Variable valve timing mechanism for internal combustion engine

A variable valve timing mechanism for an internal combustion engine, the engine having a drive shaft, a driven shaft driven by the drive shaft, and at least one valve driven by the driven shaft, the mechanism varying the rotational phase of the driven shaft with respect to the drive shaft to vary the timing of the valve, the mechanism comprising:

• a first rotary member for a rotation in synchronism with the drive shaft, the first rotary member having at least one recess therein;
• a second rotary member for a rotation in synchronism with the driven shaft, the second rotary member being located within the first rotary member, and the second rotary member having a vane movable in the recess to divide the recess into a first hydraulic chamber and a second hydraulic chamber, wherein the vane is movable in a first direction and a second direction opposite to the first direction, the vane moving in the first direction to advance the valve timing and moving in the second direction to retard the valve timing, wherein the movement of the vane rotates the second rotary member with respect to the first rotary member to change the rotational phase of the driven shaft with respect to the drive shaft;
• means for supplying hydraulic pressure to one of the first hydraulic chamber and the second hydraulic chamber to move the vane in one of the first direction and the second direction, the supplying means being selectively activated and deactivated based on an operational state of the engine;
• a lock member for locking the second rotary member to the first rotary member in a predetermined position to fix the rotational phase of the driven shaft with respect to the drive shaft, wherein the lock member is movable between a first position and a second position, wherein the lock member immovably holds the vane with respect to the hydraulic chambers to lock the second rotary member with respect to the first rotary member in the first position, and wherein the lock member releases the vane to unlock the second rotary member with respect to the first rotary member in the second position;
• one of the first rotary member and the second rotary member having an engagement recess, the other one of the first rotary member and the second rotary member having a supporting hole for movably supporting the lock member, wherein the lock member is engaged with the engagement recess in the first position and is disengaged from the engagement recess in the second position;
• means for urging the lock member toward the first position to hold the lock member in the first position when the engine is out of operation;
• and
• means for applying the hydraulic pressure to the lock member to move the lock member toward the second position against force of the urging means, wherein the hydraulic pressure is supplied by the supplying means upon the operation of the engine and maintains the lock member in the second position.