Method for checking the plausibility of the position of the clutch actuator of a clutch, method for determining the touch point of a clutch, and device for carrying out the method

1. A method for checking the plausibility of an actuation position of a clutch of a double-clutch transmission operated by an actuator, comprising the following steps:

disengaging the clutch assigned to a currently active old subtransmission and simultaneously engaging the clutch assigned to a new subtransmission to shift from a gear selected in the old subtransmission to a gear selected in the new subtransmission;

deselecting the gear selected in the old subtransmission during an overlapping operation of the clutches or immediately thereafter;

detecting a difference between a speed of rotation of a drive shaft of the double-clutch transmission driven by a drive motor and a speed of rotation of an input shaft of the old subtransmission; and

evaluating the state of the clutch assigned to the old subtransmission as disengaged when the difference in speeds of rotation of the drive shaft of the double-clutch transmission and the input shaft of the old subtransmission exceeds a predetermined value within a predetermined time after deselection of the gear.

2. The method according to claim 1 wherein with the clutch engaged and assigned to the new subtransmission, a new gear is selected in the old subtransmission and the selectability of the new gear is evaluated as a disengaged state of the clutch assigned to the old subtransmission.

3. The method according to claim 1 wherein a ratio of the speed of rotation of the drive shaft of the double-clutch transmission to that of the input shaft of the old subtransmission is registered, and conclusions are drawn from the ratio about the disengagement status of the clutch assigned to the old subtransmission.

4. The method according to claim 1 wherein the clutch assigned to the old transmission, after being disengaged, is gradually engaged with no gear selected in the old subtransmission, a pattern of the rotational speed of the input shaft of the old subtransmission is registered, and an actuating position of the clutch at which a rapid change in the speed of rotation occurs, is determined to be a touch point.

5. The method according to claim 4 wherein with the corresponding clutch disengaged, a higher gear is selected in the old subtransmission than the gear selected in the new subtransmission, and the higher gear is briefly synchronized so that the speed of the input shaft of the old subtransmission drops below that of the drive shaft, so that the input shaft of the old subtransmission rotates at a lower speed than the drive shaft as the corresponding clutch gradually begins to engage.

6. The method according to claim 4 wherein before the gradual engagement begins the speed of the drive shaft is increased so that as the gradual engagement of the clutch assigned to the old subtransmission begins the drive shaft is turning at a higher speed than the input shaft of the old subtransmission.

7. The method according to claim 6 wherein while the speed of the drive shaft is being increased the speed is compared to the input shaft of the old subtransmission, and a change of the speeds in the same direction is evaluated as a non-disengaged state of the clutch assigned to the old subtransmission.

8. The method according to claim 1 wherein, with the old subtransmission in neutral, the clutch assigned to the old transmission is at least partially engaged in such a way that the input shaft of the old subtransmission turns, the clutch is disengaged, the speed of rotation of the input shaft is registered, the clutch is gradually engaged, and an actuating position of the clutch at which a time gradient of the speed of rotation of the input shaft changes in a predefined manner during the gradual engagement of the clutch is determined to be a touch point.

9. The method according to claim 4 wherein the determined touch point position is used to check the plausibility of the clutch actuator position.

10. The method according to claim 1 wherein, with the transmission in neutral gear, the clutch is at least partially engaged in such a way that the input shaft turns,

the clutch is disengaged,

the speed of rotation of the input is registered and a gradient of the speed of rotation is determined,

the clutch is gradually engaged, and

that actuating position of the clutch at which the time gradient of the speed of rotation of the input shaft changes in a predefined manner during the gradual engagement of the clutch is determined to be a touch point.

11. A device for controlling an actuator for operating a clutch situated between a drive shaft drivable by a drive motor and an input shaft of a transmission, comprising:

sensors to register a speed of rotation of the drive shaft and of the input shaft, and an electronic control device connected to the sensors, the electronic control device controlling the actuator in accordance with the method according to claim 1 .