The present invention relates to a variable valve control apparatus and a variable valve control method for an engine provided with a mechanism varying a valve lift amount and valve timing.
Heretofore, there has been known an apparatus in which a target torque is calculated based on an accelerator opening and an engine rotation speed, and an operating characteristic of an intake valve is varied so that a target intake air amount corresponding to the target torque can be obtained (refer to Japanese Unexamined Patent Publication No. 6-272580).
Further, there has also been known a variable valve mechanism varying continuously valve lift amounts and operating angles of engine valves (intake valve and exhaust valve) (refer to Japanese Unexamined Patent Publication No. 2001-012262) Here, when a valve lift amount of intake valve is controlled in order to obtain a target intake air amount, opening timing of the intake valve is varied with a change in the valve lift amount, and thereby a valve overlap amount is varied.
Then, as a result that the valve overlap amount is varied, there often occurs a reduction in volume efficiency and the blow-by and spit-back of unburned gas.
It is therefore an object of the present invention to provide a variable valve control apparatus and a variable valve control method for an engine, which is capable of avoiding a reduction in volume efficiency and the blow-by and spit-back of unburned gas, caused by a change in valve overlap amount, while controlling a valve lift amount to a requested amount.
In order to accomplish the above-mentioned object, according to the present invention, after a target valve lift amount and a target valve overlap amount are calculated, a target valve timing is calculated based on the target valve lift amount and the target valve overlap amount, and then, a valve lift amount and valve timing of an engine valve are controlled based on the target valve lift amount and the target valve timing.
The other objects and features of the invention will become understood from the following description with reference to the accompanying drawings.