A control valve
assembly (43) for use in a
system in which a pump-
motor unit (35) can either receive drive torque from a drive-line (17) or transmit torque thereto. The
system includes a
high pressure accumulator (41) and the control valve
assembly is disposed between the pump-
motor unit and the accumulator, and includes a mode valve (45) normally biased closed by pressure in a control cavity (89), the
fluid pressure in which is controlled by a
pilot valve
assembly (49) in response to an electrical
signal (133). A step-orifice valve (47) associated with the mode valve poppet member (79) provides a relatively larger orifice (115) into the control cavity (89) when pressure therein is high, and a relatively smaller orifice (119) into the control cavity when pressure therein is low, i.e., when the
pilot valve assembly (49) is open. Thus, a large volume of flow can occur from the accumulator to the unit (35) in a motoring mode, with a relatively low pressure drop, while the poppet member is able to have softer, relatively longer opening time, but a relatively faster closing time.