JP5994124B2 - Composite magnetic powder and dust core using the composite magnetic powder - Google Patents

Description

  The present invention relates to a composite magnetic powder obtained by binding a large number of soft magnetic particles to an insulating binder resin, and a dust core using the composite magnetic powder.

  Powder magnetic cores used in boosters such as hybrid vehicles, reactors used in power generation and substation facilities, transformers, choke coils, etc., form a composite magnetic powder comprising a large number of soft magnetic powders and a binder resin. Can be obtained. The following patent document describes a composite magnetic powder (granulated powder).

  By the way, the dust core is desired to have a high electrical resistivity in order to reduce core loss, etc., but there is no patent document that optimizes the structure from the inside to the surface of the composite magnetic powder in order to obtain a high electrical resistivity. .

JP 2008-258234 A JP 2011-114321 A JP-A-8-60288

  Therefore, the present invention is to solve the above-described conventional problems, and in particular, a composite magnetic powder capable of optimizing the structure from the inside to the surface of the composite magnetic powder and obtaining a dust core having a high electrical resistivity, and An object of the present invention is to provide a dust core using the composite magnetic powder.

The present invention is a composite magnetic powder formed by binding a large number of soft magnetic particles with a binder resin,
Manufactured by spray drying,
A cross-section passing through the approximate center of the composite magnetic powder, a surface approximate line, and an inner line that is at a distance of approximately ¼ from the approximate center of the composite magnetic powder toward the surface approximate line and is similar to the surface approximate line. A first intermediate line that is approximately ½ the distance from the approximate center of the composite magnetic powder toward the surface approximate line and is similar to the surface approximate line; and from the approximate center of the composite magnetic powder to the surface approximate line. When drawing a second intermediate line that is at a distance of approximately 3/4 and is similar to the surface approximation line,
The percentage of voids on the inner line is greater than the percentage of voids on the surface approximation line,
The ratio of the voids on the inner line is 20% or more larger than the ratio of the voids on the surface approximate line,
The average particle size (D50) of the volume distribution of the soft magnetic particles is 10 μm or more and 15 μm or less,
The particle size of the cumulative value of 10% of the volume distribution of the soft magnetic particles (D10) is characterized in der Rukoto than 7μm or less or 5μm or 8μm below 4 [mu] m.

  The composite magnetic powder of the present invention is produced by a spray drying method, and therefore, the composite magnetic powder produced by the stirring / defoaming apparatus shown in the comparative example described later is not applicable. For various conditions in the spray drying method, refer to the examples described later. According to the present invention, since a large gap can be formed inside the composite magnetic powder, when the powder magnetic core is produced by compression molding the composite magnetic powder, the gap tends to remain with a certain size. Due to the presence of the voids, the contact portion of the soft magnetic particles is reduced, so that a dust core having a high electrical resistivity can be obtained.

  Moreover, in this invention, it is preferable that the ratio of the said space | gap on the said inner side line, the said 1st intermediate line, and the said 2nd intermediate line is all larger than the ratio of the said space | gap on the said surface approximate line. At this time, the ratio of the smallest void on the inner line, the first intermediate line, and the second intermediate line is 20% or more larger than the ratio of the void on the surface approximate line. Is preferred. Thus, since a certain amount of difference can be made in the ratio of the voids, a higher electrical resistivity can be obtained more effectively.

  In the present invention, it is preferable that the soft magnetic particles contained in the composite magnetic powder are subjected to particle size adjustment by cutting small particles. At this time, the ratio of the gaps on the inner line, the first intermediate line, and the second intermediate line can all be 30% or more. The small particle size particles are soft magnetic particles having a particle size of about 2/3 or less of the particle size distribution of 50% (D50) of volume accumulation in the particle size distribution of the volume distribution.

  A powder magnetic core manufactured using soft magnetic particles whose particle size is adjusted by cutting small particles as described above, and a powder magnetic core manufactured using soft magnetic particles whose particle size is not adjusted Then, when the core density was made substantially the same, it was found by an experiment described later that the former powder magnetic core can obtain a higher electrical resistivity than the latter. By adjusting the particle size to cut the small particle size particles, the inter-particle arrangement such that the small particle size particles enter between the large particle size particles agglomerated inside is suppressed. Large voids are easily formed.

In the present invention, the average particle size (D50) of the volume distribution of the soft magnetic particles is 10 μm or more and 15 μm or less . In particular, when the particle size adjustment for cutting small particles is performed, the average particle size (D50) of the volume distribution of the soft magnetic particles can be set to 13 μm or more and 15 μm or less, and the volume distribution volume of the soft magnetic particles can be reduced. The particle diameter (D10) when the cumulative value is 10% can be 5 μm or more and 8 μm or less.

With this embodiment, the soft magnetic particles _is shown by _{Fe 100-a-b-c} -x-y-z-t Ni a Sn b Cr c P x C y B z Si t, 0at% ≦ a ≦ 10 at%, 0 at% ≦ b ≦ 3 at%, 0 at% ≦ c ≦ 6 at%, 6.8 at% ≦ x ≦ 10.8 at%, 2.0 at% ≦ y ≦ 9.8 at%, 0 at% ≦ z ≦ 8. It is preferable that 0 at% and 0 at% ≦ t ≦ 5.0 at%.

  In the present invention, a large gap can be formed inside the magnetic powder. Thus, when the composite magnetic powder is compression molded to obtain a dust core, the gap tends to remain with a certain size. For this reason, it becomes possible to obtain a dust core having a high electrical resistivity.

FIG. 1 is a schematic view showing a cross section of the composite magnetic powder in the present embodiment. FIG. 2 is a SEM (scanning electron microscope) photograph of the composite magnetic powder (granulated powder) of this example. FIG. 3A is an SEM photograph in which a surface approximate line A is drawn on the cross section of the composite magnetic powder of Example-1. FIG. 3B is an SEM photograph in which the center of the cross section is drawn following FIG. FIG. 3C is an SEM photograph showing a state in which a straight line drawn from the center of the cross section to the surface approximate line A is divided into four equal parts following FIG. FIG. 3D is an SEM photograph in which the inner line D, the first intermediate line C, and the second intermediate line B are respectively drawn on a cross section following FIG. FIG. 4 is a partially enlarged schematic view showing a part of the cross section of the composite magnetic powder shown in FIG. FIG. 5 is a perspective view of the dust core (core). FIG. 6 is a plan view of the coil-embedded dust core. FIG. 7 is a schematic diagram for explaining the granulation step. FIG. 8 is a SEM (scanning electron microscope) photograph of a cross section of the composite magnetic powder of Example-1 granulated by a spray dryer. FIG. 9 is a SEM photograph (scanning electron microscope) photograph of a cross section of the composite magnetic powder of Example-2 granulated by a spray dryer. FIG. 10 is an SEM (scanning electron microscope) photograph of a cross section of a composite magnetic powder powder of a comparative example obtained by stirring and defoaming the raw materials and then pulverizing them with a screen type pulverizer. Fig.11 (a) is a graph which shows the ratio of the space | gap of each line AD in Example-1, and FIG.11 (b) shows the ratio of the space | gap of each line AD in Example-2. It is a graph and FIG.11 (c) is a graph which shows the ratio of the space | gap of each line AD in a comparative example. FIG. 12 is a graph showing the particle size distribution based on the volume distribution in Example-1 and the comparative example. FIG. 13 is a graph showing the particle size distribution based on the volume distribution in Example-2. FIG. 14 is a graph showing the relationship between the core density and the electrical resistivity in Comparative Example, Example-1, and Example-2. FIG. 15 is a graph showing the relationship between the magnetic permeability μ _{100 kHz} and the electrical resistivity in the comparative example, example-1, and example-2. FIG. 16 is a graph showing the relationship between the core loss W _{0.1T100 kHz} and the electrical resistivity in Comparative Example, Example-1, and Example-2. FIG. 17 is a SEM (scanning electron microscope) photograph of a cross section of a dust core formed using the composite magnetic powder of Example-1.

FIG. 1 is a schematic view showing a cross section of the composite magnetic powder in the present embodiment.
A composite magnetic powder (granulated powder) 10 of this embodiment shown in FIG. 1 is formed by binding a large number of soft magnetic particles 11 with a binder resin (not shown). However, in FIG. 1, reference numeral 11 is given to only one soft magnetic particle 11. The term “multiple” used herein refers to soft magnetic particles having a particle size (D50; average particle size) of 50% cumulative volume distribution in the volume distribution of about several μm to several tens of μm, and the average particle size (D50) is approximately about 100 μm. It refers to the number required to produce a composite magnetic powder of several hundred μm.

  FIG. 1 shows a cross section passing through the approximate center O of the composite magnetic powder 10. Here, the “center” can be defined as a geometric center point. If the composite magnetic powder 10 is approximately spherical or approximately ellipsoidal, the center is the point where the midpoints in the X, Y, and Z directions intersect. “Center” can be defined as “center of gravity”.

  FIG. 1 shows the composite magnetic powder 10 on an X-Y plane and an XZ cross section passing through a substantially center O.

  The composite magnetic powder 10 shown in FIG. 1 has, for example, a substantially spherical shape. FIG. 2 is a SEM (scanning electron microscope) photograph of the composite magnetic powder (granulated powder) of this example. As shown in FIG. 2, the composite magnetic powder 10 has a substantially spherical shape or an ellipsoid. In the case of an ellipsoid, the cross-sectional shape shown in FIG. 1 is an elliptical shape. Alternatively, the composite magnetic powder 10 may have a shape other than a spherical shape or an ellipsoid. However, the composite magnetic powder 10 preferably has a substantially circular or elliptical cross-sectional shape as shown in FIG. At this time, the aspect ratio of the composite magnetic powder 10 is preferably 1 to 1.5. The aspect ratio is indicated by a ratio (d / e) between the major axis d and the minor axis e passing through the center O shown in FIG.

  The composite magnetic powder 10 in the present embodiment is manufactured by a spray drying method. The spray drying method is a method in which a mixed slurry of soft magnetic particles 11 and a binder resin is sprayed from any direction and dried. Thus, any method may be used as long as it is sprayed from any direction and dried, and is not limited to a structure in which spraying is performed from above, for example, a spray dryer shown in FIG.

  A drawing method of the surface approximate line A, the inner line D, the first intermediate line C, and the second intermediate line B will be described with reference to FIGS.

  Each drawing in FIG. 3 is a SEM photograph of a cross section of the composite magnetic powder of Example-1 cut by FIB (focus ion beam).

  In the cutting by FIB, a specific portion can be cut by narrowing and scanning a sample of Ga ions drawn from Ga by an electric field.

As shown in FIG. 3A, the cross-sectional shape of the composite magnetic powder was substantially circular.
First, as shown in FIG. 3A, a surface approximation line A is drawn so as to substantially follow the cross-sectional circumferential shape. At this time, the surface approximation line A is drawn at the position of the soft magnetic particles slightly inside the outermost surface of the cross section (the outermost surface is almost covered with the binder resin, so that it is slightly inside the binder resin). For example, when α is the number of soft magnetic particles deviating from the surface approximation line A to the outermost surface side and β is the number of soft magnetic particles longitudinally crossing the surface approximation line A, β / (α + β) is 90% or more. If so, the line A can be defined as a surface approximation line.

Next, in FIG. 3B, the center of the cross section is obtained. The center measurement was made by eye.
Next, in FIG. 3C, a straight line extending from the center to the surface approximate line A is drawn, and the straight line is further divided into four equal parts.

  Next, in FIG. 3D, lines B to D similar to the surface approximation line A are drawn at the respective positions divided into four in FIG.

  As described above, the distance (radius γ) from the center O of the composite magnetic powder 10 to the surface approximate line A is measured, and the surface approximate line A and the surface approximate line A are positioned at 1/4, 1/2, and 3/4 of the radius γ. Concentric (similar) inner lines D, first intermediate lines C, and second intermediate lines B were drawn, respectively.

  The surface approximation line A may be drawn so as to follow as much as possible of the soft magnetic particles 11 located near the surface. If the arrangement of the soft magnetic particles 11 located in the vicinity of the surface as shown in FIG. 1 is substantially circular, the above-mentioned β / (α + β) can be set to 90% or more even if the surface approximation line A is drawn in a circle. In order to increase the accuracy of the void ratio on each line, as shown in FIG. 3, the surface approximation line A is drawn so as to follow the arrangement of the soft magnetic particles 11 located near the surface of the composite magnetic powder 10. It is desirable.

  FIG. 4 is a partially enlarged schematic view showing a part of the cross section of the composite magnetic powder shown in FIG.

  In FIG. 4, a part of the lines A to C is visible. The total lengths of the lines A to C and the inner line D shown in FIG. 4, the lengths of the soft magnetic particles, the binder resin, and the voids located on the lines A to D are measured with image analysis software. And the ratio of the space | gap of each line AD was calculated | required by dividing the total length of the space | gap with respect to the full length of each line AD.

  Here, a shown in FIG. 4 is the width of the gap, b is the width of the resin layer (binder resin), and c is the width of the soft magnetic particles. The width of each region is indicated by a line and an arrow.

  The composite magnetic powder 10 in the present embodiment is manufactured by a spray drying method, and the composite magnetic powder and the like manufactured by a stirring / defoaming apparatus shown in a comparative example described later does not correspond to the present embodiment.

  According to this embodiment, the soft magnetic particles 11 having a small particle size constituting the composite magnetic powder 10 are aggregated on the surface side, and the interval between the soft magnetic particles 11 is narrow on the surface side as shown in FIG. Is filled with a binder resin. On the other hand, since soft magnetic particles having a relatively large particle diameter gather inside the soft magnetic powder 10 and a portion having a large interval between the particles increases, voids are easily generated between the particles as shown in FIG. For this reason, according to this embodiment, the ratio of the space | gap on the inner side line D can be made larger than the ratio of the space | gap on the surface approximate line A. FIG. Specifically, the void ratio on the inner line D can be made 20% or more larger than the void ratio on the surface approximate line A.

  Thus, in this embodiment, since a big space | gap can be formed in the inside of the composite magnetic powder 10, the composite magnetic powder 10 is compression-molded, and the dust core 1 shown in FIG. 5 and the coil encapsulated dust core shown in FIG. When 2 (symbol 3 is a dust core and 4 is a coil), the air gap is likely to remain with a certain size inside. For this reason, it becomes possible to obtain a dust core having a high electrical resistivity.

  In the present embodiment, the ratio of the voids on the inner line D, the first intermediate line C, and the second intermediate line B can all be greater than the ratio of the voids on the surface approximate line A. At this time, the ratio of the smallest void on the inner line D, the first intermediate line C, and the second intermediate line B can be made 20% or more larger than the void ratio on the surface approximate line A. .

  Thus, in this embodiment, a large difference can be given to the ratio of the gap between the inside and the surface side of the composite magnetic powder 10, and even by compression molding for manufacturing the dust core shown in FIG. 5 and FIG. Effectively, it is possible to leave a gap with a certain size inside each composite magnetic powder, and thus it is possible to stably obtain a dust core having a higher electrical resistivity.

  In the present embodiment, the composite magnetic powder 10 can be produced without adjusting the particle size for soft magnetic particles having a particle size distribution, or a small particle size for soft magnetic particles having a particle size distribution. The composite magnetic powder 10 can also be produced by adjusting the particle size by cutting the particles. Here, the “small particle size” is a particle size of about 2/3 or less of the particle size distribution (D50; average particle size) of 50% of the cumulative value in the particle size distribution of the soft magnetic particles before the particle size adjustment. Point to.

  In the powder magnetic core manufactured using the soft magnetic particles having a particle size adjusted to cut the small particle size, and the powder magnetic core manufactured using the soft magnetic particles not specifically adjusted in the particle size, It was found by experiments described later that the former powder magnetic core can obtain a higher electrical resistivity than the latter when the density is substantially the same. By adjusting the particle size to cut the small particle size particle, the particle size distribution changes as described later, and the average particle size (D50) based on the volume distribution and the particle size (D10) at a cumulative value of 10% are both It becomes larger than the case where the particle size adjustment is not performed. As a result, not only on the inner line D, but also on the first intermediate line C and the second intermediate line B, the gap tends to increase. According to this embodiment, the inner line D, the first intermediate line C, and Any void ratio on the second intermediate line B can be increased to 30% or more.

  In this embodiment, the average particle diameter (D50) based on the volume distribution of the soft magnetic particles 11 is 10 μm or more and 15 μm or less. The particle diameter (D10) at a cumulative value of 10% based on the volume distribution was about 4 μm to 7 μm.

  Moreover, in this embodiment, the average particle diameter (D50) based on volume distribution can be set to 13 micrometers or more and 15 micrometers or less by performing the particle size adjustment which cut | disconnected the small particle diameter as mentioned above, and the volume based on volume distribution It was found that the particle diameter (D10) at a cumulative value of 10% can be made 5 μm or more and 8 μm or less.

  By cutting the small particle size in this way, the average particle size (D50) based on the volume distribution and the particle size (D10) at a volume cumulative value of 10% become larger than when the particle size is not adjusted.

  Moreover, in this embodiment, the average particle diameter of the composite magnetic powder 10 can be formed in the range of 80 micrometers-110 micrometers.

  Here, the average particle size of the composite magnetic powder is determined by classifying the composite magnetic powder with each sieve of less than 63 μm, 63 μm to 100 μm, 100 μm to 150 μm, 150 μm to 212 μm, and greater than 212 μm, and measuring the weight of each powder. Was accumulated from those having a small particle diameter, and a particle diameter having a cumulative value of 50% was determined from the accumulation curve.

The soft magnetic particles 11 in the present embodiment are amorphous soft magnetic particles produced using, for example, a water atomization method. The amorphous soft magnetic particles (Fe based metallic glass alloy particles), for example, a composition _{formula, Fe 100-a-b-} c-x-y-z-t Ni a Sn b Cr c P x C y B indicated by _{z Si t, 0at% ≦ a} ≦ 10at%, 0at% ≦ b ≦ 3at%, 0at% ≦ c ≦ 6at%, 6.8at% ≦ x ≦ 10.8at%, 2.0at% ≦ y ≦ 9.8 at%, 0 at% ≦ z ≦ 8.0 at%, and 0 at% ≦ t ≦ 5.0 at%.

  The binder resin is an acrylic resin, a silicone resin, an epoxy resin, a phenol resin, a urea resin, a melamine resin, or the like. In particular, it is preferable to use a silicone resin as a heat resistant resin for the binder resin.

  The binder resin is added in an amount of about 0.5 to 5.0% by mass with respect to the total mass of the composite magnetic powder 10 (soft magnetic particles 11, binder resin and lubricant).

A method for manufacturing the composite magnetic powder 10 and the powder magnetic core in the present embodiment will be described.
First, a soft magnetic powder 11 produced by a water atomizing method, a binder resin, a lubricant, and a coupling agent are stirred and mixed in a solvent to obtain a mud slurry. Here, water is used as the solvent. As the lubricant, zinc stearate, aluminum stearate, or the like can be used. Moreover, a silane coupling agent etc. can be used for a coupling agent.

  The slurry 19 is put into a spray dryer apparatus 20 shown in FIG. 7 (schematic diagram), and a granular composite comprising the soft magnetic powder 11 and a binder resin under a predetermined condition (shown in an example described later). Magnetic powder (granulated powder) 10 is produced.

  The spray dryer is a kind of granulation method that obtains composite magnetic powder (granulated powder) by spraying a mixed slurry of soft magnetic powder and binder resin from any direction and drying, and belongs to the spray drying method It is. The spray dryer apparatus 20 will be described in detail later with reference to FIG. 7, but it is not always necessary to spray from the upper part of the apparatus as shown in FIG. The spraying direction can be any direction other than the upper part of the apparatus, such as from the side of the apparatus or the lower part of the apparatus.

Subsequently, the mixed magnetic powder 10 is filled in a molding die and compression molded into the shape of a dust core. The pressing pressure at this time differs between the dust core 1 of FIG. 5 and the coil-embedded dust core 2 of FIG. In the dust core 1 of FIG. 5, it is about 6-20 t / cm < ² >, and in the coil enclosure dust core 2 of FIG. 6, it is about 6-7 t / cm < ² >.

  Then, heat treatment is performed on the dust core. The heat treatment temperature is lower than the crystallization temperature of the soft magnetic particles 11. This heat treatment is intended to remove distortion of the soft magnetic particles 11 and obtain good magnetic characteristics, and is not sintered. In addition, it is thought that the lubricant and the coupling agent are almost vaporized and disappear by this heat treatment, and are integrated with the binder resin. A part of the binder resin also vaporizes and disappears.

  Moreover, even if the composite magnetic powder 10 of the present embodiment is compression molded to form a powder magnetic core, if the cross-sectional shape of the powder magnetic core is seen, it is assumed that the composite magnetic powder 10 of the present embodiment is molded. Is possible.

Amorphous soft magnetic particles having a composition of Fe _{74.43 at%} Cr _{1.96 at%} P _{9.04 at%} C _{2.16 at%} B _{7.54 at%} Si _{4.87 at%} were prepared using a water atomization method.

  The particle size distribution of the soft magnetic particles at this time was measured by volume distribution using a Microtrac particle size distribution measuring device MT3300EX manufactured by Nikkiso Co., Ltd. The result is shown in FIG. This particle size distribution corresponds to the particle size distribution of Comparative Example and Example-1 shown in Table 1 below.

  Separately from Example-1 and the comparative example, the soft particle having the particle size distribution shown in FIG. The particle size adjustment was performed by an air classification method using a precision air classifier TC-15NS manufactured by Nissin Engineering Co., Ltd. In the air classification method, centrifugal force and drag force of air can be used to classify large particles and small particles. Here, a particle size of 7.1 μm or less corresponding to 2/3 or less of 10.6 μm, which is the average particle size (D50) of Example-1 and Comparative Example shown in Table 1, is set to a small particle size, and air classification is used. Soft magnetic particles obtained by cutting soft magnetic particles of 7.1 μm or less were used as the soft magnetic particles of Example-2. However, since the air classification method is classification based on centrifugal force and air drag, the cutting of small particle size particles cannot completely remove soft magnetic particles having a particle size of 7.1 μm or less. Therefore, the cut of small particle size does not necessarily mean that the soft magnetic particles having a particle size of 7.1 μm or less have been completely removed, and some soft magnetic particles having a particle size of 7.1 μm or less are somewhat removed. It may be included.

  And the particle size distribution of the soft magnetic particle which cut | disconnected the small particle size particle | grain was measured by volume distribution using the micro track particle size distribution measuring device MT3300EX by Nikkiso Co., Ltd. The result is shown in FIG. This particle size distribution corresponds to the particle size distribution of Example-2 shown in Table 1 below.

  Subsequently, the soft magnetic particles of Example 1, an acrylic resin (binder resin), zinc stearate, and a silane coupling agent were mixed in a solvent (water) to obtain a mud slurry. In addition, the soft magnetic particles of Example-2, an acrylic resin (binder resin), zinc stearate, and a silane coupling agent were mixed in a solvent (water) to obtain a mud slurry. In each slurry, the solid component (other than water) was 80 wt%, and the rest was water (solvent). The blending amount of the acrylic resin was 2.0 wt% with respect to the solid component, zinc stearate was 0.3 wt% with respect to the solid component, and the coupling agent was 0.5 wt% with respect to the soft magnetic particles.

Next, the slurry was put in a spray dryer apparatus 20 shown in FIG. 7 (schematic diagram).
The spray dryer will be described. A rotor 21 is provided in the spray dryer device 20, and the slurry 19 is injected toward the rotor 21 from the upper part of the device. The rotor 21 rotates at a predetermined rotational speed, and the slurry 19 is sprayed by centrifugal force inside the apparatus. Further, hot air is introduced into the apparatus, thereby instantly drying the solvent of the slurry 19. And the composite magnetic powder (granulated powder) 10 which became granular from the apparatus lower part is collect | recovered.

In this embodiment, the rotational speed of the rotor 21 was adjusted within a range of 4000 to 6000 rpm. The temperature of the hot air introduced into the apparatus was in the range of 130 to 170 ° C, and the temperature in the lower part of the chamber was controlled in the range of 80 to 90 ° C. The pressure in the chamber was ₂ mmH ₂ O (about 0.02 kPa). Also, the inside of the chamber was an air (air) atmosphere.

  The composite magnetic powder obtained above was passed through a sieve having an opening of 212 μm in order to remove the coarse powder, and the average particle size of the composite magnetic powder after passing through the sieve was in the range of 80 μm to 110 μm.

  Next, the composite powder of the comparative example was manufactured using soft magnetic particles having the same particle size distribution as in Example-1. In the comparative example, raw materials having soft magnetic particles and acrylic resin (binder resin), coupling agent, and lubricant (zinc steering acid) as raw materials were weighed in a container. The blending amount of the acrylic resin and zinc stearate is 2.0 wt% (acrylic resin) and 0.3 wt% (zinc stearate) with respect to the raw material excluding the coupling agent, and the coupling agent is based on the soft magnetic particles. 0.5 wt%. Subsequently, the raw materials were mixed with a planetary agitation / defoaming apparatus (Mazerustar, Kurashiki Boseki Co., Ltd.), and then the solvent was removed, followed by drying and solidification. Furthermore, the solidified raw material was pulverized by a screen type pulverizer (Fesomill manufactured by Hosokawa Micron Corporation), and further classified by a sieve having an opening of 300 μm to obtain a composite magnetic powder.

  In Table 1, the volume distribution of the soft magnetic particles of Comparative Example, Example-1 and Example-2 is 10% cumulative (D10), 50% cumulative (D50; average particle diameter) ), Particle size (D90) with a cumulative value of 90% is listed. Since the same soft magnetic particles were used in Comparative Example and Example-1, the particle diameters of D10, D50, and D90 were the same values.

  FIG. 8 is a cross-sectional SEM photograph of the composite magnetic powder of Example-1 cut by FIB (focus ion beam), and FIG. 9 is a cross-section of the composite magnetic powder of Example-2 by FIB (focus ion beam). FIG. 10 is an SEM photograph of a cross section obtained by cutting the composite magnetic powder of the comparative example with FIB (focus ion beam).

  In the cutting by FIB, a specific portion can be cut by narrowing and scanning a sample of Ga ions drawn from Ga by an electric field.

As shown in FIGS. 8 and 9, the cross-sectional shape of the composite magnetic powder of the example is approximately circular or approximately elliptical. On this SEM photograph, the surface approximate line A and 1 from the center toward the surface approximate line A are shown. The inner line D and the intermediate lines C and B having the similar shape to the surface approximate line A at the distances of / 4, 1/2, and 3/4 were drawn, respectively. Β / (α + β) is 90% or more, where α is the number of soft magnetic particles deviating from the surface approximate line A to the outermost surface side and β is the number of soft magnetic particles longitudinally crossing the surface approximate line A. Confirmed that.
Refer to FIG. 3 for the drawing method of each line.

  And, in comparison with Example-1 in FIG. 8, Example-2 in FIG. 9, and Comparative Example in FIG. 10, the total length of each line A to D and the soft magnet located on each line A to D, as in FIG. The lengths of the particles, binder resin, and voids were measured with image analysis software. And the total length of the space | gap was divided with respect to the full length of each line AD, and the ratio of the space | gap on each line AD was calculated | required. In addition, the ratio of the space | gap in Example-1, Example-2, and a comparative example is the average of five types of samples, respectively.

  Fig.11 (a) is a graph which shows the space | gap ratio of each line AD in Example-1, and FIG.11 (b) is a graph which shows the space | gap ratio of each line AD in Example-2. FIG. 11C is a graph showing the void ratio of each of the lines A to D in the comparative example.

  In the examples of FIGS. 11A and 11B, it has been found that the ratio of the voids on the inner line D is considerably larger than the ratio of the voids on the surface approximate line A. Specifically, it was found that the ratio of the voids on the inner line D was 20% or more larger than the ratio of the voids on the surface approximate line A.

  Also in the comparative example of FIG. 11C, the ratio of the voids on the inner line D is slightly larger than the ratio of the voids on the surface approximate line A. However, the difference is about 2-3%, which is an error range. That is, for example, in the case of a composite powder obtained by stirring and defoaming the raw materials and then pulverizing with a screen-type pulverizer as in the comparative example, It cannot be stable and larger than the ratio.

  On the other hand, in Example-1 and Example-2 which used the spray-drying method (spray dryer), the ratio of the space | gap on the inner side line D is certainly made more than the ratio of the space | gap on the surface approximate line A. I found that I could make it bigger. Even when the spray drying method (spray dryer) is used, various conditions are regulated as described above, and the ratio of voids on the inner line D can be determined by appropriately selecting the soft magnetic particles and binder resin material to be used. The gap ratio on the surface approximate line A can be appropriately increased. Specifically, a gap ratio difference of 20% or more can be obtained.

  Moreover, Example-2 of FIG.11 (b) is performing the particle size adjustment which cut | disconnected the small particle size with respect to the soft-magnetic particle which has a particle size distribution, However, Implementation of FIG. In contrast to Example-1, in Example-2 of FIG. 11 (b), the ratio of the gaps on the inner line D, the first intermediate line C, and the second intermediate line B all exceed 30%, It was found that the void ratio on each of the lines B to D was 20% or more higher than the void ratio on the surface approximate line A.

Next, each of the composite magnetic powders of Example-1, Example-2, and Comparative Example was separately filled into a mold and subjected to pressure molding at a surface pressure of 198 to 588 MPa (1 to 6 t / cm ² ). Each dust core having an outer diameter of 12 mm, an inner diameter of 6 mm, and a thickness of 3 mm was produced. Each obtained dust core was heat-treated at 470 ° C. for 17 minutes in a nitrogen stream atmosphere. Thereafter, it was impregnated with a silicone solution (13.5 wt%), dried at 70 ° C. for 30 minutes, and then heated at 285 ° C. for 1 minute for coating treatment.

  The electrical resistivity of each obtained powder magnetic core was calculated by measuring the electrical resistance using a super mega ohm meter (SM-8213 manufactured by DKK-TOA) and calculating the outer diameter, inner diameter, and thickness of the core. The core density was calculated from the outer diameter, inner diameter, thickness and weight of the core.

In the experiment, the core density was changed, and the electrical resistivity for each core density was measured.
Table 1 lists the electrical resistivity when the core density is about 4.7 g / cm ³ .

  FIG. 14 is a graph showing the relationship between the core density and the electrical resistivity in Example-1, Example-2, and Comparative Example.

  When the core density is the same as shown in Table 1 and FIG. 14, the electrical resistivity of Example-2 is the highest, and then the electrical resistivity of Example-1 is increased, and the electrical resistivity of the comparative example. Was found to be the lowest. In general, the electrical resistivity of Example-1 is more than twice the electrical resistivity of the comparative example, and the electrical resistivity of Example-2 is about 2.5 to 3 times the electrical resistivity of the comparative example. Became.

  Next, the specific resistance of each dust core having a different core density was measured using a super mega ohm meter (SM-8213 manufactured by DKK-TOA), and a copper wire was applied to each dust core, and an impedance analyzer (HP The core loss W was measured under the conditions of magnetic permeability at a frequency of 100 kHz using 4192A) and a frequency of 100 kHz and Bm = 100 mT using a BH analyzer (manufactured by Iwasaki Tsushin).

Table 1 lists the core loss W when the core density is about 4.7 g / cm ³ .
FIG. 15 is a graph showing the relationship between the magnetic permeability μ _{100 kHz} and the electrical resistivity of Example-1, Example-2, and Comparative Example.

As shown in FIG. 15, when the same magnetic permeability μ _{100 kHz} was used, it was found that the electrical resistivity of Example-1 and Example-2 was higher than that of the comparative example.

  Moreover, it turned out that the core loss W becomes a substantially the same value in Example-1, Example-2, and a comparative example when it is set as the same core density.

FIG. 16 is a graph showing the relationship between the core loss W _{0.1T100 kHz} and the electrical resistivity.

  As shown in FIG. 16, when it was set as the same core loss W, it turned out that the electrical resistivity of Example-1 and Example-2 becomes higher than the electrical resistivity of a comparative example.

  Thus, Example-1 and Example-2 turned out that a higher electrical resistivity can be acquired, obtaining the magnetic permeability and core loss substantially equivalent to a comparative example.

  FIG. 17 is a SEM photograph of a cross section of a powder magnetic core obtained by compression-molding the composite magnetic powder of Example-1.

  As shown in FIG. 17, even when compression molding is performed, the vicinity of the surface occupied by the soft magnetic particles having a small particle size constituting each composite magnetic powder remains faint (shown in FIG. 17 is a boundary line between the composite magnetic powders). Looking inside the line, it was confirmed that large voids remained inside.

A Surface approximate line B Second intermediate line C First intermediate line D Inner line O Center 1, 3 Powder magnetic core 2 Coiled powder magnetic core 10 Composite magnetic powder 11 Soft magnetic particle 19 Slurry 20 Spray dryer device 21 Rotor

Claims (9)

A composite magnetic powder formed by binding a large number of soft magnetic particles with a binder resin,
Manufactured by spray drying,
A cross-section passing through the approximate center of the composite magnetic powder, a surface approximate line, and an inner line that is at a distance of approximately ¼ from the approximate center of the composite magnetic powder toward the surface approximate line and is similar to the surface approximate line. A first intermediate line that is approximately ½ the distance from the approximate center of the composite magnetic powder toward the surface approximate line and is similar to the surface approximate line; and from the approximate center of the composite magnetic powder to the surface approximate line. When drawing a second intermediate line that is at a distance of approximately 3/4 and is similar to the surface approximation line,
The percentage of voids on the inner line is greater than the percentage of voids on the surface approximation line,
The ratio of the voids on the inner line is 20% or more larger than the ratio of the voids on the surface approximate line,
The average particle size (D50) of the volume distribution of the soft magnetic particles is 10 μm or more and 15 μm or less,
The composite magnetic powder, wherein a particle size (D10) at a cumulative value of 10% of the volume distribution of the soft magnetic particles is 4 μm or more and 7 μm or less, or 5 μm or more and 8 μm or less .   2. The composite magnetic powder according to claim 1, wherein a ratio of the voids on the inner line, the first intermediate line, and the second intermediate line are all larger than a ratio of the voids on the surface approximate line.   The ratio of the smallest gap among the inner line, the first intermediate line, and the second intermediate line is 20% or more larger than the ratio of the gap on the surface approximate line. Composite magnetic powder.   The composite magnetic powder according to any one of claims 1 to 3, wherein the soft magnetic particles contained in the composite magnetic powder are adjusted in particle size by cutting small particles.   5. The composite magnetic powder according to claim 4, wherein a ratio of the voids on the inner line, the first intermediate line, and the second intermediate line is 30% or more.   The composite magnetic powder according to claim 4 or 5, wherein an average particle size (D50) of the volume distribution of the soft magnetic particles is 13 µm or more and 15 µm or less.   The composite magnetic powder according to claim 6, wherein a particle size (D10) at a cumulative value of 10% of the volume distribution of the soft magnetic particles is 5 μm or more and 8 μm or less. The soft magnetic particles _is shown by _{Fe 100-a-b-c} -x-y-z-t Ni a Sn b Cr c P x C y B z Si t, 0at% ≦ a ≦ 10at%, 0at% ≦ b ≦ 3 at%, 0 at% ≦ c ≦ 6 at%, 6.8 at% ≦ x ≦ 10.8 at%, 2.0 at% ≦ y ≦ 9.8 at%, 0 at% ≦ z ≦ 8.0 at%, 0 at% The composite magnetic powder according to claim 1, wherein ≦ t ≦ 5.0 at%. A powder magnetic core obtained by compression molding the composite magnetic powder according to claim 1.