JP2001186699A - Permanent magnet electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cogging torque and torque ripple in a permanent magnet electric motor. SOLUTION: In a permanent magnet electric motor with a rotor 2 inside a stator 1, the rotor 2 is formed by laminating a number of core sheets while forming a hole for burying a permanent magnet 3, and by forming the hole of a flux guide 6 for specifying the direction of the magnetic flux of the permanent magnet 3. The permanent magnet 3 is formed in a tabular shape integrally for each pole, the long side of a sectional rectangle in a tabular shape is buried toward a shaft 4, magnetic flux in the core radius direction near a q-axis is reduced, and magnetic flux in the core radius direction near a d-axis is increased. Also, a plurality of flux guides 6 are provided in parallel at the region between the tabular permanent magnet 3 and the core outer periphery, at the same time the flux guides 6 are rotated for each core sheet for forming, and skew is performed in the lamination direction of each core sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner rotor type permanent magnet motor used for a compressor of an air conditioner, and more particularly to a permanent magnet motor for reducing vibration and noise caused by cogging torque, torque ripple and the like. is there.

[0002]

2. Description of the Related Art A permanent magnet motor includes a stator for generating a rotating magnetic field, and a rotor for forming a field using a permanent magnet inside the stator. The number of grooves of the stator is 3M (positive). ), And the number of poles of the rotor is 2N (a positive integer).

[0003] An armature iron core serving as a stator has, for example, a yoke portion having a donut-shaped cross section with a circular outer periphery, and 3M teeth extending from the yoke portion in the center direction and at equal intervals in the circumferential direction. are doing. Also, the field iron core that becomes the rotor is
Plate-shaped (rectangular cross-section) permanent magnets are embedded at equal intervals in the circumferential direction by 2N of the number of poles, so that adjacent permanent magnets have different poles.

[0004] The armature iron core of the stator of the permanent magnet motor is formed by laminating a large number of core sheets obtained by punching out electromagnetic steel sheets.
The winding is provided in a predetermined manner through the teeth. Also, in the rotor, as in the case of the stator, a large number of core sheets obtained by punching out electromagnetic steel sheets into a shape including holes for the permanent magnets and holes for the shaft are stacked, and the permanent magnets are embedded.

On the other hand, in the induction motor, since the cage rotor is skewed, cogging torque and torque ripple due to the attraction between the stator and the rotor are reduced, resulting in vibration and noise. Is small.

[0006]

However, in the above-described permanent magnet motor, it is difficult to produce a skewed high-performance magnet and the rotor is not skewed. Becomes larger,
As a result, there is a disadvantage that vibration and noise increase.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a permanent magnet motor capable of reducing cogging torque and torque ripple and reducing vibration and noise. is there.

[0008]

To achieve the above object, the present invention provides a stator for generating a rotating magnetic field and a rotor for forming a field by embedding a permanent magnet inside the stator. Wherein the number of grooves of the stator is 3M (M; a positive integer) and the number of poles of the rotor is 2N (N; a positive integer, M ≧ N);
In a permanent magnet motor in which a plurality of core sheets each having a hole for embedding the permanent magnet are formed in the axial direction of the shaft and used as an iron core of the rotor, a magnetic flux generated by the permanent magnet in the core radial direction near the q axis is used. The rotor core and the permanent magnet are structured so as to increase the magnetic flux generated by the permanent magnet in the core radial direction in the vicinity of the d-axis, and between the permanent magnet and the outer periphery of the core on the d-axis side. A flux guide for designating the flow of the magnetic flux of the permanent magnet is provided in the area, and the flux guide is formed by rotating each of the core sheets so as to skew in the stacking direction of the core sheets. It is characterized by doing.

The permanent magnet has a plate shape, and the long side of the rectangular cross section of the plate is directed toward the shaft and is buried deep or shallow from the outer peripheral surface of the core. It is preferable to form a flux barrier extending from the end to the outer periphery of the core in parallel with the d-axis. Since the flux barrier prevents the leakage and short circuit of the magnetic flux, the torque increases even if the amount of the permanent magnet used is small.

The permanent magnet may have a bathtub shape with the bottom portion of the bathtub shaped toward the shaft, or an arc shape with the apex of the arc shaped in an inverted arc shape facing the shaft. According to the shape of the permanent magnet, the amount of the permanent magnet used can be increased by effectively utilizing the inside of the core, and the torque can be improved.

The flux guide may be a flux barrier of an air layer in which a plurality of long holes in the d-axis direction are formed in parallel, or the holes may be filled with a high magnetic permeability material. In the case where the flux guide is formed by rotating each of the core sheets, the flux guide is rotated around one end of the flux guide or the center of the flux guide, and the flux guide is spirally or twisted. Or twist as a wiper,
The field core may be skewed. Accordingly, the direction of the magnetic flux of the permanent magnet can be specified without fail, and therefore, at least the same or similar effect as the skew can be reliably obtained in the field iron core as the rotor.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. 1 to 3
In this inner rotor type permanent magnet motor,
A stator having a number of grooves of 3M (for example, 6);
And a rotor 2 having 2N (for example, 4) poles.

The rotor 2 is formed by embedding four plate-shaped permanent magnets 3 having a rectangular cross section at equal intervals in the circumferential direction of the core. One permanent magnet 3 is provided for each pole. The long side of the rectangular cross section is directed toward the shaft 4 for several minutes (for example, four poles), and is embedded at a position close to the shaft 4. The adjacent permanent magnets 11 have different polarities.

Further, since the permanent magnet 3 is brought close to the shaft 4, short-circuit and leakage of magnetic flux occur in the permanent magnet 3. Therefore, on the short side of the rectangular cross section, flux barriers 5a and 5b extending from the short side to near the outer periphery of the core along the q-axis are formed. Further, in the region surrounded by the permanent magnet 3 and the flux barriers 5a and 5b and the outer periphery of the core, that is, in the region near the d-axis, the permanent magnet 3
In order to specify the direction of the magnetic flux, a plurality of flux guides 6 long in the radial direction of the core are provided.

The flux guide 6 rotates in a direction from a solid line shown in FIGS. 1 and 2 to a wavy line for each core sheet 2a of a laminated core described later. As shown in FIG. 4, for example, a flux guide 6 is formed at a predetermined angle (a sharp angle) in a counterclockwise direction with respect to the core radius on the uppermost core sheet 2aa of the core to be the rotor 2, and a plurality of fluxes are provided. Guides 6 are formed in parallel. Thus, in the uppermost core sheet 2aa, the magnetic flux of the permanent magnets 3 is directed along the flux guides 6.

Each of the core sheets 2a below the uppermost core sheet 2aa is formed with a flux guide 6 which is sequentially slightly rotated clockwise around one end of the flux guide 6. Therefore, the flux guide 6 shown in FIG. 5 is formed in the center position core sheet 2ab of the core to be the rotor 2, and the flux guide 6 shown in FIG.
Is formed.

As a result, as shown by the dashed line in FIG. 3, the outer end of the core of the flux guide 6 slides for each core sheet 2a, that is, the flux guide 6 of the rotor 2 has a spiral shape with one end as a center. Is formed. The flux guide 6 allows the permanent magnet 3
, The effect of at least the same or similar to the skew appears on the field core as the rotor 2.

In manufacturing the rotor 2, a large number of core sheets 2a obtained by punching out electromagnetic steel sheets are laminated. First, holes in the permanent magnet 3, holes in the shaft 4, and holes in the flux barriers 5a and 5b are punched. The holes of the flux guide 6 are punched and laminated for each core sheet 2a. After laminating the core sheet 2a, the rotor 2 is obtained by embedding the permanent magnet 3 in the hole. The holes of the permanent magnet 3 and the holes of the flux barriers 5a and 5b are formed integrally.

Since the flux guide 6 specifies the direction of the magnetic flux of the permanent magnet 3, it not only serves as a flux barrier for the air layer but also fills the holes of the flux guide 6 with a high permeability material. May be. That is, when the flux guide 6 is a flux barrier, the magnetic flux of the permanent magnet 3 passes between the flux barriers, and when the flux guide 6 is a high magnetic permeability material, the magnetic flux of the permanent magnet 3 is reduced. This is because most will pass through the high magnetic permeability material.

Further, since the flux guide 6 exerts the same or similar effect as the skew on the field iron core as the rotor 2, the flux guide 6 is not limited to a helical shape but a more linear shape, a twisted linear shape, and a wiper shape. Shape.
That is, if the flux guide 6 is sequentially rotated in the axial direction of the shaft 4, the magnetic flux of the permanent magnet 3 is in the direction of the rotation, which is similar to the state where the skew is applied to the field core.

When the flux guide 6 is formed in a wiper shape, the flux guide 6 is folded, for example, at the center of the rotor 2 (the center in the axial direction of the shaft 4). That is, the rotation of the flux guide 6 may be rotated in one direction from the core sheet 2aa at the uppermost position to the core sheet 2ab at the center position, and thereafter, the flux guide 6 may be rotated in the reverse direction to the core sheet 2ac at the lowermost position. Good. As described above, since the rotor 2 has a structure in which the field core is skewed,
Cogging torque and torque ripple due to the suction force between the stator 1 and the rotor 2 can be reduced.

Although the plate-shaped permanent magnet 3 is embedded at a position deep from the outer periphery of the core, it may be embedded at a position shallow from the outer periphery of the core. In this case, the thickness of the permanent magnet embedded in the shallow position can be increased, and the torque increases. In the above embodiment, the stator 1 has six slots and the rotor 2 has four poles. However, the present invention is applicable to a stator having a different number of slots and a rotor having a different number of poles. Can be.

FIGS. 7 to 9 are schematic plan views showing modified embodiments of the present invention. Note that FIG. 7 corresponds to FIG. 4, FIG. 8 corresponds to FIG. 5, and FIG. 9 corresponds to FIG. 6, respectively.

In the rotor of this embodiment, a bathtub-shaped permanent magnet 10 with reluctance is used instead of the permanent magnet 3 of the previous embodiment, and the bathtub-shaped bottom is embedded toward the shaft 4. Note that the bathtub shape is a shape formed by the upper side and both oblique sides except for the base side of the trapezoid.

A flux guide 11 is provided between the permanent magnet 10 and the outer periphery of the core (a region corresponding to the inside of the bathtub shape) as in the previous embodiment. Therefore, as shown in FIG. 7, the flux guide 11 is formed on the uppermost core sheet 12a of the core serving as the rotor at a predetermined angle (acute angle) counterclockwise with respect to the core radius. The guide 11 is formed in parallel. As a result, the magnetic flux of the permanent magnet 10 is directed along the flux guides 11.

Each of the core sheets below the uppermost core sheet 2aa is provided with the flux guide 11
The flux guide 11 is formed by sequentially slightly rotating clockwise about the center of the flux guide 11. Accordingly, the flux guide 11 shown in FIG. 8 is formed on the core sheet 12b at the center position of the core serving as the rotor, and the flux guide 11 shown in FIG. 9 is formed on the lowermost core sheet 12c. .

The area where the flux guide 11 is formed is formed through a rivet 13. For example, the rivet 13 is preferably passed almost at the center of the area on the d-axis. The flux guide 11 is formed in a twist shape, but may be formed in a spiral shape, a more linear shape, or a wiper shape as in the previous embodiment. Further, similarly to the previous embodiment, the flux guide 11 may be used not only as a flux barrier for the air layer but also to fill the holes of the flux guide 6 with a high magnetic permeability material.

In the rotor having the above-described structure, as in the previous embodiment, when laminating the core sheets punched out of the electromagnetic steel sheet, first punch out the holes of the permanent magnet 10 and the hole of the shaft 4, and then, The hole of the flux guide 11 is punched and laminated. After laminating this core sheet, the permanent magnet 11 is embedded in the hole to obtain a rotor. Therefore,
As in the previous embodiment, in addition to the effect of reducing the cogging torque and the torque ripple, the torque can be increased by the shape of the permanent magnet 11 and the like.

Incidentally, the shape of the permanent magnet embedded in the rotor may be, for example, an inverted arc shape combined with reluctance, in addition to the bathtub shape. That is, the permanent magnet may be embedded in the rotor with the arc apex facing the shaft. In addition, since a region where the flux guide can be provided (a region near the d-axis) only needs to be secured between the permanent magnet and the outer periphery of the core, the shape of the permanent magnet may be any shape that can secure the region. I just need.

[0030]

According to the present invention described above, the following effects can be obtained. According to the present invention, a large number of core sheets in which holes for embedding permanent magnets are formed are laminated in the axial direction of the shaft to form an iron core of a rotor. The magnetic flux in the core radial direction is increased near the axis to form a structure of the iron core and the permanent magnet of the rotor, and the flow of the magnetic flux of the permanent magnet flows in a region between the permanent magnet and the outer periphery of the core on the d-axis side. In addition to providing a flux guide for designating the permanent magnet, the flux guide is formed by rotating each core sheet, and skew is applied in the stacking direction of each core sheet. The direction of the magnetic flux is specified, and at least the same or similar effect as the skew appears on the field core as the rotor. Therefore, cogging torque and torque ripple due to the attraction between the stator and the rotor can be reduced, and the vibration and noise of the motor can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic plan view illustrating an embodiment of the present invention and illustrating a permanent magnet motor.

FIG. 2 is a schematic plan view illustrating a rotor of the permanent magnet electric motor shown in FIG.

FIG. 3 is a schematic partial side view for explaining the rotor shown in FIG. 2;

FIG. 4 is a schematic plan view for explaining a core sheet at an uppermost position of the rotor shown in FIG. 2;

FIG. 5 is a schematic plan view for explaining a core sheet at a center position of the rotor shown in FIG. 2;

FIG. 6 is a schematic plan view for explaining a core sheet at a lowermost position of the rotor shown in FIG. 2;

FIG. 7 is a schematic plan view for explaining a core sheet at an uppermost position of a rotor for describing a modification of the present invention.

FIG. 8 is a schematic plan view for explaining a core sheet at a center position of the rotor of the modified example shown in FIG. 7;

FIG. 9 is a schematic plan view for explaining a core sheet at a lowermost position of the rotor of the modified example shown in FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Stator 2 Rotor 2a Core sheet 2aa, 12a Uppermost core sheet 2ab, 12b Center position core sheet 2ac, 12c Lowermost core sheet 3 Permanent magnet (plate shape) 4 Shaft 5a, 5b Flux barrier 6,11 Flux guide (Flux barrier of air layer or high permeability material) 10 Permanent magnet (bathtub shape) 13 Rivets

Claims (5)

[Claims] 1. A stator for generating a rotating magnetic field, and a rotor for forming a field by embedding a permanent magnet inside the stator, wherein the number of grooves of the stator is 3M (M; a positive integer). ), The number of poles of the rotor is 2N (N; positive integer, M ≧ N),
In a permanent magnet motor in which a plurality of core sheets each having a hole for embedding the permanent magnet are formed in the axial direction of the shaft and used as an iron core of the rotor, a magnetic flux generated by the permanent magnet in the core radial direction near the q axis is used. At least, the structure of the iron core of the rotor and the permanent magnet is made so as to increase the magnetic flux by the permanent magnet in the core radial direction near the d axis, and the permanent magnet and the outer periphery of the core are arranged on the d axis side. A flux guide for specifying the flow of the magnetic flux of the permanent magnet is provided in a region between the core sheets, and the flux guide is formed by rotating each of the core sheets, and skew is applied in the stacking direction of the core sheets. A permanent magnet electric motor characterized in that: 2. The permanent magnet has a plate shape, and the longer side of the rectangular cross section of the plate shape is directed toward the shaft and is embedded deep or shallow from the outer peripheral surface of the core. 2. The permanent magnet motor according to claim 1, wherein a flux barrier is formed extending from a side end to an outer peripheral side of the core in parallel with the d-axis. 3. The permanent magnet has a bathtub shape and a bottom of the bathtub shape is embedded toward the shaft,
2. The permanent magnet motor according to claim 1, wherein a vertex of the arc is embedded in an inverted arc shape toward the shaft as the arc shape. 3. 4. The flux guide according to claim 1, wherein the flux guide is a flux barrier of an air layer in which a plurality of long holes in the d-axis direction are formed in parallel, or the holes are filled with a high magnetic permeability material. , 2 or 3. 5. When the flux guide is formed by rotating each of the core sheets, the flux guide is rotated around one end of the flux guide or around the center of the flux guide. 5. The permanent magnet motor according to claim 1, wherein the field iron core is twisted in a shape of a wire, a wire, or a wiper to skew the field core.