Method and device for controlling an electrohydraulic braking system for motor vehicles

A method for controlling an electro-hydraulic braking system for motor vehicles, comprising providing at least one first closed or open-loop brake pressure control function including an antilock control function, and a second closed or open-loop brake pressure control function, which can be activated in a “brake-by-wire” operating mode, and providing a pressurization device (50), which can be activated by means of an electronic control unit and which is or can be connected to hydraulically actuated wheel brakes (9) and by means of which the wheel brakes (9) can be hydraulically actuated by way of at least one pressure regulating valve (6), wherein the pressurization device is provided in a form having a cylinder-piston arrangement having a hydraulic pressure chamber (4), the piston (3) of which arrangement can be displaced relative to a rest position (15, 111) by an electromechanical actuator (1, 2) determining a set pressure value (PRequest—i) for each wheel brake (9), activating the cylinder-piston arrangement (3, 4) in such a way that a predetermined pre-pressure (PPre—Pressure), which is determined from the set pressure values (PRequest—i), is set in the hydraulic pressure chamber (4) by displacement(s) of the piston (3), and

• comparing the actual displacement or position (14) of the piston (3) with at least one predetermined position threshold value (17, 113;
• 18, 120) and that the piston (3) is displaced by a predetermined amount of travel, in the direction of the rest position (15, 111) if the actual displacement or position (14) of the piston (3) exceeds the predetermined position threshold value (17, 113;
• 18, 120), so that brake fluid flows out of a brake fluid reservoir (11) into the hydraulic pressure chamber (4);
• wherein the displacement of the piston (3) in the direction of the rest position is performed if the actual displacement or position (14) of the piston (3) exceeds a first position threshold value and a further condition is simultaneously fulfilled.

A device for controlling an electro-hydraulic braking system for motor vehicles, comprising at least one closed or open-loop brake pressure control function, which can be activated in a “brake-by-wire” operating mode, a pressurization device (50), which can be activated by means of an electronic control unit and which is or can be connected to hydraulically actuated wheel brakes (9) and by means of which the wheel brakes (9) can be hydraulically actuated, wherein the pressurization device in the form having a cylinder-piston arrangement having a hydraulic pressure chamber (4), a piston (3) of the cylinder piston arrangement can be displaced by an electromechanical actuator (1, 2), so that a pre-pressure set value (PV,Soll,PPre—Pressure) can be set in the hydraulic chamber (4), a means for detecting a pre-pressure actual value (PV,Ist), a means for detecting an actuator speed or actuator rotational speed actual value (ωAkt), a means for determining the pre-pressure set value (PV,Soll, PPre—Pressure) a closed-loop control circuit having a pressure regulator (20) and a speed or actuator rotational speed regulator (21) connected to the pressure regulator (20) on the output side, wherein the pre-pressure set value (PV,Soll, PPre—Pressure) and the pre-pressure actual value (PV,Ist) are fed as input variables to the closed-loop control circuit, the pressure regulator (20) delivers an actuator speed or actuator rotational speed set value (ωAkt,Soll,DR,Ctrl), and an actuator speed or actuator rotational speed set value (ωAkt,Soll) and the actuator speed or actuator rotational speed actual value (ωAkt) are fed to the actuator speed or actuator rotational speed regulator (21) as input variables.