JPH0824085B2 - Multi-pole magnetizing method for rare earth magnets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for magnetizing a rare earth magnet having a basic composition of a rare earth metal, iron and boron.

[Conventional technology]

Conventionally, as a method for magnetizing a multi-pole of a permanent magnet, a method using a multi-pole magnetizing yoke as shown in FIG. 2 or a head magnetizing method as shown in FIG. 3 has been used.

[Problems to be solved by the invention]

However, saturation magnetization (complete magnetization) is relatively easy with the method using a multi-pole magnetizing yoke, but it is difficult to make the magnetizing pitch fine. With the head magnetizing method, the magnetizing pitch is Although it can be finely divided, it has a problem that the magnetization process requires time, saturation magnetization is difficult, and only a magnetic flux density of a signal level can be obtained.

Furthermore, as shown in Japanese Patent Application No. 60-123391,
Rare earth magnets whose basic composition is rare earth metal, iron and boron cannot be saturated with a magnetizing magnetic field at a normal production level, so sufficient magnetic performance cannot be obtained. However, the magnetizing process takes time, the magnetizing device becomes large and complicated, the cost becomes high, and the quality stability cannot be obtained.

The present invention solves the above problems, and an object thereof is to make it possible to obtain saturation magnetization or a magnetic flux density close to it with a magnetizing pitch obtained by a head magnetizing method even in a low magnetic field. Another object of the present invention is to provide a method for magnetizing a multi-pole magnet of a rare earth magnet, which can be easily magnetized.

[Means for solving problems]

The multi-pole magnetizing method for rare earth magnets of the present invention is a multi-pole magnetizing method for rare earth magnets containing a rare earth metal, iron and boron as a basic composition. And a step of magnetizing the cylindrical radial magnet in a circumferential direction of a predetermined pitch in a magnetic field in a first magnetic field direction from the inside to the outside of the cylindrical radial magnet while locally irradiating with a laser. A second moving member that faces from the outside to the inside of the cylindrical radial magnet.
In a magnetic field in the magnetic field direction, the step of irradiating the laser and magnetizing while locally heating the laser is performed.

A rare earth magnet having a basic composition of rare earth metal, iron and boron has a large temperature coefficient of iHc, and this property is usually considered to be negative, but it can be used in reverse for magnetization. That is, when iHc is set to a low state by performing high temperature magnetization, the saturation magnetization can be performed with a low magnetization magnetic field.

Further, if the temperature is lower than 50 ° C, the effect of high temperature cannot be obtained as compared with the normal temperature, and conversely, if it exceeds 200 ° C, the magnetic performance after returning to room temperature is significantly deteriorated. Therefore, the above range is preferable.

Although FIG. 1 shows a principle explanatory diagram of the present invention, the present invention is not limited to the cylindrical magnet as shown in FIG.
It may be disk-shaped or plate-shaped.

Nd-Fe-B magnets are known as rare earth permanent magnets having a basic composition of rare earth metals, iron and boron, but rare earth metals include Y, La, Ce, Pr, Nd, Pm, Sm, Em, G
One of the rare earth elements of d, Tb, Dy, Ho, Er, Tm, Yb and Lu
It is only necessary to use one kind or two or more kinds. Didymium (Pr-Nd) and cerium-didymium (Ce-Pr-Nd) can obtain sufficient magnetic performance, and are advantageous in terms of supply and price. Furthermore, Dy and Tb
The coercive force iHc can be increased and a substantial improvement in temperature characteristics can be achieved by adding a small amount of the heavy rare earth element.

Also, by substituting a part of iron with cobalt, the Curie temperature is improved, the temperature coefficient of remanent magnetization Br is also improved, and even if it is replaced with another transition metal group, magnetic performance and corrosion resistance are improved. .

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

(Example -1) dissolved in an argon gas atmosphere using a high frequency melting furnace to obtain a composition of Nd ₁₅ Fe ₇₇ B _8, cast alloy stamp mill to obtain a magnetic powder with a ball mill. This magnetic powder is filled in a cylindrical mold, and magnetic field oriented in the radial direction.
Compression molding was performed at a molding pressure of / mm ² . This was sintered in an argon gas atmosphere at an optimum temperature of 1000 to 1200 ° C and aged at an optimum temperature of 400 to 1000 ° C.

This cylindrical radial magnet has 2 inside, S inside and N outside.
It was pole-polarized, and then a part of it was heated to about 100 ° C using a soldering iron while applying a magnetic field of N on the inside and S on the outside.

A Gauss meter was placed on the outer surface of this cylindrical radial magnet to measure the surface magnetic flux density. The results are shown in FIG.

As is clear from FIG. 4, the surface magnetic flux density of the peripheral portion heated to a high temperature is lowered, which indicates the possibility of multipolarization of the magnetized pattern.

(Example-2) A cylindrical radial magnet was produced in the same manner as in Example-1 so that Nd _13.5 Dy _1.5 Fe ₆₇ Co ₁₀ B ₈ was obtained.

This cylindrical radial magnet has 2 inside, S inside and N outside.
It was pole-polarized and then magnetized with a pitch width of 0.3 mm using a laser while applying a magnetic field of N on the inside and S on the outside.

As a comparative example, a head magnetizing method as shown in FIG. 3 was used to magnetize with the same pitch. Furthermore, the second
Magnetization with the same pitch was attempted even with a multi-pole magnetized yoke as shown in the figure, but it was impossible due to structural problems of the yoke.

The surface magnetic flux densities of the present invention and the comparative example were measured, and the results are shown in FIG.

As is clear from FIG. 5, the present invention can obtain a magnetized pattern having a very high surface magnetic flux density and a large amplitude as compared with the comparative example.

(Example-3) (Ce _0.2 Pr _0.2 Nd _0.5 Dy _0.1 ) ₁₅ Fe ₆₇ Co ₁₀ B ₈
Using the same method as in Example-1, a cylindrical radial magnet was created.

This cylindrical radial magnet was magnetized with a pitch width of 0.3 mm while locally applying a high temperature using a laser and applying a magnetic field N and S alternately.

FIG. 6 shows the surface magnetic flux density of this magnet together with the comparative example of Example-2.

As is clear from FIG. 6, the present invention provides a very high surface magnetic flux density and a magnetized pattern with a large amplitude, as compared with the comparative example, and is effective for applications such as stepping motors.

[Advantages of the Invention] As described above, according to the present invention, a rare earth magnet having a basic composition of rare earth metal, iron and boron is locally applied.
By performing multi-pole magnetization at a high temperature of 50 to 200 ° C, it is possible to obtain a high surface magnetic flux density and a large amplitude magnetization pattern with a magnetizing pitch that is finer than conventional ones. Is also simplified, and using this high-performance magnet,
The stepping motor has a great effect on the application side such as high output and downsizing.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle of the present invention. FIG. 2 is a schematic diagram illustrating the principle of a multipolar magnetizing yoke method of a comparative example. FIG. 3 is a schematic diagram illustrating the principle of a head magnetizing method of a comparative example. FIG. 4 is a diagram showing changes in surface magnetic flux density. FIG. 5 is a diagram showing a waveform of the surface magnetic flux density of a multi-pole magnetized pattern. FIG. 6 is a diagram showing a waveform of the surface magnetic flux density of a multi-pole magnetized pattern. 1 ... Magnet 2 ... High temperature part 3 ... Heating device 4 ... External magnetic field 5 ... Coil wire 6 ... Yoke 7 ... Yoke 8 ... Magnetization head

Claims (1)

[Claims] 1. A multi-pole magnetizing method of a rare earth magnet containing a rare earth metal, iron and boron as a basic composition, a step of forming magnetic powder into a cylindrical shape to form a cylindrical radial magnet, and the cylindrical radial magnet. In a magnetic field in a first magnetic field direction from the inner side to the outer side of the magnet, a step of magnetizing while irradiating a laser and locally heating, and moving the cylindrical radial magnet in a predetermined pitch circumferential direction,
A multi-pole magnetization of a rare earth magnet, comprising the steps of irradiating the laser and magnetizing while locally heating in a magnetic field in a second magnetic field direction from the outer side to the inner side of the cylindrical radial magnet. Method.