Method for operating a vehicle comprising an electro-hydraulic brake system, and electro-hydraulic brake system of a vehicle

An electrohydraulic brake system of a vehicle operable both in a manual and in an autonomous driving mode, comprising:

• a first and a second hydraulic brake circuit hydraulically decouplable from one another by a circuit-separating valve, each being assigned to enable at least one respective wheel brake of the vehicle;
• an actuating cylinder actuatable by a brake pedal;
• a hydraulic pressure source controllable by an electronic open-loop and/or closed-loop control unit by a pressure in which the at least one wheel brake of one of the first and second hydraulic brake circuits is controllable in an autonomous driving mode of the vehicle;
• an actuating valve to produce a hydraulic connection between the actuating cylinder and two or more wheel brakes assigned to a common brake circuit of the first and second hydraulic brake circuits, and
• a brake pedal actuator or a driver by which the brake pedal is movable into an at least partially actuated position, wherein
• the wheel brakes of the vehicle are assigned to one outlet valve that is controllable by the electronic open-loop and/or closed-loop control unit,
• in the opened state, the one outlet valve produces a hydraulic bypass of brake fluid into a brake fluid vessel, and
• the brake pedal is configured to be mechanically coupled and decoupled to an accelerator pedal such that, in the autonomous driving mode of the vehicle, the accelerator pedal is likewise held in an actuated position.

A method for operating a vehicle with an electrohydraulic brake system comprising a first and second hydraulic brake circuit that are each assigned to hydraulically enable at least one respective wheel brake of the vehicle, the method comprising:

• hydraulically decoupling the first brake circuit of the brake system from the second brake circuit;
• separating the second brake circuit from an actuating cylinder that is actuatable by a brake pedal, wherein
• the actuating cylinder comprises first and second pressure chambers assigned to the first brake circuit and second brake circuit, respectively;
• switching an outlet valve assigned to the at least one wheel brake of the first brake circuit into an opened position, in which the outlet valve produces a hydraulic connection between the at least one wheel brake of the first brake circuit and a brake fluid vessel;
• evacuating hydraulic brake fluid from only the first pressure chamber of the actuating cylinder via the first brake circuit and via the opened outlet valve at the at least one wheel brake into the brake fluid vessel;
• and
• evacuating the second pressure chamber of the actuating cylinder via the following steps:
• separating the second brake circuit of the brake system from the first brake circuit;
• separating the first brake circuit from the actuating cylinder that is actuatable by the brake pedal;
• producing a hydraulic connection between the actuating cylinder and the at least one wheel brake assigned to the second brake circuit;
• separating the hydraulic connection of the second brake circuit from a hydraulic pressure source that is controllable by a control unit;
• switching an outlet valve assigned to the at least one wheel brake of the second brake circuit into an opened position, which outlet valve produces a hydraulic connection between the at least one wheel brake and a brake fluid vessel;
• conveying hydraulic brake fluid from only the second pressure chamber of the actuating cylinder via the second brake circuit and via the opened outlet valve at the at least one wheel brake into the brake fluid vessel;
• and
• evacuating hydraulic fluid from only the second pressure chamber of the actuating cylinder.