JP3972744B2 - Control device for spark ignition type 4-cycle engine - Google Patents

Control device for spark ignition type 4-cycle engine Download PDF

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Publication number
JP3972744B2
JP3972744B2 JP2002185242A JP2002185242A JP3972744B2 JP 3972744 B2 JP3972744 B2 JP 3972744B2 JP 2002185242 A JP2002185242 A JP 2002185242A JP 2002185242 A JP2002185242 A JP 2002185242A JP 3972744 B2 JP3972744 B2 JP 3972744B2
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Japan
Prior art keywords
cylinder
fuel ratio
combustion
air
exhaust
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JP2002185242A
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Japanese (ja)
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JP2004027961A (en
Inventor
光夫 人見
孝司 住田
好徳 林
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Mazda Motor Corp
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Mazda Motor Corp
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Priority to JP2002185242A priority Critical patent/JP3972744B2/en
Application filed by Mazda Motor Corp filed Critical Mazda Motor Corp
Priority to EP03703109A priority patent/EP1362176B1/en
Priority to US10/472,563 priority patent/US7219634B2/en
Priority to DE60300437T priority patent/DE60300437T2/en
Priority to DE60309098T priority patent/DE60309098T8/en
Priority to KR10-2003-7014141A priority patent/KR20040074591A/en
Priority to KR10-2003-7014146A priority patent/KR20040074592A/en
Priority to US10/472,523 priority patent/US7182050B2/en
Priority to CNB038024594A priority patent/CN100363609C/en
Priority to CNB03802487XA priority patent/CN100368671C/en
Priority to PCT/JP2003/000961 priority patent/WO2003064837A1/en
Priority to EP03703108A priority patent/EP1366279B1/en
Priority to PCT/JP2003/000962 priority patent/WO2003064838A1/en
Publication of JP2004027961A publication Critical patent/JP2004027961A/en
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    • Y02T10/125—
    • Y02T10/144—

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  • Combustion Methods Of Internal-Combustion Engines (AREA)
  • Exhaust-Gas Circulating Devices (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、火花点火式４サイクルエンジンの制御装置に関し、より詳しくは、多気筒のエンジンにおいて燃費改善及びエミッション向上のために各気筒の燃焼状態を制御する装置に関するものである。
【０００２】
【従来の技術】
従来から、火花点火式エンジンにおいて、各気筒内の混合気の空燃比を理論空燃比よりも大きいリーン空燃比とした状態で燃焼を行わせることにより燃費改善を図る技術が知られており、例えば特開平１０−２７４０８５号公報に示されるように、燃焼室内に直接燃料を噴射する燃料噴射弁を備え、低回転低負荷域等では上記燃料噴射弁から圧縮行程で燃料を噴射することにより成層燃焼を行わせ、これによって超リーン燃焼を実現するようにしたものが知られている。
【０００３】
このようなエンジンにおいては、排気ガス浄化用の触媒として通常の三元触媒（ＨＣ，ＣＯ及びＮＯｘに対して理論空燃比付近で浄化性能の高い触媒）だけではリーン運転時にＮＯｘに対して充分な浄化性能が得られないため、上記公報にも示されるように、酸素過剰雰囲気でＮＯｘを吸着して酸素濃度低下雰囲気でＮＯｘの離脱、還元を行うリーンＮＯｘ触媒を設けている。そして、このようなリーンＮＯｘ触媒を用いる場合、リーン運転中にリーンＮＯｘ触媒のＮＯｘ吸着量が増大したときは、例えば上記公報に示されるように主燃焼以外に膨張行程中に追加燃料を噴射することで排気ガスの空燃比をリッチ化するとともにＣＯを生成し、これによってＮＯｘの離脱、還元を促進するようにしている。
【０００４】
【発明が解決しようとする課題】
上記のような従来のリーン運転を行うエンジンでは、リーン運転中のＮＯｘ浄化性能の確保のために上記リーンＮＯｘ触媒が必要となってコスト的に不利である。また、上記リーンＮＯｘ触媒の浄化性能を維持するためには、上述のようにＮＯｘ吸着量増大時にＮＯｘの離脱、還元のため追加燃料の供給等による一時的な空燃比のリッチ化を行う必要があり、さらに、使用燃料が硫黄分を多く含む場合、上記リーンＮＯｘ触媒の硫黄被毒の解消のために触媒の加熱及び還元材供給等のリジェネレーション処理が必要となり、これらによって燃費改善効果が低下する。
【０００５】
しかも、空燃比がある程度以上にリーンになると、燃焼速度が遅くなりすぎてその終期に近い燃焼が仕事に寄与しなくなるため、成層燃焼でのリーン化による燃費改善には限界があった。
【０００６】
また、燃費改善のための別の手法として、圧縮自己着火が研究されており、この圧縮自己着火は、ディーゼルエンジンと同様に圧縮行程終期に燃焼室内を高温、高圧にして燃料を自己着火させるようにするものであり、空燃比が超リーンの状態や多量のＥＧＲが導入されている状態でもこのような圧縮自己着火が行われれば燃焼室全体が一気に燃焼するため、仕事に寄与しない遅い燃焼が避けられ、燃費改善に有利となる。しかし、通常の火花点火式エンジン（ガソリンエンジン）では燃焼のために強制点火が必要であって、圧縮自己着火を行わせるためには燃焼室内の温度または圧力を大幅に高めるための格別の工夫が必要となり、高負荷域でのノッキングを避けつつ、燃費改善が要求される部分負荷域で圧縮自己着火を生じさせる程度まで燃焼室内の温度または圧力を高めることが困難であった。
【０００７】
そこで、本出願人は、リーン燃焼と圧縮自己着火とを併用して大幅な燃費改善効果をもたせるべく、エンジンの部分負荷域で、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入される２気筒接続状態とするとともに、先行気筒では空燃比を理論空燃比よりも大きいリーン空燃比にして、強制点火により燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して圧縮自己着火により燃焼を行わせるようにした火花点火式エンジンの制御装置に関する技術を出願している（特願２００２−２９８３６号）。
【０００８】
本発明は、このような技術に基づき、さらに広い運転域で効果的に後続気筒での圧縮自己着火による燃焼を行わせることができるようにし、燃費及びエミッションの改善効果を高めることができる火花点火式４サイクルエンジンの制御装置を提供するものである。
【０００９】
【課題を解決するための手段】
請求項１に係る発明は、各気筒の燃焼サイクルが所定の位相差をもって行われるようになっている多気筒の火花点火式４サイクルエンジンにおいて、エンジンの部分負荷域でエンジンの吸・排気及び燃焼状態についての制御モードを特殊運転モードとし、この特殊運転モードでは、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入され、この後続気筒から排出されるガスが排気通路に導かれるような２気筒接続状態としつつ、先行気筒では空燃比が理論空燃比よりも大きいリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して燃焼を行わせるようにした制御装置であって、上記特殊運転モードとされる運転領域のうちの少なくとも一部の運転領域で、上記後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしつつ、先行気筒では強制点火により燃焼を行わせ、後続気筒では圧縮自己着火により燃焼を行わせるようにするとともに、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中速域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より大きい値とし、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの上記中速域よりも低速側の運転域および上記中速域よりも高速側の運転域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とするように先行、後続の両気筒に対する燃料供給量を制御する燃焼状態制御手段を備えたことを特徴とするものである。
【００１０】
この発明によると、上記特殊運転モードとされるとともに後続気筒で圧縮自己着火により燃焼が行われる場合に、上記先行気筒ではリーン燃焼による熱効率向上およびポンピングロス低減により燃費改善効果が得られ、後続気筒では圧縮自己着火による燃焼効率の向上及びポンピングロス低減により燃費改善効果が得られる。また、後続気筒から排気通路に排出されるガスは理論空燃比であるため、三元触媒だけで充分に排気ガスの浄化が達成される。
【００１２】
特に、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中速域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より大きい値とすることにより、上記中速域で燃費改善効果が高められる。
【００１３】
また、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中速域よりも低速側の運転域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とすることにより、先行気筒から後続気筒へ導入されるガス温度が高められ、この低速側の運転域で自己着火性が向上される。
【００１４】
また、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中速域よりも高速側の運転域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とすることにより、後続気筒へ導入されるガス中のＥＧＲに相当する既燃ガス成分が増大する等によってノッキングの発生が抑制される。
【００１５】
また、請求項２に係る発明は、各気筒の燃焼サイクルが所定の位相差をもって行われるようになっている多気筒の火花点火式４サイクルエンジンにおいて、エンジンの部分負荷域でエンジンの吸・排気及び燃焼状態についての制御モードを特殊運転モードとし、この特殊運転モードでは、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入され、この後続気筒から排出されるガスが排気通路に導かれるような２気筒接続状態としつつ、先行気筒では空燃比が理論空燃比よりも大きいリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して燃焼を行わせるようにした制御装置であって、上記特殊運転モードとされる運転領域のうちの少なくとも一部の運転領域で、上記後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしつつ、先行気筒では強制点火により燃焼を行わせ、後続気筒では圧縮自己着火により燃焼を行わせるようにするとともに、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中負荷域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より大きい値とし、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの上記中負荷域よりも低負荷側の運転域および上記中負荷域よりも高負荷側の運転域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とするように先行、後続の両気筒に対する燃料供給量を制御する燃焼状態制御手段を備えたことを特徴とするものである。
【００１６】
このようにすると、特殊運転モードとされる運転領域のうちで燃焼室内の温度が比較的低い低負荷域等では、先行気筒から後続気筒へ導かれるガスの温度が上昇することで圧縮自己着火が可能となり、ノッキングが生じやすい高負荷域等では後続気筒の発生エネルギーが少なくなることでノッキングが抑制される。また、上記中負荷域で燃費改善効果が高められる。
【００１８】
なお、エンジン温度が低いときには、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域の全域で、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とすること（請求項３）が好ましい。このようにすると、エンジン低温時にも圧縮自己着火が可能となる。
【００１９】
また、請求項４に係る発明は、各気筒の燃焼サイクルが所定の位相差をもって行われるようになっている多気筒の火花点火式４サイクルエンジンにおいて、エンジンの部分負荷域でエンジンの吸・排気及び燃焼状態についての制御モードを特殊運転モードとし、この特殊運転モードでは、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入され、この後続気筒から排出されるガスが排気通路に導かれるような２気筒接続状態としつつ、先行気筒では空燃比が理論空燃比よりも大きいリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して燃焼を行わせるようにした制御装置であって、上記特殊運転モードとされる運転領域のうちの少なくとも一部の領域で、上記後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしつつ、先行気筒における燃焼の際の空燃比を、理論空燃比より大きくてその２倍以下となる範囲で、エンジン回転数が低いほど小さくするように、先行、後続の両気筒に対する燃料供給量を制御するとともに、先行気筒では強制点火により燃焼を行わせ、後続気筒では圧縮自己着火により燃焼を行わせるように制御する燃焼状態制御手段を備えたことを特徴とするものである。
【００２０】
この発明によっても、特殊運転モードとされるとともに後続気筒で圧縮自己着火により燃焼が行われる場合に、上記先行気筒でリーン燃焼による熱効率向上およびポンピングロス低減により燃費改善効果が得られる一方、後続気筒で圧縮自己着火による燃焼効率の向上及びポンピングロス低減により燃費改善効果が得られ、また、排気通路において三元触媒だけで充分に排気ガスの浄化が達成される。
【００２１】
また、エンジン回転数が低いほど、先行気筒の空燃比が小さくなるように燃料供給量が制御されることにより、先行気筒から後続気筒へ導入されるガスの温度が高められて自己着火性が向上される。
【００２４】
【発明の実施の形態】
以下、図面に基づいて本発明の実施の形態を説明する。
【００２５】
図１は本発明の一実施形態によるエンジンの概略構成を示し、図２はエンジン本体１の一つの気筒とそれに対して設けられた吸・排気弁等の構造を概略的に示している。これらの図において、エンジン本体１は複数の気筒を有し、図示の実施形態では４つの気筒２Ａ〜２Ｄを有している。各気筒２Ａ〜２Ｄにはピストン３が嵌挿され、ピストン３の上方に燃焼室４が形成されている。
【００２６】
各気筒２の燃焼室４の頂部には点火プラグ７が装備され、そのプラグ先端が燃焼室４内に臨んでいる。この点火プラグ７には、電子制御による点火時期のコントロールが可能な点火回路８が接続されている。
【００２７】
燃焼室４の側方部には、燃焼室4内に燃料を直接噴射する燃料噴射弁９が設けられている。この燃料噴射弁９は、図略のニードル弁及びソレノイドを内蔵し、後述のパルス信号が入力されることにより、そのパルス入力時期にパルス幅に対応する時間だけ駆動されて開弁し、その開弁時間に応じた量の燃料を噴射するように構成されている。なお、この燃料噴射弁９には図外の燃料ポンプにより燃料供給通路等を介して燃料が供給され、かつ、圧縮行程での燃焼室内の圧力よりも高い燃料圧力を与え得るように燃料供給系統が構成されている。
【００２８】
また、各気筒２Ａ〜２Ｄの燃焼室４に対して吸気ポート１１、１１ａ，１１ｂ及び排気ポート１２、１２ａ，１２ｂが開口し、これらのポートに吸気通路１５、排気通路２０等が接続されるとともに、各ポートが吸気弁３１、３１ａ，３１ｂ及び排気弁３２、３２ａ，３２ｂにより開閉されるようになっている。
【００２９】
そして、各気筒が所定の位相差をもって吸気、圧縮、膨張、排気の各行程からなるサイクルを行うようになっており、４気筒エンジンの場合、気筒列方向一端側から１番気筒２Ａ、２番気筒２Ｂ、３番気筒２Ｃ、４番気筒２Ｄと呼ぶと、図５に示すように上記サイクルが１番気筒２Ａ、３番気筒２Ｃ、４番気筒２Ｄ、２番気筒２Ｂの順にクランク角で１８０°ずつの位相差をもって行われるようになっている。なお、図５において、ＥＸは排気行程、ＩＮは吸気行程であり、また、Ｆは燃料噴射、Ｓは強制点火を表し、図中の星マークは圧縮自己着火が行われることを表している。
【００３０】
排気行程と吸気行程が重なる一対の気筒間には、排気行程と吸気行程が重なるときの排気行程側の気筒（当明細書ではこれを先行気筒と呼ぶ）から吸気行程側の気筒（当明細書ではこれを後続気筒と呼ぶ）へ既燃ガスをそのまま導くことができるように、気筒間ガス通路２２が設けられている。当実施形態の４気筒エンジンでは、図５に示すように１番気筒２Ａの排気行程（ＥＸ）と２番気筒２Ｂの吸気行程（ＩＮ）とが重なり、また４番気筒２Ｄの排気行程（ＥＸ）と３番気筒２Ｃの吸気行程（ＩＮ）が重なるので、１番気筒２Ａと２番気筒２Ｂ、及び、４番気筒２Ｄと３番気筒２Ｃがそれぞれ一対をなし、１番気筒２Ａ及び４番気筒２Ｄが先行気筒、２番気筒２Ｂ及び３番気筒２Ｃが後続気筒となる。
【００３１】
各気筒の吸・排気ポートとこれに接続される吸気通路、排気通路及び気筒間ガス通路は、具体的には次のように構成されている。
【００３２】
先行気筒である１番気筒２Ａ及び４番気筒２Ｄには、それぞれ、新気を導入するための吸気ポート１１と、既燃ガス（排気ガス）を排気通路に送り出すための第１排気ポート１２ａと、既燃ガスを後続気筒に導出するための第２排気ポート１２ｂとが配設されている。また、後続気筒である２番気筒２Ｂ及び３番気筒２Ｃには、それぞれ、新気を導入するための第１吸気ポート１１ａと、先行気筒からの既燃ガスを導入するための第２吸気ポート１１ｂと、既燃ガスを排気通路に送り出すための排気ポート３２とが配設されている。
【００３３】
図１に示す例では、１番，４番気筒２Ａ，２Ｄにおける吸気ポート１１および２番，３番気筒２Ｂ，２Ｃにおける第１吸気ポート１１ａが、１気筒当り２個ずつ、燃焼室の左半部側に並列的に設けられる一方、１番，４番気筒２Ａ，２Ｄにおける第１排気ポート１２ａ及び第２排気ポート１２ｂならびに２番，３番気筒２Ｂ，２Ｃにおける第２吸気ポート１１ｂ及び排気ポート１２が、燃焼室の右半部側に並列的に設けられている。
【００３４】
１番，４番気筒２Ａ，２Ｄにおける吸気ポート１１および２番，３番気筒２Ｂ，２Ｃにおける第１吸気ポート１１ａには、吸気通路１５における気筒別の分岐吸気通路１６の下流端が接続されている。各分岐吸気通路１６の下流端近傍には、共通の軸を介して互いに連動する多連スロットル弁１７が設けられており、この多連スロットル弁１７は制御信号に応じてアクチュエータ１８により駆動され、吸入空気量を調節するようになっている。なお、吸気通路１５における集合部より上流の共通吸気通路には吸気流量を検出するエアフローセンサ１９が設けられている。
【００３５】
１番，４番気筒２Ａ，２Ｄにおける第１排気ポート１２ａおよび２番，３番気筒２Ｂ，２Ｃにおける排気ポート１２には、排気通路２０における気筒別の分岐排気通路２１の上流端が接続されている。また、１番気筒２Ａと２番気筒２Ｂとの間及び３番気筒２Ｃと４番気筒２Ｄとの間にそれぞれ気筒間ガス通路２２が設けられ、先行気筒である１番，４番気筒２Ａ，２Ｄの第２排気ポート１２ｂに気筒間ガス通路２２の上流端が接続されるとともに、後続気筒である２番，３番気筒２Ｂ，２Ｃの第２吸気ポート１１ｂに気筒間ガス通路２２の下流端が接続されている。
【００３６】
上記気筒間ガス通路２２は、互いに隣接する気筒間を接続する比較的短い通路であり、先行気筒から排出されるガスがこの通路２２を通る間の放熱は比較的小さく抑えられるようになっている。
【００３７】
排気通路２０における分岐排気通路２１の下流の集合部には排気ガス中の酸素濃度を検出することにより空燃比を検出するＯ2センサ２３が設けられている。さらにＯ2センサ２３の下流の排気通路２１には排気浄化のために三元触媒２４が設けられている。この三元触媒２４は、一般に知られているように、排気ガスの空燃比が理論空燃比（つまり空気過剰率λがλ＝１）付近にあるときにＨＣ，ＣＯ及びＮＯｘに対して高い浄化性能を示す触媒である。
【００３８】
各気筒の吸・排気ポートを開閉する吸・排気弁とこれらに対する動弁機構は、次のようになっている。
【００３９】
１番，４番気筒２Ａ，２Ｄにおける吸気ポート１１、第１排気ポート１２ａ及び第２排気ポート１２ｂにはそれぞれ吸気弁３１、第１排気弁３２ａ及び第２排気弁３２ｂが設けられ、また、２番，３番気筒２Ｂ，２Ｃにおける第１吸気ポート１１ａ、第２吸気ポート１１ｂ及び排気ポート１２にはそれぞれ第１吸気弁３１ａ、第２吸気弁３１ｂ及び排気弁３２が設けられている。そして、各気筒の吸気行程や排気行程が上述のような所定の位相差をもって行われるように、これら吸・排気弁がそれぞれカムシャフト３３，３４等からなる動弁機構により所定のタイミングで開閉するように駆動される。
【００４０】
さらに、これらの吸・排気弁のうちで第１排気弁３２ａ、第２排気弁３２ｂ、第１吸気弁３１ａ及び第２吸気弁３１ｂに対しては、各弁を作動状態と停止状態とに切換える弁停止機構３５が設けられている。この弁停止機構３５は、従来から知られているため詳しい図示は省略するが、例えば、カムシャフト３３，３４のカムと弁軸との間に介装されたタペットに作動油の給排が可能な油圧室が設けられ、この油圧室に作動油が供給されている状態ではカムの作動が弁に伝えられて弁が開閉作動され、油圧室から作動油が排出されたときにはカムの作動が弁に伝えられなくなることで弁が停止されるようになっている。
【００４１】
上記第１排気弁３２ａの弁停止機構３５と第１吸気弁３１ａの弁停止機構３５とに対する作動油給排用の通路３６には第１コントロール弁３７が、また第２排気弁３２ｂの弁停止機構３５と第２吸気弁３１ｂの弁停止機構３５とに対する作動油給排用の通路３８には第２コントロール弁３９がそれぞれ設けられている（図３参照）。
【００４２】
図３は駆動、制御系統の構成を示している。この図において、マイクロコンピュータ等からなるエンジン制御用のＥＣＵ（コントロールユニット）４０には、エアフローセンサ１９及びＯ2センサ２３からの信号が入力され、さらに運転状態を判別するためにエンジン回転数を検出する回転数センサ４７及びアクセル開度（アクセルペダル踏込み量）を検出するアクセル開度センサ４８等からの信号も入力されている。また、このＥＣＵ４０から、各燃料噴射弁９と、多連スロットル弁１７のアクチュエータ１８と、上記第１，第２のコントロール弁３９とに対して制御信号が出力されている。
【００４３】
上記ＥＣＵ４０は、運転状態判別手段４１、弁停止機構制御手段４２、吸入空気量制御手段４３及び燃焼状態制御手段４４を備えている。
【００４４】
運転状態判別手段４１は、図４に示すようにエンジンの運転領域が低負荷低回転側の運転領域Ａ（部分負荷域）と高負荷側ないし高回転側の運転領域Ｂとに分けられた制御用マップを有し、上記回転数センサ４５及びアクセル開度センサ４６等からの信号により調べられるエンジンの運転状態（エンジン回転数及びエンジン負荷）が上記運転領域Ａ，Ｂのいずれの領域にあるかを判別する。そして、この判別に基づき、低負荷低回転側の運転領域Ａでは、排気行程にある先行気筒から排出される既燃ガスをそのまま吸気行程にある後続気筒に導入して燃焼させる特殊運転モードが選択され、高負荷側ないし高回転側の運転領域Ｂでは、各気筒をそれぞれ独立させ燃焼させる通常運転モードが選択されるようになっている。
【００４５】
さらに運転状態判別手段４１は、特殊運転モードが選択される運転領域Ａにある場合に、この領域Ａのうちの低速域Ａ１、中速域Ａ２、高速域Ａ３のいずれにあるかを判別するようになっている。
【００４６】
弁停止機構制御手段４２は、特殊運転モードでは気筒間ガス通路２２を介して先行気筒の既燃ガスを後続気筒に導入させる２気筒接続状態とし、通常運転モードでは各気筒にそれぞれ新気を導入させる各気筒独立状態とするように吸・排気流通状態を変更すべく弁停止機構制３５を制御するもので、具体的には運転状態が運転領域Ａ，Ｂのいずれにあるかに応じ、上記各コントロール弁３７，３９を制御することにより、各弁停止機構３５を次のように制御する。
【００４７】
運転領域Ａ：第１排気弁３２ａ及び第１吸気弁３１ａを停止状態
第２排気弁３２ｂ及び第２吸気弁３１ｂを作動状態
運転領域Ｂ：第１排気弁３２ａ及び第１吸気弁３１ａを作動状態
第２排気弁３２ｂ及び第２吸気弁３１ｂを停止状態
上記吸入空気量制御手段４３は、アクチュエータ１８を制御することによりスロットル弁１７の開度（スロットル開度）を制御するものであり、運転状態に応じてマップ等から目標吸入空気量を求め、その目標吸入空気量に応じてスロットル開度を制御する。この場合、特殊運転モードとされる運転領域Ａでは、後続気筒（２番、３番気筒２Ｂ，２Ｃ）においては分岐吸気通路１６からの吸気導入が遮断された状態で先行気筒から導入されるガス中の過剰空気と新たに供給される燃料との比がリーン空燃比とされつつ燃焼が行われるので、先行、後続の２気筒分の要求トルクに応じた燃料の燃焼に必要な量の空気（２気筒分の燃料の量に対して理論空燃比となる量の空気）が先行気筒（１番、４番気筒２Ａ，２Ｄ）に供給されるように、スロットル開度が調節される。
【００４８】
上記燃焼状態制御手段４４は、燃料噴射制御手段４５と点火制御手段４６とからなっており、燃料噴射制御手段４５により、各気筒２Ａ〜２Ｄに設けられた燃料噴射弁９からの燃料噴射量及び噴射タイミングをエンジンの運転状態に応じて制御するとともに、点火制御手段４６により運転状態に応じた点火時期の制御及び点火停止等の制御を行う。そして、特に運転状態が図４中の運転領域Ａにある場合と運転領域Ｂにある場合とで燃焼状態の制御（燃料噴射の制御及び点火の制御）が変更される。
【００４９】
すなわち、運転状態が低負荷低回転側の運転領域Ａにある場合、特殊運転モードでの制御として、先行気筒（１番、４番気筒２Ａ，２Ｄ）に対しては、空燃比を理論空燃比よりも大きいリーン空燃比とするように燃料噴射量を制御するとともに、圧縮行程で燃料を噴射して混合気の成層化を行わせるように噴射タイミングを設定し、かつ、圧縮上死点付近で強制点火を行わせるように点火タイミングを設定する。一方、後続気筒（２番、３番気筒２Ｂ，２Ｃ）に対しては、先行気筒から導入されたリーン空燃比の既燃ガスに対して燃料を供給し、実質的に理論空燃比となるように燃料噴射量を制御するとともに、吸気行程で燃料を噴射するように噴射タイミングを設定し、かつ、圧縮自己着火を行わせるべく、強制点火を停止させる。
【００５０】
さらにこの運転領域Ａにおいて、一対の気筒の両方に対する燃料噴射量の和が先行気筒に導入される空気の量に対して理論空燃比となる量に調整されつつ、後続気筒での圧縮自己着火が良好に行われるように、先行気筒（１番、４番気筒２Ａ，２Ｄ）に対する燃料噴射量と後続気筒（２番、３番気筒２Ｂ，２Ｃ）に対する燃料噴射量との割合が運転状態に応じて変更される。
【００５１】
具体的には、この運転領域Ａのうちの中速域Ａ２では、先行気筒に対する燃料噴射量と後続気筒に対する燃料噴射量とを略同一に、ないしは後続気筒側の燃料噴射量を少し多くすることにより、先行気筒での燃焼の際の空燃比が理論空燃比の２倍程度（Ａ／Ｆ≒３０、空気過剰率λで表せばλ＝２程度）ないしは理論空燃比の２倍より大（空気過剰率λがλ＞２）となるようにする。また、運転領域Ａのうちの低速域Ａ１では先行気筒に対する燃料噴射量を後続気筒に対する燃料噴射量よりも多くすることにより、先行気筒での燃焼の際の空燃比が理論空燃比の２倍より小（空気過剰率λが１＜λ＜２）となるようにし、例えばＡ／Ｆ≒２５となるようにする。一方、運転領域Ａのうちの高速域Ａ３でも、先行気筒に対する燃料噴射量を後続気筒に対する燃料噴射量よりも多くすることにより、先行気筒での燃焼の際の空燃比が理論空燃比の２倍より小（空気過剰率λが１＜λ＜２）となるようにし、例えばＡ／Ｆ≒２５となるようにする。
【００５２】
また、運転状態が高負荷側ないし高回転側の運転領域Ｂにある場合には、通常運転モードでの制御として、各気筒２Ａ〜２Ｄの空燃比を理論空燃比もしくはそれ以下とするように燃料噴射量を制御し、例えばこの運転領域Ｂのうちの大部分の領域において理論空燃比とし、全開負荷及びその付近の運転領域で理論空燃比よりリッチとする。そして、この場合に、各気筒２Ａ〜２Ｄに対して吸気行程で燃料を噴射して混合気を均一化するように噴射タイミングを設定し、かつ、各気筒２Ａ〜２Ｄとも強制点火を行わせるようにする。
【００５３】
以上のような当実施形態の装置の作用を、図５〜図７を参照しつつ説明する。
【００５４】
低負荷低回転側の運転領域Ａでは特殊運転モードとされ、前述のように第１排気弁３２ａ及び第１吸気弁３１ａが停止状態、第２排気弁３２ｂ及び第２吸気弁３１ｂが作動状態とされることにより、実質的な新気及びガスの流通経路は図６に示すようになり、先行気筒（１番，４番気筒）２Ａ，２Ｄから排出される既燃ガスがそのまま気筒間ガス通路２２を介して後続気筒（２番，３番気筒）２Ｂ，２Ｃに導入されるとともに、この後続気筒２Ｂ，２Ｃから排出されるガスのみが排気通路２０に導かれるような２気筒接続状態とされる。
【００５５】
この状態において、先行気筒２Ａ，２Ｄにそれぞれ吸気行程で吸気通路１５から新気が導入され（図６中の矢印ａ）、先行気筒２Ａ，２Ｄでは空燃比が理論空燃比よりも大きくて、理論空燃比の略２倍ないしそれより小さい値となるように燃料噴射量が制御されつつ圧縮行程で燃料が噴射され、かつ、所定点火時期に点火が行われて、リーン空燃比での成層燃焼が行われる（図５参照）。
【００５６】
それから、先行気筒２Ａ，２Ｄの吸気行程と後続気筒２Ｂ，２Ｃの排気行程が重なる期間に、先行気筒２Ａ，２Ｄから排出された既燃ガスがガス通路２２を通って後続気筒２Ｂ，２Ｃに導入される（図５中の白抜き矢印及び図６中の矢印ｂ）。そして、後続気筒２Ｂ，２Ｃでは、先行気筒２Ａ，２Ｄから導入されたリーン空燃比の既燃ガスに燃料が供給されて、理論空燃比となるように燃料噴射量が制御されつつ、吸気行程で燃料が噴射された後、圧縮行程の上死点付近で燃焼室内の圧力、温度の上昇により圧縮自己着火が行われる。
【００５７】
この場合、先行気筒２Ａ，２Ｄから排出された高温の既燃ガスが短い気筒間ガス通路２２を通って後続気筒２Ｂ，２Ｃに直ちに導入されるため、後続気筒２Ｂ，２Ｃでは吸気行程で燃焼室内の温度が高くなり、この状態からさらに圧縮行程で圧力、温度が上昇することにより、圧縮行程終期の上死点付近では混合気が自己着火し得る程度まで燃焼室内の温度が上昇する。しかも、上記既燃ガスは先行気筒２Ａ，２Ｄから排出されて後続気筒２Ｂ，２Ｃに導入されるまでの間に充分にミキシングされて均一に分布し、さらに吸気行程で噴射された燃料も圧縮行程終期までの間に燃焼室全体に均一に分散するため、理想的な同時圧縮自己着火条件を満たすような均一な混合気分布状態が得られる。そして、同時圧縮自己着火により燃焼が急速に行われ、これにより熱効率が大幅に向上される。
【００５８】
このように、先行気筒２Ａ，２Ｄでは、リーンでの成層燃焼により熱効率が高められるとともに、成層燃焼を行わない通常のエンジンと比べて吸気負圧が小さくなることでポンピングロスが低減され、一方、後続気筒２Ｂ，２Ｃでは、空燃比が略理論空燃比とされつつ、均一な混合気分布状態で圧縮自己着火が行われることにより熱効率が高められるとともに、先行気筒２Ａ，２Ｄから押出されたガスが送り込まれるため先行気筒２Ａ，２Ｄよりもさらにポンピングロスが低減される。これらの作用により、燃費が大幅に改善される。
【００５９】
しかも、後続気筒２Ｂ，２Ｃから排気通路２０に排出されるガスは理論空燃比であるため、従来のリーンバーンエンジンのようにリーンＮＯｘ触媒を設ける必要がなく、三元触媒２４だけで充分に排気浄化性能が確保される。
【００６０】
そして、リーンＮＯｘ触媒を設ける必要がないことから、リーンＮＯｘ触媒のＮＯｘ吸蔵量増大時におけるＮＯｘの放出、還元のための一時的な空燃比のリッチ化を行う必要がなく、燃費改善の目減りが避けられる。さらに、リーンＮＯｘ触媒の硫黄被毒の問題が生じることもない。
【００６１】
また、先行気筒２Ａ，２Ｄでは理論空燃比の略２倍もしくはそれに近いリーン空燃比とされることでＮＯｘ発生量が比較的少なく抑えられる。一方、後続気筒２Ｂ，２Ｃでは、先行気筒２Ａ，２Ｄから既燃ガスが導入されることで多量のＥＧＲが行われているのと同等の状態となるとともに、同時圧縮自己着火による急速燃焼が行われると可及的に酸素と窒素との反応が避けられることから、ＮＯｘの発生が充分に抑制される。このような点からもエミッションの向上に有利となる。
【００６２】
また、後続気筒２Ｂ，２Ｃでの圧縮自己着火が先行気筒２Ａ，２Ｄから排出される既燃ガスの熱を利用して達成されるため、格別の加熱手段を用いたりエンジンの圧縮比を極端に高くしたりする必要がなく、容易に圧縮自己着火を達成することができる。とくに、特殊運転モードでの先行気筒（１番、４番気筒２Ａ，２Ｄ）に対する燃料噴射量と後続気筒（２番、３番気筒２Ｂ，２Ｃ）に対する燃料噴射量との割合が運転状態に応じて前述のように調整されることにより、広い運転領域にわたり、有効に圧縮自己着火を行わせることができる。
【００６３】
すなわち、特殊運転モードとされる運転領域Ａのうちの低速域Ａ１では、中・高速域Ａ２，Ａ３と比べると本来的に燃焼室内の温度が低いため圧縮自己着火が行われにくい条件下にあるが、この低速域Ａ１では、後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるように調整されつつ、先行気筒に対する燃料噴射量が後続気筒より多くされて、先行気筒の空燃比が理論空燃比の２倍より小さい値となるように制御されているため、先行気筒の空燃比が理論空燃比の２倍（先行気筒と後続気筒とが同じ噴射量）とされる場合と比べ、先行気筒から後続気筒へ導かれるガスの温度が上昇する。このため、低速域Ａ１でも効果的に圧縮自己着火が行われる。
【００６４】
また、特殊運転モードとされる運転領域Ａのうちの高速域Ａ３では、燃焼温度が過度に上昇してノッキングが生じ易くなるが、この領域でも、先行気筒に対する燃料噴射量が後続気筒より多くされて、先行気筒の空燃比が理論空燃比の２倍より小さい値となるように制御される。これにより、先行気筒の空燃比が理論空燃比の２倍（先行気筒と後続気筒とが同じ噴射量）とされる場合と比べ、後続気筒に導入されるガスの温度は上昇するものの、後続気筒に導入されるガス中のＥＧＲに相当する既燃ガス成分が増大するとともに、後続気筒に対する燃料噴射量が少なくなることによって後続気筒での燃焼により発生するエネルギーが小さくなるため、ノッキングが抑制される。
【００６５】
このように、先行気筒に対する燃料噴射量が後続気筒より多くされて、先行気筒の空燃比が理論空燃比の２倍より小さい値となるように制御されると、先行気筒の空燃比が理論空燃比の２倍（先行気筒と後続気筒とが同じ噴射量）とされる場合と比べ、圧縮自己着火やノッキング抑制の面では有利となるが、その反面、先行気筒での成層リーンバーンによる燃費改善効果や先行、後続気筒のトルクバランスの面では多少不利となる。そこで、特殊運転モードにより後続気筒の圧縮自己着火が容易に可能で、かつノッキングが生じにくい中速域Ａ２では、燃費改善効果やトルクバランスの面で有利なように、先行気筒の空燃比が理論空燃比の略２倍もしくはそれより大きい値となるように燃料噴射量が制御される。
【００６６】
一方、高負荷側ないし高回転側の運転領域Ｂでは通常運転モードとされ、前述のように第１排気弁３２ａ及び第１吸気弁３１ａが作動状態、第２排気弁３２ｂ及び第２吸気弁３１ｂが停止状態とされることにより、実質的な新気及びガスの流通経路は図７に示すようになり、各気筒２Ａ〜２Ｄの吸気ポート３１，３１ａ及び排気ポート１２ａ，１２が独立し、吸気通路１５から各気筒２Ａ〜２Ｄの吸気ポート３１，３１ａに新気が導入されるとともに各気筒２Ａ〜２Ｄの排気ポート３１，３１ａから排気通路２０に既燃ガスが排出される。そしてこの場合は、理論空燃比もしくはそれよりリッチとなるように吸入空気量及び燃料噴射量が制御されることにより、出力性能が確保される。
【００６７】
なお、本発明の装置の具体的構成は上記実施形態に限定されず、種々変更可能である。他の実施形態を以下に説明する。
【００６８】
▲１▼上記の基本実施形態では、特殊運転モードとされる運転領域Ａを低速域Ａ１、中速域Ａ２及び高速域Ａ３に分けて、先行気筒の空燃比（先行気筒に対する燃料噴射量と後続気筒に対する燃料噴射量との割合）を上記各域Ａ１，Ａ２，Ａ３で変更しているが、図８に示すように、特殊運転モードとされる運転領域Ａを低負荷域Ａ１１、中負荷域Ａ１２及び高負荷域Ａ１３に分けるようにしてもよい。この場合、上記中負荷域Ａ１２では先行気筒の空燃比を理論空燃比の略２倍もしくはそれより大きい値とし、上記低負荷域Ａ１１及び高負荷域Ａ１３では先行気筒の空燃比を理論空燃比の２倍より小さい値（例えばＡ／Ｆ≒２５）とするように燃料噴射量を制御する。
【００６９】
あるいは図９に示すように、特殊運転モードとされる運転領域Ａのうち、中速中負荷域Ａ２０で先行気筒の空燃比を理論空燃比の略２倍もしくはそれより大きい値とし、それ以外の運転域で先行気筒の空燃比を理論空燃比の２倍より小さい値とするように制御してもよい。
【００７０】
これらの例でも、特殊運転モードとされる運転領域Ａのうちで燃焼室内の温度が比較的低い低負荷域等では、先行気筒から後続気筒へ導かれるガスの温度が上昇することで圧縮自己着火が可能となり、ノッキングが生じやすい高負荷域等では後続気筒の発生エネルギーが少なくなることでノッキングが抑制され、また、中負荷域Ａ１２または中速中負荷域Ａ２０では、燃費改善効果やトルクバランスに有利な状態となる。
【００７１】
▲２▼上記の基本実施形態や図８、図９に示す例では、特殊運転モードとされる運転領域Ａ内の複数の運転域で、先行気筒の空燃比を理論空燃比の略２倍もしくはそれより大きい値とそれより小さい値とに切換えているが、先行気筒の空燃比を、理論空燃比よりは大きくしつつ運転状態に応じて次第に変化させるようにしてもよい。
【００７２】
この場合、運転領域Ａのうちの少なくとも低負荷域で、低負荷側ほど、先行気筒における燃焼の際の空燃比を小さくする。あるいは、運転領域Ａのうちの少なくとも低速域で、低速側ほど、先行気筒における燃焼の際の空燃比を小さくする。
【００７３】
例えば、気筒間ガス通路２２に冷却手段を設けることなどにより特殊運転モードとされる運転領域Ａの高速高負荷側でもノッキングが生じにくくなっている場合は、図１０に示すように、特殊運転モードとされる運転領域Ａの高速高負荷側で先行気筒の空燃比を理論空燃比の略２倍もしくはそれより大きい値とし、エンジン回転数及び負荷が低くなるにつれて先行気筒の空燃比をリッチ側に変化させるようにすればよい。
【００７４】
このようにすると、特殊運転モードとされる運転領域Ａ内で、エンジン回転数（及び負荷）が低くなるにつれて後続気筒の燃焼室内の温度が低くなる傾向を補うように、先行気筒から後続気筒に導かれるガスの温度が高められ、圧縮自己着火可能な状態が確保される。
【００７５】
また、図１１に示すように、特殊運転モードとされる運転領域Ａのうちの中速中負荷域Ａ２０で先行気筒の空燃比を理論空燃比の略２倍もしくはそれより大きい値とし、この領域から低速低負荷側（矢印ａ方向）または高速高負荷側（矢印ｂ方向）へ遠ざかるほど、先行気筒における燃焼の際の空燃比を小さくするように制御してもよい。
【００７６】
このようにすると、特殊運転モードとされる運転領域Ａのうちの低速低負荷側において圧縮自己着火可能な状態を確保する作用、及び高速高負荷側においてノッキングを抑制する作用が、良好に得られる。
【００７７】
▲３▼上記のような特殊運転モードとされる運転領域Ａでの運転状態に応じた制御に加え、エンジンの温度状態に応じて先行気筒の空燃比を変更するようにしてもよい。例えば、エンジンの暖機後であってもエンジン温度が低いとき（エンジン冷却水の温度が所定温度以下のとき）には、特殊運転モードとされる運転領域Ａ内の全域で、先行気筒の空燃比を理論空燃比の２倍より小さくすることが好ましい。このようにすれば、比較的エンジン温度が低いときにも、先行気筒から後続気筒へ導入されるガスの温度を高めて圧縮自己着火可能な状態を確保することができる。
【００７８】
▲４▼上記各実施形態では、特殊運転モードとされる運転領域Ａの全域で、後続気筒を圧縮自己着火により燃焼させるようにしているが、特殊運転モードとされる運転領域Ａのうちの一部、例えば燃焼室内の温度、圧力が圧縮自己着火可能な状態に達しにくい極低速低負荷の領域では、後続気筒に対して所定の点火時期に点火プラグ７による点火を行わせ、強制点火により燃焼させるようにしてもよい。あるいはまた、エンジン温度が低いときに、後続気筒を強制点火により燃焼させるようにしてもよい。
【００７９】
▲５▼基本実施形態では弁停止機構を用いて２気筒接続状態と各気筒独立状態とに吸・排気流通状態を切換可能としているが、吸・排気通路及び気筒間ガス通路に開閉弁を設けてこれらの通路の開閉により２気筒接続状態と各気筒独立状態とに切換え得るようにしておいてもよい。
【００８０】
▲６▼本発明の装置は４気筒以外の多気筒エンジンにも適用可能である。そして、例えば６気筒等では１つの気筒の排気行程と別の気筒の吸気行程が完全に重なり合うことはないが、このような場合は、一方の気筒の排気行程が他方の気筒の吸気行程より先行するとともに、両行程が部分的に重なり合う２つの気筒を先行、後続の一対の気筒とすればよい。
【００８１】
【発明の効果】
以上のように本発明の制御装置によると、特殊運転モードとされた場合に、排気行程と吸気行程が重なる一対の気筒のうちの先行気筒ではリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して、圧縮自己着火により燃焼を行わせるようにしているため、先行気筒ではリーン燃焼による熱効率向上およびポンピングロス低減により、また後続気筒では圧縮自己着火による燃焼効率の向上及びポンピングロス低減により、燃費を改善することができる。しかも、後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしているため、排気通路での排気ガスの浄化を三元触媒だけで充分に行うことでき、リーンＮＯｘ触媒が不要となる。
【００８２】
そして、特に本発明では、上記特殊運転モードとされる運転領域のうちの少なくとも一部の運転領域で、先行、後続の両気筒に対する燃料供給量を先行気筒の方が多くなるように制御することにより先行気筒の空燃比を理論空燃比の２倍より小さい値としているため、先行気筒から後続気筒へ導入されるガスの温度を高めて後続気筒での自己着火性を向上し、かつ、このガス中のＥＧＲに相当する既燃ガス成分の増大によりノッキングを抑制することができる。このため、圧縮自己着火領域を大幅に拡大することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態による制御装置を備えたエンジン全体の概略平面図である。
【図２】エンジン本体等の概略断面図である。
【図３】制御系統のブロック図である。
【図４】運転状態に応じた制御を行うための運転領域設定の一例を示す説明図である。
【図５】各気筒の排気行程、吸気行程、燃料噴射時期および点火時期等を示す図である。
【図６】低負荷低回転時の実質的な新気およびガスの流通経路を示す説明図である。
【図７】高負荷、高低回転側の運転領域にある時の実質的な新気およびガスの流通経路を示す説明図である。
【図８】運転状態に応じた制御を行うための運転領域設定についての第２の例を示す説明図である。
【図９】運転状態に応じた制御を行うための運転領域設定についての第３の例を示す説明図である。
【図１０】運転状態に応じた制御を行うための運転領域設定についての第４の例を示す説明図である。
【図１１】運転状態に応じた制御を行うための運転領域設定についての第５の例を示す説明図である。
【符号の説明】
１ エンジン本体
２Ａ〜２Ｄ 気筒
９ 燃料噴射弁
１１ 吸気ポート
１１ａ 第１吸気ポート
１１ｂ 第２吸気ポート
１２ 排気ポート
１２ａ 第１排気ポート
１２ｂ 第２排気ポート
１５ 吸気通路
２０ 排気通路
２２ 気筒間ガス通路
３５ 弁停止機構
４０ ＥＣＵ
４１ 運転状態判別手段
４２ 弁停止機構制御手段
４３ 吸入空気量制御手段
４４ 燃焼状態制御手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spark ignition type four-cycle engine control device, and more particularly to a device for controlling the combustion state of each cylinder in a multi-cylinder engine to improve fuel consumption and emissions.
[0002]
[Prior art]
Conventionally, in a spark ignition engine, a technique for improving fuel efficiency by performing combustion in a state where the air-fuel ratio of the air-fuel mixture in each cylinder is set to a lean air-fuel ratio larger than the stoichiometric air-fuel ratio is known. As disclosed in Japanese Patent Application Laid-Open No. 10-274085, a stratified combustion is provided by injecting fuel directly into a combustion chamber and injecting fuel from the fuel injection valve in a compression stroke in a low rotation and low load region. It is known that the super lean combustion is realized by this.
[0003]
In such an engine, an ordinary three-way catalyst (a catalyst having a high purification performance in the vicinity of the theoretical air-fuel ratio with respect to HC, CO, and NOx) alone as an exhaust gas purification catalyst is sufficient for NOx during lean operation. Since purification performance cannot be obtained, a lean NOx catalyst is provided that adsorbs NOx in an oxygen-excessive atmosphere and removes and reduces NOx in an oxygen-concentrated atmosphere as shown in the above publication. When such a lean NOx catalyst is used, if the NOx adsorption amount of the lean NOx catalyst increases during the lean operation, for example, as shown in the above publication, additional fuel is injected during the expansion stroke in addition to the main combustion. As a result, the air-fuel ratio of the exhaust gas is enriched and CO is generated, thereby promoting NOx separation and reduction.
[0004]
[Problems to be solved by the invention]
The engine that performs the conventional lean operation as described above is disadvantageous in cost because the lean NOx catalyst is required to ensure the NOx purification performance during the lean operation. Further, in order to maintain the purification performance of the lean NOx catalyst, it is necessary to temporarily enrich the air-fuel ratio by removing additional NOx or supplying additional fuel for reduction when the NOx adsorption amount increases as described above. In addition, if the fuel used contains a large amount of sulfur, regenerative processing such as heating the catalyst and supplying reducing material is required to eliminate sulfur poisoning of the lean NOx catalyst. To do.
[0005]
Moreover, when the air-fuel ratio becomes leaner than a certain level, the combustion speed becomes too slow and combustion near the end does not contribute to work, so there is a limit to fuel efficiency improvement by leaning in stratified combustion.
[0006]
In addition, compression self-ignition has been studied as another method for improving fuel efficiency. This compression self-ignition, like a diesel engine, causes the combustion chamber to self-ignite at a high temperature and high pressure at the end of the compression stroke. Even if the air-fuel ratio is super lean or a large amount of EGR is introduced, if such compression self-ignition is performed, the entire combustion chamber burns at once, so slow combustion that does not contribute to work It can be avoided, which is advantageous for improving fuel economy. However, in a normal spark ignition engine (gasoline engine), forced ignition is required for combustion, and in order to perform compression self-ignition, special measures are taken to significantly increase the temperature or pressure in the combustion chamber. Therefore, it has been difficult to increase the temperature or pressure in the combustion chamber to such an extent that compression self-ignition occurs in a partial load region where fuel consumption improvement is required, while avoiding knocking in a high load region.
[0007]
Therefore, the present applicant is in the exhaust stroke between a pair of cylinders in which the exhaust stroke and the intake stroke overlap in a partial load region of the engine in order to have a significant fuel efficiency improvement effect by using both lean combustion and compression self-ignition. The burned gas discharged from the preceding cylinder is in a two-cylinder connection state in which the burned gas discharged from the preceding cylinder is directly introduced into the succeeding cylinder in the intake stroke via the inter-cylinder gas passage. A spark ignition type engine in which combustion is performed by forced ignition at a fuel ratio and fuel is supplied to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder in the subsequent cylinder and combustion is performed by compression self-ignition. A technology related to the control device has been filed (Japanese Patent Application No. 2002-29836).
[0008]
Based on such a technique, the present invention enables spark ignition by compression self-ignition in a subsequent cylinder effectively in a wider operating range, and can improve fuel efficiency and emission improvement effect. A control device for a four-cycle engine is provided.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is a multi-cylinder spark ignition type 4-cycle engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference, and the intake / exhaust and combustion of the engine in a partial load region of the engine. The control mode for the state is the special operation mode, and in this special operation mode, the burned gas discharged from the preceding cylinder in the exhaust stroke between the pair of cylinders in which the exhaust stroke and the intake stroke overlap is directly in the intake stroke In the preceding cylinder, the air-fuel ratio is higher than the stoichiometric air-fuel ratio while the two-cylinder connection state is established such that the gas discharged from the subsequent cylinder is introduced into the exhaust passage and led to the exhaust passage. It is a control device that performs combustion and supplies fuel to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder in the subsequent cylinder to perform combustion. Thus, in at least a part of the operation region set in the special operation mode, the air-fuel ratio at the time of combustion in the succeeding cylinder is substantially the stoichiometric air-fuel ratio, and the forced ignition is performed in the preceding cylinder. Combustion is performed by the following cylinder, combustion is performed by compression self-ignition in the subsequent cylinder, and combustion in the preceding cylinder is performed in the medium speed region of the operation region in which the subsequent cylinder is subjected to compression self-ignition in the special operation mode. The air-fuel ratio at this time is set to a value larger than twice the stoichiometric air-fuel ratio, and the operation region on the lower speed side than the medium-speed region in the operation region in which the subsequent cylinder is subjected to compression self-ignition in the special operation mode, the operation range of the high-speed side than the speed range, the preceding air-fuel ratio during combustion in the preceding cylinders to twice a value smaller than the stoichiometric air-fuel ratio, like combustion of controlling the fuel supply amount for a subsequent two cylinders I am characterized in that a control means.
[0010]
According to the present invention, when the special operation mode is set and combustion is performed by compression self-ignition in the succeeding cylinder, the fuel efficiency improvement effect is obtained in the preceding cylinder by improving the thermal efficiency by lean combustion and reducing the pumping loss. In this case, fuel efficiency can be improved by improving combustion efficiency and reducing pumping loss through compression self-ignition. Further, since the gas discharged from the succeeding cylinder to the exhaust passage has the stoichiometric air-fuel ratio, the exhaust gas can be sufficiently purified only with the three-way catalyst.
[0012]
In particular, in the following cylinder in the special operation mode speed range in one of the operating region that is compression ignition, by the air-fuel ratio during combustion in the preceding cylinders with greater than twice the stoichiometric air-fuel ratio, The fuel efficiency improvement effect is enhanced in the medium speed range.
[0013]
Further, 2 times the special Subsequent cylinders in operation mode operation range of low-speed side than the speed range in one of the operating region that is compressed self-ignition, stoichiometric air fuel ratio during combustion in the preceding cylinders By setting it to a smaller value, the temperature of the gas introduced from the preceding cylinder to the succeeding cylinder is increased, and the self-ignitability is improved in this low speed operation region.
[0014]
Further, 2 times the special In the following cylinders in the operation mode is the operation range of the high-speed side than the speed range in one of the operating region that is compressed self-ignition, stoichiometric air fuel ratio during combustion in the preceding cylinders By setting it to a smaller value, the occurrence of knocking is suppressed due to an increase in the burned gas component corresponding to EGR in the gas introduced into the subsequent cylinder .
[0015]
According to a second aspect of the present invention, there is provided a multi-cylinder spark ignition type four-cycle engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference. In this special operation mode, the burned gas discharged from the preceding cylinder in the exhaust stroke is in the intake stroke as it is between a pair of cylinders in which the exhaust stroke and the intake stroke overlap. A lean cylinder in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio in the preceding cylinder while the two cylinders are connected to the succeeding cylinder through the inter-cylinder gas passage and the gas discharged from the succeeding cylinder is led to the exhaust passage. A control device that performs combustion at a fuel ratio and supplies fuel to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder in the subsequent cylinder. In the preceding cylinder, the air-fuel ratio at the time of combustion in the subsequent cylinder is substantially equal to the stoichiometric air-fuel ratio in at least a part of the operation area in the special operation mode. Combustion is performed by forced ignition, combustion is performed by compression self-ignition in the subsequent cylinder, and in the middle load region of the operation region in which the subsequent cylinder is subjected to compression self-ignition in the special operation mode, the preceding cylinder The air-fuel ratio at the time of combustion in the combustion chamber is set to a value larger than twice the stoichiometric air-fuel ratio, and the operating region on the lower load side than the middle load region in the operating region in which the subsequent cylinder is subjected to compression self-ignition in the special operation mode In the operating range higher than the medium load range, the fuel supply amount to both the preceding and succeeding cylinders so that the air-fuel ratio at the time of combustion in the preceding cylinder is smaller than twice the theoretical air-fuel ratio. It is characterized in that it comprises a combustion state control means for controlling to.
[0016]
In this way, in a low load region where the temperature in the combustion chamber is relatively low in the operation region in which the special operation mode is set, the temperature of the gas guided from the preceding cylinder to the succeeding cylinder rises, thereby causing compression self-ignition. In a high load range where knocking is likely to occur, knocking is suppressed by reducing the energy generated in the subsequent cylinder. Further, fuel economy improvement effect is enhanced by the medium load region.
[0018]
When the engine temperature is low, the air-fuel ratio at the time of combustion in the preceding cylinder is set to a value smaller than twice the stoichiometric air-fuel ratio in the entire operation region where the subsequent cylinder is subjected to compression self-ignition in the special operation mode. (Claim 3 ) is preferable. If it does in this way, compression self-ignition will be attained also at the time of engine low temperature.
[0019]
According to a fourth aspect of the present invention, there is provided a multi-cylinder spark ignition type four-cycle engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference. In this special operation mode, the burned gas discharged from the preceding cylinder in the exhaust stroke is in the intake stroke as it is between a pair of cylinders in which the exhaust stroke and the intake stroke overlap. A lean cylinder in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio in the preceding cylinder while the two cylinders are connected to the succeeding cylinder through the inter-cylinder gas passage and the gas discharged from the succeeding cylinder is led to the exhaust passage. A control device that performs combustion at a fuel ratio and supplies fuel to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder in the subsequent cylinder. The combustion in the preceding cylinder is performed so that the air-fuel ratio at the time of combustion in the subsequent cylinder is substantially the stoichiometric air-fuel ratio in at least a part of the operation region set to the special operation mode. The fuel supply amount to both the preceding and succeeding cylinders is controlled so that the air-fuel ratio at the time is larger than the stoichiometric air-fuel ratio and less than twice the stoichiometric air-fuel ratio as the engine speed decreases. Is characterized in that it is provided with combustion state control means for performing control so that combustion is performed by forced ignition, and combustion is performed by compression self-ignition in the subsequent cylinders.
[0020]
According to the present invention, when the special operation mode is set and combustion is performed by compression self-ignition in the succeeding cylinder, the fuel efficiency improvement effect can be obtained by improving the thermal efficiency and reducing the pumping loss by the lean combustion in the preceding cylinder. Thus, an improvement in fuel efficiency can be obtained by improving the combustion efficiency by compression self-ignition and reducing the pumping loss, and exhaust gas can be sufficiently purified by using only the three-way catalyst in the exhaust passage.
[0021]
In addition, by controlling the fuel supply amount so that the air-fuel ratio of the preceding cylinder becomes smaller as the engine speed is lower, the temperature of the gas introduced from the preceding cylinder to the succeeding cylinder is raised and self-ignitability is improved. Is done.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 shows a schematic configuration of an engine according to an embodiment of the present invention, and FIG. 2 schematically shows a structure of one cylinder of an engine body 1 and intake / exhaust valves provided for the cylinder. In these drawings, the engine body 1 has a plurality of cylinders, and in the illustrated embodiment, has four cylinders 2A to 2D. A piston 3 is fitted into each of the cylinders 2 </ b> A to 2 </ b> D, and a combustion chamber 4 is formed above the piston 3.
[0026]
A spark plug 7 is provided at the top of the combustion chamber 4 of each cylinder 2, and the tip of the plug faces the combustion chamber 4. An ignition circuit 8 capable of controlling the ignition timing by electronic control is connected to the spark plug 7.
[0027]
A fuel injection valve 9 that directly injects fuel into the combustion chamber 4 is provided at a side portion of the combustion chamber 4. This fuel injection valve 9 incorporates a needle valve and a solenoid (not shown). When a pulse signal described later is input, the fuel injection valve 9 is driven for a time corresponding to the pulse width at the pulse input timing to open the valve. An amount of fuel corresponding to the valve time is injected. The fuel injection valve 9 is supplied with fuel by a fuel pump (not shown) through a fuel supply passage and the like, and a fuel supply system is provided so that a fuel pressure higher than the pressure in the combustion chamber in the compression stroke can be applied. Is configured.
[0028]
Further, intake ports 11, 11a, 11b and exhaust ports 12, 12a, 12b are opened to the combustion chambers 4 of the respective cylinders 2A to 2D, and an intake passage 15 and an exhaust passage 20 are connected to these ports. Each port is opened and closed by intake valves 31, 31a, 31b and exhaust valves 32, 32a, 32b.
[0029]
Each cylinder performs a cycle consisting of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. In the case of a four-cylinder engine, the first cylinder 2A, second cylinder from one end in the cylinder row direction When the cylinder 2B, the third cylinder 2C, and the fourth cylinder 2D are called, as shown in FIG. 5, the cycle is 180 degrees at a crank angle in the order of the first cylinder 2A, the third cylinder 2C, the fourth cylinder 2D, and the second cylinder 2B. It is performed with a phase difference of °. In FIG. 5, EX is an exhaust stroke, IN is an intake stroke, F is fuel injection, S is forced ignition, and a star mark in the drawing indicates that compression self-ignition is performed.
[0030]
Between a pair of cylinders in which the exhaust stroke and the intake stroke overlap, a cylinder on the intake stroke side (this specification is referred to as a preceding cylinder) from the cylinder on the exhaust stroke side when the exhaust stroke and the intake stroke overlap (this specification is referred to as a preceding cylinder) The inter-cylinder gas passage 22 is provided so that the burned gas can be directly introduced to the subsequent cylinder). In the four-cylinder engine of this embodiment, as shown in FIG. 5, the exhaust stroke (EX) of the first cylinder 2A and the intake stroke (IN) of the second cylinder 2B overlap, and the exhaust stroke (EX) of the fourth cylinder 2D. ) And the intake stroke (IN) of the third cylinder 2C overlap, so that the first cylinder 2A and the second cylinder 2B, and the fourth cylinder 2D and the third cylinder 2C form a pair, respectively, and the first cylinder 2A and the fourth cylinder The cylinder 2D is the preceding cylinder, the second cylinder 2B, and the third cylinder 2C are the subsequent cylinders.
[0031]
The intake / exhaust port of each cylinder and the intake passage, exhaust passage, and inter-cylinder gas passage connected to the cylinder are specifically configured as follows.
[0032]
The first cylinder 2A and the fourth cylinder 2D, which are the preceding cylinders, respectively include an intake port 11 for introducing fresh air, and a first exhaust port 12a for sending burned gas (exhaust gas) to the exhaust passage. A second exhaust port 12b for leading the burned gas to the subsequent cylinder is provided. The second cylinder 2B and the third cylinder 2C, which are the subsequent cylinders, respectively, have a first intake port 11a for introducing fresh air and a second intake port for introducing burned gas from the preceding cylinder. 11b and an exhaust port 32 for sending the burned gas to the exhaust passage.
[0033]
In the example shown in FIG. 1, the intake ports 11 in the first and fourth cylinders 2A and 2D and the first intake ports 11a in the second and third cylinders 2B and 2C are two per cylinder, the left half of the combustion chamber. The first exhaust port 12a and the second exhaust port 12b in the first and fourth cylinders 2A and 2D and the second intake port 11b and the exhaust port in the second and third cylinders 2B and 2C are provided in parallel on the part side. 12 are provided in parallel on the right half side of the combustion chamber.
[0034]
The intake port 11 in the first and fourth cylinders 2A and 2D and the first intake port 11a in the second and third cylinders 2B and 2C are connected to the downstream ends of the branch intake passages 16 for each cylinder in the intake passage 15. Yes. In the vicinity of the downstream end of each branch intake passage 16, a multiple throttle valve 17 that is linked to each other via a common shaft is provided. This multiple throttle valve 17 is driven by an actuator 18 in accordance with a control signal, The intake air amount is adjusted. Note that an air flow sensor 19 that detects an intake air flow rate is provided in a common intake passage upstream of the collecting portion in the intake passage 15.
[0035]
An upstream end of a branch exhaust passage 21 for each cylinder in the exhaust passage 20 is connected to the first exhaust port 12a in the first and fourth cylinders 2A and 2D and the exhaust port 12 in the second and third cylinders 2B and 2C. Yes. Further, an inter-cylinder gas passage 22 is provided between the first cylinder 2A and the second cylinder 2B and between the third cylinder 2C and the fourth cylinder 2D, and the first, fourth cylinder 2A, The upstream end of the inter-cylinder gas passage 22 is connected to the 2D second exhaust port 12b, and the downstream end of the inter-cylinder gas passage 22 is connected to the second intake port 11b of the second and third cylinders 2B and 2C as the subsequent cylinders. Is connected.
[0036]
The inter-cylinder gas passage 22 is a relatively short passage that connects between cylinders adjacent to each other, and heat radiation while the gas discharged from the preceding cylinder passes through the passage 22 is kept relatively small. .
[0037]
An O 2 sensor 23 that detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas is provided at the downstream of the branch exhaust passage 21 in the exhaust passage 20. Further, a three-way catalyst 24 is provided in the exhaust passage 21 downstream of the O 2 sensor 23 for exhaust purification. As is generally known, the three-way catalyst 24 is highly purified against HC, CO, and NOx when the air-fuel ratio of the exhaust gas is close to the stoichiometric air-fuel ratio (that is, the excess air ratio λ is λ = 1). It is a catalyst showing performance.
[0038]
The intake / exhaust valves for opening and closing the intake / exhaust ports of each cylinder and the valve operating mechanism for these valves are as follows.
[0039]
The intake port 11, the first exhaust port 12a, and the second exhaust port 12b in the first and fourth cylinders 2A, 2D are respectively provided with an intake valve 31, a first exhaust valve 32a, and a second exhaust valve 32b. A first intake valve 31a, a second intake valve 31b, and an exhaust valve 32 are provided in the first intake port 11a, the second intake port 11b, and the exhaust port 12 in the No. 3 cylinders 2B and 2C, respectively. These intake / exhaust valves are opened and closed at predetermined timings by the valve mechanisms comprising the camshafts 33, 34, etc. so that the intake stroke and exhaust stroke of each cylinder are performed with the predetermined phase difference as described above. To be driven.
[0040]
Further, among these intake / exhaust valves, the first exhaust valve 32a, the second exhaust valve 32b, the first intake valve 31a, and the second intake valve 31b are switched between an operating state and a stopped state. A valve stop mechanism 35 is provided. The valve stop mechanism 35 has been known in the art and will not be shown in detail. For example, hydraulic oil can be supplied to and discharged from a tappet interposed between the cams of the camshafts 33 and 34 and the valve shaft. When a hydraulic oil is supplied to the hydraulic chamber, the operation of the cam is transmitted to the valve and the valve is opened and closed. When the hydraulic oil is discharged from the hydraulic chamber, the cam operation is not performed. The valve is stopped by not being able to be transmitted to.
[0041]
The first control valve 37 and the second exhaust valve 32b are stopped in the hydraulic oil supply / discharge passage 36 to the valve stop mechanism 35 of the first exhaust valve 32a and the valve stop mechanism 35 of the first intake valve 31a. A second control valve 39 is provided in each of the hydraulic oil supply / discharge passages 38 to the mechanism 35 and the valve stop mechanism 35 of the second intake valve 31b (see FIG. 3).
[0042]
FIG. 3 shows the configuration of the drive and control system. In this figure, signals from the air flow sensor 19 and the O 2 sensor 23 are input to an engine control ECU (control unit) 40 comprising a microcomputer or the like, and the engine speed is detected in order to further determine the operating state. Signals from a rotation speed sensor 47 that performs the operation and an accelerator operation amount sensor 48 that detects the accelerator operation amount (accelerator pedal depression amount) are also input. Control signals are output from the ECU 40 to the fuel injection valves 9, the actuator 18 of the multiple throttle valve 17, and the first and second control valves 39.
[0043]
The ECU 40 includes an operation state determination unit 41, a valve stop mechanism control unit 42, an intake air amount control unit 43, and a combustion state control unit 44.
[0044]
As shown in FIG. 4, the operating state discriminating means 41 is a control in which the operating range of the engine is divided into an operating range A (partial load range) on the low load low rotation side and an operating range B on the high load side or high rotation side. Whether the operating state of the engine (engine speed and engine load) is in the operating range A or B, which has a map for the engine and is examined by signals from the rotational speed sensor 45 and the accelerator opening sensor 46, etc. Is determined. Based on this determination, in the operation region A on the low load low rotation side, a special operation mode is selected in which the burned gas discharged from the preceding cylinder in the exhaust stroke is directly introduced into the subsequent cylinder in the intake stroke and burned. In the operation region B on the high load side or the high rotation side, the normal operation mode in which each cylinder is made to burn independently is selected.
[0045]
Furthermore, when the operation state determination unit 41 is in the operation region A in which the special operation mode is selected, the operation state determination unit 41 determines whether the region A is in the low speed region A1, the medium speed region A2, or the high speed region A3. It has become.
[0046]
The valve stop mechanism control means 42 is in a two-cylinder connection state in which the burned gas of the preceding cylinder is introduced into the succeeding cylinder via the inter-cylinder gas passage 22 in the special operation mode, and fresh air is introduced into each cylinder in the normal operation mode. The valve stop mechanism 35 is controlled so as to change the intake / exhaust flow state so that each cylinder is in an independent state. Specifically, depending on whether the operation state is in the operation region A or B, By controlling the control valves 37 and 39, the valve stop mechanisms 35 are controlled as follows.
[0047]
Operating region A: The first exhaust valve 32a and the first intake valve 31a are stopped. The second exhaust valve 32b and the second intake valve 31b are operated. Operation region B: The first exhaust valve 32a and the first intake valve 31a are operated. The second exhaust valve 32b and the second intake valve 31b are stopped. The intake air amount control means 43 controls the opening degree (throttle opening degree) of the throttle valve 17 by controlling the actuator 18, and is in an operating state. Accordingly, the target intake air amount is obtained from a map or the like, and the throttle opening is controlled according to the target intake air amount. In this case, in the operation region A in the special operation mode, the gas introduced from the preceding cylinder in the state where the intake introduction from the branch intake passage 16 is blocked in the subsequent cylinders (second and third cylinders 2B and 2C). Since the combustion is performed while the ratio of the excess air in the fuel to the newly supplied fuel is set to the lean air-fuel ratio, the amount of air necessary for the combustion of the fuel according to the required torque for the preceding and subsequent two cylinders ( The throttle opening is adjusted so that the amount of air corresponding to the stoichiometric air-fuel ratio with respect to the amount of fuel for two cylinders is supplied to the preceding cylinders (the first and fourth cylinders 2A and 2D).
[0048]
The combustion state control means 44 is composed of a fuel injection control means 45 and an ignition control means 46. The fuel injection control means 45 causes the fuel injection amount from the fuel injection valves 9 provided in the respective cylinders 2A to 2D and The injection timing is controlled according to the operating state of the engine, and ignition control means 46 controls ignition timing and ignition stop according to the operating state. In particular, the control of the combustion state (control of fuel injection and control of ignition) is changed depending on whether the operation state is in the operation region A in FIG. 4 or in the operation region B.
[0049]
That is, when the operation state is in the operation region A on the low load and low rotation side, the air-fuel ratio is set to the stoichiometric air-fuel ratio for the preceding cylinders (first and fourth cylinders 2A and 2D) as control in the special operation mode. The fuel injection amount is controlled so that the lean air-fuel ratio is larger than that, the injection timing is set so that the fuel is injected in the compression stroke and the mixture is stratified, and near the compression top dead center. The ignition timing is set so that forced ignition is performed. On the other hand, for the succeeding cylinders (second and third cylinders 2B, 2C), fuel is supplied to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder so that the stoichiometric air-fuel ratio is substantially achieved. In addition, the fuel injection amount is controlled, the injection timing is set so as to inject fuel in the intake stroke, and the forced ignition is stopped in order to perform compression self-ignition.
[0050]
Further, in this operation region A, the sum of the fuel injection amounts for both of the pair of cylinders is adjusted to an amount that is the stoichiometric air-fuel ratio with respect to the amount of air introduced into the preceding cylinder, while the compression self-ignition in the subsequent cylinder is performed. The ratio between the fuel injection amount for the preceding cylinder (No. 1, 4 cylinders 2A, 2D) and the fuel injection amount for the subsequent cylinders (No. 2, 3 cylinders 2B, 2C) depends on the operating state so Changed.
[0051]
Specifically, in the medium speed region A2 of this operation region A, the fuel injection amount for the preceding cylinder and the fuel injection amount for the subsequent cylinder are substantially the same, or the fuel injection amount on the subsequent cylinder side is slightly increased. Thus, the air-fuel ratio at the time of combustion in the preceding cylinder is about twice the theoretical air-fuel ratio (A / F≈30, about λ = 2 in terms of excess air ratio λ) or larger than twice the theoretical air-fuel ratio (air The excess rate λ is set to satisfy λ> 2). Further, in the low speed region A1 of the operation region A, the fuel injection amount for the preceding cylinder is made larger than the fuel injection amount for the subsequent cylinder, so that the air-fuel ratio at the time of combustion in the preceding cylinder is more than twice the stoichiometric air-fuel ratio. It is set to be small (the excess air ratio λ is 1 <λ <2), for example, A / F≈25. On the other hand, even in the high speed region A3 in the operation region A, by making the fuel injection amount for the preceding cylinder larger than the fuel injection amount for the subsequent cylinder, the air-fuel ratio at the time of combustion in the preceding cylinder is twice the stoichiometric air-fuel ratio. The air excess ratio λ is set to be smaller (1 <λ <2), for example, A / F≈25.
[0052]
Further, when the operation state is in the operation region B on the high load side or the high rotation side, the control is performed in the normal operation mode so that the air-fuel ratio of each cylinder 2A to 2D is the stoichiometric air-fuel ratio or less. The injection amount is controlled so that, for example, the stoichiometric air-fuel ratio is set in most of the operating range B, and is made richer than the stoichiometric air-fuel ratio in the fully open load and the operating range in the vicinity thereof. In this case, the injection timing is set so that the air-fuel mixture is made uniform by injecting fuel to each of the cylinders 2A to 2D and the cylinders 2A to 2D are forcedly ignited. To.
[0053]
The operation of the apparatus of the present embodiment as described above will be described with reference to FIGS.
[0054]
In the operation region A on the low load and low rotation side, the special operation mode is set, and as described above, the first exhaust valve 32a and the first intake valve 31a are in the stopped state, and the second exhaust valve 32b and the second intake valve 31b are in the activated state. As a result, the actual flow path of fresh air and gas is as shown in FIG. 6, and the burned gas discharged from the preceding cylinders (first and fourth cylinders) 2A and 2D remains as it is as the inter-cylinder gas passage. 22 is introduced into the succeeding cylinders (second and third cylinders) 2B and 2C via the cylinder 22, and only a gas discharged from the succeeding cylinders 2B and 2C is brought into a two-cylinder connection state. The
[0055]
In this state, fresh air is introduced into the preceding cylinders 2A and 2D from the intake passage 15 in the intake stroke (arrow a in FIG. 6), and the air-fuel ratio in the preceding cylinders 2A and 2D is larger than the stoichiometric air-fuel ratio. Fuel is injected in the compression stroke while the fuel injection amount is controlled to be approximately twice or less than the air-fuel ratio, and ignition is performed at a predetermined ignition timing, so that stratified combustion at the lean air-fuel ratio is performed. Is performed (see FIG. 5).
[0056]
Then, burned gas discharged from the preceding cylinders 2A and 2D is introduced into the succeeding cylinders 2B and 2C through the gas passage 22 during a period in which the intake strokes of the preceding cylinders 2A and 2D overlap with the exhaust strokes of the succeeding cylinders 2B and 2C. (The white arrow in FIG. 5 and the arrow b in FIG. 6). In the succeeding cylinders 2B and 2C, fuel is supplied to the burned gas having a lean air-fuel ratio introduced from the preceding cylinders 2A and 2D, and the fuel injection amount is controlled so as to become the stoichiometric air-fuel ratio. After the fuel is injected, compression self-ignition is performed near the top dead center of the compression stroke due to an increase in pressure and temperature in the combustion chamber.
[0057]
In this case, since the high-temperature burned gas discharged from the preceding cylinders 2A and 2D is immediately introduced into the succeeding cylinders 2B and 2C through the short inter-cylinder gas passage 22, the succeeding cylinders 2B and 2C are in the combustion chamber during the intake stroke. In this state, the pressure and temperature further increase in the compression stroke, and the temperature in the combustion chamber rises to the extent that the air-fuel mixture can self-ignite near the top dead center at the end of the compression stroke. Moreover, the burned gas is sufficiently mixed and evenly distributed from the time when it is discharged from the preceding cylinders 2A and 2D to the time when it is introduced into the succeeding cylinders 2B and 2C, and the fuel injected in the intake stroke is also compressed. Since it is uniformly dispersed throughout the combustion chamber by the end, a uniform mixture distribution state that satisfies the ideal simultaneous compression self-ignition condition can be obtained. And combustion is rapidly performed by simultaneous compression self-ignition, and, thereby, thermal efficiency is improved significantly.
[0058]
In this way, in the preceding cylinders 2A and 2D, the thermal efficiency is increased by the stratified combustion in lean, and the pumping loss is reduced by reducing the intake negative pressure as compared with a normal engine that does not perform stratified combustion, In the succeeding cylinders 2B and 2C, while the air-fuel ratio is substantially the stoichiometric air-fuel ratio, compression self-ignition is performed in a uniform mixture distribution state, and the thermal efficiency is increased, and the gas extruded from the preceding cylinders 2A and 2D Since it is fed, the pumping loss is further reduced as compared with the preceding cylinders 2A and 2D. These effects greatly improve fuel efficiency.
[0059]
Moreover, since the gas discharged from the succeeding cylinders 2B and 2C into the exhaust passage 20 has a stoichiometric air-fuel ratio, it is not necessary to provide a lean NOx catalyst as in a conventional lean burn engine, and the three-way catalyst 24 is sufficient for exhausting. Purification performance is ensured.
[0060]
Since there is no need to provide a lean NOx catalyst, there is no need to temporarily enrich the air-fuel ratio for NOx release and reduction when the NOx storage amount of the lean NOx catalyst is increased, thereby reducing fuel consumption improvement. can avoid. Furthermore, the problem of sulfur poisoning of the lean NOx catalyst does not occur.
[0061]
In addition, in the preceding cylinders 2A and 2D, the lean air-fuel ratio is set to approximately twice or close to the theoretical air-fuel ratio, so that the NOx generation amount can be suppressed to be relatively small. On the other hand, in the succeeding cylinders 2B and 2C, the burned gas is introduced from the preceding cylinders 2A and 2D so that a large amount of EGR is performed, and rapid combustion by simultaneous compression self-ignition is performed. Therefore, the reaction between oxygen and nitrogen is avoided as much as possible, so that the generation of NOx is sufficiently suppressed. This is also advantageous for improving emissions.
[0062]
Further, since the compression self-ignition in the succeeding cylinders 2B and 2C is achieved by using the heat of the burned gas discharged from the preceding cylinders 2A and 2D, a special heating means is used or the compression ratio of the engine is extremely reduced. It is not necessary to make it high, and compression self-ignition can be easily achieved. In particular, the ratio between the fuel injection amount for the preceding cylinder (first and fourth cylinders 2A and 2D) and the fuel injection amount for the subsequent cylinders (second and third cylinders 2B and 2C) in the special operation mode depends on the operating state. By adjusting as described above, compression self-ignition can be effectively performed over a wide operation range.
[0063]
That is, in the low speed region A1 of the operation region A set as the special operation mode, the temperature in the combustion chamber is inherently lower than that in the middle / high speed regions A2 and A3, so that compression self-ignition is not easily performed. However, in this low speed region A1, the air-fuel ratio at the time of combustion in the succeeding cylinder is adjusted so as to be substantially the stoichiometric air-fuel ratio, while the fuel injection amount for the preceding cylinder is made larger than that for the succeeding cylinder. Since the fuel ratio is controlled to be a value smaller than twice the stoichiometric air-fuel ratio, the air-fuel ratio of the preceding cylinder is twice the stoichiometric air-fuel ratio (the preceding cylinder and the succeeding cylinder have the same injection amount). In comparison, the temperature of the gas guided from the preceding cylinder to the succeeding cylinder increases. For this reason, compression self-ignition is effectively performed even in the low speed region A1.
[0064]
Further, in the high speed region A3 in the operation region A that is set to the special operation mode, the combustion temperature rises excessively and knocking is likely to occur. In this region, the fuel injection amount for the preceding cylinder is made larger than that for the subsequent cylinder. Thus, the air-fuel ratio of the preceding cylinder is controlled to be a value smaller than twice the theoretical air-fuel ratio. As a result, the temperature of the gas introduced into the succeeding cylinder rises as compared with the case where the air-fuel ratio of the preceding cylinder is twice the stoichiometric air-fuel ratio (the preceding cylinder and the succeeding cylinder have the same injection amount). As the burned gas component corresponding to EGR in the gas introduced into the cylinder increases, the amount of fuel injected into the succeeding cylinder decreases, so that the energy generated by combustion in the succeeding cylinder decreases, so that knocking is suppressed. .
[0065]
Thus, when the fuel injection amount for the preceding cylinder is made larger than that for the succeeding cylinder and the air / fuel ratio of the preceding cylinder is controlled to be smaller than twice the stoichiometric air / fuel ratio, the air / fuel ratio of the preceding cylinder becomes the stoichiometric air / fuel ratio. Compared to the case where the fuel ratio is twice (the same injection amount in the preceding cylinder and the succeeding cylinder), it is advantageous in terms of compression self-ignition and knocking suppression, but on the other hand, the fuel consumption improvement by stratified lean burn in the preceding cylinder It is somewhat disadvantageous in terms of effect, torque balance between the preceding and subsequent cylinders. Therefore, the air-fuel ratio of the preceding cylinder is theoretically determined so that it is advantageous in terms of fuel efficiency improvement effect and torque balance in the medium speed range A2 where the compression operation of the subsequent cylinder can be easily performed by the special operation mode and knocking hardly occurs. The fuel injection amount is controlled so as to be a value approximately twice or larger than the air-fuel ratio.
[0066]
On the other hand, in the operation region B on the high load side or the high rotation side, the normal operation mode is set. As described above, the first exhaust valve 32a and the first intake valve 31a are in the operating state, and the second exhaust valve 32b and the second intake valve 31b. 7 is brought into a stopped state, the actual flow path of fresh air and gas is as shown in FIG. 7, and the intake ports 31 and 31a and the exhaust ports 12a and 12 of each cylinder 2A to 2D are independent, and the intake air Fresh air is introduced from the passage 15 to the intake ports 31 and 31a of the respective cylinders 2A to 2D, and burned gas is discharged from the exhaust ports 31 and 31a of the respective cylinders 2A to 2D to the exhaust passage 20. In this case, the output performance is ensured by controlling the intake air amount and the fuel injection amount so that the stoichiometric air-fuel ratio or richer.
[0067]
In addition, the specific structure of the apparatus of this invention is not limited to the said embodiment, A various change is possible. Other embodiments are described below.
[0068]
(1) In the basic embodiment described above, the operation region A that is in the special operation mode is divided into the low speed region A1, the medium speed region A2, and the high speed region A3, and the air-fuel ratio of the preceding cylinder (the fuel injection amount and the succeeding cylinder for the preceding cylinder). The ratio of the fuel injection amount to the cylinder) is changed in each of the above regions A1, A2, and A3. As shown in FIG. 8, the operation region A in the special operation mode is changed to the low load region A11 and the medium load region. You may make it divide into A12 and high load area A13. In this case, in the medium load region A12, the air-fuel ratio of the preceding cylinder is set to a value approximately twice or larger than the theoretical air-fuel ratio, and in the low load region A11 and high load region A13, the air-fuel ratio of the preceding cylinder is set to the theoretical air-fuel ratio. The fuel injection amount is controlled to be a value smaller than twice (for example, A / F≈25).
[0069]
Alternatively, as shown in FIG. 9, the air-fuel ratio of the preceding cylinder is set to a value that is approximately twice or larger than the theoretical air-fuel ratio in the medium-speed medium load region A20 in the operation region A that is set to the special operation mode. The air-fuel ratio of the preceding cylinder may be controlled to be a value smaller than twice the theoretical air-fuel ratio in the operating range.
[0070]
Also in these examples, in the low load region where the temperature in the combustion chamber is relatively low in the operation region A in the special operation mode, the compression self-ignition is performed by increasing the temperature of the gas led from the preceding cylinder to the subsequent cylinder. In a high load range where knocking is likely to occur, knocking is suppressed by reducing the energy generated in the subsequent cylinder, and in the middle load range A12 or the medium speed middle load range A20, the fuel efficiency improvement effect and torque balance are improved. This is an advantageous state.
[0071]
(2) In the basic embodiment and the examples shown in FIGS. 8 and 9, the air-fuel ratio of the preceding cylinder is approximately twice the stoichiometric air-fuel ratio in the plurality of operation areas within the operation area A that is set to the special operation mode. Although the value is switched between a larger value and a smaller value, the air-fuel ratio of the preceding cylinder may be gradually changed according to the operating state while being larger than the theoretical air-fuel ratio.
[0072]
In this case, at least in the low load region of the operation region A, the air-fuel ratio at the time of combustion in the preceding cylinder is reduced toward the lower load side. Alternatively, the air-fuel ratio at the time of combustion in the preceding cylinder is reduced as the speed decreases in at least the low speed region of the operation region A.
[0073]
For example, when it is difficult for knocking to occur even on the high-speed and high-load side of the operation region A that is set to the special operation mode by providing a cooling means in the inter-cylinder gas passage 22, as shown in FIG. The air-fuel ratio of the preceding cylinder is set to a value approximately twice or larger than the theoretical air-fuel ratio on the high-speed and high-load side of the operation region A, and the air-fuel ratio of the preceding cylinder is made richer as the engine speed and load decrease. Change it.
[0074]
In this way, in the operation region A in the special operation mode, the temperature in the combustion chamber of the succeeding cylinder decreases from the preceding cylinder to the succeeding cylinder so as to compensate for a decrease in the temperature of the succeeding cylinder as the engine speed (and load) decreases. The temperature of the introduced gas is increased, and a state in which compression self-ignition is possible is ensured.
[0075]
Further, as shown in FIG. 11, the air-fuel ratio of the preceding cylinder is set to a value approximately twice or larger than the stoichiometric air-fuel ratio in the medium-speed medium load region A20 in the operation region A in the special operation mode. The air-fuel ratio at the time of combustion in the preceding cylinder may be reduced as the distance from the low-speed low-load side (arrow a direction) or the high-speed high-load side (arrow b direction) is increased.
[0076]
In this way, it is possible to satisfactorily obtain the effect of ensuring a state in which compression self-ignition is possible on the low speed and low load side of the operation region A that is set to the special operation mode and the effect of suppressing knocking on the high speed and high load side. .
[0077]
(3) In addition to the control according to the operation state in the operation region A in the special operation mode as described above, the air-fuel ratio of the preceding cylinder may be changed according to the engine temperature state. For example, when the engine temperature is low even after the engine is warmed up (when the temperature of the engine cooling water is equal to or lower than a predetermined temperature), the preceding cylinder is emptied in the entire operation area A in the special operation mode. It is preferable to make the fuel ratio smaller than twice the theoretical air-fuel ratio. In this way, even when the engine temperature is relatively low, the temperature of the gas introduced from the preceding cylinder to the succeeding cylinder can be increased to ensure a state where compression self-ignition is possible.
[0078]
(4) In each of the above embodiments, the subsequent cylinders are combusted by compression self-ignition over the entire operation region A in the special operation mode, but one of the operation regions A in the special operation mode is used. In a region of extremely low speed and low load where the temperature and pressure in the combustion chamber, for example, are difficult to reach a state in which compression self-ignition is possible, the subsequent cylinder is ignited by the spark plug 7 at a predetermined ignition timing and burned by forced ignition You may make it make it. Alternatively, when the engine temperature is low, the subsequent cylinder may be burned by forced ignition.
[0079]
(5) In the basic embodiment, the intake / exhaust flow state can be switched between the two-cylinder connected state and the individual cylinder independent state by using a valve stop mechanism, but an open / close valve is provided in the intake / exhaust passage and the inter-cylinder gas passage. Thus, the two-cylinder connected state and each cylinder independent state may be switched by opening and closing these passages.
[0080]
(6) The apparatus of the present invention can be applied to multi-cylinder engines other than four-cylinder engines. For example, in the case of six cylinders, the exhaust stroke of one cylinder and the intake stroke of another cylinder do not completely overlap. In such a case, the exhaust stroke of one cylinder precedes the intake stroke of the other cylinder. In addition, two cylinders in which both strokes partially overlap may be used as a pair of preceding and succeeding cylinders.
[0081]
【The invention's effect】
As described above, according to the control device of the present invention, when the special operation mode is set, the preceding cylinder of the pair of cylinders in which the exhaust stroke and the intake stroke overlap with each other performs combustion at the lean air-fuel ratio, and the preceding cylinder performs the preceding operation. Since fuel is supplied to the burned gas with a lean air-fuel ratio introduced from the cylinder and combustion is performed by compression self-ignition, in the preceding cylinder, thermal efficiency is improved by lean combustion and pumping loss is reduced. Then, fuel efficiency can be improved by improving combustion efficiency by compression self-ignition and reducing pumping loss. In addition, since the air-fuel ratio at the time of combustion in the subsequent cylinder is substantially the stoichiometric air-fuel ratio, the exhaust gas in the exhaust passage can be sufficiently purified with only the three-way catalyst, and the lean NOx catalyst is It becomes unnecessary.
[0082]
In particular, in the present invention, the fuel supply amount to both the preceding and succeeding cylinders is controlled to be larger in the preceding cylinders in at least a part of the operating regions set as the special operation mode. As a result, the air-fuel ratio of the preceding cylinder is set to a value smaller than twice the stoichiometric air-fuel ratio, so that the temperature of the gas introduced from the preceding cylinder to the succeeding cylinder is increased to improve the self-ignitability in the succeeding cylinder, and this gas Knocking can be suppressed by increasing the burned gas component corresponding to the EGR inside. For this reason, the compression self-ignition region can be greatly expanded.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an entire engine including a control device according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of an engine body and the like.
FIG. 3 is a block diagram of a control system.
FIG. 4 is an explanatory diagram showing an example of operation region setting for performing control according to an operation state.
FIG. 5 is a diagram showing an exhaust stroke, an intake stroke, a fuel injection timing, an ignition timing, and the like of each cylinder.
FIG. 6 is an explanatory diagram showing substantial fresh air and gas flow paths during low load and low rotation.
FIG. 7 is an explanatory diagram showing a substantial fresh air and gas flow path when in an operation region on a high load, high and low rotation side.
FIG. 8 is an explanatory diagram showing a second example of operation region setting for performing control according to an operation state.
FIG. 9 is an explanatory diagram showing a third example of operation region setting for performing control according to an operation state.
FIG. 10 is an explanatory diagram showing a fourth example of operation region setting for performing control according to an operation state.
FIG. 11 is an explanatory diagram showing a fifth example of operation region setting for performing control according to an operation state.
[Explanation of symbols]
1 Engine body 2A to 2D Cylinder 9 Fuel injection valve 11 Intake port 11a First intake port 11b Second intake port 12 Exhaust port 12a First exhaust port 12b Second exhaust port 15 Intake passage 20 Exhaust passage 22 Inter-cylinder gas passage 35 Valve Stop mechanism 40 ECU
41 Operating state determination means 42 Valve stop mechanism control means 43 Intake air amount control means 44 Combustion state control means

Claims (4)

各気筒の燃焼サイクルが所定の位相差をもって行われるようになっている多気筒の火花点火式４サイクルエンジンにおいて、
エンジンの部分負荷域でエンジンの吸・排気及び燃焼状態についての制御モードを特殊運転モードとし、この特殊運転モードでは、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入され、この後続気筒から排出されるガスが排気通路に導かれるような２気筒接続状態としつつ、先行気筒では空燃比が理論空燃比よりも大きいリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して燃焼を行わせるようにした制御装置であって、
上記特殊運転モードとされる運転領域のうちの少なくとも一部の運転領域で、上記後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしつつ、先行気筒では強制点火により燃焼を行わせ、後続気筒では圧縮自己着火により燃焼を行わせるようにするとともに、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中速域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より大きい値とし、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの上記中速域よりも低速側の運転域および上記中速域よりも高速側の運転域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とするように先行、後続の両気筒に対する燃料供給量を制御する燃焼状態制御手段を備えたことを特徴とする火花点火式４サイクルエンジンの制御装置。In the multi-cylinder spark ignition type 4-cycle engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference,
The special operation mode is the control mode for engine intake / exhaust and combustion conditions in the partial load range of the engine. In this special operation mode, exhaust is performed from the preceding cylinder in the exhaust stroke between a pair of cylinders where the exhaust stroke and the intake stroke overlap. In the preceding cylinder, the burned gas is introduced into the succeeding cylinder in the intake stroke as it is through the inter-cylinder gas passage, and the gas discharged from the succeeding cylinder is led to the exhaust passage. It is a control device that performs combustion at a lean air-fuel ratio in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio, and in the subsequent cylinder, supplies fuel to the burned gas of the lean air-fuel ratio introduced from the preceding cylinder and performs combustion. There,
Combustion by forced ignition is performed in the preceding cylinder while the air-fuel ratio at the time of combustion in the subsequent cylinder is substantially the stoichiometric air-fuel ratio in at least a part of the operation area in the special operation mode. In the operation range where the subsequent cylinder is subjected to compression self-ignition in the special operation mode, in the middle speed region in the special operation mode, the combustion in the preceding cylinder is performed. The air-fuel ratio of the engine is set to a value larger than twice the stoichiometric air-fuel ratio, and the operation region on the lower speed side than the medium-speed region and the medium-speed region in the operation region where the subsequent cylinder is subjected to compression self-ignition in the special operation mode. the operation range of the high-speed side than the preceding fuel ratio during combustion in the preceding cylinders to twice a value smaller than the stoichiometric air-fuel ratio, the combustion state control for controlling the fuel supply amount for a subsequent two cylinders Control apparatus for a spark ignition type 4-cycle engine, comprising the stages. 各気筒の燃焼サイクルが所定の位相差をもって行われるようになっている多気筒の火花点火式４サイクルエンジンにおいて、In the multi-cylinder spark ignition type 4-cycle engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference,
エンジンの部分負荷域でエンジンの吸・排気及び燃焼状態についての制御モードを特殊運転モードとし、この特殊運転モードでは、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入され、この後続気筒から排出されるガスが排気通路に導かれるような２気筒接続状態としつつ、先行気筒では空燃比が理論空燃比よりも大きいリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して燃焼を行わせるようにした制御装置であって、  The special operation mode is the control mode for engine intake / exhaust and combustion conditions in the partial load range of the engine. In this special operation mode, exhaust is performed from the preceding cylinder in the exhaust stroke between a pair of cylinders where the exhaust stroke and the intake stroke overlap. In the preceding cylinder, the burned gas is introduced into the succeeding cylinder in the intake stroke as it is through the inter-cylinder gas passage, and the gas discharged from the succeeding cylinder is led to the exhaust passage. It is a control device that performs combustion at a lean air-fuel ratio in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio, and in the subsequent cylinder, supplies fuel to the burned gas of the lean air-fuel ratio introduced from the preceding cylinder and performs combustion. There,
上記特殊運転モードとされる運転領域のうちの少なくとも一部の運転領域で、上記後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしつつ、先行気筒では強制点火により燃焼を行わせ、後続気筒では圧縮自己着火により燃焼を行わせるようにするとともに、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの中負荷域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より大きい値とし、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域のうちの上記中負荷域よりも低負荷側の運転域および上記中負荷域よりも高負荷側の運転域では、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とするように先行、後続の両気筒に対する燃料供給量を制御する燃焼状態制御手段を備えたことを特徴とする火花点火式４サイクルエンジンの制御装置。Combustion by forced ignition in the preceding cylinder while the air-fuel ratio at the time of combustion in the succeeding cylinder is substantially the stoichiometric air-fuel ratio in at least a part of the operation area in the special operation mode. In the operation range where the subsequent cylinder is subjected to compression self-ignition in the special operation mode, in the middle load region in the special operation mode, the combustion in the preceding cylinder is performed. The air-fuel ratio of the engine is set to a value larger than twice the theoretical air-fuel ratio, and the operation region on the lower load side than the intermediate load region in the operation region in which the subsequent cylinder is subjected to compression self-ignition in the special operation mode, and the intermediate load In the operating region on the higher load side than the region, the fuel for controlling the fuel supply amount to both the preceding and succeeding cylinders so that the air-fuel ratio at the time of combustion in the preceding cylinders is smaller than twice the theoretical air-fuel ratio. Control apparatus for a spark ignition type 4-cycle engine comprising the state control unit. エンジン温度が低いときには、上記特殊運転モードで後続気筒が圧縮自己着火とされる運転領域の全域で、先行気筒における燃焼の際の空燃比を理論空燃比の２倍より小さい値とすることを特徴とする請求項１又は２に記載の火花点火式４サイクルエンジンの制御装置。  When the engine temperature is low, the air-fuel ratio at the time of combustion in the preceding cylinder is set to a value smaller than twice the stoichiometric air-fuel ratio in the entire operation region in which the subsequent cylinder is subjected to compression self-ignition in the special operation mode. The control device for a spark ignition type four-cycle engine according to claim 1 or 2. 各気筒の燃焼サイクルが所定の位相差をもって行われるようになっている多気筒の火花点火式４サイクルエンジンにおいて、
エンジンの部分負荷域でエンジンの吸・排気及び燃焼状態についての制御モードを特殊運転モードとし、この特殊運転モードでは、排気行程と吸気行程が重なる一対の気筒間において排気行程にある先行気筒から排出される既燃ガスがそのまま吸気行程にある後続気筒に気筒間ガス通路を介して導入され、この後続気筒から排出されるガスが排気通路に導かれるような２気筒接続状態としつつ、先行気筒では空燃比が理論空燃比よりも大きいリーン空燃比で燃焼を行わせ、後続気筒では先行気筒から導入されたリーン空燃比の既燃ガスに燃料を供給して燃焼を行わせるようにした制御装置であって、
上記特殊運転モードとされる運転領域のうちの少なくとも一部の領域で、上記後続気筒における燃焼の際の空燃比が実質的に理論空燃比となるようにしつつ、先行気筒における燃焼の際の空燃比を、理論空燃比より大きくてその２倍以下となる範囲で、エンジン回転数が低いほど小さくするように、先行、後続の両気筒に対する燃料供給量を制御するとともに、先行気筒では強制点火により燃焼を行わせ、後続気筒では圧縮自己着火により燃焼を行わせるように制御する燃焼状態制御手段を備えたことを特徴とする火花点火式４サイクルエンジンの制御装置。In the multi-cylinder spark ignition type 4-cycle engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference,
The special operation mode is the control mode for engine intake / exhaust and combustion conditions in the partial load range of the engine. In this special operation mode, exhaust is performed from the preceding cylinder in the exhaust stroke between a pair of cylinders where the exhaust stroke and the intake stroke overlap. In the preceding cylinder, the burned gas is introduced into the succeeding cylinder in the intake stroke as it is through the inter-cylinder gas passage, and the gas discharged from the succeeding cylinder is led to the exhaust passage. It is a control device that performs combustion at a lean air-fuel ratio in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio, and in the subsequent cylinder, supplies fuel to the burned gas of the lean air-fuel ratio introduced from the preceding cylinder and performs combustion. There,
In at least a part of the operation region set to the special operation mode, the air-fuel ratio at the time of combustion in the subsequent cylinder is substantially the stoichiometric air-fuel ratio, while the air-fuel ratio at the time of combustion in the preceding cylinder is substantially reduced. The fuel supply amount to both the preceding and succeeding cylinders is controlled so as to decrease as the engine speed decreases within a range that is greater than the stoichiometric air-fuel ratio and less than twice that of the stoichiometric air-fuel ratio. A control apparatus for a spark ignition type four-cycle engine, comprising combustion state control means for controlling combustion so that combustion is performed by compression self-ignition in a subsequent cylinder.
JP2002185242A 2002-01-31 2002-06-25 Control device for spark ignition type 4-cycle engine Expired - Fee Related JP3972744B2 (en)

Priority Applications (13)

Application Number Priority Date Filing Date Title
JP2002185242A JP3972744B2 (en) 2002-06-25 2002-06-25 Control device for spark ignition type 4-cycle engine
PCT/JP2003/000961 WO2003064837A1 (en) 2002-01-31 2003-01-31 Control device for spark-ignition engine
DE60300437T DE60300437T2 (en) 2002-01-31 2003-01-31 DEVICE FOR REGULATING A RADIATED INTERNAL COMBUSTION ENGINE
DE60309098T DE60309098T8 (en) 2002-01-31 2003-01-31 DEVICE FOR REGULATING A RADIATED INTERNAL COMBUSTION ENGINE
KR10-2003-7014141A KR20040074591A (en) 2002-01-31 2003-01-31 Control device for spark-ignition engine
KR10-2003-7014146A KR20040074592A (en) 2002-01-31 2003-01-31 Spark ignition engine control device
EP03703109A EP1362176B1 (en) 2002-01-31 2003-01-31 Spark ignition engine control device
CNB038024594A CN100363609C (en) 2002-01-31 2003-01-31 Spark ignition engine control device
CNB03802487XA CN100368671C (en) 2002-01-31 2003-01-31 Spark ignition engine control device
US10/472,563 US7219634B2 (en) 2002-01-31 2003-01-31 Spark ignition engine control device
EP03703108A EP1366279B1 (en) 2002-01-31 2003-01-31 Control device for spark-ignition engine
PCT/JP2003/000962 WO2003064838A1 (en) 2002-01-31 2003-01-31 Spark ignition engine control device
US10/472,523 US7182050B2 (en) 2002-01-31 2003-01-31 Control device for spark-ignition engine

Applications Claiming Priority (1)

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JP2002185242A JP3972744B2 (en) 2002-06-25 2002-06-25 Control device for spark ignition type 4-cycle engine

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JP2004027961A JP2004027961A (en) 2004-01-29
JP3972744B2 true JP3972744B2 (en) 2007-09-05

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Publication number Priority date Publication date Assignee Title
JP4259255B2 (en) 2003-09-30 2009-04-30 マツダ株式会社 Control device for spark ignition engine

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