Insulated rolling bearing device

Abstract

To provide an insulated rolling bearing device that can exhibit sufficient strength when subjected to a combined load consisting of radial and axial loads. [Solution] The bearing comprises an inner ring 2, an outer ring 3 arranged coaxially on the radially outer side 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 side of the inner ring 2. In the operating state of the bearing, the circumferential groove 5 is formed such that neither the extension direction toward the inner diameter side of the combined load F, which is the resultant force of the radial load F1 and axial load F2 acting from the balls 4 to the inner and outer rings 2 and 3, nor the extension direction toward the outer diameter side of the combined load F, overlaps with the circumferential groove 5.

Description

Technical Field

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

Background Art

[0002] For bearing devices that support the rotating shaft bodies of devices that use electricity, such as electric motors and e-Axles in which an electric motor and a speed reducer are integrated, rolling bearings, particularly deep groove ball bearings, may be used. In recent years, inverter control has been generally adopted in order to operate the motor efficiently. In particular, in the case of in-vehicle motors, miniaturization has been achieved from the perspective of mounting on vehicles, and in order to use the miniaturized motors more efficiently, finer control is being performed.

[0003] It has been found that shaft current and shaft voltage occur in this rotating shaft body. When this current passes through the inside of the bearing, electrical erosion may occur on the raceway rings and rolling elements made of metal. Therefore, for example, in the deep groove ball bearings of Patent Documents 1 and 2 below, a circumferential groove is formed in at least one of the inner diameter surface of the inner ring or the outer diameter surface of the outer ring, and the inner ring or outer ring in which the circumferential groove is formed is placed in a mold, and an insulating layer made of a resin material having insulating properties is formed on the surface where the circumferential groove is formed by injection molding (insert molding) to prevent electrical erosion caused by the current passing 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, etc. are prevented.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[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 fitting 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 combined load F consisting of a radial load F1 in the radial direction and an axial load F2 in the axial direction acts 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). At that time, the extension direction of the combined load F toward the outer diameter (particularly the central part of the area 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. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides: Insider, An outer ring is arranged coaxially with the radially outer side of the inner ring, A plurality of balls are incorporated between the inner ring and the outer ring, The circumferential groove formed on the outer diameter surface of the outer ring, An insulating layer having insulating properties is provided on the outer diameter surface of the outer ring so as to fit into the circumferential groove, A rotating shaft body that fits onto the inner diameter surface side of the inner ring, An insulated rolling bearing device was constructed in which, in the operating state of the bearing, the circumferential groove is formed such that neither the extension direction toward the inner diameter 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, nor the extension direction toward the outer diameter of the combined load, 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 linear expansion coefficient of the resin material used for the insulating layer is 1×10 -5 / °C or more in the flow direction and 4×10 -5 / °C or more in the direction orthogonal to the flow direction (fifth configuration). When the linear expansion coefficients in the flow direction and the direction orthogonal to the flow direction are within the above ranges, when the temperatures of the outer ring and the insulating layer rise during use and thermal expansion occurs, it is possible to prevent the tightening allowance or the fitting clearance between the inner and outer rings and the rotating shaft body or the housing from deviating significantly from the predetermined value.

[0015] In the first to fifth configurations, the dielectric breakdown strength of the resin material used for the insulating layer can be set to 1 kV / mm or more (sixth configuration). By doing so, it is possible to exhibit high anti-corona performance of the insulated rolling bearing device while suppressing the thickness of the insulating layer.

Advantages of the Invention

[0016] In the insulated rolling bearing device of the present invention, in the operating state of the bearing, neither the extension direction of the combined load, which is the resultant force of the radial load and the 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 formed in 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 and the like from occurring in the inner and outer rings due to the combined load acting on the circumferential groove portion, which has relatively low strength compared to other portions of the inner and outer rings.

Brief Description of the Drawings

[0017] [Figure 1] Cross-sectional view showing an embodiment of the insulated rolling bearing device according to the present invention [Figure 2] Cross-sectional view showing the main part of FIG. 1 [Figure 3] Cross-sectional view showing the dimensions of each part in the main part shown in FIG. 2 [Figure 4] Cross-sectional view showing an insulated rolling bearing device according to the prior art

Best Mode for Carrying Out the Invention

[0018] An embodiment of the insulating rolling bearing device 1 according to the present invention will be described based on the drawings. As shown in FIG. 1, this insulating rolling bearing device 1 includes an inner ring 2, an outer ring 3 coaxially disposed radially outside 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 provided on the outer diameter surface of the outer ring 3 so as to fit into the circumferential groove 5 and having insulation properties, a rotating shaft body 7 fitted on the inner diameter surface side of the inner ring 2, and a housing 8 fitted on the outer diameter surface side of the outer ring 3.

[0019] The inner and outer rings 2 and 3, the balls 4, the rotating shaft body 7, and the housing 8 are all made of steel. Also, the insulating layer 6 is made of a resin material. Hereinafter, the direction along the rotating shaft of the rotating shaft body 7 is referred to as the axial direction, the direction perpendicular to the rotating shaft is referred to as the radial direction, and the direction along the circumference that makes one full turn around the rotating shaft is 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. The balls 4 roll along both raceway surfaces 9 and 10. The plurality of balls 4 are held at predetermined intervals in the circumferential direction by a cage 11, and a bearing is constituted by the inner ring 2, the outer ring 3, the plurality of 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, in the operating state of the bearing, in addition to the radial load F1 in the radial direction, an axial load F2 in the axial direction occurs, and a combined load F that is the resultant of the radial load F1 and the axial load F2 acts on the inner and outer rings from the balls. The combined load F is directed in an oblique direction inclined with respect to both the radial load F1 and the axial load F2.

[0022] As shown in an enlarged view in Figure 3, two circumferential grooves 5 are formed on the outer diameter surface of the outer ring 3, symmetrically positioned with respect to the axial center of the outer ring 3, extending along the entire circumference. The cross-section of the circumferential grooves 5 is rectangular when cut by a plane perpendicular to the circumferential direction, and corners are formed at both axial ends of the groove bottom. In this embodiment, the ratio WG / WB of the axial width WG of the circumferential groove 5 to the axial width WB of the outer ring 3 on which the circumferential grooves 5 are formed is within the range of 0.03 to 0.30. Furthermore, the circumferential grooves 5 are formed to have a depth D of 0.5 mm or more.

[0023] If the ratio WG / WB is less than 0.03, the protective effect of the circumferential groove 5 against peeling of the insulating layer 6 may be reduced. If it is greater than 0.30, the extension direction of the combined load F is more likely to coincide with the circumferential groove 5, and this combined load F may cause cracks to occur in the inner and outer rings 2 and 3. Therefore, it is preferable to keep it within the above range. Also, if the depth D is less than 0.5 mm, the protective effect of the circumferential groove 5 against peeling of the insulating layer 6 may be reduced. Therefore, it is preferable to keep it within the above range.

[0024] On the width surfaces of both axial ends of the outer ring 3, one circumferential groove 12 is formed along the entire circumference in the circumferential direction. The cross-section of the circumferential groove 12 is rectangular 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 glass fibers, you can choose from inorganic glasses mainly composed of SiO2, B2O3, Al2O3, CaO, MgO, Na2O, K2O, Fe2O3, etc., and as thermoplastic elastomers, you can choose from polyolefin-based, polystyrene-based, polyvinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, and polybutadiene-based materials, for example.

[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 / ℃ or higher and 4 × 10 in the direction perpendicular to the flow direction -5 Materials with physical properties that fall within a range of / °C or higher have been selected. In addition, the insulating layer 6 is ensured to have a dielectric breakdown strength of 1kV / 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 insulating rolling bearing device 1 is constructed by fitting the rotating shaft 7 and the housing 8 into the bearing. When the bearing is in operation, a combined load F, which is the resultant of the radial load F1 and the axial load F2, acts on the outer ring 3 from the balls 4. In this insulating rolling bearing device 1, the circumferential groove 5 is formed such that the direction in which this combined load F extends toward the outer diameter does not coincide with the circumferential groove 5. The direction in which the combined load F extends toward the outer diameter is determined when the rotating shaft 7 and the housing 8 are fitted into the bearing.

[0030] The manufacturing process for the insulated rolling bearing device 1 shown in Figure 1 will now be described. First, circumferential grooves 5 and 12 are formed around the entire circumference of the outer diameter surface and width surface of the outer ring 3. Next, a mold (not shown) is attached to cover the outer diameter surface and width surface of the outer ring 3 on 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 width surface of the outer ring 3 and the mold. As already explained, it is preferable to use a resin material that contains PPS, glass fiber, and thermoplastic elastomer.

[0031] After the resin material has hardened, the mold is removed and the inner ring 2, the outer ring 3 with the insulating layer 6 formed on it, the balls 4, and the cage 11 are assembled to form a bearing (deep groove ball bearing). The rotating shaft 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] The above-described insulated rolling bearing device 1 has a configuration in which a portion of the insulating layer 6 provided on the outer diameter surface of the outer ring 3 is fitted into a circumferential groove 5 formed on this outer diameter surface. As a result, the circumferential groove 5 prevents peeling or lifting of the insulating layer 6, creep between the insulating layer 6 and the outer ring 3, and prevents electrolytic corrosion by blocking the current passing through the bearing with the insulating layer 6.

[0033] In particular, the insulated rolling bearing device 1 described above is designed such that, in the operating state of the bearing, the direction in which the combined load F, which is the resultant force of the radial load F1 and axial load F2 acting from the ball 4 to the outer ring 3, extends toward the outer diameter does not overlap with the circumferential groove 5. Therefore, it is possible to prevent the combined load F from acting on the circumferential groove 5, which has relatively lower strength compared to other parts of the outer ring 3, and causing cracks or other damage to the outer ring 3. Whether or not the direction in which the combined load F extends overlaps with the circumferential groove 5 can be determined, for example, by disassembling the insulated rolling bearing device 1 and visually checking the positional relationship between the rolling marks of the ball 4 formed on the outer ring raceway surface 10 and the circumferential groove 5.

[0034] Furthermore, since the insulated rolling bearing device 1 described above has a configuration in which multiple circumferential grooves 5 are formed, the effect of preventing peeling of the insulating layer 6 can be further enhanced by these multiple circumferential grooves 5. The number of circumferential grooves 5 can be increased or decreased as appropriate based on the magnitude and extension direction of the combined load F. In addition, the position of the circumferential grooves 5 can be changed as appropriate, as long as it does not coincide with the extension direction of the combined load F.

[0035] Furthermore, the insulated rolling bearing device 1 described above has a 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, which is within the range of 0.03 to 0.30. This allows the circumferential groove 5 to maintain its effect of preventing peeling of the insulating layer 6, while minimizing the coincidence between the extension direction of the combined load F and the circumferential groove 5.

[0036] Furthermore, since the depth D of the circumferential groove 5 in the above-described insulated rolling bearing device 1 is set to 0.5 mm or more, sufficient gripping space for the insulating layer 6 against the circumferential groove 5 is ensured, and the effect of preventing peeling of the insulating layer 6 can be reliably achieved.

[0037] Furthermore, in the above-described insulated rolling bearing device 1, the molding shrinkage rate of the resin material used in the insulating layer 6 is set to 0.3% or more. As the resin material shrinks, the circumferential groove 5 and the insulating layer 6 fit together securely, ensuring that the insulating layer 6 is firmly fixed to the outer ring 3.

[0038] Furthermore, the coefficient of linear expansion is 1 × 10 in the flow direction. -5 / ℃ or higher and 4 × 10 in the direction perpendicular to the flow direction -5 By setting the temperature to above / ℃, it is possible to prevent the interference fit and mating gap between the outer ring 3 and the housing 8 from deviating significantly from the predetermined value 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 present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[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 F1 Radial Load F2 Axial Load F Combined load

Claims

1. Inner ring (2), The outer ring (3) is arranged coaxially on the radially outer side of the inner ring (2), A plurality of balls (4) are incorporated between the inner ring (2) and the outer ring (3), The circumferential groove (5) formed on the outer diameter surface of the outer ring (3), An insulating layer (6) having insulating properties is provided on the outer diameter surface of the outer ring (3) so as to fit into the circumferential groove (5), A rotating shaft body (7) that fits onto the inner diameter surface side of the inner ring (2), The bearing has a radial load (F) acting from the ball (4) to the inner and outer rings (2, 3) in the operating state of the bearing. 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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