JP4045867B2 - Operation mode detection device and control device for spark ignition engine - Google Patents

Description

【００５０】
弁停止機構制御手段４２は、上記運転状態判別手段４１において判別されたエンジンの運転領域Ａ，Ｂ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。
【００５１】
この弁停止機構制御手段４２と、これにより制御される各弁停止機構３５とにより、吸気および排気の流通経路を後に詳述するように２気筒接続状態と各気筒独立状態とに切り換える経路切換手段が構成されている。
【００５２】
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、低負荷低回転側の運転領域Ａでは、後述のように後続気筒（２番、３番気筒２Ｂ，２Ｃ）に対する分岐吸気通路１６からの吸気導入が遮断された状態で、先行気筒（１番、４番気筒２Ａ，２Ｄ）から導入されるガス中の過剰空気が燃焼に供せられるように、先行気筒と後続気筒との２気筒分に相当する燃料を燃焼させるのに必要な量の空気が上記先行気筒に供給されるように、スロットル開度を調節する特殊運転モードの制御が実行される。
【００５３】
上記燃料噴射制御手段４４は、各気筒２Ａ〜２Ｄに設けられた燃料噴射弁９からの燃料噴射量およ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もので、特に運転状態が図４中の運転領域Ａにある特殊運転モードと、運転領域Ｂにある通常運転モードとに、燃料噴射の制御状態を変更するものであり、この燃料噴射制御手段４４と、上記吸入空気量制御手段４３とにより空燃比制御手段が構成されている。
【００５４】
すなわち、運転状態が低負荷低回転側の運転領域Ａにある特殊運転モードでは、先行気筒（１番、４番気筒２Ａ，２Ｄ）に対して、空燃比が理論空燃比よりも大幅にリーンな空燃比、例えば理論空燃比の略２倍もしくはそれ以上となるように燃料噴射量が制御されるとともに、圧縮行程で燃料が噴射されて成層燃焼が行われるように噴射タイミングが設定される。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燃料が供給されることにより、空燃比が理論空燃比となるように燃料噴射量が制御されるとともに、既燃ガスが多い状況下で着火、燃焼が可能なように噴射タイミングが設定され、例えば着火性確保のため圧縮行程で燃料が噴射されるようになっている。
【００５５】
上記燃料噴射量の制御は、エアフローセンサ１９およびＯ₂センサ２３等からの出力に基づくフィードバック制御により行われる。具体的には、先行気筒で所定のリーン空燃比、後続気筒で理論空燃比となるように、エアフローセンサ１９により検出される吸入空気量に応じてそれぞれの気筒に対する基本噴射量が演算されるとともに、気筒間ガス通路２２に設けられたリニアＯ₂センサ２５からの出力に基づいて先行気筒に対する燃料噴射量がフィードバック補正され、さらに排気通路２０に設けられたＯ₂センサ２３からの出力に基づいて後続気筒に対する燃料噴射量がフィードバック補正されるようになっている。
【００５６】
また、運転状態が高負荷側ないし高回転側の運転領域Ｂにある通常運転モードでは、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における大部分の領域で理論空燃比とし、全開負荷およ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することにより均一燃焼を行わせるように噴射タイミングを設定する。
【００５７】
上記経路判別手段５１は、エアフローセンサ１９により検出された吸気流量の変化状態と、回転数センサ４５により検出されたエンジン回転数とに応じ、エンジンのクランク軸一定角度だけ回転する間に発生する吸気脈動の回数を検出するとともに、この検出回数に基づいて吸気および排気の流通経路が上記各気筒独立状態にあるか２気筒接続状態にあるかを判別するように構成されている。すなわち、各気筒２Ａ〜２Ｄにそれぞれ新気が導入される各気筒独立状態では、エンジンのクランク軸が１回転する間に、４回の吸気脈動が発生するのに対し、先行気筒２Ａ，２Ｄのみに新気が導入される２気筒接続状態では、エンジンのクランク軸が１回転する間に、２回の吸気脈動が発生するだけであるため、この吸気脈動の検出回数を、予め設定された基準回数（例えば３回）と比較する等により、吸気および排気の流通経路が各気筒独立状態にあるか２気筒接続状態にあるかが判別されるようになっている。
【００５８】
また、上記始動時制御手段５２は、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあることが経路判別手段５１において確認された場合に、上記水温センサ４７の検出信号に応じてエンジンが冷間状態にあるか温間状態にあるかを判定し、エンジンが温間状態にあることが確認された場合には、上記吸気および排気の流通経路を切り換えることなく、上記特殊運転モードの制御を実行し、エンジンが冷間状態にあることが確認された場合には、上記弁停止機構制御手段４２および各弁停止機構３５からなる経路切換手段により、吸気および排気の流通経路を各気筒独立状態に切り換えて通常運転モードの制御を実行するように構成されている。
【００５９】
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。すなわち、エンジンの始動時を除く低負荷低回転側の運転領域Ａにおける特殊運転モードでは、前述のように第１排気弁３２ａおよび第１吸気弁３１ａが閉止状態、第２排気弁３２ｂおよび第２吸気弁３１ｂが作動状態とされることにより、実質的な吸気および排気の流通経路は図６に示すように、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から排出される既燃ガスのみが三元触媒２４を備えた排気通路２０に導かれる２気筒接続状態とされる。
【００６０】
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ではリニアＯ₂センサ２５により検出される空燃比が所定のリーン空燃比となるように燃料噴射量がフィードバック制御されつつ圧縮行程で燃料が噴射され、かつ、所定の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）。
【００６１】
その後、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気筒間ガス通路２２を通って後続気筒２Ｂ，２Ｃに導入される（図５中の白抜き矢印および図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、Ｏ₂センサ２３の出力に基づいて燃料噴射量が制御されつつ、適当なタイミング（例えば圧縮行程）で燃料が噴射され、かつ、所定の点火時期に点火が行われて燃焼が行われる（図５参照）。後続気筒２Ｂ，２Ｃでの燃焼後の既燃ガスは、三元触媒２４を備えた排気通路２０に排出される（図６中の矢印ｃ）。
【００６２】
このように、先行気筒２Ａ，２Ｄでは、大幅にリーンな空燃比での成層燃焼が行われることにより、熱効率が高められるとともにポンピングロスが低減され、これらの相乗効果で顕著に燃費が改善される。また、後続気筒２Ｂ，２Ｃでは、空気過剰状態の既燃ガスに対し燃料が供給されて理論空燃比に制御されつつ燃焼が行われることにより、先行気筒２Ａ，２Ｄのようにリーン空燃比で成層燃焼が行われるものと比べると熱効率では多少劣るものの、ポンピングロス低減による燃費改善効果は充分に得られる。
【００６３】
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。
【００６４】
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。
【００６５】
また、先行気筒２Ａ，２Ｄでは理論空燃比の略２倍もしくはそれ以上の大幅な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とともに、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。
【００６６】
一方、後続気筒２Ｂ，２Ｃには先行気筒２Ａ，２Ｄからの既燃ガスが気筒間ガス通路２２を介して導入されるが、この気筒間ガス通路２２で通路長に応じた放熱量が得られるため、この通路長を適正値に設定することにより、後続気筒２Ｂ，２Ｃに導入される既燃ガスの温度を調整することが可能である。そして、このように既燃ガスの温度を調整するとともに、後続気筒２Ｂ，２Ｃに対する燃料噴射タイミングを適宜調整することにより、多量の既燃ガスが導入される後続気筒２Ｂ，２Ｃにおいても、着火、燃焼性を良好に保つことができる。
【００６７】
なお、先行気筒２Ａ，２Ｄから後続気筒２Ｂ，２Ｃに導入されるガス中の過剰酸素の割合が少なくなると後続気筒２Ｂ，２Ｃでの燃焼安定性が損なわれるが、先行気筒２Ａ，２Ｄにおいて理論空燃比の略２倍もしくはそれ以上の大幅にリーンな空燃比とすれば、後続気筒２Ｂ，２Ｃでの燃焼安定性は確保される。
【００６８】
一方、エンジン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、前述のように第１排気弁３２ａおよび第１吸気弁３１ａが作動状態、第２排気弁３２ｂおよび第２吸気弁３１ｂが閉止状態とされることにより、実質的な吸気および排気の流通経路が図７に示すように、実質的に各気筒２Ａ〜２Ｄの吸気ポート３１，３１ａおよび排気ポート１２ａ，１２が独立し、分岐吸気通路１６を介して各気筒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に既燃ガスがそれぞれ排出される各気筒独立状態とされる。
【００６９】
上記のように各気筒２Ａ〜２Ｄの燃焼サイクルが所定の位相差をもつように設定されるとともに、各気筒２Ａ〜２Ｄをそれぞれ独立させて燃焼させる通常運転モードと、排気行程にある先行気筒２Ａ，２Ｄ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２Ｂ，２Ｃに導入して燃焼させる特殊運転モードとに、エンジンの運転状態に応じて運転モードを切り換えるように構成された多気筒の火花点火式エンジンにおいて、エンジンの高負荷側ないし高回転側の運転領域Ｂでは、吸気および排気の流通経路を各気筒独立状態として各気筒２Ａ〜２Ｄにそれぞれ新気を導入させるとともに、各気筒２Ａ〜２Ｄ内の空燃比を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および燃料噴射量を制御することにより、エンジンの運転状態に対応した出力性能を確保することができる。
【００７０】
そして、上記吸気通路１５に配設されて吸気の脈動を検出する吸気脈動検出手段（エアフローセンサ１９）の検出信号に応じて吸気および排気の流通経路が各気筒独立状態にあるか２気筒接続状態にあるかを判別する経路判別手段５１を備えた本発明に係る火花点火式のエンジンの制御装置では、上記吸気および排気の流通経路が、通常運転モードに対応した各気筒独立状態にあるか、特殊運転モードに対応した２気筒接続状態にあるかを上記経路判別手段５１において容易かつ正確に判別することができるとともに、この判別結果に対応した適正な運転モードの制御を実行することができる。
【００７１】
すなわち、エンジンのクランク軸が一定角度だけ回転する間に発生した吸気脈動の回数を検出するとともに、エンジンのクランク軸が一定角度だけ回転する間に発生した上記吸気脈動の検出回数と、予め設定された基準回数とを比較する等により、吸気および排気の流通経路が各気筒独立状態にあるか否かを正確に判別することができる。したがって、吸気および排気の流通経路を各気筒独立状態とすべき高負荷ないし高回転の運転領域Ｂで、上記流通経路切換手段の故障または応答遅れ等に起因して上記流通経路が２気筒接続状態にあることが上記経路判別手段５１において確認された場合に、上記通常運転モードの制御を実行することなく、先行気筒２Ａ，２Ｄにおいてリーン空燃比での成層燃焼が行われるとともに、後続気筒２Ｂ，２Ｃにおいて空気過剰状態の既燃ガスに対し燃料が供給されて理論空燃比に制御されつつ燃焼が行われる上記通常運転モードの燃焼状態とすることにより、上記流通経路と運転モードとが一致しないことに起因する弊害、例えば略理論空燃比で燃焼した先行気筒２Ａ，２Ｄの既燃ガスが後続気筒２Ｂ，２Ｃにそのまま導入されてこの後続気筒２Ｂ，２Ｃが失火状態となる等の弊害が発生するのを防止することができる。
【００７２】
逆に、吸気および排気の流通経路を２気筒接続状態とすべき低負荷ないし低回転の運転領域Ａで、上記流通経路切換手段の故障または応答遅れ等に起因して上記流通経路が各気筒独立状態にあることが上記経路判別手段５１において確認された場合には、上記特殊運転モードの制御を実行することなく、通常運転モードの燃焼状態として、各気筒２Ａ〜２Ｄ内の空燃比が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および燃料噴射量を制御することにより、上記流通経路と運転モードとが一致しないことに起因する弊害、例えば各気筒２Ａ〜２Ｄ内の空燃比がリーンになることに起因して排気ガス中のＮＯｘ量が増大する等の弊害が発生するのを防止できるという利点がある。
【００７３】
特に、上記実施形態では、各気筒２Ａ〜２Ｄにそれぞれ接続された分岐吸気通路１６の上流側部に位置する共通吸気通路１５ａに設けられた既存のエアフローセンサ１９の検出信号に応じ吸気脈動を検出するように構成したため、別体のセンサを設けることなく、簡単な構成で吸気および排気の流通経路が、通常運転モードに対応した各気筒独立状態にあるか、特殊運転モードに対応した２気筒接続状態にあるかを上記経路判別手段５１において容易かつ正確に判別することができる。しかも、上記エアフローセンサ１９からなる吸気流量検出手段、つまり吸気脈動検出手段は、音速で伝達される吸気脈動の変化状態を検出するものであるため、単位時間当たりに発生する吸気脈動の回数を迅速に検出できるという利点がある。
【００７４】
また、上記のようにエンジンの始動時に、エアフローセンサ（吸気脈動検出手段）１９から出力された検出信号に応じて吸気および排気の流通経路が各気筒独立状態にあるか、２気筒接続状態にあるかを経路判別手段５１において判別するとともに、この判別結果に対応した運転モードの制御を上記始動時制御手段５２において実行するように構成された本発明に係る火花点火式エンジンの制御装置によれば、始動時にエンジンが失火状態となるのを効果的に防止してエンジンの始動性を確保することができる。
【００７５】
すなわち、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあるとともに、エンジンが温間状態、つまり混合気が点火し易い状態にあることが確認された場合には、上記流通経路を切り換えることなく特殊運転モードの燃焼制御を実行するように構成したため、始動時にエンジンが失火状態となるのを防止しつつ、低負荷低回転のアイドル運転領域で上記特殊運転モードの燃焼制御を継続することにより、運転モードを頻繁に切り換える等の煩雑な制御を必要とすることなく、顕著な燃費の改善効果が得られるという利点がある。
【００７６】
一方、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあるとともに、エンジンが冷間状態、つまり混合気が点火しにくい状態にあることが確認された場合には、上記吸気および排気の流通経路を各気筒独立状態に切り換えて、通常運転モードの燃焼状態とすることにより、各気筒２Ａ〜２Ｄにそれぞれ新気を導入させるとともに、各気筒２Ａ〜２Ｄ内の空燃比を理論空燃比もしくはそれよりリッチとするように構成したため、上記混合気を確実に点火させて、その始動性を効果的に確保することができる。
【００７７】
また、エンジンの始動時に、吸気および排気の流通経路が各気筒独立状態にあることが上記経路判別手段５１において確認された場合には、エンジンが温間状態にあるか否かに拘わらず、上記流通経路を切り換えることなく、通常運転モードの燃焼状態とし、各気筒２Ａ〜２Ｄにそれぞれ新気を導入させるとともに、各気筒２Ａ〜２Ｄ内の空燃比を理論空燃比もしくはそれよりリッチとすることにより、エンジンの失火を防止して、その始動性を効果的に確保することができる。
【００７８】
なお、本発明に係る火花点火式エンジンの運転モード検出装置および同制御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。例えば上記基本実施形態では、共通吸気通路１５ａに設けられたエアフローセンサ１９からなる吸気流量検出手段により吸気流量の変動状態を検出することにより、吸気脈動を検出するようにしているが、吸気通路に設けられたブーストセンサにより吸気圧力の変動状態を検出し、この吸気圧力の変化状態に基づいて吸気脈動を検出するように構成してもよい。
【００７９】
また、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあるとともに、エンジンが冷間状態にあることが確認された場合に、吸気および排気の流通経路を各気筒独立状態に切り換えて通常運転モードの燃焼制御を実行するように構成された上記実施形態に代え、エンジン始動時における最初の燃焼制御時に先行気筒の燃焼を間引いて後続気筒を燃焼させるとともに、次回の燃焼制御時から先行気筒および後続気筒に噴射された燃料をそれぞれ燃焼させる特殊運転モードの燃焼状態とするように構成してもよい。
【００８０】
具体的には、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあることが確認された場合には、図８に示すように、エンジンの始動時における最初の燃焼制御時に先行気筒２Ａ，２Ｄへの燃料噴射Ｆ１を実行しつつ、その点火Ｓ１を禁止するようにしてもよい。このように構成した場合には、エンジンの始動時における最初の燃焼制御時に、先行気筒２Ａ，２Ｄに噴射された燃料が新気と充分に撹拌混合された状態で、後続気筒２Ｂ，２Ｃに供給されるとともに、この後続気筒２Ｂ，２Ｃに燃料噴射Ｆ２が行われた後に、点火Ｓ２が行われることになる。
【００８１】
したがって、エンジンの始動時に、後続気筒２Ｂ，２Ｃに多量の既燃ガスが導入されることに起因した失火の発生を効果的に防止することができるとともに、上記先行気筒２Ａ，２Ｄから後続気筒２Ｂ，２Ｃに供給された燃料（Ｆ１）および後続気筒２Ｂ，２Ｃ内に新た噴射された燃料（Ｆ２）が、新気と適正に混合された状態で、点火Ｓ２が行われることにより、混合気を確実に燃焼させてエンジンの始動性を確保することができる。そして、エンジンの始動時における次回の燃焼制御時から先行気筒２Ａ，２Ｄおよび後続気筒２Ｂ，２Ｃに対する噴射燃料Ｆ３，Ｆ４および点火Ｓ３，Ｓ４を行う特殊運転モードの燃焼状態とすることにより、各気筒２Ａ〜２Ｄを連続的に燃焼させてエンジンをスムーズに始動させることができるとともに、頻繁に運転モードを切り換える等の煩雑な制御を実行することなく、燃費の改善効果およびエミッションの向上効果が得られるという利点がある。
【００８２】
また、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあることが確認された場合には、エンジン始動時における最初の燃焼制御時に先行気筒２Ａ，２Ｄへの燃料噴射を実行しつつ、その点火を禁止することにより、先行気筒２Ａ，２Ｄの燃焼を間引くように構成された上記実施形態において、エンジン始動時における最初の燃焼制御時に先行気筒２Ａ，２Ｄへの燃料噴射Ｆ１を、図８の破線で示すように、気筒識別後で膨張行程から排気行程の初期までの間に行うようにしてもよい。このように構成した場合には、エンジンの始動時の早い段階で燃料噴射が行われることに起因して燃料の噴射圧力が低くなるという事態の発生を効果的に防止することができるため、先行気筒２Ａ，２Ｄへの燃料噴射量を正確に制御できるという利点がある。
【００８３】
また、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあることが確認された場合には、エンジン始動時における最初の燃焼制御時に先行気筒２Ａ，２Ｄへの燃料噴射を実行しつつ、その点火を禁止することにより燃焼を間引くように構成した上記実施形態に代え、図９に示すように、エンジン始動時における最初の燃焼制御時に先行気筒２Ａ，２Ｄへの燃料噴射Ｆ１をカットすることにより、先行気筒２Ａ，２Ｄの燃焼を間引くとともに、後続気筒２Ｂ，２Ｃ内の混合気濃度が略理論空燃比に対応した値となるように後続気筒２Ｂ，２Ｃへの燃料噴射Ｆ２を行う際の噴射量を制御するようにしてもよい。
【００８４】
上記の構成によっても、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあると上記経路判別手段５１において判別された場合には、先行気筒２Ａ，２Ｄに供給された新気をそのまま後続気筒２Ｂ，２Ｃに導入させるとともに、この後続気筒２Ｂ，２Ｃに導入された新気に適正量の燃料を噴射して混合気を確実に燃焼させることにより、上記後続気筒２Ｂ，２Ｃに大量の既燃ガスが導入されることに起因した失火の発生を防止しつつ、各気筒２Ａ〜２Ｄを連続的に燃焼させてエンジンをスムーズに始動させることができる。
【００８５】
上記のように各気筒２Ａ〜２Ｄの燃焼サイクルが所定の位相差をもつように設定されるとともに、各気筒２Ａ〜２Ｄをそれぞれ独立させて燃焼させる通常運転モードと、排気行程にある先行気筒２Ａ，２Ｄ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２Ｂ，２Ｃに導入して燃焼させる特殊運転モードとに、エンジンの運転状態に応じて運転モードを切り換えるように構成され、かつ排気通路２０に三元触媒２４が配設された多気筒の火花点火式エンジンにおいて、各気筒２Ａ〜２Ｄにそれぞれ接続された分岐吸気通路１６の上流側部に位置する共通吸気通路１５ａに設けられたエアフローセンサ１９からなる吸気流量検出手段と、エンジンの始動時に上記吸気流量検出手段の検出信号に応じてエンジンのクランク軸が一定角度だけ回転する間における吸気脈動の検出回数を検出するとともに、この検出回数に基づいて吸気および排気の流通経路が各気筒独立状態にあるか、２気筒接続状態にあるかを判別する経路判別手段５１と、エンジンの始動時に吸気および排気の流通経路が２気筒接続状態にあるとともに、エンジンが冷間状態にあることが上記経路判別手段５１において確認された場合に、エンジン始動時の最初の燃焼制御時における先行気筒２Ａ，２Ｄの燃焼を間引いて後続気筒２Ｂ，２Ｃを燃焼させるとともに、次回の燃焼制御時から先行気筒２Ａ，２Ｄおよび後続気筒２Ｂ，２Ｃに噴射された燃料をそれぞれ燃焼させる特殊運転モードの燃焼制御を実行する始動時制御手段５２とを設けた構成によると、例えばエンジンの低負荷低回転領域における燃費改善効果を損なうことなく、簡単な構成でＮＯｘの排出を効果的に防止することができる。
【００８６】
しかも、エンジンの高負荷高回転領域では、エンジン出力を充分に確保することができるとともに、上記吸気脈動の検出回数に基づいて吸気および排気の流通経路が各気筒独立状態にあるか、２気筒接続状態にあるかを上記経路判別手段５１において容易かつ正確に判別することができる。そして、エンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあると上記経路判別手段５１において判別されるとともに、エンジンの冷却水温度等に応じてエンジンが冷間状態にあることが確認された場合には、後続気筒２Ｂ，２Ｃに多量の既燃ガスが導入されることに起因した失火の発生を効果的に防止してエンジンの始動性を確保できるという利点がある。
【００８７】
なお、上記基本実施形態では弁停止機構３５を用いて経路切換手段を構成しているが、図１０に示すように、通路中に設けた開閉弁を用いて経路切換手段を構成してもよい。すなわち、図１０において、後続気筒である２番気筒２Ｂおよび３番気筒２Ｃの各第１吸気ポート１１ａに通じる分岐吸気通路１６に吸気側開閉弁４８ａ，４９ａが設けられるとともに、先行気筒である１番気筒２Ａおよび４番気筒２Ｄの各第１排気ポート１２ａに通じる分岐排気通路２１に排気側開閉弁４８ｂ，４９ｂが設けられ、さらに、１番気筒２Ａと２番気筒２Ｂとの間および４番気筒２Ｄと３番気筒２Ｃとの間の各気筒間ガス通路２２にガス通路開閉弁４８ｃ，４９ｃが設けられている。これらの開閉弁４８ａ，４９ａ，４８ｂ，４９ｂ，４８ｃ，４９ｃは、それぞれが設けられた通路を開通する状態と遮断する状態とに切換可能とされ、図外のアクチュエータにより作動されるようになっている。
【００８８】
そして、図外の制御手段により、運転状態が低負荷低回転側の運転領域Ａにある場合と高負荷側ないし高回転側の運転領域Ｂにある場合とに応じ、上記各開閉弁が次のように制御される。

【００８９】
運転領域ＡとＢとの間での運転状態の移行時において各開閉弁の状態を切り換える時の切換作動は、図１１中に示す切換可能期間内に行えばよい。つまり、一対の気筒の排気行程と吸気行程とが重なる期間中に各開閉弁の状態を切り換えると、後続気筒２Ｂ，２Ｃに先行気筒２Ａ，２Ｄからの既燃ガスと新気とが入り混じって導入される等の不具合が生じるので、１番気筒２Ａの排気行程と２番気筒２Ｂの吸気行程とが重なる期間を除いた期間内に開閉弁４８ａ，４８ｂ，４８ｃを切換作動させるとともに、４番気筒２Ｄの排気行程と３番気筒２Ｃの吸気行程とが重なる期間を除いた期間内に開閉弁４８ａ，４８ｂ，４８ｃを切換作動させるようにすればよい。
【００９０】
こうして、開閉弁４８ａ，４９ａ，４８ｂ，４９ｂ，４８ｃ，４９ｃとこれを制御する制御手段により経路切換手段が構成される。また、各気筒２Ａ〜２Ｄのポートに設けられた吸気弁３１、第１，第２排気弁３２ａ，３２ｂ、第１，第２吸気弁３１ａ，３１ｂおよび排気弁３２は、いずれも、図外の動弁機構により常に開閉作動されるようになっている。各燃料噴射弁９からの燃料噴射の制御等は上記実施形態と同様である。なお、図１０において、５０は吸気通路１５に設けられたスロットル弁である。
【００９１】
この実施形態によっても、運転領域Ａでは２気筒接続状態とされて、先行気筒２Ａ，２Ｄで超リーン燃焼が行われ、この先行気筒２Ａ，２Ｄから排出される既燃ガスが気筒間ガス通路２２を介して後続気筒２Ｂ，２Ｃに導入され、後続気筒２Ｂ，２Ｃで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された状態で燃焼が行われ、この後続気筒２Ｂ，２Ｃから排出されるガスのみが三元触媒２４を備えた排気通路２０に導かれる。一方、運転領域Ｂでは、各気筒２Ａ〜２Ｄの吸気ポートと排気ポートとが独立して、吸気通路１５から各気筒２Ａ〜２Ｄの吸気ポートに新気が導入されるとともに各気筒２Ａ〜２Ｄの排気ポートから排出される排気ガスが上記排気通路２０に導かれる。こうして、基本実施形態と同様の作用、効果が得られる。
【００９２】
また、当実施形態のような経路切換手段によれば、その構造が比較的簡単になるとともに、運転状態移行時における開閉弁の切換動作は図１１中に示すような切換可能期間内に行えばよく、切換タイミングに著しく高い精度が要求されることはないので、制御も容易である。
【００９３】
前述のように後続気筒２Ｂ，２Ｃで燃料を均一に分散させても着火性を確保し得る場合には、後続気筒２Ｂ，２Ｃに設ける燃料噴射弁は必ずしも気筒２Ｂ，２Ｃ内に直接燃料を噴射する直噴タイプに限定されず、例えば気筒間ガス通路２２を構成する後続気筒２Ｂ，２Ｃの吸気通路に、後続気筒２Ｂ，２Ｃに燃料を供給する燃料噴射弁を設けてもよい。この場合、後続気筒２Ｂ，２Ｃにおいては理論空燃比としつつ上記燃料噴射弁から吸気行程で燃料を噴射することにより均一燃焼を行わせるようにする。
【００９４】
このようにすると、先行気筒２Ａ，２Ｄから後続気筒２Ｂ，２Ｃに導入されるガスが適度に放熱されるとともに過剰空気と既燃ガスがミキシングされた理想的な多量のＥＧＲガス中に、このガスが後続気筒２Ｂ，２Ｃへ導入される過程で燃料が供給され、燃料の気化、さらにはこのガスとのミキシングが向上し、後続気筒２Ｂ，２Ｃにおいて多量のＥＧＲが行われつつ燃焼性がさらに向上する。
【００９５】
また、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。
【００９６】
図１２および図１３は、複数の気筒２Ａ〜２Ｄを有し、各気筒２Ａ〜２Ｄ内に燃料を直接噴射して吸気行程と排気行程との間に１回の燃焼を行う通常運転モードと、吸気行程と排気行程との間に２回の燃焼を行うように行程数を増加させる特殊運転モードとにエンジンの運転状態に応じて燃焼サイクルを切り換えるとともに、排気通路２０に排出される排気ガスの酸素濃度が略理論空燃比の燃焼状態に対応した値となるように上記吸気行程で各気筒２Ａ〜２Ｄ内に導入される吸気量および上記２回の燃焼を行うための燃料噴射量を制御するように構成され、かつ排気通路２０に三元触媒２４が配設された火花点火式エンジンの制御装置を示している。
【００９７】
上記各気筒２Ａ〜２Ｄの燃焼室４に対してそれぞれ一対の吸気ポート１１，１１および排気ポート１２，１２が開口し、これらのポート１１，１１，１２，１２が吸気弁３１，３１および排気弁３２，３２により開閉されるようになっている。そして、各気筒２Ａ〜２Ｄが所定の位相差、つまり４気筒エンジンの場合には、クランク角で１８０°ずつの位相差をもって所定の順番で燃焼が行われるようになっている。
【００９８】
上記吸・排気弁３１，３２は、それぞれ動弁機構５３により駆動されるように構成されている。この動弁機構５３は、図１３に示すように、非磁性材料からなるハウジング５４と、このハウジング５４内に摺動自在に配設されるとともに、上記吸・排気弁３１，３２と一体に連結されたアーマチュア・コア５５と、ハウジング３４内の上下両端部に配設された一対の電磁石５６，５７および戻しばね５８，５９とを備えている。そして、上方の電磁石５６に通電してアーマチュア・コア５５を上方に吸引することにより、吸気弁３１および排気弁３２をそれぞれ所定のタイミングで開放状態とし、下方の電磁石５７に通電してアーマチュア・コア５５を下方に吸引することにより、吸気弁３１および排気弁３２をそれぞれ所定のタイミングで閉止状態とするようになっている。
【００９９】
上記動弁機構５３等を制御する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、Ｏ₂センサ２３等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４５およびアクセル開度（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４６等からの信号も入力されている。
【０１００】
上記ＥＣＵ４０は、エンジンの運転状態を判別する運転状態判別手段４１、上記吸気弁３１および排気弁３２の開閉タイミングを制御する弁開閉制御手段６０と、エンジンの燃焼室４への吸入空気量を制御する吸入空気量制御手段４３と、燃料の噴射状態を制御する燃料噴射制御手段４４と、上記エアフローセンサ（吸気流量検出手段）１９により検出された吸気脈動に応じて吸気および排気の流通経路を判別する経路判別手段５１と、この経路判別手段５１の判別結果に応じて後述する始動時制御を実行する始動時制御手段５２とを備えている。
【０１０１】
上記弁開閉制御手段６０は、運転状態判別手段４１において判別されたエンジンの運転状態が低負荷ないし低回転側の運転領域Ａにある場合と、高負荷側ないし高回転側の運転領域Ｂにある場合とで、動弁機構５３に出力される制御信号の出力タイミングを変化させて吸気弁３１および排気弁３２の開閉タイミングを次のように制御するように構成されている。
【０１０２】
高負荷側ないし高回転側の運転領域Ｂでは、図１４（ａ）に示すように、燃料噴射（破線Ｆ）を伴う吸気行程ＩＮと、後期に点火Ｓを伴う圧縮行程と、燃焼を伴う膨張行程と、排気行程ＥＸとからなる通常運転モード、つまり吸気行程ＩＮと排気行程ＥＸとの間に一回の燃焼を行う一般的な４サイクルの燃焼制御を実行するように上記吸気弁３１および排気弁３２の開閉タイミングが設定される。なお、図１４において、Ｔはピストン行程の上死点、Ｂは下死点である。
【０１０３】
低負荷側ないし低回転側の運転領域Ａでは、図１４（ｂ）に示すように、吸気行程ＩＮ（第１行程）と、後期に燃料噴射Ｆおよび点火Ｓを伴う第１圧縮行程（第２行程）と、燃焼を伴う第１膨張行程（第３行程）と、第２圧縮行程（第４行程）と、燃焼を伴わない第２膨張行程（第５行程）と、後期に燃料噴射Ｆおよび点火Ｓを伴う第３圧縮行程（第６行程）と、燃焼を伴う第３膨張行程（第７行程）と、排気行程ＥＸ（第８行程）とからなる特殊運転モード、つまり吸気行程ＩＮと排気行程ＥＸとの間に二回の燃焼を行う８サイクルの燃焼制御を実行するように上記吸気弁３１および排気弁３２の開閉タイミングが設定される。
【０１０４】
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、予め設定されたマップ等から運転状態に対応した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とにより、吸入空気量を制御するように構成されている。
【０１０５】
すなわち、低負荷・低回転側の運転領域Ａにおいて実行される特殊運転モードでは、上記二回の燃焼後における排気行程ＥＸで排気通路２０に排出される排気ガスの既燃ガス濃度が、略理論空燃比の燃焼状態に対応した値となるようにスロットル開度が調節される。また、高負荷・高回転側の運転領域Ｂにおいて実行される通常運転モードでは、気筒２Ａ〜２Ｄ内の空燃比がλ≦１となるようにスロットル開度が調節される。
【０１０６】
上記燃料噴射制御手段４４は、各気筒２Ａ〜２Ｄに設けられた燃料噴射弁９からの燃料噴射量およ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もので、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にある場合とで燃料噴射の制御状態を変更するように構成されている。
【０１０７】
すなわち、低負荷・低回転側の運転領域Ａにおいて実行される特殊運転モードでは、図１４（ｂ）に示すように、第１膨張行程（第３行程）で行われる最初の燃焼が成層燃焼状態となるように、空燃比が理論空燃比よりも大きいリーン空燃比、好ましくは理論空燃比の略２倍もしくはそれ以上となるように第１圧縮行程（第２行程）の燃料噴射量を設定するとともに、燃料噴射Ｆのタイミングを設定する。また、上記最初の燃焼により生じたリーン空燃比の既燃ガス中に燃料を供給することにより、理論空燃比の条件下において第３膨張行程（第７行程）で２回目の燃焼が行われるように、燃料噴射量を制御するとともに、既燃ガスが多い状況下で着火、燃焼が可能なように燃料噴射Ｆのタイミングが設定され、例えば着火性確保のため第３圧縮行程（第６行程）で燃料噴射Ｆが行われる。
【０１０８】
なお、上記燃料噴射量の制御は、エアフローセンサ１９およびＯ₂センサ２３等からの出力に基づくフィードバック制御により行われる。
【０１０９】
一方、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、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、例えば上記運転領域Ｂの大部分の領域において理論空燃比とし、全開負荷およ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、この場合には、図１４（ａ）の破線で示すように、各気筒２Ａ〜２Ｄに対して吸気行程ＩＮ（第１行程）で燃料を噴射することにより均一燃焼を行わせるように燃料噴射Ｆのタイミングを設定する。
【０１１０】
また、上記経路判別手段５１および始動時切換手段５２は、図３に示す実施形態の経路判別手段５１および始動時制御手段５２と同様に構成されたものであり、吸気通路１５に配設されて吸気の脈動を検出する吸気脈動検出手段（エアフローセンサ１９）から出力された検出信号に応じ、エンジンの始動時に、通常運転モードの制御状態にあるか、特殊運転モードの制御状態にあるかを上記経路判別手段５１において判別し、かつこの経路判別手段５１の判別結果に応じて特殊運転モードの制御状態にあることが確認された場合には、エンジン始動時おける最初の燃焼制御時において、第１回目に噴射された燃料の点火を禁止する等の制御を上記始動時制御手段５２において実行するように構成されている。
【０１１１】
上記のように運転状態が低負荷側ないし低回転側の運転領域Ａにある場合に、吸気行程と排気行程との間に二回の燃焼が行われる特殊運転モードとし、第１膨張行程で行われる最初の燃焼を、リーン空燃比での成層燃焼状態とすることにより、熱効率が高められるとともにポンピングロスが低減され、これらの相乗効果で顕著に燃費が改善される。また、上記最初の燃焼により生成された空気過剰状態の既燃ガス中に燃料を供給して理論空燃比に制御しつつ、第３膨張行程において２回目の燃焼を行わせることにより、通常のエンジンのようにリーン空燃比で成層燃焼させるものと比べると熱効率では劣るものの、ポンピングロス低減による燃費効果は得られることになる。
【０１１２】
しかも、上記２回目の燃焼が行われた後に、排出行程で排気通路２０に排出される既燃ガスの濃度が理論空燃比に対応した値となるように構成することにより、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なり、三元触媒２４だけで充分に排気浄化性能が確保される。このようにリーンＮＯｘ触媒を設ける必要がないことから、リーンＮＯｘ触媒のＮＯｘ吸蔵量の増大時における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。
【０１１３】
上記のように特殊運転モードにおいて、吸気行程ＩＮと、第１圧縮行程と、燃焼を伴う第１膨張行程と、第２圧縮行程と、燃焼を伴わない第２膨張行程と、第３圧縮行程と、燃焼を伴う第３膨張行程と、排気行程ＥＸとからなる８サイクルの燃焼制御を実行することにより、吸気行程ＩＮと排気行程ＥＸとの間で２回の燃焼を行うように構成した実施形態に代え、図１４（ｃ）に示すように、吸気行程ＩＮと、第１圧縮行程と、燃焼を伴う第１膨張行程と、第２圧縮行程と、燃焼を伴う第３膨張行程と、排気行程ＥＸとからなる６サイクルの燃焼制御を実行することにより、吸気行程と排気行程との間で２回の燃焼を行うように構成してもよい。
【０１１４】
しかし、図１４（ａ）に示す４サイクルの燃焼状態と、図１４（ｃ）に示す６サイクルの燃焼状態とを比較すると、４サイクルの燃焼状態で吸気行程ＩＮとなる時期（第５行程）に、６サイクル燃焼状態では、燃焼を伴う第２膨張行程が実行される。このため、上記４サイクルの燃焼制御を実行する通常運転モードから、６サイクルの燃焼制御を実行する特殊運転モードに移行する際に、爆発時期がずれることに起因してエンジン回転が不安定になる等の問題が生じることになる。
【０１１５】
これに対して上記特殊運転モードで、吸気行程ＩＮと、第１圧縮行程と、燃焼を伴う第１膨張行程と、第２圧縮行程と、燃焼を伴わない第２膨張行程と、第３圧縮行程と、燃焼を伴う第３膨張行程と、排気行程ＥＸとからなる８サイクルの燃焼制御を実行するように構成した場合には、図１４（ａ）に示す通常運転モードにおける燃焼を伴う２番目の膨張行程（第７行程）と、特殊運転モードにおける燃焼を伴う第３膨張行程（第７行程）とが同時期となるため、運転モードの移行時に、爆発時期がずれることに起因してエンジンの回転が不安定になるという事態を生じることがなく、エンジンの運転状態に応じて４サイクルの燃焼制御状態から８サイクルの燃焼制御状態にスムーズに移行させることができるという利点がある。
【０１１６】
そして、上記のようにエンジンの始動時に、吸気および排気の流通経路が２気筒接続状態にあるか、各気筒独立状態にあるかを上記経路判別手段５１において判別し、２気筒接続状態にあることが確認された場合には、エンジン始動時の最初の燃焼制御時において、第１回目、つまり第２行程で噴射された燃料の点火を禁止することにより、多量の既燃ガスが存在下で２回目の燃焼が行われることに起因した失火の発生を効果的に防止できるとともに、第１回目に噴射された燃料をピストンの上下動に応じて燃焼室内の新気と充分に撹拌混合した状態で効果的に燃焼させることにより、エンジンの始動性を確保することができる。
【０１１７】
【発明の効果】
以上のように本発明は、ポンピングロス低減ならびに後続気筒でのポンピングロス低減等により、燃費を大幅に改善するとともに、三元触媒だけで充分な排気浄化作用を持たせることができるように構成された火花点火式エンジンにおいて、上記吸気通路に配設されて吸気の脈動を検出する吸気脈動検出手段の検出信号に応じて吸気および排気の流通経路が各気筒独立状態にあるか２気筒接続状態にあるか経路判別手段により判別するように構成したため、上記吸気および排気の流通経路が、通常運転モードに対応した各気筒独立状態にあるか、特殊運転モードに対応した２気筒接続状態にあるかを容易かつ正確に判別することができるとともに、この判別結果に対応した適正な運転モードの制御を実行することができるという利点がある。
【０１１８】
また、本発明は、上記エンジンの始動時に、吸気脈動検出手段から出力された検出信号に応じて吸気および排気の流通経路が各気筒独立状態にあるか、２気筒接続状態にあるかを経路判別手段において判別するとともに、この判別結果に対応した運転モードの制御を上記始動時制御手段において実行するように構成したため、エンジンの始動時に失火状態となるのを効果的に防止してエンジンの始動性を効果的に確保できるという利点がある。
【図面の簡単な説明】
【図１】本発明の一実施形態による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】運転領域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】低負荷低回転時の吸気および排気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吸気および排気の流通経路を示す説明図である。
【図８】エンジン始動時における各気筒の排気行程、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９】エンジン始動時における各気筒の排気行程、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１０】経路切換手段等の別の実施形態を示す概略平面図である。
【図１１】図１０の実施形態による場合の運転状態移行時の開閉弁の切換可能期間を示す説明図である。
【図１２】本発明の別の実施形態による装置を備えたエンジン全体の概略平面図である。
【図１３】図１２の実施形態における制御系とのブロック図である。
【図１４】図１２の実施形態における気筒の燃焼サイクル、燃焼噴射時期および点火時期を示す説明図である。
【符号の説明】
２Ａ〜２Ｄ 気筒
１５ 吸気通路
１９ エアフローセンサ（吸気脈動検出手段）
２０ 排気通路
２２ 気筒間ガス通路
２４ 三元触媒
３５ 弁停止機構（経路切換手段）
４０ ＥＣＵ
４１ 運転状態判別手段
４２ 弁停止機構制御手段（経路切換手段）
４３ 吸入空気量制御手段（空燃比制御手段）
４４ 燃料噴射制御手段（空燃比制御手段）
５１ 経路判別手段
５２ 始動時制御手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation mode detection device and a control device for a spark ignition engine.
[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 near the theoretical air-fuel ratio with respect to HC, CO, and NOx) 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, when 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 added during the expansion stroke in addition to the main combustion. By injecting, the air-fuel ratio of the exhaust gas is enriched and CO is generated, thereby promoting the separation and reduction of NOx.
[0004]
[Problems to be solved by the invention]
In an engine that performs the conventional lean operation as described above, it is necessary to provide the lean NOx catalyst in the exhaust passage in order to ensure NOx purification performance during the lean operation. A three-way catalyst is also required for exhaust purification in a region operated at a stoichiometric air-fuel ratio such as a high load region, and the lean NOx catalyst is provided in the exhaust passage in addition to the three-way catalyst. This lean NOx catalyst is disadvantageous in terms of cost because it requires a relatively large capacity in order to secure a certain amount of NOx adsorption and is expensive compared to a three-way catalyst.
[0005]
Moreover, in order to maintain the purification performance of the lean NOx catalyst, the NOx is temporarily removed by the removal of NOx, the supply of additional fuel for reduction, etc. at predetermined intervals such that the NOx adsorption amount increases as described above. It is necessary to frequently enrich the air-fuel ratio, thereby reducing the fuel efficiency improvement effect due to lean combustion.
[0006]
Furthermore, when the fuel used contains a large amount of sulfur, the lean NOx catalyst is susceptible to sulfur poisoning, and in order to eliminate this sulfur poisoning, regeneration processing such as heating the catalyst and supplying a reducing material is required. This may cause a reduction in fuel consumption improvement effect and a decrease in durability.
[0007]
Accordingly, the applicant of the present invention relates to a spark ignition engine control device that can improve the exhaust gas purification performance by using a three-way catalyst without the need for a lean NOx catalyst while providing the fuel efficiency improvement effect by lean combustion. (Japanese Patent Application No. 2002-024548).
[0008]
The present invention provides a spark ignition type engine operating mode detection device and a control device for the purpose of improving the combustibility at the time of starting the engine based on such a technique.
[0009]
[Means for Solving the Problems]
In the first aspect of the invention, the combustion cycle of each cylinder is set to have a predetermined phase difference, and the normal operation mode in which each cylinder is independently burned and the preceding cylinder in the exhaust stroke are discharged. Operation mode of a multi-cylinder spark ignition engine configured to switch the operation mode according to the operating state of the engine to the special operation mode in which the burned gas is introduced into the subsequent cylinder in the intake stroke and burned as it is In the special operation mode, the detection device In the state where intake introduction from the intake passage to the following cylinder is blocked Intake and exhaust are set to 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, and in each cylinder independent state in which fresh air is introduced into each cylinder in the normal operation mode. In the special operation mode, fuel is injected into the cylinder of the preceding cylinder to cause the air-fuel ratio to be in a lean state that is larger than the theoretical air-fuel ratio by a predetermined amount, and combustion is performed. An air-fuel ratio control means for controlling the air-fuel ratio in the cylinder to be substantially the stoichiometric air-fuel ratio by supplying burned gas and fuel having a lean air-fuel ratio derived from the preceding cylinder is disposed in the intake passage. Intake pulsation detecting means for detecting the pulsation of intake air, and the flow paths of intake and exhaust are in an independent state for each cylinder according to the detection signal output from the intake pulsation detecting means. Route determining means for determining whether the engine is in a connected state, and detecting whether the engine is in a control state of a normal operation mode or a special operation mode according to the determination data of the route determination means. is there.
[0010]
According to the above configuration, for example, in the low load and low rotation range of the engine, the combustion control in the special operation mode is executed in the connected state of the two cylinders, so that the preceding cylinder performs the combustion at the lean air-fuel ratio and the thermal efficiency is improved. The pumping loss is reduced and a remarkable fuel efficiency improvement effect is obtained, and the fuel is supplied to the burned gas of the lean air-fuel ratio introduced from the preceding cylinder in the succeeding cylinder, so that the stoichiometric air-fuel ratio is substantially obtained. Since combustion is performed in a state, at least a fuel efficiency effect by reducing pumping loss can be obtained. Further, the preceding cylinder performs combustion at a large lean air-fuel ratio, so that the amount of NOx generated is suppressed to be relatively small. In the succeeding cylinder, a large amount of EGR is performed by introducing burned gas from the preceding cylinder. Therefore, the generation of NOx is sufficiently suppressed, which is advantageous for improving the emission. Further, the high-temperature gas discharged from the preceding cylinder is appropriately radiated while passing through the inter-cylinder gas passage to adjust the temperature, and is mixed so that excess air and burned gas in this gas are uniformly dispersed. Since the fuel is injected into a relatively high temperature gas and the vaporization of the fuel is promoted by being introduced into the succeeding cylinder in a closed state, in the succeeding cylinder, Combustion is performed well. When the engine is started or when the operation mode is switched, it is easily and accurately determined whether the intake and exhaust flow paths are in an independent state of each cylinder or a connected state of two cylinders. At the same time, the appropriate operation mode control according to the determination result is executed.
[0011]
According to a second aspect of the present invention, in the spark ignition engine control device according to the first aspect, the path discriminating means is configured to take in intake air based on the number of intake pulsations detected while the crankshaft of the engine rotates by a predetermined angle. And whether the exhaust passage is in an independent state of each cylinder or in a connected state of two cylinders.
[0012]
According to the above configuration, the number of detections of intake pulsation that occurs while the crankshaft of the engine rotates by a certain angle, such as when the engine is started or when the operation mode is switched, is compared with a preset reference number. Therefore, it is possible to easily and accurately determine whether the intake and exhaust flow paths are in an independent state of each cylinder or in a connected state of the two cylinders based on the number of detected intake pulsations. Become.
[0013]
According to a third aspect of the present invention, in the spark ignition type engine control device according to the first or second aspect, the intake pulsation detecting means is located on the upstream side of a branch intake passage connected to each cylinder. It is constituted by intake flow rate detecting means provided in the intake passage.
[0014]
According to the above configuration, the crankshaft of the engine is kept at a constant angle when the engine is started or when the operation mode is switched according to the detection signal of the intake flow rate detection means including the existing airflow sensor provided in the common intake passage. The number of intake pulsations generated during rotation of the intake pulsation is detected, and the number of intake pulsations detected is compared with a preset reference number. Whether the flow path is in an independent state of each cylinder or in a connected state of two cylinders is easily and accurately determined by the path determining means.
[0015]
In the invention according to claim 4, the combustion cycle of each cylinder is set to have a predetermined phase difference, and the normal operation mode in which each cylinder is independently burned and the preceding cylinder in the exhaust stroke are discharged. Control device for a multi-cylinder spark ignition engine configured to switch the operation mode according to the operating state of the engine to a special operation mode in which the burned gas is introduced into the subsequent cylinder in the intake stroke and burned as it is In the special operation mode, each cylinder is in a two-cylinder connection state in which the burned gas of the preceding cylinder is introduced into the succeeding cylinder through the inter-cylinder gas passage, and fresh air is introduced into each cylinder in the normal operation mode. Path switching means for switching the intake and exhaust flow paths so as to be in an independent state, and in the special operation mode, by injecting fuel into the cylinder of the preceding cylinder The combustion is performed in a lean state in which the fuel ratio is larger than the stoichiometric air-fuel ratio by a predetermined amount, and the in-cylinder air-fuel ratio is reduced by supplying burned gas and fuel having a lean air-fuel ratio derived from the preceding cylinder to the subsequent cylinder. An air-fuel ratio control means for controlling the air-fuel ratio to be approximately the stoichiometric air-fuel ratio, an intake air pulsation detection means for detecting intake air pulsation, and an intake and exhaust air flow according to a detection signal output from the intake pulsation detection means when the engine is started Route discriminating means for discriminating whether the flow path is in an independent state of each cylinder or a connected state of two cylinders, and start-up control means for executing operation mode control corresponding to the discrimination result of the path discriminating means It is a thing.
[0016]
According to the above configuration, for example, in the low load and low rotation range of the engine, the combustion control in the special operation mode is executed in the connected state of the two cylinders, so that the preceding cylinder performs the combustion at the lean air-fuel ratio and the thermal efficiency is improved. The pumping loss is reduced and a remarkable fuel efficiency improvement effect is obtained, and the fuel is supplied to the burned gas of the lean air-fuel ratio introduced from the preceding cylinder in the succeeding cylinder, so that the stoichiometric air-fuel ratio is substantially obtained. Since combustion is performed in a state, at least a fuel efficiency effect by reducing pumping loss can be obtained. Further, the preceding cylinder performs combustion at a large lean air-fuel ratio, so that the amount of NOx generated is suppressed to be relatively small. In the succeeding cylinder, a large amount of EGR is performed by introducing burned gas from the preceding cylinder. Therefore, the generation of NOx is sufficiently suppressed, which is advantageous for improving the emission. Further, the high-temperature gas discharged from the preceding cylinder is appropriately radiated while passing through the inter-cylinder gas passage to adjust the temperature, and is mixed so that excess air and burned gas in this gas are uniformly dispersed. Since the fuel is injected into a relatively high temperature gas and the vaporization of the fuel is promoted by being introduced into the succeeding cylinder in a closed state, in the succeeding cylinder, Combustion is performed well. When the engine is started, the passage discriminating means easily and accurately discriminates whether the intake and exhaust flow paths are in an independent state of each cylinder or in a connected state of the two cylinders. In order to ensure startability of the engine, control of the operation mode corresponding to the state of the flow path is executed in the start time control means.
[0017]
The invention according to claim 5 is the apparatus according to claim 4, wherein when the engine is started, it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state and the engine is in the warm state. Performs combustion control in special operation mode without switching the intake and exhaust flow paths, and the engine is cold In When it is confirmed that there is, the combustion control in the normal operation mode is executed by switching the flow path of intake and exhaust to each cylinder independent state.
[0018]
According to the above configuration, when the engine is started, the passage determining means determines that the intake and exhaust flow paths are in the two-cylinder connection state, and the engine is brought into a warm state according to the engine coolant temperature or the like. If it is confirmed that the engine startability is not impaired even if the combustion control in the special operation mode is executed in this state, the intake and exhaust flow paths are not switched. Combustion control in the special operation mode is executed. Further, when the engine is started, the passage determining means determines that the intake and exhaust flow paths are in the two-cylinder connection state, and the engine is in a cold state according to the engine coolant temperature and the like. In If it is confirmed that the intake and exhaust flow paths are switched to the independent state of each cylinder and the combustion control in the normal operation mode is executed, the engine misfire is prevented and startability is ensured. Will be.
[0019]
According to a sixth aspect of the present invention, in the device according to the fourth aspect, when it is confirmed that the intake and exhaust flow paths are in a two-cylinder connection state when the engine is started, During combustion control, the combustion of the preceding cylinder is thinned out and the subsequent cylinder is burned, and the combustion state in the special operation mode in which the fuel injected into the preceding cylinder and the succeeding cylinder from the next combustion control is burned, respectively.
[0020]
According to the above configuration, when the passage discriminating unit determines that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, the combustion of the preceding cylinder is performed at the time of the first combustion control at the start of the engine. By thinning out, the occurrence of misfire due to the introduction of a large amount of burned gas into the succeeding cylinder is effectively prevented.
[0021]
According to a seventh aspect of the present invention, in the spark ignition engine control device according to the sixth aspect, when it is confirmed that the intake and exhaust flow paths are in a two-cylinder connection state when the engine is started, While performing fuel injection to the preceding cylinder at the time of the first combustion control at the time of starting the engine, the ignition is prohibited to thin out the combustion of the preceding cylinder.
[0022]
According to the above configuration, when the passage discriminating unit determines that the intake and exhaust flow paths are in the two-cylinder connection state when the engine is started, the fuel is injected into the preceding cylinder at the time of the first combustion control at the time of engine start. The mixed fuel is sufficiently agitated and mixed with the intake air, and is supplied to the succeeding cylinder and ignited in an unignited state.
[0023]
The invention according to claim 8 is the spark ignition type engine control device according to claim 7, wherein when the engine is started, it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state. The fuel injection timing to the preceding cylinder at the time of the first combustion control at the time of engine start is set between the latter half of the expansion stroke and the initial stage of the exhaust stroke.
[0024]
According to the above configuration, when the passage discriminating unit determines that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, the first cylinder is controlled to the preceding cylinder at the time of initial combustion control at the time of starting the engine. By setting the fuel injection timing between the second half of the expansion stroke and the beginning of the exhaust stroke, fuel with sufficiently high fuel pressure is injected into the preceding cylinder, and this fuel is sufficiently stirred with the intake air. In a mixed state, it is supplied to the subsequent cylinder.
[0025]
The invention according to claim 9 is the spark ignition type engine control device according to claim 6, wherein when the engine is started, it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state. By cutting the fuel injection to the preceding cylinder at the time of the first combustion control at the start of the engine, the combustion of the preceding cylinder is thinned out and the mixture concentration in the succeeding cylinder becomes a value substantially corresponding to the stoichiometric air-fuel ratio. The fuel injection amount to the cylinder is controlled.
[0026]
According to the above configuration, when the passage discriminating unit determines that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, the first cylinder is controlled to the preceding cylinder at the time of initial combustion control at the time of starting the engine. By cutting the fuel injection, the occurrence of misfire due to the introduction of a large amount of burned gas into the subsequent cylinder is prevented, and the combustibility in the subsequent cylinder is effectively ensured.
[0027]
In the invention according to claim 10, the combustion cycle of each cylinder is set to have a predetermined phase difference, and the normal operation mode in which each cylinder is independently burned and the preceding cylinder in the exhaust stroke are discharged. It is configured to switch the operation mode according to the operating state of the engine to the special operation mode in which the burned gas is introduced into the subsequent cylinder in the intake stroke and burned, and a three-way catalyst is arranged in the exhaust passage A multi-cylinder spark-ignition engine control apparatus, comprising: an intake flow rate detecting means provided in a common intake passage located upstream of a branch intake passage connected to each cylinder; The number of detections of intake pulsation during the rotation of the crankshaft of the engine by a certain angle is detected according to the detection signal of the intake flow rate detection means, and Accordingly, the route discriminating means for discriminating whether the intake and exhaust flow paths are in an independent state of each cylinder or the connected state of the two cylinders, and the intake and exhaust flow paths are in the connected state of the two cylinders when the engine is started The engine is cold In There is Is certain If it is recognized, the combustion of the preceding cylinder at the time of the first combustion control at the time of starting the engine is thinned and the subsequent cylinder is burned, and the fuel injected into the preceding cylinder and the succeeding cylinder from the next combustion control is burned respectively. And a starting-time control means for executing the combustion control in the special operation mode.
[0028]
According to the above configuration, for example, in the low load and low rotation range of the engine, the combustion control in the special operation mode is executed in the connected state of the two cylinders, so that the preceding cylinder performs the combustion at the lean air-fuel ratio and the thermal efficiency is improved. The pumping loss is reduced and a significant fuel efficiency improvement effect is obtained, and the fuel is supplied to the burned gas of the lean air-fuel ratio introduced from the preceding cylinder in the subsequent cylinder, so that the stoichiometric air-fuel ratio is substantially obtained. By performing combustion in the state, at least a fuel efficiency effect by reducing pumping loss can be obtained. Further, the preceding cylinder performs combustion at a large lean air-fuel ratio, so that the amount of NOx generated is suppressed to be relatively small. In the succeeding cylinder, a large amount of EGR is performed by introducing burned gas from the preceding cylinder. Therefore, the generation of NOx is sufficiently suppressed, which is advantageous for improving the emission. The high-temperature gas discharged from the preceding cylinder is appropriately radiated while passing through the inter-cylinder gas passage to adjust the temperature, and is mixed so that excess air and burned gas in this gas are evenly dispersed. In this state, the exhaust passage is ideal for a large amount of EGR, and only the burned gas having a substantially stoichiometric air-fuel ratio discharged from the succeeding cylinder is provided with a three-way catalyst. Therefore, exhaust purification performance is sufficiently ensured only with the three-way catalyst. When the engine is started, the number of intake pulsations that occur while the crankshaft of the engine rotates by a certain angle according to the detection signal of the intake flow rate detection means including the existing airflow sensor provided in the common intake passage is determined. Whether the intake and exhaust flow paths are in an independent state of each cylinder based on the detected number of intake pulsations, for example, by comparing the detected number of intake pulsations with a preset reference number. Whether the connection state is established is easily and accurately determined by the route determination means, and when the engine is started, the passage determination means determines that the intake and exhaust flow paths are in the two-cylinder connection state, and the engine The engine is cold depending on the coolant temperature etc. In If it is confirmed that there is a misfiring due to the introduction of a large amount of burned gas into the succeeding cylinder, the combustion of the preceding cylinder is thinned out during the initial combustion control at the start of the engine. This effectively prevents the engine startability.
[0029]
The invention according to claim 11 is a normal operation mode in which fuel is directly injected into the combustion chamber and combustion is performed once between the intake stroke and the exhaust stroke, and combustion is performed twice between the intake stroke and the exhaust stroke. The combustion cycle is switched according to the operating state of the engine to the special operation mode in which the number of strokes is increased so as to perform the operation, and the oxygen concentration of the exhaust gas discharged to the exhaust passage corresponds to the combustion state of the substantially stoichiometric air-fuel ratio. The intake air amount introduced into the cylinder in the intake stroke and the fuel injection amount for performing the two combustions are controlled so as to be a value, and a three-way catalyst is disposed in the exhaust passage A spark ignition type engine control device, which is provided in an intake passage to detect intake air pulsation, and in response to a detection signal output from the intake pulsation detection means when the engine is started. Driving mode Mode discriminating means for discriminating whether the engine is in the control state or the control state of the special operation mode, and when it is confirmed that the control state of the special operation mode is in accordance with the discrimination result of the discrimination means, the engine During the initial combustion control at the start, ignition of the fuel injected for the first time is prohibited.
[0030]
According to the above configuration, the combustion control in the special operation mode is executed in the low load and low rotation region of the engine, so that the combustion is performed twice between the intake stroke and the exhaust stroke, and the pumping loss is reduced. The fuel efficiency improvement effect is obtained by the reduction, and at the time of shifting to the high load and high speed operation region, the engine output is shifted from the combustion control state of the special operation mode to the combustion control state of the normal operation mode. Is secured. When the passage discriminating unit determines that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, the first injection is performed at the time of the first combustion control at the time of starting the engine. By prohibiting ignition of the fuel, the occurrence of misfiring due to the second combustion being performed in the presence of a large amount of burned gas is effectively prevented.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
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 main body 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.
[0032]
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.
[0033]
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, and opens. An amount of fuel corresponding to the valve opening 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 is supplied with fuel higher than the pressure in the combustion chamber during the compression stroke. A system is configured.
[0034]
Further, intake ports 11, 11 a, 11 b and exhaust ports 12, 12 a, 12 b open to the combustion chambers 4 of the respective cylinders 2 </ b> A to 2 </ b> D, and branched intake passages 16 and exhaust passages branched from the intake passage 15 to these ports. A branch exhaust passage 21 branched from 20 is connected, and the ports are opened and closed by intake valves 31, 31a, 31b and exhaust valves 32, 32a, 32b provided at the ports. .
[0035]
The combustion cycle of each of the cylinders 2A to 2D including the strokes of intake, compression, expansion and exhaust is set to have a predetermined phase difference. When referring to No. 2 cylinder 2A, No. 2 cylinder 2B, No. 3 cylinder 2C, No. 4 cylinder 2D, as shown in FIG. 5, No. 1 cylinder 2A, No. 3 cylinder 2C, No. 4 cylinder 2D and No. 2 cylinder 2B The combustion cycle is set so that the crank angle has a phase difference of 180 ° in this order. In FIG. 5, EX represents an exhaust stroke, IN represents an intake stroke, F represents fuel injection, and S represents ignition.
[0036]
Between a pair of cylinders in which the exhaust stroke and the intake stroke overlap, a cylinder on the intake stroke side (referred to herein as a preceding cylinder) from the cylinder on the exhaust stroke side when the exhaust stroke and the intake stroke overlap (this specification) The inter-cylinder gas passage 22 is provided so that the burned gas can be directly introduced to the subsequent cylinder). 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 air of the third cylinder 2C. In the four-cylinder engine of this embodiment set so that the stroke (IN) overlaps, the first cylinder 2A and the second cylinder 2B make a pair, and the fourth cylinder 2D and the third cylinder 2C make a pair, The first cylinder 2A and the fourth cylinder 2D are the preceding cylinders, the second cylinder 2B and the third cylinder 2C are the subsequent cylinders.
[0037]
The first cylinder 2A and the fourth cylinder 2D, which are the preceding cylinders, are provided with a pair of intake ports 11 and 11 for introducing fresh air supplied through the intake passage 15 and burned gas (exhaust gas), respectively. A first exhaust port 12a for discharging to the exhaust passage 20 and a second exhaust port 12b for discharging burned gas to the second cylinder 2B and the third cylinder 2C, which are subsequent cylinders, are provided.
[0038]
The second cylinder 2B and the third cylinder 2C, which are the subsequent cylinders, are a pair of first intake ports 11a and 11a for introducing fresh air supplied through the intake passage 15, respectively, and a preceding cylinder. A second intake port 11b for introducing burned gas from the first cylinder 2A and the fourth cylinder 2D and an exhaust port 32 for discharging the burned gas to the exhaust passage 20 are provided.
[0039]
In the example shown in FIG. 1, the first and fourth cylinders 2 </ b> A and 2 </ b> D, which are the preceding cylinders, and the second and third cylinders 2 </ b> B and 2 </ b> C, which are the subsequent cylinders, A port 11 and a first intake port 11a are provided in parallel. A first exhaust port 12a and a second exhaust port 12b are provided in parallel on the right half of the combustion chamber 4 of the first and fourth cylinders 2A and 2D, and the second and third cylinders 2B. , 2C, a second intake port 11b and an exhaust port 12 are provided in parallel on the right half side of the combustion chamber 4.
[0040]
The intake ports 11 in the first and fourth cylinders (preceding cylinders) 2A and 2D and the first intake ports 11a in the second and third cylinders (subsequent cylinders) 2B and 2C are connected to the branched intake passages for each cylinder in the intake passage 15. The downstream end of 16 is connected. In the vicinity of the downstream end of each branch intake passage 16, a multiple throttle valve 17 that is interlocked with each other via a common shaft is provided, and when this multiple throttle valve 17 is driven by an actuator 18, the intake air The amount is adjusted. An air flow sensor 19 for detecting the intake air flow rate is provided in the common intake passage 15a upstream of the collecting portion in the intake passage 15.
[0041]
The first exhaust port 12a in the first and fourth cylinders (preceding cylinders) 2A and 2D and the exhaust port 12 in the second and third cylinders 2B and 2C (subsequent cylinders) include a branch exhaust passage for each cylinder in the exhaust passage 20. The upstream end of 21 is connected. 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. The upstream end of the inter-cylinder gas passage 22 is connected to the second exhaust ports 12b of the first and fourth cylinders 2A and 2D as the preceding cylinders, and the second and third cylinders 2B and 2C as the subsequent cylinders are connected. The downstream end of the inter-cylinder gas passage 22 is connected to the second intake port 11b.
[0042]
An exhaust gas concentration detecting means for detecting the stoichiometric air-fuel ratio is provided at the downstream portion of the branch exhaust passage 21 in the exhaust passage 20. ₂ A sensor 23 is provided, and a three-way catalyst 24 for exhaust purification is provided in the exhaust passage 20 downstream thereof. As is generally known, the three-way catalyst 24 is highly purified with respect to HC, CO, and NOx when the air-fuel ratio of the exhaust gas is near the stoichiometric air-fuel ratio (that is, the excess air ratio λ is λ = 1). It is a catalyst showing performance. The above O ₂ The sensor 23 detects the air-fuel ratio by detecting the oxygen concentration in the exhaust gas, and particularly the λO whose output changes suddenly near the stoichiometric air-fuel ratio. ₂ It is composed of sensors.
[0043]
The inter-cylinder gas passage 22 has a linear O whose output changes linearly in response to a change in oxygen concentration (change in air-fuel ratio) in the exhaust gas. ₂ A sensor 25 (exhaust gas concentration detection means for detecting a lean air-fuel ratio) is provided.
[0044]
The intake / exhaust valves that open and close the intake / exhaust ports of the cylinders and the valve operating mechanisms for these valves are configured as follows. In other words, the intake port 11, the first exhaust port 12a, and the second exhaust port 12b in the first and fourth cylinders 2A, 2D are provided with the intake valve 31, the first exhaust valve 32a, and the second exhaust valve 32b, respectively. The first intake port 11a, the second intake port 11b and the exhaust port 12 in the second and third cylinders 2B and 2C are provided with a first intake valve 31a, a second intake valve 31b and an exhaust valve 32, respectively. . These intake / exhaust valves are opened and closed at predetermined timings by valve mechanisms having 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.
[0045]
Further, among the intake / exhaust valves, for the first exhaust valve 32a, the second exhaust valve 32b, the first intake valve 31a and the second intake valve 31b, valves for switching each valve between an operating state and a closed state. A 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.
[0046]
A first control valve 37 is provided in the hydraulic oil supply / discharge passage 36 for the valve stop mechanism 35 of the first exhaust valve 32a and the valve stop mechanism 35 of the first intake valve 31a, and the second exhaust valve 32b. A second control valve 39 is provided in each of the hydraulic oil supply / discharge passages 38 to the valve stop mechanism 35 and the valve stop mechanism 35 of the second intake valve 31b (see FIG. 3).
[0047]
FIG. 3 shows the configuration of the engine drive and control system. In this figure, an engine control ECU (engine control unit) 40 comprising a microcomputer or the like is provided with an air flow sensor 19, O ₂ Sensor 23 and linear O ₂ A signal from the sensor 25 is input, and further, a rotational speed sensor 45 for detecting the engine rotational speed in order to determine an operating state, an accelerator opening sensor 46 for detecting an accelerator opening (accelerator pedal depression amount), and engine coolant A signal from a water temperature sensor 47 for detecting the temperature is 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 37 and 39, respectively.
[0048]
The ECU 40 includes an operation state determination unit 41 that determines the operation state of the engine, a valve stop mechanism control unit 42 that controls the valve stop mechanism 35, and an intake air amount control that controls the intake air amount into the combustion chamber 4 of the engine. As will be described later, the flow paths of intake and exhaust are discriminated according to the means 43, the fuel injection control means 44 for controlling the fuel injection state, and the intake air pulsation detected by the air flow sensor (intake flow rate detecting means) 19. A route discriminating means 51 and a start-time control means 52 for executing a start-time control to be described later according to the discrimination result of the path discriminating means 51 are provided.
[0049]
The operating state discriminating means 41 discriminates the operating state of the engine corresponding to the engine speed, the engine load and the like based on the signals from the rotational speed sensor 45 and the accelerator opening sensor 46. Specifically, it is determined whether or not the low load or low rotation side operation region A, the high load side or high rotation side operation region B or the engine is in the starting state as shown in FIG. Yes.

[0050]
The valve stop mechanism control means 42 controls each of the control valves 37 and 39 according to the engine operating areas A and B determined by the operating state determination means 41, whereby each valve stop mechanism 35 is controlled as follows. To control.
[0051]
By this valve stop mechanism control means 42 and each valve stop mechanism 35 controlled thereby, a path switching means for switching the intake and exhaust flow paths between a two-cylinder connected state and an individual cylinder independent state as will be described in detail later. Is configured.
[0052]
The intake air amount control means 43 controls the opening degree of the throttle valve 17 (throttle opening degree) by controlling the actuator 18, and obtains a target intake air amount from a map or the like according to the operating state. The throttle opening is controlled according to the target intake air amount. In this case, in the operation region A on the low-load / low-rotation side, as described later, in the state in which the intake of air from the branch intake passage 16 to the subsequent cylinders (second and third cylinders 2B and 2C) is blocked, The amount necessary to burn the fuel corresponding to the two cylinders of the preceding cylinder and the succeeding cylinder so that excess air in the gas introduced from the first and fourth cylinders 2A, 2D) is used for combustion. The special operation mode for adjusting the throttle opening is executed so that the air is supplied to the preceding cylinder.
[0053]
The fuel injection control means 44 controls the fuel injection amount and the injection timing from the fuel injection valve 9 provided in each of the cylinders 2A to 2D in accordance with the operating state of the engine. The control state of the fuel injection is changed between a special operation mode in the operation region A and a normal operation mode in the operation region B. The fuel injection control means 44 and the intake air amount control means 43 Air-fuel ratio control means is configured.
[0054]
That is, in the special operation mode in which the operation state is in the operation region A on the low load low rotation side, the air-fuel ratio is significantly leaner than the stoichiometric air-fuel ratio with respect to the preceding cylinders (the first cylinder, the fourth cylinder 2A, 2D). The fuel injection amount is controlled so that the air-fuel ratio, for example, approximately twice or more than the theoretical air-fuel ratio, and the injection timing is set so that fuel is injected in the compression stroke and stratified combustion is performed. On the other hand, for the subsequent cylinders (second and third cylinders 2B and 2C), the air-fuel ratio becomes the stoichiometric air-fuel ratio by supplying fuel to the burned gas having a lean air-fuel ratio introduced from the preceding cylinder. In this way, the fuel injection amount is controlled, and the injection timing is set so that ignition and combustion are possible in a situation where there is a lot of burned gas. For example, fuel is injected in the compression stroke to ensure ignitability. ing.
[0055]
The fuel injection amount is controlled by the air flow sensor 19 and the O ₂ This is performed by feedback control based on the output from the sensor 23 or the like. Specifically, the basic injection amount for each cylinder is calculated according to the intake air amount detected by the airflow sensor 19 so that the preceding cylinder has a predetermined lean air-fuel ratio and the succeeding cylinder has a stoichiometric air-fuel ratio. The linear O provided in the inter-cylinder gas passage 22 ₂ Based on the output from the sensor 25, the fuel injection amount for the preceding cylinder is feedback-corrected, and an O provided in the exhaust passage 20 is further corrected. ₂ Based on the output from the sensor 23, the fuel injection amount for the subsequent cylinder is feedback-corrected.
[0056]
Further, in the normal operation mode in which the operation state is in the operation region B on the high load side or the high rotation side, the fuel injection amount is controlled so that the air-fuel ratio of each cylinder 2A to 2D is the theoretical air-fuel ratio or less. The stoichiometric air-fuel ratio is set in most of the operating region B, and is made richer than the stoichiometric air-fuel ratio in the fully open load and the operating region in the vicinity thereof. In this case, the injection timing is set so that uniform combustion is performed by injecting fuel to each of the cylinders 2A to 2D in the intake stroke.
[0057]
The path discriminating means 51 generates intake air that is generated while rotating by a certain angle of the crankshaft of the engine according to the change state of the intake air flow rate detected by the air flow sensor 19 and the engine speed detected by the speed sensor 45. The number of pulsations is detected, and based on the number of detections, it is determined whether the intake and exhaust flow paths are in the cylinder independent state or the two-cylinder connected state. That is, in each cylinder independent state in which fresh air is introduced into each of the cylinders 2A to 2D, four intake pulsations occur while the crankshaft of the engine rotates once, whereas only the preceding cylinders 2A and 2D In the two-cylinder connected state in which fresh air is introduced into the engine, only two intake pulsations occur while the crankshaft of the engine makes one rotation. By comparing with the number of times (for example, three times), it is determined whether the flow path of intake and exhaust is in an independent state of each cylinder or in a connected state of two cylinders.
[0058]
Further, the start time control means 52 is a path determination means that the intake and exhaust flow paths are in a two-cylinder connection state when the engine is started. 5 1 is confirmed, it is determined whether the engine is in a cold state or a warm state according to the detection signal of the water temperature sensor 47, and it is confirmed that the engine is in a warm state. The control of the special operation mode is executed without switching the intake and exhaust flow paths, and when it is confirmed that the engine is in a cold state, the valve stop mechanism control means 42 and each valve By the path switching means comprising the stop mechanism 35, the flow path of intake and exhaust is switched to an independent state of each cylinder, and control in the normal operation mode is executed.
[0059]
The operation of the apparatus of the present embodiment as described above will be described with reference to FIGS. That is, in the special operation mode in the operation region A on the low load low rotation side excluding when the engine is started, as described above, the first exhaust valve 32a and the first intake valve 31a are in the closed state, and the second exhaust valve 32b and the second exhaust valve 32a. When the intake valve 31b is activated, the substantial intake and exhaust flow paths are as shown in FIG. 6, and the burnt gas discharged from the preceding cylinders (first and fourth cylinders) 2A and 2D is reduced. As it is introduced into the subsequent cylinders (second and third cylinders) 2B and 2C through the inter-cylinder gas passage 22, only the burned gas discharged from the subsequent cylinders 2B and 2C is provided with the three-way catalyst 24. A two-cylinder connection state led to the exhaust passage 20 is established.
[0060]
In this state, fresh air is introduced into the preceding cylinders 2A and 2D from the intake passage 15 during the intake stroke (arrow a in FIG. 6), and linear O is detected in the preceding cylinders 2A and 2D. ₂ The fuel is injected in the compression stroke while the fuel injection amount is feedback controlled so that the air-fuel ratio detected by the sensor 25 becomes a predetermined lean air-fuel ratio, and ignition is performed at a predetermined ignition timing, so that the lean air-fuel ratio is achieved. The stratified combustion is performed at (see FIG. 5).
[0061]
Thereafter, the burned gas discharged from the preceding cylinders 2A and 2D passes through the inter-cylinder gas passage 22 during the 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, the fuel is supplied to the burned gas having the lean air-fuel ratio introduced from the preceding cylinders 2A and 2D so that the stoichiometric air-fuel ratio is obtained. ₂ While the fuel injection amount is controlled based on the output of the sensor 23, fuel is injected at an appropriate timing (for example, a compression stroke), and ignition is performed at a predetermined ignition timing to perform combustion (see FIG. 5). . The burned gas after combustion in the succeeding cylinders 2B and 2C is discharged to the exhaust passage 20 provided with the three-way catalyst 24 (arrow c in FIG. 6).
[0062]
In this way, in the preceding cylinders 2A and 2D, stratified combustion is performed at a significantly lean air-fuel ratio, so that the thermal efficiency is increased and the pumping loss is reduced, and the fuel efficiency is remarkably improved by their synergistic effect. . Further, in the succeeding cylinders 2B and 2C, fuel is supplied to the burned gas in an excess air state and combustion is performed while being controlled to the stoichiometric air-fuel ratio, so that stratification is performed at a lean air-fuel ratio as in the preceding cylinders 2A and 2D. Although the thermal efficiency is somewhat inferior to that in which combustion is performed, the fuel efficiency improvement effect by reducing the pumping loss can be sufficiently obtained.
[0063]
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 to exhaust the gas. Purification performance is ensured.
[0064]
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.
[0065]
Further, the preceding cylinders 2A and 2D have a lean air / fuel ratio that is substantially twice or more than the stoichiometric air / fuel ratio, so that the amount of NOx generated is suppressed to a relatively low level. In the succeeding cylinders 2B and 2C, the preceding cylinder 2A Since the burned gas is introduced from 2D, the state becomes equivalent to that in which a large amount of EGR is performed, so that the generation of NOx is sufficiently suppressed. This is also advantageous for improving emissions.
[0066]
On the other hand, the burned gas from the preceding cylinders 2A and 2D is introduced into the succeeding cylinders 2B and 2C through the inter-cylinder gas passage 22, and a heat radiation amount corresponding to the passage length is obtained in the inter-cylinder gas passage 22. Therefore, it is possible to adjust the temperature of the burned gas introduced into the succeeding cylinders 2B and 2C by setting the passage length to an appropriate value. In addition, by adjusting the temperature of the burned gas in this way and appropriately adjusting the fuel injection timing for the subsequent cylinders 2B and 2C, the subsequent cylinders 2B and 2C into which a large amount of burned gas is introduced are also ignited, Good combustibility can be maintained.
[0067]
Note that if the ratio of excess oxygen in the gas introduced from the preceding cylinders 2A and 2D to the succeeding cylinders 2B and 2C decreases, the combustion stability in the succeeding cylinders 2B and 2C is impaired. Combustion stability in the succeeding cylinders 2B and 2C is ensured if the air-fuel ratio is substantially lean, approximately twice or more than the fuel ratio.
[0068]
On the other hand, when the engine is in the operation region B on the high load side or the high rotation side, 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. By closing 31b, the intake and exhaust ports 31 and 31a and the exhaust ports 12a and 12 of each cylinder 2A to 2D are substantially independent, as shown in FIG. The fresh air is introduced into the intake ports 31 and 31a of the cylinders 2A to 2D through the branch intake passage 16, and the burned gas is discharged from the exhaust ports 31 and 31a of the cylinders 2A to 2D into the exhaust passage 20, respectively. Each cylinder is in an independent state.
[0069]
As described above, the combustion cycle of each of the cylinders 2A to 2D is set to have a predetermined phase difference, the normal operation mode in which each of the cylinders 2A to 2D is burned independently, and the preceding cylinder 2A in the exhaust stroke. The multi-cylinder is configured to switch the operation mode to the special operation mode in which the burned gas discharged from 2D is directly introduced into the subsequent cylinders 2B and 2C in the intake stroke to be burned. In the spark ignition type engine, in the operation region B on the high load side or high rotation side of the engine, the intake and exhaust flow paths are made independent of each cylinder, and fresh air is introduced into each cylinder 2A to 2D. By controlling the intake air amount and the fuel injection amount so that the air-fuel ratio in 2A to 2D becomes the stoichiometric air-fuel ratio or richer than that, It is possible to secure an output performance ready for a rolling state.
[0070]
Then, according to the detection signal of the intake pulsation detecting means (air flow sensor 19) that is disposed in the intake passage 15 and detects the pulsation of the intake air, the flow path of intake and exhaust is in an independent state for each cylinder or a two-cylinder connected state In the spark ignition type engine control device according to the present invention having the path discrimination means 51 for discriminating whether or not the engine is in the cylinder independent state corresponding to the normal operation mode, Whether or not the two-cylinder connection state corresponding to the special operation mode is established can be easily and accurately determined by the route determination means 51, and control of the appropriate operation mode corresponding to the determination result can be executed.
[0071]
That is, the intake pulsation that occurs while the crankshaft of the engine rotates by a certain angle Detect count In addition, by comparing the number of intake pulsations detected while the crankshaft of the engine is rotated by a certain angle with a preset reference number, the intake and exhaust flow paths are made independent of each cylinder. It can be accurately determined whether or not there is. Therefore, in the high load or high speed operation region B where the intake and exhaust flow paths should be in an independent state for each cylinder, the flow path is in a two-cylinder connection state due to a failure of the flow path switching means or a response delay. Is confirmed in the path discriminating means 51, the stratified combustion is performed at the lean air-fuel ratio in the preceding cylinders 2A, 2D without executing the control in the normal operation mode, and the succeeding cylinders 2B, 2B, In 2C, when the fuel is supplied to the burned gas in excess air and the combustion is performed while being controlled at the stoichiometric air-fuel ratio, the flow path does not match the operation mode. For example, the burned gas of the preceding cylinders 2A and 2D burned at a substantially stoichiometric air-fuel ratio is directly introduced into the succeeding cylinders 2B and 2C. B, 2C is an adverse effect, such as a misfire condition can be prevented from occurring.
[0072]
On the contrary, in the low load or low speed operation region A where the intake and exhaust flow paths should be connected to the two cylinders, the flow paths are independent of each cylinder due to a failure of the flow path switching means or a response delay. When it is confirmed by the path discrimination means 51 that the state is in the state, the air-fuel ratio in each of the cylinders 2A to 2D is set to the theoretical sky as the combustion state in the normal operation mode without executing the control in the special operation mode. By controlling the intake air amount and the fuel injection amount so that the fuel ratio or the fuel ratio becomes richer, adverse effects caused by the mismatch between the flow path and the operation mode, for example, the air-fuel ratio in each cylinder 2A to 2D becomes lean Therefore, there is an advantage that adverse effects such as an increase in the amount of NOx in the exhaust gas can be prevented.
[0073]
In particular, in the above-described embodiment, the existing airflow provided in the common intake passage 15a located on the upstream side of the branch intake passage 16 connected to each of the cylinders 2A to 2D. Sensor Since the intake pulsation is detected in response to the 19 detection signals, the intake and exhaust flow paths are in a cylinder independent state corresponding to the normal operation mode with a simple configuration without providing a separate sensor. The route discriminating means 51 can easily and accurately determine whether the two-cylinder connection state corresponding to the special operation mode is in effect. Moreover, the above air flow Sensor The intake air flow rate detecting means 19, that is, the intake pulsation detecting means, detects the change state of the intake pulsation transmitted at the speed of sound, so that the number of intake pulsations occurring per unit time can be detected quickly. There is.
[0074]
Further, as described above, when the engine is started, the intake and exhaust flow paths are in an independent state for each cylinder or in a two-cylinder connected state in accordance with the detection signal output from the air flow sensor (intake pulsation detecting means) 19. According to the control device for the spark ignition engine according to the present invention, which is configured to execute the control of the operation mode corresponding to the determination result in the start time control means 52, in the route determination means 51. Thus, it is possible to effectively prevent the engine from being misfired at the start, and to ensure the startability of the engine.
[0075]
That is, when it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state and the engine is in a warm state, that is, the air-fuel mixture is easily ignited when the engine is started. The combustion control in the special operation mode is performed without switching the engine, so the combustion control in the special operation mode is continued in the low load and low rotation idle operation region while preventing the engine from being misfired at the start. By doing so, there is an advantage that a significant fuel efficiency improvement effect can be obtained without requiring complicated control such as frequent switching of operation modes.
[0076]
On the other hand, when it is confirmed that the intake and exhaust flow paths are in a two-cylinder connection state and the engine is in a cold state, that is, in a state in which the air-fuel mixture is difficult to ignite, when the engine is started, By switching the exhaust flow path to the independent state of each cylinder and setting the combustion state in the normal operation mode, fresh air is introduced into each of the cylinders 2A to 2D, and the air-fuel ratio in each of the cylinders 2A to 2D is calculated theoretically. Since the air-fuel ratio is set to be richer than that, the air-fuel mixture can be reliably ignited and its startability can be effectively ensured.
[0077]
In addition, when the path discrimination means 51 confirms that the intake and exhaust flow paths are in an independent state for each cylinder when the engine is started, regardless of whether the engine is in a warm state or not. By switching to the normal operation mode without switching the flow path, introducing fresh air into each of the cylinders 2A-2D, and making the air-fuel ratio in each cylinder 2A-2D richer than the stoichiometric air-fuel ratio The engine can be prevented from misfire and its startability can be effectively ensured.
[0078]
The specific configurations of the operation mode detection device and the control device for the spark ignition engine according to the present invention are not limited to the above-described embodiment, and can be variously changed. For example, in the basic embodiment described above, the intake air pulsation is detected by detecting the fluctuation state of the intake air flow rate by the intake air flow rate detecting means including the air flow sensor 19 provided in the common intake passage 15a. A fluctuation state of the intake pressure may be detected by a provided boost sensor, and the intake pulsation may be detected based on the change state of the intake pressure.
[0079]
In addition, when the engine is started, the intake and exhaust flow paths are in a 2-cylinder connection state, and the engine is in a cold state. In In the case where it is confirmed that the combustion path in the normal operation mode is executed by switching the intake and exhaust flow paths to the independent state of each cylinder, the first combustion at the time of engine start is performed. The combustion of the preceding cylinder is thinned out at the time of control and the subsequent cylinder is combusted, and the combustion state of the special operation mode in which the fuel injected into the preceding cylinder and the succeeding cylinder is combusted from the time of the next combustion control may be set. Good.
[0080]
Specifically, when it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, as shown in FIG. 8, prior to the first combustion control at the time of starting the engine. The ignition S1 may be prohibited while performing the fuel injection F1 to the cylinders 2A and 2D. In such a configuration, the fuel injected into the preceding cylinders 2A and 2D is supplied to the succeeding cylinders 2B and 2C in a state in which the fuel injected into the preceding cylinders 2A and 2D is sufficiently agitated and mixed with the fresh air at the time of the first combustion control at the start of the engine. At the same time, after the fuel injection F2 is performed on the succeeding cylinders 2B and 2C, the ignition S2 is performed.
[0081]
Accordingly, it is possible to effectively prevent the occurrence of misfire due to the introduction of a large amount of burned gas into the succeeding cylinders 2B and 2C at the start of the engine, and also from the preceding cylinders 2A and 2D to the succeeding cylinders 2B. , 2C and the fuel (F2) newly injected into the succeeding cylinders 2B, 2C are properly mixed with fresh air, and ignition S2 is performed, whereby the air-fuel mixture is reduced. It is possible to ensure combustion and ensure engine startability. Each cylinder is set to a combustion state in a special operation mode in which injected fuels F3 and F4 and ignition S3 and S4 are performed on the preceding cylinders 2A and 2D and the succeeding cylinders 2B and 2C from the next combustion control at the time of starting the engine. The engine can be started smoothly by continuously burning 2A to 2D, and the fuel efficiency improvement effect and the emission improvement effect can be obtained without executing complicated control such as frequently switching the operation mode. There is an advantage.
[0082]
Further, when it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, the fuel injection to the preceding cylinders 2A and 2D is executed during the first combustion control at the time of starting the engine. However, in the above embodiment configured to thin out the combustion of the preceding cylinders 2A and 2D by prohibiting the ignition, the fuel injection F1 to the preceding cylinders 2A and 2D at the time of the first combustion control at the time of engine start is As indicated by a broken line in FIG. 8, the process may be performed after the cylinder identification and from the expansion stroke to the initial stage of the exhaust stroke. In such a configuration, it is possible to effectively prevent the occurrence of a situation in which the fuel injection pressure becomes low due to the fuel injection being performed at an early stage when the engine is started. There is an advantage that the fuel injection amount to the cylinders 2A and 2D can be accurately controlled.
[0083]
Further, when it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state at the time of starting the engine, the fuel injection to the preceding cylinders 2A and 2D is executed during the first combustion control at the time of starting the engine. However, instead of the above-described embodiment configured to thin out the combustion by prohibiting the ignition, as shown in FIG. 9, the fuel injection F1 to the preceding cylinders 2A and 2D is cut at the time of the first combustion control at the time of starting the engine. Thus, the combustion of the preceding cylinders 2A and 2D is thinned out, and the fuel injection F2 to the succeeding cylinders 2B and 2C is performed so that the mixture concentration in the succeeding cylinders 2B and 2C becomes a value substantially corresponding to the theoretical air-fuel ratio. The injection amount at the time may be controlled.
[0084]
Even with the above-described configuration, when the passage discriminating means 51 determines that the intake and exhaust flow paths are in the two-cylinder connection state when the engine is started, the fresh air supplied to the preceding cylinders 2A and 2D is removed. A large amount is introduced into the succeeding cylinders 2B and 2C by injecting an appropriate amount of fuel into the fresh air introduced into the succeeding cylinders 2B and 2C and burning the air-fuel mixture with certainty. The engine can be started smoothly by continuously burning each of the cylinders 2A to 2D while preventing the occurrence of misfire due to the introduction of the burned gas.
[0085]
As described above, the combustion cycle of each of the cylinders 2A to 2D is set to have a predetermined phase difference, the normal operation mode in which each of the cylinders 2A to 2D is burned independently, and the preceding cylinder 2A in the exhaust stroke. , 2D is configured to switch the operation mode to the special operation mode in which the burned gas discharged from 2D is directly introduced into the subsequent cylinders 2B and 2C in the intake stroke and burned, and the exhaust gas is exhausted. In the multi-cylinder spark ignition type engine in which the three-way catalyst 24 is disposed in the passage 20, the common intake passage 15a is provided on the upstream side of the branch intake passage 16 connected to each of the cylinders 2A to 2D. Intake flow rate detection means comprising an air flow sensor 19 and the engine crankshaft at a constant angle according to the detection signal of the intake flow rate detection means when the engine is started The route discriminating means 51 detects the number of intake pulsations detected during the rotation and determines whether the intake and exhaust flow paths are in an independent state of each cylinder or in a connected state of the two cylinders based on the detected number of times. When the engine starts, the intake and exhaust flow paths are in the 2-cylinder connection state, and the engine is in the cold state. In When it is confirmed by the route discriminating means 51 that the preceding cylinders 2A and 2D at the time of the first combustion control at the time of starting the engine are thinned, the subsequent cylinders 2B and 2C are burned, and at the next combustion control time. According to the configuration provided with the start time control means 52 for executing the combustion control in the special operation mode in which the fuel injected from the first cylinder 2A, 2D and the second cylinder 2B, 2C is combusted, for example, low engine load and low rotation NOx emissions can be effectively prevented with a simple configuration without impairing the fuel efficiency improvement effect in the region.
[0086]
In addition, in the high-load and high-rotation region of the engine, the engine output can be sufficiently secured, and the intake and exhaust flow paths are in an independent state of each cylinder based on the number of times of detection of the intake pulsation. The route discriminating means 51 can easily and accurately discriminate whether it is in a state or not. When the engine is started, the passage discriminating means 51 determines that the intake and exhaust flow paths are in the two-cylinder connection state, and the engine is in a cold state according to the engine coolant temperature and the like. In When it is confirmed that there is an advantage, it is possible to effectively prevent misfire caused by introducing a large amount of burned gas into the succeeding cylinders 2B and 2C, and to ensure the startability of the engine. .
[0087]
In the basic embodiment, the path switching unit is configured by using the valve stop mechanism 35. However, as shown in FIG. 10, the path switching unit may be configured by using an on-off valve provided in the passage. . That is, in FIG. 10, intake side on-off valves 48a and 49a are provided in the branch intake passages 16 leading to the first intake ports 11a of the second cylinder 2B and the third cylinder 2C, which are the subsequent cylinders, and the first cylinder 1 Exhaust-side on / off valves 48b and 49b are provided in the branch exhaust passage 21 leading to the first exhaust ports 12a of the No. 2 cylinder and the No. 4 cylinder 2D, and further between the No. 1 cylinder 2A and the No. 2 cylinder 2B and No. 4 Gas passage opening / closing valves 48c and 49c are provided in each inter-cylinder gas passage 22 between the cylinder 2D and the third cylinder 2C. These on-off valves 48a, 49a, 48b, 49b, 48c, and 49c can be switched between a state in which the respective passages are opened and a state in which they are blocked, and are operated by an actuator not shown in the drawing. Yes.
[0088]
Then, according to the control means (not shown), each of the on-off valves is operated as follows depending on whether the operation state is in the operation region A on the low load / low rotation side or the operation region B on the high load side or the high rotation side. To be controlled.

[0089]
The switching operation at the time of switching the state of each on-off valve at the time of transition of the operation state between the operation areas A and B may be performed within the switchable period shown in FIG. That is, when the state of each on-off valve is switched during the period in which the exhaust stroke and the intake stroke of the pair of cylinders overlap, the succeeding cylinders 2B and 2C are mixed with burned gas and fresh air from the preceding cylinders 2A and 2D. Since troubles such as introduction occur, the on-off valves 48a, 48b, and 48c are switched and operated during the period excluding the period in which the exhaust stroke of the first cylinder 2A and the intake stroke of the second cylinder 2B overlap. The on-off valves 48a, 48b, and 48c may be switched and operated within a period excluding a period in which the exhaust stroke of the cylinder 2D and the intake stroke of the third cylinder 2C overlap.
[0090]
Thus, the path switching means is constituted by the on-off valves 48a, 49a, 48b, 49b, 48c, 49c and the control means for controlling them. Further, the intake valve 31, the first and second exhaust valves 32a and 32b, the first and second intake valves 31a and 31b, and the exhaust valve 32 provided at the ports of the respective cylinders 2A to 2D are all not shown. It is always opened and closed by a valve mechanism. Control of fuel injection from each fuel injection valve 9 is the same as in the above embodiment. In FIG. 10, 50 is a throttle valve provided in the intake passage 15.
[0091]
Also in this embodiment, in the operation region A, the two cylinders are connected, super lean combustion is performed in the preceding cylinders 2A, 2D, and the burned gas discharged from the preceding cylinders 2A, 2D is the inter-cylinder gas passage 22. Is introduced into the succeeding cylinders 2B and 2C, and fuel is supplied to the burned gas having a lean air-fuel ratio in the succeeding cylinders 2B and 2C to achieve the stoichiometric air-fuel ratio, and the succeeding cylinders 2B and 2C are combusted. Only the gas discharged from the exhaust gas is guided to the exhaust passage 20 provided with the three-way catalyst 24. On the other hand, in the operation region B, the intake ports and exhaust ports of the respective cylinders 2A to 2D are independent, and fresh air is introduced from the intake passage 15 to the intake ports of the respective cylinders 2A to 2D and the respective cylinders 2A to 2D. Exhaust gas discharged from the exhaust port is guided to the exhaust passage 20. Thus, the same operation and effect as the basic embodiment can be obtained.
[0092]
Further, according to the route switching means as in the present embodiment, the structure becomes relatively simple, and the switching operation of the on-off valve at the time of shifting to the operating state is performed within the switchable period as shown in FIG. Since the switching timing is not required to have a very high accuracy, the control is easy.
[0093]
As described above, when ignitability can be ensured even if fuel is uniformly dispersed in the succeeding cylinders 2B and 2C, the fuel injection valve provided in the succeeding cylinders 2B and 2C does not necessarily inject fuel directly into the cylinders 2B and 2C. For example, a fuel injection valve for supplying fuel to the succeeding cylinders 2B and 2C may be provided in the intake passage of the succeeding cylinders 2B and 2C constituting the inter-cylinder gas passage 22. In this case, in the succeeding cylinders 2B and 2C, uniform combustion is performed by injecting fuel through the intake stroke from the fuel injection valve while maintaining the stoichiometric air-fuel ratio.
[0094]
In this way, the gas introduced into the succeeding cylinders 2B and 2C from the preceding cylinders 2A and 2D is appropriately radiated, and this gas is contained in an ideal amount of EGR gas in which excess air and burned gas are mixed. Is supplied in the process of being introduced into the succeeding cylinders 2B and 2C, fuel vaporization and further mixing with the gas are improved, and a large amount of EGR is performed in the succeeding cylinders 2B and 2C, and the combustibility is further improved. To do.
[0095]
The apparatus of the present invention can also be applied to multi-cylinder engines other than four cylinders. 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.
[0096]
12 and 13 each have a plurality of cylinders 2A to 2D, a normal operation mode in which fuel is directly injected into each cylinder 2A to 2D and combustion is performed once between the intake stroke and the exhaust stroke, The combustion cycle is switched in accordance with the operating state of the engine to a special operation mode in which the number of strokes is increased so that combustion is performed twice between the intake stroke and the exhaust stroke, and the exhaust gas discharged to the exhaust passage 20 is changed. The intake air amount introduced into each of the cylinders 2A to 2D in the intake stroke and the fuel injection amount for performing the two combustions are controlled so that the oxygen concentration becomes a value corresponding to the combustion state of the substantially stoichiometric air-fuel ratio. The control device for a spark ignition engine in which the three-way catalyst 24 is arranged in the exhaust passage 20 is shown.
[0097]
A pair of intake ports 11, 11 and exhaust ports 12, 12 open to the combustion chamber 4 of each of the cylinders 2 </ b> A to 2 </ b> D, and these ports 11, 11, 12, 12 serve as intake valves 31, 31 and exhaust valves. Opened and closed by 32, 32. When the cylinders 2A to 2D are a predetermined phase difference, that is, in the case of a four-cylinder engine, combustion is performed in a predetermined order with a phase difference of 180 ° in crank angle.
[0098]
The intake / exhaust valves 31 and 32 are configured to be driven by a valve operating mechanism 53, respectively. As shown in FIG. 13, the valve mechanism 53 is slidably disposed in a housing 54 made of a non-magnetic material and is integrally connected to the intake / exhaust valves 31 and 32. The armature core 55 and a pair of electromagnets 56 and 57 and return springs 58 and 59 disposed at both upper and lower ends in the housing 34 are provided. Then, by energizing the upper electromagnet 56 and attracting the armature core 55 upward, the intake valve 31 and the exhaust valve 32 are opened at predetermined timings, respectively, and the lower electromagnet 57 is energized to energize the armature core. By suctioning 55 downward, each of the intake valve 31 and the exhaust valve 32 is closed at a predetermined timing.
[0099]
An ECU (control unit) 40 for controlling the engine, which is a microcomputer for controlling the valve mechanism 53 or the like, includes an air flow sensor 19, an O ₂ A signal from the sensor 23 or the like is input, and a signal from an engine speed sensor 45 for detecting the engine speed and an accelerator opening sensor 46 for detecting the accelerator opening (accelerator pedal depression amount) in order to determine the operating state. Is also entered.
[0100]
The ECU 40 controls the operating state determining means 41 for determining the operating state of the engine, the valve opening / closing control means 60 for controlling the opening / closing timing of the intake valve 31 and the exhaust valve 32, and the intake air amount to the combustion chamber 4 of the engine. Intake air amount control means 43, fuel injection control means 44 for controlling the fuel injection state, and air flow sensor (intake flow rate detection means) 19 determine the intake and exhaust flow paths according to the intake air pulsations detected And a start time control means 52 that executes a start time control to be described later according to the determination result of the route determination means 51.
[0101]
The valve opening / closing control means 60 is in the operation region A on the low load or low rotation side and in the operation region B on the high load side or high rotation side when the operation state of the engine determined by the operation state determination means 41 is. Depending on the case, the output timing of the control signal output to the valve operating mechanism 53 is changed to control the opening / closing timing of the intake valve 31 and the exhaust valve 32 as follows.
[0102]
In the operation region B on the high load side or the high rotation side, as shown in FIG. 14A, the intake stroke IN with fuel injection (broken line F), the compression stroke with ignition S in the later stage, and the expansion with combustion The intake valve 31 and the exhaust gas so as to execute a normal four-cycle combustion control in which a single combustion is performed between the intake stroke IN and the exhaust stroke EX in a normal operation mode consisting of a stroke and an exhaust stroke EX. The opening / closing timing of the valve 32 is set. In FIG. 14, T is the top dead center of the piston stroke, and B is the bottom dead center.
[0103]
In the operation region A on the low load side or the low rotation side, as shown in FIG. 14B, the intake stroke IN (first stroke) and the first compression stroke (second stroke) with the fuel injection F and the ignition S in the latter period are performed. Stroke), a first expansion stroke with combustion (third stroke), a second compression stroke (fourth stroke), a second expansion stroke without combustion (fifth stroke), and later fuel injection F and Special operation mode consisting of a third compression stroke (sixth stroke) with ignition S, a third expansion stroke (seventh stroke) with combustion, and an exhaust stroke EX (eighth stroke), that is, intake stroke IN and exhaust The opening / closing timings of the intake valve 31 and the exhaust valve 32 are set so as to execute 8-cycle combustion control in which combustion is performed twice during the stroke EX.
[0104]
The intake air amount control means 43 controls the opening degree of the throttle valve 17 (throttle opening degree) by controlling the actuator 18, and the target intake air amount corresponding to the operating state from a preset map or the like. And the intake air amount is controlled by controlling the throttle opening according to the target intake air amount.
[0105]
That is, in the special operation mode executed in the operation region A on the low load / low rotation side, the burned gas concentration of the exhaust gas discharged into the exhaust passage 20 in the exhaust stroke EX after the two combustions is substantially theoretical. The throttle opening is adjusted so as to have a value corresponding to the combustion state of the air-fuel ratio. Further, in the normal operation mode executed in the operation region B on the high load / high rotation side, the throttle opening is adjusted so that the air-fuel ratio in the cylinders 2A to 2D becomes λ ≦ 1.
[0106]
The fuel injection control means 44 controls the fuel injection amount and the injection timing from the fuel injection valve 9 provided in each of the cylinders 2A to 2D in accordance with the operating state of the engine. The control state of the fuel injection is changed between when in the operation region A and when in the operation region B.
[0107]
That is, in the special operation mode executed in the operation region A on the low load / low rotation side, as shown in FIG. 14B, the first combustion performed in the first expansion stroke (third stroke) is the stratified combustion state. The fuel injection amount in the first compression stroke (second stroke) is set so that the air-fuel ratio is greater than the stoichiometric air-fuel ratio, preferably approximately twice or more than the stoichiometric air-fuel ratio. At the same time, the timing of the fuel injection F is set. Further, by supplying the fuel into the burned gas having the lean air-fuel ratio generated by the first combustion, the second combustion is performed in the third expansion stroke (seventh stroke) under the theoretical air-fuel ratio condition. In addition, the fuel injection amount is controlled, and the timing of the fuel injection F is set so that ignition and combustion can be performed in a situation where there is a large amount of burned gas. Then, fuel injection F is performed.
[0108]
The fuel injection amount is controlled by the air flow sensor 19 and the O ₂ This is performed by feedback control based on the output from the sensor 23 or the like.
[0109]
On the other hand, when the operation state is in the operation region B on the high load side or the high rotation side, the fuel injection amount is controlled so that the air-fuel ratio of each of the cylinders 2A to 2D is equal to or lower than the theoretical air-fuel ratio. 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, as shown by broken lines in FIG. 14A, the fuel is injected into the cylinders 2A to 2D in the intake stroke IN (first stroke) so that uniform combustion is performed. The timing of the injection F is set.
[0110]
The route discriminating means 51 and the start time Switching The means 52 is configured in the same manner as the route discriminating means 51 and the starting time control means 52 of the embodiment shown in FIG. 3, and is provided in the intake passage 15 to detect intake air pulsation detecting means ( In response to the detection signal output from the air flow sensor 19), the path determination means 51 determines whether the engine is in the normal operation mode control state or the special operation mode control state when the engine is started. When it is confirmed that the control state of the special operation mode is in accordance with the determination result of the determination means 51, ignition of the first injected fuel is prohibited at the first combustion control at the time of engine start. Such control is executed by the start time control means 52.
[0111]
As described above, when the operation state is in the low load side or low rotation side operation region A, a special operation mode in which combustion is performed twice between the intake stroke and the exhaust stroke is performed, and the operation is performed in the first expansion stroke. By making the first combustion to be a stratified combustion state at a lean air-fuel ratio, the thermal efficiency is increased and the pumping loss is reduced, and the fuel efficiency is remarkably improved by these synergistic effects. In addition, by supplying fuel to the burned gas in excess air produced by the first combustion and controlling the stoichiometric air-fuel ratio, the second combustion is performed in the third expansion stroke, so that a normal engine Thus, although the thermal efficiency is inferior to that in which stratified combustion is performed at a lean air-fuel ratio, the fuel efficiency effect by reducing the pumping loss can be obtained.
[0112]
In addition, the conventional lean burn engine is configured such that the concentration of burned gas discharged into the exhaust passage 20 in the discharge stroke after the second combustion is set to a value corresponding to the stoichiometric air-fuel ratio. Thus, it is not necessary to provide a lean NOx catalyst, and the exhaust purification performance is sufficiently ensured by the three-way catalyst 24 alone. Since it is not necessary to provide a lean NOx catalyst in this way, there is no need to temporarily enrich the air-fuel ratio for NOx release and reduction when the NOx occlusion amount of the lean NOx catalyst is increased. Loss of eyes is avoided. Furthermore, the problem of sulfur poisoning of the lean NOx catalyst does not occur.
[0113]
In the special operation mode as described above, the intake stroke IN, the first compression stroke, the first expansion stroke with combustion, the second compression stroke, the second expansion stroke without combustion, and the third compression stroke, Embodiment in which combustion is performed twice between the intake stroke IN and the exhaust stroke EX by executing eight cycles of combustion control including the third expansion stroke with combustion and the exhaust stroke EX Instead, as shown in FIG. 14C, the intake stroke IN, the first compression stroke, the first expansion stroke with combustion, the second compression stroke, the third expansion stroke with combustion, and the exhaust stroke. By performing 6-cycle combustion control including EX, the combustion may be performed twice between the intake stroke and the exhaust stroke.
[0114]
However, when the four-cycle combustion state shown in FIG. 14 (a) is compared with the six-cycle combustion state shown in FIG. 14 (c), the timing when the intake stroke IN is reached in the four-cycle combustion state (fifth stroke). In addition, in the 6-cycle combustion state, the second expansion stroke with combustion is executed. For this reason, when shifting from the normal operation mode in which the 4-cycle combustion control is executed to the special operation mode in which the 6-cycle combustion control is executed, the engine rotation becomes unstable due to the shift of the explosion timing. Such problems will occur.
[0115]
In contrast, in the special operation mode, the intake stroke IN, the first compression stroke, the first expansion stroke with combustion, the second compression stroke, the second expansion stroke without combustion, and the third compression stroke. And the third expansion stroke with combustion, and the exhaust stroke EX, the second cycle with combustion in the normal operation mode shown in FIG. Since the expansion stroke (seventh stroke) and the third expansion stroke (seventh stroke) with combustion in the special operation mode are the same period, when the operation mode is shifted, the engine timing is shifted due to the shift of the explosion timing. There is an advantage that it is possible to smoothly shift from the 4-cycle combustion control state to the 8-cycle combustion control state in accordance with the operating state of the engine without causing a situation in which the rotation becomes unstable.
[0116]
Then, as described above, when the engine is started, the passage discriminating means 51 discriminates whether the intake and exhaust flow paths are in the two-cylinder connection state or each cylinder independent state, and is in the two-cylinder connection state. In the case of the first combustion control at the time of starting the engine, the ignition of the fuel injected in the first time, that is, the second stroke is prohibited, so that 2 in the presence of a large amount of burned gas. In addition to effectively preventing misfiring due to the second combustion, the fuel injected in the first time is sufficiently agitated and mixed with fresh air in the combustion chamber according to the vertical movement of the piston. By making it burn effectively, the startability of the engine can be ensured.
[0117]
【The invention's effect】
As described above, the present invention is configured to significantly improve fuel efficiency and reduce the pumping loss and reduce the pumping loss in the succeeding cylinders, and to provide a sufficient exhaust purification action with only a three-way catalyst. In the spark ignition type engine, the flow path of intake and exhaust is in an independent state of each cylinder or in a connected state of two cylinders according to a detection signal of an intake pulsation detecting means disposed in the intake passage to detect intake pulsation. Since it is configured to determine whether or not there is a path determination means, it is determined whether the intake and exhaust flow paths are in an independent state of each cylinder corresponding to the normal operation mode or a two-cylinder connection state corresponding to the special operation mode. There are advantages that it is possible to easily and accurately discriminate, and that it is possible to execute control of an appropriate operation mode corresponding to the discrimination result.
[0118]
Further, according to the present invention, when the engine is started, it is determined whether the intake and exhaust flow paths are in an independent state of each cylinder or in a connected state of two cylinders according to a detection signal output from the intake pulsation detecting means. And the control of the operation mode corresponding to the determination result is executed by the start time control means, so that it is possible to effectively prevent a misfire state at the start of the engine and to start the engine. There is an advantage that can be effectively secured.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an entire engine including an apparatus 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 operation region.
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 intake and exhaust flow paths during low load and low rotation.
FIG. 7 is an explanatory diagram showing substantial intake and exhaust flow paths when the vehicle is in an operating region on a high load, high and low rotation side.
FIG. 8 is a diagram showing an exhaust stroke, an intake stroke, a fuel injection timing, an ignition timing, and the like of each cylinder at the time of engine start.
FIG. 9 is a diagram showing an exhaust stroke, an intake stroke, a fuel injection timing, an ignition timing, and the like of each cylinder when the engine is started.
FIG. 10 is a schematic plan view showing another embodiment of the path switching means and the like.
FIG. 11 is an explanatory diagram showing a switchable period of the on-off valve when shifting to an operation state in the case of the embodiment of FIG.
FIG. 12 is a schematic plan view of an entire engine equipped with a device according to another embodiment of the present invention.
FIG. 13 is a block diagram of a control system in the embodiment of FIG.
14 is an explanatory diagram showing a combustion cycle, combustion injection timing and ignition timing of a cylinder in the embodiment of FIG.
[Explanation of symbols]
2A to 2D cylinder
15 Intake passage
19 Airflow Sensor (Intake pulsation detection means)
20 Exhaust passage
22 Gas passage between cylinders
24 Three-way catalyst
35 Valve stop mechanism (path switching means)
40 ECU
41 Operating state discriminating means
42 Valve stop mechanism control means (path switching means)
43 Intake air amount control means (air-fuel ratio control means)
44 Fuel injection control means (air-fuel ratio control means)
51 route Discrimination means
52 Control means at start

Claims (11)

The combustion cycle of each cylinder is set to have a predetermined phase difference, and the normal operation mode in which each cylinder is burned independently, and the burned gas exhausted from the preceding cylinder in the exhaust stroke is directly in the intake stroke The multi-cylinder spark ignition engine operation mode detection device is configured to switch the operation mode according to the operating state of the engine to a special operation mode that is introduced into a subsequent cylinder and combusted. In the operation mode, a two-cylinder connection state in which the burned gas of the preceding cylinder is introduced into the succeeding cylinder through the inter-cylinder gas passage in a state where the intake air introduction from the intake passage to the succeeding cylinder is interrupted is established. In the special operation mode, the path switching means for switching the intake and exhaust flow paths so that each cylinder is in an independent state in which fresh air is introduced. By injecting fuel into the cylinder of the cylinder, the air-fuel ratio is made to be in a lean state larger than the stoichiometric air-fuel ratio by a predetermined amount, and combustion is performed, and the burned gas and fuel of the lean air-fuel ratio derived from the preceding cylinder are made to the subsequent cylinder an intake pulsation detecting means for detecting the air-fuel ratio control means for the air-fuel ratio in the cylinder substantially stoichiometric air-fuel ratio, the pulsation of the intake air is disposed in the intake passage by supplying the door, the intake Path discriminating means for discriminating whether the intake and exhaust flow paths are in an independent state of each cylinder or in a connected state of two cylinders in accordance with a detection signal output from the pulsation detecting means. An operation mode detection device for a spark ignition type engine, which detects whether the engine is in a control state of a normal operation mode or a control state of a special operation mode according to data. The path discriminating means discriminates whether the intake and exhaust flow paths are in an independent state of each cylinder or in a connected state of two cylinders based on the number of intake pulsations detected while the crankshaft of the engine rotates by a certain angle. The operation mode detection device for a spark ignition type engine according to claim 1, wherein: 3. The spark according to claim 1, wherein the intake pulsation detecting means is an intake flow rate detecting means provided in a common intake passage located upstream of a branched intake passage connected to each cylinder. An operation mode detector for an ignition engine. The combustion cycle of each cylinder is set to have a predetermined phase difference, and the normal operation mode in which each cylinder is burned independently, and the burned gas discharged from the preceding cylinder in the exhaust stroke is directly in the intake stroke The multi-cylinder spark ignition engine control device is configured to switch the operation mode according to the operating state of the engine to a special operation mode that is introduced into the subsequent cylinder and burned, and the special operation mode In the normal operation mode, the intake and exhaust states are set so that each cylinder is introduced with fresh air through the inter-cylinder gas passage. In the special operation mode, the air-fuel ratio is changed from the stoichiometric air-fuel ratio by injecting fuel into the cylinder of the preceding cylinder in the special operation mode. Combustion is performed in a lean state that is larger by a predetermined amount, and the air-fuel ratio in the cylinder is made to be substantially the stoichiometric air-fuel ratio by supplying the burned gas and fuel of the lean air-fuel ratio derived from the preceding cylinder to the subsequent cylinder. Air-fuel ratio control means for controlling the intake pulsation, intake pulsation detection means for detecting the pulsation of intake air, and the flow paths of the intake and exhaust are independent for each cylinder in accordance with the detection signal output from the intake pulsation detection means when the engine is started And a starting point control means for executing control of the operation mode corresponding to the determination result of the path determination means. Control device for ignition engine. When the engine is started, if the intake and exhaust flow paths are in the 2-cylinder connection state and the engine is confirmed to be in a warm state, the special operation mode is not switched without switching the intake and exhaust flow paths. When combustion control is executed and it is confirmed that the engine is in a cold state , the combustion control in the normal operation mode is executed by switching the flow path of intake and exhaust to each cylinder independent state. The control device for the spark ignition type engine according to claim 4. When it is confirmed that the intake and exhaust flow paths are in a two-cylinder connection state at the time of starting the engine, the subsequent cylinder is burned by thinning out the combustion of the preceding cylinder during the first combustion control at the time of starting the engine, 5. The control device for a spark ignition engine according to claim 4, wherein the combustion state is in a special operation mode in which the fuel injected into the preceding cylinder and the succeeding cylinder is combusted from the time of the next combustion control. When it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state when the engine is started, the fuel is injected into the preceding cylinder during the initial combustion control at the time of engine start, and the ignition is performed. 7. The control device for a spark ignition engine according to claim 6, wherein the combustion of the preceding cylinder is thinned out by prohibiting. When it is confirmed that the intake and exhaust flow paths are in the two-cylinder connection state when the engine is started, the fuel injection timing to the preceding cylinder at the time of the first combustion control at the start of the engine is set to the expansion stroke. 8. The spark ignition engine control apparatus according to claim 7, wherein the control apparatus is set between the latter half and the initial stage of the exhaust stroke. When it is confirmed that the intake and exhaust flow paths are in a two-cylinder connection state at the time of starting the engine, the fuel injection to the preceding cylinder is cut at the time of the first combustion control at the time of starting the engine. 7. The spark ignition engine according to claim 6, wherein the amount of fuel injected into the succeeding cylinder is controlled so that the combustion mixture is thinned and the air-fuel mixture concentration in the succeeding cylinder becomes a value substantially corresponding to the stoichiometric air-fuel ratio. Control device. The combustion cycle of each cylinder is set to have a predetermined phase difference, and the normal operation mode in which each cylinder is burned independently, and the burned gas exhausted from the preceding cylinder in the exhaust stroke is directly in the intake stroke The multi-cylinder spark ignition type is configured to switch the operation mode according to the operating state of the engine to the special operation mode to be introduced and burned in the subsequent cylinder in the engine, and the three-way catalyst is disposed in the exhaust passage An engine control device, an intake flow rate detecting means provided in a common intake passage located upstream of a branch intake passage connected to each cylinder, and a detection signal of the intake flow rate detecting means when the engine is started In response to this, the number of detected intake pulsations while the crankshaft of the engine rotates by a certain angle is detected, and the intake and exhaust airflows are detected based on the detected number of times. Or passing path is in each cylinder independently state, a path determination means for determining whether the two-cylinder connection state, the flow paths of intake and exhaust at the start of the engine is in the two-cylinder connection state, the engine is cold state if it is confirmed in the, along with the combustion of the following cylinders by thinning combustion preceding cylinders during initial combustion control at the start of the engine, is injected into the preceding cylinders and following cylinders from the time of the next combustion control A control device for a spark ignition engine, characterized by comprising start-up control means for performing combustion control in a special operation mode in which each fuel is combusted. The normal operation mode in which fuel is directly injected into the combustion chamber and combustion is performed once between the intake stroke and the exhaust stroke, and the number of strokes is set so that the combustion is performed twice between the intake stroke and the exhaust stroke. The intake stroke is switched so that the combustion cycle is switched to the increasing special operation mode according to the operating state of the engine, and the oxygen concentration of the exhaust gas discharged to the exhaust passage becomes a value substantially corresponding to the combustion state of the stoichiometric air-fuel ratio. A spark ignition type engine control device configured to control the intake air amount introduced into the cylinder and the fuel injection amount for performing the above-mentioned two combustions, and having a three-way catalyst disposed in the exhaust passage. Whether the intake pulsation detecting means is disposed in the intake passage and detects the pulsation of the intake air, and is the control state of the normal operation mode according to the detection signal output from the intake pulsation detecting means when the engine is started? , Special luck A mode discriminating unit for discriminating whether the mode is in the control state, and when it is confirmed that the control state is in the special operation mode according to the discrimination result of the discriminating unit, at the time of the first combustion control at the engine start A spark-ignition engine control apparatus for prohibiting ignition of fuel injected for the first time in

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