JPH11285185A - Permanent magnet motor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To maintain the strength of a rotor core in a permanent magnet motor by effectively utilizing magnet torque and reluctance torque. SOLUTION: In an inner rotor type permanent magnet electric motor, one permanent magnet 11 having a bathtub curve cross section per pole of a rotor core 10 is used, and a bottom portion of the bathtub curve cross section of the permanent magnet 11 is provided in a center hole 4. The bathtub curved permanent magnets 11 are embedded at equal intervals in the circumferential direction of the rotor core 10 by the number of poles. A caulked portion 12 is formed on the q-axis in a region between the permanent magnet 11 and the center hole 4, and a rivet 13 is passed on the d-axis in a region between the permanent magnet 11 and the outer periphery of the rotor core 10. Permanent magnet 1
Holes 14 for flux barriers are provided at one corner of both ends of
To form

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 or the like, and more particularly, to an improvement in the effective use of reluctance torque to increase the total torque and the strength of a rotor core. And a permanent magnet electric motor in which the configuration of a rotor core (rotor) is devised.

[0002]

2. Description of the Related Art An inner rotor of a permanent magnet motor has, for example, the structure shown in FIG. In FIG. 4, a magnet-embedded field iron core (rotor core) 2 in a stator core 1 has permanent magnets 3 having a substantially fan-shaped cross section buried one per pole and arranged at equal intervals in the circumferential direction by the number of poles. And the adjacent permanent magnets 3 have different polarities.
Reference numeral 4 denotes a hole (center hole) through which the shaft passes.

Here, assuming that the magnetic flux distribution in the gap (between the teeth of the stator core and the permanent magnet) formed by the permanent magnet is sinusoidal, the torque T of the permanent magnet motor is T
= Pn ｛Φa ・ Ia ・ cosβ-0.5 (Ld-Lq)
It is represented by I ² · sin 2β｝. Here, T is the output torque, Φa is the armature interlinkage flux by the permanent magnets on the d and q coordinate axes, Ld and Lq are the d and q axis inductances, Ia is the amplitude of the armature current on the d and q coordinate axes, and β is The lead angle of the armature current on the d and q coordinate axes from the q axis, and Pn is the number of pole pairs. In the above equation, the first term is the magnet torque by the permanent magnet, and the second two terms are the reluctance torque generated by the difference between the d-axis inductance and the q-axis inductance.

[0004] For details, see T.A. IEEE Japan
n, Vol. See article 117-D, No 7, 1997. Further, according to the above-mentioned paper, it is described that the reluctance torque is effectively used by forming the permanent magnet of each pole in a multilayer structure.

[0005] For example, the rotor core in the stator core 1 has two permanent magnets having an arc-shaped cross section per pole.
It has a layer structure. This is one piece per pole (1
Layer), the d-axis inductance Ld is small, and the q-axis inductance Lq is greatly increased. As a result, the value of the inductance difference (Ld−Lq) of the parameter in the above equation is large, and as a result, the motor torque T is reduced. growing.

As described above, if the reluctance torque is used effectively, the motor torque T can be increased.
If the permanent magnet per pole has a multilayer structure, the reluctance torque can be more effectively used. For details, see the above-mentioned paper.

[0007]

By the way, in the permanent magnet motor, the distance w between the permanent magnet 3 having a substantially fan-shaped cross section and the center hole 4 needs to be a minimum dimension in view of the strength of the rotor core (core sheet). There is a useless area (see solid arrow a in FIG. 4) in which there is no magnet in the rotor core 2. In addition, if the radius of curvature of the arc having a sectoral cross section is increased in order to increase the usage amount (magnet amount) of the permanent magnet, the useless area is increased.

Accordingly, the area between the permanent magnet 3 and the outer periphery of the rotor core 1 (see the solid arrow b in FIG. 4) becomes smaller, the q-axis inductance becomes smaller, and the inductance difference from the d-axis becomes smaller. At the same time, the reluctance torque decreases, and therefore, the motor efficiency cannot be improved. In addition, if the area indicated by the arrow b in FIG. 4 becomes narrow, it becomes difficult to form a caulked portion or to rivet, which may affect the strength of the rotor core 2 and the like.

In the case of a rotor core having a multilayered permanent magnet described in the above-mentioned article, the above-mentioned disadvantages can be solved, but a plurality of permanent magnets are used per pole. Therefore, the manufacturing cost increases.
Therefore, in terms of manufacturing, it is preferable to use one permanent magnet per pole.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to use one permanent magnet per pole to effectively use magnet torque and reluctance torque, to increase motor efficiency, and to improve rotor core performance. It is an object of the present invention to provide a permanent magnet motor capable of improving strength.

[0011]

In order to achieve the above object, the present invention relates to a permanent magnet motor in which a magnet-embedded field iron core (rotor core) is arranged in a stator core. One permanent magnet having a cross-section bathtub curve shape is used, and the bottom portion of the cross-section bathtub curve shape of the permanent magnet is embedded toward the center hole, and the permanent magnet having the bathtub curve shape is disposed in a circumferential direction of the rotor core. It is characterized by being buried at equal intervals by the number of poles.

In this case, it is preferable that a caulked portion is formed in a region between the permanent magnet and the center hole, and a rivet is passed through a region between the permanent magnet and the outer periphery of the rotor core.

The bottom and both oblique sides of the cross section of the bathtub curve shape of the permanent magnet are linearized, the corners are rounded, and holes for flux barrier are formed at one corner of both ends of the permanent magnet. May be cut at a predetermined angle.

The permanent magnet is preferably a ferrite magnet. The rotor core may be incorporated into a DC brushless motor.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. In the figure,
The same parts as those in FIG.

The permanent magnet motor according to the present invention has one pole per pole.
The shape of the two permanent magnets is not limited to a cross-sectional curved shape (for example, a fan shape), and the rotor core is made to have a shape that can be used effectively, that is, the distance between the adjacent permanent magnets of different polarities is reduced, and Focusing on making it possible to widen the area between the outer periphery of the rotor core, for example, by making the cross-sectional shape along the bathtub curve, to reduce the area between adjacent permanent magnets, and The focus is on the fact that the area between the permanent magnet and the outer periphery of the rotor core can be widened.

Therefore, as shown in FIG. 1 and FIG. 2, the rotor core (embedded field core; hereinafter, referred to as core) 10 of the three-phase four-pole permanent magnet motor has one bathtub curve shape per pole. (For example, a ferrite magnet) 11 and a bottom portion (convex portion) of this bathtub curve shape in cross section
Are arranged toward the center hole 4, four permanent magnets 11 are buried in the circumferential direction, and the permanent magnets 11 of adjacent poles are buried in different poles.

Although the permanent magnet 11 has a bathtub curve shape in cross section, the amount of use (magnet amount) of the permanent magnet 11 is almost the same as that of the conventional permanent magnet 3 having a fan-shaped cross section. It can be said that the shape is large, that is, the shape is a deformed bathtub curve. Further, since the area corresponding to the solid arrow a shown in FIG. 4 can be effectively used, the amount of permanent magnet used (magnet amount) is the same as or larger than the conventional one, and the magnet torque can be effectively used. Become.

In this case, both oblique sides (sides) of the permanent magnet 11
Is substantially straight, and the oblique sides of the permanent magnets 11 of adjacent poles are substantially parallel, that is, the interval (width including the q axis) is a predetermined value (at least the thickness of the core sheet). In addition, the interval is continuous and serves to secure a path (magnetic path) of the magnetic flux from the stator core 1 and to connect the inner peripheral portion and the outer peripheral portion of the rotor core 10.

The bottom portion of the cross section of the bathtub curve of the permanent magnet 11 is linear and close to the center hole 4, but the distance is set to the minimum necessary value as described in the conventional example, and the strength of the rotor core 10 is taken into consideration. Plan. Furthermore, since the bottom is linear, a substantially square region appears on the inner periphery of the rotor core 10 due to the connection between the bottom and the two oblique sides, so that the region between the permanent magnet 11 and the center hole 4 is formed. The caulked portion 12 can be formed.

The inside of the cross section of the bathtub curve of the permanent magnet 11 is a concave portion, and a region c (a region corresponding to a solid arrow b shown in FIG. 4) between the permanent magnet 11 and the outer periphery of the rotor core 10.
Is becoming wider. Therefore, the rivet 13 can be passed with a margin and a path (magnetic path) of the magnetic flux from the stator core 1 can be secured, so that the value of the inductance difference (Ld-Lq) increases. Further, a hole 14 for a flux barrier is formed at an end of the permanent magnet 11 (an upper edge having a bathtub shape in cross section) to prevent leakage of magnetic flux and short circuit.

As shown in FIG. 2, with respect to both ends of the permanent magnet 11 having a bathtub cross section, a flux barrier hole 1 is formed at one corner (outer corner of the permanent magnet 11).
4 is formed, and the other corner side (the inside corner of the permanent magnet 11) is cut at a predetermined angle (for example, an angle along the outer periphery of the rotor core 10) (see solid arrows d and e in the figure). Then, even if the thickness (width) of the permanent magnet 11 is further increased, the other corner does not protrude from the rotor core 10. Therefore,
The usage amount (magnet amount) of the permanent magnet 11 can be further increased, and the same or higher magnet torque as that of the related art can be obtained.

The hole for burying the permanent magnet 11 and the hole for the flux barrier are angular, but at least at the angular portion around the burying of the permanent magnet 11 (for example, the corners f to m shown in FIG. 2). R may be applied. That is, by rounding, the shape of the permanent magnet 11 also becomes a rounded bathtub curve shape, and chipping of a corner when the permanent magnet 11 is embedded can be prevented.

In the manufacture of the rotor core 10, a core laminating system (automatic laminating system) in which an electromagnetic steel sheet is punched out by an automatic press using a core press die and caulked and formed integrally in the die is adopted. .

In this pressing step, the center hole 4,
The hole for burying the permanent magnet 11, the caulking portion 12, the hole for passing the rivet 13, and the hole 14 for the flux barrier are punched out.
As shown in FIG. 3, the core sheet 10 is automatically pressed.
The rotor core 10 is formed by laminating a while caulking a.
The buried hole of the permanent magnet 11 and the hole 14 for flux barrier are integrated holes.

Thereafter, a low-cost ferrite magnet formed in the hole of the permanent magnet 11 is embedded, and the permanent magnet 11 is magnetically oriented in the thickness direction (radial direction of the rotor core 10) and magnetized. Further, as shown in FIG. 3, after covering both ends of the rotor core 10, the rotor core 10 is caulked through the rivets 14, thereby completing the manufacture of the rotor core 10.

Referring additionally to FIG. 1, this is the case where the permanent magnet motor is a three-phase four-pole motor, and the U-phase, V-phase and W-phase armature windings are provided on the 24-slot stator core 10. The armature winding on the outer diameter side is U-phase, the armature winding on the inner diameter side is W-phase, and the intermediate armature winding is V-phase. May be different.

If the rotor core 10 described above is used for a DC brushless motor and is applied to, for example, a compressor of an air conditioner, the performance and reliability of the air conditioner can be improved.

[0029]

As described above, according to the first aspect of the present invention, there is provided a permanent magnet motor in which a magnet-embedded field core (rotor core) is disposed in a stator core. One permanent magnet having a bathtub curved cross section per pole is used, and the bottom portion of the bathtub curved cross section of the permanent magnet is buried toward the center hole, and the permanent magnet having the bathtub curved shape is inserted into a circle of the rotor core. Since it is buried at equal intervals in the circumferential direction by the number of poles, the inside of the rotor core can be effectively used due to the cross-section of the bathtub curve, so that the amount of permanent magnet used (magnet amount) is not reduced, and By securing the path (magnetic path) of the magnetic flux from the stator core, the magnet torque and the reluctance torque can be used effectively,
As a result, there is an effect that the motor efficiency can be increased.

According to the second aspect of the present invention, in the first aspect, a caulking portion is formed in a region between the permanent magnet and the center hole, and a caulked portion is formed in a region between the permanent magnet and the outer periphery of the rotor core. Since the rivet is formed, in addition to the effect of the first aspect, the cross-sectional shape of the bathtub allows the formation of the caulked portion and the rivet to allow a margin, thereby maintaining the strength of the rotor core.

According to a third aspect of the present invention, in the first or second aspect, the bottom and both oblique sides of the cross section of the bathtub curve of the permanent magnet are linearized, and the corners are rounded.
A hole for a flux barrier is formed at one corner of both ends of the permanent magnet, and the other corner is cut at a predetermined angle. When the magnet is embedded in the rotor core, chipping of the corners can be prevented, and leakage and short circuit of magnetic flux can be prevented by the flux barrier. Further, by cutting one corner, there is an effect that the thickness (width) of the cross section of the bathtub curve can be increased to increase the use amount (magnet) of the permanent magnet and increase the magnet torque.

According to the invention described in claim 4, according to claim 1,
Since the permanent magnet in 2 or 3 is a ferrite magnet, in addition to the effect of claim 1, 2, or 3, it is possible to obtain necessary magnet torque and reluctance torque without using expensive materials such as rare earth magnets. And
That is, there is an effect that a high-efficiency motor can be realized at low cost.

According to the invention described in claim 5, according to claim 1,
Since a DC brushless motor is formed by incorporating the rotor core in 2, 3 or 4, the performance of the air conditioner can be improved by applying the present invention to a motor such as a compressor of an air conditioner in addition to the effects of claims 1, 2, 3 or 4. This has the effect of increasing the reliability and improving the reliability, and further reducing the cost.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a permanent magnet electric motor for describing an embodiment of the present invention.

FIG. 2 is a schematic partial plan view of a rotor core constituting a permanent magnet electric motor for describing a modified embodiment of the present invention.

FIG. 3 is a schematic sectional view of a rotor core constituting the permanent magnet shown in FIG. 1;

FIG. 4 is a schematic plan view for explaining a conventional permanent magnet motor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Stator core 4 Center hole (for shaft) 10 Rotor core (magnet embedded field core) 11 Permanent magnet (of rotor core 10) 12 Swaged part 13 Rivets 14 hole (for flux barrier)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Okudera 1116, Suenaga, Takatsu-ku, Kawasaki, Kanagawa Prefecture Inside Fujitsu General Co., Ltd.

Claims (5)

[Claims] 1. A permanent magnet motor in which a magnet-embedded field core (rotor core) is disposed in a stator core, wherein one permanent magnet having a bathtub curve cross section per one pole of the rotor core is used. The bottom portion of the cross-section bathtub curve shape is buried toward the center hole, and the bathtub curve-shaped permanent magnets are buried at equal intervals in the circumferential direction of the rotor core by the number of poles. Permanent magnet motor. 2. The permanent magnet motor according to claim 1, wherein a caulked portion is formed in a region between the permanent magnet and the center hole, and a rivet is passed through a region between the permanent magnet and an outer periphery of the rotor core. 3. A flux barrier hole is formed at one corner of both ends of the permanent magnet by making the bottom and both oblique sides of the cross section of the bathtub curve of the permanent magnet straight, and rounding the corner. 3. The permanent magnet motor according to claim 1, wherein the other corner is cut at a predetermined angle. 4. The permanent magnet motor according to claim 1, wherein said permanent magnet is a ferrite magnet. 5. A permanent magnet motor according to claim 1, wherein said rotor core is incorporated into a DC brushless motor.