Patent ID: 6962133

Claim:
A variable valve timing control device comprising: a housing member integrally rotating with one of a crankshaft and a camshaft of an internal combustion engine; a rotor member assembled to the housing member so as to be rotatable relative thereto, including at least one of vane portions forming an advanced angle chamber and a retarded angle chamber within the housing member, and integrally rotating with the other of the crankshaft and the camshaft; a fluid pressure circuit for controlling operation fluid to be supplied to or discharged from the advanced angle chamber and the retarded angle chamber; an engaging groove formed at the housing member in circumferential direction and including an advanced angle side end portion and a retarded angle side end portion; a retracting groove formed on the housing member and connected to the engaging groove; a lock member provided at the retracting groove and being freely projecting/retreating, and a projecting portion provided at the rotor member and projecting outward, which is in a locked state when being sandwiched between one of the end portions of the engaging groove while the lock member being in a first projecting state, and which is in a unlocked state when contacting the other of the end portions of the engaging groove while the lock member being in a second projecting state, wherein the lock member is gradually retreated from the engaging groove by an engagement between a top portion of the lock member and a top portion of the projecting portion, while the projecting portion moves away from said one of the end portions of the engaging groove towards said the other of the end portions of the engaging groove.