DE102008040457A1 - Method for controlling a drive train - Google Patents

Abstract

A method is proposed for activating a drive train of a vehicle with a drive motor (1) and a main transmission and a transfer case (5), wherein a shift request for the transfer case (5) is processed by a control unit. According to the invention, the speed synchronization required for the execution of the shift request is performed with the control unit, wherein the shift request is triggered manually by the driver and / or in predetermined driving conditions of the vehicle automatically by the control unit.

Description

The The present invention relates to a method for driving a Drivetrain according to the preamble of Claim 1 further defined type.

switchable Transfer cases are usually in the commercial vehicle sector For example, used in off-road vehicles. For cost reasons, the transfer cases are not synchronized. To protect the gears from damage, Switching is only possible when the vehicle is at a standstill and in powershift transmissions allowed in neutral. As a result, a driver has to face a shift request for the transfer case first the vehicle bring to a halt before the switching request is carried out can be. From the vehicle technology, it is also known that a Shift request even at very slow speed of the vehicle is allowed. Another disadvantage arises in non-synchronized Transfer cases when a shift request in a tooth to tooth position of the gearbox, as in this state several manually triggered Switching requirements are necessary until the transmission finally can be switched through.

For example, from the document DE 103 25 354 A1 a method for operating a drive train of a motor vehicle is known, with the presence of a switching request for the transfer case before the start of the circuit, a torque on the switching elements involved in the circuit is automatically reduced by a control device. After the reduction of the torque, the circuit by means of suitable control of actuators power-operated without the intervention of the driver is performed.

outgoing of the known method, the invention is based on the object, to propose a method of the kind described in the beginning, with the improved control of the transfer case independent of the type of shift request for the transfer case is possible.

This Task is for an automated transmission according to the invention the features of claim 1 solved. Further advantageous embodiments result in particular from the dependent claims and the Drawings.

Therefore is a method for driving a drive train of a vehicle with a drive motor and a main gear and a transfer case proposed, wherein a shift request for the transfer case over a control unit is processed. According to the invention with the control unit or the like for execution the shift request required speed synchronization performed be, with the shift request manually by the driver and / or in predetermined driving conditions of the vehicle automatically is triggered by the control unit. To this Way is an automatic switchability for a transfer case realized, whereby by the inventive method it is ensured that the transfer case is only in permissible Switched driving situations and performed the speed synchronization becomes.

When Control device can be any suitable electronic device used, for example, an electric or pneumatic Control via a corresponding actuator of the transfer case allows. For example, the controller as input signal, the transmission electronics or a separate Use transfer case electronics. The transmission electronics can thereby take over the control of the switching valves on the transfer case and thus ensure that only in permissible driving situations the Verteilerge gear is switched or the required speed synchronization he follows.

in the Frame of a first possible embodiment The invention can be provided that the inventive Method in an automated manual transmission as the main transmission is used.

For example can the inventive switching logic for the circuit of the transfer case of a terrain translation to a street translation during the Drive to be used. It is initially provided that the engine load or the engine torque is reduced and the drive train separated by opening the clutch becomes. After that, the transfer case can be switched to neutral then at least a partial closure the separating clutch and adjusting the speeds in the transfer case for example, by an engine and / or transmission brake control to the same speed on the shift dog in the transfer case provided. Optionally, a speed reserve due a possible after-effect of the engine brake and to avoid a tooth on tooth position are taken into account. The Speed ratio in the transfer case, for example, over an output sensor or the like on the transmission and over an output sensor can be determined at the transfer case. There are Other speed detections can be used.

When a speed equality at the shift claw or, if the speeds within a predetermined tolerance windows, the transfer case can be switched in the direction of faster translation, ie, for example, in the road ratio. Preferably z. B. parallel to the separating clutch can be opened again.

Should when switching through the transfer case a tooth to tooth position may occur, for example, provided that the Trennkupp development again at least partially closed and by the applied Störmoment the tooth lifted to tooth position again becomes.

Preventive can be provided as part of a next training be that the disconnect at the same time when switching the shift claw of the transfer case is closed or too in the above-described partial closing of the separating clutch is kept closed. Other approaches are conceivable.

Subsequently the main gear can be switched to a suitable gear, As a rule, the current gear is too big a translation having. The right gear can be torque-controlled as required or speed-oriented. The speed should be close to maximum torque or maximum power. Finally can the load build up on the drive motor and z. B. parallel To do this, close the disconnect clutch.

With The method according to the invention can also be a Switching logic for a circuit of the transfer case of a road translation to a terrain translation while driving the vehicle become. For this type of switching requirements, first an examination for the presence of a permissible driving condition or a permissible range. To can be checked, even after the circuit of the transfer case in the terrain or terrain translation a sufficiently large main gear is available. The vehicle speed must not be arbitrarily large but must be at least smaller than a predetermined, definable Be vehicle speed. In addition, it must be ensured that the Vehicle can be accelerated during the circuit. From the maximum permissible speed So there must be an additional speed value for Security deducted.

To Check is the engine load or reduces the engine torque and the drive train by opening the separating clutch disconnected. Subsequently, the main gearbox be switched to a suitable gear, as a rule, the currently switched gear is too small to by an engine speed synchronization restore a speed equality after the transfer case shift to be able to. The appropriate gear can be selected be that before the transfer case shift a lower engine speed, z. B. 1000 U / min or the like and for the Speed synchronization the engine speed window up to the Abregeldrehzahl can be exploited. There are also other requirements considered.

Then switching the transfer case to neutral, then after at least a partial closure of the separating clutch and a Adjusting the speeds in the transfer case, z. B. by an active Provide engine management. The target speed of the drive motor is through the defined ratios and the speed sensors known. At a speed equal to the shift claw of the transfer case or, if the speeds within a z. B. predetermined Tolerance window, the transfer case is in the direction of slower translation connected. This means that z. B. a terrain translation is switched. Preferably, in parallel to the separating clutch again be opened.

Should when switching through the transfer case a tooth to tooth position occur, the separating clutch can be closed again at least partially become and by the applied disturbing moment the tooth on Tooth position be repealed. Preferably, preventative the clutch also at the same time for switching through the shift claw the transfer case are closed or starting from the process step, in which at equal speed, the transfer case is switched, the separating clutch at least partially closed being held. Finally, the load is built up or the torque build-up on the drive motor and, for example, parallel the clutch will be closed again.

The above-described procedures for upshifting or downshifting of a transfer case can also be applied starting from a transmission neutral position. For this purpose, z. B. waived the load reduction in the above-described procedures and then inserted in the switching request of the transfer case a gear in the main transmission and then the transfer case circuit are performed. In a shift request from the terrain ratio to the road ratio, a gear at high speed, z. B. be inserted at 1800 U / min. In a shift request from a road ratio to a terrain ratio of the gear at a low speed, z. B. be inserted at 1000 U / min. The rest of the shift sequence of Verteilergetrie bes done, as already described above. After successful transfer of the transfer case, it is possible to switch back to neutral.

With the proposed method according to the invention can according to another embodiment of the invention Also be provided that the switching request at a standstill engaged gear in the main transmission is done. For switching support at standstill of the vehicle and to cancel a possible Tooth to tooth position, the above procedure can also be applied at standstill of the vehicle. When a switching request is present, the transfer case can be switched directly. To support the disconnect clutch can be parallel immediately or indented to tooth position even after a recognized tooth become. To prevent unwanted acceleration of the vehicle, For example, the disconnect clutch can only be up to a specified one Way or until reaching a certain gear speed or engaged until successful through the transfer case become. It is also possible that the process described also be carried out starting from a main transmission neutral position can. For transfer case switching, for example, a Gear engaged as soon as the transfer case changeover should be done or only after recognized tooth on tooth position. Preferably, a relatively large gear can be inserted, to the effect on the vehicle as possible to keep low. Then you can go back to Neutral be switched.

in the Frame of a second possible embodiment The invention can be provided that the inventive Method as switching logic for the switching request of a Transfer case in a designed as a power shift main gear is used.

According to one possible embodiment, the switching logic for a circuit of the transfer case of a terrain translation to a street translation during the Ride as follows.

First can reduce the engine load or the engine torque and the drive train by neutral switching of the powershift transmission be separated. Thereafter, the transfer case to neutral be switched. It follows the insertion of a gear in the powershift transmission, from the previous overall translation to one high engine speed, for example 1800 rpm leads. Then the adjustment of the speeds in the transfer case takes place an engine brake control and / or primary retarder control to the same speed on the shift dog in the transfer case. If necessary, a speed reserve can also be taken into account due to possible after-effects of the engine brake and to avoid a tooth on tooth position. The speed ratio in the transfer case can via a driven sensor on Powershift transmission and an output sensor on the transfer case be determined.

at a speed equal to the shift claw of the transfer case or, if the speeds within a given Tolerance window, the transfer case in the direction a faster translation, ie z. B. be switched to a street translation. Preferably parallel to this, the powershift transmission can be switched back to neutral become.

Should when switching through the transfer case a tooth to tooth position occur again, a gear engaged in the powershift transmission become. Ideally, a gear can be engaged, depending on the situation an immediate onward journey after successful switching allows z. B. near the maximum engine torque. By the applied disturbance torque the tooth can be picked up again on tooth position. Preventive can z. B. the situation depending correctly selected Gang also inserted simultaneously for switching through the shift claw be or starting from the process step in which a Gear has been inserted in the powershift transmission, inserted stay.

Subsequently a suitable gear can be switched at the main gear, if not already done in previous procedural steps. The selected gear can be torque-controlled as required. or speed-oriented. The speed should be close to maximum torque or maximum power. Finally, the load is built up on the drive motor.

According to one Another embodiment of the invention is a switching logic for a circuit of the transfer case of a road translation to a terrain translation while driving the Vehicle proposed.

First, a check is made for a permissible range. It is checked whether a sufficiently large main gear is available even after the circuit of the transfer case in the terrain ratio. The vehicle speed may not be arbitrarily large, but must be at least smaller than a predetermined definable vehicle speed. Care should be taken that the vehicle can accelerate during the shift. From the mathematically maximum permissible speed thus still a predetermined speed value must be deducted for security. After that, the Re Ducation of the engine load or the engine torque and the separation of the drive train by neutral switching of the power shift done. Then, a gear can be engaged in the power shift transmission, starting from the previous overall ratio to a lower engine speed, z. B. 1000 revs / min and can exploit the engine speed window up to the Abregeldrehzahl for speed synchronization in the transfer case. Subsequently, an adjustment of the speeds in the transfer case by the active engine management. The target speed of the drive motor is known through the defined ratios and the speed sensors. With equal speed on the shift claw of the transfer case or, if the speeds are within a tolerance window, the transfer case in the direction of a slower ratio, ie z. B. in the terrain translation, be switched. Preferably, for example, parallel to the power shift transmission can be switched back to neutral.

Should when switching through a tooth occur on tooth position, can again a gear in the powershift transmission are inserted. Ideally should a gear are inserted, depending on the situation immediate onward journey after successful switching, z. B. near the maximum engine torque. By the applied disturbance torque can the tooth is lifted to tooth position again. Preventive can z. B. the situation dependent right gear also at the same time for switching through the shift claw are inserted or starting from the step in which already in the powershift transmission a gear has been engaged, remain engaged.

Subsequently the main gear can be switched to a suitable gear, if not already done in a previous process step is. The right gear can be torque or torque depending on the requirement be selected speed-oriented. Preferably, the Speed close to the maximum torque or maximum power. Finally, the load is built up on the drive motor.

The procedures described above for upshift or downshift a transfer case in a trained as a power shift transmission Main transmissions can also be based on a transmission neutral position be applied. For this purpose, the load reduction can be omitted and subsequently at the transfer request of the transfer case a gear in the main gearbox or in the powershift transmission and then the transfer case circuit be performed. With a switching request from one Terrain translation to a street translation the gear at high speed, z. B. 1800 U / min are inserted. When a shift request for the transfer case of a road translation to a terrain translation can the gear at a lower speed, z. B. 1000 U / min inserted become. The remainder of the procedure for executing the shift request for the transfer case as already described above. After successful switching, you can return to neutral be switched.

A Switching request at standstill of the vehicle can with a circuit of the power shift to neutral, if not already has happened. Thereafter, the direct switching of the transfer case be performed. To support immediately or after a recognized tooth on tooth position can be a great gear be inserted in the power shift transmission. To an unwanted acceleration prevent the vehicle and not too big a moment to apply, which the risk of repelling the tooth flanks respectively a rattling conditional, should be as large as possible Gear to be selected. Once a transmission output speed at the power shift output or a successful switching of the Transfer case was detected, the power shift can again switched to neutral.

In the above-described review of the shift request, the speed of the vehicle can be determined, wherein it is checked whether the speed of the vehicle is at least less than an allowable speed v_Vehicle_permitted. The allowed speed should be less than the following value: (r_dyn × πn_Mot_Abregel) / (30 × i_Hinterachse × i_Verteilergetriebe_Gelände × i_Getriebe_Maxgang) - v_Vehicle_Safety

A Shift request for the transfer case can be manual by the driver and / or automatically in predetermined driving conditions of the vehicle triggered by the control unit or the like become. Regardless of the type of switching request is this first by the controller for plausibility checked. With the method according to the invention Switching requirements are not only at a standstill, but also in other predetermined, definable driving situations possible.

Preferably, an automatic shift request can be triggered, for example, in the shunting operation and / or in the superstructure operation of a mobile crane or comparable vehicle when using a commercial vehicle. There are also other driving situations conceivable in which an automatic switching request on the STEU can be done device. Due to the automatic switching, the clutch can be spared, for example, in automated manual transmissions or when using a power shift transmission as the main transmission, the heating of the medium can be reduced in the torque converter.

With the proposed method according to the invention can also be a manual triggering a switching or a shift request for the transfer case the driver. For example, the driver during the Drive a change between a road trip and a Off-road or vice versa by a speaking switching request carry out.

Preferably can the inventive method in the switching strategy the main gearbox, for example, the spread of to the main transmission through the downstream transfer case increase and extend the application of the main gearbox. For example, this is for military missions the vehicles advantageous in which on the one hand a demand for high rigidity and on the other hand a high final speed is required.

In summary is not only a method for driving a drive train, in particular a transfer case, but also the drive train or claimed the automated transfer case itself.

following The present invention will become more apparent from the drawings explained. Show it:

1 a flowchart of a first possible embodiment of a method for driving a drive train of a vehicle;

2 a schematic view of a drive train, with the method according to 1 is controllable;

3 a flowchart of a second possible embodiment of the method for driving a drive train of a vehicle; and

4 a schematic view of a drive train, with the method according to 3 is controllable.

The proposed method can be used both for powershift transmission as well as for automated manual transmission as the main transmission. In the 1 and 2 a first possible embodiment of the method for driving a drive train of a vehicle is shown, wherein as the main transmission an automated transmission 3 is provided. In the 3 and 4 a second possible embodiment of the method for controlling a drive train of a vehicle is shown, wherein as a main transmission, a power shift transmission 10 is provided.

Independently from the respective embodiment is with the inventive Implemented an automatically switchable transfer case. The control of the transfer case can be electric, pneumatic or the like. In the inventive Procedure, the transmission electronics takes over the control the switching valves on the transfer case. For the control the switching valves are usually several outputs provided the transmission control. About the exits, the between-connected valves and one usually used adjusting cylinder, the switching requirements be switched in the transfer case, the control of the Transfer case is not shown in the figures.

Possible is however also another arrangement, for example with one each Valve for off-road and street gears, as well as the neutral position. A feedback, in the form of a Position measurement or the like, to the transmission can either over a switch or via a displacement sensor done. Accordingly should have digital inputs on the transmission control unit or a suitable input for the displacement sensor be. Also conceivable is the use of a data bus capable Displacement sensor responsible for recording and evaluation is and transmits the determined path via a data bus system. Alternatively, the path detection and the valve control via a standalone controller and the Communication of the relevant signals with the transmission control unit via a data bus system. Furthermore, for the speed detection provide at least one speed sensor at the transfer case output, to calculate the present speed ratios in the transmission to be able to. Alternatively, this can also be a vehicle speed signal z. B. used by a speedometer, an ABS / EBS system and due the gear ratios and half tire diameter the downforce be recalculated.

1 shows a possible flowchart or flow chart for the switching requirements for a transfer case with a designed as an automated manual transmission main gear, wherein the associated drive train in 2 is shown. The powertrain includes a drive motor 1 that has a disconnect clutch 2 with an automated manual transmission 3 is coupled. The output shaft of the automated manual transmission 3 is at the same time the drive shaft 4 of the transfer case 5 , The transfer case 5 also has two output shafts 6 . 7 with which a Vorderachsdiffe ential 8th and a rear axle differential 9 connected is. About the output shaft 6 can the wheels of the Vorachsdifferentials 8th and over the output shaft 7 the wheels of the rear axle differential 9 are driven.

The first embodiment of the method according to the invention begins with the switching request from an operator or a driver of a switching operation. The switching request is checked by the control unit. In this case, a required speed under consideration of external influences, such. B. the driving resistance or the like. The control unit detects as part of the review of the shift request speed sensor information for the input and output speed and possibly also speed signals, for example, from a speedometer of the vehicle. The above-described calculation of the required speed and the above-described detection of speed sensor information are by the box 12 in 1 indicated.

When the controller accepts the shift requests, the engine load is reduced and the disconnect clutch is opened. Thereafter, an adjustment of the speed in the transfer case by an engine and / or Getriebebremsansteuerung. Upon reaching a speed equality or, if the speeds are within a tolerance window, the switching can be done. During the speed synchronization access to sensor data from the transmission and the transfer case via the control unit is possible, this is indicated by an arrow 11 in 1 indicated.

After all the right gear can be selected in the main gearbox and the load build-up on the engine with simultaneous clutch closing respectively. The choice of the right gear will depend on the requirement torque or speed oriented by the controller established.

If when switching through a tooth is on tooth position, the Disconnect at least partially closed to the tooth to tooth position to fix. When tooth is fixed to tooth position can be switched through with the to be started. If the tooth can not be removed to tooth position, is an error message and a restart, again with the Reduction of engine load and opening of the separating clutch is started.

3 shows a possible flowchart or flow chart for the switching requirements for a transfer case with a main gear designed as a power transmission, the associated drive train in 4 is shown. The powertrain according to 2 is different from the one in 4 shown drive train only in that as a main transmission, a power shift transmission 10 is used.

The second embodiment of the method according to the invention begins with the switching request from an operator or from a driver of a switching operation. First, the control device checks the switching request. For this purpose, the required speed under consideration of external influences, such. B. driving resistance or the like. In addition, as part of the review of the shift request, the control unit records rotational speed sensor information of input and output rotational speeds as well as possibly speed signals. The above-described calculation of the required speed and the above-described detection of speed sensor information are by the box 13 in 3 indicated.

When the controller accepts the shift request, the engine load is reduced and a neutral shift of the power shift transmission is performed. The transfer case can then be switched to the neutral position. This is followed by the gear engagement with the powershift transmission and the speed adjustment for the shifting claw operation of the transfer case. The previous overall translation is taken into account. With equal speed or when the speeds are within a tolerance window, the switching of the transfer case and the switching of the powershift can begin to neutral. In speed synchronization, the controller has access to sensor data from the powershift transmission and transfer case indicated by an arrow 14 in 3 is indicated.

If a tooth is in the tooth position, this can be remedied by an optimal gear selection followed by engagement with the powershift transmission. When the tooth is fixed to the tooth position, the load can be built up on the motor. The optimal gear selection is situation dependent. The selected gear should also serve for immediate driving or driving on. This is in 3 through the box 16 indicated. If the tooth can not be cleared to tooth position, an error message and a restart occur, so that the reduction of the engine load is started again.

If there is no tooth to tooth position after reaching the speed equalization, the through-connection of the transfer case and the shift of the powershift transmission to neutral can take place. After choosing the right gear in the powershift transmission, the load build-up on the engine can begin. The choice of gear in the power shift transmission is depending on the requirement torque or speed-oriented determined by the controller, which in 3 through the box 17 is hinted at.

It is also possible that after reaching the speed equality, the switching through and maintaining the previously selected gear in the powershift transmission takes place, so that then can be started equal to the load build-up on the engine. This possibility is indicated by an arrow 15 in 3 indicated.

1

drive motor

2

separating clutch

3

automated manual transmission

4

drive shaft

5

Transfer Case

6

output shaft

7

output shaft

8th

front axle

9

rear differential

10

power shift

11

arrow

12

box

13

box

14

arrow

15

arrow

16

box

17

box

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10325354 A1 [0003]

Claims (17)

Method for controlling a drive train of a vehicle, having a drive motor ( 1 ) and a main transmission and a transfer case ( 5 ), wherein a shift request for the transfer case ( 5 ) is processed via a control unit, characterized in that with the control unit, the required for the execution of the shift request speed synchronization is performed, wherein the shift request is triggered manually by the driver and / or in predetermined driving conditions of the vehicle automatically by the control unit. Method according to claim 1, characterized in that in an automated manual transmission ( 3 ) as the main transmission in a shift request for the transfer case ( 5 ) reduces the engine torque while driving from a terrain ratio to a road ratio and the powertrain by opening the clutch ( 2 ), that the transfer case ( 5 ) is switched to neutral, then that the separating clutch ( 2 ) is at least partially closed and a rotational speed synchronization is performed, that at speed equality, the transfer case ( 5 ) is switched through in the road transmission that the separating clutch ( 2 ) and a suitable gear in the automated manual transmission ( 3 ) is switched and that then carried out the torque build-up and parallel to the separating clutch ( 2 ) is closed again. Method according to one of the preceding claims, characterized in that in an automated manual transmission ( 3 ) as the main transmission in a shift request for the transfer case ( 5 ) while traveling from a road ratio to a terrain ratio before reducing the engine torque and opening the disconnect clutch ( 2 ) in the drive train is checked whether the shift request for the transfer case ( 5 ) in the terrain translation is possible that the automated transmission ( 3 ) is switched into a suitable gear, that the transfer case ( 5 ) is switched to neutral, then that the separating clutch ( 2 ) is at least partially closed in the drive train and the rotational speed synchronization is carried out such that, when the rotational speed is equal, the transfer case ( 5 ) and the separating clutch ( 2 ) is opened again in the drive train, and that then carried out the torque build-up and parallel to the separating clutch ( 2 ) is closed again. Method according to claim 3, characterized that the speed of the vehicle when checking the switching request is determined, whereby it is checked whether the speed of the vehicle is at least less than one permissible speed (v_vehicle-permitted) is. Method according to one of claims 2 to 4, characterized in that when switching through the transfer case ( 5 ) a tooth occurs on tooth position, the separating clutch ( 2 ) is at least partially closed again and the tooth is lifted to tooth position by the applied moment of disturbance. Method according to one of claims 2 to 5, characterized in that the separating clutch ( 2 ) for preventing a tooth to tooth position simultaneously with the switching of the shift claw of the transfer case ( 5 ) is closed. Method according to one of claims 2 to 6, characterized in that the switching request for the transfer case ( 5 ) is carried out starting from a transmission neutral position without engine torque withdrawal. Method according to one of the preceding claims, characterized in that in a power shift transmission ( 10 ) as the main transmission in a shift request for the transfer case ( 5 ) reduces the engine torque while driving from a terrain ratio to a road ratio and the powertrain by neutral switching of the power shift transmission ( 10 ), that the transfer case ( 5 ) is switched to neutral that in the power shift transmission ( 10 ) a gear is engaged, that a speed synchronization is performed, that at speed equality, the transfer case ( 5 ) is switched through in the road transmission, and that thereafter the torque build-up is performed. Method according to one of the preceding claims, characterized in that in a power shift transmission ( 10 ) as the main transmission in a shift request for the transfer case ( 5 ) while driving from a road ratio to a terrain ratio before the reduction of the engine torque and the separation of the drive train by neutral switching of the power shift transmission ( 10 ), whether the shift request for the transfer case ( 5 ) for the terrain ratio is possible that after a gear in the power shift transmission ( 10 ) is inserted, that the speed synchronization is performed, that at speed equality, the transfer case ( 5 ) is switched through in the terrain ratio and that thereafter the torque build-up is performed. A method according to claim 9, characterized in that the speed of the vehicle is determined in the review of the shift request, wherein it is checked whether the speed of Vehicle is at least smaller than an allowable speed (v_Vehicle Permitted). Method according to one of claims 8 to 10, characterized in that when switching through the transfer case ( 5 ) a tooth occurs on tooth position, again a gear in the power shift transmission ( 10 ) is inserted, so that the tooth is lifted to tooth position again by the applied disturbing moment. A method according to claim 11, characterized in that simultaneously with the switching of the shift claw of the transfer case ( 5 ) a gear on the powershift transmission ( 10 ) is inserted. A method according to claim 11 or 12, characterized in that as gear in the power shift transmission ( 10 ) a gear is selected, which allows an immediate onward journey after successful switching. Method according to one of claims 8 to 13, characterized in that the switching request for the transfer case ( 5 ) is carried out starting from a transmission neutral position without withdrawal of the engine torque. Method according to one of claims 8 to 14, characterized in that at a switching request at standstill of the vehicle, the power shift transmission ( 10 ) is switched to neutral, that a direct changeover of the transfer case ( 5 ) is carried out, and that after successful switching through the transfer case ( 5 ) the power shift transmission ( 10 ) is switched back to neutral. Method according to one of the preceding claims, characterized in that a switching request in shunting and / or in the superstructure operation of a commercial vehicle automatically from the control unit is triggered. Method according to one of the preceding claims, characterized in that a manual shift request for Change between a terrain translation and a street translation is triggered.