Valve timing control apparatus for internal combustion engine

A valve timing control apparatus for an internal combustion engine, comprising:

• a cam shaft rotatable in synchronism with rotation of a crank shaft of said internal combustion engine for thereby setting valve timing for at least one of an intake valve and an exhaust valve of said engine;
• a cam phase actuator having a valve timing advancing hydraulic chamber and a valve timing retarding hydraulic chamber to which hydraulic pressure is fed for changing a relative angle of said cam shaft to said crank shaft in a valve timing advancing direction or alternatively in a valve timing retarding direction;
• a locking mechanism provided in association with said cam phase actuator for locking said relative angle at a predetermined relative angle;
• an oil pump for generating said hydraulic pressure;
• hydraulic pressure regulating means for feeding said hydraulic pressure to said valve timing advancing hydraulic chamber or alternatively to said valve timing retarding hydraulic chamber;
• and
• an engine control unit for controlling said hydraulic pressure regulating means;
• said locking mechanism being released under the effect of the hydraulic pressure fed to either one of said valve timing advancing hydraulic chamber or said valve timing retarding hydraulic chamber of said cam phase actuator upon changing of said relative angle, wherein when said relative angle is to be changed from the locked state validated by said locking mechanism, a phase feedback control of said relative angle is performed after having executed a control for releasing said locked state in advance;
• wherein said engine control unit includes change quantity limiting means for limiting a change quantity of said valve timing,
• said change quantity limiting means being designed for limiting said change quantity of said valve timing to a predetermined value upon transition of said locked state releasing control to said phase feedback control.