Rolling bearing and method for producing a rolling bearing cage

Abstract

The invention relates to a rolling bearing (1), for example a spherical rolling bearing, in particular for media lubrication, comprising multiple bearing rings (2, 3), rolling bodies (4) which roll between the bearing rings (2, 3), and a coated cage (7) which guides the rolling bodies (4). The coating (11) of the cage (7) is produced in multiple layers and comprises an NiP layer as a first layer (12), said NiP layer covering a cage (7) main part (10) which is made of a nonferrous metal, and a TiN layer as a cover layer (13).

Description

[0001] Rolling bearing and method for producing a rolling bearing cage

[0002] The invention relates to a rolling bearing, in particular a roller bearing, having at least one coated component according to the preamble of claim 1. Furthermore, the invention relates to a method for producing a rolling bearing cage.

[0003] A rolling bearing of this type is known, for example, from DE 10 2006 057 484 B4. The known rolling bearing comprises roller-shaped rolling elements and a cylindrical bearing cage, with at least one outer surface of the bearing cage being provided with a coating containing carbon and hydrogen. In the case of DE 10 2006 057 484 B4, the coating of the bearing cage is metal-free. In contrast, the bearing rings and / or rolling elements of the known rolling bearing have a metal-containing, carbon-containing coating. Possible metal components include tungsten, titanium, cadmium, germanium, chromium, tantalum, and nickel.

[0004] DE 102 18 238 A1 discloses a two-part, electrically conductive cage for rolling bearings. The electrically conductive cage comprises two cage halves held together by a metal bolt with thickened ends. The material of the metal bolt is formable by resistance heating. This enables the production of form-fitting rivet heads.

[0005] DE 10 2016 212 200 A1 describes a cylindrical roller bearing including a rolling bearing cage. In this case, the rolling bearing cage is formed integrally from two spaced-apart side rings and connecting webs. The cylindrical roller bearing according to DE 10 2016 212 200 A1 can be designed, in particular, as a large-diameter bearing. Deep drawing and 3D printing are listed as technologies for manufacturing the rolling bearing cage. WO 2007 / 104395 A1 discloses a hybrid bearing designed as a double-row angular contact ball bearing, which comprises steel rolling element raceways and ceramic rolling elements, i.e., balls. The hybrid bearing is said to be operable without special lubricants and is especially designed for applications with low speeds and high axial loads.

[0006] If a bearing, particularly a rolling bearing, is lubricated with a medium that is already present in the bearing's environment but whose primary purpose is not to lubricate the bearing, it is referred to as a media-lubricated bearing. If a bearing is used in the open sea, for example, seawater is the medium that surrounds the surfaces of bearing components instead of a lubricant. So-called media lubrication is therefore not lubrication in the strict sense. The corresponding substances can also be used for media lubrication in process engineering plants that convey liquid or pasty substances. Typically, media lubrication places a particular burden on bearing wear.

[0007] The invention is based on the object of achieving progress compared to the prior art in rolling bearings which are suitable for media lubrication, with particular emphasis on achieving high wear resistance, even under tribologically unfavourable operating conditions.

[0008] This object is achieved according to the invention by a rolling bearing having the features of claim 1. The object is also achieved by a method for producing a rolling bearing cage according to claim 9. The rolling bearing cage produced by the method according to claim 9 is particularly suitable for use in the rolling bearing according to claim 1. The rolling bearing comprises, in a basic concept known per se, bearing rings, which can each be formed in one or more parts, rolling elements rolling between the bearing rings, and a cage guiding the rolling elements and having a coating.

[0009] According to claim 1, the cage coating has a multi-layer structure, comprising a NiP layer as the first layer and a TiN layer as the top layer. The cage base body covered by the NiP layer is made of non-ferrous metal. In particular, it is a brass cage.

[0010] The use of non-ferrous metal, especially brass, for the cage base body has the particular advantage that even if the coating wears, steel-to-steel contact cannot occur, which would otherwise be conceivable when using rolling elements and a steel cage. Rather, even if the cage coating were to wear out completely, which is theoretically conceivable, the lubricating properties of the non-ferrous metal base body remain usable, at least for emergency operation.

[0011] The first layer, located directly on the base body, i.e., the nickel-containing layer, has a thickness in the range of 2 μm to 30 μm, for example, in particular a thickness of 15 ± 3 μm. The top layer of TiN deposited thereon is, for example, 0.5 μm to 10 μm, in particular 2 ± 1 μm, thick. In various typical designs, which cover a wide range of different bearing sizes, the thickness of the top layer is at least 5% and no more than 20% of the total thickness of the multilayer coating of the bearing cage.

[0012] In addition to the bearing cage, at least one other component of the rolling bearing, for example, a bearing and / or the rolling elements, can also be coated. In contrast to the bearing cage, a coating containing carbon atoms can be used. A suitable coating is aC:H:W, marketed by the applicant under the name Triondur C. Regarding carbon coatings, VDI Guideline 2840 "Carbon Coatings - Basics, Coating Types and Properties" (09 / 2020) is relevant. This guideline addresses the characteristic properties of carbon coatings produced using physical or chemical vapor deposition (PVD or CVD) processes. In this context, reference is also made to the following publication by the applicant:

[0013] Triondur coating systems for surfaces subject to high tribomechanical stress, Schaeffler Technologies AG & Co. KG, July 2019, TPI 115 DD

[0014] Triondur C is a metal- and hydrogen-containing amorphous carbon layer, which is deposited particularly well using the PVD (physical vapor deposition) process. It is characterized, among other things, by a very ductile layer structure and a hardness of more than 1200 HV. Replacing the tungsten contained in aC:H:W with any other metal (Me) results in the general composition aC:H:Me.

[0015] Regardless of the type of coating applied to various bearing components, the bearing cage of the rolling bearing can be designed, in particular, as a solid brass cage in the form of a comb cage. Overall, the bearing is, in particular, a double-row spherical roller bearing. For possible designs of spherical roller bearings, reference is made to documents DE 102019 104 395 A1 and DE 10 2018 120 592 A1. Spherical roller bearings are generally characterized by their ability to accommodate high axial and radial loads while simultaneously compensating for misalignment.

[0016] The bearing cage suitable for use in the rolling bearing according to the application can be produced in the following steps: electroless deposition of a nickel-containing layer on a

[0017] Non-ferrous metal base body of the cage,

[0018] - Applying a top layer of titanium nitride on the nickel-containing layer.

[0019] A nickel-phosphorus layer is particularly suitable as a layer containing nickel. For the technological and scientific background, please refer to the following dissertation:

[0020] Christoph Wiegmann; Characterization of NiP coatings and alternative coating systems as wear and corrosion protection on wrought aluminum alloys, TU Ilmenau, date of submission: December 11, 2017

[0021] The TiN layer covering the nickel-containing layer, specifically the NiP layer, can be deposited using the PACVD (plasma-assisted chemical vapor deposition) process. During the manufacturing process, the NiP layer beneath the TiN layer serves as a diffusion barrier, preventing the lead contained in the brass alloy of the base body from outgassing during the PACVD process and disrupting the coating process. As a later layer component of the finished bearing cage, the NiP layer serves as a support layer for the significantly thinner, very hard TiN functional layer.

[0022] The medium used for media lubrication in connection with the rolling bearing according to the invention is, in particular, a plastic melt. In particular, the plastic melt is used to lubricate the bearing at a temperature in the range of 150 to 200 °C, preferably at a pressure in the order of 2000 bar. An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. These show, partially simplified or exaggerated, geometric structures:

[0023] Fig. 1 a rolling bearing in perspective, sectional view,

[0024] Fig. 2 in a sectional view features of a coated cage of the rolling bearing according to Figure 1,

[0025] Fig. 3 shows a detail of a coated rolling element of the rolling bearing according to Figure 1,

[0026] Fig. 4 shows a detail of a coated bearing ring, namely the inner ring, of the rolling bearing according to Figure 1.

[0027] A rolling bearing, designated overall by reference numeral 1, is designed as a double-row spherical roller bearing. The rolling bearing 1 comprises an inner ring 2 and an outer ring 3 as bearing rings 2, 3. Barrel rollers roll between the bearing rings 2, 3 as rolling elements 4, with two mutually symmetrical rows of rolling elements 5, 6 existing in the exemplary embodiment. Alternatively, the rolling bearing 1 could be designed as an asymmetric spherical roller bearing.

[0028] The rolling elements 4 are guided in a cage 7, which is designed as a comb cage and is mainly made of brass. The cage 7 has a cage ring 8 placed between the rows of rolling elements 5, 6, from which webs 9 extend and protrude on both sides of the cage ring 8 between the rolling elements 4. The base body of the cage 7, i.e. the bearing cage, is made of brass and is designated 10. On the base body 10 there is a layer structure 11, which is illustrated in Figure 2. The total thickness of the layer structure 11 is designated D 1 . The layer structure 11 is composed of a first layer 12 covering the base body 10 and a cover layer 13 located thereon. The thickness of the first layer 12, designated D 12, is 15 ± 3 pm in the exemplary embodiment. The cover layer 13 has a thickness D 13 in the range from 1 pm to 3 pm.

[0029] The first layer 12 is a NiP layer, which is applied to the base body 10 by electroless deposition and is also referred to as chemical nickel for short. The cover layer 13 is deposited as a titanium nitride layer on the first layer 12 using the PACVD process.

[0030] Figure 3 outlines the structure of the barrel-shaped rolling element 4. A base body 14 of the rolling element 4, i.e., the barrel roller, is made of commercially available rolling bearing steel. A coating 15 containing carbon and hydrogen is applied to the base body 14. In the exemplary embodiment, the coating 15 is in the form of a Triondur coating (aC:H:W), as offered by the applicant for various applications.

[0031] The same type of coating, i.e., an amorphous carbon coating, is also present on the inner ring 2, as sketched in Figure 4, where in the case of the inner ring 2, the base body is designated 16 and the coating 18. 19 designates a rim of the inner ring 2. The rolling elements 4 roll on a rolling element raceway 17 of the inner ring 2. In a manner not shown, the outer ring 3 can also be coated in a similar manner. No special lubricant is used for the operation of the rolling bearing 1. Rather, the surfaces of the components 2, 3, 4, 7 of the rolling bearing 1 are wetted by a medium that flows in an apparatus to which the rolling bearing 1 belongs. The medium is, for example, a plastic melt that is present at a temperature in the range of 150 to 200 °C and at a pressure in the order of 2000 bar.The various layers 11, 15, 18 enable low-wear operation of the rolling bearing 1 even under such extreme conditions. List of reference symbols.

[0032] 1 rolling bearing

[0033] 2 inner ring

[0034] 3 Outer ring

[0035] 4 rolling elements, barrel roller

[0036] 5 rolling element row

[0037] 6 rolling element rows

[0038] 7 cage

[0039] 8 Cage ring

[0040] 9 jetty

[0041] 10 Basic body of the cage

[0042] 11 Layer structure of the cage

[0043] 12 first layer, NiP layer

[0044] 13 Top layer, TiN layer

[0045] 14 Base body of the barrel roller

[0046] 15 Coating of the barrel roller

[0047] 16 Base body of the inner ring

[0048] 17 Rolling element raceway

[0049] 18 Coating of the inner ring

[0050] 19 Board

[0051] The thickness of the entire layer structure

[0052] D12 Thickness of the nickel layer

[0053] D13 Thickness of the top layer

Claims

Patent claims 1. Rolling bearing (1), with bearing rings (2, 3), rolling elements (4) rolling between the bearing rings (2, 3), and a coated cage (7) guiding the rolling elements (4), characterized in that the coating (11) of the cage (7) has a multi-layer structure and comprises, as a first layer (12), an NiP layer covering a base body (10) of the cage (7) made of non-ferrous metal, and a TiN layer as a cover layer (13).

2. Rolling bearing (1) according to claim 1, characterized in that the NiP layer (12) has a thickness of 2 pm to 30 pm.

3. Rolling bearing (1) according to claim 1 or 2, characterized in that the TiN layer (13) has a thickness of 0.5 pm to 10 pm.

4. Rolling bearing (1) according to one of claims 1 to 3, characterized in that at least one of the bearing rings (2, 3) has a carbon-containing coating (18).

5. Rolling bearing (1) according to one of claims 1 to 4, characterized in that the rolling elements (4) are provided with a carbon-containing coating (15).

6. Rolling bearing (1) according to claim 4 or 5, characterized in that aC:H:W is provided as the carbon-containing coating (15, 18).

7. Rolling bearing (1) according to one of claims 1 to 6, characterized in that the cage (7) is designed as a solid brass cage in the form of a comb cage.

8. Rolling bearing (1) according to one of claims 1 to 7, characterized in that it is designed as a spherical roller bearing.

9. Method for producing a rolling bearing cage (7), comprising the following steps: - electroless deposition of a nickel-containing layer (12) on a non-ferrous metal base body (10) of the cage, - Applying a cover layer (13) of titanium nitride on the nickel-containing layer (12). Method according to claim 9, characterized in that the cover layer (13) is applied using the PACVD process.

Images