Bypass device, rolling bearing comprising bypass device, and method for discharging electrostatic charges in rolling bearing

Abstract

The invention relates to a bypass device (2) for transmitting an electric current to a rotating component, comprising a flexurally elastic arc-shaped machine element (3) having a first portion (4) and a second portion (5), the first portion (4) being designed to contact a first bearing ring (7) or an intermediate component (8) and the second portion (5) being designed to contact a second bearing ring (9), the second portion (5) being designed to contact a second bearing ring (9). The flexurally elastic arc-shaped machine element (3) can establish an electrically conductive connection between the first bearing ring (7) and the second bearing ring (9), the first part (4) forming a seat region of the flexurally elastic arc-shaped machine element (3) and the second part (5) forming a dynamic contact region (10), the flexurally elastic arc-shaped machine element (3) has a cross-section (B-B) or a longitudinal cross-section (F-F) in the dynamic contact region (10), the flexurally elastic arc-shaped machine element (3) has a cross-section (B-B) with a basic shape (GF) in the dynamic contact region (10), and at least in the dynamic contact region (10), the flexurally elastic arc-shaped machine element (3) has a longitudinal cross-section (F-F). The basic shape (GF) of the cross-section (B-B) of the flexurally elastic arc-shaped machine element (3) has an additional electrically conductive layer (6) applied thereto.

Description

TECHNICAL FIELD

[0001] The present application relates to a bypass device, a rolling bearing having a bypass device, and a method for discharging electrostatic charges in a rolling bearing. BACKGROUND

[0002] In many applications, for example between a rotor shaft and a housing of an electric motor and a generator, undesired voltage potentials often arise. If no countermeasures are taken, these voltage potentials can discharge via a rolling bearing. The current flowing through the affected rolling bearing can produce sparks in the rolling contact between the rolling elements and the raceways. The rolling raceways are damaged by molten recesses or erosion recesses.

[0003] Measures are already known in the technical field which are intended to prevent the build-up of voltage potentials or the discharge of these voltage potentials in machine elements which move in rotation relative to one another. For example, bypass devices are used by means of which the discharge is guided in a bypass manner via so-called shaft grounding rings "around” the rolling bearings of an electric motor. DE 10 2016 010 926 A1 discloses such a bypass device which comprises a shaft grounding ring. The shaft grounding ring has a disc-shaped, electrically conductive bypass conductor which is clamped between two electrically conductive angle plates facing the housing and rests on the shaft in an internally spring-loaded manner. The angle plates forming the holder of the bypass conductor are inserted into the housing at any suitable point. The bypass conductor comprises an electrically conductive material which has a lower resistance to the flow of current. The advantage of such a bypass device is that the shaft grounding ring is simple and inexpensive to manufacture.

[0004] Experts also like to incorporate the bypass conductor into a sealing device. An example of a buffer seal designed as a bypass conductor is disclosed in DE 10 2014 010 269 B4. The pre-seal is connected in a sealing manner in series upstream of the main seal and at the same time establishes an electrically conductive connection between the two machine elements in the manner of a bypass conductor. The disc-shaped bypass conductor is also intended to protect the sealing lip of the main seal from contaminants from the environment and is fastened to the main seal. The main seal is seated in the housing by means of a holder formed by the angle plates.

[0005] In general, bearing manufacturers are interested in using such a bypass conductor in the immediate vicinity of the rolling bearing region, which can be exposed to the damage described at the outset as a result of the discharge of voltage potentials. In addition, the bypass conductor should be accommodated in such a way that the demand on space is minimized. This is the reason for incorporating such a bypass conductor into, for example, the main seal of a rolling bearing. Such an arrangement is disclosed in DE 10 2015 224 044 A1. The main seal used in this device is mixed with an electrically conductive filler. SUMMARY

[0006] The object of the present invention is to form an improved bypass device and to propose an improved method for releasing bearing currents.

[0007] The object is achieved according to the subject matter of claim 1. According to the invention, the bypass device for transmitting electrical currents to a rotating component is designed as a flexurally elastic arc-shaped machine element comprising a first portion and a second portion, wherein the first portion is designed to contact a first bearing ring or an intermediate component and the second portion is designed to contact a second bearing ring. The flexurally elastic arc-shaped machine element can establish an electrically conductive connection between the first bearing ring and the second bearing ring. The first portion forms a seating region of the flexurally elastic arc-shaped machine element and the second portion forms a dynamic contact region, wherein the flexurally elastic arc-shaped machine element has a basic shape in cross section in the dynamic contact region and at least in the dynamic contact region the basic shape of the cross section of the flexurally elastic arc-shaped machine element has an additional electrically conductive layer applied to the basic shape. The basic shape refers to the bearing shape of the flexurally elastic arc-shaped machine element, i.e. the element itself without coating.

[0008] Generally, the contact elements for transmitting electrical currents are designed to be as simple as possible to some extent due to their small size. These contact elements are made of, for example, metal, highly conductive material or metal alloy.

[0009] It is also known to manufacture the conductor from carbon, since carbon is a good conductor. For this purpose, for example, a pyrolytic deposition process is used. It is conceivable that the basic material is formed mainly from carbon fibers, which form a fiber web, a fiber mat and / or a fiber fleece coated with pyrolytic carbon. The coating with pyrolytic carbon allows the carbon fibers to be fixed in the desired shape. Although the term "coating" is frequently used here, it only describes the generation of the basic shape of the conductor. It is known that the conductor is formed by shaping the fiber web or cutting the conductor out of the fiber web, for example from a plate, and that the conductor is essentially rigid. It is not intended that this basic shape is subjected to any wear, since the bearing ring wear caused by the contact arrangement is known to be negligible.

[0010] A common feature of all known electrically conductive elements, i.e. bypass conductors, is that the critical region, i.e. the region that determines the resistance of the entire bypass, is the dynamic contact region. Since the counter surfaces are not highly conductive, for example because they are made of conventionally used rolling bearing steel, a silver sleeve or a silver coating is often used to improve the electrical conductivity.

[0011] Surprisingly, it has been found that the measures described above for increasing the electrical conductivity of the dynamic contact area can be omitted if the arc-shaped machine element has a cross-section with a basic shape in the dynamic contact area and at least in the dynamic contact area an additional electrically conductive layer is applied to the basic shape of the cross-section of the flexurally elastic arc-shaped machine element. This layer is applied on the outside so that it can at least partially wear off during operation. Therefore, a penetration or filling of the basic material with the layer, i.e. the basic form of the material, should be avoided. The purpose of this additional electrically conductive layer is to adhere to the counter surface by its own wear and to significantly improve the dynamic contact conductivity of the counter surface, similar to a coating. The advantage of this is that the electrical resistance is even lower compared to a silver sleeve with a similar additional contact surface, which, although not dynamically formed, inevitably occurs at its seat. Furthermore, the coated conductor is significantly more cost-effective in terms of production and due to the elimination of the assembly process of such a sleeve.

[0012] As already mentioned, an electrical connection can be formed between two machine elements, for example two bearing rings, using a bypass device. In a preferred embodiment, the intermediate part can be designed as a metal disc, for example a cover disc, a metal sealing disc or an electrically conductive dirt cover. This offers the ideal opportunity to combine a significant sealing effect with particularly good electrical conductivity.

[0013] In another preferred embodiment, the basic shape of the flexurally elastic arc-shaped machine element comprises a carbon fiber arrangement with a fiber braid, a fiber mat and / or a fiber fleece provided with a pyrolytic deposited carbon coating. This combines the particularly good electrical conductivity of the carbon conductor with a coating, thereby reducing the electrical contact resistance of the dynamic contact area.

[0014] In another advantageous embodiment of the bypass device, it is provided that the additional electrically conductive layer of the flexurally elastic arc-shaped machine element comprises a part made of silver. Silver is particularly suitable for such a coating because it has an ideal strength and adheres perfectly to the counter surface.

[0015] It is also preferred that the flexurally elastic arc-shaped machine element has a cross-section in the dynamic contact area, at least in the dynamic contact area in the cross-section or longitudinal section of the flexurally elastic arc-shaped machine element, which has a geometrically defined recess. For the purposes of the present invention, the defined recess is to be understood as any uniform geometric shape, such as a circular, rectangular or similar shape, or a combination thereof. This can be implemented as a profiled recess, or following the principle of a thread around the circumference of the conductor. This geometrically defined recess in the cross-section also promotes the absorption of another material, which ideally adheres to both the flexurally elastic arc-shaped machine element and the contact surface in the dynamic contact area.

[0016] Generally, due to the typical small size and for cost reasons, the electrical conductor is designed to have a uniform, i.e. consistently homogeneous, cross section. Circular, rounded or angular shapes can be envisaged. Surprisingly, however, it has proven that a flexurally elastic arc-shaped machine element having a geometrically defined recess, in particular in the contact region, exhibits special properties. For example, as mentioned above, a material which increases the electrical conductivity of the counter surface can be deposited in the recess and ensures a continuously improved electrical conductivity of the conductor in the dynamic contact region, or such a material can already be provided in the recess.

[0017] In a further preferred embodiment, the flexurally elastic arc-shaped machine element has an additional element which is inserted into the geometrically defined recess of the flexurally elastic arc-shaped machine element and establishes an electrical contact.

[0018] Preferably, the additional element can protrude beyond the contour, i.e. beyond the maximum protruding outer contour of the flexurally elastic arc-shaped machine element, and thus establishes an electrical contact with the second bearing ring during operation. This allows the contact to be formed from a material which is particularly electrically conductive and / or particularly smooth and low-wear. The advantage of this is that the above-mentioned material does not necessarily have to have the same properties as the flexurally elastic arc-shaped machine element must have.

[0019] It is also conceivable that, in a further advantageous development, the additional element is incorporated into the flexurally elastic arc-shaped machine element as a separately designed insert.

[0020] It can also be particularly suitable from the point of view of manufacturing engineering that the geometrically defined recess of the cross section of the flexurally elastic arc-shaped machine element of the bypass device has the form of a circular sector.

[0021] Furthermore, it can be particularly advantageous for the provision and insertion of the additional element that the geometrically defined recess of the cross section of the flexurally elastic arc-shaped machine element of the bypass device has a rectangular shape at the recess base. Thus, a geometrically very simple additional element can be incorporated into the flexurally elastic arc-shaped machine element.

[0022] The rolling bearing according to the application has a discharge device according to the application. Further advantageous embodiments of the rolling bearing result from the features of the dependent claims relating to the device claim 1.

[0023] The two machine elements are mounted such that they can be rotated relative to each other by means of the rolling bearing. In this case, one of the machine elements or the other machine element is mounted in a rotatable manner about the axis of rotation of the rolling bearing by means of the rolling bearing, or one machine element or the other machine element is fixed to the housing. Alternatively, both machine elements are arranged to be able to rotate relative to each other about the axis of rotation of the rolling bearing. The machine elements are: a shaft, for example a rotor shaft of an electric machine; a housing, for example an end shield or a housing, or a housing section or an end shield of an electric machine; a gearwheel or a shaft or a housing of a transmission; or any other machine element which is suitable for being mounted on or against each other by means of a rolling bearing.

[0024] In the cases considered, the axis of rotation of the rolling bearing is always axially oriented, but can extend horizontally or vertically and be inclined in space. Radially perpendicular to the axis of rotation.

[0025] Rolling bearings are used for the rotatable mounting of machine parts, elements and assemblies and have, in order to reduce friction, rolling elements which roll between an inner ring and an outer ring and thus reduce the friction in the rotatable bearing. As already described above, the rolling bearing has an inner ring and an outer ring. Alternatively, the rolling bearing also has more than one inner ring and / or outer ring. In addition, the bearing rings are also alternatively split and each have a raceway or a part of a raceway. One or more outer raceways are usually formed on the inner ring and correspondingly one or more inner raceways are formed on the outer ring. The rolling elements which roll on the raceways are balls or rollers. The balls or rollers are usually guided and held in a cage. The rolling elements of the rolling bearing are arranged in a row one after the other in the circumferential direction, or alternatively, the rolling bearing has multiple rows of rolling elements which are arranged next to each other. Alternatively, the rolling bearing is also an axial bearing. In this case, both the inner ring and the outer ring are axial discs with axial raceways.

[0026] In the context of the present invention, bypass is understood to be a diversion of the current or voltage around one or more rolling bearings and / or machine parts. The rolling elements and the bearing rings are usually made of rolling bearing steel and contact each other on the raceways. The contact area formed in this way is a potential channel for current in which the discharge of interest can lead to the damage to the raceways already described in the "BACKGROUND" section.

[0027] The current will be diverted via the bypass or bypass means. This can be "controlled" by the bypass means, on the one hand, or in any case, the bypass conductor has a relatively low or specific electrical resistance relative to the rolling bearing.

[0028] In the proposed method for discharging electrostatic charges in rolling bearings, the bypass device described above is used, wherein the conductor is formed by a first portion and a second portion which form a contact arrangement at the rolling bearing, wherein the first portion is designed to contact a first bearing ring or an intermediate part of the rolling bearing and the second portion is designed to contact a second bearing ring of the rolling bearing, so that the arc-shaped machine element which is flexible and elastic establishes an electrically conductive connection between the first bearing ring and the second bearing ring, wherein the bypass device is formed by the arc-shaped machine element which is flexible and elastic. The arc-shaped machine element which is flexible and elastic has a basic shape in cross section in the dynamic contact region, wherein at least in the dynamic contact region the basic shape of the cross section of the arc-shaped machine element which is flexible and elastic has an additional electrically conductive layer applied to the basic shape, which is arranged to adhere to the opposite surface and thereby improves the electrical conductivity.

[0029] Advantageous effects of the method according to the invention are referred to the description of the advantages of the current discharge device according to the invention. Advantageous embodiments of the method result from the description of the features of the dependent claims related to claim 1 of the device. BRIEF DESCRIPTION OF DRAWINGS

[0030] In the following, the invention is explained in more detail with reference to exemplary embodiments. In the drawings:

[0031] - Figure 1 - arrangement with bypass device in front view

[0032] - Figure 2 - arrangement with bypass device in preferred embodiment in front view

[0033] - Figure 3 - position of relevant views of the arc-shaped machine element which is flexible and elastic

[0034] - Figure 4 - cross section of the arc-shaped machine element which is flexible and elastic in a preferred exemplary embodiment

[0035] - Figure 5 - cross section and longitudinal section of the arc-shaped machine element which is flexible and elastic in another preferred exemplary embodiment

[0036] - Figure 6 - cross section and longitudinal section of the arc-shaped machine element which is flexible and elastic in another exemplary embodiment

[0037] - Figure 7 - rolling bearing with possible arrangement of a bypass device DETAILED DESCRIPTION

[0038] Figure 1 -Figure 1 The basic structure of the bypass device 1 is shown. The bypass device 1 for transmitting electrical current to the rotating component 2 comprises a flexurally elastic arc-shaped machine element 3 having a first portion 4 and a second portion 5, wherein the first portion 4 is designed to contact the first bearing ring 7 and the second portion 5 is designed to contact the second bearing ring 9. The flexurally elastic arc-shaped machine element 3 can establish an electrically conductive connection between the first bearing ring 7 and the second bearing ring 9. The first portion 4 forms a seating region of the flexurally elastic arc-shaped machine element 3 and the second portion 5 forms a dynamic contact region 10. The shape of the flexurally elastic arc-shaped machine element 3 is shown by way of example. It is conceivable that the form can differ from the shown form, whereby a corresponding portion 4 and portion 5 must be provided in terms of their functionality.

[0039] Figure 2 Figure 2 Another possible embodiment of the bypass device 1 is shown. Here, the portion 4 is designed to contact the first bearing ring, so that this portion is formed at both ends of the flexurally elastic arc-shaped machine element 3, and the second portion 5 contacting the second bearing ring 9 is realized in the middle and can be said to divide the portion 4 into two portions.

[0040] Figure 3 Figure 3 It is shown that the first portion 4 of the flexurally elastic arc-shaped machine element 3 can also be designed to contact an intermediate component 8, such as a cover plate, a cover disk or a metal seal, which in turn contacts the first bearing ring 7.

[0041] Figure 4 Figure 4 The positions of the relevant views B-B, C-C and F-F are shown in order to clarify the invention and the preferred embodiment and the viewing direction of the corresponding views.

[0042] Figure 5 Figure 5 A cross section on the section B-B is shown, wherein the flexurally elastic arc-shaped machine element 3 can have a geometrically defined recess 11 in the cross section or longitudinal section of the flexurally elastic arc-shaped machine element 3 at least in the dynamic contact region. The recess can be realized as a profiled recess, as a circular segment in the shown embodiment. The cross section B-B of the flexurally elastic arc-shaped machine element has a basic shape GF, on which an additional electrically conductive layer 6 is applied at least in the dynamic contact region 10.

[0043] Figure 6 Figure 6 ​​​​​A further embodiment of the cross section B-B of the flexurally elastic arc-shaped machine element 3 of the bypass device 1 is illustrated. The flexurally elastic arc-shaped machine element 3 has an additional element 12 in the geometrically defined recess 11, which establishes an electrical contact. The cross section B-B of the flexurally elastic arc-shaped machine element has a basic shape GF, on which a further electrically conductive layer 6 is applied at least in the dynamic contact area 10.

[0044] In the view A, i.e. the view from the bearing center to the flexurally elastic arc-shaped machine element, this is the elongated area. In the preferred embodiment, it resembles a slice of cake, if filled with an insert made of a material that is particularly electrically conductive and / or minimizes friction. It is conceivable that this only occurs in the dynamic contact area 10 or also over the entire circumference of the flexurally elastic arc-shaped machine element and establishes an electrical contact directly with the first bearing ring 7 or the intermediate part 8. Figure 6 It is further illustrated that the additional element 12 protrudes beyond the contour of the flexurally elastic arc-shaped machine element 3 in the preferred embodiment shown. Thus, in cross section, a distance s is formed between the outer end of the basic material of the flexurally elastic arc-shaped machine element 3 and the second bearing ring 9 or the rotating part 2.

[0045] Figure 7 — Figure 7 A rolling bearing 14 with bypass device is shown in the cross section C-C and in the cross section B-B, the cross section C-C illustrates the first part 4 of the flexurally elastic arc-shaped machine element 3 and its seating area on the first bearing ring 7, in the cross section B-B the second part 5 of the flexurally elastic arc-shaped machine element 3 is designed to contact the second bearing ring 9. It is also apparent that the cross section B-B or longitudinal section of the flexurally elastic arc-shaped machine element 3 has the applied additional electrically conductive layer 6 at least in the dynamic contact area 10. The bearing can also have one or more seals 15, as Figure 7 is shown.

[0046] Reference signs

Claims

1. A bypass device (1) for transmitting electrical current to a rotating component (2), the bypass device comprising a flexurally elastic arc-shaped machine element (3) having a first portion (4) and a second portion (5), wherein the first portion (4) being designed to contact a first bearing ring (7) or an intermediate component (D) and the second portion (5) being designed to contact a second bearing ring (9), wherein the flexurally elastic arc-shaped machine element (3) is capable of establishing an electrically conductive connection between the first bearing ring (7) and the second bearing ring (9), wherein the first portion (4) forms a seating region of the flexurally elastic arc-shaped machine element (3) and the second portion (5) forms a dynamic contact region (10), and wherein the flexurally elastic arc-shaped machine element (3) has a cross section (B-B) with a basic shape (GF) in the dynamic contact region (10), characterized in that at least in the dynamic contact region (10) the basic shape (GF) of the cross section (B-B) of the flexurally elastic arc-shaped machine element (3) has an additional electrically conductive layer (6) applied to the basic shape.

2. The bypass device (1) according to claim 1, characterized in that The intermediate component (D) can be designed as a metal disc.

3. Bypass device (1) according to any one of the preceding claims, characterized in that The basic shape of the flexurally elastic arc-shaped machine element (3) comprises a carbon fiber arrangement having a fiber braid, a fiber mat and / or a fiber fleece provided with a pyrolytic deposited carbon coating.

4. The bypass device (1) according to any one of the preceding claims, characterized in that The additional electrically conductive layer (6) of the flexurally elastic arc-shaped machine element (3) comprises a component made of silver.

5. Bypass device (1) according to any one of the preceding claims, characterized in that At least in the dynamic contact region (10) the cross section (B-B) or longitudinal section (F-F) of the flexurally elastic arc-shaped machine element (3) has a geometrically defined recess (11).

6. The bypass device (1) according to claim 5, characterized in that The flexurally elastic arc-shaped machine element (3) has an additional element (12) establishing an electrical contact in the geometrically defined recess (11).

7. The bypass device (1) according to claim 3, characterized in that The additional element (12) protrudes beyond the contour (K) of the flexurally elastic arc-shaped machine element (3).

8. The bypass device (1) according to claim 3 or 4, characterized in that The additional element (11) is a separately formed insert.

9. A rolling bearing, characterized in that The rolling bearing (14) comprises a bypass device (1) according to any one of the preceding claims.

10. A method for discharging electrostatic charges in a rolling bearing (14), the method comprising a rolling bearing (14) and a bypass device (1), wherein, The bypass device is formed by a flexurally elastic arc-shaped machine element (3) having a first portion (4) and a second portion (5) forming a contact arrangement at the rolling bearing (14), wherein the first portion (4) is designed to contact a first bearing ring (7) or an intermediate component (D) of the rolling bearing (14) and the second portion is designed to contact a second bearing ring (9) of the rolling bearing, such that the flexurally elastic arc-shaped machine element (3) establishes an electrically conductive connection between the first bearing ring (7) and the second bearing ring (9), characterized in that The bypass device (1) is formed by a flexurally elastic arc-shaped machine element (3), wherein the flexurally elastic arc-shaped machine element (3) has a cross section (B-B) with a basic form (GF) in the dynamic contact region (10), wherein at least in the dynamic contact region (10) the basic form of the cross section (B-B) of the flexurally elastic arc-shaped machine element (3) has an additional electrically conductive layer (6) applied to the basic form, which is arranged to adhere to the opposite surface and thereby improves the electrical conductivity.

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