Braking pressure control apparatus in a wheel slip control system

Abstract

The invention is directed to a braking pressure control apparatus for controlling a wheel slip of a driven wheel during braking and driving operations, wherein pressure control valves are disposed in the fluid passage between a master cylinder and a wheel brake cylinder, and a changeover valve is disposed in the passage between the master cylinder and the pressure control valves, for blocking the flow of the brake fluid when the wheel slip of the driven wheel is controlled during the driving operation. A first reservoir having a first variable volume chamber for storing the brake fluid discharged from the wheel brake cylinder is provided and normally urged to be of its minimum volume. Also, a second reservoir having a second variable volume chamber for storing the brake fluid discharged from the wheel brake cylinder is provided and normally urged to expand for storing a predetermined amount of the brake fluid. A fluid pump is provided for pumping the brake fluid from the first and second reservoirs, and supplying the pumped brake fluid to the passage between the pressure control valves and the changeover valve in the wheel slip control during the braking and driving operations. Thus, the apparatus may be easily installed in a conventional braking system without any change to the master cylinder reservoir.