JP2016156403A - Insulated roller bearing for electric corrosion prevention - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the film strength by decreasing the vacancy of an insulated film in an insulated roller bearing for electric corrosion prevention on which a ceramic insulation layer is formed.SOLUTION: An insulated roller bearing for electric corrosion prevention has an insulated film including, as a main ingredient, alumina (AlO) containing calcia (CaO) of 10-40 mass% on a surface other than a surface on which a raceway surface of at least one bearing ring is provided.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulating rolling bearing for preventing electric corrosion in which a bearing ring is covered with a ceramic insulating layer.

  In a rolling bearing that supports a rotating shaft of various electric devices such as an electric motor and a generator, a current such as a return current and a motor shaft current flows through the bearing itself. When a current flows through the rolling bearing, electrolytic corrosion occurs in a portion serving as a current path, and the life of the rolling bearing is remarkably shortened. In order to prevent the occurrence of such electric corrosion, an insulating rolling bearing for preventing electric corrosion has been used in which an insulating layer is formed on the surface of the outer ring or inner ring constituting the rolling bearing so that no current flows through the bearing. .

  A resin layer is also formed as an insulating layer, but it is formed by spraying ceramics from the viewpoint of insulation performance, durability, etc., and droplets of the ceramic material are sprayed from the spray nozzle to a surface other than the raceway surface, that is, The outer peripheral surface and both end surfaces of the outer ring and the inner peripheral surface and both end surfaces of the inner ring are sprayed to form an insulating layer having a predetermined thickness (see, for example, Patent Documents 1 to 3).

  However, many holes are generated in the insulating coating formed by spraying a ceramic material, and the distribution of the holes also varies. If there are such holes, the insulating coating becomes brittle, and in some cases, cracks may be generated and peeled off.

Japanese Patent No. 4795888 Japanese Patent No. 4920066 Japanese Patent No. 4826427

  This invention is made | formed in view of such a condition, and it aims at reducing the void | hole of an insulating film and improving film | membrane intensity | strength.

In order to solve the above problems, the present invention provides the following insulated rolling bearing for preventing electrolytic corrosion.
(1) Provided in a freely rollable manner between a pair of raceways arranged concentrically and made of metal, respectively, and a pair of raceways formed on opposite surfaces of these raceways. And a plurality of rolling elements each made of metal, and a surface other than the surface provided with the raceway surface of at least one of the race rings is covered with a ceramic insulating layer to prevent electric corrosion. In
An insulating rolling bearing for electrolytic corrosion prevention, characterized in that the insulating layer is mainly composed of alumina (Al ₂ O ₃ ) containing calcia (CaO) in a proportion of 10 to 40% by mass.
(2) The insulating rolling bearing for electrolytic corrosion prevention according to (1), wherein the insulating layer is sealed with a sealing agent containing a synthetic resin.

  The insulating rolling bearing for preventing galvanic corrosion of the present invention is formed by forming a thermal spray coating made of alumina containing a specific amount of calcia as an insulating layer, and this thermal spray coating has more voids than a conventional thermal spray coating. Since the film strength is small and the film strength is excellent, a high insulating effect can be maintained for a long time.

It is sectional drawing which shows an example of the insulated rolling bearing for electric corrosion prevention of this invention. It is a graph which shows the relationship between CaO content and porosity. It is a graph which shows the relationship between CaO content and fracture toughness value.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  In the present invention, the structure of the electric rolling prevention insulating rolling bearing is not limited, and for example, the electric corrosion prevention insulating rolling bearing shown in FIG. 1 can be exemplified. In the illustrated insulating rolling bearing for preventing electric corrosion, a plurality of rolling elements 5 are provided between the inner ring raceway 2 formed on the outer peripheral surface of the inner ring 1 and the outer ring raceway 4 formed on the inner peripheral surface of the outer ring 3, A surface of the outer ring 3 other than the surface on which the outer ring raceway 4 is formed, that is, an outer peripheral surface 7 of the outer ring 3, axial end surfaces 8, 8, and a curved portion 9, which continuously connects the outer peripheral surface 7 and both end surfaces 8, 8. 9, the insulating layer 6 is formed. In such an electric rolling prevention insulating rolling bearing, the insulating layer 6 insulates the outer ring 3 from the housing in a state where the outer ring 3 is fitted and supported in a metal housing. As a result, no current flows between the outer ring 3 and the housing, and no electrolytic corrosion occurs on other bearing components.

  Although not shown, an insulating layer may be formed on the inner ring 1 other than the surface on which the inner ring raceway 2 is formed.

The insulating layer 6 is a thermal spray coating obtained by thermal spraying a thermal spray material containing CaO (calcia) and Al ₂ O ₃ (alumina). Since the melting point of alumina-calcia is lower than composite ceramics of other oxides and alumina, such as alumina-zirconia, the sinterability is improved and the amount of voids generated is reduced. Therefore, film properties such as wear resistance are better than those of an insulating layer mainly composed of alumina-zirconia.

  In the insulating layer 6 made of the sprayed coating, the calcia content is 10 to 40% by mass. When the calcia content is less than 10% by mass, the melting point of the sprayed material is not sufficiently lowered, and the pores are not reduced. On the other hand, if the calcia content exceeds 40% by mass, coarse CaO particles are generated, voids are generated around the CaO particles, and the strength of the coating is lowered. The CaO content is preferably 20 to 30% by mass.

Alumina is preferably highly pure, and specifically, high-purity alumina having Na ₂ O ₃ of 0.5% by mass or less and Fe ₂ O ₃ of 0.1% by mass or less is preferred. Such high-purity alumina can be produced, for example, by the Bayer method.

  The thermal spray material is obtained by dissolving alumina and calcia in an electric furnace in an oxygen stream to uniformly disperse calcia in alumina, and then pulverizing and sizing the obtained ingot. It is preferable that the particle size is fine and the particle size is uniform, and the particle size is 5-100 μm, preferably 10-50 μm. By using the sprayed material thus sized, it is possible to form a dense and high-strength insulating layer 6 without voids.

Thus, by making the insulating layer 6 a sprayed coating of CaO—Al ₂ O ₃ system, the number of pores can be reduced, specifically, the porosity can be reduced to 8% or less, and the film strength can be reduced. Greatly improve.

  In addition, there is no restriction | limiting in the spraying method, For example, a plasma spraying method is employable. The thickness of the insulating layer 6 is not limited, and is about 0.5 to 0.7 μm as in the conventional case.

  Moreover, you may perform a sealing process after thermal spraying. When there are many holes, the sealing agent did not sufficiently penetrate into all the holes, and many holes that were not sealed remained, but the alumina sprayed coating containing a specific amount of calcia was denser than before. Since the pores are extremely small, the pores can be reliably filled by this sealing treatment, and excellent insulation performance can be ensured.

  For the sealing treatment, a synthetic resin such as an acrylic resin, an epoxy resin, a fluororesin, a phenol resin, a polyester resin, or a sealing agent obtained by dissolving or dispersing a composite resin of these in an organic solvent is applied and dried. Good. The sealing agent penetrates into the pores of the sprayed coating, and the synthetic resin fills the pores and seals them.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

  An ingot made of a thermal spray material having a calcia content of 5, 10, 20, 30, 40, or 50% by mass is prepared, and the obtained ingot is pulverized and sized to a particle size of 10 to 50 μm to have a different calcia content. A thermal spray material was prepared.

A single-row deep groove ball bearing having an identification number 6316 (outer diameter: 170 mm, inner diameter: 80 mm, width: 39 mm) is shown in FIG. The film thickness of the sprayed coating was fixed at 200 μm by processing and polishing. After spraying, a test piece was taken from the film forming part, and after the cross-section polishing, the porosity of the cross section of the sprayed coating was determined by the following procedure.
(1) Using a digital microscope, capture a cross-sectional image of the test piece into a personal computer.
(2) The captured image is binarized with an appropriate threshold (converted into two colors of black and white).
(3) The area of the black part is counted as a pore, and the porosity is calculated from “black part area / measurement range area”.
(4) This work is performed at 12 locations per test piece, and the average value is calculated.

  The results are shown in FIG. 2, and the porosity is maximum when the calcia content is less than 10% by mass, and the porosity is large even when it exceeds 40% by mass. On the other hand, the porosity is reduced when the calcia content is in the range of 10 to 40% by mass, and the lowest is particularly obtained in the range of 20 to 30% by mass.

The strength of the coating was evaluated from the fracture toughness value. The results are shown in FIG. 3, and the same tendency as the porosity is observed. When the calcia content is less than 10% by mass, the fracture toughness value is low due to the generation of many vacancies. The fracture toughness value is minimum at over 40% by mass, which is due to the formation of coarse CaO. On the other hand, if the calcia content is in the range of 10 to 40% by mass, the fracture toughness value is high, and is particularly maximum in the range of 20 to 30% by mass. The fracture toughness value of the thermal spray coating with a commercially available thermal spray material is about 3 MPa · m ^0.5 , and it can be seen that a high-strength thermal spray coating can be obtained by containing 10-40 mass% of calcia.

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Inner ring track 3 Outer ring 4 Outer ring track 5 Rolling element 6 Insulating layer 7 Outer peripheral surface 8 End surface 9 Curved portion

Claims (2)

Rollers are provided between a pair of raceways arranged concentrically, each made of metal, and a pair of raceways formed on opposite surfaces of these raceways. In an insulating rolling bearing for preventing electric corrosion, comprising a plurality of rolling elements each made of metal and having a surface other than the surface provided with the raceway surface of at least one raceway ring covered with a ceramic insulating layer,
An insulating rolling bearing for electrolytic corrosion prevention, characterized in that the insulating layer is mainly composed of alumina (Al ₂ O ₃ ) containing calcia (CaO) in a proportion of 10 to 40% by mass.   2. The insulating rolling bearing for preventing electrolytic corrosion according to claim 1, wherein the insulating layer is sealed with a sealing agent containing a synthetic resin.

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