JP2000124052A - Manufacture of bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a bonded magnet, in which failures which are caused by association of components and insufficiency of strength are not generated. SOLUTION: In a manufacturing process of a bonded magnet, a molded object in which magnet powder and first binder are mixed and compression- molded is heat-treated, and a hardened object is obtained. It is vacuum- impregnated with second binder and hardened by heating, and a cubic magnet whose edge is at most 5 mm is obtained. The unwanted second binder which is stuck on the surface of the hardened object after vacuum impregnation is performed is eliminated by centrifugal force, or heating is performed while the hardened object is vibrated or made to flow in a manufacturing process for thermosetting the impregnated second binder, or heating is performed while the hardened object is vibrated or made to flow, after the unwanted second binder which is stuck on the surface of the hardened object after vacuum impregnation is performed is eliminated by centrifugal force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a bonded magnet comprising magnet powder and resin, and more particularly to a production process after vacuum impregnation of resin.

[0002]

2. Description of the Related Art Bonded magnets are inferior in maximum energy product to sintered magnets, but have recently been widely used due to their superior workability and manufacturing cost compared to sintered magnets. The method of manufacturing a bonded magnet is generally performed by heat-treating a cured product obtained by compression-molding a compound obtained by mixing a first binder with magnet powder, vacuum-impregnating a cured product obtained with a second binder, and then heating and curing the magnet. The steps to get it done.

The applicant of the present invention has proposed a method for manufacturing a bonded magnet in order to manufacture a component having an extremely small component size for use in a precision machine such as an electronic timepiece or the like, as Japanese Patent Application No. 8-1200.
79, Japanese Patent Application Laid-Open No. 9-260134, and Japanese Patent Application No. 10-113043 proposed as a rotor for an electronic timepiece and a method for manufacturing the same, in which the steps from vacuum impregnation of a second binder in the manufacturing process to heat curing of the binder are performed. Then, after being impregnated with a second binder under vacuum, heat-cured as it is,
Alternatively, a method is employed in which excess resin adhering to the periphery of the cured body is washed with ethanol and cured by heating. FIG. 5 is a flowchart of a conventional method for manufacturing a bonded magnet.

[0004]

However, when the bond magnet is cured by heating in such a manner, the second binder adhered to the periphery of the cured body becomes an adhesive when cured by heating after vacuum impregnation. If the pieces are cured together to produce defective products, or washed with ethanol, the second binder impregnated in the cured product will also be removed, so the strength after heat curing will decrease, There is a problem that defective products are produced. Such a phenomenon does not cause a serious problem in the case of a normal component size, but appears when a small bonded magnet such as a watch component is manufactured so as to have a size such that one side does not come out of a cubic space with a side of 5 mm. In particular, when the conventional method is applied to small particles such as sand particles, the whole becomes a lump or the effect of vacuum impregnation is lost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a bonded magnet that does not produce defective products after heat curing.

[0006]

Means for Solving the Problems In order to solve the above problems, the present invention provides a cured product obtained by subjecting a compound obtained by compression molding a compound obtained by mixing a magnetic powder and a first binder in a magnetic field to a heat treatment. In the manufacturing process of a bonded magnet in which a magnet is obtained by performing heat curing after vacuum impregnation of the second binder, unnecessary vacuum binder adhered to the surface after vacuum impregnation is removed by centrifugal force. I do. Alternatively, in a manufacturing process of heating and curing the impregnated second binder, the cured product is heated while being vibrated or fluidized. Alternatively, after performing vacuum impregnation, an unnecessary second binder attached to the surface is removed by centrifugal force, and then the cured product is heated while being vibrated or fluidized. Alternatively, the size of the magnet used in the above-described manufacturing method is a size that does not leave a cubic space with one side of 5 mm.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following configuration.

In the present invention, the magnet powder is SmCo-based, N
Any of dFeB type and SmFeN type may be used. Further, as the first binder for performing compression molding, any resin that can be subjected to compression molding such as a thermosetting adhesive such as an epoxy resin or a phenol resin can be used. The second binder for vacuum impregnation of the cured product obtained by compression molding and heat treatment of the compound obtained by mixing the magnetic powder and the first binder may be a liquid, and is preferably inexpensive, has a strong adhesive strength, and has high workability. It is selected from good thermosetting adhesives such as epoxy resin, phenol resin and urethane resin. When impregnating, it is desirable to use a resin having good permeability and low viscosity.

Next, a method for manufacturing a bonded magnet will be described. First, a compound is obtained by mixing the first binder with the magnet powder. The compound is compression-molded under pressure to obtain a molded body having a predetermined shape, and a heat treatment is performed to obtain a cured product. Next, the cured product is immersed in the second binder in an environment where the pressure is reduced to about 1 Torr, and the pressure is gradually returned to the atmospheric pressure to complete the vacuum impregnation.

[0010] In the post-process until the bonded magnet product is obtained from the cured product after vacuum impregnation, in the method for manufacturing a bonded magnet according to the first aspect, an unnecessary second binder adhered to the surface is centrifugally applied. The binder is completely cured by heat curing after removal. 3. The method for producing a bonded magnet according to claim 2, wherein the cured product is heated and cured while vibrating or flowing the cured product to prevent association of the cured product.
In the method for manufacturing a bonded magnet according to the third aspect, a bonded magnet product is obtained by removing unnecessary second binder attached to the surface by centrifugal force, and then heating the cured product while vibrating or flowing. . FIG. 1 shows a flowchart of the method for manufacturing a bonded magnet of the present invention. Regarding the location where the process has a branch, claims 1 to 3 are described next to arrows 1 to 3
The number is shown.

First, as a method of removing the second binder by a centrifugal force, there is a method of placing the cured body after vacuum impregnation in a net container or the like and placing the cured body in a centrifuge. The conditions for removing the second binder by centrifugal force can be changed by centrifugal force and time, but the hardened body of the bonded magnet is weak and brittle, so it is not possible to apply a large centrifugal force, so by changing the time The conditions for removing the excess second binder are changed.

Next, an example of a method of flowing a cured product will be described with reference to a schematic view of a flow device shown in FIG. The fluidizing device shown in FIG. 2A puts a cured body 103 impregnated with a second binder in a rotating drum 101 that can rotate in the direction of arrow r, and rotates the rotating drum 101 to rotate the rotating drum 101. The cured body 103 impregnated with a binder in a vacuum is made to flow in the rotating drum 101. In order to enhance the flow effect, the flow fins 10
5 should be provided. The flow conditions can be changed by the rotation speed of the rotary drum 101 and the shape of the flow fins 105. In order to heat the cured body 103 in which the second binder is vacuum impregnated, hot air is blown from the direction indicated by the arrow A on the side of the opening. Direction) How to blow hot air,
There is a method of heating the rotating drum 101 itself.

The fluidizing device shown in FIG.
Cured body 1 vacuum impregnated with second binder charged in 1
03 can be caused to flow by rotating the fin 205 in the direction of the arrow r. In order to heat the cured body 103 in which the second binder is vacuum impregnated, a method in which hot air is blown from the direction indicated by the arrow A on the upper surface of the opening, the fluidized vessel 201 is made into a net bottom, and from the bottom of the fluidized vessel 201 (in the direction of arrow B) There are a method of blowing hot air and a method of heating the fluidized vessel 201 itself.

The flow device shown in FIG. 2 (c) is a device in which a cured body 103 impregnated with a second binder in a vacuum is poured into a flow vat 301 which can be tilted in the direction of arrow r to flow. Flow conditions can be varied by tilting angle and speed. In order to heat the cured body 103 in which the second binder is vacuum-impregnated, a method of blowing hot air from the direction shown by the arrow A on the upper surface of the opening is used. There are a method of blowing hot air and a method of heating the fluidized vat 301 itself.

Further, an example of a method of vibrating the cured body will be described with reference to a schematic diagram of a vibration device shown in FIG. The vibration device shown in FIG. 3 is a device in which a cured body 103 impregnated with a second binder in a vacuum is put into a vibration bat 401 capable of swinging in the horizontal and vertical directions of the container and vibrated. The vibration condition can be changed by the period and the amplitude of the vibration. In addition, an ultrasonic vibrator or the like can be used to vibrate. In order to heat the cured body 103 vacuum impregnated with the second binder, a method of blowing hot air from the direction of the upper surface of the opening indicated by the arrow A, the vibrating bat 401 is made into a net bottom, and from the bottom of the vibrating bat 401 (in the direction of the arrow B) There are a method of blowing hot air and a method of heating the vibration bat 401. The above heating conditions can be changed by temperature and time.

If the thermosetting resin obtains activation energy by heating, the curing reaction proceeds. The state in which the curing reaction has completely progressed and the reaction no longer progresses is complete curing. In the preheating curing, the heating is stopped at a stage before the curing is completed, and the heating is temporarily stopped at an intermediate stage of the curing reaction. Before the curing reaction, the second binder is liquid, but when the curing reaction has progressed about 50% of the completely cured state, the resin is already solid. In this state, no association occurs even if the bonded magnet being cured is in contact. For this reason, the heat treatment for completely proceeding the curing reaction does not cause any problem even if the preliminarily cured body is put into a cup or the like at once. The yield required in the production process of the bonded magnet is 95% or more.

(Examples 1 to 9) A compound was prepared by adding 1 part by weight of a first binder composed of bisphenol A and an amine-based curing agent to a magnet powder, and a compound having a pressure of 7 to 12 t /
cm2, outer diameter 1.25mm x inner diameter 0.36mm
× compression molding into a cylindrical shape having a thickness of 0.52 mm to obtain a molded body. The molded body was heated at 180 degrees for 90 minutes to obtain a cured body. This cured product was subjected to vacuum impregnation using a second binder composed of bisphenol F, tetrahydromethylphthalic anhydride and 2-ethyl-4-methylimidazole. Vacuum impregnation was performed by degassing the parts at 0.3 Torr for 5 minutes, and pouring the second binder under the same pressure while impregnating the parts for 30 minutes. Subsequently, the pressure was maintained at 5 atm for 10 minutes to sufficiently impregnate the cured body with the second binder, and then returned to the atmospheric pressure. Next, 1000 pieces of each of the cured products impregnated with the vacuum were centrifuged at 1500 G, 2500 G, and 3500 G for 10 times.
The excess second binder was removed by a centrifugal separator for 20 minutes, 20 minutes, and 30 minutes, respectively, and then heat-cured in a thermostat at 180 ° C. for 2 hours to prepare a bonded magnet. The evaluation is performed by associating at the time of thermosetting and forming an inferior product, and a strength test is performed on a product having a predetermined shape that is not associated, and has a strength of 1.5 kg or less. The percentage of strength failure, which is a ratio, was measured, and the yield was determined.

The method of measuring the intensity will be described with reference to FIG. FIG. 4A is an explanatory diagram of the intensity measurement. In order to measure the strength, the load meter 503 and the taper pin 501 attached to the load meter 503 are moved at a constant speed in the direction of the arrow, and the taper pin 501 is inserted into the center hole of the bond magnet 505. The strength is defined as the maximum load applied to the tapered pin 501 when the 501 is broken. The value of the strength can be known by reading the indicated value of the load cell 503. Tapered pin 50 used in this embodiment
The shape of No. 1 is shown in FIG. The speed at which the load meter 503 and the tapered pin 501 were moved was 1 mm per minute.

As a result, the centrifugal force was increased to 2500 G, 3500
No meeting was found in any of the bonded magnets from which the second binder was removed over G. When the strength was measured, in each case, the value was 1.5 kg or more, and no defect was found. Therefore, the yield was 100%. In the case of the bonded magnet from which the second binder was removed by applying a centrifugal force of 1500 G, no association was found in any of the bonded magnets which were removed for 20 minutes and 30 minutes. When the strength was measured, in any case, the value was 1.5 kg or more, and no defect was found.
It was 0%. In contrast, 3.4% of the bonded magnets that had been removed for 10 minutes had associated. When the strength of the unbonded bond magnet was measured, all values were 1.5 kg or more. Centrifugation condition is 1500
G, the yield was 96.6% for 10 minutes,
In other cases, it was 100%. As a result, in each case, the target yield was achieved. (Summary in Table 1.)

[0020]

[Table 1]

Example 10 A cured product impregnated with vacuum in the same manner as in Example 1 until vacuum impregnation was obtained. Next, 1000 cured products after vacuum impregnation were taken and cured by heating using the flow device shown in FIG. The diameter of the rotating drum is 20c
m, and heated with 180 ° C. hot air applied from the side. The rotation speed of the drum was set at 2 rpm.
(It was confirmed by experiments that the cured body impregnated in vacuum was broken when the rotation speed was 10 rpm or more.) Four flow fins having a height of 8 mm and an angle of 30 degrees were mounted in the drum. The treatment was heat-cured for 2 hours to produce a bonded magnet. The evaluation was performed in the same manner as in Example 1. As a result, the association rate of the product was 3.8%, the strength failure rate of the unassociated bond magnet was 0%, and the yield was 96.2%. As a result, the target yield was reached.

Example 11 Two fins having a diameter of 10 cm, a height of 10 mm, and an angle of 30 ° were rotated at a rotation speed of 2 rpm, and hot air of 180 ° C. was blown from the A direction for a processing time of 2 hours. A bonded magnet was prepared in the same manner as in Example 10, except that the mixture was heated and cured using the flow device shown in FIG. 2 (b). The evaluation was performed in the same manner as in Example 1. As a result, the association rate of the product was 4.2%, the strength failure rate of the unassociated bond magnet was 0%, and the yield was 95.
8%. As a result, the target yield was reached.

(Example 12) A square flowing vat having a side of 10 cm was alternately tilted to the left and right at 45 ° alternately twice twice a minute to flow the cured product impregnated with vacuum, and 180 ° C. from the direction A.
The bonded magnet was prepared in the same manner as in Example 10 except that the hot air was blown and the treatment time was 2 hours, and the mixture was heated and cured using the fluidizing device shown in FIG. 2C. Evaluation was performed in the same manner as in Example 1, and the product association rate was 4.0%.
The non-associated bonded magnet had a strength failure rate of 0% and a yield of 96.0%. As a result, the target yield was reached.

(Example 13) A vibrating bat having a square shape of 10 cm on a side is vibrated in the horizontal and vertical directions to make the cured body impregnated with a vacuum flow, and hot air of 180 ° C is blown from the A direction for a processing time of 2 hours. A bond magnet was prepared in the same manner as in Example 10, except that the heat hardening was performed using the vibration device shown in FIG. The evaluation was performed in the same manner as in Example 1. As a result, the association rate of the product was 4.8%, the strength failure rate of the unassociated bond magnet was 0%, and the yield was 95.
2%. As a result, the target yield was reached.

(Examples 14 to 21) A cured product vacuum-impregnated was obtained in the same manner as in Example 1 up to vacuum impregnation. Next, 1000 pieces of the vacuum-impregnated cured products are each centrifuged at 1500 G for 5 minutes and 10 minutes to remove the excess second binder, and then thermally cured while flowing or vibrating as in Examples 10 to 13. Processing was performed. When the obtained bonded magnet was evaluated, in any case, there was no association between the products and no strength defect occurred, so that the yield was 1
00%. As a result, by sequentially performing the removal of the second binder by centrifugal force and the process of heating and hardening while vibrating or flowing, the time for removing the second binder by centrifugal force can be reduced, and the yield can be further improved. .
(Summary in Table 2.)

[0026]

[Table 2]

(Examples 22 to 29) The time for the heat curing treatment while flowing or vibrating was shortened to 10 minutes, and the cured product impregnated with vacuum was treated in the same manner as in Examples 14 to 21. Was subjected to a heat curing treatment for 1 hour and 50 minutes in a constant temperature bath. When the obtained bonded magnet was evaluated, in any case, there was no association between the products, and no strength failure occurred, so that the yield was 100%. As a result,
If the removal of the second binder by centrifugal force and the process of heating and curing while vibrating or flowing are used together, the process is stopped in the state of pre-curing at the stage of heating and curing while vibrating or flowing, and the remaining curing is kept at a constant temperature By performing the treatment in a tank, the processing time of the apparatus that heats while vibrating or flowing can be shortened. That is, since the thermostatic bath can process a large amount of products by stacking the products on the container, the pretreatment time up to the thermostatic bath could be shortened, so that the processing capacity could be improved. (Summary in Table 3)

[0028]

[Table 3]

(Comparative Example 1) 1000 pieces of cured products vacuum-impregnated in the same manner as in Example 1 until vacuum impregnation were obtained. Next, the cured product impregnated in vacuum was heated and cured in a thermostat at 180 ° C. for 2 hours to prepare a bonded magnet. When the bond magnet was evaluated, the product association rate was 24.1%, the strength failure rate of the unassociated bond magnet was 0%, and the yield was 75.9.
%Met.

(Comparative Example 2) 1000 cured products were vacuum-impregnated in the same manner as in Example 1 until vacuum impregnation. Next, the cured product impregnated in vacuum was immersed in ethanol and vibrated to remove an excessive second binder. Subsequently, the mixture was cured by heating in a thermostat at 180 ° C. for 2 hours to form a bonded magnet. When the bond magnet was evaluated, the product association rate was 0%, the strength failure rate of the non-associated bond magnet was 62.0%, and the yield was 38.0%.

[0031]

As described above, according to the present invention, in the manufacturing process of the bonded magnet, the hardened body impregnated with the second binder in a vacuum is removed by centrifugal force to remove the excess second binder, or vibrated or flowed. Since the heat hardening treatment is performed while performing the heat hardening treatment, it is possible to manufacture the bonded magnet with a good yield even when manufacturing a bonded magnet that obtains a magnet within a cube having a side of 5 mm. In addition, by performing the step of removing the excess second binder by centrifugal force and the heat-curing treatment while vibrating or flowing, the processing time for removing the second binder by centrifugal force can be reduced, and the yield can be further improved. After performing pre-curing in the vibration or flow treatment, a heat treatment for complete curing was performed, so that the time required for using the centrifugal device and the vibration or flow device was greatly reduced, so that the processing capacity was improved. In addition, the improvement in the processing capacity has reduced the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining a method for manufacturing a bonded magnet of the present invention.

FIG. 2 is a schematic view of a flow device used in the present invention.

FIG. 3 is a schematic view of a vibration device used in the present invention.

FIG. 4 is a diagram for explaining a method of measuring intensity.

FIG. 5 is a flowchart for explaining a conventional method for manufacturing a bonded magnet.

[Explanation of symbols]

 Reference Signs List 101 rotating drum 103 cured body in which second binder is vacuum impregnated 105 fluid fin 201 fluid tank 205 fin 301 fluid bat 401 vibrating butt 501 taper pin 503 load meter 505 bonded magnet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eikichi Sashida 6-11-12, Honcho, Tanashi-shi, Tokyo F-term (reference) in Citizen Watch Co., Ltd. Tanashi Works 5E062 CD05 CE04 CG01 CG02

Claims (4)

[Claims] 1. A bond for obtaining a magnet by subjecting a cured product obtained by heat-treating a compact obtained by compression-molding a compound obtained by mixing a first binder to a magnet powder to a second binder under vacuum and then heating and curing. A method for manufacturing a bonded magnet, comprising removing unnecessary second binder adhered to a surface by centrifugal force after performing vacuum impregnation in a magnet manufacturing process. 2. A bond for obtaining a magnet by heat impregnating a cured product obtained by compression-molding a compound obtained by compression molding a compound obtained by mixing a magnetic powder and a first binder with a second binder and then performing heat curing. A method for manufacturing a bonded magnet, wherein a cured product is heated while vibrating or flowing in a manufacturing process of heating and curing an impregnated second binder in a manufacturing process of the magnet. 3. A bond for obtaining a magnet by subjecting a cured product obtained by compressing and molding a compound obtained by mixing a first binder to a magnet powder to a cured product obtained by vacuum impregnation of a second binder and then heating and curing. In a manufacturing process of a magnet, after performing vacuum impregnation, an unnecessary second binder adhering to a surface is removed by centrifugal force, and then the cured product is heated while being vibrated or fluidized. 4. The method for producing a bonded magnet according to claim 1, wherein the magnet has a dimension not protruding from a cubic space having a side of 5 mm.