This invention relates to an anti-lock-controlled brake system for automotive vehicles.
Such a brake system is already known from patent application, official Ser. No. P 40 15 884.5. If, within the scope of an anti-lock control operation, in this brake system, the braking pressure or rather the volume in the wheel brake threatened by a lock-up is reduced by means of actuating the inlet and outlet valves the electronic control unit simultaneously will cause the auxiliary pressure pump to start in order to provide the auxiliary pressure. The auxiliary pressure will switch a locking valve into its locking position so that the braking pressure generator will be separated from the pump pressure prevailing in the main pressure line. Due to the pressure limiting valve preadjusted via a compression spring as well as because of the hydraulic connection of the pressure limiting valve with the wheel brake on the front axle and because of the hydraulic communication towards the auxiliary pressure pump the pump pressure will automatically regulate itself in dependence on the wheel brake pressure active at the pressure limiting valve as well as in dependence on the spring-force-adjusted hydraulic prepressure. Consequently, the pressure limiting valve will adjust the pump pressure to the respective wheel brake pressure plus the adjusted prepressure of the effective compression spring. Thus, in case of need, on the one hand, pressure build-up of the auxiliary pressure pump can take place at a quicker rate as, due to the inventive hydraulic operating position, a relatively smaller pressure has to be overcome. On the other hand, the noise emission of the inlet valve is markedly reduced as the pressure difference at the inlet valve cannot be higher than the compression-spring-generated prepressure of the pressure limiting valve.
As compared with the generic brake system, this invention has the advantage that the return line is no longer connected to the open storage reservoir but rather communicates with the master cylinder whereby an accumulator system connected to the auxiliary pressure pump is controlled in an economically reasonable manner in dependence on the actual wheel brake volume requirements or rather on the actually required wheel brake pressure.
It is thus an object of this invention to further develop an anti-lock-controlled brake system of the type referred to at the beginning such as to enable a brake-slip-dependent adaptation of the auxiliary pressure supply to the actual pressure medium requirements in the wheel brake in a brake system decoupled from the storage reservoir.