Energization unit and bearing unit

Abstract

An energization unit (1) is configured to have an electroconductive annular case body (2) in which a circumferential groove that opens on the inner diameter side is formed, an electroconductive energization member (3) that is provided in the circumferential groove and that protrudes radially inward from the case body (2), and a radial elastic member (4) that is provided in the circumferential groove and that urges the energization member (3) radially inward.

Description

Current-carrying unit and bearing unit

[0001] The present invention relates to an energizing unit that is attached to a bearing that supports a rotating shaft such as a motor shaft, and to a bearing unit that employs 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] Furthermore, for example, in Patent Document 3 listed below, an electrically conductive brush 32 is housed within a bearing 1 that supports the motor shaft, and the electrically conductive brush 32 is biased by a spring 31, thereby ensuring a predetermined electrical conductivity even if the electrically conductive brush 32 is worn.

[0005] U.S. Patent No. 8,199,453, Japanese Patent No. 7,033,538, Japanese Patent No. 6,777,178

[0006] 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.

[0007] Furthermore, the configuration shown in Patent Document 3 is intended for use in a dry environment, and the bearing 1 and the conductive brush 32 are provided with a seal 7 and a labyrinth gap S for sealing. This hinders the flow of lubricating oil in the axial direction when used in an oil bath, and requires a large space to mount the bearing unit (bearing 1), which limits the conditions of use and mounting.

[0008] The first problem that the present invention aims to solve is to provide an energized unit and bearing unit that can maintain the effect of preventing electrolytic corrosion over a long period of time, and the second problem is to provide an energized unit and bearing unit that has an electrolytic corrosion prevention effect and is compact and suitable for use in an oil bath.

[0009] In order to solve the first problem, the present invention provides an electrically conductive unit (first configuration) having: a conductive annular case body having a circumferential groove formed therein 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; and a radial elastic member that is provided within the circumferential groove and urges the current-carrying member radially inward.

[0010] 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 radially 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.

[0011] In the first configuration, it is preferable to provide a configuration (second configuration) that includes a pressing mechanism that presses the current-carrying member from one side to the other side in the axial direction within the circumferential groove.

[0012] In this way, the pressing mechanism presses the conductive member from one side to the other in the axial direction, thereby maintaining contact between the conductive member and the case main body, thereby achieving stable conductive performance.

[0013] In the second configuration, the pressing mechanism is preferably a bent portion formed on at least one of the pair of wall portions constituting the circumferential groove, the bent portion being bent toward the inside of the circumferential groove on the inner diameter side relative to the outer diameter side (third configuration), or an axially elastic member interposed in an axial gap between the inner surface of the circumferential groove and the current-carrying member (fourth configuration). With these configurations, the current-carrying member can be pressed from one side to the other in the axial direction, and the current-carrying member and the case main body can be reliably maintained in contact with each other.

[0014] Furthermore, in order to solve the second problem in the first configuration, it is preferable to configure the case body so that an oil hole is formed in the case body to allow lubricating oil to flow in the axial direction (fifth configuration). In this way, when a bearing used in combination with this current-carrying unit is used in an oil bath, the axial flow of lubricating oil inside the bearing can be improved and electrolytic corrosion of the bearing can be prevented.

[0015] In the fifth configuration, it is preferable that the case body has a bearing fitting portion extending in the axial direction (sixth configuration), which makes it possible to easily integrate the current-carrying unit and the bearing used in combination with this current-carrying unit.

[0016] In the sixth configuration, it is preferable to use a seventh configuration in which an insulating portion is provided on at least one of the radially inner surface of the bearing fitting portion and the surface of the case main body facing the extension direction of the bearing fitting portion. In this way, it is possible to prevent current from flowing between the case main body and the bearing used in combination with this current-carrying unit, and to more reliably prevent electrolytic corrosion of the bearing.

[0017] The insulating portion is preferably made of a material with high insulating properties, such as various ceramics and various resins, but from the viewpoints of insulation resistance, breakdown voltage, mechanical strength, processability, etc., a fired film containing at least one of various ceramics, polyphenylene sulfide resin, polyamide-imide resin, and epoxy resin is preferred.

[0018] In the first to seventh configurations, it is preferable to use a configuration (eighth 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.

[0019] In the eighth 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 (ninth 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.

[0020] Furthermore, in the present invention, a bearing unit is configured (tenth configuration) that includes an energization unit according to any one of the first to ninth configurations, and a bearing having an outer ring, an inner ring arranged on the inner diameter side of the outer ring, rolling elements provided between the outer ring and the inner ring, and a retainer that holds the rolling elements at predetermined intervals in the circumferential direction, and in which the energization unit and the bearing are integrated by fitting the energization unit into the bearing.

[0021] In particular, in the fifth to seventh configurations, when used in an oil bath, the axial fluidity of the lubricating oil inside the bearing unit can be improved, and by eliminating the need for a sealing seal or labyrinth in the bearing, the bearing unit can be made more compact while preventing electrolytic corrosion of the bearing.

[0022] In the tenth configuration, it is preferable that the outer ring be arranged so as to abut against the current-carrying unit (eleventh configuration). Also, in the eleventh configuration, it is preferable that the outer ring be arranged so that an end face of the outer ring abuts against the current-carrying unit (twelfth configuration).

[0023] Furthermore, in the tenth configuration, it is preferable that the outer periphery of the case main body is fitted onto the inner diameter surface of the outer ring, and the current-carrying member is biased so as to slide against the motor shaft inserted through the axis of the inner ring (thirteenth configuration).

[0024] The current-carrying unit may also be configured as a fourteenth configuration, including the current-carrying unit according to the sixth or seventh configuration, and a bearing having an outer ring, an inner ring disposed radially inward of the outer ring, rolling elements disposed between the outer ring and the inner ring, and a cage that holds the rolling elements at predetermined intervals in the circumferential direction, wherein the bearing fitting portion is fitted onto the outer diameter surface of the outer ring, and the current-carrying member is biased so as to slide against the motor shaft inserted through the axis of the inner ring or against the outer diameter surface of the inner ring. This configuration allows the current-carrying unit and the bearing to be easily integrated. Furthermore, by sliding the current-carrying member against the outer diameter surface of the inner ring, so that it does not directly slide against the motor shaft, there is no need for special processing or manufacturing methods to give the motor shaft a predetermined surface roughness or hardness, which may reduce costs.

[0025] The current-carrying unit may also be configured as in the seventh configuration, and a bearing having an outer ring, an inner ring disposed on the inner diameter side of the outer ring, rolling elements disposed between the outer ring and the inner ring, and a cage that holds the rolling elements at predetermined intervals in the circumferential direction, wherein the insulating portion is in contact with at least one of the outer diameter surface or end face of the outer ring (fifteenth configuration). In this way, it is possible to prevent current from flowing between the case body and the outer ring, and to more reliably prevent electrolytic corrosion of the bearing.

[0026] The current-carrying unit of the present invention creates a new bypass path for current to flow from the motor shaft to the housing, thereby 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 an elastic member, even if the current-carrying member wears over time, the motor shaft and the current-carrying member remain in contact, maintaining the bearing unit's electrolytic corrosion prevention effect over a long period of time. Furthermore, by forming an oil hole in the case body that allows lubricating oil to flow axially, the axial flow of lubricating oil inside the bearing unit can be improved when used in an oil bath. Furthermore, by eliminating the need for a bearing seal or labyrinth, the bearing unit can be made more compact while preventing electrolytic corrosion of the bearings.

[0027] 4A cross-sectional view of a main part of the energizing unit shown in FIG. 4A exploded perspective view of the energizing unit shown in FIG. 4B. sectional view of a main part of a first modified energizing unit shown in FIG. 4B. sectional view of a main part of a second modified energizing unit shown in FIG. 4B. sectional view of a main part of a third modified energizing unit shown in FIG. 4B. sectional view of a main part of a first modified energizing unit shown in FIG. 4B. 12A sectional view showing a modified example of the bearing unit (current-carrying unit) shown in FIG. 12B sectional view showing a third embodiment of the bearing unit (current-carrying unit) according to the present invention sectional view taken along line XIII-XIII in FIG. 12B sectional view showing an enlarged cross-sectional view of the bearing unit (current-carrying unit) shown in FIG. 12C sectional view showing a modified example of the bearing unit (current-carrying unit) shown in FIG. 12C sectional view showing a further modified example of the bearing unit (current-carrying unit) shown in FIG. 12C sectional view showing a fourth embodiment of the bearing unit (current-carrying unit) according to the present invention sectional view showing a fifth embodiment of the bearing unit (current-carrying unit) according to the present invention

[0028] The drawings show a bearing unit A employing a current-carrying unit 1 according to the present invention. As shown in FIGS. 1 to 3, the current-carrying unit 1 mainly comprises a case body 2, a current-carrying member 3, and a radially elastic member 4. 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 (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 radially 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. An outer 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 radial elastic members 4 are members for biasing the current-carrying members 3 radially inward toward the motor shaft 5 (see the arrows in FIG. 2 ). As shown in FIG. 2 , the radial elastic members 4 are suspended across the peripheral grooves 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 radial elastic member 4. However, for example, a circlip (C-type retaining ring) having a slit in a portion of the ring or an annular rubber member may also be used. Note that, although this embodiment is configured such that one radial elastic member 4 biases all the current-carrying members 3, a configuration in which each current-carrying member 3 is individually provided with a radial elastic member 4 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 radially 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 radially 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 radially 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 when 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 biased radially inward by the radial 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 radial elastic member 4.

[0041] In the first embodiment, as shown in FIG. 1, the current-carrying unit 1 and the bearing 7 that constitute the bearing unit 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.

[0042] A second embodiment of a bearing unit A employing a current-carrying unit 1 according to the present invention is shown in Figure 4. 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.

[0043] 4 to 7 , the current-carrying unit 1 mainly comprises a case main body 2, a current-carrying member 3, a radially elastic member 4, and a pressing mechanism 16. 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. Hereinafter, the direction along the rotational axis of the motor shaft 5 will be referred to as the axial direction, the direction perpendicular to the rotational axis as the radial direction, and the direction along the circumference around the rotational axis as the circumferential direction.

[0044] 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 17 extending in one axial direction at its outer peripheral edge and an extension piece 18 extending radially inward from the outer peripheral edge, and an annular retainer 9 having a flange 19 extending in another axial direction opposite the one axial direction at its outer peripheral edge and an extension piece 20 extending radially inward from the outer peripheral edge. As shown in FIG. 4 , the flange 17 formed on the outer ring 8 and the flange 19 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 17, 19 and the extension pieces 18, 20 formed on the outer ring 8 and the retainer 9, respectively. Maintenance can also be improved by inserting the flange 19 formed on the retainer 9 into the flange 17 formed on the outer ring 8 and then fastening the outer ring 8 and the retainer 9 with a retaining ring on the width surface.

[0045] 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 made 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 its extension piece 20 in the other axial direction (the same direction as the flange 19 formed on the retainer 9).

[0046] 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 is formed on the outer periphery of the current-carrying member 3.

[0047] 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.

[0048] The radially elastic members 4 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 radially elastic members 4 are suspended across the circumferential grooves 11 formed in each current-carrying member 3. In this embodiment, a garter spring, which is a ring-shaped member made of a coiled steel wire, is used as the radially elastic member 4. 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 radially elastic member 4 biases all the current-carrying members 3. However, each current-carrying member 3 may be individually provided with a radially elastic member 4.

[0049] The pressing mechanism 16 is a mechanism for pressing the current-carrying member 3 from one axial side to the other. In this embodiment, the pressing mechanism 16 is a bent portion 16a formed on at least one of a pair of wall portions (the outer ring portion 8 and the extension pieces 18, 20 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 16a is formed by inclining the entire extension piece 18 of the outer ring portion 8 by a predetermined angle from the connection point with the flange 17 toward the inside of the circumferential groove. Note that the bent portion 16a may be formed only on the retainer 9, or may be formed on both the outer ring portion 8 and the retainer 9.

[0050] 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 radially 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 radially elastic member 4, so the contact state (current-carrying state) between the motor shaft 5 and the current-carrying member 3 is maintained.

[0051] The current-carrying member 3 is pressed against the retainer 9 by a pressing mechanism 16 (bent portion 16a formed on the extension piece 18 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.

[0052] 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 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 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.

[0053] 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 16a serving as the pressing mechanism 16, so that the current-carrying member 3 can be maintained in contact with the case main body 2, thereby achieving stable current-carrying performance.

[0054] 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.

[0055] 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.

[0056] 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 16 a serving as the pressing mechanism 16 is formed only on a portion of the inner diameter tip of the extension piece 18 of the outer ring portion 8. Even in this configuration, the bent portion 16 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 16 a may be formed only on the retainer 9, or on both the outer ring portion 8 and the retainer 9.

[0057] 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 16 is an axially elastic member 16b 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 16b 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 (outer ring portion 8) and achieving stable current-carrying performance. In the second modified example, the axially elastic member 16b is interposed between the retainer 9 and the current-carrying member 3. However, the axially elastic member 16b may also be interposed between the outer ring portion 8 and the current-carrying member 3.

[0058] In the current-carrying unit 1 according to the second modification, the axially elastic member 16b 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 16b, thereby achieving more stable current-carrying performance.

[0059] 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 16 is an inclined surface 16c formed at the contact portion of the current-carrying member 3 with the radially elastic member 4, the inclined surface 16c having a normal inclined to one side in the axial direction. The inclined surface 16c 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 4 contacts the inclined surface 16c, 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 18 of the outer ring portion 8.

[0060] In this way, by dividing the biasing force of the radially elastic member 4 into a radial component and an axial component by the inclined surface portion 16c, 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), and to exhibit stable current-carrying performance. Note that, contrary to the configuration shown in Fig. 10, the inclined surface portion 16c can also be inclined so as to approach the motor shaft 5 from the retainer 9 side toward the outer ring portion 8 side.

[0061] In the current-carrying unit 1 according to the third modification, it is preferable that the radially elastic members 4 are 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 members 3 to the case main body 2 (outer ring portion 8) and a current-carrying route in which current flows from the current-carrying members 3 to the case main body 2 (retainer 9) via the radially elastic members 4, thereby achieving more stable current-carrying performance.

[0062] 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 17 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.

[0063] In the second 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 radial 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 radial elastic member 4.

[0064] A third embodiment of a bearing unit A (current-carrying unit 1) according to the present invention will be described with reference to the drawings. As shown in FIGS. 12 to 15 , the bearing unit A according to the third embodiment includes a current-carrying unit 1 and a bearing 7, which are integrated together. The bearing unit A is interposed between a motor shaft 5 of an e-axle or the like and a housing 6 to rotatably support the motor shaft 5. The housing 6 is electrically grounded. Hereinafter, the direction along the rotational axis of the motor shaft 5 will be referred to as the axial direction, the direction perpendicular to the rotational axis as the radial direction, and the direction along the circumference around the rotational axis as the circumferential direction.

[0065] The current-carrying unit 1 has a conductive annular case main body 2, a conductive current-carrying member 3 that protrudes radially inward from the case main body 2, and a radial elastic member 4 that urges the current-carrying member 3 radially inward.

[0066] The case body 2 has an annular outer ring portion 8 having a flange 17 extending in one axial direction at its outer peripheral edge and an extension piece 18 extending radially inward from the outer peripheral edge, and an annular retainer 9 having a flange 19 extending in another axial direction opposite to the one axial direction at its outer peripheral edge and an extension piece 20 extending radially inward from the outer peripheral edge. A plurality of oil holes 21, 22 (four oil holes 21, 22 each at 90-degree intervals in this embodiment) are formed in the outer ring portion 8 and the extension pieces 18, 20 of the retainer 9 at predetermined angular intervals in the circumferential direction. A bearing fitting portion 23 is extended in the flange 17 of the outer ring portion 8 in the one direction.

[0067] As shown in Figure 14, the flange 17 formed on the outer annular portion 8 and the flange 19 formed on the retainer 9 are integrated by press-fitting. When the two are integrated, the circumferential positions of the oil holes 21 formed on the outer annular portion 8 and the oil holes 22 formed on the retainer 9 are aligned. As a result of this integration, a circumferential groove that opens toward the inner diameter side is formed by the flanges 17, 19 and extension pieces 18, 20 formed on the outer annular portion 8 and the retainer 9, respectively. Note that, after inserting the flange 19 formed on the retainer 9 into the flange 17 formed on the outer annular portion 8, a retainer ring can be provided on the width surface to fix the outer annular portion 8 and the retainer 9, thereby improving maintainability.

[0068] Both the outer annular portion 8 and the retainer 9 are made of steel. An axial gap is formed between the fitted outer annular portion 8 and retainer 9, allowing the current-carrying member 3 and the radially elastic member 4 to be accommodated therein. 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 19 formed on the retainer 9). Each bent portion 10 is formed corresponding to the circumferential center position of an oil hole 22 formed in the retainer 9.

[0069] The current-carrying member 3 has a substantially arc-shaped base 24 and current-carrying portions 25 that protrude radially inward from the base 24, and the current-carrying portions 25 are configured to slide against the motor shaft 5. Each current-carrying member 3 is housed between two circumferentially adjacent bent portions 10 formed in the retainer 9. 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 needed, but a plurality of current-carrying members is preferred. The number of bent portions 10 formed in the retainer 9 is determined according to the number of current-carrying members 3. In this embodiment, the current-carrying portions 25 are made of carbon-added polytetrafluoroethylene (PTFE). An outer circumferential groove 11 is formed on the outer periphery of the base 24.

[0070] The current-carrying performance of the current-carrying unit can be ensured with a simple configuration by using, as the material for the current-carrying part 25, not only carbon-added PTFE, but also metal, carbon, conductive resin such as polyether ether ketone (PEEK) with carbon or the like, rubber, ceramics, or a composite of these. Furthermore, the surface of the current-carrying part 25 (particularly the part that comes into sliding contact with the motor shaft 5) can be subjected to a surface treatment such as a coating (e.g., a conductive diamond-like carbon (DLC) film, a metal film (plated layer, etc.)) that improves current-carrying property and abrasion resistance.

[0071] The radial elastic members 4 are members for biasing the current-carrying members 3 radially inward toward the motor shaft 5 (see the arrows in FIG. 13 ). As shown in FIG. 13 , the radial elastic members 4 are suspended across the peripheral grooves 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 radial elastic member 4. However, for example, a circlip (C-type retaining ring) having a slit in a portion of the ring or an annular rubber member may also be used. Note that, although this embodiment is configured such that one radial elastic member 4 biases all the current-carrying members 3, a configuration in which each current-carrying member 3 is individually provided with a radial elastic member 4 may also be used.

[0072] The bearing 7 is a ball bearing having 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 cage 15 that holds the rolling elements 14 at predetermined intervals in the circumferential direction. The bearing 7 according to this embodiment is not provided with a hermetic seal, ensuring the axial flow of lubricating oil inside the bearing unit A. The current-carrying unit 1 and the bearing 7 are integrated by fitting a bearing fitting portion 23 formed on the outer ring portion 8 of the case main body 2 onto the outer diameter surface of the outer ring 12.

[0073] The bearing unit A is designed so that the inner diameter, outer diameter, and axial width of the bearing unit A when the current-carrying unit 1 and bearing 7 are integrated match any combination of the main dimensions (bearing inner diameter d, bearing outer diameter D, bearing width B) of the bearing specified in Japanese Industrial Standard JIS B1512-1:2011.

[0074] The operation of bearing unit A will now be described. The motor shaft 5 is inserted through the axis of bearing unit A (current-carrying unit 1 and bearing 7). When the motor shaft 5 and the current-carrying portion 25 of the current-carrying member 3, which is biased toward the motor shaft 5 by the biasing force of the radial elastic member 4, come into sliding contact, the sliding portion of the current-carrying portion 25 that comes into contact with the motor shaft 5 gradually wears. Even if this wear occurs, the current-carrying member 3 (current-carrying portion 25) is always biased toward the motor shaft 5 by the radial elastic member 4, so the contact state (current-carrying state) between the motor shaft 5 and the current-carrying member 3 is maintained.

[0075] The current-carrying portion 25 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 portion 25, the case body 2, and the housing 6. By forming the 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.

[0076] The above-mentioned bearing unit A has oil holes 21, 22 formed in the case main body 2 that allow the flow of lubricating oil in the axial direction. Therefore, when used in an oil bath, the axial flow of lubricating oil inside the bearing unit A can be improved, and by eliminating the need for a sealing seal or labyrinth for the bearing 7, the bearing unit A can be made more compact while preventing electrolytic corrosion of the bearing 7.

[0077] Furthermore, by providing multiple current-carrying members 3, the bearing unit A can reliably exhibit electrolytic corrosion prevention effects, because even if a problem occurs that impairs the electrical conduction of some of the current-carrying members 3, the electrical conduction can be ensured by the other current-carrying members 3. Furthermore, the aligning function of the multiple current-carrying members 3 can stabilize the contact state between the motor shaft 5 and each current-carrying member 3, further improving the electrolytic corrosion prevention effects.

[0078] Furthermore, the above-mentioned bearing unit A is configured so that the inner diameter, outer diameter, and axial width when the current-carrying unit 1 and bearing 7 are integrated match any of the combinations of main dimensions of bearings specified in Japanese Industrial Standard JIS B1512-1:2011, so it is possible to directly replace bearings standardized in the above-mentioned Japanese Industrial Standards (standard bearings, base bearings) with the bearing unit A of the present invention.

[0079] FIG. 16 shows a modified example of the bearing unit A (current-carrying unit 1) according to the third embodiment. This modified bearing unit A differs from the above-described configuration in that an insulating portion 26 is formed on the inner surface of the bearing fitting portion 23 formed on the outer ring portion 8 (the surface facing the outer ring 12 of the bearing 7). By forming the insulating portion 26 between the bearing fitting portion 23 and the outer diameter surface of the outer ring 12, current can be prevented from flowing between the outer ring portion 8 and the outer ring 12, thereby more reliably preventing electrolytic corrosion of the bearing 7. In this modified example, as shown in FIG. 17 , an insulating portion 26 is further formed between the case body 2 (extension piece 20 of the retainer 9) and the end face of the outer ring 12, further enhancing the electrolytic corrosion resistance of the bearing 7. Alternatively, the insulating portion 26 may be provided only between the case body 2 (extension piece 20 of the retainer 9) and the end face of the outer ring 12.

[0080] A fourth embodiment of a bearing unit A (current-carrying unit 1) according to the present invention is shown in Figure 18. The bearing unit A according to the fourth embodiment is similar to the bearing unit A according to the third embodiment in that the current-carrying unit 1 and the bearing 7 are integrated by fitting a bearing fitting portion 23 formed on the outer ring portion 8 of the case body 2 to the outer diameter surface of the outer ring 12. However, it differs in that the axial length of one of a pair of groove shoulders formed on the outer diameter surface of the inner ring 13 is longer than the other, and the current-carrying member 3 (current-carrying portion 25) is in sliding contact with this one groove shoulder (the outer diameter surface of the inner ring 13).

[0081] In the configuration according to the fourth embodiment, a current-carrying circuit is formed as a bypass path between the motor shaft 5, inner ring 13, current-carrying portion 25, case body 2, and housing 6. By forming a current-carrying circuit in this manner, the current passing through bearing 7 interposed between the motor shaft 5 and housing 6 is reduced. With this configuration, the current-carrying member 3 (current-carrying portion 25) does not directly slide on the motor shaft 5, so there is no need to perform special processing or manufacturing methods to give the motor shaft 5 a predetermined surface roughness or hardness, potentially reducing costs.

[0082] A fifth embodiment of a bearing unit A (current-carrying unit 1) according to the present invention is shown in Figure 19. The bearing unit A according to the fifth embodiment is similar to the bearing unit A according to the third embodiment in that the current-carrying member 3 (current-carrying portion 25) is biased by the radially elastic member 4 so as to be in sliding contact with the motor shaft 5 inserted through the axis of the inner ring 13. However, it differs in that the axial length of one of a pair of groove shoulders formed on the inner diameter surface of the outer ring 12 is longer than the other, and the outer periphery of the case main body 2 is fitted onto this one groove shoulder (on the inner diameter surface of the outer ring 12).

[0083] In the configuration according to the fifth embodiment, a current-carrying circuit is formed as a bypass path between the motor shaft 5, the current-carrying unit 25, the case main body 2, the outer ring 12, and the housing 6. By forming the 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. With this configuration, no radially inward force is applied from the current-carrying unit 1 to the outer ring 12, and this force can be prevented from causing the size of the bearing internal clearance to deviate from a predetermined appropriate value.

[0084] In the third to fifth embodiments, the motor shaft 5 is inserted through the axis of the bearing unit A, and the current-carrying member 3 is biased radially inward by the radial elastic member 4, thereby causing the current-carrying portion 25 to slide against the outer diameter surface of the motor shaft 5 or the inner ring 13. However, conversely, if the motor shaft 5 is provided on the outer diameter side of the bearing unit A and the housing 6 is provided on the inner diameter side of the bearing unit A, the current-carrying member 3 can also be biased radially outward by the radial elastic member 4.

[0085] 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.

[0086] REFERENCE SIGNS LIST 1 Current-carrying unit 2 Case body 3 Current-carrying member 4 Radial elastic member 5 Motor shaft 7 Bearing 8 Outer ring 9 Retainer 10 Bent portion 12 Outer ring 13 Inner ring 14 Rolling element 15 Cage 16 Pressing mechanism 16a Bent portion 16b Axial elastic member 16c Inclined surface portion 21, 22 Oil hole 23 Bearing fitting portion 26 Insulating portion A Bearing unit

Claims

1. An energization unit comprising: a conductive annular case body (2) having a circumferential groove formed therein that opens toward the inner diameter side; a conductive current-carrying member (3) provided within said circumferential groove and protruding radially inward from said case body (2); and a radial elastic member (4) provided within said circumferential groove for biasing said current-carrying member (3) radially inward.

2. The current-carrying unit according to claim 1, further comprising a pressing mechanism (16) for pressing the current-carrying member (3) from one side to the other in the axial direction within the circumferential groove.

3. An energizing unit as described in claim 2, wherein the pressing mechanism (16) is a bent portion (16a) 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.

4. The current-carrying unit according to claim 2, wherein the pressing mechanism (16) is an axially elastic member (16b) disposed in the axial gap between the inner surface of the circumferential groove and the current-carrying member (3).

5. The current-carrying unit according to claim 1, wherein the case body (2) is formed with oil holes (21, 22) that allow lubricating oil to flow in the axial direction.

6. An energizing unit according to claim 5, wherein the case body (2) has a bearing fitting portion (23) extending in the axial direction.

7. An electrically conductive unit as described in claim 6, wherein an insulating portion (26) is provided on at least one of the radial inner surface of the bearing fitting portion (23) or the surface of the case main body portion (2) facing the extension direction of the bearing fitting portion (23).

8. An energizing unit according to any one of claims 1 to 7, wherein a plurality of the energizing members (3) are provided.

9. An energizing unit as described in claim 8, 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 energizing members (3) at equal intervals in the circumferential direction.

10. A bearing unit comprising: an energized unit (1) according to any one of claims 1 to 9; a bearing (7) having 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) that holds the rolling elements (14) at a predetermined interval in the circumferential direction, wherein the energized unit (1) is fitted into the bearing (7) to form an integrated unit.

11. A bearing unit according to claim 10, wherein the outer ring (12) is arranged to abut against the current-carrying unit (1).

12. A bearing unit according to claim 11, wherein an end face of the outer ring (12) is arranged to abut against the current-carrying unit (1).

13. A bearing unit as described in claim 10, wherein the outer periphery of the case main body (2) is fitted into the inner diameter surface of the outer ring (12), and the conductive member (3) is biased so as to come into sliding contact with the motor shaft (5) inserted through the axis of the inner ring (13).

14. A bearing unit comprising: an electrically conductive unit (1) as defined in claim 6 or 7; a bearing (7) having 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; wherein the bearing fitting portion (23) fits into the outer diameter surface of the outer ring (12), and the electrically conductive member (3) is biased so as to come into sliding contact with a motor shaft (5) inserted into the axis of the inner ring (13) or the outer diameter surface of the inner ring (13).

15. A bearing unit comprising: an electric current-carrying unit (1) as defined in claim 7; a bearing (7) having 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) that holds the rolling elements (14) at a predetermined interval in the circumferential direction, wherein the insulating portion (26) is in contact with at least one of the outer diameter surface or end surface of the outer ring (12).

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