Bypass device, rolling bearing with a bypass device, and methods for dissipating electrostatic charges from a rolling bearing

Abstract

The invention relates to a bypass device (2) for transmitting electrical currents to a rotating component, comprising a flexible, arc-shaped machine element (3) with a first section (4) and a second section (5), wherein the first section (4) is designed to abut a first bearing ring (7) or an intermediate component (8) and the second section (5) is designed to abut 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 flexible, arc-shaped machine element (3), wherein the first section (4) forms a seating area for the flexible, arc-shaped machine element (3) and the second section (5) forms a dynamic contact area (10), wherein the flexible, arc-shaped machine element (3) has a cross-section (BB) or a longitudinal section (FF) in the dynamic contact area (10), characterized in thatthat the cross-section (BB) or the longitudinal section (FF) of the flexible, arc-shaped machine element (3) has a geometrically defined recess (11) at least in the dynamic contact area (10).

Description

Field of the invention

[0001] 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. 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] 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 inexpensive to manufacture.

[0004] 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.

[0005] 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. Description of the invention

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

[0007] 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 in the dynamic contact area that, in the cross-section or longitudinal section of the flexurally elastic, curved machine element, has a geometrically defined recess, at least in the dynamic contact area. A defined recess 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 implemented either as a profiled notch or following the principle of a screw thread over the circumference of the conductor.

[0008] Generally, due to their typically small size and cost considerations, 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 discovered that flexurally elastic, curved machine elements with geometrically defined recesses, especially in the contact area, exhibit special properties. For example, 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.

[0009] 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.

[0010] 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.

[0011] Preferably, the additional element can protrude beyond the 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.

[0012] 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.

[0013] From a manufacturing point of view, it is 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.

[0014] For the provision and insertion of the additional element, it is particularly advantageous if the geometrically defined recess of the cross-section of the flexible, curved machine element of the bypass device has a rectangular shape in the base of the recess. This allows a particularly simple geometrically designed additional element to be inserted into the flexible, curved machine element.

[0015] To ensure both low electrical contact resistance with the static contact partner, such as a first bearing ring or an intermediate additional element, and electrical contact with the rotating contact partner, such as a second bearing ring, the flexible, curved machine element of the bypass device can have a conductive coating, which, for example, consists of silver or contains silver components. A coating that also reduces the coefficient of friction of the flexible, curved machine element is also conceivable. This coating can be made of molybdenum sulfide, PTFE, antimony, etc.Since this coating can also reduce the electrical contact resistance in this area through its own wear and subsequent deposition in the geometrically defined recess of the cross-section of the flexurally elastic, curved machine element, a coating that is deposited on the outer surface and is not infiltrated into the conductor is particularly advantageous.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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 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.

[0020] For the purposes of the invention, bypassing refers to the diversion 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 damage to the raceways already described in the "Background of the Invention" chapter.

[0021] 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.

[0022] 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 in such a way 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, wherein the cross section of the flexurally elastic, arc-shaped machine element has a geometrically defined depression at least in the dynamic contact region.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. Description of the drawings

[0023] The invention is explained in more detail below using exemplary embodiments. They show: - Fig. 1 - an arrangement with a bypass device in a front view; - Fig. 2 - an arrangement with a bypass device in a front view in a preferred embodiment; - Fig. 3 - Position of the relevant views of the flexible, curved machine element; - Fig. 4 - Cross-section and longitudinal section of the flexurally elastic, curved machine element in a further preferred embodiment; - Fig. 5 - Cross section of the flexurally elastic, curved machine element in a further preferred embodiment; - Fig. 6 - Cross section of the flexurally elastic, curved machine element in further preferred embodiments; - Fig. 7 - another embodiment of the cross-section of the flexible, curved machine element; - Fig. 8 - a rolling bearing with a possible arrangement of the bypass device;

[0024] Fig. 1 - Fig. 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, 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 and the second section 5 is designed to bear against a second bearing ring 9. By means of the flexurally elastic, arcuate 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, arcuate machine element 3 and the second section 5 forms a dynamic contact area 10. The shape of the flexurally elastic, arcuate 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.

[0025] Fig. 2 - Fig. 2 shows in this regard a further possible embodiment of the bypass device 1. In this case, the section 4 for contact with the first bearing ring is designed in such a way 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 implemented centrally and, so to speak, divides the section 4 into two parts.

[0026] Fig. 3 - Fig. 3 illustrates that the first section 4 of the flexurally elastic, arcuate machine element 3 can also be designed to bear against an intermediate component 8, as shown a cover plate, cover disk or metallic seal, which in turn contacts the first bearing ring 7.

[0027] Fig. 4 - Fig. Figure 4 illustrates the position of the relevant cross sections BB, CC and FF to illustrate the invention and the preferred embodiments as well as the viewing direction (view) for the corresponding views.

[0028] Fig. 5 - Fig. Figure 5 shows the cross-section along section BB, wherein the flexurally elastic, curved machine element 3 has a geometrically defined recess 11 in the cross-section or longitudinal section of the flexurally elastic, curved machine element, at least in the dynamic contact area. This can be a profiled notch, as in the illustrated embodiment, a circular segment. In view A, i.e., the view from the bearing center to 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 flexible, curved machine element and directly establishes the electrical contact with a first bearing ring 7 or an intermediate component 8. Fig. Figure 4 also illustrates that the additional element 12 protrudes beyond the contour of the flexurally elastic, curved 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, curved machine element 3 and the second bearing ring 9 or the rotating component 2.

[0029] Fig. 6 - Fig. Figure 6 illustrates another embodiment of the bypass device, wherein the recess 11 of the flexurally elastic, curved machine element 3 can have a double circular segment shape in cross-section BB. This has the particular advantage that accumulations of particularly highly conductive material, for example, removed from the counter-running surface, can also form in area 13 between the actual geometrically defined recesses 11, which can be filled, and thus also reduce the electrical contact resistance.

[0030] Fig. 7 - Fig. Figure 7 shows a further preferred embodiment of the bypass device, wherein the flexurally elastic, curved machine element 3 has a recess 11, or a plurality of recesses 11, in the shape of a rectangle in cross-section BB. These can be present either as recesses 11 or in a material-filled form, or in a combination. It is also conceivable for them to protrude beyond the cross-section of the flexurally elastic, curved machine element 3.

[0031] Fig. 8 - Fig. 8 illustrates that the flexurally elastic, curved machine element 3 can have a conductive coating 15.

[0032] Fig. 9 - Fig. Figure 9 shows a rolling bearing 14 with a bypass device, in section CC, which illustrates the first section 4 of the flexurally elastic, curved machine element 3 with its one seating area on a first bearing ring 7, as well as section BB, wherein here the second section 5 of the flexurally elastic, curved machine element 3 is designed to bear against a second bearing ring 9. It is also evident that the cross section B - B or the longitudinal section of the flexurally elastic, curved machine element 3 has a geometrically defined recess 11 at least in the dynamic contact area 10. The bearing can also be designed as in Fig. 9, have one or more seals 15. Reference symbol 1 bypass device 2 Rotating component 3 flexible, curved machine element 4 first section 5 second section 6 - 7 first bearing ring 8 Intermediate component 9 second bearing ring 10 dynamic contact area 11 geometrically defined recess 12 Additional element 13 Area between depressions 14 rolling bearings 15 Conductive coating A View from direction A BB cross section BB CC Cut CC FF longitudinal section K Contour s Distance between the outer end of the base material of the flexible, curved machine element and the second bearing ring or the rotating component 2 QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2016 010 926 A1

[0003] DE 10 2014 010 269 B4

[0004] DE 10 2015 224 044 A1

[0005]

Claims

[1] Bypass device (1) for transmitting electrical currents to a rotating component (2), comprising 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) 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, arc-shaped machine element (3), wherein the first section (4) forms a seating area for the flexurally elastic, curved machine element (3) and the second section (5) forms a dynamic contact area (10), wherein the flexurally elastic, curved machine element (3) has a cross-section (BB) or a longitudinal section (FF) in the dynamic contact area (10), characterized by , that the cross-section (BB) or the longitudinal section (FF) of the flexurally elastic, curved machine element (3) has a geometrically defined recess (11) at least in the dynamic contact area (10). [2] Bypass device (1) according to claim 1, characterized by that the intermediate component (D) can be formed as a metallic disc. [3] Bypass device (1) according to claim 1 or 2, characterized by that the flexurally elastic, curved machine element (3) has an additional element (12) which establishes the electrical contact. [4] Bypass device (1) according to claim 3, characterized by that the additional element (12) projects beyond the contour (K) of the flexurally elastic, curved machine element (3). [5] Bypass device (1) according to claim 3 or 4, characterized by that the additional element (11) is a separately formed insert. [6] Bypass device (1) according to one of the preceding claims, characterized by that the geometrically defined recess (11) of the cross-section (BB) of the flexurally elastic, arcuate machine element (3) has the shape of a circular sector. [7] Bypass device (1) according to one of the preceding claims, characterized by that the geometrically defined recess (11) of the cross-section (BB) of the flexurally elastic, arched machine element (3) has the shape of a rectangle. [8] Bypass device (1) according to one of the preceding claims, characterized by that the flexurally elastic, curved machine element (3) has a conductive coating (15). [9] Rolling bearings, characterized bythat the rolling bearing (14) comprises a bypass device (1) according to one of the preceding claims. [10] 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 an electrically conductive connection is formed between the first bearing ring (7) and the second bearing ring (9) by means of the flexurally elastic, arcuate machine element (3), characterized bythat the bypass device (1) is formed from a flexurally elastic, arc-shaped machine element (3), wherein the cross-section (BB) or the longitudinal section (FF) of the flexurally elastic, arc-shaped machine element (3) has a geometrically defined recess (11) at least in the dynamic contact area (10).

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