US Patent 7444971 Valve timing control apparatus of internal combustion engine

A valve timing control apparatus is adapted to an exhaust valve side of an internal combustion engine. A vane member is arranged to rotate with a camshaft relative to a timing sprocket member. The vane member is rotated at low speed engine operation dominantly by a camshaft-torque actuation mechanism and at high speed engine operation dominantly by a hydraulic actuation mechanism. The camshaft-torque actuation mechanism is actuated by an alternating torque of the camshaft, whereas the hydraulic actuation mechanism is actuated by a fluid pump. The camshaft-torque actuation mechanism and hydraulic actuation mechanism are controlled independently of each other.