Rolling bearing unit with bearing seal and integrated grounding brush

Abstract

Rolling bearing unit (1, 1') with protection against damage by electrical discharge, comprising: • a radially inner bearing ring (2, 2') with a radially inner raceway (6) and a radially outer bearing ring (4, 4') with a radially outer raceway (8); • Rolling elements (10) that roll on the radially inner raceway (6) and on the radially outer raceway (8); • at least one seal (12, 12a, 12b) extending radially between the radially outer bearing ring (4, 4') and the radially inner bearing ring (2, 2') with a defined sealing end (14, 14a, 14b) that is attached to one of the two radially inner and radially outer bearing rings (2, 2' or 4, 4'); • a flexible sealing lip (16, 16a, 16b) that is in contact with the other of the two radially inner or radially outer bearing rings (4, 4' or 2, 2'); • at least one electrically conductive ring (18, 18a, 18b) with a first ring end (20, 20a, 20b) that comes into contact with one of the two radially inner or radially outer bearing rings (2, 2' or 4, 4') at the specified sealing end (14, 14a, 14b), wherein the seal (12, 12a, 12b) is integrally connected with the electrically conductive ring (18, 18a, 18b), and • electrically conductive brush fibers (21, 21a, 21b) connected to the electrically conductive ring (18, 18a, 18b) and in contact with the other of the two radially inner or radially outer bearing rings (4, 4' or 2, 2') opposite the fixed sealing end (14, 14a, 14b); characterized in that the electrically conductive ring (18) has two electrically conductive sub-rings (18', 18"), wherein one of the two electrically conductive sub-rings (18', 18") is arranged on each axial side (21', 21") of the brush fibers (21) and a first of the two electrically conductive sub-rings (18', 18") or a first of the electrically conductive rings (32a, 32b, 32c, 32d) each has a first ring end (20', 20a, 20b) with a projection (22, 22a, 22b) extending in an axial direction and in contact with an axial end surface (24, 24a, 24b) of a second of the two electrically conductive sub-rings (18', 18") orone of the second electrically conductive rings (32a, 32b, 32c, 32d) is facing away from the brush fibers (21, 21a, 21b).

Description

Field of the invention

[0001] The present application relates to a rolling bearing unit, in particular to protection of a rolling bearing against damage caused by electrical discharge. Background of the invention

[0002] Rolling bearings are widely used in various mechanical applications, including automotive and industrial applications. Grounding devices are used in a variety of bearing applications, including AC or DC motors, generators, and other applications with rotating shafts. In such applications, grounding devices are used to prevent shaft-induced current from causing electrical discharge machining (EDM) by flowing through a rolling bearing component. EDM causes pitting, scoring, and melt cratering on the bearing components, leading to premature bearing failure. Known methods for preventing EDM include dielectric ceramic coatings on bearings, Faraday cages, electrically conductive bearing greases, and shaft-contacting ground brushes.

[0003] Dielectric ceramic coatings on bearings consist of a hard, brittle coating that can crack during installation or use. Cracks in the coating allow current to flow through the bearing, leading to EDM. Dielectric ceramic coatings on bearings also have limited dielectric strength, and at high voltage potentials, current can flow through the coating structure and compromise the coating's protection against EDM. Faraday cages are also known, as disclosed, for example, in US Pat. No. 7,878,814 B2. For most rolling bearing applications, the use of Faraday cages is very cost-prohibitive.Electrically conductive greases or liquid metal, as disclosed in US 8,248,725 B2, are used to continuously flow current through bearing surfaces to prevent EDM-causing arcing, but may contain elements such as copper, carbon, or phosphorus, which can cause excessive wear on the bearing surfaces and lead to premature bearing failure.

[0004] Spring-loaded grounding brushes for shafts are also well known and allow a continuous flow of current to the ground. Common grounding brushes are prone to excessive wear, material transfer, and oxide formation at the mating surface. These oxides can become a dielectric and prevent effective current transfer from the shaft through the brushes to the ground. This can cause electrical arcing and lead to shaft damage from EDM. Once the impedance of the shaft's grounding brush exceeds the impedance of the bearings, the current can seek its way to the ground through the bearings, causing bearing damage from EDM. Grounding brushes for shafts can vibrate due to imperfections in the shaft surface, i.e., due to an out-of-round shaft.If the grounding brush momentarily loses contact with the shaft during vibration, the current can arc from the grounding brush to the shaft, causing EDM damage. Alternatively, the current can flow through the bearings if the voltage potential is high enough during the brush's loss of contact with the shaft. Traditional spring-loaded shaft grounding brushes are prone to rapid and excessive wear and can eventually lose contact with the shaft, causing the current to seek its way to ground through the bearings, causing EDM damage to the bearing. Known bearing assemblies with EDM protection include separately molded seal assemblies as part of the bearing to retain lubricant and prevent debris ingress, and also separately mounted grounding brush assemblies, which require significant axial clearance and increase the overall package size of the rolling element bearing assembly.As explained above, known solutions for EDM protection for bearings are either too expensive, unreliable, too large, or can damage the bearing components.

[0005] Generic rolling bearing units are known from DE 10 2014 204 719 A1 and DE 299 16 854 U1. Object of the invention

[0006] The invention is therefore based on the object of providing an improved rolling bearing unit with a cost-effective and reliable EDM protection in a suitable size. Description of the invention

[0007] The invention provides an improved EDM-protected rolling bearing unit having a compact seal and brush arrangement. This rolling bearing unit has radially inner and outer bearing rings. The radially inner bearing ring has a radially inner raceway, and the radially outer bearing ring has a radially outer raceway. A plurality of rolling elements are supported such that the rolling elements can roll on the radially outer raceway and the radially inner raceway. A seal extends radially between the radially outer bearing ring and the radially inner bearing ring. The seal has a fixed sealing end attached to one of the radially inner or radially outer bearing rings, and a flexible sealing lip that comes into contact with the other of the radially inner or radially outer bearing rings.At least one electrically conductive ring has a first ring end that contacts one of the radially inner or radially outer bearing rings at the specified seal end. The seal is integrally connected to the electrically conductive ring. Electrically conductive brush fibers are connected to the electrically conductive ring and contact the other of the radially inner or radially outer bearing rings opposite the specified seal end.

[0008] The electrically conductive ring has two electrically conductive partial rings, wherein one of the two electrically conductive partial rings is arranged on each axial side of the brush fibers and a first of the two electrically conductive partial rings or a first of the electrically conductive rings each has a first ring end with a projection which extends in an axial direction and is in contact with an axial end surface of a second of the two electrically conductive partial rings or a second of the electrically conductive rings, which faces away from the brush fibers.

[0009] Preferred arrangements incorporating one or more features of the invention are described below and in the claims. Short description of the drawings

[0010] The rolling bearing unit designed according to the invention is explained in more detail below in two preferred embodiments with reference to the accompanying drawings. Fig. 1 a cross-sectional view of the first embodiment of the rolling bearing unit; Fig. 2 a cross-sectional view of the second embodiment of the rolling bearing unit. Detailed description of the preferred versions

[0011] Certain terms used in the following description are for convenience only and are not to be construed as limiting. The terms "inner," "outer," "inward," and "outward" refer to directions toward or away from the parts referenced in the drawings. A reference to a list of items or parts mentioned with the phrase "at least one of a, b, or c," where a, b, and c represent the listed items, means any one of the listed items a, b, c, or combinations of these items. The terminology includes the specifically mentioned terms, derivatives thereof, and terms of similar import.

[0012] In Fig. 1 shows a rolling bearing unit 1 provided with protection against damage caused by electrical discharge. The rolling bearing unit 1 has a radially inner bearing ring 2 and a radially outer bearing ring 4. The radially inner bearing ring 2 has a radially inner raceway 6, and the radially outer bearing ring 4 has a radially outer raceway 8. A plurality of rolling elements 10 are supported such that the rolling elements 10 can roll on the radially outer raceway 8 and on the radially inner raceway 6. The rolling bearing unit 1 preferably has a cage 36 for the rolling elements 10.

[0013] A seal 12 extends radially between the radially outer bearing ring 4 and the radially inner bearing ring 2. The seal 12 has a fixed sealing end 14 that is attached to one of the radially inner or radially outer bearing rings 2, 4, and a flexible sealing lip 16 that comes into contact with the other of the radially inner or radially outer bearing rings 2, 4. The fixed sealing end 14 is preferably attached to the radially outer bearing ring 4 and the flexible sealing lip 16 comes into contact with the radially inner bearing ring 2. However, it will be clear to those skilled in the art from the present disclosure that the fixed sealing end 14 could also be attached to the radially inner bearing ring 2 and the flexible sealing lip 16 could come into contact with the radially outer bearing ring 4.

[0014] At least one electrically conductive ring 18 has a first ring end 20 that comes into contact with one of the radially inner or radially outer bearing rings 2, 4 at the fixed sealing end 14. The seal 12 is integrally connected to the electrically conductive ring 18. Electrically conductive brush fibers 21 are attached to the electrically conductive ring 18 and come into contact with the other of the radially inner or radially outer bearing rings 2, 4 opposite the fixed sealing end 14. The brush fibers 21 preferably contact the radially inner bearing ring 2. However, it will be clear to those skilled in the art from the present disclosure that the brush fibers 21 could also contact the radially outer bearing ring 4.

[0015] The seal 12 is preferably cast onto the electrically conductive ring 18. By casting the seal 12 together with the electrically conductive ring 18 to form a single piece, the seal 12 is fully supported without additional reinforcements, and the overall axial profile of the rolling bearing unit is reduced, simplifying its assembly. As shown in Fig. As shown in Figure 1, the radially outer bearing ring 4 has a groove 26. The fixed end 14 engages the groove 26 of the radially outer bearing ring 4. The seal 12 is preferably made of an elastomer, which is made of a rubber or polymeric material. The electrically conductive ring 18 is preferably made of a metallic material.

[0016] The electrically conductive ring 18 preferably consists of two electrically conductive partial rings 18', 18", wherein one of the two electrically conductive partial rings 18', 18" is arranged on each of the two axial sides 21', 21" of the brush fibers 21. A first partial ring 18' of the two electrically conductive partial rings 18', 18" has the first ring end 20', which preferably has a projection 22 extending in an axial direction and coming into contact with an axial end surface 24 of a second partial ring 18" of the two electrically conductive partial rings 18', 18", which faces away from the brush fibers 21. In this embodiment, the shoulder 22 of the first electrically conductive partial ring 18' comes into contact with the radially outer bearing ring 4. It will be clear to a person skilled in the art from the present disclosure that the design of the two electrically conductive partial rings 18', 18" could be varied depending on a particular application. As in Fig. 1, the brush fibers 21 are axially interposed between the two electrically conductive partial rings 18', 18" to approximately 80-90% of a radial extent of the brush fibers 21. One axial end of the brush fibers 21, which is in contact with the radially inner bearing ring 2, is exposed, ie it is not interposed between the two electrically conductive partial rings 18', 18".

[0017] A second version of the rolling bearing unit 1' is shown in Fig. 2. The rolling bearing unit 1' has a radially outer bearing ring 4' with two grooves 26a, 26b, one of the grooves 26a, 26b being located on each of the axial sides 30a, 30b of the radially outer bearing ring 4'. In this embodiment, two of the seals 12a, 12b are provided, with the fixed seal ends 14a, 14b being attached to the radially outer bearing ring 4' and flexible sealing lips 16a, 16b being in contact with the radially inner bearing ring 2'. As shown in Fig.As shown in Figure 2, one of the seals 12a, 12b is arranged on each of the axial sides of the rolling elements 10. The rolling bearing unit 1' has two electrically conductive rings 18a, 18b, wherein a first ring end 20a, 20b contacts the radially outer bearing ring 4' at the fixed seal end 14a, 14b of the seals 12a, 12b, and wherein one of the electrically conductive rings 18a, 18b is located on each of the axial sides. The seals 12a, 12b are each integrally connected to a respective one of the electrically conductive rings 18a, 18b. Brush fibers 21a, 21b are attached to each of the electrically conductive rings 18a, 18b and are in contact with the radially inner bearing ring 2' opposite the fixed seal ends 14a, 14b. The seals 12a, 12b are preferably cast onto the electrically conductive rings 18a, 18b in the same manner as described above.Preferably, each of the electrically conductive rings 18a, 18b comprises two of the electrically conductive rings 32a, 32b, 32c, 32d, wherein one of the two electrically conductive rings 32a, 32b, 32c, 32d is arranged on each of the two axial sides 34a, 34b, 34c, 34d of the brush fibers 21a, 21b. A first ring of the two electrically conductive rings 32a, 32c comprises the first ring end 20a, 20b, and the first ring end 20a, 20b comprises a projection 22a, 22b extending in an axial direction and coming into contact with an axial end surface 24a, 24b of a second ring of the two electrically conductive rings 32b, 32d, which faces away from the brush fibers 21a, 21b.

[0018] Having thus far described various embodiments of the present rolling bearing unit in detail, it should be understood and readily apparent to those skilled in the art that numerous modifications, only some of which are exemplified in the foregoing detailed description, could be made without altering the inventive ideas and principles embodied herein. Therefore, the present embodiments are to be considered in all respects as exemplary and not restrictive, since the scope of the invention is indicated by the appended claims rather than by the foregoing description, so that all modifications within the meaning of, and within the range of equivalence of, the claims are thus covered by the claims. List of reference symbols 1, 1' rolling bearing unit 2, 2' inner bearing ring 4, 4' outer bearing ring 6 inner career 8 outer raceway 10 rolling elements 12 Seal 12a, 12b Seals 14 Seal end 14a, 14b Sealing ends 16 flexible sealing lip 16a, 16b flexible sealing lips 18 electrically conductive ring 18', 18" partial rings 18a, 18b electrically conductive rings 20, 20' first wrestling end 20a, 20b first ring ends 21 brush fibers 21', 21" axial sides 21a, 21b brush fibers 22 Approach 22a, 22b approaches 24 End face 24a, 24b End faces 26 groove on 4 26a, 26b grooves on 4' 30a, 30b axial sides 32a, 32b, 32c, 32d electrically conductive rings 34a, 34b, 34c, 34d axial sides 36 cage

Claims

[1] Rolling bearing unit (1, 1') with protection against damage by electrical discharge, comprising: • a radially inner bearing ring (2, 2') with a radially inner raceway (6) and a radially outer bearing ring (4, 4') with a radially outer raceway (8); • rolling elements (10) which roll on the radially inner raceway (6) and on the radially outer raceway (8); • at least one seal (12, 12a, 12b) extending radially between the radially outer bearing ring (4, 4') and the radially inner bearing ring (2, 2') with a fixed seal end (14, 14a, 14b) which is fastened to one of the two radially inner and radially outer bearing rings (2, 2' or 4, 4'); • a flexible sealing lip (16, 16a, 16b) which is in contact with the other of the two radially inner or radially outer bearing rings (4, 4' or 2, 2'); • at least one electrically conductive ring (18, 18a, 18b) having a first ring end (20, 20a, 20b) which comes into contact with one of the two radially inner or radially outer bearing rings (2, 2' or 4, 4') at the fixed seal end (14, 14a, 14b), wherein the seal (12, 12a, 12b) is integrally connected to the electrically conductive ring (18, 18a, 18b), and • electrically conductive brush fibers (21, 21a, 21b) which are connected to the electrically conductive ring (18, 18a, 18b) and are in contact with the other of the two radially inner or radially outer bearing rings (4, 4' or 2, 2') opposite the fixed sealing end (14, 14a, 14b); characterized bythat the electrically conductive ring (18) has two electrically conductive partial rings (18', 18"), wherein one of the two electrically conductive partial rings (18', 18") is arranged on each axial side (21', 21") of the brush fibers (21) and a first of the two electrically conductive partial rings (18', 18") or a first of the electrically conductive rings (32a, 32b, 32c, 32d) each has a first ring end (20', 20a, 20b) with a shoulder (22, 22a, 22b) extending in an axial direction and in contact with an axial end surface (24, 24a, 24b) of a second of the two electrically conductive partial rings (18', 18") or a second of the electrically conductive rings (32a, 32b, 32c, 32d) which is surrounded by the brush fibers (21, 21a, 21b) is turned away. [2] Rolling bearing unit (1, 1') according to claim 1, wherein the seal (12, 12a, 12b) is cast onto the electrically conductive ring (18, 18a, 18b). [3] Rolling bearing unit (1, 1') according to claim 1, wherein the electrically conductive ring (18, 18a, 18b) consists of a metallic material. [4] Rolling bearing unit (1, 1') according to claim 1, wherein at least one of the two radially outer or radially inner bearing rings (2, 2' or 4, 4') has at least one groove (26, 26a, 26b). [5] Rolling bearing unit (1') according to claim 4, wherein the radially outer bearing ring (4, 4') has two grooves (26a, 26b) which are respectively arranged on the axial sides (30a, 30b) of the radially outer bearing ring (4, 4'), wherein two of the seals (12a, 12b) are provided and each of the seals (12a, 12b) is connected to one of the electrically conductive rings (32a, 32b, 32c, 32d), and the fixed seal end (14a, 14b) of each of the seals (12a, 12b) is in engagement with a respective one of the grooves (26a, 26b) on the radially outer bearing ring (4, 4'), and the respective ones of the electrically conductive brush fibers (21a, 21b) are connected to the respective ones of the electrically conductive rings (32a, 32b, 32c, 32d).

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