Bearing

Abstract

To provide a bearing securing insulation performance.SOLUTION: A plurality of rolling elements (15) are incorporated in an annular space (14) formed between the outer ring (12) and the inner ring (13) at intervals in a circumferential direction, and are in rolling contact with an outer ring raceway surface 12a and an inner ring raceway surface 13a, wherein a film made of a metallic phosphate film is formed on an outer peripheral surface 12a of the outer ring (12) and an inner peripheral surface 13a of the inner ring (13). 12c 13c.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bearing, and more particularly to a bearing used in automobiles, industrial machinery, wind power generators, etc. [Background technology]

[0002] Rolling bearings are used in drive motors used in electric vehicles (EVs) and hybrid vehicles (HEVs), as well as in motors used in industrial machinery, such as fan motors and servo motors. To provide lubrication, these rolling bearings are filled with lubricant or equipped with a mechanism for distributing lubricant at the contact points between the components that make up the bearing.

[0003] In recent years, most of the drive motors used in electric vehicles (EVs) and hybrid electric vehicles (HEVs), as well as motors used in industrial machinery, are controlled by inverters to improve efficiency. This inverter control adjusts voltage and frequency according to the set rotation speed, and as the inverter's switching frequency increases, the frequency of shaft voltage increases. As a result, a potential difference may occur between the raceways of the rolling bearings installed in the inverter-driven motor. If this potential difference becomes large enough to exceed the breakdown voltage of the oil film formed between the raceways and rolling elements inside the bearing, an electric discharge may occur between the raceways and rolling elements, causing damage inside the bearing known as electrolytic corrosion.

[0004] Furthermore, if the power supply voltage is increased, the current can be reduced even with the same output, reducing copper loss in the cables and inverter elements. However, the potential difference between the shaft potential and the ground potential increases, making the oil film more susceptible to dielectric breakdown. As damage to bearings due to this electrolytic corrosion progresses, striped irregularities called ridge marks form on the rolling element's contact surfaces, which can cause noise and vibration. For this reason, efforts are underway to develop bearings that are designed to prevent ridge marks from forming on the raceway surfaces.

[0005] For example, Patent Document 1 discloses that the insulation properties of a bearing are improved by forming a resin film on the outer peripheral surface of the outer ring of the bearing. As shown in Fig. 5, this bearing 1 comprises an outer ring 2, an inner ring 3, a plurality of balls 4 disposed in the bearing space between a raceway surface 2a of the outer ring 2 and a raceway surface 3a of the inner ring 3, a cage 5 that holds the balls 4 at predetermined circumferential intervals, and a seal member 6 that seals the inside of the bearing. The outer peripheral surface of the outer ring 2 is covered with a resin coating 7 containing polyphenylene sulfide resin, glass fiber, inorganic filler, and thermoplastic elastomer. This resin coating 7 provides insulation to the bearing 1. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-146905 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the case of a bearing provided with the resin coating 7 described in Patent Document 1, changes in bearing dimensions due to the resin coating 7 may require changes in the design of the housing, etc., and when the bearing provided with the resin coating 7 is press-fitted into a housing, etc., there is a risk that the resin coating 7 may tear or peel off, resulting in a loss of insulation.

[0008] The inventors of the present application have noticed that the use of a resin coating to impart insulation to a bearing can lead to design changes or the resin coating can tear or peel, resulting in a loss of insulation. They have also noticed that if these issues can be improved, design changes will not be necessary and insulation can be ensured. [Means for solving the problem]

[0009] Based on this focus, the present invention provides a bearing having the following configuration in order to solve the above-mentioned problems. [Configuration 1] A bearing that is to be incorporated into an inverter-controlled device, comprising an outer ring having an outer ring raceway surface formed on its inner circumference, an inner ring having an inner ring raceway surface formed on its outer circumference, and a plurality of rolling elements that are incorporated at intervals circumferentially into an annular bearing space formed between the outer ring and the inner ring and that are in rolling contact with the outer ring raceway surface and the inner ring raceway surface, wherein a coating made of a metal phosphate coating is formed on the outer peripheral surface of the outer ring and the inner peripheral surface of the inner ring.

[0010] When this configuration is adopted, a coating made of a metal phosphate coating is formed on the surface layer of the outer peripheral surface of the outer ring and the inner peripheral surface of the inner ring, so there is no need to change the dimensions of the bearing, and it can be used as is without changing the design of the housing, etc. Furthermore, because tearing and peeling do not occur, the insulation properties of the bearing can be maintained. Furthermore, because insulation is possible between the housing, etc. and the outer ring of the bearing, and between the shaft, etc. and the inner ring, it is possible to prevent electricity from flowing from the housing, etc. or shaft, etc. to the bearing, and prevent electrolytic corrosion.

[0011] [Configuration 2] The bearing according to [Configuration 1], further comprising a coating made of a metal phosphate coating formed on the outer ring raceway surface, the shoulder surface of the outer ring, the width surface of the outer ring, the inner ring raceway surface, the shoulder surface of the inner ring, and the width surface of the inner ring. By adopting this configuration, the insulation properties of the bearing can be maintained more reliably.

[0012] [Configuration 3] A bearing according to [Configuration 1] or [Configuration 2], wherein the thickness of the coating is 1.0 μm or more and 4.0 μm or less. By adopting this configuration, the insulation properties of the bearing can be improved.

[0013] [Configuration 4] The bearing according to [Configuration 1], wherein the inverter-controlled device is a motor, a reducer, or a transmission. Since the insulating properties of the bearing can be maintained, it can be used in inverter-controlled devices such as motors, reducers, and transmissions.

[0014] [Configuration 5] [Configuration 1] or [Configuration 2]. A bearing device in which the bearing according to [Configuration 1] or [Configuration 2] is mounted on a shaft, the distance between the outer ring and the inner ring of the bearing in a stationary state is 1.0 x 10 2 Hz~5.0×10 3 The impedance value at Hz is 3.0 x 10 5 Ω or more 1.0×10 8 Ω or less. By adopting this configuration, the impedance value within a specified frequency range is approximately doubled to 1.0 x 10 compared to bearings without a coating. 5 Since the insulation resistance can be increased by about 2 times, the insulation properties of the bearing can be ensured.

[0015] [Configuration 6] The shaft is a horizontal shaft, and the distance between the outer ring and the inner ring of the bearing in a stationary state is 1.0 × 10 3 Hz~5.0×10 6 The impedance value at Hz is 5.0 x 10 2 Ω or more 1.0×10 7 The bearing device according to [Configuration 5], wherein the resistance is Ω or less. By adopting this configuration, the impedance value at higher frequencies is approximately doubled to 1.0 x 10 compared to bearings without a coating. 4 Since the insulation resistance can be increased by about 2 times, the insulation properties of the bearing can be more reliably achieved. [Effects of the Invention]

[0016] In the bearing of this invention, a metal phosphate coating is formed on the surface layer portions of the outer ring and inner ring in predetermined locations, so there is no change in the dimensions of the outer ring and inner ring, and therefore the bearing can be used as is without changing the design of the housing, etc. Additionally, Parkerizing (chemical conversion treatment) turns the metal surface layers in specified locations on the outer ring and inner ring into a metal phosphate coating, making them less susceptible to peeling and ensuring insulation properties. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing an example of a bearing according to an embodiment of the present invention; [Figure 2]FIG. 10 is a cross-sectional view showing another example of a bearing according to an embodiment of the present invention. [Figure 3] FIG. 1 is a perspective view showing an example of a bearing device in which a bearing according to the present invention is arranged on a horizontal shaft; [Figure 4] FIG. 1 is a perspective view showing an example of a bearing device in which a bearing according to the present invention is arranged on a vertical shaft; [Figure 5] Cross-sectional view showing an example of a conventional bearing DETAILED DESCRIPTION OF THE INVENTION

[0018] Figure 1 shows a bearing 11 according to an embodiment of the present invention. This bearing 11 has an outer ring 12, an inner ring 13 provided coaxially and radially inward of the outer ring 12, a plurality of rolling elements 15 incorporated at regular intervals in the circumferential direction into an annular bearing space 14 formed between the outer ring 12 and the inner ring 13, a cage 16 that holds the plurality of rolling elements 15, and a seal member 17 that seals the interior of the bearing.

[0019] The axial direction is the direction parallel to the central axis of the outer ring 12 (the central axis of the bearing), the radial direction is the direction perpendicular to the central axis of the outer ring 12, and the circumferential direction is the direction along the circumference that revolves around the central axis of the outer ring 12.

[0020] An outer ring raceway surface 12a with which the rolling elements 15 roll and make contact, and a pair of outer ring shoulder surfaces 12b extending circumferentially and adjacent to each other in the axial direction on either side of the outer ring raceway surface 12a, are formed on the inner circumference of the outer ring 12. The outer ring raceway surface 12a is the inner surface of a groove with an arc-shaped cross section that extends circumferentially around the inner circumference of the outer ring 12, and the outer ring shoulder surfaces 12b are cylindrical surfaces with a constant inner diameter along the axial direction. Furthermore, an outer ring outer peripheral surface 12c that fits into a housing or the like (not shown) is formed on the outer periphery of the outer ring 12, and width surfaces 12d are formed on both axial end surfaces of the outer ring 12.

[0021] An inner ring raceway 13a with which the rolling elements 15 roll and make contact, and a pair of inner ring shoulder surfaces 13b extending circumferentially and adjacent to each other in the axial direction on both sides of the inner ring raceway 13a, are formed on the outer periphery of the inner ring 13. The inner ring raceway 13a is the outer surface of a groove with an arc-shaped cross section that extends circumferentially around the outer periphery of the inner ring 13, and the inner ring shoulder surfaces 13b are cylindrical surfaces with a constant outer diameter along the axial direction. Furthermore, the inner periphery of the inner ring 13 is formed with an inner ring inner peripheral surface 13c that fits onto a shaft or the like (not shown), and the inner ring 13 is formed with width surfaces 13d on both axial end surfaces.

[0022] Rolling elements 15 are in rolling contact with outer ring raceway surface 12a and inner ring raceway surface 13a. Outer ring raceway surface 12a is formed symmetrically with respect to the axial center of outer ring 12, and inner ring raceway surface 13a is also formed symmetrically with respect to the axial center of inner ring 13. In bearing 11, rolling elements 15 are ball or roller rolling bearings, and examples of bearings in which rolling elements 15 are balls include ball bearings such as deep groove ball bearings.

[0023] The cage 16 is a member that partially surrounds the rolling elements 15 and maintains a constant spacing in the circumferential direction. The cage 16 may be made of a metal plate such as an iron plate, or resin. In addition, if the rolling elements 15 can be held at a fixed interval by means other than the retainer 16, for example by filling the bearing space 14 with a solid lubricant or the like as described below, the retainer 16 does not necessarily have to be installed.

[0024] The sealing member 17 is a member for sealing both axial sides of the bearing space 14 between the outer ring 12 and the inner ring 13, and is preferably installed to prevent leakage of a lubricant or the like that is placed in the bearing space 14, or to prevent foreign matter, dust, etc. from entering the bearing space 14. On the other hand, if a solid lubricant or the like is used as the lubricant and leakage of the lubricant is unlikely, or if the usage environment does not mean that foreign matter, dust, etc. will enter the bearing space 14, the bearing space 14 can be left open and the sealing member 17 need not be installed.

[0025] The lubricant is made of lubricating oil, grease containing base oil as a lubricating component, etc. The lubricating oil or base oil of the grease seeps into the rolling contact portions between the rolling elements 15 and the outer ring raceway surface 12 a or the inner ring raceway surface 13 a, thereby providing lubrication.

[0026] Examples of the lubricating oil or base oil include, but are not limited to, one or more oils such as liquid paraffin, PAO (poly-α-olefin) oil, vegetable oil, animal oil, and normal paraffin components whose mode of content in the linear carbon atom number distribution is between 30 and 33 linear carbon atoms. In addition to the base oil, additives such as thickeners, viscosity index improvers, and rust inhibitors are used in greases, but the types are not particularly limited and any additives can be used. In the grease, the content of the base oil can be freely adjusted to 5% by mass or more.

[0027] Alternatively, a resin component such as a general-purpose plastic or engineering plastic, such as ultra-high molecular weight polyolefin, polyamide, polyacetal, fluororesin, silicone, polyurethane, polyolefin, polystyrene, or polyvinyl chloride, may be added to the grease, and the grease may be solidified by heating, ultraviolet curing, or two-component mixing curing, and used as a solid lubricant.

[0028] Incidentally, coating 18 made of a metal phosphate coating is formed on at least outer ring outer peripheral surface 12c and inner ring inner peripheral surface 13c of outer ring 12 and inner ring 13. This coating 18 can prevent the flow of electricity and can impart insulating properties. This metal phosphate coating is formed on the surface of metals such as iron by Parkerizing, a chemical conversion treatment that uses a solution of a metal phosphate such as iron phosphate, zinc phosphate, manganese phosphate, or calcium phosphate to grow and form an insoluble metal phosphate coating on the surface of the metal.

[0029] This metal phosphate coating is formed by immersing outer ring 12 and inner ring 13 in the phosphate solution at a treatment temperature of about 50°C to 100°C for about 5 to 30 minutes. By immersing the outer ring 12 or the inner ring 13 in the phosphate solution, as shown in FIG. 2 , a metal phosphate coating can be formed on the entire surface of the outer ring 12 or the inner ring 13, i.e., on the outer ring outer peripheral surface 12c, outer ring raceway surface 12a, outer ring shoulder surface 12b, outer ring width surface 12d, inner ring inner peripheral surface 13c, inner ring raceway surface 13a, inner ring shoulder surface 13b, inner ring width surface 13d, etc. Furthermore, by masking the areas where the metal phosphate coating is not desired to be formed, it is possible to form the metal phosphate coating on specific locations of the outer ring 12 or the inner ring 13.

[0030] The thickness of the metal phosphate coating is preferably 1.0 μm or more, and more preferably 2.0 μm or more. By setting the thickness within this range, sufficient insulation properties can be imparted. There is no particular upper limit to the thickness, and a thickness of 4.0 μm is sufficient.

[0031] When a shaft is mounted on the inner ring 13 of the bearing 11 according to the present invention to form a bearing device, the impedance value between the coating formed on the outer ring 12 and the coating formed on the inner ring 13 is 1.0×10 2 Hz~5.0×10 3 Hz range, 3.0 x 10 5 Ω or more is good, 3.5×10 5 Ω or more is preferable, 4.0×10 5 Ω or more is more preferable. 8 Ω or less is good, 5.0×10 7 Ω or less is preferable, 2.0×10 7 Ω or less is more preferable. By having an impedance value within these ranges, the bearing can fully exhibit its insulating properties.

[0032] In addition, in the above-mentioned bearing device, when the shaft is a horizontal shaft, the impedance value between the film formed on the outer ring 12 and the film formed on the inner ring 13 is 1.0×10 3 Hz~5.0×10 6Hz range, 5.0 x 10 2 Ω or more is good, 6.0×10 2 Ω or more is preferable, 7.0×10 2 Ω or more is more preferable. 7 Ω or less is good, 5.0×10 6 Ω or less is preferable, 3.0×10 6 Ω or less is more preferable. By having an impedance value within these ranges, the bearing can fully exhibit its insulating properties.

[0033] The bearing according to the present invention can be used as a bearing for inverter-controlled devices such as motors, reducers, and transmissions used in electric vehicles (EVs) and hybrid cars (HEVs). [Example]

[0034] Parkerization (chemical conversion coating) was performed by immersing the outer ring 12 and the inner ring 13 in a Parkerization solution (manganese phosphate solution, a mixed solution of calcium phosphate and zinc phosphate), forming a coating made of a metal phosphate coating on the entire surface of the outer ring 12 and the inner ring 13, as shown in FIG. 2. Specifically, the outer ring 12 and the inner ring 13 were first immersed in an alkaline degreasing solution to remove dirt and other contaminants from the surfaces of the outer ring 12 and the inner ring 13. After rinsing with water, they were then immersed in a Parkerization solution at 97°C for 10 minutes, forming a coating made of a metal phosphate coating on the surface of the outer ring 12 and the inner ring 13. Two types of metal phosphate coatings were formed: a manganese phosphate coating and a zinc calcium phosphate coating. The coating thickness averaged 2.5 μm. A bearing device was assembled using this outer ring 12 and inner ring 13, with a shaft 19 incorporated into the inner peripheral surface 13c of the inner ring. As a comparison, the bearing device was also assembled using an outer ring 12 and inner ring 13 on which no coating was formed. Then, with shaft 19 in a horizontal position (see FIG. 3), alternating current of a predetermined frequency was passed between the coating of outer ring 12 and the coating of inner ring 13, and the impedance value was measured. Example 1 was an example using bearing 11 in which the metal phosphate coating was a manganese phosphate coating, Example 2 was an example using bearing 11 in which the metal phosphate coating was a zinc calcium phosphate coating, and Comparative Example 1 was a comparative example using bearing 11 in which no coating was formed. Next, an experiment similar to the above was conducted with shaft 19 in a vertical position (see FIG. 4). Example 3 was an example in which bearing 11 was used in which the metal phosphate coating was a manganese phosphate coating, Example 4 was an example in which bearing 11 was used in which the metal phosphate coating was a zinc calcium phosphate coating, and Comparative Example 2 was a comparative example in which bearing 11 was used in which no coating was formed. The results are shown in Table 1. In addition, in Figures 3 and 4, the seal member 17 is removed.

[0035] [Table 1]

[0036] In both the manganese phosphate coating (Examples 1 and 3) and the zinc calcium phosphate coating (Examples 2 and 4), the impedance values ​​were higher than when no metal phosphate coating was formed (Comparative Examples 1 and 2), demonstrating sufficient insulating properties.

[0037] When the axis is horizontal (Examples 1 and 2) or vertical (Examples 3 and 4), if a metal phosphate film is formed, the frequency is 1.0 × 10 2 Hz~5.0×10 3 Within the Hz range, the impedance value is 4.34 x 10 5 Ω or more, and the resistance of the specimen without a metal phosphate film (Comparative Examples 1 and 2) was 2.75 × 10 5 It was found that the impedance value was higher compared to Ω or less. In addition, when the axis is the horizontal axis (Examples 1 and 2), when a metal phosphate film is formed, the frequency is 1.0 × 10 3Hz~5.0×10 6 Within the Hz range, the impedance value is 7.27 x 10 2 Ω or more, and the resistance of the specimen without a metal phosphate film (Comparative Example 1) was 3.54 × 10 2 It was found that the impedance value was higher compared to Ω or less.

[0038] Incidentally, when no metal phosphate coating is formed, the impedance value is significantly lower when the shaft is horizontal (Comparative Example 1) than when the shaft is vertical (Comparative Example 2). This is thought to be because when the shaft is horizontal, there are areas where the gaps between the outer ring 12, rolling elements 15, and inner ring 13 are narrower than when the shaft is vertical, making it easier for electricity to flow and resulting in a lower impedance value. [Explanation of symbols]

[0039] 1. Bearings 2 outer ring 2a Outer ring raceway 3. Inner circle 3a Inner ring raceway 4 balls 5 Cage 6 Sealing material 7 Resin film 11 Bearings 12 outer ring 12a Outer ring raceway 12b Outer ring shoulder surface 12c Outer ring outer surface 12d Outer ring width surface 13 Inner Circle 13a Inner ring raceway surface 13b Inner ring shoulder surface 13c Inner ring inner surface 13d Inner ring width face 14 Bearing space 15 Rolling elements 16 Cage 17 Sealing material 18 Membrane 19 axes

Claims

1. an outer ring (12) having an outer ring raceway (12a) formed on its inner periphery; an inner ring (13) having an inner ring raceway (13a) formed on its outer periphery; a plurality of rolling elements (15) that are incorporated at intervals in the circumferential direction into an annular bearing space (14) formed between the outer ring (12) and the inner ring (13) and that are in rolling contact with the outer ring raceway surface (12 a) and the inner ring raceway surface (13 a); A bearing incorporated into an inverter-controlled device, The bearing has a coating (18) made of a metal phosphate coating formed on the outer peripheral surface (12c) of the outer ring (12) and the inner peripheral surface (13c) of the inner ring (13).

2. 2. The bearing according to claim 1, further comprising a coating (18) made of a metal phosphate coating formed on the outer ring raceway surface (12a), the shoulder surface (12b) of the outer ring (12), the width surface (12d) of the outer ring (12), the inner ring raceway surface (13a), the shoulder surface (13b) of the inner ring (13), and the width surface (13d) of the inner ring (13).

3. 3. The bearing according to claim 1, wherein the thickness of the coating (18) is 1.0 μm or more and 4.0 μm or less.

4. 2. The bearing according to claim 1, wherein the inverter-controlled device is a motor, a reducer, or a transmission.

5. A bearing device in which the bearing according to claim 1 or 2 is mounted on a shaft, 1.0 x 10 between the outer ring (12) and the inner ring (13) of the bearing in a stationary state ２ Hz to 5.0 x 10 ３ The impedance value at Hz is 3.0 x 10 ５ Ω or more 1.0×10 ８ Ω or less.

6. The axis is a horizontal axis, 1.0 x 10 between the outer ring (12) and the inner ring (13) of the bearing in a stationary state ３ Hz to 5.0 x 10 ６ The impedance value at Hz is 5.0 x 10 2 Ω or more 1.0×10 ７ 6. The bearing device according to claim 5, wherein the resistance is Ω or less.

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