Drive-slip control device (ASR) on a road vehicle also equipped with an anti-lock system (ABS)

DETAILED DESCRIPTION The invention relates to a drive-slip control device (ASR) for a road vehicle brake system equipped with an anti-lock system (ABS) and having a hydraulic dual-circuit brake system.
One brake circuit is assigned to the driven vehicle wheels and the other brake circuit to the non-driven vehicle wheels and the two brake circuits are designed as static brake circuits, each of which is assigned to an outlet-pressure space of a brake unit provided for brake actuation.
The brake system operates in accordance with the following: At least on the brake circuit of the driven vehicle wheels, the ABS works on the return-flow principle during pressure-reduction phases of the anti-lock control, to return a quantity of brake fluid (corresponding to that quantity of brake fluid flowing off from the wheel brake(s) undergoing the control) into a return line connected to a buffer accumulator for pumping back into the brake unit by a return pump which has its inlet side connected to the buffer accumulator and its outlet side to the brake unit; Wherein the ASR works on the principle of decelerating a vehicle wheel tending to spin by subjecting its wheel brake to pressure from an auxiliary-pressure source such that its drive slip remains within a value range compatible with a sufficient dynamic stability of the vehicle; Wherein during drive-slip control mode, the return pump of the ABS assigned to the brake circuit of the driven vehicle wheels is utilized as an auxiliary-pressure source from which pressure is supplied to the wheel brake(s) in pressure build-up phases; Wherein there is an ASR control valve which can be changed over from a basic normal braking mode position in which brake fluid can be positively displaced into the wheel-brake cylinders of the brakes of the driven vehicle wheels as a result of the actuation of the brake unit, into an alternative functional position, in which brake fluid is prevented from flowing off from the main brake line of the brake circuit of the driven vehicle wheels towards the respective outlet-pressure space of the brake unit