JPH06302418A - Bond-type permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE:To improve magnetic characteristic, mechanical strength and corrosion resistance by manufacturing a bond-type permanent magnet through compression molding by using raw magnet powder whose entire surface is uniformly coated with thermosetting resin for bonding in advance. CONSTITUTION:A surface of magnet powder is uniformly coated with thermosetting resin by coating rare earth/iron magnet powder consisting of rare earth/iron magnet powder of an average diameter of 300mum or below or two kinds of mixtures of average grain diameters of 63mum or less and 150 to 300mum by using a low viscosity liquid-like composition wherein thermosetting resin is dissolved in organic solvent. Thereafter, the acquired resin coated magnet powder is filled up in a die and molded by compression, and a bond-type permanent magnet is manufactured by heating and setting the molded item. Thereby, it is possible to acquire a bond-type permanent magnet whose magnetic characteristic, mechanical strength, heat resistance and corrosion resistance are good, and its manufacturing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bond type permanent magnet excellent in magnetic properties, mechanical strength, heat resistance and corrosion resistance (oxidation resistance), and a method for producing the same.

[0002]

2. Description of the Related Art Bonded permanent magnets are made of hard ferrite or R-Fe-B (R is at least one kind of rare earth element) magnet powder such as rare earth / iron based magnet powder, which is made of epoxy resin, phenol resin, A magnet that is easily molded by being uniformly dispersed in a thermosetting resin such as polyester resin and bonded with the resin. It is widely applied to various household electric appliances and peripheral terminals of large computers. .

Compared with the conventional sintered permanent magnets and rare earth / iron permanent magnets, the bond permanent magnets have resin properties that do not exhibit magnetism and thus have a slightly inferior magnetic property, but do not shrink due to sintering. Therefore, there is a feature that magnets of various shapes can be manufactured with high dimensional accuracy. Therefore, it has been widely used in recent years in small motors such as spindle motors and stepping motors.

[0004] Generally, a bond-type permanent magnet is manufactured by mixing raw magnet powder with a thermosetting resin in a liquid state (containing additives such as a curing agent if necessary), and coating the obtained resin. If necessary, the magnet powder is crushed, then filled in a mold and compression-molded by a press to give a desired shape, and the coating resin is cured by heating.

The compression molding has a drawback that the process is a little complicated and the cost is higher than that of the injection molding. However, it is possible to increase the filling rate of the magnet powder (reduce the resin ratio) and to obtain excellent magnetic characteristics. Obtainable. However, the recent progress in miniaturization and high performance of electric and electronic products is remarkable, and in response to this, further improvement in the magnetic characteristics of the bonded magnet is desired. For that purpose, it is necessary to improve the magnetic properties of the magnet powder to be used or to increase the filling amount of the magnet powder in a unit volume.

As a means for improving the magnetic characteristics of Sm-Co type and rare earth / iron type (eg Nd-Fe-B type) rare earth magnet powders, the same magnetic characteristics are exhibited regardless of the direction of magnetization. Anisotropic magnets having improved magnetic properties in a specific direction have been developed as compared with anisotropic magnet powders. This anisotropic magnet has high magnetic properties only in a certain specific direction (direction of easy magnetization), so the easy axes of magnetization of each magnet powder are aligned in the same direction (orientated) inside the magnet body. That is the condition for improving the magnetic characteristics.

This orientation is generally performed by applying a magnetic field at the time of molding and rotating each anisotropic magnet powder so that its easy axis of magnetization is oriented in the magnetic field direction. Therefore, in the case of a bond-type permanent magnet, it is essential to devise such that individual magnet powders easily rotate during molding (that is, the frictional resistance of the powder surface decreases).

On the other hand, in order to increase the filling amount of the magnet powder in the unit volume of 1, it is necessary to reduce the resin ratio or to reduce the voids of the molded body produced by compression molding. However, considering the formability and mechanical strength of the bond-type permanent magnet, there is a limit to the reduction of the resin ratio. Therefore, the voids of the molded body should be reduced with the minimum required resin ratio. Methods for improving the powder filling rate have been investigated.

For example, in Japanese Patent Laid-Open No. 60-207302, 11
A method for producing a bond-type permanent magnet that improves the packing ratio of magnet powder by compression molding at a high pressure of ton / cm ² or higher is disclosed.

However, the compression molding at high pressure requires an expensive large press machine, and there is a problem that the punch and the die are significantly worn and damaged due to the high pressure. Further, it is difficult to further increase the pressing pressure from the viewpoint of the strength of punches and the like, and a method of increasing the filling rate of the magnet powder without increasing the pressure higher than in the past is desirable.

Since the rare earth / iron-based magnet is mainly composed of a rare earth metal which easily binds to oxygen and iron, it is easily oxidized in the air, and even if it is directly mixed with a thermosetting resin, it has a predetermined magnetic characteristic. It has been experienced that it could not be exhibited and that it was difficult to stabilize the magnetic properties. It is presumed that this is due to the influence of the oxidation of the magnet powder by the outside air in the manufacturing process. Further, the deterioration of the magnetic properties was remarkable especially when used at high temperature.

In order to prevent the oxidation of the magnet powder and improve the filling rate and the degree of orientation by reducing friction, the surface of the magnet powder is coated with a lubricant or a silane coupling agent, or these are thermosettable. Several treatment methods have been proposed so far, which are mixed with the resin component.

For example, in JP-A-60-220920, the surface of the magnet powder is coated with a lubricant to reduce the friction between the magnet powders during compression molding and between the magnet powder and the binding resin, thereby improving the bond type. Magnet density (filling degree of magnet powder)
And the degree of orientation is improved to improve the magnetic properties. The bond-type permanent magnet obtained by this method has excellent magnetic properties as compared with the case where a lubricant is not used, but since the adhesion between the magnet powder and the resin decreases, the mechanical strength and corrosion resistance are low. There is a problem of decrease.

In JP-A-62-264602, an epoxy resin is mixed with a silane coupling agent in an amount of 1 to 15% by weight, and then the epoxy resin is added to a rare earth magnet powder whose surface is previously coated with a lubricant. A method of kneading and kneading and compression molding is disclosed. By mixing the silane coupling agent in the epoxy resin, the wettability between the resin and the lubricant is improved, and as a result, the magnetic properties are improved.However, the surface treatment of the magnet powder with the silane coupling agent is mechanical. No improvement in strength and corrosion resistance can be expected.

In Japanese Patent Laid-Open No. 3-74810, a mixture of a rare earth / iron-based magnet powder whose surface is coated with a silane coupling agent and an epoxy resin mixed with a curing agent and a lubricant is compressed. A method of heat curing after molding is disclosed. According to this method, the oxidation of the rare earth / iron-based magnet powder in the air is suppressed, and this action continues even at high temperatures, so that heat resistance can be imparted to some extent. In addition, since a lubricant is added and mixed in the epoxy resin of the binder, friction between the magnet powders during molding and between the magnet powder and the epoxy resin is reduced, improving moldability and magnetic properties. It will be possible. However, only the magnetic powder surface treatment with a silane coupling agent or the like does not sufficiently improve the mechanical strength, and the corrosion resistance is not sufficiently improved.

[0016]

DISCLOSURE OF THE INVENTION The present invention has solved the problems existing in the above-mentioned prior art, that is, a bond type permanent magnet excellent in magnetic properties, mechanical strength, heat resistance and corrosion resistance (oxidation resistance). It is an object to provide a magnet and a method for manufacturing the magnet.

[0017]

In order to solve such a problem, the present inventors have conducted a microscopic observation such as a microscope observation of a resin-coated magnet powder as a compression molding raw material and a surface of a compression molded bond type magnet. At the same time, the fracture surface of the bond magnet after the strength test was microscopically observed by, for example, a microscope. As a result, the following knowledge was obtained and the present invention was completed.

The uniformity of the thickness of the resin coating in the raw magnet powder has a great influence on the magnetic properties, mechanical strength, heat resistance and corrosion resistance of the bond-type permanent magnet obtained by compression molding. That is, when the surfaces of all the magnet powders are coated with the resin in a uniform thickness, it is possible to obtain a bond-type permanent magnet excellent in magnetic characteristics, mechanical strength, heat resistance and corrosion resistance. To uniformly coat the surface of the magnet powder with the resin, do not knead the thermosetting resin with the magnet powder while keeping the viscosity high as in the past, for example, dissolve and dilute in an organic solvent to obtain a low-viscosity liquid. It is necessary to mix with magnet powder at.

Here, the gist of the present invention is a bond-type permanent magnet in which magnet powder is bonded with a thermosetting resin, the surface of which is uniformly coated with a thermosetting resin layer. Is a bond-type permanent magnet obtained by heating and curing the pressure-molded body.

Here, "uniformly coated" means that the entire surface of each magnet powder is coated with a substantially uniform thickness, and such a uniform coating includes a thermosetting resin. It can be achieved by mixing with a magnet powder in a low viscosity liquid. However, it suffices that a uniform coating equivalent to this is achieved, and in the bonded magnet of the present invention, the resin coating means for the raw material magnet powder is not limited to coating with a low-viscosity liquid resin. The uniformly coated state of the magnet powder can be confirmed by observing the resin-coated magnet powder powder with an electron microscope.

That is, the magnet powder is not previously coated with the silane coupling agent or the lubricant as in the prior art, but is uniformly coated with the thermosetting resin as the binding resin in advance. This is a feature of the present invention.

According to a preferred embodiment of the present invention, the magnet powder is a rare earth / iron-based magnet powder having an average particle size of 300 μm or less, or a rare earth / iron-based magnet powder and an average particle size of 63 μm or less. It consists of a mixture of 150-300 μm rare earth / iron-based magnet powder.

The thickness of the thermosetting resin layer that coats the magnet powder may be in the range of 0.3 to 5 μm in order to achieve uniform coating.

From another aspect, the present invention provides a resin obtained by mixing magnet powder with a low-viscosity liquid thermosetting resin composition and uniformly coating the surface of the magnet powder with a thermosetting resin layer. Fill the mold with the coated magnet powder, press-mold and heat the compact.
A method for producing a bond-type permanent magnet, which is characterized by curing.

The compression molding may be carried out at room temperature, but if it is carried out by heating to a temperature between the softening temperature and the hardening temperature of the thermosetting resin coating the magnet powder, the filling rate of the magnet powder will be further increased. And the magnetic characteristics are further improved.

[0026]

[Function] The magnet powder used in the present invention includes Nd, Pr,
Rare earth / iron-based magnet powder represented by R-Fe-B (R is at least one rare earth element) containing Ce, Dy, Tb, and other rare earth elements and Fe and B as main components, as well as rare earth elements -Cobalt-based magnet powder, hard ferrite powder containing iron oxide as a main component, and the like. A typical example of the R-Fe-B system magnet is an Nd-Fe-B system magnet, and a typical example of the rare earth / cobalt system magnet is an Sm-Co system magnet. A preferred magnet powder is a rare earth / iron-based magnet powder that has excellent magnetic properties and is cheaper than the rare earth / cobalt-based magnet powder.

The average particle size of the raw magnet powder is preferably 300 μm or less in order to ensure uniform coating with the resin. If the average particle size of the raw magnet powder exceeds 300 μm, even if the thermosetting resin is coated with a low-viscosity liquid, the resin does not adhere evenly to the magnet powder and the coating is unevenly distributed. Is reduced. Further, in such a coarse magnet powder, the gap between the magnet powders after compression molding becomes large,
The resin bond between the powders becomes insufficient and the mechanical strength of the bonded magnet decreases.

Further, as the raw material magnet powder, two kinds of powder having a small average particle diameter and powder having a large average particle diameter can be mixed and used. This mixed powder is preferably a mixture of rare earth / iron-based magnet powder having an average particle size of 63 μm or less and rare earth / iron-based magnet powder having an average particle size of 150 to 300 μm. When such a mixed powder is used, a small powder enters between the voids of a large powder, so that the filling rate of the magnet powder can be improved and the magnetic characteristics are improved under the necessary minimum resin amount. .

With respect to the lower limit of the average particle size of the magnet powder, it is desirable that the average particle size of the rare earth magnet powder such as rare earth / iron magnet and rare earth magnet / cobalt magnet is 20 μm or more. When the average particle diameter is smaller than 20 μm, the magnetic properties such as coercive force and squareness of the hysteresis curve of the magnet are deteriorated, and the specific surface area becomes too large, which causes a problem in terms of corrosion resistance. However, in the case of hard ferrite magnet powder, since the average particle diameter is usually 10 μm or less, such a limitation is not imposed.

In the present invention, a thermosetting resin is used as the binding resin for coating the magnet powder. The type of thermosetting resin is not particularly limited, but examples thereof include epoxy resin, phenol resin, and polyester resin. A preferred thermosetting resin is an epoxy resin. The thermosetting resin is used together with a curing agent (crosslinking agent) as needed.

In the present invention, the surface of the raw material magnet powder is uniformly coated with the thermosetting resin layer in advance. This uniform resin coating is a low-viscosity liquid binder resin (thermosetting resin).
It is achieved by mixing with magnet powder in the form of (for example, a resin solution having a low viscosity by dissolving in a suitable organic solvent). The low-viscosity liquid resin used for coating is not limited to a solution, and may be an emulsion, suspension or the like. The viscosity of the resin liquid is preferably 5000 cps or less at 25 ° C, more preferably 1000 cps or less, and particularly preferably 100.
cps or less.

When water is used as the solvent used for dissolving or dispersing the resin, it is preferable to use an organic solvent because it may cause a decrease in corrosion resistance as described above. The type of organic solvent may be selected according to the type of thermoplastic resin used. For example, for epoxy resins, ketones such as methyl ethyl ketone and cyclohexanone, and ethers can be used.

If desired, a small amount of additives such as silane coupling agents and lubricants can be added to the resin liquid used. Further, the magnetic powder may be surface-treated in advance with a silane coupling agent or a lubricant as in the above-mentioned conventional technique.

The coating of the magnet powder with the thermosetting resin is carried out by mixing the magnet powder with a predetermined amount of a low-viscosity liquid thermosetting resin in a container and heating the solvent if necessary to evaporate it. be able to. Of course, if uniform coating equivalent to this is possible, the magnet powder may be coated with a thermosetting resin by another coating method.

The compounding amount of the thermosetting resin with respect to the magnet powder is preferably in the range of 1 to 20% by weight. If the amount of the resin compounded is less than 1% by weight, the bonding of the magnet powder in the molded bond-type magnet becomes insufficient, the moldability becomes poor, and the mechanical strength decreases. On the other hand, if the compounding amount of the resin exceeds 20% by weight, the filling rate of the magnet powder becomes small, and it becomes impossible to exhibit the predetermined high magnetic characteristics.

In the present invention, by uniformly coating the raw material magnet powder with the binding resin in advance, the slippage of the magnet powder is improved (friction between the powder particles is reduced). The fluidity of the powder is improved and the packing density is increased. In addition, since the friction between the magnet powders during compression molding and between the magnet powders and the binding resin is also reduced, the filling rate of the magnet powder of the bond type permanent magnet is increased, and the voids of the powder are improved due to the uniformly existing resin. Is filled. Furthermore, since the entire surface of the magnet powder is pre-coated with resin, oxidation of the magnet powder during the manufacturing process does not easily occur, and even in the obtained bond-type magnet, each magnet powder is completely covered with resin and is protected from the outside air. Be protected. In the case of anisotropic magnet powder,
Since the magnet powder has low friction and good slippage, rotation for aligning the easy axis of magnetization of the magnet powder easily occurs during compression molding,
A molded product having a high degree of orientation can be obtained. As a result of the above,
It is presumed that magnetic properties, mechanical strength, heat resistance and corrosion resistance are all improved.

The thickness of the thermosetting resin layer coating the raw material magnet powder is preferably in the range of 0.3 to 5 μm, particularly preferably 0.4 to 2 μm. If the thickness of the resin coating layer is less than 0.3 μm, the entire circumference of the magnet powder cannot be uniformly coated, and the effect of the resin coating described above cannot be sufficiently obtained. On the other hand, when the thickness of the resin coating layer of the magnet powder exceeds 5 μm, the resin amount of the obtained bond-type magnet is too large, and the compounding ratio of the magnet powder becomes small. As a result, it is difficult to exhibit predetermined high magnetic characteristics. Become.

The total surface area per unit weight of the magnet powder depends on the average particle diameter of the powder, and the larger the average particle diameter of the magnet powder, the smaller the surface area per unit weight. as a result,
When the ratio of the thermosetting resin to the raw material magnet powder is constant in weight%, the magnet powder having a larger average particle size has a smaller total surface area, and therefore the thickness of the resin coating layer of each magnet powder is smaller. growing.

Therefore, in order to make the resin coating thickness a predetermined constant thickness, it is necessary to change the compounding amount of the thermosetting resin as the binder according to the particle diameter of the raw material magnet powder. The smaller the average particle size, the more binder resin must be used. That is, in order to obtain the preferable thickness of the resin coating layer within the range of 0.3 to 5 μm, the compounding amount of the resin with respect to the magnet powder must be appropriately selected within the range of 1 to 20% by weight according to the average particle size of the powder. There is.

As a result of examination from this viewpoint, for example, when the raw magnet powder has an average particle diameter of 30 μm, the compounding amount of the binder resin is in the range of 3 to 20% by weight, and when the average particle diameter of 100 μm is 2 to 10%.
The weight% range is preferably 1 to 8% by weight when the average particle size is 200 μm, and the range is 1 to 6% by weight when the average particle size is 300 μm. Thereby, the resin coating layer having a preferable thickness within the range of 0.3 to 5 μm can be formed on the surface of the magnet powder.

Further, as described above, 2 having different average particle diameters are used.
When two kinds of raw material magnet powders are used, when both powders are mixed and then coated with a thermosetting resin, there are cases where the binder resin is not uniformly coated with the magnet powder. This is because the resin is well dispersed in the magnet powder with the smaller particle diameter and the resin is uniformly coated, but the binder resin is not sufficiently dispersed on the surface of the magnet powder with the large average particle diameter, It is speculated that this may be due to uneven adhesion.

Therefore, when the raw magnet powder is a mixture of two kinds of powders having different average particle diameters (preferably a mixture of powders having an average particle diameter of 63 μm or less and powders having an average particle diameter of 150 to 300 μm), It is desirable that the two kinds of magnet powders are separately and uniformly coated with the thermosetting resin layer before mixing. In this case, as described above, the compounding amount of the resin with respect to the magnet powder having a large average particle size is smaller than that of the magnet powder having a small average particle size so that the resin coating layer has the same thickness. If the thickness of the resin coating layer of both magnet powders is different and the thickness of one resin coating layer deviates from the range of 0.3 to 5 μm, the distribution of the magnet powder in the obtained bond-type permanent magnet will not be uniform, and The characteristics may deteriorate.

The magnet powder coated with the thermosetting resin is filled in a mold, compression-molded, and then the molded body is heated and cured to produce a bond-type permanent magnet. The compression molding may be performed by a conventional method. The pressing pressure for compression molding is appropriately in the range of ^{2 to} 10 ton / cm ² .

When the raw material magnet powder is anisotropic, it is well known to those skilled in the art that a magnetic field is applied from the periphery of the die to perform compression molding in the magnetic field, thereby producing individual magnets. It is possible to obtain a molded product in which the easy magnetization direction of the powder is aligned in the same direction (that is, oriented). In the present invention, the magnet powder is coated with a thermosetting resin having a uniform thickness, and the friction between the magnet powders is reduced. Therefore, rotation of the magnet powder under the action of a magnetic field easily occurs, and the degree of orientation is increased. It is possible to obtain a molded product having a high quality. As a result, the magnetic properties of the obtained bonded magnet are improved.

The compression molding temperature may be room temperature, but if the compression molding is carried out at a temperature between the softening temperature and the curing temperature of the thermosetting resin, the magnet powders are compressed and the magnet powders are bonded to the binder resin. Friction is reduced, the packing ratio and orientation degree of the magnet powder are improved, and a bonded magnet having few voids and an increased density is obtained. As a result, magnetic properties are improved and mechanical strength, heat resistance and corrosion resistance are further improved in both cases of anisotropic and isotropic magnet powders. For that purpose, the die to be used may be heated to a temperature between the softening temperature and the curing temperature, and the heated die may be used for compression molding of the magnet powder.

After demolding, the molded body obtained is heated to a temperature higher than the curing temperature of the thermosetting resin used for coating the resin to cure the resin, whereby the bond-type permanent magnet of the present invention is obtained.
The heating conditions for this curing may be appropriately selected depending on the types of thermosetting resin and curing agent.

[0047]

[Examples] Raw magnet powder The raw magnet powder used in this example is manufactured as follows. Atomic fraction of 13% Nd, 12% Co, 1%
Ga, 6% B, balance Fe: Nd-Fe-B alloy 970-1170
It was kept in the hydrogen gas of K and decomposed into Nd hydride, Fe ₂ B and Fe. Next, the hydrogen pressure was lowered in this temperature range to dissociate the hydrogen from the Nd hydride to prepare a fine Nd ₂ Fe ₁₄ B crystalline magnet powder. The obtained magnet powder was further pulverized and Table 1
A magnet powder having a predetermined average particle size shown in was obtained.

Thermosetting resin composition (epoxy resin liquid) A cresol novolac type epoxy resin 32% by weight and a curing agent 3% by weight which are solid at room temperature are dissolved in 65% by weight of an organic solvent of methyl ethyl ketone to obtain a viscosity at 25 ° C. A low-viscosity liquid epoxy resin solution having a viscosity of 5 cps was obtained.

To coat the resin-coated magnet powder, the magnet powder and the epoxy resin liquid were mixed so as to have the compounding ratio shown in Table 1 (% by weight of resin solids [epoxy resin + curing agent] relative to the magnet powder). After evaporating methyl ethyl ketone at room temperature, it was crushed in a mortar to obtain a resin-coated magnet powder for compression molding.

Compression molding After filling the resin-coated magnet powder described above in a mold , a magnetic field (1
It was compression-molded at a pressure of 6 ton / cm ² under the application of 0 kOe). Except for Example 8, compression molding was performed at room temperature. After demolding, the epoxy resin coating the magnet powder is cured by heating at 150 ° C for 60 minutes in Ar gas to give a strip shape with a length of 100 mm, a width of 10 mm and a thickness of 5 mm and a cubic shape of 10 mm cubic. A shaped bond-type permanent magnet was obtained.

The properties of the bond type permanent magnet obtained as described above were evaluated by (1) magnetic property measurement, (2) bending strength test, and (3) moisture resistance test. The evaluation method is as follows.

(1) Measurement of magnetic properties Using a bond type permanent magnet of 10 mm cubic, the residual magnetic flux density (Br), coercive force (iHc) and maximum energy product (BHmax) were measured by a BH tracer.

(2) Bending strength test Using a bond type permanent magnet of 100 mm × 10 mm × 5 mm, JIS
The test was performed according to the bending test method for hard plastics of K7203. The distance between fulcrums was 75 mm, the test speed was 2 mm / min, and the bending fracture strength was calculated from the results.

(3) Humidity resistance test A 10 mm cubic bond type permanent magnet was preheated to 80 ° C. and then left in an atmosphere of a temperature of 80 ° C. and a relative humidity of 90% for 24 hours. twenty four
Visually observe the rust occurrence on the surface of the test piece after a while,
The number of rust occurrences was counted and evaluated according to the following criteria. ◯: No rust generation, Δ: Rust generation number 3 to 5 / cm ² , X: Rust generation number 6 to 12 / cm ² .

Examples 1 to 5 Nd-Fe-B magnet powder A having various average particle diameters as shown in Table 1 and an epoxy resin solution were mixed at a ratio shown in Table 1 to obtain resin-coated magnet powder. It was The resin-coated magnet powder thus obtained was compression-molded under the above conditions to obtain a bond-type permanent magnet.

Examples 6 to 7 Two types of Nd-Fe-B magnet powders A and B having different average particle sizes shown in Table 1 were mixed with an epoxy resin solution at a ratio shown in Table 1 before mixing. Two types of resin-coated magnet powder were obtained. The two types of resin-coated magnet powders were mixed at the mixing ratio shown in Table 1 and compression-molded to obtain a bond-type permanent magnet.

Example 8 A resin-coated magnet powder obtained by using a magnet powder A having an average particle size shown in Table 1 and an epoxy resin solution was kept at this temperature in a mold heated to 80 ° C. It was compression molded. After cooling, the mold was removed, and the molded body was heated under the above conditions to obtain a bond-type permanent magnet.

Comparative Examples 1 to 3, 9 Using magnet powder A having an average particle size shown in Table 1, Example 1
Resin coating was performed in the same manner as in (1) and compression bonding was performed to obtain a bond-type permanent magnet.

Comparative Examples 4 to 5 Two types of magnet powders A and B having different average particle diameters shown in Table 1 were used, and similarly to Example 5, they were separately coated with an epoxy resin solution before mixing, and then compression molded. Then, a bond-type permanent magnet was obtained.

Comparative Examples 6 to 7 Two types of magnet powders A and B having different average particle sizes shown in Table 1 were used. After mixing the two types of powders, the epoxy resin liquids in the amounts shown in Table 1 were used. The mixture was mixed and resin-coated, and the resin-coated magnet powder obtained was compression-molded to obtain a bond-type permanent magnet.

Comparative Example 8 Magnet powder A having an average particle size shown in Table 1 was directly mixed with the above-mentioned epoxy resin + hardening agent mixture without being solubilized, and the mixture was heated to 80 ° C.
Was heated to melt the resin and coat the magnet powder. Since the obtained resin-coated magnet powder was fused, it was crushed in a mortar and compression-molded in the same manner as above to obtain a bond-type permanent magnet.

Table 2 shows the measurement results of (1) measurement of magnetic properties, (2) bending strength test, and (3) moisture resistance test of the bond-type permanent magnets obtained above. Further, the uniformity of resin coating was examined by observing the resin-coated raw material magnet powders prepared in the above Examples and Comparative Examples with a scanning electron microscope (SEM). In each of the magnet powders of Examples having a resin layer thickness within the range of 0.3 to 5 μm, the magnet powder was coated with the resin having a uniform thickness. On the other hand, in the magnet powder having a resin layer thickness of less than 0.3 μm in the comparative example, the resin did not uniformly coat the entire periphery of the magnet powder.

[0063]

[Table 1]

[0064]

[Table 2]

The bond-type permanent magnet of the present invention has a resin coating having a uniform thickness in the proper range of the raw material magnet powder, and therefore has a magnetic characteristic and a bending test as compared with the permanent magnets of Comparative Examples 1 to 7. Excellent in both results and rust occurrence,
It can be seen that the magnetic properties, mechanical strength, heat resistance, and corrosion resistance are all improved.

[0066]

According to the present invention, a bond-type permanent magnet is manufactured by compression molding using a raw material magnet powder whose entire surface is coated with a thermosetting resin for bonding in a uniform thickness in advance, The following effects can be achieved.

(1) The slippage of the magnet powder at the time of filling the mold is improved, its fluidity is improved, and the packing density when it is filled in the mold is improved. Moreover, since the friction between the magnet powders and between the magnet powders and the binder resin is reduced during compression molding, the density of the obtained bond-type permanent magnet is increased, and the magnet powders are easily rotated when a magnetic field is applied. As a result, a bonded permanent magnet having a small void between powders and a high packing rate of magnet powder is obtained, and the orientation degree when anisotropic magnet powder is used is also improved, so that the magnetic characteristics are improved.

(2) Since the raw material magnet powder is completely bonded with the resin and the voids between the magnet powders are small and the magnetic powders are packed at a high density, the mechanical strength of the bonded permanent magnet is improved.

(3) Since the entire surface of the raw material magnet powder is coated with the thermosetting resin for bonding in a uniform thickness, oxidation of the magnet powder during molding and heat curing is prevented, and the magnet powder is magnetized by oxidation. The deterioration of characteristics can be prevented. Also in the obtained bond-type permanent magnet, since the entire surface of the magnet powder is coated with the resin, the antioxidant effect of the magnet powder is maintained even when exposed to a high temperature and high humidity environment during use. The heat resistance and humidity resistance are improved.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location // H01F 7/02 A (72) Inventor Akira Kitagawa 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Sumitomo Yamazaki Seisakusho Co., Ltd.

Claims (6)

[Claims] 1. A bond-type permanent magnet in which magnet powder is bonded with a thermosetting resin, the surface of which is uniformly coated with a thermosetting resin layer to heat and cure a pressure-molded body of the magnet powder. The obtained bond-type permanent magnet. 2. The bond-type permanent magnet according to claim 1, wherein the magnet powder is a rare earth / iron-based magnet powder having an average particle diameter of 300 μm or less. 3. The bond type permanent magnet according to claim 1, wherein the magnet powder is a mixture of rare earth / iron-based magnet powder having an average particle size of 63 μm or less and rare earth / iron-based magnet powder having an average particle size of 150 to 300 μm. . 4. A magnet powder is mixed with a low-viscosity liquid thermosetting resin composition to uniformly coat the surface of the magnet powder with a thermosetting resin layer, and the obtained resin-coated magnet powder is filled in a mold. And then compression-molding the molded body to heat and cure the molded body. 5. The method for producing a bonded permanent magnet according to claim 5, wherein the magnet powder is a rare earth / iron-based magnet powder having an average particle diameter of 300 μm or less. 6. The magnet powder comprises a rare earth / iron-based magnet powder having an average particle size of 63 μm or less and a rare earth / iron-based magnet powder having an average particle size of 150 to 300 μm. The method for producing a bonded permanent magnet according to claim 5, wherein the curable resin layer is uniformly coated.