JP2004176644A - Cylinder intake air quantity detecting device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect intake air quantity irregularity ratio between cylinders in an internal combustion engine. <P>SOLUTION: Area of output waveform (intake air quantity) for a prescribed period by an air flow meter 14 is determined for every intake stroke in each cylinder, and intake air quantity irregularity ratio between cylinders is determined based on the area. Intake valve lift quantity is corrected based on the intake air quantity irregularity ratio between cylinders to correct intake air quantity irregularity between cylinders. In this case, the period for determining the area of the output waveform by the air flow meter 14 may be set in a period in which effects of reflection waves of intake pulsation or intake interference from other cylinders are less likely to be given, or specifically, in a period including the maximal value of intake air quantity. Otherwise, it may be set in a valve opening period of an intake valve, or a period in which intake air quantity becomes more than average. In the case of setting it in the valve opening period of the intake valve, detection delay time of the air flow meter 14 is considered in setting the period for determining the area. <P>COPYRIGHT: (C)2004,JPO

Description

【００６３】
上式の分母は、全気筒の吸入空気量面積なまし値ＧＡＳＵＭＳＭ（＃ｉ）の平均値であり、Ｋ２は、吸入空気量面積のばらつきを吸入空気量のばらつきに変換するための補正係数であり、図１２のマップにより設定される。一般に、各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間Ｐが短くなるほど、吸入空気量面積ＧＡＳＵＭ（＃ｉ）のばらつきが小さくなるため、所定期間Ｐが短くなるほど、補正係数Ｋ２が大きくなるように設定される。
【００６４】
上記［数１］式から明らかなように、各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）は、各気筒の気筒間吸入空気量ばらつき率なまし値ＧＡＳＵＭＳＭ（＃ｉ）を全気筒の気筒間吸入空気量ばらつき率なまし値の平均値で割り算して、それに補正係数Ｋ２を乗算した値である。
【００６５】
この気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）に、エアフローメータ１４で検出した吸入空気量ＧＡ（平均空気流量）を乗算すれば、気筒別吸入空気量を求めることができる。
【００６６】
以上説明した本実施形態（１）の気筒間ばらつき補正の実行例を図１３及び図１４に示すタイムチャートを用いて説明する。
気筒間ばらつき補正実行条件が成立して気筒間ばらつき補正実行フラグがＯＮされている期間は、図１３に示すように、各気筒の吸気行程毎に、所定期間（瞬時空気流量ＧＡＦＭが極大値となる時点ｔを中心にしてその前後Ｐ／２以内の期間）の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出し、各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を気筒間でなまし処理して、各気筒の吸入空気量面積なまし値ＧＡＳＵＭＳＭ（＃ｉ）を求める。このようにして、全気筒の吸入空気量面積なまし値ＧＡＳＵＭＳＭ（＃ｉ）を求める毎（７２０℃Ａ毎）に、各気筒の吸入空気量面積なまし値ＧＡＳＵＭＳＭ（＃ｉ）を全気筒の吸入空気量面積なまし値の平均値で割り算して、それに補正係数Ｋ２を乗算して各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を求める。
【００６７】
図１４に示すように、各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を算出する毎に、気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）とエンジン運転条件に応じてリフト補正量ＦＶＶＬ（＃ｉ）を算出し、１８０℃Ａ毎に、補正前の全気筒の平均バルブリフト量ＶＶＬに該当気筒のリフト補正量ＦＶＶＬ（＃ｉ）を加算して、最終目標バルブリフト量ＶＶＬＭを求める。
【００６８】
このようにして、各気筒の吸気行程に対応して変化する各気筒の最終目標バルブリフト量ＶＶＬＭに応じて吸気バルブ２８の可変バルブリフト機構３０のモータ４１を高速駆動して、各気筒の吸気行程毎に吸気バルブリフト量を補正して各気筒の吸入空気量を補正する。これにより、気筒間の吸入空気量ばらつきを補正する。
【００６９】
尚、各気筒の吸気バルブ２８を電磁アクチュエータで駆動する構成の可変バルブ機構に本発明を適用する場合には、各気筒の最終目標バルブリフト量ＶＶＬＭに応じて各気筒の電磁アクチュエータの制御量を補正することで、各気筒の吸気バルブリフト量を補正して各気筒の吸入空気量を補正するようにすれば良い。
【００７０】
以上説明した本実施形態（１）によれば、吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間Ｐを、瞬時空気流量ＧＡＦＭの極大値を含む期間に設定したので、この所定期間Ｐを吸気脈動の反射波や他気筒の吸気干渉の影響を受けにくい期間に設定することができる。これにより、各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を用いて各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を精度良く算出することができ、この気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を用いて吸気バルブリフト量を補正することで、気筒間の吸入空気量ばらつきを精度良く補正することができ、それによって、気筒間のトルクばらつきや空燃比ばらつきを両方とも低減することができる。
【００７１】
《実施形態（２）》
上記実施形態（１）では、吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間Ｐを瞬時空気流量ＧＡＦＭの極大値を含む期間に設定したが、図１５乃至図１８に示す本発明の実施形態（２）では、吸気バルブ２８の開弁期間内に瞬時空気流量ＧＡＦＭの極大点が存在することを考慮して、吸入空気量面積ＧＡＳＵＭ（＃１）を算出する所定期間を吸気バルブ２８の開弁期間に設定するようにしている（図１７参照）。
【００７２】
この場合、吸気管１２内を流れる吸入空気がエアフローメータ１４の周辺を通過してから実際に気筒内に吸入されるまでに時間的な遅れ（エアフローメータ１４の検出遅れ）があるため、本実施形態（２）では、吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間をエアフローメータ１４の検出遅れを考慮して設定するようにしている。
【００７３】
本実施形態（２）では、図１５のルーチンを実行して各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を次のようにして算出する。まず、ステップ３０１で、図１６のマップを用いて、現在の吸気バルブリフト量ＶＶＬとエンジン回転速度ＮＥに応じたエアフローメータ１４の検出遅れ時間ＤＬＹを算出する。図１６のマップは低回転域で吸気バルブリフト量ＶＶＬが大きくなるほど、気筒内に吸入される空気の流速が遅くなることを考慮して、低回転域で吸気バルブリフト量ＶＶＬが大きくなるほど、検出遅れ時間ＤＬＹが大きくなるように設定されている。
【００７４】
検出遅れ時間ＤＬＹの算出後、ステップ３０２に進み、吸気バルブ２８の開弁期間（吸気バルブ開弁フラグのＯＮ期間）に対してエアフローメータ１４の検出遅れ時間ＤＬＹ分遅れた期間であるか否かを判定する。ここで、吸気バルブ２８の開弁期間は、吸気バルブリフト量ＶＶＬを検出するリフトセンサ（図示せず）の出力に基づいて判定したり、或は、開弁期間の制御目標値を用いるようにしても良い。
【００７５】
もし、吸気バルブ２８の開弁期間に対してエアフローメータ１４の検出遅れ時間ＤＬＹ分遅れた期間でなければ、以降の処理を行うことなく、本ルーチンを終了する。その後、吸気バルブ２８の開弁期間に対してエアフローメータ１４の検出遅れ時間ＤＬＹ分遅れた期間になった時点で、ステップ３０３に進み、クランク角カウンタＣＣＲＮＫ＝１２〜１７の期間（つまり第１気筒＃１の吸気行程に対応する期間）であるか否かを判定し、ＣＣＲＮＫ＝１２〜１７であれば、ステップ３０４に進み、前回までの第１気筒吸入空気量面積ＧＡＳＵＭ（＃１）の記憶値に今回の瞬時空気流量ＧＡＦＭを積算して第１気筒吸入空気量面積ＧＡＳＵＭ（＃１）の記憶値を更新する。
【００７６】
上記ステップ３０３で「Ｎｏ」と判定されて、ステップ３０５で、クランク角カウンタＣＣＲＮＫ＝６〜１１の期間（つまり第２気筒＃２の吸気行程に対応する期間）であると判定されれば、ステップ３０６に進み、前回までの第２気筒吸入空気量面積ＧＡＳＵＭ（＃２）の記憶値に今回の瞬時空気流量ＧＡＦＭを積算して第２気筒吸入空気量面積ＧＡＳＵＭ（＃２）の記憶値を更新する。
【００７７】
上記ステップ３０３、３０５で「Ｎｏ」と判定されて、ステップ３０７で、クランク角カウンタＣＣＲＮＫ＝１８〜２３の期間（つまり第３気筒＃３の吸気行程に対応する期間）であると判定されれば、ステップ３０８に進み、前回までの第３気筒吸入空気量面積ＧＡＳＵＭ（＃３）の記憶値に今回の瞬時空気流量ＧＡＦＭを積算して第３気筒吸入空気量面積ＧＡＳＵＭ（＃３）の記憶値を更新する。
【００７８】
上記ステップ３０３、３０５、３０７で全て「Ｎｏ」と判定された場合、つまり、クランク角カウンタＣＣＲＮＫ＝０〜５の期間（第４気筒＃４の吸気行程に対応する期間）である場合は、ステップ３０９に進み、前回までの第４気筒吸入空気量面積ＧＡＳＵＭ（＃４）の記憶値に今回の瞬時空気流量ＧＡＦＭを積算して第４気筒吸入空気量面積ＧＡＳＵＭ（＃４）の記憶値を更新する。
【００７９】
以上説明した本実施形態（２）によれば、図１８に示すように、各気筒の吸気バルブ２８の開弁期間終了タイミング（吸気バルブ開弁フラグのＯＮ期間終了タイミング）からエアフローメータ１４の検出遅れ時間ＤＬＹ経過する毎に、各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を更新する。その他の処理は、前記実施形態（１）と同じである。
【００８０】
本実施形態（２）でも、前記実施形態（１）と同じ効果を得ることができる。しかも、吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間を吸気バルブ２８の開弁期間に設定するようにしたので、設計・開発段階で、運転領域毎に所定期間を設定する必要がなくなり、適合工数を削減することができる利点がある。
【００８１】
《実施形態（３）》
図１９乃至図２１に示す本発明の実施形態（３）は、吸入空気量面積ＧＡＳＵＭ（＃１）を算出する所定期間を、瞬時空気流量ＧＡＦＭが平均値以上となる期間に設定したところに特徴がある（図２０参照）。
【００８２】
本実施形態（３）では、図１９のルーチンを実行して各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を次のようにして算出する。まず、ステップ３０１ａで、エアフローメータ１４で検出した平均空気流量ＧＡを読み込む。この後、ステップ３０２ａに進み、瞬時空気流量ＧＡＦＭが平均空気流量ＧＡ以上であるか否かを判定する。
【００８３】
もし、瞬時空気流量ＧＡＦＭが平均空気流量ＧＡ未満であれば、以降の処理を行うことなく、本ルーチンを終了するが、瞬時空気流量ＧＡＦＭが平均空気流量ＧＡ以上であれば、前記実施形態（２）と同じ処理（ステップ３０３〜３０９）によって各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する。
【００８４】
以上説明した本実施形態（３）によれば、図２１に示すように、各気筒の瞬時空気流量ＧＡＦＭが平均値以上となる期間が終了する毎に、各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を更新する。その他の処理は、前記実施形態（１）と同じである。
【００８５】
本実施形態（３）のように、吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間を瞬時空気流量ＧＡＦＭが平均値以上となる期間に設定すれば、前記実施形態（２）と同じく、設計・開発段階で、運転領域毎に所定期間を設定する必要がなくなり、適合工数を削減することができる利点がある。
【００８６】
《実施形態（４）》
上記実施形態（１）〜（３）では、エアフローメータ１４で検出した瞬時空気流量ＧＡＦＭを用いて各気筒の所定期間の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出するようにしたが、図２２乃至図２５に示す本発明の実施形態（４）では、吸気管圧力センサ１８（検出手段）で検出した瞬時吸気管圧力ＰＭＡＰを用いて瞬時空気流量ＧＭＡＰを算出し、この瞬時空気流量ＧＭＡＰを用いて各気筒の所定期間の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出するようにしたところに特徴がある。
【００８７】
エンジン運転中は、図２５に示すように、エアフローメータ１４の出力（瞬時空気流量ＧＡＦＭ）の脈動に同期して吸気管圧力センサ１８の出力（瞬時吸気管圧力ＰＭＡＰ）が脈動し、エアフローメータ１４の出力（瞬時空気流量ＧＡＦＭ）が極大になるときに吸気管圧力センサ１８の出力（瞬時吸気管圧力ＰＭＡＰ）が極小となる。
また、吸気管圧力センサ１８で検出した瞬時吸気管圧力ＰＭＡＰは、次のノズルの式により瞬時空気流量ＧＭＡＰに変換できる。
【００８８】
【数２】

【００８９】
従って、吸気管圧力センサ１８の出力（瞬時吸気管圧力ＰＭＡＰ）を上記ノズルの式により瞬時空気流量ＧＭＡＰに変換すれば、前記実施形態（１）〜（３）とほぼ同じ手法で各気筒の所定期間の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出することができる。
【００９０】
本実施形態（４）では、吸気管圧力センサ１８の出力から各気筒の所定期間の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出するために、図２２に示す吸入空気量面積算出メインルーチンを吸気管圧力センサ１８の出力のＡ／Ｄ変換タイミング（例えば４ｍｓ周期）で実行する。本ルーチンが起動されると、まずステップ４０１で、前記図３のステップ１０１と同じ気筒間ばらつき補正実行条件が成立しているか否かを判定し、気筒間ばらつき補正実行条件が成立していなければ、ステップ４０２以降の所定期間の吸入空気量面積の算出に関する処理を実行することなく、本ルーチンを終了する。
【００９１】
一方、上記ステップ４０１で、気筒間ばらつき補正実行条件が成立していると判定されれば、ステップ４０２以降の所定期間の吸入空気量面積の算出に関する処理を次のようにして実行する。まず、ステップ４０２で、吸気管圧力センサ１８のフィルタ処理後の出力電圧ＶＭＡＰを読み込んだ後、ステップ４０３に進み、図２３の瞬時吸気管圧力ＰＭＡＰマップを用いて、吸気管圧力センサ１８の出力電圧ＶＭＡＰを、吸気管圧力センサ１８周辺部の瞬時吸気管圧力ＰＭＡＰに変換する。
【００９２】
この後、ステップ４０４に進み、前記［数２］式を用いて、瞬時吸気管圧力ＰＭＡＰを、吸気管圧力センサ１８を通過する瞬時空気流量ＧＭＡＰに変換する。そして、次のステップ４０５で、クランク角カウンタＣＣＲＮＫのカウント値を読み込んだ後、ステップ４０６に進み、図２４に示す各気筒の所定期間の吸入空気量面積算出ルーチンを実行して、各気筒の所定期間の吸入空気量の面積ＧＡＳＵＭ（＃ｉ）を次のようにして算出する。
【００９３】
まず、ステップ４１１で、各気筒の吸入空気量面積（瞬時空気流量ＧＭＡＰの面積）を算出する所定期間Ｐを前記図９のマップを用いて算出する。ここで、所定期間Ｐは、吸気脈動の反射波や他気筒の吸気干渉の影響を受けにくい期間、具体的には、吸気管圧力センサ１８の出力（瞬時吸気管圧力ＰＭＡＰ）から換算した瞬時空気流量ＧＭＡＰの極大値（瞬時吸気管圧力ＰＭＡＰの極小値）を含む期間に設定されている。
【００９４】
そして、次のステップ４１２で、吸気管圧力センサ１８の出力（瞬時吸気管圧力ＰＭＡＰ）から換算した瞬時空気流量ＧＭＡＰが極大値であるか否かを判定する。この極大値の判定方法は、例えば瞬時空気流量ＧＭＡＰの今回値を前回値と比較して、瞬時空気流量ＧＭＡＰの変化方向が増加から減少に反転したか否かによって判定すれば良い。
【００９５】
もし、瞬時空気流量ＧＭＡＰが極大値でなければ、以降の処理を行うことなく、本ルーチンを終了する。その後、瞬時空気流量ＧＭＡＰが極大値になった時点で、ステップ４１３に進み、クランク角カウンタＣＣＲＮＫ＝１２〜１７の期間（つまり第１気筒＃１の吸気行程に対応する期間）であるか否かを判定し、ＣＣＲＮＫ＝１２〜１７であれば、ステップ４１４に進み、第１気筒＃１の吸気行程の所定期間Ｐ（極大値となる時点ｔを中心にしてその前後Ｐ／２以内の期間）について瞬時空気流量ＧＭＡＰを積算して第１気筒吸入空気量面積ＧＡＳＵＭ（＃１）を求める。
【００９６】
上記ステップ４１３で「Ｎｏ」と判定されて、ステップ４１５で、クランク角カウンタＣＣＲＮＫ＝６〜１１の期間（つまり第２気筒＃２の吸気行程に対応する期間）であると判定されれば、ステップ４１６に進み、第２気筒＃２の吸気行程の所定期間Ｐについて瞬時空気流量ＧＭＡＰを積算して第２気筒吸入空気量面積ＧＡＳＵＭ（＃２）を求める。
【００９７】
上記ステップ４１３、４１５で「Ｎｏ」と判定されて、ステップ４１７で、クランク角カウンタＣＣＲＮＫ＝１８〜２３の期間（つまり第３気筒＃３の吸気行程に対応する期間）であると判定されれば、ステップ４１８に進み、第３気筒＃３の吸気行程の所定期間Ｐについて瞬時空気流量ＧＭＡＰを積算して第３気筒吸入空気量面積ＧＡＳＵＭ（＃３）を求める。
【００９８】
上記ステップ４１３、４１５、４１７で全て「Ｎｏ」と判定された場合、つまり、クランク角カウンタＣＣＲＮＫ＝０〜５の期間（第４気筒＃４の吸気行程に対応する期間）である場合は、ステップ４１９に進み、第４気筒＃４の吸気行程の所定期間Ｐについて瞬時空気流量ＧＭＡＰを積算して第４気筒吸入空気量面積ＧＡＳＵＭ（＃４）を求める。その他の処理は、前記実施形態（１）と同じである。以上説明した本実施形態（４）では、前記実施形態（１）と同じ効果を得ることができる。
【００９９】
《実施形態（５）》
上記実施形態（４）では、吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する所定期間Ｐを瞬時空気流量ＧＭＡＰの極大値（瞬時吸気管圧力ＰＭＡＰの極小値）を含む期間に設定したが、図２６に示す本発明の実施形態（５）では、前記実施形態（２）と同じように、吸入空気量面積ＧＡＳＵＭ（＃１）を算出する所定期間を、吸気バルブ２８の開弁期間に対して吸気管圧力センサ１８の検出遅れ時間ＤＬＹ分遅れた期間に設定するようにしている。
【０１００】
本実施形態（５）では、図２６のルーチンを実行して各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を次のようにして算出する。まず、ステップ５０１で、前記図１６と同様のマップを用いて、現在の吸気バルブリフト量ＶＶＬとエンジン回転速度ＮＥに応じた吸気管圧力センサ１８の検出遅れ時間ＤＬＹを算出する。
【０１０１】
この後、ステップ５０２に進み、吸気バルブ２８の開弁期間に対して吸気管圧力センサ１８の検出遅れ時間ＤＬＹ分遅れた期間であるか否かを判定し、吸気バルブ２８の開弁期間に対して吸気管圧力センサ１８の検出遅れ時間ＤＬＹ分遅れた期間でなければ、以降の処理を行うことなく、本ルーチンを終了する。
【０１０２】
その後、吸気バルブ２８の開弁期間に対して吸気管圧力センサ１８の検出遅れ時間ＤＬＹ分遅れた期間になった時点で、ステップ５０３に進み、クランク角カウンタＣＣＲＮＫ＝１２〜１７の期間（つまり第１気筒＃１の吸気行程に対応する期間）であるか否かを判定し、ＣＣＲＮＫ＝１２〜１７であれば、ステップ５０４に進み、前回までの第１気筒吸入空気量面積ＧＡＳＵＭ（＃１）の記憶値に今回の瞬時空気流量ＧＭＡＰを積算して第１気筒吸入空気量面積ＧＡＳＵＭ（＃１）の記憶値を更新する。
【０１０３】
上記ステップ５０３で「Ｎｏ」と判定されて、ステップ５０５で、クランク角カウンタＣＣＲＮＫ＝６〜１１の期間（つまり第２気筒＃２の吸気行程に対応する期間）であると判定されれば、ステップ５０６に進み、前回までの第２気筒吸入空気量面積ＧＡＳＵＭ（＃２）の記憶値に今回の瞬時空気流量ＧＭＡＰを積算して第２気筒吸入空気量面積ＧＡＳＵＭ（＃２）の記憶値を更新する。
【０１０４】
上記ステップ５０３、５０５で「Ｎｏ」と判定されて、ステップ５０７で、クランク角カウンタＣＣＲＮＫ＝１８〜２３の期間（つまり第３気筒＃３の吸気行程に対応する期間）であると判定されれば、ステップ５０８に進み、前回までの第３気筒吸入空気量面積ＧＡＳＵＭ（＃３）の記憶値に今回の瞬時空気流量ＧＭＡＰを積算して第３気筒吸入空気量面積ＧＡＳＵＭ（＃３）の記憶値を更新する。
【０１０５】
上記ステップ５０３、５０５、５０７で全て「Ｎｏ」と判定された場合、つまり、クランク角カウンタＣＣＲＮＫ＝０〜５の期間（第４気筒＃４の吸気行程に対応する期間）である場合は、ステップ５０９に進み、前回までの第４気筒吸入空気量面積ＧＡＳＵＭ（＃４）の記憶値に今回の瞬時空気流量ＧＭＡＰを積算して第４気筒吸入空気量面積ＧＡＳＵＭ（＃４）の記憶値を更新する。
以上説明した本実施形態（５）でも、前記実施形態（２）と同じ効果を得ることができる。
【０１０６】
《実施形態（６）》
図２７に示す本発明の実施形態（６）は、前記実施形態（３）と同じく、吸入空気量面積ＧＡＳＵＭ（＃１）を算出する所定期間を、瞬時空気流量ＧＭＡＰが平均値以上となる期間に設定したところに特徴がある。
【０１０７】
本実施形態（６）では、図２７のルーチンを実行して各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を次のようにして算出する。まず、ステップ５０１ａで、エアフローメータ１４で検出した平均空気流量ＧＡを読み込む。この後、ステップ５０２ａに進み、瞬時吸気管圧力ＰＭＡＰから算出した瞬時空気流量ＧＭＡＰが平均空気流量ＧＡ以上であるか否かを判定する。
【０１０８】
もし、瞬時空気流量ＧＭＡＰが平均空気流量ＧＡ未満であれば、以降の処理を行うことなく、本ルーチンを終了するが、瞬時空気流量ＧＭＡＰが平均空気流量ＧＡ以上であれば、前記実施形態（５）と同じ処理（ステップ５０３〜５０９）によって各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出する。その他の処理は、前記実施形態（１）と同じである。
以上説明した本実施形態（６）でも、前記実施形態（３）と同じ効果を得ることができる。
【０１０９】
尚、上記実施形態（４）〜（６）では、吸気管圧力センサ１８の出力（瞬時吸気管圧力ＰＭＡＰ）を瞬時空気流量ＧＭＡＰに換算して、各気筒の所定期間の吸入空気量面積ＧＡＳＵＭ（＃ｉ）を算出し、各気筒の吸入空気量面積ＧＡＳＵＭ（＃ｉ）から各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を算出するようにしたが、吸気管圧力センサ１８のの所定期間の出力（瞬時吸気管圧力ＰＭＡＰ）を積算して、各気筒の所定期間の吸気管圧力の面積を求め、各気筒の吸気管圧力面積から各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を算出するようにしても良い。
【０１１０】
《実施形態（７）》
図２８乃至図３４に示す本発明の実施形態（７）では、気筒内に吸入される吸入空気量が多くなるほど、筒内圧が大きくなるという特性に着目して、各気筒の筒内圧を検出して、この筒内圧の検出波形の所定期間の面積を求めるようにしている。これを実現するために、本実施形態（７）では、各気筒毎に、筒内圧を検出する筒内圧センサ（検出手段）が設けられている。尚、筒内圧センサは、点火プラグ２１に組み込まれたものを用いても良いし、点火プラグ２１とは別に設けても良い。
【０１１１】
一般に、筒内圧の波形は、図３２に示すように、点火前は、筒内充填空気の圧縮に応じて筒内圧が上昇するが、点火後は、燃焼圧によって筒内圧が急上昇するため、点火後の筒内圧の極大値（ピーク値）は、筒内充填空気のみの圧力よりもかなり大きくなる。しかも、筒内充填空気量が同じでも、燃料量や燃焼状態によって点火後の筒内圧の極大値が増減するため、点火後の筒内圧の極大値から筒内充填空気量を推定することは困難である。
【０１１２】
そこで、本実施形態（７）では、筒内圧の検出波形の面積を算出する所定期間を点火タイミング前に設定するようにしている。但し、図３３に示すように、燃料カット期間中やクランキング時（非燃焼時）には、筒内で燃焼が発生しておらず、筒内圧の極大値が筒内充填空気の最大圧縮圧力であるため、筒内圧の極大値を含む期間（圧縮ＴＤＣ前後の期間）に筒内圧の検出波形の面積を算出するようにしている。
【０１１３】
本実施形態（７）では、図２８に示す筒内圧面積算出メインルーチンを筒内圧センサのＡ／Ｄ変換タイミング（例えば４ｍｓ周期）で実行する。本ルーチンが起動されると、まずステップ６０１で、前記図３のステップ１０１と同じ気筒間ばらつき補正実行条件が成立しているか否かを判定し、気筒間ばらつき補正実行条件が成立していなければ、ステップ６０２以降の所定期間の筒内圧面積の算出に関する処理を実行することなく、本ルーチンを終了する。
【０１１４】
一方、上記ステップ６０１で、気筒間ばらつき補正実行条件が成立していると判定されれば、ステップ６０２以降の所定期間の筒内圧面積の算出に関する処理を次のようにして実行する。まず、ステップ６０２で、各気筒の筒内圧センサのフィルタ処理後の出力電圧ＶＣＰＳ（＃ｉ）を読み込んだ後、ステップ６０３に進み、図２９のマップを用いて、筒内圧センサの出力電圧ＶＣＰＳ（＃ｉ）を筒内圧ＣＰＳ（＃ｉ）に変換する。
【０１１５】
この後、ステップ６０４に進み、クランク角カウンタＣＣＲＮＫのカウント値を読み込む。そして、次のステップ６０５で、燃料カット期間中又はクランキング時（非燃焼時）であるか否かを判定し、燃料カット期間中又はクランキング時でなければ、ステップ６０６に進み、後述する図３０に示す燃焼時の各気筒の所定期間の筒内圧面積算出ルーチンを実行し、一方、燃料カット期間中又はクランキング時であれば、ステップ６０７に進み、後述する図３１に示す非燃焼時の各気筒の所定期間の筒内圧面積算出ルーチンを実行する。
【０１１６】
上記ステップ６０６で、図３０に示す燃焼時の各気筒の所定期間の筒内圧面積算出ルーチンが起動されると、まずステップ６１１で、各気筒の筒内圧面積を算出する所定期間Ｐを算出する。燃焼時は、図３２に示すように、所定期間Ｐを点火タイミング前に設定すると共に、所定期間Ｐの長さをエンジン回転速度ＮＥと吸入空気量ＧＡに応じてマップ等により算出する。この際、エンジン回転速度ＮＥが低い領域や、吸入空気量ＧＡが多い領域で、脈動波の振幅が大きくなるほど、所定期間Ｐが長くなるように設定される。
【０１１７】
そして、次のステップ６１２で、点火タイミングであるか否かを判定し、点火タイミングでなければ、以降の処理を行うことなく、本ルーチンを終了する。その後、点火タイミングになった時点で、ステップ６１３に進み、クランク角カウンタＣＣＲＮＫ＝２２〜３の期間（つまり第１気筒＃１の圧縮ＴＤＣの前後９０℃Ａ以内の期間）であるか否かを判定し、ＣＣＲＮＫ＝２２〜３であれば、ステップ６１４に進み、第１気筒＃１の点火前の所定期間Ｐについて第１気筒＃１の筒内圧ＣＰＳ（＃１）の記憶データを積算して第１気筒筒内圧面積ＣＰＳＳＵＭ（＃１）を求める。尚、各気筒の筒内圧ＣＰＳ（＃ｉ）のデータは、所定のサンプリング周期で検出する毎にＥＣＵ２７のＲＡＭに各気筒毎に時系列的に記憶され、各気筒の点火前の所定期間Ｐについて各気筒の筒内圧ＣＰＳ（＃ｉ）の記憶データを積算して各気筒の筒内圧面積ＣＰＳＳＵＭ（＃ｉ）を求めた後に、各気筒の筒内圧ＣＰＳ（＃ｉ）の記憶データがクリアされる。
【０１１８】
上記ステップ６１３で「Ｎｏ」と判定されて、ステップ６１５で、クランク角カウンタＣＣＲＮＫ＝１６〜２１の期間（つまり第２気筒＃２の圧縮ＴＤＣの前後９０℃Ａ以内の期間）であると判定されれば、ステップ６１６に進み、第２気筒＃２の点火前の所定期間Ｐについて第２気筒＃２の筒内圧ＣＰＳ（＃２）を積算して第２気筒筒内圧面積ＣＰＳＳＵＭ（＃２）を求める。
【０１１９】
上記ステップ６１３、６１５で「Ｎｏ」と判定されて、ステップ６１７で、クランク角カウンタＣＣＲＮＫ＝４〜９の期間（つまり第３気筒＃３の圧縮ＴＤＣの前後９０℃Ａ以内の期間）であると判定されれば、ステップ６１８に進み、第３気筒＃３の点火前の所定期間Ｐについて第３気筒＃３の筒内圧ＣＰＳ（＃３）を積算して第３気筒筒内圧面積ＣＰＳＳＵＭ（＃３）を求める。
【０１２０】
上記ステップ６１３、６１５、６１７で全て「Ｎｏ」と判定された場合、つまり、クランク角カウンタＣＣＲＮＫ＝１０〜１５の期間（第４気筒＃４の圧縮ＴＤＣの前後９０℃Ａ以内の期間）である場合は、ステップ６１９に進み、第４気筒＃４の点火前の所定期間Ｐについて第４気筒＃４の筒内圧ＣＰＳ（＃４）を積算して第４気筒筒内圧面積ＣＰＳＳＵＭ（＃４）を求める。
【０１２１】
一方、前記図２８のステップ６０７で、図３１に示す非燃焼時の各気筒の所定期間の筒内圧面積算出ルーチンが起動されると、まずステップ６２１で、非燃焼時（燃料カット期間中又はクランキング時）に各気筒の筒内圧面積を算出する所定期間Ｐを算出する。非燃焼時は、図３３に示すように、所定期間Ｐを極大値を含む期間に設定すると共に、所定期間Ｐの長さをエンジン回転速度ＮＥと吸入空気量ＧＡに応じてマップ等により算出する。この際、エンジン回転速度ＮＥが低い領域や、吸入空気量ＧＡが多い領域で、脈動波の振幅が大きくなるほど、所定期間Ｐが長くなるように設定される。
【０１２２】
そして、次のステップ６２２で、筒内圧センサで検出した筒内圧ＣＰＳ（＃ｉ）がが極大値であるか否かを判定する。この極大値の判定方法は、例えば筒内圧ＣＰＳ（＃ｉ）の今回値を前回値と比較して、筒内圧ＣＰＳ（＃ｉ）の変化方向が増加から減少に反転したか否かによって判定すれば良い。
【０１２３】
もし、筒内圧ＣＰＳ（＃ｉ）が極大値でなければ、以降の処理を行うことなく、本ルーチンを終了する。その後、筒内圧ＣＰＳ（＃ｉ）の極大値になった時点で、ステップ６２３に進み、クランク角カウンタＣＣＲＮＫ＝２２〜３の期間（つまり第１気筒＃１の圧縮ＴＤＣの前後９０℃Ａ以内の期間）であるか否かを判定して、ＣＣＲＮＫ＝２２〜３であれば、ステップ６２４に進み、第１気筒＃１の圧縮ＴＤＣ前後の所定期間Ｐ（極大値となる時点ｔを中心にしてその前後Ｐ／２以内の期間）について第１気筒＃１の筒内圧ＣＰＳ（＃１）を積算して第１気筒筒内圧面積ＣＰＳＳＵＭ（＃１）を求める。
【０１２４】
上記ステップ６２３で「Ｎｏ」と判定されて、ステップ６２５で、クランク角カウンタＣＣＲＮＫ＝１６〜２１の期間（つまり第２気筒＃２の圧縮ＴＤＣの前後９０℃Ａ以内の期間）であると判定されれば、ステップ６２６に進み、第２気筒＃２の圧縮ＴＤＣ前後の所定期間Ｐについて第２気筒＃２の筒内圧ＣＰＳ（＃２）を積算して第２気筒筒内圧面積ＣＰＳＳＵＭ（＃２）を求める。
【０１２５】
上記ステップ６２３、６２５で「Ｎｏ」と判定されて、ステップ６２７で、クランク角カウンタＣＣＲＮＫ＝４〜９の期間（つまり第３気筒＃３の圧縮ＴＤＣの前後９０℃Ａ以内の期間）であると判定されれば、ステップ６２８に進み、第３気筒＃３の圧縮ＴＤＣ前後の所定期間Ｐについて第３気筒＃３の筒内圧ＣＰＳ（＃３）を積算して第３気筒筒内圧面積ＣＰＳＳＵＭ（＃３）を求める。
【０１２６】
上記ステップ６２３、６２５、６２７で全て「Ｎｏ」と判定された場合、つまり、クランク角カウンタＣＣＲＮＫ＝１０〜１５の期間（第４気筒＃４の圧縮ＴＤＣの前後９０℃Ａ以内の期間）である場合は、ステップ６２９に進み、第４気筒＃４の圧縮ＴＤＣ前後の点火前の所定期間Ｐについて第４気筒＃４の筒内圧ＣＰＳ（＃４）を積算して第４気筒筒内圧面積ＣＰＳＳＵＭ（＃４）を求める。
【０１２７】
以上説明した本実施形態（７）の気筒間ばらつき補正の実行例を図３４に示すタイムチャートを用いて説明する。
気筒間ばらつき補正実行条件が成立して気筒間ばらつき補正実行フラグがＯＮされている期間は、各気筒の圧縮行程毎に、各気筒の所定期間の筒内圧面積ＣＰＳＳＵＭ（＃ｉ）を算出した後、前記実施形態（１）と同様の方法で、各気筒の筒内圧面積ＣＰＳＳＵＭ（＃ｉ）を気筒間でなまし処理して、各気筒の筒内圧面積なまし値ＣＰＳＳＵＭＳＭ（＃ｉ）を求める。このようにして、全気筒の筒内圧面積なまし値ＣＰＳＳＵＭＳＭ（＃ｉ）を求める毎（７２０℃Ａ毎）に、各気筒の筒内圧面積なまし値ＣＰＳＳＵＭＳＭ（＃ｉ）を全気筒の筒内圧面積なまし値の平均値で割り算して、それに補正係数Ｋ２を乗算して各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を求める。その他の処理は、前記実施形態（１）と同じである。
以上説明した本実施形態（７）でも、前記実施形態（１）と同じ効果を得ることができる。
【０１２８】
尚、本実施形態（７）では、各気筒の筒内圧センサの出力波形から所定期間の筒内圧面積ＣＰＳＳＵＭ（＃ｉ）を算出して、各気筒の筒内圧面積ＣＰＳＳＵＭ（＃ｉ）から各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を算出するようにしたが、各気筒の筒内圧センサで検出した筒内圧ＣＰＳ（＃ｉ）を瞬時空気流量に換算して、各気筒の所定期間の吸入空気量面積を算出し、各気筒の吸入空気量面積から各気筒の気筒間吸入空気量ばらつき率ＤＥＶ（＃ｉ）を算出するようにしても良い。
【０１２９】
また、上記各実施形態（１）〜（７）では、可変吸気バルブ制御による吸入空気量制御を行うシステムに本発明を適用したが、スロットル制御による吸入空気量制御のみを行うシステムに本発明を適用しても良い。
また、本発明の適用範囲は４気筒のエンジンに限定されず、５気筒以上又は３気筒以下の複数気筒エンジンンに本発明を適用しても良い。
【図面の簡単な説明】
【図１】本発明の実施形態（１）におけるエンジン制御システム全体の概略構成図
【図２】可変バルブリフト機構の正面図
【図３】実施形態（１）の気筒間ばらつき補正ルーチンの処理の流れを示すフローチャート
【図４】基本リフト補正量ＦＶＶＬ１のマップを概念的に示す図
【図５】補正係数ＦＶＶＬ２のマップを概念的に示す図
【図６】実施形態（１）の吸入空気量面積算出メインルーチンの処理の流れを示すフローチャート
【図７】エアフローメータの出力電圧ＶＡＦＭを瞬時空気流量ＧＡＦＭに変換するマップを概念的に示す図
【図８】実施形態（１）の各気筒の所定期間の吸入空気量面積算出ルーチンの処理の流れを示すフローチャート
【図９】実施形態（１）の所定期間Ｐマップを概念的に示す図
【図１０】実施形態（１）の所定期間Ｐの吸入空気量面積を算出する方法を説明するタイムチャート
【図１１】実施形態（１）の気筒間吸入空気量ばらつき率算出ルーチンの処理の流れを示すフローチャート
【図１２】補正係数Ｋ２のマップを概念的に示す図
【図１３】実施形態（１）の気筒間吸入空気量ばらつき率算出処理の一例を説明するタイムチャート
【図１４】実施形態（１）の気筒間ばらつき補正の一例を説明するタイムチャート
【図１５】実施形態（２）の各気筒の所定期間の吸入空気量面積算出ルーチンの処理の流れを示すフローチャート
【図１６】実施形態（２）のエアフローメータの検出遅れ時間ＤＬＹを算出するマップを概念的に示す図
【図１７】実施形態（２）の所定期間の吸入空気量面積を算出する方法を説明するタイムチャート
【図１８】実施形態（２）の気筒間吸入空気量ばらつき率算出処理の一例を説明するタイムチャート
【図１９】実施形態（３）の各気筒の所定期間の吸入空気量面積算出ルーチンの処理の流れを示すフローチャート
【図２０】実施形態（３）の所定期間の吸入空気量面積を算出する方法を説明するタイムチャート
【図２１】実施形態（３）の気筒間吸入空気量ばらつき率算出処理の一例を説明するタイムチャート
【図２２】実施形態（４）の吸入空気量面積算出メインルーチンの処理の流れを示すフローチャート
【図２３】吸気管圧力センサの出力電圧ＶＭＡＰを瞬時吸気管圧力ＰＭＡＰに変換するマップを概念的に示す図
【図２４】実施形態（４）の各気筒の所定期間の吸入空気量面積算出ルーチンの処理の流れを示すフローチャート
【図２５】エアフローメータの出力と吸気管圧力センサの出力との相関関係を説明するタイムチャート
【図２６】実施形態（５）の各気筒の所定期間の吸入空気量面積算出ルーチンの処理の流れを示すフローチャート
【図２７】実施形態（６）の各気筒の所定期間の吸入空気量面積算出ルーチンの処理の流れを示すフローチャート
【図２８】実施形態（７）の筒内圧面積算出メインルーチンの処理の流れを示すフローチャート
【図２９】筒内圧センサの出力電圧ＶＣＰＳ（＃ｉ）を筒内圧ＣＰＳ（＃ｉ）に変換するマップを概念的に示す図
【図３０】実施形態（７）の燃焼時の各気筒の所定期間の筒内圧面積算出ルーチンの処理の流れを示すフローチャート
【図３１】実施形態（７）の非燃焼時の各気筒の所定期間の筒内圧面積算出ルーチンの処理の流れを示すフローチャート
【図３２】燃焼時の筒内圧波形を示すタイムチャート
【図３３】非燃焼時の筒内圧波形を示すタイムチャート
【図３４】実施形態（７）の気筒間吸入空気量ばらつき率算出処理の一例を説明するタイムチャート
【符号の説明】
１１…エンジン（内燃機関）、１２…吸気管、１４…エアフローメータ（検出手段）、１５…スロットルバルブ、１８…吸気管圧力センサ（検出手段）、２０…燃料噴射弁、２１…点火プラグ、２２…排気管、２４…空燃比センサ、２６…クランク角センサ、２７…ＥＣＵ（面積算出手段，気筒間吸入空気量ばらつき算出手段）、２８…吸気バルブ、２９…排気バルブ、３０，３１…可変バルブリフト機構。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cylinder-by-cylinder intake air amount detection device for detecting a variation rate of intake air amount between cylinders or an intake air amount by cylinder.
[0002]
[Prior art]
In general, in an internal combustion engine having a plurality of cylinders, the intake air amount (in-cylinder charged air amount) of each cylinder varies due to a difference in intake manifold shape of each cylinder, a variation in valve clearance of an intake valve, and the like. Such variation in intake air amount between cylinders causes variation in torque and air-fuel ratio of each cylinder. When the torque variation between the cylinders becomes large, the fluctuation of the engine torque in the cycle becomes large, and there is a possibility that an uncomfortable vibration is generated for the driver. Also, if the air-fuel ratio variation among the cylinders becomes large, the fluctuation of the air-fuel ratio of the exhaust gas flowing into the catalyst within the cycle becomes large. May decrease.
[0003]
As a countermeasure for these, some methods have been proposed for correcting torque variation and air-fuel ratio variation between cylinders. For example, as disclosed in Japanese Patent Application Laid-Open No. 62-17342, torque is detected for each cylinder by a torque sensor provided on a crankshaft, and the torque of each cylinder becomes the average torque of all cylinders. In some cases, the fuel injection amount is corrected for each cylinder.
[0004]
Further, as shown in Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-220489), the air-fuel ratio of each cylinder is estimated based on the output of an air-fuel ratio sensor installed in an exhaust pipe, and the air-fuel ratio variation among the cylinders is reduced. In some cases, the fuel injection amount is corrected for each cylinder.
[0005]
In general, the amount of intake air is controlled by a throttle valve, but recently, a variable intake valve mechanism that varies the amount of lift of the intake valve is provided, and the amount of lift of the intake valve is adjusted according to the accelerator opening and the engine operating state. A technology for controlling the intake air amount by making it variable has been developed. In the intake air amount control by the variable intake valve control, by reducing the lift amount of the intake valve, the intake air amount can be reduced without narrowing the intake passage with a throttle valve, so that pumping loss is reduced and fuel consumption is reduced. There is an advantage that can be improved.
[0006]
However, in the intake air amount control by the variable intake valve control, since the lift amount of the intake valve becomes small at a low load, the variation of the actual lift amount with respect to the target lift amount in each cylinder (variation due to component tolerance or assembly tolerance of each cylinder). ) Tends to increase, and the variation in the amount of intake air between cylinders tends to increase. For this reason, the torque and the air-fuel ratio of each cylinder tend to fluctuate under the influence of the intake air amount variation between the cylinders, and the torque variation and the air-fuel ratio variation between the cylinders tend to increase.
[0007]
[Patent Document 1]
JP-A-62-17342 (page 2 etc.)
[Patent Document 2]
JP-A-2000-220489 (Pages 2 to 3 etc.)
[0008]
[Problems to be solved by the invention]
In the above-mentioned Patent Documents 1 and 2, the torque and air-fuel ratio are detected for each cylinder, and the fuel injection amount is corrected for each cylinder based on the detection result. The variation is corrected. However, if the variation in the intake air amount between the cylinders becomes large, it is difficult to correct the torque variation and the air-fuel ratio variation in each cylinder with sufficient accuracy by simply correcting the fuel injection amount. Moreover, even when a plurality of factors such as a variation in the intake air amount and a variation in the intake fuel amount among the cylinders are intertwined and a variation in torque and a variation in the air-fuel ratio occur between the cylinders, it is difficult to correct the variation with sufficient accuracy. .
[0009]
Therefore, in order to correct the torque variation and the air-fuel ratio variation of the cylinders with sufficient accuracy, it is desirable to have a function of correcting the intake air amount variation between the cylinders. It is necessary to develop a technology for accurately detecting variations in the amount of intake air.
[0010]
Therefore, the present inventors have researched a technique for detecting variations in intake air amount between cylinders using an output of an air flow meter that detects an intake air amount flowing through an intake pipe and an intake pipe pressure sensor that detects an intake pipe pressure. However, since the airflow meter and the intake pipe pressure sensor are installed in the intake pipe assembly that is affected by reflected waves of intake pulsation and the intake interference of other cylinders, the output waveforms of the airflow meter and the intake pipe pressure sensor Includes noise components due to reflected waves of intake pulsation and intake interference of other cylinders. Therefore, in order to accurately detect variations in the intake air amount between cylinders from the outputs of the air flow meter and the intake pipe pressure sensor, it is necessary to eliminate the influence of reflected waves of intake pulsation and intake interference of other cylinders.
[0011]
The present invention has been made in view of these circumstances, and therefore has as its object to provide a cylinder-by-cylinder intake air amount detection device capable of accurately detecting the intake air amount variation rate between cylinders or the cylinder-by-cylinder intake air amount. Is to provide.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a cylinder-by-cylinder intake air amount detection device of an internal combustion engine according to claim 1 of the present invention comprises: an intake air amount flowing through an intake pipe of an internal combustion engine having a plurality of cylinders; an intake pipe pressure; At least one is detected by the detecting means, and the area of the output waveform of the detecting means for a predetermined period is calculated by the area calculating means for each intake stroke or each compression stroke of each cylinder. Then, the inter-cylinder intake air amount variation rate or the cylinder-by-cylinder intake air amount variation calculation unit calculates the inter-cylinder intake air amount variation rate based on the area of the cylinder during the predetermined period.
[0013]
Here, the reason for calculating the area of the output waveform of the detecting means is that the influence of noise or the like can be reduced by using the area of the output waveform than by using the instantaneous value of the output of the detecting means. The reason why the period for calculating the area of the output waveform is limited to the “predetermined period” is to limit the period for calculating the area of the output waveform to a period having few error factors.
[0014]
For example, when the intake air amount or the intake pipe pressure is detected, the predetermined period for calculating the area of the output waveform of the detection means is determined by the reflected wave of intake pulsation or the influence of intake interference of another cylinder. It is preferable to set a period that is difficult to receive. With this configuration, even when the detection means for detecting the intake air amount or the intake pipe pressure is installed in the intake pipe aggregate that is affected by the reflected wave of intake pulsation or the intake interference of another cylinder, the output of the detection means can be reduced. The area of the waveform can be calculated only for the period that is hardly affected by the reflected wave of intake pulsation or the intake interference of other cylinders, and the variation rate of intake air amount between cylinders or the intake air amount for each cylinder can be accurately calculated using the area. It can be calculated well.
[0015]
In general, when the intake air amount is maximized (the intake pipe pressure is minimized), it is least susceptible to the influence of the intake interference of other cylinders. It may be set to a period including the value or a period including the minimum value of the intake pipe pressure. In this way, it is possible to calculate the area of the output waveform of the detection means only in the period in which the influence of the intake interference of the other cylinder is less likely.
[0016]
In addition, in consideration of the fact that the maximum point of the intake air amount (the minimum point of the intake pipe pressure) exists within the opening period of the intake valve, the predetermined period is set to the opening period of the intake valve. May be set. This eliminates the need to set a predetermined period for each operation area at the design / development stage, and has the advantage that the number of adaptation steps can be reduced. In this case, the predetermined period may be set to a period in which the intake air amount is larger than the intake interference wave of the other cylinder in the valve opening period of the intake valve. In this way, it is possible to calculate the area of the output waveform of the detection means only in the period in which the influence of the intake interference of the other cylinder is less likely.
[0017]
Further, since there is a time delay (detection delay of the detection means) from the time when the intake air flowing in the intake pipe passes around the detection means to the time when it is actually sucked into the cylinder, The predetermined period may be set in consideration of the detection delay of the detection unit. With this configuration, it is possible to avoid a problem of a decrease in accuracy due to a detection delay of the detection unit.
[0018]
Further, the predetermined period may be set to a period in which the intake air amount is equal to or more than the average value or a period in which the intake pipe pressure is equal to or less than the average value. In this manner, it is not necessary to set a predetermined period for each operation area at the design / development stage, as in the case of the fourth aspect, and there is an advantage that the number of adaptation steps can be reduced.
[0019]
Further, in the present invention, the in-cylinder pressure may be detected to calculate the area of the detection waveform of the in-cylinder pressure during a predetermined period. It is desirable to set a predetermined period for calculating the area before the ignition timing. The in-cylinder pressure before ignition is the compression pressure of the in-cylinder charged air, but since the in-cylinder pressure after ignition is increased by the combustion pressure, it is difficult to extract information on the in-cylinder charged air amount from the in-cylinder pressure after ignition. is there. Therefore, it is desirable to set the predetermined period for calculating the area of the detected waveform of the in-cylinder pressure before the ignition timing, thereby limiting the period for calculating the area of the detected waveform of the in-cylinder pressure to a period having few error factors. it can.
[0020]
In this case, the predetermined period may be set to a period including the maximum value of the in-cylinder pressure during the fuel cut period or during cranking. During the fuel cut period or during cranking, no combustion occurs in the cylinder, and the maximum value of the in-cylinder pressure is the maximum compression pressure of the in-cylinder charging air. By calculating the area of the detected waveform, the calculation accuracy can be improved.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
<< Embodiment (1) >>
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. For example, a four-cylinder engine 11, which is an internal combustion engine, has four cylinders of a first cylinder # 1 to a fourth cylinder # 4, and an air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of the engine 11. An air flow meter 14 (detection means) for detecting the amount of intake air is provided downstream of the air cleaner 13. As the air flow meter 14, an air flow meter capable of detecting a reverse flow of intake air is used. A throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided downstream of the air flow meter 14.
[0022]
Further, a surge tank 17 is provided downstream of the throttle valve 15, and the surge tank 17 is provided with an intake pipe pressure sensor 18 (detection means) for detecting an intake pipe pressure. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached near an intake port of the intake manifold 19 of each cylinder. I have. An ignition plug 21 is attached to a cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 21.
[0023]
Further, the intake valve 28 and the exhaust valve 29 of the engine 11 are provided with variable valve lift mechanisms 30 and 31 for varying the valve lift amount, respectively. Further, the intake valve 28 and the exhaust valve 29 may be provided with a variable valve timing mechanism for varying the valve timing (opening / closing timing). Note that the exhaust valve 29 may be provided with only the variable valve timing mechanism without providing the variable valve lift mechanism 31.
[0024]
On the other hand, a catalyst 23 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas is provided in an exhaust pipe 22 of the engine 11, and an air-fuel ratio of the exhaust gas is detected upstream of the catalyst 23. An air-fuel ratio sensor 24 is provided. In the cylinder block of the engine 11, a cooling water temperature sensor 25 for detecting a cooling water temperature and a crank angle sensor 26 for outputting a pulse signal every time the crankshaft of the engine 11 rotates at a constant crank angle (for example, 30 ° C. A). Installed. The crank angle and the engine speed are detected based on the output signal of the crank angle sensor 26.
[0025]
Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), thereby controlling the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the ignition plug 21 is controlled.
[0026]
Next, the configuration of the variable valve lift mechanism 30 of the intake valve 28 will be described with reference to FIG. Note that the variable valve lift mechanism 31 of the exhaust valve 29 has substantially the same configuration as the variable valve lift mechanism 30 of the intake valve 28, and a description thereof will be omitted.
[0027]
As shown in FIG. 2, a link arm 34 is provided between the camshaft 32 for driving the intake valve 28 and the rocker arm 33, and is rotated above the link arm 34 by a motor 41 such as a stepping motor. A dynamically driven control shaft 35 is provided. An eccentric cam 36 is provided on the control shaft 35 so as to be integrally rotatable. The link arm 34 swings via a support shaft (not shown) at a position eccentric with respect to the axis of the eccentric cam 36. It is movably supported. A swing cam 38 is provided at the center of the link arm 34, and a side surface of the swing cam 38 is in contact with an outer peripheral surface of a cam 37 provided on the camshaft 32. A pressing cam 39 is provided at the lower end of the link arm 34, and the lower end surface of the pressing cam 39 is in contact with the upper end surface of a roller 40 provided at the center of the rocker arm 33.
[0028]
Thus, when the cam 37 rotates by the rotation of the camshaft 32, the swing cam 38 of the link arm 34 moves right and left following the outer peripheral surface shape of the cam 37, and the link arm 34 swings left and right. . When the link arm 34 swings left and right, the pressing cam 39 moves left and right, so that the roller 40 of the rocker arm 33 moves up and down according to the lower end surface shape of the pressing cam 39, and the rocker arm 33 swings up and down. Move. The vertical movement of the rocker arm 33 causes the intake bubble 28 to move up and down.
[0029]
On the other hand, when the eccentric cam 36 rotates by the rotation of the control shaft 35, the position of the support shaft of the link arm 34 moves, and the initial contact point position between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 is changed. Change. The lower end surface of the pressing cam 39 of the link arm 34 has a base curved surface 39a formed on the left side thereof with a curvature such that the pressing amount of the rocker arm 33 is 0 (the valve lift amount of the intake valve 28 is 0). The pressing curved surface 39b is formed with a curvature such that the pressing amount of the rocker arm 33 increases toward the right from the base curved surface 39a (the valve lift amount of the intake valve 28 increases).
[0030]
In the case of the high lift mode in which the valve lift amount of the intake valve 28 is increased, the initial contact point between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 is moved rightward by the rotation of the control shaft 35. Let it. As a result, when the pressing cam 39 moves left and right due to the rotation of the cam 37, the section of the lower end surface of the pressing cam 39 that contacts the roller 40 moves to the right, and the maximum pressing amount of the rocker arm 33 increases. As a result, the maximum valve lift amount of the intake valve 28 increases, and the period during which the rocker arm 33 is pressed becomes longer, so that the valve opening period of the intake bubble 28 becomes longer.
[0031]
On the other hand, in the low lift mode in which the valve lift of the intake valve 28 is reduced, the initial contact point between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 is moved to the left by the rotation of the control shaft 35. Move to Accordingly, when the pressing cam 39 moves left and right due to the rotation of the cam 37, the section of the lower end surface of the pressing cam 39 that contacts the roller 40 moves to the left, and the maximum pressing amount of the rocker arm 33 decreases. As a result, the maximum valve lift of the intake valve 28 is reduced, and the period during which the rocker arm 33 is pressed is shortened, so that the valve opening period of the intake bubble 28 is shortened.
[0032]
In the variable valve lift mechanism 30 described above, if the control shaft 35 is rotated by the motor 41 to continuously move the initial contact point position between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33, The maximum valve lift amount and the valve opening period (hereinafter simply referred to as “intake valve lift amount”) of the intake valves 28 of all cylinders (# 1 to # 4) can be continuously and collectively changed.
[0033]
The ECU 27 executes a variable valve control program (not shown) stored in the ROM to control the variable valve lift mechanism 30 of the intake valve 28 on the basis of the accelerator opening, the engine operating state, and the like, thereby controlling the intake valve. The intake air amount is controlled by continuously varying the valve lift amount of the valve. In the case of a system using both the variable valve lift mechanism 30 and the variable valve timing mechanism, both the valve lift amount and the valve timing may be continuously varied to control the intake air amount.
[0034]
Further, the ECU 27 calculates the area of the output waveform (intake air amount) of the air flow meter 14 for each cylinder during the intake stroke of each cylinder during a predetermined period by executing each routine for cylinder-to-cylinder variation correction, which will be described later. DEV (i) is calculated based on the following equation, the intake valve lift VVL is corrected based on the cylinder-to-cylinder intake air variation DEV (i), and the intake air between cylinders is corrected. Correct for variations in volume. In this case, the period during which the area of the output waveform of the air flow meter 14 is calculated is a period in which the reflected wave of the intake pulsation and the intake interference of other cylinders are less susceptible, specifically, a period including the maximum value of the intake air amount. Is set.
[0035]
Hereinafter, processing contents of each routine for correcting variation between cylinders executed by the ECU 27 in the embodiment (1) will be described.
[0036]
[Cylinder variation correction routine]
The cylinder-to-cylinder variation correction routine shown in FIG. 3 is executed at a predetermined cycle during engine operation. When this routine is started, first, in step 101, it is determined whether or not the condition for executing the cylinder-to-cylinder variation correction is satisfied. Here, the condition for executing the cylinder-to-cylinder variation correction is, for example, to satisfy both of the following two conditions (1) and (2).
(1) A predetermined time or more has passed since the start (that is, the operation is not unstable immediately after the start)
(2) Not in a transient operation state (that is, in a steady operation state)
[0037]
If these two conditions (1) and (2) are both satisfied, the condition for executing the cylinder-to-cylinder variation correction is satisfied, but if any of the conditions is not satisfied, the condition for executing the cylinder-to-cylinder variation correction is not satisfied.
If it is determined that the condition for performing the cylinder-to-cylinder variation correction is not satisfied, the routine ends without executing the processing related to the cylinder-to-cylinder variation correction in step 102 and subsequent steps.
[0038]
On the other hand, if it is determined in step 101 that the conditions for executing the cylinder-to-cylinder variation correction are satisfied, the processing related to the cylinder-to-cylinder variation correction from step 102 is executed as follows. First, in step 102, the inter-cylinder intake air amount variation ratio DEV (#i) calculated by the inter-cylinder intake air amount variation ratio calculation routine of FIG.
[0039]
Thereafter, the routine proceeds to step 103, where the basic lift correction amount FVVL1 (#i) corresponding to the inter-cylinder intake air amount variation rate DEV (#i) is calculated for each cylinder using the map of FIG. Here, (#i) is a cylinder number, which means any of (# 1) to (# 4). In the map of FIG. 4, in a region where the cylinder-to-cylinder intake air amount variation rate DEV (#i) is a positive value, the basic lift correction amount FVVL1 (#i) is a decrease value (minus value), and the cylinder-to-cylinder intake air amount variation In a region where the rate DEV (#i) is a negative value, the basic lift correction amount FVVL1 (#i) is an increased value (plus value). That is, as the intake air amount of a certain cylinder becomes larger than the average intake air amount of all cylinders, the amount of reduction correction by the basic lift correction amount FVVL1 (#i) becomes larger, and conversely, the intake air amount of a certain cylinder becomes The smaller the average intake air amount is, the larger the increase correction amount by the basic lift correction amount FVVL1 (#i) becomes. Note that in a predetermined region where the inter-cylinder intake air amount variation rate DEV (#i) is around 0, the basic lift correction amount FVVL1 (#i) = 0 is set, and the intake valve lift amount VVL is not corrected.
[0040]
Then, in the next step 104, after reading the engine rotational speed NE and the intake air amount GA (average air flow rate) detected by the air flow meter 14, the routine proceeds to step 105, where a map of the correction coefficient FVVL2 shown in FIG. Then, a correction coefficient FVVL2 (#i) corresponding to the current engine operating conditions (for example, the engine speed NE and the intake air amount GA) is calculated for each cylinder.
[0041]
In general, when the intake air amount GA decreases (the intake valve lift amount decreases), the intake valve lift amount is more likely to be affected by the correction. Therefore, the map of the correction coefficient FVVL2 in FIG. The correction coefficient FVVL2 is set to be small.
[0042]
Thereafter, the routine proceeds to step 106, where the basic lift correction amount FVVL1 (#i) of each cylinder is multiplied by the correction coefficient FVVL2 (#i) to obtain the lift correction amount FVVL (#i) of each cylinder.
FVVL (#i) = FVVL1 (#i) × FVVL2 (#i)
[0043]
Thereafter, the routine proceeds to step 107, where the final target valve lift amount VVLM is obtained by adding the lift correction amount FVVL (#i) of each cylinder to the average valve lift amount VVL of all cylinders before correction.
[0044]
In this case, during the period of the crank angle counter CCRNK = 12 to 17, that is, the period corresponding to the intake stroke of the first cylinder # 1, the final valve lift correction amount FVVL (# 1) of the first cylinder # 1 is used. The target valve lift amount VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 1)
[0045]
During the period of the crank angle counter CCRNK = 6 to 11, that is, the period corresponding to the intake stroke of the second cylinder # 2, the final target valve lift is calculated using the valve lift correction amount FVVL (# 2) of the second cylinder # 2. The quantity VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 2)
[0046]
During the period of the crank angle counter CCRNK = 18 to 23, that is, the period corresponding to the intake stroke of the third cylinder # 3, the final target valve lift is calculated using the valve lift correction amount FVVL (# 3) of the third cylinder # 3. The quantity VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 3)
[0047]
During the period of the crank angle counter CCRNK = 0 to 5, that is, the period corresponding to the intake stroke of the fourth cylinder # 4, the final target valve lift is calculated using the valve lift correction amount FVVL (# 4) of the fourth cylinder # 4. The quantity VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 4)
[0048]
Thereafter, the process proceeds to step 108, in which the motor 41 of the variable valve lift mechanism 30 of the intake valve 28 is driven at a high speed in accordance with the final target valve lift amount VVLM of each cylinder which changes in accordance with the intake stroke of each cylinder. The intake valve lift is corrected for each intake stroke of the cylinder to correct the intake air amount of each cylinder. Thereby, the variation in the intake air amount between the cylinders is corrected.
[0049]
[Intake air volume area output main routine]
The intake air amount area calculation main routine shown in FIG. 6 is started at an A / D conversion timing (for example, a 4 ms period) of the output voltage of the air flow meter 14. When this routine is started, first, in step 201, it is determined whether or not the same inter-cylinder variation correction execution condition as in step 101 is satisfied. If the inter-cylinder variation correction execution condition is not satisfied, step 202 is performed. This routine ends without executing the processing relating to the calculation of the intake air amount area for the subsequent predetermined period.
[0050]
On the other hand, if it is determined in step 201 that the condition for executing the cylinder-to-cylinder variation correction is satisfied, the process related to calculation of the intake air amount area for a predetermined period after step 202 is executed as follows. First, in step 202, after reading the output voltage VAFM of the air flow meter 14 after the filtering process, the process proceeds to step 203, where the output voltage VAFM of the air flow meter 14 is calculated using the instantaneous air flow rate GAFM map of FIG. 14 to the instantaneous air flow rate GAFM. Note that the instantaneous air flow rate GAFM map in FIG. 7 is a map in a case where the air flow meter 14 can also detect a reverse flow. In the case of a reverse flow, the instantaneous air flow rate GAFM has a negative value.
[0051]
Thereafter, the routine proceeds to step 204, where the count value of the crank angle counter CCRNK is read. Since the crank angle counter CCRNK is incremented by “1” every 30 ° C. based on the output signal of the crank angle sensor 26, 24 counts of the crank angle counter CCRNK correspond to one cycle (720 ° C. A). . Note that the crank angle counter CCRNK is reset to “0” when it becomes “24”. The crank rotation position of the crank angle counter CCRNK = 0 corresponds to the compression top dead center (compression TDC) of the first cylinder # 1, and the crank rotation positions of the crank angle counter CCRNK = 6, 12, and 18 correspond to the first rotation position, respectively. The compression TDC is set to correspond to the compression TDC of the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2.
[0052]
Then, in the next step 205, an intake air amount area calculation routine of each cylinder for a predetermined period shown in FIG. 8 is executed, and an area GASUM (output waveform of the air flow meter 14) of the intake air amount (output waveform of the air flow meter 14) of each cylinder for a predetermined period. #I) is calculated.
[0053]
[Routine for calculating the intake air amount area of each cylinder for a predetermined period]
The intake air amount area calculation routine for each cylinder shown in FIG. 8 for a predetermined period is a subroutine started in step 205 in FIG. 6, and plays a role as an area calculation means in claims. When this routine is started, first, in step 211, a predetermined period P for calculating the intake air amount area of each cylinder (the area of the output waveform of the air flow meter 14) is calculated using the map of FIG. Here, as shown in FIG. 10, the predetermined period P is a period that is hardly affected by reflected waves of intake pulsation or intake interference of other cylinders, specifically, the output waveform (intake air amount) of the air flow meter 14. The period is set to include the maximum value.
[0054]
The map of the predetermined period P in FIG. 9 is a map for calculating the predetermined period P using the engine rotation speed NE and the intake air amount GA as parameters. The predetermined period P is set to be longer as the amplitude of the pulsating wave increases.
[0055]
After the calculation of the predetermined period P, the routine proceeds to step 212, where it is determined whether or not the instantaneous air flow rate GAFM detected by the air flow meter 14 is a local maximum value. This maximum value may be determined by comparing the current value of the instantaneous air flow rate GAFM with the previous value, for example, and determining whether or not the change direction of the instantaneous air flow rate GAFM has reversed from increasing to decreasing.
[0056]
If it is determined in step 212 that the instantaneous air flow rate GAFM is not the local maximum value, the routine ends without performing the subsequent processing. Thereafter, when the instantaneous air flow rate GAFM reaches the maximum value, the process proceeds to step 213, and it is determined whether or not the crank angle counter CCRNK is a period of 12 to 17 (that is, a period corresponding to the intake stroke of the first cylinder # 1). If CCRNK = 12 to 17, the routine proceeds to step 214, where a predetermined period P of the intake stroke of the first cylinder # 1 (a period within P / 2 before and after the predetermined time t around the maximum value t). The first cylinder intake air amount area GASUM (# 1) is obtained by integrating the instantaneous air flow rate GAFM. The data of the instantaneous air flow rate GAFM is stored in the RAM of the ECU 27 in chronological order each time it is detected at a predetermined sampling cycle (for example, a 4 ms cycle). After obtaining the intake air amount area GASUM (# 1), the stored data of the instantaneous air flow rate GAFM is cleared.
[0057]
If "No" is determined in step 213, and if it is determined in step 215 that the crank angle counter CCRNK is a period of 6 to 11 (that is, a period corresponding to the intake stroke of the second cylinder # 2), the process proceeds to step 215. Proceeding to 216, the instantaneous air flow rate GAFM is integrated for a predetermined period P of the intake stroke of the second cylinder # 2 to obtain the second cylinder intake air amount area GASUM (# 2).
[0058]
If “No” is determined in steps 213 and 215 and if it is determined in step 217 that the crank angle counter CCRNK is a period of 18 to 23 (that is, a period corresponding to the intake stroke of the third cylinder # 3). Then, the process proceeds to step 218, where the instantaneous air flow rate GAFM for the predetermined period P of the intake stroke of the third cylinder # 3 is integrated to determine the third cylinder intake air amount area GASUM (# 3).
[0059]
If the determinations in steps 213, 215, and 217 are all “No”, that is, if the crank angle counter CCRNK is a period of 0 to 5 (a period corresponding to the intake stroke of the fourth cylinder # 4), Proceeding to 219, the instantaneous air flow rate GAFM for the predetermined period P of the intake stroke of the fourth cylinder # 4 is integrated to determine the fourth cylinder intake air amount area GASUM (# 4).
[0060]
[Routine for calculating variation rate of intake air amount between cylinders]
The routine for calculating the variation rate of the intake air amount between the cylinders shown in FIG. 11 is executed for each cycle (every 180 ° A in the case of the four-cylinder engine), and serves as a means for calculating the variation amount of the intake air amount between the cylinders in the claims. Fulfill. When this routine is started, first, in step 221, the intake air amount area GASUM (#i) of each cylinder is read, and in the next step 222, the intake air amount area GASUM (#i) of each cylinder is read between the cylinders. Through the smoothing process, a smoothed intake air amount area GASUSMM (#i) of each cylinder is obtained.
[0061]
GASUMSM (#i) = GASUMSM (# i-1) + K1 × {GASUM (#i) -GASUMSM (# i-1)}
Here, K1 is a smoothing coefficient, and GASUMSM (# i-1) is a smoothed intake air amount area of the (# i-1) th cylinder.
Thereafter, the process proceeds to step 223, where the inter-cylinder intake air amount variation ratio DEV (#i) of each cylinder is calculated by the following equation.
[0062]
(Equation 1)

[0063]
The denominator of the above equation is the average of the smoothed values of the intake air amount areas GASUMSM (#i) of all cylinders, and K2 is a correction coefficient for converting the variation of the intake air amount area into the variation of the intake air amount. Yes, and is set by the map in FIG. Generally, as the predetermined period P for calculating the intake air amount area GASUM (#i) of each cylinder becomes shorter, the variation of the intake air amount area GASUM (#i) becomes smaller. Therefore, as the predetermined period P becomes shorter, the correction coefficient K2 becomes smaller. Is set to be large.
[0064]
As is apparent from the above [Equation 1], the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder is obtained by subtracting the smoothed value GASUSMSM (#i) of the inter-cylinder intake air amount variation rate of each cylinder from all cylinders. Is divided by the average value of the smoothed values of the variation rate of the intake air amount between cylinders, and multiplied by the correction coefficient K2.
[0065]
By multiplying the intake air amount variation ratio DEV (#i) between cylinders by the intake air amount GA (average air flow rate) detected by the air flow meter 14, the cylinder-by-cylinder intake air amount can be obtained.
[0066]
An example of the execution of the cylinder-to-cylinder variation correction of the embodiment (1) described above will be described with reference to time charts shown in FIGS.
As shown in FIG. 13, during the period in which the cylinder-to-cylinder variation correction execution condition is satisfied and the cylinder-to-cylinder variation correction execution flag is ON, a predetermined period (the instantaneous air flow rate GAFM is set to a maximum value) for each intake stroke of each cylinder. The intake air amount area GASUM (#i) is calculated for a period within a period P / 2 before and after the certain time point t, and the intake air amount area GASUM (#i) of each cylinder is smoothed between cylinders. Then, the smoothed intake air amount area GASUMSM (#i) of each cylinder is obtained. In this manner, every time the smoothed intake air amount area value GASUSM (#i) of all cylinders is obtained (every 720 ° C. A), the smoothed intake air amount area value GASAMSM (#i) of each cylinder is calculated for all cylinders. The average value of the smoothed intake air area values is divided by a correction coefficient K2 to determine the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder.
[0067]
As shown in FIG. 14, every time the inter-cylinder intake air amount variation ratio DEV (#i) of each cylinder is calculated, the lift correction amount according to the inter-cylinder intake air amount variation ratio DEV (#i) and the engine operating conditions. FVVL (#i) is calculated, and for each 180 ° C., the final target valve lift amount VVLM is obtained by adding the lift correction amount FVVL (#i) of the corresponding cylinder to the average valve lift amount VVL of all cylinders before correction. Ask.
[0068]
In this way, the motor 41 of the variable valve lift mechanism 30 of the intake valve 28 is driven at a high speed in accordance with the final target valve lift amount VVLM of each cylinder which changes according to the intake stroke of each cylinder, and the intake of each cylinder is The intake valve lift is corrected for each stroke to correct the intake air amount of each cylinder. Thereby, the variation in the intake air amount between the cylinders is corrected.
[0069]
When the present invention is applied to a variable valve mechanism configured to drive the intake valve 28 of each cylinder by an electromagnetic actuator, the control amount of the electromagnetic actuator of each cylinder is controlled according to the final target valve lift amount VVLM of each cylinder. The correction may correct the intake valve lift amount of each cylinder to correct the intake air amount of each cylinder.
[0070]
According to the embodiment (1) described above, the predetermined period P for calculating the intake air amount area GASUM (#i) is set to a period including the maximum value of the instantaneous air flow rate GAFM. It can be set to a period that is not easily affected by reflected waves of intake pulsation or intake interference of other cylinders. As a result, the inter-cylinder intake air amount variation rate DEV (#i) can be accurately calculated using the intake air amount area GASUM (#i) of each cylinder, and the inter-cylinder intake air amount variation rate can be calculated. By correcting the intake valve lift amount using DEV (#i), it is possible to accurately correct variations in intake air amount between cylinders, thereby reducing both torque variations and air-fuel ratio variations between cylinders. can do.
[0071]
<< Embodiment (2) >>
In the above embodiment (1), the predetermined period P for calculating the intake air amount area GASUM (#i) is set to a period including the maximum value of the instantaneous air flow rate GAFM, but the embodiment of the present invention shown in FIGS. In the mode (2), a predetermined period for calculating the intake air amount area GASUM (# 1) is determined by taking into consideration that the maximum point of the instantaneous air flow rate GAFM exists during the opening period of the intake valve 28. The valve opening period is set (see FIG. 17).
[0072]
In this case, there is a time delay (detection delay of the air flow meter 14) from when the intake air flowing through the intake pipe 12 passes around the air flow meter 14 to when it is actually sucked into the cylinder. In the mode (2), the predetermined period for calculating the intake air amount area GASUM (#i) is set in consideration of the detection delay of the air flow meter 14.
[0073]
In the present embodiment (2), the routine of FIG. 15 is executed to calculate the intake air amount area GASUM (#i) of each cylinder as follows. First, in step 301, the detection delay time DLY of the air flow meter 14 according to the current intake valve lift amount VVL and the engine rotation speed NE is calculated using the map of FIG. Considering that the intake valve lift VVL increases in the low rotation range and the flow rate of the air taken into the cylinder decreases in the map of FIG. 16, the map is detected as the intake valve lift VVL increases in the low rotation range. The delay time DLY is set to be large.
[0074]
After calculating the detection delay time DLY, the process proceeds to step 302, where it is determined whether or not the period is delayed by the detection delay time DLY of the air flow meter 14 with respect to the opening period of the intake valve 28 (the ON period of the intake valve opening flag). Is determined. Here, the valve opening period of the intake valve 28 is determined based on the output of a lift sensor (not shown) that detects the intake valve lift amount VVL, or the control target value of the valve opening period is used. May be.
[0075]
If the period is not delayed by the detection delay time DLY of the air flow meter 14 with respect to the valve opening period of the intake valve 28, this routine ends without performing the subsequent processing. Thereafter, at the point in time when the detection delay time DLY of the air flow meter 14 is delayed with respect to the valve opening period of the intake valve 28, the routine proceeds to step 303, where the crank angle counter CCRNK = 12 to 17 (that is, the first cylinder). (CCRNK = 12 to 17), the process proceeds to step 304, and the first cylinder intake air amount area GASUM (# 1) up to the previous time is stored. The instantaneous air flow rate GAFM is integrated with the value to update the stored value of the first cylinder intake air amount area GASUM (# 1).
[0076]
If "No" is determined in step 303, and if it is determined in step 305 that the crank angle counter is CCRNK = 6 to 11 (that is, a period corresponding to the intake stroke of the second cylinder # 2), the process proceeds to step 305. Proceeding to 306, the stored value of the second cylinder intake air amount area GASUM (# 2) is updated by integrating the current instantaneous air flow rate GAFM with the previous stored value of the second cylinder intake air amount area GASUM (# 2). I do.
[0077]
If "No" is determined in steps 303 and 305, and if it is determined in step 307 that the crank angle counter CCRNK is in the period of 18 to 23 (that is, the period corresponding to the intake stroke of the third cylinder # 3). Proceeding to step 308, the stored value of the third cylinder intake air amount area GASUM (# 3) is integrated by adding the current instantaneous air flow rate GAFM to the stored value of the third cylinder intake air amount area GASUM (# 3) up to the previous time. To update.
[0078]
If it is determined as “No” in steps 303, 305, and 307, that is, if it is the period of the crank angle counter CCRNK = 0 to 5 (the period corresponding to the intake stroke of the fourth cylinder # 4), Proceeding to 309, the stored value of the fourth cylinder intake air amount area GASUM (# 4) is updated by integrating the current instantaneous air flow rate GAFM with the stored value of the fourth cylinder intake air amount area GASUM (# 4) up to the previous time. I do.
[0079]
According to the above-described embodiment (2), as shown in FIG. 18, the air flow meter 14 detects from the opening timing of the intake valve 28 of each cylinder (end timing of the ON period of the intake valve opening flag). Every time the delay time DLY elapses, the intake air amount area GASUM (#i) of each cylinder is updated. Other processes are the same as those in the embodiment (1).
[0080]
Also in the present embodiment (2), the same effect as in the embodiment (1) can be obtained. In addition, since the predetermined period for calculating the intake air amount area GASUM (#i) is set to the opening period of the intake valve 28, it is not necessary to set the predetermined period for each operation region at the design and development stages. There is an advantage that the number of fitting steps can be reduced.
[0081]
<< Embodiment (3) >>
The embodiment (3) of the present invention shown in FIGS. 19 to 21 is characterized in that the predetermined period for calculating the intake air amount area GASUM (# 1) is set to a period when the instantaneous air flow rate GAFM is equal to or more than the average value. (See FIG. 20).
[0082]
In the present embodiment (3), the routine of FIG. 19 is executed to calculate the intake air amount area GASUM (#i) of each cylinder as follows. First, in step 301a, the average air flow rate GA detected by the air flow meter 14 is read. Thereafter, the routine proceeds to step 302a, where it is determined whether or not the instantaneous air flow rate GAFM is equal to or higher than the average air flow rate GA.
[0083]
If the instantaneous air flow rate GAFM is less than the average air flow rate GA, this routine is terminated without performing the subsequent processing. ) Is calculated (steps 303 to 309) to calculate the intake air amount area GASUM (#i) of each cylinder.
[0084]
According to the above-described embodiment (3), as shown in FIG. 21, each time the period in which the instantaneous air flow rate GAFM of each cylinder becomes equal to or more than the average value ends, the intake air amount area GASUM (# Update i). Other processes are the same as those in the embodiment (1).
[0085]
As in the present embodiment (3), if the predetermined period for calculating the intake air amount area GASUM (#i) is set to a period in which the instantaneous air flow rate GAFM is equal to or more than the average value, the same as in the embodiment (2), In the design / development stage, there is no need to set a predetermined period for each operation area, and there is an advantage that the number of adaptation steps can be reduced.
[0086]
<< Embodiment (4) >>
In the above-described embodiments (1) to (3), the intake air amount area GASUM (#i) of each cylinder for a predetermined period is calculated using the instantaneous air flow rate GAFM detected by the air flow meter 14. In the embodiment (4) of the present invention shown in FIG. 25 to FIG. 25, the instantaneous air flow rate GMAP is calculated using the instantaneous intake pipe pressure PMAP detected by the intake pipe pressure sensor 18 (detection means), and the instant air flow rate GMAP is used. This is characterized in that the intake air amount area GASUM (#i) of each cylinder for a predetermined period is calculated.
[0087]
During the operation of the engine, as shown in FIG. 25, the output of the intake pipe pressure sensor 18 (the instantaneous intake pipe pressure PMAP) pulsates in synchronization with the pulsation of the output of the air flow meter 14 (the instantaneous air flow rate GAFM). When the output (instantaneous air flow rate GAFM) becomes maximum, the output of the intake pipe pressure sensor 18 (instantaneous intake pipe pressure PMAP) becomes minimum.
The instantaneous intake pipe pressure PMAP detected by the intake pipe pressure sensor 18 can be converted into an instantaneous air flow rate GMAP by the following nozzle equation.
[0088]
(Equation 2)

[0089]
Therefore, if the output of the intake pipe pressure sensor 18 (instantaneous intake pipe pressure PMAP) is converted into the instantaneous air flow rate GMAP by the above-described nozzle equation, the predetermined value of each cylinder is determined in substantially the same manner as in the embodiments (1) to (3). The intake air amount area GASUM (#i) for the period can be calculated.
[0090]
In the present embodiment (4), in order to calculate the intake air amount area GASUM (#i) of each cylinder for a predetermined period from the output of the intake pipe pressure sensor 18, the intake air amount area calculation main routine shown in FIG. It is executed at the A / D conversion timing of the output of the pipe pressure sensor 18 (for example, at a cycle of 4 ms). When this routine is started, first, in step 401, it is determined whether or not the same inter-cylinder variation correction execution condition as in step 101 in FIG. 3 is satisfied. This routine is terminated without executing the processing relating to the calculation of the intake air amount area for a predetermined period after step 402.
[0091]
On the other hand, if it is determined in step 401 that the condition for performing the cylinder-to-cylinder variation correction is satisfied, the process related to the calculation of the intake air amount area for a predetermined period after step 402 is executed as follows. First, in step 402, after reading the output voltage VMAP after the filtering process of the intake pipe pressure sensor 18, the process proceeds to step 403, where the output voltage of the intake pipe pressure sensor 18 is calculated using the instantaneous intake pipe pressure PMAP map of FIG. The VMAP is converted into an instantaneous intake pipe pressure PMAP around the intake pipe pressure sensor 18.
[0092]
Thereafter, the routine proceeds to step 404, where the instantaneous intake pipe pressure PMAP is converted into the instantaneous air flow rate GMAP passing through the intake pipe pressure sensor 18 by using the above [Equation 2]. Then, in the next step 405, after reading the count value of the crank angle counter CCRNK, the routine proceeds to step 406, where a routine for calculating the intake air amount area of each cylinder for a predetermined period shown in FIG. The area GASUM (#i) of the intake air amount during the period is calculated as follows.
[0093]
First, in step 411, a predetermined period P for calculating the intake air amount area (the area of the instantaneous air flow rate GMAP) of each cylinder is calculated using the map of FIG. Here, the predetermined period P is a period that is hardly affected by the reflected wave of the intake pulsation or the intake interference of another cylinder, specifically, the instantaneous air converted from the output of the intake pipe pressure sensor 18 (instantaneous intake pipe pressure PMAP). The period is set to include the maximum value of the flow rate GMAP (the minimum value of the instantaneous intake pipe pressure PMAP).
[0094]
Then, in the next step 412, it is determined whether or not the instantaneous air flow rate GMAP converted from the output of the intake pipe pressure sensor 18 (instantaneous intake pipe pressure PMAP) is a maximum value. This maximum value may be determined, for example, by comparing the current value of the instantaneous air flow rate GMAP with the previous value and determining whether or not the change direction of the instantaneous air flow rate GMAP has reversed from increasing to decreasing.
[0095]
If the instantaneous air flow rate GMAP is not the local maximum value, this routine ends without performing the subsequent processing. Thereafter, when the instantaneous air flow rate GMAP reaches the maximum value, the process proceeds to step 413, and it is determined whether or not the crank angle counter CCRNK is a period of 12 to 17 (that is, a period corresponding to the intake stroke of the first cylinder # 1). If CCRNK = 12 to 17, the routine proceeds to step 414, where a predetermined period P of the intake stroke of the first cylinder # 1 (a period within P / 2 before and after the time t at which the maximum value is at the center). The first cylinder intake air amount area GASUM (# 1) is obtained by integrating the instantaneous air flow rate GMAP for
[0096]
If “No” is determined in step 413, and if it is determined in step 415 that the crank angle counter CCRNK is a period of 6 to 11 (that is, a period corresponding to the intake stroke of the second cylinder # 2), the process proceeds to step 415. Proceeding to 416, the instantaneous air flow rate GMAP is integrated for a predetermined period P of the intake stroke of the second cylinder # 2 to obtain the second cylinder intake air amount area GASUM (# 2).
[0097]
If “No” is determined in steps 413 and 415, and if it is determined in step 417 that the period is the crank angle counter CCRNK = 18 to 23 (that is, the period corresponding to the intake stroke of the third cylinder # 3). Then, the process proceeds to a step 418, where the instantaneous air flow rate GMAP is integrated for a predetermined period P of the intake stroke of the third cylinder # 3 to obtain a third cylinder intake air amount area GASUM (# 3).
[0098]
If all of the above steps 413, 415, and 417 are determined to be “No”, that is, if the crank angle counter CCRNK is in the period of 0 to 5 (the period corresponding to the intake stroke of the fourth cylinder # 4), Proceeding to 419, the instantaneous air flow rate GMAP for the predetermined period P of the intake stroke of the fourth cylinder # 4 is integrated to determine the fourth cylinder intake air amount area GASUM (# 4). Other processes are the same as those in the embodiment (1). In the embodiment (4) described above, the same effect as in the embodiment (1) can be obtained.
[0099]
<< Embodiment (5) >>
In the above embodiment (4), the predetermined period P for calculating the intake air amount area GASUM (#i) is set to a period including the maximum value of the instantaneous air flow rate GMAP (the minimum value of the instantaneous intake pipe pressure PMAP). In the embodiment (5) of the present invention shown in FIG. 26, the predetermined period for calculating the intake air amount area GASUM (# 1) is set to the opening period of the intake valve 28 in the same manner as in the embodiment (2). It is set to a period delayed by the detection delay time DLY of the intake pipe pressure sensor 18.
[0100]
In this embodiment (5), the routine of FIG. 26 is executed to calculate the intake air amount area GASUM (#i) of each cylinder as follows. First, in step 501, a detection delay time DLY of the intake pipe pressure sensor 18 according to the current intake valve lift amount VVL and the engine speed NE is calculated using a map similar to that shown in FIG.
[0101]
Thereafter, the routine proceeds to step 502, where it is determined whether or not the opening period of the intake valve 28 is delayed by the detection delay time DLY of the intake pipe pressure sensor 18 to determine whether the opening period of the intake valve 28 is longer. If the period is not delayed by the detection delay time DLY of the intake pipe pressure sensor 18, this routine is terminated without performing the subsequent processing.
[0102]
Thereafter, when the period is delayed by the detection delay time DLY of the intake pipe pressure sensor 18 with respect to the valve opening period of the intake valve 28, the process proceeds to step 503, where the crank angle counter CCRNK = 12 to 17 (that is, (CCRNK = 12 to 17), the process proceeds to step 504, and the first cylinder intake air amount area GASUM (# 1) up to the previous time is determined. Is integrated with the current instantaneous air flow rate GMAP to update the stored value of the first cylinder intake air amount area GASUM (# 1).
[0103]
If "No" is determined in step 503, and if it is determined in step 505 that the crank angle counter CCRNK is a period of 6 to 11 (that is, a period corresponding to the intake stroke of the second cylinder # 2), the process proceeds to step 505. Proceeding to 506, the stored value of the second cylinder intake air amount area GASUM (# 2) is updated by integrating the current instantaneous air flow rate GMAP with the stored value of the second cylinder intake air amount area GASUM (# 2) up to the previous time. I do.
[0104]
If "No" is determined in steps 503 and 505, and if it is determined in step 507 that the crank angle counter CCRNK is a period of 18 to 23 (that is, a period corresponding to the intake stroke of the third cylinder # 3). Proceeding to step 508, the current instantaneous air flow rate GMAP is integrated with the stored value of the third cylinder intake air amount area GASUM (# 3) up to the previous time, and the stored value of the third cylinder intake air amount area GASUM (# 3) is obtained. To update.
[0105]
If all of the above steps 503, 505, and 507 are determined to be “No”, that is, if the crank angle counter CCRNK is a period of 0 to 5 (a period corresponding to the intake stroke of the fourth cylinder # 4), Proceeding to 509, the stored value of the fourth cylinder intake air amount area GASUM (# 4) is updated by integrating the current instantaneous air flow rate GMAP with the stored value of the fourth cylinder intake air amount area GASUM (# 4) up to the previous time. I do.
In the embodiment (5) described above, the same effect as in the embodiment (2) can be obtained.
[0106]
<< Embodiment (6) >>
In the embodiment (6) of the present invention shown in FIG. 27, similarly to the embodiment (3), a predetermined period for calculating the intake air amount area GASUM (# 1) is a period for which the instantaneous air flow rate GMAP is equal to or more than the average value. There is a characteristic in the place set.
[0107]
In the present embodiment (6), the routine of FIG. 27 is executed to calculate the intake air amount area GASUM (#i) of each cylinder as follows. First, in step 501a, the average air flow rate GA detected by the air flow meter 14 is read. Thereafter, the routine proceeds to step 502a, where it is determined whether or not the instantaneous air flow rate GMAP calculated from the instantaneous intake pipe pressure PMAP is equal to or greater than the average air flow rate GA.
[0108]
If the instantaneous air flow rate GMAP is less than the average air flow rate GA, the routine is terminated without performing the subsequent processing. ) Is calculated (steps 503 to 509) to calculate the intake air amount area GASUM (#i) of each cylinder. Other processes are the same as those in the embodiment (1).
In the embodiment (6) described above, the same effect as in the embodiment (3) can be obtained.
[0109]
In the above embodiments (4) to (6), the output of the intake pipe pressure sensor 18 (instantaneous intake pipe pressure PMAP) is converted into the instantaneous air flow rate GMAP, and the intake air amount area GASUM ( #I), and the inter-cylinder intake air amount variation ratio DEV (#i) of each cylinder is calculated from the intake air amount area GASUM (#i) of each cylinder. The output (instantaneous intake pipe pressure PMAP) of a predetermined period is integrated to obtain the area of the intake pipe pressure of each cylinder for a predetermined period, and the variation rate DEV of the intake air amount between cylinders of each cylinder is calculated from the intake pipe pressure area of each cylinder. #I) may be calculated.
[0110]
<< Embodiment (7) >>
In the embodiment (7) of the present invention shown in FIGS. 28 to 34, the in-cylinder pressure of each cylinder is detected by paying attention to the characteristic that the in-cylinder pressure increases as the amount of intake air drawn into the cylinder increases. Thus, the area of the detection waveform of the in-cylinder pressure during a predetermined period is obtained. To achieve this, in the present embodiment (7), an in-cylinder pressure sensor (detection means) for detecting an in-cylinder pressure is provided for each cylinder. The in-cylinder pressure sensor may be one incorporated in the ignition plug 21 or may be provided separately from the ignition plug 21.
[0111]
Generally, as shown in FIG. 32, the waveform of the in-cylinder pressure increases before the ignition according to the compression of the in-cylinder charging air, but after the ignition, the in-cylinder pressure sharply increases due to the combustion pressure. The subsequent maximum value (peak value) of the in-cylinder pressure is considerably larger than the pressure of only the in-cylinder charged air. Moreover, even if the in-cylinder charged air amount is the same, it is difficult to estimate the in-cylinder charged air amount from the in-cylinder pressure maximum value after ignition because the maximum value of the in-cylinder pressure after ignition depends on the fuel amount and the combustion state. It is.
[0112]
Therefore, in the present embodiment (7), the predetermined period for calculating the area of the detected waveform of the in-cylinder pressure is set before the ignition timing. However, as shown in FIG. 33, during the fuel cut period or during cranking (non-combustion), no combustion occurs in the cylinder, and the maximum value of the cylinder pressure is equal to the maximum compression pressure of the cylinder charging air. Therefore, the area of the detected waveform of the in-cylinder pressure is calculated during the period including the maximum value of the in-cylinder pressure (the period before and after the compression TDC).
[0113]
In the present embodiment (7), the in-cylinder pressure area calculation main routine shown in FIG. 28 is executed at the A / D conversion timing (for example, 4 ms cycle) of the in-cylinder pressure sensor. When this routine is started, first, in step 601, it is determined whether or not the same cylinder-to-cylinder variation correction execution condition as in step 101 of FIG. 3 is satisfied, and if the cylinder-to-cylinder variation correction execution condition is not satisfied, This routine ends without executing the processing related to the calculation of the in-cylinder pressure area for a predetermined period after step 602.
[0114]
On the other hand, if it is determined in step 601 that the condition for executing the cylinder-to-cylinder variation correction is satisfied, the process related to the calculation of the in-cylinder pressure area for a predetermined period after step 602 is executed as follows. First, in step 602, after reading the output voltage VCPS (#i) of the in-cylinder pressure sensor of each cylinder after filtering, the process proceeds to step 603, and the output voltage VCPS ( #I) is converted into the in-cylinder pressure CPS (#i).
[0115]
Thereafter, the process proceeds to step 604, where the count value of the crank angle counter CCRNK is read. Then, in the next step 605, it is determined whether or not it is during the fuel cut period or during cranking (when not burning). If it is not during the fuel cut period or during cranking, the process proceeds to step 606, and FIG. A routine for calculating the in-cylinder pressure area of each cylinder during the combustion shown in FIG. 30 for a predetermined period is executed. On the other hand, if it is during the fuel cut period or during cranking, the routine proceeds to step 607, and the routine shown in FIG. An in-cylinder pressure area calculation routine for a predetermined period of each cylinder is executed.
[0116]
When the in-cylinder pressure area calculation routine for a predetermined period of each cylinder during combustion shown in FIG. 30 is started in step 606, first, in step 611, a predetermined period P for calculating the in-cylinder pressure area of each cylinder is calculated. During combustion, as shown in FIG. 32, the predetermined period P is set before the ignition timing, and the length of the predetermined period P is calculated from a map or the like according to the engine speed NE and the intake air amount GA. At this time, in a region where the engine rotation speed NE is low or a region where the intake air amount GA is large, the predetermined period P is set to be longer as the amplitude of the pulsation wave increases.
[0117]
Then, in the next step 612, it is determined whether or not it is the ignition timing. If it is not the ignition timing, this routine ends without performing the subsequent processing. Thereafter, when the ignition timing comes, the routine proceeds to step 613, where it is determined whether or not the crank angle counter CCRNK is a period of 22 to 3 (that is, a period within 90 ° C. before and after the compression TDC of the first cylinder # 1). If CCRNK = 22-3, the routine proceeds to step 614, where the stored data of the in-cylinder pressure CPS (# 1) of the first cylinder # 1 is integrated for a predetermined period P before the ignition of the first cylinder # 1. The first cylinder in-cylinder pressure area CPSSUM (# 1) is obtained. Note that the data of the in-cylinder pressure CPS (#i) of each cylinder is stored in the RAM of the ECU 27 in time series for each cylinder every time it is detected at a predetermined sampling cycle, and for a predetermined period P before ignition of each cylinder. After accumulating the stored data of the in-cylinder pressure CPS (#i) of each cylinder to obtain the in-cylinder pressure area CPSUM (#i) of each cylinder, the stored data of the in-cylinder pressure CPS (#i) of each cylinder is cleared. .
[0118]
In step 613, “No” is determined, and in step 615, it is determined that the crank angle counter CCRNK is a period of 16 to 21 (that is, a period within 90 ° C. before and after the compression TDC of the second cylinder # 2). If so, the routine proceeds to step 616, where the in-cylinder pressure CPS (# 2) of the second cylinder # 2 is integrated for the predetermined period P before the ignition of the second cylinder # 2, and the second cylinder in-cylinder pressure area CPSSUM (# 2) is obtained. Ask.
[0119]
In steps 613 and 615, “No” is determined, and in step 617, the crank angle counter CCRNK is a period of 4 to 9 (that is, a period within 90 ° C. before and after the compression TDC of the third cylinder # 3). If it is determined, the process proceeds to step 618, in which the in-cylinder pressure CPS (# 3) of the third cylinder # 3 is integrated for a predetermined period P before the ignition of the third cylinder # 3, and the third cylinder in-cylinder pressure area CPSSUM (# 3 ).
[0120]
If all of the above steps 613, 615, and 617 are judged as "No", that is, the period of the crank angle counter CCRNK = 10 to 15 (the period within 90 ° C before and after the compression TDC of the fourth cylinder # 4). In this case, the process proceeds to step 619, in which the in-cylinder pressure CPS (# 4) of the fourth cylinder # 4 is integrated for a predetermined period P before the ignition of the fourth cylinder # 4 to obtain the fourth cylinder in-cylinder pressure area CPSSUM (# 4). Ask.
[0121]
On the other hand, when the in-cylinder pressure area calculation routine for each cylinder during the non-combustion period shown in FIG. 31 is started at step 607 in FIG. During a ranking), a predetermined period P for calculating the in-cylinder pressure area of each cylinder is calculated. At the time of non-combustion, as shown in FIG. 33, the predetermined period P is set to a period including the maximum value, and the length of the predetermined period P is calculated by a map or the like according to the engine speed NE and the intake air amount GA. . At this time, in a region where the engine rotation speed NE is low or a region where the intake air amount GA is large, the predetermined period P is set to be longer as the amplitude of the pulsation wave increases.
[0122]
Then, in the next step 622, it is determined whether or not the in-cylinder pressure CPS (#i) detected by the in-cylinder pressure sensor is a local maximum value. The method of determining the maximum value is, for example, comparing the current value of the in-cylinder pressure CPS (#i) with the previous value and determining whether or not the change direction of the in-cylinder pressure CPS (#i) is reversed from increasing to decreasing. Good.
[0123]
If the in-cylinder pressure CPS (#i) is not the local maximum value, the routine ends without performing the subsequent processing. Thereafter, when the in-cylinder pressure CPS (#i) reaches the maximum value, the routine proceeds to step 623, where the crank angle counter CCRNK is 22 to 3 (that is, within 90 ° C. before and after the compression TDC of the first cylinder # 1). If CCRNK = 22-3, the routine proceeds to step 624, where a predetermined period P before and after the compression TDC of the first cylinder # 1 (centering around the time point t at which the maximum value is reached). The period CPS (# 1) of the first cylinder # 1 is integrated for the period within P / 2 before and after the period P2) to determine the first cylinder in-cylinder pressure area CPSSUM (# 1).
[0124]
The determination at step 623 is “No”, and the determination at step 625 is that the crank angle counter is CCRNK = 16 to 21 (that is, a period within 90 ° C. before and after the compression TDC of the second cylinder # 2). If so, the process proceeds to step 626, in which the in-cylinder pressure CPS (# 2) of the second cylinder # 2 is integrated for a predetermined period P before and after the compression TDC of the second cylinder # 2, and the second cylinder in-cylinder pressure area CPSSUM (# 2). Ask for.
[0125]
In steps 623 and 625, “No” is determined, and in step 627, it is determined that the crank angle counter CCRNK is a period of 4 to 9 (that is, a period within 90 ° C. before and after the compression TDC of the third cylinder # 3). If it is determined, the process proceeds to step 628, where the cylinder pressure CPS (# 3) of the third cylinder # 3 is integrated for a predetermined period P before and after the compression TDC of the third cylinder # 3, and the third cylinder cylinder pressure area CPSSUM (# Find 3).
[0126]
If all of the above steps 623, 625, and 627 result in "No", that is, the period of the crank angle counter CCRNK = 10 to 15 (the period within 90 ° C before and after the compression TDC of the fourth cylinder # 4). In this case, the routine proceeds to step 629, where the in-cylinder pressure CPS (# 4) of the fourth cylinder # 4 is integrated for the predetermined period P before and after the compression TDC of the fourth cylinder # 4 before ignition, and the fourth cylinder in-cylinder pressure area CPSSUM ( # 4) is requested.
[0127]
An execution example of the above-described cylinder-to-cylinder variation correction of the embodiment (7) will be described with reference to a time chart shown in FIG.
During the period in which the condition for executing the cylinder-to-cylinder variation correction is satisfied and the flag for executing the cylinder-to-cylinder variation correction is ON, after calculating the in-cylinder pressure area CPSSUM (#i) of each cylinder for a predetermined period for each compression stroke of each cylinder. In the same manner as in the embodiment (1), the in-cylinder pressure area CPSSUM (#i) of each cylinder is smoothed between the cylinders to obtain the in-cylinder pressure area smoothed value CPSSUMSM (#i) of each cylinder. . In this way, every time the cylinder pressure area smoothing value CPSSUMSM (#i) is obtained (every 720 ° C. A), the cylinder pressure area smoothing value CPSSUMSM (#i) is calculated for all cylinders. The average value of the area smoothing values is divided, and the resultant value is multiplied by the correction coefficient K2 to obtain the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder. Other processes are the same as those in the embodiment (1).
In the embodiment (7) described above, the same effect as in the embodiment (1) can be obtained.
[0128]
In this embodiment (7), the cylinder pressure area CPSSUM (#i) for a predetermined period is calculated from the output waveform of the cylinder pressure sensor of each cylinder, and the cylinder pressure area CPSSUM (#i) is calculated from the cylinder pressure area CPSSUM (#i) of each cylinder. Is calculated, the in-cylinder pressure CPS (#i) detected by the in-cylinder pressure sensor of each cylinder is converted into an instantaneous air flow rate, and a predetermined value of each cylinder is calculated. The intake air amount area during the period may be calculated, and the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder may be calculated from the intake air amount area of each cylinder.
[0129]
In each of the above embodiments (1) to (7), the present invention is applied to a system that performs intake air amount control by variable intake valve control. However, the present invention is applied to a system that performs only intake air amount control by throttle control. May be applied.
The application range of the present invention is not limited to a four-cylinder engine, and the present invention may be applied to a multi-cylinder engine having five or more cylinders or three or less cylinders.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment (1) of the present invention.
FIG. 2 is a front view of a variable valve lift mechanism.
FIG. 3 is a flowchart showing a processing flow of an inter-cylinder variation correction routine according to the embodiment (1).
FIG. 4 is a diagram conceptually showing a map of a basic lift correction amount FVVL1.
FIG. 5 is a diagram conceptually showing a map of a correction coefficient FVVL2.
FIG. 6 is a flowchart showing a processing flow of an intake air amount area calculation main routine according to the embodiment (1).
FIG. 7 is a diagram conceptually showing a map for converting an output voltage VAFM of an air flow meter into an instantaneous air flow rate GAFM.
FIG. 8 is a flowchart showing a processing flow of an intake air amount area calculation routine for a predetermined period of each cylinder according to the embodiment (1).
FIG. 9 is a diagram conceptually showing a P map for a predetermined period according to the embodiment (1).
FIG. 10 is a time chart illustrating a method for calculating an intake air amount area during a predetermined period P according to the embodiment (1).
FIG. 11 is a flowchart showing a flow of a routine of a routine for calculating a variation rate of intake air amount between cylinders according to the embodiment (1).
FIG. 12 is a diagram conceptually showing a map of a correction coefficient K2.
FIG. 13 is a time chart for explaining an example of an inter-cylinder intake air amount variation rate calculation process of the embodiment (1).
FIG. 14 is a time chart for explaining an example of correction between cylinders according to the embodiment (1).
FIG. 15 is a flowchart showing a processing flow of an intake air amount area calculation routine for a predetermined period of each cylinder in the embodiment (2).
FIG. 16 is a diagram conceptually showing a map for calculating a detection delay time DLY of the air flow meter according to the embodiment (2).
FIG. 17 is a time chart illustrating a method of calculating an intake air amount area during a predetermined period according to the embodiment (2).
FIG. 18 is a time chart for explaining an example of an intake air amount variation ratio calculation process between cylinders according to the embodiment (2).
FIG. 19 is a flowchart showing a process flow of an intake air amount area calculation routine for a predetermined period of each cylinder in the embodiment (3).
FIG. 20 is a time chart illustrating a method for calculating an intake air amount area during a predetermined period according to the embodiment (3).
FIG. 21 is a time chart for explaining an example of an inter-cylinder intake air amount variation rate calculation process of the embodiment (3).
FIG. 22 is a flowchart showing the flow of processing of an intake air amount area calculation main routine according to the embodiment (4).
FIG. 23 is a diagram conceptually showing a map for converting an output voltage VMAP of an intake pipe pressure sensor into an instantaneous intake pipe pressure PMAP.
FIG. 24 is a flowchart showing the flow of processing of an intake air amount area calculation routine for a predetermined period of each cylinder in the embodiment (4).
FIG. 25 is a time chart for explaining the correlation between the output of the air flow meter and the output of the intake pipe pressure sensor.
FIG. 26 is a flowchart showing the flow of processing of an intake air amount area calculation routine for a predetermined period of each cylinder in the embodiment (5).
FIG. 27 is a flowchart showing a processing flow of an intake air amount area calculation routine for a predetermined period of each cylinder in the embodiment (6).
FIG. 28 is a flowchart showing the flow of processing of an in-cylinder pressure area calculation main routine according to the embodiment (7).
FIG. 29 is a diagram conceptually showing a map for converting an output voltage VCPS (#i) of an in-cylinder pressure sensor into an in-cylinder pressure CPS (#i).
FIG. 30 is a flowchart showing a processing flow of a cylinder pressure area calculation routine for a predetermined period of each cylinder during combustion according to the embodiment (7).
FIG. 31 is a flowchart showing a processing flow of an in-cylinder pressure area calculation routine for a predetermined period of each cylinder during non-combustion according to the embodiment (7).
FIG. 32 is a time chart showing an in-cylinder pressure waveform during combustion.
FIG. 33 is a time chart showing an in-cylinder pressure waveform during non-combustion.
FIG. 34 is a time chart for explaining an example of a calculation process of the variation rate of the intake air amount between cylinders according to the embodiment (7).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter (detection means), 15 ... Throttle valve, 18 ... Intake pipe pressure sensor (detection means), 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... exhaust pipe, 24 ... air-fuel ratio sensor, 26 ... crank angle sensor, 27 ... ECU (area calculation means, means for calculating variation in intake air amount between cylinders), 28 ... intake valve, 29 ... exhaust valve, 30, 31 ... variable valve Lift mechanism.

Claims (8)

Detecting means for detecting at least one of an intake air amount flowing through an intake pipe of an internal combustion engine having a plurality of cylinders, an intake pipe pressure, and an in-cylinder pressure;
Area calculation means for calculating the area of the output waveform of the detection means for a predetermined period for each intake stroke or each compression stroke of each cylinder;
Cylinders for an internal combustion engine, comprising means for calculating an intake air amount variation rate between cylinders or an intake air amount for each cylinder based on an area of each cylinder during the predetermined period. Separate intake air amount detection device. The detection unit detects the intake air amount or the intake pipe pressure, and the area calculation unit sets the predetermined period to a period that is hardly affected by a reflected wave of intake pulsation or intake interference of another cylinder. The cylinder-by-cylinder intake air amount detection device according to claim 1, wherein: 3. The cylinder-by-cylinder intake air for an internal combustion engine according to claim 2, wherein the area calculation means sets the predetermined period to a period including a maximum value of the intake air amount or a period including a minimum value of the intake pipe pressure. Quantity detection device. The cylinder-specific intake air amount detection device for an internal combustion engine according to claim 2, wherein the area calculation unit sets the predetermined period as an intake valve opening period. The cylinder-by-cylinder intake air amount detection device according to any one of claims 2 to 4, wherein the area calculation unit sets the predetermined period in consideration of a detection delay of the detection unit. 4. The internal combustion engine according to claim 2, wherein the area calculation unit sets the predetermined period to a period in which the intake air amount is equal to or more than the average value or a period in which the intake pipe pressure is equal to or less than the average value. 5. Cylinder intake air amount detection device. The detecting means detects an in-cylinder pressure,
The cylinder-by-cylinder intake air amount detection device according to claim 1, wherein the area calculation means sets the predetermined period before an ignition timing. 8. The cylinder-by-cylinder intake air amount detection of an internal combustion engine according to claim 7, wherein the area calculation means sets the predetermined period to a period including a maximum value of the in-cylinder pressure during a fuel cut period or at the time of cranking. apparatus.

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