JP2002057039A - Composite magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic core which has low permeability and high saturation magnetic flux density and is decreased in eddy current loss induced in a winding. SOLUTION: Soft magnetic metal powder and a binder are mixed together and molded into a bar-shaped magnetic core 14, the magnetic core 14 is made to serve as the middle leg of a squarish eight-shaped core 13 of ferrite or a composite magnetic core, where the bar-shaped magnetic core 14 is fabricated through a potting method, an injection molding method, or a press molding method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic core for inductors such as choke coils and transformers used in electric circuits.

[0002]

2. Description of the Related Art Conventionally, Mn-Zn ferrite magnetic cores have been widely used as magnetic cores for inductors such as main transformers and choke coils used in switching power supplies. In general, the shape of the ferrite core is a combination of the individual magnetic cores, and the entire shape is a Japanese character, and the magnetic flux generated in the center rod portion of the Japanese character (usually called the middle leg) is the magnetic core. It is configured to divert to the two outer legs on the outside. EE, EI, EE, depending on the shape of each magnetic core constituting the whole
R, EIR, PQ, RM, EPC, LP, etc. are subdivided and called. These magnetic cores are generally prepared by separately preparing a resin bobbin through which the middle leg penetrates, and winding the bobbin on the bobbin.

[0003] In the case of an inductor for use in which a large current flows with a relatively low inductance, such as an RCC type (flyback type) main transformer, a smoothing choke coil, a choke coil for harmonic countermeasures (PFC choke coil), etc. By providing a gap (so-called gap) in the center of the leg portion, the magnetic permeability is reduced to prevent magnetic saturation of the magnetic core. In the case of a ferrite core without a gap, the magnetic permeability is usually several thousands, but by providing a gap, magnetic saturation with respect to current is suppressed, and the magnetic permeability is reduced to about 30 to 300.

[0004]

In the case of a ferrite core having a gap, the following problems have been pointed out. (1) By providing the gap, magnetic flux leaks out of the magnetic core, and the leaked magnetic flux generates an eddy current on the surface of the copper wire in the winding portion. When not using the litz wire described in the next section,
The eddy current loss of this winding portion becomes so large as to be equal to the total loss of the iron loss generated inside the magnetic core and the copper loss due to the resistance of the copper wire itself, and the temperature rise of the inductor becomes extremely unusable. (2) As a countermeasure against the eddy current loss in the winding portion due to the leakage magnetic flux described in the preceding paragraph, a so-called litz wire in which a number of thin copper wires are bundled is used. However, the litz wire is bulkier than the single wire and causes a decrease in the number of coil turns. As a result, it is necessary to employ a magnetic core having a larger size than the single wire in order to obtain the same inductance value. Also, litz wire is more expensive than single wire.

Further, ferrite has an excellent feature that magnetic core loss (iron loss) is remarkably low as compared with other soft magnetic materials such as a silicon steel sheet and an amorphous ribbon. However, when the gap is provided as described above, the advantage cannot be sufficiently utilized due to the eddy current loss in the winding portion due to the leakage magnetic flux. Furthermore, since ferrite is made of a metal oxide, it has a drawback that the saturation magnetic flux density is essentially lower than that of a metal-based soft magnetic material, and magnetic saturation easily occurs. For this reason, the ferrite magnetic core has to prevent the magnetic saturation by increasing the cross-sectional area of the magnetic core as compared with the magnetic core made of a metal-based soft magnetic material, resulting in an increase in the volume of the magnetic core. . In view of the above, it is an object of the present invention to provide a magnetic core having low magnetic permeability, high saturation magnetic flux density, and further reducing eddy current loss generated in a winding.

[0006]

According to the present invention, there is provided a Japanese-character composite magnetic core composed of a combination of a plurality of soft magnetic materials, wherein the magnetic material constituting the center leg of the magnetic core has a different particle size. A powder resin molded magnet is formed by mixing two kinds of soft magnetic metal powders A and B and a liquid binder to form a slurry once, casting the mixture in the middle leg portion, and curing the binder. Using a core, the soft magnetic material constituting the remaining part of the Japanese character type magnetic core is a soft magnetic sintered ferrite, the mode of the particle size distribution of the powder A is at least 5 times that of the powder B, and The compound ratio of the powder A and the powder B is a day-shaped composite magnetic core in which the volume percentage of the powder B is 15% or more and 60% or less with respect to the total volume of the powders A and B.

Further, the present invention provides a Japanese-character composite magnetic core constituted by combining a plurality of soft magnetic materials, wherein two types of soft magnetic particles having different particle diameters are used as the magnetic material constituting the middle leg portion of the magnetic core. Using a powdered resin molded magnetic core molded by mixing metal powders A and B and a resin powder and injecting into a mold, the soft magnetic material constituting the remaining part of the Japanese character type magnetic core is soft magnetic. Sintered ferrite, the mode of the particle size distribution of the powder A is 5 times or more that of the powder B, and the compounding ratio of the powder A and the powder B is the powder with respect to the total volume of the powder A and the powder B. B is a letter-shaped composite magnetic core having a volume percentage of 15% or more and 60% or less.

[0008] The present invention also relates to a letter-shaped composite magnetic core composed of a combination of a plurality of soft magnetic materials, wherein soft magnetic metal powder and an inorganic or organic binder are used as the magnetic material constituting the middle leg portion of the magnetic core. Is a dust-type composite magnetic core using a soft magnetic sintered ferrite as a soft magnetic material constituting the remaining part of the Japanese-type magnetic core using a dust core obtained by pressing and molding.

The present invention also relates to a method of using a resin mixed with a soft magnetic metal powder as an adhesive for bonding between a powdered resin molded magnetic core or a dust core used for a middle leg portion and a soft magnetic sintered ferrite. It is a letter-shaped composite magnetic core.

Further, the present invention is a character-shaped composite magnetic core in which at least one of the soft magnetic metal powders to be used is made of an amorphous alloy powder or a microcrystalline soft magnetic alloy that precipitates nanoscale microcrystals.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to make up for the drawbacks of the ferrite core described in the prior art, the present invention relates to a rod-shaped core formed by mixing a soft magnetic metal powder and a binder with the middle leg of a Japanese character-shaped core. It is composed of a magnetic core. As a method of molding the rod-shaped magnetic core, once the mixture of magnetic powder and resin is liquefied,
A casting method of casting and curing the middle leg part, an injection molding method of molding by injection molding in a mold, filling a mold with a mixture of a magnetic powder and a binder composed of an organic or inorganic substance and applying pressure. Any of the press molding methods of molding a dust core by using a press method is used.

According to the present invention, a gap which has been a source of leakage magnetic flux in a conventional ferrite core is removed, and a soft magnetic metal powder core having a magnetic permeability of about 25 to 120 is used in the middle leg instead. I have. The magnetic permeability of the air constituting the gap is 1, and the magnetic flux having a much higher magnetic permeability is used in place of the gap to significantly reduce the leakage magnetic flux. As a result, the eddy current loss generated in the winding part does not increase significantly even if the litz wire, which was conventionally required, is replaced with a single wire, and the magnetic permeability of the soft magnetic metal powder core is significantly higher than that of ferrite. And the magnetic permeability as a whole of the magnetic core is greatly reduced due to the influence of the magnetic core portion, which is suitable for use in inductors for large currents.

Further, since the soft magnetic metal material has a saturation magnetic flux density at least about twice as high as that of ferrite, the cross-sectional area of the middle leg is reduced by about 1 times compared to the case where the middle leg is made of ferrite.
Even if it is reduced to / 2, magnetic saturation does not occur. As a result, the cross-sectional area of the winding portion (so-called winding frame area) can be increased, resulting in an increase in inductance due to an increase in the number of windings, and a decrease in winding resistance due to an increase in the winding diameter, resulting in a copper loss. Reduction can be realized.

[0014]

EXAMPLES (Example 1) In Example 1, a powder resin molded magnetic core used for the middle leg portion was produced by the following casting method. As the powder A, a water atomized powder of a soft magnetic amorphous alloy (hereinafter referred to as powder A-1) having a composition in which B, Si, etc. are added in combination, and as the powder B, a water atomized fine powder having a sendust composition (hereinafter referred to as powder B) -1) is used. Powder A-1 was heat-treated at 400 ° C, and powder B-1 was heat-treated at 550 ° C. Powder A-
The particle size distribution of No. 1 is shown in FIG. The particle size distribution was measured by a laser scattering method. The mode value of the particle size of this powder A-1 is 44
The median value of 53 μm is the mode value of the powder A-1. Hereinafter, the mode of the particle size of each powder was calculated by this method. FIG. 2 shows the particle size distribution of the powder B-1. The mode has a rank of 5.5 to 7.8 μm, and the median of 6.7 μm is the mode of the powder B-1. Powder A,
The mode particle size ratio of B is 7.9. Note that a solventless varnish (styrene-polymerized unsaturated polyester-based) was used as the binder.

[0015] The solventless varnish is added little by little to a mixture of a predetermined amount of powders A-1 and B-1 in a mortar and stirred, and the mixture is repeatedly stirred, whereby the mixture becomes a slurry and starts to flow. Solvent-free varnish was added and the weight of the varnish was recorded. After vacuum-defoaming the slurry for 5 minutes, the slurry was poured into a toroidal plastic case having an outer diameter of 26 mm in order to confirm the magnetic properties of the powder resin-cured magnetic core alone, and then heated and cured at 120 ° C. × 3H. The inner volume of the case is 24φ outside diameter, 13.5φ inside diameter, and 6.6H in height.
mm. The slurry density was calculated from the weight of the injected slurry and the volume in the case, and the space factor of the magnetic core was calculated from the weight of the powder and the amount of the binder added.

The above-obtained toroidal magnetic core was wound with a 0.8φ wire, and the windings were measured with an LCR meter.
The magnetic permeability at 00 kHz was measured. The core loss at 100 kHz and 50 mT was measured by a BH analyzer. The sum of the saturation magnetic flux densities of the individual magnetic materials multiplied by the volume percentage was defined as the composite saturation magnetic flux density, which was multiplied by the space factor to obtain the composite saturation magnetic flux density of the obtained magnetic core.

Table 1 shows the results of preparing toroidal magnetic cores by changing the mixing ratio of powder A (A-1) and powder B (B-1) and measuring various magnetic properties. In the table, for comparison, Fe
The values of the -Al-Si based dust cores are also shown. When the compounding ratio of the powder B is 25 vol%, the space factor and the magnetic permeability are maximum, and when the compounding ratio of the powder B is 20%, the magnetic core loss becomes minimum. The magnetic characteristics are greatly improved as compared with the case. From these results, it was decided to use a powder B having a compounding ratio of 25% in the production of the following composite magnetic core.

[0018]

[Table 1]

A further comparative example with respect to the above embodiment will be described below. As the powder A, the powder A-1 of the above example was classified with a sieve (# 440 mesh), and the fine powder that passed through was used. The mode of the particle size is 26.5 μm. As the powder B, the aforementioned B-1 was used. The mode frequency particle ratio of powders A and B is 4.0. The procedure of the experiment is the same as in the above embodiment.
Table 2 shows the evaluation results. If the ratio of the mode of the particle size is less than 5, the effect of improving the space factor will be small, and optimum magnetic characteristics will not be obtained.

[0020]

[Table 2]

Next, a Japanese-shaped composite magnetic core was prepared by combining the slurry (the present invention 1-4) selected above and a ferrite magnetic core in the following manner. The ferrite magnetic core to be used is a so-called EE-type Mn-Zn ferrite, and its outer dimensions are 28 × 21.5 × 11 tmm. The center leg portion of the magnetic core was cut off, and the cut center leg portion was formed of a powder molded core. 3 (c) and 3 (d), the entire middle leg of the Japanese character type magnetic core 11 is constituted by the powder molded magnetic core 14, and the other magnetic core portion is formed by the ferrite magnetic core 13. In addition, as a comparative example, a part of the center leg was made of a powder molded magnetic core 14 (b), and a part other than the outer leg including the middle leg was made of a powder molded magnetic core 14 (e), and a ferrite having a gap 12 was provided. Japanese character type magnetic core (a) composed of magnetic core 13 only, powder molded magnetic core 1
Further, a Japanese character type magnetic core (f) composed of only 4 was also manufactured.

FIG. 4 shows a method of manufacturing the magnetic core shown in FIG.
EE-shaped magnetic core with winding 15
Bobbin 16 and ferrite core 13 with middle leg removed
It is placed at the corresponding position of the shaped Japanese-made magnetic core, and thin resin
A plate 17 is stuck between the bobbin 16 and the ferrite core 13
To form a recess 18 for casting the slurry.
-4 (powder B: 25 vol%) slurry 19
It was cast to the same height as the magnetic core 13 and cured. Hardening
Later, DC superposition characteristics (permeability-bias magnetic field), core loss
Pc was measured. The core loss is due to the leakage flux described above.
Eddy current loss generated in the winding part
In order to confirm the influence, the measurement of the core loss was carried out by measuring the wire diameter of the winding at 0.
2 litz wire bundled with 55φ single wire and 0.12φ wire
The measurement was performed with the following winding specifications. Measurement of DC superposition characteristics is wire diameter
Of 0.55φ single wire
Out. The calculation of the magnetic permeability and the magnetic core loss was performed by calculating the magnetic core cross-sectional area: 89
mm ², Magnetic core magnetic path length: 49.6 mm.

FIG. 5 shows a DC superposition characteristic of each magnetic core configuration shown in FIG. Compared with the ferrite core with a gap of (a), (c) and (d) of the present invention in which the entire middle leg is formed of a soft magnetic metal powder core have higher magnetic permeability near a bias magnetic field of 0 A / m, In addition, the magnetic permeability does not decrease rapidly even in a high bias magnetic field region. It is preferable that the inductance at the time of a large current does not rapidly decrease as an inductor in order to reduce noise and loss generated in a semiconductor element of a power supply circuit. In addition, having a high inductance near a zero current and having a so-called swing property is most suitable for a choke coil for a power supply circuit having a large load current fluctuation. When the bias magnetic field is 2000 to 40
The magnetic permeability in the range of 00 A / m is inferior to (a) composed of only ferrite, but this can be dealt with by increasing the number of turns as described later.

Table 3 shows the magnetic core loss values of the respective magnetic core configurations shown in FIG. The measurement conditions were 100 kHz and 50 mT,
The magnetic permeability (amplitude relative magnetic permeability μa) under this condition is also shown. The entire middle leg was composed of a soft magnetic metal powder core (c),
In (d), even when a single wire is used, the same magnetic core loss value as when using the litz wire of the ferrite magnetic core in (a) is obtained. Also,
The amplitude relative permeability of (c) and (d) is about twice as large as that of the magnetic core composed of only the soft magnetic metal powder of (f).

[0025]

[Table 3]

An actual trial production example of a choke coil using the comparative example (a) in Table 3 and the present invention (c) is shown below. The bobbin for the EE-shaped magnetic core to be used can wind a single 0.55φ wire for 87 Ts. 0.12φ having the same cross-sectional area as the single wire
The × 21 litz wire can be wound around the same bobbin only 56Ts because of its bulk. Direct superposition characteristics (inductance-bias current) when the litz wire is wound for 56 Ts in the comparative example (a) and the solid wire is wound for 87 Ts in the present invention (c).
6 are shown in FIG. According to the present invention, as a result of using a single wire and increasing the number of turns, higher inductance is obtained in almost all bias current regions than in the comparative example of the conventional structure.

(Example 2) A-1 used in Example 1 is used as the powder A. Powder B is composed of Fe, Cu, Nb, B,
An amorphous alloy powder was prepared by a water atomization method by adding Si in a complex manner, and then heat-treated at 550 ° C. to classify a powder in which microcrystals having a thickness of about 10 nm were precipitated. ) Is used. The mode of particle size of powder B-2 is 6.7.
μm. The ratio of the mode of particle size between powder A and powder B is 7.
9

In the same manner as in Example 1, the two kinds of soft magnetic metal powder and the solventless varnish were mixed, cast into a toroidal case, and cured. Table 4 shows the evaluation results of the magnetic characteristics. By using an ultra-microcrystalline soft magnetic alloy powder having a low magnetic core loss, a low magnetic core loss value is obtained in a wide blending range. By using the soft magnetic metal powder molded magnetic core according to the present embodiment in the middle leg portion of the Japanese character type magnetic core in the same manner as in the first embodiment, a composite magnetic core having high permeability and low loss can be formed. .

[0029]

[Table 4]

(Embodiment 3) As described in Embodiments 1 and 2, a soft magnetic metal powder core having a low magnetic permeability is used for the middle leg portion, and a ferrite core having a high magnetic permeability is arranged in other portions. By doing so, the magnetic permeability of the entire magnetic core increases to about 2 to 3 times that of the soft magnetic metal powder magnetic core. This effect is the same regardless of the method of molding the powder magnetic core, and the powder magnetic core can be mass-produced by the injection molding method with good productivity. The powder used was the same as that of Example 1 (powder A-1: 7).
5 vol% and B-1: a mixture of 25 vol%). As the resin, 12 nylon was used, and the space factor of the powder was 76%. A ring core was cut out from a molded body obtained by injection molding, and magnetic properties were evaluated. Table 5 shows the results
Shown in

[0031]

[Table 5]

Next, using this injection-molded magnetic core, a letter-shaped composite magnetic core was manufactured. The procedure for producing the magnetic core dimensions and the like was the same as in Example 1. The middle leg portion of the Japanese character magnetic core was cut out from the injection molded magnetic core, and a magnetic core having the structure shown in FIG. Table 6 shows the evaluation results of the core loss. Although the value of the magnetic core loss is deteriorated as compared with the first embodiment, in the case of the single wire winding, a magnetic core loss value lower than that of the ferrite core of (a) is obtained.

[0033]

[Table 6]

(Embodiment 4) A soft magnetic metal powder core used for the middle leg portion can be manufactured by a press molding method with good productivity. As the powder used, A-1 described in Example 1 is used alone. A predetermined amount of powder A-1 and a polyimide varnish as a binder were put in a mortar, mixed, and granulated through a 60-mesh screen. The amount of the binder was determined so that the solid content of the varnish after the solvent was dried was 1.0 part by weight based on 100 parts of the powder. Further, 0.3 part of zinc stearate was added and mixed as a lubricant to 100 parts of the granulated powder. Next, the powder was placed in a mold, and a molding pressure of 15 × 10 ⁸ Pa
Was press molded. After the molded body was heat-treated at 470 ° C. for 60 minutes, a magnetic core having a toroidal shape was cut out and wound to measure the magnetic properties. Table 7 shows the results.

[0035]

[Table 7]

Next, using this press-molded magnetic core, a compound character core in the shape of a letter was prepared. The procedure for manufacturing the magnetic core dimensions and the like is described in Example 1.
In the same manner as described above, the middle leg portion of the Japanese character type magnetic core was cut out from the press-formed magnetic core, and a magnetic core having a structure shown in FIG. Table 8 shows the evaluation results of the core loss. By using a soft magnetic amorphous alloy powder core with low core loss for the middle leg, the core loss value lower than that of the ferrite core of (a) at the time of litz wire winding can be obtained with a single wire winding. Have been obtained.

[0037]

[Table 8]

A problem in using the above-described injection-molded magnetic core or press-molded magnetic core for the middle leg of the Japanese-shaped magnetic core is that the sintered ferrite magnetic core has large dimensional variations. The dimensional variation between the injection molded core and the press molded core is within the dimensional accuracy of ± 0.1mm or less regardless of the magnetic core size.
The ferrite core sintered after press molding is ±
Only a dimensional accuracy of about 1.0 to ± 1.5% is guaranteed.
When a gap is formed between the center leg core and the ferrite core, the gap functions as an air gap, and the magnetic permeability of the entire core is rapidly reduced.

In order to solve this problem, the magnetic cores may be joined with an adhesive having a high magnetic permeability to fill the gap. This adhesive can be easily produced by mixing, for example, a soft magnetic metal powder with an epoxy resin or the like. As described in the first embodiment, as the metal powder to be used, it is desirable to increase the powder space factor and the magnetic permeability by combining the coarse powder A and the fine powder B.

Example 5 Using the powder used in Example 1, powder A-1: 100 vol% and powder A-1: 75 v
ol%, B-1: Two kinds of compounded powders of 25 vol% were prepared, and a liquid epoxy resin was mixed with each compounded powder and added until a slurry was obtained. The slurry was cast into a toroidal case and cured to measure magnetic properties. Table 9 shows the results.

[0041]

[Table 9]

Next, using the above two types of slurries as an adhesive, a change in the magnetic permeability of the entire magnetic core when the gap between the magnetic cores was filled was measured. In the configuration using the center leg magnetic core by press molding used in Example 4, the length of the center leg made of the powder molded magnetic core was reduced by 0.5 mm, and the length of the mid leg was combined with the ferrite magnetic core. The magnetic permeability was measured with a BH analyzer as a composite magnetic core having a diameter of 5 mm. Next, the gaps were filled with the adhesives of the inventions 5-1 and 5-2 of Table 9 and the magnetic permeability was measured after the adhesives were cured. Table 10 shows the results. By forming the gap of 0.5 mm, the amplitude relative magnetic permeability sharply decreases, but by filling the gap with a material having a high magnetic permeability, the amplitude relative magnetic permeability of the entire magnetic core becomes close to the original value (before the gap is formed). Was able to recover.

[0043]

[Table 10]

The composite magnetic core of the present invention is shown in FIGS.
The intermediate structure shown in FIGS. 3C and 3D shown in FIG. 7 is also included in the composite magnetic core of the present invention. In addition, although the composite magnetic core shape described in the examples is a Japanese character shape made of EE type, EI, EER, EIR, PQ, RM, EPC, L
As long as the shape is a Japanese character formed of P or the like, the same effect as that of the embodiment of the present invention can be obtained by using the composite magnetic core of the present invention.

[0045]

According to the present invention, by forming the middle leg portion of the Japanese character-shaped magnetic core made of ferrite with a soft magnetic metal powder magnetic core, the saturation magnetic flux density of the whole magnetic core is increased, and the DC superposition characteristic is reduced. The decrease in magnetic permeability was improved. Also, instead of the gap that was conventionally provided on ferrite cores,
By forming the magnetic core center leg with a soft magnetic metal powder core, eddy current loss generated in the windings generated by the leakage magnetic flux of the magnetic core is reduced, and the soft magnetic metal material is changed to a ferrite material. Since it has a higher saturation magnetic flux density, the cross-sectional area of the middle leg can be reduced. As a result, the winding bobbin area of the winding portion is increased and the number of turns of the winding is increased, so that the loss of the inductor using the magnetic core is suppressed, and the inductance value can be increased. .

In the composite magnetic core of the present invention, an adhesive formed by mixing a soft magnetic metal powder described in the specification of the present invention with a resin is used to form a gap generated at a joint between a powder molded magnetic core and a ferrite magnetic core. By filling in the composite magnetic core, it is possible to prevent a decrease in the magnetic permeability, which is one of the causes of the characteristic deterioration when the composite magnetic core is formed.

[Brief description of the drawings]

FIG. 1 is a particle size distribution of powder A of Example 1 according to a composite magnetic core of the present invention.

FIG. 2 is a particle size distribution of powder B of Example 1 according to the composite magnetic core of the present invention.

FIG. 3 is a configuration diagram of a letter-shaped composite magnetic core according to the composite magnetic core of the present invention.

FIG. 4 is a production example of a Japanese character-shaped composite magnetic core according to the composite magnetic core of the present invention.

FIG. 5 is a diagram showing a DC superposition characteristic of a letter-shaped composite core according to the composite core of the present invention

FIG. 6 is a diagram showing a DC superposition characteristic of an inductor using a Japanese-character composite core according to the composite core of the present invention.

FIG. 7 is another embodiment of a Japanese character type composite magnetic core according to the composite magnetic core of the present invention.

[Explanation of symbols]

 13 Ferrite core 14 Soft magnetic metal powder molded core

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 3/08 H01F 41/02 C 27/24 D 41/02 B29C 45/00 H01F 27/24 D // B29C 45/00 CF term (reference) 4F206 AA49 AC04 AE04 AH33 JA07 JF02 JL02 4K018 AA25 BA15 BB06 BB07 CA11 CA29 CA33 GA04 KA43 5E041 AA04 AA11 AA19 AB02 AB19 BB03 BD03 CA02 HB05 NN17 5E062 A

Claims (6)

[Claims] 1. In a Japanese character-shaped composite magnetic core composed of a combination of a plurality of soft magnetic materials, two types of soft magnetic metal powders A having different particle diameters are used as a magnetic material constituting a middle leg portion of the magnetic core. , B and a liquid binder are mixed to form a slurry, then poured into the middle leg portion, and a powder resin molded magnetic core molded by curing the binder is used. The soft magnetic material constituting the remaining part of the core is soft magnetic sintered ferrite, and the mode of the particle size distribution of the powder A is at least 5 times that of the powder B, and the mixing of the powder A and the powder B The ratio of powder B to the sum of the volumes of powder A and powder B
Wherein the volume percentage is 15% or more and 60% or less. 2. A two-piece soft magnetic metal powder A having different particle diameters as a magnetic material constituting a middle leg portion of a Japanese-character composite magnetic core formed by combining a plurality of soft magnetic materials. , B and a resin powder are mixed and injection-molded into a mold using a powdered resin molded magnetic core, and the soft magnetic material constituting the remaining part of the Japanese character type magnetic core is soft magnetic sintered ferrite. And the mode of the particle size distribution of the powder A is powder B
And the compounding ratio of powder A and powder B is 15% or more and 60% or less with respect to the total volume of powder A and powder B. Japanese character type magnetic core. 3. In a Japanese character type composite magnetic core constituted by combining a plurality of soft magnetic materials, a soft magnetic metal powder and an inorganic or organic binder are mixed as a magnetic material constituting a middle leg portion of the magnetic core. A soft magnetic sintered core comprising soft magnetic sintered ferrite as a soft magnetic material constituting the remaining portion of the soft magnetic core using a pressed and pressed magnetic core. 4. A resin mixed with a soft magnetic metal powder is used as an adhesive for bonding between a powder resin molded core or a dust core used for a middle leg portion and a soft magnetic sintered ferrite. The Japanese-character composite magnetic core according to claim 2 or 3, wherein 5. The Japanese-made composite magnetic core according to claim 1, wherein at least one of the soft magnetic metal powders used is an amorphous alloy powder. 6. The composite according to claim 1, wherein at least one of the soft magnetic metal powders used is a microcrystalline soft magnetic alloy that precipitates nanoscale microcrystals. Magnetic core.