JP2022085600A - Insulated bearing - Google Patents

Abstract

To provide an insulated bearing that comprises an insulating film capable of obtaining excellent insulation performance and thermal conductivity even in a high-frequency environment, thereby has good durability, and can restrain occurrence of electrolytic corrosion.SOLUTION: An insulated bearing 10 comprises an outer ring (bearing ring) 1 comprising an outer ring side raceway surface 1a, an inner ring (bearing ring) 2 comprising an inner ring side raceway surface 2a, and a plurality of rolling elements 3 held so as to be rollable between the outer ring side raceway surface 1a and the inner ring side raceway surface 2a. For example, the outer ring 1 comprises an insulating film 5 on an outer surface 1b on the side opposite to the outer ring side raceway surface 1a, and both side surfaces 1c continuous with the outer surface 1b, and the insulating film 5 is a composite film in which a resin layer 6 and a ceramic layer 7 are stacked.SELECTED DRAWING: Figure 1

Description

The present invention relates to an insulated bearing that is mounted on a rotating shaft of a motor, a generator, or the like, and is particularly suitable for mounting on a portion where a current may flow.

Conventionally, in a device equipped with a rotating body, a metal bearing is mounted on a rotating shaft in order to reduce the frictional resistance caused by the rotation. For example, in a motor that rotates a rotating body (so-called rotor) by electromagnetic force or a generator that rotates a rotating body (so-called turbine) by hydraulic power or the like to generate power, a bearing is attached to the rotating shaft of the rotating body. ..

These motors, generators, and the like have a problem that a current leaks to a bearing and corrosion caused by the current flowing (hereinafter referred to as "electrolytic corrosion") easily progresses. Therefore, various techniques for preventing electrolytic corrosion of bearings have been studied.
For example, Patent Document 1 discloses an insulating bearing in which at least one of an outer ring and an inner ring is coated with an insulating film, in which the components of the insulating film and the content of additives are appropriately controlled. Further, Patent Document 1 describes that the above-mentioned insulated bearing can maintain good electrolytic corrosion resistance and thermal conductivity for a long period of time.

Japanese Unexamined Patent Publication No. 2017-53481

By the way, in general, the insulation resistance value and the frequency such as electromagnetic noise are in an inverse proportional relationship. That is, it is known that the insulation resistance value is lower in a high frequency environment due to electromagnetic noise or the like than in a low frequency environment.

However, due to the recent promotion of energy saving, motors that are generally used are often used by inverter control, and frequent operation control is required for the motor, so it is generated from the inverter. The frequency of electromagnetic noise is increasing.
When a metal bearing is used in an environment where such electromagnetic noise is generated, the electromagnetic noise generated from the inverter causes a potential difference inside the bearing, a current flows inside the bearing, and electrolytic corrosion occurs inside the bearing. The possibility is high. In particular, as the frequency of electromagnetic noise increases, the insulation resistance value of the bearing decreases as described above, so that electrolytic corrosion of the bearing is more likely to occur.

Further, if the thermal conductivity of the insulating film is low, heat generation of frictional resistance generated by rotation is accumulated in the bearing, which causes the life of the bearing to be shortened. Therefore, it is required to develop a bearing having good thermal conductivity of the film and excellent electrolytic corrosion resistance even in an environment at high frequency.

The present invention has been made in view of the above problems, has excellent thermal conductivity, has a film capable of obtaining excellent insulating properties even in an environment at high frequencies, has good durability, and is electric. It is an object of the present invention to provide an insulated bearing capable of suppressing the occurrence of erosion.

As a result of diligent research to solve the above problems, the present inventors have focused on the fact that a low dielectric constant of the coating has a positive effect on the insulating property of the bearing. That is, the present inventors have an insulating film having excellent thermal conductivity and insulating property by laminating a resin layer having a low dielectric constant and a ceramic layer having an excellent thermal conductivity in a predetermined region of a bearing. Found that can be obtained. The present invention has been made based on these findings.

The insulated bearing according to the present invention has the configuration of the following [1].

[1] In an insulated bearing including a pair of raceway rings having a pair of raceway surfaces and a plurality of rolling elements that are rotatably held between the pair of raceway surfaces.
At least one of the pair of raceway rings has an insulating film on the outer surface opposite to the raceway surface and on both side surfaces continuous with the outer surface.
The insulating film is an insulating bearing, which is a composite film in which a resin layer and a ceramic layer are laminated.

Further, preferred embodiments of the present invention relating to insulated bearings relate to the following [2] to [4].
[2] The insulating bearing according to [1], wherein the resin layer has a relative permittivity of 5.0 or less at 20 ° C.

[3] The insulating bearing according to [1] or [2], wherein the insulating film is laminated in the order of the resin layer and the ceramic layer from the raceway ring side.

[4] The insulating bearing according to any one of [1] to [3], wherein the film thickness of the insulating film is 50 to 500 μm.

According to the present invention, since the insulating film has an insulating film on the outer surface and both side surfaces of at least one of the pair of raceway rings, and the insulating film is a composite film in which a resin layer and a ceramics layer are laminated, this insulating film has a high frequency. It has excellent insulation and thermal conductivity even in the environment of. Thereby, it is possible to provide an insulated bearing having good durability and capable of suppressing the occurrence of electrolytic corrosion.

FIG. 1 is a schematic cross-sectional view showing an insulated bearing according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an insulated bearing according to a second embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing an insulated bearing according to a third embodiment of the present invention.

Hereinafter, embodiments of the present invention will be specifically described. The present invention is not limited to the embodiments described below.

<First Embodiment>
FIG. 1 is a schematic cross-sectional view showing an insulated bearing according to the first embodiment of the present invention. In this embodiment, a radial bearing will be described as an insulating bearing.

As shown in FIG. 1, the insulating bearing 10 is rollable between an outer ring (race ring) 1 and an inner ring (race ring) 2 arranged concentrically, and an outer ring 1 and an inner ring 2 (a pair of race rings). It has a plurality of rolling elements 3 held in a. The outer ring 1 is formed with an outer ring-side raceway surface (raceway surface) 1a, the inner ring 2 is formed with an inner ring-side raceway surface (raceway surface) 2a, and the plurality of rolling elements 3 are formed on the outer ring-side raceway surface 1a. And between the inner ring side raceway planes 2a (a pair of raceway planes), they are held while being separated at equal intervals by the cage 4.

In the first embodiment, the resin layer 6 is formed on the outer surface 1b on the opposite side of the outer ring side raceway surface 1a of the outer ring 1 and on both side surfaces 1c continuous with the outer surface 1b, and the resin layer 6 is formed. The ceramic layer 7 is laminated on the top, and the insulating film 5 is a composite film in which the resin layer 6 and the ceramic layer 7 are laminated.

(Resin layer)
The resin constituting the resin layer generally has a low relative permittivity and has high insulation performance. The present inventors have found that when the dielectric constant of the coating film is lowered, the capacitance becomes smaller and the insulation resistance value becomes higher, and excellent insulation property can be obtained even in an environment at a high frequency.
As the resin constituting the resin layer 6, for example, an epoxy resin, a fluororesin, a polyamide, or the like can be applied. Further, the resin layer 6 can be formed on the outer surface 1b and both side surfaces 1c of the outer ring 1 by a method such as a spraying method, an electrostatic coating method, or a flow dipping method.

The lower the relative permittivity of the resin layer 6 formed in the predetermined region of the outer ring 1, the higher the insulating performance can be obtained. Therefore, the relative permittivity of the resin layer at 20 ° C. is preferably 5.0 or less, and more preferably 3.0 or less. The relative permittivity of the resin layer can be a value measured in accordance with ASTM D150.

(Ceramics layer)
Since the ceramics constituting the ceramic layer 7 generally have a higher thermal conductivity than the resin, forming the ceramic layer 7 in a predetermined region of the outer ring 1 causes heat generation of frictional resistance generated by the rotation of the bearing. Accumulation in the bearing can be suppressed, which can improve the durability of the bearing.
In the first embodiment, the resin layer 6 and the ceramic layer 7 are formed in this order from the outer ring 1 side (that is, the raceway ring side), that is, the ceramic layer 7 is formed outside the resin layer 6. In the present embodiment, the order in which the resin layer 6 and the ceramic layer 7 are laminated is not particularly limited. However, since the ceramic layer 7 has a high hardness, if the ceramic layer 7 is formed on the surface of the resin layer 6, the durability of the insulating film 5 can be improved.

As the base material constituting the ceramic layer 7, for example, aluminum oxide (Al ₂ O ₃ ) or zirconia (ZrO ₂ ) can be used. Further, the ceramic layer 7 can be formed by thermal spraying, and by adjusting the direction of the thermal spray nozzle, the ceramic layer 7 can be formed on the outer surface 1b and both side surfaces 1c of the outer ring 1.

Further, when the ceramic layer 7 contains a component having good heat dissipation in addition to the base material, it is possible to further suppress the accumulation of heat generation of frictional resistance generated by the rotation of the bearing in the bearing. ,preferable. Examples of the component having good heat dissipation include silicon carbide (SiC), aluminum nitride (AlN), silicon nitride (Si _{3N 4 )} and the like.

(Insulation film)
As described above, in the first embodiment, the insulating film 5 is provided on the outer surface 1b and both side surfaces 1c of the outer ring 1. When the resin layer 6 is formed up to the outer ring side raceway surface 1a of the outer ring 1 or its vicinity, the insulating film is peeled off and enters between the outer ring side raceway surface 1a and the inner ring side raceway surface 2a, and the rolling elements 3 and the like are formed. If it adheres to the bearing, the performance of the bearing may be deteriorated.
On the other hand, if the insulating film 5 is formed only on the outer surface 1b of the outer ring 1, the desired insulating performance may not be obtained. Therefore, it is assumed that the insulating film 5 is formed on the surfaces (outer surface 1b and both side surfaces 1c) in three directions excluding the surface on which the raceway surface is formed.

When the film thickness of the insulating film 5 is 50 μm or more, excellent insulating performance can be obtained. Therefore, the film thickness of the insulating film 5 is 50 μm or more, preferably 100 μm or more. On the other hand, when the film thickness of the insulating film 5 is 500 μm or less, an increase in cost can be suppressed. Therefore, the film thickness of the insulating film 5 is 500 μm or less, preferably 300 μm or less.

Further, in the first embodiment, the insulating film 5 has an insulating film 5 on the outer surface 1b and both side surfaces 1c of the outer ring 1, but in the present invention, the component forming the insulating film 5 is the outer ring. Not limited to 1.

<Second Embodiment>
FIG. 2 is a schematic cross-sectional view showing an insulated bearing according to a second embodiment of the present invention. In FIG. 2, the same or equivalent parts as those in the first embodiment are designated by the same reference numerals in the drawings, and the description thereof will be omitted or simplified.

As shown in FIG. 2, in the insulating bearing 20 according to the second embodiment, the insulating film 15 is formed on the inner ring 2 side. Specifically, the resin layer 16 is formed on the outer surface 2b opposite to the inner ring side raceway surface 2a of the inner ring 2 and on both side surfaces 2c continuous with the outer surface 2b, and further, the resin layer 16 is formed. The ceramic layer 17 is laminated on the top. The insulating film 15 is formed by the resin layer 16 and the ceramic layer 17.

Also in the second embodiment configured in this way, the resin layers 6 and 16 and the ceramic layers 7 and 17 constituting the insulating films 5 and 15 are the same as those in the first embodiment, and the same effect can be obtained. be able to. That is, the resin layers 6 and 16 are formed to have excellent insulating properties even in an environment at high frequencies, and the ceramic layers 7 and 17 are formed to provide excellent thermal conductivity insulation. Films 5 and 15 can be obtained. Therefore, it is possible to obtain an insulated bearing having excellent durability and capable of suppressing the occurrence of electrolytic corrosion.

<Third Embodiment>
FIG. 3 is a schematic cross-sectional view showing an insulated bearing according to a third embodiment of the present invention. In FIG. 3, the same or equivalent parts as those in the first embodiment are designated by the same reference numerals in the drawings, and the description thereof will be omitted or simplified.

As shown in FIG. 3, in the insulating bearing 30 according to the third embodiment, the insulating film 5 is formed on the outer ring 1 and the insulating film 15 is formed on the inner ring 2. Specifically, the resin layer 6 is formed on the outer surface 1b of the outer ring 1 and on both side surfaces 1c, and the ceramic layer 7 is further laminated on the resin layer 6. The insulating film 5 is formed by the resin layer 6 and the ceramic layer 7.
Further, a resin layer 16 is formed on the outer surface 2b of the inner ring 2 and on both side surfaces 2c, and a ceramic layer 17 is further laminated on the resin layer 16. The insulating film 15 is formed by the resin layer 16 and the ceramic layer 17.

Also in the third embodiment configured in this way, the resin layers 6 and 16 and the ceramic layers 7 and 17 constituting the insulating films 5 and 15 are the same as those in the first embodiment, and the same effect can be obtained. be able to. That is, the resin layers 6 and 16 are formed to have excellent insulating properties even in an environment at high frequencies, and the ceramic layers 7 and 17 are formed to provide excellent thermal conductivity insulation. Films 5 and 15 can be obtained. Therefore, it is possible to obtain an insulated bearing having excellent durability and capable of suppressing the occurrence of electrolytic corrosion.

<Matters common to each embodiment>
The insulating films 5 and 15 may have other functional layers, if necessary, in addition to the resin layers 6 and 16 and the ceramic layers 7 and 17. Further, if necessary, the plurality of resin layers 6 and 16 and the plurality of ceramic layers 7 and 17 may be alternately laminated to form the insulating films 5 and 15.
However, in order to suppress the heat generation of frictional resistance generated by the rotation of the bearing from being accumulated in the bearing, the resin layers 6 and 16 and the ceramic layers 7 and 17 are each one layer, and the ceramic layers 7 and 17 are used. It is preferably formed on the outer side of the resin layers 6 and 16.

Further, as described above, the insulating film may be formed on the outer ring 1 side or the inner ring 2 side, and by having the insulating film in a predetermined region in at least one of the outer ring 1 and the inner ring 2. Insulation can be obtained. For example, in the case of a small insulating bearing 10, as shown in FIG. 1, it is difficult to form an insulating film on the outer surface and both side surfaces located inside the inner ring 2, so that the insulating film 5 is on the outer ring 1 side. It is preferable to form.

On the other hand, in the case of the large insulated bearing 20, as shown in FIG. 2, it is easy to form the insulating film 15 on the outer surface 2b and the both side surfaces 2c of the inner ring 2, and further, the inner ring 2 side is located on the inner ring 2 side. Since the region where the film is formed becomes narrow, the insulating film 15 can be formed at low cost.

The first to third embodiments are examples in which an insulating film is formed on a ball bearing as a bearing, but the present invention is not limited to the ball bearing and can be applied to various rolling bearings. Further, the present invention can be applied not only to radial bearings but also to thrust bearings.

1 Outer ring 1a Outer ring side raceway surface 1b, 2b Outer surface 1c, 2c Both sides 2 Inner ring 2a Inner ring side raceway surface 3 Rolling element 4 Cage 5,15 Insulation film 6,16 Resin layer 7,17 Ceramic layer 10,20,30 Insulated bearing

Claims (4)

In an insulated bearing comprising a pair of raceway rings having a pair of raceway surfaces and a plurality of rolling elements rotatably held between the pair of raceway surfaces.
At least one of the pair of raceway rings has an insulating film on the outer surface opposite to the raceway surface and on both side surfaces continuous with the outer surface.
The insulating film is an insulating bearing, which is a composite film in which a resin layer and a ceramic layer are laminated. The insulating bearing according to claim 1, wherein the resin layer has a relative permittivity of 5.0 or less at 20 ° C. The insulating bearing according to claim 1 or 2, wherein the insulating film is laminated in the order of the resin layer and the ceramic layer from the raceway ring side. The insulating bearing according to any one of claims 1 to 3, wherein the insulating film has a film thickness of 50 to 500 μm.

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