Abstract: A motor vehicle brake system operable in a brake-by-wire and fallback modes. The system includes a brake pedal (1), a master cylinder (2), a reservoir (4), a travel simulator (3), an electrically controllable pressure source (5), isolation valves (23a, 23b) pumps (32a, 32b) and a low-pressure accumulator (14a, 14b), an inlet valve (6a-6d) and an outlet valve (7a-7d) for each wheel brake (8, 9, 10, 11), valves (34a, 34b; 134a, 134b) connected to the pumps (32a, 32b), and a control and regulation unit (110, 210). A valve arrangement (23a, 23b) establishes for each brake circuit (I, II) a connection from the pressure chamber (17, 18) of the master cylinder (2) to the modulator admission pressure line (13a, 13b; 113a, 113b) and disconnects the connection when unenergized, the valve arrangement (23a, 23b) preventing the pressure source (5) from being subjected to pressure from the pressure chambers (17, 18).

Abstract: A motor vehicle brake system operable in a brake-by-wire and fallback modes. The system includes a brake pedal (1), a master cylinder (2), a reservoir (4), a travel simulator (3), an electrically controllable pressure source (5), isolation valves (23a, 23b) pumps (32a, 32b) and a low-pressure accumulator (14a, 14b), an inlet valve (6a-6d) and an outlet valve (7a-7d) for each wheel brake (8, 9, 10, 11), valves (34a, 34b; 134a, 134b) connected to the pumps (32a, 32b), and a control and regulation unit (110, 210). A valve arrangement (23a, 23b) establishes for each brake circuit (I, II) a connection from the pressure chamber (17, 18) of the master cylinder (2) to the modulator admission pressure line (13a, 13b; 113a, 113b) and disconnects the connection when unenergized, the valve arrangement (23a, 23b) preventing the pressure source (5) from being subjected to pressure from the pressure chambers (17, 18).