Method for setting a clutch torque

1. A method for setting a clutch torque of a clutch, which is disposed in a drive train of a motor vehicle, the clutch ( 1 ) being adjusted using a clutch actuator ( 7 ) that has at least two actuator parts that may be positioned relative to each other at raster values ( 9 a , 9 b , 9 c ) of a position raster, a position setpoint being determined for the actuator parts that corresponds to a clutch torque and is disposed between the raster values ( 9 a , 9 b , 9 c ) of the position raster, and the actuator parts being positioned relative to each other at a raster value ( 9 a ) of the position raster adjacent to the position setpoint, wherein a second position raster value ( 9 b ) is determined in addition to a first position raster value ( 9 a ) in such a manner that the position setpoint is disposed between the first position raster value ( 9 a ) and the second position raster value ( 9 b ), and the actuator parts are alternately positioned at the first position raster value ( 9 a ) and the second position raster value ( 9 b ) in such a manner that a average clutch torque more precisely matches the clutch torque setpoint than the clutch torques of the first and second position raster values ( 9 a , 9 b ).

2. The method as described in claim 1 , wherein a position setpoint signal ( 14 ) is generated that corresponds to the position setpoint, a heterodyning signal containing an alternating signal portion is heterodyned to this position setpoint signal ( 14 ) in such a manner that the sum signal from the position setpoint signal ( 14 ) and the heterodyning signal is essentially within the position raster, and the clutch actuator ( 7 ) is driven with the sum signal as setpoint signal.

3. The method as described in claim 1 , wherein the heterodyning signal is pulse-width-modulated as a function of the location of the position setpoint relative to the first and second position raster values ( 9 a , 9 b ).

4. The method as described in claim 1 , wherein the heterodyning signal is pulse-width-modulated using a constant period of oscillation, and the pulse/pause ratio is altered as a function of the location of the position setpoint relative to the first and second position raster values ( 9 a , 9 b ).

5. The method as described in claim 1 , wherein the heterodyning signal is pulse-width-modulated using a constant period of oscillation, and the pause duration is altered as a function of the location of the position setpoint relative to the first and second position raster values ( 9 a , 9 b ).

6. The method as described in claim 1 , wherein the heterodyning signal is pulse-width-modulated using a constant pause period, and the period of oscillation is altered as a function of the location of the position setpoint relative to the first and second position raster values ( 9 a , 9 b ).

7. The method as described in claim 1 , wherein the alternating signal portion has a fundamental frequency that is set between a system-specific juddering frequency of the clutch and a system-specific base frequency of the system of the clutch actuator as a whole.

8. The method as described in claim 7 , wherein the fundamental frequency is 1 to 10 Hz.

9. A method for setting the clutch torque of a clutch ( 1 ), which is disposed in a drive train of a motor vehicle, which is described in claim 1 , the clutch ( 1 ) being adjusted using a clutch actuator ( 7 ) that is in a drive connection with the clutch ( 1 ) via a disengagement device having a travel hysteresis, and a position setpoint corresponding to a clutch torque setpoint being calculated and the clutch actuator ( 7 ) being positioned corresponding to the position setpoint, wherein a juddering movement is heterodyned to the positioning movement of the clutch actuator ( 7 ) for at least partial compensation of the travel hysteresis.

10. The method as described in claim 9 , wherein the amplitude of the juddering movement is at least twice as large as the maximum value of the travel hysteresis.

11. The method as described in claim 9 , wherein a position setpoint signal ( 14 ) corresponding to the position setpoint is generated, a heterodyning signal for the juddering movement that contains an alternating signal portion is heterodyned to this position setpoint signal ( 14 ), and the clutch actuator ( 7 ) is driven using the signal formed in this way.

12. The method as described in claim 9 , wherein the alternating signal portion has a frequency that is higher than the juddering frequency.

13. The method as described in claim 12 , wherein the frequency is higher than 25 Hz.

14. The method as described in claim 13 , wherein the frequency is 30 Hz.

15. The method as described in claim 13 , wherein the frequency is 35 Hz.

16. The method as described in claim 8 , wherein the fundamental frequency is 3 to 7 Hz.

17. The method as described in claim 16 , wherein the fundamental frequency is 4 to 6 Hz.

18. The method as described in claim 17 , wherein the fundamental frequency is approximately 5 Hz.