METERING VALVE WITH INTEGRAL RELIEF AND MAKEUP FUNCTION

摘要

A metering valve (36) for a work machine hydraulic system (22) is disclosed. The metering valve has an inlet (86) and an outlet (88), a main poppet (76), and a solenoid-operated pilot element (74). The main poppet is movable to pass fluid from the inlet to the outlet, and to block fluid from the inlet to the outlet. The solenoid-operated pilot element is movable between a first position at which pressurized fluid from the inlet pressurizes a control chamber (126) in communication with a control end (76b) of the main poppet to urge the main poppet toward the flow-blocking position, and a second position at which the control chamber is communicated with a drain (24) to move the main poppet toward the flow-passing position. The metering valve also has a relief valve element (77) configured to drain pressurized fluid from the control chamber to move the main poppet toward the flow-passing position in response to a pressure at the inlet exceeding a predetermined pressure.