JPH0222804A - Rare-earth, iron resin-bonded magnet - Google Patents

Abstract

PURPOSE:To enabled magnet to be prevented completely from corrosion even when it is cut on its midway by costing the surface of the magnet with two or more layers of an organic resin so that any pin hole in a coating film is covered with an overlaying coating film. CONSTITUTION:An organic resin is added to magnetic powder basically composed of a rare earth metal, iron and boron and produced by the super- quenching process. The mixture is molded and the surface of a magnet thus obtained is covered with two or more layers of organic resin having a total thickness of 1 to 50mum. The organic resin is one of epoxy resin, phenol resin, acryl resin and melamine resin or a mixture of two or more of them. If coating film has a thickness less than 1mum, it becomes so uninform that reliability can not be ensured. If it has a thickness over 50mum, however, it requires a prolonged working time and increases the cost. In said rate-earth magnet powder produced by said super-quenching process, the rare-earth metal, iron and boron occupy 8 to 18%, 73 to 88% and 4 to 9%, respectively, in atomic percentage. The rare-earth metal may be one of Y, La, Ce, Pr, Sm, Nd, Eu, Gd, Tb and Dy or a mixture of two or more of them. A part of iron is substituted with one or more transitions metals such as Al, Co and Nb.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method of mixing magnetic powder made by an ultra-quenching method with a basic composition of rare earth metals, iron, and boron with an organic resin, and then molding the mixture into two layers. The present invention relates to a highly oxidation-resistant, high-strength rare-earth and iron-based resin bonded magnet in which the surface of the magnet is coated with the above-mentioned organic resin.

[Conventional technology]

Permanent magnets can be divided into three types: ferrite magnets, alnico magnets, and rare earth magnets. Demand for rare earth magnets has increased significantly in recent years as OA equipment and FAIL equipment have become smaller and more efficient. Ta.

Rare earth magnets are broadly classified into rare earth/cobalt based magnets and rare earth/iron based magnets based on their composition.

Rare earth and iron magnets were introduced in 1983 by General Motors Corporation (GM) and Sumitomo Special Metals, both of which contain Nd.
The main component is FeB, but while GM uses an ultra-quenching method to manufacture magnet powder, Sumitomo Special Metals manufactures sintered magnets using a powder metallurgy method.

In the case of the ultra-quenching method, a quenched thin film with a thickness of about 20 μm is obtained, and each film contains crystal grains on the submicron order (0.1 to 0.5 μm), which are finer than the critical radius of single-domain grains. It is configured. Therefore, even when crushed into a bulk powder of 177 μm or less, the coercive force is maintained, so it can be used as a raw material for resin-bonded magnets.Magnets made by adding organic resin using 0 or more raw materials are compression molded. Products of desired shapes were obtained by injection molding, extrusion molding, roll molding, etc.

[Problem to be solved by the invention]

However, rare earth and iron-based resin-bonded magnets are extremely susceptible to rust, and when incorporated into motors, speakers, relays, etc., there has been a problem in that the rust significantly degrades performance. For this reason, conventionally, the magnet surface was coated with organic resin to prevent rust, but the solvent and air used when coating the organic resin create pinholes in the coating layer, making it impossible to achieve complete rust prevention. There wasn't.

Therefore, in order to solve these conventional problems, the present invention coats the surface of the magnet with two or more layers of organic resin.
The purpose is to completely prevent rust by cutting out pinholes in the coating by creating a layered coating. Figure 1 shows a model diagram.

[Means to solve the problem]

In order to solve the above problems, the rare earth of the present invention.

The basic composition of iron-based resin bonded magnets is rare earth metals.

It is characterized by adding an organic resin to magnet powder made of iron and boron and made by an ultra-quenching method, and after molding, the surface of the magnet is coated with two or more layers of organic resin of 1 to 50 μm.

The organic resin used for the coating of the present invention is one or a mixture of two or more of epoxy resin, phenol resin, acrylic resin, and melamine resin. If the thickness of the film is less than 1 μm, it is difficult to ensure reliability due to the occurrence of a non-uniform layer;
If the coating thickness is more than μm, the working time becomes longer and the cost becomes higher, so the coating thickness was set as above.

In addition, the basic composition of rare earth magnet powder produced by an ultra-quenching method consisting of rare earth metals, iron, and boron is 8 to 18%, 73 to 88%, and 4 to 9% in atomic ratio, and the rare earth metals are: Y, La, Ce.

Pr, Sm, Nd, Eu, Gd, Tb, Dy alone and 2
A mixture of seeds or more, and some of the iron is Af.

It is assumed that one or more transition metals such as Co and Nb are substituted.

In addition, the organic resin used during magnet molding is epoxy resin for compression molding, nylon for injection molding,
In the case of extrusion molding and roll molding, it is common to use epoxy resin, nylon, and PPS.

[Example] (Example 1) After pulverizing a powder having an atomic ratio of N d + aF e soB h and obtained by an ultra-quenching method to a size of 177 μm or less,
2% epoxy resin was added and compression molded. This is 150
The magnet was thermally cured by holding it at °C for 1 hour to obtain a magnet. After coating the surface of this magnet under various conditions, an environmental test of 70"c x 95% was conducted.The experimental results were
Shown in the table.

From Table 1, samples with a film thickness of 1 μm or less, such as Nal and 7, have low rust prevention ability. Also, Sō 4.5 or 9,1
Comparing samples with the same film thickness but different numbers of film layers, such as 0, 11, and 12, it can be seen that the multi-layered film has higher rust prevention ability.

Table 1 ○: No indirect rust when visually observed △: Some rust when visually observed ×: A large amount of rust (Example 2) Atomic ratio is N d 13 Fe? &COb B5 powder obtained by an ultra-quenching method was pulverized to 120 μm or less, and then 20% of epoxy resin was added and compression molded.

This was fired at 150° C.XIH to obtain a magnet. After coating the magnet surface under various conditions, a salt spray test was conducted. The results are shown in Table 2. The symbols for surface conditions are the same as in Example 1.

Table 2 As shown in Table 2, it can be seen that the antirust ability is increased by making the coating film multilayered.

(Example 3) After the powder used in Example 2 was mixed with 12.5% nylon, the surface of the magnet was coach-treated under various conditions. Table 3 shows the results of an environmental test of this magnet at 80°C x 95%. Symbols for surface conditions are the same as in Example 1.

From the experimental results in Table 3, it can be seen that high rust prevention power is obtained by increasing the film thickness and multilayering the coating film.

(Example 4) The powder used in Example 2 was compression molded into φ18×φ16
) 14 ring-shaped magnets were obtained. This magnet has a film thickness of 10μ.
Three coats of m were applied to give a 30 μm coating.

This magnet was incorporated into a stepping motor as shown in FIG.

When this motor was subjected to an operation test in a 60°C x 95% environment, no rust was observed on the internal magnets and it operated normally up to 5000 hours.

〔Effect of the invention〕

As described above, the present invention has extremely excellent corrosion resistance because the surface of the rare earth/iron resin-bonded magnet is coated with two or more layers of organic resin, making it suitable for use in remoters, speakers, sensors, relays, etc. However, the magnetic flux in the magnetic circuit is stable, and high reliability can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magnet with a multilayer coating according to the invention. 1...Magnet 2...First coating layer 3...Second coating layer 4...Third coating layer Five River pinholes Figure 2 shows the three-layer coating explained in Example 4. A cross-sectional view of a stepping motor using rare earth and iron-based resin bonded magnets. l...Shut 2...Coil 3...Magnet 4...Bearing and above Applicant: Seiko Epson Co., Ltd. Representative Patent Attorney Kizobe Suzuki and 1 other person

Claims (3)

[Claims] (1) In a magnet formed by adding an organic resin to magnetic powder made by an ultra-quenching method whose basic composition is rare earth metal, iron, and boron, the surface is coated with two or more layers of organic resin for 1 to 5
A rare earth and iron-based resin bonded magnet characterized by a 0μm coating. (2) The rare earth/iron resin bonded magnet according to claim 1, wherein a part of the iron is replaced with a transition metal other than iron, such as cobalt. (3) A stepping motor using the magnet according to claim 1 or 2.