Variable valve timing mechanism for internal combustion engine

A variable valve timing mechanism for an internal combustion engine, the engine having at least one valve, which is driven by a driven shaft, and a drive shaft, the variable valve timing mechanism serving to vary the timing of the engine valve by varying the rotational phase of the driven shaft with respect to the drive shaft, wherein the variable valve timing mechanism includes a first rotary member for rotating in fixed synchronism with the drive shaft, a second rotary member for rotating in fixed synchronism with the driven shaft, and a hydraulic actuating mechanism for varying the position of the first rotary member with respect to the second rotary member, which changes the phase of the driven shaft with respect to the drive shaft, the hydraulic actuating mechanism comprising:

• a movable actuator that is movable in two opposite directions between a valve advance limit position, at which the actuator is stopped at a position where the valve timing is advanced to a maximum degree, and a valve retard limit position, at which the actuator is stopped at a position where the valve timing is retarded to a maximum degree, wherein movement of the actuator causes the first rotary member to rotate with respect to the second rotary member thus changing the rotary phase of the drive shaft with respect to the driven shaft;
• a first hydraulic chamber located on one side of the actuator;
• a second hydraulic chamber located on the opposite side of the actuator;
• means for selectively applying hydraulic fluid pressure to the first and second pressure chambers to cause the actuator to move in a selected direction;
• a lock member for locking the first rotary member to the second rotary member at a predetermined position for fixing the phase of the driven shaft with respect to the drive shaft, wherein the lock member has a locked position, at which the first rotary member is fixed with respect to the second rotary member and the actuator is fixed with respect to the hydraulic pressure chambers, and an unlocked position, at which the actuator may move with respect to the hydraulic pressure chambers to permit relative movement between the first and second rotary members, wherein the lock member is biased such that the locking member is moved toward its locked position when the engine is not running, and wherein the actuator is spaced from both limit positions when the locking means is locked.

A variable valve timing mechanism for an internal combustion engine for varying a timing of a valve actuated by a driven shaft by varying a rotational phase of the driven shaft with respect to a rotational phase of a drive shaft of the engine, the mechanism comprising:

• a first rotary member for rotating in synchronism with one of the drive shaft and the driven shaft and having at least one recess therein;
• a second rotary member located within the first rotary member for rotating integrally with the other of the driven shaft and the drive shaft, the second rotary member having a vane associated with the recess, the vane being movable between two limit positions within the recess and dividing the recess into first and second pressure chambers;
• actuating means for causing relative rotation of the second rotary member with respect to the first rotary member by selectively applying pressures to the first and second pressure chambers to move the vane;
• and
• lock means for locking the relative rotation of the second rotary member to the first rotary member such that the vane is kept between the two limit positions when the engine starts with the phase of the second rotary member being fixed with respect to the reference rotational phase and for releasing the lock means after the engine reaches a predetermined running condition.

A variable valve timing mechanism for an internal combustion engine for varying a timing of a valve actuated by a driven shaft by varying, a rotational phase of the driven shaft with respect to a reference rotation phase of a drive shaft of the engine, the mechanism comprising:

• a sprocket for rotating in synchronism with the drive shaft and having a plurality of recesses therein;
• a rotor located within the sprocket for rotating integrally with the driven shaft, the rotor having a plurality of vanes associated with the recesses, each vane being movable between two limit positions within each recess and dividing each recess into first and second pressure chambers;
• actuating means for making a relative rotation of the rotor to the sprocket by applying pressures to the first and second pressure chambers to move each vane;
• and
• lock means for restricting the relative rotation of the rotor to the sprocket such that each vane is kept at position that is between the two limit positions when the engine is cranked such that the phase of the rotor is fixed with respect to the reference rotational phase and for releasing the restriction after the engine reaches a predetermined running condition.