Patent ID: 6857408
Filing Date: 2005-02-22
Classification: F01L,F02B

Abstract:
1. An internal combustion engine comprising: a crankshaft; a camshaft driven for rotation in synchronism with the crankshaft a valve-operating cam formed on the camshaft; engine valves operated for opening and closing by the valve-operating cam; and a decompressing mechanism which opens the engine valve in a compression stroke in a starting phase; wherein the decompressing mechanism comprises a flyweight supported for swinging motion by a pin on the camshaft, a decompression cam that operates together with the flyweight to exert a valve-operating force on one of the engine valves, and an arm connecting the flyweight and the decompression cam, said decompression cam having a contact surface facing the cam shaft and slidingly guided by a guide surface formed on the cam shaft when the flyweight undergoes the swinging motion together with the decompression cam, and a cam lobe for exerting force on one of said engine valves, said cam lobe being formed on the decompression cam at the opposite side of the guide surface to protrude in a direction parallel to said axis of swing motion, the flyweight has a weight body and projections projecting from the weight body and engaged with the pin, the pin is disposed such that an axis of swinging motion of the flyweight is included in a plane substantially perpendicular to an axis of rotation of the camshaft, the weight body is a block of a width along the axis of swinging motion and a thickness along a radial direction which are greater than a thickness along the axis of swinging motion of the arm, the weight body overlaps the camshaft as viewed from a direction perpendicular to a reference plane including the axis of rotation of the camshaft and parallel to the axis of swing motion.