Energizing unit and bearing unit

Abstract

To provide an energizing unit capable of maintaining energizing performance for a long period of time and exhibiting stable energizing performance, and a bearing unit.SOLUTION: A energizing unit 1 has: a conductive annular case body part 7 fitted into a housing 12 and having a circumferential groove opening toward an inner diameter side; a conductive energizing member 8 provided in the circumferential groove, protruding radially inward from the case body part 7, and being in sliding contact with a motor shaft 11; a radial elastic member 9 that is provided in the circumferential groove, and biases the energizing member 8 radially inward; and a pressing mechanism 10 that presses the energizing member 8 from one axial side to the other axial side in the circumferential groove. A bearing unit A has the energizing unit 1 and a bearing 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power supply unit provided in a bearing that supports a rotating shaft such as a motor shaft, and a bearing unit employing this power supply unit.

Background Art

[0002] As a bearing that supports a motor shaft such as an e-axle for an automobile, a rolling bearing, particularly a ball bearing, is generally used. In recent years, inverter control has been generally adopted in order to operate the motor efficiently. In particular, in the case of an in-vehicle motor, miniaturization has been achieved from the viewpoint of mounting on a vehicle, and in order to use the miniaturized motor more efficiently, finer control is being performed.

[0003] It has been found that shaft current and shaft voltage are generated in this motor shaft. When this current passes through the inside of the bearing, electrolytic corrosion may occur on the raceway ring and rolling elements made of metal. Therefore, for example, in Patent Document 1 below, a filament 30 (grounding brush) is brought into contact with the shaft 16 of the motor 12, and the electric charge generated on the shaft 16 is discharged to the housing through the filament 30 so that the current does not pass through the inside of the bearing (see Fig. 2 of Patent Document 1, etc.). Further, in Patent Document 2 below, a discharge body 8 (region 10) is brought into contact with the shaft 68, and the electric charge generated on the shaft 68 is discharged to the housing 69 through the discharge body 8 so that the current does not pass through the inside of the bearing (see Fig. 24 of Patent Document 2, etc.).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the configurations shown in Patent Documents 1 and 2, since the sliding contact members (filament 30, discharge body 8) are brought into sliding contact with the motor shaft (shaft 16, shaft 68) to release electric charges, the energization performance may deteriorate due to wear or deformation of the sliding contact members over time, and the effect of preventing electrolytic corrosion may be insufficient.

[0006] The problem to be solved by the present invention is to provide an energization unit and a bearing unit capable of maintaining the energization performance over a long period of time and stably exhibiting the energization performance.

Means for Solving the Problem

[0007] To solve the above problems, in the present invention, An annular case main body portion having conductivity, which is fitted into the housing and has a circumferential groove opening toward the inner diameter side; An electrically conductive energization member provided in the circumferential groove, protruding radially inward from the case main body portion and slidingly contacting the motor shaft; A radial elastic member provided in the circumferential groove for biasing the energization member radially inward; A pressing mechanism for pressing the energization member from one axial side to the other side in the circumferential groove; An energization unit having the above is configured.

[0008] In this way, a bypass path for passing an electric current from the motor shaft through the energization member and the case main body portion to the housing is newly formed, and electrolytic corrosion of the bearing provided between the motor shaft and the housing can be prevented. Further, since the energization member is biased toward the motor shaft by the radial elastic member, even if the energization member wears over time, the contact state between the motor shaft and the energization member is maintained, and the energization performance can be maintained over a long period of time. Furthermore, since the energization member is pressed from one axial side to the other side by the pressing mechanism, the contact state between the energization member and the case main body portion can be maintained, and stable energization performance can be exhibited.

[0009] In the above configuration, the pressing mechanism is a bent portion formed on at least one of the pair of wall portions constituting the circumferential groove, which bends toward the inside of the circumferential groove on the inner diameter side with respect to the outer diameter side, or an axial elastic member interposed in the axial gap between the inner surface of the circumferential groove and the energizing member, or a configuration in which an inclined surface portion having a normal line inclined to one side in the axial direction is formed at the contact portion of the energizing member with the radial elastic member. According to these configurations, the energizing member can be pressed from one side in the axial direction toward the other side, and the contact state between the energizing member and the case main body portion can be surely maintained.

[0010] Further, in the configuration in which the pressing mechanism is an axial elastic member, it is preferable that the axial elastic member is made of a conductive material composed of metal, carbon, or resin, rubber, ceramics, or a composite material thereof to which conductivity is imparted. In this way, a plurality of current conduction routes can be ensured, including a current conduction route in which current flows directly from the energizing member toward the case main body portion and a current conduction route in which current flows from the energizing member through the axial elastic member to the case main body portion, so that more stable current conduction performance can be exhibited.

[0011] In all of the above configurations, it is preferable that a plurality of the energizing members are provided. In this way, even if the current conduction performance of some of the energizing members is impaired, it can be covered by other energizing members, so that stable current conduction performance can be ensured.

[0012] In the configuration in which a plurality of the energizing members are provided, it is preferable that the case main body portion has an annular outer ring portion and a retainer fitted to the outer ring portion, and a plurality of bent portions for arranging the plurality of energizing members at equal intervals in the circumferential direction are formed on the retainer. In this way, a centering function is exhibited by urging the energizing members respectively housed between the plurality of bent portions radially inward by the radial elastic members, and the contact state between the motor shaft and the energizing members can be stabilized.

[0013] In all of the above configurations, it is preferable that the radially elastic member is a metal spring member provided across the plurality of current-carrying members. By doing so, the plurality of current-carrying members can be collectively biased toward the motor shaft with a simple configuration.

[0014] In all of the above configurations, it is preferable that the current-carrying member is made of a conductive material composed of metal, carbon, or resin, rubber, ceramics, or a composite material thereof having conductivity imparted thereto. By doing so, the current-carrying performance of the current-carrying unit can be ensured with a simple configuration.

[0015] The current-carrying unit according to all of the above configurations includes a current-carrying unit, an outer ring, an inner ring disposed 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, and can be adopted in a bearing unit having a bearing that supports the motor shaft and is arranged such that the outer ring abuts against the current-carrying unit.

Advantages of the Invention

[0016] According to the current-carrying unit of the present invention and the bearing unit employing this current-carrying unit, a bypass path for passing current from the motor shaft to the housing is newly formed, so that electrolytic corrosion of the bearing provided between the motor shaft and the housing can be prevented. In addition, since the current-carrying member is biased toward the motor shaft by the radially elastic member, even if the current-carrying member wears over time, the contact state between the motor shaft and the current-carrying member is maintained, and the electrolytic corrosion prevention effect of the electrolytic corrosion prevention bearing device can be maintained over a long period. Furthermore, since the current-carrying member is pressed from one side in the axial direction to the other side by the pressing mechanism, the contact state between the current-carrying member and the case main body portion can be maintained, and stable current-carrying performance can be exhibited.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0018] FIG. 1 shows an embodiment of a bearing unit A employing an energization unit 1 according to the present invention. The bearing unit A is composed of an energization unit 1 and a bearing 2 (a ball bearing in this embodiment). The bearing 2 has an outer ring 3, an inner ring 4 disposed on the inner diameter side of the outer ring 3, rolling elements 5 provided between the outer ring 3 and the inner ring 4, and a cage 6 that holds the rolling elements 5 at predetermined intervals in the circumferential direction. The outer ring 3 of the energization unit 1 and the bearing 2 are in contact with each other.

[0019] As shown in FIGS. 1 to 4, this energization unit 1 mainly includes a case body portion 7, an energization member 8, a radially elastic member 9, and a pressing mechanism 10. This energization unit 1 is interposed between a motor shaft 11 such as an e-axle and a housing 12, and is provided between the motor shaft 11 and the housing 12 so as to be adjacent to the bearing 2 that supports the motor shaft 11. The housing 12 is electrically grounded. Hereinafter, the direction along the rotation axis of the motor shaft 11 is referred to as the axial direction, the direction perpendicular to the rotation axis is referred to as the radial direction, and the direction along the circumference that makes one full turn around the rotation axis is referred to as the circumferential direction.

[0020] The case main body 7 is an annular member having conductivity that is fitted into the housing 12. The case main body 7 includes an annular outer ring portion 15 having a flange 13 extending in one axial direction at the outer peripheral edge and an extension piece 14 extending radially inward from the outer peripheral edge, and an annular retainer 18 having a flange 16 extending in the other axial direction opposite to the one axial direction at the outer peripheral edge and an extension piece 17 extending radially inward from the outer peripheral edge. As shown in FIG. 1, the flange 13 formed on the outer ring portion 15 and the flange 16 formed on the retainer 18 are integrated by press-fitting. Along with this integration, a circumferential groove that opens toward the inner diameter side is formed by the flanges 13, 16 and the extension pieces 14, 17 formed on the outer ring portion 15 and the retainer 18, respectively. Note that after inserting the flange 16 formed on the retainer 18 into the flange 13 formed on the outer ring portion 15, a retaining ring may be provided on the width surface to fix the outer ring portion 15 and the retainer 18, thereby improving maintainability.

[0021] Both the outer ring portion 15 and the retainer 18 are made of steel. The size of the axial gap of the circumferential groove formed by the integration of the outer ring portion 15 and the retainer 18 is formed slightly larger than the axial width of the current-carrying member 8 so that the current-carrying member 8 can move freely in the radial direction. A plurality (four in this embodiment) of bent portions 19 extending in the other axial direction (the same direction as the flange 16 formed on the retainer 18) from the inner edge of the extension piece 17 are formed on the retainer 18 at predetermined angular intervals.

[0022] The energizing member 8 is an arc-shaped member provided in the circumferential groove, protruding radially inward from the case main body portion 7 and slidingly contacting the motor shaft 11, having conductivity. The energizing members 8 are each accommodated between circumferentially adjacent bent portions 19 formed in the retainer 18. In this embodiment, four energizing members 8 are arranged at equal intervals in the circumferential direction. The number of energizing members 8 can be appropriately changed, but it is preferably plural. The number of bent portions 19 formed in the retainer 18 is determined corresponding to the number of energizing members 8. In this embodiment, as the material of the energizing member 8, polytetrafluoroethylene (PTFE) added with carbon is adopted. The inner diameter surface of the energizing member 8 is composed of a part of a cylindrical surface and is in surface contact with the outer peripheral surface of the motor shaft 11. An outer circumferential groove 20 is formed in the outer peripheral edge of the energizing member 8.

[0023] As the material of the energizing member 8, in addition to PTFE added with carbon, metals, carbon, or conductive materials composed of resins, rubbers, ceramics, or composites thereof having conductivity, such as polyetheretherketone (PEEK) added with carbon, can also be adopted. Further, the surface of the energizing member 8 (especially the inner diameter surface slidingly contacting the motor shaft) can be subjected to surface treatment such as coating (for example, diamond-like carbon (DLC) film having conductivity, metal film (such as plating layer)) to improve conductivity and wear resistance.

[0024] The radial elastic member 9 is a member provided in the circumferential groove for urging the energizing member 8 radially inward (refer to the arrow in FIG. 2). As shown in FIG. 2, this radial elastic member 9 is stretched so as to straddle the outer circumferential groove 20 formed in each energizing member 8. In this embodiment, a garter spring formed by processing a coiled steel wire into a ring shape is used as the radial elastic member 9. However, for example, a circlip (C-type retaining ring) having a cut in a part of the ring or an annular rubber can also be adopted. In this embodiment, all the energizing members 8 are urged by one radial elastic member 9, but a configuration in which a radial elastic member 9 is provided individually for each energizing member 8 can also be adopted.

[0025] The pressing mechanism 10 is a mechanism for pressing the energizing member 8 from one axial side toward the other side. In this embodiment, as the pressing mechanism 10, it is a bent portion 10a formed on at least one of a pair of wall portions (the extended pieces 14 and 17 of the outer ring portion 15 and the retainer 18) that constitute the circumferential groove, which bends toward the inside of the circumferential groove on the inner diameter side with respect to the outer diameter side. More specifically, the bent portion 10a is formed by inclining the entire extended piece 14 of the outer ring portion 15 by a predetermined angle in the radial direction toward the inside of the circumferential groove with the connection portion with the flange 13 as the starting point. Note that the bent portion 10a can also be formed only on the retainer 18, or formed on both the outer ring portion 15 and the retainer 18.

[0026] The operation of this energizing unit 1 will be described. A motor shaft 11 is inserted through the axis of this energizing unit 1. As the motor shaft 11 rotates, when the inner diameter surface of the motor shaft 11 and the energizing member 8 biased toward the motor shaft 11 by the biasing force of the radial elastic member 9 come into sliding contact, this inner diameter surface gradually wears. Even when such wear occurs, since the energizing member 8 is always biased toward the motor shaft 11 by the radial elastic member 9, the contact state (energizing state) between the motor shaft 11 and the energizing member 8 is maintained.

[0027] The energizing member 8 is pressed toward the retainer 18 by the pressing mechanism 10 (the bent portion 10a formed on the extended piece 14 of the outer ring portion 15). As a result, the axial clearance between the energizing member 8 and the case main body portion 7 (the outer ring portion 15 and the retainer 18) disappears, and an energizing circuit as a bypass path is formed among the motor shaft 11, the energizing member 8, the case main body portion 7, and the housing 12. By forming the energizing circuit in this way, the current passing through the bearing 2 interposed between the motor shaft 11 and the housing 12 is reduced, and electrolytic corrosion of the constituent members of the bearing 2 is prevented.

[0028] Since the above-mentioned energization unit 1 and bearing unit A are configured to discharge the electric charge generated on the motor shaft 11 to the housing 12 via the energization member 8 and the case main body 7, it is possible to prevent electrolytic corrosion of the bearing 2 provided between the motor shaft 11 and the housing 12. Moreover, since the energization member 8 is urged radially inward, that is, toward the motor shaft 11, by the radially elastic member 9, even if the energization member 8 wears over time, the contact state between the motor shaft 11 and the energization member 8 is maintained, and the electrolytic corrosion prevention effect can be maintained over a long period. It is preferable to use the energization member 8 having an initial radial width that can withstand long-term use even when wear occurs over time.

[0029] Also, since the above-mentioned energization unit 1 and bearing unit A are configured to press the energization member 8 from one axial side to the other side by the bent portion 10a as the pressing mechanism 10, the contact state between the energization member 8 and the case main body 7 can be maintained, and stable energization performance can be exhibited.

[0030] Also, since the above-mentioned energization unit 1 and bearing unit A ensure a wide energization area by bringing the inner diameter surface of the energization member 8 into surface contact with the outer peripheral surface of the motor shaft 11, the amount of electric current discharged from the motor shaft 11 to the housing 12 via the energization unit 1 can be increased, and electrolytic corrosion of the bearing 2 can be more effectively prevented.

[0031] Also, since the above-mentioned energization unit 1 and bearing unit A are provided with a plurality of energization members 8, even if a trouble occurs in which the energization action of some of the energization members 8 is impaired, the energization action by the other energization members 8 can be ensured, so that the electrolytic corrosion prevention effect can be surely exhibited. Further, the centering function by the plurality of energization members 8 can stabilize the contact state between the motor shaft 11 and each energization member 8, so that the electrolytic corrosion prevention effect can be further improved.

[0032] A first modified example of the energization unit 1 is shown in FIG. 5. The energization unit 1 according to the first modified example has the same basic configuration as the energization unit 1 shown in FIG. 1 and the like, but is different in that the bent portion 10a as the pressing mechanism 10 is formed only on a part of the inner diameter tip of the extending piece 14 of the outer ring portion 15. Also in this configuration, since the energization member 8 can be pressed from one axial side to the other side by the bent portion 10a, the contact state between the energization member 8 and the case main body portion 7 can be maintained, and stable energization performance can be exhibited. Note that, similar to the energization unit 1 shown in FIG. 1 and the like, the bent portion 10a may be formed only on the retainer 18, or may be formed on both the outer ring portion 15 and the retainer 18.

[0033] A second modified example of the energization unit 1 is shown in FIG. 6. The energization unit 1 according to the second modified example has the same basic configuration as the energization unit 1 shown in FIG. 1 and the like, but is different in that the pressing mechanism 10 is an axial elastic member 10b interposed in the axial gap between the inner surface of the circumferential groove and the energization member 8. Also in this configuration, since the energization member 8 can be pressed from one axial side to the other side by the axial elastic member 10b, the contact state between the energization member 8 and the case main body portion 7 (outer ring portion 15) can be maintained, and stable energization performance can be exhibited. In the second modified example, the axial elastic member 10b is interposed between the retainer 18 and the energization member 8, but the axial elastic member 10b may be interposed between the outer ring portion 15 and the energization member 8.

[0034] In the energization unit 1 according to the second modified example, the axial elastic member 10b may be made of a conductive material composed of metal, carbon, or resin, rubber, ceramics, or a composite material having conductivity imparted thereto. By doing so, a plurality of current conduction routes can be ensured, that is, a current conduction route in which current directly flows from the energization member 8 toward the case main body portion 7 (outer ring portion 15) and a current conduction route in which current flows from the energization member 8 through the axial elastic member 10b to the case main body portion 7 (retainer 18), so that more stable energization performance can be exhibited.

[0035] A third modification example of the energization unit 1 is shown in FIG. 7. The energization unit 1 according to the third modification example has the same basic configuration as the energization unit 1 shown in FIG. 1 and the like, but the pressing mechanism 10 is different in that it is an inclined surface portion 10c having a normal line inclined to one axial side, which is formed at the contact portion of the energization member 8 with the radial elastic member 9. The inclined surface portion 10c is inclined so as to approach the motor shaft 11 from the outer ring portion 15 side toward the retainer 18 side. When the radial elastic member 9 comes into contact with the inclined surface portion 10c, the radial component of the contact force acts as a force for pressing the energization member 8 against the motor shaft 11, and the axial component acts as a force for pressing the energization member 8 against the extended piece 14 of the outer ring portion 15.

[0036] In this way, by branching the biasing force of the radial elastic member 9 into a radial component and an axial component by the inclined surface portion 10c, the contact state between the energization member 8 and the motor shaft 11 and between the energization member 8 and the case main body portion 7 (outer ring portion 15) can be maintained, and stable energization performance can be exhibited. Conversely, contrary to the configuration shown in FIG. 7, the inclined surface portion 10c can be inclined so as to approach the motor shaft 11 from the retainer 18 side toward the outer ring portion 15 side.

[0037] In the energization unit 1 according to the third modification example, similar to the energization unit 1 shown in FIG. 1, it is preferable that the radial elastic member 9 is made of metal. By doing so, a plurality of current-carrying routes can be ensured, including a current-carrying route in which current flows directly from the energization member 8 toward the case main body portion 7 (outer ring portion 15) and a current-carrying route in which current flows from the energization member 8 through the radial elastic member 9 to the case main body portion 7 (retainer 18), so that more stable current-carrying performance can be exhibited.

[0038] A modified example of the bearing unit A is shown in Fig. 8. The bearing unit A according to this modified example has the same basic configuration as the bearing unit A shown in Fig. 1. However, in this bearing unit A, the energizing unit 1 and the bearing 2 are separate members, while in the bearing unit A according to the modified example, the flange 13 of the outer ring portion 15 of the energizing unit 1 shown in Fig. 1 and the like is extended axially to the outer diameter side of the outer ring 3 of the bearing 2, making the energizing unit 1 and the bearing 2 an integrated bearing unit A. By doing so, the same operational effects as those of the energizing unit 1 and the bearing unit A shown in Fig. 1 are exhibited, and by making the size of the bearing unit A common with the main dimensions of the bearing standardized in Japanese Industrial Standards (JIS B1512-1:2011), it is possible to reduce the weight and width of the bearing unit A provided with the energizing unit 1.

[0039] In each of the above embodiments, the motor shaft 11 is inserted through the axis of the energizing unit 1, and the energizing member 8 is urged radially inward by the radially elastic member 9 to be in sliding contact with the motor shaft 11. Conversely, when the motor shaft 11 is provided on the outer diameter side of the energizing unit 1 and the housing 12 is provided on the inner diameter side of the energizing unit 1, respectively, the energizing member 8 can be configured to be urged radially outward by the radially elastic member 9.

[0040] It should be considered that all the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0041] 1 Energizing unit 2 Bearing 3 Outer ring 4 Inner ring 5 Rolling element 6 Retainer 7 Case main body portion 8 Energizing member 9 Radially elastic member 10 Pressing mechanism 10a Flexure portion 10b Axial elastic member 10c Inclined surface portion 11 Motor shaft 12 Housing 15 Outer ring portion 18 Retainer 19 Bending portion

Claims

1. An annular case body part (7) having conductivity, which is fitted into a housing (12) and has a circumferential groove formed therein that opens toward the inner diameter side; A conductive current-carrying member (8) provided in the circumferential groove, protruding radially inward from the case body part (7) and making sliding contact with a motor shaft (11); A radial elastic member (9) provided in the circumferential groove for biasing the current-carrying member (8) radially inward; A pressing mechanism (10) for pressing the current-carrying member (8) from one axial side to the other side in the circumferential groove; A current-carrying unit having the above.

2. The current-carrying unit according to claim 1, wherein the pressing mechanism (10) is a bent part (10a) formed on at least one of a pair of wall parts constituting the circumferential groove, bending toward the inside of the circumferential groove on the inner diameter side with respect to the outer diameter side.

3. The current-carrying unit according to claim 1, wherein the pressing mechanism (10) is an axial elastic member (10b) interposed in an axial clearance between the inner surface of the circumferential groove and the current-carrying member (8).

4. The current-carrying unit according to claim 3, wherein the axial elastic member (10b) is made of a conductive material composed of metal, carbon, or resin, rubber, ceramics, or a composite material thereof having conductivity imparted thereto.

5. The current-carrying unit according to claim 1, wherein the pressing mechanism (10) is an inclined surface part (10c) formed at a contact part of the current-carrying member (8) with the radial elastic member (9) and having a normal line inclined to one axial side.

6. The current-carrying unit according to claim 1, wherein a plurality of the current-carrying members (8) are provided.

7. The current-carrying unit according to claim 6, wherein the case body part (7) has an annular outer ring part (15) and a retainer (18) fitted to the outer ring part (15), and a plurality of bent parts (19) for arranging a plurality of the current-carrying members (8) at equal intervals in the circumferential direction are formed on the retainer (18).

8. The current-carrying unit according to claim 1, wherein the radial elastic member (9) is a metal spring member provided across the plurality of current-carrying members (8).

9. The current-carrying unit according to claim 1, wherein the current-carrying member (8) is made of a conductive material composed of metal, carbon, or resin, rubber, ceramics, or a composite material thereof having conductivity imparted thereto.

10. The current-carrying unit (1) according to any one of claims 1 to 9; An outer ring (3), an inner ring (4) disposed on the inner diameter side of the outer ring (3), rolling elements (5) provided between the outer ring (3) and the inner ring (4), and a cage (6) for holding the rolling elements (5) at predetermined intervals in the circumferential direction, and a bearing (2) for supporting the motor shaft (11), wherein the outer ring (3) is arranged to abut against the energizing unit (1). A bearing unit having the same.

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