Patent ID: 6782852
Filing Date: 2004-08-31
Classification: F01L

Abstract:
A hydraulic actuator for operating an engine cylinder valve comprises:a driver piston to move the engine cylinder valve into open and closed states; a hydraulic valve in fluid communication with the driver piston, a first conduit carrying fluid at a first pressure, and a second conduit carrying fluid at a second pressure that is less than the first pressure; the hydraulic valve having a valve spool which in a first position enables fluid flow between the first conduit and the driver piston to open the engine cylinder valve and in a second position enables fluid flow between the second conduit and the driver piston to allow the engine cylinder valve to close; an operator operably coupled to produce movement of the valve spool into the first position and the second position; and a feedback mechanism coupled to the valve spool and responsive to movement of the driver piston by moving the valve spool into a third position at which neither the first conduit nor the second conduit is in fluid communication with the driver piston.