Rolling bearing arrangement, axial flux machine and method for assembling a rolling bearing arrangement in an axial flux machine

Abstract

An electric axial flux machine (20) for a drive train (21) of a motor vehicle (22), comprising a disk-shaped stator (23) and a disk-shaped rotor (24) axially spaced therefrom and rotatable relative to the stator (23), characterized in that the rotor (24) comprises a shaft (6) which is supported by means of a rolling bearing arrangement (1), wherein the rolling bearing arrangement (1) comprises: - a rolling bearing (2) with an inner ring (3) which is fixed to a hollow shaft section (4) and - an outer ring (5) which is connected to a rotatable shaft (6) and - a plurality of rolling elements (7) which are received in a rolling manner between the inner ring (3) and the outer ring (5) in the rolling bearing (2), wherein the hollow shaft section (4) has a ramp which widens radially towards the inner ring (3) and is designed as a conical, annular section of the hollow shaft section. (8) exhibitswherein a circumferential groove (9) is formed in the hollow shaft section (4) in the axial direction between the ramp (8) and the inner ring (3), in which a retaining ring (10) is axially fixed and on which a support ring disc (12) rests on its axial end face (11) facing the inner ring (3) and a spring element (13) is axially supported on the one hand on the support ring disc (12) and on the other hand on the inner ring (3).

Description

The present invention relates to a rolling bearing arrangement, in particular for an axial flux machine within a drive train of a motor vehicle, comprising a rolling bearing with an inner ring fixed to a rotationally fixed hollow shaft section and an outer ring, which is in particular connected to a rotatable shaft, and a plurality of rolling elements which are mounted in a rolling manner between the inner ring and the outer ring in the rolling bearing. The invention further relates to an axial flux machine and a method for mounting a rolling bearing arrangement in an axial flux machine. Electric motors are increasingly being used for propulsion in motor vehicles to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday usability of electric drives and to offer users the familiar driving comfort. Axial flux machines are also increasingly being used as drive units in such automotive applications. An axial flux machine is a dynamoelectric machine in which the magnetic flux between the rotor and stator runs parallel to the rotor's axis of rotation. Often, both the stator and rotor are largely disk-shaped. Axial flux machines are particularly advantageous when the available axial installation space is limited in a given application. This is frequently the case, for example, with the electric drive systems for electric or hybrid vehicles described earlier. Besides its shorter axial length, another advantage of the axial flux machine lies in its comparatively high torque density. This is due to the larger air gap area available within a given installation space compared to radial flux machines. Furthermore, a smaller iron volume is required compared to conventional machines, which has a positive effect on the machine's efficiency. An axial flux machine typically comprises at least one stator, which has windings to generate the axially aligned magnetic field. At least one rotor is equipped, for example, with permanent magnets whose magnetic field interacts with the magnetic field of the stator windings across an air gap, generating a driving torque. Especially in hybrid or fully electric drive concepts, noise generation from the drive system plays an increasingly important role. Due to the nature of the system, the operation of such an electric motor in a hybrid or fully electric powertrain can, for example, generate high levels of electromagnetic excitation, which can also lead to acoustic vibrations in the structural components of the electric motor or the powertrain. This can then be audibly perceptible in the vehicle interior, which is regularly perceived as disturbing. This is all the more significant because such noises are particularly noticeable in electric mode and negatively impact the otherwise exceptionally quiet driving experience. In such electric machines, rolling bearing arrangements are typically used to support the rotors. For example, floating bearings are usually pressed onto the rotor shaft, creating a tight fit against the inner ring of the rolling bearing. The outer ring of the bearing is generally designed to be displaceable to compensate for thermally induced expansion of the rotor shaft during operation. To ensure optimal running conditions between the ball set and the raceways of the floating bearing, and to improve acoustics, the outer ring is regularly preloaded. This preload prevents unwanted noise from the rolling bearing by eliminating play between the moving bearing components. Furthermore, for the efficiency and safe operation of axial flux machines, it is particularly important that the axial air gap between the rotor magnet plates and the stator is precisely adjusted. The rolling bearing supporting the rotor must be designed so that deviations in the axial gap width caused by magnetic or external forces (e.g., from vehicle dynamics) remain within a tight tolerance. In addition to the precise design of the axial bearing clearance, it is necessary that both the inner and outer bearing rings are axially fixed without play to keep the deviations in the motor's axial gap within the required range. For this purpose, it is known to axially fix the inner bearing ring, for example, with a slotted nut. In axial flux machines, for example, there are also designs where an output shaft passes through the center of the motor, so that the rotor and its rotor shaft are arranged coaxially to this output shaft, thus significantly restricting the installation space for the slotted nut. Furthermore, the slotted nut must be designed to ensure the axial preload of the rolling bearing under all operating conditions and to prevent the nut from loosening. Since, due to the desirable lightweight construction, the connection structure of the inner bearing ring can be made of aluminum, while the inner bearing ring itself is made of steel, the relatively large bearing width of such rolling bearings for supporting the rotor shaft of an axial flux machine, combined with a possible temperature difference of up to 180 K during operation, can result in significant differences in length due to the differing thermal expansion of the materials.Since the thread strength for the slotted nut in the aluminum is a limiting factor for the design, the geometry of the clamped parts must be designed to allow sufficient deformation within the elastic range. Due to the typically limited installation space in an axial fluxing machine, the slotted nut and the connection to the mounting structure must be very delicate, which can increase costs and the risk of failure, and is generally undesirable. WO 2018 / 015011A1 shows a rolling bearing arrangement and an X-ray tube bearing arrangement. The AT 015 088 U1 and the US 5 975 766 A each show a shaft bearing. US 2004 / 0 131 294 A1 and US 2020 / 0 200 214 A1 each show a rolling bearing preload mechanism. WO 2022 / 073 547 A1 shows a bearing arrangement for an axial flux machine. DE 10 2007 056 365 A1 discloses an electric machine designed as a disc rotor motor, comprising a rotor mounted in a multi-part housing, consisting of a rotor shaft with a permanent magnet disk fixed on it, the end faces of which are covered by cover plates, the permanent magnet disk having an axial distance at its end faces forming an air gap to the stator halves also arranged on the rotor shaft, and the rotor shaft being supported at its end faces by means of rolling bearings provided on the housing, wherein the rotor is supported directly in the area of ​​the inner diameter of the permanent magnet disk. The object of the invention is to provide a rolling bearing arrangement, particularly for an axial flux machine within the drivetrain of a motor vehicle, which has a particularly compact design, smooth running, and is cost-effective to manufacture. Furthermore, the invention aims to realize an axial flux machine with improved rotor bearings. Finally, the invention provides an improved method for mounting a rolling bearing arrangement in an axial flux machine. This problem is solved by a rolling bearing arrangement, in particular for an axial flux machine within a drive train of a motor vehicle, comprising a rolling bearing with an inner ring fixed to a rotationally fixed hollow shaft section and an outer ring connected to a rotatable shaft, and a plurality of rolling elements which are mounted in a rolling manner between the inner ring and the outer ring in the rolling bearing, wherein the hollow shaft section has a ramp that expands radially axially towards the inner ring and is designed as a conical, annular section of the hollow shaft section, wherein a circumferential groove is formed in the hollow shaft section in the axial direction between the ramp and the inner ring.in which a retaining ring is axially fixed and on which a support ring disc rests at its axial end face facing the inner ring, and a spring element is axially supported on the one hand on the support ring disc and on the other hand on the inner ring. This allows the inner ring of the rolling bearing to be securely fixed axially to the hollow shaft section, even with large differences in thermal expansion between the inner ring and the hollow shaft section. The inner ring can be fixed to the hollow shaft section in such a way that, even within very confined installation spaces, the fixing of the inner ring can be implemented securely, robustly, easily assembled, and cost-effectively. According to the invention, the axial fixing of the inner ring is achieved by means of a combination of a spring element, a support ring washer, and a retaining ring. The spring element ensures that, in all operating conditions, temperature-induced thermal expansions can be compensated without significant stress increases in the components. The support ring washer ensures reliable force transmission to the retaining ring, which is axially fixed in the groove.The ramp of the hollow shaft section allows the retaining ring to be easily inserted axially into the groove, as the ramp can radially expand the retaining ring during axial insertion, which facilitates the installation of the retaining ring. The spring element can, in particular, have an annular shape. Preferably, the spring element can be designed as a disc spring, wave spring, compression spring, or coil spring. Particularly preferably, the spring element has an inner diameter that is larger than the diameter of the hollow shaft section on which the inner ring of the rolling bearing is fixed. The retaining ring is formed from a metallic material and is preferably designed to be fully open, allowing it to expand easily and elastically in the radial direction. However, it is also conceivable that the retaining ring is fully closed, provided it can expand sufficiently elastically in the radial direction. The retaining ring is particularly preferably designed to have an inner diameter that is smaller than the diameter of the hollow shaft section on which the inner ring of the rolling bearing is fixed. The support ring disc is preferably made of a metallic material. Particularly preferably, the support ring disc has an inner diameter that is larger than the diameter of the hollow shaft section on which the inner ring of the rolling bearing is fixed. First, the individual elements of the claimed invention are explained in the order they appear in the claim set, followed by a description of particularly preferred embodiments of the invention. The features listed individually in the dependent claims can be combined in a technologically meaningful way and can define further embodiments of the invention. Furthermore, the features specified in the claims are further detailed and explained in the description, which also presents further preferred embodiments of the invention. Rolling bearings can be used, in particular, to enable rotary movements with minimal friction losses. Rolling bearings can be used especially for fixing and / or supporting axles and shafts, absorbing radial and / or axial forces depending on their design, while simultaneously allowing the rotation of the shaft or the components mounted on it. For this purpose, rolling elements are arranged between an inner and an outer ring of the rolling bearing. Between these three main components – inner ring, outer ring, and rolling elements – rolling friction typically occurs primarily within the rolling bearing. Since the rolling elements in the inner and outer rings preferably roll on hardened steel surfaces with optimized lubrication, the rolling friction of such bearings is relatively low. The inner ring can connect the bearing housing or connection to the hollow shaft section with the rolling bearing or the rolling elements. In particular, the hollow shaft can be connected to the side of the inner ring's outer surface facing the hollow shaft, with the rolling elements of the bearing rolling on the inner ring raceway opposite this outer surface. The inner ring can be made of a metallic and / or ceramic material. Preferably, the inner ring is made of steel. It is generally conceivable to design the inner ring as a single piece or in multiple parts, particularly as a two-piece design. The inner ring may have an inner ring groove. A cover plate, sealing washer, and / or gasket may be arranged in this inner ring groove, particularly in a force-fit and / or form-fit manner. Preferably, the inner ring groove is designed as a circumferential groove in the inner ring. The outer ring can, in particular, connect a rotating rotor shaft of an axial flux machine to the rolling bearing or the rolling elements. The rotor shaft can be connected to the side of the outer ring's outer surface facing the rotor shaft, with the rolling elements of the rolling bearing rolling on the outer ring raceway opposite this outer surface. The outer ring can be made of a metallic and / or ceramic material. It is generally possible to design the outer ring as a single piece or in multiple parts, particularly as a two-piece design. The outer ring may have a groove. A cover plate, sealing washer, and / or gasket may be arranged in this groove, particularly in a force-fit and / or form-fit manner. Preferably, the groove is designed as a circumferential groove in the outer ring. Depending on the type of rolling bearing, the rolling elements are either spherical or cylindrical. They roll on the raceways of the rolling bearing and their function is to transmit 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 transmit the forces acting on the bearing between the raceways. Cylindrical rolling elements are also called roller bearings, and spherical rolling elements are called bearing balls. Roller-shaped rolling elements can be selected, for example, from the group of symmetrical oscillating rollers, asymmetrical oscillating rollers, cylindrical rollers, needle rollers and / or conical rollers. The rolling bearing can be single-row or multi-row, in particular double-row. In connection with the invention, it is preferred to design the rolling bearing as a double-row arrangement. Furthermore, it is also possible for two rolling bearings to axially abut each other, thus forming a double-row rolling bearing arrangement. Within the rolling bearing, the rolling elements can roll, particularly on the inner ring raceway of the inner ring. For this purpose, the surface of the inner ring raceway can advantageously be designed to be wear-resistant, for example, through a suitable surface treatment process and / or by applying an additional layer of material. The inner ring raceway can be flat or profiled. A profiled inner ring raceway can, for example, guide the rolling elements on the inner ring raceway. A flat inner ring raceway, on the other hand, can allow, for example, a certain degree of axial displacement of the rolling elements on the inner ring raceway. The rolling elements can roll within the rolling bearing, particularly on the outer ring raceway. For this purpose, the surface of the outer ring raceway can advantageously be designed to be correspondingly wear-resistant, for example, by means of a suitable surface treatment process and / or by applying a suitable additional material layer. The outer ring raceway can be flat or profiled. A profiled outer ring raceway can, for example, guide the rolling elements on the outer ring raceway. A flat outer ring raceway, on the other hand, can, for example, allow a certain degree of axial displacement of the rolling elements on the outer ring raceway. Rolling elements can be guided and spaced apart within a cage or by spacers. It is also possible, in principle, to design a cageless rolling bearing, which is also known as a full complement rolling bearing. In full complement rolling bearings, adjacent rolling elements can make contact. A rolling bearing can have a cage, which guides the rolling elements. The cage is designed so that the rolling element balls and / or rollers are spaced apart from each other, thus minimizing friction and heat generation. Furthermore, the cage maintains a fixed distance between the rolling element balls and / or rollers during rolling, ensuring a uniform load distribution. The cage can be made of a single piece or multiple pieces. A rolling bearing may have a seal to prevent lubricant from leaking out or dirt or moisture from entering. For this purpose, the seals used may have one or more sealing lips that bear against a component of the rolling bearing. These are designed to seal the bearing for as long as possible, ideally for its entire service life, while also ensuring that the friction caused by the seal is not too high. According to an advantageous embodiment of the invention, the hollow shaft section can be made of aluminum or an aluminum alloy, and the inner ring of the rolling bearing can be made of steel. This allows, in particular, the requirements of lightweight construction to be combined with the requirements of the rolling bearing's durability. The object of the invention is further solved by an electric axial flux machine, in particular for a drive train of a motor vehicle, comprising a disk-shaped stator and a disk-shaped rotor axially spaced therefrom and rotatable relative to the stator, wherein the rotor comprises a shaft which is supported by means of at least one rolling bearing arrangement according to one of the independent claims. The electric axial flux machine exhibits a magnetic flux in the air gap between the stator and rotor, directed axially to one direction of rotation of the rotor. There are different types of axial flux machines. One known type is the so-called I-arrangement, in which the rotor is arranged axially next to a stator or between two stators. Another known type is the 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. In principle, it is also possible for multiple rotor-stator configurations of I-type and / or H-type to be arranged axially side by side. It would also be possible in this context to arrange one or more I-type rotor-stator configurations and one or more H-type rotor-stator configurations axially side by side. In particular, it is also preferred that the H-type and / or I-type rotor-stator configurations are essentially identical, so that they can be assembled modularly into a complete configuration. Such rotor-stator configurations can, in particular, be arranged coaxially to one another and be connected to a common rotor shaft or to multiple rotor shafts. In particular, the electric axial flux 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 is particularly preferably configured to have a power 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 rotational speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm. The electric axial flux machine preferably has a motor housing. The motor housing encloses the electric axial flux machine. A motor housing can also accommodate the control and power electronics. Furthermore, the motor housing can be part of a cooling system for the electric machine and be designed such 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. In addition, the motor housing protects the electric machine and any electronics present from external influences. A motor housing can be made of a metallic material. Advantageously, the motor housing can be formed from a metallic casting material, such as die-cast aluminum, die-cast magnesium, gray cast iron, or cast steel. The motor housing can preferably be made of multiple parts.In particular, the hollow shaft section can be part of the motor housing. Preferably, the hollow shaft section is made of aluminum. For the purposes of this application, motor vehicles are defined as land vehicles that are moved by mechanical power and are not bound to railway tracks. A motor vehicle may be selected, for example, from the groups of passenger cars, trucks, mopeds, light vehicles, motorcycles, buses, or tractors. Furthermore, according to another advantageous embodiment of the invention, the rolling bearing can be designed as a double-row angular contact ball bearing. This achieves, in particular, a high degree of safety against tilting of the rotor shaft. The double-row angular contact ball bearing has a particularly suitable support base for absorbing tilting forces such as those that can occur during operation of the electric machine. The double-row angular contact ball bearing can be configured in an O or X configuration. In connection with the invention, an O arrangement is preferred. According to a further particularly preferred embodiment of the invention, the rolling bearing can be arranged radially below the stator, which has a positive effect on avoiding or reducing tilting and wobbling movements of the rotor, especially if the axial flux machine has an H-configuration. Furthermore, the invention can therefore also be further developed in such a way that the axial flux machine is configured in an H-arrangement. In a further preferred embodiment of the invention, the outer ring can also be positioned axially free of play on both sides of the shaft, while the inner ring is arranged axially free of play on both sides of the hollow shaft section. One of the axially free-play securing mechanisms for the inner ring is achieved by the retaining ring, on whose axial end face the support ring disc is axially supported by the spring element, with the support ring disc being positioned intermediately. This allows for a secure fixation of the inner ring to the hollow shaft section that compensates for thermal expansion. The object of the invention can also be achieved by a method for assembling a rolling bearing arrangement in an electric axial flux machine, in particular for a motor vehicle drive train, comprising the following steps: • Providing a rolling bearing with an inner ring, • Axially sliding the inner ring onto a hollow shaft section, wherein the hollow shaft section has a ramp that widens radially towards the inner ring and is designed as a conical, bevel-shaped section of the hollow shaft section, and a circumferential groove is formed in the hollow shaft section in the axial direction between the ramp and the inner ring, • Axially sliding the spring element onto the hollow shaft section, • Axially sliding the support ring disc onto the hollow shaft section, • Axially inserting an assembly tool with a centering sleeve and an assembly piston that encompasses the centering sleeve and is axially displaceable relative to the centering sleeve.so that the centering sleeve is fixed axially and radially relative to the hollow shaft section, • Axial insertion of a retaining ring that expands elastically in the radial direction over the ramp of the hollow shaft section by means of the axially displaceable assembly piston of the assembly tool, so that the retaining ring snaps into the groove. The described method and assembly tool provide a user-friendly, safe and cost-effective axial fixing of the inner ring relative to the hollow shaft section, compensating for thermal expansion. The centering sleeve can preferably be fixed radially and axially to the hollow shaft section. For example, the centering sleeve can have a corresponding cylindrical geometry such that, when the centering sleeve is axially inserted into the hollow shaft section, it rests against the inner diameter of the hollow shaft section. Furthermore, the centering sleeve can preferably have a radially extending collar which, when the centering sleeve is inserted into the hollow shaft section, abuts it in the axial direction, thus fixing the centering sleeve axially relative to the hollow shaft section. According to a further preferred embodiment of the invention, the assembly piston may have a radially inner section and a radially outer section, wherein during the assembly of the support ring disc and the retaining ring the radially inner section bears at least temporarily against the retaining ring and the radially outer section bears at least temporarily against the support ring disc, so that the support ring disc and the retaining ring can be axially displaced by means of the assembly piston in such a way that the retaining ring can snap into the groove without being in contact with the support ring disc. This allows the stepped assembly piston to simultaneously slide the spring element, the support washer, and the retaining ring axially onto the hollow shaft section via the assembly cone defined by the ramp, until the retaining ring snaps into the groove of the hollow shaft section. Preferably, the assembly piston and the components to be mounted—spring element, support washer, and retaining ring—are guided over the centering sleeve. Finally, the invention can also advantageously be implemented such that the assembly piston is axially freed between the radially inner section and the radially outer section, so that the retaining ring does not contact the assembly piston during its axial insertion in the radial direction. In other words, the stepped assembly piston is radially freed in the diameter range "above" the retaining ring, so that the latter can expand radially unhindered during assembly over the mounting cone defined by the ramp on the hollow shaft section. Furthermore, the support disc and the geometrically maintained axial clearance in the stepped assembly piston most preferably enable the retaining ring to snap into the groove of the hollow shaft section without axial force, which facilitates assembly. The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention. It shows: Fig. 1 a first embodiment of an axial flux machine in a schematic axial section view, Fig. 2 a second embodiment of an axial flux machine in a schematic axial section view, Fig. 3 a third embodiment of an axial flux machine in a schematic axial section view, Fig. 4 a third embodiment of an axial flux machine in a schematic axial section view, Fig. 5 a detailed view of the rolling bearing arrangement during the assembly process of axially fixing the inner ring relative to the hollow shaft section in a schematic axial section view, Fig. 6 a motor vehicle with an axial flux machine in the drive train in a schematic block diagram. Figures 1-4 show various embodiments of axial flux machines 20, in particular for a drive train 21 of a motor vehicle 22, as also shown by way of example in Figure 6. All embodiments of Figures 1-3 have in common that they have a disk-shaped stator 23 and a disk-shaped rotor 24 axially spaced from it and rotatable relative to the stator 23, wherein the rotor 24 comprises a shaft 6 which is supported by means of at least one rolling bearing arrangement 1. Fig. 1 shows an axial flux machine in I configuration and Figs. 2-3 show two different designs in H configuration. The rolling bearing arrangement 1 in Figures 1-4 comprises a rolling bearing 2 with an inner ring 3, which is fixed to a rotationally fixed hollow shaft section 4, and an outer ring 5, which, in the embodiments of Figures 1-2, is connected to the stator 23 of the axial flux machine 20. In the embodiments of Figures 3 and 4, the outer ring 5 is connected to a rotatable shaft 6 of the rotor 24. A plurality of rolling elements 7 are mounted in the rolling bearing 2 between the inner ring 3 and the outer ring 5. The hollow shaft section 4 has a ramp 8 that widens radially towards the inner ring 3, so that a cone-like conical ring-shaped section is formed on the hollow shaft section 4. As can be seen from the comparison of Figs. 1-4 with Fig. 5, a circumferential groove 9 is formed in the hollow shaft section 4 in the axial direction between the ramp 8 and the inner ring 3, in which a retaining ring 10 is axially fixed and on which a support ring disc 12 rests on its axial end face 11 facing the inner ring 3 and a spring element 13 is axially supported on the one hand on the support ring disc 12 and on the other hand on the inner ring 3. The hollow shaft section 4 is made of aluminium or an aluminium alloy and the inner ring 3 of the rolling bearing 2 is made of steel. The rolling bearing 2 in Fig. 5 is arranged radially below the stator 23, with the axial flux machine 20 of Fig. 4 configured in an H-arrangement, as also shown in Fig. 4. In this embodiment, the rolling bearing 2 is designed as a double-row angular contact ball bearing. In the embodiments of Figs. 3-4, the hollow shaft section 4 is penetrated by a shaft (not specified). Such configurations are known, for example, when the axial flux machine 20 is coupled to a differential gear which has two output shafts leading to the wheels of a motor vehicle. The outer ring 5 is positioned axially free of play on both sides of the shaft 6, while the inner ring 3 is arranged axially free of play on both sides of the hollow shaft section 4, wherein one of the axially free of play securing the inner ring 3 is realized by the retaining ring 10, on which the support ring disc 12 is supported axially on its axial end face 11 facing the inner ring 3 with the spring element 13 intermediately arranged against the support ring disc 12. The method for mounting the rolling bearing arrangement 1 in the electric axial flux machine 20 can be easily understood using Fig. 5 and is explained in more detail below. First, a rolling bearing 2 with an inner ring 3 can be provided, which is then positioned by axially sliding it onto the hollow shaft section 4. The hollow shaft section 4 has a ramp 8 that widens radially towards the inner ring 3. A circumferential groove 9 is formed in the hollow shaft section 4 in the axial direction between the ramp 8 and the inner ring 3. The spring element 13 and the support ring disc 12 are then axially pushed onto this hollow shaft section 4. Then an assembly tool 30 with a centering sleeve 31 and an assembly piston 32 encompassing the centering sleeve 31 and axially displaceable relative to the centering sleeve 31 is brought axially into or to the hollow shaft section 4, so that the centering sleeve 31 is fixed axially and radially relative to the hollow shaft section 4. Now, an axial insertion of a retaining ring 10, which expands in a spring-elastic manner in the radial direction, can take place via the ramp 8 of the hollow shaft section 4 by means of the axially displaceable assembly piston 32 of the assembly tool 30, so that the retaining ring 10 snaps into the groove 9. The assembly piston 32 has a radially inner section 33 and a radially outer section 34, wherein during the assembly of the support ring washer 12 and the retaining ring 10 the radially inner section 33 bears at least temporarily against the retaining ring 10 and the radially outer section 34 bears at least temporarily against the support ring washer 12, so that the support ring washer 12 and the retaining ring 10 can be axially displaced by means of the assembly piston 32 in such a way that the retaining ring 10 can snap into the groove 9 without being in contact with the support ring washer 12. The mounting piston 32 is axially freed between the radially inner section 33 and the radially outer section 34 so that the retaining ring 10 does not contact the mounting piston 32 during its axial insertion in the radial direction. It is understood that the described assembly method, although explained with reference to Figs. 4-5, is also applicable to the embodiments of Figs. 1-3. The terms "radial," "axial," "tangential," and "circumferential direction" used in this application always refer to the axis of rotation of the axial flux machine 20. The terms "left," "right," "above," "below," "above," and "below" serve only to clarify which areas of the figures are currently being described in the text. Later embodiments of the invention may be arranged differently. Furthermore, the invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features.If the patent claims and the preceding description define 'first' and 'second' feature, this designation serves to distinguish between two similar features without establishing a hierarchy. Reference symbol list 1 Rolling bearing assembly 2 Rolling bearing 3 Inner ring 4 Hollow shaft section 5 Outer ring 6 Shaft 7 Rolling elements 8 Ramp 9 Groove 10 Retaining ring 11 End face 12 Support ring washer 13 Spring element 20 Axial flux machine 21 Drive train 22 Motor vehicle 23 Stator 24 Rotor 30 Mounting tools 31 Centering sleeve 32 Mounting piston 33 Section 34 Section

Claims

An electric axial flux machine (20) for a drive train (21) of a motor vehicle (22), comprising a disk-shaped stator (23) and a disk-shaped rotor (24) axially spaced therefrom and rotatable relative to the stator (23), characterized in that the rotor (24) comprises a shaft (6) which is supported by means of a rolling bearing arrangement (1), wherein the rolling bearing arrangement (1) comprises: - a rolling bearing (2) with an inner ring (3) which is fixed to a hollow shaft section (4) and - an outer ring (5) which is connected to a rotatable shaft (6) and - a plurality of rolling elements (7) which are received in a rolling manner between the inner ring (3) and the outer ring (5) in the rolling bearing (2), wherein the hollow shaft section (4) has a ramp which widens radially towards the inner ring (3) and is designed as a conical, annular section of the hollow shaft section. (8) exhibitswherein a circumferential groove (9) is formed in the hollow shaft section (4) in the axial direction between the ramp (8) and the inner ring (3), in which a retaining ring (10) is axially fixed and on which a support ring disc (12) rests on its axial end face (11) facing the inner ring (3) and a spring element (13) is axially supported on the one hand on the support ring disc (12) and on the other hand on the inner ring (3). Electric axial flux machine (20) according to claim 1, characterized in that the rolling bearing (2) is designed as a double-row angular contact ball bearing. Electric axial flux machine (20) according to claim 1, characterized in that the rolling bearing (2) is arranged radially below the stator (23). Electric axial flux machine (20) according to one of claims 1-3, characterized in that the axial flux machine (20) is configured in an H-arrangement. Electric axial flux machine (20) according to one of claims 1-4, characterized in that the outer ring (5) is positioned axially free of play on both sides on the shaft (6), while the inner ring (3) is arranged axially free of play on both sides on the hollow shaft section (4), wherein one of the axially free of play securing the inner ring (3) is realized by the retaining ring (10), on which the support ring disc (12) is axially supported on its axial end face (11) facing the inner ring (3) with the spring element (13) intermediately arranged. A method for assembling the rolling bearing arrangement (1) of the electric axial flux machine (20) according to one of the preceding claims, comprising the following steps: - Providing a rolling bearing (2) with an inner ring (3), - Axially sliding the inner ring (3) onto a hollow shaft section (4), wherein the hollow shaft section (4) has a ramp (8) that widens radially towards the inner ring (3) and is designed as a conical, annular section of the hollow shaft section, and a circumferential groove (9) is formed in the hollow shaft section (4) in the axial direction between the ramp (8) and the inner ring (3), - Axially sliding the spring element (13) onto the hollow shaft section (4), - Axially sliding the support ring disc (12) onto the hollow shaft section (4), - Axially inserting an assembly tool (30) with a centering sleeve (31) and a centering ring that encompasses the centering sleeve (31) and is relative to the centering sleeve (31) axially movable assembly piston (32),so that the centering sleeve (31) is fixed axially and radially relative to the hollow shaft section (4), - Axial insertion of a retaining ring (10) that expands elastically in the radial direction over the ramp (8) of the hollow shaft section (4) by means of the axially displaceable assembly piston (32) of the assembly tool (30), so that the retaining ring (10) snaps into the groove (9). Method according to claim 6, characterized in that the assembly piston (32) has a radially inner section (33) and a radially outer section (34), wherein during the assembly of the support ring disc (12) and the retaining ring (10) the radially inner section (33) rests against the retaining ring (10) and the radially outer section (34) rests against the support ring disc (12), so that the support ring disc (12) and the retaining ring (10) can be axially displaced by means of the assembly piston (32) in such a way that the retaining ring (10) can snap into the groove (9) without being in contact with the support ring disc (12). Method according to claim 6 or 7, characterized in that the assembly piston (32) is released in the axial direction between the radially inner section (33) and the radially outer section (34) such that the retaining ring (10) does not contact the assembly piston (32) during its axial insertion in the radial direction.

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