JPS59136910A - Manufacture of radially anisotropic magnet - Google Patents

Abstract

PURPOSE:To obtain a ring type radially anisotropic magnet of high performance and having little limitation of shape by a method wherein after magnet powder having uniaxial anisotropy is magnetized previously in a magnetic field larger than intrinsically coercive force thereof, the powder is mixed with a liquid to be suspended, and powder compression molding is performed in the magnetic field utilizing centrifugal force. CONSTITUTION:After magnet powder having uniaxial anisotropy is magnetized previously in a magnetic field larger than intrinsically coercive force iHe of the magnet powder thereof, the magnet powder thereof is mixed to a liquid to be suspended,and the suspension 7 thereof is sealed in a ring type vessel 8. An outside magnetic field in the radial direction facing to the radius vector direction of the ring 8 is applied to the suspension 7, and after the magnet powder is oriented to the radial direction in the ring type vessel 8, the ring 8 is rotated in the condition applying the magnetic field as it is, and by applying centrifugal force to act in parallel with the outside magnetic field, the magnet powder is minutely molded. For example, currents are flowed to magnetic field coils 2, 6 to generate magnetic fields, and at this time, the directions of the currents are made to opposite in the coils 2, 6 mutually to make a radially directional magnetic field to be generated according to mutual repulsion of the generated magnetic fields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides magnetic powders having -axis anisotropy, such as barium ferrite (BaO Fe203), strontium ferrite (Sr@Fe203), RCo5 series (R represents rare earth), R2C0□ 7 series and manganese aluminum (
Magnet powder such as M n -A L ) system is magnetized in advance in a magnetic field larger than its true coercive force He The present invention relates to a method of manufacturing an anisotropic magnet having anisotropy in the radial direction by molding.

Conventionally, there are roll methods and press molding methods for manufacturing magnets having radial anisotropy. In the roll method, a mixture of forming aid and magnetic powder is passed between rolls, and the particles are mechanically oriented perpendicularly to the roll direction so as to have anisotropy. The resulting temporary molded product is then rolled into a cylindrical shape, with the anisotropy direction radial. This is a method of manufacturing a radial anisotropic magnet in which the material is then sintered and cut into a magnet. This method can only be used for ferrite magnet powder, and the degree of orientation of the particles is also mechanical, so it is not sufficient. The press molding method is a manufacturing method in which a magnetic circuit is assembled to orient the brewerite powder in the press 4v in the radial direction using the magnetic field of the coil, and then compression molding is performed while applying the magnetic field.

An example of molding using this method is shown in FIG. The part 9 shown in the figure is a cavity into which the magnetic powder is placed, and the powder is compressed in the P direction by the punch 1. The molded ring-shaped radially anisotropic magnet has a shape as shown in FIG.

The outer diameter is R1, the inner diameter is r1, the length is t, and the wall thickness is t.

In compression molding, pressure is applied in one direction, resulting in significant density variations in the opposite direction. Further, during the press R3, the friction between the powder and the wall surfaces of the press molds (1 and 4 in FIG. 1) disturbs the orientation of the magnetic material, resulting in a decrease in performance. Therefore, the smaller the wall thickness t, the more difficult the molding becomes. In compression molding, if you want to get a large radial magnet, the pressure depends on the press pressure, so it can only be manufactured up to a certain size. On the other hand, the size of the inner diameter r is also limited in compression molding, and it is not possible to manufacture a product with a very small r. This is because when the diameter of 2 in Figure 1 is made smaller, the available radial orientation magnetic field decreases, and with the compression method, when trying to obtain a long t magnet as shown in Figure 2, the orientation before compression is ,
This is because the cavities shown in FIG. 19 require about 6 cavities, so the play area is further reduced to about 115 cavities.

The object of the present invention is to overcome the drawbacks of the roll method and press molding method, to produce a radially anisotropic magnet with high performance, uniform density, and shape flexibility. Specifically, it is as follows. - Magnet powder with axial anisotropy is prepared in advance in 1. iHc of the magnetic powder
After being magnetized with a magnetic field larger than After applying a magnetic field to the suspension and orienting the magnetic powder in the radial direction within the ring trough, the ring is rotated while an electric field is applied to generate a centrifugal force that acts parallel to the magnetic field. This is a method for producing a radial anisotropic magnet, characterized by magnetizing magnet powder by applying Also, when magnet powder is made of an alloy of cobalt-based transition metals (indicated by TM) and rare earth elements (R), and is coated with RTMZ, the value of 2 is 7~? This is a method for manufacturing a high-performance radial anisotropic magnet characterized by using an alloy mainly having a type 7 crystal structure of R2Co and having a composition as follows. What is the method of magnetizing magnetic powder in advance in a high magnetic field and then molding it? Furthermore, this method is effective when the magnet powder has a high temperature iHc. In particular, it is sometimes effective for R2TM□7-based magnet powder, since the powder generates a coercive force due to the pinning of domain walls. Explain why it is effective.

The force f when the magnet powder is oriented in the direction of the magnetic field is f=rXHX
It is given by I. However, r is the particle diameter, H is the magnetic field strength, and x is the magnetization. If the magnetic powder is not completely saturated,
Not only is the magnetization low, but the magnetization in the opposite direction (I cr-
I ) causes a force to work in the opposite direction, and the rotational force of the magnetic and magnetic parts is △
It is weakened by f=2 rH (Ior). However, fo is saturation magnetization, and fo is I. This is the rotational force when .

The present invention will be described below with reference to Examples.

Example (1) FIG. 5 shows a centrifugal pressure molding machine for radially anisotropic magnets according to the present invention. 1.5.9 is made of a ferromagnetic material, and a radial magnetic field is induced from coils 1 and 6 into the cavity containing the magnetic powder suspension in 7.

5 is a rotor made of a non-magnetic material. 4 supports the rotor 5 with a bearing. The rotor is a belt or (d
It rotates when force is transmitted from the outside through gears. The rotor contains a magnetic suspension injected into a ring-shaped container 8.

Next, a method for manufacturing a radial magnet using a centrifugal pressure molding machine according to the present invention will be described. A suspension of magnetic powder and liquid as shown in Table 1 was prepared. The volume ratio of magnetic powder and liquid is 50 V for magnetic powder.
o 7%. The average particle size is 1.2μm for strontium ferrite, 5μm for rare earth transition metal alloys 2 and 5.
m, A4 is 10 μm.

Two types of suspensions were prepared for each type of suspension: one was pre-magnetized and the other was not.

All celadon in Table 1 was tested at 20 KOe. The suspension that has been prepared is first poured into a ring-shaped container inside the rotor shown in FIG. The rotor has a structure that splits into upper and lower halves, and the container can be easily attached and detached. When the entire set is completed as shown in FIG. 5, the magnetic field coil 2. A current is passed through B to generate magnetism.

The directions of W, d'i, and m are reversed for 2 and 6,
The magnetic fields that come out after being induced repel each other. The /a4 repelled by the pole is guided to the outer circular yoke as shown in FIG. 5, and a radial magnetic field is generated at the cavity take. In this way, when tap water is first generated, the magnetic particles in the suspension rotate with almost no friction and are oriented in the direction of the magnetic field. Next, while applying a magnetic field, the rotor is gradually caused to rotate one revolution by external power, and finally, the rotor is made to rotate at high speed. Then, the magnetic particles are pressurized by centrifugal force, forming a magnet with radial anisotropy inside the container. After applying sufficient pressure, demagnetize the magnet by applying a reverse magnetic field, stop rotating, and remove the container.

Samples A1 to A5 are dried, then taken out and sintered. A2 and A5 are subjected to post-sintering heat treatment to impart coercive force. The flat plate 4 uses magnetic powder that has a coercive force from the beginning, and after the magnet is removed from the container and the resin is washed, curing is performed to harden the resin. Various radially anisotropic magnets can be manufactured by such a method. The performance of the obtained magnet was measured by vibrating sample magnetic measurement and punching, and the results are shown in Table 2. Measurements were carried out by cutting small cylindrical samples from various women's baths in the magnet. The density variation is 1
It looks like compression molding ((, second
There was almost no variation in density in the t direction shown in the figure. Therefore, variation in residual magnetic flux density was suppressed to within 1%, and variation in maximum energy product was suppressed to within 4%. Furthermore, it was confirmed by x4 diffraction that the present force method has very good orientation.

2nd coating (Note: The ' symbol indicates a product that has not been magnetized with powder) In addition, the number 1 (the powder magnetized product with the ' symbol has the same remarkable orientation as above, and this is also reflected in the magnetic performance. There is.

According to the method of the present invention, radial magnets with a long t dimension, which cannot be manufactured by compression molding, can also be manufactured.

In addition, it is also possible to easily fabricate a structure between o and g in Fig. 2. Since the uninvented device applies pressure using centrifugal force, it can produce large magnets that are impossible with compression molding.

Then, if you repeat the process of pressurizing, draining the liquid, adding more suspension, and pressurizing, you will get t compared to R.
It is also possible to make thick grinding stones.

As described above, due to inventiveness, a ring-shaped radial anisotropic magnet has been developed which has higher performance than conventional magnets and has a smaller shape. Possible uses for uninvented magnets include step motors, DC servo motors, baud rx coils, magnetic bearings, etc., and the impact on miniaturization and performance enhancement of these is significant.

[Brief explanation of the drawing]

FIG. 1 shows one method of creating a radially anisotropic magnet using the serpentine compression method. 1... Upper bunch, 2... 5 aa core, 6, 5... Coil, 4... Press die, 6...
Lower punch, 7... ferromagnetic material, 8... non-magnetic material, 9.
...Cavity (6g powder) Figure 2 shows a radially anisotropic magnet with a square and square shape. φR...outer diameter, φr...inner diameter, t...length, t.
...The wall thicknesses in Fig. 3 a and b are determined by the radial anisotropic magnet molding machine according to the present invention. 1...Ferromagnetic pole, 2,6...
・Coil, 3...Rotor, 4...Bearing, 5.
...Ferromagnetic yoke, 7. Magnetic powder suspension, 8. Container, 9. Ferromagnetic core. Applicant: Suwa Seikodai Co., Ltd. 232 Figure 3 Procedural Amendment (Method) 1 Table of bow f I'I 1981 Special Patent Application No. 1181552 Title of Invention Method for Manufacturing Radial Anisotropic Magnet 3 Amendment Representative Tsuneya Nakamura 4 Agent 5 F of the amendment order 7.3 is a radial anisotropy 2 drawing according to the present invention. Figure 6 has been amended and attached hereto.

Claims (2)

[Claims] (1) - Magnet powder having axial anisotropy is magnetized in advance in a magnetic field larger than the true coercive force iHc of the magnet powder, and then the magnet powder is mixed with a liquid and suspended; is sealed in a ring-shaped container, a radial external magnetic field directed in the radial direction of the ring is applied to the suspension, the magnetic powder is radially oriented in the ring container, and then the magnetic field is applied as it is. This is a patented method for manufacturing radial anisotropic magnets that involves forming magnet powder into compact shapes by rotating a ring while applying a centrifugal force that acts in parallel with an external magnetic field. (2) Magnet powder is an alloy of transition metals (TM) mainly composed of cobalt and rare earth elements (denoted by R),
Moreover, it is recommended to use an alloy mainly composed of an R2C017 type crystal structure with a composition in which the value of 2 when expressed as RTMZ is 7 to 9! The method for manufacturing a radially anisotropic magnet according to claim 1, wherein the magnet is f9.