US Patent 7318398 Engine valve actuation system

An engine valve actuation system includes an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid. The system also includes a valve actuation assembly connected to move the engine valve between the first position and the second position and a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position. The fluid actuator includes a first piston. The system further includes an accumulator including a second piston, wherein the second piston is slidably movable in the first piston.