Energization unit and electric corrosion prevention bearing device

Abstract

To provide an energization unit capable of maintaining an electric corrosion effect over a long period of time, and an electric corrosion prevention bearing device.SOLUTION: An energization unit 1 is configured to have: an annular conductive case body part 2 that is fitted into a housing 6; an energization member 3 that protrudes radially inward from the case body part 2 and slides against the motor shaft 5; and an elastic member 4 that biases the energization member 3 toward the motor shaft 5.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an energizing unit that is provided in a bearing that supports a rotating shaft such as a motor shaft, and to an electrolytic corrosion prevention bearing device that employs this energizing unit. [Background technology]

[0002] Rolling bearings, especially ball bearings, are commonly used as bearings to support 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, it may cause electrolytic corrosion in the metal raceway and rolling elements. For example, in the following Patent Document 1, a filament 30 (grounding brush) is brought into 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, so that the current does not pass through the inside of the bearing (see Fig. 2 in Patent Document 1, etc.). In the following Patent Document 2, an emitter 8 (region 10) is brought into contact with the shaft 68, and the charge generated on the shaft 68 is released to the housing 69 via the emitter 8, so that the current does not pass through the inside of the bearing (see Fig. 24 in Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 8,199,453 [Patent Document 2] Patent No. 7033538 Summary of the Invention [Problem to be solved by the invention]

[0005] The configurations shown in Patent Documents 1 and 2 allow electric charges to escape by having sliding members (filament 30, emitter 8) slide against the motor shaft (shaft 16, shaft 68). As a result, there is a risk that the electrical conductivity will decrease over time due to wear and deformation of the sliding members, resulting in insufficient prevention of electrolytic corrosion.

[0006] The problem to be solved by the present invention is to provide a current-carrying unit and an electrolytic corrosion-prevention bearing device that are capable of maintaining the electrolytic corrosion prevention effect for a long period of time. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a conductive annular case body portion that is fitted into the housing; a conductive member protruding radially inward from the case body and in sliding contact with a motor shaft; an elastic member that biases the current-carrying member toward the motor shaft; A current-carrying unit having the above structure was constructed.

[0008] In this way, a bypass path for passing current from the motor shaft to the housing is newly formed, making it possible to prevent electrolytic corrosion of the bearing provided between the motor shaft and the housing. Moreover, because the current-carrying member is biased toward the motor shaft by the 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, making it possible to maintain the electrolytic corrosion prevention effect for a long period of time.

[0009] In the above configuration, It is preferable that the case main body portion has an annular outer ring portion and a retainer that fits into the outer ring portion, and that the retainer is formed with a plurality of bent portions that arrange the plurality of conductive members at equal intervals in the circumferential direction.

[0010] In this way, an alignment function is achieved by biasing the conductive members housed between the multiple folded portions radially inward with an elastic member, thereby stabilizing the contact state between the motor shaft and the conductive members.

[0011] In the configuration having the plurality of current-carrying members, It is preferable that the elastic member is a spring member provided across the plurality of current-carrying members.

[0012] In this way, the plurality of current-carrying members can be urged toward the motor shaft all at once with a simple structure.

[0013] In all of the above configurations, The current-carrying member is preferably made of metal, carbon, or a resin, rubber, or ceramics that has been given electrical conductivity, or a composite material of these materials.

[0014] In this way, the current-carrying function of the current-carrying unit can be ensured with a simple configuration.

[0015] The energizing unit according to all of the above configurations includes: The present invention can be employed in an electric corrosion prevention bearing device having a current-carrying unit and a bearing supporting a motor arranged so that an end face of an outer ring abuts against the current-carrying unit. Effect of the Invention

[0016] According to the current-carrying unit of the present invention, a bypass path for passing current from the motor shaft to the housing is newly formed, so that it is possible to prevent electrolytic corrosion of the bearing provided between the motor shaft and the housing. Moreover, because the current-carrying member is biased toward the motor shaft by an 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 for a long period of time. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing an embodiment of a bearing device that prevents electrolytic corrosion and that employs a current-carrying unit according to the present invention. [Diagram 2] Cross-sectional view taken along line II-II in Figure 1. [Diagram 3] FIG. 2 is an exploded perspective view of the energizing unit shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The drawings show an electrolytic corrosion prevention bearing device A that employs a current-carrying unit 1 according to the present invention. As shown in Figs. 1 to 3, the current-carrying unit 1 has a case main body 2, a current-carrying member 3, and an elastic member 4 as its main components. This current-carrying unit 1 is provided between a motor shaft 5 of an e-axle or the like and a housing 6 so as to be adjacent to a bearing 7 (a ball bearing in this embodiment) that is interposed between the motor shaft 5 and the housing 6 and supports the motor shaft 5. The housing 6 is electrically grounded.

[0019] From the viewpoint of preventing electrolytic corrosion, it is preferable to provide the current-carrying unit 1 and the bearing 7 in contact with each other in the axial direction as shown in Fig. 1, but a configuration in which a gap is provided between them is also acceptable. In the following, the direction along the rotation axis of the motor shaft 5 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 going around the rotation axis is referred to as the circumferential direction.

[0020] The case body 2 is a conductive annular member that is fitted into the inner diameter surface of the housing 6. The case body 2 is composed of an annular outer ring portion 8 having a flange extending in one axial direction on its outer periphery, and a retainer 9 having a flange extending in another axial direction opposite to the one axial direction on its outer periphery. As shown in FIG. 1, the flange formed on the outer ring portion 8 and the flange formed on the retainer 9 are integrated by press-fitting. Note that, after the flange formed on the retainer 9 is inserted into the flange formed on the outer ring portion 8, a stop ring is provided on the width surface to fix the outer ring portion 8 and the retainer 9, thereby improving maintainability.

[0021] Both the outer ring portion 8 and the retainer 9 are made of steel. An axial gap capable of accommodating the current-carrying member 3 and the elastic member 4 is formed between the fitted outer ring portion 8 and the retainer 9. The retainer 9 has a plurality of (four in this embodiment) bent portions 10 formed at predetermined angular intervals, extending from its inner edge in the other axial direction (the same direction as the flange formed on the retainer 9).

[0022] The current-carrying member 3 is a conductive arc-shaped member that protrudes radially inward from the case body 2 and slides against the motor shaft 5 supported by the bearing 7. The current-carrying member 3 is accommodated between adjacent folded parts 10 formed in the retainer 9 in the circumferential direction. In this embodiment, four current-carrying members 3 are arranged at equal intervals in the circumferential direction. The number of current-carrying members 3 can be changed as appropriate, but it is preferable to have a plurality of current-carrying members 3. The number of folded parts 10 formed in the retainer 9 is determined according to the number of current-carrying members 3. In this embodiment, polytetrafluoroethylene (PTFE) with added carbon is used as the material for the current-carrying member 3. The inner diameter surface of the current-carrying member 3 is composed of a part of a cylindrical surface and is in surface contact with the outer circumferential surface of the motor shaft 5. A circumferential groove 11 is formed on the outer circumferential edge of the current-carrying member 3.

[0023] In addition to carbon-added PTFE, metal, carbon, conductive resin such as carbon-added polyether ether ketone (PEEK), rubber, ceramics, or a composite material of these may be used as the material for the conductive member 3. In addition, the surface of the conductive member 3 (particularly the inner diameter surface that comes into sliding contact with the motor shaft 5) may be subjected to surface treatment such as a coating (for example, a conductive diamond-like carbon (DLC) film, a metal film (plating layer, etc.)) that improves electrical conductivity and wear resistance.

[0024] The elastic member 4 is a member for biasing the current-carrying members 3 radially inward toward the motor shaft 5 (see the arrow in FIG. 2). As shown in FIG. 2, the elastic member 4 is hung so as to straddle a circumferential groove 11 formed on the outer periphery of each current-carrying member 3. In this embodiment, a garter spring made of a coiled steel wire processed into a ring shape is used as the elastic member 4, but for example, a circlip (C-type retaining ring) having a slit in a part of the ring or an annular rubber may also be used. Note that, in this embodiment, a single elastic member 4 is used to bias all the current-carrying members 3, but a configuration in which an elastic member 4 is provided for each current-carrying member 3 may also be used.

[0025] The operation of this current-carrying unit 1 will now be described. A motor shaft 5 is inserted through the axis of this current-carrying unit 1. As the motor shaft 5 rotates, the motor shaft 5 comes into sliding contact with the inner diameter surface of the current-carrying member 3, which is biased toward the motor shaft 5 by the biasing force of the elastic member 4, and this inner diameter surface gradually wears. Even if wear occurs in this way, the contact state (current-carrying state) between the motor shaft 5 and the current-carrying member 3 is maintained, because the current-carrying member 3 is always biased toward the motor shaft 5 by the elastic member 4.

[0026] The current-carrying member 3 is in contact with the case body 2 (at least one of the outer ring portion 8 or the retainer 9), and a current-carrying circuit is formed as a bypass path among the motor shaft 5, the current-carrying member 3, the case body 2, and the housing 6. By forming a current-carrying circuit in this manner, the current passing through the bearing 7 interposed between the motor shaft 5 and the housing 6 is reduced, and electrolytic corrosion of the components of the bearing 7 is prevented.

[0027] The above-mentioned current-carrying unit 1 allows electric charges generated on the motor shaft 5 to escape to the housing 6 via the current-carrying member 3 and the case main body 2, thereby preventing electrolytic corrosion of the bearing 7 provided between the motor shaft 5 and the housing 6. Moreover, since the current-carrying member 3 is biased radially inward, i.e., toward the motor shaft 5, by the elastic member 4, even if the current-carrying member 3 wears over time, the contact state between the motor shaft 5 and the current-carrying member 3 is maintained, and the electrolytic corrosion prevention effect can be maintained over a long period of time. Note that the current-carrying member 3 has an initial radial width that is sufficient to withstand long-term use even if it wears over time.

[0028] In addition, the above-mentioned current-carrying unit 1 ensures a wide current-carrying area by bringing the inner diameter surface of the current-carrying member 3 into surface contact with the outer diameter surface of the motor shaft 5, so that the amount of current that escapes from the motor shaft 5 to the housing 6 via the current-carrying unit 1 can be increased, making it possible to more effectively prevent electrolytic corrosion of the bearing 7.

[0029] Furthermore, since the above-mentioned current-carrying unit 1 is provided with a plurality of current-carrying members 3, even if a problem occurs that impairs the current-carrying action of some of the current-carrying members 3, the current-carrying action of the other current-carrying members 3 can be ensured, so that the electrolytic corrosion prevention effect can be reliably exhibited. Furthermore, the aligning function of the plurality of current-carrying members 3 can stabilize the contact state between the motor shaft 5 and each current-carrying member 3, so that the electrolytic corrosion prevention effect can be further improved.

[0030] In the above embodiment, the motor shaft 5 is inserted through the axis of the current-carrying unit 1, and the current-carrying member 3 is biased radially inward by the elastic member 4 to slide against the motor shaft 5. However, conversely, if the motor shaft 5 is provided on the outer diameter side of the current-carrying unit 1 and the housing 6 is provided on the inner diameter side of the current-carrying unit 1, the current-carrying member 3 can also be biased radially outward by the elastic member 4.

[0031] 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.

[0032] In the above embodiment, as shown in FIG. 1, the current-carrying unit 1 and the bearing 7 that constitute the electrolytic corrosion prevention bearing device A are separate components. However, for example, the flange of the outer ring portion 8 of the current-carrying unit 1 can be extended in the axial direction toward the outer ring of the bearing 7, thereby forming a configuration in which the current-carrying unit 1 and the bearing 7 are integrated. [Explanation of symbols]

[0033] 1 Power supply unit 2 Case body 3. Electrically Conductive Materials 4 Elastic member 5 Motor shaft 6. Housing 7. Bearings 8 Outer ring 9 Retainer 10 Bending section

Claims

1. a conductive annular case body (2) fitted into a housing (6); a conductive current-carrying member (3) that protrudes radially inward from the case body portion (2) and is in sliding contact with a motor shaft (5); an elastic member (4) that biases the current-carrying member (3) toward the motor shaft (5); An energizing unit having the above structure.

2. The conductive unit according to claim 1, wherein the case main body portion (2) has an annular outer ring portion (8) and a retainer (9) that fits into the outer ring portion (8), and the retainer (9) has a plurality of bent portions (10) that arrange the plurality of conductive members (3) at equal intervals in the circumferential direction.

3. 3. The current-carrying unit according to claim 2, wherein the elastic member (4) is a spring member provided across the plurality of current-carrying members (3).

4. 4. The current-carrying unit according to claim 1, wherein the current-carrying member (3) is made of metal, carbon, or a conductive resin, rubber, ceramics, or a composite material thereof.

5. An electrolytic corrosion prevention bearing device comprising: an electric current unit (1) according to any one of claims 1 to 3; and a bearing (7) supporting a motor arranged so that an end face of an outer ring abuts against the electric current unit (1).

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