Patent ID: 7503297

Claim:
A valve drive mechanism for an engine, the valve drive mechanism comprising: a drive shaft that is configured for rotation about an axis; a valve member that is configured to be driven by the rotation of the drive shaft to open and close a valve; and a variable valve mechanism positioned at least partially between the valve member and the drive shaft, the variable valve mechanism configured to vary a valve open period of the valve; wherein the variable valve mechanism is configured such that, during a specific operation range, the valve open period includes a main valve open period during which the valve is open in a suction or exhaust stroke, and a sub valve open period during which the valve is open in an expansion or compression stroke; wherein the variable valve mechanism comprises a rocker cam having a main lift portion on one end and a sub lift portion on an opposite end, the main lift portion configured to engage the valve member during the main valve open period, and the sub lift portion configured to engage the valve member during the sub valve open period.