Brake System for Motor Vehicles. and Method for Operating the Brake System

A method for operating a brake system comprising the steps of providing a brake master cylinder (2) with a housing (21) and two pistons (15, 16) which delimit two pressure spaces (17, 18) in the housing (21), which pressure spaces (17, 18) are assigned to one of the two brake circuits (I, II) with wheel brakes (8, 9, 10, 11),

• a pressure medium storage vessel (4) for a pressure medium with at least two chambers which are assigned to the two brake circuits (I, II),
• a brake pedal (1) which is coupled to the brake master cylinder for actuating the brake master cylinder (2),
• an electrically operated normally open, separating valve (23a, 23b) for each of the two brake circuits (I, II) for separating the brake circuits into two sections including a first section (22a, 22b) which is connected to an inlet connector of the separating valve being connected to the brake master cylinder (2), and a second section (13a, 13b) which is connected to an outlet connector of the separating valve being connected to the wheel brakes,
• a first electrically controllable pressure provision device (5) which is formed by a cylinder and a piston arrangement, the piston (36) of which can be actuated by an electromechanical actuator (35),
• a simulation device (3) which can be connected hydraulically by means of an electrically actuable simulator release valve (32) to at least one pressure space (17) of the brake master cylinder (2) and imparts a pleasant brake pedal haptic feeling to the vehicle driver in the brake-by-wire operating mode, and
• a first electronic control and regulating unit (12) for actuating the first pressure provision device (5), the separating valves (23a, 23b) and the simulator release valve (32),
• a second electrically controllable pressure provision device (49, 149, 249) with a suction connector and a pressure connector for each of the two brake circuits (I, II), the pressure connector per brake circuit being connected to the inlet connector of the separating valve (23a;
• 23b) which is assigned to the brake circuit (I;
• II),
• the pressure medium is sucked by means of the second electrically controllable pressure provision device (49, 149, 249) from one of the pressure spaces (17, 18) of the brake master cylinder (2) or from a pressure medium container (4, 150) and is fed into at least one of the brake circuits (I, II), if no pressure build-up or dissipation can be carried out by means of the first pressure provision device (5) and the vehicle driver actuates the brake pedal (1).