JP2004104143A - Resin-bonded magnet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide resin-bonded magnets which are excellent in a magnetic characteristic and accuracy of dimensions and are of a thin-wall arc shape and thin-wall cylindrical shap; and provide a means for manufacturing them. <P>SOLUTION: One of the resin-bonded magnets is of an arc shape which is 1.5 mm to 50 mm in the outer radius and is at least 0.1 mm or smaller than 1.0 mm in the wall thickness, and another resin-bonded type magnet is of a cylindrical shape which is 3 mm to 100 mm in the outer diameter and is at least 0.1 mm or smaller than 1.0 mm in the wall thickness. The composition of the magnet is cooled and solidified passing at a temperature lower than the melting point of the composition through a mold 105, and the magnet has high dimensional precision and magnetic charateristics by extrusion. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a resin-bonded magnet used for a small motor or an actuator used in an electronic device or the like, and a method for manufacturing the resin-bonded magnet using extrusion molding.

Conventionally, sintered ferrite magnets and resin-bonded ferrite magnets are mainly used as arc-shaped magnets used for small DC motors, and sintered ferrite magnets and resin-bonded magnets are used as cylindrical magnets. In addition to ferrite magnets, sintered rare earth magnets and resin-bonded rare earth magnets have also been used. In molding these magnets, a sintering method is as follows. For example, as disclosed in Japanese Patent Publication No. 51-38917, only a magnetic powder is filled in a metal mold and molded, and then the magnetic powder is sintered. As disclosed in JP-A-56-125814 or JP-A-63-209108, a method comprising molding a mixture comprising a magnetic powder and a binder and then sintering the molded product. Injection molding, compression molding, and extrusion molding have been mainly used for molding resin-bonded magnets. The injection molding method involves heating a magnet raw material comprising a magnetic powder and a thermoplastic resin to a temperature at which sufficient fluidity can be obtained, as disclosed in, for example, Japanese Patent Publication No. 55-33173 or Japanese Patent Publication No. 58-53491. In this state, the mold is filled into a mold and molded into a predetermined shape. In the compression molding method, as disclosed in Japanese Patent Publication No. 50-18559 or JP-A-1-310522, a magnet raw material comprising a magnetic powder and a thermosetting resin is filled in a press die. It is a method of molding by compression. In addition, the extrusion molding method provides sufficient fluidity of a magnet raw material comprising a magnetic powder and a thermoplastic resin as disclosed in JP-A-61-121307 or JP-A-62-208612. This is to pass through a mold while being heated to a temperature, and then cool and mold it into a predetermined shape.

JP-B-51-38917 JP-A-56-125814 JP-A-63-209108 JP-B-55-33173 JP-B-58-53491 Japanese Patent Publication No. 50-18559 JP-A-1-310522 JP-A-61-121307 JP-A-62-208612

  However, the above-described related art has the following problems.

In recent years, miniaturization of OA equipment, cameras, home electric appliances, and the like has been more and more advanced, and motors used in these equipment have also been reduced in size. Accordingly, the demand for small magnets used in motors is increasing. One of the problems with conventional magnets is that arc-shaped magnets
(1) Generally, an arc-shaped magnet is used for a magnetic field outside an armature (rotor), and is used in such a manner that an inner armature provided with a winding is rotated. The conventional arc-shaped magnet has only a magnet thickness of 1.0 mm or more, and there is no thin magnet having a thickness of less than 1.0 mm. Therefore, when the motor is downsized, the size of the armature becomes small, so that it is difficult to downsize the motor while maintaining the motor characteristics (torque, etc.), and it is difficult to wind the coil wire and it is easy to disconnect. was there.

(2) Conventional magnets are mainly ferrite magnets having low magnetic properties. If a magnet is reduced in size and its volume is reduced for a small motor, it becomes difficult to obtain a required magnetic field strength, and the motor properties deteriorate. There was also a problem.

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

(A) Magnets manufactured by the sintering method have low toughness and are susceptible to cracking and chipping. For this reason, a magnet having a magnet thickness of less than 1.0 mm causes cracking when assembled into a motor, and is difficult to use for a motor.

(B) In the injection molding method, it is necessary to fill the cavity with a magnet raw material, but in order to fill the magnet raw material containing a large amount of magnetic powder, the cavity must have a thickness of 1.0 mm or more. Therefore, a magnet having a thickness of less than 1.0 mm cannot be formed.

(C) Also in the compression molding method, the gap of the mold is desirably 1.0 mm or more in order to uniformly fill the material powder into the mold. In terms of the strength of the forming punch, the arc-shaped punch is liable to buckle, and if 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, it is impossible to form a magnet having a thickness of less than 1.0 mm.

(D) Also in the extrusion molding method, in the conventional method, since the magnet is cooled when it is extruded from the mold, the magnet having a thickness of less than 1.0 mm is easily deformed, and it is difficult to obtain a magnet satisfying the required dimensional accuracy. It is.

(E) As a method for obtaining a magnet having a thickness of less than 1.0 mm, a method of processing the above-mentioned injection-molded, compression-molded or extruded magnet by cutting to a thickness of less than 1.0 mm is also conceivable. However, these magnets have low mechanical strength due to minute scratches caused by the cutting process, density variations inside the magnet, and low density portions appearing on the surface by the cutting process. For this reason, cracks occur when assembled into the motor, and it is difficult to use the motor for the motor.

For cylindrical magnets,
(1) A cylindrical magnet is installed outside of an armature (rotor) for field use similarly to an arc-shaped magnet, and is used by a method of rotating an inner armature on which a winding is applied, It is sometimes used as a rotor by adhering to a cylindrical yoke. Many of the conventional cylindrical magnets have a magnet thickness of 1.0 mm or more. Therefore, when the motor is downsized and used for an outer field, the size of the armature is reduced, so that the motor characteristics are reduced. (Torque, etc.), it is difficult to reduce the size of the motor, and there is a problem that the winding of the coil wire is difficult and the wire is easily broken. Also, when used as a rotor, there is a problem that it is difficult to reduce the size because the outer diameter of the rotor is large.

(2) When the magnet thickness is less than 0.1 mm, the magnetic properties are low for the following reasons. Therefore, if the magnet is reduced in size and the volume is reduced for a small motor, it becomes difficult to obtain the required magnetic field strength. However, there is a problem that the motor characteristics are deteriorated.

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

(A) Magnets manufactured by the sintering method have low toughness and are susceptible to cracking and chipping. Therefore, it is difficult to obtain a cylindrical magnet having a thickness of less than 1.0 mm.

(B) In the injection molding method, as in the case of the arc-shaped magnet, the cavity must have a thickness of 1.0 mm or more in order to fill a magnet raw material containing a large amount of magnetic powder. Magnets less than 0 mm cannot be molded.

(C) In the compression molding method, the gap of the mold is desirably 1.0 mm or more in order to uniformly fill the material powder into the mold. If the thickness of the formed punch is less than 1.0 mm in mechanical strength, the punch is likely to be broken due to insufficient strength, and it is difficult to form a magnet. Therefore, it is difficult to form a magnet having a thickness of less than 1.0 mm even by using the compression molding method. When a magnet having a wall thickness of less than 1.0 mm is forcibly formed, since the pressing force cannot be increased, the number of pores in the molded product increases, the density decreases, and both the magnetic properties and the mechanical strength decrease.

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

(E) As a method of obtaining a magnet having a thickness of less than 1.0 mm, a method of processing a magnet formed by injection molding, compression molding, or extrusion molding to a thickness of less than 1.0 mm by cutting may be considered. However, as in the case of the arc-shaped magnet, the mechanical strength is weakened, so that when the magnet is incorporated into a motor, cracks occur, and it is difficult to use the magnet for the motor.
Accordingly, the present invention is to solve the above-mentioned problems, and a first object is to provide a thin resin-coupled arc-shaped magnet and a resin-coupled cylinder having excellent mechanical strength and a wall thickness of 0.1 mm or more and less than 1.0 mm. It is to provide a shape magnet. A second object of the present invention is to provide an effective method for producing the above-mentioned magnet by extruding while cooling and solidifying in a mold to a temperature lower than the melting point of the magnet composition. A third object is to use a rare-earth magnetic powder as a magnetic powder to obtain a thin resin-bonded arc-shaped magnet having a thickness of 0.1 mm or more and less than 1.0 mm, which is excellent in both magnetic properties and mechanical strength, and a resin-bonded cylindrical shape. An object of the present invention is to provide magnets and to provide an effective method for manufacturing the magnets.

The resin-bonded magnet of the present invention is a resin-bonded magnet obtained by mixing a magnetic powder and a thermoplastic resin and bonding them by an extrusion molding method, and has an outer radius of 1.5 mm or more and 50 mm or less, and a thickness of 0 mm. An arc-shaped magnet having a crushing strength K of 2 N / mm or more when the length of the magnet is L (mm) and the crushing load is P (N). There is a feature.

K = P / L
The resin-bonded magnet of the present invention is a resin-bonded magnet obtained by mixing a magnetic powder and a thermoplastic resin and bonding them by an extrusion molding method, and has an outer diameter of 2 mm or more and 100 mm or less, and a wall thickness of 0.1 mm. A cylindrical magnet having a length of L (mm) and a crushing load of P (N), and a crushing strength K determined by the following equation is 1 N / mm or more, which is not less than 1.0 mm and less than 1.0 mm. It is characterized by.

K = P / L
Further, the magnetic powder is a rare earth magnetic powder composed of a rare earth element (including yttrium (Y)) and a transition metal mainly composed of cobalt, and a rare earth magnetic powder composed of a transition metal composed mainly of a rare earth element and iron and boron. Alternatively, it is a rare earth magnetic powder comprising a transition metal mainly composed of a rare earth element and iron and nitrogen.

The method for producing a resin-bonded magnet of the present invention comprises extruding a magnet composition comprising a mixture of a magnetic powder and a thermoplastic resin while cooling and solidifying the magnet composition in a mold to a temperature equal to or lower than the melting point of the magnet composition. Then, an arc-shaped magnet having an outer radius of 1.5 mm or more and 50 mm or less and a wall thickness of 0.1 mm or more and less than 1.0 mm, the length of the magnet was L (mm), and the crushing load was P (N). The molding is characterized in that the crushing strength K determined by the following equation is formed to be 2 N / mm or more.

K = P / L
The method for producing a resin-bonded magnet of the present invention comprises extruding a magnet composition comprising a mixture of a magnetic powder and a thermoplastic resin while cooling and solidifying the magnet composition in a mold to a temperature equal to or lower than the melting point of the magnet composition. Then, when a cylindrical magnet having an outer diameter of φ2 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 crushing load is P (N), Is characterized in that the crushing strength K determined by the following formula is 1 N / mm or more.

K = P / L
Further, the magnetic powder is a rare earth magnetic powder composed of a rare earth element (including yttrium (Y)) and a transition metal mainly composed of cobalt, and a rare earth magnetic powder composed of a transition metal composed mainly of a rare earth element and iron and boron. Alternatively, it is a rare earth magnetic powder comprising a transition metal mainly composed of a rare earth element and iron and nitrogen.
(Action)

  By using the thin arc-shaped and cylindrical resin-coupled magnets of the present invention, it is possible to produce a small-sized and high-performance motor or actuator. Further, by using the manufacturing method of the present invention, it is possible to manufacture the thin-walled arc-shaped and cylindrical resin-coupled magnet.

In the present invention, the reason why the outer radius of the arc-shaped magnet is set to 1.5 mm or more and 50 mm or less is that when the outer radius is larger than 50 mm, the formed body has a large diameter and is thin and is easily deformed, and generally required dimensional accuracy. This is because it is difficult to manufacture a magnet that satisfies (within ± 0.05 mm outer diameter dimensional tolerance). Also, if the outer radius is less than 1.5 mm, it is difficult to mold and it is difficult to produce a mold with high dimensional accuracy, so that the dimensional accuracy of the formed magnet is reduced. In addition, the reason why the outer diameter of the cylindrical magnet is set to not less than φ2 mm and not more than φ100 mm is that when the outer diameter is larger than 100 mm, the formed body is large in diameter and thin and easily deformed. This is because it becomes difficult to manufacture a magnet satisfying a tolerance of ± 0.05 mm. On the other hand, 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 that the thickness of the magnet is set to 0.1 mm or more and less than 1.0 mm is that when the thickness is reduced to less than 0.1 mm, the magnet contains a high volume ratio of magnetic powder, and thus has sufficient mechanical strength. This is because they cannot be obtained, and problems such as cracking at the time of assembling occur, which makes practical use difficult. Further, if the thickness is 1.0 mm or more, there is a problem that, for example, the size of the armature of the motor cannot be reduced, and the effect as a thin magnet is no longer reduced.

In the present invention, the mechanical strength is both arc-shaped magnet and cylindrical magnet,
K = P / L
The value shown by the following equation was used. Since the mechanical strength of arc-shaped magnets and cylindrical magnets is not defined by official standards, the value of the crushing load per unit length was used as the crushing strength. In practical use, this value can be sufficiently evaluated. In the present invention, the crushing strength of the arc-shaped magnet is set to 2 N / mm or more, and the crushing strength of the cylindrical magnet is set to 1 N / mm or more. This is because the magnet is likely to be damaged when the motor is assembled, and when the motor is completed, the motor is likely to malfunction due to damage to the magnet in an impact test such as a drop test.

In the method for producing a resin-bonded magnet of the present invention, a magnet material in a fluidized state is fed into a mold using a screw or a plunger, and the injected magnet composition is passed through the mold while being cooled, and the outside of the mold is cooled. Extrusion molding. At that time, by performing extrusion molding while cooling and solidifying to a temperature equal to or lower than the melting point of the magnet composition in a mold, a magnet having uniform density and high dimensional accuracy in both arc shape and cylindrical shape can be formed. .
Here, the temperature is set to be equal to or lower than the melting point of the magnet composition.If the temperature is higher than the melting point, the molded body is easily extruded from the mold in a soft state and is easily deformed outside the mold, and the dimensional accuracy is reduced. It is because. When using magnetic powder having anisotropy, an anisotropic magnet can be produced by applying a magnetic field to a mold during molding to orient the magnetic powder in the magnet composition. Also in this case, a magnet having high magnetic properties can be formed by performing extrusion molding while cooling and solidifying the magnet composition to a temperature equal to or lower than the melting point of the magnet composition in a mold. Again, the temperature was set to be equal to or lower than the melting point of the magnet composition, because if the temperature is higher than the melting point, the molded body is extruded from the mold in a still soft state, the magnetic powder orientation is disturbed outside the mold, and the magnetic properties are reduced. This is because

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

樹脂 The resin that can be used in the present invention is a thermoplastic resin, for example, a plastic such as polyamide and polyphenylene sulfide (PPS), an elastomer such as chlorinated polyethylene, and a synthetic rubber. As additives, metal soaps (zinc stearate, calcium stearate, etc.), lubricants such as wax, antioxidants and the like can be used.

By using the manufacturing method of the present invention, it is possible to manufacture a thin resin-bonded magnet having high magnetic properties, good dimensional accuracy, and excellent mechanical strength, which could not be conventionally manufactured.

Further, according to the present invention, it is possible to provide a thin arc-shaped resin-coupled magnet and a thin-cylindrical resin-coupled magnet excellent in mechanical strength. It has an excellent effect that a very small motor and actuator can be manufactured. Therefore, it is very effective in reducing the size and weight of OA equipment, consumer equipment, and the like, and eventually saving resources.

Hereinafter, more detailed examples will be described.

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

Powder A, PPS powder and zinc stearate powder were mixed so that the respective ratios were 90%, 9.9% and 0.1% by weight. Also, powder B, nylon 12 powder, zinc stearate powder, and hydrazine-based antioxidant were mixed such that the respective ratios were 95% by weight, 4.9% by weight, 0.05% by weight, and 0.05% by weight. did. The powder C, the polypropylene powder and the calcium stearate powder were mixed so that the proportions were 92% by weight, 7.9% by weight and 0.1% by weight, respectively. These mixtures were kneaded with a twin screw extruder at 340 ° C. using PPS and 260 ° C. using nylon 12 and polypropylene. The kneaded product was pulverized to particles having an outer diameter of 1 to 10 mm to obtain a raw material compound. Compound 1 using powder A, compound 2 using powder B, and compound 3 using powder C. The melting point of each compound was 290 ° C. for Compound 1, 175 ° C. for Compound 2, and 165 ° C. for Compound 3. Using this compound, an arc-shaped magnet having an outer radius of 4.5 mm and a wall thickness of 0.5 mm and an arc-shaped magnet having an outer radius of 25 mm and a wall thickness of 0.9 mm were formed using the extruder and the mold shown in FIG. Molded. During molding of Compounds 1 and 3, a magnetic field of 15 kOe was applied to the mold to mold an anisotropic magnet. In forming Compound 2, an isotropic magnet was formed without applying a magnetic field. At this time, the temperature of the molded article was measured at the exit of the mold, and the relationship between the molded article temperature, the magnetic properties of the molded article, and the dimensional accuracy (outer radius variation) was examined. Table 1 shows the measurement results.

寸 法 Generally, the dimensional accuracy required for an arc-shaped resin-coupled magnet is, for example, ± 0.05 mm or less in outer radius tolerance. As is clear from Table 1, it is possible to manufacture a thin arc-shaped magnet having good dimensional accuracy by cooling and solidifying to a temperature lower than the melting point of the magnet composition and extruding the molded article. Further, by using this method, it is also possible to manufacture a thin-walled arc-shaped magnet having good magnetic properties.

(4) Using the same compounds 1, 2, and 3 as in Example 1, arc-shaped magnets having different dimensions were produced by the same molding method, and dimensional accuracy (variation in outer radius) and mechanical strength (crushing strength) were measured. The crushing strength is obtained by placing a circular arc-shaped magnet cut to a length of 10 mm as shown in FIG. 6, applying a crushing load P (N) from above, and dividing the load when the magnet breaks by the magnet length. Was. Table 2 shows the results.

As is clear from Table 2, if the outer radius is less than 1.5 mm or greater than 50 mm, good dimensional accuracy cannot be obtained. On the other hand, if the thickness is less than 0.1 mm, the crushing strength is sharply 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.

用 い Using the arc-shaped magnet produced by using the compound 2 in Example 2, the mechanical strength (crushing strength) and the failure rate when the motor was assembled were investigated. The failure rate indicates the failure rate when 300 motors are incorporated. Table 3 shows the results.

明 ら か As is clear from Table 3, when the crushing strength is less than 2 N / mm, the failure rate when the motor is incorporated into the motor increases rapidly. This is due to the fact that the mechanical strength is small and the damage of the magnet during handling is increased. If the crushing strength is 2 N / mm or more, the defective rate is small and there is no practical problem.

(4) An arc-shaped magnet having an inner radius of 4.6 mm and a varied thickness was produced by using the same compounds 1, 2, and 3 as in Example 2 and using the same molding method as in Example 1. This was mounted on a DC motor case having an outer diameter of φ12 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 an armature obtained by winding a coil wire 10 times. FIG. 7 shows the measurement results of the relationship between the magnet 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 motor characteristics (torque value) are proportional to the amount of generated magnetic flux.
As is clear from FIG. 7, it is possible to produce a motor having sufficiently higher characteristics than the conventional motor by using an arc-shaped magnet having a thickness of 0.1 mm or more.

Using the same compounds 1, 2, and 3 as in Example 1, a cylindrical magnet having an outer diameter of 5.0 mm, a wall thickness of 0.1 mm, and an outer diameter of 50 mm was obtained using the extruder and the mold shown in FIG. A cylindrical magnet having a thickness of 0.5 mm and a cylindrical magnet having an outer diameter of 80 mm and a thickness of 0.9 mm were formed. At the time of molding the compounds 1 and 3, a 13 kOe radial magnetic field was applied to the mold to mold the anisotropic magnet. In forming Compound 2, an isotropic magnet was formed without applying a magnetic field. At this time, the temperature of the molded product was measured at the exit of the mold, and the relationship between the temperature of the molded product, the magnetic properties of the molded product, and the dimensional accuracy (outer diameter variation) was examined. Table 4 shows the measurement results.

寸 法 Generally, the dimensional accuracy required for a cylindrical resin-coupled magnet is, for example, ± 0.05 mm or less in outer diameter tolerance. As is clear from Table 4, it is possible to manufacture a thin-walled cylindrical magnet having good dimensional accuracy by cooling and solidifying the magnet composition to a temperature equal to or lower than the melting point of the magnet composition and extruding the molded article. Also, by using this method, it is possible to produce a thin cylindrical magnet having good magnetic properties.

円 筒 Using the same compounds 1, 2 and 3 as in Example 4, cylindrical magnets of different dimensions were produced by the same molding method, and dimensional accuracy (outer diameter variation) and mechanical strength (crushing strength) were measured. The crushing strength is obtained by placing a cylindrical magnet cut to a predetermined length as shown in FIG. 8, applying a crushing load P (N) from above, and calculating the load when the magnet breaks by the magnet length (L). The divided value was used. Table 5 shows the results.

As is clear from Table 5, if the outer diameter is larger than 100 mm, good dimensional accuracy cannot be obtained. On the other hand, when the outer diameter is less than 2 mm, it is difficult to manufacture a mold and molding is difficult. Further, if the thickness is less than 0.1 mm, the crushing strength is rapidly reduced, which is not suitable for practical use. When the outer diameter is 2 mm 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.

(4) The cylindrical magnet produced in Example 6 was incorporated into a motor as a rotor, and the relationship between the failure rate of a motor drop test and mechanical strength (crushing strength) was investigated. The failure rate indicates the rate of occurrence of failure by a drop test of 50 motors. Table 6 shows the results.

(4) As is clear from Table 6, when the crushing strength is less than 1 N / mm, the motor failure rate sharply increases. This is because the magnets were low in mechanical strength, and the magnets were damaged by the impact of the drop test, thereby increasing motor failure. If the crushing strength is 1 N / mm or more, the defect rate is small and there is no practical problem.

円 筒 A cylindrical magnet having an outer diameter of 24 mm and a different thickness was produced by the same molding method using Compounds 1, 2, and 3 as in Example 6. 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 motor characteristics (torque value) are proportional to the surface magnetic flux density. As is clear from FIG. 9, it is possible to manufacture a motor having sufficiently higher characteristics than the conventional motor by using a cylindrical magnet having a thickness of 0.1 mm or more.

The present invention can be used as a resin-bonded magnet used for small motors and actuators used in electronic devices and the like, and as a manufacturing method using extrusion molding of the resin-bonded magnet.

The figure which shows one Example of the arc-shaped resin coupling type magnet of this invention. The figure which shows one Example of the cylindrical resin coupling type magnet of this invention. FIG. 3 is a diagram showing a manufacturing process of the resin-bonded magnet in the embodiment of the present invention. The figure which shows the extrusion-molding apparatus of the arc-shaped resin coupling type magnet in the Example of this invention. The figure which shows the extrusion-molding apparatus of the cylindrical resin coupling type magnet in the Example of this invention. The figure which shows the load application direction of the crushing strength measurement of the arc-shaped magnet in the Example of this invention. The figure which shows the relationship between the arc-shaped magnet thickness and the magnetic flux amount in the Example of this invention. The figure which shows the load application direction of the crushing strength measurement of the cylindrical magnet in the Example of this invention. The figure which shows the relationship between the cylindrical magnet thickness and surface magnetic flux density in the Example of this invention.

Explanation of reference numerals

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 Crush load R Magnet outer radius D Magnet outer diameter T Magnet thickness L Magnet length

Claims (6)

A resin-bonded magnet obtained by mixing a magnetic powder and a thermoplastic resin and bonding them together by an extrusion molding method, wherein the arc has an outer radius of 1.5 mm to 50 mm and a wall thickness of 0.1 mm to less than 1.0 mm. A resin-bonded type magnet having a crushing strength K defined by the following equation, where the length of the magnet is L (mm) and the crushing load is P (N), and the crushing strength K is 2 N / mm or more. magnet.
K = P / L A resin-bonded magnet obtained by mixing a magnetic powder and a thermoplastic resin and bonding them together by extrusion molding, wherein the outer diameter is 2 mm or more and 100 mm or less, and the thickness of the cylindrical magnet is 0.1 mm or more and less than 1.0 mm. Wherein the length of the magnet is L (mm) and the crushing load is P (N), and the crushing strength K determined by the following equation is 1 N / mm or more.
K = P / L The magnetic powder is a rare earth magnetic powder composed of a rare earth element (including yttrium (Y)) and a transition metal mainly composed of cobalt, a rare earth magnetic powder composed of a transition metal composed mainly of a rare earth element and iron and boron, or a rare earth magnetic powder. The resin-bonded magnet according to claim 1, wherein the magnet is a rare-earth magnetic powder composed of a transition metal mainly composed of an element and iron and nitrogen. A magnet composition obtained by mixing a magnetic powder and a thermoplastic resin is extruded while being cooled and solidified in a mold at a temperature equal to or lower than the melting point of the magnet composition, and has 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, where the length of the magnet is L (mm) and the crushing load is P (N), the crushing strength K determined by the following equation is obtained. A method for producing a resin-bonded magnet, characterized in that the magnet is molded to 2 N / mm or more.
K = P / L A magnet composition obtained by mixing a magnetic powder and a thermoplastic resin is extruded while being cooled and solidified in a mold at a temperature equal to or lower than the melting point of the magnet composition, and has an outer diameter of 2 mm or more and 100 mm or less. When the thickness of the cylindrical magnet is 0.1 mm or more and less than 1.0 mm, and the length of the magnet is L (mm) and the crushing load is P (N), the crushing strength K determined by the following formula is 1 N / A method for producing a resin-bonded magnet, characterized in that the magnet is molded to a thickness of at least mm.
K = P / L The magnetic powder is a rare earth magnetic powder composed of a rare earth element (including yttrium (Y)) and a transition metal mainly composed of cobalt, a rare earth magnetic powder composed of a transition metal composed mainly of a rare earth element and iron and boron, or a rare earth magnetic powder. The method for producing a resin-bonded magnet according to claim 4, wherein the rare-earth magnetic powder comprises a transition metal mainly composed of an element and iron and nitrogen.

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