JPH06236807A - Resin-bonded magnet and its manufacture - Google Patents

Abstract

PURPOSE:To provide a resin-bonded magnet wherein its magnetic characteristic and its dimensional accuracy are good and its shape is thin-arc-shaped and thin-cylinder-shaped and to provide a means for manufacturing it. CONSTITUTION:In an arc-shaped resin-bonded magnet, its outside radius is at 1.5mm or larger and 50mm or smaller and its thickness is at 0.1mm or larger and less than 1.0mm. In a cylinder-shaped resin-bonded magnet, its outside diameter is at 3mm or larger and 100mm or smaller and its thickness is at o.1mm or larger and less that 1.0mm. A magnet composition is passed inside a metal mold 105 while it is being cooled and solidified to a temperature at the melting point of lower of the magnet composition, and it is extrusion-molded. Thereby, a magnet whose dimensional accuracy and magnetic characteristic are high can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-bonded magnet used for small motors and actuators used in electronic equipment and a method for manufacturing the resin-bonded magnet by extrusion molding.

[0002]

2. Description of the Related Art Sintered ferrite magnets and resin-bonded ferrite magnets are mainly used as arc-shaped magnets used in small DC motors and the like, and sintered ferrite magnets are used as cylindrical magnets. In addition to magnets and resin-bonded ferrite magnets, sintered rare earth magnets and resin-bonded rare earth magnets have also been used. In the molding of these magnets, the sintering method is, for example, as disclosed in Japanese Patent Publication No. S51-38917, in which only the magnetic powder is filled in a mold and molded, and then the magnetic powder is sintered. As disclosed in Japanese Laid-Open Patent Publication No. 56-125814 or Japanese Laid-Open Patent Publication No. 63-209108, a method is used in which a mixture of magnetic powder and a binder is molded and then the molded body is sintered. Injection molding, compression molding, and extrusion molding have been mainly used for molding resin-bonded magnets. The injection molding method is, for example, Japanese Patent Publication No. 55-33173 or Japanese Patent Publication No. 58-5349.
As disclosed in Japanese Patent Publication No. 1 etc., a magnet raw material composed of a magnetic powder and a thermoplastic resin is filled in a mold while being heated to a temperature at which sufficient fluidity is obtained, and molded into a predetermined shape. is there. Further, the compression molding method is described in Japanese Examined Patent Publication No. 50-18.
As disclosed in Japanese Patent No. 559 or Japanese Patent Laid-Open No. 1-310522, it is a method in which a magnet raw material composed of a magnetic powder and a thermosetting resin is filled in a die of a press and compressed. Further, the extrusion molding method is described in JP-A-61-121
No. 307 or JP-A-62-208612, a magnet raw material composed of a magnetic powder and a thermoplastic resin is passed through a mold while being heated to a temperature at which sufficient fluidity is obtained, Then, it is cooled and molded into a predetermined shape.

[0003]

However, the above-mentioned prior art has the following problems.

In recent years, OA equipment, cameras, home electric appliances and the like have been further miniaturized, and motors used in these equipment have also been miniaturized. Along with this, there is an increasing demand for small magnets used in motors. Regarding the arc-shaped magnets, the conventional magnets have the following problems. (1) Generally, the arc-shaped magnet is installed as a field magnet on the outer side of the armature (rotor), and the inner armature with the winding is rotated. Used in that way. Conventional arc-shaped magnets have a magnet wall thickness of 1.0 mm or more, and there is no thin magnet having a wall thickness of less than 1.0 mm. Therefore, when the motor is downsized, the size of the armature is reduced, which makes it difficult to maintain the motor characteristics (torque and the like) and downsize the motor, and it is difficult to wind the coil wire and easily break. was there.

(2) The conventional magnets are mainly ferrite magnets having low magnetic characteristics, and it becomes difficult to obtain a necessary magnetic field strength when the magnet is downsized and the volume thereof is reduced for a small motor, resulting in deterioration of motor characteristics. There was also a problem of doing it.

(3) The conventional method of manufacturing an arc-shaped magnet also has the following problems.

The magnet manufactured by the sintering method has low toughness and is apt to be cracked or chipped. Therefore, a magnet having a magnet wall thickness of less than 1.0 mm will be cracked when incorporated into a motor and is difficult to use in a motor.

In the injection molding method, it is necessary to fill the cavity with the magnet raw material. In order to fill the magnet raw material containing a large amount of magnetic powder, the cavity has a thickness of 1.
0 mm or more is required. Therefore, a magnet having a magnet wall thickness of less than 1.0 mm cannot be molded.

Also in the compression molding method, it is desirable that the mold gap be 1.0 mm or more in order to uniformly fill the raw material powder into the mold. In terms of strength of the forming punch, an arc-shaped punch is likely to cause buckling deformation. Therefore, when the wall thickness is less than 1.0 mm, the punch is broken and the magnet cannot be formed. Therefore, even if the compression molding method is used, a magnet having a wall thickness of less than 1.0 mm cannot be molded.

Even in the extrusion molding method, in the conventional method, the thickness is 1.0 because the material is cooled when it is extruded from the mold.
A magnet having a diameter of less than mm is likely to be deformed, and it is difficult to obtain a magnet satisfying the required dimensional accuracy.

As a method of obtaining a magnet having a wall thickness of less than 1.0 mm, a method of cutting the injection-molded, compression-molded or extrusion-molded magnet into a wall thickness of less than 1.0 mm can be considered. However, the mechanical strength of these magnets is weakened due to fine scratches due to cutting, and density variations inside the magnets, and low density portions appearing on the surface due to cutting. Therefore, it is difficult to use it for a motor because it will crack when it is incorporated into the motor.

Regarding the cylindrical magnet, (1) the cylindrical magnet is installed as a field magnet on the outer side of the armature (rotor) like the circular arc magnet, and the inner armature wound is wound. It may be used by a method of rotating or may be used as a rotor by being bonded to a cylindrical yoke. Conventional cylindrical magnets have a magnet wall thickness of 1.
Most of them are 0 mm or more. Therefore, when used as an external field for miniaturizing the motor, the size of the armature is reduced, so that the motor characteristics (torque etc.) are maintained and the motor is miniaturized. However, there is a problem that it is difficult to wind the coil wire and the wire is easily broken. Further, when used as a rotor, there is a problem that it is difficult to reduce the size because the outer diameter of the rotor becomes large.

(2) If the thickness of the magnet is less than 0.1 mm, the magnetic characteristics are low for the following reason. Therefore, if the magnet is downsized and the volume is reduced for a small motor, the required magnetic field strength can be obtained. There was a problem that it became difficult and the motor characteristics deteriorate.

(3) The conventional method of manufacturing a cylindrical magnet has the following problems as in the case of manufacturing an arc magnet.

The magnet manufactured by the sintering method has low toughness and is apt to be cracked or chipped. Therefore, the cylindrical shape has a wall thickness of 1.0
It is difficult to obtain a magnet of less than mm.

In the injection molding method as well, as in the case of the arc-shaped magnet, the thickness of the cavity must be 1.0 mm or more to fill the magnet raw material containing a large amount of magnetic powder.
Therefore, a magnet having a magnet wall thickness of less than 1.0 mm cannot be molded.

In the compression molding method, it is desirable that the mold gap be 1.0 mm or more in order to uniformly fill the raw material powder into the mold. In terms of the mechanical strength of the forming punch, when the wall thickness is less than 1.0 mm, the punch is easily broken due to insufficient strength, and it is difficult to form the magnet. Therefore, even if the compression molding method is used, it is difficult to mold a magnet having a wall thickness of less than 1.0 mm. When a magnet having a wall thickness of less than 1.0 mm is forcibly formed, the pressing force cannot be increased, so that the number of holes in the formed product increases and the density decreases, resulting in a decrease in both magnetic properties and mechanical strength.

Even in the case of a cylindrical magnet, in the conventional extrusion molding method, since the magnet is cooled when it is extruded from the mold, a magnet having a wall thickness of less than 1.0 mm is likely to be deformed, and a magnet satisfying the required dimensional accuracy cannot be obtained. Have difficulty.

As a method of obtaining a magnet having a wall thickness of less than 1.0 mm, a method of cutting an injection-molded, compression-molded or extrusion-molded magnet to a wall thickness of less than 1.0 mm can be considered. However, as in the case of the arc-shaped magnet, the mechanical strength becomes weak, so that cracks occur when it is incorporated into the motor, and it is difficult to use it in the motor.

Therefore, the present invention is to solve the above problems, and a first object thereof is to achieve a wall thickness of 0.1 which is excellent in mechanical strength.
An object is to provide a thin resin-bonded arc-shaped magnet and a resin-bonded cylindrical magnet having a thickness of not less than 1.0 mm and less than 1.0 mm.
A second object is to provide an effective method for producing the above-mentioned magnet by extruding while cooling and solidifying in a mold at a temperature below the melting point of the magnet composition. The third purpose is to use a rare earth magnetic powder as the magnetic powder, which has excellent magnetic properties and mechanical strength, and has a wall thickness of 0.1 mm or more and 1.0 or more.
A thin resin-bonded arc-shaped magnet having a thickness of less than mm, a resin-bonded cylindrical magnet, and an effective manufacturing method of these magnets are provided.

[0021]

The resin-bonded magnet of the present invention has a composition of magnetic powder and a thermoplastic resin, or magnetic powder, a thermoplastic resin and an additive, and an outer radius of 1.5 mm or more and 50 mm or less. , An arc-shaped magnet having a wall thickness of 0.1 mm or more and less than 1.0 mm, and the length of the magnet is L
(Mm) and the crush load is P (N), the crush strength K defined by the following formula is 2 N / mm or more.

K = P / L Further, the composition is composed of magnetic powder and thermoplastic resin, or magnetic powder, thermoplastic resin and additive, and the outer diameter is φ.
A cylindrical magnet having a diameter of 2 mm or more and φ100 mm or less and a wall thickness of 0.1 mm or more and less than 1.0 mm, and the length of the magnet is L
(Mm) and the crush load is P (N), the crush strength K determined by the following formula is 1 N / mm or more.

K = P / L Further, in the method for producing a resin-bonded magnet of the present invention, a magnetic powder and a thermoplastic resin, or a magnet composition comprising a magnetic powder, a thermoplastic resin and an additive is used. It is characterized in that it is extruded while being cooled and solidified in a mold at a temperature below the melting point of the product.

The magnetic powder is a rare earth magnetic powder composed of a rare earth element (including yttrium (Y)) and a transition metal mainly containing cobalt, and a rare earth element and a transition metal mainly containing iron and boron. It is characterized in that it is a rare earth magnetic powder or a rare earth magnetic powder composed of a transition metal mainly composed of a rare earth element and iron and nitrogen.

[0025]

By using the thin-walled arc-shaped and cylindrical resin-bonded magnets of the present invention, it becomes possible to manufacture a motor and an actuator having a small size and high characteristics. Also,
By using the manufacturing method of the present invention, it is possible to manufacture the thin-walled arc-shaped and cylindrical resin-bonded magnet.

In the present invention, the arc-shaped magnet has an outer radius of 1.5 mm or more and 50 mm or less when the outer radius is 50 mm.
If it is larger than mm, the molded body has a large diameter and thin wall and is easily deformed, and the generally required dimensional accuracy (outer diameter dimensional tolerance ±
This is because it is difficult to manufacture a magnet that satisfies (0.05 mm or less). When the outer radius is less than 1.5 mm,
This is because it is difficult to process the metal mold, and it is difficult to manufacture a metal mold having high dimensional accuracy, and thus the dimensional accuracy of the molded magnet becomes low. In addition, the outer diameter of the cylindrical magnet is φ2.
mm to φ100 mm or less is that the outer diameter is 100 m
If it is larger than m, the molded product is large in diameter and thin and easily deforms, and generally required dimensional accuracy (outer diameter dimensional tolerance ±
This is because it becomes difficult to manufacture a magnet satisfying the condition (0.05 mm or less). Also, if the outer diameter is less than φ2 mm, it is difficult to manufacture the mold itself and magnet molding cannot be performed.

In the present invention, the reason why the magnet wall thickness is set to 0.1 mm or more and less than 1.0 mm is that when the wall thickness is made thinner than 0.1 mm, it is a magnet containing a magnetic powder at a high volume ratio, so that a sufficient mechanical strength can be obtained. This is because practical strength is not obtained and problems such as cracking at the time of assembly occur, which makes practical use difficult. Further, when the wall thickness is 1.0 mm or more, there is a problem that, for example, the armature of the motor cannot be miniaturized, and the effect as a thin magnet is no longer small.

In the present invention, as the mechanical strength, a value represented by the equation K = P / L was used for both the arc-shaped magnet and the cylindrical magnet. Since the mechanical strength of arc-shaped magnets and cylindrical magnets is not specified by official standards, the value of the crush load per unit length was used as the crush strength. In practice, this value can be used for sufficient evaluation. In the present invention, the crushing strength of the arc-shaped magnet is set to 2 N / mm or more, and the radial crushing strength of the cylindrical magnet is set to 1 N / mm or more. This is because the magnet is apt to be damaged during the assembling, and when the motor is completed, the motor is apt to malfunction due to the damage to the magnet in an impact test such as a drop test.

The method for producing a resin-bonded magnet according to the present invention is carried out by feeding a magnet raw material in a fluidized state into a mold using a screw or a plunger and allowing the injected magnet composition to pass through while cooling the mold. Extrude out of the mold. At that time, by extruding while cooling and solidifying in the mold to a temperature not higher than the melting point of the magnet composition, it is possible to form a magnet having uniform density and high dimensional accuracy in both arcuate shape and cylindrical shape. . Here, the temperature is set to be equal to or lower than the melting point of the magnet composition because when the temperature is higher than the melting point, the molded body is extruded from the mold in a still soft state and easily deformed outside the mold, and the dimensional accuracy decreases. Because it will be. Also,
When the magnetic powder having anisotropy is used, it is also possible to manufacture a anisotropic magnet by applying a magnetic field in the mold during molding to orient the magnetic powder in the magnet composition. Also in this case, a magnet having high magnetic characteristics can be formed by extrusion molding while cooling and solidifying in the mold to a temperature not higher than the melting point of the magnet composition. Here again, the temperature is set to be equal to or lower than the melting point of the magnet composition because, when the temperature is higher than the melting point, the molded body is extruded from the mold in a still soft state, the orientation of the magnetic powder is disturbed outside the mold, and the magnetic properties are deteriorated. This is because it ends up.

The magnetic powder used in the present invention includes ferrite powder and rare earth magnetic powder, but rare earth magnetic powder having high magnetic properties is desirable.

The resin that can be used in the present invention is a thermoplastic resin such as polyamide or polyphenylene sulfide (P
Examples include plastics such as PS), elastomers such as chlorinated polyethylene, and synthetic rubber. As the additives, metal soap (zinc stearate, calcium stearate, etc.), lubricants such as wax, and antioxidants can be used.

[0032]

EXAMPLES The present invention will now be described in detail based on examples.

FIG. 1 shows an embodiment of an arc-shaped resin-bonded magnet of the present invention. In FIG. 1, R is the outer radius, T is the wall thickness, and L is the length. FIG. 2 shows one embodiment of the cylindrical resin-bonded magnet of the present invention. In FIG. 2, D is the outer diameter, T is the wall thickness, and L is the length.

FIG. 3 shows one embodiment of the manufacturing process of the resin-bonded magnet of the present invention. The magnetic powder, the resin and, if necessary, the additives are weighed and mixed in a desired mixing ratio, and then heated to a temperature at which the resin is melted or higher in a kneader such as a twin-screw extruder and kneaded to prepare a compound. This compound is crushed into a size that can be easily put into a molding machine and then put into an extrusion molding machine.
The charged magnet composition is heated again in the cylinder of the extrusion molding machine and is sent in a fluidized state by a screw or a plunger into a mold connected to the extrusion machine. When molding an isotropic magnet, the magnet composition is extruded from the mold while being cooled and solidified without applying a magnetic field. When molding an anisotropic magnet, the magnet composition injected into the mold is passed through the mold to which a magnetic field is applied to orient the easy axis of magnetization of the magnetic powder in the raw material in the magnetic field direction. Then, it is cooled, solidified, and extruded from the mold as a magnet molded body. The extruded magnet molded body is taken out and cut into an appropriate length. In this way, the resin-bonded magnet is manufactured.

An embodiment of the extrusion molding process among the above manufacturing processes will be described with reference to FIG. FIG. 4 shows an embodiment of an apparatus for manufacturing an arc-shaped magnet. The extrusion molding machine includes a hopper 101 and a cylinder 10 which are material input parts.
2, a screw 103, an adapter plate 104 for attaching a die to the cylinder portion, a die 105, and a screw driving motor (not shown in the figure). When a magnetic field is applied to the inside of the mold, the electromagnetic coil 110 and the pole piece 111 are arranged outside so as to sandwich the mold. The crushed raw material compound 112 is put into this extruder. This raw material compound is heated in the cylinder 102 by the heater 106, and is passed through the mold 105 in a fluidized state. At this time, the mold temperature is adjusted by the heater 108 and the cooling plate 109, and the magnet molded body is extruded from the mold while being cooled and solidified. The cooling plate 109 is cooled by a refrigerant such as air or cooling water. Alternatively, cooling may be performed by directly blowing air or cooling water onto the molded body instead of using the cooling plate.

When a cylindrical magnet is manufactured, it can be manufactured by changing the mold to a cylindrical magnet molding tool as shown in FIG. The manufacturing method is the same as the manufacturing method of the above arc-shaped magnet, and the mold temperature is set to the heater 208,
The magnet molded body is extruded from the mold 205 while being cooled and solidified by adjusting with the cooling plate 209.

A more detailed embodiment will be described below.

(Example 1) The composition was Sm (Co _0.672 Cu).
_0.08 Fe _0.22 Zr _0.028 ) _8.35 After melting and casting the raw material, the resulting ingot was heat-treated and magnetically hardened, and then the ingot was crushed to obtain an average particle size of 15
A magnetic powder of μm was obtained. This powder is designated as powder A. As another type of powder, Nd ₁₄ (Fe _0.95 C
The raw material was melted and cast to have a composition of _0.05 ) _80.5 B _5.5 , and a quenched ribbon was produced from the obtained ingot using an apparatus for producing a quenched ribbon in an argon gas atmosphere. The quenched ribbon was crushed to obtain magnet powder having an average particle size of 20 μm. This powder is designated as powder B. As another type of powder, the raw material was melted and cast so as to have a composition of Sm ₂ Fe ₁₇ , and the obtained ingot was roughly crushed. This powder was subjected to a nitriding treatment in nitrogen at 460 ° C., and then further pulverized to obtain a magnet powder having an average particle size of 20 μm. This powder is designated as powder C.

Powder A, PPS powder and zinc stearate powder were mixed so that their respective proportions were 90% by weight, 9.9% by weight and 0.1% by weight. Also, powder B, nylon 12 powder and zinc stearate powder,
The hydrazine-based antioxidants were mixed so that the respective proportions were 95% by weight, 4.9% by weight, 0.05% by weight and 0.05% by weight. Further, the powder C, the polypropylene powder and the calcium stearate powder were mixed so that the respective proportions were 92% by weight, 7.9% by weight and 0.1% by weight. These mixtures were mixed with a twin-screw extrusion kneader using PPS at 340 ° C, nylon 1
2. Those using polypropylene were kneaded at 260 ° C. This kneaded material was crushed to give particles having an outer diameter of 1 to 10 mm to obtain a raw material compound. The powder A is used as compound 1, the powder B is used as compound 2, and the powder C is used as compound 3. The melting point of each compound is compound 1
Was 290 ° C., Compound 2 was 175 ° C., and Compound 3 was 165 ° C. Using this compound,
An outer radius of 4.5 using the extruder and mold shown in
mm, thickness 0.5 mm arc magnet and outer radius 25 m
An arc-shaped magnet having a thickness of 0.9 mm and a wall thickness of 0.9 mm was formed. At the time of molding the compounds 1 and 3, a magnetic field of 15 kOe was applied to the mold to mold the anisotropic magnet. In the molding of compound 2, an isotropic magnet was molded without applying a magnetic field. On this occasion,
The temperature of the molded product was measured at the die outlet, and the relationship between the molded product temperature, the magnetic characteristics of the molded product, and the dimensional accuracy (outer radius variation) was investigated. The measurement results are shown in Table 1.

[0040]

[Table 1]

The dimensional accuracy generally required for an arc-shaped resin-bonded magnet is, for example, an outer radius tolerance of ± 0.05 m.
m or less. As is clear from Table 1, it is possible to manufacture a thin-walled arc-shaped magnet having good dimensional accuracy by cooling and solidifying to a temperature below the melting point of the magnet composition and extruding the molded product. It is also possible to manufacture a thin-walled arc-shaped magnet having good magnetic characteristics by using this method.

(Example 2) Using the same compounds 1, 2 and 3 as in Example 1, an arc-shaped magnet having different dimensions was manufactured by the same molding method, and dimensional accuracy (outer radius variation) and mechanical strength ( The crush strength) was measured. Crush strength, length 10
An arc-shaped magnet cut into mm was placed as shown in FIG. 6, a crushing load P (N) was applied from above, and a value obtained by dividing the load when the magnet broke by the magnet length was used. The results are shown in Table 2.

[0043]

[Table 2]

As is clear from Table 2, the outer radius is 1.5.
If it is less than mm or greater than 50 mm, good dimensional accuracy cannot be obtained. Further, if the wall thickness is less than 0.1 mm, the crush strength is drastically reduced, which is not suitable for practical use.
When the outer radius is 1.5 mm or more and 50 mm or less and the wall thickness is 0.1 mm or more, good dimensional accuracy and mechanical strength are obtained. (Example 3) Using the arc-shaped magnet produced by using the compound 2 in Example 2, the mechanical strength (crush strength) and the failure rate at the time of incorporating the motor were investigated.
The defect rate indicates the rate of occurrence of defects when incorporating 300 motors. The results are shown in Table 3.

[0045]

[Table 3]

As is clear from Table 3, the crush strength is 2 N /
If it is less than mm, the defective rate at the time of assembling the motor rapidly increases. This is because the mechanical strength is low and the damage to the magnet during handling is increased. If the crush strength is 2 N / mm or more, the defective rate is small and there is no practical problem.

(Example 4) Similar to Example 2, using the same compounds 1, 2 and 3 as in Example 1 and by the same molding method, an arc-shaped magnet having an inner radius of 4.6 mm and varying wall thickness was produced. did. This was attached to a case of a DC motor having an outer diameter of 12 mm, and the amount of magnetic flux was measured. The measurement was performed by a method of measuring the amount of magnetic flux from the electromotive force generated in a coil wire wound around an armature 10 times. FIG. 7 shows the measurement result of the relationship between the magnet wall thickness and the amount of magnetic flux. As a comparative example, the results of a sintered ferrite magnet having a wall thickness of 1.1 mm are also shown.

It is known that the motor characteristic (torque value) is proportional to the amount of magnetic flux generated. As is apparent from FIG. 7, it is possible to manufacture a motor having sufficiently high characteristics as compared with a conventional one by using an arc-shaped magnet having a wall thickness of 0.1 mm or more.

(Embodiment 5) Using the same compounds 1, 2 and 3 as in Embodiment 1, using the extruder and mold shown in FIG. 3, the outer diameter is 5.0 mm and the wall thickness is 0.1 mm. A cylindrical magnet, an outer diameter of 50 mm and a wall thickness of 0.5 mm, and a cylindrical magnet having an outer diameter of 80 mm and a wall thickness of 0.9 mm were molded. When molding compounds 1 and 3, 1 in the mold
An anisotropic magnet was molded by applying a radial magnetic field of 3 kOe. In the molding of compound 2, an isotropic magnet was molded without applying a magnetic field. At this time, the temperature of the molded product was measured at the die outlet, and the relationship between the molded product temperature, the magnetic characteristics of the molded product, and the dimensional accuracy (outer diameter variation) was investigated. The measurement results are shown in Table 4.

[0050]

[Table 4]

The dimensional accuracy generally required for a cylindrical resin-bonded magnet is, for example, an outer diameter tolerance of ± 0.05 mm or less. As is clear from Table 4, it is possible to manufacture a thin-walled cylindrical magnet having good dimensional accuracy by cooling and solidifying to a temperature below the melting point of the magnet composition and extruding the molded product. It is also possible to manufacture a thin-walled cylindrical magnet having good magnetic characteristics by using this method.

(Example 6) Cylindrical magnets having the same compounds 1, 2 and 3 as in Example 4 but different dimensions were produced by the same molding method, and dimensional accuracy (outer diameter variation) and mechanical strength ( The crush strength) was measured. As for the crushing strength, a cylindrical magnet cut to a predetermined length is placed as shown in FIG. 8 and a crushing load P (N) is applied from above, and the load when the magnet breaks is the magnet length (L). The divided value was used. The results are shown in Table 5.

[0053]

[Table 5]

As is clear from Table 5, the outer diameter is 100 m.
If it is larger than m, good dimensional accuracy cannot be obtained. Further, if the outer diameter is less than 2 mm, it is difficult to manufacture a mold and molding is difficult. Further, if the wall thickness is less than 0.1 mm, the crushing strength sharply decreases, which is not suitable for practical use. Outer diameter 2m
When the thickness is m or more and 100 mm or less and the wall thickness is 0.1 mm or more, good dimensional accuracy and mechanical strength are obtained.

Example 7 The cylindrical magnet produced in Example 6 was incorporated into a motor as a rotor, and the relationship between the defective rate of the motor drop test and the mechanical strength (crush strength) was investigated. The defect rate indicates the rate of occurrence of defects in the drop test of 50 motors. The results are shown in Table 6.

[0056]

[Table 6]

As is clear from Table 6, the crushing strength is 1 N /
If it is less than mm, the defective rate of the motor increases rapidly. This is because the mechanical strength of the magnet is small and the magnet is damaged by the impact of the drop test, which increases the defects of the motor. If the crush strength is 1 N / mm or more, the defective rate is small and there is no problem in practical use.

(Embodiment 8) An outer diameter of 24 mm was obtained by the same molding method using compounds 1, 2 and 3 as in Embodiment 6.
A cylindrical magnet having different wall thickness was manufactured. This was mounted on a rotor and magnetized to 24 poles to measure the surface magnetic flux density. FIG. 9 shows the relationship between the magnet wall thickness and the surface magnetic flux density. As a comparative example, the results of a sintered ferrite magnet having a thickness of 2 mm are also shown.

It is known that the motor characteristic (torque value) is proportional to the surface magnetic flux density. As is clear from FIG. 9, by using a cylindrical magnet having a wall thickness of 0.1 mm or more, it is possible to manufacture a motor having sufficiently high characteristics as compared with the conventional one.

[0060]

As described above, by using the arc-shaped or cylindrical resin-bonded magnet of the present invention, it is possible to manufacture a motor and an actuator which are much smaller than conventional ones. Have. Further, by using the manufacturing method of the present invention, it is possible to manufacture the above thin-walled arc-shaped magnet and cylindrical magnet having high magnetic characteristics and good dimensional accuracy, which could not be conventionally manufactured. Therefore, it is very effective in reducing the size and weight of office automation equipment, consumer equipment, etc., and thus saving resources.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an arc-shaped resin-bonded magnet of the present invention.

FIG. 2 is a diagram showing an embodiment of a cylindrical resin-bonded magnet of the present invention.

FIG. 3 is a diagram showing a manufacturing process of a resin-bonded magnet in an example of the present invention.

FIG. 4 is a diagram showing an extrusion molding device for an arc-shaped resin-bonded magnet in an example of the present invention.

FIG. 5 is a diagram showing an extrusion molding apparatus for a cylindrical resin-bonded magnet in an example of the present invention.

FIG. 6 is a diagram showing a load application direction of crush strength measurement of an arc-shaped magnet in an example of the present invention.

FIG. 7 is a diagram showing a relationship between an arc-shaped magnet wall thickness and a magnetic flux amount in the example of the present invention.

FIG. 8 is a diagram showing a load application direction for measuring the crushing strength of a cylindrical magnet in an example of the present invention.

FIG. 9 is a diagram showing the relationship between the wall thickness of a cylindrical magnet and the surface magnetic flux density in the example of the present invention.

[Explanation of symbols]

 101, 201 Hopper 102, 202 Cylinder 103, 203 Screw 104, 204 Adapter plate 105, 205 Mold 106, 206 Heater 107, 207 Heater 108, 208 Heater 109, 209 Cooling plate 110, 210 Electromagnetic coil 111 Pole piece 112, 211 Raw material compound 113,212 Magnet molded product P Crash load R Magnet outer radius D Magnet outer diameter T Magnet wall thickness L Magnet length

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Claims (5)

[Claims] 1. A composition comprising a magnetic powder and a thermoplastic resin, or a magnetic powder, a thermoplastic resin and an additive,
Outer radius is 1.5 mm or more and 50 mm or less, wall thickness is 0.1 m
An arc-shaped magnet having a length of m or more and less than 1.0 mm, where the length of the magnet is L (mm) and the crush load is P (N), the crush strength K determined by the following formula is 2 N / mm or more. Resin-bonded magnets characterized by the above. K = P / L 2. A composition comprising a magnetic powder and a thermoplastic resin, or a magnetic powder, a thermoplastic resin and an additive,
Outer diameter φ2 mm or more φ100 mm or less, wall thickness 0.1 m
A cylindrical magnet of m or more and less than 1.0 mm, where the length of the magnet is L (mm) and the crush load is P (N), the crush strength K determined by the following formula is 1 N / mm or more. Resin-bonded magnets characterized by the above. K = P / L 3. A magnetic powder and a thermoplastic resin, or
The magnet composition comprising a magnetic powder, a thermoplastic resin and an additive is extruded while being cooled and solidified in a mold at a temperature not higher than the melting point of the magnet composition. A method for manufacturing a resin-bonded magnet. 4. The magnetic powder comprises a rare earth magnetic powder consisting of a rare earth element (including yttrium (Y)) and a transition metal mainly containing cobalt, and a rare earth element and a transition metal mainly containing iron and boron. A rare earth magnetic powder or a rare earth magnetic powder composed of a transition metal mainly composed of a rare earth element and iron and nitrogen.
2. The resin-bonded magnet according to item 2 above. 5. The rare earth magnetic powder comprising a rare earth element (including yttrium (Y)) and a transition metal mainly containing cobalt, and the rare earth element and a transition metal mainly containing iron and boron. 4. A rare earth magnetic powder or a rare earth magnetic powder composed of a transition metal mainly composed of a rare earth element and iron and nitrogen.
A method for producing the resin-bonded magnet described.