Anti-blocking system

Abstract

In an anti-blocking system for a road vehicle with statically pressure-actuatable brake circuits, a pressure modulator with an outlet pressure connected with the wheel brake cylinder is coordinated to each wheel brake, whereby pressure reduction-, pressure build-up and pressure-maintaining-phases of the anti-blocking regulation are attainable by its controllable volume change respectively maintaining constant of its volume. The pressure modulators are constructed as stepped cylinders with bore steps of different diameters passing over one into the other, in which a smaller and a larger control pressure space is movably delimited by piston steps of corresponding different diameters of a stepped piston, as well as the outlet pressure space, which is formed by an annular space remaining between the piston steps. The larger control pressure space is permanently connected with the main brake line of the respective brake circuit. One pressure inlet control valve each is connected between the outlet pressure space of the respective pressure modulator and the main brake line, whose base position is the passage position, and which, for the purpose of the anti-blocking regulation is adapted to be activated into the closing position. A function-control valve is further provided for each wheel brake, by way of which an auxiliary pressure source, also valve-controlled, is adapted to be connected to the smaller control pressure space. The output pressure P.sub.A is higher by a minimum amount, for example, 10 to 30 bar than the maximum output pressure P.sub.B of the brake pressure control apparatus multiplied with the ratio F.sub.1 /F.sub.2 of the areas F.sub.1 and F.sub.2 of the larger piston step and of the smaller piston step.