Rolling bearing and method for producing rolling bearing cage

Abstract

The invention relates to a rolling bearing (1), for example a spherical rolling bearing, in particular for medium lubrication, comprising a plurality of bearing rings (2, 3), a rolling body (4) which rolls between the bearing rings (2, 3), and a coated cage (7) which guides the rolling body (4). The coating (11) of the cage (7) is produced as a plurality of layers and comprises a NiP layer as a first layer (12) covering a main part (10) of the cage (7) made of a non-ferrous metal and a TiN layer as a covering layer (13).

Description

Technical Field

[0001] 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. The invention also relates to a method for producing a rolling bearing cage. Background Art

[0002] For example, a universal rolling bearing is known from DE 10 2006 057 484 B4. The known rolling bearing has roller-shaped rolling elements and a cylindrical bearing cage, wherein at least one lateral surface of the bearing cage is 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 a metal-free coating. 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.

[0003] DE 102 18 238 A1 discloses a two-part conductive cage for rolling bearings. The conductive cage has two cage halves, which are held together by metal bolts with thickened ends. The material of the metal bolts can be formed by means of resistance heating. This enables the production of form-fitting rivet heads.

[0004] DE 10 2016 212 200 A1 describes a cylindrical roller bearing comprising a rolling bearing cage. In this case, the rolling bearing cage is formed in one piece from two side rings arranged at a distance from one another and a carrier web connecting the two side rings. The cylindrical roller bearing according to DE 10 2016 212 200 A1 can be designed in particular as a large bearing. Deep drawing and 3D printing are listed as technologies for producing the bearing cage.

[0005] WO 2007 / 104395 A1 discloses a hybrid bearing designed as a double row angular contact ball bearing, which comprises rolling element raceways made of steel and rolling elements, i.e. rollers, made of ceramic. The hybrid bearing is intended to operate without special lubricants and is particularly designed for applications with low speeds and high axial loads.

[0006] If a bearing, in particular a rolling bearing, is lubricated with a medium which is already present in the environment of the bearing but which does not have the lubrication of the bearing as its main purpose, then the bearing is called a medium-lubricated bearing. For example, if the bearing is used in the open sea, the seawater is the medium which washes around the surface of the bearing components, not the lubricant. Therefore, so-called medium lubrication is not considered to be lubrication in the narrow sense. In process engineering systems where liquid or pasty substances are transported, the corresponding substances can also be used for medium lubrication. Usually, medium lubrication imposes certain loads on the bearing in terms of wear. Summary of the invention

[0007] The invention is based on the object of achieving an improvement over the prior art in rolling bearings suitable for medium lubrication, wherein, in particular, a higher wear resistance is sought even under tribologically unfavorable operating conditions.

[0008] According to the invention, this object is achieved by a rolling bearing having the features of claim 1. This object is also achieved by a method for producing a rolling bearing cage according to claim 9. A rolling bearing cage produced by the method according to claim 9 is particularly suitable for use in a rolling bearing according to claim 1.

[0009] In a basic concept known per se, a rolling bearing comprises bearing rings which can be designed in one or more parts, rolling elements which roll between the bearing rings, and a cage which has a coating and guides the rolling elements.

[0010] According to claim 1, the coating of the cage is manufactured in multiple layers, wherein the coating comprises a NiP layer as a first layer and a TiN layer as a covering layer. The main part of the cage covered by the NiP layer is made of non-ferrous metal. In particular, the cage is a brass cage.

[0011] The use of non-ferrous metal, in particular brass, for the production of the main part of the cage has the particular advantage that even in the case of worn coating, no steel-to-steel contact can occur, as is otherwise possible when using rolling elements and cages made of steel. On the contrary, even in the theoretically conceivable case of complete wear of the cage coating, the lubricating properties of the main part made of non-ferrous metal are still available, at least for emergency operations.

[0012] The thickness of the first layer, the nickel-containing layer, which is located directly on the main part, is in the range of 2 µm to 30 µm, in particular 15 µm ± 3 µm. The thickness of the TiN covering layer deposited on the nickel-containing layer is, for example, 0.5 µm to 10 µm, in particular 2 µm ± 1 µm. In various typical embodiments covering a wide range of different bearing sizes, the thickness of the covering layer is at least 5% and not more than 20% of the total thickness of the multilayer coating of the bearing cage.

[0013] In addition to the bearing cage, at least one other component of the rolling bearing, such as a bearing ring and / or a rolling element, may also be provided with a coating. In contrast to the bearing cage, coatings containing carbon atoms can in particular be used here. A suitable coating is aC:H:W sold by the applicant as Triondur C. With regard to carbon coatings, the VDI guideline 2840 “Carbon films – Fundamentals, film types, and properties” (09 / 2020) is relevant. The guideline relates to the properties of carbon coatings or carbon films produced using a physical vapor deposition process or a chemical vapor deposition (PVD or CVD) process. In this context, reference is also made to the following publications of the applicant:

[0014] “Triondur-Schichtsysteme für tribomechanisch hochbeanspruchte Oberflächen” [Triondur coating system for highly stressed surfaces in tribomechanics], Schaeffler Technologies AG & Co. KG, July 2019, TPI 115 DD

[0015] Triondur C is an amorphous carbon layer containing metal and hydrogen, which can be deposited using a PVD (Physical Vapor Deposition) process and is characterized by a very ductile layer structure and a hardness of over 1200 HV. If the tungsten contained in aC:H:W is replaced by any other metal (Me), the general composition aC:H:Me is obtained.

[0016] Regardless of the type of coating of the various bearing components, the bearing cage of the rolling bearing can in particular be designed as a solid brass cage in the form of a comb-shaped cage. In general, the bearing is in particular a double-row spherical rolling bearing. With regard to possible designs of spherical rolling bearings, reference is made by way of example to the documents DE 10 2019 104 395 A1 and DE 102018 120 592 A1. Spherical rolling bearings are generally characterized by the fact that they can support high axial and radial loads and at the same time can compensate for alignment errors.

[0017] A bearing cage suitable for use in a rolling bearing according to the present application can be produced according to the following steps:

[0018] - a nickel-containing layer is deposited in an electroless process on the main part of the cage made of non-ferrous metal,

[0019] - A covering layer made of titanium nitride is applied onto the nickel-containing layer.

[0020] Nickel-phosphorus layers are particularly suitable as nickel-containing layers. For the technical and scientific background, reference is made to the following papers:

[0021] Christoph Wiegmann; “Characterization of NiP coatings and alternative coating systems as wear and corrosion protection on wrought aluminum alloys” [Characterization of NiP coatings and alternative coating systems as wear and corrosion protection on wrought aluminum alloys], Technical University of Ilmenau, submission date: 11 / 12 / 2017

[0022] In the present case, the TiN layer covering the nickel-containing layer, in particular the NiP layer, can be deposited using a PACVD (plasma-assisted chemical vapor deposition) process. During the production process, the NiP layer beneath the TiN layer serves as a diffusion barrier to prevent the lead contained in the main brass alloy from outgassing during the PACVD process and interfering with the coating process. As a subsequent component of the finished bearing cage, the NiP layer serves as a supporting layer for the much thinner, very hard TiN functional layer.

[0023] The medium used for the medium lubrication associated 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°C to 200°C and preferably at a pressure of about 2000 bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the following, exemplary embodiments of the present invention are explained in more detail with reference to the accompanying drawings. These drawings show geometric structures, some of which are simplified or exaggerated, and are as follows:

[0025] Figure 1 shows a cross-sectional perspective view of a rolling bearing,

[0026] Figure 2 Shown according to Figure 1 Cross-sectional view of the features of a coated cage of a rolling bearing,

[0027] Figure 3 Shown according to Figure 1 Details of the coated rolling elements of rolling bearings,

[0028] Figure 4 Shown according to Figure 1 Detail of a coated bearing ring, namely the inner ring, of a rolling bearing. DETAILED DESCRIPTION

[0029] The rolling bearing, which is designated as a whole by the reference numeral 1, is designed as a double-row spherical rolling bearing. The rolling bearing 1 comprises an inner ring 2 and an outer ring 3 as bearing rings 2, 3. Barrel rollers roll as rolling elements 4 between the bearing rings 2, 3, wherein in the exemplary embodiment there are two rows of rolling elements 5, 6 which are symmetrical to one another. Alternatively, the rolling bearing 1 can be designed as an asymmetrical spherical rolling bearing.

[0030] The rolling elements 4 are guided in a cage 7 which is designed as a comb-shaped cage and is mainly made of brass. The cage 7 has a cage ring 8 which is placed between the rows of rolling elements 5, 6 and from which webs 9 extend, which protrude between the rolling elements 4 on both sides of the cage ring 8. The cage 7, i.e. the main part of the bearing cage, is made of brass and is denoted by reference numeral 10. A layer structure 11 is arranged on the main part 10, which is Figure 2 The total thickness of the layer structure 11 is denoted by D 11 The layer structure 11 is composed of a first layer 12 covering the main part 10 and a cover layer 13 located on top. In the exemplary embodiment, D 12 The thickness of the first layer 12 is 15 µm ± 3 µm. The thickness D of the cover layer 13 13 In the range of 1 µm to 3 µm.

[0031] The first layer 12 is a NiP layer applied to the main part 10 by means of electroless deposition and is also referred to as electroless nickel for short. The cover layer 13 is deposited on the first layer 12 as a titanium nitride layer using a PACVD process.

[0032] Figure 3 The structure of a barrel-shaped rolling element 4 is shown. The main part 14 of the rolling element 4, i.e. the barrel roller, is made of standard bearing steel. On the main part 14 there is a coating 15, which contains carbon and hydrogen. In an exemplary embodiment, the coating 15 is provided in the form of a Triondur coating (aC:H:W), as provided by the applicant for various application areas.

[0033] The same type of coating, i.e. an amorphous carbon coating, is also provided on the inner ring 2. Figure 4 , wherein in the case of the inner ring 2 the main part is denoted by 16 and the coating by 18. Reference numeral 19 denotes the edge of the inner ring 2. The rolling elements 4 roll on the rolling element raceway 17 of the inner ring 2. In a manner not shown, the outer ring 3 can also be coated in a corresponding manner. The operation of the rolling bearing 1 does not use special lubricants. Instead, the surfaces of the components 2, 3, 4, 7 of the rolling bearing 1 are wetted by the medium flowing in the device to which the rolling bearing 1 can be assigned. The medium is, for example, a plastic melt, which is present at a temperature in the range of 150° C. to 200° C. and at a pressure of approximately 2000 bar. Even under such extreme conditions, the individual layers 11, 15, 18 allow low-wear operation of the rolling bearing 1.

[0034] Reference numerals list

[0035] 1 Rolling bearing

[0036] 2Inner ring

[0037] 3 Outer Ring

[0038] 4Rolling elements, barrel rollers

[0039] 5 Row of rolling elements

[0040] 6 rolling elements in a row

[0041] 7 Cage

[0042] 8 Cage ring

[0043] 9 belly plate

[0044] 10Main parts of the cage

[0045] 11 Layer structure of cage

[0046] 12First layer, NiP layer

[0047] 13 Cover layer, TiN layer

[0048] 14 Main parts of barrel roller

[0049] 15 Barrel roller coating

[0050] 16Main part of the inner ring

[0051] 17 Rolling element raceway

[0052] 18Inner ring coating

[0053] 19 Edge

[0054] D 11 Thickness of the entire layer structure

[0055] D 12 Nickel layer thickness

[0056] D 13 Thickness of the covering layer

Claims

1. A rolling bearing (1), comprising 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) is manufactured in multiple layers and comprises a NiP layer as a first layer (12), which covers a main part (10) of the cage (7) made of non-ferrous metal, and a TiN layer as a covering layer (13).

2. The rolling bearing (1) according to claim 1, characterized in that: The NiP layer (12) has a thickness of 2 μm to 30 μm.

3. The rolling bearing (1) according to claim 1 or 2, characterized in that: The TiN layer (13) has a thickness of 0.5 μm to 10 μm.

4. The rolling bearing (1) according to any 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. The rolling bearing (1) according to any one of claims 1 to 4, characterized in that The rolling element (4) is provided with a carbon-containing coating (15).

6. The 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. The rolling bearing (1) according to any 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. The rolling bearing (1) according to any one of claims 1 to 7, characterized in that The rolling bearing is designed as a spherical rolling bearing.

9. A method for producing a rolling bearing cage (7), the method comprising the following steps: - depositing a nickel-containing layer (12) on the main part (10) of the cage made of non-ferrous metal in an electroless process, - A covering layer (13) made of titanium nitride is applied on the nickel-containing layer (12).

10. The method according to claim 9, characterized in that The cover layer (13) is applied by means of a plasma-assisted chemical vapor deposition process.

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