JP2004316613A - Variable valve control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for varying valve variation quantity of all the intake valves of a plurality of cylinders wholly by a single variable valve mechanism, in which torque irregularity between the cylinders due to intake air quantity irregularity between two intake valves of the same cylinder can be corrected. <P>SOLUTION: Normally, intake air quantity irregularity ratio between the cylinders is determined to control lift quantity for each cylinder by driving a variable valve lift mechanism at high speed at every prescribed timing based on the intake air quantity irregularity ratio between the cylinders for controlling the intake air quantity for each cylinder so as to correct the intake air quantity irregularity between the cylinders. In a case where torque irregularity between the cylinders exceeds a tolerable range during control to correct the intake air quantity irregularity between the cylinders, torque irregularity ratio between the cylinders is determined to drive the variable lift mechanism at high speed at every prescribed timing based on the torque irregularity ratio between the cylinders for controlling the lift quantity for each cylinder. Torque can thus be controlled for each cylinder to correct torque irregularity between the cylinders. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００９６】
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１１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ＤＥＶＡＩＲ（＃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ＤＥＶＡＩＲ（＃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。
【００９７】
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ＤＥＶＡＩＲ（＃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ＤＥＶＡＩＲ（＃ｉ）を算出するようにしても良い。
【００９８】
［気筒間トルクばらつき率算出ルーチン］
図１２に示す気筒間トルクばらつき率算出ルーチンは、図１０のステップ５０２で起動され、特許請求の範囲でいう気筒間トルクばらつき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７０１で、クランク角カウンタＣＣＲＮＫのカウント値を読み込む。前述したように、このクランク角カウンタＣＣＲＮＫは、クランク角センサ２６の出力信号に基づいて例えば３０℃Ａ毎に「１」ずつインクリメントされる。
【００９９】
この後、ステップ７０２に進み、クランク軸が３０℃Ａ回転するのに要した時間Ｔ３０（クランク角カウンタＣＣＲＮＫの前回のインクリメントタイミングから今回のインクリメントタイミングまでの時間）を読み込む。
【０１００】
そして、次のステップ７０３で、各気筒の燃焼行程に対応する期間のＴ３０の最小値Ｔ３０ＭＩＮ（＃ｉ）と最大値Ｔ３０ＭＡＸ（＃ｉ）を算出する。
第１気筒＃１の最小値Ｔ３０ＭＩＮ（＃１）と最大値Ｔ３０ＭＡＸ（＃１）を算出する場合は、クランク角カウンタＣＣＲＮＫ＝０〜５の期間、つまり、第１気筒＃１の燃焼行程に対応する期間のＴ３０の最小値と最大値を算出する。
【０１０１】
第２気筒＃２の最小値Ｔ３０ＭＩＮ（＃２）と最大値Ｔ３０ＭＡＸ（＃２）を算出する場合は、クランク角カウンタＣＣＲＮＫ＝１８〜２３の期間、つまり、第２気筒＃２の燃焼行程に対応する期間のＴ３０の最小値と最大値を算出する。
【０１０２】
第３気筒＃３の最小値Ｔ３０ＭＩＮ（＃３）と最大値Ｔ３０ＭＡＸ（＃３）を算出する場合は、クランク角カウンタＣＣＲＮＫ＝６〜１１の期間、つまり、第３気筒＃３の燃焼行程に対応する期間のＴ３０の最小値と最大値を算出する。
【０１０３】
第４気筒＃４の最小値Ｔ３０ＭＩＮ（＃４）と最大値Ｔ３０ＭＡＸ（＃４）を算出する場合は、クランク角カウンタＣＣＲＮＫ＝１２〜１７の期間、つまり、第４気筒＃４の燃焼行程に対応する期間のＴ３０の最小値と最大値を算出する。
【０１０４】
この後、ステップ７０４に進み、各気筒の回転変動ΔＴ３０（＃ｉ）を次式により算出する。
ΔＴ３０（＃ｉ）＝Ｔ３０ＭＡＸ（＃ｉ）−Ｔ３０ＭＩＮ（＃ｉ）
【０１０５】
この後、ステップ７０５に進み、全気筒の回転変動ΔＴ３０（＃１）〜ΔＴ３０（＃４）の平均値ΔＴ３０（ａｖｅ） を算出した後、ステップ７０６に進み、各気筒の気筒間トルクばらつき率ＤＥＶＴＲＱ（＃ｉ）を次式により算出する。
ＤＥＶＴＲＱ（＃ｉ）＝ΔＴ３０（＃ｉ）／ΔＴ３０（ａｖｅ）
【０１０６】
この後、ステップ７０７に進み、気筒間トルクばらつき幅ΔＤＥＶＴＲＱを次式により算出する。
ΔＤＥＶＴＲＱ＝ＤＥＶＴＲＱ（＃ｉ）の最大値−ＤＥＶＴＲＱ（＃ｉ）の最小値
尚、図１２の気筒間トルクばらつき率算出ルーチンでは、各気筒の回転変動ΔＴ３０（＃ｉ）を用いて気筒間トルクばらつき率ＤＥＶＴＲＱ（＃ｉ）を算出したが、燃焼圧変動を用いて気筒間トルクばらつき率ＤＥＶＴＲＱ（＃ｉ）を算出するようにしても良い。
【０１０７】
以上説明した本実施形態の実行例を図１３乃至図１５に示すタイムチャートを用いて説明する。図１３に示すように、通常（気筒別可変バルブ制御切換フラグＸＴＲＱＡＣＴがＯＦＦされている期間）は、気筒間吸入空気量ばらつき補正用の気筒別可変バルブ制御を実行する。この気筒間吸入空気量ばらつき補正用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ＤＥＶＡＩＲ（＃ｉ）に基づいて気筒間の吸入空気量ばらつきが小さくなるように各気筒の目標リフト量ＶＶＬＭを設定する。そして、図１４に示すように、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して吸気バルブ２８のリフト量を気筒別に制御することで、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。これにより、気筒間の吸入空気量ばらつきによって発生する気筒間のトルクばらつきを補正することができる。
【０１０８】
その後、気筒別モータ制御が正常（気筒別モータ制御の異常診断フラグＸＡＣＴＤ＝ＯＦＦ）で、且つ、気筒別吸入空気量検出が正常（気筒別吸入空気量検出の異常診断フラグＸＡＩＲＤ＝ＯＦＦ）の状態、つまり、気筒間吸入空気量ばらつき補正用の気筒別可変バルブ制御が正常に行われている状態で、気筒間トルクばらつき幅ΔＤＥＶＴＲＱ（気筒間トルクばらつき率ＤＥＶＴＲＱの最大値と最小値との差）が判定値Ｄ１ を越えると、その時点ｔ１ で、気筒内バルブ間リフト量ばらつき（つまり気筒内バルブ間吸入空気量ばらつき）が大きいと判断して、気筒別可変バルブ制御切換フラグＸＴＲＱＡＣＴをＯＮにセットする。これにより、気筒間吸入空気量ばらつき補正用の気筒別可変バルブ制御を禁止して、気筒間トルクばらつき補正用の気筒別可変バルブ制御を実行する。
【０１０９】
この気筒間トルクばらつき補正用の気筒別可変バルブ制御では、各気筒の気筒間トルクばらつき率ＤＥＶＴＲＱ（＃ｉ）に基づいて気筒間のトルクばらつきが小さくなるように各気筒の目標リフト量ＶＶＬＭを設定し、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して吸気バルブ２８のリフト量を気筒別に制御することで、トルクを気筒別に制御して気筒間のトルクばらつきを補正する。これにより、気筒内バルブ間吸入空気量ばらつきによって気筒間のトルクばらつきが発生している場合でも、気筒間のトルクばらつきを補正することができ、ドライバビリティを向上させることができる。
【０１１０】
また、気筒間トルクばらつき補正用の気筒別可変バルブ制御では、気筒間の吸入空気量ばらつき、気筒内バルブ間吸入空気量ばらつき、気筒間の燃料量ばらつき等の複数の要因が絡み合って発生した気筒間のトルクばらつきを小さくするように各気筒のリフト量を制御するため、必ずしも、気筒間の吸入空気量ばらつきが減少するとは限らず、場合によっては、気筒間の吸入空気量ばらつきが増大して、気筒間の空燃比ばらつきが増大してしまう可能性がある。気筒間の空燃比ばらつきが大きくなると、排出ガス空燃比の変動幅が触媒２３の浄化ウインドからはみ出して排気エミッションが悪化する懸念がある。
【０１１１】
その点、本実施形態では、気筒間吸入空気量ばらつき補正用の気筒別可変バルブ制御を優先的に実行して、気筒間トルクばらつき幅ΔＤＥＶＴＲＱが判定値Ｄ１ を越えた場合にのみ、気筒間トルクばらつき補正用の気筒別可変バルブ制御を実行するようにしたので、気筒間トルクばらつき補正用の気筒別可変バルブ制御による排気エミッションへの悪影響を最小限に抑えることができる。
【０１１２】
また、本実施形態では、気筒別モータ制御が異常（気筒別モータ制御の異常診断フラグＸＡＣＴＤ＝ＯＮ）、又は、気筒別吸入空気量検出が異常（気筒別吸入空気量検出の異常診断フラグＸＡＩＲＤ＝ＯＮ）の場合は、気筒別可変バルブ制御を正常に行うことができないと判断して、スロットルバルブ制御による吸入空気量制御に切り換えるようにしたので、気筒別可変バルブ制御を正常に行うことができない状態になった場合でも、スロットルバルブ制御による吸入空気量制御によって、ドライバビリティや排気エミッションを悪化させないようにエンジン１１を運転することができる。
【０１１３】
尚、本実施形態では、エンジン１１の複数気筒の全ての吸気バルブ２８のリフト量を一括して１つの可変バルブリフト機構３０で制御するようにしたが、複数気筒の一方の吸気バルブのバルブ可変量を一括して可変する第１の可変バルブ機構と、前記複数気筒の他方の吸気バルブのバルブ可変量を一括して可変する第２の可変バルブ機構と備えたシステムに本発明を適用しても良い。
【０１１４】
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。
【０１１５】
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】本発明の一実施形態におけるエンジン制御システム全体の概略構成図
【図２】吸気バルブ及び排気バルブとその周辺部の平面図
【図３】可変バルブリフト機構の正面図
【図４】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５】気筒別可変バルブ制御切換判定ルーチンの処理の流れを示すフローチャート
【図６】気筒別モータ制御の異常診断ルーチンの処理の流れを示すフローチャート
【図７】気筒別吸入空気量検出の異常診断ルーチンの処理の流れを示すフローチャート
【図８】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】リフト補正量ＦＶＶＬのマップを概念的
【図１０】気筒間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１１】気筒間吸入空気量ばらつき率算出ルーチンの処理の流れを示すフローチャート
【図１２】気筒間トルク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】気筒間ばらつき補正の実行例を示すタイムチャート
【図１４】気筒内バルブ間リフト量ばらつきが小さい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１５】気筒内バルブ間リフト量ばらつきが大きい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
【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、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（気筒間吸入空気量ばらつき算出手段，気筒別可変バルブ制御手段，気筒間トルクばらつき算出手段，診断手段，スロットル制御手段）、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、４５…吸気ポート、４６…排気ポート。[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 the throttle valve, so that pumping loss can be reduced. In addition, by reducing the lift amount of the intake valve, the driving force of the camshaft can be reduced, and there is an advantage that fuel efficiency 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 developed in which lift amounts of intake valves of a plurality of cylinders are collectively controlled by one variable valve mechanism.
[0005]
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.
[0006]
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.
[0007]
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.
[0008]
[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.)
[0009]
[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. .
[0010]
As a countermeasure for this, it is conceivable to reduce the component tolerance and the assembly tolerance of each cylinder (that is, reduce the variation of the intake valve lift amount between the cylinders) to reduce the variation of the intake air amount between the 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 disadvantage that the parts cost and the manufacturing cost are increased.
[0011]
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 variations in intake valve lift between cylinders (or variations in intake air amount) by driving the variable valve mechanism at high speed.
[0012]
By the way, in recent years, internal combustion engines having two intake valves in each cylinder in order to increase intake efficiency have become mainstream. In such an internal combustion engine, in addition to the variation in the intake valve lift between cylinders, it is inevitable that the lift also varies between two intake valves of the same cylinder. In this case, if the variation in the lift amount between the two intake valves of one cylinder becomes large, the intake amount of air also varies greatly between the two intake valves of one cylinder, thereby causing the flow of the gas in the cylinder. Since the state (such as swirl flow intensity) changes, the combustion state changes and the torque changes. Therefore, even if the intake air amount per cylinder (total intake air amount of the two intake valves) is substantially the same between the cylinders, the variation in the intake air amount between the two intake valves in any one of the cylinders (hereinafter referred to as “the intake air amount”). (Referred to as “in-cylinder intake air amount variation between valves”), the torque variation among the cylinders increases.
[0013]
As described above, when torque variation between cylinders is caused by variation in intake air amount between valves in a cylinder, even if variation in intake air amount between cylinders is corrected by the above-described variable valve control for each cylinder, even if variation in intake air amount between cylinders is corrected, Since it is impossible to correct the variation in intake air amount between valves, it is not possible to sufficiently correct the variation in torque between cylinders, and there is a concern that drivability is adversely affected.
[0014]
The present invention has been made in view of such circumstances, and accordingly, an object thereof is to correct torque variation between cylinders even when torque variation between cylinders occurs due to variation in intake air amount between valves in a cylinder. It is an object of the present invention to provide a variable valve control device for an internal combustion engine that can improve drivability.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is applied to an internal combustion engine having a plurality of intake valves in each cylinder, and the valve variable amounts of all the intake valves of the plurality of cylinders are collectively changed by one variable. In a system controlled by a valve mechanism, information on variation in intake air amount between cylinders (hereinafter referred to as “intake air amount between cylinders”) based on a detection result or an estimation result of intake air amount detection means for detecting or estimating an intake air amount of each cylinder. This is referred to as "variation information") by the inter-cylinder intake air amount variation calculating means, and a target valve variable amount is set for each cylinder in consideration of the inter-cylinder intake air amount variation information. Is driven to a position corresponding to the target valve variable amount of the cylinder in which the intake valve is opened next, thereby correcting the variation in intake air amount between cylinders. Variable valve controls another cylinder carried by cylinder variable valve control means. Further, information on inter-cylinder torque variation (hereinafter referred to as "inter-cylinder torque variation information") is calculated by inter-cylinder torque variation calculation means, and when the inter-cylinder torque variation information exceeds a predetermined allowable range, inter-cylinder intake air Prohibits cylinder-specific variable valve control for correcting the amount variation, sets the target valve variable amount for each cylinder in consideration of the inter-cylinder torque variation information, and opens the variable valve mechanism at each predetermined timing, and then opens the intake valve By driving the cylinder to a position corresponding to the target valve variable amount of the cylinder to be controlled, cylinder-by-cylinder variable valve control for correcting cylinder-to-cylinder torque variation is performed.
[0016]
In this configuration, the variable valve control for each cylinder based on the information on the variation in the intake air amount between the cylinders is performed by executing the variable valve control for each cylinder for correcting the variation in the intake air amount between the cylinders, and the intake air amount between the cylinders is controlled. Variation can be corrected. Thus, it is possible to correct a variation in torque between cylinders caused by a variation in intake air amount between cylinders.
[0017]
Even if the variation in intake air amount between cylinders is corrected by the variable valve control for each cylinder for correcting the variation in intake air amount between cylinders, if the variation in torque between cylinders exceeds the allowable range, the cylinder It is determined that torque variation between cylinders has increased due to variation in intake air amount between the inner valves (variation in intake air amount between a plurality of intake valves of the same cylinder), and switching to cylinder-specific variable valve control for correcting cylinder-to-cylinder torque variation is performed. . By performing the cylinder-by-cylinder variable valve control for correcting the cylinder-to-cylinder torque variation, it is possible to control the valve variable amount of the intake valve for each cylinder based on the cylinder-to-cylinder torque variation information and correct the torque variation between the cylinders. it can. As a result, even when torque variation between cylinders occurs due to variation in intake air amount between valves in a cylinder, torque variation between cylinders can be corrected, and drivability can be improved.
[0018]
In addition, in the variable valve control for each cylinder for correcting the inter-cylinder torque variation, a plurality of factors such as a variation in intake air amount between cylinders, a variation in intake air amount between valves in a cylinder, and a variation in fuel amount between cylinders are generated. In order to control the valve variable amount of the intake valve of each cylinder so as to reduce the torque variation between the cylinders, the control is not always performed in a direction in which the variation in the intake air amount between the cylinders decreases. There is a possibility that the intake air amount variation between the cylinders increases, and the air-fuel ratio variation between the cylinders increases. If the air-fuel ratio variation between the cylinders becomes too large, the fluctuation range of the exhaust gas air-fuel ratio may protrude from the purification window of the catalyst, and the exhaust emission may be deteriorated.
[0019]
In this regard, the present invention preferentially executes the cylinder-specific variable valve control for correcting the inter-cylinder intake air amount variation, and performs the cylinder-to-cylinder torque variation correction only when the torque variation between the cylinders exceeds an allowable range. Since the cylinder-by-cylinder variable valve control is executed, the influence on the exhaust emission by the cylinder-by-cylinder variable valve control for inter-cylinder torque variation correction can be minimized.
[0020]
Further, according to a second aspect of the present invention, a diagnosis unit diagnoses whether the cylinder-specific variable valve control by the cylinder-specific variable valve control unit is normal or abnormal, and as a result, when it is determined that the cylinder-specific variable valve control is abnormal. The variable valve control for each cylinder may be prohibited, and the throttle control means may control the throttle valve of the internal combustion engine to control the amount of intake air. In this way, even when it becomes impossible to perform the cylinder-specific variable valve control normally, the internal combustion engine is operated by the intake air amount control by the throttle valve control so as not to deteriorate the drivability and the exhaust emission. be able to.
[0021]
In this case, if the intake air amount detecting means is normal and one or both of the response time and the control error of the variable valve mechanism are within a predetermined allowable range, the cylinder-by-cylinder variable It may be determined that the cylinder-specific variable valve control by the valve control means is normally performed. For example, if the intake air amount detecting means becomes abnormal, the calculation result of the inter-cylinder intake air amount variation information becomes abnormal, and the variable valve control for each cylinder becomes abnormal. In addition, if the response time of the variable valve mechanism becomes longer, the variable valve mechanism cannot be driven at a high speed, so the intake valve opening timing comes during the driving of the variable valve mechanism (during the variable lift operation), The intake valve cannot be opened with an appropriate valve profile corresponding to the target lift amount, and cylinder-by-cylinder variable valve control cannot be performed normally. Further, if the control error of the variable valve mechanism becomes abnormally large, cylinder-by-cylinder variable valve control cannot be performed normally. Therefore, when the intake air amount detecting means is abnormal, or when the response time and control error of the variable valve mechanism are beyond the allowable range, it can be determined that the cylinder-specific variable valve control is abnormal.
[0022]
Further, as in claim 4, the inter-cylinder torque variation information may be calculated based on the rotation fluctuation and / or the combustion pressure fluctuation of the internal combustion engine. Since there is a correlation between the torque of the internal combustion engine and the rotation fluctuation / combustion pressure fluctuation, if the inter-cylinder torque fluctuation information is calculated based on the rotation fluctuation and the combustion pressure fluctuation of the internal combustion engine, the torque fluctuation between the cylinders can be reduced. Accurately reflected inter-cylinder torque variation information can be calculated.
[0023]
According to a fifth aspect of the present invention, in an internal combustion engine having a plurality of intake valves in each cylinder, a first variable valve mechanism for collectively varying a valve variable amount of one intake valve of the plurality of cylinders. And a second variable valve mechanism for collectively varying the variable amount of the other intake valve of the plurality of cylinders. Even in this case, the intended object of the present invention can be achieved.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 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.
[0025]
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.
[0026]
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).
[0027]
As shown in FIG. 2, the engine 11 is a four-valve engine having four valves in each cylinder. Each cylinder of the engine 11 is provided with two intake ports 45 and two exhaust ports 46, and Each of the ports 45 is provided with an intake valve 28, and each of the exhaust ports 46 is provided with an exhaust valve 29. The lift amounts of the two intake valves 28 of each cylinder are collectively controlled by one variable valve lift mechanism 30, and the lift amounts of the two exhaust valves 29 of each cylinder are collectively controlled by one variable valve lift mechanism 31. It is supposed to be.
[0028]
On the other hand, as shown in FIG. 1, 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 the air-fuel ratio or rich / lean of the exhaust gas 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.
[0029]
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.
[0030]
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.
[0031]
As shown in FIG. 3, a link arm 34 is provided between the camshaft 32 for driving the intake valve 28 and the rocker arm 33. The link arm 34 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. Further, 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 rotating shaft 41a).
[0032]
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.
[0033]
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.
[0034]
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).
[0035]
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.
[0036]
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.
[0037]
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. 4, 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 collectively and continuously performed. Variable.
[0038]
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, and the like, to thereby control the intake valve. The amount of intake air is controlled by continuously varying the lift amount of the air conditioner. 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.
[0039]
In addition, the ECU 27 normally executes cylinder-specific variable valve control for correcting variation in intake air amount between cylinders by executing each routine for variable valve control for each cylinder described later. In the variable valve control for each cylinder for correcting the variation in the intake air amount between cylinders, the variation ratio DEVAIR of the intake air amount between cylinders of each cylinder is calculated based on the output signal of the air flow meter 14, and the variation ratio DEVAIR of the intake air amount between cylinders is calculated. The target lift amount VVLM of the intake valve 28 is set for each cylinder such that the intake air amount variation among the cylinders is reduced based on Then, as shown in FIG. 14, each time the intake valve 28 of all cylinders is closed, the motor 41 of the variable valve lift mechanism 30 changes the target lift amount VVLM of the next intake cylinder. By controlling the lift amount of the intake valve 28 for each cylinder by driving at a high speed to a position corresponding to, the intake air amount is controlled for each cylinder and the variation in the intake air amount between cylinders is corrected. As a result, the variation in torque between cylinders caused by the variation in intake air amount between cylinders is corrected.
[0040]
Further, the ECU 27 calculates the inter-cylinder torque variation rate DEVTRQ and the inter-cylinder torque variation width ΔDEVTRQ (the inter-cylinder torque variation rate DEVTRQ) based on the rotation variation ΔT30 of each cylinder calculated based on the output signal of the crank angle sensor 26. The difference between the maximum value and the minimum value) is calculated.
[0041]
When the inter-cylinder intake air amount variation is corrected by the above-described cylinder-specific variable valve control for correcting the inter-cylinder intake air amount variation, the inter-cylinder torque variation width ΔDEVTRQ exceeds a predetermined allowable range. As shown in FIG. 15, the variation in the lift amount between the two intake valves 28 of the same cylinder (hereinafter referred to as “variation in the lift amount between the valves in the cylinder”) increases, and the two intake valves 28 of the same cylinder increase. It is determined that the variation in the intake air amount between cylinders (hereinafter referred to as “variation in the intake air amount between the valves in the cylinder”) has increased, and the variation in the intake air amount between the cylinders has increased. Cylinder-specific variable valve control is prohibited, and cylinder-specific variable valve control for correcting inter-cylinder torque variation is executed.
[0042]
In the cylinder-specific variable valve control for correcting the inter-cylinder torque variation, the target lift amount VVLM of the intake valve 28 is set for each cylinder based on the inter-cylinder torque variation rate DEVTRQ such that the inter-cylinder torque variation is reduced. Every time the full intake valve closing period is reached, 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 to control the lift amount of the intake valve 28 for each cylinder. Thus, the torque is controlled for each cylinder to correct the torque variation between the cylinders. As a result, the variation in torque between cylinders caused by the variation in intake air amount between valves in the cylinder is corrected.
[0043]
Hereinafter, processing contents of each routine for cylinder-specific variable valve control executed by the ECU 27 in the present embodiment will be described.
[0044]
[Variable valve control switching determination routine for each cylinder]
The cylinder-specific variable valve control switching determination routine shown in FIG. 5 is executed at a predetermined cycle after an ignition switch (not shown) is turned on, for example. When this routine is started, first, in step 101, an abnormality diagnosis routine for cylinder-by-cylinder motor control shown in FIG. 6 to be described later is executed, and an abnormality diagnosis flag XACTD for cylinder-by-cylinder motor control is determined. It is set to "ON", meaning "ON", or reset to "OFF", meaning normal motor control for each cylinder.
[0045]
Thereafter, the routine proceeds to step 102, in which an abnormality diagnosis routine for detecting the intake air amount for each cylinder shown in FIG. 7 described later is executed, and the abnormality diagnosis flag XAIRD for detecting the intake air amount for each cylinder indicates an abnormality in the detection of the intake air amount for each cylinder. Set to “ON” or reset to “OFF”, which means that the intake air amount detection for each cylinder is normal.
[0046]
Thereafter, the routine proceeds to step 103, where it is determined whether the cylinder-by-cylinder motor control is normal (XACTD = OFF) and the cylinder-by-cylinder intake air amount detection is normal (XAIRD = OFF). It is determined whether the variable valve control is performed normally. The processing in step 103 plays a role as a diagnostic means in the claims.
[0047]
As a result, when it is determined that the cylinder-by-cylinder motor control is normal (XACTD = OFF) and the cylinder-by-cylinder intake air amount detection is normal (XAIRD = OFF), the cylinder-specific variable valve control is performed normally. When it is determined that the process has been performed, the process proceeds to step 104, and the inter-cylinder torque variation width ΔDEVTRQ calculated by the inter-cylinder torque variation rate calculation routine of FIG.
[0048]
Thereafter, the routine proceeds to step 105, where it is determined whether or not the inter-cylinder torque variation width ΔDEVTRQ is equal to or smaller than a predetermined determination value D1. This determination value D1 is a value for setting a limit value of an allowable range of the inter-cylinder torque variation width ΔDEVTRQ. The determination value D1 is set so that the allowable range of the inter-cylinder torque variation width ΔDEVTRQ does not adversely affect drivability. Is set.
[0049]
If it is determined in step 105 that the inter-cylinder torque variation width ΔDEVTRQ is equal to or smaller than the determination value D1, the inter-cylinder torque variation correction variable correction is performed because the inter-cylinder torque variation width ΔDEVTRQ is within the allowable range. It is determined that there is no need to switch to the valve control, and the routine proceeds to step 106, where the cylinder-specific variable valve control switching flag XTRQACT is set to “OFF” meaning execution of the cylinder-specific variable valve control for correcting variation in intake air amount between cylinders. Maintain (or reset) and end this routine.
[0050]
On the other hand, when it is determined in step 105 that the inter-cylinder torque variation width ΔDEVTRQ is larger than the determination value D1, that is, the inter-cylinder intake valve inter-cylinder variable valve control for correcting the inter-cylinder intake air amount variation corrects the intake between the cylinders. If the inter-cylinder torque variation width ΔDEVTRQ exceeds the allowable range despite the correction of the air amount variation, it is determined that the inter-cylinder torque variation has increased due to the in-cylinder valve intake air amount variation. Then, the process proceeds to a step 107, wherein the cylinder-specific variable valve control switching flag XTRQACT is set to "ON" which means the execution of the cylinder-specific variable valve control for correcting the inter-cylinder torque variation, and the routine ends.
[0051]
On the other hand, if it is determined in step 103 that the cylinder-by-cylinder motor control is abnormal (XACTD = ON), or if the cylinder-by-cylinder intake air amount detection is abnormal (XAIRD = ON), When it is determined that the cylinder-specific variable valve control cannot be performed normally, the routine proceeds to step 108, in which the cylinder-specific variable valve control is prohibited, and the routine proceeds to step 109, where the throttle valve is controlled based on the accelerator opening, the engine operating state, and the like. The intake air amount is controlled by controlling the valve 15. The processing in step 109 plays a role as a throttle control means referred to in the claims.
[0052]
In this step 109, only the intake air amount control by the throttle valve control may be executed, but the target lift amount common to each cylinder is limited to a predetermined lower limit lift amount or more, and the intake air amount control by the variable valve control is performed. , The intake air amount control by the throttle valve control may be executed.
[0053]
[Cylinder-specific motor control abnormality diagnosis routine]
When the abnormality diagnosis routine of the cylinder-by-cylinder motor control shown in FIG. 6 is started in step 101 of FIG. 5, first, in step 201, the motor of the variable valve lift mechanism 30 is controlled based on the output signal of the motor rotation angle sensor 44. The motor drive time TACT required to drive the motor 41 from the current position to the position corresponding to the target lift amount VVLM of the next intake cylinder is calculated. The motor drive time TACT is information for evaluating the response time of the variable valve lift mechanism 30.
[0054]
Thereafter, the process proceeds to step 202, where the motor drive time TACT is smoothed to obtain a final motor drive time TACTSM (an average value).
TACTSM = TACTSM (old) + K × {TACT-TACTSM (old)}
Here, TACTSM (old) is the previous motor drive time TACTSM (average value), and K is the average coefficient.
[0055]
Then, after reading the actual motor rotation angle VVLACT of the variable valve lift mechanism 30 detected by the motor rotation angle sensor 44 in step 203, the process proceeds to step 204, where the target motor rotation angle TGVVLACT of the variable valve lift mechanism 30 (cylinder described later) (A rotation angle corresponding to another target lift amount VVLM).
[0056]
Thereafter, the routine proceeds to step 205, where the count value of the crank angle counter CCRNK is read. Since the crank angle counter CCRNK is incremented by “1” every 30 ° C. based on the output signal of the crank angle sensor 26, 24 counts of the crank angle counter CCRNK correspond to one cycle (720 ° C. A). . Note that the crank angle counter CCRNK is reset to “0” when it becomes “24”. The crank rotation position of the crank angle counter CCRNK = 0 corresponds to the compression top dead center (compression TDC) of the first cylinder # 1, and the crank rotation positions of the crank angle counter CCRNK = 6, 12, and 18 correspond to the first rotation position, respectively. 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.
[0057]
Thereafter, the process proceeds to step 206, where the control accuracy value ACCURA (#i) for each cylinder is calculated. Here, (#i) is a cylinder number, which means any of (# 1) to (# 4). The cylinder-specific control accuracy value ACCURA (#i) serves as information for evaluating a control error of the variable valve lift mechanism 30.
[0058]
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 or more points in the period and the target motor rotation The deviation from the angle TGVVLACT is integrated, 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 first cylinder # 1 is updated, and the integrated value is used for the first cylinder # 1. The cylinder-based control accuracy value ACCURA (# 1) is used.
[0059]
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 or more points in the period are used. , The integrated value of the difference 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 used as the cylinder-by-cylinder control of the second cylinder # 2. The accuracy value is ACCURA (# 2).
[0060]
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 actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT detected at one or more points in the period are used. And updates the integrated value of the difference between the actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT in the intake stroke of the third cylinder # 3, and uses the integrated value as the cylinder-by-cylinder control of the third cylinder # 3. The precision value is ACCURA (# 3).
[0061]
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 actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT detected at one or more points in the period are used. Of the actual motor rotation angle VVLACT and the target motor rotation angle TGVVLACT in the intake stroke of the fourth cylinder # 4, and the integrated value is used as the cylinder-by-cylinder control of the fourth cylinder # 4. The accuracy value is ACCURA (# 4).
[0062]
Thereafter, the process proceeds to step 207, where it is determined whether or not the motor drive time TACTSM is equal to or less than a predetermined determination value T1. It is determined whether or not there is.
[0063]
Here, the determination value T1 of the motor drive time TACTSM is a value for setting a limit value of an allowable range of the motor drive time TACTSM, and is set so that the allowable range of the motor drive time TACTSM does not adversely affect drivability. The judgment value T1 is set.
[0064]
The determination value A1 of the control accuracy value ACCURA (#i) for each cylinder is a value for setting a limit value of an allowable range of the control accuracy value ACCURA (#i) for each cylinder, and the control accuracy value ACCURA (#i for each cylinder). The determination value A1 is set so that the allowable range of ()) does not adversely affect drivability.
[0065]
When it is determined in step 207 that the motor drive time TACTSM is equal to or less than the determination value T1, and that the cylinder-specific control accuracy values ACCURA (#i) of all cylinders are equal to or less than the determination value A1, Proceeding to step 208, the abnormality diagnosis flag XACTD for the cylinder-by-cylinder motor control is maintained (or reset) to "OFF", which means that the cylinder-by-cylinder motor control is normal.
[0066]
On the other hand, if it is determined in step 207 that the motor drive time TACTSM is greater than the determination value T1, or the cylinder-specific control accuracy value ACCURA (#i) of at least one cylinder is greater than the determination value A1. If it is determined to be larger, the routine proceeds to step 209, where the abnormality diagnosis flag XACTD for the cylinder-by-cylinder motor control is set to "ON" which indicates an abnormality in the cylinder-by-cylinder motor control, and this routine ends.
[0067]
[Abnormal diagnostic routine for detecting intake air amount for each cylinder]
When the abnormality diagnosis routine for detecting the intake air amount for each cylinder shown in FIG. 7 is started in step 102 of FIG. 5, first, in step 301, it is determined whether or not the air flow meter 14 is normal, for example, by the air flow meter abnormality diagnosis. The determination is made based on a diagnosis result of a routine (not shown). For example, if a disconnection of the signal line of the air flow meter 14 or a power supply voltage abnormality occurs, the output voltage of the air flow meter 14 becomes an abnormal voltage, so that the output voltage of the air flow meter 14 is in a normal voltage range. The normal / abnormal state of the air flow meter 14 may be determined based on this.
[0068]
If it is determined in step 301 that the air flow meter 14 is normal, the process proceeds to step 302, in which the abnormality diagnosis flag XAIRD for detecting the intake air amount for each cylinder is set to "normal" for detecting the intake air amount for each cylinder. It is maintained (or reset) at "OFF", and this routine ends.
[0069]
On the other hand, if it is determined in step 301 that the air flow meter 14 is abnormal, the routine proceeds to step 303, where the abnormality diagnosis flag XAIRD for detecting the intake air amount for each cylinder is set to the value for detecting the intake air amount for each cylinder. The flag is set to "ON" indicating an abnormality, and the routine ends.
[0070]
When detecting the intake air amount based on the output signal of the intake pipe pressure sensor 18, ON / OFF of the abnormality diagnosis flag XAIRD for detecting the intake air amount for each cylinder according to whether the intake pipe pressure sensor 18 is abnormal or normal. Should be switched.
[0071]
[Variable valve control routine for each cylinder]
The cylinder-specific variable valve control routine shown in FIG. 8 is started at an A / D conversion timing (for example, a cycle of 4 ms) of the output voltage of the air flow meter 14 and plays a role as a cylinder-specific variable valve control means described in the claims. . When the present routine is started, first, in step 401, it is determined whether or not the execution condition of the variable valve control for each cylinder is satisfied. Here, the cylinder-specific variable valve control execution condition 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)
[0072]
If these two conditions (1) and (2) are both satisfied, the cylinder-specific variable valve control execution condition is satisfied, but if any one of the conditions is not satisfied, the cylinder-specific variable valve control execution condition is not satisfied. Become. If it is determined that the condition for executing the variable valve control for each cylinder is not satisfied, the routine ends without executing the processing related to the variable valve control for each cylinder after step 402.
[0073]
On the other hand, if it is determined in step 401 that the execution condition of the variable valve control for each cylinder is satisfied, the process related to the variable valve control for each cylinder from step 402 is executed as follows. First, in step 402, an inter-cylinder variation rate calculation routine of FIG. 10 described later is executed to calculate an inter-cylinder intake air amount variation rate DEV (#i) = DEVAIR (#i) of each cylinder. Alternatively, an inter-cylinder torque variation ratio DEV (#i) = DEVTRQ (#i) of each cylinder is calculated.
[0074]
Thereafter, the process proceeds to step 403, where the lift correction amount FVVL (#i) corresponding to the inter-cylinder variation rate DEV (#i) is calculated for each cylinder using the map of FIG. In the map of FIG. 9, in the region where the inter-cylinder variation rate DEV (#i) is greater than 1, the lift correction amount FVVL (#i) becomes a reduced value (negative value), and the inter-cylinder variation rate DEV (#i) is reduced. In an area smaller than 1, the lift correction amount FVVL (#i) becomes an increase value (plus value). That is, as the intake air amount (or torque) of a certain cylinder becomes larger than the average intake air amount (or average torque) of all the cylinders, the reduction correction amount by the lift correction amount FVVL (#i) increases, and conversely, As the intake air amount (or torque) of the cylinders becomes smaller than the average intake air amount (or average torque) of all cylinders, the increase correction amount by the lift correction amount FVVL (#i) increases, and the actual intake air between the cylinders increases. The variation in the amount (variation in the actual torque) is reduced. In a predetermined region where the inter-cylinder variation ratio DEV (#i) is around 1, the lift correction amount FVVL (#i) is set to 0, and the intake valve lift amount VVL is not corrected.
[0075]
After calculating the lift correction amount FVVL (#i), the process proceeds to step 404, 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, the routine ends.
[0076]
Thereafter, when it is determined in step 404 that the intake valves 28 of all cylinders are closed, the process proceeds to step 405, where the lift correction amount FVVL of the next intake cylinder is added to the average lift amount VVL of all cylinders before correction. By adding (#i), a target lift amount VVLM for each cylinder is obtained.
[0077]
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)
[0078]
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)
[0079]
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)
[0080]
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)
[0081]
In this manner, every time the full 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 for the next intake cylinder. The target lift amount VVLM is set.
[0082]
Thereafter, the routine proceeds to step 406, where 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 every time the full intake valve closing period is reached. 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.
[0083]
Accordingly, when the target lift amount VVLM for each cylinder is set based on the cylinder-to-cylinder intake air amount variation rate DEV (#i) = DEVAIR (#i), the target lift amount VVLM for each cylinder is set. By controlling the lift amount of the intake valve 28 for each cylinder, the "variable valve control for each cylinder for correcting the variation in intake air amount between cylinders" that controls the intake air amount for each cylinder and corrects the variation in intake air amount between cylinders. Execute.
[0084]
On the other hand, when the target lift amount VVLM for each cylinder is set based on the inter-cylinder torque variation rate DEV (#i) = DEVTRQ (#i) of each cylinder, the intake valve 28 is set based on the target lift amount VVLM for each cylinder. By controlling the lift amount of each cylinder, the "variable valve control for individual cylinders for correcting inter-cylinder torque variation" is performed, in which the torque is controlled for each cylinder and the torque variation between cylinders is corrected.
[0085]
[Routine of calculating variation ratio between cylinders]
When the inter-cylinder variation rate calculation routine shown in FIG. 10 is started in step 402 of FIG. 8, first, in step 501, an inter-cylinder intake air amount variation rate calculation routine of FIG. A variation ratio DEVAIR (#i) of each cylinder is calculated based on the output voltage of the respective cylinders.
[0086]
Thereafter, the process proceeds to step 502, in which a cylinder torque variation rate calculation routine shown in FIG. 12 described below is executed, and based on the rotation fluctuation ΔT30 (#i) of each cylinder calculated based on the output signal of the crank angle sensor 26. The inter-cylinder torque variation rate DEVTRQ (#i) of each cylinder is calculated.
[0087]
Thereafter, the process proceeds to step 503, at which it is determined whether or not there is a command to execute the cylinder-specific variable valve control for correcting the inter-cylinder intake air amount variation, and whether the cylinder-specific variable valve control switching flag XTRQACT has been reset to “OFF”. Is determined by
[0088]
As a result, when it is determined that there is an instruction to execute the variable valve control for each cylinder for correcting the variation in intake air amount between cylinders (XTRQACT = OFF), the process proceeds to step 504, and the process proceeds to step 504. In order to execute the variable valve control, the inter-cylinder intake air amount variation ratio DEVAIR (#i) is adopted as the inter-cylinder variation ratio DEV (#i) (DEV (#i) = DEVAIR (#i)), and this routine is executed. To end.
[0089]
On the other hand, if it is determined in step 503 that there is no command to execute the cylinder-specific variable valve control for correcting the inter-cylinder intake air amount variation, the process proceeds to step 505, and the cylinder-specific variable valve control for correcting the cylinder-to-cylinder torque variation. Is performed, the inter-cylinder torque variation rate DEVTRQ (#i) is adopted as the inter-cylinder variation rate DEV (#i) (DEV (#i) = DEVTRQ (#i)), and the routine ends.
[0090]
[Routine for calculating variation rate of intake air amount between cylinders]
The inter-cylinder intake air amount variation rate calculation routine shown in FIG. 11 is started in step 501 of FIG. 10 and plays a role as an inter-cylinder intake air amount variation calculation means referred to in the claims. When this routine is started, first, at step 601, the instantaneous air flow rate GA detected by the air flow meter 14 is read, and then the routine proceeds to step 602, at which the count value of the crank angle counter CCRNK is read.
[0091]
Thereafter, the routine proceeds to step 603, 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. Average value GAave (# 1).
[0092]
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).
[0093]
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).
[0094]
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 604, the inter-cylinder intake air amount variation ratio DEVAIR (#i) of each cylinder is calculated by the following equation.
[0095]
(Equation 1)

[0096]
The denominator of the above equation is the average value of the average values of the intake air flow rates GAave (# 1) to GAave (# 4) of all the cylinders.
In the inter-cylinder intake air amount variation rate calculation routine of FIG. 11, the inter-cylinder intake air amount variation rate DEVAIR (#i) is calculated using the average intake air flow rate GAave (#i) of each cylinder. The inter-cylinder intake air amount variation rate DEVAIR (#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.
[0097]
Further, the variation ratio DEVAIR (#i) of the intake air amount between cylinders may be calculated based on the output of the intake pipe pressure sensor 18. In addition, in a system including an in-cylinder pressure sensor that detects an in-cylinder pressure of each cylinder and a lift sensor that detects a valve lift amount of each cylinder, a variation in intake air amount between the cylinders based on an output of the in-cylinder pressure sensor and an output of the lift sensor. The ratio DEVAIR (#i) may be calculated.
[0098]
[Routine for calculating variation in torque between cylinders]
The inter-cylinder torque variation rate calculation routine shown in FIG. 12 is started in step 502 of FIG. 10 and plays a role as an inter-cylinder torque variation calculation means referred to in the claims. When this routine is started, first, in step 701, the count value of the crank angle counter CCRNK is read. As described above, the crank angle counter CCRNK is incremented by “1”, for example, every 30 ° C. based on the output signal of the crank angle sensor 26.
[0099]
Thereafter, the process proceeds to step 702, where the time T30 required for the crankshaft to rotate by 30 ° C. (the time from the previous increment timing of the crank angle counter CCRNK to the current increment timing) is read.
[0100]
Then, in the next step 703, the minimum value T30MIN (#i) and the maximum value T30MAX (#i) of T30 in the period corresponding to the combustion stroke of each cylinder are calculated.
When calculating the minimum value T30MIN (# 1) and the maximum value T30MAX (# 1) of the first cylinder # 1, it corresponds to the period of the crank angle counter CCRNK = 0 to 5, that is, the combustion stroke of the first cylinder # 1. Then, the minimum value and the maximum value of T30 during the period are calculated.
[0101]
When calculating the minimum value T30MIN (# 2) and the maximum value T30MAX (# 2) of the second cylinder # 2, it corresponds to the period of the crank angle counter CCRNK = 18 to 23, that is, the combustion stroke of the second cylinder # 2. Then, the minimum value and the maximum value of T30 during the period are calculated.
[0102]
When calculating the minimum value T30MIN (# 3) and the maximum value T30MAX (# 3) of the third cylinder # 3, it corresponds to the period of the crank angle counter CCRNK = 6 to 11, that is, the combustion stroke of the third cylinder # 3. Then, the minimum value and the maximum value of T30 during the period are calculated.
[0103]
When calculating the minimum value T30MIN (# 4) and the maximum value T30MAX (# 4) of the fourth cylinder # 4, it corresponds to the period of the crank angle counter CCRNK = 12 to 17, that is, corresponds to the combustion stroke of the fourth cylinder # 4. Then, the minimum value and the maximum value of T30 during the period are calculated.
[0104]
Thereafter, the process proceeds to step 704, where the rotation fluctuation ΔT30 (#i) of each cylinder is calculated by the following equation.
ΔT30 (#i) = T30MAX (#i) -T30MIN (#i)
[0105]
Thereafter, the routine proceeds to step 705, where the average value ΔT30 (ave) of the rotation fluctuations ΔT30 (# 1) to ΔT30 (# 4) of all the cylinders is calculated, and then proceeds to step 706, where the inter-cylinder torque variation rate DEVTRQ of each cylinder (#I) is calculated by the following equation.
DEVTRQ (#i) = ΔT30 (#i) / ΔT30 (ave)
[0106]
Thereafter, the routine proceeds to step 707, where the inter-cylinder torque variation width ΔDEVTRQ is calculated by the following equation.
ΔDEVTRQ = maximum value of DEVTRQ (#i) −minimum value of DEVTRQ (#i)
In the cylinder-to-cylinder torque variation rate calculation routine of FIG. 12, the cylinder-to-cylinder torque variation rate DEVTRQ (#i) is calculated using the rotation variation ΔT30 (#i) of each cylinder, but the cylinder-to-cylinder torque variation rate is calculated using the combustion pressure variation. The torque variation ratio DEVTRQ (#i) may be calculated.
[0107]
An execution example of the present embodiment described above will be described with reference to time charts shown in FIGS. As shown in FIG. 13, during the normal period (period in which the cylinder-specific variable valve control switching flag XTRQACT is OFF), the cylinder-specific variable valve control for correcting the variation in the intake air amount between cylinders is executed. In the variable valve control for each cylinder for correcting the variation in the intake air amount between the cylinders, the variation of the intake air amount between the cylinders is reduced based on the variation ratio DEVAIR (#i) of the intake air amount between the cylinders of each cylinder. The target lift amount VVLM is set. Then, as shown in FIG. 14, each time the intake valve 28 of all cylinders is closed, the motor 41 of the variable valve lift mechanism 30 changes the target lift amount VVLM of the next intake cylinder. By controlling the lift amount of the intake valve 28 for each cylinder by driving at a high speed to a position corresponding to, the intake air amount is controlled for each cylinder and the variation in the intake air amount between cylinders is corrected. Thus, it is possible to correct a variation in torque between cylinders caused by a variation in intake air amount between cylinders.
[0108]
Thereafter, the state in which the cylinder-by-cylinder motor control is normal (cylinder motor control abnormality diagnosis flag XACTD = OFF) and the cylinder-by-cylinder intake air amount detection is normal (cylinder intake air amount detection abnormality diagnosis flag XAIRD = OFF) In other words, in a state where the cylinder-by-cylinder variable valve control for correcting the inter-cylinder intake air amount variation is performed normally, the inter-cylinder torque variation width ΔDEVTRQ (the difference between the maximum value and the minimum value of the inter-cylinder torque variation rate DEVTRQ) Exceeds the determination value D1, it is determined at time t1 that the in-cylinder lift amount variation (that is, the in-cylinder intake air amount variation) is large, and the variable valve control switching flag XTRQACT for each cylinder is set to ON. I do. As a result, the cylinder-by-cylinder variable valve control for inter-cylinder intake air amount variation correction is prohibited, and the cylinder-by-cylinder variable valve control for inter-cylinder torque variation correction is executed.
[0109]
In the variable valve control for each cylinder for correcting the inter-cylinder torque variation, the target lift amount VVLM of each cylinder is set based on the inter-cylinder torque variation rate DEVTRQ (#i) of each cylinder so that the inter-cylinder torque variation is reduced. Each time the intake valve is closed, 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 to control the lift amount of the intake valve 28 for each cylinder. By doing so, the torque is controlled for each cylinder to correct the torque variation between the cylinders. As a result, even when torque variation between cylinders occurs due to variation in intake air amount between valves in a cylinder, torque variation between cylinders can be corrected, and drivability can be improved.
[0110]
In addition, in the variable valve control for each cylinder for correcting the inter-cylinder torque variation, a plurality of factors such as a variation in intake air amount between cylinders, a variation in intake air amount between valves in a cylinder, and a variation in fuel amount between cylinders are generated. In order to control the lift amount of each cylinder so as to reduce the torque variation between the cylinders, the variation in the intake air amount between the cylinders does not always decrease, and in some cases, the variation in the intake air amount between the cylinders increases. Therefore, there is a possibility that the variation in the air-fuel ratio between the cylinders increases. If the air-fuel ratio variation among the cylinders becomes large, the fluctuation range of the exhaust gas air-fuel ratio protrudes from the purification window of the catalyst 23, and there is a concern that the exhaust emission deteriorates.
[0111]
In this regard, in the present embodiment, the cylinder-by-cylinder variable valve control for correcting the inter-cylinder intake air amount variation is preferentially executed, and only when the inter-cylinder torque variation width ΔDEVTRQ exceeds the determination value D1, the inter-cylinder torque is increased. Since the cylinder-by-cylinder variable valve control for the variation correction is executed, the adverse effect on the exhaust emission due to the cylinder-by-cylinder variable valve control for the inter-cylinder torque variation correction can be minimized.
[0112]
In this embodiment, the cylinder-by-cylinder motor control is abnormal (the cylinder-by-cylinder motor control abnormality diagnosis flag XACTD = ON), or the cylinder-by-cylinder intake air amount detection is abnormal (by the cylinder-by-cylinder intake air amount detection abnormality diagnosis flag XAIRD = In the case of ON), it is determined that the cylinder-specific variable valve control cannot be performed normally, and the control is switched to the intake air amount control by the throttle valve control. Therefore, the cylinder-specific variable valve control cannot be performed normally. Even in the state, the engine 11 can be operated by the intake air amount control by the throttle valve control so as not to deteriorate the drivability and the exhaust emission.
[0113]
In the present embodiment, the lift amounts of all the intake valves 28 of the plurality of cylinders of the engine 11 are collectively controlled by one variable valve lift mechanism 30. The present invention is applied to a system including a first variable valve mechanism that collectively varies the amount of the intake valve and a second variable valve mechanism that simultaneously varies the valve variable amount of the other intake valve of the plurality of cylinders. Is also good.
[0114]
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.
[0115]
In addition, the present invention is not limited to the 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 appropriately changed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment of the present invention.
FIG. 2 is a plan view of an intake valve, an exhaust valve, and peripheral portions thereof.
FIG. 3 is a front view of a variable valve lift mechanism.
FIG. 4 is a valve lift characteristic diagram for explaining a continuous variable operation of a valve lift amount by a variable valve lift mechanism.
FIG. 5 is a flowchart showing a processing flow of a cylinder-specific variable valve control switching determination routine;
FIG. 6 is a flowchart showing a flow of processing of an abnormality diagnosis routine of cylinder-by-cylinder motor control;
FIG. 7 is a flowchart showing the flow of processing of an abnormality diagnosis routine for detecting intake air amount for each cylinder;
FIG. 8 is a flowchart showing a processing flow of a cylinder-specific variable valve control routine.
FIG. 9 conceptually shows a map of a lift correction amount FVVL.
FIG. 10 is a flowchart showing a processing flow of an inter-cylinder variation rate calculation routine;
FIG. 11 is a flowchart showing a processing flow of a routine for calculating a variation rate of intake air amount between cylinders;
FIG. 12 is a flowchart showing a processing flow of an inter-cylinder torque variation rate calculation routine.
FIG. 13 is a time chart showing an example of execution of inter-cylinder variation correction;
FIG. 14 is a time chart showing an execution example of the variable valve control for each cylinder when the variation in the lift amount between the valves in the cylinder is small.
FIG. 15 is a time chart showing an execution example of the variable valve control for each cylinder when the variation in the lift amount between the valves in the cylinder is large.
[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, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 26 ... Crank angle Sensors 27 ECU (inter-cylinder intake air amount variation calculation means, cylinder-specific variable valve control means, cylinder-to-cylinder torque variation calculation means, diagnostic means, throttle control means), 28 intake valves, 29 exhaust valves 30, 31 ... variable valve lift mechanism (variable valve mechanism), 41 ... motor, 44 ... motor rotation angle sensor, 45 ... intake port, 46 ... exhaust port.

Claims (5)

A variable valve control apparatus for an internal combustion engine, which is applied to an internal combustion engine having a plurality of intake valves in each cylinder, wherein the variable valve amounts of all the intake valves of the plurality of cylinders of the internal combustion engine are collectively changed by one variable valve mechanism. At
Intake air amount detection means for detecting or estimating the intake air amount of each cylinder;
An inter-cylinder intake air amount variation calculating unit that calculates information on an intake air amount variation between cylinders (hereinafter referred to as “inter-cylinder intake air amount variation information”) based on a detection result or an estimation result of the intake air amount detection unit;
A target valve variable amount is set for each cylinder in consideration of the inter-cylinder intake air amount variation information, and the variable valve mechanism corresponds to a target valve variable amount of a cylinder in which an intake valve is opened next at every predetermined timing. Cylinder variable valve control means for performing cylinder-specific variable valve control for cylinder-to-cylinder intake air amount variation correction for correcting intake air amount variation between cylinders by driving to a position,
Inter-cylinder torque variation calculating means for calculating information on torque variation between cylinders (hereinafter referred to as “inter-cylinder torque variation information”),
The cylinder-specific variable valve control means prohibits the cylinder-specific variable valve control for correcting the cylinder-to-cylinder intake air amount variation when the cylinder-to-cylinder torque variation information exceeds a predetermined allowable range, and the cylinder-to-cylinder torque variation information In consideration of the above, the target valve variable amount is set for each cylinder, and at predetermined timing, 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, so that the inter-cylinder A variable valve control device for an internal combustion engine, which performs cylinder-by-cylinder variable valve control for correcting cylinder-to-cylinder torque variation for correcting torque variation. Diagnostic means for diagnosing whether cylinder-specific variable valve control by the cylinder-specific variable valve control means is normal or abnormal;
When the diagnosis means diagnoses that the cylinder-specific variable valve control by the cylinder variable valve control means is abnormal, the cylinder-specific variable valve control by the cylinder variable valve control means is prohibited, and the throttle of the internal combustion engine is reduced. 2. The variable valve control device for an internal combustion engine according to claim 1, further comprising: throttle control means for controlling a valve to control an intake air amount. The diagnosing unit is configured to control the variable valve control for each cylinder if the intake air amount detecting unit is normal and one or both of the response time and the control error of the variable valve mechanism are within a predetermined allowable range. 3. The variable valve control apparatus for an internal combustion engine according to claim 2, wherein it is determined that the cylinder-specific variable valve control by the means is performed normally. The internal combustion engine according to any one of claims 1 to 3, wherein the inter-cylinder torque variation calculation means calculates the inter-cylinder torque variation information based on a rotation variation and / or a combustion pressure variation of the internal combustion engine. Variable valve control device. A first variable valve mechanism which is applied to an internal combustion engine having a plurality of intake valves in each cylinder and which collectively changes a valve variable amount of one intake valve of the plurality of cylinders of the internal combustion engine; and the other of the plurality of cylinders A variable valve control device for an internal combustion engine, comprising: a second variable valve mechanism for collectively varying a valve variable amount of an intake valve;
Intake air amount detection means for detecting or estimating the intake air amount of each cylinder;
An inter-cylinder intake air amount variation calculating unit that calculates information on an intake air amount variation between cylinders (hereinafter referred to as “inter-cylinder intake air amount variation information”) based on a detection result or an estimation result of the intake air amount detection unit;
A target valve variable amount is set for each cylinder in consideration of the inter-cylinder intake air amount variation information, and the target variable of the first and second variable valve mechanisms is set at predetermined timings. Cylinder variable valve control means for performing cylinder-specific variable valve control for cylinder-to-cylinder intake air amount variation correction for correcting intake air amount variation between cylinders by driving to a position corresponding to the valve variable amount,
Inter-cylinder torque variation calculating means for calculating information on torque variation between cylinders (hereinafter referred to as “inter-cylinder torque variation information”),
The cylinder-specific variable valve control means prohibits the cylinder-specific variable valve control for correcting the cylinder-to-cylinder intake air amount variation when the cylinder-to-cylinder torque variation information exceeds a predetermined allowable range, and the cylinder-to-cylinder torque variation information In consideration of the above, the target valve variable amount is set for each cylinder, and at each predetermined timing, the first and second variable valve mechanisms are moved to a position corresponding to the target valve variable amount of the cylinder in which the intake valve is opened next. A variable valve control device for an internal combustion engine, which performs cylinder-by-cylinder variable valve control for correcting cylinder-to-cylinder torque variation by driving the cylinder.

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