JPH0562850A - Manufacture of magnetic core - Google Patents

Abstract

PURPOSE:To obtain a magnetic core wherein its permeability at a high frequency is high and its eddy current loss is small by a method wherein an electrical insulation treatment is executed to the surface of flake-shaped high- permeability alloy powders, the powders are kneaded with an organic binder, films in which flake faces of the powders are arranged inside a film face are obtained and the films are laminated and bonded to each other. CONSTITUTION:An electrical insulation treatment is executed to the surface of flake-shaped high-permeability alloy powders whose aspect ratio is two or higher. The powders are kneaded with an organic binder or with the organic binder to which an inorganic binder has been added. After that, a film in which flake faces of the flake-shaped high-permeability allay powders have been arranged inside a film face is obtained. Then, a magnetic core is manufactured from a molded body in which two or more films have been laminated and bonded to each other. For example, a kneaded substance is changed to a film 2 having a thickness of 20 by using a drum 1 by a casting method; the film is rolled up on a drum 3. One hundred sheets of films 2 are laminated; they are compression-bonded at 150 deg.C; they are molded after that, a binder is removed and a heat treatment is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic core which does not require high magnetic permeability, and more particularly to a method for reducing eddy current loss.

[0002]

2. Description of the Related Art High permeability alloys such as permalloy, amorphous, silicon steel, pure iron and sendust alloys have a higher saturation magnetic flux density than ferrites and can be miniaturized. However, since it is a metal, it has a large eddy current loss, and when used at a high frequency, there is a drawback that the eddy current loss increases in proportion to the square of the frequency.

Conventionally, it is known as a so-called dust core in which a high permeability alloy powder having a grain size of about 100 μm is hardened with a binder for a magnetic core for which a high permeability such as a choke coil is not required, that is, a magnetic permeability of about 100 is sufficient. A magnetic core is used. However, these dust cores have a large loss and a large amount of heat generation when the operating frequency is 1 MHz or higher. The eddy current loss can be reduced by reducing the particle size of the high-permeability alloy powder used as a method for solving this problem. However, since the magnetic resistance increases and the magnetic permeability decreases, the number of windings must be increased, which increases copper loss and eventually makes it impossible to use. Further, it has been practiced to stack thin plates of a high-permeability alloy and use the core as a gap to reduce the magnetic permeability and use it as a choke coil, but there is a drawback that magnetic flux leaks from the gap. Further, even with ferrite, at frequencies above 1 MHz, the residual loss becomes large, making it difficult to use as a magnetic core for choke coils.

As another method, the magnetic permeability is improved only in the uniaxial direction by a magnetic field molding method so that the longitudinal direction of the flake surface of the flake-shaped high-permeability metal powder is provided in the direction in which the magnetic field is applied to improve the magnetic loss. However, since the direction of the powder is aligned only on one axis of the flake surface, there is a difference depending on the direction of the magnetic characteristics, and the average value of the magnetic characteristics is not high.

In order to solve this problem and obtain a molded product having high magnetic properties and no unevenness in the direction, it is necessary to align the two axes of the flake surface of the flake-like high magnetic permeability alloy powder in the same plane. In order to achieve this, compression molding of flaky high-permeability alloy powder is performed. According to this, it is possible to obtain a molded body having a structure in which the flake surface of the flake powder is aligned to a certain extent in the plane perpendicular to the compression direction, but since the orientation of the flakes was not sufficient before, the surface of the magnetic flux density and the magnetic permeability was obtained. The magnetic properties were inferior.

[0006]

As a result of various studies in view of the above, the present invention has been made by forming a flaky high-permeability alloy powder into a film by a plastic film forming method using an organic binder. The flake surface of the powder can be easily aligned within the plastic film surface, and the magnetic core thus obtained has a good powder orientation,
By finding that the magnetic permeability at high frequencies is high and the eddy current loss is also small, and by further performing the binder removal treatment by baking the organic binder of the core formed from the plastic film containing the flaky high-permeability alloy powder, The inventors have found that the magnetic properties are further improved, and as a result of further studies, they have developed an excellent method for producing a magnetic core.

That is, according to the present invention, the surface of flaky high-permeability alloy powder having an aspect ratio of 2 or more is electrically insulated and kneaded with an organic binder or an organic binder to which an inorganic binder is added, followed by a casting method and an extrusion. A film obtained by aligning the flake surface of the flaky high-permeability alloy powder within the film surface by a plastic film-forming processing method such as a calendering method, a calendering method, or a stretching method, and laminating two or more films and adhering them to each other. A magnetic core is manufactured from the magnetic core.

Further, in the production method of the present invention, it is effective to subject the molded body obtained by laminating and adhering two or more films to each other and subjecting it to a deorganization binder and a heat treatment.

[0009]

According to the present invention, as described above, the flaky high-permeability alloy powder is formed into a film by a plastic film forming method using an organic binder, so that the flake surface of the flake powder is formed within the plastic film surface. The magnetic cores obtained in this way have good powder orientation, high magnetic permeability at high frequencies, and low eddy current loss. Further, magnetic properties are further improved by performing a binder removal treatment by baking the organic binder of the core formed from the plastic film containing the flake-shaped high magnetic permeability alloy powder.

In the present invention, however, the flaky high-permeability alloy powder has an aspect ratio of 2 or more when the granular powder and the flake-shaped powder of the same size are compared but the magnetic permeability is almost the same. The powder is thinner,
This is because the effect of reducing eddy current loss can be obtained. The reason why the inorganic binder is added to the organic binder is to firmly bond the flake-shaped high magnetic permeability alloy powder with the inorganic binder by the heat treatment after the deorganization binder treatment. Further, in the present invention, the binder removal treatment of baking the organic binder of the core is performed in the case where a magnetic core is directly produced from a film or a molded product containing a large amount of the organic binder, the film forming processability is good, but the high permeability alloy powder This is because the content ratio of is reduced and the saturation magnetic flux density and magnetic permeability of the core are reduced.

[0011]

EXAMPLES The present invention will be described below with reference to examples. Fe-9.6% Si- having a thickness of about 3 μm and an aspect ratio of about 30
5.4% Al alloy, Fe-78% Ni permalloy alloy, Fe
-6.5% Si alloy or pure iron with each surface coated with 5% by weight of water glass, polyvinyl butyral, glycerin, and ethyl alcohol in a ratio of 6: 2: 1: 2 by weight, respectively. Were mixed and stirred to prepare four kinds of alloy powder slurries, and defoaming was performed to form a film (2) having a thickness of 20 μm on the drum (1) by the casting method shown in FIG. 1 and wound on the drum (3). In the figure, (4) is a slurry supply tank, (5) is a high-permeability alloy slurry, (6) is a cover, and (7) is a hot air inlet.

100 sheets of the above film are laminated and heated at a heating temperature of 1
After press-bonding each other at a pressure of 4 ton / cm ² at 50 ° C to form a sheet with a thickness of 1.5 mm, a ring with an outer diameter of 12 mm and an inner diameter of 7.2 mm is punched out, and debinding is performed in the air at 320 ° C for 24 hours.
Sintering was carried out in an inert gas at 1100 ° C for 3 hours to prepare a ring for magnetic measurement having an outer diameter of 10 mm x an inner diameter of 6 mm x 1 mm. Saturation magnetic flux densities, magnetic permeability and iron loss at 1 MHz were examined for these ring-shaped samples which are the magnetic cores of the present invention, and the results are shown in Table 1.

Also, as a comparative example, a saturated magnetic flux density was similarly obtained for a ring-shaped sample formed by compression molding of 5 wt% phenol resin using granular powder having the same alloy composition as those of the rings and a particle size of 100 μm and a ring-shaped sample made of ferrite. , 1MHz and permeability and iron loss were investigated. The results are shown in Table 1.

[0014]

[Table 1]

According to Table 1, the magnetic core of the present invention has a magnetic flux density and magnetic permeability which are not so different from those of a magnetic core obtained by compacting a conventional granular high-permeability alloy powder, but the loss is remarkably reduced. It is understood that there is. It can be seen that the loss is smaller than that of ferrite. Further, the choke coil using the magnetic core of the present invention can be used at a high frequency of 1 MHz.

[0016]

As described above, according to the present invention, it is possible to obtain a magnetic core having a magnetic flux density equivalent to that of a conventional magnetic core and a remarkably small iron loss as compared with a magnetic core such as a choke coil which does not require high magnetic permeability. It has a humble effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a plastic film forming method (casting method) used in the method of the present invention.

[Explanation of symbols]

 1 film forming drum 2 film 3 winding drum 4 slurry supply tank 5 high permeability alloy slurry 6 cover 7 hot air inlet

Claims (2)

[Claims] 1. A flaky high-permeability alloy powder having an aspect ratio of 2 or more is electrically insulated and kneaded with an organic binder or an organic binder to which an inorganic binder is added. A method for producing a magnetic core, characterized in that a magnetic core is produced from a molded body obtained by laminating two or more sheets of the film obtained by laminating the flake surface of magnetic permeability alloy powder within the film surface .. 2. The method for producing a magnetic core according to claim 1, wherein a molded body obtained by laminating and adhering two or more films is subjected to a deorganization binder and a heat treatment.