Rolling bearings

Abstract

To provide a rolling bearing that offers excellent insulation performance while also reducing costs. [Solution] The rolling bearing 1 comprises an inner ring 2 having an inner ring raceway surface 21a on its outer circumferential surface 21, an outer ring 3 having an outer ring raceway surface 31a on its inner circumferential surface 31, and a plurality of balls 4 interposed between the inner ring raceway surface 21a and the outer ring raceway surface 31a, wherein the insulating thermal spray layer L is formed only on the outer circumferential surface 21 of the inner ring 2, and the insulating thermal spray layer L is formed over the entire area of ​​the outer circumferential surface 21, including the inner ring raceway surface 21a and the shoulder surfaces 21b connected to both sides of the inner ring raceway surface 21a.

Description

Technical Field

[0001] The present invention relates to a rolling bearing used in motors, generators and the like for the purpose of preventing electric corrosion, and particularly relates to a rolling bearing that has excellent insulation performance and is less expensive than ceramic rolling element bearings.

Background Art

[0002] Rolling bearings are used in fan motors and servo motors employed in industrial machinery motors, as well as driving motors used in EV vehicles and hybrid vehicles.

[0003] In recent years, for the purpose of achieving higher efficiency in industrial machinery motors and driving motors, most such motors are controlled by inverters. Inverter control controls the voltage and frequency input to the motor in accordance with the set rotation speed of the motor. As the switching frequency of the inverter increases, the occurrence frequency of shaft voltage in the motor increases accordingly. As a result, in a rolling bearing incorporated in an inverter-driven motor, a potential difference may occur between the outer ring, the inner ring and the rolling elements. When this potential difference becomes large, sparking may occur through the oil film formed between the bearing ring and the rolling elements inside the bearing. This sparking causes "electric corrosion" in which the raceway surface and the like are locally melted, which may degrade the bearing function.

[0004] Furthermore, in recent years, as a driving system, e-Axle, which integrates conventionally separately arranged components such as a driving motor, an inverter, and a speed increasing / decreasing gear, has been becoming widespread. Countermeasures against electric corrosion are also important for rolling bearings that support the motor shaft of such e-Axles.

[0005] Conventionally, hybrid bearings have been known as a means of preventing galvanic corrosion, using ceramic rolling elements (e.g., ceramic balls) to electrically insulate the bearing. However, ceramic rolling elements have the problem of high manufacturing costs. On the other hand, inexpensive resin-molded bearings are also known, but there are concerns regarding their insulation performance, and they may be difficult to use in applications requiring higher insulation performance.

[0006] Conventionally, insulated bearings are known in which a ceramic thermal spray layer is formed on the outer surface of the raceway ring of a rolling bearing to electrically insulate the bearing. For example, Patent Document 1 describes a rolling bearing in which a ceramic thermal spray layer is formed on the outer circumferential surface and both axial ends of the outer ring of the rolling bearing. However, the amount of ceramic material used is relatively large, and there is a need for inexpensive insulated rolling bearings. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2006-077944 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention has been made in view of these circumstances, and aims to provide a rolling bearing that has excellent insulation performance and can reduce costs. [Means for solving the problem]

[0009] The rolling bearing of the present invention comprises an inner ring having an inner ring raceway surface on its outer circumference, an outer ring having an outer ring raceway surface on its inner circumference, and a plurality of rolling elements interposed between the inner ring raceway surface and the outer ring raceway surface, wherein the rolling bearing is characterized in that an insulating thermal spray layer is formed at least on the inner ring raceway surface. Furthermore, in the rolling bearing, it is preferable that the insulating thermal spray layer is formed only on the outer circumference surface of the inner ring, and that the insulating thermal spray layer is formed at least on the inner ring raceway surface. In this specification, the outer circumference surface of the inner ring is the surface facing the annular bearing space between the inner ring and the outer ring, and includes the inner ring raceway surface and the shoulder surfaces on both sides thereof. The inner circumference surface of the outer ring is the surface facing the bearing space, and includes the outer ring raceway surface and the shoulder surfaces on both sides thereof.

[0010] The insulating spray layer described above is formed over the entire area of ​​the outer circumferential surface, including the inner ring raceway surface and the shoulder surfaces connected to both sides of the inner ring raceway surface, or in the area adjacent to the inner ring raceway surface and the shoulder surfaces on both sides of the inner ring raceway surface. This adjacent area refers to an area that can prevent surface discharge occurring along the edge of the insulating spray layer interposed between the rolling element and the inner ring, and is, for example, a range of about 0.3 mm axially outward from the boundary between the inner ring raceway surface and the shoulder surface.

[0011] The insulating thermal spray layer described above is formed on the inner ring raceway surface and a portion of the shoulder surfaces connected to both sides of the inner ring raceway surface. The thickness of the insulating thermal spray layer formed on the inner ring raceway surface is 50 μm to 300 μm, and the insulating thermal spray layer formed on the shoulder surfaces is characterized by decreasing thickness as it extends axially outward.

[0012] The insulating thermal spray layer has a porosity of 1% or more and less than 5%, and the pores in the insulating thermal spray layer are not sealed with a sealing material.

[0013] The insulating thermal spray layer described above is formed only on the inner ring raceway surface and is not formed on the shoulder surfaces connected to both sides of the inner ring raceway surface.

[0014] The rolling elements are made of steel, and the area on which the insulating thermal spray layer is formed is 80% or less of the total surface area of ​​all the rolling elements.

[0015] The rolling bearing described above is characterized by comprising a contact-type conductive sealing member fixed to one of the outer ring and the inner ring, and slidingly contacting the other.

[0016] The above insulating thermal spray layer is characterized by being a ceramic thermal spray layer. [Effects of the Invention]

[0017] In the rolling bearing of the present invention, an insulating thermal spray layer is formed at least on the inner ring raceway surface, specifically on the entire area of ​​the outer circumferential surface including the inner ring raceway surface and the shoulder surfaces connected to both sides of the inner ring raceway surface, or in the area adjacent to the inner ring raceway surface and the shoulder surfaces on both sides of the inner ring raceway surface, thereby blocking the flow of electricity from the inner ring raceway surface to the rolling elements and suppressing the occurrence of electrolytic corrosion between the rolling elements and the raceway surface.

[0018] Furthermore, since the surface area of ​​the outer circumferential surface of the inner ring is generally smaller than the total surface area of ​​all rolling elements, it is possible to reduce the amount of ceramic material used compared to ceramic rolling element bearings while still achieving excellent insulation performance with the insulating thermal spray layer, thereby reducing costs. Moreover, since the surface area of ​​the outer circumferential surface of the inner ring is smaller than the surface area of ​​the inner circumferential surface and width surface of the inner ring, it results in a less expensive rolling bearing.

[0019] The insulating spray layer described above is formed on the inner ring raceway surface and a portion of the shoulder surfaces connected to both sides of the inner ring raceway surface. The thickness of the insulating spray layer formed on the inner ring raceway surface is 50 μm to 300 μm, and the thickness of the insulating spray layer formed on the shoulder surfaces decreases as it moves axially outward. This provides excellent peel resistance on the inner ring raceway surface, and also allows lubricating oil to be easily retained in the insulating spray layer formed on the shoulder surfaces, contributing to the continuous supply of lubricating oil to the inner ring raceway surface.

[0020] The porosity of the above-mentioned insulating thermally sprayed layer is 1% or more and less than 5%, and since it is a dense insulating layer, dielectric breakdown is unlikely to occur. Further, since the pores in the insulating thermally sprayed layer are not sealed with a sealing material, lubricating oil can enter the pores, resulting in excellent wear resistance. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0021] [Figure 1] FIG. 1 is an enlarged cross-sectional view showing a first embodiment of the rolling bearing of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a second embodiment of the rolling bearing of the present invention. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing a third embodiment of the rolling bearing of the present invention. [MODE FOR CARRYING OUT THE INVENTION]

[0022] The rolling bearing of the present invention is a rolling bearing that is incorporated into an apparatus having a structure where current may flow inside the bearing during use. The present inventors focused on the fact that the surface area of the outer peripheral surface (including the inner ring raceway surface) of an inner ring is smaller than the total surface area of rolling elements (for example, balls), and in the rolling bearing, an insulating thermally sprayed layer is formed on at least the inner ring raceway surface. More specifically, the insulating thermally sprayed layer is formed only on the outer peripheral surface of the inner ring, and the insulating thermally sprayed layer is formed on at least the inner ring raceway surface. That is, by forming the insulating thermally sprayed layer only at locations necessary for ensuring insulation, the same insulating effect can be obtained while being less expensive than a ceramic rolling element bearing.

[0023] Each embodiment will be described below with reference to the drawings. Note that the "axial direction" in the present application refers to a direction parallel to the central axis of the bearing, and "axially outer side" refers to a side away from the rolling elements in the axial direction.

[0024] (First Embodiment) Figure 1 is a cross-sectional view showing a rolling bearing according to a first embodiment of the rolling bearing of the present invention. As shown in Figure 1, the rolling bearing 1 is an open-type deep groove ball bearing and comprises an inner ring 2 having an inner ring raceway surface 21a on its outer circumferential surface 21, an outer ring 3 having an outer ring raceway surface 31a on its inner circumferential surface 31, and a plurality of balls 4 interposed between the inner ring raceway surface 21a and the outer ring raceway surface 31a. The balls 4 are held in a cage 5 positioned between the inner ring 2 and the outer ring 3. The space between the inner ring raceway surface 21a and the balls 4, and the space between the outer ring raceway surface 31a and the balls 4 are lubricated with lubricating oil.

[0025] In the rolling bearing 1, an insulating thermal spray layer L is formed only on the outer circumferential surface 21 of the inner ring 2. In this configuration, the insulating thermal spray layer L is formed over the entire area of ​​the outer circumferential surface 21, including the inner ring raceway surface 21a and the shoulder surfaces 21b connected to both sides of the inner ring raceway surface 21a. This ensures reliable insulation between the inner ring 2 and the balls 4, preventing current from flowing into the bearing through the shaft member (not shown) inserted into the inner ring 2. In the rolling bearing 1, the insulating thermal spray layer is not formed on the inner circumferential surface 22 and axial end surface 23 of the inner ring 2, or on the inner circumferential surface 31, outer circumferential surface 32, and axial end surface 33 of the outer ring 3.

[0026] Here, for example, for bearing model 6207 (inner diameter 35 mm, outer diameter 72 mm, width 17 mm), the surface areas of the outer circumferential surface of the inner ring, the outer circumferential surface and axial end face of the outer ring, the inner circumferential surface of the outer ring, the inner circumferential surface and axial end face of the inner ring, and the balls are calculated to obtain the values ​​shown in Table 1 below. As shown in Table 1, the surface area of ​​the outer circumferential surface of the inner ring is smaller than the surface area of ​​the balls, the inner circumferential surface of the outer ring, and the outer circumferential surface and axial end face of the outer ring. Therefore, even when an insulating thermal spray layer L is formed over the entire area of ​​the outer circumferential surface 21 of the inner ring 2, as shown in Figure 1, the amount of thermal spray material used can be significantly reduced compared to conventional ceramic rolling element bearings. In the case of rolling bearing 1 in Figure 1, model 6207, the area over which the insulating thermal spray layer L is formed is approximately 69% of the surface area of ​​the balls 4. On the other hand, the surface area of ​​the inner circumferential surface and end face of the inner ring is at a similar level to that of the outer circumferential surface of the inner ring. However, in many cases, the motor support bearings within the e-Axle are used for inner ring rotation, raising concerns that the insulation performance may deteriorate due to sliding wear during use.

[0027] [Table 1]

[0028] Therefore, considering the need to achieve both low cost and high insulation performance, it is preferable to form an insulating thermal spray layer on the outer surface of the inner ring.

[0029] The inner ring 2, outer ring 3, and ball 4 can be made of ferrous material. Any ferrous material commonly used as a bearing material can be used. For example, high-carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; ISO 683-17), carburized steel (SCr420, SCM420, etc.; ISO 683-5), stainless steel (SUS440C, etc.; ISO 16143-2), high-speed steel (M50, etc.), cold-rolled steel, etc. can be used. Note that the steel materials used for each bearing component may be different from each other.

[0030] The insulating spray layer L is formed on the substrate surface of the outer circumferential surface 21 of the inner ring 2. The substrate surface of the outer circumferential surface 21 of the inner ring 2 on which the insulating spray layer L is formed is, for example, degreased and cleaned, and then blasted to adjust the surface roughness. The insulating spray layer L is, for example, a ceramic spray layer, and is formed by spraying spray powder containing metal oxide particles such as alumina (Al2O3) particles, zirconia (ZrO2) particles, titania (TiO2) particles, silica (SiO2) particles, and yttria (Y2O3) particles.

[0031] In the rolling bearing 1, the insulating spray layer L is formed on the inner ring raceway surface 21a that slides with the ball 4, so it is preferable that the main component be alumina (Al2O3), which has excellent wear resistance. The alumina content in the insulating spray layer L is, for example, 90.0% by mass or more, and may be 95.0% by mass or more, or 97.0% by mass or more. Furthermore, it is preferable that the insulating spray layer L contains metal oxides other than alumina. The content of metal oxides other than alumina is, for example, 1.0% by mass to 10.0% by mass, and may be 1.0% by mass to 5.0% by mass, or 1.0% by mass to 3.0% by mass.

[0032] The insulating spray layer L may be formed such that its thickness is substantially constant over the entire outer surface 21 of the inner ring 2. The thickness of the insulating spray layer L is not particularly limited and can be, for example, 50 μm to 1000 μm, preferably 50 μm to 500 μm, and more preferably 50 μm to 300 μm. If the insulating spray layer L is too thin, the anti-corrosion effect will be difficult to obtain, and conversely, if it is too thick, the insulating spray layer L will be prone to cracking. In addition, the insulating spray layer L may have an uneven thickness depending on the part, taking into consideration sliding with the ball 4. For example, the thickness of the insulating spray layer L formed on the inner ring raceway surface 21a may be set to be smaller than the thickness of the insulating spray layer L formed on the shoulder surface 21b. In this case, the thickness of the insulating spray layer L formed on the inner ring raceway surface 21a can be, for example, 50 μm to 100 μm, taking into consideration peel resistance. Furthermore, the thickness of the insulating thermal spray layer formed on the shoulder surface may be formed to decrease as it moves outward in the axial direction.

[0033] Generally, insulating sprayed layers formed by thermal spraying of thermal spray material generate numerous voids. Therefore, sealing treatment is performed after spraying by impregnating and hardening a sealing material into the voids to maintain the insulating structure. However, the insulating sprayed layer L of the rolling bearing 1 has few voids and is a dense insulating layer, so sealing treatment is not necessary.

[0034] For example, the porosity of the insulating thermal spray layer L is 0.5% or more and less than 10%. From the viewpoint of suppressing variations in insulating performance and wear resistance, the porosity is preferably 0.5% or more and less than 8%, and more preferably 1% or more and less than 5%. A method for determining the porosity can be, for example, a calculation method using relative comparison with a limit sample in an observation field of view at a measurement magnification of 200x. In this case, the captured image (magnification 200x) can be binarized using image analysis software, and the area ratio of the darker-looking parts (pores) (total area of ​​pores ÷ observation field area × 100) can be determined as the porosity.

[0035] Furthermore, it is preferable that the insulating thermal spray layer L has a smoothing treatment such as polishing. Thermal spraying involves spraying material particles onto the object to be coated, so the surface roughness depends on the size of the material particles. Therefore, the coated thermal spray film tends to be rough, which may adversely affect wear due to friction during sliding with the ball 4. For this reason, it is preferable to reduce the roughness by smoothing the surface of the thermal spray film.

[0036] For example, the smoothing process can be carried out by blasting the surface of the deposited thermal spray coating with a slurry containing powder media using compressed air or other compressed gas. Diamond grinding wheels can also be used.

[0037] The arithmetic mean roughness Ra of the insulating thermal spray layer L is, for example, 0.025 μm to 2.5 μm, preferably 0.025 μm to 0.2 μm. The arithmetic mean roughness Ra is measured in accordance with ISO 4287:1997, for example, with a reference length of 200 μm.

[0038] The insulating thermal spray layer L may be sealed with a sealing material as needed. As the sealing material, resin materials such as epoxy resin, urethane resin, acrylic resin, silicone resin, and fluororesin can be used, and the resin material is cured by heat curing or photocuring. Inorganic materials such as water glass and polysiloxane can also be used as the sealing material.

[0039] The average particle size of the metal oxide particles contained in the thermal spray powder can be set, for example, in the range of 5 μm to 40 μm. From the viewpoint of densification of the thermal spray coating and surface roughness, the average particle size is preferably 5 μm to 30 μm, more preferably 5 μm to 20 μm, and even more preferably 5 μm to 15 μm. When the average particle size of the metal oxide particles is 5 μm to 40 μm, the thermal spray powder melts more easily compared to the case of coarser particles, and the glassy metal oxides can fill the voids without gaps, resulting in a denser thermal spray coating. The average particle size is the particle size at the point where the cumulative value reaches 50% when the particle size distribution is considered as a cumulative distribution (D50), and can be measured, for example, using a particle size distribution measuring device that utilizes laser light scattering.

[0040] For example, to densify the insulating thermal spray layer L, it is preferable to use alumina particles as the main component of the thermal spray material and fill the voids between the alumina particles with a glassy molten metal oxide having a smaller average particle size. In this case, the added metal oxide should have a lower melting point than alumina. For example, easily vitrified metal oxides such as silica, yttria, titania, and zirconia can fill the voids formed by alumina by vitrifying themselves during film formation.

[0041] The composition of the thermal spray material may be, for example, 95.0 to 98.5% by mass of alumina and 1.5 to 5.0% by mass of other metal oxides (such as zirconia or silica), or for example, 97.0% by mass or more of alumina and 1.5 to 2.5% by mass of other metal oxides. Furthermore, well-known metal oxides may be added.

[0042] As for thermal spraying methods, well-known plasma spraying methods such as atmospheric pressure plasma spraying, powder flame spraying, high-speed gas flame spraying, and arc spraying can also be employed.

[0043] (Second Embodiment) Figure 2 is a cross-sectional view showing a rolling bearing according to a second embodiment of the rolling bearing of the present invention. This rolling bearing 1A differs from the rolling bearing 1 described above in the manner in which the insulating thermal spray layer L is formed. Specifically, the insulating thermal spray layer L is formed on the inner ring raceway surface 21a and in the area adjacent to the shoulder surfaces 21b on both sides from the inner ring raceway surface 21a, but not on the entire area of ​​the outer circumferential surface 21 of the inner ring 2. In other words, compared to the rolling bearing 1, the insulating thermal spray layer is not formed on the axially outer portion of the shoulder surface 21b, resulting in a smaller area on which the insulating thermal spray layer L is formed than in the rolling bearing 1, which further contributes to cost reduction.

[0044] From the perspective of cost reduction, it is conceivable to form the insulating spray layer L only on the inner ring raceway surface 21a. However, in such a case, the creepage distance between the ball 4 and the inner ring 2 (non-insulated part) will be only the thickness of the insulating spray layer L. Therefore, if a potential difference of a certain level or more occurs between the ball 4 and the inner ring 2, creepage discharge may occur along the edge of the insulating spray layer L, potentially causing electrolytic corrosion. Note that "creepage distance" refers to the minimum distance along the surface of an insulating layer (insulating member) sandwiched between two conductors.

[0045] Therefore, in the rolling bearing 1A, an insulating thermal spray layer L is formed not only on the inner ring raceway surface 21a but also on a portion of the shoulder surface 21b adjacent to the inner ring raceway surface 21a. Specifically, the area adjacent to the shoulder surface 21b where the insulating thermal spray layer L is provided is, for example, within 2.0 mm from the boundary between the inner ring raceway surface 21a and the shoulder surface 21b (corresponding to the width W in Figure 2), but may also be within 1.0 mm, or within 0.2 mm to 0.5 mm (for example, about 0.3 mm). Furthermore, in relation to the axial dimension of the shoulder surface 21b, the adjacent area is within 1 / 4 of the axial dimension of the shoulder surface 21b from the boundary between the inner ring raceway surface 21a and the shoulder surface 21b, or it may also be within 1 / 5. By setting the width W of the insulating thermal spray layer L formed on the shoulder surface 21b to a certain extent, it is possible to further reduce costs while ensuring the insulation performance of the rolling bearing 1A.

[0046] The insulating thermal spray layer L of the rolling bearing 1A is formed, for example, by masking all but a portion of the outer circumferential surface 21 of the inner ring 2 on which the insulating thermal spray layer L is formed (i.e., the axially outer portion of the shoulder surface 21b of the inner ring 2, the inner circumferential surface 22, and the axial end surface 23), and then performing atmospheric plasma spraying or the like.

[0047] Furthermore, the insulating spray layer L may be formed on the shoulder surface 21b by performing thermal spraying without masking. For example, the insulating spray layer L formed on the shoulder surface 21b may be formed so that its thickness gradually or continuously decreases toward the axially outward direction.

[0048] Furthermore, the insulating spray layer L may be formed not only in the area adjacent to the shoulder surface 21b, but also in other parts of the shoulder surface 21b. Because some lubricating oil is retained in the pores of the insulating spray layer L formed on the shoulder surface 21b, oil seeps out from the insulating spray layer L and is supplied appropriately to the insulating spray layer L on the inner ring raceway surface 21a, making it easier to maintain lubrication with the ball 4.

[0049] (Third embodiment) Figure 3 is a cross-sectional view showing a rolling bearing according to a third embodiment of the rolling bearing of the present invention. This rolling bearing 1B is a contact seal type deep groove ball bearing and, unlike the rolling bearings 1 and 1A described above, is equipped with a sealing member 6 that seals the annular bearing space between the inner ring 2 and the outer ring 3. The bearing space is filled with grease (not shown) and lubrication is provided by grease lubrication.

[0050] A seal groove 21c with a substantially U-shaped cross-section is formed on the outer circumferential surface 21 of the inner ring 2, axially outward from the shoulder surface 21b. The insulating thermal spray layer L is formed on the inner ring raceway surface 21a and the shoulder surface 21b, but not on the seal groove 21c.

[0051] Furthermore, the sealing member 6 is a conductive sealing member, and in the rolling bearing 1B, a conductive path is formed through the inner ring 2, the sealing member 6, and the outer ring 3. In this rolling bearing 1B, as a measure against electrolytic corrosion, insulation is ensured by an insulating thermal spray layer L formed on the inner ring raceway surface 21a, and the occurrence of electrolytic corrosion is further suppressed by providing conductivity through the conductive sealing member 6.

[0052] The sealing member 6 has a conductive rubber portion 6a made of conductive rubber material and a core metal portion 6b made of metal. The core metal portion 6b is a disc-shaped core metal formed by press working from, for example, a cold-rolled steel sheet (such as SPCC), and the conductive rubber portion 6a is integrally vulcanized and bonded to the core metal portion 6b. The conductive rubber portion 6a has a main lip portion formed at the end on the inner ring 2 side, with its tip branching into two, and a dust lip portion located on the outside of the bearing side of the main lip portion. The sealing member 6 is fitted into the seal groove on the inner circumference of the end of the outer ring 3 via the conductive rubber portion 6a, and the conductive rubber material 6a is in sliding contact with the seal groove 21c of the inner ring 2. Each lip portion is installed with a predetermined overlap and elastically deforms to contact the inner ring 2 when installed. The rolling bearing 1B is an inner ring rotating type bearing.

[0053] The conductive rubber portion 6a of the sealing member 6 is made by compounding conductive particles in a predetermined ratio with an insulating rubber material. Examples of rubber materials include natural rubber, styrene-butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber, nitrile rubber, ethylene-propylene rubber, fluororubber, acrylic rubber, urethane rubber, and silicone rubber. Examples of conductive particles include nickel particles, copper particles, gold particles, silver particles, carbon powder, carbon black, carbon nanotubes, carbon nanohorns, and graphene. The shape of the above-mentioned particles is not limited to spherical, but can be freely selected from columnar, flaky, or flat shapes.

[0054] The average particle size of the various particles incorporated into the conductive rubber portion 6a is, for example, within the range of 1 to 100 μm, or it may be within the range of 1 to 20 μm. If the average particle size is smaller than 1 μm, a large number of particles will need to come into contact with each other to form a conductive path, which may result in lower sensitivity. If the average particle size is larger than 100 μm, the conductivity will change easily during deformation, and variations in the presence of particles within the conductive rubber portion 6a may lead to variations in characteristics between manufacturing lots. Here, the average particle size refers to the number-average particle diameter observed using an electron microscope.

[0055] For example, in a rolling bearing 1B, the insulating thermal spray layer L may be formed only on the inner ring raceway surface 21a and not on the shoulder surface 21b. Since the conductive sealing member 6 makes it difficult for a potential difference to occur between the inner ring 2 and the ball 4, sufficient insulation can be ensured even with such a configuration.

[0056] In the first to third embodiments described above, deep groove ball bearings were used as rolling bearings, but the same embodiments can also be applied to angular contact ball bearings, for example.

[0057] Furthermore, in angular contact ball bearings where axial loads are generated from only one direction, insulation can be ensured by forming an insulating thermal spray layer on only a portion of the inner ring raceway surface. In this case, if the position where the ball passes through the inner ring raceway surface is constant, the insulating thermal spray layer can be formed in the area where the contact ellipse is plus the creepage distance (e.g., 0.3 mm). In this case as well, it is possible to reduce costs while still achieving excellent insulation performance with the insulating thermal spray layer.

[0058] The rolling bearing of the present invention can be used in environments and applications where electrolytic corrosion is likely to occur. For example, it is suitable for bearings that rotatably support the rotating shafts of motors and refrigerant compressors, and for bearings in inverters. It can also be used as a bearing to support the motor shaft of a drive motor used in electric vehicles (EVs) and hybrid electric vehicles (HEVs).

[0059] The rolling bearing of the present invention is not limited to the configuration described above, and can be modified as appropriate. For example, the configurations of each embodiment can be combined as appropriate. [Industrial applicability]

[0060] The rolling bearing of the present invention has excellent insulation performance and can reduce costs, so it can effectively suppress electrolytic corrosion and can be widely used as a rolling bearing to support the rotating shafts of motors, generators, and the like. [Explanation of Symbols]

[0061] 1, 1A, 1B Rolling bearings 2 Inner ring 21 Outer surface 21a Inner ring raceway surface 21b Shoulder surface 21c seal groove 22 Inner surface 23 Axial end face 3 Outer ring 4 Balls (rolling elements) 5 Cage 6. Sealing member 6a Conductive rubber part 6b Core metal part L insulating spray layer

Claims

1. A rolling bearing comprising an inner ring having an inner ring raceway surface on its outer circumference, an outer ring having an outer ring raceway surface on its inner circumference, and a plurality of rolling elements interposed between the inner ring raceway surface and the outer ring raceway surface, A rolling bearing characterized in that an insulating thermal spray layer is formed at least on the inner ring raceway surface.

2. The rolling bearing according to claim 1, characterized in that the insulating thermal spray layer is formed over the entire area of ​​the outer circumferential surface, including the inner ring raceway surface and the shoulder surfaces connected to both sides of the inner ring raceway surface, or in the area adjacent to the inner ring raceway surface and the shoulder surfaces on both sides of the inner ring raceway surface.

3. The insulating thermal spray layer is formed on the inner ring raceway surface and a portion of the shoulder surfaces connected to both sides of the inner ring raceway surface. The rolling bearing according to claim 1, characterized in that the thickness of the insulating thermal spray layer formed on the inner ring raceway surface is 50 μm to 300 μm, and the thickness of the insulating thermal spray layer formed on the shoulder surface decreases as it moves outward in the axial direction.

4. The rolling bearing according to claim 1 or 2, characterized in that the porosity of the insulating thermal spray layer is 1% or more and less than 5%, and the pores in the insulating thermal spray layer are not sealed with a sealing material.

5. The rolling bearing according to claim 1, characterized in that the insulating thermal spray layer is formed only on the inner ring raceway surface and not on the shoulder surfaces connected to both sides of the inner ring raceway surface.

6. The rolling elements are made of steel, and the area on which the insulating thermal spray layer is formed is 80% or less of the total surface area of ​​all the rolling elements, as described in claim 1 or 2.

7. The rolling bearing according to claim 1, characterized in that the rolling bearing comprises a contact-type conductive sealing member fixed to one of the outer ring and the inner ring and slidingly in contact with the other.

8. The rolling bearing according to claim 1 or 2, characterized in that the insulating thermal spray layer is a ceramic thermal spray layer.

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