JP2004204689A - Variable valve control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely correct deviation in real intake air volumes between cylinders when batchedly controlling valve lift amounts of a plurality of cylinders by a single variable valve mechanism. <P>SOLUTION: A target lift amount VVLM is set for every cylinder so as to reduce the deviation in the real intake air volumes between the cylinders and a drive start timing Tstart (#i) is so calculated that an intermediate timing of a drive period (or a drive quantity) of the variable valve lift mechanism necessary for driving the variable valve lift mechanism to a position corresponding to a target lift amount VVLM of the next intake cylinder agrees with an intermediate timing Tcentr (#i) of a whole intake valve closed period when intake valves of the whole cylinders are closed. Whenever becoming the drive start timing Tstart (#i), the variable valve lift mechanism is driven to a position corresponding to the target lift amount VVLM of the next intake cylinder and the variable valve lift mechanism is driven for the whole intake valve closed period or in a period overlapping with the period so as to control the intake air volume for every cylinder. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００６４】
上式の分母は、全気筒の筒内圧ピーク値ＣＰＳpeak(#1)〜ＣＰＳpeak(#4)の平均値である。
尚、図６の気筒間吸入空気量ばらつき率算出ルーチンでは、各気筒の筒内圧ピーク値ＣＰＳpeak(#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、各気筒の筒内圧平均値又は筒内圧面積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。或は、各気筒の筒内圧に基づいて算出した図示平均有効圧やポンピングロス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。
【００６５】
［バルブ開閉状態検出ルーチン］
図４のステップ１０４で起動される図７に示すバルブ開閉状態検出ルーチンは、特許請求の範囲でいうバルブ開閉状態検出手段としての役割を果たす。本ルーチンが起動されると、まず、ステップ３０１で、各気筒のリフトセンサ４５で検出した吸気バルブ２８のリフト量ＶＬＩＦＴを読み込んだ後、ステップ３０２に進み、全気筒の吸気バルブ２８のリフト量ＶＬＩＦＴが「０」であるか否かを判定する。尚、１つの気筒のみにリフトセンサ４５が設けられている場合には、その１つの気筒のリフトセンサ４５の出力がリフト量「０」になるクランク角から全気筒の吸気バルブ２８のリフト量ＶＬＩＦＴが「０」となるクランク角を推定して、現在のクランク角が全気筒の吸気バルブ２８のリフト量ＶＬＩＦＴが「０」となるクランク角であるか否かを判定するようにしても良い。
【００６６】
その結果、全気筒の吸気バルブ２８のリフト量ＶＬＩＦＴが「０」であると判定された場合には、ステップ３０３に進み、バルブ開閉状態フラグＸＬＩＦＴ０を、全気筒の吸気バルブ２８が閉弁していることを意味する「ＯＮ」にセットする。
【００６７】
一方、少なくとも１つの吸気バルブ２８のリフト量ＶＬＩＦＴが「０」でないと判定された場合には、ステップ３０４に進み、バルブ開閉状態フラグＸＬＩＦＴ０を、少なくとも１つの吸気バルブ２８が開弁していることを意味する「ＯＦＦ」にリセットする。
【００６８】
［駆動開始時期算出ルーチン］
図４のステップ１０５で起動される図８に示す駆動開始時期算出ルーチンは、特許請求の範囲でいう駆動タイミング算出手段としての役割を果たす。本ルーチンが起動されると、まず、ステップ４０１で、現在の吸気気筒の吸気バルブ２８が閉弁されたか否かを、バルブ開閉状態フラグＸＬＩＦＴ０が「ＯＦＦ」から「ＯＮ」に切り換わったか否かによって判定し、吸気バルブ２８が閉弁されたと判定された時点で、ステップ４０２に進み、そのときのクランク角を吸気バルブ２８の閉弁時期Ｔclose(#i) としてＥＣＵ２７のメモリに記憶する。
【００６９】
この後、ステップ４０３に進み、次の吸気気筒の吸気バルブ２８が開弁されたか否かを、バルブ開閉状態フラグＸＬＩＦＴ０が「ＯＮ」から「ＯＦＦ」に切り換わったか否かによって判定し、吸気バルブ２８の開弁されたと判定された時点で、ステップ４０４に進み、そのときのクランク角を吸気バルブ２８の開弁時期Ｔopen(#i)としてＥＣＵ２７のメモリに記憶する。
【００７０】
この後、ステップ４０５に進み、吸気バルブ２８の閉弁時期Ｔclose(#i) と開弁時期Ｔopen(#i)を用いて、全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)を次式により算出する。
Ｔcenter(#i)＝｛Ｔclose(#i) ＋Ｔopen(#i)｝／２
【００７１】
この後、ステップ４０６に進み、可変バルブリフト機構３０の５０％駆動応答時間ＴＭＯＴＯＲ(#i)を算出する。この５０％駆動応答時間ＴＭＯＴＯＲ(#i)は、可変バルブリフト機構３０をそれまでの吸気気筒の目標リフト量ＶＶＬＭに相当する位置から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必要な駆動量の５０％だけ可変バルブリフト機構３０を駆動するのに必要な時間であり、クランク角に換算して求められる。
【００７２】
可変バルブリフト機構３０をそれまでの吸気気筒の目標リフト量ＶＶＬＭに相当する位置から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際の目標リフト量ＶＶＬＭの差ΔＶＶＬＭ、つまりリフト補正量ＦＶＶＬ(#i)の差ΔＦＶＶＬに応じて可変バルブリフト機構３０の５０％駆動応答時間ＴＭＯＴＯＲ(#i)が変化するため、このステップ４０６では、図９のマップを用いて、各気筒のリフト補正量ＦＶＶＬ(#i)の差ΔＦＶＶＬに応じて可変バルブリフト機構３０の５０％駆動応答時間ＴＭＯＴＯＲ(#i)を算出する。
【００７３】
一般に、可変バルブリフト機構３０の駆動量が大きくなるほど駆動期間が長くなるため、図９のマップは、リフト補正量の差ΔＦＶＶＬ（＝目標リフト量の差ΔＶＶＬＭ）の絶対値が大きくなるほど、５０％駆動応答時間ＴＭＯＴＯＲ(#i)が長くなるように設定されている。更に、目標リフト量ＶＶＬＭを大きくするときよりも小さくするときの方が、可変バルブリフト機構３０の駆動トルクが小さくなって駆動期間が短くなる傾向があるため、図９のマップは、リフト補正量の差ΔＦＶＶＬの絶対値が同じであれば、リフト補正量の差ΔＦＶＶＬ（＝目標リフト量の差ΔＶＶＬＭ）がプラス値のときよりもマイナス値のときの方が、５０％駆動応答時間ＴＭＯＴＯＲ(#i)が短くなるように設定されている。
【００７４】
可変バルブリフト機構３０を第２気筒＃２の目標リフト量ＶＶＬＭに相当する位置から第１気筒＃１の目標リフト量ＶＶＬＭに相当する位置まで駆動する際の５０％駆動応答時間ＴＭＯＴＯＲ(#1)を算出する場合は、第１気筒＃１のリフト補正量ＦＶＶＬ(#1)と第２気筒＃２のリフト補正量ＦＶＶＬ(#2)との差ΔＦＶＶＬに応じた５０％駆動応答時間ＴＭＯＴＯＲ(#1)を算出する。
【００７５】
可変バルブリフト機構３０を第４気筒＃４の目標リフト量ＶＶＬＭに相当する位置から第２気筒＃２の目標リフト量ＶＶＬＭに相当する位置まで駆動する際の５０％駆動応答時間ＴＭＯＴＯＲ(#2)を算出する場合は、第２気筒＃２のリフト補正量ＦＶＶＬ(#2)と第４気筒＃４のリフト補正量ＦＶＶＬ(#4)との差ΔＦＶＶＬに応じた５０％駆動応答時間ＴＭＯＴＯＲ(#2)を算出する。
【００７６】
可変バルブリフト機構３０を第１気筒＃１の目標リフト量ＶＶＬＭに相当する位置から第３気筒＃３の目標リフト量ＶＶＬＭに相当する位置まで駆動する際の５０％駆動応答時間ＴＭＯＴＯＲ(#3)を算出する場合は、第３気筒＃３のリフト補正量ＦＶＶＬ(#3)と第１気筒＃１のリフト補正量ＦＶＶＬ(#1)との差ΔＦＶＶＬに応じた５０％駆動応答時間ＴＭＯＴＯＲ(#3)を算出する。
【００７７】
可変バルブリフト機構３０を第３気筒＃３の目標リフト量ＶＶＬＭに相当する位置から第４気筒＃４の目標リフト量ＶＶＬＭに相当する位置まで駆動する際の５０％駆動応答時間ＴＭＯＴＯＲ(#4)を算出する場合は、第４気筒＃４のリフト補正量ＦＶＶＬ(#4)と第３気筒＃３のリフト補正量ＦＶＶＬ(#3)との差ΔＦＶＶＬに応じた５０％駆動応答時間ＴＭＯＴＯＲ(#4)を算出する。
【００７８】
以上のようにして可変バルブリフト機構３０の５０％駆動応答時間ＴＭＯＴＯＲ(#i)を算出した後、ステップ４０７に進み、全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)から５０％駆動応答時間ＴＭＯＴＯＲ(#i)を減算して駆動開始時期Ｔstart(#i) を求める。
Ｔstart(#i) ＝Ｔcenter(#i)−ＴＭＯＴＯＲ(#i)
【００７９】
これにより、可変バルブリフト機構３０の駆動期間の中間タイミングを全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)に一致させるように、可変バルブリフト機構３０の駆動開始時期Ｔstart(#i) を設定する。
【００８０】
尚、図８の駆動開始時期算出ルーチンでは、５０％駆動応答時間ＴＭＯＴＯＲ(#i)を用いて駆動開始時期Ｔstart(#i) を算出したが、５０％駆動応答時間ＴＭＯＴＯＲ(#i)に代えて、例えば９８％駆動応答時間の１／２の値を用いて駆動開始時期Ｔstart(#i) を算出するようにしても良い。或は、２５％駆動応答時間や７５％駆動応答時間を用いて駆動開始時期Ｔstart(#i) を算出するようにしても良い等、駆動開始時期Ｔstart(#i) の算出方法を適宜変更しても良く、要は、可変バルブリフト機構３０の駆動期間の中間タイミングが全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)に付近となるように、可変バルブリフト機構３０の駆動開始時期Ｔstart(#i) を算出すれば良い。
【００８１】
以上説明した本実施形態（１）の実行例を図１０及び図１１に示すタイムチャートを用いて説明する。図１０に示すように、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、１サイクル毎に筒内圧センサ４４の出力（筒内圧ＣＰＳ）に基づいて各気筒の気筒間吸入空気量ばらつき率ＤＥＶ(#i)を算出し、この気筒間吸入空気量ばらつき率ＤＥＶ(#i)に基づいて、気筒間の実吸入空気量のばらつきが小さくなるように各気筒のリフト補正量ＦＶＶＬ(#i)を算出する。
【００８２】
更に、図１１に示すように、それまでの吸気気筒と次の吸気気筒のリフト補正量の差ΔＦＶＶＬ（＝目標リフト量の差ΔＶＶＬＭ）に応じた５０％駆動応答時間ＴＭＯＴＯＲ(#i)を全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)から減算して駆動開始時期Ｔstart(#i) を求めることで、可変バルブリフト機構３０の駆動期間の中間タイミングを、全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)に一致させるように、駆動開始時期Ｔstart(#i) を設定すると共に、次の吸気気筒のリフト補正量ＦＶＶＬ(#i)を全気筒の平均リフト量ＶＶＬに加算して、次の吸気気筒の目標リフト量ＶＶＬＭを設定する。
【００８３】
そして、駆動開始時期Ｔstart(#i) になる毎に、気筒別目標リフト量ＶＶＬＭに応じて可変バルブリフト機構３０のモータ４１を高速駆動して、可変バルブリフト機構３０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。これにより、全吸気バルブ閉弁期間内か又はこの全吸気バルブ閉弁期間に跨がる期間内に、可変バルブリフト機構３０の駆動（目標リフト量ＶＶＬＭへのリフト可変動作）を終了して、吸入空気量を気筒別に制御し、気筒間の吸入空気量ばらつきを補正する。
【００８４】
以上説明した本実施形態（１）のように、可変バルブリフト機構３０の駆動期間の中間タイミングが全吸気バルブ閉弁期間の中間タイミングと一致するように制御すれば、可変バルブリフト機構３０の駆動期間が全吸気バルブ閉弁期間よりも短い場合には、全吸気バルブ閉弁期間内に可変バルブリフト機構３０の駆動を終了することができるので、可変バルブリフト機構３０の駆動途中で吸気バルブ２８が開弁する事態を確実に回避することができて、各気筒のバルブプロフィールが過渡状態となることを回避することができる。これにより、各気筒の実吸入空気量のばらつきを考慮して設定した目標リフト量ＶＶＬＭに対応した適正なバルブプロフィールで吸気バルブ２８を開くことができ、気筒別可変バルブ制御を精度良く行うことができる。
【００８５】
一方、可変バルブリフト機構３０の駆動期間が全吸気バルブ閉弁期間よりも長くなった場合には、全吸気バルブ閉弁期間に対する駆動期間の超過分（駆動期間と吸気バルブ２８の開弁期間とが重なり合う期間）を、全吸気バルブ閉弁期間の前後にほぼ均等に振り分けることができるので、可変バルブリフト機構３０の駆動期間と吸気バルブ２８の開弁期間とが重なり合う期間を半分に短縮することができて、吸気バルブ２８の開きがまだ小さい段階で可変バルブリフト機構３０の駆動を終了することができる（或は吸気バルブ２８の開きが小さくなってから可変バルブリフト機構３０の駆動が開始することができる）。これにより、本実施形態（１）では、可変バルブリフト機構３０の駆動期間が全吸気バルブ閉弁期間よりも長くなった場合でも、吸入空気量に与える影響を小さくすることができて、気筒別可変バルブ制御の制御精度の低下をほとんど無視できるか又は最小限に抑えることができる。
【００８６】
従って、本実施形態（１）の気筒別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精度良く補正することができ、気筒間のトルクばらつきや空燃比ばらつきを大幅に低減することができる。しかも、各気筒の部品公差や組付公差を小さくする必要がないので、低コスト化の要求を満たすことができる。
【００８７】
《実施形態（２）》
前記実施形態（１）では、筒内圧センサ４４で検出した筒内圧ＣＰＳ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たが、本発明の実施形態（２）では、図１２に示す気筒間吸入空気量ばらつき率算出ルーチンを実行することで、エアフローメータ１４で検出した瞬時空気流量ＧＡ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いる。
【００８８】
本実施形態（２）で実行する図１２の気筒間吸入空気量ばらつき率算出ルーチンでは、まず、ステップ５０１で、エアフローメータ１４で検出した瞬時空気流量ＧＡを読み込んだ後、ステップ５０２に進み、クランク角カウンタＣＣＲＮＫのカウント値を読み込む。
【００８９】
この後、ステップ５０３に進み、各気筒の吸入空気量平均値ＧＡave(#i) を算出する。
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、その期間の瞬時空気流量ＧＡの平均値を第１気筒＃１の吸入空気流量平均値ＧＡave(#1) とする。
【００９０】
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、その期間の瞬時空気流量ＧＡの平均値を、第２気筒＃２の吸入空気流量平均値ＧＡave(#2) とする。
【００９１】
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、その期間の瞬時空気流量ＧＡの平均値を、第３気筒＃３の吸入空気流量平均値ＧＡave(#3) とする。
【００９２】
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、その期間の瞬時空気流量ＧＡの平均値を、第４気筒＃４の吸入空気流量平均値ＧＡave(#4) とする。
この後、ステップ５０４で、各気筒の気筒間吸入空気量ばらつき率ＤＥＶ(#i)を次式により算出する。
【００９３】
【数２】

【００９４】
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。
以上説明した本実施形態（２）でも、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る。
【００９５】
尚、図１２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。
また、リフトセンサ４５や吸気管圧力センサ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。
【００９６】
《実施形態（３）》
前記実施形態（１）では、リフトセンサ４５で検出した吸気バルブ２８のリフト量ＶＬＩＦＴに基づいて吸気バルブ２８の開閉状態を検出したが、図１３及び図１４に示す本発明の実施形態（３）では、目標リフト量ＶＶＬＭに基づいて吸気バルブ２８の開閉状態を推定するようにしている。
【００９７】
本実施形態（３）で実行する図１３のバルブ開閉状態推定ルーチンでは、まず、ステップ６０１で、前記実施形態（１）で説明した図４のステップ１０７で算出した目標リフト量ＶＶＬＭを読み込んだ後、ステップ６０２に進み、図１４のマップを用いて、目標リフト量ＶＶＬＭに応じて全吸気バルブ閉弁期間（全気筒の吸気バルブ２８が閉弁しているクランク角範囲）を求める。
【００９８】
一般に、吸気バルブ２８のリフト量が小さくなるほど、全吸気バルブ閉弁期間が長くなるため、図１４のマップは、吸気バルブ２８の目標リフト量ＶＶＬＭが小さくなるほど、全吸気バルブ閉弁期間が長くなるように設定されている。図１４のマップは、予め、設計値、実験、シミュレーション等によって設定され、ＥＣＵ２７のＲＯＭに記憶されている。
【００９９】
この後、ステップ６０３に進み、現在のクランク角ＣＣＲＮＫが全吸気バルブ閉弁期間内であるか否かを判定する。その結果、現在のクランク角ＣＣＲＮＫが全吸気バルブ閉弁期間内であると判定された場合には、ステップ６０４に進み、バルブ開閉状態フラグＸＬＩＦＴ０を「ＯＮ」にセットする。
【０１００】
一方、現在のクランク角ＣＣＲＮＫが全吸気バルブ閉弁期間ではないと判定された場合には、ステップ６０５に進み、バルブ開閉状態フラグＸＬＩＦＴ０を「ＯＦＦ」にリセットする。
【０１０１】
以上説明した本実施形態（３）によれば、全気筒の吸気バルブ２８が閉弁している全吸気バルブ閉弁期間を推定して、バルブ開閉状態フラグＸＬＩＦＴ０をセット／リセットすることができるので、リフトセンサ４５を備えていないシステムにも適用することができる。
尚、目標リフト量ＶＶＬＭに基づいてマップ等により全吸気バルブ閉弁期間の中間タイミングＴcenter(#i)を直接推定するようにしても良い。
【０１０２】
《実施形態（４）》
次に、図１５及び図１６を用いて本発明の実施形態（４）を説明する。本実施形態（４）では、図１５に示す駆動開始時期算出ルーチンを実行することで、吸入空気量を気筒別に制御する気筒別可変バルブ制御の実行中に、気筒間の実吸入空気量のばらつきが小さくなるように、可変バルブリフト機構３０の駆動開始時期Ｔstart(#i) を補正するようにしている。
【０１０３】
尚、図１５に示す駆動開始時期算出ルーチンを実行する場合は、前記実施形態（１）で説明した図４のステップ１０３で各気筒のリフト補正量ＦＶＶＬ(#i)を算出したら、そのリフト補正量ＦＶＶＬ(#i)を所定期間（例えば、気筒間の吸入空気量ばらつきが最小であると判定されるまでの期間）だけ固定する。
【０１０４】
図１５に示す駆動開始時期算出ルーチンが起動されると、まず、ステップ７０１で、気筒間の吸入空気量ばらつきが最小であるか否かを、ばらつき最小フラグＸＤＥＶＭＩＮが、気筒間の吸入空気量ばらつきが最小であることを意味する「ＯＮ」にセットされているか否かによって判定する。その結果、気筒間の吸入空気量ばらつきが最小である（ＸＤＥＶＭＩＮ＝ＯＮ）と判定されれば、そのまま本ルーチンを終了する。
【０１０５】
一方、気筒間の吸入空気量ばらつきが最小ではない（ＸＤＥＶＭＩＮ＝ＯＦＦ）と判定された場合には、ステップ７０２に進み、前述した図６又は図１２の気筒間吸入空気量ばらつき率算出ルーチンで算出した気筒間吸入空気量ばらつき率ＤＥＶ(#i)を読み込んだ後、ステップ７０３に進み、前回も気筒間吸入空気量ばらつき率ＤＥＶ(#i)を読み込んだか否かを判定する。
【０１０６】
前回は気筒間吸入空気量ばらつき率ＤＥＶ(#i)を読み込んでいないと判定された場合、つまり、本ルーチンを最初に実行してから初めてステップ７０２、７０３の処理を行う場合は、ステップ７０３からステップ７０４に進み、駆動開始時期Ｔstart(#i) を初期値、例えば吸気気筒の吸気バルブ２８の閉弁時期Ｔclose(#i) に設定する。
【０１０７】
一方、上記ステップ７０３で、前回も気筒間吸入空気量ばらつき率ＤＥＶ(#i)を読み込んだと判定された場合、つまり、本ルーチンを２回以上起動してステップ７０２、７０３の処理を２回以上行った場合は、ステップ７０３からステップ７０５に進み、気筒間吸入空気量ばらつき率ＤＥＶ(#i)が前回よりも増加したか否かを判定する。
【０１０８】
その結果、気筒間吸入空気量ばらつき率ＤＥＶ(#i)が前回よりも減少したと判定された場合には、ステップ７０６に進み、駆動開始時期Ｔstart(#i) を所定クランク角（例えば１℃Ａ）だけ進角する。
Ｔstart(#i) ＝Ｔstart(#i) −１
【０１０９】
その後、ステップ７０５で、気筒間吸入空気量ばらつき率ＤＥＶ(#i)が前回よりも増加したと判定されたときに、ステップ７０７に進み、駆動開始時期Ｔstart(#i) を所定クランク角（例えば１℃Ａ）だけ遅角する。
Ｔstart(#i) ＝Ｔstart(#i) ＋１
【０１１０】
これにより、駆動開始時期Ｔstart(#i) を気筒間吸入空気量ばらつき率ＤＥＶ(#i)が最小となる最適時期に設定する。これらのステップ７０５〜７０７の処理が特許請求の範囲でいう駆動タイミング補正手段としての役割を果たす。
【０１１１】
この後、ステップ７０８に進み、気筒間吸入空気量ばらつき率ＤＥＶ(#i)が最小である判定して、ばらつき最小フラグＸＤＥＶＭＩＮを、気筒間の吸入空気量ばらつきが最小であることを意味する「ＯＮ」にセットした後、本ルーチンを終了する。
【０１１２】
以上説明した本実施形態（４）の実行例を図１６に示すタイムチャートを用いて説明する。図１６に示すように、気筒間ばらつき補正フラグがＯＮされて吸入空気量を気筒別に制御する気筒別可変バルブ制御を実行するときに、ばらつき最小フラグＸＤＥＶＭＩＮがＯＦＦされている期間は、気筒間吸入空気量ばらつき率ＤＥＶ(#i)が増加するまで駆動開始時期Ｔstart(#i) を、初期値である閉弁時期Ｔclose(#i) から所定クランク角（例えば１℃Ａ）ずつ進角する。その後、気筒間吸入空気量ばらつき率ＤＥＶ(#i)が増加したときに、前回の気筒間吸入空気量ばらつき率ＤＥＶ(#i)が最小であると判断して、駆動開始時期Ｔstart(#i) を所定クランク角（例えば１℃Ａ）だけ遅角して、駆動開始時期Ｔstart(#i) を気筒間吸入空気量ばらつき率ＤＥＶ(#i)が最小となる最適時期に設定し、ばらつき最小フラグＸＤＥＶＭＩＮをＯＮする。
【０１１３】
これにより、気筒別可変バルブ制御の実行中に、気筒間吸入空気量ばらつき率ＤＥＶ(#i)を監視しながら、可変バルブリフト機構３０の駆動開始時期Ｔstart(#i) を気筒間吸入空気量ばらつき率ＤＥＶ(#i)が最小になる最適時期に補正することができ、気筒間のトルクばらつきや空燃比ばらつきの補正精度を向上させることができる。
【０１１４】
《その他の実施形態》
上記各実施形態（１）〜（４）では、本発明を直列４気筒エンジンに適用したが、本発明を例えばＶ型エンジンに適用しても良い。一般に、Ｖ型エンジンでは、可変バルブリフト機構が各バンクの気筒群に対してそれぞれ設けられ、各可変バルブリフト機構がそれぞれ担当するバンクの吸気バルブのリフト量を一括して可変するように構成されている。図１７は、Ｖ型６気筒エンジンの例である。
【０１１５】
この場合、図１７に示すように、各可変バルブリフト機構が担当するバンクでは、各気筒の吸気バルブの開弁期間の間隔が広がって、そのバンクの全ての吸気バルブが閉弁している期間が同じ気筒数の直列エンジンと比べて長くなるため、本発明の気筒別可変バルブ制御を広い運転領域で精度良く実行することが可能となる。
【０１１６】
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、本発明の気筒別可変バルブ制御を適用して実施することができる。
【０１１７】
本発明の気筒別可変バルブ制御で、各気筒毎にリフト量、作用角、バルブタイミング等のバルブ可変量を変化させれば、各気筒毎に吸気流速、筒内圧、バルブオーバーラップ等を精度良く制御することが可能となり、気筒間の燃焼状態、ポンピングロス、内部ＥＧＲ量等のばらつきを精度良く補正することができ、気筒間のトルクばらつきや空燃比ばらつきを精度良く補正することができる。
【０１１８】
この場合、気筒間の実バルブ可変量のばらつきが小さくなるように各気筒の目標バルブ可変量を設定するようにしても良い。このようにすれば、気筒間の実バルブ可変量のばらつきを精度良く補正することができ、各気筒の燃焼状態、ポンピングロス、内部ＥＧＲ量等のばらつきを精度良く補正することができ、気筒間のトルクばらつきや空燃比ばらつきを精度良く補正することができる。
【０１１９】
その他、本発明は、直列エンジンとＶ型エンジンに限定されず、水平対向エンジン等、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５】リフト補正量ＦＶＶＬのマップを概念的に示す図
【図６】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７】実施形態（１）のバルブ開閉状態検出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）の駆動開始時期算出ルーチンの処理の流れを示すフローチャート
【図９】５０％駆動応答時間ＴＭＯＴＯＲのマップを概念的に示す図
【図１０】実施形態（１）の気筒間ばらつき補正の実行例を示すタイムチャート
【図１１】実施形態（１）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１２】実施形態（２）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１３】実施形態（３）のバルブ開閉状態推定ルーチンの処理の流れを示すフローチャート
【図１４】全吸気バルブ閉弁期間のマップを概念的に示す図
【図１５】実施形態（４）の駆動開始時期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（４）の気筒間ばらつき補正の実行例を示すタイムチャート
【図１７】その他の実施形態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（吸入空気量検出手段）、１５…スロットルバルブ、１８…吸気管圧力センサ、２０…燃料噴射弁、２１…点火プラグ、２２…排気管、２４…排出ガスセンサ、２６…クランク角センサ、２７…ＥＣＵ（気筒別目標バルブ可変量設定手段，バルブ開閉状態検出手段，駆動タイミング算出手段，気筒別可変バルブ制御手段，吸入空気量検出手段，バルブ可変量検出手段，駆動タイミング補正手段）、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…筒内圧センサ（吸入空気量検出手段）、４５…リフトセンサ（バルブ可変量検出手段）。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a variable valve control device for an internal combustion engine that controls a valve variable amount (a lift amount, a working angle, a 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 the internal combustion engine is controlled by a throttle valve. Recently, however, a variable valve mechanism for varying the lift amount of the intake valve is provided, and the lift of the intake valve is adjusted according to the accelerator opening, the engine operating state, and the like. Techniques for controlling the amount of intake air by varying the amount have 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.
[0003]
In such a variable valve lift control system, as disclosed in Japanese Patent Application Laid-Open No. 2001-263110, an electromagnetic actuator that drives an intake valve is provided for each cylinder. Since the same number of electromagnetic actuators as the number of cylinders are required, there is a disadvantage that the system configuration is complicated and the cost is high.
[0004]
Therefore, a system has been put to practical use in which lift amounts of intake valves of a plurality of cylinders are collectively controlled by one variable valve mechanism.
However, in the intake air amount control by the variable intake valve control, since the lift amount of the intake valve is small at a low load, the variation of the actual lift amount with respect to the target lift amount in each cylinder (due to component tolerance or assembly tolerance of each cylinder). (Variation) tends to increase, and the variation in the intake air amount 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.
[0005]
Several methods have been proposed for correcting such torque variations and air-fuel ratio variations 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.
[0006]
Alternatively, as shown in Patent Document 3 (JP-A-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 between cylinders is small. In some cases, the fuel injection amount is corrected for each cylinder.
[0007]
[Patent Document 1]
JP 2001-263110 A (Pages 3 to 6 etc.)
[Patent Document 2]
JP-A-62-17342 (page 2 etc.)
[Patent Document 3]
JP-A-2000-220489 (Pages 2 to 3 etc.)
[0008]
[Problems to be solved by the invention]
In Patent Documents 2 and 3, the torque and the 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]
As a countermeasure, it is conceivable to reduce the component tolerance and the assembly tolerance of each cylinder to reduce the variation in the intake air amount between cylinders. It is necessary to select and assemble, and there is a disadvantage that parts cost and manufacturing cost increase.
[0010]
Therefore, the present inventors have proposed a system in which the lift amounts of the intake valves of a plurality of cylinders are collectively controlled by a single variable valve mechanism, for each intake stroke of each cylinder (at 180 ° C. for a four-cylinder engine). We are studying "variable valve control for each cylinder" that corrects the variation of the lift amount of the intake valve between cylinders by driving the variable valve mechanism at high speed. However, there is a limit in driving the variable valve mechanism at a high speed, and the driving time of the variable valve mechanism cannot be ignored. Therefore, in the method of driving the variable valve mechanism for each intake stroke of each cylinder, the variable valve mechanism is driven halfway ( The valve opening timing of the intake valve is reached (during the lift variable operation), and the valve profile (valve lift curve) is in a transient state. For this reason, the intake valve cannot be opened with an appropriate valve profile corresponding to the target lift amount, and the control accuracy of the variable valve control for each cylinder is reduced, and the variation in intake air amount between cylinders is accurately corrected. There is a problem that you can not.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a system in which a variable valve mechanism for a plurality of cylinders is controlled by 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 improve accuracy.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is directed to a system for controlling variable amounts of intake valves or exhaust valves (hereinafter simply referred to as “valves”) of a plurality of cylinders collectively by one variable valve mechanism. The valve opening / closing state detecting means detects or estimates the opening / closing state of the valves of the plurality of cylinders, the valve variable amount detecting means detects or estimates the actual valve variable amount of each cylinder, and the target valve variable amount setting means for each cylinder sets the cylinder. The target valve variable amount is set for each cylinder in consideration of the variation in the actual valve variable amount between the cylinders. Then, the drive timing calculating means drives the variable valve mechanism to a position corresponding to the target valve variable amount of the cylinder in which the valve is opened next, or the drive timing or the intermediate timing of the drive amount is such that all the valves of the plurality of cylinders are closed. The drive timing of the variable valve mechanism is calculated by the drive timing calculation means so as to be near the intermediate timing of the period during which the valve is closed (hereinafter referred to as the “all valve closing period”). By controlling the variable valve mechanism to a position corresponding to the target valve variable amount of the cylinder in which the valve is opened next, the variable valve mechanism is controlled for each cylinder.
[0013]
By the way, if the variable valve mechanism can be driven during the entire valve closing period in which all the valves of the plurality of cylinders are closed, and the driving of the variable valve mechanism can be completed within the full valve closing period, A situation in which the valve is opened during driving can be reliably avoided, and a transition of the valve profile of each cylinder to a transient state can be reliably avoided.
[0014]
However, if the driving amount of the variable valve mechanism increases and the driving time increases, or if the engine rotation speed increases and the time of the full valve closing period decreases, the variable valve mechanism cannot be operated within the full valve closing period. In some cases, the driving cannot be completed, and the valve opening timing may be reached during the driving of the variable valve mechanism. In this case, if the overlap between the driving period of the variable valve mechanism and the valve opening period is small, the driving of the variable valve mechanism ends at a stage where the opening of the valve is still small, so that the intake air amount and the exhaust residual ratio (internal EGR) Rate) is small, and the reduction in control accuracy of the cylinder-specific variable valve control is almost negligible or within an allowable error range. However, when the overlap between the driving period of the variable valve mechanism and the valve opening period becomes large. In other words, the variable valve mechanism continues to be driven until the opening of the valve increases to some extent, that is, when the influence on the intake air amount and the exhaust residual ratio (internal EGR ratio) becomes large. The effect on the rate (internal EGR rate) becomes large, and a decrease in control accuracy of the cylinder-specific variable valve control cannot be ignored.
[0015]
Therefore, in claim 1, the drive timing of the variable valve mechanism is controlled such that the drive period or the intermediate timing of the drive amount of the variable valve mechanism is near the intermediate timing of the entire valve closing period. With this configuration, when the driving period of the variable valve mechanism is longer than the full valve closing period, the excess of the driving period of the variable valve mechanism with respect to the entire valve closing period (the driving period of the variable valve mechanism and the valve period). The period in which the variable valve mechanism drive period and the valve opening period overlap each other can be almost halved. The driving of the variable valve mechanism can be terminated when the opening of the valve is still small (or the driving of the variable valve mechanism can be started after the opening of the valve becomes small). As a result, in the present invention, even when the driving period of the variable valve mechanism is longer than the full valve closing period, the influence on the intake air amount and the exhaust residual ratio (internal EGR ratio) can be reduced. A decrease in control accuracy of the variable valve control for each cylinder can be almost ignored or minimized.
[0016]
In this case, if the target valve variable amount of each cylinder is set so that the variation of the actual valve variable amount between the cylinders is reduced, the actual valve control between the cylinders can be performed by the cylinder-specific variable valve control of the present invention. Variations in the variable amount can be accurately corrected. This makes it possible to accurately control the intake flow rate, the in-cylinder pressure, the valve overlap, and the like for each cylinder, and accurately correct variations in the combustion state, pumping loss, internal EGR amount, and the like between the cylinders. In addition, it is possible to accurately correct a variation in torque between cylinders and a variation in air-fuel ratio.
[0017]
Further, the actual intake air amount of each cylinder is detected or estimated by the intake air amount detection means, and the target valve variable amount is set for each cylinder in consideration of the variation of the actual intake air amount between the cylinders. Is calculated, and the drive timing of the variable valve mechanism is calculated such that the drive timing of the variable valve mechanism or the intermediate timing of the drive amount is close to the intermediate timing of the full intake valve closing period. The intake air amount may be controlled for each cylinder by driving the valve mechanism to a position corresponding to the target valve variable amount of the cylinder in which the intake valve is opened next. With this configuration, the intake air amount of each cylinder can be accurately controlled by considering the variation of the actual intake air amount between the cylinders by the variable valve control for each cylinder.
[0018]
In this case, if the target valve variable amount of each cylinder is set so that the variation of the actual intake air amount between the cylinders is reduced, the variation of the intake air amount between the cylinders can be accurately corrected. As a result, it is possible to accurately correct variations in torque and air-fuel ratio among cylinders.
[0019]
According to a fifth aspect of the present invention, there is provided a system in which a variable valve mechanism is driven during a period in which all intake valves of a plurality of cylinders are closed or a period extending over the period to control a valve variable amount for each cylinder. The drive timing of the variable valve mechanism may be corrected so that the variation in the actual valve variable amount between the two becomes small. With this configuration, the drive timing of the variable valve mechanism can be corrected to a timing at which the variation in the actual valve variable amount between the cylinders is minimized while monitoring the variation in the actual valve variable amount between the cylinders. The correction accuracy of the torque variation and the air-fuel ratio variation can be improved.
[0020]
Alternatively, as in claim 6, in a system for controlling the intake air amount for each cylinder by driving a variable valve mechanism during a period in which all intake valves of a plurality of cylinders are closed or a period extending over the period, The drive timing of the variable valve mechanism may be corrected so that the variation in the actual intake air amount between the cylinders is reduced. With this configuration, while monitoring the variation in the actual intake air amount between the cylinders, the drive timing of the variable valve mechanism can be corrected to a timing at which the variation in the actual intake air amount between the cylinders is minimized. It is possible to improve the correction accuracy of the torque variation and the air-fuel ratio variation between the two.
[0021]
Generally, when a variable valve mechanism is mounted, in an in-line engine, the valve variable amounts of the intake valves (or exhaust valves) of all cylinders are collectively controlled by a single variable valve mechanism, and in a V-type engine or a horizontally opposed engine, A variable valve mechanism is provided for each of a plurality of cylinder groups (banks), and the variable valve mechanisms are configured to collectively control a variable amount of an intake valve (or an exhaust valve) of each cylinder group. The cylinder-specific variable valve control of the present invention can be applied to any of these types of engines.
[0022]
When a variable valve mechanism is provided for each of a plurality of cylinder groups, the intervals between the opening periods of the intake valves (or exhaust valves) of the cylinder groups are widened, and all the intake valves (or exhaust valves) of each cylinder group are closed. Since the period during which the control is performed is longer than that of the in-line engine having the same number of cylinders, the variable valve control for each cylinder according to the present invention can be accurately executed in a wider operating range.
[0023]
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, an in-line 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 (intake air amount detection means) for detecting an intake air amount is provided downstream of the air cleaner 13. Downstream 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.
[0024]
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 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.
[0025]
In addition, the intake valve 28 and the exhaust valve 29 of the engine 11 are provided with variable valve lift mechanisms 30, 31 (variable valve mechanisms) for varying the 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).
[0026]
On the other hand, an exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas. An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting / lean or the like 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.
[0027]
Further, each cylinder of the engine 11 is provided with an in-cylinder pressure sensor 44 for detecting an in-cylinder pressure and a lift sensor 45 (valve variable amount detecting means) for detecting a lift amount of the intake valve 28, respectively. In addition, the in-cylinder pressure sensor 44 may be one incorporated in the ignition plug 21 or may be provided separately from the ignition plug 21.
[0028]
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.
[0029]
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.
[0030]
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. The worm 42 connected to the rotation shaft 41a of the motor 41 meshes with the worm wheel 43 provided so as to rotate integrally with the control shaft 35, so that the rotational force of the motor 41 is transmitted to the control shaft 35. It is supposed to be.
[0031]
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.
[0032]
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.
[0033]
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 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 curved surface 39a (the lift amount of the intake valve 28 increases).
[0034]
In the case of the high lift mode in which the maximum 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 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.
[0035]
On the other hand, in the case of the low lift mode in which the maximum lift amount 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 rotating 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 lift amount of the intake valve 28 decreases, 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.
[0036]
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, 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 and collectively. Can be dynamically changed.
[0037]
The ECU 27 executes a variable valve lift control program (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, and the like, and The amount of intake air is controlled by continuously varying the lift amount of the valve 28. In the case of a system using both the variable valve lift mechanism 30 and the variable valve timing mechanism, both the lift amount and the valve timing may be continuously varied to control the intake air amount.
[0038]
Further, the ECU 27 calculates each cylinder-to-cylinder intake air amount variation rate DEV based on the output of the in-cylinder pressure sensor 44 of each cylinder by executing each routine for cylinder-to-cylinder variation correction which will be described later. The target lift amount VVLM is set for each cylinder based on the inter-intake air amount variation ratio DEV such that the variation in the actual intake air amount between the cylinders is reduced.
[0039]
Further, as shown in FIG. 11, a variable valve lift mechanism 30 is driven to a position corresponding to a target lift amount VVLM of a cylinder (hereinafter, referred to as “intake cylinder”) in which the intake valve 28 is opened next. The drive start timing Tstart of the variable valve lift mechanism 30 is set so that the timing substantially coincides with the intermediate timing Tcenter of the period during which the intake valves 28 of all cylinders are closed (hereinafter referred to as “all intake valve closed period”). calculate. Instead of the driving period of the variable valve lift mechanism 30, the driving of the variable valve lift mechanism 30 is performed so that the intermediate timing of the driving amount of the variable valve lift mechanism 30 substantially matches the intermediate timing Tcenter of the full intake valve closing period. The start time Tstart may be calculated.
[0040]
During the execution of the variable valve control for each cylinder, 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 every time the drive start timing Tstart is reached, so that the full intake The drive of the variable valve lift mechanism 30 (lift variable operation to the target lift amount VVLM) is performed during the valve closing period or during a period that spans the full intake valve closing period to reduce the intake air amount for each cylinder. Control to correct the variation in intake air amount between cylinders.
[0041]
In general, in the intake air amount control by the variable intake valve control, as the lift amount of the intake valve 28 decreases, the variation in the intake air amount between cylinders increases, and the variation amount of the target lift amount VVLM between cylinders tends to increase. However, the smaller the lift amount of the intake valve 28, the shorter the opening period of the intake valve 28 and the longer the closing period of the entire intake valve. It is possible to execute the drive of the variable valve lift mechanism 30 (the lift variable operation to the target lift amount VVLM) during the period spanning the valve period.
Hereinafter, processing contents of each routine for correcting variation between cylinders executed by the ECU 27 in the embodiment (1) will be described.
[0042]
[Cylinder variation correction routine]
The cylinder-to-cylinder variation correction routine shown in FIG. 4 is started at an A / D conversion timing (for example, a cycle of 4 ms) of the output voltage of the in-cylinder pressure sensor 44. 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)
[0043]
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 executing the cylinder-to-cylinder variation correction is not satisfied, the routine ends without executing the processing related to the cylinder-to-cylinder variation correction after step 102.
[0044]
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, an inter-cylinder intake air amount variation rate calculation routine of FIG. 6 described later is executed, and based on an output of the in-cylinder pressure sensor 44 of each cylinder, an inter-cylinder intake air amount variation rate DEV (# i) is calculated. Here, (#i) is a cylinder number, which means any of (# 1) to (# 4).
[0045]
Thereafter, the routine proceeds to step 103, 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. In the map of FIG. 5, in the region where the inter-cylinder intake air amount variation ratio DEV (#i) has a positive value, the lift correction amount FVVL (#i) has a reduced value (negative value), and the inter-cylinder intake air amount variation ratio. In a region where DEV (#i) has a negative value, the lift correction amount FVVL (#i) has 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 lift correction amount FVVL (#i) increases, and conversely, the intake air amount of a certain cylinder increases As the amount becomes smaller than the average intake air amount, the increase correction amount based on the lift correction amount FVVL (#i) increases, so that the variation in the actual intake air amount among the cylinders decreases. Note that, in a predetermined region where the inter-cylinder intake air amount variation ratio DEV (#i) is around 0, the lift correction amount FVVL (#i) = 0 is set, and the intake valve lift amount VVL is not corrected.
[0046]
After calculating the lift correction amount FVVL (#i), the routine proceeds to step 104, where a valve open / closed state detection routine shown in FIG. 7 described below is executed, and based on the output of the lift sensor 45, the valve open / closed state flag XLIFT0 is set to all cylinders. Is set to "ON", which means that one of the intake valves 28 is closed, or reset to "OFF", which means that at least one intake valve 28 is open.
[0047]
Thereafter, the routine proceeds to step 105, in which a drive start timing calculation routine shown in FIG. 8 to be described later is executed, and based on the lift correction amount FVVL (#i) of each cylinder, the variable valve lift mechanism 30 sets the target of the next intake cylinder. The variable valve lift mechanism 30 is adjusted so that the intermediate timing of the drive period required to drive to the position corresponding to the lift amount VVLM (#i) matches the intermediate timing Tcenter (#i) of the full intake valve closing period. Of the drive start time Tstart (#i) is calculated.
[0048]
Thereafter, the routine proceeds to step 106, where it is determined whether or not the current crank angle CCRNK is the drive start timing Tstart (#i) of the variable valve lift mechanism 30. This routine ends.
[0049]
Thereafter, this routine is started, and when it is determined in step 106 that the current crank angle CCRNK is the drive start timing Tstart (#i), the routine proceeds to step 107, where the average lift amount of all cylinders before correction is determined. The target lift amount VVLM for each cylinder is obtained by adding the lift correction amount FVVL (#i) of the next intake cylinder to VVL.
[0050]
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 changed to the average lift amount VVL of all cylinders. The addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 1)
[0051]
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 changed to the average lift amount VVL of all cylinders. The addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 2)
[0052]
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 changed to the average lift amount VVL of all cylinders. The addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 3)
[0053]
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 changed to the average lift amount VVL of all cylinders. The addition is performed to obtain a target lift amount VVLM for each cylinder.
VVLM = VVL + FVVL (# 4)
[0054]
In this manner, each time the variable valve lift mechanism 30 starts to drive Tstart (#i), the target lift amount VVLM of the next intake cylinder is calculated using the lift correction amount FVVL (#i) of the next intake cylinder. Set. The processing in step 107 serves as a cylinder-by-cylinder target valve variable amount setting means referred to in the claims.
[0055]
Thereafter, the process proceeds to step 108, where the motor 41 of the variable valve lift mechanism 30 is driven at high speed in accordance with the target lift amount VVLM for each cylinder every time the drive start timing Tstart (#i) of the variable valve lift mechanism 30 is reached. 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, the drive of the variable valve lift mechanism 30 (target) is performed during the entire intake valve closing period or during the period from the second half of the intake stroke immediately before the full intake valve closing period to the first half of the intake stroke immediately after the full intake valve closing period. The lift variable operation to the lift amount VVLM) is completed, and the intake air amount is controlled for each cylinder to correct the intake air amount variation among the cylinders. The processing of step 108 serves as a cylinder-specific variable valve control means referred to in the claims.
[0056]
[Routine for calculating variation rate of intake air amount between cylinders]
When the inter-cylinder intake air amount variation rate calculation routine shown in FIG. 6 is started in step 102 of FIG. 4, first, in step 201, the in-cylinder pressure CPS detected by the in-cylinder pressure sensor 44 of each cylinder is read. Proceeding to 202, 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.
[0057]
Thereafter, the routine proceeds to step 203, where the in-cylinder pressure peak value CPSpeak (#i) of each cylinder is calculated.
In this case, during the period of the crank angle counter CCRNK = 0 to 5 (that is, the period corresponding to the combustion stroke of the first cylinder # 1), the maximum value of the in-cylinder pressure CPS in that period is set to the peak of the in-cylinder pressure of the first cylinder # 1. The value is CPSpeak (# 1).
[0058]
In the period of the crank angle counter CCRNK = 18 to 23 (that is, the period corresponding to the combustion stroke of the second cylinder # 2), the maximum value of the in-cylinder pressure CPS in that period is set to the in-cylinder pressure peak value CPSpeak (of the second cylinder # 2). # 2).
[0059]
In the period of the crank angle counter CCRNK = 6 to 11 (that is, the period corresponding to the combustion stroke of the third cylinder # 3), the maximum value of the in-cylinder pressure CPS in that period is set to the in-cylinder pressure peak value CPSpeak (third cylinder # 3). # 3).
[0060]
In the period of the crank angle counter CCRNK = 12 to 17 (that is, the period corresponding to the combustion stroke of the fourth cylinder # 4), the maximum value of the in-cylinder pressure CPS in that period is set to the in-cylinder pressure peak value CPSpeak (of the fourth cylinder # 4). # 4).
[0061]
The period during which the in-cylinder pressure peak value CPSpeak (#i) is calculated may be changed as appropriate. For example, the maximum value of the in-cylinder pressure CPS during a period of 90 ° C. before and after the compression TDC of each cylinder is determined by the in-cylinder pressure peak value. The value CPSpeak (#i) may be calculated.
[0062]
Since the cylinder pressure increases as the amount of intake air sucked into the cylinder increases, the cylinder pressure that accurately reflects the variation in the intake air amount of each cylinder by using the cylinder pressure peak value CPSpeak (#i) of each cylinder. DEV (#i) can be calculated. The processing in step 203 serves as an intake air amount detecting means referred to in the claims.
Then, in step 204, the inter-cylinder intake air amount variation ratio DEV (#i) of each cylinder is calculated by the following equation.
[0063]
(Equation 1)

[0064]
The denominator in the above equation is the average of the in-cylinder pressure peak values CPSpeak (# 1) to CPSpeak (# 4) of all cylinders.
In the cylinder-to-cylinder intake air amount variation rate calculation routine of FIG. 6, the cylinder-to-cylinder intake air amount variation rate DEV (#i) is calculated using the in-cylinder pressure peak value CPSpeak (#i). The inter-cylinder intake air amount variation rate DEV (#i) may be calculated using the in-cylinder pressure average value or the in-cylinder pressure area. Alternatively, the variation ratio DEV (#i) of the intake air amount between the cylinders may be calculated using the indicated average effective pressure and the pumping loss calculated based on the in-cylinder pressure of each cylinder.
[0065]
[Valve open / close state detection routine]
The valve open / closed state detection routine shown in FIG. 7 started in step 104 of FIG. 4 plays a role as a valve open / closed state detecting means referred to in the claims. When this routine is started, first, in step 301, the lift amount VLIFT of the intake valve 28 detected by the lift sensor 45 of each cylinder is read, and then the routine proceeds to step 302, where the lift amount VLIFT of the intake valve 28 of all cylinders is read. Is determined to be “0”. When only one cylinder is provided with the lift sensor 45, the lift amount VLIFT of the intake valves 28 of all the cylinders is changed from the crank angle at which the output of the lift sensor 45 of the one cylinder becomes the lift amount “0”. May be estimated to determine whether or not the current crank angle is a crank angle at which the lift amount VLIFT of the intake valves 28 of all cylinders becomes “0”.
[0066]
As a result, when it is determined that the lift amounts VLIFT of the intake valves 28 of all the cylinders are “0”, the process proceeds to step 303, the valve open / close state flag XLIFT0 is set, and the intake valves 28 of all the cylinders are closed. Is set to "ON" which means that
[0067]
On the other hand, if it is determined that the lift amount VLIFT of at least one intake valve 28 is not “0”, the process proceeds to step 304, and the valve open / close state flag XLIFT0 is opened by at least one intake valve 28. Is reset to "OFF" which means.
[0068]
[Drive start timing calculation routine]
The drive start timing calculation routine shown in FIG. 8 started in step 105 of FIG. 4 plays a role as drive timing calculation means in claims. When this routine is started, first, in step 401, it is determined whether or not the intake valve 28 of the current intake cylinder is closed by determining whether or not the valve open / closed state flag XLIFT0 has been switched from “OFF” to “ON”. When it is determined that the intake valve 28 has been closed, the routine proceeds to step 402, where the crank angle at that time is stored in the memory of the ECU 27 as the valve closing timing Tclose (#i) of the intake valve 28.
[0069]
Thereafter, the routine proceeds to step 403, where it is determined whether or not the intake valve 28 of the next intake cylinder has been opened based on whether or not the valve open / closed state flag XLIFT0 has been switched from "ON" to "OFF". When it is determined that the valve 28 has been opened, the routine proceeds to step 404, where the crank angle at that time is stored in the memory of the ECU 27 as the valve opening timing Topen (#i) of the intake valve 28.
[0070]
Thereafter, the routine proceeds to step 405, where the intermediate timing Tcenter (#i) of the entire intake valve closing period is calculated using the closing timing Tclose (#i) and the opening timing Topen (#i) of the intake valve 28 by the following equation. It is calculated by:
Tcenter (#i) = {Tclose (#i) + Topen (#i)} / 2
[0071]
Thereafter, the process proceeds to step 406, where a 50% drive response time TMOTOR (#i) of the variable valve lift mechanism 30 is calculated. This 50% drive response time TMOTOR (#i) drives the variable valve lift mechanism 30 from a position corresponding to the target lift amount VVLM of the intake cylinder up to that time to a position corresponding to the target lift amount VVLM of the next intake cylinder. This is the time required to drive the variable valve lift mechanism 30 by 50% of the required drive amount, and is calculated in terms of crank angle.
[0072]
The difference ΔVVLM of the target lift amount VVLM when the variable valve lift mechanism 30 is driven from the position corresponding to the target lift amount VVLM of the intake cylinder to the position corresponding to the target lift amount VVLM of the next intake cylinder, that is, the lift correction Since the 50% drive response time TMOTOR (#i) of the variable valve lift mechanism 30 changes according to the difference ΔFVVL of the amount FVVL (#i), in this step 406, the lift of each cylinder is determined using the map of FIG. The 50% drive response time TMOTOR (#i) of the variable valve lift mechanism 30 is calculated according to the difference ΔFVVL of the correction amount FVVL (#i).
[0073]
In general, since the drive period becomes longer as the drive amount of the variable valve lift mechanism 30 increases, the map in FIG. 9 shows that the greater the absolute value of the difference ΔFVVL of the lift correction amount (= the difference ΔVVLM of the target lift amount), the more the 50% The drive response time TMOTOR (#i) is set to be long. Further, when the target lift amount VVLM is made smaller than when the target lift amount VVLM is made larger, the drive torque of the variable valve lift mechanism 30 tends to be smaller and the drive period tends to be shorter. Therefore, the map of FIG. If the absolute value of the difference ΔFVVL is the same, the 50% drive response time TMOTOR (# is smaller when the difference ΔFVVL of the lift correction amount (= the difference ΔVVLM between the target lift amounts) is a minus value than when the difference is a plus value. i) is set to be shorter.
[0074]
50% drive response time TMOTOR (# 1) when driving the variable valve lift mechanism 30 from a position corresponding to the target lift amount VVLM of the second cylinder # 2 to a position corresponding to the target lift amount VVLM of the first cylinder # 1. Is calculated, the 50% drive response time TMOTOR (# corresponding to the difference ΔFVVL between the lift correction amount FVVL (# 1) of the first cylinder # 1 and the lift correction amount FVVL (# 2) of the second cylinder # 2. 1) is calculated.
[0075]
50% drive response time TMOTOR (# 2) when driving the variable valve lift mechanism 30 from a position corresponding to the target lift amount VVLM of the fourth cylinder # 4 to a position corresponding to the target lift amount VVLM of the second cylinder # 2. Is calculated, the 50% drive response time TMOTOR (# corresponding to the difference ΔFVVL between the lift correction amount FVVL (# 2) of the second cylinder # 2 and the lift correction amount FVVL (# 4) of the fourth cylinder # 4. 2) is calculated.
[0076]
50% drive response time TMOTOR (# 3) when driving the variable valve lift mechanism 30 from a position corresponding to the target lift amount VVLM of the first cylinder # 1 to a position corresponding to the target lift amount VVLM of the third cylinder # 3. Is calculated, the 50% drive response time TMOTOR (# corresponding to the difference ΔFVVL between the lift correction amount FVVL (# 3) of the third cylinder # 3 and the lift correction amount FVVL (# 1) of the first cylinder # 1. 3) is calculated.
[0077]
50% drive response time TMOTOR (# 4) when driving the variable valve lift mechanism 30 from a position corresponding to the target lift amount VVLM of the third cylinder # 3 to a position corresponding to the target lift amount VVLM of the fourth cylinder # 4. Is calculated, the 50% drive response time TMOTOR (# corresponding to the difference ΔFVVL between the lift correction amount FVVL (# 4) of the fourth cylinder # 4 and the lift correction amount FVVL (# 3) of the third cylinder # 3. 4) is calculated.
[0078]
After calculating the 50% drive response time TMOTOR (#i) of the variable valve lift mechanism 30 as described above, the routine proceeds to step 407, where the 50% drive response time is calculated from the intermediate timing Tcenter (#i) of the entire intake valve closing period. The drive start timing Tstart (#i) is obtained by subtracting the time TMOTOR (#i).
Tstart (#i) = Tcenter (#i) -TMOTOR (#i)
[0079]
Thus, the drive start timing Tstart (#i) of the variable valve lift mechanism 30 is set so that the intermediate timing of the drive period of the variable valve lift mechanism 30 matches the intermediate timing Tcenter (#i) of the all intake valve closing period. Set.
[0080]
In the drive start timing calculation routine of FIG. 8, the drive start timing Tstart (#i) is calculated using the 50% drive response time TMOTOR (#i), but instead of the 50% drive response time TMOTOR (#i). Thus, the drive start timing Tstart (#i) may be calculated using, for example, a value of １ ／ of the 98% drive response time. Alternatively, the drive start timing Tstart (#i) may be calculated using the 25% drive response time or the 75% drive response time, and the calculation method of the drive start timing Tstart (#i) may be appropriately changed. The point is that the driving start timing Tstart of the variable valve lift mechanism 30 is set so that the intermediate timing of the driving period of the variable valve lift mechanism 30 is close to the intermediate timing Tcenter (#i) of the full intake valve closing period. (#i) may be calculated.
[0081]
An execution example of the above-described embodiment (1) will be described with reference to time charts shown in FIGS. As shown in FIG. 10, during the period in which the inter-cylinder variation correction execution condition is satisfied and the inter-cylinder variation correction execution flag is on, each cycle is based on the output of the in-cylinder pressure sensor 44 (in-cylinder pressure CPS). The inter-cylinder intake air amount variation ratio DEV (#i) is calculated, and based on the inter-cylinder intake air amount variation ratio DEV (#i), the variation of the actual intake air amount between the cylinders is reduced. The lift correction amount FVVL (#i) of the cylinder is calculated.
[0082]
Further, as shown in FIG. 11, the 50% drive response time TMOTOR (#i) corresponding to the difference .DELTA.FVVL (= the difference .DELTA.VVLM between the target lift amounts) between the lift correction amounts of the previous intake cylinder and the next intake cylinder is completely reduced. By subtracting from the intermediate timing Tcenter (#i) of the intake valve closing period to obtain the drive start timing Tstart (#i), the intermediate timing of the driving period of the variable valve lift mechanism 30 is changed to the total intake valve closing period. The drive start timing Tstart (#i) is set so as to coincide with the intermediate timing Tcenter (#i), and the lift correction amount FVVL (#i) of the next intake cylinder is added to the average lift amount VVL of all cylinders. Then, the target lift amount VVLM of the next intake cylinder is set.
[0083]
Then, every time the drive start timing Tstart (#i) is reached, the motor 41 of the variable valve lift mechanism 30 is driven at a high speed in accordance with the target lift amount VVLM for each cylinder, and the variable valve lift mechanism 30 is set to the target of the next intake cylinder. It is driven to a position corresponding to the lift amount VVLM. As a result, the drive of the variable valve lift mechanism 30 (the lift variable operation to the target lift amount VVLM) is completed within the full intake valve closing period or during the period that spans the full intake valve closing period, The intake air amount is controlled for each cylinder, and the variation in the intake air amount among the cylinders is corrected.
[0084]
By controlling the intermediate timing of the driving period of the variable valve lift mechanism 30 to coincide with the intermediate timing of the full intake valve closing period as in the above-described embodiment (1), the driving of the variable valve lift mechanism 30 is controlled. If the period is shorter than the full intake valve closing period, the driving of the variable valve lift mechanism 30 can be completed within the full intake valve closing period. Can reliably be avoided, and the valve profile of each cylinder can be prevented from being in a transient state. As a result, the intake valve 28 can be opened with an appropriate valve profile corresponding to the target lift amount VVLM set in consideration of the variation in the actual intake air amount of each cylinder, and the variable valve control for each cylinder can be accurately performed. it can.
[0085]
On the other hand, if the driving period of the variable valve lift mechanism 30 is longer than the full intake valve closing period, the excess of the driving period with respect to the full intake valve closing period (the driving period and the opening period of the intake valve 28). Can be almost equally distributed before and after the entire intake valve closing period, so that the period in which the driving period of the variable valve lift mechanism 30 and the opening period of the intake valve 28 overlap can be reduced by half. Thus, the drive of the variable valve lift mechanism 30 can be terminated when the opening of the intake valve 28 is still small (or the drive of the variable valve lift mechanism 30 starts after the opening of the intake valve 28 becomes small). be able to). As a result, in the present embodiment (1), even when the driving period of the variable valve lift mechanism 30 is longer than the full intake valve closing period, the influence on the intake air amount can be reduced, and the A decrease in control accuracy of the variable valve control can be almost ignored or minimized.
[0086]
Therefore, if the variable valve control for each cylinder according to the embodiment (1) is executed, it is possible to accurately correct the intake air amount variation between the cylinders, and to greatly reduce the torque variation and the air-fuel ratio variation between the cylinders. Can be. Moreover, since it is not necessary to reduce the component tolerance and the assembly tolerance of each cylinder, it is possible to satisfy the demand for cost reduction.
[0087]
<< Embodiment (2) >>
In the embodiment (1), the cylinder-to-cylinder intake air amount variation ratio DEV (#i) is calculated using the in-cylinder pressure CPS detected by the in-cylinder pressure sensor 44. However, in the embodiment (2) of the present invention, By executing the inter-cylinder intake air amount variation ratio calculation routine shown in FIG. 12, the inter-cylinder intake air amount variation ratio DEV (#i) is calculated using the instantaneous air flow rate GA detected by the air flow meter 14. ing.
[0088]
In the inter-cylinder intake air amount variation rate calculation routine of FIG. 12 executed in the embodiment (2), first, at step 501, the instantaneous air flow rate GA detected by the air flow meter 14 is read, and then the routine proceeds to step 502, where the crank is started. The count value of the angle counter CCRNK is read.
[0089]
Thereafter, the routine proceeds to step 503, where the average intake air amount 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 in that period is calculated by the intake air flow rate of the first cylinder # 1. The average value is GAave (# 1).
[0090]
In 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 in that period is converted into the average value of the intake air flow rate of the second cylinder # 2. GAave (# 2).
[0091]
In 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 in that period is converted to the average intake air flow rate of the third cylinder # 3. GAave (# 3).
[0092]
In 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 in that period is converted to the average intake air flow rate of the fourth cylinder # 4. GAave (# 4).
Thereafter, in step 504, the inter-cylinder intake air amount variation rate DEV (#i) of each cylinder is calculated by the following equation.
[0093]
(Equation 2)

[0094]
The denominator in the above equation is the average of the intake air flow rate average values GAave (# 1) to GAave (# 4) of all cylinders.
Also in the embodiment (2) described above, the variation rate DEV (#i) of the intake air amount between cylinders can be calculated with high accuracy.
[0095]
In the inter-cylinder intake air amount variation rate calculation routine of FIG. 12, the inter-cylinder intake air amount variation rate DEV (#i) is calculated using the average intake air flow rate GAave (#i) of each cylinder. The inter-cylinder intake air amount variation ratio DEV (#i) may be calculated using the maximum value of the intake air flow rate of the cylinder or the integrated value of the intake air amount. Further, the calculation period of the average value of the intake air flow rate of each cylinder may be appropriately changed in consideration of, for example, 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.
Further, the inter-cylinder intake air amount variation ratio DEV (#i) may be calculated based on the outputs of the lift sensor 45 and the intake pipe pressure sensor 18.
[0096]
<< Embodiment (3) >>
In the embodiment (1), the open / close state of the intake valve 28 is detected based on the lift amount VLIFT of the intake valve 28 detected by the lift sensor 45. However, the embodiment (3) of the present invention shown in FIGS. In the above, the open / close state of the intake valve 28 is estimated based on the target lift amount VVLM.
[0097]
In the valve opening / closing state estimation routine of FIG. 13 executed in the embodiment (3), first, in step 601, the target lift amount VVLM calculated in step 107 of FIG. 4 described in the embodiment (1) is read. Then, the process proceeds to step 602, where the entire intake valve closing period (the crank angle range in which the intake valves 28 of all the cylinders are closed) is obtained according to the target lift amount VVLM using the map of FIG.
[0098]
Generally, the smaller the lift amount of the intake valve 28, the longer the full intake valve closing period. Therefore, the map in FIG. 14 shows that the smaller the target lift amount VVLM of the intake valve 28, the longer the full intake valve closing period. It is set as follows. The map in FIG. 14 is set in advance by design values, experiments, simulations, and the like, and is stored in the ROM of the ECU 27.
[0099]
Thereafter, the routine proceeds to step 603, where it is determined whether or not the current crank angle CCRNK is within the full intake valve closing period. As a result, when it is determined that the current crank angle CCRNK is within the full intake valve closing period, the process proceeds to step 604, and the valve open / closed state flag XLIFT0 is set to "ON".
[0100]
On the other hand, when it is determined that the current crank angle CCRNK is not in the full intake valve closing period, the process proceeds to step 605, and the valve open / closed state flag XLIFT0 is reset to “OFF”.
[0101]
According to the embodiment (3) described above, it is possible to set / reset the valve opening / closing state flag XLIFT0 by estimating the closing period of all intake valves in which the intake valves 28 of all cylinders are closed. Also, the present invention can be applied to a system without the lift sensor 45.
The intermediate timing Tcenter (#i) of the entire intake valve closing period may be directly estimated from a map or the like based on the target lift amount VVLM.
[0102]
<< Embodiment (4) >>
Next, an embodiment (4) of the present invention will be described with reference to FIGS. In the present embodiment (4), by executing the drive start timing calculation routine shown in FIG. 15, the variation of the actual intake air amount between the cylinders during the execution of the cylinder-specific variable valve control for controlling the intake air amount for each cylinder. The drive start timing Tstart (#i) of the variable valve lift mechanism 30 is corrected so as to reduce the pressure.
[0103]
When the drive start timing calculation routine shown in FIG. 15 is executed, the lift correction amount FVVL (#i) of each cylinder is calculated in step 103 of FIG. 4 described in the above embodiment (1). The amount FVVL (#i) is fixed for a predetermined period (for example, a period until it is determined that the variation in the intake air amount between the cylinders is minimum).
[0104]
When the drive start timing calculation routine shown in FIG. 15 is started, first, in step 701, it is determined whether or not the variation in intake air amount between the cylinders is minimum. Is set to “ON”, which means that is minimum. As a result, if it is determined that the variation in the intake air amount between the cylinders is the minimum (XDEVMIN = ON), this routine is terminated as it is.
[0105]
On the other hand, if it is determined that the variation in the intake air amount between the cylinders is not the minimum (XDEVMIN = OFF), the process proceeds to step 702, and the calculation is performed in the above-described routine for calculating the variation ratio of the intake air amount between the cylinders in FIG. After reading the inter-cylinder intake air amount variation ratio DEV (#i), the process proceeds to step 703, and it is determined whether the inter-cylinder intake air amount variation ratio DEV (#i) was also read last time.
[0106]
If it is determined that the cylinder-to-cylinder intake air amount variation rate DEV (#i) has not been read in the previous time, that is, if the processing of steps 702 and 703 is performed for the first time after the execution of this routine, the processing from step 703 is performed. Proceeding to step 704, the drive start timing Tstart (#i) is set to an initial value, for example, the closing timing Tclose (#i) of the intake valve 28 of the intake cylinder.
[0107]
On the other hand, when it is determined in step 703 that the cylinder-to-cylinder intake air amount variation rate DEV (#i) has been read last time, that is, this routine is started two or more times, and the processing of steps 702 and 703 is performed twice. In the case where the above has been performed, the process proceeds from step 703 to step 705, and it is determined whether or not the inter-cylinder intake air amount variation rate DEV (#i) has increased from the previous time.
[0108]
As a result, if it is determined that the cylinder-to-cylinder intake air amount variation rate DEV (#i) has decreased from the previous time, the process proceeds to step 706, where the drive start timing Tstart (#i) is set to a predetermined crank angle (for example, 1 ° C.). Advance by A).
Tstart (#i) = Tstart (#i) -1
[0109]
Thereafter, when it is determined in step 705 that the inter-cylinder intake air amount variation ratio DEV (#i) has increased from the previous time, the process proceeds to step 707, in which the drive start timing Tstart (#i) is set to a predetermined crank angle (for example, 1 ° A).
Tstart (#i) = Tstart (#i) +1
[0110]
As a result, the drive start timing Tstart (#i) is set to the optimal timing at which the inter-cylinder intake air amount variation rate DEV (#i) is minimized. The processing of these steps 705 to 707 plays a role as a drive timing correction means referred to in the claims.
[0111]
Thereafter, the process proceeds to step 708, in which it is determined that the inter-cylinder intake air amount variation ratio DEV (#i) is the minimum, and a variation minimum flag XDEVMIN is set to indicate that the intake air amount variation between the cylinders is minimum. After this is set to "ON", this routine ends.
[0112]
An execution example of the above-described embodiment (4) will be described with reference to a time chart shown in FIG. As shown in FIG. 16, when the cylinder-to-cylinder variation correction flag is turned on and cylinder-by-cylinder variable valve control for controlling the intake air amount for each cylinder is executed, the inter-cylinder suction is performed while the variation minimum flag XDEVMIN is off. The drive start timing Tstart (#i) is advanced by a predetermined crank angle (for example, 1 ° C. A) from the initial valve closing timing Tclose (#i) until the air amount variation rate DEV (#i) increases. Thereafter, when the inter-cylinder intake air amount variation ratio DEV (#i) increases, it is determined that the previous inter-cylinder intake air amount variation ratio DEV (#i) is the minimum, and the drive start timing Tstart (#i ) Is retarded by a predetermined crank angle (for example, 1 ° C. A), and the drive start timing Tstart (#i) is set to the optimal timing at which the inter-cylinder intake air amount variation ratio DEV (#i) is minimized. The flag XDEVMIN is turned on.
[0113]
In this way, during the execution of the variable valve control for each cylinder, the drive start timing Tstart (#i) of the variable valve lift mechanism 30 is changed while the inter-cylinder intake air amount variation rate DEV (#i) is monitored. The correction can be made at the optimal time when the variation rate DEV (#i) is minimized, and the accuracy of correcting the torque variation between the cylinders and the air-fuel ratio variation can be improved.
[0114]
<< Other embodiments >>
In the above embodiments (1) to (4), the present invention is applied to an in-line four-cylinder engine, but the present invention may be applied to, for example, a V-type engine. Generally, in a V-type engine, a variable valve lift mechanism is provided for each cylinder group of each bank, and each variable valve lift mechanism is configured to collectively change the lift amount of an intake valve of a bank in charge of each bank. ing. FIG. 17 shows an example of a V-type six-cylinder engine.
[0115]
In this case, as shown in FIG. 17, in the bank assigned to each variable valve lift mechanism, the interval between the opening periods of the intake valves of each cylinder is widened, and the period during which all the intake valves of the bank are closed is increased. Is longer than that of an in-line engine having the same number of cylinders, so that the cylinder-specific variable valve control of the present invention can be executed with high accuracy in a wide operating range.
[0116]
Further, the application range of the present invention is not limited to the variable valve control system that varies the lift amount of the intake valve, but is widely applied to the variable valve control system that varies at least one of the lift amount, the operating angle, and the valve timing of the intake valve. Can be applied. Also, the exhaust valve can be implemented by applying the cylinder-specific variable valve control of the present invention.
[0117]
With the variable valve control for each cylinder of the present invention, if the valve variable amount such as the lift amount, the operating angle, and the valve timing is changed for each cylinder, the intake flow rate, the in-cylinder pressure, the valve overlap, etc. can be accurately determined for each cylinder. Control can be performed, and variations in the combustion state, pumping loss, internal EGR amount, and the like between cylinders can be accurately corrected, and torque variations and air-fuel ratio variations between cylinders can be accurately corrected.
[0118]
In this case, the target valve variable amount of each cylinder may be set so that the variation of the actual valve variable amount between the cylinders is reduced. With this configuration, it is possible to accurately correct variations in the actual valve variable amount between the cylinders, and to accurately correct variations in the combustion state, pumping loss, internal EGR amount, and the like of each cylinder. The torque variation and the air-fuel ratio variation can be accurately corrected.
[0119]
In addition, the present invention is not limited to the in-line engine and the V-type engine, but can be applied to various multi-cylinder engines such as a horizontally opposed engine and 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 continuous variable operation of a valve lift amount by a variable valve lift mechanism.
FIG. 4 is a flowchart showing a processing flow of an inter-cylinder variation correction routine according to the embodiment (1).
FIG. 5 is a diagram conceptually showing a map of a lift correction amount FVVL.
FIG. 6 is a flowchart showing a processing flow of a routine for calculating a variation rate of intake air amount between cylinders according to the embodiment (1).
FIG. 7 is a flowchart showing a processing flow of a valve open / closed state detection routine according to the embodiment (1).
FIG. 8 is a flowchart showing a processing flow of a drive start timing calculation routine according to the embodiment (1).
FIG. 9 is a diagram conceptually showing a map of a 50% drive response time TMOTOR.
FIG. 10 is a time chart showing an example of execution of cylinder-to-cylinder variation correction in the embodiment (1).
FIG. 11 is a time chart showing an execution example of cylinder-specific variable valve control of the embodiment (1).
FIG. 12 is a flowchart showing a processing flow of a routine for calculating a variation ratio of intake air amount between cylinders according to the embodiment (2).
FIG. 13 is a flowchart showing the flow of processing of a valve opening / closing state estimation routine according to the embodiment (3).
FIG. 14 is a diagram conceptually showing a map of a period during which all intake valves are closed.
FIG. 15 is a flowchart showing the flow of processing of a drive start timing calculation routine according to the embodiment (4).
FIG. 16 is a time chart showing an example of execution of cylinder-to-cylinder variation correction according to the embodiment (4).
FIG. 17 is a time chart illustrating another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter (intake air amount detection means), 15 ... Throttle valve, 18 ... Intake pipe pressure sensor, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 24 ... exhaust gas sensor, 26 ... crank angle sensor, 27 ... ECU (cylinder target valve variable amount setting means, valve opening / closing state detecting means, drive timing calculating means, cylinder-specific variable valve control means, intake air amount detecting means , Valve variable amount detecting means, drive timing correction means), 28 ... intake valve, 29 ... exhaust valve, 30, 31 ... variable valve lift mechanism (variable valve mechanism), 41 ... motor, 44 ... in-cylinder pressure sensor (intake air amount) Detecting means), 45 ... lift sensor (valve variable amount detecting means).

Claims (8)

In a variable valve control device for an internal combustion engine, a variable valve mechanism for controlling the variable amounts of intake valves or exhaust valves (hereinafter simply referred to as “valves”) of a plurality of cylinders of the internal combustion engine collectively by one variable valve mechanism.
Valve open / closed state detecting means for detecting or estimating the open / closed state of the valves of the plurality of cylinders,
Valve variable amount detection means for detecting or estimating the actual valve variable amount of each cylinder;
Cylinder-based target valve variable amount setting means for setting a target valve variable amount for each cylinder in consideration of the variation of the actual valve variable amount of each cylinder detected or estimated by the valve variable amount detecting means,
A driving period or an intermediate timing of the driving amount in which the variable valve mechanism is driven to a position corresponding to a target valve variable amount of a cylinder in which a valve is opened next is near an intermediate timing of a period in which all valves of the plurality of cylinders are closed. Drive timing calculation means for calculating the drive timing of the variable valve mechanism so that
Each time the drive timing calculated by the drive timing calculation means is reached, the variable valve mechanism is driven to a position corresponding to the target valve variable amount of the cylinder in which the valve is opened next, thereby controlling the variable valve amount for each cylinder. A variable valve control device for an internal combustion engine, comprising: another variable valve control means. 2. The variable internal combustion engine according to claim 1, wherein the target valve variable amount setting means for each cylinder sets the target valve variable amount of each cylinder such that the variation of the actual valve variable amount among the cylinders is reduced. Valve control device. In a variable valve control device for an internal combustion engine, the variable valve amounts of intake valves of a plurality of cylinders of the internal combustion engine are collectively controlled by one variable valve mechanism.
Valve open / closed state detecting means for detecting or estimating the open / closed state of the intake valves of the plurality of cylinders,
Intake air amount detection means for detecting or estimating the actual intake air amount of each cylinder;
Cylinder-specific target valve variable amount setting means for setting a target valve variable amount for each cylinder in consideration of the variation in the actual intake air amount of each cylinder detected or estimated by the intake air amount detecting means,
A drive period or an intermediate timing of the drive amount required to drive the variable valve mechanism to a position corresponding to the target valve variable amount of the cylinder in which the intake valve is opened next has all the intake valves of the plurality of cylinders closed. Drive timing calculation means for calculating a drive timing of the variable valve mechanism so as to be near an intermediate timing of a period,
Each time the drive timing calculated by the drive timing calculating means is reached, the variable valve mechanism is driven to a position corresponding to the target valve variable amount of the cylinder in which the intake valve is opened next to control the intake air amount for each cylinder. A variable valve control device for an internal combustion engine, comprising: a variable valve control means for each cylinder. 4. The variable internal combustion engine according to claim 3, wherein the target valve variable amount setting unit for each cylinder sets the target valve variable amount of each cylinder such that a variation in the actual intake air amount among the cylinders is reduced. Valve control device. In a variable valve control device for an internal combustion engine, a variable valve mechanism for controlling the variable amounts of intake valves or exhaust valves (hereinafter simply referred to as “valves”) of a plurality of cylinders of the internal combustion engine collectively by one variable valve mechanism.
Valve open / closed state detecting means for detecting or estimating the open / closed state of the valves of the plurality of cylinders,
Valve variable amount detection means for detecting or estimating the actual valve variable amount of each cylinder;
Cylinder-based target valve variable amount setting means for setting a target valve variable amount for each cylinder in consideration of the variation of the actual valve variable amount of each cylinder detected or estimated by the valve variable amount detecting means,
The variable valve mechanism is driven by driving the variable valve mechanism to a position corresponding to a target valve variable amount of the next cylinder to be opened during a period in which all the intake valves of the plurality of cylinders are closed or a period extending over the period. Cylinder-specific variable valve control means for controlling the amount for each cylinder;
A drive timing correction means for correcting the drive timing of the variable valve mechanism such that the variation in the actual valve variable amount between the cylinders detected or estimated by the valve variable amount detection means is reduced. Engine variable valve control. In a variable valve control device for an internal combustion engine, the variable valve amounts of intake valves of a plurality of cylinders of the internal combustion engine are collectively controlled by one variable valve mechanism.
Valve open / closed state detecting means for detecting or estimating the open / closed state of the intake valves of the plurality of cylinders,
Intake air amount detection means for detecting or estimating the actual intake air amount of each cylinder;
Cylinder-specific target valve variable amount setting means for setting a target valve variable amount for each cylinder in consideration of the variation in the actual intake air amount of each cylinder detected or estimated by the intake air amount detecting means,
The variable valve mechanism is driven to a position corresponding to a target valve variable amount of the cylinder in which the intake valve is opened next during a period in which all the intake valves of the plurality of cylinders are closed or a period extending over the period. Cylinder-specific variable valve control means for controlling the amount of air for each cylinder;
A drive timing correction means for correcting the drive timing of the variable valve mechanism such that the variation in the actual intake air amount between the cylinders detected or estimated by the valve variable amount detection means is reduced. Engine variable valve control. The variable valve control device for an internal combustion engine according to any one of claims 1 to 6, wherein the variable valve mechanism changes the variable amounts of the valves of all the cylinders of the internal combustion engine collectively. The variable valve control device for an internal combustion engine according to any one of claims 1 to 6, wherein the variable valve mechanism is provided for each of a plurality of cylinder groups of the internal combustion engine.

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