記噴射機構飽和蒸気圧力Ｐｓｖｄｖに加算して、デリバリパイプ３５（燃料噴射機構３４）内で気化燃料が発生するおそれがあるか否かを判定するための気化判定圧力Ｐｖｐを算出する（ステップＳ３０５）。即ち、図１４に示すように、プロパン比率Ｒの飽和蒸気圧曲線及び噴射機構温度ＴＨｄｖを通じて噴射機構飽和蒸気圧力Ｐｓｖｄｖが推定されるとともに、次式
Ｐｖｐ←Ｐｓｖｄｖ＋Ｐｃｂ　　　　　　　　　　　　　　　…［３］
から気化判定圧力Ｐｖｐが算出される。ちなみに、飽和蒸気圧力は、任意の圧力の流体が液相あるいは気相（気液２相を含む）のいずれであるかを示す流体の温度の閾値温度であり、流体の圧力が飽和蒸気圧力以上のとき、その流体は液相状態にあり、流体の圧力が飽和蒸気圧力未満のとき、その流体は気相状態にあることになる。従って、デリバリパイプ３５（燃料噴射機構３４）内における燃料の圧力（噴射機構圧力Ｐｄｖ）が上記気化判定圧力Ｐｖｐ未満であるとき、デリバリパイプ３５内では液相燃料の気化が生じやすい状態（あるいはすでに気化が生じている状態）にあると推定される。
【０１０９】
また、同じく上記算出された飽和蒸気圧曲線に外気温度ＴＨａｔｍを適用して、給油スタンドの燃料タンク（スタンド燃料タンク）内に貯留されている燃料の飽和蒸気圧力（スタンド飽和蒸気圧力Ｐｓｖｓｔ）を推定する（ステップＳ３０６）。そして、給油スタンドにおいてスタンド燃料タンクの燃料に加えられる所定の圧力（給油時加圧力Ｐｃａ）を上記スタンド飽和蒸気圧力Ｐｓｖｓｔに加算して、スタンド燃料タンクから燃料タンク３１に供給される燃料の圧力であるスタンド給油圧力Ｐｓｔを算出する（ステップＳ３０７）。即ち、図１４に示すように、プロパン比率Ｒの飽和蒸気圧曲線及び外気温度ＴＨａｔｍを通じてスタンド飽和蒸気圧力Ｐｓｖｓｔが推定され、次式
Ｐｓｔ←Ｐｓｖｓｔ＋Ｐｃａ　　　　　　　　　　　　　　　…［２］
からスタンド給油圧力Ｐｓｔが算出される。
【０１１０】
そして、デリバリパイプ３５内の燃料の圧力（噴射機構圧力Ｐｄｖ）が上記算出された気化判定圧力Ｐｖｐ未満であるか否かを判定し（ステップＳ３０８）、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき（ステップＳ３０８：Ｙｅｓ）、燃料ポンプ３２の仕事量の大きくすることで液相燃料の吐出量を高流量に変更する（ステップＳ３０９）。一方、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満でないときは、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）が上記算出されたスタンド給油圧力Ｐｓｔ以上であるか否かを判定する（ステップＳ３１０）。燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ３１０：Ｙｅｓ）、燃料ポンプ３２の仕事量を小さくすることで液相燃料の吐出量を低流量に変更し（ステップＳ３１１）、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないときは、そのときの燃料ポンプ３２の駆動態様を維持する（ステップＳ３１０：Ｎｏ）。
【０１１１】
このように、上記燃料ポンプの吐出量変更処理によれば、
〔イ〕噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満であるとき、デリバリパイプ３５内にて気化燃料が発生するおそれがある（または気化燃料が発生している）と判定して、燃料ポンプ３２の仕事量を大きくする（液相燃料の吐出量を高流量に変更する）。
〔ロ〕燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるとき、燃料タンク３１が給油スタンドにおいて燃料の補給が行えない状態にあると判定して、燃料ポンプ３２の仕事量を小さくする（液相燃料の吐出量を低流量に変更する）。
といった態様をもって、燃料ポンプ３２の駆動態様が制御される。
【０１１２】
ところで、燃料タンク３１内の液相燃料が消費されたときも気相燃料が消費されたときと同様に、消費された液相燃料の量に応じて同燃料タンク３１内に貯留されている液相燃料が気化するとともに気化熱により燃料タンク３１内の熱が吸収されるようになる。ただし、液相燃料は気相燃料に比べて密度が高いため、液相燃料が消費されるときにあっては、気相燃料が消費されるときよりも燃料タンク３１内において気化する液相燃料の量が少ないことにともなって気化熱による同燃料タンク３１の冷却作用が小さくなる。このため、
・燃料タンク３１により圧送される液相燃料が、燃料ポンプ３２の駆動により生じる熱を受ける。
・デリバリパイプ３５（燃料噴射機構３４）内に供給された燃料が、同デリバリパイプ３５内で燃焼室１７などから熱を受ける。
といったことにより、燃料タンク３１に還流される燃料が高温となっているときには、液相燃料の気化による燃料タンク３１の冷却作用よりも上記還流される高温の燃料による燃料タンク３１の温度上昇の作用が大きくなり、同燃料タンク３１内の燃料の温度は上昇する方向に変化することになる。
【０１１３】
そこで、本実施の形態においては、上記〔ロ〕の条件が満たされるとき（燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるとき）、燃料ポンプ３２の仕事量を小さくすることで、燃料ポンプ３２の発熱を抑えるとともに同燃料ポンプ３２により圧送される液相燃料の温度上昇が抑制されるようにしている。また、燃料ポンプ３２の燃料吐出量を低流量とすることで、デリバリパイプ３５を介して燃料タンク３１に還流される燃料の流量、即ち高温となって燃料タンク３１に還流される燃料の流量が減量されるようにもしている。これにより、燃料タンク３１における液相燃料の気化による冷却作用が相対的に高められるため、同燃料タンク３１内の燃料の温度とともに同燃料の圧力が低下するようになる。
【０１１４】
このように、燃料ポンプ３２の仕事量を小さくすることで、燃料タンク３１内の燃料の圧力上昇を抑制することができるようになるものの、こうした手段を用いるときには次のようなことが懸念される。
【０１１５】
即ち、燃料ポンプ３２の仕事量が小さくされているとき（液相燃料の吐出量が低流量とされているとき）、同燃料ポンプ３２の仕事量が大きくされているとき（液相燃料の吐出量が高流量とされているとき）よりもデリバリパイプ３５（燃料噴射機構３４）に供給される燃料が少なくなっているため、液相燃料による同デリバリパイプ３５の冷却作用が小さくされていることになる。この場合、デリバリパイプ３５の冷却が不十分であることにより、同デリバリパイプ３５内の燃料の温度上昇にともなって同燃料の飽和蒸気圧力が同燃料の圧力を上回る、即ち燃料の気化が生じることも考えられる。そして、デリバリパイプ３５内で気化燃料が発生した場合に同デリバリパイプ３５内の燃料が液相であるという前提のもとに燃料噴射が行われると、実際には密度の低い燃料が内燃機関１に供給されるために必要とされる燃料量が確保できず運転性の悪化をまねくようになる。
【０１１６】
そこで、本実施の形態においては、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるか否かの判定（ステップＳ３１０）にあわせて、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満であるか否かの判定（ステップＳ３０８）を行うことで、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上となっているときであっても、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満である場合には、燃料ポンプ３２の燃料吐出量が高流量に変更されるようにしている。これにより、燃料ポンプ３２により圧送された液相燃料によるデリバリパイプ３５（燃料噴射機構３４）内の冷却作用が高められて液相燃料の気化が抑制されるようになる。即ち、燃料ポンプ３２の仕事量が小さくされている（液相燃料の吐出量が低流量に設定されている）ことに起因する内燃機関１の運転性の悪化を回避することができるようになる。
【０１１７】
次に、図１５を参照して、燃料ポンプの吐出量変更処理（図１２及び図１３）による燃料ポンプの制御態様の一例を説明する。
例えば、時刻ｔ１５１において燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上である旨検出されたとすると、燃料ポンプ３２の燃料吐出量が低流量に変更される（図１５（ａ），（ｃ））。そして、噴射機構飽和蒸気圧力Ｐｓｖｄｖの変動により気化判定圧力Ｐｖｐが噴射機構圧力Ｐｄｖ以上（噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満）となった旨が時刻ｔ１５２において検出されたとすると、燃料ポンプ３２の燃料吐出量が高流量に変更される（図１５（ｂ），（ｃ））。これにより、燃料吐出量の変更が行われなかった場合には、例えば一点鎖線で示すように噴射機構圧力Ｐｄｖ以上に位置していたと推定される気化判定圧力Ｐｖｐが、実線にて示すように噴射機構圧力Ｐｄｖ未満に位置するようになる（図１５（ｂ））。そして、時刻ｔ１５３において気化判定圧力Ｐｖｐが噴射機構圧力Ｐｄｖ未満（噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ以上）となった旨検出されたとすると、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であることにより燃料ポンプ３２の燃料吐出量が再度、低流量に変更される（図１５（ａ）〜（ｃ））。これにより、燃料吐出量の変更が行われなかった場合には、例えば一点鎖線で示す態様をもって上昇すると推定される燃料タンク圧力Ｐｔｋが、実線にて示すように下降するようになる（図１５（ａ））。
【０１１８】
以上詳述したように、この第４の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、以下に列記するような優れた効果が得られるようになる。
（１）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、同燃料ポンプ３２の仕事量を小さくして液相燃料の吐出量を低流量とすることで、燃料タンク圧力Ｐｔｋが減圧されるようにしている。これにより、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【０１１９】
（２）本実施の形態では、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（燃料ポンプ３２の燃料吐出量を低流量に変更するための条件が満たされているとき）であっても、デリバリパイプ３５内にて気化燃料が発生するおそれがあるときには、燃料ポンプ３２の燃料吐出量を高流量に変更する、即ち燃料ポンプ３２の燃料吐出量を低流量とする処理を中断するようにしている。これにより、デリバリパイプ３５内の燃料の液相状態が維持されるようになるため、内燃機関１の運転性の悪化を好適に回避することができるようになる。
【０１２０】
（３）本実施の形態では、スタンド給油圧力Ｐｓｔの算出を以下の態様をもって行うようにしている。即ち、
・燃料タンク３１内の燃料の飽和蒸気圧曲線及び外気温度ＴＨａｔｍから給油スタンドの燃料タンク（スタンド燃料タンク）内に貯留されている燃料の飽和蒸気圧力（スタンド飽和蒸気圧力Ｐｓｖｓｔ）を推定する。
・スタンド飽和蒸気圧力Ｐｓｖｓｔと給油時にスタンド燃料タンクの燃料へ加えられる所定の圧力（給油時加圧力Ｐｃａ）とを加算してスタンド給油圧力Ｐｓｔを算出する。
といった態様をもってスタンド給油圧力Ｐｓｔの算出を行うようにしている。これにより、燃料タンク３１内の燃料の圧力とスタンド給油圧力Ｐｓｔとの関係をより適切に把握することができるようになるとともに、燃料タンク３１の状態を給油スタンドにおいて燃料補給が可能な状態により好適に維持することができるようになる。
【０１２１】
（４）本実施の形態では、以下の態様をもって算出される気化判定圧力Ｐｖｐ、即ち、
・燃料タンク３１内の燃料の飽和蒸気圧曲線及び噴射機構温度ＴＨｄｖからデリバリパイプ３５内の燃料の飽和蒸気圧力（噴射機構飽和蒸気圧力Ｐｓｖｄｖ）を推定する。
・噴射機構飽和蒸気圧力Ｐｓｖｄｖと予め設定されている所定値である見込み圧力Ｐｃｂとを加算して気化判定圧力Ｐｖｐを算出する。
といった態様をもって算出される気化判定圧力Ｐｖｐに基づいて燃料ポンプ３２の燃料吐出量の変更を行うようにしている。ちなみに、推定される飽和蒸気圧力（噴射機構飽和蒸気圧力Ｐｓｖｄｖ）には若干の誤差が含まれることも考えられるため、推定される飽和蒸気圧力を燃料ポンプ３２の燃料吐出量の変更を行うための判定値として用いるときには次のようなことが懸念される。即ち、上記推定された飽和蒸気圧力が本来の飽和蒸気圧力よりも低い値であるときには、デリバリパイプ３５内の燃料の圧力が本来の飽和蒸気圧力未満となっている（デリバリパイプ３５内で液相燃料の気化が生じている）にもかかわらず同デリバリパイプ３５内の燃料の圧力が上記推定された飽和蒸気圧力以上であるために、燃料ポンプ３２の燃料吐出量が低流量に変更されないことも考えられる。そこで、本実施の形態では、上記態様をもって算出される値（気化判定圧力Ｐｖｐ）を判定値とすることで、上記推定される飽和蒸気圧力が誤差を含むものであったとしても上記懸念が解消されるようにしている。これにより、気化燃料を含む燃料が噴射供給されることに起因する内燃機関１の運転性の悪化をより好適に回避することができるようになる。
【０１２２】
（５）本実施の形態では、燃料タンク３１内の燃料の温度（燃料タンク温度ＴＨｔｋ）及び圧力（燃料タンク圧力Ｐｔｋ）から同燃料の組成（プロパン比率Ｒ）を推定し、この推定される燃料の組成から同燃料の飽和蒸気圧計算式（飽和蒸気圧曲線）を算出するようにしている。これにより、気化判定圧力Ｐｖｐ及びスタンド給油圧力Ｐｓｔを適切に算出することが可能となり、燃料の組成が変更されるようなことがあっても、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【０１２３】
（６）本実施の形態では、燃料ポンプ３２の燃料吐出量を変更するといった処理を通じて、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に維持することができるようにしている。これにより、燃料タンク３１の配置場所を変更するといった対策を講じなくとも、先のトランクルーム内の温度上昇に起因する懸念を解消することができるようになる。このように、本実施の形態にあっては、既存のＬＰＧ機関の燃料供給装置を有効に利用しつつも燃料タンク３１を給油スタンドにおいて燃料供給が可能な状態に維持することができるため、実用性の高いＬＰＧ機関の燃料供給装置を提供することができるようになる。
【０１２４】
（第５の実施の形態）
本発明を具体化した第５の実施の形態について、図１６を参照して説明する。本実施の形態において、内燃機関をはじめとした装置全体の基本的な構成は先の第４の実施の形態と同様（図１に示される構成から気相燃料インジェクタＧＩＮを除外した構成）であるが、燃料ポンプの吐出量変更処理（図１３）の一部が図１６に示す処理に変更されている。
【０１２５】
ここで、本実施の形態における燃料ポンプの吐出量変更処理の説明に先立って、その概要を説明する。
本実施の形態の処理も前記第４の実施の形態の処理（図１２及び図１３）と同様に、燃料ポンプ３２の仕事量を調整することで、燃料タンク３１内の燃料の圧力の減圧及び液相燃料の気化抑制を図るものとなっている。そして、前記第１の実施の形態では、燃料ポンプ３２の燃料吐出量を２段階に変更する処理を通じて上記機能を実現しているのに対して、本実施の形態では、以下に示す燃料ポンプ３２の燃料吐出量を３段階に変更する処理を通じて上記機能が実現されるようにしている。なお、本実施の形態の処理も、所定の時間を周期として繰り返し実行される。また、本実施の形態において、燃料ポンプ３２は、ＥＣＵ５による同燃料ポンプ３２の仕事量の調整を通じて液相燃料の吐出量を基本流量、低流量及び高流量の３段階に変更することが可能であり、内燃機関１の運転中、基本的には基本流量で駆動されるものとする。
【０１２６】
図１６に示すように、本実施の形態の燃料ポンプの吐出量変更処理では、前記第４の実施の形態に準じた態様をもって先のステップＳ３０８及びＳ３１０の各判断処理を行う。
【０１２７】
そして、
〔ａ〕噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき（ステップＳ３０８：Ｙｅｓ）、燃料ポンプ３２の燃料吐出量を高流量に変更する（ステップＳ３０９）。
〔ｂ〕燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ３１０：Ｙｅｓ）、燃料ポンプ３２の燃料吐出量を低流量に変更する（ステップＳ３１１）。
〔ｃ〕燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないとき（ステップＳ３１０：Ｎｏ）、燃料ポンプ３２の燃料吐出量を基本流量に変更する（ステップＳ３１２）。
といった態様をもって燃料ポンプ３２の燃料吐出量の変更を行う。
【０１２８】
このように、上記燃料ポンプの吐出量変更処理によれば、燃料ポンプ３２の燃料吐出量は、基本流量を基準として高流量及び低流量への変更が行われるようになる。
【０１２９】
以上詳述したように、この第５の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第４の実施の形態における前記（１）〜（６）の効果に準じた効果に加えて、さらに以下に示すような効果が得られるようになる。
【０１３０】
（７）本実施の形態では、燃料ポンプ３２の燃料吐出量を基本流量、高流量及び低流量の３段階に変更することで、同燃料ポンプ３２の燃料吐出量がより緻密に調整されるようにしている。これにより、燃料タンク３１内の燃料の減圧とデリバリパイプ３５（燃料噴射機構３４）における燃料の気化抑制とをより好適に両立することができるようになる。
【０１３１】
（第６の実施の形態）
本発明を具体化した第６の実施の形態について、図１７を参照して説明する。本実施の形態において、内燃機関をはじめとした装置全体の基本的な構成は先の第４の実施の形態と同様（図１に示される構成から気相燃料インジェクタＧＩＮを除外した構成）であるが、燃料ポンプの吐出量変更処理（図１２及び図１３）の一部が図１７に示す処理に変更されている。
【０１３２】
ここで、本実施の形態における燃料ポンプの吐出量変更処理の説明に先立って、その概要を説明する。
本実施の形態の処理も前記第４の実施の形態の処理（図１２及び図１３）と同様に、燃料ポンプ３２の仕事量を調整することで、燃料タンク３１内の燃料の圧力の減圧及び液相燃料の気化抑制を図るものとなっている。そして、前記第４の実施の形態では、デリバリパイプ３５（燃料噴射機構３４）内の燃料の飽和蒸気圧力に基づいて算出される気化判定圧力Ｐｖｐを気化燃料が発生するおそれがあるか否かを判定するための値としているのに対して、本実施の形態では、以下に示すような態様をもって上記判定値を算出するようにしている。なお、本実施の形態の処理も、所定の時間を周期として繰り返し実行される。
【０１３３】
図１７に示すように、本実施の形態の燃料ポンプの吐出量変更処理では、先のステップＳ３０３までの処理（図１２）を行った後、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力（噴射機構圧力Ｐｄｖ）を飽和蒸気圧曲線に適用して、同燃料の飽和蒸気温度（噴射機構飽和蒸気温度ＴＨｓｖｄｖ）を推定する（ステップＳ３０４ａ）。そして、予め設定されている所定値（見込み温度ＴＨｃｂ）を上記噴射機構飽和蒸気温度ＴＨｓｖｄｖに加算して、デリバリパイプ３５（燃料噴射機構３４）内で気化燃料が発生するおそれがあるか否かを判定するための気化判定温度ＴＨｖｐを算出する（ステップＳ３０５ａ）。即ち、図１８に示すように、プロパン比率Ｒの飽和蒸気圧曲線及び噴射機構圧力Ｐｄｖを通じて噴射機構飽和蒸気温度ＴＨｓｖｄｖが推定されるとともに、次式
ＴＨｖｐ←ＴＨｓｖｄｖ＋ＴＨｃｂ　　　　　　　　　　　　…［４］
から気化判定温度ＴＨｖｐが算出される。ちなみに、飽和蒸気温度は、任意の温度の流体が液相あるいは気相（気液２相を含む）のいずれであるかを示す流体の温度の閾値温度であり、流体の温度が飽和蒸気温度未満のとき、その流体は液相状態にあり、流体の温度が飽和蒸気温度以上のとき、その流体は気相状態にあることになる。従って、デリバリパイプ３５（燃料噴射機構３４）内における燃料の温度（噴射機構温度ＴＨｄｖ）が上記気化判定温度ＴＨｖｐ以上であるとき、デリバリパイプ３５内では液相燃料の気化が生じやすい状態（あるいはすでに気化が生じている状態）にあると推定される。
【０１３４】
そして、先のステップＳ３０６及びＳ３０７の処理（図１２）を行った後、デリバリパイプ３５内の燃料の温度（噴射機構温度ＴＨｄｖ）が上記算出された気化判定温度ＴＨｖｐ以上であるか否かを判定する（ステップＳ３０８ａ）。噴射機構温度ＴＨｄｖが気化判定温度ＴＨｖｐ以上のとき（ステップＳ３０８ａ：Ｙｅｓ）、先のステップＳ３０９の処理（図１３）を行い、噴射機構温度ＴＨｄｖが気化判定温度ＴＨｖｐ以上でないとき（ステップＳ３０８ａ：Ｎｏ）、先のステップＳ３１０の処理（図１３）を行う。
【０１３５】
以上詳述したように、この第６の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第４の実施の形態における前記（１）〜（６）の効果に準じた効果が得られるようになる。
【０１３６】
なお、上記第６の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第６の実施の形態では、上記ステップＳ３０８ａ（図１７）において、気化判定温度ＴＨｖｐに基づいて燃料ポンプ３２の燃料吐出量の変更を行う構成としたが、例えば次のような構成とすることも可能である。即ち、上記ステップＳ３０８ａ（図１７）において、デリバリパイプ３５内の燃料の飽和蒸気温度（噴射機構飽和蒸気温度ＴＨｓｖｄｖ）に基づいて燃料ポンプ３２の燃料吐出量の変更を行う構成とすることもできる。
【０１３７】
（第７の実施の形態）
本発明を具体化した第７の実施の形態について、図１９〜図２１を参照して説明する。
【０１３８】
本実施の形態において、装置全体の基本的な構成は前記第４の実施の形態と同様（図１に示される構成から気相燃料インジェクタＧＩＮを除外した構成）であるが、図１１に示される燃料供給装置３の構成が図１９に示す構成に変更されている。
【０１３９】
ここで、本実施の形態における燃料供給装置の説明に先立って、その概要を説明する。
本実施の形態も、前記第４の実施の形態と同様に、燃料タンク３１内の燃料の圧力を減圧するための機能、及び同圧力の減圧にともなう液相燃料の気化を抑制する機能を備えるものとなっている。そして、前記第４の実施の形態では、ＥＣＵ５による燃料ポンプ３２の仕事量の調整を通じて上記機能を実現しているのに対して、本実施の形態では、以下に説明する態様をもってデリバリパイプ３５（燃料噴射機構３４）に供給される燃料の流量を調整することで、上記機能が実現されるようにしている。
【０１４０】
図１９に示されるように、本実施の形態の燃料供給装置３の構成は、前記第４の実施の形態の燃料供給装置３（図１１）に対して破線内に示される各要素を追加した構成となっている。即ち、本実施の形態の燃料供給装置３にあって、液相燃料供給経路Ｒｄ１には、燃料ポンプ３２により圧送された液相燃料をデリバリパイプ３５（燃料噴射機構３４）内の上流から燃料タンク３１に還流させるための迂回経路Ｒｄ４が接続されている。また、この迂回経路Ｒｄ４には、デリバリパイプ３５内の燃料の圧力を所定の調整設定値に維持するためのプレッシャレギュレータ３８及び同迂回経路Ｒｄ４を選択的に開閉する迂回制御弁Ｅｖｌが設けられている。さらに、迂回経路Ｒｄ４が追加されることにともなって、還流経路Ｒｄ２を選択的に開閉する還流制御弁Ｅｖｒが同還流経路Ｒｄ２に設けられ、各制御弁Ｅｖｒ，Ｅｖｌ（切替手段）の開閉操作を通じて上記各経路Ｒｄ２，Ｒｄ４のいずれかを選択的に能動とすることが可能となる。なお、上記各制御弁Ｅｖｒ，Ｅｖｌとして、常時閉弁、即ち非通電時には閉弁されておりＥＣＵ５からの通電によって開弁される電磁弁が採用されるものとする。
【０１４１】
次に、還流制御弁Ｅｖｒ及び迂回制御弁Ｅｖｌの開閉操作を通じて切り替えられる各燃料経路について説明する。なお、以降では、還流制御弁Ｅｖｒが開弁、迂回制御弁Ｅｖｌが閉弁されているときの燃料経路を第１の燃料経路とし、還流制御弁Ｅｖｒが閉弁、迂回制御弁Ｅｖｌが開弁されているときの燃料経路を第２の燃料経路とする。
【０１４２】
まず、第１の燃料経路が能動とされる場合における燃料の循環態様について説明する。
この場合、燃料ポンプ３２により圧送された液相燃料の全量がデリバリパイプ３５（燃料噴射機構３４）に供給され、この供給された液相燃料のうちの液相燃料インジェクタＬＩＮにより噴射供給されなかった燃料は、還流経路Ｒｄ２を介して燃料タンク３１に還流されるようになる。
【０１４３】
次に、第２の燃料経路が能動とされる場合における燃料の循環態様について説明する。
この場合、燃料ポンプ３２により圧送された液相燃料のうち、液相燃料インジェクタＬＩＮにより噴射供給される燃料がデリバリパイプ３５（燃料噴射機構３４）に供給される。そして、このデリバリパイプ３５に供給されない余剰燃料は、迂回経路Ｒｄ４を介して燃料タンク３１に還流されるようになるとともに、デリバリパイプ３５を介して燃料タンク３１に還流される燃料の流量が「０」とされる。
【０１４４】
そして、本実施の形態においては、以下に示す制御弁の開閉処理を通じて上記各燃料経路のいずれかを能動とするようにしている。なお、本実施の形態において、内燃機関１の運転中、基本的には上記第１の燃料経路が能動とされた状態で燃料の供給が行われるものとする。
【０１４５】
次に、図２０を参照して制御弁の開閉処理について説明する。なお、本処理は、前記第４の実施の形態における燃料ポンプの吐出量変更処理（図１２及び図１３）に代えて行われる処理であり、所定の時間を周期として繰り返し実行される。
【０１４６】
同図２０に示すように、本実施の形態の制御弁の開閉処理では、前記第４の実施の形態に準じた態様をもって先のステップＳ３０７までの処理（図１２）を行う。
【０１４７】
そして、デリバリパイプ３５内の燃料の圧力（噴射機構圧力Ｐｄｖ）が気化判定圧力Ｐｖｐ未満であるか否かを判定し（ステップＳ３０８）、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき（ステップＳ３０８：Ｙｅｓ）、還流制御弁Ｅｖｒを開弁するとともに迂回制御弁Ｅｖｌを閉弁する（ステップＳ３０９ａ）。一方、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満でないときは、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）が上記算出されたスタンド給油圧力Ｐｓｔ以上であるか否かを判定する（ステップＳ３１０）。燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ３１０：Ｙｅｓ）、還流制御弁Ｅｖｒを閉弁するとともに迂回制御弁Ｅｖｌを開弁する（ステップＳ３１１ａ）、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないときは、そのときの各制御弁Ｅｖｒ，Ｅｖｌの開閉状態を維持する（ステップＳ３１０：Ｎｏ）。
【０１４８】
このように、上記制御弁の開閉処理によれば、
〔イ〕噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満であるとき、デリバリパイプ３５内にて気化燃料が発生するおそれがある（または気化燃料が発生している）と判定して、還流経路Ｒｄ２を能動とする。
〔ロ〕燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であるとき、燃料タンク３１が給油スタンドにおいて燃料の補給が行えない状態にあると判定して、迂回経路Ｒｄ４を能動とする。
といった態様をもって、上記各経路の切り替えが行われる。
【０１４９】
ちなみに、デリバリパイプ３５（燃料噴射機構３４）を介して燃料タンク３１に還流される燃料の流量は、同デリバリパイプ３５に供給される液相燃料の流量に応じて変化する。
【０１５０】
そこで、本実施の形態においては、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき、迂回経路Ｒｄ４を能動とする、即ち燃料ポンプ３２により圧送された液相燃料をデリバリパイプ３５の上流から燃料タンク３１に還流することで、デリバリパイプ３５に供給される燃料の流量が減量されるようにしている。これにより、デリバリパイプ３５を介して燃料タンク３１に還流される燃料が減量されて同燃料タンク３１における液相燃料の気化による冷却作用が相対的に高められるため、燃料タンク圧力Ｐｔｋが減圧されるようになる。
【０１５１】
また、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のときには、還流経路Ｒｄ２を能動とする、即ち燃料ポンプ３２により圧送された液相燃料の全量をデリバリパイプ３５に供給することで、デリバリパイプ３５に供給される燃料の流量が増量されるようにしている。これにより、燃料ポンプ３２により圧送された液相燃料によるデリバリパイプ３５の冷却作用が高められるため、液相燃料の気化が抑制されるようになる。
【０１５２】
次に、図２１を参照して、制御弁の開閉処理（図１２及び図２０）による各制御弁の制御態様の一例を説明する。
例えば、時刻ｔ２１１において燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上である旨検出されたとすると、還流制御弁Ｅｖｒが閉弁されるとともに迂回制御弁Ｅｖｌが開弁されることにより第２の燃料経路が能動とされる（図２１（ａ），（ｃ）〜（ｅ））。そして、噴射機構飽和蒸気圧力Ｐｓｖｄｖの変動により気化判定圧力Ｐｖｐが噴射機構圧力Ｐｄｖ以上（噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満）となった旨が時刻ｔ２１２において検出されたとすると、還流制御弁Ｅｖｒが開弁されるとともに迂回制御弁Ｅｖｌが閉弁されることにより第１の燃料経路が能動とされる（図２１（ｂ），（ｃ）〜（ｅ））。これにより、第１の燃料経路が能動とされなかった場合には、例えば一点鎖線で示すように噴射機構圧力Ｐｄｖ以上に位置していたと推定される気化判定圧力Ｐｖｐが、実線にて示すように噴射機構圧力Ｐｄｖ未満に位置するようになる（図２１（ｂ））。そして、時刻ｔ２１３において気化判定圧力Ｐｖｐが噴射機構圧力Ｐｄｖ未満（噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ以上）となった旨検出されたとすると、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上であることにより再度、第２の燃料経路が能動とされる（図２１（ａ）〜（ｅ））。これにより、第２の燃料経路が能動とされなかった場合には、例えば一点鎖線で示す態様をもって上昇すると推定される燃料タンク圧力Ｐｔｋが、実線にて示すように下降するようになる（図２１（ａ））。
【０１５３】
以上詳述したように、この第７の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第４の実施の形態における前記（３）〜（５）の効果に準じた効果に加えて、さらに以下に列記するような効果が得られるようになる。
【０１５４】
（７）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、燃料ポンプ３２により圧送された液相燃料をデリバリパイプ３５（燃料噴射機構３４）内の上流から燃料タンク３１に還流することで、燃料タンク圧力Ｐｔｋが減圧されるようにしている。これにより、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【０１５５】
（８）本実施の形態では、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（上記（７）記載の処理を行うための条件が満たされているとき）であっても、デリバリパイプ３５内にて気化燃料が発生するおそれがあるときには、燃料ポンプ３２により圧送された液相燃料の全量を同デリバリパイプ３５に供給するようにしている。これにより、デリバリパイプ３５内の燃料の液相状態が維持されるようになるため、内燃機関１の運転性の悪化を好適に回避することができるようになる。
【０１５６】
（９）また、上記（７）及び（８）記載の各条件に基づいて、
・燃料ポンプ３２により圧送された液相燃料をデリバリパイプ３５の下流から燃料タンク３１に還流する燃料経路（第１の燃料経路）。
・燃料ポンプ３２により圧送された液相燃料をデリバリパイプ３５の上流から燃料タンク３１に還流する燃料経路（第２の燃料経路）。
といった各燃料経路のいずれかを選択的に能動とするようにしているため、液相燃料による燃料噴射機構３４（デリバリパイプ３５）の冷却作用を維持しつつも、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【０１５７】
（１０）本実施の形態では、燃料ポンプ３２により圧送された液相燃料をデリバリパイプ３５の上流から燃料タンク３１に還流するといった構成を通じて、燃料タンク３１を給油スタンドにおける燃料供給が可能な状態に維持することができるようにしている。こうした構成によっても、先のトランクルーム内の温度上昇に起因する懸念を解消することができるようになるため、既存のＬＰＧ機関の燃料供給装置を有効に利用した実用性の高いＬＰＧ機関の燃料供給装置を提供することができるようになる。
【０１５８】
なお、上記第７の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第７の実施の形態では、還流経路Ｒｄ２に還流制御弁Ｅｖｒ及びプレッシャレギュレータ３６を、迂回経路Ｒｄ４に迂回制御弁Ｅｖｌ及びプレッシャレギュレータ３８をそれぞれ設ける構成としたが、例えば次のような構成に変更することも可能である。即ち、各プレッシャレギュレータ３６，３８の調圧設定値を異なる値に設定し、調圧設定値が低く設定されたプレッシャレギュレータが設けられる経路にのみ制御弁を設ける構成とすることもできる。
【０１５９】
・上記第７の実施の形態では、還流経路Ｒｄ２のプレッシャレギュレータ３６よりも上流に還流制御弁Ｅｖｒを、迂回経路Ｒｄ４のプレッシャレギュレータ３８よりも上流に迂回制御弁Ｅｖｌをそれぞれ設ける構成としたが、例えば次のような構成とすることも可能である。即ち、各制御弁Ｅｖｒ，Ｅｖｌの少なくとも一方を、対応するプレッシャレギュレータ３６，３８よりも下流に設ける構成とすることもできる。
【０１６０】
（第８の実施の形態）
本発明を具体化した第８の実施の形態について、図２２及び図２３を参照して説明する。
【０１６１】
本実施の形態において、装置全体の基本的な構成は前記第４の実施の形態と同様（図１に示される構成から気相燃料インジェクタＧＩＮを除外した構成）であるが、図１１に示される燃料供給装置３の構成が図２２に示す構成に変更されている。
【０１６２】
ここで、本実施の形態における燃料供給装置の説明に先立って、その概要を説明する。
本実施の形態も、前記第４の実施の形態と同様に、燃料タンク３１内の燃料の圧力を減圧するための機能、及び同圧力の減圧にともなう液相燃料の気化を抑制する機能を備えるものとなっている。そして、前記第４の実施の形態では、ＥＣＵ５による燃料ポンプ３２の仕事量の調整を通じて上記機能を実現しているのに対して、本実施の形態では、以下に説明する可変調圧機構を通じてデリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力を可変とすることで、上記機能が実現されるようにしている。
【０１６３】
図２２に示されるように、本実施の形態の燃料供給装置３の構成は、前記第４の実施の形態の燃料供給装置３（図１１）に対して破線内に示される各要素を追加した構成となっている。即ち、本実施の形態の燃料供給装置３にあって、還流経路Ｒｄ２には、同還流経路Ｒｄ２を流通する燃料をプレッシャレギュレータ３６を介することなく燃料タンク３１へ還流させることができる補助還流経路Ｒｄ５が接続されている。また、この補助還流経路Ｒｄ５には、プレッシャレギュレータ３６に対して設定されている所定の調整設定値よりも高い調圧設定値を有するハイプレッシャレギュレータ３９が設けられている。さらに、還流経路Ｒｄ２の補助還流経路Ｒｄ５との接続部よりも下流の経路には、同経路を選択的に開閉する還流制御弁Ｅｖｓが設けられており、この還流制御弁Ｅｖｓの開閉操作を通じて上記プレッシャレギュレータ３６の調圧機能を選択的に有効とすることができる。なお、上記還流制御弁Ｅｖｓとして、常時閉弁、即ち非通電時には閉弁されておりＥＣＵ５からの通電によって開弁される電磁弁が採用されるものとする。
【０１６４】
次に、還流制御弁Ｅｖｓの開閉操作を通じて切り替えられる各燃料経路について説明する。なお、以降では、還流制御弁Ｅｖｓが開弁されているときの燃料経路を第１の燃料経路とし、還流制御弁Ｅｖｓが閉弁されているときの燃料経路を第２の燃料経路とする。
【０１６５】
まず、第１の燃料経路が能動とされる場合における燃料の循環態様について説明する。
この場合、プレッシャレギュレータ３６による燃料の調圧機能が有効とされるため、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力は、プレッシャレギュレータ３６を通じて所定の調圧設定値に維持される。また、液相燃料インジェクタＬＩＮにより噴射供給されなかった燃料は、還流経路Ｒｄ２を介して燃料タンク３１に還流されるようになる。
【０１６６】
次に、第２の燃料経路が能動とされる場合における燃料の循環態様について説明する。
この場合、プレッシャレギュレータ３６による燃料の調圧機能が無効とされるため、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力は、ハイプレッシャレギュレータ３９を通じて上記所定の調圧設定値よりも高い調圧設定値に維持される。また、液相燃料インジェクタＬＩＮにより噴射供給されなかった燃料は、還流経路Ｒｄ２及び補助還流経路Ｒｄ５を介して燃料タンク３１に還流されるようになる。
【０１６７】
そして、本実施の形態においては、以下に示す制御弁の開閉処理を通じて上記各燃料経路のいずれかを能動とするようにしている。なお、本実施の形態において、内燃機関１の運転中、基本的には上記第１の燃料経路が能動とされた状態で燃料の供給が行われるものとする。
【０１６８】
次に、図２３を参照して制御弁の開閉処理について説明する。なお、本処理は、前記第４の実施の形態における燃料ポンプの吐出量変更処理（図１２及び図１３）に代えて行われる処理であり、所定の時間を周期として繰り返し実行される。
【０１６９】
同図２３に示すように、本実施の形態の制御弁の開閉処理では、前記第４の実施の形態に準じた態様をもって先のステップＳ３０７までの処理（図１２）を行う。
【０１７０】
そして、デリバリパイプ３５内の燃料の圧力（噴射機構圧力Ｐｄｖ）が気化判定圧力Ｐｖｐ未満であるか否かを判定し（ステップＳ３０８）、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき（ステップＳ３０８：Ｙｅｓ）、還流制御弁Ｅｖｓを開弁する（ステップＳ３０９ｂ）。一方、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満でないときは、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）が上記算出されたスタンド給油圧力Ｐｓｔ以上であるか否かを判定する（ステップＳ３１０）。燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ３１０：Ｙｅｓ）、還流制御弁Ｅｖｓを閉弁し（ステップＳ３１１ｂ）、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないときは、そのときの還流制御弁Ｅｖｓの開閉状態を維持する（ステップＳ３１０：Ｎｏ）。
【０１７１】
このように、上記制御弁の開閉処理によれば、
〔イ〕噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき、デリバリパイプ３５内にて気化燃料が発生するおそれがある（または気化燃料が発生している）と判定して、プレッシャレギュレータ３６の調圧機能を有効とする。
〔ロ〕燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき、燃料タンク３１が給油スタンドにおいて燃料の補給が行えない状態にあると判定して、ハイプレッシャレギュレータ３９の調圧機能を有効とする。
といった態様をもって、上記各燃料経路の切り替えが行われる。
【０１７２】
ちなみに、燃料ポンプ３２による液相燃料の吐出量は、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力に応じて変化する傾向を示す。即ち、デリバリパイプ３５内の燃料の圧力が高くなるにつれて燃料ポンプ３２の前後における圧力差が大きくなるため、同燃料ポンプ３２の仕事量が一定である場合には液相燃料の吐出量が少なくなる。
【０１７３】
そこで、本実施の形態においては、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき、ハイプレッシャレギュレータ３９の調圧機能を有効とする、即ちデリバリパイプ３５内の燃料の圧力を高くすることで、デリバリパイプ３５に供給される燃料の流量が減量されるようにしている。これにより、デリバリパイプ３５を介して燃料タンク３１に還流される燃料が減量されて同燃料タンク３１における液相燃料の気化による冷却作用が相対的に高められるため、燃料タンク圧力Ｐｔｋが減圧されるようになる。
【０１７４】
また、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のときには、プレッシャレギュレータ３６の調圧機能を有効とする、即ちデリバリパイプ３５内の燃料の圧力を低くすることで、デリバリパイプ３５に供給される燃料の流量が増量されるようにしている。これにより、燃料ポンプ３２により圧送された液相燃料によるデリバリパイプ３５の冷却作用が高められるため、液相燃料の気化が抑制されるようになる。
【０１７５】
以上詳述したように、この第８の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第４の実施の形態における前記（３）〜（５）の効果に準じた効果に加えて、さらに以下に列記するような効果が得られるようになる。
【０１７６】
（７）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力を高くすることで、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ未満に減圧されるようにしている。これにより、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。また、デリバリパイプ３５内の燃料の圧力が高められることにより同燃料の飽和蒸気温度が上昇するようになるため、デリバリパイプ３５内の燃料の温度上昇に起因する同燃料の気化を好適に抑制することができるようになる。
【０１７７】
（８）本実施の形態では、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（上記（１）記載の処理を行うための条件が満たされているとき）であっても、デリバリパイプ３５内にて気化燃料が発生するおそれがあるときには、同デリバリパイプ３５の燃料の圧力を低くするようにしている。これにより、デリバリパイプ３５内の燃料の液相状態が維持されるようになるため、内燃機関１の運転性の悪化を好適に回避することができるようになる。また、デリバリパイプ３５内の燃料の圧力が低くされることにより燃料ポンプ３２にかかる負荷が小さくなるため、同燃料ポンプ３２の寿命を好適に維持することができるようになる。
【０１７８】
（９）本実施の形態では、デリバリパイプ３５内の燃料の圧力を可変とすることで、燃料タンク３１を給油スタンドにおける燃料供給が可能な状態に維持することができるようにしている。こうした構成によっても、先のトランクルーム内の温度上昇に起因する懸念を解消することができるようになるため、既存のＬＰＧ機関の燃料供給装置を有効に利用した実用性の高いＬＰＧ機関の燃料供給装置を提供することができるようになる。
【０１７９】
なお、上記第８の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第８の実施の形態では、還流経路Ｒｄ２のプレッシャレギュレータ３６よりも上流に還流制御弁Ｅｖｒを設ける構成としたが、例えば次のような構成に変更することも可能である。即ち、還流経路Ｒｄ２のプレッシャレギュレータ３６よりも下流に還流制御弁Ｅｖｒを設ける構成とすることもできる。
【０１８０】
（第９の実施の形態）
本発明を具体化した第９の実施の形態について、図２４及び図２５を参照して説明する。
【０１８１】
本実施の形態において、装置全体の基本的な構成は前記第４の実施の形態と同様（図１に示される構成から気相燃料インジェクタＧＩＮを除外した構成）であるが、図１１に示される燃料供給装置３の構成が図２４に示す構成に変更されている。
【０１８２】
ここで、本実施の形態における燃料供給装置の説明に先立って、その概要を説明する。
本実施の形態も、前記第４の実施の形態と同様に、燃料タンク３１内の燃料の圧力を減圧するための機能、及び同圧力の減圧にともなう液相燃料の気化を抑制する機能を備えるものとなっている。そして、本実施の形態では、前記第８の実施の形態と同様に、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力を可変とすることで、上記機能が実現されるようにしている。
【０１８３】
図２４に示されるように、本実施の形態の燃料供給装置３の構成は、前記第４の実施の形態の燃料供給装置３（図１１）に対して破線内に示される各要素を追加した構成となっている。即ち、本実施の形態の燃料供給装置３にあって、還流経路Ｒｄ２には、プレッシャレギュレータ３６と協働してデリバリパイプ３５内の燃料の圧力を同プレッシャレギュレータ３６による所定の調整設定値よりも高い調圧設定値に維持するための補助プレッシャレギュレータ４０が設けられている。また、このプレッシャレギュレータ４０を迂回して燃料を流通させることができる迂回還流経路Ｒｄ６が、還流経路Ｒｄ２に接続されている。さらに、この迂回還流経路Ｒｄ６には同経路Ｒｄ６を選択的に開閉する迂回還流制御弁Ｅｖｂが設けられており、この迂回還流制御弁Ｅｖｂの開閉操作を通じて上記補助プレッシャレギュレータ４０の調圧機能を選択的に有効とすることができる。なお、上記迂回還流制御弁Ｅｖｂとして、常時閉弁、即ち非通電時には閉弁されておりＥＣＵ５からの通電によって開弁される電磁弁が採用されるものとする。
【０１８４】
次に、迂回還流制御弁Ｅｖｂの開閉操作を通じて切り替えられる各燃料経路について説明する。なお、以降では、迂回還流制御弁Ｅｖｂが開弁されているときの燃料経路を第１の燃料経路とし、迂回還流制御弁Ｅｖｂが閉弁されているときの燃料経路を第２の燃料経路とする。
【０１８５】
まず、第１の燃料経路が能動とされる場合における燃料の循環態様について説明する。
この場合、補助プレッシャレギュレータ４０による燃料の調圧機能が無効とされるため、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力は、プレッシャレギュレータ３６，４０を通じて所定の調圧設定値に維持される。また、液相燃料インジェクタＬＩＮにより噴射供給されなかった燃料は、還流経路Ｒｄ２及び迂回還流経路Ｒｄ６を介して燃料タンク３１に還流されるようになる。
【０１８６】
次に、第２の燃料経路が能動とされる場合における燃料の循環態様について説明する。
この場合、補助プレッシャレギュレータ４０による燃料の調圧機能が有効とされるため、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力は、各プレッシャレギュレータ３６，４０を通じて上記所定の調圧設定値よりも高い調圧設定値に維持される。また、液相燃料インジェクタＬＩＮにより噴射供給されなかった燃料は、還流経路Ｒｄ２を介して燃料タンク３１に還流されるようになる。
【０１８７】
そして、本実施の形態においては、以下に示す制御弁の開閉処理を通じて上記各燃料経路のいずれかを能動とするようにしている。なお、本実施の形態において、内燃機関１の運転中、基本的には上記第１の燃料経路が能動とされた状態で燃料の供給が行われるものとする。
【０１８８】
次に、図２５を参照して制御弁の開閉処理について説明する。なお、本処理は、前記第４の実施の形態における燃料ポンプの吐出量変更処理（図１２及び図１３）に代えて行われる処理であり、所定の時間を周期として繰り返し実行される。
【０１８９】
同図２５に示すように、本実施の形態の制御弁の開閉処理では、前記第４の実施の形態に準じた態様をもって先のステップＳ３０７までの処理（図１２）を行う。
【０１９０】
そして、デリバリパイプ３５内の燃料の圧力（噴射機構圧力Ｐｄｖ）が気化判定圧力Ｐｖｐ未満であるか否かを判定し（ステップＳ３０８）、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき（ステップＳ３０８：Ｙｅｓ）、迂回還流制御弁Ｅｖｂを開弁する（ステップＳ３０９ｃ）。一方、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満でないときは、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）が上記算出されたスタンド給油圧力Ｐｓｔ以上であるか否かを判定する（ステップＳ３１０）。燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ３１０：Ｙｅｓ）、迂回還流制御弁Ｅｖｂを閉弁し（ステップＳ３１１ｃ）、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないときは、そのときの迂回還流制御弁Ｅｖｂの開閉状態を維持する（ステップＳ３１０：Ｎｏ）。
【０１９１】
このように、上記制御弁の開閉処理によれば、
〔イ〕噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満のとき、デリバリパイプ３５内にて気化燃料が発生するおそれがある（または気化燃料が発生している）と判定して、補助プレッシャレギュレータ４０の調圧機能を無効とする。
〔ロ〕燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき、燃料タンク３１が給油スタンドにおいて燃料の補給が行えない状態にあると判定して、補助プレッシャレギュレータ４０の調圧機能を有効とする。
といった態様をもって、上記各燃料経路の切り替えが行われる。
【０１９２】
そして、上記〔イ〕の燃料経路が能動とされるときには、前記第８の実施の形態における前記〔イ〕の燃料経路が能動とされるときの作用効果に準じた作用効果が得られるようになる。また、上記〔ロ〕の燃料経路が能動とされるときには、前記第８の実施の形態における前記〔ロ〕の燃料経路が能動とされるときの作用効果に準じた作用効果が得られるようになる。
【０１９３】
以上詳述したように、この第９の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第４の実施の形態における前記（３）〜（５）の効果に準じた効果に加えて、先の第８の実施の形態における前記（７）〜（９）の効果に準じた効果が得られるようになる。
【０１９４】
なお、上記第９の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第９の実施の形態では、迂回還流制御弁Ｅｖｂを備える迂回還流経路Ｒｄ６をプレッシャレギュレータ４０を迂回する態様で還流経路Ｒｄ２に接続する構成としたが、例えば次のような構成に変更することも可能である。即ち、迂回還流制御弁Ｅｖｂとプレッシャレギュレータ４０との配設位置を入れ替えた構成とすることもできる。
【０１９５】
・上記第９の実施の形態では、還流経路Ｒｄ２にプレッシャレギュレータ４０を迂回する態様で迂回還流経路Ｒｄ６を接続する構成としたが、例えば次のような構成に変更することも可能である。即ち、迂回還流経路Ｒｄ６を上記プレッシャレギュレータ４０に代えてプレッシャレギュレータ３６を迂回する態様で還流経路Ｒｄ２に接続する構成とすることもできる。
【０１９６】
・上記第９の実施の形態では、還流経路Ｒｄ２に２つのプレッシャレギュレータ３６，４０を設ける構成としたが、例えば次のような構成とすることも可能である。即ち、還流経路Ｒｄ２に３つ以上のプレッシャレギュレータを設けるとともに、これら複数のプレッシャレギュレータのうちの少なくとも１つを迂回する態様で迂回還流経路Ｒｄ６を還流経路Ｒｄ２に接続する構成とすることもできる。
【０１９７】
（第１０の実施の形態）
本発明を具体化した第１０の実施の形態について、図２６及び図２７を参照して説明する。
【０１９８】
本実施の形態において、装置全体の基本的な構成は前記第１の実施の形態（図１）と同様であるが、図２に示される燃料供給装置３の構成が図２６に示す構成に変更されている（なお、この変更にともなって図１に示される気相燃料インジェクタＧＩＮは除外されるものとする）。
【０１９９】
ここで、本実施の形態における燃料供給装置の説明に先立って、その概要を説明する。
本実施の形態も、前記第１の実施の形態と同様に、燃料タンク３１内の燃料の圧力を減圧するための機能を備えるものとなっている。そして、前記第１の実施の形態では、内燃機関１への気相燃料の供給を通じて上記機能を実現しているのに対して、本実施の形態では、当該内燃機関１を搭載する車両の空調装置（車載空調装置）を通じて上記機能が実現されるようにしている。以下、図２６を参照して本実施の形態の燃料供給装置について説明する。
【０２００】
同図２６に示されるように、本実施の形態の燃料供給装置３は、前記第１の実施の形態の燃料供給装置３（図２）から気相燃料供給系統３Ｇを除外して、破線内にて示される冷却機構を追加した構成となっている。即ち、本実施の形態の燃料供給装置３は、空調装置（Ａ／Ｃ）７による冷気を燃料タンク３１に供給するためのダクト７１を備えて構成される。そして、ＥＣＵ５により空調装置ＡＣが駆動されることにより、同空調装置７から燃料タンク３１へ冷気が供給されるようになる。
【０２０１】
次に、空調装置７の駆動態様を制御するための処理（空調装置の駆動処理）について、図２７を参照して説明する。なお、本処理は、前記第１の実施の形態における気相燃料インジェクタの駆動処理（図３）に代えて行われる処理であり、所定の時間を周期として繰り返し実行される。
【０２０２】
同図２７に示されるように、本実施の形態の空調装置の駆動処理では、前記第１の実施の形態に準じた態様をもって先のステップＳ１０５までの処理（図３）を行う。
【０２０３】
そして、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上であるか否かを判定する（ステップＳ１０６）。燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき（ステップＳ１０６：Ｙｅｓ）、空調装置７による燃料タンク３１の冷却を行い（ステップＳ１０７ａ）、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でないときは空調装置７による燃料タンク３１の冷却を停止する（ステップＳ１０６：Ｎｏ）。
【０２０４】
このように、上記空調装置の駆動処理によれば、燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上のとき、即ち給油スタンドにおいて燃料タンク３１に対する燃料の補給が行えない状態にあるとき、空調装置７による燃料タンク３１の冷却が行われる。これにより、燃料タンク３１内の燃料の温度が低下するとともに、同燃料の圧力も低下するようになる。
【０２０５】
以上詳述したように、この第１０の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第１の実施の形態における前記（２）及び（３）の効果に準じた効果に加えて、さらに以下に列記するような効果が得られるようになる。
【０２０６】
（６）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、空調装置７を通じて燃料タンク３１の冷却を行うことで、燃料タンク圧力Ｐｔｋが減圧されるようにしている。これにより、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。
【０２０７】
（７）また、上記構成によっても、先のトランクルーム内の温度上昇に起因する懸念を解消することができるようになるため、既存のＬＰＧ機関の燃料供給装置を有効に利用した実用性の高いＬＰＧ機関の燃料供給装置を提供することができるようになる。
【０２０８】
なお、上記第１０の実施の形態は、これを適宜変更した、例えば次のような形態として実施することもできる。
・上記第１０の実施の形態では、空調装置７の冷気を燃料タンク３１に供給することで、同燃料タンク３１の冷却を行う構成としたが、例えば次のような構成にすることも可能である。即ち、空調装置７の冷気を還流経路Ｒｄ２に供給して、同還流経路Ｒｄ２内を流通する燃料を冷却する構成とすることもできる。
【０２０９】
・また、空調装置７内を循環する冷媒を燃料タンク３１に隣接して設けられる配管に供給し、この配管内の冷媒と燃料タンク３１との熱交換を通じて同燃料タンク３１を冷却する構成とすることもできる。
【０２１０】
・また、空調装置７内を循環する冷媒を還流経路Ｒｄ２に隣接して設けられる配管に供給し、この配管内の冷媒と還流経路Ｒｄ２内を流通する燃料との熱交換を通じて同還流経路Ｒｄ２内の燃料を冷却する構成とすることもできる。
【０２１１】
・上記第１０の実施の形態では、車両に搭載されている空調装置７を通じて燃料タンク３１の冷却を行う構成としたが、例えば次のような構成にすることも可能である。即ち、燃料タンク３１（あるいは還流経路Ｒｄ２）を冷却するための冷却装置を新たに備え、同冷却装置を通じて燃料タンク３１（あるいは還流経路Ｒｄ２）の冷却を行う構成とすることもできる。
【０２１２】
（第１１の実施の形態）
本発明を具体化した第１１の実施の形態について、図２８及び図２９を参照して説明する。
【０２１３】
本実施の形態において、内燃機関をはじめとした装置全体の基本的な構成は先の第１の実施の形態と同様であるが、気相燃料インジェクタの駆動処理（図３）の一部が図２８に示す処理に変更されている。
【０２１４】
ここで、本実施の形態における気相燃料インジェクタの駆動処理の説明に先立って、その概要を説明する。
本実施の形態の処理も前記第１の実施の形態の処理（図３）と同様に、内燃機関１に対する気相燃料の供給態様を制御することで、燃料タンク３１内の燃料の圧力の減圧を図るものとなっている。そして、前記第１の実施の形態では、給油時にスタンド燃料タンクの燃料に加えられる所定の圧力（給油時加圧力Ｐｃａ）とスタンド飽和蒸気圧力Ｐｓｖｓｔとを加算してスタンド給油圧力Ｐｓｔを算出するようにしているのに対して、本実施の形態では、以下に説明する態様をもってスタンド給油圧力Ｐｓｔを算出するようにしている。
【０２１５】
図２８に示すように、本実施の形態の気相燃料インジェクタの駆動処理では、まず前記第１の実施の形態に準じた態様をもって先のステップＳ１０４までの処理（図３）を行う。そして、給油時加圧力Ｐｃａよりも低く設定されている所定の加圧力Ｐｃｃをスタンド飽和蒸気圧力Ｐｓｖｓｔに加算して算出される値をスタンド給油圧力Ｐｓｔとする（ステップＳ１０５ｂ）。即ち、図２９に示すように、プロパン比率Ｒの飽和蒸気圧曲線及び外気温度ＴＨａｔｍを通じてスタンド飽和蒸気圧力Ｐｓｖｓｔが推定されるとともに、次式
Ｐｓｔ←Ｐｓｖｓｔ＋Ｐｃｃ　　　　　　　　　　　　　　　…［５］
からスタンド給油圧力Ｐｓｔが算出される。
【０２１６】
そして、先のステップＳ１０６（図３）において、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）が上記態様をもって算出されたスタンド給油圧力Ｐｓｔ以上であるか否かを判定するとともに、前記第１の実施の形態に準じた態様をもって気相燃料の供給を行う。
【０２１７】
このように、上記気相燃料インジェクタの駆動処理によれば、スタンド給油圧力Ｐｓｔが、給油時加圧力Ｐｃａよりも低く設定されている所定の加圧力Ｐｃｃとスタンド飽和蒸気圧力Ｐｓｖｓｔとの加算を通じて算出される。
【０２１８】
ちなみに、燃料タンク３１内の燃料（燃料タンク圧力Ｐｔｋ）の圧力が給油時加圧力Ｐｃａとスタンド飽和蒸気圧力Ｐｓｖｓｔとを加算して得られる圧力（前記第１の実施の形態におけるスタンド給油圧力Ｐｓｔ）以上となっているときには、スタンド燃料タンクから燃料タンク３１に燃料を補給することができなくなる。一方で、燃料タンク圧力Ｐｔｋが上記圧力（前記第１の実施の形態におけるスタンド給油圧力Ｐｓｔ）未満のとき、燃料タンク圧力Ｐｔｋが上記圧力（前記第１の実施の形態におけるスタンド給油圧力Ｐｓｔ）に近づくにつれてスタンド燃料タンクから燃料タンク３１へ燃料が流入しにくくなる傾向にある。このため、燃料タンク圧力Ｐｔｋが上記圧力（前記第１の実施の形態におけるスタンド給油圧力Ｐｓｔ）未満であっても、燃料タンク圧力Ｐｔｋが上記圧力に接近しているときには、燃料タンク３１への燃料の補給にかかる時間が通常よりも長くなることが懸念される。
【０２１９】
そこで、本実施の形態では、上記態様をもって算出されるスタンド給油圧力Ｐｓｔに基づいて気相燃料の供給を行うことで、給油スタンドにおける燃料補給にかかる時間が通常よりも長くなると推定されるときに燃料タンク圧力Ｐｔｋが減圧されるようにしている。これにより、上記懸念が解消されるとともに燃料タンク３１の状態を外部からの燃料補給が可能な状態に好適に維持することができるようになる。
【０２２０】
以上詳述したように、この第１１の実施の形態にかかる液化ガス内燃機関の燃料供給装置によれば、先の第１の実施の形態における前記（３）〜（５）の効果に準じた効果に加えて、さらに以下に列記するような効果が得られるようになる。
【０２２１】
（６）本実施の形態では、燃料タンク３１内の燃料の圧力（燃料タンク圧力Ｐｔｋ）がスタンド給油圧力Ｐｓｔ以上のとき、同燃料タンク３１内の気相燃料を内燃機関１に供給することで、燃料タンク圧力Ｐｔｋが減圧されるようにしている。これにより、燃料タンク３１の状態を給油スタンドにおける燃料補給が可能な状態に好適に維持することができるようになる。また、燃料タンク圧力Ｐｔｋが給油スタンドにおいて加圧されて燃料タンク３１へ供給される燃料の圧力に接近していることに起因する給油時間の増大を好適に回避することができるようになる。
【０２２２】
（７）本実施の形態では、スタンド給油圧力Ｐｓｔの算出を以下の態様をもって行うようにしている。即ち、
・燃料タンク３１内の燃料の飽和蒸気圧曲線及び外気温度ＴＨａｔｍから給油スタンドの燃料タンク（スタンド燃料タンク）内に貯留されている燃料の飽和蒸気圧力（スタンド飽和蒸気圧力Ｐｓｖｓｔ）を推定する。
・スタンド飽和蒸気圧力Ｐｓｖｓｔと給油時にスタンド燃料タンクの燃料へ加えられる所定の圧力（給油時加圧力Ｐｃａ）よりも低く設定されている所定の加圧力Ｐｃｃとを加算してスタンド給油圧力Ｐｓｔを算出する。
といった態様をもってスタンド給油圧力Ｐｓｔの算出を行うようにしている。これにより、燃料タンク３１内の燃料の圧力とスタンド給油圧力Ｐｓｔとの関係をより適切に把握することができるようになるとともに、燃料タンク３１の状態を給油スタンドにおいて燃料補給が可能な状態により好適に維持することができるようになる。
【０２２３】
（その他の実施の形態）
その他、上記各実施の形態に共通に変更可能な要素としては、次のようなものがある。
【０２２４】
・上記第１〜第３の実施の形態では、同各実施の形態に例示した構成を通じて内燃機関１に気相燃料を供給する構成としたが、内燃機関１に適切に気相燃料を供給することができる構成であれば、上記各実施の形態にて例示した構成に限られず任意の構成を採用することができる。
【０２２５】
・上記第４及び第５の実施の形態では、燃料ポンプ３２の燃料吐出量を２段階または３段階に変更する構成としたが、例えば次のような構成とすることも可能である。即ち、燃料タンク３１内の燃料の圧力と燃料ポンプ３２の燃料吐出量との関係を設定したマップに基づいて燃料ポンプ３２の燃料吐出量を上記圧力の変化に応じて無段階で調整する構成とすることもできる。要するに、給油スタンドにおける燃料タンク３１に対する燃料供給が可能な状態の維持及びデリバリパイプ３５内における燃料の液相状態の維持を図ることができる構成であれば、燃料ポンプ３２の制御態様（仕事量の調整による燃料吐出量の変更）は適宜変更可能である。
【０２２６】
・上記第８及び第９の実施の形態では、同各実施の形態にて例示した構成を通じてデリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力が可変とされる構成としたが、例えば次のような構成とすることも可能である。即ち、上記第４の実施の形態における燃料供給装置３（図１１）の還流経路Ｒｄ２に複数の調圧設定値を有する可変プレッシャレギュレータを備える構成とすることもできる。要するに、デリバリパイプ３５（燃料噴射機構３４）内の燃料の圧力を可変とすることができる構成であれば、そのための構成は上記各実施の形態にて例示した構成に限られず任意の構成を採用することができる。
【０２２７】
・上記第４、第５及び第７〜第９の実施の形態では、上記ステップＳ３０８（図１３、図１６、図２０、図２３、図２５）の処理において、噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満であるか否かを判定する構成としたが、例えば次のような構成とすることも可能である。即ち、噴射機構圧力Ｐｄｖがデリバリパイプ３５内の燃料の飽和蒸気圧力（噴射機構飽和蒸気圧力Ｐｓｖｄｖ）以上であるか否かを判定する構成とすることもできる。
【０２２８】
・上記第５及び第７〜第９の実施の形態に、上記第６の実施の形態にて例示した構成を適用することもできる。即ち、上記第５及び第７〜第９の実施の形態におけるステップＳ３０８の処理（図１６、図２０、図２３、図２５）に代えて、上記第６の実施の形態におけるステップＳ３０８ａの処理（図１７）を行うことも可能である。
【０２２９】
・また、さらには上記ステップＳ３０８ａ（図１７）の処理に代えて、噴射機構温度ＴＨｄｖがデリバリパイプ３５内の燃料の飽和蒸気温度（噴射機構飽和蒸気温度ＴＨｓｖｄｖ）以上であるか否かを判定する処理を行うこともできる。
【０２３０】
・上記第４〜第９の実施の形態におけるステップＳ３０８（ステップＳ３０８ａ）の処理（図１３、図１６、図１７、図２０、図２３、図２５）の処理を、例えば次のように変更することも可能である。即ち、上記処理に代えて、デリバリパイプ３５内の燃料の温度が予め設定されている所定の温度以上であるか否かを判定する処理を行い、上記燃料の温度が所定の温度以上のときにはステップＳ３０９（ステップＳ３０９ａ〜ｃ）へ移り、上記燃料の温度が所定の温度以上でないときにはステップＳ３１０へ移る構成とすることもできる。
【０２３１】
・上記第４〜第９の実施の形態では、デリバリパイプ３５内にて液相燃料の気化が生じるおそれがあるか否かを判定するための処理（ステップＳ３０８，Ｓ３０８ａ）を行う構成としたが、例えばデリバリパイプ３５内における液相燃料の気化が懸念されないような燃料供給装置３の構成である場合には、上記処理を省略することもできる。
【０２３２】
・上記第３〜第１０の実施の形態に、上記第２の実施の形態にて例示した構成を適用することもできる。即ち、上記第３及び第１０の実施の形態にあってはステップＳ１０５（図３）の次にステップＳ１０５ａ（図８）を行い、ステップＳ１０６（図３、図２７）に代えてステップＳ１０６ａ（図８）を行うことも可能である。また、上記第４〜第９の実施の形態にあってはステップＳ３０７（図１２）の次にステップＳ１０５ａ（図３）を行い、ステップＳ３１０（図１３、図１６、図２０、図２３、図２５）に代えてステップＳ１０６ａ（図８）を行うことも可能である。
【０２３３】
・上記第２〜第１０の実施の形態に、上記第１１の実施の形態にて例示した構成を適用することもできる。即ち、上記第２〜第１０の実施の形態において、スタンド飽和蒸気圧力Ｐｓｖｓｔと給油時加圧力Ｐｃａよりも低く設定されている所定の加圧力Ｐｃｃとを加算して算出される値をスタンド給油圧力Ｐｓｔとして用いることも可能である。
【０２３４】
・上記各実施の形態では、スタンド給油圧力Ｐｓｔを上記各実施の形態にて例示した態様をもって算出する構成としたが、このスタンド給油圧力Ｐｓｔを予め設定した値として用いることもできる。
【０２３５】
・上記各実施の形態では、燃料タンク圧力Ｐｔｋを減圧するための処理、即ち〔イ〕上記第１〜第３及び第１１の実施の形態では、内燃機関１に気相燃料を供給する。
〔ロ〕上記第４〜第６の実施の形態では、燃料ポンプ３２の燃料吐出量を低流量に変更する。
〔ハ〕上記第７の実施の形態では、還流制御弁Ｅｖｒを閉弁するとともに迂回制御弁Ｅｖｌを開弁する。
〔ニ〕上記第８の実施の形態では、還流制御弁Ｅｖｓを閉弁する。
〔ホ〕上記第９の実施の形態では、迂回還流制御弁Ｅｖｂを閉弁する。
〔ヘ〕上記第１０の実施の形態では、空調装置７を駆動する。
といった各処理を、「燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上である」ときに開始し、「燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上でない」ときに停止する構成としたが（ステップＳ１０６及びステップＳ３１０）、例えば次のように変更することも可能である。即ち、上記各処理を「燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔ以上である」ときに開始し、「燃料タンク圧力Ｐｔｋがスタンド給油圧力Ｐｓｔよりも低く設定される所定の圧力未満である」ときに停止する構成とすることもできる。
【０２３６】
・上記第４〜第９実施の形態では、デリバリパイプ３５内での液相燃料の気化を抑制するための処理、即ち
〔イ〕上記第４〜第６の実施の形態では、燃料ポンプ３２の燃料吐出量を高流量に変更する。
〔ロ〕上記第７の実施の形態では、還流制御弁Ｅｖｒを開弁するとともに迂回制御弁Ｅｖｌを閉弁する。
〔ハ〕上記第８の実施の形態では、還流制御弁Ｅｖｓを開弁する。
〔ニ〕上記第９の実施の形態では、迂回還流制御弁Ｅｖｂを開弁する。
といった各処理を、「噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満である」（第６の実施の形態では「噴射機構温度ＴＨｄｖが気化判定温度ＴＨｖｐ以上である」）ときに開始し、「噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満でない」（第６の実施の形態では「噴射機構温度ＴＨｄｖが気化判定温度ＴＨｖｐ以上でない」）ときに停止する構成としたが（ステップＳ３０８及びステップＳ３０８ａ）、例えば次のように変更することも可能である。即ち、上記各処理を「噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐ未満である」（第６の実施の形態では「噴射機構温度ＴＨｄｖが気化判定温度ＴＨｖｐ以上である」）ときに開始し、「噴射機構圧力Ｐｄｖが気化判定圧力Ｐｖｐよりも高く設定される所定の圧力以上である」（第６の実施の形態では「噴射機構温度ＴＨｄｖが気化判定温度ＴＨｖｐよりも低く設定される所定の温度未満である」）ときに停止する構成とすることもできる。
【０２３７】
・上記各実施の形態では、図４に例示したプロパン比率のマップから燃料（ＬＰＧ）中のプロパン比率Ｒを推定する構成としたが、同プロパン比率のマップは上記各実施の形態にて例示したものに限られず、適宜のマップを採用することができる。
【０２３８】
・上記各実施の形態では、同各実施の形態にて例示した飽和蒸気圧計算式［１］に基づいて燃料の飽和蒸気圧曲線を決定する構成としたが、この飽和蒸気圧計算式［１］は上記各実施の形態にて例示した計算式に限られず、適宜の計算式を採用することができる。
【０２３９】
・上記各実施の形態では、燃料タンク３１内の燃料の温度及び圧力から推定されるプロパン比率Ｒに基づいて燃料の飽和蒸気圧曲線を決定する構成としたが、例えば次のように変更することも可能である。即ち、燃料の飽和蒸気圧曲線を予め設定しておくとともに、プロパン比率Ｒの推定を行わない構成とすることもできる。
【０２４０】
・上記各実施の形態では、ＬＰＧ機関の燃料供給装置に対して本発明を適用したが、本発明の適用対象となる燃料供給装置はＬＰＧ機関の燃料供給装置に限られるものではない。要するに、燃料ポンプにより圧送された燃料を燃料噴射機構を介して燃料タンクに還流させる燃料循環方式を採用しているとともに、例えば液化天然ガス（ＬＮＧ）、液体水素及びジメチルエーテル等といった液化ガスを燃料とする内燃機関の燃料供給装置であれば本発明の適用は可能であり、そうした燃料供給装置に本発明を適用した場合にあっても上記各実施の形態の作用効果に準じた作用効果が奏せられるようになる。
【０２４１】
以上の事項も含めて、最後に、この発明にかかる液化ガス内燃機関の燃料供給装置は、次のような技術思想を含むものであることを付記しておく。
（１）請求項１５記載の液化ガス内燃機関の燃料供給装置において、前記減圧手段は、前記燃料ポンプに供給される電流量を少なくすることで前記燃料ポンプの仕事量を小さくするものである。
【０２４２】
（２）請求項１８記載の液化ガス内燃機関の燃料供給装置において、前記切替手段は、前記還流経路を選択的に開閉する還流制御弁と、前記迂回経路を選択的に開閉する迂回制御弁とを備えて構成され、前記減圧手段は、前記還流制御弁を閉弁するとともに前記迂回制御弁を開弁することで、前記迂回経路を能動とするものである。
【０２４３】
（３）請求項２１記載の液化ガス内燃機関の燃料供給装置において、前記可変調圧機構は、前記還流経路に設けられて前記燃料噴射機構内の燃料の圧力を第１の調圧設定値に維持する第１の調圧機構と、前記還流経路の前記第１の調圧機構よりも上流から分岐して前記燃料タンクに接続される補助還流経路に設けられて前記燃料噴射機構内の燃料の圧力を前記第１の調圧設定値よりも高い第２の調圧設定値に維持する第２の調圧機構と、前記還流経路に設けられて同還流経路を選択的に開閉する還流制御弁とを備えて構成され、前記減圧手段は、前記還流制御弁を閉弁することで、前記可変調圧機構の調圧設定値を高い値に変更するものである。
【０２４４】
（４）請求項２１記載の液化ガス内燃機関の燃料供給装置において、前記可変調圧機構は、前記還流経路に設けられて前記燃料噴射機機構内の燃料の圧力を所定の調圧設定値に維持する複数の調圧機構と、これら複数の調圧機構のうちの少なくとも１つを迂回する態様で前記還流経路から分岐される迂回還流経路に設けられて同迂回還流経路を選択的に開閉する迂回還流制御弁とを備えて構成され、前記減圧手段は、前記迂回還流制御弁を閉弁することで、前記可変調圧機構の調圧設定値を高い値に変更するものである。
【０２４５】
（５）請求項２１記載の液化ガス内燃機関の燃料供給装置において、前記可変調圧機構は、前記還流経路に設けられて調圧設定値が可変である可変プレッシャレギュレータを備えて構成され、前記減圧手段は、前記可変プレッシャレギュレータの調圧設定値をより高い値に変更することで、前記可変調圧機構の調圧設定値を高い値に変更するものである。
【０２４６】
（６）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の圧力が、外部の補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力である補給圧力以上となるとき、前記燃料タンク内の気相燃料を前記内燃機関に供給する気相燃料供給手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２４７】
（７）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の温度が、外部の補給用燃料タンク内の燃料の飽和蒸気特性に同補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力である補給圧力を適用することにより得られる飽和蒸気温度以上となるとき、前記燃料タンク内の気相燃料を前記内燃機関に供給する気相燃料供給手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２４８】
（８）前記気相燃料供給手段は、前記補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力と同補給用燃料タンク内の燃料が前記燃料タンクに補給される際に同燃料に加えられる補給時加圧力とを加算して前記補給圧力を算出する前記（６）または（７）記載の液化ガス内燃機関の燃料供給装置。
【０２４９】
（９）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の圧力が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力よりも高く、且つ前記補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力以下に設定される補給圧力以上となるとき、前記燃料タンク内の気相燃料を前記内燃機関に供給する気相燃料供給手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５０】
（１０）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の温度が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力よりも高く、且つ前記補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力以下に設定される補給圧力を前記補給用燃料タンク内の燃料の飽和蒸気特性に適用することにより得られる飽和蒸気温度以上となるとき、前記燃料タンク内の気相燃料を前記内燃機関に供給する気相燃料供給手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５１】
（１１）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の圧力が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力と同補給用燃料タンク内の燃料が前記燃料タンクに補給される際に同燃料に加えられる補給時加圧力よりも低い所定の圧力とを加算して得られる補給圧力以上となるとき、前記燃料タンク内の気相燃料を前記内燃機関に供給する気相燃料供給手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５２】
（１２）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の温度が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力と同補給用燃料タンク内の燃料が前記燃料タンクに補給される際に同燃料に加えられる補給時加圧力よりも低い所定の圧力とを加算して得られる補給圧力を前記補給用燃料タンク内の燃料の飽和蒸気特性に適用することにより得られる飽和蒸気温度以上となるとき、前記燃料タンク内の気相燃料を前記内燃機関に供給する気相燃料供給手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５３】
（１３）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の圧力が、外部の補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力である補給圧力以上となるとき、前記燃料ポンプの仕事量を小さくするポンプ制御手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５４】
（１４）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の温度が、外部の補給用燃料タンク内の燃料の飽和蒸気特性に同補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力である補給圧力を適用することにより得られる飽和蒸気温度以上となるとき、前記燃料ポンプの仕事量を小さくするポンプ制御手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５５】
（１５）前記ポンプ制御手段は、前記補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力と同補給用燃料タンク内の燃料が前記燃料タンクに補給される際に前記補給用燃料タンクの燃料に加えられる補給時加圧力とを加算して前記補給圧力を算出する前記（１３）または（１４）記載の液化ガス内燃機関の燃料供給装置。
【０２５６】
（１６）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の圧力が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力よりも高く、且つ前記補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力以下に設定される補給圧力以上となるとき、前記燃料ポンプの仕事量を小さくするポンプ制御手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５７】
（１７）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の温度が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力よりも高く、且つ前記補給用燃料タンクから前記燃料タンクへ加圧されて補給される燃料の圧力以下に設定される補給圧力を前記補給用燃料タンク内の燃料の飽和蒸気特性に適用することにより得られる飽和蒸気温度以上となるとき、前記燃料ポンプの仕事量を小さくするポンプ制御手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５８】
（１８）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の圧力が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力と同補給用燃料タンク内の燃料が前記燃料タンクに補給される際に前記補給用燃料タンクの燃料に加えられる補給時加圧力よりも低い所定の圧力とを加算して得られる補給圧力以上となるとき、前記燃料ポンプの仕事量を小さくするポンプ制御手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２５９】
（１９）飽和状態で燃料タンク内に貯留されている液相燃料を燃料ポンプにより圧送し、この圧送された液相燃料を燃料噴射機構により内燃機関に噴射供給するとともに前記燃料噴射機構内の燃料を同燃料噴射機構の下流から前記燃料タンクに還流する液化ガス内燃機関の燃料供給装置において、前記燃料タンク内の燃料の温度が、外部の補給用燃料タンク内に貯留されている燃料の飽和蒸気圧力と同補給用燃料タンク内の燃料が前記燃料タンクに補給される際に前記補給用燃料タンクの燃料に加えられる補給時加圧力よりも低い所定の圧力とを加算して得られる補給圧力を前記補給用燃料タンク内の燃料の飽和蒸気特性に適用することにより得られる飽和蒸気温度以上となるとき、前記燃料ポンプの仕事量を小さくするポンプ制御手段を備えることを特徴とする液化ガス内燃機関の燃料供給装置。
【０２６０】
（２０）前記ポンプ制御手段は、前記燃料噴射機構内の燃料の圧力が同燃料の飽和蒸気圧力未満であるとき、前記燃料ポンプの仕事量を小さくする処理を中断する前記（１３）〜（１９）のいずれかに記載の液化ガス内燃機関の燃料供給装置。
【０２６１】
（２１）前記ポンプ制御手段は、前記燃料噴射機構内の燃料の圧力が同燃料の飽和蒸気圧力未満であるとき、前記燃料ポンプの仕事量を大きくする前記（１３）〜（１９）のいずれかに記載の液化ガス内燃機関の燃料供給装置。
【図面の簡単な説明】
【図１】本発明にかかる液化ガス内燃機関の燃料供給装置の第１の実施の形態についてその全体構成を模式的に示す概略図。
【図２】同実施の形態の燃料供給装置についてその全体構成を模式的に示す概略図。
【図３】同実施の形態にて行われる気相燃料インジェクタの駆動処理を示すフローチャート。
【図４】同実施の形態にて行われる気相燃料インジェクタの駆動処理に用いられるプロパン比率のマップ。
【図５】液化石油ガスの飽和蒸気圧曲線を示すグラフ。
【図６】同実施の形態にて行われる気相燃料インジェクタの駆動処理によるスタンド給油圧力の算出態様を示すグラフ。
【図７】同実施の形態にて行われる気相燃料インジェクタの駆動処理による気相燃料の供給態様についてその一例を示すタイミングチャート。
【図８】本発明にかかる液化ガス内燃機関の燃料供給装置の第２の実施の形態について同実施の形態で行われる気相燃料インジェクタの駆動処理の一部を示すフローチャート。
【図９】同実施の形態にて行われる気相燃料インジェクタの駆動処理による給油時飽和蒸気温度の算出態様を示すグラフ。
【図１０】本発明にかかる液化ガス内燃機関の燃料供給装置の第３の実施の形態についてその全体構成を模式的に示す概略図。
【図１１】本発明にかかる液化ガス内燃機関の燃料供給装置の第４の実施の形態についてその全体構成を模式的に示す概略図。
【図１２】同実施の形態にて行われる燃料ポンプの吐出量変更処理の一部を示すフローチャート。
【図１３】同実施の形態にて行われる燃料ポンプの吐出量変更処理の一部を示すフローチャート。
【図１４】同実施の形態にて行われる燃料ポンプの吐出量変更処理によるスタンド給油圧力及び気化判定圧力の算出態様を示すグラフ。
【図１５】同実施の形態にて行われる燃料ポンプの吐出量変更処理による燃料ポンプの燃料吐出量変更態様についてその一例を示すタイミングチャート。
【図１６】本発明にかかる液化ガス内燃機関の燃料供給装置の第５の実施の形態について同実施の形態で行われる燃料ポンプの吐出量変更処理の一部を示すフローチャート。
【図１７】本発明にかかる液化ガス内燃機関の燃料供給装置の第６の実施の形態について同実施の形態で行われる燃料ポンプの吐出量変更処理の一部を示すフローチャート。
【図１８】同実施の形態にて行われる燃料ポンプの吐出量変更処理による気化判定温度の算出態様を示すグラフ。
【図１９】本発明にかかる液化ガス内燃機関の燃料供給装置の第７の実施の形態についてその全体構成を模式的に示す概略図。
【図２０】同実施の形態にて行われる制御弁の開閉処理の一部を示すフローチャート。
【図２１】同実施の形態にて行われる制御弁の開閉処理による各制御弁の駆動態様についてその一例を示すタイミングチャート。
【図２２】本発明にかかる液化ガス内燃機関の燃料供給装置の第８の実施の形態についてその全体構成を模式的に示す概略図。
【図２３】同実施の形態にて行われる制御弁の開閉処理の一部を示すフローチャート。
【図２４】本発明にかかる液化ガス内燃機関の燃料供給装置の第９の実施の形態についてその全体構成を模式的に示す概略図。
【図２５】同実施の形態にて行われる制御弁の開閉処理の一部を示すフローチャート。
【図２６】本発明にかかる液化ガス内燃機関の燃料供給装置の第１０の実施の形態についてその全体構成を模式的に示す概略図。
【図２７】同実施の形態にて行われる空調装置の駆動処理の一部を示すフローチャート。
【図２８】本発明にかかる液化ガス内燃機関の燃料供給装置の第１１の実施の形態について同実施の形態で行われる気相燃料インジェクタの駆動処理の一部を示すフローチャート。
【図２９】同実施の形態にて行われる気相燃料インジェクタの駆動処理によるスタンド給油圧力の算出態様を示すグラフ。
【図３０】従来の液化石油ガス内燃機関の燃料供給装置の全体構成を模式的に示す概略図。
【符号の説明】
１…内燃機関、３…燃料供給装置、５…電子制御装置（ＥＣＵ）、６…検出系、７…空調装置（Ａ／Ｃ）、１１…シリンダブロック、１２…シリンダ、１２ａ…ウォータージャケット、１３…シリンダヘッド、１４…クランクシャフト、１５…コネクティングロッド、１６…ピストン、１７…燃焼室、２１…エアクリーナ、２２…スロットルバルブ、２３…サージタンク、２４…吸気通路、２５…触媒装置、２６…排気通路、３Ｌ…液相燃料供給系統、３Ｇ…気相燃料供給系統、ＬＩＮ…液相燃料インジェクタ、ＧＩＮ…気相燃料インジェクタ、３１…燃料タンク、３２…燃料ポンプ、３３…燃料フィルタ、３４…燃料噴射機構、３５…デリバリパイプ、３６…プレッシャレギュレータ、３７…絞り機構、３８…プレッシャレギュレータ、３９…ハイプレッシャレギュレータ、４０…補助プレッシャレギュレータ、６１…外気温度センサ、６２…タンク温度センサ、６３…タンク圧力センサ、６４…噴射機構温度センサ、６５…噴射機構圧力センサ、７１…ダクト、Ｒｄ１…液相燃料供給経路、Ｒｄ２…還流経路、Ｒｄ３…気相燃料供給経路、Ｒｄ４…迂回経路、Ｒｄ５…補助還流経路、Ｒｄ６…迂回還流経路、Ｅｖｇ…気相制御弁、Ｅｖｌ…迂回制御弁、Ｅｖｒ…還流制御弁、Ｅｖｓ…還流制御弁、Ｅｖｂ…迂回還流制御弁。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel supply device for a liquefied gas internal combustion engine which is employed in an internal combustion engine using a liquefied gas such as liquefied petroleum gas or liquefied natural gas as a fuel and supplies the liquefied gas fuel to the internal combustion engine.
[0002]
[Prior art]
As is well known, as an internal combustion engine (LPG engine) using liquefied petroleum gas (LPG) as a fuel, an LPG engine including a fuel supply device for injecting and supplying fuel (LPG) in a liquid phase has been put to practical use. Here, the fuel supply device of such an LPG engine basically has a configuration using a fuel circulation system called a fuel return system schematically shown in FIG.
[0003]
As shown in FIG. 30, in the fuel supply device 300 employing the above-described fuel circulation system, the liquid fuel in the fuel tank 301 is pressure-fed to a fuel supply path 303 by a fuel pump 302, and The fuel is supplied to a delivery pipe 306 constituting a fuel injection mechanism 305 together with an injector 304 via a supply path 303. The fuel supplied into the delivery pipe 306 is injected and supplied to the internal combustion engine through the injector 304, while the fuel remaining in the delivery pipe 306 is supplied to the fuel tank via the pressure regulator 308 provided in the return path 307. It is configured to return to 301.
[0004]
As described above, in the fuel supply device of the LPG engine, the liquid-phase fuel pumped by the fuel pump 302 is returned to the fuel tank 301 through the delivery pipe 306, so that the liquid-phase fuel pumped by the pump The delivery pipe 306 (fuel injection mechanism 305) is cooled. As a result, the liquid phase state of the LPG is maintained even in the delivery pipe 306, which tends to be heated to a high temperature by receiving heat from the internal combustion engine.
[0005]
[Problems to be solved by the invention]
By the way, LPG is a liquefied fuel that exists in a gas phase at normal temperature and normal pressure and is stored in a fuel tank in a pressurized and liquefied state. For this reason, replenishment of LPG from the fuel tank (stand fuel tank) provided at the refueling station to the fuel tank (engine fuel tank) of the fuel supply device of the LPG engine is performed in the following manner. That is, when replenishing LPG, the above-mentioned fuel tanks are connected in a state of being cut off from the atmosphere, and the fuel in the stand fuel tank is pressurized by a predetermined pressure, so that the LPG is transferred from the stand fuel tank to the engine fuel tank. So that it flows in.
[0006]
From these facts, the following may be a concern in the fuel supply device of the LPG engine adopting the fuel return type fuel circulation system.
That is, since the fuel in the delivery pipe 306 receives heat from the combustion chamber of the internal combustion engine and becomes high temperature and is returned to the fuel tank 301 (engine fuel tank), the temperature of the fuel in the engine fuel tank rises. Accordingly, the pressure of the fuel tends to increase. When the pressure of the fuel is equal to or higher than the pressure of the fuel supplied to the engine fuel tank at the refueling station (the pressure of the fuel pressurized and supplied to the engine fuel tank), the fuel is supplied to the fuel tank. You can't do that.
[0007]
In addition, even if it is not a fuel supply device for an internal combustion engine using LPG as a fuel, liquefaction using a liquefied fuel stored in a fuel tank in a gaseous state at normal temperature and normal pressure and liquefied by pressurization as a fuel. A fuel supply device for a gas internal combustion engine may cause the same problem as described above.
[0008]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel supply device for a liquefied gas internal combustion engine that can maintain a state of a fuel tank in a state where external fuel can be supplied. To provide.
[0009]
[Means for Solving the Problems]
Hereinafter, the means for achieving the above object and the effects thereof will be described.
According to the present invention, the liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism. In a fuel supply device for a liquefied gas internal combustion engine that recirculates fuel in an injection mechanism from a downstream side of the fuel injection mechanism to the fuel tank, a pressure of the fuel in the fuel tank increases from an external replenishment fuel tank to the fuel tank. The gist of the present invention is to provide a pressure reducing means for reducing the pressure of the fuel in the fuel tank when the pressure becomes equal to or higher than the supply pressure which is the pressure of the fuel to be replenished by pressurization.
[0010]
According to the above configuration, the pressure of the fuel in the fuel tank is equal to or higher than the replenishment pressure that is the pressure of the fuel that is pressurized and replenished from the external replenishment fuel tank provided in the refueling stand or the like to the fuel tank. At this time, the pressure of the fuel in the fuel tank is reduced. As a result, the pressure rise of the fuel in the fuel tank is suppressed more than the original pressure rise (the pressure rise when the pressure of the fuel in the fuel tank is not reduced). It is possible to suitably maintain a state in which refueling from is possible.
[0011]
According to a second aspect of the present invention, the liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism. In a fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel in an injection mechanism from downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is determined by the saturation of the fuel in the external replenishment fuel tank. When the saturated fuel temperature is equal to or higher than the saturated steam temperature obtained by applying the replenishing pressure, which is the pressure of the fuel that is pressurized from the replenishing fuel tank to the fuel tank and replenished, the pressure of the fuel in the fuel tank The gist of the present invention is to provide a pressure reducing means for reducing the pressure.
[0012]
According to the above configuration, the temperature of the fuel in the fuel tank is adjusted to the saturated vapor characteristic of the fuel in the external replenishing fuel tank by the pressure of the fuel that is pressurized and replenished from the replenishing fuel tank to the fuel tank. When the temperature becomes equal to or higher than the saturated steam temperature obtained by applying a certain supply pressure, the pressure of the fuel in the fuel tank is reduced. Incidentally, the temperature of the fuel in the fuel tank is a saturated steam temperature obtained by applying the above-described replenishing pressure to the saturated vapor characteristic of the fuel in the replenishing fuel tank, that is, the replenishment is performed by pressurizing the fuel from the replenishing fuel tank to the fuel tank. When the temperature is equal to or higher than the saturated vapor temperature of the fuel to be discharged, the pressure of the fuel in the fuel tank is higher than the above-described replenishment pressure. Also in such a case, it becomes impossible to replenish the fuel from the replenishing fuel tank to the fuel tank of the fuel supply device. Therefore, the operation and effect of the invention according to claim 1 can also be achieved by reducing the pressure of the fuel in the fuel tank when the temperature of the fuel in the fuel tank becomes equal to or higher than the saturated steam temperature as in the above configuration. The operation and effect according to the above can be obtained.
[0013]
According to a third aspect of the present invention, in the fuel supply system for a liquefied gas internal combustion engine according to the first or second aspect, the pressure reducing means is configured to supply the same saturated vapor pressure of the fuel stored in the replenishing fuel tank as the same as the replenishing pressure. The gist is that the replenishment pressure is calculated by adding a replenishing pressure applied to the fuel in the replenishment fuel tank when the fuel in the fuel tank is replenished to the fuel tank.
[0014]
According to the above configuration, the saturated vapor pressure of the fuel stored in the replenishment fuel tank and the replenishment pressure applied to the fuel when the fuel in the replenishment fuel tank is replenished to the fuel tank. The addition pressure is calculated by the addition. Incidentally, when fuel is supplied from an external replenishment fuel tank to the fuel tank of the fuel supply device of the liquefied gas internal combustion engine, a predetermined pressure (pressure during replenishment) is applied to the fuel in the replenishment fuel tank. Can be Since the liquefied fuel is stored in a saturated state in the replenishment fuel tank, the pressure (replenishment pressure) of the fuel supplied from the replenishment fuel tank to the fuel tank of the fuel supply device is basically It can be said that the value becomes substantially equal to a value obtained by adding the saturated vapor pressure of the fuel in the replenishment fuel tank and the predetermined pressure (replenishment pressure). Therefore, in the above configuration, by calculating the supply pressure in the above-described manner, an accurate relationship between the pressure of the fuel stored in the fuel tank of the fuel supply device and the supply pressure can be obtained. As a result, the state of the fuel tank can be more suitably maintained in a state where external fuel supply is possible.
[0015]
According to a fourth aspect of the present invention, the liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism. In a fuel supply device for a liquefied gas internal combustion engine that recirculates fuel in an injection mechanism from downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is stored in an external replenishment fuel tank. The fuel pressure in the fuel tank is higher than the saturated vapor pressure of the fuel and the replenishment pressure is set to be equal to or less than the pressure of the fuel that is pressurized and replenished from the replenishment fuel tank to the fuel tank. The gist of the invention is to provide a pressure reducing means for reducing the pressure.
[0016]
According to the above configuration, the pressure of the fuel in the fuel tank is higher than the saturated vapor pressure of the fuel stored in the external replenishing fuel tank, and the fuel is pressurized from the replenishing fuel tank to the fuel tank. When the pressure becomes equal to or higher than the replenishment pressure set to be equal to or lower than the pressure of the fuel to be replenished, the pressure of the fuel in the fuel tank is reduced. Incidentally, when the pressure of the fuel in the fuel tank of the fuel supply device is equal to or higher than the pressure of the fuel to be replenished by being pressurized from the replenishing fuel to the fuel tank, the fuel is replenished from the replenishing fuel tank to the fuel tank. Can not be done. On the other hand, when the pressure of the fuel in the fuel tank is lower than the pressure of the fuel that is pressurized and replenished, as the pressure of the fuel in the fuel tank approaches the pressure of the fuel that is pressurized and refilled, There is a tendency that fuel does not easily flow from the replenishing fuel tank to the fuel tank. For this reason, even if the pressure of the fuel in the fuel tank is lower than the pressure of the fuel to be replenished by being pressurized, there is a concern that the time required for refueling the fuel tank becomes long. Therefore, in the above configuration, by reducing the pressure of the fuel in the fuel tank in the above-described manner, the above-mentioned concerns are resolved, and the state of the fuel tank is preferably maintained in a state where external fuel supply is possible. I can do it.
[0017]
According to a fifth aspect of the present invention, liquid fuel stored in a fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism. In a fuel supply device for a liquefied gas internal combustion engine that recirculates fuel in an injection mechanism from downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is stored in an external replenishment fuel tank. The replenishment pressure set to be higher than the saturated vapor pressure of the fuel being supplied and to be equal to or less than the pressure of the fuel to be replenished by being pressurized from the replenishment fuel tank to the fuel tank. The gist of the present invention is to provide a pressure reducing means for reducing the pressure of the fuel in the fuel tank when the temperature becomes equal to or higher than the saturated steam temperature obtained by applying the characteristic.
[0018]
According to the above configuration, the temperature of the fuel tank is higher than the pressure of the fuel stored in the supplementary fuel tank provided outside the fuel supply device, and the fuel tank is pressurized from the supplementary fuel tank to the fuel tank. When the replenishment pressure set to be equal to or less than the pressure of the fuel to be replenished becomes equal to or higher than the saturated steam temperature obtained by applying the saturated steam characteristic of the fuel in the refilling fuel tank, the pressure of the fuel in the fuel tank Is decompressed. By the way, even when the temperature of the fuel in the fuel tank is equal to or higher than the saturated steam temperature obtained by applying the above-mentioned replenishment pressure to the saturated steam characteristic of the fuel in the replenishing fuel tank, the pressure of the fuel in the fuel tank is not higher than the above. This means that the supply pressure has been exceeded. Therefore, the effect of the invention according to claim 4 can also be achieved by reducing the pressure of the fuel in the fuel tank when the temperature of the fuel in the fuel tank becomes equal to or higher than the saturated steam temperature as in the above configuration. The operation and effect according to the above can be obtained.
[0019]
According to a sixth aspect of the present invention, the liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism. In a fuel supply device for a liquefied gas internal combustion engine that recirculates fuel in an injection mechanism from downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is controlled by a replenishing device provided outside the fuel supply device. A predetermined vapor pressure lower than a saturated vapor pressure of the fuel stored in the fuel tank and a replenishing pressure applied to the fuel in the replenishing fuel tank when the fuel in the replenishing fuel tank is replenished to the fuel tank. And a pressure reducing means for reducing the pressure of the fuel in the fuel tank when the pressure becomes equal to or higher than the replenishment pressure obtained by adding the pressures.
[0020]
According to the above configuration, the pressure of the fuel in the fuel tank is
[A] The saturated vapor pressure of the fuel stored in the external replenishing fuel tank.
[B] A predetermined pressure lower than the replenishing pressure applied to the fuel in the replenishing fuel tank when fuel is replenished from the replenishing fuel tank to the fuel tank.
, The pressure of the fuel in the fuel tank is reduced. With such a configuration, an operation and effect similar to the operation and effect of the invention described in claim 4 can be obtained.
[0021]
According to a seventh aspect of the present invention, liquid fuel stored in a fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism. In a fuel supply device for a liquefied gas internal combustion engine that recirculates fuel in an injection mechanism from downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is stored in an external replenishment fuel tank. Adding the saturated vapor pressure of the fuel and the predetermined pressure lower than the replenishing pressure applied to the fuel in the replenishing fuel tank when the fuel in the replenishing fuel tank is replenished to the fuel tank. When the obtained replenishment pressure is equal to or higher than the saturated vapor temperature obtained by applying the saturated vapor characteristic of the fuel in the replenishment fuel tank, the pressure of the fuel in the fuel tank is reduced. It is summarized as further comprising a stage.
[0022]
According to the above configuration, the temperature of the fuel in the fuel tank is
[A] The saturated vapor pressure of the fuel stored in the external replenishing fuel tank.
[B] A predetermined pressure lower than the replenishing pressure applied to the fuel in the replenishing fuel tank when fuel is replenished from the replenishing fuel tank to the fuel tank.
The pressure of the fuel in the fuel tank is reduced when the replenishment pressure obtained by adding the respective pressures is equal to or higher than the saturated steam temperature obtained by applying the replenishment pressure to the saturated vapor characteristic of the fuel in the replenishment fuel tank. . With such a configuration, an operation and effect similar to the operation and effect of the invention described in claim 5 can be obtained.
[0023]
The invention according to claim 8 is the fuel supply device for a liquefied gas internal combustion engine according to any one of claims 1 to 7, wherein the pressure reducing means cools the fuel tank to reduce the pressure of the fuel in the fuel tank. The gist is to reduce the pressure.
[0024]
According to the above configuration, by cooling the fuel tank, the pressure of the fuel in the fuel tank is reduced. Incidentally, the pressure of the fluid stored in the sealed container tends to fluctuate according to the temperature of the fluid. Therefore, by cooling the fuel tank as in the above configuration, the operation and effect similar to the operation and effect of the invention according to any one of claims 1 to 7 can be obtained. Further, since the pressure of the fuel in the fuel tank can be reduced with a simple configuration such as cooling the fuel tank, a highly practical fuel supply device can be provided.
[0025]
According to a ninth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the eighth aspect, the pressure reducing means cools the fuel tank by supplying gaseous fuel in the fuel tank to the internal combustion engine. The main point is that the
[0026]
According to the above configuration, the fuel tank is cooled by supplying the gaseous fuel in the fuel tank to the internal combustion engine. By the way, in the fuel tank of the fuel supply device, the liquefied gas fuel (liquid phase fuel) in the liquid phase and the liquefied gas fuel (gas phase fuel) in the gas phase are stored in a saturated state, respectively. When the gaseous phase fuel in the tank is consumed, an amount of the liquid phase fuel corresponding to the consumed amount of the gaseous phase fuel is vaporized. At this time, the heat in the fuel tank is absorbed by the heat of vaporization when the liquid-phase fuel is vaporized, and the pressure of the fuel tends to decrease together with the temperature of the fuel in the fuel tank due to the heat of vaporization. Thus, even when the gaseous phase fuel in the fuel tank is consumed as in the above configuration, the operation and effect similar to the operation and effect of the invention according to claim 8 can be obtained. Further, since the fuel tank is cooled by consuming the gaseous fuel, the fuel tank can be cooled more accurately.
[0027]
According to a tenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the eighth aspect, the pressure reducing means cools the fuel tank by driving a cooling device for cooling the fuel tank. The gist is that
[0028]
According to the configuration, the fuel tank is cooled by driving the cooling device for cooling the fuel tank. As described above, by cooling the fuel tank through the cooling device, the operation and effect similar to the operation and effect of the invention described in claim 8 can be obtained. Further, since the fuel tank is cooled through the cooling device, the fuel tank can be cooled more accurately.
[0029]
According to an eleventh aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the tenth aspect, the cooling device for cooling the fuel tank is provided in a vehicle equipped with the internal combustion engine. The gist is that there is.
[0030]
According to the above configuration, the on-vehicle air conditioner provided in the vehicle equipped with the internal combustion engine is used as a cooling device for cooling the fuel tank. As described above, by cooling the fuel tank through the on-vehicle air conditioner, an operation effect similar to the operation effect of the tenth aspect of the invention can be obtained. In addition, since the in-vehicle air conditioner provided in the vehicle is used, it is possible to appropriately suppress an increase in the scale of the device.
[0031]
According to a twelfth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the eighth aspect, the pressure reducing means cools fuel returned to the fuel tank via the fuel injection mechanism, The gist is to cool the fuel tank.
[0032]
According to the above configuration, the fuel that is recirculated to the fuel tank via the fuel injection mechanism is cooled, so that the fuel tank is cooled. In this way, by cooling the fuel tank with the fuel that has been cooled and returned to the fuel tank, an operation and effect similar to the operation and effect of the invention described in claim 8 can be obtained. Further, since the fuel tank can be cooled with a simple configuration such as cooling the fuel refluxed to the fuel tank, a highly practical fuel supply device can be provided.
[0033]
According to a thirteenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the twelfth aspect, the pressure reducing means cools a fuel recirculated to the fuel tank via the fuel injection mechanism. The gist of the invention is to cool the fuel returned to the fuel tank by driving the fuel tank.
[0034]
According to the above configuration, the cooling device for cooling the fuel returned to the fuel tank via the fuel injection mechanism is driven, so that the fuel returned to the fuel tank is cooled. In this way, by cooling the fuel that is recirculated to the fuel tank through the cooling device, it is possible to obtain the same function and effect as those of the twelfth aspect. Further, since the fuel that is recirculated to the fuel tank through the cooling device is cooled, the fuel can be more accurately cooled.
[0035]
According to a fourteenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the thirteenth aspect, the cooling device for cooling the fuel recirculated to the fuel tank is provided in a vehicle equipped with the internal combustion engine. The gist is that it is a vehicle-mounted air conditioner.
[0036]
According to the above configuration, the in-vehicle air conditioner provided in the vehicle equipped with the internal combustion engine is used as a cooling device for cooling the fuel returned to the fuel tank. As described above, by cooling the fuel that is recirculated to the fuel tank through the on-vehicle air conditioner, the operation and effect similar to the operation and effect of the invention according to claim 13 can be obtained. In addition, since the in-vehicle air conditioner provided in the vehicle is used, it is possible to appropriately suppress an increase in the scale of the device.
[0037]
According to a fifteenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the eighth aspect, the pressure reducing means cools the fuel tank by reducing a work amount of the fuel pump. It is a gist.
[0038]
According to the above configuration, the fuel tank is cooled by reducing the work amount of the fuel pump. Incidentally, when the liquid-phase fuel in the fuel tank is consumed, similarly to when the gas-phase fuel is consumed, the liquid-phase fuel stored in the fuel tank is reduced according to the amount of the consumed liquid-phase fuel. As the gas evaporates, the heat in the fuel tank is absorbed by the heat of vaporization. However, since liquid-phase fuel has a higher density than gas-phase fuel, when only liquid-phase fuel is consumed, liquid-phase fuel vaporizes in the fuel tank more than when gas-phase fuel is consumed. Is small, the effect of cooling the fuel tank by the heat of vaporization tends to be small. Therefore, when the temperature of the fuel returned to the fuel tank is high due to the heat generated by driving the fuel pump or the heat from the internal combustion engine in the fuel injection mechanism, the fuel due to the vaporization of the liquid phase fuel The effect of increasing the temperature of the fuel tank by the recirculated high-temperature fuel is greater than the effect of cooling the tank, and the temperature of the fuel in the fuel tank changes in a rising direction. On the other hand, when the work amount of the fuel pump increases, the amount of heat generated by driving the fuel pump increases, so that the temperature of the fuel pumped by the fuel pump and returned to the fuel tank tends to increase. Similarly, when the work amount of the fuel pump increases, the discharge amount of the liquid-phase fuel by the fuel pump increases, so that the fuel recirculated to the fuel tank via the fuel injection mechanism, that is, the fuel injection In the mechanism, the heat from the internal combustion engine is received, the temperature becomes high, and the flow rate of the fuel returned to the fuel tank is increased. Therefore, in the above configuration, the work amount of the fuel pump is reduced so that the heat generation of the fuel pump is suppressed, and the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism is reduced. I also try to. As a result, the cooling effect of the fuel tank due to the vaporization of the liquid phase fuel is relatively increased, and the fuel tank can be cooled. As described above, according to the above configuration, the operation and effect similar to the operation and effect of the invention described in claim 8 can be obtained. Further, since the fuel tank can be cooled with a simple configuration such as reducing the work of the fuel pump, a highly practical fuel supply device can be provided.
[0039]
According to a sixteenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the eighth aspect, the pressure reducing means reduces a flow rate of fuel recirculated from downstream of the fuel injection mechanism to the fuel tank. The gist is to cool the fuel tank.
[0040]
According to the above configuration, the flow rate of the fuel recirculated from the downstream of the fuel injection mechanism to the fuel tank is reduced, so that the fuel tank is cooled. By the way, as the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism, that is, the temperature of the fuel which is heated to a high temperature by receiving heat from the internal combustion engine in the fuel injection mechanism and recirculated to the fuel tank, increases, Since the function of cooling the fuel tank by vaporization becomes relatively small, the temperature of the fuel in the fuel tank rises. From this, it can be said that in order to cool the fuel tank, it is effective to reduce the flow rate of the fuel returned to the fuel tank via the fuel injection mechanism. Therefore, as in the above configuration, by reducing the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism, the operation and effect similar to the operation and effect of the invention according to claim 8 can be obtained. Become. In addition, the fuel tank can be cooled with a simple configuration such as reducing the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism, so that a highly practical fuel supply device is provided. Will be able to do it.
[0041]
According to a seventeenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the sixteenth aspect, the pressure reducing means reduces the flow rate of the liquid phase fuel supplied to the fuel injection mechanism, thereby reducing the amount of the fuel. The gist of the invention is to reduce the flow rate of the fuel recirculated from the downstream of the injection mechanism to the fuel tank.
[0042]
According to the above configuration, the flow rate of the liquid fuel supplied to the fuel injection mechanism is reduced, so that the flow rate of the fuel recirculated from the downstream of the fuel injection mechanism to the fuel tank is reduced. Incidentally, the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism tends to change according to the flow rate of the liquid fuel supplied to the fuel injection mechanism. Therefore, as in the above-described configuration, by reducing the flow rate of the fuel supplied to the fuel injection mechanism, an operation and effect similar to the operation and effect of the invention of claim 16 can be obtained. In addition, since the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism can be reduced with a simple configuration such as reducing the flow rate of the fuel supplied to the fuel injection mechanism, the practicability is reduced. It is also possible to provide a high fuel supply device.
[0043]
According to an eighteenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the seventeenth aspect, the pressure reducing means is a recirculation path for flowing fuel recirculated from downstream of the fuel injection mechanism to the fuel tank. A detour path for recirculating the liquid-phase fuel pumped by the fuel pump from upstream of the fuel injection mechanism to the fuel tank; and a switching unit for selectively activating one of these fuel paths. The gist is that the flow rate of the liquid phase fuel supplied to the fuel injection mechanism is reduced by activating the detour path through the switching means.
[0044]
According to the above configuration, the decompression means includes a recirculation path for circulating the fuel recirculated from the downstream of the fuel injection mechanism to the fuel tank, and the liquid phase fuel pumped by the fuel pump from the upstream of the fuel injection mechanism to the fuel tank. And a switching means for selectively activating one of these fuel paths. Then, by making the bypass route active through the switching means, the flow rate of the liquid-phase fuel supplied to the fuel injection mechanism is reduced. By the way, when the detour path is made active, only the amount of the liquid phase fuel pumped by the fuel pump, which is injected and supplied to the internal combustion engine by the fuel injection mechanism, is supplied to the same fuel injection mechanism. The fuel is returned to the fuel tank without being supplied to the fuel injection mechanism. Therefore, the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism is set to “0”. Accordingly, the function and effect of the invention according to claim 17 can also be achieved by activating a bypass path for returning the fuel pumped by the fuel pump from the upstream of the fuel injection mechanism to the fuel tank as in the above configuration. The function and effect can be obtained. In addition, since the flow rate of the fuel supplied to the fuel injection mechanism can be reduced with a simple configuration such that the fuel pumped by the fuel pump is returned to the fuel tank via a bypass path, the practicability is reduced. It is also possible to provide a high fuel supply device.
[0045]
According to a nineteenth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the seventeenth aspect, the pressure reducing means reduces the discharge amount of the liquid phase fuel by the fuel pump, thereby providing the fuel injection mechanism with the fuel injection mechanism. The gist is to reduce the flow rate of the supplied liquid fuel.
[0046]
According to the above configuration, the flow rate of the liquid fuel supplied to the fuel injection mechanism is reduced by reducing the discharge amount of the liquid fuel by the fuel pump. Incidentally, the flow rate of the liquid fuel supplied to the fuel injection mechanism tends to change in accordance with the discharge amount of the liquid fuel by the fuel pump. Therefore, as in the above-described configuration, by reducing the discharge amount of the liquid-phase fuel by the fuel pump, it is possible to obtain the same operation and effect as the above-described embodiment. Also, since the flow rate of the fuel supplied into the fuel injection mechanism can be reduced with a simple configuration such as reducing the discharge amount of the liquid phase fuel by the fuel pump, a highly practical fuel supply device is provided. It can also be provided.
[0047]
According to a twentieth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the nineteenth aspect, the pressure reducing means increases the pressure of the fuel in the fuel injection mechanism so that the liquid phase by the fuel pump is increased. The gist is to reduce the amount of fuel discharged.
[0048]
According to the configuration described above, the discharge amount of the liquid phase fuel by the fuel pump is reduced by increasing the pressure of the fuel in the fuel injection mechanism. Incidentally, the discharge amount of the liquid phase fuel by the fuel pump tends to change according to the pressure of the fuel in the fuel injection mechanism. That is, as the pressure of the fuel in the fuel injection mechanism increases, the pressure difference before and after the fuel pump increases, so that the discharge amount of the liquid-phase fuel decreases when the work amount of the fuel pump is constant. Thus, as in the above-described configuration, by increasing the pressure of the fuel in the fuel injection mechanism, an operation effect similar to the operation effect of the nineteenth aspect can be obtained. Further, since the amount of liquid-phase fuel discharged by the fuel pump can be reduced with a simple structure such as increasing the pressure of the fuel in the fuel injection mechanism, a highly practical fuel supply device is provided. Will be able to do it.
[0049]
According to a twenty-first aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the twentieth aspect, the pressure reducing means recirculates fuel in the fuel injection mechanism from the downstream of the fuel injection mechanism to the fuel tank. A variable pressure mechanism that is provided in the return path of the fuel injection mechanism and varies the pressure of the fuel in the fuel injection mechanism. By changing the pressure adjustment set value of the variable pressure mechanism to a higher value, the fuel injection The gist is to increase the pressure of the fuel in the mechanism.
[0050]
According to the above configuration, the variable pressure mechanism is provided in the recirculation path for recirculating the fuel in the fuel injection mechanism from the downstream of the fuel injection mechanism to the fuel tank, and makes the pressure of the fuel in the fuel injection mechanism variable. By changing the pressure adjustment set value to a higher value, the pressure of the fuel in the fuel injection mechanism is increased. Incidentally, when the pressure of the fuel in the fuel injection mechanism is pressure-regulated through the pressure regulation mechanism, the pressure of the fuel in the fuel injection mechanism is maintained at a value corresponding to the pressure regulation set value of the pressure regulation mechanism. Therefore, as in the above configuration, by changing the pressure adjustment set value of the tunable pressure mechanism to a higher value, an operation and effect similar to the operation and effect of the twentieth aspect of the invention can be obtained. Further, since the pressure of the fuel in the fuel injection mechanism can be increased with a simple configuration such as changing the pressure adjustment set value of the variable pressure mechanism to a higher value, a highly practical fuel supply device is provided. Can also be provided.
[0051]
According to a twenty-second aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to any one of the fifteenth to twenty-first aspects, the pressure reducing means may be configured such that the pressure of the fuel in the fuel injection mechanism is a saturated vapor pressure of the fuel When it is less than the above, the gist is to interrupt the process for reducing the pressure of the fuel in the fuel tank.
[0052]
According to the above configuration, when the pressure of the fuel in the fuel injection mechanism is lower than the saturated vapor pressure of the fuel, the process for reducing the pressure of the fuel in the fuel tank is interrupted. That is,
In the invention according to claim 15, the process of reducing the work of the fuel pump is interrupted.
According to the sixteenth aspect, the process of reducing the flow rate of the fuel recirculated from the downstream side of the fuel injection mechanism to the fuel tank is interrupted.
In the seventeenth aspect, the process of reducing the flow rate of the liquid fuel supplied to the fuel injection mechanism is interrupted.
In the eighteenth aspect of the invention, the process of making the bypass route active is interrupted (the return route is made active and the bypass route is made inactive).
In the nineteenth aspect, the process of reducing the discharge amount of the liquid fuel by the fuel pump is interrupted.
In the twentieth aspect, the process of increasing the pressure of the fuel in the fuel injection mechanism is interrupted.
According to the twenty-first aspect, the process of changing the pressure adjustment set value of the variable pressure mechanism to a higher value is interrupted.
As described above, the above processes are interrupted. Incidentally, when the pressure of the fuel in the fuel injection mechanism becomes lower than the saturated vapor pressure of the fuel, low-density fuel including vaporized fuel (vapor) generated in the fuel injection mechanism is supplied to the internal combustion engine. As a result, it is conceivable that drivability is deteriorated. On the other hand, a process for reducing the pressure of the fuel in the fuel tank,
A process for reducing the work of the fuel pump (claim 15);
A process of reducing the flow rate of the fuel recirculated to the fuel tank via the fuel injection mechanism (claims 16 to 21);
When each process is performed, the amount of fuel that is returned to the fuel tank through the fuel injection mechanism is smaller than when the above processes are not performed. It can be said that the cooling effect is reduced. Therefore, in the above configuration, when it is estimated that the fuel in the fuel injection mechanism is vaporized, the above processes are interrupted, that is, the flow rate of the liquid phase fuel supplied into the fuel injection mechanism by the fuel pump is increased. By doing so, the cooling action of the fuel injection mechanism by the same liquid phase fuel is enhanced, and the vaporization of the fuel is suppressed. Thereby, the liquid phase state of the fuel in the fuel injection mechanism is maintained, so that the pressure of the fuel in the fuel tank can be reduced while suitably avoiding the deterioration of the operability of the internal combustion engine. Become.
[0053]
According to a twenty-third aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to any one of the fifteenth to twenty-first aspects, the pressure reducing means may be configured such that the pressure of the fuel in the fuel injection mechanism is a saturated vapor pressure of the fuel When it is less than the above, the gist is to reduce the degree of pressure reduction with respect to the pressure of the fuel in the fuel tank.
[0054]
According to the above configuration, when the pressure of the fuel in the fuel injection mechanism is lower than the saturated vapor pressure of the fuel, the degree of pressure reduction with respect to the pressure of the fuel in the fuel tank is reduced. That is,
According to the fifteenth aspect, the work of the fuel pump is increased.
In the sixteenth aspect, the flow rate of the fuel recirculated from the downstream of the fuel injection mechanism to the fuel tank is increased.
According to the seventeenth aspect, the flow rate of the liquid fuel supplied to the fuel injection mechanism is increased.
In the eighteenth aspect, the return path is activated and the detour path is deactivated.
In the nineteenth aspect, the discharge amount of the liquid phase fuel by the fuel pump is increased.
In the twentieth aspect, the pressure of the fuel in the fuel injection mechanism is reduced.
According to the twenty-first aspect, the pressure adjustment set value of the variable pressure mechanism is changed to a lower value.
Are performed. As described above, in the above configuration, when it is estimated that the fuel in the fuel injection mechanism is vaporized, the degree of pressure reduction of the fuel in the fuel tank is relaxed, so that the liquid phase fuel pumped by the fuel pump is reduced. To enhance the cooling effect of the fuel injection mechanism. With such a configuration, an operation and effect similar to the operation and effect of the invention described in claim 22 can be obtained.
[0055]
According to a twenty-fourth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the twenty-second or twenty-third aspect, the pressure reducing means includes a saturated vapor characteristic of the fuel stored in the fuel tank and a fuel injection mechanism. The gist is to estimate the saturated vapor pressure of the fuel in the fuel injection mechanism from the temperature of the fuel.
[0056]
According to the above configuration, the saturated vapor pressure of the fuel in the fuel injection mechanism is estimated from the saturated vapor characteristics of the fuel stored in the fuel tank and the temperature of the fuel in the fuel injection mechanism. Incidentally, the saturated vapor pressure of the fuel tends to increase as the temperature of the fuel increases, and the relationship between the saturated vapor pressure and the temperature can be grasped through the saturated vapor characteristic (saturated vapor curve) of the fuel. Therefore, by estimating the saturated vapor pressure of the fuel in the fuel injection mechanism in the above-described manner, it becomes possible to grasp an appropriate saturated vapor pressure corresponding to the fluctuation of the temperature of the fuel.
[0057]
According to a twenty-fifth aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to the second or fifth or seventh or twenty-fourth aspect, the pressure reducing means includes a temperature of the fuel stored in the fuel tank and a temperature of the fuel. The gist is to estimate the composition of the fuel based on the pressure, and to determine the saturated vapor characteristic of the fuel stored in the fuel tank based on the estimated fuel composition.
[0058]
According to the above configuration, the composition of the fuel is estimated based on the temperature and the pressure of the fuel stored in the fuel tank, and the fuel is stored in the fuel tank based on the estimated fuel composition. The saturated vapor characteristics of the fuel being used are determined. Incidentally, the saturated vapor characteristic of the fuel shows a different tendency depending on the composition of the fuel, and the composition of the fuel can be basically estimated through the temperature and pressure of the fuel. Therefore, in the above configuration, by determining the saturated vapor characteristic of the fuel in the fuel tank in the above-described manner, it is possible to grasp more appropriate saturated vapor characteristic according to the composition of the fuel.
[0059]
According to a twenty-sixth aspect of the present invention, in the fuel supply system for a liquefied gas internal combustion engine according to the twenty-fourth or twenty-fifth aspect, the pressure reducing means sets the fuel pressure obtained by anticipating a predetermined pressure to the estimated saturated steam pressure. The gist is to set the saturated vapor pressure of the fuel in the injection mechanism.
[0060]
According to the above configuration, a pressure obtained by anticipating a predetermined pressure from the estimated saturated vapor pressure (a pressure higher than the saturated vapor pressure) is set as the saturated vapor pressure of the fuel in the fuel injection mechanism. Incidentally, the saturated steam pressure estimated through the saturated steam characteristics and the temperature of the fuel may include some errors. Then, for example, when the estimated saturated steam pressure is lower than the original saturated steam pressure, the fuel pressure in the fuel injection mechanism is lower than the original saturated steam pressure, that is, the liquid pressure in the fuel injection mechanism is reduced. Although the fuel pressure in the fuel injection mechanism is equal to or higher than the estimated saturated vapor pressure despite the vaporization of the two-phase fuel, the process for suppressing the vaporization of the fuel is not performed. Could lead to Therefore, in the above configuration, the estimated saturated steam pressure includes an error by setting the pressure obtained by anticipating the predetermined pressure to the estimated saturated steam pressure as the saturated steam pressure of the fuel in the fuel injection mechanism. Even if it is, the value is not to be lower than the original saturated steam pressure. As a result, the above concern is resolved, so that the deterioration of the operability of the internal combustion engine due to the injection and supply of the fuel including the vaporized fuel can be more appropriately avoided.
[0061]
According to a twenty-seventh aspect of the present invention, in the fuel supply device for a liquefied gas internal combustion engine according to any one of the first to twenty-sixth aspects, the pressure reducing means includes a saturated vapor pressure of the fuel stored in the supplementary fuel tank. Is estimated from the saturated vapor characteristics of the fuel stored in the fuel tank and the outside air temperature to obtain the supply pressure.
[0062]
According to the above configuration, the replenishment pressure is obtained by estimating the saturated vapor pressure of the fuel stored in the fuel tank from the saturated vapor characteristics of the fuel stored in the fuel tank and the outside air temperature. Incidentally, the fuel stored in the fuel tank of the fuel supply device and the fuel stored in the replenishing fuel tank (for example, the fuel tank provided in a fueling station) usually have almost the same saturated vapor characteristics. Tend to show. Further, the temperature of the fuel stored in the replenishment fuel tank basically depends on the outside air temperature. From this, it can be said that it is possible to estimate the saturated vapor pressure of the fuel in the replenishment fuel tank based on the saturated vapor characteristics of the fuel stored in the fuel tank of the fuel supply device and the outside air temperature. Therefore, in the above configuration, a more appropriate saturated vapor pressure can be grasped by estimating the saturated vapor pressure of the fuel in the supplementary fuel tank in the above-described manner.
[0063]
The invention according to claim 28 is the liquefied gas internal combustion engine according to any one of claims 1 to 27, wherein the liquefied gas internal combustion engine is a liquefied petroleum gas internal combustion engine using liquefied petroleum gas as fuel. The gist is that.
[0064]
According to the above configuration, the invention according to any one of claims 1 to 27 is applied to a liquefied petroleum gas internal combustion engine using liquefied petroleum gas as a fuel. Incidentally, a situation in which fuel cannot be supplied to the fuel tank due to an increase in pressure of the fuel due to an increase in the temperature of the fuel in the fuel tank is of particular concern in a vehicle equipped with a liquefied petroleum gas internal combustion engine. Therefore, by applying the invention according to any one of claims 1 to 27 to a fuel supply device for an internal combustion engine that uses liquefied petroleum gas as a fuel as in the above configuration, the above concern is solved and liquefied petroleum The utility of an internal combustion engine using gas as fuel can be further enhanced.
[0065]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
A first embodiment of the present invention will be described with reference to FIGS. The fuel supply device for a liquefied gas internal combustion engine according to this embodiment is a fuel supply device for supplying LPG to an internal combustion engine (LPG engine) using liquefied petroleum gas (LPG) as fuel, and propane is used as LPG. And those containing butane as a main component are used.
[0066]
First, an outline of a fuel supply device for an internal combustion engine according to the embodiment will be described with reference to FIG. FIG. 1 shows an internal combustion engine 1 driven by using the combustion energy of an air-fuel mixture as an output, a fuel supply device 3 for supplying fuel to the engine 1, and an electronic control device for controlling the internal combustion engine 1 and the fuel supply device 3 collectively. 1 schematically shows the relationship between a control device (ECU) 5.
[0067]
As shown in FIG. 1, the internal combustion engine 1 has a cylinder block 11, a plurality of cylinders 12 provided in the cylinder block 11 and burning an air-fuel mixture therein, and disposed above the plurality of cylinders 12. It is provided with a cylinder head 13 and the like.
[0068]
Here, a water jacket 12a is provided around the cylinder 12, and the cooling water circulating through the water jacket 12a cools the cylinder 12, the cylinder head 13, and the like. Further, a piston 16 connected via a connecting rod 15 to a crankshaft 14 which is an output shaft of the internal combustion engine 1 is reciprocally accommodated in the cylinder 12, and the piston 16 and the cylinder head 13 are connected to each other. Combustion of the air-fuel mixture is performed in the combustion chamber 17 formed opposite to the combustion chamber. The combustion chamber 17 is connected to an intake passage 24 having an air cleaner 21, a throttle valve 22, a surge tank 23, and the like, and an exhaust passage 26 having a catalyst device 25, and a liquid phase fuel injector LIN provided in the fuel supply device 3. The fuel is supplied to the intake passage 24 through the gas-phase fuel injector GIN.
[0069]
Next, the configuration of the fuel supply device 3 will be described with reference to FIG. FIG. 2 schematically shows a detailed configuration of the fuel supply device 3 shown in FIG. 1 and a relationship between the fuel supply device 3 and the ECU 5.
[0070]
As shown in FIG. 2, the fuel supply device 3 includes a liquid-phase fuel supply system 3L that supplies liquid-phase fuel in a fuel tank 31 disposed in a trunk room (not shown) of the vehicle to the intake passage 24, and the fuel supply system 3L. A gas phase fuel supply system 3G for supplying gas phase fuel in the tank 31 to the surge tank 23 is provided. The decompression means is provided with the gas-phase fuel supply system 3G and the like.
[0071]
In the liquid fuel supply system 3L, the liquid fuel stored in the fuel tank 31 is pumped by a fuel pump 32 to a liquid fuel supply path Rd1 provided with a fuel filter 33. The pumped liquid fuel is supplied to the delivery pipe 35 constituting the fuel injection mechanism 34 together with the liquid fuel injector LIN, and the liquid fuel injector LIN is opened in response to a signal from the ECU 5. Injection is supplied to the intake passage 24. Then, the fuel remaining in the delivery pipe 35 is returned to the fuel tank 31 via the return path Rd2 connecting the downstream side of the delivery pipe 35 and the fuel tank 31. The pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) is maintained at a predetermined adjustment set value through a pressure regulator 36 provided in the return path Rd2.
[0072]
On the other hand, in the gas-phase fuel supply system 3G, the gas-phase fuel stagnating in the fuel tank 31 is supplied to the gas-phase fuel injector GIN via the gas-phase fuel supply path Rd3. Is opened in response to a signal from the ECU 5 to be injected and supplied to the surge tank 23. In the present embodiment, during the operation of the internal combustion engine 1, fuel is basically supplied by the liquid fuel injector LIN, and when a predetermined condition is satisfied, the fuel is supplied in accordance with the liquid fuel injector LIN. The fuel is supplied by the phase fuel injector GIN.
[0073]
Further, the fuel supply device 3 is provided with a detection system 6 including an outside air temperature sensor 61, a tank temperature sensor 62 for detecting the state of the fuel in the fuel tank 31, and a tank pressure sensor 63. Incidentally, the outside air temperature sensor 61 indicates the temperature of the outside air (outside air temperature THatm), the tank temperature sensor 62 indicates the temperature of the fuel in the fuel tank 31 (fuel tank temperature THtk), and the tank pressure sensor 63 indicates the temperature of the fuel in the fuel tank 31. The pressure (fuel tank pressure Ptk) is detected. The data detected by the sensors 61 to 63 is input to the ECU 5, and the ECU 5 performs the following process of driving the gas-phase fuel injector based on the input detection data.
[0074]
Next, a driving process of the gas-phase fuel injector will be described with reference to FIGS. This processing is repeatedly performed with a predetermined time as a cycle.
As shown in FIG. 3, in this process, first, data (outside air temperature THatm, fuel tank temperature THtk, fuel tank pressure Ptk) detected by each of the sensors 61 to 63 is read (step S101). Next, the propane ratio R in the fuel (LPG) stored in the fuel tank 31 is estimated by applying the fuel tank temperature THtk and the fuel tank pressure Ptk to the propane ratio map shown in FIG. 4 (step S102). . Then, the estimated propane ratio R is calculated by the following saturated vapor pressure calculation formula.

Then, a saturated vapor pressure curve of the LPG corresponding to the propane ratio R is determined as shown in FIG. 5 (step S103). In the above saturated vapor pressure calculation formula [1], “P” is the saturated vapor pressure of LPG (kg / cm ² ), “T” indicates the temperature of LPG, and “R” indicates the propane ratio in LPG.
[0075]
Next, based on the calculated saturated vapor pressure curve and the outside air temperature THatm, a fuel tank (stand) of a refueling station for refueling a vehicle using LPG, such as a vehicle equipped with the internal combustion engine 1, is provided. The saturated vapor pressure (stand saturated vapor pressure Psvst) of the fuel stored in the fuel tank) is estimated (step S104). Then, at the refueling station, when the fuel is supplied from the stand fuel tank to the fuel tank (fuel tank 31) of the vehicle, the refueling pressure Pca (supply pressure), which is a predetermined pressure applied to the fuel in the stand fuel tank, is obtained. The stand supply pressure Pst (supply pressure), which is the pressure of the fuel to which the predetermined pressure has been added (the pressure of the fuel supplied to the fuel tank 31), is calculated by adding to the stand saturated steam pressure Psvst (step S105). ). That is, as shown in FIG. 6, the stand saturated steam pressure Psvst is estimated through the saturated steam pressure curve of the propane ratio R and the outside air temperature THatm.
Pst ← Psvst + Pca [2]
Is used to calculate the stand oil supply pressure Pst.
[0076]
Then, it is determined whether or not the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the calculated stand-by fuel supply pressure Pst (step S106). When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (step S106: Yes), the gas-phase fuel is supplied by the gas-phase fuel injector GIN (step S107), and when the fuel tank pressure Ptk is not higher than the stand refueling pressure Pst. The supply of only the liquid phase fuel is continuously performed (Step S106: No).
[0077]
As described above, according to the driving process of the gas-phase fuel injector, when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, that is, when fuel cannot be supplied to the fuel tank 31 at the refueling station, The supply of the gaseous phase fuel by the phase fuel injector GIN is performed.
[0078]
By the way, as in the fuel supply system 3 of the present embodiment, in a fuel return type fuel circulation system in which the fuel pumped by the fuel pump 32 is returned to the fuel tank 31 via the fuel injection mechanism 34, the delivery is Since the fuel in the pipe 35 (the fuel injection mechanism 34) receives heat from the combustion chamber 17 and the like and becomes high temperature and recirculates to the fuel tank 31, the pressure increases as the temperature of the fuel in the fuel tank 31 increases. Show a tendency to. If the pressure of the fuel is equal to or higher than the pressure of the fuel supplied to the fuel tank 31 at the refueling station (the pressure of the fuel to which a predetermined pressure is applied when the fuel is supplied to the fuel tank 31), the same applies. It becomes impossible to refuel the fuel tank 31.
[0079]
Therefore, in the present embodiment, the fuel tank pressure Ptk is monitored, and when the pressure Ptk is equal to or higher than the stand refueling pressure Pst, the gaseous phase fuel in the fuel tank 31 is consumed so that the liquid in the fuel tank 31 is discharged. It promotes the vaporization of phase fuel. As a result, the pressure of the liquid-phase fuel decreases along with the temperature of the fuel in the fuel tank 31 through the heat of vaporization when the fuel is vaporized.
[0080]
Next, with reference to FIG. 7, an example of a supply mode of the gas phase fuel by the driving process of the gas phase fuel injector (FIG. 3) will be described.
For example, if it is detected at time t71 that the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, the gas-phase fuel is supplied by the gas-phase fuel injector GIN (FIGS. 7A and 7B). ). As a result, when the supply of the gaseous fuel is not performed, the fuel tank pressure Ptk, which is estimated to increase, for example, in a manner indicated by a dashed line, decreases as illustrated by a solid line (see FIG. 7 ( a)). Then, if it is detected at time t72 that the fuel tank pressure Ptk has become lower than the stand refueling pressure Pst, the supply of the gaseous fuel is stopped (FIGS. 7A and 7B).
[0081]
As described in detail above, according to the fuel supply system for a liquefied gas internal combustion engine according to the first embodiment, the following excellent effects can be obtained.
(1) In the present embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the gas-phase fuel in the fuel tank 31 is supplied to the internal combustion engine 1. , The fuel tank pressure Ptk is reduced. This makes it possible to suitably maintain the state of the fuel tank 31 in a state where fuel can be supplied at the refueling station.
[0082]
(2) In the present embodiment, the stand oil supply pressure Pst is calculated in the following manner. That is,
Estimating the saturated vapor pressure (stand saturated vapor pressure Psvst) of the fuel stored in the fuel tank (stand fuel tank) of the refueling station from the saturated vapor pressure curve of the fuel in the fuel tank 31 and the outside air temperature THatm.
The stand refueling pressure Pst is calculated by adding the stand saturated vapor pressure Psvst and a predetermined pressure (refueling pressure Pca) applied to the fuel in the stand fuel tank during refueling.
In this manner, the stand oil supply pressure Pst is calculated. Incidentally, the fuel in the fuel tank 31 and the fuel in the stand fuel tank generally show substantially the same saturated vapor characteristics, and the temperature of the fuel stored in the fuel tank in the stand basically depends on the outside air temperature. Tend to. On the other hand, the pressure of the fuel that is pressurized and supplied from the stand fuel tank to the fuel tank 31 (stand refueling pressure pst) basically corresponds to the stand saturated steam pressure Psvst in addition to the fuel in the stand fuel tank during refueling. The predetermined pressure (pressure Pca at the time of refueling) is added. Therefore, by calculating the stand refueling pressure Pst in the above manner, the relationship between the fuel pressure in the fuel tank 31 and the stand refueling pressure Pst can be grasped more appropriately, and the state of the fuel tank 31 Can be more suitably maintained at a refueling station in a state where refueling is possible.
[0083]
(3) In the present embodiment, the composition (propane ratio R) of the fuel in the fuel tank 31 is estimated from the temperature (fuel tank temperature THtk) and the pressure (fuel tank pressure Ptk) in the fuel tank 31, and the estimated fuel The saturated vapor pressure calculation formula (saturated vapor pressure curve) of the same fuel is calculated from the composition. Incidentally, the composition of the fuel (LPG) may be changed according to the season or the like, and the saturated vapor characteristic (saturated vapor pressure curve) of the fuel tends to differ depending on the composition of the fuel. Therefore, by estimating the saturated vapor pressure of the fuel in the stand fuel tank (stand saturated vapor pressure Psvst) based on the saturated vapor pressure curve calculated in the above manner, the stand refueling pressure Pst can be appropriately calculated. Become like Thus, even if the composition of the fuel is changed, the state of the fuel tank 31 can be suitably maintained at a state where fuel can be supplied at the refueling station.
[0084]
(4) In the present embodiment, the gaseous fuel in the fuel tank 31 is supplied to the internal combustion engine 1 only when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst. By doing so, the fuel tank pressure Ptk is maintained at less than the stand fuel pressure Pst. Here, in order to maintain the fuel tank pressure Ptk lower than the stand fueling pressure Pst, for example, during the operation of the internal combustion engine 1, a countermeasure such as always supplying gas-phase fuel to the internal combustion engine 1 may be considered. The following are concerns. That is, gas-phase fuel is a fuel having a lower density than liquid-phase fuel. Therefore, when gas-phase fuel is supplied to the internal combustion engine 1, the proportion of gas-phase fuel in the air-fuel mixture becomes large, so that the amount of intake air May be insufficient. If such an insufficiency of the intake air occurs, the required output cannot be obtained and the output performance of the internal combustion engine 1 will be reduced. In this regard, in the present embodiment, the supply of the gaseous phase fuel is performed only when the fuel tank pressure Ptk is equal to or higher than the stand supply pressure Pst. A decrease in the output performance of the engine 1 can be suitably suppressed.
[0085]
(5) In the present embodiment, the fuel tank pressure THk is lowered together with the fuel tank temperature THtk by supplying the gaseous fuel in the fuel tank 31 to the internal combustion engine 1. Incidentally, the rise in the pressure of the fuel due to the rise in the temperature of the fuel in the fuel tank 31 is basically caused by the fact that the fuel received in the fuel injection mechanism 34 is returned to the fuel tank 31. For example, the following factors can be cited. That is, generally, in a vehicle equipped with an LPG engine, the fuel tank is provided in a trunk room of the vehicle. Therefore, when the temperature in the trunk room becomes high due to an increase in outside air temperature, the temperature in the trunk room becomes high. It shows a tendency that the temperature and pressure of the fuel in the fuel tank increase in accordance with the increase. It is also conceivable that the fuel pressure in the fuel tank may make it impossible to refuel the fuel tank at the refueling station. Therefore, as a countermeasure to solve the above-mentioned concerns caused by the temperature rise in the trunk room, for example, a fuel tank is provided in a place other than the trunk room of the vehicle where the temperature is not likely to be high, so that the temperature rise and the pressure of the fuel in the fuel tank are increased. It is also possible to suppress the rise. However, in this case, work such as changing the location of the fuel tank is required, and significant improvements must be made to the existing fuel supply device of the LPG engine. In this regard, in the present embodiment, since the temperature and pressure of the fuel in the fuel tank are reduced by supplying the gaseous fuel, it is not necessary to take measures such as changing the location of the fuel tank. Therefore, it is possible to eliminate the concern caused by the temperature rise in the trunk room. As described above, in the present embodiment, the fuel tank can be maintained in a state in which fuel can be supplied at the refueling station while the fuel supply device of the existing LPG engine is effectively used, so that practicality is improved. It is possible to provide a fuel supply device for an LPG engine having a high fuel consumption.
[0086]
In addition, the first embodiment can be embodied as follows, for example, in which this is appropriately changed.
In the first embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the fuel is supplied by the gas-phase fuel injector GIN in accordance with the liquid-phase fuel injector LIN. However, for example, the following configuration is also possible. That is, when the above condition is satisfied, a configuration in which only the gas-phase fuel is supplied by the gas-phase fuel injector GIN may be adopted.
[0087]
(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS.
[0088]
In the present embodiment, the basic configuration of the entire apparatus including the internal combustion engine is the same as that of the first embodiment, but a part of the driving process (FIG. 3) of the gas-phase fuel injector is shown in FIG. 8 has been changed.
[0089]
Here, the outline of the driving process of the gas-phase fuel injector according to the present embodiment will be described prior to the description.
In the process of the present embodiment, similarly to the process of the first embodiment (FIG. 3), the pressure of the fuel in the fuel tank 31 is reduced by controlling the manner of supplying the gaseous fuel to the internal combustion engine 1. It is intended to be. In the first embodiment, the fuel pressure in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst as a condition for supplying the gaseous phase fuel. In the present embodiment, the supply of the gaseous fuel is performed based on the conditions described below.
[0090]
As shown in FIG. 8, in the driving process of the gas-phase fuel injector according to the present embodiment, first, the process up to the previous step S105 (FIG. 3) is performed in a manner similar to the first embodiment. Then, by applying the stand fuel pressure Pst to the saturated vapor pressure curve of the fuel in the fuel tank 31, a fuel value which is a determination value for determining whether or not to supply the gas phase fuel by the gas phase fuel injector GIN. The hourly saturated steam temperature THst is calculated (step S105a). That is, as shown in FIG. 9, a predetermined pressure (pressure during refueling Pca) is applied at the refueling station and corresponds to the pressure of fuel (stand refueling pressure Pst) supplied to the fuel tank (fuel tank 31) of the vehicle. The calculated saturated steam temperature (the refueling saturated steam temperature THst) is calculated.
[0091]
Then, it is determined whether or not the temperature of the fuel in the fuel tank 31 (fuel tank temperature THtk) is equal to or higher than the calculated refueling saturated vapor pressure THst (step S106a). When the fuel tank temperature THtk is equal to or higher than the refueling saturated steam pressure THst (step S106a: Yes), the gaseous phase fuel is supplied by the gaseous fuel injector GIN (step S107), and the refueling saturated steam temperature THst is supplied. If not, supply of only the liquid phase fuel is continued (Step S106a: No).
[0092]
As described above, according to the driving process of the gas-phase fuel injector, the driving mode of the gas-phase fuel injector GIN is determined based on whether or not the fuel tank temperature THtk is equal to or higher than the refueling-time saturated steam pressure THst.
[0093]
Incidentally, since the fuel (LPG) in the fuel tank 31 is in a saturated state, the temperature and pressure of the fuel basically show a tendency to fluctuate along the saturated vapor pressure curve of the fuel. Therefore, as shown in FIG. 9, when the fuel tank pressure Ptk rises from the pressure Ptka to a pressure Ptkb higher than the stand refueling pressure Pst, the fuel tank temperature THtk rises from the temperature THtka to a temperature THtkb higher than the refueling saturated steam temperature THst. It will be rising to.
[0094]
Therefore, by supplying the gaseous phase fuel when the fuel tank temperature THtk is equal to or higher than the refueling saturated vapor pressure THst as in the present embodiment, the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst. In this case, the same effect as when the gas-phase fuel is supplied can be obtained.
[0095]
As described above in detail, according to the fuel supply device for a liquefied gas internal combustion engine according to the second embodiment, the effects (1) to (5) in the first embodiment are applied. The effect will be obtained.
[0096]
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the basic configuration of the entire apparatus is the same as that of the first embodiment (FIG. 1), but the configuration of the fuel supply device 3 shown in FIG. 2 is changed to the configuration shown in FIG. (Note that the gas-phase fuel injector GIN shown in FIG. 1 is excluded with this change). Incidentally, as shown in the broken line in FIG. 10, the configuration is such that the following changes are added to the fuel supply device 3 (FIG. 2) in the first embodiment. .
[0097]
That is, the gas-phase fuel supply system 3G of the present embodiment selectively connects the gas-phase fuel supply path Rd3 for supplying gas-phase fuel retained in the fuel tank 31 to the surge tank 23, and the same path Rd3. And a throttle mechanism 37 that regulates the flow rate of the gas-phase fuel flowing through the same path Rd3. Then, by opening the gas phase control valve Evg in response to a signal from the ECU 5, the gas phase fuel in the fuel tank 31 is sucked into the surge tank 23 by the intake negative pressure. Note that, as the gas phase control valve Evg, an electromagnetic valve which is normally closed, that is, closed when not energized and opened by energization from the ECU 5 is employed.
[0098]
Further, in the present embodiment, the opening and closing of the gas phase control valve Evg is controlled in a manner similar to the driving process (FIG. 3) of the gas phase fuel injector in the first embodiment. That is, when the pressure of the fuel in the fuel tank 31 (the fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the gas phase control valve Evg is opened to supply the gas phase fuel to the internal combustion engine 1. Become like
[0099]
As described above in detail, according to the fuel supply device for a liquefied gas internal combustion engine according to the third embodiment, the effects (1) to (5) in the first embodiment are applied. In addition to the effects, the following effects can be obtained.
[0100]
(6) In the present embodiment, the gas phase fuel in the fuel tank 31 can be supplied to the internal combustion engine 1 by opening and closing the gas phase control valve Evg provided in the gas phase fuel supply path Rd3. ing. As described above, since the gaseous phase fuel can be supplied without using the gaseous phase fuel injector, a fuel supply device having a simpler configuration can be provided.
[0101]
Note that the third embodiment can be embodied as the following, for example, in which this is appropriately changed.
In the third embodiment, the throttle mechanism 37 is provided in the gas-phase fuel supply path Rd3. However, for example, the following structure may be used. That is, a configuration without the aperture mechanism 37 or a configuration with a variable aperture mechanism capable of changing the aperture diameter can be used instead of the aperture mechanism 37.
[0102]
(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIGS.
[0103]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the first embodiment (FIG. 1), but the configuration of the fuel supply device 3 shown in FIG. 2 is changed to the configuration shown in FIG. (Note that the gas-phase fuel injector GIN shown in FIG. 1 is excluded with this change).
[0104]
Here, prior to the description of the fuel supply device according to the present embodiment, an outline thereof will be described.
This embodiment also has a function of reducing the pressure of the fuel in the fuel tank 31 similarly to the first embodiment. In the first embodiment, the above function is realized through the supply of the gaseous fuel to the internal combustion engine 1. In the present embodiment, the work amount of the fuel pump 32 is adjusted by the ECU 5 by the ECU 5. The above function is realized through. In the present embodiment, the ECU 5 adjusts the amount of current supplied to the fuel pump 32 so that the amount of liquid-phase fuel discharged from the fuel pump 32 (fuel discharge amount) can be set in two stages, a low flow rate and a high flow rate. change. The fuel pump 32 is basically driven at a high flow rate during the operation of the internal combustion engine 1. Hereinafter, the fuel supply device of the present embodiment will be described with reference to FIG.
[0105]
As shown in FIG. 11, the fuel supply device 3 of the present embodiment is different from the fuel supply device 3 of the first embodiment (FIG. 2) in that the delivery pipe 3G is excluded. The configuration is such that each sensor shown in a broken line is added to 35. That is, in the fuel supply device 3 of the present embodiment, the detection system 6 includes an injection mechanism temperature sensor 64 and an injection mechanism pressure sensor 65 in addition to the sensors 61 to 63. Incidentally, the injection mechanism temperature sensor 64 indicates the fuel temperature (injection mechanism temperature THdv) in the delivery pipe 35 (fuel injection mechanism 34), and the injection mechanism pressure sensor 65 indicates the fuel pressure in the delivery pipe 35 (fuel injection mechanism 34). (Injection mechanism pressure Pdv) is detected. The data detected by the sensors 61 to 65 is input to the ECU 5, and the ECU 5 performs the following fuel pump discharge amount changing process based on the input detection data.
[0106]
Next, a process for changing the discharge amount of the fuel pump performed in place of the process for driving the gas-phase fuel injector (FIG. 3) in the first embodiment will be described with reference to FIGS. This processing is repeatedly executed with a predetermined time as a cycle.
[0107]
As shown in FIG. 12, in this process, first, data (outside air temperature THatm, fuel tank temperature THtk, fuel tank pressure Ptk, injection mechanism temperature THdv, injection mechanism pressure Pdv) detected by each of the sensors 61 to 65 is read ( Step S301). Next, the propane ratio R in the fuel (LPG) stored in the fuel tank 31 is estimated by applying the fuel tank temperature THtk and the fuel tank pressure Ptk to the propane ratio map (FIG. 4) (step S302). . Then, the estimated propane ratio R is calculated by the above-mentioned saturated vapor pressure calculation formula.

To determine a saturated vapor pressure curve of the LPG corresponding to the propane ratio R (step S303).
[0108]
Next, the injection mechanism temperature THdv is applied to the determined saturated vapor pressure curve to estimate the saturated vapor pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) (the injection mechanism saturated vapor pressure Psvdv) (step). S304). Then, a predetermined value (estimated pressure Pcb) set in advance is added to the injection mechanism saturated vapor pressure Psvdv to determine whether or not vaporized fuel may be generated in the delivery pipe 35 (fuel injection mechanism 34). A vaporization determination pressure Pvp for determination is calculated (step S305). That is, as shown in FIG. 14, the injection mechanism saturated vapor pressure Psvdv is estimated through the saturated vapor pressure curve of the propane ratio R and the injection mechanism temperature THdv.
Pvp ← Psvdv + Pcb [3]
Is used to calculate the vaporization determination pressure Pvp. Incidentally, the saturated vapor pressure is a threshold temperature of a fluid temperature indicating whether a fluid at an arbitrary pressure is a liquid phase or a gas phase (including two phases of gas and liquid), and the pressure of the fluid is equal to or higher than the saturated vapor pressure. At this time, the fluid is in a liquid phase, and when the pressure of the fluid is lower than the saturated vapor pressure, the fluid is in a gas phase. Therefore, when the pressure of the fuel (injection mechanism pressure Pdv) in the delivery pipe 35 (the fuel injection mechanism 34) is lower than the vaporization determination pressure Pvp, a state in which the liquid phase fuel is likely to be vaporized in the delivery pipe 35 (or has already been performed). (A state in which vaporization occurs).
[0109]
Similarly, the outside air temperature THatm is applied to the calculated saturated vapor pressure curve to estimate the saturated vapor pressure (stand saturated vapor pressure Psvst) of the fuel stored in the fuel tank of the refueling station (stand fuel tank). (Step S306). Then, a predetermined pressure applied to the fuel in the stand fuel tank at the refueling station (pressure during refueling Pca) is added to the above-mentioned saturated vapor pressure Psvst of the stand, and the pressure of the fuel supplied from the stand fuel tank to the fuel tank 31 is obtained. A certain stand refueling pressure Pst is calculated (step S307). That is, as shown in FIG. 14, the stand saturated steam pressure Psvst is estimated through the saturated steam pressure curve of the propane ratio R and the outside air temperature THatm.
Pst ← Psvst + Pca [2]
Is used to calculate the stand oil supply pressure Pst.
[0110]
Then, it is determined whether the pressure of the fuel in the delivery pipe 35 (the injection mechanism pressure Pdv) is lower than the calculated vaporization determination pressure Pvp (step S308), and the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp. At this time (step S308: Yes), the discharge amount of the liquid-phase fuel is changed to a high flow rate by increasing the work amount of the fuel pump 32 (step S309). On the other hand, when the injection mechanism pressure Pdv is not lower than the vaporization determination pressure Pvp, it is determined whether or not the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the calculated stand refueling pressure Pst (step). S310). When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (Step S310: Yes), the discharge amount of the liquid phase fuel is changed to a low flow rate by reducing the work amount of the fuel pump 32 (Step S311), and the fuel tank pressure is reduced. If Ptk is not equal to or higher than the stand refueling pressure Pst, the driving mode of the fuel pump 32 at that time is maintained (step S310: No).
[0111]
Thus, according to the discharge amount changing process of the fuel pump,
[A] When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp, it is determined that vaporized fuel is likely to be generated in the delivery pipe 35 (or vaporized fuel is being generated). Increase the amount of work (change the discharge amount of the liquid phase fuel to a high flow rate).
[B] When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, it is determined that the fuel tank 31 cannot supply fuel at the refueling station, and the work of the fuel pump 32 is reduced (liquid phase). Change the fuel discharge rate to a lower flow rate).
In this manner, the driving manner of the fuel pump 32 is controlled.
[0112]
By the way, when the liquid fuel in the fuel tank 31 is consumed, similarly to when the gaseous fuel is consumed, the liquid stored in the fuel tank 31 depends on the amount of the consumed liquid fuel. As the phase fuel vaporizes, the heat in the fuel tank 31 is absorbed by the vaporization heat. However, since the liquid phase fuel has a higher density than the gas phase fuel, when the liquid phase fuel is consumed, the liquid phase fuel which evaporates in the fuel tank 31 more than when the gas phase fuel is consumed. And the cooling effect of the fuel tank 31 by the heat of vaporization is reduced. For this reason,
The liquid fuel pumped by the fuel tank 31 receives heat generated by driving the fuel pump 32.
The fuel supplied into the delivery pipe 35 (fuel injection mechanism 34) receives heat from the combustion chamber 17 and the like in the delivery pipe 35.
As a result, when the fuel recirculated to the fuel tank 31 is at a high temperature, the effect of increasing the temperature of the fuel tank 31 by the recirculated high-temperature fuel is higher than the function of cooling the fuel tank 31 by the vaporization of the liquid phase fuel. Becomes larger, and the temperature of the fuel in the fuel tank 31 changes in a rising direction.
[0113]
Therefore, in the present embodiment, when the above condition (b) is satisfied (when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst), the work amount of the fuel pump 32 is reduced so that the fuel pump 32 And the temperature rise of the liquid-phase fuel pumped by the fuel pump 32 is suppressed. Further, by setting the fuel discharge amount of the fuel pump 32 to a low flow rate, the flow rate of the fuel recirculated to the fuel tank 31 via the delivery pipe 35, that is, the flow rate of the fuel recirculated to the fuel tank 31 at a high temperature is reduced. I also try to lose weight. Thereby, the cooling action by vaporization of the liquid phase fuel in the fuel tank 31 is relatively increased, so that the temperature of the fuel in the fuel tank 31 and the pressure of the fuel decrease.
[0114]
As described above, by reducing the work amount of the fuel pump 32, it is possible to suppress an increase in the pressure of the fuel in the fuel tank 31. However, when using such means, there are concerns about the following. .
[0115]
That is, when the work of the fuel pump 32 is reduced (when the discharge amount of the liquid fuel is set to a low flow rate), and when the work of the fuel pump 32 is increased (discharge of the liquid fuel). Since the amount of fuel supplied to the delivery pipe 35 (the fuel injection mechanism 34) is smaller than when the flow rate is set to a high flow rate, the cooling action of the delivery pipe 35 by the liquid phase fuel is reduced. become. In this case, since the cooling of the delivery pipe 35 is insufficient, the saturated vapor pressure of the fuel exceeds the pressure of the fuel due to the temperature rise of the fuel in the delivery pipe 35, that is, the fuel is vaporized. Is also conceivable. When fuel is injected on the premise that the fuel in the delivery pipe 35 is in a liquid phase when vaporized fuel is generated in the delivery pipe 35, the fuel with a low density is actually supplied to the internal combustion engine 1. The amount of fuel required to be supplied to the vehicle cannot be secured, leading to deterioration of drivability.
[0116]
Therefore, in the present embodiment, it is determined whether the injection mechanism pressure Pdv is less than the vaporization determination pressure Pvp in accordance with the determination whether the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (step S310). By performing the determination (step S308), even when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, if the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp, the fuel pump 32 The fuel discharge amount is changed to a high flow rate. Thereby, the cooling effect in the delivery pipe 35 (fuel injection mechanism 34) by the liquid fuel pumped by the fuel pump 32 is enhanced, and the vaporization of the liquid fuel is suppressed. That is, it is possible to avoid the deterioration of the operability of the internal combustion engine 1 caused by the small work amount of the fuel pump 32 (the discharge amount of the liquid phase fuel is set to a low flow rate). .
[0117]
Next, an example of a control mode of the fuel pump by the fuel pump discharge amount changing process (FIGS. 12 and 13) will be described with reference to FIG.
For example, if it is detected at time t151 that the fuel tank pressure Ptk is equal to or higher than the stand supply pressure Pst, the fuel discharge amount of the fuel pump 32 is changed to a low flow rate (FIGS. 15A and 15C). Then, if it is detected at time t152 that the vaporization determination pressure Pvp has become equal to or higher than the injection mechanism pressure Pdv (the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp) due to the fluctuation of the injection mechanism saturated vapor pressure Psvdv, the fuel pump 32 The fuel discharge amount is changed to a high flow rate (FIGS. 15B and 15C). Accordingly, when the fuel discharge amount is not changed, for example, the vaporization determination pressure Pvp estimated to be located at or higher than the injection mechanism pressure Pdv as shown by the dashed line, It is located below the mechanism pressure Pdv (FIG. 15B). Then, at time t153, if it is detected that the vaporization determination pressure Pvp has become less than the injection mechanism pressure Pdv (the injection mechanism pressure Pdv is equal to or greater than the vaporization determination pressure Pvp), the fuel tank pressure Ptk is equal to or higher than the stand oil supply pressure Pst. The fuel discharge amount of the fuel pump 32 is again changed to a low flow rate (FIGS. 15A to 15C). Accordingly, when the fuel discharge amount is not changed, for example, the fuel tank pressure Ptk estimated to increase in a manner shown by a dashed line is reduced as shown by a solid line (FIG. 15 ( a)).
[0118]
As described in detail above, according to the fuel supply device for a liquefied gas internal combustion engine according to the fourth embodiment, the following excellent effects can be obtained.
(1) In the present embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the work amount of the fuel pump 32 is reduced to reduce the discharge amount of the liquid phase fuel. By setting the flow rate to be low, the fuel tank pressure Ptk is reduced. This makes it possible to suitably maintain the state of the fuel tank 31 in a state where fuel can be supplied at the refueling station.
[0119]
(2) In the present embodiment, even when the fuel tank pressure Ptk is equal to or higher than the stand supply pressure Pst (when the condition for changing the fuel discharge amount of the fuel pump 32 to a low flow rate is satisfied), When there is a possibility that vaporized fuel may be generated in the delivery pipe 35, the fuel discharge amount of the fuel pump 32 is changed to a high flow rate, that is, the process of setting the fuel discharge amount of the fuel pump 32 to a low flow rate is interrupted. I have. As a result, the liquid state of the fuel in the delivery pipe 35 is maintained, so that deterioration of the operability of the internal combustion engine 1 can be suitably avoided.
[0120]
(3) In the present embodiment, the stand oil supply pressure Pst is calculated in the following manner. That is,
Estimating the saturated vapor pressure (stand saturated vapor pressure Psvst) of the fuel stored in the fuel tank (stand fuel tank) of the refueling station from the saturated vapor pressure curve of the fuel in the fuel tank 31 and the outside air temperature THatm.
The stand refueling pressure Pst is calculated by adding the stand saturated vapor pressure Psvst and a predetermined pressure (refueling pressure Pca) applied to the fuel in the stand fuel tank during refueling.
In this manner, the stand oil supply pressure Pst is calculated. This makes it possible to more appropriately grasp the relationship between the fuel pressure in the fuel tank 31 and the stand refueling pressure Pst, and makes the state of the fuel tank 31 more suitable for refueling at the refueling station. Can be maintained.
[0121]
(4) In the present embodiment, the vaporization determination pressure Pvp calculated in the following manner, that is,
Estimating the saturated vapor pressure of the fuel in the delivery pipe 35 (the injection mechanism saturated vapor pressure Psvdv) from the saturated vapor pressure curve of the fuel in the fuel tank 31 and the injection mechanism temperature THdv.
-The vaporization determination pressure Pvp is calculated by adding the injection mechanism saturated vapor pressure Psvdv and an expected pressure Pcb which is a predetermined value set in advance.
The fuel discharge amount of the fuel pump 32 is changed based on the vaporization determination pressure Pvp calculated in such a manner. Incidentally, since the estimated saturated steam pressure (injection mechanism saturated steam pressure Psvdv) may include a slight error, the estimated saturated steam pressure is used to change the fuel discharge amount of the fuel pump 32. When used as the determination value, the following is a concern. That is, when the estimated saturated steam pressure is a value lower than the original saturated steam pressure, the fuel pressure in the delivery pipe 35 is lower than the original saturated steam pressure (the liquid phase in the delivery pipe 35). Despite the fact that the fuel is vaporized), the fuel pressure in the delivery pipe 35 is equal to or higher than the estimated saturated vapor pressure, so that the fuel discharge amount of the fuel pump 32 may not be changed to a low flow rate. Conceivable. Thus, in the present embodiment, the value calculated in the above-described manner (the vaporization determination pressure Pvp) is used as the determination value, so that even if the estimated saturated steam pressure includes an error, the above concern is solved. I am trying to be. As a result, it is possible to more suitably avoid the deterioration of the operability of the internal combustion engine 1 due to the injection and supply of the fuel including the vaporized fuel.
[0122]
(5) In the present embodiment, the composition (propane ratio R) of the fuel in the fuel tank 31 is estimated from the temperature (fuel tank temperature THtk) and the pressure (fuel tank pressure Ptk) in the fuel tank 31, and the estimated fuel The saturated vapor pressure calculation formula (saturated vapor pressure curve) of the same fuel is calculated from the composition. As a result, the vaporization determination pressure Pvp and the stand refueling pressure Pst can be appropriately calculated, and even if the composition of the fuel is changed, the state of the fuel tank 31 can be refueled at the refueling station. In a suitable state.
[0123]
(6) In the present embodiment, the state of the fuel tank 31 can be maintained in a state in which fuel can be supplied at the refueling station through processing such as changing the fuel discharge amount of the fuel pump 32. As a result, it is possible to eliminate the concern caused by the temperature rise in the trunk room without taking measures such as changing the arrangement location of the fuel tank 31. As described above, in the present embodiment, the fuel tank 31 can be maintained in a state where fuel can be supplied at the refueling station while the fuel supply device of the existing LPG engine is effectively used. It is possible to provide a fuel supply device for an LPG engine having high reliability.
[0124]
(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, the basic configuration of the entire apparatus including the internal combustion engine is the same as that of the fourth embodiment (the configuration shown in FIG. 1 except for the gas-phase fuel injector GIN). However, a part of the fuel pump discharge amount changing process (FIG. 13) is changed to the process shown in FIG.
[0125]
Here, prior to the description of the discharge amount changing process of the fuel pump in the present embodiment, an outline thereof will be described.
In the process of the present embodiment, similarly to the process of the fourth embodiment (FIGS. 12 and 13), by adjusting the work amount of the fuel pump 32, the pressure of the fuel in the fuel tank 31 can be reduced. It is intended to suppress the vaporization of the liquid phase fuel. In the first embodiment, the above function is realized through the process of changing the fuel discharge amount of the fuel pump 32 in two stages, whereas in the present embodiment, the following fuel pump 32 The above function is realized through the process of changing the fuel discharge amount of the three stages. Note that the processing of this embodiment is also repeatedly executed with a predetermined time as a cycle. Further, in the present embodiment, the fuel pump 32 can change the discharge amount of the liquid phase fuel into three stages of the basic flow rate, the low flow rate, and the high flow rate by adjusting the work amount of the fuel pump 32 by the ECU 5. It is assumed that the internal combustion engine 1 is basically driven at a basic flow rate during operation.
[0126]
As shown in FIG. 16, in the discharge amount changing process of the fuel pump according to the present embodiment, the respective determination processes of the previous steps S308 and S310 are performed in a manner similar to the fourth embodiment.
[0127]
And
[A] When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp (step S308: Yes), the fuel discharge amount of the fuel pump 32 is changed to a high flow rate (step S309).
[B] When the fuel tank pressure Ptk is equal to or higher than the stand supply pressure Pst (step S310: Yes), the fuel discharge amount of the fuel pump 32 is changed to a low flow rate (step S311).
[C] When the fuel tank pressure Ptk is not equal to or higher than the stand refueling pressure Pst (step S310: No), the fuel discharge amount of the fuel pump 32 is changed to the basic flow rate (step S312).
The fuel discharge amount of the fuel pump 32 is changed in such a manner.
[0128]
As described above, according to the discharge amount changing process of the fuel pump, the fuel discharge amount of the fuel pump 32 is changed to a high flow rate and a low flow rate based on the basic flow rate.
[0129]
As described in detail above, according to the fuel supply system for a liquefied gas internal combustion engine according to the fifth embodiment, the effects (1) to (6) of the fourth embodiment are obtained. In addition to the effects, the following effects can be obtained.
[0130]
(7) In the present embodiment, by changing the fuel discharge amount of the fuel pump 32 to three stages of a basic flow rate, a high flow rate, and a low flow rate, the fuel discharge amount of the fuel pump 32 can be more precisely adjusted. I have to. Thereby, it is possible to more suitably achieve both the decompression of the fuel in the fuel tank 31 and the suppression of fuel vaporization in the delivery pipe 35 (the fuel injection mechanism 34).
[0131]
(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to FIG. In this embodiment, the basic configuration of the entire apparatus including the internal combustion engine is the same as that of the fourth embodiment (the configuration shown in FIG. 1 except for the gas-phase fuel injector GIN). However, a part of the discharge amount changing process of the fuel pump (FIGS. 12 and 13) is changed to the process shown in FIG.
[0132]
Here, prior to the description of the discharge amount changing process of the fuel pump in the present embodiment, an outline thereof will be described.
In the process of the present embodiment, similarly to the process of the fourth embodiment (FIGS. 12 and 13), by adjusting the work amount of the fuel pump 32, the pressure of the fuel in the fuel tank 31 can be reduced. It is intended to suppress the vaporization of the liquid phase fuel. In the fourth embodiment, the vaporization determination pressure Pvp calculated based on the saturated vapor pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) is determined based on whether or not the vaporized fuel is likely to be generated. In contrast to the values used for determination, the present embodiment calculates the above-described determination values in the following manner. Note that the processing of this embodiment is also repeatedly executed with a predetermined time as a cycle.
[0133]
As shown in FIG. 17, in the discharge amount changing process of the fuel pump according to the present embodiment, after performing the process up to the previous step S303 (FIG. 12), the fuel in the delivery pipe 35 (the fuel injection mechanism 34) is discharged. The pressure (the injection mechanism pressure Pdv) is applied to the saturated vapor pressure curve to estimate the saturated steam temperature of the same fuel (the injection mechanism saturated steam temperature THsvdv) (step S304a). Then, a predetermined value (estimated temperature THcb) set in advance is added to the injection mechanism saturated steam temperature THsvdv to determine whether or not vaporized fuel may be generated in the delivery pipe 35 (fuel injection mechanism 34). A vaporization determination temperature THvp for determination is calculated (step S305a). That is, as shown in FIG. 18, the injection mechanism saturated steam temperature THsvdv is estimated through the saturated vapor pressure curve of the propane ratio R and the injection mechanism pressure Pdv, and
THvp ← THsvdv + THcb [4]
Is used to calculate the vaporization determination temperature THvp. Incidentally, the saturated steam temperature is a threshold temperature of the fluid temperature indicating whether the fluid at an arbitrary temperature is a liquid phase or a gas phase (including two phases of gas and liquid), and the temperature of the fluid is lower than the saturated steam temperature. At this time, the fluid is in a liquid phase, and when the temperature of the fluid is equal to or higher than the saturated vapor temperature, the fluid is in a gas phase. Therefore, when the temperature of the fuel (injection mechanism temperature THdv) in the delivery pipe 35 (the fuel injection mechanism 34) is equal to or higher than the vaporization determination temperature THvp, the state in which the liquid phase fuel is likely to be vaporized in the delivery pipe 35 (or has already occurred). (A state in which vaporization occurs).
[0134]
Then, after performing the processing of the previous steps S306 and S307 (FIG. 12), it is determined whether or not the temperature of the fuel in the delivery pipe 35 (the injection mechanism temperature THdv) is equal to or higher than the calculated vaporization determination temperature THvp. (Step S308a). When the injection mechanism temperature THdv is equal to or higher than the vaporization determination temperature THvp (step S308a: Yes), the process of the previous step S309 is performed (FIG. 13), and when the injection mechanism temperature THdv is not equal to or higher than the vaporization determination temperature THvp (step S308a: No). Then, the processing of the previous step S310 (FIG. 13) is performed.
[0135]
As described above in detail, according to the fuel supply system for a liquefied gas internal combustion engine according to the sixth embodiment, the effects (1) to (6) of the fourth embodiment are applied. The effect will be obtained.
[0136]
Note that the sixth embodiment can be embodied as the following, for example, with the above-mentioned modifications being made as appropriate.
In the sixth embodiment, the configuration in which the fuel discharge amount of the fuel pump 32 is changed based on the vaporization determination temperature THvp in the step S308a (FIG. 17) is described, for example, as follows. It is also possible. That is, in step S308a (FIG. 17), the fuel discharge amount of the fuel pump 32 may be changed based on the saturated steam temperature of the fuel in the delivery pipe 35 (the injection mechanism saturated steam temperature THsvdv).
[0137]
(Seventh embodiment)
A seventh embodiment of the present invention will be described with reference to FIGS.
[0138]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the fourth embodiment (the configuration excluding the gas-phase fuel injector GIN from the configuration shown in FIG. 1), but is shown in FIG. The configuration of the fuel supply device 3 has been changed to the configuration shown in FIG.
[0139]
Here, prior to the description of the fuel supply device according to the present embodiment, an outline thereof will be described.
This embodiment also has a function of reducing the pressure of the fuel in the fuel tank 31 and a function of suppressing the vaporization of the liquid-phase fuel due to the reduction in the pressure, similarly to the fourth embodiment. It has become something. In the fourth embodiment, the above-described function is realized through adjustment of the work amount of the fuel pump 32 by the ECU 5, whereas in the present embodiment, the delivery pipe 35 ( By adjusting the flow rate of the fuel supplied to the fuel injection mechanism 34), the above function is realized.
[0140]
As shown in FIG. 19, in the configuration of the fuel supply device 3 of the present embodiment, each element shown in a broken line is added to the fuel supply device 3 of the fourth embodiment (FIG. 11). It has a configuration. That is, in the fuel supply device 3 of the present embodiment, the liquid-phase fuel supplied by the fuel pump 32 is supplied to the liquid-phase fuel supply path Rd1 from the upstream in the delivery pipe 35 (fuel injection mechanism 34). A detour route Rd4 for returning to the base 31 is connected. Further, the bypass path Rd4 is provided with a pressure regulator 38 for maintaining the fuel pressure in the delivery pipe 35 at a predetermined adjustment set value and a bypass control valve Evl for selectively opening and closing the bypass path Rd4. I have. Further, with the addition of the detour path Rd4, a recirculation control valve Evr for selectively opening and closing the recirculation path Rd2 is provided in the recirculation path Rd2, and through opening and closing operations of the control valves Evr and Evl (switching means). Either of the above-mentioned routes Rd2 and Rd4 can be selectively activated. Note that, as the control valves Evr and Evl, solenoid valves that are normally closed, that is, closed when not energized and opened by energization from the ECU 5 are employed.
[0141]
Next, each fuel path that is switched through opening and closing operations of the recirculation control valve Evr and the bypass control valve Evl will be described. Hereinafter, the fuel path when the recirculation control valve Evr is open and the detour control valve Evl is closed is referred to as a first fuel path, the recirculation control valve Evr is closed, and the detour control valve Evl is opened. The fuel path when the operation is performed is referred to as a second fuel path.
[0142]
First, the fuel circulation mode when the first fuel path is activated will be described.
In this case, the entire amount of the liquid-phase fuel pumped by the fuel pump 32 is supplied to the delivery pipe 35 (the fuel injection mechanism 34), and the liquid-phase fuel injector LIN of the supplied liquid-phase fuel is not injected and supplied. The fuel is returned to the fuel tank 31 via the return path Rd2.
[0143]
Next, a fuel circulation mode when the second fuel path is activated will be described.
In this case, of the liquid-phase fuel pumped by the fuel pump 32, the fuel injected and supplied by the liquid-phase fuel injector LIN is supplied to the delivery pipe 35 (the fuel injection mechanism 34). The surplus fuel not supplied to the delivery pipe 35 is returned to the fuel tank 31 via the bypass route Rd4, and the flow rate of the fuel returned to the fuel tank 31 via the delivery pipe 35 is “0”. It is said.
[0144]
In the present embodiment, one of the fuel paths is made active through a control valve opening / closing process described below. Note that, in the present embodiment, during operation of the internal combustion engine 1, it is assumed that fuel is supplied basically in a state where the first fuel path is active.
[0145]
Next, the opening and closing processing of the control valve will be described with reference to FIG. This process is a process performed in place of the fuel pump discharge amount changing process (FIGS. 12 and 13) in the fourth embodiment, and is repeatedly executed at a predetermined time interval.
[0146]
As shown in FIG. 20, in the control valve opening / closing processing according to the present embodiment, the processing up to the previous step S307 (FIG. 12) is performed in a manner similar to the fourth embodiment.
[0147]
Then, it is determined whether or not the pressure of the fuel in the delivery pipe 35 (the injection mechanism pressure Pdv) is lower than the vaporization determination pressure Pvp (step S308). When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp (step S308). : Yes), the recirculation control valve Evr is opened, and the bypass control valve Evl is closed (step S309a). On the other hand, when the injection mechanism pressure Pdv is not lower than the vaporization determination pressure Pvp, it is determined whether or not the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the calculated stand refueling pressure Pst (step). S310). When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (step S310: Yes), the recirculation control valve Evr is closed and the bypass control valve Evl is opened (step S311a), and the fuel tank pressure Ptk becomes the stand refueling pressure Pst. If not, the open / closed state of each control valve Evr, Evl at that time is maintained (step S310: No).
[0148]
Thus, according to the control valve opening / closing process,
[A] When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp, it is determined that vaporized fuel may be generated in the delivery pipe 35 (or vaporized fuel is generated), and the recirculation path Rd2 is set. Be active.
[B] When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, it is determined that the fuel tank 31 cannot supply fuel at the refueling station, and the bypass route Rd4 is activated.
In this manner, the above-described switching of each path is performed.
[0149]
Incidentally, the flow rate of the fuel recirculated to the fuel tank 31 via the delivery pipe 35 (the fuel injection mechanism 34) changes according to the flow rate of the liquid-phase fuel supplied to the delivery pipe 35.
[0150]
Therefore, in the present embodiment, when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, the detour path Rd4 is activated, that is, the liquid-phase fuel pumped by the fuel pump 32 is supplied from the upstream of the delivery pipe 35 to the fuel tank. By flowing back to 31, the flow rate of the fuel supplied to the delivery pipe 35 is reduced. As a result, the amount of fuel that is recirculated to the fuel tank 31 via the delivery pipe 35 is reduced, and the cooling action of the fuel tank 31 due to the vaporization of the liquid phase fuel is relatively increased, so that the fuel tank pressure Ptk is reduced. Become like
[0151]
When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, the recirculation path Rd2 is activated, that is, the entire amount of liquid-phase fuel pumped by the fuel pump 32 is supplied to the delivery pipe 35, so that the delivery pipe 35 The flow rate of the supplied fuel is increased. Thereby, the cooling action of the delivery pipe 35 by the liquid fuel pumped by the fuel pump 32 is enhanced, and the vaporization of the liquid fuel is suppressed.
[0152]
Next, an example of a control mode of each control valve by the control valve opening / closing process (FIGS. 12 and 20) will be described with reference to FIG.
For example, if it is detected at time t211 that the fuel tank pressure Ptk is equal to or higher than the stand fuel pressure Pst, the recirculation control valve Evr is closed and the bypass control valve Evl is opened, so that the second fuel path is opened. Active (FIGS. 21 (a), (c) to (e)). Then, if it is detected at time t212 that the vaporization determination pressure Pvp has become equal to or higher than the injection mechanism pressure Pdv (the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp) due to the fluctuation of the injection mechanism saturated vapor pressure Psvdv, the recirculation control valve Evr Is opened and the bypass control valve Evl is closed to activate the first fuel path (FIGS. 21 (b), (c) to (e)). Accordingly, when the first fuel path is not activated, for example, the vaporization determination pressure Pvp, which is estimated to be located at the injection mechanism pressure Pdv or higher as indicated by the dashed line, is changed as indicated by the solid line. The pressure becomes lower than the injection mechanism pressure Pdv (FIG. 21B). If it is detected at time t213 that the vaporization determination pressure Pvp is lower than the injection mechanism pressure Pdv (the injection mechanism pressure Pdv is equal to or higher than the vaporization determination pressure Pvp), the fuel tank pressure Ptk is equal to or higher than the stand oil supply pressure Pst. Again, the second fuel path is activated (FIGS. 21 (a)-(e)). As a result, when the second fuel path is not activated, the fuel tank pressure Ptk, which is estimated to increase, for example, in the manner shown by the dashed line, falls as shown by the solid line (FIG. 21). (A)).
[0153]
As described in detail above, according to the fuel supply system for a liquefied gas internal combustion engine according to the seventh embodiment, the effects (3) to (5) of the fourth embodiment are applied. In addition to the effects, the following effects can be obtained.
[0154]
(7) In the present embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the liquid-phase fuel pumped by the fuel pump 32 is supplied to the delivery pipe 35 (fuel injection mechanism). The fuel tank pressure Ptk is reduced by refluxing the fuel tank 31 from the upstream in 34). This makes it possible to suitably maintain the state of the fuel tank 31 in a state where fuel can be supplied at the refueling station.
[0155]
(8) In the present embodiment, even when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (when the conditions for performing the processing described in (7) above are satisfied), the delivery pipe 35 is When there is a possibility that vaporized fuel will be generated in the above, the entire amount of the liquid-phase fuel pumped by the fuel pump 32 is supplied to the delivery pipe 35. As a result, the liquid state of the fuel in the delivery pipe 35 is maintained, so that deterioration of the operability of the internal combustion engine 1 can be suitably avoided.
[0156]
(9) Further, based on the conditions described in the above (7) and (8),
A fuel path (first fuel path) for returning the liquid fuel pumped by the fuel pump 32 from the downstream of the delivery pipe 35 to the fuel tank 31.
A fuel path (second fuel path) for returning the liquid fuel pumped by the fuel pump 32 from the upstream of the delivery pipe 35 to the fuel tank 31.
Is selectively activated, so that the state of the fuel tank 31 is changed to the refueling station while maintaining the cooling action of the fuel injection mechanism 34 (delivery pipe 35) by the liquid phase fuel. It is possible to suitably maintain the state in which the fuel can be supplied at the time.
[0157]
(10) In the present embodiment, the fuel tank 31 is brought into a state in which fuel can be supplied at the refueling station through a configuration in which the liquid fuel pumped by the fuel pump 32 is returned to the fuel tank 31 from the upstream of the delivery pipe 35. To be able to maintain. With such a configuration as well, it is possible to solve the concern caused by the temperature rise in the trunk room, and thus the fuel supply device of the highly practical LPG engine that effectively utilizes the existing fuel supply device of the LPG engine. Can be provided.
[0158]
Note that the seventh embodiment can be embodied as the following, for example, in which this is modified as appropriate.
In the seventh embodiment, the recirculation path Rd2 is provided with the recirculation control valve Evr and the pressure regulator 36, and the detour path Rd4 is provided with the detour control valve Evl and the pressure regulator 38, respectively. It is also possible to change to That is, it is also possible to adopt a configuration in which the pressure regulation set values of the pressure regulators 36 and 38 are set to different values, and the control valve is provided only in the path where the pressure regulator set with the low pressure regulation value is provided.
[0159]
In the seventh embodiment, the recirculation control valve Evr is provided upstream of the pressure regulator 36 of the recirculation path Rd2, and the bypass control valve Evl is provided upstream of the pressure regulator 38 of the detour path Rd4. For example, the following configuration is also possible. That is, at least one of the control valves Evr and Evl may be provided downstream of the corresponding pressure regulators 36 and 38.
[0160]
(Eighth embodiment)
An eighth embodiment of the present invention will be described with reference to FIGS.
[0161]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the fourth embodiment (the configuration excluding the gas-phase fuel injector GIN from the configuration shown in FIG. 1), but is shown in FIG. The configuration of the fuel supply device 3 has been changed to the configuration shown in FIG.
[0162]
Here, prior to the description of the fuel supply device according to the present embodiment, an outline thereof will be described.
This embodiment also has a function of reducing the pressure of the fuel in the fuel tank 31 and a function of suppressing the vaporization of the liquid-phase fuel due to the reduction in the pressure, similarly to the fourth embodiment. It has become something. In the fourth embodiment, the above-described function is realized through adjustment of the work amount of the fuel pump 32 by the ECU 5, whereas in the present embodiment, the delivery is performed through the variable pressure mechanism described below. The above function is realized by making the pressure of the fuel in the pipe 35 (fuel injection mechanism 34) variable.
[0163]
As shown in FIG. 22, in the configuration of the fuel supply device 3 of the present embodiment, each element shown in a broken line is added to the fuel supply device 3 of the fourth embodiment (FIG. 11). It has a configuration. That is, in the fuel supply device 3 of the present embodiment, an auxiliary return path Rd5 that allows the fuel flowing through the return path Rd2 to return to the fuel tank 31 without passing through the pressure regulator 36 is provided in the return path Rd2. Is connected. Further, a high pressure regulator 39 having a pressure adjustment set value higher than a predetermined adjustment set value set for the pressure regulator 36 is provided in the auxiliary return path Rd5. Further, a return control valve Evs that selectively opens and closes the return path Rd2 from a connection portion of the return path Rd2 with the auxiliary return path Rd5 is provided. The pressure regulation function of the pressure regulator 36 can be selectively enabled. Note that, as the recirculation control valve Evs, an electromagnetic valve which is normally closed, that is, closed when not energized and opened by energization from the ECU 5 is employed.
[0164]
Next, each fuel path that is switched through the opening / closing operation of the reflux control valve Evs will be described. Hereinafter, the fuel path when the recirculation control valve Evs is open is referred to as a first fuel path, and the fuel path when the recirculation control valve Evs is closed is referred to as a second fuel path.
[0165]
First, the fuel circulation mode when the first fuel path is activated will be described.
In this case, since the fuel pressure regulation function of the pressure regulator 36 is enabled, the pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) is maintained at a predetermined pressure regulation value through the pressure regulator 36. Further, the fuel not injected and supplied by the liquid fuel injector LIN is returned to the fuel tank 31 via the return path Rd2.
[0166]
Next, a fuel circulation mode when the second fuel path is activated will be described.
In this case, since the fuel pressure regulation function of the pressure regulator 36 is invalidated, the pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) is higher than the predetermined pressure regulation value through the high pressure regulator 39. The pressure adjustment set value is maintained. Further, the fuel not injected and supplied by the liquid-phase fuel injector LIN is returned to the fuel tank 31 via the return path Rd2 and the auxiliary return path Rd5.
[0167]
In the present embodiment, one of the fuel paths is made active through a control valve opening / closing process described below. Note that, in the present embodiment, during operation of the internal combustion engine 1, it is assumed that fuel is supplied basically in a state where the first fuel path is active.
[0168]
Next, the control valve opening / closing process will be described with reference to FIG. This process is a process performed in place of the fuel pump discharge amount changing process (FIGS. 12 and 13) in the fourth embodiment, and is repeatedly executed at a predetermined time interval.
[0169]
As shown in FIG. 23, in the control valve opening / closing processing according to the present embodiment, the processing up to the previous step S307 (FIG. 12) is performed in a manner similar to the fourth embodiment.
[0170]
Then, it is determined whether or not the pressure of the fuel in the delivery pipe 35 (the injection mechanism pressure Pdv) is lower than the vaporization determination pressure Pvp (step S308). When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp (step S308). : Yes), the recirculation control valve Evs is opened (step S309b). On the other hand, when the injection mechanism pressure Pdv is not lower than the vaporization determination pressure Pvp, it is determined whether or not the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the calculated stand refueling pressure Pst (step). S310). When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (step S310: Yes), the recirculation control valve Evs is closed (step S311b). When the fuel tank pressure Ptk is not higher than the stand refueling pressure Pst, the recirculation at that time is performed. The open / closed state of the control valve Evs is maintained (Step S310: No).
[0171]
Thus, according to the control valve opening / closing process,
[A] When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp, it is determined that vaporized fuel may be generated in the delivery pipe 35 (or vaporized fuel is generated), and the pressure regulator 36 is adjusted. Enable the pressure function.
[B] When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, it is determined that the fuel tank 31 cannot supply fuel at the refueling station, and the pressure adjusting function of the high pressure regulator 39 is enabled.
In this manner, the switching of each fuel path is performed.
[0172]
Incidentally, the discharge amount of the liquid phase fuel by the fuel pump 32 tends to change according to the pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34). That is, as the pressure of the fuel in the delivery pipe 35 increases, the pressure difference between before and after the fuel pump 32 increases, so that the discharge amount of the liquid-phase fuel decreases when the work amount of the fuel pump 32 is constant. .
[0173]
Therefore, in the present embodiment, when the fuel tank pressure Ptk is equal to or higher than the stand supply pressure Pst, the pressure regulating function of the high pressure regulator 39 is made effective, that is, by increasing the fuel pressure in the delivery pipe 35, The flow rate of the fuel supplied to the delivery pipe 35 is reduced. As a result, the amount of fuel that is recirculated to the fuel tank 31 via the delivery pipe 35 is reduced, and the cooling action of the fuel tank 31 due to the vaporization of the liquid phase fuel is relatively increased, so that the fuel tank pressure Ptk is reduced. Become like
[0174]
When the fuel tank pressure Ptk is equal to or higher than the stand supply pressure Pst, the pressure regulation function of the pressure regulator 36 is made effective, that is, by reducing the fuel pressure in the delivery pipe 35, the fuel supplied to the delivery pipe 35 is reduced. Is increased. Thereby, the cooling action of the delivery pipe 35 by the liquid fuel pumped by the fuel pump 32 is enhanced, and the vaporization of the liquid fuel is suppressed.
[0175]
As described in detail above, according to the fuel supply system for a liquefied gas internal combustion engine according to the eighth embodiment, the effects (3) to (5) of the fourth embodiment are obtained. In addition to the effects, the following effects can be obtained.
[0176]
(7) In this embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the pressure of the fuel in the delivery pipe 35 (fuel injection mechanism 34) is increased. Thus, the fuel tank pressure Ptk is reduced to less than the stand refueling pressure Pst. This makes it possible to suitably maintain the state of the fuel tank 31 in a state where fuel can be supplied at the refueling station. Further, since the saturated vapor temperature of the fuel in the delivery pipe 35 is increased by increasing the pressure of the fuel in the delivery pipe 35, the vaporization of the fuel due to the temperature increase of the fuel in the delivery pipe 35 is suitably suppressed. Will be able to do it.
[0177]
(8) In the present embodiment, even when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (when the condition for performing the process described in (1) above is satisfied), the delivery pipe 35 When there is a possibility that vaporized fuel may be generated in the above, the pressure of the fuel in the delivery pipe 35 is reduced. As a result, the liquid state of the fuel in the delivery pipe 35 is maintained, so that deterioration of the operability of the internal combustion engine 1 can be suitably avoided. Further, since the load on the fuel pump 32 is reduced by lowering the pressure of the fuel in the delivery pipe 35, the life of the fuel pump 32 can be suitably maintained.
[0178]
(9) In this embodiment, the fuel pressure in the delivery pipe 35 is made variable so that the fuel tank 31 can be maintained in a state where fuel can be supplied to the fueling station. With such a configuration as well, it is possible to solve the concern caused by the temperature rise in the trunk room, and thus the fuel supply device of the highly practical LPG engine that effectively utilizes the existing fuel supply device of the LPG engine. Can be provided.
[0179]
Note that the eighth embodiment can be embodied as the following, for example, in which the above-described eighth embodiment is modified as appropriate.
In the eighth embodiment, the recirculation control valve Evr is provided upstream of the pressure regulator 36 in the recirculation path Rd2. However, for example, the configuration may be changed as follows. That is, a configuration may be adopted in which the recirculation control valve Evr is provided downstream of the pressure regulator 36 in the recirculation path Rd2.
[0180]
(Ninth embodiment)
A ninth embodiment of the present invention will be described with reference to FIGS.
[0181]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the fourth embodiment (the configuration excluding the gas-phase fuel injector GIN from the configuration shown in FIG. 1), but is shown in FIG. The configuration of the fuel supply device 3 has been changed to the configuration shown in FIG.
[0182]
Here, prior to the description of the fuel supply device according to the present embodiment, an outline thereof will be described.
This embodiment also has a function of reducing the pressure of the fuel in the fuel tank 31 and a function of suppressing the vaporization of the liquid-phase fuel due to the reduction in the pressure, similarly to the fourth embodiment. It has become something. In the present embodiment, as in the eighth embodiment, the above function is realized by making the pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) variable. .
[0183]
As shown in FIG. 24, in the configuration of the fuel supply device 3 of the present embodiment, each element shown in a broken line is added to the fuel supply device 3 of the fourth embodiment (FIG. 11). It has a configuration. That is, in the fuel supply device 3 of the present embodiment, the pressure of the fuel in the delivery pipe 35 is set to be lower than the predetermined adjustment set value by the pressure regulator 36 in the recirculation path Rd2 in cooperation with the pressure regulator 36. An auxiliary pressure regulator 40 for maintaining a high pressure regulation set value is provided. In addition, a bypass return path Rd6 that can bypass the pressure regulator 40 and allow fuel to flow is connected to the return path Rd2. Further, the bypass return path Rd6 is provided with a bypass return control valve Evb for selectively opening and closing the path Rd6, and the pressure regulating function of the auxiliary pressure regulator 40 is selected through the opening / closing operation of the bypass return control valve Evb. Can be effectively effective. Note that, as the bypass recirculation control valve Evb, an electromagnetic valve which is normally closed, that is, closed when not energized and opened by energization from the ECU 5 is employed.
[0184]
Next, each fuel path that is switched through the opening and closing operation of the bypass recirculation control valve Evb will be described. Hereinafter, the fuel path when the bypass recirculation control valve Evb is open is referred to as a first fuel path, and the fuel path when the bypass recirculation control valve Evb is closed is referred to as a second fuel path. I do.
[0185]
First, the fuel circulation mode when the first fuel path is activated will be described.
In this case, since the fuel pressure regulation function of the auxiliary pressure regulator 40 is invalidated, the pressure of the fuel in the delivery pipe 35 (fuel injection mechanism 34) is maintained at a predetermined pressure regulation value through the pressure regulators 36 and 40. Is done. Further, the fuel not injected and supplied by the liquid-phase fuel injector LIN is returned to the fuel tank 31 via the return path Rd2 and the bypass return path Rd6.
[0186]
Next, a fuel circulation mode when the second fuel path is activated will be described.
In this case, since the fuel pressure regulation function by the auxiliary pressure regulator 40 is made effective, the pressure of the fuel in the delivery pipe 35 (fuel injection mechanism 34) is increased through the pressure regulators 36 and 40 to the predetermined pressure regulation value. It is maintained at a higher pressure regulation set value. Further, the fuel not injected and supplied by the liquid fuel injector LIN is returned to the fuel tank 31 via the return path Rd2.
[0187]
In the present embodiment, one of the fuel paths is made active through a control valve opening / closing process described below. Note that, in the present embodiment, during operation of the internal combustion engine 1, it is assumed that fuel is supplied basically in a state where the first fuel path is active.
[0188]
Next, the control valve opening / closing process will be described with reference to FIG. This process is a process performed in place of the fuel pump discharge amount changing process (FIGS. 12 and 13) in the fourth embodiment, and is repeatedly executed at a predetermined time interval.
[0189]
As shown in FIG. 25, in the control valve opening / closing processing according to the present embodiment, the processing up to the previous step S307 (FIG. 12) is performed in a manner similar to the fourth embodiment.
[0190]
Then, it is determined whether or not the pressure of the fuel in the delivery pipe 35 (the injection mechanism pressure Pdv) is lower than the vaporization determination pressure Pvp (step S308). When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp (step S308). : Yes), the bypass recirculation control valve Evb is opened (step S309c). On the other hand, when the injection mechanism pressure Pdv is not lower than the vaporization determination pressure Pvp, it is determined whether or not the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the calculated stand refueling pressure Pst (step). S310). When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (step S310: Yes), the bypass recirculation control valve Evb is closed (step S311c), and when the fuel tank pressure Ptk is not higher than the stand refueling pressure Pst, The open / close state of the bypass recirculation control valve Evb is maintained (step S310: No).
[0191]
Thus, according to the control valve opening / closing process,
[A] When the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp, it is determined that vaporized fuel may be generated in the delivery pipe 35 (or vaporized fuel is generated). Disable the pressure adjustment function.
[B] When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, it is determined that the fuel tank 31 cannot supply fuel at the refueling station, and the pressure regulation function of the auxiliary pressure regulator 40 is enabled.
In this manner, the switching of each fuel path is performed.
[0192]
When the fuel path of [A] is activated, the operation and effect similar to the operation and effect when the fuel path of [A] in the eighth embodiment is activated are obtained. Become. Further, when the fuel path of [b] is activated, an operation and effect similar to the operation and effect when the fuel path of [b] is activated in the eighth embodiment can be obtained. Become.
[0193]
As described in detail above, according to the fuel supply device for a liquefied gas internal combustion engine according to the ninth embodiment, the effects (3) to (5) of the fourth embodiment are applied. In addition to the effects, effects similar to the effects (7) to (9) in the eighth embodiment can be obtained.
[0194]
The ninth embodiment can be implemented by appropriately modifying the ninth embodiment, for example, as follows.
In the ninth embodiment, the bypass recirculation path Rd6 including the bypass recirculation control valve Evb is configured to be connected to the recirculation path Rd2 so as to bypass the pressure regulator 40. However, for example, the configuration is changed as follows. It is also possible. That is, the arrangement positions of the bypass recirculation control valve Evb and the pressure regulator 40 may be interchanged.
[0195]
In the ninth embodiment, the bypass recirculation path Rd6 is connected to the recirculation path Rd2 so as to bypass the pressure regulator 40. However, for example, the configuration may be changed to the following configuration. That is, the bypass recirculation path Rd6 may be connected to the recirculation path Rd2 so as to bypass the pressure regulator 36 instead of the pressure regulator 40.
[0196]
In the ninth embodiment, the two pressure regulators 36 and 40 are provided in the return path Rd2. However, for example, the following configuration may be used. That is, three or more pressure regulators may be provided in the return path Rd2, and the bypass return path Rd6 may be connected to the return path Rd2 so as to bypass at least one of the plurality of pressure regulators.
[0197]
(Tenth embodiment)
A tenth embodiment of the present invention will be described with reference to FIGS.
[0198]
In the present embodiment, the basic configuration of the entire apparatus is the same as that of the first embodiment (FIG. 1), but the configuration of the fuel supply device 3 shown in FIG. 2 is changed to the configuration shown in FIG. (Note that the gas-phase fuel injector GIN shown in FIG. 1 is excluded with this change).
[0199]
Here, prior to the description of the fuel supply device according to the present embodiment, an outline thereof will be described.
This embodiment also has a function of reducing the pressure of the fuel in the fuel tank 31 similarly to the first embodiment. In the first embodiment, the above function is realized through the supply of the gaseous fuel to the internal combustion engine 1, whereas in the present embodiment, the air conditioning of the vehicle equipped with the internal combustion engine 1 is performed. The above function is realized through a device (vehicle air conditioner). Hereinafter, the fuel supply device of the present embodiment will be described with reference to FIG.
[0200]
As shown in FIG. 26, the fuel supply device 3 according to the present embodiment is different from the fuel supply device 3 (FIG. 2) according to the first embodiment in that the gas-phase fuel supply system 3G is excluded. This is a configuration in which a cooling mechanism indicated by is added. That is, the fuel supply device 3 of the present embodiment includes a duct 71 for supplying cool air from the air conditioner (A / C) 7 to the fuel tank 31. When the air conditioner AC is driven by the ECU 5, cool air is supplied from the air conditioner 7 to the fuel tank 31.
[0201]
Next, a process for controlling the drive mode of the air conditioner 7 (drive process of the air conditioner) will be described with reference to FIG. This process is a process performed in place of the driving process (FIG. 3) of the gas-phase fuel injector in the first embodiment, and is repeatedly performed at a predetermined time interval.
[0202]
As shown in FIG. 27, in the driving processing of the air conditioner of the present embodiment, the processing up to the previous step S105 (FIG. 3) is performed in a manner similar to the first embodiment.
[0203]
Then, it is determined whether or not the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst (step S106). When the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst (step S106: Yes), the fuel tank 31 is cooled by the air conditioner 7 (step S107a), and when the fuel tank pressure Ptk is not equal to or higher than the stand refueling pressure Pst. The cooling of the fuel tank 31 by Step 7 is stopped (Step S106: No).
[0204]
As described above, according to the driving process of the air conditioner, when the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst, that is, when refueling of the fuel tank 31 cannot be performed at the refueling station, the air conditioner 7 The cooling of the fuel tank 31 is performed. As a result, the temperature of the fuel in the fuel tank 31 decreases, and the pressure of the fuel also decreases.
[0205]
As described in detail above, according to the fuel supply device for a liquefied gas internal combustion engine according to the tenth embodiment, the effects of (2) and (3) in the first embodiment are obtained. In addition to the effects, the following effects can be obtained.
[0206]
(6) In the present embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the fuel tank 31 is cooled through the air conditioner 7 so that the fuel tank pressure Ptk is obtained. Is decompressed. This makes it possible to suitably maintain the state of the fuel tank 31 in a state where fuel can be supplied at the refueling station.
[0207]
(7) Also, according to the above configuration, it is possible to eliminate the concern caused by the temperature rise in the trunk room, and thus the highly practical LPG that effectively utilizes the fuel supply device of the existing LPG engine. An engine fuel supply device can be provided.
[0208]
The tenth embodiment can be embodied as follows, for example, by appropriately modifying the tenth embodiment.
In the tenth embodiment, the fuel tank 31 is cooled by supplying the cool air from the air conditioner 7 to the fuel tank 31. However, for example, the following structure may be used. is there. That is, the configuration may be such that the cool air of the air conditioner 7 is supplied to the return path Rd2 to cool the fuel flowing through the return path Rd2.
[0209]
Further, the refrigerant circulating in the air conditioner 7 is supplied to a pipe provided adjacent to the fuel tank 31, and the fuel tank 31 is cooled through heat exchange between the refrigerant in the pipe and the fuel tank 31. You can also.
[0210]
Further, the refrigerant circulating in the air conditioner 7 is supplied to a pipe provided adjacent to the return path Rd2, and the refrigerant in the pipe and the fuel flowing in the return path Rd2 exchange heat with the fuel in the return path Rd2. It is also possible to adopt a configuration for cooling the fuel.
[0211]
In the tenth embodiment, the fuel tank 31 is cooled through the air conditioner 7 mounted on the vehicle. However, for example, the following configuration may be used. That is, a configuration may be adopted in which a cooling device for cooling the fuel tank 31 (or the return path Rd2) is newly provided, and the fuel tank 31 (or the return path Rd2) is cooled through the cooling apparatus.
[0212]
(Eleventh embodiment)
An eleventh embodiment of the present invention will be described with reference to FIGS.
[0213]
In the present embodiment, the basic configuration of the entire apparatus including the internal combustion engine is the same as that of the first embodiment, but a part of the driving process (FIG. 3) of the gas-phase fuel injector is shown in FIG. The processing shown in FIG.
[0214]
Here, the outline of the driving process of the gas-phase fuel injector according to the present embodiment will be described prior to the description.
In the process of the present embodiment, similarly to the process of the first embodiment (FIG. 3), the pressure of the fuel in the fuel tank 31 is reduced by controlling the manner of supplying the gaseous fuel to the internal combustion engine 1. It is intended to be. In the first embodiment, the stand refueling pressure Pst is calculated by adding the predetermined pressure (refueling pressure Pca) applied to the fuel in the stand fuel tank at the time of refueling and the stand saturated steam pressure Psvst. On the other hand, in the present embodiment, the stand oil supply pressure Pst is calculated in a manner described below.
[0215]
As shown in FIG. 28, in the driving process of the gas-phase fuel injector according to the present embodiment, first, the process up to step S104 (FIG. 3) is performed in a manner similar to the first embodiment. Then, a value calculated by adding a predetermined pressure Pcc set lower than the refueling pressure Pca to the stand saturated steam pressure Psvst is set as the stand refueling pressure Pst (step S105b). That is, as shown in FIG. 29, the stand saturated vapor pressure Psvst is estimated through the saturated vapor pressure curve of the propane ratio R and the outside air temperature THatm, and
Pst ← Psvst + Pcc [5]
Is used to calculate the stand oil supply pressure Pst.
[0216]
Then, in the previous step S106 (FIG. 3), it is determined whether or not the fuel pressure in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand refueling pressure Pst calculated in the above-described manner. The gaseous phase fuel is supplied in a manner according to the first embodiment.
[0219]
As described above, according to the driving process of the gas-phase fuel injector, the stand refueling pressure Pst is calculated through the addition of the predetermined pressure Pcc set lower than the refueling pressure Pca and the stand saturated steam pressure Psvst. Is done.
[0218]
Incidentally, the pressure of the fuel (fuel tank pressure Ptk) in the fuel tank 31 is obtained by adding the pressurizing pressure Pca at the time of refueling and the stand saturated steam pressure Psvst (the stand refueling pressure Pst in the first embodiment). In this case, the fuel cannot be supplied from the stand fuel tank to the fuel tank 31. On the other hand, when the fuel tank pressure Ptk is lower than the above pressure (the stand fuel pressure Pst in the first embodiment), the fuel tank pressure Ptk becomes equal to the pressure (the stand fuel pressure Pst in the first embodiment). As it approaches, fuel tends to be less likely to flow from the stand fuel tank to the fuel tank 31. For this reason, even if the fuel tank pressure Ptk is lower than the above-mentioned pressure (the stand-up refueling pressure Pst in the first embodiment), when the fuel tank pressure Ptk is close to the above-mentioned pressure, the fuel to the fuel tank 31 is not supplied. It is feared that the time required for replenishment will be longer than usual.
[0219]
Therefore, in the present embodiment, by supplying the gaseous phase fuel based on the station refueling pressure Pst calculated in the above-described manner, the time required for refueling at the refueling station is estimated to be longer than usual. The fuel tank pressure Ptk is reduced. As a result, the above-mentioned concerns are resolved, and the state of the fuel tank 31 can be suitably maintained in a state where external fuel supply is possible.
[0220]
As described above in detail, according to the fuel supply device for a liquefied gas internal combustion engine according to the eleventh embodiment, the effects (3) to (5) in the first embodiment are applied. In addition to the effects, the following effects can be obtained.
[0221]
(6) In the present embodiment, when the pressure of the fuel in the fuel tank 31 (fuel tank pressure Ptk) is equal to or higher than the stand supply pressure Pst, the gas-phase fuel in the fuel tank 31 is supplied to the internal combustion engine 1. , The fuel tank pressure Ptk is reduced. This makes it possible to suitably maintain the state of the fuel tank 31 in a state where fuel can be supplied at the refueling station. Further, it is possible to suitably avoid an increase in the refueling time due to the fact that the fuel tank pressure Ptk is close to the pressure of the fuel supplied to the fuel tank 31 by being pressurized at the refueling stand.
[0222]
(7) In the present embodiment, the stand oil supply pressure Pst is calculated in the following manner. That is,
Estimating the saturated vapor pressure (stand saturated vapor pressure Psvst) of the fuel stored in the fuel tank (stand fuel tank) of the refueling station from the saturated vapor pressure curve of the fuel in the fuel tank 31 and the outside air temperature THatm.
The stand-up refueling pressure Pst is calculated by adding the stand saturated steam pressure Psvst and a predetermined pressure Pcc set lower than a predetermined pressure applied to the fuel in the stand fuel tank during refueling (refueling pressure Pca). I do.
In this manner, the stand oil supply pressure Pst is calculated. This makes it possible to more appropriately grasp the relationship between the fuel pressure in the fuel tank 31 and the stand refueling pressure Pst, and makes the state of the fuel tank 31 more suitable for refueling at the refueling station. Can be maintained.
[0223]
(Other embodiments)
Other elements that can be commonly changed in each of the above embodiments include the following.
[0224]
In the first to third embodiments, the gas-phase fuel is supplied to the internal combustion engine 1 through the configuration exemplified in each embodiment. However, the gas-phase fuel is appropriately supplied to the internal combustion engine 1. The configuration is not limited to the configuration illustrated in each of the above-described embodiments, and any configuration can be adopted.
[0225]
In the fourth and fifth embodiments, the fuel discharge amount of the fuel pump 32 is changed to two or three steps. However, for example, the following structure may be used. That is, based on a map in which the relationship between the pressure of the fuel in the fuel tank 31 and the fuel discharge amount of the fuel pump 32 is set, the fuel discharge amount of the fuel pump 32 is continuously adjusted according to the change in the pressure. You can also. In short, if the fuel supply station can maintain a state in which fuel can be supplied to the fuel tank 31 and can maintain the liquid phase state of the fuel in the delivery pipe 35, the control mode of the fuel pump 32 (the amount of work Adjustment of the fuel discharge amount by adjustment) can be appropriately changed.
[0226]
In the eighth and ninth embodiments, the pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) is made variable through the configuration exemplified in each of the above embodiments. It is also possible to adopt such a configuration. That is, a configuration in which a variable pressure regulator having a plurality of pressure regulation set values is provided in the recirculation path Rd2 of the fuel supply device 3 (FIG. 11) in the fourth embodiment may be adopted. In short, as long as the pressure of the fuel in the delivery pipe 35 (the fuel injection mechanism 34) can be made variable, the configuration for that purpose is not limited to the configuration exemplified in each of the above-described embodiments, and an arbitrary configuration is adopted. can do.
[0227]
In the fourth, fifth, and seventh to ninth embodiments, in the process of step S308 (FIGS. 13, 16, 20, 23, and 25), the injection mechanism pressure Pdv is set to the vaporization determination pressure. Although it is configured to determine whether it is less than Pvp, for example, the following configuration is also possible. That is, it may be configured to determine whether or not the injection mechanism pressure Pdv is equal to or higher than the saturated vapor pressure of the fuel in the delivery pipe 35 (the injection mechanism saturated vapor pressure Psvdv).
[0228]
The configuration exemplified in the sixth embodiment can be applied to the fifth and seventh to ninth embodiments. That is, instead of the processing of step S308 (FIGS. 16, 20, 23, and 25) in the fifth and seventh to ninth embodiments, the processing of step S308a in the sixth embodiment ( It is also possible to perform FIG. 17).
[0229]
Further, instead of the process of step S308a (FIG. 17), it is determined whether or not the injection mechanism temperature THdv is equal to or higher than the saturated steam temperature of the fuel in the delivery pipe 35 (the injection mechanism saturated steam temperature THsvdv). Processing can also be performed.
[0230]
The processing of step S308 (step S308a) (FIGS. 13, 16, 17, 20, 23, and 25) in the fourth to ninth embodiments is changed as follows, for example. It is also possible. That is, in place of the above-described processing, a processing of determining whether or not the temperature of the fuel in the delivery pipe 35 is equal to or higher than a predetermined temperature is performed, and if the temperature of the fuel is equal to or higher than the predetermined temperature, a step is performed. The process may proceed to S309 (steps S309a to S309c) and proceed to step S310 if the temperature of the fuel is not equal to or higher than the predetermined temperature.
[0231]
In the fourth to ninth embodiments, the processing (steps S308 and S308a) for determining whether there is a possibility that the liquid phase fuel is vaporized in the delivery pipe 35 is performed. For example, in the case of a configuration of the fuel supply device 3 in which the vaporization of the liquid-phase fuel in the delivery pipe 35 is not a concern, the above process can be omitted.
[0232]
-The configuration illustrated in the second embodiment can be applied to the third to tenth embodiments. That is, in the third and tenth embodiments, step S105a (FIG. 8) is performed after step S105 (FIG. 3), and step S106a (FIG. 3) is performed instead of step S106 (FIGS. 3 and 27). It is also possible to perform 8). In the fourth to ninth embodiments, step S105a (FIG. 3) is performed after step S307 (FIG. 12), and step S310 (FIG. 13, FIG. 16, FIG. 20, FIG. 23, FIG. Step S106a (FIG. 8) can be performed instead of 25).
[0233]
The configuration exemplified in the eleventh embodiment can be applied to the second to tenth embodiments. That is, in the second to tenth embodiments, a value calculated by adding the stand saturated steam pressure Psvst and the predetermined pressurizing force Pcc lower than the refueling pressurizing force Pca is used as the stand refueling pressure. It can also be used as Pst.
[0234]
In the above embodiments, the stand oil pressure Pst is calculated in the manner exemplified in the above embodiments. However, the stand oil pressure Pst may be used as a preset value.
[0235]
In each of the above embodiments, the process for reducing the fuel tank pressure Ptk, that is, [a] In the first to third and eleventh embodiments, the gaseous fuel is supplied to the internal combustion engine 1.
[B] In the fourth to sixth embodiments, the fuel discharge amount of the fuel pump 32 is changed to a low flow rate.
[C] In the seventh embodiment, the recirculation control valve Evr is closed and the bypass control valve Evl is opened.
[D] In the eighth embodiment, the recirculation control valve Evs is closed.
[E] In the ninth embodiment, the bypass recirculation control valve Evb is closed.
[F] In the tenth embodiment, the air conditioner 7 is driven.
Are started when "the fuel tank pressure Ptk is equal to or higher than the stand fuel pressure Pst" and stopped when "the fuel tank pressure Ptk is not equal to or higher than the stand fuel pressure Pst" (steps S106 and S106). S310), for example, can be changed as follows. That is, the above processes are started when "the fuel tank pressure Ptk is equal to or higher than the stand refueling pressure Pst", and when the "fuel tank pressure Ptk is lower than a predetermined pressure set lower than the stand refueling pressure Pst". It can be configured to stop.
[0236]
In the fourth to ninth embodiments, the processing for suppressing the vaporization of the liquid phase fuel in the delivery pipe 35, ie,
[A] In the fourth to sixth embodiments, the fuel discharge amount of the fuel pump 32 is changed to a high flow rate.
[B] In the seventh embodiment, the recirculation control valve Evr is opened and the bypass control valve Evl is closed.
[C] In the eighth embodiment, the recirculation control valve Evs is opened.
[D] In the ninth embodiment, the bypass recirculation control valve Evb is opened.
Are started when “the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp” (in the sixth embodiment, “the injection mechanism temperature THdv is equal to or higher than the vaporization determination temperature THvp”), and the “injection mechanism When the pressure Pdv is not lower than the vaporization determination pressure Pvp "(" the injection mechanism temperature THdv is not higher than the vaporization determination temperature THvp "in the sixth embodiment), the operation is stopped (steps S308 and S308a). It is also possible to change as follows. That is, each of the above processes is started when "the injection mechanism pressure Pdv is lower than the vaporization determination pressure Pvp" (in the sixth embodiment, "the injection mechanism temperature THdv is equal to or higher than the vaporization determination temperature THvp"), and "the injection is performed." The mechanism pressure Pdv is equal to or higher than a predetermined pressure that is set higher than the vaporization determination pressure Pvp. ”(In the sixth embodiment,“ the injection mechanism temperature THdv is lower than a predetermined temperature set lower than the vaporization determination temperature THvp. ” There is a configuration that stops when there is ").
[0237]
In each of the above embodiments, the propane ratio R in the fuel (LPG) is estimated from the propane ratio map illustrated in FIG. 4, but the propane ratio map is illustrated in each of the above embodiments. The map is not limited to this, and an appropriate map can be adopted.
[0238]
In each of the above embodiments, the configuration is such that the saturated vapor pressure curve of the fuel is determined based on the saturated vapor pressure calculation formula [1] exemplified in each embodiment. ] Is not limited to the calculation formula illustrated in each of the above embodiments, and an appropriate calculation formula can be adopted.
[0239]
In each of the above embodiments, the configuration is such that the saturated vapor pressure curve of the fuel is determined based on the propane ratio R estimated from the temperature and pressure of the fuel in the fuel tank 31. Is also possible. That is, a configuration may be adopted in which the saturated vapor pressure curve of the fuel is set in advance and the propane ratio R is not estimated.
[0240]
In the above embodiments, the present invention is applied to the fuel supply device of the LPG engine, but the fuel supply device to which the present invention is applied is not limited to the fuel supply device of the LPG engine. In short, a fuel circulation system in which fuel pumped by a fuel pump is returned to a fuel tank via a fuel injection mechanism is employed, and a liquefied gas such as liquefied natural gas (LNG), liquid hydrogen, and dimethyl ether is used as fuel. The present invention can be applied to any fuel supply device for an internal combustion engine that performs the same functions and effects as those of the above-described embodiments even when the present invention is applied to such a fuel supply device. Will be able to
[0241]
Finally, it should be noted that the fuel supply device for a liquefied gas internal combustion engine according to the present invention includes the following technical concept.
(1) The fuel supply device for a liquefied gas internal combustion engine according to claim 15, wherein the pressure reducing means reduces the amount of current supplied to the fuel pump to reduce the work of the fuel pump.
[0242]
(2) The fuel supply device for a liquefied gas internal combustion engine according to claim 18, wherein the switching means includes a recirculation control valve for selectively opening and closing the recirculation path, and a detour control valve for selectively opening and closing the detour path. The decompression means closes the recirculation control valve and opens the detour control valve to activate the detour path.
[0243]
(3) In the fuel supply device for a liquefied gas internal combustion engine according to claim 21, the variable pressure mechanism is provided in the recirculation path and adjusts a fuel pressure in the fuel injection mechanism to a first pressure regulation set value. A first pressure regulating mechanism for maintaining the fuel and a fuel recirculating path provided in an auxiliary recirculation path branched from an upstream of the first pressure regulating mechanism of the recirculation path and connected to the fuel tank; A second pressure regulation mechanism for maintaining a pressure at a second pressure regulation value higher than the first pressure regulation value, and a recirculation control valve provided in the recirculation route for selectively opening and closing the recirculation route And the pressure reducing means changes the pressure adjustment set value of the variable pressure mechanism to a higher value by closing the recirculation control valve.
[0244]
(4) The fuel supply device for a liquefied gas internal combustion engine according to claim 21, wherein the variable pressure mechanism is provided in the recirculation path and adjusts a fuel pressure in the fuel injector mechanism to a predetermined pressure regulation set value. A plurality of pressure regulating mechanisms to be maintained, and a plurality of pressure regulating mechanisms provided in a bypass return path branched from the return path so as to bypass at least one of the plurality of pressure control mechanisms to selectively open and close the bypass return path. A detour recirculation control valve, and the pressure reducing means changes the pressure regulation set value of the variable pressure mechanism to a higher value by closing the detour recirculation control valve.
[0245]
(5) The fuel supply device for a liquefied gas internal combustion engine according to claim 21, wherein the variable pressure mechanism includes a variable pressure regulator provided in the recirculation path and having a variable pressure setting value. The pressure reducing means changes the pressure adjustment set value of the variable pressure regulator to a higher value by changing the pressure adjustment set value of the variable pressure regulator to a higher value.
[0246]
(6) The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is replenished by pressurizing the fuel from an external replenishing fuel tank to the fuel tank. A fuel supply device for supplying a gaseous fuel in the fuel tank to the internal combustion engine when the pressure of the fuel to be supplied is equal to or higher than a replenishment pressure.
[0247]
(7) Liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is changed to the saturated vapor characteristic of the fuel in the external replenishing fuel tank. When the saturated vapor temperature is equal to or higher than the saturated vapor temperature obtained by applying a replenishing pressure that is the pressure of the fuel that is pressurized and replenished from the fuel tank to the fuel tank, the gaseous fuel in the fuel tank is supplied to the internal combustion engine. A fuel supply device for a liquefied gas internal combustion engine, comprising a gaseous phase fuel supply means for supplying.
[0248]
(8) The gaseous phase fuel supply means is configured to add the saturated vapor pressure of the fuel stored in the supplementary fuel tank and the fuel in the supplementary fuel tank when the fuel in the supplementary fuel tank is supplemented to the fuel tank. The fuel supply device for a liquefied gas internal combustion engine according to the above (6) or (7), wherein the replenishment pressure is calculated by adding the supplied replenishment pressure.
[0249]
(9) Liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. When the pressure is higher than the pressure and is equal to or higher than the replenishment pressure set to be equal to or lower than the pressure of the fuel to be replenished by being pressurized from the replenishment fuel tank to the fuel tank, the gaseous phase fuel in the fuel tank is supplied to the internal combustion engine A fuel supply device for a liquefied gas internal combustion engine, comprising a gaseous phase fuel supply means for supplying gas to a fuel cell.
[0250]
(10) The liquid phase fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to the internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. Applying a replenishment pressure that is higher than the pressure and equal to or lower than the pressure of the fuel to be replenished by being pressurized from the replenishment fuel tank to the fuel tank to the saturated vapor characteristic of the fuel in the replenishment fuel tank. A gaseous fuel supply means for supplying gaseous fuel in the fuel tank to the internal combustion engine when the temperature of the liquefied gas is equal to or higher than the saturated vapor temperature obtained by Fuel supply system of the engine.
[0251]
(11) The liquid fuel stored in the fuel tank in a saturated state is pumped by the fuel pump, and the pumped liquid fuel is injected and supplied to the internal combustion engine by the fuel injection mechanism, and the fuel in the fuel injection mechanism is supplied. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. When the pressure is equal to or higher than a replenishment pressure obtained by adding a pressure and a predetermined pressure lower than a replenishment pressure applied to the fuel when the fuel in the replenishment fuel tank is replenished to the fuel tank, A fuel supply device for a liquefied gas internal combustion engine, comprising: gas phase fuel supply means for supplying gaseous fuel in a fuel tank to the internal combustion engine.
[0252]
(12) Liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. The replenishment fuel tank obtains a replenishment pressure obtained by adding a pressure and a predetermined pressure lower than a replenishment pressure applied to the fuel when the fuel in the replenishment fuel tank is replenished to the fuel tank. A gaseous fuel supply means for supplying the gaseous fuel in the fuel tank to the internal combustion engine when the temperature becomes equal to or higher than the saturated vapor temperature obtained by applying the saturated vapor characteristic of the fuel in the internal combustion engine. The fuel supply system of the liquefied gas engine, characterized in that.
[0253]
(13) Liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is replenished by pressurizing the fuel from an external replenishing fuel tank to the fuel tank. A fuel supply device for a liquefied gas internal combustion engine, comprising: a pump control means for reducing a work amount of the fuel pump when the pressure becomes equal to or higher than a supply pressure which is a pressure of the fuel to be supplied.
[0254]
(14) The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is changed to the saturated vapor characteristic of the fuel in the external replenishing fuel tank. Pump control means for reducing the amount of work of the fuel pump when the temperature becomes equal to or higher than the saturated steam temperature obtained by applying a replenishing pressure, which is the pressure of fuel pressurized and replenished from the fuel tank to the fuel tank. A fuel supply device for a liquefied gas internal combustion engine, comprising:
[0255]
(15) The pump control means controls the saturation vapor pressure of the fuel stored in the supplementary fuel tank and the fuel vapor in the supplementary fuel tank when the fuel in the supplementary fuel tank is supplemented to the fuel tank. The fuel supply device for a liquefied gas internal combustion engine according to (13) or (14), wherein the replenishment pressure is calculated by adding a replenishment pressure applied to the fuel.
[0256]
(16) The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to the internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is supplied. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. Pump control means for reducing the work of the fuel pump when the pressure is higher than a pressure and equal to or higher than a replenishment pressure set to be equal to or lower than the pressure of fuel to be replenished by being pressurized from the refueling fuel tank to the fuel tank. A fuel supply device for a liquefied gas internal combustion engine, comprising:
[0257]
(17) A liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is supplied. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. Applying a replenishment pressure that is higher than the pressure and equal to or lower than the pressure of the fuel to be replenished by being pressurized from the replenishment fuel tank to the fuel tank to the saturated vapor characteristic of the fuel in the replenishment fuel tank. A fuel supply device for a liquefied gas internal combustion engine, comprising: a pump control means for reducing a work amount of the fuel pump when the temperature becomes equal to or higher than the saturated steam temperature obtained by .
[0258]
(18) Liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the pressure of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. The replenishment pressure obtained by adding the pressure and a predetermined pressure lower than the replenishment pressure applied to the fuel in the replenishment fuel tank when the fuel in the replenishment fuel tank is replenished to the fuel tank is equal to or more than the replenishment pressure obtained. A fuel supply device for a liquefied gas internal combustion engine, comprising: a pump control means for reducing a work amount of the fuel pump.
[0259]
(19) The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is injected. In the fuel supply device for a liquefied gas internal combustion engine that recirculates the fuel from the downstream of the fuel injection mechanism to the fuel tank, the temperature of the fuel in the fuel tank is changed to the saturated vapor of the fuel stored in the external replenishment fuel tank. The replenishment pressure obtained by adding the pressure and a predetermined pressure lower than the replenishment pressure applied to the fuel in the replenishment fuel tank when the fuel in the replenishment fuel tank is replenished to the fuel tank is calculated as Pump control means for reducing the work of the fuel pump when the temperature becomes equal to or higher than the saturated steam temperature obtained by applying the saturated steam characteristic of the fuel in the replenishing fuel tank; The fuel supply system of the liquefied gas engine according to claim Rukoto.
[0260]
(20) When the pressure of the fuel in the fuel injection mechanism is lower than the saturated vapor pressure of the fuel, the pump control means interrupts the process of reducing the work of the fuel pump (13) to (19). The fuel supply device for a liquefied gas internal combustion engine according to any one of (1) to (4).
[0261]
(21) The pump control means according to any one of (13) to (19), wherein when the pressure of the fuel in the fuel injection mechanism is less than the saturated vapor pressure of the fuel, the work amount of the fuel pump is increased. 3. A fuel supply device for a liquefied gas internal combustion engine according to claim 1.
[Brief description of the drawings]
FIG. 1 is a schematic diagram schematically showing the entire configuration of a first embodiment of a fuel supply device for a liquefied gas internal combustion engine according to the present invention.
FIG. 2 is a schematic diagram schematically showing the overall configuration of the fuel supply device of the embodiment.
FIG. 3 is a flowchart showing a driving process of the gas-phase fuel injector performed in the embodiment.
FIG. 4 is a map of a propane ratio used in a driving process of the gas-phase fuel injector performed in the embodiment.
FIG. 5 is a graph showing a saturated vapor pressure curve of liquefied petroleum gas.
FIG. 6 is a graph showing a mode of calculating a stand-up fuel pressure by a driving process of the gas-phase fuel injector performed in the embodiment.
FIG. 7 is a timing chart showing an example of a mode of supplying gas-phase fuel by a driving process of the gas-phase fuel injector performed in the embodiment.
FIG. 8 is a flowchart showing a part of a driving process of a gas-phase fuel injector performed in the second embodiment of the fuel supply device for a liquefied gas internal combustion engine according to the present invention.
FIG. 9 is a graph showing a calculation mode of a refueling saturated steam temperature by a driving process of the gas phase fuel injector performed in the embodiment.
FIG. 10 is a schematic diagram schematically showing the entire configuration of a third embodiment of a liquefied gas internal combustion engine fuel supply apparatus according to the present invention.
FIG. 11 is a schematic view schematically showing the entire configuration of a fourth embodiment of a fuel supply device for a liquefied gas internal combustion engine according to the present invention.
FIG. 12 is a flowchart showing a part of a fuel pump discharge amount changing process performed in the embodiment.
FIG. 13 is a flowchart showing a part of a discharge amount changing process of the fuel pump performed in the embodiment.
FIG. 14 is a graph showing a manner of calculating a stand refueling pressure and a vaporization determination pressure by a fuel pump discharge amount changing process performed in the embodiment.
FIG. 15 is a timing chart showing an example of a mode of changing the fuel discharge amount of the fuel pump by the fuel pump discharge amount changing process performed in the embodiment.
FIG. 16 is a flowchart showing a part of a fuel pump discharge amount changing process performed in the fifth embodiment of the fuel supply device for a liquefied gas internal combustion engine according to the present invention;
FIG. 17 is a flowchart showing a part of a fuel pump discharge amount changing process performed in the liquefied gas internal combustion engine according to the sixth embodiment of the present invention;
FIG. 18 is a graph showing a manner of calculating a vaporization determination temperature by a fuel pump discharge amount changing process performed in the embodiment.
FIG. 19 is a schematic diagram schematically showing the entire configuration of a seventh embodiment of a fuel supply device for a liquefied gas internal combustion engine according to the present invention.
FIG. 20 is a flowchart showing a part of a control valve opening / closing process performed in the embodiment.
FIG. 21 is a timing chart showing an example of a drive mode of each control valve in the control valve opening / closing process performed in the embodiment.
FIG. 22 is a schematic diagram schematically showing the entire configuration of an eighth embodiment of a fuel supply device for a liquefied gas internal combustion engine according to the present invention.
FIG. 23 is a flowchart showing a part of a control valve opening / closing process performed in the embodiment.
FIG. 24 is a schematic view schematically showing the entire configuration of a ninth embodiment of a fuel supply system for a liquefied gas internal combustion engine according to the present invention.
FIG. 25 is a flowchart showing a part of a control valve opening / closing process performed in the embodiment.
FIG. 26 is a schematic view schematically showing the entire configuration of a liquefied gas internal combustion engine fuel supply apparatus according to a tenth embodiment of the present invention.
FIG. 27 is a flowchart showing a part of the driving process of the air conditioner performed in the embodiment.
FIG. 28 is a flowchart showing a part of a driving process of a gas-phase fuel injector performed in the liquefied gas internal combustion engine according to the eleventh embodiment of the present invention.
FIG. 29 is a graph showing a mode of calculating a stand-up fuel supply pressure by a driving process of the gas-phase fuel injector performed in the embodiment.
FIG. 30 is a schematic diagram schematically showing the overall configuration of a conventional fuel supply device for a liquefied petroleum gas internal combustion engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 3 ... Fuel supply device, 5 ... Electronic control device (ECU), 6 ... Detection system, 7 ... Air conditioner (A / C), 11 ... Cylinder block, 12 ... Cylinder, 12a ... Water jacket, 13 ... Cylinder head, 14 ... Crank shaft, 15 ... Connecting rod, 16 ... Piston, 17 ... Combustion chamber, 21 ... Air cleaner, 22 ... Throttle valve, 23 ... Surge tank, 24 ... Intake passage, 25 ... Catalyst, 26 ... Exhaust Passages, 3L: liquid-phase fuel supply system, 3G: gas-phase fuel supply system, LIN: liquid-phase fuel injector, GIN: gas-phase fuel injector, 31: fuel tank, 32: fuel pump, 33: fuel filter, 34: fuel Injection mechanism, 35 ... delivery pipe, 36 ... pressure regulator, 37 ... throttle mechanism, 38 ... pressure regulator, 3 ... High pressure regulator, 40 ... Auxiliary pressure regulator, 61 ... Outside air temperature sensor, 62 ... Tank temperature sensor, 63 ... Tank pressure sensor, 64 ... Injection mechanism temperature sensor, 65 ... Injection mechanism pressure sensor, 71 ... Duct, Rd1 ... Liquid Phase fuel supply path, Rd2 reflux path, Rd3 gas phase fuel supply path, Rd4 bypass path, Rd5 auxiliary reflux path, Rd6 bypass path, Evg gas phase control valve, Evl bypass control valve, Evr Reflux control valve, Evs: Reflux control valve, Evb: Detour reflux control valve.

Claims (28)

The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed to the same fuel. In a fuel supply device for a liquefied gas internal combustion engine that recirculates from the downstream of an injection mechanism to the fuel tank,
When the pressure of the fuel in the fuel tank becomes equal to or higher than the replenishment pressure which is the pressure of the fuel to be replenished by being pressurized from the external replenishment fuel tank to the fuel tank, the pressure of the fuel in the fuel tank is reduced. A fuel supply device for a liquefied gas internal combustion engine, comprising: The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed to the same fuel. In a fuel supply device for a liquefied gas internal combustion engine that recirculates from the downstream of an injection mechanism to the fuel tank,
The replenishment pressure, which is the pressure of the fuel pressurized and replenished from the replenishment fuel tank to the fuel tank, is applied to the saturated vapor characteristic of the fuel in the external replenishment fuel tank. A fuel supply device for a liquefied gas internal combustion engine, comprising: a pressure reducing means for reducing the pressure of the fuel in the fuel tank when the temperature of the fuel becomes equal to or higher than the saturated steam temperature obtained by performing the process. The pressure reducing means is added to the fuel in the supplementary fuel tank when the saturated vapor pressure of the fuel stored in the supplementary fuel tank and the fuel in the supplementary fuel tank are supplied to the fuel tank. 3. The fuel supply device for a liquefied gas internal combustion engine according to claim 1, wherein the replenishment pressure is calculated by adding a replenishing pressure. The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed to the same fuel. In a fuel supply device for a liquefied gas internal combustion engine that recirculates from the downstream of an injection mechanism to the fuel tank,
A fuel in which the pressure of the fuel in the fuel tank is higher than the saturated vapor pressure of the fuel stored in the external replenishing fuel tank, and the fuel replenished by being pressurized from the replenishing fuel tank to the fuel tank A fuel supply device for a liquefied gas internal combustion engine, comprising a pressure reducing means for reducing the pressure of the fuel in the fuel tank when the supply pressure becomes equal to or higher than the supply pressure set to be equal to or lower than the pressure. The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed to the same fuel. In a fuel supply device for a liquefied gas internal combustion engine that recirculates from the downstream of an injection mechanism to the fuel tank,
The temperature of the fuel in the fuel tank is higher than the saturated vapor pressure of the fuel stored in the external replenishing fuel tank, and the fuel replenished by being pressurized from the replenishing fuel tank to the fuel tank Pressure reducing means for reducing the pressure of the fuel in the fuel tank when the replenishing pressure set to be equal to or less than the saturated vapor temperature obtained by applying the replenishing pressure to the saturated vapor characteristic of the fuel in the replenishing fuel tank. A fuel supply device for a liquefied gas internal combustion engine, comprising: The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed to the same fuel. In a fuel supply device for a liquefied gas internal combustion engine that recirculates from the downstream of an injection mechanism to the fuel tank,
The fuel pressure in the fuel tank is equal to the saturated vapor pressure of the fuel stored in the supplementary fuel tank provided outside the fuel supply device, and the fuel in the supplementary fuel tank is supplied to the fuel tank. A pressure reducing means for reducing the pressure of the fuel in the fuel tank when the pressure becomes equal to or higher than a replenishing pressure obtained by adding a predetermined pressure lower than the replenishing pressure applied to the fuel in the replenishing fuel tank when the fuel is supplied. A fuel supply device for a liquefied gas internal combustion engine, comprising: The liquid fuel stored in the fuel tank in a saturated state is pumped by a fuel pump, and the pumped liquid phase fuel is injected and supplied to an internal combustion engine by a fuel injection mechanism, and the fuel in the fuel injection mechanism is fed to the same fuel. In a fuel supply device for a liquefied gas internal combustion engine that recirculates from the downstream of an injection mechanism to the fuel tank,
When the temperature of the fuel in the fuel tank is equal to the saturated vapor pressure of the fuel stored in the external replenishing fuel tank and the fuel in the replenishing fuel tank is replenished to the fuel tank, A replenishing pressure obtained by adding a predetermined pressure lower than the replenishing pressure applied to the fuel in the tank to a saturated steam characteristic obtained by applying the replenishing pressure to the saturated vapor characteristic of the fuel in the replenishing fuel tank; A fuel supply device for the liquefied gas internal combustion engine, comprising: means for reducing the pressure of the fuel in the fuel tank. The fuel supply device for a liquefied gas internal combustion engine according to any one of claims 1 to 7, wherein the pressure reducing unit reduces the pressure of the fuel in the fuel tank by cooling the fuel tank. 9. The fuel supply device for a liquefied gas internal combustion engine according to claim 8, wherein the pressure reducing unit cools the fuel tank by supplying gaseous fuel in the fuel tank to the internal combustion engine. 9. The fuel supply device for a liquefied gas internal combustion engine according to claim 8, wherein said pressure reducing means cools said fuel tank by driving a cooling device for cooling said fuel tank. The fuel supply device for a liquefied gas internal combustion engine according to claim 10, wherein the cooling device for cooling the fuel tank is a vehicle-mounted air conditioner provided in a vehicle equipped with the internal combustion engine. 9. The fuel supply device for a liquefied gas internal combustion engine according to claim 8, wherein the pressure reducing unit cools the fuel tank by cooling fuel recirculated to the fuel tank via the fuel injection mechanism. 10. 13. The fuel pump according to claim 12, wherein the pressure reducing unit drives a cooling device for cooling the fuel returned to the fuel tank via the fuel injection mechanism, thereby cooling the fuel returned to the fuel tank. 7. A fuel supply device for a liquefied gas internal combustion engine according to claim 1. 14. The fuel supply device for a liquefied gas internal combustion engine according to claim 13, wherein the cooling device for cooling the fuel returned to the fuel tank is a vehicle-mounted air conditioner provided in a vehicle equipped with the internal combustion engine. 9. The fuel supply device for a liquefied gas internal combustion engine according to claim 8, wherein the pressure reducing means cools the fuel tank by reducing a work amount of the fuel pump. 9. The fuel supply device for a liquefied gas internal combustion engine according to claim 8, wherein the pressure reducing means cools the fuel tank by reducing a flow rate of the fuel recirculated from the downstream of the fuel injection mechanism to the fuel tank. . The said pressure reducing means reduces the flow rate of the fuel which is recirculated from the downstream of the fuel injection mechanism to the fuel tank by reducing the flow rate of the liquid phase fuel supplied to the fuel injection mechanism. 17. A fuel supply device for a liquefied gas internal combustion engine according to claim 16. The pressure reducing means includes a recirculation path for flowing fuel recirculated from the downstream of the fuel injection mechanism to the fuel tank, and the liquid phase fuel pumped by the fuel pump from the upstream of the fuel injection mechanism to the fuel. The fuel injection system is configured to include a detour path for returning the fuel to the tank, and switching means for selectively activating one of these fuel paths. By activating the detour path through the switching means, the fuel injection 18. The fuel supply device for a liquefied gas internal combustion engine according to claim 17, wherein a flow rate of the liquid phase fuel supplied to a mechanism is reduced. 18. The liquefied gas internal combustion engine according to claim 17, wherein the pressure reducing means reduces the flow rate of the liquid phase fuel supplied to the fuel injection mechanism by reducing a discharge amount of the liquid phase fuel by the fuel pump. Engine fuel supply. 20. The fuel supply device for a liquefied gas internal combustion engine according to claim 19, wherein the pressure reducing means increases a pressure of the fuel in the fuel injection mechanism to reduce a discharge amount of the liquid phase fuel by the fuel pump. . The pressure reducing means is provided in a recirculation path for recirculating the fuel in the fuel injection mechanism from downstream of the fuel injection mechanism to the fuel tank, and the variable pressure pressure is configured to change the pressure of the fuel in the fuel injection mechanism. 21. The fuel for a liquefied gas internal combustion engine according to claim 20, comprising a mechanism, wherein the pressure of the fuel in the fuel injection mechanism is increased by changing a pressure adjustment set value of the variable pressure mechanism to a higher value. Feeding device. 22. The pressure reducing device according to claim 15, wherein when the pressure of the fuel in the fuel injection mechanism is lower than the saturated vapor pressure of the fuel, the process for reducing the pressure of the fuel in the fuel tank is interrupted. 13. A fuel supply device for a liquefied gas internal combustion engine according to any one of the above. 22. The pressure reducing device according to claim 15, wherein the pressure reducing unit reduces the degree of pressure reduction with respect to the fuel pressure in the fuel tank when the pressure of the fuel in the fuel injection mechanism is lower than the saturated vapor pressure of the fuel. Fuel supply device for liquefied gas internal combustion engine. 24. The pressure reducing means estimates the saturated vapor pressure of the fuel in the fuel injection mechanism from the saturated vapor characteristic of the fuel stored in the fuel tank and the temperature of the fuel in the fuel injection mechanism. Liquefied gas internal combustion engine fuel supply device. The pressure reducing means estimates the composition of the fuel based on the temperature and the pressure of the fuel stored in the fuel tank, and stores the fuel in the fuel tank based on the estimated fuel composition. 25. The fuel supply device for a liquefied gas internal combustion engine according to claim 2, wherein the saturated vapor characteristic of the fuel is determined. 26. The fuel supply for a liquefied gas internal combustion engine according to claim 24, wherein the pressure reducing unit sets a pressure obtained by estimating a predetermined pressure to the estimated saturated vapor pressure as a saturated vapor pressure of the fuel in the fuel injection mechanism. apparatus. The pressure reducing means estimates the saturated vapor pressure of the fuel stored in the fuel tank for replenishment from the saturated vapor characteristic of the fuel stored in the fuel tank and the outside air temperature to obtain the replenishment pressure. Item 31. A fuel supply device for a liquefied gas internal combustion engine according to any one of Items 1 to 26. The fuel supply device for a liquefied gas internal combustion engine according to any one of claims 1 to 27, wherein the liquefied gas internal combustion engine is a liquefied petroleum gas internal combustion engine using liquefied petroleum gas as a fuel.

Images