The fuel efficiency and power output of an internal combustion engine can be significantly improved by optimizing the intake and exhaust valve timing and duration as the engine speed changes during operation. Valve timing refers to the angular position of the engine crank shaft the moment the valve is opened. Valve duration refers to the length of time the valve remains in an open position.
A number of devices are conventionally used in engines to open and close intake and exhaust valves. These devices include cam shafts, push rods, rocker arms and hydraulic tappets. These devices do not permit variation of either valve timing or duration during engine operation and are expensive and subject to failure. In addition, their use results in substantial energy loss due to friction.
Consequently, a need exists for a device that permits variable valve timing and variable valve duration during transient engine operation and eliminates conventional valve operation gear.
Two patents issued to Richeson, U.S. Pat. No. 4,899,700 and U.S. Pat. No. 4,915,015, disclose an electronically controlled pneumatically powered valve mechanism actuator for use in an internal combustion engine.
U.S. Pat. No. 885,459 issued to Engler et al. discloses a pneumatic or hydraulic engine valve control mechanism.