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JP2005106001A - Diesel engine exhaust gas purification system - Google Patents

Diesel engine exhaust gas purification system Download PDF

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JP2005106001A
JP2005106001A JP2003343177A JP2003343177A JP2005106001A JP 2005106001 A JP2005106001 A JP 2005106001A JP 2003343177 A JP2003343177 A JP 2003343177A JP 2003343177 A JP2003343177 A JP 2003343177A JP 2005106001 A JP2005106001 A JP 2005106001A
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exhaust gas
pipe
removal catalyst
nox removal
diesel engine
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Seiji Harufuji
聖二 春藤
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Hino Motors Ltd
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Hino Motors Ltd
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Abstract

【課題】エンジンが高負荷状態であっても効率良くＮＯｘを還元する。
【解決手段】ディーゼルエンジンの排ガス浄化装置は、ディーゼルエンジン１０の排気管１２に設けられたＮＯｘ除去触媒１３と、ＮＯｘ除去触媒に向けて還元剤２０を噴射可能な噴射ノズル１６と、噴射ノズルに液体調整弁１８を介して還元剤を供給する還元剤供給手段１９とを備える。ＮＯｘ除去触媒とディーゼルエンジンとの間の排気管に併設された冷却用バイパス管２６と、排ガスの排気管及び冷却用バイパス管へのそれぞれの流量を調整可能な流量調整弁２７と、ＮＯｘ除去触媒内を通過する排ガスの温度を検出する温度センサ２４と、温度センサの検出出力に基づいて液体調整弁とともに流量調整弁を制御するコントローラ３０とを備える。冷却用バイパス管２６は管本体２６ａと管本体２６ａの外周に長手方向に所定の間隔を開けて設けられた複数の放熱フィン２６ｂとを有する。
【選択図】 図１
Even if an engine is in a high load state, NOx is efficiently reduced.
An exhaust gas purification apparatus for a diesel engine includes a NOx removal catalyst 13 provided in an exhaust pipe 12 of the diesel engine 10, an injection nozzle 16 capable of injecting a reducing agent 20 toward the NOx removal catalyst, and an injection nozzle. And a reducing agent supply means 19 for supplying the reducing agent via the liquid regulating valve 18. A cooling bypass pipe 26 provided in the exhaust pipe between the NOx removal catalyst and the diesel engine, a flow rate adjusting valve 27 capable of adjusting the respective flow rates of the exhaust gas to the exhaust pipe and the cooling bypass pipe, and the NOx removal catalyst A temperature sensor 24 that detects the temperature of the exhaust gas that passes through the inside, and a controller 30 that controls the flow rate adjustment valve together with the liquid adjustment valve based on the detection output of the temperature sensor. The cooling bypass pipe 26 has a pipe main body 26a and a plurality of heat radiation fins 26b provided at predetermined intervals in the longitudinal direction on the outer periphery of the pipe main body 26a.
[Selection] Figure 1

Description

本発明はディーゼルエンジンの排ガスに含まれる窒素酸化物（以下、ＮＯｘという）を低減するディーゼルエンジンの排ガス浄化装置に関するものである。   The present invention relates to a diesel engine exhaust gas purification device that reduces nitrogen oxides (hereinafter referred to as NOx) contained in exhaust gas of a diesel engine.

従来、排ガス中のＮＯｘを低減する排ガス浄化装置として、ディーゼルエンジンの排気管にＮＯｘ除去触媒を設け、このＮＯｘ除去触媒に向けて炭化水素系液体を噴射可能な噴射ノズルをＮＯｘ除去触媒の入口に設け、その噴射ノズルに液体調整弁を介して液体を供給する炭化水素系液体供給手段を備えたディーゼルエンジンの排ガス浄化装置が知られている（例えば、特許文献１参照。）。ＮＯｘ除去触媒は２００℃〜５００℃の範囲で比較的高い還元作用が期待され、このＮＯｘ除去触媒を備える排ガス浄化装置では、噴射ノズルからＮＯｘ除去触媒に向けて還元剤としての炭化水素系液体を噴射することによりその触媒で還元作用が起こり、排ガス中のＮＯｘを無害なＮ2に転化するようになっている。
特開平５−２２２９２３号公報（図１） Conventionally, as an exhaust gas purification device for reducing NOx in exhaust gas, a NOx removal catalyst is provided in an exhaust pipe of a diesel engine, and an injection nozzle capable of injecting a hydrocarbon-based liquid toward the NOx removal catalyst is provided at the inlet of the NOx removal catalyst. There is known an exhaust gas purifying apparatus for a diesel engine provided with a hydrocarbon-based liquid supply means that is provided and supplies a liquid to the injection nozzle via a liquid regulating valve (for example, see Patent Document 1). The NOx removal catalyst is expected to have a relatively high reducing action in the range of 200 ° C. to 500 ° C. In the exhaust gas purification apparatus equipped with this NOx removal catalyst, a hydrocarbon-based liquid as a reducing agent is supplied from the injection nozzle toward the NOx removal catalyst. As a result of the injection, a reduction action occurs in the catalyst, and NOx in the exhaust gas is converted into harmless N 2 .
JP-A-5-222923 (FIG. 1)

しかし、上記した排ガス浄化装置で用いられるＮＯｘ除去触媒は、高いＮＯｘの選択還元機能がある反面、排ガス温度が５００℃を超えるとＮＯｘの選択還元率が低くなる欠点があり、エンジンが高負荷状態になった場合には排ガス温度が５００℃を超えて上昇し、エンジンが高負荷時にＮＯｘを有効に低減させることができない問題点があった。
本発明の目的は、エンジンが高負荷状態であっても効率良くＮＯｘを還元し得るディーゼルエンジンの排ガス浄化装置を提供することにある。 However, the NOx removal catalyst used in the exhaust gas purification apparatus described above has a high NOx selective reduction function, but has a disadvantage that the selective reduction rate of NOx decreases when the exhaust gas temperature exceeds 500 ° C., and the engine is in a high load state. In this case, the exhaust gas temperature has exceeded 500 ° C., and there has been a problem that NOx cannot be effectively reduced when the engine is under a high load.
An object of the present invention is to provide an exhaust gas purification apparatus for a diesel engine that can efficiently reduce NOx even when the engine is in a high load state.

請求項１に係る発明は、図１に示すように、ディーゼルエンジン１０の排気管１２に設けられたＮＯｘ除去触媒１３と、ＮＯｘ除去触媒１３の入口に設けられＮＯｘ除去触媒１３に向けて還元剤２０を噴射可能な噴射ノズル１６と、噴射ノズル１６に液体調整弁１８を介して還元剤２０を供給する還元剤供給手段１９とを備えたディーゼルエンジンの排ガス浄化装置の改良である。
その特徴ある構成は、ＮＯｘ除去触媒１３とディーゼルエンジン１０との間の排気管１２に併設された冷却用バイパス管２６と、排ガスの排気管１２及び冷却用バイパス管２６へのそれぞれの流量を調整可能な流量調整弁２７と、ＮＯｘ除去触媒１３内を通過する排ガスの温度を検出する温度センサ２４と、温度センサ２４の検出出力に基づいて液体調整弁１８とともに流量調整弁２７を制御するコントローラ３０とを備えたところにある。
この請求項１に係るディーゼルエンジンの排ガス浄化装置では、エンジン１０が高負荷状態になって排ガス温度が５００℃を超えると、コントローラ３０は流量調整弁２７を切り換えてバイパス管２６を開放する。すると排ガスはバイパス管２６に流入し、バイパス管２６を通過する際に排ガスの熱はそのバイパス管２６から外部に放散され、排ガスはその温度が低下した状態で排気管１２に合流してＮＯｘ除去触媒１３に流入する。排ガス温度が低下するとＮＯｘ除去触媒１３により排ガス中のＮＯｘは高い効率でＮ2に還元し、エンジンが高負荷状態であってもその排ガスに含まれるＮＯｘを有効に低減することができる。 As shown in FIG. 1, the invention according to claim 1 includes a NOx removal catalyst 13 provided in the exhaust pipe 12 of the diesel engine 10 and a reducing agent provided at the inlet of the NOx removal catalyst 13 toward the NOx removal catalyst 13. This is an improvement of an exhaust gas purifying apparatus for a diesel engine including an injection nozzle 16 capable of injecting 20 and a reducing agent supply means 19 for supplying the reducing agent 20 to the injection nozzle 16 via a liquid regulating valve 18.
The characteristic configuration is that the cooling bypass pipe 26 provided in the exhaust pipe 12 between the NOx removal catalyst 13 and the diesel engine 10 and the respective flow rates of the exhaust gas to the exhaust pipe 12 and the cooling bypass pipe 26 are adjusted. A possible flow rate adjustment valve 27, a temperature sensor 24 that detects the temperature of exhaust gas that passes through the NOx removal catalyst 13, and a controller 30 that controls the flow rate adjustment valve 27 together with the liquid adjustment valve 18 based on the detection output of the temperature sensor 24. It is in the place with.
In the exhaust gas purification apparatus for a diesel engine according to the first aspect, when the engine 10 is in a high load state and the exhaust gas temperature exceeds 500 ° C., the controller 30 switches the flow rate adjustment valve 27 to open the bypass pipe 26. Then, the exhaust gas flows into the bypass pipe 26, and when passing through the bypass pipe 26, the heat of the exhaust gas is dissipated to the outside from the bypass pipe 26, and the exhaust gas joins the exhaust pipe 12 with its temperature lowered to remove NOx. It flows into the catalyst 13. When the exhaust gas temperature falls, the NOx removal catalyst 13 reduces the NOx in the exhaust gas to N 2 with high efficiency, and the NOx contained in the exhaust gas can be effectively reduced even when the engine is in a high load state.

請求項２に係る発明は、請求項１に係る発明であって、冷却用バイパス管２６が管本体２６ａと管本体２６ａの外周に長手方向に所定の間隔を開けて設けられた複数の放熱フィン２６ｂとを有するディーゼルエンジンの排ガス浄化装置である。
この請求項２に係るディーゼルエンジンの排ガス浄化装置では、排ガスはバイパス管２６を構成する管本体２６ａに流入する。そして排ガスの熱は管本体２６ａの外周に設けられた複数の放熱フィン２６ｂに伝達して外部に放散される。従って、このバイパス管２６では排ガスの温度を有効に放散させて排ガスの温度を効果的に低下させることができる。 The invention according to claim 2 is the invention according to claim 1, wherein the cooling bypass pipe 26 is provided with a plurality of radiating fins provided on the outer periphery of the pipe body 26 a and the pipe body 26 a at predetermined intervals in the longitudinal direction. 26b is an exhaust gas purification device for a diesel engine.
In the exhaust gas purification apparatus for a diesel engine according to the second aspect, the exhaust gas flows into the pipe main body 26 a constituting the bypass pipe 26. Then, the heat of the exhaust gas is transmitted to the plurality of heat radiation fins 26b provided on the outer periphery of the tube body 26a and is dissipated to the outside. Therefore, the bypass pipe 26 can effectively dissipate the temperature of the exhaust gas and effectively reduce the temperature of the exhaust gas.

本発明の排ガス浄化装置では、ＮＯｘ除去触媒とディーゼルエンジンとの間の排気管に冷却用バイパス管を併設し、排ガスの排気管及び冷却用バイパス管へのそれぞれの流量を調整可能な流量調整弁をとＮＯｘ除去触媒内を通過する排ガスの温度を検出する温度センサとを設け、温度センサの検出出力に基づいて流量調整弁を制御するコントローラを備えたので、エンジンが高負荷状態になって排ガス温度が５００℃を超えると、コントローラは流量調整弁を切り換えて排ガスをバイパス管に流入させる。バイパス管を通過する際に排ガスの熱はそのバイパス管から外部に放散され、排ガスはその温度が低下した状態でＮＯｘ除去触媒に流入する。ＮＯｘ除去触媒ではその温度が低下した排ガス中のＮＯｘを高い効率でＮ2に還元し、エンジンが高負荷状態であってもその排ガスに含まれるＮＯｘを有効に低減させることができる。この場合、冷却用バイパス管が管本体と管本体の外周に長手方向に所定の間隔を開けて設けられた複数の放熱フィンとを有するものであれば、このバイパス管に流通する排ガスの熱を有効に放散させて排ガスの温度を効果的に低下させることができる。 In the exhaust gas purification apparatus of the present invention, a cooling bypass pipe is additionally provided in the exhaust pipe between the NOx removal catalyst and the diesel engine, and the flow rate adjusting valve capable of adjusting the respective flow rates of the exhaust gas to the exhaust pipe and the cooling bypass pipe And a temperature sensor that detects the temperature of the exhaust gas that passes through the NOx removal catalyst, and a controller that controls the flow rate adjusting valve based on the detection output of the temperature sensor, the engine becomes in a high load state and the exhaust gas When the temperature exceeds 500 ° C., the controller switches the flow rate adjusting valve to flow the exhaust gas into the bypass pipe. When passing through the bypass pipe, the heat of the exhaust gas is dissipated from the bypass pipe to the outside, and the exhaust gas flows into the NOx removal catalyst with its temperature lowered. The NOx removal catalyst can reduce NOx in the exhaust gas whose temperature has decreased to N 2 with high efficiency, and can effectively reduce NOx contained in the exhaust gas even when the engine is in a high load state. In this case, if the cooling bypass pipe has a pipe body and a plurality of radiating fins provided at predetermined intervals in the longitudinal direction on the outer periphery of the pipe body, the heat of the exhaust gas flowing through the bypass pipe is increased. It is possible to effectively dissipate and effectively reduce the temperature of the exhaust gas.

次に本発明を実施するための最良の形態を図面に基づいて説明する。
図１に示すように、ディーゼルエンジン１０の排気マニホルド１１には排気管１２が接続される。この排気管１２の途中にはＮＯｘ除去触媒１３が設けられる。この例ではＮＯｘ除去触媒１３はモノリス触媒であって、コージェライト製のハニカム担体１３ａにＰｔ又はこの酸化物を担持して構成される。ただし、触媒としての貴金属はこのＰｔの他に、Ｐｄ、Ｃｕ、Ｍｎ、Ｆｅ、Ｃｏ、Ａｇ又はこれらの酸化物を少なくとも一種類以上含むものであればよい。これらによりコージェライト製のハニカム担体１３ａにＮＯの酸化力が付与されてＮＯｘ除去触媒１３が構成される。 Next, the best mode for carrying out the present invention will be described with reference to the drawings.
As shown in FIG. 1, an exhaust pipe 12 is connected to an exhaust manifold 11 of the diesel engine 10. A NOx removal catalyst 13 is provided in the middle of the exhaust pipe 12. In this example, the NOx removal catalyst 13 is a monolith catalyst, and is configured by supporting Pt or this oxide on a cordierite honeycomb carrier 13a. However, the noble metal as the catalyst may be any material that contains at least one kind of Pd, Cu, Mn, Fe, Co, Ag, or oxides thereof in addition to Pt. As a result, NO oxidizing power is imparted to the cordierite honeycomb carrier 13a to form the NOx removal catalyst 13.

ＮＯｘ除去触媒１３の排ガス上流側であってＮＯｘ除去触媒１３の入口の排気管１２にはそのＮＯｘ除去触媒１３に向けて後述する還元剤２０を噴射可能な噴射ノズル１６がそのＮＯｘ除去触媒１３に向けて設けられる。噴射ノズル１６には供給管１７が接続され、この供給管１７は液体調整弁１８及び還元剤供給手段であるポンプ１９を介して還元剤２０が入ったタンク２１に配管される。この例では液体調整弁１８は噴射ノズル１６への還元剤２０の供給量を調整する三方弁であり、還元剤２０は軽油である。液体調整弁１８にはタンク２１に配管された戻り管１７ａが接続される。液体調整弁１８が閉じているときにはポンプ１９から吐出された還元剤２０は戻り管１７ａを通ってタンク２１に戻され、開いたときには噴射ノズル１６に吐出した還元剤２０を供給するように構成される。   An injection nozzle 16 capable of injecting a reducing agent 20 (to be described later) toward the NOx removal catalyst 13 is disposed in the NOx removal catalyst 13 upstream of the NOx removal catalyst 13 and at the inlet of the NOx removal catalyst 13. Is provided. A supply pipe 17 is connected to the injection nozzle 16, and the supply pipe 17 is piped to a tank 21 containing a reducing agent 20 through a liquid regulating valve 18 and a pump 19 which is a reducing agent supply means. In this example, the liquid adjustment valve 18 is a three-way valve that adjusts the supply amount of the reducing agent 20 to the injection nozzle 16, and the reducing agent 20 is light oil. A return pipe 17 a connected to the tank 21 is connected to the liquid regulating valve 18. When the liquid regulating valve 18 is closed, the reducing agent 20 discharged from the pump 19 is returned to the tank 21 through the return pipe 17a, and when opened, the reducing agent 20 discharged to the injection nozzle 16 is supplied. The

噴射ノズル１６の近傍の排気管１２には、ＮＯｘ除去触媒１３の入口の排気管内の排ガス温度を検出する温度センサ２４が設けられる。このセンサ２４の検出出力はマイクロコンピュータからなるコントローラ３０の制御入力に接続される。また、コントローラ３０にはエンジン１０の回転速度を検出する回転センサ２２と、エンジン１０の負荷を検出する負荷センサ（アクセルセンサ）２３の各検出出力が更に接続される。この負荷センサ２３はこの例では燃料噴射ポンプ（図示せず）のロードレバーの変位量を検出する。コントローラ３０の制御出力は液体調整弁１８及びポンプ１９に接続される。コントローラ３０は第１メモリ３１を備える。この第１メモリ３１にはエンジン回転、エンジン負荷並びにＮＯｘ除去触媒１３入口の排ガス温度に応じた液体調整弁１８の開閉及びポンプ１９の作動の有無が予め記憶される。   A temperature sensor 24 that detects the exhaust gas temperature in the exhaust pipe at the inlet of the NOx removal catalyst 13 is provided in the exhaust pipe 12 in the vicinity of the injection nozzle 16. The detection output of the sensor 24 is connected to the control input of the controller 30 comprising a microcomputer. The controller 30 is further connected with detection outputs of a rotation sensor 22 that detects the rotation speed of the engine 10 and a load sensor (accelerator sensor) 23 that detects a load of the engine 10. In this example, the load sensor 23 detects a displacement amount of a load lever of a fuel injection pump (not shown). The control output of the controller 30 is connected to the liquid regulating valve 18 and the pump 19. The controller 30 includes a first memory 31. The first memory 31 stores in advance whether or not the liquid regulating valve 18 is opened and closed and whether the pump 19 is operated according to the engine speed, the engine load, and the exhaust gas temperature at the inlet of the NOx removal catalyst 13.

ＮＯｘ除去触媒１３とディーゼルエンジン１０との間の排気管１２には冷却用バイパス管２６が併設される。即ち、バイパス管２６は排気管１２のバイパス管２６の上流端が接続された分岐部２８とバイパス管２６の排ガス下流端が接続された合流部２９との間に位置する主管１２ａにその主管１２ａより排ガスの流路が長くなるように接続される。この冷却用バイパス管２６は、管本体２６ａとその管本体２６ａの外周に長手方向に所定の間隔を開けて設けられた複数の放熱フィン２６ｂとを有し、図示しない車両の下部において走行時に風を受けるように蛇行して配置される。   A cooling bypass pipe 26 is provided in the exhaust pipe 12 between the NOx removal catalyst 13 and the diesel engine 10. That is, the bypass pipe 26 is connected to the main pipe 12a located between the branch part 28 to which the upstream end of the bypass pipe 26 of the exhaust pipe 12 is connected and the junction part 29 to which the exhaust gas downstream end of the bypass pipe 26 is connected. The exhaust gas flow path is longer connected. The cooling bypass pipe 26 has a pipe main body 26a and a plurality of radiating fins 26b provided at predetermined intervals in the longitudinal direction on the outer periphery of the pipe main body 26a. It is arranged meandering to receive.

排気管１２の分岐部２８には排ガスの主管１２ａ及びバイパス管２６へのそれぞれの流量を調整可能は流量調整弁２７が設けられる。この流量調整弁２７は主管１２ａ及びバイパス管２６を開閉するバルブ本体２７ａとこのバルブ本体２７ａを駆動する駆動手段２７ｂとを有する。バルブ本体２７ａは駆動手段２７ｂにより主管１２ａを開放しかつバイパス管２６を閉止する一点鎖線で示す主管開放位置と、主管１２ａを閉止しかつバイパス管２６を開放する波線で示すバイパス管開放位置との２つの位置に回動可能に構成される。駆動手段２７ｂにはコントローラ３０の制御出力が接続され、コントローラ３０には第２メモリ３２が備えられる。この第２メモリ３２にはＮＯｘ除去触媒１３入口の排ガス温度に応じた流量調整弁２７の切り換え位置が予め記憶される。   A branching portion 28 of the exhaust pipe 12 is provided with a flow rate adjusting valve 27 that can adjust the flow rates of the exhaust gas to the main pipe 12a and the bypass pipe 26. The flow rate adjusting valve 27 has a valve main body 27a for opening and closing the main pipe 12a and the bypass pipe 26, and a driving means 27b for driving the valve main body 27a. The valve body 27a has a main pipe opening position indicated by a one-dot chain line that opens the main pipe 12a and closes the bypass pipe 26 by the driving means 27b, and a bypass pipe opening position indicated by a wavy line that closes the main pipe 12a and opens the bypass pipe 26. It is configured to be rotatable in two positions. A control output of the controller 30 is connected to the driving means 27b, and the controller 30 includes a second memory 32. In the second memory 32, the switching position of the flow rate adjusting valve 27 corresponding to the exhaust gas temperature at the inlet of the NOx removal catalyst 13 is stored in advance.

このような構成の排ガス浄化装置では、コントローラ３０はエンジン回転、エンジン負荷並びにＮＯｘ除去触媒１３入口の排ガス温度に応じ、第１メモリ３１の記憶に基づいてポンプ１９を作動させて液体調整弁１８を開閉させ、第２メモリ３２の記憶に基づいて流量調整弁２７を切り換える。例えば、温度センサ２４の検出出力により、排ガス温度が２００〜５００℃の範囲であることを認識したときに、そのコントローラ３０は第２メモリ３２の記憶に基づいて流量調整弁２７を切り換え、主管１２ａを開放しかつバイパス管２６を閉止させる。そしてコントローラ３０はポンプ１９を作動させて、液体調整弁１８を開く。これにより噴射ノズル１６から所定量だけ還元剤２０がＮＯｘ除去触媒１３に噴射され、このＮＯｘ除去触媒１３を通過する排ガスに含まれるＮＯｘは高い効率でＮ2に還元される。これにより排ガスに含まれるＮＯｘを低減することができる。 In the exhaust gas purifying apparatus having such a configuration, the controller 30 operates the pump 19 based on the storage in the first memory 31 according to the engine rotation, the engine load, and the exhaust gas temperature at the inlet of the NOx removal catalyst 13, thereby causing the liquid regulating valve 18 to operate. The flow rate adjustment valve 27 is switched based on the memory of the second memory 32. For example, when it is recognized from the detection output of the temperature sensor 24 that the exhaust gas temperature is in the range of 200 to 500 ° C., the controller 30 switches the flow rate adjustment valve 27 based on the storage in the second memory 32, and the main pipe 12a. And the bypass pipe 26 is closed. Then, the controller 30 operates the pump 19 to open the liquid regulating valve 18. Thus, a predetermined amount of reducing agent 20 is injected from the injection nozzle 16 to the NOx removal catalyst 13, and NOx contained in the exhaust gas passing through the NOx removal catalyst 13 is reduced to N 2 with high efficiency. Thereby, NOx contained in the exhaust gas can be reduced.

一方、エンジン１０が始動直後で排気マニホルド１１から排出される排ガス温度が２００℃未満であることを認識した場合には、コントローラ３０は流量調整弁２７を切り換えて主管１２ａを開放しかつバイパス管２６を閉止させた状態で、コントローラ３０は第１メモリ３１の記憶内容に基づいてポンプ１９を不作動にして、液体調整弁１８を閉じる。このようにしてＮＯｘ除去触媒１３による還元作用が期待できないような排ガス温度が２００未満における還元剤２０の噴射は防止され、還元剤の無駄な消費を防止できる。   On the other hand, when the engine 10 recognizes that the exhaust gas temperature discharged from the exhaust manifold 11 is less than 200 ° C. immediately after the engine 10 is started, the controller 30 switches the flow rate adjustment valve 27 to open the main pipe 12a and bypass pipe 26 In the state in which is closed, the controller 30 deactivates the pump 19 based on the stored contents of the first memory 31 and closes the liquid regulating valve 18. Thus, the injection of the reducing agent 20 when the exhaust gas temperature is less than 200 at which the reduction action by the NOx removal catalyst 13 cannot be expected is prevented, and wasteful consumption of the reducing agent can be prevented.

逆に、エンジン１０が高負荷状態になって排気マニホルド１１から排出される排ガス温度が５００℃を超えたことを認識した場合には、コントローラ３０は流量調整弁２７を切り換えてバイパス管２６を開放しかつ主管１２ａを閉止させる。すると排気マニホルド１１から排出される排ガスの全てがバイパス管２６に流入する。ここで、バイパス管２６は複数の放熱フィン２６ｂを有し、分岐部２８と合流部２９との間に位置する主管１２ａより長い流路を有し、かつ車両の下部において走行時に風を受けるように蛇行して配置されているので、バイパス管２６内部を通過する際に排ガスの熱はそのバイパス管２６により外部に放散される。従って、排ガスはその温度が５００℃以下になった状態で合流部２９から排気管１２に合流してＮＯｘ除去触媒１３に流入する。排ガス温度が５００℃以下では、コントローラ３０は還元剤２０を噴射し、このＮＯｘ除去触媒１３を通過する排ガスに含まれるＮＯｘは高い効率でＮ2に還元する。これによりエンジンが高負荷状態であってもその排ガスに含まれるＮＯｘを有効に低減することができる。
なお、上記例では還元剤として軽油を用いたが、本発明はこれに限るものではなく、他の還元剤を用いてもよい。 On the contrary, when the engine 10 is in a high load state and the exhaust gas temperature discharged from the exhaust manifold 11 is recognized to exceed 500 ° C., the controller 30 switches the flow rate adjustment valve 27 and opens the bypass pipe 26. And the main pipe 12a is closed. Then, all the exhaust gas discharged from the exhaust manifold 11 flows into the bypass pipe 26. Here, the bypass pipe 26 has a plurality of heat radiating fins 26b, has a flow path longer than the main pipe 12a located between the branch portion 28 and the junction portion 29, and receives wind during traveling in the lower part of the vehicle. Therefore, when passing through the bypass pipe 26, the heat of the exhaust gas is dissipated to the outside by the bypass pipe 26. Therefore, the exhaust gas joins the exhaust pipe 12 from the joining section 29 and flows into the NOx removal catalyst 13 in a state where the temperature is 500 ° C. or lower. When the exhaust gas temperature is 500 ° C. or less, the controller 30 injects the reducing agent 20, and NOx contained in the exhaust gas passing through the NOx removal catalyst 13 is reduced to N 2 with high efficiency. Thereby, even if the engine is in a high load state, NOx contained in the exhaust gas can be effectively reduced.
In addition, although light oil was used as a reducing agent in the above example, the present invention is not limited to this, and other reducing agents may be used.

本発明実施形態の排ガス浄化装置を示す構成図。The block diagram which shows the exhaust gas purification apparatus of this invention embodiment.

符号の説明Explanation of symbols

１０ ディーゼルエンジン
１２ 排気管
１３ ＮＯｘ除去触媒
１６ 噴射ノズル
１８ 液体調整弁
１９ 還元剤供給手段
２０ 還元剤
２４ 温度センサ
２６ 冷却用バイパス管
２６ａ 管本体
２６ｂ 放熱フィン
２７ 流量調整弁
３０ コントローラ
DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Exhaust pipe 13 NOx removal catalyst 16 Injection nozzle 18 Liquid adjustment valve 19 Reducing agent supply means 20 Reducing agent 24 Temperature sensor 26 Bypass pipe for cooling 26a Pipe body 26b Radiation fin 27 Flow control valve 30 Controller

Claims (2)

ディーゼルエンジン(10)の排気管(12)に設けられたＮＯｘ除去触媒(13)と、前記ＮＯｘ除去触媒(13)の入口に設けられ前記ＮＯｘ除去触媒(13)に向けて還元剤(20)を噴射可能な噴射ノズル(16)と、前記噴射ノズル(16)に液体調整弁(18)を介して前記還元剤(20)を供給する還元剤供給手段(19)とを備えたディーゼルエンジンの排ガス浄化装置において、
前記ＮＯｘ除去触媒(13)と前記ディーゼルエンジン(10)との間の前記排気管(12)に併設された冷却用バイパス管(26)と、
排ガスの前記排気管(12)及び前記冷却用バイパス管(26)へのそれぞれの流量を調整可能な流量調整弁（27)と、
前記ＮＯｘ除去触媒(13)内を通過する排ガスの温度を検出する温度センサ(24)と、
前記温度センサ(24)の検出出力に基づいて前記液体調整弁(18)とともに前記流量調整弁(27)を制御するコントローラ(30)と
を備えたことを特徴とするディーゼルエンジンの排ガス浄化装置。 A NOx removal catalyst (13) provided in the exhaust pipe (12) of the diesel engine (10), and a reducing agent (20) toward the NOx removal catalyst (13) provided at the inlet of the NOx removal catalyst (13) Of a diesel engine comprising an injection nozzle (16) capable of injecting fuel, and a reducing agent supply means (19) for supplying the reducing agent (20) to the injection nozzle (16) via a liquid regulating valve (18). In exhaust gas purification equipment,
A cooling bypass pipe (26) provided in the exhaust pipe (12) between the NOx removal catalyst (13) and the diesel engine (10);
A flow rate adjusting valve (27) capable of adjusting a flow rate of exhaust gas to the exhaust pipe (12) and the cooling bypass pipe (26), and
A temperature sensor (24) for detecting the temperature of exhaust gas passing through the NOx removal catalyst (13);
An exhaust gas purifying apparatus for a diesel engine, comprising: a controller (30) for controlling the flow rate regulating valve (27) together with the liquid regulating valve (18) based on a detection output of the temperature sensor (24). 冷却用バイパス管(26)が管本体(26a)と前記管本体(26a)の外周に長手方向に所定の間隔を開けて設けられた複数の放熱フィン(26b)とを有する請求項１記載のディーゼルエンジンの排ガス浄化装置。
The cooling bypass pipe (26) has a pipe body (26a) and a plurality of radiating fins (26b) provided on the outer periphery of the pipe body (26a) at predetermined intervals in the longitudinal direction. Diesel engine exhaust gas purification system.
JP2003343177A 2003-10-01 2003-10-01 Diesel engine exhaust gas purification system Pending JP2005106001A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010265753A (en) * 2009-05-12 2010-11-25 Hino Motors Ltd Exhaust purification device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010265753A (en) * 2009-05-12 2010-11-25 Hino Motors Ltd Exhaust purification device

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