Shaft grounding, electric machine 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 powered motor vehicle (3), comprising a rotatably mounted shaft (4) into which a cavity (7) extends axially from an end face (6) having a shaft opening (5), and a first, rotationally fixed and electrically conductive sleeve (8) passes through the shaft opening (5) and extends axially into the cavity (7) of the shaft (4), wherein an electrically conductive retaining element (9) is rotationally fixed to or in a receptacle (50) of the rotatable shaft (4) in the cavity (7).wherein an electrically conductive centering means (10) extends coaxially into the sleeve (8) from the retaining element (9) in the axial direction or surrounds the sleeve (8) from the radial outside and an electrically conductive bearing (12) is arranged in the axial overlap area (11) of the retaining element (9) and the receptacle (50), so that an electrical contact is established between the sleeve (8) and the centering means (10) during operation of the shaft grounding (1).

Description

[0001] The present invention relates to a shaft grounding system for discharging an electrical charge and / or voltage from a shaft, in particular for a drive train of an electrically operated motor vehicle, comprising a rotatably mounted shaft into which a cavity extends axially from an end face having a shaft opening, and a first sleeve, which is non-rotatable relative to the shaft and electrically conductive, passes through the shaft opening and extends axially into the cavity of the shaft, wherein an electrically conductive holding element is non-rotatably connected to the rotatable shaft in the cavity or in a receptacle of the rotatable shaft. The invention further relates to an electrical machine and a kit of parts.

[0002] Electrical machines, especially electric traction machines, are electrically charged during operation by induced shaft voltages. In addition, circulating high-frequency currents can arise in high-power motors. Such electrical machines typically comprise a rotor and a rotor shaft, which are mounted in a housing via rolling bearings. Electrical discharges or circulating high-frequency currents can damage the rolling bearings. To prevent this, this electrical energy must be dissipated. For example, grounding brushes or radially acting sliding elements (carbon brushes) are known for grounding the rotor shaft. Axial-acting shaft grounding systems are also known.

[0003] The document DE 10 2020 119 719 A1, for example, discloses a discharge device for a motor for discharging an electrical charge and / or voltage from a rotor via a shaft to a housing, with a first contact module for electrical and mechanical connection to the shaft, with a second contact module for electrical and mechanical connection to the housing, wherein the first and the second contact module are rotatable relative to one another and are electrically connected to one another in an interior space sealed off from a housing space, wherein the interior space is filled with an electrically conductive liquid, wherein the first and the second contact module are electrically conductively connected to one another via the electrically conductive liquid.

[0004] In addition to mechanical wear caused by shaft rotation, another cause of wear in the bearings of an electric motor is electrical currents flowing from the rotor shaft to ground. Voltages of a certain magnitude can overcome the insulating properties of the bearing lubrication, generating sparks that can lead to pitting, ridged surfaces, fusion craters, and ultimately premature failure of the bearings and motor. Bearing voltage—the voltage between the two bearing shells—usually correlates with shaft voltage—the voltage between the shaft and ground.

[0005] Due to capacitive coupling between the stator winding and the rotor and the high-frequency control of the stator phases, a voltage potential builds up at the rotor bearings, which can damage the bearings through so-called discharge currents. Countermeasures include insulating the bearings (e.g., using ceramic balls) or grounding the shaft using a sliding ground contact (electrically parallel to the bearings).

[0006] DE 10 2021 213 384 A1 discloses an arrangement for grounding a shaft, in particular a rotor shaft of an electric machine, comprising an at least partially tubular grounding hub that is electrically conductively connected to an electrical ground, preferably a housing. The grounding hub is also electrically conductively connected to the shaft to be grounded via a sliding contact formed on a contact element. The contact element is guided in a holder that is attached to the end face of the grounding hub.

[0007] DE 10 2019 133 889 A1 discloses an electrical machine with a discharge device for discharging an electrical charge and / or voltage from the rotor via the shaft to the housing section, wherein the discharge device has a first contact device for electrical and mechanical connection to the shaft and a second contact device for electrical and mechanical connection to the housing section, wherein the first and second contact devices are rotatable relative to one another.

[0008] Furthermore, a device and a method for compensating a shaft voltage on a shaft are already known from DE 10 2017 109 049 A1.

[0009] A compensation circuit generates a compensation voltage, which is coupled directly or indirectly to the rotor shaft via a coupling element. The shaft voltage is detected directly or indirectly on the rotor shaft via a tapping element.

[0010] EP 1 455 434 A1 discloses an electric motor with a stator and a rotor rotatably mounted in or on the stator by means of a bearing arrangement. For electrical insulation, at least one sleeve and / or plastic layer is provided that electrically insulates the bearing arrangement from the stator or rotor and / or the rotor shaft from the rotor. This prevents capacitive displacement currents through the bearings, which primarily arise at high pulse or switching frequencies. These can lead to a reduction in the service life of the bearings.

[0011] DE 20 2017 107 755 U1 describes a device for reducing harmful bearing voltages in an electrical machine fed by an intermediate circuit voltage of an intermediate circuit, comprising a stator having windings and insulated from earth, a rotor and a motor shaft, wherein furthermore a rotor-side bearing and a stator-side bearing are each insulated from earth, and wherein the rotor and the stator are electrically connected to one another via a bypass capacitor with a predetermined capacitance.

[0012] DE 10 2017 122 466 A1 relates to a drive device comprising a rotatable rotary shaft, a rotor connected in a rotationally fixed manner to the rotary shaft, and at least one balancing disc. To enable the drive device to be manufactured without external alignment devices, it is proposed that the balancing disc be in direct contact with the rotary shaft and be connected in a rotationally fixed manner to it, with at least a partial region of the balancing disc and the rotor being located adjacent to one another in a fixing plane orthogonal to the rotary shaft.

[0013] In the field of electromobility, such electric motors are also often integrated into an axle drive train, which forms a structural unit consisting of the power electronics (inverter), electric motor, and transmission. This structural unit must be connected to the vehicle's ground for potential equalization. This is usually done via a conductor located between the body and the housing of the structural unit.

[0014] In such axle drive trains, a grounding element is usually located in the gear set of the transmission and / or directly on the rotor shaft of the electric motor, in order to be able to protect the bearings located there particularly well from harmful currents or discharges thanks to the structural proximity. These grounding elements are usually electrically connected to the housing of the axle drive train.

[0015] Generally, such grounding elements have the problem that dry-running grounding elements generate electrically conductive abrasion, which can lead to short circuits in the electrical machine. Wet-running grounding elements, on the other hand, often have the problem that they do not function efficiently at all operating points when immersed in oil.

[0016] The object of the invention is therefore to reduce or completely avoid the disadvantages known from the prior art and to provide a shaft grounding system that is simple in design and offers high operational reliability and durability. Furthermore, the object of the invention is to realize an improved electrical machine and a kit of parts for assembling a shaft grounding system.

[0017] This object is achieved by a shaft earthing system for discharging an electrical charge and / or voltage from a shaft, in particular for a drive train of an electrically operated motor vehicle, comprising a rotatably mounted shaft, into which a cavity extends axially from an end face having a shaft opening, and a first sleeve, which is non-rotatable relative to the shaft and electrically conductive, passes through the shaft opening and extends axially into the cavity of the shaft, wherein in the cavity an electrically conductive holding element is non-rotatably connected to or in a receptacle of the rotatable shaft, wherein an electrically conductive centering means extends coaxially from the holding element in the axial direction into the sleeve or surrounds the sleeve from the radial outside, and an electrically conductive bearing is arranged in the axial overlap region of the holding element and the receptacle,so that during operation of the shaft earthing an electrical contact is established between the sleeve and the centering device.

[0018] This has the advantage that the voltage (or voltage potential) across the bearing is reduced, so that the probability of spark discharges is reduced and the energy / power of the discharges that still occur is limited, with the result that bearing damage due to electrical discharges is reduced.

[0019] This provides a radially acting shaft grounding system that functions efficiently in dry and wet electrical machines and at all operating points. Existing installation space, for example, in an electrical machine or gear arrangement, can be utilized without increasing the axial or radial dimensions of the electrical machine. Furthermore, shaft grounding can also be easily integrated into existing applications at a later date. This prevents bearing damage on the rotatably mounted shaft and improves electromagnetic compatibility (EMC), reducing or preventing interference with other devices.

[0020] A further advantage of the shaft earthing according to the invention is that the shaft earthing can be constructed as an independent system and thus offered as a pre-assembled unit.

[0021] The bearing allows the first sleeve, designed, for example, as an oil lance, to be supported and guided within the shaft cavity, while simultaneously safely dissipating the currents. This allows the first sleeve to be supported within the shaft by the centering element and the retaining element.

[0022] The bearing can be designed as a plain bearing or a roller bearing. In the context of the invention, the bearing is preferably designed as a plain bearing.

[0023] The fact that the first electrically conductive sleeve is arranged in a rotationally fixed manner relative to the shaft means that the sleeve is fixedly positioned in the circumferential direction, while the shaft is rotatable relative to the rotationally fixed sleeve.

[0024] First, the individual elements of the claimed subject matter of the invention are explained in the order of their relevance or their mention in the set of claims, and particularly preferred embodiments of the subject matter of the invention are described below.

[0025] A rotor is the rotating part of an electrical machine. The rotor comprises, in particular, a rotor shaft. The rotor shaft can be partially or completely hollow, which results in weight savings and allows the supply of lubricant or coolant to the rotor body.

[0026] For the purposes of the invention, a rotor body is understood to mean the rotor without a rotor shaft.

[0027] A rotor lamination stack can, in particular, form a rotor body. A rotor lamination stack is understood to be a plurality of laminated individual laminations or rotor laminations, usually made of electrical steel, which are stacked and stacked together to form a so-called rotor lamination stack. The individual laminations can then be joined together in the lamination stack by gluing, welding, or screwing. A rotor lamination stack can, in particular, also have magnetic elements incorporated into the pockets of the rotor lamination stack or fixed circumferentially to the rotor lamination stack, as well as any axial cover parts for closing the pockets and the like.

[0028] The electric machine can be designed, in particular, as a rotary machine. The rotary machine can be configured, in particular, 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 stator extend in a radial direction. The air gap is the gap between the rotor and stator. In a radial flux machine, this is a circular-ring-shaped gap in cross-section with a radial width corresponding to the distance between the rotor body and the stator body.

[0029] The electric machine is intended in particular for use within a drive train of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and in particular greater than 100 km / h can be achieved. Particularly preferably, the electric motor has an output greater than 50 kW, preferably greater than 80 kW, and in particular greater than 150 kW. Furthermore, it is preferred that the electric machine provides rotational speeds greater than 8,000 rpm, particularly preferably greater than 12,000 rpm, and most preferably greater than 15,000 rpm.

[0030] For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PK), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOM), or tractors.

[0031] According to an advantageous embodiment of the invention, the first sleeve can have at least one passage opening on a circumferential surface through which a fluid can be guided from the sleeve into the cavity. The advantage of this embodiment is that the sleeve can thus provide cooling and / or lubrication of the shaft or components in the vicinity of the shaft. The first sleeve can therefore also be referred to as an oil lance.

[0032] Preferably, the holding element also has passage openings through which the fluid can flow, for example in the axial direction.

[0033] A further advantage of shaft grounding is that it can be used in wet electrical machines without the need for additional installation space.

[0034] The retaining element is preferably ring-shaped. The retaining element is preferably designed as a ring that is closed in the circumferential direction. The retaining element can be designed as a single piece or in multiple parts. The retaining element is preferably formed from a sheet metal.

[0035] According to a further preferred development of the invention, it can also be provided that the shaft, starting from the cavity, has at least one through-channel extending in the radial direction through the shaft, via which the fluid can be led out of the cavity, whereby a hydraulic connection for cooling the rotor and / or stator of an electrical machine can be provided.

[0036] Furthermore, according to a similarly advantageous embodiment of the invention, the retaining element can be fixed in the shaft cavity by means of a press fit. The advantageous effect of this embodiment is that the press fit ensures a firm and stable connection between the retaining element and the shaft. When using a press fit, it is generally not necessary to use additional fastening elements such as screws or bolts. This simplifies assembly and reduces the number of required components and assembly time.

[0037] According to an advantageous embodiment of the invention, the bearing can be designed as a plain bearing. The advantage of this design is that plain bearings offer a certain degree of protection against dirt and contaminants, since the lubricating layer of the plain bearing can form a barrier between the sliding surfaces and external influences such as dust, dirt, or moisture. Due to the low friction and effective damping of vibrations, plain bearings are often also particularly quiet and vibration-free. This is particularly advantageous in applications where smooth and quiet operation is required, e.g., in electric motors.

[0038] According to a further preferred development of the invention, it can also be provided that the holding element and the centering means are formed in one piece, in particular monolithically. The one-piece, preferably monolithic, design of the holding element and the centering means creates a strong and stable structure. There are therefore no connecting seams or weak connection points that could represent potential weak points. This ensures high strength and stability of the holding element and the centering means, even under load or vibration. The one-piece, monolithic design thus reduces the risk of component failure or loosening due to vibration, fatigue, or mechanical stress. The one-piece design also enables precise alignment of the holding element and the centering means.By manufacturing them as a single piece, the components can be precisely positioned and aligned. The one-piece design also simplifies the assembly of the retaining element and centering device, as they do not need to be mounted separately or connected to each other.

[0039] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the centering means is designed as a separate component that is accommodated in a receptacle of the holding element arranged coaxially to the sleeve. The advantageous effect of this embodiment is that the use of a separate centering means accommodated in a receptacle of the holding element enables a modular design of the shaft grounding. The centering means can be manufactured and replaced independently of the holding element, which offers flexibility with regard to design changes, repairs, or maintenance work. This also facilitates adaptation to different requirements or specific applications of the shaft grounding. The separate centering means is preferably designed as a cylindrical bolt.

[0040] It may also be advantageous to further develop the invention such that the receptacle is formed as an opening in the shaft that is aligned coaxially with the sleeve. Integrating the receptacle into the shaft saves installation space, and no additional components or fastening elements are required to attach or center the retaining element. This can be particularly advantageous when the available installation space is limited.

[0041] Furthermore, it is conceivable for the receptacle to be designed as a bearing pin extending axially from the shaft into the cavity. The bearing pin can preferably be formed monolithically with the shaft and coaxially with the sleeve.

[0042] Furthermore, according to a likewise advantageous embodiment of the invention, the bearing, designed as a plain bearing, can have a sliding ring that is connected in a rotationally fixed manner to the centering means and is guided in a cylindrical ring-like receptacle formed integrally with the holding element. The cylindrical ring-like receptacle formed integrally with the holding element particularly facilitates the assembly and disassembly of the bearing, since the sliding ring with the centering means can be easily inserted into the receptacle, which enables simple alignment. Furthermore, the cylindrical ring-like receptacle formed integrally with the holding element ensures robust guidance of the sliding ring and optimized structural stability of the holding element.

[0043] According to a further particularly preferred embodiment of the invention, it can be provided that the holding element has a C-shaped contour in cross-section, in which a radially outer leg extending in the axial direction rests against a jacket surface of the shaft receptacle and a radially inner leg extending in the axial direction forms the cylindrical ring-like receptacle, wherein at least one passage opening for a fluid is provided in the radial direction between the inner leg and the outer leg. The C-shaped contour of the holding element offers improved structural stability and ensures an even distribution of loads as well as increased rigidity of the bearing. The passage opening(s) between the inner leg and the outer leg also enable the flow of fluid (e.g. lubricant or coolant) in the bearing.This enables efficient fluid circulation and supply within the storage area.

[0044] Furthermore, the invention can also be further developed such that the sliding ring has a flange on its end facing the sleeve, which can provide an axial stop relative to the receptacle of the retaining element. The advantage of this design is that the flange of the sliding ring serves as an axial stop and can limit the axial displacement of the sliding ring within the bearing, which can ensure precise positioning of the sliding ring and prevent unwanted axial movements. The axial stop also ensures that the sliding ring is correctly positioned and fixed in the axial direction, which simplifies assembly processes. If necessary, the sliding ring can also be easily removed by pulling it out over the flange.Furthermore, the axial stop opposite the retaining element holder creates a narrow gap between the sliding ring and the holder, which reduces the penetration of foreign substances (e.g. dirt, dust) into the bearing, which can contribute to maintaining the lubricity and protecting the sliding surfaces.

[0045] In a likewise preferred embodiment of the invention, it can also be provided that a thrust ring is arranged on the centering means in a rotationally fixed manner, against the end face of which the flange of the sliding ring can run.

[0046] It may also be advantageous to further develop the invention in such a way that the centering means is mounted in the sleeve via a coupling ring, wherein the coupling ring has a C-shaped contour in cross section, in which a radially outer leg extending in the axial direction rests on the inner circumferential surface of the sleeve and a radially inner leg extending in the axial direction rests on the outer circumferential surface of the centering means.

[0047] The coupling ring ensures stable mounting of the centering device in the sleeve. The C-shaped leg of the coupling ring, which rests against the inner surface of the sleeve, provides good radial guidance. The coupling ring can also ensure even distribution of the loads occurring during shaft grounding operation between the sleeve and the centering device. The use of a coupling ring also enables simple assembly and disassembly, as the C-shaped contour of the coupling ring allows the centering device to be easily inserted and secured into the sleeve.

[0048] The object of the invention can further be achieved by an electric machine, in particular for a drive train of an electrically operated motor vehicle, comprising a stator and a rotor rotatable relative to the stator, wherein the rotor is coupled in a torque-transmitting manner to a shaft having a shaft earthing, wherein the shaft earthing is designed according to one of the claims.

[0049] Finally, the object of the invention can also be achieved by a kit of parts for producing a shaft earthing, in particular for a shaft earthing of an electrical machine, comprising • A shaft into which a cavity extends axially from a front side having a shaft opening into the shaft, • A first electrically conductive sleeve which can be inserted into the cavity, • an electrically conductive holding element that can be inserted into the cavity and coupled to the rotatable shaft, and from which an electrically conductive centering means extends coaxially into the sleeve in the axial direction or surrounds the sleeve from the outside radially and • an electrically conductive bearing which can be positioned in the axial overlap area of ​​the holding element and the receptacle so that an electrical contact is established between the receptacle and the holding element during shaft earthing operation.

[0050] This allows the components required for shaft grounding to be provided in a particularly convenient manner. The kit of parts can, for example, be a single packaging unit. Furthermore, it is possible to design the kit of parts as a collection of separate storage containers for storing the individual components or the respective component groups of the kit of parts.

[0051] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0052] It shows: Fig. 1 a shaft earthing in an axial section view, Fig. 2 a holding element in a perspective view, Fig. 3 a kit of parts for producing a shaft earthing in a schematic representation, Fig. 4 a motor vehicle with an electric drive train in a schematic representation.

[0053] The figure shows a shaft earthing 1 for discharging an electrical charge and / or voltage from a shaft 4, in particular for a drive train 2 of an electrically operated motor vehicle 3, as is also shown in the Fig. 4 is outlined.

[0054] The shaft earthing 1 comprises a rotatably mounted shaft 4, into which a cavity 7 extends axially from an end face 6 having a shaft opening 5, and a first sleeve 8, which is non-rotatable relative to the shaft 4 and electrically conductive, passes through the shaft opening 5 and extends axially into the cavity 7 of the shaft 4. The sleeve 8 is thus stationary while the shaft 4 rotates about the sleeve 8. Furthermore, an electrically conductive holding element 9 is non-rotatably connected to the rotatable shaft 4 in a receptacle 50 in the cavity 7.

[0055] An electrically conductive centering means 10 extends coaxially into the sleeve 8 in the axial direction from the holding element 9. Furthermore, an electrically conductive bearing 12 is arranged in the axial overlap region 11 of the holding element 9 and the receptacle 50, so that during operation of the shaft earthing device 1, an electrical contact is established between the sleeve 8 and the centering means 10.

[0056] The centering means 10 is designed in the form of a cylindrical bolt as a separate component.

[0057] The bearing 12, designed as a plain bearing, has a sliding ring 18 which is connected in a rotationally fixed manner to the centering means 10 and is guided in a cylindrical ring-like receptacle 60 formed integrally with the holding element 9. The holding element 9 has a C-shaped contour in cross-section, in which a radially outer leg 61 extending in the axial direction bears against a lateral surface 62 of the receptacle 50 of the shaft 4 and a radially inner leg 63 extending in the axial direction forms the cylindrical ring-like receptacle 60, wherein at least one passage opening 64 for a fluid is provided in the radial direction between the inner leg 63 and the outer leg 61.

[0058] The Fig. Figure 2 shows a detailed view of the retaining element 9. It can be seen that the radially outer leg 61 has tabs 78 that can act resiliently against the outer surface 62 in the radial direction. The receptacle 60, on the other hand, is cylindrically shaped. The passage openings 64 for the fluid (for example, a cooling or lubricating oil) are formed on the annular disc 79 extending in the radial direction.

[0059] The sliding ring 18 has a flange 65 on its end face facing the sleeve 8, which can provide an axial stop 66 relative to the receptacle 60 of the retaining element 9. A thrust ring 67 is arranged on the centering means 10 in a rotationally fixed manner, against whose end face 68 the flange 65 of the sliding ring 18 can abut. On the axially opposite side, the sliding ring 18 or the retaining element 9 is axially secured by the retaining ring 75.

[0060] The centering means 10 is mounted in the sleeve 8 via a coupling ring 69. The coupling ring 69 has a C-shaped cross-section, with a radially outer, axially extending leg 70 abutting the inner surface 71 of the sleeve 8, and a radially inner, axially extending leg 72 abutting the outer surface 73 of the centering means 10. The coupling ring 69 also has passage openings 74 for a fluid. The coupling ring 69 is secured axially to the centering means 10 by the retaining rings 76, 77.

[0061] It is clearly visible that this wave grounding 1, as shown in the Fig. 1, can be mounted and dismounted via the sleeve 8 designed as an oil lance.

[0062] Fig. Fig. 4 shows a drive train 2 of an electrically operated motor vehicle 3 with an electric machine 23, comprising a stator 24 and a rotor 22 rotatable relative to the stator 24, wherein the rotor 22 is coupled in a torque-transmitting manner to a shaft 4 having a shaft earthing 1, which consists of the Fig. 1-4 is known.

[0063] Finally, the Fig. 3 a kit of parts 30 for producing a shaft earthing 1, in particular for a shaft earthing 1 of an electrical machine 23, comprising • A shaft 4 into which a cavity 7 extends axially from a front side 6 having a shaft opening 5 into the shaft 4, • A first electrically conductive sleeve 8, which can be inserted into the cavity 7, • an electrically conductive holding element 9, which can be inserted into the cavity 7 and coupled to the rotatable shaft 4, and from which an electrically conductive centering means 10 extends coaxially into the sleeve 8 in the axial direction or surrounds the sleeve 8 from the outside radially and • an electrically conductive bearing 12, which can be positioned in the axial overlap area 11 of the holding element 9 and the receptacle 50, so that during operation of the shaft earthing 1 an electrical contact is established between the receptacle 50 and the holding element 9.

[0064] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols 1 shaft grounding 2 Drivetrain 3 Motor vehicle 4th wave 5 Shaft opening 6 Front side 7 Cavity 8 sleeve 9 Holding element 10 centering devices 11 Overlap area 12 Storage 18 sliding ring 22 Rotor 23 electric machine 24 Stator 30 kit of parts 50 recordings (of 4) 60 recordings (of 9) 61 outer thigh (of 9) 62 lateral surface 63 inner thigh (of 9) 64 passage opening 65 flange 66 stop 67 thrust ring 68 frontal area 69 Coupling ring 70 outer thigh (of 69) 71 inner surface (of 8) 72 inner thigh (of 69) 73 outer surface (of 8) 74 passage openings 75 retaining ring 76 Retaining ring 77 Retaining ring 78 tab 79 Ring disc

Claims

[1] Shaft earthing (1) for discharging an electrical charge and / or voltage from a shaft (4), in particular for a drive train (2) of an electrically operable motor vehicle (3), comprising a rotatably mounted shaft (4), into which a cavity (7) extends axially from an end face (6) having a shaft opening (5) into the shaft (4), and a first sleeve (8) which is non-rotatable relative to the shaft (4) and electrically conductive passes through the shaft opening (5) and extends axially into the cavity (7) of the shaft (4), characterized bythat in the cavity (7) an electrically conductive holding element (9) on or in a receptacle (50) of the rotatable shaft (4) is connected to the latter in a rotationally fixed manner, and an electrically conductive centering means (10) extends coaxially from the holding element (9) in the axial direction into the sleeve (8) or surrounds the sleeve (8) from the radial outside and an electrically conductive bearing (12) is arranged in the axial overlap region (11) of the holding element (9) and the receptacle (50), so that during operation of the shaft earthing (1) an electrical contact is established between the sleeve (8) and the centering means (10). [2] Shaft earthing (1) according to claim 1, characterized by that the centering means (10) is designed as a separate component. [3] Shaft earthing (1) according to claim 1 or 2, characterized by that the bearing (12) is designed as a plain bearing. [4] Shaft earthing (1) according to claim 3, characterized bythat the bearing (12) designed as a sliding bearing has a sliding ring (18) which is connected in a rotationally fixed manner to the centering means (10) and is guided in a cylindrical ring-like receptacle (60) formed integrally with the holding element (9). [5] Shaft earthing (1) according to claim 4, characterized by in that the holding element (9) has a C-shaped contour in cross-section, in which a radially outer leg (61) extending in the axial direction bears against a jacket surface (62) of the receptacle (50) of the shaft (4) and a radially inner leg (63) extending in the axial direction forms the cylindrical ring-like receptacle (60), wherein at least one passage opening (64) for a fluid is provided in the radial direction between the inner leg (63) and the outer leg (61). [6] Shaft earthing (1) according to claim 4 or 5, characterized bythat the sliding ring (18) has a flange (65) on its end face facing the sleeve (8), which can provide an axial stop (66) relative to the receptacle (60) of the holding element (9). [7] Shaft earthing (1) according to claim 6, characterized by that a thrust ring (67) is arranged on the centering means (10) in a rotationally fixed manner, against the end face (68) of which the flange (65) of the sliding ring (18) can run. [8] Shaft earthing (1) according to one of the preceding claims, characterized by in that the centering means (10) is mounted in the sleeve (8) via a coupling ring (69), the coupling ring (69) having a C-shaped contour in cross-section, in which a radially outer leg (70) extending in the axial direction bears against the inner circumferential surface (71) of the sleeve (8) and a radially inner leg (72) extending in the axial direction bears against the outer circumferential surface (73) of the centering means (10). [9] Electric machine (23), in particular for a drive train (2) of an electrically operable motor vehicle (3), comprising a stator (24) and a rotor (22) rotatable relative to the stator (24), wherein the rotor (22) is coupled to a shaft (4) having a shaft earthing (1) in a torque-transmitting manner, characterized by that the shaft earthing (1) is designed according to one of claims 1-8. [10] Kit-of-parts (30) for producing a shaft earthing (1) according to claim 1, in particular for a shaft earthing (1) of an electrical machine (23), comprising • a shaft (4) into which a cavity (7) extends axially from an end face (6) having a shaft opening (5) into the shaft (4), • a first electrically conductive sleeve (8) which can be inserted into the cavity (7), • an electrically conductive holding element (9) which can be inserted into the cavity (7) and coupled to the rotatable shaft (4), and from which an electrically conductive centering means (10) extends coaxially into the sleeve (8) in the axial direction or surrounds the sleeve (8) from the outside radially and • an electrically conductive bearing (12) which can be positioned in the axial overlap region (11) of the holding element (9) and the receptacle (50) so that an electrical contact is established between the receptacle (50) and the holding element (9) during operation of the shaft earthing (1).

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