Brake system for a motor vehicle, and method for operating the brake system

A brake system for a motor vehicle, comprising:

• a master brake cylinder with at least one brake circuit comprising at least one hydraulically operated wheel brake, the master brake cylinder configured to generate a hydraulic pressure for activating the at least one wheel brake through the brake circuit;
• a first actuatable switchover valve configured to disconnect and connect the brake circuit from/to the master brake cylinder;
• at least one parking brake device associated with the at least one wheel brake, the at least one parking brake device (i) including a second actuatable switchover valve configured to disconnect and connect the brake circuit from/to the master brake cylinder, (ii) a locking device mounted on the second actuatable switchover valve, and (iii) a hydraulic pressure storage device configured to be operatively connected to the brake circuit;
• and
• a control unit configured to activate the at least one parking brake device and to deactivate the at least one parking brake device,
• wherein the first switchover valve is configured as a bistable switchover valve that is closed in a first de-energized state in order to disconnect the brake circuit from the master brake cylinder and open in a second de-energized state in which the brake circuit is connected to the master brake cylinder,
• wherein the second switchover valve is normally open in a first de-energized state in order to connect the brake circuit to the master brake cylinder and is configurable in a closed position in an energized state in order to disconnect the brake circuit from the master brake cylinder,
• wherein the locking device is configured to lock the second switchover valve in the closed position,
• wherein the control unit is configured to activate the at least one parking brake by closing the first switchover valve and locking the second switchover in the closed position with the locking device to isolate the brake circuit from the master brake cylinder and to contain the hydraulic pressure generated by the master brake cylinder within the brake circuit,
• wherein the contained hydraulic pressure acts on the at least one hydraulically operated wheel brake to maintain the motor vehicle in a braked position, and
• wherein in response to a leak of the contained hydraulic pressure from the brake circuit, the control unit is further configured to supply the brake circuit with pressure from the hydraulic pressure storage device to maintain the motor vehicle in the braked position.