JP2002353025A - Plastic magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic magnet, where the disposals of its magnetic poles and the density of its magnetic flux can be set arbitrarily in order to improve the freedom of the design for miniaturizing and simplifying the apparatuses which utilize it. SOLUTION: The plastic magnet is the assembly of micro-particles made of a ferromagnetic alloy, where there is molded and magnetized the fused and kneaded substance made of spherical ferromagnetic-alloy particles and a thermoplastic resin, which has such a nanocomposite structure that the individual particles are separated from each other by metal oxide layers, scattered substances, or voids. Further, in the plastic magnet, the disposals of its magnetic poles and the density of its magnetic flux are set arbitrarily, and its leakage magnetic flux to its side surfaces is made not larger than 40% of all the total magnetic fluxes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic magnet having a high degree of design freedom for downsizing and simplifying an apparatus using a magnet.

[0002]

2. Description of the Related Art In Japanese Patent Application Laid-Open No. 2000-286120, an S pole is formed adjacent to an N pole formed on one end surface side,
The density of the magnetic flux directed from the magnet magnetized only on the one end face side or the S pole formed adjacent to the N pole from the N pole formed on the one end face side to the other end face part There is disclosed a magnet having a density higher than the density of magnetic flux from an N pole formed on one side to an S pole formed adjacent to the N pole on the other end face side. By using such a magnet, the size of the device using the magnet can be reduced,
Increase design freedom for simplicity.

As a method of manufacturing such a magnet, Japanese Patent Application Laid-Open No. 2000-286120 discloses a magnetic flux from an N pole formed on one end face to an S pole formed adjacent to the N pole on one end face. In order to form a magnet whose density is higher than the density of magnetic flux from the N pole formed on the other end face to the S pole formed adjacent to the N pole on the other end face, A magnetizing method is disclosed in which a magnetic field is applied to a magnetic body with the N pole and the S pole facing only one end surface side of the magnetic body before magnetization.

A plastic magnet is first melt-kneaded with a ferromagnetic alloy powder and a thermoplastic resin, extruded and formed into pellets, and the pellets are heated and molded in a desired shape in the presence of a magnetic field. It can be obtained by:

The ferromagnetic alloy powder is usually obtained by mechanically pulverizing an alloy having a predetermined composition. For example, rare earth-containing iron alloys (R / Fe / B system: R is rare earth)
Can be obtained by first quenching a molten alloy into a film and then mechanically pulverizing it. When the film is mechanically pulverized, it is microscopically obtained in the form of flakes, and the size is not constant. When such particles are used, the fluidity during pellet production is poor, so it is necessary to increase the amount of resin or increase the extrusion pressure. In addition, such a shape of the magnetic powder is caught by each other when being heat-formed in the presence of a magnetic field, and the magnetic poles of all the magnetic powders are not aligned in the same direction. Not preferred.

[0006]

The arrangement of magnetic poles and the magnetic flux density can be arbitrarily set in order to increase the degree of freedom of design for miniaturization and simplification of a device using a magnet, and it is excellent in magnetic characteristics. Provide plastic magnets.

[0007]

The plastic magnet according to the present invention is an aggregate of fine particles of a ferromagnetic alloy, and the individual fine particles are isolated from each other by a metal oxide layer or interspersed objects or voids. It is formed by molding and magnetizing a melt-kneaded product of a spherical ferromagnetic alloy particle having a nanocomposite structure and a thermoplastic resin, and has an arbitrarily set magnetic pole arrangement and magnetic flux density. It is characterized by being 40% or less of the total magnetic flux.

[0008] When the ferromagnetic alloy particles are spherical, they do not catch on each other when heated and formed in the presence of a magnetic field, and almost all of the magnetic powder magnetic poles are aligned in the same direction as the given magnetic field, Since the leakage of the magnetic flux is small, a plastic magnet having excellent timing characteristics can be obtained. The average particle diameter of the spherical ferromagnetic alloy particles is preferably in the range of 10 μm to 100 μm.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The plastic magnet according to the present invention having an arbitrarily set magnetic pole arrangement and magnetic flux density is disclosed in Japanese Patent Application Laid-Open No. 2000-286120. An S pole is formed adjacent to the pole, and a magnet is magnetized only on the one end face side, or an N pole formed on one end face side is formed on the one end face side adjacent to the N pole. It also includes a magnet in which the density of the magnetic flux toward the pole is higher than the density of the magnetic flux from the N pole formed on the other end face side to the S pole formed adjacent to the N pole on the other end face side.

[0010] The present invention relates to an aggregate of fine particles of a ferromagnetic alloy, wherein the fine particles have a nanocomposite structure in which individual fine particles are separated from each other by metal oxide layers or interspersed objects or voids. As an example of a method for producing magnetic alloy particles, the molten ferromagnetic alloy droplets scattered radially from the center to the centrifugal field by centrifugal force are forced into an annular upward flow of a gas mainly composed of argon in the centrifugal field. Manufactured by contact. Specifically, a molten ferromagnetic alloy is supplied onto a high-speed horizontally rotating disk, and centrifugal force is applied to the molten ferromagnetic alloy to scatter radially as small droplets in a centrifugal field. An annular upward flow of argon-based gas discharged from a slit-shaped opening provided upward or obliquely upward in a donut-shaped gas supply pipe installed at a position concentric with the disk and forced in a centrifugal field Contact.

The gas mainly composed of argon refers to a gas containing 100% of argon or a trace amount of a reactive gas, particularly an argon gas containing oxygen. The oxygen concentration in the argon gas is preferably 2 ppm by volume or less. Due to the presence of this trace amount of oxygen, an extremely thin metal oxide film is formed on the surface of the generated fine spherical ferromagnetic alloy particles, and serves to prevent further oxidation from proceeding in air.

FIG. 1 shows an example of the structure of a centrifugal granulator used for producing spherical ferromagnetic alloy particles having a nanocomposite structure. The granulation chamber 1 has a cylindrical shape at the top and a cone shape at the bottom, and has a lid 2 at the top. A nozzle 3 for pouring molten metal is inserted vertically into the center of the lid 2, and a rotating disk 4 is provided directly below the nozzle 3. The rotating disk 4 is rotated at a high speed by a motor 5 connected directly below the rotating disk 4. A discharge pipe 6 for the generated fine spherical metal particles is connected to the lower end of the cone portion of the granulation chamber 1. The upper part of the nozzle 3 is connected to an electric furnace (high frequency furnace) 7 for melting the metal to be granulated. A donut-shaped gas supply pipe 8 is provided below the upper surface of the disk 4 and at a position concentric with the disk 4 (or the rotating shaft of the motor 5 immediately below). The donut-shaped gas supply pipe 8
It has a slit-shaped opening 9 for discharging gas upward. The argon gas or the trace oxygen-containing argon gas from the gas supply tank 10 is supplied to a donut-shaped gas supply pipe 8 through a pipe 11. The gas supply amount is controlled by the valve 12. Reference numeral 13 denotes an exhaust device, and a valve 1 connected to the exhaust device.
By manipulating 4, the pressure in the granulation chamber is controlled to an arbitrary value. The granulation chamber 1 is provided with a water cooling jacket 15. Reference numeral 16 denotes a cooling water inlet pipe, and reference numeral 17 denotes a cooling water discharge pipe.

FIG. 2 is an enlarged view of the vicinity of the rotary disk and the donut-shaped gas supply pipe in the apparatus shown in FIG. 1, and FIG. 3 is a horizontal sectional view of the portion shown in FIG. The metal melted in the electric furnace 7 is supplied from the nozzle 3 onto the high-speed horizontal rotating disk 4. The supplied molten metal is formed into fine droplets by the action of the centrifugal force by the high-speed horizontal rotating disk 4 and scatters radially into the centrifugal field as shown by a dotted line 20. On the other hand, the gas mainly composed of argon discharged upward from the slit-shaped opening 9 of the donut-shaped gas supply pipe 8 forms an annular rising gas flow indicated by a dotted line 21. Both the molten metal droplet 20 scattered radially in the centrifugal field and the annular rising gas flow 21 mainly composed of argon come into contact with each other near the annular region indicated by the symbol A, and the molten metal becomes very close to a true sphere very quickly. To solidify. When a small amount of a reactive gas, for example, oxygen is contained in an annular gas flow mainly composed of argon, a part of the metal component becomes an oxide and becomes fine spherical metal particles having a nanocomposite structure.

[0014]

EXAMPLE 1 The apparatus shown in FIG.
m, rotating speed of 100,000 rpm, peripheral linear velocity of 183 m / sec.
-Fe-B; R is a rare-earth metal) supplied and melted by centrifugal force to be scattered as small droplets, which are discharged from a donut-shaped gas supply pipe (400 mm in diameter of the slit portion) having an upward slit-like opening. Contact was made with an annular ascending flow of argon gas. Further, the exhaust device 13 was operated to lower the pressure in the granulation chamber below the atmospheric pressure. An electron micrograph of the obtained particles is shown in FIG. Particles having a diameter of about 20 μm and having a nearly uniform sphere were obtained. This spherical ferromagnetic powder 92
A mixed pellet of 8% by weight and 8% by weight of a nylon resin was compression-molded into a disk having a diameter of 10 mm and a thickness of 2 mm, and was magnetized to produce a plastic magnet. The magnetic flux density of this magnet was about 1000 gauss. FIG. 5 shows an enlarged photograph of the magnet surface. It can be seen that the ferromagnetic powders of spherical and uniform size are orderly distributed. FIG. 6 is an enlarged photograph of a state where the nylon resin is dissolved and removed from the plastic magnet. Spherical magnets are connected, in which magnets having north and south poles are arranged at the north and south poles of the sphere like the earth.

[0015]

Comparative Example 1 A 92% by weight of a commercially available ferromagnetic powder obtained by quenching a rare earth-containing iron alloy (R.Fe.B system: R is a rare earth) and 8% by weight of a nylon resin was obtained. The mixed pellet was compression-molded into a disk having a diameter of 10 mm and a thickness of 2 mm, and was magnetized to produce a plastic magnet. The magnetic flux density of this magnet was about 500 gauss.

[0016]

As described above, in order to increase the degree of freedom of design for miniaturization and simplification of a device using a magnet, the arrangement of magnetic poles and the magnetic flux density can be arbitrarily set, and a plastic magnet having excellent magnetic properties can be obtained. Can be

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an apparatus for producing spherical ferromagnetic alloy particles.

FIG. 2 is an enlarged view of the vicinity of a rotating disk and a donut-shaped gas supply pipe in the apparatus shown in FIG.

FIG. 3 is a horizontal sectional view of a portion shown in FIG. 2;

FIG. 4 is an electron micrograph of the particles obtained in Example 1.

FIG. 5 is an electron micrograph of the plastic magnet obtained in Example 1.

FIG. 6 is an enlarged photograph showing a state in which a spherical magnet obtained by dissolving and removing a nylon resin from the plastic magnet obtained in Example 1 is connected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Granulation chamber 2 Cover 3 Nozzle 4 Rotating disk 5 Motor 6 Particle discharge pipe 7 Electric furnace 8 Donut-shaped gas supply pipe 9 Slit-shaped opening 10 Gas supply tank 11 Piping 12 Valve 13 Exhaust device 14 Valve 15 Water cooling jacket 16 Cooling Water inlet pipe 17 Cooling water outlet pipe 18 Gas supply pipe for comparison test 19 Valve 20 Droplets of molten metal scattered 21 Ring-shaped argon gas flow 22 Valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiki Kuwahara 6-40-11 Honcho, Shibuya-ku, Tokyo F-term (reference) 4K017 CA01 DA04 ED02 FA08 FA29 4K018 BB03 BB04 BB06 GA04 KA46 5E040 AC05 BD03 CA01 HB15 NN01

Claims (4)

[Claims] 1. A spherical ferromagnetic alloy having a nanocomposite structure, which is an aggregate of microparticles of a ferromagnetic alloy, in which individual microparticles are isolated from one another by metal oxide layers or interspersed objects or voids. It is formed by molding and magnetizing a melt-kneaded product of particles and a thermoplastic resin, has an arbitrarily set magnetic pole arrangement and magnetic flux density, and leakage magnetic flux to the side surface is 40% of the total magnetic flux.
A plastic magnet characterized by the following. 2. The plastic magnet according to claim 1, wherein the magnetic pole arrangement arbitrarily set is such that the N-pole surface and the S-pole surface have different areas on the same surface. 3. The spherical ferromagnetic alloy particles having an average particle size of 10
The plastic magnet according to claim 1, which has a size of μm to 100 μm. 4. Spherical ferromagnetic alloy particles having a nanocomposite structure in which individual microparticles are aggregates of ferromagnetic alloy microparticles and are separated from each other by metal oxide layers or interspersed objects or voids. 2. The method according to claim 1, wherein the molten ferromagnetic alloy droplets scattered radially from the center to the centrifugal field by centrifugal force are forcibly brought into contact with the annular upward flow of gas mainly composed of argon in the centrifugal field. Plastic magnet.