Method for operating an electric axle drive of a motor vehicle

Abstract

The invention relates to a method for operating an electric axle drive (30), in which the electric axle drive (30) has a first electric machine (32) which has a first rotor (34). A second electric machine (46) which has a second rotor (48) is provided. A differential gear (36) is provided which has an input shaft (38), a first output shaft (40), and a second output shaft (42). The output shafts (40, 42) are designed to transfer torques from the differential gear (36) in the direction of vehicle wheels (18, 20) of the motor vehicle (10). The first rotor (34) is or can be coupled to the input shaft (38) in such a way that torques, originating from the first rotor (34), can be introduced into the input shaft (38) and, via the input shaft (38), into the differential gear (36).A first switching element designed as a first friction clutch (44) is provided as the first clutch, by means of which the second rotor (48) can be coupled to the first output shaft (40).

Description

[0001] The invention relates to a method for operating an electric axle drive of a motor vehicle according to the preamble of patent claim 1.

[0002] DE 10 2021 006 124 B3 discloses an electric axle drive for an at least partially electrically powered motor vehicle. It provides a first electric machine having a first rotor. A second electric machine having a second rotor is also provided.

[0003] The object of the present invention is to provide a method for operating an electric axle drive of a motor vehicle so that a particularly advantageous driving behavior of the motor vehicle can be realized.

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

[0005] The invention relates to a method for operating an electric axle drive of a motor vehicle, also referred to simply as a vehicle, whose interior, also referred to as a passenger compartment, passenger cell, or cabin, is formed, for example, by a motor vehicle structure designed, in particular, as a self-supporting body. The motor vehicle, also referred to simply as a vehicle, is preferably designed as a motor vehicle, in particular as a passenger car. Preferably, in the method, the motor vehicle is driven by the electric axle drive, in particular electrically and most particularly purely electrically.

[0006] In the method, the electric axle drive has a first electric machine which has a first rotor. For example, the first electric machine also 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 axle drive also has a second electric machine which has a second rotor. For example, 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. Preferably, the respective first electric machine is a respective high-voltage component whose electrical voltage, in particular electrical operating or nominal voltage, is preferably greater than 50 volts, in particular greater than 60 volts, and very preferably amounts to several hundred volts.In the method, the electric axle drive has a differential gear, also simply referred to as a differential or axle transmission, which has an input shaft, a first output shaft, and a second output shaft. The output shafts are designed to divert, i.e., transfer torque from the differential gear in the direction of vehicle wheels of the motor vehicle. Thus, for example, a first of the vehicle wheels can be driven by the first output shaft, and a second of the vehicle wheels can be driven by the second output shaft. Thus, for example, the first output shaft can drive the first vehicle wheel, bypassing the second output shaft and bypassing the second vehicle wheel, and for example, the second output shaft can drive the second vehicle wheel, bypassing the first output shaft and bypassing the first vehicle wheel.This means, in particular, the following: With respect to a first torque flow, along which torques can be transmitted from the first output shaft to the first vehicle wheel in order to thereby drive the first vehicle wheel, the torques flow or stream along the first torque flow from the first output shaft to or onto the first vehicle wheel, wherein the torques on their way from the first output shaft to the first vehicle wheel via the first torque flow do not flow or stream from the first output shaft to the first vehicle wheel via the second output shaft or via the second vehicle wheel. The same applies to the second output shaft and the second vehicle wheel.With respect to a second torque flow, along which torques can be transmitted from the second output shaft to the second vehicle wheel in order to thereby drive the second vehicle wheel, the torques on their way from the second output shaft to or onto the second vehicle wheel along the second torque flow do not flow via the first output shaft and not via the first vehicle wheel from the second output shaft to the second vehicle wheel.

[0007] When reference is made above and below to the vehicle wheels, this means the first vehicle wheel and the second vehicle wheel, unless stated otherwise. Preferably, the first vehicle wheel and the second vehicle wheel are vehicle wheels of the same vehicle axle of the motor vehicle, also referred to as the first vehicle axle. Preferably, the motor vehicle has at least or exactly two vehicle axles arranged consecutively and thus one behind the other in the longitudinal direction of the motor vehicle, namely the aforementioned first vehicle axle and a second vehicle axle. The respective vehicle axle has at least or exactly two vehicle wheels, so that the first vehicle axle has the first vehicle wheel and the second vehicle wheel and so that, for example, the second vehicle axle has a third vehicle wheel and a fourth vehicle wheel.The respective vehicle wheels of the respective vehicle axle are preferably arranged on opposite sides of the motor vehicle in the transverse direction of the motor vehicle. 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 being 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. It can be seen that the first vehicle wheel and the second vehicle wheel can be driven by the differential gear via the output shafts.The respective torque which can be or is transmitted via the respective torque flow from the respective output shaft to or onto the respective vehicle wheel, in particular in order to thereby drive the respective vehicle wheel, results, for example, from a respective input torque which can be or is introduced via the input shaft via the differential gear.

[0008] In the method, the electric axle drive has a first shifting element which is designed as a first friction clutch. The first friction clutch is also referred to as the first clutch or is a first clutch of the electric axle drive. By means of the first friction clutch, the second rotor can be coupled to the first output shaft in such a way that torques emanating from the second rotor and thus provided or provideable by the second electric machine via the second rotor and thus by the second rotor can be introduced into the first output shaft, i.e. can be transmitted to the first output shaft, bypassing the input shaft and bypassing the second output shaft and in particular bypassing the vehicle wheels.This means that the respective torque provided or that can be provided by the second rotor and thus by the second electric machine via the second rotor does not flow or flow into or onto the first output shaft via the second output shaft and not via the input shaft and also not via the vehicle wheels.

[0009] In the method, the electric axle drive has a second switching element which is provided in addition to the first friction clutch and is designed as a second friction clutch. The second friction clutch is provided in addition to the first friction clutch and is also referred to as a second clutch. In other words, the second friction clutch is a second clutch of the axle drive. By means of the second friction clutch, the second rotor can be coupled to the second output shaft in such a way that torques emanating from the second rotor and thus provided or capable of being provided by the second rotor, and therefore by the second electric machine via the second rotor, can be introduced into the second output shaft, bypassing the input shaft and bypassing the first output shaft, and in particular also bypassing the vehicle wheels, and can therefore be transmitted to the second output shaft.This means that the respective torque provided or that can be provided by the second rotor and thus by the second electric machine via the second rotor does not flow or flow via the input shaft or via the first output shaft or via the vehicle wheels onto or into the second output shaft on its way from the second rotor to or onto the second output shaft.

[0010] In the method, the electric axle drive preferably has a positive-locking first clutch, designed for example as a claw clutch, which is provided in addition to the first clutch and in addition to the second clutch. By means of the third clutch, the second rotor can be coupled to the friction clutches in such a way, in particular simultaneously, that torques emanating from the second rotor and thus provided or capable of being provided by the second rotor, and thus by the second electric machine via the second rotor, can be introduced into the input clutches, i.e., can be transmitted to the friction clutches, bypassing the input shaft and bypassing the output shafts and in particular also bypassing the vehicle wheels, in particular simultaneously.For example, the following is provided: The first friction clutch has, for example, a first input element, a first output element, and first friction elements, in particular first friction plates, by means of which the first input element and the first output element can be connected to one another in a rotationally fixed manner, in particular by pressing the first friction elements together. The second friction clutch has, for example, a second input element, a second output element, and second friction elements, in particular second friction plates, by means of which the second input element and the second output element can be connected to one another in a rotationally fixed manner, in particular by pressing the second friction elements together.By means of the third clutch, the second rotor can be coupled, for example, in particular simultaneously, to the input elements in such a way that the torques emanating from the second rotor and thus provided or capable of being provided by the second rotor, and thus by the second electric machine via the second rotor, can be introduced into the input elements, i.e. transmitted to the input elements, bypassing the input shaft and bypassing the output shafts and in particular also bypassing the vehicle wheels, in particular simultaneously. The respective torque introduced into the respective input element can then be transmitted, for example, from the respective input element to the respective output element, in particular if the respective input element and the respective output element are connected to one another in a rotationally fixed manner by means of the respective friction elements.Thus, with reference to a first torque flow along which the torques emanating from the second rotor can be introduced into the first output shaft via the third clutch and the first friction clutch, bypassing the input shaft and the second output shaft, and in particular bypassing the vehicle wheels and in particular bypassing the second friction clutch, the third clutch being arranged downstream of the second rotor and upstream of the first friction clutch in the first torque flow, and the first friction clutch being arranged downstream of the third clutch and upstream of the first output shaft in the first torque flow. This can be achieved by the first friction clutch and the third clutch being closed, in particular simultaneously, while the second friction clutch is open.

[0011] Related to a second torque flow, along which the torques emanating from the second rotor can be introduced into the second output shaft via the third clutch and the second friction clutch, bypassing the input shaft and the first output shaft, and in particular bypassing the vehicle wheels and in particular bypassing the first friction clutch, the second rotor, the third clutch, the second friction clutch and the second output shaft being arranged in the second torque flow, the third clutch being arranged downstream of the second rotor and upstream of the second friction clutch in the second torque flow, and the second friction clutch being arranged downstream of the third clutch and upstream of the second output shaft in the second torque flow. This can be achieved by the second friction clutch and the third clutch being closed, in particular simultaneously, while the first friction clutch is open.

[0012] By means of the third clutch, the second rotor can be coupled to the respective input element in a form-fitting, torque-transmitting manner, particularly in a rotationally fixed manner. Since the third clutch is a form-fitting clutch, it is also referred to as a form-fitting shifting element. The third clutch is also referred to as a third shifting element.

[0013] In order to be able to achieve particularly advantageous driving behavior, in particular driving dynamics behavior, of the motor vehicle, also simply referred to as a vehicle, the method according to the invention provides that a first service brake, provided in addition to the clutches, is assigned to the first vehicle wheel for braking, i.e. for braking the first vehicle wheel. In particular, the first service brake is designed to brake, i.e., to brake the first vehicle wheel, while braking brought about by means of the first service brake, i.e., braking the second vehicle wheel, is omitted. In the method, a second service brake, provided in addition to the clutches and in addition to the first service brake, is assigned to the second vehicle wheel for braking, i.e., for braking the second vehicle wheel.In particular, the second service brake is designed to brake, i.e., decelerate, the second vehicle wheel, while braking, i.e., deceleration of the first vehicle wheel, effected by the second service brake, is omitted. Preferably, the respective service brake is designed as a respective friction brake. For example, the respective service brake is designed as a respective disc brake.

[0014] If, in the method, a driving dynamics controller controlled by an electronic computing device, in particular of the motor vehicle, requests a torque vectoring intervention, wherein the driving dynamics controller requests the torque vectoring intervention, for example, while the friction clutches are disengaged and while the first electric machine is providing a torque, also referred to as drive torque, via the first rotor, and preferably while the third clutch is disengaged, then, in the method, a braking torque is requested, which is to be provided by one of the service brakes and designed to brake the vehicle wheel to which the one service brake is assigned. In particular, the braking torque is requested by means of the driving dynamics controller, i.e., by the driving dynamics controller.Preferably, the braking torque is requested while the friction clutches are, in particular, still disengaged, and preferably while the third clutch is, in particular, still disengaged, and preferably while the first rotor, thus the first electric machine, is providing the drive torque via its first rotor. In the method, when the vehicle dynamics controller requests the torque vectoring intervention, an increase in the drive torque is also requested, which is provided by the first electric machine via the first rotor and thus by the first rotor and drives the vehicle wheels.The torque vectoring intervention comprises, for example, that, in particular while the first electric machine provides the drive torque, which is also referred to as the first drive torque, via its first rotor, the second electric machine provides a second drive torque via its second rotor, which, for example, is either to be transmitted or is transmitted to only one of the vehicle wheels in order to thereby drive one of the vehicle wheels, or is distributed to both vehicle wheels in such a way that a first part of the second drive torque that is greater than zero is transmitted to one of the vehicle wheels and a second part of the second drive torque that is greater than zero and less than the first part is transmitted to the other vehicle wheel.As a result of the torque vectoring intervention, for example, the vehicle wheel to which the second drive torque is transmitted or which receives the first part of the second drive torque that is greater than the second part can be driven more strongly than the other vehicle wheel, since one vehicle wheel is driven by means of the first drive torque and the second drive torque or by means of the first drive torque and the first part, and the other vehicle wheel is driven only by the first drive torque or by means of the first drive torque and the second part. This can, for example, enable the motor vehicle to travel particularly dynamically through a bend, since, for example, the vehicle wheel on the outside of the bend is driven more strongly than the vehicle wheel on the inside of the bend.Furthermore, particularly safe driving of the motor vehicle, especially through a curve, can be achieved. In particular, the torque vectoring intervention can specifically influence or cause understeering and / or oversteering of the motor vehicle, thereby enabling particularly advantageous, safe, and dynamic driving behavior to be realized as needed.

[0015] The invention makes it possible to carry out a type of torque vectoring by means of the braking torque and by increasing the first drive torque, thus realizing advantageous driving behavior of the motor vehicle until the actual torque vectoring intervention can begin and take place. For technical reasons, this can only begin when, after the request for the torque vectoring intervention, at least or exactly one of the initially opened friction clutches, and in particular the initially opened third clutch, is closed. For technical reasons, a certain period of time elapses from the request for the torque vectoring intervention until a time at which the requested torque vectoring intervention can actually begin and thus be carried out. This period of time is technically necessary to close the initially opened clutches, because the actual torque vectoring intervention can only begin after the initially opened clutches have closed.The invention now makes it possible, during the period in which the actual torque vectoring intervention cannot yet be performed, to perform torque vectoring or a type of torque vectoring in which the vehicle wheel to which the service brake is assigned is braked using the braking torque and the drive torque, which is provided by the first electric machine via the first rotor and drives the vehicle wheels, is increased. For example, the torque vectoring intervention can cause a targeted yaw moment around the vertical direction of the motor vehicle.By means of the braking torque and by increasing the drive torque, a yaw moment about the vertical direction of the vehicle can be induced, for example, during the time period and thus before the actual torque vectoring intervention begins, in particular likewise, so that a time interval lying between a first point in time at which the torque vectoring intervention is requested and a second point in time at which a yaw moment is induced by means of the braking torque and by increasing the drive torque about the vertical direction of the vehicle can be avoided or at least kept particularly short. This makes it possible to achieve particularly advantageous driving behavior. In particular, the respective yaw moment and thus the torque vectoring intervention can be a driving safety intervention in order to avoid excessive understeer and excessive oversteer.Since the said time interval can now be kept particularly short or avoided, a particularly advantageous driving behavior, in particular a particularly safe driving behavior, can be ensured.

[0016] Typically, the time span between the request for torque vectoring intervention and the actual start of torque vectoring intervention can be relatively long, since the initially opened clutches must be closed in order to carry out the torque vectoring intervention. Typically, the initially opened clutches are closed in such a way that the clutches are controlled electrically and / or hydraulically, in particular electrohydraulically, and / or that valves and / or hydraulic cylinders are controlled and / or actuated in order to supply the clutches, which must or should be closed to carry out the torque vectoring intervention, with a hydraulic fluid for actuating and in particular for closing the components. The invention is also based on the finding that torque vectoring with the aid of service brakes, also referred to as wheel brakes, can lead to efficiency losses.The invention now makes it possible, on the one hand, to implement torque vectoring by means of the braking torque and by increasing the drive torque in order to achieve the advantageous behavior. On the other hand, this torque vectoring can be kept particularly short in terms of the time it is carried out, so that particularly efficient operation can be achieved. In the context of the present disclosure, as is well known, "torque vectoring" is to be used to effect a particularly targeted application of a torque to at least or precisely one of the vehicle wheels, so that the vehicle wheels are driven with different strengths and a yaw moment can be or is specifically generated around the vertical direction of the vehicle.

[0017] Since the braking torque decelerates the vehicle wheel assigned to the service brake, the deceleration of the vehicle wheel assigned to the service brake can be compensated for by increasing the drive torque, particularly simultaneously, thus achieving advantageous driving behavior. The invention thus enables a targeted influence on the vehicle's driving dynamics even with a delayed engagement or closing of the clutches. However, excessive efficiency losses can be avoided.

[0018] In order to be able to realize particularly advantageous driving behavior, one embodiment of the invention provides that, as a result of the braking torque being requested, the one service brake actually provides the requested braking torque, by means of which the vehicle wheel to which the one service brake is assigned is actually braked, i.e., decelerated. In particular, the vehicle wheel to which the one service brake is assigned is braked by means of the braking torque provided by the one service brake, while the friction clutches are, in particular, still disengaged and while the first electric machine is providing the drive torque via the first rotor and in particular while the third clutch is, in particular, still disengaged.

[0019] It has proven particularly advantageous if, while the vehicle wheel to which one service brake is assigned is braked by means of the braking torque provided by one service brake, braking of the vehicle wheel to which the other service brake is assigned is omitted, or if the other service brake provides a second braking torque that is lower than the braking torque by means of which the vehicle wheel to which the other service brake is assigned is braked. This means that while one service brake is braking the vehicle wheel to which one service brake is assigned, the other service brake does not brake the vehicle wheel to which the other service brake is assigned, or brakes it less strongly than the vehicle wheel to which one service brake is assigned, which is braked by means of the one service brake.This allows a favorable yaw moment to be generated around the vehicle's vertical direction, especially while the friction clutches and the third clutch are open and while the drive torque is provided by the first rotor and drives the vehicle wheels, before the actual torque vectoring intervention takes place. This ensures particularly favorable driving behavior.

[0020] A further embodiment of the invention is characterized in that, as a result of the request for an increase in drive torque, the drive torque provided by the first electric machine via the first rotor is actually increased and actually drives the vehicle wheels, in particular while the friction clutches are still open and while the third clutch is still open. As a result, the braking of the vehicle wheel to which the service brake is assigned, caused by the braking torque, can be compensated, so that advantageous torque vectoring can be generated before the actual start of the torque vectoring intervention, thus enabling advantageous driving behavior.

[0021] It has proven particularly advantageous that, while the one service brake is providing the service brake and while the vehicle wheel to which the one service brake is assigned is braked by means of the braking torque provided by the one service brake, and while the first electric machine is providing the increased drive torque and while the vehicle wheels are driven by means of the increased drive torque provided by the first electric machine via the first rotor, a closing process is started and thus at least partially carried out, by means of which at least or exactly one of the initially opened friction clutches is closed. The closing process or the beginning of the closing process comprises, for example, that the at least or exactly one friction clutch is controlled, in particular hydraulically and / or electrically.The actuation of the at least one or exactly one friction clutch comprises, for example, valves and / or at least one actuator being actuated, in particular electrically, in order to thereby, for example, supply the at least one or exactly one friction clutch with the aforementioned hydraulic fluid in order to thereby actuate and thus close the at least one or exactly one friction clutch.

[0022] A further embodiment of the invention is characterized in that, while one service brake provides the braking torque and while the vehicle wheel to which the one service brake is assigned is braked by means of the braking torque provided by the one service brake, and while the first electric machine provides the increased drive torque and while the vehicle wheels are driven by means of the first drive torque provided by the first electric machine via the first rotor, an engagement process is initiated, by which the initially disengaged third clutch is closed. The start of the engagement process or the engagement process comprises, for example, the third clutch being actuated, in particular electrically and / or hydraulically.Controlling the third clutch includes, for example, controlling at least one valve and / or at least one actuator to supply the third clutch, for example, with the aforementioned hydraulic fluid, thereby actuating and thus closing the third clutch. This advantageously minimizes the time during which the vehicle wheel to which the service brake is assigned is braked, thus avoiding excessive efficiency loss. Consequently, advantageous, efficient operation can be ensured.

[0023] In order to be able to realize advantageous driving behavior and particularly efficient operation, a further embodiment of the invention provides that after and / or during the engagement of the clutches, i.e., the at least one or exactly one friction clutch and the third clutch, the drive torque provided by the first electric machine via the first rotor and driving the vehicle wheels is reduced and the braking torque is reduced. This means that the braking torque and the drive torque are transferred, so to speak, to the clutches and the second electric machine, since the torque vectoring caused by the braking torque and by the increase in the drive torque is reduced and, for example, ended, and the actual torque vectoring intervention is initiated and subsequently carried out by means of the second electric machine via the clutches.This ensures advantageous driving behavior and particularly efficient operation.

[0024] In order to be able to realize particularly efficient operation and particularly advantageous driving behavior, it is provided in a further embodiment of the invention that the reduction of the braking torque comprises that the braking torque is reduced to zero, whereby braking of the vehicle wheel to which the one service brake is assigned, effected by means of the one service brake, is prevented or ended.

[0025] It has also been shown to be particularly advantageous if the drive torque provided by the first electric machine via the first rotor has a first value before the drive torque provided by the first electric machine via the first rotor is increased, wherein the reduction of the drive torque provided by the first electric machine via the first rotor comprises reducing the torque provided by the first electric machine via the first rotor to a second value that is lower than the first value. This allows for particularly advantageous driving behavior to be achieved.

[0026] Finally, it has been shown to be particularly advantageous that while the one service brake provides the braking torque and while the vehicle wheel to which the one service brake is assigned is braked by means of the braking torque provided by the one service brake and while the first electric machine provides the increased torque and while the vehicle wheels are driven by means of the increased drive torque which is provided by the first electric machine via the first rotor, the second electric machine is controlled in a targeted manner such that a speed of the second rotor is increased and / or the second electric machine provides a torque via the second rotor, in particular in the form of the second drive torque.Thus, for example, the torque vectoring generated by the braking torque and by increasing the drive torque can be reduced, in particular continuously, and thus masked out and subsequently, for example, ended, and the actual torque vectoring intervention can be started and, so to speak, faded in and thus carried out, in particular by closing at least or exactly two of the initially opened three clutches and the second electric machine providing the second drive torque via the second rotor.

[0027] Increasing the speed of the second rotor is, for example, synchronization in which the speed of the second rotor is brought to a target value so that, for example, the second rotor rotates at the same speed as an element which can be or will be connected to the second rotor in a rotationally fixed manner by means of the third clutch and in particular by closing the third clutch. This element is, for example, the respective input element. The third clutch can therefore, for example, be closed, in particular completely, and preferably only when the element and the second rotor rotate at the same speed, in particular relative to a housing of the axle drive. This can ensure particularly advantageous driving behavior.

[0028] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. The drawing shows: Fig. 1 is a schematic representation of a motor vehicle with an electric axle drive; and Fig. 2 a diagram illustrating a method for operating the electric axle drive.

[0029] In the figures, identical or functionally identical elements are provided with the same reference numerals.

[0030] Fig. 1 shows a schematic representation of a motor vehicle 10, also simply referred to as a vehicle, which is preferably designed as a motor vehicle, in particular as a passenger car. The motor vehicle 10 has exactly two vehicle axles arranged consecutively and thus one behind the other in the longitudinal direction of the motor vehicle 10, namely a first vehicle axle 12 and a second vehicle axle 14. The vehicle longitudinal direction is illustrated by a double arrow 16. The respective vehicle axle 12, 14 has exactly two vehicle wheels arranged on opposite sides of the motor vehicle 10 in the transverse direction of the motor vehicle 10, wherein the vehicle wheels of the vehicle axle 12 are designated 18 and 20 and the vehicle wheels of the vehicle axle 14 are designated 22 and 24. The vehicle wheel 18 is also referred to as the first vehicle wheel, and the vehicle wheel 20 is also referred to as the second vehicle wheel.The vehicle wheel 22 is also referred to as the third vehicle wheel, and the fourth vehicle wheel is also referred to as the fourth vehicle wheel. The vehicle wheels 18, 20, 22, and 24 are ground contact elements by which the motor vehicle 10 can be or is supported downwards on a ground in the vehicle's vertical direction. The vehicle's transverse direction is illustrated by a double arrow 26, and the vehicle's vertical direction is illustrated by a double arrow 28, with the vehicle's vertical direction being perpendicular to the image plane of FIG. Fig. 1. If the motor vehicle 10 is driven along the ground while the motor vehicle 10 is supported downwards in the vertical direction of the motor vehicle 10 via the ground contact elements, the vehicle wheels 18, 20, 22 and 24 roll, in particular directly, on the ground.

[0031] The motor vehicle 10 has an electric axle drive 30, also simply referred to as an axle drive, by means of which the vehicle wheels 18 and 20 and thus the motor vehicle 10 can be driven, in particular purely electrically. For this purpose, the electric axle drive 30 has a first electric machine 32, which has a first rotor 34. Via its rotor 34, the electric machine 32 can provide a first drive torque for driving the vehicle wheels 18 and 20. The axle drive 30 has a differential gear 36, which has an input shaft 38, a first output shaft 40, and a second output shaft 42. The output shafts 40 and 42 are designed to transfer respective output torques from the differential gear 36 in the direction of the vehicle wheels 18 and 20.This means that, by means of the output shaft 40, a first of the output torques can be diverted from the differential gear 36 in the direction of the vehicle wheel 18, so that the vehicle wheel 18 can be driven by the first drive torque. By means of the output shaft 42, a second of the output torques can be diverted from the differential gear 36 in the direction of the vehicle wheel 20, which can be driven by the second drive torque. The first drive torque and the output torques are torques, wherein the respective output torque results or can result from the drive torque. In other words, the electric machine 32 can vary the first drive torque, in particular by controlling the electric machine 32, and thereby generate different values ​​of the first drive torque, wherein a respective value of the respective output torque depends on the respective value of the first drive torque.As is well known from the general state of the art, the differential gear 36 is designed in particular to distribute or split the first drive torque between the output shafts 40 and 42 and, for example, to allow different speeds of the vehicle wheels 18 and 20 when cornering the motor vehicle 10, in particular such that the vehicle wheel on the outside of the curve rotates or can rotate at a higher speed than the vehicle wheel on the inside of the curve.

[0032] The axle drive 30 also has a second electric machine 46, which is provided in addition to the first electric machine 32 and has a second rotor 48. Via the rotor 48, the electric machine 46 can provide a second drive torque, which is also a torque. The electric machine 46 can vary the second torque, in particular by controlling the electric machine 46, and thereby produce different values ​​for the second drive torque.

[0033] In the Fig. 1, the rotor 34 can be coupled or is coupled to the input shaft 38, in particular in a torque-transmitting and very particularly rotationally fixed manner, in such a way that the first drive torque emanating from the first rotor 34, and thus provided by the electric machine 32 via the rotor 34, can be introduced into the differential gear 36 via the input shaft 38, in particular bypassing the output shafts 40 and 42, so that the first drive torque provided by the rotor 34 and thus by the electric machine 32 via the rotor 34 does not flow or stream from the rotor 34 to or onto the input shaft 38 via the output shaft 40, nor via the output shaft 42, nor via the vehicle wheels 18 and 20.

[0034] The electric axle drive 30 has a first shifting element, which is designed as a first friction clutch 44. The first friction clutch 44 is also referred to as the first clutch. The electric axle drive 30 has a second shifting element, provided in addition to the first friction clutch 44, which is designed as a second friction clutch 50. The second friction clutch 50 is also referred to as the second clutch.By means of the first friction clutch 44, the second rotor 48 can be coupled to the first output shaft 40, in particular in a torque-transmitting and very particularly rotationally fixed manner, in such a way that the second drive torque provided or can be provided by the second rotor 48 and thus emanating from the second rotor 48 can be introduced into the first output shaft 40, i.e. can be transmitted to the first output shaft 40, bypassing the input shaft 38 and bypassing the output shaft 42 and bypassing the vehicle wheels 18 and 20 and bypassing the second friction clutch 50. This means that the second torque on its way from the rotor 48 to and onto the output shaft 40 does not flow or stream via the output shaft 42, nor via the input shaft 38, nor via the vehicle wheels 18 and 20, nor via the second friction clutch 50 from the rotor 48 to and onto the output shaft 40 via the friction clutch 44.

[0035] By means of the second friction clutch 50, the second rotor 48 can be coupled to the second output shaft 42, in particular in a torque-transmitting and very particularly rotationally fixed manner, in such a way that the second drive torque emanating from the second rotor 48 and thus provided or available by the second rotor 48, and thus by the second electric machine 46 via the second rotor 48, can be introduced into the output shaft 42, and thus transmitted to the output shaft 42, bypassing the input shaft 38 and bypassing the output shaft 40 and also bypassing the vehicle wheels 18 and 20 and bypassing the first friction clutch 44.This means that the second drive torque on its way from the rotor 48 to and onto the output shaft 42 does not flow or flow via the input shaft 38 and not via the output shaft 40 and also not via the vehicle wheels 18 and 20 and also not via the first friction clutch 44 from the rotor 48 to and onto the output shaft 42 via the friction clutch 50.

[0036] The electric axle drive 30 also has a positive-locking third clutch 52 provided in addition to the friction clutches 46 and 44, which is configured, for example, as a claw clutch. By means of the positive-locking third clutch 52, the second rotor 48 can be connected, i.e., coupled, to the friction clutches 44 and 50 in a torque-transmitting, particularly rotationally fixed manner, bypassing the output shafts 40 and 42 and the input shaft 38, as well as bypassing the vehicle wheels 18 and 20.In other words, the second rotor 48 can be coupled by means of the clutch 52, in particular simultaneously, to the friction clutches 44 and 50, in particular in a torque-transmitting and very particularly rotationally fixed manner, such that the second drive torque from the second rotor 48 can be introduced into the input clutches 44 and 50, bypassing the input shaft 38 and bypassing the output shafts 40 and 42 and bypassing the vehicle wheels 18 and 20, i.e. without flowing via the input shaft 38, the output shafts 40 and 42 and the vehicle wheels 18 and 20, in particular simultaneously. This is to be understood in particular as the following: The first friction clutch 42 has a first input element 54 and a first output element 56 and first friction elements, by means of which the input element 54 and the output element 56 can be connected to one another in a rotationally fixed manner.The second friction clutch 50 has a second input element 58, a second output element 60, and second friction elements, by means of which the input element 58 and the output element 60 can be connected to one another in a rotationally fixed manner. The rotor 48 can be connected, in particular rotationally fixed, to the input elements 54 and 58 by means of the clutch 52 in a torque-transmitting manner, i.e., can be coupled, in particular in such a way that the second drive torque emanating from the rotor 48 and thus provided or can be provided by the rotor 48, and thus by the electric machine 46 via the rotor 48, can be introduced into the input elements 54 and 58, bypassing the output shafts 40 and 42, bypassing the input shaft 38, and also bypassing the vehicle wheels 18 and 20, and can thus be transmitted to the input elements 54 and 58. The second drive torque can be transmitted from the input element 54 to the output element 56, in particular via the first friction elements.The second drive torque is transmittable, in particular, via the second friction elements from the second input element 58 to the second output element 60. Thus, for example, with respect to a first torque flow, via which the second drive torque can be transmitted from the rotor 48 to the output shaft 40, bypassing the input shaft 38 and the output shaft 42, the vehicle wheels 18 and 20, and the friction clutch 50, the clutch 52, the friction clutch 44, and the output shaft 40 are arranged in the first torque flow such that the clutch 52 is arranged downstream of the rotor 48 and upstream of the friction clutch 44, and the friction clutch 44 is arranged downstream of the clutch 52 and upstream of the output shaft 40.With respect to a second torque flow, via which the second drive torque can be transmitted from the rotor 48 to the output shaft 42, bypassing the input shaft 38, bypassing the output shaft 40, bypassing the vehicle wheels 18 and 20, and bypassing the friction clutch 44, the rotor 48, the clutch 52, the friction clutch 50, and the output shaft 42 are arranged in the second torque flow such that the clutch 52 is arranged downstream of the rotor 48 and upstream of the friction clutch 50, and the friction clutch 50 is arranged downstream of the clutch 52 and upstream of the output shaft 42. The friction clutch 50 is not arranged in the first torque flow, and the friction clutch 44 is not arranged in the second torque flow.

[0037] The first vehicle wheel 18 is assigned a first service brake 62, by means of which the vehicle wheel 18 can be braked, in particular while braking of the vehicle wheel 20 caused by the service brake 62 is not performed. The second vehicle wheel 20 is assigned a second service brake 64, by means of which the vehicle wheel 20 can be braked, in particular while braking of the vehicle wheel 18 caused by the service brake 64 is not performed. The service brakes 62 and 64 are preferably designed as friction brakes, in particular as disc brakes.

[0038] In the following, a method for operating the electric axle drive 30 is described, whereby a particularly advantageous driving behavior of the motor vehicle 10 can be realized by means of the method. The method is carried out by means of an electronic computing device 66, which is, for example, a component of the motor vehicle 10. In the method, by means of the electronic computing device 66, a Fig. 1 schematically illustrated driving dynamics controller 68. This means that the driving dynamics controller 68 runs on the electronic computing device 66, for example in the form of an algorithm. When, in the method, the driving dynamics controller 68 requests torque vectoring intervention, a braking torque is requested, in particular by the driving dynamics controller 68, to be provided by one of the service brakes 62 and 64 and designed to brake the vehicle wheel 18, 20 to which the one service brake 62, 64 is assigned. In addition, when the driving dynamics controller 68 requests the aforementioned torque vectoring intervention, in particular by the driving dynamics controller 68 requests an increase in the first drive torque, which is provided by the first electric machine 32 via the first rotor 34 and drives the vehicle wheels 18 and 20 via the differential gear 36 and the output shafts 40 and 42.

[0039] In the following, the method is explained in more detail using the example of a cornering of the motor vehicle 10, which travels through a left turn while cornering, thus describing a left turn. Furthermore, the method is explained using Fig. 2 explained. Fig. Figure 2 shows a diagram with time plotted on the abscissa 70. The first drive torque, the second drive torque, and the braking torque are plotted on the ordinate 72 of the diagram.

[0040] During a first time period Z1, the motor vehicle 10 travels straight ahead. During the first time period Z1, the rotor 34 and thus the electric machine 32, via the rotor 34, provide the first drive torque, by means of which the vehicle wheels 18 and 20 are driven via the differential gear 36. Driving of the vehicle wheels 18 and 20 by the electric machine 46 does not occur during the first time period Z1. Furthermore, braking of the vehicle wheels 18 and 20 by means of the service brakes 62 and 64 does not occur during the time period Z1. At a first time t1, the aforementioned cornering begins, so that the time period Z1 ends at the time t1. At the time t1, a second time period Z2 begins, which comprises a first phase I and a second phase II of the method. The first phase I begins at the time t1 and ends at a second time t2, which chronologically follows the time t1.The second phase II begins at time t2 and ends at a third time t3, which temporally follows time t1 and time t2. It can be seen that the second time period Z2 extends, in particular continuously, from time t1 to time t3. The vehicle dynamics controller 68 requests the torque vectoring intervention at time t1. During the time period Z1, the friction clutches 44 and 50 and also the third clutch 52 are open. In order to actually begin and subsequently carry out the torque vectoring intervention, it is necessary to close at least or exactly two of the three initially open clutches.However, for technical reasons, the clutches can be closed, in particular completely, at the earliest at time t2, so that the torque vectoring intervention requested at time t1 actually begins only, and in particular at the earliest, at time t2 and thus can be carried out, in particular only from time t2. In order to be able to realize an advantageous yaw moment acting around the vehicle's vertical direction and thus advantageous driving behavior of the motor vehicle 10 as a result of the request for the torque vectoring intervention already at time t1 or only shortly after time t1 and after time t2, the first drive torque is increased and the braking torque is provided, as previously described.In the embodiment shown in the figures and thus during the aforementioned cornering, the braking torque is provided by the service brake 64 assigned to the left vehicle wheel 20, so that the left vehicle wheel 20 is braked by means of the braking torque.

[0041] A time profile 74 is a time profile of the first drive torque. A second time profile 76 is a time profile of the second drive torque. A third time profile 78 is a time profile of the braking torque. It can be seen that the service brake 64 begins to provide the braking torque at time t1, so that the left vehicle wheel 20 is braked from time t1. In particular, during the time period Z2, the vehicle wheel 20 is braked by means of the service brake 64, i.e., by means of the braking torque provided by the service brake 64. From time t1, the first drive torque is increased, with the increased drive torque being provided, for example, by the rotor 34 until the second time t2.By increasing the first drive torque and by providing the braking torque, an agility-increasing yaw moment acting about the vehicle's vertical direction is deliberately generated at time t1 or shortly after time t1 and before time t2 in order to drive the motor vehicle 10 agilely, i.e. dynamically and safely, through the left-hand bend. In the time period Z2, in particular in phase I, for example, the electric machine 46 is specifically controlled in such a way that a rotational speed of the rotor 48 is increased and that the rotor 48 provides the second drive torque. In addition, for example, in the time period Z2, in particular in phase I, a closing process is initiated by which the initially opened friction clutch 44 is closed, in particular while the friction clutch 50 remains opened.Furthermore, in the time period Z2, in particular in phase I, an engagement process is initiated, by which the initially disengaged third clutch 52 is closed. The initiation of the engagement process and the initiation of the engagement process comprise, for example, at least one valve and / or at least one actuator, in particular electrically and / or hydraulically and / or pneumatically, being controlled, in particular in order to thereby supply the clutches with hydraulic fluid for actuating and engaging the clutches, for example. As a result of the engagement process and as a result of the engagement process, the first clutch and the third clutch are engaged, in particular completely engaged, at time t2 and from time t2 onwards, in particular while the second clutch is disengaged.As can be seen from the curve 78, a reduction in the braking torque begins at time t2, so that in phase II the braking torque is reduced, in particular such that at time t3 the braking torque is zero. Thus, from time t3 onwards, braking of the vehicle wheel 20 by the service brake 64 ceases. In addition, the first drive torque is reduced at and from time t2. It can be seen that during the time period Z1 and thus before the first drive torque is increased, the first drive torque has a first value. By reducing the first drive torque starting at time t2 and extending, for example, continuously until time t3, the first drive torque is reduced to a second value which is lower than the first value.In addition, for example, at time t2, the increase in the speed of the rotor 48 and the increase in the second drive torque begin, so that, for example, from time t3, the second drive torque has a value greater than zero and is provided by the rotor 48, thus by the electric machine 46 via the rotor 48. Increasing the speed of the rotor 48, for example, causes the rotor 48 and the input element 54 to rotate at the same speed. Since the motor vehicle 10 travels through the aforementioned left-hand bend when cornering, the friction clutch 44 assigned to the right vehicle wheel 18 is closed, in particular with regard to the friction clutches 44 and 50 exclusively.From time t3 onward, the vehicle wheels 18 and 20 are thus driven by the first drive torque, and the vehicle wheel 18, i.e., the right vehicle wheel, is additionally driven by the second drive torque, while the left vehicle wheel 20 is not driven by the second drive torque. As a result, the motor vehicle 10 can be driven agilely and safely through the left-hand bend when cornering. List of reference symbols 10 motor vehicle 12 first vehicle axle 14 second vehicle axle 16 Double arrow 18 first vehicle wheel 20 second vehicle wheel 22 third vehicle wheel 24 fourth vehicle wheel 26 Double arrow 28 Double arrow 30 electric axle drive 32 first electric machine 34 first rotor 36 differential gears 38 Input shaft 40 first output shaft 42 second output shaft 44 first friction clutch 46 second electric machine 48 second rotor 50 second friction clutch 52 third clutch 54 first input element 56 first output element 58 second input element 60 second output element 62 first service brake 64 second service brake 66 electronic computing device 68 Driving dynamics controller 70 Abscissa 72 ordinates 74 first chronological course 76 second time course 78 third temporal progression I first phase II second phase t1 first time point t2 second time point t3 third time point Z1 first time period Z2 second time period QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 006 124 B3

[0002]

Claims

[1] Method for operating an electric axle drive (30) of a motor vehicle (10), in which the electric axle drive (30) comprises: - a first electric machine (32) having a first rotor (34); - a second electric machine (46) having a second rotor (48); - a differential gear (36) having an input shaft (38), a first output shaft (40) and a second output shaft (42), wherein the output shafts (40, 42) are designed to transfer torques from the differential gear (36) in the direction of vehicle wheels (18, 20) of the motor vehicle (10), and wherein the first rotor (34) is or can be coupled to the input shaft (38) in such a way that torques, originating from the first rotor (34), can be introduced into the input shaft (38) and via the input shaft (38) into the differential gear (36); - a first switching element designed as a first friction clutch (44) as the first clutch, by means of which the second rotor (48) can be coupled to the first output shaft (40) in such a way that torques originating from the second rotor (48) can be introduced into the first output shaft (40), bypassing the input shaft (38) and bypassing the second output shaft (42); and - a second switching element designed as a second friction clutch (50) as a second clutch, by means of which the second rotor (48) can be coupled to the second output shaft (42) in such a way that torques, originating from the second rotor (48), can be introduced into the second output shaft (42) bypassing the input shaft (38) and bypassing the first output shaft (40); characterized by , that: - a first service brake (62) for braking the first vehicle wheel (18) is assigned to a first of the vehicle wheels (18, 20); - a second of the vehicle wheels (18, 20) is assigned a second service brake (64) provided in addition to the first service brake (62) for braking the second vehicle wheel (20); - when a driving dynamics controller (68) implemented by an electronic computing device (66) requests a torque vectoring intervention ◯ a braking torque to be provided by one of the service brakes (62, 64) and designed to brake the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned is requested; and ◯ an increase in torque is requested, which is provided by the first electric machine (32) via the first rotor (34) and drives the vehicle wheels (18, 20) via the differential gear (36). [2] Method according to claim 1, characterized bythat, as a result of the braking torque being requested, the one service brake (62, 64) provides the braking torque by means of which the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned is braked. [3] Method according to claim 2, characterized by that while the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned is braked by means of the braking torque provided by the one service brake (62, 64): - braking of the vehicle wheel (20, 18) to which the other service brake (64, 62) is assigned is omitted; or - the other service brake (20, 18) provides a second braking torque which is lower than the braking torque and by means of which the vehicle wheel (20, 18) to which the other service brake (64, 62) is assigned is braked. [4] Method according to one of the preceding claims, characterized bythat as a result of the increase in torque being requested, the torque provided by the first electric machine (32) via the first rotor (34) is increased and drives the vehicle wheels (18, 20) via the differential gear (36). [5] Method according to claim 4 as referred to in claim 2 or 3, characterized bythat while the one service brake (62, 64) provides the braking torque and while the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned is braked by means of the braking torque provided by the one service brake (62, 64), and while the first electric machine (32) provides the increased torque and while the vehicle wheels (18, 20) are driven via the differential gear (36) by means of the increased torque provided by the first electric machine (32) via the first rotor (34), a closing process is started, by means of which at least or exactly one of the initially opened friction clutches (44, 50) is closed. [6] Method according to claim 5 or claim 4 when referred back to claim 2 or 3, characterized by , that: - a positive-locking third clutch (52) is provided, by means of which the second rotor (48) can be coupled to the friction clutches (44, 50) in such a way that torques originating from the second rotor (48) can be introduced into the friction clutches (44, 50) bypassing the input shaft (38) and the output shafts (40, 42); and - while the one service brake (62, 64) provides the braking torque and while the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned is braked by means of the braking torque provided by the one service brake (62, 64) and while the first electric machine (32) provides the increased torque and while the vehicle wheels (18, 20) are driven via the differential gear (36) by means of the increased torque provided by the first electric machine (32) via the first rotor (34), an engagement process is started by means of which the initially opened third clutch (52) is closed. [7] Method according to claims 5 and 6, characterized by that after and / or during the closing of the couplings (44, 50, 52): - the torque provided by the first electric machine (32) via the first rotor (34) and driving the vehicle wheels (18, 20) via the differential gear (36) is reduced; and - the braking torque is reduced. [8] Method according to claim 7, characterized by that reducing the braking torque comprises reducing the braking torque to zero, whereby braking of the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned, effected by means of the one service brake (62, 64), is avoided. [9] Method according to claim 7 or 8, characterized bythat the torque provided by the first electric machine (32) via the first rotor (34) has a first value before increasing the torque provided by the first electric machine (32) via the first rotor (34), wherein reducing the torque provided by the first electric machine (32) via the first rotor (34) comprises reducing the torque provided by the first electric machine (32) via the first rotor (34) to a second value which is lower than the first value. [10] Method according to one of claims 5 to 9 or according to claim 4 when referred back to claim 2 or 3, characterized bythat while the one service brake (62, 64) provides the braking torque and while the vehicle wheel (18, 20) to which the one service brake (62, 64) is assigned is braked by means of the braking torque provided by the one service brake (62, 64), and while the first electric machine (32) provides the increased torque and while the vehicle wheels (18, 20) are driven via the differential gear (36) by means of the increased torque provided by the first electric machine (32) via the first rotor (34), the second electric machine (46) is controlled in a targeted manner such that a rotational speed of the second rotor (48) is increased and / or the second electric machine (46) provides a torque greater than zero via the second rotor (48).

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