Method for operating an electric drive system for a motor vehicle and motor vehicle

Abstract

The invention relates to a method for operating an electric drive system (10) for a motor vehicle, in which the drive system (10) has a first electric machine (12) which has a first rotor (14). A second electric machine (18) is provided which has a second rotor (20) arranged coaxially to the first rotor (14). A first vehicle wheel (28) is provided which is permanently coupled to the first rotor (14) in a torque-transmitting manner and can thus be driven by the first rotor (14) and is assigned to the first electric machine (12). A second vehicle wheel (30) is provided which is permanently coupled to the second rotor (20) in a torque-transmitting manner and can thus be driven by the second rotor (20) and is assigned to the second electric machine (18).A friction clutch (34) is provided which is designed to connect the first rotor (14) to the second rotor (20) in a rotationally fixed manner, wherein the friction clutch (34) is the only means for coupling the two rotors (14, 20).

Description

[0001] The invention relates to a method for operating an electric drive system for a motor vehicle. The invention also relates to a motor vehicle with such an electric drive system.

[0002] DE 10 2018 221 601 A1 discloses a drive axle of an electrically driven vehicle, wherein the drive axle has an electric drive system with two drivable vehicle wheels, two electric motors, and a multi-speed transmission system. A shifting method for the multi-speed transmission system is presented. Similarly, DE 20 2022 106 631 U1 shows a drive system for a vehicle axle with two electric motors, each associated with a transmission unit. WO 2023 / 126 183 A1 also shows an electric drive system in which two electric motors are used for one vehicle axle, wherein both electric motors are coupled to each other via a transmission.DE 10 2015 216 689 A1, DE 10 2017 107 322 A1 and the generic DE 10 2018 103 483 A1 each show an electric vehicle axle with two coaxially arranged electric machines, the rotors of which can be connected to one another in a rotationally fixed manner via a coupling.

[0003] The object of the present invention is to provide a method for operating an electric drive system for a motor vehicle and a motor vehicle with such an electric drive system, so that a particularly advantageous operation and a particularly compact and lightweight design of the drive system can be realized.

[0004] This object is achieved by a method having the features of patent claim 1 and by a motor vehicle having the features of patent claim 5. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] A first aspect of the invention relates to a method for operating an electric drive system, also referred to as a drive device or designed as a drive device, for a motor vehicle, also simply referred to as a vehicle. This means that the motor vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car, has the electric drive system in a fully manufactured state and can be driven by means of the electric drive system, in particular purely electrically. In the method, the electric drive system has a first electric machine which has a first rotor. In particular, the first electric machine has a first stator, by means of which the first rotor can be driven and is therefore rotatable about a first machine axis of rotation relative to the first stator.In the method, the electric drive system has a second electric machine which has a second rotor. In particular, the second electric machine has a second stator, by means of which the second rotor can be driven and is therefore rotatable about a second machine axis of rotation relative to the second stator. The rotors and thus the electric machines are arranged coaxially to one another such that the machine axes of rotation coincide. In the method, the drive system has a first vehicle wheel which is permanently coupled to the first rotor in a torque-transmitting manner and is therefore drivable by the first rotor and is assigned to the first electric machine. This means that the first vehicle wheel is assigned to the first electric machine, which is assigned to the first vehicle wheel.In the method, the drive system has a second vehicle wheel, which is permanently coupled to the second rotor in a torque-transmitting manner and can thus be driven by the second rotor and is assigned to the second electric machine. This means that the second vehicle wheel is assigned to the second electric machine, which is assigned to the second vehicle wheel. Very particularly, the first vehicle wheel can be driven by the first rotor, bypassing the second vehicle wheel. This is to be understood in particular as follows: The first electric machine can provide first drive torques via its first rotor for driving the first vehicle wheel, in particular purely electrically.With respect to a first torque flow, along which the respective first drive torque can be or is transmitted from the first rotor to the first vehicle wheel, in particular in order to thereby drive the first vehicle wheel, the second vehicle wheel is not arranged downstream of the first rotor and upstream of the first vehicle wheel in the first torque flow. Furthermore, it is preferably provided that the second vehicle wheel can be driven by the second rotor, bypassing the first vehicle wheel. This is to be understood in particular as follows: The second electric machine can provide second drive torques via its second rotor for driving the second vehicle wheel, in particular purely electrically.With respect to a second torque flow along which the respective second drive torque can be or is transmitted from the second rotor to the second vehicle wheel, in particular to drive the second vehicle, the first vehicle wheel is not arranged downstream of the second rotor and upstream of the second vehicle wheel in the second torque flow. The electric drive system is thus designed as a dual drive.

[0006] The expression that a second element is driven by a first element bypassing a third element means that the third element is not arranged between the first element and the second element with respect to a torque flow emanating from the first element and directed to the second element.

[0007] In the method, the electric drive system has a friction clutch, designed for example as a multi-plate clutch, which is configured to connect the first rotor to the second rotor in a rotationally fixed manner. In other words, the rotors can be connected to one another in a rotationally fixed manner by means of the friction clutch. The friction clutch can thus be switched, for example, between a coupled state and a decoupling state. In the coupled state, the rotors are connected to one another in a rotationally fixed manner by means of the friction clutch. In the decoupling state, the friction clutch releases the rotors for a relative rotation between the rotors, in particular about the respective machine rotational axis, in particular in such a way that in the decoupling state no torque can be transmitted between rotors via the friction clutch, so that, for example, in the decoupling state the rotors are completely decoupled from one another.It is particularly conceivable for the friction clutch to be switchable into at least one or more intermediate states. In the intermediate state, for example, the rotors are coupled to one another via the friction clutch in a torque-transmitting manner, but are rotatable relative to one another about the respective machine rotational axis, so that, for example, in the intermediate state the friction clutch is operated with slipping. In the intermediate state, for example, a torque which is greater than 0 in magnitude can be transmitted between the rotors via the friction clutch. In other words, the following is provided, for example: In the coupled state of the friction clutch, at most a first torque can be transmitted between the rotors via the friction clutch, which torque is also referred to as the first clutch torque and is greater than 0 in magnitude.In the intermediate state, for example, a maximum of a second torque can be transmitted between the rotors via the friction clutch, which is also referred to as the second clutch torque and is greater than 0 and less than the first torque in terms of magnitude. In the uncoupled state, for example, no torque can be transmitted between rotors via the friction clutch. In particular, it is conceivable that the friction clutch can be or is operated in a slipping manner in the intermediate state, so that a torque is transmitted between the rotors via the friction clutch, but the rotors rotate relative to one another, in particular about the respective machine axis of rotation. Thus, in particular in the coupled state, the rotors are connected to one another in a rotationally fixed manner by means of the friction clutch. In the uncoupled state, the rotors are decoupled from one another, in particular completely.In the intermediate state, the rotors are connected to each other via the friction clutch to transmit torque, but can rotate relative to each other about the respective machine rotation axis.

[0008] In this process, the friction clutch is the sole means for torque-transmitting coupling of the two rotors. This means that there is no additional clutch, no additional coupling gear, no differential gear, and no other coupling device by means of which the two rotors could be directly or indirectly coupled to one another in a torque-transmitting manner. This allows the number of parts and thus the installation space required, costs, and weight of the drive system to be kept to a particularly low level. In other words, this enables a particularly streamlined design of the drive system, while at the same time enabling particularly advantageous operation of the drive system. The term "means" here therefore refers to a vehicle-side means.Of course, it is also the case that the vehicle wheels are, to a certain extent, coupled to one another via the road or the surface on which the vehicle is traveling, which also means that the two rotors are coupled to one another via the roads or the surface.

[0009] In the method, the drive system is operated in single-engine mode when the motor vehicle is cornering. Cornering of the motor vehicle means that the motor vehicle drives through a curve, for example in the form of a left-hand bend or a right-hand bend. The motor vehicle has, for example, at least one vehicle axle. Very particularly, in its fully manufactured state, the motor vehicle has at least or exactly two vehicle axles, namely the aforementioned vehicle axle as the first vehicle axle and a second vehicle axle. When reference is made above and below to the vehicle axle, this means the first vehicle axle, unless otherwise stated. The vehicle axle preferably comprises the first vehicle wheel and the second vehicle wheel, such that the first vehicle wheel and the second vehicle wheel are preferably vehicle wheels of the same first vehicle axle.When reference is made above and below to the vehicle wheels, this refers to the first vehicle wheel and the second vehicle wheel, unless otherwise stated. The vehicle wheels are ground contact elements by means of which the motor vehicle can be or is supported downwards on a ground in the vertical direction of the vehicle. If the motor vehicle is driven along the ground while the motor vehicle is supported downwards on the ground in the vertical direction of the vehicle via the ground contact elements, the ground contact elements roll, in particular directly, on the ground. In particular, the vehicle wheels are steerable vehicle wheels to which a steering system of the motor vehicle is assigned. By means of the steering system, the vehicle wheels can be pivoted relative to a body of the motor vehicle and thus steered. By steering the vehicle wheels, for example, lane changes, i.e.Lane changes, changes of direction, and cornering of the motor vehicle are effected, so that, for example, during the aforementioned cornering, the vehicle wheels are pivoted out of a straight-ahead position, particularly relative to the body, in order to thereby execute the cornering, thus enabling the motor vehicle to negotiate the curve. The straight-ahead position of the vehicle wheels is intended to cause the motor vehicle to travel straight ahead, whereby the motor vehicle does not corner when traveling straight ahead.The feature that the vehicle wheels are pivoted out of the straight-ahead position when cornering is to be understood as meaning that when cornering the vehicle wheels are pivoted relative to the straight-ahead position, thus assuming a respective first pivot position which differs from a respective second pivot position, whereby the vehicle wheels are in the respective second pivot position when driving straight ahead or in the straight-ahead position.

[0010] Single-motor operation means that in or during single-motor operation, with respect to the electrical machines, only one of the electrical machines is operated in a driving manner, so that with respect to the electrical machines, only one electrical machine drives exactly one of the vehicle wheels or both vehicle wheels, while the other electrical machine drives neither exactly one of the vehicle wheels nor both vehicle wheels, thus while the other electrical machine does not drive either of the vehicle wheels and, in particular, does not provide any torque, i.e., outputs any torque via its rotor. In single-motor operation, the other electrical machine is, for example, towed by the one electrical machine or operated in zero-torque control.

[0011] In the method, in or during single-engine operation and when the motor vehicle is cornering, with regard to the electric machines, only the electric machine to which the outside vehicle wheel is assigned during cornering is driven, while driving exactly one of the vehicle wheels or both vehicle wheels by the other electric machine, to which the inside vehicle wheel is assigned during cornering, is omitted. Furthermore, the method provides that in or during single-engine operation and when the motor vehicle is cornering, the friction clutch is closed up to a degree of engagement which is selected such that a specific, and therefore predetermined, drive torque distribution takes place between the electric machine to which the outside vehicle wheel is assigned during cornering, and the two vehicle wheels.In particular, the degree of engagement is or will be selected such that in or during single-engine operation and cornering, the friction clutch is operated in a slipping manner, thus the friction clutch is in the intermediate state.The aforementioned drive torque distribution is to be understood in particular as follows: During single-motor operation and during cornering, the electric machine, which is operated in a driving capacity, provides at least one of the aforementioned drive torques via its rotor, which is transmitted during or through the drive torque distribution from the rotor of the electric machine to which the vehicle wheel on the outside of the curve is assigned during cornering, to the two vehicle wheels, so that a first wheel torque and a second wheel torque result from the at least one drive torque, such that the first wheel torque is transmitted to the first vehicle wheel and the second wheel torque to the second vehicle wheel, wherein, for example, the first vehicle wheel is driven by means of the first wheel torque and the second vehicle wheel by means of the second wheel torque. The respective wheel torque is preferably greater than 0 in terms of magnitude.

[0012] The electric machine assigned to the outside vehicle wheel during cornering is also referred to as the outside electric machine, and the electric machine assigned to the inside vehicle wheel during cornering is also referred to as the inside electric machine. The wheel torques can be equal in magnitude, or they can differ in magnitude, thereby providing a particularly advantageous drive. The invention is based in particular on the following findings and considerations: Dual drives with two electric machines are generally less efficient than single drives, i.e. drives with only one electric machine for driving both vehicle wheels, if these dual drives can only be operated in a dual mode in which both electric machines are operated simultaneously and thus drive the vehicle wheels. In order to operate a dual drive such as the electric drive system of the method according to the invention efficiently, it is advantageous to implement a so-called single mode, also referred to as individual mode, in which only one electric machine is operated in a driving or driving manner with respect to the electric machines, while the other electric machine does not drive either of the vehicle wheels. However, this usually requires several clutches and, if necessary, additional differential gears.Switching from dual mode to single mode often cannot be performed without delay. Torque vectoring intervention is also often not possible without delay. The aforementioned problems and disadvantages can now be avoided by the invention. In the invention, the friction clutch is used as the sole coupling between the rotors and as a locking clutch, whereby the torque capacity of the friction clutch can advantageously be low. For example, the torque distribution is adjusted depending on the steering angle, i.e., depending on the value by which the respective vehicle wheel is pivoted relative to the straight-ahead position when cornering.In particular, depending on a relative speed difference at the friction clutch and depending on one side of the active, thus driving or driving-operated electric machine, a torque from the driving-operated electric machine can be transferred to the opposite vehicle wheel, thereby achieving a particularly advantageous drive. Furthermore, the invention enables torque vectoring capabilities to be always and immediately available without excessive activation times, unfavorable mode transitions, or other unfavorable constraints. Furthermore, it enables the realization of different efficiency modes that are available in at least almost all driving situations, but without having to use a mechanical separation unit between the electric machines. Furthermore, the number of mechanical components can be kept low, thus enabling a particularly space-efficient design of the drive system.

[0013] The term torque vectoring refers to an operating mode in which the two vehicle wheels on the vehicle axle are each driven with individually adjustable torques. In an operating mode without the two vehicle wheels on the vehicle axle being driven with individually adjustable torques, both vehicle wheels on an axle are driven with the same torque.

[0014] The method allows the drive system to be designed as a lean, cost-, weight-, and space-efficient system, while simultaneously enabling the realization of various advantageous operating modes. A first operating mode is single-motor operation, which can, for example, be the aforementioned single mode or a first single mode. In this case, the friction clutch can, for example, be implemented or function as a type of differential gear, in particular by operating the friction clutch with slippage. A second operating mode is a two-motor operation, also referred to as dual operation, which can, for example, be the aforementioned dual mode.In dual-motor operation, for example, the electric machines are driven simultaneously, so that the electric machines simultaneously drive the vehicle wheels, in particular such that the first electric machine drives the first vehicle wheel via its first rotor, in particular bypassing the second vehicle wheel, and that simultaneously the second electric machine drives the second vehicle wheel via its second rotor, in particular bypassing the first vehicle wheel. Furthermore, torque vectoring can be carried out in a particularly advantageous manner, in particular as a third operating mode of the operating modes.

[0015] In the context of the present disclosure, the feature that two rotatably mounted components are connected to one another in a rotationally fixed manner is to be understood as meaning that the components connected to one another in a rotationally fixed manner are arranged coaxially to one another and, in particular when the components are driven, rotate together or simultaneously about a component rotation axis common to the components, which is, for example, the respective machine rotation axis, at the same angular velocity, in particular relative to a reference element such as, for example, a housing of the drive system. In other words, two rotatably mounted elements are connected to one another in a rotationally fixed manner if they are arranged coaxially to one another, relative to their component rotation axis or relative to a rotational symmetry axis, and if they are connected to one another in such a way that they rotate at the same angular velocity.An element is connected to the housing in a rotationally fixed manner if it cannot be rotated relative to the housing.

[0016] The feature that two components, such as the rotors, are connected or coupled to one another in a torque-transmitting manner means that the components are connected or coupled to one another in such a way that torque can be transmitted between the components. If the components are connected or coupled to one another in a rotationally fixed manner, the components are also connected or coupled to one another in a torque-transmitting manner. Two components connected to one another in a torque-transmitting manner can thus be connected to one another in a rotationally fixed manner.Furthermore, it is conceivable that two components connected to one another in a torque-transmitting manner are connected to one another in a torque-transmitting manner via an intermediate transmission unit and / or coupling unit, such as the friction clutch, so that torques can be transmitted between the components via the transmission unit or coupling unit, while the components are connected to one another in a torque-transmitting manner, wherein the components can, however, be rotatable relative to one another, in particular about the component rotation axis.

[0017] The feature that two components are permanently connected or coupled to one another in a torque-transmitting manner does not mean that a switching element is provided that can be switched between a coupling state that connects or couples the components to one another in a torque-transmitting manner and a decoupling state in which no torque can be transmitted between the components via the switching element. Rather, the components are always and therefore permanently torque-transmitting, i.e., connected or coupled to one another in such a way that torque can be transmitted between the components. Thus, for example, one of the components can be driven by the other component, or vice versa.

[0018] In particular, the feature that two components are permanently connected or coupled to one another in a rotationally fixed manner is to be understood as meaning that a switching element is not provided which can be switched between a coupling state which connects or couples the components to one another in a rotationally fixed manner and a decoupling state in which the components are decoupled from one another and can be rotated relative to one another, so that no torque can be transmitted between the components via the switching element, but rather the components are always, and therefore permanently, connected or coupled to one another in a rotationally fixed manner.

[0019] Furthermore, the feature that two components can be connected or coupled to one another in a rotationally fixed manner means that the components are assigned a switching element which can be switched between at least one coupling state and at least one decoupling state. In the coupling state, the components are connected or coupled to one another in a rotationally fixed manner by means of the switching element. In the decoupling state, the components are decoupled from one another, so that in the decoupling state the components can be rotated relative to one another about the component rotation axis and so that, in particular, no torque can be transmitted between the components via the switching element. The same applies to the feature that two components can be connected or coupled to one another in a torque-transmitting manner.Thus, for example, the feature that two components can be connected or coupled to one another in a torque-transmitting manner is understood to mean that a switching element is assigned to the components, wherein the switching element can be switched between at least one connected state and at least one released state. In the connected state, the components are coupled or connected to one another in a torque-transmitting manner by means of the switching element, so that torques can be transmitted between the components, in particular via the switching element. In the released state, the components are decoupled from one another, so that in the released state, no torque can be transmitted between the components via the switching element.

[0020] The friction clutch is preferably a wet multi-plate clutch. This means, in particular, that the multi-plate clutch has friction plates that are lubricated by a fluid, such as oil, at least during operation of the drive system. In particular, they come into direct contact with the fluid, with the friction plates running in a sump formed by the fluid. The friction clutch allows the rotors to be connected to one another in a frictionally locked manner.

[0021] In order to achieve a particularly slim design of the drive system and a particularly advantageous drive of the vehicle wheels, it is provided in a manner known per se that precisely one first transmission device is arranged between the first vehicle wheel and the first rotor, via which the first vehicle wheel is permanently coupled to the first rotor in a torque-transmitting manner. Furthermore, precisely one second transmission device is arranged between the second vehicle wheel and the second rotor, via which the second vehicle wheel is permanently coupled to the second rotor in a torque-transmitting manner.

[0022] According to the invention, the first transmission device is designed as a first planetary gear set and the second transmission device is designed as a second planetary gear set, whereby the installation space requirement, the weight and the costs of the drive system can be kept within a particularly low range.

[0023] In order to be able to realize a particularly slim design of the drive system, it is further provided according to the invention that the respective planetary gear set is designed as a respective simple planetary gear set.

[0024] In order to be able to realize a design of the drive system that is particularly weight-, cost-, and space-efficient, the invention further provides that a first sun gear of the first planetary gear set is permanently connected in a rotationally fixed manner to the first rotor, that a first ring gear of the first planetary gear set is permanently connected in a rotationally fixed manner to the housing of the drive system, and that a first planet carrier of the first planetary gear set is permanently connected in a rotationally fixed manner to the first vehicle wheel. It has proven particularly advantageous if a second sun gear of the second planetary gear set is permanently connected in a rotationally fixed manner to the second rotor, if a second ring gear of the second planetary gear set is permanently connected in a rotationally fixed manner to the housing of the drive system, and if a second planet carrier of the second planetary gear set is permanently connected in a rotationally fixed manner to the second vehicle wheel.

[0025] Finally, in order to realize a particularly slim design of the drive system, the respective electrical machine is designed according to the invention as a respective axial flux machine (AFM), which is also referred to as an axial flux motor.

[0026] In order to achieve particularly advantageous operation in a particularly space-saving, weight-saving, and cost-effective manner, one embodiment of the invention provides that, during single-motor operation, an operating mode in which the two vehicle wheels of the vehicle axle are each driven with individually adjustable, different torques is carried out by selecting the degree of locking such that the vehicle wheel on the outside of the curve receives more drive torque than the vehicle wheel on the inside of the curve. Thus, the wheel torque transmitted to the vehicle wheel on the outside of the curve, in order to thereby drive the vehicle wheel on the outside of the curve, is greater than the wheel torque transmitted to the vehicle wheel on the inside of the curve, in order to thereby drive the vehicle wheel on the inside of the curve. In this case, both wheel torques are preferably greater than zero in magnitude.

[0027] A further embodiment is characterized in that, in single-motor operation, an operating mode in which the two vehicle wheels of the vehicle axle are driven with individually adjustable, different torques is avoided, as both vehicle wheels receive the same drive torque. This means that the wheel torque transmitted to the outside vehicle wheel during the curve, thereby driving the outside vehicle wheel, and the wheel torque transmitted to the inside vehicle wheel during the curve, thereby driving the inside vehicle wheel, are equal in magnitude.

[0028] Preferably, when performing torque vectoring and omitting the operating mode in which the two vehicle wheels of the vehicle axle are driven with individually adjustable different torques, the wheel torques are greater than zero in magnitude.

[0029] In order to be able to realize a particularly slim design of the drive system, it is provided in a further embodiment of the invention that the rotors are arranged at least substantially coaxially to the vehicle wheels. This means that the rotors are either arranged strictly coaxially to the vehicle wheels, or the rotors are arranged with a slight axial offset to the vehicle wheels, wherein the axial offset is brought about, for example, by a respective intermediate cardan shaft. Thus, it is conceivable, for example, that the first rotor is permanently coupled to the first vehicle wheel via a first cardan shaft and the second rotor is permanently coupled to the second vehicle wheel via a second cardan shaft, wherein the respective cardan shaft brings about a respective axial offset with or below which the first rotor is arranged to the first vehicle wheel and the second rotor to the second vehicle wheel.This creates a particularly slim design.

[0030] A second aspect of the invention relates to a simple motor vehicle, also referred to as a vehicle and preferably designed as a motor vehicle, in particular as a passenger car, which has an electric drive system and can be driven by the electric drive system, in particular purely electrically. The electric drive system of the motor vehicle is designed according to the second aspect of the invention to carry out a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

[0031] Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing.

[0032] The drawing shows: Fig. 1 a schematic representation of an electric drive system for a motor vehicle; Fig. 2 is a schematic diagram illustrating a method for operating the electric drive system; and Fig. 3 another schematic representation to further illustrate the process.

[0033] In the figures, identical or functionally identical elements are provided with the same reference symbols.

[0034] Fig. 1 shows a schematic representation of an electric drive system 10 for a motor vehicle, also simply referred to as a vehicle, which, in its fully manufactured state, has the electric drive system 10 and can be driven by means of the electric drive system 10, in particular purely electrically. The electric drive system 10 has a first electric machine 12, which has a first rotor 14 and a first stator 16. Via its rotor 14, the electric machine 12 can provide first drive torques for driving the motor vehicle. The electric drive system 10 has a second electric machine 18, which has a second rotor 20 and a second stator 22. Via its second rotor 20, the second electric machine 18 can provide second drive torques for driving the motor vehicle. The drive system 10 also has a housing 24.For example, the respective electric machine 12, 18 is at least partially arranged in the housing 24. In particular, the respective stator 16, 22 is connected, in particular permanently, in a rotationally fixed manner to the housing 24. In the embodiment shown in . Fig. In the embodiment shown in Figure 1, the respective electrical machine 12, 18 is designed as a respective axial flux machine (AFM).

[0035] The motor vehicle has at least or exactly two vehicle axles, namely a first vehicle axle and a second vehicle axle. The vehicle axles are also arranged consecutively in the longitudinal direction of the motor vehicle and thus one behind the other. The first vehicle axle is in Fig. 1 and designated 26. The first vehicle axle 26 has at least or exactly two vehicle wheels, namely a first vehicle wheel 28 and a second vehicle wheel 30. Thus, the vehicle wheels 28 and 30 are vehicle wheels of the same first vehicle axle 26. The vehicle wheels 28 and 30 are ground contact elements of the motor vehicle. In the present case, the drive system 10 has the vehicle wheels 28 and 30. The vehicle wheels 28 and 30 are arranged on opposite sides of the motor vehicle in the transverse direction of the motor vehicle. The transverse direction of the vehicle is illustrated by a double arrow 32. The electric drive system 10 comprises the first vehicle wheel 28 and the second vehicle wheel 30.

[0036] The first vehicle wheel 28 is permanently coupled to the first rotor 14 in a torque-transmitting manner, by means of which the first vehicle wheel 28 can be driven, in particular by bypassing the second vehicle wheel 30. Thus, the first vehicle wheel 28 is associated with the first electric machine 12 and vice versa. The second vehicle wheel 30 is permanently connected to the second rotor 20 in a torque-transmitting manner, by means of which the second vehicle wheel 30 can be driven, in particular by bypassing the first vehicle wheel 28. The second vehicle wheel 30 is associated with the second electric machine 18 and vice versa.

[0037] The drive system 10 also includes a friction clutch 34, embodied, for example, as a multi-plate clutch, which is designed to connect the rotors 14 and 20 in a rotationally fixed manner. The friction clutch 34 is the sole means for torque-transmitting coupling of the two rotors 14 and 20.

[0038] In the Fig. In the exemplary embodiment shown in Figure 1, exactly one transmission device, namely a first transmission device 36, is arranged between the first vehicle wheel 28 and the first rotor 14, via which transmission device the first vehicle wheel 28 is permanently coupled to the first rotor 14 in a torque-transmitting manner. This means that, with respect to a first torque flow along which the respective first drive torque can be transmitted from the first rotor 14 to the first vehicle wheel 28, in particular bypassing the second vehicle wheel 30, the first transmission device 36 is arranged downstream of the rotor 14 and upstream of the vehicle wheel 28 in the first torque flow.

[0039] Between the second vehicle wheel 30 and the second rotor 20, precisely one second transmission device 38 is arranged, via which the second vehicle wheel 30 is permanently coupled to the second rotor 20 in a torque-transmitting manner. This means that, with respect to a second torque flow along which the respective second drive torque can be and is transmitted from the second rotor 20 to the second vehicle wheel 30, the second transmission device 38 is arranged downstream of the second rotor 20 and upstream of the second vehicle wheel 30 in the second torque flow.

[0040] In the Fig. 1, the respective transmission device 36, 38 is designed as a respective simple planetary gear set, namely a first planetary gear set 40 and a second planetary gear set 42. The first planetary gear set 40 has a first sun gear 44 permanently connected to the first rotor 14 in a rotationally fixed manner, and a first ring gear 46 permanently connected to the housing 24 in a rotationally fixed manner. The first planetary gear set 40 has a first planet carrier 48 which is rotatable about a main axis of rotation 50 relative to the housing 24. The first sun gear 44 and the respective rotor 14, 20 are also rotatable about the main axis of rotation 50 relative to the housing 24. The first planetary gear set 40 also has first planet gears 52 which are rotatably held on the first planet carrier 48.The respective first planetary gear 52 meshes on the one hand with the first ring gear 46 and on the other hand with the first sun gear 44, whereby meshing of the first sun gear 44 with the first ring gear 46 is omitted.

[0041] The first transmission device 36 and the second transmission device 38 are non-switchable transmission devices 36, 38, each with a fixed gear ratio.

[0042] The second planetary gear set 42 has a second sun gear 54 permanently connected to the second rotor 20 in a rotationally fixed manner, and a second ring gear 56 permanently connected to the housing 24 in a rotationally fixed manner. The second planetary gear set 42 has a second planet carrier 58, which, like the first planet carrier 48, is rotatable about the main axis of rotation 50 relative to the housing 24. The second sun gear 54 is also rotatable about the main axis of rotation 50 relative to the housing 24. The second planetary gear set 42 has second planet gears 60, which are rotatably mounted on the second planet carrier 58. The respective second planet gear 60 meshes with the second ring gear 56 on the one hand and with the second sun gear 54 on the other hand, whereby meshing of the second sun gear 54 with the second ring gear 56 is omitted. The planetary gear sets 40 and 42 are arranged coaxially with one another. As can be seen from Fig. 1 is also that the rotors 14 and 20, and thus the electric machines 12 and 18, are arranged coaxially with each other. The first planetary carrier 48 is permanently connected to the first vehicle wheel 28 in a torque-transmitting manner, and the second planetary carrier 58 is permanently connected to the second vehicle wheel 30 in a torque-transmitting manner.

[0043] The electric drive system 10 can be operated in different operating modes. A method for operating the electric drive system 10 is described below.

[0044] A first operating mode of the operating modes is, for example, a dual operation, in or during which the first electric machine 12 drives the first vehicle wheel 28 and simultaneously the second electric machine 18 drives the second vehicle wheel 30, in particular while the friction clutch 34 is open, in particular completely, so that the friction clutch 34 is in its decoupling state, in which no torque can be transmitted between the rotors 14 and 20 via the friction clutch 34. In or during the first operating mode, torque vectoring is possible in that the first electric machine 12 and the second electric machine 18 provide different torques.

[0045] The aforementioned dual operation, designed as the first operating mode, is also referred to as the first dual operation, wherein in or during the first dual operation the friction clutch 34, also referred to as a multi-plate clutch or designed as a multi-plate clutch, is opened, in particular completely, and is therefore in the uncoupled state.

[0046] In the first operating mode, torque vectoring is also possible using the friction clutch 34.

[0047] The friction clutch 34 can generally be switched between the aforementioned decoupling state and a coupling state. In the coupling state, the rotors 14 and 20 are connected to one another in a rotationally fixed manner by means of the friction clutch 34, so that, for example, in the coupling state of the friction clutch 34, a first torque can be transmitted between the rotors 14 and 20 via the friction clutch 34. The magnitude of the first torque is greater than 0. The friction clutch 34 can also be switched, for example, into at least one intermediate state, preferably several intermediate states, so that the friction clutch 34 can preferably be operated in the decoupling state, the coupling state, and the respective intermediate state. In the respective intermediate state, for example, a second torque can be transmitted between the rotors 14 and 20 via the friction clutch 34, wherein the second torque is greater than 0 and smaller than the first torque.In particular, the intermediate state is a slipping operation of the friction clutch 34, so that the friction clutch 34 is operated in a slipping manner in its intermediate state. This means that when the friction clutch 34 is slipping, i.e., operated in the intermediate state, a torque, also referred to as the transmission torque and greater in magnitude than zero, can be transmitted or is transmitted between the rotors 14 and 20 via the friction clutch 34, while, however, the friction clutch 34 permits relative rotations between the rotors 14 and 20 about the main axis of rotation 50, i.e., while the rotors 14 and 20 are rotatable relative to one another about the main axis of rotation 50 or rotate relative to one another about the main axis of rotation 50. In this case, the transmission torque is greater in magnitude than 0 and, in particular, smaller than the first torque.

[0048] A second operating mode of the operating modes is a second dual operation, in or during which the first electric machine 12 drives the first vehicle wheel 28 and simultaneously the second electric machine 18 drives the second vehicle wheel 30, while the friction clutch 34 is fully engaged, i.e., while the friction clutch 34 is in its coupled state, so that the rotors 14 and 20 are rotationally fixedly connected to one another by means of the friction clutch 34. As a result, the friction clutch 34 functions as a differential lock.

[0049] A third operating mode of the operating modes is a first individual operation, which is also referred to as first single operation. In the third operating mode, with respect to the electric machines 12 and 18, exclusively one of the electric machines 12 and 18 drives the vehicle wheels 28 and 30, while the other electric machine 18, 12 does not drive any of the vehicle wheels 28 and 30. In or during the third operating mode, the friction clutch 34 is closed, in particular completely, so that the friction clutch 34 is in its coupled state and the rotors 14 and 20 are connected to one another in a rotationally fixed manner. The third operating mode is a first efficiency mode with an activated differential lock, since in the third operating mode the friction clutch 34 functions as a differential lock.

[0050] A fourth operating mode of the operating modes is a second individual operation, which is also referred to as second single operation. In or in the fourth operating mode, the friction clutch 34 is operated in a slipping manner and thus in particular in the intermediate state, wherein in the fourth operating mode an uneven distribution of torque to the vehicle wheels is avoided. As in the first individual operation, in the second individual operation, with respect to the electric machines 12 and 18, only one of the electric machines 12 and 18 drives the vehicle wheels 28 and 30, while the other electric machine 18, 12 does not drive any of the vehicle wheels 28 and 30. Thus, for example, the fourth operating mode is a second efficiency operation.

[0051] A fifth operating mode is a third individual operation, which is also referred to as third single operation. In or during the fourth operating mode, an operating mode in which the two vehicle wheels of the vehicle axle are driven with individually adjustable, different torques is omitted, whereas in or during the fifth operating mode, an operating mode in which the two vehicle wheels of the vehicle axle are driven with individually adjustable, different torques is carried out. The fifth operating mode is a third efficiency mode because, in the fifth operating mode, with respect to the electric machines 12 and 18, only one of the electric machines 12 and 18 drives the vehicle wheels 28 and 30, while the other electric machine 18, 12 does not drive either of the vehicle wheels 28 and 30.

[0052] The fourth operating mode is in Fig. 2, and the fifth operating mode is shown in Fig. 3. For example, in the method the respective operating mode is carried out during a respective time phase of the method. For example, the fourth operating mode is carried out during normal cornering of the motor vehicle. For example, the fifth operating mode is carried out during sporty cornering of the motor vehicle. During the aforementioned cornering, the motor vehicle travels through a bend, for example designed as a left bend or a right bend. During cornering, depending in particular on whether the bend is a right bend or a left bend, one of the vehicle wheels 28 and 30 is an outside vehicle wheel, while the other vehicle wheel 30, 28 is an inside vehicle wheel. The respective individual operation is also referred to as single-motor operation.

[0053] Sporty cornering is understood to mean, for example, cornering with a particularly high vehicle speed and / or a particularly high vehicle acceleration in the curve.

[0054] In an upper part T1 of Fig. 2 shows the fourth operating mode during a first cornering of the motor vehicle, which travels through a curve designed as a left-hand bend during or during the first cornering. For example, vehicle wheel 30 is the outside vehicle wheel and vehicle wheel 28 is the inside vehicle wheel. During the first cornering, with respect to the electric machines 12 and 18, only the second electric machine 18, to which the second vehicle wheel 30, which is outside the curve during the first cornering, is assigned, is driven, so that with respect to the electric machines 12 and 18, only the electric machine 18 drives the vehicle wheels 28 and 30, while the first electric machine 12 does not drive any of the vehicle wheels 28 and 30.During the first cornering, the friction clutch 34 is closed to a degree selected such that a uniform drive torque distribution originating from the second electric machine 18, to which the first vehicle wheel 28, which is on the outside of the curve during the first cornering, is assigned, to the two vehicle wheels 28 and 30, and the friction clutch 34 is operated with slipping. In . Fig. 2 schematically shows a steering handle 62 of the motor vehicle, designed as a steering wheel. As shown in the first part T1, the first part T1 illustrates the first cornering, i.e., the motor vehicle traveling through the aforementioned left-hand bend. A bar B1 illustrates a torque acting on the friction clutch 34, which is transmitted via the friction clutch 34. A bar B2 illustrates a torque applied to the first electric machine 12 (but not provided by it), and a bar B3 illustrates a torque provided by the second electric machine 18. A bar B4 illustrates a torque, also referred to as the first wheel torque or first wheel torque, which acts on the first vehicle wheel 28, and a bar B5 illustrates a torque, also referred to as the second wheel torque or second wheel torque, which acts on the second vehicle wheel 30.It can be seen in particular from bars B2 and B3 that during the first cornering, the second electric machine 18 drives the vehicle wheels 28 and 30, while the first electric machine 12 does not drive any of the vehicle wheels 28, 30 and in particular does not provide any torque via its first rotor 14. It can also be seen from bars B4 and B5 that the torques transmitted to the vehicle wheels 28 and 30, in particular simultaneously and also referred to as wheel torques or wheel torques, are of equal magnitude, so that the vehicle wheel on the outside of the curve and the vehicle wheel on the inside of the curve receive the same wheel torque, also referred to as drive torque, wherein the respective vehicle wheel 28, 30 is driven by means of the respective wheel torque transmitted to the respective vehicle wheel 28, 30. Torque vectoring with unequal torque distribution to the vehicle wheels 28, 30 is thus avoided.A bar B6 illustrates a rotational speed of the first vehicle wheel 28, and a bar B7 illustrates a rotational speed of the second vehicle wheel 30. It can be seen that during the first cornering, the second vehicle wheel 30 is the vehicle wheel on the outside of the curve and thus rotates at a higher speed than the first vehicle wheel 28 on the inside of the curve. The first cornering is thus a driving journey of the motor vehicle through a left-hand bend.

[0055] In a second part T2 of Fig. 2 illustrates a driving movement of the motor vehicle through a right-hand bend. In other words, part T2 illustrates a second bend of the motor vehicle, which travels through a right-hand bend during the second bend. During the first bend, the fourth operating mode is implemented, i.e., the drive system 10 is operated in the fourth operating mode. During the second bend, the drive system 10 is operated in the fourth operating mode, in which the multi-plate clutch (friction clutch 34) is operated with slipping, and an operating mode in which the two vehicle wheels of the vehicle axle are driven with individually adjustable, different torques is omitted.During the second cornering, the first vehicle wheel 28 is the outside vehicle wheel and the second vehicle wheel 30 is the inside vehicle wheel, so that during the second cornering, the first vehicle wheel 28 rotates at a higher speed than the inside second vehicle wheel 30. During the second cornering, with respect to the electric machines 12 and 18, only the first electric machine 12, to which the outside first vehicle wheel 28 is assigned during the second cornering, is driven, while the second electric machine 18 does not drive any of the vehicle wheels 28 and 30 and in particular does not provide, i.e. output, any driving torque.During the second cornering, the friction clutch 34 is also closed to a degree of engagement which is selected such that a specific drive torque distribution, originating from the first electric machine 12, to which the first vehicle wheel 28 on the outside of the curve is assigned during the second cornering, occurs between the two vehicle wheels 28 and 30, and the friction clutch 34 is operated in a slipping manner. During the second cornering, an operating mode in which the two vehicle wheels of the vehicle axle are each driven with individually adjustable, different torques is also omitted, so that the wheel torques transmitted to the vehicle wheels 28 and 30 for driving the vehicle wheels 28 and 30 are the same. In other words, the vehicle wheels 28 and 30 receive the same drive torque, also referred to as drive torque, both during the first cornering and during the second cornering.

[0056] In a third part T3 of Fig. 2 illustrates a first straight-ahead travel of the motor vehicle. During the first straight-ahead travel, the drive system 10 is operated in the fourth operating mode, in which the friction clutch 34 is operated with slipping, and an operating mode in which the two vehicle wheels of the vehicle axle are driven with individually adjustable, different torques is omitted. During the first straight-ahead travel, with respect to the electric machines 12 and 18, only one of the electric machines 12 and 18, in this case, for example, the second electric machine 18, is operated in a driving manner, so that the second electric machine 18 drives the vehicle wheels 28 and 30, while the first electric machine 12 does not drive any of the vehicle wheels 28 and 30 and, in particular, does not provide any driving torque. Bars B6 and B7 show that during the first straight-ahead travel, the vehicle wheels 28 and 30 rotate at the same speed.The first cornering is a first driving cornering, and the second cornering is a second driving cornering. The first straight-ahead travel is a first driving straight-ahead travel. If, for example, deceleration occurs while the motor vehicle is traveling through a left-hand bend, i.e., if the motor vehicle is cornering with deceleration through a left-hand bend, then deceleration of the motor vehicle with respect to the electric machines 12 and 18 is effected exclusively by means of the first electric machine 12, to which the vehicle wheel 28 on the inside of the bend is assigned, while deceleration by the second electric machine 18, to which the second vehicle wheel 30 on the outside of the bend is assigned, is omitted.If, for example, a decelerating corner is negotiated through a right-hand bend, the deceleration of the motor vehicle with respect to the electric machines 12 and 18 is effected exclusively by the second electric machine 18, to which the second vehicle wheel 30 on the inside of the curve is assigned, while deceleration by the first electric machine 12, to which the first vehicle wheel 28 on the outside of the curve is assigned, is omitted. In the fourth operating mode, for example, the friction clutch 34 is operated with slipping such that the slip of the friction clutch 34 is adjusted such that the respective vehicle wheel 28, 30 on the inside of the curve receives half of the respective drive torque.

[0057] In a first part T4 of Fig. 3 illustrates a third cornering of the motor vehicle, which is driving through a left turn during the third cornering. In a second part 5 of Fig. 3 illustrates a fourth cornering of the motor vehicle, which travels through a right-hand bend during the fourth cornering. During the third cornering and the fourth cornering, the drive system 10 is operated in the fifth operating mode, which essentially corresponds to the fourth operating mode, but with the difference that in the fifth operating mode, torque vectoring and an unequal distribution of drive torque to the vehicle wheels 28, 30 are performed. Such an operating mode, in which the two vehicle wheels of the vehicle axle are each driven with individually adjustable, different torques, does not occur in the fourth operating mode. The torque vectoring of the fifth operating mode means that the respective vehicle wheel 28, 30 on the outside of the curve receives more, i.e., a greater, drive torque than the vehicle wheel 30, 28 on the inside of the curve.

[0058] Since the second vehicle wheel 30 is the outside vehicle wheel during the third cornering through the left-hand bend, the wheel torque transmitted to the outside second vehicle wheel 30 for driving the second vehicle wheel 30 is greater than the wheel torque transmitted to the inside first vehicle wheel 28 for driving the first vehicle wheel 28, so that the outside second vehicle wheel 30 receives more drive torque than the inside first vehicle wheel 28. Preferably, both wheel torques are greater than 0 in magnitude. The different wheel torques or drive torques of the vehicle wheels 28 and 30 can be seen on the bars B4 and B5.

[0059] Since the first vehicle wheel 28 is the outside vehicle wheel and the second vehicle wheel 30 is the inside vehicle wheel during the fourth cornering through the right-hand bend, the outside first vehicle wheel 28 receives more drive torque than the inside second vehicle wheel 30, so that the wheel torque transmitted to the first vehicle wheel 28 for driving the first vehicle wheel 28 is greater than the wheel torque transmitted to the second vehicle wheel 30 for driving the second vehicle wheel 30. This can again be seen from bars B4 and B5. The wheel torque transmitted to the respective inside vehicle wheel can be 0 or greater than 0 in magnitude. The wheel torque transmitted to the respective outside vehicle wheel is preferably greater than 0 in magnitude.

[0060] In a third part T6 of Fig.3 illustrates a second straight-ahead travel of the motor vehicle, which travels straight ahead during the second straight-ahead travel. During the second straight-ahead travel, the drive system 10 is operated in the fifth operating mode or in the fourth operating mode, as already described with reference to part T3. The highest possible torque that can be transmitted between the rotors 14 and 20 via the friction clutch 34 is also referred to as the clutch torque. Using the clutch torque, a drive torque distribution between the vehicle wheels 28 and 30 corresponding to the lateral dynamics requirement can be set with only one active electric machine 12, 18. For this purpose, it is advantageous to switch from one electric machine to the other electric machine if the electric machine assigned to the vehicle wheel on the inside of the curve is preselected.By using position signals, such as GPS signals, which characterize the current position of the vehicle on Earth and are determined, for example, by satellite, and map data, it is possible to switch in advance. However, the goal is to achieve an unnoticeable switchover regardless of this. Switching from one drive unit to another is practically energy-neutral. List of reference symbols 10 electric drive system 12 first electric machine 14 first rotor 16 first stator 18 second electric machine 20 second rotor 22 second stator 24 housings 26 vehicle axle 28 first vehicle wheel 30 second vehicle wheel 32 double arrow 34 Friction clutch 36 first gear device 38 second transmission device 40 first planetary gear set 42 second planetary gear set 44 first sun gear 46 first ring gear 48 first planet carrier 50 Main axis of rotation 52 Planetary gear 54 second sun gear 56 second ring gear 58 second planet carrier 60 planetary gear 62 Steering handle B1 beam B2 beam B3 beam B4 beam B5 beam B6 beam B7 beam T1 part T2 Part T3 part T4 part T5 part T6 part

Claims

[1] Method for operating an electric drive system (10) for a motor vehicle, in which the drive system (10) comprises: - a first electric machine (12) having a first rotor (14); - a second electric machine (18) having a second rotor (20) arranged coaxially to the first rotor (14); - a first vehicle wheel (28) which is permanently coupled to the first rotor (14) in a torque-transmitting manner and is thereby drivable by the first rotor (14) and is associated with the first electric machine (12); - a second vehicle wheel (30) which is permanently coupled to the second rotor (20) in a torque-transmitting manner and is thereby drivable by the second rotor (20) and is associated with the second electric machine (18); and - a friction clutch (34) which is designed to connect the first rotor (14) to the second rotor (20) in a rotationally fixed manner, the friction clutch (34) being the only means for coupling the two rotors (14, 20); Wherein, in the case of single-engine operation, when cornering the motor vehicle: o with respect to the electrical machines (12, 18), only the electrical machine (12, 18) to which the vehicle wheel (28, 30) on the outside of the curve is assigned is driven; and o the friction clutch (34) is closed to a degree of engagement which is selected such that a specific drive torque distribution is effected from the electric machine (12, 18), to which the vehicle wheel (28, 30) on the outside of the curve is assigned, to the two vehicle wheels (28, 30), wherein between the first vehicle wheel (28) and the first rotor (14) there is arranged exactly one first transmission device (36), via which the first vehicle wheel (28) is permanently coupled to the first rotor (14) in a torque-transmitting manner; and between the second vehicle wheel (30) and the second rotor (20) there is arranged exactly one second transmission device (38), via which the second vehicle wheel (30) is permanently coupled to the second rotor (20) in a torque-transmitting manner, characterized by , that the first transmission device (36) is designed as a first planetary gear set (40); and the second transmission device (38) is designed as a second planetary gear set (42), wherein the respective planetary gear set (40, 42) is designed as a respective simple planetary gear set (40, 42), wherein a first sun gear (44) of the first planetary gear set (40) is permanently connected to the first rotor (14) in a rotationally fixed manner, wherein a first ring gear (46) of the first planetary gear set (40) is permanently connected in a rotationally fixed manner to a housing (24) of the drive system (10); wherein a first planet carrier (48) of the first planetary gear set (40) is permanently connected in a rotationally fixed manner to the first vehicle wheel (28), wherein a second sun gear (54) of the second planetary gear set (42) is permanently connected to the second rotor (20) in a rotationally fixed manner, wherein a second ring gear (56) of the second planetary gear set (42) is permanently connected in a rotationally fixed manner to the housing (24) of the drive system (10), and wherein a second planet carrier (58) of the second planetary gear set (42) is permanently connected in a rotationally fixed manner to the second vehicle wheel (30), wherein the respective electrical machine (12, 18) is designed as a respective axial flux machine. [2] Method according to claim 1, characterized bythat in the single-engine operation, an operating mode in which the two vehicle wheels (28, 30) are driven with individually adjustable different torques is carried out by selecting the degree of closure such that the vehicle wheel (28, 30) on the outside of the curve receives more drive torque than the vehicle wheel (28, 30) on the inside of the curve. [3] Method according to claim 1, characterized by that in single-engine operation, an operating mode in which the two vehicle wheels (28, 30) are driven with individually adjustable different torques is avoided by both vehicle wheels (28, 30) receiving the same drive torque. [4] Method according to one of the preceding claims, characterized by that the rotors (14, 20) are arranged at least substantially coaxially to the vehicle wheels (28, 30). [5] Motor vehicle, with an electric drive system (10) which is designed to carry out a method according to one of the preceding claims.

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