JP2007012745A - Dust core and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dust core capable of improving magnetic characteristic irrespective of the frequency of a magnetic field to be applied and improving mechanical strength, and a manufacturing method thereof. <P>SOLUTION: The dust core is provided with complex magnetic particles 30a each having a metal magnetic particle 10a containing Fe as a main component and an insulation coating film 20a for coating the metal magnetic particle 10a, and having a grain size of 50 μm-150 μm; and complex magnetic particles 30b each having a metal magnetic particle 10b containing Fe as a main component and an insulation coating film 20b for coating the metal magnetic particle 10a, and having a grain size of 250 μm-350 μm. A ratio of the total number of the metal magnetic particles 30a and 30b to the total number of the complex magnetic particles is 80% or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dust core and a method for manufacturing the same, and more specifically, a dust core capable of improving magnetic characteristics and improving mechanical strength regardless of the frequency of an applied magnetic field. And a manufacturing method thereof.

  In recent years, electric devices including a solenoid valve, a motor, a power supply circuit, and the like have been strongly demanded for downsizing, high efficiency, and high output. As a means to meet such demands, it is effective to increase the operating frequency of these electric devices, such as electromagnetic valves and motors, several hundred Hz to several kHz, and power supply circuits to several tens kHz to several hundred kHz. Is progressing.

  It is known that a dust core has a relatively high magnetic flux density and low iron loss. For this reason, it is widely used as an iron core material for electric devices such as electromagnetic valves and motors. The dust core is composed of a plurality of composite magnetic particles in a form in which an insulating coating is formed on metal magnetic particles.

  When a dust core is used in an alternating magnetic field, an energy loss called iron loss occurs. This iron loss is represented by the sum of hysteresis loss and eddy current loss. Hysteresis loss is energy loss caused by energy required to change the magnetic flux density of soft magnetic material, and eddy current loss is energy loss caused mainly by eddy current flowing between the metal magnetic particles constituting the soft magnetic material. is there. Hysteresis loss is proportional to the operating frequency, and eddy current loss is proportional to the square of the operating frequency. For this reason, hysteresis loss is predominant in the low frequency region, and eddy current loss is predominant in the high frequency region. The dust core is required to have magnetic characteristics that reduce the occurrence of iron loss, that is, high AC magnetic characteristics.

  It is known that the iron loss of the dust core varies depending on the combination of the frequency of the applied magnetic field and the particle size of the composite magnetic particles constituting the dust core. When a dust core is used under a magnetic field having a high frequency (for example, 800 Hz to 10 kHz), the smaller the particle size of the composite magnetic particles (for example, 50 to 150 μm), the lower the iron loss. In addition, when using a dust core under a magnetic field having a low frequency (for example, 50 Hz to 800 Hz), the larger the particle size of the composite magnetic particles (for example, 100 to 300 μm), the lower the iron loss. For this reason, when using a dust core under a low frequency magnetic field, a dust core of composite magnetic particles having a large particle size is selected.

In addition, the technique regarding a powder magnetic core is disclosed by Unexamined-Japanese-Patent No. 2004-273564 (patent document 1) etc., for example. In Patent Document 1, a mixed powder of a soft magnetic powder having a large particle size of 50 μm to 200 μm, a medium particle size of 20 to 50 μm, a small particle size of 20 μm or less and at least three levels of particle size is used. A dust core having a relative density of 83% or more is disclosed. The soft magnetic powder of the dust core is composed of Si: 7 to 11% by mass, Al: 4 to 8% by mass, the balance is Fe and inevitable impurities, and the dust core has an aspect ratio of 1. 1 to 2.0.
JP 2004-273564 A

  As described above, conventionally, in order to reduce the iron loss of the dust core, it is necessary to select composite magnetic particles having a particle size suitable for the frequency of the applied magnetic field. For this reason, there has been a problem that the magnetic properties of the dust core cannot be improved regardless of the frequency of the applied magnetic field.

  In addition, the powder magnetic core generates mechanical strength when the composite magnetic particles are plastically deformed and entangled with each other when the soft magnetic material is pressed. However, when the composite magnetic particles have a large particle size, gaps are likely to occur between the particles, so that the density of the powder magnetic core is low and the composite magnetic particles are difficult to intertwine. As a result, there is a problem that the mechanical strength of the dust core decreases when the particle size of the composite magnetic particles is large. If the mechanical strength of the dust core is low, the powder core is likely to be damaged or missing when cutting or drilling the dust core or winding a coil around the dust core.

  Accordingly, an object of the present invention is to provide a dust core capable of improving the magnetic characteristics regardless of the frequency of the applied magnetic field and improving the mechanical strength, and a method for manufacturing the same.

  The dust core of the present invention has first metal magnetic particles mainly composed of Fe (iron) and a first insulating film covering the first metal magnetic particles, and has a particle size of 50 μm or more and 150 μm or less. A second composite magnetic particle having a first composite magnetic particle, a second metal magnetic particle containing Fe as a main component, and a second insulating film covering the second metal magnetic particle, and having a particle size of 250 μm or more and 350 μm or less. With particles. The ratio of the total number of the first and second composite magnetic particles to the total number of composite magnetic particles is 80% or more.

  The method for manufacturing a dust core according to the present invention includes a first forming step of forming a first insulating film on a first metal magnetic particle having a particle size of 50 μm or more and 150 μm or less and containing Fe as a main component; The second forming step of forming the second insulating film on the second metal magnetic particles having a main component of Fe of 250 μm or more and 350 μm or less, and the first and second metal magnetic particles with respect to the total number of metal magnetic particles are combined And a mixing step of mixing so that the ratio of the number is 80% or more.

  According to the dust core and the manufacturing method thereof of the present invention, since the dust core includes the first composite magnetic particles having a small particle size, compared to a dust core using only the composite magnetic particles having a large particle size. Iron loss under a magnetic field of high frequency (for example, 800 Hz to 10 kHz) can be reduced. In addition, since the dust core includes the first composite magnetic particles having a large particle size, the magnetic field has a lower frequency (for example, 50 Hz to 800 Hz) than the dust core using only the composite magnetic particles having a small particle size. The iron loss at can be reduced. Therefore, the magnetic characteristics can be improved regardless of the frequency of the applied magnetic field.

  In addition, since the dust core is composed of the first composite magnetic particles having a large particle size and the second composite magnetic particles having a small particle size, a small particle size is formed in the gap between the second composite magnetic particles having a large particle size. The first composite magnetic particles can enter and the density of the dust core can be improved. Accordingly, the composite magnetic particles are easily entangled with each other, and the mechanical strength can be improved as compared with the dust core using only the composite magnetic particles having a large particle size.

  Further, the ratio of the total number of the first and second composite magnetic particles (first and second metal magnetic particles) to the total number of composite magnetic particles (metal magnetic particles) is 80% or more, whereby the first and second The ratio of the second composite magnetic particles (first and second metal magnetic particles) can be increased, and the above-described effects of the first and second composite magnetic particles (first and second metal magnetic particles) can be obtained. it can.

  In the dust core of the present invention, preferably, the first metal magnetic particles and the second metal magnetic particles are pure iron, Fe (iron) -Si (silicon) alloy, Fe-N (nitrogen) alloy, Fe -Ni (nickel) alloy, Fe-C (carbon) alloy, Fe-B (boron) alloy, Fe-Co (cobalt) alloy, Fe-P (phosphorus) alloy, Fe-Ni-Co alloy It consists of at least 1 or more types chosen from the group which consists of an alloy, a Fe-Cr (chromium) type alloy, and a Fe-Al (aluminum) -Si type alloy. Thereby, magnetic characteristics, such as the saturation magnetic flux density in a dust core, can be improved.

  In the dust core of the present invention, preferably, the resin is at least one selected from the group consisting of polyethylene resin, silicone resin, polyamide resin, polyimide resin, polyamideimide resin, epoxy resin, phenol resin, acrylic resin, and fluorine resin. It is made up of the above.

  These organic substances firmly bond the composite magnetic particles and function as a lubricant during pressure molding of the soft magnetic material to prevent the composite magnetic particles from rubbing against each other and destroying the insulating coating. For this reason, the intensity | strength of a powder magnetic core can be improved and also an eddy current loss can be reduced. Further, since the metal magnetic particles are covered with an insulating film, oxygen or carbon contained in these resins can be prevented from diffusing into the metal magnetic particles.

  In the method for manufacturing a dust core according to the present invention, preferably, the mixing step is performed after the first forming step and the second forming step.

  As a result, since the first forming step and the second forming step are performed in separate steps, the first and second insulating coatings are formed under optimum conditions for each of the first and second metal magnetic particles. can do.

  In the present specification, “mainly comprising Fe” means that the proportion of Fe (iron) is 50 mass% or more. Further, “pure iron” means that the proportion of Fe is 99.9% by mass or more.

  According to the dust core and the manufacturing method thereof of the present invention, the magnetic characteristics can be improved regardless of the frequency of the applied magnetic field, and the mechanical strength can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view of a dust core according to an embodiment of the present invention. As shown in FIG. 1, the dust core in the present embodiment includes a composite magnetic particle 30a having a particle size in the range of 50 μm to 150 μm, and a composite magnetic particle 30b having a particle size in the range of 250 μm to 350 μm. Is included. The composite magnetic particle 30b enters the gap between the composite magnetic particles 30a. The composite magnetic particle 30a has a metal magnetic particle 10a containing Fe as a main component and an insulating coating 20a covering the metal magnetic particle 10a. The composite magnetic particle 30b includes a metal magnetic particle 10b containing Fe as a main component and an insulating coating 20b that covers the metal magnetic particle 10b.

  An organic substance 40 may be interposed between the composite magnetic particles 30. Each of the plurality of composite magnetic particles 30 is joined by engagement of the organic matter 40 or the unevenness of the composite magnetic particles 30a and 30b. In addition to the composite magnetic particles 30a and 30b, composite magnetic particles having a particle size outside the particle size range of the composite magnetic particles 30a and 30b may be included in the dust core.

  FIG. 2 is a diagram showing the particle size distribution of the composite magnetic particles constituting the dust core in one embodiment of the present invention. Referring to FIG. 2, in the dust core of the present embodiment, the particle size distribution of the composite magnetic particles has two peaks. One peak is in the range of 50 μm to 150 μm, and the other peak is in the range of 250 μm to 350 μm. The total number of composite magnetic particles constituting the dust core is defined as N. The number of composite magnetic particles having a particle size of 50 μm or more and 150 μm or less, that is, the number of composite magnetic particles 30a is N1. The number of composite magnetic particles having a particle diameter of 250 μm or more and 350 μm or less, that is, the number of composite magnetic particles 30b is N2. In the dust core of the present embodiment, the ratio of the total number (N1 + N2) of the composite magnetic particles 30a and the composite magnetic particles 30b to the total number N of composite magnetic particles is 80% or more. The average particle diameter of the composite magnetic particles is, for example, 250 μm.

  Here, the particle size of the composite magnetic particles is defined by the following method. A cross section of the dust core corresponding to FIG. 1 is observed by an optical method (for example, observation with an optical microscope). Then, the shape of each of the composite magnetic particles existing in a certain region is specified, and the surface area S of the composite magnetic particles when viewed in plan is measured. And it calculates from the surface area S using the following formula | equation (1).

Particle size of composite magnetic particles = 2 × {surface area S / π} ^1/2 (1)
Referring to FIG. 1, metal magnetic particles 10a and 10b include, for example, Fe, Fe—Si based alloy, Fe—N (nitrogen) based alloy, Fe—Ni (nickel) based alloy, Fe—C (carbon) based alloy. Fe-B (boron) alloy, Fe-Co (cobalt) alloy, Fe-P alloy, Fe-Ni-Co alloy, Fe-Cr (chromium) alloy, Fe-Al-Si alloy, etc. Formed from. The metal magnetic particles 10 need only have Fe as a main component, and are preferably pure iron.

  Each of the insulating coatings 20a and 20b functions as an insulating layer between each of the metal magnetic particles 10a and 10b. The electric resistivity ρ of the dust core can be increased by covering each of the metal magnetic particles 10a and 10b with each of the insulating coatings 20a and 20b. Thereby, it can suppress that an eddy current flows between each of the metal magnetic particles 10a and 10b, and can reduce the eddy current loss of a powder magnetic core. Insulating coatings 20a and 20b are made of, for example, an aluminum phosphate compound, a manganese phosphate compound, or a zinc phosphate compound. Note that the insulating coating 20a and the insulating coating 20b may be made of the same material or different materials.

  The thickness of each of the insulating coatings 20a and 20b is preferably 0.005 μm or more and 20 μm or less. By setting the thickness of each of the insulating coatings 20a and 20b to 0.005 μm or more, energy loss due to eddy current can be effectively suppressed. Moreover, the ratio of the insulation film which occupies for a powder magnetic core does not become large too much because each thickness of the insulation films 20a and 20b shall be 20 micrometers or less. For this reason, it can prevent that the magnetic flux density of a powder magnetic core falls remarkably. The insulating coating 20a and the insulating coating 20b may have the same film thickness or may have different film thicknesses.

  The organic substance 40 plays a role of strengthening the bond between the composite magnetic particles 30a and 30b and improving the mechanical strength of the dust core. The organic material 40 contains at least carbon, and is made of, for example, polyethylene resin, silicone resin, polyamide resin, polyimide resin, polyamideimide resin, epoxy resin, phenol resin, acrylic resin, or fluorine resin.

  Then, the method to manufacture the powder magnetic core shown in FIG. 1 is demonstrated. FIG. 3 is a diagram showing a method of manufacturing a dust core in one embodiment of the present invention in the order of steps.

  Referring to FIG. 3, first, a fine powder composed of fine metal magnetic particles and a coarse powder composed of coarse metal magnetic particles are prepared (step 1). As the fine powder, a powder containing 80% or more of metal magnetic particles 10a having a particle size of 50 μm or more and 150 μm or less is prepared. As the coarse powder, a powder containing 80% or more of metal magnetic particles 10b having a particle size of 250 μm or more and 350 μm or less is prepared.

  Here, by using the metal magnetic particles 10a having a particle diameter of 50 μm or more and 150 μm or less, each particle diameter of the composite magnetic material 30a in the dust core can be 50 μm or more and 150 μm or less. This is because the thickness of the insulating coating 20a is negligibly small compared to the particle size of the metal magnetic particle 10a, and the particle size of the composite magnetic particle 30a and the particle size of the metal magnetic particle 10a in the dust core are almost the same. This is because the particle diameter of the composite magnetic particle 30a hardly changes during the pressure molding. For the same reason, by using the metal magnetic particles 10b having a particle size of 250 μm or more and 350 μm or less, each particle size of the composite magnetic material 30b in the dust core can be set to 250 μm or more and 350 μm or less.

  Next, each of the fine powder and the coarse powder is heat-treated at a temperature of 400 ° C. or higher and lower than 900 ° C. (Step S2). The heat treatment temperature is more preferably 700 ° C. or higher and lower than 900 ° C. Numerous strains (dislocations, defects) exist in the metal magnetic particles before the heat treatment. Therefore, this distortion can be reduced by performing a heat treatment on the metal magnetic particles. This heat treatment may be omitted.

  Next, an insulating coating 20a is formed on the surface of each metal magnetic particle (metal magnetic particle 10a) constituting the fine powder, and insulation is provided on each surface of the metal magnetic particle (metal magnetic particle 10b) constituting the coarse powder. A film 20b is formed (step S3). As a result, each of the composite magnetic particle 30a and the composite magnetic particle 30b is obtained. The insulating film can be formed by subjecting metal magnetic particles to a phosphate chemical conversion treatment. By the phosphate chemical conversion treatment, for example, an insulating coating made of manganese phosphate, zinc phosphate, calcium phosphate, aluminum phosphate or the like in addition to iron phosphate containing phosphorus and iron is formed.

  Moreover, you may form the insulating film containing an oxide as the insulating film 20a or 20b. As the insulating film containing the oxide, an oxide insulator such as silicon oxide, titanium oxide, aluminum oxide, or zirconium oxide can be used.

  Next, the fine powder and the coarse powder are mixed (step S4). As a result, a soft magnetic material composed of the composite magnetic particles 30a and the composite magnetic particles 30b is obtained. Here, the fine powder contains 80% or more of the metal magnetic particles 10a, and the coarse powder contains 80% or more of the metal magnetic particles 10b. The ratio of the total number of the metal magnetic particles 10a and the metal magnetic particles 10b to the total number is 80% or more.

  The mixing method is not particularly limited. For example, mechanical alloying method, vibration ball mill, planetary ball mill, mechanofusion, coprecipitation method, chemical vapor deposition method (CVD method), physical vapor deposition method (PVD method), Any of a plating method, a sputtering method, a vapor deposition method, a sol-gel method, and the like can be used. In addition, you may add the organic substance 40 in said mixing.

  Next, the obtained powder of the soft magnetic material is put into a mold, and pressure-molded with a pressure of, for example, 390 (MPa) to 1500 (MPa) (step S5). Thereby, the molded object by which the soft-magnetic material was compacted is obtained. Note that the pressure forming atmosphere is preferably an inert gas atmosphere or a reduced pressure atmosphere. In this case, the mixed powder can be prevented from being oxidized by oxygen in the atmosphere.

  Next, the molded body obtained by pressure molding is heat-treated at a temperature of 300 ° C. or higher and 900 ° C. or lower in a nitrogen gas atmosphere (step S6). Since many distortions and dislocations are generated inside the compacted body that has been subjected to pressure molding, such distortions and dislocations can be removed by heat treatment. The dust core shown in FIG. 1 is completed by the steps described above.

  In the present embodiment, after forming the insulating coatings 20a and 20b (step S3), the fine powder and the coarse powder are mixed (step S4). However, in the present invention, in addition to such a case, the insulating coatings 20a and 20b may be formed simultaneously after the fine powder and the coarse powder are mixed.

  According to the dust core and the manufacturing method thereof of the present embodiment, since the dust core includes the composite magnetic particles 30a having a small particle size, compared with a dust core using only the composite magnetic particles having a large particle size. Thus, iron loss under a magnetic field of high frequency (for example, 800 Hz to 10 kHz) can be reduced. Further, since the powder magnetic core is provided with the composite magnetic particles 30b having a large particle size, the magnetic field is at a lower frequency (for example, 50 Hz to 800 Hz) than a powder magnetic core using only the composite magnetic particles having a small particle size. Iron loss can be reduced. Therefore, the magnetic characteristics can be improved regardless of the frequency of the applied magnetic field.

  Further, since the dust core is composed of the composite magnetic particles 30a and 30b having different particle diameters, the composite magnetic particles 30a having a small particle diameter enter the gap between the composite magnetic particles 30a having a large particle diameter. The density can be improved. Accordingly, the composite magnetic particles are easily entangled with each other, and the mechanical strength can be improved as compared with the dust core using only the composite magnetic particles having a large particle size.

  Further, the ratio of the total number of composite magnetic particles 30a and 30b (metal magnetic particles 10a and 10b) to the total number N of composite magnetic particles (metal magnetic particles) is set to 80% or more, whereby composite magnetic particles 30a and 30b ( The ratio of the metal magnetic particles 10a and 10b) can be increased, and the above-described effects due to the composite magnetic particles 30a and 30b (metal magnetic particles 10a and 10b) can be obtained.

  Furthermore, by controlling the mixing ratio of the composite magnetic particles 30a and the composite magnetic particles 30b according to the application, a dust core having appropriate magnetic characteristics and mechanical strength can be obtained.

  In the dust core of the present embodiment, it is preferable that both the metal magnetic particles 10a and 10b are made of pure iron. Thereby, magnetic characteristics, such as the saturation magnetic flux density in a dust core, can be improved.

  In the manufacturing method, it is preferable to mix the metal magnetic particles 10a and 10b after forming the insulating coatings 20a and 20b. As a result, since the first forming step and the second forming step are performed in separate steps, the first and second insulating coatings are formed under optimum conditions for each of the first and second metal magnetic particles. can do.

  Examples of the present invention will be described below.

  In this example, each of the dust cores of Samples A1 to A5 was manufactured, and the mechanical strength and magnetic characteristics were examined. Each of the dust cores of Samples A1 to A5 was produced by the following method.

  First, metal magnetic particles made of pure iron having a purity of 99.98% or more are classified to contain 80% or more of metal magnetic particles having a particle size of 50 to 150 μm and an average particle size of about A fine powder of 100 μm was prepared. Similarly, a coarse powder having 80% or more of metal magnetic particles having a particle size of 250 μm or more and 350 μm or less and an average particle size of about 300 μm was prepared. Next, each of the fine powder and the coarse powder was heat-treated at a temperature of 600 ° C. in a hydrogen stream. Subsequently, each of the fine powder and coarse powder was immersed in an aqueous phosphate solution to form an insulating coating. Thereby, composite magnetic particles were obtained. Next, the blending ratio of the fine powder to the coarse powder is changed to 0 mass% (coarse powder only), 20 mass%, 50 mass%, 80 mass%, and 100 mass% (fine powder only), respectively. Coarse powder and fine powder were mixed. Thereby, a soft magnetic material was obtained.

Next, the obtained soft magnetic material was pressure-molded to produce a molded body 50 shown in FIG. The molded body 50 was a rectangular parallelepiped having a height d ₁ = 10 mm, a depth d ₂ = 10 mm, and a width d ₃ = 55 mm. The pressure molding was performed at a pressing surface pressure of 10 ton / cm ² (1000 MPa). Subsequently, the molded body 50 was heat-treated. Thus, each of the dust cores of Samples A1 to A5 was manufactured. Samples 2 to 4 are products of the present invention, and sample 1 and sample 5 are comparative products.

Subsequently, a three-point bending test was performed by the method shown in FIG. 5 to measure the three-point bending strength of the dust cores of Samples A1 to A5. Specifically, first, the dust core 50 was supported from below by the two support portions 45. The span d ₄ of the support portion 45 was 40 mm. Then, a load was applied from above to the middle part of the two support parts 45, and the pressure when the dust core 50 was broken was measured.

  Subsequently, the iron loss of the dust cores of Samples A1 to A5 was measured using a BH curve tracer. The iron loss was measured at an excitation magnetic flux density of 10 kG (= 1T (Tesla)) and at two measurement frequencies of 800 Hz (high frequency) and 50 Hz (low frequency).

  Table 1 shows the three-point bending strength and iron loss of each of the dust cores of Samples A1 to A5. FIG. 6 shows the relationship between the mixing ratio of the fine powder and the three-point bending strength, and FIG. 7 shows the relationship between the mixing ratio of the fine powder and the iron loss under a high frequency magnetic field. FIG. 8 shows the relationship between the ratio and the iron loss under a low frequency magnetic field.

  Referring to Table 1 and FIG. 6, the three-point bending strength of sample A1 manufactured only from coarse powder was 117.3 MPa, whereas sample A2 manufactured from coarse powder and fine powder The three-point bending strength of each of -A4 was 122.4 MPa to 128.1 MPa. In other words, the three-point bending strength of the powder magnetic core improved as the blending ratio of the fine powder increased. In particular, Sample 3 containing 50% by mass of fine powder improved the three-point bending strength by about 6% compared to Sample 1. From this result, it can be seen that according to the dust core of the present invention, the mechanical strength can be improved as compared with the dust core using only the composite magnetic particles having a large particle size.

Moreover, referring to Table 1 and FIG. 7, the iron loss W _10/800 at a high frequency of the sample A1 produced only from the coarse powder was 911.6 W / kg, whereas the coarse powder The iron loss W _10/800 at the high frequency of each of the samples A2 to A4 produced from the powder and the fine powder was 870 W / kg to 840 W / kg. In other words, the iron loss W _10/800 at a high frequency of the dust core was reduced as the blending ratio of the fine powder increased. In particular, Sample 3 containing 50% by mass of fine powder reduced iron loss by about 6% compared to Sample 1. From this result, it can be seen that according to the dust core of the present invention, iron loss at a high frequency can be reduced as compared with a dust core using only composite magnetic particles having a large particle size.

Furthermore, referring to Table 1 and FIG. 8, the iron loss W _10/50 at a low frequency of Sample A5 produced only from fine powder was 16.01 W / kg, whereas coarse powder and The iron loss W _10/50 at low frequency of each of the samples A2 to A4 manufactured from the fine powder was 14.72 W / kg to 15.1 W / kg. In other words, the iron loss W _10/50 at the low frequency of the dust core was reduced as the blending ratio of the fine powder decreased. From this result, it can be seen that according to the dust core of the present invention, iron loss at a low frequency can be reduced as compared with a dust core using only composite magnetic particles having a small particle size.

  The embodiments and examples disclosed above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

  The dust core of the present invention is generally used for, for example, a motor core, a solenoid valve, a reactor, or an electromagnetic component.

It is an expanded sectional view of the dust core in one embodiment of the present invention. It is a figure which shows the particle size distribution of the composite magnetic particle which comprises the powder magnetic core in one embodiment of this invention. It is a figure which shows the manufacturing method of the powder magnetic core in one embodiment of this invention in order of a process. It is a perspective view which shows the structure of a molded object. It is a figure for demonstrating a 3 point | piece bending test. It is a figure which shows the relationship between the compounding ratio of a fine particle powder, and 3 point | piece bending strength. It is a figure which shows the relationship between the mixture ratio of a fine powder, and the iron loss under the magnetic field of a high frequency. It is a figure which shows the relationship between the mixture ratio of a fine powder, and the iron loss under the magnetic field of a low frequency.

Explanation of symbols

  10a, 10b metal magnetic particles, 20a, 20b insulating coating, 30a, 30b composite magnetic particles, 40 organic matter, 45 support part, 50 molded body.

Claims (5)

First composite magnetic particles having first metal magnetic particles containing Fe as a main component and a first insulating film covering the first metal magnetic particles and having a particle size of 50 μm or more and 150 μm or less;
A second composite magnetic particle having a second metal magnetic particle containing Fe as a main component and a second insulating film covering the second metal magnetic particle and having a particle size of 250 μm or more and 350 μm or less;
The powder magnetic core, wherein a ratio of the combined number of the first and second composite magnetic particles to the total number of composite magnetic particles is 80% or more.   The first metal magnetic particles and the second metal magnetic particles are all pure iron, Fe—Si alloy, Fe—N alloy, Fe—Ni alloy, Fe—C alloy, Fe—B alloy, 2. It consists of at least 1 or more types chosen from the group which consists of a Fe-Co alloy, a Fe-P alloy, a Fe-Ni-Co alloy, a Fe-Cr alloy, and a Fe-Al-Si alloy. The dust core described in 1.   The said resin consists of at least 1 or more types chosen from the group which consists of a polyethylene resin, a silicone resin, a polyamide resin, a polyimide resin, a polyamideimide resin, an epoxy resin, a phenol resin, an acrylic resin, and a fluororesin. The dust core described in 1. A first forming step of forming a first insulating film on the first metal magnetic particles having a particle size of 50 μm or more and 150 μm or less and having Fe as a main component;
A second forming step of forming a second insulating film on the second metal magnetic particles having a particle size of 250 μm or more and 350 μm or less and having Fe as a main component;
And a mixing step of mixing so that the ratio of the total number of the first and second metal magnetic particles to the total number of metal magnetic particles is 80% or more.   The method of manufacturing a dust core according to claim 4, wherein the mixing step is performed after the first forming step and the second forming step.

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