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

Abstract

The invention relates to a bypass device (2) for transmitting electrical currents to a rotating component, said 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) is designed to contact a first bearing ring (7) or an intermediate component (8), and the second portion (5) is designed to contact a second bearing ring (9), wherein 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), wherein the first portion (4) forms a seat region for the flexurally elastic, arc-shaped machine element (3) and the second portion (5) forms a dynamic contact region (10), wherein the flexurally elastic, arc-shaped machine element (3) has, in the dynamic contact region (10), a cross section (B-B) or a longitudinal section (F-F), wherein the flexurally elastic, arc-shaped machine element (3) has, in the dynamic contact region (10), a cross section (B-B) with a basic shape (GF), and the basic shape (GF) of the cross section (B-B) of the flexurally elastic, arc-shaped machine element (3) has an additional conductive layer (6) applied to it at least in the dynamic contact region (10).

Description

[0001] Title of the invention

[0002] Bypass device, rolling bearing with a bypass device and method for discharging electrostatic charges on a rolling bearing

[0003] Field of the invention

[0004] The invention relates to a bypass device, a rolling bearing with a bypass device and a method for discharging electrostatic charges on a rolling bearing.

[0005] Background of the invention

[0006] 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.

[0007] Measures are already known in the field to prevent the buildup 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 of the bypass conductor are inserted into a housing at any suitable location. The bypass conductor is made of a 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 inexpensive to manufacture.

[0008] Bypass conductors are also popular among experts in sealing devices. An example of a bypass seal is disclosed in DE 10 2014 010 269 B4. The bypass 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.

[0009] 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 housed in the most space-saving manner possible. Therefore, such bypass conductors are integrated, for example, into the main seals of rolling bearings. One such device is disclosed in DE 10 2015 224 044 A1. The main seal used in this device is filled with conductive filler. Description of the invention

[0010] The object of the invention is to provide an improved bypass device and to propose an improved method for discharging bearing currents.

[0011] This 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 comprises a flexurally elastic, arcuate machine element with a first section and a second section, wherein the first section is designed to bear against a first bearing ring or an intermediate component, and the second section is designed to bear against a second bearing ring. An electrically conductive connection can be formed between the first bearing ring and the second bearing ring by means of the flexurally elastic, arcuate machine element.The first section forms a seating area for the flexurally elastic, curved machine element, and the second section forms a dynamic contact area. The flexurally elastic, curved machine element has a cross-section with a basic shape in the dynamic contact area, and an additional conductive layer is applied to the basic shape of the cross-section of the flexurally elastic, curved machine element, at least in the dynamic contact area. The basic shape refers to the supporting shape of the flexurally elastic, curved machine element, i.e., the element itself, excluding the coating. Contact elements for current transmission are generally constructed as simply as possible, also due to their small dimensions. They are made, for example, from metallic, highly conductive materials or metallic alloys.

[0012] It is also known to manufacture the conductor from carbon due to its good conductivity. One such process is pyrolytic deposition. It is conceivable to form the base material primarily from carbon fibers, forming a fiber mesh, fiber felt, and / or fiber fleece coated with pyrolytic carbon. By coating with pyrolytic carbon, the carbon fibers can be fixed in a desired shape. Although the term "coating" is often used, this merely describes the production of the basic form of the conductor. It is known that the conductor is formed by shaping the fiber mesh or by cutting the conductor out of a fiber mesh, for example, from a plate, and is essentially rigid.It is not intended that abrasion of this basic shape occurs, since it is known that wear of the bearing rings due to the contact arrangement can be neglected.

[0013] What all known current-conducting elements, i.e., bypass conductors, have in common is that the critical area, i.e., the area that determines the electrical resistance of the entire bypass, is the dynamic contact area. Due to the counter-surface, which is not highly conductive (for example, because it is made of standard roller bearing steel), silver sleeves or silver coatings are often used to improve its conductivity.

[0014] Surprisingly, it has been found that the previously mentioned measures to improve conductivity in the dynamic contact area can be dispensed with if the curved machine element has a cross-section with a basic shape in the dynamic contact area and an additional conductive layer is applied to the basic shape of the cross-section of the flexurally elastic, curved machine element, at least in the dynamic contact area. This layer is applied externally so that it can be at least partially worn away during operation. Therefore, infiltration or filling of the base material with the layer, i.e. the material of the basic shape, must be avoided. The task of this additional conductive layer is to deposit itself on the mating surface through its own wear and, similar to a coating, to significantly improve the dynamic contact conductivity of the mating surface.One advantage is that the electrical resistance is even lower than with comparable silver sleeves, as the latter has a larger contact surface, which, although not dynamically formed, is inevitably created at its seat. Furthermore, coating the conductor is significantly more cost-effective, both in terms of production and due to the elimination of the assembly process for such a sleeve.

[0015] As previously stated, the bypass device can be used to create an electrical connection between two machine elements, for example, two bearing rings. In a preferred embodiment, the intermediate component can be designed as a metallic disc, for example, a cover disc, a metallic sealing disc, or a conductive dust cover. This represents an ideal way to combine a pronounced sealing effect with particularly good conductivity.

[0016] In a further preferred embodiment, the basic shape of the flexurally elastic, curved machine element is a carbon fiber arrangement comprising a fiber mesh, fiber felt, and / or fiber fleece provided with a coating of pyrolytically deposited carbon. This combines the particularly good conductivity of the carbon conductor with a coating, with a reduction in the electrical contact resistance in the dynamic contact area. In a further advantageous embodiment of the bypass device, the additional conductive layer of the flexurally elastic, curved machine element comprises silver components. Silver is particularly suitable for such a layer because it has ideal strength and adheres perfectly to the counter-running surface.

[0017] It is further preferred that the flexurally elastic, curved machine element has a cross-section in the dynamic contact area which, in the cross-section or longitudinal section of the flexurally elastic, curved machine element, has a geometrically defined depression, at least in the dynamic contact area. A defined depression within the meaning of the invention is any uniform geometry, such as a circle, a rectangle, or the like, or a combination thereof. This can be achieved either as a profiled notch or following the principle of a screw thread over the circumference of the conductor. Such geometrically defined depressions in the cross-section also promote the absorption of further material, which, in the dynamic contact area, ideally adheres both to the flexurally elastic, curved machine element and to the contact surface.

[0018] Generally, due to their typically small size and for cost reasons, electrical conductors are designed with a uniform, i.e., consistently homogeneous, cross-section. Round, rounded, or angular shapes are conceivable. Surprisingly, however, it has been found that flexurally elastic, curved machine elements with geometrically defined recesses, especially in the contact area, exhibit special properties. For example, as previously described, material with increased conductivity of the counter-surface can be embedded in the recess, ensuring consistent, improved conductivity of the conductor in the dynamic contact area, or such material can already be provided in the notch.In a further preferred embodiment, the flexurally elastic, arcuate machine element has an additional element which is introduced into the geometrically defined recess of the flexurally elastic, arcuate machine element and which establishes the electrical contact.

[0019] Preferably, the additional element can protrude beyond the contour, i.e., beyond the maximum projecting outer contour of the flexurally elastic, curved machine element, thus establishing electrical contact with the second bearing ring during use. Thus, the contact can be made of a particularly conductive and / or a particularly low-friction and wear-resistant material. The advantage here is that the aforementioned material does not necessarily have to have the same properties as the flexurally elastic, curved machine element.

[0020] It is also conceivable that, in a further advantageous development, the additional element is introduced into the flexurally elastic, curved machine element as a separately formed insert.

[0021] From a manufacturing point of view, it may also be particularly suitable if the geometrically defined recess of the cross-section of the flexible, curved machine element of the bypass device has the shape of a circular sector.

[0022] For the provision and introduction of the additional element, it can also be particularly advantageous if the geometrically defined recess of the cross-section of the flexurally elastic, curved machine element of the bypass device has the shape of a rectangle in the base of the recess. Thus, a geometrically particularly simple additional element can be introduced into the flexurally elastic, curved machine element. The rolling bearing according to the invention has a discharge device according to the invention. Further advantageous embodiments of the rolling bearing emerge from the feature descriptions of the subclaims referring back to device claim 1.

[0023] Two machine elements are mounted relative to each other by means of rolling bearings. One of the machine elements or the other machine element is mounted by the rolling bearing for rotation about the rotational axis of the rolling bearing, or one or the other machine element is fixed to the housing. Alternatively, both machine elements are arranged for rotation relative to each other about the rotational axis of the rolling bearing. Machine elements include 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 against or against each other by means of rolling bearings.

[0024] 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.

[0025] 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 accordingly 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 rolling 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 washers, which have axial raceways.

[0026] For the purposes of the invention, bypassing refers to 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 already described in the "Background of the Invention" chapter.

[0027] 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.

[0028] In the proposed method for discharging electrostatic charges on a rolling bearing, the aforementioned bypass device is used, wherein the conductor is formed with a first section and a second section which form a contact arrangement on the rolling bearing, wherein the first section is applied to a first bearing ring or an intermediate component and the second section is applied to a second bearing ring of the rolling bearing, such that an electrically conductive connection is formed between the first bearing ring and the second bearing ring by means of the conductor, wherein the bypass device is formed from a flexurally elastic, arc-shaped machine element.The flexurally elastic, arcuate machine element has a cross-section with a basic shape in the dynamic contact area, wherein an additional conductive layer is applied to the basic shape of the cross-section of the flexurally elastic, arcuate machine element, at least in the dynamic contact area, which additional conductive layer is intended to adhere to the counter surface and thereby improve the conductivity.

[0029] Regarding the advantageous effects of the method according to the invention, reference is made to the description of the advantages of the discharge device according to the invention. Advantageous embodiments of the method emerge from the descriptions of the features of the dependent claims referring back to the device claim 1.

[0030] Description of the drawings

[0031] The invention is explained in more detail below using exemplary embodiments. They show:

[0032] Figure 1 - an arrangement with a bypass device in a front view;

[0033] Figure 2 - an arrangement with a bypass device in a front view in a preferred embodiment;

[0034] Figure 3 - Position of the relevant views of the flexible, curved machine element

[0035] Figure 4 - Cross section of the flexurally elastic, curved machine element in a preferred embodiment; Figure 5 - Cross and longitudinal section of the flexurally elastic, curved machine element in another preferred embodiment;

[0036] Figure 6 - Cross-section and longitudinal section of the flexible, curved machine element in a further embodiment;

[0037] Figure 7 - a rolling bearing with a possible arrangement of the bypass device;

[0038] Figure 1 - Figure 1 shows the basic structure of the bypass device 1. The bypass device 1 for transmitting electrical currents to a rotating component 2 comprises a flexurally elastic, arc-shaped machine element 3, with a first section 4 and a second section 5, wherein the first section 4 is designed to bear against a first bearing ring 7 and the second section 5 is designed to bear against a second bearing ring 9. By means of the flexurally elastic, arc-shaped machine element 3, an electrically conductive connection can be formed between the first bearing ring 7 and the second bearing ring 9. The first section 4 forms a seating area for the flexurally elastic, arc-shaped machine element 3 and the second section 5 forms a dynamic contact area 10. The shape of the flexurally elastic, arc-shaped machine element 3 shown is exemplary.It is conceivable that the form may differ from that shown, whereby the relevant sections 4 and 5 must be provided in their function.

[0039] Figure 2 - Figure 2 shows a further possible embodiment of the bypass device 1. Here, the section 4 for contact with the first bearing ring is designed such that it is formed at the two ends of the flexurally elastic, arc-shaped machine element 3, and the second section 5 for contact with a second bearing ring 9 is centrally implemented and, so to speak, divides the section 4 into two parts. Figure 3 - Figure 3 illustrates that the first section 4 of the flexurally elastic, arc-shaped machine element 3 can also be designed for contact with an intermediate component 8, as shown a cover plate, cover disk or metallic seal, which in turn contacts the first bearing ring 7.

[0040] Figure 4 - Figure 4 illustrates the position of the relevant views BB, CC and FF to illustrate the invention and the preferred embodiments as well as the viewing direction (view) for the corresponding views.

[0041] Figure 5 - Figure 5 shows the cross-section in section BB, wherein the flexurally elastic, curved machine element 3 can have a geometrically defined recess 11 in the cross-section or longitudinal section of the flexurally elastic, curved machine element 3, at least in the dynamic contact area. This can be done as a profiled notch, as in the illustrated embodiment as a circular segment. The cross-section BB of the flexurally elastic, curved machine element has a basic shape GF, to which an additional conductive layer 6 is applied, at least in the dynamic contact area 10.

[0042] Figure 6 - Figure 6 illustrates a further embodiment of the cross section BB of the flexurally elastic, curved machine element 3 of the bypass device 1. The flexurally elastic, curved machine element 3 has an additional element 12 in the geometrically defined recess 11, which establishes the electrical contact. The cross section BB of the flexurally elastic, curved machine element has a basic shape GF, to which an additional conductive layer 6 is applied, at least in the dynamic contact area 10. In view A, i.e. the view from the bearing center onto the flexurally elastic, curved machine element, this is an elongated area. If, in a preferred embodiment, this is filled, for example with an insert, made of particularly conductive and / or friction-minimizing material, it resembles a slice of pie.It is conceivable that this occurs only in the dynamic contact area 10, or also over the entire circumference of the flexurally elastic, arcuate machine element and directly establishes electrical contact with a first bearing ring 7 or an intermediate component 8. Figure 6 also illustrates that the additional element 12, in the illustrated, preferred embodiment, protrudes beyond the contour of the flexurally elastic, arcuate machine element 3. Thus, a distance s is formed in the cross-section between the outer end of the base material of the flexurally elastic, arcuate machine element 3 and the second bearing ring 9 or the rotating component 2.

[0043] Figure 7 - Figure 7 shows a rolling bearing 14 with a bypass device, in section CC, which illustrates the first section 4 of the flexurally elastic, arcuate machine element 3 with its one seating area on a first bearing ring 7, as well as section BB, wherein the second section 5 of the flexurally elastic, arcuate machine element 3 is designed to bear against a second bearing ring 9. It can also be seen that an additional conductive layer 6 is applied to the cross section B - B or the longitudinal section of the flexurally elastic, arcuate machine element 3, at least in the dynamic contact area 10. The bearing can also have one or more seals 15, as shown in Figure 7.

[0044] Reference symbol

Claims

Patent claims 1. Bypass device (1) for transmitting electrical currents to a rotating component (2), comprising a flexurally elastic, arcuate machine element (3) with a first section (4) and a second section (5), wherein the first section (4) is designed to bear against a first bearing ring (7) or an intermediate component (D) and the second section (5) is designed to bear against a second bearing ring (9), wherein an electrically conductive connection between the first bearing ring (7) and the second bearing ring (9) can be formed by means of the flexurally elastic, arcuate machine element (3), wherein the first section (4) forms a seating area for the flexurally elastic, arcuate machine element (3) and the second section (5) forms a dynamic contact area (10), and wherein the flexurally elastic, arcuate machine element (3) has a cross-section (BB) with a basic shape (GF) in the dynamic contact area (10), characterized in thatthat an additional conductive layer (6) is applied to the basic shape (GF) of the cross-section (BB) of the flexurally elastic, arc-shaped machine element (3) at least in the dynamic contact area (10).

2. Bypass device (1) according to claim 1, characterized in that the intermediate component (D) can be designed as a metallic disc.

3. Bypass device (1) according to 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 which has a fiber mesh, fiber felt and / or fiber fleece which is provided with a coating of pyrolytically deposited carbon.

4. Bypass device (1) according to one of the preceding claims, characterized in that the additional conductive layer (6) of the flexurally elastic, arcuate machine element (3) comprises components of silver.

5. Bypass device (1) according to one of the preceding claims, characterized in that the cross section (BB) or the longitudinal section (FF) of the flexurally elastic, arcuate machine element (3) has a geometrically defined recess (11) at least in the dynamic contact area (10).

6. Bypass device (1) according to claim 5, characterized in that the flexurally elastic, arcuate machine element (3) has an additional element (12) in the geometrically defined recess (11) which establishes the electrical contact.

7. Bypass device (1) according to claim 3, characterized in that the additional element (12) projects beyond the contour (K) of the flexurally elastic, arcuate machine element (3).

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

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

10. A method for discharging electrostatic charges on a rolling bearing (14), comprising a rolling bearing (14) and a bypass device (1), wherein the bypass device is formed with a flexurally elastic, arcuate machine element (3), having a first section (4) and a second section (5) which form a contact arrangement on the rolling bearing (14), wherein the first section (4) is applied to a first bearing ring (7) or an intermediate component (D) and the second section is applied to a second bearing ring (9) of the rolling bearing (14), such that by means of the flexurally elastic, arcuate machine element (3) an electrically conductive connection is formed between the first bearing ring (7) and the second bearing ring (9), characterized in that the bypass device (1) is formed from a flexurally elastic, arcuate machine element (3), wherein the flexurally elastic,arcuate machine element (3) in the dynamic contact area (10) has a cross-section (BB) with a basic shape, wherein an additional conductive layer (6) is applied to the basic shape of the cross-section (BB) of the flexurally elastic, arcuate machine element (3) at least in the dynamic contact area (10), which is intended to be deposited on the counter surface and thereby improve the conductivity.

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