Jidosha Kiki Co., Ltd.

Isao Yagi

Takashi Kushiyama

Ryuta Sugawara

Jiro Satoh

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.

Antiskid brake control method

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. As a result, the brake pedal can be caused to move slowly, and the amount of brake-pedal movement can be reduced, even when the vehicle is traveling on a road surface having a low coefficient of friction (a low .mu.).

A hydraulic pressure booster which may be used in a brake system of a vehicle is constructed to allow a brake output to be increased upon ceasing the depression of a brake pedal, thus imparting a brake feeling which is favorable to a driver. Hydraulic pressure from a first power chamber flows into a second power chamber through a passage provided with an orifice in shunt with a check valve, such that flow from the first power chamber to the second power chamber is retarded while flow from the second power chamber to the first power chamber is unrestricted.

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Higashimatsuyama, Japan

Isao Yagi