JP2003070214A - Method of manufacturing permanent magnet segment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for manufacturing a permanent magnet for a motor wherein the number of divided permanent magnet segments and the shapes of the divided permanent magnet segments, which are most suitable for suppressing the loss and heat produced by an eddy current with a necessary ratio and for reducing the cost as low as possible, are obtained. SOLUTION: A permanent magnet base material is divided into a plurality of permanent magnet segments only in the shaft direction or in the circumferential direction of a motor so as to make the shapes of the magnet segments have aspect ratios in magnetizing directions within a range of 2 to 10. Further, the number of the divided permanent magnet segments are determined according to corresponding relations between eddy current losses and the aspect ratios in the magnetizing directions or the number of the divided segments.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a permanent magnet piece constituting a permanent magnet for an electric motor, which is provided in a permanent magnet electric motor used as a drive source for a railway vehicle, an electric car, or the like.

[0002]

2. Description of the Related Art Conventionally, for example, a permanent magnet electric motor has been used as a drive source for railway vehicles. As an example of a permanent magnet electric motor, for example, a plurality of coils are attached to a stator (stator) side that is fixed so as not to rotate, and a plurality of permanent magnets are connected to a drive shaft to apply torque to the rotor (rotor) side. There is a permanent magnet synchronous motor with a magnet attached. In this case, the coils and the permanent magnets are arranged to face each other. Therefore, the rotor rotates in synchronization with the alternating magnetic field due to the interaction between the alternating magnetic field generated when the three-phase alternating current or the like is supplied to the coil and the static magnetic field of the permanent magnet.

By the way, in particular, a permanent magnet synchronous motor used as a drive source for a railway vehicle or the like is equipped with a large permanent magnet because a large torque is required, and the alternating magnetic field generated by the coil is also strong. Designed to porcelain. In this case, when the electric motor is driven to rotate, the strong magnetic flux generated by the coil penetrates the large permanent magnet,
A large eddy current is generated in the permanent magnet, and the generated eddy current causes the permanent magnet to generate heat, resulting in a large loss of the motor.

As a countermeasure against this, a plurality of permanent magnet pieces obtained by dividing and insulating a permanent magnet base material are combined to form a permanent magnet for an electric motor, and an eddy current generated therein is retained in each permanent magnet piece. Therefore, the amount of eddy current generated in the permanent magnet is reduced. The size of the permanent magnet piece of the present invention is not particularly limited, but if the size is limited, in particular, the permanent magnet area viewed from the magnetization direction of the permanent magnet piece is 2500 [mm ² ] ~ 90000
The target is a [mm ² ] magnet.

[0005]

According to such a technique, since the generation of eddy current is suppressed, the loss due to the eddy current is suppressed, and the temperature of the permanent magnet for the electric motor is increased to a region where demagnetization occurs. Although it has been difficult to reach the target and was useful for solving the above-mentioned problems, the reality is that a technique for more effectively suppressing the generation of eddy currents is desired.

In order to reduce the eddy current and suppress the loss, it is sufficient to increase the division of the magnet to infinity. However, as shown in FIG.
The cost increases as the number of divisions increases. For this reason, it is desired to divide the permanent magnets by the minimum necessary number of divisions. However, there is no case where eddy current loss countermeasures have been taken in large permanent magnets used in, for example, electric motors for driving railway vehicles. It's a reality.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for more effectively suppressing the generation of eddy currents. Another object of the present invention is to provide a technique for manufacturing a permanent magnet for an electric motor, in which loss and heat generation due to eddy current can be suppressed at a required ratio, and an optimal number of magnet divisions / division shapes and cost are minimized. There is.

[0008]

The present invention adopts the following constitution in order to achieve this object. In the following, in each of the matters specifying the invention, reference numerals in the drawings corresponding to the subordinate concepts are shown in parentheses. However, it goes without saying that the respective matters specifying the invention are not limited thereto.

The manufacturing method according to claim 1 which achieves the above object is a manufacturing method for manufacturing a permanent magnet piece for constituting a permanent magnet for an electric motor by dividing a permanent magnet base material. By dividing the magnet base material only in the axial direction or the circumferential direction of the electric motor, the step of setting the shape of the divided magnets to have an aspect ratio in the range of 2 to 10 when viewed from the magnetization direction is included. Here, when the axial length of the permanent magnet base material is represented by La and the circumferential length is represented by Lb, when La> Lb, Lb is divided, and when the division number is n, the shape of the divided magnet is La. And Lb / n. On the other hand, in the case of La <Lb, if La is divided and the number of divisions is n, the shape of the divided magnet is La / n and Lb. Further, the aspect ratio of the divided magnet is in the range of 2 to 10.

Here, the aspect ratio means a value obtained by dividing the long side of the permanent magnet piece by the short side as seen from the magnetization direction of the permanent magnet.

The invention according to claim 2 for achieving the above object is a manufacturing method for manufacturing a permanent magnet piece for constituting a permanent magnet for an electric motor by dividing a permanent magnet base material. The method includes the step of determining the number of divisions of the permanent magnet base material by the correspondence relationship between the current loss and the aspect ratio or the number of divisions viewed from the magnetization direction of the permanent magnet pieces.
As described in the embodiments of the invention, the present invention has been made based on a quantitative evaluation of eddy current loss. That is, according to the second aspect of the invention, the number of divisions of the permanent magnet base material is determined by the correspondence relationship between the eddy current loss and the aspect ratio or the number of divisions in the magnetizing direction surface of the divided permanent magnet pieces. The permanent magnet base material can be divided with the minimum necessary optimum number of divisions corresponding to the desired eddy current loss.

Further, in the manufacturing method for achieving the above object, a permanent magnet base material having an axial length of La and a circumferential length of Lb is divided to form a permanent magnet for an electric motor. In a manufacturing method for manufacturing a permanent magnet piece, there is a correspondence relationship between eddy current loss and cost, and by a relational expression that determines the number of divisions selected according to a desired eddy current loss,
It is characterized by including a step of determining the number of divisions of the permanent magnet base material.

As described in the embodiments of the present invention, the present invention was made based on the quantitative evaluation of eddy current loss. That is, the eddy current loss, the aspect ratio as viewed from the magnetization direction of the divided permanent magnet pieces, and the cost, which is a relational expression that determines the number of divisions selected according to the desired eddy current loss, Since the number of divisions of the magnet base material is determined, it is possible to divide the permanent magnet base material with the minimum necessary optimum number of divisions corresponding to the desired eddy current loss.

Further, the manufacturing method for achieving the above object is characterized in that the aspect ratio in the magnetizing direction surface is formed in the range of 2 to 10 with the determined number of divisions. A method for manufacturing a permanent magnet piece for achieving the above object is the method according to claim 1 or 2,
The area viewed from the magnetization direction of the permanent magnet base material is 2500 m
It is characterized by being in the range of m ^{2 to} 90000 mm ² .

According to the present manufacturing method, the area seen from the magnetization direction of the permanent magnet base material is in the range of 2500 mm ² ～90000Mm ^2, and an aspect ratio in the magnetizing direction surface of the permanent magnet piece from 2 10 Since it is formed in the range, the eddy current in each permanent magnet piece can be effectively suppressed, and the optimum division can be given in terms of cost.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below.
It will be described with reference to FIGS. 1 to 4. The power of this embodiment
The area of the permanent magnet for motive is 2500 when seen from the magnetization direction.
[Mm ²] ~ 90000 [mm²] Permanent magnet base material
A plurality of rectangular permanent magnets having an aspect ratio of 2 to 10
Dividing process to divide into stone pieces and permanent obtained by dividing
In the joining process of joining the magnet pieces to each other via the insulating layer,
The magnet pieces that are finally divided are
Bonded via adhesive and equivalent to the permanent magnet base material before splitting
It is characterized by having a different shape. Of these, especially the minutes
The splitting step is a feature of the present invention.

First, an analysis of the effect of reducing the eddy current by dividing the permanent magnet base material, which led to the present invention, will be described. [Analysis 1] In the dividing step, the axial length La = 20
0 [mm], circumferential length Lb = 70 [mm], thickness 2
The plate-shaped permanent magnet base material of 0 [mm] (magnetization direction is the thickness direction) is evenly divided into 10 parts only in the axial direction, and in the joining step, the respective permanent magnet pieces are joined to obtain the original The eddy current generated in the permanent magnet 1 for an electric motor (see FIG. 1A) manufactured when a bonded body having a size substantially matching the permanent magnet base material was formed was analyzed.

FIG. 1B shows the distribution of the eddy current density vector representing the eddy current generated in the electric motor permanent magnet 1, and FIG. 1C shows the distribution of the eddy current density vector for comparison with the eddy current density vector. It shows the distribution of the generated eddy current density vector. 1 (b) and 1 (c), only the portion corresponding to the left half of the permanent magnet 1 for an electric motor and the permanent magnet base material when viewed from the magnetization direction are shown.

When the permanent magnet base material is not divided, the structure shown in FIG.
As shown in (c), a large eddy current is generated at the edge of the permanent magnet base material. On the other hand, as shown in FIG. 1B, an eddy current is generated in each permanent magnet piece. It can be seen that the value of each eddy current is small and is considerably smaller than the case where the permanent magnet base material is not divided.

Therefore, when the permanent magnet base material is divided,
It can be seen that the amount of eddy current generated in the permanent magnet for the electric motor as a whole can be reduced as compared with the case where it is not divided. From this, it can be said that manufacturing the permanent magnet for an electric motor by including the dividing step of dividing the permanent magnet base material is effective for reducing the eddy current loss of the electric motor.

Next, the causal relationship between the number of divisions of the permanent magnet base material in the division step and the eddy current loss in the permanent magnet for the electric motor will be described. [Analysis 2] In the dividing step, the axial length La = 20
0 [mm], circumferential length Lb = 70 [mm], thickness 2
A plate-shaped permanent magnet base material of 0 [mm] is evenly divided only in the longitudinal direction, and in the joining process, the permanent magnet pieces are joined to each other, so that the size of the original permanent magnet base material is matched. The eddy current loss of a permanent magnet for an electric motor (see FIG. 1A) manufactured when a body was formed was analyzed. In this case, the number of divisions of the permanent magnet base material was changed in two division steps from a state of not dividing to a state of dividing into 16 and the eddy current loss of the permanent magnet for a motor was analyzed for each number of divisions.

In this case, since the permanent magnet base material is divided only in the axial direction, the length of one side of the rectangular permanent magnet piece as viewed in the magnetization direction is Lb, and the length of the side perpendicular to the side is the permanent magnet base material. It changes according to the number of divisions. Letting A be a variable that represents the length of the side that changes according to the number of divisions, the size of each permanent magnet piece can be expressed as Lb × A (FIG. 1A).
reference).

The eddy current loss depends on whether the drive power source of the motor is a sine wave power source or an inverter power source.
Two cases were analyzed. Further, the current value of each power source was set to a continuous rated value of 108 [A].

FIG. 2 (a) shows quantitatively the eddy current loss of the permanent magnet electric motor due to the permanent magnet for the electric motor for each number of divisions of the permanent magnet base material, with the number of divisions on the horizontal axis. , The ordinate indicates the eddy current loss [W]. As shown in the figure, the eddy current loss value is absolutely larger when the inverter current is driven than when it is sinusoidal current driven. This means that the inverter current contains harmonic components. It is due to.

However, in any case, it can be seen that the eddy current loss of the electric motor is reduced as the number of divisions of the permanent magnet base material is increased. From this, in order to reduce the eddy current loss of the motor in the case of joining the permanent magnet pieces obtained by the division and manufacturing the permanent magnet for the motor of a size that substantially matches the original permanent magnet base material, It can be said that it is effective to divide the magnet base material as much as possible.

On the other hand, if the number of divisions of the permanent magnet is increased, the number of manufacturing steps is correspondingly increased, and more materials such as an insulating film are required. Therefore, the manufacturing cost of the permanent magnet for an electric motor is high. In addition, there is a processing limit in increasing the number of divisions. Therefore, it may not always be practical to increase the number of divided permanent magnet base materials. Therefore, in order to find a more realistic number of divisions of the permanent magnet base material, the following analysis was performed.

FIG. 2B shows the magnetic field analysis results when the number of divisions (aspect ratio viewed from the magnetization direction) was changed. Aspect ratio of 200 /
70 (in this specification, the aspect ratio is always 1 or more because a long side is divided by a short side). The loss due to the eddy current at this time was set to 1. When the number of divisions is 2 (aspect ratio 100/70), the loss can be suppressed to about 0.85 to 0.9.

It can be confirmed that the inclination changes when the aspect ratio is 1. This can be classified into a case where the shape of the split magnet approaches a square (aspect ratio of 1) and a case where it goes away. As a result, it is understood that the effect of suppressing the eddy current differs depending on the shape of the magnet base material in the magnet division. The effect of suppressing eddy current is small when the aspect ratio as seen from the magnetization direction of the permanent magnet piece approaches 1 and the number of divisions increases, and the effect is greater when the aspect ratio moves away from 1 and the number of divisions increases. I understand.

Since the effect of suppressing the loss due to the eddy current of the split magnet can be confirmed by the relational expression when the aspect ratio moves away from 1 and the split number increases, the split number is increased unnecessarily.
It is possible to prevent the cost from increasing. The relationship between the loss due to the eddy current when there is no division and the loss due to the eddy current when the division is n is shown when the aspect ratio moves away from 1. Loss P without division, number of divisions n, loss P _{n with} division into _n
Then, P _n = P / n

From this fact, reducing the aspect ratio of the permanent magnet pieces relatively reduces the eddy current suppressing effect due to the division, while increasing the aspect ratio of the permanent magnet pieces means the eddy current due to the division. It is considered that the suppression effect is relatively promoted.

Considering this point, it can be seen that when the aspect ratio of the permanent magnet piece becomes small due to the division, the effect of the division is not obtained so much. On the other hand, when the aspect ratio of the permanent magnet piece is increased by the division, it is understood that the division effect can be reasonably obtained.

Therefore, when dividing a fixed number of permanent magnet base materials by the same number, it is rational to divide each permanent magnet piece so that the aspect ratio of each permanent magnet piece is as large as possible. Specifically, it is effective to divide the permanent magnet base material into only one of the longitudinal direction and the width direction. This is because when the permanent magnet base material is divided in both the longitudinal direction and the width direction, the shape of each permanent magnet piece approaches a square.

[Embodiment] FIGS. 3A to 3D show permanent magnets for electric motors manufactured when the permanent magnet base material is divided as described above.

Since the electric motor permanent magnets 2 and 3 shown in FIGS. 3 (a) and 3 (b) are La> Lb, it is effective to divide Lb in order to increase the aspect ratio. is there. Therefore, 21, 22, 23 or 31, 3
The permanent magnets are divided like 2, 33 and 34.

FIG. 3 (c) shows that, due to the convenience of manufacturing the magnet,
Assuming that one permanent magnet piece is composed of a combination of five permanent magnets, the division direction is determined by the lengths La and Lb of the magnetic pieces 4, 5 respectively. Since La> Lb, in order to increase the aspect ratio of the divided magnets, 41, 42, 4
3 and 51, 52, 53. However, 4, 5
The magnets are insulated and bonded with an adhesive E.

It is assumed that FIG. 3 (d) is also composed of two magnets. In this case as well, since La> Lb, it is effective to divide the permanent magnets 6 and 7 into 61-65 and 71-75. However, the magnets 6 and 7 are insulated and joined by an adhesive E.

In this way, the dividing direction of the permanent magnet base material can be determined by the original shape of the permanent magnet base material itself, without depending on the directions related to the structure of the permanent magnet motor, such as the axial direction and the circumferential direction. .

FIG. 4 shows the relationship between the eddy current loss ratio and the manufacturing cost in each aspect ratio. As shown in FIG. 4, as the aspect ratio increases (synonymous with the increase in the number of divisions), the cost increases, but the eddy current loss decreases. It can be said that it is effective to divide the shape of the divided magnet into an aspect ratio in the range of 2 to 10 in consideration of the trade-off between the two.

As described above, according to this embodiment, the following effects can be obtained. Since the permanent magnet base material that is rectangular in plan view is divided only in the width direction, the length in the longitudinal direction of the original permanent magnet base material can be utilized, and a permanent magnet piece with a large aspect ratio can be rationalized. It can be manufactured. Thereby, the amount of eddy current generated in each permanent magnet piece can be effectively reduced.

This is a relational expression between the eddy current loss and the aspect ratio in the magnetizing direction surface of the permanent magnet piece. The relational expression determines the number of divisions by increasing the aspect ratio, and corresponds to the desired eddy current loss. It is possible to divide the permanent magnet base material with the optimum minimum number of divisions required. Therefore,
Since the permanent magnet base material can be divided by the necessary minimum number of divisions, the manufacturing cost of the permanent magnet for an electric motor can be minimized.

In order to make the effect of division effective, by setting the aspect ratio of the magnet shape viewed from the magnetization direction of the divided magnet in the range of 2 to 10, the eddy current is effectively generated by taking the cost into consideration. The loss can be reduced.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example, the entire surface of the divided permanent magnet pieces of the permanent magnet base material may be surface-treated with an insulator before the above-mentioned joining step.

Although a plate-shaped permanent magnet is shown in FIGS. 1 and 3, it is also possible to use a tile-shaped permanent magnet base material having a rectangular shape in plan view and a fan-shaped cross section. The type of magnet of the permanent magnet base material is not particularly limited,
For example, it is suitable to apply the present invention to a magnet having a small electric resistance such as a rare earth magnet or an alnico magnet. In the embodiment, the size of the permanent magnet is 2500 [mm
² ] to 90000 [mm ² ] but the size to which the present invention is applicable is not limited to this size.

[0044]

According to the present invention, the generation of eddy current can be suppressed more effectively. Further, according to the present invention, when manufacturing a permanent magnet for an electric motor, the permanent magnet base material can be divided with an optimum number of divisions.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an eddy current reduction effect by dividing a permanent magnet base material.

FIG. 2 is a diagram for explaining a causal relationship between the number of divisions of a permanent magnet base material and an eddy current loss in a permanent magnet for an electric motor.

FIG. 3 is a view exemplifying a division mode of a permanent magnet base material.

FIG. 4 is a diagram for explaining a relationship between an aspect ratio of a split permanent magnet, a ratio of eddy current loss in a permanent magnet for an electric motor, and a cost.

[Explanation of symbols]

1,2 Permanent magnet for electric motor 21,22,23 Permanent magnet pieces E adhesive

Continued front page    (72) Inventor Koichi Matsuoka             38-8, Hikarimachi, Kokubunji, Tokyo 38 Foundation             Corporate Railway Technical Research Institute (72) Inventor Ken Ohashi             2-1-5 Kitafu, Takefu City, Fukui Prefecture Shin-Etsu Chemical Co., Ltd.             Industry Magnetic Materials Research Center F-term (reference) 5E062 AA06 CC03                 5H622 AA03 CA02 CA03 CA07 CB03                       DD02 DD03 QA06 QA08

Claims (3)

[Claims] 1. A manufacturing method for manufacturing a permanent magnet piece for constituting a permanent magnet for an electric motor by dividing the permanent magnet base material, wherein the permanent magnet base material is axially or circumferentially of the electric motor. By dividing only in the direction, the aspect ratio of the shape of the divided magnet as viewed from the magnetization direction is in the range of 2 to 10,
And a method for manufacturing a permanent magnet piece. 2. A manufacturing method for manufacturing a permanent magnet piece for constituting a permanent magnet for an electric motor by dividing a permanent magnet base material, the method comprising: an eddy current loss; A method of manufacturing a permanent magnet piece, comprising the step of determining the number of divisions of the permanent magnet base material according to a correspondence relationship with the aspect ratio or the number of divisions. 3. The method for producing a permanent magnet piece according to claim 1 or 2 area, as viewed from the magnetization direction of the permanent magnet base material is equal to or is in the range of 2500mm ² ~90000mm ^2.