JP2004098886A

JP2004098886A - Automotive fuel tank and manufacturing method thereof

Info

Publication number: JP2004098886A
Application number: JP2002264258A
Authority: JP
Inventors: Joji Kasugai; 春日井　条治
Original assignee: Toyota Motor Corp; FTS Co Ltd
Current assignee: Toyota Motor Corp; FTS Co Ltd
Priority date: 2002-09-10
Filing date: 2002-09-10
Publication date: 2004-04-02

Abstract

【課題】ガスバリヤ性の優れた、重量の少ない自動車用燃料タンクをうること。
【解決手段】アッパタンク１０とロアタンク２０をそれぞれの分割開口の周縁部で接合、溶着して一体とした合成樹脂製の自動車用燃料タンクにおいて、アッパタンクとロアタンクをいずれも、硬質合成樹脂からなる基材層１１と、基材層のタンク内側表面に燃料透過性の低い合成樹脂からなるバリヤ層１２の２層の合成樹脂層で構成し、基材層は、射出成形により形成し、上記バリヤ層は、射出成形または射出圧縮成形により一体に形成した自動車用燃料タンク及びその製造方法である。
これによって、基材層とバリヤ層が密着してガスバリヤ性の優れた、肉厚の均一な軽量化に貢献できる燃料タンクをうることができる。
【選択図】　　　　図１An object of the present invention is to provide an automobile fuel tank having excellent gas barrier properties and low weight.
A synthetic resin automotive fuel tank in which an upper tank (10) and a lower tank (20) are joined and welded together at the peripheral edges of respective divided openings, wherein both the upper tank and the lower tank are made of a hard synthetic resin. A layer 11 and a barrier layer 12 made of a synthetic resin with low fuel permeability are formed on the tank inner surface of the base material layer. The base material layer is formed by injection molding. A fuel tank for an automobile integrally formed by injection molding or injection compression molding, and a method of manufacturing the same.
As a result, a fuel tank that is excellent in gas barrier properties and can contribute to uniform thickness reduction in weight can be obtained by the close contact between the base material layer and the barrier layer.
[Selection diagram] Fig. 1

Description

【０００１】
【発明の属する技術分野】
この発明は、ガソリンなどの燃料を収納する自動車用燃料タンクおよびその製造方法に関する。
【０００２】
【従来の技術】
従来、自動車用に使用されるガソリン等の燃料タンクとしては、強度等の観点から、鉄板等のプレス加工と溶接により製造された金属製の燃料タンクやあるいは加工性等の観点から、合成樹脂をブロー成形した合成樹脂製の燃料タンクが用いられてきた。特に車両の軽量化やデザインの自由度を向上させるために合成樹脂製の燃料タンクが用いられるようになってきた。
【０００３】
しかしながら、このブロー成形で大型の燃料タンクを製造する場合に、加熱され流動状態にあるパリソンを成形機の上部から金型に入れるときに上部の肉厚が下部の肉厚よりも薄くなり、肉厚の均一性が図れなくなる場合があった。また、燃料タンクの形状の凹凸が大きかったり、複雑な場合は、パリソンを金型内で膨張させたときにパリソンの膨張の割合が製品の部位によって異なる場合があり、製品の肉厚にバラツキが生じる場合があった。そのため、製品の肉厚をコントロールすることが難しく、タンク強度等の性能を満足させるためには、製品の全体の肉厚を厚くせざるを得なかった。したがって燃料タンクの重量が増加していた。
また、ブロー成形においてパリソンを金型で挟んで成形するため、比較的大きなバリが発生して、材料の無駄が多く、生産性がよくなかった。
【０００４】
さらに、ブロー成形においてはパリソンを金型内で膨張させるため、燃料タンク内に燃料ポンプユニット、フロート等の装置を配置することに制約があった。そのため、図９と図１０に示すように、金型を用いて燃料タンクの上部と下部を別々に成形してアッパタンク１１０とロアタンク１２０とし、冷却後にそのアッパタンク１１０とロアタンク１２０の成形品を接合して燃料タンクを製造するものがある（例えば、特許文献１参照。）。
しかし、一旦冷却した成形品を接合する場合は、接合部に十分な強度をうるためには接合部が大きくなって燃料タンクの重量が増加していた。
【０００５】
一方、燃料タンクは、地球環境の保護のためにガソリン等が透過しないガスバリヤ性が必要とされている。そこで従来は、ガソリン等の燃料が透過することを防止するために、まずガスバリヤ性を有するフィルムを金型にセットして、真空成形によりそのフィルムを燃料タンク１の形状に成形することによりアッパタンク１１０とロアタンク１２０のバリヤ層１１２、１２２を形成する。その後、図９に示すように、バリヤ層１１２、１２２の上に、即ちバリヤ層１１２、１２２が燃料タンク内側面になるように、基材層１１１、１２１を構成する合成樹脂を射出成形することにより燃料タンクを製造していた。しかし、基材層１１１、１２１を構成する合成樹脂を射出成形するときにバリヤ層１１２、１２２のフィルムがその合成樹脂で引伸ばされる場合があり、十分なバリヤ性を得ることができない恐れもあった。また、バリヤ層１１２、１２２のフィルムと基材層１１１、１２１を構成する合成樹脂との密着性、接合性も十分ではない場合があった。
さらに、接合した周縁部付近では、ガスバリヤ性のシートをすべての周縁部の末端まで漏れなく行き渡らせることが困難な場合があり、ガスバリヤ性も十分ではなかった。
【０００６】
また、燃料タンクを２つに分割したアッパタンクとロアタンクの上下の分割体を成形する金型を一対設けて、それぞれの金型で分割体を射出成形により成形した後に、金型をスライドさせてその各分割体を互いに突き合わせた後に、つき合わせた面の周縁に溶融樹脂を射出して各分割体を互いに融着させる製造方法もあった（例えば、特許文献２参照。）。
しかしながら、この方法では、金型をスライドさせる設備等が複雑で高価なものとなっていた。
【０００７】
【特許文献１】
特開平１０−１５７７３８号公報（第３−４頁、第１図）
【特許文献２】
特開２００１−１２９８５１号公報（第３−５頁、第１図）
【０００８】
【発明が解決しようとする課題】
本発明はかかる事実を考慮して、射出成形または射出圧縮成形により、簡単な設備で製造が容易でガスバリヤ性の優れ、かつ重量を軽くした自動車用燃料タンクを得ること、及びその製造方法を得ることが目的である。
【０００９】
【課題を解決するための手段】
請求項１の本発明は、上下に２分割された燃料タンクの上部を構成するアッパタンクと下部を構成するロアタンクをそれぞれの分割開口の周縁部で接合して一体とした合成樹脂製の自動車用燃料タンクにおいて、アッパタンクとロアタンクをいずれも、硬質合成樹脂からなる基材層と、基材層のタンク内側表面に形成した燃料透過性の低い合成樹脂からなるバリヤ層の２層の合成樹脂層で構成し、基材層は、射出成形により形成し、バリヤ層は、基材層のタンク内側表面に射出成形または射出圧縮成形により一体に形成していることを特徴とする。
【００１０】
請求項１の本発明では、アッパタンクとロアタンクを別々に成形したので、燃料ポンプユニット等を燃料タンク内に装着することが容易である。基材層を射出成形により形成したため、均一な肉厚の燃料タンクを得ることができ、ブロー成形で成形した燃料タンクよりも全体として、薄肉に成形することができ、軽い燃料タンクを得ることができる。また、バリヤ層を基材層のタンク内側表面に射出成形または射出圧縮成形により一体に形成したため、バリヤ層を燃料タンク内側に均一にかつ満遍なく、確実に設けることができ、バリヤ層と基材層が十分に密着したため、ガスバリヤ性の優れた燃料タンクを得ることができる。
【００１１】
請求項２の本発明は、基材層は、そのタンク内側表面に細かい凹凸を設けたものである。
請求項２の本発明は、基材層のタンク内側表面に細かい凹凸を設けたため、バリヤ層を基材層のタンク内側表面に射出成形または射出圧縮成形するときに、バリヤ層が基材層の細かい凹凸の中に進入することができ、接触面積が増加するため、基材層とバリヤ層の密着力が増加する。
【００１２】
請求項３の本発明は、アッパタンクとロアタンクの分割開口の各周縁部において、それぞれ分割開口の全周にわたりアッパタンクとロアタンクのタンク壁は、それぞれの先端が相互に当接するよう先端部を形成し、先端部のそれぞれの当接面にはタンク壁内面から連続して延接したバリヤ層を設けたものである。
【００１３】
請求項３の本発明では、アッパタンクとロアタンクの分割開口の各周縁部に先端部と接合凹部と外周突起部を設け、先端部を互いに当接させたため、分割開口の各周縁部が確実に密着した燃料タンクを得ることができる。
さらに、アッパタンクとロアタンクの先端部が相互に当接する面にもバリヤ層を設けたため、アッパタンクとロアタンクの内面に設けられたバリヤ層から連続して先端部の当接面までバリヤ層が設けられるため、アッパタンクとロアタンクの接合部のガスバリヤ性が確保できる。
【００１４】
請求項４の本発明は、アッパタンクとロアタンクの周縁接合部において、アッパタンクとロアタンクのタンク壁外面の先端部近傍に、断面略Ｌ字状の外周突起部を形成し、周突起部の一端がタンク壁外面と略直角に一体に形成されるとともに他端はタンク壁外面と平行かつ分割開口方向に形成され、アッパタンクとロアタンクの外周突起部とタンク壁の先端部の間には、相互に向き合う方向に開口する断面略Ｕ字状の接合凹部を設け、アッパタンクとロアタンクのそれぞれ設けた接合凹部に、アッパタンクとロアタンクの溶着のために、アッパタンクとロアタンクの基材と相溶性のある融着合成樹脂が注入され、融着合成樹脂とアッパタンクとロアタンクの接合凹部が融着しているものである。
【００１５】
請求項４の本発明では、接合凹部に、アッパタンクとロアタンクの基材層と相溶性のある融着合成樹脂が注入され、融着合成樹脂とアッパタンクとロアタンクの接合凹部の壁面が融着しており、接合凹部がＵ字状になっており融着面積が大きいためアッパタンクとロアタンクが強固に溶着される。
また、接合凹部に融着合成樹脂を注入するのみでよいため、手間がかからず、製造が容易である。
【００１６】
請求項５の本発明は、アッパタンクとロアタンクのタンク壁外面の先端部近傍に、断面略Ｌ字状の外周突起部を形成し、外周突起部の一端がタンク壁外面と略直角に一体に形成されるとともに他端はタンク壁外面と平行かつ分割開口方向に形成され、アッパタンクとロアタンクの周縁部の外周突起部は、相互に熱融着しているものである。
請求項５の本発明では、アッパタンクとロアタンクの周縁部の外周突起部を相互に熱溶着しているため、アッパタンクとロアタンクが強固に接合される。
また、単に熱溶着するのみでよいため、手間がかからず、製造が容易である。
【００１７】
請求項６の本発明は、上下に２分割された燃料タンクの、上部を構成するアッパタンクと下部を構成するロアタンクを別々に形成した後、アッパタンクとロアタンクの分割開口の周縁部を接合して製造する合成樹脂製の自動車用燃料タンクの製造方法において、アッパタンクとロアタンクはいずれも、硬質合成樹脂を金型に射出成形することにより基材層を形成する工程と、金型を少し開いて燃料透過性の低い合成樹脂を基材層のタンク内側表面に射出し、射出成形または射出圧縮成形によりバリヤ層を一体に形成する工程と、アッパタンクとロアタンクの周縁接合部を接合する工程を有するものである。
【００１８】
請求項６の本発明では、基材層を射出成形により成形した後に、金型を少し開いて燃料透過性の低い合成樹脂を基材層のタンク内側表面に射出し、金型を閉じバリヤ層を一体に形成する工程を有するため、同じ金型を用いて成形でき、コストを下げることができるとともに、簡単な工程で薄層のバリヤ層を形成することができ、基材層の全面にバリヤ層を設けることができる。
また、金型を用いて射出成形により燃料タンクを製造するため、均一なタンク壁を形成できるため、全体としてタンク壁を薄くすることができ、燃料タンクを軽くすることができるとともに、均一なバリヤ層を形成することができ、燃料タンクのガスバリヤ性を向上することができる。
【００１９】
請求項７の本発明は、アッパタンクとロアタンクの周縁部を接合する工程において、アッパタンクとロアタンクの周縁部にそれぞれ設けた接合凹部に、アッパタンクとロアタンクの基材と相溶性のある融着合成樹脂を射出成形することによりアッパタンクとロアタンクを融着したものである。
請求項７の本発明では、アッパタンクとロアタンクの周縁部にそれぞれ設けた接合凹部に、アッパタンクとロアタンクの基材と相溶性のある合成樹脂を射出成形するのみで、アッパタンクとロアタンクを強固に融着することができ、簡単な工程で確実に接合することができる。
【００２０】
請求項８の本発明は、アッパタンクとロアタンクの周縁部を接合する工程において、アッパタンクとロアタンクの周縁部の外周突起部を、それぞれ熱板により融解し、相互に熱溶着したものである。
請求項８の本発明では、アッパタンクとロアタンクの周縁部の外周突起部を熱板を使用して熱溶着したため、簡単な設備と工程で、強固に溶着された燃料タンクを得ることができる。
【００２１】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づき説明する。
図１は、本発明の実施の態様を示す合成樹脂製の自動車用燃料タンクの斜視図である。図２は、図１のＬ−Ｌ線に沿った断面図であり、図３は、図１のＷ−Ｗ線に沿った断面図である。
燃料タンク１は、半割の上部半分を形成するアッパタンク１０と半割の下部半分を形成するロアタンク２０からなり、アッパタンク１０とロアタンク２０には燃料タンク１の外表面に燃料タンク１の強度を増すために、それぞれ補強リブ１５、２５が設けられている。
アッパタンク１０には、ポンプユニット２を取付けるポンプユニット取付孔３と燃料供給管を取付けるパイプ取付孔４が設けられている。
【００２２】
アッパタンク１０とロアタンク２０は、それぞれ基材層１１、２１とバリヤ層１２、２２の２層から構成される。
図２のＡで示す部分の拡大図が図４である。図４に示すように、アッパタンク１０とロアタンク２０のそれぞれ基材層１１、２１は、燃料タンク１の内側の表面に細かい凹凸が設けられている。
この細かい凹凸は、例えば基材層１１、２１の表面に、シボ模様、ディンプル模様、細かいアンダーカット模様を付けることにより設けることができる。この細かい凹凸にバリヤ層１２、２２を構成する合成樹脂が入り込み、基材層１１、２１とバリヤ層１２、２２が強固に接合される。
【００２３】
図１に示すように、アッパタンク１０とロアタンク２０は、分割開口の周縁部で全周にわたり強固に接合されている。接合の詳細な２つの態様を図５と図６に示す。図５の態様における接合は、接合されるアッパタンク１０とロアタンク２０の間に溶融樹脂を注入して融着する方法であり、図６の態様における接合は、接合されるアッパタンク１０とロアタンク２０の接合面を溶融して直接接合する溶着方法である．
図５の態様において、アッパタンク１０とロアタンク２０の分割開口の周縁部１６、２６は、先端部１６ａ、２６ａと外周突起部１６ｃ、２６ｃおよびその間にある接合凹部１６ｂ、２６ｂからなる。
アッパタンク１０の周縁部１６を例にとり説明するが、ロアタンク２０の周縁部２６も同様である。
アッパタンク１０の周縁部１６の先端部１６ａは、アッパタンク１０のタンク壁の一部としてその先端の部分に分割開口の全周にわたり形成され、ロアタンク２０の先端部２６ａと全周にわたり当接している。このため、先端部１６ａがロアタンク２０の先端部２６ａに当接すると、アッパタンク１０とロアタンク２０の分割開口の周縁部１６、２６の燃料タンク１の内面は一体的にスムースな連続した面を構成する。
【００２４】
先端部１６ａは、その先端でロアタンク２０の先端部２６ａに当接する面が平面状をなし、その平面にはアッパタンク１０の内面のバリヤ層１２から連続したバリヤ層１２が設けられている。ロアタンク２０の先端部２６ａの平面にも同様にロアタンク２０の内面のバリヤ層２２から連続したバリヤ層２２が設けられている。したがって、アッパタンク１０の先端部１６ａの先端がロアタンク２０の先端部２６ａの先端に当接すると、バリヤ層１２、２２は燃料タンク１の内面に一様に連続して設けられるとともに、周縁部１６、２６の先端部１６ａ、２６ａの接合面までバリヤ層１２、２２が形成されるため、燃料タンク１の接合面のバリヤ性が確保できる。
【００２５】
接合凹部１６ｂは、先端部１６ａの外周側に隣接して、先端部１６ａと外周突起部１６ｃとの間に設けられ、断面略Ｕ字状の凹部である。接合凹部１６ｂの断面略Ｕ字状の凹部は、ロアタンク２０と接合する方向に開口している。このため、先端部１６ａがロアタンク２０の先端部２６ａに当接すると、接合凹部１６ｂの断面略Ｕ字状の凹部は、ロアタンク２０の接合凹部２６ｂの開口と向かい合うようになり、断面略楕円形の凹部を形成する。
この断面略楕円形の凹部、即ち両接合凹部１６ｂ、２６ｂに、図５の実施態様では、アッパタンクとロアタンクの基材層１１、２１と相溶性のある融着合成樹脂が注入される。そのため、注入された融着合成樹脂とアッパタンクとロアタンクの接合凹部の壁が融着することができる。また、接合凹部１６ｂが断面Ｕ字状になっており融着面積が大きいためアッパタンクとロアタンクが強固に接合される。
【００２６】
外周突起部１６ｃは、先端部１６ａの近傍で、接合凹部１６ｂの外周側に隣接して設けられる。即ち、先端部１６ａと外周突起部１６ｃで接合凹部１６ｂを挟むように形成される。
外周突起部１６ｃは、アッパタンク１０のタンク壁外面の先端部１６ａ近傍に、断面略Ｌ字状に形成される。即ち、その一端がアッパタンクの先端部１６ａの先端から若干離れたタンク壁外面からそのタンク壁外面略直角に一体に形成されるとともに、他端がタンク壁外面と平行でかつ分割開口方向に形成されて、ロアタンク２０の外周突起部２６ｃと向い合うように設けられる。従って、外周突起部１６ｃは、接合凹部１６ｂの底壁と外周側の側壁を構成することとなる。
【００２７】
外周突起部１６ｃは、アッパタンク１０の分割開口の周縁部１６近傍の外壁から断面略Ｔ字状に一体的に延設することもできる。この場合は、Ｔ字状の脚部がアッパタンク１０の外壁から延びる点と、Ｔ字状の頭部の一方の端がロアタンク２０の外周突起部２６ｃに向い合う方向に突出する点は断面略Ｌ字状の実施の態様と同じであるが、Ｔ字状の頭部の他方の端がその反対方向に突出している点が断面略Ｌ字状の実施の態様と異なる。断面略Ｔ字状の外周突起部１６ｃの場合は、アッパタンク１０とロアタンク２０が接合するときに、断面略Ｌ字状の実施の態様と異なるＴ字状の頭部の他方の端を、挟持して互いに圧接することができるため、アッパタンク１０とロアタンク２０の周縁部をより強固に接合できる。
【００２８】
図５の実施の態様では、アッパタンク１０とロアタンク２０が接合されると、前述の通り両外周突起部１６ｃ、２６ｃは、相互に向き合って断面略楕円形の凹部を形成する。しかし、両外周突起部１６ｃ、２６ｃの先端は、接触せずに、隙間がある。この隙間からアッパタンクとロアタンクの基材層１１，２１と相溶性のある融着合成樹脂が注入されるため、アッパタンク１０とロアタンク２０が強固に接合される。
【００２９】
図６の実施の態様では、両外周突起部１６ｃ、２６ｃの先端は、図５の実施の態様よりも長く延設される。その両外周突起部１６ｃ、２６ｃの先端は、熱溶着により相互に溶着される。このため、アッパタンク１０とロアタンク２０が強固に接合される。溶着されるときに、先端部１６ａ、２６ａが分割開口の全周にわたり相互に当接するまで、両外周突起部１６ｃ、２６ｃが相互に強く圧接され先端が溶融される。先端部１６ａ、２６ａの平面にはアッパタンク１０とロアタンク２０の内面から連続したバリヤ層１２、２２が設けられている。したがって、アッパタンク１０の先端部１６ａがロアタンク２０の先端部２６ａに当接すると、バリヤ層１２、２２は燃料タンク１の内面に一様に連続して設けられるとともに、周縁部１６、２６の接合面までバリヤ層１２、２２が形成されるため、燃料タンク１のバリヤ性が確保できる。
【００３０】
また、両接合凹部１６ｂ、２６ｂが相互に向き合って断面略楕円形の凹部を形成した凹部は、熱溶着時に発生した両外周突起部１６ｃ、２６ｃの溶融樹脂のはみ出し部分を収容することができるため、アッパタンク１０とロアタンク２０の溶着が確実に十分できる。
この熱溶着は、先端部１６ａ、２６ａが相互に強固に当接するように、前述のとおり先端が加熱溶融された両外周突起部１６ｃ、２６ｃを相互に押圧することによりなされる。
【００３１】
本発明で基材層１１，２１に用いられる合成樹脂は、強度がある硬質熱可塑性樹脂材料であれば特に限定されないが、好ましくはポリオレフィン系樹脂を主成分とするポリオレフィン系樹脂材料を用いることができる。ポリオレフィン系樹脂としては、ポリプロピレン系樹脂、ポリエチレン系樹脂のいずれでもよい。
ポリプロピレン系樹脂としては、プロピレン単独重合体、プロピレンーエチレンブロック共重合体を用いることができる。
ポリエチレン系樹脂としては、高密度ポリエチレンまたは中密度ポリエチレンを用いることができる。
【００３２】
ポリオレフィン系樹脂以外の硬質熱可塑性樹脂としては、ポリアミド系樹脂、ポリビニール系樹脂を用いることができる。これらの熱可塑性樹脂は単独で用いることもできるし、２種類以上の樹脂をブレンドして用いることもできる。
さらに本発明で基材層１１，２１に用いられる硬質合成樹脂は、補強のために用いられるガラス繊維、無機繊維、炭素繊維、金属繊維等を充填することもできる。
また、弾性向上のためにゴム成分例えばＥＰＤＭ，ＥＰＲ等をブレンドして用いることもできる。
【００３３】
本発明でバリヤ層１２、２２に用いられる合成樹脂は、ガソリン等の燃料透過を防止することができるガスバリヤ性のよい、流動性の優れた樹脂を用いる。この樹脂としては例えばエチレンビニルアルコール樹脂（ＥＶＯＨ）、ポリフェニレンスルフィド（ＰＰＳ）、液晶性ポリマー（ＬＣＰ）等を用いることができる。しかしこれらの樹脂に限られることなく燃料透過に対してガスバリヤ性を有し、流動性の優れた樹脂であれば使用することができる。
【００３４】
次に本発明の自動車用燃料タンクの製造方法を、図７と図８に基づいて説明する。
アッパタンク１０とロアタンク２０は、別々に成形される。アッパタンク１０を例に取り説明する。アッパタンク１０の成形は、まず図７の（ａ）に示すように、金型４０にその射出ゲート４３ａから基材層１１を形成する上記の硬質合成樹脂を射出し、基材層１１を成形する。
その後、まず図７の（ｂ）に示すように、可動型４２を僅かに開き、バリヤ層１２を形成する合成樹脂を射出ゲート４３ｂから基材層１１に射出する。これにより基材層１１の内側面、即ち燃料タンク１の内面を形成する側に、バリヤ層１２を薄く均一に形成する。射出する合成樹脂は流動性が高い合成樹脂を使用するので基材層１１の内側面の全域に流動し、バリヤ層１２を形成することができる。
【００３５】
バリヤ層１２の形成は、可動型４２を僅かに開きバリヤ層１２を形成する樹脂を基材層１１に射出した後に、金型４０を再度閉じて射出したバリヤ層１２の樹脂を圧縮する射出圧縮成形により成形することもできる。この場合はバリヤ層１２を基材層１１に強く圧縮することができるためバリヤ層１２を薄肉にできるとともにより一層バリヤ層１２と基材層１１の密着度が向上する。
【００３６】
バリヤ層１２を成形するときに、金型４０を僅かに開いて、バリヤ層１２の樹脂を射出するが、このとき図８に示すように、アッパタンク１０の周縁部１６の先端部１６ａは、外周側の壁即ち、接合凹部１６ｂを形成する壁の面が金型４０の移動方向と同じであるため、先端部１６ａの外周側の壁と固定型４１との間に隙間が生じない。このため、射出されたバリヤ層１２を形成する合成樹脂は、先端部１６ａの先端面で止まる。したがって、バリヤ層１２はアッパタンク１０の内面から先端部１６ａの先端の面まで確実に形成され、それ以上に接合凹部１６ｂにまで形成されることはない。
【００３７】
このようにしてアッパタンク１０とロアタンク２０は別々に成形される。その後アッパタンク１０とロアタンク２０の周縁部１６、２６は、相互に強固に接合される。
図５の実施の態様では、アッパタンク１０とロアタンク２０の周縁部１６、２６の先端部１６ａ、２６ａが相互に当接する。このとき接合凹部１６ｂ、２６ｂは、互いに開口が向き合って断面略楕円状の空間を形成し、外周突起部１６ｃ、２６ｃは互いに向い合った状態でその間には隙間がある。この隙間から断面略楕円状の空間に基材層１１、２１と相溶性のある合成樹脂を注入する。基材層１１、２１と相溶性のある融着合成樹脂とは、基材層１１、２１と同じ合成樹脂が好ましいが、相溶性のある合成樹脂であれば適宜用いることができる。この融着合成樹脂と基材層１１、２１が融着することによりアッパタンク１０とロアタンク２０が強固に接合される。この融着合成樹脂を注入するときに先端部１６ａ、２６ａは相互に強く圧接されているので、アッパタンク１０とロアタンク２０の接合面は密着して隙間が生じることはない。
【００３８】
図６の実施の態様では、前述の通り外周突起部１６ｃ、２６ｃが長く延設されている。この長く延設された外周突起部１６ｃ、２６ｃの先端を熱板等の加熱手段で加熱し、溶融または軟化させる。このアッパタンク１０とロアタンク２０の溶融または軟化された外周突起部１６ｃ、２６ｃを相互に当接し、強固に圧接する。そうすると、外周突起部１６ｃ、２６ｃの先端は相互に溶着し、外周突起部１６ｃ、２６ｃの寸法が溶融して短くなるとともに、先端部１６ａ、２６ａの先端も相互に強く接合し、アッパタンク１０とロアタンク２０の接合面は密着して隙間が生じることはない。
【００３９】
外周突起部１６ｃ、２６ｃを相互に当接し、強固に押しつけると溶融または軟化した合成樹脂は、両側にはみ出すが、車内側にはみ出した合成樹脂は、接合凹部１６ｂ、２６ｂの中に収容することができ先端部１６ａ、２６ａの当接面に影響を及ぼすことがないため、燃料タンク１のバリヤ性は確保される。
車外側にはみ出した合成樹脂は、ナイフ等で切り取ることができる。
以上の工程により、アッパタンク１０とロアタンク２０を別々に成形し、その後接合、溶着して一体とした自動車用の燃料タンク１を製造することができる。
【００４０】
【発明の効果】
本発明は、燃料透過に対するガスバリヤ性の優れた燃料タンクの壁を均一にすることができ、その重量を軽くすることができたため、車両の軽量化に貢献できる。また、アッパタンクとロアタンクを強固に接合した燃料タンクを得ることができる。さらに、材料の無駄が減少し、低コストで、燃料タンクのバリヤ層と基材層が強固に接合した燃料タンクを得ることができる。
また、本発明は、燃料透過に対するガスバリヤ性の優れた燃料タンクを簡単な方法で、早く、安価に製造することができる燃料タンクの製造方法である。
【図面の簡単な説明】
【図１】本発明の自動車用燃料タンクの斜視図である。
【図２】本発明の自動車用燃料タンクの図１のＬ−Ｌ線に沿った断面図である。
【図３】本発明の自動車用燃料タンクの図１のＷ−Ｗ線に沿った断面図である。
【図４】本発明の自動車用燃料タンクの図２のＡ部分の一部拡大断面図である。
【図５】本発明の自動車用燃料タンクの図２のＢ部分の一部拡大断面図である。
【図６】本発明の自動車用燃料タンクの図２のＢ部分の一部拡大断面図である。
【図７】本発明の自動車用燃料タンクを製造する金型の断面図である。（ａ）は、基材層の合成樹脂を射出する前の図であり、（ｂ）は、基材層の合成樹脂を射出した後、金型を僅かに開いた図である。
【図８】本発明の自動車用燃料タンクを製造する金型の断面図でＣ部分の一部拡大断面図である。
【図９】従来の自動車用燃料タンクを製造する金型の断面図である。
【図１０】従来の自動車用燃料タンクの断面図である。
【符号の説明】
１　燃料タンク
１０　アッパタンク
１１、２１　基材層
１２、２２　バリヤ層
１６、２６　周縁部
１６ａ、２６ａ　先端部
１６ｂ、２６ｂ　接合凹部
１６ｃ、２６ｃ　外周突起部
２０　ロアタンク
４０　金型[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automobile fuel tank for storing fuel such as gasoline and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, as a fuel tank for gasoline or the like used for automobiles, from the viewpoint of strength and the like, a metal fuel tank manufactured by pressing and welding an iron plate or the like, or a synthetic resin from the viewpoint of workability, etc. Blow molded synthetic resin fuel tanks have been used. In particular, fuel tanks made of synthetic resin have been used in order to reduce the weight of the vehicle and improve the degree of freedom in design.
[0003]
However, when manufacturing a large-sized fuel tank by blow molding, when a heated and fluid parison is put into a mold from the upper part of the molding machine, the upper part becomes thinner than the lower part. In some cases, thickness uniformity could not be achieved. Also, if the shape of the fuel tank is large or complex, the expansion ratio of the parison when the parison is expanded in the mold may differ depending on the part of the product, and the thickness of the product may vary. May have occurred. Therefore, it is difficult to control the thickness of the product, and in order to satisfy the performance such as the tank strength, the entire thickness of the product must be increased. Therefore, the weight of the fuel tank was increased.
In addition, since the parison is sandwiched between molds in blow molding, relatively large burrs are generated, waste of material is large, and productivity is not good.
[0004]
Further, in the blow molding, since the parison is expanded in the mold, there is a restriction in disposing devices such as a fuel pump unit and a float in the fuel tank. Therefore, as shown in FIGS. 9 and 10, the upper and lower parts of the fuel tank are separately molded using a mold to form an upper tank 110 and a lower tank 120, and after cooling, the molded articles of the upper tank 110 and the lower tank 120 are joined. There is one that manufactures a fuel tank by using a conventional method (for example, see Patent Document 1).
However, when joining molded articles that have been cooled once, the joints become large and the weight of the fuel tank increases in order to obtain sufficient strength at the joints.
[0005]
On the other hand, a fuel tank is required to have a gas barrier property that does not allow gasoline or the like to pass therethrough in order to protect the global environment. Therefore, conventionally, in order to prevent fuel such as gasoline from permeating, first, a film having gas barrier properties is set in a mold, and the film is formed into the shape of the fuel tank 1 by vacuum forming, thereby forming the upper tank 110. Then, barrier layers 112 and 122 of the lower tank 120 are formed. Thereafter, as shown in FIG. 9, the synthetic resin forming the base material layers 111 and 121 is injection-molded on the barrier layers 112 and 122, that is, such that the barrier layers 112 and 122 are on the inner side surfaces of the fuel tank. Manufactured the fuel tank. However, when the synthetic resin forming the base layers 111 and 121 is injection-molded, the films of the barrier layers 112 and 122 may be stretched by the synthetic resin, and there is a possibility that sufficient barrier properties may not be obtained. Was. Further, the adhesiveness and the bondability between the films of the barrier layers 112 and 122 and the synthetic resin constituting the base layers 111 and 121 are sometimes insufficient.
Further, in the vicinity of the joined peripheral portion, it may be difficult to spread the gas barrier sheet to the ends of all the peripheral portions without leakage, and the gas barrier property is not sufficient.
[0006]
Also, a pair of molds for forming upper and lower divided bodies of the upper tank and the lower tank in which the fuel tank is divided into two are provided, and after the divided bodies are formed by injection molding with the respective molds, the mold is slid. There has also been a manufacturing method in which, after abutting the divided bodies with each other, a molten resin is injected into a peripheral edge of a face to which the divided bodies are fused to fuse the divided bodies together (for example, see Patent Document 2).
However, in this method, the equipment for sliding the mold and the like are complicated and expensive.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. H10-1557738 (page 3-4, FIG. 1)
[Patent Document 2]
JP 2001-129851 A (Pages 3-5, FIG. 1)
[0008]
[Problems to be solved by the invention]
In view of the above, the present invention provides an automobile fuel tank which is easy to manufacture with simple equipment, has excellent gas barrier properties, and has a reduced weight, by injection molding or injection compression molding. That is the purpose.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an automobile fuel made of a synthetic resin in which an upper tank constituting an upper part of a fuel tank divided into upper and lower parts and a lower tank constituting a lower part are joined together at a peripheral portion of each divided opening. In the tank, both the upper tank and the lower tank are composed of two synthetic resin layers, a base layer made of a hard synthetic resin and a barrier layer made of a synthetic resin with low fuel permeability formed on the tank inner surface of the base layer. The base layer is formed by injection molding, and the barrier layer is integrally formed on the inner surface of the base layer in the tank by injection molding or injection compression molding.
[0010]
According to the first aspect of the present invention, since the upper tank and the lower tank are separately formed, it is easy to mount the fuel pump unit and the like in the fuel tank. Since the base material layer is formed by injection molding, a fuel tank having a uniform thickness can be obtained, and as a whole, it can be formed thinner than a fuel tank formed by blow molding, and a light fuel tank can be obtained. it can. Further, since the barrier layer is integrally formed on the inner surface of the base layer by injection molding or injection compression molding, the barrier layer can be provided uniformly and evenly inside the fuel tank without fail. Are sufficiently adhered to each other, so that a fuel tank having excellent gas barrier properties can be obtained.
[0011]
According to a second aspect of the present invention, the substrate layer is provided with fine irregularities on the inner surface of the tank.
According to the present invention of Claim 2, since fine irregularities are provided on the tank inner surface of the base material layer, when the barrier layer is injection-molded or injection-compressed on the tank inner surface of the base material layer, the barrier layer is formed of the base material layer. Since it can penetrate into fine irregularities and the contact area increases, the adhesion between the base material layer and the barrier layer increases.
[0012]
According to a third aspect of the present invention, at each peripheral portion of the divided openings of the upper tank and the lower tank, the tank walls of the upper tank and the lower tank are formed with a leading end portion such that their leading ends contact each other over the entire circumference of the divided opening, Each of the abutting surfaces of the tip portions is provided with a barrier layer continuously extending from the inner surface of the tank wall.
[0013]
According to the third aspect of the present invention, the front end, the joining recess, and the outer peripheral projection are provided at the respective peripheral edges of the divided openings of the upper tank and the lower tank, and the front ends are brought into contact with each other. Fuel tank can be obtained.
Furthermore, since the barrier layer is also provided on the surface where the tip of the upper tank and the lower tank contact each other, the barrier layer is provided continuously from the barrier layer provided on the inner surface of the upper tank and the lower tank to the contact surface of the tip. The gas barrier property at the joint between the upper tank and the lower tank can be ensured.
[0014]
According to a fourth aspect of the present invention, an outer peripheral projection having a substantially L-shaped cross section is formed near the front end of the outer wall surface of the tank between the upper tank and the lower tank at a peripheral edge joint between the upper tank and the lower tank. The other end is formed substantially at right angles to the wall outer surface, and the other end is formed in parallel with the tank wall outer surface and in the direction of the divided opening, and between the outer protrusions of the upper tank and the lower tank and the tip of the tank wall, the directions facing each other A joint concave portion having a substantially U-shaped cross section that opens into the upper and lower tanks is provided with a fusion synthetic resin compatible with the base material of the upper tank and the lower tank in order to weld the upper tank and the lower tank. The injected synthetic resin is fused to the joint concave portions of the upper tank and the lower tank.
[0015]
According to the fourth aspect of the present invention, a fusion synthetic resin compatible with the base layer of the upper tank and the lower tank is injected into the joint recess, and the fusion synthetic resin and the wall surface of the joint recess of the upper tank and the lower tank are fused. Since the joining concave portion is U-shaped and has a large fusion area, the upper tank and the lower tank are firmly welded.
In addition, since it is only necessary to inject the fusion synthetic resin into the joint concave portion, no labor is required and the production is easy.
[0016]
According to a fifth aspect of the present invention, an outer peripheral projection having a substantially L-shaped cross section is formed near the front end of the outer wall of the tank of the upper tank and the lower tank, and one end of the outer peripheral projection is integrally formed substantially perpendicular to the outer surface of the tank wall. At the same time, the other end is formed parallel to the outer surface of the tank wall and in the direction of the divided opening, and the outer peripheral projections at the peripheral edges of the upper tank and the lower tank are thermally fused to each other.
According to the fifth aspect of the present invention, since the outer peripheral projections at the peripheral edges of the upper tank and the lower tank are mutually heat-welded, the upper tank and the lower tank are firmly joined.
Further, since only heat welding is required, no labor is required and the production is easy.
[0017]
According to a sixth aspect of the present invention, the upper and lower fuel tanks of the fuel tank divided into upper and lower parts are separately formed, and then the upper tank and the lower tank are joined by joining the peripheral edges of the divided openings. In the method of manufacturing an automotive fuel tank made of a synthetic resin, the upper tank and the lower tank are both formed by injection molding a hard synthetic resin into a mold to form a base material layer, and by slightly opening the mold to transmit fuel. A step of injecting a low-resistance synthetic resin into the tank inner surface of the base material layer to form a barrier layer integrally by injection molding or injection compression molding, and a step of joining a peripheral joint portion between the upper tank and the lower tank. .
[0018]
According to the sixth aspect of the present invention, after the base material layer is formed by injection molding, the mold is slightly opened to inject a synthetic resin having low fuel permeability into the tank inner surface of the base material layer to close the mold and close the barrier layer. Since it has a process of integrally forming the same, the same mold can be used to reduce the cost, and a thin barrier layer can be formed by a simple process. Layers can be provided.
In addition, since the fuel tank is manufactured by injection molding using a mold, a uniform tank wall can be formed, so that the tank wall can be made thinner as a whole, and the fuel tank can be made lighter and a uniform barrier can be obtained. A layer can be formed, and the gas barrier properties of the fuel tank can be improved.
[0019]
According to a seventh aspect of the present invention, in the step of joining the peripheral portions of the upper tank and the lower tank, a fusion synthetic resin compatible with the base material of the upper tank and the lower tank is filled in the joining concave portions provided on the peripheral portions of the upper tank and the lower tank. The upper tank and the lower tank are fused by injection molding.
According to the seventh aspect of the present invention, the upper tank and the lower tank are firmly fused only by injection molding a synthetic resin having compatibility with the base material of the upper tank and the lower tank in the joint concave portions provided on the peripheral edges of the upper tank and the lower tank. And the joining can be reliably performed by a simple process.
[0020]
According to an eighth aspect of the present invention, in the step of joining the peripheral portions of the upper tank and the lower tank, the outer peripheral protruding portions of the peripheral portions of the upper tank and the lower tank are melted by a hot plate, respectively, and heat-welded to each other.
According to the eighth aspect of the present invention, since the outer peripheral projections at the peripheral edges of the upper tank and the lower tank are heat-welded using a hot plate, a strongly welded fuel tank can be obtained with simple equipment and steps.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of an automotive fuel tank made of synthetic resin showing an embodiment of the present invention. FIG. 2 is a sectional view taken along line LL of FIG. 1, and FIG. 3 is a sectional view taken along line WW of FIG.
The fuel tank 1 includes an upper tank 10 that forms an upper half of a half and a lower tank 20 that forms a lower half of a half. The upper tank 10 and the lower tank 20 increase the strength of the fuel tank 1 on the outer surface of the fuel tank 1. For this purpose, reinforcing ribs 15 and 25 are provided, respectively.
The upper tank 10 is provided with a pump unit mounting hole 3 for mounting the pump unit 2 and a pipe mounting hole 4 for mounting the fuel supply pipe.
[0022]
The upper tank 10 and the lower tank 20 are respectively composed of two layers of base layers 11, 21 and barrier layers 12, 22.
FIG. 4 is an enlarged view of a portion indicated by A in FIG. As shown in FIG. 4, the base layers 11 and 21 of the upper tank 10 and the lower tank 20 have fine irregularities on the inner surface of the fuel tank 1.
The fine unevenness can be provided, for example, by forming a grain pattern, a dimple pattern, or a fine undercut pattern on the surfaces of the base material layers 11 and 21. The synthetic resin forming the barrier layers 12 and 22 enters into these fine irregularities, and the base layers 11 and 21 and the barrier layers 12 and 22 are firmly joined.
[0023]
As shown in FIG. 1, the upper tank 10 and the lower tank 20 are firmly joined over the entire periphery at the peripheral edge of the divided opening. Two detailed embodiments of the joining are shown in FIGS. The joining in the embodiment of FIG. 5 is a method of injecting and fusing a molten resin between the upper tank 10 and the lower tank 20 to be joined, and the joining in the embodiment of FIG. 6 is the joining of the upper tank 10 and the lower tank 20 to be joined. This is a welding method in which surfaces are fused and joined directly.
In the embodiment shown in FIG. 5, the peripheral edges 16, 26 of the divided openings of the upper tank 10 and the lower tank 20 are composed of tip portions 16a, 26a, outer peripheral projections 16c, 26c, and joining recesses 16b, 26b located therebetween.
The description will be made taking the peripheral portion 16 of the upper tank 10 as an example, but the same applies to the peripheral portion 26 of the lower tank 20.
The front end 16a of the peripheral portion 16 of the upper tank 10 is formed as a part of the tank wall of the upper tank 10 over the entire circumference of the divided opening at the front end thereof, and is in contact with the front end 26a of the lower tank 20 over the entire circumference. Therefore, when the distal end portion 16a abuts on the distal end portion 26a of the lower tank 20, the inner surfaces of the fuel tank 1 at the peripheral edges 16, 26 of the divided openings of the upper tank 10 and the lower tank 20 integrally form a smooth continuous surface. .
[0024]
The front end portion 16a has a flat surface in contact with the front end portion 26a of the lower tank 20 at the front end, and a barrier layer 12 continuous from the barrier layer 12 on the inner surface of the upper tank 10 is provided on the flat surface. Similarly, a barrier layer 22 continuous from the barrier layer 22 on the inner surface of the lower tank 20 is provided on the flat surface of the distal end portion 26 a of the lower tank 20. Therefore, when the tip of the tip 16a of the upper tank 10 abuts on the tip of the tip 26a of the lower tank 20, the barrier layers 12, 22 are uniformly and continuously provided on the inner surface of the fuel tank 1, and the peripheral edges 16, Since the barrier layers 12 and 22 are formed up to the joint surface between the tip portions 16a and 26a of the fuel cell 26, the barrier properties of the joint surface of the fuel tank 1 can be secured.
[0025]
The joint concave portion 16b is provided between the distal end portion 16a and the outer peripheral protrusion 16c, adjacent to the outer peripheral side of the distal end portion 16a, and is a concave portion having a substantially U-shaped cross section. The concave portion having a substantially U-shaped cross section of the joint concave portion 16b opens in a direction in which the joint concave portion 16b is joined to the lower tank 20. Therefore, when the distal end portion 16a comes into contact with the distal end portion 26a of the lower tank 20, the concave portion having a substantially U-shaped cross section of the joint concave portion 16b faces the opening of the joint concave portion 26b of the lower tank 20, and has a substantially elliptical cross section. A recess is formed.
In the embodiment shown in FIG. 5, a fused synthetic resin compatible with the base layers 11 and 21 of the upper tank and the lower tank is injected into the recesses having a substantially elliptical cross section, that is, the two joining recesses 16b and 26b. Therefore, the injected fused synthetic resin and the wall of the joint concave portion between the upper tank and the lower tank can be fused. Further, since the joining concave portion 16b has a U-shaped cross section and has a large fusion area, the upper tank and the lower tank are strongly joined.
[0026]
The outer peripheral protrusion 16c is provided near the distal end 16a and adjacent to the outer peripheral side of the joint recess 16b. That is, it is formed so that the joint concave portion 16b is sandwiched between the front end portion 16a and the outer peripheral protrusion 16c.
The outer peripheral projection 16c is formed in a substantially L-shaped cross section near the tip 16a on the outer surface of the tank wall of the upper tank 10. That is, one end is formed integrally with the outer surface of the tank wall at a substantially right angle from the outer surface of the tank wall slightly separated from the tip of the tip portion 16a of the upper tank, and the other end is formed parallel to the outer surface of the tank wall and in the direction of the divided opening. The lower tank 20 is provided so as to face the outer peripheral projection 26c. Therefore, the outer peripheral projection 16c constitutes the bottom wall and the outer peripheral side wall of the joint recess 16b.
[0027]
The outer peripheral projection 16c can also be integrally extended from the outer wall near the peripheral edge 16 of the divided opening of the upper tank 10 in a substantially T-shaped cross section. In this case, the point at which the T-shaped leg extends from the outer wall of the upper tank 10 and the point at which one end of the T-shaped head projects in the direction facing the outer peripheral projection 26c of the lower tank 20 are approximately L-section. This is the same as the embodiment of the character shape, except that the other end of the T-shaped head protrudes in the opposite direction to that of the embodiment having a substantially L-shaped cross section. In the case of the outer peripheral projection 16c having a substantially T-shaped cross section, when the upper tank 10 and the lower tank 20 are joined, the other end of the T-shaped head different from that of the embodiment having a substantially L-shaped cross section is sandwiched. Can be pressed against each other, so that the peripheral portions of the upper tank 10 and the lower tank 20 can be more firmly joined.
[0028]
In the embodiment of FIG. 5, when the upper tank 10 and the lower tank 20 are joined, the outer peripheral projections 16c and 26c face each other to form a recess having a substantially elliptical cross section as described above. However, the tips of the outer peripheral projections 16c and 26c do not come into contact with each other and there is a gap. Since the fusion synthetic resin compatible with the base layers 11 and 21 of the upper tank and the lower tank is injected from this gap, the upper tank 10 and the lower tank 20 are firmly joined.
[0029]
In the embodiment of FIG. 6, the distal ends of both outer peripheral projections 16c and 26c extend longer than the embodiment of FIG. The tips of the outer peripheral projections 16c and 26c are welded to each other by thermal welding. For this reason, the upper tank 10 and the lower tank 20 are firmly joined. When welding, the outer peripheral projections 16c and 26c are strongly pressed against each other until the distal ends 16a and 26a abut against each other over the entire circumference of the divided opening, and the distal ends are melted. Barrier layers 12 and 22 continuous from the inner surfaces of the upper tank 10 and the lower tank 20 are provided on the planes of the tip portions 16a and 26a. Therefore, when the distal end portion 16a of the upper tank 10 abuts on the distal end portion 26a of the lower tank 20, the barrier layers 12, 22 are uniformly and continuously provided on the inner surface of the fuel tank 1, and the joining surfaces of the peripheral portions 16, 26 are formed. Since the barrier layers 12 and 22 are formed to this extent, the barrier properties of the fuel tank 1 can be ensured.
[0030]
Further, the concave portion in which the two joining concave portions 16b and 26b face each other to form a concave portion having a substantially elliptical cross section can accommodate the protruding portions of the molten resin of the two outer peripheral projecting portions 16c and 26c generated at the time of heat welding. Thus, the welding between the upper tank 10 and the lower tank 20 can be sufficiently performed.
This thermal welding is performed by pressing the outer peripheral projections 16c and 26c, the distal ends of which are heated and melted, as described above, so that the distal ends 16a and 26a come into strong contact with each other.
[0031]
The synthetic resin used for the base layers 11 and 21 in the present invention is not particularly limited as long as it is a hard thermoplastic resin material having strength. Preferably, a polyolefin resin material containing a polyolefin resin as a main component is used. it can. As the polyolefin resin, any of a polypropylene resin and a polyethylene resin may be used.
As the polypropylene resin, a propylene homopolymer or a propylene-ethylene block copolymer can be used.
As the polyethylene resin, high-density polyethylene or medium-density polyethylene can be used.
[0032]
As the hard thermoplastic resin other than the polyolefin resin, a polyamide resin or a polyvinyl resin can be used. These thermoplastic resins can be used alone or as a blend of two or more resins.
Further, the hard synthetic resin used for the base material layers 11 and 21 in the present invention can be filled with glass fiber, inorganic fiber, carbon fiber, metal fiber or the like used for reinforcement.
Further, rubber components such as EPDM and EPR can be blended and used for improving elasticity.
[0033]
As the synthetic resin used for the barrier layers 12 and 22 in the present invention, a resin having a good gas barrier property and capable of preventing fuel permeation of gasoline or the like and having excellent fluidity is used. As this resin, for example, ethylene vinyl alcohol resin (EVOH), polyphenylene sulfide (PPS), liquid crystalline polymer (LCP), or the like can be used. However, the resin is not limited to these resins, and any resin having gas barrier properties against fuel permeation and excellent fluidity can be used.
[0034]
Next, a method for manufacturing a fuel tank for an automobile according to the present invention will be described with reference to FIGS.
The upper tank 10 and the lower tank 20 are formed separately. The description will be made taking the upper tank 10 as an example. As shown in FIG. 7A, the upper tank 10 is formed by injecting the above-described hard synthetic resin for forming the base layer 11 into the mold 40 from the injection gate 43a to form the base layer 11 first. .
Thereafter, as shown in FIG. 7B, the movable mold 42 is slightly opened, and the synthetic resin forming the barrier layer 12 is injected from the injection gate 43b into the base material layer 11. Thereby, the barrier layer 12 is thinly and uniformly formed on the inner surface of the base material layer 11, that is, on the side on which the inner surface of the fuel tank 1 is formed. Since the synthetic resin to be injected uses a synthetic resin having a high fluidity, the synthetic resin flows over the entire inner surface of the base layer 11 and the barrier layer 12 can be formed.
[0035]
The barrier layer 12 is formed by injection compression in which the movable mold 42 is slightly opened to inject the resin forming the barrier layer 12 into the base material layer 11, and then the mold 40 is closed again to compress the injected resin in the barrier layer 12. It can also be formed by molding. In this case, since the barrier layer 12 can be strongly compressed to the base material layer 11, the barrier layer 12 can be made thinner and the adhesion between the barrier layer 12 and the base material layer 11 is further improved.
[0036]
When the barrier layer 12 is formed, the mold 40 is slightly opened to inject the resin of the barrier layer 12. At this time, as shown in FIG. Since the side wall, that is, the surface of the wall forming the joining concave portion 16b is the same as the moving direction of the mold 40, no gap is formed between the outer peripheral wall of the distal end portion 16a and the fixed mold 41. Therefore, the injected synthetic resin forming the barrier layer 12 stops at the distal end surface of the distal end portion 16a. Therefore, the barrier layer 12 is reliably formed from the inner surface of the upper tank 10 to the front end surface of the front end portion 16a, and is not further formed to the joint recess 16b.
[0037]
Thus, the upper tank 10 and the lower tank 20 are formed separately. Thereafter, the peripheral edges 16, 26 of the upper tank 10 and the lower tank 20 are firmly joined to each other.
In the embodiment shown in FIG. 5, the distal ends 16a, 26a of the peripheral portions 16, 26 of the upper tank 10 and the lower tank 20 abut against each other. At this time, the joint concave portions 16b and 26b have openings facing each other to form a space having a substantially elliptical cross section, and the outer peripheral protrusions 16c and 26c face each other with a gap therebetween. A synthetic resin compatible with the base layers 11 and 21 is injected into the space having a substantially elliptical cross section from this gap. The fusion synthetic resin compatible with the base layers 11 and 21 is preferably the same synthetic resin as the base layers 11 and 21, but any suitable synthetic resin can be used. The upper tank 10 and the lower tank 20 are firmly joined by fusing the fusion synthetic resin and the base layers 11 and 21. Since the tip portions 16a and 26a are strongly pressed against each other when the fusion synthetic resin is injected, the joining surfaces of the upper tank 10 and the lower tank 20 are in close contact with each other and no gap is generated.
[0038]
In the embodiment shown in FIG. 6, the outer peripheral projections 16c and 26c are extended as described above. The distal ends of the long outer projections 16c and 26c are heated by a heating means such as a hot plate to be melted or softened. The melted or softened outer peripheral projections 16c and 26c of the upper tank 10 and the lower tank 20 are brought into contact with each other and firmly pressed. Then, the tips of the outer peripheral projections 16c and 26c are welded to each other, and the dimensions of the outer peripheral projections 16c and 26c are melted and shortened. The joining surfaces of 20 are in close contact with each other and no gap is generated.
[0039]
When the outer peripheral projections 16c and 26c abut against each other and are pressed firmly, the synthetic resin that has melted or softened protrudes to both sides, but the synthetic resin that protrudes to the vehicle interior can be accommodated in the joint recesses 16b and 26b. The barrier properties of the fuel tank 1 are ensured because the contact surfaces of the tips 16a and 26a are not affected.
The synthetic resin protruding outside the vehicle can be cut off with a knife or the like.
Through the above steps, the upper fuel tank 10 and the lower tank 20 can be separately formed, and then joined and welded to produce the integrated fuel tank 1 for an automobile.
[0040]
【The invention's effect】
ADVANTAGE OF THE INVENTION Since the wall of the fuel tank which was excellent in the gas barrier property with respect to fuel permeation was able to be made uniform and the weight was lightened, it can contribute to the weight reduction of a vehicle. Further, a fuel tank in which the upper tank and the lower tank are firmly joined can be obtained. Further, it is possible to obtain a fuel tank in which the barrier layer and the base material layer of the fuel tank are firmly joined at a low cost with less waste of material.
Further, the present invention is a method for manufacturing a fuel tank which can manufacture a fuel tank having excellent gas barrier properties against fuel permeation by a simple method quickly and inexpensively.
[Brief description of the drawings]
FIG. 1 is a perspective view of an automotive fuel tank of the present invention.
FIG. 2 is a cross-sectional view of the vehicle fuel tank of the present invention, taken along line LL of FIG.
FIG. 3 is a sectional view of the fuel tank for an automobile of the present invention, taken along line WW of FIG. 1;
FIG. 4 is a partially enlarged sectional view of a portion A in FIG. 2 of the fuel tank for an automobile of the present invention.
FIG. 5 is a partially enlarged sectional view of a portion B of FIG. 2 of the fuel tank for an automobile of the present invention.
6 is a partially enlarged sectional view of a portion B of FIG. 2 of the fuel tank for an automobile of the present invention.
FIG. 7 is a cross-sectional view of a mold for manufacturing the automobile fuel tank of the present invention. (A) is a diagram before the synthetic resin of the base material layer is injected, and (b) is a diagram in which the mold is slightly opened after the synthetic resin of the base material layer is injected.
FIG. 8 is a cross-sectional view of a mold for manufacturing the automotive fuel tank of the present invention, and is a partially enlarged cross-sectional view of a portion C.
FIG. 9 is a sectional view of a mold for manufacturing a conventional automobile fuel tank.
FIG. 10 is a cross-sectional view of a conventional automobile fuel tank.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel tank 10 Upper tank 11, 21 Base material layer 12, 22 Barrier layer 16, 26 Peripheral edge 16a, 26a Tip 16b, 26b Joint recess 16c, 26c Outer peripheral projection 20 Lower tank 40 Mold

Claims

In an automotive fuel tank made of synthetic resin, an upper tank constituting an upper part of a fuel tank divided into two parts and a lower tank constituting a lower part are joined together at a peripheral portion of each divided opening.
Each of the upper tank and the lower tank is composed of two synthetic resin layers, a base layer made of a hard synthetic resin and a barrier layer made of a synthetic resin with low fuel permeability formed on the tank inner surface of the base layer. ,
A fuel tank for an automobile, wherein the base layer is formed by injection molding, and the barrier layer is integrally formed on the tank inner surface of the base layer by injection molding or injection compression molding.

2. The fuel tank for an automobile according to claim 1, wherein the base material layer has fine irregularities on the inner surface of the tank.

At each peripheral edge of the divided opening of the upper tank and the lower tank,
The tank walls of the upper tank and the lower tank are formed with a leading end so that their leading ends abut each other over the entire circumference of the divided opening, and the abutting surfaces of the leading ends extend continuously from the inner surface of the tank wall. 3. The fuel tank for an automobile according to claim 1, further comprising a barrier layer in contact therewith.

At the peripheral joint of the upper tank and the lower tank,
An outer peripheral projection having a substantially L-shaped cross section is formed near the front end of the outer wall of the tank of the upper tank and the lower tank, and one end of the outer peripheral projection is integrally formed substantially perpendicular to the outer surface of the tank wall, and the other end is formed. Is formed parallel to the outer surface of the tank wall and in the direction of the divided opening,
Between the outer peripheral protrusion of the upper tank and the lower tank and the tip of the tank wall, a joint concave portion having a substantially U-shaped cross section that opens in a direction facing each other is provided.
For the welding of the upper tank and the lower tank, a fusion synthetic resin compatible with the base material of the upper tank and the lower tank is injected into the joining recesses provided in the upper tank and the lower tank, respectively. 4. The fuel tank for an automobile according to claim 3, wherein the joint concave portions of the upper tank and the lower tank are fused.

An outer peripheral projection having a substantially L-shaped cross section is formed near the front end of the outer wall of the tank of the upper tank and the lower tank, and one end of the outer peripheral projection is integrally formed substantially perpendicular to the outer surface of the tank wall, and the other end is formed. Is formed parallel to the outer surface of the tank wall and in the direction of the divided opening,
4. The fuel tank for an automobile according to claim 3, wherein the outer peripheral projections at the peripheral edges of the upper tank and the lower tank are thermally fused to each other.

A synthetic resin automobile fuel manufactured by separately forming an upper tank constituting an upper part and a lower tank constituting a lower part of a vertically divided fuel tank and joining peripheral edges of the divided openings of the upper tank and the lower tank. In the tank manufacturing method,
Both upper tank and lower tank, a step of forming a base material layer by injection molding a hard synthetic resin into a mold,
A step of injecting a synthetic resin having a low fuel permeability into the tank inner surface of the base material layer by slightly opening the mold, and integrally forming a barrier layer by injection molding or injection compression molding,
A method of manufacturing a synthetic resin-made automobile fuel tank, comprising a step of joining a peripheral joint portion between the upper tank and the lower tank.

In the step of joining the upper tank and the periphery of the lower tank,
7. The upper tank and the lower tank according to claim 6, wherein the upper tank and the lower tank are fused by injection-molding a fusion synthetic resin having compatibility with the base material of the upper tank and the lower tank in a joint recess provided at a peripheral edge of the upper tank and the lower tank. A method for manufacturing an automotive fuel tank made of synthetic resin.

In the step of joining the upper tank and the periphery of the lower tank,
7. The method for manufacturing a synthetic resin fuel tank for an automobile according to claim 6, wherein the outer peripheral projections at the peripheral edges of the upper tank and the lower tank are melted by a hot plate and heat-welded to each other.