Electric motors, fans and air conditioners

Abstract

The electric motor comprises: a rotor having a shaft, a rotor core and a permanent magnet, the rotor core surrounds the shaft from the radial outer side centered on the central axis of the shaft, the permanent magnet is mounted on the rotor core, the permanent magnet constitutes a magnet pole, and a part of the rotor core constitutes a virtual pole; a stator surrounds the rotor from the radial outer side; a first bearing and a second bearing support the shaft; a first bearing retaining portion having an inner peripheral surface facing the outer peripheral surface of the first bearing; and a second bearing retaining portion having an inner peripheral surface facing the outer peripheral surface of the second bearing. One side in the direction of the central axis of the shaft is a load side that bears a load. The first bearing of the first bearing and the second bearing is located on the load side. The distance D1 from the central axis to the inner peripheral surface of the first bearing retaining portion, the distance D2 from the central axis to the inner peripheral surface of the second bearing retaining portion, the distance d1 from the central axis to the outer peripheral surface of the first bearing, and the distance d2 from the central axis to the outer peripheral surface of the second bearing satisfy D1-d1<D2-d2.

Description

Technical Field

[0001] The present disclosure relates to a motor, a blower, and an air conditioning device. Background Art

[0002] The electric motor includes a rotor and a stator having a shaft. A bearing supporting the shaft is held by a bearing holding portion such as a bracket (see, for example, Patent Document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Utility Model Publication No. 60-141651 ( Figure 1 ) Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In recent years, a shunned-pole type rotor has been developed in which permanent magnets form magnetic poles and a part of the rotor core forms virtual magnetic poles. In a shunned-pole type rotor, since the magnetic flux density on the rotor surface is different between the magnetic poles and the virtual magnetic poles, radial exciting force is likely to act on the rotor. Therefore, there is a tendency for the radial load acting on the bearing supporting the shaft to increase.

[0008] If a large radial load acts on the bearing supporting the shaft, peripheral creep may occur. Peripheral creep is a phenomenon in which the outer ring of the bearing moves in the circumferential direction relative to the bearing retaining portion. Since peripheral creep is related to bearing wear, it is required to suppress the occurrence of peripheral creep.

[0009] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to suppress the occurrence of peripheral creep.

[0010] Means of solving the problem

[0011] The electric motor of the present invention comprises: a rotor having a shaft, a rotor core and a permanent magnet, the rotor core surrounding the shaft from the radial outer side with the central axis of the shaft as the center, the permanent magnet being mounted on the rotor core, the permanent magnet constituting a magnet pole, and a part of the rotor core constituting a virtual pole; a stator surrounding the rotor from the radial outer side; a first bearing and a second bearing, the first bearing and the second bearing supporting the shaft; a first bearing retaining portion, the first bearing retaining portion having an inner peripheral surface facing the outer peripheral surface of the first bearing; and a second bearing retaining portion, the second bearing retaining portion having an inner peripheral surface facing the outer peripheral surface of the second bearing. One side in the direction of the central axis of the shaft is a load side that bears a load. The first bearing of the first bearing and the second bearing is located on the load side. The distance D1 from the center axis to the inner circumferential surface of the first bearing retaining portion, the distance D2 from the center axis to the inner circumferential surface of the second bearing retaining portion, the distance d1 from the center axis to the outer circumferential surface of the first bearing, and the distance d2 from the center axis to the outer circumferential surface of the second bearing satisfy D1-d1<D2-d2, and in addition, D1<D2 and d1=d2, or d1>d2.

[0012] Effects of the Invention

[0013] In the present disclosure, since the distances D1, D2, d1, and d2 satisfy D1-d1<D2-d2, the outer ring of the first bearing to which a larger radial load acts is less likely to move in the circumferential direction, thereby suppressing the occurrence of peripheral creep. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a partial longitudinal sectional view showing the electric motor in the first embodiment.

[0015] Figure 2 It is a cross-sectional view showing the electric motor in the first embodiment.

[0016] Figure 3 This is a cross-sectional view showing the rotor in the first embodiment.

[0017] Figure 4 It is a partial longitudinal sectional view showing the electric motor in the first embodiment.

[0018] Figure 5 (A) is a diagram showing a first bearing and a first bearing holding portion in Embodiment 1, Figure 5 (B) is a diagram showing the second bearing and the second bearing holding portion.

[0019] Figure 6 This is a diagram showing the molded stator in Embodiment 1 as viewed from the load side.

[0020] Figure 7 Yes Figure 6FIG. 1 is an enlarged view of a portion of an electric motor.

[0021] Figure 8 It is a flux diagram showing the flow of magnetic flux in the motor.

[0022] Fig. 9 is a schematic diagram showing the shaft, the first bearing and the bracket.

[0023] Fig.10 This is a diagram showing a configuration for suppressing an axial current in the first embodiment.

[0024] Fig.11 It is a cross-sectional view showing the shaft and the second bearing in the first embodiment.

[0025] Fig.12 It is a partial longitudinal sectional view showing the electric motor in the second embodiment.

[0026] Fig.13 (A) is a diagram showing a first bearing and a second bearing in Embodiment 2, Fig.13 (B) is a diagram showing another example of the first bearing and the second bearing.

[0027] Fig.14 It is a longitudinal sectional view showing the electric motor in the third embodiment.

[0028] Fig.15 This is a longitudinal sectional view showing a part of the motor in the third embodiment in an enlarged manner.

[0029] Fig.16 (A) is a diagram showing an air conditioning device to which the electric motor of each embodiment can be applied. Fig.16 (B) is a cross-sectional view showing the outdoor unit. DETAILED DESCRIPTION

[0030] Implementation Method 1

[0031] <Structure of the electric motor 100>

[0032] Figure 1 1 is a longitudinal sectional view showing the electric motor 100 in Embodiment 1. The electric motor 100 is used in, for example, a blower of an air conditioner. The electric motor 100 is an IPM (Interior Permanent Magnet) motor in which a permanent magnet 16 is embedded in a rotor 1 .

[0033] The electric motor 100 includes a rotor 1 having a shaft 15 as a rotation axis and a molded stator 4 surrounding the rotor 1. The molded stator 4 includes a stator 5 provided so as to surround the rotor 1 and a molded resin portion 40 covering the stator 5.

[0034] In the following description, the direction of the central axis C1 of the shaft 15 is referred to as the "axial direction". The circumferential direction centered on the central axis C1 is referred to as the "circumferential direction". Figure 2 The radial direction about the central axis C1 is referred to as the “radial direction”. A cross-sectional view of a cross section parallel to the axial direction is referred to as a “longitudinal cross-sectional view”, and a cross-sectional view of a cross section perpendicular to the axial direction is referred to as a “transverse cross-sectional view”.

[0035] The shaft 15 is loaded on one side in the axial direction. More specifically, the shaft 15 is loaded from the mold stator 4 to the Figure 1 The left side of the protrusion is protruded, and an impeller 505 (for example, of a blower) is installed on the mounting portion 15a formed at the front end of the protruding side. Fig.16 (A)). Therefore, the protruding side of the shaft 15 is referred to as the "load side", and the opposite side thereof is referred to as the "anti-load side".

[0036] <Structure of molded stator 4>

[0037] As described above, the molded stator 4 includes the stator 5 and the molded resin portion 40. The molded resin portion 40 is formed of a thermosetting resin such as BMC (Bulk Molding Compound), or may be formed of a thermoplastic resin such as PBT (polybutylene terephthalate) or PPS (polyphenylene sulfide).

[0038] The molded resin portion 40 has mounting legs 45 on its outer periphery. Here, four mounting legs 45 are formed at equal intervals in the circumferential direction. A hole portion 46 ( Figure 6 The mounting leg 45 is fixed to, for example, a frame of an outdoor unit of an air conditioner by means of screws inserted through the hole 46 .

[0039] The molded resin part 40 has an opening 41 on the load side. The rotor 1 is inserted into the hollow portion inside the molded stator 4 from the opening 41. A bracket 6 as a first bearing holding portion is attached to the opening 41 of the molded resin part 40. The bracket 6 is formed of a metal such as a galvanized steel plate. The bracket 6 is fitted into an annular step 41a formed around the opening 41.

[0040] The first bearing 21 supporting the shaft 15 is held by the bracket 6. Moreover, a waterproof cover 9 for preventing water and the like from intruding into the first bearing 21 is attached to the shaft 15 so as to surround the bracket 6 from the outside.

[0041] The molded resin portion 40 has a bearing holding portion 42 as a second bearing holding portion on the opposite side to the load. The second bearing 22 supporting the shaft 15 is held in the bearing holding portion 42 of the molded resin portion 40 .

[0042] A circuit board 7 is arranged radially outside the second bearing 22. The circuit board 7 is covered and held by the molded resin portion 40. Components 71 such as power transistors and magnetic sensors for driving the motor 100 are mounted on the circuit board 7, and leads 73 are wired thereto. The leads 73 of the circuit board 7 are led out to the outside of the motor 100 from a lead-out portion 72 mounted on the outer peripheral portion of the molded resin portion 40.

[0043] In addition, a heat sink 8 is provided so as to cover the opposite load side of the molded resin portion 40. A portion of the heat sink 8 is covered by the molded resin portion 40, and a portion is exposed from the molded resin portion 40. The heat sink 8 has a function of dissipating heat generated by the motor 100 to the outside. In addition, a structure without the heat sink 8 may be provided.

[0044] <Structure of stator 5>

[0045] Figure 2 is a cross-sectional view showing the motor 100. Figure 2 As shown, the stator 5 includes a stator core 50, an insulating portion 53 provided on the stator core 50, and a coil 55 wound on the stator core 50 via the insulating portion 53. The stator core 50 is formed by stacking a plurality of electromagnetic steel sheets in the axial direction and fixing them by caulking, etc. The thickness of the electromagnetic steel sheets is, for example, 0.2 mm to 0.5 mm.

[0046] The stator core 50 has an annular yoke 51 centered on the central axis C1 and a plurality of teeth 52 extending radially inward from the yoke 51. The teeth 52 are arranged at equal intervals in the circumferential direction. The number of teeth 52 is twelve here, but is not limited to twelve. A slot is formed between adjacent teeth 52 as a space for accommodating the coil 55.

[0047] An insulating portion 53 made of polybutylene terephthalate (PBT) or the like is attached to the stator core 50 . The insulating portion 53 is formed of, for example, a thermoplastic resin such as PBT. The insulating portion 53 is obtained by integrally molding a thermoplastic resin with the stator core 50 or assembling a thermoplastic resin molded body on the stator core 50 .

[0048] <Structure of rotor 1>

[0049] Figure 3 is a cross-sectional view showing the rotor 1. Figure 3 As shown, the rotor 1 includes a shaft 15 , a rotor core 10 surrounding the shaft 15 from the radially outer side, and a plurality of permanent magnets 16 embedded in the rotor core 10 .

[0050] The rotor core 10 is an annular member centered on the central axis C1. The rotor core 10 is formed by stacking a plurality of electromagnetic steel sheets in the axial direction and fixing them by caulking or the like. The thickness of the electromagnetic steel sheets is, for example, 0.2 mm to 0.5 mm.

[0051] The rotor core 10 has a plurality of magnet insertion holes 11 a. The magnet insertion holes 11 a are arranged at equal intervals in the circumferential direction and at equal distances from the central axis C1. The number of the magnet insertion holes 11 a is five here. The magnet insertion holes 11 a are formed along the outer circumference of the rotor core 10.

[0052] The magnet insertion hole 11a extends linearly in a direction perpendicular to a radial straight line (referred to as a magnetic pole center line) passing through the circumferential center, ie, the pole center. However, the magnet insertion hole 11a is not limited to such a shape, and may extend in a V shape, for example.

[0053] At both ends of the magnet insertion hole 11a in the circumferential direction, magnetic flux barriers 11b are formed as hole portions. A thin wall portion is formed between the magnetic flux barriers 11b and the outer periphery of the rotor core 10. In order to suppress leakage magnetic flux between adjacent magnetic poles, the thickness of the thin wall portion is preferably the same as the plate thickness of the electromagnetic steel sheet constituting the rotor core 10.

[0054] A permanent magnet 16 is inserted into each magnet insertion hole 11a. The permanent magnet 16 is in the form of a flat plate, and the cross-section perpendicular to the axial direction is in a rectangular shape. The permanent magnet 16 is made of a rare earth magnet. More specifically, the permanent magnet 16 is made of a neodymium sintered magnet containing Nd (neodymium) -Fe (iron) -B (boron).

[0055] The permanent magnets 16 are arranged so that the same magnetic poles (eg, N poles) face the outer circumference of the rotor core 10. In the rotor core 10, the regions between the circumferentially adjacent permanent magnets have magnetic poles (eg, S poles) opposite to the permanent magnets.

[0056] Therefore, five magnet poles P1 formed by permanent magnets 16 and five virtual poles P2 formed by rotor core 10 are formed in rotor 1. Such a structure is called a consequent pole type. Hereinafter, when simply referring to a "magnetic pole", both magnet poles P1 and virtual poles P2 are included. Rotor 1 has ten magnetic poles.

[0057] Here, the number of poles of the rotor 1 is 10, but the number of poles may be an even number greater than 4. In addition, here, one permanent magnet 16 is arranged in one magnet insertion hole 11a, but two or more permanent magnets 16 may be arranged in one magnet insertion hole 11a. The magnet pole P1 may be an S pole, and the virtual pole P2 may be an N pole.

[0058] The outer circumference of the rotor core 10 has a so-called flower-shaped shape in a cross section perpendicular to the axial direction. In other words, the outer diameter of the rotor core 10 is the largest at the pole center of each of the magnetic poles P1 and P2, and the outer diameter is the smallest at the inter-pole M, and is arc-shaped from the pole center to the inter-pole M. The outer circumference of the rotor core 10 is not limited to the flower-shaped shape, and can also be a circular shape.

[0059] In the rotor core 10 , a caulking portion 14 is provided radially inside the magnet insertion hole 11 a. The caulking portion 14 is a portion for fixing a plurality of electromagnetic steel sheets constituting the rotor core 10 .

[0060] A resin portion 30 is provided between the inner periphery of the rotor core 10 and the shaft 15. The resin portion 30 is formed of a resin such as polybutylene terephthalate (PBT). The resin portion 30 includes an annular inner cylinder portion 31 fixed to the shaft 15, an annular outer cylinder portion 33 fixed to the inner periphery of the rotor core 10, and a plurality of ribs 32 connecting the inner cylinder portion 31 and the outer cylinder portion 33.

[0061] The shaft 15 is fixed inside the inner cylinder portion 31 of the resin portion 30. The ribs 32 are arranged at equal intervals in the circumferential direction and extend radially outward from the inner cylinder portion 31. A cavity portion 35 is formed between the ribs 32 adjacent to each other in the circumferential direction. Here, the number of ribs 32 is half the number of poles, and the circumferential position of the ribs 32 coincides with the pole center of the virtual magnetic pole P2, but is not limited to such a number and arrangement.

[0062] return Figure 1 A sensor magnet 17 is disposed on the opposite load side of the rotor core 10. The sensor magnet 17 is held by a resin portion 30. The magnetic field of the sensor magnet 17 is detected by a magnetic sensor mounted on the circuit board 7, thereby detecting the rotation position of the rotor 1.

[0063] <Bearings 21, 22 and their supporting structure>

[0064] Next, the bearings 21 and 22 that rotatably support the shaft 15 and their supporting structure will be described. Figure 4 1 is a partial longitudinal sectional view showing the motor 100. As described above, the shaft 15 is rotatably supported by the first bearing 21 and the second bearing 22. The first bearing 21 is arranged on the load side, and the second bearing 22 is arranged on the opposite side to the load side.

[0065] The first bearing 21 includes an inner ring 21a, an outer ring 21b, and a plurality of rolling elements 21c. The inner ring 21a is fixed to the shaft 15 by press fitting. The outer ring 21b is fixed to the cylindrical portion 61 (described later) of the bracket 6 by clearance fitting. The rolling element 21c is, for example, a ball, and is disposed between the inner ring 21a and the outer ring 21b. The inner ring 21a, the outer ring 21b, and the rolling element 21c are all made of metal.

[0066] The second bearing 22 includes an inner ring 22a, an outer ring 22b, and a plurality of rolling elements 22c. The inner ring 22a is fixed to the shaft 15 by press-fitting. The outer ring 22b is fixed to the bearing holding portion 42 of the molded resin portion 40 by clearance fitting. The rolling element 22c is, for example, a ball, and is disposed between the inner ring 22a and the outer ring 22b. The inner ring 22a, the outer ring 22b, and the rolling element 22c are all made of metal.

[0067] Figure 5 (A) is a cross-sectional view showing the first bearing 21 and the bracket 6. The bracket 6 includes a cylindrical portion 61 surrounding the first bearing 21 and a flange portion 62 extending radially outward from the cylindrical portion 61. The inner peripheral surface 61a of the cylindrical portion 61 faces the outer peripheral surface 21d of the outer ring 21b of the first bearing 21 (also referred to as the outer peripheral surface 21d of the first bearing 21).

[0068] A step portion 41a ( Figure 4 ) The bracket 6 is fixed to the molded resin portion 40 by fitting the fitting portion 63 into the step portion 41a.

[0069] The bracket 6 further includes an end surface portion 64 facing the axial end surface of the first bearing 21. A shaft insertion hole 65 for inserting the shaft 15 is formed at the center of the end surface portion 64. In addition, a washer 66 for urging the outer ring 21b of the first bearing 21 in the axial direction is arranged between the end surface portion 64 and the first bearing 21.

[0070] The distance from the center axis C1 to the outer peripheral surface 21d of the outer ring 21b of the first bearing 21 is defined as distance d1. The distance from the center axis C1 to the inner peripheral surface 61a of the cylindrical portion 61 of the bracket 6 is defined as distance D1. Distance D1 is greater than distance d1.

[0071] The difference (D1-d1) between the distance D1 and the distance d1 is the gap between the outer peripheral surface 21d of the outer ring 21b of the first bearing 21 and the inner peripheral surface 61a of the cylindrical portion 61 of the bracket 6, and is 5 μm, for example.

[0072] Figure 5 (B) is a cross-sectional view showing the second bearing 22 and the bearing holding portion 42. The bearing holding portion 42 has an inner peripheral surface 42a surrounding the second bearing 22 and an end surface 42b abutting against the outer ring 22b of the second bearing 22 in the axial direction. The inner peripheral surface 42a of the bearing holding portion 42 is opposed to the outer peripheral surface 22d of the outer ring 22b of the second bearing 22 (also referred to as the outer peripheral surface 22d of the second bearing 22).

[0073] The distance from the center axis C1 to the outer peripheral surface 22d of the outer ring 22b of the second bearing 22 is defined as distance d2. The distance from the center axis C1 to the inner peripheral surface 42a of the bearing holding portion 42 is defined as distance D2. Distance D2 is greater than distance d2.

[0074] The difference (D2-d2) between the distance D2 and the distance d2 is the gap between the outer peripheral surface 22d of the outer ring 22b of the second bearing 22 and the inner peripheral surface 42a of the bearing holding portion 42, and is, for example, 10 μm.

[0075] In Embodiment 1, D1-d1<D2-d2 holds. That is, the gap on the outer circumference side of the outer ring 21b of the first bearing 21 on the load side is narrower than the gap on the outer circumference side of the outer ring 22b of the second bearing 22 on the opposite load side.

[0076] Figure 6 This is a diagram of the molded stator 4 viewed from the load side. Figure 6 In the embodiment, since the rotor 1 is not inserted into the molded stator 4 , the bearing holding portion 42 is exposed through the opening 41 of the molded resin portion 40 .

[0077] Figure 7 It is a magnified representation Figure 6 The radial center portion of the molded stator 4 is shown. Figure 7 In FIG. 1 , circles representing inner peripheral surfaces 61 a and 42 a of the bearing holding portions 6 and 42 are shown together with circles representing outer peripheral surfaces 21 d and 22 d of outer rings 21 b and 22 b of the bearings 21 and 22 .

[0078] <Function>

[0079] Next, the operation of the first embodiment will be described. Figure 8 It is a magnetic flux diagram showing the flow of magnetic flux in the electric motor 100 having the consequent-pole type rotor 1 .

[0080] As described above, the consequent-pole rotor 1 has the magnet poles P1 provided with the permanent magnets 16 and the virtual poles P2 not provided with the permanent magnets 16. The magnetic flux density on the surface of the rotor 1 is high at the magnet poles P1 and low at the virtual poles P2.

[0081] Therefore, the force acting between the magnet pole P1 and the tooth 52 becomes greater than the force acting between the virtual pole P2 and the tooth 52, and the radial exciting force acts on the rotor 1. The radial exciting force acting on the rotor 1 acts on the shaft 15.

[0082] Fig. 9 is a schematic diagram showing the shaft 15, the first bearing 21, and the bracket 6 holding the first bearing 21. Fig. 9 In FIG. 1 , a gap ( D1 − d1 ) between an outer peripheral surface 21 d of an outer ring 21 b of the first bearing 21 and an inner peripheral surface 61 a of the bracket 6 is exaggeratedly shown.

[0083] The inner ring 21a of the first bearing 21 is fixed to the shaft 15 by press fitting, and the outer ring 21b is fixed to the bracket 6 by clearance fitting. Therefore, there is a difference between the circumference of the outer peripheral surface 21d of the outer ring 21b of the first bearing 21 and the circumference of the inner peripheral surface 61a of the bracket 6.

[0084] When the shaft 15 rotates in the direction indicated by arrow R2 while radial load Fr acts on the first bearing 21, the outer ring 21b moves circumferentially relative to the inner circumferential surface 61a of the bracket 6 as indicated by arrow F1 due to radial load Fr and the circumferential length difference. This phenomenon is called peripheral creep.

[0085] In particular, the first bearing 21 disposed on the load side is subjected to the weight of the impeller 505 mounted on the shaft 15 in addition to the radial exciting force generated in the rotor 1. Therefore, the radial load Fr acting on the first bearing 21 is greater than the radial load Fr acting on the second bearing 22.

[0086] Therefore, in the first embodiment, the bearings 21, 22 and the bearing holders 6, 42 are configured so that the distances D1, D2, d1, d2 satisfy D1-d1<D2-d2. That is, the gap on the outer peripheral side of the outer ring 21b of the first bearing 21 is narrower than the gap on the outer peripheral side of the outer ring 22b of the second bearing 22.

[0087] As a result, the outer ring 21b of the first bearing 21 is less likely to move in the circumferential direction in the bracket 6. That is, in the first bearing 21 on which a larger radial load Fr acts, the occurrence of outer peripheral creep can be suppressed.

[0088] As a case where the above-mentioned relationship D1-d1<D2-d2 holds, for example, a case where the distances D1 and D2 satisfy D1<D2 and a case where the distances d1 and d2 satisfy d1>d2 are considered.

[0089] For example, if the inner diameter of the cylindrical portion 61 of the bracket 6 is made smaller than the inner diameter of the bearing holding portion 42, the distances D1 and D2 satisfy D1<D2. In this case, as long as D1-d1<D2-d2 holds, the distances d1 and d2 are not limited. For example, the distances d1 and d2 may be the same (d1=d2). In this way, since the bearings 21 and 22 can be configured to have the same outer diameter, the manufacturing cost can be reduced.

[0090] In addition, if the outer diameter of the outer ring 21b of the first bearing 21 is larger than the outer diameter of the outer ring 22b of the second bearing 22, the distances d1 and d2 satisfy d1>d2. In this case, as long as D1-d1<D2-d2 holds, the distances D1 and D2 are not limited. For example, the distances D1 and D2 may be the same (D1=D2). In this way, since the cylindrical portion 61 of the bracket 6 and the bearing retaining portion 42 can have the same inner diameter, the manufacturing cost can be reduced.

[0091] And, if Figure 5As shown in (A) and (B), the distance e1 from the center axis C1 to the inner circumference of the inner ring 21a of the first bearing 21 is the same as the distance e2 from the center axis C1 to the inner circumference of the inner ring 22a of the second bearing 22. In other words, the inner diameter (2×e1) of the first bearing 21 is the same as the inner diameter (2×e2) of the second bearing 22.

[0092] Therefore, in the shaft 15, the outer diameter of the portion supported by the first bearing 21 and the outer diameter of the portion supported by the second bearing 22 can be made the same. This can reduce the manufacturing cost.

[0093] <Structure for suppressing shaft current>

[0094] Next, the suppression of the shaft current in the motor 100 is described. When the motor 100 is driven by the inverter, the carrier frequency is set to a frequency higher than the audible frequency in order to suppress the noise associated with the switching operation. However, when the carrier frequency becomes high, a voltage called shaft voltage is generated in the shaft 15 due to high-frequency induction.

[0095] When the shaft voltage increases, the potential difference between the inner rings 21a, 22a and the outer rings 21b, 22b of the bearings 21, 22 supporting the shaft 15 increases, and the current easily flows through the bearings 21, 22 to the shaft 15. This current is called shaft current. When the shaft current is generated, the raceway surfaces of the inner rings 21a, 22a and the outer rings 21b, 22b, and the rolling surfaces of the rolling elements 21c, 22c will be damaged by what is called electrical corrosion.

[0096] Fig.10 This is a schematic diagram for explaining the flow of current when shaft current is generated. Fig.10 As shown by the middle arrow, there is a path A1 from the stator 5 via the bracket 6 and the first bearing 21 to the shaft 15 , a path A2 from the stator 5 via the circuit board 7 and the second bearing 22 to the shaft 15 , and a path A3 from the stator 5 via the rotor core 10 to the shaft 15 .

[0097] In implementation mode 1, Fig.11 As shown, an insulator 18 is provided between the shaft 15 and the second bearing 22. More specifically, the outer diameter of the end 15b on the opposite side of the load of the shaft 15 is reduced, and the cylindrical insulator 18 is attached to the end 15b. The insulator 18 is formed of a thermoplastic resin such as BMC, for example.

[0098] Since the shaft 15 and the second bearing 22 can be electrically insulated by the insulator 18 , the flow of current through the path A2 can be suppressed.

[0099] In addition, in the rotor 1, since the resin portion 30 is disposed between the rotor core 10 and the shaft 15, it is possible to suppress the flow of current from the rotor core 10 to the shaft 15. That is, the flow of current through the path A3 can be suppressed.

[0100] Since the flow of current through the paths A2 and A3 is suppressed among the three paths A1, A2, and A3 of the current, the flow of current through the path A1 is also suppressed. This can suppress the generation of shaft current and the generation of electrical corrosion in the bearings 21 and 22.

[0101] Since the insulator 18 is attached to the end 15 b of the shaft 15 , it is sufficient to thin the end 15 b of the shaft 15 and attach the cylindrical insulator 18 , which can reduce the manufacturing cost.

[0102] In addition, the insulator 18 is not limited to being provided between the shaft 15 and the second bearing 22, but may be provided between the shaft 15 and the first bearing 21. In addition, the insulator 18 may be provided between the shaft 15 and the first bearing 21 and between the shaft 15 and the second bearing 22, respectively.

[0103] <Effects of implementation>

[0104] As described above, the electric motor 100 of the first embodiment includes: the common-pole type rotor 1; the stator 5 surrounding the rotor 1 from the radially outer side; the first bearing 21 and the second bearing 22 supporting the shaft 15 of the rotor 1; the bracket 6 (first bearing holding portion) having the inner peripheral surface 61a facing the outer peripheral surface 21d of the first bearing 21; and the bearing holding portion 42 (second bearing holding portion) having the inner peripheral surface 42a facing the outer peripheral surface 22d of the second bearing 22. The first bearing 21 is located on the load side, and the second bearing 22 is located on the opposite side of the load. The distance D1 from the center axis C1 to the inner peripheral surface 61a of the bracket 6, the distance D2 from the center axis C1 to the inner peripheral surface 42a of the bearing holding portion 42, the distance d1 from the center axis C1 to the outer peripheral surface 21d of the first bearing 21, and the distance d2 from the center axis C1 to the outer peripheral surface 22d of the second bearing 22 satisfy D1-d1<D2-d2.

[0105] Therefore, the clearance on the outer peripheral side of the first bearing 21, which is subjected to a larger radial load, can be made smaller than the clearance on the outer peripheral side of the second bearing 22, and the outer ring 21b of the first bearing 21 can be made less likely to move in the circumferential direction. Thus, the occurrence of peripheral creep can be suppressed, and the performance of the motor 100 can be improved.

[0106] Furthermore, when the distance D1 is made smaller than the distance D2 , the first bearing 21 and the second bearing 22 having the same outer diameter can be used, so that the manufacturing cost can be reduced.

[0107] Furthermore, when the distance d1 is made larger than the distance d2 , the cylindrical portion 61 of the bracket 6 and the bearing holding portion 42 can be formed to have the same inner diameter, so that the manufacturing cost can be reduced.

[0108] Furthermore, since the bracket 6 is formed of metal and the bearing holding portion 42 is formed of resin, the first bearing 21 to which a larger radial load acts can be held with high positional accuracy by the bracket 6. Furthermore, by forming the bearing holding portion 42 of resin, the manufacturing cost can be reduced.

[0109] Furthermore, since the inner diameter of the first bearing 21 is the same as that of the second bearing 22 , the outer diameter of the portion of the shaft 15 held by the first bearing 21 and the outer diameter of the portion held by the second bearing 22 can be made the same, thereby reducing manufacturing costs.

[0110] Furthermore, since the insulator 18 is provided between the shaft 15 and at least one of the first bearing 21 and the second bearing 22 , the generation of shaft current can be suppressed, and the generation of electrical corrosion in the bearings 21 and 22 can be suppressed.

[0111] Furthermore, since the resin portion 30 is provided between the rotor core 10 and the shaft 15 , the generation of shaft current can be suppressed, and the generation of electrical corrosion in the bearings 21 and 22 can be suppressed.

[0112] Implementation Method 2

[0113] Next, embodiment 2 will be described. Fig.12 1 is a partial longitudinal sectional view showing the motor 100A according to Embodiment 2. The material of the rolling element of the first bearing 21 or the rolling element of the second bearing 22 of the motor 100A according to Embodiment 2 is different from that of the motor 100 according to Embodiment 1.

[0114] like Fig.12 As shown, the insulator 18 ( Fig.11 ). That is, the inner peripheral surface of the second bearing 22 is in contact with the surface of the shaft 15 .

[0115] Fig.13 (A) is an enlarged view showing the first bearing 21 and the second bearing 22 according to Embodiment 2. The first bearing 21 according to Embodiment 2 includes an inner ring 21a, an outer ring 21b, and a plurality of rolling elements 21e.

[0116] The rolling element 21e of the first bearing 21 is formed of ceramic. An example of ceramic is alumina (Al2O3). However, the ceramic is not limited to alumina, and any ceramic may be used as long as it has the strength required for the rolling element and has insulation properties.

[0117] The structures of the inner ring 21a and the outer ring 21b of the first bearing 21 are as described in the first embodiment. In addition, the structure of the second bearing 22 is as described in the first embodiment.

[0118] Since the rolling element 21e of the first bearing 21 is formed of ceramic, the inner ring 21a and the outer ring 21b can be electrically insulated. That is, the flow of the current through the path A1 described in the first embodiment can be suppressed.

[0119] Furthermore, as described in the first embodiment, the flow of current through the path A3 is suppressed by the resin portion 30 disposed between the rotor core 10 and the shaft 15 .

[0120] Since the flow of current through the three current paths A1, A2, and A3 is suppressed, the flow of current through the path A2 is also suppressed. This can suppress the generation of shaft current and the generation of electrical corrosion in the bearings 21 and 22.

[0121] In addition, since the first bearing 21 on the load side is subjected to a large radial load, the oil film of the lubricating oil around the rolling element 21e tends to become thinner. The thinner the oil film, the more likely it is that electrical corrosion caused by conduction will occur. By forming the rolling element 21e of the first bearing 21 from ceramic, the occurrence of electrical corrosion can be suppressed even when the oil film becomes thinner.

[0122] In addition, here, the rolling element 21 e of the first bearing 21 is formed of ceramics, and the rolling element 21 c of the second bearing 22 is formed of metal, but at least one of the rolling elements of the bearings 21 and 22 may be formed of ceramics.

[0123] For example, Fig.13 As shown in (B), the rolling element 21e of the first bearing 21 and the rolling element 22e of the second bearing 22 may be both made of ceramic. In this structure, the generation of shaft current can be more effectively suppressed, and the effect of suppressing the generation of electric corrosion can be improved.

[0124] In addition, as described in the first embodiment, the insulator 18 may be provided between the shaft 15 and the second bearing 22 .

[0125] The motor 100A according to the second embodiment is configured similarly to the motor 100 according to the first embodiment except for the above-described points.

[0126] As described above, in the second embodiment, at least one of the first bearing 21 and the second bearing 22 that hold the shaft 15 has a rolling element made of ceramic. Therefore, the generation of shaft current can be effectively suppressed, and the effect of suppressing the generation of electric corrosion can be improved.

[0127] Implementation 3

[0128] Next, implementation mode 3 will be described. Fig.14 1 is a partial longitudinal sectional view showing an electric motor 100B according to Embodiment 3. The electric motor 100B according to Embodiment 3 has a metal bearing holding member 80 as a second bearing holding portion and does not have a heat sink 8 ( Figure 1 ) This point is different from the motor 100 of embodiment 1.

[0129] The bearing holding member 80 is provided so as to cover the load-opposite side of the molded stator 4. The bearing holding member 80 is formed of metal. More specifically, the bearing holding member 80 is formed of a hot-dip galvanized-aluminum-magnesium alloy steel sheet. The hot-dip galvanized-aluminum-magnesium alloy steel sheet has the advantages of being able to be stamped and easily obtaining high dimensional accuracy.

[0130] The bearing holding member 80 may be made of an aluminum alloy such as ADC12 (JIS H5302). Since an aluminum alloy such as ADC12 can be processed by die casting, the degree of freedom of shape is higher than that of extrusion molding.

[0131] The bearing holding member 80 includes a flange portion 81 located radially outside the second bearing 22 , and a plate-shaped portion 82 located on the anti-load side of the second bearing 22 .

[0132] Fig.15 1 is a diagram showing an enlarged portion of a bearing holding member 80. An inner peripheral surface 83 is formed on a flange portion 81 of the bearing holding member 80, and contacts the outer peripheral surface 22d of the outer ring 22b of the second bearing 22. An end surface 84 contacts the axial end surface of the outer ring 22b, and an opposing surface 85 is formed on the plate-like portion 82, and is opposed to the axial end surface of the inner ring 22a at a distance.

[0133] The bearing holding member 80 is held by the molded resin portion 40. The outer peripheral side of the flange portion 81 of the bearing holding member 80 is covered by the molded resin portion 40. The bearing holding member 80 is separated from the circuit substrate 7, and the molded resin portion 40 is interposed between the bearing holding member 80 and the stator 5. That is, the bearing holding member 80 does not contact the circuit substrate 7 and the stator 5.

[0134] Since the bearing holding member 80 is formed of metal, the inner peripheral surface 83 of the bearing holding member 80 can be formed with high dimensional accuracy, similarly to the inner peripheral surface 61a of the bracket 6. Therefore, while satisfying D1-d1<D2-d2 described in the first embodiment, the gap (D2-d2) on the outer peripheral side of the second bearing 22 is narrowed, thereby suppressing the occurrence of peripheral creep.

[0135] Furthermore, since a portion of the bearing holding member 80 is covered by the mold resin portion 40 and does not come into contact with the circuit board 7 and the stator 5 , the generation of shaft current can be suppressed.

[0136] Furthermore, since the bearing holding member 80 is in contact with the outer ring 22b but is not in contact with the inner ring 22a, it is possible to suppress the flow of electric current between the inner ring 22a and the outer ring 22b.

[0137] Furthermore, since the bearing holding member 80 is formed of metal and a part thereof is exposed from the mold resin portion 40 , it is also possible to exert a heat dissipation effect of dissipating heat generated by the coil 55 or the circuit board 7 to the outside.

[0138] The motor 100B according to the third embodiment is configured similarly to the motor 100 according to the first embodiment except for the above-described points.

[0139] As described above, in the third embodiment, since the second bearing 22 is held by the metal bearing holding member 80 (second bearing holding portion), the gap on the outer peripheral side of the second bearing 22 can be narrowed, and the occurrence of outer peripheral creep of the second bearing 22 can be suppressed.

[0140] In addition, in the first embodiment, the bracket 6 as the first bearing holding portion is formed of metal, and the bearing holding portion 42 as the second bearing holding portion is formed of resin. In the third embodiment, the bracket 6 and the bearing holding member 80 are both formed of metal. However, the first bearing holding portion and the second bearing holding portion may be both formed of resin such as BMC, or the first bearing holding portion may be formed of resin and the second bearing holding portion may be formed of metal.

[0141] <Air conditioning unit>

[0142] Next, an air conditioning apparatus to which the electric motors 100 , 100A, and 100B according to the above-described first to third embodiments can be applied will be described. Fig.16 (A) is a diagram showing a configuration of an air-conditioning apparatus 500 to which the electric motor 100 according to Embodiment 1 is applied. The air-conditioning apparatus 500 includes an outdoor unit 501, an indoor unit 502, and a refrigerant pipe 503 connecting these.

[0143] The outdoor unit 501 includes an outdoor blower 510 such as a propeller fan, a compressor 504, and a heat exchanger 507. The outdoor blower 510 includes an impeller 505 and a motor 100 for driving the impeller 505. The structure of the motor 100 is as described in the first embodiment.

[0144] Fig.16 (B) is a cross-sectional view of the outdoor unit 501. The electric motor 100 is mounted on a frame 509 by screws 48, and the frame 509 is arranged in a housing 508 of the outdoor unit 501. An impeller 505 is mounted on the shaft 15 of the electric motor 100 via a hub 506.

[0145] In the outdoor blower 510, the impeller 505 rotates by the rotation of the motor 100, and blows air to the heat exchanger 507. During the cooling operation of the air conditioner 500, the heat released when the refrigerant compressed by the compressor 504 is condensed in the heat exchanger 507 (condenser) is released to the outside through the air blown by the outdoor blower 510.

[0146] Indoor unit 502( Fig.16 (A)) includes an indoor air-sending machine 520, which is a cross-flow fan, for example, and a heat exchanger 523. The indoor air-sending machine 520 includes an impeller 521 and a motor 522 for driving the impeller 521.

[0147] In the indoor blower 520, the impeller 521 rotates by the rotation of the motor 522 to blow air into the room. During the cooling operation of the air conditioner 500, the air from which the heat is removed when the refrigerant evaporates in the heat exchanger 523 (evaporator) is blown into the room by the indoor blower 520.

[0148] In the electric motor 100 described in the first embodiment, since the occurrence of peripheral creep is suppressed, the operation of the outdoor fan 510 can be stabilized for a long period of time, and the reliability of the air-conditioning apparatus 500 can be improved.

[0149] Here, the motor 100 of Embodiment 1 is used for the outdoor fan 510, but at least one of the outdoor fan 510 and the indoor fan 520 may use the motor 100 of Embodiment 1. In addition, the motor 100 of Embodiment 1 may be replaced by either the motor 100A or the motor 100B of Embodiments 2 to 3.

[0150] Furthermore, the electric motors 100 , 100A, and 100B described in the first to third embodiments may also be mounted on electrical equipment other than the blower of the air conditioner.

[0151] As mentioned above, although the preferred embodiment of the present invention was specifically described, the present invention is not limited to the above-mentioned embodiment, and various improvements and modifications can be made without departing from the scope of the present invention.

[0152] Description of Reference Numerals

[0153] 1 rotor; 4 molded stator; 5 stator; 6 bracket (first bearing holding portion); 7 circuit board; 8 heat sink; 9 waterproof cover; 10 rotor core; 15 shaft; 16 permanent magnet; 18 insulator; 21 first bearing; 21a inner ring; 21b outer ring; 21c rolling element; 21d outer peripheral surface; 21e rolling element; 22 second bearing; 22a inner ring; 22b outer ring; 22c rolling element; 22d outer peripheral surface; 22e rolling element; 30 resin portion; 31 inner cylinder portion; 32 rib; 33 outer cylinder portion; 40 molded resin portion; 41 opening portion; 42 bearing holding portion (second bearing holding portion); 4 2a inner circumferential surface; 42b end surface; 45 mounting leg; 50 stator core; 55 coil; 61 cylindrical portion; 61a inner circumferential surface; 62 flange portion; 63 fitting portion; 64 end surface portion; 71 element; 72 lead portion; 73 lead wire; 80 bearing retaining member (second bearing retaining portion); 81 flange portion; 82 plate-shaped portion; 83 inner circumferential surface; 84 end surface; 85 opposing surface; 100, 100A, 100B electric motor; 500 air conditioning device; 501 outdoor unit; 502 indoor unit; 503 refrigerant piping; 505 impeller; 509 frame; 510 outdoor fan; 520 indoor fan.

Claims

1. An electric motor, wherein: have: a rotor having a shaft, a rotor core, and permanent magnets, the rotor core surrounding the shaft from the radially outer side centered on the central axis of the shaft, the permanent magnets being mounted on the rotor core, the permanent magnets constituting magnet poles, and a portion of the rotor core constituting virtual poles; a stator, the stator surrounding the rotor from the outer side in the radial direction; a first bearing and a second bearing, wherein the first bearing and the second bearing support the shaft; a first bearing holding portion, the first bearing holding portion having an inner peripheral surface facing the outer peripheral surface of the first bearing; as well as a second bearing holding portion, the second bearing holding portion having an inner peripheral surface facing the outer peripheral surface of the second bearing, One side of the shaft in the direction of the central axis is a load side that receives load, The first bearing of the first bearing and the second bearing is located on the load side, A distance D1 from the center axis to the inner circumferential surface of the first bearing holding portion, a distance D2 from the center axis to the inner circumferential surface of the second bearing holding portion, a distance d1 from the center axis to the outer circumferential surface of the first bearing, and a distance d2 from the center axis to the outer circumferential surface of the second bearing satisfy D1-d1<D2-d2, In addition, D1<D2 and d1=d2 are satisfied, or d1>d2 is satisfied.

2. The electric motor according to claim 1, wherein: D1=D2 and d1>d2 are satisfied.

3. The electric motor according to claim 1 or 2, wherein: The first bearing holding portion is formed of metal, The second bearing holding portion is formed of resin.

4. The electric motor according to claim 1 or 2, wherein: The first bearing holding portion is formed of metal, The second bearing holding portion is formed of metal.

5. The electric motor according to claim 4, wherein: The invention further includes a molded resin portion that holds the first bearing holding portion and the second bearing holding portion.

6. The electric motor according to claim 1 or 2, wherein: The first bearing and the second bearing have the same inner diameter.

7. The electric motor according to claim 1 or 2, wherein: An insulator is provided between at least one of the first bearing and the second bearing and the shaft.

8. The electric motor according to claim 1 or 2, wherein: The rotor has a resin portion between the rotor core and the shaft.

9. The electric motor according to claim 1 or 2, wherein: At least one of the first bearing and the second bearing has a rolling element formed of ceramic.

10. The electric motor according to claim 9, wherein The first bearing has rolling elements formed of ceramic.

11. The electric motor according to claim 9, wherein: The first bearing and the second bearing each have rolling elements formed of ceramic.

12. A blower, wherein: have: The electric motor according to any one of claims 1 to 11; and An impeller is rotationally driven by the electric motor.

13. An air conditioning device, wherein: An outdoor unit and an indoor unit connected to the outdoor unit via a refrigerant pipe. At least one of the outdoor unit and the indoor unit includes the air blower according to claim 12.

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