Fluid pressure control device

摘要

A fluid pressure control device has a sliding member fitted in a housing for switching over the connection and the disconnection between an input port connected to a fluid pressure supply source, an output port connected to a fluid pressure operated device and a release port connected to a reservoir; a reaction chamber for generating a fluid pressure urging the sliding member in a retracting direction; an urging piston operatively connected to the rear end of the sliding member; an input piston operatively connected to an operation member; and a pressure chamber formed between a back surface of the urging piston and a front surface of the input piston; wherein a first pressure receiving area of the sliding member exposed to the reaction chamber is set smaller than a second pressure receiving area of the urging piston exposed to the pressure chamber, and the second pressure receiving area is set smaller than a third pressure receiving area of the input piston exposed to the pressure chamber. The ratio of the pressure receiving area of the urging piston, exposed to the pressure chamber to the pressure receiving area of the sliding member, exposed to the reaction chamber is greater than a ratio of the pressure receiving area of the input piston, exposed to the pressure chamber of the urging piston, exposed to the pressure chamber (i.e., A2/A1>A3/A2).