To miniaturize a shockless relief valve which is also used as a flow control valve in which the shockless relief function is given to a seat valve provided with the flow rate control function.
When an actuator 42 is rapidly operated, and the pressure P0 of an inlet port 6 rises, the working oil is introduced to a pressure bearing chamber 23 through communication passages 4, 11, a pressure bearing chamber 12, a communication passage 24, and a fixed restrictor 18a. When a piston 19 is in motion, the working oil from the inlet port 6 is introduced to the pressure bearing chamber 23 through the same route. Because the pressure P2 in a spring chamber 16 is less than the pressure P1 to be applied to a pressure bearing end part 13A, the force to be applied to the other end part 13B becomes smaller compared with that in the normal relief where P2=P1. Because the force in the valve-opening direction due to the difference in the pressure bearing area between the pressure bearing end part 13A and the end part 13B, a poppet valve 13 is opened to perform the relief even when the pressure on the inlet port 6 side of a seat valve 2 is lower compared with that in the normal relief.
NOZAWA YUSAKU
ICHIKI NOBUHIKO
TAKAHASHI KINYA
NISHIMURA YOSHIZUMI
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