Energization unit, electrolytic corrosion prevention bearing device, and bearing unit

Abstract

This energization unit (1) is configured by including: a conductive annular case body (2) that is fitted into a housing (6); a conductive energization member (3) that protrudes radially inward from the case body (2) and is in sliding contact with a motor shaft (5); and an elastic member (4) that urges the energization member (3) toward the motor shaft (5). Alternatively, this energization unit is configured by including: a case body (2); a conductive energization member (3) that protrudes radially inward from the case body (2) and is in sliding contact with a motor shaft (5); a radial-direction elastic member (16) that urges the energization member (3) radially inward; and a pressing mechanism (17) that presses the energization member (3) from one side in the axial direction toward the other side. A bearing unit (A) has the energization unit (1) and a bearing (7).

Description

Electrically conductive unit, electrolytic corrosion prevention bearing device, and bearing unit

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

[0002] Rolling bearings, especially 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 becoming 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. When these currents pass through the bearing, they can cause electrolytic corrosion in the metal raceways and rolling elements. Therefore, for example, 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 electric charge generated on the shaft 16 is released to the housing via the filament 30, preventing the current from passing through the bearing (see, for example, Fig. 2 in Patent Document 1). Also, in Patent Document 2 listed below, an emitter 8 (region 10) is placed in contact with the shaft 68, and the electric charge generated on the shaft 68 is released to the housing 69 via the emitter 8, preventing the current from passing through the bearing (see, for example, Fig. 24 in Patent Document 2).

[0004] U.S. Patent No. 8,199,453

[0005] In the configurations shown in Patent Documents 1 and 2, the sliding contact members (filament 30, emitter 8) are brought into sliding contact with the motor shaft (shaft 16, shaft 68) to allow electric charges to escape. However, wear and deformation of the sliding contact members over time can cause a decrease in electrical conductivity, which can lead to insufficient prevention of electrolytic corrosion.

[0006] The problem that the present invention aims to solve is to provide an electric-conducting unit, an electric-corrosion-preventing bearing device, and a bearing unit that can maintain the electric-corrosion prevention effect (electrical-conducting performance) over a long period of time and can exhibit stable electric-conducting performance.

[0007] In order to solve the above problem, the first invention of the present application provides an energization unit (first configuration) having: an annular conductive case body that is fitted into a housing; an electrically conductive current-carrying member that protrudes radially inward from the case body and slides against the motor shaft; and an elastic member that urges the current-carrying member toward the motor shaft.

[0008] This creates a new bypass path for current to flow from the motor shaft to the housing, preventing electrolytic corrosion of the bearings 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 motor shaft and the current-carrying member are maintained in contact, maintaining the electrolytic corrosion prevention effect for a long period of time.

[0009] In the first 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 multiple bent portions that arrange the multiple conductive members at equal intervals in the circumferential direction (second configuration).

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

[0011] In the second configuration, it is preferable that the elastic member is a spring member provided across the plurality of current-carrying members (third configuration).

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

[0013] In the first to third configurations, it is preferable that the conductive member is made of metal, carbon, or a resin, rubber, ceramics, or a composite material of these that has been made conductive (fourth configuration).

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

[0015] The current-carrying units according to the first to fourth configurations can be employed in an electrolytic corrosion-preventing bearing device (fifth configuration) having a current-carrying unit and a bearing supporting a motor arranged so that the end face of the outer ring abuts against the current-carrying unit.

[0016] In order to solve the above problem, the second invention of the present application provides an energization unit (sixth configuration) that includes: a conductive annular case body that is fitted into a housing and has a circumferential groove that opens toward the inner diameter side; a conductive current-carrying member that is provided within the circumferential groove and protrudes radially inward from the case body to come into sliding contact with the motor shaft; a radially elastic member that is provided within the circumferential groove and urges the current-carrying member radially inward; and a pressing mechanism that presses the current-carrying member from one axial side to the other axial side within the circumferential groove.

[0017] This creates a new bypass path for current to flow from the motor shaft through the current-carrying member and the case body to the housing, preventing electrolytic corrosion of the bearings provided between the motor shaft and the housing. Furthermore, because the current-carrying member is biased toward the motor shaft by the radially elastic member, contact between the motor shaft and the current-carrying member is maintained even if the current-carrying member wears over time, allowing current-carrying performance to be maintained over a long period of time. Furthermore, because the pressing mechanism presses the current-carrying member from one side to the other in the axial direction, contact between the current-carrying member and the case body is maintained, allowing current-carrying performance to be stable.

[0018] In the sixth configuration, the pressing mechanism is preferably a bent portion formed on at least one of a pair of wall portions constituting the circumferential groove and bent toward the inside of the circumferential groove on the inner diameter side relative to the outer diameter side (seventh configuration), or an axially elastic member interposed in an axial gap between the inner surface of the circumferential groove and the current-carrying member (eighth configuration), or an inclined surface portion having a normal inclined toward one side in the axial direction and formed at a contact portion of the current-carrying member with the radially elastic member (tenth configuration). With these configurations, the current-carrying member can be pressed from one side to the other in the axial direction, and a state of contact between the current-carrying member and the case main body can be reliably maintained.

[0019] In the eighth configuration, it is preferable that the axially elastic member be made of a conductive material such as metal, carbon, or a conductive resin, rubber, ceramic, or a composite of these (ninth configuration). This ensures multiple current-carrying routes, including a current-carrying route from the current-carrying member directly to the case body, and a current-carrying route from the current-carrying member to the case body via the axially elastic member, thereby achieving more stable current-carrying performance.

[0020] In the sixth to tenth configurations, it is preferable to use a configuration (eleventh configuration) in which a plurality of the current-carrying members are provided, so that even if the current-carrying performance of one of the current-carrying members is impaired, the other current-carrying members can cover for this, thereby ensuring stable current-carrying performance.

[0021] In the eleventh 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 the retainer has a plurality of bent portions that arrange the plurality of current-carrying members at equal intervals in the circumferential direction (twelfth configuration). In this way, the current-carrying members housed between the plurality of bent portions are biased radially inward by radial elastic members, thereby achieving an aligning function and stabilizing the contact state between the motor shaft and the current-carrying members.

[0022] In the sixth configuration, it is preferable that the radially elastic member is a metal spring member provided across the plurality of current-carrying members (thirteenth configuration). In this way, it is possible to urge the plurality of current-carrying members collectively toward the motor shaft with a simple configuration.

[0023] In the sixth to thirteenth configurations, it is preferable that the current-carrying member is made of a conductive material such as metal, carbon, or a resin, rubber, ceramic, or a composite of these materials (fourteenth configuration). In this way, the current-carrying performance of the current-carrying unit can be ensured with a simple configuration.

[0024] The energizing units according to the sixth to fourteenth configurations can be employed in a bearing unit (fifteenth configuration) having an energizing unit, 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, a retainer that holds the rolling elements at predetermined intervals circumferentially, and a bearing that supports the motor shaft, the outer ring being arranged so as to abut against the energizing unit.

[0025] The current-carrying unit of the first invention of the present application creates a new bypass path for current to flow from the motor shaft to the housing, thereby preventing 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, contact between the motor shaft and the current-carrying member is maintained even if the current-carrying member wears over time, and the electrolytic corrosion prevention effect of the electrolytic corrosion-resistant bearing device can be maintained for a long period of time.

[0026] Furthermore, the current-carrying unit of the second invention and the bearing unit incorporating this current-carrying unit create a new bypass path for current to flow from the motor shaft to the housing, thereby preventing electrolytic corrosion of the bearing provided between the motor shaft and the housing. Furthermore, because the current-carrying member is biased toward the motor shaft by a radially elastic member, even if the current-carrying member wears over time, contact between the motor shaft and the current-carrying member is maintained, thereby maintaining the electrolytic corrosion prevention effect of the electrolytic corrosion-preventive bearing device over a long period of time. Furthermore, because the pressing mechanism presses the current-carrying member from one side to the other in the axial direction, contact between the current-carrying member and the case main body is maintained, allowing for stable current-carrying performance.

[0027] 1A and 1B are cross-sectional views showing an embodiment of an electrolytic corrosion prevention bearing device employing an energizing unit according to the first invention of the present application; sectional view taken along line II-II in FIG. 1; sectional view taken along line V-V in FIG. 4; sectional view of a main part of the energizing unit shown in FIG. 4; sectional view of a first modified energizing unit shown in FIG. 4; sectional view of a main part of a second modified energizing unit shown in FIG. 4; sectional view of a main part of a third modified energizing unit shown in FIG. 4; sectional view of a modified bearing unit shown in FIG. 4.

[0028] The drawings show an electrolytic corrosion prevention bearing device A employing a current-carrying unit 1 according to the first aspect of the present invention. As shown in Figures 1 to 3, the current-carrying unit 1 primarily comprises a case body 2, a current-carrying member 3, and an elastic member 4. The current-carrying unit 1 is disposed between a motor shaft 5 (such as an e-axle) and a housing 6, adjacent to a bearing 7 (a ball bearing in this embodiment) that supports the motor shaft 5. The housing 6 is electrically grounded.

[0029] From the viewpoint of preventing electrolytic corrosion, it is preferable to provide the current-carrying unit 1 and bearing 7 in axial contact as shown in Figure 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.

[0030] The case body 2 is a conductive annular member fitted onto the inner diameter surface of the housing 6. The case body 2 is composed of an annular outer ring 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 on its outer periphery, the other flange being opposite to the one axial direction. As shown in FIG. 1 , the flange formed on the outer ring 8 and the flange formed on the retainer 9 are integrated by press-fitting. Note that, after inserting the flange formed on the retainer 9 into the flange formed on the outer ring 8, a retaining ring can be provided on the width surface to fix the outer ring 8 and the retainer 9 together, thereby improving maintainability.

[0031] 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 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).

[0032] The current-carrying members 3 are arc-shaped conductive members that protrude radially inward from the case body 2 and slide against the motor shaft 5 supported by the bearing 7. Each current-carrying member 3 is housed between two circumferentially adjacent bent portions 10 formed on the retainer 9. In this embodiment, four current-carrying members 3 are arranged at equal circumferential intervals. The number of current-carrying members 3 can be varied as needed, but a plurality of bent portions 10 is preferred. The number of bent portions 10 formed on the retainer 9 is determined according to the number of current-carrying members 3. In this embodiment, the current-carrying members 3 are made of carbon-added polytetrafluoroethylene (PTFE). The inner diameter surface of the current-carrying member 3 is a portion 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 periphery of the current-carrying member 3.

[0033] 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 also be used as the material for the current-carrying member 3. Furthermore, the surface of the current-carrying member 3 (particularly the inner diameter surface that comes into sliding contact with the motor shaft 5) may be subjected to a surface treatment such as a coating (e.g., a conductive diamond-like carbon (DLC) film or a metal film (plating layer, etc.)) that improves electrical conductivity and wear resistance.

[0034] 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 suspended across 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. However, for example, a circlip (C-type retaining ring) with a slit in a portion of the ring or an annular rubber may also be used. Note that, although this embodiment is configured such that one elastic member 4 biases all the current-carrying members 3, a configuration in which an individual elastic member 4 is provided for each current-carrying member 3 may also be used.

[0035] The operation of this current-carrying unit 1 will now be described. The 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 this wear occurs, the current-carrying member 3 is always biased toward the motor shaft 5 by the elastic member 4, so the contact state (current-carrying state) between the motor shaft 5 and the current-carrying member 3 is maintained.

[0036] The current-carrying member 3 is in contact with the case body 2 (at least one of the outer ring portion 8 and the retainer 9), and a current-carrying circuit is formed as a bypass path between 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.

[0037] The above-described 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. Furthermore, because the elastic member 4 biases the current-carrying member 3 radially inward, i.e., toward the motor shaft 5, even if the current-carrying member 3 wears over time, the motor shaft 5 and the current-carrying member 3 are maintained in contact, thereby maintaining the electrolytic corrosion prevention effect 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 wear occurs over time.

[0038] Furthermore, 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 can be dissipated from the motor shaft 5 to the housing 6 via the current-carrying unit 1 can be increased, and electrolytic corrosion of the bearing 7 can be more effectively prevented.

[0039] Furthermore, since the above-described 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 can be ensured by the other current-carrying members 3, thereby reliably exhibiting the electrolytic corrosion prevention effect. Furthermore, the alignment function of the plurality of current-carrying members 3 stabilizes the contact state between the motor shaft 5 and each current-carrying member 3, thereby further improving the electrolytic corrosion prevention effect.

[0040] 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 forced 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 forced radially outward by the elastic member 4.

[0041] FIG. 4 shows one embodiment of a bearing unit A (an electrolytic corrosion prevention bearing device) employing the current-carrying unit 1 according to the second aspect of the present invention. The bearing unit A comprises the current-carrying unit 1 and a bearing 7 (a ball bearing in this embodiment). The bearing 7 has an outer ring 12, an inner ring 13 disposed on the inner diameter side of the outer ring 12, rolling elements 14 disposed between the outer ring 12 and the inner ring 13, and a cage 15 that holds the rolling elements 14 at predetermined intervals in the circumferential direction. The current-carrying unit 1 and the outer ring 12 of the bearing 7 abut against each other.

[0042] 4 to 7 , the current-carrying unit 1 mainly comprises a case main body 2, a current-carrying member 3, a radially elastic member 16, and a pressing mechanism 17. The current-carrying unit 1 is disposed between a motor shaft 5 of an e-axle or the like and a housing 6, adjacent to a bearing 7 that supports the motor shaft 5. The housing 6 is electrically grounded. In the following description, the direction along the rotational axis of the motor shaft 5 is referred to as the axial direction, the direction perpendicular to the rotational axis as the radial direction, and the direction along the circumference around the rotational axis as the circumferential direction.

[0043] The case body 2 is a conductive annular member fitted into the housing 6. The case body 2 includes an annular outer ring 8 having a flange 18 extending in one axial direction at its outer peripheral edge and an extension piece 19 extending radially inward from the outer peripheral edge, and an annular retainer 9 having a flange 20 extending in another axial direction opposite the one axial direction at its outer peripheral edge and an extension piece 21 extending radially inward from the outer peripheral edge. As shown in FIG. 4 , the flange 18 formed on the outer ring 8 and the flange 20 formed on the retainer 9 are integrated by press-fitting. As a result of this integration, a circumferential groove opening toward the inner diameter is formed by the flanges 18, 20 and the extension pieces 19, 21 formed on the outer ring 8 and the retainer 9, respectively. After inserting the flange 20 formed on the retainer 9 into the flange 18 formed on the outer ring 8, a retainer ring can be attached to the width surface to secure the outer ring 8 and the retainer 9, thereby improving maintainability.

[0044] Both the outer ring portion 8 and the retainer 9 are made of steel. The size of the axial gap of the circumferential groove formed by integrating the outer ring portion 8 and the retainer 9 is slightly larger than the axial width of the current-carrying member 3 so that the current-carrying member 3 can move freely in the radial direction. The retainer 9 has multiple (four in this embodiment) bent portions 10 formed at predetermined angular intervals, extending from the inner edge of the extension piece 21 in the other axial direction (the same direction as the flange 20 formed on the retainer 9).

[0045] The current-carrying members 3 are arc-shaped conductive members disposed within the circumferential groove, protruding radially inward from the case body 2 and slidingly contacting the motor shaft 5. Each current-carrying member 3 is accommodated between two adjacent circumferentially adjacent bent portions 10 formed on the retainer 9. In this embodiment, four current-carrying members 3 are disposed at equal circumferential intervals. The number of current-carrying members 3 can be varied as needed, but a plurality of bent portions 10 is preferred. The number of bent portions 10 formed on the retainer 9 is determined according to the number of current-carrying members 3. In this embodiment, the current-carrying members 3 are made of carbon-added polytetrafluoroethylene (PTFE). The inner diameter surface of the current-carrying member 3 is formed as a portion of a cylindrical surface and is in surface contact with the outer circumferential surface of the motor shaft 5. An outer circumferential groove 11 (circumferential groove) is formed on the outer periphery of the current-carrying member 3.

[0046] In addition to carbon-added PTFE, conductive materials such as metal, carbon, or conductive resin such as carbon-added polyether ether ketone (PEEK), rubber, ceramics, or a composite of these may also be used as the material for the current-carrying member 3. Furthermore, the surface of the current-carrying member 3 (particularly the inner diameter surface that comes into sliding contact with the motor shaft 5) may be subjected to a surface treatment such as a coating (e.g., a conductive diamond-like carbon (DLC) film or a metal film (plating layer, etc.)) that improves electrical conductivity and wear resistance.

[0047] The radial elastic members 16 are provided in the circumferential grooves and bias the current-carrying members 3 radially inward (see the arrows in FIG. 5 ). As shown in FIG. 5 , the radial elastic members 16 are suspended across the circumferential grooves 11 formed in 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 radial elastic member 16. However, other members such as a circlip (C-type retaining ring) with a slit in a portion of the ring or an annular rubber member may also be used. In this embodiment, a single radial elastic member 16 biases all the current-carrying members 3. However, each current-carrying member 3 may be individually provided with a radial elastic member 16.

[0048] The pressing mechanism 17 is a mechanism for pressing the current-carrying member 3 from one axial side to the other. In this embodiment, the pressing mechanism 17 is a bent portion 17a formed on at least one of a pair of wall portions (the outer ring portion 8 and the extension pieces 19, 21 of the retainer 9) that constitute the circumferential groove, and bent toward the inside of the circumferential groove on the inner diameter side relative to the outer diameter side. More specifically, the bent portion 17a is formed by inclining the entire extension piece 19 of the outer ring portion 8 by a predetermined angle from the connection point with the flange 18 toward the inside of the circumferential groove in the radial direction. Note that the bent portion 17a may be formed only on the retainer 9, or may be formed on both the outer ring portion 8 and the retainer 9.

[0049] The operation of this current-carrying unit 1 will now be described. The 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 radial elastic member 16, and this inner diameter surface gradually wears. Even if this wear occurs, the current-carrying member 3 is always biased toward the motor shaft 5 by the radial elastic member 16, so the contact state (current-carrying state) between the motor shaft 5 and the current-carrying member 3 is maintained.

[0050] The current-carrying member 3 is pressed against the retainer 9 by a pressing mechanism 17 (bent portion 17a formed on the extension piece 19 of the outer ring portion 8). This eliminates an axial gap between the current-carrying member 3 and the case main body 2 (outer ring portion 8 and retainer 9), and a current-carrying circuit is formed as a bypass path between the motor shaft 5, the current-carrying member 3, the case main body 2, and the housing 6. By forming the current-carrying circuit in this way, the current passing through the bearing 7 interposed between the motor shaft 5 and the housing 6 is reduced, preventing electrolytic corrosion of the components of the bearing 7.

[0051] The above-described current-carrying unit 1 and bearing unit A allow 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. Furthermore, because the radially elastic member 16 biases the current-carrying member 3 radially inward, i.e., toward the motor shaft 5, even if the current-carrying member 3 wears over time, the motor shaft 5 and the current-carrying member 3 are maintained in contact, thereby maintaining the electrolytic corrosion prevention effect over a long period of time. Note that it is preferable to use current-carrying members 3 with an initial radial width large enough to withstand long-term use even when they wear over time.

[0052] Furthermore, the above-mentioned current-carrying unit 1 and bearing unit A are configured so that the current-carrying member 3 is pressed from one side of the axial direction to the other side by the bending portion 17a serving as the pressing mechanism 17, so that the current-carrying member 3 can be maintained in contact with the case main body 2, thereby achieving stable current-carrying performance.

[0053] Furthermore, the above-mentioned current-carrying unit 1 and bearing unit A ensure 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 can escape from the motor shaft 5 to the housing 6 via the current-carrying unit 1 can be increased, and electrolytic corrosion of the bearing 7 can be more effectively prevented.

[0054] Furthermore, by providing the above-described current-carrying unit 1 and bearing unit A with multiple 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 can be ensured by the other current-carrying members 3, thereby reliably achieving the electrolytic corrosion prevention effect. Furthermore, the aligning function of the multiple current-carrying members 3 stabilizes the contact state between the motor shaft 5 and each current-carrying member 3, thereby further improving the electrolytic corrosion prevention effect.

[0055] A first modified example of the current-carrying unit 1 is shown in FIG. 8 . The current-carrying unit 1 according to the first modified example has the same basic configuration as the current-carrying unit 1 shown in FIG. 4 and other figures, but differs in that the bent portion 17 a serving as the pressing mechanism 17 is formed only on a portion of the inner diameter tip of the extension piece 19 of the outer ring portion 8. Even in this configuration, the bent portion 17 a can press the current-carrying member 3 from one axial side to the other, thereby maintaining contact between the current-carrying member 3 and the case main body 2 and achieving stable current-carrying performance. As with the current-carrying unit 1 shown in FIG. 4 and other figures, the bent portion 17 a can be formed only on the retainer 9, or on both the outer ring portion 8 and the retainer 9.

[0056] A second modified example of the current-carrying unit 1 is shown in FIG. 9 . The current-carrying unit 1 according to the second modified example has the same basic configuration as the current-carrying unit 1 shown in FIG. 4 and other figures, but differs in that the pressing mechanism 17 is an axially elastic member 17b interposed in the axial gap between the inner surface of the circumferential groove and the current-carrying member 3. Even in this configuration, the axially elastic member 17b can press the current-carrying member 3 from one side to the other in the axial direction, thereby maintaining contact between the current-carrying member 3 and the case main body 2 (outer ring portion 8) and achieving stable current-carrying performance. In the second modified example, the axially elastic member 17b is interposed between the retainer 9 and the current-carrying member 3. However, the axially elastic member 17b may also be interposed between the outer ring portion 8 and the current-carrying member 3.

[0057] In the current-carrying unit 1 according to the second modification, the axially elastic member 17b may be made of a conductive material such as metal, carbon, or a conductive resin, rubber, ceramic, or a composite of these. This ensures multiple current-carrying routes, including a current-carrying route from the current-carrying member 3 directly to the case main body 2 (outer ring portion 8) and a current-carrying route from the current-carrying member 3 to the case main body 2 (retainer 9) via the axially elastic member 17b, thereby achieving more stable current-carrying performance.

[0058] A third modified example of the current-carrying unit 1 is shown in Figure 10. The current-carrying unit 1 according to the third modified example has the same basic configuration as the current-carrying unit 1 shown in Figure 4 and other figures, but differs in that the pressing mechanism 17 includes an inclined surface 17c, the normal of which is inclined axially to one side, formed at the contact portion of the current-carrying member 3 with the radially elastic member 16. The inclined surface 17c is inclined so as to approach the motor shaft 5 from the outer ring portion 8 toward the retainer 9. When the radially elastic member 16 contacts the inclined surface 17c, the radial component of the contact force acts to press the current-carrying member 3 against the motor shaft 5, and the axial component acts to press the current-carrying member 3 against the extension piece 19 of the outer ring portion 8.

[0059] In this way, by using the inclined surface portion 17c to divide the biasing force of the radial elastic member 16 into a radial component and an axial component, it is possible to maintain contact between the current-carrying member 3 and the motor shaft 5, and between the current-carrying member 3 and the case main body 2 (outer ring portion 8), thereby achieving stable current-carrying performance. Note that, contrary to the configuration shown in Fig. 10, the inclined surface portion 17c can also be inclined so as to approach the motor shaft 5 from the retainer 9 side toward the outer ring portion 8 side.

[0060] In the current-carrying unit 1 according to the third modification, it is preferable that the radially elastic member 16 be made of metal, as in the current-carrying unit 1 shown in Fig. 4. This ensures multiple current-carrying routes, including a current-carrying route in which current flows directly from the current-carrying member 3 to the case main body 2 (outer ring portion 8) and a current-carrying route in which current flows from the current-carrying member 3 to the case main body 2 (retainer 9) via the radially elastic member 16, thereby achieving more stable current-carrying performance.

[0061] A modified example of the bearing unit A is shown in Figure 11. The bearing unit A according to this modified example shares the basic configuration with the bearing unit A shown in Figure 4, but differs in that, whereas the current-carrying unit 1 and the bearing 7 are separate members in this bearing unit A, the flange 18 of the outer ring portion 8 of the current-carrying unit 1 shown in Figure 4 etc. is extended in the axial direction to the outer diameter side of the outer ring 12 of the bearing 7, thereby forming a bearing unit A in which the current-carrying unit 1 and the bearing 7 are integrated. In this way, the same effects as those of the current-carrying unit 1 and bearing unit A shown in Figure 4 can be achieved, and by making the size of the bearing unit A consistent with the main dimensions of bearings standardized in the Japanese Industrial Standards (JIS B1512-1:2011), the weight and width of the bearing unit A including the current-carrying unit 1 can be reduced.

[0062] In each of the above embodiments, the motor shaft 5 is inserted through the axis of the current-carrying unit 1, and the current-carrying member 3 is forced radially inward by the radial elastic member 16 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 forced radially outward by the radial elastic member 16.

[0063] 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.

[0064] In the above-described embodiment of the first invention of the present application, as shown in Figure 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 integrating the current-carrying unit 1 and the bearing 7 into one unit.

[0065] REFERENCE SIGNS LIST 1 Current-carrying unit 2 Case main body 3 Current-carrying member 4 Elastic member 5 Motor shaft 6 Housing 7 Bearing 8 Outer ring portion 9 Retainer 10 Bent portion 12 Outer ring 13 Inner ring 14 Rolling element 15 Cage 16 Radial elastic member 17 Pressing mechanism 17a Bent portion 17b Axial elastic member 17c Inclined surface portion

Claims

1. An energization unit comprising: a conductive annular case body (2) fitted into a housing (6); a conductive current-carrying member (3) protruding radially inward from the case body (2) and in sliding contact with a motor shaft (5); and an elastic member (4) that biases the current-carrying member (3) toward the motor shaft (5).

2. An electric current-carrying unit as described in 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) is formed with a plurality of bent portions (10) that arrange a plurality of the electric current-carrying members (3) at equal intervals in the circumferential direction.

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. An electric current-carrying unit according to any one of claims 1 to 3, wherein the electric current-carrying member (3) is made of a conductive material selected from the group consisting of metal, carbon, resin, rubber, ceramics, or a composite material thereof that has been made electrically conductive.

5. An anti-electrolytic corrosion bearing device comprising: an electric current unit (1) according to any one of claims 1 to 4; and a bearing (7) supporting a motor, the end face of the outer ring of which is arranged to abut against the electric current unit (1).

6. An energization unit comprising: a conductive annular case body (2) fitted into a housing (6) and having a circumferential groove opening toward the inner diameter side; a conductive current-carrying member (3) provided within the circumferential groove, protruding radially inward from the case body (2) and in sliding contact with a motor shaft (5); a radial elastic member (16) provided within the circumferential groove for biasing the current-carrying member (3) radially inward; and a pressing mechanism (17) for pressing the current-carrying member (3) from one axial side to the other axial side within the circumferential groove.

7. An energizing unit as described in claim 6, wherein the pressing mechanism (17) is a bent portion (17a) formed on at least one of a pair of wall portions constituting the circumferential groove, which is bent toward the inside of the circumferential groove on the inner diameter side relative to the outer diameter side.

8. The current-carrying unit according to claim 6, wherein the pressing mechanism (17) is an axially elastic member (17b) disposed in the axial gap between the inner surface of the circumferential groove and the current-carrying member (3).

9. An electric current-carrying unit according to claim 8, wherein the axial elastic member (17b) is made of a conductive material such as metal, carbon, or a conductive resin, rubber, ceramics, or a composite of these materials.

10. An electric current unit as described in claim 6, wherein the pressing mechanism (17) is an inclined surface portion (17c) having a normal inclined to one side in the axial direction, formed at the contact portion between the electric current member (3) and the radial elastic member (16).

11. The current-carrying unit according to any one of claims 6 to 10, wherein a plurality of the current-carrying members (3) are provided.

12. An electric current unit as described in claim 11, 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) is formed with a plurality of bent portions (10) that arrange a plurality of the electric current-carrying members (3) at equal intervals in the circumferential direction.

13. The current-carrying unit according to claim 6, wherein the radial elastic member (16) is a metallic spring member provided across the plurality of current-carrying members (3).

14. An electric current-carrying unit according to any one of claims 6 to 13, wherein the electric current-carrying member (3) is made of a conductive material selected from the group consisting of metal, carbon, resin, rubber, ceramics, or a composite material thereof that has been made electrically conductive.

15. A bearing unit comprising: an electric current unit (1) according to any one of claims 6 to 14; an outer ring (12); an inner ring (13) arranged on the inner diameter side of the outer ring (12); rolling elements (14) provided between the outer ring (12) and the inner ring (13); and a retainer (15) for holding the rolling elements (14) at a predetermined interval in the circumferential direction, and a bearing (7) supporting the motor shaft (5) arranged so that the outer ring (12) abuts against the electric current unit (1).

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