Electro-hydraulic engine valve actuation system providing an actuator
and an actuator control system. The actuator includes primary and secondary actuation
chambers, defined by a piston, connected to the engine valve, and characterized
by increasing and correspondingly decreasing chamber volumes, as the piston is
urged away from neutral position. A fluid inlet is connected to a flow control
valve. A control valve includes an actuator, and has flow states for controlling
flow between two fluid inlets and a fluid outlet. The control valve includes first
and second opposed, control chambers, each connected to the actuator. There is
a spring in the second control chamber. The actuator of the flow control valve
is controlled to a first and second state, and there is an electrically uncontrolled
third flow state. There is a pair of temperature-compensated orifices which create
internal feedback, with the control chambers, between the engine valve motion and
the control valve position.