ROLLING-ELEMENT BEARING

Abstract

A rolling element bearing includes inner and outer rings having raceways and rolling elements between the raceways. The raceways of the inner and outer rings are coated with a first coating, such as a phosphate coating, and the rolling elements are coated with a second, different, coating such as a black oxide coating.

Claims

1. A rolling element bearing comprising: an inner ring having a raceway, an outer ring having a raceway, and a plurality of rolling elements rotatably disposed between the inner ring and the outer ring, wherein the raceway of the inner ring and/or the raceway of the outer ring is coated with a first coating, wherein the rolling elements are at least partially coated with a second coating, wherein the first coating is different than the second coating.

2. The rolling-element bearing according to claim 1, wherein the first coating or the second coating is a phosphate coating.

3. The rolling-element bearing according to claim 2, wherein the phosphate coating is a coating selected from the group consisting of a manganese phosphate coating, a zinc phosphate coating, a zinc calcium phosphate coating, and a tricationic phosphate coating.

4. The rolling-element bearing according claim 3, wherein the first coating is the phosphate coating, and wherein the second coating has a greater hardness than the first coating.

5. The rolling-element bearing according to claim 4, wherein the first coating has a thickness of 2 to 4 m.

6. The rolling-element bearing according to claim 3, wherein the second coating is a black oxide coating.

7. The rolling-element bearing according to claim 3, wherein the second coating is a bluing.

8. The rolling-element bearing according to claim 3, wherein the second coating is a carbon layer.

9. The rolling-element bearing according to claim 1, wherein the rolling elements are completely coated with the second coating.

10. The rolling-element bearing according to claim 1, wherein the raceway of the inner ring and/or the raceway of the outer ring are completely coated with the first coating.

11. The rolling-element bearing according to claim 1, wherein the inner ring and/or the outer ring are completely coated with the first coating.

12. The rolling-element bearing according to claim 1, wherein the phosphate coating is a coating selected from the group consisting of a manganese phosphate coating, a zinc phosphate coating, a zinc calcium phosphate coating, and a tricationic phosphate coating, the phosphate coating having a thickness of from 2 to 4 m, wherein the second coating is a bluing, and wherein the rolling elements are completely coated with the second coating and the inner ring and the outer ring are completely coated with the first coating.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0035] FIG. 1 is a sectional view of a rolling-element bearing including an inner ring and an outer ring according to the present disclosure.

DETAILED DESCRIPTION

[0036] In the following, identical or functionally equivalent elements are designated by the same reference numbers.

[0037] In FIG. 1 a rolling-element bearing 1 is depicted in a greatly simplified outline. The rolling-element bearing 1 includes an inner ring 2 and an outer ring 4. Rolling elements 6 are rotatably disposed between the two rings 2, 4. Here the rolling elements 6 run against an outer surface 8 of the inner ring 2 as well as an inner surface 10 of the outer ring 4. In order to protect the raceways 8, 10 as well as the rolling elements 6 against wear, these are each provided with a coating. Here the coating of the rolling elements 6 can have a greater hardness than a coating of the raceways 8, 10. The coating of the rolling elements 6 can be, for example, a bluing.

[0038] The ring raceways 8, 10, and preferably the entire rings 2, 4 are provided with a phosphate coating in order to provide a sliding layer for the rolling elements 6. In particular, a smearing of the rolling elements 6 can be prevented by the coating of the rolling elements 6.

[0039] Here both the phosphate coating and the coating of the rolling elements 6 can be configured so thin that even with wear of the coatings the bearing clearance in the rolling-element bearing is increased only in an acceptable range. Since the coating of the rolling elements 6 is harder than the phosphate coating, the coating of the rolling elements 6 is preferably not worn and thus remains even with a reduced thickness of the phosphate coating as a separating layer between the rolling elements 6 and the raceways 8, 10.

[0040] Furthermore, a bluing is preferably provided for the rolling elements 6, since this can be applied very thinly. In comparison thereto the phosphate coating is thicker. If the phosphate coating were to be applied onto the rolling elements 6, with a reduction of the thickness of the phosphate coating (which occurs very quickly due to the softness of the phosphate coating in operation) the layer thickness of the rolling elements 6 would be reduced and a clearance would be present between the rolling elements 6. In order to prevent the phosphate coating from rapidly losing layer thickness in operation, which would unacceptably increase the bearing clearance, the phosphate coating may not be applied to all components. Phosphate on rings and rollers would generate too large a clearance change. The phosphate coating is therefore preferably applied onto the rings since the essential effects of phosphate, inter alia corrosion protection and prevention of fretting corrosion, are predominantly required on the rings. The rollers are therefore provided with a thin and dimensionally stable layer, preferably a bluing. In this way the coatings of the rollers do not additionally contribute to the phosphate-typical clearance enlargement.

[0041] With the disclosed rolling-element bearing it is possible to provide a rolling-element bearing that can reduce wear of the rolling-element bearing under the most diverse conditions of use, for example, even in an acidic or alkaline environment, since at least one of the layers used remains and thus a protective layer remains between the surfaces of the bearing rings and of the rolling elements, which surfaces move against one another. Furthermore, due to the two different coatings the running properties of the rolling-element bearing can be improved since the advantages of both coatings can be utilized.

[0042] 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. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved rolling-element bearings.

[0043] 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.

[0044] 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.

REFERENCE NUMBER LIST

[0045] 1 Rolling-element bearing [0046] 2 Inner ring [0047] 4 Outer ring [0048] 6 Rolling element [0049] 8 Raceway [0050] 10 Raceway