| 摘要 |
PROBLEM TO BE SOLVED: To prevent early lockup of the front or rear wheels alone of a vehicle by bringing the distribution of braking forces to the front and read wheels as close to an ideal distribution curve as possible. SOLUTION: A variable piston spring load means 30 is provided which gradually increases the load of a piston spring 11 on a control piston 8 by compressing the piston spring 11 as hydraulic pressure generated from a hydraulic pressure generator rises, the piston spring 11 expanding and contracting as the control piston 8 reciprocates. When the resultant force of the generated hydraulic pressure acting on the control piston 8 and the load of the piston spring 11 is greater than hydraulic pressure reaction from rear wheel brakes because of the actuation of the variable piston spring load 30, the control piston 8 is moved in the direction of an output hydraulic pressure chamber 21 to hold a valve in an open state during which closure of a liquid passage 22 by a valve element 32 is canceled; when the resultant force acting on the control piston 8 is smaller than the hydraulic pressure reaction, the control piston 8 is moved in the direction of the piston spring 11 to hold the valve in a closed state during which the liquid passage is closed by the valve element. These two states are repeated.
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