JPH033215A - Manufacturing method of resin bonded magnet - Google Patents

Abstract

PURPOSE:To enable an anisotropic or isotropic resin coupling-type magnet to be formed with high performance, improved dimensional accuracy, and stable for a long period of time by specifying the formation speed in an extrusion molding of the resin coupling-type magnet consisting of a magnet powder and a resin constituent. CONSTITUTION:A mixture of a magnet powder and a resin constituent is heated to a melting point of a resin or a temperature exceeding the flexibility point where the resin is melted. is kneaded, and is crashed to form a pellet-shaped compound. The compound within a mold passes through a part where magnetic field is applied to and an axis of easy magnetization of the magnet powder within the compound is oriented and formed in the direction of the magnetic field. In this case, the extrusion speed on molding is 0.1<=V1<=50mm/sec when molding a cylindrical, sheet, or tile anisotropic magnet which is 5mm or less in thickness and 0.1<=V2<=100nm/sec when molding a sheet or tile isotropic magnet. With these conditions, it is possible to form a magnet with long dimensions or that which is thin easily.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a 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.

As mentioned above, this compression molding method has a lower amount of resin component in the magnet composition than other molding methods, so the magnetic performance of the molded magnet is high, but the injection molding method has less freedom in the shape of the magnet. This 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 W%. The magnetic performance of the compact 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. Regarding the wall thickness of the magnet molded body, as with the molding of long-sized magnets, if the wall thickness of the magnet molded body becomes 1 mm or less, it becomes a problem to fill the magnet composition into the mold and take out the molded body. It is difficult to mold magnets with a thickness of 1 mm or less.

The present invention is intended to solve these problems, and its purpose is to provide long magnets or thin wall magnets that are difficult to mold using conventional molding techniques. .

[Means for Solving the Problems] The method for manufacturing a resin-bonded magnet of the present invention includes extrusion molding of a resin-bonded magnet made of magnet powder and a resin component. 2. The molded magnet has a cylindrical shape with a wall thickness of 5 mm or less; When the magnet is an anisotropic magnet in the form of a sheet or straw, it is characterized in that the molding speed (1) of the magnet molded body is 0.1≦■1≦50 mm/sec. In addition, in extrusion molding of a resin-bonded magnet made of magnet powder and a resin component, when the magnet molded body is a cylindrical, sheet-shaped, or straw-shaped isotropic magnet with a molded body thickness of 5 mm or less, the magnet molding It is characterized in that the molding speed (V2) of the body is 0.1≦V2≦100 mm/sec.

The magnetic powder used in the present invention has a basic composition of rare earth metals and transition metals mainly consisting of cobalt;
Alternatively, there are magnet powders whose basic composition is composed of rare earth metals, transition metals mainly composed of iron, and boron. The resin may be either thermoplastic or thermosetting resin.
Examples of thermoplastic resins include plastics such as polypropylene and polyamide, thermoplastic elastomers, and synthetic rubber. Examples of thermosetting resins include epoxy resin,
There are polyimide resins, etc. As additives, a lubricant for reducing resistance during extrusion molding, a plasticizer for improving processability, or an accelerator for crosslinking reaction of the thermosetting resin is used.

These magnet powders and resin components are weighed and mixed. Next, this mixture is heated to a temperature above the melting point or softening point of the resin at which the resin melts, kneaded, and pulverized to produce a pellet-shaped magnet composition (hereinafter referred to as a compound). This compound is put into a screw-type or plunger-type extruder, becomes fluid in a cylinder, and is sent into a mold. In the mold, the compound passes through a region to which a magnetic field is applied, so that the axis of easy magnetization of the magnet powder in the compound is oriented in the direction of the magnetic field, and the compound is molded. Alternatively, it is molded without applying a magnetic field and without orientation.

At this time, the extrusion speed during molding was changed to a cylindrical shape with a wall thickness of 5 mm or less,
0.1≦■1≦50mm/sec when forming an anisotropic magnet in the form of a sheet or a piece of paper; 0.1≦ when forming an isotropic magnet in the form of a cylinder, sheet or piece with a wall thickness of 5 mm or less ■Mold at 2≦100mm/sec. In extrusion molding of resin-bonded magnets, the extrusion molding speed greatly affects the productivity, dimensional accuracy, and magnetic performance of the magnet molded body. That is, as for productivity, it goes without saying that the slower the extrusion speed, the worse the productivity, which increases the cost of the magnet. Regarding dimensional accuracy, when molding the compound to the final dimensions in the mold, the compound must be sufficiently cooled and solidified in the mold or sufficiently heated. Therefore, if the extrusion speed is too high, cooling or heating may not be sufficient. As a result, it is extruded with insufficient solidification, and the molded magnet is deformed or dimensionally fluctuated upon exiting the mold, resulting in poor dimensional accuracy. This phenomenon becomes noticeable when the extrusion speed exceeds 100 mm/sec, so the upper limit of the extrusion speed of isotropic magnets is 100 mm/sec.
mm/sec. Regarding the magnetic performance of magnets, when molding isotropic magnets in the absence of a magnetic field, if the extrusion speed is too high, the filling properties of the magnet powder in the magnet will be poor, the density will decrease, and as a result, the magnetic performance of the magnet will deteriorate. descend. When molding anisotropic magnets by applying a magnetic field, if the extrusion speed is too high, the residence time of the compound in the magnetic field application section will be shortened, resulting in insufficient orientation of the magnet powder in the compound.
Furthermore, if the magnet powder is extruded without being sufficiently solidified, the orientation of the magnet powder cannot be maintained upon exiting the mold, and the orientation is disturbed, resulting in a decrease in magnetic performance. This means that the extrusion speed is 50mm/
sec, the upper limit of the extrusion speed of the anisotropic magnet is 50 mm/sec. However, in the case of isotropic magnet molding, since there is no need to orient the magnet powder, the molding temperature can be lowered, so especially in the case of cooling solidification molding, even if the extrusion speed is increased, sufficient cooling can be achieved, so the extrusion speed can be lowered. Therefore, the upper limit of the extrusion speed is higher for isotropic magnets than for anisotropic magnets.If the extrusion speed is too slow for both isotropic and anisotropic magnets, the magnetic performance will decrease. decreases.

When a thermosetting resin is used as the resin, a curing reaction occurs due to the heat and pressure during extrusion molding, the viscosity of the resin increases, the filling properties of the magnet powder decrease, the density of the magnet decreases, and the magnetic performance also decreases. Particularly in the case of molding an anisotropic magnet, when the resin viscosity increases, the resin becomes resistant to orientation when magnet powder is oriented, resulting in insufficient orientation and decreased magnetic performance. When a thermoplastic resin is used as the resin, the lower the extrusion speed, the higher the molding temperature, so if the magnet powder is exposed to an oxidizing atmosphere for a longer period of time, the magnet powder will be oxidized, resulting in a decrease in magnetic performance. These phenomena occur when the extrusion speed is 0.1 m.
The lower limit of the extrusion speed for isotropic magnets and anisotropic magnets is 0.1 mm/s, as it becomes significant when the extrusion speed is lower than m/sec.
It becomes ec.

[Example] Hereinafter, the present invention will be explained in detail according to examples.

(Example 1) The composition of the magnet powder was button (Cos, et2Cus, 1IsFeQ, 22Zre
, 52e) After melting and casting the raw materials to a particle size of 1.36, the produced ingot was heat-treated to magnetically harden it, and then pulverized to produce magnet powder with an average particle size of 20 μm. The composition ratio of this magnet powder and a thermosetting resin mainly composed of epoxy resin is 90 wt% of the magnet powder and 10% of the resin component.
They were mixed so that the weight ratio was %. The epoxy resin used here had a softening temperature of 80°C and a crosslinking temperature of 200°C.

This mixture was kneaded at about 90°C using a twin-screw extruder, and ground into particles with an outer diameter of 1 to 10 mm to obtain a raw material compound. This compound is put into a screw extruder, heated and melted in the extruder cylinder, and then kneaded by the shear force generated by the rotation of the screw.
Lead to the mold shown in the figure. The temperature inside the cylinder was heated with a temperature gradient of 90° C. to 120° C. from the compound injection part to the joint part with the mold. The compound is further heated in the mold and squeezed into its final shape. An orientation magnetic field is applied to the orientation section 1. The orientation section is divided into three layers: orientation layer 2, heat insulation layer 3, and cooling layer 4. The orientation layer orients the magnet powder in the compound, and the cooling layer maintains the orientation and shape of the magnet powder. Cool the compound to a temperature that can be maintained. The heat insulating layer is a layer having a heat insulating effect to create a temperature gradient between the alignment layer and the cooling layer, and the material used is metal, ceramic, or plastic with low thermal conductivity. The cooling layer is cooled by a cooler attached to the front of the mold. The compound was oriented and molded into the final shape by this orientation section. At this time, the orientation layer temperature was 130° C., the cooling layer temperature was 60° C., and the strength of the applied magnetic field was 15 kOe in the orientation layer. The molded magnet was a cylindrical radially oriented magnet with an outer diameter of 30 mm and an inner diameter of 29 mm.

Figure 2 shows the changes in magnetic performance and density of the molded magnet when the extrusion speed was changed. As the extrusion speed increases, the density and Br values decrease.

However, when the extrusion speed is 100 mm/sec or less, the rate of decrease is small. Extrusion speed is 100mm/se
Above c, the density and magnetic performance decrease rapidly. This is because when the extrusion speed exceeds 100 mm/sec, cooling becomes insufficient, the density becomes insufficient, and the oriented magnet powder becomes unable to maintain its orientation. The 3rd Z shows the change over time in the magnetic performance of the molded magnet when molded at different extrusion speeds. The extrusion speed was 0.05.5.
Changes in magnetic performance over time were measured by changing the speed to 50 mm/sec. As is clear from the figure, it is clear that the change in magnetic performance over time changes as the extrusion speed changes. Extrusion speed is 50
When the speed is mm/sec, there is almost no change in magnetic performance over time, and when the speed is 5 mm/sec, there is a slight decrease in magnetic performance, but it is only slight. However, the extrusion speed is 0.05mm
/sec, the magnetic performance deteriorates significantly over time. This is because when the extrusion speed becomes slower, the viscosity of the condoland resin increases due to heating in the mold, the density decreases, and orientation of the magnetic powder becomes difficult to occur. It is. From this, it is clear that if the extrusion speed is too slow, the magnetic performance of the magnet will deteriorate over time, making stable extrusion molding impossible.

(Example 2) Next, the influence of the extrusion speed on the magnetic performance of the magnet when molding an isotropic magnet was investigated. Regarding the molding conditions, first, Nd+2Fet7.5Co4.3BS, 9 was used as the magnet powder, and thermoplastic polyamide resin was used as the resin. The melting point of this resin was about 180°C. The molding procedure was the same as in Example 1. However, the crosstalk temperature was 260°C, the extruder cylinder temperature was 280 to 300°C, and the orientation layer and cooling layer temperatures were 210°C and 1170°C, respectively.

The shape of the molded magnet is the same as in Example 1, with an outer diameter of 30 mm.
, the inner diameter was 29 mm.

As can be seen from Figure 4, which shows the magnetic performance and density of the molded magnet when the extrusion speed is changed, when the extrusion speed exceeds 100 mm/sec, the density and magnetic performance decrease rapidly. This means that the temperature of the alignment layer and cooling layer is only 4
Even though it can be molded at around 0℃, the extrusion speed is 1
If it exceeds 00 mm/sec, the compound cannot be cooled in time, so the density of the magnet molded body decreases, and the magnetic performance also decreases accordingly. FIG. 5 shows the change in magnetic performance over time when the extrusion speed was changed. 0.0 where the extrusion speed is lower than 0.1 mm/sec
It is clear that the change in magnetic performance over time is large at 5 mm/sec. This is because when the extrusion speed is slow, the resin deteriorates due to long-term heating, and because thermoplastic resin is used here, the molding temperature is high, so the magnet powder deteriorates due to oxidation. Next, the extrusion speed and dimensional accuracy of the magnet molded body were investigated.

When the extrusion speed was 100 mm'/sec or less, the outer diameter tolerance was within 57,100 mm, although the accuracy decreased slightly as the extrusion speed increased. However, the extrusion speed is 10
If it exceeds 0 mm/sec, the cooling of the magnet becomes insufficient, and the outer diameter tolerance becomes 57,100 or more in all cases.

[Effects of the Invention] As described above, by the manufacturing method of the present invention, it is possible to form an anisotropic or isotropic resin-bonded magnet with high performance, good dimensional accuracy, and stability over a long period of time. . Magnets manufactured using this manufacturing method can be widely used in stepping motors, DC motors, sensor mag rolls, etc., which require small precision and high performance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an extrusion mold used in the present invention. 1. Orientation section 2, Orientation layer 3゜Heat insulation layer 4゜Cooling layer 5゜Deep part of the mold Figure 2 shows the change in magnetic performance and density over time with extrusion speed when molding an anisotropic magnet. . FIG. 4 is a diagram showing changes in magnetic performance and density over time as a function of extrusion speed when molding an isotropic magnet. that's all

Claims (1)

[Scope of Claims] (1) In extrusion molding of a resin-bonded magnet made of magnet powder and a resin component, the magnet molded body is an anisotropic magnet in the form of a cylinder, sheet, or straw with a wall thickness of 5 mm or less. One day,
A method for manufacturing a resin-bonded magnet, characterized in that the molding speed (V_1) of the magnet molded body is 0.1≦V_1≦50 mm/sec. (2) In extrusion molding of a resin-bonded magnet made of magnet powder and a resin component, when the magnet molded body is a cylindrical, sheet-shaped, or straw-shaped isotropic magnet with a molded body thickness of 5 mm or less, the magnet A method for manufacturing a resin-bonded magnet, characterized in that the molding speed (V_2) of the molded body is 0.1≦V_2≦100 mm/sec.