Patent ID: 7980210

Claim:
A valve drive device comprising: an exhaust or intake valve configure to open and close an intake or exhaust port; a valve drive member configured to move the valve from an open position to a closed position; a drive shaft configured to drive the valve drive member; and a variable valve timing mechanism configured to continuously change a working angle of the intake or exhaust valve in response to an operation state of the engine, the variable valve timing mechanism comprising a variable valve clearance mechanism configured to change a valve clearance between the valve and the valve drive member from a first value during a first condition in which the working angle of the valve is large to a second different value during a second condition in which the working angle of the valve is small; wherein the variable valve timing mechanism includes a swing cam member, which has a drive surface and is swingably supported, and swung by the drive shaft, and a cam follower disposed between the drive surface of the swing cam member and a pressed surface of the valve drive member such that a relative position to a fulcrum of the valve drive member is adjustable, and the variable valve clearance mechanism is configured such that a center of curvature of the pressed surface pressed by the cam follower of the valve drive member is displaced relative to a center of curvature of a base circular part of the drive surface of the swing cam member so that the valve clearance becomes larger as the valve working angle becomes smaller.