grounding device

Abstract

The invention relates to a grounding device (1, 1a, 1b) for grounding a rotor shaft (2, 2a, 2b), the grounding device (1, 1a, 1b) comprising a grounded housing (3) and a rotatable rotor shaft (2, 2a, 2b) extending axially from the grounded housing (3), further comprising at least one bearing (7) which is mounted in the housing (3), wherein the bearing (7) comprises an inner ring (8) and an outer ring (9) and rolling elements (10) arranged between them, and wherein the inner ring (8) is non-rotatably connected to the rotor shaft (2, 2a, 2b) so that the rotor shaft (2, 2a, 2b) is supported against the housing (3) via the at least one bearing (7), and wherein the bearing (7) is arranged adjacent to a gearbox (14) and wherein a shaft seal (4) is provided which is located between the housing (3) and the rotor shaft. (2,2a,2b) is arranged sealingly on the rotor shaft (2,2a,2b), wherein the shaft seal (4) is axially mounted on the rotor shaft (2,2a, 2b) away from the gearbox (14).2b) is located adjacent to the storage facility (7), , characterized by the fact that an earthing element (12,12a,12b) with an earthing element circumference is provided, wherein the grounding element (12,12a,12b) is electrically conductive, and wherein the grounding element (12, 12a, 12b) is electrically connected to the outer ring (9) by means of a radial outer end (13) and to the rotor shaft (2,2a,2b) by means of a radial inner end radially opposite the outer end (13), wherein one of the connections is designed as a fixed connection and the other as a clamped connection, and wherein the grounding element (12,12a,12b) has equidistant openings (16) around the circumference of the grounding element for allowing a fluid flowing along the gearbox (14) through the bearing (7) to the shaft seal (4).

Description

[0001] The invention relates to a grounding device for grounding a rotor shaft, the grounding device comprising a grounded housing and a rotatable rotor shaft extending in an axial direction from the grounded housing, further comprising at least one bearing which is mounted in the housing, wherein the bearing comprises an inner ring and an outer ring and rolling elements arranged therebetween, and wherein the inner ring is connected to the rotor shaft in a rotationally fixed manner, so that the rotor shaft is supported relative to the housing via the at least one bearing.

[0002] In the case of shafts that are rotatably mounted in housings, it is often necessary to create an electrically conductive connection between the shaft and the housing via a separate device for earthing purposes, since the lubricants used in the shaft bearing cannot ensure a reliable electrically conductive connection between the shaft and the housing.

[0003] The lack of electrical discharge in electric motors or electric drives can significantly reduce the service life of bearings and gears due to unwanted spark discharges between rolling elements and bearing housings or between gears. Likewise, the media used for lubrication are exposed to electrical discharges and can be damaged or destroyed.

[0004] The grounding ring is designed as a pre-sealing element for a sealing ring and is made of an electrically conductive material that, during its intended use, is in close contact with the surface of the rotor shaft to be grounded. The housing is made of an electrically conductive material and is grounded to a defined ground potential, with the rotor shaft and the housing being electrically connected by the grounding ring.

[0005] Such grounding rings are known in the art as shaft grounding devices or grounding devices.

[0006] EP 3 982 520 A1 discloses an arrangement for sealing and grounding a rotor shaft protruding from a housing, wherein a radial shaft sealing ring with a sealing lip is provided for sealing a radial gap between the rotor shaft and the housing from the environment, wherein a shaft grounding device is provided for establishing an electrically conductive connection between the rotor shaft and the housing, wherein the shaft grounding device is arranged on the environment side next to the radial shaft sealing ring, wherein the shaft grounding device has at least one contact element which forms a sliding contact with a sleeve applied to the rotor shaft, wherein the sleeve is formed from a thin-walled sheet metal and has a radially outwardly directed section, and wherein an effective diameter of the sealing lip is smaller than a diameter of the sliding contact of the at least one contact element.

[0007] EP 3 086 448 B1 discloses a grounding device for an electrical machine having a rotating component and a stationary component, the grounding device comprising: a core; and a plurality of conductive fibers coupled to and extending from the core such that at least a portion of the plurality of conductive fibers contacts the rotating component, and such that at least a portion of the plurality of conductive fibers contacts the stationary component, wherein the plurality of conductive fibers are configured to electrically couple the rotating component to the stationary component such that an electrostatic charge on the rotating component is conducted through the plurality of conductive fibers to the stationary component, wherein the core includes a first end and a second end and is curved to form a loop or an arc.

[0008] From document US 2022 / 0 018 399 A1, a bearing is known that includes an integrated electrical shunt. The shunt contains electrically conductive fibers enclosed between two washers, at least one of which is electrically conductive. The fibers are attached to the electrically conductive disc using electrically conductive epoxy. An outer shield protects the fibers. The outer shield is held to the washers by a drawn cup. The washers, the drawn cup, and the outer shield all have oil drain holes to allow lubricant to flow to the rollers.

[0009] It is therefore an object to provide an improved earthing device.

[0010] The problem is solved by an earthing device with the features of claim 1

[0011] Advantageous embodiments emerge from the dependent patent claims, the description and the figures.

[0012] The object is achieved by a grounding device for grounding a rotor shaft, the grounding device comprising a grounded housing and a rotatable rotor shaft extending in an axial direction from the grounded housing, further comprising at least one bearing which is mounted in the housing, wherein the bearing comprises an inner ring and an outer ring and rolling elements arranged therebetween, and wherein the inner ring is connected to the rotor shaft in a rotationally fixed manner, so that the rotor shaft is supported relative to the housing via the at least one bearing, wherein a grounding element having a grounding element circumference is provided, wherein the grounding element is designed to be electrically conductive, and wherein the grounding element is electrically connected to the outer ring by means of a radial outer end and to the rotor shaft by means of a radial inner end radially opposite the outer end, wherein one of the connections is designed as a fixed connection and the other as a clamped connection, and wherein the grounding element has equidistant openings over the grounding element circumference for allowing a fluid flowing therealong to pass through.

[0013] The respective radial ends of the earthing element are referred to as the radial outer end and the radial inner end.

[0014] Such a grounding element eliminates the need for a grounding ring. The grounding element is particularly suitable in conjunction with a gearbox and a dry-running electric motor, where the gearbox's lubricating fluid is directed to the bearing during rotation to lubricate it and then to a shaft seal arranged axially downstream of the bearing to lubricate / oil it. Such a radial shaft seal, in particular with a sealing lip, is intended to seal a radial gap between the rotor shaft and the housing from the environment.

[0015] Through the equidistant openings around the circumference of the grounding element, an oil flow coming from the gearbox, for example, can now flow through the bearing and the openings and lubricate such a shaft seal.

[0016] The space between the bearing and the shaft seal can also be ventilated. Such a grounding element can create an electrically conductive connection between the rotor shaft and the housing, which can dissipate existing shaft currents / shaft voltages. This can prevent a significant reduction in the bearing's service life, which could occur, for example, as a result of the decomposition of components of the lubricating grease (e.g., oil), which would in turn negatively affect the rolling properties of the bearing.

[0017] The earthing element according to the invention makes it possible to dispense with a separate earthing ring, which may be difficult to arrange due to lack of space.

[0018] In a further development, the grounding element is clamped at the outer end between the outer ring and the housing. This allows for a simple, force-locking, and rotationally fixed fixation of the grounding element to the outer ring.

[0019] In a further embodiment, the radial inner end of the grounding element forms an end edge, wherein the end edge is resiliently clamped against the inner ring, allowing the grounding element to be rotated relative to the inner ring. This means that the grounding element exerts a spring force on the end edge, which acts from the end edge toward the inner ring. This force preferably acts axially, i.e., essentially parallel to an existing rotor axis. The spring force acting on the end edge can clamp the end edge.

[0020] In a further embodiment, the end edge is bent towards the inner ring and rubs against the inner ring. This creates a bulge in the middle section of the grounding element that projects axially from the center of the bearing. The end edge is thus clamped against the inner ring. Since the end edge can be rotated relative to the inner ring, when the inner ring rotates, the end edge wears into the inner ring over time due to material removal. This creates gaps along the end edge in the form of a labyrinth seal. The current / voltage is conducted via these narrow gaps from the rotor, i.e. the rotor shaft, via the inner ring and via the grounding element to the outer ring and via this to the housing. The current path therefore corresponds to the rotor shaft, inner ring, grounding element, outer ring and housing.

[0021] Lubrication, preferably oiling of the bearing as well as a downstream element, such as the shaft seal, is also possible. The oil can flow through the openings in the grounding element, which also serve to ventilate the elements behind the bearing.

[0022] In a further embodiment, the earthing element is clamped at the outer end between the outer ring and the housing, wherein the earthing element is formed axially spaced from the bearing center as well as from the inner ring, and wherein the earthing element ends at its inner end in a sliding manner on the rotor shaft.

[0023] This allows current to be conducted through the inner ring, or even reduced, by removing the inner ring. This provides better protection for the bearing against potential currents that may be conducted through the bearing despite the presence of a grounding element. The bearing, its lubricated rolling elements, and the oil cannot be damaged or destroyed by current, which would reduce the bearing's service life.

[0024] In a further embodiment, the rotor shaft has an electrically conductive bushing, wherein the inner end of the grounding element ends in a sliding manner on the bushing.

[0025] For example, the bushing can be made of a different material than the rotor shaft, which conducts voltage / current particularly well. This can also protect the rotor shaft itself.

[0026] In a further embodiment, the rotor shaft has at least two stepped sections, with a first section and an adjacent second section facing the bearing. The diameter of the first section is larger than the diameter of the second section, so that the rotor shaft forms a side wall between the first section and the second section, and the bushing is arranged, in particular clamped, between the side wall and the inner ring. The side wall is preferably made of the same sheet metal / material as the rotor shaft itself. This design enables simple attachment of such a bushing.

[0027] Alternatively, the outer end may be bent towards the outer ring, whereby the outer end forms an end edge, and wherein the end edge is clamped to the outer ring in a sliding manner and wherein the inner end is fixed to the inner ring in a rotationally fixed manner.

[0028] Here, too, the current can be diverted via the inner and outer rings. Due to the rotation, the end edge works its way into the outer ring. This creates gaps along the end edge in the form of a labyrinth seal. Currents are diverted through these narrow gaps from the rotor—i.e., the rotor shaft—via the inner ring, through the grounding element, to the outer ring, and from there to the housing. The current path thus corresponds to the rotor shaft, inner ring, grounding element, outer ring, and housing.

[0029] In a further embodiment, the rotor shaft can also have at least two stepped sections, with a first section and an adjacent second section pointing towards the bearing, wherein the diameter of the first section is greater than the diameter of the second section, so that the rotor shaft forms a side wall between the first section and the second section, and wherein the earthing element is clamped at its outer end to the outer ring and is axially spaced from the bearing center and from the inner ring, and wherein the earthing element forms an end edge at its inner end, which is resiliently clamped against the side wall, so that the earthing element is rotatable relative to the side wall.

[0030] The sidewall, for example, is made of the same sheet metal / material as the rotor shaft itself. In a further embodiment, the end edge is formed by a bend in the radial inner end toward the sidewall, which is arranged in a rubbing manner against the sidewall.

[0031] Because the end edge is rotatable relative to the side wall, the end edge gradually wears into the side wall as the rotor shaft rotates. This creates gaps along the end edge, resembling a labyrinth seal. Through these narrow gaps, the current / voltage from the rotor, i.e., the rotor shaft, is diverted directly via the grounding element to the outer ring, and then to the housing.

[0032] The current path therefore corresponds to the rotor shaft, earthing element, outer ring and housing.

[0033] This allows for better current dissipation via this gap while leaving the inner ring free.

[0034] This allows the bearing to be better protected from possible current discharges, which may be conducted via the bearing despite the earthing element.

[0035] The bearing, its lubricated rolling elements, and the oil cannot be damaged by current, which would reduce the bearing's service life. The small gaps, formed by a labyrinth seal between the stationary part (grounding element) and the rotating part (rotor shaft), completely divert the currents from the rotor to the housing.

[0036] Lubrication, preferably oiling the bearing and subsequent sealing, is also possible. The oil can flow through the openings in the grounding element, which also serve to ventilate the elements behind the bearing. The oil can then easily flow out through holes in the housing.

[0037] In particular, the grounding element is formed in one piece, wherein the grounding element consists of a conductive / conductive material, for example a metal such as stainless steel, etc. The grounding element can also consist of two interlocking components, which, however, both must be conductive and must have a permanent connection.

[0038] In a further embodiment, the grounding element can have a consistent wall thickness, which allows for particularly simple manufacturing. Alternatively, at least the radial inner end can have a thinner wall thickness to create low friction.

[0039] According to the invention, the grounding device comprises a grounded housing and a rotatable rotor shaft extending in an axial direction from the grounded housing, further comprising at least one bearing mounted in the housing, wherein the bearing comprises an inner ring and an outer ring and rolling elements arranged therebetween, and wherein the inner ring is connected in a rotationally fixed manner to the rotor shaft, so that the rotor shaft is supported relative to the housing via the at least one bearing, and wherein the bearing is arranged adjacent to a gear box, and wherein a shaft seal is provided, which is arranged sealingly on the rotor shaft between the housing and the rotor shaft, wherein the shaft seal is arranged axially on the rotor shaft away from the gear box, adjacent to the bearing, and wherein a grounding element with a grounding element circumference is provided, wherein the grounding element is designed to be electrically conductive,and wherein the earthing element is electrically connected to the outer ring by means of a radial outer end and to the rotor shaft by means of a radial inner end radially opposite the outer end, , wherein one of the connections is designed as a fixed connection and the other as a clamped connection, and wherein the grounding element has equidistant openings over the grounding element circumference for allowing a fluid flowing out of the transmission during operation to pass through the bearing to the shaft seal.

[0040] Such a grounding device is, for example, a drive device with an electric motor, an interior in which the rotor connected to the rotor shaft is rotatably mounted, and a gearbox. The rotor shaft of the electric drive device is rotatably mounted in the housing. The rotor is coupled to a rotor shaft. One end of the rotor shaft protrudes from the housing. The rotor shaft is rotatably mounted via the bearing supported on the housing. The rotor shaft has a shaft seal that seals the electric motor from the gearbox.

[0041] The shaft seal is designed in particular as a radial shaft seal or as a labyrinth seal.

[0042] The rotation directs oil from the gearbox to the bearing for bearing lubrication. The openings according to the invention allow the oil to be further directed to the shaft seal. Targeted lubrication and venting of the shaft seal is also possible. Furthermore, the resulting currents can be diverted without a separate grounding ring, resulting in a longer service life. The openings can be designed as bores or orifices.

[0043] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying figures, which schematically show: Fig. 1: a drive device with an earthing device according to the invention in a first embodiment during operation, Fig. 2: the earthing device according to the invention in the first embodiment, Fig. 3: a grounding device according to the invention in a second embodiment, Fig. 4: a grounding device according to the invention in a third embodiment.

[0044] Fig. 1 schematically shows a grounding device 1 in a first embodiment for grounding a rotor shaft 2 in a drive device 5 with an electric machine 6. However, such a rotor shaft 2 can also be arranged in other devices and is not limited to a drive device 5.

[0045] The rotor shaft 2 of the electric drive device 5 is rotatably mounted in a grounded housing 3 extending in an axial direction. One end of the rotor shaft 2 protrudes from the grounded housing 3.

[0046] The rotor shaft 2 carries a rotor (not shown). During operation, the rotor shaft 2 rotates around a rotor axis.

[0047] The rotor shaft 2 is rotatably mounted on a bearing 7 supported on the housing 3. The bearing 7 is supplied with oil during operation via a gear 14. The housing 3 has a lubricant supply, in this case oil, through which oil can be supplied to the bearing 7 via the gear 14. Due to the rotation, oil is thrown off the gear 14 and directed to the bearing 7, lubricating it.

[0048] A shaft seal 4 is arranged on the rotor shaft 2 downstream of the bearing 7 in the axial direction.

[0049] The shaft seal 4 is designed, in particular, as a radial shaft seal or a labyrinth seal. Together with the housing 3, the shaft seal 4 seals the interior of the electric motor 6 from the transmission 14.

[0050] The bearing 7 comprises an inner ring 8, which is arranged in a rotationally fixed manner with the rotor shaft 2, so that the rotor shaft 2 is supported relative to the housing 3 via at least one bearing 7. The outer ring 9 of the bearing 7 is arranged opposite the inner ring 8 in the housing 3. Rolling elements 10 are arranged between the inner ring 8 and the outer ring 9.

[0051] While other components of the respective transmission 14 are encapsulated and shielded by the surrounding housing 3, the rotor shaft 2 extending from the housing 3 can cause electromagnetic interference, which can result in malfunctions in electronic components in the vicinity of a motor vehicle. For this reason, rotor shafts 2 extending from a housing 3 should be grounded if possible. Even with electric motors otherwise provided in a motor vehicle, a respective shaft must be grounded to eliminate or reduce electromagnetic interference.

[0052] According to the invention, an earthing device 1 is provided for this purpose.

[0053] The earthing device 1 is in Fig. 2 described in more detail.

[0054] The grounding device 1 has an electrically conductive grounding element 12. This can be made of metal, for example, hardened steel.

[0055] The earthing element 12 has an outer end 13.

[0056] The outer end 13 is arranged adjacent to the outer ring 9 and clamped between the outer ring 9 and the housing 3. This creates a force-locking, rotationally fixed fixation of the outer end 13 and thus of the grounding element 12. Furthermore, an electrical connection is created between the outer ring 9 and the housing 3.

[0057] A radial inner end of the grounding element 12 opposite the outer end 14 forms an end edge 11, wherein the end edge 11 is resiliently clamped against the inner ring 8, so that the grounding element 12 is rotatable relative to the inner ring 8.

[0058] The end edge 11 is formed by a bend towards the inner ring 8 and rests against the inner ring 8 in a sliding manner. This creates a bulge 15 in the central part, which protrudes axially from the center of the bearing 7.

[0059] The end edge 11 is clamped against the inner ring 8. Since the end edge 11 is rotatable relative to the inner ring 8, the end edge 11 gradually wears into the inner ring 8 as the inner ring 8 rotates due to material removal. This creates gaps along the end edge 11 in the form of a labyrinth seal. The current / voltage is conducted through these narrow gaps from the rotor, i.e., the rotor shaft 2, via the inner ring 8, via the grounding element 12 to the outer ring 9, and via the outer ring 9 to the housing 3. The current path thus corresponds to the rotor shaft 2, inner ring 8, grounding element 12, outer ring 9, and housing 3.

[0060] The grounding element 12 also has openings 16 distributed over its grounding element circumference, for example in the form of apertures, bores, etc. These are distributed equidistantly over the grounding element circumference of the grounding element 12.

[0061] Through the openings 16, the oil can be directed to the shaft seal 4 for targeted lubrication. It is also possible to vent the shaft seal 4 or the space between bearing 7 and the shaft seal 4.

[0062] This allows targeted discharge of the resulting currents without a separate earthing ring, resulting in a longer service life.

[0063] The oil can flow through the openings 16 in the grounding element 12, wherein the openings 16 serve to ventilate all elements located behind the bearing 7.

[0064] Likewise, bores can be provided in the housing 3, which are arranged between the shaft seal 4 and the bearing 7 in the housing 3, for easy drainage of the oil flowing through the bearing 7.

[0065] Fig. 3 shows a further embodiment of an earthing device 1a according to the invention with an earthing element 12a.

[0066] The bearing 7 with the inner ring 8 and the outer ring 9 is also present, which is arranged on a rotor shaft 2a.

[0067] The rotor shaft 2a has at least a first section 17 and an adjacent second section 18 facing the bearing 7, wherein the diameter of the first section 17 is larger than the diameter of the second section 18. As a result, the rotor shaft 2a forms a side wall 19 between the first section 17 and the second section 18.

[0068] The side wall 19 is electrically conductive and preferably made of the same sheet metal / material as the rotor shaft 2a itself. Furthermore, the rotor shaft 2a has an electrically conductive bushing 20. The bushing is arranged, in particular clamped, between the side wall 19 and the inner ring 8. Such a design enables simple attachment of a bushing 20, which is electrically connected to the rotor shaft 2a.

[0069] Furthermore, the earthing element 12a is clamped at the outer end 13 between the outer ring 9 and the housing 3.

[0070] The earthing element 12a is designed to be axially spaced from the bearing center as well as from the inner ring 8 (bulge).

[0071] Furthermore, the inner end ends as a straight end edge 11a of the grounding element 12a, sliding on the bushing 20 for the direct discharge of the current / voltage from the rotor shaft 2a to the housing 3.

[0072] This allows for or reduces current dissipation through the recess of the inner ring 8. This allows for better protection of the bearing 7 from potential current dissipation, which may be conducted via the bearing 7 despite the presence of a grounding element. The bearing 7, or the lubricated rolling elements 10, and also the oil, cannot be decomposed or damaged by current, which would reduce the service life of the bearing 7.

[0073] This also allows the rotor shaft 2a itself to be protected by the bushing 20. Openings 16 are also provided through which the oil is directed to the shaft seal 4 for targeted lubrication. Ventilation can also be performed through the openings 16. Likewise, light lubrication of the bearing 7 with oil can be achieved.

[0074] Alternatively, the earthing element 12a can end at its inner end in a sliding manner on the rotor shaft 2a.

[0075] Fig. 4 shows an earthing device 1b according to the invention with an earthing element 12b in a third embodiment.

[0076] The bearing 7 with the inner ring 8 and the outer ring 9 is also present, which is arranged on a rotor shaft 2b.

[0077] The rotor shaft 2b has at least a first section 17 and an adjacent second section 18 facing the bearing 7, wherein the diameter of the first section 17 is larger than the diameter of the second section 18. As a result, the rotor shaft 2b forms a side wall 19 between the first section 17 and the second section 18. The side wall 19 is electrically conductive and preferably made of the same sheet metal / material as the rotor shaft 2b itself.

[0078] Furthermore, the earthing element 12b is clamped at the outer end 13 between the outer ring 9 and the housing 3 and is axially spaced from the bearing center as well as from the inner ring 8.

[0079] Furthermore, the grounding element 12b forms an end edge 11b at its inner end by bending the inner end, with the bend pointing away from the inner ring 8. The end edge 11b is resiliently braced against the side wall 19, so that the grounding element 12b is rotatable relative to the side wall 19. The grounding element 12b is thus arranged in a sliding manner against the side wall 19.

[0080] Since the end edge 11b is rotatable relative to the side wall 19, the end edge 11b gradually wears into the side wall 19 as the rotor shaft 2b rotates. This creates gaps along the end edge 11b in the form of a labyrinth seal. Through these narrow gaps, the current / voltage from the rotor, i.e., the rotor shaft 2b, is diverted directly via the grounding element 12b to the outer ring 9, and via the outer ring to the housing 3.

[0081] The current path thus corresponds to rotor shaft 2b, earthing element 12b, outer ring 9 and housing 3.

[0082] This allows for better current dissipation via this gap while completely removing the inner ring 8. This allows for better protection of the bearing 7 against potential current dissipation, which may be conducted via the bearing 7 despite the grounding element 12b. The bearing 7 or the lubricated rolling elements 10, as well as the oil, cannot be damaged by current, which would reduce the service life of the bearing 7. Due to the small gaps in the form of the labyrinth seal, which are created between the stationary part (grounding element 12b) and the rotating part (rotor shaft 2b), the currents from the rotor or the rotor shaft 2b are completely diverted to the housing 3.

[0083] Lubrication, preferably oiling, of the bearing 7 and the shaft seal 4 is also possible. The oil can flow through the openings 16 in the grounding element 12b, whereby the openings 16 also serve to ventilate the shaft seal 4 arranged behind the bearing 7. List of reference symbols 1,1a,1b Earthing device 2,2a,2b rotor shaft 3 housings 4 Shaft seal 5 Drive device 6 electric motor 7 camps 8 inner ring 9 Outer ring 10 rolling elements 11,11a,11b End edge 12,12a,12b Earthing element 13 Outer end 14 gearboxes 15 Bulge 16 openings 17 first section 18 second section 19 Side wall 20 socket

Claims

[1] Grounding device (1, 1a, 1b) for grounding a rotor shaft (2, 2a, 2b), the grounding device (1, 1a, 1b) comprising a grounded housing (3) and a rotatable rotor shaft (2, 2a, 2b) projecting from the grounded housing (3) and extending in an axial direction, further comprising at least one bearing (7) which is mounted in the housing (3), wherein the bearing (7) comprises an inner ring (8) and an outer ring (9) and rolling elements (10) arranged therebetween, and wherein the inner ring (8) is connected in a rotationally fixed manner to the rotor shaft (2, 2a, 2b) so that the rotor shaft (2, 2a, 2b) is supported relative to the housing (3) via the at least one bearing (7), and wherein the bearing (7) is arranged adjacent to a gear (14) and wherein a shaft seal (4) is provided which is arranged between the housing (3) and the rotor shaft (2,2a,2b) is arranged sealingly on the rotor shaft (2,2a,2b), wherein the shaft seal (4) is arranged axially on the rotor shaft (2,2a,2b) is arranged adjacent to the bearing (7), characterized by that a grounding element (12, 12a, 12b) with a grounding element circumference is provided, wherein the grounding element (12, 12a, 12b) is designed to be electrically conductive, and wherein the grounding element (12, 12a, 12b) is electrically connected to the outer ring (9) by means of a radial outer end (13) and to the rotor shaft (2, 2a, 2b) by means of a radial inner end radially opposite the outer end (13), wherein one of the connections is designed as a fixed connection and the other as a clamped connection, and wherein the grounding element (12, 12a, 12b) has equidistant openings (16) over the grounding element circumference for allowing a fluid flowing along the gear (14) through the bearing (7) to the shaft seal (4). [2] Earthing device (1,1a,1b) according to claim 1, characterized by that the earthing element (12, 12a, 12b) is clamped at the outer end (13) between the outer ring (9) and the housing (3). [3] Earthing device (1,1a,1b) according to claim 2, characterized by that the radial inner end of the earthing element (12, 12a, 12b) forms an end edge (11, 11a, 11b), wherein the end edge (11, 11a, 11b) is resiliently braced against the inner ring (8), so that the earthing element (12, 12a, 12b) is rotatable relative to the inner ring (8). [4] Earthing device (1,1a,1b) according to claim 3, characterized by that the end edge (11,11a,11b) is formed by a bend towards the inner ring (8) and rests against the inner ring (8) in a sliding manner. [5] Earthing device (1,1a,1b) according to claim 1 or 2, characterized by that the earthing element (12, 12a, 12b) is clamped at the outer end (13) between the outer ring (9) and the housing (3), wherein the earthing element (12, 12a, 12b) is designed to be axially spaced from the bearing center as well as from the inner ring (8), and wherein the earthing element (12, 12a, 12b) ends at its inner end in a sliding manner on the rotor shaft (2, 2a, 2b). [6] Earthing device (1,1a,1b) according to claim 5, characterized by that the rotor shaft (2,2a,2b) has an electrically conductive bushing (20) and the inner end of the earthing element (12,12a,12b) ends in a sliding manner on the bushing (20). [7] Earthing device (1,1a,1b) according to claim 6, characterized by in that the rotor shaft (2, 2a, 2b) has at least two stepped sections, with a first section (17) and an adjacent second section (18) pointing towards the bearing (7), wherein the diameter of the first section (17) is greater than the diameter of the second section (18), so that the rotor shaft (2, 2a, 2b) forms a side wall (19) between the first section (17) and the second section (18), and wherein the bushing (20) is arranged between the side wall (19) and the inner ring (8). [8] Earthing device (1,1a,1b) according to claim 1, characterized bythat the outer end (13) is bent towards the outer ring (9), whereby the outer end (13) forms an end edge (11,11a,11b), and wherein the end edge (11,11a,11b) is clamped to the outer ring (9) in a sliding manner and wherein the inner end is fixed to the inner ring (8) in a rotationally fixed manner. [9] Earthing device (1,1a,1b) according to claim 1, characterized bythat the rotor shaft (2, 2a, 2b) has at least two stepped sections, with a first section (17) and an adjacent second section (18) pointing towards the bearing (7), wherein the diameter of the first section (17) is greater than the diameter of the second section (18), so that the rotor shaft (2, 2a, 2b) forms a side wall (19) between the first section (17) and the second section (18), and wherein the earthing element (12, 12a, 12b) is clamped at its outer end (13) to the outer ring (9) and is axially spaced from the bearing center as well as from the inner ring (8), and wherein the earthing element (12, 12a, 12b) forms at its inner end an end edge (11, 11a, 11b) which is resiliently braced against the side wall (19), so that the earthing element (12, 12a, 12b) is rotatable relative to the side wall (19). [10] Earthing device (1,1a,1b) according to claim 9, characterized bythat the end edge (11,11a,11b) is formed by a bending of the radial inner end towards the side wall (19), which is arranged in a sliding manner on the side wall (19). [11] Earthing device (1,1a,1b) according to one of the preceding claims, characterized by that the earthing element (12,12a,12b) is formed in one piece. [12] Earthing device (1,1a,1b) according to one of the preceding claims, characterized by that the earthing element (12,12a,12b) has a constant wall thickness.

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