JP4134678B2 - Exhaust gas recirculation device for an internal combustion engine with a supercharger - Google Patents

Exhaust gas recirculation device for an internal combustion engine with a supercharger Download PDF

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Publication number
JP4134678B2
JP4134678B2 JP2002308281A JP2002308281A JP4134678B2 JP 4134678 B2 JP4134678 B2 JP 4134678B2 JP 2002308281 A JP2002308281 A JP 2002308281A JP 2002308281 A JP2002308281 A JP 2002308281A JP 4134678 B2 JP4134678 B2 JP 4134678B2
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exhaust gas
gas recirculation
supercharger
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internal combustion
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JP2004143985A (en
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浩成 橋本
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Toyota Motor Corp
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Toyota Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/146—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration
    • 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
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • F02B37/04—Engines with exhaust drive and other drive of pumps, e.g. with exhaust-driven pump and mechanically-driven second pump
    • F02B37/10—Engines with exhaust drive and other drive of pumps, e.g. with exhaust-driven pump and mechanically-driven second pump at least one pump being alternatively or simultaneously driven by exhaust and other drive, e.g. by pressurised fluid from a reservoir or an engine-driven pump
    • 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
    • F02B39/00—Component parts, details, or accessories relating to, driven charging or scavenging pumps, not provided for in groups F02B33/00 - F02B37/00
    • F02B39/02—Drives of pumps; Varying pump drive gear ratio
    • F02B39/08—Non-mechanical drives, e.g. fluid drives having variable gear ratio
    • F02B39/10—Non-mechanical drives, e.g. fluid drives having variable gear ratio electric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0002—Controlling intake air
    • F02D41/0007—Controlling intake air for control of turbo-charged or super-charged engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/0047—Controlling exhaust gas recirculation [EGR]
    • F02D41/005—Controlling exhaust gas recirculation [EGR] according to engine operating conditions
    • 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
    • F02M26/02—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
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/09—Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine
    • F02M26/10—Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
    • 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
    • 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
    • F02M26/39—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 series
    • 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
    • F02M26/45—Sensors specially adapted for EGR systems
    • F02M26/46—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition
    • F02M26/47—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition the characteristics being temperatures, pressures or flow rates
    • 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
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • 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
    • 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
    • F02M26/33—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 controlling the temperature of the recirculated gases
    • 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
    • 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
    • Y02T10/40—Engine management systems

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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)
  • Fluid Mechanics (AREA)
  • Analytical Chemistry (AREA)
  • Exhaust-Gas Circulating Devices (AREA)
  • Supercharger (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関の排気ガス再循環装置に係り、特に過給機を備えた内燃機関の排気ガス再循環装置に係る。
【０００２】
【従来の技術】
内燃機関の燃焼に於ける最高温度を下げ、ＮＯｘの発生を抑制する目的で行われる排気ガス再循環（ＥＧＲ）は、内燃機関が過給機を備えている場合、通常過給機のタービンの上流側から過給機のコンプレッサの下流側へ排気ガスを導く経路に沿って行われている。これは、もし排気ガス再循環が過給機タービンの下流側から過給機コンプレッサの上流側へ排気ガスを導く要領にて行われると、過給機タービン上流に於ける圧力上昇に相当して内燃機関にポンピングロスが生ずるからである。但し、上記の特許文献１には、再循環される排気ガスを冷却すると共にそれにより発生したミストを除去する手段を有する排気ガス再循環装置を提案するものであるが、その実施の形態を示す図には、過給機タービンの下流側から取り出された排気ガスを冷却し且つミストを除去して過給機コンプレッサの上流側へ注入する構造が示されている。
【０００３】
一方、内燃機関の運転がコンピュータを用いて電子制御されるようになったことに伴い、従来排気タービンにてコンプレッサを駆動するのみであった過給機に電動駆動手段を組み込み、過給を電気的に補助制御することが、例えば上記の特許文献２に示されている如く知られている。
【特許文献１】
特開２００２−８９３７５公報
【特許文献２】
特開平１１−１８２２５６号公報
【０００４】
【発明が解決しようとする課題】
上記の通り過給機を備えた内燃機関に於いては、上記のポンピングロスを避ける観点から排気ガス再循環は過給機タービンの上流側から過給機コンプレッサの下流側へ向けて行われるのが望ましいが、過給機の作動状態の如何によっては、過給機タービンの上流側に於ける排気ガス圧力と過給機コンプレッサ下流側に於ける吸気圧力との差の如何によって、排気ガス再循環量が好ましい値に達しない場合がある。かかる不都合は過給機が補助電動駆動手段を備えている場合に特に起こりやすい。
【０００５】
本発明は、上記の問題に鑑み、過給機を備えた内燃機関に於いて、内燃機関のより広い運転領域にわたって過給機運転と排気ガス再循環との間に好ましい調和を図ることができるよう改良された排気ガス再循環装置を提供することを課題としている。
【０００６】
【課題を解決するための手段】
上記の課題を解決するものとして、本発明は、過給機を有する内燃機関の排気ガス再循環装置にして、前記過給機のタービンの上流側から該過給機のコンプレッサの下流側へ排気ガスを再循環させる第一の排気ガス再循環手段と、前記過給機のタービンの下流側から該過給機のコンプレッサの上流側へ排気ガスを再循環させる第二の排気ガス再循環手段と、前記第一の排気ガス再循環手段により所期の排気ガス再循環量が得られるか否かを判断する第一の判断手段と、前記第一の判断手段により前記第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないと判断されるとき前記第一の排気ガス再循環手段による排気ガス再循環を前記第二の排気ガス再循環手段による排気ガス再循環に切り換える切換え手段とを有することを特徴とする排気ガス再循環装置を提供するものである。
【０００７】
上記の如き排気ガス再循環装置に於いて、前記判断手段は前記過給機の上流側に於ける排気ガス圧力が前記過給機コンプレッサの下流側に於ける吸気圧力より所定値以上大きくないとき前記第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないと判断するようになっていてよい。この場合、前記判断手段は前記過給機タービンの上流側に於ける排気ガス圧力を内燃機関の運転状態から推定する手段を含んでいてよい。
【０００８】
また、過給機が補助電動駆動手段を備えている場合、前記第一の判断手段は前記補助電動駆動手段に対する駆動要求量が所定のしきい値を越えるとき前記第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないとの判断を行なうようになっていてよい。
【０００９】
以上いずれの場合にも、排気ガス再循環装置は、内燃機関の運転状態基づいて排気ガス中のＮＯｘ量の目標値を算出する手段と、排気ガス中のＮＯｘ量を検出する手段とを有し、検出されたＮＯｘ量の前記目標値に対する偏差に基づいて前記第一の排気ガス再循環手段と前記第二の排気ガス再循環手段の少なくとも一方に於ける排気ガス再循環量を制御する制御手段を有していてよい。
【００１０】
また、以上いずれの場合にも、排気ガス再循環装置は、更に前記第二の排気ガス再循環手段により所期の排気ガス再循環量が得られるか否かを判断する第二の判断手段と、前記第二の判断手段により前記第二の排気ガス再循環手段によって所期の排気ガス再循環量が得られないと判断されるとき前記過給機への新気の導入を制限する手段とを有していてよい。
【００１１】
【発明の作用及び効果】
上記の如く過給機を有する内燃機関の排気ガス再循環装置が、過給機タービンの上流側から過給機コンプレッサの下流側へ排気ガスを再循環させる第一の排気ガス再循環手段と、過給機タービンの下流側から過給機コンプレッサの上流側へ排気ガスを再循環させる第二の排気ガス再循環手段とを有し、前記第一の排気ガス再循環手段により所期の排気ガス再循環量が得られるか否かを判断する判断手段によりそれを判断し、前記第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないと判断されるときには、前記第一の排気ガス再循環手段による排気ガス再循環を前記第二の排気ガス再循環手段による排気ガス再循環に切り換える切換え手段を有していれば、内燃機関の運転状態とそれに伴う過給機の運転状態に応じて、排気ガス再循環によって内燃機関にポンピングロスを生ずる恐れはないが、排気ガス圧と吸気圧の差の如何によって排気ガス再循環が行われにくくなる場合のある第一の排気ガス再循環態様と、上記のポンピングロスは伴うが、排気ガス圧と吸気圧の差の如何にかかわらず排気ガス再循環が確実に行われる第二の排気ガス再循環態様とを選択的に使い分け、内燃機関の広い運転領域にわたって過給機運転との調和がよりよく取れた排気ガス再循環を実行することができる。
【００１２】
上記の判断、即ち、第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないとの判断を、過給機のタービンの上流側に於ける排気ガス圧力が過給機コンプレッサの下流側に於ける吸気圧力より所定値以上大きくないことによって行なうようになっていれば、排気ガス再循環に於ける排気ガス取出し部の圧力と排気ガス注入部の圧力とを途中の流れ抵抗を加味して直接対比することにより、当該第一の排気ガス再循環手段による排気ガス再循環の可否を極めて直截的に判断することができる。
【００１３】
この場合、上記２つの圧力は適当な圧力計により検出できるが、特に過給機タービン上流側の排気ガス圧力は内燃機関の運転状態からも推定できるので、これを用いれば過給機タービン上流側に於ける圧力測定を省略することができる。
【００１４】
過給機が補助電動駆動手段を備えている場合、補助電動駆動手段が駆動され或はその駆動量が大きくなる程、過給機タービンの入口の排気ガス圧は低下し、一方、過給機コンプレッサの出口の吸気圧は増大するので、第一の排気ガス再循環手段によって得られる排気ガス再循環量は低下してくる。従って、第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られなくなるのは、補助電動駆動手段に対する駆動要求量が高く、それに応じて過給機の補助電動駆動が行われるかまたは強く行われる場合である。このことから、補助電動駆動手段に対する駆動要求量が所定のしきい値を越えることによって第一の判断手段が第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないとの判断を行なうようになっていれば、補助電動駆動手段の作動に関連させて第一の排気ガス再循環手段より第二の排気ガス再循環手段への切り替えを適切に行わせることができる。尚、この場合、第一の排気ガス再循環手段から第二の排気ガス再循環手段への切り替えが行われたときには、補助電動駆動手段に対する駆動要求量が上記のしきい値より低い第二のしきい値以下に下がったとき、第二の排気ガス再循環手段による排気ガス再循環より第一の排気ガス再循環手段による排気ガス再循環へ戻す逆の制御が行われればよい。
【００１５】
排気ガス再循環はＮＯｘが排出されることを抑制するために行われるものであるので、上記の第一または第二のいずれの排気ガス再循環手段により排気ガス再循環が行われる場合にも、排気ガス再循環の度合はＮＯｘの排出量を所定の目標値内に抑えるように行われればよい。そこで内燃機関の運転状態基づいて排気ガス中のＮＯｘ量の目標値を算出する手段と、排気ガス中のＮＯｘ量を検出する手段とが設けられ、検出されたＮＯｘ量の目標値に対する偏差に基づいて排気ガス再循環量を制御する制御手段が設けられれば、第一または第二のいずれの排気ガス再循環手段により排気ガス再循環が行われても、排気ガス再循環量を適切に制御することができる。
【００１６】
また、以上いずれの場合にも、更に、前記第二の排気ガス再循環手段により所期の排気ガス再循環量が得られるか否かを判断する第二の判断手段が設けられ、該第二の判断手段により第二の排気ガス再循環手段によって所期の排気ガス再循環量が得られないと判断されるときには過給機への新気の導入を制限する手段が設けられれば、これによって過給機コンプレッサの入口に於ける負圧を増大させることにより、第二の排気ガス再循環手段による排気ガス再循環量を確実に高めることができる。
【００１７】
【発明の実施の形態】
図１は過給機を備えた内燃機関に本発明による排気ガス再循環装置を組み込んだ一つの実施の形態を示す概略図である。尚、以下に順次説明されるが、図１、３および４に於いて、上記第一の排気ガス再循環手段による排気ガスの流路は実線により示されており、第二の排気ガス再循環手段による排気ガスの流路は、第一のそれと異なる部分に於いて、破線により示されている。
【００１８】
図１に於いて、１０は内燃機関（エンジン）であり、過給機１２を備えている。即ち、内燃機関の排気ガスは排気通路１４を経て過給機のタービン１６へ導かれ、タービンを駆動した後、排気通路１８より排出されるようになっている。図には示されていないが、排気通路１８の途中には触媒コンバータ、マフラー等が設けられている。一方、吸気は、排気ガス再循環装置が第一の排気ガス再循環手段により作動するときには、図には示されていないエアクリーナ等の通常の手段を別として、過給機のコンプレッサ２０の入口に直接供給され、コンプレッサ２０がタービン１６により駆動されることによって昇圧され、インタークーラ２２、スロットル弁２４を含む吸気通路２６を経て内燃機関へ供給されるようになっている。
【００１９】
過給機１２はタービン１６とコンプレッサ２０とを連結する軸２８の途中にこの実施の形態では電動発電機（Ｍ／Ｇ）として構成された補助電動駆動手段３０を備えている。
【００２０】
第一の排気ガス再循環手段は、過給機タービン１６の上流側に当たる排気通路１４より排気ガス再循環切換制御弁（以下、簡単のためＥＧＲ弁と云う）Ａを通る経路を経てＥＧＲクーラ３２へ通じ、更にこれよりＥＧＲ弁Ｂを経て、過給機コンプレッサ２０の下流側に当たる吸気通路２６に通じる経路により構成されている。これに対し、第二の排気ガス再循環手段は、図中破線にて示されている如く過給機タービン１６の下流側に当たる排気管１８よりＥＧＲ弁Ｃを経てＥＧＲクーラ３２に通じ、更にこれよりＥＧＲ弁Ｄを経て過給機コンプレッサ２０の上流側に当たる吸気通路３４に通じる経路により構成されている。吸気通路３４の上流端は吸気絞り弁Ｅにより絞られるようになっている。
【００２１】
ＥＧＲ弁Ａ〜Ｄおよび吸気絞り弁Ｅはそれぞれこの内燃機関を組み込んだ車輌を総合的に制御する電子制御装置（ＥＣＵ）３６の制御出力端子ａ〜ｅより供給される制御信号により開閉制御され、また場合によっては任意の中間開度に制御されるようになっている。電子制御装置３６には、その入力端子ｐを経て吸気通路２６内の吸気圧力を検出する圧力センサ３８より吸気圧力Ｐscに関する情報を与えられ、入力端子ｑを経て排気通路１４内の排気ガス圧力を検出する圧力センサ４０よりタービン上流側の排気ガス圧力Ｐtiに関する情報を与えられ、入力端子rを経て吸気通路３４内の吸気圧力を検出する圧力センサ４２より吸気通路３４内の吸気圧力Ｐciに関する情報を与えられ、入力端子ｓを経て排気通路１８内の排気ガス圧力を検出する圧力センサ４４よりタービン下流側の排気ガス圧力Ｐtoに関する情報を与えられ、更に本発明の実行に際して望まれる任意のその他の信号ｚを与えられるようになっている。
【００２２】
次に、図１に示す排気ガス再循環装置の作動を図２のフローチャートに従って説明する。内燃機関１０の運転が開始されると、ステップ１に於いて排気ガス再循環（ＥＧＲ）を行うべきときか否かが判断される。かかるフローチャート従った制御の流れは、内燃機関の運転中、常時数十ミリセカンドの周期にて繰り返し行われるものであり、従って図示のフローチャートは、内燃機関の運転中、常時ＥＧＲが必要とされているか否かがチェックされていることを意味する。答がノーのときにはそれにて１回の制御はそのまま終了するが、答がイエスのときには制御はステップ２へ進む。
【００２３】
ステップ２に於いては、圧力センサ４０により検出された排気ガス通路１４内の排気ガス圧力Ｐtiが圧力センサ３８により検出された吸気通路２６内の吸気圧力Ｐscよりα以上高いか否かが判断される。このαの値は、ＥＧＲ弁Ａ、ＥＧＲクーラ３２およびＥＧＲ弁Ｂを通る第一の排気ガス再循環手段の経路を経て排気通路１４より吸気通路２６へ向かう排気ガスの必要な再循環流を起こさせるに十分なだけ排気通路１４内の排気ガス圧力が吸気通路２６内の吸気圧力より高いか否かの目安となる値である。答がイエスであるときには、制御はステップ３へ進み、ＥＧＲ弁ＡおよびＢを開いて上記第一の排気ガス再循環装置を作動させ、ＥＧＲ弁ＣおよびＤを閉じて上記第二の排気ガス再循環装置を作動させない制御行われる。このとき排気ガス再循環の流れは図中実線の経路に沿う矢印にて示されている如く生ずる。尚、ＥＧＲ弁ＡまたはＢ或は両方の開度は排気ガス再循環量を調整するよう制御されてよい。ステップ１および２の答がイエスである限り、制御は各サイクル毎にこの経路を通って終了し、第一の排気ガス再循環手段による排気ガス再循環が続けられる。
【００２４】
これ対しステップ２の答がノーのときには、制御はステップ４へ進み、ＥＧＲ弁ＣおよびＤを開いて上記第二の排気ガス再循環手段を作動させ、ＥＧＲ弁ＡおよびＢを閉じて上記第一の排気ガス再循環手段を作動させない制御が行われる。このとき制御は更にステップ５へ進み、圧力センサ４４にて検出された過給機タービン下流側の排気ガス圧力Ｐtoが圧力センサ４２により検出された過給機コンプレッサ上流側の吸気圧力Ｐciよりβ以上高いか否かが判断される。このβの値は、ＥＧＲ弁Ｃ、ＥＧＲクーラ３２およびＥＧＲ弁Ｄを通る第二の排気ガス再循環手段の経路を経て排気通路１８より吸気通路３４へ向かう排気ガスの必要な再循環流を起こさせるに十分なだけ排気通路１８内の排気ガス圧力が吸気通路３４内の吸気圧力より高いか否かの目安となる値である。答がイエスである限り、第二の排気ガス再循環手段による排気ガス再循環が続けられる。
【００２５】
しかし、ステップ５の答がノーであるときには、制御はステップ６へ進み、吸気絞り弁Ｅを閉じる制御が行われ、吸気通路３４に対する外気の新たな流入を制限することにより吸気通路３４内に負圧を生じさせ、第二の排気ガス再循環手段を経て所望の量の排気ガス再循環が行なわれるようにする。尚、この場合にもＥＧＲ弁Ｃ、Ｄおよび吸気絞り弁Ｅの開度は排気ガス再循環量を調整するよう開閉の中間位置で制御されてよい。
【００２６】
図３は図１に示した本発明の実施の形態の一部を修正した本発明による排気ガス再循環装置の他の一つの実施の形態を示す同様の概略図である。図３に於いて、図１に示す部分に対応する部分は図１に於けると同じ符号により示されている。この実施の形態の於いては、ＥＧＲ弁ＡとＣとが２系列の同時切換弁Ｍにより置き換えられており、またＥＧＲ弁ＢとＤとが２系列の同時切換弁Ｎにより置き換えられている。これらの同時切換弁ＭおよびＮは、それぞれＥＣＵの出力端子ｍおよびｎより供給される制御信号により切り換えられ、第一の排気ガス再循環手段または第二の排気ガス再循環手段のいずれかを択一的に作動させるようになっている。この場合、２系列同時切換弁ＭまたはＮの一方または両方の切り換えに於けるデューティ比の制御により排気ガス再循環量を制御することができる。この実施の形態に於ける作動のその他の点については、図１に示す実施の形態に於けるものと同じである。
【００２７】
図４は図１に示す実施の形態に於ける排気通路１８にＮＯｘセンサ４６を設けた本発明の更に他の一つの実施の形態を示す同様の図である。図４に於いても、図１に於けると同じ部分は同じ符号により示されており、図１に於けると同様に作動する。かかるＮＯｘセンサを設けることにより、装置の作動は図５のフローチャートに示す如くＥＧＲの目的であるＮＯｘの排出抑制に関し、より繊細に制御される。
【００２８】
図５に示す制御に於いては、図２示す制御の場合と同様にまずステップ１０１に於いてＥＧＲを行うべきときであることが判断されると、次のステップ１０２に於いて、その時の内燃機関および車輌の運転状態基づいて目標とすべき排気ガス中のＮＯｘの値が算出される。その後制御はステップ１０３へ進み、図２の制御に於けるステップ２と同様に排気ガス通路１４に於ける排気ガス圧力Ｐtiが吸気通路２６に於ける吸気圧力Ｐscよりα以上高いか否かが判断される。そして答がイエスのときには、制御はステップ１０４へ進み、ＥＧＲ弁ＡおよびＢを開いて第一の排気ガス再循環手段による排気ガス再循環が行われる。このときＥＧＲ弁ＡおよびＢは単に開かれるだけでなく、ステップ１０２に於いて算出された目標ＮＯｘ値に関連してマップ等により可変の開度に設定される。尚、ＥＧＲ弁ＣおよびＤは全閉とされ、第二の排気ガス再循環手段は作動しないようにされる。
【００２９】
次いで制御はステップを１０５へ進み、ＮＯｘセンサ４６による排気ガス中のＮＯｘの値の読み取りが行われる。次いで制御はステップ１０６へ進み、実測されたＮＯｘ値が上に算出された目標ＮＯｘ値より大きいか否かが判断される。そして答がイエスのときには制御はステップ１０７へ進み、ＥＧＲ弁ＡまたはＢを１段階だけ開く制御が行われる。これはＮＯｘ値を低減すべく排気ガス再循環量を１段階だけ増大させる制御である。（尚，ＥＧＲ弁ＡまたはＢを１段階開く制御は，ＥＧＲ弁ＡおよびＢの両方を１段階開く制御を含んでいてよい。）一方、ステップを１０６の答がノーのときには、制御はステップ１０８へ進み、ＥＧＲ弁ＡまたはＢを１段階だけ閉じる制御行われる。これはＮＯｘ値の抑制を弛めるべく排気ガス再循環量を１段階だけ低減する制御である。（尚，この場合にもＥＧＲ弁ＡまたはＢを１段階閉じる制御は，ＥＧＲ弁ＡおよびＢの両方を１段階閉じる制御を含んでいてよい。）いずれにしても、 １サイクルの制御はこれにて終了する。
【００３０】
ステップ１０３の答がノーであるときには、制御はステップ１０９へ進み、ＥＧＲ弁ＣおよびＤを開いて第二の排気ガス再循環手段による排気ガス再循環が行われる。このときにもＥＧＲ弁ＣおよびＤは単に開かれるだけでなく、ステップ１０２に於いて算出された目標ＮＯｘ値のに関連しマップ等により可変の開度に設定される。ＥＧＲ弁ＡおよびＢは全閉とされ、第一の排気ガス再循環手段は作動しないようにされる。
【００３１】
以下のステップ１１０〜１１３に於ける制御は、ステップ１０５〜１０８に於ける制御と同様の制御を第二の排気ガス再循環手段について行うものである。また、ステップ１１４および１１５は、第二の排気ガス再循環手段により排気ガス再循環が行われる場合に、図２のステップ５および６に於けると同様の制御を行うものである。
【００３２】
図６は図１、３または４に示す装置に於ける上記の如き第一および第二の排気ガス再循環手段の切換えを、過給機の補助電動駆動手段３０の作動との関係に於いて制御する一つの実施の形態を示すフローチャートである。この場合、ステップ２０１にて図２または図５のフローチャートに於けるステップ１または１０１に於けると同様にＥＧＲの必要性が判断されると、制御はステップ２０２へ進み、フラグＦが１にセットされているか否かが判断される。この種のフラグは制御開始時に０にリセットされるので、それが改めて１にセットされるまでは０である。従って、当初答はノーであり、制御はステップ２０３へ進み、ＥＧＲ弁ＡおよびＢを開き、ＥＧＲ弁ＣおよびＤを閉じ、第一の排気ガス再循環手段による排気ガス再循環が開始される。次いで制御はステップ２０４へ進み、過給機の補助電動駆動手段の出力Ｄmaが所定のしきい値Ｄs1以上であるか否かが判断される。
【００３３】
答がノー、即ち、補助電動駆動手段がさして強力に作動されていない状態にあるときには、制御サイクルはそのまま終わり、ＥＧＲが必要とされる間、第一の排気ガス再循環手段による排気ガス再循環が行われる。これに対し、ステップ２０４の答がイエスのとき、即ち過給機が補助電動駆動手段によるかなりの補助駆動を伴って作動されているときには、制御はステップ２０５へ進み、フラグＦが１にセットされる。
【００３４】
フラグＦが１にセットされると、次のサイクルからは制御はステップ２０６へ進み、ＥＧＲ弁ＡおよびＢを閉じ、ＥＧＲ弁ＣおよびＤを開き、排気ガス再循環は第二の排気ガス再循環手段による作動に切り換えられる。
【００３５】
この後，制御はステップ２０７へ進み、ＤmaがＤs1より幾分小さいしきい値Ｄs2より大きいか否かが判断される。答がイエスである間、第二の排気ガス再循環手段による排気ガス再循環が続けられる。ステップ２０８および２０９は、図２のフローチャートに於けるステップ５および６または図５のフローチャートに於けるステップ１１４および１１５と同様の目的のためにもうけられているものである。
【００３６】
かくして第二の排気ガス再循環手段による排気ガス再循環中に過給機の補助駆動の度合が低下し、ステップ２０７の答がノーに転ずると、制御はステップ２１０へ進み、フラグＦが０にリセットされ、排気ガス再循環は第一の排気ガス再循環手段による排気ガス再循環に戻される。しきい値Ｄs2をしきい値Ｄs1より幾分小さくしたのは、切換え制御にヒステリシスを与えるためである。
【００３７】
以上に於いては本発明をいくつかの実施の形態について詳細に説明したが、これらの実施の形態について本発明の範囲内にて種々の変更が可能であることは当業者にとって明らかであろう。
【図面の簡単な説明】
【図１】過給機を備えた内燃機関に本発明による排気ガス再循環装置を組み込んだ一つの実施の形態を示す概略図。
【図２】図１に示す排気ガス再循環装置の作動を示すフローチャート。
【図３】図１に示す実施の形態の一部を修正した他の一つの実施の形態を示す概略図。
【図４】図１に示す実施の形態にＮＯｘセンサを設けた更に他の一つの実施の形態を示す概略図。
【図５】図４に示す排気ガス再循環装置の作動を示すフローチャート。
【図６】第一および第二の排気ガス再循環手段の切換えを過給機の補助電動駆動手段３０の作動との関係に於いて制御する一つの実施の形態を示すフローチャート。
【符号の説明】
１０…内燃機関、１２…過給機、１４…排気通路、１６…タービン、１８…排気通路、２０…コンプレッサ、２２…インタークーラ、２４…スロットル弁、２６…吸気通路、２８…軸、３０…補助電動駆動手段、３２…ＥＧＲクーラ、３４…吸気通路、３６…電子制御装置、３８，４０，４２，４４…圧力センサ、４６…ＮＯｘセンサ、Ａ，Ｂ，Ｃ，Ｄ…ＥＧＲ弁、Ｅ…吸気絞り弁、Ｍ，Ｎ…２系列の同時切換弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas recirculation device for an internal combustion engine, and more particularly to an exhaust gas recirculation device for an internal combustion engine equipped with a supercharger.
[0002]
[Prior art]
Exhaust gas recirculation (EGR), which is performed for the purpose of lowering the maximum temperature in combustion of an internal combustion engine and suppressing the generation of NOx, is usually performed when the internal combustion engine is equipped with a supercharger. This is performed along a path that leads the exhaust gas from the upstream side to the downstream side of the compressor of the supercharger. This corresponds to an increase in pressure upstream of the turbocharger turbine if exhaust gas recirculation is performed in a manner that leads exhaust gas from the downstream side of the turbocharger turbine to the upstream side of the turbocharger compressor. This is because a pumping loss occurs in the internal combustion engine. However, the above-mentioned Patent Document 1 proposes an exhaust gas recirculation device having means for cooling the exhaust gas to be recirculated and removing mist generated thereby, and shows an embodiment thereof. The figure shows a structure in which the exhaust gas taken from the downstream side of the turbocharger turbine is cooled and the mist is removed and injected to the upstream side of the turbocharger compressor.
[0003]
On the other hand, as the operation of the internal combustion engine has been electronically controlled using a computer, an electric drive means has been incorporated into a turbocharger that has conventionally only driven a compressor with an exhaust turbine, and the supercharging is For example, the auxiliary control is known as shown in Patent Document 2 described above.
[Patent Document 1]
JP 2002-89375 A [Patent Document 2]
Japanese Patent Laid-Open No. 11-182256
[Problems to be solved by the invention]
In an internal combustion engine equipped with a supercharger as described above, exhaust gas recirculation is performed from the upstream side of the turbocharger turbine to the downstream side of the supercharger compressor from the viewpoint of avoiding the above-mentioned pumping loss. However, depending on the operating condition of the turbocharger, the exhaust gas re-registration depends on the difference between the exhaust gas pressure upstream of the turbocharger turbine and the intake air pressure downstream of the turbocharger compressor. The circulation amount may not reach a preferable value. Such inconvenience is particularly likely when the supercharger is provided with auxiliary electric drive means.
[0005]
In view of the above problems, the present invention can achieve a favorable harmony between supercharger operation and exhaust gas recirculation over a wider operating region of an internal combustion engine in an internal combustion engine equipped with a supercharger. It is an object of the present invention to provide an exhaust gas recirculation device improved as described above.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an exhaust gas recirculation device for an internal combustion engine having a supercharger, and exhausts from an upstream side of a turbine of the supercharger to a downstream side of a compressor of the supercharger. First exhaust gas recirculation means for recirculating gas; and second exhaust gas recirculation means for recirculating exhaust gas from a downstream side of the turbocharger turbine to an upstream side of the compressor of the supercharger. The first exhaust gas recirculation means determines whether or not the desired exhaust gas recirculation amount is obtained, and the first exhaust gas recirculation is determined by the first determination means. When it is determined that the desired exhaust gas recirculation amount cannot be obtained depending on the means, the exhaust gas recirculation by the first exhaust gas recirculation means is changed to the exhaust gas recirculation by the second exhaust gas recirculation means. Having switching means for switching It is to provide an exhaust gas recirculation apparatus characterized.
[0007]
In the exhaust gas recirculation apparatus as described above, the determination means is configured such that the exhaust gas pressure on the upstream side of the supercharger is not greater than a predetermined value by the intake pressure on the downstream side of the supercharger compressor. Depending on the first exhaust gas recirculation means, it may be determined that the desired exhaust gas recirculation amount cannot be obtained. In this case, the determination means may include means for estimating the exhaust gas pressure upstream of the supercharger turbine from the operating state of the internal combustion engine.
[0008]
Further, when the supercharger is provided with auxiliary electric drive means, the first determination means is the first exhaust gas recirculation means when the required drive amount for the auxiliary electric drive means exceeds a predetermined threshold value. In some cases, it may be determined that the desired exhaust gas recirculation amount cannot be obtained.
[0009]
In any of the above cases, the exhaust gas recirculation device has means for calculating the target value of the NOx amount in the exhaust gas based on the operating state of the internal combustion engine, and means for detecting the NOx amount in the exhaust gas. And a control means for controlling an exhaust gas recirculation amount in at least one of the first exhaust gas recirculation means and the second exhaust gas recirculation means based on a deviation of the detected NOx amount from the target value. You may have.
[0010]
In any of the above cases, the exhaust gas recirculation device further includes second determination means for determining whether or not an intended exhaust gas recirculation amount can be obtained by the second exhaust gas recirculation means. Means for restricting introduction of fresh air into the supercharger when the second exhaust gas recirculation means determines that the desired exhaust gas recirculation amount cannot be obtained by the second determination means; You may have.
[0011]
[Action and effect of the invention]
An exhaust gas recirculation device for an internal combustion engine having a supercharger as described above, first exhaust gas recirculation means for recirculating exhaust gas from the upstream side of the supercharger turbine to the downstream side of the turbocharger compressor, Second exhaust gas recirculation means for recirculating exhaust gas from the downstream side of the turbocharger turbine to the upstream side of the turbocharger compressor, and the desired exhaust gas by the first exhaust gas recirculation means When it is judged by the judging means for judging whether or not the recirculation amount can be obtained, and it is judged that the desired exhaust gas recirculation amount cannot be obtained by the first exhaust gas recirculation means, If there is a switching means for switching the exhaust gas recirculation by the first exhaust gas recirculation means to the exhaust gas recirculation by the second exhaust gas recirculation means, the operating state of the internal combustion engine and the supercharger associated therewith Depending on the driving state of There is no fear of causing a pumping loss in the internal combustion engine due to the gas gas recirculation, but the first exhaust gas recirculation mode in which exhaust gas recirculation may be difficult to be performed depending on the difference between the exhaust gas pressure and the intake pressure, Although the above pumping loss is involved, the second exhaust gas recirculation mode in which exhaust gas recirculation is reliably performed regardless of the difference between the exhaust gas pressure and the intake pressure is selectively used selectively. Exhaust gas recirculation that is better harmonized with turbocharger operation can be performed across the region.
[0012]
The above judgment, that is, the judgment that the desired exhaust gas recirculation amount cannot be obtained by the first exhaust gas recirculation means, the exhaust gas pressure on the upstream side of the turbocharger turbine is supercharged. If the pressure is not greater than a predetermined value than the intake pressure on the downstream side of the compressor, the exhaust gas recirculation pressure and the exhaust gas injection pressure in the exhaust gas recirculation By directly comparing with the flow resistance taken into consideration, it is possible to determine whether or not the exhaust gas recirculation by the first exhaust gas recirculation means is possible.
[0013]
In this case, the above two pressures can be detected by an appropriate pressure gauge. In particular, the exhaust gas pressure upstream of the turbocharger turbine can be estimated from the operating state of the internal combustion engine. The pressure measurement in can be omitted.
[0014]
When the supercharger is equipped with auxiliary electric drive means, the exhaust gas pressure at the inlet of the supercharger turbine decreases as the auxiliary electric drive means is driven or the amount of drive increases. Since the intake pressure at the outlet of the compressor increases, the exhaust gas recirculation amount obtained by the first exhaust gas recirculation means decreases. Therefore, the reason why the desired exhaust gas recirculation amount cannot be obtained by the first exhaust gas recirculation means is that the drive request amount for the auxiliary electric drive means is high, and the auxiliary electric drive of the supercharger is performed accordingly. It is a case that is done or strongly done. Therefore, when the required amount of drive for the auxiliary electric drive means exceeds a predetermined threshold value, the first judgment means cannot obtain the desired exhaust gas recirculation quantity by the first exhaust gas recirculation means. Can be appropriately switched from the first exhaust gas recirculation means to the second exhaust gas recirculation means in connection with the operation of the auxiliary electric drive means. . In this case, when switching from the first exhaust gas recirculation means to the second exhaust gas recirculation means is performed, the second required drive amount for the auxiliary electric drive means is lower than the above threshold value. When the value falls below the threshold value, reverse control may be performed to return from the exhaust gas recirculation by the second exhaust gas recirculation means to the exhaust gas recirculation by the first exhaust gas recirculation means.
[0015]
Since the exhaust gas recirculation is performed in order to suppress the discharge of NOx, even when the exhaust gas recirculation is performed by any of the first or second exhaust gas recirculation means, The degree of exhaust gas recirculation may be performed so as to keep the NOx emission amount within a predetermined target value. Therefore, means for calculating the target value of the NOx amount in the exhaust gas based on the operating state of the internal combustion engine and means for detecting the NOx amount in the exhaust gas are provided, and based on the deviation of the detected NOx amount from the target value. If the control means for controlling the exhaust gas recirculation amount is provided, the exhaust gas recirculation amount is appropriately controlled regardless of whether the exhaust gas recirculation is performed by the first or second exhaust gas recirculation means. be able to.
[0016]
In any of the above cases, the second exhaust gas recirculation device further includes second determination means for determining whether or not the desired exhaust gas recirculation amount can be obtained. If it is determined by the determination means that the second exhaust gas recirculation means cannot obtain the desired exhaust gas recirculation amount, if means for restricting the introduction of fresh air to the supercharger is provided, By increasing the negative pressure at the inlet of the supercharger compressor, the exhaust gas recirculation amount by the second exhaust gas recirculation means can be reliably increased.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic view showing an embodiment in which an exhaust gas recirculation device according to the present invention is incorporated in an internal combustion engine equipped with a supercharger. In FIGS. 1, 3 and 4, the exhaust gas flow path by the first exhaust gas recirculation means is indicated by a solid line in FIG. The exhaust gas flow path by the means is indicated by a broken line in a portion different from the first one.
[0018]
In FIG. 1, reference numeral 10 denotes an internal combustion engine (engine), which includes a supercharger 12. That is, the exhaust gas of the internal combustion engine is guided to the turbocharger turbine 16 through the exhaust passage 14 and is discharged from the exhaust passage 18 after driving the turbine. Although not shown in the drawing, a catalytic converter, a muffler, and the like are provided in the middle of the exhaust passage 18. On the other hand, when the exhaust gas recirculation device is operated by the first exhaust gas recirculation means, the intake air enters the inlet of the compressor 20 of the supercharger apart from normal means such as an air cleaner not shown in the figure. Directly supplied, the compressor 20 is driven by the turbine 16 to increase the pressure, and is supplied to the internal combustion engine via an intake passage 26 including an intercooler 22 and a throttle valve 24.
[0019]
The supercharger 12 includes auxiliary electric drive means 30 configured as a motor generator (M / G) in this embodiment in the middle of a shaft 28 connecting the turbine 16 and the compressor 20.
[0020]
The first exhaust gas recirculation means passes through an exhaust gas recirculation switching control valve (hereinafter referred to as an EGR valve for the sake of simplicity) A from the exhaust passage 14 corresponding to the upstream side of the turbocharger turbine 16 and then the EGR cooler 32. To the intake air passage 26 that contacts the downstream side of the turbocharger compressor 20 through the EGR valve B. On the other hand, the second exhaust gas recirculation means communicates with the EGR cooler 32 via the EGR valve C from the exhaust pipe 18 which is downstream of the turbocharger turbine 16 as shown by the broken line in the figure. Further, it is configured by a path that leads to an intake passage 34 that passes through the EGR valve D and reaches the upstream side of the turbocharger compressor 20. The upstream end of the intake passage 34 is throttled by an intake throttle valve E.
[0021]
The EGR valves A to D and the intake throttle valve E are controlled to be opened and closed by control signals supplied from control output terminals a to e of an electronic control unit (ECU) 36 that comprehensively controls a vehicle incorporating the internal combustion engine, In some cases, it is controlled to an arbitrary intermediate opening. Information regarding the intake pressure Psc is given to the electronic control unit 36 from a pressure sensor 38 that detects the intake pressure in the intake passage 26 via the input terminal p, and the exhaust gas pressure in the exhaust passage 14 is adjusted via the input terminal q. Information on the exhaust gas pressure Pti upstream of the turbine is given from the pressure sensor 40 to be detected, and information on the intake pressure Pci in the intake passage 34 is received from the pressure sensor 42 that detects the intake pressure in the intake passage 34 via the input terminal r. Is provided with information about the exhaust gas pressure Pto downstream of the turbine from a pressure sensor 44 which detects the exhaust gas pressure in the exhaust passage 18 via the input terminal s, and any other signals desired in the practice of the invention. z can be given.
[0022]
Next, the operation of the exhaust gas recirculation device shown in FIG. 1 will be described with reference to the flowchart of FIG. When the operation of the internal combustion engine 10 is started, it is determined in step 1 whether or not exhaust gas recirculation (EGR) should be performed. The flow of control according to this flowchart is repeatedly performed at a cycle of several tens of milliseconds at all times during the operation of the internal combustion engine. Therefore, the illustrated flowchart always requires EGR during the operation of the internal combustion engine. It means that it is checked whether or not. When the answer is no, one control is finished as it is, but when the answer is yes, the control proceeds to step 2.
[0023]
In step 2, it is determined whether or not the exhaust gas pressure Pti in the exhaust gas passage 14 detected by the pressure sensor 40 is higher than the intake pressure Psc in the intake passage 26 detected by the pressure sensor 38. The The value of α causes a necessary recirculation flow of exhaust gas from the exhaust passage 14 toward the intake passage 26 via the path of the first exhaust gas recirculation means passing through the EGR valve A, the EGR cooler 32 and the EGR valve B. This is a value indicating whether or not the exhaust gas pressure in the exhaust passage 14 is sufficiently higher than the intake pressure in the intake passage 26. If the answer is yes, control proceeds to step 3 where EGR valves A and B are opened to operate the first exhaust gas recirculation device, EGR valves C and D are closed and the second exhaust gas recirculation is performed. Control is performed so as not to operate the circulation device. At this time, the exhaust gas recirculation flow occurs as indicated by the arrows along the solid line in the figure. The opening degree of the EGR valve A or B or both may be controlled so as to adjust the exhaust gas recirculation amount. As long as the answer to steps 1 and 2 is yes, control ends through this path every cycle and exhaust gas recirculation by the first exhaust gas recirculation means continues.
[0024]
On the other hand, if the answer to step 2 is no, the control proceeds to step 4, the EGR valves C and D are opened, the second exhaust gas recirculation means is operated, the EGR valves A and B are closed, and the first The exhaust gas recirculation means is not controlled. At this time, the control further proceeds to step 5 where the exhaust gas pressure Pto on the downstream side of the turbocharger turbine detected by the pressure sensor 44 is β or more than the intake pressure Pci on the upstream side of the turbocharger compressor detected by the pressure sensor 42. It is determined whether it is high. This β value causes a necessary recirculation flow of exhaust gas from the exhaust passage 18 toward the intake passage 34 via the path of the second exhaust gas recirculation means passing through the EGR valve C, the EGR cooler 32 and the EGR valve D. This is a value indicating whether or not the exhaust gas pressure in the exhaust passage 18 is sufficiently higher than the intake pressure in the intake passage 34. As long as the answer is yes, exhaust gas recirculation by the second exhaust gas recirculation means is continued.
[0025]
However, if the answer to step 5 is no, the control proceeds to step 6 where control to close the intake throttle valve E is performed and negative intake in the intake passage 34 is restricted by restricting new inflow of outside air into the intake passage 34. A pressure is generated so that a desired amount of exhaust gas recirculation is achieved via the second exhaust gas recirculation means. In this case as well, the opening degrees of the EGR valves C and D and the intake throttle valve E may be controlled at an intermediate position for opening and closing so as to adjust the exhaust gas recirculation amount.
[0026]
FIG. 3 is a similar schematic view showing another embodiment of the exhaust gas recirculation device according to the present invention, which is a modification of the embodiment of the present invention shown in FIG. In FIG. 3, portions corresponding to the portions shown in FIG. 1 are denoted by the same reference numerals as in FIG. In this embodiment, the EGR valves A and C are replaced by two simultaneous switching valves M, and the EGR valves B and D are replaced by two simultaneous switching valves N. These simultaneous switching valves M and N are switched by control signals supplied from the output terminals m and n of the ECU, respectively, and select either the first exhaust gas recirculation means or the second exhaust gas recirculation means. It is designed to work in unison. In this case, the exhaust gas recirculation amount can be controlled by controlling the duty ratio in switching one or both of the two-line simultaneous switching valves M or N. Other points of operation in this embodiment are the same as those in the embodiment shown in FIG.
[0027]
FIG. 4 is a similar view showing still another embodiment of the present invention in which the NOx sensor 46 is provided in the exhaust passage 18 in the embodiment shown in FIG. Also in FIG. 4, the same parts as in FIG. 1 are indicated by the same reference numerals and operate in the same manner as in FIG. By providing such a NOx sensor, the operation of the apparatus is more delicately controlled with respect to NOx emission suppression, which is the purpose of EGR, as shown in the flowchart of FIG.
[0028]
In the control shown in FIG. 5, as in the case of the control shown in FIG. 2, when it is first determined in step 101 that EGR should be performed, in the next step 102, the internal combustion at that time is determined. Based on the operating conditions of the engine and the vehicle, the value of NOx in the exhaust gas to be targeted is calculated. Thereafter, the control proceeds to step 103, where it is determined whether or not the exhaust gas pressure Pti in the exhaust gas passage 14 is higher than the intake pressure Psc in the intake passage 26 by α or more, as in step 2 in the control of FIG. Is done. If the answer is yes, control proceeds to step 104 where the EGR valves A and B are opened and exhaust gas recirculation is performed by the first exhaust gas recirculation means. At this time, the EGR valves A and B are not only opened, but are set to a variable opening by a map or the like in relation to the target NOx value calculated in step 102. The EGR valves C and D are fully closed so that the second exhaust gas recirculation means is not operated.
[0029]
Next, the control proceeds to step 105, where the NOx value in the exhaust gas is read by the NOx sensor 46. Control then proceeds to step 106, where it is determined whether or not the actually measured NOx value is greater than the target NOx value calculated above. If the answer is yes, the control proceeds to step 107, and control is performed to open the EGR valve A or B by one stage. This is a control for increasing the exhaust gas recirculation amount by one step in order to reduce the NOx value. (Note that the control for opening EGR valve A or B by one step may include the control for opening both EGR valves A and B by one step.) On the other hand, when the answer to step 106 is NO, the control is step 108. Control is performed to close the EGR valve A or B by one stage. This is a control for reducing the exhaust gas recirculation amount by one step so as to relax the suppression of the NOx value. (In this case, the control for closing the EGR valve A or B in one step may include the control for closing both the EGR valves A and B in one step.) To finish.
[0030]
If the answer to step 103 is no, the control proceeds to step 109 where the EGR valves C and D are opened and exhaust gas recirculation is performed by the second exhaust gas recirculation means. At this time, the EGR valves C and D are not only opened, but are also set to variable opening amounts by a map or the like in relation to the target NOx value calculated in step 102. The EGR valves A and B are fully closed, and the first exhaust gas recirculation means is disabled.
[0031]
In the following control in steps 110 to 113, the same control as that in steps 105 to 108 is performed on the second exhaust gas recirculation means. Steps 114 and 115 perform the same control as in steps 5 and 6 of FIG. 2 when exhaust gas recirculation is performed by the second exhaust gas recirculation means.
[0032]
FIG. 6 shows the switching of the first and second exhaust gas recirculation means as described above in the apparatus shown in FIG. 1, 3 or 4 in relation to the operation of the auxiliary electric drive means 30 of the supercharger. It is a flowchart which shows one embodiment to control. In this case, if the necessity of EGR is determined in step 201 as in step 1 or 101 in the flowchart of FIG. 2 or FIG. 5, control proceeds to step 202 and flag F is set to 1. It is determined whether or not it has been done. Since this kind of flag is reset to 0 at the start of control, it is 0 until it is set to 1 again. Accordingly, the initial answer is no, control proceeds to step 203, EGR valves A and B are opened, EGR valves C and D are closed, and exhaust gas recirculation by the first exhaust gas recirculation means is started. Control then proceeds to step 204, where it is determined whether the output Dma of the auxiliary electric drive means of the supercharger is equal to or greater than a predetermined threshold value Ds1.
[0033]
If the answer is no, i.e., the auxiliary electric drive means is not operating strongly, the control cycle ends and exhaust gas recirculation by the first exhaust gas recirculation means is required while EGR is required. Is done. On the other hand, when the answer to step 204 is yes, that is, when the supercharger is operated with considerable auxiliary drive by the auxiliary electric drive means, the control proceeds to step 205 and the flag F is set to 1. The
[0034]
When flag F is set to 1, control proceeds to step 206 from the next cycle, EGR valves A and B are closed, EGR valves C and D are opened, and exhaust gas recirculation is the second exhaust gas recirculation. Switching to operation by means.
[0035]
Thereafter, control proceeds to step 207, where it is determined whether Dma is greater than a threshold value Ds2, which is somewhat smaller than Ds1. While the answer is yes, exhaust gas recirculation by the second exhaust gas recirculation means is continued. Steps 208 and 209 are provided for the same purpose as steps 5 and 6 in the flowchart of FIG. 2 or steps 114 and 115 in the flowchart of FIG.
[0036]
Thus, if the degree of auxiliary driving of the supercharger decreases during the exhaust gas recirculation by the second exhaust gas recirculation means, and the answer to step 207 turns to no, the control proceeds to step 210 and the flag F is set to 0. The exhaust gas recirculation is reset to the exhaust gas recirculation by the first exhaust gas recirculation means. The reason why the threshold value Ds2 is made somewhat smaller than the threshold value Ds1 is to give hysteresis to the switching control.
[0037]
While the present invention has been described in detail with respect to several embodiments thereof, it will be apparent to those skilled in the art that various modifications can be made to these embodiments within the scope of the present invention. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment in which an exhaust gas recirculation device according to the present invention is incorporated in an internal combustion engine equipped with a supercharger.
FIG. 2 is a flowchart showing the operation of the exhaust gas recirculation device shown in FIG.
FIG. 3 is a schematic diagram showing another embodiment in which a part of the embodiment shown in FIG. 1 is modified.
FIG. 4 is a schematic view showing still another embodiment in which a NOx sensor is provided in the embodiment shown in FIG. 1;
FIG. 5 is a flowchart showing the operation of the exhaust gas recirculation device shown in FIG. 4;
FIG. 6 is a flowchart showing one embodiment for controlling the switching of the first and second exhaust gas recirculation means in relation to the operation of the auxiliary electric drive means 30 of the supercharger.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Supercharger, 14 ... Exhaust passage, 16 ... Turbine, 18 ... Exhaust passage, 20 ... Compressor, 22 ... Intercooler, 24 ... Throttle valve, 26 ... Intake passage, 28 ... Shaft, 30 ... Auxiliary electric drive means, 32 ... EGR cooler, 34 ... intake passage, 36 ... electronic control unit, 38, 40, 42,44 ... pressure sensor, 46 ... NOx sensor, A, B, C, D ... EGR valve, E ... Inlet throttle valve, M, N ... Simultaneous switching valve of 2 series

Claims (3)

補助電動駆動手段を備えた過給機を有する内燃機関の排気ガス再循環装置にして、前記過給機のタービンの上流側から該過給機のコンプレッサの下流側へ排気ガスを再循環させる第一の排気ガス再循環手段と、前記過給機のタービンの下流側から該過給機のコンプレッサの上流側へ排気ガスを再循環させる第二の排気ガス再循環手段と、前記補助電動駆動手段に対する駆動要求量が所定のしきい値を越えるとき前記第一の排気ガス再循環手段により所期の排気ガス再循環量が得られないと判断する第一の判断手段と、前記第一の判断手段により前記第一の排気ガス再循環手段によっては所期の排気ガス再循環量が得られないと判断されるとき前記第一の排気ガス再循環手段による排気ガス再循環を前記第二の排気ガス再循環手段による排気ガス再循環に切り換える切換え手段とを有することを特徴とする排気ガス再循環装置。An exhaust gas recirculation device for an internal combustion engine having a supercharger provided with auxiliary electric drive means is used to recirculate exhaust gas from the upstream side of the turbine of the supercharger to the downstream side of the compressor of the supercharger. One exhaust gas recirculation means, second exhaust gas recirculation means for recirculating exhaust gas from the downstream side of the turbine of the supercharger to the upstream side of the compressor of the supercharger, and the auxiliary electric drive means First determination means for determining that the desired exhaust gas recirculation amount can not be obtained by the first exhaust gas recirculation means when the drive request amount for the engine exceeds a predetermined threshold; and the first determination When the first exhaust gas recirculation means determines that the desired exhaust gas recirculation amount cannot be obtained by the first exhaust gas recirculation means, the second exhaust gas recirculation is performed by the first exhaust gas recirculation means. Exhaust gas by gas recirculation means Exhaust gas recirculation apparatus characterized by having a switching means for switching into the recirculation. 内燃機関の運転状態に基づいて排気ガス中のＮＯｘ量の目標値を算出する手段と、排気ガス中のＮＯｘ量を検出する手段とを有し、検出されたＮＯｘ量の前記目標値に対する偏差に基づいて前記第一の排気ガス再循環手段と前記第二の排気ガス再循環手段の少なくとも一方に於ける排気ガス再循環量を制御する制御手段を有することを特徴とする請求項１に記載の排気ガス再循環装置。  A means for calculating a target value of the NOx amount in the exhaust gas based on an operating state of the internal combustion engine; and a means for detecting the NOx amount in the exhaust gas, the deviation of the detected NOx amount from the target value being The control unit according to claim 1, further comprising a control unit that controls an exhaust gas recirculation amount in at least one of the first exhaust gas recirculation unit and the second exhaust gas recirculation unit based on the first exhaust gas recirculation unit. Exhaust gas recirculation device. 前記第二の排気ガス再循環手段により所期の排気ガス再循環量が得られるか否かを判断する第二の判断手段と、前記第二の判断手段により前記第二の排気ガス再循環手段によって所期の排気ガス再循環量が得られないと判断されるとき前記過給機への新気の導入を制限する手段とを有することを特徴とする請求項１または２に記載の排気ガス再循環装置。  Second judgment means for judging whether or not an intended exhaust gas recirculation amount can be obtained by the second exhaust gas recirculation means; and the second exhaust gas recirculation means by the second judgment means. 3. The exhaust gas according to claim 1, further comprising means for restricting introduction of fresh air to the supercharger when it is determined that the desired exhaust gas recirculation amount cannot be obtained by Recirculation device.
JP2002308281A 2002-10-23 2002-10-23 Exhaust gas recirculation device for an internal combustion engine with a supercharger Expired - Fee Related JP4134678B2 (en)

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