Antiskid control apparatus for automobiles

Claim 1

An antiskid control apparatus for use in an automobile having a brake master cylinder and at least one wheel cylinder, comprising: (a) a fluid pressure circuit for connecting the brake master cylinder and the wheel cylinder; (b) a cutoff valve disposed in said fluid pressure circuit and adapted to be interposed between the brake master cylinder and the wheel cylinder for hydraulically separating the wheel cylinder from the master cylinder; (c) a pump for generating a working fluid pressure; (d) a brake fluid-pressure adjusting piston movable in one direction by a fluid pressure from the wheel cylinder for closing said cutoff valve and for increasing the volume of said fluid pressure circuit between said cutoff valve and said wheel cylinder and also movable in an opposite direction by the working fluid pressure for reducing the volume of said fluid pressure circuit between said cutoff valve to increase the fluid pressure applied to said wheel cylinder and opening said cutoff valve; (e) a pressure regulating valve for regulating the working fluid pressure generated by said pump by applying a resistance responsive to the fluid pressure imposed by said brake master cylinder to a working fluid flowing from a discharge port of said pump to a reservoir; (f) a solenoid-operated valve for supplying and discharging said working fluid pressure to and from said brake fluid-pressure adjusting piston; (g) a wheel speed sensor for detecting the speed of rotation of a wheel associated with said wheel cylinder; (h) an electronic control circuit for detecting whether said wheel is subject to a skid or not based on a signal from said wheel speed sensor, for controlling said solenoid-operated valve to supply said working fluid pressure to said brake fluid-pressure adjusting piston when said wheel is not subject to a skid, and for controlling said solenoid-operated valve to discharge said working fluid pressure from said brake fluid-pressure adjusting piston when said wheel is subject to a skid; (i) a motor for actuating said pump, said motor being controlled by said electronic control circuit for being de-energized at least when said wheel is not braked; and (j) a pressure compensating piston having a pair of pressure bearing areas to which the fluid pressure from said master cylinder and said working fluid pressure are applied, respectively, for generating said working fluid pressure simultaneously with the generation of said fluid pressure from said master cylinder.