Current-carrying unit and bearing unit

Abstract

To provide an energizing unit and a bearing unit capable of ensuring a stable energized state. [Solution] The current-carrying unit 1 comprises a conductive annular case main body 2 having a gap 10 opening radially inward, a conductive current-carrying member 3 provided within the gap 10, protruding radially inward from the case main body 2 and sliding against the rotating shaft 5, and an elastic member 4 that biases the current-carrying member 3 radially inward, with the inner peripheral edge formed so that the axial length of the current-carrying member 3 becomes shorter as it moves radially inward; and the bearing unit A comprises the current-carrying unit 1, an outer ring 13, an inner ring 14 arranged on the inner diameter side of the outer ring 13, rolling elements 15 arranged between the outer ring 13 and the inner ring 14, and a retainer 16 that holds the rolling elements 15 at a predetermined circumferential interval, and a bearing 7 supporting the rotating shaft 5 arranged so that the outer ring 13 abuts against the current-carrying unit 1.

Description

[Technical Field]

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

[0002] Rolling bearings, especially ball bearings, are commonly used to support rotating shafts such as the motor shaft of an automotive e-axle. In recent years, inverter control has become common to operate motors efficiently. In particular, in-vehicle motors are being made smaller to make them easier to install in vehicles, and more precise control is being implemented to use these smaller motors more efficiently.

[0003] It is known that axial currents and axial voltages occur in this rotating shaft. If this current passes through the inside of the bearing, it can cause electrolytic corrosion in the metal raceways and rolling elements. Therefore, for example, in Patent Document 1 listed below, a sliding brush assembly 25 is provided near a countershaft 3c to which the rotation of the motor shaft 1b is transmitted, and brush contacts 5a protruding from a brush holder 5c of the sliding brush assembly 25 are brought into contact with a shaft end 3c' of the countershaft 3c, thereby dissipating electricity into the housing 3a and preventing the current from passing through the ball bearing 13 (see Figure 2 of Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-110149 Summary of the Invention [Problem to be solved by the invention]

[0005] The configuration shown in Patent Document 1 is configured so that the brush contact 5a comes into contact with a predetermined position on the shaft end 3c', but if the sliding brush assembly 25 (brush contact 5a) is tilted due to installation errors and the resulting increase in the amount of oil at the contact point with the shaft end 3c' increases the oil film thickness, making the contact state between the shaft end 3c' and the brush contact 5a unstable and making it impossible to ensure a stable current flow state.

[0006] Therefore, an object of the present invention is to provide a current-carrying unit and a bearing unit that can ensure a stable current-carrying state. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides: a conductive annular case body portion having a gap formed therein that opens radially inward; a conductive member provided in the gap, protruding radially inward from the case body and in sliding contact with the rotating shaft; an elastic member that biases the current-carrying member radially inward; The current-carrying unit has an inner peripheral edge formed so that the axial length of the current-carrying member becomes shorter toward the inside in the radial direction (first configuration).

[0008] By forming the inner peripheral edge of the current-carrying member so that its axial length decreases radially inward, the contact pressure of the current-carrying member against the rotating shaft increases, suppressing the formation of an oil film, and the aligning effect reduces the influence of assembly errors. This stabilizes the contact state between the rotating shaft and the current-carrying member, ensuring a stable current flow.

[0009] In the first configuration, the inner peripheral edge can be configured to be concave when viewed from the axial direction, and the radius of curvature of the portion of the inner peripheral edge that contacts the rotating shaft can be larger than the radius of curvature of the rotating shaft (second configuration). In this way, a single-point contact state occurs in a narrow area between the inner peripheral edge of the current-carrying member and the rotating shaft, increasing the contact surface pressure of the current-carrying member against the rotating shaft, thereby effectively suppressing the formation of an oil film.

[0010] In the first configuration, the inner peripheral edge can be configured to be concave when viewed from the axial direction, and the radius of curvature of the portion of the inner peripheral edge that contacts the rotating shaft can be smaller than the radius of curvature of the rotating shaft (third configuration). In this way, two-point contact is formed between both ends of the inner peripheral edge of the current-carrying member and the rotating shaft, and the contact surface pressure can be made to peak at the contact edge, thereby effectively suppressing the formation of an oil film.

[0011] In the first configuration, the portion of the inner peripheral edge that comes into contact with the rotating shaft can be configured to be flat or convex when viewed in the axial direction (fourth configuration). In this way, as in the second configuration, a single-point contact state is formed in a narrow area between the inner peripheral edge of the current-carrying member and the rotating shaft, and the contact surface pressure of the current-carrying member against the rotating shaft is increased, thereby effectively suppressing the formation of an oil film.

[0012] In the first to fourth configurations, a fifth configuration (fifth configuration) can be adopted in which a cross section of the portion of the inner peripheral edge that contacts the rotating shaft, taken along the rotation axis of the rotating shaft, has a convex arc shape facing the rotating shaft. This prevents changes in the contact state between the current-carrying member and the rotating shaft due to installation errors, and ensures stable contact between the current-carrying member and the rotating shaft during bearing operation, ensuring a stable current-carrying state. Furthermore, as with the second to fourth configurations, this also has the effect of increasing the contact surface pressure of the current-carrying member against the rotating shaft.

[0013] In the first to fifth configurations, a configuration (sixth configuration) can be adopted in which a plurality of the current-carrying members are provided in the circumferential direction. In this way, even if the current-carrying performance of some of the current-carrying members is impaired, the other current-carrying members can cover for this, thereby ensuring stable current-carrying performance.

[0014] In the first to sixth configurations, the case body may have an annular outer ring portion and a retainer fitted into the outer ring portion (seventh configuration). In this way, the current-carrying member and the elastic member can be easily housed in the circumferential groove of the case body.

[0015] In the first to seventh configurations, the current-carrying member may be made of a conductive material such as metal, carbon, or conductive resin, rubber, ceramics, or a composite of these (eighth configuration). In this way, the current-carrying function of the current-carrying unit can be ensured with a simple configuration.

[0016] The current-carrying units according to the first to eighth configurations can be applied to a bearing unit having this current-carrying 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, and a retainer that holds the rolling elements at predetermined intervals in the circumferential direction, and a bearing that supports the rotating shaft body, with the outer ring arranged so as to abut against the current-carrying unit (ninth configuration). [Effects of the Invention]

[0017] The current-carrying unit of the present invention and the bearing unit incorporating this current-carrying unit form a bypass path for current separate from the current-carrying route from the inner ring through the rolling elements to the outer ring, thereby preventing electrolytic corrosion in bearings installed between a rotating shaft (such as a motor shaft) and a housing. In particular, by forming the inner peripheral edge of the current-carrying member so that it does not make surface contact with the rotating shaft over the entire surface of the current-carrying member projected toward the axis of the rotating shaft, the contact pressure of the current-carrying member against the rotating shaft is increased, suppressing the formation of an oil film, and the alignment effect reduces the influence of assembly errors. This stabilizes the contact state between the rotating shaft and the current-carrying member, ensuring a stable current flow. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing a first example of an energizing unit according to the present invention; [Figure 2] Cross-sectional view along line II-II in Figure 1 [Figure 3] Cross-sectional view along line III-III in Figure 2 [Figure 4] 10 is a cross-sectional view of a main part showing a second example of an energizing unit according to the present invention; [Figure 5] 10 is a cross-sectional view of a main part showing a third example of an energizing unit according to the present invention; [Figure 6] 10 is a cross-sectional view of a main part showing a fourth example of an energizing unit according to the present invention; [Figure 7] Cross-sectional view taken along line VII-VII in Figure 6 [Figure 8] 1 is a cross-sectional view of a bearing unit in which a current-carrying unit and a bearing are integrated according to a first example; DETAILED DESCRIPTION OF THE INVENTION

[0019] A first example of a current-carrying unit 1 according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the current-carrying unit 1 has a case main body 2, a current-carrying member 3, and an elastic member 4 as its main components. The current-carrying unit 1 is disposed between the motor shaft 5 (hereinafter, designated by the same reference numeral as the rotating shaft 5) of an e-axle or the like serving as a rotating shaft 5 and the housing 6, adjacent to a bearing 7 that supports the motor shaft 5. The diameter of the motor shaft 5 is generally about 25 to 40 mm. The housing 6 is electrically grounded.

[0020] 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 Fig. 1, but a configuration in which a gap is provided between them is also acceptable. In the following, the direction along the axis of the motor shaft 5 is referred to as the axial direction, the direction perpendicular to the axis is referred to as the radial direction, and the direction along the circumference going around the axis is referred to as the circumferential direction.

[0021] The case body 2 is a conductive annular member that is 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 that is 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.

[0022] Both the outer ring portion 8 and the retainer 9 are made of steel. A gap 10 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 11 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).

[0023] The current-carrying member 3 is a conductive, circumferentially extending member that protrudes radially inward from the case body 2 and makes sliding contact with the motor shaft 5 supported by the bearing 7. The inner peripheral edge is formed so that its axial length becomes shorter toward the radially inward direction. The current-carrying members 3 are housed one by one between adjacent circumferentially adjacent bent portions 11 formed on 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 it is preferable to have more than one. The number of bent portions 11 formed on the retainer 9 is determined corresponding to the number of current-carrying members 3.

[0024] The inner peripheral edge of the current-carrying member 3 facing the motor shaft 5 is concave when viewed in the axial direction. The radius of curvature of the portion of the inner peripheral edge that comes into contact with the motor shaft 5 (the circumferential center of the inner peripheral edge) is greater than the radius of curvature of the outer peripheral surface of the motor shaft 5. As a result, gaps are formed between both ends of the inner peripheral edge of the current-carrying member 3 and the outer peripheral surface of the motor shaft 5 when viewed in the axial direction. The outer peripheral edge of the current-carrying member 3 is convex when viewed in the axial direction. A circumferential groove 12 is formed in this outer peripheral edge along the circumferential direction.

[0025] A cross section of the inner circumferential edge of the current-carrying member 3, taken along the rotation axis of the motor shaft 5, at a portion that contacts the motor shaft 5, has a convex arc shape (R-shape) that faces the motor shaft 5. Therefore, the current-carrying member 3 contacts the motor shaft 5 only near the center of the current-carrying member 3 in the axial direction.

[0026] In addition to carbon-added PTFE, metal, carbon, or conductive resin such as carbon-added polytetrafluoroethylene (PTFE) or 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 peripheral edge 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 (plated layer, etc.)) that improves electrical conductivity and wear resistance.

[0027] 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 12 formed on the outer periphery of each current-carrying member 3. In this embodiment, a garter spring made of a coiled steel wire processed into a ring shape is used as the elastic member 4, but it is also possible to use, for example, a circlip (C-type retaining ring) with a slit in part of the ring or an annular rubber. Note that in this embodiment, a single elastic member 4 is used to bias all of the current-carrying members 3, but it is also possible to configure each current-carrying member 3 to have its own elastic member 4.

[0028] The bearing 7, which is arranged adjacent to the current-carrying unit 1, is a ball bearing having an outer ring 13, an inner ring 14 arranged on the inner diameter side of the outer ring 13, balls as rolling elements 15 arranged between the outer ring 13 and the inner ring 14, and a retainer 16 that holds the rolling elements 15 at a predetermined interval in the circumferential direction.

[0029] The operation of the current-carrying unit 1 will now be described. The motor shaft 5 is inserted into the inner periphery of the current-carrying unit 1 (the inner periphery of the current-carrying member 3), and the outer periphery of the current-carrying unit 1 is fitted into the housing 6. The current-carrying member 3 of the current-carrying unit 1 is pressed against the motor shaft 5 by the biasing force of the elastic member 4. However, the inner periphery of the current-carrying member 3 is concave when viewed axially, and the radius of curvature of the portion of the inner periphery that contacts the motor shaft 5 (the circumferential center portion of the inner periphery) is larger than the radius of curvature of the outer periphery of the motor shaft 5, resulting in a single-point contact between the inner periphery of the current-carrying member 3 and the motor shaft 5 in a narrow area. In other words, the inner periphery of the current-carrying member 3 facing the outer periphery of the motor shaft 5 does not come into surface contact with the entire surface of the projection of the current-carrying member 3 toward the axis of the motor shaft 5. As a result, the contact surface pressure of the current-carrying member 3 against the motor shaft 5 increases, effectively suppressing the formation of an oil film and ensuring a stable current flow state between the current-carrying member 3 and the motor shaft 5.

[0030] In particular, the cross section of the inner periphery of the current-carrying member 3, taken along the rotation axis of the motor shaft 5, at the portion that comes into contact with the motor shaft 5, has a convex arc shape (R-shape) facing the motor shaft 5, which prevents changes in the contact state between the current-carrying member 3 and the motor shaft 5 due to installation errors and ensures stable contact between the current-carrying member 3 and the motor shaft 5 during bearing operation, ensuring a stable current-carrying state. Furthermore, this arc shape also has the effect of increasing the contact surface pressure of the current-carrying member 3 against the motor shaft 5.

[0031] Furthermore, even if the inner peripheral edge of the current-carrying member 3 wears over time due to sliding contact between the current-carrying member 3 and the motor shaft 5, 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 current-carrying member 3 and the motor shaft 5 is maintained. 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.

[0032] 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.

[0033] Furthermore, by providing multiple current-carrying members 3 in the above-described current-carrying unit 1, even if a problem occurs that impairs the current-carrying action of some of the current-carrying members 3, the current-carrying action of the other current-carrying members 3 can be ensured, thereby reliably demonstrating the electrolytic corrosion prevention effect. Furthermore, the alignment 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.

[0034] In the above embodiment, the motor shaft 5 is inserted through the axis of the current-carrying unit 1, and the current-carrying member 3 is biased radially inward by the elastic member 4 to slide against the motor shaft 5. However, conversely, if the motor shaft 5 is provided on the outer diameter side of the current-carrying unit 1 and the housing 6 is provided on the inner diameter side of the current-carrying unit 1, the current-carrying member 3 can also be biased radially outward by the elastic member 4.

[0035] A second example of the current-carrying unit 1 according to the present invention is shown in FIG. 4 , and a third example is shown in FIG. 5 . The second and third examples share the same basic configuration as the first example, except that the portion of the inner periphery of the current-carrying member 3 that contacts the motor shaft 5 is flat (second example) or convex (third example) when viewed from the axial direction. By making the inner periphery of the current-carrying member 3 flat or convex when viewed from the axial direction, a single-point contact state is achieved between the inner periphery of the current-carrying member 3 and the motor shaft 5 in a narrow area, as in the first example. This increases the contact pressure of the current-carrying member 3 against the motor shaft 5, effectively suppressing the formation of an oil film and ensuring stable current flow between the current-carrying member 3 and the motor shaft 5.

[0036] A fourth example of the current-carrying unit 1 according to the present invention is shown in FIGS. 6 and 7. The basic configuration of the current-carrying unit 1 according to the fourth example is the same as that of the first to third examples, except that the inner circumferential edge of the current-carrying member 3, which contacts the motor shaft 5, is concave when viewed from the axial direction and has a smaller radius of curvature than the motor shaft 5. By making the inner circumferential edge of the current-carrying member 3 concave when viewed from the axial direction and making the radius of curvature of the inner circumferential edge that contacts the motor shaft 5 (the circumferential center of the inner circumferential edge) smaller than the radius of curvature of the outer circumferential surface of the motor shaft 5, two-point contact is achieved between both ends of the inner circumferential edge of the current-carrying member 3 and the motor shaft 5, creating a peak contact pressure at the contact edges. This effectively suppresses the formation of an oil film and ensures stable current flow between the current-carrying member 3 and the motor shaft 5.

[0037] In the first to fourth examples, the shape of the inner peripheral edge of the current-carrying member 3 in the portion that contacts the motor shaft 5 is specified as convex, flat, or concave with a predetermined curvature, as described above, but the shape of other portions (portions that are not in contact with the current-carrying member 3 and the motor shaft 5) is not particularly limited. For example, in the first example, the shape of the portion that contacts the motor shaft 5 is concave when viewed from the axial direction, and the radius of curvature of this portion is larger than the radius of curvature of the outer peripheral surface of the motor shaft 5. However, the shape of the portion other than the portion that contacts the motor shaft 5 can also be a composite surface, for example, flat, or a curved surface with a different radius of curvature from the portion that contacts the motor shaft 5.

[0038] FIG. 8 shows one embodiment of a bearing unit A according to the present invention. This bearing unit A is constructed by integrating a current-carrying unit 1 and a bearing 7. A flange formed on the outer ring portion 8 of the current-carrying unit 1 extends in the axial direction and fits onto the outer diameter surface of the outer ring 12 of the bearing 7. By integrating the current-carrying unit 1 and the bearing 7 into the bearing unit A in this way, it is possible to reduce the weight and width. Furthermore, by making the size of this bearing unit A consistent with the major bearing dimensions standardized in the Japanese Industrial Standards (JIS B1512-1:2011), it is possible to replace existing bearings with the bearing unit A, which has the effect of preventing electrolytic corrosion.

[0039] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0040] 1 Power supply unit 2 Case body 3. Current-carrying materials 4 Elastic member 5 Rotating shaft (motor shaft) 6. Housing 7. Bearings 8 Outer ring 9 Retainer 10 Gap 11 Bending section 12 Circumferential groove 13 Outer ring 14 Inner Circle 15 Rolling elements 16 Cage A bearing unit

Claims

1. a conductive annular case body (2) having a gap (10) opening radially inward; a conductive member (3) provided in the gap (10), protruding radially inward from the case body (2) and in sliding contact with the rotating shaft body (5); an elastic member (4) that biases the current-carrying member (3) radially inward; and an inner peripheral edge of the current-carrying member (3) is formed so that the axial length of the current-carrying member (3) becomes shorter toward the radially inner side.

2. The energizing unit according to claim 1, wherein the inner peripheral edge is concave when viewed from the axial direction, and the radius of curvature of the portion of the inner peripheral edge that contacts the rotating shaft body (5) is larger than the radius of curvature of the rotating shaft body (5).

3. The energizing unit according to claim 1, wherein the inner peripheral edge is concave when viewed from the axial direction, and the radius of curvature of the portion of the inner peripheral edge that contacts the rotating shaft body (5) is smaller than the radius of curvature of the rotating shaft body (5).

4. 2. The current-carrying unit according to claim 1, wherein the portion of the inner periphery that comes into contact with the rotary shaft body (5) is flat or convex when viewed in the axial direction.

5. An energizing unit as described in claim 1, wherein a cross section of the portion of the inner peripheral edge that contacts the rotating shaft body (5) taken along the rotation axis of the rotating shaft body (5) has a convex arc shape facing the rotating shaft body (5).

6. The current-carrying unit according to claim 1, wherein a plurality of the current-carrying members (3) are provided in the circumferential direction.

7. 2. The energizing unit according to claim 1, wherein the case body (2) has an annular outer ring portion (8) and a retainer (9) fitted into the outer ring portion (8).

8. 2. The current-carrying unit according to claim 1, wherein the current-carrying member (3) is made of a conductive material formed from metal, carbon, or a conductive resin, rubber, ceramic, or a composite of these.

9. A current-carrying unit (1) according to any one of claims 1 to 8; a bearing (7) supporting the rotating shaft body (5), the bearing (7) having an outer ring (13), an inner ring (14) arranged on the inner diameter side of the outer ring (13), rolling elements (15) provided between the outer ring (13) and the inner ring (14), and a retainer (16) that holds the rolling elements (15) at predetermined intervals in the circumferential direction, the outer ring (13) being arranged so that it abuts against the current-carrying unit (1); A bearing unit having:

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