WO2014045445A1

WO2014045445A1 - Permanent magnet-embedded electric motor

Info

Publication number: WO2014045445A1
Application number: PCT/JP2012/074421
Authority: WO
Inventors: 馬場　和彦; 昌弘仁吾; 和慶土田
Original assignee: 三菱電機株式会社
Priority date: 2012-09-24
Filing date: 2012-09-24
Publication date: 2014-03-27
Also published as: CN104662777A; US20150318743A1; WO2014046228A1; CN104662777B; US10084354B2

Abstract

A permanent magnet-embedded electric motor (1) wherein it is possible to increase the output of the motor without the torque declining by strengthening demagnetization resistance. The permanent magnet-embedded electric motor (1) is provided with a stator (3), and a rotor (5) having a rotor core (19), wherein the rotor core contains multiple magnet housing holes (21) and multiple permanent magnets (23), the thickness of the magnet housing holes in the short direction is smallest at the center part of the magnetic pole and becomes gradually larger towards the outside of the rotor core in the radial direction, and at least the thickness of the permanent magnets at the center part of the magnetic pole in the short direction is the same as the thickness of the magnetic housing holes at the center part of the magnetic pole in the short direction.

Description

Permanent magnet embedded motor

The present invention relates to an embedded permanent magnet electric motor in which a permanent magnet is embedded in a rotor core.

In recent years, with increasing awareness of energy saving, many permanent magnet type motors that have realized high efficiency by using rare earth permanent magnets with high coercive force for the rotor have been proposed. However, since rare earth permanent magnets are expensive and increase the cost of the motor, sintered ferrite magnets are used instead of rare earth permanent magnets in the rotors of conventional general permanent magnet embedded motors. Thus, when a sintered ferrite magnet is used instead of the rare earth permanent magnet, the residual magnetic flux density indicating the magnitude of the magnetic force is reduced to about 1/3. In order to make up for the shortage of torque due to a decrease in magnetic force, it is necessary to dispose a sintered ferrite magnet having the permanent magnet surface area as large as possible inside the rotor core. In addition to the reluctance torque in addition to the torque due to the permanent magnet, it is possible to compensate for the lack of magnetic force due to the sintered ferrite magnet.

For example, Patent Document 1 discloses the following rotor of a permanent magnet embedded motor. The rotor of the permanent magnet embedded motor includes a laminated iron core and a shaft, and the laminated iron core has a plurality of arc-shaped permanent magnets and a plurality of punched holes for receiving the permanent magnets. A plurality of punching holes are provided at a rate of one per one pole. The plurality of punching holes are arranged with the convex portion side of the arc facing the rotor center.

Moreover, in the permanent magnet embedded type electric motor shown in Patent Document 2, a permanent magnet having a shape in which circumferential end portions have different shapes is used, and the end portion having a small thickness is on the front side in the rotational direction. The permanent magnet is arranged so that the thick end portion is located on the rear side in the rotation direction. And by such a structure, while suppressing the increase in the magnetic flux which generate | occur | produces a reverse torque, an inductance is increased, and thereby the reluctance torque is increased effectively and the increase in iron loss is suppressed.

Moreover, in the permanent magnet embedded type electric motor shown in Patent Document 3, a pair of permanent magnet slots constituting one pole are arranged in a V shape on the outer peripheral portion of the rotor core, and permanent magnets are embedded in each permanent magnet slot. Has been. That is, two homopolar permanent magnets are embedded in a V shape in each rotor core. The thickness of each permanent magnet increases from the radially inner end of the rotor core, which is the central portion of the V-shape, toward the radially outer end of the rotor core, which is the left and right ends of the V-shape. To do. Moreover, the curved part is formed in the both ends of each permanent magnet.

Shokai 58-1057779 (mainly Figure 1) JP-A-11-98721 (mainly FIG. 7) Japanese Patent No. 4627788 (mainly FIG. 1)

However, the permanent magnet embedded motor shown in Patent Document 1 has a uniform thickness in the radial direction of the permanent magnet. When the thickness of the permanent magnet is uniform, the magnetic resistance has a feature that the magnetic resistance is larger toward the center side of the rotor core and is smaller toward the outer side in the radial direction of the rotor core. Therefore, the magnetic resistance is the smallest near both ends of the permanent magnet, the demagnetizing field produced by the stator coil tends to concentrate on both ends of the permanent magnet, the both ends of the permanent magnet are demagnetized, and the torque is reduced. There was a problem that.

Moreover, in the permanent magnet embedded type electric motor shown in Patent Document 2, since permanent magnets having different shapes at the circumferential end portions are used, the magnetic resistance is unbalanced and the magnetic resistance is small. When the demagnetizing field is concentrated on the end of the permanent magnet on the front side in the rotation direction and operated in a region where the current is large, demagnetization is caused and torque is reduced.

Further, in the permanent magnet type electric motor shown in Patent Document 3, a connecting portion is provided at the radially inner end of the rotor core, which is the V-shaped central portion, so that the magnetic flux easily flows and the V-shaped central portion. The magnetic resistance becomes extremely small. For this reason, when a sintered ferrite magnet having a coercive force smaller than that of the sintered rare earth permanent magnet is used, there is a problem that the permanent magnet near the center of the V shape is demagnetized by the demagnetizing field. Further, since the sintered ferrite magnet has a large electric resistance, it has a characteristic that eddy current does not easily flow and demagnetizes easily at a lower temperature. There was a problem that no effect was obtained.

The present invention has been made in view of the above, and even when a sintered ferrite magnet is used, by increasing the demagnetization resistance against a demagnetizing field, the output of the motor is reduced without reducing the torque. An object of the present invention is to provide a permanent magnet embedded type electric motor capable of increasing the motor.

In order to achieve the above-described object, an embedded permanent magnet electric motor of the present invention includes a rotor having a rotor core, and a stator provided so as to surround the rotor. A plurality of magnet housing holes formed in the circumferential direction corresponding to the number of poles, and a plurality of permanent magnets housed in the plurality of magnet housing holes, each of the magnet housing holes rotating the rotor It is formed in a concave shape when viewed along the axial direction, and is disposed so that the concave side faces the outside of the rotor, and each of the magnet receiving holes is viewed along the rotational axis direction of the rotor. The thickness of each of the magnet housing holes in the short direction is formed so as to be symmetrical with respect to the center line of the magnetic pole, and is formed in an integral structure without being divided in the same pole. The center part of the magnetic pole is the smallest, and the rotor The thickness in the short direction of the central portion of the magnetic pole in the permanent magnet is at least as large as the thickness in the short direction of the central portion of the magnetic pole in the corresponding magnet housing hole. equal.

According to the present invention, there is an effect that the output of the motor can be increased without increasing the torque by increasing the demagnetization resistance against the demagnetizing field.

1 is a cross-sectional view of a permanent magnet embedded electric motor according to a first embodiment of the present invention. It is sectional drawing which shows the state which has not set the permanent magnet in the magnet accommodation hole regarding the rotor core shown by FIG. It is the elements on larger scale which show the dimension characteristic of the magnet accommodation hole of FIG. It is sectional drawing of the rotor of the state which set the permanent magnet in the magnet accommodation hole in FIG. It is a figure which shows an example of the magnetic orientation of a permanent magnet. FIG. 5 is a diagram of the same mode as that of FIG. It is the elements on larger scale which show the dimension characteristic of the magnet accommodation hole of FIG.

Hereinafter, embodiments of an embedded permanent magnet motor according to the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

Embodiment 1 FIG.
1 is a cross-sectional view of a permanent magnet embedded electric motor according to Embodiment 1 of the present invention, and more specifically, a cross-sectional view in which a rotation axis of a rotor is a perpendicular line. Moreover, FIG. 2 is sectional drawing which shows the state which has not set the permanent magnet in the magnet accommodation hole regarding the rotor core shown by FIG. 3 is a partially enlarged view showing the dimensional characteristics of the magnet accommodation hole of FIG. 2, and FIG. 4 is a cross-sectional view of the rotor in which a permanent magnet is set in the magnet accommodation hole in FIG. These are figures which show an example of the magnetic orientation of a permanent magnet.

In FIG. 1, an embedded permanent magnet motor 1 according to the first embodiment includes a stator 3 and a rotor 5. The stator 3 includes an annular stator core 7, a plurality of teeth 9 formed at equiangular pitches in the circumferential direction (rotating direction of the rotor 5) in the inner peripheral portion of the stator core 7, and each tooth. 3 and the coil 11 wound around.

The rotor 5 is rotatably disposed on the inner peripheral side of the stator 3, and an annular gap 15 is formed between the outer peripheral surface 13 of the rotor 5 and the plurality of teeth 9. The stator 1 of the first embodiment shown in FIG. 1 is a distributed winding stator as an example, but a concentrated winding stator can be used as the present invention as will be described later.

FIG. 2 shows the structure of the rotor core 19 before the permanent magnet is inserted. The rotor 5 shown in FIG. 2 has a rotary shaft 17 for transmitting rotational energy as a main structure, and this structure. A rotor core 19 provided on the outer periphery of the rotating shaft 17 is included. The rotating shaft 17 and the rotor iron core 19 are connected by, for example, shrink fitting and press fitting.

The rotor iron core 19 is manufactured by laminating a plurality of silicon steel plates (electromagnetic steel plates), called iron core punches, punched with a mold in the extending direction of the rotating shaft 17 (the front and back direction in FIG. 2). . The outer peripheral surface 13 of the rotor core 19 is formed in a cylindrical shape.

The rotor core 19 is formed with a plurality (six in the illustrated example) of magnet housing holes 21 arranged on the same circumference so as to be arranged in the circumferential direction. The magnet accommodation holes 21 are arranged by the number of poles. Each of the magnet housing holes 21 is formed in an integral structure (one pole as one hole) without being divided in the same pole.

Each of the magnet housing holes 21 is formed in a concave shape when viewed along the direction of the rotation axis of the rotor 3 (as viewed in the cross section of FIGS. 1 to 7). More specifically, the concave shape has a substantially U shape in which both the inner defined arc line 21a and the outer defined arc line 21b extend in an arc shape. In addition, each of the magnet housing holes 21 is arranged such that the U-shaped concave side faces the radially outer side of the rotor 5. Further, the thickness of the magnet housing hole 21 in the short direction (the distance between the inner defined arc line 21 a and the outer defined arc line 21 b) is the smallest at the pole center portion of the magnetic pole, and is radially outward of the rotor core 19. It is set to gradually increase as you go.

The rotor core 19 is provided with an outer peripheral thin core portion 25 between the outer peripheral surface 13 of the rotor core 19 and the radially outer surface 23c of the permanent magnet 23 (see the enlarged reference portion in FIG. 1). ). In addition, the some hole 27 formed between the rotating shaft 17 and the some magnet accommodation hole 21 is for a refrigerant | coolant and refrigerator oil to pass through. More specifically, each hole 27 is disposed at the center of the three of the rotating shaft 17 and a pair of magnet housing holes 21 adjacent to each other.

By configuring the rotor core 19 in this way, the magnetic resistance in the vicinity of both ends of the magnet housing hole 21 can be increased. Thereby, the salient pole ratio (ratio of the minimum inductance to the maximum inductance) of the rotor core 19 can be increased, the reluctance torque can be used effectively, and a high torque can be realized.

Next, the dimensional characteristics of the magnet accommodation hole will be described mainly based on FIG. In FIG. 3, the radius of curvature (the radius of the arc on the center side of the rotor core 19) of the concave radially outer defined arc line 21 b of the magnet housing hole 21 is R 1, and the defined arc on the radially inner side of the magnet housing hole 21. When the radius of curvature of the line 21a (the radius of the arc on the outer peripheral side of the rotor core 19) is R2, the relationship of R1> R2 is satisfied. Further, the center of curvature of the radius R1 is located outside the outer peripheral surface 13 as seen in FIG. 3, and the center of curvature of the radius R2 is located inside the outer peripheral surface 13 as seen in FIG. Both the center of curvature and the center of curvature of radius R2 are located on the center line CL (the center line of the magnetic pole) CL of the corresponding magnet housing hole 21 as seen in FIG. In the first embodiment, the permanent magnets 23 are symmetric with respect to the center line of each magnetic pole, that is, the center line CL is a symmetric center line.

Next, the permanent magnet 23 will be described. As shown in FIG. 4, each of the plurality of permanent magnets 23 is accommodated in the corresponding magnet accommodation hole 21. That is, the permanent magnets 23 constituting the magnetic poles of the rotor core 19 are arranged in the outer circumferential side of the rotor core 19 in a number corresponding to the number of poles in the circumferential direction of the rotor core 19. The plurality of permanent magnets 23 are composed of sintered ferrite magnets.

The outer edge shape of the permanent magnet 23 is such that at least the thickness in the short direction of the central portion of the magnetic pole in the permanent magnet 23 is equal to the thickness in the short direction of the central portion of the magnetic pole in the corresponding magnet housing hole 21. In the first embodiment, the shape is substantially the same as the shape of the magnet accommodation hole 21 (strictly speaking, a similarity having a size relationship such that the permanent magnet 23 can be inserted into the magnet accommodation hole 21). The circumferential corner 29 of the permanent magnet 23 is appropriately chamfered to avoid local partial demagnetization. Each permanent magnet 23 is magnetized so that N poles and S poles alternate with respect to the rotation direction of the rotor 5.

The embedded permanent magnet electric motor configured as described above has the following excellent advantages.

First, sintered ferrite magnets have higher electrical resistance than Nd / Fe / B sintered rare earth permanent magnets, so eddy current loss is less likely to flow, but the coercive force is very small (sintered rare earth permanent magnets). About 1/3), it is easy to demagnetize when a demagnetizing field is applied. On the other hand, when there is no magnet accommodation hole, the magnetic resistance increases toward the center side of the iron core.

In view of the above, in the first embodiment, the thickness of the magnet housing hole in the short direction is minimized on the iron core center side (pole center portion), and is increased as it moves outward in the iron core radial direction. Unbalance can be mitigated and demagnetization can be prevented from concentrating near the end of the permanent magnet.

In addition, each of the permanent magnets 23 has a configuration in which both end portions are positioned on the radially outer side of the rotor core with respect to the center portion, but there is no connecting portion as shown in Patent Document 3 described above. Further, demagnetization at the pole center can be prevented.

As shown in FIG. 5, the permanent magnet 23 has a focal point 33 of the magnetic orientation 31 on a center line CL passing through the center CP of the rotor 5 and the central portion of the permanent magnet 23, and outside the rotor 5. Oriented and magnetized so as to be positioned. Further, on the center line CL, the radius of curvature of the demarcated arc line 21b outside the magnet housing hole 21 (the radius of the arc on the center side of the rotor core among the arcs demarcating the magnet housing hole) R1 and the outside demarcation. The rotor 5 is configured such that the relationship with the distance A between the arc line 21b and the focal point 33 is A ≧ 2 · R1.

With this configuration, the magnetic flux generated by the permanent magnet 23 can be easily linked to the coil of the stator 3, and the magnetic force of the permanent magnet 23 can be effectively used. Further, the demagnetization resistance at both ends of the permanent magnet 23 can be improved.

As described above, in the permanent magnet embedded electric motor according to the first embodiment, even when a sintered ferrite magnet is used, an appropriate magnetic force is ensured and a demagnetization resistance against a demagnetizing field is increased. Thus, the output of the motor can be increased without lowering the torque.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, this Embodiment 2 shall be comprised similarly to Embodiment 1 mentioned above except the part demonstrated below. 6 is a view of the same mode as FIG. 4 relating to the second embodiment, and FIG. 7 is a partially enlarged view showing the dimensional characteristics of the magnet accommodation hole of FIG.

As shown in FIGS. 6 and 7, the radius of curvature of the arc line defined outside the concave portion of the magnet housing hole 121 in the second embodiment (the radius of the arc on the center side of the rotor core 19) is R1, and the magnet is housed. The radius of curvature of the defined arc line inside the hole 121 (the radius of the arc on the outer peripheral side of the rotor core 19) is R2, and further, the radius of the arc on the outer peripheral side of the rotor core 19 among the arcs defining the permanent magnet 23 When R3 is R3, the magnet housing hole 121 and the permanent magnet 23 are configured so that the relationship of R1> R3> R2 is satisfied. In addition, due to this relationship, a space portion 135 is provided between the magnet accommodation hole 121 and both end portions of the permanent magnet 23. The space 135 gradually becomes larger toward the end of the permanent magnet 121.

In the permanent magnet embedded electric motor of the second embodiment configured as described above, the demagnetization resistance can be improved as in the first embodiment. In addition, a space is provided between the magnet housing hole and the vicinity of both ends of the permanent magnet, and the space is configured to gradually increase toward the end of the permanent magnet. The effect of the applied demagnetizing field is reduced, which also has the advantage of further improving the demagnetization resistance.

The content of the present invention has been specifically described above with reference to the preferred embodiment. However, the above-described embodiment shows an example of the content of the present invention, and is combined with another known technique. Of course, it is possible to change the configuration such as omitting a part without departing from the gist of the present invention.

1 Embedded permanent magnet motor, 3 stator, 5,105 rotor, 7 stator core, 19 rotor core, 21, 121 magnet housing hole, 23 permanent magnet, 31 magnetic orientation, 33 focal point, 135 space.

Claims

A rotor having a rotor core;
A stator provided so as to surround the rotor,
The rotor core includes a plurality of magnet housing holes formed in the number of poles along the circumferential direction, and a plurality of permanent magnets housed in the plurality of magnet housing holes,
Each of the magnet housing holes is formed in a concave shape when viewed along the rotation axis direction of the rotor, and the concave side is disposed so as to face the outside of the rotor,
Each of the magnet housing holes is formed so as to be symmetrical with respect to the center line of the magnetic pole when viewed along the rotation axis direction of the rotor, and is integrated without being divided within the same pole. Formed with a structure,
The thickness in the short direction of each of the magnet housing holes is the smallest at the center of the magnetic pole, and gradually increases toward the radially outer side of the rotor core,
At least the thickness in the short direction of the center part of the magnetic pole in the permanent magnet is equal to the thickness in the short direction of the center part of the magnetic pole in the corresponding magnet housing hole,
Permanent magnet embedded motor.
Along the rotation axis direction of the rotor, the radius of the arc on the center side of the rotor core among the arcs defining the magnet accommodation hole is R1, and the radius of the arc on the outer peripheral side of the rotor core is R2. Each of the magnet accommodation holes is configured so that the relationship of R1> R2 is satisfied.
The embedded permanent magnet electric motor according to claim 1.
Along the rotation axis direction of the rotor, the radius of the arc on the center side of the rotor core among the arcs defining the magnet housing hole is R1, the radius of the arc on the outer peripheral side of the rotor core is R2, Further, when the radius of the arc on the outer peripheral side of the rotor core among the arcs defining the permanent magnet is R3, each of the magnet receiving holes and the permanent magnets are set such that the relationship of R1>R3> R2 is satisfied. Is configured,
A space portion is provided between each of the magnet housing holes and the corresponding end portions of the permanent magnet, and the space portion gradually increases toward the end portion of the corresponding permanent magnet.
The embedded permanent magnet electric motor according to claim 1.
When viewed along the direction of the rotation axis of the rotor, the permanent magnet has a magnetic orientation focal point on a center line passing through the center of the rotor and the center of the magnetic pole of the permanent magnet, and outside the rotor. Is oriented and magnetized to be located at
When the radius of the arc on the center side of the rotor core is R1 and the distance between the arc on the center side and the focal point is A, among the arcs defining the magnet accommodation hole, A ≧ 2 · R1 is satisfied. As such, the rotor is configured,
The permanent magnet embedded type electric motor according to any one of claims 1 to 3.