JP2008082413A - Insulated rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulated rolling bearing with excellent insulation properties capable of being manufactured at a low cost, capable of arranging an insulation layer with reduced processing man-hours and free from defect of a chamfer part. <P>SOLUTION: This insulated rolling bearing comprises an inner ring 1, an outer ring 2, and a plurality of rolling elements 4 interposed between raceway surfaces of these inner and outer rings. The insulation layer 7 is formed on at least one of the inner peripheral surface 1a of the inner ring 1 and the outer peripheral surface 2a of the outer ring 2. The insulation layer 7 comprises a layer of a ceramics film 7b formed on an inner diameter surface of the inner ring or an outer diameter surface of the outer ring in at least one peripheral surface by an AD (aerosol deposition) method and a layer of a coating 7a formed on at least one peripheral surface by a sol-gel method by using metal alkoxide solution while covering the layer of the ceramics film 7b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an insulated rolling bearing used for an apparatus having a structure in which a current mainly flows inside a bearing, such as a general-purpose motor, a generator for a generator, and a main motor of a railway vehicle.

  Rolling bearings used in the main motors of railroad vehicles use the current of the main motor that passes through the inner and outer rings of the rolling bearings and rolling elements when the grounding current collector that grounds the current of the main motor from the wheels to the rail is incomplete. Flowing between the wheel and the rail. At this time, electric discharge may occur between the bearing rolling element and the outer ring rolling surface or between the inner ring rolling surface and electrolytic corrosion may occur in the discharge portion. Similarly, in a bearing used in a device having a structure in which a current flows inside the bearing, such as a generator for other generators, electrolytic corrosion may occur. As an effective means for preventing such electrolytic corrosion, it is conventionally known to form a thermal spray coating of an insulator such as ceramics on the outer surface of the bearing race.

  However, the method of providing ceramic layers on the outer diameter and width of the bearing using thermal spraying technology is to prevent the tempering of the bearing steel cured by heat treatment during the thermal spraying process, while cooling the workpiece while cooling the ceramics. Layers had to be deposited, which was very cumbersome and reduced productivity. Furthermore, if an attempt is made to provide ceramic layers on the bearing outer diameter surface and width surface by the thermal spraying method, it is necessary to thermally spray a layer of nickel aluminum or the like as a base treatment, which also causes a decrease in productivity.

  Further, since the ceramic layer obtained by the thermal spraying method is porous, it is necessary to take measures against the decrease in insulation resistance due to the ingress of moisture due to condensation or the like by sealing treatment. For the sealing treatment, a method using a sealing resin containing at least one selected from the group consisting of a synthetic resin, a polymerizable organic solvent, and a fluorosurfactant and a perfluoro group-containing organosilicon compound (Patent Document 1). And a method of sealing by forming a combination layer having a sealing treatment layer with an insulating resin having good permeability as a lower layer and an upper layer with a sealing treatment layer with an insulating resin having poor permeability (Patent Document 2) For example). However, when these sealing methods are used, there is a problem that the cost becomes very high.

  On the other hand, in order to deal with these problems, the present inventor has applied an alumina ceramic layer to the outer peripheral surface of the outer ring or the like (all from the outer diameter surface to the width surface through the chamfer portion) by an aerosol deposition (hereinafter referred to as AD) method. The formed ceramic insulated bearing is proposed (Japanese Patent Application No. 2006-62638). In order to provide an insulating bearing by providing an insulating layer on the bearing outer ring in this way, ceramic insulation is possible without any defects on the outer diameter surface, front side width surface, front side chamfer portion, back side width surface and back side chamfer portion of the bearing outer ring where conduction can be considered. It is necessary to form a layer.

However, since the bearing outer diameter surface, width surface and chamfer part cannot be formed at once, the bearing outer diameter surface, front side width surface, front side chamfer part, back side width surface and back side chamfer part must be formed independently. The man-hours were enormous. The chamfer part is rough because it is not polished like the outer surface of the bearing, and defects are likely to occur when the ceramic layer is formed by the AD method. For this reason, an attempt to polish the chamfer portion caused an increase in cost.
Japanese Patent Laid-Open No. 2003-183806 Japanese Patent No. 3009516

  The present invention has been made in order to cope with such a problem, and can be manufactured at a low cost with a small number of processing steps for providing an insulating layer, and there is no defect in the chamfer part, and an insulating rolling bearing having excellent insulating properties. The purpose is to provide.

  The insulated rolling bearing of the present invention comprises an inner ring and an outer ring, and a plurality of rolling elements interposed between the raceway surfaces of the inner and outer rings, and at least selected from the inner peripheral surface of the inner ring and the outer peripheral surface of the outer ring. An insulating rolling bearing having an insulating layer on one peripheral surface, wherein the insulating layer is a ceramic formed by an AD method on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring on the at least one peripheral surface. A coating layer and a coating layer formed by a sol-gel method using a metal alkoxide solution on the at least one peripheral surface while covering the ceramic coating layer.

The average particle diameter of ceramic fine particles used as an aerosol raw material for forming the ceramic coating is 0.01 to 2 μm.
The ceramic coating is a coating using silicon nitride fine particles as an aerosol raw material.

The insulated rolling bearing of the present invention includes a metal alkoxide coating layer formed by a sol-gel method on an outer peripheral surface of a bearing outer ring (including a width surface and a chamfer part in addition to an outer diameter surface), and the coating film. As an underlayer, an insulating layer composed of a ceramic film layer directly formed on the outer diameter surface by the AD method is used, so that the width surface and the chamfer part are insulated by a metal alkoxide film, and particularly high dielectric breakdown characteristics are required. The outer diameter surface is sufficiently insulated by a metal alkoxide coating and a ceramic coating. Further, since the ceramic coating can be formed only on the outer diameter surface, the number of processing steps can be greatly reduced as compared with the case where the ceramic coating is formed on the entire outer peripheral surface including the width surface and the chamfer portion by the AD method. In addition, since the chamfered portion of the rough surface is densely and uniformly formed and insulated by the metal alkoxide film, the problem of pinholes and defects can be solved.
In addition, the manufacturing cost is significantly reduced compared with the case of using the thermal spraying method because the workpiece is not cooled, the base treatment such as nickel aluminum is not necessary, and the sealing treatment is unnecessary.

An embodiment of the insulated rolling bearing according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of an insulating rolling bearing in which an insulating layer composed of a metal alkoxide coating and a ceramic coating is formed on the outer peripheral surface of the outer ring. Note that the metal alkoxide film and ceramic film constituting the insulating layer are very thin films of several μm to several tens of μm, but in FIG.
As shown in FIG. 1, the insulated rolling bearing has a large number of rolling elements 4 held by a cage 3 interposed between an inner ring 1 and an outer ring 2, and the outer ring 2 is accommodated in a housing 5 or the like, and a shaft 6 is The bearing is fixed to the inner diameter of the inner ring 1, and an insulating layer 7 is formed on the outer peripheral surface 2 a of the outer ring 2. The insulating layer 7 has a structure composed of a ceramic film 7b formed by the AD method and a metal alkoxide film 7a formed on the outer peripheral surface 2a while covering the ceramic film 7b by the sol-gel method. The inner ring 1, the outer ring 2 and the rolling element 4 are made of a metal material such as bearing steel.

In the present invention, the outer peripheral surface 2a of the outer ring 2 forming the metal alkoxide coating 7a is not only the outer diameter surface a of the outer ring 2, but at least the entire surface of the outer ring 2 in contact with the housing 5 or the like holding the outer ring. As shown in FIG. 1, the outer ring 2 is a surface in a range including the outer diameter surface a to the width surface b and including a chamfer portion (chamfered portion) c.
In the present invention, as shown in FIG. 1, the ceramic coating 7b is formed on the outer diameter surface a of the outer ring 2 by the AD method as an underlayer of the metal alkoxide coating 7a. Insulated bearings are required to have high dielectric breakdown characteristics in the portion, and this requirement can be met by forming the ceramic coating 7b in the portion. The width surface b and the chamfer portion c are sufficiently insulated by the metal alkoxide film 7a.

  Although FIG. 1 illustrates the case where an insulating layer is formed on the outer peripheral surface 2 a of the outer ring 2, the insulating layer 7 is formed on the inner peripheral surface 1 a of the inner ring 1 in addition to the outer peripheral surface 2 a of the outer ring 2. It may be. In this case, the metal alkoxide coating 7a is formed on the inner diameter surface, the width surface, and the chamfer portion of the inner ring 1, and the ceramic coating 7b is formed on the inner diameter surface of the inner ring 1 as a base layer of the metal alkoxide coating 7a.

In the present invention, the AD method is a method in which an aerosol in which fine particles of raw material ceramics are dispersed in a gas is sprayed from an aerosol spray nozzle toward a bearing outer ring or the like as a base material, and the aerosol collides with the base material surface at a high speed. This is a method of forming a coating film made of the above constituent material on a substrate. The ceramic fine particles are pulverized by collision to form a clean new surface and cause low-temperature bonding, so that bonding between the fine particles can be realized at room temperature.
In the aerosol, the ceramic fine particles are maintained in a dispersed state. The coating obtained by the thermal spraying method is porous, whereas the coating obtained by the AD method forms the coating from the fine particles dispersed in the aerosol as described above, so that the resulting coating becomes an extremely dense ceramic layer. . For this reason, an insulating rolling bearing provided with an insulating layer made of the coating is protected by a ceramic layer having no pores through which moisture can permeate even if it is exposed to moisture due to condensation, etc. There is no reduction in resistance.
In addition, unlike the thermal spraying method, the AD method does not require high-temperature treatment, and therefore does not cause a decrease in insulation due to transformation of the raw material ceramic due to exposure to a high temperature. For example, even if α-alumina with excellent insulating properties is used, the thermal spraying method transforms to γ-alumina and lowers the insulating properties. Therefore, it is necessary to increase the film thickness. Since the film can be formed with high α alumina, a ceramic layer having high insulation can be obtained without increasing the film thickness.

Examples of the ceramic fine particles used as an aerosol raw material for forming a ceramic film by the AD method in the present invention include oxide ceramics such as alumina, magnesia, zirconia, and titania having good insulation properties and fine particles such as silicon nitride. Among these, since the fracture toughness value and the compressive strength value are large, fine particles of silicon nitride are preferable.
The average particle size of the ceramic fine particles that can be used in the present invention is preferably 0.01 to 2 μm. If it is less than 0.01 μm, it is easy to agglomerate and it is difficult to form an aerosol. In the present invention, the average particle diameter is a value measured by Nikkiso Co., Ltd .: Laser type particle size analyzer Microtrac MT3000.
In addition, in order to satisfactorily form a film, it is preferable to previously form a crack using a pulverizer such as a ball mill or a jet mill so that the silicon nitride fine particles are easily pulverized at the time of collision with the substrate.

In the present invention, as a method for forming a ceramic coating by the AD method, a method is used in which a coating is formed by fixing a bearing outer ring and the aerosol injection nozzle is moved, or a method in which a bearing outer ring is moved by fixing the aerosol injection nozzle. Any method of forming a film can be employed.
Among these methods, the aerosol can be sprayed in a stable state, and the ceramic coating is obtained by using the positioning XY table and the object rotation motor together and moving the bearing outer ring and the like in the axial direction while rotating. It is preferable to use the latter method because it is possible to easily coat and form the film.

The AD method in the present invention will be described with reference to FIG. FIG. 2 is a view showing a film forming apparatus by the AD method, and illustrates the case where an insulating layer is formed on the outer diameter surface of the outer ring 2.
As shown in FIG. 2, the film forming apparatus 11 by the AD method has a vacuum chamber 12. In the vacuum chamber 12, an outer ring 2 of an insulating rolling bearing, which is a ceramic film formation target, and an aerosol injection nozzle 18 are disposed. Aerosol is supplied from the aerosol generator 17 to the aerosol injection nozzle 18. As an aerosol carrier gas, an inert gas is used and supplied from the gas supply facility 16 to the aerosol generator 17. Usable inert gases include argon, nitrogen, helium and the like.
The inside of the vacuum chamber 12 is depressurized by a vacuum pump 13. In order to prevent mixing of ceramic fine particles, a fine particle filter 19 is provided immediately before the vacuum pump 13. The outer ring 2 is rotated in the vacuum chamber 12 by an object rotating motor 15 (A in the figure), and is moved in the axial direction by a positioning XY table 14 (B in the figure).

The aerosol injection nozzle 18 injects ceramic fine particles from the nozzle tip having an opening such as a rectangle onto the outer diameter surface of the outer ring 2. In addition, the aerosol injection nozzle 18 may be one or plural. The aerosol injection nozzle 18 may be configured to be displaceable in the vacuum chamber 12.
From the fixed aerosol spray nozzle 18, aerosol made of ceramic fine particles is sprayed onto the outer ring 2 rotating at a predetermined number of revolutions by the object rotating motor 15, and a ceramic coating is applied to the outer diameter surface of the outer ring 2. Formed. At the same time, the outer ring 2 is moved in the axial direction by the positioning XY table 14, so that a film is uniformly formed in the axial direction.

The ceramic film formation by the AD method is preferably performed until the film thickness reaches about 30 μm. If it is less than 30 μm, sufficient insulation resistance cannot be obtained, and if it exceeds 200 μm, the manufacturing cost increases.
In the present invention, the width surface of the outer ring or the like and the chamfer portion are insulated by the metal alkoxide coating, and the portion does not need to be formed with a ceramic coating by the AD method. Therefore, the processing man-hour by the AD method can be greatly reduced.

  In the present invention, the metal alkoxide film is formed by a sol-gel method using a metal alkoxide solution. In the sol-gel method, a raw material (starting metal compound) solution is applied to an outer ring or the like, a gel is produced through a chemical reaction such as hydrolysis or condensation polymerization, and the solvent left inside is removed by heat treatment. Furthermore, it is a method of forming a film or the like by promoting densification. By performing a sol-gel method using a solution of a metal alkoxide, it is possible to form a dense, uniform and excellent insulating film by bonding to a base metal such as bearing steel.

Examples of starting metal compounds that can be used in the present invention include tetramethoxysilane, tetraethoxysilane (orthosilicate tetraester), tetrabutoxysilane, aluminum ethoxide, aluminum n-butoxide, aluminum s-butoxide, aluminum t-butoxide, A simple substance such as aluminum isobutoxide, aluminum isopropoxide, or a mixture thereof can be used.
Among these, tetraethoxysilane, aluminum isopropoxide, and the like are preferable because they are excellent in film-forming properties and low in cost.
Moreover, the insulation of a film can be improved by disperse | distributing ceramic particles, such as an alumina, a silica, and magnesia, in a metal alkoxide solution.

  While covering the ceramic coating on the outer peripheral surface (including the outer diameter surface, the width surface and the chamfer part) of the outer ring having the ceramic coating formed on the outer diameter surface by the above-mentioned AD method, the sol-gel method By forming the metal alkoxide film, the outer ring of the insulated rolling bearing of the present invention can be obtained.

For the outer ring of the bearing (bearing model number NU214, outer diameter 125 mm), the outer ring outer diameter surface is coated with a ceramic coating made of silicon nitride fine particles (Ube Industries, SN-E10 average particle size 0.55 μm) as an aerosol raw material by 30 μm. It was formed with a thickness. The AD method uses a bearing drive device that uses a positioning XY table and a motor for rotating an object as shown in FIG. 2 for a bearing outer ring that moves in the axial direction while rotating at a peripheral speed of 60 mm / min. Under reduced pressure of Pa or less, the above silicon nitride fine particle aerosol was sprayed through a nozzle having an opening size of 10 mm × 2.0 mm to form a film.
For this bearing outer ring, the metal alkoxide solution is applied to the outer peripheral surface of the bearing outer ring by the spray method after masking the race surface inside the bearing outer ring, and hydrolyzed with moisture in the air to produce alcohol as a by-product. After evaporating by air drying for 1 hour, it was cured in a heated atmospheric furnace at 150 ° C. for 1 hour to form a metal alkoxide film. Further, this operation was repeated three times to obtain a metal alkoxide film having a thickness of 4 μm. As the metal alkoxide solution, orthosilicic acid tetraester (reagent manufactured by Wako Pure Chemical Industries) 50 g, aluminum isopropoxide 50 g (reagent manufactured by Wako Pure Chemical Industries), and high-purity alumina powder AKP-50 (Sumitomo Chemical Co., Ltd.) 10 g) was prepared by mixing with a homogenizer.

  When the insulation resistance of the obtained bearing was measured with an insulation resistance meter, it was 2000 MΩ or more when 1000 V was applied. Moreover, when the breakdown voltage was measured according to JIS K 6911, it showed a sufficient breakdown characteristic of 3.1 kV.

  The insulated rolling bearing of the present invention can be manufactured at a low cost with a small number of processing steps for providing an insulating layer, and it has excellent insulation properties without causing defects in the chamfer part. It can be suitably used as an anti-corrosion rolling bearing or an insulating rolling bearing.

It is sectional drawing which shows one Example of the insulated rolling bearing of this invention. It is a figure which shows the ceramic film formation apparatus by AD method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Cage 4 Rolling body 5 Housing 6 Shaft 7 Insulating layer 7a Metal alkoxide film 7b Ceramic film 11 Film forming apparatus 12 Vacuum chamber 13 Vacuum pump 14 Positioning XY table 15 Object rotation motor 16 Gas supply equipment 17 Aerosol generator 18 Aerosol spray nozzle 19 Fine particle filter

Claims (3)

An inner ring and an outer ring, and a plurality of rolling elements interposed between the raceway surfaces of the inner and outer rings, and an insulating layer on at least one peripheral surface selected from the inner peripheral surface of the inner ring and the outer peripheral surface of the outer ring An insulated rolling bearing having
The insulating layer is formed on an inner diameter surface of the inner ring or an outer diameter surface of the outer ring on the at least one peripheral surface, and a ceramic coating layer formed by an aerosol deposition method and covering the ceramic coating layer An insulating rolling bearing comprising: a coating layer formed by a sol-gel method using a metal alkoxide solution on at least one peripheral surface.   2. The insulated rolling bearing according to claim 1, wherein an average particle diameter of ceramic fine particles used as an aerosol raw material for forming the ceramic coating is 0.01 to 2 [mu] m.   3. The insulating rolling bearing according to claim 1, wherein the ceramic coating is a coating using silicon nitride fine particles as an aerosol raw material.

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