Shaft grounding device, motor and kit of parts

Abstract

The invention relates to a shaft grounding device (1) for dissipating an electrical charge and / or voltage from a shaft (4), in particular for a drive train (2) of an electrically drivable motor vehicle (3), comprising: a rotatably mounted shaft (4), in which a hollow space (7) projects axially into the shaft (4) starting from an end face (6) having a shaft opening (5); the shaft (4) has a shaft opening (5), and a first electrically conductive sleeve (8) which is rotationally fixed relative to the shaft (4), engages through the shaft opening (5) and extends axially into the hollow space (7) of the shaft (4), a second electrically conductive sleeve (9) being arranged in and / or on the first sleeve (8), an electrically conductive bridging sleeve (26) being arranged in the second electrically conductive sleeve (9), the bridge sleeve (26) has an electrically conductive ground rod (10), which is accommodated in the bridge sleeve and is mounted in a rotatable manner relative to the bridge sleeve (26), the ground rod (10) being connected in an electrically conductive manner on the one hand to the bridge sleeve (26) and in an electrically conductive manner on the other hand to a third electrically conductive sleeve (11), the third conductive sleeve is in turn connected to a shaft (4).

Description

Technical Field

[0001] The present invention relates to a shaft grounding device for dissipating electrical charge and / or voltage from a shaft, particularly for a drivetrain of an electrically driven motor vehicle. The shaft grounding device comprises: a rotatably mounted shaft, wherein a hollow space protrudes axially into the shaft from an end face having a shaft opening; and a first electrically conductive sleeve, which is rotationally fixed relative to the shaft, engages through the shaft opening, and extends axially into the hollow space of the shaft. The invention also relates to an electric machine and a set of components. Background Art

[0002] Electric motors, particularly electric traction machines, are electrically charged during operation by induced shaft voltages. Furthermore, high-power motors can generate circulating high-frequency currents. Such electric motors typically have a rotor and a rotor shaft mounted in a housing via rolling bearings. The rolling bearings can be damaged by electrical discharge or circulating high-frequency currents. To prevent this, this electrical energy must be dissipated. For example, grounding brushes or radially acting grinding elements (carbon brushes) are known for grounding the rotor shaft. Furthermore, axially acting systems for shaft grounding are also known.

[0003] Document DE 10 2020 119 719 A1, which represents the closest prior art, discloses an emission device for a motor, which is used to discharge charge and / or voltage from a rotor to a housing via a shaft, the emission device comprising a first contact module for electrically and mechanically connecting to the shaft, and a second contact module for electrically and mechanically connecting to the housing, wherein the first contact module and the second contact module can rotate relative to each other and be electrically connected to each other in an internal space sealed relative to the housing chamber, the internal space is filled with a conductive liquid, and the first contact module and the second contact module are electrically connected to each other via the conductive liquid. Summary of the Invention

[0004] The object of the present invention is to create a shaft grounding device that is characterized by good mountability, improved dissipation, and freedom from wear. It is also an object of the present invention to provide a correspondingly improved electric machine. Finally, it is also an object of the present invention to provide a component kit that allows for simplified and routine assembly of the shaft grounding device.

[0005] This object is achieved by a shaft grounding device for dissipating electric charges and / or voltages from a shaft, in particular for a drive train of an electrically driven motor vehicle, the shaft grounding device comprising: a rotatably mounted shaft, wherein a hollow space protrudes axially into the shaft starting from an end face having a shaft opening; and a first electrically conductive sleeve, which is rotationally fixed relative to the shaft, engages through the shaft opening and extends axially into the hollow space of the shaft, wherein a second electrically conductive sleeve is arranged in and / or on the first sleeve, in which a conductive bridging sleeve is arranged and which has a conductive grounding rod, which is accommodated in the bridging sleeve and is rotatably mounted relative to the bridging sleeve, wherein the grounding rod is electrically conductively connected to the bridging sleeve on the one hand and to a third electrically conductive sleeve on the other hand, which is in turn connected to the shaft.

[0006] This makes it possible to provide an axially acting system for shaft grounding that operates effectively in both dry and wet motors and at all operating points. Existing installation space can be utilized without axially or radially enlarging the motor. Furthermore, the shaft grounding system can be easily incorporated into existing applications at a later date. This prevents bearing damage on rotatably mounted shafts and improves electromagnetic compatibility (EMC), thereby reducing or preventing interference with other devices.

[0007] A further advantage of the shaft grounding device system according to the invention is that the shaft grounding device can be designed as a standalone system and can therefore be provided as a preassembled unit.

[0008] With regard to the fluids used and the structure of the shaft grounding device unit, reference is made to the applicant's pre-publication DE 102 022 113 208 A1, the entire content of which is incorporated by reference into the disclosure content of the present application.

[0009] The fact that the electrically conductive sleeve is rotationally fixed relative to the shaft means that the sleeve is firmly positioned in the circumferential direction, whereas the shaft can rotate relative to the non-rotatable sleeve.

[0010] First, the various elements of the claimed subject matter of the present invention are explained according to the relevance of the various elements in the claims or the order in which the various elements are mentioned in the claims, and then particularly preferred embodiments of the claimed subject matter of the present invention are described.

[0011] The rotor is the rotating (rotating) part of the electric machine. The rotor comprises in particular a rotor shaft. The rotor shaft can be hollow, which on the one hand reduces weight and on the other hand allows lubricant or coolant to be supplied to the rotor body.

[0012] For the purposes of the present invention, the rotor body is therefore understood to mean the rotor without the rotor shaft. The rotor body is thus made in particular of the rotor laminations and the permanent magnets, which are inserted into the pockets of the rotor laminations or fixed to the periphery of the rotor laminations, as well as any axial covering parts for closing the pockets.

[0013] The rotor preferably has multiple rotor bodies. Particularly preferably, the rotor bodies are formed from essentially identical components, in particular, in essentially the same manner. It is highly preferred that the rotor bodies be formed from identical, in particular essentially identical, rotor laminations. Therefore, the rotor body is particularly preferably formed from a rotor lamination stack, which consists of a plurality of laminated individual laminations or rotor laminations, typically made of electrical steel, layered one on top of the other and stacked to form a stack, referred to as a rotor lamination stack. The individual laminations can be joined together in the rotor lamination stack by gluing, welding, or screwing. In particular, the rotor lamination stack can also include permanent magnets, which are inserted into recesses in the rotor lamination stack or are circumferentially fixed to the rotor lamination stack. The rotor lamination stacks may be offset relative to one another, i.e., arranged at an angle relative to one another. This offset can be linear or V-shaped to avoid or at least reduce axial forces.

[0014] Permanent magnets to be introduced into the pockets of the laminated rotor core are understood to be rotor magnets. The permanent magnets can preferably be inserted into pockets in the rotor lamination stack. Each pocket can be provided with a single, larger rotor magnet designed as a bar magnet or with a plurality of smaller rotor magnets designed as permanent magnet elements.

[0015] The rotor lamination stack can in particular form the rotor body. A laminated rotor core is understood to mean a plurality of laminated individual laminations or rotor laminations, which are usually made of electrical metal sheets and are stacked and packaged one on top of the other to form a stack or "laminated rotor core". The individual laminations can then be joined together in the laminated core by adhesive bonding, welding or screwing. In particular, the rotor lamination stack can also have magnetic elements, which are inserted into recesses in the rotor lamination stack or are fixed around the circumference of the rotor lamination stack, as well as any axial covering parts and the like for closing the recesses.

[0016] In particular, the electric machine can be designed as a rotary machine. In particular, the rotary machine can be configured as a radial flux machine. A radial flux machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and the stator extend in a radial direction. The gap between the rotor and the stator is called the air gap. In a radial flux machine, the air gap is a gap having a circular cross-section whose radial width corresponds to the distance between the rotor and stator bodies.

[0017] The electric motor is particularly intended for use in the drivetrain of a hybrid or fully electric motor vehicle. In particular, the electric motor is dimensioned to enable vehicle speeds exceeding 50 km / h, preferably exceeding 80 km / h, and in particular exceeding 100 km / h. The electric motor particularly preferably has an output exceeding 50 kW, preferably exceeding 80 kW, and in particular exceeding 150 kW. Furthermore, it is preferred that the electric motor provide a rotational speed exceeding 8,000 rpm, particularly preferably exceeding 12,000 rpm, and very particularly preferably exceeding 15,000 rpm.

[0018] For the purposes of this application, a motor vehicle is a land vehicle that moves by machine power and is not constrained by railway tracks. The motor vehicle may for example be selected from the group of a passenger car, a truck, a scooter, a light motor vehicle, a motorcycle, a motor bus / coach or a tractor.

[0019] According to an advantageous embodiment of the present invention, the first sleeve can have at least one feedthrough opening on its lateral surface, through which fluid can be directed from the sleeve into the hollow space. This embodiment has the advantage that the sleeve can thus provide cooling and / or lubrication for the shaft or components adjacent to the shaft. Therefore, the first sleeve can also be referred to as a grease gun.

[0020] Preferably, the third sleeve also has a feed-through opening, through which the fluid can flow, for example in the axial direction.

[0021] Another advantage of the shaft grounding device is that it can be used in wet motors without requiring additional installation space. For example, the small size of the second sleeve means that the oil supply to the rotor is unimpeded.

[0022] According to another preferred further development of the present invention, it can also be provided that the shaft has at least one through-channel extending through the shaft in a radial direction starting from the hollow space, and the fluid can be guided out of the hollow space via the through-channel, thereby providing a hydraulic connection for cooling the rotor and / or stator of the electric motor.

[0023] Furthermore, according to an equally advantageous embodiment of the invention, it can be provided that the second sleeve is fixed in the first sleeve by means of an interference fit. This embodiment has the advantageous effect that the first sleeve and the second sleeve can be preassembled in a manner advantageous in terms of production technology, which can correspondingly simplify subsequent assembly.

[0024] According to another particularly preferred embodiment of the invention, it can be provided that the first sleeve, the second sleeve, the bridging sleeve, the third sleeve and the grounding rod are arranged coaxially with respect to one another, which has proven to be advantageous in terms of installation and particularly reliable in operation.

[0025] Furthermore, the present invention can be further developed so that the grounding rod protrudes axially from the second sleeve, and the third sleeve is arranged on the section protruding axially from the second sleeve by means of an interference fit. This embodiment has the advantage that it provides a shaft grounding device that is particularly easy to install and reliable in operation. In principle, it is also conceivable to arrange the third sleeve on the section protruding axially from the second sleeve in a rotationally fixed manner by means of a form fit, for example, by means of a spline.

[0026] The object of the present invention is also achieved by an electric machine, in particular an electric machine for a drive train of an electrically driven motor vehicle, comprising a stator and a rotor rotatable relative to the stator, wherein the rotor is coupled to a shaft having a shaft grounding device in a torque-transmitting manner, wherein the shaft grounding device is designed according to one of claims 1 to 6.

[0027] It may also be advantageous to further develop the invention such that the first sleeve is connected to the motor housing in a non-rotatable and electrically conductive manner, which generally results in good grounding of the shaft.

[0028] According to another preferred embodiment of the present invention, the first sleeve can be connected to the fluid circuit of the electric machine, so that fluid can pass through the first sleeve and the shaft and thus supply the rotor and / or stator with fluid. This means that the shaft grounding device can also be cooled, which is beneficial for extending its service life.

[0029] Finally, the object of the present invention can also be achieved by a kit of parts for producing a shaft grounding device, in particular for producing a shaft grounding device for an electric machine, the kit comprising: a shaft, wherein a hollow space extends axially into the shaft starting from an end face having a shaft opening; a first conductive sleeve, which can be inserted into the hollow space; a second conductive sleeve, which can be arranged in the first sleeve and / or on the first sleeve, wherein a conductive bridging sleeve is arranged in the second sleeve and the bridging sleeve has a conductive grounding rod, which is accommodated in the bridging sleeve and is mounted in a rotatable manner relative to the bridging sleeve, wherein the grounding rod is connected to the bridging sleeve in an electrically conductive manner on the one hand and can be coupled in an electrically conductive manner to a third conductive sleeve, which in turn can be coupled to the shaft; a third conductive sleeve, which can be positioned in the hollow space and on the grounding rod in an electrically conductive manner with respect to the shaft.

[0030] This allows the components required for producing the shaft grounding device to be manufactured in a particularly convenient manner. For example, the component kit can be a packaged unit. Furthermore, the component kit can be designed as a combination of separate storage containers for storing the individual components of the component kit or corresponding component groups. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention is explained in more detail below with reference to the accompanying drawings without limiting the general concept of the invention.

[0032] In the attached figure:

[0033] Figure 1 A motor vehicle with an electric drive train is shown in a schematic block diagram.

[0034] Figure 2 An electric machine with a shaft grounding arrangement is shown in a schematic axial cross-section.

[0035] Figure 3 A detailed representation of a shaft with a shaft grounding device is shown in axial cross-section.

[0036] Figure 4 An axial cross-sectional representation of the shaft grounding device is shown in exploded view.

[0037] Figure 5 A schematic diagram shows a kit of parts for producing a shaft grounding device. DETAILED DESCRIPTION

[0038] Figure 1 An electric machine 20 is shown in a drive train 2 of an electrically driven motor vehicle 3. Figure 2The electric machine 20 shown in FIG. 1 comprises a stator 21 and a rotor 22 rotatable relative to the stator 21 , wherein the rotor 22 is coupled to a shaft 4 having a shaft grounding device 1 in a torque-transmitting manner.

[0039] Figure 3 A detailed view of a shaft grounding device 1 for dissipating electrical charges and / or voltages is shown. The shaft grounding device comprises a rotatably mounted shaft 4, wherein a hollow space 7 extends axially into the shaft 4, starting from an end face 6 having a shaft opening 5. A first sleeve 8, which is electrically conductive and non-rotatable relative to the shaft 4, engages through the shaft opening 5 and extends axially into the hollow space 7 of the shaft 4. Thus, the electrically conductive sleeve 8 cannot rotate relative to the shaft 4. Thus, the sleeve 8 is fixed in the circumferential direction, while the shaft 4 can rotate relative to the non-rotatable sleeve 8. The first sleeve 8 is electrically conductively and non-rotatably connected to the motor housing 23 via a housing cover 25. The shaft 4 is mounted in the motor housing 23 via roller bearings (not further illustrated).

[0040] from Figure 1 as well as Figure 2 As can be seen in summary, the first sleeve 8 is connected to the fluid circuit 24 of the electric machine 20 , such that the fluid 14 can pass through the first sleeve 8 and the shaft 4 and thus can supply the rotor 22 and / or the stator 21 with the fluid 14 .

[0041] Arranged in the first hollow cylindrical sleeve 8 is a second electrically conductive hollow cylindrical sleeve 9, in which is arranged an electrically conductive bridging sleeve 26, which has an electrically conductive grounding rod 10 housed in the bridging sleeve and mounted rotatably relative to the bridging sleeve 26. The grounding rod 10 is electrically conductively connected on the one hand to the bridging sleeve 26 and on the other hand to a third electrically conductive sleeve 11. The third hollow cylindrical sleeve 11 is in turn connected to the shaft 4.

[0042] In the exemplary embodiment shown, the second sleeve 9 is fixed in the first sleeve 8 by means of an interference fit. The first sleeve 8, the second sleeve 9, the bridging sleeve 26, the third sleeve 11, and the grounding rod 10 are arranged coaxially with one another. The grounding rod 10 protrudes axially from the second sleeve 9, wherein the third sleeve 11 is arranged in a rotationally fixed manner on the section 16 protruding axially from the second sleeve 9 by means of an interference fit. In principle, it is also conceivable that the third sleeve 11 is arranged in a rotationally fixed manner on the section 16 protruding axially from the second sleeve by means of a form fit, for example, by means of a spline.

[0043] The first sleeve 8 has at least one feedthrough opening 13 on its lateral surface 12, via which a fluid 14 can be conducted from the sleeve 8 into the hollow space 7. The shaft 4, in turn, has at least one through-channel 15 extending radially from the hollow space 7 through the shaft 4, via which the fluid 14 can be conducted out of the hollow space 7. In the illustrated embodiment, the first sleeve 8 thus functions as a grease gun. This is sealed against the surrounding environment by a seal 17 in the first sleeve 8.

[0044] To ensure electrical contact, the interior of the second sleeve 9 is filled with a conductive liquid 19. The grounding rod 10 and the second sleeve 9 are in electrically conductive contact with each other via the conductive liquid 19 and the sleeve 26 coaxially arranged between the grounding rod 10 and the second sleeve 9. For example, the conductive liquid can be a conductive oil, grease, liquid metal, or ionic liquid. Due to the structure described below, oils and greases without special conductive components can also be used. The second sleeve 9 is fluid-tightly separated from the first sleeve 8 or the environment surrounding the shaft grounding device 1, preventing the conductive liquid 19 from escaping the second sleeve 9. This results in an axially insertable and effective shaft grounding device 1 that can be used in both dry and humid environments. Because the electrical contact between the second sleeve 9 and the grounding rod 10 is established via the conductive liquid 19 and the sleeve 26 coaxially arranged between the grounding rod 10 and the second sleeve 9, the shaft grounding device 1 operates with low friction and is wear-free during operation of the motor 20, eliminating the risk of conductive wear. Furthermore, since the conductive liquid 19 always ensures contact between the bridging sleeve 26 and the ground rod 10 , the conductive liquid 19 enables operation regardless of the position.

[0045] In a preferred embodiment of the present invention, the annular gap has a simple annular gap width, ie the distance between the inner periphery of the bridging sleeve 26 and the outer periphery of the ground rod 10 is less than 200 μm, preferably less than 60 μm, and in particular less than 30 μm.

[0046] A small annular gap width increases the electrical conductivity and / or reduces the electrical resistance of the shaft grounding device 1 .

[0047] The conductive liquid—fluid 14—is preferably conductive itself and / or mixed with conductive additives. In principle, the conductive liquid can be in the form of a liquid metal, an ionic liquid, or the like. However, the conductive liquid is preferably in the form of a conductive oil or grease. Although conductive oils and greases generally have lower conductivity than, for example, liquid metals, they are less toxic and / or easier to handle. The use of the bridging sleeve 26 compensates for the lower conductivity and thus enables the technically appropriate use of conductive oils and / or greases. In particular, conductive liquids with a conductivity greater than 10,000 nS / m, particularly greater than 30,000 nS / m at 25°C, such as oils or greases with conductive additives or other oil- and / or fat-free liquids are used. These are particularly suitable for low-impedance applications.

[0048] For lower transmission resistance requirements, ie for higher transmission resistances, even standard gear oils can be used with the bridge sleeve.

[0049] In an alternative embodiment, the conductive liquid has a conductivity of less than 500 nS / m, preferably less than 300 nS / m, and in particular less than 100 nS / m or less than 50 nS / m at 25°C. On the other hand, a conductivity greater than 1 nS / m, preferably greater than 5 nS / m, and in particular greater than 10 nS / m is preferred. This conductivity allows the use of commonly used transmission oils, thus eliminating the need for specially formulated liquids, particularly those containing conductive additives. This can be achieved by using a bridging sleeve 26 and the resulting reduced annular gap width.

[0050] The current path through the shaft grounding device 1 is Figure 3 The dotted line indicates .

[0051] The grounding rod 10 is designed as a metallic, particularly electrically conductive, cylindrical rod. It is inserted axially into the second sleeve 9 so that the grounding rod 10 is partially immersed in the conductive liquid 19 in the axial region of the second sleeve 9. Thus, an electrical path is established between the grounding rod 10 and the second sleeve 9 via the conductive liquid 19, the bridging sleeve 26, and the second sleeve 9. Induced currents are safely dissipated to ground via this path of least resistance, allowing the current to be diverted away from the bearings through the system. This also protects the bearings of connected components, such as transmissions. The shaft grounding device 1 includes a seal 18, through which the grounding rod 10 is guided in a sealed manner into the second sleeve 9. The grounding rod 10 is positioned radially above the seal 18, thereby sealing it against the second sleeve 9.

[0052] For assembly, a kit 30 may be provided for producing the shaft grounding device 1, such as Figure 5 shown.

[0053] The kit 30 comprises a shaft 4, wherein a hollow space 7 extends axially into the shaft 4 starting from an end face 6 having a shaft opening 5. The kit 30 further comprises a first electrically conductive sleeve 8, which can be inserted into the hollow space 7, and a second electrically conductive sleeve 9, which can be arranged in and / or on the first sleeve 8, wherein the second sleeve 9 comprises an electrically conductive grounding rod 10, which is accommodated in the second sleeve and is rotatably mounted relative to the second sleeve 9, wherein the grounding rod 10 is electrically conductively connected to the second sleeve 9.

[0054] An electrically conductive bridging sleeve 26 is arranged in the second sleeve 9 , the bridging sleeve being designed to be rotatable relative to the electrically conductive ground rod 10 .

[0055] Furthermore, the kit 30 has a third electrically conductive sleeve 11 which can be positioned in an electrically conductive manner in the hollow space 7 and on the ground rod 10. This can also be based on Figure 4 is well understood.

[0056] The present invention is not limited to the embodiments shown in the accompanying drawings. Therefore, the above description should not be regarded as restrictive, but rather as illustrative. The appended claims should be understood to mean that the recited features are present in at least one embodiment of the present invention. This does not exclude the presence of other features. Where the claims and the above description define a “first” feature and a “second” feature, such designation is used to distinguish between two features of the same type and does not define an order of precedence.

[0057] Reference Signs List

[0058] 1 Shaft grounding device

[0059] 2 Drivetrain

[0060] 3 Motor vehicles

[0061] 4-axis

[0062] 5-axis opening

[0063] 6 End face

[0064] 7 Hollow Space

[0065] 8 First sleeve

[0066] 9 Second sleeve

[0067] 10 ground rods

[0068] 11 Third sleeve

[0069] 12 lateral surfaces

[0070] 13 Feedthrough opening

[0071] 14 Fluid

[0072] 15 Through Channel

[0073] 16 sections

[0074] 17 Seals

[0075] 18 seals

[0076] 19 liquid

[0077] 20 motors

[0078] 21 stator

[0079] 22 rotors

[0080] 23 Motor housing

[0081] 24 Fluid circuit

[0082] 25 Housing cover

[0083] 26 bridge sleeve

[0084] 30 complete sets of parts

Claims

1. A shaft grounding device (1) for dissipating electrical charge and / or voltage from a shaft (4), in particular for a drive train (2) of an electrically drivable motor vehicle (3), comprising: A rotatably mounted shaft (4), wherein a hollow space (7) protrudes axially into the shaft (4) starting from an end face (6) having a shaft opening (5); and a first electrically conductive sleeve (8), which is rotationally fixed relative to the shaft (4), engages through the shaft opening (5) and extends axially into the hollow space (7) of the shaft (4), Characterized in that a second conductive sleeve (9) is arranged in the first sleeve (8) and / or on the first sleeve, a conductive bridging sleeve (26) is arranged in the second conductive sleeve, and the bridging sleeve (26) has a conductive grounding rod (10), which is accommodated in the bridging sleeve and is mounted in a rotatable manner relative to the bridging sleeve (26), wherein the grounding rod (10) is connected to the bridging sleeve (26) in an electrically conductive manner on the one hand and to a third conductive sleeve (11) in an electrically conductive manner on the other hand, which is in turn connected to the shaft (4).

2. The shaft grounding device (1) according to claim 1, It is characterized by: The first sleeve (8) has at least one feed-through opening (13) on a lateral surface (12), via which a fluid (14) can be conducted from the sleeve (8) into the hollow space (7).

3. The shaft grounding device (1) according to claim 1 or 2, It is characterized by: The shaft (4) has at least one through-channel (15) extending from the hollow space (7) in a radial direction through the shaft (4), and the fluid (14) can be conducted out of the hollow space (7) via the through-channel.

4. Shaft grounding device (1) according to one of the preceding claims, It is characterized by: The second sleeve (9) is fixed in the first sleeve (8) by means of an interference fit.

5. Shaft grounding device (1) according to one of the preceding claims, It is characterized by: The first sleeve (8), the second sleeve (9), the bridging sleeve (26), the third sleeve (11) and the grounding rod (10) are arranged coaxially with each other.

6. Shaft grounding device (1) according to one of the preceding claims, It is characterized by: The grounding rod (10) protrudes axially from the second sleeve (9), and the third sleeve (11) is arranged in a non-rotatable manner on a section (16) protruding axially from the second sleeve (9) by means of an interference fit or a form fit.

7. An electric machine (20), in particular for a drive train (2) of an electrically drivable motor vehicle (3), comprising a stator (21) and a rotor (22) rotatable relative to the stator (21), wherein: The rotor (22) is coupled to a shaft (4) having a shaft grounding device (1) in a torque-transmitting manner, Characterized in that the shaft grounding device (1) is designed according to one of claims 1 to 6.

8. The electric motor (20) according to claim 7, It is characterized by: The first sleeve (8) is connected to the motor housing (23) in a non-rotatable and electrically conductive manner.

9. The electric machine (20) according to claim 7 or 8, It is characterized by: The first sleeve (8) is connected to a fluid circuit (24) of the motor (20) such that a fluid (14) can pass through the first sleeve (8) and the shaft (4) and thus supply the rotor (22) and / or the stator (21) with the fluid (14).

10. A kit of parts (30) for producing a shaft grounding device (1), in particular for producing a shaft grounding device (1) of an electric machine (20), comprising: - a shaft (4), wherein a hollow space (7) extends axially into the shaft (4) starting from an end face (6) having a shaft opening (5), - a first electrically conductive sleeve (8) which is insertable into the hollow space (7), - a second electrically conductive sleeve (9) which can be arranged in the first sleeve (8) and / or on the first sleeve, wherein an electrically conductive bridging sleeve (26) is arranged in the second sleeve (9) and the bridging sleeve (26) has an electrically conductive grounding rod (10) which is accommodated in the bridging sleeve and is mounted rotatably relative to the bridging sleeve (26), wherein the grounding rod (10) is electrically conductively connected to the bridging sleeve (26) on the one hand and can be electrically conductively coupled to a third electrically conductive sleeve (11) on the other hand, which in turn can be coupled to the shaft (4), - a third electrically conductive sleeve (11) positionable in the hollow space (7) and on the ground rod (10) in an electrically conductive manner with the shaft (4).

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