Current-carrying unit and bearing unit

Abstract

To provide a compact current-carrying unit suitable for use in an oil bath, and to provide a bearing unit with an electrolytic corrosion preventive effect.SOLUTION: A current-carrying unit 2 includes a conductive annular case body part 6, a conductive energization member 7 that protrudes radially inward from the case body part 6, and an elastic member 8 that biases the energization member 7 radially inward. The case body part 6 is configured such that oil holes 15 and 16 are formed to allow a lubricant to flow in an axial direction. The bearing unit 1 includes the current-carrying unit 2, and a bearing 3 having an outer ring 22, an inner ring 23 disposed on an inner diameter side of the outer ring 22, rolling elements 24 provided between the outer ring 22 and the inner ring 23, and a retainer 25 that holds the rolling elements 24 at predetermined intervals in a circumferential direction. The current-carrying unit 2 and the bearing 3 are both integrally configured by having the former fitted into the latter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an energizing unit and a bearing unit in which the energizing unit and a bearing are integrated. [Background technology]

[0002] Rolling bearings such as ball bearings are commonly used to support rotating shafts such as motor shafts. In recent years, inverter control has become commonplace for efficient motor operation. In particular, motors for vehicles are being made smaller to facilitate installation in vehicles, and more precise control is being implemented to use these smaller motors more efficiently.

[0003] It is known that shaft currents and voltages occur on the motor shaft. If this current passes through the inside of the bearing, it can cause electrolytic corrosion in the metal raceways and rolling elements. Therefore, in Patent Document 1 listed below, a filament 30 (grounding brush) is placed in contact with the shaft 16 of the motor 12, and the charge generated on the shaft 16 is released to the housing via the filament 30, preventing the current from passing through the inside of the bearing (see Fig. 2 in Patent Document 1, etc.). Also, in Patent Document 2 listed below, an emitter 8 (region 10) is placed in contact with the shaft 68, and the charge generated on the shaft 68 is released to the housing 69 via the emitter 8, preventing the current from passing through the inside of the bearing (see Fig. 24 in Patent Document 2, etc.).

[0004] In the configurations shown in Patent Documents 1 and 2, the electric charge is released by sliding contact members (filament 30, emitter 8) against the motor shaft (shaft 16, shaft 68), but wear and deformation of the sliding contact members over time can reduce the electrical conductivity, potentially resulting in insufficient prevention of electrolytic corrosion. Therefore, in Patent Document 3 listed below, for example, an electrical brush 32 is housed in a bearing 1 that supports the motor shaft, and the electrical brush 32 is biased by a spring 31, thereby ensuring a predetermined electrical conductivity even when the electrical brush 32 is worn. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 8,199,453 [Patent Document 2] Patent No. 7033538 [Patent Document 3] Patent No. 6777178 Summary of the Invention [Problem to be solved by the invention]

[0006] The configuration shown in Patent Document 3 is intended for use in a dry environment, and is provided with a seal 7 and labyrinth gap S for sealing the bearing 1 and the conductive brush 32. This hinders the flow of lubricating oil in the axial direction when used in an oil bath, and requires a large space to mount the bearing unit (bearing 1), which limits the conditions for use and mounting.

[0007] The problem to be solved by the present invention is to provide a compact current-carrying unit and a bearing unit having an anti-galvanic corrosion function, which is suitable for use in an oil bath. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a current-carrying unit (first configuration) that includes an annular conductive case body, conductive current-carrying members that protrude radially inward from the case body, and an elastic member that biases the current-carrying members radially inward, the case body having an oil hole that allows lubricating oil to flow in the axial direction. This configuration improves the axial flow of lubricating oil inside the bearing when a bearing used in combination with this current-carrying unit is used in an oil bath, and prevents electrolytic corrosion of the bearing.

[0009] In the first configuration, the case body can have a bearing fitting portion extending in the axial direction (second configuration), which makes it possible to easily integrate the energizing unit and the bearing used in combination with this energizing unit.

[0010] In the second configuration, an insulating portion can be provided on at least one of the radially inner surface of the bearing fitting portion and the surface of the case main body facing the extension direction of the bearing fitting portion (third configuration). In this way, it is possible to prevent current from flowing between the case main body and the bearing used in combination with this current-carrying unit, and to more reliably prevent electrolytic corrosion of the bearing.

[0011] The insulating portion is preferably made of a material with high insulating properties, such as various ceramics and various resins, but from the viewpoints of insulation resistance, breakdown voltage, mechanical strength, processability, etc., a fired film containing at least one of various ceramics, polyphenylene sulfide resin, polyamide-imide resin, and epoxy resin is preferred.

[0012] In the first to third configurations, it is preferable to provide a configuration (fourth configuration) in which a plurality of the current-carrying members are provided, so that even if the current-carrying performance of some of the current-carrying members is impaired, the other current-carrying members can cover for this, thereby ensuring stable current-carrying performance.

[0013] In the fourth configuration, it is preferable that the case main body has an annular outer ring portion and a retainer that fits into the outer ring portion, and that the retainer has a plurality of bent portions that arrange the plurality of current-carrying members at equal intervals in the circumferential direction (fifth configuration). In this way, the current-carrying members housed between the plurality of bent portions are biased radially inward by elastic members, thereby achieving a centering function and stabilizing the sliding contact state of the current-carrying members.

[0014] Furthermore, to solve the above problems, the present invention provides a bearing unit (sixth configuration) that includes an energization unit of any one of the first to fifth configurations, and a bearing having an outer ring, an inner ring arranged on the inner diameter side of the outer ring, rolling elements provided between the outer ring and the inner ring, and a cage that holds the rolling elements at predetermined intervals in the circumferential direction, the energization unit being fitted into the bearing to integrate the two. This configuration improves the axial fluidity of lubricating oil inside the bearing unit when used in an oil bath, and makes it possible to make the bearing unit more compact by eliminating the need for a sealing seal or labyrinth in the bearing, while preventing electrolytic corrosion of the bearing.

[0015] In a sixth configuration, the outer periphery of the case body can be fitted onto the inner diameter surface of the outer ring, and the current-carrying member can be biased so as to slide against the motor shaft inserted through the axis of the inner ring (seventh configuration). In this way, no radially inward force acts on the outer ring from the current-carrying unit, and it is possible to prevent the size of the bearing internal clearance from deviating from a predetermined appropriate value due to that force.

[0016] Furthermore, a bearing unit (eighth configuration) can be configured that includes the current-carrying unit of the second or third configuration, and a bearing having an outer ring, an inner ring disposed on the inner diameter side of the outer ring, rolling elements disposed between the outer ring and the inner ring, and a cage that holds the rolling elements at predetermined intervals in the circumferential direction, wherein the bearing fitting portion is fitted onto the outer diameter surface of the outer ring, and the current-carrying member is biased so as to slide against a motor shaft inserted through the axis of the inner ring or against the outer diameter surface of the inner ring. This configuration allows the current-carrying unit and the bearing to be easily integrated. Furthermore, by sliding the current-carrying member against the outer diameter surface of the inner ring so that it does not directly slide against the motor shaft, there is no need for special processing or manufacturing methods to give the motor shaft a predetermined surface roughness or hardness, which may reduce costs.

[0017] Furthermore, a bearing unit (ninth configuration) can be configured that includes the current-carrying unit of the third configuration, and a bearing having an outer ring, an inner ring arranged on the inner diameter side of the outer ring, rolling elements provided between the outer ring and the inner ring, and a cage that holds the rolling elements at predetermined intervals in the circumferential direction, wherein the insulating portion is in contact with at least one of the outer diameter surface or end face of the outer ring. In this way, it is possible to prevent current from flowing between the case body and the outer ring, and to more reliably prevent electrolytic corrosion of the bearing. [Effects of the Invention]

[0018] The current-carrying unit and bearing unit of the present invention have oil holes formed in the case body that allow lubricating oil to flow in the axial direction, so that when used in an oil bath, the axial flow of lubricating oil inside the bearing unit can be improved, and by eliminating the need for a sealing seal or labyrinth on the bearing, the bearing unit can be made more compact while preventing electrolytic corrosion of the bearing. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a first embodiment of a bearing unit (current-carrying unit) according to the present invention; [Figure 2] Cross-sectional view along line II-II in Figure 1 [Figure 3] Enlarged cross-sectional view of the bearing unit (current-carrying unit) shown in Figure 1 [Figure 4] FIG. 2 is an exploded perspective view of the energizing unit shown in FIG. 1. [Figure 5] FIG. 2 is a cross-sectional view showing a modified example of the bearing unit (current-carrying unit) shown in FIG. 1. [Figure 6] FIG. 2 is a cross-sectional view showing a further modified example of the bearing unit (current-carrying unit) shown in FIG. [Figure 7] FIG. 10 is a cross-sectional view showing a second embodiment of the bearing unit (current-carrying unit) according to the present invention. [Figure 8] FIG. 10 is a cross-sectional view showing a third embodiment of the bearing unit (current-carrying unit) according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] A first embodiment of a bearing unit 1 (current-carrying unit 2) according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 4, the bearing unit 1 according to the first embodiment has a current-carrying unit 2 and a bearing 3, which are integrated together. The bearing unit 1 is interposed between a motor shaft 4 of an e-axle or the like and a housing 5, and rotatably supports the motor shaft 4. The housing 5 is electrically grounded. In the following, the direction along the rotational axis of the motor shaft 4 will be referred to as the axial direction, the direction perpendicular to the rotational axis as the radial direction, and the direction along the circumference going around the rotational axis as the circumferential direction.

[0021] The current-carrying unit 2 has a conductive annular case main body 6, a conductive current-carrying member 7 that protrudes radially inward from the case main body 6, and an elastic member 8 that urges the current-carrying member 7 radially inward.

[0022] The case body 6 has an annular outer ring portion 11 having a flange 9 extending in one axial direction at its outer peripheral edge and an extension piece 10 extending radially inward from the outer peripheral edge, and an annular retainer 14 having a flange 12 extending in another axial direction opposite to the one axial direction at its outer peripheral edge and an extension piece 13 extending radially inward from the outer peripheral edge. A plurality of oil holes 15, 16 (four oil holes 15, 16 each at 90-degree intervals in this embodiment) are formed in the outer ring portion 11 and the extension pieces 10, 13 of the retainer 14 at predetermined angular intervals in the circumferential direction. A bearing fitting portion 17 is extended in the one direction from the flange 9 of the outer ring portion 11.

[0023] As shown in Fig. 3, the flange 9 formed on the outer annular portion 11 and the flange 12 formed on the retainer 14 are integrated by press-fitting. When the two are integrated, the circumferential positions of the oil holes 15 formed on the outer annular portion 11 and the oil holes 16 formed on the retainer 14 are aligned. As a result of this integration, a circumferential groove that opens toward the inner diameter side is formed by the flanges 9, 12 and extension pieces 10, 13 formed on the outer annular portion 11 and the retainer 14, respectively. Note that, after inserting the flange 12 formed on the retainer 14 into the flange 9 formed on the outer annular portion 11, a retaining ring can be provided on the width surface to fix the outer annular portion 11 and the retainer 14, thereby improving maintainability.

[0024] Both the outer annular portion 11 and the retainer 14 are made of steel. An axial gap is formed between the fitted outer annular portion 11 and retainer 14, which is large enough to accommodate the current-carrying member 7 and the elastic member 8. The retainer 14 has a plurality of (four in this embodiment) bent portions 18 formed at predetermined angular intervals, extending from its inner edge in the other axial direction (the same direction as the flange 12 formed on the retainer 14). Each bent portion 18 is formed to correspond to the circumferential center position of the oil hole 16 formed in the retainer 14.

[0025] The current-carrying member 7 has a substantially arc-shaped base 19 and a current-carrying portion 20 that protrudes radially inward from the base 19, and the current-carrying portion 20 is configured to slide against the motor shaft 4. Each current-carrying member 7 is housed between two circumferentially adjacent bent portions 18 formed on the retainer 14. In this embodiment, four current-carrying members 7 are arranged at equal intervals in the circumferential direction. The number of current-carrying members 7 can be changed as needed, but a plurality is preferable. The number of bent portions 18 formed on the retainer 14 is determined according to the number of current-carrying members 7. In this embodiment, carbon-added polytetrafluoroethylene (PTFE) is used as the material for the current-carrying portion 20. An outer circumferential groove 21 is formed on the outer circumferential edge of the base 19.

[0026] In addition to carbon-added PTFE, conductive resins such as metal, carbon, or polyether ether ketone (PEEK) with carbon or the like, rubber, ceramics, or composites of these can be used as the material for the current-carrying part 20, thereby ensuring the current-carrying performance of the current-carrying unit with a simple configuration. Furthermore, the surface of the current-carrying part 20 (particularly the part that comes into sliding contact with the motor shaft 4) can be subjected to a surface treatment such as a coating (e.g., a conductive diamond-like carbon (DLC) film, a metal film (plated layer, etc.)) that improves current conduction and wear resistance.

[0027] The elastic member 8 is a member for biasing the current-carrying members 7 radially inward toward the motor shaft 4 (see the arrow in FIG. 2). As shown in FIG. 2, the elastic member 8 is suspended across an outer circumferential groove 21 formed on the outer periphery of each current-carrying member 7. In this embodiment, a garter spring made of a coiled steel wire processed into a ring shape is used as the elastic member 8, but it is also possible to use, for example, a circlip (C-type retaining ring) with a slit in part of the ring or an annular rubber. Note that in this embodiment, a single elastic member 8 is used to bias all of the current-carrying members 7, but it is also possible to configure each current-carrying member 7 to have its own elastic member 8.

[0028] The bearing 3 is a ball bearing having an outer ring 22, an inner ring 23 arranged on the inner diameter side of the outer ring 22, rolling elements 24 provided between the outer ring 22 and the inner ring 23, and a cage 25 that holds the rolling elements 24 at predetermined intervals in the circumferential direction. The bearing 3 according to this embodiment is not provided with a seal, ensuring the axial flow of lubricating oil inside the bearing unit 1. The current-carrying unit 2 and the bearing 3 are integrated by fitting a bearing fitting portion 17 formed on the outer ring portion 11 of the case main body 6 onto the outer diameter surface of the outer ring 22.

[0029] The bearing unit 1 is designed so that the inner diameter, outer diameter, and axial width of the bearing unit 1 when the current-carrying unit 2 and bearing 3 are integrated match any combination of the main dimensions (bearing inner diameter d, bearing outer diameter D, bearing width B) of the bearing specified in Japanese Industrial Standard JIS B1512-1:2011.

[0030] The operation of the bearing unit 1 will now be described. The motor shaft 4 is inserted through the axis of the bearing unit 1 (current-carrying unit 2 and bearing 3). When the motor shaft 4 and the current-carrying portion 20 of the current-carrying member 7, which is biased toward the motor shaft 4 by the biasing force of the elastic member 8, come into sliding contact, the portion of the current-carrying portion 20 that slides against the motor shaft 4 gradually wears. Even if this wear occurs, the current-carrying member 7 (current-carrying portion 20) is always biased toward the motor shaft 4 by the elastic member 8, so the contact state (current-carrying state) between the motor shaft 4 and the current-carrying member 7 is maintained.

[0031] The current-carrying part 20 is in contact with the case main body 6 (at least one of the outer ring part 11 and the retainer 14), and a current-carrying circuit is formed as a bypass path between the motor shaft 4, the current-carrying part 20, the case main body 6, and the housing 5. By forming the current-carrying circuit in this way, the current passing through the bearing 3 interposed between the motor shaft 4 and the housing 5 is reduced.

[0032] The above-mentioned bearing unit 1 has oil holes 15, 16 formed in the case main body 6 that allow lubricating oil to flow in the axial direction. This improves the axial flow of lubricating oil inside the bearing unit 1 when used in an oil bath, and by eliminating the need for a sealing seal or labyrinth in the bearing 3, the bearing unit 1 can be made more compact while preventing electrolytic corrosion of the bearing 3.

[0033] Furthermore, by providing multiple current-carrying members 7, the bearing unit 1 described above can reliably exhibit electrolytic corrosion prevention effects, even if a problem occurs that impairs the electrical conduction of some of the current-carrying members 7, as the electrical conduction effects of the other current-carrying members 7 can be ensured. Furthermore, the aligning function of the multiple current-carrying members 7 can stabilize the contact state between the motor shaft 4 and each current-carrying member 7, further improving the electrolytic corrosion prevention effects.

[0034] Furthermore, the above-mentioned bearing unit 1 is configured so that the inner diameter, outer diameter, and axial width when the current-carrying unit 2 and bearing 3 are integrated match any of the combinations of main dimensions of bearings specified in Japanese Industrial Standard JIS B1512-1:2011, making it possible to directly replace bearings standardized in the above-mentioned Japanese Industrial Standards (standard bearings, base bearings) with the bearing unit 1 of the present invention.

[0035] FIG. 5 shows a modified example of the bearing unit 1 (current-carrying unit 2) according to the first embodiment. The bearing unit 1 according to this modified example differs from the above-described configuration in that an insulating portion 26 is formed on the inner surface of the bearing fitting portion 17 formed on the outer ring portion 11 (the surface facing the outer ring 22 of the bearing 3). By forming the insulating portion 26 between the bearing fitting portion 17 and the outer diameter surface of the outer ring 22, it is possible to prevent current from flowing between the outer ring portion 11 and the outer ring 22, thereby more reliably preventing electrolytic corrosion of the bearing 3. In this modified example, as shown in FIG. 6, an insulating portion 26 is further formed between the case main body 6 (extension piece 13 of the retainer 14) and the end face of the outer ring 22, thereby further improving the electrolytic corrosion resistance of the bearing 3. Alternatively, the insulating portion 26 may be provided only between the case main body 6 (extension piece 13 of the retainer 14) and the end face of the outer ring 22.

[0036] A second embodiment of a bearing unit 1 (current-carrying unit 2) according to the present invention is shown in Figure 7. The bearing unit 1 according to the second embodiment is similar to the bearing unit 1 according to the first embodiment in that the current-carrying unit 2 and the bearing 3 are integrated together by fitting the bearing fitting portion 17 formed on the outer ring portion 11 of the case body 6 to the outer diameter surface of the outer ring 22. However, it differs in that the axial length of one of a pair of groove shoulders formed on the outer diameter surface of the inner ring 23 is longer than the other, and the current-carrying member 7 (current-carrying portion 20) is in sliding contact with this one groove shoulder (the outer diameter surface of the inner ring 23).

[0037] In the configuration according to the second embodiment, a current-carrying circuit is formed as a bypass path between the motor shaft 4, inner ring 23, current-carrying portion 20, case main body 6, and housing 5. By forming a current-carrying circuit in this manner, the current passing through bearing 3 interposed between motor shaft 4 and housing 5 is reduced. With this configuration, current-carrying member 7 (current-carrying portion 20) does not directly slide on motor shaft 4, so there is no need for special processing or manufacturing methods to give motor shaft 4 a predetermined surface roughness or hardness, potentially reducing costs.

[0038] A third embodiment of a bearing unit 1 (current-carrying unit 2) according to the present invention is shown in Fig. 8. The bearing unit 1 according to the third embodiment is similar to the bearing unit 1 according to the first embodiment in that a current-carrying member 7 (current-carrying portion 20) is biased by an elastic member 8 so as to be in sliding contact with the motor shaft 4 inserted through the axis of the inner ring 23. However, it differs in that one of a pair of groove shoulders formed on the inner diameter surface of the outer ring 22 has a longer axial length than the other, and the outer periphery of the case main body 6 is fitted into this one groove shoulder (inner diameter surface of the outer ring 22).

[0039] In the configuration according to the third embodiment, a current-carrying circuit is formed as a bypass path between the motor shaft 4, the current-carrying unit 20, the case main body 6, the outer ring 22, and the housing 5. By forming the current-carrying circuit in this manner, the current passing through the bearing 3 interposed between the motor shaft 4 and the housing 5 is reduced. With this configuration, no radially inward force is applied from the current-carrying unit 2 to the outer ring 22, and this force can be prevented from causing the size of the bearing internal clearance to deviate from a predetermined appropriate value.

[0040] In each of the above embodiments, the motor shaft 4 is inserted through the axis of the bearing unit 1, and the current-carrying member 7 is biased radially inward by the elastic member 8, causing the current-carrying portion 20 to slide against the outer diameter surface of the motor shaft 4 or the inner ring 23. However, conversely, if the motor shaft 4 is provided on the outer diameter side of the bearing unit 1 and the housing 5 is provided on the inner diameter side of the bearing unit 1, the current-carrying member 7 can also be biased radially outward by the elastic member 8.

[0041] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0042] 2 Power supply unit 3. Bearings 4 Motor shaft 6 Case body 7 Conductive materials 8 Elastic member 11 Outer ring 14 Retainer 15, 16 oil hole 17 Bearing fitting part 18 Bending section 22 outer ring 23 Inner Circle 24 rolling elements 25 Retainer 26 Insulation section

Claims

1. The device has a conductive annular case body (6), a conductive current-carrying member (7) protruding radially inward from the case body (6), and an elastic member (8) that biases the current-carrying member (7) radially inward, The energizing unit has oil holes (15, 16) formed in the case body (6) to allow lubricating oil to flow in the axial direction.

2. 2. The energizing unit according to claim 1, wherein the case body (6) has a bearing fitting portion (17) extending in the axial direction.

3. An electrically conductive unit as described in claim 2, wherein an insulating portion (26) is provided on at least one of the radial inner surface of the bearing fitting portion (17) or the surface of the case main body portion (6) facing the extension direction of the bearing fitting portion (17).

4. The current-carrying unit according to claim 1, wherein a plurality of the current-carrying members (7) are provided.

5. The energizing unit according to claim 4, wherein the case main body (6) has an annular outer ring portion (11) and a retainer (14) that fits into the outer ring portion (11), and the retainer (14) has a plurality of bent portions (18) that arrange the plurality of energizing members (7) at equal intervals in the circumferential direction.

6. A current-carrying unit (2) according to any one of claims 1 to 5; a bearing (3) having an outer ring (22), an inner ring (23) arranged on the inner diameter side of the outer ring (22), rolling elements (24) provided between the outer ring (22) and the inner ring (23), and a cage (25) that holds the rolling elements (24) at predetermined intervals in the circumferential direction; and The current-carrying unit (2) is fitted into the bearing (3) to form an integrated bearing unit.

7. The outer periphery of the case body (6) is fitted to the inner diameter surface of the outer ring (22), 7. The bearing unit according to claim 6, wherein the current-carrying member (7) is biased so as to be in sliding contact with a motor shaft (4) inserted through the axis of the inner ring (23).

8. A current-carrying unit (2) according to claim 2 or 3; a bearing (3) having an outer ring (22), an inner ring (23) arranged on the inner diameter side of the outer ring (22), rolling elements (24) provided between the outer ring (22) and the inner ring (23), and a cage (25) that holds the rolling elements (24) at predetermined intervals in the circumferential direction; and The bearing fitting portion (17) fits onto the outer diameter surface of the outer ring (22), The bearing unit is such that the current-carrying member (7) is biased so as to be in sliding contact with the motor shaft (4) inserted through the axis of the inner ring (23) or the outer diameter surface of the inner ring (23).

9. The current-carrying unit (2) according to claim 3; a bearing (3) having an outer ring (22), an inner ring (23) arranged on the inner diameter side of the outer ring (22), rolling elements (24) provided between the outer ring (22) and the inner ring (23), and a cage (25) that holds the rolling elements (24) at predetermined intervals in the circumferential direction; and The bearing unit has an insulating portion (26) in contact with at least one of an outer diameter surface and an end surface of the outer ring (22).

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