| 摘要 |
An antilocking braking system for a road vehicle performs brake pressure control on the principle of changing the volume of an output pressure chamber of a pressure modulator connected to the wheel brake. The modulator has a control pressure chamber which is separated by a piston from the output pressure chamber into which the output pressure of an auxiliary pressure source is permanently introduced via an inlet control valve. The piston is held in its end position associated with minimal volume of the output pressure chamber. Connected in series with the inlet control valve is a non-return valve which prevents a drop in the pressure in the control pressure chamber in the event of a failure of the auxiliary pressure source. Volume increases in the output pressure chamber required for pressure reduction phases of the antilock braking control are controlled by an outlet control valve. It is possible to block off the output pressure chamber from the brake booster for the duration of antilock braking control cycles. The pressure modulator is equipped with a position sensor which generates output signals characteristic of the piston position. The modulator piston is displaced in the sense of an increase in the volume of the output pressure chamber by a resilient restoring element. With the aid of a test valve, periodic reductions in the output pressure of the auxiliary pressure source can be controlled. The piston displacements occurring as a consequence of such pressure reductions and sensed by the position sensor are signalled as an indication of leakage of the non-return valve.
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