JPS59141202A - Manufacture of radially anisotropic cylinder type magnet - Google Patents

Abstract

PURPOSE:To enable to manufacture the titled device having a high magnetic characteristics, generating no crack at molding time and at low cost by a method wherein mixed powder of pulverized powder of ferrite of the specified grain size, and granulated powder of the specified grain size and different from the pulverized powder thereof are filled up in a cylindrical molding die, and press molding in a magnetic field is performed applying the magnetic field in the radial direction of the molding substance. CONSTITUTION:Molding space is constructed of a die 4, lower core 5, lower punch 6, an upper core 8 and an upper punch 9. The upper and lower punches 6, 9 are consisting of a non-magnetic material, the others are consisting of a magnetic material, and the inside surface of the magnetic material die 4 is flame-coated with non-magnetic material. Mixed powder of ferrite consisting of the average grain size of 2mum or less and granulated powder consisting of grain size of 14-200 mesh and different from the pulverized powder thereof is filled up in the molding space of the die thereof, a magnetizing current of Bg 4,000 gauss or less is flowed to an upper coil 10 and a lower coil 11 as to make lines of magnetic force to repel mutually, and press molding in a magnetic field is performed applying the magnetic field radially in the radial direction of the molding substance.

Description

Detailed Description of the Invention The present invention relates to a method for manufacturing a radially anisotropic cylindrical magnet having magnetic anisotropy radially in the radial direction of the cylindrical magnet.
The present invention relates to a press-molding method in a magnetic field that can produce radially anisotropic cylindrical magnets with excellent magnetic properties and a good production yield.

Generally, as magnets used in motors, isotropic cylindrical magnets are used for low output applications, and anisotropic bow-shaped magnets assembled into a cylindrical body are used for high output applications. However, recently,
In order to simplify the assembly process, the high-output magnet is an integrally molded cylindrical magnet with a Br2500 Gauss or higher (B
)() max 1.5 A radially anisotropic cylindrical magnet having magnetic properties higher than that of MGO is desperately needed.

As a method for manufacturing such an integrated radially anisotropic cylindrical magnet, Japanese Patent Application Laid-Open No. 57-31108 discloses a method of manufacturing 32 meshes to 200 meshes in which finely ground ferrite powder is anisotropically granulated in a magnetic field. A method has been proposed in which anisotropic granulated powder is press-molded in a magnetic field.

With this manufacturing method, the magnetic properties of the obtained magnet are good, but the raw material powder consisting only of anisotropic granulated powder increases the manufacturing cost, and the molded product is likely to crack during press molding. There was a problem that manufacturing yield decreased.

The object of the present invention is to provide a manufacturing method for producing a radially anisotropic cylindrical magnet, in which the resulting magnet has high magnetic properties, prevents cracking during molding, and can be produced at low cost.

That is, the present invention provides a die for a cylindrical molded body using a mixed powder of a finely crushed ferrite powder having an average particle size of 2 AIIN or less and a granulated powder different from the finely crushed powder and having a particle size of 14 mesh to +200 mesh. This is a method for producing a radially anisotropic cylindrical magnet, the gist of which is to press-form the molded body in a magnetic field while applying a magnetic field radially in the radial direction of the molded body.

Next, the manufacturing method according to the present invention will be explained based on drawings of a specific press molding apparatus.

The press forming apparatus shown in Fig. 1 has dies (4
), a lower core (5) fixed to the base is placed in the center of the inner space of the die (4), a lower punch (6) is inserted through the lower core (5), and the die holder ( 3) A lower coil (11) is disposed on the lower surface, and an upper core (8) is disposed on the upper plate (7) that can be raised and lowered.
hangs down, and the upper punch (9) is inserted together with the presser foot.
An upper coil (10) is disposed, and a molding space is constituted by a die (4), a lower core (5), a lower punch (6), an upper core (8), and an upper punch (9). The upper and lower punches (6) and (9) are made of non-magnetic material and the others are made of magnetic material, and the inner surface of the die (4) made of magnetic material is coated with non-magnetic material by thermal spraying.

The molding space of the die described above is filled with a mixed powder of finely pulverized ferrite powder having an average particle size of 2ρ or less and granulated powder different from the finely pulverized powder and having a particle size of 14 mesh to 200 mesh. Coil (10) and lower coil (1
5o4o so that the lines of magnetic force repel as shown in 1)
A magnetizing current of less than 0 Gauss is applied, and a magnetic field is applied radially in the radial direction of the molded body while press-molding is performed in a magnetic field.

According to the method of the present invention, when manufacturing a radially anisotropic cylindrical magnet, the resulting magnet has high magnetic properties, prevents cracking during molding, and can be manufactured at low cost.

In this invention, the reason why the particle size of the raw material powder is limited is as follows.
If the average particle size of the finely ground ferrite powder exceeds 2ρ, the magnetic properties will deteriorate, which is undesirable.
This is because if it is less than mesh, press formability will deteriorate.

3- Also, various ferrites etc. can be used as the raw material powder, but for example, Sr ferrite, Ba ferrite, Ca
, SL, N, Pb, BL, and Cr.

The granulated powder in this invention may be anisotropic or isotropic, but isotropic is preferable in terms of moldability and cost.

Examples according to the present invention will be shown below to clarify its effects.

Here, Sr ferrite is added to finely ground ferrite powder.
An example will be explained in which Ba ferrite is used for the isotropic granulated powder, but conversely, if Ba ferrite is used for the finely pulverized powder and Sr ferrite is used for the isotropic granulated powder at an appropriate mixing ratio, the same results will be obtained. It provides excellent magnetic properties and press formability.

A finely pulverized powder of Sr ferrite having an average particle size of 2ρ or less and an isotropic granulated powder of 8a ferrite having a particle size of 14 to 200 mesh are used as a mixed raw material powder at the mixing ratio shown in Table 1, Using the above-mentioned press molding device, 6g3oo was formed into the magnetic circuit.

-Fl -t 4- Apply Gaussian magnetizing current, outer diameter 50mm x inner diameter 35mm
It was molded into a cylindrical molded body with a height of 15 mm in a magnetic field.

After the obtained molded body was subjected to binder removal treatment, 1200
Calcined at ℃. Thereafter, the magnetic properties of the obtained cylindrical magnet were measured. The results are shown in Table 1 along with the crack occurrence rate during molding. In addition, the raw material powder includes only finely ground ST ferrite powder, only Sr ferrite powder granulated in a magnetic field, and B
A The case of using only ferrite granulated powder was similarly carried out and used as a comparative example.

As is clear from Table 1, the method of the present invention provides excellent magnetic properties and significantly reduces the occurrence of cracks during molding. In particular, the mixing ratio of Sr ferrite fine powder colored Ba ferrite granulated powder is
50-80: In the case of 50-20, the most favorable results were obtained with high magnetic properties and no cracks.

Below margin −〇− JP-A-59-141202 (3)

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a press molding apparatus for carrying out the present invention. In the figure, 1... Base, 2... Support, 3... Dice holder, 4... Dice, 5... Lower core, 6...
Lower punch, 7... Upper plate, 8... Upper core, 9... Upper punch, 10... Upper coil, 11.
・Lower coil. Applicant: Sumitomo Special Metals Co., Ltd.

Claims (1)

[Claims] 1. A mixed powder of finely crushed ferrite powder having an average particle size of 2 m or less and granulated powder different from the finely crushed powder and having a particle size of 14 to 200 mesh is filled into a die for a cylindrical compact, A method for producing a radially anisotropic cylindrical magnet, which comprises press-molding in a magnetic field while applying a magnetic field radially in the radial direction of the compact.