Patent ID: 8146550

Claim:
A variable valve timing control apparatus for an internal combustion engine that has a camshaft and a crankshaft, comprising: a variable valve timing unit adapted to adjust valve timing by shifting a camshaft phase that is a rotational angular position of the camshaft relative to a rotational angular position of the crankshaft; a lock pin that is movable in a lock direction for locking the camshaft phase at an intermediate lock phase that is generally middle of an adjustable range of the camshaft phase; a hydraulic control unit adapted to control oil pressure that actuates the variable valve timing unit and the lock pin; and lock control means for controlling the hydraulic control unit such that the lock pin is caused to lock the camshaft phase at the intermediate lock phase when a lock request is issued, wherein: when the lock request is issued, the lock control means executes a phase shift control while the lock pin is urged in the lock direction, in which control the lock control means controls the hydraulic control unit such that the camshaft phase is shifted in a reference direction to go beyond the intermediate lock phase; when the camshaft phase stops around the intermediate lock phase during the phase shift control, the lock control means changes a control amount of the hydraulic control unit by a certain amount to shift the camshaft phase; and the lock control means determines that the camshaft phase has been locked at the intermediate lock phase when the camshaft phase is limited from being shifted even after the lock control means changes the control amount of the hydraulic control unit by the certain amount.