Slip-controlled brake device for automotive vehicles including vacuum power generator assembly used both as brake power booster and as modulator

A slip-controlled brake device for automotive vehicles, said device comprising a hydraulic pressure generating arrangement connected to at least one hydraulic wheel cylinder brake circuit via a pneumatically actuated pressure modulator, the pressure modulator comprising a vacuum power generator having a piston wall and further comprising a compensating cylinder including a hydraulic piston connected with the piston wall of the vacuum power generator, the piston wall being pre-loaded into an inoperative position by means of a return spring, said compensating cylinder including a compensating chamber communicating with the wheel cylinder brake circuit, and brake slip control circuitry for detecting a wheel slip and issuing a brake slip signal, said brake slip signal being operative to apply a higher pressure to the piston wall of the vacuum power generator in the direction in which the volume in the compensating chamber is increased, said piston wall being normally supplied a vacuum on both sides, a normally open isolating valve inserted in a connecting line from the pressure generating arrangement to the compensating chamber, said brake slip signal closing said isolating valve, said vacuum power generator being operative as a brake power booster in that

• (a) the hydraulic piston assumes, in the inoperative position, the end position providing the largest possible volume in the compensating chamber;
• (b) a vacuum-atmospheric pressure-control valve is, via an alternating valve, connected to the vacuum power generator via an alternating valve such that, during normal braking, a first cylinder chamber is located so that in the event of a pressurization it acts upon the piston wall in the direction in which the volume in the compensating cylinder is decreased, said first cylinder chamber being pressurized to a smaller or larger degree by atmospheric pressure and is controlled by the hydraulic pressure of the pressure generating arrangement, a second cylinder chamber connected to the vacuum, after switching over of the alternating valve, the first cylinder chamber is connected to the vacuum and the second cylinder chamber is pressurized to atmospheric pressure when a brake slip signal is issued and
• (c) said isolating valve being closed each time at the beginning of the pressure build-up by means of the pressure generating arrangement.