US Patent 7159556 Control apparatus and method for internal combustion engine

A working angle (lift amount) of an intake valve is set to a predetermined first set value A1 during a period from when starting of the engine is initiated until when the engine is shifted to an initial combustion state, and the working angle is changed to a second set value A2 (=previous value (initial value is A1)+α) that is larger than the first set value A1 during a period from when the engine is shifted to the initial combustion state until when the engine is shifted to a perfect combustion state. When an engine rotational speed becomes equal to or higher than a reference rotational speed n1, it is determined that the engine has been shifted to the perfect combustion state, after which an engine starting routine ends.