CN101162638B - Permanent magnet motor, electrical device and method for manufacturing permanent magnet - Google Patents

Abstract

The invention provides a permanent magnet motor and a manufacturing method thereof. The permanent magnet motor is composed of a rotor and a stator, the rotor has a polygonal column-shaped rotor core made of magnetic materials, and permanent magnets arranged on the outer peripheral surface of the rotor core, the stator is opposite to the outer peripheral surface of the rotor and With electrical winding. The permanent magnet has a concave portion with a circular arc cross-section at a position corresponding to each corner of the polygonal prism shape, and has a thickest wall portion in the middle of the concave portion and the adjacent concave portion, and the permanent magnet makes the thickest wall portion It becomes the center of the magnetic pole and is magnetized.

Description

Permanent magnet motor, electric equipment and method for manufacturing permanent magnet

technical field

The invention relates to a permanent magnet motor in which permanent magnets are fixed on the outer peripheral surface of a rotor core made of magnetic materials and a manufacturing method thereof.

Background technique

Conventionally, in permanent magnet motors, bonded magnets have been mainly used as permanent magnets fixed to the outer peripheral surface of the rotor core. Here, the bonded magnet refers to a composite permanent magnet formed by solidifying ferrite or rare earth permanent magnet powder with a bonding material such as rubber, thermoplastic resin, or thermosetting resin. Since this bonded magnet contains a bonding component, it has lower magnetic properties than a sintered magnet produced by a sintering method that does not contain a bonding component.

However, such bonded magnets have the advantage of being able to manufacture special shapes such as ring shapes, arc shapes, and thin-walled shapes with high dimensional accuracy because there is little shrinkage problem due to sintering. Furthermore, even if it is formed into such a special shape such as an annular shape, an arc shape, or a thin-walled shape, problems such as cracks and chipping can be avoided. Therefore, in recent years, ring-shaped bonded magnets are often used in motors for home appliances and motors for information equipment.

Here, bonded magnets are classified into anisotropic bonded magnets and isotropic bonded magnets. Anisotropic bonded magnets contribute to the miniaturization and performance enhancement of motors because they generate strong magnetic force in a predetermined direction. However, when producing an anisotropic bonded magnet, it is necessary to form it while arranging magnet powder in a predetermined direction in a magnetic field. In particular, when producing a permanent magnet having a special shape in which magnet powder is arranged in a ring shape in the radial direction, it is difficult to achieve 100% performance even with high-coercivity rare earth magnet powder, for example. Therefore, when producing ring-shaped permanent magnets, isotropic bonded magnets that can be easily produced only by compression molding or injection molding without a magnetic field are often used.

In addition, rare earth magnet powders are generally more expensive than ferrite magnet powders. Therefore, when producing a ring-shaped permanent magnet using rare earth magnet powder, it is necessary to reduce the radial thickness of the permanent magnet and reduce the amount of magnet powder.

However, if the radial thickness of the permanent magnet is reduced in this way, the deviation between the magnetic flux waveform on the surface and the sinusoidal waveform tends to increase. Therefore, when a motor using such a permanent magnet is rotated, there is a problem that the cogging torque increases, and the sound or vibration during the rotation of the motor increases.

Here, the relationship between the radial thickness of the ring-shaped permanent magnet and the surface magnetic flux waveform will be described.

FIG. 16 shows the relationship between the radial thickness of the ring-shaped permanent magnet and the surface magnetic flux waveform. In this figure, the surface magnetic flux of a rare earth isotropic bonded magnet having an eight-pole magnetic pole and an outer diameter of 50 mm was measured with a magnetometer (Gauss meter). Then, the inner diameter was changed to 46 mm (magnet thickness 2 mm), 42 mm (magnet thickness 4 mm), 38 mm (magnet thickness 6 mm), and 35.6 mm (magnet thickness 7.2 mm).

It can be seen from this figure that the peak value of the surface magnetic flux decreases as the thickness of the ring-shaped permanent magnet decreases. In addition, it can be seen that the surface magnetic flux waveform deviates from the sinusoidal waveform as the thickness of the ring-shaped permanent magnet decreases.

Therefore, in order to bring such a surface magnetic flux waveform close to a sinusoidal waveform, the following proposals have been made.

In the technique disclosed in Japanese Patent Application Laid-Open No. 6-217418, the inner peripheral surface of the permanent magnet is formed into a cylindrical shape, and the outer peripheral surface is formed into a non-cylindrical shape. In addition, the radial thickness of the inter-magnetic pole portion of the permanent magnet is set within a range of 0.3 to 0.7 times the radial thickness of the magnetic pole center portion. According to the technology disclosed in this patent document, the surface magnetic flux waveform can be made close to a sine wave waveform, and cogging torque, noise, and vibration can be reduced.

In addition, the technology disclosed in Japanese Patent Application Laid-Open No. 2003-111360 relates to a ring-shaped permanent magnet having a plurality of magnetic poles magnetized in a substantially sinusoidal wave shape. According to the technology disclosed in this patent document, the surface magnet waveform can be made close to a sine wave waveform, and cogging torque, noise, and vibration can be reduced.

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 6-217418, the concave and convex portions of the permanent magnets are arranged opposite to the stator, and the distance between the stator and the permanent magnets in the inter-magnetic pole portion becomes large, making it impossible to effectively utilize the magnetic force. .

In addition, in the technique disclosed in Japanese Patent Application Laid-Open No. 2003-111360, since the magnetic flux in the interpole portion is made zero and magnetized in an incompletely magnetized state, there is a problem that the magnetic force cannot be effectively utilized.

Contents of the invention

The permanent magnet motor of the present invention is composed of a rotor and a stator, the rotor has a polygonal column-shaped rotor core made of magnetic materials, and permanent magnets provided on the outer peripheral surface of the rotor core, the stator and the stator The outer peripheral surfaces of the rotor are opposite and have electrical windings. The permanent magnet has a concave portion with an arc-shaped cross-section at a position corresponding to each corner of the polygonal prism shape, and has a thickest wall portion at an intermediate position between the concave portion and an adjacent concave portion, and the permanent magnet makes the thickest wall portion The part becomes the center of the magnetic pole and is magnetized.

In addition, the present invention includes a method of manufacturing a permanent magnet used in the above-mentioned permanent magnet motor. The manufacturing method includes the steps of: a magnet powder filling step of filling magnet powder between a mold formed with a cylindrical through hole and a polygonal column-shaped core having a central axis coaxial with the through hole; a compression molding step , compress and mold the filled magnet powder through the upper punch and the lower punch; maintain the pressure and press the step, apply a prescribed maintaining pressure relative to the magnet powder formed by the compression molding step; move the step, apply a prescribed maintaining pressure In the state, the mold and the core are moved to make a permanent magnet of a predetermined shape.

Through the above structure and manufacturing method, the present invention can reduce the cost by reducing the volume of the permanent magnet, and realize the high efficiency of the permanent magnet motor and the reduction of cogging torque, vibration and noise. In addition, it is possible to provide a high-quality permanent magnet motor by preventing cracks or chipping that occur during the production of the permanent magnets.

Description of drawings

FIG. 1 is a perspective view of a motor according to an embodiment of the present invention.

Fig. 2 is a plan view of the motor according to the embodiment of the present invention.

Fig. 3A is a plan view of a rotor constituting the above motor.

Fig. 3B is a perspective view of a rotor constituting the above motor.

4A and 4B are explanatory diagrams showing the state of permanent magnet molding.

Fig. 5 is a flow chart showing a manufacturing process of a permanent magnet.

FIG. 6 is an explanatory diagram comparing the performance of motors based on different shapes of permanent magnets.

7 is a graph showing the relationship between the sectional radius of the permanent magnet-shaped concave portion 15 and the maximum internal stress of the permanent magnet with respect to the thickness of each thickest wall portion (in the case of a permanent magnet outer shape of 30 mm).

8 is a graph showing the relationship between the sectional radius of the permanent magnet-shaped concave portion 15 and the maximum internal stress of the permanent magnet corresponding to the thickness of each thickest wall portion (in the case of a permanent magnet outer shape of 40 mm).

9 is a graph showing the relationship between the sectional radius of the permanent magnet-shaped concave portion 15 and the maximum internal stress of the permanent magnet corresponding to the thickness of each thickest wall portion (in the case of a permanent magnet outer shape of 50 mm).

FIG. 10 is an explanatory diagram comparing breaking loads based on different shapes of permanent magnets.

Fig. 11 is an explanatory view showing the structure of an electric device (air conditioner indoor unit) according to the embodiment of the present invention.

Fig. 12 is an explanatory view showing the structure of an electric device (air conditioner outdoor unit) according to the embodiment of the present invention.

Fig. 13 is an explanatory diagram showing the structure of an electric device (water heater) according to an embodiment of the present invention.

Fig. 14 is an explanatory view showing the structure of an electric device (air cleaner) according to an embodiment of the present invention.

Fig. 15A is a plan view of a rotor of another motor according to the embodiment of the present invention.

15B is a perspective view of a rotor of another motor according to the embodiment of the present invention.

FIG. 16 is an explanatory diagram showing surface magnetic flux waveforms of different shapes of permanent magnets in a conventional motor.

Detailed ways

Embodiments of the present invention will be described below using the drawings.

(implementation mode)

FIG. 1 is a perspective view of a permanent magnet motor (hereinafter referred to as a motor) according to an embodiment of the present invention, and FIG. 2 is a plan view thereof.

The motor of this embodiment is an 8-pole, 12-slot inner-rotor motor composed of a rotor 101 and a stator 103 facing its outer peripheral surface. The rotor 101 has a rotor core 3 made of a magnetic material, a shaft 2 disposed at the center of the rotor core 3 , and a permanent magnet 1 fixedly provided on the outer peripheral surface of the rotor core 3 . The stator 103 has an electrical winding 102 .

FIG. 3A is a plan view of a rotor constituting the motor of this embodiment, and FIG. 3B is a perspective view thereof. The rotor core 3 is formed by laminating thin magnetic steel plates, has a shaft hole in the center, and has a polygonal prism shape, specifically, an octagon prism shape on the outer peripheral surface. Each corner of the polygonal prism shape is chamfered.

The permanent magnet 1 is fixed to the rotor core 3, and its outer peripheral surface has a cylindrical shape. The inner peripheral surface of the permanent magnet 1 is closely attached to the rotor core 3 , and eight recesses 15 are provided at positions corresponding to each corner of the octagonal prism shape of the rotor core 3 . Viewed from the cross section of the permanent magnet 1 , each concave portion 15 forms the thinnest portion 17 , and the thickest portion 16 is formed at an intermediate position between each concave portion 15 and the adjacent concave portion 15 . Then, magnetization is performed by making the thickest portion 16 a magnetic pole center and the thinnest portion 17 a magnetic pole boundary. That is, magnetization is performed as indicated by NS in FIG. 3A . Each concave portion 15 is formed in an arc shape, and the radius R of the arc is set within a range of 4 mm to 9 mm. Described in detail later.

In addition, the permanent magnet 1 is manufactured by compressing a resin composition for a bonded magnet, which is a flaky NdFeB magnet powder produced by a melt-spinning method, and a molecular chain The epoxy resin with two epoxy groups and the curing agent are the main components. That is, as the permanent magnet 1 of the present embodiment, a rare earth bonded magnet is suitable.

With the above configuration, the gap between the stator 103 and the permanent magnet 1 can always be the same distance in the rotation direction of the motor. That is, since the gap between the stator 103 and the permanent magnet 1 can be prevented from actively expanding, the maximum magnetization state can be formed on the entire peripheral surface of the permanent magnet 1, and cogging torque, noise, and vibration can be reduced.

In addition, by forming the concave portion 15 of the permanent magnet 1 in an arc shape with an arc radius R of 4 mm or more, the strength of the thinnest portion 17 can be ensured and cracks or chipping can be prevented.

Next, a method for manufacturing the permanent magnet 1 constituting the motor of the present invention will be described. 4A and 4B are diagrams showing the state when the permanent magnet 1 is molded. In addition, FIG. 5 is a flowchart showing the manufacturing process of the permanent magnet 1 . FIG. 4A shows a state in which the upper punch 12 and the lower punch 13 are held under pressure, and FIG. 4B shows a state in which the upper punch 12 and the lower punch 13 are held under pressure and removed from the die 10 and the core 11 .

The compression molding mold of manufacturing permanent magnet 1 comprises: mold 10, and it is formed with the through hole of cylindrical shape; Octagonal prism shape core 11, it has the central axis coaxial with the through hole of mold 10; The punch 13 has an outer peripheral surface substantially the same shape as the through hole of the die 10 and an inner peripheral surface substantially the same shape as the octagonal prism shape of the core 11 . In addition, the upper punch 12 and the lower punch 13 are movable in the vertical direction in the gap formed between the die 10 and the core 11 .

First, magnet powder is filled between the mold 10 and the core 11 (step S1). The magnet powder filled in step S1 is compression-molded by the upper punch 12 and the lower punch 13 (step S2). After the compression molding of the magnet powder is completed, a predetermined holding pressure is applied to the permanent magnet 1 (step S3). Then, the mold 10 and the core 11 are lowered in a state where the holding pressure is applied (step S4). As described above, by molding the permanent magnet 1 , it is possible to prevent cracks, cracks, or chipping from occurring in the thinnest portion 17 .

Next, the reason for forming the inner peripheral surface of the permanent magnet 1 into an octagonal prism shape will be described.

FIG. 6 is an explanatory diagram showing performance comparison between a permanent magnet having an octagonal prism-shaped inner peripheral surface (Example 1) and a permanent magnet having a cylindrical inner peripheral surface (Examples 2 and 3). In addition, in this Figure 6, the motor in Example 1 uses a regular octagonal prism with an inscribed circle diameter of 36.9 mm in the inner peripheral surface, a cylindrical shape with a diameter of 40.9 mm in the outer peripheral surface, and an octapole with the thickest wall part as the center of the magnetic pole. Magnetized permanent magnets. For comparison, the motor in Example 2 uses permanent magnets with an inner peripheral surface of a cylindrical shape with a diameter of 37.9 mm and an outer peripheral surface of a cylindrical shape with a diameter of 40.9 mm and magnetized with eight poles. The motor of Example 3 uses a permanent magnet with an inner peripheral surface of 37.4 mm in diameter. It is a permanent magnet with a cylindrical shape and an outer peripheral surface of a cylindrical shape with a diameter of 40.9 mm and an eight-pole magnetization. Example 1, Example 2, and Example 3 were all constructed using rare earth isotropic bonded magnets with a height of 14 mm. In addition, in Example 1 and Example 2, the permanent magnets are configured to have the same volume.

Compared with the surface magnetic flux waveforms of Examples 2 and 3, the surface magnetic flux waveform of Example 1 is similar to a sine wave waveform. From this, it can be seen that the octagonal prism-shaped permanent magnet on the inner peripheral surface can reduce the cogging torque compared with the cylindrical permanent magnet on the inner peripheral surface. In addition, when the induced voltage value of Example 1 is set as a reference value of 1, the induced voltage value of Example 2 with the same magnet volume is 0.88. In addition, the induced voltage value of Example 3 in which the volume of the magnet was 1.16 times was 0.98. From these results, it can be seen that the induced voltage value is higher for permanent magnets having an inner peripheral octagonal prism shape than for permanent magnets having a cylindrical inner peripheral surface.

In addition, when the efficiency of Example 1 is taken as a reference value of 1, the efficiency of Example 2 with the same magnet volume is 0.96. In addition, the efficiency of Example 3 in which the volume of the magnet is 1.16 times is 0.98. From this result, it can be seen that the permanent magnet having the octagonal prism shape on the inner peripheral surface is more efficient than the permanent magnet having the cylindrical shape on the inner peripheral surface.

Next, the reason why the strength of the thinnest portion 17 is ensured by setting the arc radius R of the concave portion 15 of the permanent magnet 1 to 4 mm or more will be described.

7 to 9 are graphs showing the relationship between the arc radius R of the concave portion 15 of the permanent magnet 1 and the maximum internal stress of the permanent magnet for each thickness of the thickest portion. In addition, in these FIGS. 7 to 9 , the permanent magnet with the thickness of the thickest wall portion being 2 mm is represented by a dotted line, the permanent magnet with a thickness of 3 mm in the thickest portion is represented by a dotted line, and the thickest portion is represented by a solid line. A permanent magnet with a thickness of 4mm. In addition, in FIG. 7, the diameter of the outer peripheral surface of the permanent magnet is shown as 30 mm, and in FIG. 8, the diameter of the outer peripheral surface of the permanent magnet is shown as 40 mm. In FIG. 9, the diameter of the outer peripheral surface of the permanent magnet is 50 mm. to express.

When the diameter of the outer peripheral surface is 30 mm, as shown in Figure 7, the thickness of the thickest wall part is 2 mm, 3 mm, and 4 mm for each permanent magnet, and the maximum internal stress of the magnet is 25 MPa to 30 MPa when the arc radius R = 0 mm. . In addition, when R is 0 mm to 4 mm, the maximum internal stress of the magnet decreases sharply, and when R is 4 mm or more, the maximum internal stress of the magnet is always 15 MPa or less.

In addition, when the diameter of the outer peripheral surface is 40mm, as shown in FIG. 8, when the arc radius R=0mm, between the permanent magnets with the thickness of the thickest wall part of 2mm, 3mm, and 4mm, the inside of the magnet is the largest. Stress has fluctuations. However, for the permanent magnets with the thickness of the thickest part of 2mm, 3mm, and 4mm, the maximum internal stress of the magnet decreases sharply when R is 0mm to 4mm, and the maximum internal stress of the magnet is 15MPa or less when R is greater than 4mm.

In addition, when the diameter of the outer peripheral surface is 50mm, as shown in Fig. 9, when the arc radius R = 0mm, the maximum stress inside the magnet is There are fluctuations. However, for permanent magnets with thicknesses of 2 mm, 3 mm, and 4 mm at the thickest wall, when R is 0 mm to 4 mm, the maximum internal stress of the magnet drops sharply, and when R is 4 mm or more, the maximum internal stress of the magnet is 15 MPa or less. .

From the above description, if the arc radius R of the concave portion 15 is set to 4 mm or more, the maximum internal stress of the magnet can be significantly reduced, and cracks or chipping can be prevented.

In addition, FIG. 10 is a graph comparing the breaking load of a permanent magnet having an octagonal prism shape on the inner peripheral surface and a permanent magnet having a cylindrical inner peripheral surface.

In this Fig. 10, the permanent magnet whose inner peripheral surface is a regular octagonal prism shape with an inscribed circle diameter of 36.9 mm, and whose outer peripheral surface is a cylindrical shape with a diameter of 40.9 mm, and the inner peripheral surface is a cylindrical shape with a diameter of 37.9 mm, and the outer peripheral surface is a permanent magnet with a diameter of 40.9mm cylindrical permanent magnet for comparison.

The breaking load of the permanent magnet with the arc shape R=0mm of the octagonal prism-shaped concave portion 15 on the inner peripheral surface is 4.5N, and the breaking load of the permanent magnet with the cylindrical shape on the inner peripheral surface is 45N, resulting in a difference of about 10 times.

In contrast, the breaking load of a permanent magnet with an octagonal prism-shaped concave portion 15 on the inner peripheral surface with an arc radius R=4mm is 20N, which is about twice the breaking load of a permanent magnet with a cylindrical inner peripheral surface. middle. Accordingly, if the arc radius R of the concave portion 15 is set to be 4 mm or more, the breaking load can be significantly increased, and cracks and chipping can be prevented.

In addition, the breaking load of the permanent magnet with the arc radius R=9mm of the octagonal prism-shaped recess 15 on the inner peripheral surface is 35N, which is about 1.3 times lower than the breaking load of the cylindrical permanent magnet on the inner peripheral surface. . Accordingly, if the arc radius R of the concave portion 15 is set to 9 mm, the breaking load can be further increased, and cracks and chipping can be prevented. In addition, if the arc radius of the concave portion 15 is set to 9 mm or more, the octagonal prism shape on the inner peripheral surface is close to a cylindrical shape, which reduces the effect of the present invention to make the magnetic flux density on the surface of the permanent magnet into a sine wave waveform, so it is not preferable. . Ideally, the arc radius of the concave portion 15 is in the range of 4 mm to 9 mm.

Next, an air conditioner indoor unit, an air conditioner outdoor unit, a water heater, and an air cleaner will be described as examples of the electric equipment of the present invention.

Fig. 11 is an explanatory view showing the structure of an electric device (air conditioner indoor unit) according to the embodiment of the present invention.

As shown in FIG. 11 , a motor 201 is mounted on a casing 211 of an air conditioner indoor unit 210 . A cross-flow fan 212 is installed on the rotating shaft of the motor 201 . The motor 201 is driven by a motor drive device 213 . The motor 201 is rotated by energization from the motor drive device 213, and the cross-flow fan 212 is rotated accordingly. By the rotation of the cross-flow fan 212, air is blown into the room of the hollow body air-conditioned by the heat exchanger (not shown) for the indoor unit.

Here, as the motor 201 , a motor using the above-mentioned permanent magnet 1 is applied. Thereby, cogging torque, noise, and vibration can be reduced. In addition, even if the current value input to the indoor unit decreases, high output can be obtained, and the effect of reducing power consumption can be obtained.

Next, FIG. 12 is a structural explanatory diagram of an electric device (air conditioner outdoor unit) according to an embodiment of the present invention. As shown in FIG. 12 , the air conditioner outdoor unit 301 has a motor 308 mounted inside a housing 311 . The motor 308 has a fan 312 attached to its rotating shaft, and functions as a fan motor for blowing air. The compressor chamber 306 and the heat exchanger chamber 309 are divided by a partition plate 304 erected on the bottom plate 302 of the housing 311 . A compressor 305 is arranged in the compressor chamber 306 . A heat exchanger 307 and a blower fan motor 308 are arranged in the heat exchanger chamber 309 . An electrical component box 310 is disposed on the upper portion of the partition plate 304 .

The blower fan motor 308 rotates the blower fan 312 according to the rotation of the motor 308 driven by the motor driver housed in the electrical component box 310 , and blows air to the heat exchanger chamber 309 through the heat exchanger 307 . Here, as the motor 308, a motor using the permanent magnet 1 described above is applied. Thereby, cogging torque, noise, and vibration can be reduced. In addition, even if the value of the current input to the outdoor unit decreases, high output can be obtained, and the effect of reducing power consumption can be obtained.

Next, FIG. 13 is an explanatory diagram of the structure of an electric device (water heater) according to an embodiment of the present invention. A motor 333 is mounted in a casing 331 of the water heater 330 . A fan 332 is installed on the rotating shaft of the motor 333 . The motor 333 is driven by a motor drive device 334 . The motor 333 is rotated by energization of the motor drive device 334 , and the fan 332 is thereby rotated. The rotation of the fan 332 blows air necessary for combustion to a fuel vaporization chamber (not shown). Here, as the motor 333, a motor using the permanent magnet 1 described above is applied. Thereby, cogging torque, noise, and vibration can be reduced. In addition, even if the current value input to the water heater decreases, high output can be obtained, and the effect of reducing power consumption can be obtained.

Next, FIG. 14 is an explanatory diagram showing the structure of the electric device (air cleaner) according to the embodiment of the present invention. A motor 343 is mounted in a casing 341 of the air cleaner 340 . An air circulation fan 342 is attached to the rotation shaft of the motor 343 . The motor 343 is driven by a motor drive device 344 . The motor 343 is rotated by energization from the motor drive unit 344 , and the fan 342 is thereby rotated. Air is circulated by the rotation of the fan 342 . Here, as the motor 343, a motor using the permanent magnet 1 described above is used. Thereby, cogging torque, noise, and vibration can be reduced. In addition, even if the value of the current input to the air cleaner decreases, high output can be obtained, and the effect of reducing power consumption can be obtained.

In addition, in the above description, as the electrical equipment of the present invention, an air-conditioning indoor unit, an air-conditioning outdoor unit, a water heater, and an air cleaner are exemplified, but other electrical equipment equipped with motors (such as various information equipment or industrial equipment).

In addition, in the above-mentioned embodiment, the rotor core 3 having an octagonal prism shape and the permanent magnet 1 whose inner peripheral surface is an octagonal prism shape are provided. That is, it has a plurality of magnetic poles in the circumferential direction, and its inner peripheral surface has recesses corresponding to the spaces between the magnetic poles.

In addition, in the above-mentioned embodiment, the permanent magnet 1 can be made of isotropic bonded magnet, isotropic sintered magnet, isotropic ferrite magnet, anisotropic bonded magnet, anisotropic sintered magnet or anisotropic iron magnet. Either of the body magnets.

In addition, in the above-mentioned embodiment, the cross section of the concave portion 15 of the permanent magnet 1 is configured in an arc shape, but a configuration in which the concave portion 15 of the permanent magnet 1 is chamfered may also be employed.

Next, FIG. 15A is a plan view of a rotor of another motor according to the embodiment of the present invention, and FIG. 15B shows the plan view. The rotor includes: a rotor core 403 formed of a magnetic material with a polygonal prism-shaped hollow; a shaft 402 arranged at the center of the rotor core 403; Cylindrical permanent magnet 401 . The invention can also be extended to a so-called outer rotor type motor with this rotor.

Claims (5)

1. a permanent magnet motor, it is made of rotor and stator, and described rotor has the rotor core of the octagonal prism shape that is made of magnetic material and the permanent magnet that is fixed on the outer peripheral surface of described rotor core, and described stator and the outer peripheries of the rotors are opposite and have electrical windings, The outer peripheral surface of the permanent magnet forms a cylindrical shape, the inner peripheral surface of the permanent magnet is closely attached to the rotor core and forms the same shape as the octagonal prism, The permanent magnet has a concave portion with an arc-shaped cross-section at a position corresponding to each corner of the octagonal prism shape, and the thinnest wall portion is formed in the concave portion, and the intermediate position between the concave portion and the adjacent concave portion is having the thickest wall portion, the permanent magnet is magnetized so that the thickest wall portion becomes the center of the magnetic pole, The diameter of the outer peripheral surface of the permanent magnet is 40.9 mm, the diameter of the inscribed circle of the inner peripheral surface is 36.9 mm, and the arc radius of the arc-shaped recess is in the range of 4 mm to 9 mm. 2. The permanent magnet motor according to claim 1, wherein the permanent magnet is a rare earth bonded magnet. 3. An electric device equipped with the permanent magnet motor according to claim 1 or 2. 4. The electric device according to claim 3, wherein the electric device is any one of an air conditioner indoor unit, an air conditioner outdoor unit, a water heater or an air cleaner. 5. A manufacturing method of a permanent magnet, which is used in a permanent magnet motor, wherein the permanent magnet motor consists of a rotor and a stator, the rotor has an octagonal prism-shaped rotor core made of magnetic material, and a fixed permanent magnets on the outer peripheral surface of the rotor core, the stator is opposite to the outer peripheral surface of the rotor and has electrical windings, The outer peripheral surface of the permanent magnet forms a cylindrical shape, the inner peripheral surface of the permanent magnet is closely attached to the rotor core and forms the same shape as the octagonal prism, The permanent magnet has a concave portion with an arc-shaped cross-section at a position corresponding to each corner of the octagonal prism shape, and the thinnest wall portion is formed in the concave portion, and the intermediate position between the concave portion and the adjacent concave portion is having the thickest wall portion, the permanent magnet is magnetized so that the thickest wall portion becomes the center of the magnetic pole, The diameter of the outer peripheral surface of the permanent magnet is 40.9 mm, the diameter of the inscribed circle of the inner peripheral surface is 36.9 mm, and the arc radius of the arc-shaped recess is in the range of 4 mm to 9 mm. The manufacturing method comprises the steps of: A magnet powder filling step of filling magnet powder between a mold formed with a cylindrical through hole and a polygonal column-shaped core having a central axis coaxial with the through hole; A compression molding step, compressing and molding the filled magnet powder through an upper punch and a lower punch; a maintaining pressure pressing step of applying a prescribed maintaining pressure to the magnet powder molded by the compression molding step; In the moving step, the mold and the core are moved while the predetermined holding pressure is applied to form a permanent magnet of a predetermined shape.

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