Clutch parameters

1. A method of determining clutch parameters at an initial start of operation of a friction clutch in a motor vehicle comprising the steps of:

in a first phase:

moving, using a control unit, the clutch from an open state into a closed state and into the open state again at a predetermined constant slip of the clutch; and

determining and storing, using the control unit, a position of the clutch during the movement when predetermined clutch torque thresholds are reached;

in a second phase, in a first step, determining, using the control unit, a touch point, a position hysteresis, and a torque hysteresis from the determined position;

determining, using the control unit, a preliminary friction coefficient;

determining, using the control unit, preliminary form factors;

determining, using the control unit, a final friction coefficient; and,

determining, using the control unit, final form factors.

2. The method as set forth in claim 1 , wherein the clutch torque thresholds are equidistantly distributed across a clutch torque range provided by the clutch.

3. The method as set forth in claim 1 , further comprising:

determining, using the control unit, the touch point from a mean value of end points of a hysteresis width for the lowest clutch torque threshold.

4. The method as set forth in claim 1 , further comprising:

determining, using the control unit, the position hysteresis from a mean value of a number of hysteresis widths for clutch torque thresholds within a range of first values.

5. The method as set forth in claim 4 , further comprising:

determining, using the control unit, the torque hysteresis from a mean value of a number of hysteresis widths for clutch torque thresholds within a range of second values greater than the first values.

6. The method as set forth in claim 1 , further comprising:

determining, using the control unit, the preliminary friction coefficient from a mean value of determined positions of end points of a hysteresis width of the highest clutch torque threshold.

7. The method as set forth in claim 1 , further comprising:

determining, using the control unit, the determined touch point, the determined preliminary friction coefficient, and a nominal clutch characteristic, a scaled clutch characteristic without form factors.

8. The method as set forth in claim 1 , further comprising:

determining, using the control unit, the preliminary form factors from a ratio of torque values at nodes of a scaled clutch characteristic without form factors and associated torque values of characteristic of hysteresis centers.

9. The method as set forth in claim 1 , further comprising:

determining, using the control unit, the final friction coefficient from the preliminary friction coefficient by correction by a factor that incorporates a mean value of the preliminary form factors.

10. The method as set forth in claim 1 , further comprising:

correcting, using the control unit, the preliminary form factors by a mean value of the preliminary form factors by subtracting a determined mean value; and

scaling, using the control unit, values resulting from the correction of the preliminary form factors by a factor in such a way that the values resulting after scaling meet predetermined requirements and represent the final form factors.

11. The method as set forth in claim 10 , wherein the predetermined requirements include that the final form factors need to be distributed within a band about zero and differences between two form factors also need to be distributed within the band about zero.

12. A device including a control device for determining clutch parameters at an initial start of operation of a friction clutch in a motor vehicle, the control device arranged to:

in a first phase, move the clutch from an open state to a closed state and back to the open state at a predetermined, constant slip of the clutch when a torque is transmitted and, during the movement, to determine and store a position of the clutch when a predetermined clutch torque threshold is reached;

in a second phase, determine:

a touch point;

a position hysteresis using a parallel displacement of a modified nominal characteristic curve in a direction of the position as a function of a speed of a clutch actuator; and

a torque hysteresis from the determined position;

determine a preliminary friction coefficient;

determine preliminary form factors;

determine a final friction coefficient; and

determine final form factors.

13. A device including a control device for determining clutch parameters at an initial start of operation of a friction clutch in a motor vehicle, the control device arranged to:

in a first phase, move the clutch from an open state to a closed state and back to the open state at a predetermined, constant slip of the clutch when a torque is transmitted and, during the movement, to determine and store a position of the clutch when a predetermined clutch torque threshold is reached;

in a second phase, determine:

a touch point;

a position hysteresis; and

a torque hysteresis from the determined position by superimposing a torque-dependent scaling to a parallel displacement of a modified nominal characteristic curve in a direction of the position;

determine a preliminary friction coefficient;

determine preliminary form factors;

determine a final friction coefficient; and

determine final form factors.