DE19915207A1 - Determining servo coupling engagement point involves driving auxiliary device, coupling in definable manner in response to detection/setting of defined operating state, evaluating shaft speed - Google Patents

Abstract

The method involves detecting a parameter representing the revolution rate of the output shaft. A predefinable operating state is detected or set; the auxiliary device (17) and servo coupling (11) are driven in a predefinable manner in response to the detection or setting of the operating state and the point of engagement is determined during the driving activity at least depending on the detected revolution rate parameter. An Independent claim is also included for an arrangement for determining the engagement point of a servo coupling.

Description

State of the art

The method according to the invention or the inventive method Device from a system with the features of the Oberbe handles of claim 1 and claim 14.

Automatic clutches or servo clutches are included known for example from "Automotive Bags book ", edition 1991, pages 538 and 539. Servo couplings offer ent in connection with electronic control units neither an automated starting process or, together with servo-operated gearboxes, a fully automatic Transmission. With such couplings, the opening and The clutch is generally closed by a servo instinct. The control of this servo drive should realize a desired clutch torque.  

To do this, however, the relationship between the adjustment of the servo motor and that to be transmitted by the clutch Moment.

In such vehicles with electronic clutch management ment must constantly the entire characteristic that the together hang between the position of the servo motor and the over portable moment describes to be adapted. This will, as described for example in DE 195 40 921 A, in the areas from medium to strong moments done well that in normal driving the clutch open slowly until there is a gap between the Speeds of the input and output shaft of the clutch one measurable difference results. That when the speed occurs The difference between the engine output torque reported by the engine is that transferable associated with this position of the servo motor Clutch torque. This procedure is difficult to use at very low moments because the clutch characteristic at low moments is very flat. In particular the point at which the clutch begins to transmit a moment that so-called gripping point, is difficult to determine, though he both for starting off and for comfortable Switching operations is of great interest.

Can also be used to adapt the clutch on the vehicle the clutch is at a standstill and the gear is engaged be closed until the moment or the speed of the engine changes. In addition, when the vehicle is stationary stood and not engaged gearbox the clutch et what will be closed until there is a certain change engine speed comes.  

DE 197 12 871 A describes a method for adaptation the clutch characteristic in the range of very small moments, by the given operating conditions Operating parameters of the vehicle engine set in this way be that the output power of the vehicle engine in we is substantially constant.

However, if an auxiliary unit is installed in the vehicle, for example the electric generator, which also functions as a combined star ter generator can be executed with the input shaft the gearbox instead of the crank, as usual shaft of the vehicle engine, can with the input shaft at rest no electrical energy is generated. Should still be electrical even when the vehicle is at a standstill This arrangement requires energy to be generated that when the vehicle is stationary, the clutch is closed is so that the input shaft of the gearbox with the Vehicle engine speed rotates. So that the vehicle is in this arrangement, the transmission must then in a Be positioned where there is no power from the vehicle engine can be transferred to the drive wheels (neutral position tion).

In the above-described methods for adapting the coupling However, it is assumed that when the vehicle is stationary the clutch was open most of the time net or is even a gear in the transmission. The Invention describes an adaptation that also functions kidney, when the clutch is in the we is substantially closed so that the electrical genera can work. In addition, the electric generator, which, as already mentioned, also as  combined starter-generator can be executed and which is connected to the input shaft of the transmission new possibilities for an improved adaptation of the dome characteristic curve.

The object of the present invention application is therefore in the optimal coupling adaptation, if such an additional gregat with the output shaft of the clutch or gearbox input shaft is connected.

This task is characterized by the characteristics of the Claims 1 and 14 solved.

Advantages of the invention

As mentioned, the invention is based on a method or a device for determining the gripping point controllable servo clutch. The servo clutch is in the Drive train of a motor vehicle together with a drive Witness motor and a gear arranged and has a gear and output shaft. As already described at the beginning is a controllable by the output shaft of the servo clutch res auxiliary unit, in particular an electrical generator, driven. Furthermore, the speed of the output shaft representing speed variable detected.

The essence of the invention is that a predeterminable or predetermined operating state of the drive train is detected or is set. In response to the capture or Setting the operating state then becomes the secondary unit gat and the servo coupling in predeterminable or specified  Controlled way. Little is done during this activation The gripping point depends on the detected speed determined. It is therefore advantageous in the Invention The auxiliary unit is integrated according to the clutch adaptation.

Further advantageous embodiments of the invention are in Subordinate claims can be found and detailed in the context of the Exemplary embodiments described.

The investigators deal with a first embodiment of the invention the gripping point and thus the adaptation in normal use drove the vehicle at lower clutch torques while a second embodiment, the adaptation in normal operation of the Includes vehicle in the area of larger clutch torques. A third embodiment relates to the determination of the griffin point or the adaptation during commissioning or in Service case, for example in a workshop.

The invention according to the first embodiment allows Adaptation of the gripping point via an actuator from egg ner electronic control operated clutch in the An drove a motor vehicle even when at rest the vehicle had this clutch closed and therefore the transmission is in neutral. Previous procedures allow adaptation of the gripping point only if the clutch is open when the vehicle is at a standstill. This adaptation is for comfortable and quick control tion of such a coupling is required. Closing the Clutch when the vehicle is at a standstill, as mentioned, used especially when the electrical genera gate no longer with the crank, as was usually the case up to now shaft of the vehicle engine, but with the input shaft of the transmission is connected.  

The invention according to the second embodiment enables the exact adaption of the clutch characteristic in as possible many operating points, also in the area of higher couplings moments, and is therefore important for the comfortable Control of a servo clutch.

The invention according to the third embodiment enables Vehicles with an automated clutch and a clutch release Auxiliary unit attached on the gear side, the clutch characteristic indi to record vidually for each copy. Ferti tolerances and variations in the friction lining of the clutch Record during commissioning and combat appropriately in the characteristic curve. In addition, the aging and ver Compensate for clutch wear. An ad downstream in operation aption has to compensate less and can do it all the more precisely. There the exact knowledge of the course of the clutch characteristic in poss as many operating points as possible for convenient control a servo clutch can, by the inventive method the comfort of such couplings can be significantly improved.

drawing

Figs. 1a, b and c show the three embodiments of the invention, schematically, the drive train of a vehicle with the associated clutch control. Figs. 2, 3, 5 and 6 show flowcharts of the different execution forms. In FIG. 4 is a time sequence of an adaptation to see, while the Fig. 7 example discloses a clutch characteristic.

Embodiment

Using the exemplary embodiments described below the invention is intended to be clarified.

The basic structure of the drive train of a vehicle is shown in FIGS . 1a, b and c. Between the vehicle engine 10 and the transmission 12 there is a servo clutch 11 , which is controlled by an electronic clutch control 14 via an actuator 15 . The actuator 15 is able to adjust the distance of the clutch discs (not shown) and thus the transmissible torque of the clutch 11 . The transmission 12 with an input and an output shaft transmits the torque of the vehicle engine 10 to the drive wheels 13 . Through the output shaft of the clutch 11 , an electric generator 17 , which can also be designed as a combined starter generator, is driven. The electric generator 17 has an electronic control 16 , which can influence at least the load of the generator and thus the torque which is taken from the input shaft of the transmission. In addition, the electric generator has a device for recording its speed n_gen.

For the invention, the type of connection of the electrical generator's 17 with the input shaft of the transmission 12 is irrelevant. This connection can be rigid, belted via a wedge or also by another, possibly switchable, transmission.

The translation between the speed n_ge of the input shaft of the transmission 12 and the speed n_gen of the electric generator 17 can be assumed to be known.

The clutch control 14 is the speed n_ge of the transmission input shaft or the output shaft of the clutch, the Ge generator speed n_gen and the engine output speed n_m.

In addition, in Fig. 1b and 1c with the reference numeral 18, a motor control is designated, which can be controlled for setting a certain engine torque or a certain engine output speed n_m. The clutch control 14 continues to be supplied with the current engine torque md_ma and the engine speed n_m.

In Figs. 1b and 1c, the generator controller 16 may md_gen or for setting a generator torque of a genera tor-torque increase md_gen_delta be controlled.

1. The first embodiment of the invention 1a) To determine the gripping point

The determination of the gripping point (the point at which the clutch begins to transmit a torque) of the clutch 11 is advantageously carried out in situations where little or no torque is to be transmitted via the clutch. Such situations usually occur when the vehicle is at a standstill. Section 1b provides a more in-depth discussion of the situations in which the gripping point can be determined.

Fig. 2 shows a first sequence of a Greifpunktbe determination. After starting step 21 , it is first checked in step 22 whether there is a situation where the transmission 12 is in the neutral position and the clutch 11 can transmit the torque of the vehicle engine 10 completely to the input shaft of the transmission 12 and the electrical generator 17 . If this is not the case (query result "no" in step 22 ), no adaptation is carried out. If this is the case, the process moves on to step 23 .

Because of the neutral position of the transmission 12 , no torque can be transmitted to the drive wheels 13 . Now the clutch control 14 carries a signal "adaptation active" to the generator control 16 to inform this that ei ne adaptation of the gripping point is active. The generator control 16 then controls in step 23 the electrical Ge generator 17 so that it loads the input shaft of the transmission 12 , which is fixedly connected to the output shaft of the clutch 11 , with a small torque (typically in the order of 1-3 Nm) .

In addition, in step 23, the clutch control 14 via the actuator 15 opens the clutch 11 slowly, ie it slowly increases the distance between the clutch plates.

For this purpose, the position of the actuator starting from the current position slowly increased with a ramp and so that the clutch can be opened. Particularly advantageous it is, however, the position of the actuator based on the current position quickly in an applier distance before the last saved gripping point  drive (where the clutch is still securely closed) and you only then slowly increase with a ramp. To this This way, the entire adaptation is faster.

Since the generator 17 is now loaded and the required torque can no longer be transmitted from the clutch 11 from a certain position of the actuator 15 , the speed n_gen of the electrical generator (and thus the speed n_ge of the input shaft of the Gearbox). This is checked by the step "and / or" link (dn_gen / dt <threshold2 <0) in step 24 .

As soon as a drop in the speed of the electrical generator is registered, the current position of the actuator in the clutch control is stored as a gripping point in step 25 and the generator control is instructed to go back to normal operation. The clutch is firmly closed again. After the end step 26 , the sequence shown in FIG. 2 is started again.

In a further advantageous embodiment of the method the current position of the actuator will not be the new one Gripping point saved in the clutch control, but the gripping point stored in the clutch control becomes only according to the deviation between the current position of the Actuator and the last saved gripping point different.

There are several methods for detecting the gripping point (further “and / or” link shown in step 24 )

• 1. It can be checked whether the amount of the difference between the speed of the electrical generator and the speed of the vehicle engine, divided by the translation of the electrical generator, is greater than an applicable threshold.
  (| n_m - (n_gen / u_gen) | <Threshold1?)
• 2. Alternatively or additionally, it can be checked whether the gradient of the speed of the electrical generator is less than an applicable (negative) threshold2.
  (dn_gen / dt <threshold2 <0?)
• 3.If the vehicle has a device for recording the speed of the input shaft of the transmission, it can alternatively be checked whether the amount of the difference between the speed of the vehicle engine and the speed of the input shaft of the transmission is greater than an applicable threshold1.
  (| n_m - n_ge | <threshold1?)
• 4. Alternatively or additionally, it can be checked whether the gradient of the speed of the input shaft of the transmission is less than an applicable (negative) threshold3.
  (dn_ge / dt <threshold3 <0?)
• 5. Since the vehicle engine is loaded by the load of the electric generator at the beginning of the adaptation, the vehicle engine is relieved by opening the clutch and its speed increases briefly. Therefore, the condition that the gradient of the rotational speed of the vehicle engine is greater than an applicable (positive) threshold4 can also be used to detect the gripping point.
  (dn_m / dt <threshold4 <0).
• 6. Since the gearbox is in neutral position during the adaptation of the gripping point, the speed of the input shaft of the gearbox and the associated speed of the electric generator can only decrease by opening the clutch. Therefore, the formation of the absolute amount in points 1 and 3 can also be dispensed with.
• 7. If the vehicle engine has precise control ner speed and means for recording the given by him torque, there may also be an increase in torque serve the vehicle engine to recognize the gripping point.
• 8. A further advantageous embodiment is shown with reference to FIG. 3. Steps 31 , 32 , 33 and 34 correspond to steps 21 , 22 , 23 and 24 already described. If conditions 1 to 5 exist (individually or in combination), however, the current position of the actuator is not yet saved as a gripping point, but the clutch is closed again (step 35 ). For this purpose, either the same ramp as for opening can be used, only the sign of the gradient being interchanged. However, it is particularly advantageous here to control the actuator in such a way that the clutch is closed again more quickly than it was previously opened.

In this variant, the current position of the actuator is only saved as a gripping point in step 37 when the following situations (individually or in combination) exist (step 36 ):

• - | n n_m - (n_gen / u_gen) | <Threshold1?  
• - dn_gen / dt <- threshold2 <0?
• - | n_m - n_ge | <Threshold1?
• - dn_ge / dt <- threshold3 <0?
• - dn_m / dt <- threshold4 <0
• - The delivered torque of the vehicle engine drops

After saving the gripping point in the clutch control, the generator control is instructed to go back to normal operation. The clutch is firmly closed again. After the end step 38 , the sequence shown in FIG. 3 is started again.

Fig. 4 shows schematically the position of the clutch actuator 15 during an adaptation according to the method described in point B be. It is assumed here that the clutch is closed when the position of the actuator is small and open when the value is large. For this purpose, the temporal change in the position of the actuator 15 is recorded in FIG. 4.

The adaptation and the actuator begin at time t1 is quickly adapted to a position before the last one Gripping point moved. At time t2, this position is he is enough and the actuator slowly opens the clutch white ter. At time t3 is one of the conditions mentioned above conditions met, e.g. B. a sufficiently large difference between the speeds of the vehicle engine and the input shaft of the Gearbox. Now the clutch is closed again. H. the actuator reduces the distance between the clutch plates again. The gripping point is recognized at time t4, e.g. B. because the difference between the speeds mentioned is small again  is not enough. Now the current position of the actuator saved as a new gripping point or the saved one Gripping point modified according to the deviation. On the actuator then moves to a position where the clutch is securely closed again.

1b) To determine the situations in which the gripping point can be determined

The adaptation of the gripping point of the clutch according to the above-explained method can only take place if no torque is passed from the vehicle engine 10 to the drive wheels 13 . In order to carry out the adaptation correctly, it should only begin in situations in which, even in the near future, it cannot be expected that a torque from the vehicle engine 10 will be directed to the drive wheels 13 . This is the case, for example, when the vehicle is at a standstill with the brake applied. It is particularly advantageous here if the adaptation of the gripping point is terminated as soon as the brake is no longer actuated. Signals from both the service brake and the parking brake of the vehicle can be evaluated. It is also advantageous to abort the adaptation as soon as a request for torque is made to the drive train. This requirement can e.g. B. can be recognized when the driver operates the accelerator pedal or an automatic drive (z. B. distance radar system ACC) makes a corresponding request.

Since in some variants of the invention the gradient of the number of revolutions of the vehicle engine or the gradient of the speed of the input shaft of the transmission or the gradient of the speed of the electric generator is evaluated, it is particularly advantageous to only start with the adaptation if these gradients are smaller than an applicable threshold. The thresholds can be different for the different speeds. These gradients can be evaluated individually or in combination. The individual conditions are summarized again in detail in the two sections below.

• - To determine the situations that must exist before and during the adaptation:
  It is imperative that the transmission 12 is in the neutral position. Furthermore, the coupling must be closed at the start of an adaptation. Optionally, it can be requested that the brake is actuated (service brake and / or parking brake) and / or that there is no desire for drive torque (recognizable e.g. from an unactuated accelerator pedal or non-positive torque request from a driving machine such as ACC) . As soon as one of the above conditions is no longer met, the adaption of the gripping point is canceled.
• - To determine the situations that should exist before the start of the adaptation:
  In addition, it is advantageous to check whether an adaptation of the clutch's gripping point begins
  • - The amount of the gradient of the speed of the vehicle engine is less than an applicable threshold and / or
  • - The amount of the gradient of the speed of the electrical generator is smaller than a further applicable threshold and / or
  • - The amount of the gradient of the speed of the input shaft of the transmission is smaller than a further applicable threshold.

If one of these conditions does not apply, the one with the Application not started.

2. The second embodiment of the invention

While the first embodiment of the invention the Adap tion of the clutch characteristic in the area of lower clutch moments described, shows the description below benen embodiment, the adaptation of the clutch characteristic in the range of medium to high moments using one connected to the input shaft of the transmission electrical generator.

For the second embodiment of the invention, FIG. 1b already described shows the basic structure of the drive train of a vehicle. As already described, the electrical generator 17 has an electronic control 16 , which can influence at least the load of the generator and thus the torque which is taken from the input shaft of the transmission 12 . To increase the load z. B. the excitation can be increased, whereupon the electrical generator 17 emits more electrical energy than before. This increased electrical energy can e.g. B. can be used to charge the vehicle battery or be converted into heat in the inverter. Wei terhin is in Fig. 1b, the vehicle engine 10 controlled by an electronic controller 18 , which can specify the torque of the engine. This control can receive a signal (md_ma_delta) from the clutch control and then increase the torque output by the engine. In addition, facilities or methods are provided for detecting the torque md_ma delivered by the vehicle engine. Such methods are known and generally evaluate the masses of air and fuel flowing into the engine, as well as other variables known in engine control (e.g. ignition angle in gasoline engines, exhaust gas recirculation in diesel engines).

The course of the adaptation is shown in FIG. 5 Darge.

2a) Adaptation of the clutch characteristic

The determination of the clutch characteristic is advantageously carried out in situations where, on the one hand, the torque md_ma emitted by the vehicle engine 10 is known relatively precisely and, on the other hand, a short, short slip of the clutch 11 is not particularly disruptive. This takes place in step 52 of FIG. 5 to be processed after the start step 51 .

Such situations are usually in normal driving powered with only little dynamics in the torque requirement the vehicle engine. A prerequisite is in any case closed clutch. The adaptation of the clutch characteristic So especially when starting with a sliding clutch tion and during a circuit. A ver deep discussion of the situations in which the clutch characteristic can be done in the following section 2c.

At the beginning of an adaptation of the clutch characteristic, there is a situation where a gear is engaged in the transmission 12 and the clutch 11 is closed. The torque md_ma of the vehicle engine 10 is transmitted to the electric generator 17 via the clutch 11 and to the drive wheels 13 via the transmission 12 . During the adaptation, the clutch controller 14 carries signals to the generator controller 17 and to the engine controller 18 . To the engine control 18 , a signal md_ma_delta for increasing the torque is transmitted, which causes the engine 10 to deliver an increased torque by this amount. It is particularly advantageous to slowly increase this torque increase md_ma_delta with a rising ramp starting from the value zero.

A signal md_gen_delta is simultaneously transmitted to the generator controller 17 which veran cause the generator 17 to absorb more torque. For this, e.g. B. the excitation can be increased, whereupon the electrical generator 17 delivers more electrical energy than before. As already mentioned, this increased electrical energy can be used to charge the vehicle battery or can be converted into heat in the inverter.

It is particularly advantageous to increase the torque absorption of the electric generator 17 to the same extent as the torque emitted by the motor increases (md_gen_delta = md_ma_delta). In this case, the torque acting on the drive wheels 13 does not change, which ensures that the acceleration of the vehicle does not change due to the adaptation.

At the beginning of the adaptation of the clutch characteristic, the clutch control 14 instructs the actuator 15 to adjust the clutch 11 so that the torque just output by the vehicle engine 10 can be transmitted at md_ma_delta = 0 with a certain safety reserve (for example about 15%) ( Step 53 ). For this, the last saved values of the clutch characteristic are used. During the adaptation, the clutch control 14 holds the position of the actuator 15 and thus the torque that can be transmitted from the clutch 11 (step 54 ). As soon as the torque output by the vehicle engine 10 and received by the electrical generator 17 and the drive wheels 13 exceeds the torque that can be transmitted by the clutch, slip occurs on the clutch 11 . Slip detection methods are described below in section 2b below.

As soon as a clutch slip has been detected in step 55 , the clutch characteristic curve can be modified based on the current position of the actuator 15 and the torque md_ma output by the vehicle engine 10 (step 56 ).

In one embodiment of the invention, the clutch characteristic is multiplied by a factor which corresponds to the deviation between the torque currently output by the vehicle engine 10 and the transferable clutch torque stored for the current clutch position. In a further advantageous embodiment, only individual points on the clutch characteristic curve, which are close to the torque currently output by the vehicle engine 10 , can be modified accordingly.

2b) detection of clutch slip

There are several ways to detect clutch slip, which are shown in step 55 :

• 1. Possibility to detect the clutch slip:
  It can be checked whether the amount of the difference between the speed n_gen of the electric generator 17 and the speed n_m of the vehicle engine 10 , divi ded by the translation of the electric generator 17 , is greater than an applicable threshold.
  (| n_m - (n_gen / u_gen) | <Threshold1?)
• 2. Possibility to detect the clutch slip:
  If the vehicle has a device for detecting the speed n_ge of the input shaft of the transmission 12 (which corresponds to the clutch output speed), it can alternatively be checked whether the amount of the difference between the speed n_m of the vehicle engine 10 and the speed n_ge of the input shaft of the Gearbox is larger than an applicable threshold1.
  (| n_m - n_ge | <threshold1?)
• 3. Possibility to detect the clutch slip:
  As is charged at the start of the adaptation of the vehicle engine 10 by the load of the electric generator 17, the vehicle engine is relieved by opening the coupling 11, 10 and its rotation speed increases n_m short term. Therefore, the condition that the gradient d n_m / dt of the speed of the vehicle engine 10 is greater than an applicable (positive) threshold4 can be used to detect clutch slip.
  (dn_m / dt <threshold2 <0).

An advantageous embodiment of the invention can be seen in FIG. 6. 61 , 62 , 63 and 64 correspond to steps 51 , 52 , 53 and 54 shown in FIG. 5. According to this variant, if conditions 1 to 3 listed above (individually or in combination, step 65 ) are met, the clutch characteristic curve is not initially modified, but the additional torques for the vehicle engine and the electric generator (md_ma_delta and md_gen_delta) are reduced again ( Step 66 ). For this purpose, either the same ramp as for increasing can be used, only the sign of the gradient being exchanged. It is particularly advantageous here, however, to control the controls 14 and 16 of the vehicle engine 10 and the electric generator 17 in such a way that the additional moments are reduced more quickly than they were previously built up.

In this variant, the clutch characteristic curve is only modified in step 68 when it has been detected in step 67 that the following situations (individually or in combination) exist:

• - | n_m - (n_gen / u_gen) | <Threshold1?
• - | n_m - n_ge | <Threshold1?
• - dn_m / dt <- threshold2 <0

After the modification of the clutch characteristic in step 68 , the actuator is set again so that the clutch development can safely transmit the torque of the vehicle engine.

After the final step 57 or 69 , depending on the embodiment, the processes of FIGS . 5 and 6 are started again.

2c) Situations in which the clutch characteristic curve adapts can be

For the adaptation of the clutch characteristic according to the method described above, on the one hand, the torque delivered by the vehicle engine 10 must be known relatively precisely and, on the other hand, short-term low slip of the clutch 11 must be acceptable. In addition, a reserve for increasing the torque must be available both in the vehicle engine and in the internal combustion engine.

• - Situations that should exist before and during the adaptation:
  It is imperative that a gear is engaged in the transmission 12 . Furthermore, the coupling must be closed at the start of an adaptation. Optionally, it can be requested that the desire for drive torque does not change significantly during the adaptation. This means that the position of the accelerator pedal must not change significantly or, in the case of a driving machine such as ACC (from a radar system), its torque requirement must not change significantly. As soon as one of the above conditions is no longer met, the adaptation of the clutch characteristic curve is aborted. As soon as a circuit is initiated, the adaptation must also be aborted.
• - Situations that should exist before the start of the adaptation:
  In addition, it is advantageous to check whether an adjustment of the clutch's gripping point begins
• - the amount | dn_m / dt | of the gradient of the speed of the Vehicle engine less than an applicable threshold is and / or
• - the amount | dn_m / dt | of the gradient of the speed of the electrical generator smaller another appli threshold is and / or
• - the amount | dn_m / dt | the gradient of the speed of the Input shaft of the gearbox smaller than another applicable threshold is and / or
• - The torque md_ma emitted by the vehicle engine at least one factor (about 25% in size) below the maximum at the current speed achievable torque.

If one of these conditions does not apply, use the Application not started.

3. The third embodiment of the invention

The first embodiment or second embodiment of the invention describes the adaptation of the clutch characteristic in the range of lower or medium to high moments in normal driving operation of the vehicle. The third embodiment of the invention, on the other hand, relates to the start-up of an automatic clutch in motor vehicles using an auxiliary unit connected to the transmission input. In particular, this embodiment shows a possibility to take an individual clutch characteristic for each vehicle with a starter generator attached to the transmission during commissioning and when servicing. The precise knowledge of the characteristic curve, which reflects the relationship between the setting of the actuator 15 and the torque that can be transmitted by the clutch 11 , is important for a precise and comfortable clutch control. Several methods are known to adapt this characteristic curve. A characteristic clutch characteristic curve for this type of clutch is always stored or saved in the control unit program and adapted by addition and multiplication with parameters that can be determined by adaptation.

The third embodiment describes how the coupling characteristic curve defined above can be determined with the aid of a controllable electrical generator or starter generator on the input shaft of the transmission. The prerequisite is that the vehicle engine is equipped with an electronic control system which controls the torque or the engine speed. The basic construction on the third embodiment shows Fig. 1c with the elements already described be.

3a) Determination of the coupling characteristic

To determine the clutch characteristic, a sequence of loading is triggered which comes from a diagnostic device connected to a communication line (not shown in FIG. 1c). First, the transmission is brought into the neutral position and the program of the transmission control (not shown in FIG. 1c) is electronically locked there. This locking is only released after the determination of the characteristic curve, so that all further measures are taken in the neutral position of the transmission.

The internal combustion engine 10 must be running at the beginning and is kept running by its idle controller throughout the process. In the three phases described below, which are shown in FIG. 9, the values for the moments to be transmitted are determined via the path of the clutch release bearing. These correspond to the three moment areas. The first area and thus the first phase is characterized in that almost no or only a very low ring torque is transmitted. Essentially, the point (path) at which the clutch begins to transmit torque is sought here. This value is called the gripping point. In the second phase, the values for the path are determined, which correspond to relatively low moments. In the third phase, high moments and paths are identified. The positions that correspond to very high moments are only interpolated with the help of empirical values from the known values.

Phase 1

The gripping point is first determined. For this purpose, the clutch 11 is opened to the maximum. The engine 10 runs at a predetermined speed or at idle, the transmission input shaft is stopped by the generator 17 . The generator 17 is de-energized and the clutch 11 is slowly moved in the "closing" direction. The gripping point is reached when a speed other than zero is detected on the transmission input shaft and or on the generator. The clutch 11 is opened again, the transmission input shaft with the generator 17 is stopped and the process is repeated several times. The final value for the gripping point is then the average of the determined values.

Phase 2

The further values of the clutch characteristic curve are determined by the occurrence of slip over the clutch 11 at a defined torque. The clutch 11 is moved to a travel position (target position) in which a high torque can be transmitted. A defined fixed speed is required from the internal combustion engine 10 . This speed is set with a high quality speed controller. A Lastmo element is set with the generator 17 on the transmission input shaft. The clutch 11 is slowly moved in the "open" direction. When slip occurs, the value that the clutch 11 can transmit in this position has just been reached. Since this value for the path at the release bearing is subject to hysteresis, a second value is determined in which the slip is reduced again at the same moment. The two values are averaged in a suitable manner and stored as a base value of the clutch characteristic. This procedure is fen with different moments, so that a sufficient number of support points in the middle Momentenbe are richly determined. Care is taken to ensure that this determination is made at a constant coupling temperature. This is achieved, among other things, by following a determination with a low one after a determination with a high torque value.

Slip detection

As already mentioned, there are several methods for detecting clutch slip:

• - It can be checked whether the amount of the difference between the speed of the electrical generator and the speed of the vehicle engine, divided by the translation of the electrical generator, is greater than an applicable threshold.
  (| n_m - (n_gen / u_gen) | <Threshold1?)
• - If the vehicle has a device for detecting the speed of the input shaft of the transmission, it can alternatively be checked whether the amount of the difference between the speed of the vehicle engine and the speed of the input shaft of the transmission is greater than an applicable threshold1.
  (| n_m - n_ge | <threshold1?)
• - The condition that the gradient of the speed of the vehicle engine is greater than an applicable (positive) threshold le2 can also be used for the detection of clutch slip, since when the clutch is released the engine is relieved if slip occurs and it accelerates.
  (d n_m / dt <threshold2 <0)

Phase 3

Using the phase 2 method, only those clutch torques can be determined that can also be generated by the generator 17 . The higher torque values are determined in phase three. Here the gradient of the speed is used with known mass inertia to determine the moment. The procedure is as follows:

The internal combustion engine 10 is regulated to an increased speed (approx. 3500 rpm). The clutch 11 is open, the transmission input shaft stopped with the help of the generator 17 . The clutch release bearing is quickly moved to a target position that should correspond to a high moment. A defined load torque can be required from the generator 17 . When the clutch 11 has reached its target position, the gradient of the rotational speed is determined and the moment that was required for this acceleration is determined with the aid of the known mass moment of inertia. This acceleration moment and the load moment of the generator 17 together form the value of the moment which could be transferred from the clutch 11 at the given position of the back bearing. This pair of values forms a further point of support for the coupling characteristic. This measurement is repeated.

With the methods described above, the entire coupling characteristic curve, which is shown as an example in FIG. 9, can take up men. It is irrelevant whether the processing of the measurement data takes place di rectly in the clutch control unit 14 or whether they are processed in the connected diagnostic unit and then subsequently written back into the clutch control unit 14 as a finished characteristic.

Claims (15)

1. A method for determining the gripping point in a drive train of a motor vehicle together with a driving engine ( 10 ) and a transmission ( 12 ) arranged and having an input and output shaft having controllable servo clutch ( 11 ), with a through the output shaft of the servo coupling controllable auxiliary unit ( 17 ), in particular an electric generator, is driven and a speed variable representing the speed of the output shaft (n_ge, n_gen) is detected, characterized in that

• - A predeterminable or predetermined operating state of the drive train is detected or set,
• - The auxiliary unit ( 17 ) and the servo clutch ( 11 ) in response to the detection or setting of the operating state be controlled in a predetermined or predetermined manner, and
• - During this activation, the gripping point is determined at least depending on the speed variable (n_ge, n_gen).

2. The method according to claim 1, characterized in that the predeterminable or predetermined operating state is detected when the transmission ( 12 ) is in its neutral position and the clutch ( 11 ) is closed, in particular it being provided that a predeterminable or predefined operating state of the drive train is then detected if at least one of the conditions continues

• - the vehicle is at a standstill,
• - actuation of the service and / or parking brake,
• - no drive requirement,
• - is recorded.

3. The method according to claim 1, characterized in that the predeterminable or predetermined operating state is detected when the transmission ( 12 ) is in a driving position (no neutral position) and the clutch ( 11 ) is closed, in particular providing that a predefinable or predefined operating state of the drive train is detected if it is furthermore at least detected that there is an essentially constant drive request. 4. The method according to claim 1, characterized in that

• - An output speed of the vehicle engine ( 10 ) representing engine speed size (n_m) and / or
• - An output torque of the vehicle engine ( 10 ) representing engine torque size (md_ma) is detected, and
• - The predeterminable or predetermined operating state then it is captured when
• - The change over time in the engine speed variable (n_m), in particular the amount of the change over time, is smaller than a predetermined or predeterminable first threshold value and / or
• - The temporal change in the speed variable (n_ge, n_gen), in particular the amount of the change in time, is smaller than a predetermined or predeterminable second threshold value and / or
• - The engine torque size (md_ma) is smaller than the currently maximum achievable engine output torque.

5. The method according to claim 1, characterized in that the determination of the gripping point is ended if the before The operating state of the drive that can be specified or specified strangs is no longer detected. 6. The method according to claim 1, characterized in that in response to the detection of the operating state

• - The auxiliary unit ( 17 ) is controlled such that the output shaft of the servo clutch ( 11 ) is loaded in a predetermined or predetermined manner, in particular with a low torque, and
• - The servo clutch ( 11 ) is controlled in the sense of opening and
• - The gripping point is determined during the opening of the clutch depending on the detected speed variable (n_ge, n_gen).

7. The method according to claim 6, characterized in that during the opening of the clutch ( 11 ) the gripping point depending on the speed variable (n_ge, n_gen) and / or depending on the change over time (d n_ge / dt, d n_gen / dt) the speed variable and / or depending on a determined slip variable representing the clutch slip [n_m-n_ge, n_m- (n_gen / u_gen)] and / or depending on a motor speed variable (n_m) representing the output speed of the vehicle engine ( 10 ) and / or depending on a from the output torque of the vehicle engine ( 10 ) representing engine torque size (md_ma) is determined, in particular re is provided that the gripping point is determined when

• - The temporal change (d n_ge / dt, d n_gen / dt) of the speed variable falls below a predetermined or predeterminable third threshold value, and / or
• - The slip size exceeds a predetermined or predeterminable fourth threshold and / or
• - The change over time (d n_m / dt) of the engine speed variable (n_m) exceeds a predetermined or predeterminable fourth threshold value and / or
• - The temporal change in the engine torque size (md_ma) exceeds a predetermined or predeterminable fifth threshold value.

8. The method according to claim 6, characterized in that

• - A first value for the gripping point is determined during the opening of the clutch and
• - Closing of the clutch then takes place and a second value for the gripping point is determined during the closing of the clutch depending on the speed variable (n_ge, n_gen)
• - The gripping point is determined from the first and second values.

9. The method according to claim 1, characterized in that in response to the detection of the operating state, the vehicle engine ( 10 ) is controlled in a predeterminable or predetermined Wei se, it being provided in particular that in response to the detection of the operating state

• - The servo clutch ( 11 ) are controlled such that it transmits the currently existing output torque (md_ma) of the vehicle engine, in particular with a predeterminable safety reserve, transmits,
• - The output torque (md_ma) of the vehicle engine, in particular ramp-shaped, is increased, and / or
• - The auxiliary unit ( 17 ) in the sense of increased torque absorption, in particular depending on the increase in the starting torque (md_ma) of the vehicle engine, is controlled and
• - While increasing the output torque (md_ma) of the vehicle engine depending on the detected speed variable (n_ge, n_gen) the gripping point is determined, it being provided in particular that the clutch slip is detected and the gripping point is determined depending on the detected clutch slip.

10. The method according to claim 1, characterized in that the predeterminable or predetermined operating state is set such that

• - The transmission ( 12 ) is switched to its neutral position,
• - The auxiliary unit ( 17 ) is controlled such that it absorbs a predetermined or predeterminable torque, the clutch ( 11 ) is initially fully open and is then controlled in the sense of closing and
• - The gripping point is determined while the clutch is being closed, depending on the speed variable (n_ge, n_gen).

11. The method according to claim 1, characterized in that the predeterminable or predetermined operating state is set such that

• - The transmission ( 12 ) is switched to its neutral position,
• - A predetermined or predeterminable output speed is set on the vehicle engine,
• - The auxiliary unit ( 17 ) is controlled such that it receives a predetermined or predeterminable torque,
• - The clutch ( 11 ) is initially closed for transmission of a high torque and is then controlled in the sense of an opening and
• - During the opening of the clutch depending on the detected speed (n_ge, n_gen) the gripping point is determined, it being provided in particular that the clutch slip is detected and depending on the detected clutch slip the gripping point is determined.

12. The method according to claim 11, characterized in that

• - a first value for the gripping point is determined during the opening of the clutch depending on the detected speed variable (n_ge, n_gen) and
• - The clutch ( 11 ) is then actuated in the sense of a closing and a second value for the gripping point is determined during the closing of the clutch depending on the detected speed variable (n_ge, n_gen)
• - The gripping point is determined from the first and second values.

13. The method according to claim 1, characterized in that the predeterminable or predetermined operating state is set such that

• - The transmission ( 12 ) is switched to its neutral position,
• - The auxiliary unit ( 17 ) is controlled such that it receives a predetermined or predeterminable torque,
• - A predetermined or predeterminable output speed is set on the vehicle engine,
• - The clutch ( 11 ) is initially completely open and is then actuated in the sense of closing, it being provided in particular that the clutch assumes a predetermined or predeterminable target position, and
• - During the closing of the clutch depending on the speed variable (n_ge, n_gen), in particular depending on the change in speed over time, the gripping point is determined.

14. Device for determining the gripping point in a drive train of a motor vehicle together with a driving engine ( 10 ) and a gear ( 12 ) arranged and having an input and output shaft having a controllable servo clutch ( 11 ), with a through the output shaft of the servo clutch controllable auxiliary unit ( 17 ), in particular an electric generator, is driven and a speed variable representing the speed of the output shaft (n_ge, n_gen) is detected, characterized in that that means ( 14 , 16 ) are provided by means of

• - A predeterminable or predetermined operating state of the drive train is detected or set,
• - The auxiliary unit ( 17 ) and the servo clutch ( 11 ) in response to the detection or setting of the operating state be controlled in a predetermined or predetermined manner, and
• - During this activation, the gripping point is determined at least depending on the speed variable (n_ge, n_gen).