Patent ID: 7444964

Claim:
A variable valve timing control device comprising: a driving side rotational member ( 2 ) synchronously rotating with a crankshaft; a driven side rotational member ( 1 ) positioned coaxially with the driving side rotational member, and synchronously rotating with a camshaft; a fluid pressure chamber ( 40 ), formed in at least one of the driving side rotational member and the driven side rotational member, for generating a biasing force for changing a relative rotational phase between the driving side rotational member and the driven side rotational member by hydraulic fluid supplied into or discharged from the fluid pressure chamber; a lock mechanism ( 6 ) movable between a lock position for preventing a relative rotation between the driving side rotational member and the driven side rotational member and a lock release position for allowing the relative rotation; a lock release pressure chamber ( 62 ) for generating a biasing force to move the lock mechanism ( 6 ) to the lock release position by supply of the hydraulic fluid; a phase control device ( 71 ) for controlling a rate of the relative rotational phase change by controlling supply or discharge of hydraulic fluid into or out of the fluid pressure chamber; and a lock control device ( 72 ) for controlling supply or discharge of hydraulic fluid into or out of the lock release pressure chamber; and an operational state detection means ( 100 ) for detecting operational state of an internal combustion engine, wherein when the lock control device supplies hydraulic fluid to the lock release pressure chamber, the phase control device restricts upper limit of the rate of the relative rotational phase change so that a pressure of hydraulic fluid in the lock release pressure chamber is greater than or equal to a pressure necessary to maintain the lock mechanism in the lock release position based on a detection result by the operational state detection means.