Variable valve timing system

摘要

A variable valve timing system in which a lock member of a lock mechanism is not caught between a rotor member and the housing member during phase shift from an initial phase to an target advanced value. The hydraulic pressure control condition of a hydraulic pressure circuit is shifted from an initial hydraulic pressure control condition in which phase can be maintained at the initial phase and phase can be locked by the lock mechanism to the hydraulic pressure control condition in which the phase can be varied to the target advanced angel after passing the hydraulic pressure control condition in which the phase can be maintained at the initial phase and the lock mechanism can be unlocked during a predetermined time when the phase is shifted from the initial phase to the target advanced angle value.