Electric axle drive train with an axial flux machine and two grounding elements

Abstract

Electric axle drive train (1), in particular for driving a motor vehicle (2), comprising an electric machine (3) with a stator (4) and a rotor (5) which is rotatably mounted relative to the stator (4) and which is connected to a transmission input shaft (7) of a transmission arrangement (6) designed as a hollow shaft, and the transmission arrangement (6) further comprises a transmission output shaft (8) at which a different rotational speed than that of the transmission input shaft (7) is applied during operation of the axle drive train (1), and the rotor (5) has an axis of rotation (9) which is arranged coaxially with an axis of rotation (10) of the transmission input shaft (7) and the transmission output shaft (8), characterized in that in the transmission input shaft (7) designed as a hollow shaft for receiving a first earthing element (17), a first pot-shaped receiving element (31) with a first circumferential collar (32) is arranged in a rotationally fixed manner, wherein the first collar (32) forms an axial stop at a first axial end of the transmission input shaft (7), and in the transmission input shaft (7) designed as a hollow shaft for receiving a second earthing element (33), a second pot-shaped receiving element (34) with a second circumferential collar (35) is arranged in a rotationally fixed manner, wherein the second collar (35) forms an axial stop at a second axial end of the transmission input shaft (7), and the first earthing element (17) has a first contact body (11) which, by means of a first spring element (19), rests against a first earthing element (36) in an axial direction pointing out of the transmission input shaft (7) and the second earthing element (33) has a second contact body (12) which, by means of a second spring element (37), rests against a second earthing element (38) in an axial direction pointing out of the transmission input shaft (7), and the electrical machine (3) designed as an axial flux machine has a rotor shaft (13) designed as a hollow shaft, into which a bearing shaft (14) fixed relative to the stator (4) engages, wherein the rotor shaft (13) is rotatably mounted relative to the bearing shaft (14) by means of a rolling bearing (16) and a bearing preload device (20) is arranged on and / or in the bearing shaft (14) designed as a hollow shaft, by means of which a bearing preload in the rolling bearing (16) can be adjusted, wherein the first contact body (11) of the first grounding element (17) bears against the bearing preload device (20).

Description

[0001] The present invention relates to an electric axle drive train, in particular for driving a motor vehicle, comprising an electric machine with a stator and a rotor which is rotatably mounted relative to the stator and which is connected to a transmission input shaft of a transmission arrangement designed as a hollow shaft, and the transmission arrangement further comprises a transmission output shaft at which a rotational speed different from that of the transmission input shaft is applied during operation of the axle drive train, and the rotor has an axis of rotation which is arranged coaxially with an axis of rotation of the transmission input shaft and the transmission output shaft.

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

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

[0004] DE 10 2010 048 837 A1 discloses such a drive device comprising at least one electric motor and at least one planetary differential drivable by a rotor of the electric motor. The planetary differential comprises at least one planetary carrier operatively connected to a rotor of the electric motor, first planetary gears and second planetary gears rotatably mounted on the planetary carrier, and a first sun gear and a second sun gear, each of which is operatively connected to an output shaft of the planetary differential. The first planetary gears mesh with the first sun gear, and each of the second planetary gears meshes with the second sun gear and with one of the first planetary gears. Furthermore, the sun gears are arranged coaxially with a rotational axis of the rotor.

[0005] Very strong voltage slopes in the power supply of the electric drive generate unwanted electrical currents in the electric drive. These electrical currents flow through the housing, the shaft, and also the rotor bearings, which are damaged by mechanical wear and also by the passage of current. To prevent this, this electrical energy must be dissipated. The dissipation of electrical currents through the shaft into the housing is already known from the prior art. For example, grounding brushes or radially acting sliding elements (carbon brushes) are known for grounding the rotor shaft. Axial-acting shaft grounding systems are also known.These earthing and / or insulation elements prevent the electrical voltage induced in the mechanical structural elements of the electric motor from discharging via the bearings or being transferred to the adjacent components of the electric motor.

[0006] For example, publication CN 104 037 985 A describes an antistatic discharge device for the rotor of an electric motor. The antistatic discharge device comprises a discharge pin located in a bore at the rear end of the motor's rotor spindle. The discharge pin is screwed to the electric motor housing for grounding and electrical discharge of the rotor spindle.

[0007] DE 10 2019 133 889 A1 shows an electrical machine with a discharge device.

[0008] DE 38 43 048 A1 shows a coaxial starter motor with a planetary reduction gear.

[0009] DE 10 2019 133 677 A1 shows an electric machine with a rotor having a rotor shaft and a stator, and a housing assigned to the electric machine, as well as a lance arranged within the rotor shaft and electrically conductively connected to the rotor shaft, which lance is supported on the rotor shaft and floatingly mounted on the housing, wherein the lance and the housing are electrically conductively coupled to one another via at least one radially resilient, electrically conductive connecting element.

[0010] It is the object of the invention to provide an electric axle drive train, in particular for driving a motor vehicle, which provides improved grounding, has a compact design and a high level of durability.

[0011] This object is achieved by an electric axle drive train, in particular for driving a motor vehicle, comprising an electric machine with a stator and a rotor which is rotatably mounted relative to the stator and which is connected to a transmission input shaft of a transmission arrangement designed as a hollow shaft, and the transmission arrangement further comprises a transmission output shaft at which a rotational speed different from that of the transmission input shaft is applied during operation of the axle drive train, and the rotor has an axis of rotation which is arranged coaxially with an axis of rotation of the transmission input shaft and the transmission output shaft, wherein a first pot-shaped receiving element with a first circumferential collar is arranged in a rotationally fixed manner in the transmission input shaft designed as a hollow shaft for receiving a first grounding element, wherein the first collar forms an axial stop at a first axial end of the transmission input shaft,and in the transmission input shaft designed as a hollow shaft, a second pot-shaped receiving element with a second circumferential collar is arranged in a rotationally fixed manner for receiving a second grounding element, wherein the second collar forms an axial stop at a second axial end of the transmission input shaft, and the first grounding element has a first contact body which, by means of a first spring element, bears against a first grounding element in a direction axially pointing out of the transmission input shaft in a spring-loaded manner, and the second grounding element has a second contact body which, by means of a second spring element, bears against a second grounding element in a direction axially pointing out of the transmission input shaft in a spring-loaded manner.

[0012] According to the invention, the electric machine designed as an axial flux machine has a rotor shaft configured as a hollow shaft, into which a bearing shaft fixed relative to the stator engages. The rotor shaft is rotatably mounted relative to the bearing shaft by means of a rolling bearing. A bearing preload device is arranged on and / or in the bearing shaft designed as a hollow shaft, by means of which a bearing preload in the rolling bearing can be adjusted. The first contact body of the first grounding element bears against the bearing preload device. This allows for a particularly compact axle drive train to be realized.

[0013] This provides the advantage of providing a particularly reliable and low-loss grounding of the rotor. Furthermore, not only the grounding of the rotor shaft to the stator housing is detected, but also the grounding of the transmission output shaft, which significantly improves the EMC properties of the drive train.

[0014] The spring force applied to the contact bodies ensures, in particular, constant electrical contact between the grounding partners to be connected. The spring force also allows for the compensation of tolerances or wobbling movements of the grounding partners. Furthermore, the preferably coaxial positioning of the contact bodies allows for particularly low-friction grounding.

[0015] First, the individual elements of the claimed subject matter of the invention are explained in the order in which they appear in the set of claims, and subsequently particularly preferred embodiments of the subject matter of the invention are described.

[0016] An electrically operable drive train comprises an electric machine and preferably a transmission assembly coupled to the electric machine. The transmission assembly and the electric machine form a structural unit. This can be formed, for example, by a drive train housing in which the transmission assembly and the electric machine are jointly accommodated.

[0017] The electric machine preferably has a motor housing and / or the gearbox a gearbox housing, whereby the structural unit is then achieved by fixing the gearbox relative to the electric machine. The gearbox housing is a housing for accommodating a gearbox. Its task is to guide existing shafts via the bearings and to grant the wheels (and possibly cam disks) the degrees of freedom they require under all loads without hindering their rotational and possibly path-related movement, as well as to absorb bearing forces and support moments. A gearbox housing can be single- or multi-shell, i.e., undivided or split. In particular, the gearbox housing should also dampen noise and vibrations and be able to safely accommodate hydraulic fluid.The gear housing is preferably formed from a metallic material, particularly preferably from aluminum, gray cast iron or cast steel, in particular by means of a primary forming process such as casting or die casting.

[0018] The motor housing encloses the electric machine. A motor housing can also accommodate the control and power electronics. The motor housing can also be part of a cooling system for the electric machine and be designed so that hydraulic fluid can be supplied to the electric machine via the motor housing and / or heat can be dissipated to the outside via the housing surfaces. Furthermore, the motor housing protects the electric machine and any electronics from external influences.

[0019] A motor housing can, in particular, be formed from a metallic material. Advantageously, the motor housing can be formed from a metallic cast material, such as die-cast aluminum, die-cast magnesium, gray cast iron, or cast steel.

[0020] The electrical machine is used to convert electrical energy into mechanical energy and / or vice versa, and it generally comprises a stationary part known as a stator, stand or armature and a part known as a rotor or runner which is movable, in particular rotatable, relative to the stationary part.

[0021] The electric machine of the axle drive train according to the invention is preferably designed as an axial flux machine. The magnetic flux in an electric axial flux machine (AFM) is directed axially in the air gap between the stator and rotor relative to a rotational direction of the rotor of the axial flux machine. There are different types of axial flux machines. One known type is a so-called I-arrangement, in which the rotor is arranged axially next to a stator or between two stators. Another known type is a so-called H-arrangement, in which two rotors are arranged on opposite axial sides of a stator. The electric axial flux machine is preferably configured as an H-type.

[0022] In principle, it is also possible for a plurality of I-type and / or H-type rotor-stator configurations to be arranged axially next to one another. In this context, it would also be possible to arrange one or more I-type rotor-stator configurations and one or more H-type rotor-stator configurations next to one another in the axial direction. In particular, it is also preferable for the H-type and / or I-type rotor-stator configurations to be essentially identical in design, so that they can be combined in a modular manner to form an overall configuration. Such rotor-stator configurations can, in particular, be arranged coaxially to one another and connected to a common rotor shaft or to multiple rotor shafts.

[0023] In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and especially greater than 100 km / h can be achieved. The electric motor particularly preferably has an output greater than 30 kW, preferably greater than 50 kW, and especially greater than 70 kW. It is further preferred that the electric machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm.

[0024] For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PCs), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOM), or tractors.

[0025] The transmission arrangement can be coupled, in particular, to the electric motor, which is designed to generate a drive torque for the motor vehicle. The drive torque is particularly preferably a main drive torque, so that the motor vehicle is driven exclusively by the drive torque. The transmission arrangement is preferably designed as a planetary gear. Most preferably, the planetary gear is wet-running.

[0026] A contact body can have a contour that forms a point-like contact with a contact structure adjacent to it. Spherical shapes, spherical sections, pyramid shapes, or the like are particularly suitable. The point-like contact particularly preferably occurs along the rotational axis of the transmission input shaft.

[0027] A contact element can, in particular, be subjected to force by a spring element. The spring element can be formed from one or more springs.

[0028] The spring element preferably comprises a compression spring. However, it is also possible for the spring element to comprise a disc spring. The spring element is preferably configured such that it can exert an axial contact force on a contact body that is suitable for ensuring secure electrical contact between the contact body and a contact structure, particularly in the presence of a fluid in the electrical contact area.

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

[0030] According to an advantageous embodiment of the invention, it can be provided that the first receiving element and / or the second receiving element are formed from a deep-drawn sheet metal, which is particularly advantageous from a manufacturing point of view and thus also realizes cost advantages.

[0031] According to a further preferred development of the invention, it can also be provided that the first receiving element and the second receiving element are formed of essentially the same parts. This can achieve a reduction in component variance, which also leads to cost advantages.

[0032] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the first grounding element and the second grounding element are formed essentially in the same part, whereby the component variance can be further reduced.

[0033] According to another particularly preferred embodiment of the invention, it can be provided that the first contact body and / or the second contact body is each a ball. This can achieve, in particular, the effect of forming a point-like contact between the contact body and a contact associated with it, which has proven particularly reliable, especially in wet operating environments.

[0034] Furthermore, the invention can also be further developed such that the first contact body and the second contact body are arranged coaxially with the rotational axis of the transmission input shaft. The coaxial positioning of the contact bodies allows for particularly low-friction grounding.

[0035] The rolling bearing can be single-row or multi-row. Preferably, the rolling bearing is configured as a ball bearing.

[0036] The inner ring can, in particular, connect the shaft accommodating the rolling bearing to the rolling bearing or the rolling elements. In this case, the shaft can, in particular, be connected to the side of the inner ring's outer surface facing the shaft, with the rolling elements of the rolling bearing rolling on the inner ring raceway opposite this outer surface. The inner ring can be formed from a metallic and / or ceramic material. It is generally conceivable for the inner ring to be constructed in one or more parts, particularly in two parts.

[0037] The outer ring can, in particular, connect the bearing accommodating the rolling bearing to the rolling bearing or the rolling elements. In this case, the bearing can, in particular, be connected to the side of the outer ring's lateral surface facing the bearing, with the rolling elements of the rolling bearing rolling on the outer ring raceway opposite this lateral surface. The outer ring can be formed from a metallic and / or ceramic material. It is generally conceivable for the outer ring to be constructed in one or more parts, in particular in two parts.

[0038] The rolling elements are in the shape of a ball or roller. They roll along the raceways of the rolling bearing and are responsible for transferring the force acting on a radial rolling bearing from the outer ring to the inner ring and vice versa. In an axial rolling bearing, the rolling elements transfer the forces acting on the axial rolling bearing between the running disks. Roller-shaped rolling elements can, for example, be selected from the group of symmetrical spherical rollers, asymmetrical spherical rollers, cylindrical rollers, needle rollers, and / or tapered rollers. According to a further preferred development of the invention, the rolling elements can also be made of ceramic.

[0039] The rolling elements are preferably guided in a cage and spaced apart from each other. The cage can be constructed in one piece or in multiple pieces. The cage is preferably configured as a pocket cage.

[0040] According to a further preferred development of the invention, the rolling bearing can also be designed as a double-row angular contact ball bearing. The double-row angular contact ball bearing has a particularly suitable support base for absorbing tilting forces, such as those that may occur during operation of the electrical machine. The double-row angular contact ball bearing can be designed in an O- or X-configuration. In the context of the invention, an O-arrangement is preferred.

[0041] It may also be advantageous to further develop the invention such that the bearing preload device has an adjusting screw with a screw thread and a screw head that is axially supported relative to the bearing shaft, and a sleeve-like clamping element formed from sheet metal with an internal thread that engages the screw thread, wherein the clamping element has a collar that bears against the rolling bearing. The advantage that can be realized in this way is that the adjusting screw thus combines two functions, which also contributes to a high level of system integration and a compact design. According to a further preferred embodiment of the subject matter of the invention, it can therefore also be provided that the first contact body bears against the adjusting screw.

[0042] Finally, the invention can also be advantageously designed in such a way that a retaining ring penetrated by the screw thread is arranged in the bearing shaft designed as a hollow shaft, wherein the retaining ring is axially fixed on one side to a shoulder formed in the bearing shaft and the screw head rests against the retaining ring, which has proven to be advantageous in terms of manufacturing and assembly technology.

[0043] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0044] It shows: Fig. 1 an electric axle drive train in a schematic axial section, Fig. 2 a detailed view of the rotor shaft and the gearbox input shaft in a schematic axial section, Fig. 3 an electric axle drive train with current conduction paths running through the housing in a schematic axial section, Fig. 4 a motor vehicle with an electric axle drive train in three different designs, each in a schematic block diagram.

[0045] The Fig. 1 shows an electric axle drive train 1, in particular for driving a motor vehicle 2, as is also shown by way of example in the Fig. 4. The axle drive train 1 can, as shown in Figure b of the Fig. 4, arranged coaxially to the vehicle axle and operable by an electric machine 3. It is also possible for the axle drive train 1 to have two electric machines 3 and two transmission arrangements 6, wherein an electric machine 3 and a transmission arrangement 6 are assigned in pairs to a vehicle wheel of the motor vehicle 2, as shown in Figure b of the Fig. 4. It is preferable that the electrical machines 3 and gear arrangements 6 are essentially of the same construction. Fig. the Fig. 1 finally shows an axle drive train 1 which has an axially parallel arrangement with respect to the vehicle axle.

[0046] The axle drive train 1 comprises an electric machine 3 configured as an axial flux machine with a stator 4 and a rotor 5 rotatably mounted relative to the stator 4, which rotor is connected to a transmission input shaft 7 of a transmission arrangement 6. The electric machine 3 and the transmission arrangement 6 are structurally combined by the common housing 15. The transmission arrangement 6 further has a transmission output shaft 8, at which a different speed than the transmission input shaft 7 is applied during operation of the axle drive train 1. In the exemplary embodiment shown, the transmission arrangement 6 is designed as a wet-running planetary gear, wherein the transmission input shaft 7 is a sun gear of the planetary gear.

[0047] Planetary gears 22, mounted in a planetary gear carrier 24, are in gear engagement with the transmission input shaft 7 and are rotatably mounted on the planetary gear shaft 25. Furthermore, the planetary gears 22 are in gear engagement radially outwardly with an internally toothed ring gear 23. The planetary gear carrier 24 is non-rotatably connected to the transmission output shaft 8, which is also designed as a hollow shaft. The transmission input shaft 7 is rotatably mounted relative to the transmission output shaft 8 via the rolling bearing 26.

[0048] The rotor 5 has a rotational axis 9 which is arranged coaxially with a rotational axis 10 of the transmission input shaft 7 and the transmission output shaft 8.

[0049] The electric machine 3, designed as an axial flux machine, further comprises a rotor shaft 13 configured as a hollow shaft, into which a bearing shaft 14, which is stationary relative to the stator 4, engages. The rotor shaft 13 is rotatably mounted relative to the bearing shaft 14 by means of a rolling bearing 16. A bearing preload device 20 is arranged on the bearing shaft 14, by means of which a bearing preload in the rolling bearing 16 can be adjusted, with the first contact body 11 resting against the bearing preload device 20.

[0050] A first cup-shaped receiving element 31 with a first circumferential collar 32 is arranged in a rotationally fixed manner in the transmission input shaft 7, which is designed as a hollow shaft, for receiving a first grounding element 17. The first collar 32 forms an axial stop at a first axial end of the transmission input shaft 7, while the receiving element 31 extends axially into the transmission input shaft 7.

[0051] Furthermore, a second cup-shaped receiving element 34 with a second circumferential collar 35 is arranged in a rotationally fixed manner in the transmission input shaft 7, which is designed as a hollow shaft, for receiving a second grounding element 33. Here, too, the second collar 35 forms an axial stop at a second axial end of the transmission input shaft 7, and the receiving element 34 also extends axially into the transmission input shaft 7. The first receiving element 31 and the second receiving element 34 are formed from a deep-drawn sheet metal and are formed essentially in the same part.

[0052] The first grounding element 17 has a first contact body 11, which, by means of a first spring element 19, rests against a first grounding element 36 in an axial direction pointing outward from the transmission input shaft 7. In the embodiment shown, the first grounding element 36 is an adjusting screw 39, which will be explained in more detail below.

[0053] The second grounding element 33 has a second contact body 12, which, by means of a second spring element 37, rests against a second grounding element 38 in an axial direction pointing outward from the transmission input shaft 7. The second grounding element 38 is a metallic disc connected in a rotationally fixed manner to the transmission output shaft 8.

[0054] As in the Fig. 2, the first grounding element 17 and the second grounding element 33 are essentially of the same design.

[0055] How to see in the detailed view of the Fig. 2, the grounding element 17, 33 has an axially displaceable piston 21, on which the spring element 19 is axially supported on the one hand and on which the first contact body 11 and the second contact body 12 rest axially on the other hand. The first contact body 11 and the second contact body 12 are each designed as a ball, which can be formed from steel or graphite. As can be clearly seen from the Fig. 1, the first contact body 11 and the second contact body 12 are arranged coaxially to the axis of rotation 10 of the transmission input shaft 7.

[0056] A bearing preload device 20 is arranged in the bearing shaft 14, which is designed as a hollow shaft. By means of this device, a bearing preload in the rolling bearing 16 can be adjusted. The first contact body 11 of the first grounding element 17 rests against the bearing preload device 20.

[0057] The bearing preload device 20 has an adjusting screw 39 with a screw thread 41 and a screw head 40, which is axially supported against the bearing shaft 14. The first contact body 11 bears against the adjusting screw 39. A sleeve-like clamping element 46 formed from sheet metal and having an internal thread 42 engages with the screw thread 41, so that rotation of the adjusting screw 39 causes an axial offset of the clamping element 46. The clamping element 46 has a collar 43, which bears against the rolling bearing 16. The clamping element 46 is formed from a deep-drawn sheet metal, with the internal thread 42 being embossed into the clamping element 46 without the need for cutting.

[0058] A retaining ring 44 through which the screw thread 41 extends is arranged in the bearing shaft 14 designed as a hollow shaft, wherein the retaining ring 44 is axially fixed on one side to a shoulder 45 formed in the bearing shaft 14 and the screw head 40 rests against the retaining ring 44.

[0059] The special mode of operation of the earthing elements 17,33 can also be clearly seen from the illustration of the Fig. 3, in which the current conduction paths 30 are sketched as dashed lines through the axle drive train 1. It is clearly visible that through the use and arrangement of the two grounding elements 17, 27, essentially all components are electrically connected to the housing 15 of the axle drive train 1 and are grounded thereby. In particular, the transmission output shaft is also correspondingly grounded, which leads to a significant improvement in the EMC properties of the drive train 1.

[0060] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols 1 axle drive train 2 motor vehicles 3 electric machine 4 Stator 5 Rotor 6 Gear arrangement 7 Gearbox input shaft 8 Gearbox output shaft 9 axis of rotation 10 axis of rotation 11 Contact body 12 contact bodies 13 Rotor shaft 14 Bearing shaft 15 housings 16 rolling bearings 17 Earthing element 19 Spring element 20 Bearing preload device 21 pistons 22 planetary gears 23 ring gear 24 planetary gear carriers 25 Planetary gear shaft 26 rolling bearings 27 Earthing element 30 current conduction paths 31 receiving element 32 collars 33 Earthing element 34 receiving element 35 collars 36 Earthing element 37 spring elements 38 Earthing element 39 Adjusting screw 40 screw head 41 screw threads 42 internal thread 43 collar 44 Retaining ring 45 shoulder 46 clamping element

Claims

[1] Electric axle drive train (1), in particular for driving a motor vehicle (2), comprising an electric machine (3) with a stator (4) and a rotor (5) which is rotatably mounted relative to the stator (4) and which is connected to a transmission input shaft (7) of a transmission arrangement (6) designed as a hollow shaft, and the transmission arrangement (6) further comprises a transmission output shaft (8) at which a rotational speed different from that of the transmission input shaft (7) is applied during operation of the axle drive train (1), and the rotor (5) has an axis of rotation (9) which is arranged coaxially with an axis of rotation (10) of the transmission input shaft (7) and the transmission output shaft (8), characterized by , that in the transmission input shaft (7) designed as a hollow shaft for receiving a first earthing element (17), a first pot-shaped receiving element (31) with a first circumferential collar (32) is arranged in a rotationally fixed manner, wherein the first collar (32) forms an axial stop at a first axial end of the transmission input shaft (7), and in the transmission input shaft (7) designed as a hollow shaft for receiving a second earthing element (33), a second pot-shaped receiving element (34) with a second circumferential collar (35) is arranged in a rotationally fixed manner, wherein the second collar (35) forms an axial stop at a second axial end of the transmission input shaft (7), and the first earthing element (17) has a first contact body (11) which, by means of a first spring element (19), rests against a first earthing element (36) in an axial direction pointing out of the transmission input shaft (7) and the second earthing element (33) has a second contact body (12) which, by means of a second spring element (37), rests against a second earthing element (38) in an axial direction pointing out of the transmission input shaft (7), and the electrical machine (3) designed as an axial flux machine has a rotor shaft (13) designed as a hollow shaft, into which a bearing shaft (14) fixed relative to the stator (4) engages, wherein the rotor shaft (13) is rotatably mounted relative to the bearing shaft (14) by means of a rolling bearing (16) and a bearing preload device (20) is arranged on and / or in the bearing shaft (14) designed as a hollow shaft, by means of which a bearing preload in the rolling bearing (16) can be adjusted, wherein the first contact body (11) of the first grounding element (17) bears against the bearing preload device (20). [2] Axle drive train (1) according to claim 1, characterized bythat the first receiving element (31) and / or the second receiving element (34) are formed from a deep-drawn sheet metal. [3] Axle drive train (1) according to one of the preceding claims, characterized by that the first receiving element (31) and the second receiving element (34) are formed essentially of the same part. [4] Axle drive train (1) according to one of the preceding claims, characterized by that the first earthing element (17) and the second earthing element (33) are formed essentially in the same part. [5] Axle drive train (1) according to one of the preceding claims, characterized by that the first contact body (11) and / or the second contact body (12) is each a ball. [6] Axle drive train (1) according to one of the preceding claims, characterized by that the first contact body (11) and the second contact body (12) are arranged coaxially to the axis of rotation (10) of the transmission input shaft (7). [7] Axle drive train (1) according to claim 1, characterized by that the bearing preload device (20) has an adjusting screw (39) with a screw thread (41) and with a screw head (40) which is supported axially relative to the bearing shaft (14) and a sleeve-like clamping element (46) formed from a sheet metal and having an internal thread (42) is in engagement with the screw thread (41), wherein the clamping element (46) has a collar (43) which bears against the rolling bearing (16). [8] Axle drive train (1) according to claim 7, characterized by that the first contact body (11) rests against the adjusting screw (39). [9] Axle drive train (1) according to claim 7 or 8, characterized bythat a retaining ring (44) through which the screw thread (41) passes is arranged in the bearing shaft (14) designed as a hollow shaft, wherein the retaining ring (44) is axially fixed on one side to a shoulder (45) formed in the bearing shaft (14) and the screw head (40) bears against the retaining ring (44).

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