JPH11204320A - Bonded magnet and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a bonded magnet which is improved in corrosion resistance and mechanical strength. SOLUTION: A main body 12 of a rare-earth bonded magnet 10 is obtained by injection or compression-molding a kneaded material of rare-earth magnet powder and a binder composed of a high polymer material into a required shape. It is preferable to adjust the mixing ratio of the rare-earth magnet powder and an epoxy resin which is used as the high polymer material as the high polymer material in the main body 12 to 90-99 wt.% and 1-10 wt.%, respectively. The entire surface of the main body 12 is covered with a first resin film 14 composed of an epoxy resin, which is a high polymer material and having a thickness of 5-50 μm. Then the entire surface of the first resin film 14 is furthermore covered with a second resin film 16 which is composed of an epoxy resin and having a thickness of 1-20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonded magnet and a method of manufacturing the same, and more particularly, to a magnet body covered with a polymer material coating layer or a metal plating layer. The present invention relates to a bonded magnet covered with a coating layer and a method for producing the same.

[0002]

2. Description of the Related Art Rare earth obtained by injection molding or compression molding of a mixture obtained by mixing a powder of a magnetic material containing one or more kinds of rare earth elements such as Sm, Nd, Pr and a resin binder in a required ratio. Bond magnets are suitably used, for example, as rotors in spindle motors for hard disks. However, since rare-earth bonded magnets contain raw materials that are easily oxidized, rust easily occurs over time if the surface is unmodified, and if used as such for motor parts, the durability and failure may be reduced. Will be invited. Therefore, measures are generally taken to coat the surface of the rare-earth bonded magnet with a resin film by a spray coating method, an electrodeposition coating method, a dip coating method or the like to prevent rust.

[0003]

In the case of the above-mentioned spray coating method or dip coating method, it is difficult to control the film thickness formed by the coating method, and there is a disadvantage that the corrosion resistance of the resin film alone is generally low. On the other hand, in the case of the electrodeposition coating method, a uniform resin film can be formed, and the corrosion resistance is excellent. However, a coating is not formed on the electrode portion in contact with the magnet surface, and there is a concern that rust is generated from the trace of the electrode and that the magnet powder is scattered. In addition, products using rare-earth bonded magnets whose surface is coated with a resin coating have low mechanical strength, and the resin coating may be damaged during the assembly process or may be easily broken if dropped accidentally during transportation. Some difficulties are pointed out. That is, in any case, it is pointed out that a sufficient corrosion resistance and mechanical strength cannot be obtained only by coating the surface of the rare-earth bonded magnet only with the resin film.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks inherent in the prior art, and has been proposed in order to suitably solve the drawback. The present invention provides high corrosion resistance and high mechanical strength. An object of the present invention is to provide a bond magnet that can be improved and a method for manufacturing the same.

[0005]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned problems and appropriately attain the intended purpose, a bonded magnet according to the present invention is a mixture of a rare earth magnet powder and a polymer material in a required ratio. And the entire surface of the magnet body is coated with a coating layer or a metal plating layer of a polymer material, and the entire outer surface of the coating layer or the metal plating layer is further coated with a coating layer of a polymer material. Characterized by being coated with

[0006] In order to overcome the above-mentioned problems and achieve the intended object, a bonded magnet according to another invention of the present application comprises Nd-Fe.
The magnet main body is composed of a mixture in which the rare earth magnet powder of -B type is 90 to 99 wt% and the epoxy resin as a polymer material is mixed at a ratio of 1 to 10 wt%, and the entire surface of the magnet main body is 5 to 50 μm. While being coated with a thick epoxy resin coating layer, the entire outer surface of the coating layer is further 1 to
It is characterized by being coated with a resin coating layer having a thickness of 20 μm.

[0007] In order to overcome the above-mentioned problems and achieve the intended object, a bonded magnet according to still another invention of the present application is an Nd-bonded magnet.
The magnet body is composed of a mixture of a Fe-B-based rare earth magnet powder and an epoxy resin as a polymer material in a required ratio, and the entire surface of the magnet body is covered with a nickel plating layer. The entire outer surface of the layer is further coated with an epoxy resin coating layer.

[0008] In order to overcome the above problems and achieve the intended object, a method for manufacturing a bonded magnet according to another invention of the present application is as follows.
An epoxy resin coating layer having a thickness of 5 to 50 μm is formed by electrodeposition or dip coating on the entire surface of the magnet body made of a mixture of the rare earth magnet powder and the epoxy resin as a polymer material in a required ratio. After performing the forming step, an epoxy resin coating layer is further applied to the entire outer surface of the coating layer by 1 to 20 μm by electrodeposition or spray coating.
A step of forming with a thickness of

In order to overcome the above problems and achieve the intended object, a method for manufacturing a bonded magnet according to still another invention of the present application is to mix a rare earth magnet powder and an epoxy resin as a polymer material at a required ratio. A step of forming a nickel plating layer with a thickness of 5 to 50 μm on the entire surface of the magnet main body made of the molded product of the mixture by electrometal plating, and then electrodepositing or dipping the entire outer surface of the nickel plating layer The method is characterized in that a step of forming an epoxy resin coating layer with a thickness of 1 to 20 μm by a coating method is performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a bonded magnet and a method for manufacturing the same according to the present invention will be described below with reference to the accompanying drawings.

[0011]

FIG. 1 shows a rare earth bonded magnet according to a first embodiment. The magnet main body 12 of the rare earth bonded magnet 10 is one of rare earth elements such as Sm, Nd and Pr. Alternatively, it is obtained by adding or kneading a binder made of a polymer material to a magnetic material powder containing two or more kinds and injecting or kneading the mixture into a required shape.
The magnet main body 12 is preferably composed of a mixture of Nd-Fe-B-based rare earth magnet powder in a proportion of 90 to 99 wt% and an epoxy resin as a polymer material in a proportion of 1 to 10 wt%.

The entire surface of the magnet body 12 is 5 to 50
It is covered with a first resin coating layer 14 made of an epoxy resin which is a polymer material having a thickness of μm. And this first
The entire outer surface of the resin coating layer 14 is further covered with a second resin coating layer 16 made of an epoxy resin which is a polymer material. The thickness of the second resin coating layer 16 is 1 to 20 μm.
Is set to

FIG. 2 is a flowchart showing the steps of manufacturing the rare earth bonded magnet according to the first embodiment. The magnet main body 12 used in this embodiment includes, for example, Nd 27% by weight, Fe 67% by weight, B1% by weight,
An alloy powder having an average particle size of 150 μm having a composition of Co 5 wt%, a coupling agent 0.1 wt%, and an epoxy resin 1.
It is manufactured by adding and mixing 5 to 3.0 wt% of a lubricant, kneading, compression molding at a required pressure, and curing by heat treatment at 180 ° C for 30 to 60 minutes. The composition of the alloy powder was as follows: Nd 30 wt%, Fe 69 wt%, B1
wt%.

The magnet body 12 is washed with pure water to remove impurities adhering to the surface. Then, the first resin coating layer 14 is formed on the entire surface of the magnet main body 12 by an electrodeposition coating method. That is, the magnet body 1 is placed in a solution in which the epoxy resin to be coated is dissolved in pure water at a required ratio.
2 is immersed, a required voltage is applied to an electrode disposed in a container in which the solution is stored, so that a first resin coating layer 14 of epoxy resin having a required thickness is formed on the entire surface of the magnet body 12. It is formed. The thickness of the first resin coating layer 14 is
By controlling the applied voltage and immersion time, 5 to 50
It is set to be μm. The magnet main body 12 on which the first resin coating layer 14 is formed is dried through a washing step. The first resin coating layer 14 may be formed by a spray coating method or a coating method disclosed in JP-A-8-265994.

Next, a second resin coating layer 16 is further formed on the entire outer surface of the first resin coating layer 14 covering the surface of the magnet main body 12 by a dip coating method. That is, the magnet body 12 is immersed in a resin solution containing an epoxy resin to be coated, the magnet body 12 taken out of the resin solution is dried and drained, and then left in an oven at a required temperature for a predetermined time. And perform a hardening process. Thereby, the rare-earth bonded magnet 10 having high corrosion resistance and improved mechanical strength, which is double-coated with the first resin coating layer 14 and the second resin coating layer 16, is obtained. The thickness of the second resin coating layer 16 is set to 1 to 20 μm by controlling the concentration of the epoxy resin in the resin solution. As an example of the composition of the resin solution, epoxy resin: 7.0 wt%,
Xylene: 8.0 wt%, MEK (methyl ethyl ketone): 85.0 wt%, and curing agent: 2.0 wt% are preferably used. As for the second resin coating layer 16,
It may be formed by an electrodeposition coating method as in the case of the first resin coating layer 14.

[0016]

[Test Example of First Embodiment] For each of the 20 rare-earth bonded magnets obtained by the manufacturing method according to the above-described first embodiment and the rare-earth bonded magnets coated only with a resin film by the conventional electrodeposition coating method. Table 3 shows the results of inspection for the presence or absence of rust by holding the sample in boiling water for 3 hours. The test results are shown as the ratio of the number of rusts generated to 20 rare-earth bonded magnets (the number of rusts generated / 20). The magnet body used for the test was φ20 × φ18 ×
In this embodiment, the first resin coating layer 14 having a thickness of 20 μm is formed on the molded body.
A second resin coating layer 16 having a thickness of 20 μm is formed.
A resin coating of μm is formed. Further, each of the rare earth bonded magnet of the first embodiment and the rare earth bonded magnet of the conventional example is 2
About 0 pieces, the result which measured the radial crushing strength by applying a stress load with a load cell is also shown.

[0017]

That is, from the test results, the magnet body 1
2 is doubly covered with the first resin coating layer 14 and the second resin coating layer 16 in the rare earth bonded magnet 10 of the first embodiment, compared with the conventional rare earth bonded magnet coated only with the resin coating. It became clear that both corrosion resistance (rust prevention effect) and radial crushing strength (breaking strength) were improved.

[0019]

FIG. 3 shows a rare earth bonded magnet according to a second embodiment. The magnet main body 22 of the rare earth bonded magnet 20 has one or two rare earth elements similar to those described above. It can be obtained by adding or kneading a binder made of a polymer material to a magnetic material powder containing at least one kind and injecting or compression-molding it into a required shape. The magnet main body 22 is preferably composed of a mixture of Nd-Fe-B-based rare earth magnet powder in a proportion of 90 to 99 wt% and an epoxy resin as a polymer material in a proportion of 1 to 10 wt%. The magnet body 22 has a surface roughness of 10
0μm or less, density preferably between 5.0~6.5g / cm ³ is set to 6.0 g / cm ^3.

The entire surface of the magnet main body 22 is covered with a nickel plating layer (metal plating layer) 24 made of nickel as a metal material, and has a thickness of 5 to 50 μm.
m. And this nickel plating layer 2
The entire outer surface of No. 4 is further covered with a resin coating layer 26 made of an epoxy resin which is a polymer material. In addition, the thickness of the resin coating layer 26 is set to 1 to 20 μm.

FIG. 4 is a flowchart showing the steps of manufacturing the rare earth bonded magnet according to the second embodiment. The magnet main body 22 used in this embodiment includes, for example, Nd 27 wt%, Fe 67 wt%, B 1 wt%
An alloy powder having an average particle size of 150 μm having a composition of Co 5 wt%, a coupling agent 0.1 wt%, and an epoxy resin 1.
It is manufactured by adding and mixing 5 to 3.0 wt% of a lubricant, kneading, compression molding at a required pressure, and curing by heat treatment at 180 ° C for 30 to 60 minutes. Each manufacturing condition is set such that the surface roughness of the obtained magnet main body 22 is 100 μm or less and the density is 5.0 to 6.5 g / cm ³ . The composition of the alloy powder is Nd30w
t%, Fe69wt%, B1wt%.

The magnet body 22 is washed with pure water to remove impurities adhering to the surface. Then, after the magnet main body 22 is plated by an electrometal plating method using nickel as a plating metal, the magnet body 22 is dried through a washing step. Thus, the entire surface of the magnet body 22 is directly covered with the nickel plating layer 24. The thickness of the nickel plating layer 24 is set to 5 to 50 μm by controlling the plating time and the like. In the metal electroplating method, a magnet main body 22 is charged into a barrel tank in which a plating solution is stored, and the barrel is rotated by rotating the tank and applying a current to an electrode provided in the tank. The method is preferably used. A well-known watt bath is suitable as the plating solution.

Next, a resin coating layer 26 is further formed on the entire outer surface of the nickel plating layer 24 covering the surface of the magnet main body 22 by a dip coating method. That is, the magnet body 22 is immersed in a resin solution containing an epoxy resin to be coated, the magnet body 22 taken out of the resin solution is dried and drained, and then left in an oven at a required temperature for a predetermined time. And perform a hardening process. Thereby, the magnet body 22
Is coated directly with a nickel plating layer 24, and the plating layer 24 is further coated with a resin coating layer 26, thereby obtaining a rare earth bonded magnet 20 having high corrosion resistance and improved mechanical strength. The thickness of the resin coating layer 26 is set to 1 to 20 μm by controlling the concentration of the epoxy resin in the resin solution. Examples of the composition of the resin solution include: epoxy resin: 7.0 wt%, xylene: 8.0 wt%, MEK (methyl ethyl ketone):
Those having 85.0 wt% and a curing agent of 2.0 wt% are suitably used. Regarding the resin coating layer 26, the electrodeposition coating method disclosed in the above-mentioned first embodiment and the method disclosed in Japanese Patent Application Laid-Open No. 8-265994.
It may be formed by using the coating method disclosed in Japanese Patent Application Laid-Open Publication No. H10-15095.

[0024]

Test Example of the Second Embodiment Boiling water was applied to each of the 20 rare-earth bonded magnets obtained by the manufacturing method according to the above-described second embodiment and the 20 rare-earth bonded magnets whose magnet bodies were covered only with a nickel plating layer. The results of inspection for the presence or absence of rust after holding for 3 hours are shown in Table 2 below. The test results are shown as the ratio of the number of rusts generated to 20 rare-earth bonded magnets (the number of rusts generated / 20). The magnet body used for the test was φ20 × φ18 ×
In this embodiment, a nickel plating layer 24 having a thickness of 20 μm was formed, and a resin coating layer 26 having a thickness of 5 μm was formed.
m nickel plating layer is formed. Further, the results obtained by applying a stress load by a load cell to each of the 20 rare-earth bonded magnets of the second embodiment and the rare-earth bonded magnet of the comparative example and measuring the radial crushing strength are also shown.

[0025]

That is, from the test results, the magnet body 2
2 is double-coated with a nickel plating layer 24 and a resin coating layer 26, the rare-earth bonded magnet 20 of the second embodiment has a higher corrosion resistance (anti-corrosion) than the rare-earth bonded magnet of the comparative example having only the nickel plating layer. It became clear that both the rust effect) and the radial crushing strength (breaking strength) were improved.

[0027]

As described above, according to the bonded magnet and the method of manufacturing the same according to the present invention, the entire surface of the magnet main body is covered with the coating layer of the polymer material or the metal plating layer, and the entire outer surface is further covered. By covering with a coating layer of a polymer material, the corrosion resistance and mechanical strength of the bonded magnet are improved. Therefore, it is possible to improve the reliability of the product using the bonded magnet according to the present invention, and to prevent the product from being damaged during the assembling process or from being erroneously damaged during transportation,
It has the advantage of easy handling. In particular, when the surface of the magnet main body is covered with a metal plating layer such as a nickel plating layer, the efficiency of forming the plating layer is improved, so that higher corrosion resistance can be ensured and mechanical strength is also improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a rare-earth bonded magnet according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing steps of a method for manufacturing a rare-earth bonded magnet according to the first embodiment.

FIG. 3 is a sectional view showing a rare earth bonded magnet according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating steps of a method for manufacturing a rare-earth bonded magnet according to a second embodiment.

[Explanation of symbols]

 12 magnet main body 14 first resin coating layer 16 second resin coating layer 22 magnet main body 24 nickel plating layer (metal plating layer) 26 resin coating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 41/02 H01F 1/04 H

Claims (7)

[Claims] A magnet body (12, 22) is composed of a mixture of a rare earth magnet powder and a polymer material in a required ratio, and the entire surface of the magnet body (12, 22) is coated with a polymer material. Covered with a layer (14) or a metal plating layer (24),
A bonded magnet, wherein the entire outer surface of the coating layer (14) or the metal plating layer (24) is further covered with a coating layer (16, 26) of a polymer material. 2. An Nd—Fe—B-based rare earth magnet powder containing 9
The magnet body (1) is prepared from a mixture of 0 to 99 wt% and an epoxy resin as a polymer material mixed at a ratio of 1 to 10 wt%.
2) is constituted, and the entire surface of the magnet main body (12) is 5 to 50
μm thick epoxy resin coating layer (14), and the entire outer surface of the coating layer (14) is further coated with a 1-20 μm thick resin coating layer (16). And bond magnets. 3. A magnet body (22) is composed of a mixture of a Nd—Fe—B-based rare earth magnet powder and a polymer material of epoxy resin in a required ratio, and the magnet body (22).
A bonded magnet, characterized in that the entire surface is coated with a nickel plating layer (24), and the entire outer surface of the nickel plating layer (24) is further coated with an epoxy resin coating layer (26). 4. The nickel plating layer (24) has a thickness of 5
The bonded magnet according to claim 3, wherein the thickness of the bonded magnet is from 50 to 50 m. 5. The bonded magnet according to claim 3, wherein the thickness of the epoxy resin coating layer is 1 to 20 μm. 6. A coating of an epoxy resin on the entire surface of a magnet body (12) made of a mixture of a rare earth magnet powder and an epoxy resin as a polymer material at a required ratio by electrodeposition or spray coating. Layer (14) is 5 to 50 μm
After the step of forming a layer having a thickness of 1 m, a step of further forming a layer of epoxy resin (16) with a thickness of 1 to 20 μm on the entire outer surface of the film layer (14) by electrodeposition or dip coating A method for producing a bonded magnet, comprising: 7. A nickel plating layer (24) formed by electrometal plating on the entire surface of a magnet body (22) formed of a mixture of a rare earth magnet powder and an epoxy resin as a polymer material in a required ratio. Is formed in a thickness of 5 to 50 μm, and a coating layer (26) of an epoxy resin is formed in a thickness of 1 to 20 μm on the entire outer surface of the nickel plating layer (24) by electrodeposition or dip coating. A method of manufacturing a bonded magnet.