JP4126730B2 - Exhaust gas recirculation device - Google Patents

Exhaust gas recirculation device Download PDF

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Publication number
JP4126730B2
JP4126730B2 JP07350397A JP7350397A JP4126730B2 JP 4126730 B2 JP4126730 B2 JP 4126730B2 JP 07350397 A JP07350397 A JP 07350397A JP 7350397 A JP7350397 A JP 7350397A JP 4126730 B2 JP4126730 B2 JP 4126730B2
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exhaust gas
path
gas recirculation
exhaust
cooling
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JPH10266902A (en
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圭樹 田邊
晋 纐纈
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Mitsubishi Fuso Truck and Bus Corp
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Mitsubishi Fuso Truck and Bus Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/35—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with means for cleaning or treating the recirculated gases, e.g. catalysts, condensate traps, particle filters or heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23—Layout, e.g. schematics
    • F02M26/28—Layout, e.g. schematics with liquid-cooled heat exchangers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B29/00—Engines characterised by provision for charging or scavenging not provided for in groups F02B25/00, F02B27/00 or F02B33/00 - F02B39/00; Details thereof
    • F02B29/04—Cooling of air intake supply
    • F02B29/0406—Layout of the intake air cooling or coolant circuit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor

Description

【０００１】
【発明の属する技術分野】
本発明は、排気ガスの一部を吸気経路に還流させる排気ガス還流装置に関するものである。
【０００２】
【従来の技術】
一般に、車両の内燃機関を駆動することにより排出される排気ガス中には、窒素酸化物（以下、ＮＯｘという）等が含まれており、これらのＮＯｘ等は有害成分としてその排出量が規制されている。このＮＯｘを低減する装置として、排気ガスを吸気経路に還流させて、燃焼温度の上昇を抑えてＮＯｘの生成量を低減する排気ガス還流装置（以下、ＥＧＲ装置という）が知られている。
【０００３】
さらに、ＥＧＲ装置の排気ガス還流通路にＥＧＲクーラを設け、このＥＧＲクーラによって、吸気経路に還流する排気ガスを冷却し、排気ガスの体積を減少して密度を増加させ、大量の排気ガスを吸気経路に還流させて、燃焼温度の上昇を抑えてＮＯｘの生成量を低減することも知られている。
【０００４】
【発明が解決しようとする課題】
ところが、上述のＥＧＲクーラを有するＥＧＲ装置では、ＥＧＲを長時間に亘って行うと、ＥＧＲクーラ内における排気ガス通路の壁面に煤（ＨＣ、パティキュレート等）が付着して、この通路の断面積が減少する。この煤の付着により、ＥＧＲクーラにおいて圧力損失が増大するという問題点や、ＥＧＲクーラの冷却性能が低下するという問題点が発生する。
【０００５】
よって、本発明は、冷却手段内における排気ガス通路の壁面に煤が付着して冷却手段の冷却性能が低下することを防止できる排気ガス還流装置を提供することにある。
【０００６】
【課題を解決するための手段】
請求項１の発明は、内燃機関の排気経路の排気ガスを吸気経路に還流させる排気ガス還流経路と、この排気ガス還流経路に設けられ、上記排気ガスを冷却する冷却手段とを有する排気ガス還流装置において、上記冷却手段はそのコア部に上記排気ガス還流経路の排気ガスが流動する排気ガス層と内燃機関の冷却水が流通して上記排気ガス層の排ガスを冷却する冷却液層とを備えると共に上記排気ガス層と対向する排気ガス流路の内壁面に酸化触媒が設けられており、上記排気ガス還流経路の上記冷却手段の下流に配設されており、上記排気ガス還流経路を上記吸気経路と排気経路とのうち何れか一方に接続する経路切換手段と、上記排気ガスが上記酸化触媒を活性化する温度であって、かつ、排気ガス還流を行わないとき、上記冷却手段の冷却液層への冷却水の供給を停止することで上記排気ガス還流経路の排気ガスの冷却を停止するとともに、上記排気ガス還流経路を上記排気経路に接続するように上記経路切換手段を切り換える制御手段と、を有することを特徴とする。
この構成によれば、排気ガスが酸化触媒を活性化する温度であって、かつ、排気ガス還流を行わないときに、制御手段が、冷却手段による排気ガスの冷却を停止するとともに、排気ガス還流経路を排気経路に接続するように経路切換手段を切り換えるので、冷却手段の内部を高温の排気ガスが通過して酸化触媒が活性化し、冷却手段の内部に付着した煤が酸化（再燃焼）される。
【０００７】
請求項２の発明は、内燃機関の排気経路の排気ガスを吸気経路に還流させる排気ガス還流経路と、この排気ガス還流経路に設けられ、上記排気ガスを冷却する冷却手段とを有する排気ガス還流装置において、上記冷却手段はそのコア部に上記排気ガス還流経路の排気ガスが流動する排気ガス層と内燃機関の冷却水が流通して上記排気ガス層の排気ガスを冷却する冷却液層とを備えると共に上記冷却手段の排気ガス層と対向する排気ガス流路の内壁面に酸化触媒が設けられており、上記排気ガス還流経路の上記冷却手段の下流に配設されており、上記排気ガス還流経路を上記吸気経路と排気経路とのうち何れか一方に接続する経路切換手段と、上記経路切換手段を切換える制御手段と、を備え、上記内燃機関は排気経路に排気タービンを吸気経路にコンプレッサを配したターボチャージャと、上記排気ガス還流経路を経て上記吸気経路に還流される排気ガス量を制御するＥＧＲ制御弁とを備え、上記経路切換手段は上記排気ガス還流経路を、上記吸気経路の上記ターボチャージャの下流に連通する第１の経路と、排気経路に連通する第２の経路とのうち何れか一方に接続し、上記制御手段は上記内燃機関が高負荷・高回転であるとき、上記ＥＧＲ制御弁を開弁し、上記排気ガス還流経路が上記第１の経路に接続する状態より第２の経路に接続するように上記経路切換手段を切換える制御手段と、を有することを特徴とする。
この構成によれば、内燃機関が高負荷・高回転であるとき、すなわち、ターボチャージャによる過給圧が高いとき、制御手段が、ＥＧＲ制御弁を開弁し、排気ガス還流経路が第２の経路に接続するように経路切換手段を切換えるので、排気ガスが第２の経路を介して排気経路に排出される。しかも、冷却手段の内部を高温の排気ガスが通過して酸化触媒が活性化し、冷却手段の内部に付着した煤が酸化（再燃焼）される。
【０００８】
請求項３の発明は、請求項２記載の排気ガス還流装置において、上記排気ガスが上記酸化触媒を活性化する温度であって、かつ、排気ガス還流を行わないとき、上記制御手段が、上記冷却手段による上記排気ガスの冷却を停止するとともに、上記排気ガス還流経路を上記第２の経路に接続するように上記経路切換手段を切り換えることを特徴とする。
この構成によれば、特に、酸化触媒を活性化する温度であって、排気ガス還流を行わないとき、制御手段が、冷却手段による排気ガスの冷却を停止するとともに、ＥＧＲ制御弁を開弁し、排気ガス還流経路が第２の経路に接続するように経路切換手段を切換えるので、排気ガスが第２の経路を介して排気経路に排出されて、高温の排気ガスが冷却手段の内部を通過して酸化触媒が活性化し、冷却手段の内部に付着した煤が酸化（再燃焼）される。
【０００９】
【実施例】
以下、本発明の第１の実施例を図面を参照して説明する。図１にＥＧＲ装置（排気ガス還流装置）の概略構成図を示す。図１において、符号１は、ディーゼルエンジン本体（以下、エンジンという）を、符号２は、エンジン１の吸気マニホールドを、符号３は、吸気マニホールド２に接続された吸気経路としての吸気管を、符号４は、エンジン１の排気マニホールドを、符号５は、排気マニホールド４に接続された排気経路としての排気管をそれぞれ示している。符号６は、ターボチャージャを示し、その排気タービン６ａが排気管５に、そのコンプレッサ６ｂが吸気管３にそれぞれ介装されている。吸気管３のコンプレッサ６ｂの下流には、インタクーラ７及び過給圧センサ８がこの順にそれぞれ配設されている。過給圧センサ８は、コンプレッサ６ｂによる吸気管３の過給圧を検出し、後述するＥＣＵ２０に接続されている。
【００１０】
排気管５の排気マニホールド４と排気タービン６ａとの間には、排気ガス還流経路を構成する排気ガス還流管１０の排気ガス導入部１０ａが接続されている。排気ガス還流管１０の排気ガス還流部１０ｂは、吸気管３の過給圧センサ８の下流に、換言すると、過給圧センサ８と吸気マニホールド２との間に接続されている。
【００１１】
排気ガス還流管１０には、吸気管３への還流排気ガス量を制御するＥＧＲ制御弁１５と、還流排気ガスを冷却する冷却手段としてのＥＧＲクーラ１６と、排気ガス還流管１０を吸気管３と排気管５とのうち何れか一方に接続する経路切換手段としての三方切換弁１７とがそれぞれ配設されている。ＥＧＲ制御弁１５、ＥＧＲクーラ１６及び三方切換弁１７は、排気ガス還流管１０の上流からこの順にそれぞれ配設されている。
【００１２】
三方切換弁１７は、周知のように三つの接続口ａ，ｂ，ｃを有し、接続口ａはＥＧＲクーラ１６に、接続口ｂは吸気管３にそれぞれ接続されている。三方切換弁１７の接続口ｃには、排気ガス還流管１０を排気管５に接続する排気ガス戻し管１１の排気ガス導入部１１ａが接続されている。排気ガス戻し管１１の排気ガス排出部１１ｂは、排気管５の排気タービン６ａの下流に接続されている。排気ガス還流管１０の三方切換弁１７と排気ガス還流部１０ｂとの間によって第１の経路が、排気ガス戻し管１１によって第２の経路がそれぞれ構成されている。
【００１３】
ＥＧＲ制御弁１５と三方切換弁１７は、制御手段としてのＥＣＵ２０にそれぞれ接続されており、このＥＣＵ２０によってその動作を制御される。ＥＣＵ２０には、図示しない各種の検出手段からアクセル開度（Ａｃｃ）、エンジン回転数（Ｎｅ）及びエンジン負荷（Ｔｗ）の信号が入力される。ＥＣＵ２０は、図４に示すように、ＥＧＲ制御弁１５の開閉及び弁開度を調整するＥＧＲマップを有している。このＥＧＲマップにおいて、横軸はエンジン回転数（Ｎｅ）を、縦軸はエンジン負荷（Ｔｗ）を、線Ｅはエンジンの運転領域をそれぞれ示している。また、領域ＡはＥＧＲを行う領域を、領域ＢはＥＧＲを行わない領域を、領域Ｃはエンジン１が高負荷、高回転である領域を示し、ＥＧＲを行わず、かつ、後述の酸化触媒４０を活性化する領域をそれぞれ示している。領域Ａにおいては、矢印Ａ１で示すように、領域Ａの上部の領域ではＥＧＲ制御弁１５の開度を小さく、その反対に領域Ａの下部の領域ではＥＧＲ制御弁１５の開度を大きくする。
ＥＧＲ制御弁１５、ＥＧＲクーラ１６、三方切換弁１７、排気ガス還流管１０、排気ガス戻し管１１及びＥＣＵ２０によって、ＥＧＲ装置が主に構成されている。
【００１４】
ＥＧＲクーラ１６のコア部は、図２，３に示すように、冷却液が流通する冷却液流路３０によって平板状に形成された冷却液層３１と、排気ガスが流通する排気ガス流路３２によって平板状に形成された排気ガス層３３とが互いに積層されて構成されている。冷却液層３１と排気ガス層３３との間には、冷却液流路３０からの冷却液の漏れと、排気ガス流路３２からの排気ガスの漏れとを防止するための薄板３４が介在されている。
【００１５】
ＥＧＲクーラ１６の上部には、冷却液層３１に対して冷却液の供給、排出を行う冷却液給排管３５，３６がそれぞれ接続されている。冷却液給排管３５，３６は、エンジン１のウォータジャケットにそれぞれ接続されている。ＥＧＲクーラ１６内の冷却液は、エンジン冷却用のラジエータのウォータポンプによって、ＥＧＲクーラ１６、ウォータジャケット及びラジエータを循環される。冷却液供給管３５には、ＥＧＲクーラ１６への冷却液の供給を制御する冷却液制御弁３７が配設されている（図１参照）。冷却液制御弁３７も、ＥＣＵ２０に接続されており、ＥＣＵ２０によってその作動を制御される。
【００１６】
ＥＧＲクーラ１６の下部には、ＥＧＲ制御弁１５によってその量を制御された排気ガスが流入する流入口３８と、ＥＧＲクーラ１６によって冷却された排気ガスを排出する排出口３９とがそれぞれ設けられている。なお、図２において、冷却液及び排気ガスをＥＧＲクーラ１６にそれぞれ供給する向きを互いに逆向きとすることにより、排気ガスを効率良く冷却することができる。
【００１７】
排気ガス流路３２は、図３に示すように、排気ガスの温度が効率良く低下するように、波状に形成されている。排気ガス流路３２の内壁面には、酸化触媒４０が担持されている。酸化触媒４０としては、白金（Ｐｔ）、パラジウム（Ｐｄ）等が知られており、排気ガスにより昇温されたときに排気ガス中の酸素（Ｏ2）により煤（ＨＣ、パティキュレート等）を酸化する。本実施例では、酸化触媒４０に活性温度が高いパラジウム触媒を使用している。酸化触媒４０は、触媒の温度によってその浄化率が変化することが知られている。ここで、触媒温度と浄化率との関係を図５に示す。同図において、横軸は触媒温度、すなわち、排気ガスの温度を、縦軸は浄化率をそれぞれ示している。図４に示す浄化率の特性から明らかなように、酸化触媒は、排気ガス温度がＴ1（略３００°Ｃ）以上となると浄化率が急激に上昇する。
【００１８】
次に、ＥＣＵ２０により制御されるＥＧＲ装置の動作について、図６に示すフローチャートを参照して説明する。
まず、ステップＳ１では、各種の検出手段からエンジン回転数（Ｎｅ）及びエンジン負荷（Ｔｗ）の信号を読み込み、ステップＳ２に進む。ステップＳ２では、ＥＧＲを行うか行わないかをＥＧＲマップに基づいて判定する。すなわち、現在の運転状態（Ｎｅ，Ｔｗ）がＥＧＲマップ上においてどの領域に位置するかを検出する。このとき、運転状態が、領域Ａに位置していれば、ＥＧＲを行うと判断し、ステップＳ３に進む。また、運転状態が、領域Ｂまたは領域Ｃに位置していれば、ＥＧＲを行わないと判断し、ステップＳ１０に進む。
【００１９】
ステップＳ３では、ステップＳ１において読み込んだエンジン回転数（Ｎｅ）及びエンジン負荷（Ｔｗ）に対応するＥＧＲ制御弁１５の開度をＥＧＲマップから読み込み、ステップＳ４に進む。ステップＳ４では、ＥＧＲマップから読み込んだＥＧＲ制御弁１５の開度に基づいてＥＧＲ制御弁１５の開度を調整し、冷却液制御弁３７を開弁してＥＧＲクーラ１６に冷却液を供給し、三方切換弁１７を図１中ａ→ｂの向きに切り換える。すなわち、ＥＧＲクーラ１６の排気ガス排出口と吸気管３とを連通させて、ＥＧＲを行う。ＥＧＲを行った後、ステップＳ１に戻る。
【００２０】
よって、エンジンから排出された排気ガスは、排気ガス還流管１０を通り、ＥＧＲ制御弁１５によってその流量を制限され、ＥＧＲクーラ１６に流入する。ＥＧＲクーラ１６により冷却された排気ガスは、三方切換弁１７を介して排出部１０ｂに送られ、吸気管３に還流される。排気ガスは、ＥＧＲクーラ１６によりその温度をＴ0（略１５０°Ｃ）（図５参照）まで冷却される。その結果、排気ガスの比熱を高められるので、排気ガスを冷却しない場合よりも高いＮＯｘ低減効果を得ることができる。排気ガスは、過給圧センサ８の下流に還流されるので、コンプレッサ６ｂ、インタクーラ７及び過給圧センサ８を汚すことがなく、これらを排気ガスの煤（ＨＣ、パティキュレート等）による汚染から守ることができる。
【００２１】
一方、ステップＳ１０では、ターボチャージャ６による過給圧を過給圧センサ８によって検出し、ステップＳ１１に進む。ステップＳ１１では、過給圧が所定値Ｑよりも大きいかどうかを判定し、酸化触媒４０の活性化を行うかどうかを判断する。ここで、所定値Ｑについて説明する。所定値Ｑは、排気ガス増加による排気タービン６ａの過回転を防止するためのしきい値である。排気タービン６ａの過回転により過給圧が上昇すると、大量の圧縮空気がシリンダ内に送り込まれて強力な爆発力が発生し、エンジンを破損するおそれがある。そこで、排気ガス増加による排気タービン６ａの過回転を防止するために、過給圧と所定値Ｑとを比較する。比較の結果、過給圧が所定値Ｑ以下である場合には、ＥＧＲマップ上において、運転状態が領域Ｂに位置しているので、ＥＧＲを行わないと判断し、ステップＳ１２に進み、過給圧が所定値Ｑよりも大きい場合には、ＥＧＲマップ上において、運転状態が領域Ｃに位置しているので、酸化触媒４０の活性化を行うと判断し、ステップＳ１３に進む。
【００２２】
ステップＳ１２では、ＥＧＲ制御弁１５を閉弁し、排気ガスのＥＧＲ制御弁１５よりも下流側への流出を遮断する。冷却液制御弁３７及び三方切換弁１７は、ＥＧＲを行っている状態、すなわち、冷却液制御弁３７を開弁、三方切換弁１７を図中ａ→ｂの向きに切り換えた状態にそれぞれ維持していても良いし、冷却液制御弁３７を閉弁してＥＧＲクーラ１６への冷却液の供給を停止するとともに、三方切換弁１７を図中ａ→ｃの向きに切り換えても良い。本実施例では、ステップＳ１２において、冷却液制御弁３７及び三方切換弁１７の制御を特に行っていない。すなわち、冷却液制御弁３７及び三方切換弁１７は開弁状態、図１中ａ→ｂの向きに切り換えられた状態にそれぞれ維持されている。各弁１５，１７，３７の制御を行った後、ステップＳ１に戻る。
【００２３】
ステップＳ１３では、過給圧が所定値Ｑ以下となるようにＥＧＲ制御弁１５の開度を調整し、冷却液制御弁３７を閉弁してＥＧＲクーラ１６への冷却液の供給を停止し、三方切換弁１７を図１中ａ→ｃの向きに切り換える。排気ガスが増加しても、ＥＧＲ制御弁１５が開弁することにより、エンジンから排出された排気ガスは、排気ガス還流管１０を通り、ＥＧＲ制御弁１５によってその流量を制限され、ＥＧＲクーラ１６に流入し、三方切換弁１７及び排気ガス戻し管１１を介して排出部１１ｂに送られ、排気管５に排出される。
【００２４】
よって、排気ガスが増加して過給圧が所定値Ｑを越えても、排気ガスが排気ガス戻し管１１を介して排気管５に排出されるので、排気タービン６ａの過回転を防止することができる。換言すると、ＥＧＲ制御弁１５、三方切換弁１７及び排気ガス戻し管１１によって、ウエストゲートバルブの役割を行っており、ターボチャージャ機構におけるウエストゲートバルブを省略することができる。
【００２５】
排気ガス戻し管１１を介して排気ガスを排気管５に排出しているときには、ＥＧＲクーラ１６への冷却液の供給を停止しているので、ＥＧＲクーラ１６内を通過する排気ガスは冷却されず、排気ガス温度は高温のままである。このときの排気ガス温度は、Ｔ2（略４００°Ｃ）（図５参照）であり、酸化触媒４０が活性化する温度を満たしている。
【００２６】
よって、高温の排気ガスがＥＧＲクーラ１６内を通過するときに、酸化触媒４０が活性化して、ＥＧＲクーラ１６の排気ガス流路３２の内壁面に付着した煤（ＨＣ、パティキュレート等）が酸化（再燃焼）される。したがって、排気ガス流路３２の内壁面に付着した煤（ＨＣ、パティキュレート等）が除去され、排気ガス流路３２の内壁面が初期状態に維持されるので、ＥＧＲクーラ１６における圧力損失の増大を防止でき、ＥＧＲクーラ１６の冷却性能を維持できる。
【００２７】
次に、第２の実施例を図７に示し、この実施例について説明する。同図において、図１に示す部材と同様の部材は、図１で用いた符号と同一符号を付すにとどめてその説明を省略し、相違する点について説明する。第２の実施例は、第１の実施例のディーゼルエンジンに対して、ターボチャージャを備えていない点で相違している。
【００２８】
この実施例では、排気ガスが酸化触媒４０を活性化する温度、例えば、３００°Ｃ以上であって、かつ、ＥＧＲを行わないときに、ＥＣＵ２０による制御によって、ＥＧＲ制御弁１５を開弁してＥＧＲクーラ１６に排気ガスを供給し、冷却液制御弁３７を閉弁してＥＧＲクーラ１６への冷却液の供給を停止し、三方切換弁１７を図１中ａ→ｃの向きに切り換える。このとき、ＥＧＲクーラ１６内を通過する排気ガスは冷却されないので、高温の排気ガスによって酸化触媒４０が活性化して、排気ガス流路３２の内壁面に付着した煤（ＨＣ、パティキュレート等）が酸化（再燃焼）される。
【００２９】
また、ＥＧＲクーラ１６の排気ガス流路３２内に、排気ガス流路３２の内壁面に付着した煤（ＨＣ、パティキュレート等）の付着量を検出する煤付着量センサを設け、このセンサからの信号に基づいて、酸化触媒４０の活性化を行っても良い。
【００３０】
上述した第１の実施例では、ターボチャージャを備えたディーゼルエンジンについて説明したが、ターボチャージャに代えてスーパーチャージャを適用しても良い。また、本発明の排気ガス還流装置をガソリンエンジンに適用した場合でも、本実施例の効果と同様の効果を得ることができる。
【００３１】
【発明の効果】
以上説明したように、本発明の請求項１の発明によれば、排気ガスが酸化触媒を活性化する温度であって、かつ、排気ガス還流を行わないときに、制御手段が、冷却手段による排気ガスの冷却を停止するとともに、排気ガス還流経路を排気経路に接続するように経路切換手段を切り換えるので、冷却手段の内部を高温の排気ガスが通過して酸化触媒が活性化し、冷却手段の内部に付着した煤が酸化（再燃焼）される。したがって、冷却手段の内部に付着した煤（ＨＣ、パティキュレート等）が除去されるので、冷却手段における圧力損失の増大を防止でき、冷却手段の冷却性能を維持できる。
【００３２】
請求項２の発明によれば、内燃機関が高負荷・高回転であるとき、すなわち、ターボチャージャによる過給圧が高いとき、制御手段が、ＥＧＲ制御弁を開弁し、排気ガス還流経路が第２の経路に接続するように経路切換手段を切換えるので、排気ガスが第２の経路を介して排気経路に排出される。したがって、ターボチャージャによる過給圧の異常上昇を防止することができ、ターボチャージャ機構におけるウエストゲートバルブを省略することができる。しかも、高温の排気ガスが冷却手段の内部を通過して酸化触媒が活性化し、冷却手段の内部に付着した煤が酸化（再燃焼）される。
【００３３】
請求項３の発明によれば、内燃機関が高負荷・高回転であるとき、すなわち、ターボチャージャによる過給圧が高いとき、制御手段が、冷却手段による排気ガスの冷却を停止するとともに、ＥＧＲ制御弁を開弁し、排気ガス還流経路が第２の経路に接続するように経路切換手段を切換えるので、排気ガスが第２の経路を介して排気経路に排出されて、高温の排気ガスが冷却手段の内部を通過して酸化触媒が活性化し、冷却手段の内部に付着した煤が酸化（再燃焼）される。したがって、冷却手段の内部に付着した煤（ＨＣ、パティキュレート等）が除去されて、冷却手段における圧力損失の増大を防止でき、冷却手段の冷却性能を維持できる。また、ターボチャージャによる過給圧の異常上昇を防止することができ、ターボチャージャ機構におけるウエストゲートバルブを省略することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施例を示すＥＧＲ装置の概略構成図である。
【図２】ＥＧＲクーラの拡大図である。
【図３】ＥＧＲクーラのコア部の分解斜視図である。
【図４】ＥＧＲ制御弁の開閉及び弁開度を調整するＥＧＲマップである。
【図５】触媒温度と浄化率との関係を示す特性線図である。
【図６】ＥＣＵによる制御内容を示すフローチャートである。
【図７】本発明の第２の実施例を示すＥＧＲ装置の概略構成図である。
【符号の説明】
３ 吸気管（吸気経路）
５ 排気管（排気経路）
６ ターボチャージャ
１０ 排気ガス還流管（排気ガス還流経路、第１の経路）
１１ 排気ガス戻し管（第２の経路）
１５ ＥＧＲ制御弁
１６ ＥＧＲクーラ（冷却手段）
１７ 三方切換弁（経路切換手段）
２０ 制御手段
３７ 冷却液制御弁
４０ 酸化触媒[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas recirculation device that recirculates part of exhaust gas to an intake passage.
[0002]
[Prior art]
In general, exhaust gas exhausted by driving an internal combustion engine of a vehicle contains nitrogen oxides (hereinafter referred to as NOx), and these NOx and the like are regulated as harmful components. ing. As an apparatus for reducing this NOx, an exhaust gas recirculation apparatus (hereinafter referred to as an EGR apparatus) is known that recirculates exhaust gas to an intake passage to suppress an increase in combustion temperature and reduce the amount of NOx produced.
[0003]
Further, an EGR cooler is provided in the exhaust gas recirculation passage of the EGR device, and the exhaust gas recirculated to the intake passage is cooled by the EGR cooler, the volume of the exhaust gas is reduced to increase the density, and a large amount of exhaust gas is sucked in. It is also known that the amount of NOx produced is reduced by recirculating to the path to suppress the rise in combustion temperature.
[0004]
[Problems to be solved by the invention]
However, in the above-described EGR apparatus having an EGR cooler, when EGR is performed for a long time, soot (HC, particulates, etc.) adheres to the wall surface of the exhaust gas passage in the EGR cooler, and the cross-sectional area of this passage Decrease. The adhesion of the soot causes a problem that the pressure loss increases in the EGR cooler and a problem that the cooling performance of the EGR cooler decreases.
[0005]
Therefore, an object of the present invention is to provide an exhaust gas recirculation device capable of preventing soot from adhering to the wall surface of the exhaust gas passage in the cooling means and lowering the cooling performance of the cooling means.
[0006]
[Means for Solving the Problems]
The invention of claim 1 is an exhaust gas recirculation having an exhaust gas recirculation path for recirculating exhaust gas in an exhaust path of an internal combustion engine to an intake path, and a cooling means provided in the exhaust gas recirculation path for cooling the exhaust gas. In the apparatus, the cooling means includes, in its core, an exhaust gas layer in which exhaust gas in the exhaust gas recirculation path flows and a coolant layer in which cooling water of the internal combustion engine flows to cool the exhaust gas in the exhaust gas layer. In addition, an oxidation catalyst is provided on the inner wall surface of the exhaust gas flow path facing the exhaust gas layer, and is disposed downstream of the cooling means in the exhaust gas recirculation path. A path switching means connected to one of the path and the exhaust path, and when the exhaust gas is at a temperature at which the oxidation catalyst is activated and the exhaust gas is not recirculated, the cooling means is cooled. Control means for stopping the cooling of the exhaust gas in the exhaust gas recirculation path by stopping the supply of cooling water to the liquid layer and switching the path switching means so as to connect the exhaust gas recirculation path to the exhaust path It is characterized by having.
According to this configuration, when the exhaust gas is at a temperature that activates the oxidation catalyst and exhaust gas recirculation is not performed, the control unit stops cooling the exhaust gas by the cooling unit, and the exhaust gas recirculation is performed. Since the path switching means is switched so that the path is connected to the exhaust path, the high temperature exhaust gas passes through the inside of the cooling means and the oxidation catalyst is activated, soot adhering to the inside of the cooling means is oxidized (reburned). The
[0007]
According to a second aspect of the present invention, there is provided an exhaust gas recirculation path having an exhaust gas recirculation path for recirculating exhaust gas in an exhaust path of an internal combustion engine to an intake path, and a cooling means provided in the exhaust gas recirculation path for cooling the exhaust gas. In the apparatus, the cooling means includes an exhaust gas layer in which the exhaust gas in the exhaust gas recirculation path flows and a cooling liquid layer in which cooling water of the internal combustion engine flows and cools the exhaust gas in the exhaust gas layer. And an oxidation catalyst is provided on the inner wall surface of the exhaust gas passage facing the exhaust gas layer of the cooling means, and is disposed downstream of the cooling means in the exhaust gas recirculation path. Path switching means for connecting a path to one of the intake path and the exhaust path, and control means for switching the path switching means, and the internal combustion engine introduces an exhaust turbine into the exhaust path. A turbocharger having a compressor disposed therein, and an EGR control valve that controls the amount of exhaust gas recirculated to the intake path via the exhaust gas recirculation path, wherein the path switching means connects the exhaust gas recirculation path to the intake air The control means is connected to one of a first path communicating with the downstream of the turbocharger and a second path communicating with the exhaust path, and the control means is configured so that the internal combustion engine has a high load and a high rotation speed. Control means for opening the EGR control valve and switching the path switching means so that the exhaust gas recirculation path is connected to the second path rather than being connected to the first path. Features.
According to this configuration, when the internal combustion engine has a high load and a high rotation, that is, when the supercharging pressure by the turbocharger is high, the control means opens the EGR control valve and the exhaust gas recirculation path is the second. Since the path switching means is switched so as to be connected to the path, the exhaust gas is discharged to the exhaust path via the second path. Moreover, the high temperature exhaust gas passes through the inside of the cooling means and the oxidation catalyst is activated, so that the soot adhering to the inside of the cooling means is oxidized (reburned).
[0008]
According to a third aspect of the present invention, in the exhaust gas recirculation apparatus according to the second aspect, when the exhaust gas is at a temperature at which the oxidation catalyst is activated and the exhaust gas recirculation is not performed, the control means The cooling of the exhaust gas by the cooling means is stopped, and the path switching means is switched so as to connect the exhaust gas recirculation path to the second path.
According to this configuration, particularly when the exhaust gas recirculation is not performed at a temperature at which the oxidation catalyst is activated , the control unit stops cooling the exhaust gas by the cooling unit and opens the EGR control valve. Since the path switching means is switched so that the exhaust gas recirculation path is connected to the second path, the exhaust gas is discharged to the exhaust path via the second path, and the hot exhaust gas passes through the inside of the cooling means. As a result, the oxidation catalyst is activated and the soot adhering to the inside of the cooling means is oxidized (reburned).
[0009]
【Example】
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of an EGR device (exhaust gas recirculation device). In FIG. 1, reference numeral 1 denotes a diesel engine body (hereinafter referred to as an engine), reference numeral 2 denotes an intake manifold of the engine 1, and reference numeral 3 denotes an intake pipe as an intake path connected to the intake manifold 2. Reference numeral 4 denotes an exhaust manifold of the engine 1, and reference numeral 5 denotes an exhaust pipe as an exhaust path connected to the exhaust manifold 4. Reference numeral 6 denotes a turbocharger, in which an exhaust turbine 6a is interposed in the exhaust pipe 5, and a compressor 6b is interposed in the intake pipe 3. An intercooler 7 and a supercharging pressure sensor 8 are arranged in this order downstream of the compressor 6b of the intake pipe 3. The supercharging pressure sensor 8 detects the supercharging pressure of the intake pipe 3 by the compressor 6b and is connected to an ECU 20 described later.
[0010]
Between the exhaust manifold 4 of the exhaust pipe 5 and the exhaust turbine 6a, an exhaust gas introduction part 10a of the exhaust gas recirculation pipe 10 that constitutes an exhaust gas recirculation path is connected. The exhaust gas recirculation part 10 b of the exhaust gas recirculation pipe 10 is connected downstream of the supercharging pressure sensor 8 of the intake pipe 3, in other words, between the supercharging pressure sensor 8 and the intake manifold 2.
[0011]
The exhaust gas recirculation pipe 10 includes an EGR control valve 15 that controls the amount of recirculated exhaust gas to the intake pipe 3, an EGR cooler 16 that serves as a cooling means for cooling the recirculated exhaust gas, and the exhaust gas recirculation pipe 10. And a three-way switching valve 17 as a path switching means connected to either one of the exhaust pipe 5 and the exhaust pipe 5. The EGR control valve 15, the EGR cooler 16, and the three-way switching valve 17 are arranged in this order from the upstream side of the exhaust gas recirculation pipe 10.
[0012]
As is well known, the three-way switching valve 17 has three connection ports a, b, and c. The connection port a is connected to the EGR cooler 16 and the connection port b is connected to the intake pipe 3. An exhaust gas introduction part 11 a of an exhaust gas return pipe 11 that connects the exhaust gas recirculation pipe 10 to the exhaust pipe 5 is connected to the connection port c of the three-way switching valve 17. The exhaust gas discharge part 11 b of the exhaust gas return pipe 11 is connected downstream of the exhaust turbine 6 a of the exhaust pipe 5. A first path is constituted by the three-way switching valve 17 of the exhaust gas recirculation pipe 10 and the exhaust gas recirculation part 10b, and a second path is constituted by the exhaust gas return pipe 11.
[0013]
The EGR control valve 15 and the three-way switching valve 17 are respectively connected to an ECU 20 as control means, and the operation of the ECU 20 is controlled. The ECU 20 receives signals of accelerator opening (Acc), engine speed (Ne), and engine load (Tw) from various detection means (not shown). As shown in FIG. 4, the ECU 20 has an EGR map that adjusts the opening and closing of the EGR control valve 15 and the valve opening. In this EGR map, the horizontal axis indicates the engine speed (Ne), the vertical axis indicates the engine load (Tw), and the line E indicates the engine operating region. Region A is a region where EGR is performed, region B is a region where EGR is not performed, region C is a region where the engine 1 is at high load and high rotation, EGR is not performed, and an oxidation catalyst 40 described later is used. Each of the regions that activates is shown. In the region A, as indicated by the arrow A1, the opening degree of the EGR control valve 15 is decreased in the upper region of the region A, and on the contrary, the opening amount of the EGR control valve 15 is increased in the lower region of the region A.
The EGR control valve 15, the EGR cooler 16, the three-way switching valve 17, the exhaust gas recirculation pipe 10, the exhaust gas return pipe 11, and the ECU 20 mainly constitute an EGR device.
[0014]
As shown in FIGS. 2 and 3, the core portion of the EGR cooler 16 includes a cooling liquid layer 31 formed in a flat plate shape by a cooling liquid flow path 30 through which a cooling liquid flows, and an exhaust gas flow path 32 through which exhaust gas flows. The exhaust gas layer 33 formed in a flat plate shape is stacked on each other. A thin plate 34 is interposed between the coolant layer 31 and the exhaust gas layer 33 to prevent leakage of coolant from the coolant channel 30 and exhaust gas from the exhaust gas channel 32. ing.
[0015]
Cooling liquid supply and discharge pipes 35 and 36 for supplying and discharging the cooling liquid to and from the cooling liquid layer 31 are respectively connected to the upper part of the EGR cooler 16. The coolant supply / discharge pipes 35 and 36 are connected to the water jacket of the engine 1, respectively. The coolant in the EGR cooler 16 is circulated through the EGR cooler 16, the water jacket, and the radiator by a water pump of a radiator for cooling the engine. The coolant supply pipe 35 is provided with a coolant control valve 37 that controls supply of coolant to the EGR cooler 16 (see FIG. 1). The coolant control valve 37 is also connected to the ECU 20 and its operation is controlled by the ECU 20.
[0016]
In the lower part of the EGR cooler 16, an inflow port 38 through which the exhaust gas whose amount is controlled by the EGR control valve 15 flows and an exhaust port 39 through which the exhaust gas cooled by the EGR cooler 16 is discharged are provided. Yes. In FIG. 2, the exhaust gas can be efficiently cooled by reversing the directions in which the coolant and the exhaust gas are supplied to the EGR cooler 16, respectively.
[0017]
As shown in FIG. 3, the exhaust gas flow path 32 is formed in a wave shape so that the temperature of the exhaust gas is efficiently lowered. An oxidation catalyst 40 is supported on the inner wall surface of the exhaust gas passage 32. Platinum (Pt), palladium (Pd), and the like are known as the oxidation catalyst 40. When the temperature is raised by the exhaust gas, soot (HC, particulates, etc.) is generated by oxygen (O 2 ) in the exhaust gas. Oxidize. In this embodiment, a palladium catalyst having a high activation temperature is used as the oxidation catalyst 40. It is known that the purification rate of the oxidation catalyst 40 varies depending on the temperature of the catalyst. Here, the relationship between the catalyst temperature and the purification rate is shown in FIG. In the figure, the horizontal axis indicates the catalyst temperature, that is, the exhaust gas temperature, and the vertical axis indicates the purification rate. As is clear from the characteristics of the purification rate shown in FIG. 4, the purification rate of the oxidation catalyst increases rapidly when the exhaust gas temperature becomes T 1 (approximately 300 ° C.) or higher.
[0018]
Next, the operation of the EGR device controlled by the ECU 20 will be described with reference to the flowchart shown in FIG.
First, in step S1, the engine speed (Ne) and engine load (Tw) signals are read from various detection means, and the process proceeds to step S2. In step S2, whether or not to perform EGR is determined based on the EGR map. That is, it is detected in which region the current operating state (Ne, Tw) is located on the EGR map. At this time, if the operation state is located in the region A, it is determined that EGR is performed, and the process proceeds to step S3. If the operating state is located in the region B or the region C, it is determined that EGR is not performed, and the process proceeds to step S10.
[0019]
In step S3, the opening degree of the EGR control valve 15 corresponding to the engine speed (Ne) and engine load (Tw) read in step S1 is read from the EGR map, and the process proceeds to step S4. In step S4, the opening degree of the EGR control valve 15 is adjusted based on the opening degree of the EGR control valve 15 read from the EGR map, the cooling liquid control valve 37 is opened, and the cooling liquid is supplied to the EGR cooler 16. The three-way switching valve 17 is switched in the direction a → b in FIG. That is, EGR is performed by communicating the exhaust gas discharge port of the EGR cooler 16 and the intake pipe 3. After performing EGR, the process returns to step S1.
[0020]
Therefore, the exhaust gas discharged from the engine passes through the exhaust gas recirculation pipe 10, the flow rate is limited by the EGR control valve 15, and flows into the EGR cooler 16. The exhaust gas cooled by the EGR cooler 16 is sent to the discharge unit 10b via the three-way switching valve 17 and is recirculated to the intake pipe 3. The temperature of the exhaust gas is cooled to T 0 (approximately 150 ° C.) (see FIG. 5) by the EGR cooler 16. As a result, the specific heat of the exhaust gas can be increased, so that a higher NOx reduction effect can be obtained than when the exhaust gas is not cooled. Since the exhaust gas is recirculated downstream of the supercharging pressure sensor 8, the compressor 6b, the intercooler 7 and the supercharging pressure sensor 8 are not polluted, and these are not contaminated by exhaust gas soot (HC, particulates, etc.). I can protect it.
[0021]
On the other hand, in step S10, the supercharging pressure by the turbocharger 6 is detected by the supercharging pressure sensor 8, and the process proceeds to step S11. In step S11, it is determined whether or not the supercharging pressure is greater than a predetermined value Q, and it is determined whether or not the oxidation catalyst 40 is to be activated. Here, the predetermined value Q will be described. The predetermined value Q is a threshold value for preventing over-rotation of the exhaust turbine 6a due to an increase in exhaust gas. If the supercharging pressure rises due to excessive rotation of the exhaust turbine 6a, a large amount of compressed air is sent into the cylinder, generating a powerful explosive force and possibly damaging the engine. Therefore, the supercharging pressure is compared with the predetermined value Q in order to prevent over-rotation of the exhaust turbine 6a due to an increase in exhaust gas. As a result of the comparison, when the supercharging pressure is equal to or less than the predetermined value Q, since the operating state is located in the region B on the EGR map, it is determined that EGR is not performed, and the process proceeds to step S12. When the pressure is larger than the predetermined value Q, since the operating state is located in the region C on the EGR map, it is determined that the oxidation catalyst 40 is to be activated, and the process proceeds to step S13.
[0022]
In step S <b> 12, the EGR control valve 15 is closed, and the outflow of exhaust gas to the downstream side of the EGR control valve 15 is blocked. The coolant control valve 37 and the three-way switching valve 17 are maintained in a state where EGR is performed, that is, in a state where the coolant control valve 37 is opened and the three-way switching valve 17 is switched from a to b in the drawing. Alternatively, the coolant control valve 37 may be closed to stop the supply of coolant to the EGR cooler 16, and the three-way switching valve 17 may be switched in the direction of a → c in the drawing. In the present embodiment, in step S12, the coolant control valve 37 and the three-way switching valve 17 are not particularly controlled. That is, the coolant control valve 37 and the three-way switching valve 17 are maintained in the open state and the state switched from a to b in FIG. After controlling the valves 15, 17, and 37, the process returns to step S1.
[0023]
In step S13, the opening degree of the EGR control valve 15 is adjusted so that the supercharging pressure is equal to or less than the predetermined value Q, the cooling liquid control valve 37 is closed, and the supply of the cooling liquid to the EGR cooler 16 is stopped. The three-way switching valve 17 is switched in the direction a → c in FIG. Even if the exhaust gas increases, the EGR control valve 15 opens, so that the exhaust gas discharged from the engine passes through the exhaust gas recirculation pipe 10 and the flow rate thereof is limited by the EGR control valve 15. And is sent to the discharge portion 11 b via the three-way switching valve 17 and the exhaust gas return pipe 11 and discharged to the exhaust pipe 5.
[0024]
Therefore, even if the exhaust gas increases and the supercharging pressure exceeds the predetermined value Q, the exhaust gas is discharged to the exhaust pipe 5 through the exhaust gas return pipe 11, so that the exhaust turbine 6a is prevented from over-rotating. Can do. In other words, the EGR control valve 15, the three-way switching valve 17 and the exhaust gas return pipe 11 serve as a waste gate valve, and the waste gate valve in the turbocharger mechanism can be omitted.
[0025]
When the exhaust gas is discharged to the exhaust pipe 5 via the exhaust gas return pipe 11, the supply of the coolant to the EGR cooler 16 is stopped, so that the exhaust gas passing through the EGR cooler 16 is not cooled. The exhaust gas temperature remains high. The exhaust gas temperature at this time is T 2 (approximately 400 ° C.) (see FIG. 5), which satisfies the temperature at which the oxidation catalyst 40 is activated.
[0026]
Therefore, when high-temperature exhaust gas passes through the EGR cooler 16, the oxidation catalyst 40 is activated, and soot (HC, particulates, etc.) adhering to the inner wall surface of the exhaust gas flow path 32 of the EGR cooler 16 is oxidized. (Reburned). Therefore, soot (HC, particulates, etc.) adhering to the inner wall surface of the exhaust gas flow path 32 is removed and the inner wall surface of the exhaust gas flow path 32 is maintained in the initial state, so that the pressure loss in the EGR cooler 16 increases. The cooling performance of the EGR cooler 16 can be maintained.
[0027]
Next, a second embodiment is shown in FIG. 7, and this embodiment will be described. In the figure, members similar to those shown in FIG. 1 are given the same reference numerals as those used in FIG. The second embodiment is different from the diesel engine of the first embodiment in that a turbocharger is not provided.
[0028]
In this embodiment, when the exhaust gas is at a temperature at which the oxidation catalyst 40 is activated, for example, 300 ° C. or higher, and EGR is not performed, the EGR control valve 15 is opened by the control of the ECU 20. Exhaust gas is supplied to the EGR cooler 16, the coolant control valve 37 is closed to stop the supply of coolant to the EGR cooler 16, and the three-way selector valve 17 is switched from a to c in FIG. At this time, since the exhaust gas passing through the EGR cooler 16 is not cooled, the oxidation catalyst 40 is activated by the high-temperature exhaust gas, and soot (HC, particulates, etc.) adhering to the inner wall surface of the exhaust gas passage 32 is formed. Oxidized (reburned).
[0029]
Further, a soot adhesion amount sensor for detecting the amount of soot (HC, particulates, etc.) adhering to the inner wall surface of the exhaust gas flow channel 32 is provided in the exhaust gas flow channel 32 of the EGR cooler 16, and from this sensor The oxidation catalyst 40 may be activated based on the signal.
[0030]
In the first embodiment described above, the diesel engine having the turbocharger has been described. However, a supercharger may be applied instead of the turbocharger. Further, even when the exhaust gas recirculation device of the present invention is applied to a gasoline engine, the same effect as that of the present embodiment can be obtained.
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, when the exhaust gas is at a temperature that activates the oxidation catalyst and the exhaust gas recirculation is not performed, the control means is the cooling means. Since the cooling of the exhaust gas is stopped and the path switching means is switched so that the exhaust gas recirculation path is connected to the exhaust path, the high temperature exhaust gas passes through the cooling means and the oxidation catalyst is activated. Soot adhering to the inside is oxidized (reburned). Therefore, soot (HC, particulates, etc.) adhering to the inside of the cooling means is removed, so that an increase in pressure loss in the cooling means can be prevented and the cooling performance of the cooling means can be maintained.
[0032]
According to the invention of claim 2, when the internal combustion engine has a high load and high rotation, that is, when the supercharging pressure by the turbocharger is high, the control means opens the EGR control valve and the exhaust gas recirculation path is Since the path switching means is switched to connect to the second path, the exhaust gas is discharged to the exhaust path via the second path. Therefore, an abnormal increase in supercharging pressure due to the turbocharger can be prevented, and the wastegate valve in the turbocharger mechanism can be omitted. Moreover, the high temperature exhaust gas passes through the inside of the cooling means and the oxidation catalyst is activated, so that the soot adhering to the inside of the cooling means is oxidized (reburned).
[0033]
According to the invention of claim 3, when the internal combustion engine has a high load and a high rotation, that is, when the supercharging pressure by the turbocharger is high, the control means stops cooling the exhaust gas by the cooling means, and EGR Since the control valve is opened and the path switching means is switched so that the exhaust gas recirculation path is connected to the second path, the exhaust gas is discharged to the exhaust path through the second path, and the high-temperature exhaust gas is discharged. The oxidation catalyst is activated through the inside of the cooling means, and the soot adhering to the inside of the cooling means is oxidized (reburned). Therefore, soot (HC, particulates, etc.) adhering to the inside of the cooling means is removed, an increase in pressure loss in the cooling means can be prevented, and the cooling performance of the cooling means can be maintained. Further, an abnormal increase in supercharging pressure due to the turbocharger can be prevented, and a wastegate valve in the turbocharger mechanism can be omitted.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an EGR apparatus showing a first embodiment of the present invention.
FIG. 2 is an enlarged view of an EGR cooler.
FIG. 3 is an exploded perspective view of a core portion of an EGR cooler.
FIG. 4 is an EGR map for adjusting the opening and closing of the EGR control valve and the valve opening degree.
FIG. 5 is a characteristic diagram showing the relationship between catalyst temperature and purification rate.
FIG. 6 is a flowchart showing the contents of control by an ECU.
FIG. 7 is a schematic configuration diagram of an EGR apparatus showing a second embodiment of the present invention.
[Explanation of symbols]
3 Intake pipe (intake route)
5 Exhaust pipe (exhaust path)
6 Turbocharger 10 Exhaust gas recirculation pipe (exhaust gas recirculation path, first path)
11 Exhaust gas return pipe (second path)
15 EGR control valve 16 EGR cooler (cooling means)
17 Three-way switching valve (route switching means)
20 Control means 37 Coolant control valve 40 Oxidation catalyst

Claims (3)

内燃機関の排気経路の排気ガスを吸気経路に還流させる排気ガス還流経路と、この排気ガス還流経路に設けられ、上記排気ガスを冷却する冷却手段とを有する排気ガス還流装置において、
上記冷却手段はそのコア部に上記排気ガス還流経路の排ガスが流動する排気ガス層と内燃機関の冷却水が流通して上記排気ガス層の排気ガスを冷却する冷却液層とを備えると共に上記排気ガス層と対向する排気ガス流路の内壁面に酸化触媒が設けられており、
上記排気ガス還流経路の上記冷却手段の下流に配設されており、上記排気ガス還流経路を上記吸気経路と排気経路とのうち何れか一方に接続する経路切換手段と、上記排気ガスが上記酸化触媒を活性化する温度であって、かつ、排気ガス還流を行わないとき、上記冷却手段の冷却液層への冷却水の供給を停止することで上記排気ガス還流経路の排気ガスの冷却を停止するとともに、上記排気ガス還流経路を上記排気経路に接続するように上記経路切換手段を切り換える制御手段と、を有することを特徴とする排気ガス還流装置。 In an exhaust gas recirculation apparatus having an exhaust gas recirculation path for recirculating exhaust gas in an exhaust path of an internal combustion engine to an intake path, and a cooling means provided in the exhaust gas recirculation path for cooling the exhaust gas,
The cooling means includes, in its core portion, an exhaust gas layer in which exhaust gas in the exhaust gas recirculation path flows and a coolant layer in which cooling water of the internal combustion engine flows and cools the exhaust gas in the exhaust gas layer, and the exhaust gas An oxidation catalyst is provided on the inner wall surface of the exhaust gas passage facing the gas layer ,
A path switching means disposed downstream of the cooling means in the exhaust gas recirculation path and connecting the exhaust gas recirculation path to either the intake path or the exhaust path; and the exhaust gas is oxidized Stop the cooling of the exhaust gas in the exhaust gas recirculation path by stopping the supply of the cooling water to the cooling liquid layer of the cooling means when the exhaust gas recirculation is not performed at a temperature that activates the catalyst And an exhaust gas recirculation apparatus comprising: a control means for switching the path switching means so as to connect the exhaust gas recirculation path to the exhaust path. 内燃機関の排気経路の排気ガスを吸気経路に還流させる排気ガス還流経路と、この排気ガス還流経路に設けられ、上記排気ガスを冷却する冷却手段とを有する排気ガス還流装置において、
上記冷却手段はそのコア部に上記排気ガス還流経路の排気ガスが流動する排気ガス層と内燃機関の冷却水が流通して上記排気ガス層の排気ガスを冷却する冷却液層とを備えると共に上記冷却手段の排気ガス層と対向する排気ガス流路の内壁面に酸化触媒が設けられており、
上記排気ガス還流経路の上記冷却手段の下流に配設されており、上記排気ガス還流経路を上記吸気経路と排気経路とのうち何れか一方に接続する経路切換手段と、
上記経路切換手段を切換える制御手段と、を備え、
上記内燃機関は排気経路に排気タービンを吸気経路にコンプレッサを配したターボチャージャと、上記排気ガス還流経路を経て上記吸気経路に還流される排気ガス量を制御するＥＧＲ制御弁とを備え、
上記経路切換手段は上記排気ガス還流経路を、上記吸気経路の上記ターボチャージャの下流に連通する第１の経路と、排気経路に連通する第２の経路とのうち何れか一方に接続し、
上記制御手段は上記内燃機関が高負荷・高回転であるとき、上記ＥＧＲ制御弁を開弁し、上記排気ガス還流経路が上記第１の経路に接続する状態より第２の経路に接続するように上記経路切換手段を切換える、ことを特徴とする排気ガス還流装置。 In an exhaust gas recirculation apparatus having an exhaust gas recirculation path for recirculating exhaust gas in an exhaust path of an internal combustion engine to an intake path, and a cooling means provided in the exhaust gas recirculation path for cooling the exhaust gas,
The cooling means includes an exhaust gas layer in which the exhaust gas in the exhaust gas recirculation path flows and a cooling liquid layer in which cooling water of the internal combustion engine flows and cools the exhaust gas in the exhaust gas layer in the core portion. An oxidation catalyst is provided on the inner wall surface of the exhaust gas passage facing the exhaust gas layer of the cooling means,
A path switching means that is disposed downstream of the cooling means in the exhaust gas recirculation path, and connects the exhaust gas recirculation path to either the intake path or the exhaust path;
Control means for switching the path switching means,
The internal combustion engine comprises a turbocharger which arranged compressor to the intake path of the exhaust turbine in the exhaust passage, and an EGR control valve for controlling the amount of exhaust gas recirculated to the upper Symbol intake path via the exhaust gas recirculation passage,
The path switching means connects the exhaust gas recirculation path to either one of a first path communicating with the downstream of the turbocharger of the intake path and a second path communicating with the exhaust path ,
The control means opens the EGR control valve when the internal combustion engine is at a high load and a high speed, so that the exhaust gas recirculation path is connected to the second path rather than being connected to the first path. switching El said path switching means, this exhaust gas recirculation apparatus according to claim. 請求項２記載の排気ガス還流装置において、
上記排気ガスが上記酸化触媒を活性化する温度であって、かつ、排気ガス還流を行わないとき、上記制御手段が、上記冷却手段による上記排気ガスの冷却を停止するとともに、上記排気ガス還流経路を上記第２の経路に接続するように上記経路切換手段を切り換えることを特徴とする請求項２記載の排気ガス還流装置。 The exhaust gas recirculation device according to claim 2,
When the exhaust gas is at a temperature that activates the oxidation catalyst and exhaust gas recirculation is not performed, the control means stops cooling the exhaust gas by the cooling means, and the exhaust gas recirculation path 3. The exhaust gas recirculation device according to claim 2, wherein the path switching means is switched so as to connect to the second path.
JP07350397A 1997-03-26 1997-03-26 Exhaust gas recirculation device Expired - Fee Related JP4126730B2 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20140135692A (en) * 2012-02-10 2014-11-26 하엑스 홀딩 게엠베하 Exhaust gas cooler

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2833653B1 (en) * 2001-12-14 2004-07-09 Peugeot Citroen Automobiles Sa EXHAUST GAS RECYCLING SYSTEM FOR A MOTOR VEHICLE DIESEL ENGINE
KR20040050267A (en) * 2002-12-10 2004-06-16 현대자동차주식회사 Exhaust gas reduction device
BRPI0414441A (en) * 2003-09-18 2006-11-14 Behr Gmbh & Co Kg exhaust gas heat exchanger, in particular exhaust gas cooler for exhaust gas recirculation in motor vehicles
KR20050123353A (en) * 2004-06-25 2005-12-29 현대자동차주식회사 Egr cooler for vehicle and method for control the same
WO2006004468A1 (en) * 2004-07-02 2006-01-12 Volvo Technology Corporation Internal combustion engine exhaust gas system
JP2006105577A (en) * 2004-09-08 2006-04-20 Usui Kokusai Sangyo Kaisha Ltd Fin structure, heat-transfer tube having the fin structure housed therein, and heat exchanger having the heat-transfer tube assembled therein
FR2885178A1 (en) * 2005-04-27 2006-11-03 Renault Sas Power train for motor vehicle, has exhaust gas recirculation valves and back pressure valve circulating exhaust gas in cleaning circuit and evacuating gas in exhaust pipe, where circuit cleans section of exhaust gas recirculation circuit
KR20070080672A (en) * 2006-02-08 2007-08-13 현대자동차주식회사 Vehicle for exhaust gas recirculation cooler
JP4984711B2 (en) * 2006-07-25 2012-07-25 いすゞ自動車株式会社 EGR system and method for controlling EGR system
FR2908830B1 (en) * 2006-11-16 2008-12-19 Renault Sas DEVICE AND METHOD FOR DRAINING A THERMAL EXCHANGER FOR RECYCLING EXHAUST GASES IN A DIESEL ENGINE
DE102009058609A1 (en) * 2009-12-17 2011-06-22 Volkswagen AG, 38440 Device for exhaust gas recirculation and method for heating a cooling medium of an internal combustion engine and use of the device for exhaust gas recirculation
JP2013119823A (en) * 2011-12-08 2013-06-17 Toyota Motor Corp Egr mechanism and internal combustion engine with egr mechanism
JP6284356B2 (en) * 2013-12-26 2018-02-28 ダイハツ工業株式会社 Internal combustion engine
JP6470632B2 (en) * 2015-05-22 2019-02-13 カルソニックカンセイ株式会社 Engine exhaust circulation system
DE102018116983A1 (en) * 2018-07-13 2020-01-16 Iav Gmbh Ingenieurgesellschaft Auto Und Verkehr Method and device for operating an internal combustion engine with an exhaust gas recirculation system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20140135692A (en) * 2012-02-10 2014-11-26 하엑스 홀딩 게엠베하 Exhaust gas cooler
KR102047914B1 (en) * 2012-02-10 2019-11-22 켈비온 홀딩 게엠베하 Exhaust gas cooler

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