Electrically operated axle drive train, method for controlling an axle drive train, computer program product and control unit for controlling an axle drive train

Abstract

Electrically operated axle drive train (1) of a motor vehicle, comprising an electric machine (3) which can be coupled to at least one vehicle wheel (4) of the motor vehicle in a torque-transmitting manner, and a transmission arrangement (5) arranged in the torque flow between the vehicle wheel (4) and the electric machine (3), as well as a braking device (6) by means of which the vehicle wheel (4) can be braked, wherein the braking device (6) is connected to a fluid circuit (22) by means of which heat generated by the braking device (6) during operation of the axle drive train (1) can be dissipated and wherein a) a first coupling device (7) is arranged in the torque flow between the electric machine (3) and the brake device (6), by means of which the brake device (6) can be engaged and disengaged from the torque flow, and a second coupling device (8) is arranged in the torque flow between the electric machine (3) and the transmission arrangement (5), by means of which the transmission arrangement (5) can be engaged and disengaged from the torque flow, or b) a first coupling device (7) is arranged in the torque flow between the electric machine (3) and the brake device (6), by means of which the brake device (6) can be coupled in and out of the torque flow, and a second coupling device (8) is arranged in the torque flow between the brake device (6) and the transmission arrangement (5), by means of which the transmission arrangement (5) can be coupled in and out of the torque flow.

Description

[0001] The present invention relates to an electrically operable axle drive train of a motor vehicle, comprising an electric machine that can be coupled to at least one vehicle wheel of the motor vehicle in a torque-transmitting manner, a transmission arrangement arranged in the torque flow between the vehicle wheel and the electric machine, and a braking device by means of which the vehicle wheel can be braked. The invention further relates to a method for controlling an axle drive train, a computer program product, and a control unit for controlling an axle drive train.

[0002] Electric motors are increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same level of driving comfort they are accustomed to.

[0003] A detailed description of an electric drive can be found in an article in the magazine ATZ, Volume 113, May 2011, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, entitled "Highly Integrative and Flexible Electric Drive Unit for E-Vehicles." This article describes a drive unit for one axle of a vehicle. It includes an electric motor arranged concentrically and coaxially with a bevel gear differential. A switchable 2-speed planetary gear set is arranged in the power train between the electric motor and the bevel gear differential, which is also positioned coaxially with the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between climbing ability, acceleration, and energy consumption.Such drive units are also referred to as e-axles or electrically operated drive trains.

[0004] Such electrified vehicles already have good efficiency compared to traditional combustion-engine vehicles, and constantly evolving technology in this area enables further reductions in energy consumption. However, the technology used is not the only factor responsible for energy savings in autonomous and / or manually controlled vehicles. Driving style also significantly influences the consumption of such vehicles.

[0005] It is already known that so-called "coasting" of a motor vehicle can further reduce energy consumption. Studies show that "coasting" can save up to 25% of energy in an electrically powered vehicle. In "coasting" mode, the vehicle's kinetic energy is used to cover a certain distance without active propulsion.

[0006] DE 10 2017 100 988 A1 discloses a method for controlling the coasting mode of a vehicle with an automated clutch. In this method, the clutch is opened to disconnect the internal combustion engine from the drivetrain when the gear is engaged, and the clutch is closed to exit the coasting mode. In a method in which the coasting mode is automatically adjusted, the entry into or exit from the coasting mode is automatically determined depending on the driver's behavior.

[0007] DE 10 2016 209 230 A1 discloses a method for controlling a coasting mode of a vehicle with an automatic clutch. A vehicle-specific parameter is determined and compared with a threshold. Activation or deactivation of the coasting mode is determined based on the comparison with the threshold. In the method, in which the decision to activate or deactivate the coasting mode is made solely from a technical perspective, a vehicle-specific parameter is selected for the comparison, which is partially influenced by the actuation state of at least one accelerator pedal.

[0008] There is a continuing need for such axle drive trains to provide a variety of different operating modes for the driver or vehicle control in order to provide the highest level of energy efficiency, comfort and safety.

[0009] DE 10 2018 131 981 A1 discloses an electrically operable axle drive train of a motor vehicle, which comprises an electric machine that can be coupled to at least one vehicle wheel of the motor vehicle in a torque-transmitting manner, and a braking device by means of which the vehicle wheel can be braked. A first clutch device is arranged in the torque flow between the electric machine and the braking device, by means of which the braking device can be coupled into and out of the torque flow, and a second clutch device is arranged in the torque flow between the electric machine and the drive wheel. Further prior art is disclosed in DE 10 2015 221 861 A1 and DE 10 2020 005 357 A1.

[0010] Therefore, the object of the invention is to provide an electrically operable axle drive train of a motor vehicle that implements a multitude of different selectable operating modes while being as simple and cost-effective as possible. Furthermore, the object of the invention is to provide an improved method for controlling an axle drive train, an optimized computer program product for controlling an axle drive train, and an improved control unit for controlling an axle drive train.

[0011] This object is achieved by an electrically operable axle drive train of a motor vehicle, comprising an electric machine which can be coupled to at least one vehicle wheel of the motor vehicle in a torque-transmitting manner, and a transmission arrangement arranged in the torque flow between the vehicle wheel and the electric machine, as well as a braking device by means of which the vehicle wheel can be braked, wherein a) a first coupling device is arranged in the torque flow between the electric machine and the braking device, by means of which the braking device can be coupled into and out of the torque flow, and a second coupling device is arranged in the torque flow between the electric machine and the transmission arrangement, by means of which the transmission arrangement can be coupled into and out of the torque flow, or b) a first coupling device is arranged in the torque flow between the electric machine and the braking device, by means of which the braking device can be coupled into and out of the torque flow, and a second coupling device is arranged in the torque flow between the braking device and the transmission arrangement, by means of which the transmission arrangement can be coupled into and out of the torque flow.

[0012] This has the advantage that a variety of different operating modes can be realized, which will be explained in more detail below.

[0013] The advantage of the design variant designated with a) is that the rotating part of the braking device can be deactivated during driving operation so that it does not generate any drag torque, thus enabling particularly efficient driving operation.

[0014] In the axle drivetrain design alternative designated b), a fully integrated variant is implemented, which also features switchable clutch devices. The arrangement of the clutch devices implemented in variant b) makes it possible, for example, to completely decouple the engine from the drivetrain when simply braking the vehicle wheel with the brake device.

[0015] An electrically operable drivetrain comprises an electric motor and preferably a transmission assembly coupled to the electric motor. The transmission assembly and the electric motor form, in particular, a structural unit. This can be formed, for example, by a drivetrain housing in which the transmission assembly and the electric motor are jointly housed. This structural unit is occasionally also referred to as an electric axle.

[0016] The electrical machine serves to convert electrical energy into mechanical energy and / or vice versa. It typically comprises a stationary part known as a stator, stand, or armature, and a part known as a rotor or runner, which is movable, particularly rotatable, relative to the stationary part. The electrical machine can be configured as a radial flux or axial flux machine.

[0017] In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and especially greater than 100 km / h can be achieved. The electric motor particularly preferably has an output greater than 30 kW, preferably greater than 50 kW, and especially greater than 70 kW. It is further preferred that the electric machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm.

[0018] For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PCs), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOM), or tractors.

[0019] The drive train may further comprise a control unit. A control unit as used in the present invention serves, in particular, for the electronic control and / or regulation of one or more technical systems of the drive train, in particular the electric motor and / or the clutch and / or braking devices.

[0020] A control unit has, in particular, a wired or wireless signal input for receiving, in particular, electrical signals, such as sensor signals. Furthermore, a control unit preferably also has a wired or wireless signal output for transmitting, in particular, electrical signals, for example, to electrical actuators or electrical consumers of the electrically operable axle drive train or the motor vehicle.

[0021] Control and / or regulation operations can be performed within the control unit. It is particularly preferred that the control unit comprises hardware configured to execute software. The control unit preferably comprises at least one electronic processor for executing program sequences defined in the software.

[0022] The control unit may further comprise one or more electronic memories in which the data contained in the signals transmitted to the control unit can be stored and read again. Furthermore, the control unit may comprise one or more electronic memories in which data can be stored in a modifiable and / or non-modifiable manner.

[0023] A control unit can comprise a plurality of control units, which are arranged, in particular, spatially separated from one another in the motor vehicle. Control units are also referred to as electronic control units (ECUs) or electronic control modules (ECMs) and preferably have electronic microcontrollers for performing computing operations for processing data, particularly preferably using software. The control units can preferably be networked with one another, enabling wired and / or wireless data exchange between control units. In particular, it is also possible to network the control units with one another via bus systems present in the motor vehicle, such as the CAN bus or LIN bus.

[0024] Most preferably, the control unit has at least one processor and at least one memory, which in particular contains a computer program code, wherein the memory and the computer program code are configured, with the processor, to cause the control unit to execute the computer program code.

[0025] The control unit can particularly preferably comprise a power electronics module for supplying current to the electrical machine. A power electronics module is preferably a combination of various components which control or regulate a current to the electrical machine, preferably including the peripheral components required for this purpose, such as cooling elements or power supplies. In particular, the power electronics module contains power electronics or one or more power electronics components which are designed to control or regulate a current. These are particularly preferably one or more power switches, e.g., power transistors. The power electronics particularly preferably has more than two, particularly preferably three, separate phases or current paths, each with at least one dedicated power electronics component.The power electronics are preferably designed to control or regulate a power with a peak power, preferably continuous power, of at least 100 W, preferably at least 1000 W, particularly preferably at least 10,000 W per phase.

[0026] A clutch device can be a manual, semi-automatic or automatic clutch device. Preferably, a clutch device can be a disconnect clutch. The clutch device can be an e-clutch. An e-clutch is an automated clutch device that is electrically controlled and actuated. The clutch device can also be a dual clutch or a multi-plate clutch. Furthermore, it is possible for the clutch device to be frictionally engaged and / or positively engaged. According to a further preferred development of the invention, it can also be provided that the clutch device can be actuated by means of a hydraulic release system. A hydraulic release system generally has a master cylinder which transmits the pressure generated in the master cylinder to the slave cylinder, preferably a central release cylinder, via a hydraulic pressure line. The hydraulic pressure can in particular also be transmitted by means of a so-calledA power pack can be provided, which consists of a hydraulic pump and a hydraulic pressure accumulator that can be pressurized by the hydraulic pump. In this case, a pressure chamber of the slave cylinder can also be hydraulically pressurized, for example, by a master cylinder controlled by a control unit via an electric motor, or by a hydraulic pump, possibly with the assistance of a pressure accumulator. A so-called power pack can advantageously be used, which switches several pressure circuits via a central hydraulic pump and corresponding valves.

[0027] The slave cylinder, which in the present case is designed in particular as a central release cylinder, transmits the hydraulic pressure to a clutch device in the hydraulic release system, preferably by means of an axially displaceable piston, for example in order to form a frictional engagement and to close the friction clutch or to open it when the frictional engagement is released.

[0028] The hydraulic clutch release system thus particularly preferably actuates a clutch device hydraulically by applying pressure to the master cylinder. This can be done—as explained—either by means of an actuator controlled by a control unit or by manual actuation by the driver.

[0029] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0030] According to an advantageous embodiment of the invention, the braking device can be encapsulated in a housing. The advantage of this embodiment is that wear particles from the braking device cannot enter the environment through the encapsulated housing, thus preventing environmental and health impacts from brake wear particles during axle drive train operation.

[0031] According to a further preferred development of the invention, it can also be provided that the braking device, the transmission arrangement, the electric motor, the first clutch device, and the second clutch device form a structural unit. This can provide a prefabricated functional module that can then be integrated into a vehicle with comparatively little assembly effort.

[0032] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the axle drive train has a control unit that is connected to the braking device, the first clutch device, and the second clutch device and is configured such that the control unit can place the axle drive train into a plurality of different operating states by coupling and decoupling the clutch devices, and by releasing and actuating the braking device. The advantageous effect of this embodiment is based on the fact that the various operating modes that the axle drive train allows due to its architecture can be provided by the electronic control.

[0033] According to a further particularly preferred embodiment of the invention, it can be provided that the control unit is configured in such a way that for the design alternative a( of the axle drive train, it i. into a first operating state in which the first coupling device and the second coupling device are in a decoupled state and the braking device is released, and / or ii. into a second operating state in which the first coupling device is in a disengaged state and the second coupling device is in an engaged state and the braking device is released, and / or iii. into a third operating state in which the first coupling device and the second coupling device are in a coupled state and the braking device is actuated, and / or iv. into a fourth operating state in which the first coupling device is in a disengaged state and the second coupling device is in a coupled state and the braking device is actuated, or the control unit is configured in such a way that it, for the embodiment alternative b) of the axle drive train, i. into a first operating state in which the first coupling device and the second coupling device are in a decoupled state and the braking device is released, and / or ii. into a second operating state in which the first coupling device and the second coupling device are in a coupled state and the braking device is released, and / or iii. into a third operating state in which the first coupling device and the second coupling device are in a coupled state and the braking device is actuated, and / or iv. into a fourth operating state in which the first coupling device is in a disengaged state and the second coupling device is in an engaged state and the braking device is actuated, and / or v. into a fifth operating state in which the first coupling device is in a coupled state and the second coupling device is in a disengaged state and the braking device is actuated.

[0034] In the first operating states (i) of the design alternatives a) and b), the axle drive train is put into a so-called sailing mode, in which the electric machine is decoupled from the vehicle wheel in order to avoid corresponding resistances generated by the electric machine.

[0035] A coasting process of the vehicle means a driving state of the vehicle, in particular a coasting, in which a vehicle wheel is decoupled at least from the electric machine of the drive train by the corresponding clutch device or devices being opened, whereby in particular lost torque of the electric machine and possibly the braking device are decoupled from the vehicle wheel and thus the energy efficiency of the motor vehicle can be increased and energy consumption reduced. During the coasting process, the electric machine can be switched off or in operation. A coasting process can thus, for example, bring about a reduction in the speed of the motor vehicle without actively braking a vehicle wheel, for example due to the air and rolling resistance of the motor vehicle.

[0036] In the second operating state (ii) of the first embodiment alternative a) and the second embodiment variant b), a “standard” driving mode can be set in which the electric machine drives the vehicle wheel in engine mode and / or brakes it in generator mode (recuperation).

[0037] In the third operating state (iii) of the first embodiment variant a) and the second embodiment variant b), the braking device is coupled to the vehicle wheel, thus achieving "mechanical" braking of the vehicle wheel. The electric motor can be switched to generator mode, thus supporting the braking effect of the mechanical braking device.

[0038] In this third operating state, the electric machine can also be put into motor operation, for example in order to realize a thermal heating and / or cooling circuit in the vehicle during driving operation via increased frictional heat of the braking device, in particular for air conditioning the passenger compartment.

[0039] In the fourth operating state (iv) of the first embodiment a) and the second embodiment, a parking heater function can be implemented, for example, when the vehicle is stationary. In this function, the electric motor drives the braking device during engine operation, generating corresponding frictional heat. This frictional heat can then be utilized, for example, via a thermal heating and / or cooling circuit in the vehicle, in particular for air conditioning the passenger compartment.

[0040] It is understood that the axle drive train can be placed in one and / or more of these operating states.

[0041] Furthermore, the invention can also be further developed such that in the third operating state of the axle drive train, the electric machine is in a torque-generating operating state in order to realize some of the above operating modes, such as an auxiliary heating function when the vehicle is stationary.

[0042] According to the invention, it is also provided that the braking device is connected to a fluid circuit, by means of which heat generated by the braking device during operation of the axle drive train can be dissipated. This can enable a simplification of the thermal management system within the vehicle, for example, by eliminating a PTC heating element.

[0043] The object of the invention is further achieved by a method for controlling an axle drive train of a motor vehicle, comprising an electric machine which can be coupled to at least one vehicle wheel of the motor vehicle in a torque-transmitting manner, and a transmission arrangement arranged in the torque flow between the vehicle wheel and the electric machine, as well as a braking device by means of which the vehicle wheel can be braked, wherein a) a first coupling device is arranged in the torque flow between the electric machine and the braking device, by means of which the braking device can be coupled into and out of the torque flow, and a second coupling device is arranged in the torque flow between the electric machine and the transmission arrangement, by means of which the transmission arrangement can be coupled into and out of the torque flow, or b) a first coupling device is arranged in the torque flow between the electric machine and the braking device, by means of which the braking device can be coupled into and out of the torque flow, and a second coupling device is arranged in the torque flow between the braking device and the transmission arrangement, by means of which the transmission arrangement can be coupled into and out of the torque flow, wherein the axle drive train has a control unit which is connected to the braking device, the first coupling device and the second coupling device and is configured such that the control unit can place the axle drive train into a plurality of different operating states by coupling and uncoupling the coupling devices, and by releasing and actuating the braking device, wherein the control unit is configured such that for the design alternative a of the axle drive train, it i. into a first operating state in which the first coupling device and the second coupling device are in a decoupled state and the braking device is released, and / or ii. into a second operating state in which the first coupling device is in a disengaged state and the second coupling device is in an engaged state and the braking device is released, and / or iii. into a third operating state in which the first coupling device and the second coupling device are in a coupled state and the braking device is actuated, and / or iv. into a fourth operating state in which the first coupling device is in a disengaged state and the second coupling device is in an engaged state and the braking device is actuated, or i. the control unit is configured in such a way that for the design alternative b of the axle drive train, it ii. into a first operating state in which the first coupling device and the second coupling device are in a disengaged state and the braking device is released, and / or iii. into a second operating state in which the first coupling device and the second coupling device are in a coupled state and the braking device is released, and / or iv. into a third operating state in which the first coupling device and the second coupling device are in a coupled state and the braking device is actuated, and / or v. into a fourth operating state in which the first coupling device is in a disengaged state and the second coupling device is in a coupled state and the braking device is actuated, and / or vi. into a fifth operating state in which the first coupling device is in an engaged state and the second coupling device is in a disengaged state and the braking device is actuated.

[0044] The object of the invention can also be achieved by a computer program product stored on a machine-readable carrier, or computer data signal embodied by an electromagnetic wave, with a computer program code suitable for carrying out a method according to claim 7.

[0045] Finally, the object of the invention can also be achieved by a control unit for controlling an axle drive train of a motor vehicle, wherein the control unit comprises a processor and a memory containing a computer program code, wherein the memory and the computer program code are configured, with the processor, to cause the control unit to carry out a method according to claim 7.

[0046] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0047] It shows: Fig. 1 shows a first embodiment of an axle drive train in a first operating state in a schematic block diagram, Fig. 2 shows a first embodiment of an axle drive train in a second operating state in a schematic block diagram, Fig. 3 shows a first embodiment of an axle drive train in a third operating state in a schematic block diagram, Fig. 4 shows a first embodiment of an axle drive train in a fourth operating state in a schematic block diagram, Fig. 5 shows a second embodiment of an axle drive train in a first operating state in a schematic block diagram, Fig. 6 shows a second embodiment of an axle drive train in a second operating state in a schematic block diagram, Fig. 7 shows a second embodiment of an axle drive train in a third operating state in a schematic block diagram, Fig. 8 shows a second embodiment of an axle drive train in a fourth operating state in a schematic block diagram, Fig. 9 shows a second embodiment of an axle drive train in a fifth operating state in a schematic block diagram,

[0048] The Fig. 1-9 show an electrically operable axle drive train 1 of a motor vehicle, comprising an electric machine 3 which can be coupled to at least one vehicle wheel 4 of the motor vehicle in a torque-transmitting manner, and a transmission arrangement 5 arranged in the torque flow between the vehicle wheel 4 and the electric machine 3, as well as a braking device 6 by means of which the vehicle wheel 4 can be braked.

[0049] In the first embodiment of the axle drive train 1 (alternative embodiment a)), which in different operating states in the Fig. As shown in Figures 1-4, a first clutch device 7 is arranged in the torque flow between the electric machine 3 and the braking device 6, by means of which the braking device 6 can be coupled into and out of the torque flow. Additionally, a second clutch device 8 is arranged in the torque flow between the electric machine 3 and the transmission arrangement 5, by means of which the transmission arrangement 5 can be coupled into and out of the torque flow.

[0050] In the second embodiment of the axle drive train 1 (alternative embodiment b)), which is shown in different operating states in the Fig. 5-9, a first clutch device 7 is arranged in the torque flow between the electric machine 3 and the braking device 6, by means of which the braking device 6 can be coupled into and out of the torque flow, and furthermore a second clutch device 8 is arranged in the torque flow between the braking device 6 and the transmission arrangement 5, by means of which the transmission arrangement 5 can be coupled into and out of the torque flow.

[0051] From the Fig. 1-9 it is also apparent that the braking device 6 in both embodiments is encapsulated in a housing 9. In the first embodiment of the Fig. 1-4, the braking device 6 is accommodated in a separate housing 9 associated with the braking device 6, which can be connected, for example, to the motor housing 12 of the electric machine 3. In the second embodiment of the Fig. 5-9, the housing 9 encloses the electric machine 3, the gear arrangement 5 and the braking device 6. It is understood that the braking device 6 can also have a separate housing for encapsulation in this embodiment, but this is not shown in the figures.

[0052] In the shown embodiments of the Fig. 1-9, the braking device 6, the transmission arrangement 5, the electric machine 3, the first clutch device 7 and the second clutch device 8 form a structural unit 10 and can thus be supplied as a module and mounted on the vehicle.

[0053] In the embodiments shown, the braking device 6 is connected to a fluid circuit 22, by means of which heat generated by the braking device 6 during operation of the axle drive train 1 can be dissipated, for example in order to cool the braking device 6 and / or to use the dissipated heat for air conditioning the passenger compartment of the vehicle.

[0054] In both embodiments, the axle drive train 1 has a control unit 11, which is connected to the braking device 6, the first coupling device 7, and the second coupling device 8 and is configured such that the control unit 11 can place the axle drive train 1 into a plurality of different operating states by coupling and decoupling the coupling devices 7, 8 and by releasing and actuating the braking device 6. The control unit 11 comprises a processor 23 and a memory 24 containing computer program code, wherein the memory 24 and the computer program code are configured, with the processor 23, to cause the control unit 11 to carry out a method that sets the various operating states described below.

[0055] The Fig. Figure 1 shows a first operating state 13, into which the control unit 11 has placed the axle drive train 1 for embodiment alternative a). In this first operating state 13, the first clutch device 7 and the second clutch device 8 are in a disengaged state. The braking device 6 is released, allowing the axle drive train 1 to coast.

[0056] In the Fig. 2 is the one from the Fig. 1 known axle drive train is placed in a second operating state 14, in which the first clutch device 7 is in a disengaged state and the second clutch device 8 is in an engaged state and the braking device 6 is still released, so that regular driving operation or regenerative braking can be effected, depending on whether the electric machine 3 is in a motor or generator operating state.

[0057] In a third operating state 15, which is in the Fig. 3, the first clutch device 7 and the second clutch device 8 are in a coupled state. Furthermore, the brake device 6 is actuated, so that the brake device 6 is coupled to the vehicle wheel 4 and a "mechanical" braking of the vehicle wheel is realized. The electric machine 3 can be put into generator mode and thus support the braking effect of the mechanical brake device 6. In this third operating state 15, the electric machine 3 can also be put into motor mode, for example in order to realize a thermal heating and / or cooling circuit (fluid circuit 22) in the vehicle, in particular for air conditioning the passenger compartment, via increased frictional heat of the brake device 6 during driving operation.

[0058] In the Fig. 4, the axle drive train 1 is placed in a fourth operating state 16, in which the first clutch device 7 is in a disengaged state and the second clutch device 8 is in an engaged state, and the braking device 6 is actuated. In the fourth operating state 16 of the first embodiment, for example, when the vehicle is stationary, a parking heater function can be implemented, in which the electric machine 3, in engine mode, drives the braking device 6, generating corresponding frictional heat. This frictional heat can then be used, for example, via a thermal heating and / or cooling circuit (fluid circuit 22) in the vehicle, in particular for air conditioning the passenger compartment.

[0059] The Fig. Figure 5 shows a first operating state 17 into which the control unit 11 has placed the axle drive train 1 for embodiment alternative b). In this first operating state 17, the first clutch device 7 and the second clutch device 8 are in a disengaged state, and the brake device 6 is released. This realizes a coasting operation of the axle drive train 1.

[0060] In the Fig. 6 is the axle drive train from the Fig. 5 is placed into a second operating state 18, in which the first clutch device 7 and the second clutch device 8 are in an engaged state and the braking device 6 is released. This allows for regular driving operation or regenerative braking, depending on whether the electric machine 3 is in a motor or generator operating state.

[0061] In a third operating state 19, which is in the Fig. 7, the first clutch device 7 and the second clutch device 8 are in a coupled state and the brake device 6 is actuated, so that the brake device 6 is coupled to the vehicle wheel 4 and a "mechanical" braking of the vehicle wheel 4 is realized. The electric machine 3 can be put into generator mode and thus support the braking effect of the mechanical brake device 6. In this third operating state 15, the electric machine 3 can also be put into motor mode, for example in order to realize a thermal heating and / or cooling circuit (fluid circuit 22) in the vehicle, in particular for air conditioning the passenger compartment, via increased frictional heat of the brake device 6 during driving operation.

[0062] In the Fig. 8, the axle drive train 1 was placed in a fourth operating state 20, in which the first clutch device 7 is in a disengaged state and the second clutch device 8 is in a coupled state and the braking device 6 is actuated, so that the vehicle wheel 4 can be braked solely by the braking device 6, without the braking device 6 being additionally subjected to a drag torque of the electric machine 3.

[0063] The second embodiment of the axle drive train 1 can also be set to a fifth operating state 21, which in the Fig.9, in which the first clutch device 7 is in an engaged state and the second clutch device 8 is in a disengaged state, and the braking device 6 is actuated. In the fifth operating state 21 of the second embodiment, for example, when the vehicle is stationary, a parking heater function can be implemented, in which the electric machine 3, in engine mode, drives the braking device 6, generating corresponding frictional heat. This frictional heat can then be used, for example, via a thermal heating and / or cooling circuit (fluid circuit 22) in the vehicle, in particular for air conditioning the passenger compartment.

[0064] The terms "radial," "axial," "tangential," and "circumferential direction" used in this application always refer to the rotational axis of a rotor of the electric machine. The terms "left," "right," "top," "bottom," "above," and "below" serve only to clarify which areas of the figures are currently being described in the text. The later embodiment of the invention can also be arranged differently. Furthermore, the invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be regarded as limiting, but as explanatory. The following patent claims are to be understood in such a way that a named feature is present in at least one embodiment of the invention. This does not exclude the presence of further features.If the patent claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a ranking. List of reference symbols 1 axle drive train 3 electric machine 4 vehicle wheel 5 Gear arrangement 6 Braking device 7 Coupling device 8 Coupling device 9 housings 10 units 11 Control unit 12 engine housing 13 Operating status 14 Operating status 15 Operating status 16 Operating status 17 Operating status 18 Operating status 19 Operating status 20 Operating status 21 Operating status 22 Fluid circuit 23 processor 24 storage

Claims

[1] Electrically operable axle drive train (1) of a motor vehicle, comprising an electric machine (3) which can be coupled to at least one vehicle wheel (4) of the motor vehicle in a torque-transmitting manner, and a transmission arrangement (5) arranged in the torque flow between the vehicle wheel (4) and the electric machine (3), as well as a braking device (6) by means of which the vehicle wheel (4) can be braked, wherein the braking device (6) is connected to a fluid circuit (22) by means of which heat generated by the braking device (6) during operation of the axle drive train (1) can be dissipated, and wherein a) a first coupling device (7) is arranged in the torque flow between the electric machine (3) and the braking device (6), by means of which the braking device (6) can be coupled into and out of the torque flow, and a second coupling device (8) is arranged in the torque flow between the electric machine (3) and the transmission arrangement (5), by means of which the transmission arrangement (5) can be coupled into and out of the torque flow, or b) a first coupling device (7) is arranged in the torque flow between the electric machine (3) and the braking device (6), by means of which the braking device (6) can be coupled into and out of the torque flow, and a second coupling device (8) is arranged in the torque flow between the braking device (6) and the transmission arrangement (5), by means of which the transmission arrangement (5) can be coupled into and out of the torque flow. [2] Axle drive train (1) according to claim 1,characterized by that the braking device (6) is encapsulated in a housing (9). [3] Axle drive train (1) according to claim 1 or 2, characterized by that the braking device (6), the transmission arrangement (5), the electric machine (3), the first clutch device (7) and the second clutch device (8) form a structural unit (10). [4] Axle drive train (1) according to one of the preceding claims, characterized by in that the axle drive train (1) has a control unit (11) which is connected to the braking device (6), the first coupling device (7) and the second coupling device (8) and is configured such that the control unit (11) can place the axle drive train (1) into a plurality of different operating states by coupling and decoupling the coupling devices (7, 8) and by releasing and actuating the braking device (6). [5] Axle drive train (1) according to claim 4, characterized by , that the control unit (11) is configured such that for the alternative design a) of the axle drive train (1) it i. into a first operating state (13) in which the first coupling device (7) and the second coupling device (8) are in a decoupled state and the braking device (6) is released, and / or ii. into a second operating state (14), in which the first coupling device (7) is in a decoupled state and the second coupling device (8) is in a coupled state and the braking device (6) is released, and / or iii. into a third operating state (15), in which the first coupling device (7) and the second coupling device (8) are in a coupled state and the braking device (6) is actuated, and / or iv. into a fourth operating state (16), in which the first coupling device (7) is in a disengaged state and the second coupling device (8) is in an engaged state and the braking device (6) is actuated, or the control unit (11) is configured such that for the alternative embodiment b) of the axle drive train (1) it i. into a first operating state (17) in which the first coupling device (7) and the second coupling device (8) are in a decoupled state and the braking device (6) is released, and / or ii. into a second operating state (18) in which the first coupling device (7) and the second coupling device (8) are in a coupled state and the braking device (6) is released, and / or iii. into a third operating state (19), in which the first coupling device (7) and the second coupling device (8) are in a coupled state and the braking device (6) is actuated, and / or iv. into a fourth operating state (20), in which the first coupling device (7) is in a decoupled state and the second coupling device (8) is in a coupled state and the braking device (6) is actuated, and / or v. into a fifth operating state (21), in which the first coupling device (7) is in a coupled state and the second coupling device (8) is in a decoupled state and the braking device (6) is actuated. [6] Axle drive train (1) according to claim 5, characterized bythat in the third operating state (15, 19) of the axle drive train (1) the electric machine (3) is in a torque-generating operating state. [7] Method for controlling an axle drive train (1) of a motor vehicle, comprising an electric machine (3) which can be coupled to at least one vehicle wheel (4) of the motor vehicle in a torque-transmitting manner, and a transmission arrangement (5) arranged in the torque flow between the vehicle wheel (4) and the electric machine (3), as well as a braking device (6) by means of which the vehicle wheel (4) can be braked, wherein a) a first coupling device (7) is arranged in the torque flow between the electric machine (3) and the braking device (6), by means of which the braking device (6) can be coupled into and out of the torque flow, and a second coupling device (8) is arranged in the torque flow between the electric machine (3) and the transmission arrangement (5), by means of which the transmission arrangement (5) can be coupled into and out of the torque flow, or b) a first coupling device (7) is arranged in the torque flow between the electric machine (3) and the braking device (6), by means of which the braking device (6) can be coupled into and out of the torque flow, and a second coupling device (8) is arranged in the torque flow between the braking device (6) and the transmission arrangement (5), by means of which the transmission arrangement (5) can be coupled into and out of the torque flow, wherein the axle drive train (1) has a control unit (11) which is connected to the braking device (6), the first coupling device (7) and the second coupling device (8) and is configured such that the control unit (11) can place the axle drive train (1) into a plurality of different operating states by coupling and decoupling the coupling devices (7, 8) and by releasing and actuating the braking device (6), wherein the control unit (11) is configured such that for the alternative embodiment a) of the axle drive train (1) it i. into a first operating state (13) in which the first coupling device (7) and the second coupling device (8) are in a decoupled state and the braking device (6) is released, and / or ii. into a second operating state (14), in which the first coupling device (7) is in a decoupled state and the second coupling device (8) is in a coupled state and the braking device (6) is released, and / or iii. into a third operating state (15), in which the first coupling device (7) and the second coupling device (8) are in a coupled state and the braking device (6) is actuated, and / or iv. into a fourth operating state (16), in which the first coupling device (7) is in a disengaged state and the second coupling device (8) is in an engaged state and the braking device (6) is actuated, or the control unit (11) is configured such that for the alternative embodiment b) of the axle drive train (1) it i. into a first operating state (17) in which the first coupling device (7) and the second coupling device (8) are in a decoupled state and the braking device (6) is released, and / or ii. into a second operating state (18) in which the first coupling device (7) and the second coupling device (8) are in a coupled state and the braking device (6) is released, and / or iii. into a third operating state (19), in which the first coupling device (7) and the second coupling device (8) are in a coupled state and the braking device (6) is actuated, and / or iv. into a fourth operating state (20), in which the first coupling device (7) is in a decoupled state and the second coupling device (8) is in a coupled state and the braking device (6) is actuated, and / or v. into a fifth operating state (21), in which the first coupling device (7) is in a coupled state and the second coupling device (8) is in a decoupled state and the braking device (6) is actuated. [8] A computer program product stored on a machine-readable medium or a computer data signal embodied by an electromagnetic wave, comprising a computer program code suitable for carrying out a method according to claim 7. [9] Control unit (11) for controlling an axle drive train (1) of a motor vehicle, wherein the control unit (11) comprises a processor (23) and a memory (24) containing a computer program code, wherein the memory (24) and the computer program code are configured, with the processor (23), to cause the control unit (11) to carry out a method according to claim 7.

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