JPS5980904A - Manufacture of bond magnet - Google Patents

Abstract

PURPOSE:To obtain an isotropic bond magnet easily by a simple equipment by a method wherein an extruded body is given an isotropic property by a pulse magnetic field applied to its magnetized surface and, after being dried, treated by a thermal process and impregnated by organic macromolecule compound and, after being solidified or hardened, magnetized to the same direction as the isotropic property has been given. CONSTITUTION:Organic binder, fine particle additive and mixing medium are added according to the requirement to ferrite particles and mixed and kneaded. This mixture is supplied into a hopper 1 and mixed and kneaded and compressed by a kneader screw 2 and cut by a shredder 3 and extruded by an extruding screw 6 through a tapered barrel 7 and a die 8. The extruded body is cut to a prescribed length at an outlet of the die. Reduction ratio at the extrusion is expressed by the ratio So/S of the area So of the auger of the extruder and the area S of the outlet of the die. The suitable So/S ratio is 3-100 and especially a range of 20-70 is desirable. When the reduction ratio is too small, isotropicalization isn's progressed enough and when the reduction ratio is too large, cracking or breaking occurs at the time of extrusion. The extruded body thus obtained is dried and treated by a thermal process and then impregnated by macromolecule compound and solidified or hardened and magnetized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing ferrite magnets used in electronic copying machines, audio equipment, rotating equipment, and the like.

BACKGROUND ART Injection molding, compression molding, and extrusion molding methods are generally used to mold bonded magnets such as plastic magnets and rubber magnets used in speakers, small DC motors, magnetic rotating machines, and the like. Among these forming methods, when obtaining anisotropic bonded magnets with particularly high magnetic properties, a contaminant consisting of magnetic powder, a binder, and optionally added surface modifiers, lubricants, etc. is used in a magnetic field. This is done by magnetic field molding using hot compression molding. In addition, studies have recently begun on injection molding in a magnetic field, and disk-shaped anisotropic plastic magnets have been produced. The extrusion molding method is applied to the production of cylindrical or plate-shaped rubber magnets or plastic magnets used in small motors and the like.

In addition, it is also possible to form long cylindrical ferrite magnets for magnet rolls by extrusion molding according to Japanese Patent Application Laid-open No. 49-7553.
It is shown in No.6.

Among the various molding methods mentioned above, extrusion molding has high molding efficiency, does not require a mold with a complicated structure like injection molding, and can be continuously molded, making it possible to significantly improve productivity. In addition, since anisotropy is imparted during extrusion molding, improvement in magnetic properties can be expected, but this is insufficient to satisfy the properties of an anisotropic ferrite bonded magnet. In addition to extrusion molding, which is generally used for sintered magnets, as shown in Japanese Patent Publication No. 47-34192, special nozzles are used in addition to applying a magnetic field. proposals have been made. In order to obtain an anisotropic bonded magnet by extrusion molding in this way, molding in a magnetic field is generally used, but the applied external magnetic field becomes a resistance during extrusion molding. When the external magnetic field is strengthened for the purpose of strengthening the dissimilarity, especially in screw type continuous extrusion molding machines,
Auger slippage occurs, often making forming difficult or impossible.

Furthermore, the magnetic a device itself becomes larger.

An object of the present invention is to provide a manufacturing method that allows anisotropic bonded magnets to be easily obtained by extrusion using a simple device.

The method for manufacturing a bonded magnet of the present invention involves extrusion molding a mixture consisting mainly of magnet plumbite magnetic particles and optionally adding a mixing medium, a binder, and particulate additives, and drying the obtained molded product. In the method for producing a ferrite magnet by sintering, a pulsed magnetic field is applied to the magnetized surface of the molded body to impart anisotropy, and after drying and heat treatment, an organic high-component It is characterized in that after the compound is impregnated into the molded body and solidified or hardened, it is deposited in the same direction as the direction in which the appearance is imparted.

The details of the present invention will be explained below based on the drawings. FIG. 1 shows a schematic sectional view of a screw type extrusion molding machine. First, magnetic plumbite type ferrite particles are prepared as a raw material, but if the particle size of the particles is small, the formability will decrease, while if the particle size is too large, multidomains will be formed and the coercive force will drop sharply. The particle size of the particles preferably ranges from about 0.7 to 1.8 μm. In addition to the ferrite particles, an organic binder such as methyl cellulose carboxymethyl cellulose may be added in an amount of about 2% by weight or less based on the ferrite particles to improve moldability.

In the conventional manufacturing method of bonded magnets, it is necessary to use particles that have been annealed in advance at about 800 DEG C. to 1100 DEG C., since the presence of dislocations, defects, etc. in the Ferrite particles deteriorates the magnetic properties. The binders used include polyamide resin, 71-noryl resin, ethylene vinyl acetate copolymer resin, polypropylene, polyamide 1 imide, polystyrene, polyphenylene sulfide, and rubber-based polymers such as chloroprene butadiene, chlorosulfonated polyethylene, and nitrile. High-component materials such as rubber and acrylic rubber are known and used. That is, a bonded magnet is usually obtained by heating and mixing pre-annealed ferrite particles and the binder at an appropriate temperature to create a compound, and then heating and forming the compound. When obtaining an anisotropic magnet, molding is performed in a magnetic field.

In the method of the present invention, the ferrite magnetic powder does not need to be annealed in advance, and the above-mentioned normal ferrite powder of about 0.7 to 1.5 μm is sufficient. As a binder during molding, the above-mentioned methylcellulose or the like is used. Also, a mixed medium such as water or alcohol may be added, but the amount of mixed medium is 10
If the viscosity is less than % by weight, the viscosity will be too high, and the drawing effect during extrusion will not promote differentiating properties, and the forming density will locally vary, and cracks may occur after forming, drying, or heat treatment. It becomes. On the other hand, if the amount of the mixed medium is 30 weight, although anisotropy is promoted, problems such as cracks occurring during drying and densification during molding are inhibited occur. Therefore, the mixing amount is preferably in the range of 10 to 30% by weight based on the ferrite particles.

Organic binder as required for the above ferrite particles,
Fine particle additives and a mixing medium are added and kneaded for two nights, etc., and this mixture is charged into the hopper 1 shown in FIG.
At this time, the vacuum chamber 4 is degassed by the vacuum pump 5, and the extrusion screw 6 is used to cut the tapered barrel 7.
The molded body is then extruded through the mold 8 and cut into a predetermined length at the mold exit. The drawing ratio during extrusion molding is expressed as So/S, where the auger area of the extrusion molding machine is SO and the surface of the mold is S, and So/S is preferably in the range of 3 to 100. More preferred is 20-7
It is 0. That is, if the reduction ratio becomes too small, anisotropy will not be sufficiently promoted, while if the reduction ratio becomes too large, cracks and cracks will occur during molding.

The molded body thus obtained is dried and heat treated, then impregnated with a polymer compound, solidified or hardened, and roughly magnetized to form the final product. The first feature of the present invention is that instead of using ferrite particles that have been annealed in advance, a heat treatment equivalent to annealing is performed after forming. It is possible to obtain high properties by promoting the secondary orientation of .

The temperature of the heat treatment is 700 to 11, depending on the particle size, composition, etc.
The temperature is preferably 50°C, preferably 800 to 1050°C.

In addition, as a result of various studies on the method of anisotropy, which is the second feature of the present invention, we found that before drying the extruded product, it was placed in a magnetizing device and a magnetic field was applied once or multiple times as necessary. It has been found that by doing so, it is possible to achieve a magnetic force that is about 40% higher than that of conventional isotropic bonded magnets made by extrusion molding.

A case in which the application of this magnetic field is applied to a cylindrical molded body will be described below. First, the yoke 9 is prepared as shown in Fig. 2, and then the molded body 10 is inserted into the yoke.In order to prevent the molded body 10 from drying out, its surface is covered with a conductive material such as paper, cloth, vinyl, brass, etc. It is preferable to coat with 11. Next, a coil (not shown) of the yoke 9 is energized to instantaneously generate a pulsed magnetic field. The application of this pulsed magnetic field deforms the molded body and orients the ferrite grains, and eventually the portions corresponding to the magnetic poles protrude to form a polygonal shape. Furthermore, a static magnetic field may be used for the magnet instead of a pulsed magnetic field. After magnetic field treatment in this way, a cylindrical permanent magnet is obtained by drying, heat treatment, impregnation solidification, further processing and magnetization. In this case, when observing the flow of magnetic lines in the cross section of the cylindrical molded body after drying, it is clear that the magnetic lines have become different as shown in FIG. When paper was placed on top of this cylindrical molded body and several pieces of iron powder were placed on top of it, the iron powder was arranged along the lines of magnetic force as shown in Figure 3-4.

In applying the above-mentioned pulsed magnetic field, the yoke coil may be connected to an instantaneous DC power supply that inputs, for example, a commercial AC power supply, boosts and rectifies it to a predetermined free-current voltage, charges a group of capacitors, and then discharges it via a Neuristor. Further, if the pulse magnetic field is approximately 10 KOe or more, it is sufficient to obtain a normal anisotropic ferrite magnet. In addition, the cylindrical magnet used in the magnet 1-roll is approximately 20 KOe.
A magnetic field of the above is sufficient.

As a result of various experiments, the present inventors confirmed that when the present invention was applied to a cylindrical magnet with an outer diameter of 20 to 73 mm for a magnet roll, a B r of 2000 G or more could be obtained. Also, the thickness for speakers is 15-30m1+1
．． It was confirmed that B r of 2000 G or more can be obtained even in a plate-shaped magnet with a width of about 100 mm and a length of about 500 nm. It should be noted that the present invention can be applied to magnets of various shapes by changing the shape of the mold, and it goes without saying that in addition to the above, ring-shaped or arc-shaped magnets can also be manufactured.

Example 1 Average grain i: 11 μm 3a fluorite grains 7K (+.

70 g each of CaO and 3i 02, 709 carboxymethyl cellulose, and 1.5 KO of water were uniformly kneaded in a badge-type kneader, and then mixed into DE-1 manufactured by Honda Iron Works.
It was inserted into a 50-type extrusion molding machine, molded, and then cut at the exit of the mold to have an outer diameter of 30 m+ and an inner diameter of 12 m+++.

A cylindrical molded body with a length of 300 mm was obtained. The surface of this molded body was covered with vinyl and inserted into a symmetrical 8-pole magnetizing yoke, and a pulsed magnetic field of approximately 20) (Qe) was applied.Next, the vinyl was peeled off from the surface of the molded body, and after drying, ~10
After heat treatment at 50° C., vacuum impregnation with phenolic resin I R3000 manufactured by Jifu Jizai Kogyo @J was performed.

Table 1 shows the results of magnetic properties. As the heat treatment temperature increases, the density also increases slightly, and both the Br value and the surface magnetic flux density Ba value improve.

In any case, the bonded magnet obtained by the method of the present invention is
Despite the low density, the magnetic properties are equal to or better than those of isotropic sintered crystals.

The bottom row of Table 1 shows the final values obtained by subjecting the anisotropic compact obtained by the method of the present invention to normal sintering. Naturally, the magnetic properties are higher than that of bonded magnets, but the density is also higher. In the case of sintered crystals, the Ba value may be about 2000G, but if the orientation progresses too much, cracks and cracks will occur during cooling due to thermal stress.For long cylindrical magnets, reduce the rotational torque. Therefore, weight reduction is required,
The 1000° C. heat-treated material of the present invention has optimal characteristics as a mag roll for copying machines.

Comparative Example 1 Average particle size 1.3 annealed at 1000°C in advance
The same treatment as in Example 1 was carried out using μm 3a frit particles. As a result of reheating the molded body, 100
At temperatures below 0°C, the molded product easily collapsed. 105
The magnetic properties at 0°C were similar to those of the 950°C heat-treated product in Example 1. That is, although it is of course possible to apply ordinary magnetic powder for bonded magnets to the manufacturing method of the present invention, the heat treatment temperature becomes about 100° C. higher, which is not a good idea in terms of energy.

Example 2 7 kg of 3r fluorite particles with an average particle size of 1 μl.

62 g of Ba Q, 70 Q each of Ca O and St 02, 709 Q of methylcellulose and 1.5 g of water.
kQ was mixed in the same manner as in Example 1, and further, only the mold of the extrusion molding machine of Example 1 was changed to extrude molding, and then cut at the exit of the mold to obtain a plate-shaped molded product. Cover the surface of this ferrite magnet with paper and insert it into the magnetizing yoke to generate approximately 10K
A pulsed magnetic field of e was applied. Next, the paper was peeled off from the surface of the molded body, and after drying and heat treatment at 1050℃, lock ties 1~
SMS-1008 was vacuum impregnated.

The outer periphery is processed and magnetized to a thickness of 20 mm and a width of 100 mm.
A plate-shaped ferrite magnet with a length of 500 mm and a length of 500 mm was obtained. The Br of this magnet is 2800G x Hc = 3500G
, conventional high-performance plastic or rubber mug (Br
2600G max), 13r is 2
00G and a significant improvement in magnetic properties was observed.

As described above, according to the present invention, the following effects can be obtained.

(1) A high-performance anisotropic ferrite magnet can be obtained using a simpler device than forming in a magnetic field and in a relatively low magnetic field.

(2) A normal magnetizing yoke can be used to apply a pulsed magnetic field to impart anisotropy, so there is no need to provide special equipment.

(3) Since an extruded molded body is used, ferrite magnets of various shapes such as cylindrical, plate, and 9-arc shapes can be obtained by simply changing the mold.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of an extrusion molding machine used in the present invention, Fig. 2 is a cross-sectional view to explain the application of a pulsed magnetic field in the present invention, and Fig. 3 is a cross-sectional view showing an example of an extrusion molding machine used in the present invention. FIG. 3 is a diagram showing the flow of magnetic lines of force in a cylindrical ferrite magnet. 1: Hopper, 2: Kneading screw, 3: Extrusion screw, 8: Mold, 9: Yoke, 10: Molded body, 11: Insulator. Figure 1, Figure 2 @ / 1 Figure 3

Claims (1)

[Claims] 1 Mainly composed of magnet plumbite type magnetic particles,
A mixture prepared by adding a mixing medium, a binder, and particulate additives as necessary is extruded, the resulting molded body is dried, and then heat treated, and then a polymer compound is impregnated into the molded body for solidification or curing. In the manufacturing method of a bonded magnet obtained by A method for manufacturing a bonded magnet, characterized by: 2. A cylindrical or ring-shaped molded body is formed by extrusion molding, the outer peripheral surface of the molded body is coated with an insulating material or a conductive material, and then inserted into a magnetizing device, and then in a direction perpendicular to or parallel to the axis. The method for manufacturing a bonded magnet according to claim 1, characterized in that a magnetic field is applied to the molded body. 3. The method for manufacturing a bonded magnet according to claim 2, characterized in that the magnetic field applied to the molded body is a magnetic field of about 5KO8 or more. 4. Claim 1, characterized in that a pulsed magnetic field of about 20 KOe or more is instantaneously applied once or multiple times to a molded body with an outer diameter of 20 to 80 m111 to make the B' of 1 final product 2000 G or more. The method for manufacturing a bonded magnet described in 5. After coating the surface of a plate-shaped molded body with an insulator or a conductor, applying a pulsed magnetic field of about 10 KOe or more to the molded body,
2. The method of manufacturing a bonded magnet according to claim 1, wherein the final product has a 3r of 2000G or more. 6. It is characterized by forming an arc-shaped molded body with an outer diameter of 20 mm or more by extrusion molding, coating the outer peripheral surface of the molded body with an insulator or a conductor, and then applying a pulsed magnetic field of about 10 K Oe or more. Method for manufacturing bonded magnets. 7. The method for manufacturing a bonded magnet according to claim 1, which comprises applying a magnetic field to the molded body, drying it, and then subjecting it to heat treatment. 8 After heat treating the molded body, impregnate it with a polymer compound.
A method for manufacturing a bonded magnet according to claim 1, characterized in that the bonded magnet is hardened and then assimilated or hardened.