Method and Device for Operating a Braking Device, Braking Device

#This application claims priority under 35 U.S.C. §119 to application no. DE 10 2014 220 793.2, filed on Oct. 14, 2014 in Germany, the disclosure of which is incorporated herein by reference in its entirety.

#The disclosure relates to a method for operating a braking device, in particular a parking brake device, which comprises an actuator having an electric motor that displaces an actuator element as desired into a brake application position or into a brake release position, wherein the electric motor is controlled in dependence upon a motor constant and an electrical resistance of the electric motor.

#Moreover, the disclosure relates to a device for operating a braking device of this type having the features of the disclosure and a braking device having the features of the disclosure.

#Exemplary embodiments of the disclosure are presented in the drawings an are explained in more detail in the description below.

#In the drawings:

#FIG. 1 illustrates a braking device of a motor vehicle having an integrated parking brake function in a simplified cross-sectional view,

#FIG. 1 illustrates in a simplified cross-sectional view a braking device 1 of a motor vehicle not illustrated in the figure in detail. The braking device 1 is embodied as a disc brake and comprises for this purpose a brake caliper 2 that supports the brake linings 3 and between which it is possible to jam or clamp a brake disc 4 that is connected in a non-rotatable manner to a wheel of the motor vehicle. For this purpose, a hydraulic actuator 5 is allocated to the brake caliper 2 and said hydraulic actuator comprises a brake piston 6 that can be actuated in a hydraulic manner in order to clamp the brake disc 4 as required between the brake linings 3. As a consequence, a braking torque is applied during the driving operation to the brake disc 4 and thus to the wheels and said braking torque is used for the purpose of decelerating the vehicle.

#Furthermore, the braking device 1 is embodied as a parking brake device or rather has a parking brake function and comprises for this purpose an electrically motorized actuator 7 that is formed by an electric motor 8, an actuating gear 9 that is embodied in this case as a spindle gear, and an actuator element 10. An output shaft of the electric motor 8 is connected in a non-rotatable manner to a drive spindle 11 of the actuator gear 9. The drive spindle 11 comprises an outer thread that cooperates with an inner thread of the actuator element 10 that can move along the drive spindle 11. By means of controlling the electric motor 8, the drive spindle 11 is consequently set into a rotational movement in order to displace the actuator element 10. The actuator element 10 can be displaced from a brake release position into a brake application position in which the actuator element 10 urges the brake piston 6 against the brake disc 4 and as a consequence applies force to the brake caliper 2. The actuator element 10 is arranged for this purpose in a coaxial manner with respect to the brake piston 6 and within the brake piston 6. The rotational movement of the drive spindle 11 is converted by means of the actuator gear 9 into a translatory movement of the actuator element 10. In this respect, the wheel brake device corresponds to known wheel brake devices. In order to be able to optimize the control of the electric motor 8 and the operation of the wheel brake device 1, motor parameters of the electric motor 8 are ascertained during the operation of the wheel brake device 1 and used to control the wheel brake device 1 in particular the actuator 7 in order by way of example to be able to estimate the clamping force as accurately as possible and to be able to calculate easily the travel distance of the actuator element 10, in particular during a brake release procedure.

#The control device measures the motor current i(t) and the motor input voltage u(t), which corresponds to the control device voltage at its output, after the point in time in which the electric motor 8 is controlled. The control device calculates from these input values the typical motor parameters, motor constant and electrical resistance. The prevailing brake application force FC(t) is calculated from said parameters during a brake application procedure. The travel distance of the actuator element 10 is ascertained from the information relating to the current and voltage as the parking brake is being released. The said travel distance is presently advantageously ascertained in a specific phase of the brake application procedure.