JPH081852B2 - Resin-bonded rare earth magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-bonded rare earth magnet manufactured by an injection molding method.

[0002]

2. Description of the Related Art Demand for rare earth cobalt magnets is increasing year by year as a third magnet after ferrite and alnico. The types are RCO ₅ type and R ₂ TM when divided by alloy type.
There are ₁₇ series (R = rare earth element, TM = transition metal centered on cobalt), and there are a sintering method and a resin bonding method when classified by the manufacturing method. Resin bonding methods include compression molding, injection molding, and extrusion molding.

The method capable of producing the resin-bonded rare earth magnet having the thinnest wall is an extrusion molding method and then an injection molding method from the manufacturing mechanism.

The RCO ₅ system was the first magnetized alloy system and currently occupies the mainstream of sintered magnets. On the other hand, the R ₂ TM ₁₇ system was developed later than the RCO ₅ system, but the performance is excellent. The maximum energy product (BH) ma currently obtained by the sintering method
It is the R ₂ TM ₁₇ system that gives x = 30 MGOe. As described above, manufacturing by a sintering method is used to achieve high performance. However, sintered rare earth magnets have the drawback of being hard and brittle, which leaves a problem in production and use. In order to make up for this drawback, a resin-bonded rare earth magnet has been developed. Since this magnet contains a resin which is a non-magnetic material, its performance is lower than that obtained by the sintering method, but it has many other advantages. When listed, it has low cost, mechanical strength, no risk of cracks and chips, dimensional accuracy can be easily obtained, the shape of the magnet follows the shape of the mold, so straw magnets, elliptical shapes, magnets with gears, etc. Magnets with anisotropy in the radial direction that can be made in any shape, can be easily manufactured, and normal cutting can be performed. It can be manufactured and the variation between magnets is small.

[0005]

In recent years, as the fields of application of magnets have expanded, the magnets have been increasingly used with other poles magnetized. Examples are magnetic couplings and small motors. In particular, there is a great demand for magnets with multiple poles magnetized in the field of small motors. PM for small motors
Type stepping motor magnets are the most numerous. P
The magnet used in the M-type stepping motor is a so-called radial anisotropic magnet, which can be magnetized from inside to outside or from outside to inside, as shown in FIG.
It can easily be multipolar. At first, ferrite magnets were used for this type of magnet, but rare earth cobalt magnets have come to be used as motors have become smaller and have higher performance.
However, the use of rare earth magnets has created new problems. In other words, it cannot be magnetized sufficiently due to high cost and high coercive force. In the first place, since it is a competition with a motor using a ferrite magnet in terms of cost, it is not possible to compete with a rare earth cobalt whose price of the raw material powder is 30 to 50 times as high as that of ferrite without a proper design.

Therefore, a magnet must be used so as to bring out the characteristics of the rare earth element 100%. Therefore, it is necessary to manufacture a magnet that is completely magnetically saturated and stable by multi-pole magnetization while avoiding the problem of cracking or chipping.

[0007]

The present invention has been made to overcome the above problems. That is, from the present application
The bright resin-bonded rare earth magnet has a coercive force of 7 kOe or more.
Resin-bonded rare earths magnetized by a thin magnet
For magnets, the thin wall thickness of the thin wall magnet is required for the thin wall magnet.
It is less than 1/3 of the magnetized width per pole
To collect. Therefore, it is necessary to completely magnetize the high coercive force magnet.
It is possible to realize high magnetic flux density inside the device.
It Specifically, from FIG. 4, the thickness of the thin magnet is 0.8
mm or less is preferable. Here, the wall thickness is limited to 0.8 mm or less because the width required for a current magnet per pole is 2 mm or less, and the coercive force of the magnet is 7 kO.
Therefore, the reason is that sufficient magnetization cannot be achieved unless the thickness is at least 1/3 or less.

Further, a resin-bonded rare earth magnet having a thinner wall could be provided by using the extrusion molding method.

[0009]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 A radial anisotropic magnet as shown in FIG. 1 was produced by a magnetic field injection molding method. There are three types of magnet dimensions: an outer diameter of 18 mm, a height of 5 mm, and wall thicknesses of 0.5, 0.8, and 1.1 mm. The injection molding raw material was obtained by kneading 60 vol% of R ₂ TM ₁₇ series magnetic powder and 40 vol% of nylon 6. The obtained sample was magnetized with 24 poles by pulse magnetization. The magnetic flux density of the sample was measured by rotating the magnet using a Hall element. The data obtained is a graph as shown in FIG. The results are shown in Table 1. However, all permeance coefficients are 1.2. Table 1 shows that the magnetization is not perfect when the wall thickness is large. 0.8 mm or less is desirable.

[0011]

[Table 1]

Example 2 A magnet as shown in FIG. 3 was produced by a magnetic field injection molding method. The same injection raw material as in Example 1 was used. The magnetization direction is indicated by the arrow in the figure. l is 50 mm, w is 1
A total of 17 kinds of magnets were produced at 0.1 mm intervals from 0 mm and t to 0.4 to 2.0 mm. These magnets were magnetized to 100 poles in the manner shown in FIG. The permeance was set to 1.5 and the Hall element was moved in the l direction to measure the surface magnetic flux density Bd. FIG. 4 shows the results. t is 0.8 m
It can be seen that high magnetic performance is obtained at m or less.

[0013]

As described above, according to the present invention, magnetic poles having a surface magnetic flux density of more than 2500 G can be magnetized in multiple poles, and a high-performance magnetized in multiple poles can be provided. The magnet according to the method of the present invention can be widely used in the fields of step motors and linear motors, and its contribution to the consumer and industrial fields is great.

[Brief description of drawings]

FIG. 1 is a view of a ring-shaped radial anisotropic magnet magnetized with multiple poles.

FIG. 2 is a diagram showing an example of measurement of magnetic flux density of a multi-pole magnetized radial anisotropic magnet.

FIG. 3 is a diagram showing a flat-plate magnet that is magnetized in multiple poles.

FIG. 4 is a diagram showing the relationship between the thickness and the surface magnetic flux density of a flat magnet magnetized with multiple poles.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuhiro Oguchi 3-5 Yamato, Suwa City, Nagano Suwa Seikosha Co., Ltd. (56) References

Claims (1)

[Claims] 1. A resin-bonded rare earth magnet obtained by multi-pole magnetizing a thin-walled magnet having a coercive force of 7 kOe or more , wherein the thin-walled magnet has a one-pole equivalent thickness required for the thin-walled magnet.
A tree characterized by being less than one-third of the magnetized width
Fat-bonded rare earth magnet .