Patent ID: 7007648

Claim:
An oil passage structure for an engine, the engine including: a tensioner arm provided in sliding-contact with a cam chain, the cam chain being adapted to reduce the speed of a crankshaft by half and transmit the resultant power to intake and exhaust camshafts of the engine for driving an intake valve and an exhaust valve of the engine; a screw type lifter having a lifter rod with one end in contact with the tensioner arm, the screw type lifter being provided in a cylinder head of the engine; an oil passage formed so as to extend around said cylinder head, oil discharged from an oil pump of the engine being fed through said oil passage, wherein the camshafts are rotatably supported by a plurality of cam journal walls provided in the cylinder head and a plurality of cam holders fastened to the plurality of cam journal walls, respectively, wherein said oil passage is formed in such a manner as to pass through sliding-contact portions between said camshafts and one of the plurality of cam journal walls and one of the plurality of cam holders, wherein said oil passage includes: a pair of annular grooves surrounding the camshafts, said annular grooves being provided in said one cam journal wall and said one cam holder; a communication groove for connecting said annular grooves to each other, said communication groove being provided in at least one of joining faces of said one cam journal wall and said one cam holder in said cylinder head; and a pair of communication passages provided in a straight line in said one cam journal wall in such a manner as to be in communication with said annular grooves, respectively, wherein a downstream end of said oil passage is in communication with the screw type lifter.