JPH09129466A - Manufacture of bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance bond magnet of high density, in which the binder content is reduced by increasing the fluidity of magnetic powder to be charged in a compression mold. SOLUTION: Magnetic powder 1 is mixed with additives of sodium silicate 2 and surfactant 3 so that it can be given fluidity. The fluid powder 1 is poured into a mold cavity, and compressed into a compact. After dried, the compact is subjected to a treatment for making it nonhygroscopic, and then it is magnetized to form a bond magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a bond magnet, which is particularly required to be thin and compact, among magnets used for a speaker or a sensor of rotating equipment such as electric motors and generators and audio equipment.

[0002]

2. Description of the Related Art Speakers for electric motors and audio equipment,
A magnet is used to apply a rotational force to a rotor or to efficiently vibrate a cone, which is a vibrating plate. Then, such a magnet is molded as a bond magnet having a desired shape by, for example, adding a binder to magnet powder, flowing it into a mold cavity, and performing compression molding.

Further, as the electric motor and the speaker are being made thinner and smaller, the bond magnet itself is required to be thinner and smaller, and accordingly, the metal for compression molding is required. Various types have been developed.

By the way, it has been very difficult to produce a thin bond magnet by using the compression molding technique, because it is not easy to pour magnet powder into a cavity of, for example, about 1 to 2 mm. The injection molding method was widely used exclusively for making bond magnets.

In this method of producing a bond magnet by injection molding, for example, as shown in FIG. 2, a kneading means 13 such as a mixer is prepared by adding a resin binder 12 to magnet powder 11.
The magnetic powder 11 and the resin binder 12 kneaded by the kneading means 13 are poured into the injection molding means 14 for injection molding, and the magnetizing means 1 is attached to the released molded body.
5 was used to obtain a thin bond magnet.

[0006]

However, in such a method for manufacturing a bond magnet by injection molding, when a thin bond magnet is molded, the fluidity of the magnet powder is improved and it is poured into a mold. Therefore, the amount of the binder used is larger than that in the case of compression molding, and the density of the obtained molded body itself is lowered. There was a problem that I could not get it.

In addition, such insufficient magnetic characteristics have limited the improvement of the rotation characteristics of the generator and the vibration characteristics of the speaker.

The present invention has been made in order to solve the above-mentioned conventional problems, and facilitates pouring of magnet powder into a mold and suppresses the binder content to achieve a high-density and high-performance bond. An object of the present invention is to provide a method for manufacturing a bond magnet that can obtain a magnet.

[0009]

A method for producing a bonded magnet according to the present invention comprises: kneading magnet powder together with sodium silicate and a surfactant added to the magnet powder; It was poured into a mold cavity and compression-molded, and the molded body thus obtained was dried and solidified, then surface-treated to prevent moisture absorption, and subsequently, the molded body was magnetized to form a bond magnet. It is a thing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram conceptually showing a bond magnet manufacturing apparatus used for carrying out the present invention. In FIG. 1, 1 is a magnet powder, 2 is sodium silicate added to the magnet powder 1 and functioning as a binder,
A surfactant 3 is added to the magnet powder to impart fluidity to the magnet powder.

Further, 4 is a kneading means for kneading the magnet powder 1 and sodium silicate 2 as a binder and a surfactant 3 added to the magnet powder, and 5 is a kneading material poured from the kneading means 4 in advance. It is a compression molding means for performing compression molding in a designed shape.

Further, 6 is a drying and solidifying means for solidifying the molded body molded by the compression molding means 5 by heating and drying, and 7 is a surface for carrying out a surface treatment for preventing moisture absorption by coating or the like on the surface of the dried and solidified molded body. It is a processing means.

Numeral 8 is a magnetizing means for magnetizing the surface-treated compact by passing it through a strong magnetic field.

Next, a method of manufacturing a thin bond magnet using the bond magnet manufacturing apparatus having the above-described structure will be described. First, to a magnet powder 1 prepared in a predetermined amount, sodium silicate 2 as a binder and a surfactant 3 are added.

Specifically, for example, 93.7% by weight of anisotropic rare earth magnet powder, 6.0% by weight of sodium silicate 2 (molar ratio of 2.9) and 0.3% by weight of surfactant. Add 3. Here, as the surfactant 3, sodium alkylallyl sulfonate or the like is used.

Next, the magnet powder 1 to which the sodium silicate 2 and the surfactant 3 have been added as described above is put into the kneading means 4 and sufficiently kneaded. Then, in this kneading operation, the surfactant 3 generates bubbles, and the magnet powder 1 is fluidized by the micro-bearing effect of the bubbles.

Therefore, the kneaded material of the magnetic powder fluidized in this way is sent into the compression molding means 5, and at this time, it is possible to penetrate into the thin and narrow cavity of the mold without any gap. Then, subsequently, compression molding is performed. After the kneaded product is poured into a narrow cavity, it is optional to perform compression molding by the compression molding unit 5 in a magnetic field having a magnetic field strength of 10 kilo Oersted for magnetic orientation, if necessary.

Further, at the time of such compression molding, the excess liquid component contained in the kneaded product is squeezed out and removed, and then the molded product is taken out to reduce the content (residual amount) of the binder contained in the kneaded product, As a result, it is possible to realize a high density of the molded body.

Subsequently, the molded body thus obtained is subjected to 60 at a temperature of, for example, 150 ° C. in a drying and solidifying machine 6 as a drying furnace.
Solidify while heating and drying for minutes.

If the molded product thus solidified is left to stand, it will be adsorbed and the quality and magnetic properties will be deteriorated. For this reason, the surface treatment means 7 performs surface treatment for preventing moisture absorption, such as forming a coating film on the surface by painting.

The molded body thus surface-treated is passed through a strong magnetic field generated by the magnetizing device 8, where it is magnetized to form a thin bond magnet.

Thus, by adding the sodium silicate 2 as a binder to the magnet powder 1 and thereby allowing the surfactant 3 to be added, a kneaded product of the magnet powder 1, the sodium silicate 2 and the surfactant 3 is added. The fluidity of can be sufficiently increased. As a result, it is possible to form a bond magnet by compression molding and realize a high density of the molded body by this compression molding to improve the magnetic characteristics and rotation characteristics of a motor, a generator, a speaker of an audio device, and the like. be able to.

[0023]

As described above, according to the present invention, the magnet powder is kneaded together with the sodium silicate and the surfactant added thereto, and the magnet powder to which the fluidity is imparted by the kneading is poured into the mold cavity. Then, the molded body thus obtained was dried and solidified and then subjected to a surface treatment for preventing moisture absorption, and subsequently, the molded body was magnetized to form a bond magnet. A high-thinness bond magnet can be formed by using the compression molding method. Therefore, it is possible to manufacture a small-sized electric motor, generator, speaker or the like having good magnetic characteristics at low cost.

[Brief description of the drawings]

FIG. 1 is a block connection diagram showing a bond magnet manufacturing apparatus used for carrying out the method of the present invention.

FIG. 2 is a block connection diagram showing a conventional bond magnet manufacturing apparatus.

[Explanation of symbols]

 1 Magnet powder 2 Sodium silicate 3 Surfactant

Claims (1)

[Claims] 1. A magnet powder is kneaded together with sodium silicate and a surfactant added to the magnet powder, and the magnet powder to which fluidity is imparted by the kneading is poured into a mold cavity and compression-molded. A method for producing a bond magnet, comprising drying and solidifying the molded body, performing surface treatment for preventing moisture absorption, and subsequently magnetizing the molded body to form a bond magnet.