Motor, blower, and air conditioning device

Abstract

The present invention provides a motor comprising: a rotor having a shaft and a bonded ferrite magnet secured to the shaft; and a stator having a stator core facing the rotor in the radial direction centered on the shaft and a coil formed from aluminum wire and wound around the stator core. The coil has two coil ends on both end faces of the stator core in the axial direction of the shaft. Provided that Lc is the distance between two most distant points in the axial direction at said two coil ends and Lm is the axial length of the bonded ferrite magnet, Lc ≤ Lm is satisfied.

Description

Motors, blowers and air conditioners

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

[0002] Conventionally, motors have been known that include a stator having a stator core and a coil, and a rotor having a permanent magnet. To reduce the manufacturing cost of the motor, a motor has been proposed in which the coil is made of aluminum wire and the permanent magnet is a ferrite bonded magnet (see, for example, Patent Document 1).

[0003] International Publication WO2018 / 066084 (paragraphs 0014 and 0029)

[0004] However, aluminum wire has a higher electrical resistance than copper wire. Also, ferrite bonded magnets have a weaker magnetic force than rare earth bonded magnets or sintered ferrite magnets, so more current needs to be passed through the coil. As a result, the amount of heat generated by the coil increases, making the motor prone to temperature rise.

[0005] A rise in motor temperature can lead to deformation or melting of the resin contained in the ferrite bond magnet or the insulating portion provided between the stator core and the coil, so there is a demand for improving the heat dissipation performance of motors.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to improve the heat dissipation performance of a motor.

[0007] The motor disclosed herein includes a rotor having a shaft and a ferrite bonded magnet fixed to the shaft, a stator core facing the rotor in a radial direction centered on the shaft, and a stator including a coil made of aluminum wire wound around the stator core. The coil has two coil ends on both end surfaces of the stator core in the axial direction of the shaft. The distance Lc between the two axially most distant points of the two coil ends and the axial length Lm of the ferrite bonded magnet satisfy Lc≦Lm.

[0008] According to the present disclosure, heat generated in the coil can be efficiently transferred from the coil end to the ferrite bond magnet and dissipated via the shaft, thereby improving the heat dissipation performance of the motor.

[0009] 1 is a longitudinal cross-sectional view showing a motor of embodiment 1. FIG. 2 is a cross-sectional view showing a motor of embodiment 1. FIG. 3 is a schematic diagram showing teeth, insulating portions, and coils of embodiment 1. FIG. 4 is a cross-sectional view showing an enlarged portion of the motor of embodiment 1. FIG. 5 is a schematic diagram showing a mold for molding the ferrite bonded magnet of embodiment 1. FIG. 6 is a schematic diagram showing heat dissipation paths in the motor of embodiment 1. FIG. 7 is a graph showing the relationship between the radial width of the ferrite bonded magnet of embodiment 1 and the magnetic field on the inner periphery of the ferrite bonded magnet in the magnetizing process. FIG. 8 is a longitudinal cross-sectional view showing a motor of embodiment 2. FIG. 9 is a longitudinal cross-sectional view showing a motor of embodiment 3. FIG. 10 is a longitudinal cross-sectional view showing a motor of embodiment 4. FIG. 11 is a longitudinal cross-sectional view showing another example configuration of the motor of embodiment 4. FIG. 12 is a diagram showing a blower of embodiment 5. FIG. 13 is a diagram showing an air conditioning apparatus of embodiment 6.

[0010] Embodiment 1. <Overall Configuration of Motor 1> A motor according to embodiment 1 will now be described. Fig. 1 is a longitudinal cross-sectional view showing motor 1 according to embodiment 1. Motor 1 is a synchronous motor, and is used, for example, in a blower of an air conditioning device 100 (Fig. 13).

[0011] The motor 1 includes a rotor 2 having a shaft 20, a stator 3 surrounding the rotor 2, a molded resin portion 35 covering the stator 3, and bearings 11 and 12 supporting the shaft 20. A central axis Ax of the shaft 20 defines the center of rotation of the rotor 2. The stator 3 and the molded resin portion 35 constitute a molded stator 4.

[0012] Hereinafter, the direction of the central axis Ax will be referred to as the "axial direction." The radial direction centered on the central axis Ax will be referred to as the "radial direction." The circumferential direction centered on the central axis Ax will be referred to as the "circumferential direction." Furthermore, a cross-sectional view taken along a plane perpendicular to the central axis Ax will be referred to as a "transverse cross-sectional view," and a cross-sectional view taken along a plane parallel to the central axis Ax will be referred to as a "longitudinal cross-sectional view."

[0013] The shaft 20 protrudes from the molded stator 4 to one side in the axial direction. For example, an impeller 81 (FIG. 12) of a blower is attached to the protruding portion of the shaft 20. Therefore, the side from which the shaft 20 protrudes is referred to as the "load side," and the opposite side is referred to as the "anti-load side."

[0014] <Configuration of molded stator 4> As described above, the molded stator 4 includes the stator 3 and the molded resin portion 35. The molded resin portion 35 is formed of a thermosetting resin such as an unsaturated polyester resin or an epoxy resin. The unsaturated polyester resin is, for example, a bulk molding compound (BMC).

[0015] The molded resin portion 35 is an outer shell member that covers the radially outer side and the anti-load side of the stator 3. The molded resin portion 35 has an opening 35a on the load side and a bottom 35b on the anti-load side. The rotor 2 is inserted into the inside of the stator 3 through the opening 35a. The molded resin portion 35 also has an annular stepped portion 35e formed to surround the opening 35a.

[0016] A metal bracket 13 that supports the load-side bearing 11 is attached to the stepped portion 35e of the molded resin portion 35. The bracket 13 is an annular member centered on the central axis Ax. The bracket 13 has a bearing holding portion 13a, which is a recess that holds the bearing 11, in its radial center.

[0017] A bottom portion 35b of the molded resin portion 35 is formed so as to cover the anti-load side of the stator 3. A bearing holding portion 35c, which is a recess that accommodates the bearing 12, is formed in the bottom portion 35b.

[0018] The outer casing member covering the stator 3 is not limited to the molded resin portion 35, but may be, for example, a metal shell. The shell is, for example, a cylindrical member whose main component is iron (Fe), and the stator 3 is fixed inside the shell by shrink fitting or the like.

[0019] 2 is a cross-sectional view showing the rotor 2 and the stator 3. The molded resin portion 35 is omitted in FIG. 2. The stator 3 has a stator core 30 and a coil 32 wound around the stator core 30.

[0020] The stator core 30 has a laminated body in which a plurality of magnetic laminated elements are stacked in the axial direction. The laminated elements are thin plates whose main component is Fe, more specifically, electromagnetic steel sheets. The thickness of the laminated elements is, for example, 0.2 mm to 0.5 mm. Instead of the laminated body of laminated elements, processed ingots whose main component is Fe may also be used.

[0021] The stator core 30 has an annular yoke 30a and a plurality of teeth 30b extending radially inward from the yoke 30a. The number of teeth 30b is nine in this example, but is not limited to this.

[0022] The teeth 30b have extending portions 30c that extend radially inward from the yoke 30a and tooth tips 30d formed at the tips of the extending portions 30c. The tooth tips 30d face the outer peripheral surface of the rotor 2 in the radial direction.

[0023] A slot S is formed between the teeth 30b adjacent to each other in the circumferential direction. The coil 32 is wound around the teeth 30b with the insulating portion 31 interposed therebetween and is housed in the slot S.

[0024] The insulating portion 31 is made of insulating resin such as PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), liquid crystal polymer (LCP), PET (polyethylene terephthalate), etc. An insulating film may also be provided to cover the inner surface of the slot S.

[0025] 1, the insulating portion 31 has a body portion 31b formed to surround the extension portion 30c (FIG. 2) of the tooth 30b, a wall portion 31a formed radially outward from the body portion 31b, and a wall portion 31c formed radially inward from the body portion 31b. Both the wall portions 31a and 31c protrude in the axial direction from the stator core 30. The protrusion amount of the wall portion 31a is greater than the protrusion amount of the wall portion 31c.

[0026] The coil 32 is wound around the tooth 30b via the insulating portion 31. More specifically, the coil 32 is wound around the extension portion 30c of the tooth 30b via the body portion 31b of the insulating portion 31. The coil 32 is guided from both radial sides by the wall portions 31a and 31c of the insulating portion 31.

[0027] The coil 32 is made of aluminum wire. The aluminum wire is an aluminum conductor covered with an insulating coating. The coil 32 is wound by concentrated winding or distributed winding.

[0028] 3 is a cross-sectional view taken along a plane perpendicular to the direction in which the teeth 30b extend, showing two teeth 30b, the insulating portion 31, and the coil 32. As described above, the body portion 31b of the insulating portion 31 is provided so as to surround the extending portion 30c of the teeth 30b.

[0029] The coil 32 has coil ends 32a located on the axial end faces of the stator core 30 (more specifically, the axial end faces of the teeth 30b) and coil sides 32b housed in slots S between adjacent teeth 30b. Note that although Fig. 3 shows an example in which the coil 32 is wound around the teeth 30b using concentrated winding, the winding method may also be distributed winding.

[0030] <Configuration of Rotor 2> As shown in FIG. 2, the rotor 2 has a shaft 20, a ferrite bond magnet 21 surrounding the shaft 20 from the outside in the radial direction, and a resin part 22 as a connecting part provided between them.

[0031] The shaft 20 is made of a metal such as carbon steel for mechanical construction (S45C) and has a circular cross section. The shaft 20 is rotatably supported by the bearings 11 and 12 described above.

[0032] The ferrite bond magnet 21 is formed in an annular shape centered on the central axis Ax. The outer periphery 21 a of the ferrite bond magnet 21 forms the outer periphery of the rotor 2.

[0033] The ferrite bonded magnet 21 is a magnet made by kneading ferrite magnet powder and resin and molding it. The resin contained in the ferrite bonded magnet 21 is, for example, nylon, PPS (polyphenylene sulfide), EEA (ethylene-ethyl acrylate copolymer), or epoxy resin.

[0034] Figure 4 is an enlarged view of a portion of the rotor 2 and stator 3. The ferrite bonded magnet 21 is magnetized to have a polar anisotropic orientation. As a result, north and south poles are formed alternately in the circumferential direction on the outer periphery 21a of the ferrite bonded magnet 21. In Figure 4, the circumferential position of the pole center of the magnetic pole is indicated by the symbol P, and the circumferential position of the inter-pole portion is indicated by the symbol M.

[0035] The outer periphery 21a of the ferrite bonded magnet 21 extends so that the outer diameter is greatest at the pole center and smallest at the inter-pole portion. Specifically, the outer periphery 21a of the ferrite bonded magnet 21 has a first arc-shaped portion A1 that includes the pole center of the magnetic pole, and a second arc-shaped portion A2 that includes the inter-pole portion.

[0036] The radius of curvature R1 of the first arc-shaped portion A1 is smaller than the distance R2 from the central axis Ax to the outer periphery 21a of the pole center. That is, R1<R2 holds. Therefore, the first arc-shaped portion A1 extends radially outward in a convex manner, and the second arc-shaped portion A2 extends radially inward in a concave manner.

[0037] It is desirable that the outer periphery 21a of the ferrite bond magnet 21 has a first arc-shaped portion A1 and a second arc-shaped portion A2 as described above, but this is not limited to this and may be, for example, circular (shown by the dotted line C1 in Figure 4).

[0038] 2 is formed of a thermoplastic resin such as PBT (polybutylene terephthalate). The shaft 20 is fixed to the inner periphery of the resin part 22, and the ferrite bond magnet 21 is fixed to the outer periphery of the resin part 22. The resin part 22 is formed, for example, by integrally molding the shaft 20 and the ferrite bond magnet 21 with resin.

[0039] 1, resin portion 22 has main portion 22a located radially inward of ferrite bond magnet 21, protruding portion 22b protruding from main portion 22a toward the load side, and protruding portion 22c protruding toward the anti-load side. Protruding portion 22b abuts against bearing 11, and protruding portion 22c abuts against bearing 12.

[0040] Next, we will explain the axial length of each element of the motor 1. The distance between the two axially most distant points of the coil ends 32a at both axial ends of the stator core 30 (i.e., the two coil ends 32a) is defined as Lc.

[0041] The axial length of ferrite bond magnet 21 of rotor 2 is defined as Lm. Axial length Lm of ferrite bond magnet 21 is the distance from one end of ferrite bond magnet 21 to the other end in the axial direction.

[0042] Li denotes the distance between the two axially most distant points on the wall portions 31a at both axial ends of the stator core 30 (i.e., the two wall portions 31a). The distance Li is the axial length of the insulating portion 31 of the stator 3. Note that although Li is used here as the distance between two points on the wall portion 31a, it may also be used as the distance between two points on the wall portion 31c.

[0043] The axial length of the resin portion 22 of the rotor 2 is defined as Lr. The axial length Lr of the resin portion 22 is the axial distance between the two axially most distant points on the protrusions 22b and 22c.

[0044] The relationship between Lc, Lm, Li, and Lr is as follows: The distance Lc between the two axially most distant points on coil ends 32a at both axial ends of stator core 30 is equal to or less than the axial length Lm of ferrite bond magnet 21. In other words, Lc≦Lm holds.

[0045] The axial length of insulating portion 31 (i.e., distance Li) is equal to or greater than axial length Lm of ferrite bond magnet 21. In other words, Lc≦Lm≦Li holds.

[0046] The axial length Lr of resin portion 22 is longer than the axial length Lm of ferrite bond magnet 21. In other words, Lc≦Lm<Lr holds.

[0047] The axial length of the insulating portion 31 (i.e., the distance Li) and the axial length of the resin portion 22 Lr may be longer or may be the same.

[0048] The radial width T (FIG. 4) of ferrite bonded magnet 21 is the distance between outer periphery 21a and inner periphery 21b of ferrite bonded magnet 21. The radial width T of ferrite bonded magnet 21 is 2 mm or more and 10 mm or less. In other words, 2 mm≦T≦10 mm holds.

[0049] As described above, the outer periphery 21a of the ferrite bond magnet 21 has the first arc-shaped portion A1 and the second arc-shaped portion A2, and therefore the width T varies in the circumferential direction. Both the maximum and minimum values ​​of the width T need only be 2 mm or more and 10 mm or less.

[0050] <Manufacturing Method of Motor 1> Next, we will explain the manufacturing method of motor 1. Fig. 5 is a schematic diagram showing a cross section perpendicular to the axial direction of a mold 60 used to mold ferrite bond magnet 21. Ferrite bond magnet 21 is formed by injection molding.

[0051] The mold 60 has an annular cavity 61, which is the molding space in which the ferrite bond magnet 21 is molded. The inner peripheral surface of the cavity 61 has a shape corresponding to the first arc-shaped portion A1 and the second arc-shaped portion A2 (FIG. 4) described above, but is shown in a simplified form in FIG. 5. A core 62 is provided in the center of the cavity 61 of the mold 60. The core 62 has an outer diameter that is the same as the outer diameter of the main portion 22a of the resin portion 22, which will be formed in a subsequent process.

[0052] A plurality of magnetizers 63 are arranged circumferentially around the cavity 61 of the mold 60. For simplicity, Figure 5 shows an example in which four magnetizers 63 are provided on the mold 60, but the number of magnetizers 63 is the same as the number of poles of the ferrite bond magnet 21. The magnetizer 63 is made by winding a magnetizing coil 65 around a magnetic body 64, and an orientation magnetic field f is generated within the cavity 61 by passing a current through the magnetizing coil 65. Alternatively, a magnet may be arranged adjacent to the magnetic body 64, and the magnetic field of the magnet may be induced within the cavity 61 to generate the orientation magnetic field f.

[0053] During molding, the raw material of ferrite bonded magnet 21 is filled into cavity 61 of mold 60. Then, a polar anisotropic magnetic field f is generated by magnetizer 63, and heat and pressure are applied to the raw material of ferrite bonded magnet 21, thereby orienting and molding ferrite bonded magnet 21.

[0054] The molded ferrite bond magnet 21 is then removed from the mold 60 and placed in another mold together with the shaft 20. The cavity of the mold is then filled with a thermosetting resin such as unsaturated polyester resin or a thermoplastic resin such as PBT to form the resin portion 22. In this way, the shaft 20 and the ferrite bond magnet 21 are integrated via the resin portion 22, and the rotor 2 is formed.

[0055] After the rotor 2 is completed, the motor 1 is assembled. That is, a plurality of laminated elements are stacked in the axial direction and fixed by caulking or the like to form the stator core 30. An insulating section 31 is formed on the stator core 30, and a coil 32 is wound around it to obtain the stator 3. The stator 3 is placed in a mold for a molded stator, and a resin (molding resin) such as BMC is injected and heated to form the molded resin section 35. This completes the molded stator 4.

[0056] Thereafter, bearings 11 and 12 are attached to shaft 20 of rotor 2, and this is inserted into the hollow portion through opening 35a of molded stator 4, with bearing 12 fitted into bearing holder 35c of molded resin portion 35. Next, bracket 13 is attached to stepped portion 35e of molded stator 4, and bearing 11 is fitted into bearing holder 13a of bracket 13. This completes motor 1.

[0057] <Operation> Next, a description will be given of the operation of the motor 1 of embodiment 1. In the motor 1 of embodiment 1, the coil 32 of the stator 3 is formed from aluminum wire, and the rotor 2 has the ferrite bond magnet 21.

[0058] The resistivity of aluminum wire is 1.6 times that of copper wire, which is a common coil material. If the electrical resistance of the coil 32 is R (Ω) and the number of phases of the coil 32 is N, the heat generation amount Q (W) when a current I (A) flows through the coil 32 is calculated as follows: Q = N × R × I ２ If the resistance increases by 1.6 times due to the use of aluminum wire, the calorific value Q also increases by 1.6 times.

[0059] Furthermore, the magnetic force of the ferrite bonded magnet 21 is half that of the sintered ferrite magnet. In other words, to obtain the same output as the sintered ferrite magnet using the ferrite bonded magnet 21, twice the current is required. Therefore, the above Q = N x R x I ２ Therefore, the heat generation amount Q is four times larger.

[0060] When the amount of heat generated by the coil 32 increases, the temperature of the motor 1 rises. The temperature rise of the motor 1 can cause deformation or melting of the resin or insulating portion 31 of the ferrite bond magnet 21, leading to failure of the motor 1. For this reason, there is a demand for improving the heat dissipation performance of the motor 1.

[0061] 6 is a schematic diagram showing the heat dissipation path in the motor 1. A portion of the heat generated in the coil 32 is transferred radially outward from the coil end 32a and dissipated to the outside from the molded resin portion 35.

[0062] Of the heat generated in coil 32, the heat that is conducted radially inward from coil end 32a passes through the air gap and reaches ferrite bond magnet 21. The heat conducted to ferrite bond magnet 21 is conducted to shaft 20 via resin portion 22 and is dissipated from the end of shaft 20, or via bracket 13 or bottom portion 35b of molded resin portion 35.

[0063] Since the ferrite bond magnet 21 has a higher thermal conductivity than air, by having the coil end 32a radially facing the ferrite bond magnet 21, some of the heat generated in the coil 32 is more easily transferred from the coil end 32a to the ferrite bond magnet 21.

[0064] In the first embodiment, as described above, the distance Lc between the two axially most distant points in the coil ends 32a at both axial ends of the stator core 30 is equal to or less than the axial length Lm of the ferrite bond magnet 21. In other words, Lc≦Lm holds.

[0065] Therefore, the entire coil end 32a faces the ferrite bond magnet 21 in the radial direction. This allows the heat transferred from the coil end 32a to the radially inward direction to be transferred to the ferrite bond magnet 21 efficiently.

[0066] Furthermore, resin portion 22 is provided between shaft 20 and ferrite bond magnet 21, thereby electrically insulating shaft 20 from ferrite bond magnet 21. This reduces the potential difference between the inner and outer rings of bearings 11 and 12, preventing electrolytic corrosion.

[0067] Furthermore, the dimensions and shape of the resin portion 22 can be flexibly determined depending on molding conditions, etc., so that the natural frequency of the rotor 2 can be adjusted, thereby reducing noise.

[0068] Furthermore, the axial length Lm of ferrite bond magnet 21 is equal to or less than the axial length (i.e., distance Li) of insulating portion 31. In other words, Lc≦Lm≦Li holds.

[0069] The longer the axial length Lm of ferrite bonded magnet 21, the less air with low thermal conductivity there is in the heat dissipation path, improving heat dissipation performance. Also, the longer the axial length Lm of ferrite bonded magnet 21, the more magnetic flux is generated, so less current needs to be passed through coil 32, improving copper loss.

[0070] On the other hand, if the axial length Lm of the ferrite bond magnet 21 is too long, the motor 1 will become larger, the installation of the motor 1 will be reduced, or costs will increase due to the increased amount of molding resin, etc. used to form the outer casing of the motor 1.

[0071] In addition to insulating the stator core 30 from the coils 32, the insulating portion 31 holds the coils 32 and may also hold the crossover wires or circuit boards of the coils 32, serving as a base for the various components of the motor 1. Therefore, the axial length of the insulating portion 31 (i.e., distance Li) determines the axial length of the motor 1.

[0072] If the axial length Lm of ferrite bond magnet 21 is made longer than the axial length of insulating portion 31 (i.e., distance Li), it will be necessary to further increase the axial length of motor 1. For this reason, it is desirable that the axial length Lm of ferrite bond magnet 21 be equal to or less than the axial length of insulating portion 31 (i.e., distance Li).

[0073] Furthermore, the axial length Lr of resin portion 22 is longer than the axial length Lm of ferrite bond magnet 21 (Lr>Lm). Gaps are provided on both axial sides of rotor 2 to avoid contact with bracket 13 or bottom portion 35b of molded resin portion 35, and because air is present in these gaps, the thermal resistance is high.

[0074] By having protrusions 22b and 22c in resin portion 22, the axial length Lr of resin portion 22 is longer than the axial length Lm of ferrite bond magnet 21. This reduces the thermal resistance of the gaps on both sides of rotor 2 in the axial direction, and improves heat dissipation from rotor 2.

[0075] In particular, the protrusions 22b and 22c of the resin part 22 come into contact with the bearings 11 and 12, which further reduces the thermal resistance in the gaps between the rotor 2 and the bearings 11 and 12. This allows the heat of the rotor 2 to be diffused to surrounding members (for example, the bracket 13 or the bottom part 35b of the molded resin part 35) via the bearings 11 and 12, which have high thermal conductivity, thereby improving heat dissipation.

[0076] Furthermore, because ferrite bonded magnet 21 has the polar anisotropic orientation shown in Figure 4, the magnetic path can be made longer compared to when it has a radial orientation. As a result, the permeance of ferrite bonded magnet 21 can be increased, and the magnetic force can be increased. Since the current can be reduced by the amount of the increase in magnetic force, copper loss can be reduced and heat generation in coil 32 can be suppressed.

[0077] Furthermore, the radial width T of ferrite bonded magnet 21 is 2 mm or more and 10 mm or less. If the width T of ferrite bonded magnet 21 is less than 2 mm, there is a possibility that cracks will occur in ferrite bonded magnet 21 when it is cooled after injection molding, so it is desirable that the width T of ferrite bonded magnet 21 be 2 mm or more.

[0078] Furthermore, although a polar anisotropic orientation is imparted to the ferrite bonded magnet 21, if the width T of the ferrite bonded magnet 21 is too wide, the magnetic field for orientation may not sufficiently reach the inner periphery 21b of the ferrite bonded magnet 21.

[0079] 7 is a graph showing the relationship between the radial width T (mm) of ferrite bonded magnet 21 and the magnetic field (A / m) for alignment at inner circumference 21b of ferrite bonded magnet 21. The magnetic field required for alignment of ferrite bonded magnet 21 is designated as Ho. The magnetic field Ho required for alignment is not particularly limited, but an example is 1000 kA / m.

[0080] 7, if the radial width T of ferrite bonded magnet 21 exceeds 10 mm, the magnetic field that reaches inner periphery 21b of ferrite bonded magnet 21 will be smaller than the magnetic field Ho required for alignment. Therefore, it is desirable that the radial width T of ferrite bonded magnet 21 be 10 mm or less.

[0081] Therefore, it is desirable that the radial width T of the ferrite bond magnet 21 be 2 mm or more and 10 mm or less (i.e., 2 mm≦T≦10 mm) both at the inter-pole portion and at the pole center.

[0082] 4, the outer periphery 21a of the ferrite bond magnet 21 has a first arc-shaped portion A1 that includes the pole center and a second arc-shaped portion A2 that includes the inter-pole portion. The radius of curvature R1 of the first arc-shaped portion A1 and the distance R2 from the central axis Ax of the shaft 20 to the outer periphery 21a at the pole center satisfy the relationship R1<R2.

[0083] Because ferrite bonded magnet 21 has a polar anisotropic orientation, the magnetic path between adjacent magnetic poles P extends in a U-shape centered on the inter-pole portion, and the closer to the outer periphery 21a in the inter-pole portion, the shorter the magnetic path becomes. Because the permeance coefficient decreases in the portion with a short magnetic path, demagnetization of ferrite bonded magnet 21 is likely to occur. Furthermore, the magnetic force generated in the inter-pole portion is small.

[0084] When the above R1 < R2 holds, outer periphery 21a of ferrite bonded magnet 21 extends so that the outer diameter is greatest at the pole center and smallest in the inter-pole area. Therefore, compared to when outer periphery 21a of ferrite bonded magnet 21 is circular, it is possible to remove short sections of magnetic path, thereby suppressing demagnetization of ferrite bonded magnet 21. Furthermore, the amount of material used for ferrite bonded magnet 21 can be reduced in areas that have little effect on magnetic force, thereby reducing manufacturing costs.

[0085] Here, an example has been described in which resin portion 22 is provided between shaft 20 and ferrite bond magnet 21, but ferrite bond magnet 21 may be formed on the outer periphery of shaft 20 without providing resin portion 22.

[0086] <Effects of the embodiment> As described above, the motor 1 of the first embodiment includes the rotor 2 having the shaft 20 and the ferrite bond magnet 21 fixed to the shaft 20, the stator core 30 radially facing the rotor 2, and the stator 3 having the coil 32 made of aluminum wire wound around the stator core 30. The coil 32 has two coil ends 32a on both axial end surfaces of the shaft 20 of the stator core 30. The distance Lc between the two axially most distant points on the two coil ends 32a and the axial length Lm of the ferrite bond magnet 21 satisfy Lc≦Lm.

[0087] As described above, because the rotor 2 has the ferrite bond magnet 21 and the coil 32 of the stator 3 is formed from aluminum wire, it is possible to reduce the manufacturing cost of the motor 1. Furthermore, because the above-mentioned Lc≦Lm holds, the entire coil end 32a of the coil 32 faces the ferrite bond magnet 21 in the radial direction. Therefore, some of the heat generated in the coil 32 can be efficiently transferred from the coil end 32a to the ferrite bond magnet 21 and dissipated via the shaft 20. This improves the heat dissipation performance of the motor 1, enabling the motor 1 to provide stable output over a long period of time.

[0088] Furthermore, the insulating portion 31 has two wall portions 31a on both axial end surfaces of the stator core 30, and the distance Li between the two axially farthest points on the two wall portions 31a and the above-mentioned distances Lc and Lm satisfy Lc≦Lm≦Li, thereby improving heat dissipation performance while suppressing an increase in the size of the motor 1 and the resulting increase in manufacturing costs.

[0089] In addition, a resin portion 22 is provided between the shaft 20 and the ferrite bond magnet 21, and the axial length Lr of the resin portion 22 and the above-mentioned distance Lm satisfy Lm < Lr, thereby reducing the thermal resistance on both sides of the axial direction of the rotor 2 and improving the heat dissipation performance of the motor 1.

[0090] Furthermore, since the protrusions 22b, 22c of the resin part 22 are in contact with the bearings 11, 12, the heat of the rotor 2 can be dissipated via the protrusions 22b, 22c and the bearings 11, 12, thereby further improving the heat dissipation performance of the motor 1.

[0091] Furthermore, since the radial width T of the ferrite bonded magnet 21 is 2 mm or more and 10 mm or less, cracking of the ferrite bonded magnet 21 during cooling after injection molding can be prevented, and the ferrite bonded magnet 21 can be sufficiently oriented up to the inner circumference 21b.

[0092] Furthermore, outer periphery 21a of ferrite bonded magnet 21 has a first arc-shaped portion A1 that includes the pole center and a second arc-shaped portion A2 that includes the inter-pole portion, and the radius of curvature R1 of first arc-shaped portion A1 and the distance R2 from central axis Ax of shaft 20 to outer periphery 21a at the pole center satisfy R1 < R2. Therefore, it is possible to remove short magnetic path portions in ferrite bonded magnet 21, and demagnetization of ferrite bonded magnet 21 can be suppressed.

[0093] Second Embodiment Fig. 8 is a longitudinal cross-sectional view showing a motor 1A according to a second embodiment. The second embodiment relates to a lead wire 34 extending from the motor 1A. The lead wire 34 is connected to, for example, a circuit board or the like disposed outside the motor 1A. The lead wire 34 is used, for example, to supply current from the circuit board to the coil 32.

[0094] A metal terminal 33 is fixed to the axial end surface of the wall portion 31a of the insulating portion 31. The terminal 33, together with the insulating portion 31, is covered with a molded resin portion 35. A lead wire 34 is fixed to the terminal 33 and is drawn out from the molded resin portion 35. An end portion 32e of the coil 32 is fixed to the terminal 33. The lead wire 34 and the coil 32 are electrically connected via the terminal 33.

[0095] The lead wire 34 is formed of a material having lower electrical resistance than the aluminum wire forming the coil 32. Specifically, the lead wire 34 is formed of a copper wire or a clad wire having a copper layer and an aluminum layer.

[0096] When a current flows through the coil 32, the current also flows through the lead wire 34, which also generates heat. If the heat of the lead wire 34 is transferred to the molded resin portion 35, this will lead to a rise in the temperature of the motor 1A.

[0097] In the second embodiment, the lead wires 34 are made of a material with lower electrical resistance than aluminum wire, so the amount of heat generated in the lead wires 34 is reduced, thereby suppressing the temperature rise of the motor 1A.

[0098] Furthermore, since a material with lower electrical resistance has higher thermal conductivity, the lead wires 34 can be made of a material with higher thermal conductivity than aluminum wire. This makes it easier for heat generated in the coil 32 to be dissipated from the lead wires 34 via the circuit board or the like, thereby suppressing the temperature rise of the motor 1A.

[0099] 8 shows one terminal 33 and one lead wire 34, it is also possible to provide two or more terminals 33 and two or more lead wires 34. For example, it is also possible to provide three terminals 33 and three lead wires 34 corresponding to the U-phase, V-phase, and W-phase of the coil 32.

[0100] Except for the points mentioned above, the motor 1A of the second embodiment is configured similarly to the motor 1 of the first embodiment.

[0101] As described above, the motor 1A of the second embodiment includes the lead wires 34 connected to the coil 32 and drawn out to the outside, and the lead wires 34 are formed of a material with lower electrical resistance than aluminum wire. This prevents heat generation in the lead wires 34 and allows heat generated in the coil 32 to be dissipated via the lead wires 34. This further improves the heat dissipation performance of the motor 1A.

[0102] 9 is a longitudinal cross-sectional view showing a motor 1B of embodiment 3. The motor 1B of embodiment 3 differs from the motor 1 of embodiment 1 in the shape of the ferrite bond magnet 23 of the motor 2B.

[0103] The outer periphery 23a of the ferrite bond magnet 23 is inclined so that the outer diameter of the ferrite bond magnet 23 is smallest at the axial center and largest at the axial ends.

[0104] The ferrite bond magnet 23 has a first portion S1 that faces the stator core 30 in the radial direction, and a second portion S2 that does not face the stator core 30 in the radial direction. The second portion S2 protrudes in the axial direction beyond the stator core 30. The second portions S2 are located on both axial sides of the first portion S1.

[0105] The longest distance from the central axis Ax to the outer periphery 23a of the first portion S1 of the ferrite bonded magnet 23 is defined as distance D1. The longest distance from the central axis Ax to the outer periphery 23a of the second portion S2 of the ferrite bonded magnet 23 is defined as distance D2.

[0106] Twice the distance D1, i.e., D1×2, corresponds to the maximum outer diameter of the first portion S1 of the ferrite bonded magnet 23. Twice the distance D2, i.e., D2×2, corresponds to the maximum outer diameter of the second portion S2 of the ferrite bonded magnet 23.

[0107] Distances D1 and D2 satisfy D2 > D1. That is, second portion S2 of ferrite bond magnet 23, which does not face stator core 30, protrudes radially outward, i.e., toward stator 3, more than first portion S1 facing stator core 30.

[0108] In other words, the air gap between the ferrite bond magnet 23 and the stator 3 is narrower in the second portion S2 where the ferrite bond magnet 23 does not face the stator core 30 than in the first portion S1 where the ferrite bond magnet 23 faces the stator core 30.

[0109] In this way, the second portion S2 of the ferrite bond magnet 23 approaches the stator 3, narrowing the gap between the coil end 32a and the ferrite bond magnet 23, thereby reducing the thermal resistance between them. As a result, part of the heat generated in the coil 32 can be efficiently dissipated from the coil end 32a to the shaft 10 via the ferrite bond magnet 23, further improving heat dissipation.

[0110] The difference between the distances D1 and D2 is preferably 0.1 mm, for example. When ferrite bond magnet 23 is injection molded into a cylindrical shape, the difference in shrinkage rate after molding causes the axial center to shrink more than the axial ends, resulting in a shape where D2 - D1 = 0.1 mm. Therefore, the aforementioned effect of improving heat dissipation can be achieved with a simple manufacturing process.

[0111] Except for the points mentioned above, the motor 1B of the third embodiment is configured similarly to the motor 1 of the first embodiment.

[0112] Here, the second portion S2 is provided on both axial sides of the first portion S1 of the ferrite bond magnet 23, but it is sufficient that the second portion S2 is provided on at least one axial side of the first portion S1.

[0113] As explained above, in the third embodiment, ferrite bond magnet 23 has first portion S1 that faces stator core 30 in the radial direction and second portion S2 that does not face stator core 30, and the longest distance D2 from central axis Ax to outer periphery 23a of ferrite bond magnet 23 in second portion S2 is longer than the longest distance D1 from central axis Ax to outer periphery 23a of ferrite bond magnet 23 in first portion S1, so that the gap between coil end 32a and ferrite bond magnet 23 can be narrowed and heat generated in coil 32 can be efficiently dissipated from coil end 32a via ferrite bond magnet 23 to shaft 10. In other words, the heat dissipation performance of motor 1B can be further improved.

[0114] Embodiment 4 Fig. 10 is a vertical cross-sectional view showing a motor 1C of embodiment 4. The motor 1C of embodiment 4 differs from the motor 1 of embodiment 1 in the shape of the rotor 2C.

[0115] As shown in Figure 10, the rotor 2C of the motor 1C of embodiment 4 has a shaft 20, a ferrite bond magnet 21 surrounding the shaft 20 from the radial outside, and a resin part 22 provided between them, and further has a non-magnetic steel plate 25 on the axial end face of the ferrite bond magnet 21.

[0116] Steel plate 25 is made of, for example, stainless steel. However, it is not limited to stainless steel, and any non-magnetic metal with a higher thermal conductivity than ferrite bond magnet 21 will do. Steel plate 25 is annular, and covers the axial end faces of ferrite bond magnet 21. Resin part 22 is fitted onto the inner periphery of steel plate 25.

[0117] The outer diameter of steel plate 25 is preferably equal to or smaller than the outer diameter of ferrite bond magnet 21. This is to prevent steel plate 25 from protruding radially outward beyond ferrite bond magnet 21.

[0118] Since the steel plate 25 has a higher thermal conductivity than the ferrite bonded magnet 21, by placing the steel plate 25 on the end face of the ferrite bonded magnet 21, some of the heat generated in the coil 32 is more easily transferred from the coil end 32a to the shaft 20 via the steel plate 25, thereby improving heat dissipation.

[0119] Furthermore, because steel plate 25 is non-magnetic, the magnetic flux emitted from ferrite bond magnet 21 is prevented from flowing into steel plate 25 and becoming leakage magnetic flux. In other words, the magnetic flux emitted from ferrite bond magnet 21 can be efficiently allowed to flow into stator core 30.

[0120] It is desirable that the outer peripheral end surface of the steel plate 25 faces, in the radial direction, the wall portion 31c of the insulating portion 31. In this case, part of the heat generated in the coil 32 is easily transferred to the steel plate 25 via the wall portion 31c and the air gap, thereby further improving heat dissipation.

[0121] The motor 1C of embodiment 4 can be manufactured by molding the ferrite bond magnet 21, and then, when molding the ferrite bond magnet 21 and the shaft 20 together (i.e., when forming the resin portion 22), placing a steel plate 25 on the axial end face of the ferrite bond magnet 21 in a mold and molding it.

[0122] Although steel plates 25 are arranged on both axial end surfaces of ferrite bond magnet 21 here, it is sufficient that steel plates 25 are arranged on at least one axial end surface of ferrite bond magnet 21 .

[0123] Fig. 11 is a diagram showing another example configuration of motor 1C according to embodiment 4. In the example configuration shown in Fig. 11, steel plate 25 covers the axial end face of ferrite bond magnet 21 and also covers the axial end face of main portion 22a of resin portion 22. Steel plate 25 is annular, and protrusion 22b or protrusion 22c of resin portion 22 is fitted into the inner periphery of steel plate 25.

[0124] In this configuration example, too, some of the heat generated in the coil 32 is more easily transferred from the coil end 32a to the shaft 20 via the steel plate 25, improving heat dissipation. Furthermore, since the area of ​​the steel plate 25 is larger than in the configuration example shown in Figure 10, heat dissipation can be further improved.

[0125] Except for the points mentioned above, the motor 1C of the fourth embodiment is configured similarly to the motor 1 of the first embodiment.

[0126] As explained above, motor 1C of embodiment 4 has non-magnetic steel plates 25 on the axial end faces of ferrite bond magnet 21, which makes it easier for heat generated at coil end 32a of stator 3 to be transferred to shaft 20 via steel plates 25, improving heat dissipation. Furthermore, because steel plates 25 are non-magnetic, it is possible to prevent magnetic flux emitted from ferrite bond magnet 21 from becoming leakage flux.

[0127] The motors 1, 1A to 1C of the above embodiments can be combined as appropriate. For example, the lead wire 34 described in embodiment 2 may be applied to the motors 1B, 1C of embodiments 3 and 4. Furthermore, the steel plate 25 of embodiment 4 may be disposed on the axial end face of the ferrite bond magnet 23 of embodiment 3.

[0128] Fifth Embodiment Next, a description will be given of the configuration of a blower 80 according to a fifth embodiment. Fig. 12 is a diagram showing the configuration of a blower 80 according to the fifth embodiment.

[0129] 12, blower 80 includes motor 1 described in the first embodiment and impeller 81 driven by motor 1. Impeller 81 is attached to shaft 20 of motor 1.

[0130] When the shaft 20 of the motor 1 rotates, the impeller 81 rotates and generates an airflow. The blower 80 is used, for example, as an outdoor blower in an outdoor unit 120 of an air conditioning apparatus 100 (FIG. 13) described below. The impeller 81 is, for example, a propeller fan.

[0131] The manufacturing cost of blower 80 of embodiment 5 can be reduced because it includes motor 1 described in embodiment 1. Furthermore, the improved heat dissipation of motor 1 allows stable motor output to be obtained over a long period of time, thereby improving the reliability of blower 80.

[0132] The same effect can be obtained when the motors 1A to 1C described in the second to fourth embodiments are used instead of the motor 1 described in the first embodiment.

[0133] Sixth Embodiment Next, a description will be given of the configuration of an air conditioning apparatus 100 according to a sixth embodiment. Fig. 13 is a diagram showing the configuration of an air conditioning apparatus 100 according to the sixth embodiment.

[0134] 13, the air conditioning apparatus 100 has an indoor unit 110 and an outdoor unit 120. The indoor unit 110 and the outdoor unit 120 are connected by a refrigerant pipe 130 to form a refrigerant circuit through which a refrigerant circulates.

[0135] The indoor unit 110 has a blower 111 as an indoor blower and a housing 112 that houses the blower 111. The blower 111 has an electric motor 111a and an impeller 111b driven by the electric motor 111a. The impeller 111b is attached to the shaft of the electric motor 111a. When the electric motor 111a rotates, the impeller 111b rotates and generates an airflow. The impeller 111b is, for example, a crossflow fan.

[0136] The outdoor unit 120 has a blower 80 as an outdoor blower, a compressor 121, and a housing 122 that houses these components. The blower 80 has a motor 1 and an impeller 81 as described in the eighth embodiment ( FIG. 12 ). The compressor 121 has a compression mechanism 121a that compresses the refrigerant, an electric motor 121b that drives the compression mechanism 121a, and a shaft 121c that connects these components. Note that the motor 1 of the first embodiment may be used for the electric motor 121b of the compressor 121.

[0137] The outdoor unit 120 further includes a four-way valve (not shown) for switching the flow direction of the refrigerant. The four-way valve of the outdoor unit 120 directs the high-temperature, high-pressure refrigerant gas sent from the compressor 121 to the heat exchanger of the outdoor unit 120 during cooling operation, and to the heat exchanger of the indoor unit 110 during heating operation.

[0138] For example, during cooling operation of the air conditioning apparatus 100, the heat released when the refrigerant compressed by the compressor 121 of the outdoor unit 120 condenses in a heat exchanger (a condenser in this case) is released to the outside by the air blown by the blower 80. In addition, the air from which heat has been removed when the refrigerant evaporates in the heat exchanger (an evaporator in this case) of the indoor unit 110 is supplied into the room by the blower 111.

[0139] The air conditioning apparatus 100 of the sixth embodiment has the blower 80 explained in the eighth embodiment, and therefore can reduce manufacturing costs and improve reliability.

[0140] The blower 80 is not limited to being a blower for the outdoor unit 120, but may also be used as the blower 111 for the indoor unit 110. The blower 80 is not limited to being provided in the air conditioning apparatus 100, but may also be provided in other electrical equipment.

[0141] The motors 1 to 1C of the first to fourth embodiments are used in the blower 80 of the outdoor unit 120 here, but may also be used in the blower 111 of the indoor unit 110, or in both the blowers 80 and 111.

[0142] 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.

[0143] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C Motor, 2, 2B, 2C Rotor, 3 Stator, 4 Molded stator, 11, 12 Bearing, 13 Bracket, 20 Shaft, 21 Ferrite bonded magnet (permanent magnet), 22 Resin portion, 22b, 22c Protrusion, 23 Ferrite bonded magnet, 25 Steel plate, 30 Stator core, 31 Insulating portion, 31a Wall portion, 31b Body portion, 31c Wall portion, 32 Coil (aluminum wire), 32a Coil end, 32b Coil side, 33 Terminal, 34 Lead wire, 35 Molded resin portion (outer casing member), 80 Fan (outdoor fan), 81 Impeller, 100 Air conditioning apparatus, 110 Indoor unit, 111 Blower (indoor blower), 120 outdoor unit.

Claims

1. A motor comprising: a rotor having a shaft and a ferrite bonded magnet fixed to the shaft; a stator having a stator core facing the rotor in a radial direction centered on the shaft; and a coil made of aluminum wire wound around the stator core, wherein the coil has two coil ends on both end surfaces of the stator core in the axial direction of the shaft, and the distance Lc between the two most distant points in the axial direction of the two coil ends and the length Lm of the ferrite bonded magnet in the axial direction satisfy Lc≦Lm.

2. The motor according to claim 1, wherein an insulating section is provided between the stator core and the coil, the insulating section has two wall sections on both end surfaces in the axial direction of the stator core, and a distance Li between two points on the two wall sections that are furthest apart in the axial direction, the distance Lc and the distance Lm satisfy Lc≦Lm≦Li.

3. The motor according to claim 1 or 2, further comprising a resin portion between the shaft and the ferrite bonded magnet that supports the ferrite bonded magnet.

4. The motor according to claim 3, wherein the axial length Lr of the resin portion and the distance Lm satisfy Lm<Lr.

5. The motor according to claim 3 or 4, further comprising a bearing supporting said shaft, said resin portion being in contact with said bearing.

6. The motor according to any one of claims 1 to 5, wherein the outer periphery of the ferrite bonded magnet has a first arc-shaped portion including the pole center and a second arc-shaped portion including the inter-pole portion, and the radius of curvature R1 of the first arc-shaped portion and the distance R2 from the center of the shaft to the first arc-shaped portion satisfy R1 < R2.

7. The motor according to any one of claims 1 to 6, wherein the ferrite bonded magnet has a width T in a radial direction centered on the shaft, the width T being 2 mm or more and 10 mm or less.

8. The motor according to any one of claims 1 to 5, further comprising a lead wire connected to the coil and extending to the outside of the motor, the lead wire being made of a material having a higher thermal conductivity than the coil.

9. A motor as claimed in any one of claims 1 to 8, wherein the ferrite bonded magnet has a first portion that faces the stator core in a radial direction centered on the shaft, and a second portion that does not face the stator core in the radial direction, and wherein the longest distance from the center of the shaft to the outer periphery of the ferrite bonded magnet in the first portion is D1, and the longest distance from the center of the shaft to the outer periphery of the ferrite bonded magnet in the second portion is D2, such that D1 < D2 holds.

10. The motor according to any one of claims 1 to 9, wherein the rotor has a non-magnetic steel plate on at least one end face in the axial direction of the ferrite bonded magnet.

11. The motor according to claim 10, further comprising a resin portion between the shaft and the ferrite bonded magnet that supports the ferrite bonded magnet, and the steel plate is provided so as to cover at least a portion of the resin portion.

12. A blower comprising a motor according to any one of claims 1 to 11 and an impeller attached to the shaft of the motor.

13. An air-conditioning apparatus comprising an outdoor unit and an indoor unit, at least one of the outdoor unit and the indoor unit having a blower according to claim 12.

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