Insulated rolling bearing device

Abstract

The present invention comprises: an inner ring (2); an outer ring (3); a plurality of balls (4) disposed between the inner ring (2) and the outer ring (3); circumferential grooves (5) formed on an outer diameter surface of the outer ring (3); an insulating layer (6) having insulating properties and provided on the outer diameter surface of the outer ring (3) so as to be fitted into the circumferential groove (5); and a rotating shaft body (7) fitted into an inner diameter surface side of the inner ring (2). In an operating state of the bearing, the circumferential grooves (5) are formed so as not to overlap with either an extension of a composite load (F) toward the inner diameter side nor an extension of the composite load (F) toward the outer diameter side, the composite load (F) being a resultant force of a radial load (F1) and an axial load (F2) acting on the inner and outer rings (2, 3) from the balls (4).

Description

Insulated rolling bearing device

[0001] This invention relates to an insulated rolling bearing device.

[0002] Rolling bearings, particularly deep groove ball bearings, are sometimes used in bearing systems that support the rotating shafts of electrically powered devices such as electric motors and e-Axles, which integrate electric motors and reduction gears. In recent years, inverter control has been commonly adopted to operate motors efficiently. In particular, in the case of automotive motors, miniaturization is pursued for the sake of mounting in vehicles, and more precise control is implemented to use these miniaturized motors more efficiently.

[0003] It is known that axial current and axial voltage are generated in this rotating shaft. When this current passes through the inside of the bearing, electrolytic corrosion can occur in the metal raceways and rolling elements. Therefore, in the deep groove ball bearings described in Patent Documents 1 and 2 below, for example, a circumferential groove is formed on at least one of the inner diameter surface of the inner ring or the outer diameter surface of the outer ring. The inner ring or outer ring with the circumferential groove is placed in a mold, and an insulating layer made of resin material is formed on the surface where the circumferential groove is formed by injection molding (insert molding) to prevent electrolytic corrosion caused by the passage of current through the inside of the bearing. By forming a circumferential groove and fitting a part of the insulating layer into the circumferential groove, peeling or lifting of the insulating layer, creep between the insulating layer and the inner and outer rings are prevented.

[0004] Patent No. 3068311 Patent No. 4286573

[0005] The deep groove ball bearings shown in Patent Documents 1 and 2 can be applied, for example, to the insulated rolling bearing device 20 shown in Figure 4. This insulated rolling bearing device 20 is constructed by fitting a rotating shaft (not shown) to the inner diameter surface of the inner ring of a bearing (deep groove ball bearing) having an inner ring (not shown), an outer ring 21 arranged coaxially on the radially outer side of the inner ring, a plurality of balls 23 incorporated between the inner ring and the outer ring 21 and held by a cage 22, a circumferential groove 24 formed on the outer diameter surface of the outer ring 21, and an insulating layer 25 having insulating properties provided on the outer diameter surface of the outer ring 21 so as to fit into the circumferential groove 24, and a housing 26 to the outer diameter surface side of the outer ring 21 via the insulating layer 25.

[0006] In this insulated rolling bearing device 20, during use, a radial load F is applied from the ball 23 to the outer ring 21 (the area indicated by arrow a in Figure 4 where the ball 23 and the outer ring 21 are in direct contact). １ and axial load F ２ A combined load F consisting of the above is acting. In this case, the extension direction of the combined load F toward the outer diameter (particularly the central part of the region indicated by arrow a) may coincide with the circumferential groove 24 formed in the outer ring 21.

[0007] The portion of the outer ring 21 where the circumferential groove 24 is formed is thinner in the radial direction compared to other parts, resulting in lower strength in that area. Therefore, if the extension direction of the combined load F coincides with the circumferential groove 24 (especially the corners of the groove bottom), the combined load F may cause cracks or other damage to the outer ring 21. This is also true when the circumferential groove 24 is formed on the inner diameter surface of the inner ring and an insulating layer 25 is formed on this inner diameter surface, and when the circumferential groove 24 is formed on both the inner diameter surface of the inner ring and the outer diameter surface of the outer ring 21 and an insulating layer 25 is formed on both the inner and outer diameter surfaces.

[0008] Therefore, the object of the present invention is to provide an insulated rolling bearing device that can exhibit sufficient strength when subjected to a combined load consisting of a radial load and an axial load.

[0009] To solve the above problems, the present invention provides an insulated rolling bearing device comprising: an inner ring; an outer ring coaxially arranged radially outward of the inner ring; a plurality of balls incorporated between the inner ring and the outer ring; a circumferential groove formed on the outer diameter surface of the outer ring; an insulating layer having insulating properties provided on the outer diameter surface of the outer ring so as to fit into the circumferential groove; and a rotating shaft body fitted to the inner diameter side of the inner ring, wherein, in the operating state of the bearing, the circumferential groove is formed such that neither the extension direction of the combined load, which is the resultant force of the radial load and axial load acting from the balls to the inner and outer rings toward the inner diameter side, nor the extension direction of the combined load toward the outer diameter side, overlaps with the circumferential groove (first configuration).

[0010] In this way, the action of the circumferential groove prevents peeling, lifting, and creep between the insulating layer and the inner and outer rings, while also preventing cracks from occurring in the inner and outer rings due to the combined load acting on the circumferential groove portion, which has relatively lower strength compared to other parts of the inner and outer rings.

[0011] In the first configuration, a configuration in which multiple circumferential grooves are formed (second configuration) can be used. In this way, the effect of preventing peeling of the insulating layer can be further enhanced by the multiple circumferential grooves.

[0012] In the first or second configuration, the ratio WG / WB between the axial width WG of the circumferential groove and the axial width WB of the inner and outer rings in which the circumferential groove is formed can be set to a range of 0.03 to 0.30 (third configuration). In this way, it is possible to prevent the extension direction of the combined load from coinciding with the circumferential groove as much as possible while maintaining the effect of preventing peeling of the insulating layer by the circumferential groove.

[0013] In the first to third configurations, a configuration in which the depth of the circumferential groove is 0.5 mm or more (fourth configuration) can be adopted. In this way, sufficient gripping space for the insulating layer against the circumferential groove is ensured, and the effect of preventing peeling of the insulating layer can be reliably achieved.

[0014] In the first to fourth configurations, the coefficient of linear expansion of the resin material used in the insulating layer is 1 × 10 in the flow direction. －５ / °C or higher and in a direction perpendicular to the flow direction, 4 × 10 －５ A configuration (fifth configuration) can be made in which the coefficient of linear expansion is 1 / °C or higher. If the coefficient of linear expansion in the flow direction and in the direction perpendicular to the flow direction is within the above range, it is possible to prevent the interference fit or fitting gap between the inner and outer rings and the rotating shaft or housing from deviating significantly from a predetermined value when the temperature of the outer ring and insulating layer rises during use and thermal expansion occurs.

[0015] In configurations 1 through 5, a configuration (sixth configuration) can be used in which the dielectric breakdown strength of the resin material used in the insulating layer is 1 kV / mm or more. In this way, the thickness of the insulating layer can be reduced while achieving high corrosion prevention performance of the insulated rolling bearing device.

[0016] In the insulated rolling bearing device of the present invention, in the operating state of the bearing, the direction in which the combined load, which is the resultant force of the radial load and axial load acting from the balls to the inner and outer rings, extends toward the inner diameter, and the direction in which the combined load extends toward the outer diameter, do not overlap with the circumferential groove formed on at least one of the inner and outer rings. Therefore, while preventing peeling, lifting, and creep between the insulating layer and the inner and outer rings due to the action of the circumferential groove, it is possible to prevent cracks from occurring in the inner and outer rings due to the combined load acting on the circumferential groove portion, which has relatively lower strength compared to other parts of the inner and outer rings.

[0017] Cross-sectional view showing one embodiment of the insulated rolling bearing device according to the present invention. Cross-sectional view showing the main part of Figure 1. Cross-sectional view showing the dimensions of each part in the main part shown in Figure 2. Cross-sectional view showing a conventional insulated rolling bearing device.

[0018] An embodiment of the insulated rolling bearing device 1 according to the present invention will be described with reference to the drawings. As shown in Figure 1, the insulated rolling bearing device 1 includes an inner ring 2, an outer ring 3 coaxially arranged radially outward of the inner ring 2, a plurality of balls 4 incorporated between the inner ring 2 and the outer ring 3, a circumferential groove 5 formed on the outer diameter surface of the outer ring 3, an insulating layer 6 having insulating properties provided on the outer diameter surface of the outer ring 3 so as to fit into the circumferential groove 5, a rotating shaft 7 fitted to the inner diameter side of the inner ring 2, and a housing 8 fitted to the outer diameter side of the outer ring 3.

[0019] The inner and outer rings 2 and 3, the ball 4, the rotating shaft 7, and the housing 8 are all made of steel. The insulating layer 6 is made of resin. In the following, the direction along the axis of rotation of the rotating shaft 7 will be referred to as the axial direction, the direction perpendicular to the axis of rotation will be referred to as the radial direction, and the direction along the circumference that completes one revolution around the axis of rotation will be referred to as the circumferential direction.

[0020] An inner ring raceway surface 9 is formed on the outer diameter surface of the inner ring 2, and an outer ring raceway surface 10 is formed on the inner diameter surface of the outer ring 3, and the balls 4 roll along both raceway surfaces 9 and 10. Multiple balls 4 are held at predetermined intervals in the circumferential direction by a cage 11, and the bearing is composed of the inner ring 2, the outer ring 3, the multiple balls 4, and the cage 11. This bearing is a deep groove ball bearing.

[0021] As shown in Fig. 2, in this deep groove ball bearing, a radial load F in the radial direction acts in the operating state of the bearing. １ In addition to this, an axial load F in the axial direction ２ occurs, and a combined load F, which is the resultant force of the radial load F １ from the balls on the inner and outer rings and the axial load F ２ , acts. The combined load F is directed in an oblique direction inclined with respect to both the radial load F １ and the axial load F. ２

[0022] As shown in an enlarged view in Fig. 3, on the outer diameter surface of the outer ring 3, two circumferential grooves 5 are formed over the entire circumference along the circumferential direction at positions symmetric with respect to the axial center of the outer ring 3. The cross-section of the circumferential groove 5 forms a rectangle when cut by a plane perpendicular to the circumferential direction, and corners are formed at both axial ends of the groove bottom. The ratio WG / WB of the axial width WG of the circumferential groove 5 according to this embodiment to the axial width WB of the outer ring 3 in which the circumferential groove 5 is formed is within the range of 0.03 or more and 0.30 or less. Further, the circumferential groove 5 is formed such that its depth D is 0.5 mm or more.

[0023] If the ratio WG / WB is less than 0.03, the preventive effect such as peeling of the insulating layer 6 by the circumferential groove 5 may be reduced. If it is greater than 0.30, the circumferential groove 5 is likely to coincide with the extension direction of the combined load F, and there is a possibility that cracks or the like may occur in the inner and outer rings 2 and 3 due to the combined load F. Therefore, it is preferable to be within the above range. Also, if the depth D is less than 0.5 mm, the preventive effect such as peeling of the insulating layer 6 by the circumferential groove 5 may be reduced. Therefore, it is preferable to be within the above range.

[0024] On the width surfaces at both axial ends of the outer ring 3, one circumferential groove 12 is formed over the entire circumference along the circumferential direction. The cross-section of the circumferential groove 12 forms a rectangle when cut by a plane perpendicular to the circumferential direction, similar to the circumferential groove 5 formed on the outer diameter surface.

[0025] The insulating layer 6 is provided so as to cover the outer diameter surface and width surface of the outer ring 3. This insulating layer 6 is preferably made of a resin material containing polyphenylene sulfide (PPS), a type of super engineering plastic that has heat resistance, dimensional stability, chemical resistance, etc. In particular, it is preferably made of a resin material containing PPS, glass fibers, and a thermoplastic elastomer.

[0026] As a glass fiber, for example, SiO ２ , B ２ O ３ Al ２ O ３ , CaO, MgO, Na ２ O, K ２ O, Fe ２ O ３ Inorganic glass can be selected from those primarily composed of such materials, and as thermoplastic elastomers, for example, polyolefin-based, polystyrene-based, polyvinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, and polybutadiene-based materials can be selected.

[0027] The resin material used in the insulating layer 6 has a molding shrinkage rate of 0.3% or more and a coefficient of linear expansion of 1 × 10 in the flow direction. －５ / °C or higher and in a direction perpendicular to the flow direction, 4 × 10 －５ Materials with physical properties that fall within a range of / °C or higher are selected. In addition, the insulating layer 6 is ensured to have a dielectric breakdown strength of 1 kV / mm or higher.

[0028] The rotating shaft 7 is, for example, the rotating shaft 7 of an electrical device such as an electric motor or an e-Axle which integrates an electric motor and a reduction gear. In this embodiment, the rotating shaft 7 is directly fitted to the inner diameter surface of the inner ring 2. A stepped portion is formed in the housing 8, and the outer diameter surface side of the outer ring 3 is fitted to this stepped portion via an insulating layer 6.

[0029] The rotating shaft 7 and housing 8 are fitted into the bearing to form an insulated rolling bearing device 1. When the bearing is in operation, a radial load F is applied from the balls 4 to the outer ring 3. １ and axial load F ２A combined load F, which is the resultant force, acts. In this insulated rolling bearing device 1, the circumferential groove 5 is formed so that the extension direction of the combined load F toward the outer diameter side does not overlap with the circumferential groove 5. The extension direction of the combined load F toward the outer diameter side is determined at the stage when the rotating shaft body 7 and the housing 8 are fitted to the bearing.

[0030] The manufacturing process of the insulated rolling bearing device 1 shown in FIG. 1 will be described. First, circumferential grooves 5 and 12 are formed over the entire circumferential direction of the outer diameter surface and the width surface of the outer ring 3. Next, a mold (not shown) is attached so as to cover the outer diameter surface and the width surface of the outer ring 3 in which the circumferential grooves 5 and 12 are formed, and an insulating layer 6 is formed by injection molding (insert molding) in which a resin material is filled and cured in the gap formed between the outer diameter surface and the width surface of the outer ring 3 and the mold. As this resin material, as already described, it is preferable to adopt one containing PPS, glass fiber, and a thermoplastic elastomer.

[0031] After the resin material is cured, the mold is removed, and then the inner ring 2, the outer ring 3 formed with the insulating layer 6, the balls 4, and the cage 11 are assembled to form a bearing (deep groove ball bearing). The rotating shaft body 7 is fitted to the inner diameter side of the inner ring 2, and the housing 8 is fitted to the outer diameter side of the outer ring 3 via the insulating layer 6 to complete the insulated rolling bearing device 1.

[0032] In the above-described insulated rolling bearing device 1, since a part of the insulating layer 6 having insulating properties provided on the outer diameter surface of the outer ring 3 is fitted into the circumferential groove 5 formed on this outer diameter surface, the circumferential groove 5 prevents peeling and floating of the insulating and creep insulating layer 6, creep between the insulating layer 6 and the outer ring 3, etc., and at the same time, the insulating layer 6 can block the current passing through the bearing to prevent electrical erosion.

[0033] In particular, in the above-described insulated rolling bearing device 1, in the operating state of the bearing, the radial load F acting from the balls 4 on the outer ring 3 １ and the axial load F ２Since the circumferential groove 5 is formed so that the extension direction of the combined load F, which is the resultant force, toward the outer diameter side does not overlap with the circumferential groove 5, it is possible to prevent the combined load F from acting on the circumferential groove 5 portion, which has relatively low strength compared to other portions of the outer ring 3, and causing cracks or the like in the outer ring 3. The determination of whether the extension direction of the combined load F overlaps with the circumferential groove 5 can be made, for example, by visually checking the positional relationship between the rolling trace of the ball 4 formed on the outer ring raceway surface 10 and the circumferential groove 5 after once disassembling the insulated rolling bearing device 1.

[0034] Further, in the above-described insulated rolling bearing device 1, since a plurality of circumferential grooves 5 are formed, the effect of preventing peeling or the like of the insulating layer 6 can be further enhanced by the plurality of circumferential grooves 5. The number of the circumferential grooves 5 can be appropriately increased or decreased based on the magnitude of the combined load F and its extension direction. Also, the formation position of the circumferential groove 5 can be appropriately changed as long as it does not coincide with the extension direction of the combined load F.

[0035] Further, in the above-described insulated rolling bearing device 1, since the ratio WG / WB between the axial width WG of the circumferential groove 5 and the axial width WB of the outer ring 3 in which the circumferential groove 5 is formed is within the range of 0.03 or more and 0.30 or less, it is possible to prevent the coincidence between the extension direction of the combined load F and the circumferential groove 5 while maintaining the effect of preventing peeling or the like of the insulating layer 6 by the circumferential groove 5.

[0036] Further, in the above-described insulated rolling bearing device 1, since the depth D of the circumferential groove 5 is set to 0.5 mm or more, a sufficient engagement margin of the insulating layer 6 with respect to the circumferential groove 5 is ensured, and the effect of preventing peeling or the like of the insulating layer 6 can be surely exhibited.

[0037] Further, in the above-described insulated rolling bearing device 1, since the molding shrinkage rate of the resin material used for the insulating layer 6 is set to 0.3% or more, the circumferential groove 5 and the insulating layer 6 are firmly fitted due to the shrinkage of the resin material, and the fixing of the insulating layer 6 to the outer ring 3 can be made reliable.

[0038] Further, the linear expansion coefficient is 1×10 －５ / °C or more in the flow direction and 4×10 －５By setting the temperature to above / °C, it is possible to prevent the interference fit and mating gap between the outer ring 3 and the housing 8 from deviating significantly from predetermined values ​​when the temperature of the outer ring 3 and the insulating layer 6 rises during use, causing thermal expansion.

[0039] Furthermore, since the insulating rolling bearing device 1 described above has a dielectric breakdown strength of 1 kV / mm or more for the resin material used in the insulating layer 6, this insulating rolling bearing device 1 can exhibit high corrosion prevention performance.

[0040] In the above embodiment, a resin material was used as the insulating layer 6, but it is also possible to use rubber or ceramics. Furthermore, the thickness and material of the insulating layer 6 can be appropriately determined considering the magnitude of the axial current and axial voltage acting on the rotating shaft 7.

[0041] Furthermore, in this embodiment, a circumferential groove 5 is formed on the outer diameter surface of the outer ring 3 and an insulating layer 6 is provided on its outer diameter surface. However, it is also possible to form a configuration in which a circumferential groove 5 is formed on the inner diameter surface of the inner ring 2 and an insulating layer 6 is provided on its inner diameter surface, or a configuration in which a circumferential groove 5 is formed on both the inner diameter surface of the inner ring 2 and the outer diameter surface of the outer ring 3 and an insulating layer 6 is provided on both the inner and outer diameter surfaces.

[0042] Alternatively, instead of forming a circumferential groove 12 on the width surface of the outer ring 3, a circumferential groove (not shown) can be formed on the inner diameter surface of the outer ring 3, and the insulating layer 6 can be wrapped around this inner diameter surface. Furthermore, if the insulating layer 6 can be securely fixed by the circumferential groove 5 formed on the outer diameter surface of the outer ring 3 alone, it may be possible to omit the formation of the circumferential groove 12 on the width surface of the outer ring 3. In addition, the cross-sectional shape of the circumferential groove 5 is not limited to a rectangular shape, and may be, for example, dovetail groove-shaped.

[0043] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of equivalents of the claims are intended.

[0044] 1. Insulated rolling bearing device 2. Inner ring 3. Outer ring 4. Balls 5. Circumferential groove (formed on the outer diameter surface) 6. Insulating layer 7. Rotating shaft F １ Radial load F２ Axial load F Combined load

Claims

1. The bearing comprises an inner ring (2), an outer ring (3) coaxially positioned radially outward of the inner ring (2), a plurality of balls (4) incorporated between the inner ring (2) and the outer ring (3), a circumferential groove (5) formed on the outer diameter surface of the outer ring (3), an insulating layer (6) having insulating properties provided on the outer diameter surface of the outer ring (3) so as to fit into the circumferential groove (5), and a rotating shaft body (7) fitted to the inner diameter surface side of the inner ring (2), wherein, in the operating state of the bearing, the radial load (F) acting from the balls (4) to the inner and outer rings (2, 3) １ ) and axial load (F ２ An insulated rolling bearing device in which the circumferential groove (5) is formed such that neither the extension direction of the combined load (F), which is the resultant force of the two forces, toward the inner diameter side, nor the extension direction of the combined load (F) toward the outer diameter side, overlaps with the circumferential groove (5).

2. The insulating rolling bearing device according to claim 1, wherein a plurality of circumferential grooves (5) are formed.

3. The insulated rolling bearing device according to claim 2, wherein the ratio WG / WB between the axial width WG of the circumferential groove (5) and the axial width WB of the inner and outer rings (2, 3) on which the circumferential groove (5) is formed is in the range of 0.03 or more and 0.30 or less.

4. The insulated rolling bearing device according to claim 2 or 3, wherein the depth of the circumferential groove (5) is 0.5 mm or more.

5. The coefficient of linear expansion of the resin material used in the insulating layer (6) is 1 × 10 in the flow direction. －５ / °C or higher and in a direction perpendicular to the flow direction, 4 × 10 －５ The insulating rolling bearing device according to claim 1, wherein the temperature is above / ℃.

6. The insulating rolling bearing device according to claim 1, wherein the dielectric breakdown strength of the resin material used in the insulating layer (6) is 1 kV / mm or more.

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