JP4003182B2 - Variable valve control device for internal combustion engine - Google Patents

Description

【００９８】
上式の分母は、全気筒の吸入空気流量平均値ＧＡave(#1) 〜ＧＡave(#4) の平均値である。
尚、図９の気筒間吸入空気量ばらつき率算出ルーチンでは、各気筒の吸入空気流量平均値ＧＡave(#i) を用いて気筒間吸入空気量ばらつき率ＤＥＶ(#i)を算出したが、各気筒の吸入空気流量極大値や吸入空気量積算値を用いて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。また、各気筒の吸入空気量に応じて発生する吸気脈動がエアフローメータ１４で検出されるまでの時間遅れ等を考慮して、各気筒の吸入空気流量平均値の算出期間を適宜変更しても良い。
【００９９】
また、吸気管圧力センサ１８の出力に基づいて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。また、各気筒の筒内圧を検出する筒内圧センサや各気筒のバルブリフト量を検出するリフトセンサを備えたシステムでは、筒内圧センサの出力やリフトセンサの出力に基づいて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。
【０１００】
以上説明した本実施形態（１）の実行例を図１１乃至図１３に示すタイムチャートを用いて説明する。図１１に示すように、気筒別可変バルブ制御精度値ＡＣＣＵＲＡ(#i)が許容範囲内にあり、気筒別可変バルブ制御禁止フラグＸＳＴＯＰがＯＦＦされている期間は、気筒別可変バルブ制御を実行して吸入空気量を制御する。この気筒別可変バルブ制御では、各気筒の気筒間吸入空気量ばらつき率ＤＥＶ(#i)に基づいて各気筒の目標リフト量ＶＶＬＭを設定し、図１２に示すように、全吸気バルブ閉弁期間になる毎に、可変バルブリフト機構３０のモータ４１を次の吸気気筒の目標リフト量ＶＶＬＭに相当する位置まで高速駆動することで、吸入空気量を気筒別に制御して気筒間の吸入空気量ばらつきを補正する。
【０１０１】
この気筒別可変バルブ制御の実行中は、各気筒の吸気バルブ２８の実リフト量と目標リフト量ＶＶＬＭとの偏差（各気筒の吸気行程の実モータ回転角度ＶＶＬＡＣＴと目標モータ回転角度ＴＧＶＶＬＡＣＴとの偏差）を積算して各気筒の気筒別可変バルブ制御精度値ＡＣＣＵＲＡ(#i)を求める。
【０１０２】
その後、図１３に示すように、バッテリ電圧の低下等により各気筒の目標リフト量ＶＶＬＭに対する実リフト量の収束性が悪化して、気筒別可変バルブ制御精度が悪化し、それによって、気筒別可変バルブ制御精度値ＡＣＣＵＲＡ(#i)が許容範囲を越えたた時点（図１１のｔ1 ）で、気筒別可変バルブ制御禁止フラグＸＳＴＯＰがＯＮされて、気筒別可変バルブ制御が禁止される。
【０１０３】
これにより、気筒別可変バルブ制御精度の悪化による気筒間のリフト量のばらつき（又は吸入空気量のばらつき）の悪化や、同一気筒のサイクル間のリフト量のばらつき（又は吸入空気量のばらつき）の悪化を未然に防止することができ、ドライバビリティや排気エミッションへの悪影響を回避することができる。
【０１０４】
また、図１１に示すように、気筒別可変バルブ制御の禁止中は、リフト量制限モード可変バルブ制御とスロットルバルブ制御により吸入空気量を制御する。リフト量制限モード可変バルブ制御では、各気筒共通の目標リフト量ＴＧＶＶＬを下限リフト量ＶＶＬmin （例えば１ｍｍ）以上に制限して可変バルブリフト機構３０のモータ４１を各気筒共通の目標リフト量ＴＧＶＶＬに相当する位置に制御する。
【０１０５】
目標リフト量ＴＧＶＶＬを下限リフト量ＶＶＬmin 以上に制限すれば、目標リフト量ＴＧＶＶＬに対する実リフト量のばらつき（各気筒の部品公差や組付公差によるばらつき）の割合を所定のばらつき許容値（例えば５％）以下に抑えて、気筒間の吸入空気量ばらつきをに許容範囲内に抑えることができる。従って、気筒別可変バルブ制御の禁止中に、リフト量制限モード可変バルブ制御を実行すれば、気筒間の吸入空気量ばらつきをドライバビリティや排気エミッションが悪化しない許容範囲内に抑えながら、可変バルブ制御による吸入空気量制御を行うことができ、気筒別可変バルブ制御の禁止中に、スロットルバルブ制御のみで吸入空気量制御を行う場合よりも燃費を少なくすることができる。
【０１０６】
また、気筒別可変バルブ制御の禁止中に、リフト量制限モード可変バルブ制御を行って目標リフト量ＴＧＶＶＬを下限リフト量ＶＶＬmin 以上に制限する場合、可変バルブ制御による吸入空気量制御だけでは吸入空気量の制御領域の下限側が制限されて、アイドル等の低負荷時に吸入空気量を通常の最小空気量（アイドル時の目標空気量）付近に制御できなくなるが、スロットルバルブ制御による吸入空気量制御を併用することで、吸入空気量の制御領域の下限側を通常の最小空気量まで広げることができる。
【０１０７】
更に、図１１に示すように、気筒別可変バルブ制御の禁止中に、燃料カット（又は減速）が開始された時点ｔ2 で、気筒別可変バルブ制御を試行し、そのときの気筒別可変バルブ制御精度値ＡＣＣＵＲＡ(#i)が許容範囲以内で且つバッテリ電圧が所定値以上と判定されて復帰条件が成立した時点ｔ3 で、気筒別可変バルブ制御復帰フラグＸＲＥＡＣＴがＯＮされて、気筒別可変バルブ制御が再開される。
【０１０８】
これにより、気筒別可変バルブ制御精度が回復したことを実際に確認してから気筒別可変バルブ制御を再開することができる。しかも、燃料カット中又は減速中に気筒別可変バルブ制御を試行するので、もし、気筒別可変バルブ制御精度が回復していない場合でも、気筒別可変バルブ制御の試行によるドライバビリティ等への悪影響を少なくすることができる。
【０１０９】
《実施形態（２）》
前記実施形態（１）では、各気筒の吸気バルブ２８の実リフト量と目標リフト量ＶＶＬＭとの偏差に基づいて各気筒の気筒別可変バルブ制御精度値ＡＣＣＵＲＡ（#i）を求めたが、本発明の実施形態（２）では、図１４に示す気筒別可変バルブ制御精度値算出ルーチンを実行することで、各気筒の吸気バルブ２８の実リフト量のサイクル間ばらつきに基づいて各気筒の気筒別可変バルブ制御精度値ＡＣＣＵＲＡ（#i）を求めるようにしている。尚、本実施形態（２）では、気筒別可変バルブ制御精度値ＡＣＣＵＲＡ（#i）を求める際に、吸気バルブ２８の実リフト量の代用情報として、可変バルブリフト機構３０の実モータ回転角度ＶＶＬＡＣＴを用いる。
【０１１０】
本実施形態（２）で実行する図１４の気筒別可変バルブ制御精度値算出ルーチンでは、まず、ステップ７０１で、モータ回転角度センサ４４により検出した可変バルブリフト機構３０の実モータ回転角度ＶＶＬＡＣＴを読み込み、次のステップ７０２で、クランク角カウンタＣＣＲＮＫのカウント値を読み込む。
【０１１１】
この後、ステップ７０３に進み、各気筒別に吸気行程毎（サイクル毎）に検出した実モータ回転角度の１番目の記憶値ＶＶＬＡＣＴ(#i)(1) からｎ番目（例えば２０番目）の記憶値ＶＶＬＡＣＴ(#i)(n) を更新する。
【０１１２】
この場合、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）は、その期間の１点で検出した実モータ回転角度ＶＶＬＡＣＴを記憶すると共に、第１気筒＃１の吸気行程の実モータ回転角度の１番目の記憶値ＶＶＬＡＣＴ(#1)(1) から（ｎ−１）番目の記憶値ＶＶＬＡＣＴ(#1)(n-1) を、それぞれ２番目の記憶値ＶＶＬＡＣＴ(#1)(2) からｎ番目の記憶値ＶＶＬＡＣＴ(#1)(n) で更新し、ｎ番目の記憶値ＶＶＬＡＣＴ(#1)(n) を今回の記憶値ＶＶＬＡＣＴで更新する。
【０１１３】
同じようにして、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）は、第２気筒＃２の吸気行程の実モータ回転角度の１番目の記憶値ＶＶＬＡＣＴ(#2)(1) からｎ番目の記憶値ＶＶＬＡＣＴ(#2)(n) を更新し、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）は、第３気筒＃３の吸気行程の実モータ回転角度の１番目の記憶値ＶＶＬＡＣＴ(#3)(1) からｎ番目の記憶値ＶＶＬＡＣＴ(#3)(n) を更新し、クランク角カウンタＣＣＲＮＫ＝０〜５の期間（つまり第４気筒＃４の吸気行程に対応する期間）は、第４気筒＃４の吸気行程の実モータ回転角度の１番目の記憶値ＶＶＬＡＣＴ(#4)(1) からｎ番目の記憶値ＶＶＬＡＣＴ(#4)(n) を更新する。
【０１１４】
この後、ステップ７０４に進み、各気筒の吸気行程毎（サイクル毎）に検出した実モータ回転角度の１番目の記憶値ＶＶＬＡＣＴ(#i)(1) からｎ番目の記憶値ＶＶＬＡＣＴ(#i)(n) のばらつき度合（例えば標準偏差）を算出し、それを気筒別可変バルブ制御精度値ＡＣＣＵＲＡ（#i）とする。
【０１１５】
以上説明した本実施形態（２）では、各気筒の吸気バルブ２８の実リフト量（実モータ回転角度ＶＶＬＡＣＴ）のサイクル間ばらつきに基づいて気筒別可変バルブ制御精度値ＡＣＣＵＲＡを算出するようにしたので、気筒別可変バルブ制御精度として、各気筒の吸気バルブ２８の実リフト量のサイクル間ばらつき（繰り返し精度）を評価することができ、吸気バルブ２８の実リフト量のサイクル間ばらつきが悪化したときに、気筒別可変バルブ制御を禁止することができる。
【０１１６】
《実施形態（３）》
本発明の実施形態（３）では、図１５に示す気筒別可変バルブ制御精度値算出ルーチンを実行することで、可変バルブリフト機構３０のモータ駆動時間ＴＡＣＴ（図１２、図１３参照）のサイクル間ばらつきに基づいて各気筒の気筒別可変バルブ制御精度値ＡＣＣＵＲＡ（#i）を求めるようにしている。
【０１１７】
本実施形態（３）で実行する図１５の気筒別可変バルブ制御精度値算出ルーチンでは、まず、ステップ８０１で、モータ回転角度センサ４４の出力に基づいて可変バルブリフト機構３０のモータ４１を次の吸気気筒の目標リフト量ＶＶＬＭに相当する位置まで駆動するのに要したモータ駆動時間ＴＡＣＴを検出する。
【０１１８】
この後、ステップ８０２に進み、各気筒別に吸気行程を迎える毎（サイクル毎）に検出したモータ駆動時間の１番目の記憶値ＴＡＣＴ(#i)(1) からｎ番目（例えば２０番目）の記憶値ＴＡＣＴ(#i)(n) を更新する。
【０１１９】
この場合、次の吸気気筒が第１気筒＃１のときは、第１気筒＃１の吸気行程前のモータ駆動時間の１番目の記憶値ＴＡＣＴ(#1)(1) から（ｎ−１）番目の記憶値ＴＡＣＴ(#1)(n-1) を、それぞれ２番目の記憶値ＴＡＣＴ(#1)(2) からｎ番目の記憶値ＴＡＣＴ(#1)(n) で更新し、ｎ番目の記憶値ＴＡＣＴ(#1)(n) を今回の記憶値ＴＡＣＴで更新する。
【０１２０】
同じようにして、次の吸気気筒が第２気筒＃２のときは、第２気筒＃２の吸気行程前のモータ駆動時間の１番目の記憶値ＴＡＣＴ(#2)(1) からｎ番目の記憶値ＴＡＣＴ(#2)(n) を更新し、次の吸気気筒が第３気筒＃３のときは、第３気筒＃３の吸気行程前のモータ駆動時間の１番目の記憶値ＴＡＣＴ(#3)(1) からｎ番目の記憶値ＴＡＣＴ(#3)(n) を更新し、次の吸気気筒が第４気筒＃４のときは、第４気筒＃４の吸気行程前のモータ駆動時間の１番目の記憶値ＴＡＣＴ(#4)(1) からｎ番目の記憶値ＴＡＣＴ(#4)(n) を更新する。
【０１２１】
この後、ステップ８０３に進み、各気筒の吸気行程を迎える毎（サイクル毎）に検出したモータ駆動時間の１番目の記憶値ＴＡＣＴ(#i)(1) からｎ番目の記憶値ＴＡＣＴ(#i)(n) のばらつき度合（例えば標準偏差）を算出し、それを気筒別可変バルブ制御精度値ＡＣＣＵＲＡ（#i）とする。
【０１２２】
以上説明した本実施形態（３）では、可変バルブリフト機構３０のモータ駆動時間ＴＡＣＴのサイクル間ばらつきに基づいて気筒別可変バルブ制御精度値ＡＣＣＵＲＡを算出するようにしたので、気筒別可変バルブ制御精度として、可変バルブリフト機構３０のモータ駆動時間ＴＡＣＴのサイクル間ばらつき（繰り返し精度）を評価することができ、可変バルブリフト機構３０のモータ駆動時間ＴＡＣＴのサイクル間ばらつきが悪化したときに、気筒別可変バルブ制御を禁止することができる。
【０１２３】
尚、上記各実施形態（１）〜（３）では、各気筒の気筒別可変バルブ制御精度値ＡＣＣＵＲＡを算出するようにしたが、全気筒のうちの１つ又は２つ以上の気筒について気筒別可変バルブ制御精度値ＡＣＣＵＲＡを算出するようにしても良い。
【０１２４】
また、上記各実施形態（１）〜（３）では、気筒別可変バルブ制御の禁止中にリフト量制限モード可変バルブ制御による吸入空気量制御とスロットルバルブ制御による吸入空気量制御を併用するようにしたが、スロットルバルブ制御による吸入空気量制御のみを行うようにしても良い。
【０１２５】
また、上記各実施形態（１）〜（３）では、気筒別可変バルブ制御の禁止中に気筒別可変バルブ制御を試行し、そのときの気筒別可変バルブ制御精度値ＡＣＣＵＲＡが許容範囲以内で且つバッテリ電圧が所定電圧以上と判定されたときに復帰条件が成立するようにしたが、気筒別可変バルブ制御精度値ＡＣＣＵＲＡが許容範囲以内と判定されたときに復帰条件が成立するようにしても良い。
【０１２６】
勿論、バッテリ電圧が所定値以上と判定されたときに復帰条件が成立するようにしても良い。バッテリ電圧の低下によって気筒別可変バルブ制御精度が悪化した場合、バッテリ電圧が所定電圧以上に回復すると、気筒別可変バルブ制御精度が回復するため、バッテリ電圧が所定電圧以上に回復したときに、復帰条件が成立するようにすれば、気筒別可変バルブ制御精度が回復したときに、気筒別可変バルブ制御を再開することができる。
【０１２７】
また、本発明の適用範囲は、吸気バルブのリフト量を可変する可変バルブ制御システムに限定されず、吸気バルブのリフト量、作用角、バルブタイミングの少なくとも１つを可変する可変バルブ制御システムに広く適用することができる。また、排気バルブについても、本発明を適用して実施できる。
【０１２８】
更に、本発明は、気筒間の吸入空気量ばらつきに基づいて気筒別可変バルブ制御を行うシステムに限定されず、気筒間のバルブ可変量ばらつきに基づいて気筒別可変バルブ制御を行うシステムに適用しても良い。
【０１２９】
その他、本発明は、直列エンジンに限定されず、Ｖ型エンジン、水平対抗エンジン等、種々の複数気筒エンジンに適用でき、気筒数も適宜変更しても良いことは言うまでもない。
【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】可変バルブリフト機構によるバルブリフト量の連続可変動作を説明するためのバルブリフト特性図
【図４】実施形態（１）の気筒別可変バルブ制御実行・禁止ルーチンの処理の流れを示すフローチャート
【図５】実施形態（１）の気筒別可変バルブ制御禁止判定ルーチンの処理の流れを示すフローチャート
【図６】実施形態（１）の気筒別可変バルブ制御精度値算出ルーチンの処理の流れを示すフローチャート
【図７】実施形態（１）の気筒別可変バルブ制御復帰判定ルーチンの処理の流れを示すフローチャート
【図８】実施形態（１）の気筒別可変バルブ制御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１０】リフト補正量ＦＶＶＬのマップを概念的に示す図
【図１１】実施形態（１）の可変バルブ制御の実行例を示すタイムチャート
【図１２】気筒別可変バルブ制御精度の正常時の気筒別可変バルブ制御の実行例を示すタイムチャート
【図１３】気筒別可変バルブ制御精度の悪化時の気筒別可変バルブ制御の実行例を示すタイムチャート
【図１４】実施形態（２）の気筒別可変バルブ制御精度値算出ルーチンの処理の流れを示すフローチャート
【図１５】実施形態（３）の気筒別可変バルブ制御精度値算出ルーチンの処理の流れを示すフローチャート
【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、１５…スロットルバルブ、２０…燃料噴射弁、２１…点火プラグ、２２…排気管、２６…クランク角センサ、２７…ＥＣＵ（気筒間ばらつき算出手段，気筒別目標バルブ可変量設定手段，気筒別可変バルブ制御手段，制御精度算出手段，気筒別可変バルブ制御禁止手段，リフト量制限モード可変バルブ制御手段，スロットル制御手段，復帰制御手段，試行手段）、２８…吸気バルブ、２９…排気バルブ、３０，３１…可変バルブリフト機構（可変バルブ機構）、４１…モータ、４４…モータ回転角度センサ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve control device for an internal combustion engine that controls variable valve amounts (lift amount, operating angle, valve timing, etc.) of an intake valve or an exhaust valve of the internal combustion engine.
[0002]
[Prior art]
In general, the intake air amount of an internal combustion engine is controlled by a throttle valve. Recently, a variable valve mechanism for changing the lift amount of the intake valve is provided, and the intake valve lift is controlled according to the accelerator opening, the engine operating state, and the like. A technique for controlling the amount of intake air by varying the amount has been developed. The intake air amount control by this variable intake valve control can reduce the pumping loss because the intake air amount can be reduced without reducing the intake passage by the throttle valve by reducing the lift amount of the intake valve. In addition, by reducing the lift amount of the intake valve, there is an advantage that the driving force of the camshaft can be reduced and fuel consumption can be improved.
[0003]
In such a variable valve lift control system, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2001-263110), there is one provided with an electromagnetic actuator for driving an intake valve for each cylinder. Since the number of electromagnetic actuators is the same as the number of cylinders, there is a disadvantage that the system configuration is complicated and the cost is increased.
[0004]
Therefore, a system has been developed in which the lift amounts of the intake valves of a plurality of cylinders are collectively controlled by a single variable valve mechanism.
[0005]
However, in the intake air amount control by this variable intake valve control, the lift amount of the intake valve becomes small at low load. Therefore, the variation of the actual lift amount with respect to the target lift amount in each cylinder (depending on the component tolerance and assembly tolerance of each cylinder) The ratio of (variation) tends to increase, and the variation in intake air amount between cylinders tends to increase. For this reason, the torque and air-fuel ratio of each cylinder tend to fluctuate due to the influence of the intake air amount variation between the cylinders, and the torque variation and air-fuel ratio variation between the cylinders tend to increase.
[0006]
Several methods for correcting such torque variations between cylinders and air-fuel ratio variations have been proposed. For example, as shown in Patent Document 2 (Japanese Patent Laid-Open No. Sho 62-17342), torque is detected for each cylinder by a torque sensor provided on the crankshaft, and the torque of each cylinder becomes the average torque of all cylinders. In this way, the fuel injection amount is corrected for each cylinder.
[0007]
Alternatively, as shown in Patent Document 3 (Japanese Patent 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 the exhaust pipe, and the variation in air-fuel ratio among the cylinders is small. In some cases, the fuel injection amount is corrected for each cylinder.
[0008]
[Patent Document 1]
JP 2001-263110 A (pages 3 to 6 etc.)
[Patent Document 2]
JP-A-62-17342 (second page, etc.)
[Patent Document 3]
JP 2000-220489 A (2nd to 3rd pages, etc.)
[0009]
[Problems to be solved by the invention]
In Patent Documents 2 and 3, 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. Variations are corrected. However, if the intake air amount variation between the cylinders becomes large, it is difficult to correct the torque variation and air-fuel ratio variation of each cylinder with sufficient accuracy by simply correcting the fuel injection amount. Moreover, it is difficult to correct with sufficient accuracy even when multiple factors such as variation in intake air amount and variation in intake fuel amount between cylinders are intertwined to cause torque variation and air-fuel ratio variation between cylinders. .
[0010]
As a countermeasure, it is conceivable to reduce the variation in intake air amount between cylinders by reducing the component tolerance and assembly tolerance of each cylinder (that is, reducing the variation in intake valve lift amount between cylinders). In order to realize this, it is necessary to improve the processing accuracy of the parts, or to select and assemble the parts, and there is a drawback that the part cost and the manufacturing cost increase.
[0011]
Therefore, the inventors of the present invention collectively control the lift amount of the intake valves of a plurality of cylinders with one variable valve mechanism for each intake stroke of each cylinder (180 ° C. A for a 4-cylinder engine). We are researching "variable valve control for each cylinder" that corrects variations in intake valve lift between cylinders (or variations in intake air amount) by driving a variable valve mechanism at high speed.
[0012]
However, in this variable valve control for each cylinder, if the responsiveness of the variable valve mechanism changes due to a decrease in battery voltage (or a decrease in hydraulic pressure) driving the variable valve mechanism, deterioration over time of the variable valve mechanism, failure, etc., The accuracy of the actual lift amount with respect to the target lift amount is deteriorated, or the variation of the actual lift amount in each cycle (every 720 ° C.) is increased. Can get worse. If the variable valve control for each cylinder is continued with the control accuracy deteriorated in this way, the effect of reducing the variation in intake air amount between cylinders need not be reduced. There is a possibility of increasing. There is also a possibility that the variation in intake air amount between cycles of the same cylinder will increase. As a result, torque variation between cylinders and air-fuel ratio variation increase, torque variation and air-fuel ratio variation between cycles of the same cylinder increase, combustion pressure fluctuation increases, drivability, exhaust emission, etc. There is a possibility that various engine performances will deteriorate.
[0013]
The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is to improve the variable valve control accuracy for each cylinder in a system that controls valve variable amounts of a plurality of cylinders with a single variable valve mechanism. An object of the present invention is to provide a variable valve control device for an internal combustion engine that can avoid adverse effects on various engine performances caused by deterioration.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention provides a system in which valve variable amounts of intake valves or exhaust valves (hereinafter simply referred to as “valves”) of a plurality of cylinders are collectively controlled by a single variable valve mechanism. The cylinder-to-cylinder variation calculation means calculates the variation information of the actual valve variable amount or the actual intake air amount between the cylinders (hereinafter referred to as “inter-cylinder variation information”). The target valve variable amount is set for each cylinder by the valve variable amount setting means, and the variable valve control means for each cylinder is set to the position corresponding to the target valve variable amount of the cylinder where the valve is next opened at a predetermined timing by the cylinder-specific variable valve control means. The variable valve control for each cylinder is executed to control the variable valve amount for each cylinder. Then, the cylinder-by-cylinder variable valve control accuracy value representing the cylinder-by-cylinder variable valve control accuracy value is calculated by the control accuracy calculation means, and the cylinder-by-cylinder variable valve control accuracy value is deteriorated beyond a predetermined allowable range. The variable valve control for each cylinder is prohibited by the separate variable valve control prohibiting means.
[0015]
In this way, if the variable valve control accuracy for each cylinder deteriorates and the variable valve control accuracy value for each cylinder exceeds a predetermined allowable range, the variable valve control for each cylinder is not executed. It is possible to prevent the deterioration of the variation in the variable amount of the valve (or the variation of the intake air amount) due to the deterioration of the cylinder or the variation of the variable amount of the valve between the cycles of the same cylinder (or the variation of the intake air amount). In addition, adverse effects on various engine performances such as drivability and exhaust emission due to deterioration of the variable valve control accuracy for each cylinder can be avoided.
[0016]
In this case, it is preferable to calculate the variable valve control accuracy value for each cylinder based on the deviation between the actual valve variable amount and the target valve variable amount of each cylinder or predetermined cylinder. In this way, the convergence accuracy of the actual valve variable amount with respect to the target valve variable amount of each cylinder or a predetermined cylinder can be evaluated as the variable valve control accuracy for each cylinder, and the convergence of the actual valve variable amount with respect to the target valve variable amount can be evaluated. When the performance deteriorates, the variable valve control for each cylinder can be prohibited.
[0017]
In addition, as described in claim 3, the cylinder-by-cylinder variable valve control accuracy value may be calculated based on the cycle-to-cycle variation of the actual valve variable amount of each cylinder or a predetermined cylinder. In this way, as the variable valve control accuracy for each cylinder, it is possible to evaluate the cycle variation (repetition accuracy) of the actual valve variable amount of each cylinder or a predetermined cylinder, and the cycle variation of the actual valve variable amount deteriorated. Sometimes, variable valve control for each cylinder can be prohibited.
[0018]
Further, as in claim 4, the variable valve control accuracy value for each cylinder may be calculated based on the cycle-to-cycle variation of the drive time of the variable valve mechanism. In this way, the cycle-to-cycle variation (repeat accuracy) of the variable valve mechanism drive time can be evaluated as the variable valve control accuracy for each cylinder. Therefore, the variable valve control for each cylinder can be prohibited.
[0019]
In addition, when the cylinder-specific variable valve control accuracy deteriorates, the valves of each cylinder cannot be opened with an appropriate valve profile (valve lift curve) corresponding to the target valve variable amount. The in-cylinder temperature and the like fluctuate to change the combustion state, and the combustion pressure fluctuation and the rotation speed fluctuation of the internal combustion engine occur. When the combustion pressure fluctuation and the rotational speed fluctuation increase, drivability is adversely affected.
[0020]
Therefore, as described in claim 5, the permissible range of the cylinder-by-cylinder variable valve control accuracy value is preferably set to a range in which the rotational speed fluctuation or the combustion pressure fluctuation of the internal combustion engine becomes a predetermined value or less. In this way, the variable valve control for each cylinder can be prohibited when the variable valve control accuracy value for each cylinder exceeds the permissible range and the fluctuation of the rotational speed or the combustion pressure increases significantly. It is possible to prevent adverse effects on drivability and the like by suppressing rotational speed fluctuation and combustion pressure fluctuation due to deterioration of control accuracy to a predetermined value or less.
[0021]
By the way, if the normal variable valve control (that is, the variable valve control for controlling the variable valve mechanism to a position corresponding to the target valve variable amount common to each cylinder) is performed while the variable valve control for each cylinder is prohibited, The variation suppressed by the control increases again. In other words, in a region where the target valve lift amount is small, the ratio of variation in the actual valve lift amount with respect to the target valve lift amount (variation due to component tolerance or assembly tolerance of each cylinder) increases in each cylinder. The amount variation becomes large.
[0022]
As a countermeasure against this, as described in claim 6, while the variable valve control for each cylinder is prohibited, the target valve lift amount common to each cylinder is limited to a predetermined value or more, and the variable valve mechanism is set to a target valve variable amount common to each cylinder. You may make it perform the lift amount restriction | limiting mode variable valve control controlled to the corresponding position. In this way, if the target valve lift amount is limited to a predetermined value or more, the ratio of the variation of the actual valve lift amount to the target valve lift amount (variation due to component tolerance or assembly tolerance of each cylinder) is reduced, and Variation in the intake air amount can be suppressed within an allowable range. Therefore, if the variable valve control for lift amount restriction mode is executed while the variable valve control for each cylinder is prohibited, the variable valve control is performed while suppressing the variation in intake air amount between cylinders within the allowable range that does not deteriorate the drivability and exhaust emission. It can be performed.
[0023]
Further, in the system for controlling the intake air amount by controlling the variable valve mechanism, the intake air amount is controlled by controlling the throttle valve of the internal combustion engine while the variable valve control for each cylinder is prohibited. You may do it. As described above, if the target valve lift amount is limited to a predetermined value or more by performing the lift amount limit mode variable valve control while the cylinder-by-cylinder variable valve control is prohibited, the intake air amount control only by the intake valve control by the variable valve control. The lower limit side of the control area is limited, and the intake air amount cannot be controlled near the normal minimum air amount (target air amount during idling) at low loads such as idle, but the intake air amount control by throttle valve control is also used. Thus, the lower limit side of the intake air amount control region can be expanded to the normal minimum air amount.
[0024]
By the way, when the variable valve control accuracy for each cylinder deteriorates due to a decrease in the battery voltage for driving the variable valve mechanism or a temporary failure of the variable valve mechanism, the variable for each cylinder is changed while the variable valve control for each cylinder is prohibited. The valve control accuracy may be restored.
[0025]
Therefore, as described in claim 8, when the predetermined return condition is satisfied while the cylinder-by-cylinder variable valve control is prohibited, the cylinder-by-cylinder variable valve control may be returned. In this way, when a predetermined return condition is satisfied, it is determined that the cylinder-by-cylinder variable valve control accuracy has been recovered, and the cylinder-by-cylinder variable valve control can be resumed.
[0026]
For example, as in claim 9, when the battery voltage for driving the variable valve mechanism is lower than a predetermined value while the variable valve control for each cylinder is prohibited, the return condition is that the battery voltage recovers to a predetermined value or more. It is good to make it hold when you do. When the variable valve control accuracy for each cylinder deteriorates due to a decrease in the battery voltage, the variable valve control accuracy for each cylinder recovers when the battery voltage recovers to a predetermined value or higher. If the condition is satisfied, the cylinder-by-cylinder variable valve control can be resumed when the cylinder-by-cylinder variable valve control accuracy is restored.
[0027]
Further, as in claim 10, the cylinder-by-cylinder variable valve control is temporarily tried during fuel cut or deceleration while the cylinder-by-cylinder variable valve control is prohibited. It may be established when the cylinder-by-cylinder variable valve control accuracy value at the time of the trial is restored within a predetermined allowable range. In this way, it is possible to restart the variable valve control for each cylinder after actually confirming that the accuracy of the variable valve control for each cylinder has been recovered. Moreover, since the variable valve control for each cylinder is tried during fuel cut or deceleration, even if the accuracy of the variable valve control for each cylinder has not recovered, there is an adverse effect on the drivability and the like due to the trial of variable valve control for each cylinder. Can be reduced.
[0028]
DETAILED DESCRIPTION OF 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. An in-line four-cylinder engine 11 that is an internal combustion engine, for example, has four cylinders, a first cylinder # 1 to a fourth cylinder # 4, and an air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11. An air flow meter 14 for detecting the intake air amount is provided on the downstream side of the air cleaner 13. On the downstream side of the air flow meter 14, 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.
[0029]
Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. 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 in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.
[0030]
Further, the intake valve 28 and the exhaust valve 29 of the engine 11 are provided with variable valve lift mechanisms 30 and 31 (variable valve mechanisms) for varying the lift amount, respectively. Further, the intake valve 28 and the exhaust valve 29 may each be provided with a variable valve timing mechanism that varies the valve timing (opening / closing timing).
[0031]
On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas. / An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean or the like is provided. The cylinder block of the engine 11 includes a coolant temperature sensor 25 that detects the coolant temperature, and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates by a certain crank angle (for example, 30 ° C. A). It is attached. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.
[0032]
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), so that the fuel injection amount of the fuel injection valve 20 can be changed according to the engine operating state. The ignition timing of the spark plug 21 is controlled.
[0033]
Next, the configuration of the variable valve lift mechanism 30 of the intake valve 28 will be described based on 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 thus description thereof is omitted.
[0034]
As shown in FIG. 2, a link arm 34 is provided between the camshaft 32 and the rocker arm 33 for driving the intake valve 28, and a motor 41 such as a stepping motor is rotated above the link arm 34. A control shaft 35 that is driven by movement is provided. The worm 42 connected to the rotation shaft 41 a of the motor 41 and the worm wheel 43 provided so as to rotate integrally with the control shaft 35 mesh with each other, whereby the rotational force of the motor 41 is transmitted to the control shaft 35. It has come to be. In addition, the motor 41 is provided with a motor rotation angle sensor 44 (see FIG. 1) such as an encoder that detects the rotation angle of the motor 41 (the rotation angle of the rotation shaft 41a).
[0035]
The control shaft 35 is provided with an eccentric cam 36 so as to be integrally rotatable, and 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 supported movably. 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 cam shaft 32. Further, a pressing cam 39 is provided at the lower end portion of the link arm 34, and the lower end surface of the pressing cam 39 is in contact with the upper end surface of the roller 40 provided at the central portion of the rocker arm 33.
[0036]
Accordingly, when the cam 37 rotates due to the rotation of the cam shaft 32, the swing cam 38 of the link arm 34 moves to the left and right following the outer peripheral surface shape of the cam 37, and the link arm 34 swings to the left and right. . When the link arm 34 swings left and right, the pressing cam 39 moves left and right. Therefore, 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 intake bubble 28 moves up and down by the up and down movement of the rocker arm 33.
[0037]
On the other hand, when the eccentric cam 36 is rotated by the rotation of the control shaft 35, the position of the support shaft of the link arm 34 is moved, 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 surface of the pressing cam 39 of the link arm 34 is formed with a base curved surface 39a on the left side with a curvature such that the pressing amount of the rocker arm 33 is 0 (the 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 (the lift amount of the intake valve 28 increases) as it goes rightward from the curved surface 39a.
[0038]
In the high lift mode in which the maximum lift amount of the intake valve 28 is increased, 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 moved rightward by the rotation of the control shaft 35. Let Thereby, when the pressing cam 39 moves to the 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, so that the maximum pressing amount of the rocker arm 33 increases. As a result, the maximum lift amount of the intake valve 28 increases, the period during which the rocker arm 33 is pressed becomes longer, and the valve opening period of the intake bubble 28 becomes longer.
[0039]
On the other hand, in the low lift mode in which the maximum lift amount of the intake valve 28 is reduced, 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 set to the left by the rotation of the control shaft 35. Move to. As a result, when the pressing cam 39 moves to the 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, so that the maximum pressing amount of the rocker arm 33 is reduced. As a result, the maximum lift amount of the intake valve 28 is reduced, the period during which the rocker arm 33 is pressed is shortened, and the valve opening period of the intake bubble 28 is shortened.
[0040]
In the variable valve lift mechanism 30 described above, if the control shaft 35 is rotated by the motor 41 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 continuously moved, For example, as shown in FIG. 3, the maximum lift amount and the valve opening period (hereinafter simply referred to as “lift amount”) of the intake valves 28 of all the cylinders (# 1 to # 4) of the in-line four-cylinder engine 11 are continuously collected. Variable.
[0041]
The ECU 27 executes a variable valve control routine (not shown) stored in the ROM, thereby controlling the variable valve lift mechanism 30 of the intake valve 28 based on the accelerator opening, the engine operating state, etc. The amount of intake air is controlled by continuously changing the lift amount of 28. In the case of a system using both the variable valve lift mechanism 30 and the variable valve timing mechanism, the intake air amount may be controlled by continuously varying both the lift amount and the valve timing.
[0042]
At that time, the ECU 27 controls the variable valve lift mechanism 30 of the intake valve 28 as follows by executing each routine for variable valve control shown in FIGS. 4 to 9 described later.
[0043]
The ECU 27 calculates the intake air amount variation rate DEV between the cylinders based on the output of the air flow meter 14, and the variation in the actual intake air amount between the cylinders is reduced based on the intake air amount variation rate DEV between the cylinders. Thus, the target lift amount VVLM is set for each cylinder. Then, as shown in FIG. 12, every time the intake valves 28 of all the cylinders are closed (hereinafter referred to as “all intake valve closed periods”), the motor 41 of the variable valve lift mechanism 30 is changed to the following. By performing high-speed driving to a position corresponding to the target lift amount VVLM of the intake cylinder, “individual variable valve control” is performed in which the intake air amount is controlled for each cylinder to correct variations in intake air amount among the cylinders.
[0044]
In general, in the intake air amount control by the variable intake valve control, the smaller the lift amount of the intake valve 28, the larger the variation in the intake air amount between the cylinders, and the larger the change amount of the target lift amount VVLM between the cylinders. However, as the lift amount of the intake valve 28 becomes smaller, the valve opening period of the intake valve 28 becomes shorter and the entire intake valve closing period becomes longer. Therefore, the variable valve lift mechanism 30 of the variable valve lift mechanism 30 is within the entire intake valve closing period. It is possible to execute driving (lift variable operation to the target lift amount VVLM).
[0045]
Further, during execution of the variable valve control for each cylinder, the ECU 27 integrates the deviation between the actual lift amount of the intake valve 28 for each cylinder and the target lift amount VVLM to obtain the variable valve control accuracy value ACCURA for each cylinder. . In the present embodiment (1), the actual motor rotation angle of the variable valve lift mechanism 30 is used as substitute information for the actual lift amount of the intake valve 28 and the target lift amount VVLM when determining the variable valve control accuracy value ACCURA for each cylinder. VVLACT and target motor rotation angle TGVVLACT are used. When the cylinder-specific variable valve control accuracy value ACCURA exceeds a predetermined allowable range, it is determined that the cylinder-specific variable valve control accuracy (convergence of the actual lift amount with respect to the target lift amount) has deteriorated. Prohibit valve control. This prevents deterioration in lift amount variation (or intake air amount variation) between cylinders due to deterioration of variable valve control accuracy for each cylinder and lift amount variation (or intake air amount variation) between cycles of the same cylinder. To do.
[0046]
Further, while prohibiting the variable valve control for each cylinder, the ECU 27 limits the target lift amount TGVVL common to each cylinder set based on the accelerator opening, the engine operating state, and the like to a predetermined lower limit lift amount VVLmin or more. Lift amount limit mode variable valve control is performed to control the motor 41 of the valve lift mechanism 30 to a position corresponding to the target lift amount TGVVL common to each cylinder. In this case, by limiting the target lift amount TGVVL to the lower limit lift amount VVLmin or more, the ratio of the variation of the actual lift amount to the target lift amount TGVVL (the variation due to the component tolerance or assembly tolerance of each cylinder) is set to a predetermined tolerance. By suppressing the amount to less than (for example, 5%), it is possible to suppress variation in intake air amount between cylinders within an allowable range in which drivability and exhaust emission do not deteriorate.
[0047]
Further, when a predetermined return condition is satisfied while the cylinder-by-cylinder variable valve control is prohibited, the ECU 27 determines that the cylinder-by-cylinder variable valve control accuracy has been recovered and restarts the cylinder-by-cylinder variable valve control.
[0048]
The processing contents of the routines for variable valve control shown in FIGS. 4 to 9 executed by the ECU 27 will be described below.
[0049]
[Variable valve control execution / prohibition routine for each cylinder]
The variable valve control execution / prohibition routine for each cylinder in FIG. 4 is executed at a predetermined cycle after, for example, an ignition switch (not shown) is turned on. When this routine is started, first, in step 101, the set state (ON / OFF) of the cylinder specific variable valve control prohibition flag XSTOP is read. The cylinder-by-cylinder variable valve control prohibition flag XSTOP is set to “ON” when a cylinder-by-cylinder variable valve control prohibition determination routine in FIG.
[0050]
Thereafter, the routine proceeds to step 102, where it is determined whether or not the prohibition condition for the cylinder-by-cylinder variable valve control is satisfied, depending on whether or not the cylinder-by-cylinder variable valve control prohibition flag XSTOP is “ON”. As a result, if it is determined that the prohibition condition for the cylinder-by-cylinder variable valve control is not established, the routine proceeds to step 110 where a cylinder-by-cylinder variable valve control routine of FIG. Execute.
[0051]
On the other hand, if it is determined in step 102 that the cylinder-by-cylinder variable valve control prohibition condition is satisfied, the process proceeds to step 103 while the cylinder-by-cylinder variable valve control is prohibited, and the cylinder-by-cylinder variable valve control return flag is set. Read the set state (ON / OFF) of XREACT. The cylinder-by-cylinder variable valve control return flag XREACT is set to “ON” when a return condition for the cylinder-by-cylinder variable valve control is established by a cylinder-by-cylinder variable valve control return determination routine of FIG.
[0052]
Thereafter, the routine proceeds to step 104, where it is determined whether or not the return condition for the variable valve control for each cylinder is satisfied depending on whether or not the variable valve control return flag for each cylinder XREACT is “ON”. As a result, if it is determined that the return condition for the cylinder-by-cylinder variable valve control is satisfied, the routine proceeds to step 110, where a cylinder-by-cylinder variable valve control routine of FIG. To resume.
[0053]
On the other hand, if it is determined in step 102 that the cylinder-by-cylinder variable valve control prohibition condition is satisfied and it is determined in step 104 that the cylinder-by-cylinder variable valve control return condition is not satisfied, the cylinder While the separate variable valve control is prohibited, the processing related to the lift amount limiting mode variable valve control after Step 105 is executed as follows.
[0054]
First, in step 105, a lower limit lift amount VVLmin for limiting the target lift amount TGVVL common to each cylinder set based on the accelerator opening, the engine operating state, and the like is read. This lower limit lift amount VVLmin is a lower limit value of the target lift amount TGVVL that makes the ratio of the variation of the actual lift amount (the variation due to the component tolerance and assembly tolerance of each cylinder) to the target lift amount TGVVL equal to or less than a predetermined variation allowable value. For example, when the variation allowable value is 5% and the maximum variation of the actual lift amount is 50 μm, the lower limit lift amount VVLmin is set to 1 mm.
[0055]
Thereafter, the routine proceeds to step 106, where it is determined whether or not the target lift amount TGVVL common to each cylinder is smaller than the lower limit lift amount VVLmin. As a result, when it is determined that the target lift amount TGVVL common to each cylinder is equal to or greater than the lower limit lift amount VVLmin, the routine proceeds to step 107, and the target common to each cylinder set based on the accelerator opening, the engine operating state, and the like. The lift amount TGVVL is employed as it is (target lift amount TGVVL = TGVVL), and the motor 41 of the variable valve lift mechanism 30 is controlled to a position corresponding to the target lift amount TGVVL.
[0056]
On the other hand, if it is determined in step 106 that the target lift amount TGVVL common to each cylinder is smaller than the lower limit lift amount VVLmin, the routine proceeds to step 108, where the target lift amount TGVVL is guarded with the lower limit lift amount VVLmin. (Target lift amount TGVVL = VVLmin), the motor 41 of the variable valve lift mechanism 30 is controlled to a position corresponding to the target lift amount TGVVL (= VVLmin).
[0057]
By the processing of these steps 105 to 108, while the variable valve control for each cylinder is prohibited, the target lift amount TGVVL common to each cylinder is limited to the lower limit lift amount VVLmin or more, and the motor 41 of the variable valve lift mechanism 30 is set to each cylinder. Lift amount limit mode variable valve control is performed to control to a position corresponding to the common target lift amount TGVVL. The processing in these steps 105 to 108 serves as a lift amount limiting mode variable valve control means in the claims.
[0058]
If the target lift amount TGVVL is guarded at the lower limit lift amount VVLmin in step 108, the routine proceeds to step 109, where the throttle valve 15 is controlled based on the accelerator opening, engine operating condition, etc., and the intake air amount is reduced. Control. The processing in step 109 serves as throttle control means in the claims.
[0059]
[Cylinder-specific variable valve control prohibition determination routine]
The cylinder-by-cylinder variable valve control prohibition determination routine of FIG. 5 is executed at a predetermined cycle after the ignition switch is turned on, for example. When this routine is started, first, at step 201, it is determined whether or not the variable valve control for each cylinder is being executed. If the variable valve control for each cylinder is not being executed, this routine is ended as it is.
[0060]
On the other hand, if it is determined that the variable valve control for each cylinder is being executed, the routine proceeds to step 202, where the variable variable valve control accuracy value calculation routine for each cylinder shown in FIG. The valve control accuracy value ACCURA (#i) is calculated. Here, (#i) is a cylinder number and means any one of (# 1) to (# 4).
[0061]
Thereafter, the routine proceeds to step 203, where whether or not the cylinder-by-cylinder variable valve control prohibition condition is satisfied, whether at least one of the cylinder-by-cylinder variable valve control accuracy values ACCURA (#i) is greater than a predetermined determination value. Judgment is made based on whether or not the value of the
[0062]
This determination value is a value for setting the upper limit value of the permissible range of the variable valve control accuracy value ACCURA (#i) for each cylinder, and the permissible range of the variable valve control accuracy value ACCURA (#i) for each cylinder is the rotation of the engine 11. The determination value is set so that the speed fluctuation or the combustion pressure fluctuation falls within a predetermined value.
[0063]
If it is determined in step 203 that the cylinder-by-cylinder variable valve control prohibition condition is not satisfied, that is, it is determined that all cylinder-by-cylinder variable valve control accuracy values ACCURA (#i) are less than or equal to the determination value. In this case, it is determined that the cylinder-by-cylinder variable valve control is being performed with high accuracy, and this routine is immediately terminated.
[0064]
On the other hand, when the prohibition condition for the variable valve control for each cylinder is satisfied, that is, it is determined that at least one of the cylinder-specific variable valve control accuracy values ACCURA (#i) of each cylinder is larger than the determination value. In this case, it is determined that the variable valve control accuracy value ACCURA (#i) for each cylinder exceeds the allowable range and the rotational speed fluctuation or the combustion pressure fluctuation has deteriorated beyond the allowable level. The valve control prohibition flag XSTOP is set to “ON”. Thereby, it is determined as “Yes” in step 102 of FIG. 4 and the cylinder-by-cylinder variable valve control is prohibited. This function plays a role as cylinder-by-cylinder variable valve control prohibiting means in the claims.
[0065]
Thereafter, the routine proceeds to step 205, where the cylinder specific variable valve control return flag XREACT is reset to "OFF", and this routine ends.
[0066]
[Cylinder-specific variable valve control accuracy value calculation routine]
The variable valve control accuracy value calculation routine for each cylinder in FIG. 6 is started in step 202 in FIG. 5 and serves as control accuracy calculation means in the claims. When this routine is started, first, in step 301, the actual motor rotation angle VVLACT of the variable valve lift mechanism 30 detected by the motor rotation angle sensor 44 is read.
[0067]
Thereafter, the process proceeds to step 302, and a target motor rotation angle TGVVLACT (a rotation angle corresponding to a cylinder-specific target lift amount VVLM described later) of the variable valve lift mechanism 30 is read.
[0068]
Thereafter, the process proceeds to step 303, and the count value of the crank angle counter CCRNK is read. Since the crank angle counter CCRNK is incremented by “1” every 30 ° C. A, for example, 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). . The crank angle counter CCRNK is reset to “0” when it reaches “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 counters CCRNK = 6, 12, 18 are respectively It is set so as to correspond to the compression TDC of the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2.
[0069]
Thereafter, the process proceeds to step 304, and the cylinder-by-cylinder variable valve control accuracy value ACCURA (#i) of each cylinder is calculated.
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 actual motor rotation angle VVLACT detected at one point or a plurality of points in the period and the target motor rotation By integrating the deviation from the angle TGVVLACT, the integrated value of the deviation between the actual motor rotation angle VVLACT of the intake stroke of the first cylinder # 1 and the target motor rotation angle TGVVLACT is updated, and the integrated value is updated for the first cylinder # 1. The cylinder-specific variable valve control accuracy value ACCURA (# 1) is used.
[0070]
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 actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT detected at one point or a plurality of points in the period And the integrated value of the deviation between the actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT in the intake stroke of the second cylinder # 2 is updated, and the integrated value is variable for each cylinder of the second cylinder # 2. The valve control accuracy value is ACCURA (# 2).
[0071]
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 actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT detected at one point or a plurality of points in the period And the integrated value of the deviation between the actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT in the intake stroke of the third cylinder # 3 is updated, and the integrated value is variable for each cylinder of the third cylinder # 3. The valve control accuracy value is ACCURA (# 3).
[0072]
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 actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT detected at one point or a plurality of points in the period And the integrated value of the deviation between the actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT in the intake stroke of the fourth cylinder # 4 is updated, and the integrated value is variable for each cylinder of the fourth cylinder # 4. The valve control accuracy value is ACCURA (# 4).
[0073]
[Variable valve control return judgment routine for each cylinder]
The cylinder-by-cylinder variable valve control return determination routine of FIG. 7 is executed at a predetermined cycle after the ignition switch is turned on, for example. When this routine is started, first, at step 401, it is determined whether or not the fuel is being cut or decelerated. If the fuel is not being cut or decelerated, this routine is terminated.
[0074]
On the other hand, if it is determined that the fuel is being cut or decelerated, the routine proceeds to step 402 where a cylinder-by-cylinder variable valve control routine of FIG. To try variable valve control for each cylinder. The processing in step 402 serves as trial means in the claims.
[0075]
Thereafter, the routine proceeds to step 403, where the above-mentioned variable variable valve control accuracy value calculation routine for each cylinder shown in FIG. 6 is executed to calculate the variable variable valve control accuracy value ACCURA (#i) for each cylinder.
[0076]
Thereafter, the process proceeds to step 404, where it is determined whether or not a return condition for the variable valve control for each cylinder is satisfied. Here, the return condition of the variable valve control for each cylinder is, for example, that both of the following two conditions (1) and (2) are satisfied.
[0077]
(1) The variable valve control accuracy value ACCURA (#i) for each cylinder is less than the judgment value.
(2) The battery voltage is higher than a predetermined voltage (for example, 12V)
If both of these two conditions (1) and (2) are satisfied, the return condition for the variable valve control for each cylinder is established, but if either condition is not satisfied, the return condition for the variable valve control for each cylinder is Not established.
[0078]
If it is determined that the return condition of the variable valve control for each cylinder is not satisfied, it is determined that the accuracy of the variable valve control for each cylinder has not been recovered, and the process proceeds to step 405 where the cylinder-specific variable valve control return flag XREACT is set to “OFF”. This routine is terminated while resetting to "."
[0079]
On the other hand, if it is determined in step 404 that the return condition for the variable valve control for each cylinder is satisfied, it is determined that the accuracy for the variable valve control for each cylinder has been recovered, and the process proceeds to step 406 to change the variable for each cylinder. The valve control return flag XREACT is set to “ON”. Thereby, it is determined as “Yes” in Step 104 of FIG. 4 and the cylinder-by-cylinder variable valve control is resumed. This function serves as a return control means in the claims.
Thereafter, the process proceeds to step 407, the cylinder-by-cylinder variable valve control prohibition flag XREACT is reset to “OFF”, and this routine is terminated.
[0080]
[Variable valve control routine for each cylinder]
When the cylinder-by-cylinder variable valve control routine of FIG. 8 is started in step 110 of FIG. 4, first, in step 501, it is determined whether or not the cylinder-by-cylinder variable valve control execution condition is satisfied. Here, the cylinder-by-cylinder variable valve control execution condition is, for example, that both of the following two conditions (1) and (2) are satisfied.
(1) More than a predetermined time has passed after starting (that is, not in an unstable driving state immediately after starting)
(2) Not in a transient operation state (that is, in a steady operation state)
[0081]
If both of these two conditions (1) and (2) are satisfied, the cylinder-by-cylinder variable valve control execution condition is satisfied, but if either condition is not satisfied, the cylinder-by-cylinder variable valve control execution condition is not satisfied. Become. If it is determined that the cylinder-by-cylinder variable valve control execution condition is not satisfied, the routine is terminated without executing the processing related to the cylinder-by-cylinder variable valve control after step 502.
[0082]
On the other hand, when it is determined in step 501 that the cylinder-by-cylinder variable valve control execution condition is satisfied, the processing related to cylinder-by-cylinder variable valve control in step 502 and subsequent steps is executed as follows. First, in step 502, an inter-cylinder intake air amount variation rate calculation routine of FIG. 9 described later is executed to calculate an inter-cylinder intake air amount variation rate DEV (#i) of each cylinder.
[0083]
Thereafter, the process proceeds to step 503, where the lift correction amount FVVL (#i) corresponding to the inter-cylinder intake air amount variation rate DEV (#i) is calculated for each cylinder using the map of FIG. The map of FIG. 10 shows that in a region where the inter-cylinder intake air amount variation rate DEV (#i) is greater than 1, the lift correction amount FVVL (#i) is a reduced value (minus value), and the inter-cylinder intake air amount variation rate. In a region where DEV (#i) is smaller than 1, the lift correction amount FVVL (#i) becomes an increase value (plus value). That is, as the intake air amount of a certain cylinder becomes larger than the average intake air amount of all the cylinders, the reduction correction amount by the lift correction amount FVVL (#i) becomes larger. As the average intake air amount becomes smaller, the increase correction amount based on the lift correction amount FVVL (#i) becomes larger, and the variation in the actual intake air amount between the cylinders becomes smaller. Note that when the inter-cylinder intake air amount variation rate DEV (#i) is in a predetermined region near 1, the lift correction amount FVVL (#i) = 0 is set, and the intake valve lift amount VVL is not corrected.
[0084]
After calculating the lift correction amount FVVL (#i), the routine proceeds to step 504, where it is determined whether the intake valves 28 of all the cylinders are closed, and it is determined that at least one intake valve 28 is open. If so, this routine is terminated.
[0085]
Thereafter, when it is determined in step 504 that the intake valves 28 of all the cylinders are closed, the process proceeds to step 505, and the lift correction amount FVVL of the next intake cylinder is added to the average lift amount VVL of all cylinders before correction. (#i) is added to obtain the cylinder target lift amount VVLM.
[0086]
When the next intake cylinder is the first cylinder # 1 (that is, before the intake stroke of the first cylinder # 1), the lift correction amount FVVL (# 1) of the first cylinder # 1 is set to the average lift amount VVL of all the cylinders. Addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 1)
[0087]
When the next intake cylinder is the second cylinder # 2 (that is, before the intake stroke of the second cylinder # 2), the lift correction amount FVVL (# 2) of the second cylinder # 2 is set to the average lift amount VVL of all the cylinders. Addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 2)
[0088]
When the next intake cylinder is the third cylinder # 3 (that is, before the intake stroke of the third cylinder # 3), the lift correction amount FVVL (# 3) of the third cylinder # 3 is set to the average lift amount VVL of all the cylinders. Addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 3)
[0089]
When the next intake cylinder is the fourth cylinder # 4 (that is, before the intake stroke of the fourth cylinder # 4), the lift correction amount FVVL (# 4) of the fourth cylinder # 4 is set to the average lift amount VVL of all the cylinders. Addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 4)
[0090]
In this way, every time the intake valve closing period in which the intake valves 28 of all the cylinders are closed, the lift correction amount FVVL (#i) of the next intake cylinder is used to determine the next intake cylinder. A target lift amount VVLM is set. The processing in step 505 serves as a cylinder-specific target valve variable amount setting means in the claims.
[0091]
Thereafter, the process proceeds to step 506, and every time the all intake valve closing period is reached, the motor 41 of the variable valve lift mechanism 30 is driven at a high speed in accordance with the cylinder specific target lift amount VVLM, and within the all intake valve closing period. The variable valve lift mechanism 30 is driven to a position corresponding to the target lift amount VVLM of the next intake cylinder. As a result, before the opening timing of the intake valve 28 of each cylinder, the variable valve lift mechanism 30 is driven (lift variable operation to the target lift amount VVLM) to control the intake air amount for each cylinder. Correct the variation in intake air amount. The processing of step 506 serves as cylinder-by-cylinder variable valve control means in the claims.
[0092]
[Inter-cylinder intake air amount variation rate calculation routine]
When the routine for calculating the variation ratio between cylinders in FIG. 9 is started in step 502 in FIG. 8, first, in step 601, the instantaneous air flow rate GA detected by the air flow meter 14 is read, and then the process proceeds to step 602, where the crank angle The count value of the counter CCRNK is read.
[0093]
Thereafter, the process proceeds to step 603, and an intake air amount average value GAave (#i) of each cylinder is calculated.
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 average value of the instantaneous air flow rate GA during that period is determined as the intake air flow rate of the first cylinder # 1. The average value is GAave (# 1).
[0094]
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 average value of the instantaneous air flow rate GA during that period is used as the average value of the intake air flow rate of the second cylinder # 2. Let GAave (# 2).
[0095]
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 average value of the instantaneous air flow rate GA during that period is used as the average value of the intake air flow rate of the third cylinder # 3. Let GAave (# 3).
[0096]
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 average value of the instantaneous air flow rate GA during that period is used as the average value of the intake air flow rate of the fourth cylinder # 4. Let GAave (# 4).
Thereafter, in step 604, the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder is calculated by the following equation.
[0097]
[Expression 1]

[0098]
The denominator of the above equation is the average value of the intake air flow average values GAave (# 1) to GAave (# 4) of all cylinders.
In the inter-cylinder intake air amount variation rate calculation routine of FIG. 9, the inter-cylinder intake air amount variation rate DEV (#i) is calculated using the intake air flow rate average value GAave (#i) of each cylinder. The inter-cylinder intake air amount variation rate DEV (#i) may be calculated using the maximum intake air flow rate of the cylinder and the integrated intake air amount. In addition, the calculation period of the intake air flow rate average value of each cylinder may be appropriately changed in consideration of a time delay until the intake air pulsation generated according to the intake air amount of each cylinder is detected by the air flow meter 14. good.
[0099]
Further, the inter-cylinder intake air amount variation rate DEV (#i) may be calculated based on the output of the intake pipe pressure sensor 18. In addition, in a system equipped with an in-cylinder pressure sensor that detects the in-cylinder pressure of each cylinder and a lift sensor that detects the valve lift amount of each cylinder, the intake air amount variation between cylinders varies based on the output of the in-cylinder pressure sensor and the output of the lift sensor. The rate DEV (#i) may be calculated.
[0100]
An execution example of the embodiment (1) described above will be described with reference to time charts shown in FIGS. As shown in FIG. 11, the cylinder-by-cylinder variable valve control is executed while the cylinder-by-cylinder variable valve control accuracy value ACCURA (#i) is within the allowable range and the cylinder-by-cylinder variable valve control prohibition flag XSTOP is OFF. To control the intake air volume. In this variable valve control for each cylinder, the target lift amount VVLM of each cylinder is set based on the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder, and as shown in FIG. Each time, the motor 41 of the variable valve lift mechanism 30 is driven at a high speed to a position corresponding to the target lift amount VVLM of the next intake cylinder, whereby the intake air amount is controlled for each cylinder to vary the intake air amount between the cylinders. Correct.
[0101]
During the execution of the variable valve control for each cylinder, the deviation between the actual lift amount of the intake valve 28 of each cylinder and the target lift amount VVLM (deviation between the actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT of the intake stroke of each cylinder). ) To obtain a variable valve control accuracy value ACCURA (#i) for each cylinder.
[0102]
Thereafter, as shown in FIG. 13, the convergence of the actual lift amount with respect to the target lift amount VVLM of each cylinder is deteriorated due to a decrease in battery voltage or the like, and the cylinder-by-cylinder variable valve control accuracy is deteriorated. When the valve control accuracy value ACCURA (#i) exceeds the allowable range (t1 in FIG. 11), the cylinder-by-cylinder variable valve control prohibition flag XSTOP is turned on, and the cylinder-by-cylinder variable valve control is prohibited.
[0103]
As a result, the variation in lift amount (or variation in intake air amount) between cylinders due to the deterioration of the variable valve control accuracy for each cylinder, or the variation in lift amount (or variation in intake air amount) between cycles of the same cylinder. Deterioration can be prevented and adverse effects on drivability and exhaust emission can be avoided.
[0104]
Further, as shown in FIG. 11, while the variable valve control for each cylinder is prohibited, the intake air amount is controlled by the lift amount limiting mode variable valve control and the throttle valve control. In the lift amount limit mode variable valve control, the target lift amount TGVVL common to each cylinder is limited to a lower limit lift amount VVLmin (for example, 1 mm) or more, and the motor 41 of the variable valve lift mechanism 30 corresponds to the target lift amount TGVVL common to each cylinder. Control the position to be.
[0105]
If the target lift amount TGVVL is limited to the lower limit lift amount VVLmin or more, the ratio of the variation of the actual lift amount to the target lift amount TGVVL (variation due to component tolerance or assembly tolerance of each cylinder) is set to a predetermined tolerance (for example, 5%). ) It is possible to reduce the intake air amount variation between the cylinders within an allowable range by suppressing to the following. Therefore, if the variable valve control for lift amount restriction mode is executed while the variable valve control for each cylinder is prohibited, the variable valve control is performed while suppressing the variation in intake air amount between cylinders within the allowable range that does not deteriorate the drivability and exhaust emission. The intake air amount can be controlled by the control, and the fuel consumption can be reduced as compared with the case where the intake air amount control is performed only by the throttle valve control while the cylinder-by-cylinder variable valve control is prohibited.
[0106]
In addition, when the target lift amount TGVVL is limited to the lower limit lift amount VVLmin or more by performing the lift amount limit mode variable valve control while the cylinder-by-cylinder variable valve control is prohibited, the intake air amount only by the intake valve control by the variable valve control is used. The lower limit side of the control area is limited, and the intake air amount cannot be controlled near the normal minimum air amount (the target air amount at the time of idling) at low loads such as idle, but the intake air amount control by throttle valve control is also used Thus, the lower limit side of the intake air amount control region can be expanded to the normal minimum air amount.
[0107]
Further, as shown in FIG. 11, the cylinder-by-cylinder variable valve control is tried at the time t2 when fuel cut (or deceleration) is started while the cylinder-by-cylinder variable valve control is prohibited. At the time t3 when the accuracy value ACCURA (#i) is within the allowable range and the battery voltage is determined to be equal to or higher than the predetermined value and the return condition is satisfied, the cylinder specific variable valve control return flag XREACT is turned ON and the cylinder variable valve control is performed. Is resumed.
[0108]
As a result, the cylinder-by-cylinder variable valve control can be restarted after actually confirming that the cylinder-by-cylinder variable valve control accuracy has been recovered. Moreover, since the variable valve control for each cylinder is tried during fuel cut or deceleration, even if the accuracy of the variable valve control for each cylinder has not recovered, there is an adverse effect on the drivability and the like due to the trial of variable valve control for each cylinder. Can be reduced.
[0109]
<< Embodiment (2) >>
In the embodiment (1), the variable valve control accuracy value ACCURA (#i) for each cylinder is obtained based on the deviation between the actual lift amount of the intake valve 28 of each cylinder and the target lift amount VVLM. In the embodiment (2) of the invention, the variable valve control accuracy value calculation routine for each cylinder shown in FIG. 14 is executed, so that the cylinder-by-cylinder for each cylinder is based on the cycle-to-cycle variation of the actual lift amount of each cylinder. The variable valve control accuracy value ACCURA (#i) is obtained. In this embodiment (2), the actual motor rotation angle VVLACT of the variable valve lift mechanism 30 is used as substitute information for the actual lift amount of the intake valve 28 when determining the cylinder-specific variable valve control accuracy value ACCURA (#i). Is used.
[0110]
In the variable valve control accuracy value calculation routine for each cylinder shown in FIG. 14 executed in this embodiment (2), first, in step 701, the actual motor rotation angle VVLACT of the variable valve lift mechanism 30 detected by the motor rotation angle sensor 44 is read. In the next step 702, the count value of the crank angle counter CCRNK is read.
[0111]
Thereafter, the process proceeds to step 703, and the nth (for example, 20th) stored value from the first stored value VVLACT (#i) (1) of the actual motor rotation angle detected for each cylinder for each intake stroke (cycle). Update VVLACT (#i) (n).
[0112]
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 actual motor rotation angle VVLACT detected at one point of the period is stored and the first From the first stored value VVLACT (# 1) (1) to the (n-1) th stored value VVLACT (# 1) (n-1) of the actual motor rotation angle of the intake stroke of the cylinder # 1, the second The stored value VVLACT (# 1) (2) is updated with the nth stored value VVLACT (# 1) (n), and the nth stored value VVLACT (# 1) (n) is updated with the current stored value VLACT. To do.
[0113]
Similarly, 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 first storage of the actual motor rotation angle of the intake stroke of the second cylinder # 2 is performed. The nth stored value VVLACT (# 2) (n) is updated from the value VVLACT (# 2) (1) and corresponds to the period of the crank angle counter CCRNK = 18 to 23 (that is, the intake stroke of the third cylinder # 3). Period), the first stored value VVLACT (# 3) (1) of the actual motor rotation angle of the intake stroke of the third cylinder # 3 is updated from the first stored value VVLACT (# 3) (n) to the crank During the period of the angle counter CCRNK = 0 to 5 (that is, the period corresponding to the intake stroke of the fourth cylinder # 4), the first stored value VVLACT (# 4) of the actual motor rotation angle of the intake stroke of the fourth cylinder # 4 The nth stored value VVLACT (# 4) (n) is updated from (1).
[0114]
Thereafter, the process proceeds to step 704, where the first stored value VVLACT (#i) (1) of the actual motor rotation angle detected for each intake stroke (cycle) of each cylinder is changed to the nth stored value VVLACT (#i). The degree of variation (for example, standard deviation) of (n) is calculated, and is set as a cylinder-specific variable valve control accuracy value ACCURA (#i).
[0115]
In the present embodiment (2) described above, the cylinder-specific variable valve control accuracy value ACCURA is calculated based on the cycle-to-cycle variation of the actual lift amount (actual motor rotation angle VVLACT) of the intake valve 28 of each cylinder. As the variable valve control accuracy for each cylinder, the cycle-to-cycle variation (repetition accuracy) of the actual lift amount of the intake valve 28 of each cylinder can be evaluated, and when the cycle-to-cycle variation of the actual lift amount of the intake valve 28 deteriorates Therefore, the variable valve control for each cylinder can be prohibited.
[0116]
<< Embodiment (3) >>
In the embodiment (3) of the present invention, by executing the variable valve control accuracy value calculation routine for each cylinder shown in FIG. 15, the motor drive time TACT (see FIGS. 12 and 13) of the variable valve lift mechanism 30 is changed between cycles. The cylinder-by-cylinder variable valve control accuracy value ACCURA (#i) of each cylinder is obtained based on the variation.
[0117]
In the variable valve control accuracy value calculation routine for each cylinder shown in FIG. 15 executed in the present embodiment (3), first, in step 801, the motor 41 of the variable valve lift mechanism 30 is changed to the following based on the output of the motor rotation angle sensor 44. A motor drive time TACT required to drive to a position corresponding to the target lift amount VVLM of the intake cylinder is detected.
[0118]
Thereafter, the process proceeds to step 802, and the nth (for example, the 20th) storage from the first stored value TACT (#i) (1) of the motor driving time detected every time the intake stroke is reached for each cylinder (each cycle). Update the value TACT (#i) (n).
[0119]
In this case, when the next intake cylinder is the first cylinder # 1, the first stored value TACT (# 1) (1) of the motor drive time before the intake stroke of the first cylinder # 1 is (n-1). The nth stored value TACT (# 1) (n-1) is updated with the nth stored value TACT (# 1) (n) from the second stored value TACT (# 1) (2), respectively. Stored value TACT (# 1) (n) is updated with the current stored value TACT.
[0120]
Similarly, when the next intake cylinder is the second cylinder # 2, the first stored value TACT (# 2) (1) of the motor drive time before the intake stroke of the second cylinder # 2 is changed to the nth. When the stored value TACT (# 2) (n) is updated and the next intake cylinder is the third cylinder # 3, the first stored value TACT (# of the motor drive time before the intake stroke of the third cylinder # 3 is stored. 3) The nth stored value TACT (# 3) (n) is updated from (1), and when the next intake cylinder is the fourth cylinder # 4, the motor drive time before the intake stroke of the fourth cylinder # 4 The nth stored value TACT (# 4) (n) is updated from the first stored value TACT (# 4) (1).
[0121]
Thereafter, the process proceeds to step 803, and the nth stored value TACT (#i) from the first stored value TACT (#i) (1) of the motor driving time detected every time the intake stroke of each cylinder is reached (each cycle). ) (n) variation degree (for example, standard deviation) is calculated and used as a cylinder specific variable valve control accuracy value ACCURA (#i).
[0122]
In the embodiment (3) described above, the cylinder-by-cylinder variable valve control accuracy value ACCURA is calculated based on the cycle-to-cycle variation of the motor drive time TACT of the variable valve lift mechanism 30. Therefore, the cylinder-by-cylinder variable valve control accuracy is calculated. As described above, the cycle-to-cycle variation (repetition accuracy) of the motor drive time TACT of the variable valve lift mechanism 30 can be evaluated. Valve control can be prohibited.
[0123]
In each of the above embodiments (1) to (3), the variable valve control accuracy value ACCURA for each cylinder of each cylinder is calculated. However, one or more cylinders of all cylinders are classified by cylinder. The variable valve control accuracy value ACCURA may be calculated.
[0124]
In each of the above embodiments (1) to (3), the intake air amount control by the lift amount limit mode variable valve control and the intake air amount control by the throttle valve control are used in combination while the variable valve control for each cylinder is prohibited. However, only intake air amount control by throttle valve control may be performed.
[0125]
In each of the above embodiments (1) to (3), the cylinder-by-cylinder variable valve control is tried while the cylinder-by-cylinder variable valve control is prohibited, and the cylinder-by-cylinder variable valve control accuracy value ACCURA is within the allowable range. The return condition is satisfied when the battery voltage is determined to be equal to or higher than the predetermined voltage. However, the return condition may be satisfied when it is determined that the cylinder-specific variable valve control accuracy value ACCURA is within the allowable range. .
[0126]
Of course, the return condition may be satisfied when the battery voltage is determined to be equal to or higher than a predetermined value. When the variable valve control accuracy for each cylinder deteriorates due to a decrease in the battery voltage, the variable valve control accuracy for each cylinder recovers when the battery voltage recovers to the specified voltage or higher. If the condition is satisfied, the cylinder-by-cylinder variable valve control can be resumed when the cylinder-by-cylinder variable valve control accuracy is restored.
[0127]
The scope of application of the present invention is not limited to a variable valve control system that varies the lift amount of the intake valve, but is widely applicable to a variable valve control system that varies at least one of the lift amount, working angle, and valve timing of the intake valve. Can be applied. The present invention can also be applied to the exhaust valve.
[0128]
Furthermore, the present invention is not limited to a system that performs variable valve control for each cylinder based on intake air amount variation between cylinders, but is applied to a system that performs variable valve control for each cylinder based on valve variable amount variation between cylinders. May be.
[0129]
In addition, the present invention is not limited to an in-line engine, but can be applied to various multi-cylinder engines such as a V-type engine and a horizontally opposed engine, and it goes without saying that the number of cylinders may be changed as appropriate.
[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 valve lift characteristic diagram for explaining a continuously variable operation of a valve lift amount by a variable valve lift mechanism.
FIG. 4 is a flowchart showing the flow of processing of a variable valve control execution / prohibition routine for each cylinder in the embodiment (1).
FIG. 5 is a flowchart showing the flow of processing of a cylinder-by-cylinder variable valve control prohibition determination routine of the embodiment (1).
FIG. 6 is a flowchart showing a flow of processing of a variable valve control accuracy value calculation routine for each cylinder in the embodiment (1).
FIG. 7 is a flowchart showing a process flow of a variable valve control return determination routine for each cylinder according to the embodiment (1).
FIG. 8 is a flowchart showing a processing flow of a variable valve control routine for each cylinder according to the embodiment (1).
FIG. 9 is a flowchart showing a flow of processing of an inter-cylinder intake air amount variation rate calculation routine of the embodiment (1).
FIG. 10 is a diagram conceptually showing a map of a lift correction amount FVVL.
FIG. 11 is a time chart showing an execution example of variable valve control according to the embodiment (1).
FIG. 12 is a time chart showing an execution example of variable valve control for each cylinder when the variable valve control accuracy for each cylinder is normal.
FIG. 13 is a time chart showing an execution example of variable valve control for each cylinder when the accuracy of variable valve control for each cylinder is deteriorated.
FIG. 14 is a flowchart showing a flow of processing of a variable valve control accuracy value calculation routine for each cylinder in the embodiment (2).
FIG. 15 is a flowchart showing a process flow of a variable valve control accuracy value calculation routine for each cylinder in the embodiment (3).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 26 ... Crank angle sensor, 27 ... ECU (cylinder) Variation variation calculation means, cylinder-specific target valve variable amount setting means, cylinder-specific variable valve control means, control accuracy calculation means, cylinder-specific variable valve control prohibition means, lift amount limit mode variable valve control means, throttle control means, return control means , Trial means), 28 ... intake valve, 29 ... exhaust valve, 30, 31 ... variable valve lift mechanism (variable valve mechanism), 41 ... motor, 44 ... motor rotation angle sensor.

Claims (10)

In a variable valve control device for an internal combustion engine that controls a variable amount of intake valves or exhaust valves (hereinafter simply referred to as “valves”) of a plurality of cylinders of the internal combustion engine collectively with a single variable valve mechanism,
Inter-cylinder variation calculating means for calculating information on variation in actual valve variable amount or actual intake air amount between cylinders (hereinafter referred to as “inter-cylinder variation information”);
Cylinder target valve variable amount setting means for setting a target valve variable amount for each cylinder in consideration of the inter-cylinder variation information;
Cylinder variable valve control for performing cylinder-by-cylinder variable valve control for controlling the valve variable amount for each cylinder by driving the variable valve mechanism to a position corresponding to the target valve variable amount of the cylinder in which the valve is opened next at predetermined timing. Means,
Control accuracy calculation means for calculating a cylinder-specific variable valve control accuracy value representing the control accuracy of the cylinder-specific variable valve control;
An internal combustion engine comprising: a cylinder-by-cylinder variable valve control prohibiting unit that prohibits the cylinder-by-cylinder variable valve control when the cylinder-by-cylinder variable valve control accuracy value deteriorates beyond a predetermined allowable range. Variable valve control device. The said control accuracy calculation means calculates the said variable valve control accuracy value according to said cylinder based on the deviation of the actual valve variable amount and target valve variable amount of each cylinder or a predetermined cylinder. A variable valve control device for an internal combustion engine. 2. The variable internal combustion engine according to claim 1, wherein the control accuracy calculation means calculates the variable valve control accuracy value for each cylinder based on a cycle-to-cycle variation of an actual valve variable amount of each cylinder or a predetermined cylinder. Valve control device. 2. The variable valve control for an internal combustion engine according to claim 1, wherein the control accuracy calculation unit calculates the variable valve control control value for each cylinder based on a cycle-to-cycle variation of the driving time of the variable valve mechanism. apparatus. The permissible range of the cylinder-by-cylinder variable valve control accuracy value is set to a range in which the rotational speed fluctuation or the combustion pressure fluctuation of the internal combustion engine becomes a predetermined value or less. Variable valve control device for internal combustion engine. While the variable valve control for each cylinder is prohibited, the target valve lift amount common to each cylinder is limited to a predetermined value or more, and the variable valve mechanism is controlled to a position corresponding to the target valve variable amount common to each cylinder. 6. The variable valve control device for an internal combustion engine according to claim 1, further comprising lift amount limiting mode variable valve control means for performing mode variable valve control. Applied to a system for controlling the variable valve mechanism to control the amount of intake air;
The internal combustion engine according to any one of claims 1 to 6, further comprising throttle control means for controlling an intake air amount by controlling a throttle valve of the internal combustion engine while the variable valve control for each cylinder is prohibited. Variable valve control device for engine. 8. A return control means for returning the variable valve control for each cylinder when a predetermined return condition is satisfied while the variable valve control for each cylinder is prohibited. Variable valve control device for internal combustion engine. When the battery voltage for driving the variable valve mechanism is lower than a predetermined value while the variable valve control for each cylinder is prohibited, the return condition is satisfied when the battery voltage recovers to a predetermined voltage or higher. The variable valve control device for an internal combustion engine according to claim 8. Trial means for temporarily trying the variable valve control for each cylinder during fuel cut or deceleration during prohibition of the variable valve control for each cylinder;
10. The return condition is satisfied when the cylinder-by-cylinder variable valve control accuracy value when the cylinder-by-cylinder variable valve control is temporarily tried is restored within a predetermined allowable range. A variable valve control device for an internal combustion engine according to claim 1.

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