JP2007107725A - Electrolytic corrosion prevention rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic corrosion prevention rolling bearing capable of being easily manufactured at low cost with the small number of processes while keeping adhesiveness of an insulating layer to a bearing ring. <P>SOLUTION: Coating layers 5A of two-layered structure of the ceramic insulating layer 6 and a metallic layer 8 are formed on faces a-c disposed on a housing of an outer ring 2. The metallic layer 8 is positioned between the face a-c and the insulating layer 6. A thickness of the insulating layer 6 is 0.15-0.45 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention needs to prevent the current from flowing into the bearing from the structure of the device in which the bearing is incorporated, including the bearing used for the main motor, the driving device, and the axle of the railway vehicle. The present invention relates to an electric corrosion prevention type rolling bearing used for applications.

Rolling bearings used in the main motors of railroad vehicles use a current flowing through the inner and outer rings and rolling elements of the rolling bearings 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. For this reason, sparking may occur between the rolling elements and the rolling surface of the outer ring, or between the rolling elements and the rolling surface of the inner ring, so-called galvanic corrosion may occur to shorten the bearing life.
For this reason, a surface in which the outer ring is attached to the housing with a resin insulating layer is proposed. However, the resin layer has a large coefficient of linear expansion, and heat is generated by the operation of the bearing, causing an error in the fit between the outer ring and the housing.
As the insulating layer, ceramics are preferred because they have a low coefficient of linear expansion and high electrical insulating properties, and a thermal sprayed ceramic layer has been proposed as the insulating layer. However, ceramics are difficult to adjust to the material of the bearing race, are not easily sprayed, and have a problem in adhesion with the outer race. Further, when the outer ring is press-fitted into the housing, peeling may occur.

In order to solve such a problem, a three-layer coating layer composed of a metal layer, a ceramic insulating layer, and a metal layer is provided on the mounting surface of the outer ring on the housing (for example, a patent) Reference 1). Each layer is provided by thermal spraying. Among the three layers, the inner metal layer is provided to improve the adhesion of the insulating layer because the ceramic of the insulating layer is not easily adapted to the material of the bearing race and is not easily sprayed. The metal layer on the outer layer side is provided so that the insulating layer does not easily peel off when press-fitted when the outer ring is tightly fitted to the housing.
Japanese Utility Model Publication No. 02-46119 Japanese Utility Model Publication No. 02-80221 Japanese Patent Laid-Open No. 01-182621 Japanese Utility Model Publication No. 61-2454

  As described above, the insulating layer having the three-layer structure and the inner and outer metal layers are both obtained by thermal spraying. That is, the steps of spraying the inner metal layer, spraying the insulating layer, and spraying the outer metal layer are sequentially performed. Thermal spraying is a time-consuming process that requires attaching and detaching the mask jig, and when performing such multiple layers of thermal spraying, the number of times the jig is attached and detached increases, and there are many changes such as changing the spraying material and changing the spraying conditions. This process is required. For this reason, thermal spraying occupies most of the bearing manufacturing cost, and the bearing price is very high.

  An object of the present invention is an electrolytic corrosion that is excellent in electrical insulation, hardly causes a fitting error due to heat generation, has few processing steps, and is easy to manufacture and reduces cost while obtaining adhesion of the insulating layer to the raceway. It is to provide a prevention type rolling bearing.

An electric corrosion prevention type rolling bearing according to the present invention has a two-layer coating structure comprising a ceramic insulating layer and a metal layer interposed between the insulating layer and the surface on a surface attached to the housing or shaft of the bearing ring. A layer is provided. The track ring may be an inner ring, an outer ring, or both.
According to this configuration, ceramics are used as the insulating layer, so it has excellent electrical insulation and a low coefficient of linear expansion, preventing the heat generated by the operation of the bearing from causing errors in the fit between the outer ring and housing. Is done. In addition, since the coating layer has a two-layer structure in which a metal layer is provided on the insulating layer, the metal layer provides adhesion of the insulating layer made of ceramics to the raceway. In addition, since the coating layer has a two-layer structure, the number of processing steps is small, the manufacturing is simple, and the cost is reduced as compared with the case of the three-layer structure.

In the present invention, the thickness of the ceramic insulating layer is, for example, 0.15 mm to 0.45 mm.
If the thickness of the insulating layer is too thin, insulation cannot be ensured, but if it is too thick, the material is wasted, the film formation time becomes longer, and the heat dissipation of the bearing becomes worse due to the low thermal conductivity of the ceramics. . In addition, when the insulating layer is thick, there is a concern that cracking may occur due to the ceramic material, and the insulating property may decrease. For this reason, when an appropriate thickness is obtained by experiment, about 0.3 mm is most preferable, but it may vary from 0.15 mm to 0.45 mm due to processing ability such as a general thermal spraying technique. Although processing with high thickness accuracy is possible, processing with high accuracy increases the cost of a thin film forming apparatus such as a thermal spraying apparatus. Therefore, the thickness of the ceramic insulating layer is preferably in the range of 0.15 mm to 0.45 mm.

The electric corrosion prevention type rolling bearing according to the present invention has a two-layer coating structure comprising a ceramic insulating layer and a metal layer interposed between the insulating layer and the surface on a surface attached to the housing or shaft of the bearing ring. Since it is provided with a layer, it has excellent electrical insulation, it is difficult to cause a fitting error due to heat generation, and while obtaining the adhesion of the insulating layer to the raceway, there are few processing steps, manufacturing is easy, and cost reduction is achieved. I can plan.
When the thickness of the ceramic insulating layer is 0.15 mm to 0.45 mm, the processing time can be shortened, the material can be saved, and the heat dissipation can be improved while sufficiently ensuring the electric insulation by the film thickness. Further, there is no decrease in electrical insulation due to the occurrence of cracks and the like, and stable electrical insulation can be obtained.

  Prior to the embodiment of the present invention, a proposed example of an electric corrosion prevention type rolling bearing will be described with reference to FIG. This electric corrosion prevention type rolling bearing is such that a rolling element 3 is interposed between an inner ring 1 and an outer ring 2 which are raceways, respectively, and a coating layer 5 having a two-layer structure is provided on the outer ring 2. This bearing is used, for example, as a rotor support bearing in a main motor of a railway vehicle. This bearing is a cylindrical roller bearing, and the outer ring 2 has flanges 2a on both sides. The rolling element 3 may be held in a pocket of a cage (not shown), or the cage may be omitted as a full roller bearing. The inner and outer rings 1 and 2 and the rolling element 3 are made of a metal material such as bearing steel.

The covering layer 5 includes a ceramic insulating layer 6 provided directly on the outer ring 2 and a metal layer 7 covering the insulating layer 6. The range in which the coating layer 5 is provided is a surface that is attached to the housing (not shown) of the outer ring 2. In the illustrated example, the coating layer 5 is provided in a range from the outer diameter surface a of the outer ring 2 to the width surfaces b on both sides. ing. The covering layer 5 is continuously provided from the outer diameter surface a to the width surface b including the chamfered portion c. The surfaces a and b on which the insulating layer 6 of the outer ring 2 is provided are treated as adhesion improving surfaces. This adhesion improving surface is, for example, a roughened surface, specifically a sandblasted surface. The insulating layer 6 and the metal layer 7 are both sprayed layers. The metal layer 7 may have a machined surface. That is, the metal layer 7 is sprayed to a thickness including a grinding allowance, and after spraying, machining such as grinding is performed on the outer diameter surface, the width surface, and in some cases, each surface of the chamfered portion so as to have a predetermined dimension. May be applied.
Thermal spraying is to form a surface film by melting the material (powder or rod) to be sprayed at an ultra-high temperature and making it collide with a workpiece by a jet jet. It is necessary to set an appropriate thermal spraying condition using a thermal spraying apparatus capable of obtaining a super-high-speed jet and an ultra-high temperature.

The thickness of the insulating layer 6 is preferably in the range of 0.15 mm to 0.45 mm, and most preferably about 0.3 mm. For example, the insulating layer 6 may be provided with a target thickness of 0.3 mm, and may vary within a range of 0.15 mm to 0.45 mm as a result of accuracy due to the thermal spraying processing capability. In other words, spraying may be performed with a target thickness of about 0.3 mm using a spraying means that causes a variation of about plus or minus 0.15 mm.
The thickness of the metal layer 7 is preferably 0.1 mm or more. This thickness is the thickness after machining when the metal layer 7 is machined.
Since the insulating layer 6 and the metal layer 7 to be sprayed have fine pores, a sealing process is performed so that moisture does not enter the pores after the spraying is completed. The sealing treatment is performed by impregnating with a highly permeable adhesive or the like.
When the surfaces a and b on which the insulating layer 6 of the outer ring 2 is provided are roughened surfaces as the adhesion improving surface, the center line roughness is rougher than 3.2a and the maximum height is rougher than 25S. It is preferable.

Examples of the ceramic material used for the insulating layer 6 include metal oxides such as alumina (Al2 O3), gray alumina, titanium oxide (TiO2), chromium oxide (Cr2 O3), or composite metal oxides based on these. Used.
As the material of the metal layer 7, Al, Ni, Cr, Fe or the like is used, or a composite material obtained by mixing these materials is used. The metal layer 7 is preferably made of a relatively soft material having a hardness after spraying of Hv 450 or less, preferably Hv 300 or less. Moreover, it is preferable that the metal layer 7 is what has electroconductivity.

  According to this configuration, since the ceramic insulating layer 6 is interposed between the outer ring 2 and the housing, insulation is ensured between them, and electrical insulation between the shaft fitted to the inner ring 1 and the housing is achieved. Secured. In the experiment, it was confirmed that the electric corrosion prevention type rolling bearing of the above proposed example can obtain a predetermined insulation performance (at least 10 MΩ / 500 V load). Further, even if the bearing of the above-mentioned proposed example is mounted in a bearing box having a fitting size equivalent to that of an actual machine and is heated to a temperature rise that can occur in use, it has a predetermined insulation performance. Thus, it was confirmed that even if the thickness of the insulating layer 6 is reduced to the above-mentioned thickness of 0.15 mm to 0.45 mm, it can be used practically. By making the thickness of the insulating layer 6 as thin as this range, there is less concern about the occurrence of cracks or the like as compared with the case of increasing the thickness, and the insulating property is stably maintained.

  Further, the surfaces a, b, and c on which the insulating layer 6 of the outer ring 2 is provided are sand-blasted so that the surface roughness is rougher than 3.2a in the center line average roughness and rougher than 25S in the maximum height. Thus, the adhesion of the insulating layer 6 to the outer ring 2 can be ensured while using ceramics as the insulating layer 6. Note that recent advances in thermal spraying technology have also facilitated ensuring the adhesion of the insulating layer 6 to the outer ring 2. When the adhesion strength of the insulating layer 6 was measured in accordance with the adhesion strength measurement method by JIS, a result of 44.8 MPa or more was obtained, and it was confirmed that it was sufficiently practical. This eliminates the need for a metal layer on the inner layer provided to improve adhesion in the conventional three-layer coating layer, and further eliminates the manufacturing process of the coating layer, thereby reducing manufacturing costs. .

  For press-fitting between the outer ring 2 and the housing, the metal layer 7 covering the insulating layer 6 prevents the insulating layer 6 from peeling off. As described above, the metal layer 7 is preferably made of a relatively soft material having an Hv of 450 or less. By using such a material, it is difficult to transmit an impact load or the like from the outside to the insulating layer 6. Can be prevented from being damaged. Furthermore, by making the metal layer 7 conductive, by bringing the terminal of the insulation resistance measuring instrument into contact with part of the sprayed metal layer 7 on the outer surface and part of the material surface inside the outer ring 2, Insulation performance can be confirmed, making measurement management easier.

In this bearing, the two coating layers 5 of the insulating layer 6 and the metal layer 7 have the following advantages in detail compared to the conventional three coating layers. In the thermal spraying process, it is necessary to use a predetermined jig for each thermal spraying of each layer so that the thermal spray layer is formed only at a necessary portion. However, in this proposed example, since only two layers are required, the jig can be attached and detached. In addition to being able to reduce work, the number of processes can be reduced, such as the number of times the spraying conditions are changed (the conditions differ between metal materials and ceramics) and the number of times the spraying material (powder) is replaced in the spraying device. Work is no longer necessary. Furthermore, by reducing the thickness of the insulating layer 6 to 0.15 mm to 0.45 mm, the spraying time can be shortened and the material cost can be reduced, and the cost can be greatly reduced by the number of processes and thinning. In addition, by reducing the thickness of the insulating layer 6 having a lower thermal conductivity than that of the bearing steel, it can be expected to improve heat dissipation.
As described above, according to this proposed example, by simplifying the insulating structure and reducing the thickness of the insulating layer 6, it is possible to save processing man-hours, processing time, and materials, and a significant cost reduction can be achieved.

FIG. 2 shows an embodiment of the present invention. In this embodiment, the coating layer 5 </ b> A provided on the outer ring 2 has a two-layer structure of a ceramic insulating layer 6 and a metal layer 8 provided between the insulating layer 6 and the outer ring 2. As the material of the metal layer 8, any of the materials described as the material of the metal layer 7 in the proposed example of FIG. 1 may be used. Both the metal layer 8 and the insulating layer 6 are sprayed layers. Unlike the proposal example of FIG. 1, the surface which provides the metal layer 8 of the outer ring | wheel 2 does not perform an adhesive improvement process. The other structure in this embodiment is the same as the proposal example of FIG.
In the case of this configuration, the insulating layer 6 of ceramics is interposed between the outer ring 2 and the housing, as in the above-described proposal example, so that insulation is ensured between them. The insulating layer 6 is made of a ceramic sprayed layer, which is a hard material. Adhesiveness to the outer ring 2 can be obtained by an inner soft metal layer 8 serving as an undercoat. Further, since the covering layer 5A has a two-layer structure, the number of processing steps is smaller than that of the three-layer structure, and the manufacturing is simple and the cost can be reduced.

  In the above embodiment, the case where the outer ring 2 is provided with the coating layer has been described. However, in the present invention, the inner ring 1 may be provided with a coating layer made of a ceramic insulating layer and a metal layer. When providing the said coating layer in the inner ring | wheel 1, a coating layer is provided in the range extending from the internal diameter surface used as the attachment surface to a shaft, or an internal diameter surface to a width surface.

It is a fragmentary sectional view of the electric corrosion prevention type rolling bearing concerning a proposal example. It is a fragmentary sectional view of the electric corrosion prevention type rolling bearing concerning one embodiment of this invention.

Explanation of symbols

1 ... Inner ring (Raceway)
2 ... Outer ring (Raceway)
3 ... rolling element 5A ... coating layer 6 ... insulating layer 8 ... metal layer

Claims (2)

  An electric corrosion prevention type rolling bearing in which a ceramic insulating layer and a coating layer having a two-layer structure of a metal layer interposed between the insulating layer and the surface are provided on a surface attached to the housing or shaft of the bearing ring.   The electric corrosion prevention type rolling bearing according to claim 1, wherein the ceramic insulating layer has a thickness of 0.15 mm to 0.45 mm.

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