JPH10271722A - Permanent magnet buried rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the demagnetization hard to occur in a rotor with a permanent magnet rotor. SOLUTION: This rotor has a rotor body 13a comprising material with high permeability. The rotor body 13a includes a plurality of sets of buried permanent magnets 18 and 19 put radially at intervals in a laminated state for each pole. Each permanent magnet 18 or 19 has an arc shape projected toward the center of the rotor 13. In addition, only part of the rotor body 13a, which inner magnetic flux density is increased when a counter field is applied, is made of magnetic material with high coercive force. As a result, demagnetization is hardly caused and a decrease in characteristics can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet embedded rotor in which a plurality of sets of permanent magnets arranged in inner and outer layers are embedded in a rotor body.

[0002]

2. Description of the Related Art Conventionally, as a rotor used for an electric motor, a rotor in which a permanent magnet is embedded in a rotor body made of a material having high magnetic permeability such as iron is known.

FIG. 5 shows a rotor of a conventional motor with a permanent magnet having a two-layer structure (Japanese Patent Application No. 7-134023).
issue). This conventional rotor 3 includes an iron rotor body 3a,
Four sets of permanent magnets 8 and 9 arranged at intervals in two layers per pole in the radial direction of the rotor are embedded, and each set of permanent magnets 8 and 9 has S poles and N poles alternated. The permanent magnets 8 and 9 which are arranged adjacent to each other and have a two-layer relationship are configured so that the polarities on the outer peripheral side are the same. Each of the outer peripheral side permanent magnet 8 and the inner peripheral side permanent magnet 9 is formed in an arc shape that is convex in the centripetal direction of the rotor, and has a two-layer relationship between the outer peripheral side permanent magnet 8 and the inner peripheral side. The permanent magnets 9 are arranged so as to be parallel to each other, and the interval between them is constant.

The permanent magnets 8 and 9 are made of the same magnetic material and have the same thickness in the radial direction.

[0005] As described above, the rotor 3 in which the permanent magnets 8 located on the outer peripheral side of the rotor and the permanent magnets 9 located on the inner peripheral side of the rotor are buried in two layers with a space therebetween, is composed of a group of windings 10 on the stator 2 side. The magnet torque generated in the relationship between the rotating magnetic field generated by the rotating magnetic field and the magnetic fields of the permanent magnets 8 and 9 and the magnetic path formed by the rotating magnetic field are formed on the surface side of the rotor body 3a and at the space between the inner and outer permanent magnets 8 and 9. It rotates in the R direction with a combined torque with the reluctance torque generated by the rotation.

FIG. 4 shows the result of a magnetic field analysis when a reverse magnetic field is applied to the rotor 3 from the stator 2. In the figure, (1) the magnetic flux density of the outer permanent magnet 8 is higher than that of the inner permanent magnet 9. (2) In the permanent magnets 8 and 9 for each layer and each pole, the magnetic flux density at both ends of the magnet arc-shaped cross section is higher than the magnetic flux density at the center. (3) In the permanent magnets 8 and 9 for each layer and each pole, the magnetic flux density on the magnet surface on the outer peripheral side of the rotor is higher than the magnetic flux density on the magnet surface on the inner peripheral side of the magnet.

[0007]

However, when a reverse magnetic field is applied from the stator 2 to the rotor 3 in the above-described conventional configuration, as described above in the analysis result of FIG. 9, the magnetic flux density of the permanent magnet 8 on the outer peripheral side is higher. (2) Each layer, each pole 1
In the permanent magnets 8 and 9 for each sheet, the magnetic flux density at both ends of the magnet arc-shaped cross section is higher than the magnetic flux density at the center. (3) In the permanent magnets 8 and 9 for each layer and each pole, the magnetic flux density on the magnet surface on the outer peripheral side of the rotor is higher than the magnetic flux density on the magnet surface on the inner peripheral side of the magnet.

For this reason, when the permanent magnet 8 located on the outer peripheral side of the rotor of the permanent magnet having the multilayer structure is made of the same magnetic material as the permanent magnet 9 on the inner peripheral side of the rotor, If the permanent magnets 8 and 9 have a structure in which the configuration of the magnetic material is not changed, there is a problem that demagnetization is likely to occur.

As a means for solving this problem, it is conceivable that the permanent magnets 8 and 9 are made of a magnetic material having a high coercive force. In a typical permanent magnet, for example, a ferrite magnet, when the coercive force of the magnet is increased, the residual magnetic flux density is reduced, so that the characteristics of the electric motor are also reduced.

[0010] The present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a permanent magnet embedded rotor in which demagnetization is less likely to occur and characteristics are less reduced.

[0011]

According to the present invention, there is provided a rotor having a permanent magnet embedded therein, wherein a plurality of sets of permanent magnets are buried at intervals of two or more layers per pole in a radial direction of the rotor. Each of the permanent magnets forms a convex shape in the centripetal direction of the rotor, and the coercive force of the permanent magnet located on the outer peripheral side of the rotor of the permanent magnet having a multilayer structure is the coercive force of the permanent magnet located on the inner peripheral side of the rotor. The configuration is made larger, and the demagnetization effect is less likely to occur.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotor having a plurality of sets of permanent magnets buried at intervals of two or more layers per pole in the radial direction of the rotor. The coercive force of the permanent magnet located on the outer peripheral side of the rotor is larger than that of the permanent magnet located on the inner peripheral side of the rotor.

According to the present invention, one pole is provided in the radial direction of the rotor.
In a rotor in which a plurality of sets of permanent magnets arranged at intervals in layers or more are embedded, each of the permanent magnets has a convex shape in a centripetal direction of the rotor, and each of the permanent magnets has a rotor outer peripheral side. The coercive force of the magnet surface is made larger than the coercive force of the magnet surface on the inner circumferential side of the rotor.

According to the present invention, one pole is provided in the radial direction of the rotor.
In a rotor in which a plurality of sets of permanent magnets are buried at a distance of more than one layer, each permanent magnet has a convex shape in the centripetal direction of the rotor, and both ends of each permanent magnet are protected. The magnetic force is larger than the coercive force at the center.

According to the present invention, two poles are provided per pole in the radial direction of the rotor.
In a rotor in which a plurality of sets of permanent magnets are buried at a distance of more than one layer, each permanent magnet has a convex shape in the centripetal direction of the rotor, and both ends of each permanent magnet are protected. The magnetic force is larger than the coercive force of the central part, and the coercive force of the permanent magnet located on the outer peripheral side of the rotor of the multilayered permanent magnet is larger than the coercive force of the permanent magnet located on the inner peripheral side of the rotor. is there.

With this configuration, according to the present invention, when a reverse magnetic field is applied to the rotor from the stator, a portion of each permanent magnet having a high magnetic flux density is made of a magnetic material having a high coercive force, so that demagnetization hardly occurs. In addition, since a magnetic material having a high coercive force is used only in a portion of the permanent magnet where the demagnetizing magnetic flux density is high, a permanent magnet embedded rotor with less characteristic deterioration can be obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) An embodiment 1 is shown in FIGS.

The rotor 13 includes an iron rotor body 13a,
Four sets of permanent magnets 18 and 19 arranged at intervals in two layers per pole in the radial direction of the rotor are embedded, and each set of permanent magnets 18 and 19 has S poles and N poles alternated. Permanent magnets 18 and 1 arranged adjacent to each other and in a two-layer relationship.
Reference numeral 9 denotes a configuration in which the outer periphery has the same polarity. Each of the outer permanent magnet 18 and the inner permanent magnet 19 is formed in an arc shape that is convex in the centripetal direction of the rotor 13, and has a two-layer relationship between the outer peripheral permanent magnet 18 and the inner peripheral permanent magnet 18. 19 are arranged in parallel, and the interval between them is constant.

The permanent magnet of each pole and each layer is formed of a magnetic material having a coercive force higher at both ends 18c and 19c of the permanent magnet arc-shaped cross section than at the center of the arc-shaped cross section 18d and 19d. Is formed of a magnetic material having a higher coercive force than the inner permanent magnet 19b.

On the other hand, a plurality of teeth are provided on the stator 12 side, and a winding 20 is arranged between the teeth 14. When an alternating current is applied to the winding 20, a rotating magnetic field is generated. I have.

FIG. 4 shows that, as described above,
It shows the result of a magnetic field analysis at a certain point when a reverse magnetic field is applied to the rotor 3. In FIG. 4, the magnetic flux generated from the teeth 4 of the stator 2 enters from the outer peripheral portion of the rotor 3 and passes through the outer peripheral permanent magnet 8, the inner peripheral permanent magnet 9, and the yoke portion of the rotor inner diameter in the order of the rotor. The circumferential permanent magnet 9 and the outer circumferential permanent magnet 8 return to the stator 2. At this time, as apparent from the figure, (1) the magnetic flux density of the outer peripheral side permanent magnet 8 is higher than that of the inner peripheral side permanent magnet 9. (2) Permanent magnets 8 and 9 for each layer and each pole
It can be seen that the magnetic flux density at both ends 8c and 9c of the magnet arc-shaped cross section is higher than the magnetic flux density at the central portions 8d and 9d.

Therefore, when the outer peripheral permanent magnet 8 is made of the same magnetic material as the inner peripheral permanent magnet 9 as in the conventional example, the magnetic material is also used in the permanent magnet for each pole of each layer. If the structure is not changed, the demagnetization effect is likely to occur.

In the present invention, as described above, each pole and each layer 1
The permanent magnets for each sheet are the both ends 18c of the permanent magnet arc-shaped cross section.
19c is formed of a magnetic material having a higher coercive force than the center portions 18d and 19d of the arc-shaped cross section, and the outer peripheral permanent magnet 18b of each pole is made of a magnetic material having a higher coercive force than the inner peripheral permanent magnet 19b. Since it is formed, it is possible to provide a permanent magnet embedded rotor in which demagnetization hardly occurs.

Further, since a magnetic material having a high coercive force is used only for a portion having a high demagnetizing magnetic flux density, the deterioration of characteristics is reduced.

(Embodiment 2) In FIG.
When looking at the permanent magnets of each sheet, it can be seen that the magnetic flux density of the magnet surfaces 8, 9 on the outer peripheral side of the rotor is higher than the magnetic flux density of the magnet surfaces 8, 9 on the inner peripheral side of the magnet. As a result, as shown in FIG. 3, in the permanent magnet for each layer and each pole, the outer magnet surface portions 38e and 39e have a higher coercive force than the inner magnet surface portions 38f and 39f. Even in this case, it is possible to provide a permanent magnet embedded rotor in which the demagnetizing effect is less likely to occur and the characteristics are less reduced.

[0027]

As described above, according to the first aspect of the present invention, when a reverse magnetic field is applied to each of the permanent magnets from the stator, the coercive force of the outer permanent magnets is reduced because a high magnetic material is used. An advantageous effect that the magnetic action is less likely to occur is obtained. In addition, since a magnetic material having a high coercive force is used for a portion having a high demagnetizing magnetic flux density, deterioration in characteristics is reduced.

In the second aspect of the invention, since a high magnetic material is used outside the surface of the permanent magnet, the demagnetizing effect is less likely to occur.

Further, in the third aspect of the present invention, since the arc-shaped both ends are made of a high magnetic material, the demagnetizing effect hardly occurs.

Further, in the invention according to claim 4, since the magnetic force of the embedded outer magnet is large and the magnetic force of both ends of the magnet is large, the demagnetizing effect hardly occurs.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a partial sectional view of the same.

FIG. 3 is a partial sectional view showing a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a magnetic field analysis of a permanent magnet embedded rotor.

FIG. 5 is a sectional view of a conventional electric motor.

[Explanation of symbols]

 13 rotor 13a rotor body 18 permanent magnet 19 permanent magnet

Continuing on the front page (72) Inventor Hiroshi Murakami 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. ▲ Nara ▼ Kazunari Saki 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A rotor comprising a plurality of sets of permanent magnets buried at intervals of two or more layers per pole in a radial direction of the rotor, wherein each of the permanent magnets has a convex shape in the centripetal direction of the rotor. A permanent magnet embedded rotor, wherein a coercive force of a permanent magnet located on the outer peripheral side of the rotor of a permanent magnet having a multilayered structure is made larger than a coercive force of a permanent magnet located on an inner peripheral side of the rotor. 2. A rotor comprising a plurality of sets of permanent magnets buried at intervals of one or more layers per pole in a radial direction of the rotor, wherein each of the permanent magnets has a convex shape in the centripetal direction of the rotor. A permanent magnet-embedded rotor, wherein each permanent magnet has a coercive force on a magnet surface on an outer peripheral side of the rotor that is larger than a coercive force on a magnet surface on an inner peripheral side of the rotor. 3. A rotor comprising a plurality of sets of permanent magnets buried at intervals of one or more layers per pole in a radial direction of the rotor, wherein each of the permanent magnets has a convex shape in the centripetal direction of the rotor. A permanent-magnet embedded rotor, wherein the permanent magnet has a shape formed therein, and a coercive force at both ends of each permanent magnet is larger than a coercive force at a central portion. 4. A rotor comprising a plurality of sets of permanent magnets buried at intervals of two or more layers per pole in the radial direction of the rotor, wherein each of the permanent magnets has a convex shape in the centripetal direction of the rotor. The coercive force at both ends of each permanent magnet is made larger than the coercive force at the central portion, and the coercive force of the permanent magnets located on the outer peripheral side of the rotor of the permanent magnet having a multilayer structure is formed on the inner periphery of the rotor. A permanent magnet embedded rotor having a coercive force larger than a coercive force of a permanent magnet located on the side. 5. The permanent magnet embedded rotor according to claim 1, wherein the embedded permanent magnet has an arc shape.