US Patent 7198015 Variable valve timing system

A variable valve timing system in which the cam shaft is rotated with respect to the crankshaft position by moving a shaft disposed interior to the cam shaft longitudinally has been developed. The variable valve timing system provides for varying the timing of the opening and closing of an engine's poppet valves (relative to the crankshaft angular position) to enhance the engine's efficiency and output. The timing system can be used with both intake and exhaust valves in both diesel and gasoline engines. The timing system is inexpensive to produce, and performs reliably over a lengthy period of time.