JPH05205959A - Method and device for manufacturing bow-type anisotropic magnet - Google Patents

Abstract

PURPOSE:To enable a bow-shaped anisotropic magnet of high magnetic force to be easily mass-producted at a low cost by a method wherein a magnet is made to pass through a magnetic field wider than its cross section in area, anisotropically orientated, and cooled down while it passes so as to be enhanced in hardness and fixed in orientation. CONSTITUTION:Mixture of magnetic powder and binder is introduced into an extruder, kneaded and degased through a kneading/extruding mechanism, heated at a temperature of 50-90 deg.C, and successively and continuously extruded out from the discharge opening 1 of the extruder. The mixture introduced into a sizing die 3 is successively formed into a magnet of bow-shaped cross section conforming to the cross section of a forming hole 3a, and concurrently magnetic particles contained in the kneaded mixture are oriented in a prescribed direction by the action of a magnetic field generated by a magnetic field generator 6. In succession, the body of bow-shaped cross section through the sizing die 3 is successively introduced into a prolong 5 as it is successively subjected to the action of a magnetic field generated by the magnetic field generator 6, cooled down gradually to a normal temperature or below while it passes through the prolong 5, and successively discharged out from the prolong 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method and a manufacturing apparatus for permanent magnets made of magnetic powder such as ferrite magnets and rare earth magnets, especially bow-shaped anisotropic magnets.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a permanent magnet using a magnetic powder such as a ferrite magnet or a rare earth magnet as a raw material,
Mostly, it is based on the sintering-finishing process, and the molding process is mostly based on the compression molding method. For example, most of the ferrite bow-shaped anisotropic magnets currently on the market are manufactured by the dry method and the wet method of compression molding.

For example, a unit crystal grain m of a ferrite magnet
7 is a magnet plumbite type that belongs to the hexagonal system, has a hexagonal plate shape with a particle diameter of about 1 μm, and exhibits a strong spontaneous magnetizing force in the direction of its crystal axis (C axis). Anisotropy of the ferrite magnet means that iron oxide and strontium or barium oxide are mixed at a ratio of 6: 1 and calcined to mature the raw material, and then the unit crystal grain size is increased. Up to C and apply a magnetic field
This means that the axis is aligned in the direction of the magnetic field, compression and fixation are performed, and then sintering is performed. However, the molded body W anisotropically oriented in molding shrinks 20% in the direction of the magnetic field M, that is, the direction of the C axis of the hexagonal plate-shaped particles in sintering, as shown in FIG. It shows 10-12% shrinkage in the direction of the right angle. This indicates that a large amount of strain remains in the sintered body. That is, even though the shape is simple in the field, the powder in the inner hole of the mold in the steps of powder filling, magnetic field, and compression, the orientation of the powder due to the density of the magnetic field, the disorder of the direction of the magnetic force lines, etc. Since the uneven distribution of the partial density is unavoidable, the difference in shrinkage ratio results in a large and complicated strain remaining in the sintered body. Therefore, for example, even in the case of manufacturing a simple disk-shaped anisotropic magnet, the density is high in the center and low in the periphery, and the sintered body is cracked or cracked due to internal strain due to leakage of magnetic field lines. And so on. This causes more problems when compression molding an irregular magnet such as the bow-shaped anisotropic magnet Mg shown in FIG.

FIG. 10 shows the above-mentioned bow-shaped anisotropic magnet Mg.
FIG. 1 shows an example of a conventional molding die in the case of manufacturing by compression molding. In the figure, 50 is a die made of a non-magnetic material,
1 and 52 are upper and lower punches made of a ferromagnetic material which are arranged above and below in the inner hole 50a of the die 50, and 53 is a magnetic field coil. When the magnetic powder is compression-molded by the above-mentioned molding die, first, the magnetic powder is filled in the upper part of the lower punch 52 arranged in the die inner hole 50a. At that time, the bulk density of the magnetic powder is about 1.0, which is in an extremely coarse state. When the upper punch 51 is lowered in this state, and the lower end of the upper punch reaches the upper end of the die, the magnetic field coil 53 is energized and a magnetic field is generated in the inner hole of the die. The magnetic field causes the magnetic particles to be oriented with the C-axis oriented in the direction of the magnetic field, that is, in the vertical direction in the figure. At the same time, the upper punch 51 further descends and moves to the position indicated by the chain line in the figure, and the magnetic powder is densely compressed in the above-mentioned oriented state. The pressure at that time is about 1 to 2 t / cm, and the bulk density of the magnetic powder at the end of compression is about 3.0. Next, after the above-mentioned compression operation is completed, the magnetic field is released, and a reverse damping magnetic field is applied for demagnetization to demagnetize the molded body. After that, the pressure of the upper and lower punches is released, the die 50 descends, and the inner hole 50
After the molded body is extracted from the inside of a and is sintered, it is polished to a predetermined shape and dimension.

The upper and lower punches 51, 52 used for the compression molding as described above are formed so that the opposing surfaces have a convex arc surface on one side and a concave arc surface on the other side so as to have an arc shape close to a product shape.
Both ends of the convex arc surface and the concave arc surface are often formed into substantially horizontal surfaces as shown in FIG. Therefore, the upper surface of the magnetic powder when the magnetic powder is filled in the inner hole of the die during compression molding is generally flat, and the upper surface of the lower punch is an arc surface. The filling thickness is different, and when compression molding is performed on the upper punch concave surface, the density of the molded body is unevenly distributed. Further, the above compression molding gradually progresses under a magnetic field, and the magnetic force is focused on the upper and lower punches, so that the magnetic flux density changes as the upper and lower punches approach, and the magnetic force is strong in the center, weak on the side and weak on the side. Also, leakage of magnetic field lines occurs. As a result, the central portion has a high density, and the side portions and the concave portions have a low density. Further, due to the local generation of the light and shade of the magnetic field, the orientation direction of the particles also deviates.

As described above, when manufacturing the arcuate magnet by the compression molding method, the density shading in the molded body and the deviation of the orientation direction are unavoidable. Therefore, during sintering, shrinkage ratio deviation and shrinkage direction deviation occur in the molded body,
Frequent distortion, cracks, cracks, etc. To deal with this, magnet manufacturers put a lot of effort into the field technology, but the current situation is that there is no deciding factor.

On the other hand, it is also known to manufacture a permanent magnet by extrusion molding, and there are an extrusion molding method as a so-called resin magnet manufacturing method and a molding for manufacturing a magnet by molding and sintering magnetic powder. Some are performed by extrusion molding. The former is easy to manufacture because a product can be obtained without sintering after extrusion molding, but an anisotropic magnet having a large magnetic force cannot be obtained. In addition, as the latter one in which magnetic powder is extruded, there is one in which extrusion molding is applied to the production of a cylindrical radial anisotropic magnet (for example, JP-A-56-125).
813 and 56-125814.

[0008]

However, the above conventional manufacturing method has the following problems, and even if the manufacturing method is applied to manufacture of an arched anisotropic magnet, good results are not always obtained. In fact, bow-shaped anisotropic magnets have not been manufactured by extrusion. The biggest reason is that the magnetic force is inferior to that produced by the compression molding method. The cause is that in the compression molding method, the orientation of the particles achieved at the time of molding is compressed and fixed as it is and demagnetized.
This is because it is difficult to fix the orientation when using the extrusion molding method.

For example, in the case where extrusion molding is applied to the manufacture of the above-mentioned conventional cylindrical radial anisotropic magnet, the material of the discharge port of the extruder is a soft magnetic material, and a cylindrical die connected to this is used. A radial magnetic field is formed in the molding hole of the magnetic coil etc. to continuously extrude and knead the kneaded material of the magnetic powder and the binder, and at the same time, the particle orientation is performed, but the orientation state of the magnetic particles after passing through the die. However, there is a defect that the orientation is broken because no means for maintaining the above is taken. That is, in the above-mentioned conventional device, the ratio of the magnetic powder to the binder and the water does not change even after passing through the die, so that the magnetic powder is free to move, and therefore, as shown in (a) and (b) of FIG. Magnet 56 and iron yoke 5
When passing through a die equipped with a magnetic field generating means such as No. 7, even if the particles are oriented in the magnetic field, at the time of exiting the magnetic field, they may be attracted by the magnetic field of the die and deflect backward. It was Further, since the molded product (work) is magnetized even after molding, for example, the one oriented as shown in (a) of FIG. Due to the action of the internal demagnetizing field, there is a problem that the orientation is broken as shown in FIG.

The present invention has been proposed in view of the above problems, and an object thereof is to provide a manufacturing method and a manufacturing apparatus capable of mass-producing bow-shaped anisotropic magnets having a strong magnetic force easily and at low cost. To do.

[0011]

In order to achieve the above object, the present invention has the following constitution. That is, in the method for manufacturing an arched anisotropic magnet according to the present invention, as a main step, a molding step of continuously extruding a kneaded material of magnetic powder and a binder into a cross-section bow shape, and a molding step formed by the molding step. And a sintering step of cutting the product into a predetermined length and sintering, and in the molding step, a kneaded product of the magnetic powder and the binder is maintained in a predetermined heating state and oriented in a flowable state. Extruded into an arcuate cross section, and during the extrusion, the kneaded product is passed through a magnetic field generated in a region wider than the arcuate cross section to impart anisotropic orientation and cooled during passage of the magnetic field. The feature is that the orientation is fixed by increasing the hardness. As the above-mentioned binder, for example, one or both of hydroxyethyl cellulose and polyethylene oxide, water, and polyethylene glycol are used. In that case, the heating temperature of the kneaded product is 5
The temperature may be within the range of 0 ° C to 90 ° C, and the cooling may be performed at room temperature or lower. Further, the bow-shaped anisotropic magnet manufacturing apparatus according to the present invention is provided with a heating means, and the kneaded material of the magnetic powder and the binder is extruded while maintaining the kneaded product in a predetermined warmed state, and is formed into a cross-section bowed shape. A sizing die having a hole and a prolong provided with a cooling means are continuously provided, and a magnetic field is generated in at least a part of the sizing die and the prolong to generate a magnetic field in the sizing die in a region wider than the forming hole. Means are provided.

[0012]

According to the above-described method for manufacturing the bow-shaped anisotropic magnet of the present invention, the kneaded material of the magnetic powder and the binder is extruded into a bow-shaped cross section in a fluid state in which the kneaded material can be oriented while maintaining a predetermined heating state. By doing so, a molded product having an arcuate cross-section is continuously formed. At that time, the kneaded product is passed through a magnetic field generated in a region wider than the arcuate cross-section to form an anisotropic orientation. By performing the treatment, both the circumferential ends of the arcuate cross section are favorably and averagely oriented, and the orientation is fixed by cooling while increasing the hardness during passage of the magnetic field to fix the orientation. It becomes possible to fix the orientation in the same state as it was. Further, the manufacturing apparatus of the bow-shaped anisotropic magnet according to the present invention is provided with a heating means, and the kneaded product of the magnetic powder and the binder is extruded while maintaining the kneaded product in a predetermined warmed state, and the cross-section has a bow-shaped cross section. A sizing die having a forming hole and a prolong provided with a cooling means are continuously provided, and a magnetic field for generating a magnetic field in the sizing die in a region wider than the forming hole in at least a part of the sizing die and the prolong. By providing the generating means, the kneaded material of the magnetic powder and the binder is subjected to anisotropic orientation by passing through the magnetic field generated in a region wider than the above-mentioned arcuate section at the time of extrusion molding, and while passing through the magnetic field. By cooling, the hardness of the work can be increased and the orientation can be fixed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and an apparatus for manufacturing an arched anisotropic magnet according to the present invention will be specifically described below based on the embodiments shown in the drawings. FIG. 1 is a vertical sectional side view of a main part showing an embodiment of a bow-shaped anisotropic magnet manufacturing apparatus according to the present invention, and FIG. 2 is an enlarged cross-sectional front view of the main part. In the figure, 1 is a discharge port of the extruder, and the kneading / extruding mechanism and the like of the extruder are omitted in the figure. However, if the magnetic powder and the binder can be kneaded, deaerated, and extruded, various conventionally known ones can be used. The configuration is applicable.
A sizing die 3 made of a non-magnetic and abrasion resistant material is connected to the discharge port 1 through a non-magnetic material introducing member 2, and the kneaded material from the discharge port is placed inside the sizing die 3. A forming hole 3a having an arcuate cross section (arcuate shape) for forming a predetermined arcuate shape is formed.

Introducing passages 1a and 2 for introducing the kneaded material into the molding hole 3a are provided inside the discharge port 1 and the introducing member 2.
a is formed, and the heating coil 4 for keeping the temperature of the kneaded material is provided on the outer periphery thereof. Reference numerals 1b and 2b are flanges for connecting the discharge port 1 and the introduction member 2. Also the above sizing die 3
A prolong 5 made of a material similar to that of the sizing die 3 or a non-magnetic material having a good thermal conductivity is provided on the extension line of. The cross-sectional shape of the prolong 5 is formed to be substantially the same as that of the sizing die 3, and the inner hole 5
"a" is formed to be equal to or slightly larger than the molding hole 3a of the sizing die 3 so as to reduce the frictional resistance of the kneaded material.

Further, magnetic field generating means 6 is provided on the outer circumferences of the sizing die 3 and the prolong 5 so as to cover the entire circumference of the sizing die 3 and a part of the prolong 5. The magnetic field generating means 6 may be either a permanent magnet or an electromagnetic coil, but it is economical to use a permanent magnet such as a rare earth iron magnet. In the embodiment, as shown in FIG. 2, the rare earth iron magnets 6a and 6b are arranged in close contact with each other on the upper and lower sides of the sizing die 3 and the prolong 5, and the facing surfaces of the magnets 6a and 6b are the sizing die 3 and the sizing die 3 respectively. Forming hole 3 through the slight thickness of
The magnets 6a and 6b are opposed to each other so that their opposing surfaces have different polarities so that a magnetic field in the radial direction is generated as indicated by an arrow in the figure. In the illustrated example, the opposing surfaces of the magnets 6a and 6b are set to be larger than the circumferential length of the bow-forming hole 3a of the sizing die 3,
At least within the circumferential length of the molding hole 3a, the strength and direction of the magnetic field are uniformly generated.

A cooling means 7 is provided in close contact with the outer periphery of the prolongation on the side of the magnetic field generating means 6, and the cooling means 7 is provided with a water passage hole 7b inside the cooling member 7a in the case of the figure.
Is formed, and cooling water is circulated in the hole 7b to cool the hole. The cooling member 7a and the prolong 5
Is preferably made of a material having a high thermal conductivity, and when the magnets 6a and 6b as the magnetic field generating means are also made of a material having a high thermal conductivity, the magnets are also cooled by the cooling means to cool the molded product. Can be increased. In this example, a rare earth iron magnet having a thermal conductivity of 7.7 kcal / m · h · ° C was used.

Next, the manufacturing method according to the present invention will be specifically described by taking as an example the case of manufacturing an arched anisotropic magnet using the manufacturing apparatus shown in FIGS. First, add magnetic powder such as ferrite magnets that have been sufficiently crushed to approximately the unit crystal grain size,
Mix the binder. As the binder, for example, one or both of hydroxyethyl cellulose and polyethylene oxide, water, and polyethylene glycol are used. In that case, the mixing ratio is
0.1 to 6.0 parts by weight of either or both of hydroxyethyl cellulose and polyethylene oxide, 100 to 5 parts by weight of magnetic powder, 5 to 25 parts by weight of water, and 0.1 to 20 parts of polyethylene glycol. It is about parts by weight.

The mixture of the magnetic powder and the binder is put into an extruder, and is sufficiently kneaded and deaerated by a kneading / extruding mechanism (not shown in the figure) in the extruder to 50 ° C. to 90 ° C.
Within a range of, for example, 70 ° C., and the kneaded product is continuously and continuously extruded from the discharge port 1 of the extruder. Then, the kneaded material is introduced into the sizing die 3 via the introducing member 2. At this time, the kneaded product is kept in a fluid state by being maintained at the above-mentioned 70 ° C. by the heating coil 4 for keeping heat in order to improve the mobility of the magnetic particles.

The kneaded material introduced into the above-mentioned sizing die 3 is successively shaped into an arcuate cross-section in accordance with the cross-sectional shape of the shaping hole 3a, and at the same time the magnetic field generated by the magnetic field generating means 6 causes the kneaded material to remain in the kneaded material. The magnetic particles are oriented in a predetermined direction. That is, in the embodiment, the C-axis of the magnetic particles is oriented in the radial direction of the arcuate section. Further, since the magnetic field generated by the magnetic field generating means 6 is widely formed in the circumferential direction of the above-mentioned arcuate cross section, the orientation treatment is satisfactorily performed up to both circumferential end portions of the molded body.

Next, the formed body (workpiece) formed by the sizing die 3 to have an arcuate cross section is successively guided into the prolong 5 while being subjected to the action of the magnetic field by the magnetic field generating means 6, and the prolong 5 is produced. In the process of passing through the inside of 5, it is gradually cooled to about room temperature, for example, about 25 ° C., and is sequentially discharged from the prolong 5. Therefore, the hardness of the molded body increases rapidly, and the magnetic particles are fixed while maintaining the above-mentioned orientation state.

FIG. 3 shows the relationship between the temperature change of the kneaded product and the molded product at this time and the orientation of the particles, the orientation fixing, and the shape fixing. The properties of the kneaded product are shown on the right side of the figure.
After the viscosity is lowered in the temperature range of about 90 ° C. to 90 ° C. to improve the fluidity of the kneaded product and the orientation is completed, the temperature is about 60 ° C. to 4 °
At 0 ° C., the viscosity is increased, the hardness is increased, the progress is made, and the cooling and hardening is performed so as to be 40 ° C. or less before passing through the mold magnetic field. Eventually, the molded body is cooled to approximately room temperature and leaves the prolong 5 in a solidified or semi-solidified state. Since the molded product is almost solidified at this stage,
The molded product is discharged from Prolong 5 without disturbing the particle orientation.

Next, the molded product is dehydrated by performing vacuum dehydration operation at room temperature, that is, the molded product is completely cured (completely solidified), and an alternating damping magnetic field is applied to force demagnetization and a predetermined length. The cutting is performed to complete the process for the sintering process. Then, a product is obtained through a sintering process.

As described above, when the high-temperature melting binder is used, the binder and the magnetic powder are sufficiently kneaded, and the kneaded product is sufficiently soft for the particles to orient and the magnetic field has sufficient strength. The degree of grain orientation is high and average,
Moreover, a good bow-shaped anisotropic magnet can be obtained without any density deviation in the molded product. In particular, in Examples, since a binder having a low melting point of 55 ° C to 60 ° C is adopted,
The kneaded product increases in softness with a slight heating, and the molded product has the characteristic of solidifying with a slight cooling.The magnetic field is taken a little longer, orientation is completed in the first half of the magnetic field, and the molded product is solidified by cooling immediately. Since the orientation can be fixed, the problems of the conventional extrusion molding and the defects of the compression molding can be eliminated. When a rare earth iron magnet is used as the magnetic field generating means as in the embodiment, a magnetic flux density of about 6000 G to 6640 G is obtained in the die forming hole at a distance of 6 mm between both poles, and a magnetic flux density of 4000 G in the case of the conventional compression forming. ~ 5
It can be much higher than 000G.

Further, as described above, the biggest reason why the extrusion molding method is not adopted for manufacturing the bow-shaped anisotropy is that the magnetic force is inferior to that of the compression molding method. It was found that while the conventional compression molding method has a value of about 4.9 to 5.0, the present invention can achieve a small difference of about 4.8 to 4.85. Moreover, by fixing the orientation by the extrusion molding method according to the present invention,
An arcuate anisotropic magnet having a magnetic force equal to or higher than that of the conventional compression molding method can be manufactured more easily than the compression molding method.

In the above embodiment, the facing surfaces of the magnets 6a and 6b as the magnetic field generating means 6 are arranged at equal intervals over substantially the entire length in the circumferential direction as shown in FIG. 2, but as shown in FIG. The interval at the center in the direction may be gradually larger than the interval at both ends. By doing so, knocking can be reduced when used as a magnet for a motor, for example. That is, for example, when the radially oriented bow-shaped anisotropic magnet Mg is used as a motor magnet as shown in FIG. 5, the C axes of the magnetic particles are arranged so as to point to the center of the rotor R, and When the magnetic flux density is measured by placing the probe in close contact with the inner circumference and rotating it by 360 °, a curve like a solid line a in FIG. 6 is drawn. When such a trapezoidal curve is shown and the opposite polarities clearly appear at both ends, unevenness of slow speed occurs when the rotor rotates, knocking occurs, and smooth and smooth rotation cannot be achieved. This is a fatal drawback when used as a motor for audio equipment and electronic computers. It is known that the magnetic flux distribution as shown by the broken line b in FIG. Therefore, as shown in FIG. 4, when the distance between the facing surfaces of the pole magnets 6a and 6b is gradually made larger in the circumferential center than at both ends, the magnetic force lines M are separated from the inner pole of the arc as shown in the figure. Bend to gradually expand to both sides as you go to the pole,
The C axis of the magnetic particles will be oriented along it. As a result, when viewed microscopically, the C-axis is inclined and directed toward the center of the inner arc of the manufactured arc-shaped magnet, so that the magnetic force is concentrated on the center of the inside of the arc. The magnetic flux density when used as a motor magnet as shown in FIG. 6 is as shown by the broken line b in FIG. 6, and it is possible to reduce the knocking. Although the shape of the lower surface of the upper permanent magnet 6a in FIG. 4 is changed,
The shape of the upper surface of the lower permanent magnet 6b may be changed, or both may be changed. In short, the inclination of the magnetic force line passing through the arcuate shaped hole 3a can be easily controlled by changing the radii of the arcs of both poles, and the user's request can be easily met.

[Experimental Example] 40 kg of strontium ferrite powder, 3 kg of polyethylene glycol powder,
0.2 kg of hydroxyethyl cellulose was prepared in advance. Strontium ferrite powder has an average particle size of 1.0μ,
First, polyethylene glycol having an average molecular weight of 20,000 and being in powder form and hydroxyethyl cellulose being in powder form are first thoroughly mixed with a mixer. Next 5.5k of water
g was added to this, and the mixture was put into a kneading machine for kneading and deaeration. Next, the mixture was put into an extrusion molding machine having a vacuum deaeration and heating cylinder to perform extrusion molding. In addition, the dimension of the magnetic field sizing die forming hole in the discharge part of the extruder is set to be 17.5 m
m × outer diameter 22 mm × chord width 21.2 mm, sandwiching a sizing die, Br12.2KG, bHe11.4K
Both poles were formed using a rare earth iron magnet of Oe. Magnetic flux density 6440 near the center of the sizing die forming hole
G was obtained and its length was 120 mm. The temperature of the kneaded material in the extruder was 70 ° C., and the cooling was water at 20 ° C. The molded product was elongated to obtain a semi-solid product.
This was cut into a length of about 300 mm and placed in a vacuum dryer. The vacuum dryer was a 5.5 kW water-sealed vacuum pump, and the degree of vacuum was 500 mmHg, and it took about 2 hours.

As a result, the water content in the molded product became a little less than 4%, and the molded product became a hard solid. Next, this was demagnetized by a pulse demagnetizer from a peak output of 1500 A by alternating attenuation, then cut to 22 mm, and sintered at 1220 ° C. for 10 hours. After sintering, the outer radius is 11 mm by polishing
× Inner radius 8.1 mm × Chord width 16.0 mm × Length 13 mm
I got a bow-shaped magnet. Magnetizer is 450μF, 1500V
By the output of the above, an arc magnet having an N pole inside and an magnet having an S pole inside are formed.

Comparative Example 1 Next, as the above-mentioned comparative example, 40 kg of strontium ferrite powder was taken, and extrusion molding was carried out in the same manner as in the above-mentioned example for the binder, water and pretreatment. However, no cooling treatment was applied to the molding. As a result, a molded product having a high temperature and a high degree of softness was obtained. When it was left in the air, cooled and hardened, it was dehydrated, cut, and subjected to sintering and polishing finish under exactly the same conditions as in Example to obtain an arc-shaped magnet having the same dimensions as in Example. The magnetization was also performed under the same conditions as in the example.

[Comparative Example 2] As yet another comparative example, an isotropic arc-shaped magnet having the same size was produced by a usual compression molding method, and magnetized in the same manner as in the above-mentioned example.

The magnets obtained in the above Examples and Comparative Examples 1 and 2 were set inside a cylinder having a thickness of 1 mm and an inner diameter of 22.05 mm with arcuate magnets having N and S poles facing each other. When the total flux was measured, the magnetic force shown in Table 1 below was obtained for each example. The ratios in the table below are ratios when the isotropic case of Comparative Example 2 is 100. As is clear from the above table, the examples according to the present invention are 99% more than isotropic in Comparative Example 2 and 27% more than the conventional extrusion molding method, that is, the extrusion molding method in which cooling and solidification is not performed.
Has improved.

[0031]

As described above, according to the method for manufacturing the bow-shaped anisotropic magnet of the present invention, the kneaded material of the magnetic powder and the binder is maintained in a predetermined heating state and can be oriented in a cross-section in a flowable state. Extruded into a bow shape, the kneaded product at the time of the extrusion molding is passed through a magnetic field generated in a region wider than the cross section of the bow to give an anisotropic orientation, and is cooled and hardened while passing through the magnetic field. Since the orientation is fixed by raising the temperature, the orientation is satisfactorily extended to both ends in the circumferential direction of the above-mentioned arcuate section, and the orientation is fixed by cooling while passing through a magnetic field to increase the hardness. As a result, the orientation can be fixed in the state in which the orientation is excellent as described above. Therefore, as in the conventional extrusion molding method, the magnetic particles in the molded product are drawn backward to disturb the orientation, or the orientation is disturbed by the internal repulsive magnetic force when the magnetic field is emitted in a state where the molded article is not sufficiently cured. It is possible to prevent the disorder, and it is possible to mold with a simpler mold and mechanism than the conventional compression molding method. Further, according to the manufacturing apparatus of the present invention, a sizing die having a cross-sectionally arcuate forming hole at a discharge port of an extruder for extruding while maintaining a kneaded material of magnetic powder and a binder in a predetermined heating state, and a cooling means. And a prolong provided continuously, and at least a part of the sizing die and the prolong are provided with a magnetic field generating means for generating a magnetic field in the sizing die in a region wider than the molding hole, which is an extremely simple structure. This makes it possible to mass-produce bow-shaped anisotropic magnets with strong magnetic force easily and inexpensively.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a bow-shaped anisotropic magnet manufacturing apparatus according to the present invention.

FIG. 2 is a cross-sectional front view of the main part of the manufacturing apparatus in the above embodiment.

FIG. 3 is an explanatory diagram showing the relationship between the temperature of the kneaded material and the orientation state during the extrusion process.

FIG. 4 is a cross-sectional front view of essential parts showing a modified example of the manufacturing apparatus for the arched anisotropic magnet according to the present invention.

FIG. 5 is an explanatory diagram showing an arrangement configuration when an arcuate magnet is used as a motor magnet.

FIG. 6 is an explanatory diagram showing a magnetic flux density distribution when an arc magnet is used as a motor magnet.

FIG. 7 is a perspective view of unit crystal particles of a ferrite magnet.

FIG. 8 is an explanatory diagram showing a shrinkage ratio when a magnet is manufactured by a compression molding method.

FIG. 9 is a perspective view of an arched anisotropic magnet.

FIG. 10 is an explanatory view of a method for manufacturing a bow-shaped anisotropic magnet by a conventional compression molding method.

11 (a) and (b) are explanatory views showing disorder of orientation during extrusion molding.

12A and 12B are explanatory views showing the alignment state in a magnetic field and the alignment disorder after magnetization.

[Explanation of symbols]

 1 Extruder Projection Port 2 Introducing Member 3 Sizing Die 3a Forming Hole 5 Prolong 6 Magnetic Field Generating Means 7 Cooling Means

Claims (4)

[Claims] 1. A molding step of continuously extruding a kneaded material of magnetic powder and a binder in a cross-section bow shape as a main step, and cutting the molded article molded in the molding step to a predetermined length. Sintering step of sintering, in the molding step, a kneaded product of the magnetic powder and the binder,
Extruded into an arcuate cross-section in a flowable state that can be orientated while maintaining a predetermined heating state, and during the extrusion molding, the kneaded product is
An arched anisotropic shape characterized in that it is anisotropically oriented by passing through a magnetic field generated in a region wider than the above-mentioned cross section, and is fixed by cooling to increase hardness during passage of the magnetic field. Method for manufacturing a transparent magnet. 2. The anisotropic magnet according to claim 1, wherein the binder is made by adding one or both of hydroxyethyl cellulose and polyethylene oxide, water, and polyethylene glycol. Manufacturing method. 3. The heating temperature of the kneaded product is 50 ° C. to 90 ° C.
The method for producing an anisotropic magnet according to claim (2), wherein the temperature is within the range of and the cooling is performed at room temperature or lower. 4. A sizing die having heating means, a sizing die having a cross-sectionally arcuate forming hole at a discharge port of an extruder for extruding a kneaded material of magnetic powder and a binder while maintaining a predetermined heating state, and a cooling means. And a prolong provided continuously, and at least a part of the sizing die and the prolong are provided with magnetic field generating means for generating a magnetic field in the sizing die in a region wider than the molding hole. Equipment for manufacturing bow-shaped anisotropic magnets.