Energization unit and bearing unit

Abstract

An energization unit (1) is configured to have: a conductive annular case body part (2) in which a gap that opens radially inward is formed; a conductive energization member (3) that is provided within the gap and protrudes radially inward from the case body part (2); and an energization assistance member (4) that is provided between the case body part (2) and the energization member (3) and assists energization between the case body part (2) and the energization member (3). A bearing unit (A) is configured to have: the energization unit (1); and a bearing (7) that has an outer ring (14), an inner ring (15), a rolling element (16), and a holder (17), the outer ring (14) being disposed so as to abut the energization unit (1).

Description

Current-carrying unit and bearing unit

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

[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 commonplace for efficient motor operation. In particular, in-vehicle motors 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 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, for example, Figure 2 of Patent Document 1).

[0004] JP 2012-110149 A

[0005] The configuration shown in Patent Document 1 is configured so that the brush contact 5a contacts a predetermined position on the shaft end 3c', but there is a risk that the contact state between the shaft end 3c' and the brush contact 5a will become unstable due to tilting of the sliding brush assembly 25 (brush contact 5a) caused by installation errors, making it impossible to ensure a stable electrical 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.

[0007] In order to solve the above problem, the present invention provides an electrically conductive unit (first configuration) having: a conductive annular case main body portion having a gap formed therein that opens radially inward; a conductive current-carrying member provided within the gap and protruding radially inward from the case main body portion; and a current-carrying auxiliary member provided between the case main body portion and the current-carrying member that assists current flow between the case main body portion and the current-carrying member.

[0008] In this way, by using the current-carrying auxiliary member to assist the flow of electricity between the case main body and the current-carrying member, it is possible to prevent gaps from occurring between the case main body and the current-carrying member, which would cause a deterioration in the current-carrying state, and to ensure a stable current-carrying state.

[0009] In the first configuration, the auxiliary current-carrying member may be a biasing member that is provided adjacent to the current-carrying member in the axial direction and biases the current-carrying member axially toward the case main body (second configuration), the auxiliary current-carrying member may be a conductive elastic member that biases the current-carrying member radially inward (third configuration), or the auxiliary current-carrying member may be a conductive conductor that connects the case main body and the current-carrying member (fourth configuration). In this way, a current-carrying path in the radial or axial direction between the case main body and the current-carrying member is secured, thereby making the current-carrying state more stable.

[0010] In the first to fourth configurations, a bent portion that bends inwardly of the gap as it moves from the outer diameter side to the inner diameter side may be formed on at least one of a pair of axially opposing wall portions of the case main body (fifth configuration). In this way, when the current-carrying member is protruded radially inward, the current-carrying member can come into contact with the bent portion, thereby making it possible to further stabilize the electrical conduction state between the case main body and the current-carrying member.

[0011] 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, so that 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.

[0012] In the first to sixth configurations, the case body may have a seventh configuration (seventh configuration) in which the case body has an annular outer ring portion having a flange on its outer periphery extending in one axial direction, and a retainer fitted to the outer ring portion in the axial direction and having a flange on its outer periphery extending in the opposite axial direction from the one side. In this way, the current-carrying member and the elastic member can be easily stored in the gap in the case body.

[0013] In the first to seventh configurations, the current-carrying member may be made of a conductive material such as metal, carbon, or resin, rubber, or ceramics to which a conductive material has been added, or a composite of these materials, and the volume resistivity of the conductive material may be 10 Ω cm or less (eighth configuration). In this way, the current-carrying function of the current-carrying unit can be ensured with a simple configuration.

[0014] In the first to eighth configurations, a configuration (ninth configuration) can be adopted in which an annular elastic member is disposed in an outer circumferential groove formed on the outer circumferential surface of the current-carrying member and biases the current-carrying member radially inward.

[0015] The current-carrying units according to the first to ninth 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, a retainer that holds the rolling elements at predetermined intervals circumferentially, and a bearing arranged so that the outer ring abuts the current-carrying unit (tenth configuration).

[0016] The current-carrying unit of the present invention has a current-carrying auxiliary member that assists current flow between the case main body and the current-carrying member that protrudes radially inward from the case main body, thereby preventing a gap from occurring between the case main body and the current-carrying member, which would otherwise cause a deterioration in the current-carrying state, and ensuring a stable current-carrying state.

[0017] 1A sectional view showing a first example of a current-carrying unit according to the present invention; sectional view of a main part of the current-carrying unit shown in FIG. 1; sectional view taken along line III-III in FIG. 1; sectional view taken along line IV-IV in FIG. 3; sectional view taken along line V-V in FIG. 1; sectional view taken along line VI-VI in FIG. 5; sectional view showing a free state of the biasing member (leaf spring) of the current-carrying unit shown in FIG. 1;

[0018] 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 Figures 1 to 7, the current-carrying unit 1 mainly comprises a case body 2, a current-carrying member 3, and an auxiliary current-carrying member 4. The current-carrying unit 1 is disposed between a motor shaft 5 of an e-axle or the like and the housing 6, adjacent to a bearing 7 that supports the motor shaft 5. The housing 6 is electrically grounded.

[0019] From the viewpoint of preventing electrolytic corrosion, it is preferable to provide the current-carrying unit 1 and bearing 7 in contact with each other in the axial direction, 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 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.

[0020] The case body 2 is a conductive annular member that is fitted onto the inner diameter surface of the housing 6. As shown in Fig. 2, 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. The outer ring 8 and the retainer 9 are integrated by press-fitting a flange formed on the retainer 9 into the flange formed on the outer ring 8.

[0021] Both the outer annular portion 8 and the retainer 9 are made of steel. A gap that opens toward the inner diameter side is formed between the fitted outer annular portion 8 and retainer 9, and is capable of accommodating the current-carrying member 3 and the auxiliary current-carrying member 4. The outer annular portion 8, which forms one of a pair of axially opposing wall portions that form this gap, has a bent portion 10 that bends inwardly into the gap as it moves from the outer diameter side to the inner diameter side. As shown in FIG. 4 , the retainer 9 has multiple (four in this embodiment) bent portions 11 that extend from its inner edge in the other axial direction (the same direction as the flange formed on the retainer 9) at predetermined angular intervals (every 90 degrees in this embodiment).

[0022] The current-carrying member 3 is a conductive member extending in the circumferential direction that protrudes radially inward from the case body 2 and is in sliding contact with the motor shaft 5 supported by the bearing 7. As shown in FIG. 2 , both axial end surfaces of the current-carrying member 3 are parallel to each other and have inclined surfaces inclined with respect to the axial direction (inclination angle: 1 to 5 degrees, preferably 1.5 to 2.5 degrees). The inclination angle of these inclined surfaces is approximately the same as the inclination angle of the bent portion 10 formed in the outer ring portion 8, and one axial end surface of the current-carrying member 3 and the inner surface of the bent portion 10 of the outer ring portion 8 are in surface contact.

[0023] 3, the inner peripheral surface of the current-carrying member 3 that contacts the motor shaft 5 is formed in an arc shape when viewed in the axial direction. The radius of curvature of this inner peripheral surface is approximately the same as the radius of curvature of the outer peripheral surface of the motor shaft 5, and the inner peripheral surface of the current-carrying member 3 and the outer peripheral surface of the motor shaft 5 are in surface contact. In addition, an outer peripheral groove 12 is formed in the outer peripheral surface of the current-carrying member 3 along the circumferential direction.

[0024] The current-carrying members 3 are housed one by one between adjacent bent portions 11 formed on the retainer 9 in the circumferential direction. In this embodiment, four current-carrying members 3 are arranged at equal intervals in the circumferential direction. The number of current-carrying members 3 can be changed as appropriate, but it is preferable to have 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.

[0025] The current-carrying member 3 may be made of a metal, carbon, a resin such as polytetrafluoroethylene (PTFE) or polyether ether ketone (PEEK) to which a conductive material such as carbon has been added, rubber, ceramics, or a composite of these. The volume resistivity of the current-carrying member 3 is preferably 10 Ω·cm or less. The volume resistivity can be measured, for example, by a method described in JIS K 7194 (Testing Method for Resistivity of Conductive Plastics Using the Four-Probe Method). Furthermore, the surface of the current-carrying member 3 (particularly the inner peripheral 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 coating (e.g., a plating layer)) to improve electrical conductivity and wear resistance.

[0026] As shown in Figure 3, an annular elastic member 13 is fitted across the outer circumferential groove 12 formed on the outer circumferential surface of each current-carrying member 3. The annular elastic member 13 is a member for urging the current-carrying member 3 radially inward toward the motor shaft 5 (see the arrow in Figure 3). In this embodiment, a garter spring made of a coiled steel wire processed into a ring shape is used as the annular elastic member 13. Other annular elastic members 13 than garter springs can also be used, for example, a circlip (C-type retaining ring) with a slit in a portion of the ring, or an annular rubber.

[0027] The auxiliary current-carrying member 4 is disposed between the case body 2 and the current-carrying member 3 and assists in the conduction of current between the case body 2 and the current-carrying member 3. In the first example, the auxiliary current-carrying member 4 is a biasing member 4a disposed adjacent to the current-carrying member 3 in the axial direction and biasing the current-carrying member 3 axially toward the case body 2 (outer ring portion 8). Specifically, the biasing member 4a is a leaf spring (hereinafter, the same reference numeral as the biasing member 4a is used). As shown in FIGS. 2 , 6 , and 7 , the leaf spring 4a is a V-shaped member in cross section having an annular base portion 4a1 that contacts the inner surface of the retainer 9 and a biasing portion 4a2 that biases the current-carrying member 3 in the axial direction. As shown in FIG. 5 , the biasing portion 4a2 is formed corresponding to the circumferential position of the current-carrying member 3.

[0028] The shapes of the case body 2 (outer ring 8, retainer 9), current-carrying member 3, and annular elastic member 13 that constitute the current-carrying unit 1 can be determined as appropriate. For example, if the motor shaft 5 has a shaft diameter of 35 mm, it is particularly preferable that the inner diameters of the outer ring 8 and retainer 9 be 36.5 mm or greater to prevent contact between the motor shaft 5 and the case body 2 (outer ring 8, retainer 9) due to wear of the current-carrying member 3 over long-term use. This is because the inner diameters of the outer ring 8 and retainer 9 should be larger than the shaft diameter to prevent contact with the motor shaft 5. In this embodiment, the inner diameter of the outer ring 8 is 39 mm, and the inner diameter of the retainer 9 is 40.6 mm. For example, if the axial width of the current-carrying member 3 is 2.5 mm, the coil diameter of the annular elastic member 13 (garter spring) can be 2 mm, and the ring diameter can be 35 mm. The current-carrying member 3 has an initial radial width that is sufficient to withstand long-term use even when wear occurs over time.

[0029] As shown in FIG. 1 , the bearing 7 arranged adjacent to the current-carrying unit 1 is a ball bearing having an outer ring 14, an inner ring 15 arranged on the inner diameter side of the outer ring 14, balls as rolling elements 16 arranged between the outer ring 14 and the inner ring 15, and a retainer 17 that holds the rolling elements 16 at a predetermined interval in the circumferential direction.

[0030] When using the current-carrying unit 1, the motor shaft 5 is inserted into the inner periphery of the current-carrying unit 1 (current-carrying member 3), and the outer periphery of the current-carrying unit 1 (case main body 2) is fitted into the housing 6. The current-carrying member 3 of the current-carrying unit 1 is pressed radially inward onto the motor shaft 5 by the biasing force of the annular elastic member 13. Furthermore, the current-carrying member 3 is pressed axially against the bent portion 10 formed on the outer ring portion 8 by the biasing force of the leaf spring 4a provided axially adjacent to the current-carrying member 3.

[0031] The current-carrying unit 1 according to the first example uses the biasing member 4a (leaf spring 4a) as the current-carrying auxiliary member 4 to assist current flow between the case body 2 and the current-carrying member 3. This prevents a gap from occurring between the case body 2 and the current-carrying member 3, which could cause a deterioration in the current-carrying state, and ensures a stable current flow from the motor shaft 5 through the current-carrying member 3, the case body 2 (outer ring portion 8), and the housing 6. In particular, in the current-carrying unit 1 described above, the biasing member 4a (leaf spring 4a) is positioned axially adjacent to the current-carrying member 3 and biases the current-carrying member 3 axially toward the case body 2. This ensures an axial current path between the case body 2 and the current-carrying member 3, further stabilizing the current-carrying state. By ensuring a stable current flow through the current-carrying unit 1 in this manner, electrolytic corrosion of the bearing 7 can be effectively suppressed.

[0032] Furthermore, the current-carrying unit 1 according to the first example is configured such that the outer ring portion 8, which is one of a pair of axially opposing wall portions that form the gap, has a bending portion 10 formed therein that bends inward into the gap as it moves from the outer diameter side to the inner diameter side. Therefore, when the current-carrying member 3 is protruded radially inward, the current-carrying member 3 can be brought into contact with the bending portion 10, thereby making the current-carrying state between the case main body portion 2 (outer ring portion 8) and the current-carrying member 3 more stable.

[0033] Furthermore, the current-carrying unit 1 according to the first example is provided with a plurality of current-carrying members 3, so that 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 exerting 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.

[0034] While the above description illustrates a configuration using a leaf spring 4a as the biasing spring 4a, a push nut as shown in FIG. 8 or a wave washer as shown in FIG. 9 can also be used as the biasing spring 4a (hereinafter, the push nut and wave washer will be denoted by the same reference numerals as the biasing member 4a). The push nut 4a is a member having an annular base portion 4a1 that contacts the inner surface of the retainer 9 and a biasing portion 4a2 that extends radially inward from the base portion 4a1 while tilting in the axial direction and biases the current-carrying member 3 in the axial direction. The wave washer 4a is an annular member that is wavy in the axial direction. In either configuration, similar to the leaf spring 4a, the current-carrying member 3 is biased axially toward the case main body 2, thereby stabilizing the current-carrying state of the current-carrying unit 1.

[0035] A second example of the current-carrying unit 1 according to the present invention is shown in Figure 10. The current-carrying unit 1 according to the second example has the same basic configuration as the current-carrying unit 1 according to the first example, but differs in the auxiliary current-carrying member 4. Specifically, in the second example, the auxiliary current-carrying member 4 is a conductive elastic member 4b that is provided between the case main body 2 and the current-carrying member 3 and biases the current-carrying member 3 toward the motor shaft 5. This elastic member 4b is a compression spring made of steel (hereinafter, denoted by the same reference numeral as the elastic member 4b). A pocket 18 is formed on the outer circumferential surface of the current-carrying member 3, and the compression spring 4b is attached to this pocket 18.

[0036] The second example of the current-carrying unit 1 is configured such that a conductive compression spring 4b is interposed between the case main body 2 (retainer 9) and the current-carrying member 3, and the current-carrying member 3 is biased radially toward the motor shaft 5. This ensures a radial current-carrying path between the case main body 2 and the current-carrying member 3 via the compression spring 4b, making the current-carrying state more stable.

[0037] FIG. 11 shows a third example of the current-carrying unit 1 according to the present invention. The current-carrying unit according to the third example has the same basic configuration as the current-carrying unit 1 according to the first example, but differs in the auxiliary current-carrying member 4. Specifically, in the third example, the auxiliary current-carrying member 4 is a conductive conductor 4c that connects the case body 2 and the current-carrying member 3. The end of the conductor 4c on the case body 2 (retainer 9) side is fixed to the case body 2 by a conductive fixing means such as soldering or a conductive adhesive. Meanwhile, the end of the conductor 4c on the current-carrying member 3 side is sandwiched between the case body 2 and the current-carrying member 3 and is capable of sliding radially relative to the current-carrying member 3. A bend is formed in the middle of the conductor 4c, allowing the conductor 4c to move slightly radially.

[0038] The third example of the current-carrying unit 1 is configured so that the case main body 2 and the current-carrying member 3 are directly connected by a conductor 4c, thereby ensuring a current-carrying path between the case main body 2 and the current-carrying member 3 via the conductor 4c, thereby making the current-carrying state more stable.

[0039] 12 shows a fourth example of the current-carrying unit 1 according to the present invention. The current-carrying unit 1 according to the fourth example has the same basic configuration as the current-carrying unit 1 according to the second example, but differs in that the biasing spring 4a (leaf spring 4a) used in the first example is also included as the current-carrying auxiliary member 4 in addition to the conductive elastic member 4b (compression spring 4b). The current-carrying unit 1 according to the fourth example ensures a radial current path between the case body 2 and the current-carrying member 3 via the compression spring 4b, and also ensures an axial current path between the case body 2 and the current-carrying member 3 through the action of the leaf spring 4a, thereby making it possible to more stabilize the current flow state.

[0040] 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 annular elastic member 13 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 annular elastic member 13.

[0041] Furthermore, in each of the above-described embodiments, the outer ring portion 8 is configured to have a bent portion 10 formed therein. However, if a stable current flow state can be ensured solely by the action of the current-carrying auxiliary member 4, the inner diameter edge of the outer ring portion 8 can be extended radially inwardly in parallel with the inner diameter edge of the retainer 9 without forming the bent portion 10.

[0042] FIG. 13 shows one embodiment of a bearing unit A according to the present invention. This bearing unit A is constructed by integrating the current-carrying unit 1 according to the first example with a bearing 7. A flange formed on the outer ring portion 8 of the current-carrying unit 1 extends axially and fits onto the outer diameter surface of the outer ring 14 of the bearing 7. By integrating the current-carrying unit 1 and 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 B 1512-1:2011), it is possible to replace existing bearings with the bearing unit A, which has the effect of preventing electrolytic corrosion.

[0043] 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.

[0044] REFERENCE SIGNS LIST 1 Current-carrying unit 2 Case main body 3 Current-carrying member 4 Current-carrying auxiliary member 4a Urging member (leaf spring, push nut, wave washer) 4b Elastic member (compression spring) 4c Conductor 7 Bearing 8 Outer ring 9 Retainer 10 Bent portion 12 Outer peripheral groove 13 Annular elastic member 14 Outer ring 15 Inner ring 16 Rolling element 17 Cage A Bearing unit

Claims

1. An energization unit comprising: a conductive annular case body (2) having a gap formed therein that opens radially inward; a conductive current-carrying member (3) that is provided within the gap and protrudes radially inward from the case body (2); and an auxiliary current-carrying member (4) that is provided between the case body (2) and the current-carrying member (3) and that assists in the flow of current between the case body (2) and the current-carrying member (3).

2. An energizing unit as described in claim 1, wherein the auxiliary energizing member (4) is a biasing member (4a) arranged axially adjacent to the energizing member (3) and biases the energizing member (3) axially toward the case main body portion (2).

3. The current-carrying unit according to claim 1, wherein the auxiliary current-carrying member (4) is a conductive elastic member (4b) that biases the current-carrying member (3) radially inward.

4. The current-carrying unit according to claim 1, wherein the auxiliary current-carrying member (4) is a conductive conductor (4c) that connects the case main body (2) and the current-carrying member (3).

5. An energizing unit as described in claim 1, wherein at least one of a pair of axially opposing wall portions of the case main body portion (2) has a bent portion (10) that bends toward the inside of the gap as it moves from the outer diameter side to the inner diameter side.

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. An energizing unit as described in claim 1, wherein the case main body (2) has an annular outer ring portion (8) having a flange extending in one axial direction on its outer peripheral edge, and a retainer (9) that fits axially into the outer ring portion (8) and has a flange extending in the opposite axial direction on its outer peripheral edge.

8. The current-carrying unit according to claim 1, wherein the current-carrying member (3) is made of a conductive material such as metal, carbon, or resin, rubber, ceramics, or a composite of these materials with an added conductive material, and the volume resistivity of the conductive material is 10 Ω·cm or less.

9. An energizing unit as described in claim 1, further comprising an annular elastic member (13) disposed in an outer circumferential groove (12) formed on the outer circumferential surface of the energizing member (3) and biasing the energizing member (3) radially inward.

10. A bearing unit comprising: an energizing unit (1) according to any one of claims 1 to 9; an outer ring (14); an inner ring (15) arranged on the inner diameter side of the outer ring (14); rolling elements (16) provided between the outer ring (14) and the inner ring (15); and a bearing (7) arranged so that the outer ring (14) abuts against the energizing unit (1).

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