JPH1042499A - Rotor of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent vibrations and noises due to the torque ripple of cogging torque component, by forming a beveling notched part in the portion of a recessed part side edge part in a magnetic the portion of which is adjacent to the outer periphery of a rotor. SOLUTION: Nearly V-shaped magnets 3a-3d are so arranged that the recessed part side faces outside and magnetized in four poles setting the central part of each magnet as the magnetic pole center. To each of the magnets 3a, 3d, a beveling part 20 is formed in the portion of the recessed part side edge part 33 the portion of which is adjacent to the outer periphery of a rotor. When a rotor 1s is arranged in a stator 5, the stator magnetic flux entering the rotor core 2a from specific tooth parts 8a of the stator core 6 passes the conventional flow path shown by a sign 12, and further a flow path shown by a sign 14 is newly formed on account of the existence of the beveling parts 20. A magnetic path is dispersed, interposing the magnet 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adduction type rotor having a permanent magnet mounted thereon, such as a motor for driving a compressor of a refrigerator or an air conditioner, and more particularly, to a rotor in which a magnet is embedded inside an iron core. And a rotor of a so-called interior permanent magnet motor (IPM).

[0002]

2. Description of the Related Art As a rotor of the above-mentioned electric motor, one having a construction shown in FIG. 10 is known.
No. 241. Rotor 1 shown in FIG.
e, a shaft 4 is fitted into a shaft hole provided at the center of a cylindrical iron core 2e, and a plurality of housing holes substantially similar to magnets are provided in parallel with the shaft 4, and magnets 3u, 3v are provided in the housing holes. , 3w, and 3x are inserted.

[0003] The iron core 2e is formed by laminating a number of thin iron plates punched in a predetermined shape in the axial direction, and the concave and convex portions formed by the projections provided on each thin iron plate are fitted to each other in the axially adjacent thin iron plates. It is fixed by well-known caulking clamp means. The configuration of this iron core is the same as in the case of a stator core described later. Magnets 3u-3
x is made of a ferrite magnet or a rare earth magnet, has a substantially C shape in a cross section perpendicular to the axis 4 shown, and is inserted into the accommodation hole of the iron core 2e so as to be concave toward the outside of the rotor. . Adjacent magnets are magnetized such that the center of each magnet is the center of the magnetic pole so that they have different polarities. In the case of FIG. 10, a four-pole field is formed. The magnets may be configured so as to be buried multiple times with the direction of the concavities and convexities aligned in each pole. An example of such an example is the 1995 IEEJ National Conference on Industrial Applications, Proc.
Page 388 (article number 306).

[0004] As a magnet having a different shape from the above-mentioned rotor, there is a rotor as shown in FIG. In the rotor 1d shown in FIG. 11, the magnets 3q, 3r, 3s, 3t are substantially V-shaped in a cross section perpendicular to the axis 4, and are inserted into the receiving hole of the iron core 2d so as to be concave toward the outside of the rotor. The other components are the same as those of the rotor shown in FIG. Each V-shaped magnet 3q to 3t may be formed by using two plate-like magnets at each pole.

The rotor is arranged in a stator having three-phase windings to form a permanent magnet type synchronous motor, and rotates by exciting the stator windings via an inverter. ing. FIG. 12 shows the rotor 1d of FIG.
5 shows a configuration of an electric motor in which the number of slots of the stator is 24 and the number of poles of the motor is 4. A large number of teeth 8 are provided on the inner periphery of the iron core 6 of the stator 5.
And a slot 7 is provided between the teeth, and a winding 9 schematically shown is mounted in this slot via an insulator. The rotor 1d is magnetized as shown by N and S to form a four-pole field, and is opposed to the inner peripheral portion of the stator core 6 via a predetermined gap. It is rotatably supported by a shaft 4.

[0006] Such a motor is characterized by a reverse saliency, so that in a low-speed range, a so-called maximum torque control in which the motor is driven at the maximum torque points of both the reluctance torque generated thereby and the main magnetic flux torque generated by the magnet is performed. On the other hand, in the high-speed range, it is effective to perform so-called advance phase control for supplementing the main magnetic flux torque with the reluctance torque, and is used for driving the above-described compressor and the like.

That is, in general, the torque T of the electric motor is as follows, where T1 is the main magnetic flux torque, T2 is the reluctance torque, and Tc is the cogging torque.

(Equation 1) If the amount of magnetic flux by the magnet is Φ, the q-axis current is Iq, the d-axis current is Id, the q-axis inductance is Lq, and the d-axis inductance is Ld,

(Equation 2)

(Equation 3) It is represented by

In general, the trapezoidal wave 120 ° energization applied to the stator of the motor is performed by UV, UW, VW,
It consists of six conduction patterns VU, WU, and WV, and each conduction section has an electrical angle of 60 °. Therefore, while a certain winding is energized at an electrical angle of 60 °, energization is controlled so that the relationship between the electromagnetic force of the specific winding and the magnetic flux of the magnet is a relationship that produces the highest torque. It has become.

FIG. 6 shows that the stator is energized by, for example, UV, the position where the main magnetic flux torque T1 becomes maximum is set to 0 °, and the rotor is rotated while energizing the UV. The tendency of the torque change with respect to the rotor advance angle θ that occurs in the case is shown. The lead angle θ represents an electrical angle, and the lead direction of θ is opposite to the rotation direction of the rotor during operation of the electric motor. The main magnetic flux torque T1 and the reluctance torque T2 show changes as shown in the range of the electric angle of 180 °, and the torque T of the electric motor, which is a composite of these, becomes the curve T It shows such a tendency.

[0010]

The windings 9 of the stator 5 shown in FIG. 12 show U-phase and V-phase windings when, for example, U-V is applied. Assuming that a current flows in the direction and magnetic poles indicated by N and S are formed in the stator 5, in the case of FIG. 12, the rotor 1d is at the position where the main magnetic flux torque T1 is maximum, that is, the lead angle θ in FIG. = 0 °. The rotation direction of the rotor 1d during the operation of the electric motor in FIG. 12 is clockwise. For example, the position of the lead angle θ = −90 ° is the position shown in FIG. 13 where the rotor 1d is rotated clockwise by 45 ° in mechanical angle. Similarly, the position of the advance angle θ = 90 ° is 45 degrees in mechanical angle in the counterclockwise direction.
゜ The position is rotated.

When the rotor 1d is rotated in the range of θ = −90 ° to 90 ° in the motor shown in FIG. 12 without changing the energized state, the torque T changes as shown by a broken line B in FIG. The dashed line B has a much larger ripple than the curve T in FIG. 6 because of the cogging torque due to the presence of the slots 7 and the teeth 8 of the stator core 6. For example, the state shown in FIG. 14 shows the case where the lead angle θ = 10 °. At this point, the cogging torque is added to increase the motor torque, while the state shown in FIG. 15 shows the case where θ = 20 °. At this point, conversely, the cogging torque is subtracted and the motor torque decreases. The cogging torque component that causes such torque ripple is relatively small due to the magnetic flux of the magnet, and mainly involves the cogging torque component generated by the stator magnetic flux.

FIG. 16 is an enlarged view of the state of the lead angle θ = 10 ° shown in FIG. 14 and the state of θ = 20 ° shown in FIG.
And FIG. 16 and 17, the winding 9
The stator magnetic flux 11 generated by energizing the rotor core 2 is transferred from the N pole teeth 8 of the stator core 6 through the air gap 10 to the rotor core 2.
d, flows through the rotor core 2d, and returns to the air gap 10d.
To return to the S-pole tooth portion 8 of the stator core 6 via However, magnet 3 embedded in rotor core
Since the magnetic resistance is large in the portions of q to 3t, the stator magnetic flux is significantly restricted particularly in the portion where the magnet is close to the outer periphery of the rotor.

That is, in the state of θ = 10 ° in FIG. 16, a specific tooth portion 8a of the stator core 6 moves from the rotor core 2d to the rotor core 2d.
Most of the stator magnetic flux 12 entering the rotor flows toward the iron core portion between the poles of the rotor, which is present at a slight distance in the counterclockwise direction from the tooth portion 8a. As a result, a magnetic attraction force acts on this portion, and the rotor 1d receives a force in the clockwise direction, which is the direction of rotation, and the torque of the electric motor increases. In the state of θ = 20 ° in FIG. 17, most of the stator magnetic flux 13 entering the rotor core 2d from the specific tooth portion 8b of the stator core 6 is slightly separated clockwise from the tooth portion 8b. As a result, the current flows toward the iron core between the poles of the existing rotor. As a result, as described above, magnetic attraction acts on this portion, and the rotor 1d receives a force in the counterclockwise direction, which is the anti-rotation direction, and the torque of the electric motor decreases. These phenomena shown in FIG. 16 and FIG.
The same occurs at all ends close to the outer peripheral portion of the rotor from 1 to 3t, and also in the case of the rotor 1e using the substantially C-shaped magnets 3u to 3x as shown in FIG. .

Conventionally, due to the remarkable torque ripple caused by the cogging torque component as described above, the vibration and noise accompanying the operation of the motor have been extremely large, and the magnet having a V-shaped or C-shaped cross section has a concave side. This has been a major problem with motors that are located inside the iron core so that they face outward.

[0015]

According to the present invention, there is provided a rotor for an electric motor comprising a magnet having a substantially V-shaped or substantially C-shaped cross section at each pole embedded in an iron core such that a concave side faces outward. A portion of the magnet, which is close to the outer periphery of the rotor at the side edge of the concave portion, is provided with a chamfered notch. Since this magnet is inserted into a housing hole having a substantially similar shape to the magnet provided in the iron core, the cutout portion is filled with the iron core.

It is desirable that the size of the cut-out portion of the side edge of the concave portion of the magnet is in a range that does not intersect with the chamfer existing on the side edge portion of the convex portion. In the case where the notched portion of the side edge of the concave portion of the magnet is provided in a straight line at both ends of the magnet, it is convenient to manufacture the two ends of the magnet by cutting them out on the same straight line. Further, in a rotor configured by embedment of a magnet having a substantially V-shaped or substantially C-shaped cross section in the same direction as that of the magnet in each pole in a multiplex manner,
The invention is equally applicable to individual magnets.

[0017]

[Function] The stator magnetic flux flowing in and out between the teeth of the stator core and the rotor core is dispersed in two directions with the magnet interposed therebetween in a portion where the magnet is close to the outer periphery of the rotor. Is performed, the magnetic attraction is dispersed, and the cogging torque component acting on the rotor is reduced.

[0018]

FIG. 1 shows a first embodiment of a rotor according to the present invention. This figure shows a cross section perpendicular to the shaft 4, in which substantially V-shaped magnets 3a, 3b, 3c, 3d are inserted into receiving holes provided in the iron core 2a and substantially similar in shape to these magnets. Each of the magnets 3a to 3d is arranged so that the concave side faces outward, and is magnetized to four poles with the center of each magnet being the center of the magnetic pole. Each of the magnets 3a to 3d is provided with a chamfered portion 20 at a portion of the concave side edge 33 near the outer periphery of the rotor. Each of the magnets 3a to 3d may be formed integrally with a V-shape, but may be formed by combining two plate-shaped magnets at each pole to form a V-shape.

The rotor 1a constructed as shown in FIG.
2 and FIG. 3 show the flow of the stator magnetic flux in the case where the motor is constructed by arranging it in the same stator 5 as shown in FIG. 2 and the rotor advance angles θ = 10 ° and θ = 20 °, respectively. . The state of θ = 10 ° shown in FIG.
6, corresponding to the specific tooth portion 8 of the stator core 6.
The stator magnetic flux entering the rotor core 2a from a causes a flow path indicated by reference numeral 14 to be newly generated due to the presence of the chamfered portion 20 in addition to the conventional flow path indicated by reference numeral 12.
The magnetic paths are dispersed across the magnet 3a.

The state of θ = 20 ° shown in FIG. 3 corresponds to the state of FIG. 17 in the conventional example, and the stator magnetic flux entering the rotor core 2a from a specific tooth portion 8b of the stator core 6 is: In addition to the conventional flow path indicated by reference numeral 13,
, A flow path indicated by reference numeral 15 is newly generated, and the magnetic paths are dispersed with the magnet 3d interposed therebetween. These phenomena shown in FIG. 2 and FIG.
Of the magnets 3a to 3d at all ends close to the outer periphery of the rotor. As a result, the magnetic attraction force due to the stator magnetic flux between the stator and the rotor causes the rotation direction of the rotor 1a to rotate. And the cogging torque component acting on the rotor 1a is reduced.

In the electric motor using the rotor 1a,
When the rotor 1a is rotated in the range of the advancing angle θ = −90 ° to 90 ° with the energized state kept constant, the torque is measured.
It can be seen that the ripple is alleviated as compared with the broken line B indicating the torque of the conventional example measured under the same conditions, and a shape close to the curve T in FIG. 6 is obtained. For example, even when the number of slots of the stator becomes twelve, the only difference is that the cogging interval increases, and the same effect can be obtained.

FIG. 4 shows a second embodiment of the rotor according to the present invention, in which the substantially V-shaped magnets 3a to 3d shown in FIG.
Instead of the magnets 3e, 3f, 3 having a substantially C-shaped cross section
An example is shown in which g and 3h are inserted into receiving holes of the iron core 2b which are substantially similar in shape to the magnets. Also in this rotor 1b, the concave side edges 3 facing the outside of each of the magnets 3e to 3h.
5 is provided with a chamfered portion 21 at a portion close to the outer periphery of the rotor, so that the same operation and effect as those of the rotor 1a of FIG. 1 can be obtained.

The rotors 1a and 1a shown in FIGS.
In b, the chamfered portions 20 and 21 of each magnet do not necessarily need to be provided in a straight line, but may be a gentle R chamfer, etc. In short, the lines forming the concave side edges of the magnets are chamfered at the ends. The cutout may have any shape as long as the receiving hole for inserting the magnet in the rotor core can be formed without difficulty so that the rotor core exists in the cutout portion.

As shown in FIGS. 1 and 4, the substantially V-shaped or substantially C-shaped magnets as shown in the embodiment have the convex side edges 34, 36 and the end of the magnet along the outer periphery of the rotor. In order to form an acute angle with the lines 18 and 19 forming the portions, chamfered portions 16 and 17 are generally provided at the ends of the convex side edges 34 and 36. Therefore, the concave side edges 33, 3 of the magnet according to the present invention.
It is desirable that the area where the chamfered portions 20 and 21 are provided does not intersect with the chamfered portions 16 and 17 of the convex side edges 34 and 36, thereby causing an acute angle portion at the edge of the magnet. In addition, the chipping of the magnet can be prevented.

The chamfer angle of the chamfers 20 and 21 is not particularly limited as long as the stator magnetic flux can be smoothly guided to the rotor core.
In the case where 0 and 21 are provided in a straight line as shown in the figure, if both ends of the magnet are cut out on the same straight line, the magnet can be easily manufactured and the magnet material can be reduced. The reason for this will be described with reference to FIGS. 8 and 9 taking a C-shaped magnet as an example.

FIGS. 8A and 8B are cross-sectional views showing a molding process of the sintered magnet, wherein FIG. 8A shows the case of the magnet according to the present invention, and FIG. 8B shows the case of the conventional magnet. In order to manufacture the magnets 3u to 3x used in the conventional rotor 1e shown in FIG. 10, as shown in FIG. 8B, dies 24, 25 designed based on individual product shapes. , 26, 28 are used to mold the magnet material 30 in a magnetic field. In this case, the lower mold 28 generally has a configuration in which a flat receiving surface 38 is required in order to stabilize the load during molding and make the density of the magnet material 30 uniform. Molded magnet material 3
0 is baked in a furnace, and shrinks in this process, but the original shape of the magnet 3u including the broken line portion 32 is generally obtained as shown in FIG. 9B. The portion corresponding to the receiving surface 38 of the mold shown in FIG.
In order to form the conventional magnet 3u, the fired product is ground to remove the broken line portion 32 so as to obtain the final shape of the magnet 3u.

On the other hand, in order to manufacture the magnets 3e to 3h used in the rotor 1b according to the present invention shown in FIG. 4, a lower die having a flat receiving surface 37 as shown in FIG. After firing, the magnet material 29 formed by this mold has a shape including a broken line portion 31 shown in FIG. 9A, and a portion corresponding to the receiving surface 37 of the mold is a straight portion 39.
And fired. The straight portion 39 corresponds to the chamfered portion 21 on the concave side edge of the magnet 3e.
The grinding portion for obtaining e is only the broken line portion 31,
It has the advantages of not only improving the yield compared to conventional products, but also significantly reducing the grinding time. Therefore, when the magnets 3e to 3h according to the present invention are formed in the above-described steps, the chamfered portions 21 on the side edges of the concave portions necessarily exist on the same straight line at both ends of the magnet.

FIG. 5 shows a third embodiment of the rotor according to the present invention, in which a magnet having a substantially C-shaped cross section as shown in FIG. It is what it was. Also in this rotor 1c, each magnet 3i, 3
J, 3k, 31, 3m, 3n, 3o, and 3p are provided with chamfered portions 22 and 23 at the portions near the outer periphery of the rotor at the side edges of the concave portions facing the outside. In the rotor 1a of FIG. The operations and effects as described above can be similarly obtained. It should be noted that even when the magnets at each pole have a multi-layer structure, they may be configured in the same manner, and the same applies to a magnet having a substantially V-shaped magnet having a multi-layer structure.

[0029]

According to the present invention, the stator magnetic flux flowing in and out between the teeth of the stator core and the rotor core is biased in a specific direction at a portion where the magnet is close to the outer periphery of the rotor. As a result, the magnetic attraction force is dispersed and the cogging torque component acting on the rotor is reduced. As a result, the torque ripple is reduced, and the vibration and noise accompanying the operation of the electric motor can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional plan view showing a first embodiment of a rotor according to the present invention.

FIG. 2 is an enlarged explanatory view of a main part of an electric motor using the rotor of FIG. 1;

FIG. 3 is an enlarged explanatory view of a main part of an electric motor using the rotor of FIG. 1;

FIG. 4 is a cross-sectional plan view showing a second embodiment of the rotor according to the present invention.

FIG. 5 is a sectional plan view showing a third embodiment of the rotor according to the present invention.

FIG. 6 is an explanatory diagram showing a change in torque of the electric motor with respect to a rotor position.

FIG. 7 is a characteristic diagram showing a change in torque of an electric motor with respect to a rotor position in both a rotor according to the present invention and a conventional rotor.

FIG. 8 is a cross-sectional view illustrating a molding process of the magnet.
(A) shows an example of the present invention, and (b) shows a conventional example.

9A and 9B are cross-sectional views illustrating grinding of a magnet. FIG. 9A illustrates an example of the present invention, and FIG. 9B illustrates a conventional example.

FIG. 10 is a plan sectional view of a rotor showing a conventional example.

FIG. 11 is a plan sectional view of a rotor showing another conventional example.

FIG. 12 is a plan sectional view of an electric motor using the rotor of FIG. 11;

13 is a cross-sectional plan view showing an example in which the rotor advancing angle in the electric motor of FIG. 12 is different.

14 is a cross-sectional plan view showing an example in which the rotor lead angle of the electric motor in FIG. 12 is different.

FIG. 15 is a cross-sectional plan view showing an example in which the rotor advancing angle in the electric motor of FIG. 12 is different.

FIG. 16 is an enlarged explanatory view of a main part of FIG. 14;

FIG. 17 is an enlarged explanatory view of a main part of FIG. 15;

[Explanation of symbols]

 1a to 1e Rotor 2a to 2e Rotor core 3a to 3x Magnet 4 Axis 5 Stator 6 Stator core 7 Slot 8 Tooth 9 Winding 10 Air gap 20, 21, 22, 23 Chamfer 33, 35 Magnet recess 33 Edges 34, 36 Edges on the convex side of the magnet

Claims (4)

[Claims] In a rotor of an electric motor, a magnet having a substantially V-shaped or substantially C-shaped cross section at each pole is embedded in an iron core such that a concave side faces outward, rotation of a concave side edge of the magnet. A rotor for an electric motor, wherein a cut-out portion is provided in a portion close to an outer peripheral portion of the armature in a chamfered shape, and the cut-out portion is filled with the iron core. 2. The rotor for an electric motor according to claim 1, wherein a cut-out portion of the concave side edge of the magnet does not intersect with a chamfer of the convex side edge. 3. The magnet according to claim 1, wherein the notched portion of the side of the concave portion of the magnet is linearly provided at both ends of the magnet, and both ends are cut out on the same straight line. A rotor for an electric motor according to claim 1. 4. The rotor for an electric motor according to claim 1, wherein the magnets are buried in multiple layers with the direction of the concavo-convex in each pole aligned.