Discharge device for discharging electrical charge and / or voltage via shaft of drive train, and drive train having such discharge device

Abstract

The invention relates to a discharge device (15) for an electric machine (1) for discharging electrical charge and / or voltage from a rotor (2) via a shaft (4) to a housing part (7), the housing part (7) delimiting a housing chamber (6). The discharge device comprises first contact means (16) for electrically and mechanically connecting to the shaft (4) and second contact means (17) for electrically and mechanically connecting to the housing part (7). The first contact means (16) and the second contact means (17) are rotatable relative to each other about a main axis (100). One contact means (16) is in the form of a sleeve (20) and the other contact means (17) is in the form of a ground rod (21), the sleeve (20) has a contact chamber (18) with an electrically conductive liquid (19), the ground rod (21) is partially arranged in the sleeve (20), and the sleeve (20) and the ground rod (21) are electrically connected to each other by means of the added electrically conductive liquid (19). The discharge device further comprises a bridging sleeve (34) which is arranged in the contact chamber (18) and which at least partially electrically bridges the distance between the ground rod (21) and the sleeve (20).

Description

Technical Field

[0001] The invention relates to an exhaust device having the features of the preamble of claim 1. The invention also relates to a drive train comprising the exhaust device. Background Art

[0002] Electric machines, in particular electric traction machines, are electrically charged during operation by induction of shaft voltages. In addition, circulating high-frequency currents can be generated in high-power motors. Such electric machines usually have a rotor and a rotor shaft, which are mounted in a housing via rolling bearings. Due to electrical discharge or circulating high-frequency currents, the rolling bearings can be destroyed. In order to avoid this, this electrical energy must be dissipated. For example, grounding brushes or radially acting grinding elements (carbon brushes) are known, which serve to ground the rotor shaft. Furthermore, axially acting systems for shaft grounding are known.

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

[0004] The invention is based on the object of creating a discharge device which is characterized by an increased discharge capacity and is free from wear.

[0005] This object is achieved by an exhaust device having the features of claim 1 and a drive train having the features of claim 10. Preferred or advantageous embodiments of the invention are apparent from the dependent claims, the following description and the drawings.

[0006] The invention relates to a discharge device which is designed for a drive train with an electric machine and / or is preferably suitable for a drive train with an electric machine. The drive train or the electric machine has a housing part, wherein the housing part defines and / or delimits a housing chamber. In particular, the housing part is a component of the housing and / or forms the housing. Preferably, the housing consists of a plurality of parts, wherein the housing part forms a part of the housing, for example a bearing plate. In particular, the housing part is connected to the ground and / or is grounded.

[0007] The electric motor has or is coupled to a shaft, which is, for example, an input shaft or an intermediate shaft of a transmission, which defines a main axis through its axis of rotation. In addition, the electric motor has a stator and a rotor, which are arranged concentrically and / or coaxially relative to each other. The shaft is electrically connected and connected to the rotor in a transmission manner. In particular, the shaft is driven via the rotor and / or by the rotor. In particular, the shaft is designed as a rotor shaft, which is preferably connected to the rotor in a rotationally fixed, rigid and / or integral manner. Preferably, the housing part is electrically and mechanically connected to the stator of the electric motor.

[0008] The shaft and optionally the rotor are rotatably mounted in the housing chamber. In particular, the electrical machine has at least two or exactly two bearing devices which form or help to form a rotor bearing assembly. The rotor is preferably arranged between two bearing devices in the housing chamber, the shaft being rotatably mounted in the housing chamber and / or on the housing part via the bearing devices. Preferably, at least one of the bearing devices is designed as a rolling bearing device.

[0009] The discharge device is designed and / or adapted to discharge the charge and / or voltage starting from the rotor via the shaft to the housing part and optionally additionally to the stator. In particular, the discharge device forms an electrical connection between the shaft and the housing part. In particular, there is a permanent electrical connection between the shaft and the housing part, which exists not only statically but also dynamically, i.e. during operation of the electrical machine.

[0010] The discharge device has a first contact device and a second contact device. The first contact device is used for electrical connection to the shaft. In addition, the first contact device is used for mechanical connection to the shaft, in particular so that the first contact device is fixed to the shaft. The second contact device is used for electrical connection to the housing part. In addition, the second contact device is used for mechanical connection to the housing part, in particular so that the second contact device is fixed to the housing part. The two contact devices can rotate relative to each other, in particular during operation of the electric machine. During operation of the electric machine, the shaft rotates about the main axis, the first contact device is driven by the rotating shaft, and the second contact device remains stationary on the housing part.

[0011] The first contact device and the second contact device are electrically connected to each other in a contact chamber that is sealed relative to the housing chamber. Preferably, the contact chamber and the housing chamber are separated from each other and / or sealed from each other in a sealed manner. The contact chamber is delimited by the first contact device and / or the second contact device, in particular in the axial direction and / or radial direction. Preferably, the contact chamber is defined as an annular space that surrounds the main axis and is formed between the first contact device and the second contact device. The two contact devices are arranged coaxially relative to each other with respect to the main axis, the first contact device is arranged on the axial end face of the shaft, and the second contact device is arranged opposite to the first contact device on the housing part. Therefore, the discharge device is realized as a so-called "end face shaft grounding device". Alternatively, the discharge device can also be installed in a hollow shaft, for example, when an oil gun is used, instead of being installed in a solid shaft.

[0012] The contact chamber is filled with a conductive liquid. Preferably, the contact chamber is completely filled with a conductive liquid. Alternatively, the contact chamber can also be partially and / or mostly filled with a conductive liquid. The first contact device and the second contact device are electrically connected to each other via the conductive liquid. In particular, the two contact devices are spaced apart from each other in the contact chamber, wherein the electrical contact is formed exclusively or additionally via the conductive liquid. In particular, through the added conductive liquid, the current path thus extends from the rotor via the shaft and the first contact device to the second contact device and the housing part. Compared with the bearing device, the current path formed by the discharge device has a lower resistance, so that the discharge current and / or voltage is discharged via the discharge device.

[0013] The conductive liquid creates a wear-free contact between the two discharge devices, so that the discharge devices can be operated with little friction and without wear. In contrast to the friction contacts known from the prior art, the proposed discharge device does not generate any conductive wear, thereby eliminating the risk of short circuits caused by wear in the motor. A further advantage is that the contact via the conductive liquid enables position-independent operation of the discharge device, since a permanent contact is established between the two contact elements by the added conductive liquid.

[0014] It is provided that one of the contact means is designed as a sleeve and the other contact means is designed as a grounding rod. In principle, the sleeve can be assigned to the housing part and the grounding rod to the shaft. However, preferably, the sleeve is assigned to the shaft and the grounding rod to the housing part. In particular, the basic shape of the sleeve is designed as a cylindrical sleeve that is closed on one side. In particular, the basic shape of the grounding rod is designed as a cylindrical rod. Preferably, the sleeve and the grounding rod are formed of an electrically conductive material, such as steel, iron, copper or the like. The sleeve comprises a contact chamber with an electrically conductive liquid, wherein the grounding rod is partially arranged in the sleeve so that the grounding rod is immersed in the electrically conductive liquid in the contact chamber. In particular, the grounding rod and the sleeve can be rotated relative to each other about the main axis, and the grounding rod and the sleeve are permanently in contact during the relative rotation by the introduced electrically conductive liquid. For this purpose, the sleeve and the grounding rod are arranged coaxially with respect to the main axis and / or concentrically with respect to each other. Preferably, the grounding rod is inserted into the sleeve in the axial direction with respect to the main axis and is sealed relative to the sleeve. The contact chamber is delimited in the axial direction on the one hand by the sleeve itself and on the other hand by the ground rod received in a sealing manner in the sleeve.Therefore, a drain device is proposed which features a simple and cost-effective structure and which can also be easily integrated into existing systems.

[0015] In the scope of the invention, it is proposed that the discharge device has a bridging sleeve, which is arranged in the contact chamber. In particular, the bridging sleeve is designed to be electrically conductive. The bridging sleeve is designed in particular as a component separate from the sleeve. The bridging sleeve bridges the distance, in particular the radial distance, between the ground rod and the sleeve at least partially and in an electrically conductive manner. The bridging sleeve is in particular made of or comprises an electrically conductive material, which is preferably a metal. In particular, the ground rod is arranged in the bridging sleeve and the bridging sleeve is supported against the sleeve in the radial direction and / or in the axial direction in the contact chamber. In particular, the bridging sleeve is arranged coaxially with respect to the main rotation axis and / or concentrically between the ground rod and the sleeve. In particular, the bridging sleeve is rigidly connected to the sleeve and / or is arranged to rotate freely relative to the ground rod. It can be provided that the ground rod is arranged in the bridging sleeve in a contacting manner, but preferably, the ground rod is arranged in the bridging sleeve in a non-contacting manner, for example in a play manner, and / or has contact at least only in certain areas. The conductive liquid ensures electrical contact between the ground rod and the bridge sleeve.

[0016] The bridging sleeve can be designed as an end sleeve and open only on one side and / or have a blind opening for the ground rod. Preferably, however, the bridging sleeve is designed with a through opening for receiving, at least partially receiving, the ground rod. Particularly preferably, the bridging sleeve has a straight hollow cylindrical shape.

[0017] Advantageously, the bridging sleeve can be manufactured in a simple, cost-effective manner with low tolerances and / or high manufacturing quality, in particular with respect to the receiving opening for the ground rod. This means that the sleeve in the contact chamber no longer needs to have high manufacturing quality and / or low tolerances, since the contact surface with the ground rod is formed by the inner circumference of the bridging sleeve. In addition, the radial distance between the bridging sleeve, in particular the inner circumference of the bridging sleeve and the outer circumference of the ground rod, is reduced, so that the conductive liquid only has to bridge a very short section of the conductive path between the ground rod and the bridging sleeve. This increases the conductivity of the discharge device and / or reduces the electrical resistance in the discharge device.

[0018] In a preferred improvement of the present invention, the bridging sleeve is designed as a sliding bushing, which forms a sliding bearing assembly and / or an emergency bearing assembly for the ground rod. This gives the bridging sleeve a second function, namely a support function for the ground rod. The sliding bushing can realize a permanent bearing assembly or a temporary bearing assembly, which is particularly designed to realize the emergency running performance of the ground rod in the bridging sleeve. By selecting the bridging sleeve as a component separated from the sleeve, for example, the material of the sliding bushing can be freely selected, so that a low-friction material pairing between the ground rod and the bridging sleeve can be realized. For example, soft metals such as copper alloys, bronze alloys or brass alloys can be used for the bridging sleeve. Alternatively or additionally, an additional sliding coating can also be applied to the inner circumference of the bridging sleeve as a sliding bushing, because this measure for reducing the friction with the bridging sleeve can also be realized in a cost-effective manner. In particular, the conductive liquid forms a lubricating film between the ground rod and the bridging sleeve as a sliding bearing partner.

[0019] In a preferred embodiment, the bridging sleeve is mechanically connected and thus conductively connected to the sleeve. For example, the bridging sleeve is pressed into the sleeve and thus mechanically connected and thus conductively connected to the sleeve. Alternatively, the bridging sleeve can be connected to the sleeve in one piece. It is provided that the conductive liquid only conductively bridges a possible annular gap between the bridging sleeve and the grounding rod. During operation, a relative rotation between the sleeve and the grounding rod can lead to contact, possibly permanent contact. However, this contact is not reliable; process reliability is only achieved by the conductive liquid in the annular gap. Strictly speaking, it is not always necessary to provide an annular gap between the bridging sleeve and the grounding rod.

[0020] In a preferred development of the invention, the annular gap has a simple annular gap width, i.e. the distance between the inner circumference of the bridging sleeve and the outer circumference of the ground rod is less than 200 μm, preferably less than 60 μm and in particular less than 30 μm. A small annular gap width increases the electrical conductivity and / or reduces the electrical resistance of the discharge device.

[0021] Preferably, the conductive liquid itself is conductive and / or is mixed with conductive additives. In principle, the conductive liquid can be formed as a liquid metal or an ionic liquid or the like. However, the conductive liquid is preferably in the form of a conductive oil or grease. Although conductive oils and greases generally have a lower conductivity than, for example, liquid metals, they are less toxic and / or easier to handle. The use of a bridging sleeve compensates for the lower conductivity, so that the bridging sleeve enables the technically rational use of conductive oils and / or greases. In particular, conductive liquids with a conductivity of greater than 10,000 nS / m, in particular greater than 30,000 nS / m at 25° C. are used, such as oils or greases with conductive additives or other oil-free and / or fat-free liquids. These are particularly suitable for low-impedance applications.

[0022] For lower transmission resistance requirements, ie for higher transmission resistances, even conventional transmission oils can be used due to the bridging sleeve.

[0023] In an alternative embodiment, the conductivity of the conductive liquid at 25° C. is then less than 500 nS / m, preferably less than 300 nS / m and in particular less than 100 nS / m or less than 50 nS / m. On the other hand, it is preferred that the conductivity is greater than 1 nS / m, preferably greater than 5 nS / m and in particular greater than 10 nS / m. Such conductivity makes it possible to use commonly used transmission oils, so that specially adjusted liquids, in particular those containing conductive additives, can be omitted. This can be achieved by using a bridging sleeve and the resulting reduced annular gap width.

[0024] Furthermore, conductive oil and / or grease improves the emergency running performance of the ground rod in the bridging sleeve.

[0025] Particularly preferably, the sleeve has a radial shoulder, in particular a taper and / or a step, by means of which the bridging sleeve is fixed in the contact chamber in an axial direction in a form-fitting manner. Preferably, the bridging sleeve is inserted and / or pressed into the contact chamber during production and the radial shoulder is subsequently produced by forming such that the bridging sleeve is captured in the contact chamber.

[0026] More specifically, the sleeve has a sealing portion for receiving the sealing device and a contact portion adjacent to the sealing portion for forming a contact chamber. In particular, the contact portion directly adjoins the sealing portion in an axial direction with respect to the main axis. The sleeve can be designed as a shaped sheet metal part, the contact portion and the sealing portion being made by forming. Preferably, the ground rod is supported on the sleeve in a sealed manner within the sealing portion and / or is guided in a sealed manner via the sealing portion. Preferably, the contact portion is closed in an axial direction with respect to the main axis and the sealing portion is open in an opposite axial direction, so that the ground rod is inserted into the contact portion in an axial direction via the sealing portion and / or can be inserted into the contact portion in an axial direction via the sealing portion. For example, before the ground rod is installed, the contact portion is pre-filled with a conductive liquid, and the ground rod is immersed in the conductive liquid when inserted into the sleeve and / or the contact chamber is closed in a fluid-tight manner. The following discharge device is proposed: the discharge device is characterized by simple assembly and thus simple and cost-effective installation.

[0027] In another specific embodiment, the discharge device has a sealing device, which is designed for sealing the contact chamber and / or is suitable for sealing the contact chamber. In particular, the sealing device has the following function: protecting the contact chamber from the surrounding environment, in particular the housing chamber, from the escape of conductive liquid and / or from the ingress of foreign particles from the surrounding environment, such as dust, moisture, water spray, oil, etc. For this purpose, the contact chamber is preferably designed to be closed and separated from the surrounding environment in the axial direction by the sealing device. In particular, the sealing device is used for dynamic and static sealing of the contact chamber, so that the contact chamber is sealed relative to the surrounding environment, in particular the housing chamber, when stationary and during operation. Preferably, the sealing device forms a fluid-tight, in particular oil-tight separation of the contact chamber. The sealing device is received in the sealing part in a form-fitting manner and / or in a frictional manner with respect to the main axis in the axial direction, and the ground rod is supported on the inner periphery of the sleeve in a sealed manner via the sealing device. In particular, the sealing device is retained in the sealing part in a frictional manner by a press fit. Alternatively or additionally optionally, the sealing means is held in a form-fitting manner in the axial direction and / or in the opposite axial direction. Preferably, the sealing means is designed as a contact-type rotary seal, for example a radial shaft sealing ring, a felt ring or a shaft lip seal. Thus, a particularly watertight system is proposed, which can be used, for example, in dry environments and in wet environments.

[0028] In a further improvement, the sealing device is designed as a double-acting rotary seal. For this purpose, the sealing device has a first sealing lip and a second sealing lip, which extend radially at a distance from each other in the axial direction on the outer periphery of the ground rod. In principle, the first sealing lip and the second sealing lip can each be formed by two separate seals, such as radial shaft sealing rings. However, preferably, the sealing device has a cylindrical body, and the two sealing lips are formed on the inner periphery of the body. In particular, the body and the two sealing lips are made of elastic material. Alternatively, the body can be made of a material harder than the two sealing lips, such as hard plastic, metal or the like. The two sealing lips ensure a particularly high degree of sealing, especially during the rotation of the shaft, wherein the escape of conductive liquid or the entry of foreign particles is significantly reduced or prevented.

[0029] In another embodiment, the sleeve has a form-fitting profile on its inner circumference and the ground rod has a mating profile on its outer circumference. The form-fitting profile and the mating profile engage with each other in a form-fitting manner in the axial direction with respect to the main axis, so that the ground rod is fixed to prevent being pulled out of the sleeve. Preferably, the ground rod is fixed to the sleeve at a fixed insertion depth via the form-fitting profile. In particular, the form-fitting profile can be formed by at least one radially inwardly pointing collar and the mating profile is formed by at least one radially outwardly pointing collar, so that an end stop for the ground rod is formed by the sleeve at least in one axial direction. In particular, the form-fitting profile or the mating profile has a further collar, so that an end stop for the ground rod is formed in the axial direction and in the opposite axial direction. Thus, the ground rod can be rotated in the circumferential direction and is fixed to prevent displacement in the sleeve in the axial direction. Therefore, a discharge device designed as a preassembled unit is proposed.

[0030] In another embodiment, it is provided that the second contact device has a fastening portion at the end. In particular, the fastening portion is used to fasten the second contact device to the housing part. In principle, the sleeve can include a fastening portion for fastening the sleeve to the housing part. However, preferably, the ground rod includes a fastening portion for fastening the ground rod to the housing part. The discharge device has a fastening device, which is designed and / or suitable for fastening the fastening portion to the housing part in a releasable manner. The fastening device can be arranged and / or can be arranged on the fastening portion in a form-fitting manner and / or in a frictional manner in order to fix the second contact device to the housing part. For example, the fastening part has an external thread or an internal thread, and the fastening device can be designed as a nut for an external thread or a screw for an internal thread accordingly. Preferably, the second contact device can be connected to the housing part and / or connected to the housing part in a fixed manner, in particular in a rotationally fixed manner, via the fastening portion and the fastening device. Therefore, the following discharge device is proposed: the discharge device can be easily mounted on the housing part and can be replaced cost-effectively during maintenance.

[0031] Another object of the invention relates to an electric machine comprising at least one or exactly one emission device as described above or according to one of claims 1 to 7. In particular, the electric machine is suitable for and / or is designed to be used in a vehicle. Preferably, the vehicle is designed as an electric vehicle, in particular as a pure electric vehicle or a hybrid vehicle. The vehicle can be designed as a single-track or double-track and / or single-axle or multi-axle, especially double-axle vehicle. In principle, the vehicle is designed as a passenger car, a truck or a bus. However, alternatively, the vehicle can also be designed as, for example, an electrically driven bicycle (electrically assisted bicycle), a motorcycle (electric motorcycle), an electric scooter or a similar vehicle. The electric machine is particularly used to generate and / or provide a traction torque for the vehicle, in particular a main traction torque. The electric machine can be connected or connected to an energy device, in particular an energy storage device, in particular a battery or a rechargeable battery, to obtain energy for generating a traction torque. Preferably, the electric machine is designed as an electric motor.

[0032] In a particular embodiment, it is provided that the shaft has a shaft opening extending coaxially relative to the main axis at the end face, wherein the sleeve is held in the shaft opening, preferably held in the shaft opening in a frictional manner. In particular, the shaft opening is designed as a blind hole or a through hole, such as in a hollow shaft. Preferably, the sleeve, in particular the contact portion and / or the sealing portion is pressed into the shaft opening. Alternatively or additionally optionally, the housing part has a housing opening extending coaxially relative to the main axis, and the grounding rod is held in the housing opening, in particular held in the housing opening in a frictional manner. In particular, the housing opening is designed as a through hole or a blind hole. Preferably, the grounding rod, in particular the fastening portion, is screwed into the housing opening and / or fixed in the housing opening via a fastening device. Optionally, the discharge device has a sealing element, and the fastening portion is sealed relative to the housing opening by the sealing element. In particular, the sealing element is used to seal the housing chamber to prevent foreign particles from entering and / or escaping. Therefore, a discharge device that can be particularly easily installed in or on the shaft at the end face is proposed. In particular, the sleeve is fastened in the opening in the rotor shaft at the end face and establishes direct contact with the rotor. On the opposite side, the grounding rod is then inserted into the housing opening and fastened to the housing, thereby establishing direct contact with the stator. The structure of the shaft grounding device also allows reverse installation so that different installation spaces can be coped with.

[0033] In another specific embodiment, the housing chamber has a motor part, which is designed and / or suitable for receiving a rotor and a stator. In addition, the housing chamber has a transmission part, which is designed and / or suitable for connecting a shaft to a transmission device in a transmission manner. The transmission device can be designed as a clutch device and / or a switching device and / or a transmission ratio device. The shaft is connected to the transmission device in a transmission manner, and in particular, the shaft forms an input shaft entering the transmission device. For this purpose, the shaft can, for example, have a gear part or be fixedly connected to a gear. The gear part can, for example, be formed by a tooth geometry arranged on the shaft. Alternatively, the gear can be designed as a toothed wheel connected to the shaft to rotate together. Preferably, the motor part and the transmission part are separated from each other via a separation part in the axial direction relative to the main axis, and are particularly separated from each other in a dirt-proof and / or oil-proof manner. Preferably, the motor part and the transmission part form a housing chamber together. Preferably, the shaft is guided through the separation part and is sealed relative to the separation part by a sealing member, for example, another shaft sealing ring. Particularly preferably, the motor part is implemented as an oil region or a dry region, and the transmission part is implemented as an oil region.

[0034] According to this embodiment, the discharge device is arranged on the motor side of the motor part. In particular, the discharge device is arranged on the end face of the shaft at the end, and the discharge device is arranged in the motor part and / or is led out from the motor part. Therefore, the discharge device is arranged on one side of the rotor and is installed at a position where the charge and / or voltage is generated in the rotor so that the charge and / or voltage can be discharged nearby. Alternatively, the discharge device or optionally another discharge device is arranged on the transmission side of the transmission part. In particular, the discharge device or another discharge device is arranged on the other end face of the shaft at the end, and the discharge device or another discharge device is arranged in the transmission part and / or is led out from the transmission part. Therefore, the discharge device or another discharge device is arranged on one side of the transmission device, and this arrangement protects the transmission part and the transmission device so that any bearing in the transmission device will not be damaged due to the current passing through.

[0035] In summary, according to the specific implementation, the following advantages and implementation methods can be achieved:

[0036] The ground rod is guided via a conductive bridge sleeve and is sealed from the environment by a sealing device. The bridge sleeve serves as a guide for the ground rod (with advantages in terms of fastening and emergency operating performance - the bridge sleeve is therefore preferably a sliding bushing with conductive properties) and as a bridge, because in such conductive liquids, the conductivity decreases with increasing distance (gap). The discharge device particularly relates to the application of conductive oils and greases, which are introduced as a substitute for expensive and sometimes toxic conductive metals - that is, the implementation is the result of the introduction of new liquids: conductive liquids (such as oil, grease, liquid metal or ionic liquid, etc.) establish direct contact between the ground rod and the conductive bridge sleeve and the housing connected to the sleeve. The induced current is safely discharged to the earth via this path of least resistance. Therefore, the current is discharged from the bearing through the system. The bearings of connected components such as transmissions are also reliably protected. The system operates particularly reliably when the gap width reaches 120μm, and the highest operating efficiency is in the range of 0μm to 30μm. The main advantage of the drain as a shaft grounding device is that the drain is constructed as an independent system and can therefore be provided as a finished unit. Another advantage is that the drain can be used both in dry and wet motors (continuation of the principle). Since the contact is made via a conductive liquid, the drain is completely wear-free and no conductive wear occurs, unlike all currently known solutions. This means that the drain operates with very little friction. The internal seal provides the drain with additional protection against environmental influences that could impair efficiency. Since the conductive liquid always establishes contact between the two contact partners, the construction also allows position-independent operation. In addition, the shaft grounding device can be replaced during maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, advantages and effects of the present invention are apparent from the following description of preferred exemplary embodiments of the present invention. In the accompanying drawings:

[0038] Figure 1 shows a schematic cross-sectional view of a motor as an exemplary embodiment of the present invention;

[0039] Figure 2 Shows Figure 1 A schematic detailed diagram of a motor;

[0040] Figure 3a and Figure 3b Shown for Figure 1 and Figure 2 Different representations of the emission devices of electric motors. DETAILED DESCRIPTION

[0041] Figure 1 A schematic cross-sectional representation of an electric machine 1 as an exemplary embodiment of the invention is shown. The electric machine is designed for a vehicle and / or is suitable for a vehicle, in particular an electric vehicle or a hybrid vehicle, for example. The electric machine 1 is designed as an electric traction machine and is used 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 DC motor, a synchronous motor or an asynchronous motor.

[0042] The electric machine 1 has a rotor 2 and a stator 3 which are arranged coaxially and / or concentrically relative to each other about a main axis 100. For example, the electric machine 1 may be electrically connected to an energy device such as a battery or a rechargeable battery to obtain energy for generating traction torque.

[0043] Furthermore, the electric machine 1 has a shaft 4 for transmitting traction torque. The rotor 2 is connected to the shaft 4 in a driving manner, so that the shaft 4 is driven via and / or by the rotor 2. The shaft 4 is therefore designed as a rotor shaft and for this purpose is mechanically connected, for example non-rotatably connected and electrically connected to the rotor 2. The shaft 4 defines a main axis 100 via its axis of rotation.

[0044] The electric machine 1 has a housing 5 which defines a housing chamber 6. In the exemplary embodiment shown, the housing 5 is formed by the stator 3 and a housing part 7 and a further housing part 8, wherein the housing part 7 is arranged on one axial side of the stator 3 and the further housing part 8 is arranged on the other axial side of the stator. The housing chamber 6 is thus delimited in the radial direction by the stator 3 and in the axial direction by the two housing parts 7, 8.

[0045] The shaft 4 and the rotor 2 are rotatably mounted in the housing chamber 6 via a first bearing device 9a and a second bearing device 9b. The two housing parts 7, 8 each form a bearing shield, the shaft 4 being supported on the housing part 7 via the first bearing device 9a and on the other housing part 8 via the second bearing device 9b. In the exemplary embodiment shown, the bearing devices 9a, 9b are each designed as rolling bearings / ball bearings, in particular deep groove ball bearings.

[0046] The housing chamber 6 is divided into a motor part 10 for receiving the rotor 2 and a transmission part 11 for connecting the shaft 4 to a transmission device (not shown), wherein the motor part 10 and the transmission part 11 are spatially separated from each other via a separation part 12 and are connected to each other in a transmission manner via the shaft 4. For example, the separation part 12 is formed by or together with another housing part 8.

[0047] For this purpose, the separation part 12 is arranged between the motor part 10 and the transmission part 11 in the axial direction with respect to the main axis 100 and is designed as a partition wall. For example, the motor part 10 is designed as a dry area, and the adjacent transmission part 11 is designed as an oil area, and the separation part 12 forms an oil-tight separation between the motor part 10 and the transmission part 11. For this purpose, the shaft 4 is guided from the motor part 10 through the separation part 12 into the transmission part 11 and is sealed relative to the separation part 12 by a shaft sealing ring 13.

[0048] The shaft 4 forms the input shaft into the transmission. For this purpose, the electric machine 1 has a gear 14 which is non-rotatably connected to the shaft 4 and is arranged in the transmission part 11. The gear 14 is designed as a toothed wheel and can, for example, mesh with another toothed wheel (not shown) of the transmission in order to transmit the traction torque to the transmission.

[0049] During operation, destructive voltages can be induced on the shaft 4 and therefore in the rotor 2, resulting in capacitive coupling between the stator 3 and the rotor 2. These voltages are usually discharged via the bearing device 9a of the motor part 10, or partially also via the bearing device 9b of the transmission part 11. In addition, circulating high-frequency currents can appear in the electric machine 1, especially in AC motors of high power levels. The circulating high-frequency currents circulate due to the imbalance of the magnetic flux in the stator 3, for example, through the bearing devices 9a, 9b of the electric machine 1. Bearing failures may occur due to the destructive voltages and the discharge of the circulating high-frequency currents via the bearing devices 9a, 9b. In this case, sparks jump over the dielectric oil or grease film between the rotating parts and the bearing raceway - also called spark erosion, thereby causing craters and / or a type of bearing profile (groove) in the bearing raceways of the bearing devices 9a, 9b.

[0050] In order to avoid damaging the bearing means 9a, 9b, this electrical energy must be dissipated. For this purpose, the electric machine 1 has a discharge device 15. The discharge device 15 is used to discharge the charge and / or voltage from the rotor 2 via the shaft 4 to the housing 5. The housing 5 is connected to the earth and / or the stator 2 and / or is grounded so that the charge and / or voltage can be safely discharged via the housing 5. For this purpose, the discharge device 15 is arranged on the axial end face of the shaft 4 in the motor side, in particular the motor part 10, and is electrically connected to the shaft 4 on the one hand and to the housing 5, in particular the housing part 7 on the other hand.

[0051] Figure 2 Shows Figure 1 Detailed view of a motor part 10 with an exhaust device 15 mounted thereon. The exhaust device 15 has a first contact means 16 and a second contact means 17, which are arranged coaxially and / or concentrically relative to one another about a main axis 100. The first contact means 16 is electrically and mechanically connected, in particular non-rotatably connected to the shaft 4, and the second contact means 17 is electrically and mechanically connected, in particular non-rotatably connected to the housing part 7. The two contact means 16, 17 are mechanically decoupled from one another, so that the two contact means 16, 17 can rotate relative to one another, in particular during operation of the electric machine 1.

[0052] A contact chamber 18 designed as an annular space is formed between the first contact device 16 and the second contact device 17, via which the two contact devices 16, 17 are electrically connected to each other. For this purpose, the contact chamber 18 is filled with a conductive liquid 19, and the first contact device 16 and the second contact device 17 are in conductive contact with each other through the added conductive liquid 19. For example, the conductive liquid is formed as conductive oil, grease, liquid metal or ionic liquid. The contact chamber 18 is isolated from the surrounding environment of the housing chamber 6 or the discharge device 15 in a fluid-tight manner, so that the conductive liquid 19 is prevented from escaping from the contact chamber 18 into the housing chamber 6, and foreign particles are prevented from entering the contact chamber 18 from the housing chamber 6. Therefore, an axially acting discharge device 15 is proposed, which can be used in a dry environment and in a humid environment. Since the electrical contact between the first contact device 16 and the second contact device 17 is established by the addition of the conductive liquid 19, the discharge device 15 operates in a low-friction and wear-free manner during the operation of the motor 1, so that no conductive wear occurs. Furthermore, the conductive liquid 19 enables position-independent operation, since the conductive liquid 19 always ensures contact between the two contact means 16 , 17 .

[0053] The first contact means 16 is designed as a sleeve 20, and the second contact means 17 is designed as a ground rod 21. The sleeve 20 is designed as a metallic, in particular conductive, cylindrical sleeve, which is closed in an axial direction 101 with respect to the main axis 100 and is open in an opposite axial direction 102. A bridging sleeve 34 is arranged in the contact chamber 18, which is coaxially oriented with respect to the main axis 100. The bridging sleeve 34 has a straight hollow cylindrical shape and is conductive. For example, the bridging sleeve 34 is realized as a metal sleeve. The bridging sleeve 34 is supported by its outer circumference in a mechanical and / or conductive manner against the inner circumference of the contact portion 26. For example, the bridging sleeve 34 is pressed into the contact portion 26. The bridging sleeve 34 forms a component of the first contact means 16.

[0054] The ground rod 21 is designed as a metallic, in particular conductive, cylindrical rod which is inserted into the sleeve 20 in the axial direction 101, so that the ground rod 21 is partially immersed in the conductive liquid 19 in the axial region of the bridging sleeve 34. Thus, an electrical path is formed between the ground rod 21 (stator) and the sleeve 20 (rotor) via the conductive liquid 19 and the bridging sleeve 34. This path of least resistance transfers the induced current safely to the earth, so that the current is discharged away from the bearing through the system. The bearings of connected components such as transmissions can also be protected in this way.

[0055] The discharge device 15 has a sealing device 22, and the ground rod 21 is guided in a sealed manner 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 101, and the ground rod 21 is inserted into the contact portion 26 in the axial direction via the sealing device 22. The ground rod 21 bears against the sleeve 20 in a sealed manner via the sealing device 22 in the radial direction, so that the contact chamber 18 is sealed in the opposite axial direction 102. The internal seal protects the contact chamber 18 from environmental influences that could impair efficiency.

[0056] The housing part 7 has a first housing part 7a and a second housing part 7b, which are electrically and mechanically connected to each other. The first housing part 7a has a central housing opening 23, which is particularly arranged coaxially with respect to the main axis 100 and through which the housing chamber 6 can be accessed from the outside. The second housing part 7b is designed as a housing cover that closes the housing opening 23. For example, the discharge device 15 can be mounted on the shaft 4 via the housing opening 23 and then connected to the housing part 7. For this purpose, the second housing cover 7b can be mounted on the first housing cover 7a in a form-fitting manner and / or in a frictional manner, for example via a screw connection in the axial direction 101.

[0057] The shaft 4 has a shaft opening 24 arranged coaxially with respect to the main axis 100 at the end face, and the sleeve 20 is mounted in the shaft opening 24 in a form-fitting manner and / or in a frictional manner, especially in a rotationally fixed manner. The second housing part 7b has a housing opening 25 arranged coaxially with respect to the main axis 100, and the grounding rod 21 is mounted in the housing opening 25 in a form-fitting manner and / or in a frictional manner, especially in a rotationally fixed manner in the housing chamber 6. Therefore, the sleeve 20 is in direct contact with the shaft 4, and the grounding rod 21 is in direct contact with the housing part 7.

[0058] Figure 3a An exploded view of the discharge device 15 is shown. The sleeve 20 has a contact portion 26 and a sealing portion 27, the contact portion 26 forming the contact chamber 18 and the sealing portion 27 forming a receptacle for the sealing device 22. The sleeve 20 is designed as a shaped sheet metal component, the contact portion 26 and the sealing portion 27 being produced by forming. The contact portion 26 has a smaller diameter than the sealing portion 27, via which the sleeve 20 is pressed into the shaft opening 24. The grounding rod 21 is arranged in the radial direction in the contact portion 26 and is spaced apart from the sleeve 20 in the axial direction with respect to the main axis 100, the free space formed thereby being defined as the contact chamber 18. The bridging sleeve 34 is arranged in the contact chamber 18, the remaining free volume in the contact chamber 18 being completely or at least partially and / or mostly filled with the conductive liquid 19.

[0059] Therefore, the bridging sleeve 34 is concentrically arranged between the sleeve 20 and the ground rod 21 in the contact portion 26. Due to the bridging sleeve 34, the conductive liquid 19 does not have to bridge the radial distance between the ground rod 21 and the sleeve 20, but only bridges the annular gap between the ground rod 21 and the bridging sleeve 34. The simple annular gap width, i.e. the simple radial distance between the outer circumference of the ground rod 21 and the inner circumference of the bridging sleeve 34, is less than 120 μm, and for example less than 30 μm.

[0060] This also makes it possible to use less conductive liquid 19 , such as conductive grease or oil, as in this exemplary embodiment. The conductive liquid 19 , being conductive grease or oil, also forms an excellent lubricant between the ground rod 21 and the bridging sleeve 34 .

[0061] The bridging sleeve 34 can also achieve a smaller radial distance because the bridging sleeve 34 is initially manufactured as a separate component and therefore has only low tolerances as a simple component. Therefore, the inner circumference of the bridging sleeve 34 is precisely shaped so that the annular gap width can be dimensioned to be smaller.

[0062] The bridging sleeve 34 is particularly designed as a sliding bushing, the material of which is softer than the material of the ground rod 21 , so that the bridging sleeve 34 can provide emergency running performance for the rotation of the ground rod 21 .

[0063] The contact portion 26 is closed in the axial direction 101 and the sealing portion 27 is open in the opposite axial direction 102, the ground rod 21 being guided in a sealed manner into the contact portion 26 via a sealing device 22 arranged in the sealing portion 27. The sealing device 22 is designed as a contact-type rotary seal, which bears against the inner circumference of the sealing portion 27 in a sealed manner on the one hand and against the outer circumference of the ground rod 21 in a sealed manner on the other hand. For this purpose, the sealing device 22 is designed as a cylindrical elastomer seal, which has a first sealing lip 22a and a possible second sealing lip 22b on its inner circumference. The two sealing lips 22a, 22b are spaced apart in the axial direction with respect to the main axis 100 and bear circumferentially against the outer circumference of the ground rod 21 in a sealed manner in the circumferential direction.

[0064] The sealing means 22 is held in the sealing portion 27 in a form-fitting manner and / or in a frictional manner. In particular, the sealing means 22 bears against a radial shoulder 28 of the sleeve 20 in the axial direction 101, and the sleeve 20 tapers in the region of the shoulder 28. The shoulder 28 is formed in the transition region between the contact portion 26 and the sealing portion 27, and the shoulder 28 can simultaneously form a radial stop for the ground rod 21 in the event of unstable rotation. The bridging sleeve 34 can rest on the axially opposite side of the radial shoulder 28. At least the free inner diameter of the radial shoulder is smaller than the outer diameter of the bridging sleeve 34, so that the bridging sleeve is optionally held in a captive manner in the contact portion 26.

[0065] Furthermore, the sleeve 20 has a form-fitting contour 29 on its inner circumference, and the ground rod 21 has a mating contour 30 on its outer circumference, with which the form-fitting contour 29 engages in order to fix the ground rod 21 in a captive manner in the sleeve 20. The form-fitting contour 29 is formed by a radially inwardly directed collar, and the mating contour 30 is formed 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 ground rod 21 is fixed in the axial direction 101 by one collar and in the opposite axial direction 102 by the other collar of the mating contour 30. Thus, the ground rod 21 is received in the sleeve 20 in a captive manner, so that the discharge device 15 can be provided as a preassembled unit.

[0066] The ground rod 21 has a fastening portion 31 at its free axial end, via which the ground rod 21 can be mounted in the housing opening 25, such as Figure 3bAs shown. For this purpose, the drain device 15 has a fastening device 32 and a sealing element 33, which can be mounted at the end of the fastening part 31. During installation, the ground rod 21 with the fastening part 31 is pushed through the housing opening 25 and then fixed to the housing part 7, in particular the second housing part 7b, via the fastening device 32 by inserting the sealing element 33. The mating contour 30, in particular the collar closest to the housing part 7, can serve as a stop for the ground rod 21 in the opposite axial direction 102. For example, the fastening part 31 has an external thread, the fastening device 32 is designed as a nut, and the sealing element 33 is designed as a sealing disk, and the sealing element 33 can be pushed onto the fastening part 31 for installation, and the fastening device 32 can be screwed onto the fastening part 31. Therefore, the following drain device 15 is proposed: the drain device can be easily and inexpensively installed and can be easily replaced during maintenance.

[0067] Reference numerals

[0068] 1 Motor

[0069] 2 Rotors

[0070] 3. Stator

[0071] 4 Axis

[0072] 5 Housing

[0073] 6 Shell chamber

[0074] 7 Shell part

[0075] 7a, 7b Housing parts

[0076] 8 Another housing part

[0077] 9a, 9b Bearing components

[0078] 10 Motor part

[0079] 11 Transmission part

[0080] 12 Separation section

[0081] 13 Sealing member

[0082] 14 Gear

[0083] 15 Discharge device

[0084] 16 First contact device

[0085] 17 Second contact device

[0086] 18 Contact Room

[0087] 19 Conductive liquid

[0088] 20 Sleeve

[0089] 21 Ground rod

[0090] 22 Sealing device

[0091] 22a, 22b Sealing lip

[0092] 23 Shell opening

[0093] 24 Axis opening

[0094] 25 Shell opening

[0095] 26 Contact part

[0096] 27 Sealing part

[0097] 28 Shoulder

[0098] 29 Form-fitting contour

[0099] 30 Pairing contours

[0100] 31 Fastening part

[0101] 32 Fastening devices

[0102] 33 Sealing element

[0103] 34 Bridge sleeve

[0104] 100 Main axis

[0105] 101 Axial direction

[0106] 102 Opposite axial direction

Claims

1. A discharge device (15) for discharging an electric charge and / or voltage via a shaft (4) of a drive train of a motor vehicle to a housing part (7), the housing part (7) delimiting a housing chamber (6), the discharge device comprising: a first contact device (16) for electrically and mechanically connecting to the shaft (4), a second contact device (17) for electrical and mechanical connection to the housing part (7), wherein: The first contact means (16) and the second contact means (17) are rotatable relative to each other about a main axis (100), One of the contact means (16) is in the form of a sleeve (20) and the other of the contact means (17) is in the form of a grounding rod (21), or one of the contact means (16) is in the form of a grounding rod and the other of the contact means (17) is in the form of a sleeve, The sleeve (20) has a contact chamber (18) with a conductive liquid (19), and the ground rod (21) is partially arranged in the sleeve (20) so that the ground rod (21) is immersed in the conductive liquid (19) in the contact chamber (18), The sleeve (20) and the ground rod (21) are electrically connected to each other through the added conductive liquid (19). It is characterized in that A bridging sleeve (34) is disposed in the contact chamber (18) and at least partially electrically bridges the distance between the ground rod (21) and the sleeve (20).

2. The discharge device (15) according to claim 1, characterized in that The bridging sleeve (34) is designed as a sliding bushing which forms a sliding bearing assembly and / or an emergency bearing assembly for the ground rod (21).

3. The discharge device (15) according to claim 1 or 2, characterized in that: The bridging sleeve (34) is mechanically and thus electrically conductively connected to the sleeve (20), so that the electrically conductive liquid (19) electrically conductively bridges a possible annular gap between the bridging sleeve (34) and the grounding rod (21).

4. Discharge device (15) according to any one of the preceding claims, characterized in that The conductive liquid (19) is designed as conductive oil, in particular transmission oil or grease, wherein the conductivity of the conductive liquid at 25° C. is less than 500 nS / m, in particular less than 300 nS / m, and especially less than 100 nS / m.

5. Discharge device (15) according to any one of the preceding claims, characterized in that The sleeve (20) has a radial shoulder (28) for delimiting the contact chamber (18), and the bridging sleeve (34) is fixed in the contact chamber (18) in an axial direction by means of the radial shoulder (28) in a form-fitting manner.

6. Discharge device (15) according to any one of the preceding claims, characterized in that The sleeve (20) has a sealing portion (27) for receiving a sealing device (22) and a contact portion (26) adjacent to the sealing portion (27) for forming the contact chamber (18), the grounding rod (21) being guided into the contact portion (26) in a sealed manner via the sealing portion (27).

7. The discharge device (15) according to claim 6, characterized in that A sealing device (22) for sealing the contact chamber (18), the sealing device (22) being received in the sealing portion (27) in the axial direction with respect to the main axis (100) in a form-fitting manner and / or in a frictional manner, and the grounding rod (21) being supported on the inner periphery of the sleeve (20) in a sealed manner via the sealing device (22).

8. Discharge device (15) according to any one of the preceding claims, characterized in that The sleeve (20) has a form-fitting contour (29) on its inner circumference, and the ground rod (21) has a mating contour (30) on its outer circumference, the form-fitting contour (29) and the mating contour (30) engaging with each other so that the ground rod (21) is fixed in the sleeve (20) to prevent it from being lost.

9. Discharge device (15) according to any one of the preceding claims, characterized in that The ground rod has a fastening portion (31) at an end, and the discharge device (15) has a fastening means (32) for releasably fastening the fastening portion (31) to the housing portion (7).

10. A powertrain for a motor vehicle, comprising an electric machine (1) with a rotor (2), the electric machine comprising a housing part (7), the housing part (7) defining a housing chamber (6), and the electric machine comprising a shaft (4), the shaft (4) being electrically and drivingly connected to the rotor (2) and being rotatably mounted in the housing chamber (6), the shaft (4) defining a main axis (100), characterized in that At least one discharge device (15) according to any one of the preceding claims, for discharging charge and / or voltage from the rotor (2) via the shaft (4) to the housing part (7).

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