| 摘要 |
PROBLEM TO BE SOLVED: To strongly operate a boosted hydraulic pressure proportional to an output hydraulic pressure by allowing a hydraulic source port to communicate with a booster port by a spool valve element in the forward movement of a control piston by the pressure rise of a control hydraulic chamber. SOLUTION: A control piston 16 advances forward with a spool valve element 17 while compressing a return spring 25, and when the spool valve element 17 reaches a forward position contact with the inner end wall of a valve port 19, the spool valve element 17 allows a hydraulic source port 20 to communicate with a booster port 22. Since the hydraulic pressure of an accumulator is transmitted to the second input hydraulic chamber 552 of a front secondary master cylinder M2f through the hydraulic source port 20 and the booster port 22 to press the minor diameter piston part 53s of an operating piston 53, the operating piston 53 is moved forward. Since a relief port valve 60 is immediately closed, a hydraulic pressure is generated in an output hydraulic chamber 54 according to the forward movement of the operating piston 53, and this hydraulic pressure is outputted to a front main brake oil passage 3f and transmitted to front wheel brakes to boost and operate them. |
