EP2118511A1

EP2118511A1 - Method for dynamically determining a clutch rest point

Info

Publication number: EP2118511A1
Application number: EP08701278A
Authority: EP
Inventors: Anthony Robert Sayman
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2007-01-16
Filing date: 2008-01-08
Publication date: 2009-11-18
Also published as: WO2008087065A1; US20100048351A1; DE102007002343A1; CN101631965A

Abstract

The invention relates to a method for determining a rest point of a clutch, for example a multiple-disc clutch, in a dynamic and event-dependent fashion. The rest point is here an actuation path point or an actuation path region just before the slip region of the clutch in which the clutch still cannot transmit any appreciable torque but which permits a position of the clutch, in which an appreciable torque can be transmitted, to be reached very quickly. According to one preferred variant, the rest point can be determined on the basis of a basic rest point by taking into account various offset values or correction values. A control device determines these correction values in this context at favourable, event-dependent times, for example during or shortly after the disengagement of a gear speed, as a function of specific parameters such as, for example, an original gear speed and/or a target gear speed and/or the type of gear shifting operation, for example, shifting up, shifting down or shifting out of the neutral position of the transmission. A clutch actuator is then activated in such a way that the friction clutch is closed up to the clutch rest point. This makes it possible to minimize, as a function of the specific parameters, both increased wear of the clutch and a required switching time until a slip region of the clutch is reached.

Description

Method for the dynamic determination of a clutch resting point

The invention relates to a method for the dynamic calculation of a rest point position of an automatic or automatable friction clutch, wherein a control device controls a clutch actuator such that its actuator assumes corresponding actuator positions and thereby sets a controllable torque transmission between a drive shaft coupled to a drive motor and an output side of the friction clutch, wherein, in preparation for a closing of the friction clutch for the purpose of transmitting a torque, the control means initially adjusts the actuator of the clutch actuator to a home position wherein a dead travel of the friction clutch is greatly reduced until a torque is transmitted relative to a full opening of the clutch.

Friction clutches are used in various contexts for a long time and are well known. In particular, in the automotive sector, almost every vehicle is equipped with a main friction clutch in the form of a disc clutch or multi-plate clutch, which allows a controllable introduction of a provided by a drive motor drive torque in the other drive train of the vehicle. It is particularly common to provide a friction clutch between the drive motor or its output shaft or flywheel and the input shaft of a transmission, which allows implementation of the speed provided by the drive motor in a desired to drive the vehicle speed. This is especially necessary in today's conventional internal combustion engines, as they work optimally only in a relatively small speed range. However, such friction clutches are also provided in any other drive motors, on other vehicle units and also on many units external to the vehicle, since they are switchable under load and so in particular a tarnish allow a machine or a start of the vehicle from standstill.

Usually there are multi-plate clutches as axial friction clutches of two or more slats designated disk-shaped friction partners. In this case, so-called inner disks on a shaft rotatably fixed but axially displaceable, while outer disks are also axially displaceable and rotationally fixed in a hollow cylindrical, coaxial with the shaft carrier and arranged axially alternately with the inner disks. In automotive main clutches of the hollow cylindrical carrier is usually designed as a rigid coupled to the output shaft of the drive motor, often acting simultaneously as a flywheel clutch bell, while said shaft on the output side of the friction clutch is an input shaft of a gearbox. By axially displacing the lamellae, these can e.g. be pressed against each other by means of spring force, whereby the multi-plate clutch can transmit a dependent of the type, size and number of slats, the coefficient of friction and the contact force torque between the clutch bell and the transmission input shaft.

In order to make the clutch switchable, the lamellae are usually pressed together by means of compression springs, wherein a pressure plate opposing the pressure plate is in turn biased by engagement springs in the direction of the closed position of the multi-plate clutch. This pressure plate is adjustable by an actuator against the spring force of the engagement springs.

In a by a clutch pedal to be operated by the driver clutch to open it a release lever is provided, which is actuated by the clutch pedal via a cable. In automatic and automated, or even power-assisted, manually operated clutches, an actuator deflectable by an auxiliary power source is used to provide the Adjust pressure plate so that the compression springs exert a desired according to the respective requirements desired contact force on the slats. Usual are here, for example, electric actuators or pressure-actuated actuators hydraulic or pneumatic design.

During operation, a distinction is made between the following coupling positions:

a) A full-open position of the clutch, wherein the actuator and thus the pressure plate are adjusted so that the lamellae are no longer pressed together by the compression springs and in addition have a certain axial play with each other. In the case of foot pedal actuated clutches, this corresponds to a pedal position that is completely or at least largely permeated, which results in at least one defined opening of the clutch, even beyond a pressure-free contact of the slats.

b) A full-closed position in which the actuator exerts substantially no force on the clutch and the compression springs and engagement springs press the blades together with maximum force accordingly. In this position, the clutch has its highest torque transmission capability.

c) A contact point position, in which the clutch plates completely but without pressure abut each other. From this point in the travel of the clutch actuator further adjustment of the actuator towards a closed clutch only leads to a very small axial movement of the slats and almost exclusively to an increase in the contact force between them. This point of contact is strictly speaking an axial adjustment range. Since the clutch plates on the one hand partially touch due to their axial displacement even at a small clearance between the slats and on the other hand, the clutch plates in a conventional, oil-cooled clutch separated by a fine film of oil, and there finally by the viscosity of the oil even with completely separate Slats a certain, low torque transmission capability is present, the contact point or contact area is defined here functionally:

The point of contact is to be understood as meaning that point or narrow axial region in a clutch setting in which largely no free play is left between the disks and results in a low torque transmission capacity of the clutch which exceeds the oil viscosity-related torque transmission. With the drive motor running and an unrestrained output side of the clutch, this will therefore start moving when the clutch is set at the touch point. In a braked output side of the clutch, however, the drive shaft or the input side of the clutch is only slightly slowed down, and the frictional heat generated in the clutch is so low that it leads to only a slight warming of the clutch, at least in the short term.

A slip range of the clutch closes axially starting from the point of contact when the clutch closes further, and is characterized in that the clutch can transmit increasingly more torque, but this transmittable torque is not yet sufficient to completely transmit the torque applied to the input side of the clutch , The size of the slip region is thus substantially dependent on the particular torque to be transmitted.

As soon as the clutch is able to transmit the entire applied torque without slipping, the closed area is reached. With sufficient Finally, when sizing the clutch, the closed area includes the full-closed position of the clutch where the clutch has at least reached its maximum torque transfer capability. However, if the clutch is too weak or excessively worn for the applied torque, then it may happen that even in the fully closed position, in which the maximum possible contact pressure between the disks acts, slipping of the clutch occurs. The slip area is thus functionally defined, while the full-closed position of the clutch is logically defined as the position of maximum torque transfer capability thereof.

In automatic and automated clutches, wherein a clutch here and below always a friction clutch and preferably, but not exclusively, a multi-plate clutch is understood, it is particularly desirable in conjunction with automatic or automated transmissions, that the clutch as soon as possible each requested state can take.

However, a particularly rapid adjustment of the Kupplungsak- tuators, which is referred to below as an actuator, either an increasing tolerance in the target position to be set or a reduction in the achievable positioning accuracy of the actuator or a significantly increased effort. A high positioning accuracy of the actuator is of interest primarily in closing the clutch between the contact point of the clutch and the end of the slip range.

In order to achieve an increased positioning accuracy and at the same time a rapid achievement of the desired actuator or clutch position, it is already known from the patent US 5,624,350, the actuator starting from an open position or full-open position initially in a fast motion mode to a quiet point, which is called the approach point. This corresponds to a comparison with the touch point (touch point) slightly further opened coupling.

This ensures that, for example, in a forthcoming for the near future, expected or currently present command for closing the clutch of the actuator can be adjusted in a fast movement mode to the approach point of the clutch without this leads to the clutch output side to a noticeable response , This process step can be carried out with maximum or at least increased adjustment speed and only needs to be so precise that a significant torque transmission of the clutch is reliably avoided. However, to make use of the advantages of this method, it is absolutely necessary to know the approach point of the coupling with sufficient accuracy.

For this purpose, US Pat. No. 5,624,350 proposes, in a calibration step, first of all slowly adjusting the actuator when the gearbox in the neutral position and the gearbox input side are driven until a speed sensor on the output side of the clutch just detects a rotational movement. This point is defined as the approach point. Subsequently, the process is repeated with the transmission brake engaged to determine the point of contact at which the clutch is transmitting a significant torque.

The values for the actuator positions representing the approach point and the touch point may be periodically updated according to US 5,624,350 to account for wear and / or changes in the operating temperature of the clutch or the like. These are, as I said, periodic recalibrations, which are thus independent of the event and do not take other factors into account when determining the time. In unfavorable cases, the Period after which a recalibration is triggered, even fall into a high-performance acceleration process, which of course would be very undesirable.

Even if recalibration were not carried out at periodic intervals, but at the expiration of a minimum period of time at a favorable time, this would probably be appropriate in relation to the rather slow and steadily progressive wear of the clutch linings, but in practice leads only to a satisfactory extent Results, since, for example, the working temperature of the clutch can vary greatly within short periods of time and numerous other factors can have an influence on the optimum position of the rest point for an upcoming shift of the transmission.

In addition, a consideration of the temperature of the clutch according to US 5,624,350 in practice is difficult, since a recalibration of Kupplungsstellwegpunkte would be connected at a time interval of a few seconds in the long run with a considerable load on the clutch. In addition, frequent periods of recalibration would disrupt the overall driving experience.

On the other hand, a longer period of time between two calibration operations would result in a substantial omission of consideration of the current working temperature of the clutch. This would be particularly critical in a clutch control according to US 5,624,350, as for example due to thermal expansion earlier reaching the actual approach point in the assumed and adjusted by the actuator approach point would transmit a significant torque, which in addition to increased wear of the friction linings of the clutch also to a friction-related further strong heating of the clutch and optionally too Problems with the gear change or an unexpected self-starting or accelerating the vehicle would result.

The well-known periodic calibration of the clutch actuator is in other words therefore particularly critical because the approach point is there determined so that there is already a rotation of the Kupplungsabtriebsseite at this point with inlaid idle and switched-off transmission brake. From this point, the transmittable torque of the clutch increases sharply with increasing closing of the clutch, so that even low thermal expansions of the clutch components and / or the adjusting device or other influences lead to a significant increase in the transmittable torque and the frictional heat generated at a braked output shaft, and so greatly increase wear and cause further heating.

It is also disadvantageous that US Pat. No. 5,624,350 only proposes a consideration of wear and of a change in the working temperature by recalibration. A different consideration of various factors is hereafter provided as little, such as a forward-looking controlling the position of the clutch resting point in anticipation of future conditions.

Against this background, the object of the invention is to provide a method for the dynamic calculation of a clutch home position in which an event-dependent calibration is possible. Next, the clutch resting point should be determined so that increased wear of the clutch on the one hand and a required switching time to reach a slip range of the clutch on the other hand, depending on certain parameters can be minimized. The solution of this problem arises from the features of the main claim, while advantageous embodiments and further developments of the invention are the dependent claims can be removed.

The invention is based on the finding that the position of the clutch resting point should advantageously not be determined periodically but at least also as a function of the event. Furthermore, it is based on the knowledge that the clutch resting point should not be dimensioned solely after the beginning of a measurable torque transmission through the clutch, but additionally has to take into account a certain offset value, for example the positioning accuracy achievable in a quick adjustment mode and certain short-term possible or probable parameter changes should be included.

The coupling rest point is thus not identical in the following with the approach point defined in US Pat. No. 5,624,350, but is generally characterized by a certain minimum safety distance from this approach point. This safety distance can be set optimally and in particular as a function of the respective operating conditions by the parameters which are listed below and which are to be taken into account advantageously in the calculation of the rest point.

Accordingly, the invention is based on a method for the dynamic calculation of a rest point position of an automatic or automatable friction clutch, wherein a control device controls a clutch actuator such that its actuator assumes corresponding actuator positions and thereby controllable torque transmission between a drive shaft coupled to a drive motor and a The output side of the friction clutch adjusts, wherein the control device in preparation for a closing of the friction clutch for the purpose of transmitting a torque, the actuator of the Kupplungsaktuators first in a Ruhepunkt- Setting position in which a dead travel of the friction clutch is greatly reduced until the transmission of torque compared to a complete opening of the clutch. This has the consequence that the clutch is at the time in which it is to transmit a torque, already close to the point of contact and therefore particularly fast and yet can be adjusted exactly in the desired range.

To achieve the object, it is provided that the control device determines the rest point position as a function of the event. Subsequently, a related control command can be issued to the clutch actuator, which brings the actuator or the friction clutch in the desired rest position.

According to the invention, the rest point position can be determined at a favorable time, which on the one hand increases the timeliness of the calculation and, on the other hand, reliably prevents the determination from taking place at an unfavorable time, in which, for example, the control device is heavily loaded by other calculations, and itself so in the worst case, the setting of the clutch to a desired position by a delay in the determination of the rest point also delayed.

It should be noted that the concept of determining the rest point in a particular case may include a calibration step performing actual Kupplungsstellbewegungen and an evaluation of reactions to this, but that here and just a determination of the concrete to be controlled rest point including a previously by, for example Calibration step determined basic value, for example in the form of a calculation or a readout of correction values from tables or characteristic value stores, is to be understood as a determination. If the control device carries out the calculation of the rest point or the rest point position on the basis of such a basic value or base rest point of the friction clutch with the inclusion of further correction factors, time-consuming and wear-prone physical calibration steps can be dispensed with in the specific situation. In this way, the calculation can be done very quickly. In addition, a determination of a base rest point by means of a calibration is only necessary at relatively long time intervals in order to determine, for example, a deviation between a predicted wear behavior and an actual wear behavior.

An advantageous variant of the method provides that the control device performs the determination of the rest position during a phase of Gangauslegens connected to the output side of the clutch, automatic or automatic transmission, because at this time mostly for the determination of the home position important parameters are known and the Determining the rest point position can still be done relatively early. At the same time or at least alternatively, it is possible to carry out the determination with the aid of a very low computing power of the control device. Therefore, relatively heavily loaded or weakly dimensioned control devices can take over this task easily.

Alternatively, it can also be provided that the control device carries out the determination of the home position while the automatic or automated manual transmission is in its neutral position. This point in time is particularly suitable in many cases, since it is somewhat later compared to the above-described determination during the design of the original course, and the calculation results can thus tend to be more up-to-date. However, in order to minimize the load on the control device at the time of engagement or shortly before, it is again desirable if the control device carries out the determination of the rest point position immediately after the presence of a neutral position in the automatic or automated transmission.

Of course, it is useful, for example, after a standstill of the vehicle without gear engaged or even after a long time without gear engaged and after the start of the vehicle, when the control device determines the rest point position of the friction clutch for the first time or again at a time in which an insert a Ganges is expected in the short term.

Further, it is advantageous if the control device determines the rest point or the rest point position of the friction clutch, starting from a base rest point including a speed-dependent correction value, since the driving speed allows conclusions about the general operating state of the vehicle. For example, it can be provided that at higher driving speeds, the rest point position is placed closer to the contact point of the friction clutch, is transmitted from the torque, to allow a particularly fast coupling reaction.

The speed-dependent correction value can be determined in various ways. Since the vehicle speed signal is already available in all modern vehicles as an electrical or electronic signal, it makes sense to use this signal for the determination of the speed-dependent correction value. The measurement of a measured value corresponding to the driving speed can also be effected by detecting the rotational speed of the transmission output shaft. On the other hand, it may be advantageous for the control device to determine the speed-dependent correction value as a function of the rotational speed of the clutch output side or a transmission input shaft coupled thereto, since this value, in combination with the known engine rotational speed, enables a direct and particularly simple consideration of the differential rotational speed applied to the clutch.

As already mentioned above, it often makes sense if the control device reduces the speed-dependent correction value with increasing vehicle speed, since a high speed can be expected with a desired speedy gear change. This may possibly even tolerate a possible tolerance-related achievement of the friction range of the clutch, since this condition only occurs for a short time. A heat-generating, wear-prone and therefore actually undesirable shift of the rest point position into the friction region of the clutch is so far not so critical, as would be the case with a longer-lasting traffic light stop. It is therefore to be noted that an increasing speed expressly also an increasing differential speed, for example between the drive side and the output side of the clutch should be understood.

Furthermore, alternatively or additionally, it may be provided that the control device takes into account as a correction value a gear-dependent value GDO (Gear-Dependent Offset), for example, particularly simple and with very little computational effort depending on an initial gear or preferably a target gear or particularly preferably a combination of Both can be read from a table.

In particular, this gear-dependent correction value GDO can remain the same or become larger as the gear number increases, by which is meant that the gear-dependent correction value GDO indeed has several gear steps can remain constant, but ultimately has a steady and increasing course. The advantages to be achieved are primarily due to the fact that higher gears tend to correspond to higher driving speeds. Thus, for example, be provided for a 16-speed automatic transmission that the gear-dependent correction value GDO for starting gears RL (backward small), RH (reverse large), gear 1, gear 2, gear 3 and gear 4 has the value zero, and for medium forward gears (gear 5, gear 6, gear 7, gear 8) greater than zero and smaller than the gear-dependent correction value GDO for large gears (gear 9, gear 10, gear 1 1, gear 12, gear 13, gear 14, gear 15 , Gear 16) is.

In addition, the control device may alternatively or additionally take into account a circuit-type-dependent value STO (shift-type offset) as a correction value, which may be dependent, for example, on whether it is an upshift or a downshift. In upshifts, the shortest possible interruption of traction is often desirable in order to achieve an overall optimal acceleration behavior of the vehicle. In downshifts, the traction interruption is, with the exception of some special cases, such as driving on particularly steep gradients, usually comparatively unimportant, so the rest point position can be located in these cases further from the touch point of the friction clutch.

Furthermore, it makes sense if the control device takes into account in the determination of the circuit-type-dependent value STO, whether it is a shift from the neutral position of the transmission during the switching process, as is common, for example when starting from a stand. Here, the safe avoidance of a frictional state of the clutch at rest is to attach particular importance, since this condition can be indefinitely or indefinitely long time. Accordingly, the circuit type dependent value for increasing the safety distance of the rest point from the contact point of the friction clutch is here for the most part relatively great to choose. However, the same applies to other neutral switching states of the transmission, as they may occur when rolling the vehicle with gear laid on an elongated slope.

According to another advantageous development of the invention, it is provided that the control device for determining the circuit-type-dependent value STO takes into account whether the current switching operation is one which is carried out only in a primary gearbox or only in a main gearbox of a multigrain transmission device.

Finally, there are special advantages if the control device takes into account in the determination of the rest point position of the friction clutch as a correction value an offset value DO (Disengagement Offset), which they determined at neutral position of the gearbox and the presence of certain other conditions. In this way, as a base value or base resting point of the friction clutch, a fixed, vehicle-dependent value can be used, which is corrected by the offset value DO. The offset value DO can preferably be determined if the vehicle is a further condition, an optionally existing transmission brake is released and the friction clutch has a normal operating temperature.

To ensure, for example, even with faulty sensor values or Signaleinstreuungen that the determination and adjustment of the rest position in no case leads to a dangerous driving condition in which the vehicle, for example, unintentionally sets in motion or the coupling is damaged by unacceptably high friction by overheating, it is Finally advantageous if the control device varies the rest point position only within predetermined or calculated upper and lower limits. In addition, it should be noted that the consideration of the correction factors presented here can of course be carried out either individually or in any desired combinations. For each correction factor applies that this can be considered in the form of an additive or subtractive correction value, in the form of a multiplier or in any other forms to self-learning neural networks in the determination of the rest point position of the friction clutch and the actuator of the clutch actuator.

In addition, it is possible and useful to also consult other parameters for the formation of the named correction factors or to determine with their help further correction factors and to take into account in the determination of the rest point position. For example, a transmission temperature which is already known on the basis of the measurement of a transmission temperature sensor can also be taken into account, for example a physical-mathematical model of the expected wear of the clutch disks.

Finally, it is also possible to give the driver a direct or indirect influence on the determination of the home position by direct input possibilities or evaluation of his behavior. For example, the rest point position can be moved in a very "sporty" driving behavior of the driver further toward the point of contact of the friction clutch as in a calm and comfortable driving driver.

Also, it is possible, for example, for motor racing with motor vehicles to provide a direct input option and optionally an override function by the driver or a technician, for example, the rest point position of the clutch even during shifts from the neutral position of the transmission out in the direction of the touch point of the Clutch or even beyond can shift. The invention can be further explained with reference to an embodiment. For this purpose, two drawing figures are attached to the description. Showing:

1 is a diagram for the possible determination of a speed-dependent correction value for a rest position of a clutch actuator or a friction clutch and

Fig. 2 is a tabular representation of a possible assignment of gear-dependent correction values to gear stages of a transmission with two reverse gears and sixteen forward gears.

For the following exemplary embodiment, it is assumed that a motor vehicle has an internal combustion engine whose output shaft is connected in a rotationally fixed manner to the drivable side of a multi-disc clutch. Likewise, single-disc or double-disc clutches are applicable in a corresponding manner of operation. The output side of the multi-plate clutch is rotatably connected to the input shaft of an automated manual transmission. The mode of operation of the multi-plate clutch is determined by the actuating position of a clutch actuator, which is controlled by an electronic control device.

The basic resting point of the clutch has been determined by a first time at the end of a production line of the vehicle and later repeated, for example on occasion of workshop inspections calibration process for this clutch at a Aktuatorstellwert, for example, 27 mm. This control value can be determined, for example, by a slow closing of the clutch when the engine output shaft is rotating and the transmission input shaft is stationary, as well as the gearbox being designed with the transmission brake open. In this case, that Aktuatorstellwert or coupling point is determined, in which the clutch output shaft or the transmission input shaft begins to turn straight. Subsequently, for example, a Aktuatorweg of 2.5 mm as Added basic safety margin in the opening direction of the clutch and adjusts the actuator of the clutch actuator to the entire Aktuatorstellweg in the clutch opening direction. This ensures that the clutch clearly transmits no torque at rest under normal operating conditions.

This basic safety margin has preferably been determined in such a way that it corresponds to the maximum safety margin desired during operation, taking account of the usual wear of the clutch until the next calibration procedure to be expected.

When driving, the control device then adjusts the resting point to be actually set, for example by reducing this basic safety margin. The control device can, for example, as soon as sensors report that a previously inserted original gear of the automated gearbox has been designed to determine the currently set rest point and then issue a corresponding control command to the clutch actuator for adjusting the rest position of the friction clutch.

In this example, the controller detects the vehicle speed and uses this to determine a base home point using a stored table or mathematical equation. This can, as shown schematically in Fig. 1, thereby, that in accordance with the determined driving speed, such as V1 or V2, each Kupplungsstellweg Y1 or Y2 is determined, which of the value of Y3 as a horizontal, dot-dashed line drawn maximum security surcharge is deducted. At a speed of 0 km / h, as can be seen from FIG. 1, due to the graph starting in the axis origin, no correction of the basic safety margin results. of 2.5 mm, so that the base resting point corresponds to the basic resting point when the vehicle is stationary.

However, at a speed V1 of, for example, 30 km / h, the basic safety margin Y3 is reduced by the corresponding value Y1 of 1.2 mm assumed here, whereby a base rest point shifts toward the point of contact of the clutch. At a speed of V2 of, for example, 80 km / h, the controller reduces the basic safety margin Y3 by the value Y2, which is assumed to be 2.0 mm as shown in FIG. The base resting point is therefore at a driving speed of 80 km / h only 0.5 mm from the touch point of the friction clutch.

In this way, the clutch can be closed very quickly when there is a corresponding command at higher speeds, while at lower speeds a slightly greater safety distance is given to the touch point. Instead of the driving speed can be used in the same way a rotational speed of an output shaft of the transmission as an output for reducing the safety distance.

Alternatively or additionally, the new gear stage to be engaged can be taken into account by changing the safety distance when adjusting the clutch position. For example, the control device can read from the table shown in FIG. 2 a correction factor which depends on the gear ratio to be engaged and, in this case, for example, reduce the safety distance by a further 10% (offset) for the planned engagement of the 10th driving gear. As illustrated in FIG. 2, in this exemplary embodiment, no offset value is provided for the two reverse gears RL and RH and for the starting gears 1 to 4 or the amount thereof is equal to zero It usually does not depend on the fastest possible gear change when using these Anfahrgänge.

The control device can also carry out further corrections of the said safety distance on the basis of further parameters. It is irrelevant in the context of the method according to the invention, whether initially a safety distance is determined, which is then reduced or increased in the manner described above depending on certain parameters, or if the target variables to be calculated, for example, the control position of the actuator or the Position of the pressure plate are. The decisive factor here is merely that ultimately the safety distance between a rest point to be set and the point of contact of the clutch is optimized in accordance with the named parameters.

Claims

claims

1. A method for dynamically calculating a rest point position of an automatic or automatable friction clutch, wherein a control device controls a clutch actuator so that its actuator assumes corresponding actuator positions and thereby adjusts a controllable torque transmission between a drive motor coupled to a drive shaft and an output side of the friction clutch, wherein the Control device in preparation for closing the friction clutch for the purpose of transmitting a torque setting the actuator of the clutch actuator first in a rest position, in which a dead travel of the friction clutch is greatly reduced until the transmission of torque compared to a complete opening of the clutch, characterized in that the control device determines the rest point position as a function of the event.

2. The method according to at least one of the preceding claims, characterized in that the control device determines the rest point position on the basis of a base rest point of the friction clutch, including other correction factors.

3. The method according to at least one of claims 1 or 2, characterized in that the control device determines the rest point position during a phase of Gangauslegens connected to the output side of the friction clutch, automatic or automated manual transmission.

4. The method according to at least one of claims 1 or 2, characterized in that the control device determines the rest point position while the automatic or automated transmission is in its neutral position.

5. The method according to claim 4, characterized in that the control device determines the rest point position immediately after the setting of the neutral position in the automatic or automated manual transmission.

6. The method according to at least one of the preceding claims, characterized in that the control device determines the rest point position starting from a base rest point including a speed-dependent correction value.

7. The method according to claim 6, characterized in that the control device determines the speed-dependent correction value as a function of the driving speed of the vehicle or of the rotational speed of a transmission output shaft.

8. The method according to at least one of claims 6 or 7, characterized in that the control device determines the speed-dependent correction value as a function of the rotational speed of the clutch output shaft.

9. The method according to at least one of claims 6 to 8, characterized in that the control device reduces the speed-dependent correction value with increasing speed.

10. The method according to at least one of the preceding claims, characterized in that the control device takes into account as a correction value a gear-dependent value GDO.

11. The method according to claim 10, characterized in that the control device reads out the gear-dependent correction value GDO from a table.

12. The method according to at least one of claims 10 or 11, characterized in that the gear-dependent correction value GDO for reverse and forward starting gears (RL, RH, gear 1, gear 2, gear 3, gear 4) is equal to zero, and for intermediate forward gears (gear 5, gear 6, gear 7, gear 8) greater than zero and smaller than the gear-dependent correction value GDO for large gears (gear 9, gear 10, gear 11, gear 12, gear 13, gear 14, gear 15, Gang 16) is.

13. The method according to at least one of the preceding claims, characterized in that the control device takes into account as a correction value a circuit type-dependent value STO.

14. The method according to claim 13, characterized in that the control device takes into account in the determination of the circuit-type-dependent value STO, whether it is an upshift or a downshift.

15. The method according to at least one of claims 13 or 14, characterized in that the control device takes into account in the determination of the circuit-type-dependent value STO, whether it is a starting process.

16. The method according to at least one of claims 13 to 15, characterized in that the control device for determining the circuit type dependent value STO takes into account whether the current switching operation is one which is performed only in a primary gear or only in a main gear of a multi-group transmission device.

17. The method according to at least one of claims 1 to 16, characterized in that the control device takes into account as a correction value an offset value DO, which they determined at a neutral position of the gearbox and the presence of certain further condition.

18. The method according to claim 17, characterized in that the control device determines the offset value DO when the vehicle is a further condition, an optionally present transmission brake is released and the friction clutch has a normal operating temperature.

19. The method according to at least one of claims 1 to 18, characterized in that the control device varies the rest point position only within predetermined or calculated upper and lower limits.