Method for operating a drive train of a vehicle

Abstract

Method for operating a drive train (52) in a vehicle (10), wherein the drive train (52) has at least two drive axles (14, 16), characterized in that the drive axles (14, 16) can be operated without coupling from one another, wherein the first drive axle (14) has a first drive torque (M A1 ) in a first direction of rotation (D1) and the second drive axle (16) has a second drive torque (M A2 ) in a second direction of rotation (D2) opposite to the first direction of rotation (D1) in order to enable the vehicle (10) to dig into a loose ground (70), wherein the first drive axle (14) and the second drive axle (16) rotate in opposite directions such that no propulsion is generated, wherein the vehicle digs into the loose ground by rotating wheels (36) on the drive axles (14, 16) and under its own weight.

Description

[0001] The invention relates to a method for operating a drive train of a vehicle with at least two driven axles according to the preamble of claim 1. The invention further relates to a control unit, a computer program and a vehicle with a drive train according to the independent claims. State of the art

[0002] Commercial vehicles with multiple drive axles are known for transporting goods and loads. Drive concepts are particularly well known in which the commercial vehicle has a non-driven front axle and two or more driven rear axles. A typical commercial vehicle of this type is also referred to as a 6x4 truck, which has a non-driven front axle and two driven rear axles. In commercial vehicles powered by an internal combustion engine, the driven axles are mechanically connected to one another so that the axles always rotate in the same direction and at the same speed. Commercial vehicles with electrically driven axles or a hybrid drive concept open up new possibilities, as an electrically driven axle does not necessarily have to be connected to the rest of the drive train and can therefore be controlled independently of the rest of the drive train.

[0003] DE 10 2011 056 168 A1 discloses a control device and a method for controlling a motor vehicle with two driven drive axles, wherein the first drive axle is driven purely electrically and the second drive axle is driven by a hybrid drive train comprising an internal combustion engine and an electric drive motor. The drive torque is distributed between the first and second drive axles for optimal driving dynamics. Due to the purely electric drive of the first drive axle, it can be controlled completely independently of the second drive axle, in particular without a mechanical coupling between the drive axles.

[0004] DE 10 2020 202 462 A1 discloses a method for drive optimization in a motor vehicle with at least two drivable wheels on a vehicle axle with individually adjustable drive torque, in which, in order to increase the propulsive force, the drive torque on at least one wheel is increased in such a way that an increased longitudinal slip of at least 20% is achieved on the wheel.

[0005] US 2022 / 0176829 A1 discloses a method and system for controlling the power of an electric motor of a vehicle.

[0006] DE 10 2021 125 332 B3 discloses a drive and braking system for a motor vehicle having at least one front axle and one rear axle, wherein at least one wheel on each axle is connected to a vehicle frame of a chassis via a respective wheel suspension.

[0007] DE 10 2022 002 678 A1 discloses a method for operating a vehicle, wherein wheels of an axle of the vehicle are driven by at least one electric drive motor. When performing an emergency braking maneuver, the rotation of the wheels of this axle is reduced to a standstill by a maximum braking force of a braking system of the vehicle, and the wheels of this axle are subsequently rotated in the opposite direction by means of the at least one electric drive motor.

[0008] DE 10 2019 006 736 A1 discloses a method for operating a motor vehicle with at least one electric drive unit and a braking system acting on the wheels of the motor vehicle. Upon detection of an emergency situation in the motor vehicle and detection of continuous braking performed by the braking system, the at least one electric drive unit, in a mechanically coupled state with at least one wheel driven by the drive unit, is automatically operated, at least temporarily, in a second direction of rotation opposite to the first direction of rotation. General description of the invention

[0009] The object of the invention is to increase the stability of a vehicle on loose ground and thus to facilitate additional functions, such as the recovery of crashed vehicles.

[0010] The object is achieved by a method for operating a drive train in a vehicle, wherein the drive train has at least two drive axles. It is provided that the drive axles can be operated independently of one another, with the first drive axle generating a first drive torque in a first direction of rotation and the second drive axle generating a second drive torque in a second direction of rotation opposite to the first direction of rotation, in order to enable the vehicle to dig into loose ground.

[0011] A drivetrain is generally understood to be a system that generates drive torque and transmits this torque to a driving unit, in particular to an axle drive or a drive wheel. A drive axle, in this context, is an axle that is operatively connected to a drive motor that can cause the wheels on the drive axle to rotate.

[0012] A loose surface is defined as a surface that can be changed by the rotation of the vehicle's wheels. Such a loose surface includes, in particular, sand, gravel, a meadow, a field, forest floor, or similar surfaces.

[0013] The proposed method allows the first drive axle and the second drive axle to rotate in opposite directions, so that no propulsion is generated, and the drive power can be used to dig the vehicle into the loose ground by rotating the wheels on the drive axles and under its own weight. This can improve the vehicle's stability on loose ground. If the vehicle is designed as a recovery vehicle, it can, in particular, assume a stable position on the loose ground in order to carry out a recovery operation using a recovery device of the vehicle, in particular a crane or cable winch.

[0014] The features listed in the dependent claims enable advantageous further developments and improvements of the method listed in the independent claim for operating a drive train of a vehicle.

[0015] In an advantageous embodiment of the drive train, the first drive axle is driven by a first electric drive motor and the second drive axle is driven by a second electric drive motor. In this context, an electric drive motor is understood to be a device that converts electrical energy into mechanical energy. The term electric drive motor refers to both asynchronous and synchronous electric machines. The electric drive motor can be designed as a brushless motor or as an electric drive motor with sliding contacts. Two drive axles, each driven by an electric drive motor, enable completely independent control of the two drive axles in terms of speed, torque, and direction of rotation.This makes it possible to achieve a function in a simple manner, namely by rotating the first drive axle in the opposite direction to the second drive axle, in which the vehicle does not move forward and digs into the loose ground due to its own weight and the different directions of rotation of the drive axles.

[0016] In an alternative embodiment of the invention, the first drive axle is driven by an internal combustion engine and the second drive axle by an electric drive motor. In this context, an internal combustion engine is understood to be a heat engine that converts the chemical energy of a fuel into mechanical energy through combustion. Such an internal combustion engine can be designed, in particular, as a reciprocating piston engine or a rotary piston engine. Such a combination of an internal combustion engine on one drive axle and an electric drive motor on another drive axle also enables completely independent control of the two drive axles with regard to speed, torque, and direction of rotation of the drive axles. This also enables the proposed function of burying the vehicle in loose ground.

[0017] According to an advantageous embodiment of the method, the first drive axle is rotated in the direction of travel and the second drive axle is rotated against the direction of travel in such a way that a first material pile-up is generated between the first drive axle and the second drive axle. In this context, a direction of travel is understood to be a direction in which the vehicle moves forward during normal operation. In this context, a material pile-up is understood to be a pile-up of loose material, in particular sand, earth, gravel or similar, which is generated when the vehicle digs into loose ground. This can increase the stability of the vehicle on the loose ground and prevent it from slipping during a rescue operation.

[0018] Alternatively or additionally, a further advantageous embodiment of the method provides for the first drive axle to be rotated counter to the direction of travel and the second drive axle to be rotated in the direction of travel, such that a second pile of material is created in front of the first drive axle in the direction of travel and a third pile of material is created behind the second drive axle in the direction of travel. This allows a particularly deep trough to be created in which the vehicle achieves a particularly stable footing. This allows recovery operations to be carried out particularly safely, and comparatively high forces can be transmitted without the vehicle being pulled out of this trough.

[0019] The drivetrain comprising the two driven axles can, for example, be configured as a 4x4 drive system. In addition to the two driven axles, the drivetrain can have at least one additional axle, which can be configured as a driven axle or as a non-driven axle. Thus, the drivetrain can be configured as a 6x6, 6x4, 8x8, or 8x4 drive system, for example.

[0020] The vehicle can preferably be designed as a commercial vehicle. In this context, the driven rear axles of the commercial vehicle are understood to be drive axles. A front axle is understood to be an axle that is operatively connected to the steering system of the commercial vehicle and, with appropriate control of the front axle wheels, enables the commercial vehicle to corner. Such a front axle can be designed either as a driven axle or as a non-driven axle.

[0021] If the drive train has at least one non-driven axle in addition to the at least two driven axles, then in a preferred embodiment of the invention, the wheels of the at least one non-driven axle are each held in place by a wheel brake during the implementation of the method. The at least one non-driven axle of the drive train can be designed as a front axle. A non-driven front axle enables the commercial vehicle to be steered free of drive forces that counteract the steering forces on the front axle. Furthermore, a non-driven front axle can be designed more cost-effectively than a driven front axle. In order to prevent the commercial vehicle from rolling away during the implementation of the method, it is advantageous if the wheels of the front axle are blocked by the wheel brakes and the commercial vehicle remains in a defined location during the method.

[0022] According to an advantageous embodiment of the method, a differential lock for an axle differential of the corresponding drive axle is activated on at least one of the driven axles, preferably on all driven axles, while the method is being carried out. A differential lock can prevent a single wheel on a drive axle from spinning and thus preventing sufficient traction from being built up on the drive axle to dig into loose ground. Furthermore, the differential lock can be helpful after the method has ended to free the vehicle from its dug-in position and to transfer sufficient drive torque to the loose ground to leave this position.

[0023] In a typical embodiment of the invention, the method is initiated when a driver of the vehicle presses a brake pedal and simultaneously actuates an operating element to activate the method. In this context, an operating element is understood to mean, in particular, buttons, rotary switches, toggle switches, touch display surfaces and the like. This makes it particularly easy to activate the method according to the invention during a rescue operation. Furthermore, the combination of brake pedal and additional operating element can reliably prevent unwanted activation and initiation of such a method. It is particularly preferred if the brake pedal and accelerator pedal must be pressed in parallel and the operating element must be activated at the same time. This can further increase operational reliability compared to the previous embodiment.

[0024] A further aspect of the invention relates to a computer program. The computer program can also be referred to as a computer program product or computer program code.

[0025] A further aspect of the invention relates to a computer-readable medium comprising a computer program with computer program code for carrying out a method for operating a drive train in a vehicle described in the preceding sections. The term "computer-readable medium" refers in particular, but not exclusively, to hard drives and / or servers and / or memory sticks and / or flash memories and / or DVDs and / or Blu-rays and / or CDs. In addition, the term "computer-readable medium" also refers to a data stream, such as that generated when a computer program and / or a computer program product is downloaded from the Internet.

[0026] A further aspect of the invention relates to a control unit for controlling a drive train in a vehicle, wherein the control unit advantageously comprises a memory unit and a computing unit, as well as a computer program stored in the memory unit. The control unit is configured to carry out a method described in the preceding paragraphs, in particular when the machine-readable computer program is executed by the computing unit of the control unit.

[0027] A further aspect of the invention relates to a vehicle with a drive train, wherein the drive train has at least two drive axles. The drive axles can be operated independently of one another. The first drive axle generates a first drive torque in a first direction of rotation, and the second drive axle generates a second drive torque in a second direction of rotation opposite to the first direction of rotation, in order to enable the vehicle to dig into loose ground. The vehicle also has a control unit as described in the previous paragraph. Such a vehicle enables more difficult rescue operations, in which other vehicles would slide due to insufficient grip on the loose ground. Furthermore, the improved stability can improve safety during a rescue operation.

[0028] In advantageous embodiments, the vehicle comprises a control unit according to at least one of the previously described embodiments. In advantageous embodiments, the vehicle is suitable for executing, at least in part, a method according to at least one of the previously described embodiments. Character list

[0029] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. They show: Fig. 1 a schematic view of a commercial vehicle according to the invention with a drive train according to the invention, which has a front axle and two drive axles different from the front axle, Fig. 2 shows a further preferred embodiment of a commercial vehicle according to the invention, Fig. 3 shows a further preferred embodiment of a commercial vehicle according to the invention, Fig. 4 a sketch illustrating a method according to the invention, in which a commercial vehicle according to the invention digs into a loose ground by an opposite rotation of the drive axles. Description of preferred embodiments

[0030] Fig. 1 shows a schematic view of a commercial vehicle 10 according to the invention with a drive train 52 according to the invention. The drive train 52 comprises at least one front axle 12 and two drive axles 14, 16 different from the front axle 12. A first electric drive motor 20 is arranged on the first drive axle 14, which has a first drive torque M A1to the first drive axle 14. Furthermore, a first axle differential 24 can be formed on the first drive axle 14 in order to enable a speed difference between an inside wheel 36 and an outside wheel 36 of the first drive axle 14, in particular when cornering. The first axle differential 24 can be locked by a first differential lock 32 in order to prevent such speed compensation and to prevent an individual drive wheel 36 from spinning, in particular when driving on a smooth or loose surface 70 or on terrain 78.

[0031] A second electric drive motor 22 is arranged on the second drive axle 16, which has a second drive torque M A2to the second drive axle 16. Furthermore, a second axle differential 26 can be formed on the second drive axle 16 in order to enable a speed difference between an inside wheel 36 and an outside wheel 36 of the second drive axle 16, in particular when cornering. The second axle differential 26 can be locked by a second differential lock 34 in order to prevent such speed compensation and, in particular when driving on smooth or loose surfaces 70 or off-road 78, to prevent an individual drive wheel 36 from spinning. The first drive axle 14 and the second drive axle 16 can be operated independently of one another. Furthermore, wheel brakes 30 are each provided on the wheels 36 of the front axle 12 and the drive axles 14, 16 in order to be able to decelerate the commercial vehicle 10 from moving or to hold it at a standstill.A cable winch 74 is provided on the commercial vehicle 10 in order to pull objects, in particular crashed motor vehicles 76, from the terrain 78.

[0032] The commercial vehicle 10 further comprises a control unit 60 with a memory unit 62 and a computing unit 64, as well as a computer program 66 stored in the memory unit 62. The control unit 60 is configured to execute a method according to the invention for operating a drive train 52 in a commercial vehicle 10 when the computer program 66 is executed by the computing unit 64 of the control unit 60. The control unit 60 may further comprise a computer-readable medium 68 for storing the computer program 66.

[0033] In Fig. 2 shows a further preferred embodiment of a commercial vehicle 10 according to the invention with a drive train 52 according to the invention. The drive train 52 comprises a first front axle 12, a second front axle 18, a first drive axle 14 and a second drive axle 16. A first drive motor is arranged on the first drive axle 14, which can be designed as an internal combustion engine 38 or as a first electric drive motor 20, which has a first drive torque M A1transmitted to the first drive axle 14. Alternatively, the first drive axle 14 can also be assigned a hybrid drive 50, which comprises an internal combustion engine 38 and a first electric drive motor 20. Furthermore, a first axle differential 24 can be formed on the first drive axle 14 in order to enable a speed difference between an inside wheel 36 and an outside wheel 36 of the first drive axle 14, in particular when cornering. The first axle differential 24 can be locked by a first differential lock 32 in order to prevent such speed compensation and to prevent an individual drive wheel 36 from spinning, in particular when driving on smooth or loose surfaces 70 or off-road 78.

[0034] A second electric drive motor 22 is arranged on the second drive axle 16, which has a second drive torque M A2to the second drive axle 16. Furthermore, a second axle differential 26 can be formed on the second drive axle 16 in order to enable a speed difference between an inside wheel 36 and an outside wheel 36 of the second drive axle 16, in particular when cornering. The second axle differential 26 can be locked by a second differential lock 34 in order to prevent such speed compensation and, in particular when driving on smooth or loose surfaces 70 or off-road 78, to prevent an individual drive wheel 36 from spinning. The first drive axle 14 and the second drive axle 16 can be operated independently of one another. Furthermore, wheel brakes 30 are each provided on the wheels 36 of the front axle 12 and the drive axles 14, 16 in order to be able to decelerate the commercial vehicle 10 or hold it at a standstill.

[0035] A third electric drive motor 23 can be arranged on the first front axle 12, which generates a third drive torque M A3 to the first front axle 12 in order to drive the first front axle 12. Furthermore, a fourth electric drive motor 25 can be arranged on the second front axle 18, which generates a fourth drive torque M A4 to the second front axle 18 in order to drive the second front axle 18. The first front axle 12 and the second front axle 18 can be operated independently of one another.

[0036] The commercial vehicle 10 further comprises a control unit 60 with a memory unit 62 and a computing unit 64, as well as a computer program 66 stored in the memory unit 62. The control unit 60 is configured to execute a method according to the invention for operating a drive train 52 in a commercial vehicle 10 when the computer program 66 is executed by the computing unit 64 of the control unit 60. The control unit 60 may further comprise a computer-readable medium 68 for storing the computer program 66.

[0037] In Fig. 3 shows a further preferred embodiment of a commercial vehicle 10 according to the invention with a drive train 52 according to the invention. The drive train 52 comprises at least one front axle 12 and two drive axles 14, 16 different from the front axle. A wheel hub motor 28 is arranged as an electric drive motor on each of the wheels 36 of the first drive axle 14, wherein a first drive torque M A1is transmitted to the first drive axle 14. Furthermore, a first axle differential 24 can be formed on the first drive axle 14 in order to enable a speed difference between an inside wheel 36 and an outside wheel 36 of the first drive axle 14, in particular when cornering. The first axle differential 24 can be locked by a first differential lock 32 in order to prevent such speed compensation and, in particular when driving on smooth or loose surfaces 70 or off-road 78, to prevent an individual drive wheel 36 from spinning. Alternatively, such speed compensation can also be achieved by a correspondingly different control of the respective wheel hub motors 28 on the first drive axle 14.

[0038] A wheel hub motor 28 is arranged as an electric drive motor on each of the wheels 36 of the second drive axle 16, wherein a second drive torque MA2 is transmitted to the second drive axle 16. Furthermore, a second axle differential 26 can be formed on the second drive axle 16 in order to enable a speed difference between an inside wheel 36 and an outside wheel 36 of the second drive axle 16, in particular when cornering. The second axle differential 26 can be locked by a second differential lock 34 in order to prevent such speed compensation and, in particular when driving on smooth or loose surfaces 70 or off-road 78, to prevent an individual drive wheel 36 from spinning. Alternatively, such speed compensation can also be achieved by correspondingly different control of the respective wheel hub motors 28 on the second drive axle 16. The first drive axle 14 and the second drive axle 16 can be operated without coupling to one another.

[0039] In Fig. 4 shows a commercial vehicle 10 according to the invention with a drive train 52 according to the invention during the implementation of a method according to the invention for operating the drive train 52 of the commercial vehicle 10. In order to improve the stability of the commercial vehicle 10 on loose ground 70, for example on a gravel path, a meadow, a field, or in other terrain 78, the first drive axle 14 and the second drive axle 16 can be controlled and operated independently and without coupling. The first drive axle 14 generates a first drive torque M A1 in a first direction of rotation D1 and the second drive axle 16 a second drive torque M A2 in a second direction of rotation D2 opposite to the first direction of rotation D1, in order to enable the commercial vehicle 10 to dig into a loose ground 70.

[0040] The commercial vehicle 10 has a driver's cab 40 with a dashboard 42, on which an operating element 44 is arranged or formed for activating a method according to the invention for operating a drive train 52 of a commercial vehicle 10. Furthermore, an accelerator pedal 46 and a brake pedal 48 for controlling the commercial vehicle 10 are arranged in the driver's cab 40.

[0041] Due to the mechanical decoupling of the first drive axle 14 and the second drive axle 16, the drive axles 14, 16 can be operated individually with regard to torque, speed, and direction of rotation. If a commercial vehicle 10 is to be positioned off-road in order to increase the stability of the commercial vehicle 10, for example, to recover a motor vehicle 76 that has crashed in the terrain 78, the commercial vehicle 10 can dig into the loose ground 70 by driving the first drive axle 14 with a first drive torque M A1and the second drive axle 16 with a first drive torque M A1 opposite drive torque M A2is operated. If the first drive axle 14 rotates in the direction of travel and the second drive axle 16 rotates against the direction of travel, a first material pile 72 is generated between the first drive axle 14 and the second drive axle. Alternatively, the first drive axle 14 can rotate against the direction of travel and the second drive axle 16 can rotate in the direction of travel, so that a second material pile 84 is generated in front of the first drive axle 14 and a third material pile 86 is generated behind the second drive axle 16. This allows the commercial vehicle 10 to dig into the loose ground 70 to increase stability. Optionally, all three material piles 72, 84, 86 can also be realized by appropriately controlling the driven axles 14, 16 by first selecting a first direction of rotation D1 and then a second direction of rotation D2 of the drive axles 14, 16.

[0042] To facilitate the digging of the drive axles 14, 16, the front axle 12 of the commercial vehicle 10 can be blocked during the execution of the method by wheel brakes 30 on the wheels 36 of the front axle 12. Furthermore, the digging of the commercial vehicle 10 can be facilitated by activating differential locks 32, 34 on the drive axles 14, 16 to prevent speed compensation between a spinning wheel 36 and a wheel 36 transmitting a drive torque to the ground. As an alternative to a differential lock 32, 34, the spinning of the faster-rotating wheel 36 of the respective drive axle 14, 16 can also be prevented by targeted braking intervention via a wheel brake 30.By burying the commercial vehicle 10, its stability is improved, so that the commercial vehicle 10 is wedged securely enough on the loose ground 70 to, for example, pull a crashed motor vehicle 76 out of a ditch or difficult-to-access terrain 78 using a cable winch 74. Furthermore, an acceleration sensor 80 and / or a position sensor 82 can be arranged on the commercial vehicle 10 to align the commercial vehicle 10 substantially horizontally and thus minimize the risk of tipping during a rescue operation.

[0043] The method can be initiated by specifically activating the function. Such activation can occur, for example, by simultaneously actuating a brake pedal 48 and an operating element 44. The operating element 44 can, in particular, be a button, a switch, or a control panel on a touch display of a dashboard 42 of the commercial vehicle 10. Alternatively, the function can also be activated by simultaneously pressing the brake pedal 48 and an accelerator pedal 46 of the commercial vehicle 10 and additionally activating the operating element 44. This ensures a particularly high level of security against incorrect operation or an unwanted initiation of the method. By actuating the operating element 44 again, the function can be deactivated again and the commercial vehicle 10 can be driven away in normal operation.

[0044] In the Fig.In the commercial vehicle 10 shown in Figure 2, not only the drive axles 14, 16 but also the front axles 12, 18 can be operated in opposite directions, so that in this embodiment the driven front axles 12, 18 can also dig into the loose ground 70. Reference symbol 10 commercial vehicles 12 front axle 14 first drive axle 16 second drive axle 18 second front axle 20 first electric drive motor 22 second electric drive motor 23 third electric drive motor 24 first axle differential 25 fourth electric drive motor 26 second axle differential 28 Wheel hub motor 30 Wheel brake 32 first differential lock 34 second differential lock 36 wheels 38 combustion engine 40 Driver's cab 42 Dashboard 44 Control element 46 Accelerator pedal 48 Brake pedal 50 hybrid drive 52 Drivetrain 60 control unit 62 storage unit 64 computing unit 66 computer program 68 computer-readable medium 70 Underground 72 first material throw 74 cable winch 76 crashed vehicles 78 terrain 80 Accelerometer 82 Position sensor 84 second material throw 86 third material throw D1 first direction of rotation D2 second direction of rotation M A1 Drive torque on the first drive axle M A2 Drive torque on the second drive axle M A3 Drive torque on the first front axle M A4 Drive torque on the second front axle

Claims

[1] Method for operating a drive train (52) in a vehicle (10), wherein the drive train (52) has at least two drive axles (14, 16), characterized by that the drive axles (14, 16) can be operated without coupling from one another, wherein the first drive axle (14) has a first drive torque (M A1 ) in a first direction of rotation (D1) and the second drive axle (16) has a second drive torque (M A2 ) in a second direction of rotation (D2) opposite to the first direction of rotation (D1) in order to enable the vehicle (10) to dig into a loose ground (70), wherein the first drive axle (14) and the second drive axle (16) rotate in opposite directions such that no propulsion is generated, wherein the vehicle digs into the loose ground by rotating wheels (36) on the drive axles (14, 16) and under its own weight. [2] Method according to claim 1, characterized bythat the first drive axle (14) is driven by a first electric drive motor (20) and the second drive axle (16) is driven by a second electric drive motor (22). [3] Method according to claim 1 or 2, characterized by that the first drive axle (14) is rotated in the direction of travel and the second drive axle (16) is rotated counter to the direction of travel, such that a first material throw-up (72) is generated between the first drive axle (14) and the second drive axle (16). [4] Method according to one of claims 1 to 3, characterized by that the first drive axle (14) is rotated counter to the direction of travel and the second drive axle (16) is rotated in the direction of travel, such that a second material throw-up (84) is generated in front of the first drive axle (14) and a third material throw-up (86) is generated behind the second drive axle (16). [5] Method according to one of claims 1 to 4, characterized bythat the drive train (52) has at least one front axle (12), wherein the front axle (12) of the vehicle (10) is designed as a non-driven front axle (12) and the wheels (36) of the non-driven front axle (12) are each held by a wheel brake (30) when carrying out the method. [6] Method according to one of claims 1 to 5, characterized by that a differential lock (32, 34) for an axle differential (24, 26) of the corresponding drive axle (14, 16) is activated on at least one of the driven axles (14, 16) during the implementation of the method. [7] Method according to one of claims 1 to 6, characterized by that the method is initiated when a driver of the vehicle (10) presses a brake pedal (48) and simultaneously actuates an operating element (44) to activate the method. [8] A computer program (66) comprising instructions which, when the computer program (66) is executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 7. [9] Computer-readable medium (68), characterized by that the computer-readable medium (68) comprises a computer program (66) with computer program code for carrying out a method according to one of claims 1 to 7. [10] Control unit (60) for controlling a drive train (52) in a vehicle (10), wherein the control unit (60) is configured to carry out a method according to one of claims 1 to 7. [11] Vehicle (10) with a drive train (52), wherein the drive train (52) has at least two drive axles (14, 16), wherein the drive axles (14, 16) can be operated without coupling to one another, wherein the first drive axle (14) has a first drive torque (M A1) in a first direction of rotation (D1) and the second drive axle (16) has a second drive torque (M A2 ) in a second direction of rotation (D2) opposite to the first direction of rotation (D1) in order to enable the vehicle (10) to dig into a loose surface (70), and with a control device (60) according to claim 10.

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