Pressure shifted valve timing

Abstract

A hydraulic pump-motor includes a cylinder block including a plurality of fluid chambers, a piston in each of the fluid chambers, a cam, a fixed valve area profile, and a timing adjustment actuator. The cam includes a cam surface that engages the pistons and drives movement of the pistons relative to the fluid chambers in response to relative rotation between the cam and the fluid chambers. The fixed valve area profile is configured to control fluid flows between the fluid chambers and first and second ports. The timing adjustment actuator is configured to adjust an angular orientation of the fixed valve area profile relative to an angular orientation of the cam based on a pressure differential between a pressure at the first port and a pressure at the second port.