JP3714495B2

JP3714495B2 - Internal combustion engine control device

Info

Publication number: JP3714495B2
Application number: JP21224596A
Authority: JP
Inventors: 耕一大畑; 兼仁中村; 肇勝呂; 司窪島
Original assignee: Denso Corp; Toyota Motor Corp
Current assignee: Denso Corp; Toyota Motor Corp
Priority date: 1996-08-12
Filing date: 1996-08-12
Publication date: 2005-11-09
Anticipated expiration: 2016-08-12
Also published as: JPH1054251A

Description

【０００１】
【発明の属する技術分野】
本発明は、過給機と排気浄化用の触媒とを備えた内燃機関制御装置に関するものである。
【０００２】
【従来の技術】
例えば、ディーゼルエンジンから排気ガスに含まれる窒素酸化物（ＮＯｘ）を浄化する触媒は、図４に示すように所定の活性温度範囲（例えば２００から４００℃）においてのみＮＯｘ浄化率が高いことが一般的に知られている。従って、ＮＯｘ排出量を低減するには、触媒温度を活性温度範囲内に維持することが効果的である。しかし、実際には、エンジンの運転状態により排気温度が大きく変化して、触媒温度が活性温度範囲から外れることがあり、安定したＮＯｘ浄化性能が得られない。
【０００３】
そこで、ターボ過給機を備えたエンジンでは、特開平７−１８９７２０号公報に示すように、ターボ過給機の上流側の吸気通路とターボ過給機の下流側の排気通路とをバイパス通路で連通させ、このバイパス通路の途中に、過給圧によって開閉する通路開閉弁を設け、過給圧が所定値以上になったときに、上記通路開閉弁を開放させて過給気の一部を排気通路側にバイパスさせることで、排気温度を低下させて触媒を冷却するようにしている。しかし、過給気の一部を排気通路へバイパスさせると、エンジン出力が低下してドライバビリティが悪化するため、上記特開平７−１８９７２０号公報では、過給気の一部をバイパスさせることに伴って生じるエンジン出力低下を、ターボ過給機に過給圧を増幅させる補助機を設置することにより解決しようとしている。
【０００４】
【発明が解決しようとする課題】
しかし、上記公報の構成では、バイパス通路の通路開閉弁を過給圧によって開閉するため、触媒温度が高くても、過給圧が低いと、通路開閉弁が開放されず、触媒を冷却することができない。それ故に、上記公報の構成では、エンジン負荷が小さい場合でも、触媒温度（排気温度）が高いときには、エンジンの出力で補助機を駆動して過給圧を高める必要があり、そのために燃費が悪化してしまう。しかも、エンジン負荷が大きい場合には、過給圧が高くなるので、触媒温度が適温でも、過給圧によって通路開閉弁が開放されてしまい、触媒温度が適温以下に低下して、排気浄化能力が低下してしまう。更に、補助機を設けることで、装置全体が大型化し、コンパクト化、低コスト化の要求を満たすことができない。
【０００５】
本発明はこのような事情を考慮してなされたものであり、従ってその目的は、燃費向上、コンパクト化、低コスト化を実現しながら、排気浄化性能とドライバビリティとを両立させることができる内燃機関制御装置を提供することにある。
【０００６】
【課題を解決するための手段】
上記目的を達成するために、本発明の請求項１の内燃機関制御装置は、過給機よりも下流側の吸気通路と触媒よりも上流側の排気通路とをバイパスさせる吸気バイパス通路を設けると共に、この吸気バイパス通路にバイパス空気量制御弁を設ける。そして、内燃機関に供給する吸入空気の酸素量（以下「供給酸素量」という）を供給酸素量推定手段により推定すると共に、内燃機関に供給する燃料を燃焼するのに必要な吸入空気の酸素量（以下「目標酸素量」という）を目標酸素量算出手段により算出する。その上で、触媒温度判定手段で判定した触媒温度と目標触媒温度との差及び前記供給酸素量と前記目標酸素量との差に基づいて前記バイパス空気量制御弁の開度を制御手段によって制御する。ここで、「開度を制御する」とは、モータ等で弁開度を制御する場合のほか、電磁弁のＯＮ・ＯＦＦデューティの制御により弁を開閉する時間的な度合を制御する場合も含む。
【０００７】
この場合、供給酸素量と目標酸素量との差が少なくなるほど、内燃機関に供給する燃料の燃焼状態が良好となり、ドライバビリティ向上、エミッション低減につながる。また、触媒温度と目標触媒温度との差が少なければ、触媒温度が所定の活性温度範囲内に収まり、ＮＯｘ浄化率が高くなる。このような特性を考慮して、本発明のように、触媒温度と目標触媒温度との差及び供給酸素量と目標酸素量との差に基づいてバイパス空気量制御弁の開度を制御すれば、ドライバビリティ（内燃機関の出力）を確保しながら、過給気のバイパス量（触媒冷却効果）を調整して排気浄化性能を確保することができる。しかも、本発明では、過給圧とは関係なく、バイパス空気量制御弁の開度を制御手段によって制御できるので、従来のように内燃機関の出力で補助機を駆動して過給圧を高める必要がなくなり、燃費を向上できると共に、補助機が不要になる分、コンパクト化、低コスト化を実現することができる。
【０００８】
更に、請求項１に係る発明は、過給機としてターボ過給機を用い、ターボ過給機の排気タービンの上流側と下流側とをバイパスさせる排気バイパス通路を設けると共に、該排気バイパス通路にバイパス排気量制御弁を設けた構成としている。この場合には、触媒温度と目標触媒温度との差及び供給酸素量と目標酸素量との差に基づいてバイパス空気量制御弁及びバイパス排気量制御弁の開度を総合的に制御すれば良い。このようにすれば、排気バイパス通路を流れる排気ガスのバイパス量を制御することで、排気タービンを通過する排気ガスの量を制御して、排気タービンの回転数（過給圧）を制御することができ、制御特性を向上できる。
【０００９】
この場合、請求項３では、触媒温度が目標触媒温度以下の場合、つまり触媒の冷却が不要な場合には、バイパス空気量制御弁を全閉することで、排気通路の触媒上流側への過給気のバイパスを遮断して、過給気による触媒の冷却を停止し、触媒温度の上昇を促進して排気浄化能力を高める。これと共に、バイパス排気量制御弁の開度を制御することで、排気タービンの回転数（過給圧）を制御して、供給酸素量を目標酸素量に合わせるように制御し、内燃機関の燃焼効率を向上させて、燃費とドライバビリティを向上させる。
【００１０】
一方、触媒温度が目標触媒温度より高い場合、つまり触媒の冷却が必要な場合には、供給酸素量を目標酸素量に合わせるようにバイパス空気量制御弁及びバイパス排気量制御弁の開度を制御する。具体的には、触媒温度が前記目標触媒温度より高い場合には、前記供給酸素量が前記目標酸素量と一致すると仮定して前記触媒温度を前記目標触媒温度に合わせるように前記バイパス空気量制御弁の開度を算出した後、この算出した前記バイパス空気量制御弁の開度にて前記供給酸素量を前記目標酸素量に合わせるように前記バイパス排気量制御弁の開度を算出し、算出したバイパス排気量制御弁の開度が０（＝全閉）よりも大きい場合には、前記バイパス空気量制御弁の開度及び前記バイパス排気量制御弁の開度をそれぞれ前記算出した開度に調整する（請求項１）。また、算出したバイパス排気量制御弁の開度が０以下の場合には、バイパス排気量制御弁を全閉して前記バイパス空気量制御弁の開度を制御することで、前記供給酸素量を前記目標酸素量に合わせるように制御するようにすると良い（請求項２）。これにより、内燃機関の出力を確保した上で、ターボ過給機の過給能力に余力がある範囲内でバイパス空気量制御弁の開度を前記触媒温度と目標触媒温度との差に応じて制御し、過給気の一部を排気通路側にバイパスさせることで、排気温度を低下させて触媒を冷却して、排気浄化能力を高める。この場合、排気通路側への過給気のバイパス（触媒の冷却）は、ターボ過給機の過給能力に余力がある範囲内で行われるので、内燃機関への過給気が供給不足になることはなく、内燃機関の出力が確保されて、ドライバビリティが低下することはない。
【００１１】
また、請求項４では、過給機よりも下流側の吸気通路と触媒よりも上流側の排気通路とをバイパスさせる第１の吸気バイパス通路と、前記過給機よりも下流側の吸気通路と触媒よりも下流側の排気通路とをバイパスさせる第２の吸気バイパス通路とを設け、これら両吸気バイパス通路に設けた第１及び第２の各バイパス空気量制御弁を、触媒温度と目標触媒温度との差及び供給酸素量と目標酸素量との差に基づいて制御手段により総合的に制御する。このようにすれば、第１及び第２の各バイパス空気量制御弁を制御することで、排気通路の触媒上流側への過給気のバイパス量の制御と過給圧の制御とを同時に行うことが可能となり、排気浄化性能とドライバビリティとを両立させることができる。
【００１２】
この場合、請求項５では、触媒温度が目標触媒温度より低い場合（触媒の冷却が不要な場合）には、第１のバイパス空気量制御弁を閉鎖することで、排気通路の触媒上流側への過給気のバイパスを遮断して、過給気による触媒の冷却を停止し、触媒温度の上昇を促進して排気浄化能力を高める。これと共に、第２のバイパス空気量制御弁の開度を制御することで、排気通路の触媒下流側への過給気のバイパス量を制御して過給圧を制御し、供給酸素量を目標酸素量に合わせるように制御して、内燃機関の燃焼効率を向上させ、燃費とドライバビリティを向上させる。
【００１３】
一方、触媒温度が目標触媒温度より高い場合には、供給酸素量を目標酸素量に合わせるように第１及び第２のバイパス空気量制御弁の開度を制御して、内燃機関の出力を確保した上で、過給機の過給能力に余力がある範囲内で触媒温度と目標触媒温度との差に応じて第１のバイパス空気量制御弁の開度を制御し、過給気の一部を排気通路の触媒上流側にバイパスさせることで、触媒上流側の排気温度を低下させて触媒を冷却する。この場合、触媒上流側への過給気のバイパス（触媒の冷却）は、過給機の過給能力に余力がある範囲内で行われるので、内燃機関への過給気が供給不足になることはなく、内燃機関の出力が確保されて、ドライバビリティが低下することはない。
【００１４】
また、請求項６では、前記供給酸素量推定手段は、吸気圧を検出する吸気圧センサ、吸入空気量を検出する吸入空気量センサ、吸気系への排気ガスの還流量を検出する排気還流量センサ、前記内燃機関に吸入される酸素量を検出する酸素センサのうちの少なくとも１つのセンサの出力信号に基づいて供給酸素量を推定する。ここで、吸気圧センサや吸入空気量センサは、内燃機関の制御のために車両に搭載されている既存のセンサを用いれば良く、コスト的な負担が少なくて済む。更に、吸気圧センサと吸入空気量センサのいずれか一方の検出値と排気還流量センサの検出値とを組み合わせて供給酸素量を推定するようにしても良い。このようにすれば、吸気系へ還流する排気ガス中の酸素を考慮した正確な供給酸素量を推定することができる。また、酸素センサを用いれば、供給酸素量を直接検出することができる。
【００１５】
また、請求項７では、前記目標酸素量算出手段は、前記過給機の過給圧限界値に相当する最大酸素量以下の範囲内で前記目標酸素量を内燃機関の運転状態に基づいて算出する。これにより、内燃機関が過負荷状態にならないように目標酸素量を設定でき、内燃機関の耐久性を向上できる。
【００１６】
【発明の実施の形態】
以下、本発明の第１の実施形態を図１乃至図５に基づいて説明する。まず、図１に基づいてエンジン制御系全体の概略構成を説明する。内燃機関であるディーゼルエンジン１１の吸気通路１２にはターボ過給機１３が設置されている。このターボ過給機１３は、排気通路１４内を流れる排気ガスの運動エネルギによって回転駆動される排気タービン１５を駆動源としている。そして、排気タービン１５よりも下流側の排気通路１４には排気浄化用の触媒１７が設置されている。
【００１７】
更に、ターボ過給機１３よりも下流側の吸気通路１２と触媒１７よりも上流側の排気通路１４とをバイパスさせる吸気バイパス通路１８が設けられ、この吸気バイパス通路１８には、開度調節可能なバイパス空気量制御弁１９が設けられている。このバイパス空気量制御弁１９の開度調整は、ステップモータ等のモータ（図示せず）で行えば良い。或は、バイパス空気量制御弁１９を電磁弁で構成する場合には、電磁弁のソレノイドコイルへの通電をデューティ制御することで、弁を開閉する時間的な度合を制御して弁を通過する空気量を制御すれば良い。このような電磁弁のデューティ制御により弁を開閉する時間的な度合を制御する場合も、特許請求の範囲でいう「バイパス空気量制御弁の開度を制御する」の概念に含まれる。また、吸気バイパス通路１８の入口１８ａよりも下流側の吸気通路１２には、吸気圧を検出する吸気圧センサ２０が設置されている。
【００１８】
一方、排気通路１４には、排気タービン１５の上流側と下流側とをバイパスさせる排気バイパス通路２１（ウェイストゲート）が設けられ、この排気バイパス通路２１には開度調節可能なバイパス排気量制御弁２２が設けられている。このバイパス排気量制御弁２２の開度調整も、前記バイパス空気量制御弁１９の開度調整と同じく、モータ（図示せず）、又は電磁弁のデューティ制御で行えば良い。また、触媒１７の上流側端面の近傍には、排気温度を検出する排気温度センサ２３が設置され、この排気温度センサ２３で検出した排気温度から触媒１７の温度が判定される。従って、本実施形態では、排気温度センサ２３を特許請求の範囲でいう触媒温度判定手段として用いる。
【００１９】
尚、アクセル２４には、アクセル開度（アクセル操作量）を検出するアクセル開度センサ２５が設けられ、ディーゼルエンジン１１には、エンジン回転数を検出するエンジン回転数センサ２６が設けられている。
【００２０】
これらアクセル開度センサ２５、エンジン回転数センサ２６、排気温度センサ２３、吸気圧センサ２０等、エンジン制御に関する各種情報を検出するセンサの出力信号は、エンジン制御用の電子制御回路（以下「ＥＣＵ」という）２７に入力される。このＥＣＵ２７は、マイクロコンピュータを主体として構成され、上記各種センサ情報に基づいて燃料噴射装置（図示せず）の動作を制御すると共に、図２及び図３に示す過給制御プログラムを実行することで、触媒温度と目標触媒温度との差及び後述する供給酸素量と目標酸素量との差に基づいてバイパス空気量制御弁１９とバイパス排気量制御弁２２の開度を制御する制御手段として機能する。
【００２１】
以下、図２及び図３の過給制御プログラムの処理の流れを説明する。本プログラムは、所定時間毎（例えば１秒毎）又は所定クランク角毎に割り込み処理にて起動される。本プログラムが起動されると、まずステップＳ１０１で、エンジン回転数センサ２６、アクセル開度センサ２５、吸気圧センサ２０、排気温度センサ２３から出力されるエンジン回転数Ｎｅ、アクセル開度Ａｃ、吸気圧Ｐｑ及び排気温度Ｔを読み込む。そして、次のステップＳ１０２で、読み込んだエンジン回転数Ｎｅとアクセル開度Ａｃとに応じて、目標とするエンジン出力を確保するのに必要な目標吸気圧Ｐ1 を予め設定されたマップデータより算出する。この際、目標吸気圧Ｐ1 は、ディーゼルエンジン１１が過負荷状態にならないようにターボ過給機１３の過給圧限界値以下の範囲内で設定される。
【００２２】
そして、目標吸気圧Ｐ1 の算出後、ステップＳ１０３で、排気温度Ｔと目標触媒温度Ｔ1 とを比較し、触媒１７の温度状態（活性状態）を判定する。この場合、触媒１７は主として排気ガスの熱で温度上昇し、触媒温度は排気温度Ｔとほぼ等しいと推定できるため、本実施形態では、触媒温度の代用データとして排気温度Ｔを用いる。また、目標触媒温度Ｔ1 は、触媒１７のＮＯｘ浄化率が最大となる触媒温度Ｔmax （図４参照）に設定されている。
【００２３】
上記ステップＳ１０３で、排気温度Ｔ（＝触媒温度）が目標触媒温度Ｔ1 以下と判定された場合には、触媒１７の冷却は不要である。この場合には、ステップＳ１０４に進み、バイパス空気量制御弁１９を全閉と仮定して、吸気圧Ｐｑ＝目標吸気圧Ｐ1 となるようにバイパス排気量制御弁２２の開度を算出する。この後、ステップＳ１０５で、バイパス空気量制御弁１９の全閉信号を出力してバイパス空気量制御弁１９を全閉し、排気通路１４の触媒１７上流側への過給気のバイパスを遮断して、排気温度の低下を防ぎ、触媒１７の温度上昇を促進する。更に、このステップＳ１０５では、ステップＳ１０４で算出したバイパス排気量制御弁２２の開度信号を出力し、バイパス排気量制御弁２２の開度を調整して、ターボ過給機１３の排気タービン１５をバイパスさせる排気ガス量を調整する。これにより、排気タービン１５を通過する排気ガス量を調整して、排気タービン１５の回転数を調整し、ターボ過給機１３の過給圧を吸気圧Ｐｑが目標吸気圧Ｐ1 となるように調整し、ディーゼルエンジン１１の燃焼効率を向上させて、燃費とドライバビリティを向上させる。
【００２４】
この場合、ディーゼルエンジン１１に供給する吸入空気の酸素量（供給酸素量）は、吸気圧Ｐｑから推定できるため、供給酸素量の代用データとして吸気圧Ｐｑを用いる。従って、本実施形態では、吸気圧Ｐｑを検出する吸気圧センサ２０が特許請求の範囲でいう供給酸素量推定手段として用いられる。そして、ディーゼルエンジン１１に供給する燃料を燃焼するのに必要な吸入空気の酸素量（目標酸素量）の代用データとしてステップＳ１０２で算出する目標吸気圧Ｐ1 を用いる。従って、本実施形態では、目標吸気圧Ｐ1 を算出するステップＳ１０２の処理が特許請求の範囲でいう目標酸素量算出手段としての役割を果たしている。
【００２５】
一方、前述したステップＳ１０３で、排気温度Ｔ（＝触媒温度）が目標触媒温度Ｔ1 より高いと判定された場合には、触媒１７の冷却が必要となる。この場合には、図３のステップＳ１０６に進み、吸気圧Ｐｑ＝目標吸気圧Ｐ1 と仮定して排気温度Ｔ＝目標触媒温度Ｔ1 となるようにバイパス空気量制御弁１９の開度を算出する。この後、ステップＳ１０７に進み、上記ステップＳ１０６で算出したバイパス空気量制御弁１９の開度で、吸気圧Ｐｑ＝目標吸気圧Ｐ1 となるようにバイパス排気量制御弁２２の開度を算出する。
【００２６】
この後、ステップＳ１０８で、バイパス排気量制御弁２２の開度が０（＝全閉）よりも大きいか否かを判定し、大きい場合には、ステップＳ１０９に進んで、ステップＳ１０６で算出したバイパス空気量制御弁１９の開度信号と、ステップＳ１０７で算出したバイパス排気量制御弁２２の開度信号とを出力し、両制御弁１９，２２の開度を調整する。これにより、吸気圧Ｐｑ＝目標吸気圧Ｐ1 となるように過給圧を制御して、必要なエンジン出力を確保すると共に、排気温度Ｔ（＝触媒温度）を目標触媒温度Ｔ1 に一致させるようにバイパス空気量制御弁１９の開度を制御して、過給気の一部を排気通路１４側にバイパスさせて排気ガスと混合させることで、排気温度を低下させて触媒１７を冷却し、触媒温度を目標触媒温度Ｔ1 まで速やかに低下させる。
【００２７】
一方、前述したステップＳ１０８で、バイパス排気量制御弁２２の開度が０（＝全閉）以下と判定された場合には、ステップＳ１１０に進み、バイパス排気量制御弁２２を全閉と仮定して、吸気圧Ｐｑ＝目標吸気圧Ｐ1 となるようにバイパス空気量制御弁１９の開度を算出する。この後、ステップＳ１１１で、上記ステップＳ１１０で算出したバイパス空気量制御弁１９の開度信号とバイパス排気量制御弁２２の全閉信号を出力し、バイパス排気量制御弁２２を全閉して、バイパス空気量制御弁１９の開度調整により吸気圧Ｐｑ＝目標吸気圧Ｐ1 となるように過給圧を制御して、必要なエンジン出力を確保した上で、ターボ過給機１３の過給能力に余力がある範囲内で過給気の一部を排気通路１４側にバイパスさせることで、排気温度を低下させて触媒１７を冷却し、触媒温度を低下させる。
【００２８】
以上説明した過給制御によれば、触媒温度（排気温度Ｔ）が目標触媒温度Ｔ1 以下の場合、つまり触媒１７の冷却が不要な場合には、バイパス空気量制御弁１９を全閉することで、排気通路１４側への過給気のバイパスを遮断して、過給気による触媒の冷却を停止し、触媒温度の上昇を促進して排気浄化能力を高める。これと共に、バイパス排気量制御弁２２の開度を制御することで、排気タービン１５の回転数（過給圧）を制御して吸気圧Ｐｑ（供給酸素量）を目標吸気圧Ｐ1 （目標酸素量）に合わせるように制御し、ディーゼルエンジン１１の燃焼効率を向上させて、燃費とドライバビリティを向上させる。
【００２９】
一方、触媒温度（排気温度Ｔ）が目標触媒温度Ｔ1 より高い場合、つまり触媒１７の冷却が必要な場合には、吸気圧Ｐｑ（供給酸素量）を目標吸気圧Ｐ1 （目標酸素量）に合わせるようにバイパス空気量制御弁１９及びバイパス排気量制御弁２２の開度を制御して、ディーゼルエンジン１１の出力を確保した上で、ターボ過給機１３の過給能力に余力がある範囲内で触媒温度（排気温度Ｔ）と目標触媒温度Ｔ1 との差に応じてバイパス空気量制御弁１９の開度を制御し、過給気の一部を排気通路１４側にバイパスさせることで、排気温度を低下させて触媒１７を冷却し、排気浄化能力を高める。
【００３０】
以上説明した過給制御の挙動を図５に示すタイムチャートに従って説明する。図５のタイムチャートは、市街地走行時に頻繁に生じる加速→定速走行→減速の走行パターンの例である。アイドル運転中の時刻ｔ0 では、触媒温度が目標触媒温度Ｔ1 よりも低いため、バイパス空気量制御弁１９が全閉されて、触媒１７の冷却は行われない。また、アイドル運転中は、ディーゼルエンジン１１の出力は最低で良いため、バイパス排気量制御弁２２が全開され、排気タービン１５を通過する排気ガスの量が最少となって、ターボ過給機１３の仕事量（過給圧）が最低となる。
【００３１】
その後、時刻ｔ1 で加速を開始すると、エンジン出力を大きくする必要があるため、バイパス排気量制御弁２２が全閉され、ターボ過給機１３の仕事量が増大されて過給圧が高められる。この加速開始とほぼ同時に、排気温度が上昇するが、触媒１７には熱容量があるため、触媒温度の上昇が排気温度の上昇よりも遅れる。従って、加速時間（ｔ1 −ｔ2 ）が比較的短ければ、その加速中は、触媒温度が目標触媒温度Ｔ1 よりも低いため、触媒１７の冷却は必要ない。この場合には、加速中（ｔ1 −ｔ2 ）は、バイパス空気量制御弁１９が引き続き全閉状態に維持され、排気通路１４側への過給気のバイパスが遮断されて過給気が全て過給圧を高めるのに使用され、エンジン出力が効果的に高められ、良好な加速性が確保される。
【００３２】
その後、時刻ｔ2 で加速を終了して定速走行に移行すると、エンジン出力は加速時よりも少なくて済むため、バイパス排気量制御弁２２が開放されてターボ過給機１３の仕事量（過給圧）が加速時よりも低下する。
【００３３】
このとき、触媒温度は、定速走行に移行しても、暫く上昇し続け、時刻ｔ3 で触媒温度が目標触媒温度Ｔ1 を越える。このようになると、触媒１７の冷却が必要となるため、バイパス空気量制御弁１９が触媒温度と目標触媒温度Ｔ1 との差に応じた開度まで開放され、過給気の一部が排気通路１４側にバイパスされて、触媒１７が冷却される。このようにして、過給気の一部を触媒１７の冷却に用いると、ディーゼルエンジン１１に供給する過給気が減少するため、それを補うように、バイパス排気量制御弁２２の開度が絞られ、ターボ過給機１３の仕事量が増大されて、定速走行を維持するために必要なエンジン出力が確保される。
【００３４】
触媒温度が目標触媒温度Ｔ1 に達してからは、エンジン出力を確保した上で、ターボ過給機１３の過給能力に余力がある範囲内で触媒温度を目標触媒温度Ｔ1 に一致させるようにバイパス空気量制御弁１９の開度を制御し、排気浄化能力を高める。
【００３５】
従来の一般的なディーゼルエンジンのように、触媒１７の冷却（過給気のバイパス）を行わない場合には、図５に点線で示すように、定速走行中に触媒温度が目標触媒温度Ｔ1 を大きく越えて、触媒温度と目標触媒温度Ｔ1 との差が大きくなり、ＮＯｘ浄化率が低下してＮＯｘ排出量が多くなる。
【００３６】
これに対し、本実施形態では、エンジン出力を確保した上で、ターボ過給機１３の過給能力に余力がある範囲内で触媒温度と目標触媒温度Ｔ1 との差に応じてバイパス空気量制御弁１９の開度を制御して、触媒１７を冷却する過給気のバイパス量を調整するので、ＮＯｘ浄化率が高い触媒温度に維持できて、ＮＯｘ排出量を効果的に低減できる。しかも、排気通路１４側への過給気のバイパス（触媒１７の冷却）は、ターボ過給機１４の過給能力に余力がある範囲内で行われるので、ディーゼルエンジン１１への過給気が供給不足になることはなく、エンジン出力が確保されて、ドライバビリティが低下することはなく、排気浄化能力とドライバビリティとを両立できる。
【００３７】
尚、ターボ過給機１３の下流側の吸気通路１２にインタークーラ（過給気を冷却する熱交換器）を設けて、過給効率を高めるようにしても良い。この場合には、吸気バイパス通路１８の入口１８ａをインタークーラよりも下流側に設けることが好ましい。このようにすれば、インタークーラにより冷却された過給気の一部を排気通路１４側にバイパスさせることで、触媒１７の冷却効果をより高めることができる。
【００３９】
一方、図６に示す本発明の第２の実施形態では、ターボ過給機１３よりも下流側の吸気通路１２と触媒１７よりも上流側の排気通路１４とをバイパスさせる第１の吸気バイパス通路３１が設けられ、この第１の吸気バイパス通路３１の出口側には、開度調節可能な第１のバイパス空気量制御弁３２が設けられている。更に、第１のバイパス空気量制御弁３２よりも上流側の第１の吸気バイパス通路３１と触媒１７よりも下流側の排気通路１４とをバイパスさせる第２の吸気バイパス通路３３が設けられ、この第２の吸気バイパス通路３３には、開度調節可能な第２のバイパス空気量制御弁３４が設けられている。前記第１の実施形態で設けた排気バイパス通路２１とバイパス排気量制御弁２２は廃止されている。これ以外の構成は、第１の実施形態と同じである。
【００４０】
以上のように構成した第２の実施形態では、第１の吸気バイパス通路３１と第１のバイパス空気量制御弁３２が、第１の実施形態における吸気バイパス通路１８とバイパス空気量制御弁１９と全く同じ役割を果たす。また、第２の吸気バイパス通路３３と第２のバイパス空気量制御弁３４は、触媒１７の下流側にバイパスさせる過給気の量を調整することで、ディーゼルエンジン１１に供給する過給圧を調整するものであり、第１の実施形態における排気バイパス通路２１とバイパス排気量制御弁２２とほぼ同じ役割を果たす。従って、第１のバイパス空気量制御弁３２と第２のバイパス空気量制御弁３４の制御は、第１の実施形態におけるバイパス空気量制御弁１９とバイパス排気量制御弁２２の制御と同一であり、図２及び図３に示す過給制御プログラムにおいて、「バイパス空気量制御弁１９」を「第１のバイパス空気量制御弁３２」と読み替え、「バイパス排気量制御弁２２」を「第２のバイパス空気量制御弁３４」と読み替えて制御すれば良い。
【００４１】
以上説明した第２の実施形態では、第１の実施形態と同じ効果が得られる上に、排気バイパス通路２１（ウェイストゲート）を廃止しても、第２のバイパス空気量制御弁３４の開度調整によってディーゼルエンジン１１への過負荷を防止することができて、エンジンルーム内のスペースが問題でウェーストゲートを設置できない場合に有効である。
【００４２】
尚、第２の実施形態では、第２の吸気バイパス通路３３を第１の吸気バイパス通路３１の途中から分岐させた構成としたが、これら両吸気バイパス通路３１，３３を完全に独立させた構成としても良い。
【００４３】
また、上記各実施形態では、ディーゼルエンジン１１に供給する吸入空気の酸素量（供給酸素量）を吸気圧Ｐｑから推定できる点に着目し、供給酸素量の代用データとして吸気圧Ｐｑを用いるようにした。つまり、吸気圧Ｐｑを検出する吸気圧センサ２０を供給酸素量推定手段として用いるようにしたが、吸入空気量を検出する吸入空気量センサ、吸気系への排気ガスの還流量を検出する排気還流量センサ、ディーゼルエンジン１１に吸入される酸素量を検出する酸素センサのうちの少なくとも１つのセンサの出力信号に基づいて供給酸素量を推定するようにしても良い。
【００４４】
この場合、吸気圧センサ２０や吸入空気量センサは、ディーゼルエンジン１１の制御のために車両に搭載されている既存のセンサを用いれば良く、コスト的な負担が少なくて済む。更に、吸気圧センサと吸入空気量センサのいずれか一方の検出値と排気還流量センサの検出値とを組み合わせて供給酸素量を推定するようにしても良い。このようにすれば、吸気系へ還流する排気ガス中の酸素を考慮した正確な供給酸素量を推定することができ、制御精度を向上できる。また、酸素センサを用いれば、供給酸素量を直接検出することができて、制御精度を向上できる。
【００４５】
また、上記各実施形態では、触媒温度判定手段として排気温度センサ２３を用い、触媒温度の代用データとして排気温度Ｔを用いるようにしたが、触媒温度を直接検出する触媒温度センサを触媒温度判定手段として設けるようにしても良い。その他、本発明は、ガソリンエンジンに適用して実施しても良い等、要旨を逸脱しない範囲内で、種々変更して実施できる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態におけるエンジン制御システム全体の概略構成を示す図
【図２】過給制御プログラムの処理の流れを示すフローチャート（その１）
【図３】過給制御プログラムの処理の流れを示すフローチャート（その２）
【図４】触媒温度とＮＯｘ浄化率との関係を示す図
【図５】過給制御の挙動を示すタイムチャート
【図６】本発明の第２の実施形態におけるエンジン制御システム全体の概略構成を示す図
【符号の説明】
１１…ディーゼルエンジン（内燃機関）、１２…吸気通路、１３…ターボ過給機（過給機）、１４…排気通路、１５…排気タービン、１７…触媒、１８…吸気バイパス通路、１９…バイパス空気量制御弁、２０…吸気圧センサ（供給酸素量推定手段）、２１…排気バイパス通路、２２…バイパス排気量制御弁、２３…排気温度センサ（触媒温度判定手段）、２５…アクセル開度センサ、２６…エンジン回転数センサ、２７…ＥＣＵ（制御手段，目標酸素量算出手段）、３１…第１の吸気バイパス通路、３２…第１のバイパス空気量制御弁、３３…第２の吸気バイパス通路、３４…第２のバイパス空気量制御弁。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine control device including a supercharger and an exhaust purification catalyst.
[0002]
[Prior art]
For example, a catalyst for purifying nitrogen oxide (NOx) contained in exhaust gas from a diesel engine generally has a high NOx purification rate only in a predetermined activation temperature range (for example, 200 to 400 ° C.) as shown in FIG. Known. Therefore, in order to reduce the NOx emission amount, it is effective to maintain the catalyst temperature within the activation temperature range. However, in practice, the exhaust gas temperature varies greatly depending on the operating state of the engine, and the catalyst temperature may deviate from the activation temperature range, so that stable NOx purification performance cannot be obtained.
[0003]
Therefore, in an engine equipped with a turbocharger, as shown in Japanese Patent Application Laid-Open No. 7-189720, an intake passage on the upstream side of the turbocharger and an exhaust passage on the downstream side of the turbocharger are connected by a bypass passage. A passage opening / closing valve that opens and closes by the supercharging pressure is provided in the middle of the bypass passage, and when the supercharging pressure exceeds a predetermined value, the passage opening / closing valve is opened to remove a part of the supercharged air. By bypassing to the exhaust passage side, the exhaust temperature is lowered to cool the catalyst. However, if a part of the supercharged air is bypassed to the exhaust passage, the engine output decreases and the drivability deteriorates. Therefore, in Japanese Patent Laid-Open No. 7-189720, a part of the supercharged air is bypassed. We are trying to solve the accompanying engine power reduction by installing an auxiliary machine that amplifies the supercharging pressure in the turbocharger.
[0004]
[Problems to be solved by the invention]
However, in the configuration of the above publication, since the passage opening / closing valve of the bypass passage is opened / closed by the supercharging pressure, even if the catalyst temperature is high, if the supercharging pressure is low, the passage opening / closing valve is not opened and the catalyst is cooled. I can't. Therefore, in the configuration of the above publication, even when the engine load is small, when the catalyst temperature (exhaust temperature) is high, it is necessary to drive the auxiliary machine with the output of the engine to increase the supercharging pressure. Resulting in. In addition, when the engine load is large, the boost pressure increases, so even if the catalyst temperature is appropriate, the passage on / off valve is opened due to the boost pressure, and the catalyst temperature drops below the optimal temperature, resulting in an exhaust purification capability. Will fall. Furthermore, by providing an auxiliary machine, the entire apparatus becomes large, and the demands for compactness and cost reduction cannot be satisfied.
[0005]
The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is an internal combustion engine capable of achieving both exhaust purification performance and drivability while realizing improvement in fuel consumption, compactness, and cost reduction. It is to provide an engine control device.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an internal combustion engine controller according to claim 1 of the present invention is provided with an intake bypass passage that bypasses an intake passage downstream of the supercharger and an exhaust passage upstream of the catalyst. In this intake bypass passage, a bypass air amount control valve is provided. Then, the oxygen amount of the intake air supplied to the internal combustion engine (hereinafter referred to as “supply oxygen amount”) is estimated by the supply oxygen amount estimating means, and the oxygen amount of the intake air necessary for burning the fuel supplied to the internal combustion engine (Hereinafter referred to as “target oxygen amount”) is calculated by the target oxygen amount calculating means. Then, the opening degree of the bypass air amount control valve is controlled by the control means based on the difference between the catalyst temperature determined by the catalyst temperature determination means and the target catalyst temperature and the difference between the supply oxygen amount and the target oxygen amount. To do. Here, “controlling the opening” means not only controlling the valve opening with a motor, but also controlling the ON / OFF duty of the solenoid valve. Valve It also includes the case of controlling the degree of time for opening and closing.
[0007]
In this case, the smaller the difference between the supplied oxygen amount and the target oxygen amount, the better the combustion state of the fuel supplied to the internal combustion engine, leading to improved drivability and reduced emissions. Further, if the difference between the catalyst temperature and the target catalyst temperature is small, the catalyst temperature falls within a predetermined activation temperature range, and the NOx purification rate becomes high. In consideration of such characteristics, as in the present invention, if the opening degree of the bypass air amount control valve is controlled based on the difference between the catalyst temperature and the target catalyst temperature and the difference between the supply oxygen amount and the target oxygen amount. While ensuring drivability (output of the internal combustion engine), it is possible to adjust the bypass amount of the supercharged air (catalyst cooling effect) to ensure exhaust purification performance. Moreover, in the present invention, since the opening degree of the bypass air amount control valve can be controlled by the control means regardless of the supercharging pressure, the auxiliary pressure is driven by the output of the internal combustion engine to increase the supercharging pressure as in the prior art. This eliminates the need to improve fuel efficiency, and can reduce the size and cost by eliminating the need for auxiliary equipment.
[0008]
Furthermore, the invention according to claim 1 Use turbocharger as turbocharger Yes, An exhaust bypass passage that bypasses the upstream side and the downstream side of the exhaust turbine of the turbocharger is provided, and a bypass exhaust amount control valve is provided in the exhaust bypass passage. Have . In this case, the opening degree of the bypass air amount control valve and the bypass exhaust amount control valve may be comprehensively controlled based on the difference between the catalyst temperature and the target catalyst temperature and the difference between the supply oxygen amount and the target oxygen amount. . In this way, by controlling the bypass amount of the exhaust gas flowing through the exhaust bypass passage, the amount of exhaust gas passing through the exhaust turbine is controlled, and the rotational speed (supercharging pressure) of the exhaust turbine is controlled. Control characteristics can be improved.
[0009]
In this case, in claim 3, when the catalyst temperature is equal to or lower than the target catalyst temperature, that is, when cooling of the catalyst is unnecessary, the bypass air amount control valve is set. all closed Thus, the bypass of the supercharged air to the upstream side of the catalyst in the exhaust passage is shut off, the cooling of the catalyst by the supercharged air is stopped, the catalyst temperature rise is promoted, and the exhaust gas purification capacity is enhanced. At the same time, by controlling the opening of the bypass exhaust amount control valve, the rotational speed (supercharging pressure) of the exhaust turbine is controlled so that the supplied oxygen amount matches the target oxygen amount. Improve efficiency and improve fuel economy and drivability.
[0010]
On the other hand, when the catalyst temperature is higher than the target catalyst temperature, that is, when the catalyst needs to be cooled, the opening degree of the bypass air amount control valve and the bypass exhaust amount control valve is controlled so that the supplied oxygen amount matches the target oxygen amount. To do. Specifically, when the catalyst temperature is higher than the target catalyst temperature, the bypass air amount control is performed so that the supply oxygen amount matches the target oxygen amount on the assumption that the supply oxygen amount matches the target catalyst temperature. After calculating the opening of the valve, calculate the opening of the bypass exhaust amount control valve so that the supplied oxygen amount matches the target oxygen amount at the calculated opening of the bypass air amount control valve. When the opening degree of the bypass exhaust amount control valve is larger than 0 (= fully closed), the opening degree of the bypass air amount control valve and the opening degree of the bypass exhaust amount control valve are respectively set to the calculated opening degrees. It adjusts (Claim 1). Further, when the calculated opening degree of the bypass exhaust amount control valve is 0 or less, the bypass exhaust amount control valve is fully closed and the opening degree of the bypass air amount control valve is controlled, so that the supplied oxygen amount is reduced. Control may be performed so as to match the target oxygen amount (claim 2). This The opening of the bypass air amount control valve is controlled in accordance with the difference between the catalyst temperature and the target catalyst temperature within a range in which the turbocharger has a surplus capacity while ensuring the output of the internal combustion engine. By bypassing a part of the supercharged air to the exhaust passage side, the exhaust temperature is lowered to cool the catalyst, thereby improving the exhaust purification capability. In this case, bypassing of the supercharged air to the exhaust passage side (catalyst cooling) is performed within a range in which the turbocharger has sufficient capacity for supercharging, so that the supercharged air to the internal combustion engine is insufficiently supplied. The output of the internal combustion engine is ensured, and drivability does not decrease.
[0011]
According to a fourth aspect of the present invention, the first intake bypass passage for bypassing the intake passage downstream of the supercharger and the exhaust passage upstream of the catalyst, and the intake passage downstream of the supercharger A second intake bypass passage for bypassing the exhaust passage downstream of the catalyst is provided, and the first and second bypass air amount control valves provided in both the intake bypass passages are connected to the catalyst temperature and the target catalyst temperature. And the control means comprehensively control based on the difference between them and the difference between the supplied oxygen amount and the target oxygen amount. In this way, by controlling the first and second bypass air amount control valves, the control of the bypass amount of the supercharged air to the upstream side of the catalyst in the exhaust passage and the control of the supercharging pressure are simultaneously performed. This makes it possible to achieve both exhaust purification performance and drivability.
[0012]
In this case, in claim 5, when the catalyst temperature is lower than the target catalyst temperature (when cooling of the catalyst is not required), the first bypass air amount control valve is closed to the upstream side of the catalyst in the exhaust passage. The supercharged air bypass is shut off, the cooling of the catalyst by the supercharged air is stopped, the catalyst temperature rise is promoted, and the exhaust gas purification capacity is enhanced. At the same time, by controlling the opening degree of the second bypass air amount control valve, the bypass amount of the supercharged air to the downstream side of the catalyst in the exhaust passage is controlled to control the supercharging pressure, and the target oxygen amount is targeted. Control to match the amount of oxygen to improve the combustion efficiency of the internal combustion engine and improve fuel efficiency and drivability.
[0013]
On the other hand, when the catalyst temperature is higher than the target catalyst temperature, the opening degree of the first and second bypass air amount control valves is controlled so as to match the supplied oxygen amount with the target oxygen amount, thereby ensuring the output of the internal combustion engine. Then, the opening degree of the first bypass air amount control valve is controlled in accordance with the difference between the catalyst temperature and the target catalyst temperature within a range in which the supercharging capacity of the supercharger has a surplus capacity, By bypassing the part to the upstream side of the catalyst in the exhaust passage, the exhaust temperature on the upstream side of the catalyst is lowered to cool the catalyst. In this case, since the bypass of the supercharged air to the upstream side of the catalyst (cooling of the catalyst) is performed within a range where the supercharging capability of the supercharger has a surplus capacity, the supercharged air to the internal combustion engine becomes insufficiently supplied. In other words, the output of the internal combustion engine is ensured and drivability does not deteriorate.
[0014]
According to a sixth aspect of the present invention, the supply oxygen amount estimation means includes an intake pressure sensor that detects an intake pressure, an intake air amount sensor that detects an intake air amount, and an exhaust gas recirculation amount that detects an exhaust gas recirculation amount to the intake system. A supply oxygen amount is estimated based on an output signal of at least one of a sensor and an oxygen sensor for detecting an oxygen amount taken into the internal combustion engine. Here, as the intake pressure sensor and the intake air amount sensor, an existing sensor mounted on the vehicle for controlling the internal combustion engine may be used, and the cost burden may be reduced. Furthermore, the supply oxygen amount may be estimated by combining the detection value of one of the intake pressure sensor and the intake air amount sensor and the detection value of the exhaust gas recirculation amount sensor. In this way, it is possible to estimate an accurate supply oxygen amount in consideration of oxygen in the exhaust gas recirculated to the intake system. Moreover, if an oxygen sensor is used, the amount of supplied oxygen can be directly detected.
[0015]
According to a seventh aspect of the present invention, the target oxygen amount calculating means calculates the target oxygen amount based on an operating state of the internal combustion engine within a range equal to or less than a maximum oxygen amount corresponding to a supercharging pressure limit value of the supercharger. To do. As a result, the target oxygen amount can be set so that the internal combustion engine does not become overloaded, and the durability of the internal combustion engine can be improved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. A turbocharger 13 is installed in an intake passage 12 of a diesel engine 11 that is an internal combustion engine. The turbocharger 13 is driven by an exhaust turbine 15 that is rotationally driven by the kinetic energy of the exhaust gas flowing in the exhaust passage 14. An exhaust purification catalyst 17 is installed in the exhaust passage 14 on the downstream side of the exhaust turbine 15.
[0017]
Further, an intake bypass passage 18 for bypassing the intake passage 12 downstream of the turbocharger 13 and the exhaust passage 14 upstream of the catalyst 17 is provided. The intake bypass passage 18 can be adjusted in opening. A bypass air amount control valve 19 is provided. The opening degree of the bypass air amount control valve 19 may be adjusted by a motor (not shown) such as a step motor. Alternatively, when the bypass air amount control valve 19 is configured by a solenoid valve, the duty of energization of the solenoid coil of the solenoid valve is controlled to control the degree of time with which the valve is opened and closed and the valve passes through the valve. What is necessary is just to control the amount of air. Controlling the degree of time for opening and closing the valve by duty control of the electromagnetic valve is also included in the concept of “controlling the opening degree of the bypass air amount control valve” in the claims. An intake pressure sensor 20 that detects intake pressure is installed in the intake passage 12 downstream of the inlet 18 a of the intake bypass passage 18.
[0018]
On the other hand, the exhaust passage 14 is provided with an exhaust bypass passage 21 (waste gate) that bypasses the upstream side and the downstream side of the exhaust turbine 15. The exhaust bypass passage 21 has a bypass exhaust amount control valve whose opening degree can be adjusted. 22 is provided. The opening adjustment of the bypass exhaust amount control valve 22 may be performed by duty control of a motor (not shown) or an electromagnetic valve, similarly to the opening adjustment of the bypass air amount control valve 19. An exhaust temperature sensor 23 for detecting the exhaust temperature is installed in the vicinity of the upstream end face of the catalyst 17, and the temperature of the catalyst 17 is determined from the exhaust temperature detected by the exhaust temperature sensor 23. Therefore, in the present embodiment, the exhaust gas temperature sensor 23 is used as catalyst temperature determination means in the claims.
[0019]
The accelerator 24 is provided with an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount), and the diesel engine 11 is provided with an engine speed sensor 26 for detecting the engine speed.
[0020]
The output signals of these accelerator opening sensor 25, engine speed sensor 26, exhaust temperature sensor 23, intake pressure sensor 20, and other sensors for detecting various information relating to engine control are transmitted to an engine control electronic control circuit (hereinafter referred to as "ECU"). 27). The ECU 27 is mainly composed of a microcomputer, controls the operation of a fuel injection device (not shown) based on the various sensor information, and executes a supercharging control program shown in FIGS. 2 and 3. It functions as a control means for controlling the opening degree of the bypass air amount control valve 19 and the bypass exhaust amount control valve 22 based on the difference between the catalyst temperature and the target catalyst temperature and the difference between the supply oxygen amount and the target oxygen amount, which will be described later. .
[0021]
Hereinafter, the flow of processing of the supercharging control program of FIGS. 2 and 3 will be described. This program is started by interruption processing at predetermined time intervals (for example, every second) or at predetermined crank angles. When this program is started, first, in step S101, the engine speed Ne, the accelerator opening Ac, the intake pressure output from the engine speed sensor 26, the accelerator opening sensor 25, the intake pressure sensor 20, and the exhaust temperature sensor 23 are displayed. Pq and exhaust temperature T are read. Then, in the next step S102, the target intake pressure P1 required to ensure the target engine output is calculated from preset map data in accordance with the read engine speed Ne and accelerator opening degree Ac. . At this time, the target intake pressure P1 is set within a range equal to or lower than the supercharging pressure limit value of the turbocharger 13 so that the diesel engine 11 does not become overloaded.
[0022]
After calculating the target intake pressure P1, the exhaust gas temperature T and the target catalyst temperature T1 are compared in step S103 to determine the temperature state (active state) of the catalyst 17. In this case, the temperature of the catalyst 17 rises mainly due to the heat of the exhaust gas, and it can be estimated that the catalyst temperature is substantially equal to the exhaust temperature T. Therefore, in this embodiment, the exhaust temperature T is used as substitute data for the catalyst temperature. The target catalyst temperature T1 is set to a catalyst temperature Tmax (see FIG. 4) at which the NOx purification rate of the catalyst 17 is maximized.
[0023]
If it is determined in step S103 that the exhaust temperature T (= catalyst temperature) is equal to or lower than the target catalyst temperature T1, cooling of the catalyst 17 is not necessary. In this case, the process proceeds to step S104, and the opening degree of the bypass exhaust amount control valve 22 is calculated so that the intake pressure Pq = the target intake pressure P1 assuming that the bypass air amount control valve 19 is fully closed. Thereafter, in step S105, a fully-closed signal for the bypass air amount control valve 19 is output to close the bypass air amount control valve 19, and the bypass of the supercharged air upstream of the catalyst 17 in the exhaust passage 14 is shut off. Thus, the exhaust temperature is prevented from lowering and the temperature of the catalyst 17 is increased. Furthermore, in this step S105, the opening signal of the bypass displacement control valve 22 calculated in step S104 is output, the opening of the bypass displacement control valve 22 is adjusted, and the exhaust turbine 15 of the turbocharger 13 is adjusted. Adjust the amount of exhaust gas to bypass. Thus, the amount of exhaust gas passing through the exhaust turbine 15 is adjusted, the rotational speed of the exhaust turbine 15 is adjusted, and the supercharging pressure of the turbocharger 13 is adjusted so that the intake pressure Pq becomes the target intake pressure P1. Thus, the combustion efficiency of the diesel engine 11 is improved, and the fuel consumption and drivability are improved.
[0024]
In this case, since the oxygen amount (supply oxygen amount) of the intake air supplied to the diesel engine 11 can be estimated from the intake pressure Pq, the intake pressure Pq is used as substitute data for the supply oxygen amount. Therefore, in the present embodiment, the intake pressure sensor 20 that detects the intake pressure Pq is used as the supply oxygen amount estimating means in the claims. Then, the target intake pressure P1 calculated in step S102 is used as substitute data for the oxygen amount (target oxygen amount) of the intake air necessary for burning the fuel supplied to the diesel engine 11. Therefore, in the present embodiment, the process of step S102 for calculating the target intake pressure P1 serves as a target oxygen amount calculation means in the claims.
[0025]
On the other hand, if it is determined in step S103 described above that the exhaust gas temperature T (= catalyst temperature) is higher than the target catalyst temperature T1, the catalyst 17 needs to be cooled. In this case, the routine proceeds to step S106 in FIG. 3, and the opening degree of the bypass air amount control valve 19 is calculated so that the exhaust temperature T = target catalyst temperature T1 assuming that the intake pressure Pq = target intake pressure P1. Thereafter, the process proceeds to step S107, and the opening degree of the bypass exhaust amount control valve 22 is calculated by the opening degree of the bypass air amount control valve 19 calculated in step S106 so that the intake pressure Pq = the target intake pressure P1.
[0026]
Thereafter, in step S108, it is determined whether or not the opening degree of the bypass exhaust amount control valve 22 is larger than 0 (= fully closed). If so, the process proceeds to step S109, and the bypass calculated in step S106 is determined. The opening degree signal of the air amount control valve 19 and the opening degree signal of the bypass exhaust amount control valve 22 calculated in step S107 are output, and the opening degree of both control valves 19 and 22 is adjusted. Thus, the supercharging pressure is controlled so that the intake pressure Pq = the target intake pressure P1, and the necessary engine output is secured, and the exhaust temperature T (= catalyst temperature) is made to coincide with the target catalyst temperature T1. By controlling the opening degree of the bypass air amount control valve 19 and bypassing a part of the supercharged air to the exhaust passage 14 side and mixing with the exhaust gas, the exhaust temperature is lowered and the catalyst 17 is cooled. The temperature is quickly lowered to the target catalyst temperature T1.
[0027]
On the other hand, if it is determined in step S108 described above that the opening degree of the bypass exhaust amount control valve 22 is 0 (= fully closed) or less, the process proceeds to step S110, and the bypass exhaust amount control valve 22 is assumed to be fully closed. Thus, the opening degree of the bypass air amount control valve 19 is calculated so that the intake pressure Pq = the target intake pressure P1. Thereafter, in step S111, the opening degree signal of the bypass air amount control valve 19 calculated in step S110 and the fully closed signal of the bypass exhaust amount control valve 22 are output, the bypass exhaust amount control valve 22 is fully closed, By adjusting the opening degree of the bypass air amount control valve 19 to control the supercharging pressure so that the intake pressure Pq = the target intake pressure P1, the required engine output is ensured, and the supercharging capability of the turbocharger 13 By bypassing a part of the supercharged air to the exhaust passage 14 within a range where there is a surplus power, the exhaust temperature is lowered, the catalyst 17 is cooled, and the catalyst temperature is lowered.
[0028]
According to the supercharging control described above, when the catalyst temperature (exhaust temperature T) is equal to or lower than the target catalyst temperature T1, that is, when cooling of the catalyst 17 is unnecessary, the bypass air amount control valve 19 is fully closed. The bypass of the supercharged air to the exhaust passage 14 side is shut off, the cooling of the catalyst by the supercharged air is stopped, the catalyst temperature rise is promoted, and the exhaust gas purification capacity is enhanced. At the same time, by controlling the opening degree of the bypass exhaust amount control valve 22, the rotational speed (supercharging pressure) of the exhaust turbine 15 is controlled, and the intake pressure Pq (supplied oxygen amount) is set to the target intake pressure P1 (target oxygen amount). ) To improve the combustion efficiency of the diesel engine 11 and improve fuel efficiency and drivability.
[0029]
On the other hand, when the catalyst temperature (exhaust temperature T) is higher than the target catalyst temperature T1, that is, when the catalyst 17 needs to be cooled, the intake pressure Pq (supply oxygen amount) is adjusted to the target intake pressure P1 (target oxygen amount). In this way, the opening degree of the bypass air amount control valve 19 and the bypass exhaust amount control valve 22 is controlled to ensure the output of the diesel engine 11 and within a range in which the turbocharger 13 has a surplus capacity. By controlling the opening degree of the bypass air amount control valve 19 according to the difference between the catalyst temperature (exhaust temperature T) and the target catalyst temperature T1, the exhaust temperature is bypassed to the exhaust passage 14 side. Is reduced to cool the catalyst 17 and enhance the exhaust gas purification capacity.
[0030]
The behavior of the supercharging control described above will be described according to the time chart shown in FIG. The time chart of FIG. 5 is an example of a driving pattern of acceleration → constant speed driving → deceleration frequently occurring during city driving. At time t0 during the idling operation, the catalyst temperature is lower than the target catalyst temperature T1, so the bypass air amount control valve 19 is fully closed and the catalyst 17 is not cooled. Further, during idle operation, since the output of the diesel engine 11 may be the lowest, the bypass exhaust amount control valve 22 is fully opened, the amount of exhaust gas passing through the exhaust turbine 15 is minimized, and the turbocharger 13 Work volume (supercharging pressure) is lowest.
[0031]
After that, when acceleration is started at time t1, it is necessary to increase the engine output. Therefore, the bypass exhaust amount control valve 22 is fully closed, the work amount of the turbocharger 13 is increased, and the supercharging pressure is increased. Almost simultaneously with the start of acceleration, the exhaust temperature rises. However, since the catalyst 17 has a heat capacity, the rise in the catalyst temperature is delayed from the rise in the exhaust temperature. Therefore, if the acceleration time (t1 -t2) is relatively short, the catalyst 17 does not need to be cooled during the acceleration because the catalyst temperature is lower than the target catalyst temperature T1. In this case, during acceleration (t1-t2), the bypass air amount control valve 19 is maintained in the fully closed state, the bypass of the supercharged air to the exhaust passage 14 side is shut off, and all the supercharged air is excessive. Used to increase the supply pressure, engine output is effectively increased and good acceleration is ensured.
[0032]
Thereafter, when the acceleration is terminated at the time t2 and the vehicle shifts to the constant speed running, the engine output can be smaller than that during acceleration. Therefore, the bypass displacement control valve 22 is opened and the work of the turbocharger 13 (supercharging) Pressure) is lower than during acceleration.
[0033]
At this time, the catalyst temperature continues to rise for a while even after shifting to constant speed running, and the catalyst temperature exceeds the target catalyst temperature T1 at time t3. In this case, since the catalyst 17 needs to be cooled, the bypass air amount control valve 19 is opened to an opening degree corresponding to the difference between the catalyst temperature and the target catalyst temperature T1, and a part of the supercharged air is exhausted from the exhaust passage. Bypassing to the 14 side, the catalyst 17 is cooled. In this way, when a part of the supercharged air is used for cooling the catalyst 17, the amount of supercharged air supplied to the diesel engine 11 is reduced. Therefore, the opening degree of the bypass displacement control valve 22 is set to compensate for this. As a result, the amount of work of the turbocharger 13 is increased, and the engine output necessary for maintaining constant speed traveling is ensured.
[0034]
After the catalyst temperature reaches the target catalyst temperature T1, the engine output is secured, and the bypass is performed so that the catalyst temperature matches the target catalyst temperature T1 within a range where the turbocharger 13 has a surplus capacity. The opening degree of the air amount control valve 19 is controlled to enhance the exhaust purification capability.
[0035]
When the catalyst 17 is not cooled (bypass of the supercharged air) as in the conventional general diesel engine, the catalyst temperature is set to the target catalyst temperature T1 during constant speed running as shown by the dotted line in FIG. Is greatly exceeded, the difference between the catalyst temperature and the target catalyst temperature T1 increases, the NOx purification rate decreases, and the NOx emission amount increases.
[0036]
On the other hand, in the present embodiment, the engine output is ensured, and the bypass air amount control is performed according to the difference between the catalyst temperature and the target catalyst temperature T1 within a range in which the turbocharger 13 has a surplus capacity. By controlling the opening degree of the valve 19 and adjusting the bypass amount of the supercharged air that cools the catalyst 17, it is possible to maintain the catalyst temperature at a high NOx purification rate, and to effectively reduce the NOx emission amount. In addition, bypassing of the supercharged air to the exhaust passage 14 side (cooling of the catalyst 17) is performed within a range in which the turbocharger 14 has sufficient capacity, so that the supercharged air to the diesel engine 11 is reduced. There is no supply shortage, engine output is secured, drivability does not deteriorate, and both exhaust purification ability and drivability can be achieved.
[0037]
Note that an intercooler (a heat exchanger that cools the supercharged air) may be provided in the intake passage 12 on the downstream side of the turbocharger 13 to increase the supercharging efficiency. In this case, the inlet 18a of the intake bypass passage 18 is preferably provided on the downstream side of the intercooler. In this way, the cooling effect of the catalyst 17 can be further enhanced by bypassing a part of the supercharged air cooled by the intercooler to the exhaust passage 14 side.
[0039]
On the other hand, in the second embodiment of the present invention shown in FIG. 6, a first intake bypass passage that bypasses the intake passage 12 downstream of the turbocharger 13 and the exhaust passage 14 upstream of the catalyst 17. 31 is provided, and on the outlet side of the first intake bypass passage 31, a first bypass air amount control valve 32 whose opening degree can be adjusted is provided. Furthermore, a second intake bypass passage 33 is provided for bypassing the first intake bypass passage 31 upstream of the first bypass air amount control valve 32 and the exhaust passage 14 downstream of the catalyst 17. The second intake bypass passage 33 is provided with a second bypass air amount control valve 34 whose opening degree can be adjusted. The exhaust bypass passage 21 and the bypass exhaust amount control valve 22 provided in the first embodiment are eliminated. The other configuration is the same as that of the first embodiment.
[0040]
In the second embodiment configured as described above, the first intake bypass passage 31 and the first bypass air amount control valve 32 are the same as the intake bypass passage 18 and the bypass air amount control valve 19 in the first embodiment. Play exactly the same role. Further, the second intake bypass passage 33 and the second bypass air amount control valve 34 adjust the amount of supercharged air to be bypassed downstream of the catalyst 17, thereby increasing the supercharging pressure supplied to the diesel engine 11. It adjusts and plays almost the same role as the exhaust bypass passage 21 and the bypass exhaust amount control valve 22 in the first embodiment. Therefore, the control of the first bypass air amount control valve 32 and the second bypass air amount control valve 34 is the same as the control of the bypass air amount control valve 19 and the bypass exhaust amount control valve 22 in the first embodiment. In the supercharging control program shown in FIGS. 2 and 3, “bypass air amount control valve 19” is read as “first bypass air amount control valve 32”, and “bypass exhaust amount control valve 22” is replaced with “second What is necessary is just to read and control as the bypass air quantity control valve 34 ".
[0041]
In the second embodiment described above, the same effect as that of the first embodiment can be obtained, and the opening degree of the second bypass air amount control valve 34 can be obtained even if the exhaust bypass passage 21 (waste gate) is eliminated. Adjustment can prevent overloading the diesel engine 11 and is effective when the wastegate cannot be installed due to a problem in the engine room.
[0042]
In the second embodiment, the second intake bypass passage 33 is branched from the middle of the first intake bypass passage 31, but the two intake bypass passages 31 and 33 are completely independent. It is also good.
[0043]
Further, in each of the above embodiments, paying attention to the point that the oxygen amount (supply oxygen amount) of intake air supplied to the diesel engine 11 can be estimated from the intake pressure Pq, the intake pressure Pq is used as substitute data for the supply oxygen amount. did. That is, the intake pressure sensor 20 that detects the intake pressure Pq is used as the supply oxygen amount estimation means, but the intake air amount sensor that detects the intake air amount and the exhaust gas return that detects the recirculation amount of the exhaust gas to the intake system. The supplied oxygen amount may be estimated based on the output signal of at least one of the flow rate sensor and the oxygen sensor that detects the amount of oxygen sucked into the diesel engine 11.
[0044]
In this case, as the intake pressure sensor 20 and the intake air amount sensor, an existing sensor mounted on the vehicle for controlling the diesel engine 11 may be used, and the cost burden may be reduced. Furthermore, the supply oxygen amount may be estimated by combining the detection value of one of the intake pressure sensor and the intake air amount sensor and the detection value of the exhaust gas recirculation amount sensor. In this way, it is possible to estimate an accurate supply oxygen amount in consideration of oxygen in the exhaust gas recirculated to the intake system, thereby improving control accuracy. Moreover, if an oxygen sensor is used, the amount of supplied oxygen can be detected directly, and the control accuracy can be improved.
[0045]
In each of the above embodiments, the exhaust gas temperature sensor 23 is used as the catalyst temperature determination means and the exhaust gas temperature T is used as the substitute data for the catalyst temperature. However, the catalyst temperature sensor that directly detects the catalyst temperature is used as the catalyst temperature determination means. You may make it provide as. In addition, the present invention can be implemented with various modifications without departing from the gist, such as being applied to a gasoline engine.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an entire engine control system according to a first embodiment of the present invention.
FIG. 2 is a flowchart (part 1) showing a processing flow of a supercharging control program.
FIG. 3 is a flowchart (part 2) showing the flow of processing of a supercharging control program.
FIG. 4 is a graph showing the relationship between catalyst temperature and NOx purification rate.
FIG. 5 is a time chart showing the behavior of supercharging control.
FIG. 6 is a diagram showing a schematic configuration of the entire engine control system according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Diesel engine (internal combustion engine), 12 ... Intake passage, 13 ... Turbocharger (supercharger), 14 ... Exhaust passage, 15 ... Exhaust turbine, 17 ... Catalyst, 18 ... Intake bypass passage, 19 ... Bypass air 20 ... Intake pressure sensor (supply oxygen amount estimating means), 21 ... Exhaust bypass passage, 22 ... Bypass exhaust amount control valve, 23 ... Exhaust temperature sensor (catalyst temperature determining means), 25 ... Accelerator opening sensor, DESCRIPTION OF SYMBOLS 26 ... Engine speed sensor, 27 ... ECU (control means, target oxygen amount calculation means), 31 ... First intake bypass passage, 32 ... First bypass air amount control valve, 33 ... Second intake bypass passage, 34: Second bypass air amount control valve.

Claims

吸気通路に設けられた過給機と、排気通路に設けられた排気浄化用の触媒とを備え、前記過給機として、排気エネルギで駆動される排気タービンを駆動源とするターボ過給機を用いた内燃機関制御装置において、
前記触媒の温度を判定する触媒温度判定手段と、
前記過給機よりも下流側の吸気通路と前記触媒よりも上流側の排気通路とをバイパスさせる吸気バイパス通路と、
前記吸気バイパス通路を通過する空気量を制御するバイパス空気量制御弁と、
前記排気通路に設けられ、前記排気タービンの上流側と下流側とをバイパスさせる排気バイパス通路と、
前記排気バイパス通路に設けられたバイパス排気量制御弁と、
内燃機関に供給する吸入空気の酸素量（以下「供給酸素量」という）を推定する供給酸素量推定手段と、
内燃機関に供給する燃料を燃焼するのに必要な吸入空気の酸素量（以下「目標酸素量」という）を算出する目標酸素量算出手段と、
前記触媒温度判定手段で判定した触媒温度と目標触媒温度との差及び前記酸素量推定手段で求めた供給酸素量と前記目標酸素量算出手段で求めた目標酸素量との差に基づいて前記バイパス空気量制御弁の開度及び前記バイパス排気量制御弁の開度を制御する制御手段とを備え、
前記制御手段は、前記触媒温度が前記目標触媒温度より高い場合には、前記供給酸素量が前記目標酸素量と一致すると仮定して前記触媒温度を前記目標触媒温度に合わせるように前記バイパス空気量制御弁の開度を算出した後、この算出した前記バイパス空気量制御弁の開度にて前記供給酸素量を前記目標酸素量に合わせるように前記バイパス排気量制御弁の開度を算出し、算出した前記バイパス排気量制御弁の開度が０よりも大きい場合に前記バイパス空気量制御弁の開度及び前記バイパス排気量制御弁の開度をそれぞれ前記算出した開度に調整することを特徴とする内燃機関制御装置。A turbocharger comprising a supercharger provided in the intake passage and an exhaust purification catalyst provided in the exhaust passage, and the turbocharger using an exhaust turbine driven by exhaust energy as a drive source. In the internal combustion engine controller used ,
Catalyst temperature determining means for determining the temperature of the catalyst;
An intake bypass passage that bypasses an intake passage downstream of the supercharger and an exhaust passage upstream of the catalyst;
A bypass air amount control valve for controlling the amount of air passing through the intake bypass passage;
An exhaust bypass passage provided in the exhaust passage and bypassing the upstream side and the downstream side of the exhaust turbine;
A bypass displacement control valve provided in the exhaust bypass passage;
Supply oxygen amount estimation means for estimating the oxygen amount of intake air supplied to the internal combustion engine (hereinafter referred to as “supply oxygen amount”);
A target oxygen amount calculating means for calculating an oxygen amount of intake air (hereinafter referred to as “target oxygen amount”) necessary for burning fuel supplied to the internal combustion engine;
The bypass is based on the difference between the catalyst temperature determined by the catalyst temperature determining means and the target catalyst temperature, and the difference between the supply oxygen amount determined by the oxygen amount estimating means and the target oxygen amount determined by the target oxygen amount calculating means. Control means for controlling the opening of the air amount control valve and the opening of the bypass exhaust amount control valve ,
When the catalyst temperature is higher than the target catalyst temperature, the control means assumes that the supplied oxygen amount matches the target oxygen amount, and the bypass air amount so as to match the catalyst temperature with the target catalyst temperature. After calculating the opening degree of the control valve, the opening degree of the bypass exhaust amount control valve is calculated so as to match the supplied oxygen amount with the target oxygen amount at the calculated opening degree of the bypass air amount control valve. When the calculated opening degree of the bypass exhaust amount control valve is larger than 0, the opening degree of the bypass air amount control valve and the opening degree of the bypass exhaust amount control valve are adjusted to the calculated opening degree, respectively. An internal combustion engine control device.

前記制御手段は、算出した前記バイパス排気量制御弁の開度が０以下の場合には、前記バイパス排気量制御弁を全閉して前記バイパス空気量制御弁の開度を制御することで、前記供給酸素量を前記目標酸素量に合わせるように制御することを特徴とする請求項１に記載の内燃機関制御装置。 When the calculated opening degree of the bypass exhaust amount control valve is 0 or less, the control means fully closes the bypass exhaust amount control valve to control the opening degree of the bypass air amount control valve, 2. The internal combustion engine controller according to claim 1, wherein the supply oxygen amount is controlled to match the target oxygen amount .

前記制御手段は、前記触媒温度が前記目標触媒温度以下の場合には、前記バイパス空気量制御弁を全閉して、前記バイパス排気量制御弁の開度を制御することで、前記供給酸素量を前記目標酸素量に合わせるように制御することを特徴とする請求項１又は２に記載の内燃機関制御装置。Wherein when the catalyst temperature is below the target catalyst temperature, the bypass air quantity control valve and fully closed, by controlling the opening degree of the bypass exhaust gas amount control valve, the supply amount of oxygen the internal combustion engine control apparatus according to claim 1 or 2, characterized in that controlled to match the target oxygen amount.

吸気通路に設けられた過給機と、排気通路に設けられた排気浄化用の触媒とを備えた内燃機関制御装置において、
前記触媒の温度を判定する触媒温度判定手段と、
前記過給機よりも下流側の吸気通路と前記触媒よりも上流側の排気通路とをバイパスさせる第１の吸気バイパス通路と、
前記第１の吸気バイパス通路を通過する空気量を制御する第１のバイパス空気量制御弁と、
前記過給機よりも下流側の吸気通路と前記触媒よりも下流側の排気通路とをバイパスさせる第２の吸気バイパス通路と、
前記第２の吸気バイパス通路を通過する空気量を制御する第２のバイパス空気量制御弁と、
内燃機関に供給する吸入空気の酸素量（以下「供給酸素量」という）を推定する供給酸素量推定手段と、
内燃機関に供給する燃料を燃焼するのに必要な吸入空気の酸素量（以下「目標酸素量」という）を算出する目標酸素量算出手段と、
前記触媒温度判定手段で判定した触媒温度と目標触媒温度との差及び前記酸素量推定手段で求めた供給酸素量と前記目標酸素量算出手段で求めた目標酸素量との差に基づいて前記第１及び第２のバイパス空気量制御弁の開度を制御する制御手段と
を備えていることを特徴とする内燃機関制御装置。In an internal combustion engine control device comprising a supercharger provided in an intake passage and an exhaust purification catalyst provided in an exhaust passage,
Catalyst temperature determining means for determining the temperature of the catalyst;
A first intake bypass passage that bypasses an intake passage downstream of the supercharger and an exhaust passage upstream of the catalyst;
A first bypass air amount control valve for controlling the amount of air passing through the first intake bypass passage;
A second intake bypass passage that bypasses an intake passage downstream of the supercharger and an exhaust passage downstream of the catalyst;
A second bypass air amount control valve for controlling the amount of air passing through the second intake bypass passage;
Supply oxygen amount estimation means for estimating the oxygen amount of intake air supplied to the internal combustion engine (hereinafter referred to as “supply oxygen amount”);
A target oxygen amount calculating means for calculating an oxygen amount of intake air (hereinafter referred to as “target oxygen amount”) necessary for burning fuel supplied to the internal combustion engine;
Based on the difference between the catalyst temperature determined by the catalyst temperature determination means and the target catalyst temperature, and the difference between the supply oxygen amount determined by the oxygen amount estimation means and the target oxygen amount determined by the target oxygen amount calculation means. An internal combustion engine control device comprising: control means for controlling the opening degree of the first and second bypass air amount control valves.

前記制御手段は、前記触媒温度が目標触媒温度より低い場合には、前記第１のバイパス空気量制御弁を閉鎖して、前記第２のバイパス空気量制御弁の開度を制御することで、前記供給酸素量を前記目標酸素量に合わせるように制御し、
前記触媒温度が目標触媒温度より高い場合には、前記供給酸素量を前記目標酸素量に合わせるように前記第１及び第２のバイパス空気量制御弁の開度を制御した上で前記過給機の過給能力に余力がある範囲内で前記触媒温度と目標触媒温度との差に応じて前記第１のバイパス空気量制御弁の開度を制御することを特徴とする請求項４に記載の内燃機関制御装置。When the catalyst temperature is lower than the target catalyst temperature, the control means closes the first bypass air amount control valve and controls the opening degree of the second bypass air amount control valve, Controlling the supply oxygen amount to match the target oxygen amount;
When the catalyst temperature is higher than the target catalyst temperature, the supercharger is controlled after opening degrees of the first and second bypass air amount control valves so that the supplied oxygen amount matches the target oxygen amount. 5. The opening degree of the first bypass air amount control valve is controlled according to a difference between the catalyst temperature and a target catalyst temperature within a range in which there is a surplus capacity in the supercharging capacity of the engine. Internal combustion engine control device.

前記供給酸素量推定手段は、吸気圧を検出する吸気圧センサ、吸入空気量を検出する吸入空気量センサ、吸気系への排気ガスの還流量を検出する排気還流量センサ、前記内燃機関に吸入される酸素量を検出する酸素センサのうちの少なくとも１つのセンサの出力信号に基づいて供給酸素量を推定することを特徴とする請求項１乃至５のいずれかに記載の内燃機関制御装置。 The supply oxygen amount estimation means includes an intake pressure sensor that detects an intake pressure, an intake air amount sensor that detects an intake air amount, an exhaust gas recirculation amount sensor that detects a recirculation amount of exhaust gas to the intake system, and an intake air that is sucked into the internal combustion engine 6. The internal combustion engine controller according to claim 1, wherein the supply oxygen amount is estimated based on an output signal of at least one of oxygen sensors for detecting the amount of oxygen to be detected.

前記目標酸素量算出手段は、前記過給機の過給圧限界値に相当する最大酸素量以下の範囲内で前記目標酸素量を内燃機関の運転状態に基づいて算出することを特徴とする請求項１乃至６のいずれかに記載の内燃機関制御装置。 The target oxygen amount calculating means calculates the target oxygen amount based on an operating state of an internal combustion engine within a range equal to or less than a maximum oxygen amount corresponding to a supercharging pressure limit value of the supercharger. Item 7. The internal combustion engine controller according to any one of Items 1 to 6.