Hydraulic actuator as an element of a system for controlling an engine
valve is presented. The actuator includes a fluidic actuation chamber,
defined by an actuation piston that increases chamber volume as the
actuation piston is urged away from a neutral. Chamber includes a high
pressure fluid inlet and a fluid outlet. A fluidic actuator control
chamber, defined by a control piston connected to the actuation piston
that increases chamber volume as the actuation piston is urged away from
neutral. A control fluid outlet is connected to a fluid control spool
valve. The fluid outlet of the actuation chamber is fluidly connected to
an inlet of the control valve. There is a valve actuation plunger
operably connected to the actuation piston, and a drain outlet to
maintain a fluidic backpressure to the actuator control chamber.