Valve mechanism for an internal combustion engine

摘要

A valve drive mechanism for actuating a valve of an internal combustion engine includes a camshaft that is rotated by a crankshaft of the internal combustion engine. The crankshaft has a cam with positive and negative acceleration portions. A swing member rocked on a support shaft by rotation of the cam. The swing member has a cam surface configured to drive the valve. The cam surface has a base circle portion, a lift portion, and a ramp portion extending between the base circle portion and the lift portion. The ramp portion is configured such that when the positive or negative acceleration portions of the cam actuate the swing member, a lift speed of the valve is substantially constant.