Discharge device for an electric machine and electric machine with the discharge device

Abstract

Discharge device (15) for an electric machine (1) for discharging an electric charge and / or voltage from a rotor (2) via a shaft (4) to a housing section (7), wherein the housing section (7) defines a housing space (6), with a first contact device (16) for electrical and mechanical connection to the shaft (4), with a second contact device (17) for electrical and mechanical connection with the housing section (7), wherein the first and the second contact device (16, 17) are rotatable relative to each other about a main axis (H) and are electrically connected to each other in a contact chamber (18) sealed against the housing space (6), characterized by the fact that the contact space (18) is filled with an electrically conductive liquid (19), wherein the first and the second contact device (16, 17) are electrically connected to each other via the electrically conductive liquid (19).

Description

[0001] The invention relates to a discharge device having the features of the preamble of claim 1. Furthermore, the invention relates to an electrical machine having the discharge device.

[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 JP 2013174326 A discloses an electronic corrosion protection device comprising a rotary shaft driven by an electric motor; bearings that rotatably support the rotary shaft; a discharge element that is electrically connected to the rotary shaft; and a ground wire that grounds the discharge element, in which the discharge element is electrically connected to the rotary shaft via a conductor body that is connected to the end face of the rotary shaft.

[0004] JP 2001 - 193 412 A shows a diverting device that can be used in various units. The diverting device engages a rotor shaft 1 with impellers 2 in a turbine, pump, or similar device. The pump shaft is supported by three bearings. According to one example, a diverting device is disclosed at one end of the rotor shaft, which is essentially formed by a grounding rod that engages the rotor shaft from a radial direction on one side. The grounding rod is preloaded radially against the rotor shaft by means of a compression spring. The grounding rod and the compression spring are supported or guided radially in a housing. The susceptibility of the diverting device to corrosion and the resulting failures and vibrations on the rotor shaft are considered disadvantageous. Therefore, the same document proposes an arrangement in which a grounding rod with a conductive disk is attached to the end face of the rotor shaft.A sleeve is fixed to an opposite housing, and the contact space of the sleeve is filled with a conductive fluid. The grounding rod engages axially in the contact space, and the disc attached to the end face of the grounding rod is immersed radially in the conductive fluid.

[0005] JP H04 -256 542 A shows a discharge device with which explosions of oil mist from low-viscosity lubricant due to potential discharges on devices such as spindle bearings of machine tools are to be avoided - this is particularly the case on spindles which are mounted with ceramic ball bearings but also with steel ball bearings for applications with high speeds. The electrical charges are created by friction. In the case described, the discharge device acts in a hydraulically-mechanically operated tool holder of the spindle. The spindle is rotatably mounted in a spindle head by means of rolling bearings and carries a clamping head which can be clamped with a spring-loaded rod. The rod is actuated by a hydraulic piston which is arranged so as to be axially displaceable in a housing separate from the spindle head. This piston is directed towards the end of the rod and can move it to the left via its piston rod.In the arrangement described in JP H04 - 256 542 A, potential differences between the spindle and the hydraulic actuator or its housing, which develop due to friction, are generated by a dissipation device consisting of a conductive shaft and a mercury-filled housing. The shaft is attached to the rod and projects axially into an opening in the piston, in which the housing, designed as a second contact device and filled with mercury as a conductive fluid, is accommodated.

[0006] The invention is based on the object of creating a discharge device which is characterized by improved discharge capacity and freedom from wear.

[0007] This object is achieved by a discharge device according to the subject matter of claim 1 and by an electrical machine with such a discharge device. Preferred or advantageous embodiments of the invention emerge from the subclaims, the following description and the attached figures.

[0008] According to the invention, the second housing section is mounted to the first housing part in a form-fitting and / or force-fitting manner. The first housing part is designed as a housing cover and has a housing opening through which the housing space is accessible from the outside. The housing cover closes the second housing part. The first and second contact devices are electrically connected to one another in the contact space, which is sealed from the housing space. The sleeve is held in a shaft bore of the shaft that runs coaxially to the main axis. The grounding rod is held in a housing bore of the second housing part.

[0009] The invention relates to a discharge device designed and / or suitable for an electrical machine. The electrical machine has a housing section, wherein the housing section defines and / or delimits a housing space. In particular, the housing section is a component of a housing and / or forms the latter. The housing is constructed in several parts, wherein the housing section forms part of the housing, for example, a bearing plate. In particular, the housing section is connected to ground and / or earthed.

[0010] The electric machine has a shaft, which defines a main axis with its rotational axis. Furthermore, the electric machine has a stator and a rotor, which are arranged concentrically and / or coaxially to one another. The shaft is connected to the rotor electrically and via a gear mechanism. In particular, the shaft is driven via and / or by the rotor. Particularly preferably, the shaft is designed as a rotor shaft, which is preferably connected to the rotor in a rotationally fixed, rigid, and / or integral manner. The housing section is preferably electrically and mechanically connected to the stator.

[0011] The shaft and the rotor are rotatably mounted in the housing space. In particular, the electric machine has at least two bearing devices that form or co-form the rotor bearing. The rotor is preferably arranged between the two bearing devices in the housing space, with the shaft being rotatably mounted via the bearing devices in the housing space and / or on the housing section.

[0012] The discharge device is designed and / or suitable for discharging an electrical charge and / or voltage from the rotor via the shaft to the housing section. In particular, the discharge device forms an electrical connection between the shaft and the housing section. In particular, this is a permanent electrical connection between the shaft and the housing section, which exists both stationary and dynamically, i.e., during operation of the electric machine.

[0013] The diverter device has a first contact device and a second contact device. The first contact device serves for the electrical connection to the shaft. Furthermore, the first contact device serves for the mechanical connection to the shaft, in particular such that the first contact device is fixed to the shaft. The second contact device serves for the electrical connection to the housing section. Furthermore, the second contact device serves for the mechanical connection to the housing section, in particular such that the second contact device is fixed to the housing section. The two contact devices are rotatable relative to one another, in particular during operation of the electrical machine. During operation of the electrical machine, the shaft rotates about the main axis, wherein the first contact device is driven by the rotating shaft and the second contact device remains stationary on the housing section.

[0014] The first and second contact devices are electrically connected to one another in a contact space sealed from the housing space. Preferably, the contact space and the housing space are sealed from one another and / or sealed from one another. The contact space is delimited, in particular, in the axial and / or radial direction by the first and / or second contact devices. The contact space is preferably defined as an annular space surrounding the main axis, which is formed between the first and second contact devices. The two contact devices are arranged coaxially with one another with respect to the main axis, with the first contact device being arranged on an axial end face of the shaft, and the second contact device being arranged opposite thereto on the housing section. The discharge device is thus implemented as a so-called "end face shaft earthing device."

[0015] Within the scope of the invention, it is proposed that the contact space be filled with an electrically conductive liquid. For example, the electrically conductive liquid can be in the form of an oil, grease, liquid metal, ionic liquid or the like, which are themselves electrically conductive and / or mixed with electrically conductive additives. Preferably, the contact space is completely filled with the electrically conductive liquid. Alternatively, however, the contact space can also be partially and / or largely filled with the electrically conductive liquid. The first and second contact devices are electrically conductively connected to one another via the electrically conductive liquid. In particular, the two contact devices are spaced apart from one another in the contact space, with electrical contact being made exclusively via the electrically conductive liquid.In particular, a current path thus runs from the rotor via the shaft and the first contact device via the electrically conductive fluid to the second contact device and the housing section. The current path formed by the discharge device has a lower resistance than the bearing devices, so that the discharge currents and / or voltages are discharged via the discharge device.

[0016] The advantage of the invention is in particular that the electrically conductive liquid creates a wear-free contact between the two discharge devices, so that the discharge device can be operated with very low friction and without wear. In contrast to friction contacts, as is known from the prior art, the proposed discharge device does not create any conductive abrasion, thereby eliminating the risk of short circuits caused by abrasion in the electrical machine. A further advantage of the invention is that the contact via the electrically conductive liquid enables position-independent operation of the discharge device, since the electrically conductive liquid creates permanent contact between the two contact devices.

[0017] The invention provides that one of the contact devices is designed as a sleeve and the other contact device as an earthing rod. The sleeve is assigned to the shaft and the earthing rod is assigned to the housing section. In particular, the sleeve is designed in a rough form as a cylindrical sleeve closed on one side. In particular, the earthing rod is designed in a rough form as a cylindrical rod. Preferably, the sleeve and the earthing rod are made of an electrically conductive material, such as steel, iron, copper or the like. The sleeve has the contact space with the electrically conductive liquid, wherein the earthing rod is arranged in sections in the sleeve such that the earthing rod is immersed in the electrically conductive liquid in the contact space.In particular, the earthing rod and the sleeve are rotatable relative to one another about the main axis, wherein the earthing rod and the sleeve are permanently in contact via the electrically conductive liquid during relative rotation. The sleeve and the earthing rod are preferably arranged coaxially and / or concentrically with respect to the main axis. The earthing rod is preferably inserted into the sleeve in the axial direction with respect to the main axis and sealed against the sleeve. The contact space is delimited in the axial direction on the one hand by the sleeve itself and on the other hand by the earthing rod which is sealingly received in the sleeve. A discharge device is thus proposed which is characterized by a simple and cost-effective design and can also be easily integrated into an existing system.

[0018] In a further specific embodiment, the sleeve has a sealing section for accommodating a sealing device and a contact section adjoining the sealing section to form the contact space. In particular, the contact section directly adjoins the sealing section in the axial direction with respect to the main axis. The sleeve can be designed as a sheet metal component, wherein the contact section and the sealing section are formed by forming. Preferably, the contact section has a smaller inner diameter than the sealing section. In particular, the earthing rod is arranged at a distance from the contact section in the axial and radial directions. The distance in the axial and radial directions is dimensioned so large that there is no contact between the earthing rod and the sleeve beyond the tolerances.Alternatively or optionally additionally, the distance in the axial and / or radial direction is dimensioned so small that the volume of the contact space is minimal. Preferably, the earthing rod is supported in a sealing manner on the sleeve within the sealing section and / or is guided in a sealing manner via the sealing section. Preferably, the contact section is closed in an axial direction with respect to the main axis and the sealing section is open in an axial opposite direction, such that the earthing rod can be pushed and / or pushed into the contact section in the axial direction via the sealing section. For example, the contact section is pre-filled with the electrically conductive liquid before assembly of the earthing rod, wherein the earthing rod is immersed in the electrically conductive liquid when pushed into the sleeve and / or closes the contact space in a fluid-tight manner.A discharge device is proposed which is characterized by simple assembly and thus by simple and cost-effective installation.

[0019] In a further specific implementation, the discharge device has a sealing device which is designed and / or suitable for sealing the contact space. In particular, the sealing device has the function of protecting the contact space from the environment, in particular the housing space, against the escape of the electrically conductive liquid and / or against the ingress of foreign particles, such as dust, moisture, splash water, oil, etc., from the environment. For this purpose, the contact space is preferably designed to be closed and separated from the environment in the axial direction by the sealing device. In particular, the sealing device serves to dynamically and statically seal the contact space so that it is sealed from the environment, in particular the housing space, both when at a standstill and during operation. The sealing device preferably forms a fluid-tight, in particular oil-tight, separation of the contact space.The sealing device is received in the sealing section in a form-fitting and / or force-fitting manner in the axial direction with respect to the main axis, wherein the grounding rod is sealingly supported on an inner circumference of the sleeve via the sealing device. In particular, the sealing device is held in a force-fitting manner in the sealing section via a press fit. Alternatively or optionally additionally, the sealing device is held in a form-fitting manner in the axial direction and / or in the opposite axial direction. The sealing device is preferably designed as a contacting rotary seal, for example as a radial shaft seal, a felt ring, or a shaft lip seal. Thus, a particularly tight system is proposed, which can be used, for example, in dry as well as wet environments.

[0020] In a further development, the sealing device is designed as a double-acting rotary seal. For this purpose, the sealing device has a first and a second sealing lip which run radially onto an outer circumference of the grounding rod at a distance from one another in the axial direction. In principle, the first and the second sealing lip can each be formed by two separate seals, e.g. radial shaft sealing rings. Preferably, however, the sealing device has a cylindrical base body, wherein the two sealing lips are integrally formed on an inner circumference of the base body. In particular, the base body and the two sealing lips are formed from an elastic material. Alternatively, however, the base body can be formed from a harder material than the two sealing lips, e.g. a hard plastic, metal or the like.The two sealing lips ensure a particularly high level of sealing, especially during rotation of the shaft, whereby the escape of the electrically conductive fluid or the entry of foreign particles is significantly reduced or prevented.

[0021] In a further embodiment, the sleeve has a form-fitting contour on its inner circumference and the earthing rod has a mating contour on its outer circumference. The form-fitting contour and the mating contour engage with each other in a form-fitting manner in the axial direction with respect to the main axis, such that the earthing rod is secured against being pulled out of the sleeve. The earthing rod is preferably secured to the sleeve via the form-fitting contour at a defined insertion depth. In particular, the form-fitting contour can be formed by at least one radially inwardly directed collar and the mating contour can be formed by at least one radially outwardly directed collar, such that an end stop for the earthing rod is formed from the sleeve at least in one axial direction.Specifically, the form-fitting contour or the counter-contour has a further collar, forming an end stop for the grounding rod both in the axial direction and in the opposite axial direction. Thus, the grounding rod is circumferentially rotatable and axially secured against displacement within the sleeve. Thus, a discharge device is proposed that is designed as a preassembled unit.

[0022] It is provided that the second contact device has a fastening section at its end. This fastening section serves to fasten the second contact device to the housing section. Preferably, however, the earthing rod has the fastening section for fastening the earthing rod to the housing section. The discharge device has a fastening means which is designed and / or suitable for releasably fastening the fastening section to the housing section. The fastening means can be arranged and / or can be arranged on the fastening section in a form-fitting and / or force-fitting manner in order to secure the second contact device to the housing section. For example, the fastening section has an external or internal thread, wherein the fastening means can be designed accordingly as a nut for the external thread or a screw for the internal thread.The second contact device is fixedly connectable and / or connected to the housing section via the fastening section and the fastening means, in particular in a rotationally fixed manner. Thus, a discharge device is proposed that can be easily mounted on the housing section and cost-effectively replaced during servicing.

[0023] A further subject matter of the invention relates to an electrical machine with at least or precisely one diverting device, as already described above. In particular, the electrical machine is suitable and / or designed for a vehicle. Preferably, the vehicle is designed as an electric vehicle, in particular as a purely electric vehicle or as a hybrid vehicle. The vehicle can be designed as a single-track or two-track and / or single-axle or multi-axle, in particular two-axle, vehicle. In principle, the vehicle is designed as a passenger car, a truck, or a bus. Alternatively, however, the vehicle can also be designed as an electrically powered bicycle (pedelec), motorcycle (electric motorcycle), e-scooter, or the like. The electrical machine serves, in particular, to generate and / or provide a traction torque, in particular a main traction torque, for the vehicle.For this purpose, the electric machine can be coupled or can be coupled to an energy device, in particular to an energy storage device, specifically to a battery or accumulator, in order to obtain energy for generating the traction torque. The electric machine is preferably designed as an electric motor.

[0024] In a specific embodiment, the shaft has a shaft bore on its end face that runs coaxially to the main axis, wherein the sleeve is held in the shaft bore, preferably in a force-fitting manner. In particular, the shaft bore is designed as a blind hole. Preferably, the sleeve, in particular the contact section and / or the sealing section, is pressed into the shaft bore. Alternatively or optionally additionally, the housing section has a housing bore that runs coaxially to the main axis, wherein the earthing rod is held in the housing bore, in particular in a force-fitting manner. In particular, the housing bore is designed as a through-bore. Preferably, the earthing rod, in particular the fastening section, is screwed into the housing bore and / or secured in the housing bore by the fastening means.Optionally, the diverter device comprises a sealing element, whereby the fastening section is sealed from the housing opening via the sealing element. In particular, the sealing element serves to seal the housing space against the ingress and / or egress of foreign particles. Thus, a diverter device is proposed that can be mounted particularly easily on the front side of or in the shaft.

[0025] In a further specific implementation, it is provided that the housing space has a motor section which is designed and / or suitable for accommodating the rotor and stator. Furthermore, the housing space has a gear section which is designed and / or suitable for connecting the shaft to a gear device. The gear device can be designed as a clutch device and / or as a switching device and / or as a transmission device. The shaft is connected to the gear device in a gear-related manner; in particular, the shaft forms an input shaft in the gear device. For this purpose, the shaft can, for example, have a gear wheel section or be fixedly connected to a gear wheel. The gear wheel section can, for example, be formed by a toothing geometry arranged on the shaft. Alternatively, the gear wheel can be designed as a gear wheel that is connected to the shaft in a rotationally fixed manner.Preferably, the motor section and the transmission section are separated from one another by a separating section in the axial direction relative to the main axis, in particular in a dirt-tight and / or oil-tight manner. Preferably, the motor section and the transmission section jointly form the housing space. Preferably, the shaft passes through the separating section and is sealed from the separating section by a sealing element, e.g., a further shaft seal. Particularly preferably, the motor section is implemented either as an oil zone or as a dry zone, and the transmission section as an oil zone.

[0026] According to this embodiment, the discharge device is arranged on a motor side of the motor section. In particular, the discharge device is arranged at the end on the front side of the shaft, which is arranged in the motor section and / or leads out of it. The discharge device is thus arranged on the rotor side and installed where the electrical charge and / or electrical voltage arises in the rotor, so that it can be discharged in close proximity. Alternatively, the discharge device or, optionally, a further discharge device is arranged on a transmission side of the transmission section. In particular, the discharge device or the further discharge device is arranged at the end on the other front side of the shaft, which is arranged in the transmission section and / or leads out of it. The discharge device orthe further diverting device is arranged on the side of the transmission device, whereby this arrangement protects the transmission section with the transmission device so that any bearings in the transmission device do not suffer damage due to current passage.

[0027] Further features, advantages, and effects of the invention will become apparent from the following description of preferred embodiments of the invention. It shows: Fig. 1 is a schematic sectional view of an electrical machine as an embodiment of the invention; Fig. 2 a schematic detailed view of the electrical machine from Fig. 1; Fig. 3a, b different representations of a discharge device for the electrical machine of the Fig. 1 and Fig. 2.

[0028] Fig. 1 shows a schematic sectional view of an electric machine 1 as an exemplary embodiment of the invention. For example, the electric machine is designed and / or suitable for a vehicle, in particular an electric or hybrid vehicle. The electric machine 1 is designed as an electric traction machine and serves to generate and / or provide a traction torque, in particular a main traction torque, for the vehicle. The electric machine 1 can be designed, for example, as a direct current, synchronous, or asynchronous motor, etc.

[0029] The electric machine 1 has a rotor 2 and a stator 3, which are arranged coaxially and / or concentrically with respect to a main axis H. For example, the electric machine 1 can be electrically connected to an energy device, e.g., a battery or accumulator, in order to receive energy for generating the traction torque.

[0030] Furthermore, the electric machine 1 has a shaft 4 for transmitting the traction torque. The rotor 2 is drive-connected to the shaft 4, so that the shaft 4 is driven via and / or by the rotor 2. The shaft 4 is thus designed as a rotor shaft and is mechanically, e.g., rotationally fixed, and electrically connected to the rotor 2. The shaft 4 defines the main axis H with its rotational axis.

[0031] The electric machine 1 has a housing 5, which defines a housing space 6. In the exemplary embodiment shown, the housing 5 is formed by the stator 3 as well as a housing section 7 and a further housing section 8, wherein the housing section 7 is arranged on one axial side and the further housing section 8 is arranged on the other axial side of the stator 3. The housing space 6 is thus delimited in the radial direction by the stator 3 and in the axial direction by the two housing sections 7, 8.

[0032] The shaft 4 and the rotor 2 are rotatably mounted in the housing space 6 via a first and a second bearing device 9a, b. The two housing sections 7, 8 each form a bearing plate, with the shaft 4 being supported on the housing section 7 via the first bearing device 9a and on the further housing section 8 via the second bearing device 9b. In the illustrated embodiment, the bearing devices 9a, b are each designed as ball bearings, in particular deep groove ball bearings.

[0033] The housing space 6 is divided into a motor section 10 for accommodating the rotor 2 and a gear section 11 for connecting the shaft 4 to a gear device (not shown). The motor section 10 and the gear section 11 are spatially separated from one another by a separating section 12 and are connected to one another via the shaft 4. For example, the separating section 12 is formed by or co-formed with the further housing section 8.

[0034] For this purpose, the separating section 12 is arranged in the axial direction with respect to the main axis H between the motor section 10 and the transmission section 11 and is designed as a partition wall. The motor section 10 is designed, for example, as a dry area and the adjacent transmission section 11 as an oil area, with the separating section 12 forming an oil-tight partition between the motor section 10 and the transmission section 11. For this purpose, the shaft 4 is guided from the motor section 10 through the separating section 12 into the transmission section 11 and is sealed from the separating section 12 by a shaft seal 13.

[0035] Shaft 4 forms an input shaft to the transmission device. For this purpose, electric machine 1 has a gear 14, which is non-rotatably connected to shaft 4 and arranged in transmission section 11. Gear 14 is designed as a toothed wheel and can mesh with another toothed wheel (not shown) of the transmission device, for example, to transmit the traction torque to the transmission device.

[0036] During operation, damaging voltages can be induced on the shaft 4 and thus in the rotor 2, creating a capacitive coupling between the stator 3 and the rotor 2. These voltages are typically dissipated via the bearing device 9a of the motor section 10 or, in part, also via the bearing device 9b of the transmission section 11. Furthermore, circulating high-frequency currents can arise in the electrical machine 1, particularly in high-power AC motors. Due to imbalances in the magnetic flux in the stator 3, the circulating high-frequency currents circulate, for example, through the bearing devices 9a, b of the electrical machine 1. Bearing failures can occur as a result of the dissipation of the damaging voltages and the circulating high-frequency currents via the bearing devices 9a, b.In this case, sparks jump over the dielectric oil or grease film, also called spark erosion, between the rotating parts and the bearing raceway, causing melt craters and / or a type of bearing profiling (fluting) in the bearing raceway of the bearing devices 9a, b.

[0037] In order to prevent the bearing devices 9a, b from being damaged, this electrical energy must be dissipated. For this purpose, the electrical machine 1 has a dissipation device 15. The dissipation device 15 serves to dissipate an electrical charge and / or electrical voltage, starting from the rotor 2 via the shaft 4 to the housing 5. The housing 5 is connected to ground and / or earthed so that the electrical charges and / or voltages can be safely dissipated via the housing 5. For this purpose, the dissipation device 15 is arranged on the motor side, in particular in the motor section 10, on an axial end face of the shaft 4 and is electrically connected on the one hand to the shaft 4 and on the other hand to the housing 5, in particular the housing section 7.

[0038] The Fig. 2a shows a detailed view of the motor section 10 with the mounted deflection device 15 from Fig. 1. The diverter device 15 has a first and a second contact device 16, 17, which are arranged coaxially and / or concentrically with respect to the main axis H. The first contact device 16 is electrically and mechanically connected, in particular rotationally fixed, to the shaft 4, and the second contact device 17 is electrically and mechanically connected, in particular rotationally fixed, to the housing section 7. The two contact devices 16, 17 are mechanically decoupled from one another, such that the two contact devices 16, 17 are rotatable relative to one another, in particular during operation of the electrical machine 1.

[0039] Between the first and second contact devices 16, 17, a contact chamber 18 is formed as an annular chamber, via which the two contact devices 16, 17 are electrically connected to one another. For this purpose, the contact chamber 18 is filled with an electrically conductive liquid 19, wherein the first and second contact devices 16, 17 are electrically connected to one another via the electrically conductive liquid 19. For example, the electrically conductive liquid is in the form of an electrically conductive oil, grease, liquid metal, or ionic liquid. The contact chamber 18 is separated from the housing chamber 6 in a fluid-tight manner, thereby preventing the electrically conductive liquid 19 from escaping from the contact chamber 18 into the housing chamber 6, and preventing foreign particles from entering the contact chamber 18 from the housing chamber 6.Thus, an axially acting discharge device 15 is proposed that can be used in both dry and wet environments. Since the electrical contact between the first and second contact devices 16, 17 is established via the electrically conductive fluid 19, the discharge device 15 operates with low friction and wear during operation of the electrical machine 1, so that no conductive abrasion can occur. Furthermore, the electrically conductive fluid 19 enables position-independent operation, since the electrically conductive fluid 19 always ensures contact between the two contact devices 16, 17.

[0040] The first contact device 16 is designed as a sleeve 20 and the second contact device 17 as a grounding rod 21. The sleeve 20 is designed as a metallic, in particular electrically conductive, cylindrical sleeve that is closed in an axial direction AR with respect to the main axis H and open in an axial opposite direction GR. The grounding rod 21 is designed as a metallic, in particular electrically conductive, cylindrical rod that is pushed into the sleeve 20 in the axial direction AR so far that the grounding rod 21 is partially immersed in the electrically conductive liquid 19. Direct contact is thus established between the grounding rod 21 (stator) and the sleeve 20 (rotor) via the electrically conductive liquid 19. Via this path of least resistance, the induced currents are safely diverted to earth, so that the currents are diverted away from the bearing through this system.The bearings of the connected components, such as gearboxes, etc., can also be protected in this way.

[0041] The discharge device 15 has a sealing device 22, wherein the grounding rod 21 is sealingly guided in the sleeve 20 via the sealing device 22. The sealing device 22 is arranged in front of the contact chamber 18 in the axial direction AR, wherein the grounding rod 21 is inserted into the contact section 26 in the axial direction via the sealing device 22. The grounding rod 21 rests sealingly against the sleeve 20 in the radial direction via the sealing device 22, so that the contact chamber 18 is sealed in the opposite axial direction GR. The internal sealing thus protects the contact chamber 18 from environmental influences that could impair efficiency.

[0042] The housing section 7 has a first and a second housing part 7a, b, wherein the two housing parts 7a, b are electrically and mechanically connected to one another. The first housing part 7a has a central housing opening 23, which is arranged in particular coaxially to the main axis H and through which the housing space 6 is accessible from the outside. The second housing part 7b is designed as a housing cover which closes the housing opening 23. For example, the diverter device 15 can be mounted on the shaft 4 via the housing opening 23 and then connected to the housing section 7. For this purpose, the second housing cover 7b can be mounted in the axial direction AR on the first housing cover 7a in a form-fitting and / or force-fitting manner, e.g. via a screw connection.

[0043] The shaft 4 has a shaft bore 24 on its end face arranged coaxially to the main axis H, wherein the sleeve 20 is mounted in the shaft bore 24 in a form-fitting and / or non-positive manner, in particular in a rotationally fixed manner. The second housing part 7b has a housing bore 25 arranged coaxially to the main axis H, wherein the grounding rod 21 is mounted within the housing space 6 in a form-fitting and / or non-positive manner, in particular in a rotationally fixed manner, in the housing bore 25. Thus, the sleeve 20 establishes direct contact with the shaft 4, and the grounding rod 21 establishes direct contact with the housing section 7.

[0044] Fig. 3a shows the discharge device 15 in an exploded view. The sleeve 20 has a contact section 26 and a sealing section 27, wherein the contact section 26 forms the contact space 18 and the sealing section 27 forms a receptacle for the sealing device 22. The sleeve 20 is designed as a sheet metal component, wherein the contact section 26 and the sealing section 27 are formed by forming. The contact section 26 has a smaller diameter than the sealing section 27, wherein the sleeve 20 is pressed into the shaft bore 24 via the sealing section 27. The grounding rod 21 is arranged in the contact section 26 at a distance from the sleeve 20 in the radial direction and in the axial direction with respect to the main axis H, wherein the free space formed thereby is defined as the contact space 18 and is completely or at least partially and / or largely filled with the electrically conductive liquid 19.

[0045] The contact section 26 is closed in the axial direction AR and the sealing section 27 is open in the opposite axial direction GR, wherein the earthing rod 21 is guided in a sealing manner into the contact section 26 via the sealing device 22 arranged in the sealing section 27. The sealing device 22 is designed as a contacting rotary seal which, on the one hand, bears sealingly against an inner circumference of the sealing section 27 and, on the other hand, against an outer circumference of the earthing rod 21. For this purpose, the sealing device 22 is designed as a cylindrical elastomer seal which has a first and a second sealing lip 22a, b on its inner circumference. The two sealing lips 22a, b are spaced apart in the axial direction with respect to the main axis H and bear sealingly against the outer circumference of the earthing rod 21 in the circumferential direction.

[0046] The sealing device 22 is held in the sealing section 27 in a form-fitting and / or force-fitting manner. In particular, the sealing device 22 bears against a radial shoulder 28 of the sleeve 20 in the axial direction AR, with the sleeve 20 tapering in the region of the shoulder 28. The shoulder 28 is formed in a transition area between the contact section 26 and the sealing section 27, and the shoulder 28 can simultaneously form a radial stop for the grounding rod 21 in the event of irregular rotation.

[0047] Furthermore, the sleeve 20 has a form-fitting contour 29 on its inner circumference and the earthing rod 21 has a mating contour 30 on its outer circumference, wherein the form-fitting contour 29 engages with the mating contour 30 in order to secure the earthing rod 21 in the sleeve 20 against loss. The form-fitting contour 29 is formed by a radially inwardly directed collar and the mating contour 30 by a groove which is defined by two axially spaced and radially outwardly directed collars. The collar of the form-fitting contour 29 engages in the groove of the mating contour 30, so that the earthing rod 21 is secured in the axial direction AR by one collar and in the opposite axial direction GR by the other collar of the mating contour 30. The earthing rod 21 is thus held captively in the sleeve 20, so that the discharge device 15 can be offered as a pre-assembled unit.

[0048] At its free axial end, the earthing rod 21 has a fastening section 31, via which the earthing rod 21 is inserted into the housing bore 25, as shown in Fig.3b. For this purpose, the discharge device 15 has a fastening means 32 and a sealing element 33, which can be mounted at the end of the fastening section 31. During assembly, the earthing rod 21 with the fastening section 31 is pushed through the housing bore 25 and then secured to the housing section 7, in particular the second housing part 7b, via the fastening means 32 with the interposition of the sealing element 33. The counter contour 30, in particular the collar closest to the housing section 7, can serve as a stop in the axial opposite direction GR for the earthing rod 21.For example, the fastening section 31 has an external thread, wherein the fastening means 32 is designed as a screw nut and the sealing element 33 is designed as a sealing washer, wherein the sealing element 33 can be pushed onto the fastening section 31 for assembly and the fastening means 32 can be screwed onto the fastening section 31. Thus, a discharge device 15 is proposed which can be installed simply and cost-effectively and easily replaced during servicing. List of reference symbols 1 electric machine 2 rotors 3 Stator 4th wave 4a, b bore 5 housings 6 Housing space 7 Housing section 7a, b Housing parts 8 additional housing section 9a, b Storage facilities 10 Engine section 11 Gearbox section 12 Separation section 13 Sealing organ 14 Gear wheel 15 Discharge device 16 first contact device 17 second contact device 18 Contact room 19 electrically conductive liquid 20 sleeves 21 Earthing rod 22 Sealing device 22a, b sealing lips 23 housing openings 24 shaft bore 25 Housing bore 26 Contact section 27 Sealing section 28 paragraph 29 Form-fitting contour 30 Counter contour 31 Fastening section 32 fasteners 33 Sealing element H main axis AR axial direction GR axial opposite direction

Claims

[1] Discharge device (15) for an electrical machine (1) for discharging an electrical charge and / or voltage from a rotor (2) via a shaft (4) to a housing section (7), wherein the housing section (7) delimits a housing space (6), with a first contact device (16) for electrical and mechanical connection to the shaft (4), with a second contact device (17) for electrical and mechanical connection to the housing section (7), wherein the first and the second contact device (16, 17) are rotatable relative to each other about a main axis (H) and are electrically connected to each other in a contact space (18) sealed off from the housing space (6), characterized by , that the contact space (18) is filled with an electrically conductive liquid (19), wherein the first and the second contact device (16, 17) are electrically conductively connected to one another via the electrically conductive liquid (19). [2] Discharge device (15) according to claim 1, characterized by in that one contact device (16) is designed as a sleeve (20) and the other contact device (17) is designed as an earthing rod (21), wherein the sleeve (20) has the contact space (18) with the electrically conductive liquid (19) and wherein the earthing rod (21) is arranged in sections in the sleeve (20) so that the earthing rod (21) is immersed in the electrically conductive liquid (19) in the contact space (18). [3] Discharge device (15) according to claim 2, characterized bythat the sleeve (20) has a sealing section (27) for receiving a sealing device (22) and a contact section (26) adjoining the sealing section (27) for forming the contact space (18), wherein the earthing rod (21) is guided in a sealing manner via the sealing section (27) into the contact section (26). [4] Discharge device (15) according to claim 3, characterized by a sealing device (22) for sealing the contact space (18), wherein the sealing device (22) is received in the sealing section (27) in a form-fitting and / or force-fitting manner in the axial direction with respect to the main axis (H), wherein the earthing rod (21) is sealingly supported on an inner circumference of the sleeve (20) via the sealing device (22). [5] Discharge device (15) according to claim 4, characterized bythat the sealing device (22) is designed as a rotary seal, wherein the sealing device (22) has at least one sealing lip (22a, b), wherein the at least one sealing lip (22a, b) runs radially on an outer circumference of the earthing rod (21). [6] Discharge device (15) according to one of claims 2 to 5, characterized by that the sleeve (20) has a form-fitting contour (29) on its inner circumference and the earthing rod (21) has a counter-contour (30) on its outer circumference, wherein the form-fitting contour (29) and the counter-contour (30) engage with one another, so that the earthing rod (31) is secured against loss in the sleeve (20). [7] Discharge device (15) according to one of the preceding claims, characterized bythat the second contact device (17) has a fastening section (31) at its end, wherein the diverting device (15) has a fastening means (32) for releasably fastening the fastening section (31) to the housing section (7). [8] Electrical machine (1) with a housing section (7), wherein the housing section (7) delimits a housing space (6), with a rotor (2) and with a shaft (4), wherein the shaft (4) is connected to the rotor (2) electrically and by means of a transmission, and wherein the shaft (4) and the rotor (2) are rotatably mounted in the housing space (6), wherein the shaft (4) defines a main axis (H), characterized by at least one diverter device (15) according to one of the preceding claims. [9] Electrical machine (1) according to claim 8, characterized bythat the shaft (4) has a shaft bore (24) on the end face which runs coaxially to the main axis (H), wherein the sleeve (20) is held in the shaft bore (24) and / or that the housing section (7) has a housing bore (25) which runs coaxially to the main axis (H), wherein the earthing rod (21) is held in the housing bore (25). [10] Electrical machine (1) according to claim 8 or 9, characterized by that the housing space (6) has a motor section (10) for receiving the rotor (2) and a gear section (11) for the gear connection of the shaft (4) to a gear device, wherein the diverter device (15) is arranged optionally on a motor side of the motor section (10) or on a gear side of the gear section (11).

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