Variable valve timing mechanism of engine

An apparatus for adjusting the valve timing of at least one of an intake valve and an exhaust valve of an engine, the apparatus comprising:

• a camshaft for actuating one of said intake valve and said exhaust valve;
• a rotary member surrounding a distal end of said camshaft, said rotary member having a first surface and a second surface for respectively receiving fluid pressure from opposite directions;
• a gear member positioned between said camshaft and said rotary member, said gear member being arranged to move in an axial direction to change the relative rotational relationship between said camshaft and said rotary member;
• a first cover fixed to the distal end of the camshaft, wherein said first cover defines a first chamber between the first cover and the gear member for receiving fluid pressure to move the gear member axially;
• a second cover fixed to the camshaft, wherein said second cover defines a second chamber between the second cover and the gear member for receiving fluid pressure to move said gear axially;
• a first clearance defined between the first surface and the first cover to communicate with the first chamber;
• a second clearance defined between the second surface and the second cover to communicate with the second chamber;
• a third surface provided on said rotary member between the first surface and the second surface, said third surface being arranged to receive a force resulting from fluid pressure directed opposite to a force resulting from the fluid pressure received by the second surface;
• a first inner surface provided on the rotary member adjacent to said first surface;
• and
• a second inner surface provided on the rotary member adjacent to said second surface, wherein said first inner surface has a diameter greater than that of said second inner surface, and
• wherein said engine comprises a crankshaft, and the torque of said crankshaft actuates said apparatus.