Rotating electric machine

Abstract

The present invention provides a rotating electric machine capable of achieving both long life of a bearing and miniaturization of the rotating electric machine. This rotating electric machine according to the present invention is provided with: a rotor (2); a rotary shaft (5) that is connected to the rotor (2) and that rotates together with the rotor (2); a bearing (4) that supports the rotary shaft (5); a labyrinth seal (16) that is installed on the side of the bearing (4); a grounding brush (10) that removes shaft voltage generated in the rotary shaft (5); and a housing (1) that accommodates the rotor (2), the rotary shaft (5), the bearing (4), the labyrinth seal (16), and the grounding brush (10). The labyrinth seal (16) is provided with: a fixing member (11) that is fixed to the housing (1); and a rotating member (12) that is fixed to the rotary shaft (5) and that rotates together with the rotary shaft (5). The grounding brush (10) is installed on the rotating member (12).

Description

Rotating electric machines

[0001] The present invention relates to a rotating electric machine equipped with an earth brush.

[0002] Rotating electric machines such as generators and electric motors are sometimes equipped with earth brushes. Earth brushes are devices that neutralize the shaft voltage generated on the rotating shaft of the rotating electric machine and reduce the current flowing from the rotating shaft to the bearings.

[0003] Examples of conventional rotating electrical machines equipped with earth brushes are described in Patent Documents 1 and 2. Patent Document 1 describes an earth brush installed inside the rotating electrical machine, while Patent Document 2 describes a rotating machine in which the earth brush and the bearing are separated by a seal.

[0004] JP 2018-78704 A JP 2017-60401 A

[0005] When an earth brush comes into contact with the rotating shaft of a rotating electrical machine, it generates wear particles (wear debris). This wear debris may enter the bearing and shorten the life of the bearing. The earth brush described in Patent Document 1 does not take measures to prevent wear debris from the earth brush from entering the bearing.

[0006] In the rotating machine described in Patent Document 2, the earth brush and the bearing are separated by a seal, which prevents wear debris from the earth brush from entering the bearing. However, the rotating machine described in Patent Document 2 requires space for the earth brush to contact the rotating shaft and space for installing the seal, which raises concerns about the increased length in the rotating shaft direction and the resulting increased size. It is preferable for a rotating electric machine to be as small as possible so that it can be installed regardless of the size of the installation space.

[0007] As described above, conventional rotating electrical machines have a problem in that it is difficult to achieve both a long life for the bearings and a compact size for the rotating electrical machine.

[0008] An object of the present invention is to provide a rotating electric machine that can achieve both a longer life for the bearings and a smaller size for the rotating electric machine.

[0009] A rotating electric machine according to the present invention includes a rotor, a rotating shaft connected to the rotor and rotating together with the rotor, a bearing supporting the rotating shaft, a labyrinth seal installed on a side of the bearing, an earth brush for removing a shaft voltage generated in the rotating shaft, and a housing accommodating the rotor, the rotating shaft, the bearing, the labyrinth seal, and the earth brush. The labyrinth seal includes a fixed member fixed to the housing and a rotating member fixed to the rotating shaft and rotating together with the rotating shaft. The earth brush is installed on the rotating member.

[0010] According to the present invention, it is possible to provide a rotating electric machine that can achieve both a longer life for the bearings and a smaller size of the rotating electric machine.

[0011] FIG. 1 is a side view of a rotating electric machine according to a first embodiment of the present invention. FIG. 2 is a diagram showing the flow of a refrigerant flowing inside the rotating electric machine according to the first embodiment. FIG. 3 is a diagram showing an example of the configuration of earth brushes provided in a rotating electric machine according to a second embodiment of the present invention. FIG. 4 is a diagram showing an example of the arrangement of earth brushes provided in a rotating electric machine according to a third embodiment of the present invention, and is a diagram corresponding to the A-A cross section of the rotating electric machine shown in FIG. 1. FIG. 5 is a side view of a rotating electric machine according to a fourth embodiment of the present invention. FIG. 6 is a diagram for explaining earth brushes provided in a rotating electric machine according to the fourth embodiment. FIG. 7 is an enlarged view showing the periphery of a window portion in the rotating electric machine according to the fourth embodiment. FIG. 8 is a diagram schematically showing an example of the configuration of a dump truck provided with a rotating electric machine in a fifth embodiment of the present invention.

[0012] Hereinafter, a rotating electric machine according to an embodiment of the present invention will be described with reference to the drawings. The embodiment described below merely shows an example of an embodiment of the present invention, and is not intended to limit the present invention to the specific aspects described below. In the drawings used in this specification, the same or corresponding components are designated by the same reference numerals, and repeated description of these components may be omitted.

[0013] In the following description, the direction along the rotating shaft of the rotating electric machine is referred to as the axial direction, the rotation direction of the rotating shaft is referred to as the circumferential direction, and the radial direction of the rotating shaft is referred to as the radial direction. In the axial direction, the direction toward the inside of the rotating electric machine is referred to as the axial inner direction, and the direction toward the outside of the rotating electric machine is referred to as the axial outer direction. In the radial direction, the direction toward the inside of the rotating electric machine is referred to as the radial inner direction, and the direction toward the outside of the rotating electric machine is referred to as the radial outer direction.

[0014] A rotating electrical machine according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

[0015] 1 is a side view of a rotating electrical machine 100 according to this embodiment. The overall configuration of the rotating electrical machine 100 according to this embodiment will be described with reference to FIG.

[0016] The rotating electric machine 100 according to this embodiment includes a housing 1, a rotor 2, a stator 3, bearings 4, a rotating shaft 5, air holes 6, an air inlet 7, an exhaust port 8, a rear ventilation passage 9, earth brushes 10, a labyrinth seal 16, and a brush holder 13. The labyrinth seal 16 includes, as its constituent members, a fixed member 11 fixed to the housing 1 and a rotating member 12 that rotates together with the rotating shaft 5.

[0017] The rotating electric machine 100 is used as a generator or an electric motor. For example, the rotating electric machine 100 can be connected to an engine and used as a generator. In the following, as an example, the rotating electric machine 100 will be described as a generator connected to an engine.

[0018] The housing 1 is the enclosure of the rotating electrical machine 100 and includes an air inlet 7 and an exhaust port 8. The housing 1 accommodates a rotor 2, a stator 3, a bearing 4, a rotating shaft 5, earth brushes 10, a labyrinth seal 16, and a brush holder 13. The housing 1 also includes a ground (not shown).

[0019] The rotor 2 is made of laminated electromagnetic steel plates. The rotor 2 may be provided with permanent magnets, and the rotating electric machine 100 may be configured as a permanent magnet synchronous motor. The rotor 2 may also be provided with windings, and the rotating electric machine 100 may be configured as a wound-rotor synchronous motor. The rotor 2 may also be provided with a secondary conductor and a short-circuit ring, and the rotating electric machine 100 may be configured as an induction motor. The effects achieved by the rotating electric machine 100 according to this embodiment can be obtained regardless of the type of motor. The rotor 2 also has air holes 6, which are ventilation holes for cooling.

[0020] The stator 3 includes laminated electromagnetic steel plates and coils, is positioned with a gap (air gap) between it and the rotor 2, and is fixed to the housing 1. The stator 3 and the housing 1 are fixed to each other by a plurality of fixing parts provided at predetermined intervals in the circumferential direction. A rear ventilation passage 9 is provided between these fixing parts to allow the refrigerant to flow in the axial direction.

[0021] The bearing 4 is fixed to the housing 1 and supports the rotating shaft 5 so that the rotating shaft 5 rotates smoothly. The bearing 4 may be provided at one end or both ends of the rotating shaft 5. A labyrinth seal 16 is provided on the side (the inner side in the axial direction) of the bearing 4. In this embodiment, since the rotating electric machine 100 is a generator connected to an engine, the bearing 4 is provided at one end in the axial direction of the rotating electric machine 100. The bearing 4 may also be provided at both ends in the axial direction.

[0022] The rotating shaft 5 is connected to the rotor 2 and rotates together with the rotor 2. In this embodiment, since the rotating electric machine 100 is a generator connected to an engine, one end of the rotating shaft 5 is supported by the bearing 4 and the other end is supported by a bearing provided in the engine. The rotating shaft 5 may be supported by the bearing 4 at both ends.

[0023] The air holes 6 are provided in the rotor 2 and are flow paths for a coolant that cools the rotor 2 .

[0024] The air inlet 7 is an inlet for the refrigerant and is provided at one axial end of the housing 1. If the refrigerant contains dust and there is a risk of the interior of the rotating electrical machine 100 being contaminated, the air inlet 7 may be provided with a filter for removing dust.

[0025] The exhaust port 8 is provided at the other axial end of the housing 1 and serves as an outlet for the refrigerant. The exhaust port 8 may be provided with a filter or the like for collecting dust such as abrasion powder of the earth brush 10 generated inside the rotating electrical machine 100.

[0026] The rear ventilation passage 9 is provided in the stator 3 and is a flow path for a coolant that cools the stator 3 .

[0027] The earth brush 10 is a conductive member provided inside the housing 1 of the rotating electric machine 100 and attached to the rotating member 12 of the labyrinth seal 16. The earth brush 10 contacts the rotating member 12 to remove the shaft voltage generated on the rotating shaft 5 and suppress electrolytic corrosion of the bearing 4. As shown in FIG. 1 , for example, the earth brush 10 is provided radially outward of the rotating member 12 and contacts the radially outer portion of the rotating member 12. The earth brush 10 may also be provided axially inward of the rotating member 12 and contacts the axially inner portion of the rotating member 12. Note that although the rotating electric machine 100 includes one earth brush 10 in the configuration shown in FIG. 1 , it may also include multiple earth brushes 10 to improve the effect of removing the shaft voltage.

[0028] When the earth brush 10 comes into contact with the rotating member 12 of the labyrinth seal 16, it wears and generates wear debris.

[0029] The labyrinth seal 16 includes a fixed member 11 and a rotating member 12, and is installed on the side (on the inner side in the axial direction) of the bearing 4. In this embodiment, since the bearing 4 is installed at one end in the axial direction, the labyrinth seal 16 is also located at one end in the axial direction of the rotating electric machine 100.

[0030] Furthermore, the earth brush 10 is disposed so as to come into contact with the rotating member 12 of the labyrinth seal 16 , and is therefore located at one end in the axial direction of the rotating electrical machine 100 .

[0031] The fixed member 11 and the rotating member 12 of the labyrinth seal 16 are disk-shaped members with concave and convex portions. The labyrinth seal 16 has a labyrinth structure formed by combining the concave and convex portions of the fixed member 11 and the convex and convex portions of the rotating member 12, and prevents dust such as wear particles from the earth brush 10 from entering the inside of the bearing 4.

[0032] The concave-convex portions of the fixed member 11 and the rotating member 12 may have concave and convex portions extending in the axial direction, or may have concave and convex portions extending in the radial direction. In the example shown in Fig. 1, the concave-convex portions of the fixed member 11 and the rotating member 12 have concave and convex portions extending in the axial direction. Furthermore, the number of concave and convex portions in the concave-convex portions of the fixed member 11 and the rotating member 12 is not limited to the number shown in Fig. 1 and may be any number.

[0033] The fixed member 11 is fixed to the housing 1. The rotating member 12 is fixed to the rotating shaft 5. Therefore, the rotating member 12 has the same center of rotation as the rotating shaft 5 and rotates together with the rotating shaft 5. The rotating member 12 is made of a conductive material. Therefore, the earth brush 10 is electrically connected to the rotating shaft 5 via the rotating member 12.

[0034] The brush holder 13 is a member that fixes the earth brush 10 to the housing 1, and is fixed to the housing 1. The brush holder 13 electrically connects the earth brush 10 to the housing 1. Since the earth brush 10 is fixed to the brush holder 13, it does not rotate even when the rotating shaft 5 rotates.

[0035] In the rotating electric machine 100 according to this embodiment, with the above-described configuration, the rotating shaft 5 is electrically connected to the rotating member 12 of the labyrinth seal 16, the rotating member 12 is electrically connected to the earth brush 10, the earth brush 10 is electrically connected to the brush holder 13, and the brush holder 13 is electrically connected to the housing 1. Therefore, the shaft voltage generated in the rotating shaft 5 is transmitted to the housing 1 via the rotating member 12, earth brush 10, and brush holder 13, without passing through the bearing 4. The shaft voltage transmitted to the housing 1 is neutralized by the earth ground provided to the housing 1.

[0036] The flow of the refrigerant inside the rotating electrical machine 100 will be described with reference to FIG.

[0037] 2 is a diagram showing the flow of the coolant flowing inside the rotating electrical machine 100 according to this embodiment. In FIG. 2, the flow of the coolant is indicated by arrows 17.

[0038] The refrigerant flows into the interior of the rotating electric machine 100 through the air inlet 7 and cools the rotor 2 and the stator 3. The refrigerant that has flowed into the interior of the rotating electric machine 100 passes through the air holes 6, the gap between the rotor 2 and the stator 3, and the rear ventilation passage 9, and is discharged to the outside of the rotating electric machine 100 through the exhaust port 8. Inside the rotating electric machine 100, the refrigerant flows toward the rotor 2 and the stator 3, with the earth brush 10 on the windward side. It is preferable that the earth brush 10 be located axially downwind of the bearing 4 (i.e., axially inward).

[0039] In the rotating electric machine 100 according to this embodiment, the labyrinth seal 16 comprising the fixed member 11 and the rotating member 12 can prevent foreign matter such as wear debris from the earth brush 10 from entering the bearing 4. Furthermore, in the rotating electric machine 100 according to this embodiment, the earth brush 10 is located downwind of the bearing 4, and the refrigerant flows from the earth brush 10 toward the rotor 2 and stator 3, so wear debris from the earth brush 10 is less likely to enter the bearing 4. Therefore, in the rotating electric machine 100 according to this embodiment, the life of the bearing 4 can be extended.

[0040] Furthermore, in the rotating electric machine 100 according to this embodiment, the earth brush 10 is installed on the rotating member 12 of the labyrinth seal 16, and the earth brush 10 is provided on the radially outer side or the axially inner side of the rotating member 12. This eliminates the need for the space required in conventional rotating electric machines for bringing the earth brush 10 into contact with the rotating shaft 5, thereby shortening the axial length and making it possible to reduce the size.

[0041] The rotating electrical machine 100 according to this embodiment has the configuration described above, and can achieve both a longer life for the bearings 4 and a smaller size for the rotating electrical machine 100 .

[0042] Second Embodiment A rotating electrical machine 100 according to a second embodiment of the present invention will be described with reference to Fig. 3. In this embodiment, an example of the configuration of the earth brush 10 provided in the rotating electrical machine 100 will be described.

[0043] FIG. 3 is a diagram showing an example of the configuration of the earth brush 10 provided in the rotating electrical machine 100 according to this embodiment.

[0044] The earth brush 10 includes a brush head 101 that contacts the rotating member 12 of the labyrinth seal 16, a conductive member 102 with a spring function, and a fastening portion 103 that is fixed to the brush holder 13. The conductive member 102 is a member that presses the brush head 101 against the rotating member 12 by its spring function.

[0045] The effects achieved by the rotating electrical machine 100 according to this embodiment will be described.

[0046] In the rotating electric machine 100 according to this embodiment, the earth brush 10 includes the conductive member 102 having a spring function, so that even if the brush head 101 wears due to sliding against the rotating member 12, the conductive member 102 can provide a force pressing the brush head 101 against the rotating member 12. Therefore, in the rotating electric machine 100 according to this embodiment, the state of contact between the earth brush 10 and the rotating member 12 of the labyrinth seal 16 can be maintained good over a long period of time, and it is possible to neutralize the rotating shaft 5 and suppress electrolytic corrosion of the bearing 4 over a long period of time. Therefore, in the rotating electric machine 100 according to this embodiment, the life of the bearing 4 can be further extended.

[0047] Third Embodiment A rotating electrical machine 100 according to a third embodiment of the present invention will be described with reference to Fig. 4. In this embodiment, an example of the arrangement of the earth brushes 10 provided in the rotating electrical machine 100 will be described.

[0048] Fig. 4 is a diagram showing an example of the arrangement of the earth brushes 10 provided in the rotating electric machine 100 according to this embodiment, and corresponds to a view of the AA cross section of the rotating electric machine 100 shown in Fig. 1 as viewed along the axial direction. Fig. 4 shows the rotating shaft 5, the rotating member 12 of the labyrinth seal 16, and the earth brushes 10.

[0049] In Fig. 4, a dashed line 18 extending horizontally indicates a horizontal line passing through the center of the rotary shaft 5. In Fig. 4, the concave portions of the concave and convex portions of the rotary member 12 are indicated by diagonal lines.

[0050] In the rotating electric machine 100 according to this embodiment, the earth brush 10 is located below the center of the rotating shaft 5 and is disposed at the bottom of the rotating electric machine 100. The position of the earth brush 10 shown in FIG. 4 is merely an example, and the earth brush 10 can be disposed at any position below the center of the rotating shaft 5.

[0051] The effects achieved by the rotating electrical machine 100 according to this embodiment will be described.

[0052] The earth brush 10 comes into contact with the rotating member 12 of the labyrinth seal 16 and wears, generating wear debris. As described in the first embodiment, the labyrinth seal 16 has a labyrinth structure formed by the fixed member 11 and the rotating member 12, so that the bearing 4 is prevented from receiving dust such as wear debris from the earth brush 10. However, if dust does enter the inside of the bearing 4, there is a concern that the life of the bearing 4 may be shortened.

[0053] In the rotating electric machine 100 according to this embodiment, the earth brush 10 is located below the center of the rotating shaft 5, so that wear debris from the earth brush 10 falls from a position below the center of the rotating shaft 5 to the bottom of the rotating electric machine 100. That is, in this embodiment, the flying distance of wear debris blown by the refrigerant can be made shorter than when the earth brush 10 is located above the center of the rotating shaft 5. Therefore, in the rotating electric machine 100 according to this embodiment, the amount of wear debris that penetrates into the bearing 4 can be reduced, and the life of the bearing 4 can be further extended.

[0054] The vertical position of the earth brush 10 may be determined according to the flow rate of the refrigerant so as to prevent wear particles from the earth brush 10 from entering the inside of the bearing 4. For example, when the flow rate of the refrigerant is high (when the refrigerant air speed is high), the wear particles are blown away by the refrigerant to a position far from the bearing 4 (the wear particles fly a long distance), so the vertical position of the earth brush 10 may be close to the center of the rotating shaft 5 (a high position). Also, when the flow rate of the refrigerant is low (when the refrigerant air speed is low), the wear particles fall near the bearing 4 (the wear particles fly a short distance), so the vertical position of the earth brush 10 is preferably far from the center of the rotating shaft 5 (a low position).

[0055] A rotating electric machine 100 according to a fourth embodiment of the present invention will be described with reference to Figs. 5 to 7. In this embodiment, an example of a window portion provided in the rotating electric machine 100 will be described. In the following description, differences between the rotating electric machine 100 according to this embodiment and the rotating electric machine 100 according to the first embodiment will be mainly described.

[0056] FIG. 5 is a side view of the rotating electrical machine 100 according to this embodiment.

[0057] In the rotating electric machine 100 according to this embodiment, the housing 1 includes a window 14. The window 14 is, for example, an inspection window, and includes an opening 14a provided in the housing 1 and a lid 14b provided on the opening 14a. The lid 14b is openable and closable. The lid 14b is normally closed to prevent dust from entering the interior of the rotating electric machine 100 from the outside, and is opened to expose the window 14 in certain cases, such as when inspecting the interior of the rotating electric machine 100.

[0058] FIG. 6 is a diagram for explaining the earth brush 10 provided in the rotating electrical machine 100 according to this embodiment.

[0059] In the rotating electric machine 100 according to this embodiment, the brush holder 13 includes a fastener 15 that fixes the earth brush 10 to the brush holder 13. The earth brush 10 is fastened to the brush holder 13 by the fastener 15. Any member (e.g., a fastening member such as a bolt) can be used as the fastener 15 as long as it is a member that fixes the earth brush 10 to the brush holder 13.

[0060] 7 is an enlarged view of the periphery of the window 14 in the rotating electrical machine 100 according to this embodiment. A cover 14b of the window 14 is provided with a handle 14c. An operator can open the cover 14b using the handle 14c.

[0061] As described in the first embodiment, the brush holder 13 is fixed to the housing 1. The fasteners 15 that fasten the earth brushes 10 to the brush holder 13 are arranged to face the openings 14a of the window portion 14. That is, the fasteners 15 are arranged in positions that allow them to be seen from outside the housing 1 through the openings 14a of the window portion 14. When the fasteners 15 are arranged to face the openings 14a of the window portion 14, workers can easily perform work on the fasteners 15 through the window portion 14.

[0062] The effects achieved by the rotating electrical machine 100 according to this embodiment will be described.

[0063] In the rotating electric machine 100 according to this embodiment, the housing 1 is provided with the window portion 14 , so that workers can easily inspect the inside of the rotating electric machine 100 without dismantling the rotating electric machine 100 .

[0064] Furthermore, the earth brush 10 is subject to particularly rapid wear among the components of the rotating electric machine 100, and therefore requires more frequent inspection than other components. In the rotating electric machine 100 according to this embodiment, the fastener 15 for fixing the earth brush 10 is disposed so as to face the opening 14a of the window portion 14, so that an operator can easily remove the earth brush 10 from the brush holder 13 and attach it to the brush holder 13.

[0065] Therefore, in the rotating electric machine 100 according to this embodiment, inspection costs can be reduced by reducing the labor required for inspecting the earth brushes 10 and shortening the inspection time, and it is also possible to increase the frequency of inspection and replacement work on the earth brushes 10, thereby further extending the life of the bearings 4.

[0066] A fifth embodiment of the present invention will be described with reference to Fig. 8. In this embodiment, an example of a vehicle equipped with the rotating electric machine 100 according to any one of the first to fourth embodiments will be described. In this embodiment, an example will be described in which the vehicle equipped with the rotating electric machine 100 is a dump truck.

[0067] FIG. 8 is a diagram schematically illustrating an example of the configuration of a dump truck 1000 equipped with the rotating electric machine 100.

[0068] The dump truck 1000 includes a rotating electric machine 100, an engine 200, and a hydraulic pump 300. The rotating shaft 5 of the rotating electric machine 100 and the rotating shaft of the engine 200 are coupled to each other. The rotating shaft 5 of the rotating electric machine 100 and the rotating shaft of the hydraulic pump 300 are also coupled to each other. With this configuration, the driving force generated by the engine 200 is transmitted to the rotating electric machine 100 and the hydraulic pump 300. The rotating electric machine 100 converts the driving force of the engine 200 into electric power. The hydraulic pump 300 converts the driving force of the engine 200 into power for lifting the bed of the dump truck 1000.

[0069] In this embodiment, the dump truck 1000 is equipped with the rotating electric machine 100 according to any one of Embodiments 1 to 4, i.e., the long-life and small-sized rotating electric machine 100. Therefore, in this embodiment, the life of the dump truck 1000 itself can be extended, and the functionality of the dump truck 1000 can be improved by, for example, expanding the bed space.

[0070] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments that include all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations.

[0071] 1...housing, 2...rotor, 3...stator, 4...bearing, 5...rotating shaft, 6...air hole, 7...air inlet, 8...exhaust port, 9...rear ventilation duct, 10...earth brush, 11...fixing member, 12...rotating member, 13...brush holder, 14...window portion, 14a...opening, 14b...lid, 14c...handle, 15...fastener, 16...labyrinth seal, 17...arrow indicating refrigerant flow, 18...dashed line indicating horizontal line passing through the center of the rotating shaft, 100...rotating electric machine, 101...brush head, 102...conductive member, 103...fastening portion, 200...engine, 300...hydraulic pump, 1000...dump truck

Claims

1. A rotating electric machine comprising: a rotor; a rotating shaft connected to the rotor and rotating together with the rotor; a bearing supporting the rotating shaft; a labyrinth seal installed to the side of the bearing; an earth brush for removing shaft voltage generated in the rotating shaft; and a housing accommodating the rotor, the rotating shaft, the bearing, the labyrinth seal, and the earth brush; wherein the labyrinth seal comprises a fixed member fixed to the housing and a rotating member fixed to the rotating shaft and rotating together with the rotating shaft, and the earth brush is installed on the rotating member.

2. The rotating electric machine according to claim 1, wherein the rotating member is disk-shaped and has a common center of rotation with the rotating shaft.

3. A rotating electric machine as claimed in claim 1, wherein the bearing and the earth brush are located at one end in the axial direction along the rotating shaft, and the housing has an air inlet at the one end and an exhaust port at the other end in the axial direction.

4. A rotating electric machine according to claim 1, wherein the earth brush comprises a brush head that contacts the rotating member, and a conductive member having a spring function.

5. The rotating electric machine according to claim 1, wherein the earth brush is located below the center of the rotating shaft.

6. The rotating electric machine according to claim 1, wherein the housing is provided with a window portion having an opening and an openable / closable lid provided at the opening.

7. A rotating electric machine according to claim 6, further comprising a brush holder fixed to said housing for fixing said earth brush to said housing, said brush holder being provided with a fastener for fixing said earth brush to said brush holder, said fastener being positioned so as to face said opening of said window portion.

8. A rotating electric machine according to claim 1, wherein the radial direction of the rotating shaft is the radial direction, the direction along the rotating shaft is the axial direction, and the earth brush is provided on the outside of the rotating member in the radial direction or on the inside of the axial direction.

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