JP4302843B2 - Internal combustion engine control method - Google Patents

Description

【００８３】
なお、このときの燃焼サイクルが燃料遮断である場合には、数１において第２補正基準値Ｄを差し引くことをせず、上死点後圧力積分値Ｂから上死点前圧力積分値Ａを差し引いた値を第１補正基準値Ｃで除して得られる値を有効圧指数Ａｎとして算出するとともに、この有効圧指数Ａｎを第２補正基準値Ｄに代入して記憶する。
【００８４】
さらに、Ｓ１５０では、算出した有効圧指数Ａｎの値を、前回の有効圧指数Ａｎ-1に代入し、また、点火時期Ｔｉｇを予め定められた進角量Ｔａだけ進めた値に更新し、そして、初期ＦＬＧをセット（ＳＥＴ）する。こうしてＳ１５０の処理が行われると、Ｓ２４０に移行する。
【００８５】
そして、Ｓ２４０では、最後に算出された点火時期Ｔｉｇにて点火を行い、点火が行われるとＳ１１０に移行する。
また、Ｓ１４０に移行した際に、初期ＦＬＧがセットされていると、Ｓ１４０で肯定判定され、Ｓ１６０に移行する。Ｓ１６０では、まず、点火プラグ１１の圧力センサ１１ｂにて検出された燃焼圧信号が記憶された図示しない記憶部から、クランク角が９０°ＣＡ（ＢＴＤＣ９０゜ＣＡ）から２７０°ＣＡ（ＡＴＤＣ９０°ＣＡ）までの燃焼圧信号（筒内圧）を取込み、取込んだ筒内圧を用いて有効圧指数Ａｎを算出する。なお、有効圧指数Ａｎの算出方法は、Ｓ１５０の処理における算出方法と同様である。
【００８６】
続くＳ１７０では、最新（ｎ回目）の有効圧指数Ａｎが、前回（ｎ−１回目）の有効圧指数Ａｎ-1よりも大きいか否かを判断しており、肯定判定されるとＳ１８０に移行し、否定判定されるとＳ２１０に移行する。
Ｓ１７０に移行した際に、最新の有効圧指数Ａｎが前回の有効圧指数Ａｎ-1よりも大きい場合、Ｓ１７０で肯定判定され、Ｓ１８０に移行する。Ｓ１８０では、最新の有効圧指数Ａｎの値を前回の有効圧指数Ａｎ-1に代入し、点火時期Ｔｉｇを予め定められた進角量Ｔａだけ進めた値に更新する。
【００８７】
続くＳ１９０では、Ｓ１８０で更新した点火時期Ｔｉｇの値が、点火時期の進角限界値として予め定められた進角リミット点火時期ＴＬａよりも大きいか否かを判断しており、肯定判定されるとＳ２００に移行し、否定判定されるとＳ２４０に移行する。このとき、点火時期Ｔｉｇが進角リミット点火時期ＴＬａよりも大きい場合、Ｓ１９０で肯定判定されてＳ２００に移行し、Ｓ２００では、進角リミット点火時期ＴＬａの値を点火時期Ｔｉｇに代入する。これにより、点火時期が過度に進角してしまい、内燃機関の運転状態が不安定になることを防いでいる。Ｓ２００の処理が行われると、Ｓ２４０に移行する。
【００８８】
Ｓ１９０に移行した際に、点火時期Ｔｉｇが進角リミット点火時期ＴＬａ以下である場合、Ｓ１９０で否定判定されてＳ２４０に移行し、Ｓ２４０では、最後に算出された点火時期Ｔｉｇにて点火を行い、点火が行われるとＳ１１０に移行する。
【００８９】
また、Ｓ１７０に移行した際に、最新の有効圧指数Ａｎが前回の有効圧指数Ａｎ-1以下である場合、Ｓ１７０で否定判定され、Ｓ２１０に移行する。Ｓ２１０では、最新の有効圧指数Ａｎの値を前回の有効圧指数Ａｎ-1に代入し、点火時期Ｔｉｇを予め定められた遅角量Ｔｒだけ遅らせた値に更新する。
【００９０】
続くＳ２２０では、Ｓ２１０で更新した点火時期Ｔｉｇの値が、点火時期の遅角限界値として予め定められた遅角リミット点火時期ＴＬｒよりも小さいか否かを判断しており、肯定判定されるとＳ２３０に移行し、否定判定されるとＳ２４０に移行する。このとき、点火時期Ｔｉｇが遅角リミット点火時期ＴＬｒよりも小さい場合、Ｓ２２０で肯定判定され、Ｓ２３０に移行し、Ｓ２３０では、遅角リミット点火時期ＴＬｒの値を点火時期Ｔｉｇに代入する。これにより、点火時期が過度に遅角してしまい、内燃機関の運転状態が不安定になることを防いでいる。Ｓ２３０の処理が行われると、Ｓ２４０に移行する。
【００９１】
Ｓ２２０に移行した際に、点火時期Ｔｉｇが遅角リミット点火時期ＴＬｒ以上である場合、Ｓ２２０で否定判定され、Ｓ２４０に移行し、Ｓ２４０では、最後に算出された点火時期Ｔｉｇにて点火を行い、点火が行われるとＳ１１０に移行する。
【００９２】
このように、本点火時期制御処理では、Ｓ２４０で点火を行うと、Ｓ１１０に移行し、上述の処理を繰り返し実行することで、有効圧指数Ａｎに基づいて点火時期Ｔｉｇを更新して、点火時期Ｔｉｇを制御している。
以上説明したように、本点火時期制御処理では、運転状態が変化しているときには、エンジン回転数およびスロットル開度に基づいて点火時期Ｔｉｇを制御している。そして、運転状態が安定しているときには、エンジン回転数およびスロットル開度に基づいて設定された点火時期Ｔｉｇを初期値として、点火時期Ｔｉｇを変化させたことによる有効圧指数Ａｎの変動に基づいて、内燃機関の燃焼状態を判断し、点火時期Ｔｉｇを制御している。
【００９３】
つまり、Ｓ１５０にて点火時期Ｔｉｇを進角させた後に、Ｓ１６０で算出される有効圧指数Ａｎが、進角させる前に算出された有効圧指数Ａｎ-1よりも大きくなる場合（Ｓ１７０で肯定判定される場合）には、燃焼状態が良好となったと判断できる。このため、続くＳ１８０にて次回の点火時期Ｔｉｇを更に進角させることで、次回の点火における燃焼状態を更に良好になるようにしている。
【００９４】
反対に、Ｓ１５０にて点火時期Ｔｉｇを進角させた後に、Ｓ１６０で算出される有効圧指数Ａｎが、進角させる前に算出された有効圧指数Ａｎ-1以下になる場合（Ｓ１７０で否定判定される場合）には、燃焼状態が不良となったと判断できる。このため、続くＳ２１０にて次回の点火時期Ｔｉｇを遅角させることで、次回の点火において燃焼状態が良好になるようにしている。
【００９５】
そして、内燃機関の運転状態が安定している状態が続く間、Ｓ１１０、Ｓ１２０、Ｓ１４０、Ｓ１６０からＳ２４０の各ステップが繰り返し実行されて、点火時期Ｔｉｇが有効圧指数Ａｎに基づいて最適な値に制御される。これにより、内燃機関の効率が最も良い点火時期であるＭＢＴ（Minimum Spark Advance for Best Torque ）に点火時期を設定して、内燃機関を運転することが可能になる。
【００９６】
なお、本実施例では、進角量Ｔａおよび遅角量Ｔｒは、予め設定された固定値としているが、例えば、運転状態に応じて設定される可変値としてもよい。また、遅角量Ｔｒを進角量Ｔａよりも大きい値に設定することで、不安定な燃焼状態からの回避を迅速に行うことが可能になる。また、進角リミット点火時期ＴＬａおよび遅角リミット点火時期ＴＬｒについても、例えば、運転状態に応じて設定される可変値としてもよい。
【００９７】
また、数１において第２補正基準値Ｄを差し引くことをせず有効圧指数Ａｎを算出し、この有効圧指数Ａｎを第２補正基準値Ｄに代入して記憶する処理は、燃料カット（燃料遮断）時に限ることはなく、失火運転時において筒内圧の残圧が検出可能な特定のエンジン条件下となる時に行うようにしてもよい。
【００９８】
次に、本実施例の空燃比制御処理について、図７に示すフローチャートに従って説明する。この空燃比制御処理は、内燃機関の運転が開始されると共に起動され、内燃機関の運転を停止するまで実行される。また、空燃比は混合気を形成する燃料と空気との比率を表していることから、本実施例の内燃機関では、空燃比制御は燃料噴射量を制御することで行っている。
【００９９】
図７に示すように、空燃比制御処理が開始されると、まずＳ３１０（Ｓはステップを表す）では、別途実行される運転状態検出処理にて検出されたエンジン回転数およびスロットル開度を測定する。続く、Ｓ３２０では、内燃機関の運転状態が安定した状態であるか（規定条件内であるか）否かを判断しており、具体的には、Ｓ３１０にて測定したエンジン回転数およびスロットル開度の変動が一定範囲内に収束しているか否かを判断している。そして、Ｓ３２０で肯定判定されるとＳ３４０に移行し、Ｓ３２０で否定判定されるとＳ３３０に移行する。
【０１００】
Ｓ３２０に移行した際に、内燃機関の運転状態が変化していると、Ｓ３２０で否定判定され、Ｓ３３０に移行する。Ｓ３３０では、Ｓ３１０で測定されたエンジン回転数およびスロットル開度に基づいて、予め設定されたマップから燃料噴射量Ｆｉｎを読込むことで燃料噴射量Ｆｉｎを設定し、さらに、初期ＦＬＧをリセット（ＲＥＳＥＴ）し、初期Ｓ算出カウンタＳＰＣＮＴをクリアする。なお、初期ＦＬＧは、有効圧指数Ａｎの比較を行うための初期値が算出されたことを表す指標であり、初期Ｓ算出カウンタＳＰＣＮＴは、有効圧指数Ａｎの標準偏差および平均を算出するための、データ数をカウントするためのカウンタである。Ｓ３３０の処理が行われると、Ｓ４６０に移行する。
【０１０１】
そして、Ｓ４６０では、最後に算出された最新の燃料噴射量Ｆｉｎにて燃料噴射を行い、燃料噴射が行われるとＳ３１０に移行する。
また、Ｓ３２０に移行した際に、内燃機関の運転状態が安定していると、Ｓ３２０で肯定判定され、Ｓ３４０に移行する。Ｓ３４０では、初期ＦＬＧがセット（ＳＥＴ）されているか否かを判断しており、肯定判定されるとＳ３８０に移行し、否定判定されるとＳ３５０に移行する。このとき、初期ＦＬＧがリセットされていると、Ｓ３４０で否定判定され、Ｓ３５０に移行する。
【０１０２】
Ｓ３５０では、まず、Ｓ３１０で測定されたエンジン回転数およびスロットル開度に基づいて、予め設定されたマップから燃料噴射量Ｆｉｎを読込むことで燃料噴射量Ｆｉｎを設定する。そして、点火プラグ１１の圧力センサ１１ｂにて検出された燃焼圧信号が記憶された図示しない記憶部から、クランク角が９０°ＣＡ（ＢＴＤＣ９０゜ＣＡ）から２７０°ＣＡ（ＡＴＤＣ９０°ＣＡ）までの燃焼圧信号（筒内圧）を取込み、取込んだ筒内圧を用いて有効圧指数Ａｎを算出する。なお、有効圧指数Ａｎの算出方法は、前述の点火時期制御処理のＳ１５０での処理における算出方法と同様である。
【０１０３】
そして、本空燃比制御処理が実行される間に算出された、最新の初期Ｓ算出回数Ｎ個の有効圧指数Ａｎにおける標準偏差および平均を算出し、標準偏差を平均で除することで得られる値を偏差／平均Ｓに設定する。このとき、標準偏差の算出には数２の計算式を用い、平均の算出には数３の計算式を用いる。
【０１０４】
【数２】

【０１０５】
【数３】

【０１０６】
なお、有効圧指数Ａｎの個数が、初期Ｓ算出回数Ｎに満たない場合には、標準偏差および平均の算出は行わない。
さらに、Ｓ３５０では、初期Ｓ算出カウンタＳＰＣＮＴを１加算（インクリメント）して、初期Ｓ算出カウンタＳＰＣＮＴを更新する。
【０１０７】
続くＳ３６０では、初期Ｓ算出カウンタＳＰＣＮＴが、初期Ｓ算出回数Ｎ以上であるか否かを判断しており、肯定判定されるとＳ３７０に移行し、否定判定されるとＳ４６０に移行する。このとき、初期Ｓ算出カウンタＳＰＣＮＴが、初期Ｓ算出回数Ｎよりも小さい場合、Ｓ３６０で否定判定され、Ｓ４６０に移行する。そして、Ｓ４６０では、最後に算出された燃料噴射量Ｆｉｎにて燃料噴射を行い、燃料噴射が行われるとＳ３１０に移行する。
【０１０８】
また、Ｓ３６０に移行した際に、初期Ｓ算出カウンタＳＰＣＮＴが、初期Ｓ算出回数Ｎ以上である場合、Ｓ３６０で肯定判定され、Ｓ３７０に移行する。そして、Ｓ３７０では、初期ＦＬＧをセットする。
Ｓ３７０の処理が行われるか、あるいは、Ｓ３４０にて肯定判定されると、Ｓ３８０に移行し、Ｓ３８０では、まず、点火プラグ１１の圧力センサ１１ｂにて検出された燃焼圧信号が記憶された図示しない記憶部から、クランク角が９０°ＣＡ（ＢＴＤＣ９０゜ＣＡ）から２７０°ＣＡ（ＡＴＤＣ９０°ＣＡ）までの燃焼圧信号（筒内圧）を取込み、取込んだ筒内圧を用いてＳ３５０での処理と同様の計算方法で有効圧指数Ａｎを算出する。そして、Ｓ３５０で算出した場合と同様に、本空燃比制御処理が実行される間に算出された、最新の初期Ｓ算出回数Ｎ個の有効圧指数Ａｎにおける標準偏差および平均を算出し、標準偏差を平均で除することで得られる値を偏差／平均Ｓに設定する。
【０１０９】
続くＳ３９０では、Ｓ３８０で算出した偏差／平均Ｓが、空燃比の希薄限界として予め設定されたリーンリミット判定値ＬＬ以下であるか否かを判定しており、肯定判定されるとＳ４００に移行し、否定判定されるとＳ４３０に移行する。このとき、偏差／平均Ｓがリーンリミット判定値ＬＬ以下である場合、Ｓ３９０で肯定判定され、Ｓ４００に移行する。Ｓ４００では、燃料噴射量Ｆｉｎを予め定められた燃料減量量Ｆａだけ減量した値に更新する。
【０１１０】
続くＳ４１０では、Ｓ４００で更新した燃料噴射量Ｆｉｎの値が、燃料噴射量の希薄限界値として予め定められた噴射燃料減量リミットＦＬａよりも小さいか否かを判断しており、肯定判定されるとＳ４２０に移行し、否定判定されるとＳ４６０に移行する。このとき、燃料噴射量Ｆｉｎが噴射燃料減量リミットＦＬａよりも小さい場合、Ｓ４１０で肯定判定されてＳ４２０に移行し、Ｓ４２０では、噴射燃料減量リミットＦＬａの値を燃料噴射量Ｆｉｎに代入する。これにより、燃料噴射量が過度に減量されてしまい、内燃機関の運転状態が不安定になることを防いでいる。Ｓ４２０の処理が行われると、Ｓ４６０に移行する。
【０１１１】
また、Ｓ４１０に移行した際に、燃料噴射量Ｆｉｎが噴射燃料減量リミットＦＬａ以上である場合、Ｓ４１０で否定判定されてＳ４６０に移行し、Ｓ４６０では、最後に算出された燃料噴射量Ｆｉｎにて燃料噴射を行い、燃料噴射が行われるとＳ３１０に移行する。
【０１１２】
また、Ｓ３９０に移行した際に、偏差／平均Ｓがリーンリミット判定値ＬＬよりも大きい場合、Ｓ３９０で否定判定され、Ｓ４３０に移行する。Ｓ４３０では、燃料噴射量Ｆｉｎを予め定められた燃料増量量Ｆｂだけ増量した値に更新する。
【０１１３】
続くＳ４４０では、Ｓ４３０で更新した燃料噴射量Ｆｉｎの値が、燃料噴射量の増量限界値として予め定められた噴射燃料増量リミットＦＬｂよりも大きいか否かを判断しており、肯定判定されるとＳ４５０に移行し、否定判定されるとＳ４６０に移行する。このとき、燃料噴射量Ｆｉｎが噴射燃料増量リミットＦＬｂよりも大きい場合、Ｓ４４０で肯定判定されてＳ４５０に移行し、Ｓ４５０では、噴射燃料増量リミットＦＬｂの値を燃料噴射量Ｆｉｎに代入する。これにより、燃料噴射量が過度に増量されてしまい、内燃機関の運転状態が不安定になることを防いでいる。Ｓ４５０の処理が行われると、Ｓ４６０に移行する。
【０１１４】
また、Ｓ４４０に移行した際に、燃料噴射量Ｆｉｎが噴射燃料増量リミットＦＬｂ以下である場合、Ｓ４４０で否定判定されてＳ４６０に移行し、Ｓ４６０では、最後に算出された燃料噴射量Ｆｉｎにて燃料噴射を行い、燃料噴射が行われるとＳ３１０に移行する。
【０１１５】
このように、本空燃比制御処理では、Ｓ４６０で燃料噴射を行うと、Ｓ３１０に移行し、上述の処理を繰り返し実行することで、有効圧指数Ａｎの標準偏差および平均から算出される偏差／平均Ｓの値に基づいて燃料噴射量Ｆｉｎを更新して、燃料噴射量Ｆｉｎを制御している。
【０１１６】
なお、有効圧指数Ａｎの標準偏差は、算出した有効圧指数Ａｎの分布の広がりを表す尺度であり、この値が小さいほど、算出した有効圧指数Ａｎのばらつきが小さく、燃焼状態が安定していることを示し、反対に、この値が大きいほど、算出した有効圧指数Ａｎのばらつきが大きく、燃焼状態が不安定であることを示すことになる。
【０１１７】
また、有効圧指数Ａｎの標準偏差を有効圧指数Ａｎの平均で除することで正規化した偏差／平均Ｓと判定値とを比較して内燃機関の燃焼状態を判定することで、運転状態に応じて判定値を更新する必要がなくなり、判定値として定数の値を用いることができる。
【０１１８】
以上説明したように、本空燃比制御処理では、運転状態が変化しているときには、エンジン回転数およびスロットル開度に基づいて燃料噴射量Ｆｉｎを制御している。そして、運転状態が安定しているときには、エンジン回転数およびスロットル開度に基づいて設定された燃料噴射量Ｆｉｎを初期値として、燃料噴射量Ｆｉｎを変化させたことによる有効圧指数Ａｎの標準偏差の値に基づいて、内燃機関の燃焼状態を判断し、燃料噴射量Ｆｉｎを制御している。
【０１１９】
つまり、Ｓ３８０にて算出された偏差／平均Ｓがリーンリミット判定値ＬＬ以下であるとき（Ｓ３９０で肯定判定される時）には、燃焼状態が安定していると判断できる。このため、続くＳ４００で次回の燃料噴射量Ｆｉｎを減量させる（空燃比を高くする）ことで、内燃機関の燃費の向上を図るようにしている。
【０１２０】
また、Ｓ３８０にて算出された偏差／平均Ｓがリーンリミット判定値ＬＬよりも大きいとき（Ｓ３９０で否定判定される時）には、燃焼状態が不安定であると判断できる。このため、続くＳ４３０で次回の燃料噴射量Ｆｉｎを増量させる（空燃比を低くする）ことで、内燃機関の燃料状態を安定化させている。
【０１２１】
そして、内燃機関の運転状態が安定している状態が続く間、Ｓ３１０、Ｓ３２０、Ｓ３４０、Ｓ３８０からＳ４６０までの各ステップが繰り返し実行されて、燃料噴射量Ｆｉｎが有効圧指数Ａｎの標準偏差に基づいて最適な値に制御される。これにより、最も薄い混合気となる空燃比（リーンリミット）での内燃機関の運転が可能になる。
【０１２２】
なお、有効圧指数Ａｎの平均の算出には、数４の計算式を用いてもよい。
【０１２３】
【数４】

【０１２４】
平均値を算出する際に、数３の計算式での算出には、ｎ個分のデータ（有効圧指数Ａｎ）を記憶しておく必要があるが、数４の計算式では、前回までの平均値と有効圧指数Ａｎの２個のデータで平均を算出することが出来るため、メモリ容量の節約が可能になる。
【０１２５】
なお、本実施例では、燃料減量量Ｆａおよび燃料増量量Ｆｂは、予め設定された固定値としているが、例えば、運転状態に応じて設定される可変値としてもよい。また、燃料増量量Ｆｂを燃料減量量Ｆａよりも大きい値に設定することで、不安定な燃焼状態からの回避を迅速に行うことが可能になる。また、噴射燃料減量リミットＦＬａおよび噴射燃料増量リミットＦＬｂについても、例えば、運転状態に応じて設定される可変値としてもよい。
【０１２６】
次に、本実施例のＥＧＲ量制御処理について、図８に示すフローチャートに従って説明する。このＥＧＲ量制御処理は、内燃機関の運転が開始されると共に起動され、内燃機関の運転を停止するまで実行される。
また、ＥＧＲ量制御処理は、空燃比制御処理と基本的な制御処理の流れは同様であることから、処理内容が同一のステップについては同一ステップ番号を付してフローチャートを表し、空燃比制御処理と異なる部分を中心に、ＥＧＲ量制御処理について以下に説明する。
【０１２７】
まず、空燃比制御処理において燃料噴射量Ｆｉｎを読み込んでいたＳ３３０、Ｓ３５０に対応する、ＥＧＲ量制御処理のＳ５３０、Ｓ５５０では、Ｓ３１０で測定されたエンジン回転数およびスロットル開度に基づいて、予め設定されたマップからＥＧＲ量Ｅｇｒを読込むことでＥＧＲ量Ｅｇｒを設定している。また、Ｓ５３０の処理が行われると、Ｓ６６０に移行する。
【０１２８】
そして、Ｓ３９０に対応するＳ５９０では、Ｓ３８０で算出した偏差／平均Ｓが、ＥＧＲ量増量限界として予め設定されたＥＧＲ量リミット判定値ＥＬ以下であるか否かを判定しており、肯定判定されるとＳ６００に移行し、否定判定されるとＳ６３０に移行する。なお、空燃比制御処理におけるＳ４００からＳ４６０が、ＥＧＲ量制御処理におけるＳ６００からＳ６６０に対応する。
【０１２９】
Ｓ５９０に移行したとき、偏差／平均ＳがＥＧＲ量リミット判定値ＥＬ以下である場合、Ｓ５９０で肯定判定され、Ｓ６００に移行する。Ｓ６００では、ＥＧＲ量Ｅｇｒを予め定められたＥＧＲ増量量Ｅａだけ増量した値に更新する。
続くＳ６１０では、Ｓ６００で更新したＥＧＲ量Ｅｇｒの値が、ＥＧＲ量Ｅｇｒの増量限界値として予め定められたＥＧＲ量増量リミットＥＬａよりも大きいか否かを判断しており、肯定判定されるとＳ６２０に移行し、否定判定されるとＳ６６０に移行する。このとき、ＥＧＲ量ＥｇｒがＥＧＲ量増量リミットＥＬａより大きい場合、Ｓ６１０で肯定判定され、Ｓ６２０に移行し、Ｓ６２０では、ＥＧＲ量増量リミットＥＬａの値をＥＧＲ量Ｅｇｒに代入する。Ｓ６２０の処理が行われると、Ｓ６６０に移行する。
【０１３０】
また、Ｓ６１０に移行した際に、ＥＧＲ量ＥｇｒがＥＧＲ量増量リミットＥＬａ以下である場合、Ｓ６１０で否定判定され、Ｓ６６０に移行し、Ｓ６６０では、最後に算出されたＥＧＲ量ＥｇｒにてＥＧＲ制御動作を行い、ＥＧＲ制御動作が行われるとＳ３１０に移行する。
【０１３１】
また、Ｓ５９０に移行したとき、偏差／平均ＳがＥＧＲ量リミット判定値ＥＬよりも大きい場合、Ｓ５９０で否定判定され、Ｓ６３０に移行する。Ｓ６３０では、ＥＧＲ量Ｅｇｒを予め定められたＥＧＲ減量量Ｅｂだけ減量した値に更新する。
【０１３２】
続くＳ６４０では、Ｓ６３０で更新したＥＧＲ量Ｅｇｒの値が、ＥＧＲ量Ｅｇｒの減量限界値として予め定められたＥＧＲ量減量リミットＥＬｂよりも小さいか否かを判断しており、肯定判定されるとＳ６５０に移行し、否定判定されるとＳ６６０に移行する。このとき、ＥＧＲ量ＥｇｒがＥＧＲ量減量リミットＥＬｂより小さい場合、Ｓ６４０で肯定判定され、Ｓ６５０に移行し、Ｓ６５０では、ＥＧＲ量減量リミットＥＬｂの値をＥＧＲ量Ｅｇｒに代入する。Ｓ６５０の処理が行われると、Ｓ６６０に移行する。
【０１３３】
また、Ｓ６４０に移行した際に、ＥＧＲ量ＥｇｒがＥＧＲ量減量リミットＥＬｂ以上である場合、Ｓ６４０で否定判定され、Ｓ６６０に移行し、Ｓ６６０では、最後に算出されたＥＧＲ量ＥｇｒにてＥＧＲ制御動作を行い、ＥＧＲ制御動作が行われるとＳ３１０に移行する。
【０１３４】
このように、本ＥＧＲ量制御処理では、Ｓ６６０でＥＧＲ制御動作を行うと、Ｓ３１０に移行し、上述の処理を繰り返し実行することで、有効圧指数Ａｎの標準偏差および平均から算出される偏差／平均Ｓの値に基づいてＥＧＲ量Ｅｇｒを更新して、ＥＧＲ量Ｅｇｒを制御している。
【０１３５】
以上説明したように、本ＥＧＲ量制御処理では、運転状態が変化しているときには、エンジン回転数およびスロットル開度に基づいてＥＧＲ量Ｅｇｒを制御している。そして、運転状態が安定しているときには、エンジン回転数およびスロットル開度に基づいて設定されたＥＧＲ量Ｅｇｒを初期値として、ＥＧＲ量Ｅｇｒを変化させたことによる有効圧指数Ａｎの標準偏差の値に基づいて、内燃機関の燃焼状態を判断し、ＥＧＲ量Ｅｇｒを制御している。
【０１３６】
つまり、Ｓ３８０にて算出された偏差／平均ＳがＥＧＲ量リミット判定値ＥＬ以下であるとき（Ｓ５９０で肯定判定される時）には、燃焼状態が安定していると判断できる。このため、続くＳ６００で次回のＥＧＲ量Ｅｇｒを増量させることで、排出ガス中の有害物質を更に減少させるようにしている。
【０１３７】
また、Ｓ３８０にて算出された偏差／平均ＳがＥＧＲ量リミット判定値ＥＬよりも大きいとき（Ｓ５９０で否定判定される時）には、燃焼状態が不安定であることを表しており、Ｓ６３０で次回のＥＧＲ量Ｅｇｒを減量させることで、内燃機関の燃料状態を安定化させている。
【０１３８】
そして、内燃機関の運転状態が安定している状態が続く間、Ｓ３１０、Ｓ３２０、Ｓ３４０、Ｓ３８０、Ｓ５９０からＳ６６０までの各ステップが繰り返し実行されて、ＥＧＲ量Ｅｇｒが有効圧指数Ａｎの標準偏差に基づいて最適な値に制御される。これにより、燃焼状態を低下させることなく、有害物質の発生を抑えた状態での内燃機関の運転が可能になる。
【０１３９】
なお、本実施例では、ＥＧＲ増量量ＥａおよびＥＧＲ減量量Ｅｂは、予め設定された固定値としているが、例えば、運転状態に応じて設定される可変値としてもよい。また、ＥＧＲ量増量リミットＥＬａおよびＥＧＲ量減量リミットＥＬｂについても、例えば、運転状態に応じて設定される可変値としてもよい。
【０１４０】
次に、本実施例の燃料噴射時期制御処理について、図９に示すフローチャートに従って説明する。この燃料噴射時期制御処理は、内燃機関の運転が開始されると共に起動され、内燃機関の運転を停止するまで実行される。
また、燃料噴射時期制御処理は、点火時期制御処理と基本的な制御処理の流れ方法は同様であることから、処理内容が同一のステップについては同一ステップ番号を付してフローチャートを表し、点火時期制御処理と異なる部分を中心に、燃料噴射時期制御について以下に説明する。
【０１４１】
まず、点火時期制御処理において点火時期Ｔｉｇを読み込んでいたＳ１３０、Ｓ１５０に対応する、燃料噴射時期制御処理のＳ７３０、Ｓ７５０では、Ｓ１１０で測定されたエンジン回転数およびスロットル開度に基づいて、予め設定されたマップから燃料噴射時期Ｔｉｎを読込むことで燃料噴射時期Ｔｉｎを設定している。そして、Ｓ７５０では、燃料噴射時期Ｔｉｎを予め定められた進角量Ｔｉａだけ進めた値に更新する。
【０１４２】
また、点火時期制御におけるＳ１８０からＳ２４０が、燃料噴射時期制御におけるＳ７８０からＳ８４０に対応しており、Ｓ１７０に移行した際に、最新の有効圧指数Ａｎが前回の有効圧指数Ａｎ-1よりも大きい場合、Ｓ１７０で肯定判定され、Ｓ７８０に移行する。Ｓ７８０では、最新の有効圧指数Ａｎの値を前回の有効圧指数Ａｎ-1に代入し、燃料噴射時期Ｔｉｎを予め定められた進角量Ｔｉａだけ進めた値に更新する。
【０１４３】
続くＳ７９０では、Ｓ７８０で更新した燃料噴射時期Ｔｉｎの値が、燃料噴射時期の進角限界値として予め定められた噴射時期進角リミットＴＬｉａよりも大きいか否かを判断しており、肯定判定されるとＳ８００に移行し、否定判定されるとＳ８４０に移行する。このとき、燃料噴射時期Ｔｉｎが噴射時期進角リミットＴＬｉａよりも大きい場合、Ｓ７９０で肯定判定され、Ｓ８００に移行し、Ｓ８００では、噴射時期進角リミットＴＬｉａの値を燃料噴射時期Ｔｉｎに代入する。Ｓ８００の処理が行われると、Ｓ８４０に移行する。
【０１４４】
そして、Ｓ７９０に移行した際に、燃料噴射時期Ｔｉｎが噴射時期進角リミットＴＬｉａ以下である場合、Ｓ７９０で否定判定されてＳ８４０に移行し、Ｓ８４０では、最後に算出された燃料噴射時期Ｔｉｎにて燃料噴射を行い、燃料噴射点火が行われるとＳ１１０に移行する。
【０１４５】
また、Ｓ１７０に移行した際に、最新の有効圧指数Ａｎが前回の有効圧指数Ａｎ-1以下である場合、Ｓ１７０で否定判定され、Ｓ８１０に移行する。Ｓ８１０では、最新の有効圧指数Ａｎの値を前回の有効圧指数Ａｎ-1に代入し、燃料噴射時期Ｔｉｎを予め定められた遅角量Ｔｉｒだけ遅らせた値に更新する。
【０１４６】
続くＳ８２０では、Ｓ８１０で更新した燃料噴射時期Ｔｉｎの値が、燃料噴射時期の遅角限界値として予め定められた噴射時期遅角リミットＴＬｉｒよりも小さいか否かを判断しており、肯定判定されるとＳ８３０に移行し、否定判定されるとＳ８４０に移行する。このとき、燃料噴射時期Ｔｉｎが噴射時期遅角リミットＴＬｉｒよりも小さい場合、Ｓ８２０で肯定判定されてＳ８３０に移行し、Ｓ８３０では、噴射時期遅角リミットＴＬｉｒの値を燃料噴射時期Ｔｉｎに代入する。Ｓ８３０の処理が行われると、Ｓ８４０に移行する。
【０１４７】
そして、Ｓ８２０に移行した際に、燃料噴射時期Ｔｉｎが噴射時期遅角リミットＴＬｉｒ以上である場合、Ｓ８２０で否定判定されてＳ８４０に移行し、Ｓ８４０では、最後に算出された燃料噴射時期Ｔｉｎにて燃料噴射を行い、燃料噴射が行われるとＳ１１０に移行する。
【０１４８】
このように、本燃料噴射時期制御処理では、Ｓ８４０で点火を行うと、Ｓ１１０に移行し、上述の処理を繰り返し実行することで、有効圧指数Ａｎに基づいて燃料噴射時期Ｔｉｎを更新して、燃料噴射時期Ｔｉｎを制御している。
以上説明したように、本燃料噴射時期制御処理では、運転状態が変化しているときには、エンジン回転数およびスロットル開度に基づいて燃料噴射時期Ｔｉｎを制御している。そして、運転状態が安定しているときには、エンジン回転数およびスロットル開度に基づいて設定された燃料噴射時期Ｔｉｎを初期値として、燃料噴射時期Ｔｉｎを変化させたことによる有効圧指数Ａｎの変動に基づいて、内燃機関の燃焼状態を判断し、燃料噴射時期Ｔｉｎを制御している。
【０１４９】
つまり、Ｓ７５０にて燃料噴射時期Ｔｉｎを進めた後に、Ｓ１６０で算出される有効圧指数Ａｎが、進める前に算出された有効圧指数Ａｎ-1よりも大きくなる場合（Ｓ１７０で肯定判定される場合）には、燃焼状態が良好となったと判断できる。このため、続くＳ７８０にて次回の燃料噴射時期Ｔｉｎを進めることで、次回の燃焼における燃焼状態が更に良好になるようにしている。
【０１５０】
反対に、Ｓ７５０にて燃料噴射時期Ｔｉｎを進めた後に、Ｓ１６０で算出される有効圧指数Ａｎが、進める前に算出された有効圧指数Ａｎ-1以下になる場合（Ｓ１７０で否定判定される場合）には、燃焼状態が不良となったと判断できる。このため、続くＳ８１０にて次回の燃料噴射時期Ｔｉｎを遅らせることで、次回の燃焼において燃焼状態が良好になるようにしている。
【０１５１】
そして、内燃機関の運転状態が安定している状態が続く間、Ｓ１１０、Ｓ１２０、Ｓ１４０、Ｓ１６０、Ｓ１７０、Ｓ７８０からＳ８４０の各ステップが繰り返し実行されて、燃料噴射時期Ｔｉｎが有効圧指数Ａｎに基づいて最適な値に制御される。これにより、燃料噴射時期を、内燃機関の効率が最も良い燃料噴射時期に設定して、内燃機関を運転することが可能になる。
【０１５２】
なお、本実施例では、進角量Ｔｉａおよび遅角量Ｔｉｒは、予め設定された固定値としているが、例えば、運転状態に応じて設定される可変値としてもよい。また、噴射時期進角リミットＴＬｉａおよび噴射時期遅角リミットＴＬｉｒについても、例えば、運転状態に応じて設定される可変値としてもよい。
【０１５３】
以上説明したように、本実施例の内燃機関では、有効圧指数の算出に用いる筒内圧を、圧力センサ内蔵型点火プラグによって検出しているが、上死点前９０゜ＣＡから上死点後９０゜ＣＡまでの期間における筒内圧を用いているため、吸気弁・排気弁の着座ノイズの影響を受けることなく、有効圧指数を正確に算出することができる。そして、圧力センサ内蔵型点火プラグにおける、感度、締め付けトルクおよび温度などの個体差によって生じる筒内圧の誤差を補正して有効圧指数を算出している。さらに、圧力センサ内蔵型点火プラグが検出する筒内圧における残圧の影響による誤差を補正して有効圧指数を算出している。これらのことから、本実施例の内燃機関では、精度良く有効圧指数を算出することができる。
【０１５４】
よって、本実施例の内燃機関は、このように精度良く算出された有効圧指数に基づいて、点火時期、空燃比（燃料噴射量）、ＥＧＲ量および燃料噴射時期を制御しており、内燃機関の燃焼状態を最適に制御することが可能になる。これにより、燃焼効率を向上させることができ、燃費の向上や有害物質の低減などを図ることもできる。
【０１５５】
以上、本発明の実施例について説明したが、本発明は、上記実施例に限定されるものではなく、種々の態様を採ることができる。
本実施例では、有効圧指数を算出するための筒内圧積分値を、クランク角１°ＣＡ毎に積算することで算出しているが、例えば、圧電素子の出力した電荷をコンデンサに蓄積し、蓄積された電荷の容量によって筒内圧積分値を算出する方法を用いてもよい。
【０１５６】
また、筒内圧を検出する圧力センサとしては、点火プラグとは別体に備えられ、点火プラグと内燃機関本体との間にガスケットと共に挟持されることで、締め付け荷重の変化を検出する形式のものを用いてもよい。
さらに、本実施例は、直噴型内燃機関であるが、吸気管内に燃料を噴射する方式の内燃機関において、本発明の制御方法を用いることにより、点火時期、空燃比、ＥＧＲ量を制御することも可能である。
【図面の簡単な説明】
【図１】 実施例の内燃機関の構成を表す説明図である。
【図２】 座型圧力センサにより検出した筒内圧の波形を示す説明図である。
【図３】 座型圧力センサを用いて算出した感度補正前および感度補正後の有効圧指数を示すグラフである。
【図４】 座型圧力センサおよび筒内挿通型圧力センサにより検出した筒内圧の波形を示す説明図である。
【図５】 有効圧指数を測定した結果を表す説明図である。
【図６】 制御装置による点火時期制御処理を表すフローチャートである。
【図７】 制御装置による空燃比制御処理を表すフローチャートである。
【図８】 制御装置によるＥＧＲ量制御処理を表すフローチャートである。
【図９】 制御装置による燃料噴射時期制御処理を表すフローチャートである。
【図１０】 温度変化および点火プラグの締め付けトルクの変化に対する圧電素子の出力特性を示すグラフである。
【図１１】 増幅回路の構成を表す説明図である。
【図１２】 座型圧力センサを用いて算出した有効圧指数と、筒内挿通型圧力センサを用いて算出した図示平均有効圧力との関係を示すグラフである。
【図１３】 圧力センサ内蔵プラグの構成を示す説明図である。
【符号の説明】
１…内燃機関、１１…点火プラグ、１１ａ…主体金具、１１ｂ…圧力センサ、１１ｃ…出力ケーブル、１１ｄ…外側電極、１１ｅ…中心電極、１１ｆ…端子部、１３…イグナイタ、１５…燃料噴射弁、１７…ＥＧＲバルブ、１９…制御装置（ＥＣＵ）、３１…燃焼室、６１…増幅回路、６３…オペアンプ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine control method for calculating an effective pressure index of an internal combustion engine based on an in-cylinder pressure detected by a piezoelectric element provided in the internal combustion engine and controlling the internal combustion engine based on the calculated effective pressure index.
[0002]
[Prior art]
In an internal combustion engine, as a method for determining the combustion state of the internal combustion engine, detecting knocking, improving fuel consumption and normalizing exhaust gas, etc., the pressure (in-cylinder pressure) in the combustion chamber is detected, and based on this in-cylinder pressure. There is a way to judge. Further, since the in-cylinder pressure changes according to the operation of the internal combustion engine, the indicated mean effective pressure used as a power source for the internal combustion engine can be calculated based on the change in the in-cylinder pressure. In particular, by calculating the indicated mean effective pressure based on the change in the in-cylinder pressure over the entire combustion cycle, it is possible to obtain the indicated mean effective pressure that accurately reflects the combustion state of the internal combustion engine.
[0003]
As a method for detecting the in-cylinder pressure, for example, a pressure guide hole communicating with the combustion chamber is provided in the cylinder head, and a pressure sensor is provided in the pressure guide hole. There is a way to detect. However, this in-cylinder pressure detection method has a problem that the structure of the internal combustion engine is complicated and the cost is increased because it is necessary to process the cylinder head in order to provide the pressure guide hole.
[0004]
In order to solve this problem, a seat-type pressure sensor has been proposed that detects the in-cylinder pressure based on fluctuations in the tightening load when the pressure sensor is disposed in the mounting seat portion of the spark plug and the spark plug is tightened to the cylinder head. (See JP-A-6-290853). This eliminates the need for a machining operation for providing the pressure guide hole in the cylinder head, and allows the in-cylinder pressure to be detected at a low cost without complicated machining of the structure of the internal combustion engine.
[0005]
[Problems to be solved by the invention]
However, the seat-type pressure sensor has a structure that detects the in-cylinder pressure due to fluctuations in the tightening load of the spark plug. There is a problem that it is far from the pressure change. For this reason, when a seat-type pressure sensor is used, it is difficult to accurately detect the in-cylinder pressure for one combustion cycle including when the intake valve and the exhaust valve are operated, and the pressure is calculated based on the in-cylinder pressure in the entire one combustion cycle. It is difficult to accurately calculate the indicated mean effective pressure of the internal combustion engine.
[0006]
Here, in order to confirm the influence of noise caused by the intake and exhaust valves, the output signal waveform of the seat-type pressure sensor during operation of the internal combustion engine is shown in FIG. According to the output signal waveform shown in Fig. 2, in the seat pressure sensor, the output signal waveform (in-cylinder pressure) fluctuates when the intake valve is closed (INTAKE VALVE CLOSE) and when the exhaust valve is opened (EXHAUST VALVE OPEN). You can see that
[0007]
It is also known that the output characteristics of the piezoelectric element constituting the pressure sensor change depending on the temperature. Here, the change of the characteristic with respect to the temperature change of a piezoelectric element is shown to Fig.10 (a). FIG. 10A shows the change rate of the output charge of the pressure sensor due to temperature change with the output charge of the pressure sensor at 20 ° C. being 0%, the horizontal axis is the temperature, and the vertical axis is the change rate. The rate of change is expressed on the coordinate plane. From the characteristics of the pressure sensor shown in FIG. 10A, it can be seen that the output charge of the pressure sensor (hereinafter also referred to as an output signal) changes with temperature changes.
[0008]
And it has been found that there is a slight individual difference in sensitivity among the piezoelectric elements constituting the pressure sensor, and the output signal has a slight error due to the individual difference. In addition, since the electric charge output from the piezoelectric element is very small, the output signal of the piezoelectric element is generally used after being amplified by an amplifier circuit. For this reason, an error that is in an allowable range as a single piezoelectric element is amplified by the amplifier circuit, and this error becomes a value that cannot be ignored.
[0009]
Here, FIG. 3A shows the measurement result of the measurement performed to confirm the presence or absence of an error in the output signal in the piezoelectric element. In the measurement, an in-cylinder pressure is detected by using two amplifying circuits and two seat-type pressure sensors (sensor 1 and sensor 2) of the same type and an in-cylinder insertion type pressure sensor provided in a pressure guide hole leading to the combustion chamber. This was done by calculating the difference in the integrated value of the in-cylinder pressure before and after top dead center. In FIG. 3A, the difference between the integral values is referred to as an effective pressure index, and each effective value calculated using a seat-type pressure sensor with respect to the effective pressure index calculated using an in-cylinder insertion type pressure sensor. The relationship of the pressure index is shown. From the measurement results shown in FIG. 3 (a), it can be seen that the calculated effective pressure index is different even for the seat-type pressure sensor of the same type. From this, it can be seen that there is an error in the output signal due to individual differences in sensitivity of the piezoelectric elements.
[0010]
Furthermore, since the seat-type pressure sensor detects the in-cylinder pressure by detecting the tightening load of the spark plug, if the tightening load when the spark plug is attached differs, the variation in the tightening load due to the change in the in-cylinder pressure occurs. End up. Even if an instrument for measuring the tightening load such as a torque wrench is used, it is practically difficult to unify the tightening load strictly to such an extent that the pressure detection of the seat-type pressure sensor is not affected. Therefore, the output characteristic of the detected pressure of the seat-type pressure sensor is affected by individual differences in the tightening load of the spark plug.
[0011]
Here, the rate of change of the detected pressure of the seat-type pressure sensor due to the change of the tightening torque is shown in FIG. FIG. 10B shows the relationship between the tightening torque and the output signal when the tightening torque is changed with the output signal of the seat-type pressure sensor being 100% when the tightening torque is 25 N · m. As shown in FIG. 10B, the rate of change decreases (output charge decreases) when the tightening torque decreases, and the rate of change increases (output charge increases) when the tightening torque increases. From this, it can be seen that the output signal of the seat-type pressure sensor changes as the tightening torque changes.
[0012]
As described above, the seat-type pressure sensor includes an error in the output signal due to individual differences such as temperature, sensitivity, and tightening torque. Therefore, there is a possibility that the cylinder pressure with high accuracy cannot be detected. For this reason, it is difficult to accurately calculate the effective pressure index of the internal combustion engine based on the change in the in-cylinder pressure detected by the seat-type pressure sensor.
[0013]
Further, the change in the tightening load due to the in-cylinder pressure is caused by the combustion gas holding the spark plug. At the same time, the combustion gas enters the gap existing between the threaded portion of the spark plug metal shell and the cylinder head threaded portion. Therefore, even if the actual in-cylinder pressure decreases, Residual pressure is generated due to the delay in outflow.
[0014]
Here, FIG. 4 shows the measurement results of measurements performed to confirm that the in-cylinder pressure detected by the seat-type pressure sensor is affected by the residual pressure. The measurement was performed by detecting the in-cylinder pressure in the same combustion chamber using a seat-type pressure sensor and a cylinder insertion type pressure sensor provided in a pressure guide hole leading to the combustion chamber. In FIG. 4 (a), the in-cylinder pressure detected by the in-cylinder pressure sensor is indicated by a solid line on the coordinate plane with the abscissa as the crank angle and the ordinate as the in-cylinder pressure. Is marked with a dotted line to show the measurement results. From the measurement results shown in FIG. 4A, each pressure sensor detects the same in-cylinder pressure until the in-cylinder pressure peak value is reached, but after the in-cylinder pressure peak value has elapsed, The value of the in-cylinder pressure detected by the seat-type pressure sensor is larger than the in-cylinder pressure detected by the insertion type pressure sensor. Further, in FIG. 4B, the in-cylinder pressure detected by the seat pressure sensor is set on the vertical axis and the in-cylinder pressure detected by the in-cylinder pressure sensor is set on the horizontal axis, and the in-cylinder pressure detected by each pressure sensor is set. A Lissajous waveform is shown. 4B also shows that the in-cylinder pressure detected by the seat-type pressure sensor has a larger value than the in-cylinder pressure detected by the in-cylinder insertion type pressure sensor.
[0015]
From this measurement result, after the top dead center (hereinafter also referred to as TDC), the seat pressure sensor detects a pressure (residual pressure) higher than the in-cylinder pressure detected by the in-cylinder pressure sensor. I understand. Due to the residual pressure, the in-cylinder pressure detected by the seat-type pressure sensor after combustion of the air-fuel mixture is gradually reduced from the in-cylinder pressure detected by the in-cylinder insertion type pressure sensor. It becomes difficult to accurately detect the internal pressure.
[0016]
Therefore, the effective pressure index calculated based on the in-cylinder pressure detected by the seat-type pressure sensor is affected by noise caused by intake and exhaust valves, individual differences due to the tightening torque and temperature of the spark plug, and the residual pressure of the screw part. May cause an error. Such errors due to individual differences and residual pressure are determined when the seat-type pressure sensor is actually attached to the internal combustion engine body. It is impossible to perform correction by measuring and setting a correction reference value. It is also possible to measure the error when the seat-type pressure sensor is installed and correct the error using a correction reference value set according to the error. However, the operating internal combustion engine always changes its state. Since the output characteristics of the seat-type pressure sensor may change over time, there is a problem that errors due to changes over time cannot be corrected.
[0017]
The present invention has been made in view of these problems, and calculates an effective pressure index with high accuracy from the in-cylinder pressure detected by the seat-type pressure sensor, and optimizes the combustion state of the internal combustion engine based on the calculated effective pressure index. It is an object of the present invention to provide an internal combustion engine control method for controlling.
[0018]
[Means for Solving the Problems]
  In order to achieve this object, the invention according to claim 1 detects the in-cylinder pressure of the internal combustion engine by detecting a change in the ignition plug tightening load by a piezoelectric element provided on a mounting seat of the ignition plug. An internal combustion engine control method for controlling an internal combustion engine based on an effective pressure index that is a power source of the internal combustion engine calculated based on an internal pressure, from when the intake valve is closed until the crank angle reaches top dead center The pressure integrated value before top dead center is calculated by integrating the in-cylinder pressure within a certain period of time, and the cylinder within a certain period of time defined between the crank angle reaching top dead center and the exhaust valve opening is calculated. Calculate the integrated pressure value after top dead center by integrating the internal pressure,The integration period of the pressure integration value before the top dead center and the integration period of the pressure integration value after the top dead center are symmetric with respect to the top dead center, and have the same length.Calculates the difference between the post-top dead center pressure integrated value and the pre-top dead center pressure integrated value as an effective pressure index, calculates the effective pressure index in all operating states including misfire operation, and calculates during misfire operation The effective pressure index is set as the second correction reference value, and the effective pressure index during normal operation is corrected by subtracting the second correction reference value from the effective pressure index calculated during normal operation. An internal combustion engine control method comprising controlling an internal combustion engine based on a pressure index.
[0019]
In an internal combustion engine, power is generated by the pressure generated by burning the air-fuel mixture in the combustion chamber. The pressure used as the power source of the internal combustion engine is the pressure in the combustion chamber after top dead center (cylinder pressure). ). However, the pressure in the combustion chamber generated before top dead center is used to generate the pressure in the combustion chamber after top dead center. From this, it can be determined that the difference between the integrated value of the in-cylinder pressure after the top dead center and the integrated value of the in-cylinder pressure before the top dead center is the pressure actually used as the power source of the internal combustion engine. Therefore, as in the method for calculating the effective pressure index in the internal combustion engine control method of the present invention (Claim 1), the internal combustion engine is obtained by obtaining the difference between the post-top dead center pressure integrated value and the pre-top dead center pressure integrated value. It is possible to calculate the pressure actually used as the power source of the. In this specification, this pressure is defined as an effective pressure index.
[0020]
Further, since the in-cylinder pressure detected by the piezoelectric element provided on the seat for attaching the spark plug is detected by a change in tightening load, it is affected by vibration noise caused by the seating of the intake valve and the exhaust valve. Therefore, by determining the in-cylinder pressure detection period as in the method for calculating the effective pressure index in the internal combustion engine control method according to claim 1, the in-cylinder pressure is reduced while avoiding the influence of vibration noise caused by the seating of the intake valve and the exhaust valve. It can be detected, and no error due to seating noise occurs in calculating the effective pressure index.
[0021]
Here, the value calculated as the effective pressure index by the method for calculating the effective pressure index in the internal combustion engine control method of the present invention (Claim 1) replaces the value indicating the indicated mean effective pressure used as the power source of the internal combustion engine. The measurement result of the measurement performed in order to confirm that it becomes a value is shown in FIG. In the measurement, an effective pressure index is calculated by a method of calculating an effective pressure index in the method of the present invention using a seat-type pressure sensor, and an indicated mean effective pressure in one entire combustion cycle is calculated using an in-cylinder insertion type pressure sensor. I went there. The indicated mean effective pressure is an index that is also used when comparing the combustion efficiencies of internal combustion engines with different displacements, and shows a value that accurately reflects the pressure used as the power source of the internal combustion engine.
[0022]
From the measurement results shown in FIG. 12, it can be seen that the effective pressure index is proportional to the indicated mean effective pressure. Therefore, the effective pressure index calculated by the effective pressure index calculation method in the method of the present invention can be used as a value instead of the value representing the indicated mean effective pressure used as the power source of the internal combustion engine.
[0023]
Since the effective pressure index changes depending on the combustion state of the internal combustion engine, it can be used as an index representing the combustion state of the air-fuel mixture in the internal combustion engine. Therefore, the internal combustion engine can be operated in an optimal combustion state by controlling the internal combustion engine based on the effective pressure index so that the combustion state is improved.
[0024]
  Therefore, according to the internal combustion engine control method of the present invention (Claim 1), the internal combustion engine is effective without being affected by the seating noise of the intake valve and the exhaust valve based on the in-cylinder pressure detected by the seat-type pressure sensor. The pressure index can be calculated with high accuracy, and the combustion state of the internal combustion engine can be optimally controlled based on the effective pressure index.
Incidentally, the seat-type pressure sensor detects the in-cylinder pressure by detecting a change in the tightening load of the spark plug. The change in tightening load due to the in-cylinder pressure is generated by the combustion gas holding the spark plug. At the same time, the combustion gas enters the gap existing between the threaded portion of the spark plug metal shell and the cylinder head threaded portion. Therefore, even if the actual in-cylinder pressure decreases, Residual pressure is generated by the outflow delay (see FIG. 4). Due to this residual pressure, the decrease in the cylinder pressure after combustion of the air-fuel mixture becomes gradual, it becomes difficult to accurately detect the actual cylinder pressure, and an error may occur in the effective pressure index.
Therefore, as in the internal combustion engine control method of the present invention (Claim 1), the effective pressure index in all operating states including the misfire operation is calculated, and the effective pressure index calculated in the misfire operation is the second correction reference value. By subtracting the second correction reference value from the effective pressure index calculated during normal operation, the corrected effective pressure index during normal operation is corrected, and the internal combustion engine is corrected based on the corrected effective pressure index. It is good to control.
That is, during misfire operation of the internal combustion engine, the integrated pressure value before TDC and the integrated pressure value after TDC are ideally the same value, but the actually calculated pressure integrated value is the residual pressure as described above. As a result, the pressure integrated value after TDC shows a larger value. The effective pressure index calculated under specific engine conditions during misfire operation indicates an increase in the in-cylinder pressure caused by the residual pressure. Therefore, the effective pressure index at this time is stored and calculated. By subtracting from the effective pressure index, an effective pressure index in which an error due to the residual pressure is corrected can be calculated.
Therefore, the internal combustion engine can be operated in an optimal combustion state by controlling the internal combustion engine based on the effective pressure index so that the combustion state is improved. Therefore, according to the internal combustion engine control method of the present invention (Claim 1), an error due to the influence of the residual pressure in the seat pressure sensor can be corrected, and the effective pressure index can be calculated with high accuracy. Based on this, it becomes possible to optimally control the combustion state of the internal combustion engine.
[0025]
As a method for calculating the integrated pressure value of the in-cylinder pressure, for example, a method of calculating the integrated pressure value by integrating the in-cylinder pressure every predetermined time or every constant crank angle may be used.
The in-cylinder pressure during operation of the internal combustion engine starts to increase around 90 ° CA before top dead center (hereinafter also referred to as BTDC 90 ° CA), reaches its maximum value after a slight passage of top dead center, and then decreases. And then continues to descend to about 90 ° CA (hereinafter also referred to as ATDC 90 ° CA) after top dead center. In general, the closing timing of the intake valve is before BTDC 90 ° CA, and the opening timing of the exhaust valve is after ATDC 90 ° CA.
[0026]
  Therefore, in the above internal combustion engine control method, as described in claim 2,Integrated pressure value before top dead centerIs calculated by integrating the in-cylinder pressure within the period from 90 ° CA before the top dead center to the top dead center,Integrated pressure value after top dead centerBy integrating the in-cylinder pressure in the period from when the crank angle reaches top dead center until it reaches 90 ° CA after top dead center.It is good to calculate.
[0027]
  That is, like thisIntegrated pressure value before top dead centerWhenIntegrated pressure value after top dead centerTherefore, it is possible to reliably detect changes in the in-cylinder pressure due to the combustion of the air-fuel mixture, and to detect the in-cylinder pressure without being affected by the seating noise of the intake and exhaust valves. The effective pressure index used as a source can be reliably calculated.
[0028]
  Also,Integrated pressure value before top dead centerWhenIntegrated pressure value after top dead centerIf the lengths of the periods for calculating are different from each other, an erroneous effective pressure index is calculated. However, in the present invention (Claim 2), the integration period from 90 ° CA before top dead center to top dead center and the integration period from top dead center to 90 ° CA after top dead center are symmetrical with respect to TDC. Since the length of the period for calculating the integral value is the same, the effective pressure index can be accurately calculated.
[0029]
Therefore, the internal combustion engine can be operated in an optimal combustion state by controlling the internal combustion engine based on the effective pressure index so that the combustion state is improved.
Therefore, according to the internal combustion engine control method of the present invention (Claim 2), the internal combustion engine is effective without being affected by the seating noise of the intake valve and the exhaust valve based on the in-cylinder pressure detected by the seat-type pressure sensor. The pressure index can be calculated with high accuracy, and the combustion state of the internal combustion engine can be optimally controlled based on the effective pressure index.
[0030]
On the other hand, the piezoelectric element is a mechanism for detecting the in-cylinder pressure by outputting a charge according to the detected pressure. However, since the output charge is very small, in actual use, for example, FIG. The output signal is amplified by an amplifier circuit 61 as shown.
[0031]
Here, in the amplifier circuit 61, the non-inverting input terminal 63a is grounded, the inverting input terminal 63b is connected to the piezoelectric element through the resistor 65, and the output terminal 63c and the inverting input terminal 63b are connected in parallel to the resistor 67 and The operational amplifier 63 is connected by a capacitor 69 and supplied with a power supply voltage of 5V. The potential input to the inverting input terminal 63b fluctuates due to the charge output from the piezoelectric element in accordance with the in-cylinder pressure to be detected. The operational amplifier 63 amplifies the potential fluctuation and outputs it as an output signal from the output terminal 63c. ing. Thereby, the piezoelectric element is not affected by the stray capacitance of the connected cable, and the output signal of the piezoelectric element can be accurately detected.
[0032]
However, if the output signal of the piezoelectric element is amplified, even an error within an allowable range for the piezoelectric element alone is amplified by the amplifier circuit, and it may be difficult to accurately detect the in-cylinder pressure. As can be seen from FIG. 3 (a) showing the above measurement results, the calculated effective pressure index is different even in the same type of seat-type pressure sensor, and there is an individual difference in the sensitivity of the piezoelectric element. It can be judged.
[0033]
However, from the measurement results shown in FIG. 3A, the calculation result of the effective pressure index calculated using the same seat-type pressure sensor is the same as the change of the effective pressure index calculated using the in-cylinder insertion type pressure sensor. It can be seen that the output characteristics of the seat-type pressure sensor have a certain proportional relationship with the in-cylinder pressure.
[0034]
In-cylinder pressure actually detected by the seat-type pressure sensor before the TDC is different among the seat-type pressure sensors, and as can be seen from the measurement result shown in FIG. This is because an error is caused by the difference in sensitivity. Since the magnitude of this error changes according to the sensitivity of each pressure sensor, the sensitivity of the seat-type pressure sensor can be known from the magnitude of the change rate of the in-cylinder pressure detected before TDC.
[0035]
Therefore, as a control method for the internal combustion engine, as described in claim 3, the difference between the in-cylinder pressures at two different time points among the in-cylinder pressures detected after the intake valve is closed and before the ignition timing is calculated as a first correction reference value. The effective pressure index calculated as the difference between the post-top dead center pressure integrated value and the pre-top dead center pressure integrated value is further divided by the first correction reference value, and the corrected effective pressure is corrected. The internal combustion engine may be controlled based on the index.
[0036]
That is, the difference in the in-cylinder pressure at two different time points detected from when the intake valve is closed to before the ignition timing is large if the pressure sensor is sensitive, and small if the pressure sensor is not sensitive. If the pressure sensor has a high sensitivity, the calculated effective pressure index increases. If the pressure sensor has a low sensitivity, the calculated effective pressure index decreases. Therefore, by dividing the effective pressure index by the difference in in-cylinder pressure at two different points in time from when the intake valve reflecting the sensitivity of the pressure sensor is closed until before the ignition timing, an error in in-cylinder pressure due to individual differences in sensitivity Therefore, the effective pressure index can be accurately calculated.
[0037]
Actually, the calculation result of the effective pressure index calculated by the effective pressure index calculation method in the internal combustion engine control method of the present invention (Claim 3) is shown in FIG. Specifically, the difference in in-cylinder pressure between BTDC 90 ° CA and BTDC 20 ° CA in the seat-type pressure sensor used for calculating the effective pressure index shown in FIG. 3A is shown in FIG. Correction was made by dividing the effective pressure index, and the effective pressure index was calculated.
[0038]
Before the sensitivity correction (FIG. 3 (a)), the effective pressure index, which showed different values for each seat-type pressure sensor, showed almost the same value after the sensitivity correction (FIG. 3 (b)). It can be seen that the error due to was successfully corrected. In addition, the in-cylinder pressure error detected by the seat-type pressure sensor is caused not only by the sensitivity of the piezoelectric element but also by the difference in the tightening torque of the spark plug and the difference in temperature at the time of measurement. However, the error due to the tightening torque, temperature, etc. also appears as the magnitude of the in-cylinder pressure detected before TDC, similarly to the error due to the difference in the sensitivity of the piezoelectric element. Therefore, the effective pressure in the method of the present invention (Claim 3) By using the index calculation method, an effective pressure index with an error corrected can be obtained.
[0039]
Therefore, the internal combustion engine can be operated in an optimal combustion state by controlling the internal combustion engine based on the effective pressure index so that the combustion state is improved. Therefore, according to the internal combustion engine control method of the present invention (Claim 3), the error of the in-cylinder pressure caused by individual differences such as the sensitivity of the piezoelectric element, the tightening torque and the temperature change is corrected, and the effective pressure index is more accurately determined. And the combustion state of the internal combustion engine can be optimally controlled based on the effective pressure index.
[0044]
On the other hand, an internal combustion engine is operated by obtaining a control reference value by using a calculation formula or a map using operating conditions such as the rotational speed and engine load as parameters and controlling ignition timing, air-fuel ratio, and the like. That is, the ignition timing, the air-fuel ratio, and the like are set based on the rotational speed representing the operating state, the engine load, and the like. For this reason, in a stable operating state where the rotational speed, engine load, etc. are constant, the same control reference value is set and the internal combustion engine is controlled. However, it is known that in the internal combustion engine, the combustion state of the air-fuel mixture slightly changes even in a stable operating state where the rotation speed and load do not vary. For this reason, it is desired to control the ignition timing, the air-fuel ratio, and the like so that a more optimal combustion state is obtained even in a stable operation state.
[0045]
  Therefore, as an internal combustion engine control method for controlling the internal combustion engine,Claim 4Thus, it is determined whether or not the operating state of the internal combustion engine is stable, and at least during steady operation where the operating state of the internal combustion engine is stable, the effective pressure index is calculated, and based on the calculated effective pressure index Thus, the internal combustion engine may be controlled.
[0046]
Since the effective pressure index shows a larger value as the combustion state becomes better, it can be used as an index representing the combustion state of the air-fuel mixture in the internal combustion engine. Therefore, by controlling the internal combustion engine in a stable operation state based on the effective pressure index, it is possible to realize an operation in a better combustion state.
[0047]
  In the internal combustion engine control method for controlling the ignition timing based on the effective pressure index calculated during the steady operation of the internal combustion engine,Claim 5When the effective pressure index calculated after changing the ignition timing by a predetermined ignition timing change amount becomes larger than the effective pressure index calculated before changing the ignition timing, the next time The effective pressure index calculated after changing the ignition timing in the same direction as the change due to the ignition timing change amount and changing the ignition timing by a predetermined ignition timing change amount changes the ignition timing. When it is less than or equal to the effective pressure index calculated before the ignition timing, the ignition timing may be controlled by changing the next ignition timing in a direction opposite to the direction of change due to the ignition timing change amount.
[0048]
In general, it is known that the combustion state of the air-fuel mixture becomes better when the ignition timing is advanced. However, if the ignition timing is excessively advanced, knocking occurs and the combustion state is It will decline.
Here, in order to confirm the change in the combustion state with respect to the ignition timing, the change in the effective pressure index when the ignition timing was changed was measured. The measurement results are shown in FIG. The measurement was performed using a direct injection internal combustion engine, and the effective pressure index when the fuel injection timing was changed in addition to the ignition timing was calculated for three stages of air-fuel ratios (A / F). In FIG. 5, the measurement results are shown by showing the distribution of the effective pressure index at each air-fuel ratio on the coordinate plane with the vertical axis as the ignition timing and the horizontal axis as the fuel injection timing. The vertical axis shows the ignition timing advance angle (crank angle before top dead center) as a positive value and retard angle (crank angle after top dead center), where top dead center is 0 ° CA. Expressed as a negative value. The horizontal axis represents the top dead center as 0 ° CA and the crank angle before the top dead center as a positive value. In addition, the effective pressure index has a distribution showing four stages of 130 to 160, 160 to 180, 180 to 200, and 200 to 210 with different patterns.
[0049]
From the measurement results shown in FIG. 5, the effective pressure index distribution at the same air-fuel ratio is advanced when the ignition timing is determined based on the top dead center (when the ignition timing is 0 ° CA). The effective pressure index increases as the value increases, but it can be seen that the effective pressure index decreases if the angle is excessively advanced.
[0050]
  Therefore,The present invention (Claim 5)Then, rather than simply advancing the ignition timing, the combustion state is determined based on the change in the effective pressure index due to the change in the ignition timing, and the ignition timing is set based on the determination result. It is designed to be optimally controlled.
[0051]
For example, if the effective pressure index calculated after the ignition timing is advanced is larger than the effective pressure index calculated before the ignition timing, it indicates that the combustion state is good. By advancing the next ignition timing, it can be expected that the combustion state will be further improved in the next ignition. On the other hand, if the effective pressure index calculated after the ignition timing is advanced is smaller than the effective pressure index calculated before the ignition timing, this indicates that the combustion state is poor. By retarding the next ignition timing, the combustion state at the next ignition is improved.
[0052]
In this way, by controlling the ignition timing, it is possible to improve the combustion state in a stable operation state, and it is possible to avoid the occurrence of knocking and the deterioration of the combustion state.
When controlling the internal combustion engine by determining the combustion state from the change in the effective pressure index when the ignition timing is changed to retard, the effective pressure index calculated after the change in the ignition timing is When it becomes larger than the effective pressure index, the combustion state can be more optimally controlled by further retarding the next ignition timing. On the other hand, if the effective pressure index calculated after the ignition timing changes is smaller than the effective pressure index before the change, the combustion state can be controlled more optimally by advancing the next ignition timing. It becomes possible.
[0053]
  Therefore,The present invention (Claim 5)According to this internal combustion engine control method, the ignition timing can be controlled so that the combustion state during steady operation where the operation state of the internal combustion engine is stable becomes better, and the combustion state of the internal combustion engine is improved. It becomes possible to control. As a result, the ignition timing can be set to MBT (Minimum Spark Advance for Best Torque), which is the ignition timing with the best efficiency of the internal combustion engine, and the internal combustion engine can be operated in an optimum state.
[0054]
Further, from the measurement results shown in FIG. 5, the greater the air-fuel ratio (A / F) (the smaller the fuel injection amount), the smaller the effective pressure index region indicating a higher value, and the smaller the air-fuel ratio ( It can be seen that the more the fuel injection amount), the easier it is to realize a good combustion state. However, in order to improve fuel efficiency, it is better to set the air-fuel ratio larger.
[0055]
  Therefore, in the internal combustion engine control method for controlling the air-fuel ratio or the EGR amount based on the effective pressure index calculated during the steady operation of the internal combustion engine,Claim 6As described above, after changing at least one of the fuel injection amount and the EGR amount by a predetermined amount, a value representing the spread of the effective pressure index distribution calculated a predetermined number of times is determined in advance. If it is equal to or less than the determined value, at least one of control for decreasing the fuel injection amount and control for increasing the EGR amount is executed, and conversely, at least one of the fuel injection amount and the EGR amount When the value representing the spread of the distribution of the effective pressure index calculated by a predetermined number of times after changing the predetermined amount by a predetermined amount becomes larger than a predetermined determination value, the fuel injection amount is The air-fuel ratio or the EGR amount may be controlled by executing at least one of the control for increasing and the control for decreasing the EGR amount.
[0056]
It should be noted that the smaller the value representing the spread of the effective pressure index distribution, the smaller the variation in the calculated effective pressure index and the more stable the combustion state, and vice versa. This indicates that the combustion state is unstable.
[0057]
Therefore, when the value representing the spread of the effective pressure index distribution is small (when the combustion state is stable), the fuel efficiency of the internal combustion engine can be improved by increasing the air-fuel ratio (decreasing the fuel injection amount). When the value representing the spread of the effective pressure index distribution is large (when the combustion state is unstable), the combustion state of the internal combustion engine can be reduced by lowering the air-fuel ratio (increasing the fuel injection amount). Should be stabilized.
[0058]
Here, the EGR amount is the amount of exhaust gas that is recirculated from the exhaust system to the intake system. Thus, by mixing the exhaust gas into the combustion mixture, the maximum combustion temperature is lowered, The generation of NOx, which is a harmful substance, can be reduced. However, if the EGR amount increases, the combustion state becomes unstable and the drivability (responsiveness, smoothness, etc.) of the internal combustion engine decreases, so the EGR amount depends on the operating state of the internal combustion engine. Need to be controlled.
[0059]
Therefore, when the value representing the spread of the effective pressure index distribution is small (when the combustion state is stable), the generation of harmful substances in the exhaust gas can be reduced by increasing the EGR amount. . When the value representing the spread of the effective pressure index distribution is large (when the combustion state is unstable), the combustion state of the internal combustion engine can be stabilized by decreasing the EGR amount.
[0060]
When controlling the EGR amount in order to reduce the generation of harmful substances, the EGR amount becomes the maximum value (limit value) while maintaining the combustion state in a stable state so as not to reduce the drivability of the internal combustion engine. Control (EGR limit control) is most desirable.
[0061]
Therefore, based on the result of comparing the value representing the spread of the effective pressure index distribution with a predetermined determination value, control of at least one of the fuel injection amount and the EGR amount is executed, and the air-fuel ratio control or the EGR limit By controlling, the combustion state of the internal combustion engine can be stabilized.
[0062]
  Therefore,The present invention (Claim 6)Therefore, by determining the combustion state based on the value representing the spread of the distribution of the effective pressure index, the air-fuel ratio can be controlled to an optimum value, so that the fuel consumption can be improved. , Knocking can be prevented. Further, since the EGR amount can be controlled to an optimal value, harmful substances in the exhaust gas can be reduced, and the combustion state of the internal combustion engine can be stabilized.
[0063]
Next, in a direct-injection internal combustion engine that directly injects fuel into the combustion chamber to generate an air-fuel mixture, in addition to the ignition timing, air-fuel ratio, and EGR amount, the fuel injection timing is also operated at the rotational speed and load. Control is performed by obtaining a control reference value using a calculation formula or map using the state as a parameter.
[0064]
  Therefore, in a direct injection internal combustion engine, an internal combustion engine control method for controlling fuel injection timing based on an effective pressure index calculated during steady operation of the internal combustion engine,Claim 7When the effective pressure index calculated after changing the fuel injection timing by a predetermined fuel injection timing change amount becomes larger than the effective pressure index calculated before changing the fuel injection timing, The effective pressure index calculated after the next fuel injection timing is changed in the same direction as the fuel injection timing change amount, and the fuel injection timing is changed by a predetermined fuel injection timing change amount is When the fuel pressure is equal to or less than the effective pressure index calculated before the injection timing is changed, the fuel injection timing may be controlled by changing the next fuel injection timing in a direction opposite to the direction of the fuel injection timing change amount.
[0065]
  From the measurement results shown in FIG. 5, it can be seen that in the direct injection internal combustion engine, the effective pressure index changes as the fuel injection timing changes. Therefore,Claim 5 aboveAs in the case where the ignition timing is controlled in step 1, the combustion state is determined based on the change in the effective pressure index due to the change in the fuel injection timing, and the fuel injection timing is set based on the determination result. Can be optimally controlled.
[0066]
For example, if the effective pressure index calculated after the fuel injection timing is advanced is greater than the effective pressure index calculated before the fuel injection timing, this indicates that the combustion state is good and the next fuel It can be expected that the combustion state is further improved by advancing the injection timing. On the other hand, if the effective pressure index calculated after the fuel injection timing is advanced is smaller than the effective pressure index calculated before the fuel injection timing, it indicates that the combustion state has become defective. By delaying the fuel injection timing, the combustion state is improved.
[0067]
In this way, by controlling the fuel injection timing, it is possible to improve the combustion state in a stable operation state, and it is possible to avoid the deterioration of the combustion state.
In order to determine the combustion state from the change in the effective pressure index when the fuel injection timing is changed to be delayed, the effective pressure index calculated after the change in the fuel injection timing is larger than the effective pressure index before the change. In this case, the combustion state can be more optimally controlled by further delaying the next fuel injection timing. On the other hand, if the effective pressure index calculated after the change in fuel injection timing is smaller than the effective pressure index before the change, the combustion state can be controlled more optimally by advancing the next fuel injection timing. It becomes possible.
[0068]
  Therefore,The present invention (Claim 7)According to the internal combustion engine control method, the direct injection type internal combustion engine can control the fuel injection timing so that the combustion state when the operation state of the internal combustion engine is stable becomes better. It becomes possible to better control the combustion state of the internal combustion engine.
[0069]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram showing the configuration of an internal combustion engine to which an internal combustion engine control method of the present invention is applied.
[0070]
The configuration other than the control unit (ECU) 19, the EGR valve 17, and the crankshaft 47 is provided for each cylinder of the internal combustion engine. In FIG. 1, only one cylinder is shown to make the drawing easier to see. ing.
As shown in FIG. 1, the ignition device for an internal combustion engine of the present embodiment generates a spark discharge for burning an air-fuel mixture and detects a pressure (in-cylinder pressure) in a combustion chamber 31 from a change in tightening load. A pressure sensor built-in spark plug (hereinafter also referred to as a spark plug) 11, an igniter 13 for generating a high voltage for ignition for generating a spark discharge in the spark plug 11, and fuel for generating an air-fuel mixture A fuel injection valve (injector) 15 for injection, an EGR valve 17 for circulating the exhaust gas of the exhaust port 35 to the intake port 33, and the igniter 13, the fuel injection valve 15, and the EGR valve 17 according to a command from the outside And a control device (ECU) 19 composed of a microcomputer that outputs a command signal and controls the operation of the internal combustion engine 1. Since the internal combustion engine of the present embodiment is a direct injection internal combustion engine, the fuel injection valve 15 is provided so as to inject fuel directly into the combustion chamber.
[0071]
Further, the spark plug 11 has a structure as shown in FIG. 13, and a pressure sensor 11b (not shown) is built in the metal shell 11a to detect the in-cylinder pressure by detecting a change in tightening load. The electric charge according to the in-cylinder pressure is output from the output cable 11c. Since the output charge of the pressure sensor 11b is very small, for example, the pressure signal amplified by the amplification circuit 61 as shown in FIG. In FIG. 1, the amplification circuit is not shown. The spark plug 11 receives the ignition high voltage supplied from the igniter 13 at the terminal portion 11f, and generates a spark discharge between the center electrode 11e and the outer electrode 11d.
[0072]
The internal combustion engine 1 transmits power to the outside of the internal combustion engine 1 by the piston 41 reciprocating in the cylinder 43 rotating the crankshaft 47 via the connecting rod 45. Further, since the internal combustion engine 1 is a direct injection type, when the piston 41 descends in the intake stroke, the intake valve 37 opens to send air into the combustion chamber 31 and fuel when the piston 41 rises in the compression stroke. The injection valve 15 injects fuel into the combustion chamber 31 to generate an air-fuel mixture. The fuel injection timing and the fuel injection amount at this time are set by a control process described later executed by the ECU 19.
[0073]
In the combustion process, before the piston 41 reaches top dead center, a spark discharge is generated by the spark plug 11 and the air-fuel mixture is combusted to increase the pressure in the combustion chamber (in-cylinder pressure) and lower the piston 41. As a result, the power of the internal combustion engine is generated. Subsequently, when the piston 41 rises in the exhaust stroke, the exhaust valve 39 is opened, and the exhaust gas inside the combustion chamber 31 is discharged to the exhaust port 35. Subsequently, the internal combustion engine is operated by repeating the process of performing the compression stroke and shifting to the next combustion cycle.
[0074]
Such operation of the internal combustion engine is controlled by the ECU 19, and the ignition timing control, air-fuel ratio control (fuel injection amount control), EGR control and fuel injection timing control performed by the ECU 19 will be described below.
Note that the control device 19 separately operates the engine operating states such as the intake air amount (intake pipe pressure), the rotational speed, the throttle opening, the cooling water temperature, and the intake air temperature of the internal combustion engine for the control process described below. An operation state detection process is performed to detect.
[0075]
First, the ignition timing control process of the present embodiment will be described with reference to the flowchart shown in FIG. This ignition timing control process is started when the operation of the internal combustion engine is started, and is executed until the operation of the internal combustion engine is stopped.
As shown in FIG. 6, when the ignition timing control process is started, first, in S110 (S represents a step), the engine speed and the throttle opening detected in the operation state detection process that is separately executed are measured. To do. Subsequently, in S120, it is determined whether or not the operating state of the internal combustion engine is in a stable state (within specified conditions). Specifically, the engine speed and the throttle opening measured in S110 are determined. It is determined whether or not the fluctuation of the value converges within a certain range. If a positive determination is made in S120, the process proceeds to S140. If a negative determination is made in S120, the process proceeds to S130.
[0076]
If the operating state of the internal combustion engine has changed when the process proceeds to S120, a negative determination is made in S120, and the process proceeds to S130. In S130, based on the engine speed and throttle opening measured in S110, the ignition timing Tig is set by reading the ignition timing Tig from a preset map, and the initial FLG is reset (RESET). . The initial FLG is an index representing that an initial value for comparing the effective pressure index An is calculated. When the process of S130 is performed, the process proceeds to S240.
[0077]
In S240, ignition is performed at the latest ignition timing Tig calculated last, and when ignition is performed, the process proceeds to S110.
If the operation state of the internal combustion engine is stable when the process proceeds to S120, an affirmative determination is made in S120, and the process proceeds to S140. In S140, it is determined whether or not the initial FLG is set (SET). If an affirmative determination is made, the process proceeds to S160, and if a negative determination is made, the process proceeds to S150. At this time, if the initial FLG is reset, a negative determination is made in S140, and the flow proceeds to S150.
[0078]
In S150, first, the ignition timing Tig is set by reading the ignition timing Tig from a preset map based on the engine speed and the throttle opening measured in S110. Then, from a storage unit (not shown) in which the combustion pressure signal detected by the pressure sensor 11b of the spark plug 11 is stored, combustion is performed from 90 ° CA (BTDC 90 ° CA) to 270 ° CA (ATDC 90 ° CA). A pressure signal (in-cylinder pressure) is taken in, and an effective pressure index An is calculated using the taken in-cylinder pressure.
[0079]
Here, in calculating the effective pressure index An, first, of the captured combustion pressure signal (in-cylinder pressure), the cylinder during which the crank angle moves from 90 ° CA (BTDC 90 ° CA) to top dead center (TDC). The internal pressure is integrated at every crank angle of 1 ° CA to obtain the pressure integrated value A before top dead center. Similarly, using the taken in-cylinder pressure, the in-cylinder pressure during the period in which the crank angle moves from top dead center (TDC) to 270 ° CA (ATDC 90 ° CA) is accumulated for each crank angle 1 ° CA. The post-point pressure integral value B is obtained. Further, the difference between the in-cylinder pressure when the crank angle is 160 ° CA (BTDC 20 ° CA) and the in-cylinder pressure when the crank angle is 90 ° CA (BTDC 90 ° CA) is obtained and set as the first correction reference value C.
[0080]
Note that the in-cylinder pressure integration interval is not limited to each crank angle of 1 ° CA. If the integration interval is shortened, the number of in-cylinder pressure data can be increased, and the effective pressure index An with higher accuracy can be obtained. Can be calculated. On the contrary, by increasing the integration interval, the processing load on the ECU 19 can be reduced, but at the same time, the number of in-cylinder pressure data to be integrated is reduced, so the accuracy of the effective pressure index An is reduced. . For this reason, the integration interval may be set to be long enough to collect at least the number of data necessary for calculating the effective pressure index An, and within a range where the processing load on the ECU 19 does not become abnormally high.
[0081]
Further, in this step, it is determined whether or not the combustion cycle at this time is a fuel cut (fuel cut-off). If not, the effective pressure index value at the time of the fuel cut is stored. 2 Take in the value of the correction reference value D.
Then, after the effective pressure index An is subtracted by the first correction reference value C, the value obtained by subtracting the pre-top dead center pressure integrated value A from the post-top dead center pressure integrated value B in accordance with the calculation formula shown in Equation 1, Calculation is performed by subtracting the second correction reference value D.
[0082]
[Expression 1]

[0083]
If the combustion cycle at this time is a fuel cutoff, the second correction reference value D is not subtracted in Equation 1, and the pre-top dead center pressure integrated value A is calculated from the post-top dead center pressure integrated value B. A value obtained by dividing the subtracted value by the first correction reference value C is calculated as an effective pressure index An, and the effective pressure index An is substituted for the second correction reference value D and stored.
[0084]
In S150, the calculated effective pressure index An is substituted into the previous effective pressure index An-1, and the ignition timing Tig is updated to a value advanced by a predetermined advance amount Ta. The initial FLG is set (SET). When the process of S150 is thus performed, the process proceeds to S240.
[0085]
In S240, ignition is performed at the ignition timing Tig calculated last, and when ignition is performed, the process proceeds to S110.
If the initial FLG is set when the process proceeds to S140, a positive determination is made in S140, and the process proceeds to S160. In S160, first, the crank angle is changed from 90 ° CA (BTDC 90 ° CA) to 270 ° CA (ATDC 90 ° CA) from a storage unit (not shown) in which the combustion pressure signal detected by the pressure sensor 11b of the spark plug 11 is stored. The combustion pressure signal (cylinder pressure) is taken in, and the effective pressure index An is calculated using the taken in-cylinder pressure. The calculation method of the effective pressure index An is the same as the calculation method in the process of S150.
[0086]
In subsequent S170, it is determined whether or not the latest (n-th) effective pressure index An is larger than the previous (n-1) effective pressure index An-1, and if an affirmative determination is made, the process proceeds to S180. If a negative determination is made, the process proceeds to S210.
If the latest effective pressure index An is larger than the previous effective pressure index An-1 when the process proceeds to S170, an affirmative determination is made in S170, and the process proceeds to S180. In S180, the latest effective pressure index An is substituted for the previous effective pressure index An-1, and the ignition timing Tig is updated to a value advanced by a predetermined advance amount Ta.
[0087]
In subsequent S190, it is determined whether or not the value of the ignition timing Tig updated in S180 is larger than the advance limit ignition timing TLa that is set in advance as the advance limit value of the ignition timing. The process proceeds to S200, and if a negative determination is made, the process proceeds to S240. At this time, if the ignition timing Tig is greater than the advance limit ignition timing TLa, an affirmative determination is made in S190 and the routine proceeds to S200. In S200, the value of the advance limit ignition timing TLa is substituted into the ignition timing Tig. This prevents the ignition timing from being advanced excessively and the operating state of the internal combustion engine from becoming unstable. When the process of S200 is performed, the process proceeds to S240.
[0088]
If the ignition timing Tig is less than or equal to the advance limit ignition timing TLa when the process proceeds to S190, a negative determination is made in S190 and the process proceeds to S240. In S240, ignition is performed at the last calculated ignition timing Tig, When ignition is performed, the process proceeds to S110.
[0089]
If the latest effective pressure index An is equal to or less than the previous effective pressure index An-1 when the process proceeds to S170, a negative determination is made in S170, and the process proceeds to S210. In S210, the value of the latest effective pressure index An is substituted into the previous effective pressure index An-1, and the ignition timing Tig is updated to a value delayed by a predetermined delay amount Tr.
[0090]
In subsequent S220, it is determined whether or not the value of the ignition timing Tig updated in S210 is smaller than a retard limit ignition timing TLr that is set in advance as a retard limit value of the ignition timing. The process proceeds to S230, and if a negative determination is made, the process proceeds to S240. At this time, if the ignition timing Tig is smaller than the retard limit ignition timing TLr, an affirmative determination is made in S220, and the routine proceeds to S230. In S230, the value of the retard limit ignition timing TLr is substituted into the ignition timing Tig. This prevents the ignition timing from being retarded excessively and the operating state of the internal combustion engine from becoming unstable. When the process of S230 is performed, the process proceeds to S240.
[0091]
When the process proceeds to S220, if the ignition timing Tig is equal to or greater than the retard limit ignition timing TLr, a negative determination is made in S220, and the process proceeds to S240. In S240, ignition is performed at the last calculated ignition timing Tig, When ignition is performed, the process proceeds to S110.
[0092]
As described above, in the ignition timing control process, when ignition is performed in S240, the process proceeds to S110, and by repeatedly executing the above-described process, the ignition timing Tig is updated based on the effective pressure index An. Tig is controlled.
As described above, in the ignition timing control process, when the operating state changes, the ignition timing Tig is controlled based on the engine speed and the throttle opening. When the operating state is stable, the ignition timing Tig set based on the engine speed and the throttle opening is set as the initial value, and the effective pressure index An is changed by changing the ignition timing Tig. The combustion state of the internal combustion engine is determined, and the ignition timing Tig is controlled.
[0093]
That is, after the ignition timing Tig is advanced in S150, the effective pressure index An calculated in S160 is larger than the effective pressure index An-1 calculated before the advance (Yes in S170). In the case where the combustion state is good). For this reason, the next ignition timing Tig is further advanced in S180, so that the combustion state in the next ignition is further improved.
[0094]
On the contrary, after the ignition timing Tig is advanced in S150, the effective pressure index An calculated in S160 is equal to or less than the effective pressure index An-1 calculated before the advance (negative determination in S170). In the case where the combustion state is poor. For this reason, in the subsequent S210, the next ignition timing Tig is retarded so that the combustion state becomes good in the next ignition.
[0095]
Then, while the operating state of the internal combustion engine continues to be stable, the steps S110, S120, S140, S160 to S240 are repeatedly executed, and the ignition timing Tig is set to an optimum value based on the effective pressure index An. Be controlled. As a result, the internal combustion engine can be operated by setting the ignition timing to MBT (Minimum Spark Advance for Best Torque), which is the ignition timing with the best efficiency of the internal combustion engine.
[0096]
In the present embodiment, the advance amount Ta and the retard amount Tr are fixed values set in advance, but may be variable values set according to the driving state, for example. Further, by setting the retard amount Tr to a value larger than the advance amount Ta, it is possible to quickly avoid an unstable combustion state. Further, the advance limit ignition timing TLa and the retard limit ignition timing TLr may also be variable values set according to the operating state, for example.
[0097]
Further, the process of calculating the effective pressure index An without subtracting the second correction reference value D in Equation 1, and substituting the effective pressure index An into the second correction reference value D and storing it is the fuel cut (fuel This is not limited to when the engine is shut off, and may be performed under certain engine conditions in which the residual pressure of the in-cylinder pressure can be detected during misfire operation.
[0098]
Next, the air-fuel ratio control process of this embodiment will be described with reference to the flowchart shown in FIG. This air-fuel ratio control process is started when the operation of the internal combustion engine is started, and is executed until the operation of the internal combustion engine is stopped. In addition, since the air-fuel ratio represents the ratio of fuel and air forming the air-fuel mixture, in the internal combustion engine of this embodiment, air-fuel ratio control is performed by controlling the fuel injection amount.
[0099]
As shown in FIG. 7, when the air-fuel ratio control process is started, first, in S310 (S represents a step), the engine speed and the throttle opening detected in the operation state detection process executed separately are measured. To do. Subsequently, in S320, it is determined whether or not the operating state of the internal combustion engine is stable (within specified conditions). Specifically, the engine speed and throttle opening measured in S310 are determined. It is determined whether or not the fluctuation of the value converges within a certain range. If a positive determination is made in S320, the process proceeds to S340, and if a negative determination is made in S320, the process proceeds to S330.
[0100]
If the operating state of the internal combustion engine has changed when the process proceeds to S320, a negative determination is made in S320, and the process proceeds to S330. In S330, based on the engine speed and throttle opening measured in S310, the fuel injection amount Fin is set by reading the fuel injection amount Fin from a preset map, and the initial FLG is reset (RESET). The initial S calculation counter SPCNT is cleared. The initial FLG is an index indicating that the initial value for comparing the effective pressure index An is calculated, and the initial S calculation counter SPCNT is used to calculate the standard deviation and average of the effective pressure index An. This is a counter for counting the number of data. When the process of S330 is performed, the process proceeds to S460.
[0101]
In S460, fuel injection is performed with the latest fuel injection amount Fin calculated last, and when fuel injection is performed, the process proceeds to S310.
If the operation state of the internal combustion engine is stable when the process proceeds to S320, an affirmative determination is made in S320, and the process proceeds to S340. In S340, it is determined whether or not the initial FLG is set (SET). If an affirmative determination is made, the process proceeds to S380, and if a negative determination is made, the process proceeds to S350. At this time, if the initial FLG is reset, a negative determination is made in S340, and the flow proceeds to S350.
[0102]
In S350, first, the fuel injection amount Fin is set by reading the fuel injection amount Fin from a preset map based on the engine speed and the throttle opening measured in S310. Then, from a storage unit (not shown) in which the combustion pressure signal detected by the pressure sensor 11b of the spark plug 11 is stored, combustion is performed from 90 ° CA (BTDC 90 ° CA) to 270 ° CA (ATDC 90 ° CA). A pressure signal (in-cylinder pressure) is taken in, and an effective pressure index An is calculated using the taken in-cylinder pressure. The calculation method of the effective pressure index An is the same as the calculation method in the process in S150 of the ignition timing control process described above.
[0103]
Then, it is obtained by calculating the standard deviation and the average of the N effective pressure indexes An calculated in the latest initial S calculation times calculated during the execution of the air-fuel ratio control process, and dividing the standard deviation by the average. Set the value to Deviation / Average S. At this time, Formula 2 is used for calculating the standard deviation, and Formula 3 is used for calculating the average.
[0104]
[Expression 2]

[0105]
[Equation 3]

[0106]
When the number of effective pressure indexes An is less than the initial S calculation number N, standard deviation and average are not calculated.
Further, in S350, the initial S calculation counter SPCNT is incremented by 1 and the initial S calculation counter SPCNT is updated.
[0107]
In subsequent S360, it is determined whether or not the initial S calculation counter SPCNT is equal to or greater than the initial S calculation count N. If an affirmative determination is made, the process proceeds to S370, and if a negative determination is made, the process proceeds to S460. At this time, if the initial S calculation counter SPCNT is smaller than the initial S calculation count N, a negative determination is made in S360, and the process proceeds to S460. In S460, fuel injection is performed with the fuel injection amount Fin calculated last, and when fuel injection is performed, the process proceeds to S310.
[0108]
If the initial S calculation counter SPCNT is equal to or greater than the initial S calculation count N when the process proceeds to S360, an affirmative determination is made in S360 and the process proceeds to S370. In S370, the initial FLG is set.
If the process of S370 is performed or an affirmative determination is made in S340, the process proceeds to S380, and in S380, first, the combustion pressure signal detected by the pressure sensor 11b of the spark plug 11 is stored (not shown). A combustion pressure signal (in-cylinder pressure) with a crank angle of 90 ° CA (BTDC 90 ° CA) to 270 ° CA (ATDC 90 ° CA) is taken from the storage unit, and the same processing as in S350 is performed using the taken in-cylinder pressure. The effective pressure index An is calculated by the following calculation method. Then, as in the case of the calculation in S350, the standard deviation and average of the N effective pressure indexes An of the latest initial S calculation times calculated during the execution of the air-fuel ratio control process are calculated, and the standard deviation is calculated. The value obtained by dividing by the average is set to the deviation / average S.
[0109]
In subsequent S390, it is determined whether or not the deviation / average S calculated in S380 is equal to or less than a lean limit determination value LL set in advance as a lean limit of the air-fuel ratio. If an affirmative determination is made, the process proceeds to S400. If a negative determination is made, the process proceeds to S430. At this time, when the deviation / average S is equal to or less than the lean limit determination value LL, an affirmative determination is made in S390, and the process proceeds to S400. In S400, the fuel injection amount Fin is updated to a value reduced by a predetermined fuel reduction amount Fa.
[0110]
In subsequent S410, it is determined whether or not the value of the fuel injection amount Fin updated in S400 is smaller than an injection fuel reduction limit FLa that is predetermined as a lean limit value of the fuel injection amount. The process proceeds to S420, and if a negative determination is made, the process proceeds to S460. At this time, if the fuel injection amount Fin is smaller than the injected fuel reduction limit FLa, an affirmative determination is made in S410 and the routine proceeds to S420. In S420, the value of the injected fuel reduction limit FLa is substituted into the fuel injection amount Fin. This prevents the fuel injection amount from being excessively reduced and the operating state of the internal combustion engine from becoming unstable. When the process of S420 is performed, the process proceeds to S460.
[0111]
If the fuel injection amount Fin is equal to or greater than the injected fuel reduction limit FLa when the process proceeds to S410, a negative determination is made in S410 and the process proceeds to S460. In S460, the fuel is calculated with the fuel injection amount Fin calculated last. When the fuel injection is performed, the process proceeds to S310.
[0112]
If the deviation / average S is larger than the lean limit determination value LL when the process proceeds to S390, a negative determination is made in S390, and the process proceeds to S430. In S430, the fuel injection amount Fin is updated to a value increased by a predetermined fuel increase amount Fb.
[0113]
In subsequent S440, it is determined whether or not the value of the fuel injection amount Fin updated in S430 is larger than the injection fuel increase limit FLb that is predetermined as the increase limit value of the fuel injection amount. The process proceeds to S450, and if a negative determination is made, the process proceeds to S460. At this time, if the fuel injection amount Fin is larger than the injected fuel increase limit FLb, an affirmative determination is made in S440 and the process proceeds to S450. In S450, the value of the injected fuel increase limit FLb is substituted for the fuel injection amount Fin. This prevents the fuel injection amount from being excessively increased and the operating state of the internal combustion engine from becoming unstable. When the process of S450 is performed, the process proceeds to S460.
[0114]
If the fuel injection amount Fin is equal to or less than the injected fuel increase limit FLb when the process proceeds to S440, a negative determination is made in S440 and the process proceeds to S460. In S460, the fuel is calculated at the last calculated fuel injection amount Fin. When the fuel injection is performed, the process proceeds to S310.
[0115]
As described above, in the present air-fuel ratio control process, when fuel injection is performed in S460, the process proceeds to S310, and the above-described process is repeatedly executed, whereby the deviation / average calculated from the standard deviation and average of the effective pressure index An is calculated. The fuel injection amount Fin is controlled by updating the fuel injection amount Fin based on the value of S.
[0116]
The standard deviation of the effective pressure index An is a scale representing the spread of the distribution of the calculated effective pressure index An, and the smaller this value, the smaller the variation in the calculated effective pressure index An and the more stable the combustion state. On the contrary, the larger the value, the greater the variation in the calculated effective pressure index An, indicating that the combustion state is unstable.
[0117]
Further, by dividing the standard deviation of the effective pressure index An by the average of the effective pressure index An and comparing the normalized deviation / average S with the determination value, the combustion state of the internal combustion engine is determined, so that the operating state is obtained. Accordingly, it is not necessary to update the determination value, and a constant value can be used as the determination value.
[0118]
As described above, in this air-fuel ratio control process, when the operating state changes, the fuel injection amount Fin is controlled based on the engine speed and the throttle opening. When the operating state is stable, the standard deviation of the effective pressure index An due to the change of the fuel injection amount Fin with the fuel injection amount Fin set based on the engine speed and the throttle opening as an initial value. Based on this value, the combustion state of the internal combustion engine is determined, and the fuel injection amount Fin is controlled.
[0119]
That is, when the deviation / average S calculated in S380 is equal to or less than the lean limit determination value LL (when an affirmative determination is made in S390), it can be determined that the combustion state is stable. For this reason, in the subsequent S400, the fuel consumption of the internal combustion engine is improved by reducing the next fuel injection amount Fin (increasing the air-fuel ratio).
[0120]
Further, when the deviation / average S calculated in S380 is larger than the lean limit determination value LL (when a negative determination is made in S390), it can be determined that the combustion state is unstable. For this reason, the fuel state of the internal combustion engine is stabilized by increasing the next fuel injection amount Fin (lowering the air-fuel ratio) in the subsequent S430.
[0121]
Then, while the operation state of the internal combustion engine is stable, the steps from S310, S320, S340, S380 to S460 are repeatedly executed, and the fuel injection amount Fin is based on the standard deviation of the effective pressure index An. Is controlled to the optimum value. As a result, the internal combustion engine can be operated at an air-fuel ratio (lean limit) that provides the thinnest air-fuel mixture.
[0122]
In addition, you may use the formula of several 4 for calculation of the average of the effective pressure index | exponent An.
[0123]
[Expression 4]

[0124]
When calculating the average value, it is necessary to store n pieces of data (effective pressure index An) in order to calculate with the formula (3). Since the average can be calculated from the two data of the average value and the effective pressure index An, the memory capacity can be saved.
[0125]
In this embodiment, the fuel decrease amount Fa and the fuel increase amount Fb are fixed values set in advance, but may be variable values set according to the operating state, for example. Moreover, by setting the fuel increase amount Fb to a value larger than the fuel decrease amount Fa, it is possible to quickly avoid the unstable combustion state. Also, the injected fuel reduction limit FLa and the injected fuel increase limit FLb may be variable values set according to the operating state, for example.
[0126]
Next, the EGR amount control process of this embodiment will be described with reference to the flowchart shown in FIG. The EGR amount control process is started and started until the operation of the internal combustion engine is started and stopped.
In addition, since the EGR amount control process has the same basic control process flow as the air-fuel ratio control process, steps having the same process contents are denoted by the same step numbers and are represented by flowcharts. The EGR amount control process will be described below with a focus on the different parts.
[0127]
First, in S530 and S550 of the EGR amount control processing corresponding to S330 and S350 in which the fuel injection amount Fin was read in the air-fuel ratio control processing, it is preset based on the engine speed and throttle opening measured in S310. The EGR amount Egr is set by reading the EGR amount Egr from the mapped map. When the process of S530 is performed, the process proceeds to S660.
[0128]
In S590 corresponding to S390, it is determined whether or not the deviation / average S calculated in S380 is equal to or less than the EGR amount limit determination value EL set in advance as the EGR amount increase limit. If the determination is negative, the process proceeds to S630. Note that S400 to S460 in the air-fuel ratio control process correspond to S600 to S660 in the EGR amount control process.
[0129]
When the process proceeds to S590, if the deviation / average S is equal to or less than the EGR amount limit determination value EL, an affirmative determination is made in S590, and the process proceeds to S600. In S600, the EGR amount Egr is updated to a value increased by a predetermined EGR increase amount Ea.
In subsequent S610, it is determined whether or not the value of the EGR amount Egr updated in S600 is larger than an EGR amount increase limit ELa that is predetermined as an increase limit value of the EGR amount Egr. If the determination is negative, the process proceeds to S660. At this time, if the EGR amount Egr is larger than the EGR amount increase limit ELa, an affirmative determination is made in S610, and the process proceeds to S620. In S620, the value of the EGR amount increase limit ELa is substituted for the EGR amount Egr. When the process of S620 is performed, the process proceeds to S660.
[0130]
If the EGR amount Egr is equal to or less than the EGR amount increase limit ELa when the process proceeds to S610, a negative determination is made in S610, the process proceeds to S660, and in S660, the EGR control operation is performed with the last calculated EGR amount Egr. When the EGR control operation is performed, the process proceeds to S310.
[0131]
If the deviation / average S is larger than the EGR amount limit determination value EL when the process proceeds to S590, a negative determination is made in S590, and the process proceeds to S630. In S630, the EGR amount Egr is updated to a value reduced by a predetermined EGR reduction amount Eb.
[0132]
In the subsequent S640, it is determined whether or not the value of the EGR amount Egr updated in S630 is smaller than the EGR amount reduction limit ELb set in advance as the reduction limit value of the EGR amount Egr. If the determination is negative, the process proceeds to S660. At this time, if the EGR amount Egr is smaller than the EGR amount decrease limit ELb, an affirmative determination is made in S640, and the process proceeds to S650. In S650, the value of the EGR amount decrease limit ELb is substituted into the EGR amount Egr. When the process of S650 is performed, the process proceeds to S660.
[0133]
If the EGR amount Egr is equal to or greater than the EGR amount reduction limit ELb when the process proceeds to S640, a negative determination is made in S640, the process proceeds to S660, and in S660, the EGR control operation is performed with the last calculated EGR amount Egr. When the EGR control operation is performed, the process proceeds to S310.
[0134]
As described above, in the present EGR amount control process, when the EGR control operation is performed in S660, the process proceeds to S310, and the above-described process is repeatedly executed, whereby the deviation / calculated from the standard deviation and the average of the effective pressure index An. Based on the average S value, the EGR amount Egr is updated to control the EGR amount Egr.
[0135]
As described above, in the present EGR amount control process, when the operating state changes, the EGR amount Egr is controlled based on the engine speed and the throttle opening. When the operating state is stable, the standard deviation value of the effective pressure index An obtained by changing the EGR amount Egr with the EGR amount Egr set based on the engine speed and the throttle opening as an initial value. Based on this, the combustion state of the internal combustion engine is determined, and the EGR amount Egr is controlled.
[0136]
That is, when the deviation / average S calculated in S380 is equal to or less than the EGR amount limit determination value EL (when an affirmative determination is made in S590), it can be determined that the combustion state is stable. For this reason, in the subsequent S600, the next EGR amount Egr is increased to further reduce the harmful substances in the exhaust gas.
[0137]
Further, when the deviation / average S calculated in S380 is larger than the EGR amount limit determination value EL (when a negative determination is made in S590), this indicates that the combustion state is unstable, and in S630 The fuel state of the internal combustion engine is stabilized by reducing the next EGR amount Egr.
[0138]
Then, while the operating state of the internal combustion engine continues to be stable, the steps from S310, S320, S340, S380, S590 to S660 are repeatedly executed, and the EGR amount Egr becomes the standard deviation of the effective pressure index An. Based on this, the optimum value is controlled. As a result, the internal combustion engine can be operated in a state where generation of harmful substances is suppressed without reducing the combustion state.
[0139]
In the present embodiment, the EGR increase amount Ea and the EGR decrease amount Eb are fixed values set in advance, but may be variable values set according to the operating state, for example. Also, the EGR amount increase limit ELa and the EGR amount decrease limit ELb may be variable values set according to the operating state, for example.
[0140]
Next, the fuel injection timing control process of the present embodiment will be described with reference to the flowchart shown in FIG. This fuel injection timing control process is started and started until the operation of the internal combustion engine is started and stopped.
In addition, since the fuel injection timing control process and the basic control process flow method are the same as the ignition timing control process, steps having the same processing contents are denoted by the same step numbers and are represented by flowcharts. The fuel injection timing control will be described below with a focus on differences from the control process.
[0141]
First, in S730 and S750 of the fuel injection timing control process corresponding to S130 and S150 in which the ignition timing Tig was read in the ignition timing control process, it is set in advance based on the engine speed and the throttle opening measured in S110. The fuel injection timing Tin is set by reading the fuel injection timing Tin from the mapped map. In S750, the fuel injection timing Tin is updated to a value advanced by a predetermined advance amount Tia.
[0142]
Further, S180 to S240 in the ignition timing control correspond to S780 to S840 in the fuel injection timing control, and when the process proceeds to S170, the latest effective pressure index An is larger than the previous effective pressure index An-1. In this case, an affirmative determination is made in S170, and the flow proceeds to S780. In S780, the value of the latest effective pressure index An is substituted into the previous effective pressure index An-1, and the fuel injection timing Tin is updated to a value advanced by a predetermined advance amount Tia.
[0143]
In subsequent S790, it is determined whether or not the value of the fuel injection timing Tin updated in S780 is larger than an injection timing advance limit TLia that is predetermined as the advance limit value of the fuel injection timing. Then, the process proceeds to S800, and if a negative determination is made, the process proceeds to S840. At this time, if the fuel injection timing Tin is larger than the injection timing advance limit TLia, an affirmative determination is made in S790, and the process proceeds to S800. In S800, the value of the injection timing advance limit TLia is substituted for the fuel injection timing Tin. When the process of S800 is performed, the process proceeds to S840.
[0144]
If the fuel injection timing Tin is equal to or less than the injection timing advance limit TLia when the process proceeds to S790, a negative determination is made in S790 and the process proceeds to S840. In S840, the fuel injection timing Tin calculated last is used. When fuel injection is performed and fuel injection ignition is performed, the process proceeds to S110.
[0145]
If the latest effective pressure index An is less than or equal to the previous effective pressure index An-1 when the process proceeds to S170, a negative determination is made in S170, and the process proceeds to S810. In S810, the value of the latest effective pressure index An is substituted into the previous effective pressure index An-1, and the fuel injection timing Tin is updated to a value delayed by a predetermined retardation amount Tir.
[0146]
In the subsequent S820, it is determined whether or not the value of the fuel injection timing Tin updated in S810 is smaller than an injection timing delay limit TLir set in advance as a delay limit value of the fuel injection timing, and an affirmative determination is made. Then, the process proceeds to S830, and if a negative determination is made, the process proceeds to S840. At this time, if the fuel injection timing Tin is smaller than the injection timing retardation limit TLir, an affirmative determination is made in S820 and the routine proceeds to S830. In S830, the value of the injection timing retardation limit TLir is substituted for the fuel injection timing Tin. When the process of S830 is performed, the process proceeds to S840.
[0147]
If the fuel injection timing Tin is greater than or equal to the injection timing retard limit TLir when the routine proceeds to S820, a negative determination is made in S820 and the routine proceeds to S840. In S840, the fuel injection timing Tin calculated at the end is used. When the fuel is injected and the fuel is injected, the process proceeds to S110.
[0148]
Thus, in this fuel injection timing control process, when ignition is performed in S840, the process proceeds to S110, and the above process is repeated to update the fuel injection timing Tin based on the effective pressure index An, The fuel injection timing Tin is controlled.
As described above, in the fuel injection timing control process, when the operating state changes, the fuel injection timing Tin is controlled based on the engine speed and the throttle opening. When the operating state is stable, the fuel injection timing Tin set based on the engine speed and the throttle opening is set as an initial value, and the fluctuation of the effective pressure index An due to the change of the fuel injection timing Tin is caused. Based on this, the combustion state of the internal combustion engine is determined, and the fuel injection timing Tin is controlled.
[0149]
That is, after the fuel injection timing Tin is advanced in S750, the effective pressure index An calculated in S160 is larger than the effective pressure index An-1 calculated before the advance (when affirmative determination is made in S170). ), It can be determined that the combustion state is good. For this reason, the next fuel injection timing Tin is advanced in the subsequent S780, so that the combustion state in the next combustion is further improved.
[0150]
On the contrary, after the fuel injection timing Tin is advanced in S750, the effective pressure index An calculated in S160 is equal to or less than the effective pressure index An-1 calculated before the advance (a negative determination is made in S170). ), It can be determined that the combustion state is poor. For this reason, by delaying the next fuel injection timing Tin in subsequent S810, the combustion state is improved in the next combustion.
[0151]
Then, while the operation state of the internal combustion engine remains stable, the steps S110, S120, S140, S160, S170, S780 to S840 are repeatedly executed, and the fuel injection timing Tin is based on the effective pressure index An. Is controlled to the optimum value. Thus, the internal combustion engine can be operated by setting the fuel injection timing to the fuel injection timing at which the internal combustion engine has the highest efficiency.
[0152]
In the present embodiment, the advance amount Tia and the retard amount Tir are fixed values set in advance, but may be variable values set in accordance with the operating state, for example. Also, the injection timing advance limit TLia and the injection timing retard limit TLir may be variable values set according to the operating state, for example.
[0153]
As described above, in the internal combustion engine of the present embodiment, the in-cylinder pressure used for calculating the effective pressure index is detected by the pressure sensor built-in type spark plug, but from 90 ° CA before top dead center to after top dead center. Since the in-cylinder pressure during the period up to 90 ° CA is used, the effective pressure index can be accurately calculated without being affected by the seating noise of the intake and exhaust valves. The effective pressure index is calculated by correcting the in-cylinder pressure error caused by individual differences such as sensitivity, tightening torque, and temperature in the pressure sensor built-in type spark plug. Further, the effective pressure index is calculated by correcting the error due to the residual pressure in the in-cylinder pressure detected by the pressure sensor built-in type spark plug. From these things, in the internal combustion engine of the present embodiment, the effective pressure index can be calculated with high accuracy.
[0154]
Therefore, the internal combustion engine of the present embodiment controls the ignition timing, the air-fuel ratio (fuel injection amount), the EGR amount, and the fuel injection timing based on the effective pressure index calculated with high accuracy in this way. It is possible to optimally control the combustion state. Thereby, combustion efficiency can be improved, fuel consumption can be improved, and harmful substances can be reduced.
[0155]
As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken.
In this embodiment, the in-cylinder pressure integral value for calculating the effective pressure index is calculated by accumulating every crank angle of 1 ° CA. For example, the charge output from the piezoelectric element is accumulated in the capacitor, A method of calculating the in-cylinder pressure integral value based on the accumulated charge capacity may be used.
[0156]
In addition, the pressure sensor for detecting the in-cylinder pressure is provided separately from the spark plug, and is used to detect a change in tightening load by being sandwiched with a gasket between the spark plug and the internal combustion engine body. May be used.
Further, the present embodiment is a direct injection type internal combustion engine. In an internal combustion engine that injects fuel into an intake pipe, the ignition timing, air-fuel ratio, and EGR amount are controlled by using the control method of the present invention. It is also possible.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of an internal combustion engine according to an embodiment.
FIG. 2 is an explanatory diagram showing a waveform of in-cylinder pressure detected by a seat-type pressure sensor.
FIG. 3 is a graph showing an effective pressure index before and after sensitivity correction calculated using a seat-type pressure sensor.
FIG. 4 is an explanatory diagram showing a waveform of in-cylinder pressure detected by a seat-type pressure sensor and an in-cylinder insertion type pressure sensor.
FIG. 5 is an explanatory diagram showing a result of measuring an effective pressure index.
FIG. 6 is a flowchart showing an ignition timing control process by a control device.
FIG. 7 is a flowchart showing air-fuel ratio control processing by the control device.
FIG. 8 is a flowchart showing an EGR amount control process by a control device.
FIG. 9 is a flowchart showing a fuel injection timing control process by the control device.
FIG. 10 is a graph showing output characteristics of a piezoelectric element with respect to temperature change and change in ignition plug tightening torque.
FIG. 11 is an explanatory diagram illustrating a configuration of an amplifier circuit.
FIG. 12 is a graph showing a relationship between an effective pressure index calculated using a seat-type pressure sensor and an indicated mean effective pressure calculated using a cylinder insertion type pressure sensor.
FIG. 13 is an explanatory view showing a configuration of a plug with a built-in pressure sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 11 ... Spark plug, 11a ... Metal fitting, 11b ... Pressure sensor, 11c ... Output cable, 11d ... Outer electrode, 11e ... Center electrode, 11f ... Terminal part, 13 ... Igniter, 15 ... Fuel injection valve, DESCRIPTION OF SYMBOLS 17 ... EGR valve, 19 ... Control apparatus (ECU), 31 ... Combustion chamber, 61 ... Amplifier circuit, 63 ... Operational amplifier.

Claims (7)

An in-cylinder pressure of the internal combustion engine is detected by detecting a change in the ignition plug tightening load by a piezoelectric element provided on a mounting seat of the ignition plug, and an effective pressure index that is a power source of the internal combustion engine calculated based on the in-cylinder pressure An internal combustion engine control method for controlling an internal combustion engine based on
By calculating the in-cylinder pressure before the top dead center by integrating the in-cylinder pressure within a predetermined period between the time when the intake valve is closed and the crank angle reaches the top dead center,
Calculate the post-top dead center pressure integrated value by integrating the in-cylinder pressure within a predetermined period between the crank angle reaching the top dead center and the exhaust valve opening.
The integration period of the pressure integration value before the top dead center and the integration period of the pressure integration value after the top dead center are symmetric with respect to the top dead center and have the same length.
While calculating the difference between the pressure integrated value after the top dead center and the pressure integrated value before the top dead center as an effective pressure index,
Calculate the effective pressure index in all operating states, including during misfire operation,
An effective pressure index calculated during the misfire operation is set as a second correction reference value,
By subtracting the second correction reference value from the effective pressure index calculated during the normal operation, the effective pressure index during the normal operation is corrected,
Controlling the internal combustion engine based on the corrected effective pressure index;
An internal combustion engine control method. The pressure integrated value before the top dead center is calculated by integrating the in-cylinder pressure within a period until the crank angle reaches the top dead center from 90 ° CA before the top dead center,
Calculating the integrated pressure value after the top dead center by integrating the in-cylinder pressure in a period from when the crank angle reaches the top dead center until it reaches 90 ° CA after the top dead center;
The internal combustion engine control method according to claim 1. A difference between the in-cylinder pressures at two different time points among the in-cylinder pressures detected from when the intake valve is closed to before the ignition timing is set as a first correction reference value;
The effective pressure index calculated as the difference between the pressure integrated value after the top dead center and the pressure integrated value before the top dead center is further corrected by dividing by the first correction reference value, and the corrected effective pressure is corrected. Controlling the internal combustion engine based on the index,
The internal combustion engine control method according to claim 1 or 2, characterized by the above. Determine whether the operating state of the internal combustion engine is stable,
At least during steady operation in which the operating state of the internal combustion engine is stable, calculating the effective pressure index, and controlling the internal combustion engine based on the calculated effective pressure index;
The internal combustion engine control method according to any one of claims 1 to 3, wherein: An internal combustion engine control method for controlling ignition timing based on the effective pressure index calculated during steady operation of the internal combustion engine,
When the effective pressure index calculated after changing the ignition timing by a predetermined ignition timing change amount is larger than the effective pressure index calculated before changing the ignition timing, the next ignition timing is Change it in the same direction as the amount of ignition timing change,
On the contrary, when the effective pressure index calculated after changing the ignition timing by a predetermined ignition timing change amount is less than or equal to the effective pressure index calculated before changing the ignition timing, the next ignition timing To control the ignition timing by changing in a direction opposite to the direction of change due to the ignition timing change amount,
The internal combustion engine control method according to claim 4. An internal combustion engine control method for controlling an air-fuel ratio or an EGR amount based on the effective pressure index calculated during steady operation of the internal combustion engine,
A value representing the spread of the effective pressure index distribution calculated a predetermined number of times after changing at least one of the fuel injection amount and the EGR amount by a predetermined amount is a predetermined determination value. When it is below, at least one of the control to decrease the fuel injection amount and the control to increase the EGR amount is executed,
On the contrary, after changing at least one of the fuel injection amount and the EGR amount by a predetermined amount, a value representing the spread of the effective pressure index distribution calculated a predetermined number of times is determined in advance. The control value for increasing the fuel injection amount and the control for decreasing the EGR amount are executed, thereby controlling the air-fuel ratio or the EGR amount,
6. The internal combustion engine control method according to claim 4 or 5, wherein: An internal combustion engine control method for controlling fuel injection timing based on the effective pressure index calculated during steady operation of a direct injection internal combustion engine,
When the effective pressure index calculated after changing the fuel injection timing by a predetermined amount of fuel injection timing change is greater than the effective pressure index calculated before changing the fuel injection timing, the next fuel injection Change the timing in the same direction as the fuel injection timing change amount,
Conversely, when the effective pressure index calculated after changing the fuel injection timing by a predetermined amount of change in the fuel injection timing is less than or equal to the effective pressure index calculated before changing the fuel injection timing, the next fuel Controlling the fuel injection timing by changing the injection timing in a direction opposite to the direction of the fuel injection timing change amount;
The internal combustion engine control method according to any one of claims 4 to 6, wherein:

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