Electric drive device for a motor vehicle and methods for operating such an electric drive device

Abstract

The invention relates to an electric drive device (10) for a motor vehicle, comprising a freewheel (18) which has an input element (20) and an output element (22) which are rotatable about a common freewheel axis of rotation (24) relative to a reference element (26), a first electric machine (28) which has a first stator (30) and a first rotor (32), a second electric machine (36) which has a second stator (38) and a second rotor (40) which is rotatable about a machine axis of rotation (42) relative to the second stator (38), and a vehicle axle (12) which has two vehicle wheels (14, 16) which can be driven by means of the first rotor (32) bypassing the freewheel (18) and bypassing the second rotor (40) and by means of the second rotor (40) via the freewheel (18) and bypassing the first rotor (32).

Description

[0001] The invention relates to an electric drive device for a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to a method for operating such an electric drive device according to the preamble of claim 2.

[0002] Such an electric drive device for a motor vehicle and such a method for operating such an electric drive device for a motor vehicle are, for example, already known from DE 20 2009 014 490 U1. The electric drive device has a freewheel which has an input element and an output element. The input element and the output element are rotatable about a common freewheel axis of rotation relative to a reference element such as a housing of the freewheel, in whose housing, for example, the input element and the output element are each at least partially arranged. The electric drive device also has a first electric machine which has a first stator and a first rotor. The electric drive device also has a second electric machine which has a second stator and a second rotor.The second rotor is rotatable about a machine axis relative to the second stator. The electric drive unit also includes a vehicle axle. This vehicle axle, also simply referred to as the axle, has two vehicle wheels, also simply referred to as wheels: a first vehicle wheel and a second vehicle wheel. The vehicle wheels of the vehicle axle can be driven by the first rotor, bypassing the freewheel and the second rotor. Furthermore, the vehicle wheels of the vehicle axle can be driven by the second rotor via the freewheel and bypassing the first rotor.

[0003] US 2017 / 0 282 752 A1 and US 2013 / 0 152 570 A1 each show an electric drive device with two electric machines that can be coupled together via a freewheel clutch.

[0004] The object of the present invention is to improve an electric drive device and a method of the type mentioned at the outset.

[0005] This problem is solved by an electric drive device having the features of claim 1 and by a method having the features of claim 2.

[0006] To improve an electric drive device of the type specified in the preamble of claim 1, the invention provides that, in a driving mode of the second electric machine, whose driving mode is designed to propel the motor vehicle in a forward direction by means of the second rotor, i.e., to propel the motor vehicle forward, the second stator drives the second rotor and thereby rotates it about the machine's axis of rotation relative to the second stator in a first direction of rotation. In the driving mode of the second electric machine, the second rotor drives the input element, whereby the second rotor rotates the input element about the freewheel axis of rotation in a first freewheel direction of rotation relative to the reference element.In the driving mode, the freewheel completely locks, preventing the input element from rotating at a higher speed than the output element around the freewheel axis in the first freewheel direction relative to the reference element. This prevents the input element from driving the output element, causing it to rotate around the freewheel axis in the first freewheel direction relative to the reference element. As a result, the input and output elements rotate at the same speed in the same freewheel direction relative to the reference element around the freewheel axis. The freewheel thus prevents, particularly automatically, the input element from rotating around the freewheel axis at a higher speed than the output element in the first freewheel direction by completely locking, particularly automatically.This allows the second electric machine, in its driving mode, to drive the vehicle wheels via its second rotor, thus propelling the vehicle forward, i.e., driving it in the forward direction. In other words, the freewheel prevents, specifically automatically and consistently, the input element from overtaking the output element in the first freewheel direction of rotation.

[0007] The freewheel, however, allows the output element to overtake the input element in the first freewheel direction of rotation. In other words, the freewheel, particularly its automatic function, allows the output element to rotate in the first freewheel direction around the freewheel axis of rotation at a higher speed than the input element relative to the reference element. Put another way, the freewheel enables the output element to rotate in the first freewheel direction, around the freewheel axis of rotation, and relative to the reference element, allowing the output element to rotate around the freewheel axis of rotation in the first freewheel direction at a higher speed than the input element. For this to occur, the freewheel, particularly its automatic function, does not lock. In other words, for this to occur, the freewheel, particularly its automatic function, opens completely. Regarding a situation or condition,In which or where the output element overtakes the input element in the first freewheel direction of rotation, which is made possible by the fact that the freewheel opens here, in particular independently and / or completely, and thus does not lock, this occurs, for example, when neither the first stator drives the first rotor nor the second stator drives the second rotor, and the motor vehicle (also simply referred to as a vehicle) rolls forward, causing the vehicle wheels to rotate and thereby drive, for example, the output element, such that the vehicle wheels rotate the output element around the freewheel axis of rotation in the first freewheel direction of rotation relative to the reference element. Furthermore, such a situation and condition can occur if, for example, the second rotor, and thus the second electric machine, drives the vehicle wheels in such a way that the motor vehicle is driven forward, that is, in its forward direction of travel.so that the vehicle wheels drive the output element and thereby rotate it around the freewheel axis in the first freewheel direction of rotation relative to the reference element, while the second rotor, and thus the input element, is not driven by the second stator, or while the second stator drives the second rotor in such a way that the second rotor rotates the input element around the freewheel axis of rotation in the first freewheel direction of rotation relative to the reference element, but at a speed that is lower than the speed at which the output element rotates around the freewheel axis of rotation relative to the reference element in the first freewheel direction of rotation due to the vehicle wheels rotating it around the freewheel axis of rotation relative to the reference element. Since the freewheel, especially on its own, allows the output element to overtake the input element in the first freewheel direction of rotation, it can be avoided that then,When a vehicle is moving or rolling forward, the wheels drive the output element and thereby rotate it around the freewheel axis in the first freewheel direction relative to the reference element. This causes the wheels to excessively drag the input element and, via the input element, the second rotor. This allows for particularly efficient operation of the drive system. Since the freewheel is used for this purpose, the need for complex, heavy, bulky, and expensive coupling devices can be avoided.

[0008] Furthermore, according to the invention, it is provided that in reverse operation of the second electrical machine, in which the second stator drives the second rotor and thereby rotates around the machine's axis of rotation relative to the second stator in a second rotor direction opposite to the first rotor direction of rotation, the freewheel locks, in particular automatically, partially and slipping.In reverse operation of the second electric machine, the freewheel allows the input element to be driven by the second rotor in the second rotor direction around the machine axis of rotation relative to the second stator, such that the input element is rotated around the freewheel axis in a second freewheel direction opposite to the first freewheel direction relative to the reference element and, in particular, also relative to the output element, while a torque can be transmitted or is transmitted between the input element and the output element, which is, for example, greater than when the freewheel is open and when the freewheel is completely locked.This torque thus opposes, for example, the rotation of the input element around the freewheel axis in the second freewheel direction relative to the reference element, and therefore, via the input element, the rotation of the second rotor around the machine axis in the second rotor direction relative to the second stator. For example, it can be provided that in reverse operation of the second electric machine, the first stator drives the first rotor in such a way that the first rotor drives the vehicle wheels in such a way that the vehicle is driven forward, i.e., propelled in the forward direction, whereby, for example, the vehicle wheels rotate the output element around the freewheel axis in the first freewheel direction relative to the reference element and, in particular, relative to the input element.By partially and thus intermittently locking the freewheel, the second electric machine, in particular the second rotor, can, for example, brake the vehicle wheels and thus the vehicle itself during reverse operation, or counteract the rotation of the vehicle wheels of a forward-moving or rolling vehicle. In other words, the freewheel is designed such that when, during reverse operation, the input element is rotated relative to the reference element around the freewheel axis of rotation in the second freewheel direction by means of the second rotor, and thus rotated backward, the output element, which is rotating forward and thus around the freewheel axis of rotation and relative to the reference element in the first freewheel direction, is braked by the backward-rotating input element.For example, the input element is an input shaft of the freewheel, or the input element of the freewheel is, in particular, permanently and non-rotatably connected to an input shaft. For example, the output element of the freewheel is an output shaft, or the output element is, in particular, permanently and non-rotatably connected to an output shaft. The input element, and thus, for example, the input shaft, can be driven by the second rotor. In particular, for example, the input element can be driven by the second rotor via the input shaft. For example, the input element is, in particular, permanently and non-rotatably connected to the second rotor. In particular, the second rotor can be, in particular, permanently and non-rotatably connected to the input shaft and, via this, in particular, permanently and non-rotatably connected to the input element. For example, the second rotor is arranged coaxially with the input element.For example, the second rotor is arranged coaxially to the input shaft and coaxially to the input element. In particular, the vehicle wheels can be driven by the output element via the output shaft, especially to propel the vehicle in the forward direction.

[0009] To improve a method of the type specified in the preamble of claim 2, it is provided according to the invention that in a driving operation of the second electric machine, the driving operation of which is intended to drive the motor vehicle in a forward direction of travel of the motor vehicle, also referred to simply as the vehicle, by means of the second rotor, the second rotor is driven by means of the second stator in such a way that the second rotor is rotated about the machine axis of rotation relative to the second stator in a rotor direction of rotation, and the input element is driven by the second rotor and thereby rotated about the freewheel axis of rotation in a first freewheel direction of rotation relative to the reference element.In the driving mode, the freewheel locks completely, particularly automatically, thereby preventing the input element from rotating at a higher speed than the output element in the first freewheel direction relative to the reference element around the freewheel axis. This ensures that the output element is driven and carried along by the input element and thus rotated in the first freewheel direction relative to the reference element around the freewheel axis. The input element and output element then rotate at the same speed in the same first freewheel direction relative to the reference element around the freewheel axis. Furthermore, the vehicle wheels are driven by the second rotor via the freewheel.

[0010] The freewheel allows the output element to rotate at a higher speed than the input element in the first freewheel direction relative to the reference element. In other words, the freewheel allows the output element to overtake the input element in the first freewheel direction.This prevents the vehicle wheels from dragging the input element and, via the input element, the second rotor when the vehicle is driven or rolling forward, especially if the second rotor is not driven by the second stator or, for example, if the second rotor is driven by the second stator in such a way that the second rotor rotates around the machine axis of rotation in the first rotor direction of rotation such that the input element is rotated relative to the reference element around the freewheel axis of rotation in the first freewheel direction of rotation at a speed which is lower than the speed at which the output element rotates around the freewheel axis of rotation in the first freewheel direction of rotation relative to the reference element.In other words, if the second electric machine is stationary, i.e., if the second rotor is not driven by the second stator, or if the second rotor is only slowly rotated by the second stator, i.e., at a low speed, around the machine's axis of rotation in the first rotor direction, such that the input element rotates around the freewheel axis relative to the reference element in the first freewheel direction at a speed lower than the speed at which the output element rotates around the freewheel axis relative to the reference element in the first freewheel direction, then the freewheel does not lock; in other words, the freewheel opens, in particular automatically and / or completely.

[0011] In the method according to the invention, the first electric machine is operated in recuperation mode, whereby, while the vehicle is decelerating and the first electric machine is operating as a generator, the first rotor is driven by the vehicle wheels, while the second electric machine is operated in reverse mode, in which the second rotor is driven by the second stator such that the second rotor rotates around the machine's axis of rotation relative to the second stator in a second direction of rotation opposite to the first rotor's direction of rotation. This, for example, drives the input element by means of the second rotor such that the input element is rotated by the second rotor around its freewheel axis of rotation in a second freewheel direction of rotation opposite to the first freewheel direction of rotation relative to the reference element and preferably also relative to the input element.In reverse operation, the freewheel, in particular independently, only partially locks and thus slips, allowing the input element to be rotated around the freewheel axis of rotation in the second freewheel direction of rotation relative to the reference element and in particular also relative to the input element, especially while a torque can be transmitted or is transmitted between the input element and the output element, which is, for example, greater than in a state in which the freewheel does not lock, i.e., opens completely.Thus, for example, the torque opposes the rotation of the input element around the freewheel axis in the second freewheel direction relative to the reference element and preferably also relative to the input element, so that, for example, the torque opposes the rotation of the second rotor around the machine axis in the second rotor direction relative to the second stator.

[0012] The invention is based on the following findings and considerations: The motor vehicle has an electrical energy storage device, also referred to as a battery, in which electrical energy, particularly electrochemically, is stored. The stored electrical energy can supply the respective electric motor. At particularly cold temperatures during operation, it is advantageous for the battery's lifespan (also referred to as battery service life), usable performance, and usable energy content to warm the battery to a desired operating temperature. This warming is promoted by maintaining as high a current as possible in the electric currents (also referred to as battery currents) that are, for example, drawn from the battery and supplied to the electric motors and / or supplied back to the battery.This can be achieved by the invention because the second electric machine operates in reverse mode while the first electric machine operates in recuperation mode. A further insight underlying the invention is that under certain driving conditions, the battery can absorb little or no power from the electric machines via recuperation, for example, when the battery is very cold, very hot, or fully charged. In such cases, a service brake, such as a friction brake, must be used to decelerate the vehicle. Consequently, the friction brake must be dimensioned accordingly.The invention makes it possible to operate the first electric machine in recuperation mode and simultaneously the second electric machine in reverse mode, thereby enabling the vehicle to be sufficiently decelerated without the need for a friction brake. Furthermore, it advantageously allows for the realization of high electrical currents, which are supplied by and / or fed to the battery, thus enabling the battery to be heated effectively and efficiently.

[0013] Since the vehicle wheels can be driven by the second electric machine via the freewheel, the second electric machine is also referred to as a disengageable or decoupled electric machine. The first electric machine is also referred to as a coupled or non-disengaged electric machine.

[0014] Since the freewheel only partially locks in reverse operation, allowing slippage between the input and output elements, a unidirectional increase in resistance is achieved or can be achieved through the freewheel. This means that a deliberately high resistance exists in the freewheel during reverse operation. Therefore, if, for example, the battery can only store a small amount of energy or no energy at all, while a high deceleration requirement exists, the decoupled electric machine can be driven against the direction of travel by electrical coupling with the other, first electric machine. This causes the non-decoupled electric machine to operate as a generator, effectively braking the drive torque, similar to recuperation. The decoupled electric machine then operates as a motor against the direction of travel.If the freewheeling resistance is increased, a braking torque can be applied to the decoupled electric motor at a constant speed. To maintain the speed, the motor torque of the decoupled electric motor is applied, thus enabling electrical coupling between the decoupled and the non-decoupled electric motors. The latter can then decelerate the vehicle without feeding electrical energy into the battery. In other words, the decoupled electric motor converts electrical energy into heat through the freewheeling resistance, with this electrical energy being supplied by the non-decoupled motor through deceleration, i.e., through recuperation.The freewheeling resistance can be reduced by hydrodynamic means, such as hydraulic bearings, by liquid or air cooling with appropriate ribbing or ventilation vanes, or by similar modifications opposite to the direction of rotation. The resulting increased losses would only be significant in normal operation when the vehicle is reversing. However, the disconnectable electric motor is not typically used to initiate reverse movement, except in cases of very high torque requirements at low speeds, where the proposed modifications would result in only a minor efficiency loss. The present invention enables continuous braking of the vehicle without the use of a friction brake under any operating conditions.This reduces the load on the vehicle's friction brakes and keeps particulate emissions advantageously low. This can lead to a reduction in the size of the friction brakes, resulting in cost and weight savings. Furthermore, the waste heat from the decoupled electric motor can be used for battery and interior temperature control.

[0015] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown individually in some figures, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0016] The drawing shows in the only Fig. 1 A schematic representation of an electric drive system for a motor vehicle.

[0017] The only Fig. Figure 1 shows a schematic representation of an electric drive unit 10, also referred to as an electric drive system, of a motor vehicle, also referred to simply as a vehicle, which is preferably designed as a motor car, in particular as a passenger car. In its fully manufactured state, the motor vehicle has, in particular, exactly two vehicle axles, also referred to simply as axles, namely a first vehicle axle and a second vehicle axle. The first vehicle axle is in Fig. 1 identifiable and designated 12. The vehicle axle 12 is a component of the electric drive unit 10. Each vehicle axle has, in particular, exactly two vehicle wheels, also simply referred to as wheels. The respective vehicle wheels of each vehicle axle are arranged on opposite sides of the vehicle in the transverse direction of the vehicle. The vehicle wheels are ground contact elements by means of which the vehicle can be supported or is supported downwards against a ground in the vertical direction of the vehicle. If the vehicle is driven along the ground while it is supported downwards in the vertical direction by the ground contact elements, the ground contact elements roll, in particular directly, along the ground. The vehicle wheels of the vehicle axle 12 are in Fig. 1 is recognizable and labelled 14 and 16.

[0018] The electric drive unit 10 has a freewheel 18, which comprises an input element 20 and an output element 22. The input element 20 and the output element 22 are also referred to as elements or freewheel elements. The freewheel elements are arranged coaxially to each other and are rotatable about a freewheel axis of rotation 24 common to the freewheel elements relative to a reference element 26 of the drive unit 10. For example, the reference element 26 is a housing in which, for example, the freewheel 18 is at least partially arranged.

[0019] The drive unit 10 comprises a first electric machine 28, which has a first stator 30 and a first rotor 32. The rotor 32 can be driven by means of the stator 30 and is thus rotatable about a rotor axis 34 relative to the stator 30. The drive unit 10 comprises a second electric machine 36, which has a second stator 38 and a second rotor 40. The rotor 40 can be driven by means of the stator 38 and is thus rotatable about a machine axis 42 relative to the stator 38. It can be seen that the freewheeling elements and the rotor 40 are all arranged coaxially with each other, so that the machine axis 42 coincides with the freewheel axis 24. Furthermore, in the Fig. In the embodiment shown in Figure 1, the rotor 40 is, in particular, permanently and non-rotatably connected to the input element 20. This allows the input element 20 to be driven by the rotor 40 and thus rotatable about the machine axis of rotation 42 or the freewheel axis of rotation 24 relative to the reference element 26 and relative to the stator 38.

[0020] It can be seen that the vehicle wheels 14 and 16 can be driven by the first rotor 32, bypassing the freewheel 18 and the second rotor 40. Furthermore, the vehicle wheels 14 and 16 can be driven by the second rotor 40 via the freewheel 18 and bypassing the first rotor 32. The vehicle axle 12, and thus the drive unit 10, also has a differential gear 44, also referred to simply as a differential, through which the vehicle wheels 14 and 16 can be driven by the respective rotors 32 and 40. Thus, the vehicle wheels 14 and 16 can be driven by the rotor 40 via the differential gear 44 and via the freewheel 18 and bypassing the rotor 32, and the vehicle wheels 14 and 16 can be driven by the rotor 32 via the differential gear 44 and bypassing the rotor 40 and bypassing the freewheel 18.

[0021] The differential gear 44 has an input element 46, which is designed, for example, as a first gear. By driving the input element 46, output elements 48 and 50 of the differential gear 44 can be driven, whereby the vehicle wheel 14 can be driven by driving the output element 48 and the vehicle wheel 16 can be driven by driving the output element 50.

[0022] A first rotor wheel 52, which is, for example, a second gear, is associated with the rotor 32. For example, the input element 46 and the first rotor wheel 52 are in, in particular, permanent engagement with each other. In this case, the rotor wheel 52 is, in particular, permanently, connected to the rotor 32 in a rotationally fixed manner, so that the rotor wheel 52 can be driven by the rotor 32 and is thus rotatable about the machine's axis of rotation 42 relative to the stator 30 and relative to the reference element 26. By driving the rotor wheel 52, the rotor wheel 52 can drive the input element 46, whereby the output elements 48 and 50 can be driven by driving the input element 46. A second rotor wheel 54, which is, for example, designed as a third gear, is associated with the rotor 40. For example, the rotor wheel 54 and the input element 46 are in, in particular, permanent engagement with each other. It can be seen that the rotor wheel 52 is arranged coaxially to the rotor 32.Furthermore, the rotor 40, the freewheel elements, and the rotor wheel 54 are all arranged coaxially. In this case, the rotor wheel 54 is permanently connected to the output element 22 in a rotationally fixed manner, so that the rotor wheel 54 can rotate about the machine axis of rotation 42 and about the freewheel axis of rotation 24 relative to the stator 38 and relative to the reference element 26. By driving the output element 22, the rotor wheel 54 can be driven and thus rotated about the machine axis of rotation 42 and the freewheel axis of rotation 24 relative to the reference element 26. By driving the rotor wheel 54, the input element 46 can be driven.

[0023] The motor vehicle, in particular the drive unit 10, can contain a device also referred to as a battery, in Fig.1. An electrical energy storage device (not shown) in which electrical energy, in particular electrochemical energy, is to be stored or stored. The electrical energy stored in the battery can, for example, supply the respective electric machine 28, 36, in order to operate the respective electric machine 28, 36 in motor mode and thus as an electric motor. For example, in order to drive the vehicle wheels 14 and 16 by means of the electric machine 28 and thereby rotate them in such a way that the vehicle is driven forward, i.e., propelled in a forward direction, the stator 30 drives the rotor 32 in such a way that the rotor 32 is rotated in a first direction of rotation about the rotor axis 34 relative to the stator 30.For example, to drive the vehicle wheels 14 and 16 using the electric machine 28, and thus rotate them in such a way that the vehicle is driven in reverse, i.e., driven in a reverse direction opposite to the forward direction of travel, the stator 30 drives the rotor 32 such that the rotor 32, and thus the rotor wheel 52, is rotated around the rotor axis 34 in a second direction of rotation opposite to the first. To drive the rotor 32 using the stator 30, the electric machine 28 is operated in its motor mode and thus supplied with electrical energy from the battery. The electric machine 28 can also be operated in recuperation mode. In recuperation mode, the rotating vehicle wheels 14 and 16 drive the rotor 32 via the differential gear 44 and the rotor wheel 52, causing the rotor 32 to rotate around the rotor axis 34 relative to the stator 30.In recuperation mode, the vehicle wheels 14 and 16 rotate, for example, because the vehicle rolls, particularly forwards. Thus, in recuperation mode, the vehicle's kinetic energy can be converted into electrical energy by the electric machine 28, which can be provided or is provided by the electric machine 28. Therefore, in its recuperation mode, the electric machine 28 operates as a generator.

[0024] For example, to rotate the vehicle wheels 14 and 16 using the electric machine 36 in such a way that the vehicle is driven forward, i.e., propelled in its forward direction, the electric machine 36 is operated in a driving mode, in which the stator 38 drives the rotor 40 such that the rotor 40 is rotated about the machine axis of rotation 42 in a first rotor direction relative to the stator 38. This rotates the input element 20 and the freewheel axis of rotation 24 relative to the reference element 26 in a first freewheel direction. The electric machine 36 can also be operated in reverse mode, in which the stator 38 drives the rotor 40 such that the rotor 40 is rotated about the machine axis of rotation 42 in a second rotor direction opposite to the first rotor direction.This causes the input element 20 to rotate relative to the reference element 26 about the freewheel axis 24 in a second freewheel direction opposite to the first freewheel direction. In both the driving and reverse operation, the electric machine 36 operates in its motor mode, in which it is supplied with electrical energy. In the driving mode, for example, the electrical energy supplied to the electric machine 36 comes from the battery. In the reverse operation of the electric machine, the electrical energy supplied to the electric machine 36 does not come from the battery, but is provided by the electric machine 28 in its recuperation mode and supplied to the electric machine 36, bypassing the battery.

[0025] The freewheel 18 allows the output element 22 to rotate at a higher speed than the input element 20 in the first freewheel direction relative to the reference element 26. Thus, the freewheel 18 allows the output element 22 to overtake the input element 20 in the first freewheel direction. However, the freewheel 18 prevents the input element 20 from overtaking the output element 22 in the first freewheel direction.This results in the following in particular: In the driving mode of the second electric machine 36, whose driving mode is intended to drive the vehicle wheels 14 and 16 by means of the rotor 40 in such a way that the vehicle is driven in the forward direction by means of the rotor 40 and thus propelled forward, the second rotor 40 is driven by means of the second stator 38 in such a way that the second rotor 40 is rotated about the machine axis of rotation 42 relative to the second stator 38 in the first rotor direction of rotation, whereby the input element 20 is rotated in the first freewheel direction of rotation about the freewheel axis of rotation 24 relative to the reference element 26. This means that in the driving mode of the second electric machine 36, the input element 20 is driven by the second rotor 40 and thereby becomes straight about the freewheel axis of rotation 24 in the first freewheel direction of rotation relative to the reference element 26.In the driving mode, the freewheel 18 locks completely, particularly automatically, thereby preventing the input element 20 from rotating at a higher speed than the output element 22 in the first freewheel direction relative to the reference element 26 about the freewheel axis of rotation 24. As a result, the output element 22 is driven by the input element 20 and thus rotated in the first freewheel direction relative to the reference element 26 about the freewheel axis of rotation 24, and the input element 20 and the output element 22 rotate at the same speed in the same first freewheel direction relative to the reference element 26 about the freewheel axis of rotation 24. Furthermore, in the driving mode, the vehicle wheels 14 and 16 are driven by the second rotor 40 via the freewheel 18 and rotated, particularly forwards, in such a way that the vehicle is driven forwards, i.e., propelled in the forward direction of travel.

[0026] In order to decelerate the motor vehicle sufficiently without using a friction brake, i.e., to brake, and, in particular, to heat the battery effectively and efficiently at the same time, a method for operating the drive device 10 provides that the first electric machine 28 is operated in recuperation mode, whereby, while braking, i.e., decelerating the motor vehicle and operating the first electric machine 28 as the aforementioned generator, the first rotor 32 is driven by the rotating vehicle wheels 14 and 16 of the motor vehicle, which is rolling, in particular, forwards, while the second electric machine 36 is operated in its reverse mode.In reverse operation, the second rotor 40 is driven by means of the second stator 38 such that the second rotor 40 is rotated about the machine axis of rotation 42 relative to the second stator 38 in the second rotor direction opposite to the first rotor direction of rotation, whereby the input element 20 is rotated about the freewheel axis of rotation 24 in the second freewheel direction of rotation relative to the reference element 26 and in particular also relative to the output element 22, which is driven, for example, by the rotating vehicle wheels 14 and 16 of the vehicle rolling forward and thus in the forward direction of travel via the differential gear 44 and the rotor wheel 52 and is thereby rotated about the freewheel axis of rotation 24 in the first freewheel direction of rotation relative to the reference element 26 and also relative to the input element 20.In reverse operation, the freewheel 18, particularly when operating independently, only partially locks and thus slips, resulting in a torque being transmitted between the freewheel elements that is greater than in the state where the freewheel 18 is not locked, i.e., fully open. This leads, for example, to an advantageous heating of the electric machines 28 and 36, which then efficiently provide waste heat that can be used for effective and efficient battery heating. Reference symbol list 10 electric drive unit 12 vehicle axle 14 vehicle wheel 16 vehicle wheel 18 Freewheel 20 Entrance element 22 Output element 24 Freewheel pivot axis 26 Reference element 28 first electric machine 30 first stator 32 first rotor 34 Rotor axis 36 second electric machine 38 second stator 40 second rotor 42 Machine rotary axis 44 Differential gears 46 Entrance element 48 Starting element 50 output element 52 first rotor wheel 54 second rotor wheel

Claims

[1] Electric drive device (10) for a motor vehicle, comprising a freewheel (18) having an input element (20) and an output element (22) rotatable about a common freewheel axis of rotation (24) relative to a reference element (26), comprising a first electric machine (28) having a first stator (30) and a first rotor (32), comprising a second electric machine (36) having a second stator (38) and a second rotor (40) rotatable about a machine axis of rotation (42) relative to the second stator (38), and comprising a vehicle axle (12) having two vehicle wheels (14, 16) which can be driven by means of the first rotor (32) bypassing the freewheel (18) and bypassing the second rotor (40), and by means of the second rotor (40) via the freewheel (18) and bypassing the first rotor (32), characterized by , that: - in a driving operation of the second electric machine (36), the driving operation of which is intended to drive the motor vehicle via the vehicle wheels (14, 16) by means of the second rotor (40) in a forward direction of travel of the motor vehicle: ◯ the second stator (38) drives the second rotor (40) and thereby rotates around the machine axis of rotation (42) relative to the second stator (38) in a first rotor direction of rotation; ◯ the second rotor (40) drives the input element (20) and thereby rotates about the freewheel axis (24) in a first freewheel direction of rotation relative to the reference element (26); and ◯ the freewheel (18) completely locks, thereby: ▪ the freewheel (18) prevents the input element (20) from rotating at a higher speed than the output element (22) in the first freewheel direction of rotation relative to the reference element (26) about the freewheel axis of rotation (24), so that the input element (20) drives the output element (22) and rotates in the first freewheel direction of rotation relative to the reference element (26) about the freewheel axis of rotation (24), and the input element (20) and the output element (22) rotate at the same speed in the same first freewheel direction of rotation relative to the reference element (26) about the freewheel axis of rotation (24); and ▪ the second rotor (40) drives the vehicle wheels (14, 16) via the freewheel (18); - the freewheel (18) allows the output element (22) to rotate at a higher speed than the input element (20) in the first freewheel direction of rotation relative to the reference element (26); and - in a reverse operation of the second electric machine (36), in whose reverse operation the second stator (38) drives the second rotor (40) and thereby rotates about the machine axis of rotation (42) relative to the second stator (38) in a second rotor direction opposite to the first rotor direction of rotation and thereby the second rotor (40) rotates the input element (20) relative to the reference element (26) and relative to the output element (22) about the freewheel axis of rotation (24) in a second freewheel direction opposite to the first freewheel direction of rotation, the freewheel (18) partially and thereby slips. [2] Method for operating an electric drive unit (10) of a motor vehicle, wherein the drive unit (10) comprises: - a freewheel (18); - a first electric machine (28) comprising a first stator (30) and a first rotor (32); - a second electric machine (36) comprising a second stator (38) and a second rotor (40) which is rotatable about a machine axis of rotation (42) relative to the second stator (38); and - a vehicle axle (12) which has two vehicle wheels (14, 16) which can be driven by means of the first rotor (32) bypassing the freewheel (18) and bypassing the second rotor (40) and by means of the second rotor (40) via the freewheel (18) and bypassing the first rotor (32); characterized by , that: - in a driving operation of the second electric machine (36), the driving operation of which is intended to drive the motor vehicle via the vehicle wheels (14, 16) by means of the second rotor (40) in a forward direction of travel of the motor vehicle: ◯ the second rotor (40) is driven by means of the second stator (38) in such a way that the second rotor (40) is rotated around the machine axis of rotation (42) relative to the second stator (38) in a first rotor direction of rotation; ◯ the input element (20) is driven by the second rotor (40) and thereby rotated about the freewheel axis (24) in a first freewheel direction of rotation relative to the reference element (26); and ◯ the freewheel (18) completely locks, thereby: ▪ the freewheel (18) prevents the input element (20) from rotating at a higher speed than the output element (22) in the first freewheel direction of rotation relative to the reference element (26) about the freewheel axis of rotation (24), so that the output element (22) is driven by the input element (20) and thereby rotated in the first freewheel direction of rotation relative to the reference element (26) about the freewheel axis of rotation (24), and the input element (20) and the output element (22) rotate at the same speed in the same first freewheel direction of rotation relative to the reference element (26) about the freewheel axis of rotation (24); and ▪ the vehicle wheels (14, 16) are driven by the second rotor (40) via the freewheel (18); - the freewheel (18) allows the output element (22) to rotate at a higher speed than the input element (20) in the first freewheel direction of rotation relative to the reference element (26); and - the first electric machine (28) is operated in a recuperation mode, whereby, while braking the motor vehicle and operating the first electric machine (28) as a generator, the first rotor (32) is driven by the vehicle wheels (14, 16), while the second electric machine (36) is operated in a reverse mode, in which: ◯ the second rotor (40) is driven by means of the second stator (38) such that the second rotor (40) rotates about the machine axis of rotation (42) relative to the second stator (38) in a second rotor direction opposite to the first rotor direction of rotation, and thereby the second rotor (40) rotates the input element (20) relative to the reference element (26) and relative to the output element (22) about the freewheel axis of rotation (24) in a second freewheel direction opposite to the first freewheel direction of rotation; and ◯ the freewheel (18) partially locks and thus slips.

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