US Patent 7757645 Variable valve system for internal combustion engine

A variable valve system for an internal combustion engine includes a drive shaft rotated by an engine crankshaft, a drive cam integrally mounted on the drive shaft, first and second swing cams mounted on first and second engine valves in each engine cylinder, a valve lift mechanism for converting a rotational movement of the drive cam into swing movements of the first and second swing cams to open and close the first and second engine valves, and a control mechanism for controlling the operating position of the valve lift mechanism to vary the valve lifts of the first and second engine valves according to engine operating conditions. The valve lifts of the first and second engine valves are different from each other when the control mechanism performs minimum lift control on the valve lift mechanism to control the valve lifts of the first and second engine valves to minimum lifts.