ROLLING BEARING WITH ELECTRICALLY INSULATING COATING

Abstract

An electrically insulated bearing ring includes a polymeric insulating coating for blocking the passage of leakage currents, the coating being formed by spraying on at least one surface of the bearing ring. The electrically insulated bearing ring or rings may be incorporated into a rolling bearing. By using electrically insulated bearing rings, the rolling bearing is able to achieve a minimal electrical leakage current.

Claims

1. An electrically insulated bearing ring comprising: a bearing ring having a polymeric insulating coating configured to block the passage of electrical leakage currents, the coating being formed by spraying a polymeric material on a corresponding surface of the bearing ring.

2. The bearing ring according to claim 1, wherein the polymeric insulating coating is formed of at least one of polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and nylon (PA).

3. The bearing ring according to claim 1, wherein the spraying is an electrostatic spraying, a solution spraying, or a flame spraying.

4. The bearing ring according to claim 3, wherein when the spraying is an electrostatic spraying, polymer particles are first sprayed on the corresponding surface of the bearing ring, then heated and cured, after which the surface morphology and structural dimensions of the coating are precisely adjusted by machining.

5. The bearing ring according to claim 4, wherein a thickness of the polymeric insulating coating is between ten microns (10 ?m) and three thousand microns (3000 ?m).

6. The bearing ring according to claim 5, wherein the thickness of the polymeric insulating coating is between fifty microns (50 ?m) and two hundred microns (200 ?m).

7. A rolling bearing comprising a bearing ring as recited in claim 1.

8. The rolling bearing according to claim 7, wherein the corresponding surface is at least one of an inner circumferential surface of an inner bearing ring and an outer circumferential surface of an outer bearing ring.

9. The rolling bearing according to claim 8, wherein the corresponding surface further includes at least one of end surfaces on both axial sides of the inner bearing ring and end surfaces on both axial sides of the outer bearing ring.

10. The rolling bearing according to claim 9, wherein the corresponding surface further includes at least one of surfaces of shoulders on both sides of an inner ring raceway and surfaces of shoulders on both sides of an outer ring raceway.

11. An electrically insulated bearing ring comprising: an annular body with a raceway surface formed in a circumferential surface, an opposing circumferential surface and two end surfaces; and a polymeric insulating coating formed on at least one of the opposing circumferential surface and the two end surfaces, the coating being configured to block the passage of electrical leakage currents.

12. The bearing ring according to claim 11, wherein the coating is formed by spraying a polymeric material onto the at least one of the opposing circumferential surface and the two end surfaces.

13. The bearing ring according to claim 11, wherein the polymeric insulating coating is formed of at least one of polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and nylon (PA).

14. The bearing ring according to claim 11, wherein a thickness of the polymeric insulating coating is between ten microns (10 ?m) and three thousand microns (3000 ?m).

15. The bearing ring according to claim 14, wherein the thickness of the polymeric insulating coating is between fifty microns (50 ?m) and two hundred microns (200 ?m).

16. A method of forming an electrically insulated bearing ring, the method comprising the steps of comprising: providing an annular body, the annular body having an inner circumferential surface, an outer circumferential surface and two end surfaces, and a polymeric material; and spraying the polymeric material onto at least one of the inner circumferential surface, the outer circumferential surface and the two end surfaces so as to form a polymeric insulating coating configured to block the passage of leakage currents.

17. The method according to claim 16, wherein the polymeric material is formed of at least one of polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and nylon (PA).

18. The method according to claim 16, wherein the spraying is conducted by an electrostatic spraying process, a solution spraying process, or a flame spraying process.

19. The method according to claim 16, wherein the spraying is a conducted by an electrostatic spraying process and the method further comprises the steps of: heating and curing the polymeric insulating coating; and machining the coating to precisely adjust the surface morphology and dimensions of the coating.

20. The method according to claim 16, wherein a thickness of the polymeric insulating coating is between ten microns (10 ?m) and three thousand microns (3000 ?m).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] The foregoing summary, as well as the detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

[0011] FIG. 1 shows a cross-sectional view of a partial structure of a rolling bearing and a polymeric insulating coating in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] In the following description, the same or similar reference numerals are used throughout to indicate the same or similar elements. In addition, terms indicating orientation, such as axial, radial and circumferential, refer to the axial, radial and circumferential direction of the element being described unless otherwise limited or specified.

[0013] FIG. 1 shows a cross-sectional view of a partial structure of an insulated rolling bearing 1 in accordance with the present invention, which in the depicted embodiment is a ball bearing. The insulated rolling bearing 1 includes an inner ring 2, an outer ring 3 and at least one row of rolling bodies 4 (e.g., balls) disposed between an inner ring raceway 24 and an outer ring raceway 34. In contrast to other known bearings, the insulated bearing 1 has an insulating coating 44 formed on a corresponding surface of the inner ring 2 and/or outer ring 3 for blocking or preventing the passage of electric current. In the specific embodiment shown, the insulating coating 44 may be formed on an inner circumferential surface 21 of the inner ring 2 and/or on an outer circumferential surface 31 of the outer ring 3. In addition, the insulating coating 44 may further be formed on the end surfaces 22 on both axial sides of the inner ring 2 and/or on the end surfaces 32 on both axial sides of the outer ring 3 of the bearing 1.

[0014] In principle, the insulating coating 44 may be formed on all surfaces of the inner ring 2 and outer ring 3 of the bearing except for the raceways 24 and 34, even including the respective surfaces of the shoulders 23 on both sides of the inner ring raceway 24 and the shoulders 33 on both sides of the outer ring raceway 34. As used herein in the preceding and following description, each one of the above-mentioned surfaces of the bearing ring 2 or 3 that can be coated with an insulating coating 44 to prevent the leakage current through the rolling bearing 1 is referred to as a corresponding surface.

[0015] Unlike ceramic coatings, the present invention uses at least one polymer as the constituent material of the insulating coating 44, particularly polymers with relative dielectric constants between 3.0 and 3.5. The average dielectric constant of such polymers is about one third (?) of the dielectric constant of ceramics, and therefore the capacitance value of these polymers is also only about ? of the capacitance value of such ceramics. Since the capacitive impedance is inversely proportional to the capacitance value, the polymer coating 44 allows the capacitive impedance of the insulated bearing 1 to be on average three times the capacitive impedance of bearings with a ceramic coating. The substantially increased capacitive impedance of the insulated bearing 1 significantly weakens the electrical leakage current of the bearing 1 without considering other factors, thus significantly inhibiting electric corrosion of the bearing 1.

[0016] In the present invention, the polymer insulating layer or coating 44 is preferably formed on a corresponding surface(s) of a bearing ring 2 and/or 3 by means of spraying. Compared with an injection molding method used to form ceramic coatings, the spraying method or process has certain obvious advantages. On one hand, the injection molding process generally requires the formation of an embedded structure, such as for example slots, on the corresponding surface of a bearing ring to increase the bonding force between the injection molded insulation layer and the bearing ring. Such an embedded structure not only increases the processing cost of the bearing ring, but also changes or adversely affects the performance of the bearing ring. In contrast to the injection molding process, a spraying process generally creates microscopic craters on the surface of the bearing ring by sandblasting, which naturally improves the adhesion between the coating 44 and the substrate (bearing ring), thus eliminating the need for any embedded structure to be formed between the injection material layer and the substrate as with the injection molding process.

[0017] On the other hand, a spraying process may be performed without a mold, and therefore does not require a demolding process, and is not only highly productive but may also provide an arbitrarily adjustable thickness of a coating 44, which is also more continuously (as opposed to incrementally) adjustable. The spraying process may provide coating thicknesses as low as ten microns (10 ?m) and as high as three thousand microns (3000 ?m). The coating 44 may withstand breakdown voltages of three thousand volts (3000 V) to five thousand volts (5000 V), or even higher, at coating thicknesses ranging from fifty microns (50 ?m) to two hundred microns (200 ?m). Such relatively minimal coating thicknesses have less impact or effect on the dimensions of the bearing 1, thus enabling a perfect replacement of existing, non-insulated bearings; i.e., without the need for dimensional modifications to fit a specific application. The present invention is not limited to any particular type of coating process. Common coating processes, such as for example, electrostatic spraying, solution spraying, or even flame spraying, may all be used to form the insulating coating 44 as long as the particular polymer used may be uniformly coated or applied on one or more corresponding surfaces of the bearing ring 1 and the desired dimensional requirements can be achieved. With an electrostatic spraying process, for example, polymer particles are first sprayed onto the corresponding surface(s) of a bearing ring, then heated and cured, followed by post-machining and finishing to precisely adjust the structural dimensions of the coating 44 and refine its surface form to the desired degree.

[0018] In addition, there is no strict limitation on the type of polymer or polymeric material used in the above spraying process. As long as the dielectric constant of a particular polymer is low enough and the mechanical properties of the polymer are capable of handling the various loads that the bearing 1 is subjected to during use, the purposes of the present invention can be achieved. Suitable coating materials for the present invention include, but are not limited to, polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and/or nylon (PA). Of these three coating materials, PPS has a dielectric constant of only slightly greater than 3 at 100 Hz, which not only has good electrical insulation and excellent mechanical properties, but also has strong coating adhesion, small coefficient of thermal expansion and good dimensional stability. PEEK is both rigid and flexible, with particularly good fatigue resistance under alternating stresses, and has good electrical insulation properties at very high temperatures and low dielectric losses at high frequencies. PA materials in general have high mechanical strength, good fatigue resistance and excellent electrical insulation properties. All of the above materials are suitable candidates for the insulating coating 44 of the bearing rings 2, 3 as described in the present invention.

[0019] It should be understood by those skilled in the art that the above rolling bearing and its insulating coating are not limited by the specific embodiments and that the more general technical solutions will be subject to the limitations in the accompanying claims. Any changes and modifications to the present invention are within the scope of protection of the present invention, provided they conform to the limitations of the accompanying claims.

[0020] Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention.

[0021] Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0022] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. The invention is not restricted to the above-described embodiments, and may be varied within the scope of the following claims.