Relief valve

摘要

In the relief valve (R1), a piston (4) is provided with a rearward acting face (21) and a forward acting face (31) formed behind a first sliding portion (4a). A third liquid chamber (40) and a first liquid chamber (22) on which the rearward acting face (21) fronts communicate with each other in a piston. The third liquid chamber (40) and a second liquid chamber (32) on which the forward acting face (31) fronts communicate with each other in the piston. A restriction is provided in a communicating hole (11,12) for causing the third liquid chamber (40) and the first liquid chamber (22) or the third liquid chamber (40) and the second liquid chamber (32) to communicate with each other.