ANTI-SKID CONTROL APPARATUS FOR A VEHICLE BRAKING SYSTEM

Anti-skid control apparatus includes wheel speed sensors for front and rear wheels. First and second fluid pressure control valve devices control brake fluid pressures of wheel cylinders of the front and rear wheels, arranged between fluid pressure generating chambers of a tandem master cylinder and the wheel cylinders respectively. A control unit receives outputs of the sensors for measuring or judging the skid conditions of the wheels and for generating instructions for controlling the valve devices. A valve apparatus generates fluid pressure in accordance with the lower one of the brake fluid pressures of the front wheels controlled with the valve devices arranged between the wheel cylinders of the front wheels and those of the rear wheels. When the wheel speed difference between the front and rear wheels on the same side of the road becomes larger than a predetermined value, or when the deceleration of the one rear wheel becomes larger than a predetermined deceleration for the one rear wheel which is smaller than a second predetermined deceleration for the one front wheel running on the same side as the one rear wheel, before the one front or rear wheel on the same side first generates a brake relieving signal, the control unit generates the instruction which controls the first or second fluid pressure control valve device for the same side so as to maintain the pressure constant, or to reduce the rising gradient of the pressure.