Electric motors, blowers and ventilation fans

Abstract

This electric motor has: a rotating shaft; a rotor fixed to the rotating shaft; a stator having a stator core that surrounds the rotor from the outer side in the radial direction of the rotor, and a coil wound on the stator core; a bearing for supporting the rotating shaft; and a conduction member for enabling conduction between the stator core and an outer race of the bearing. The rotor has a facing part that is formed from a bond magnet and that faces the stator core in the radial direction, and an insulated linking part that links the facing part and the rotating shaft. The length L1 of the facing part in the axial direction of the rotating shaft is equal to or less than the length L2 of the stator core in the axial direction.

Description

[Technical field]

[0001] The present disclosure relates to electric motors, blowers and ventilation fans. [Background technology]

[0002] In electric motors in which the stator is held in a metal housing, the housing is generally grounded. Meanwhile, the rotating shaft of the electric motor is supported by a bearing. The inner ring of the bearing is fixed to the rotating shaft, and the outer ring is fixed to the housing (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-5307 A (see paragraph 0018) Summary of the Invention [Problem to be solved by the invention]

[0004] Of the inner and outer rings of the bearing, only the outer ring is grounded via the housing, so there is a possibility that a potential difference may occur between the inner and outer rings. If this potential difference becomes large, an electric discharge occurs between the inner and outer rings, causing unevenness on the raceway surface that comes into contact with the rolling elements. This phenomenon is called electrolytic corrosion. When electrolytic corrosion occurs, vibrations and noise are generated when the rolling elements run on the raceway surface.

[0005] The present disclosure has been made to solve the above problems, and aims to suppress the occurrence of electrolytic corrosion. [Means for solving the problem]

[0006] The electric motor of the present disclosure includes a rotating shaft, a rotor fixed to the rotating shaft, a stator having a stator core surrounding the rotor from the outside in the radial direction and a coil wound around the stator core, a bearing having an inner ring and an outer ring, the inner ring being in contact with the rotating shaft, and a conductive member that provides electrical conductivity between the stator core and the outer ring and is grounded. A magnet assembly having a first magnet portion and a second magnet portion disposed on an outer periphery of the first magnet portion, The rotor has an opposing portion that faces the stator core in the radial direction, and an insulating connecting portion that connects the opposing portion to the rotating shaft. The first magnet portion and the connecting portion are formed of a ferrite bonded magnet, and the second magnet portion is formed of a rare earth bonded magnet. The axial length L1 of the rotating shaft of the opposing portion is equal to or less than the axial length L2 of the stator core. The electric motor of the present disclosure includes a rotating shaft, a rotor fixed to the rotating shaft, a stator core surrounding the rotor from the outside in the radial direction, a stator having a coil wound around the stator core, a bearing having an inner ring and an outer ring, the inner ring being in contact with the rotating shaft, and a conductive member that provides electrical conductivity between the stator core and the outer ring and is grounded. The rotor includes a ferrite bonded magnet that faces the stator core in the radial direction, and a connecting portion that connects the ferrite bonded magnet to the rotating shaft and is made of a material with a lower dielectric constant than the ferrite bonded magnet. The axial length L1 of the ferrite bonded magnet of the rotating shaft is equal to or less than the axial length L2 of the stator core. Effect of the Invention

[0007] According to the present disclosure, since the axial length L1 of the opposing portion formed of the bonded magnet is equal to or less than the axial length L2 of the stator core, it is possible to reduce the area of ​​high dielectric constant located between the coil end of the coil and the rotating shaft. As a result, the potential difference between the inner and outer rings of the bearing can be reduced, and the occurrence of electrolytic corrosion can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a vertical cross-sectional view showing an electric motor according to a first embodiment. [Diagram 2] 2 is a cross-sectional view of the electric motor taken along line II-II shown in FIG. 1. [Diagram 3] 1 is a cross-sectional view showing a rotor according to a first embodiment. [Figure 4] 1 is a partially cutaway perspective view showing a rotor according to a first embodiment. [Diagram 5] 1 is a partially cutaway perspective view showing a bearing according to a first embodiment. [Figure 6] 1 is a partially cutaway perspective view showing an outer ring and an inner ring of a bearing according to a first embodiment of the present invention. [Figure 7] FIG. 2 is a vertical sectional view showing the electric motor of Comparative Example 1. [Figure 8] 1A is a longitudinal sectional view showing an electric motor of Comparative Example 2, and FIG. 1B is a partially cutaway perspective view showing a rotor of Comparative Example 2. [Figure 9] 11 is a graph showing a comparison of bearing voltage ratios between the first embodiment and the second comparative example. [Figure 10] FIG. 11 is a vertical cross-sectional view showing an electric motor according to a first modified example. [Figure 11] FIG. 11 is a partially cutaway perspective view showing a rotor of a first modified example. [Figure 12] 10 is a graph showing the relationship between the length of the opposing portion of the rotor and the bearing voltage ratio in the first embodiment and the first modified example. [Figure 13] FIG. 11 is a diagram showing a rotor according to a second modified example. [Figure 14] FIG. 11 is a vertical cross-sectional view showing an electric motor according to a second embodiment. [Figure 15] FIG. 11 is a partially cutaway perspective view showing a rotor according to a second embodiment. [Figure 16] 10 is a graph showing the relationship between the length of an opposing portion of a rotor in the second embodiment and a bearing voltage ratio. [Figure 17] FIG. 11 is a vertical cross-sectional view showing an electric motor according to a third embodiment. [Figure 18] FIG. 11 is a vertical sectional view showing an electric motor of Comparative Example 3. [Figure 19] 13 is a graph showing the relationship between the length of the opposing portion of the rotor in Comparative Example 3 and the bearing voltage ratio. [Figure 20] FIG. 11 is a vertical cross-sectional view showing a ventilation fan according to a fourth embodiment. [Figure 21] FIG. 21 is a perspective view showing the ventilation fan shown in FIG. 20. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Embodiment 1 <Overall configuration of electric motor> The electric motor of embodiment 1 will be described below. Fig. 1 is a vertical cross-sectional view showing an electric motor 1 of embodiment 1. The electric motor 1 is a synchronous motor, and is used, for example, in a blower 9 of a ventilation fan (Fig. 20).

[0010] The electric motor 1 includes a rotating shaft 10, a rotor 2 fixed to the rotating shaft 10, a stator 5 surrounding the rotor 2, a housing 6 that accommodates the stator 5, and bearings 11 and 12 that support the rotating shaft 10. A central axis Ax of the rotating shaft 10 defines the center of rotation of the rotor 2.

[0011] In the following, the direction of the central axis Ax is referred to as the "axial direction." The radial direction centered on the central axis Ax is referred to as the "radial direction." The circumferential direction centered on the central axis Ax is referred to as the "circumferential direction." A cross-sectional view taken on a plane parallel to the central axis Ax is referred to as a longitudinal cross-sectional view, and a cross-sectional view taken on a plane perpendicular to the central axis Ax is referred to as a transverse cross-sectional view.

[0012] The housing 6 has a first frame 61 and a second frame 62 in the axial direction. Both the first frame 61 and the second frame 62 are formed of metal, more specifically, a steel plate.

[0013] The first frame 61 has a cylindrical peripheral wall portion 61a centered on the central axis Ax, and a bottom portion 61b formed at one axial end of the peripheral wall portion 61a. An annular flange portion 61e is formed at the other axial end of the peripheral wall portion 61a.

[0014] The second frame 62 has a cylindrical peripheral wall portion 62a centered on the central axis Ax, and a bottom portion 62b formed at one axial end of the peripheral wall portion 62a. An annular flange portion 62e is formed at the other axial end of the peripheral wall portion 62a.

[0015] The first frame 61 and the second frame 62 are assembled so that the flanges 61e, 62e are butted against each other. The flanges 61e, 62e of the first frame 61 and the second frame 62 are fixed to each other by adhesion, fastening, or welding. The housing 6 consisting of the first frame 61 and the second frame 62 is grounded.

[0016] A bearing holding portion 61c that holds the bearing 11 is formed on the bottom portion 61b of the first frame 61. The bearing holding portion 61c is formed, for example, by deforming the center portion of the bottom portion 61b into a cylindrical shape. The bearing 11 is fitted into the bearing holding portion 61c.

[0017] A bearing holding portion 62c that holds the bearing 12 is formed on the bottom portion 62b of the second frame 62. The bearing holding portion 62c is formed, for example, by deforming the center portion of the bottom portion 62b into a cylindrical shape. The bearing 12 is fitted into the bearing holding portion 62c.

[0018] The bearings 11 and 12 rotatably support the rotating shaft 10. The bearing 11 is positioned in the axial direction by abutment with an inner cylindrical portion 22 of a ferrite bond magnet 20 (described later) of the rotor 2. The bearing 12 is positioned in the axial direction by an e-ring or the like attached to the rotating shaft 10.

[0019] The rotating shaft 10 protrudes to the outside from an opening formed in the bottom 61b of the first frame 61. For example, a blade portion 90 (FIG. 20) is attached to the tip of the rotating shaft 10. Therefore, the protruding side of the rotating shaft 10 is called the load side, and the opposite side is called the anti-load side.

[0020] <Stator configuration> Fig. 2 is a cross-sectional view of the electric motor 1 taken along line II-II shown in Fig. 1. As shown in Fig. 2, the stator 5 has a stator core 50 and a coil 55 wound around the stator core 50. The stator core 50 has an annular yoke 51 centered on the central axis Ax, and a plurality of teeth 52 extending radially inward from the yoke 51. The outer peripheral surface of the yoke 51 is fitted into the inner peripheral surface of the housing 6.

[0021] The teeth 52 are arranged at equal intervals in the circumferential direction. The tips of the teeth 52 face the outer circumferential surface of the rotor 2 via an air gap. The number of the teeth 52 is 12 here, but is not limited to 12. A slot 53 is formed between adjacent teeth 52.

[0022] Coil 55 is made of, for example, a magnet wire. Coil 55 is wound around teeth 52 via insulating parts 54 (FIG. 1) and accommodated in slots 53. Parts of coil 55 that do not fit in slots 53 and extend on the axial end faces of stator core 50 are referred to as coil ends 55a (FIG. 1).

[0023] 1 is made of a resin such as PPS (polyphenylene sulfide), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), etc. Note that the insulating portion 54 is omitted in FIG.

[0024] A circuit board 45 is disposed on the anti-load side of the stator 5. The circuit board 45 is supported by a pin (not shown) fixed to the insulating portion 54. A drive circuit such as an inverter for driving the electric motor 1 is mounted on the circuit board 45. The circuit board 45 may be disposed outside the housing 6.

[0025] <Rotor configuration> 3 is a cross-sectional view showing the rotor 2. The rotor 2 has a ferrite bonded magnet 20 as a first permanent magnet fixed to the rotating shaft 10 (FIG. 2), and a rare earth bonded magnet 30 as a second permanent magnet provided on the outer periphery of the ferrite bonded magnet 20. The ferrite bonded magnet 20 and the rare earth bonded magnet 30 are molded integrally with the rotating shaft 10.

[0026] The ferrite bonded magnet 20 contains magnetic powder of a ferrite magnet and resin. The resin contained in the ferrite bonded magnet 20 is, for example, polyamide (nylon), but it may also be PPS (Poly Phenylene Sulfide) or the like. The magnetic powder of the ferrite magnet is insulating, and the resin surrounding the magnetic powder is also insulating, so the ferrite bonded magnet 20 as a whole is insulating.

[0027] The ferrite bonded magnet 20 is oriented so that it has four S poles and four N poles alternating in the circumferential direction. The number of poles of the ferrite bonded magnet 20 is eight. However, the number of poles of the ferrite bonded magnet 20 is not limited to eight, and may be two or more.

[0028] The rare earth bonded magnet 30 includes magnetic powder of a rare earth magnet and a resin. The rare earth magnet is, for example, a neodymium magnet including neodymium (Nd), iron (Fe) and boron (B), or a samarium iron nitrogen magnet including samarium (Sm), iron (Fe) and nitrogen (N).

[0029] The resin contained in the rare earth bonded magnet is, for example, polyamide (nylon), but it may also be PPS, etc. The magnetic powder of the rare earth magnet is conductive, but the resin surrounding the magnetic powder is insulating, so the rare earth bonded magnet 30 as a whole is insulating.

[0030] Similar to the ferrite bonded magnet 20, the rare earth bonded magnet 30 is oriented to have four south poles and four north poles alternating in the circumferential direction. In other words, the rare earth bonded magnet 30 has eight poles. However, the number of poles of the rare earth bonded magnet 30 is not limited to eight, and may be the same as the number of poles of the ferrite bonded magnet 20.

[0031] The magnetic force of the ferrite bonded magnet 20 is different from that of the rare earth bonded magnet 30. Specifically, the magnetic force of the rare earth bonded magnet 30 is stronger than that of the ferrite bonded magnet 20.

[0032] 4 is a partially cutaway perspective view showing the rotor 2. The ferrite bond magnet 20 has an annular portion 21 having an annular shape centered on the central axis Ax, an inner cylindrical portion 22 fixed to the rotating shaft 10 (FIG. 1), and a connecting portion 23 connecting the annular portion 21 and the inner cylindrical portion 22.

[0033] The annular portion 21 has a length L1 in the axial direction, the inner cylindrical portion 22 has a length L3 in the axial direction, and the connecting portion 23It has an axial length L4. In the example shown in FIG. 4, the lengths L1 and L3 are in the relationship of L1 < L3, and the inner cylindrical portion 22 protrudes from the annular portion 21 to one side in the axial direction (here, the bearing 11 side), positioning the bearing 11 in the axial direction.

[0034] However, when positioning the bearing 11 with an e-ring or the like, it is also possible to set L1 ≥ L3 so that the inner cylindrical portion 22 does not protrude from the annular portion 21. On the other hand, the lengths L1 and L4 are in the relationship of L1 > L4, and the connecting portion 23 is accommodated inside the annular portion 21 in the axial direction.

[0035] A rare earth bonded magnet 30 is fixed to the outer peripheral surface 20b of the ferrite bonded magnet 20, that is, the outer peripheral surface of the annular portion 21. A rotating shaft 10 is fixed to the inner peripheral surface 20a of the ferrite bonded magnet 20, that is, the inner peripheral surface of the inner cylindrical portion 22.

[0036] The rare earth bonded magnet 30 is entirely formed in an annular shape. The inner peripheral surface 30a of the rare earth bonded magnet 30 is fixed to the outer peripheral surface 20b of the ferrite bonded magnet 20. The outer peripheral surface 30b of the rare earth bonded magnet 30 faces the teeth 52 (FIG. 2) of the stator 5 through an air gap.

[0037] The axial length L1 of the rare earth bonded magnet 30 is the same as the axial length L1 of the opposing portion 25 of the ferrite bonded magnet 20.

[0038] The annular portion 21 of the ferrite bonded magnet 20 and the rare earth bonded magnet 30 together are referred to as the opposing portion 25. The opposing portion 25 faces the stator core 50 through an air gap in the radial direction. The axial length of the opposing portion 25 is the above-mentioned length L1.

[0039] Among the annular portion 21 and the rare earth bonded magnet 30 that constitute the opposing portion 25, the annular portion 21 is also referred to as the first magnet portion, and the rare earth bonded magnet 30 is also referred to as the second magnet portion. The inner cylindrical portion 22 and the connecting portion 23 of the ferrite bonded magnet 20 constitute a connecting portion located between the opposing portion 25 and the rotating shaft 10.

[0040] The ferrite bonded magnet 20 and the rare earth bonded magnet 30 are molded integrally with the rotating shaft 10 by insert molding using an injection molding machine.

[0041] Specifically, the rotating shaft 10 is inserted into a first mold, and molten ferrite bonded magnet material is filled therein to mold the ferrite bonded magnet 20 integrally with the rotating shaft 10. By applying a polar anisotropic magnetic field during molding, the ferrite bonded magnet 20 is oriented so as to have the magnetic poles shown in FIG.

[0042] Next, the rotating shaft 10 and the ferrite bonded magnet 20 are placed in a second mold, and molten rare earth bonded magnet material is filled therein to form the rare earth bonded magnet 30 on the outer peripheral surface 20b of the ferrite bonded magnet 20. By applying a polar anisotropic magnetic field during molding, the rare earth bonded magnet 30 is oriented so as to have the magnetic poles shown in FIG.

[0043] Since the rotating shaft 10, the ferrite bonded magnet 20, and the rare earth bonded magnet 30 are molded as a single unit, they are firmly integrated, and the manufacturing costs are reduced.

[0044] 5 is a partially cutaway perspective view showing the bearing 11. The bearing 11 has an inner ring 11a fixed to the rotating shaft 10, an outer ring 11b fixed to the housing 6, and a plurality of rolling elements 11c provided between the inner ring 11a and the outer ring 11b.

[0045] The rolling elements 11c are, for example, balls. The inner ring 11a, the outer ring 11b, and the rolling elements 11c are all made of metal. Shield plates 11d are provided on both axial sides of the inner ring 11a and the outer ring 11b.

[0046] 6 is a partially cutaway perspective view showing the inner ring 11a and the outer ring 11b of the bearing 11. A raceway surface 11e for guiding the rolling elements 11c is formed along the outer periphery of the inner ring 11a. A raceway surface 11f for guiding the rolling elements 11c is formed along the inner periphery of the outer ring 11b.

[0047] Grease is applied between the raceway surfaces 11e, 11f and the rolling elements 11c for lubrication. A retainer (not shown) is disposed between the inner ring 11a and the outer ring 11b to keep the circumferential spacing of the rolling elements 11c constant.

[0048] 5 and 6 show the configuration of the load side bearing 11, but the anti-load side bearing 12 (FIG. 1) also has a similar configuration.

[0049] The outer rings 11b, 12b of the bearings 11, 12 are in contact with the housing 6 and therefore have the same potential as the stator core 50 fitted into the housing 6. The housing 6 corresponds to a conductive member that provides electrical continuity between the outer rings 11b, 12b of the bearings 11, 12 and the stator core 50.

[0050] <effect> Next, the operation of the first embodiment will be described in comparison with a first comparative example. FIG. 7 shows an electric motor 1E of the first comparative example. Longitudinal section 1 is a diagram showing a rotor 2E of Comparative Example 1, which is entirely made up of ferrite bonded magnets 20 and does not have rare earth bonded magnets.

[0051] Similar to the first embodiment, the ferrite bonded magnet 20 has an annular portion 21, an inner cylindrical portion 22, and a connecting portion 23. The annular portion 21 of the ferrite bonded magnet 20 constitutes a facing portion 25 that faces the stator core 50. The axial length L1 of the facing portion 25 is longer than the axial length L2 of the stator core 50 (L1>L2).

[0052] In Comparative Example 1, opposing portion 25 of rotor 2E protrudes on both axial sides from stator core 50. Therefore, coil ends 55a of coils 55 of stator 5 face opposing portion 25 of rotor 2E in the radial direction.

[0053] As described above, the ferrite bonded magnet 20 contains magnetic powder of ferrite magnet and resin such as polyamide. The relative dielectric constant of polyamide is generally 3 to 4, but the relative dielectric constant of the ferrite bonded magnet 20 is 40 to 200 because it contains magnetic powder.

[0054] In the electric motor 1E of the comparative example, between the coil end 55a of the coil 55 and the rotating shaft 10, the annular portion 21 and the inner cylindrical portion 22 of the ferrite bonded magnet 20 having a high dielectric constant are present.

[0055] 5 and 6, when the rotating shaft 10 rotates, the inner ring 11a rotates together with the rotating shaft 10, and the rolling elements 11c also rotate. A thin film of grease is formed between the inner ring 11a and the rolling elements 11c, and between the outer ring 11b and the rolling elements 11c. The formation of the thin film of grease electrically insulates the inner ring 11a, the outer ring 11b, and the rolling elements 11c.

[0056] The housing 6 to which the outer ring 11b of the bearing 11 is fixed is grounded, but the rotating shaft 10 to which the inner ring 11a is fixed is not grounded. A potential difference is generated between the inner ring 11a and the outer ring 11b due to the potential of the rotating shaft 10. When this potential difference exceeds the dielectric breakdown voltage of the thin film of grease, a discharge occurs between the inner ring 11a and the outer ring 11b.

[0057] The phenomenon in which the energy of the discharge causes unevenness on the raceway surfaces 11e, 11f of the inner ring 11a and the outer ring 11b is called electrolytic corrosion. When unevenness occurs on the raceway surfaces 11e, 11f, vibrations and noise are generated when the rolling elements 11c run on the raceway surfaces 11e, 11f. Although the load side bearing 11 has been described here, the same can be said for the non-load side bearing 12 (Fig. 1).

[0058] Since the housing 6 is grounded, the potential of the stator core 50 and the outer rings 11b, 12b in contact with the housing 6 is at the ground potential (GND). Meanwhile, power is supplied to the coil 55 wound around the stator core 50 via the insulating part 54, so a potential difference occurs between the coil 55 and the stator core 50, etc. This creates a potential distribution in the internal space of the electric motor 1E, and a potential is generated on the rotating shaft 10.

[0059] The potential of the rotating shaft 10 depends on the capacitance between the stator core 50 and the rotating shaft 10, the capacitance between the coil end 55a and the rotating shaft 10, and the capacitance between the inner rings 11a, 12a and the outer rings 11b, 12b of the bearings 11, 12.

[0060] Capacitance C is expressed as C=ε×S / d, where d is the distance between two opposing conductors, S is the opposing area, and ε is the dielectric constant of the material between the conductors.

[0061] As described above, in the electric motor 1E of Comparative Example 1 (FIG. 7), the annular portion 21 and inner cylindrical portion 22 of the ferrite bonded magnet 20 are present between the coil end 55a of the coil 55 and the rotating shaft 10. In other words, there are many parts with high dielectric constant between the coil end 55a and the rotating shaft 10. Therefore, the electrostatic capacitance between the coil end 55a and the rotating shaft 10 increases, and the potential of the rotating shaft 10 increases. As a result, a potential difference between the inner rings 11a, 12a and the outer rings 11b, 12b, i.e., a bearing voltage, is generated.

[0062] Patent Document 1 also discloses circumferentially arranging multiple axially long conductive layers on the radially inner side of the coil end (see paragraph 0020 of Patent Document 1). In this case, it is considered possible to lower the electric potential of the shaft by conducting the conductive layers to the stator core, due to a shielding effect. However, the number of parts increases, which increases manufacturing costs, and there is a possibility that parts (i.e., conductive layers) may fall off during operation, or efficiency may decrease due to eddy currents generated on the surface of the parts.

[0063] 1, the axial length L1 of opposing portion 25 of rotor 2 (i.e., annular portion 21 of ferrite bonded magnet 20 and rare earth bonded magnet 30) is equal to or less than axial length L2 of stator core 50 (L1≦L2). In other words, opposing portion 25 of rotor 2 does not protrude from stator core 50 in the axial direction.

[0064] Because of this configuration, the coil end 55a of the stator 5 does not face the opposing portion 25 of the rotor in the radial direction. As a result, the only high dielectric constant portion located between the coil end 55a and the rotating shaft 10 in the radial direction is the inner cylinder portion 22 of the ferrite bond magnet 20. The volume of the inner cylinder portion 22 is sufficiently smaller than that of the opposing portion 25. Furthermore, if the rotor 2 is configured so that the inner cylinder portion 22 does not protrude axially from the annular portion 21, neither the inner cylinder portion 22 nor the opposing portion 25 faces the coil end 55a.

[0065] In this way, since there are few high dielectric constant portions between the coil end 55a and the rotating shaft 10, the electrostatic capacitance between the coil end 55a and the rotating shaft 10 can be reduced, and the potential of the rotating shaft 10 can be lowered.

[0066] Since the potential of the outer rings 11b, 12b is at ground potential, by lowering the potential of the rotating shaft 10 in contact with the inner rings 11a, 12a, the potential difference between the inner rings 11a, 12a and the outer rings 11b, 12b can be reduced, and the occurrence of electrolytic corrosion can be suppressed.

[0067] That is, by making the length L1 of the opposing portion 25 of the rotor 2 equal to or less than the length L2 of the stator core 50, the effect of suppressing the occurrence of electrolytic corrosion in the bearings 11, 12 can be obtained.

[0068] 8(A) is a vertical cross-sectional view showing an electric motor 1F of Comparative Example 2. A rotor 2F of the electric motor 1F of Comparative Example 2 has an annular ferrite bonded magnet 24 and a conductive support 46 that connects the rotating shaft 10 and the ferrite bonded magnet 24.

[0069] That is, the ferrite bonded magnet 24 of Comparative Example 2 does not have the inner cylinder portion 22 and the connecting portion 23 like the ferrite bonded magnet 20 of Embodiment 1. The ferrite bonded magnet 24 as a whole constitutes the opposing portion 25. The axial length L1 of the opposing portion 25 of the rotor 2F is equal to or shorter than the axial length L2 of the stator core 50.

[0070] 8(B) is a perspective view showing a rotor 2F of Comparative Example 2. The conductive support 46 is made by laminating circular electromagnetic steel plates in the axial direction. The rotating shaft 10 is fixed to the inner peripheral surface 46a of the conductive support 46, and the ferrite bond magnet 24 is fixed to the outer peripheral surface 46b of the conductive support 46.

[0071] In Comparative Example 2, since the conductive support 46 is interposed between the stator core 50 and the rotating shaft 10, the capacitance between the stator core 50 and the rotating shaft 10 increases, similar to the case where the distance between the stator core 50 and the rotating shaft 10 is narrowed. Therefore, in the electric motor 1F of Comparative Example 2, it is difficult to obtain the effect of reducing the bearing voltage.

[0072] 9 is a graph showing a comparison of the bearing voltage ratio between electric motor 1 of embodiment 1 and electric motor 1F of comparative example 2. The bearing voltage ratio on the vertical axis is the ratio of the bearing voltage to the voltage applied to coil 55.

[0073] The axial length L1 of the ferrite bond magnet 24 is set to 40 mm, which is the same as the axial length L2 of the stator core 50. Note that the inner rings 11a, 12a of the bearings 11, 12 are electrically connected via the shaft 10, and the outer rings 11b, 12b are electrically connected via the housing 6, so that the bearing voltage ratio value is the same for both the bearings 11, 12.

[0074] 9, the electric motor 1F of Comparative Example 2 has a smaller effect of reducing the bearing voltage than the electric motor 1 of Embodiment 1. This is because the conductive support 46 is interposed between the stator 5 and the rotating shaft 10, as described above.

[0075] In embodiment 1, as shown in FIG. 1, the inner cylindrical portion 22 and the connecting portion 23 of the ferrite bonded magnet 20 are interposed between the opposing portion 25 of the rotor 2 and the rotating shaft 10, and since these have insulating properties, they can achieve the effect of reducing the bearing voltage.

[0076] <Effects of the embodiment> As described above, the electric motor 1 of the first embodiment includes the rotating shaft 10 supported by the bearings 11 and 12, the rotor 2 fixed to the rotating shaft 10, and the stator 5 having the stator core 50 and the coil 55 surrounding the rotor 2. The rotor 2 has a facing portion 25 formed of a bonded magnet and facing the stator core 50 in the radial direction, and an insulating coupling portion (i.e., the inner cylinder portion 22 and the connection portion 23) that couples the facing portion 25 to the rotating shaft 10. The axial length L1 of the facing portion 25 is equal to or less than the axial length L2 of the stator core 50.

[0077] This configuration reduces the number of high dielectric constant portions located between the coil end 55a and the rotating shaft 10, thereby reducing the electrostatic capacitance between the coil end 55a and the rotating shaft 10 and lowering the potential of the rotating shaft 10. As a result, the bearing voltage can be reduced, the occurrence of electrolytic corrosion can be suppressed, and the vibration and noise of the electric motor 1 can be reduced.

[0078] Furthermore, because opposing portion 25 of rotor 2 has annular portion 21 of ferrite bonded magnet 20 and rare earth bonded magnet 30, a strong magnetic force can be generated even if length L1 of opposing portion 25 is shortened. Furthermore, because rare earth bonded magnet 30 is provided so as to cover annular portion 21 of ferrite bonded magnet 20 from the radial outside, a particularly strong magnetic force can be generated.

[0079] In addition, since the inner cylinder portion 22 and the connection portion 23 of the ferrite bond magnet 20 are interposed between the opposing portion 25 of the rotor 2 and the rotating shaft 10, the electrostatic capacitance between the stator core 50 and the rotating shaft 10 can be made smaller than when a conductor is interposed (FIGS. 8(A) and (B)). This further reduces the bearing voltage and effectively suppresses the occurrence of electrolytic corrosion.

[0080] In addition, since the ferrite bonded magnet 20 and the rare earth bonded magnet 30 are molded integrally with the rotating shaft 10, the ferrite bonded magnet 20, the rare earth bonded magnet 30 and the rotating shaft 10 can be firmly integrated, and manufacturing costs can be reduced.

[0081] Although rotor 2 in the first embodiment is configured with ferrite bonded magnets and rare earth bonded magnets, it is not limited to this combination, and may be configured with two types of bonded magnets.

[0082] Variation 1. FIG. 10 shows an electric motor 1A according to a first modified example. Longitudinal section 11 is a perspective view showing a rotor 2A of an electric motor 1A of modified example 1. As shown in FIGS. 10 and 11, in the electric motor 1A of modified example 1, the rotor 2A is made of a ferrite bonded magnet 20 and does not have a rare earth bonded magnet 30.

[0083] Similar to the first embodiment, the ferrite bonded magnet 20 has an annular portion 21, an inner cylinder portion 22, and a connecting portion 23. The annular portion 21 of the ferrite bonded magnet 20 constitutes a facing portion 25. The axial length L1 of the facing portion 25 is equal to or less than the axial length L2 of the stator core 50 (L1≦L2). The facing portion 25 does not protrude from the stator core 50 in the axial direction.

[0084] The ferrite bonded magnet 20 is molded integrally with the rotating shaft 10 by insert molding using an injection molding machine. By applying a polar anisotropic magnetic field during molding, the ferrite bonded magnet 20 is oriented so as to have the magnetic poles shown in FIG.

[0085] Generally, the magnetic force of a ferrite bonded magnet is weaker than that of a rare earth bonded magnet, so the magnetic force of rotor 2A of modified example 1, which does not have a rare earth bonded magnet, is weaker than the magnetic force of rotor 2 of embodiment 1, which has a rare earth bonded magnet.

[0086] On the other hand, in rare earth bonded magnets, conductive magnetic powder is surrounded by resin, whereas in ferrite bonded magnets, insulating magnetic powder is surrounded by resin. In other words, the overall conductivity of the ferrite bonded magnet is lower than the overall conductivity of the rare earth bonded magnet. Therefore, the electrostatic capacitance between the coil end 55a and the rotating shaft 10 is smaller in the first modification than in the first embodiment.

[0087] 12 is a graph showing the relationship between the length L1 of the opposing portion 25 of the rotors 2, 2A of the first embodiment and the first modified example, and the bearing voltage ratio, determined by electric field analysis. The horizontal axis shows the length L1 of the opposing portion 25. The bearing voltage ratio on the vertical axis is the ratio of the bearing voltage to the voltage applied to the coil 55. As described above, the bearing voltage ratios of the bearings 11, 12 are the same.

[0088] Here, the axial length L2 of the stator core 50 is fixed at 40 mm, and the axial length L1 of the opposing portion 25 of the rotors 2, 2A is varied from 36 mm to 58 mm.

[0089] 12, in both the first embodiment and the first modification, the bearing voltage increases as the length L1 of the opposing portion 25 of the rotors 2, 2A increases. Furthermore, in the region where the length L1 of the opposing portion 25 is longer than the length L2 of the stator core 50, i.e., where L1>L2, the bearing voltage in the first embodiment is higher than the bearing voltage in the first modification.

[0090] On the other hand, in the region where the length L1 of the opposing portion 25 is less than or equal to the length L2 of the stator core 50, i.e., the region where L1≦L2, there is no difference in the bearing voltage between embodiment 1 and variant 1, and the bearing voltage is kept low in both cases.

[0091] From this, it can be seen that in both the electric motor 1 of embodiment 1 and the electric motor 1A of variant example 1, the bearing voltage can be reduced and the occurrence of electrolytic corrosion can be suppressed by making the length L1 of the opposing portion 25 equal to or less than the length L2 of the stator core 50.

[0092] Although the rotor 2 in the first embodiment is composed of a ferrite bonded magnet 20 and a rare earth bonded magnet 30, and the rotor 2A in the first modification is composed of a ferrite bonded magnet 20, the rotor may be composed of only rare earth bonded magnets, or only other types of bonded magnets. However, if the rotor is composed of only rare earth bonded magnets, the bearing voltage tends to become too high, so it is desirable to include a ferrite bonded magnet.

[0093] Variation 2. FIG. 13 shows a rotor 2 of the second modified example. B In rotor 2 of embodiment 1, an annular rare earth bonded magnet 30 covers outer peripheral surface 20b of ferrite bonded magnet 20. In contrast, in rotor 2B of modification 2, a plurality of rare earth bonded magnets 31 are arranged along outer peripheral surface 20b of ferrite bonded magnet 20.

[0094] The rare earth bonded magnets 31 are arranged at equal intervals in the circumferential direction. The number of rare earth bonded magnets 31 is the same as the number of poles of the rotor 2B. The rare earth bonded magnets 31 adjacent to each other in the circumferential direction are magnetized with opposite polarities.

[0095] A plurality of recesses 20c in which rare earth bonded magnets 31 are disposed are formed on outer peripheral surface 20b of ferrite bonded magnet 20, i.e., the outer peripheral surface of annular portion 21 (FIG. 4). An opposing portion 25 is formed by annular portion 21 of ferrite bonded magnet 20 and rare earth bonded magnet 31.

[0096] The rotor 2B of the second modification has a ferrite bonded magnet 20 and a rare earth bonded magnet 31, and therefore, similar to the first embodiment, can generate a strong magnetic force even if the axial length L1 of the opposing portion 25 of the rotor 2B is shortened.

[0097] Embodiment 2 Next, a description will be given of embodiment 2. Fig. 14 is a longitudinal sectional view showing an electric motor 1C of embodiment 2. A rotor 2C of embodiment 2 has an annular ferrite bonded magnet 24 and a resin part 40 as a connecting part that connects the rotating shaft 10 and the ferrite bonded magnet 24.

[0098] That is, the ferrite bonded magnet 24 of the second embodiment does not have the inner cylinder portion 22 and the connecting portion 23 of the ferrite bonded magnet 20 of the first embodiment. The ferrite bonded magnet 24 as a whole constitutes the opposing portion 25. The axial length L1 of the opposing portion 25 of the rotor 2C is equal to or shorter than the axial length L2 of the stator core 50.

[0099] Fig. 15 is a perspective view showing the rotor 2C. The resin part 40 has an inner cylinder part 42 fixed to the rotating shaft 10 (Fig. 14), an annular part 41 that surrounds the inner cylinder part 42 from the radial outside, and a connecting part 43 that connects the annular part 41 and the inner cylinder part 42. The ferrite bond magnet 24 is fixed to the annular part 41.

[0100] The resin portion 40 is made of a resin such as PBT, polyamide (nylon), or liquid crystal polymer (LCP), and is an insulator. The relative dielectric constant of the resin forming the resin portion 40 is approximately 4, which is sufficiently lower than the relative dielectric constant of the ferrite bonded magnet 24.

[0101] By fixing the ferrite bond magnet 24 to the rotating shaft 10 via the resin part 40 with a lower dielectric constant, it is possible to reduce the electrostatic capacitance between the coil end 55a and the rotating shaft 10. As a result, it is possible to reduce the bearing voltage of the bearings 11 and 12 and suppress the occurrence of electrolytic corrosion.

[0102] 16 is a graph showing the relationship between the axial length L1 of ferrite bond magnet 24 of rotor 2C of embodiment 2 and the bearing voltage ratio, determined by electric field analysis. The horizontal axis shows length L1 of facing portion 25. The bearing voltage ratio on the vertical axis is the ratio of the bearing voltage to the voltage applied to coil 55. As described above, bearings 11 and 12 have the same bearing voltage ratio.

[0103] From Fig. 16, it can be seen that the bearing voltage is particularly low when the length L1 of the ferrite bonded magnet 24 is equal to or less than the length L2 of the stator core 50 (L1≦L2). Also, comparing Fig. 12 with Fig. 16, it can be seen that the bearing voltage is lower in the second embodiment than in the first embodiment. This is due to the placement of the low dielectric constant resin part 40 between the ferrite bonded magnet 24 and the shaft 10.

[0104] A rare earth bonded magnet 30 may be provided on the outer periphery of the ferrite bonded magnet 24. By providing the rare earth bonded magnet 30, the magnetic force of the rotor 2C can be increased.

[0105] Except for the points mentioned above, the electric motor 1C of the second embodiment is configured similarly to the electric motor 1 of the first embodiment.

[0106] As described above, in the electric motor 1C of the second embodiment, the ferrite bond magnet 24 is connected to the rotating shaft 10 via the resin part 40, which has a lower dielectric constant than the ferrite bond magnet 24, so that it is possible to reduce the electrostatic capacitance between the coil end 55a and the rotating shaft 10. This makes it possible to reduce the bearing voltage of the bearings 11 and 12 and suppress the occurrence of electrolytic corrosion.

[0107] Embodiment 3 Next, a third embodiment will be described. Fig. 17 is a vertical cross-sectional view showing an electric motor 1D of the third embodiment. In the electric motor 1 of the first embodiment, the stator 5 is held by a metal housing 6, but in the electric motor 1D of the third embodiment, the stator 5 is held by a molded resin part 80.

[0108] The molded resin portion 80 serving as the resin portion is made of BMC (bulk molding compound) containing unsaturated polyester. The molded resin portion 80 is formed so as to cover the stator 5 from the radial outside and the anti-load side.

[0109] The molded resin part 80 has an opening 81 on the load side and a bearing holder 82 on the anti-load side. The rotor 2A is inserted into the stator 5 from the opening 81. The stator 5 and the molded resin part 80 constitute the molded stator 8.

[0110] The load-side bearing 11 is held by a metal bracket 71 attached to an opening 81 of a molded resin part 80. The bracket 71 has a cylindrical part 71a that supports the bearing 11, a plate-like part 71b that extends radially outward from the cylindrical part 71a, and a fitting part 71c that fits into a step part around the opening 81. The cylindrical part 71a of the bracket 71 contacts an outer ring 11b of the bearing 11. The bracket 71 is also referred to as a conductive member or a first conductive member.

[0111] The bearing 12 on the anti-load side is held by a conductive cap 72. The cap 72 is, for example, cylindrical with a bottom, and is covered from the radially outer side by a bearing holding part 82 of a molded resin part 80. The cap 72 contacts the outer ring 12b of the bearing 12. The cap 72 is also referred to as a conductive member or a second conductive member.

[0112] In the first embodiment, the housing 6 is grounded, but in the third embodiment, the molded resin part 80 is insulating and cannot be grounded. Therefore, in the third embodiment, the bracket 71 and the cap 72 are grounded.

[0113] More specifically, conductive pin 85 provided on bracket 71 and conductive pin 56 provided on the load side of stator core 50 are electrically connected by lead wire 58. In addition, conductive pin 86 provided on cap 72 and conductive pin 57 provided on the anti-load side of stator core 50 are electrically connected by lead wire 59.

[0114] A drive circuit such as an inverter is mounted on the circuit board 45, and is grounded to the ground outside the electric motor 1D via a lead wire (not shown). Therefore, the outer ring 11b of the bearing 11 is grounded via the bracket 71, the lead wire 58, and the circuit board 45. The outer ring 12b of the bearing 12 is grounded via the cap 72, the lead wire 59, and the circuit board 45.

[0115] The electric motor 1D has the rotor 2A described in the modified example 1. The length L1 of the annular portion 21 of the rotor 2A is equal to or less than the length L2 of the stator core 50. Note that the rotor 2 in the embodiment 1, the rotor 2B in the modified example 2, or the rotor 2C in the embodiment 2 may be used instead of the rotor 2A.

[0116] Except for the points mentioned above, the electric motor 1D of the third embodiment is configured similarly to the electric motor 1 of the first embodiment.

[0117] 18 is a vertical cross-sectional view showing an electric motor 1G of Comparative Example 3. In the electric motor 1G of Comparative Example 3, the load-side bearing 11 is held by a metal bracket 71, but the bracket 71 is not grounded. Also, there is no metal cap 72 that holds the non-load-side bearing 12. That is, neither of the outer rings 11b, 12b of the bearings 11, 12 is grounded.

[0118] In the bearing 12 on the anti-load side, the outer ring 12b is close to the circuit board 45, which is grounded by a lead wire, so that the potential of the outer ring 12b is close to the ground potential. On the other hand, the inner ring 12a is in contact with the rotating shaft 10, and since there is electrostatic capacitance between the rotating shaft 10 and the coil end 55a, the potential of the inner ring 12a is likely to be higher than the ground potential. As a result, a potential difference is likely to occur between the inner ring 12a and the outer ring 12b.

[0119] On the other hand, in the load-side bearing 11, the inner ring 11a is in contact with the rotating shaft 10, and since there is capacitance between the rotating shaft 10 and the coil end 55a, the potential of the inner ring 11a is likely to be high. However, since the bearing 11 is separated from the circuit board 45 and the potential of the outer ring 11b is not at ground potential, a potential difference between the inner ring 11a and the outer ring 11b is unlikely to occur.

[0120] Fig. 19 is a graph showing the relationship between the length L1 of the annular portion 21 of the rotor 2A in the electric motor 1G of Comparative Example 3 and the bearing voltages at the bearings 11 and 12. As shown in Fig. 19, the bearing voltage at the anti-load side bearing 12 is higher than the bearing voltage at the load side bearing 11.

[0121] 19, the bearing voltage of both bearings 11 and 12 is constant regardless of length L1. This is because, in electric motor 1G of comparative example 3, outer rings 11b and 12b of bearings 11 and 12 are not conductive, and therefore the bearing voltage reduction effect due to the above-mentioned relationship of L1≦L2 cannot be obtained.

[0122] 17, in the third embodiment, the outer ring 11b of the bearing 11 is grounded via a bracket 71 and a lead wire 58, and the outer ring 12b of the bearing 12 is grounded via a cap 72 and a lead wire 59. That is, the potential of the outer rings 11b, 12b of the bearings 11, 12 is the ground potential.

[0123] Therefore, similar to embodiment 1 in which the bearings 11, 12 are held in the conductive housing 6, by making the axial length L1 of the opposing portion 25 of the rotor 2A equal to or less than the axial length L2 of the stator core 50, the capacitance between the coil end 55a and the rotating shaft 10 can be reduced, and the bearing voltage of the bearings 11, 12 can be reduced.

[0124] As described above, in electric motor 1D of embodiment 3, stator core 50 is held by molded resin part 80, outer ring 11b of bearing 11 is grounded via bracket 71 and lead wire 58, outer ring 12b of bearing 12 is grounded via cap 72 and lead wire 59, and length L1 of annular part 21 of rotor 2A is equal to or less than length L2 of stator core 50. Therefore, the electrostatic capacitance between coil end 55a and rotating shaft 10 is reduced, the bearing voltage of bearings 11 and 12 is reduced, and the occurrence of electrolytic corrosion can be suppressed.

[0125] Embodiment 4 Next, a fourth embodiment will be described. The fourth embodiment relates to a blower 9 to which the motors of the above-mentioned embodiments and modifications are applied, and a ventilation fan 100 equipped with the blower 9. FIG. 20 is a cross-sectional view of the ventilation fan 100. FIG. 21 is a perspective view of the ventilation fan 100. The ventilation fan 100 is disposed on an indoor ceiling, and exhausts indoor air to the outdoors via an exhaust duct. The ventilation fan 100 is also called a duct ventilation fan.

[0126] Ventilation fan 100 includes a blower 9 and a housing 101 to which blower 9 is attached. Blower 9 has electric motor 1 described in the first embodiment and blade portion 90 attached to a rotating shaft 10 of electric motor 1. Note that electric motor 1 described in the first embodiment may be replaced by an electric motor described in the second or third embodiment or each of the modified examples.

[0127] The blade portion 90 is also called a sirocco fan, and has a plurality of blades 94 arranged in the circumferential direction between a main plate 92 and a side plate 93 that face each other in the axial direction. The main plate 92 is fixed to the rotating shaft 10. When the blade portion 90 rotates, an air flow is generated that flows radially outward from the central axis Ax.

[0128] The housing 101 is a rectangular parallelepiped container made of steel plate or resin. The housing 101 has a top plate 103 and a bottom plate 104 that face each other in the axial direction, and a side wall 102 formed between them. The top plate 103 has an opening 108 for mounting the electric motor 1. The electric motor 1 is mounted in the opening 108 so that the first frame 61 side fits inside the housing 101, and the flange portions 61e, 62e are fixed around the periphery of the opening 108.

[0129] The outer peripheral edge of the bottom plate 104 is fixed to the lower surface of the ceiling plate 200. The bottom plate 104 is formed with a grill 105 for drawing air in from inside the room as indicated by arrow A.

[0130] A ventilation duct 106 for discharging air to the outside of the housing 101 is attached to the side wall 102 of the housing 101. The ventilation duct 106 is connected to an exhaust duct (not shown) that leads to the outdoors.

[0131] When the electric motor 1 is driven, the blade portion 90 fixed to the rotating shaft 10 rotates. As a result, indoor air is sucked into the housing 101 through the grill 105 as shown by arrow A. The air sucked into the housing 101 is directed radially outward by the blade portion 90, discharged from the housing 101 through the ventilation duct 106, and exhausted to the outdoors through the exhaust duct.

[0132] Since the ventilation fan 100 is installed on the ceiling indoors, vibrations and noise are easily transmitted indoors. By using the electric motor 1 described in the first embodiment as the driving source of the ventilation fan 100, it is possible to reduce vibrations and noise caused by electrolytic corrosion of the bearings 11 and 12. As a result, it is possible to reduce the vibrations and noise transmitted indoors and improve quietness.

[0133] Furthermore, the occurrence of electrolytic corrosion in bearings 11 and 12 is suppressed, thereby extending the life and improving the reliability of ventilation fan 100. The same applies when the electric motor described in embodiments 2 and 3 or each of the modified examples is used instead of electric motor 1 described in embodiment 1.

[0134] Although a ventilation fan using a sirocco fan has been described here, the shape of the blades is not limited to a sirocco fan, and may be a propeller fan, a cross-flow fan, or the like.

[0135] Furthermore, the blower having the electric motor described in each embodiment and each modified example is not limited to being used as a ventilation fan, but may also be used in a range hood, a bathroom dryer, an electric fan, a dehumidifier, an air conditioner, or the like.

[0136] Although the preferred embodiments have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various improvements and modifications can be made. [Explanation of symbols]

[0137] REFERENCE SIGNS LIST 1,1A,1B,1C,1D electric motor, 2,2A,2B,2C rotor, 5 stator, 6 housing (conductive member), 8 molded stator, 9 blower, 10 rotating shaft, 11,12 bearing, 11a,12a inner ring, 11b,12b outer ring, 11c,12c rolling element, 11e,11f raceway surface, 20 ferrite bonded magnet, 21 annular portion, 22 inner cylinder portion (connecting portion), 23 connection portion (connecting portion), 24 ferrite bonded magnet, 25 opposing portion, 30 rare earth bonded magnet, 31 rare earth bonded magnet, 40 resin portion, 45 circuit board, 50 stator core, 51 yoke, 52 teeth, 53 Slot, 54 insulating portion, 55 coil, 55a coil end, 56, 57 pins, 58, 59 lead wires (conductive member, conductive member), 61 first frame, 61c, 62c bearing retaining portion, 61e, 62e flange portion, 62 second frame, 71 bracket, 72 cap, 80 molded resin portion, 85, 86 pins, 90 blade portion, 100 ventilation fan, 101 housing, 106 ventilation duct.

Claims

1. A rotating shaft; A rotor fixed to the rotating shaft; a stator including a stator core that surrounds the rotor from the outside in the radial direction thereof and a coil wound around the stator core; a bearing having an inner ring and an outer ring, the inner ring being in contact with the rotating shaft; a conductive member that electrically connects the stator core and the outer ring and is grounded; having The rotor is a facing portion having a first magnet portion and a second magnet portion disposed on an outer periphery of the first magnet portion and facing the stator core in the radial direction; an insulating connecting portion that connects the opposing portion and the rotating shaft; having the first magnet portion and the connecting portion are formed of a ferrite bond magnet, The second magnet portion is formed of a rare earth bonded magnet, The length L1 of the opposing portion in the axial direction of the rotating shaft is equal to or less than the length L2 of the stator core in the axial direction. Electric motor.

2. The second magnet portion is provided so as to cover the outer periphery of the first magnet portion.

2. The electric motor according to claim 1.

3. The second magnet portion is one of a plurality of second magnet portions provided at intervals in the circumferential direction on the outer periphery of the first magnet portion.

2. The electric motor according to claim 1.

4. The opposing portion and the connecting portion are integrally formed with the rotating shaft.

4. An electric motor according to claim 1.

5. A rotating shaft; A rotor fixed to the rotating shaft; a stator including a stator core that surrounds the rotor from the outside in the radial direction thereof and a coil wound around the stator core; a bearing having an inner ring and an outer ring, the inner ring being in contact with the rotating shaft; a conductive member that electrically connects the stator core and the outer ring and is grounded; having The rotor is a ferrite bond magnet facing the stator core in the radial direction; a connecting portion that connects the ferrite bond magnet and the rotating shaft and is made of a material having a lower dielectric constant than the ferrite bond magnet; having The length L1 of the ferrite bond magnet in the axial direction of the rotating shaft is equal to or less than the length L2 of the stator core in the axial direction. Electric motor.

6. The connecting portion is made of resin.

6. The electric motor according to claim 5.

7. The conductive member is a metal housing that holds the stator and the bearing.

7. An electric motor according to any one of claims 1 to 6.

8. a resin portion for holding the stator and the bearing; The conductive member includes a conductive member that connects the stator and the bearing.

8. An electric motor according to any one of claims 1 to 7.

9. the stator core, the outer ring, and the conductive member are at ground potential; The rotating shaft and the inner ring are at the same potential and at a potential higher than the ground potential.

9. An electric motor according to any one of claims 1 to 8.

10. An electric motor according to any one of claims 1 to 9; a blade portion attached to the rotating shaft of the electric motor; A blower equipped with

11. A blower according to claim 10; A housing in which the blower is attached; Equipped with a ventilation fan.

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