Bearing ring and method for the production thereof, and rolling bearing or plain bearing having at least one such bearing ring
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-19
- Publication Date
- 2026-04-15
AI Technical Summary
Current electrically insulated rolling bearings require long curing times for thermal spray layers, which increase costs and hinder efficient production, especially in the context of electromobility where cost-effective solutions are needed.
A bearing ring with a metallic ring body and a ceramic layer formed by thermal spraying, where the open pore space is filled with a plastic material containing a polymeric binder, reactive diluent, photoinitiator, and hardener, which is partially cured using UV radiation, reducing curing time to a maximum of 10 minutes and ensuring efficient infiltration and hardening.
The solution enables the rapid and cost-effective production of electrically insulating bearing rings with improved adhesion and crosslinking properties, allowing for quick hardening of the plastic material and enhanced infiltration into the ceramic layer, thus reducing production costs and time.
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Abstract
Description
[0001] Bearing and method for its manufacture, as well as rolling bearings or plain bearings with at least one such bearing ring
[0002] The invention relates to a bearing arrangement for a rolling bearing or plain bearing, comprising a metallic annular body and a ceramic layer arranged at least on the outer circumference or at least on the inner circumference of the annular body and formed with open pores by thermal spraying, wherein an open pore space of the ceramic layer is filled with a plastic material. The ceramic layer and the cured plastic material form an electrically insulating coating. The invention further relates to a method for producing such a bearing ring and to a rolling bearing or plain bearing comprising at least one such bearing ring.
[0003] Bearing rings of the type mentioned above are already known. WO 2014 174 382 A1 describes a bearing ring with a body having an electrically insulating coating consisting of a ceramic layer with 10 to 50% pores and a plastic intended to fill the pores and form a coating on the ceramic layer. The ceramic layer is applied to the body using a thermal spraying process and is formed in particular from one or more oxides, nitride, or spinel. The electrically insulating coating on the bearing ring ensures high insulation performance against high-frequency or capacitive currents when the bearing ring is used in a rolling bearing.
[0004] DE 100 29 917 A1 describes a molded body comprising an electrically conductive base body, to which at least one porous layer is applied, which is infiltrated with a polymerizable plastic under vacuum. The porous layer, which in particular has a pore content of up to 20 vol. %, can be applied to the base body by thermal spraying. The porous layer is preferably formed from a material from a group comprising, among others, ceramic materials in the form of chromium oxide, aluminum oxide, zirconium oxide, spinels of aluminum oxide and aluminum titanate, as well as mullite. The polymerizable plastic is cured by heating or UV irradiation. The infiltrated layer is intended to protect the base body from corrosion and to electrically insulate it.
[0005] Electrically insulated rolling bearings are increasingly being used in today's electric motors. Due to the increased demand in the field of electromobility, there is a shortage of cost-effective composite materials for electrical insulation of components. The curing times of the currently known plastic materials used to seal thermal spray coatings are generally longer than 30 minutes, negatively impacting coating costs. Furthermore, heat input is usually required to initiate and accelerate curing.
[0006] It is therefore an object of the invention to achieve a reduction in the curing times of the plastic materials for sealing thermal spray layers made of ceramic.
[0007] The object is achieved for a bearing ring of a rolling bearing or plain bearing, comprising a metallic ring body and a ceramic layer arranged at least on the outer circumference or at least on the inner circumference of the ring body, formed by thermal spraying with open pores and containing a pore volume in the range from 2 vol.% to less than 10 vol.%, in that an open pore space of the ceramic layer is filled with a plastic material which comprises at least one polymeric binder, at least one reactive diluent, at least one photoinitiator and at least one hardener and is at least partially cured by means of UV radiation, wherein the ceramic layer and the cured plastic material form an electrically insulating coating.
[0008] Such a bearing ring can be manufactured quickly and cost-effectively, with the plastic material curing being achieved in a maximum of 10 minutes.
[0009] Preferably, at least 20%, in particular at least 50%, and preferably at least 80%, of the open pores, especially those located on the surface of the ceramic layer, are filled by the plastic material. A correspondingly low viscosity of the plastic material, in particular in the range of a dynamic viscosity q in the range of <250 ± 25 mPa*s (at 20 °C), can enable and improve infiltration of the ceramic layer.
[0010] The not yet cured plastic material therefore preferably has a dynamic viscosity q in the range of 250 ± 25 mPa*s (at 20°C) to ensure sufficient infiltration of the ceramic layer.
[0011] By combining a photoinitiator with at least one polymeric binder, a plastic material can be provided that can be at least partially or fully cured by UV irradiation. The activation energy introduced by the UV irradiation can cause polymerization of the plastic material not directly exposed to the UV radiation. This also allows reliable curing of areas of the plastic material that cannot be irradiated with a UV lamp, for example, particularly because these areas are located within pores and not on the surface of the ceramic layer.
[0012] Photoinitiators can decompose upon absorption of UV light, thus forming reactive radicals or cations that can initiate polymerization of the plastic material, in particular of the polymer components. It is preferred that the photoinitiator is preferably a radical photoinitiator. The at least one photoinitiator can be one from the group of α-hydroxy, α-alkoxy, or α-amino aryl ketones, phosphine oxides, in particular acylphosphine oxides, and / or combinations thereof. The aforementioned photoinitiators can reliably trigger polymerization, in particular chain polymerization, after UV irradiation and therefore enable essentially complete curing of the plastic material.
[0013] By providing at least one reactive diluent, the viscosity of the plastic material can be adjusted, allowing the plastic material to be reliably introduced into the pores of the ceramic layer. Likewise, the addition of reactive diluents can improve the adhesion and crosslinking of the plastic material to the ceramic layer. The at least one diluent can comprise, for example, acrylic acid esters.According to a further preferred embodiment of the invention, the diluent is selected from the group comprising vinyl esters, mono-, di-, tri- or poly(meth)acrylates, such as hydroxyalkyl (meth)acrylates, such as hydroxypropyl methacrylate, such as trimethyl-1,5pentanediol diacrylate, other (meth)acrylic acid esters, such as acetoacetoxyalkyl (meth)acrylate, (meth)acrylic acid methyl ester, butanediol di(meth)acrylate, diacrylates ethanediol di(meth)acrylate, diethyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, or polyethylene glycol di(meth)acrylate; styrenes, such as styrene, a-methylstyrene, vinyltoluene, butylstyrene, divinylbenzene, epoxides, and / or combinations thereof. In particular, this can enable an advantageous viscosity of the sealing agent so that the sealing agent can be introduced into the pores of the structure in a reliable manner.
[0014] By appropriately selecting the at least one binder, the sealing and crosslinking properties of the plastic material can be improved. For example, the at least one binder can be a water-soluble binder. The binder preferably comprises urethane acrylate. For example, it can be an OH-functional acrylate, in particular urethane acrylate.
[0015] A further preferred embodiment of the invention is characterized in that the binder is selected from the group comprising acrylates, in particular methyl methacrylate, (poly)urethane acrylate, isocyanate, silicone, silicate, epoxy resin, polyester, in particular unsaturated polyester, vinyl ester, polyester resin, in particular unsaturated polyester resin, vinyl ester resin, phenol-formaldehyde resin, diallyl phthalate resin, methacrylate resin, polyurethane, amino resins, such as melamine resin, in particular hexamethoxymethylmelamine, and / or urea resin, and / or combinations thereof. The aforementioned constituents can, for example, enable advantageous sealing and crosslinking properties for the plastic material. The binder is preferably present in the plastic material in a range of 20 to 70 wt.%, in particular from 30 to 55 wt.%, particularly preferably from 35 to 45 wt.%.
[0016] The at least one diluent or reactive diluent is preferably contained in the sealant in a range of 30 to 70 wt.%, in particular in a range of 40 to 60 wt.%.
[0017] According to a further preferred embodiment of the invention, the thinner is selected from the group comprising vinyl esters, mono-, di-, tri- or poly-(meth)acrylates, such as hydroxyalkyl (meth)acrylates, such as hydroxypropyl methacrylate, such as trimethyl-1,5-pentanediol diacrylate, other (meth)acrylic acid esters, such as acetoacetoxyalkyl (meth)acrylate, (meth)acrylic acid methyl ester, butanediol di(meth)acrylate, diacrylates, ethandiol di(meth)acrylate, diethyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, or polyethylene glycol di(meth)acrylate; styrenes, such as styrene, α-methylstyrene, vinyltoluene, butylstyrene, divinylbenzene, epoxides, and / or combinations thereof. In particular, this can enable an advantageous viscosity of the plastic material, so that it can be reliably introduced into the pores of the ceramic layer.
[0018] Furthermore, it is preferred to add additives to the plastic material to achieve certain desired properties. For example, up to 1.0 wt.% of a drying agent, in particular a drying agent comprising zinc, can be provided as an additive. Preferably, up to 1.5 wt.% of a catalyst can also be added to improve the curing properties of the plastic material. For example, the catalyst can comprise p-toluenesulfonic acid.
[0019] The addition of additives, such as at least one UV stabilizer and / or at least one antioxidant, has also proven effective, particularly for suppressing color changes in the cured plastic material with increasing service life of the bearing ring due to temperature influences. The plastic material further comprises at least one hardener or a hardener mixture. The addition of a hardener can further accelerate the curing of the plastic material. The hardener or hardener mixture is preferably selected from the group comprising polyamine amides, polyamines, polyamide amines, phenalkamines, phenalkamine amides, isocyanates, and / or combinations thereof. In particular, this can further improve the curing of the sealing agent arranged in the pores.
[0020] The plastic material preferably comprises 40 to 45 wt.% of a binder, in particular urethane acrylate, 35 to 40 wt.% of a first reactive diluent, in particular isobornyl acrylate, 15 to 20 wt.% of a second reactive diluent, in particular trimethyl-1,5-pentanediol diacrylate, 3 to 4 wt.% of a photoinitiator, in particular phosphine oxide, and up to 2 wt.% of an additive, in particular a drying agent comprising zinc. The individual components in this example add up to 100 wt.%.
[0021] Such a plastic material is applied, for example, in atmospheric conditions (i.e., without a vacuum atmosphere) to the surface of a ceramic layer to be sealed. Due to its low viscosity, the plastic material can penetrate deeply into the open pores. Preferably, the penetration depth is at least 80%. Alternatively, the plastic material can also be applied to the ceramic layer under a protective gas atmosphere or in a vacuum.
[0022] The plastic material is preferably applied to the ceramic layer by spraying, brushing, squeegeeing or dipping.
[0023] In the ceramic layer, preferably a maximum of 10% of the open pores have a pore diameter in the range of >20 pm to <35 pm and the remaining open pores preferably have a pore diameter of <20 pm. This ensures penetration of the plastic material into the open pores. The ceramic layer is preferably made of aluminum oxide or of aluminum oxide with proportions of titanium dioxide and / or silicon dioxide or of mullite. The ceramic layer preferably contains an aluminum silicate with a proportion of Al2O3 in the range of 70 to 80 wt.% and of SiO2 in the range of 20 to 30 wt.%. The ceramic layer preferably also contains <1 wt.% TiC or 0.1 to 3 wt.% Cr2O5.
[0024] The thickness of the electrically insulating coating is in particular in the range of 0.05 to 2 mm.
[0025] The object is further achieved by a method for producing the bearing ring according to the invention with the following steps: a) providing the metallic ring body, b) applying the ceramic layer to the ring body by means of thermal spraying, c) optionally evacuating the coated ring body, d) infiltrating the ceramic layer with the plastic material, e) irradiating the infiltrated ceramic layer with ultraviolet light with at least partial curing of the plastic material and optionally storing the bearing ring at room temperature or a temperature of at least 120 °C, wherein the irradiation and optional storage take place for a total of a maximum of 10 minutes, preferably a maximum of 2 minutes, wherein the plastic material is completely cured.
[0026] The irradiation in step e) is particularly preferably carried out over a maximum period of 1 minute.
[0027] Curing of the plastic material is achieved primarily by irradiation with a UV lamp for 30 to 60 seconds. In principle, any UV lamp can be used. A preferred UV lamp has the following specifications: 250 W; Fe-doped; light output approximately 800 mW / cm² 2 ; Quartz glass filter; Wavelength: 320-400 nm. After irradiation with the UV lamp, a further curing step preferably takes place as part of a polymerization, so that the plastic material arranged in the pores, which cannot be irradiated by the UV lamp, also cures essentially completely. The further curing step preferably lasts between 30 and 60 seconds, so that curing can be completed in under 2 minutes, in particular in under 1 minute. As a further curing step, the bearing ring is preferably stored at room temperature or a temperature of at least 120°C.
[0028] It has proven effective to repeat steps d) and e) after step e). This further improves the degree of filling of the open pores.
[0029] The not yet cured plastic material is preferably applied with a dynamic viscosity rj in the range of 250 ± 25 mPa*s (at 20°C) to ensure sufficient infiltration of the ceramic layer.
[0030] A rolling bearing or plain bearing comprising at least one bearing ring according to the invention has proven successful, wherein the bearing ring forms an outer bearing ring and has the electrically insulating coating at least on the outer circumference or wherein the bearing ring forms an inner bearing ring and has the electrically insulating coating at least on the inner circumference.
[0031] The rolling bearing can be a cylindrical roller bearing, a ball bearing, a tapered roller bearing, a spherical roller bearing, a needle bearing and the like.
[0032] Figures 1 and 2 are intended to illustrate a bearing ring according to the invention and its manufacture by way of example.
[0033] Figure 1 shows a bearing ring in three-dimensional view,
[0034] Figure 2 shows a section through the bearing ring according to Figure 1, Figure 3 shows an enlarged section from Figure 2 in the area of a transition of the outer circumference to a front side of the metallic ring body,
[0035] Figure 4 shows a rolling bearing in three-dimensional view comprising the bearing outer ring according to Figure 1, and
[0036] Figure 5 shows a section view of a plain bearing.
[0037] Figure 1 shows a three-dimensional view of a bearing ring 1 in the form of a bearing outer ring 3b. The bearing ring 1 comprises a metallic ring body 2, which has an electrically insulating coating 4 on its outer circumference and also on its adjacent end faces.
[0038] Figure 2 shows a section through the bearing ring 1 according to Figure 1, showing in detail the electrically insulating coating 4 and its arrangement on the metallic ring body 2. The electrically insulating coating 4 consists of a ceramic layer 5 formed by thermal spraying, for example, made of mullite, whose open porosity is at least predominantly filled with a cured plastic material 6.
[0039] Figure 3 shows an enlarged section of Figure 2 in the region of a transition of the outer circumference to an end face of the metallic ring body 2. The electrically insulating coating 4 on the metallic ring body 2 has a total thickness D of 0.5 mm.
[0040] Figure 4 shows a rolling bearing 8 in a three-dimensional view, comprising the bearing rings 1, 1' and a number of rolling elements 7 therebetween. The bearing ring 1 corresponds to the bearing outer ring 3b according to Figure 1. The same reference numerals as in Figure 1 denote the same elements. The bearing ring 1' forms a bearing inner ring 3a of the rolling bearing 8. Figure 5 shows a plain bearing 9 in a sectional view, comprising the bearing rings 1, 1', wherein the bearing 1 forms a bearing outer ring 3b and the bearing 1' forms a bearing inner ring 3a. The bearing inner ring 3a comprises a metallic ring body 2 which has an electrically insulating coating 4 on its inner diameter. The electrically insulating coating 4 is made of a ceramic layer 5 formed by thermal spraying, which is infiltrated with cured plastic material 6.
[0041] List of reference symbols
[0042] 1 , 1' bearing ring metallic ring body
[0043] 3a Bearing inner ring
[0044] 3b Bearing outer ring
[0045] 4 electrically insulating coating
[0046] 5 Ceramic layer
[0047] 6 Plastic material
[0048] 7 rolling elements
[0049] 8 rolling bearings
[0050] 9 plain bearings
[0051] D Thickness
Claims
Patent claims 1. Bearing ring (1, 1') of a rolling bearing (8) or plain bearing (9), comprising a metallic annular body (2) and a ceramic layer (5) arranged at least on the outer circumference or at least on the inner circumference of the annular body (2) and formed with open pores by thermal spraying, containing a pore volume in the range from 2 vol.% to less than 10 vol.%, wherein an open pore space of the ceramic layer (5) is filled with a plastic material (6) which comprises at least one polymeric binder, at least one reactive diluent, at least one photoinitiator and at least one hardener and is at least partially cured by means of UV radiation, wherein the ceramic layer (5) and the cured plastic material (6) form an electrically insulating coating (4).
2. Bearing (1, 1') according to claim 1, wherein a maximum of 10% of the open pores have a pore diameter in the range of > 20 pm to < 35 pm and the remaining open pores have a pore diameter of < 20 pm.
3. Bearing (1, 1') according to claim 1 or 2, wherein the ceramic layer (5) is formed from aluminum oxide or from aluminum oxide with proportions of titanium dioxide and / or silicon dioxide or from mullite.
4. Bearing (1, 1') according to one of claims 1 to 3, wherein the plastic material (6) further comprises at least one drying agent and / or at least one catalyst.
5. Bearing (1, 1') according to one of claims 1 to 4, wherein the at least one binder is formed by or comprises a (poly)urethane acrylate.
6. A method for producing a bearing ring (1, 1') according to one of claims 1 to 5, comprising the following steps: a) providing the metallic ring body (2), b) applying the ceramic layer (5) to the ring body (2) by means of thermal spraying, c) optionally evacuating the coated ring body (2), d) infiltrating the ceramic layer (5) with the plastic material (6), e) irradiating the infiltrated ceramic layer (5, 6) with ultraviolet light to at least partially cure the plastic material (6) and optionally storing the bearing ring (1, 1') at room temperature or a temperature of at least 120 °C, wherein the irradiation and optional storage take place for a total of a maximum of 10 minutes, preferably a maximum of 1 minute, wherein the plastic material (6) is completely cured.
7. The method according to claim 6, wherein the irradiation in step e) takes place over a maximum period of 2 minutes.
8. The method according to claim 6 or 7, wherein after step e) a repetition of step d) and step e) takes place.
9. Method according to one of claims 6 to 8, wherein the plastic material (6) for infiltration of the ceramic layer (5) is adjusted to a viscosity of 250 ± 25 mPas (at 20°C).
10. Rolling bearing (8) or plain bearing (9), comprising at least one bearing ring (1, 1') according to one of claims 1 to 5, wherein the bearing ring (1) forms a bearing outer ring (3b) and has the electrically insulating coating (4) at least on the outer circumference or wherein the bearing ring (1') forms a bearing inner ring (3a) and has the electrically insulating coating (4) at least on the inner circumference.