JPS6037112A - Manufacture of anisotropic composite magnet - Google Patents

Abstract

PURPOSE:To increase magnetic force largely by a simple facility by using a mold with a magnetic circuit for pulses, generating a pulse magnetic field and orientating magnetic particles in the mold by the magnetic field. CONSTITUTION:A mold is constituted by mounting a yoke section 5 consisting of a magnetic material and conductors 4 around a cylindrical molding space 2, to the inside thereof a core 1 is fitted concentrically, through a thin cylinder 3 composed of a nonmagnetic material. A kneaded material consisting of ferromagnetic powder, such as ferrite powder having magnet plumbite type crystallographic structure, alnico magnet powder, etc. and one kind or two kinds or more of thermoplastic resins, such as polyethylene, polypropylene, etc. is prepared as raw materials. The kneaded material is charged to an injection molding machine with the mold, and a pulse magnetic field is applied into the mold at least once during the time when a molded material is cooled and solidified on an injection molding or after a molding. A obtained anisotropic molded shape is cooled and solidified, and taken out of the mold. The outer diameter of the obtained molded shape is processed to predetermined size as required, and the molded shape is magnetized in the same direction as the anisotropic direction, thus acquiring an anisotropic cylindrical magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a composite magnet made by adding resin or plastic material to magnetic powder such as 7-elite powder,
In particular, the present invention relates to a manufacturing method of a cylindrical, swing-shaped, or cylindrical polar anisotropic composite magnet using injection molding.

1 of 5 manufacturing methods for bonded magnets made by adding resin or plastic material and, if necessary, a surface modification material of magnetic powder to magnetic powder such as Bα ferrite or Sr ferrite
Injection molding is known as one method. - As is well known, the injection molding method consists of the following steps. First, the above-mentioned starting materials are mixed in a predetermined ratio, mixed by heating, and then uniformly mixed into a roughly granular kneaded material (hereinafter referred to as a compound) in a predetermined particle size range using a pelletizer or hot-cut device. ). Next, after putting the compound into an injection molding machine, the compound is injection molded into a mold with a molding space from a molding machine set at an appropriate temperature condition.
After cooling and solidifying in the mold, the formed body is taken out and magnetized to obtain a composite magnet. The composite magnet obtained by such a method is, for example.

JP-A-56-108207, JP-A No. 57-150407
The 6th Duke of No.

As described in the report, application to magnetic rolls has been proposed, and application to small motors has also been proposed.

By the way, when manufacturing a composite magnet, the composite magnet has a lower magnetic powder content than a sintered magnet by an amount corresponding to the resin content (matrix) (in order to obtain magnetic properties equivalent to a sintered magnet, For example, as described in Japanese Utility Model Application Publication No. 51-62596, so-called anisotropy is achieved by aligning the axis of easy magnetization of ferromagnetic powder with the direction of the lines of magnetic force inside the magnet after magnetization until cooling solidification is completed. It is well known that a process of ferromagnetic powder is necessary, especially when using cylindrical, ring-shaped, and cylindrical composite magnets whose surfaces are magnetized with multiple magnets. It is important to match the easy axis of magnetization with the direction of the lines of magnetic force inside the magnet after magnetization, and this internal magnetic structure is most advantageous in obtaining high magnetic properties.

Regarding the manufacturing method by injection molding of cylindrical, ring-shaped, and cylindrical composite magnets having anisotropy (hereinafter collectively referred to simply as anisotropic cylindrical magnets), for example, Japanese Patent Publication No. 1987- As described in Japanese Patent No. 170501, a mold is used in which a magnetic yoke and a non-magnetic spacer are alternately combined surrounding a molding space, and a magnetizing coil is installed on the outside, or a mold is provided with a magnetizing coil around the outer periphery of the molding space. It is common to use a mold in which the When using these molds, in order to generate a magnetic field of a predetermined strength in the molding space, a high-voltage, low-current power source is used, and the number of turns of the magnetizing coil is increased to increase the magnetomotive force. However, it has the following drawbacks.

In other words, the space for accommodating the coil becomes large, resulting in an increase in the size of the equipment. Furthermore, in order to effectively converge the magnetic field excited by the magnetized coil by the yoke from outside the mold into the molding space, the length of the magnetic path must be increased, and therefore a considerable portion of the magnetomotive force is consumed as leakage magnetic flux. It ends up.

An object of the present invention is to provide a method for manufacturing an anisotropic composite magnet that eliminates the drawbacks of the prior art and allows for a wide range of magnetic directions with relatively simple equipment.

The manufacturing method of the anisotropic composite magnet of the present invention basically consists of adding a polymer compound such as resin or plastic material to ferromagnetic powder, and then adding a surface modifying material to the ferromagnetic powder as necessary. A mixture made by adding additives is injection molded, the molded body is then cooled and solidified, and then magnetized.
During the manufacturing process, during injection molding or immediately after molding and before cooling and solidification, a magnetic pole is placed at a predetermined position around the molding space in a temperature range above the softening point of the polymer material or below one Curie point of the magnetic particles. A mold is used in which an orientation yoke is installed and a conducting wire is placed inside the yoke, and a pulsed magnetic field is generated by passing a pulsed current through the conducting wire one or more times, and the magnetic field causes the magnetic particles to It is characterized by the orientation and closing.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a mold used in the present invention. In Fig. 1, the mold has a cylindrical molding space 2 in which a core 1 made of a non-magnetic or magnetic material is disposed concentrically, and a thin cylinder 3 made of a non-magnetic material surrounded by a cylindrical molding space 2. A yoke portion 5 made of a magnetic material and a conductive wire 4 are attached thereto. The magnetic pole part 6 during orientation is formed integrally with the yoke part 5. However, it is of course possible to manufacture the magnetic pole part 6 separately from the yoke part 5 and then integrally combine the two.

The magnetic circuit of the mold having the above structure is created by passing pulse currents in opposite directions alternately through the conductor parts 4 and 4P (for example, in FIG. ) Each magnetic pole section 6 (8 pieces in the figure) constitutes an N pole and an S pole alternately. Figure 1 shows the case of 8 symmetrical poles, but the number of magnetic poles is not limited to an even number, but may be an odd number, and the magnetic pole arrangement may be symmetrical, or asymmetrical, and various modifications can be made according to requirements. However, the present invention is not limited to the magnetic circuit shown in Fig. 1. By using the above mold, the magnetic flux generated by the pulsed current can be effectively focused within the molding space. Compared to the conventional electromagnetic method that uses high voltage and low current.

The circuit is significantly miniaturized.

When observing the crossing of the magnetic lines of force in the cross section of the cylindrical permanent magnet obtained with the above mold (but under the same conditions as the specific example described later), it is clear that it has become anisotropic as shown in Figure 2. be. In other words, this cylinder.

When paper was placed on top of the shaped injection molded article and iron powder was sprinkled on top of it, the iron powder was arranged along the lines of magnetic force as shown in FIG. As a source for generating the above-mentioned pulsed magnetic field, for example, an instantaneous DC power supply that takes commercial AC current as input and generates pulsed current multiple times intermittently using an all-thyristor full-wave phase control method, or a source that is boosted and rectified to a predetermined DC voltage. After charging the capacitor group, connect it to an instantaneous DC power source that discharges through the thyristor. Also, the magnitude of the pulsed magnetic field.

Therefore, 8 Koe, preferably 1 oKo- or more is sufficient to obtain a normal cylindrical anisotropic ferrite magnet. As a result of various experiments, the inventors of the present invention found that the outer diameter of 15° to 73 m used in magnet rolls for electrophotography was 1.5 mm.
When the present invention was applied to the manufacture of a cylindrical magnet of mφ, it was found that it had eight symmetrical poles and a surface magnetic flux density BO of aooG or more.

The above magnet is obtained with an isotropic plastic of the same shape.

High performance compared to bear magnet rolls.

It was confirmed. The present invention can be applied to the production of magnets of nine different shapes by changing the shape and number of poles of the mold and magnetic circuit. Of course, magnets can also be obtained.

In the present invention, an anisotropic composite grinding stone can be obtained using the above-mentioned mold, for example, through the following steps. - First, as raw materials, ferrite powder having a magnetic plumbite type crystal structure such as Ba ferrite and Sr7 elite, alnico magnet powder, and FeCrCol.

ferromagnetic powder such as magnet powder or rare earth cobalt magnet powder, and one or more thermoplastic resins such as polyethylene, polypropylene, polyamide (for example, nylon (trade name)), I-ethylene vinyl acetate copolymer, etc. Prepare a mixer consisting of.

The amount of ferromagnetic powder mixed depends on the specific gravity of the powder.

From the viewpoint of magnetic properties, the content is preferably 60% by weight or more. In addition, a small amount of lubricant such as calcium stearate may be added to improve moldability, and an organic silicate compound or organic titanate may be added to improve the wettability between the ferromagnetic powder and the polymer compound.

Compounds may also be added in small amounts. Note that the contaminants are made into approximately granular form by pelletizers, hot-cut equipment, etc.

It is preferable to keep them aligned.

Next, the above-mentioned contaminant is put into an injection molding machine equipped with a mold as shown in Fig. .

Apply the magnetic field at least once. The obtained anisotropic molded body is taken out from the mold after being cooled and solidified.

The obtained molded body is processed to have an outer diameter of a predetermined size θ as necessary, and then magnetized in the same direction as the anisotropic direction, so that it has a magnetic flux density distribution as shown in FIG. 3, for example. An anisotropic cylindrical magnet is obtained. FIG. 3 shows the surface magnetic flux density in the radial direction of the surface of the magnet shown in FIG. 2, which is anisotropically made into eight symmetrical poles using Sr-ferrite as the ferromagnetic powder.

In the above explanation, we have described the manufacture of a composite magnet for Maznet rolls that is magnetized with 8 symmetrical poles. However, by changing the number of magnetic poles of the orientation yoke, the position between the poles, etc. Of course, it is possible to obtain a composite magnet that is anisotropic in an asymmetric 9-magnitude state. Further, the shape and dimensions of the yoke constituting the magnetic circuit may be appropriately set by an analysis method such as the finite element method depending on the required magnetic properties.

The present invention will be explained in detail below.

Sr-7 elite magnetic powder with an average particle size of 1 to 2 μm 7.65
Polyamide resin (Toshi nylon-6) 1.5s for Kf
After mixing Kf, kneading was carried out at approximately 250° C. using a fractured, pressurized viscera kneader manufactured by Moriyama. Next, the mixture was pulverized using a durbo cutter to create a granular compound with a diameter of about 3 to 5 mm. This compound was put into an injection molding machine (manufactured by Nisshin Jushi Kogyo Co., Ltd.) equipped with the mold shown in FIG. 1, and injection molding was performed at a temperature of about 270° C. and a pressure of νd. Immediately after molding, the magnetic circuit inside the mold is powered by a power source based on the all-Sirisk full-wave phase control method.
A magnetic field (approximately 1 DKoa) was intermittently applied by a pulsed current under the conditions of mION and 120 FF. After cooling, the outer diameter is 5Qmmφ.

A long cylindrical magnet with an inner diameter of 10 mmφ and a length of 2 dQms was obtained.

Note that by placing the metal shaft in the mold in advance during injection molding, conductor insert molding of the shaft and the composite magnet can be performed. The outer diameter of the obtained molded body was 29rIL.
? When 7Lφ was magnetized after processing and the distribution of surface magnetic flux density in the radial direction was measured, the waveform shown in FIG. 3 was obtained.

It can be seen that this value of approximately 1000G is more than 1.5 times the characteristic of approximately 600G of the isotropic composite magnet.

As described above, according to the present invention, multipolar anisotropic composite magnets of various shapes such as a cylindrical shape with sufficient anisotropy can be obtained by using a mold having a pulsed magnetic circuit. In comparison, equipment can be significantly downsized.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of a mold used in the present invention, FIG. 2 is a sectional view showing the anisotropy of a cylindrical composite magnet obtained by the present invention, and FIG. FIG. 3 is a diagram showing a radial surface magnetic flux density distribution on the surface of a long cylindrical composite magnet obtained by the invention. 1: Core 2: Molding space 3: Thin cylinder 4: Conductor 5: Yoke part 6: Magnetic pole part (nooo1

Claims (1)

[Claims] A mixture whose main components are ferromagnetic powder and a polymer compound,
In a method for manufacturing a composite permanent magnet, injection molding is performed in a mold having a molding space with a circular cross section, and then the resulting molded product is cooled and solidified.・Using a mold in which an orientation yoke is installed and a conductive wire needle is provided in the orientation yoke, a pulse current is applied to the conductor wire one or more times to a temperature above the softening point of the polymer compound or to the ferromagnetic material. 1. A method for producing an anisotropic composite magnet, characterized in that a pulsed magnetic field is generated by applying electricity within a temperature range of one point or less of the powder, and the orientation of the ferromagnetic powder is promoted by the magnetic field.