Variable valve timing system

摘要

A variable valve timing system have a rotor member relatively rotatably mounted into a housing member and forming an advanced angle chamber and a retarded angle chamber at a vane portion in the housing member. In the system, a lock member of a lock mechanism is not caught between the rotor member and the housing member when a volume of either the advanced angle chamber or the retarded angle chamber shifts from an initial volume to a target volume. The hydraulic pressure within the system is shifted from an initial condition in which the volume is maintained at the initial volume and locked by the lock mechanism, to another condition in which the volume is varied to the target volume after passing a transition in which the volume is maintained at the initial volume and the lock mechanism is being unlocked during a predetermined time.