JP2008154299A - Rotor structure of permanent magnet-embedded type motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce excessive tensile stress and bending stress generated, when a motor operates at a high speed. <P>SOLUTION: In the rotor structure of a permanent magnet-embedded type synchronous motor in which magnets are each embedded in each of housing holes of the rotor, the housing holes and the magnet are rounded in corners and the rounded portions, each having a radius R substantially a half of the thickness of each of the magnets. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

As a conventional example, there is one disclosed in Patent Document 1. FIG. 1 shows the structure. A permanent magnet is inserted into the accommodation hole of the rotor core, and a thin portion (bridge portion) is secured at the end of the permanent magnet in order to ensure the rotor strength.
Moreover, there exists what is shown by patent document 2. FIG. FIG. 2 shows an overall view, and FIG. 3 shows a state where a magnet is inserted into the accommodation hole and an enlarged view of the slit.
In FIG. 3A, a slit is formed in order to improve the centrifugal strength, and the resin is filled therein to prevent stress concentration due to contact between the slit corner and the magnet.
FIG. 3 (b) shows a nonmagnetic magnetic coil spring in the slit, with the left coil spring biased to the right and the right coil spring biased to the left to position the magnet in the center and contact the corners. Prevents damage to the magnet.

  However, the rotor structure shown in FIG. 1 has the following problems. That is, when the rotor is rotated at a high speed, the tensile force and bending stress are applied by the centrifugal force acting on the outer part of the magnet, and the thin part may be broken, and the rotor core part (bridge part) between the magnet and the gap ) Is supported by two thin-walled portions, and excessive stress is applied, which may damage the rotor.

The rotor structure shown in FIGS. 2 and 3 has the following problems. That is, by filling the slit part with resin or providing a coil spring, the stress concentration when the slit corner and the magnet are in contact is alleviated. However, a resin or a coil spring is required and costs increase. There is no slit on the point and the shaft side of the magnet (that is, the slit is only half of the magnet thickness), and excessive tension is applied to the corner of the receiving hole during high-speed rotation. Stress is applied and the rotor may be damaged.
JP 2000-152538 A JP 2002-359942 A

  The present invention has been made in view of the circumstances as described above, and has a rotor structure of a permanent magnet embedded synchronous motor that can relieve excessive tensile stress and bending stress generated when the motor rotates at high speed. The purpose is to provide.

  The present invention relates to a rotor structure of a permanent magnet embedded synchronous motor in which a magnet is embedded in a rotor receiving hole, and the object of the present invention is to process the receiving hole and the corner of the magnet by R machining, This is achieved by making it approximately the same as half the magnet thickness.

Further, the above object of the present invention is achieved by providing a bridge portion at one end in the longitudinal direction of the accommodation hole and providing at least one protrusion for fixing the magnet to the bridge portion.
Furthermore, the object of the present invention is to make the length of the round portion (R portion) of the bridge portion more than half of the magnet thickness, or to provide a rib between adjacent magnets of the same polarity, This is effectively achieved by providing the bridge portion at the end opposite to the rib.

According to the rotor structure of a permanent magnet embedded synchronous motor according to the present invention, the magnet corner portion and the accommodation hole have an R shape, so that stress concentration when the accommodation hole and the magnet come into contact can be reduced. Can prevent damage.
Further, by providing a protrusion for fixing the magnet in a portion where stress is not so much applied, the magnet can be fixed without causing stress concentration even in a state where the bridge portion is provided.
Furthermore, by providing ribs between the magnets, the rotor portion between the magnet and the gap is supported at least at three locations, so stress can be relaxed and the rotor can be prevented from being damaged during high-speed rotation. it can.
Furthermore, by setting the length of R of the bridge portion to more than half of the magnet thickness, it is possible to relieve excessive tensile stress and bending stress generated during high-speed rotation.

  FIG. 4 is a cross-sectional view of an embodiment of an embedded magnet type synchronous motor having a rotor structure according to the present invention, and is an example of a 4 pole 24 slot embedded magnet type synchronous motor. The stator is provided with 24 slots for receiving coils, and is formed of a laminated copper plate in order to reduce eddy current loss. There are several embodiments depending on the rotor structure.

図８より、ブリッジ部Ｒの長さを長くすることにより、応力は低減できることが分かる。ブリッジ部Ｒの長さを0．5（対磁石厚比）以上とすることにより、ブリッジ部応力を約６割以下に減らすことができて、従来の構造では実現できなかった回転数でも回すことが出来る。 [Embodiment 1]
FIG. 5 shows a first embodiment of the rotor structure according to the present invention (hereinafter referred to as embodiment 1; the same applies hereinafter). A rotor core is attached to the shaft, and the rotor core is formed of a laminated copper plate. An accommodation hole is provided in the rotor core, and an Nd—Fe—B sintered magnet serving as a field is inserted into this portion. The accommodation hole is provided with a bridge portion to relieve the tensile stress and bending stress generated by the rotation of the rotor, and the magnet hole is formed in an R shape so that the accommodation hole and the magnet are in contact with each other. The stress concentration at the time is reduced to prevent the magnet from being damaged. The R shape means a round shape. Further, the magnet for one pole is divided into two and arranged in parallel. By dividing into two, the rotor part between a magnet and a gap will be supported at three places, and stress can be relieved compared with the case where it is not divided. The divided part between the two magnets is called a rib.
FIG. 6 shows an enlarged view of the magnet portion. In this embodiment, the rotor outer diameter R and the bridge portion R are substantially concentric circles (that is, the thickness of the thin portion is constant), and the length of the bridge portion R is substantially the same as the magnet thickness. The rotor is prevented from being damaged during rotation.
Further, a protrusion is provided in a portion where the stress is hardly applied, and even when the bridge portion is provided, stress concentration is prevented and the magnet is fixed. This protrusion also serves as a spring when the magnet is inserted, and the magnet is firmly fixed to the storage hole.
Table 1 shows the results of analyzing the stress of the shape of the type (FIG. 7) without the slit as in Conventional Example 1 and the shape of Embodiment 1 (FIG. 5) by the finite element method. The value shows the value divided by the stress value of Conventional Example 1. Table 2 shows the dimensions of the bridge portion. FIG. 6 shows the dimensions. The value is divided by the magnet thickness. The rotor diameter, shaft diameter, magnet size, material, and rotation speed are analyzed under the same conditions. This analysis is the result of a rotor diameter of 80 mm and a rotation speed of 50000 rpm. Conventional example 2 is a case where the length R of the bridge portion is 0.4 (magnet thickness ratio).

FIG. 8 shows that the stress can be reduced by increasing the length of the bridge portion R. By setting the length of the bridge part R to 0.5 (thickness ratio to the magnet) or more, the bridge part stress can be reduced to about 60% or less, and it can be rotated even at a rotational speed that could not be realized with the conventional structure. I can do it.

[Embodiment 2]
The basic structure is the same as in the first embodiment. FIG. 9 shows an enlarged view of the magnet part.
The rotor outer diameter R and the bridge portion R are not substantially concentric circles, and the bridge portion R is made smaller than the rotor outer diameter R to provide a partially thin portion. The length of the R portion is substantially the same as the magnet thickness. As a result, although the tensile stress and bending stress increase in the thin part and the allowable maximum rotational speed decreases, the magnetic flux is saturated in the thin part and the short magnetic flux decreases, so the amount of magnetic flux guided to the stator increases and the generated torque increases. There is an advantage.

[Embodiment 3]
The basic structure is the same as in the first embodiment. FIG. 10 shows an enlarged view of the magnet part.
The rotor outer diameter R and the bridge portion R are not substantially concentric circles, and the bridge portion R is made larger than the rotor outer diameter R to increase the width of the bridge portion. The length of the bridge portion R is substantially the same as the magnet thickness. As a result, the width of the bridge is increased, so the short-circuit magnetic flux increases and the generated torque decreases.However, because the tensile stress and bending stress decrease as the thickness increases, the maximum allowable rotational speed increases. is there.

[Embodiment 4]
In Embodiments 1 to 3, the magnet arrangement is parallel, but the same holds true if the two magnet arrangements are V-shaped. Since the reluctance torque can be used effectively, it is particularly effective when a large torque is required. A typical shape is shown in FIG.

[Embodiment 5]
In Embodiments 1 to 3, the magnet arrangement is parallel, but the same holds true for the shape when the two magnet arrangements are close to the surface magnet arrangement. In this case, since the stress between the magnets on the side where there is no bridge is relieved, it is particularly effective when higher speed rotation is required. A typical shape is shown in FIG.

[Embodiment 6]
In Embodiments 1 to 5, the R length of the bridge portion is substantially the same as the magnet thickness. However, if it is used for a relatively low rotation, the R length of the bridge portion as shown in FIG. The same effect can be obtained even with half the length. In addition, R of the joint part shown in FIG. 13 is the same as half of the magnet thickness.

In FIG. 5, the magnets are arranged in parallel, but of course, the same effect can be obtained with the arrangements of the embodiment 4 (FIG. 11) and the embodiment 5 (FIG. 12).
In the first to sixth embodiments, an example of a 4-pole 24-slot motor has been described.
An example of the Nd—Fe—B sintered magnet is shown as the magnet material, but the present invention is not limited to this, and another magnet material such as a ferrite magnet may be used.
Although an example in which the stator is not skewed has been shown, the same is true even if the stator is skewed.
In Embodiments 1 to 6, an example in which one rib is provided is shown, but the present invention is not limited to this, and can be changed as appropriate.

It is an enlarged view of the rotor structure of the prior art example 1 (patent document 1). It is an enlarged view of the rotor structure of the prior art example 2 (patent document 2). It is an enlarged view of the magnet part of the rotor structure of the prior art example 2 (patent document 2). 1 is an overall view of a motor having a rotor structure according to the present invention. It is an enlarged view of the rotor structure of Embodiment 1 of this invention. It is a magnet part enlarged view of Embodiment 1 of this invention. It is an example of the rotor shape in case this invention is not applied. It is a graph which shows the change of the stress by the length of a bridge part. It is a magnet part enlarged view of Embodiment 2 of this invention. It is a magnet part enlarged view of Embodiment 3 of this invention. It is a figure which shows the typical example of Embodiment 4 of this invention. It is a figure which shows the typical example of Embodiment 5 of this invention. It is a magnet part enlarged view of Embodiment 6 of this invention.

Claims (5)

In the rotor structure of the permanent magnet embedded synchronous motor in which the magnet is embedded in the rotor receiving hole,
A rotor structure of a permanent magnet embedded synchronous motor, wherein the housing hole and the corner of the magnet are R-processed, and the radius of the R is substantially the same as half of the magnet thickness. The embedded permanent magnet according to claim 1, wherein a bridge portion is provided at one end in the longitudinal direction of the accommodation hole, and at least one protrusion for fixing the magnet is provided on the bridge portion. Synchronous motor rotor structure. 3. The rotor structure of a permanent magnet embedded synchronous motor according to claim 2, wherein the rounded portion (R portion) of the bridge portion has a length equal to or more than half of the magnet thickness. The rotor structure of a permanent magnet embedded synchronous motor according to claim 2 or 3, wherein a rib is provided between adjacent magnets of the same polarity, and the bridge portion is provided at an end opposite to the rib. A permanent magnet embedded synchronous motor comprising a rotor having the rotor structure according to claim 1.

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