Method for controlling a hydraulic brake system during a regenerative braking process, hydraulic brake system, computer program product, control unit and motor vehicle

A hydraulic brake system for a motor vehicle, comprising:

• a brake cylinder and a wheel brake which are hydraulically connected to one another via a feed line, wherein the brake cylinder is configured to displace a hydraulic fluid in the direction of the wheel brake, and the wheel brake is configured to impart a hydraulic braking torque by means of the hydraulic fluid;
• an isolation valve which is fluidically assigned to the feed line and which is configured to close the feed line;
• a return line for returning at least one volume fraction of the hydraulic fluid from a region positioned downstream of the isolation valve into a region positioned upstream of the isolation valve;
• a pressure dissipation valve, a pump and an accumulator, which are fluidically assigned to the return line, wherein the pump is configured to convey at least one volume fraction of the hydraulic fluid, the accumulator is configured to store at least one volume fraction of the hydraulic fluid, and the pressure dissipation valve is configured to open the return line;
• a control unit which is connected in signal-exchanging fashion to the isolation valve, the pressure dissipation valve and the pump and which is configured such that, in the presence of an actuation of the brake cylinder and in the presence of a generator braking torque of an electric machine and when the pressure dissipation valve is in an open position, the control unit activates the pressure dissipation valve for adjustment in the direction of a closed state, in order to realize an increase of a hydraulic braking torque effected by the wheel brake, if an overall braking torque which is made up of the hydraulic braking torque and the generator braking torque is lower than a braking torque demand, and if the generator braking torque lies below a braking torque limit of the electric machine.