Method for operating a hydraulic brake system in a motor vehicle with regenerative braking function, hydraulic brake system and method for the control thereof, computer program product, control unit and motor vehicle

A hydraulic brake system (10) for a motor vehicle with regenerative braking function, comprising:

• a brake cylinder (16) and a wheel brake (28) which have a hydraulic connection (80) to one another, wherein the brake cylinder (16) is configured to displace a hydraulic fluid in the direction of the wheel brake (28), and the wheel brake (28) is configured to impart a hydraulic braking force with the hydraulic fluid;
• an opening device (82) for opening a return line (32) for the hydraulic connection (80);
• a pump (38) and an accumulator (42) fluidically assigned to the return line (32), the accumulator (42) being configured to store at least one volume fraction of the hydraulic fluid, and the pump (48) being configured to convey at least one volume fraction of the hydraulic fluid;
• and
• a control unit (48) for activating the opening device (82), wherein the control unit (48) is configured to utilize a signal with information regarding a presence or onset of a generator braking force of an electric machine (50), and wherein the control unit (48) is configured to activate the opening device (82) to open the return line (32) for the hydraulic connection (80) before the hydraulic fluid is displaced in the direction of the wheel brake (28) and following the generator being switched from a motor mode to a generator mode,
• the control unit (48) also being configured to close the opening device (82) and activate the pump (38) so as to impart a conveying action in order to return a volume fraction of the hydraulic fluid, which has flowed out of the hydraulic connection (80) through the opening device (82), via the return line (32) back into the hydraulic connection (80) between the brake cylinder (16) and the wheel brake (28) in response to a brake pedal (12) for the brake cylinder (16) being actuated with a speed higher than a predefined speed.