JP2016072995A - Embedded magnet type rotor and electric motor provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an embedded magnet type rotor, which has a magnet insertion hole filled with a bond magnet fluid, capable of solving a conventional problem that flux leaks from both ends in axial direction of a rotor core causing a reduction of the magnetic flux flowing to the stator side resulting in a reduction of effective magnetic flux amount contributing to the torque.SOLUTION: The embedded magnet type rotor includes: a rotor core constituted of plural punched steel plates which are laminated in a direction of rotation axis; and a bond magnet filled in a magnet insertion hole of the rotor core, and the bond magnet is positioned in the rotor core. In a cross section in a direction perpendicular to the rotation axis of the rotor core, a convex embedding part and an outer edge part of the convex which is positioned on both end faces of the rotor core are integrally formed in the rotation axis.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an embedded magnet rotor in which a rotor core is filled with a plurality of bonded magnets and an electric motor including the same.

  A conventional permanent magnet type electric motor is provided with a substantially cylindrical stator that generates a rotating magnetic field, and a rotor having a magnetic pole formed by a permanent magnet on the inner peripheral side of the stator, with a gap provided on the inner peripheral side of the stator. A configuration that rotates around a shaft is common.

  In addition, the rotor is inserted with a permanent magnet into the magnet insertion hole provided in the rotor core in order to ensure the strength against centrifugal force applied at high speed rotation, and to provide reluctance torque by giving the saliency by arranging the permanent magnet. Embedded magnet rotors are widely used.

  By the way, segment magnets formed by casting, sintering, etc. are often used as permanent magnets. To improve workability during rotor assembly, the magnet insertion hole provided in the rotor core is larger than the segment magnet outline. Since it is configured with a slightly larger shape, there is a problem that the magnetic flux density on the rotor surface decreases due to the gap between the rotor core and the permanent magnet, and the magnet shape cannot be complicated because the segment magnet is hard and brittle. doing.

  In order to solve this problem, as disclosed in Patent Document 1, a small piece of cast or sintered magnet having a high energy density is placed in a magnet insertion hole, and then a bonded magnet mixed with a resin material is filled and cured. An embedded magnet type rotor has been devised.

  Since the bond magnet mixed with a resin material has a lower energy density than a cast or sintered magnet, a cast or sintered magnet piece having a high energy density is placed in the magnet insertion hole, and then the bond magnet is filled and cured. This suppresses a decrease in the surface magnetic flux density of the rotor.

  Further, since the bonded magnet is formed without a gap in accordance with the shape of the magnet insertion hole provided in the rotor core, it is possible to prevent a decrease in the surface magnetic flux density of the rotor due to the gap with the magnet insertion hole.

Japanese Patent Laid-Open No. 10-304610

  However, in an embedded magnet type rotor in which a magnet insertion hole is filled and cured with a bonded magnet fluid, leakage magnetic flux is generated from both axial end portions of the rotor core, so that the magnetic flux flowing to the stator side is reduced. Thereby, there exists a subject that the amount of effective magnetic flux which contributes to a torque reduces.

  The present invention solves such a problem, and suppresses the leakage magnetic flux from both axial end portions of the rotor core, increases the magnetic flux flowing to the stator side, and increases the effective magnetic flux amount contributing to the torque. An object of the present invention is to provide an embedded magnet type rotor.

In order to solve the above problems, an embedded magnet type rotor according to the present invention includes a rotor core made of a plurality of punched steel plates stacked in the rotation axis direction, and a bond magnet filled in a magnet insertion hole of the rotor core. In the cross section in the direction perpendicular to the rotation axis of the rotor core, located inside the rotor core, the convex embedded portions toward the rotation axis direction, and the outer edges convex toward the rotation axis, located at both end faces of the rotor core The unit is configured as a unit.

  The buried portion is magnetized in a direction orthogonal to the rotation axis, and the outer edge portion is magnetized so as to have an axial component.

  With the configuration described above, leakage magnetic flux from both axial ends of the rotor core can be suppressed.

  According to the present invention, by suppressing leakage magnetic flux from both axial ends of the rotor core, it is possible to increase the magnetic flux flowing to the stator side and increase the effective magnetic flux amount contributing to the torque.

Schematic of the electric motor according to Embodiment 1 of the present invention. (A) Perspective view of embedded magnet type rotor according to embodiment 1 of the present invention, (b) Cross-sectional perspective view of the embedded magnet type rotor (A) Perspective view of rotor core of embedded magnet type rotor, (b) Perspective view of bonded magnet of embedded magnet type rotor Diagram showing induced voltage and induced voltage per unit volume of permanent magnet The perspective view of the embedded magnet rotor which concerns on Embodiment 2 of this invention. Cross section of the embedded magnet rotor The figure which shows the relationship between the ratio X of the thickness A of the axial direction of a back yoke, and the thickness B of a permanent magnet, and an induced voltage. Perspective view of a conventional embedded magnet type rotor

  Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a permanent magnet type electric motor (hereinafter simply referred to as an electric motor) in an embodiment of the present invention. The electric motor 1 includes a stator 3 around which a winding 2 is wound, and an embedded magnet type rotor 4 that is disposed inside the stator 3 via a minute gap. A shaft 5 is fixed to the center of the embedded magnet type rotor 4, and the shaft 5 is rotatably held by two bearings 6.

  FIG. 2A is a perspective view of the embedded magnet type rotor 4. FIG. 2B is a cross-sectional perspective view taken along the two-dot chain line shown in FIG. FIG. 3B is a perspective view of the rotor core 41 constituting the embedded magnet type rotor 4, and FIG. 3B is a perspective view of the bond magnet 42.

  The embedded magnet rotor 4 has a rotor core 41 in which a plurality of punched steel plates are stacked in the rotation axis direction, a plurality of magnet insertion holes 43 provided so as to penetrate the rotor core 41, and a plurality of magnet insertion holes 43 filled. The bonded magnet 42 is a permanent magnet.

The bond magnets 42 are located on both end faces of the rotor core 41 and are surrounded by a semicircular shape (accurately speaking, the age of the moon 20) surrounded by a convex arc toward the center of the shaft that is the rotation axis and the outer periphery of the rotor core 41.
The outer edge portion 42a having the shape of the moon) and the cross-sectional shape in a plane orthogonal to the rotation axis is convex arcuately toward the shaft center. The embedded portion 42b. The outer edge portion 42a and the embedded portion 42b are integrally formed, and have a shape in which both ends of the embedded portion 42b in the rotation axis direction are covered with the outer edge portion 42a.

  The outer edge portion 42a has a smaller thickness than the buried portion 42b in the axial direction, the buried portion 42b is magnetized in a direction substantially perpendicular to the axial direction, and the outer edge portion 42a is formed as shown in FIG. As indicated by the arrow, it is magnetized to have an axial component.

  Conventionally, as shown in the perspective view of the embedded magnet type rotor in FIG. 8, the magnetic flux generated from the bond magnet 102 on the both end surfaces in the axial direction of the embedded magnet type rotor 101 is air from both end surfaces in the axial direction of the rotor core 103. The short circuit magnetic path (arrow in the figure) that leaks to the adjacent bonded magnet 102 is formed, so that the rotor surface magnetic flux is reduced, and the amount of effective magnetic flux contributing to torque is reduced.

  On the other hand, in the embedded magnet type rotor 4 of the present embodiment, both end surfaces of the rotor core 41 in the axial direction are covered with the bond magnets 42 magnetized so as to have an axial component. The amount of magnetic flux leaking into the air from both end faces can be reduced.

  In order to confirm this, numerical analysis of the magnetic field by the finite element method was performed. FIG. 4 shows a comparison of the calculation results of the induced voltage and the induced voltage per unit permanent magnet volume for the present embodiment and the conventional example. As can be seen from FIG. 4, the embedded magnet type rotor of this embodiment can increase the induced voltage as compared with the conventional rotor structure, and can also increase the induced voltage per unit permanent magnet volume.

  In this embodiment, the number of poles of the magnet-embedded rotor is 6 (the number of magnet insertion holes 43 is 6), but is not limited to this number, and may be 2n times (n is a natural number). If applicable. In addition, although the cross-sectional shape of the embedded portion 42b of the bond magnet 42 is an arc shape, this is not limited to this shape, and may be a U shape, a U shape, a V shape, or the like. May be.

(Embodiment 2)
FIG. 5 is a perspective view of the embedded magnet type rotor according to the second embodiment, and FIG. 6 is a cross-sectional view of the embedded magnet type rotor in the rotation axis direction.

  The embedded magnet type rotor 7 of the present embodiment further includes back yokes 8 on both end surfaces of the embedded magnet type rotor 4 shown in the first embodiment.

  In the embedded magnet type rotor 7 configured in this way, as described above, the amount of magnetic flux leaking to the air from the both axial end surfaces of the rotor core is reduced, and furthermore, between the adjacent bonded magnets 42, 5 is formed, the magnetic flux from the bonded magnet 42 passes through the back yoke 8 having a small magnetic resistance, thereby reducing the magnetic resistance between the adjacent bonded magnets 42. Therefore, the rotor surface magnetic flux increases, and the amount of effective magnetic flux contributing to torque can be further increased.

  Further, by making the outer diameter dimension of the back yoke 8 smaller than the outer diameter dimension of the rotor core 41, the rotor surface magnetic flux leaks into the air, and a short-circuit magnetic path (arrow in FIG. 6) returning to the back yoke 8 is formed. It is possible to suppress a decrease in the effective magnetic flux amount contributing to the torque.

Furthermore, by making the axial thickness of the back yoke 8 and the axial thickness of the outer edge portion 42a of the bonded magnet 42 have an appropriate relationship, the effect of increasing the effective magnetic flux amount contributing to torque can be enhanced. FIG. 7 shows the calculation result of the numerical analysis of the magnetic field by the finite element method. When the thickness of the back yoke 8 in the axial direction is A and the thickness of the outer edge portion 42a is B, the ratio X of A to B and the prior art The relationship of the induced voltage of the electric motor using the rotor structure of an example is shown. FIG. 7 shows that a large effect of increasing the induced voltage is obtained when X is 0.5 or more.

  The material of the back yoke is not limited to a specific material, and may be any magnetic material such as a silicon steel plate, a dust core, and a cold rolled steel plate.

  As described above, according to the electric motor of the present invention, it is possible to suppress the leakage magnetic flux from both axial ends of the rotor core, increase the magnetic flux flowing to the stator side, and increase the effective magnetic flux amount contributing to the torque, Since stable characteristics can be obtained, the present invention can be applied to various electric devices such as home appliances such as air conditioners and industrial devices such as robots without any particular limitation.

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Winding 3 Stator 4, 7 Embedded magnet type rotor 41 Rotor core 42 Bonded magnet 42a Outer edge part 42b Embedded part 43 Magnet insertion hole 5 Shaft 6 Bearing 8 Back yoke

Claims (6)

A rotor core made of a plurality of punched steel plates stacked in the direction of the rotation axis, and a bond magnet filled in a magnet insertion hole of the rotor core,
The bonded magnet is
In the cross section in a direction perpendicular to the rotation axis of the rotor core, which is located inside the rotor core, a convex embedded portion toward the rotation axis direction, and
An embedded magnet type rotor, which is located on both end faces of the rotor core and has a convex outer edge portion integrally formed toward the rotating shaft. 2. The embedded magnet type rotor according to claim 1, wherein the embedded portion is magnetized in a direction orthogonal to the rotation axis, and the outer edge portion is magnetized so as to have an axial component. The embedded magnet rotor according to claim 1, wherein a back yoke made of a magnetic material is provided on both end faces of the rotor core. 4. The embedded magnet type rotor according to claim 3, wherein the material of the back yoke is a silicon steel plate, a dust core, or a cold rolled steel plate. 5. The embedded magnet type rotor according to claim 3, wherein A / B is 0.5 or more, where A is a thickness of the back yoke and B is a thickness of the outer edge portion. 6. The electric motor provided with the embedded magnet type | mold rotor of any one of Claims 1-5.

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