JPH04324914A - Manufacture of rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture a highly efficient rare-earth/resin bonded type magnet at low cost and with good productive efficiency. CONSTITUTION:When a rare earth/resin bonding type magnet is extrusion-- molded, the molding operation is conducted at the extrusion pressure of 200kg/cm<2> or higher at the junction part between the cylinder part of an extrusion-molding machine and the metal mold. Also, a ram type extruding machine is adopted as the extrusion machine in the above-mentioned manufacturing method. As a result, a highly efficient rare-earth/resin bonded type magnet can be manufactured at low cost and with good productive efficiency.

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 rare earth resin bonded magnets.

0002

2. Description of the Related Art Examples of methods for molding resin bonded magnets include the following molding methods.

[0003]1. Compression molding method 2. Injection molding method In the compression molding method, a magnetic composition consisting of magnet powder and thermosetting resin is filled into a press mold, compressed and molded by applying pressure, and then heated to harden the resin. This is a method of molding. 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.

[0004] The injection molding method is a method in which a magnet composition consisting 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.

[0005]

However, the above manufacturing method has the following problems.

First, both the compression molding method and the injection molding method involve a fixed cycle of filling a mold with a magnetic composition, molding, and removing the molded product, and are basically batch-type production systems. Therefore, its productivity is limited. 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.

[0007] 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. There is a problem in that variations occur in the magnetic properties, and variations in magnetic performance also occur. On the other hand, in the case of injection molding, there is a high degree of freedom in shape, and arc-shaped molding is possible, but sprues and runners are produced, which must be reused (recycled). Powders, especially R-Fe-B magnet powders, are susceptible to deterioration in high-temperature atmospheres, so the use of recycled products has the problem of degrading the magnetic performance of the magnets.

[0008] Therefore, an extrusion molding method can be cited as a means to solve these problems. In the extrusion molding method, magnet powder is kneaded with resin, and this kneaded material (hereinafter referred to as magnet compound) is heated in an extruder, and when it is molten, it is fed into a mold and shaped and molded within the mold. This is the way to do it. In the case of this method, the production process is continuous, so productivity is high, 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. Does not occur. 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.

As mentioned above, in extrusion molding, the magnetic compound is melted in an extruder and extrusion force is created by applying stress to it, but since the molten magnetic compound contains magnetic powder, which is metal powder, Poor liquidity. Furthermore, when the magnetic powder flows, it increases the frictional force with the mold wall surface, etc., and this causes a decrease in fluidity. In a resin-bonded magnet, the higher the amount of magnet powder packed, the higher the magnetic performance becomes. Therefore, from the viewpoint of magnetic performance, it is desirable that the amount of filling is higher. However, there is a problem in that the fluidity described above decreases as the filling amount of magnetic powder increases.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its object is to provide a high-performance rare earth resin bonded magnet at low cost and with good productivity.

[0011]

[Means for Solving the Problems] The method for producing a rare earth permanent magnet of the present invention involves the extrusion molding of a rare earth resin bonded magnet consisting of rare earth magnet powder and a resin component (including inorganic additives). The extrusion pressure at the joint between the mold and the mold is 200 kg/cm2 or more.

[0012] Furthermore, the above production method is characterized in that a ram type extruder is used as the extruder.

The rare earth magnet powder is a rare earth magnet powder whose basic components are R (R is a rare earth element containing Y), a transition metal element mainly composed of Fe, and boron.

Alternatively, the rare earth magnet powder is a rare earth magnet powder whose basic components are transition metal elements mainly composed of R and Co.

[0015]

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

[0016] The extrusion pressure of the molten magnetic compound at the joint between the cylinder part and the mold of the extruder was set to 200 kg/c.
The reason why the magnetic compound made of rare earth magnet powder and a resin component is set to be more than m2 is that since the compound contains magnetic powder which is a metal powder, the viscosity of the compound when melted increases and the fluidity decreases. In the case of resin-bonded magnets, the magnetic performance generally improves as the content of magnet powder increases, so it is necessary to increase the amount of magnetic powder packed in order to manufacture a high-performance magnet. Since the viscosity of the molten magnetic compound increases as the content of magnet powder increases, the fluidity of the molten magnetic compound becomes even lower when manufacturing high-performance magnets. In order to compensate for this decrease in fluidity, the mechanical stress applied during molding of the magnetic compound must be increased.
It is necessary to increase the extrusion pressure.

Furthermore, in the case of resin-bonded magnets, it is necessary to sufficiently increase the packing density of the molded product, and for this purpose it is necessary to apply molding pressure during molding. For this reason as well, extrusion pressure is required during molding.

[0018] The lower limit of this extrusion pressure is 200 kg/cm2.
The reason for this is that if the pressure is lower than this, the flow to the entire surface of the mold will be insufficient, making it difficult to form into the desired shape. Furthermore, the density of the molded product becomes low even when it is shaped, so that the magnetic performance of the molded product decreases. As for the upper limit of the extrusion pressure, a higher pressure is more desirable, and this is limited by the specifications of the extruder or the mechanical strength of the mold material.

[0019] Also, in one of the claims, a ram type extruder is adopted as an extruder. A ram extruder is a machine that puts a magnetic compound into a cylinder and extrudes it using the compression force of a plunger, but compared to a screw extruder, the extruder itself performs batch processing, which reduces productivity. Although it has drawbacks, the extrusion pressure is
While the upper limit of the formula is about 500 kg/cm2,
This is because it has the advantage that it is possible to expand the moldable range since it can be applied sufficiently at a weight of 000 kg/cm2 or more.

[0020] Regarding the magnet powder used, R-Co type,
Alternatively, it may be R-Fe-B rare earth magnet powder, and if necessary, a magnetic circuit is installed at the tip of the mold to perform magnetic field orientation.

[0021] As the resin to be used, both thermosetting resins and thermoplastic resins can be used. For example, thermosetting resins include epoxy resins and phenol resins, and thermoplastic resins include polyamide resins and polyphenylene sulfide. Examples include resin (PPS). The resins listed here are just examples and do not limit the invention. These resins may be used as base resins, and in order to lower the viscosity of the mixture, treatments such as lowering the average molecular weight or adding additives such as plasticizers may be performed as necessary.

[0022] Hereinafter, a detailed explanation will be given according to examples.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the manufacturing process of a rare earth resin bonded magnet according to 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. Here, a single screw type extruder or a ram type extruder was used as the 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 feasibility of molding when compounds containing different amounts of magnet powder were molded at various extrusion pressures. The magnet powder used here is Nd-Fe-B
The resin used was a thermoplastic polyamide resin (nylon 12). A single screw extruder with a cylinder diameter of 40 mm was used as the extruder. Molding was performed at the optimum molding temperature for each compound. The molded shape was a pipe-shaped magnet with an outer diameter of 20 mm and an inner diameter of 18 mm.

[0026]

[Table 1]

When the extrusion pressure was less than 200 kg/cm 2 , it was possible to perform molding when the magnetic powder filling amount was 60 vol % or less, but it was not possible to perform molding when it was 60 vol % or more. Moreover, when the filling amount becomes high, it is difficult to perform molding when the extrusion pressure is lowered. The table does not show results for extrusion pressures of 600 kg/cm2 or more because the screw extruder used here could not apply a pressure of 600 kg/cm2.

Furthermore, when looking at the density of the molded magnet, when the extrusion pressure was 200 kg/cm2 or more, a value of 97% or more of the theoretical density was obtained;
For those molded with less than 2, a value of 95% or less of the theoretical density was obtained.

(Example 2) Next, in the same way as in Example 1, Table 2 shows the feasibility of molding when compounds with different filling amounts of magnet powder were molded at various extrusion pressures. However, the magnet powder used here was an Sm-Co based magnet powder, and the resin used was a thermosetting epoxy resin. This epoxy resin is a solid resin at room temperature, and its viscosity decreases rapidly at temperatures above 100°C, and the curing conditions are 200°C and above.
℃ for 1 hour. As an extruder, the cylinder diameter is 30
A mm ram extruder was used. The molding temperature was set to the optimum molding temperature for each compound. The molded shape was a plate magnet with a width of 15 mm and a wall thickness of 1 mm.

[0030]

[Table 2]

[0031] As in Example 1, the extrusion pressure was 200 kg/
When it was less than cm2, sufficient molding could not be carried out, and even when molded, the density was less than 95% of the theoretical density, and sufficient filling was not achieved. On the other hand, when the molding pressure is 200 kg/cm2 or more, the theoretical density is 9
Molding of 7% or more was achieved and satisfactory results were obtained. When a ram extruder is used, it is possible to increase the extrusion pressure compared to a screw extruder, which makes it possible to obtain magnets with even higher performance.

[0032]

As explained above, by using the method for producing a rare earth permanent magnet of the present invention, it is possible to provide a high performance rare earth resin bonded magnet with high productivity and at low cost. Furthermore, it is possible to provide long or thin magnets that are difficult to mold using conventional molding methods.

[Brief explanation of the drawing]

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

Claims (4)

[Claims] Claim 1: In extrusion molding of a rare earth resin-bonded magnet made of rare earth magnet powder and a resin component (including inorganic additives), the extrusion pressure at the joint between the cylinder part of the extruder and the mold is 200 kg/cm2 or more. A method for producing a rare earth permanent magnet, characterized in that: 2. The method for producing a rare earth permanent magnet according to claim 1, wherein a ram extruder is used as the extruder. 3. The rare earth permanent magnet powder according to claim 1, wherein the rare earth magnet powder is a rare earth magnet powder whose basic components are R (R is a rare earth element containing Y), a transition metal element mainly composed of Fe, and boron. How to manufacture magnets. 4. The method for producing a rare earth permanent magnet according to claim 1, wherein the rare earth magnet powder is a rare earth magnet powder whose basic component is a transition metal element mainly composed of R and Co.