A brake system providing traction slip of the controlled driven wheels. The rotating pattern of the driven wheels is permanently monitored by sensors (S1, S3 and S2, S4, respectively). In the event that one of the driven wheels tends to spin, the system switches to the traction slip mode so that a drive M of two pumps (21, 26) is actuated and an ASR valve (80) reswitched causing the air pressure to be applied to the booster chamber of the servo system (3) and the master cylinder to be actuated independently of the pedal actuation. During the start-up phase of the pumps (21, 26) pressure fluid is passed from the master brake cylinder to the driven wheels enabling a fast and effective pressure build-up in the wheel brakes of the driven wheels to effectively prevent the wheels from spinning. The master cylinder (2) therefore provides the function of an accumulator.
In a method of operating an anti-lock automotive vehicle brake system for driving stability control and/or traction slip control which includes a brake force booster operable irrespective of the driver's wish, the brake force booster, at the commencement of control, will achieve its maximum attainable boosting force irrespective of the driver's wish, and the desired wheel braking pressures are adjusted by way of the ABS hydraulic unit, and at the end of the control, the independent actuation of the brake force booster will not be deactivated until the brake force booster has been reset to its initial position by returning the pressure fluid discharged from the wheel brakes into the low-pressure accumulators.
The proposed brake system eliminates breather bores and central valves in the working pistons of the master brake cylinder and establishes short-term pressure fluid connections between the supply reservoir and the working chambers when the brake is not applied by controlling replenishment valves and outlet valves. Therefore, connection of the supply reservoir to the working chambers of the working cylinder is constituted solely via electromagnetically controllable connections.
The proposed brake system eliminates breather bores and central valves in the working pistons of the master brake cylinder and establishes short-term pressure fluid connections between the supply reservoir and the working chambers when the brake is not applied by controlling replenishment valves and outlet valves. Therefore, connection of the supply reservoir to the working chambers of the working cylinder is constituted solely via electromagnetically controllable connections.
An anti-lock-controlled brake system which, with a minimum number of locking valves between the pressure medium storage reservoir (20) and the wheel brakes (31, 32, 33, 34), is equally suitable for traction slip control with all types of brake circuit allocation. An electromagnetically operated locking valve (27) is provided in the connection line (18) from the pressure medium storage reservoir (20) to the first pressure chamber (8), while the connection through connection line (19) to the second pressure chamber (9) is controlled via the stroke of the floating piston (7) applied by the pressure of the primary brake circuit (I). The pressure build-up required in the primary brake circuit (I) at the beginning of a traction slip control operation is brought about by a pump (26) or the like which either is already provided for brake-slip-dependent braking pressure control or is additionally incorporated in the hydraulic circuitry exclusively for traction slip control.
An active compensation system for an anti-locking brake system eliminates undesirable brake fluid pressure buildup and, therefore, brake drag by controlling the normally closed valves within the anti-locking brake system through the anti-locking brake system electronic control module to allow the undesired pressure to be released as the brake fluid passes through the normally closed outlet valves into pressure relieving conduits.
