WO2024213317A1 - Conducting device for establishing an electrical connection between two components which can be rotated relative to one another - Google Patents

Abstract

The invention relates to a conducting device (7) for establishing an electrical connection between two components which can be rotated relative to one another, in particular between a shaft (2) and a grounding hub (6) provided for grounding the shaft (2), the conducting device comprising a holder (14) which is provided for electrically conductive fastening to one component and which is equipped with a cavity (15). A contact element (16) is guided in the cavity (15) for axial movement relative to the holder (14) and is electrically connected to the holder (14). An end (20) of the contact element (16) is led out of a first axial side (17) of the holder, said end being provided for forming an electrically conductive sliding contact (12) of the contact element (16) with the other component. Furthermore, in the holder (14) at least one supply channel (23) is formed, each of which opens at the first axial side (17) of the holder (14) and is used for feeding lubricating and/or cooling medium to the sliding contact (12). In order to achieve a compact design of the conducting device (7), each of the at least one supply channel (23) runs, at least in parts, along the cavity (15) in spatial overlap with the cavity (15).

Description

Conductive device for establishing an electrically conductive connection between two components that can rotate relative to each other

The invention relates to a guide device for producing an electrically conductive connection between two components that can rotate relative to one another, in particular between a shaft and a grounding hub provided for the purpose of grounding the shaft, comprising a holder that is provided for an electrically conductive attachment to one component and is equipped with a recess, wherein a contact element is guided in the recess so as to be axially displaceable to the holder and is thereby electrically conductively connected to the holder, wherein the contact element is led out of a first axial side of the holder with an end face that is provided for forming an electrically conductive sliding contact of the contact element with the other component, and wherein at least one supply channel is designed in the holder, which opens out at the first axial side of the holder and serves to supply lubricant and/or coolant to the sliding contact. In addition, the invention relates to an arrangement for grounding a shaft, an electric axle drive unit and an electric machine.

In the field of motor vehicles, electrical machines are used to design the respective motor vehicle as a hybrid or electric vehicle. For example, electrical machines are sometimes also provided in motor vehicle transmissions in order to make the respective motor vehicle transmission suitable for use in a hybrid or electric vehicle. While other components of the respective transmission are encapsulated and shielded by the respective surrounding transmission housing, the shafts leading out of the transmission housing can cause electromagnetic interference, which can result in interference with other electronic components in the area of a motor vehicle. In addition, a potential difference can build up between the respective shaft and the transmission housing, which can lead to breakdowns in the bearings of the respective shaft and thus a reduction in the service life of these bearings. For this reason, the respective affected shaft should be earthed if possible. Even with electrical machines otherwise provided in a motor vehicle, such as For example, in the case of electric axle drive units, a respective shaft must be earthed to eliminate or reduce electromagnetic interference and to prevent the build-up of a potential difference. The respective earthing is usually carried out by an electrically conductive connection of the shaft to be earthed to a mass, which is usually a housing, whereby the electrically conductive connection is usually made as a sliding contact via a guide device. In addition, arrangements for earthing a shaft are also known in which lubricant and/or coolant are specifically fed into the area of the sliding contact in order to minimize wear in this area and to cool the sliding contact.

For example, WO 2022/135715 A1 discloses an arrangement for grounding a shaft, which can be a rotor shaft of an electric machine. In this arrangement, an electrically conductive connection is made between the shaft and a mass in the form of a housing to ground the shaft, this connection being made as a sliding contact via an intermediate guide device. The guide device comprises a holder which is attached in an electrically conductive manner on the ground side. In the holder, a contact element is guided axially displaceably in a recess and protrudes with an end face on an axial side of the holder in order to establish sliding contact with the shaft located here on the end face. In order to minimize thermal component loading, a liquid can also be guided into the area of the sliding contact, for which purpose the holder of the guide device is equipped with a supply channel in a variant of WO 2022/135715 A1, which runs at a distance from the recess in the holder.

Based on the prior art described above, it is now the object of the present invention to provide a guide device for producing an electrically conductive connection between two components that can rotate relative to one another, wherein this guide device should enable a reliable supply of a sliding contact with a lubricant and/or coolant and at the same time realize a compact design. This object is achieved on the basis of the preamble of claim 1 in conjunction with its characterizing features. The dependent claims that follow thereon each reflect advantageous developments of the invention. An arrangement provided for grounding a shaft, in which a guide device according to the invention is provided, is also the subject of claims 16 and 17. In addition, claim 18 relates to an electric axle drive unit and claim 19 to an electric machine.

According to the invention, a guide device which is designed to produce an electrically conductive connection between two components which can rotate relative to one another comprises a holder which is provided for an electrically conductive attachment to one component and is equipped with a recess. In the recess, a contact element is guided axially displaceably to the holder and is thereby electrically conductively connected to the holder, wherein the contact element is led out on a first axial side of the holder with an end face which is provided for forming an electrically conductive sliding contact of the contact element with the other component. In addition, at least one supply channel is designed in the holder, which opens out on the first axial side of the holder and serves to supply lubricant and/or coolant to the sliding contact.

The guide device according to the invention is therefore intended to produce an electrically conductive connection between two components that rotate relative to one another or can rotate relative to one another. One component is preferably a fixed grounding hub that is electrically connected to a shaft via the guide device in order to ground this shaft. In particular, the shaft to be grounded is a rotor shaft that is intended for a rotationally fixed connection to a rotor of an electrical machine.

For the purposes of the invention, an “electrically conductive” or “electrically conductive” connection is understood to mean a connection that enables a current to flow between the connected components. This respective connection can can be realized directly through a direct contact or indirectly via other intermediate components.

The guide device according to the invention has a holder which, when the guide device is installed, is designed to be attached in an electrically conductive manner to one of the components to be connected in an electrically conductive manner. A contact element is guided axially displaceably in the holder, with this guidance taking place in a recess in the holder. For this purpose, the recess in the holder defines in particular an inner contour which at least essentially corresponds to an outer contour of the displaceably guided contact element. In the sense of the invention, "axial" means a parallel alignment to an axis along which the contact element is displaceably guided in the holder.

The contact element is led out of a first axial side of the holder with a front side, so that the contact element protrudes with this front side relative to the first axial side of the holder. For this purpose, the contact element is preferably prestressed in the direction of the first axial side of the holder, wherein this prestress is carried out in particular via a spring element, which can be placed axially between the contact element and a section of the holder delimiting the recess. When the guide device is installed, an electrically conductive sliding contact with the other component is established on the front side of the contact element, wherein the contact element is also electrically conductively connected to the holder, whereby the electrically conductive connection between the two components is formed via the holder and the contact element together.

Furthermore, in the guide device in the holder, at least one supply channel is defined, via which lubricant and/or coolant can be guided to the first axial side of the holder, in that the at least one supply channel opens out on the first axial side of the holder, ie has an outlet opening on the first axial side of the holder. In this case, the at least one supply channel is provided for the lubricant supplied to the at least one supply channel Lubricant and/or coolant are then supplied to the sliding contact of the contact element with the other component. This is done to reduce wear on the components that are in sliding contact with one another and to reduce thermal stress on the components by cooling this area. Accordingly, the at least one supply channel opens out on the first axial side in such a way that the lubricant and/or coolant can reach the sliding contact between the contact element and the other component. The lubricant and/or coolant is preferably a liquid and in particular oil, such as a gear oil.

The invention now includes the technical teaching that the at least one supply channel runs at least in sections along the recess, spatially overlapping the recess. In other words, at least one respective partial section of the at least one supply channel is guided directly along the recess in such a way that the at least one supply channel and the recess spatially overlap and accordingly the at least one supply channel is open at least in the respective partial section to an inner region defined by the recess.

Such a design of a guide device has the advantage that the extension of the guide device according to the invention in the transverse direction to the axial guidance of the contact element can be reduced due to the at least partially spatially overlapping course of the at least one supply channel with the recess in this area, which makes it possible to have a compact design of the guide device overall. This also makes it possible to make components placed on the outside of the holder, such as a bearing to be provided here, smaller in size when the guide device according to the invention is installed.

Because the at least one supply channel spatially overlaps the recess at least in sections, the lubricant and/or coolant guided via the at least one supply channel also reaches the guide of the contact element in the holder. When designed as a lubricant, this the guide of the contact element in the holder is lubricated, which reduces friction in the guide and can therefore reduce a hysteresis effect if the contact element is pre-tensioned via a spring element. Due to the spatial overlap of the at least one supply channel with the recess, the at least one supply channel is also limited by the contact element guided in the recess, whereby the lubricant and/or coolant guided via the at least one supply channel flows along the contact element in this area. In this way, the supply of the front side of the contact element with the lubricant and/or coolant can be significantly improved in the case of spatial overlap in the area of the mouth of the supply channel on the first axial side.

For the purposes of the invention, the at least one supply channel running at least partially along the recess means that the at least one supply channel also runs parallel to the recess at least in the respective section and is accordingly also axially aligned here. In addition, the at least one supply channel overlaps with the recess in the area of running along it, which for the purposes of the invention means that in the respective section a respective line volume defined by the at least one supply channel is partially covered by an internal volume defined by the recess. The at least one supply channel is therefore open towards the recess in this respective section, whereby the lubricant and/or coolant guided via the at least one supply channel can be guided along the contact element running in the recess.

In contrast, the supply channel of the guide device in WO 2022/135715 A1 is designed at a distance from the recess in which the contact element is guided in an axially displaceable manner. As a result, the guide device of WO 2022/135715 A1 has a greater extension in the transverse direction to the guide.

Preferably, the guide device according to the invention is provided with several supply channels, which are arranged at least in sections along the recess spatially overlapping with the recess. In particular, the supply channels are designed in a uniform arrangement around the guide of the contact element in the holder.

According to one embodiment of the invention, the at least one supply channel runs completely along an axial extension of the recess in the holder, overlapping with the recess. In this way, a compact structure of the guide device can advantageously be achieved over the complete axial extension of the recess.

According to an alternative or additional embodiment of the invention to the aforementioned embodiment, the at least one supply channel is spatially connected to a second axial side, which is located on the holder facing away from the first axial side. The at least one supply channel can thus be fed with the lubricant and/or coolant from the second axial side of the holder, which enables good accessibility.

In a further development of the aforementioned design option, the recess is delimited towards the second axial side by a section, wherein at least one opening is formed in the section, which connects the at least one supply channel to the second axial side. This has the advantage that by designing a respective cross section of the at least one opening, a volume flow of lubricant and/or coolant supplied to the at least one supply channel can be adjusted. In this respect, the at least one opening can function as a throttle point. The connection is preferably made via the at least one opening in that the at least one opening, starting from the second axial side, opens into an inner region of the recess, which overlaps with the at least one supply channel over its axial extent. This means that the at least one supply channel can be fed from the inner region without any problem. Alternatively or additionally, several openings are preferably formed in the section delimiting the recess. In particular, the holder can have a housing part in which the recess is formed, with a disk being attached to the housing part in which the at least one opening is formed. In this case, the holder is designed in several parts, which can reduce the manufacturing and assembly costs of the guide device. Alternatively, the holder of the guide device can also be designed in one piece.

It is a further embodiment of the invention that the at least one supply channel is designed with a constant cross-section along its respective course. Alternatively, however, the at least one supply channel can also be designed to be variable in terms of cross-section along its respective course, with the at least one supply channel widening or narrowing in cross-section in particular along its respective course in a respective inlet area and/or in a respective outlet area. As a result, a throttling of a volume flow of lubricant and/or coolant guided via the at least one supply channel can be implemented directly by appropriate design of the at least one supply channel.

In a further development of the invention, the at least one supply channel has an oval cross-section at least in sections. This advantageously allows additional installation space to be saved in the transverse direction to the axial guide of the contact element in the holder. The at least one supply channel can also have another round cross-section, in particular a circular cross-section, or another cross-section.

According to one possible embodiment of the invention, the contact element has a rectangular cross-section, wherein the at least one supply channel runs in the area of one side of the rectangular cross-section of the contact element, spatially overlapping the recess. In a further development of this possible embodiment, a supply channel runs on each side of the rectangular cross-section, spatially overlapping the recess. This creates an advantageous arrangement of several supply channels, via which a suitable volume flow of lubricant and/or Coolant can be guided to the sliding contact. The arrangement of the supply channels on each side of the rectangular cross-section enables the supply channels to be evenly placed around the guide of the contact element in the holder.

However, the contact element can also have another angular cross-section, with the at least one supply channel running at each corner of the angular cross-section of the contact element, spatially overlapping the recess. This also makes it possible to arrange one or more supply channels in a suitable manner.

In a further development of the invention, the contact element consists of an electrically conductive material, in particular carbon, an electrically conductive plastic or felt, or an electrically conductive material combination. The contact element is particularly preferably made of carbon, which achieves high electrical conductivity. If necessary, another material, such as silver, can be applied to the front side in order to improve the electrically conductive sliding contact. However, a composite material made of several suitable materials can also be used as the material combination.

According to one embodiment of the invention, at least one orifice is introduced into the at least one supply channel along its respective course, in particular in a respective inlet area and/or in a respective outlet area. This also makes it possible to throttle the volume flow of lubricant and/or coolant guided via the at least one supply channel, and this can be done in a simple manner by introducing a corresponding orifice. This can be done as an alternative or in addition to a corresponding design of at least one opening in the holder.

Particularly preferably, in the region of the respective spatially overlapping course of the at least one supply channel with the recess on the holder, a bearing seat is designed which is designed to accommodate a bearing for the rotatable Storage of the components in relation to each other. This has the advantage that, due to the compact design of the holder in this area, the bearing to be placed here can also be designed to be compact.

The invention also relates to an arrangement for grounding a shaft. This arrangement comprises a grounding hub which is electrically connected to a ground, preferably a housing. The grounding hub is also electrically connected to the shaft to be grounded via a sliding contact which is formed on a guide device, the guide device being designed according to one or more of the preceding variants. Lubricant and/or coolant can be supplied to the sliding contact at least partially via the guide device.

The shaft to be grounded is preferably a rotor shaft that is intended for a rotationally fixed connection to a rotor of an electrical machine. The rotor and the rotor shaft can also be designed as one piece or as separate and rotationally fixed individual components. The electrical machine can be part of a motor vehicle transmission. The component to be grounded can in principle also be another shaft, such as a transmission shaft, or another, particularly rotating, component.

In the arrangement according to the invention, the grounding hub is provided for electrically connecting the shaft to be grounded to the ground, in that the grounding hub is electrically connected to the shaft to be grounded at a first axial end and is also electrically connected to the ground at a second axial end. At least in contact areas with the ground and the shaft to be grounded and in an intermediate area connecting these contact areas, the grounding hub consists of an electrically conductive material. Preferably, however, the grounding hub is made entirely of an electrically conductive material, which is in particular a metallic material such as steel or aluminum. The mass to which the electrically conductive connection of the shaft to be grounded is made via the intermediate grounding hub is, in the sense of the invention, an electrically conductive body to which the potential zero is assigned as a reference potential. This mass is preferably in the form of a housing, whereby the electrically conductive connection of the grounding hub can be made specifically to this housing, a housing part or a component that is permanently electrically connected to it.

On the other hand, the grounding hub also preferably serves within the arrangement to supply the lubricant and/or coolant to the guide device. To supply the lubricant and/or coolant, the grounding hub is designed at least in sections as a tube through which a supply line is defined that runs axially and thus in the longitudinal direction of the grounding hub. This supply line opens at one end of the grounding hub, to which the guide device is attached to the grounding hub. This allows the lubricant and/or coolant to reach the guide device along the supply line formed by the grounding hub, via which it is then fed to the sliding contact with the shaft. The grounding hub can have further openings, from which other areas can be supplied with lubricant and/or coolant.

In the sense of the invention, the grounding hub has a rod-like shape in particular, i.e. it is designed as an elongated component similar to a shaft in order to establish the electrically conductive connection between the shaft to be grounded and the mass, preferably axially, within the arrangement according to the invention. The grounding hub is also preferably designed to be rotationally symmetrical. As already described above, the grounding hub is preferably designed to be tubular over at least part of its axial extent in order to enable the supply of the lubricant and/or coolant to the guide device.

An arrangement according to the invention for grounding a shaft can be a component of an electric axle drive unit for a motor vehicle or an electric machine. Advantageous embodiments of the invention, which are explained below, are shown in the drawings. It shows:

Fig. 1 is a sectional view of an arrangement for grounding a shaft according to a preferred embodiment of the invention;

Fig. 2 is a schematic representation of a guide device of the arrangement from Fig. 1, according to a first embodiment of the invention;

Fig. 3 is a further illustration of the guide device from Fig. 2;

Fig. 4 to 6 show different views of a guide device according to a second embodiment of the invention;

Fig. 7 is a schematic representation of a drive train of a motor vehicle; and

Fig. 8 is a schematic view of an electrical machine.

Fig. 1 shows a sectional view of an arrangement 1 for grounding a shaft 2, this arrangement 1 being implemented in accordance with a preferred embodiment of the invention. The shaft 2 is a rotor shaft 3 of an electric machine (not shown in more detail), the rotor shaft 3 being connected in a rotationally fixed manner to a rotor of the electric machine. Within the arrangement 1, the rotor shaft 3 is electrically connected to a mass 4 in the form of a housing cover 5 in order to ground the rotor shaft 3 to the housing cover 5 and thus to a housing (not shown in more detail here).

The electrically conductive connection of the rotor shaft 3 with the housing cover 5 is made via a grounding hub 6 and a guide device 7, whereby the grounding hub 6 is coaxial with the rotor shaft 3 and is predominantly connected by a tubular body. The grounding hub 6 extends axially from the housing cover 5 through a further shaft 8 designed as a hollow shaft into the rotor shaft 3, which is designed as a hollow shaft in this area for this purpose. The shaft 8 is also arranged coaxially to the rotor shaft 3 and is also rotationally connected to the rotor shaft 3, whereby the shaft 8 can be a transmission shaft of a transmission via which the electric machine is or can be integrated.

The grounding hub 6 is made of an electrically conductive material, which is preferably metal. In the area of an axial end 9 of the grounding hub 6, the grounding hub 6 is mounted in a floating manner on the side of the housing cover 5, wherein at this end 9, in addition to establishing the electrically conductive connection of the grounding hub 6 to the housing cover 5, an axial preload of the grounding hub 6 in the direction of the rotor shaft 3 is also carried out.

At an end 10 opposite to the axial end 9, the guide device 7 is also attached to the grounding hub 6, the guide device 7 being pressed into the grounding hub 6 in particular. A bearing 11 is also arranged on the guide device 7, which is designed as a roller bearing and via which the permanently stationary grounding hub 6 and the permanently stationary guide device 7 are mounted in the rotor shaft 3 rotating relative to it. A sliding contact 12 is made to the rotor shaft 3 via the guide device 7 in order to electrically contact the guide device 7 with the rotor shaft 3 and to ground it to the housing cover 5 via the electrically conductive connection of the guide device 7 with the grounding hub 6 and further via the electrically conductive connection of the grounding hub 6 with the housing cover 5.

Apart from establishing the electrically conductive connection between the rotor shaft 3 to be grounded and the housing cover 5, the grounding hub 6 also serves to supply lubricant and/or coolant to an area of the sliding contact 12 in order to cool this area and also the rotor shaft 3 and in particular the rotor of the electric machine. The lubricant and/or coolant is preferably oil. The lubricant and/or coolant is introduced from the axial end 9 into an internal volume 13 of the grounding hub 6, wherein this introduction is preferably carried out in the region of the housing cover 5.

The lubricant and/or coolant introduced into the internal volume 13 then reaches the axial end 10 along the grounding hub 6, wherein at the end 10 of the grounding hub 6 a further supply to the sliding contact 12 is then carried out by supplying the lubricant and/or coolant via the guide device 7, which is designed for this purpose according to a first possible embodiment of the invention and is shown in more detail in Figs. 2 and 3.

As can be seen in particular in Fig. 2, the guide device 7 comprises a holder 14 which is fastened to the grounding hub 6 at the axial end 10 of the grounding hub 6. For this purpose, the holder 14, as can be seen in Fig. 3, is equipped with a cylindrical outer contour at least in the area where the holder 14 is fastened to the grounding hub 6. The electrically conductive connection of the holder 14 of the guide device 7 to the grounding hub 6 is established via the fastening, wherein the holder 14 consists of an electrically conductive material.

In addition, a recess 15 is formed in the holder 14, which is designed as a blind hole with a circular cross-section. In the recess 15, a contact element 16 is guided axially displaceably to the holder 14 and is preloaded in the direction of a first axial side 17 of the holder 14. This preload is preferably carried out via a spring element, which is arranged in particular between the contact element 16 and a section 18, by which the recess 15 is limited in the direction of a second axial side 19 of the holder 14. Due to the preload, the contact element 16 is guided out of the holder 14 with an end face 20, wherein the sliding contact 12 with the rotor shaft 3 is formed on the end face 20 of the contact element 16.

Due to the design of the recess 15 with a circular cross-section, the contact element 16 also has a circular cross-section. Furthermore, the contact element 16 consists of carbon, with additional another material, such as silver, can be applied. Due to the guidance of the contact element 16 in the holder 14 and due to the sliding contact 12 with the rotor shaft 3, the contact element 16 establishes the electrically conductive connection of the earthing hub 6 via the holder 14 to the rotor shaft 3 rotating relative thereto.

In order to supply the lubricant and/or coolant introduced into the inner volume 13 of the grounding hub 6 to the sliding contact 12, the holder 14 is provided with an opening 21 on its section 18, through which the lubricant and/or coolant can pass from the inner volume 13 into an inner region 22 defined by the recess 15, as indicated by the arrow in Fig. 2. From the inner region 22, the lubricant and/or coolant can then pass via a supply channel 23 to the axial side 17 of the holder 14 and there into the region of the sliding contact 12.

As a special feature, the supply channel 23, as can be seen in Fig. 2, runs along the recess 15, with this running along the supply channel 23 taking place over the complete axial extent of the recess 15. In addition, the supply channel 23 spatially overlaps with the recess 15, which can be seen in particular in Fig. 3, so that the supply channel 23 is open towards the recess 15. This has the consequence that the lubricant and/or coolant can easily pass from the inner region 22 into the supply channel 23, flows along between the holder 14 and the contact element 15 and exits the holder 14 on the axial side 17, with the lubricant and/or coolant being able to run further along the contact element 16 and finally reach the area of the sliding contact 12. By flushing around the contact element 16, better cooling can be brought about in the area of the contact element 16. In addition, due to the course of the supply channel 23 along the guide, the guide of the contact element 16 in the holder 14 is also lubricated, thus reducing the friction in this area.

Due to the arrangement of the supply channel 23 directly at the recess 15 and the spatial overlap with the recess 15, the Bracket 14 can be designed to be compact and thus the guide device 7 itself can also be designed to be compact. This then also means that the bearing 11 placed on a bearing seat on the outside of the bracket 14 can be designed with a smaller diameter, whereby less friction and therefore lower drag losses occur in the area of the bearing 11.

The supply channel 23 has an oval cross-section, whereby additional installation space can be saved in the transverse direction to the guide of the contact element 16 in the holder 14. The supply channel 23 is designed with a constant cross-section along its course, but alternatively the cross-section of the supply channel 23 can also be widened or narrowed in an inlet area 24 and/or in an outlet area 25 of the supply channel 23.

The opening 21 also has an oval cross-section, whereby the design of this cross-section adjusts a volume flow of lubricant and/or coolant guided into the inner area 22. Alternatively or in addition to this, a separate aperture could also be introduced into the opening 21 of the section 18 or into the supply channel 23.

4 to 6 show views of a guide device 26 according to a second possible embodiment of the invention. This guide device 26 essentially corresponds to the guide device 7 according to FIGS. 2 and 3 and can be used as an alternative to the guide device 7 in the arrangement 1 from FIG. 1. As a difference, on the one hand, several openings 27 are designed in a section 28, through which, as in the variant according to FIGS. 2 and 3, a recess of a holder 29 of the guide device 26 is delimited. The openings 27 are designed in a disk 30, which is part of the multi-part holder 29 and forms the section 28.

As can also be seen in Fig. 5 and also in Fig. 6, a contact element 31 of the guide device 26 has a rectangular cross-section, whereby the recess 32 which can be partially seen in Figs. 5 and 6 corresponds to this is also rectangular in shape. Furthermore, the guide device 26 is now provided with a plurality of supply channels 33, 34, 35 and 36, each of which runs along the recess 32 and spatially overlaps with the recess 32. The individual supply channel 33 or 34 or 35 or 36 is placed on a respective side 37 or 38 or 39 or 40 of the rectangular contact element 31. Otherwise, the embodiment according to Figs. 4 to 6 corresponds to the variant according to Figs. 2 and 3, so that reference is made to what has been described in this regard.

Fig. 7 shows a schematic view of a purely electric drive train of a motor vehicle, which has an electric axle drive unit 41. The electric axle drive unit 41 comprises an electric machine 42, the power of which is transmitted to drive wheels 45 and 46 of a motor vehicle via a reduction gear set 43 and a differential gear 44. For this purpose, the electric machine 42 is connected to the reduction gear set 43 on the output side on a rotor shaft 47. Output shafts 48 and 49 of the differential gear 44 are connected to the drive wheels 45 and 46. The electric machine 42, the reduction gear set 43 and the differential gear 44 are enclosed in a housing 50. A converter 51 is attached to the housing 50. The converter 51 is connected on the one hand to the electric machine 42 and on the other hand to a battery 52. The converter 51 is used to convert the direct current of the battery 52 into an alternating current suitable for operating the electric machine 42 and has several power semiconductors for this purpose. The conversion between direct current and alternating current takes place through a controlled pulse-like operation of the power semiconductors.

In the present case, the rotor shaft 47 is earthed as part of an arrangement which is implemented in an analogous manner to the variant according to Fig. 1. Here too, an earthing hub 53 is provided which is electrically connected to the rotor shaft 47 via an intermediate guide device (not shown here) by means of a sliding contact. The structure of this guide device corresponds to the guide device 7 according to Figs. 2 and 3 or the guide device 26 according to Figs. 4 to 6. The earthing hub 53 and the guide device are used to In addition, a supply of lubricant and/or coolant to the area of the sliding contact.

Finally, Fig. 8 shows a schematic view of an electrical machine 54. The electrical machine 54 has a housing 55 which accommodates a stator 56 and a rotor 57. The stator 56 is fixed in the housing 55 in a rotationally fixed manner. The rotor 57 is coupled to a rotor shaft 58, wherein the rotor shaft 58 is rotatably mounted via two roller bearings 59 and 60 supported on the housing 55. One end of the rotor shaft 58 protrudes from the housing 55.

The rotor shaft 58 is earthed in the present case as part of an arrangement according to the invention, which is implemented in principle in a manner analogous to the variant according to Fig. 1. Here, too, a grounding hub 61 is provided, which is in sliding contact with the rotor shaft 58 via an intermediate guide device in order to become the rotor shaft 58. The intermediate guide device can be designed either in accordance with the guide device 7 from Figs. 2 and 3 or in accordance with the guide device 26 according to Figs. 4 to 6. In addition, a supply of lubricant and/or coolant to the sliding contact is implemented via the grounding hub 61 and the intermediate guide device.

By means of the embodiments according to the invention, a compact construction of a guide device can be achieved while at the same time reliably supplying a sliding contact with lubricant and/or coolant.

reference sign

Arrangement Shaft Rotor shaft Mass Housing cover Earthing hub Guide device Shaft End End Bearing Sliding contact Internal volume Bracket Recess Contact element Axial side Section Axial side Front side Breakthrough Internal area

Supply channel Entrance area Exit area Guide device Breakthroughs Section Bracket Disc Contact element Recess Supply channel Supply channel Supply channel Supply channel Page Page Page Page

Axle drive unit electric machine reduction gear set differential gear drive wheel drive wheel rotor shaft output shaft output shaft housing inverter

Battery grounding hub electric machine housing

Stator Rotor Rotor shaft Rolling bearing Rolling bearing Grounding hub

Claims

patent claims 1. Conducting device (7; 26) for producing an electrically conductive connection between two components that can rotate relative to one another, in particular between a shaft (2) and a grounding hub (6) provided for the purpose of grounding the shaft (2), comprising a holder (14; 29) which is provided for an electrically conductive attachment to one component and is equipped with a recess (15; 32), wherein in the recess (15; 32) a contact element (16; 31) is guided axially displaceably to the holder (14; 29) and is thereby electrically conductively connected to the holder (14; 29), wherein the contact element (16; 31) is led out of a first axial side (17) of the holder with an end face (20) which is provided for forming an electrically conductive sliding contact (12) of the contact element (16; 31) with the other component, and wherein in the holder (14; 29) at least one supply channel (23; 33 to 36) is designed, which opens in each case at the first axial side (17) of the holder (14; 29) and serves to supply lubricant and/or coolant to the sliding contact (12), characterized in that the at least one supply channel (23; 33 to 36) runs in each case at least in sections along the recess (15; 32) spatially overlapping with the recess (15; 32). 2. Guide device (7; 26) according to claim 1, characterized in that the at least one supply channel (23; 33 to 36) runs completely along an axial extension of the recess (15; 32) in the holder (14; 29) overlapping with the recess (15; 32). 3. Guide device (7; 26) according to claim 1 or 2, characterized in that the at least one supply channel (23; 33 to 36) is spatially connected to a second axial side (19) which is located on the holder (14; 29) facing away from the first axial side (17). 4. Guide device (7; 26) according to claim 3, characterized in that the recess (15; 32) is limited to the second axial side (17) by a section (18; 28), wherein in the section (18; 28) at least one opening (21; 27) which connects the at least one supply channel (23; 33 to 36) with the second axial side (17). 5. Guide device (7; 26) according to claim 4, characterized in that the connection is established via the at least one opening (21; 27) in that the at least one opening (21; 27) opens out from the second axial side (19) into an inner region (22) of the recess (15; 32). 6. Guide device (26) according to claim 4 or 5, characterized in that the holder (29) has a housing part in which the recess (32) is formed, wherein a disk (30) is fastened to the housing part, in which the at least one opening (27) is formed. 7. Guide device (7; 26) according to one of the preceding claims, characterized in that the at least one supply channel (23; 33 to 36) is designed with a constant cross-section along its respective course. 8. Guide device according to one of claims 1 to 6, characterized in that the at least one supply channel widens or narrows in cross-section along its respective course in a respective input region and/or in a respective output region. 9. Guide device (7; 26) according to one of the preceding claims, characterized in that the at least one supply channel (23; 33 to 36) has an oval cross-section at least in sections. 10. Guide device (26) according to one of the preceding claims, characterized in that the contact element (31) has a rectangular cross-section, wherein the at least one supply channel (33 to 36) runs in the region of one side (37 to 40) of the rectangular cross-section of the contact element (31) spatially overlapping with the recess (32). 11. Guide device (26) according to claim 10, characterized in that on each side (37 to 40) of the rectangular cross-section a supply channel (33 to 36) runs spatially overlapping with the recess (32). 12. Guide device according to one of the preceding claims, characterized in that the contact element has a square cross-section, wherein the at least one supply channel runs at each corner of the square cross-section of the contact element, spatially overlapping with the recess. 13. Guide device (7; 26) according to one of the preceding claims, characterized in that the contact element (16; 31) consists of an electrically conductive material, in particular of carbon, of an electrically conductive plastic or felt, or of an electrically conductive material combination. 14. Guide device according to one of the preceding claims, characterized in that at least one aperture is introduced into the at least one supply channel along its respective course, in particular in a respective input area and/or in a respective output area. 15. Guide device (7; 26) according to one of the preceding claims, characterized in that in the region of the respective spatially overlapping course of the at least one supply channel (23; 33 to 36) with the recess (15; 32) on the holder (14; 29) a bearing seat is designed which is designed to receive a bearing (11) for the rotatable mounting of the components relative to one another. 16. Arrangement (1) for earthing a shaft (2), in particular a rotor shaft (3) of an electrical machine, comprising an earthing hub (6) which is electrically conductively connected to a ground (4), preferably a housing, wherein the earthing hub (6) is also electrically conductively connected to the shaft (2) to be earthed via a sliding contact (12) which is formed on a guide device (7; 26), wherein the guide device (7; 26) is designed according to one or more of claims 1 to 15, and wherein lubricant and/or coolant can be fed to the sliding contact (12) at least partially via the guide device (7; 26). 17. Arrangement (1) according to claim 16, characterized in that the holder (14; 29) of the guide device (7; 26) is fastened to the grounding hub (6) on the front side of the grounding hub (6), the grounding hub (6) being tubular at least in sections and an inner volume (13) of the grounding hub (6) formed thereby defining a supply line for supplying lubricant and/or coolant to the guide device (7; 26). 18. Electric axle drive unit (41) for a motor vehicle, characterized by a shaft which is earthed according to an arrangement according to claim 16 or 17. 19. Electrical machine (54) with a rotationally fixed stator (56) and a rotatable rotor (57), wherein the rotor (57) is coupled to a rotor shaft (58), characterized in that the rotor shaft (58) is grounded according to an arrangement according to claim 16 or 17.