ROLLING BEARING AND METHOD OF MANUFACTURING SAME

Abstract

A rolling bearing includes an outer ring having an outer surface configured to be fitted into a first component, an inner ring having an inner surface configured to be fitted onto a second component, at least one rolling element arranged between the outer ring and the inner ring, and a polymer composite sheet bonded on the outer surface of the outer ring and/or the inner surface of the inner ring by a bonding agent, where the polymer composite sheet includes at least one perfluoroalkyl and/or polyfluoroalkyl component.

Claims

1. A rolling bearing comprising: an outer ring having an outer surface configured to be fitted into a first component, an inner ring having an inner surface configured to be fitted onto a second component, at least one rolling element arranged between the outer ring and the inner ring, and a polymer composite sheet bonded on the outer surface of the outer ring and/or the inner surface of the inner ring by a bonding agent, wherein the polymer composite sheet includes at least one perfluoroalkyl and/or polyfluoroalkyl component.

2. The rolling bearing according to claim 1, wherein the polymer composite sheet has a thickness of 2 to 200 m.

3. The rolling bearing according to claim 1, wherein the polymer composite sheet has a thickness of 5 to 30 m.

4. The rolling bearing according to claim 1, wherein the polymer composite sheet is made of polytetrafluoroethylene (PTFE), fluroethylenepropylene (FEP), and/or perfluoroalkoxy (FPA).

5. The rolling bearing according to claim 1, wherein the polymer composite sheet comprises a polytetrafluoroethylene (PTFE) impregnated glass and/or polyester carrier.

6. The rolling bearing according to claim 1, wherein the polymer composite sheet comprises fluroethylenepropylene (FEP), perfluoroalkoxy (FPA), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyester (PET), polyurethane (TPU), polyethylene (PE), polypropylene (PP), polyimide (PI), and/or polyamideimide (PAI), and wherein the polymer composite sheet includes 1 to 50 wt % polytetrafluoroethylene (PTFE).

7. The rolling bearing according to claim 1, wherein the bonding agent is an epoxy adhesive or a cyanoacrylate glue.

8. The rolling bearing according to claim 7, wherein the bonding agent has a thickness of less than 25 m.

9. The rolling bearing according to claim 1, wherein the polymer composite sheet includes a silicone or acrylic adhesive on one side.

10. The rolling bearing according to claim 1, wherein a backside of the polymer composite sheet is chemically and/or plasma etched.

11. The rolling bearing according to claim 1, wherein the polymer composite sheet has a dielectric strength greater than 15 kV/mm and a dielectric constant of lower than 4.

12. The rolling bearing according to claim 1, wherein the polymer composite sheet has a thickness of 5 to 30 m, and wherein the polymer composite sheet is made of polytetrafluoroethylene (PTFE), fluroethylenepropylene (FEP), and/or perfluoroalkoxy (FPA).

13. An assembly comprising: a rolling bearing according to claim 1, wherein the outer ring is fitted into the first component, and wherein the inner ring is mounted on the second component.

14. A method of manufacturing a rolling bearing comprising: providing an outer ring having an outer surface configured to be fitted into a first component, providing an inner ring having an inner surface configured to be fitted onto a second component, providing at least one rolling element arranged between the outer ring and the inner ring, and bonding a polymer composite sheet on the outer surface of the outer ring and/or the inner surface of the inner ring using a bonding agent, wherein the polymer composite sheet includes at least one perfluoroalkyl and/or polyfluoroalkyl component

15. The method according to claim 14, further including, before bonding the polymer composite sheet, pretreating a backside of the polymer composite sheet using chemical etching and/or plasma etching.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the following, preferred embodiments of the invention are described in connection with the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

[0024] FIG. 1 is a sectional view of a rolling bearing according to an embodiment of the present invention.

[0025] FIG. 2 is a graph obtained in an experiment, depicting an aluminum wear depth for different polymer composite sheet layers, and reference examples.

[0026] FIG. 3 is a graph obtained in an experiment, depicting a wear depth of the polymer composite sheet layer for different polymer composite sheet layers, and reference examples.

[0027] FIG. 4 is a graph obtained in an experiment, depicting a friction coefficient for different polymer composite sheet layers, and reference examples.

DETAILED DESCRIPTION

[0028] In the following same or similar functioning elements are indicated with the same reference numerals.

[0029] A ball bearing is shown as an example of a rolling-element bearing in FIG. 1. However, the present disclosure is not limited to any particular type of rolling-element bearing. The ball bearing includes an outer ring 1 having an outer ring raceway 1a, an inner ring 2 having an inner ring raceway 2a, and a plurality of balls 3 arranged between the inner and outer raceways 1a, 2a. Also, an outer diameter surface 1b of the outer ring 1 of the ball bearing is fitted to a first component 7, such as a housing, and an inner peripheral surface of the inner ring 2 is fitted to a second component 8, such as a shaft.

[0030] The outer ring 1 and the inner ring 2 are made of metal, for example bearing steel. Further, the outer diameter surface 1b of the outer ring 1 is provided with a bonding layer 5 comprising a bonding agent, which bonds a polymer composite sheet layer 6 to the outer diameter surface 1b of the outer ring 1. The housing is made of aluminum or aluminum alloy (for example, aluminum die-cast material) for weight reduction, in many cases. Since the polymer composite sheet layer 6 of the present invention is softer than aluminum or aluminum alloy (for example, aluminum die-cast material), the housing is not damaged even though the outer diameter surface 1b of the outer ring and the housing may move with respect to each other.

[0031] The polymer composite sheet layer 6 comprises a polymer such as fluroethylenepropylene (FEP), perfluoroalkoxy (FPA), and/or polytetrafluoroethylene (PTFE). Additionally or alternatively, polymer composite sheet layer 6 comprising polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyester (PET), polyurethane (TPU), polyethylene (PE), polypropylene (PP), polyimide (PI), and/or polyamideimide (PAI) as well as at least one solid lubricant may be used.

[0032] If a solid lubricant is added to the polymer composite sheet layer 6, the solid lubricant is required to have lubrication performance and to be softer than a material of the housing, which in the present embodiment is aluminum or aluminum alloy. As the solid lubricant, polytetrafluoroethylene (PTFE) and/or molybdenum disulfide (MoS2) may be used. The content of the solid lubricant in the polymer composite sheet layer 6 may be between 1 and 50 wt %, preferable 5 to 20 wt %.

[0033] Alternatively, the polymer composite sheet layer is made of polytetrafluoroethylene (PTFE) and/or comprises a polytetrafluoroethylene (PTFE) polymer impregnated carrier, wherein the carrier is a glass and/or polyester carrier.

[0034] The polymer composite sheet layer 6 may be formed by an extruding method. For example, the raw materials for the polymer composite such as the used polymer or polymer mixture is dissolved (melted) and subsequently flow casted, using for example a drum cast. The obtained cast material is then forwardly and/or laterally stretched to the predetermined dimensions and finally rolled to obtain a roll of a polymer composite sheet material. This material can then be cut the needed size. Additives such as a solid lubricant may either be added at the beginning of the extruding method when the raw materials are dissolved (melted) and mixed and/or by using a coating method to coat the additives on the sheet material.

[0035] As the bonding agent an epoxy adhesive or a cyanoacrylate glue can be used. The bonding layer 5 has a thickness of less than 25 m, preferably less than 5 m, and can be applied directly on the outer diameter surface 1b of the outer ring. Alternatively, the polymer composite sheet layer 6 is provided with an adhesive on one side, wherein the adhesive is an acrylic adhesive or a silicone.

[0036] Before the polymer composite sheet layer 6 is applied to the outer ring 1, a surface of the outer ring 1 is machined to have a surface roughness Ra of 0.5 to 10 m, preferably 1 to 3 m. This allows for an improved bonding of the bonding layer 5 on the surface. Then, the polymer composite sheet layer 6 is applied to the bonding layer 5. Preferably, the polymer composite sheet layer 6 may be cut to size before the polymer composite sheet layer 6 is bonded to the outer ring 1.

[0037] The thickness of the polymer composite sheet layer 6 is between 2 to 200 m. When the thickness of the polymer composite sheet layer 6 is smaller than 2 m, the polymer composite sheet layer 6 may wear prematurely and the creep wear resistance will not last long. On the other hand, when the thickness of the polymer composite sheet layer 6 exceeds 200 m, the strength of the polymer composite sheet layer 6 is lowered, so that the polymer composite sheet layer 6 may be peeled off. The thickness of the polymer composite sheet layer 6 is more preferably 5 m to 30 m.

[0038] Alternatively, when the creep occurs in the inner ring and a shaft, the polymer composite sheet layer 6 may be bonded to the inner surface of the inner ring 2.

[0039] The present invention will be further described with reference to test examples. However, it should be noted that the present invention is not limited thereto.

[0040] In this test, the effects that are to be accomplished by the bonded film of the present invention was verified.

[0041] As shown in Table 1, as Example 1 a sheet material made of polytetrafluorethylene (PTFE) and polyester was used and as Example 2 sheet material made of fluoroethylenepropylene (FEP) was used.

[0042] For the test, a pin on disk test was performed, wherein a pin is moved with defined load and defined contact pressure over a disk for a predetermined amount of time. This allows to determine the wear depth as well as the average coefficient of friction. Two set were performed for the test, wherein in the first set a steel pin is moved over an aluminum disk and in the second set an aluminum pin is moved over a steel disk. In both sets, the steel component, namely the pin in the first set and the disk in the second set, were provided with a polymer composite sheet layer according to examples 1, and 2. Furthermore, uncoated reference samples were prepared as well. The polymer composite sheet layer was bonded to the workpiece with epoxy or cyanoacrylate. As reference samples, a coating containing a binder, molybdenum disulfide (MoS2) as a solid lubricant, as well as antimony according to the prior art as described for example in EP 3505783 A1 were used.

[0043] The steel pin had a diameter of 82 mm, and the aluminum pin had a diameter of 64 mm. The defined load was 20 N for the steel pin and 10 N for the aluminum pin, wherein the average contact pressure was 130 MPa for the steel pin, and 124 MPa for the aluminum pin. The results for the wear depth of the aluminum and the polymer composite sheet layer as well as the average coefficient of friction are shown in FIG. 2 to 4.

TABLE-US-00001 Example Solid lubricant No. type Polymer 1 PTFE + polyester 2 FEP Ref. MoS.sub.2, Sb.sub.2O.sub.3 Uncoated

[0044] It can be seen from FIGS. 2 and 3 that wear on the aluminum and the polymer composite sheet layer can be significantly reduced and is significantly smaller than the reference coating. With regard to the average coefficient of friction, it can be seen from FIG. 4 that depending on the used polymer the average coefficient of friction is at least comparable to the reference coating or even lower than the reference coating.

[0045] In summary, the described polymer composite sheet layer 6 can reduce the wear on an element which is fitted to the outer and/or inner ring, such as an aluminum housing, such that abnormal vibrations and/or noise may be mitigated. The described polymer composite sheet layer 6 has a low coefficient of friction which may allow to reduce the number of debris resulting in a longer life of the bearing and/or the mechanical apparatus.

[0046] Also, the polymer composite sheet layer 6 can be cut to size before being bonded on the metal surfaces of the outer and/or inner ring. The bonding agent can be applied as a bonding layer and/or on one side of the polymer composite sheet layer 6.

[0047] 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 bearings.

[0048] 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.

[0049] 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 NUMERALS

[0050] 1 outer ring [0051] 1a outer raceway [0052] 1b outer surface [0053] 2 inner ring [0054] 2a inner raceway [0055] 3 rolling element [0056] 5 bonding layer [0057] 6 polymer composite sheet layer [0058] 7 first component [0059] 8 second component