DE102015207312A1 - Method and control device for operating a drive train - Google Patents

Abstract

Method for operating a drive train of a motor vehicle, wherein the drive train has a plurality of drive units (1, 2), a transmission (3) and an output (4), wherein a first drive unit (1) acts on a first transmission shaft (6) of the transmission (3 A second drive unit (2) acts on a second transmission shaft (7) of the transmission (3), wherein the transmission (3) comprises a plurality of shift elements (9), wherein the output (4) provides a drive torque dependent output torque is, and wherein the opening of a switching element (9) of the transmission (3) the openable switching element (9) is provided free of load. For the load release of the switching element (9) to be opened, target torques are calculated for the first drive unit (1) and for the second drive unit (2), to which they start for the load release of the switching element (9) to be opened while maintaining an output torque corresponding to the driver's desired torque are to be guided by the current actual moment. Depending on the current actual moments of the drive units (1, 2) and depending on the calculated target moments of the same is checked whether the openable switching element (9) with a requested target dynamics and / or in a requested target time period load can be made, and if it is determined that this is the case, the target moments of the drive units (1, 2) remain unchanged, whereas if it is determined that this is not the case, the target moments of Drive units (1, 2) are changed under provision of deviating from the driver's desired torque output torque such that for the load exemptions of the switching element (9) requested target dynamics or target period is met or maintained approximately.

Description

The invention relates to a method for operating a drive train. Furthermore, the invention relates to a control device for operating a drive train.

Drive trains of hybrid vehicles comprise a plurality of drive units, namely a first drive unit designed as an internal combustion engine and a second drive unit embodied as an electric machine, a transmission and an output drive. In such a drive train, the first drive unit acts on a first transmission shaft of the transmission, whereas the second drive unit acts on a second, other transmission shaft of the transmission. The transmission of the power plant comprises a plurality of switching elements, which are typically designed as frictional switching elements, such as clutches or brakes. At the output of the drive train a dependent of a driver's desired torque output torque is provided. In defined operating situations of such a drive train, it is necessary to open a previously closed switching element of the transmission. Then, when a frictional switching element is to be opened, this can be done in a simple manner, that the frictional switching element is brought into slippage. This results in friction moments or drag torques, which have a negative effect on consumption. Therefore, frictionally engaged shift elements are increasingly being replaced by positive shift elements, such as claw shift elements, in transmissions of a drive train. However, such positive switching elements must, so that they can be opened, transferred to a no-load condition or be made free of charge. However, this is only possible to an insufficient extent in the case of drive trains known from practice.

On this basis, the invention is based on the object to provide a method for operating a drive train and a control device for carrying out the method, by means of which openable switching elements can be reliably made load-free.

This object is achieved by a method for operating a drive train according to claim 1.

According to the invention, target moments are calculated for the load-free position of the switching element to be opened for the first drive unit and for the second drive unit, to which they are to be guided starting from the current actual torque for the load release of the switching element to be opened while maintaining an output torque corresponding to the driver's desired torque. Depending on the current actual moments of the drive units and depending on the calculated target moments of the same, it is checked whether the switching element to be opened can be made load-free with a requested target dynamic and / or in a requested target time span, and then, if found is that this is the case, the target moments of the drive units remain unchanged, whereas if it is determined that this is not the case, the target moments of the drive units to provide a deviating from the driver's desired torque output torque are changed so that the For the load clearances of the switching element requested target dynamics or target time period is met or maintained approximately.

Hereby, a reliable load release of an openable switching element with the requested target dynamics or within the requested target time period is possible. Only if, while maintaining the driver's desired torque at the output, the target dynamic or target time span required for the load clearing of the shift element can not be met, in order to be able to comply as far as possible with the requested target dynamic or target time span, changed the target moments of the drive units to provide a deviating from the driver's desired torque output torque. This allows a particularly advantageous operation of a drive train with a gearbox and drive units which are driven into different transmission shafts of the transmission, namely a particularly advantageous opening of an opening switching element of the transmission, which is in particular a form-locking switching element such as a jaw switching element.

According to an advantageous embodiment of the invention are dependent on the current actual moments of the drive units, depending on the calculated target moments of the drive units and dependent on the Lastfreistellen the switching element required target dynamics or target time for the first drive unit and the second drive unit calculated either in a first alternative target torque curves or in a second alternative torque gradient ranges. For both drive units is checked while guiding them in the direction of the target moments, whether according to the first alternative, the respective actual torque curve of the respective desired torque curve or according to the second alternative, the respective actual torque gradient of the respective torque gradient range such impermissibly deviates in that the target time span or target dynamic demanded for the load-freeing of the switching element can not be met, and if it is determined that this is not the case, the target torques of the Drive units remain unchanged, whereas then, if it is determined that this is the case, the target moments of the drive units to provide a deviating from the driver's desired torque output torque are changed such that the required for the load exemptions of the switching element target time or target dynamics met or is approximately maintained. This allows a particularly advantageous operation of a drive train with a gearbox and drive units which are driven into different transmission shafts of the transmission, namely a particularly advantageous opening of an opening switching element of the transmission, which is in particular a form-locking switching element such as a jaw switching element.

Preferably, if it is determined that, according to the first alternative, the respective actual torque curve deviates inadmissibly from the respective desired torque curve or according to the second alternative, the respective actual torque gradient from the respective torque gradient range, the target moments of the drive assemblies are immediately adjacent or changed after an applicable period of time. The immediately subsequent change of the target moments is preferred for providing the shortest possible period of time for opening the switching element.

Preferably, if it is determined that after the first alternative, the respective actual torque curve of the respective desired torque curve or according to the second alternative, the respective actual moment gradient of the respective torque gradient range inadmissible deviates, the target torque of that drive unit, for which the undue deviation is detected, kept constant at the level of the current actual torque or further increased to the extent possible, depending on the target torque of the other drive unit is adjusted so that the time required for the load clearances of the switching element target time or target Dynamic is maintained or maintained approximately. This allows a particularly advantageous operation of a drive train with a gearbox and drive units which are driven into different transmission shafts of the transmission, namely a particularly advantageous opening of an opening switching element of the transmission, which is in particular a form-locking switching element such as a jaw switching element.

Preferably, after changing the target moments of the drive units, the same are guided in the direction of the changed target torques, wherein it is checked for both drive units while guiding them in the direction of the changed target moments, whether that is the switching element to be opened with a requested destination And, if it is determined that this is the case, the changed target torques of the drive units remain unchanged, whereas if it is determined that this is not the case , the target moments of the drive units to be changed again under provision of an even more deviating from the driver's desired torque output torque. This allows a particularly advantageous operation of a drive train with a gearbox and drive units which are driven into different transmission shafts of the transmission, namely a particularly advantageous opening of an opening switching element of the transmission, which is in particular a form-locking switching element such as a jaw switching element.

The control device according to the invention is defined in claim 9.

Preferred developments emerge from the subclaims and the following description. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 a schematic of a powertrain;

2 a timing diagram to illustrate an ideal behavior when load release of an openable switching element;

3 a timing diagram to illustrate a setting without the inventive method real behavior when load release of a switching element to be opened; and

4 a timing diagram to illustrate an adjusting with the inventive method real behavior when load release of a switching element to be opened.

The invention relates to a method and a control device for operating a drive train.

1 shows a schematic of a powertrain of a motor vehicle, in which the inventive method is preferably used. So includes the powertrain of 1 two drive units 1 . 2 , a gearbox 3 and a downforce 4 , The gear 3 includes a planetary stage 5 , The two drive units 1 . 2 act on different transmission shafts of the transmission 3 a, namely the first drive unit 1 on a first gear shaft 6 and the second drive unit 2 on a second gear shaft 7 , In the embodiment shown, it is the first power unit 1 around an internal combustion engine, on the first transmission shaft 6 acts, in which it is the transmission input shaft of the transmission in the illustrated embodiment 3 is. For the second drive unit 2 In the exemplary embodiment shown, this is an electrical machine that is based on the second transmission shaft 7 of the transmission 3 acting, wherein the second transmission shaft 7 in the illustrated embodiment of the planetary stage 5 is provided, namely in the illustrated embodiment of a ring gear of the same.

A transmission output shaft 8th of the transmission 3 acts on an output 4 of the powertrain, ultimately to the output 4 to provide a driver's request moment. In the illustrated embodiment of the 1 this is the first drive unit 1 to a gearbox external drive unit and the drive unit 2 to an internal gear drive unit.

According to 1 includes the gearbox 3 several switching elements 9 , where in 1 only two switching elements 9 are shown by way of example. So is a first switching element 9 according to 1 between the transmission input shaft 6 and the planetary stage 5 and a second switching element 9 between the planetary stage 5 and the transmission output shaft 8th connected. For both switching elements 9 In the exemplary embodiment shown, these are interlocking switching elements, for example claw switching elements.

Between the first drive unit 1 and the transmission input shaft 6 of the transmission 3 is in the embodiment of 1 a separating clutch 10 connected, which is preferably designed as a frictional clutch, via the separating clutch, the first drive unit 1 from the transmission input shaft 6 can be disconnected. The separating clutch 10 is an optional assembly and can be omitted.

1 further shows a controller 20 in the embodiment shown, the operation of the first drive unit 1 and the transmission 3 including the second drive unit 2 controls and / or regulates. In this control device 20 it is preferably a hybrid control device of a motor vehicle.

The control device 20 exchanged according to the dashed arrows with both the first drive unit 1 as well as with the gearbox 3 Data from to the operation of the first drive unit 1 , the transmission 3 and the second drive unit 2 to control and / or to regulate.

As already stated, the transmission includes 3 switching elements 9 , where in 1 exemplarily two form-fitting, formed as claws switching elements 9 are shown. In defined operating situations of the drive train, a previously closed switching element must 9 be opened, so for example when performing a gear change. In particular, when a switching element to be opened 9 is designed as a positive switching element, the same must be made free to open.

The present invention relates to a method by means of which a switching element 9 a gearbox 3 a powertrain of a motor vehicle, the two in different transmission shafts 6 . 7 driving drive units 1 and 2 includes, can be made load-free in a particularly advantageous manner. Furthermore, the invention relates to a control device for carrying out the method.

If the control side is a request to open a closed switching element 9 of the transmission 3 before, so become the load release of the switching element to be opened 9 from the controller 20 for the two drive units 1 and 2 Calculates target moments to which they are to lead to the load release of the openable switching element while maintaining a torque corresponding to a driver output torque output starting from the current actual torque. This can be checked first, whether the drive units 1 . 2 In principle, these calculated target moments can ever be provided, whether as the calculated target moments, torque limits of the drive units 1 . 2 hurt or not hurt. Would the calculated target moments torque limits of the drive units 1 . 2 hurt, this would mean that the drive units 1 . 2 can not be performed on these target moments, so then the target moments would have to be changed to the opening switching element 9 to provide load-free, in particular while providing a deviating from the driver's desired torque output torque. On the other hand, the calculated target moments do not violate torque limits of the drive units 1 . 2 , so the drive units can always be performed on the target moments.

2 aims at the temporal curves 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 and 19 an ideal behavior when load release of an openable switching element 9 , Before the time t1, the transmission becomes an output torque 11 provided, which is a driver's desired moment 12 equivalent. Before the time t1 put the drive units 1 and 2 to provide this output torque 11 each actual moments 17 . 18 ready.

At time t1 lies in 2 control side, a request for load release of a switching element 9 in front. There will then be goal moments 13 . 14 for the two drive units 1 . 2 calculated, to which the same for load release of the switching element to be opened 9 while maintaining the driver's desired torque 12 corresponding output torque 11 starting from the current actual moments 17 . 18 are to lead. In the embodiment, the 2 depending on the prevailing at the time t1, current actual moments 17 . 18 the drive units 1 and 2 , depending on the calculated target moments 13 . 14 the drive units 1 . 2 and depending on a load release of the switching element 9 required target time interval .DELTA.t for both drive units 1 . 2 Target torque curves 15 . 16 along which the actual moments are calculated 17 . 18 towards the goal moments 13 . 14 be guided to within the required target time period .DELTA.t, ie at the latest until the time t2, according to the curve 19 the switching element to be opened 9 load-free, namely such that at the latest at time t2 according to the curve 19 the switching element to be opened 9 no longer transmits a moment. According to the in 2 shown ideal behavior, the drive units 1 . 2 because of their dynamic behavior, the calculated setpoint torque curves 15 . 16 follow, so in 2 between the times t1 and t2 the actual torque curves 17 . 18 the drive units 1 . 2 with the setpoint torque curves 15 . 16 coincide with it.

The drive units 1 . 2 However, not in all operating situations, ie not in all speed ranges and / or torque ranges thereof, have a sufficiently good dynamics to the ideal behavior of 2 when load release of an openable switching element 9 to ensure.

So shows 3 temporal curves, which then adjust, if, for example, the dynamics of the first drive unit 1 is not sufficient to the ideal behavior of 2 provide.

So is in 3 before the time t1, the switching element to be opened 9 closed, the two drive units 1 and 2 each represent actual moments 17 . 19 ready, so that the output torque 11 the driver's desired moment 12 equivalent. At the time t1, a circuit request is present on the control side, so that in turn, at the time t1, the load is cleared of the switching element to be opened 9 for the two drive units 1 . 2 the goal moments 13 . 14 to be calculated, to which the same for load release of the switching element to be opened 9 while maintaining the driver's desired torque 12 corresponding output torque 11 based on their current actual moments 17 . 19 are to lead.

Furthermore, in 3 then depending on the current actual moments 17 . 19 at time t1, depending on the calculated target moments 14 . 15 and depending on the load release of the switching element 9 required target time interval .DELTA.t for the drive units 1 . 2 the desired torque curves 15 . 16 along which the actual moments are calculated 17 . 19 to be performed at the latest by the time t2, ie within the required target time period .DELTA.t, the openable switching element 9 to be free of load.

Here, the real behavior of the 3 be taken that, although the second drive unit has sufficient dynamics to the actual torque curve 18 the same along the desired torque curve 16 However, the first drive unit does not have sufficient dynamics, so starting at time t1, the actual moment 17 ' of the first drive unit to the desired torque curve 15 of the same can not follow.

This then turns into the 3 exemplarily shown output torque 11 ' a, which is the driver's request moment 12 differs.

Due to the insufficient dynamics of the first drive unit 1 can in 3 only at the time t3, the switching element to be opened 9 be made load-free, the training moment course 19 ' of the switching element to be opened 9 Therefore, in comparison to the ideal behavior of 2 amount to a smaller gradient, so that only at time t3 according to the moment course 19 ' the switching element to be opened 9 is free of load.

The time required for the load exemption is therefore extended by the insufficient drive of the first drive unit 1 by the time interval Δt 'between the times t2 and t3. This is disadvantageous because the extended period of time for load-relieving the switching element to be opened has effects on further processes in the transmission, which are thereby delayed.

To now a switching element 9 of the transmission 3 To be able to provide optimum load-free is inventively proposed, depending on the current actual moments of the drive units 1 and 2 which are present at the time t1 of the control-side request of the load release, and depending on the calculated target moments 13 . 14 the drive units 1 . 2 on which the drive units 1 . 2 while maintaining the driver's desired torque corresponding output torque for load release of the switching element 9 should be conducted to check whether the switching element to be opened with a requested target dynamics or in a requested target period can actually be made load-free. Then, if it is determined that this is the case, that is, the requested target Dynamics and / or the requested target time period for load release of the switching element 9 can be maintained, the calculated target moments remain 13 . 14 unchanged. Then, on the other hand, if it is determined that this is not the case, that is to say that the requested target dynamic and / or the requested target time span are used to load-free the switching element 9 can not be met, the target moments of the drive units 1 . 2 under the provision of a deviating from the driver's desired torque output torque, in such a way that the load release of the switching element 9 requested target dynamic or target time period is adhered to or approximately adhered to.

To show 4 Curves that can be adjusted using the method according to the invention. In 4 is before the time t1, the switching element to be opened 9 closed again, before time t1 put both drive units actual moments 17 . 18 ready, so that the output torque 11 the driver's desired moment 12 equivalent. At time t1, in turn, there is a control-side request for the load-free position of the switching element 9 in front. At time t1 then turn for both drive units 1 and 2 the goal moments 13 . 14 calculated on which the drive units 1 . 2 for load release of the openable switching element 9 while maintaining a driver's desired torque 12 corresponding drive torque 11 starting from current actual moments at time t1 17 . 18 are to lead.

In the embodiment of 4 as already related to 2 and 3 explained, depending on the current actual moments 17 . 18 the drive units 1 . 2 at time t1, depending on the calculated target moments 13 . 14 the drive units 1 and 2 and dependent on the load exemptions of the switching element required target time interval .DELTA.t the desired torque curves 15 . 16 for the drive units 1 . 2 along which the actual moments are calculated 17 . 18 are to lead to the switching element 9 be able to load-free in the requested target time span.

From the time t1 both drive units 1 . 2 that is, the actual moments 17 . 18 the same, along the desired torque curves 15 . 16 in the direction of the respective target moment 13 . 14 guided, in which case it is monitored whether the respective actual torque curve 17 . 18 from the respective nominal torque curve 15 . 16 deviates so inadmissible that the for the load release of the switching element 9 predetermined or requested target time or target dynamics can not be met. It will be in 4 Check if while driving the drive units 1 . 2 towards the goal moments 13 . 14 the actually actual moments 17 respectively. 17 '' . 18 from the nominal torque curves 15 . 16 to deviate for more than a defined period of time.

In the example of 4 At time t4, it is determined that the actual actual moment 17 '' of the first drive unit from the desired torque curve 15 the same by more than a defined period of time deviates impermissibly, in which case at time t4, the previously calculated at time t1 target moments 13 . 14 be changed, namely in the target moments 13 '' and 14 '' , these new goal moments 13 '' and 14 '' be calculated such that the switching element 9 in compliance with or approximate adherence to the load release of the switching element 9 predetermined target time period or predetermined target dynamics can be made load-free, namely providing a driver's desired torque 12 deviating output torque 11 '' ,

In the embodiment of 4 are then, if it is determined at time t4 that the switching element to be opened 9 can not be made load-free with the required target dynamics or in the required target time period, the target moments 13 . 14 the drive units 1 . 2 directly into the changed target moments 13 '' . 14 '' changed. For this purpose, in the embodiment of 4 the target moment 15 '' that drive unit for which the impermissible deviation has been determined at the level of the current actual torque 17 '' kept constant, depending on the target moment 14 '' the other drive unit is adapted so that the load release of the switching element 9 can be performed in the predetermined target time or in the specified target dynamics. This is in 4 according to the curve 19 '' at the time t5 the case, ie before the time t2 and thus within the target time period .DELTA.t. At the same time, the moment gradients change 15 '' . 16 '' along which the actual moments 17 '' . 18 '' towards the changed goal moments 13 '' . 14 '' be guided.

As stated above, in the exemplary embodiment shown, according to the control-side requirement of the load release of a closed switching element 9 depending on current actual moments of the drive units, depending on the calculated target moments of the drive units 1 . 2 and depending on the load release of the switching element 9 required target dynamics or target time span for the drive units 1 and 2 Calculated desired torque curves along which the target moments are guided torque-controlled in the direction of the target moments.

In contrast, it is also possible that depends on the current actual moments in the control-side requirement of Load release of the switching element 9 as well as dependent on the calculated target moments of the drive units 1 . 2 and, depending on the required target dynamics or target time, no exact desired torque profiles are calculated, but only moment gradient ranges for the guidance of the actual moments in the direction of the target moments. In this case, it is then checked during the guidance of the actual moments in the direction of the target moments, whether the actually forming actual moment gradients of the drive units 1 . 2 deviate impermissibly from the respective moment gradient range, ie whether they lie within the respective moment gradient range or outside thereof.

If the actual torque gradients forming are within the moment gradient ranges, this is an indication that the switching element 9 can be made free of load within the required target period or the required target dynamics, so then the target moments of the drive units remain unchanged. If, on the other hand, an actual torque gradient of a drive unit forming outside of the respective torque gradient range is formed, this is an indication that the load release of the shift element 9 can not be performed within the required target time or target dynamics, in turn, then the target moments of the drive units 1 . 2 under the provision of a deviating from the driver's desired torque torque can be changed such that for the load release of the switching element 9 specified target time span or target dynamic is maintained or approximately adhered to.

Another difference to the embodiment of 4 may be that, when it is determined that the switching element to be opened 9 can not be made load-free with the required target dynamics or in the required target time period, the target moments of the drive units 1 . 2 can not be changed immediately afterwards, but rather only after expiry of an applicable period of time.

This is for example in turbocharged internal combustion engines advantage to check within the applicable period of time, if the turbo-charged engine is possibly in a turbo lag, after leaving the required target dynamics can be ensured again, while maintaining the driver's desired torque on output.

Another alternative to the embodiment of 4 may be that, when it is determined that the switching element to be opened 9 can not be made load-free with a requested target dynamics or not in a requested target time period, the target moment of that drive unit for which the impermissible deviation is detected is not kept constant at the level of the current actual torque, but rather this target moment is further increased to the extent possible. Depending on this, then the target torque of the other drive unit is adjusted to comply with the predetermined target time or required target dynamics for load release of the switching element or approximately comply.

After changing the target moments of the drive units 1 and 2 the same, namely their actual moments, are guided in the direction of the changed target moments. In this case, it is further monitored whether the switching element to be opened can be made load-free with the requested target dynamics and / or the requested target time span. If it is determined that this is not possible despite the changed target moments, then the target moments are adjusted again, with an even greater deviation of the output torque from the driver's desired torque.

The invention further relates to a control device 20 to carry out the process. The control device 20 includes means for performing the method, which means are hardware means and software means.

The hardware-side means are interfaces for exchanging data with the modules involved in carrying out the method according to the invention.

Furthermore, the hardware means are a processor for data processing and a memory for data storage.

The software resources are program modules for carrying out the method according to the invention.

In the exemplary embodiment shown, the control device is 20 to a hybrid control device, both the control of the internal combustion engine 1 as well as the transmission 3 including the electric machine 2 serves. In contrast, it may be in the controller 20 also act to a transmission control device, which then interfaces with the transmission 3 and the electric machine 2 directly exchanges data, and with a motor control device, the control and / or regulation of the operation of the internal combustion engine 1 serves to indirectly influence the internal combustion engine 1 Exchanges data.

LIST OF REFERENCE NUMBERS

1

 first drive unit

2

 second drive unit

3

 transmission

4

 output

5

 planetary stage

6

 first transmission shaft / transmission input shaft

7

 second transmission shaft

8th

 Transmission output shaft

9

 switching element

10

separating clutch

11, 11 ', 11' '

Output torque curve

12

Driver input torque

13, 13 ''

Target moment first prime mover

14, 14 ''

Target torque second drive unit

15, 15 ''

Nominal torque curve of the first drive unit

16, 16 ''

Nominal torque curve second drive unit

17, 17 ', 17' '

Actual torque curve of the first drive unit

18, 18 ''

Actual torque curve second drive unit

19, 19 ', 19' '

Moment switching element to be opened

20

control device

Claims (9)

Method for operating a drive train of a motor vehicle, wherein the drive train comprises a plurality of drive units ( 1 . 2 ), a transmission ( 3 ) and an output ( 4 ), wherein a first drive unit ( 1 ) to a first transmission shaft ( 6 ) of the transmission ( 3 ), wherein a second drive unit ( 2 ) to a second transmission shaft ( 7 ) of the transmission ( 3 ), wherein the transmission ( 3 ) a plurality of switching elements ( 9 ), wherein at the output ( 4 ) a driver torque dependent output torque is provided, and wherein for opening a switching element ( 9 ) of the transmission ( 3 ) the switching element to be opened ( 9 ) is provided free of load, wherein the load release of the openable switching element ( 9 ) for the first drive unit ( 1 ) and for the second drive unit ( 2 ) Target moments are calculated, to which the same for load release of the openable switching element ( 9 ) are to be performed starting from the current actual torque while maintaining an output torque corresponding to the driver's desired torque; depending on the current actual moments of the drive units ( 1 . 2 ) and depending on the calculated target moments of the same is checked whether the openable switching element ( 9 ) can be made load-free with a requested target dynamic and / or in a requested target time interval, wherein, if it is determined that this is the case, the target torques of the drive units ( 1 . 2 ) remain unchanged, whereas if it is determined that this is not the case, the target moments of the drive units ( 1 . 2 ) are changed under provision of a deviating from the driver's desired torque output torque such that for the load release of the switching element ( 9 ) requested target dynamics or target time period is adhered to or approximately adhered to. A method according to claim 1, characterized in that for this purpose depends on the current actual moments of the drive units ( 1 . 2 ), depending on the calculated target moments of the drive units ( 1 . 2 ) and depending on the load release of the switching element ( 9 ) required target dynamics or target time period for the first drive unit ( 1 ) and the second drive unit ( 2 ) are calculated either in a first alternative desired torque profiles or in a second alternative torque gradient ranges; for both drive units ( 1 . 2 ) is checked while guiding them in the direction of the target moments, whether according to the first alternative, the respective actual torque curve of the respective desired torque curve or after the second alternative, the respective actual moment gradient of the respective torque gradient range such impermissibly deviates that for the load release of the switching element ( 9 ) can not be met, and if it is determined that this is not the case, the target moments of the drive units ( 1 . 2 ) remain unchanged, whereas if it is determined that this is the case, the target moments of the drive units ( 1 . 2 ) are changed under provision of a deviating from the driver's desired torque output torque such that for the load release of the switching element ( 9 ) requested target dynamics or target time period is adhered to or approximately adhered to. A method according to claim 2, characterized in that it is checked whether after the first alternative, the actual torque curve of the respective drive unit ( 1 . 2 ) of the desired torque curve of the respective drive unit ( 1 . 2 ) by more than a defined period of time or whether according to the second alternative, the actual torque gradient of the respective drive unit ( 1 . 2 ) from the moment gradient range of the respective drive unit ( 1 . 2 ) deviates impermissibly for more than a defined period of time. Method according to one of claims 1 to 3, characterized in that, when during the guiding of the drive units ( 1 . 2 ) is detected in the direction of the target moments that the switching element to be opened ( 9 ) not with the requested target dynamic range or can not be made load-free in the requested target time span, the target torques of the drive units ( 1 . 2 ) are changed immediately afterwards. Method according to one of claims 1 to 3, characterized in that, when it is determined that the switching element to be opened ( 9 ) can not be made load-free with the requested target dynamics or not in the requested target time period, the target torques of the drive units ( 1 . 2 ) are changed after an applicable period of time. Method according to one of claims 1 to 5, characterized in that, when during the guiding of the drive units ( 1 . 2 ) is detected in the direction of the target moments that the switching element to be opened ( 9 ) can not be made load-free with the requested target dynamics or not in the requested target time period, the target torque of that drive unit ( 1 . 2 ), for which the impermissible deviation is determined, is kept constant at the level of the current actual torque, and in dependence thereon the target torque of the other drive unit ( 2 . 1 ) is adjusted so that the requested for the load exemptions of the switching element target dynamic or target period is met or maintained approximately. Method according to one of claims 1 to 5, characterized in that, when during the guiding of the drive units ( 1 . 2 ) is detected in the direction of the target moments that the switching element to be opened ( 9 ) can not be made load-free with the requested target dynamics or not in a requested target time period, the target torque of that drive unit ( 1 . 2 ), for which the impermissible deviation is detected, is further increased to the extent possible, and that depending on the target torque of the other drive unit is adjusted so that the requested for the load exemptions of the switching element target dynamic or target time period met or maintained becomes. Method according to one of claims 1 to 7, characterized in that after changing the target moments of the drive units ( 1 . 2 ) are guided in the direction of the changed target moments, wherein for both drive units ( 1 . 2 ) is checked in the direction of the same in the direction of the changed target moments, whether the openable switching element ( 9 ) can be made load-free with the requested target dynamics and / or in the requested target time period, and if this is the case, the changed target torques of the drive units ( 1 . 2 ) remain unchanged, whereas if it is determined that this is not the case, the target moments of the drive units ( 1 . 2 ) are changed again under provision of an even more deviating from the driver's desired torque output torque.  Control device for operating a drive train, characterized by means for carrying out the method according to one of claims 1 to 8.

Images