Vehicle brake system for motor vehicles and their methods of operation

The present invention relates to a vehicle braking system for motor vehicles with a hydraulic brake system comprising a pedal-actuated, hydraulic pressure transducer with non-pressurized pressure fluid supply reservoir and a downstream master cylinder and is divided into two brake circuits, wherein the first brake circuit acting on a first axis of the motor vehicle and a fremdansteuerbare, hydraulic pump , comprising a separating valve, an electrical changeover valve and with inlet and outlet valves provided hydraulically operated wheel brakes comprising, while the second brake circuit acting on a second axle of the motor vehicle and a fremdansteuerbare, hydraulic pump, a separating valve and with inlet and outlet valves provided hydraulically operated wheel brakes wherein the wheels of the second vehicle axle are at least temporarily driven by an electric motor which is operable to recuperation of brake energy as a generator and generator operation in an Bremskraf t effected on the wheels of the second vehicle axle, and wherein a pedal sensor detects the driver's braking intention and a control and regulating unit supplies. Moreover, the invention relates to a method for operating a vehicle brake system. In the inventive vehicle brake system is provided that the suction side of the hydraulic pump of the second brake circuit is connected directly without interposition of a hydraulic valve to the unpressurized pressure fluid supply reservoir, ...