Electric corrosion preventing electric conductive cover and rolling bearing

Abstract

To provide an electric corrosion preventing electric conductive cover and a rolling bearing which can prevent electric corrosion to lengthen a service life thereof.SOLUTION: An electric corrosion preventing electric conductive cover 1 has: a bearing fitting part 9 having a cylindrical part fitted in a first bearing ring 3 of a rolling bearing 2 and having electric conductivity; and an electric conductive part 10 radially extending from the bearing fitting part 9 to come into contact with a second bearing ring 4 of the rolling bearing 2 and having electric conductivity. A rolling bearing 2 includes the electric corrosion preventing electric conductive cover 1.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electrolytic corrosion-preventing conductive cover used in a rolling bearing that supports a rotating shaft such as a motor shaft, and to a rolling bearing that employs this electrolytic corrosion-preventing conductive cover. [Background technology]

[0002] Rolling bearings, especially ball bearings, are commonly used as bearings for supporting rotating shafts such as motor shafts. In recent years, inverter control has become common to operate motors efficiently. In particular, motors for vehicles are being made smaller to make them easier to mount on vehicles, and more precise control is being implemented to use the smaller motors more efficiently.

[0003] It is known that shaft current and shaft voltage are generated in the motor shaft. When this current passes through the inside of the bearing, electrolytic corrosion may occur in the metal raceway and rolling elements. Therefore, for example, in the following Patent Document 1, in addition to the conductive brush that has been generally used in the past, the bearing components (raceway and rolling elements) are made of insulating materials (ceramics, etc.) to prevent the current from passing through the inside of the bearing. Conversely, in the following Patent Document 2, conductive materials such as carbon are dispersed in the sealing rubber member and grease to improve the electrical conductivity inside the bearing, thereby preventing electrolytic corrosion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-222841 A [Patent Document 2] JP 2017-67111 A Summary of the Invention [Problem to be solved by the invention]

[0005] The configuration shown in Patent Document 1 requires the use of expensive insulating materials such as ceramics, which is problematic in terms of material cost. In addition, the configuration shown in Patent Document 2 may have problems such as variation in electrical conductivity and instability in durability due to variation and deterioration in the dispersion of conductive materials in the sealing rubber members and grease. In addition, conventional motor brushes require installation space inside the unit, leaving room for improvement.

[0006] An object of the present invention is to provide an electrolytic corrosion-preventing conductive cover and a rolling bearing that can prevent electrolytic corrosion and extend the life of the bearing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a bearing fitting portion having a cylindrical portion that fits into a first race of the rolling bearing and that is electrically conductive; a conductive current-carrying portion extending radially from the bearing fitting portion and contacting a second race of the rolling bearing; An electrolytic corrosion prevention conductive cover having the above structure was formed.

[0008] In this way, the current generated between the housing and the rotating shaft is bypassed by the conductive part, thereby preventing electrolytic corrosion from occurring in the raceways and rolling elements, and thereby extending the life of the rolling bearing.

[0009] In the above configuration, It is preferable that the current-carrying portion has spring elasticity toward the second bearing ring.

[0010] With this arrangement, even if the axial gap inside the bearing is displaced, the spring elasticity ensures that the current-carrying portion remains in contact with the second race, thereby ensuring a stable prevention effect against electrolytic corrosion.

[0011] In all of the above configurations: It is preferable that an insulating portion is provided on at least one of the inner and outer surfaces of the cylindrical portion.

[0012] In this way, the insulating part can prevent current from passing through the first race, so that electrolytic corrosion of the components of the rolling bearing can be more reliably prevented. On the other hand, even if dielectric breakdown occurs in the insulating part, the current bypassing part can prevent current from passing through the rolling elements, so that the electrolytic corrosion prevention effect can be maintained.

[0013] In the configuration in which the insulating portion is provided, The insulating portion is preferably configured to have an insulating coating layer made of resin, rubber, or ceramics.

[0014] In this way, an insulating portion with high insulating reliability can be formed on the surface of the cylindrical portion.

[0015] In all of the above configurations: The bearing fitting portion and the current-carrying portion may be made of steel.

[0016] In this way, a current circuit from the housing to the rotating shaft can be constructed at relatively low cost.

[0017] In all of the above configurations: It is preferable that a portion of the current-carrying portion that comes into contact with the second raceway be treated to enhance electrical conductivity and wear resistance.

[0018] This is expected to further reduce electrolytic corrosion inside the bearing by reducing the contact resistance between the current-carrying part and the second raceway, and to extend the bearing life by preventing wear caused by sliding between the current-carrying part and the second raceway.

[0019] In all of the above configurations: It is preferable that the electrical conductivity and wear resistance of the current-carrying portion be imparted by a metal coating, a coating mainly composed of hydrocarbon or carbon, carbon fiber, or a conductive resin.

[0020] In this way, good electrical conductivity and wear resistance of the current-carrying portion can be ensured.

[0021] In all of the above configurations: It is preferable that the electric current supplying portion has a plurality of the electric current supplying portions.

[0022] In this way, the rotational balance of the second raceway with which the current-carrying portion comes into contact can be balanced, and even if the axial gap becomes uneven, the contact state between the current-carrying portion and the second raceway can be reliably maintained. In addition, since the load due to sliding is less likely to be concentrated on some of the current-carrying portions, the long-term durability can be improved.

[0023] In addition, in the present invention, A first race; a second raceway provided coaxially with the first raceway; A rolling element disposed between the races; and The electrolytic corrosion prevention conductive cover according to any one of the above configurations, A rolling bearing having the above structure was constructed.

[0024] In this way, the action of the electrolytic corrosion-preventing conductive cover can prevent electrolytic corrosion of the rolling bearing, thereby making it possible to extend the service life of the rolling bearing. Effect of the Invention

[0025] The electrolytic corrosion-preventing conductive cover of the present invention has an electrically conductive portion that is electrically conductive, allowing electricity to flow between the housing and the rotating shaft via a path separate from the rolling elements arranged between the two raceways of the rolling bearing.This makes it possible to prevent electrolytic corrosion from occurring in the raceways and rolling elements, and to extend the life of the rolling bearing. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view showing an embodiment of a rolling bearing provided with an electrolytic corrosion-preventing conductive cover according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the main part of FIG. 1. [Diagram 3] Cross-sectional view taken along line III-III in Figure 1 [Figure 4] FIG. 2 is a partially cutaway perspective view of the electrolytic corrosion prevention conductive cover shown in FIG. 1. [Diagram 5] 2 is a cross-sectional view of a main portion of a modified example of the rolling bearing shown in FIG. 1. [Figure 6] FIG. 6 is a perspective view showing a part of the electrolytic corrosion prevention conductive cover shown in FIG. 5 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] An embodiment of a rolling bearing 2 provided with an electrolytic corrosion-preventing conductive cover 1 according to the present invention will be described with reference to the drawings. As shown in Figures 1 to 3, the rolling bearing 2 is a ball bearing whose main components are a first raceway 3 (hereinafter referred to as the outer raceway and given the same reference number as the first raceway 3), a second raceway 4 of the rolling bearing 2 provided coaxially with the outer raceway 3 (hereinafter referred to as the inner raceway and given the same reference number as the second raceway 4), rolling elements 5 (hereinafter referred to as balls and given the same reference number as the rolling elements 5) disposed between the inner and outer raceways 3 and 4, and the electrolytic corrosion-preventing conductive cover 1.

[0028] This rolling bearing 2 is used, for example, as a support bearing that supports a rotating shaft 6 (hereinafter referred to as a motor shaft and given the same reference number as the rotating shaft 6) of an e-axle or the like. In the following, the direction along the rotating shaft of the rolling bearing 2 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 going around the rotating shaft is referred to as the circumferential direction.

[0029] Raceway grooves are formed on the inner peripheral surface of the outer ring 3 and the outer peripheral surface of the inner ring 4, and balls 5 are arranged between the two raceway grooves, held at a specified circumferential interval by a cage 7. The inner and outer rings 3, 4 and the balls 5 are all made of steel. The bearing space formed between the inner and outer rings 3, 4 is sealed by seal members 8 provided on both axial ends of the inner and outer rings 3, 4. A lubricant is held in this bearing space, and a lubricant film is formed between the raceway grooves of the inner and outer rings 3, 4 and the balls 5.

[0030] As shown in Fig. 4, the electrolytic corrosion prevention conductive cover 1 mainly comprises a bearing fitting portion 9 and a conductive portion 10. The bearing fitting portion 9 and the conductive portion 10 are integrally made of steel and are electrically conductive members.

[0031] The bearing fitting portion 9 is a member having a cylindrical portion that fits to the outer peripheral surface of the outer ring 3 of the rolling bearing 2, and has a substantially L-shaped cross section cut along a plane including the rotating shaft. This bearing fitting portion 9 is fitted inside a housing 11 made of steel. An insulating portion 12 is provided on the inner surface of the bearing fitting portion 9, and insulation is achieved between the housing 11 (bearing fitting portion 9) and the outer ring 3. This insulating portion 12 is an insulating coating layer formed by coating with resin. The thickness and material of this insulating portion 12 can be appropriately determined taking into consideration the magnitude of the axial current and axial voltage acting on the motor shaft 6, and for example, rubber, ceramics, etc. can be used as the material in addition to resin.

[0032] The current-carrying part 10 is a tongue-shaped member extending radially inward from one axial end side of the bearing fitting part 9, and is in contact with the axial end part of the inner ring 4. The tip of the current-carrying part 10 is bent in a direction away from the inner ring 4 in the axial direction, thereby reducing sliding resistance and suppressing heat generation. By bringing the current-carrying part 10 into contact with the axial end part of the inner ring 4, a bypass circuit is formed that allows electricity to flow between the housing 11 in which the rolling bearing 2 is provided and the motor shaft 6 supported by the rolling bearing 2, via a route separate from the balls 5 arranged between the inner and outer rings 3, 4.

[0033] The current-carrying parts 10 are formed at eight locations at equal angular intervals in the circumferential direction of the bearing fitting part 9. It is sufficient that the current-carrying parts 10 are formed in at least one location, and the number can be increased or decreased as appropriate taking into consideration long-term durability associated with sliding wear with the inner ring 4. Furthermore, the circumferential positions of the current-carrying parts 10 are not limited to equal angular intervals and can be changed as appropriate.

[0034] The current-carrying part 10 extends radially inward from the bearing fitting part 9 and constitutes a leaf spring having spring elasticity toward the axial end of the inner ring 4. A contact part 13 is formed on the surface of the current-carrying part 10 facing the axial end of the inner ring 4. Due to this spring elasticity, a constant pressing force acts from the current-carrying part 10 toward the axial end of the inner ring 4 via the contact part 13.

[0035] The contact portion 13 is treated to enhance its electrical conductivity or wear resistance. In this embodiment, a diamond-like carbon (hereinafter abbreviated as DLC) film is formed on the surface of the current-carrying portion 10, thereby forming the contact portion 13 having both electrical conductivity and wear resistance. By changing the bonding state between carbon atoms by adjusting the DLC film formation conditions, the balance between the electrical conductivity and wear resistance of the contact portion 13 can be appropriately adjusted.

[0036] In this configuration, the shapes of the electro-corrosion prevention conductive cover 1 and the contact portion 13 are determined and the materials are selected so that the electrical resistance value from the housing 11 through the electro-corrosion prevention conductive cover 1 and the inner ring 4 to the motor shaft 6 is smaller than the electrical resistance value from the housing 11 through the outer ring 3, balls 5, and inner ring 4 to the motor shaft 6.

[0037] In this embodiment, a DLC layer is formed on the contact portion 13. However, instead, the contact portion 13 can be provided with electrical conductivity and wear resistance by a metal coating (a plating layer of gold, silver, etc.), a coating mainly composed of hydrocarbon or carbon, carbon fiber, conductive resin, etc.

[0038] The function of this electrolytic corrosion-preventing conductive cover 1 will now be described. When an axial current or axial voltage occurs in the motor shaft 6, an electric current is generated between the housing 11, in which the rolling bearing 2 is provided, and the motor shaft 6. This current passes from the housing 11 through the bearing fitting portion 9 and the conductive portion 10 of the electrolytic corrosion-preventing conductive cover 1, and reaches the motor shaft 6 via the inner ring 4. Since an insulating portion 12 is formed on the inner surface of the bearing fitting portion 9 of the electrolytic corrosion-preventing conductive cover 1, the housing 11 and the outer ring 3 are insulated, and no electric current is generated between the outer ring 3 and the balls 5, or between the balls 5 and the inner ring 4. This makes it possible to reliably prevent electrolytic corrosion from occurring in the inner and outer rings 3, 4, and the balls 5.

[0039] Fig. 5 shows the main parts of a modified example of the above-mentioned rolling bearing 2. The rolling bearing 2 according to this modified example has the same configuration as the above-mentioned bearing itself, but differs in the configuration of the electrolytic corrosion-preventing electrolytic cover 1. As shown in Fig. 6, the electrolytic corrosion-preventing electrolytic cover 1 according to this modified example is provided with an insulating part 12 on the outer surface of the bearing fitting part 9, and insulation is achieved between the housing 11 and the bearing fitting part 9.

[0040] In the rolling bearing 2 according to this modified example, even if an axial current or axial voltage occurs in the motor shaft 6, the insulating action of the bearing fitting portion 9 (insulating portion 12) prevents current from flowing between the housing 11 and the motor shaft 6, and therefore prevents current from flowing between the outer ring 3 and the balls 5, and between the balls 5 and the inner ring 4. This makes it possible to reliably prevent electrolytic corrosion from occurring in the inner and outer rings 3, 4 and the balls 5.

[0041] Furthermore, even if insulation breakdown occurs in the insulating portion 12, the current generated between the housing 11 and the bearing fitting portion 9 flows from the bearing fitting portion 9 through the conductive portion 10 to the inner ring 4 side. As a result, as described above, no current will be generated between the outer ring 3 and the balls 5, or between the balls 5 and the inner ring 4, and it is possible to reliably prevent electrical corrosion from occurring in the inner and outer rings 3, 4 and the balls 5.

[0042] In the above embodiment, the insulating portion 12 is formed on only one of the inner and outer surfaces of the bearing fitting portion 9, but it may be possible to form the insulating portion 12 on both the inner and outer surfaces. Also, in the above embodiment, the insulating portion 12 is formed on the electrolytic corrosion-preventing electrolytic cover 1 made of steel, but the electrolytic corrosion-preventing electrolytic cover 1 can also be formed by using a nonconductive material base such as resin or rubber and forming a conductive coating on the surface, or by insert-molding a conductive member into the nonconductive material.

[0043] In addition, in the above embodiment, the bearing fitting portion 9 is fitted into the outer peripheral surface of the outer ring 3, and the current-carrying portion 10 is in contact with the axial end of the inner ring 4. However, it is possible to configure it in the opposite way, where the bearing fitting portion 9 is fitted into the inner peripheral surface of the inner ring 4, and the current-carrying portion 10 is in contact with the axial end of the outer ring 3.

[0044] The electrolytic corrosion-preventing conductive cover 1 is configured so that the electrolytic part 10 extending radially inward from the bearing fitting part 9 comes into contact with the axial end of the inner ring 4, so that the current generated between the housing 11 and the rotating shaft 6 is bypassed by the electrolytic part 10. This makes it possible to prevent electrolytic corrosion from occurring in the inner and outer rings 3, 4 and the balls 5, thereby lengthening the life of the rolling bearing 2.

[0045] Furthermore, the electrolytic corrosion prevention electrolytic cover 1 is configured so that the electrolytic part 10 has spring elasticity toward the axial end face of the inner ring 4, so that even if displacement occurs in the axial gap inside the bearing, the spring elasticity ensures that the electrolytic part 10 remains in contact with the inner ring 4. This makes it possible to stably exert the electrolytic corrosion prevention effect.

[0046] Furthermore, the electrolytic corrosion-preventing conductive cover 1 described above has an insulating portion 12 formed on at least one of the inner and outer surfaces of the cylindrical portion of the bearing fitting portion 9, so that the insulating portion 12 can prevent current from passing through the outer ring 3. This makes it possible to more reliably prevent electrolytic corrosion of the components of the rolling bearing 2. On the other hand, even if dielectric breakdown occurs in the insulating portion 12, the current bypass effect of the conductive portion 10 can prevent current from passing through the balls 5, thereby maintaining the electrolytic corrosion prevention effect.

[0047] In addition, the above-mentioned electrolytic corrosion-preventing conductive cover 1 has been treated at the contact portion 13 of the electrolytic part 10 with the inner ring 4 to improve electrical conductivity and wear resistance, so that it is expected that the contact resistance between the electrolytic part 10 and the inner ring 4 will be reduced, thereby further reducing electrolytic corrosion inside the bearing, and that the service life will be extended by preventing wear due to sliding between the electrolytic part 10 and the inner ring 4.

[0048] In addition, since the electrolytic corrosion prevention conductive cover 1 has a plurality of conductive parts 10, it is possible to achieve a balanced rotation of the inner ring 4 with which the conductive parts 10 come into contact, and even if an imbalance occurs in the axial clearance, it is possible to reliably maintain the contact state between the conductive parts 10 and the inner ring 4. In addition, since the load due to sliding is unlikely to be concentrated on some of the conductive parts 10, it is also possible to improve long-term durability.

[0049] Furthermore, the rolling bearing 2 employs the electrolytic corrosion-preventing conductive cover 1 described above, which serves to prevent electrolytic corrosion of the rolling bearing 2 and thereby extend the life of the rolling bearing 2.

[0050] Furthermore, since the above-mentioned rolling bearing 2 is constructed by simply attaching the electrolytic corrosion prevention conductive cover 1 to a conventional rolling bearing in the axial direction, it requires almost no extra installation space, and the entire motor unit can be made lighter and more compact.

[0051] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0052] 1. Electrical corrosion prevention conductive cover 2. Rolling bearings 3 First raceway (outer race) 4 Second raceway (inner race) 5 Rolling elements (balls) 9 Bearing fitting part 10 Electrical Conductor 12 Insulation 13 Contact part

Claims

1. a bearing fitting portion (9) having a cylindrical portion that fits into a first race (3) of the rolling bearing (2) and having electrical conductivity; a conductive current-carrying portion (10) extending radially from the bearing fitting portion (9) and contacting a second raceway (4) of the rolling bearing (2); A conductive cover that prevents electrolytic corrosion.

2. 2. The electrolytic corrosion prevention current-carrying cover according to claim 1, wherein the current-carrying portion (10) has spring elasticity toward the second race (4).

3. 3. The electrolytic corrosion prevention conductive cover according to claim 1, wherein an insulating portion (12) is provided on at least one of the inner and outer surfaces of the cylindrical portion.

4. 4. The electrolytic corrosion prevention conductive cover according to claim 3, wherein the insulating portion (12) is made of an insulating coating layer made of resin, rubber, or ceramics.

5. 3. The electrolytic corrosion prevention conductive cover according to claim 1, wherein the bearing fitting portion (9) and the conductive portion (10) are made of steel.

6. 3. The electrolytic corrosion prevention conductive cover according to claim 1, wherein a contact portion (13) of the conductive portion (10) with the second raceway ring (4) is treated to enhance electrical conductivity and wear resistance.

7. The electrolytic corrosion prevention conductive cover according to claim 6, wherein the electrical conductivity and wear resistance of the conductive portion (10) are imparted by a metal coating, a coating mainly composed of hydrocarbon or carbon, carbon fiber, or a conductive resin.

8. The electrolytic corrosion prevention conductive cover according to claim 1 or 2, comprising a plurality of the conductive parts (10).

9. A first race (3), a second bearing ring (4) provided coaxially with the first bearing ring (3); A rolling element (5) disposed between the races (3, 4); The electrolytic corrosion prevention conductive cover (1) according to claim 1 or 2, A rolling bearing having

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