Control apparatus for internal combustion engine

Abstract

A control apparatus for an internal combustion engine that varies the amount of lift of an intake valve is disclosed. In one embodiment, the control apparatus includes a fuel injection timing correcting device that, when lift of the intake valve is varied, corrects and varies fuel injection termination timing according to the variation of the lift of the intake valve. In another embodiment, an injection quantity correcting device is included that, when lift of the intake valve is varied, corrects and varies an injection quantity. In still another embodiment, a swirl flow generating device is included that generates a swirl flow in the cylinder. In a further embodiment, an intake valve closing timing correcting device is included that, when lift of the intake valve is varied, controls the variable valve timing mechanism so that the valve closing timing of the intake valve remains substantially constant.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] The following is based on and claims priority to Japanese Patent Application No. 2005-264566, filed Sep. 13, 2005, which is incorporated herein by reference. FIELD [0002] The present invention relates to a control apparatus for an internal combustion engine that varies the amount of lift of an intake valve. BACKGROUND [0003] Internal combustion engines have been proposed that include a variable intake valve lifter that varies the amount of lift of an intake valve. An example of this type of variable intake valve lifter is disclosed in Japanese Patent No. 2827768. Specifically, the control mode of the variable intake valve lifter is switched between low lift mode and high lift mode in accordance with the state of operation of the internal combustion engine. In low lift mode, a cam for driving and opening / closing an intake valve is changed to a cam for low lift to reduce the amount of lift of the intake valve. In high lift mode, the cam fo...

AI Technical Summary

Benefits of technology

[0059] Thus, when the variable intake valve lifter 30 is switched from low lift mode to high lift mode to increase the amount of lift of the intake valve 29, the injection quantity is corrected and increased. Therefore, even though the amount of lift of the intake valve 29 is increased, the valve closing timing of the intake valve 29 is delayed, and the back flow of rich gas in the cylinder is increased (i.e., the residual volume of rich gas in the cylinder is reduced), the injection quantity can be corrected and accordingly increased to increase the quantity of fuel sucked into the cylinder. Also, the average air-fuel ratio in the cylinder can be kept substantially constant. Thus, when the amount of lift of the intake valve 29 is increased, a lean spike is less likely, drivability is improved, and the exhaust emission is also improved.

[0060] Meanwhile, when the variable intake valve lifter 30 is switched from high lift mode to low lift mode to reduce the amount of lift of the intake valve 29, the injection quantity is corrected and reduced. Therefore, even though the amount of lift of the intake valve 29 is reduced, the valve closing timing of the intake valve 29 is advanced, and the back flow of rich gas in the cylinder is reduced (i.e., the residual volume of rich gas in the cylinder is increased), the injection quantity can be corrected and accordingly reduced to reduce the quantity of fuel sucked into the cylinder. Also, the average air-fuel ratio in the cylinder can be kept substantially constant. Thus, when the amount of lift of the intake valve 29 is reduced, a rich spike is less likely, the drivability is improved, and the exhaust emission is also improved.

[0061] When the amount of lift of the intake valve 29 is varied, a variation (i.e., increment or decrement) in the back flow of rich gas in a cylinder changes in accordance with a variation in the valve closing timing of the intake valve 29. In the second embodiment, this change is taken into account, and when the amount of lift of the intake valve 29 is varied, a fuel correction factor, α, is set based on a variation in the valve closing timing of the intake valve 29. Therefore, it is possible to appropriately set a fuel correction factor, α, in accordance with a change (i.e., increment or decrement) in variation in the back flow of rich gas corresponding to a variation in the valve closing timing of the intake valve 29. As a result, the occurrence of a lean spike or a rich spike is less likely.

[0062] Furthermore in this embodiment, when the amount of lift of the intake valve 29 is varied, purge control is prohibited. Therefore, external disturbance to the air-fuel ratio can be avoided when the amount of lift of the intake valve is varied. Thus, it is possible to enhance the accuracy of controlling the air-fuel ratio of fuel mixture when the amount of lift of an intake valve is varied, and the occurrence of a lean spike or a rich spike is even less likely.

Problems solved by technology

Such systems can pose certain problems.

During the period from the intake stroke to the initial stage of the compression stroke, the air-fuel ratio distribution of the fuel mixture in the cylinder is not uniform.

This lean spike or rich spike can cause torque shock, which can lead to degraded drivability or deteriorated exhaust emission.

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