Brake system for the control of brake force distribution and slip

Claim 1

A brake system for automotive vehicles having front and rear wheels and front and rear wheel brakes, comprising: a pedal-actuated braking pressure generator unit for generating braking pressure in the wheel brakes of the front wheels; an electrically-controlled braking pressure generator unit for varying the braking pressure in the wheel brakes of the rear wheels, said unit having a vacuum chamber and a working chamber with a closeable outside-air inlet; a vacuum source attached to said vacuum chamber; sensors associated with said wheels to determine the vehicle speed and the wheel rotational behavior and to generate signals indicating this information; electronic circuits for receiving and logically processing said signals, and for generating control signals; and a three-way/three-position rotary spool valve for receiving said control signals, said valve having a stationary control disc and a movable control disc with an opening therein permitting communication between either of said vacuum source or outside air through said inlet and the working chamber of said electrically-controlled braking pressure generator unit, whereby said valve varies the pressure difference between said vacuum and working chambers depending upon the angular position of said two discs relative to each other and to the opening cross-section and whereby the braking pressure on the wheels can be adjusted in response to said control signals from any of the three valve positions directly to any other valve position.