The invention relates to a hydraulic vehicle brake system as generally defined hereinafter.
In brake systems in which the braking pressure is regulated upon a tendency toward wheel lock or skidding, and in which at least one main brake cylinder (that is, at least one static brake circuit) is used, it is known, in addition to applying the principle of recirculating the discharged pressure medium in the event of a pressure drop, to deliver the pressure medium directly to a pressure-free supply container, and it is also known to connect an external energy supply system, comprising a pump and pressure reservoir, to the brake pressure control valves in order to avoid running out of pressure medium in the static brake circuit during regulation. In brake systems known from German laid-open applications DE-OS 1 655 448 or (U.S. Pat. No. 3,706,479) or DE-OS 3 040 548 (British Pat. No. 2,086,506) this supply system is connected during regulation with the pressure regulating valves instead of the main brake cylinder, while in other known systems such as that of DE-OS 3 040 561(British Pat. No. 2,086,509), the pressure of the supply system is fed into the main brake cylinders during regulation. It is thereby possible for the [external] supply system to be provided only for feeding pressure during regulation; however, this supply system is preferably used in addition to an amplification of braking force.