Road vehicle drive-slip control device and anti-lock system

Claim 1

A drive-slip control device and anti-lock system in a road vehicle, comprising a hydraulic multi-circuit brake system, in which wheel brakes of driven vehicle wheels are combined in a static brake circuit which is connected to an outlet-pressure space of a brake unit and in which anti-lock control is operative on the return-flow principle and drive-slip control is operative on the principle of decelerating again a driven vehicle wheel tending to spin by actuating an associated wheel brake, brake-pressure regulating valves assigned individually to the wheel brakes of the driven vehicle wheels and utilized in both the anti-lock mode and the drive-slip control mode for controlling brake-pressure build-up, holding and reduction phases, in the course of which the wheel brakes are at least individually connected to a main brake line of the brake system, being one of shut off therefrom and connected to a system return line, a buffer accumulator operatively connected therein, a high-pressure return flow pump operatively connected on an inlet side thereof to the system return line and the buffer accumulator and to a brake-fluid reservoir of the brake system, and on an outlet side thereof to the main brake line of the brake circuit of the driven vehicle wheels and which, in this course of control phases of the anti-lock control, conveys a quantity of brake fluid corresponding to a quantity of brake fluid bled in pressure-reduction phases of the anti-lock control into the return line and the buffer accumulator from a wheel brake subjected to the control, back into an outlet-pressure space of the brake unit and is utilized for the drive-slip control as an auxiliary pressure source which conveys brake fluid from at least one of the brake-fluid reservoir of the brake system and the return line and from the buffer accumulator into the main brake line of the brake circuit of the driven vehicle wheels, a drive-slip control solenoid valve which, for the drive-slip control, can be moved out of a basic position assigned to a normal braking mode and to a braking mode subjected to an anti-lock control and in which the outlet-pressure space of the brake unit assigned to the brake circuit of the driven vehicle wheels is connected to the main brake line of the brake system, into a functional position in which the main brake line and the outlet of the return-flow pump are shut off from the outlet-pressure space of the brake unit, a pressure relief valve connected in parallel with the drive-slip control valve and via which, even when the drive-slip control valve is in the closing position, brake fluid can be conveyed back towards the brake unit by the return-flow pump and an electronic control unit for generating control signals necessary for actuating the brake-pressure regulating valves, the return-flow pump and the drive-slip control valve in one of the anti-lock mode and drive-slip control mode, as a result of a processing of output signals from wheel-speed sensors assigned to the vehicle wheels and emitting electrical output signals which in terms of at least one of level and frequency contain the information on the dynamic behavior of the vehicle wheels, wherein, after termination of a situation requiring the drive-slip control and in the event of an interruption of a drive-slip control cycle as a result of the actuation of the brake system, the electronic control unit generates control signals, by way of which for a delay time, the return-flow pump continues to operate and the drive-slip control valve is maintained in a closing position assigned to the drive-slip control mode, the duration of this delay time being sufficient to ensure that a quantity of brake fluid corresponding to a quantity previously received by the buffer accumulator of the brake circuit of the driven vehicle wheels is conveyed out of the brake circuit back into the outlet-pressure space of the brake unit assigned thereto.