| 摘要 |
PURPOSE: To enable the pressure limit of a brake fluid passage to be designed to be low by forming a control valve with a sliding member which is stopped in a non- operating position within a communicating line by the compression of springs with the fluid pressure of pressure chambers on which braking fluid pressure works, and allowing the control valve to function also as a limiter which prevents the operation of a pressure increasing mechanism beyond a full-load point. CONSTITUTION: An engagement member 38 is provided which, when a stepped piston 22 is in a non-operating position, moves a valve element 28 apart from a valve seat 33 against a spring 31 by forcing the piston end inserted in a communicating line 22f to abut to the valve element 28. A fourth pressure chamber 37 is formed inside the stepped piston 22 and on that side of the large-diameter portion of a sliding member 27 facing a first pressure chamber 23, and is communicated with a third pressure chamber 25 by a passage 22h. If fluid pressure working on the pressure chambers 25, 37 becomes zero as a result of the failure of an accumulator 12 and under these conditions a braking fluid pressure at the operation of a brake pedal works on the first pressure chamber 23 and lowers the stepped piston 22, the valve element 28 pressed by springs 36, 31 is seated on the valve seat 33 to close the communicating line 22f. |
