JPH0148643B2 - - Google Patents

Description

Detailed Description of the Invention Field of Application 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, which provides excellent magnetic properties and good manufacturing performance. The present invention relates to a press molding method in a magnetic field that can produce radially anisotropic cylindrical magnets with a low yield. BACKGROUND ART In general, as magnets used in motors, isotropic cylindrical magnets are used for low output, and anisotropic bow-shaped magnets assembled into a cylindrical body are used for high output. However, recently, in order to simplify the assembly process, high-output magnets have been developed using integrally molded cylindrical magnets.
A radially anisotropic cylindrical magnet with high magnetic properties of Br2800 Gauss or higher and (BH)max1.8MGO or higher 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 for producing 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 the manufacturing yield decreased. Purpose of the Invention The object of the present invention is to provide a 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. Structure of the Invention This invention consists of 50wt% to 80wt% of finely pulverized Sr ferrite powder having an average particle size of 2 μm or less, and Ba having a particle size of 14 mesh to +200 mesh.
The gist is to fill a cylindrical compact die with a mixed powder of 50wt% to 20wt% isotropic granulated powder of ferrite, and press-form in a magnetic field while applying a magnetic field radially in the radial direction of the compact. This is a method of manufacturing a radially anisotropic cylindrical magnet. Disclosure Based on Drawings of the Invention 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.
The lower core 5 fixed to the base is placed at the center of the inner space of the die 4. A lower punch 6 is inserted through the lower core 5.
A lower coil 11 is arranged on the lower surface of the die holder 3. Further, an upper core 8 hangs down from the upper plate 7 which is held movably up and down, and an upper punch 9 is attached together with the presser foot.
is inserted through it, and an upper coil 10 is disposed therein. A molding space is constituted by the die 4, the lower core 5, the lower punch 6, the upper core 8, and the upper punch 9. The upper and lower punches 6 and 9 are made of non-magnetic material and the other punches 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. In the molding space of the above die, an average particle size of 2μm
Finely ground powder of Sr ferrite consisting of 50wt%~
Isotropic granulated powder of Ba ferrite consisting of 80wt% and particle size of 14 to 200 mesh 50wt% to 20wt
Filling the mixed powder with %. As shown in the figure, a magnetizing current of Bg4000 Gauss or less is passed through the upper coil 10 and the lower coil 11 so that the lines of magnetic force repel each other, and press molding is performed in a magnetic field while applying a magnetic field radially in the radial direction of the compact. 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. Reason for limitation In this invention, the reason why the particle size of the raw sulfur powder is limited is that the average particle size of the finely pulverized Sr ferrite powder is 2μ.
If it exceeds m, the magnetic properties will deteriorate, which is undesirable, and if the particle size of the isotropic granulated powder of Ba ferrite exceeds 14 meshes and becomes less than 200 meshes, press formability will deteriorate. In addition, the reason for limiting the amount of finely ground Sr ferrite powder and isotropic Ba ferrite powder is that
If the finely ground powder of ferrite is less than 50wt%, or if the isotropic granulation of Ba ferrite exceeds 50wt%, the magnetic properties will deteriorate, which is undesirable, and if the finely ground powder of Sr ferrite exceeds 80wt%, Alternatively, if the isotropic granulated powder of Ba ferrite is less than 20 wt%, cracks occur during molding and press formability deteriorates, which is not preferable. Further, various ferrites can be used as the raw material powder, and for example, powder containing one or more of Ca, Si, Al, Pb, Bi, and Cr in Sr ferrite and Ba ferrite may be used. The granulated powder in this invention is preferably isotropic from the viewpoint of cost. Examples Examples according to the present invention will be shown below to clarify its effects. Finely pulverized Sr ferrite powder with an average particle size of 2 μm or less and isotropic granulated Ba ferrite powder with a particle size of 14 to 200 mesh were mixed into raw material powder at the mixing ratio shown in Table 1. . Using the press molding equipment described above, a magnetizing current of Bg3000 Gauss was passed through the magnetic circuit, and the outer diameter was 50 mm.
A cylindrical molded body with dimensions of 35 mm inner diameter and 15 mm height was molded in a magnetic field. After the obtained molded body was subjected to binder removal treatment,
It was fired at 1200℃. 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, when a mixed powder of finely pulverized Sr ferrite powder and isotropic granulated Ba ferrite powder outside the scope of the present invention is used as the raw material powder, and only finely pulverized Sr ferrite powder is used, Sr ferrite granulated in a magnetic field is used. Comparative examples were carried out in the same manner using powder only and Ba ferrite granulated powder only. As is clear from Table 1, it can be seen that the method of the present invention not only provides excellent magnetic properties but also significantly reduces the occurrence of cracks during formation. 【table】

[Brief explanation of drawings]

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.

Claims (1)

[Claims] 1. 50 wt% to 80 wt% of finely pulverized Sr ferrite powder with an average particle size of 2 μm or less, and Ba consisting of a different kind from the finely pulverized powder with a particle size of 14 to 200 mesh.
A mixed powder of 50wt% to 20wt% of isotropic granulated ferrite powder 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.