JP3674254B2 - EGR device for supercharged engine - Google Patents

EGR device for supercharged engine Download PDF

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Publication number
JP3674254B2
JP3674254B2 JP22511397A JP22511397A JP3674254B2 JP 3674254 B2 JP3674254 B2 JP 3674254B2 JP 22511397 A JP22511397 A JP 22511397A JP 22511397 A JP22511397 A JP 22511397A JP 3674254 B2 JP3674254 B2 JP 3674254B2
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egr
passage
engine
intake
exhaust
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JPH1162715A (en
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隆広 植田
瓏 張
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Isuzu Motors Ltd
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Isuzu Motors Ltd
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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
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/07—Mixed pressure loops, i.e. wherein recirculated exhaust gas is either taken out upstream of the turbine and reintroduced upstream of the compressor, or is taken out downstream of the turbine and reintroduced downstream of the compressor
    • 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
    • F02M26/34—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with compressors, turbines or the like in the recirculation passage
    • 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
    • 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
    • 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
    • F02M26/38—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with two or more EGR valves disposed in parallel

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Supercharger (AREA)
  • Exhaust-Gas Circulating Devices (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、過給機付きディーゼルエンジンなどにおいて、ＮＯｘの排出量を低減するために、排気ガスの一部を吸気側に還流する過給式エンジンのＥＧＲ装置に関するものである。
【０００２】
【従来の技術】
ディーゼルエンジン等の排気ガス対策において、排気ガス中のＮＯｘの排出量を低減するために、不活性ガスである排気ガスの一部を吸気側に還流することによって、燃焼温度を低く抑えて、ＮＯｘの生成を抑制するＥＧＲ（排気再循環）が有効であることが知られており、広く実用化されている。
【０００３】
このＥＧＲ装置は過給式エンジンにも適用され、図５に示すように排気マニホールド12ａから排気ガスＧを取り出し、ＥＧＲクーラー７を配設したＥＧＲ通路９を経由して、吸気通路11の新気Ａに混入して吸気マニホールド11ａへ還流させてＥＧＲを行っている。
しかし、過給式エンジンにおいては、エンジン負荷の上昇に伴い、吸気圧（ブート圧）が高くなり、排気圧より高圧になってくるので、ＥＧＲガスＧを吸気通路11へ還流させることができなくなる。
【０００４】
そのため、排気通路12に通じるウェイストゲート12ｂを開いて排気圧力を下げ、それによってタービン２の回転数を低下させることにより吸気圧力を低減して、ＥＧＲガスＧを吸気通路11に還流させる方法がある。しかし、この方法を取ると新気Ａの量が減少し、スモークの増大を引き起こすので、ＥＧＲできる領域Ｅは、図４（ａ）に示すように、低負荷でかつ中回転以下のエンジンの運転領域に限られてしまうという問題がある。
【０００５】
また、タービン２の入口の断面積を可変にした可変容量型ターボチャージャ（ＶＧターボ）では、入口の断面積をコントロールすることでタービン回転数を変化させて、排気圧と吸気圧を制御してＥＧＲ可能な領域を拡大している。この場合においては、図４（ｂ）に示すような中負荷のＥで示すエンジン運転領域までＥＧＲ可能となるが、更にＮＯｘを低減して排気ガスを浄化するために、エンジンの高負荷運転領域でもＥＧＲ可能にしたいという要求がある。
【０００６】
この要求に関して、特開平３−１１７６６５号、特開平５−１８００８９号、特開平５−８９８５９号等に、ＥＧＲガスをコンプレッサによって圧縮して昇圧し、この昇圧したＥＧＲガスを吸気通路側に還流するように構成することによって、ＥＧＲ領域を拡大するＥＧＲ装置が提案されている。
【０００７】
【発明が解決しようとする課題】
しかしながら、特開平３−１１７６６５号の装置は、エンジンによって駆動されるコンプレッサによりＥＧＲガスを圧縮し、アキュムレータタンク内に蓄圧してから供給しているために、エンジンの駆動力がこのコンプレッサに使用されるのでその分エンジン出力のロスが大きくなる。このロスは、エンジンが高回転、高負荷になるほど大きくなるので、高出力が必要な時程ロスが大きくなるという問題がある。更に、高回転、高負荷領域においてＥＧＲを行うために、容量の大きいコンプレッサ、アキュムレータが必要になるという問題がある。
【０００８】
また、特開平５−１８００８９号の装置は、排気ガスで駆動されるタービンを排気通路に設けてこのタービンに連結したＥＧＲガスコンプレッサでＥＧＲガスを加圧して、吸気通路に還流させている。しかし、この装置においては排気通路に直列に排気ガスのパワーを回収するパワータービンを含めて３つのタービンを設けているため、ＥＧＲ作動時に排気マニホールドの排気圧が大幅に上昇するので、ポンピングロスが大きくなって燃費が悪化するという問題と、高負荷運転において新気の減少を招き黒煙が発生してＥＧＲを行うことのできる領域が限定されるという問題がある。
【０００９】
そして、特開平５−８９８５９号の装置は、第１のターボチャージャで得られた圧縮空気を分岐して第２のターボチャージャを駆動し、この第２のターボチャージャのコンプレッサでＥＧＲガスを昇圧し、それと共に、このコンプレッサから圧縮空気を逃がして吸気圧を下げてＥＧＲを行っている。しかし、この装置では、圧縮空気を分岐するため、シリンダへ供給される圧縮吸気量が減少するので、ＥＧＲガス量に対する吸気量が減少してスモークが発生するという問題がある。
【００１０】
本発明は、上述の問題を解決するためになされたものであり、その目的は、エンジンの高負荷運転時でもＥＧＲが可能で、しかも、シリンダへの吸気量を十分に確保できてスモークの発生や燃料消費の悪化を防止できると共に、更に、エンジンの運転状態に応じてＥＧＲガスを昇圧して、効率よくＥＧＲを行うことができて、エンジンの全運転領域で排気ガス中のＮＯｘの排出量を低減できる過給式エンジンのＥＧＲ装置を提供することにある。
【００１１】
【課題を解決するための手段】
以上のような目的を達成するための過給式エンジンのＥＧＲ装置は、エンジンの排気通路に設けたタービンによって、吸気通路に設けたコンプレッサを駆動する過給式エンジンにおいて、排気通路と吸気通路とを接続して第１ＥＧＲ通路を設けると共に、該第１ＥＧＲ通路に、ＥＧＲガスを昇圧して吸気通路に還流するＥＧＲガスコンプレッサを設け、該ＥＧＲガスコンプレッサと前記タービンとの間をクラッチ機構を介して継脱自在に連結して構成したものであり、排気通路にＥＧＲガスコンプレッサ用のタービンを新たに設ける必要がなくなるので、排気圧の上昇を防ぐことができ、燃料消費の悪化を防止できる。しかも、吸気の分岐及び逃がしによる吸気量の減少がないので、シリンダに供給される吸気量を十分に確保でき、スモークの発生を防止しながら、ＥＧＲを行うことができる。
【００１２】
また、前記排気通路の前記タービンより下流側と吸気通路とを、前記ＥＧＲガスコンプレッサを配設した前記第１ＥＧＲ通路で連結すると共に、前記排気通路の前記タービンより上流側と吸気通路とを第２ＥＧＲ通路で連結する。
更に、前記第１ＥＧＲ通路と前記第２ＥＧＲ通路に、第１ＥＧＲ弁と第２ＥＧＲ弁をそれぞれ配設すると共に、エンジンの回転数を検出する回転数センサーとエンジンの負荷を検出する負荷センサーを設け、更に、前記回転数センサーの出力と前記負荷センサーの出力とを入力して前記クラッチ機構と前記第１ＥＧＲ弁と前記第２ＥＧＲ弁の制御を行うコントローラを設けて構成する。
【００１３】
この構成により、エンジンの回転数や負荷を入力してＥＧＲガス圧と吸気圧を推定し、この大小関係に対応して２つのＥＧＲ通路を使い分けできるので、エンジンのロスを防止しながら効率よくＥＧＲを行うことができ、エンジンの運転領域全体において排気ガス中のＮＯｘの低減を図ることができる。
【００１４】
【発明の実施の形態】
以下、図面を用いて、本発明に係る過給式エンジンのＥＧＲ装置の実施の形態を説明する。
図１に示すように、第１の実施の形態の過給式エンジン１においては、タービン２を排気通路12に設けて、吸気通路11に設けたコンプレッサ３を駆動して、新気Ａを圧縮して、この新気Ａをインタークーラ６を経由して、吸気マニホールド11ａに供給している。
【００１５】
このエンジン１の排気通路12と吸気通路11とを第１ＥＧＲ通路９で連結し、更に、この第１ＥＧＲ通路９にＥＧＲガスコンプレッサ５を設け、このＥＧＲガスコンプレッサ５とタービン２との間をクラッチ機構４を介して継脱自在に連結し、ＥＧＲガスコンプレッサ５がタービン２の駆動力を受けて駆動されるように構成する。
【００１６】
また、エンジン１の回転数を検出する回転数センサー14とエンジンの負荷を検出する負荷センサー15とコントローラ20を設ける。このコントローラ20が回転数センサー14の出力と負荷センサー15の出力とを入力して、クラッチ機構４の制御を行うように構成する。
つまり、通常の新気Ａ用のコンプレッサ３に加えてＥＧＲガスＧを圧縮するＥＧＲガスコンプレッサ５を第１ＥＧＲ通路９に設けて、エンジン１が高負荷運転状態で排気ガス圧＜吸気圧（ブースト圧）のときに、クラッチ機構４を連結してＥＧＲガスコンプレッサ５を駆動し、ＥＧＲガスの圧縮及び昇圧を行って、昇圧したＥＧＲガスＧを吸気通路11に供給するように構成する。
【００１７】
以上の構成により、第１ＥＧＲ通路９に設けたＥＧＲガスコンプレッサ５により、ＥＧＲガスＧの圧力を過給機のコンプレッサ３によって圧縮された新気Ａの吸気圧よりも高圧にすることができるので、エンジン１の高負荷運転領域でもＥＧＲを行うことができる。
また、図２に示す、第２の実施の形態では、排気通路13のタービン２より下流側と吸気通路11とを、ＥＧＲガスコンプレッサ５を配設した第１ＥＧＲ通路９で連結すると共に、排気通路12のタービン２より上流側と吸気通路11とを、第２ＥＧＲ通路19で連結する。
【００１８】
このＥＧＲガスコンプレッサは、タービン２の駆動力を受けて駆動できるように、図１の第１の実施の形態と同様に、ＥＧＲガスコンプレッサ５とタービン２との間をクラッチ機構４を介して継脱自在に連結して構成する。
そして、更に、第１ＥＧＲ通路９に第１ＥＧＲ弁８を、また、第２ＥＧＲ通路19に、第２ＥＧＲ弁18をそれぞれ配設し、また、エンジン１の回転数を検出する回転数センサー14とエンジンの負荷を検出する負荷センサー15とコントローラ20を設ける。このコントローラ20が回転数センサー14の出力と負荷センサー15の出力とを入力して、クラッチ機構４と第１ＥＧＲ弁８と第２ＥＧＲ弁18の制御を行うように構成する。
【００１９】
以上の構成により、図３のＮ部分で示すエンジン１の低・中負荷運転領域では、吸気圧が排気圧より低いので、第１ＥＧＲ弁８を閉弁し、クラッチ機構４をオフにすると共に、第２ＥＧＲ弁を開弁して、ＥＧＲガスＧを第２ＥＧＲ通路19を経由させて、ＥＧＲガスＧを昇圧せずにそのまま吸気通路11に供給してＥＧＲを行う。これにより、比較的低温・低圧の排気ガスＧが持つ少ない排気エネルギーをＥＧＲガスの昇圧に使用することなく、タービン２でコンプレッサ３だけを駆動して、吸気側に十分利用できるので、シリンダへの十分な圧縮空気量を確保することができる。
【００２０】
また、この第２ＥＧＲ通路19の入口をタービン２より上流側に設けて構成したので、タービン２の上流側の比較的圧力の高い部分の排気ガスＧをＥＧＲに使用できるので、円滑にかつ効率的にＥＧＲガスを吸気通路に還流できる。
また、図３のＣ部分で示す高負荷運転領域では、吸気圧が排気圧よりも高いので、第１ＥＧＲ弁８を開弁し、クラッチ機構４をオンにして駆動力を伝達すると共に、第２ＥＧＲ弁18を閉弁して、ＥＧＲガスＧを第１ＥＧＲ通路９に導いて、ＥＧＲガスＧをＥＧＲガスコンプレッサ５で昇圧して吸気通路11に供給してＥＧＲを行う。
【００２１】
この高負荷運転領域Ｃでは、排気ガスＧのエネルギーも大きくなるので、ＥＧＲガスコンプレッサ５を駆動しても、コンプレッサ３で新気Ａを十分に圧縮でき、しかも、圧縮された吸気Ａを全量シリンダへ供給して、シリンダへの圧縮吸気量を確保できるので、適切なＥＧＲ率を確保して、効率よくＥＧＲを行うことができる。
【００２２】
即ち、ウェイストゲート12ｂを開けて排気ガスＧの一部逃がして吸気圧を下げる必要がなくなるので、排気ガスＧのエネルギーをタービン２で十分に利用できる。
また、この第１ＥＧＲ通路９の入口をタービン２より下流側に設けて構成したので、ＥＧＲガスＧが吸気通路11側に還流される前に、タービン２を通過させて排気ガスＧのエネルギーを回収できるので、効率よくコンプレッサ３を駆動できる。
【００２３】
従って、ＥＧＲガスＧの経路を、エンジン１の回転数や負荷の状況に応じて、ＥＧＲガスＧを昇圧する第１ＥＧＲ通路９とＥＧＲガスＧを昇圧しない第２ＥＧＲ通路19を選択して、エンジンの運転状況に適したＥＧＲを効率よく行うことができる。
【００２４】
【発明の効果】
以上の説明したように、請求項１に係る本発明の過給式エンジンのＥＧＲ装置によれば、ＥＧＲガスコンプレッサで昇圧したＥＧＲガスを吸気通路側に供給してＥＧＲを行うので、ＥＧＲ可能なエンジンの運転領域を高負荷領域にまで拡大することができる。
【００２５】
そして、ＥＧＲガスコンプレッサをクラッチ機構を介して、排気通路に設けた吸気コンプレッサ用のタービンで駆動するように構成したので、排気通路にＥＧＲガスコンプレッサ用のタービンを新たに設ける必要がなくなり、排気圧の上昇を防止できるので、ポンピングロスを抑制でき、燃料消費の悪化を防止できる。
また、請求項２及び請求項３に係る本発明の過給式エンジンのＥＧＲ装置によれば、ＥＧＲガスを昇圧せずに吸気側へ還流させるＥＧＲ通路を加えて、ＥＧＲ通路を２系列にしたので、排気圧が吸気圧より高い運転領域では第２ＥＧＲ通路を経由して吸気側へ還流させ、また、排気圧が吸気圧より低い運転領域ではＥＧＲガスコンプレッサを設けた第１ＥＧＲ通路を経由させて昇圧したＥＧＲガスを還流させることができるので、エンジンの回転数や負荷の状況に応じて、エンジン出力のロスを防止しながら、効率よくＥＧＲを行うことができる。
【図面の簡単な説明】
【図１】本発明に係る第１の実施の形態の過給式エンジンのＥＧＲ装置の構成図である。
【図２】本発明に係る第２の実施の形態の過給式エンジンのＥＧＲ装置の構成図である。
【図３】本発明に係る過給式エンジンのＥＧＲ装置のＥＧＲ領域とＥＧＲ運転方法を示す模式図である。
【図４】従来技術のＥＧＲ領域を示す模式図で、（ａ）は、過給式エンジンのＥＧＲ装置のＥＧＲ領域を、（ｂ）はＶＧターボエンジンにおけるＥＧＲ装置のＥＧＲ領域を示す。
【図５】従来技術の過給式エンジンのＥＧＲ装置の構成図である。
【符号の説明】
１ エンジン ２ 過給機のタービン
３ 過給機のコンプレッサ ４ クラッチ機構
５ ＥＧＲガスコンプレッサ ６ インタークーラ
７ ＥＧＲクーラ ８ 第１ＥＧＲ弁
９ 第１ＥＧＲ通路 11 吸気通路
11ａ 吸気マニホールド 12 上流側排気通路
12ａ 排気マニホールド 12ｂ ウェイストゲート
13 下流側排気通路 14 回転数センサー
15 負荷センサー 18 第２ＥＧＲ弁
19 第２ＥＧＲ通路 20 コントローラ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an EGR device for a supercharged engine that recirculates a part of exhaust gas to an intake side in order to reduce NOx emission in a turbocharged diesel engine or the like.
[0002]
[Prior art]
In exhaust gas countermeasures for diesel engines and the like, in order to reduce the amount of NOx emissions in the exhaust gas, a part of the exhaust gas that is an inert gas is recirculated to the intake side, thereby suppressing the combustion temperature to a low level. It is known that EGR (exhaust gas recirculation) that suppresses the generation of is effective, and is widely put into practical use.
[0003]
This EGR device is also applied to a supercharged engine. As shown in FIG. 5, the exhaust gas G is taken out from the exhaust manifold 12a, and the fresh air in the intake passage 11 is passed through the EGR passage 9 in which the EGR cooler 7 is disposed. EGR is performed by mixing with A and returning to the intake manifold 11a.
However, in the supercharged engine, as the engine load increases, the intake pressure (boot pressure) increases and becomes higher than the exhaust pressure, so that the EGR gas G cannot be recirculated to the intake passage 11. .
[0004]
Therefore, there is a method of reducing the intake pressure by opening the waste gate 12b leading to the exhaust passage 12 and lowering the exhaust pressure, thereby reducing the intake pressure and returning the EGR gas G to the intake passage 11. . However, if this method is used, the amount of fresh air A decreases and smoke increases, so the region E where EGR can be performed is the operation of the engine with a low load and a medium rotation or less as shown in FIG. There is a problem that it is limited to the area.
[0005]
Further, in a variable capacity turbocharger (VG turbo) in which the cross-sectional area of the inlet of the turbine 2 is variable, the turbine rotational speed is changed by controlling the cross-sectional area of the inlet to control the exhaust pressure and the intake pressure. The area where EGR is possible is expanded. In this case, EGR is possible up to the engine operating range indicated by E of medium load as shown in FIG. 4B, but in order to further reduce NOx and purify the exhaust gas, the engine high-load operating range. However, there is a demand to make EGR possible.
[0006]
Regarding this requirement, in Japanese Patent Laid-Open No. 3-117665, Japanese Patent Laid-Open No. 5-180089, Japanese Patent Laid-Open No. 5-89859, etc., the EGR gas is compressed and compressed by a compressor, and the pressurized EGR gas is returned to the intake passage side An EGR device that expands the EGR region by configuring as described above has been proposed.
[0007]
[Problems to be solved by the invention]
However, since the apparatus disclosed in Japanese Patent Laid-Open No. 3-117665 compresses EGR gas by a compressor driven by an engine and stores it after accumulating in an accumulator tank, the driving force of the engine is used for this compressor. Therefore, the loss of engine output increases accordingly. Since this loss increases as the engine speed increases and the load increases, there is a problem that the loss increases as high output is required. Further, there is a problem that a compressor and an accumulator having a large capacity are required to perform EGR in a high rotation and high load region.
[0008]
In the apparatus disclosed in Japanese Patent Laid-Open No. 5-180089, a turbine driven by exhaust gas is provided in an exhaust passage, and EGR gas is pressurized by an EGR gas compressor connected to the turbine and is recirculated to the intake passage. However, since this apparatus has three turbines including a power turbine that recovers the exhaust gas power in series with the exhaust passage, the exhaust pressure of the exhaust manifold significantly increases during EGR operation, so that the pumping loss is reduced. There is a problem that the fuel consumption increases and the fuel consumption deteriorates, and there is a problem that the area where the EGR can be performed due to the generation of black smoke due to a decrease in fresh air in a high load operation is limited.
[0009]
The device disclosed in Japanese Patent Laid-Open No. 5-89859 branches the compressed air obtained by the first turbocharger to drive the second turbocharger, and boosts the EGR gas by the compressor of the second turbocharger. At the same time, EGR is performed by releasing the compressed air from the compressor and lowering the intake pressure. However, in this apparatus, since the compressed air is branched, the amount of compressed intake air supplied to the cylinder is reduced, so there is a problem that the amount of intake air with respect to the amount of EGR gas is reduced and smoke is generated.
[0010]
The present invention has been made to solve the above-described problems, and its purpose is to enable EGR even during high-load operation of the engine, and also to ensure a sufficient amount of intake air to the cylinder to generate smoke. As well as preventing deterioration of fuel consumption, the EGR gas can be boosted according to the operating state of the engine to efficiently perform EGR, and the amount of NOx in the exhaust gas in the entire operating range of the engine It is an object to provide an EGR device for a supercharged engine that can reduce the engine.
[0011]
[Means for Solving the Problems]
An EGR device for a supercharged engine for achieving the above-described object is a supercharged engine in which a compressor provided in an intake passage is driven by a turbine provided in the exhaust passage of the engine. Are connected to each other to provide a first EGR passage, and an EGR gas compressor is provided in the first EGR passage to increase the pressure of EGR gas and return to the intake passage. A clutch mechanism is provided between the EGR gas compressor and the turbine. Since it is configured to be connected and disengaged freely, there is no need to newly provide a turbine for an EGR gas compressor in the exhaust passage, so that an increase in exhaust pressure can be prevented and fuel consumption can be prevented from deteriorating. In addition, since there is no decrease in the intake air amount due to the branching and escape of the intake air, the intake air amount supplied to the cylinder can be sufficiently secured, and EGR can be performed while preventing the occurrence of smoke.
[0012]
Further, the downstream side of the exhaust passage from the turbine and the intake passage are connected by the first EGR passage provided with the EGR gas compressor, and the upstream side of the exhaust passage from the turbine and the intake passage are connected by a second EGR. Connect by aisle.
Furthermore, a first EGR valve and a second EGR valve are provided in the first EGR passage and the second EGR passage, respectively, and a rotation speed sensor for detecting the rotation speed of the engine and a load sensor for detecting the load of the engine are further provided. And a controller for controlling the clutch mechanism, the first EGR valve, and the second EGR valve by inputting the output of the rotational speed sensor and the output of the load sensor.
[0013]
With this configuration, the EGR gas pressure and intake pressure can be estimated by inputting the engine speed and load, and the two EGR passages can be used properly according to this magnitude relationship, so EGR can be performed efficiently while preventing engine loss. NOx in the exhaust gas can be reduced over the entire engine operating range.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an EGR device for a supercharged engine according to the present invention will be described below with reference to the drawings.
As shown in FIG. 1, in the supercharged engine 1 of the first embodiment, the turbine 2 is provided in the exhaust passage 12, and the compressor 3 provided in the intake passage 11 is driven to compress the fresh air A. The fresh air A is supplied to the intake manifold 11a via the intercooler 6.
[0015]
The exhaust passage 12 and the intake passage 11 of the engine 1 are connected by a first EGR passage 9. Further, an EGR gas compressor 5 is provided in the first EGR passage 9, and a clutch mechanism is provided between the EGR gas compressor 5 and the turbine 2. The EGR gas compressor 5 is configured to be driven by receiving the driving force of the turbine 2.
[0016]
Further, a rotational speed sensor 14 for detecting the rotational speed of the engine 1, a load sensor 15 for detecting the engine load, and a controller 20 are provided. The controller 20 is configured to control the clutch mechanism 4 by inputting the output of the rotation speed sensor 14 and the output of the load sensor 15.
That is, an EGR gas compressor 5 that compresses the EGR gas G in addition to the normal fresh air A compressor 3 is provided in the first EGR passage 9 so that the exhaust gas pressure <intake pressure (boost pressure) when the engine 1 is in a high-load operation state. ), The clutch mechanism 4 is connected to drive the EGR gas compressor 5, the EGR gas is compressed and boosted, and the boosted EGR gas G is supplied to the intake passage 11.
[0017]
With the above configuration, the EGR gas compressor 5 provided in the first EGR passage 9 can make the pressure of the EGR gas G higher than the intake pressure of the fresh air A compressed by the compressor 3 of the supercharger. EGR can also be performed in the high load operation region of the engine 1.
In the second embodiment shown in FIG. 2, the downstream side of the exhaust passage 13 from the turbine 2 and the intake passage 11 are connected by the first EGR passage 9 provided with the EGR gas compressor 5, and the exhaust passage The upstream side of the 12 turbines 2 and the intake passage 11 are connected by a second EGR passage 19.
[0018]
This EGR gas compressor is connected between the EGR gas compressor 5 and the turbine 2 via the clutch mechanism 4 as in the first embodiment of FIG. 1 so that it can be driven by the driving force of the turbine 2. Removably connected.
Further, a first EGR valve 8 is disposed in the first EGR passage 9 and a second EGR valve 18 is disposed in the second EGR passage 19, respectively, and a rotational speed sensor 14 for detecting the rotational speed of the engine 1 and the engine A load sensor 15 for detecting the load and a controller 20 are provided. The controller 20 is configured to input the output of the rotation speed sensor 14 and the output of the load sensor 15 to control the clutch mechanism 4, the first EGR valve 8, and the second EGR valve 18.
[0019]
With the above configuration, the intake pressure is lower than the exhaust pressure in the low / medium load operation region of the engine 1 indicated by N in FIG. 3, so that the first EGR valve 8 is closed and the clutch mechanism 4 is turned off. The second EGR valve is opened, and the EGR gas G is supplied to the intake passage 11 as it is without increasing the pressure through the second EGR passage 19 to perform EGR. As a result, the turbine 2 can drive only the compressor 3 without using the low exhaust energy of the relatively low temperature / low pressure exhaust gas G for boosting the EGR gas, and can be fully utilized on the intake side. A sufficient amount of compressed air can be secured.
[0020]
Further, since the inlet of the second EGR passage 19 is provided on the upstream side of the turbine 2, the exhaust gas G in a relatively high pressure portion on the upstream side of the turbine 2 can be used for EGR, so that it is smooth and efficient. In addition, the EGR gas can be returned to the intake passage.
Further, in the high load operation region indicated by C portion in FIG. 3, since the intake pressure is higher than the exhaust pressure, the first EGR valve 8 is opened, the clutch mechanism 4 is turned on to transmit the driving force, and the second EGR is transmitted. The valve 18 is closed, the EGR gas G is guided to the first EGR passage 9, and the EGR gas G is boosted by the EGR gas compressor 5 and supplied to the intake passage 11 to perform EGR.
[0021]
In this high load operation region C, the energy of the exhaust gas G also increases, so that even if the EGR gas compressor 5 is driven, the compressor 3 can sufficiently compress the fresh air A, and the compressed intake air A can be fully compressed in the cylinder. Since the compressed intake air amount to the cylinder can be secured, an appropriate EGR rate can be secured and EGR can be performed efficiently.
[0022]
That is, it is not necessary to open the waste gate 12b to release a part of the exhaust gas G to lower the intake pressure, so that the energy of the exhaust gas G can be sufficiently utilized by the turbine 2.
Further, since the inlet of the first EGR passage 9 is provided downstream of the turbine 2, the energy of the exhaust gas G is recovered by passing through the turbine 2 before the EGR gas G is recirculated to the intake passage 11 side. Therefore, the compressor 3 can be driven efficiently.
[0023]
Therefore, the EGR gas G path is selected according to the rotational speed of the engine 1 and the load condition by selecting the first EGR passage 9 for boosting the EGR gas G and the second EGR passage 19 for not boosting the EGR gas G. EGR suitable for the driving situation can be performed efficiently.
[0024]
【The invention's effect】
As described above, according to the EGR device of the supercharged engine of the present invention according to claim 1, EGR is performed by supplying the EGR gas boosted by the EGR gas compressor to the intake passage side, so that EGR is possible. The engine operating range can be expanded to a high load range.
[0025]
Since the EGR gas compressor is configured to be driven by the turbine for the intake compressor provided in the exhaust passage via the clutch mechanism, it is not necessary to newly provide the turbine for the EGR gas compressor in the exhaust passage. As a result, the pumping loss can be suppressed and the deterioration of fuel consumption can be prevented.
Further, according to the EGR device of the supercharged engine of the present invention according to claim 2 and claim 3, the EGR passage is recirculated to the intake side without increasing the pressure of EGR gas, and the EGR passage is made into two series. Therefore, in the operation region where the exhaust pressure is higher than the intake pressure, it is recirculated to the intake side via the second EGR passage, and in the operation region where the exhaust pressure is lower than the intake pressure, it is passed through the first EGR passage provided with the EGR gas compressor Since the boosted EGR gas can be recirculated, EGR can be performed efficiently while preventing loss of engine output in accordance with the engine speed and load conditions.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an EGR device for a supercharged engine according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of an EGR device for a supercharged engine according to a second embodiment of the present invention.
FIG. 3 is a schematic diagram showing an EGR region and an EGR operation method of an EGR device for a supercharged engine according to the present invention.
4A and 4B are schematic views showing an EGR region of the prior art, in which FIG. 4A shows an EGR region of an EGR device of a supercharged engine, and FIG. 4B shows an EGR region of an EGR device in a VG turbo engine.
FIG. 5 is a block diagram of a conventional supercharged engine EGR device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 Supercharger turbine 3 Supercharger compressor 4 Clutch mechanism 5 EGR gas compressor 6 Intercooler 7 EGR cooler 8 First EGR valve 9 First EGR passage 11 Intake passage
11a Intake manifold 12 Upstream exhaust passage
12a Exhaust manifold 12b Waste gate
13 Downstream exhaust passage 14 Speed sensor
15 Load sensor 18 2nd EGR valve
19 2nd EGR passage 20 Controller

Claims (3)

エンジンの排気通路に設けたタービンによって、吸気通路に設けたコンプレッサを駆動する過給式エンジンにおいて、排気通路と吸気通路とを接続して第１ＥＧＲ通路を設けると共に、該第１ＥＧＲ通路に、ＥＧＲガスを昇圧して吸気通路に還流するＥＧＲガスコンプレッサを設け、該ＥＧＲガスコンプレッサと前記タービンとの間をクラッチ機構を介して継脱自在に連結した過給式エンジンのＥＧＲ装置。In a supercharged engine that drives a compressor provided in an intake passage by a turbine provided in an exhaust passage of the engine, the exhaust passage and the intake passage are connected to provide a first EGR passage, and an EGR gas is provided in the first EGR passage. An EGR device for a supercharged engine in which an EGR gas compressor that boosts the pressure to the intake passage is provided, and the EGR gas compressor and the turbine are detachably connected via a clutch mechanism. 前記排気通路の前記タービンより下流側と吸気通路とを、前記ＥＧＲガスコンプレッサを配設した前記第１ＥＧＲ通路で連結すると共に、前記排気通路の前記タービンより上流側と吸気通路とを第２ＥＧＲ通路で連結した請求項１記載の過給式エンジンのＥＧＲ装置。The downstream side of the exhaust passage from the turbine and the intake passage are connected by the first EGR passage provided with the EGR gas compressor, and the upstream side of the exhaust passage from the turbine and the intake passage are connected by a second EGR passage. The supercharged engine EGR device according to claim 1, which is connected. 前記第１ＥＧＲ通路と前記第２ＥＧＲ通路に、第１ＥＧＲ弁と第２ＥＧＲ弁をそれぞれ配設すると共に、エンジンの回転数を検出する回転数センサーとエンジンの負荷を検出する負荷センサーを設け、更に、前記回転数センサーの出力と前記負荷センサーの出力とを入力して前記クラッチ機構と前記第１ＥＧＲ弁と前記第２ＥＧＲ弁の制御を行うコントローラを設けた請求項２記載の過給式エンジンのＥＧＲ装置。The first EGR passage and the second EGR passage are provided with a first EGR valve and a second EGR valve, respectively, provided with a rotation speed sensor for detecting the rotation speed of the engine and a load sensor for detecting the load of the engine, The supercharged engine EGR device according to claim 2, further comprising a controller that inputs an output of a rotational speed sensor and an output of the load sensor to control the clutch mechanism, the first EGR valve, and the second EGR valve.
JP22511397A 1997-08-21 1997-08-21 EGR device for supercharged engine Expired - Fee Related JP3674254B2 (en)

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