Rotary machine

Abstract

Provided is a rotary machine in which the shaft and the housing are electrically connected by a first conductive path provided at one end of the shaft and a second conductive path provided in the housing, wherein the first conductive path (40) has a planar electrode portion (43) extending in the radial direction from the rotational center (on a line CA1) of the shaft (10) in order to, even when the position of the contact point between the first conductive path and the second conductive path is deviated from the rotational center of the shaft, suppress wear and torque loss of the contact point. The second conductive path (50) has: an attachment portion (51) that is fixed to the housing (20); a spring portion (52) that protrudes in the axial direction from the attachment portion (51) to the planar electrode portion (43); and a curved surface electrode portion (53) that is supported by the spring portion (52) in a state of being in contact with the planar electrode portion (43) at one point and being movable in the radial direction on the planar electrode portion (43).

Description

Rotating Machinery

[0001] The present invention relates to a rotary machine in which a shaft and a housing are electrically connected.

[0002] Conventionally, the rotor shaft of an electric motor is generally rotatably supported relative to the housing by rolling bearings such as ball bearings. For example, in the case of electric motors mounted on e-axle units in which an electric motor, an inverter, and a reducer are integrated, the drive voltage has been increasing in recent years. As a result, high shaft voltages are generated on the rotor shaft and the input shaft of the reducer connected to it. The potential difference between the shaft and the housing causes discharges at the contact points between the rolling elements and the raceways of the rolling bearings located between the shaft and the housing, raising concerns about the possibility of electrolytic corrosion at the contact points.

[0003] To prevent such electrolytic corrosion, a first conductive path is provided on the shaft and a second conductive path is provided in the housing. The shaft and housing are electrically connected at the contact point of these two conductive paths, thereby creating a conductive path that does not pass through the rolling bearing and preventing current from passing through the rolling bearing (Patent Document 1).

[0004] The rotating machine disclosed in Patent Document 1 has a cap member that constitutes a first electrical conduction path fitted to one end of a shaft. A curved electrode portion is provided on the side of the cap member. The curved electrode portion is a sphere fixed to the cap member while fitted to it, or a hemispherical bulge on the cap member. The center of the curved electrode portion is located on the rotational center of the shaft. The second electrical conduction path includes a cylindrical guide fixed to the housing, a compression coil spring disposed inside the cylindrical guide, and a brush shaft guided axially by the inner circumferential surface of the cylindrical guide. One end surface of the brush shaft has a flat electrode portion extending radially and making single-point contact with the curved electrode portion. The brush shaft is biased toward the curved electrode portion by the elastic force of the compression coil spring. This bias presses the flat electrode portion against the curved electrode portion. This connection structure, in which the first electrical conduction path on the shaft side and the second electrical conduction path on the housing side make point contact at the rotational center of the shaft, is resistant to wear at the contact point and has excellent durability. Furthermore, direct contact between the two conductive paths is ensured by the elastic force of the spring, so that the reliability of electrical conduction between the shaft and the housing is high.

[0005] International Publication No. 2023 / 188525

[0006] However, in the rotating machine of Patent Document 1, in order to position the contact point between the curved electrode portion and the flat electrode portion at the rotation center of the shaft, strict precision requirements are required for the attachment precision of the electrode member to one end of the shaft, the dimensional precision of each part of the electrode member including the contact portion, etc., which causes an increase in cost. If the contact point is allowed to be located radially away from the rotation center of the shaft, the precision requirements can be relaxed, but at that contact point, the sliding speed of the curved electrode portion and the flat electrode portion relative to each other around the rotation center of the shaft will be high, raising concerns about wear at the contact point and torque loss.

[0007] In view of the above background, the problem that this invention aims to solve is to suppress wear and torque loss at the contact point between the first power transmission path and the second power transmission path in a rotating machine in which the shaft and the housing are electrically connected by a first power transmission path provided at one end of the shaft and a second power transmission path provided in the housing, even if the contact point is located away from the center of rotation of the shaft.

[0008] In order to solve the above-mentioned problems, the present invention employs Configuration 1, which is a rotating machine comprising a shaft, a housing that accommodates at least one end of the shaft, a first electrical conduction path provided on one end of the shaft, and a second electrical conduction path provided on the housing, wherein the shaft and the housing are electrically connected at a contact point between the first electrical conduction path and the second electrical conduction path, wherein the first electrical conduction path has a flat electrode portion extending radially from the center of rotation of the shaft, and the second electrical conduction path has an attachment portion fixed to the housing, a spring portion that protrudes axially from the attachment portion towards the flat electrode portion, and a curved electrode portion that makes single-point contact with the flat electrode portion and is supported by the spring portion in a state where it can move radially on the flat electrode portion.

[0009] According to the above-mentioned configuration 1, when the shaft rotates at high speed with the contact point between the flat electrode portion on the shaft side and the curved electrode portion on the housing side positioned radially off from the center of rotation of the shaft, the elastic force of the spring portion that supports the curved electrode portion so that it can move radially on the flat electrode portion provides an aligning action that moves the contact point between the curved electrode portion and the flat electrode portion closer to the center of rotation of the shaft. Therefore, even if the contact point is positioned off from the center of rotation of the shaft, wear and torque loss at the contact point are suppressed.

[0010] In the above configuration 1, a configuration 2 can be adopted in which the bearing includes a rolling bearing having an inner ring, an outer ring, and a plurality of rolling elements arranged between the inner ring and the outer ring, the housing has a bearing seat portion supporting the outer ring and a female thread portion, the spring portion is made of a spring member wound in a cylindrical shape around a spring axis, the curved electrode portion is fitted onto one end of the spring portion, the mounting portion has a shaft portion fitted onto the other end of the spring portion and a male thread portion that screws into the female thread portion of the housing, and the curved electrode portion contacts the flat electrode portion at or near the center of rotation of the shaft. In this configuration 2, "near the center of rotation of the shaft" means a position radially deviated from the center of rotation of the shaft and a position where the contact point between the curved electrode portion and the flat electrode portion can be guided to the center of rotation of the shaft by the above-mentioned aligning action.

[0011] According to the above configuration 2, the contact point between the curved electrode portion and the flat electrode portion can be positioned approximately at the center of rotation of the shaft by simple assembly based on the housing.

[0012] In the above configuration 2, a configuration 3 can be adopted in which the curved electrode portion is formed of a sphere fitted onto the inner periphery of the spring portion.

[0013] According to the above configuration 3, the center of the curved electrode portion can be positioned on the spring axis simply by fitting the curved electrode portion onto the inner circumference of the cylindrical spring portion, and the curved electrode portion can be constructed using inexpensive general-purpose steel balls, etc.

[0014] In the above configurations 2 or 3, a configuration 4 can be adopted in which the shaft is hollow and has an oil hole formed in the axial center, the first power transmission path is made of a cap member that is fitted onto one end of the shaft and has an oil window portion, the housing and the rolling bearing form a space that surrounds the contact point between the first power transmission path and the second power transmission path, and the oil hole, the oil window portion, and the space are in communication.

[0015] According to the above-mentioned configuration 4, it is possible to position the flat electrode portion of the first power transmission path that is fitted onto one end of the shaft at the center of rotation of the shaft, while simultaneously supplying lubricating oil to the side of the rolling bearing via the oil hole of the shaft, the oil window portion of the first power transmission path, and the space between the housing and the rolling bearing.

[0016] In any one of the above configurations 1 to 3, configuration 5 can be adopted, in which the shaft has a center hole portion concentric with the center of rotation of the shaft, and the first power transmission path consists of a cap member fitted onto one end of the shaft so as to cover the center hole portion.

[0017] According to the above configuration 5, it is possible to adopt a turned shaft and to position the planar electrode portion of the first electrical conduction path, which is fitted to one end of the shaft, at the center of rotation of the shaft.

[0018] A sixth configuration may be adopted, in which the rotary machine according to any one of the first to fifth configurations is configured as an electric motor.

[0019] As described above, by adopting the above configuration 1, this invention makes it possible to suppress wear and torque loss at the contact point between the first power transmission path and the second power transmission path in a rotating machine in which the shaft and the housing are electrically connected by a first power transmission path provided at one end of the shaft and a second power transmission path provided in the housing, even if the contact point between the first power transmission path and the second power transmission path is located away from the center of rotation of the shaft.

[0020] 1 is an enlarged view of the vicinity of the curved electrode portion of FIG. 1; FIG. 2 is a perspective view of the rotary machine of FIG. 1; FIG. 3 is a cross-sectional view of the rotary machine of FIG. 1;

[0021] A rotary machine according to a first embodiment (hereinafter simply referred to as "this rotary machine") as one example of the present invention will be described with reference to the accompanying drawings, FIGS. 1 to 4. FIG.

[0022] 1 and 2 , in this rotating machine, in order to prevent electrolytic corrosion of the rolling bearing 30 that supports the shaft 10 and the housing 20 so that they can rotate freely relative to each other, an electrically conductive path that does not pass through the rolling bearing 30 is constructed between one end of the shaft 10 and the housing 20. The electrically conductive path is made up of a first electrically conductive path 40 provided at one end of the shaft 10 and a second electrically conductive path 50 provided in the housing 20.

[0023] This rotating machine is configured as an electric motor driven by an inverter (not shown).

[0024] The shaft 10 is a motor shaft that serves as the center of rotation of the rotor 11 of the electric motor. The shaft 10 is hollow, with an oil hole 12 formed in the axial center portion over the entire axial length of the shaft 10. The axial center portion refers to a radial region centered on the rotation center line CA1 of the shaft 10 that rotates in the circumferential direction. The center line of the oil hole 12 coincides with the rotation center line CA1.

[0025] Here, the axial direction refers to the direction along the rotational center line CA1, the radial direction refers to the direction perpendicular to the rotational center line CA1, and the circumferential direction refers to the direction along the circumference of a circle centered on the rotational center line CA1.

[0026] The housing 20 is a casing that accommodates the shaft 10, the rotor 11, a reducer (not shown; the same applies below) that reduces the rotation input from the input gear 13 attached to the shaft 10 and outputs it to the outside.

[0027] The shaft 10 and the housing 20 are each made of a conductive material such as metal.

[0028] The rolling bearing 30 has an inner ring 31, an outer ring 32, and a plurality of rolling elements 33 arranged between the inner ring 31 and the outer ring 32. These rolling elements 33 are held at equal intervals in the circumferential direction by a cage 34. The rolling bearing 30 is configured as a deep groove ball bearing.

[0029] The inner ring 31, the outer ring 32 and the rolling elements 33 are each made of a metal such as steel.

[0030] The inner ring 31 is fitted onto the outer periphery of one end of the shaft 10. The outer ring 32 is fitted onto a bearing seat portion 21 formed on the housing 20.

[0031] As shown in Figures 3 and 4, first power transmission path 40 is made of a seamless cap member having a cylindrical portion 41 fitted onto one end of shaft 10, an outer flange portion 42 that axially engages with the end face of shaft 10, a flat electrode portion 43 extending along the radial direction, and a plurality of oil window portions 44 that form openings between flat electrode portion 43 and outer flange portion 42.

[0032] The first power transmission path 40 is made of a conductive material such as metal. The first power transmission path 40 is formed seamlessly by, for example, pressing a steel plate.

[0033] A space 60 continues from between the first electrical transmission path 40 and the housing 20 to the side surface of the rolling bearing 30 .

[0034] The cylindrical portion 41 is press-fitted onto the inner periphery of the shaft 10. The outer flange portion 42 abuts against the end face of the shaft 10 in the axial direction over the entire circumferential direction.

[0035] The flat electrode portion 43 includes a central portion located on the rotation center line CA1, and has a circular surface extending radially from the central portion.

[0036] The oil window portion 44 is formed so as to connect the flat electrode portion 43 and the outer flange portion 42 at three points equally spaced in the circumferential direction. The oil window portion 44 communicates with the oil hole 12 of the shaft 10 and the space 60.

[0037] The housing 20 shown in Figure 2 has an oil passage 24 that guides lubricating oil splashed up by the reducer inside the reducer case portion 23 to the oil hole 12 of the shaft 10. The lubricating oil that flows from the oil passage 24 into the oil hole 12 flows out from the oil window portion 44 of the first power transmission path 40 shown in Figures 1 and 4 into the space 60, and is supplied from the space 60 to the side surface of the rolling bearing 30. The lubricating oil supplied to the side surface of the rolling bearing 30 eventually penetrates the interior of the rolling bearing 30 and flows out into the internal space of the housing 20. An oil passage (not shown) is formed in the housing 20 so that this leaked lubricating oil can be returned into the reducer case portion 23.

[0038] The second power transmission path 50 shown in Figures 1 and 3 is composed of an attachment portion 51 fixed to the housing 20, a spring portion 52 connected to the attachment portion 51, and a curved electrode portion 53 supported by the spring portion 52.

[0039] The mounting portion 51, the spring portion 52, and the curved electrode portion 53 are each formed of a conductive material such as metal.

[0040] The mounting portion 51 is made of a male screw member that is screwed into the housing 20. The spring portion 52 is made of a spring member that is wound in a cylindrical shape around the spring axis. The curved electrode portion 53 is made of a sphere that is fixed to the spring portion 52.

[0041] 3, the mounting portion 51 has a seamless male thread portion 51a and a shaft portion 51b that protrudes axially from the male thread portion 51a toward the flat electrode portion 43. The central axis of the shaft portion 51b is aligned with the thread axis of the male thread portion 51a.

[0042] 1 and 3, the housing 20 has a female thread portion 22 that screws into the mounting portion 51. The thread axis of the female thread portion 22 and the central axis of the bearing seat portion 21 are set on the same straight line CA2.

[0043] The curved electrode portion 53 is fitted onto the inner periphery of one winding end side (the winding end side closer to the flat electrode portion 43) of the spring portion 52. There are no particular limitations on the means for fixing the curved electrode portion 53 to the spring portion 52, and for example, fixing means such as press-fitting, welding, or soldering to the spring portion 52 can be used.

[0044] The other winding end side of the spring portion 52 (the winding end side farther from the flat electrode portion 43) is fitted onto the shaft portion 51b of the mounting portion 51. The part of the spring portion 52 that protrudes from the shaft portion 51b in the axial direction toward the flat electrode portion 43 has flexibility that allows it to bend in any radial direction.

[0045] The curved electrode portion 53 is supported by the spring portion 52 in a state where it contacts the flat electrode portion 43 at one point and is movable radially on the flat electrode portion 43 .

[0046] The contact point between curved electrode portion 53 and flat electrode portion 43 is ideally located on rotation center line CA1 of shaft 10. In this case, even when shaft 10 rotates, there is substantially no portion that slides relative to one another in the circumferential direction at the contact point between flat electrode portion 43 on shaft 10 and curved electrode portion 53 on housing 20, and there is no concern about wear or torque loss at the contact point.

[0047] The engagement between the shaft portion 51b and the spring portion 52, and the engagement between the spring portion 52 and the curved electrode portion 53, result in these axes and centers being aligned substantially on the same line. In other words, when the mounting portion 51 is threadedly engaged with the female thread portion 22 and fixed to the housing 20, the spring axis of the spring portion 52 and the center of the curved electrode portion 53 are aligned substantially on the line CA2. Because the central axis of the bearing seat portion 21 that radially supports the outer ring 32 is also set on the line CA2, the rotational center line CA1 of the shaft 10 that is radially supported by the bearing seat portion 21 via the rolling bearing 30 and the line CA2 are aligned substantially on the same line. Therefore, the spring axis of the spring portion 52 and the center (sphere center) of the curved electrode portion 53, which are aligned substantially on the line CA2, are aligned substantially on the rotational center line CA1. That is, the contact point between the spherical surface of the curved electrode portion 53 and the flat electrode portion 43 is also located on or near the rotation center line CA1. Note that in Figures 1 and 3, the eccentricity δ of the line CA2 with respect to the rotation center line CA1 when the contact point is located near the rotation center line CA1 is exaggerated.

[0048] As shown in the figure, when the shaft 10 rotates at high speed while the contact point between the curved electrode portion 53 on the housing 20 side and the flat electrode portion 43 on the shaft 10 side is located in a position slightly radially off from the rotation center line CA1, the spring portion 52 supporting the curved electrode portion 53, which is dragged circumferentially at the contact point, bends slightly radially, and the elastic force of the spring portion 52 trying to correct the bending causes the curved electrode portion 53 to gradually approach the rotation center line CA1.As a result, the contact point between the curved electrode portion 53 and the flat electrode portion 43 gradually approaches the rotation center line CA1, and the dragging speed of the curved electrode portion 53 decreases (the whirling of the spring portion 52 gradually converges). Eventually, when the contact point between the curved electrode portion 53 and the flat electrode portion 43 reaches the rotation center line CA1, the posture of the spring portion 52 stabilizes.

[0049] As described above, this rotating machine (see Figures 1 to 3) comprises a shaft 10, a housing 20 that accommodates at least one end of the shaft 10, a first electrical transmission path 40 provided at one end of the shaft 10, and a second electrical transmission path 50 provided in the housing 20, and the shaft 10 and the housing 20 are electrically connected at the point of contact between the first electrical transmission path 40 and the second electrical transmission path 50.

[0050] In particular, this rotating machine has first power transmission path 40 having flat electrode portion 43 extending radially from the center of rotation of shaft 10 (on line CA1), second power transmission path 50 having mounting portion 51 to which housing 20 is fixed, spring portion 52 protruding axially from mounting portion 51 toward flat electrode portion 43, and curved electrode portion 53 that is in contact with flat electrode portion 43 at a single point by spring portion 52 and is supported so as to be radially movable on flat electrode portion 43.Therefore, when shaft 10 rotates at high speed in a state in which the contact point between flat electrode portion 43 on the shaft 10 side and curved electrode portion 53 on the housing 20 side is located radially away from the center of rotation of shaft 10 (on line CA1), the elastic force of spring portion 52 that supports curved electrode portion 53 so as to be radially movable on flat electrode portion 43 causes an aligning action to move the contact point between curved electrode portion 53 and flat electrode portion 43 closer to the center of rotation of shaft 10 (on line CA1). Therefore, this rotating machine can suppress wear and torque loss at the contact point between the flat electrode portion 43 of the first power transmission path 40 and the curved electrode portion 53 of the second power transmission path 50 even if the contact point is located away from the center of rotation of the shaft 10 (on line CA1).

[0051] The rotary machine also includes a rolling bearing 30 having an inner ring 31, an outer ring 32, and a plurality of rolling elements 33 arranged between the inner ring 31 and the outer ring 32, a housing 20 having a bearing seat portion 21 supporting the outer ring 32 and a female thread portion 22, a spring portion 52 made of a spring member wound in a cylindrical shape around a spring axis, a curved electrode portion 53 fitted to one winding end side of the spring portion 52, and a shaft portion 51 fitted to the other winding end side of the spring portion 52. 1b and a male thread portion 51a that screws into the female thread portion 22 of the housing 20, and the curved electrode portion 53 comes into contact with the flat electrode portion 43 on or near the rotation center line CA1 of the shaft 10, so that the contact point between the curved electrode portion 53 and the flat electrode portion 43 can be positioned approximately at the rotation center (on the line CA1) of the shaft 10 by simply assembling the second power transmission path 50, such as the mounting portion 51, based on the bearing seat surface portion 21 and the female thread portion 22 of the housing 20. Note that the contact point only needs to be positioned near the rotation center line CA1, which is within a range where the contact point can be guided to the rotation center of the shaft 10 by the aligning action based on the elastic force of the spring portion 52 described above (i.e., the radial distance allowed between the rotation center line CA1 and the contact point).

[0052] Furthermore, in this rotating machine, since the curved electrode portion 53 consists of a sphere fitted onto the inner circumference of the spring portion 52, the center of the curved electrode portion 53 can be positioned on the spring axis simply by fitting the curved electrode portion 53 onto the inner circumference of the cylindrical spring portion 52, and the curved electrode portion 53 can be constructed using an inexpensive, general-purpose steel ball, etc.

[0053] Furthermore, in this rotating machine, one end of the shaft 10 is hollow and forms an oil hole 12 at the axial center, the first power transmission path 40 consists of a cap member fitted onto one end of the shaft 10, a space 60 continues from between the first power transmission path 40 and the housing 20 to the side of the rolling bearing 30, and the first power transmission path 40 has an oil window portion 44 that communicates from the oil hole 12 to the space 60. Therefore, it is possible to position the flat electrode portion 43 of the first power transmission path 40 fitted onto one end of the shaft 10 at the center of rotation of the shaft, and to supply lubricating oil to the side of the rolling bearing 30 via the oil hole 12 of the shaft 10, the oil window portion 44 of the first power transmission path 40, and the space 60 between the first power transmission path 40 and the housing 20.

[0054] Although this rotating machine uses a cylindrically wound compression coil spring as the spring portion 52, the spring portion may be any spring that can reliably maintain the curved electrode portion pressed against the flat electrode portion while exhibiting radial flexibility without being hindered by the mounting portion. Furthermore, instead of a compression coil spring, the spring portion wound cylindrically around the spring axis may be a coiled wave spring (CWS), such as a flat-end multilayer wave spring.

[0055] Furthermore, although a deep groove ball bearing is exemplified as the rolling bearing 30, the rolling bearing 30 may be changed to various bearings such as an angular contact ball bearing or a self-aligning bearing.

[0056] Furthermore, in this rotating machine, an example has been shown in which the flat electrode portion 43 is disposed closer to the curved electrode portion 53 than the outer flange portion 42, but it is also possible to dispose it inside the shaft 10. As an example, a second embodiment is shown in Figure 5. Note that, hereinafter, only differences from the first embodiment will be described, and the same reference numerals will be used for corresponding components.

[0057] In first power transmission path 40 according to the second embodiment, flat electrode portion 43 is continuous with cylindrical portion 41 fitted onto the inner periphery of shaft 10 on the side opposite to outer flange portion 42. Flat electrode portion 43 is thereby disposed in oil hole 12, and accordingly, curved electrode portion 53 and the like of second power transmission path 50 are also disposed in oil hole 12. According to the second embodiment, the axial distance between one end of shaft 10 and housing 20 can be made narrower than in the first embodiment, allowing housing 20 to be made more compact in the axial direction.

[0058] In addition, in this rotary machine, an example in which one end of the shaft 10 is hollow has been shown, but it is also possible to change one end of the shaft 10 to a solid portion. As an example, a third embodiment is shown in Figure 6.

[0059] One end of a shaft 10 according to the third embodiment is solid and has a center hole 14 concentric with the center of rotation of the shaft 10. The first power transmission path 40 is made of a cap member fitted to the outer periphery of the one end of the shaft 10 so as to cover the center hole 14. The center hole 14 is a hole used as a center for rotating a workpiece when the workpiece that serves as the base material for the shaft 10 is subjected to cylindrical turning or the like using a lathe. For example, the cylindrical portion 41 of the first power transmission path 40 and the outer peripheral surface portion of the shaft 10 that fits into the rolling bearing 30 are formed by cylindrical turning. The third embodiment makes it possible to both employ a shaft 10 that is turned based on the center hole 14 and position the flat electrode portion 43 of the first power transmission path 40 that is fitted to the one end of the shaft 10 at the center of rotation of the shaft 10 (on line CA1).

[0060] 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.

[0061] REFERENCE SIGNS LIST 10 shaft 12 oil hole 14 center hole portion 20 housing 21 bearing seat portion 22 female thread portion 30 rolling bearing 31 inner ring 32 outer ring 33 rolling element 40 first transmission path 43 flat electrode portion 44 oil window portion 50 second transmission path 51 mounting portion 51a male thread portion 51b shaft portion 52 spring portion 53 curved electrode portion 60 space

Claims

1. A rotary machine comprising a shaft, a housing that accommodates at least one end of the shaft, a first electrical conduction path provided at one end of the shaft, and a second electrical conduction path provided in the housing, wherein the shaft and the housing are electrically connected at a contact point between the first electrical conduction path and the second electrical conduction path, wherein the first electrical conduction path has a flat electrode portion that extends radially from the center of rotation of the shaft, and the second electrical conduction path has an attachment portion fixed to the housing, a spring portion that protrudes axially from the attachment portion toward the flat electrode portion, and a curved electrode portion that contacts the flat electrode portion at one point by the spring portion and is supported so as to be radially movable on the flat electrode portion.

2. A rotating machine according to claim 1, comprising a rolling bearing having an inner ring, an outer ring, and a plurality of rolling elements arranged between the inner ring and the outer ring, wherein the housing has a bearing seat portion that supports the outer ring and a female thread portion, the spring portion is made of a spring member wound in a cylindrical shape around the spring axis, the curved electrode portion is fitted onto one end of the winding of the spring portion, and the mounting portion has a shaft portion that is fitted onto the other end of the winding of the spring portion and a male thread portion that screws into the female thread portion of the housing, and the curved electrode portion comes into contact with the flat electrode portion at or near the center of rotation of the shaft.

3. A rotating machine according to claim 2, wherein the curved electrode portion is a sphere fitted onto the inner periphery of the spring portion.

4. A rotary machine as claimed in claim 2 or 3, wherein the shaft is hollow and has an oil hole formed in the axial center, the first power transmission path is made of a cap member fitted onto one end of the shaft and having an oil window portion, the housing and the rolling bearing form a space surrounding the contact point between the first power transmission path and the second power transmission path, and the oil hole, the oil window portion and the space are in communication.

5. A rotating machine according to claim 1 or 2, wherein one end of the shaft has a center hole concentric with the center of rotation of the shaft, and the first power transmission path comprises a cap member fitted onto the one end of the shaft so as to cover the center hole.

6. A rotating machine according to claim 1 or 2 configured as an electric motor.

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