Drive slip control device

Claim 1

Drive slip control device for road vehicle having driven and non-driven wheels, wheel brakes and a hydraulic twin-circuit brake installation with front axle and rear axle brake circuit subdivisions and wherein one of the brake circuit subdivisions is associated with the non-driven vehicle wheels and the other is associated with the driven vehicle wheels; said brake circuit subdivisions having static brake circuits whose brake pressure supply is achieved by a brake device having two outlet pressure spaces, one associated with each brake circuit subdivision; an anti-lock braking system operating on the pump-back principle, comprising: brake pressure control valve means associated individually with each of the driven and non-driven vehicle wheels; two return pump means associated, one each, with the two brake circuit subdivisions; said return pump means during pressure reduction phases of the anti-lock control, pumping brake fluid out of the wheel brake(s) then subjected to anti-lock control into output pressure spaces of the brake device with a pressure space being associated with a particular brake circuit subdivision; said return pump means of the brake circuit of the driven vehicle wheels being used as a pressure source in brake pressure build-up phases of the drive slip control; a drive slip two-way two position control valve means for connecting the return pump means to the pressure space of the brake device supplying pressure to the brake circuit subdivision of the driven vehicle wheels; said drive slip control valve means being driven in response to a drive slip control signal from an electronic control unit means controlling the control phases of the drive slip control, from a basic position associated with the normal brake operation and anti-lock control operation into an excited functional position; the basic position of the drive slip control valve means connects the output pressure space of the brake device associated with the brake circuit subdivision of the driven vehicle wheels to a main brake pipe of the brake circuit subdivision of the driven wheels; the excited functional position of the drive slip control valve means shutting off this output pressure space from this main brake pipe while this main pipe continues to be connected to the pressure output of the associated return pump means; the return pump means of the brake circuit of the driven vehicle wheels providing pressure to the brake circuit subdivision of the driven vehicle means in response to a brake pressure build-up control signal from the electronic control unit means; a pressure limiting valve means being provided to limit the pressure connected to the brake circuit subdivision of the driven vehicle wheels during drive slip control operation wherein excess brake fluid flows out of the brake circuit subdivision of the driven vehicle wheels to a brake circuit subdivision of the driven vehicle wheels to a brake fluid reservoir of the brake installation when output pressure of the return pump means exceeds a specified threshold value; said electronic control unit means generating first output signal for driving the drive slip control valve means into its excited position; a second output signal for causing activation of the return pump means of the brake circuit subdivision of the driven vehicle wheels; and further output signals by means of which the brake pressure control valve means of the wheel brakes of the driven vehicle wheels are driven into their shut-off position as soon as the drive slip of at least one of the driven vehicle wheels reaches or exceeds a specified threshold value, whose magnitude is between a required slip value and a response threshold value of the drive slip control; and wherein as soon as the return pump means of the brake circuit of the drive wheels is activated, the return pump means of the brake circuit of the drive wheels pumps brake fluid from the brake fluid reservoir into the main brake pipe of the brake circuit subdivision of the driven vehicle wheels.