Modern motor vehicles increasingly have an electric parking brake, for example a parking brake actuated by an extraneous electromechanical force, and which can be applied or released by the driver by activating a parking brake pushbutton key. In order to meet the requirements defined in European Standard ECE R13H for passenger car brake systems with respect to fault scenarios and fall back levels, an emergency braking function can be activated by pressing the parking brake pushbutton key, as is known for example, from EP 741 066 B1.
In the previously known method, a pressure generator is provided which acts on a friction brake and as a result initiates an emergency braking operation. In this context, a common activation device (the parking brake pushbutton key) is provided for the emergency braking and parking brake system which makes available an emergency braking function using a logic circuit when the vehicle speed v>0 by actuating the pressure generator, while when v=0, the parking brake is activated. The previously known method therefore provides braking of the driving motor vehicle exclusively via the service brake system, in particular a hydraulic friction brake.
WO 2007/090823 A1 proposes that during the execution of an emergency braking process further measures for reducing the speed of the vehicle are carried out. In this context there is provision for the engine torque of the drive motor to be suppressed and/or for the position of the accelerator pedal to be ignored. This permits the braking distance to be reduced in the case of emergency braking, but also assumes correct functioning of the service brake system.