Abstract: A first threshold value of a fixed amount of vehicle velocity arranged on the lower side of the vehicle velocity is set, and a second threshold value of a fixed amount of vehicle velocity also arranged on the lower side of vehicle velocity, which second threshold is greater than that of the first threshold value. The difference between vehicle velocity at maximum recovery velocity of wheel velocity and the maximum recovery velocity of the wheel velocity is compared with the first and second threshold values, and the next point at which a changeover is made to repressurization of brake fluid is altered in dependence upon the results of the comparison. Accordingly, repressurization of the brake cylinder is controlled in dependence upon the condition of the road surface on which the vehicle is traveling, and more appropriate antiskid braking control can be achieved.

Abstract: An antiskid brake control system includes a supply passageway (16) bypassing a pressure-compensated flow control valve (13), and a check valve (22), which allows flow of brake fluid only toward a wheel cylinder, or a check valve (23), which allows flow of brake fluid only away from the wheel cylinder, is provided inside the supply passageway (16) and arranged in series with an orifice (15). Accordingly, antiskid brake control is such that either slow and fast pressurization modes, a fast depressurization mode and a holding mode or slow and fast depressurization modes, a fast pressurization mode and a holding mode are established. A sudden fluctuation in braking hydraulic pressure can be suppressed by establishing the holding mode when there is a transition from the fast depressurization mode to the fast pressurization mode or from the fast pressurization mode to the fast depressurization mode.

Abstract: When skidding of a wheel is detected at braking of the wheel, a passage changeover valve is changed over to allow a brake fluid within a brake cylinder to escape to a low-pressure accumulator, thereby reducing the pressure within the brake cylinder. In addition, by driving a pump, the brake fluid, which has accumulated in the low-pressure accumulator, is fed under pressure to circulate this brake fluid to a brake fluid passage between the master cylinder and the passage changeover valve. When wheel velocity recovers a predetermined amount, the passage changeover valve is changed over, thereby supplying the brake fluid from the pump to the brake cylinder so as to increase the pressure of the brake cylinder again. When the wheel velocity of the braked wheel has recovered to a predetermined wheel velocity, brake hydraulic pressure is generated a predetermined number of times in pulsed fashion, after which the brake hydraulic pressure is increased again.

Abstract: In the sump unit 1 of this invention, the sump unit 1 is installed in the operating fluid passage 4, and the fluid accommodating chamber 1a is formed as a part of the operating fluid passage 4.Therefore, the sump unit 1 does not protrude extensively from the operating fluid passage 4, and the fluid pressure control unit can be designed in more compact form. Because the fluid accommodating chamber 1a of the sump unit 1 is formed as a part of the operating fluid passage 4, the air intermingled with the operating fluid in the fluid accommodating chamber 1a can be easily withdrawn, and this extensively facilitates the air vent of the fluid pressure control unit.