JPS6216859B

A hydraulic system in which pressurized fluid fed from a hydraulic pump is distributed through a distributor valve, on one part to a hydraulic booster for a brake and on the other part to a power steering unit or other hydraulic device. The distributor valve has a spool valve slidably fitted in a casing, the spool being displaced according to a fluid pressure differential acting at opposite ends thereof to increase the discharge pressure of the hydraulic pump in response to an increase in the fluid pressure at a first outlet port of the casing leading to the hydraulic booster or in the fluid pressure at a second outlet port leading to the power steering unit. Upon application of brake, a fluid passage which drains the first outlet port through a power piston is closed by movement of an input piston which is associated with a brake pedal, thereby slidingly displacing a valve piston. At this time, the discharge pressure of the hydraulic pump is increased and a third outlet port of the distributor valve is opened to admit the pressurized fluid from the hydraulic pump into a pressure chamber of the power piston through a valve which is opened by the displacement of the input piston for applying brake. An accumulator which is connected to the third outlet port of the distributor valve stores the pressurized fluid when the discharge pressure of the hydraulic pump is high, supplying the stored fluid to the pressure chamber of the power piston in the event of trouble with the pump or when a valve for the pressure chamber is opened.