JPH05109567A - Manufacture of rare earth magnet - Google Patents

Abstract

(57) [Summary] [Objective] To provide a means for manufacturing a low-cost rare earth resin bonded magnet with high productivity, which has high compression molding processing accuracy and performance. [Structure] A rare earth resin bonded magnet having high shape accuracy, high performance and mass productivity is obtained by subjecting the magnet composition to compression molding in a mold having a hard coating layer of Hv 1800 or more and 2 microns or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rare earth magnet used for pressure molding of a rare earth magnet used for small motors, actuators, sensors and the like used in electronic equipment. ..

[0002]

2. Description of the Related Art Among the methods for producing rare earth magnets, injection molding, compression molding, calendar roll molding and extrusion molding are mainly used for pressure molding. In the injection molding method, a raw material composed of magnetic powder and a thermoplastic resin is heated and filled in a mold while being heated to a temperature at which fluidity is obtained, and molded into a predetermined shape.

In the compression molding method, a magnet raw material press die made of magnetic powder and a thermosetting resin is filled, compressed and molded.
The magnet has a predetermined shape. Further, in the calender roll method, a raw material composed of a thermoplastic resin or a thermosetting resin and magnetic powder is passed through a heated roll gap while pressurizing to obtain a sheet-like product.

Conventionally, hard materials such as die steel and cemented carbide have been mainly used for forming jigs and molds for rare earth magnets. For example, the compression mold has a pressing force of 2 to 12 tons / cm during molding.
Used as high as ² . Since the raw material rare earth magnetic powder used for magnet molding has a hardness of Hv (Vickers hardness) of 500 to 800, there is a problem that the mold is easily worn at the time of mold molding. In addition, since an organic resin is used as the binder of the magnetic powder, the molding raw material is adsorbed on the surface of the mold when the mold is released after molding, and it is difficult to maintain a desired molding shape. As a measure to prevent this, it is the current situation that the mold cleaning process must be incorporated at the expense of the molding cycle. As such a conventional example, there is a manufacturing method disclosed in, for example, Japanese Patent Application Laid-Open Nos. 1-230208 and 1-220419.

[0005]

However, the above-mentioned prior art has the following problems.

(1) Hard materials such as cemented carbide, die steel, and alloy tool steel have been mainly used as the material for the mold in the conventional resin-bonded magnet molding method. On the other hand, the pressure molding method is performed by applying a high molding pressure of 2 to 12 tons / cm ² . Therefore, there are many problems that the surface of the mold is easily scraped by the hard magnetic powder and the initial polished glossy surface cannot be maintained. This phenomenon has caused defects such as a decrease in density, a poor appearance (surface defects), and a poor dimensional accuracy with respect to the magnet molding, resulting in a decrease in yield. (2) Furthermore, since the surface of the mold is used as it is, the phenomenon that it easily wets the organic resin of the molded product (magnet) constituent material and that it is difficult to release the mold is likely to trigger defects such as defects in the molded magnet surface and dimensional defects. It was

(3) There is a problem that it is difficult to process a product having a different magnet shape, an uneven shape, or the like into a desired shape during pressure molding.

Therefore, the present invention solves the above problems, and an object of the present invention is to provide a rare earth bonded magnet having improved shape accuracy and magnet performance as the shape of a mold.

[0009]

A method for producing a rare earth magnet according to the present invention is a method of molding a magnet composition comprising rare earth magnetic powder, an organic resin and a trace amount of an inorganic substance by a pressure molding method through a mold. In particular, a hard layer is formed on the surface of the molding die.

The rare earth magnetic powder is R (rare earth metal) ₂ TM (transition metal) ₁₇ type, RCo5 type, R ₂ Fe ₁₄ B.
Type, magnetic powder consisting of R ₂ Fe ₁₇ N type, and a magnet composition mainly consisting of an organic resin and a trace amount of an inorganic compound are used. The mold is made of a tool material having a base material hardness of about Hv650 or more, and further has a hardness of at least Hv1000 or more on the surface.
The wear resistant material is formed to a thickness of micron or more. Next, the pressure molding of the rare earth bonded magnet is characterized in that a predetermined amount of the magnet composition is filled in a mold, and a pressure of 2 to 10 ton / cm ² is applied by a magnetic field press or a non-magnetic field press method. To do.

The hard material of the coating film is selected from among carbides, nitrides, carbonitrides, and oxides according to need, and is applied by an ion plating method or a CVD (chemical vapor deposition) method. Characterize things.

[0012]

[Function] When a rare earth resin bonded magnet is pressure-molded, a hard abrasion-resistant layer of Hv1000 or more is formed on the surface of the mold to a thickness of 2 microns or more, thereby eliminating the shape defect of the magnet surface and further stabilizing the performance and improving the production efficiency. And the like.

[0013]

EXAMPLES Examples of the present invention will be specifically described below. Table 1 shows the composition of the two types of magnet compositions used in this example.
It shows in Table 2.

[0014]

[Table 1]

[0015]

[Table 2]

A rare earth resin-bonded magnet was produced by a compression molding press method using the raw materials composed of the compositions shown in Tables 1 and 2. Here, the composition of Table 1 is A and the composition of Table 2 is B. The molding of A was performed by a magnetic field pressing method, and the magnetic field generated in the mold at the time of molding was about 12 K gauss, while the molding of B was performed by a non-magnetic field method.

For the compression molding method, the mold structure shown in FIG. 1 (A) was used. Reference numeral 1 is a magnet composition, and the required weight is set in the filling ring 2, and the mold space 3 is filled with a specified amount. Four
Is an outer die, and 5 is a lower punch (punch), each made of non-magnetic cemented carbide. Next, (B) pushes down the upper punch (punch) 6 and press-molds it with a compressive stress of 2 to 10 ton / cm ² and then pushes up the lower punch after (C) to pull out the magnet 7 from the die. Next, the bonded magnet of 7 is heat-treated in a dry firing furnace at about 150 ° C. for 1 hour in order to heat and cure the epoxy resin of the binder.

Using the magnet composition of A, a rare earth resin-bonded magnet was manufactured by a compression molding method in a magnetic field.

Prior to compression molding, various hard surface coating films were formed on a press die punch according to the conditions shown in Table 3.

[0020]

[Table 3]

In the coating method shown in Table 3, the component element materials are gasified by the CVD method (chemical film formation), and about 10
Heat treatment was performed at 00 ° C. On the other hand, in the PVD method, the component materials were evaporated and ionized by an arc source or an ion plasma source to form a coating on the surface of the super hard punch at a heat treatment temperature of 400 to 510 ° C. Sample No. No. 5 is a conventional example in which a hard layer is not formed on the surface of the die punch.

A compression molding experiment was carried out by mass production of the rare earth resin bonded magnet having the shape shown in FIG. 1 using the above-mentioned carbide punch. A summary of the results is shown in Table 4.

[0023]

[Table 4]

According to the results shown in Table 4, the effect of the present invention was clearly recognized under the same molding pressure conditions. To further describe the effect in detail, the magnet peeling frequency occurrence rate represents the ease of release from the die punch after compression molding (releasability), and is shown in FIG.

The conventional example is as shown in FIG.
When the punch 6 was separated from the punch 6, a part of the magnet such as 10 was easily attracted to the punch 6 on the pressing surface, and the occurrence rate was 2 to 3%. Conventionally, as a method for solving this problem, the number of molding times is 50 to
This has been dealt with by stopping the machine every 200 times for cleaning or by performing a cleaning operation every time.

Therefore, the machine operating rate is at most 60 to 70%.
Achievement was full.

In the method of the present invention, as shown in FIG. 3, a hard layer coating of 2 to 7 μm was formed on the surface 20 of the cemented carbide die punch 6. As a result, the problem of missing the surface of the compression molded body was completely eliminated. As a result, the size and shape of the magnet are improved,
It became useful for resin-bonded magnet manufacturing, such as stable performance and improved performance. The reason why the releasability between the magnet and the mold is improved is that the inner surface 8 of the die (outer mold) and the punch surface 20 are coated with a hard substance having a Hv of 1800 or more, and the surface is formed of 100% of the same substance. Is. Further, since the machine operating rate is improved to 75 to 90%, the competitiveness of the rare earth resin bonded magnet can be improved by improving the productivity and reducing the manufacturing cost. As another effect, since the extraction pressure when the magnet is extracted from the die after molding can be reduced to 1/2 to 1/3, the coaxiality and roundness of the magnet molded body can be reduced to 20 to 50 from the conventional one.
% Could be reduced.

Next, using the magnet composition of B, a resin-bonded magnet was manufactured by a compression molding method.

As shown in FIG. 3, the magnet has a ring shape, specifically, an outer diameter of 21.8 mm × inner diameter of 19.2 mm and a height of 5.
It is 6 mm.

For the punch on the mold for magnet molding, magnetic cemented carbide was used, and a hard coating was coated on the surface. Co-
PVD method for sample Nos. 10 to 13
No. 4 was performed by the CVD method. In Conventional Example 20, the base of magnetic cemented carbide was left as it was, and the surface roughness was finished to 0.5 μm or less in a micro-polished state.

[0031]

[Table 5]

Table 5 shows the effect of the method of the present invention. As a result of the method of the present invention, the shape defect occurrence rate of the magnet body after compression molding was suppressed to 0.03% or less. The upper punch life is 7
Up to 13 times. As a result, the operating rate of the molding machine is
It could be improved to about 75 to 90%, and significant effects such as cost reduction and productivity improvement could be realized. In addition, there is an advantage that a large amount of thin-walled ring-shaped high-performance magnets having high roundness accuracy can be supplied. It is very useful for the field of spindle motors for HDD (hard disk) and PM type stepping motors, which are the most suitable applications of such ring-shaped magnets.

[0033]

As described above, by using the manufacturing method of the present invention, it is possible to manufacture a thin-walled ring-shaped, irregularly shaped or irregularly shaped rare earth resin bonded magnet with high productivity and at an extremely low cost. Have the effect. As a result, it can be widely used in DC motors, stepping motors, etc., which require small size, high precision, and high performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a rare earth resin bond magnet compression molding manufacturing process of the present invention.

FIG. 2 is a diagram showing a punch on a mold and a magnet molding according to an embodiment of the present invention.

FIG. 3 is an upper die punch 20 according to an embodiment of the present invention.
The figure which shows (hard film formation) and a magnet molding.

FIG. 4 is a view showing the outer appearance of a ring-shaped resin bonded magnet according to an example of the present invention.

[Explanation of symbols]

 1 Rare Earth Resin Bonded Magnet Composition 2 Filling Ring 3 Magnet Forming Part (Filling Part) 4 Mold (Outer Mold) 5 Mold (Lower Punch) 6 Mold (Upper Punch) 7 Molded Body (Magnet) 8 Hard Coating Layer ( External type) 10 Missing magnets 11 Defective magnets 20 Hard coating layer (upper punch)

Claims (2)

[Claims] 1. A method for producing a rare earth magnet, characterized in that, in a step of producing a rare earth magnet, a die having a hard film formed on a part or the whole surface of a die is used and the die is formed by a pressure forming method. .. 2. A method for producing a rare earth magnet, wherein the hard layer formed on the surface of the mold has at least a hardness of a base material and a film thickness of 2 μm or more.