JP3893895B2 - EGR gas cooling structure - Google Patents

EGR gas cooling structure Download PDF

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Publication number
JP3893895B2
JP3893895B2 JP2001116944A JP2001116944A JP3893895B2 JP 3893895 B2 JP3893895 B2 JP 3893895B2 JP 2001116944 A JP2001116944 A JP 2001116944A JP 2001116944 A JP2001116944 A JP 2001116944A JP 3893895 B2 JP3893895 B2 JP 3893895B2
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egr
egr gas
intercooler
engine
passage
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JP2002310007A (en
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俊行 後閑
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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
    • 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
    • F02B29/045—Constructional details of the heat exchangers, e.g. pipes, plates, ribs, insulation, materials, or manufacturing and assembly
    • F02B29/0475—Constructional details of the heat exchangers, e.g. pipes, plates, ribs, insulation, materials, or manufacturing and assembly the intake air cooler being combined with another device, e.g. heater, valve, compressor, filter or EGR cooler, or being assembled on a special engine location
    • 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
    • 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
    • F02M26/50—Arrangements or methods for preventing or reducing deposits, corrosion or wear caused by impurities
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

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

Description

【０００１】
【発明の属する技術分野】
本発明は、排ガスの一部を吸気側に還流させるＥＧＲ装置に適用される、ＥＧＲガス冷却構造に関する。
【０００２】
【従来の技術】
従来より、エンジンの排ガス中に含まれるＮＯｘ（窒素酸化物）を低減すべく、エンジンの排ガスの一部をエンジンの運転状態に応じて吸気系に再循環させる排ガス再循環装置（ＥＧＲ装置）が開発、実用化されている。
そして、このようなＥＧＲ装置では、エンジンの排気系（主に排気通路）から取り込んだ排ガス（ＥＧＲガス）を吸気に混入させることで、燃焼室内での燃焼を緩慢なものとして燃焼温度を下げ、ＮＯｘの生成が抑制される。
【０００３】
図５はＥＧＲ装置を備えたエンジン全体の模式的な構成図であって、吸気通路７と排気通路４との間には排ガスを吸気通路７に還流させるためのＥＧＲ通路８が設けられている。また、このＥＧＲ通路８上には、ＥＧＲガスを冷却するためのＥＧＲクーラ１０及びＥＧＲガスの還流量（還流割合）を制御するためのＥＧＲバルブ９が設けられている。そして、このＥＧＲクーラ１０でＥＧＲガスを冷却することによりＥＧＲガスの体積を減少させて還流量を増大させることができるとともに、新気の吸入量を増大させることによりＮＯｘ及びスモークの同時低減が図られる。
【０００４】
一方、近年ではディーゼルエンジンにおいてＥＧＲ装置と過給機（ターボチャージャ）５とを組み合わせて出力の増大と排ガスの清浄化が図られている。以下、ターボチャージャ５に着目して説明すると、排気通路４及び吸気通路７にはそれぞれタービン５ａ及びコンプレッサ５ｂが設けられており、また、吸気通路７上にはコンプレッサ５ｂで過給された新気（吸気）を冷却するインタクーラ６も設けられている。そして、排ガスのエネルギによりタービン５ａが回転駆動されると、これによりコンプレッサ５ｂが回転駆動されて新気（吸気）が加圧される。また、この加圧された新気はインタクーラ６で冷却されてエンジン１に供給される。
【０００５】
次に、ＥＧＲ通路８に設けられたＥＧＲクーラ１０の構成の一例について図６（ａ），（ｂ）を用いて説明すると、図６（ａ）に示すＥＧＲクーラ１０は、いわゆる多管式ＥＧＲクーラであって、ケーシング１０１内に多数の円筒状の管（パイプ）１０２が設けられて構成されている。また、ケーシング１０１の両端にはヘッダ１０５，１０６が設けられ、これらのヘッダ１０５，１０６にはＥＧＲガスの入口１０３と出口１０４とがそれぞれ形成されている。各ヘッダ１０５，１０６内には空間が形成され、上記パイプ１０２の両端部はこのヘッダ１０５，１０６内の空間に開口して接続されている。したがって、この入口１０３からＥＧＲガスを流入させると、このＥＧＲガスは各パイプ１０２内を通って出口１０４から排出される。
【０００６】
また、ケーシング１０１には、冷却水の供給口１０７及び排出口１０８とがそれぞれ形成され、図５に示す冷却水路１１がそれぞれ接続されている。そして、このような構成により、ケーシング１０１内にエンジン１の冷却水が循環して、図６（ｂ）に示すように、ＥＧＲガスがパイプ１０２内を通る際に、パイプ１０２の外にある冷却水にＥＧＲガスの熱が奪われてガス温度が低下し、熱交換が行なわれる。
【０００７】
【発明が解決しようとする課題】
しかしながら、ＥＧＲガスを冷却すると腐食性の液体（例えば硫酸）が発生する。このため、図６（ｃ）に示すように、ＥＧＲクーラ１０内のろう付け個所が腐食してクラック等が生じ、このようなクラックからエンジン１内に冷却水が浸入するおそれがあった。なお、エンジン１内に冷却水が浸入すると、ウォータハンマ現象が生じてエンジンが破損する可能性があるほか、冷却水が本来の冷却系統から流出することでエンジン１がオーバヒートする可能性がある。
【０００８】
また、従来のＥＧＲクーラでは、ＥＧＲガスを還流させない状態では、ＥＧＲクーラ内には流体の流れが一切なくなるので、ＥＧＲガスに含まれるすすがＥＧＲクーラ内に滞留してしまい、ＥＧＲクーラの冷却効率が低下するという課題がある。
一方で、ＥＧＲガスを還流させる際に各気筒で還流量が不均一であると、スモーク発生量が増大するため、ＥＧＲガスと新気とをなるべく均一に混合して各気筒にバラツキなくＥＧＲガスを還流させたいという要望もある。このような要望に応えるには、吸気通路７のなるべく上流側でＥＧＲガスを還流させるのが好ましいが、インタクーラ６は通常アルミニウム製であるため、ＥＧＲガスをインタクーラ６よりも上流側で還流させると、上記の腐食性の液体によりインタクーラ６が損傷したりするおそれがある。
【０００９】
このため、従来はインタクーラの下流側でＥＧＲガスを還流させているが、この場合にはＥＧＲガスと新気との均一な混合が困難であり、各気筒でＥＧＲガスの還流量がばらつくおそれがあった。
なお、特開平１０−２２０３０５号公報にはインタクーラによりＥＧＲガスを冷却するようにした技術が開示されているが、この技術は、単にインタクーラの一部をＥＧＲクーラとして適用したに過ぎず、ＥＧＲガスを還流させない状態では、インタクーラのＥＧＲガス冷却部（公報の符号１１参照）に何らの流体も流れないため、やはりＥＧＲクーラ内にすすが滞留してしまい冷却効率が低下してしまう。
【００１０】
本発明は、このような課題に鑑み創案されたもので、▲１▼ＥＧＲクーラの冷却水のエンジン内への浸入に起因するエンジン破損の防止，▲２▼すすの滞留によるＥＧＲガスの冷却効率の低下の抑制，▲３▼ＥＧＲガスと新気との均一な混合の３つの課題を同時に解決できるようにした、ＥＧＲガス冷却構造を提供することを目的とする。
【００１１】
【課題を解決するための手段】
請求項１記載の本発明のＥＧＲガス冷却構造では、過給機を備えたエンジンの排気通路と吸気通路との間を接続するＥＧＲ通路と、該ＥＧＲ通路の途中に配設されたＥＧＲ弁と、該過給機よりも下流の吸気通路に配設された空冷式のインタクーラとをそなえ、該ＥＧＲ通路の吸気側接続部が該インタクーラの上流側ヘッダよりも下流のコア部に接続されて該インタクーラにＥＧＲクーラの機能が一体化されていることを特徴としている。
【００１２】
このため、ＥＧＲガスは排気通路からＥＧＲ通路及びＥＧＲ弁を介してインタクーラのコア部に流入し、このコア部で冷却され吸気通路の還流される。つまりインタクーラがＥＧＲクーラの機能をも兼ねており、インタクーラによりＥＧＲガスが冷却される。したがって、従来のようなＥＧＲクーラが不要となる。また、冷却水を用いていないので、仮にコア部に亀裂等が生じてもこの亀裂からは空気しか流入しないのでエンジンの破損を防止できる。また、ＥＧＲガスを還流させないときは、ＥＧＲガスの代わりに新気が導入されて、ＥＧＲガスに含まれるすすが掃気される。さらに、ＥＧＲガスをインタークーラに還流させることでＥＧＲガスと新気の混合部からエンジンまで十分な距離を確保でき、ＥＧＲガスと新気とを均一に混合でき、気筒毎のＥＧＲ率のばらつきが抑制される。
【００１３】
また、請求項２記載の本発明のＥＧＲガス冷却構造では、該インタクーラのうち、該ＥＧＲ通路が接続された部分のコア部が耐腐食性金属で形成されていることを特徴としている。したがって、コア部の耐腐食性が確保され、信頼性が向上する。
【００１４】
【発明の実施の形態】
以下、図面により、本発明の一実施形態にかかるＥＧＲガス冷却構造について説明すると、図１はその要部構成を示す模式図、図２，図３はいずれもその作用を説明するための図、図４は本発明が適用されるエンジン全体の模式的な構成図である。
【００１５】
まず、図４を用いてエンジンの全体的な構成について説明すると、エンジン１の吸気通路７と排気通路４との間には排ガスを吸気通路７に還流させるためのＥＧＲ通路８が設けられており、また、このＥＧＲ通路８上には、ＥＧＲガスの還流量（還流割合）を制御するためのＥＧＲバルブ（ＥＧＲ弁）９が設けられている。このＥＧＲバルブ９は、エンジン回転速度及びエンジン負荷等に基づくエンジン運転状態に応じて設定される制御信号に基づいて、その作動が制御されるようになっている。
【００１６】
また、エンジン１には吸気を過給する過給機（ターボチャージャ）５が設けられており、図示するように、排気通路４及び吸気通路７にはそれぞれタービン５ａ及びコンプレッサ５ｂが設けられている。また、吸気通路７上にはコンプレッサ５ｂで過給された新気（吸気）を冷却する空冷式のインタクーラ６が設けられている。
【００１７】
ここで、図１を用いて本願発明の一実施形態にかかるＥＧＲガス冷却構造の要部について説明すると、図示するように、上記ＥＧＲ通路８の下流端部（吸気側接続部）は、吸気通路７に設けられたインタクーラ６に部分的に接続されており、このインタクーラ６によりＥＧＲガスが冷却されるようになっている。
インタクーラ６は、図示するように上流側のヘッダ６２と下流側のヘッダ６３と、これらのヘッダ６２，６３との間を接続するコア部６１と備えて構成されており、コア部６１は通常のインタクーラ同様、断面が長円形状の多数のチューブにより構成されている。また、詳細は図示しないが、これらの各チューブ間には放熱用のフィンが取り付けられている。
【００１８】
また、図１に示すように、上記ＥＧＲ通路８は接続部６４を介してインタクーラ６のコア部６１に接続されている。ここで、接続部６４には、ヘッダ６２，６３と同様に内部に空間が形成され、この空間に上流側のチューブと下流側のチューブとがそれぞれ開口して接続されている。
また、コア部６１は、新気のみが流通する新気用コア部６１ａと、接続部６４よりも下流側であってＥＧＲ通路７からＥＧＲガスが導入されるＥＧＲ用コア部６１ｂとから構成されており、新気用コア部６１ａは従来のインタクーラと同様の素材（例えばアルミニウム）により形成されている。一方、ＥＧＲ用コア部６１ｂは、耐腐食性の金属（例えばＳＵＳ材やアルマイト処理を施したアルミニウム等）により形成されている。
【００１９】
したがって、ＥＧＲバルブ９が全閉であれば、新気用コア部６１ａ及びＥＧＲ用コア部６１ｂの両方に新気が導入され、ＥＧＲバルブ９が開くとその開度に応じてＥＧＲ用コア部６１ｂを流れるＥＧＲガスが増大するようになっている。
なお、インタクーラ６の新気用コア部６１ａは、ＥＧＲバルブ９が全開となってＥＧＲ用コア部６１ｂに新気が全く流れないような状態となっても、十分に過給された新気を冷却できる程度の容量に設定されている。
【００２０】
また、ＥＧＲ用コア部６１ｂの各チューブの両端は、本実施形態では、銅ろう又はより耐腐食性のあるニッケルろうによって、下流側ヘッダ６３及び接続部６４にそれぞれろう付けされている。
本発明の一実施形態にかかるＥＧＲガス冷却構造は、上述のように構成されているので、その作用を説明すると以下のようになる。
【００２１】
まず、エンジン１の運転状態に応じて図示しないコントロールユニット（ＥＣＵ）により目標ＥＧＲ還流量が設定され、この目標ＥＧＲ還流量となるように上記ＥＣＵからＥＧＲバルブ９に対して制御信号が設定される。
そして、ＥＧＲバルブ９がＥＣＵの制御信号に基づき作動すると、図２に示すように、このＥＧＲバルブ９の開度に応じた量のＥＧＲガスが接続部６４を介してインタクーラ６のＥＧＲ用コア部６１ｂに流入する。このＥＧＲガスは、接続部６４において上流側から流入する新気と混合されるとともに、ＥＧＲ用コア部６１ｂを流れる過程で冷却される。また、下流側ヘッダ６３においてＥＧＲガスは新気用コア部６１ａを通った新気と合流する。
【００２２】
そして、このようにＥＧＲガスをインタークーラ６に還流させることでＥＧＲガスと新気との混合部からエンジン１まで十分な距離を確保でき、吸気通路７を通る過程でＥＧＲガスと新気とを均一に混合することができる。したがって、エンジン１の各気筒に均一にＥＧＲガスが流入して、気筒間でのＥＧＲガスの還流量のばらつきが抑制される。
【００２３】
また、図３に示すように、ＥＧＲガスを還流させないとき、即ちＥＧＲバルブ９の開度が０（全閉）の時には、ＥＧＲ用コア部６１ｂには新気が流入して、ＥＧＲ用コア部６１ｂに残留した排ガスのすすが掃気される。したがって、ＥＧＲ用コア部６１ｂにすすが滞留することがなく、ＥＧＲ用コア部６１ｂのチューブへのすすの付着が抑制され、これによりＥＧＲガスの冷却効率の低下を防止できる。
【００２４】
また、従来のＥＧＲクーラを廃止してインタクーラ６と機能を兼用することによりエンジンルーム内のレイアウトが容易になるほか部品点数が低減されてコストを低減することができる。
さらに、ＥＧＲガス（排ガス）を冷却したときにＥＧＲガスから腐食性液体（又は腐食性ガス）が発生しても、ＥＧＲ用コア部６１ｂを耐腐食性金属で形成するとともに、ＥＧＲ用コア部６１ｂを構成するチューブの端部を銅ろう又はより耐腐食性のあるニッケルろうによりろう付けすることにより、十分な耐腐食性を得ることができエンジン全体の信頼性が向上するという利点がある。
【００２５】
また、仮にＥＧＲ用コア部６１ｂのチューブが腐食して穴があいたり、チューブのろう付け個所が腐食して亀裂が生じたとしても、空気によりＥＧＲガスを冷却しているので、吸気通路７には空気しか流入せず、従来のＥＧＲクーラのように冷却水がエンジン１に流入してエンジン１を破損させるようなおそれが全くない。
【００２６】
なお、本発明のＥＧＲガス冷却構造は上述の実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で種々の変形が可能である。例えばＥＧＲバルブや過給機の構造については特に限定されるものではなく、種々のタイプのＥＧＲバルブや過給機に適用することができる。また、インタクーラは走行風によって冷却してもよいし、ファンによる送風により冷却してもよい。
【００２７】
【発明の効果】
以上詳述したように、請求項１にかかる本発明のＥＧＲガス冷却構造によれば、ＥＧＲクーラの冷却水のエンジン内への浸入に起因するエンジンの破損を防止できるとともに、ＥＧＲガスの冷却効率の低下の抑制でき、さらにはＥＧＲガスと新気とを均一に混合させることができるようになる。
【００２８】
すなわち、ＥＧＲガスの冷却時に腐食性液体が発生してインタクーラ内に亀裂が生じても吸気通路には空気が流入するので、従来のＥＧＲクーラのように冷却水がエンジンに流入してエンジンを破損させるようなおそれが全くないという利点がある。
また、ＥＧＲガスをインタークーラに還流させることでＥＧＲガスと新気との混合部からエンジンまで十分な距離を確保でき、吸気通路を通る過程でＥＧＲガスと新気とを均一に混合することができる。したがって、エンジンの各気筒に均一にＥＧＲガスが流入して、気筒間でのＥＧＲガスの還流量のばらつきを抑制できるという利点がある。
【００２９】
また、ＥＧＲガスを還流させないときには、ＥＧＲガスの代わりに新気が導入されるので、ＥＧＲガスに含まれるすすが掃気されてインタクーラ内でのすすの滞留が防止されるので、チューブにすすが付着することがなくなり、ＥＧＲガスの冷却効率の低下を防止できるという利点がある。
また、従来のＥＧＲクーラを廃止してインタクーラと機能を兼用することによりエンジンルーム内のレイアウトが容易になるほか部品点数が低減されてコストを低減することができるという利点がある。
【００３０】
請求項２にかかる本発明のＥＧＲガス冷却構造によれば、インタクーラのうち、ＥＧＲ通路が接続された部分のコア部を耐腐食性金属で形成することにより、エンジン全体の信頼性をさらに向上させることができるという利点がある。
【図面の簡単な説明】
【図１】本発明の一実施形態にかかるＥＧＲガス冷却構造の要部構成を示す模式図である。
【図２】本発明の一実施形態にかかるＥＧＲガス冷却構造の作用を説明するための図である。
【図３】本発明の一実施形態にかかるＥＧＲガス冷却構造の作用を説明するための図である。
【図４】本発明の一実施形態にかかるＥＧＲガス冷却構造が適用されるエンジン全体のの模式的な構成図である。
【図５】従来のＥＧＲ装置を備えたエンジン全体の模式的な構成図である。
【図６】従来のＥＧＲクーラを示す模式的な構成図である。
【符号の説明】
１ エンジン
４ 排気通路
５ ターボチャージャ（過給機）
６ インタクーラ
７ 吸気通路
８ ＥＧＲ通路
９ ＥＧＲバルブ（ＥＧＲ弁）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an EGR gas cooling structure applied to an EGR device that recirculates a part of exhaust gas to an intake side.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an exhaust gas recirculation device (EGR device) that recirculates a part of engine exhaust gas to an intake system according to the operating state of the engine in order to reduce NOx (nitrogen oxide) contained in the exhaust gas of the engine. Developed and put into practical use.
In such an EGR device, the exhaust gas (EGR gas) taken from the exhaust system (mainly the exhaust passage) of the engine is mixed into the intake air, so that the combustion in the combustion chamber is made slow and the combustion temperature is lowered. Generation of NOx is suppressed.
[0003]
FIG. 5 is a schematic configuration diagram of the entire engine equipped with an EGR device, and an EGR passage 8 for returning exhaust gas to the intake passage 7 is provided between the intake passage 7 and the exhaust passage 4. . On the EGR passage 8, an EGR cooler 10 for cooling the EGR gas and an EGR valve 9 for controlling the recirculation amount (recirculation ratio) of the EGR gas are provided. Then, by cooling the EGR gas with the EGR cooler 10, the volume of the EGR gas can be reduced to increase the recirculation amount, and the NOx and smoke can be simultaneously reduced by increasing the intake amount of fresh air. It is done.
[0004]
On the other hand, in recent years, in an diesel engine, an EGR device and a supercharger (turbocharger) 5 are combined to increase output and purify exhaust gas. The following description will focus on the turbocharger 5. The exhaust passage 4 and the intake passage 7 are provided with a turbine 5a and a compressor 5b, respectively, and fresh air supercharged by the compressor 5b is provided on the intake passage 7. An intercooler 6 for cooling (intake air) is also provided. When the turbine 5a is rotationally driven by the energy of the exhaust gas, the compressor 5b is rotationally driven thereby to pressurize fresh air (intake air). The pressurized fresh air is cooled by the intercooler 6 and supplied to the engine 1.
[0005]
Next, an example of the configuration of the EGR cooler 10 provided in the EGR passage 8 will be described with reference to FIGS. 6A and 6B. The EGR cooler 10 shown in FIG. 6A is a so-called multi-tube EGR. It is a cooler, and a large number of cylindrical tubes (pipes) 102 are provided in a casing 101. In addition, headers 105 and 106 are provided at both ends of the casing 101, and an EGR gas inlet 103 and an outlet 104 are formed in the headers 105 and 106, respectively. A space is formed in each header 105, 106, and both end portions of the pipe 102 are opened and connected to the space in the header 105, 106. Therefore, when EGR gas is introduced from the inlet 103, the EGR gas is discharged from the outlet 104 through the pipes 102.
[0006]
In addition, a cooling water supply port 107 and a discharge port 108 are respectively formed in the casing 101, and the cooling water channel 11 shown in FIG. 5 is connected thereto. With such a configuration, the cooling water of the engine 1 circulates in the casing 101, and as shown in FIG. 6B, when the EGR gas passes through the pipe 102, the cooling outside the pipe 102 is performed. The heat of the EGR gas is taken away by water, the gas temperature is lowered, and heat exchange is performed.
[0007]
[Problems to be solved by the invention]
However, when the EGR gas is cooled, a corrosive liquid (for example, sulfuric acid) is generated. For this reason, as shown in FIG. 6C, the brazed portion in the EGR cooler 10 is corroded to cause cracks and the like, and the cooling water may enter the engine 1 from such cracks. If cooling water enters the engine 1, a water hammer phenomenon may occur and the engine may be damaged, and the cooling water may flow out of the original cooling system and the engine 1 may be overheated.
[0008]
Further, in the conventional EGR cooler, when the EGR gas is not recirculated, no fluid flows in the EGR cooler, so that the soot contained in the EGR gas stays in the EGR cooler, and the cooling efficiency of the EGR cooler There is a problem that decreases.
On the other hand, if the recirculation amount is not uniform in each cylinder when the EGR gas is recirculated, the amount of smoke generated increases. Therefore, the EGR gas and fresh air are mixed as uniformly as possible, and the EGR gas does not vary among the cylinders. There is also a demand for refluxing. In order to meet such a demand, it is preferable to recirculate the EGR gas as upstream as possible in the intake passage 7. However, since the intercooler 6 is usually made of aluminum, if the EGR gas is recirculated upstream of the intercooler 6. The intercooler 6 may be damaged by the corrosive liquid.
[0009]
For this reason, conventionally, the EGR gas is recirculated on the downstream side of the intercooler, but in this case, it is difficult to uniformly mix the EGR gas and the fresh air, and the recirculation amount of the EGR gas may vary in each cylinder. there were.
Japanese Patent Laid-Open No. 10-220305 discloses a technique in which the EGR gas is cooled by an intercooler. However, this technique is merely an application of a part of the intercooler as an EGR cooler. In the state where the refrigerant is not recirculated, no fluid flows through the EGR gas cooling section of the intercooler (see reference numeral 11 of the publication), soot still stays in the EGR cooler and cooling efficiency is lowered.
[0010]
The present invention has been devised in view of such problems. (1) Prevention of engine damage due to ingress of cooling water into the engine by EGR cooler, (2) EGR gas cooling efficiency due to soot retention It is an object of the present invention to provide an EGR gas cooling structure that can simultaneously solve the three problems of suppressing the decrease in temperature and (3) uniform mixing of EGR gas and fresh air.
[0011]
[Means for Solving the Problems]
In the EGR gas cooling structure of the present invention as set forth in claim 1, an EGR passage connecting an exhaust passage and an intake passage of an engine provided with a supercharger, and an EGR valve disposed in the middle of the EGR passage, , equipped with a intercooler air-cooled, which are disposed downstream of the intake passage than the supercharger, the inlet-side connecting portion of the EGR passage is connected downstream of the core portion of the upstream header of the intercooler It is characterized in that the function of the EGR cooler is integrated with the intercooler .
[0012]
For this reason, the EGR gas flows from the exhaust passage through the EGR passage and the EGR valve to the core portion of the intercooler, is cooled by this core portion, and is recirculated through the intake passage. That is, the intercooler also functions as an EGR cooler, and the EGR gas is cooled by the intercooler. Therefore, the conventional EGR cooler becomes unnecessary. Further, since no cooling water is used, even if a crack or the like occurs in the core portion, only air flows from the crack, so that the engine can be prevented from being damaged. When the EGR gas is not recirculated, fresh air is introduced instead of the EGR gas, and soot contained in the EGR gas is scavenged. Furthermore, by recirculating the EGR gas to the intercooler, it is possible to secure a sufficient distance from the mixing portion of the EGR gas and the fresh air to the engine, the EGR gas and the fresh air can be mixed uniformly, and the EGR rate varies from cylinder to cylinder. It is suppressed.
[0013]
In the EGR gas cooling structure according to the second aspect of the present invention, the core portion of the intercooler to which the EGR passage is connected is formed of a corrosion-resistant metal. Therefore, the corrosion resistance of the core portion is ensured and the reliability is improved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an EGR gas cooling structure according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the main part, and FIGS. FIG. 4 is a schematic configuration diagram of the entire engine to which the present invention is applied.
[0015]
First, the overall configuration of the engine will be described with reference to FIG. 4. An EGR passage 8 for returning exhaust gas to the intake passage 7 is provided between the intake passage 7 and the exhaust passage 4 of the engine 1. In addition, an EGR valve (EGR valve) 9 is provided on the EGR passage 8 for controlling the recirculation amount (recirculation ratio) of the EGR gas. The operation of the EGR valve 9 is controlled on the basis of a control signal set in accordance with the engine operating state based on the engine speed and the engine load.
[0016]
Further, the engine 1 is provided with a supercharger (turbocharger) 5 for supercharging intake air. As shown in the figure, a turbine 5a and a compressor 5b are provided in the exhaust passage 4 and the intake passage 7, respectively. . In addition, an air-cooled intercooler 6 that cools fresh air (intake air) supercharged by the compressor 5 b is provided on the intake passage 7.
[0017]
Here, the main part of the EGR gas cooling structure according to an embodiment of the present invention will be described with reference to FIG. 1. As shown in the drawing, the downstream end portion (intake side connecting portion) of the EGR passage 8 is an intake passage. 7 is partially connected to an intercooler 6 provided in the E7, and the EGR gas is cooled by the intercooler 6.
As shown in the figure, the intercooler 6 includes an upstream header 62, a downstream header 63, and a core portion 61 that connects between the headers 62 and 63. Like the intercooler, the cross section is constituted by a number of tubes having an oval shape. Although not shown in detail, a fin for heat dissipation is attached between these tubes.
[0018]
As shown in FIG. 1, the EGR passage 8 is connected to the core portion 61 of the intercooler 6 through the connection portion 64. Here, similarly to the headers 62 and 63, a space is formed in the connection portion 64, and an upstream tube and a downstream tube are opened and connected to the space.
The core portion 61 includes a fresh air core portion 61a through which only fresh air circulates, and an EGR core portion 61b that is downstream of the connection portion 64 and into which EGR gas is introduced from the EGR passage 7. The fresh air core 61a is formed of the same material (for example, aluminum) as the conventional intercooler. On the other hand, the core portion 61b for EGR is formed of a corrosion-resistant metal (for example, SUS material, anodized aluminum, or the like).
[0019]
Therefore, if the EGR valve 9 is fully closed, fresh air is introduced into both the fresh air core portion 61a and the EGR core portion 61b, and when the EGR valve 9 is opened, the EGR core portion 61b is opened according to the opening degree. The EGR gas flowing through the gas increases.
It should be noted that the fresh air core 61a of the intercooler 6 has a sufficiently supercharged fresh air even when the EGR valve 9 is fully opened and no fresh air flows into the EGR core 61b. The capacity is set so that it can be cooled.
[0020]
In addition, in this embodiment, both ends of each tube of the EGR core portion 61b are brazed to the downstream header 63 and the connecting portion 64 by copper brazing or nickel brazing having higher corrosion resistance.
Since the EGR gas cooling structure according to the embodiment of the present invention is configured as described above, its operation will be described as follows.
[0021]
First, a target EGR recirculation amount is set by a control unit (ECU) (not shown) according to the operating state of the engine 1, and a control signal is set from the ECU to the EGR valve 9 so as to be the target EGR recirculation amount. .
When the EGR valve 9 is operated based on the control signal of the ECU, as shown in FIG. 2, an amount of EGR gas corresponding to the opening of the EGR valve 9 is connected to the EGR core portion of the intercooler 6 via the connection portion 64. It flows into 61b. The EGR gas is mixed with fresh air flowing from the upstream side at the connection portion 64 and is cooled in the process of flowing through the EGR core portion 61b. In the downstream header 63, the EGR gas merges with fresh air that has passed through the fresh air core 61a.
[0022]
And by recirculating EGR gas to the intercooler 6 in this way, a sufficient distance from the mixing portion of EGR gas and fresh air to the engine 1 can be secured, and EGR gas and fresh air are passed through the intake passage 7. Uniform mixing is possible. Therefore, the EGR gas uniformly flows into each cylinder of the engine 1 and the variation in the recirculation amount of the EGR gas between the cylinders is suppressed.
[0023]
As shown in FIG. 3, when the EGR gas is not recirculated, that is, when the opening degree of the EGR valve 9 is 0 (fully closed), fresh air flows into the EGR core portion 61b, and the EGR core portion The soot of the exhaust gas remaining in 61b is scavenged. Therefore, no soot stays in the EGR core portion 61b, and the adhesion of the soot to the tube of the EGR core portion 61b is suppressed, thereby preventing a decrease in the cooling efficiency of the EGR gas.
[0024]
In addition, the conventional EGR cooler is abolished and the intercooler 6 is used as a function, so that the layout in the engine room is facilitated and the number of parts can be reduced to reduce the cost.
Further, even when corrosive liquid (or corrosive gas) is generated from the EGR gas when the EGR gas (exhaust gas) is cooled, the EGR core portion 61b is formed of a corrosion-resistant metal and the EGR core portion 61b. By brazing the ends of the tubes constituting the metal brazing with copper brazing or nickel brazing having more corrosion resistance, there is an advantage that sufficient corrosion resistance can be obtained and the reliability of the entire engine is improved.
[0025]
Even if the tube of the EGR core portion 61b corrodes and has a hole or the brazed portion of the tube corrodes and cracks, the EGR gas is cooled by air, so Only air flows in, and there is no possibility that the cooling water flows into the engine 1 and damages the engine 1 unlike the conventional EGR cooler.
[0026]
The EGR gas cooling structure of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the structure of the EGR valve and the supercharger is not particularly limited, and can be applied to various types of EGR valves and superchargers. In addition, the intercooler may be cooled by running air or may be cooled by blowing air from a fan.
[0027]
【The invention's effect】
As described above in detail, according to the EGR gas cooling structure of the present invention according to claim 1, it is possible to prevent the engine from being damaged due to the intrusion of the cooling water of the EGR cooler into the engine, and the cooling efficiency of the EGR gas. Can be suppressed, and furthermore, EGR gas and fresh air can be mixed uniformly.
[0028]
That is, even when corrosive liquid is generated during cooling of the EGR gas and cracks occur in the intercooler, air flows into the intake passage, so that cooling water flows into the engine and damages the engine as in the case of the conventional EGR cooler. There is an advantage that there is no fear of causing it.
Also, by recirculating the EGR gas to the intercooler, a sufficient distance from the mixing portion of the EGR gas and the fresh air to the engine can be secured, and the EGR gas and the fresh air can be uniformly mixed in the process of passing through the intake passage. it can. Therefore, there is an advantage that the EGR gas uniformly flows into each cylinder of the engine, and the variation in the recirculation amount of the EGR gas between the cylinders can be suppressed.
[0029]
Further, when the EGR gas is not refluxed, fresh air is introduced instead of the EGR gas, so that the soot contained in the EGR gas is scavenged and soot stays in the intercooler, so that the soot adheres to the tube. Thus, there is an advantage that the cooling efficiency of the EGR gas can be prevented from being lowered.
Further, the conventional EGR cooler is abolished so that the intercooler and the function are combined, thereby facilitating the layout in the engine room and reducing the number of parts and reducing the cost.
[0030]
According to the EGR gas cooling structure of the present invention according to claim 2, the reliability of the whole engine is further improved by forming the core portion of the intercooler to which the EGR passage is connected from the corrosion-resistant metal. There is an advantage that you can.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a main configuration of an EGR gas cooling structure according to an embodiment of the present invention.
FIG. 2 is a view for explaining the operation of the EGR gas cooling structure according to the embodiment of the present invention.
FIG. 3 is a diagram for explaining the operation of the EGR gas cooling structure according to the embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of an entire engine to which an EGR gas cooling structure according to an embodiment of the present invention is applied.
FIG. 5 is a schematic configuration diagram of an entire engine including a conventional EGR device.
FIG. 6 is a schematic configuration diagram showing a conventional EGR cooler.
[Explanation of symbols]
1 Engine 4 Exhaust passage 5 Turbocharger (supercharger)
6 Intercooler 7 Intake passage 8 EGR passage 9 EGR valve (EGR valve)

Claims (2)

過給機を備えたエンジンの排気通路と吸気通路との間を接続するＥＧＲ通路と、
該ＥＧＲ通路の途中に配設されたＥＧＲ弁と、
該過給機よりも下流の吸気通路に配設された空冷式のインタクーラとをそなえ、
該ＥＧＲ通路の吸気側接続部が該インタクーラの上流側ヘッダよりも下流のコア部に接続されて該インタクーラにＥＧＲクーラの機能が一体化されている
ことを特徴とする、ＥＧＲガス冷却構造。An EGR passage that connects between an exhaust passage and an intake passage of an engine equipped with a supercharger;
An EGR valve disposed in the middle of the EGR passage;
An air-cooled intercooler disposed in the intake passage downstream of the supercharger,
An EGR gas cooling structure, wherein an intake side connection portion of the EGR passage is connected to a core portion downstream of an upstream header of the intercooler, and the function of the EGR cooler is integrated with the intercooler . 該インタクーラのうち、該ＥＧＲ通路が接続された部分のコア部が耐腐食性金属で形成されている
ことを特徴とする、請求項１記載のＥＧＲガス冷却構造。2. The EGR gas cooling structure according to claim 1, wherein a core portion of the intercooler to which the EGR passage is connected is formed of a corrosion-resistant metal.
JP2001116944A 2001-04-16 2001-04-16 EGR gas cooling structure Expired - Fee Related JP3893895B2 (en)

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FR2847004B1 (en) * 2002-11-12 2005-07-29 Peugeot Citroen Automobiles Sa DEVICE FOR THERMALLY REGULATING THE INTAKE AIR OF A RECIRCULATED ENGINE AND EXHAUST GAS EMITTED BY THIS ENGINE
FR2856746B1 (en) * 2003-06-25 2007-10-26 Valeo Thermique Moteur Sa MODULE FOR COOLING THE EXHAUST AIR AND RECIRCULATED GASES OF AN INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE
FR2856747B1 (en) * 2003-06-25 2005-09-23 Valeo Thermique Moteur Sa MODULE FOR COOLING EXHAUST AIR AND RECIRCULATED EXHAUST GASES OF AN INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE.
SE526821C2 (en) * 2004-03-31 2005-11-08 Scania Cv Ab Arrangements for the recirculation of exhaust gases of a supercharged internal combustion engine
EP1800078B1 (en) * 2004-10-07 2018-05-30 MAHLE Behr GmbH & Co. KG Air-cooled exhaust gas heat exchanger, in particular exhaust gas cooler for motor vehicles
SE527869C2 (en) * 2004-11-17 2006-06-27 Scania Cv Ab Cooling device in a vehicle
SE528270C2 (en) * 2005-02-02 2006-10-10 Scania Cv Ab Arrangements for recirculation of exhaust gases of a supercharged internal combustion engine in a vehicle
SE530325C2 (en) * 2006-09-29 2008-05-06 Scania Cv Ab cooler arrangement
FR2908833B1 (en) * 2006-11-20 2011-06-17 Valeo Sys Controle Moteur Sas GAS ADMISSION DEVICE
FR3003345B1 (en) * 2013-03-12 2015-03-20 Valeo Systemes Thermiques HEAT EXCHANGER, PARTICULARLY EXHAUST AIR COOLER
DE102015008736A1 (en) 2015-07-07 2017-01-12 GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) A drive device for driving a vehicle and method and computer program product for operating this drive device

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