Bypass device and rolling bearing device with a bypass device

Abstract

The invention relates to a bypass device (1) comprising a holder (2) and at least one electrically conductive bypass conductor (3), wherein the holder (2) and bypass conductor (3) are electrically connected to each other and the holder (2) serves to attach the bypass conductor to a first machine element (11) and also holds the bypass conductor (3). The bypass conductor (3) is formed from loop-stitched rovings (5) which are in contact with a second machine element (12) and the bypass conductor (3) comprises at least two different materials.

Description

Field of the invention

[0001] The invention relates to a bypass device and a rolling bearing device with a bypass device. Background of the invention

[0002] In many applications, for example, between the rotor shafts and housings of electric motors and generators, unwanted voltage potentials often arise. If countermeasures are not taken, these voltage potentials can discharge through the rolling bearings. The current flowing through the affected rolling bearing can generate sparks in the rolling contact between the rolling elements and the raceways. The rolling raceways are damaged by melt pits or erosion pits.

[0003] Rotor shafts in electrical machines are usually supported by rolling bearings. Unwanted voltage potentials often arise between the rotor shafts and housings of electric motors and generators. If countermeasures are not taken, these voltage potentials discharge through the rolling bearings. The current flowing through the affected rolling bearing can generate sparks in the rolling contact between the rolling elements and the raceways. The rolling raceways are damaged by melt pits or erosion pits.

[0004] Measures are already known in the expert world to prevent the build-up of voltage potentials or the reduction of these voltage potentials in machine elements that rotate relative to one another. For example, bypass devices are used with which discharges are guided "around" the rolling bearings of the electric motor via so-called shaft grounding rings. DE 10 2016 010 926 A1 discloses such a bypass device consisting of a shaft grounding ring. This shaft grounding ring has a disk-shaped, electrically conductive bypass conductor, which is clamped towards the housing between two conductive angle plates and which rests against a shaft with elastic prestress on the inside. The angle plates forming the holder for the bypass conductor are inserted into a housing at any suitable location. The bypass conductor is made of conductive material that has low resistance to flowing currents.The advantage of such a bypass device is that the shaft grounding ring is simple and cost-effective to manufacture. DE 10 2021 114 964 A1 discloses a rolling bearing with a bypass device for transmitting electrical currents to a rotating component. The bypass device comprises a holder and an electrically conductive bypass conductor.

[0005] Bypass conductors are also often integrated into sealing devices by experts. An example of an upstream seal designed as a bypass conductor is disclosed in DE 10 2014 010 269 B4. The upstream seal is connected in series upstream of a main seal and, as a bypass conductor, simultaneously establishes an electrically conductive connection between two machine elements. The disc-shaped bypass conductor also protects the sealing lip of the main seal against environmental contaminants and is attached to the main seal. The main seal is seated in the housing with a holder formed from an angled sheet.

[0006] In general, rolling bearing manufacturers are interested in using such bypass conductors in the direct and immediate vicinity of rolling bearings, which can be exposed to the damage described above due to the reduction of voltage potentials. Furthermore, the bypass conductors should be installed in the most space-saving manner possible. Therefore, such bypass conductors are integrated, for example, into the main seals of rolling bearings. Such a device is disclosed in DE 10 2015 224 044 A1. The main seal used in this device is filled with conductive filler.

[0007] DE 10 2021 123 477 A1 discloses a potential equalization arrangement in which a thread made of the same or different fibers is used. Description of the invention

[0008] The object of the invention is to provide an improved bypass device and an improved rolling bearing device which can be manufactured easily and cost-effectively and can be installed in a space-saving manner.

[0009] The problem is solved according to the subject matter of claim 1 and claim 8.

[0010] The bypass device is intended for transmitting electrical currents to a rotating component. The bypass device comprises a holder and at least one electrically conductive bypass conductor, and the holder and the bypass conductor are electrically connected to one another. The holder serves to attach the bypass conductor to a first machine element and holds the bypass conductor. The holder can comprise one or more retaining rings and one or more retaining discs.

[0011] According to the invention, it is provided that the bypass conductor is formed from loop-shaped embroidered rovings, wherein the loop-shaped embroidered rovings are in contact with a second machine element and the loop-shaped embroidered rovings comprise fibers and the bypass conductor has at least two different materials.

[0012] A roving is a bundle, strand, or multifilament yarn composed of parallel filaments or fibers. Parallel doesn't necessarily mean straight, but naturally also curved. The rovings are knitted in loops, which not only provides ideal fixation but also allows them to be formed into a single component ideal for transmitting electrical currents in rotating components.

[0013] It has been found that loop-shaped interlacing prevents wear and is particularly suitable for conditions involving lubricant contact. The loop-shaped interlacing rovings of the bypass conductor can, for example, be interlaced in a meander shape or in a double meander shape. As mentioned above, such meander shapes are particularly suitable for conducting electrical currents despite lubricant contact. Furthermore, openings are formed that are permeable to media in so-called wet applications, i.e., when the ambient lubricant is to flow through the bypass device, for example, to lubricate a bearing or other machine element on the opposite side. The loop-shaped interlacing rovings can also be interlaced with another, concentrically arranged fiber bundle.This ensures even better fiber cohesion and prevents contamination of the bearing or the installation space of the rolling bearing assembly due to fiber loss. Furthermore, interlacing with another, concentrically arranged fiber bundle increases the rigidity of the bypass conductor, ensuring a centric fiber path for the current-conducting fibers.

[0014] Surprisingly, it has been found that the suitability of the bypass conductor can be further adapted to the necessary conditions if the loop-shaped rovings comprise fibers and the bypass conductor has at least two different materials.

[0015] In a preferred embodiment, the fibers of the loop-stitched rovings comprise different fiber materials. By combining different materials, fibers with particularly good mechanical properties, as well as those with particularly good electrical properties, can be combined. Thus, the loops can be constructed from rovings either of the same fiber material or as rovings made of different fiber materials, so-called hybrid rovings.

[0016] In another preferred embodiment, the fibers of the loop-stitched rovings comprise a fiber material, with the fibers having a coating made of a second material that differs from the fiber material. This allows the coating to be optimized with regard to its electrical properties. This also allows the use of particularly conductive coatings that would not be economically viable as a base material.

[0017] In a further preferred embodiment, each loop of the bypass conductor is constructed from fibers of the same fiber material. Thus, each loop is made of the same fiber material.

[0018] It is also conceivable, and in a preferred embodiment, for loops of the bypass conductor to be constructed from rovings of different materials. Thus, it is conceivable that loops made of rovings of a single fiber material are provided at regular or irregular intervals. Thus, for example, some loops can serve only as mechanical, elastic support with a preload that is as constant as possible over the service life, while others can conduct current. Regular spacing has the advantage of ensuring a uniform contact force across the circumference of the bypass device.

[0019] In a further advantageous embodiment, each loop comprises a roving comprising fibers made of at least two different fiber materials. Thus, the bypass conductor is formed from so-called hybrid rovings.

[0020] Precious metals are used in exceptional cases to improve the conductivity of bypass devices. Due to the high costs, this is usually disproportionate in series applications. In a preferred form of the proposed bypass conductor, one of the bypass conductor materials includes a precious metal. This allows for particularly high conductivity to be generated specifically and cost-effectively at the required locations. Furthermore, the conductivity can be precisely adapted to the necessary requirements.

[0021] The aforementioned bypass device is suitable for any application in which the transmission of electrical currents to a rotating component is intended or should be intended, for example, to mitigate damage to components caused by high voltage potentials. The bypass device is particularly suitable for use in a rolling bearing device, which is formed from at least one rolling bearing and a bypass device, and also has a third machine element and a fourth machine element. The rolling bearing has a first machine element in the form of a first bearing ring and a second machine element in the form of a second bearing ring, wherein the bearing rings are arranged concentrically on an axially aligned rotational axis of the rolling bearing.The rolling bearing is provided with rolling elements arranged radially between the bearing rings, wherein at least one electrical connection is formed between the third machine element and the fourth machine element via the aforementioned bypass device. The holder of the bypass device is fastened radially between one of the bearing rings and the third or fourth machine element to one of the bearing rings and holds the bypass conductor, wherein one of the bearing rings is fastened to the third or fourth machine element. The holder is seated, for example, on an outer ring radially between the outer ring and a housing or alternatively on an inner ring radially between the inner ring and a shaft. The holder has one or more retaining rings and one or more retaining disks. Furthermore, the bypass device comprises a bypass conductor according to one of the aforementioned embodiments or designs.

[0022] One or more bypass devices are integrated into the rolling bearing device. The advantage of the invention is that the bypass conductor is integrated into the rolling bearing and yet is attached to the rolling bearing in such a way that it is attached radially not inside the rolling bearing but in the bearing seat - i.e. on the outside of the rolling bearing between a housing or a shaft or other machine elements and one of the bearing rings of the rolling bearing. No separate axial installation space is required for attaching the bypass conductor. The radial installation space is already available due to the dimensions of the rolling bearing. This has a particularly positive effect on applications in rolling bearing devices with rolling bearings of small diameter series, in which there is little radial and axial installation space between the bearing rings for accommodating seals and bypasses. The limited space can be fully utilized to accommodate the bypass device.The components for attaching the bypass conductor therefore do not have to be as delicate and can therefore often be manufactured more cost-effectively.

[0023] The rolling bearing device comprises one or more rolling bearings. It is conceivable that the rolling bearing is sealed against the environment or surrounding structure with one or more seals. The bypass device is arranged on one side of the rolling elements in the axial direction. At least one electrical connection is formed at least between the first and second machine elements via the bypass device. It is therefore also conceivable that further electrically conductive connections between other machine elements are formed via the bypass device, either permanently or even preferably switchable on and off.

[0024] The bypass device consists of one or more holders and one or more electrically conductive bypass conductors. The holder sits in or on one of the bearing rings of the rolling bearing. It is thus integrated into the rolling bearing or into the bearing seat of the rolling bearing and can be located either on the inner or outer ring. The holder is a component of any design suitable for holding the bypass conductor in the rolling bearing.

[0025] The advantage is that the rolling bearing, including the bypass device, can be delivered as a single unit from the bearing manufacturer. This saves assembly time and storage space for both the customer and the bearing manufacturer. The properties of the bypass conductor can be precisely tailored to the bearing's contact resistance or discharge resistance.

[0026] The respective holder and the bypass conductor are electrically connected to each other. The holder is itself conductive, or the bypass conductor and the machine element are connected via a separate electrical conductor. Although not necessary due to the advantages of the proposed bypass conductor, a conductive sleeve can also be provided. Generally, the bypass device is designed so that voltage potentials are discharged via this bypass device and not via the rolling bearing.

[0027] Two machine elements are mounted so they can rotate relative to one another by means of at least one rolling bearing. One of the machine elements or the other machine element is mounted so it can rotate about the rotational axis of the rolling bearing by means of the rolling bearing, or one or the other machine element is fixed to the housing. Alternatively, both machine elements are arranged so they can rotate relative to one another about the rotational axis of the rolling bearing. Machine elements are shafts, for example rotor shafts of an electrical machine, housings, for example bearing shields or housings or housing sections or bearing shields of an electrical machine, gears or shafts or housings of a gearbox, or any other machine elements suitable for being mounted on or against one another by means of rolling bearings.

[0028] In the cases considered, the rotational axis of the rolling bearing is always axially aligned, but can be horizontal, vertical, or obliquely oriented in space. Radial is perpendicular to the rotational axis.

[0029] The rolling bearing is used to rotatably support machine parts, elements and assemblies. To reduce friction, it has rolling elements which roll between the inner and outer rings, thus reducing friction in the rotating bearing. As already explained, the rolling bearing has an inner ring and an outer ring. Alternatively, the rolling bearing can also have more than just an inner and / or outer ring. In addition, the bearing rings are also split and each have a raceway or part of a raceway. The inner ring usually has one or more outer raceways, and the outer ring has one or more inner raceways. The rolling elements rolling on the raceways can be balls or rollers. The balls or rollers are often guided and held in cages.The rolling elements of a rolling bearing are either arranged in a single row in the circumferential direction, one behind the other, or alternatively, the bearing has several rows of rolling elements arranged side by side. Rolling bearings can also be axial bearings. In this case, both the inner and outer rings are the axial discs, which have axial raceways.

[0030] In the context of the invention, a bypass is understood to mean the redirection of a current or voltage around one or more rolling bearings and / or machine parts. The rolling elements and bearing rings are usually made of bearing steel and touch each other at the raceways. The resulting contact zones are potential passageways for currents, where the dreaded discharges lead to the raceway damage described in the "Background of the Invention" chapter.

[0031] The currents are to be redirected through the bypass or bypass device. This can be "controlled" by ensuring that the bypass device, or in any case the bypass conductor, has comparatively lower electrical or specific electrical resistance than the rolling bearing.

[0032] The holder can have one or more retaining rings and one or more retaining disks. It is conceivable for the holder or the retaining ring to be provided with at least one, preferably several, recesses distributed circumferentially around the rotational axis of the rolling bearing and extending axially continuously through a substantially radially extending and annular disk-shaped base body. The retaining disk engages in the recess with at least one retaining clip and is held on the base body. The bypass conductor is held axially between the electrically conductive retaining ring and the retaining disk. The retaining clip or clips are latched or hooked into the recess in a form-fitting and / or force-fitting manner. Such an arrangement is advantageously easy to assemble. The individual parts of the holder can be manufactured inexpensively from sheet metal.

[0033] It is conceivable to design the retaining element or retaining ring of the rolling bearing device such that it has a plurality of clamps distributed around the circumference of one of the bearing rings, or the retaining elements are such clamps. These clamps are arranged radially between the bearing ring and the machine element, for example, between the outer ring and a housing or between the inner ring and a shaft, and thereby axially overlap the bearing ring and radially engage behind the bearing ring. The clamps are elastically spring-loaded and are radially preloaded against one of the bearing rings between one of the machine elements and one of the bearing rings.

[0034] The advantage of this is that the zones on the bearing ring to which the retaining ring is attached or against which the retaining elements are preloaded against the bearing ring do not need to be finely machined, because the retaining elements are at least radially elastically preloaded against this zone. The elasticity of the individual retaining elements is ensured by the fact that they are separated from one another circumferentially around the rotational axis of the rolling bearing by the axially continuous recesses. This extends the retaining elements from a base on the retaining ring by a radially extending elastic lever. In conjunction with a snap-in geometry, the retaining element can bridge large tolerances when pressed on and is securely fixed axially and radially. The retaining rings are easy and cost-effective to manufacture from sheet metal or spring steel.

[0035] It is conceivable that one or more clamping elements or retaining clips formed on the retaining disk or separately, each one or more than one, engage in one of the recesses and hold the retaining disk and the retaining ring together in a form-fitting manner. The bypass conductor is clamped axially between the clamping element and the holder or between the retaining disk and the retaining ring. The clamping element can, for example, be a simple clip that is inserted into the recess, or the clamping element or retaining clip can be formed on the retaining ring of the holder. Clamping elements are clamped detachably or permanently to the retaining ring, and retaining clips, for example, are clipped or snapped into the recesses in a form-fitting manner and can, under certain circumstances, also be detachable again.

[0036] It is conceivable that the holder, in contact with one of the bearing rings, rests electrically conductively against one of the bearing rings. The holder is made of electrically conductive material or has a conductive coating or is provided with conductive elements. It is crucial that an electrically conductive connection is formed between the machine element and the holder, either via the electrically conductive bearing ring or in direct contact with the holder. The bearing ring is made of a conductive material or has an electrically conductive coating. In this case, it can generally be assumed that the electrical resistance of the bypass device is lower than the electrical resistance passing through the rolling contacts of the rolling bearing.

[0037] The rolling contacts are the contacts at which the rolling elements rest on the raceways during operation or when the respective rolling bearing is at a standstill. The rolling contact zones are thus the zones in which the rolling elements roll along the raceways of the bearing rings during operation of the rolling bearing. The electrically conductive connection for discharging the voltage potentials between the first and second machine elements is established by means of the bypass device. As already mentioned at the beginning, the machine elements can be housings or shafts, or alternatively, other machine parts. It is conceivable that the fourth machine element is formed integrally with the inner ring of the rolling bearing. Thus, it is not impossible that, for example, in the case of a cylindrical roller bearing, the raceway of the rolling elements is directly the shaft, which in this sense represents the bearing ring and the fourth machine element in one piece.

[0038] The rolling elements of the rolling bearings concerned by the invention can be guided between the bearing ring with or without cage(s). A cage has one or two side edges. Cages with only one side edge are crown- and / or comb-shaped, i.e. cage webs protrude axially from the side edge like the points of a crown or the teeth of a comb. The circumferentially adjacent gaps between the points or teeth are the pockets in which the rolling elements are accommodated. The developed configuration of the cages is designed in imaginary flat planes like a perforated strip for balls and ladder-shaped for rollers. In both cases, the cage webs connect two side edges running parallel to one another. The gaps which appear hole- or window-shaped in the flat planes are three-dimensional pockets formed circumferentially between the cage webs, in which the rolling elements are accommodated.

[0039] As mentioned above, gearbox manufacturers often struggle for every millimeter of installation space. This also affects the requirements for rolling bearings, which consequently need to be designed to be as axially space-saving as possible. The aforementioned measure also contributes to saving axial installation space. This advantage results from the fact that the retaining elements of the retaining ring overlap the bearing ring in the axial direction and engage behind it radially. Description of the drawings

[0040] The invention is explained in more detail below using exemplary embodiments. They show: - Fig. 1 - a representation of the basic structure of the bypass device 1; - Fig. 2 - a representation of the bypass conductor 3 with loop-shaped embroidered rovings 5; - Fig. 3 - a representation of the bypass conductor 3 with loop-shaped embroidered rovings 5 ​​in a further embodiment; - Fig. 4 - a section of an embodiment of the bypass conductor 3; - Fig. 5 - a section through a roving 5 as a possible embodiment; - Fig. 6 - a rolling bearing arrangement 20 in a partial section along the rotation axis 16;

[0041] Fig. 1 - The bypass device 1 comprises a holder 2 and an electrically conductive bypass conductor 3. The bypass conductor 3 can be held by means of a holding disc 4 or holding elements 4 formed from the holder 2. The holder 2 serves to fasten the bypass conductor to a first machine element, which is Fig. 1 is not shown in detail. The bypass conductor 3 is in Fig. 1 is shown only in its basic position, but not in its intended configuration, i.e., consisting of loops. The bypass device 1 serves to transmit electrical currents to a rotating component that rotates about the rotation axis 16. It is also conceivable, although usually implemented differently, that the bypass device is arranged on the rotating machine element.

[0042] Fig. 2 - Fig. Figure 2 shows the basic structure of the bypass conductor 3, which is formed from loop-shaped, interwoven rovings 5. The bypass conductor 3 is shown schematically with regard to its structure. The loop-shaped, interwoven rovings 5 ​​of the bypass conductor 3 can be interwoven in a meander pattern. The loops 6 are formed toward the bypass conductor center M. Furthermore, a concentrically arranged, interwoven roving 7 is shown as an example, which can serve to improve fiber cohesion.

[0043] Fig. 3 - The bypass conductor 3 is shown schematically with regard to its structure. Here, the loop-shaped, embroidered rovings 5 ​​of the bypass conductor 3 are embroidered in a double meander pattern. This represents an ideal way to implement the at least two different materials of the bypass conductor 3. This design also shows another, concentrically arranged, embroidered roving 7.

[0044] Fig. 4 - A possible structure of the bypass conductor 3 is shown Fig. 4. Here, the bypass conductor 3 comprises two different materials. In this embodiment, each loop 6 of the bypass conductor 3 is formed from a roving 5 made of fibers of exclusively the same fiber material. The individual loops 6 of the bypass conductor 3 are constructed from rovings 5 ​​of a different fiber material. In the example shown, a loop made of a roving 5 of one fiber material alternates with one made of a different fiber material.

[0045] Fig. 5 - The bypass conductor 3 is shown schematically in a sectional view with respect to another conceivable structure. Here, the bypass conductor 3 comprises two different materials, in that the fibers 8 of the loop-shaped, stitched rovings 5 ​​comprise different fiber materials, thus forming a so-called hybrid roving.

[0046] Fig. 6 - The rolling bearing device 9 is made of the Fig. 6, the bypass device 1, as well as a third machine element 13 and a fourth machine element 14. The rolling bearing 10 has a first machine element 11 in the form of a first bearing ring 25 and a second machine element 12 in the form of a second bearing ring 26, wherein the bearing rings 25, 26 are arranged concentrically on an axially aligned rotational axis 16 of the rolling bearing 10. The rolling bearing 10 is provided with rolling elements 17 arranged radially between the bearing rings 25, 26. At least one electrical connection is formed between the third machine element 13 and the fourth machine element 14 via the bypass device 1. The holder 2 of the bypass device 1 is fixed radially between one of the bearing rings 25, 26 and the third or fourth machine element 13, 14 to one of the bearing rings 25, 26 and holds the bypass conductor 3.The holder 2 can be formed in one piece, for example by holding the bypass conductor 3 by bent holding elements 4, or can have a further component 12 that holds the bypass conductor 3. One of the bearing rings 25, 26 can be fastened to the third or fourth machine element 13, 14, wherein in . Fig. 6, the bearing ring 25 is attached to the first machine element 11. It is conceivable that the fourth machine element 14 is formed integrally with the inner ring 26 of the rolling bearing. Thus, it is not excluded that, for example, in the case of a cylindrical roller bearing or a cylindrical roller set, the raceway of the rolling elements is directly the shaft 15, which, in this sense, then represents the bearing ring 26 and the fourth machine element 14 in one piece. Reference symbol 1 bypass device 2 holders 3 bypass conductors 4 holding elements 5 loop-shaped embroidered rovings 6 loops 7 Concentrically arranged, knitted roving 8 fibers 9 Rolling bearing device 10 rolling bearings 11 First machine element 12 Second machine element 13 Third machine element 14 Fourth machine element 15 Wave 16 Rotation axis of the rolling bearing 17 rolling elements 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 First bearing ring (outer ring) 26 Second bearing ring (inner ring) M Center of the bypass conductor

Claims

[1] Bypass device (1) for transmitting electrical currents to a rotating component, wherein the bypass device (1) comprises a holder (2) and at least one electrically conductive bypass conductor (3), and wherein the holder (2) and bypass conductor (3) are electrically connected to each other, wherein the holder (2) serves to fasten the bypass conductor (3) to a first machine element (11) and holds the bypass conductor (3), characterized by that the bypass conductor (3) is formed from loop-shaped rovings (5), wherein the loop-shaped rovings (5) are in contact with a second machine element (12), and the loop-shaped embroidered rovings (5) comprise loops (6) made of fibers (8) and the bypass conductor (3) has at least two different materials. [2] Bypass device (1) according to claim 1, characterized bythat the fibers (8) of the loop-shaped embroidered rovings (5) have different fiber material. [3] Bypass device (1) according to claim 1 or 2, characterized by that the fibers (8) of the loop-shaped embroidered rovings (5) have a fiber material and a coating made of a second material different from the fiber material. [4] Bypass device (1) according to claim 1 or 3, characterized by that each loop (6) of the bypass conductor (3) is formed from fibers (8) of exclusively the same material. [5] Bypass device (1) according to claim 1, characterized by that loops (6) of the bypass conductor (3) are made of rovings (5) of different materials. [6] Bypass device (1) according to claim 1, characterized by that each loop (6) consists of a roving (5) which has fibres (8) of at least two different fibre materials. [7] Bypass device (1) according to one of the preceding claims, characterized by that a material of the bypass conductor (3) comprises a precious metal. [8] Rolling bearing device (9) which is formed from at least one rolling bearing (10) and a bypass device (1) and also comprises a third machine element (13) and a fourth machine element (14), wherein: the rolling bearing (10) has a first machine element (11) in the form of a first bearing ring (25) and a second machine element (12) in the form of a second bearing ring (26), and wherein the bearing rings (25, 26) are arranged concentrically on an axially aligned axis of rotation (16) of the rolling bearing (10), the rolling bearing (10) is provided with rolling elements (17) arranged radially between the bearing rings (25, 26), wherein at least one electrical connection is formed between the third machine element (13) and the fourth machine element (14) via the bypass device (1), wherein the holder (2) is fixed radially between one of the bearing rings (25, 26) and the third or fourth machine element (13, 14) to one of the bearing rings (25, 26) and holds the bypass conductor (3), wherein one of the bearing rings (25, 26) is fixed to the third or fourth machine element (13, 14), and the bypass device (1) comprises a bypass conductor (3) according to any one of claims 1-7. [9] Rolling bearing device (1) according to claim 8, characterized by that the holder (2) is fixed radially between the first bearing ring (25) and the third machine element (13) and the fourth machine element (14) is formed integrally with the second bearing ring (26).

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