JPH04134807A - Manufacture of rare earth-resin bonded magnet - Google Patents

Abstract

PURPOSE:To obtain an arc-shaped magnet of higher performance with good productivity and at low cost by selecting the viscosity eta of the mixture of rare earth magnet powder, resin and additive to be eta<=2kpoise (shear rate 1000sec<-1>) in the temperature range, where a resin ingredient is liquefied. CONSTITUTION:The viscosity eta of the mixture of rare earth magnet powder, resin and additive is selected to be eta<=2kpoise (shear rate 1000sec<-1>) in the temperature range, where a resin ingredient is liquefied, and the flow of a mixed melt is made uniform relative to the shape of a molded body. The magnet powder to be used is Sm-Co powder or Nd-Fe-B powder and its percentage content is 40-80% in volume ratio to ensure a necessary fluidity. Thus, it is possible to improve the productivity of an arc-shaped magnet and to lower its cost.

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] As a method for molding a resin-bonded magnet, the following molding method can be mentioned.

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.

As mentioned above, in this compression molding method, the amount of resin component in the magnet composition is smaller than in other molding methods, so 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.

In addition, the compression molding method has a low degree of freedom in shape, and when molding irregular shapes such as arc shapes, it is difficult to apply molding pressure uniformly during pressing, which causes variations in density within the magnet molded body. It also has the problem of variations in magnetic performance. On the other hand, injection molding has a high degree of freedom in shape, and arc-shaped molding is possible;
Since sprues and runners are generated, these need to be reused (recycled), but rare earth magnet powder, especially R-
Since Fe-B-based magnet powder easily deteriorates in a high-temperature atmosphere, there is a problem in that using a recycled product lowers the magnetic performance of the magnet.

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, the production process is continuous, so productivity is good, and unlike injection molding, sprues and runners are not produced, so it is difficult to produce recycled products, so there is no deterioration in magnetic performance due to this. . 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.

In other words, when molding an arc shape or a flat plate shape, it is difficult to make the molten mixture flow uniformly with respect to the cross-sectional shape, and especially when there is a filler such as magnet powder, the fluidity is poor. It becomes even more difficult. This creates a portion that is difficult to fill into the gap in the mold, which poses a problem in that it is difficult to shape according to the mold.

The present invention is intended to solve these problems, and its purpose is to produce arc-shaped magnets that are difficult to mold using conventional molding methods, with higher performance, higher productivity, and lower cost. The purpose is to provide.

[Means for Solving the Problems] The method for manufacturing a rare earth resin-bonded magnet of the present invention is a method for manufacturing a rare-earth resin-bonded magnet consisting of a rare earth magnet powder, a resin, and an additive (including an inorganic substance). The viscosity η of the mixture of and additives is η≦2 kpoise (shear rate 1000 sec-1) in the temperature range where the resin component becomes liquid, and the mixture is extruded into an arc shape or a flat plate shape. .

Further, the rare earth magnet powder is a magnet powder composed of a rare earth element and a transition metal element mainly consisting of cobalt, and the content thereof is 40 to 80% by volume.

Further, the rare earth magnet powder is a magnet powder consisting of a rare earth element, a transition metal element mainly composed of iron, and boron, and the content thereof is 40 to 80% by volume.

[Function] According to the configuration of the present invention, by using an extrusion molding method as a molding method for a rare earth resin-bonded magnet made of rare earth magnet powder and resin, compression molding method, injection molding method, etc., which are basically batch processes, can be used. Compared to conventional manufacturing methods, continuous molding is possible, which increases productivity and reduces costs.

The viscosity η of the mixture of rare earth magnet powder, resin and additives is set to η≦2kpois in the temperature range where the resin component becomes liquid.
e (shear rate 1000 sec-1) was chosen because in order to mold the mixture, it is necessary for the mixture to undergo plastic deformation, and in order to cause such deformation, the resin component must become liquid. , the temperature range is a temperature range in which the resin component becomes liquid. Viscosity of the mixture η
The reason why the temperature is set to 2 kpoise or less is to make the flow of the mixed melt uniform over the shape of the molded product. That is, in general, molds for flat or flat molds have different fluidity depending on the shape of the molded product, with the mixed melt flowing easily in the center of the molded product and difficult to flow in the edge portions. One way to solve this problem is to change the shape of the flow path in the mold so that it flows more easily toward the edges, but this treatment is effective if the viscosity of the mixed melt is too high. There are limits.

Therefore, it is necessary to lower the viscosity of the mixture, and the upper limit is 2
It becomes kpoise. That is, if the viscosity exceeds this value, the fluidity of the mixture is low, and there is a difference in the fluidity of the mixture depending on the cross-sectional shape of the molded product, making it impossible to mold the shape. Regarding the lower limit of the viscosity, it is desirable that the viscosity be lower if a mixture with a lower viscosity can be prepared.

The magnet powder used is Sm-Co or N.
It is a d-Fe-B rare earth magnet powder, and the reason why its content is 40 to 80% by volume is because the effect of using high-performance rare earth magnet powder cannot be obtained if it is less than 40%. This is because if it exceeds 80%, the fluidity necessary for extrusion molding cannot be secured.

Both thermosetting resins and thermoplastic resins can be used.For example, thermosetting resins include epoxy resins and phenol resins, while thermoplastic resins include polyamide resins and polyphenylene sulfide resins (P
PS) etc. The resins listed here are just examples and do not limit the invention. When these resins are used as bess resins, the viscosity of the mixture can be lowered by reducing the average molecular weight or adding additives such as plasticizers as necessary.

The arc-shaped magnet of the present invention refers to the following. In other words, it shows a magnet having an outer diameter R2, an inner diameter r, and an arc-shaped cross section with an angle of incidence θ (θ≦180°) and a length t.

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

[Example] 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 crushed into a size that can be easily fed into a molding machine, and then fed 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 the final shape in the mold, and the molded magnet is extruded from the mold. The extruded magnet is taken out and cut by a cutting machine. After this, when a thermosetting resin was used, curing was performed to form a rare earth resin bonded magnet. 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 moldability when the viscosity of a mixed melt of magnet powder and resin (hereinafter referred to as compound) was changed.

For 2kpoise or more, apply compound Table 1 to the edges. was not filled and molding was not possible.

○: Can be molded, △: Difficult to mold, ×: Cannot be molded The magnet powders used are Sm-Co type (Sm type in the table), Nd-Fe-B
system (Nd system in the table), and the filling rate was 60% by volume. Polyamide resin (nylon 12) was used as the resin, and the viscosity was changed by changing the average molecular weight of the resin to increase the viscosity, and by adding additives such as stearate to decrease the viscosity. The cross-sectional shape of the molded magnet was an arc-shaped magnet with an outer diameter of 10 mm, an inner diameter of 9 mm, and an angle of incidence of 120°. As is clear from the table, when the viscosity is low, molding is possible, but when the viscosity increases, molding becomes difficult, and around 2 kpoise is the upper limit of the moldable range. However, (Example 2) A molding experiment was conducted under the same experimental conditions as in Example 1 to form a flat magnet having a cross-sectional shape of 20 mm in width and 1.5 mm in thickness. The results are the same as the experimental results in Table 1, and the viscosity is 2kpoi
When the temperature was higher than se, the compound was not filled into the edge portion and molding could not be performed.

(Example 3) Table 2 shows the viscosity and moldability of compounds prepared by changing the filling amount of magnet powder. The magnet powder used is Nd.
-Fe-B photomagnetic powder, and thermosetting epoxy resin was used as the resin. The molded shape was an arc-shaped magnet with the same dimensions as the magnet molded in Example 1.

At this time, the epoxy resin was solid at room temperature, had a thermoplastic range at 120 to 1500°C, and hardened at 180 to 200°C. A plasticizer such as stearate was used as an additive.

Table 2 Note 1. Unit of viscosity kpoise at 140℃
2. ○・ Acceptable, △: Difficult, ×: Impossible As is clear from the table, the viscosity increases as the content of magnetic powder increases, and when the content exceeds 80vo1%, the viscosity remains 2kp○ even when additives are added. It did not fall below the ISE and could not be molded. When the filling rate of magnetic powder was 80v○1%, molding was difficult but possible. When the filling rate was 40vo1% or less, molding was sufficiently possible, but the magnetic performance of the molded magnet was 3MGOe or less, and the effect of using high-performance rare earth magnet powder could not be obtained.

(Example 4) Under the same experimental conditions as in Example 1, a flat magnet having a cross-sectional shape of 20 mm in width and 1.5 mm in thickness was molded. The results are the same as the experimental results in Table 2, and the filling factor of the magnet is 8.
When the amount exceeds 0vo1%, the viscosity becomes 2 kpoise or more, and when molding was performed, the compound did not fill the edge portions and molding could not be performed.

[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, it becomes possible to form square shapes and flat plate shapes with high performance, which have been difficult to mold up to now.

Magnets produced by this manufacturing method can be widely used in stepping motors, DC motors, sensor mag rolls, etc.

4,

[Brief explanation of drawings]

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

Claims (3)

[Claims] (1) In the manufacturing method of a rare earth resin bonded magnet consisting of rare earth magnet powder, resin, and additives (including inorganic substances), the viscosity η of the mixture of rare earth magnet powder, resin, and additives falls within the temperature range where the resin component becomes liquid. A method for manufacturing a rare earth resin bonded magnet, wherein η≦2kpoise (shear rate 1000sec^-^1) and extrusion molding into an arc shape or a flat plate shape. (2) The rare earth resin bonded magnet according to claim 1, wherein the rare earth magnet powder is a magnet powder consisting of a rare earth element and a transition metal element mainly consisting of cobalt, and the content thereof is 40 to 80% by volume. Production method. (3) The rare earth resin bond according to claim 1, wherein the rare earth magnet powder is a magnet powder consisting of a rare earth element, a transition metal element mainly composed of iron, and boron, and the content thereof is 40 to 80% by volume. Method for manufacturing type magnets.