JPH0418710A - Manufacture of rare-earth resin coupled type magnet - Google Patents

Abstract

PURPOSE:To easily obtain a magnet having excellent heat-proof property excellent chemical-resisting property and high dimensional accuracy by a method wherein the mixed molten substance consisting of rare-earth magnet powder, resin and an addition agent is shaped, thermosetting resin is hardened by heat, the final shape of a magnet is maintained, and it is extrusion-molded. CONSTITUTION:The magnetic powder consisting of the transition metal element mainly composed of R and cobalt or the magnetic powder, consisting of a transition metal element mainly composed of R and iron and boron, is used as rare-earth magnet powder. This rare-earth magnet powder, thermosetting resin and an adding agent are mixed by a roll mill, an extruding machine and the like, this compound is crushed and put in an extrusion molding machine. The compound is iron heated up in the extrusion machine, resin is brought into a molten state and sent to a mold which is connected to the extrusion machine. The compound is shaped into the final form in the mold, it is hardened by heating, and a magnet molded body is pushed out from the mold. Then, postcuring is conducted, and a rare-earth resin coupled type magnet is formed.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for manufacturing a rare earth resin bonded magnet.

[Prior Art] Examples of molding methods for resin-bonded magnets include the following molding methods.

1. Compression molding method 2. Injection molding method In the compression molding method, a magnet composition consisting of magnet powder and thermosetting resin is filled into a press mold, compressed and molded by applying pressure, and then, This is a method of molding by heating and curing the resin. At this time, the amount of magnetic powder in the magnet composition was 9
Contains 5wt% or more.

This compression molding method has a lower amount of resin component in the magnet composition than other molding methods as described in 1. Although the magnetic performance of the molded magnet is high, the degree of freedom regarding the shape of the magnet is small.

The injection molding method is a method in which a magnet composition made of magnet powder and a thermoplastic resin is heated and melted, and injected into a mold with sufficient fluidity to be molded into a predetermined shape. In the injection molding method, in order to give fluidity to the magnet composition, the amount of resin component in the magnet composition is larger than that in compression molding, and the amount of magnet powder in the magnet composition is about 90 to 95 wt%, so magnet molding is difficult. The magnetic performance of the body decreases. However, the degree of freedom in shape is greater than in compression molding.

[Problems to be Solved by the Invention] However, the above manufacturing method has the following problems.

First, the molding process for both compression molding and injection molding involves a fixed cycle of filling a mold with a magnetic composition, molding, and removing the molded product, and is basically a batch-type production system. There are limits to productivity. In addition, when molding long magnets, which have been in increasing demand recently, it is difficult to fill the raw materials and take out the molded product, and the magnetic performance of the molded magnet deteriorates. has its limits.

Therefore, an extrusion molding method can be cited as a means to solve these problems. The extrusion molding method is a method in which magnet powder is kneaded with resin, then fed into a mold using an extruder, and shaped and molded within the mold. In the case of this method, since the production process is continuous, productivity is high, and the length can be formed arbitrarily.

In this way, extrusion molding has advantages that conventional compression molding and injection molding do not have. However, this extrusion molding method also has the following problems.

That is, resins used for extrusion molding include both thermoplastic resins and thermosetting resins.

However, thermoplastic resins generally have poor heat resistance and are unsuitable for use at high temperatures. In addition, recently, some thermoplastic resins with significantly improved heat resistance have been reported, but these resins have poor moldability and the molding temperature is high, which causes the magnet powder to deteriorate during molding, resulting in poor molding. There is a problem that the magnetic properties of the magnet deteriorate. On the other hand, when a thermosetting resin is used, the molded magnet has good heat resistance and is also excellent in chemical resistance. As a method for molding using this resin, there is a method in which the resin is shaped in a mold, cooled and solidified, extruded, and then cured. but,
In this method, a curing step is added after extrusion molding, which reduces productivity and increases costs.

In order to further improve dimensional accuracy, for example,
A method like -169911 is required. Furthermore, when using thermoplastic resins or thermosetting resins as described above, which are molded by cooling and solidifying, the dimensions of the mold and the dimensions of the molded magnet do not necessarily match due to shrinkage, etc., so accuracy cannot be guaranteed. It is difficult to mold to a certain size.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a long magnet that is difficult to mold using conventional molding techniques. Another purpose is to simplify the molding process and thereby reduce costs. Another object of the present invention is to provide a high-performance magnet that has good heat resistance and chemical resistance, and suppresses deterioration of the magnet powder during molding. Another purpose is to easily provide a magnet with high dimensional accuracy.

[Means for Solving the Problems] The method for producing a rare earth resin-bonded magnet of the present invention is a method for producing a rare-earth resin-bonded magnet made of rare earth magnet powder, a thermosetting resin, and additives (including inorganic substances). The above-mentioned method is characterized in that a mixed melt of rare earth magnet powder, resin, and additives is shaped in a mold, and the thermosetting resin is heated and cured to maintain the final shape of the magnet, and then extrusion molded. The manufacturing method is characterized in that the difference Δt between the maximum wall thickness and the minimum wall thickness of the molded magnet is 0≦Δt≦0.5t with respect to the average wall thickness t of the formed magnet.

Further, the above-mentioned rare earth magnet powder is a magnet powder made of a transition metal element mainly consisting of R and cobalt.

Further, the rare earth magnet powder is a magnet powder made of R, a transition metal element mainly composed of iron, and boron.

[Function] According to the configuration of the present invention, by using extrusion molding as a molding method for a rare earth resin-bonded magnet made of rare earth magnet powder and resin, molding is difficult using conventional compression molding or injection molding methods. The shape can be molded. That is, it becomes possible to lengthen the magnet molded body. In the case of extrusion molding, a mixed melt consisting of rare earth magnet powder and resin is continuously squeezed in a mold, and since conventional molding methods are basically batch processing, conventional molding methods are magnetic molding. The length of the magnetic body depends on the shape of the mold, so there is a limit to the length of the molded body, whereas in extrusion molding, the length of the magnetic molded body is limited because it is continuously molded from the mold. Shaped arbitrarily.

As an extrusion molding method, the final shape of the molded magnet is formed in a mold, and the molding is performed by heating and curing.When cooling and solidifying molding using a thermosetting resin, it is possible to maintain the dimensions. A curing process is required, but this process also eliminates the need to maintain dimensions. For these reasons, the manufacturing method can be simplified compared to conventional molding methods, thereby reducing costs. In addition, when using thermoplastic resin to perform cooling solidification molding, or when using thermosetting resin to perform cooling solidification molding, cooling solidification is basically a method to maintain the shape through physical changes. Dimensional changes occur due to stress relaxation etc. when the magnet comes out of the mold, and the dimensions of the mold and the dimensions of the molded magnet differ, but in the method of the present invention, the resin is cured by heating within the mold and the resin is cross-linked. Because molding involves chemical changes, there is almost no dimensional change after extrusion from the mold, so it is possible to mold the product to the exact dimensions of the mold.

By employing a thermosetting resin as the resin, heat resistance and chemical resistance are improved compared to using a thermoplastic resin.

Here, the difference Δt between the maximum wall thickness and the minimum wall thickness of the molded magnet is set to 0≦Δt≦0.5t with respect to the average wall thickness t of the molded magnet. Since this is a method that involves irreversible chemical changes such as crosslinking at the blowing point, it is necessary that the chemical changes occur uniformly on the profile of the extrusion mold. If the chemical changes become non-uniform, the flow of the mixed melt of magnet powder and resin will be deflected, making it impossible to mold it. Therefore, the above regulations are required to ensure this uniformity. In other words, if the difference between the maximum thickness and the minimum thickness is more than half of the average thickness of the molded magnet, the resin in the magnet has low thermal conductivity, causing a temperature difference between the surface and the inside of the magnet, resulting in a change in temperature distribution. This results in non-uniformity in the crosslinking reaction. This makes it difficult to mold the magnet. As for the lower limit of the wall thickness specification, for the reason mentioned above, the smaller the wall thickness difference, the more uniform the molding conditions will be, so the minimum value is when the wall thickness difference is 0.

Hereinafter, a detailed explanation will be given according to examples.

[Example 1] FIG. 1 shows the manufacturing process of the rare earth resin bonded magnet of the present invention. After weighing the rare earth magnetic powder, resin, and additives to a desired mixing ratio, they are mixed in a mixer such as a roll mill or extruder to create a compound. This compound is put into a molding machine and pulverized into a size that is easy to fit, and then put into an extrusion molding machine. The extruder used here was a single screw type extruder.

The compound is heated in the extruder to melt the resin, which is then fed into a mold connected to the extruder. The compound is shaped into a final shape in the mold, heated and hardened in the mold, and a molded magnet is extruded from the mold. At this time, when cooling solidification molding was performed as a comparative example, the mold was cooled and molded at the tip of the mold. The extruded magnet is taken out and cut by a cutting machine. Thereafter, if necessary, boss curing was performed to form a rare earth resin bonded magnet. As a comparative example, when the thermosetting resin was cooled and solidified, the molded magnet was cured while keeping the dimensions of the molded magnet after cutting. Furthermore, when magnetic field orientation molding was performed, demagnetization was performed before cutting.

More detailed examples will be shown below.

(Example 1) Table 1 shows the results of thermosetting molding and thermoplastic molding in a mold using a thermosetting resin.

The resin used at this time is solid at room temperature, and 12
Thermoplastic range from 0 to 150'C, 180 to 20
An epoxy resin that hardens at 0°C was used.

SSm2T+7 (TM is a transition metal mainly composed of cobalt) was used as the magnet powder, and the mixture ratio of the magnet powder and resin (including additives) was weighed to be 60:40 by volume. The shape of the molded magnet has an outer diameter of 32.
It was a cylindrical magnet with a diameter of 80 mm and an inner diameter of 30.80 mm, and was molded as a radially oriented magnet.

Table 1*; Unit: MGOe Molding methods 1 and 2 in the table represent heat-curing molding of the present invention and cooling-hardening molding of the comparative example, respectively.

As is clear from the table, the performance of the magnet molded by the molding method of the present invention is higher than that of the magnet molded by the comparative example. This is because in the case of the comparative example, curing is performed after extrusion molding and demagnetization to form the magnet, but it is difficult to completely demagnetize, so some magnetic flux remains, and curing is performed in this state. This is thought to be because the magnetic field orientation is disturbed by the residual magnetic flux, deteriorating the magnetic performance. In addition, looking at the dimensions after molding, in the case of the molding method of the present invention, it is possible to mold almost to the dimensions of the mold, but in the case of the comparative example, after extrusion, the mold shrinks due to stress relaxation, etc. , the dimensions of the molded magnet are smaller than the dimensions of the mold. From this, it is clear that in the case of the method of the present invention, it is easy to mold the magnet to accurate dimensions, and as can be seen from the table values, it is possible to mold with high dimensional accuracy.

(Example 2) Next, the effects of using a thermosetting resin and a thermoplastic resin as the resin were investigated.

The results are shown in Table 2. As the resins used at this time, a phenol resin was used as a thermosetting resin, and nylon 12 was used as a thermoplastic resin. Nd-Fe-B quenched magnet powder is used as the magnet powder, and the mixing ratio of magnet powder and resin (including additives) is 66:34 by volume.
It was weighed so that The shape of the molded magnet is as in Example 1.
This is similar to the above, and an isotropic magnet was formed.

Table 2*; Unit: MGOe Here, resins 1 and 2 in the table are phenolic resins, respectively.
It represents nylon 12. As is clear from the table, magnetic performance is higher when phenolic resin, which is a thermosetting resin, is used than when nylon 12, which is a thermoplastic resin, is used. This is 1 if the molding temperature of the magnet is phenolic resin.
The temperature was 60 to 200°C, whereas the temperature for nylon 12 was as high as 250 to 280°C, which is thought to be due to deterioration of the magnet powder during molding when nylon 12 was used. In addition, when looking at dimensions, when nylon 12 is used, shrinkage occurs after extrusion, resulting in smaller dimensions of the molded magnet, but when phenolic resin is used, there is almost no dimensional change and molding can be performed with good dimensional accuracy. was possible.

(Example 3) Various properties of magnets formed using various resins will be described. Table 3 shows the resins used in this example.

From the values in Table 3, it is clear that the chemical resistance and heat resistance are better when a thermosetting resin is used than when a thermoplastic resin is used.

Table 4 Here, resin E is a thermoplastic resin shown as a comparative example, and is generally used in injection molding of resin-bonded magnets. Table 4 shows the properties of magnets formed using the above resins.

(Example 4) Next, the moldability of the magnet was investigated based on the difference Δt between the maximum wall thickness and the minimum wall thickness of the molded magnet and the average wall thickness t of the magnet. The results are shown in Table 5.

The molded magnet used Nd-Fe-B magnet powder as the magnet powder, and the molded magnet was a straw-shaped magnet with an arc diameter of 20 mm. Epoxy resin was used as the resin, and the mixing ratio of magnet powder and resin was 60:40 by volume.

Table 5 @ ○: For molding: Difficult to mold, ×: Unable to mold As is clear from the table, the difference △t between the maximum wall thickness and the minimum wall thickness of the molded magnet is 0.
When the thickness is more than 5t (t-average thickness), molding is difficult or impossible, and moldability is significantly reduced. This is thought to be because as the wall thickness difference increases, the temperature distribution on the magnet profile becomes non-uniform, causing a deflection in the flow of the mixed melt of magnet powder and resin, resulting in a decrease in moldability. In the table, when Δt is 0, O is selected because when the difference in wall thickness is the smallest, the flow of the mixed melt becomes uniform, and therefore the crosslinking reaction becomes the most uniform, resulting in very good moldability. It's for a reason.

[Effects of the Invention] As described above, the method for manufacturing a rare earth resin-bonded magnet of the present invention makes it possible to provide a rare earth resin-bonded magnet through a simpler process, and also reduces the manufacturing cost of the magnet. It becomes possible. Furthermore, deterioration of the magnetic properties of the magnet during molding can be prevented, thereby making it possible to provide a high-performance magnet.

Moreover, it becomes possible to more easily provide a magnet with good dimensional accuracy. Furthermore, by using a thermoplastic resin as the resin, it is possible to manufacture a magnet with excellent chemical resistance and heat resistance. Furthermore, it becomes possible to mold elongated magnets, which were difficult to mold using conventional molding methods, and this makes it possible to further expand the field of application of rare earth resin bonded magnets. Magnets produced by this manufacturing method can be widely used in stepping motors, DC motors, sensor mag rolls, etc.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the manufacturing process of the rare earth resin bonded magnet of the present invention. that's all

Claims (4)

[Claims] (1) In a method for manufacturing a rare earth resin-bonded magnet consisting of rare earth magnet powder, thermosetting resin, and additives (including inorganic substances), a mixed melt of rare earth magnet powder, resin, and additives is shaped in a mold. A method for producing a rare earth resin-bonded magnet, characterized in that the thermosetting resin is heated and cured to maintain the final shape of the magnet, and then extrusion molded. (2) In the above manufacturing method, a claim characterized in that the difference Δt between the maximum wall thickness and the minimum wall thickness of the molded magnet satisfies 0≦Δt≦0.5t with respect to the average wall thickness t of the formed magnet. Item 1. A method for producing a rare earth resin bonded magnet according to item 1. (3) Manufacturing the rare earth resin bonded magnet according to claim 1 or 2, wherein the rare earth magnet powder is a magnet powder made of a rare earth element (hereinafter referred to as R) and a transition metal element mainly consisting of cobalt. Method. (4) The method for manufacturing a rare earth resin-bonded magnet according to claim 1 or 2, wherein the rare earth magnet powder is a magnet powder consisting of R, a transition metal element mainly composed of iron, and boron.