Arrangement for shaft grounding

Abstract

The invention relates to an arrangement (14) for grounding a shaft (11), in particular a rotor shaft of an electric machine, having a grounding hub (15) via which the shaft (11) to be grounded is electrically conductively connected to an electrical grounding, preferably a housing. Furthermore, a bearing (23) is provided, by means of which the shaft (11) to be grounded is rotatably mounted relative to the grounding hub (15). The grounding hub (15) is electrically conductively connected to the grounding portion on one side and to a shaft (11) to be grounded on the other side and is axially preloaded by a spring element (30). In order to implement the arrangement (14) as compactly as possible and to thereby enable reliable grounding of the shaft (11), the spring element (30) preloads the grounding hub (15) axially to the electrically conductive connection to the grounding and the bearing (23) axially.

Description

Field of the Invention

[0001] The present invention relates to an arrangement for grounding a shaft, in particular a rotor shaft of an electric machine, the arrangement having a grounding hub through which the shaft to be grounded is conductively connected to an electrical grounding part (preferably a housing), wherein a bearing is provided through which the shaft to be grounded is rotatably supported relative to the grounding hub, and the grounding hub is in conductive connection with the grounding part on the one hand and with the shaft to be grounded on the other hand and is axially preloaded by a spring element. Furthermore, the present invention relates to a transmission, an electric axle drive unit for a motor vehicle, and an electric machine, in each case implementing the aforementioned arrangement. Background Art

[0002] Electric machines are used in the field of motor vehicles in order to design the corresponding motor vehicle as a hybrid vehicle or an electric vehicle. Thus, an electric machine is also provided in the case of a motor vehicle transmission in part in order to make the corresponding motor vehicle transmission suitable for use in a hybrid vehicle or an electric vehicle. Although the remaining components of the corresponding transmission are encapsulated and shielded by the corresponding surrounding transmission housing, the shafts led out of the transmission housing can generate electromagnetic interference, which can cause interference to other electronic components in the field of motor vehicles. In addition, a potential difference may form between the corresponding shaft and the transmission housing, which can lead to breakdown on the bearing of the corresponding shaft and thus to a reduction in the service life of the bearing. For this reason, the respective relevant shafts must be grounded as much as possible. Also in an electric machine originally provided in a motor vehicle, for example in an electric axle drive unit, the corresponding shaft is to be grounded in order to eliminate or reduce electromagnetic interference and prevent the formation of a potential difference. The corresponding grounding is mostly carried out by a conductive connection between the shaft to be grounded and an electrical grounding part, which is usually a housing.

[0003] An arrangement for shaft grounding is known from DE 10 2021 213 387 A1, in which the shaft to be grounded is conductively connected to the housing by means of a tubular grounding hub, the housing acting as an electrical grounding part for shaft grounding. The shaft to be grounded is rotatably supported relative to the grounding hub by means of a bearing, and a conductive connection is established between the end of the shaft to be grounded and the grounding hub by means of the bearing. At the opposite axial end, the grounding hub is also floatingly supported in the housing cover of the housing and is axially preloaded towards the bearing by means of a spring element, and a conductive connection between the grounding hub and the housing cover and thus also with the housing is established by means of the spring element. Here, the spring element is embodied as a wave spring. Summary of the Invention

[0004] Starting from the above prior art, the object of the present invention now is to provide an arrangement structure that is constructed as compactly as possible, in which reliable grounding of the shaft is achieved.

[0005] Starting from the preamble of claim 1 and combining the features of its characterizing part to solve this task. The following dependent claims respectively give further advantageous developments of the present invention. In addition, the transmission is the subject matter of claim 16, in which at least one shaft is arranged in accordance with the present invention. In addition, claim 17 relates to an electric vehicle axle drive unit, in which at least one shaft is arranged according to the arrangement structure of the present invention, and the subject matter of claim 18 is an electric motor, which includes a rotor shaft arranged in accordance with the present invention.

[0006] According to the present invention, an arrangement structure for shaft grounding has a grounding hub, through which the shaft to be grounded is conductively connected to an electrical grounding part. In addition, a bearing is provided, through which the shaft to be grounded is rotatably supported relative to the grounding hub. The grounding hub is conductively connected to the grounding part on the one hand and to the shaft to be grounded on the other hand and is axially preloaded by a spring element.

[0007] "Shaft" is in principle understood in the sense of the present invention as a rotatable component that is provided for transmitting rotational movement between components to be coupled. Here, the shaft can also be integrally formed with one or two components to be coupled. Particularly preferably, here, the shaft to be grounded is the rotor shaft of an electric motor, which is provided for non-rotatable connection with the rotor of the electric motor. Here, the rotor and the rotor shaft can also be integrally implemented or exist as separate and non-rotatable interconnected individual components. The electric motor can be a component of a motor vehicle transmission here. But the shaft to be grounded can in principle also be another shaft, such as a drive shaft.

[0008] In the arrangement structure according to the present invention, the grounding hub is provided for conductively connecting the shaft to be grounded to the electrical grounding part in such a way that the grounding hub is in conductive connection with the shaft to be grounded on the one hand and also in conductive connection with the electrical grounding part on the other hand. At least in the contact areas of the conductive connections with the electrical grounding part and with the shaft to be grounded and in the intermediate area connecting these contact areas, the grounding hub is made of a conductive material. But preferably, the grounding hub is completely formed of a conductive material, which is especially a metallic material, such as steel or aluminum.

[0009] The grounding hub, in the context of the present invention, particularly has a rod-like structure, i.e., it is implemented as an elongated member similar to a shaft, in order to preferably establish an electrically conductive connection axially between the shaft to be grounded and the electrical grounding part within the arrangement according to the present invention. Further preferably, the grounding hub is rotationally symmetrically constructed. In addition, the grounding hub is particularly fixedly arranged in the context of the arrangement according to the present invention, i.e., it does not perform a rotational movement, and for this purpose, an anti-rotation device is further preferably configured for the grounding hub.

[0010] The electrical grounding part is an electrically conductive body in the context of the present invention, and particularly a zero potential is assigned to the electrically conductive body as a reference potential. The electrically conductive connection from the shaft to be grounded to the electrical grounding part is established through the intermediate grounding hub. Preferably, the grounding part exists in the form of a housing, and here specifically, the electrically conductive connection of the grounding hub can be established on the housing, housing component, or a member that is permanently electrically connected thereto.

[0011] "Axially" in the scope of the present invention refers to the orientation in the direction of the rotational axis of the shaft or the longitudinal axis of the grounding hub, while "radially" refers to the orientation in the direction of a diameter having a midpoint on the rotational axis or the longitudinal axis.

[0012] An "electrically conductive" connection is understood in the context of the present invention as a connection in which an electric current can flow between the connected components. This electrically conductive connection is designed on the one hand between the electrical grounding part and the grounding hub and on the other hand between the grounding hub and the shaft to be grounded in the arrangement according to the present invention, where this can be done directly or indirectly through other intermediate components respectively.

[0013] The bearing through which the shaft to be grounded is rotatably supported relative to the grounding hub is particularly a radial bearing, where the radial bearing is preferably designed as a rolling bearing here and particularly preferably as a deep groove ball bearing. However, within the scope of the present invention, the intermediate bearing can also be implemented as a differently constructed rolling bearing, such as a roller bearing, or as a sliding bearing.

[0014] The present invention now includes the technical teaching that the spring element pre-tightens the grounding hub axially towards the electrically conductive connection with the grounding part on the one hand and pre-tightens the bearing axially on the other hand. That is to say, in other words, the spring element assumes the axial pre-tightening of the grounding hub relative to the shaft to be grounded in the direction of the electrically conductive connection, at which connection the grounding hub is electrically conductively connected to the electrical grounding part. On the other hand, the axial pre-tightening of the bearing is achieved through the spring element.

[0015] Such a design of an arrangement for shaft grounding has the advantage here that, on the one hand, a compact construction of the arrangement in the region of the conductive connection between the grounding hub and the grounding part can be achieved in that in this region no spring element is provided that pre-tensions the grounding hub against the shaft to be grounded, but rather only an electrical contact connection between the grounding part and the grounding hub is to be established. Correspondingly, the conductive connection between the grounding hub and the grounding part can also be constructed with a lower resistance. However, at the same time, the spring element ensures in a reliable manner the maintenance of the conductive connection from the grounding hub to the grounding part in that the spring element pre-tensions the grounding hub against the conductive connection to the grounding part, i.e., pre-tensions the grounding hub axially against the contact location or contact region that is formed on the side of the electrical grounding part or on the side of the component that is in permanent conductive connection with the electrical grounding part. On the other hand, the spring element ensures the pre-tensioning of the bearing, whereby a low-noise operation of the bearing can be achieved.

[0016] For the axial pre-tensioning of the grounding hub on the one hand and the bearing on the other hand, the spring element is supported axially on the one hand on the side of the grounding hub and on the other hand on the side of the shaft to be grounded in order to achieve on the one hand the axial pre-tensioning of the grounding hub relative to the shaft to be grounded against the conductive connection to the electrical grounding part and on the other hand to axially pre-tension the bearing. For this purpose, the spring element is to be arranged either between the grounded shaft and the bearing or between the bearing and the grounding hub.

[0017] Particularly preferably, by means of the axially pre-tensioning spring element, in contrast to the arrangement of DE 10 2021 213387A1, no conductive connection is established between the shaft to be grounded and the electrical grounding part, but rather the spring element is solely used in the arrangement according to the invention for the axial pre-tensioning of the grounding hub and the bearing. Thereby, the spring element does not need to be optimized with respect to conductivity and can correspondingly have a simple construction. But alternatively, it is also conceivable in the arrangement according to the invention that the spring element is also used for establishing the conductive connection from the grounding hub to the shaft to be grounded in addition to the axial pre-tensioning of the grounding hub and the bearing. But in this case, the spring element must then be constructed conductively based on its material properties or based on a corresponding coating.

[0018] Preferably, the grounded hub is supported in a floating manner on the side of the electrical grounding part. That is to say, the grounded hub can move axially with a clearance relative to the grounding part in this case, whereby an axial preloading of the conductive connection from the grounded hub to the grounding part can be formed without problems by the spring element. Because thereby the grounded hub can move axially relative to the electrical grounding part and thus also relative to the shaft to be grounded, and is preloaded towards the conductive connection with the grounding part by the spring element. In particular, the grounded hub forms a guiding section on a sub-section, on which the grounded hub is guided axially movably in a guiding hole on the side of the grounding part. Thereby, a floating support of the grounded hub on the grounding part can be achieved in a simple manner. Particularly preferably, the guiding section is formed by a cylindrical or tubular end of the grounded hub.

[0019] In particular, the grounded hub is at least partially tubularly constructed and connects the supply connection on the grounding side for lubricant and / or coolant to the shaft to be grounded through an internal volume. Thereby, in addition to achieving the conductive connection between the shaft to be grounded and the electrical grounding part, the grounded hub additionally undertakes the function of transporting the lubricant and / or coolant to the shaft to be grounded. For this purpose, the grounded hub is implemented at least partially tubularly.

[0020] Here, the lubricant and / or coolant can be guided through the internal volume of the at least one locally formed tube and the defined transport line thus formed towards the shaft to be grounded, where the agent is preferably oil, which is provided for cooling the shaft designed especially as a rotor shaft. Here, the grounded hub is tubularly constructed at least on a part of its axial extension, in such a way that in the at least one existing sub-section of the grounded hub, the internal volume is delimited by the surrounding material of the grounded hub and thus defines the transport line in this area. But particularly preferably, the grounded hub is entirely constructed as a tube, so that the transport of the lubricant and / or coolant can be achieved over the entire axial extension of the grounded hub and thus also the guiding of the agent from one axial end of the grounded hub to the other axial end.

[0021] The internal volume of the grounded hub can be connected to the radial outer region of the grounded hub through at least one hole. Thereby, a part of the lubricant and / or coolant guided through the internal volume can also be guided into the radial outer region of the grounded hub, so as to additionally provide other components, such as support parts and / or tooth parts, etc. in addition to the shaft to be grounded. Particularly preferably, the at least one hole is axially arranged near the bearing here. In addition, the at least one hole is designed to be vertically below in the installation position of the grounded hub, so as to enable the unproblematic outflow of a part of the lubricant and / or coolant through the at least one hole.

[0022] Corresponding to an embodiment of the present invention, the spring element is axially supported on the bearing on one side. That is, the spring element is placed adjacent to the bearing, and through the bearing, the shaft to be grounded is rotatably supported relative to the grounded hub, wherein the spring element is axially supported on the bearing directly with one spring end. This has the advantage that, on the one hand, axial preloading of the conductive connection between the grounded hub and the grounding part can be achieved in this way, and on the other hand, axial preloading of the bearing can also be directly achieved.

[0023] In an extension of the above-mentioned embodiment, the spring element is axially supported on the bearing on the one hand and on the grounded hub side on the other hand. That is, in this case, the spring element preloads the grounded hub axially towards the conductive connection to the grounding part by axially abutting the spring element on the bearing on the one hand and axially abutting on the grounded hub side on the other hand. Here, the support of the spring element on the grounded hub side can be carried out directly on the grounded hub or indirectly in such a way that the spring element is axially supported on at least one intermediate member connected to the grounded hub.

[0024] Preferably, at least one bearing ring on the grounded hub side of the bearing is guided with a clearance fit on the grounded hub side, wherein the bearing seat of the bearing ring arranged on the grounded hub side is axially bounded on both sides. Thereby, axial mobility relative to the bearing is achieved on the grounded hub side, so that axial preloading of the conductive connection between the grounded hub and the grounding part can also be formed without problems. In particular, the bearing ring on the grounded hub side is the inner ring of the bearing here. The axial bounding of the bearing seat on both sides is especially achieved by stop portions axially located on both sides of the bearing ring. In addition, it is also particularly preferred that the bearing ring on the shaft side - the bearing ring is especially the outer ring of the bearing - is guided with a clearance fit on the shaft side to be grounded, so as to enable the common assembly of the bearing and the grounded hub and simplify the assembly here.

[0025] However, instead of the above-mentioned extension, within the scope of the present invention, it is also conceivable that the spring element is arranged between the bearing and the shaft to be grounded and is supported here on the bearing on the one hand and on the shaft side to be grounded on the other hand. Also in this way, preloading of the bearing can be achieved on the one hand and preloading of the conductive connection between the grounded hub and the grounding part can be achieved on the other hand, in such a way that the grounded hub is axially preloaded towards the conductive connection through the intermediate bearing. In this case, the bearing ring on the shaft side is guided with a clearance fit on the shaft side to be grounded.

[0026] According to a design feasibility of the present invention, the conductive connection between the grounding hub and the shaft to be grounded is established through a guiding device, which is fixed on the grounding hub at an end facing the shaft to be grounded and is conductively connected to the grounding hub. Here, the guiding device has a guiding element, which pre-tightens the shaft to be grounded axially and conductively connects the shaft to be grounded to the guiding device. Thereby, a conductive connection between the grounding hub and the shaft to be grounded can be achieved with low resistance, in such a way that the connection is formed by the intermediate guiding device using a suitable guiding element. Particularly preferably, an element with high conductivity is used as the guiding element here, and the guiding element can in particular be configured as a graphite element here.

[0027] In an expansion of the above-mentioned design feasibility and in combination with a clearance-fit guiding of the bearing ring on the grounding hub side, the support seat is designed on the outer periphery of the guiding device, wherein the axial boundaries on both sides of the support seat are formed by the guiding device. That is to say, in addition to establishing the conductive connection between the shaft to be grounded and the grounding hub, the guiding device is additionally used for the design of the support seat, so that the bearing ring on the grounding hub side of the bearing is guided on the outer periphery of the guiding device.

[0028] Particularly preferably, the support seat is delimited in the first axial direction by abutting shoulders, which are formed circumferentially on the outer periphery of the guiding device and form an axial abutting surface for the bearing ring on the grounding hub side, wherein the support seat is formed in the second axial direction by a widened portion of the outer diameter of the guiding device caused by shaping. This widened portion of the outer diameter of the guiding device caused by shaping can be caused, for example, by pressing after the bearing ring is sleeved on the support seat. However, such a configuration of the support seat can also be achieved in a conceivable variant of the present invention, in which the support seat is arranged on the outer periphery of the grounding hub.

[0029] A variant of the present invention is that the spring element is axially supported on a support shoulder of the guiding device on the grounding hub side. That is to say, an axial abutting surface for the spring element is thus also provided by the guiding device, and the spring element pre-tightens the guiding device towards the grounding hub and thereby also pre-tightens the grounding hub towards the conductive connection to the grounding part through the intermediate guiding device. Such a support shoulder can of course also be designed directly on the grounding hub within the scope of the present invention, and the spring element is then also directly axially supported on the grounding hub.

[0030] Within the scope of the present invention, alternatively, it is also conceivable that instead of providing a guiding device, the bearing electrically connects the grounding hub to the shaft to be grounded. That is, in this case, the electrical connection between the grounding hub and the shaft to be grounded is made through the intermediate bearing. Thereby, the originally separate guiding device can be saved and thus the manufacturing cost can be reduced. Here, the bearing can be placed at a small diameter between the grounding hub and the shaft to be grounded, whereby a low circumferential speed is set on the bearing. Through this lower circumferential speed, the insulating effect of the lubricant of the bearing is avoided, which would otherwise occur increasingly as the circumferential speed increases.

[0031] In an embodiment of the present invention, the spring element is implemented as a compression spring, preferably as a helical spring. Thereby, axial preloading can be achieved in a reliable manner, and in addition, the helical spring can be arranged in a compact manner. Instead, however, the spring element can also be configured as a disc spring or as a corrugated spring, especially in the case where the electrical connection between the grounding hub and the shaft to be grounded is made through the intermediate bearing. Because in this case, the electrical connection between the bearing and the grounding hub can be re-established through the intermediate corrugated spring, which is feasible through the corrugated spring with a low contact resistance.

[0032] Another embodiment of the present invention is that the electrical connection between the grounding hub and the grounding part is established at the guiding section provided on the grounding hub. The guiding section is preloaded against the abutment surface of the grounding part by the axial preloading force generated by the grounding hub via the spring element and establishes the electrical connection from the grounding hub to the grounding part. In an advantageous manner, the electrical connection from the grounding hub to the electrical grounding part can thus be achieved in a simple and at the same time reliable manner. Particularly preferably, the guiding section projects radially outwards relative to the rest of the grounding hub.

[0033] In an embodiment of the above-mentioned embodiment, the guiding section exists as a separate annular guiding element, which is fixed to the outer diameter of the grounding hub with its inner diameter. By the guiding section existing as a separate component fixed to the grounding hub, the high-cost structure of this section can be eliminated on the side of the grounding hub.

[0034] As an alternative or supplement to the above-mentioned expansion solution, the guide section fixes the ground hub in the circumferential direction in addition. This simplifies the flow of lubricant and / or coolant through the ground hub (due to the non-rotation of the ground hub) especially in the following variants of the present invention, in which the ground hub is at least partially tubularly constructed and serves to guide the lubricant and / or coolant. The torsional stop can be achieved here by at least one radially protruding tab that extends circumferentially over a sub-section, which tabs are respectively formed on the guide section or the ground portion and engage into a respective recess, which recesses are circumferentially delimited on both sides of the at least one tab and are designed on the ground portion or the guide section. Thereby, the torsional stop can be achieved in a simple manner by form-fitting. Particularly preferably, the at least one tab is formed to protrude radially with respect to the rest of the guide section, while the associated recess is delimited on the ground portion side, especially by a corresponding configuration of the housing forming the ground portion. In particular, the guide section can be equipped with a plurality of tabs, particularly preferably with two tabs.

[0035] Particularly preferably, the guide section defines the movement of the ground hub in two axial directions by the interaction of on the one hand the abutment surface with the ground portion and on the other hand with the lock ring. The lock ring is placed in the hole of the ground portion axially on the side of the guide section facing away from the abutment surface on the electrical ground portion side.

[0036] Furthermore, the subject matter of the present invention is a transmission, in particular a motor vehicle transmission, in which at least one shaft is grounded in an arrangement according to one or more of the above-mentioned variants. Here, this arrangement can be implemented especially in the rotor shaft of an electric machine integrated into the transmission. The arrangement for shaft grounding according to the present invention can also be a component of an electric vehicle axle drive unit or an electric machine for a motor vehicle. Description of the Drawings

[0037] The advantageous embodiments of the present invention explained hereinafter are shown in the drawings. In the drawings:

[0038] Figure 1 A schematic view of the powertrain of a motor vehicle is shown;

[0039] Figure 2 A sectional view of the transmission of the powertrain in the region of the arrangement according to the present invention corresponding to the first embodiment of the present invention is shown; Figure 1 of the powertrain;

[0040] Figure 3 Shows Figure 2 A detailed view of the region of the arrangement is shown;

[0041] Figure 4 A schematic view of the powertrain of a motor vehicle is shown; and

[0042] Figure 5 Schematic view showing the electric machine. Detailed description

[0043] by Figure 1 A schematic view of a powertrain for a motor vehicle is derived. The powertrain has an internal combustion engine 1, the output of which is coupled to the input shaft 2 of a transmission 3. The output shaft 4 of the transmission 3 is connected to a differential 5. The differential 5 is designed to distribute the power acting on the output shaft 4 to the drive wheels 6 and 7 of the motor vehicle. The transmission 3 has a gear set 8, which together with switching elements not shown in Figure 1 is designed to provide different transmission ratios between the input shaft 2 and the output shaft 4. The gear set 8 is surrounded by a housing 9, which also houses an electric machine 10 connected to the input shaft 2. The electric machine 10 is designed to drive the input shaft 2, and a shaft 11 in the form of the rotor shaft of the electric machine 10 connects the input shaft 2 to the output of the internal combustion engine 1 here.

[0044] Furthermore, a converter 12 is fixed to the housing 9. The converter 12 is connected on the one hand to the electric machine 10 and on the other hand to a battery 13. The converter 12 is used to convert the direct current of the battery 13 into alternating current suitable for the operation of the electric machine 10 and for this purpose has a plurality of power semiconductors. The conversion between direct and alternating current is carried out by the controlled pulsed operation of the power semiconductors.

[0045] In order to prevent electromagnetic interference and the formation of potential differences during operation, the shaft 11 of the electric machine 10 is grounded in an arrangement 14, which is shown here in Figure 2 In Figure 2 it can also be seen here the permanently non-rotatable relative to each other (anti-torsional) connection between the input shaft 2 and the shaft 11. The arrangement 14 for grounding the shaft 11 is configured corresponding to a preferred embodiment of the present invention and includes a fixed grounding hub 15, which is conductively connected on the one hand to the shaft 11 and on the other hand to the housing cover 16 of the housing 9, where the housing acts as an electrical ground in the arrangement 14.

[0046] The grounding hub 15 is formed by a tubular body and extends axially from the housing cover 16 through the input shaft 2 designed as a hollow shaft up to the shaft 11, which is also implemented as a hollow shaft at least in this region for this purpose. Here, the grounding hub 15 is made of a conductive material, which can be aluminum.

[0047] Furthermore, on the axial end 17 of the grounded hub 15, a guiding device 18 (not shown in further detail currently) is fixed to the grounded hub 15, and for this purpose, the guiding device is pushed into the tubular body of the grounded hub 15 at the end 17. Through the guiding device 18, an electrically conductive connection from the shaft 11 to the grounded hub 15 is established here. For this purpose, the guiding device 18 is equipped with a guiding element 19, which is pre-tensioned axially against the contact surface 20 of the shaft 11. This is particularly visible here in the region of the guiding device 18 in the detailed view of the arrangement 14 in Figure 3 It can be seen in the region of the guiding device 18. The guiding element 19 of the guiding device 18 is made of a material with high electrical conductivity, such as graphite here, and establishes an electrically conductive connection between the shaft 11 and the guiding device 18 and thus also between the shaft 11 and the grounded hub 15.

[0048] As can be seen externally Figure 2 and also particularly in Figure 3 As can be seen, the guiding device 18 forms a support seat 21 for the bearing ring 22 of the bearing 23 on its outer circumference. The shaft 11 is rotatably supported relative to the guiding device 18 and thus also relative to the fixed grounded hub 15 through the bearing. The bearing ring 22 of the inner ring of the bearing 23 implemented as a deep groove ball bearing is guided on the support seat 21 with a clearance fit, that is, so that the guiding device 18 can move axially relative to the bearing ring 22. Here, this axial mobility and thus also the axial mobility of the support seat 21 in this axial direction are bounded by a abutment shoulder 24, which is designed to surround the outer circumference of the guiding device 18 and forms an axial abutment surface 25 for the bearing ring 22 here. In the opposite axial direction, the axial mobility and thus also the bounding of the support seat 21 are achieved through a widened portion 26 of the outer diameter of the guiding device 18 compared to the support seat 21. This widened portion 26 is preferably manufactured in the range of the forming process after the bearing ring 22 is pushed onto the support seat 21, for example, in a pressed form.

[0049] The bearing ring 27, which exists as the outer ring of the bearing 23, is also guided with a clearance fit on the side of the receiving hole 28 of the shaft 11, so that the bearing 23 can be assembled together with the grounded hub 15 and the guiding device 18 in the range of the assembly of the arrangement 14. Here, the bearing 23 provided on the guiding device 18 is then pushed into the receiving hole 28 with the bearing ring 27.

[0050] As a feature, a spring element 30 is provided axially between the bearing 23 and the support shoulder 29 of the guide device 18. The spring element is axially supported on the one hand on the bearing ring 22 of the bearing 23 and on the other hand on the support shoulder 29. By means of the spring element 30, which currently exists as a compression spring in the form of a helical spring, the grounded hub 15 and the guide device 18 are jointly preloaded relative to the bearing 23 and the shaft 11 in the direction towards the housing cover 16. This axial preloading also effects the preloading of the bearing 23. The support shoulder 29 is designed to surround the outer circumference of the guide device 18 here.

[0051] As can be seen in Figure 2 the grounded hub 15 is floatingly supported in the housing cover 16 at the axial end 31 opposite to the said axial end 17. Here, this floating support takes place on the guide section 32, which is formed by the pipe end 33 of the grounded hub 15, which also forms the axial end 31. On the side of the housing cover 16, the grounded hub 17 is axially movably guided at the guide hole 34 of the housing cover 18 by means of the guide section 32.

[0052] At the axial end 31, the grounded hub 15 is furthermore conductively connected to the housing cover 16 on the guide section 35, which is formed here by a separate annular guide element 36, which is fixed on the outer diameter of the grounded hub 15 with its inner diameter. Here, the guide element 36 is preferably pressed onto the grounded hub 15 in the corresponding area. By means of the axial preloading via the spring element 30, the guide element 36 is preloaded axially against the abutment surface 37, which is designed on the side of the housing cover 16. The guide element 36 is made of a conductive material here, so that a conductive connection is established between the housing cover 16 and the grounded hub 15 by the axial abutment of the guide element 36 on the abutment surface 37. Here, the material of the guide element 36 can be the same material as the grounded hub 15 or a material with a higher strength.

[0053] In addition to establishing the conductive connection between the grounded hub 15 and the housing cover 16, the guide element 36 also serves on the one hand for the anti-twist stop of the grounded hub 15 relative to the housing cover 16 and on the other hand for defining the axial movement of the grounded hub 15 relative to the housing cover 16. The limitation in one axial direction takes place here by the interaction of the guide element 36 and the abutment surface 37, while the limitation in the other axial direction is achieved by the interaction of the guide element 36 with the locking ring 38, which is received on the side of the housing cover 16.

[0054] In addition to the conductive connection established between the shaft 11 to be grounded and the housing cover 16, the grounding hub 15 is also used to convey lubricant and / or coolant to the shaft 11 to be grounded for cooling the shaft 11 and in particular the rotor of the electric machine here. Here, the lubricant and / or coolant is preferably oil. The lubricant and / or coolant is introduced into the internal volume 39 of the grounding hub 15 from the axial end 31 in such a way that a supply connection 40 for the lubricant and / or coolant is designed in the housing cover 16 on the end side of the grounding hub 15.

[0055] From Figure 4 a schematic view of a powertrain for a motor vehicle is obtained, which differs from Figure 1 a purely electric powertrain here. The powertrain has an electric axle drive unit 41. The electric axle drive unit 41 includes an electric machine 42, and the power of the electric machine is transmitted to the drive wheels 45 and 46 of the motor vehicle through a reduction gear set 43 and a differential 44. For this purpose, the electric machine 42 is connected to the reduction gear set 43 on the driven side on a shaft 47. The output shafts 48 and 49 of the differential 44 are connected to the drive wheels 45 and 46. The electric machine 42, the reduction gear set 43 and the differential 44 are surrounded by a housing 50. A converter 51 is fixed to the housing 50. The converter 51 is connected to the electric machine 42 on the one hand and to a battery 52 on the other hand. The converter 51 is used to convert the direct current of the battery 52 into alternating current suitable for the operation of the electric machine 42 and for this purpose has a plurality of power semiconductors. The conversion between direct current and alternating current is carried out by the controlled pulsed operation of the power semiconductors.

[0056] Currently, the grounding of the shaft 47 is carried out within the scope of the arrangement according to the invention, and the arrangement is implemented here in a manner similar to the variant according to Figure 2 and 3 Here, a grounding hub 53 is also provided, which is pre-tensioned against the housing 50 by a spring element. For a more accurate construction of the arrangement for the grounding of the shaft 47, reference is made to Figure 2 and 3 .

[0057] Finally, Figure 5 a schematic view of an electric machine 54 is also shown. The electric machine 54 has a housing 55, and a stator 56 and a rotor 57 are received in the housing. The stator 56 is fixed in the housing 55 in a non-rotatable manner. The rotor 57 is coupled to a rotor shaft 58, and the rotor shaft 58 is rotatably supported by two rolling bearings 59 and 60 supported on the housing 55. The end of the rotor shaft 58 projects from the housing 55.

[0058] The rotor shaft 58 is currently grounded within the scope of the arrangement according to the invention, and the arrangement is in principle similar to the one according to Figure 2 and3 is implemented in a similar manner for the variant. Thus, a ground hub 63 is also provided here, which is preloaded against the housing 55 by a spring element. For a more precise configuration of the ground arrangement with respect to the rotor shaft 58, reference is made to Figure 2 and 3 .

[0059] By means of the inventive design of the arrangement, reliable grounding of the shaft can be achieved.

[0060] List of reference numerals

[0061] 1 Internal combustion engine

[0062] 2 Input shaft

[0063] 3 Transmission

[0064] 4 Driven shaft

[0065] 5 Differential

[0066] 6 Driving wheel

[0067] 7 Driving wheel

[0068] 8 Gear set

[0069] 9 Housing

[0070] 10 Electric motor

[0071] 11 Shaft

[0072] 12 Converter

[0073] 13 Battery

[0074] 14 Arrangement

[0075] 15 Ground hub

[0076] 16 Housing cover

[0077] 17 End

[0078] 18 Guide device

[0079] 19 Guide element

[0080] 20 Contact surface

[0081] 21 Support seat

[0082] 22 Bearing ring

[0083] 23 Bearing

[0084] 24 Contact shoulder

[0085] 25 Contact surface

[0086] 26 Widening part

[0087] 27 Bearing ring

[0088] 28 Receiving hole

[0089] 29 Support shoulder

[0090] 30 Spring element

[0091] 31 End

[0092] 32 Guide section

[0093] 33 Pipe end

[0094] 34 Guide hole

[0095] 35 Guide section

[0096] 36 Guide element

[0097] 37 Contact surface

[0098] 38 Lock ring

[0099] 39 Internal volume

[0100] 40 Supply joint

[0101] 41 Axle drive unit

[0102] 42 Motor

[0103] 43 Reduction gear set

[0104] 44 Differential

[0105] 45 Driving wheel

[0106] 46 Driving wheel

[0107] 47 Shaft

[0108] 48 Output shaft

[0109] 49 Output shaft

[0110] 50 Housing

[0111] 51 Converter

[0112] 52 Battery

[0113] 53 Grounding hub

[0114] 54 Motor

[0115] 55 Housing

[0116] 56 Stator

[0117] 57 Rotor

[0118] 58 Rotor shaft

[0119] 59 Rolling bearing

[0120] 60 Rolling bearing

[0121] 61 Grounding hub

[0122] 62 Arrangement structure

[0123] 63 Grounding hub

Claims

1. An arrangement (14) for grounding a shaft (11), in particular a rotor shaft (58) of an electric machine (10; 42; 54), comprising a grounding hub (15), via which the shaft (11) to be grounded is electrically conductively connected to an electrical grounding part, which is preferably a housing (9), wherein: A bearing (23) is provided, the shaft (11) to be grounded is rotatably supported relative to the grounding hub (15) via the bearing, and the grounding hub (15) is in conductive connection with the grounding portion on the one hand and with the shaft (11) to be grounded on the other hand and is axially preloaded by a spring element (30), characterized in that the spring element (30) axially preloads the grounding hub (15) toward the conductive connection with the grounding portion on the one hand and axially preloads the bearing (23) on the other hand.

2. The arrangement (14) according to claim 1, characterized in that The spring element (30) is supported on one side in the axial direction on the bearing (23).

3. The arrangement (14) according to claim 2, characterized in that The spring element (30) is supported axially on the bearing (23) on the one hand and axially on the grounding hub (15) on the other hand.

4. The arrangement (14) according to claim 3, characterized in that At least one bearing ring (22) of the bearing (23) on the grounding hub side is guided with a clearance fit on the grounding hub (15) side, and a support seat (21) of the bearing ring (22) on the grounding hub side, which is arranged on the grounding hub (15) side, is limited on both sides in the axial direction.

5. The arrangement (14) according to one of the preceding claims, characterized in that The conductive connection between the grounding hub (15) and the shaft (11) to be grounded is established by a guide device (18), which is fixed to the grounding hub (15) at an end (17) facing the shaft (11) to be grounded and is conductively connected to the grounding hub (15), and the guide device (18) has a guide element (19) which preloads the shaft (11) to be grounded in the axial direction and conductively connects the shaft (11) to be grounded to the guide device (18).

6. The arrangement (14) according to claim 4 and according to claim 5, characterized in that The bearing seat (21) is formed on the outer circumference of the guide device (18), and the axial limitation of the bearing seat (21) on both sides is formed by the guide device (18).

7. The arrangement (14) according to claim 6, characterized in that The bearing seat (21) is limited in a first axial direction by a contact shoulder (24), which is formed circumferentially on the outer circumference of the guide device (18) and forms an axial contact surface (25) for the bearing ring (22) on the grounding hub side, and the bearing seat (21) is formed in a second axial direction by a widening (26) of the outer diameter of the guide device (18) produced by forming.

8. The arrangement (14) according to claim 3 and according to one of claims 5 to 7, characterized in that The spring element (30) is supported axially on the grounding hub (15) side on a supporting shoulder (29) of the guide device (18).

9. The arrangement (14) according to one of the preceding claims, characterized in that The spring element (30) is designed as a compression spring, preferably as a helical spring.

10. The arrangement (14) according to one of the preceding claims, characterized in that An electrically conductive connection between the grounding hub (15) and the grounding portion is established on a guide section (35) arranged on the grounding hub (15); the guide section is preloaded toward a contact surface (37) of the grounding portion by an axial prestress of the grounding hub (15) generated by the spring element (30) and an electrically conductive connection is established between the grounding hub (15) and the grounding portion.

11. The arrangement (14) according to claim 10, characterized in that The guide section (35) is present as a separate annular guide element (36) which is fastened with its inner diameter to the outer diameter of the grounding hub (15).

12. Arrangement (14) according to claim 10 or 11, characterized in that The guide section (35) also fixes the grounding hub (15) in the rotational direction.

13. The arrangement (14) according to any one of claims 10 to 12, characterized in that The guide section (35) limits the movement of the grounding hub (15) in two axial directions by interacting with a contact surface (37) of the grounding portion on the one hand and with a locking ring (38) on the other hand.

14. A transmission (3), in particular a motor vehicle transmission, comprising at least one shaft (11) which is grounded according to an arrangement (14) according to one or more of claims 1 to 13.

15. An electric axle drive unit (41) for a motor vehicle, characterized in that A shaft (47) is provided which is grounded according to an arrangement according to one or more of claims 1 to 13.

16. An electric motor (54), comprising a stator (56) which is fixed in rotation relative to one another and a rotatable rotor (57), wherein the rotor (57) is coupled to a rotor shaft (58), characterized in that: The rotor shaft (58) is grounded according to an arrangement according to one or more of claims 1 to 13.

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