Abstract: A pressure control system in which a pressure in a back pressure chamber of a flow control valve is controlled according to a throttle opening of a pilot valve to locate stationary the valve body of the flow control valve at a position corresponding to the throttle opening of the pilot valve. In the system, a fixed throttle is provided in an oil passage extended to the back pressure chamber of the flow control valve, thereby applying a dampering action to the valve body.

Abstract: A pressure control system in which a pressure in a back pressure chamber of a flow control valve is controlled according to a throttle opening of a pilot valve to locate stationary the valve body of the flow control valve at a position corresponding to the throttle opening of the pilot valve. In the system, a fixed throttle is provided in an oil passage extended to the back pressure chamber of the flow control valve, thereby applying a dampering action to the valve body.

Abstract: In a pressure control valve having a valve body (1), a pilot poppet (7) is so mounted in the body (1) as to permit/prevent communication between a low-pressure relief port (12) and a back-pressure chamber (5), while moderated and stabilized in its opening operation so as to realize a steady relief flow of the valve, which flow depends on relief-flow properties of a relief poppet (4) so provided as to permit/prevent communication between: a pressure supply port (2); and a relief port (3). A piston poppet (8) is slidably mounted in the relief poppet (4) to extend to the back-pressure chamber (5). A cross-sectional area of the piston poppet (8) is larger than an opening area of a seat portion (6a) of a passage (6) in which the pilot poppet (7) is inserted.