JP2009200320A - Permanent magnet with low iron loss, and permanent magnet type motor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet which has low iron loss and enhances efficiency of a motor without lowering magnetic characteristics. <P>SOLUTION: The permanent magnet is formed of magnetic particles 1 such as NdFeB particles or SmCo particles, and has ≤100 nm magnesia particles 3 at grain boundaries 2 or gaps of NdFeB or SmCo. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a low iron loss permanent magnet used in combination with an iron core, a yoke, or the like, and a permanent magnet type motor using the same.

In a conventional permanent magnet, an eddy current flows due to the armature of the motor, causing iron loss, resulting in a loss in the motor. For this reason, it has been proposed to increase the insulation resistance of the permanent magnet and reduce the eddy current loss.
As a method for improving the insulation of a conventional permanent magnet, a bonded magnet is produced by adding silicic acid particles (see Patent Document 1).
FIG. 5 is a schematic diagram showing the structure of the bonded magnet. Silicic acid 6 is mixed with magnetic particles 7 and resin 8 and used as a bonded magnet.
JP 2006-186107 A

However, since the conventional permanent magnet is only a metal body, the current of the armature of the motor can easily pass therethrough, which causes a problem that the iron loss increases in the permanent magnet and the efficiency of the motor decreases. Moreover, in order to increase the insulation of the permanent magnet, there is a method of adding ceramics such as silicic acid (Si02), but since it reacts with an intermetallic compound such as NdFeB or SmCo at the time of sintering, the magnetic properties are lowered. There is also a problem that it can be used only for bonded magnets.
The present invention has been made in view of such problems, and improves the efficiency without increasing the induction loss of the motor by reducing the iron loss in the permanent magnet while increasing the insulation of the permanent magnet. An object of the present invention is to provide a method for manufacturing a permanent magnet that can be used.

In order to solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a low iron loss permanent magnet comprising a magnetic particle of NdFeB particles or SmCo particles, and having magnesia particles of 100 nm or less in the crystal grain boundaries or gaps of the NdFeB or SmCo. is there.
According to a second aspect of the present invention, there is provided a permanent magnet composed of magnetic particles of NdFeB particles or SmCo particles, and a magnet body having magnesia particles of 100 nm or less in the NdFeB or SmCo crystal grain boundaries or gaps, and the NdFeB Further, it is a low iron loss permanent magnet composed of two layers of a magnet body made of only SmCo magnetic particles.
According to a third aspect of the present invention, the content of the magnesia particles is 0.5 to 4.0 wt% by weight.
According to a fourth aspect of the present invention, the average particle diameter of the NdFeB particles or SmCo particles is 6 μm or less.
The invention described in claim 5 is a permanent magnet type motor configured by using the low iron loss permanent magnet described in claim 1 or claim 2.
According to a sixth aspect of the present invention, the low iron loss permanent magnet has a cylindrical shape, the inner peripheral side of the cylindrical body is a magnetic body only of magnetic particles, and the outer peripheral side is a mixture of magnesia particles and magnetic particles. It is a magnet body.

According to the invention described in claims 1 and 3 to 5, the insulation of the permanent magnet can be increased, the iron loss of the permanent magnet can be reduced without lowering the induced voltage of the permanent magnet, and the efficiency of the motor is improved. be able to.
According to the second and sixth aspects of the invention, the insulation can be increased only in the portion where the iron loss of the permanent magnet occurs, and the iron loss can be reduced more efficiently, so that the efficiency of the motor can be further improved. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In this example, NdFeB particles were used as magnetic particles, and 100 nm particles were used as active magnesia particles.
The portion where the present invention is different from the conventional magnet is a portion sintered using magnesia particles that do not react with NdFeB or SmCo at the time of sintering, instead of silicic acid.
The magnet was produced as follows.
(1) First, various amounts of active magnesia particles having a weight ratio of 0.3 to 6 wt% were added to NdFeB particles having an average particle diameter of 5 μm and mixed by a planetary ball mill used for mixing nano-order particles.
(2) The mixed particles were filled in a mold and formed into a cylindrical shape at a pressure of 100 MPa.
(3) Sintered at a temperature of 1100 ° C. for 2 hours. The sintering temperature should just be a fixed temperature of 1050-1150 degreeC.
The structure after sintering is shown in FIG. In the figure, 1 is a magnetic particle of NdFeB, 2 is a crystal grain boundary or gap, and 3 is a magnesia particle. It can be seen that the magnesia particles 3 are distributed in the gaps 2 of the magnetic particles (NdFeB) 1.
Next, the produced cylindrical rotor magnet was incorporated into a 300 W permanent magnet motor, magnetized to 8 poles, and eddy current loss and induced voltage, which are one of iron losses at 1500 revolutions, were measured and evaluated.
Table 1 shows the amount of active magnesia particles added and the measured values. As a comparative example, a magnesia particle addition amount of 0 wt% was added.
As can be seen from Table 1, # 2 to # 4 in which the addition amount of magnesia particles is 0.5 to 4.0 wt% has an effect of lower eddy current loss and induced voltage than Comparative Example # 1 in which no magnesia particles are added. I understood that. In addition, it was found that eddy current loss was not reduced when # 1 of the magnesia particles added was 0.3 wt%, and that the induced voltage was low when # 5 of 6 wt% was not effective.
As a result, the current generated from the motor armature flows as an eddy current inside the permanent magnet, but the magnesia particles 3 segregated at the crystal grain boundaries 2 of the NdFeB particles 1 serve as an insulator to prevent the generation of eddy currents. It is thought that iron loss could be prevented. That is, it is considered that the magnesia particles 3 did not react with the magnetic particles 1 of NdFeB.

In this example, the average particle diameter of the magnetic particles 1 of NdFeB is changed to 2 to 7 μm. As active magnesia particles, 100 nm particles were fixed at 2 wt%, and the molding pressure and sintering conditions were the same as those in Example 1. The produced cylindrical rotor magnet was incorporated into a permanent magnet motor in the same manner as in Example 1 and magnetized, and eddy current loss and induced voltage were measured and evaluated.
As shown in Table 2, when the average particle diameter is larger than 6 μm, the induced voltage is lowered and the effect is lost. However, when the average particle diameter is small, the characteristics are good.

In this example, the average particle diameter of the NdFeB particles 1 as magnetic particles is made constant at 5 μm, and the average particle diameter of the active magnesia particles is changed. The average particle diameter of magnesia particles was set to three types of 50, 100, and 200 nm, and the amount of magnesia particles added was fixed at 1.5 wt%. The molding and sintering conditions are the same as in Example 1.
As shown in Table 3, it can be seen that when the average particle diameter is larger than 100 nm, the induced voltage is decreased, but it is preferable that the average particle diameter is smaller than 100 nm.

In this example, SmCo particles having an average particle diameter of 5 μm were used as magnetic particles, and 100 nm particles were used as magnesia particles.
The method for producing the magnet is that the magnetic particles are merely changed from NdFeB particles to SmCo particles, and the other conditions are the same as those in Example 1, and thus the description thereof is omitted.
The produced cylindrical rotor magnet was incorporated into a 300 W permanent magnet motor in the same manner as in Example 1, and eddy current loss and induced voltage, which are one of iron losses at 1500 revolutions, were measured and evaluated.
As can be seen from Table 4, # 14 to # 16 in which the addition amount of magnesia particles is 0.5 to 4.0 wt% has an effect of lower eddy current loss and induced voltage than Comparative Example # 1 in which no magnesia particles are added. I understood that.

In this example, NdFeB particles are mixed with active magnesia particles and molded in two colors, and a portion molded only with NdFeB particles.
FIG. 2 is a cross section showing the two-color molded magnet of the present invention. In the figure, 4 is a magnetic particle molded body formed only of NdFeB particles, and 5 is a mixed particle molded body formed by mixing magnesia particles with NdFeB particles. The magnetic particle compact 4 was formed from NdFeB particles having an average particle diameter of 5 μm, and the mixed particle compact 5 was formed by mixing 2 wt% of 100 nm particles as magnesia particles with NdFeB particles having an average particle diameter of 5 μm.
This two-color molding was performed using a mold having a punch having a triple structure as shown in FIG. 3A is a top view and FIG. 3B is a cross-sectional view. In the figure, 9 is a die, 10 and 15 are cylinders, and 11, 12 and 13 are punches.
First, the punches 13 and 14 and the cylinder 15 are inserted into the die 9. The gap between the cylinder 15 and the lower punches 13 and 14 is filled with NdFeB particles, the cylinder 10 and the punch 11 are lowered, and a pressure of 50 to 100 MPa (0.5 to 1 t / cm ² ) is applied to form the magnetic particle compact 4. To do. Next, as shown in FIG. 4, the punch 13 is lowered, the gap between the magnetic particle compact 4 and the die 9 is filled with particles mixed with NdFeB particles and magnesia particles, the punch 12 is lowered, and a pressure of 50 to 100 MPa is applied. The mixed particle molded body 5 is molded. Next, the cylinder 10, the punch 11, and the punch 12 are raised and the die 9 is lowered to take out the magnetic particle molded body 4 and the mixed particle molded body 5.
Next, it sintered for 2 hours at the temperature of 1100 degreeC. FIG. 4 is a cross-sectional view showing a cross section of a two-color molded magnet. It can be seen that there are two colors consisting of a portion 5 formed by mixing 2 wt% of magnesia particles with NdFeB particles and a portion 4 formed by molding NdFeB particles.
Table 5 shows the results of measuring the eddy current loss and induced voltage of the motor after magnetizing the two-color molded and sintered permanent magnet in the rotor. As a comparative example, # 1 described in the column of Example 1 was used. From Table 5, it can be seen that the eddy current loss is reduced and the induced voltage is improved as compared with the conventional example. That is, in this embodiment, the amount of the magnet mixed with the magnesia particles can be reduced and can be manufactured at low cost.

  In this way, NdFeB or SmCo magnetic particles are surrounded by magnesia particles, which are insulators, preventing eddy currents generated in the permanent magnets, reducing motor iron loss, and inducing The voltage can be increased.

A magnet to which magnesia particles are added can be applied to a linear motor, a magnetic encoder, a reactor, or the like used in combination with an iron core or a yoke.

The schematic diagram of the structure of the permanent magnet which shows 1st Example of this invention Schematic of a mold for molding an inner layer showing a fifth embodiment of the present invention Schematic of a mold for molding an outer layer showing a fifth embodiment of the present invention Sectional drawing which shows the magnet of 5th Example of this invention Schematic diagram showing the structure of a bonded magnet produced by a conventional method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic particle 2 Crystal grain boundary 3 Magnesia particle 4 Mixed particle molded object 5 Magnetic particle molded object 6 Silicic acid 7 Magnetic particle 8 Resin 9 Dice 10, 15 Cylinder 11, 12, 13, 14 Punch

Claims (6)

In a permanent magnet composed of magnetic particles of NdFeB particles or SmCo particles,
A low iron loss permanent magnet having magnesia particles of 100 nm or less in the crystal grain boundary or gap of the NdFeB or SmCo. In a permanent magnet composed of metal particles of NdFeB particles or SmCo particles,
It is composed of two layers, the magnet body having magnesia particles of 100 nm or less in the NdFeB or SmCo crystal grain boundaries or gaps, and the magnet body having only the magnetic particles of NdFeB or SmCo. Iron loss permanent magnet.   3. The low iron loss permanent magnet according to claim 1, wherein the content of the magnesia particles is 0.5 to 4.0 wt% in a weight ratio.   The low iron loss permanent magnet according to claim 1 or 2, wherein an average particle diameter of the NdFeB particles or SmCo particles is 6 µm or less.   A permanent magnet type motor comprising the low iron loss permanent magnet according to claim 1. The low iron loss permanent magnet has a cylindrical shape, the inner peripheral side of the cylindrical body is a magnet body only of magnetic particles, and the outer peripheral side is a magnet body in which magnesia particles and magnetic particles are mixed. The permanent magnet type motor according to claim 5.