JP6730785B2 - Metal composite core manufacturing method and reactor manufacturing method - Google Patents

Description

The present embodiment relates to a soft magnetic composite material suitable for a reactor called a metal composite type, a magnetic core using the soft magnetic composite material, and a reactor using the soft magnetic composite material.

The reactor called a metal composite type is a reactor manufactured by integrally molding a magnetic core using a material in which soft magnetic powder and resin are mixed, and a coil. This reactor is characterized in that it is less likely to be magnetically saturated in a high temperature region as compared with a laminated type reactor using ferrite for a magnetic core.

The magnetic core used for the metal composite type reactor is called a metal composite core. This is manufactured by mixing a soft magnetic powder and a resin to prepare a soft magnetic composite material and solidifying it. Patent Document 1 discloses a method of obtaining a soft magnetic composite material having a relatively low relative magnetic permeability and a high saturation magnetic flux density by using a soft magnetic powder having a predetermined density ratio.

JP, 2014-160828, A

However, even if such a soft magnetic composite material has sufficient magnetic properties after manufacturing, there is a problem that the magnetic properties deteriorate due to deterioration over time. The deterioration of magnetic properties due to deterioration over time includes a decrease in magnetic permeability and an increase in loss, and improvement thereof is required.

The present invention has been proposed to solve the above-mentioned problems of the conventional technology. An object of the present invention is to provide a soft magnetic composite material, a magnetic core using the soft magnetic composite material, and a soft magnetic composite material capable of suppressing deterioration of magnetic properties due to aging deterioration, in particular, reduction of magnetic permeability and increase of loss. The purpose is to provide the used reactor.

The present inventors have noticed that there is a close relationship between the magnetic properties of the soft magnetic composite material and the physical properties of the resin mixed with the soft magnetic powder. That is, it was considered that the physical properties of the resin mixed with the soft magnetic powder affected the deterioration of the magnetic properties of the soft magnetic composite material due to aging. The physical properties of the resin include various properties such as mechanical properties, electrical properties, thermal properties, magnetic properties, and optical properties.

The present inventors have focused on the water absorption and the glass transition point, among other physical properties of the resin. Then, it was discovered that when a material having a water absorption coefficient and a glass transition point in a specific range was used, it was possible to suppress a decrease in magnetic permeability and an increase in loss of the magnetic core. The present invention described below has been completed by developing this discovery.

(1) The metal composite core manufacturing method of the present invention has the following configuration.
(A) A resin mixing step of mixing a soft magnetic powder with an epoxy resin having a water absorption of 0.36% or less and a glass transition point of 140° C. or more to prepare a soft magnetic composite material.
(B) An injection step of injecting the soft magnetic composite material into the container after the resin mixing step.
(C) A pressurizing step of pressurizing the soft magnetic composite material at 600 Pa or less after the injecting step.
(D) A resin curing step of curing the epoxy resin by heat treatment at 120 to 150° C. after the pressing step.

(2) The soft magnetic powder may be a mixed powder of a first powder and a second powder having different average particle sizes.

(3) The amount of the epoxy resin mixed with the mixed powder may be 3 to 5 wt %.

(4) A filler may be mixed in the epoxy resin.

(5) In the method for producing a metal composite core according to any one of (1) to (4), the method for producing a reactor also includes a step of disposing a coil in the container before the injecting step. Is one aspect.

According to the present invention, it is possible to suppress a decrease in magnetic permeability and an increase in loss of a soft magnetic composite material by setting the water absorption rate and the glass transition point of the resin mixed with the soft magnetic powder within specific ranges. As a result, it is possible to provide a soft magnetic composite material capable of suppressing deterioration of magnetic properties due to deterioration over time, a magnetic core using the soft magnetic composite material, and a reactor using the soft magnetic composite material.

6 is a graph showing a relationship between a water absorption rate of a resin and a change rate of magnetic permeability (μa) of a soft magnetic composite material after a high temperature and high humidity test. 6 is a graph showing the relationship between the glass transition point of a resin and the rate of change in loss (pcv) of a soft magnetic composite material after a high temperature test.

[1. Constitution]
The constituent elements of the soft magnetic composite material of this embodiment will be described below. The soft magnetic composite material of the present embodiment is a soft magnetic composite material obtained by mixing soft magnetic powder with a resin, the resin being a curable resin, the resin having a water absorption rate of 0.36% or less, and a glass transition point. Is 140°C or higher. In the present embodiment, a mixed powder obtained by mixing two kinds of soft magnetic powders will be described as an example. However, it does not necessarily have to be a mixture of two types of powders. For example, one kind of soft magnetic powder may be used, or three or more kinds of soft magnetic powder may be mixed.

[1-1. Mixed powder]
The mixed powder is a mixture of the first powder and the second powder, which are soft magnetic powders. The average particle diameters of the first powder and the second powder are different. In the present embodiment, the average particle size of the first powder is larger than the average particle size of the second powder.

The ratio of the average particle diameter of the second powder to the average particle diameter of the first powder is preferably 0.025 to 0.12. More preferably, when the first powder is 1, the second powder is 0.04-0.10. When the second powder having a small average particle diameter enters the gap between the particles of the first powder having a large average particle diameter, the inside of the gap is filled with the soft magnetic powder, and the density of the obtained soft magnetic composite material is increased. Because. When it exceeds the above range, the second powder is too large, and a gap is generated between the first powder and the second powder, and the density is lowered.

The mixing ratio of the first powder and the second powder is preferably 60 to 80 wt% for the first powder and 20 to 40 wt% for the second powder. According to the average particle diameter and the average circularity of the first powder and the second powder, the density of the obtained soft magnetic composite material is lowered even if the compounding ratio of the both deviates from this range in any direction.

The first powder and the second powder are preferably uniformly mixed at the time of mixing. By doing so, there is an advantage that the density of the soft magnetic composite material formed by mixing the resin with the mixed powder becomes uniform, and variations in performance such as magnetic permeability do not occur.

[1-2. First powder]
Fe-6.5Si can be used as the first powder. This is because the powder hardness is suitable for this embodiment. Powder hardness is the pressure required to displace the powder by 10%. The powder hardness of Fe-6.5Si is 390 MPa. As the first powder, soft magnetic powder other than Fe-6.5Si, for example, pure iron, Fe-Si, Fe-Ni, Fe-Al, Fe-Co, Fe-Cr, Fe-N, Fe-C, Fe-based alloy powders such as Fe-B, Fe-P, and Fe-Al-Si, rare earth metal powders, amorphous metal powders, and ferrite powders can also be used.

The average particle size of the first powder is preferably 100 μm or more. Moreover, 100-300 micrometers is more preferable. If the first powder is too large, the circularity inevitably becomes low, and if it is too small, the magnetic permeability becomes low. If the average particle size exceeds 300 μm, the voids between the particles may increase, and the second powder may not be able to fill the voids. As a result, the density of the soft magnetic composite material decreases. Since the second powder cannot have a size smaller than a predetermined size, when the first powder is less than 100 μm, the difference in particle size between the second powder and the second powder filling the voids between the particles becomes small. Then, since the voids between the first powder and the second powder increase, the density of the soft magnetic composite material decreases.

The average circularity of the first powder is 0.895 or more, and it is particularly preferable to use powder of 0.94 or more. When the circularity is lower than this, voids are generated between the irregularities on the surface of the first powder and the second powder, and the density is reduced. The amount of resin to be mixed can be reduced by using the soft magnetic powder having a high circularity. As a result, the density becomes higher and high magnetic permeability can be realized.

As the first powder, those produced by a gas atomizing method, a water atomizing method, or a water gas atomizing method can be used. The soft magnetic powder obtained by the gas atomization method is almost spherical particles. Therefore, it can be used as it is without being processed. The soft magnetic powder produced by the water atomizing method is a non-spherical particle having irregularities formed on its surface. Therefore, after crushing with a ball mill or the like to form a sphere, an average circularity is adjusted to 0.895 or more by using a surface modification device. In this respect, the same applies to the second powder described below.

As the first powder, both of those having an insulating coating formed on the surface and those not having an insulating coating formed thereon can be used. As the insulating film, _MgO having a particle diameter _{7~500nm, Al 2 O 3, TiO} 2, CaO, and inorganic insulating powder obtained by mixing a silane coupling agent in an insulating film such as SiO _2, heat-curable silicone A resin coating or the like can be used.

[1-3. Second powder]
As the second powder, the same material as the first powder can be used. A material different from the material of the first powder may be used. The average particle size of the second powder is preferably 5 to 12 μm. When the average particle size exceeds 12 μm, the particle size is too large as compared with the first powder having a size of 100 to 300 μm, and the second powder cannot fill the voids formed between the first powder. Therefore, the density of the soft magnetic composite material decreases. If it is less than 5 μm, it becomes difficult to produce the second powder, and the surface tension of the resin hinders the mixing with the resin.

The average circularity of the second powder is preferably 0.895 or more. The average circularity does not have to be equal in the first powder and the second powder. When the average circularity of the second powder is lower than this, a void is generated between the surface of the first powder and the second powder, and the density is reduced. As with the first powder, a powder produced by a gas atomizing method, a water atomizing method, or a water gas atomizing method can be used as the second powder.

As the second powder, similar to the first powder, both those having an insulating coating on the surface and those not having an insulating coating can be used. As the insulating coating, an insulating coating obtained by mixing a silane coupling agent with an inorganic insulating powder such as MgO, Al ₂ O ₃ , TiO ₂ , CaO or SiO ₂ , or a heat-curable silicone resin coating can be used.

[1-3. resin]
The resin has a function of being mixed with the mixed powder and holding the first powder and the second powder in a homogeneously mixed state. A curable resin can be used as this resin. The curable resin may be a thermosetting resin or a photocurable resin that is cured by ultraviolet rays, for example. As the thermosetting resin, epoxy resin, acrylic resin, silicone resin, phenol resin, unsaturated polyester resin, polyurethane, diallyl phthalate resin, etc. can be used. As the photocurable resin, urethane acrylate-based, epoxy acrylate-based, acrylate-based, or epoxy-based resin can be used.

As described above, the resin has a water absorption of 0.36% or less and a glass transition point of 140° C. or more. Of the above resins, it is preferable to use an epoxy resin having a higher glass transition point than other resins. When an epoxy resin is used, it is difficult to decompose the obtained soft magnetic composite material even if it is heat-treated, and the magnetic characteristics can be improved. Further, the acrylic resin and the silicone resin tend to be modified at a high temperature as compared with the epoxy resin, but can be used when the usage temperature of the soft magnetic composite material is 125° C. or lower.

The resin preferably has a viscosity of 50 to 5000 mPa·s when mixed with the soft magnetic powder. If the viscosity is less than 50 mPa·s, the resin will not be entangled with the soft magnetic powder during mixing and will be biased to the lower layer portion of the soft magnetic composite material injected into the container, which may affect the density and strength of the soft magnetic composite material. Variation occurs. When the viscosity exceeds 5000 mPa·s, the viscosity becomes too high and the second powder having a small average particle diameter cannot smoothly enter into the gap between the first powder having a large average particle diameter, and the obtained soft magnetic composite material is obtained. Density is reduced. More preferably, it is 100 m to 1000 mPa·s.

The addition amount of the resin is preferably 3 to 5 wt% with respect to the mixed powder composed of the first powder and the second powder. If it is less than 3 wt %, the joining force of the soft magnetic powder will be insufficient and the strength of the obtained soft magnetic composite material will be reduced. When it exceeds 5 wt %, the resin enters the gaps formed between the first powders, the second powders cannot fill the gaps, and the density of the soft magnetic composite material decreases.

A filler may be mixed with the resin. The glass transition point of the resin can be increased by mixing the filler. However, when the filler is mixed, the soft magnetic composite material contains a non-magnetic substance, which may reduce the magnetic permeability. Therefore, when the glass transition point of the resin itself is 140° C. or higher, it is preferable to use the filler without mixing it. On the other hand, when the glass transition point of the resin itself is lower than 140°C, a filler can be mixed and used so that the glass transition point is 140°C or higher.

As the filler, Al ₂ O ₃ , BN, AlN, SiO ₂ , Fe ₂ O ₃ , ZnO, TiO ₂ or the like can be used. When the filler is mixed, the average particle size of the filler is not more than the average particle size of the second powder, preferably not more than ⅓ of the average particle size of the second powder. This is because if the particle size of the filler is large, the density of the obtained soft magnetic composite material decreases.

[2. Magnetic core manufacturing method]
The method of manufacturing the magnetic core of the present embodiment has the following steps.
(1) A preparatory step of preparing a mixed powder in which a first powder made of soft magnetic powder and a second powder having an average particle diameter smaller than that of the first powder are mixed.
(2) Resin mixing step of obtaining a soft magnetic composite material by mixing 3 to 5 wt% of a curable resin having a water absorption of 0.36% or less and a glass transition point of 140° C. or more with respect to the mixed powder.
(3) An injection step of arranging a coil embedded in a molded article of insulating resin in a container and injecting a soft magnetic composite material.
(4) A pressurizing step of pressurizing the soft magnetic composite material. (5) A resin curing step of curing the curable resin.

(1) Preparation Step To manufacture the soft magnetic composite material of the present embodiment, first, the first powder and the second powder are prepared and mixed powder is prepared.

(2) Resin mixing step A resin having a water absorption of 0.36% or less and a glass transition point of 140° C. or more is mixed with the mixed powder to prepare a soft magnetic composite material.

(3) Injecting step An insulating-treated coil is placed in the container. The soft magnetic composite material is injected into the gap between the container and the coil through the upper opening of the container. At this time, in order to prevent the soft magnetic composite material injected into the container from smoothly flowing into the gap between the container and the coil and to prevent the generation of voids, it is possible to perform vacuuming during the injection.

(4) Pressurizing Step In the pressurizing step, the soft magnetic composite material filled in the container is pressed from the opening portion of the container. In that case, the temperature of the container is preferably room temperature, but may be up to 80°C. That is, the normal temperature here means a range of 5°C to 35°C, but may be a range of 5°C to 80°C. The applied pressure is, for example, about 0 to 600 Pa. By applying pressure, voids in the soft magnetic composite material are eliminated, the density is improved, and the magnetic permeability can be increased.

(5) Resin curing step In the resin curing step, a treatment for curing the curable resin is performed. The thermosetting resin is heat-treated at a predetermined temperature to be cured. This heat treatment is preferably performed at a temperature of 120° C. to 150° C. for a predetermined time. By setting the heat treatment temperature to 120° C. or higher, the strength of the magnetic core molded body can be secured. By setting the heat treatment temperature to 150° C. or lower, it is possible to suppress an increase in loss due to dielectric breakdown of the soft magnetic powder. When a photocurable resin is used, it is cured by irradiating it with light having a predetermined wavelength.

[3. effect]
(1) The soft magnetic composite material is a soft magnetic composite material obtained by mixing a resin with a soft magnetic powder, the resin is a curable resin, the water absorption rate of the resin is 0.36% or less, and the glass transition point is It is 140°C or higher. As a result, it is possible to suppress a decrease in magnetic permeability and an increase in loss of the soft magnetic composite material. As a result, it is possible to provide a soft magnetic composite material, a magnetic core, and a method for producing the same that can suppress deterioration of magnetic properties due to deterioration over time. Then, it is possible to suppress a decrease in the inductance of the reactor using the soft magnetic composite material, and to provide a highly reliable reactor.

(2) The soft magnetic powder is a mixed powder of the first powder and the second powder having different average particle diameters. Therefore, the second powder can enter the gaps between the particles of the first powder, and the density of the obtained soft magnetic composite material can be increased. Thereby, a soft magnetic composite material having a high magnetic permeability can be obtained.

(3) The resin is an epoxy resin. By using an epoxy resin having a high glass transition point and excellent heat resistance, the resin is less likely to decompose even when the obtained soft magnetic composite material is heat-treated. As a result, the magnetic properties of the soft magnetic composite material can be improved.

(4) The amount of resin mixed with the mixed powder is 3 to 5 wt %. This makes it possible to obtain a soft magnetic composite material having excellent mechanical strength and magnetic properties. If the mixed amount of the resin is less than 3 wt %, the resin cannot be completely penetrated into the mixed powder, and the bonding force between the powders cannot be increased. When the amount of the resin mixed is 3 wt% or more, the bonding force of the soft magnetic powder can be increased and cracking of the molded body can be prevented. Further, when the content is 5 wt% or less, the density of the soft magnetic composite material is increased, the decrease of the maximum magnetic flux density and the increase of hysteresis loss can be suppressed, and the magnetic characteristics can be improved.

(5) The filler is mixed in the resin. Thereby, the glass transition point of the resin can be raised and the heat resistance can be enhanced. Therefore, even a resin having a glass transition point of 140° C. or lower can be used as the resin of this embodiment.

[4. Example]
Hereinafter, specific examples of the soft magnetic composite material and the manufacturing method thereof according to the present embodiment will be described. The present embodiment is not limited to the following examples, and various modifications can be made.

(Preparation of mixed powder)
As the first powder, Fe-6.5Si having a mean particle size of 123 μm and a mean circularity of 0.943, which was prepared by a gas atomization method, was used. As the second powder, Fe-6.5Si having an average particle diameter of 5.1 μm and an average circularity of 0.908, which was prepared by a gas atomizing method, was used. The first powder and the second powder were mixed at a ratio of 70:30 to prepare a mixed powder. The average particle size and the average circularity were measured using a particle image analyzer (Malvern Co.: morphologi G3s). The average particle diameter and the average circularity were measured for 5000 particles.

(Measurement of water absorption and glass transition point)
Five types of resins A to E having different water absorption rates and glass transition points were prepared. The water absorption of the resin was measured by the following method. Since the water absorption of resin differs depending on the size of the sample, it is necessary to unify the sizes of the samples of the resins to be compared. In this example, the water absorption was measured with the dimensions of the sample being “length 50×width 50×thickness 5 (mm)”.

(1) Method of measuring water absorption rate (a) Preparation of test piece A cured product having a predetermined size was prepared directly by a mold or by cutting. In the present embodiment, the predetermined dimension is “length 50×width 50×thickness 5 (mm)”. In addition, the drying temperature and the drying time of the resins A to E at the time of sample preparation are as follows. Resin A... 120° C. (1H), Resin B... 150° C. (4H), Resin C... 120° C. (1H), Resin D... 150° C. (4H), Resin E... 150° C. (4H).

(B) Mass measurement before water absorption The mass of the prepared test piece was measured up to 1 mg. This value was set as M0.

(C) Water Absorption Test A test piece was immersed in water controlled at room temperature for 24 hours. The room temperature is preferably 25°C, but may not be 25°C.

(D) Mass measurement after water absorption The test piece was taken out of the water, the water adhering to the surface was quickly wiped off, and the mass was measured up to 1 mg. This value was set to M1.

(E) Calculation of water absorption rate The water absorption rate was calculated by the following formula.
(M1-M0)÷M0×100=water absorption (%)

(2) Method for measuring glass transition point The glass transition point of the resin can be measured by the method specified in JIS-K-7121. It can also be measured by a thermogravimetry (TG) method or a differential thermal analysis (DTA) method.

(Preparation of magnetic core)
In this example, five types of magnetic cores were prepared using thermosetting resins A to E having different water absorption rates and glass transition points. Then, the first powder and the second powder were prepared, mixed powders were prepared, and 4 wt% of resins A to E were mixed with the mixed powder to prepare a soft magnetic composite material. The coil was placed in the container and the soft magnetic composite material was injected. The soft magnetic composite material was pressed. After that, heat treatment was performed under the conditions shown below according to the types of the resins A to E, and the resin was cured to produce a magnetic core. Resin A... 120° C. (1H), Resin B... 150° C. (4H), Resin C... 120° C. (1H), Resin D... 150° C. (4H), Resin E... 150° C. (4H). The viscosities (mPa·s) of the resins A to E at 25° C. are as follows. Resin A... 100 mPa.s, Resin B... 80 mPa.s, Resin C... 50 mPa.s, Resin D... 80 mPa.s, Resin E... 465 mPa.s.

(Accelerated test)
In this embodiment, in order to investigate the deterioration over time of the soft magnetic composite material, an acceleration test was performed for each magnetic core using the resins A to E. The details will be described below.

In the acceleration test, a high temperature test and a high temperature and high humidity test were performed on a magnetic core using five kinds of resins A to E having different water absorption rates and glass transition points. In the high temperature test, the magnetic core was left in a temperature environment of 180° C. for 100 hours. In the high temperature and high humidity test, the magnetic core was left for 100 hours in a temperature environment of 85° C. and a humidity environment of 95%.

(Measurement of magnetic permeability and loss)
With respect to the soft magnetic composite material before and after the acceleration test, the magnetic permeability μa and the loss Pcv were measured by the following method, and the change rate was calculated. In the following description, the magnetic permeability μa may be simply referred to as μa and the loss Pcv may be simply referred to as Pcv. The magnetic permeability μa is the amplitude magnetic permeability of the BH curve.

Regarding the magnetic permeability μa and the loss Pcv, each magnetic core is provided with a primary winding (40 turns) and a secondary winding (4 turns), and a BH analyzer (Iwatsu Measurement Co., Ltd.: SY-8232), which is a magnetic measuring instrument, is used. ) Was used to calculate the loss under the conditions of a frequency of 20 kHz and a maximum magnetic flux density Bm=30 mT.

(Results of accelerated test)
(1) Relationship with Water Absorption Rate The relationship between the water absorption rate of the resin and the μa change rate and Pcv change rate after the acceleration test was considered based on Table 1 below. In the present specification, the water absorption of the resin is described, but the moisture absorption of the resin has the same meaning. Both show the percentage of the total amount of water contained in the surface-dried water-saturated resin with respect to the absolute dry-state resin mass.

The μa change rate and the Pcv change rate indicate the ratio of the difference between the values before and after the accelerated test with respect to the values before the accelerated test.
μa change rate={(μa after acceleration test−μa before acceleration test)/μa before acceleration test}×100
Pcv change rate={(Pcv after accelerated test−Pcv before accelerated test)/Pcv before accelerated test}×100

As shown in Table 1, it was found that the water absorption rate of the resin and the μa change rate and the Pcv change rate after the high temperature test or the high temperature and high humidity test have a certain correlation. In particular, it was found that the water absorption of the resin and the μa change rate after the high temperature and high humidity test have a proportional relationship. FIG. 1 is a graph showing the relationship between the water absorption rate of the resin (horizontal axis) and the μa change rate after the high temperature and high humidity test (vertical axis). According to FIG. 1, after the high temperature and high humidity test, the lower the water absorption of the resin, the lower the μa change rate.

From the results of the acceleration test, when the water absorption rate was 0.36% or less, the rate of change in μa after the high temperature and high humidity test was -0.8% or less. After the high-temperature and high-humidity test, the resin having a higher water absorption has a lower magnetic permeability μa, which is considered to be because the magnetic core absorbs water vapor and expands, thereby lowering the density of the molded body. From the above, it was found that the resin preferably has a water absorption of 0.36% or less.

(2) Relationship with glass transition point The results of considering the relationship between the glass transition point of the resin and the μa change rate and Pcv change rate after the accelerated test are shown below.

As shown in Table 1, it was found that the glass transition point of the resin and the μa change rate and the Pcv change rate after the high temperature test or the high temperature and high humidity test have a certain correlation. In particular, it was found that the glass transition point of the resin and the Pcv change rate after the high temperature test have a proportional relationship. FIG. 2 is a graph showing the correlation between the glass transition point of the resin (horizontal axis) and the Pcv change rate after the high temperature test (vertical axis). According to FIG. 2, after the high temperature test, the higher the glass transition point of the resin, the lower the Pcv change rate is suppressed.

From the results of the acceleration test, when the glass transition point was 140° C. or higher, the Pcv change rate after the high temperature test was 6.3% or less. It was considered that when the glass transition point of the resin is low, a polymerization reaction occurs due to the glass transition of the resin in a high temperature state and dielectric breakdown occurs between the magnetic powders, resulting in an increase in loss. From the above, it was found that the resin preferably has a glass transition point of 140° C. or higher.

(Conclusion)
As described above, the magnetic cores using the resins D and E having a water absorption of 0.36% or less and a glass transition point of 140° C. or more had a small μa change rate and a Pcv change rate after the acceleration test. Therefore, it was found that the resin preferably has a water absorption of 0.36% or less and a glass transition point of 140° C. or more.

[5. Other Embodiments]
The present invention is not limited to the above embodiment. The above embodiment is presented as an example, and can be implemented in various other forms. Various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope of the invention, the gist, and the scope of equivalents thereof.

(1) The powder constituting the soft magnetic composite material is not limited to the mixture of two kinds of powders. For example, one kind of powder can be used, or three or more kinds of powder can be used. Even in this case, the same effect as this embodiment can be obtained. When one type of powder is used, a powder having a particle size close to that of the first powder of this embodiment is used. When using three or more kinds of powders, three or more powders having different particle sizes are used. This can eliminate the gaps between the powders and increase the density. When using three or more kinds of powders, the same kind of soft magnetic powder may be used, or another kind of soft magnetic powder may be used. In other words, the soft magnetic powder preferably has two peaks in the particle size distribution, and may have three or more peaks. In this case, the particle diameters of the first powder and the second powder are not limited to the range of the average particle diameter described above. When three or more powders are mixed, it is desirable to select the average particle diameter that gives the highest density.

(2) After forming the soft magnetic composite material, the resin can be cured by a curing method depending on the type of resin. In the present embodiment, the thermosetting resin is cured by heat treatment, but when a solvent evaporation curable resin is used, it can be cured by drying for a predetermined time. When a chemical reaction curable resin is used, it can be cured by adding a predetermined chemical reaction material or by causing a chemical reaction after a predetermined time has elapsed.

(3) The resin to be mixed with the soft magnetic powder may be a one-liquid type which is hardened by one kind of material, or may be a two-liquid type which is hardened by mixing a main agent and a hardening agent. Also, a three-liquid type can be used.

(4) In the present embodiment, the magnetic core is made by pouring a soft magnetic composite material, which is a mixture of soft magnetic powder and resin, into a container, but it may be made by the following method. After the mixed powder of the first powder and the second powder is filled in the container, the entire container is vibrated to increase the density of the mixed powder in the container. Then, the resin is permeated into the mixed powder whose density is increased by vibration, and the mixed powder is cured by a curing method depending on the type of the resin. As a method of vibrating, a method of vibrating the whole container up and down or/and back and forth and left and right by using a motor or a cam, tapping, or finely hitting the container with a hammer-shaped member may be used. The entire container may be vibrated by an ultrasonic vibrator.

Claims (5)

A resin mixing step in which a soft magnetic powder is mixed with an epoxy resin having a water absorption of 0.36% or less and a glass transition point of 140° C. or more to form a soft magnetic composite material;
An injection step of injecting the soft magnetic composite material into a container after the resin mixing step,
A pressurizing step of pressurizing the soft magnetic composite material at 600 Pa or less after the injecting step,
A resin curing step of curing the epoxy resin by heat treatment at 120 to 150° C. after the pressurizing step,
A method of manufacturing a metal composite core, comprising: The soft magnetic powder is a mixed powder of a first powder and a second powder having different average particle diameters,
The method for producing a metal composite core according to claim 1, wherein. The mixing amount of the epoxy resin with respect to the mixed powder is 3 to 5 wt %,
The method for producing a metal composite core according to claim 2, wherein A filler is mixed in the epoxy resin,
The method for producing a metal composite core according to any one of claims 1 to 3, wherein: The method for manufacturing a metal composite core according to any one of claims 1 to 4,
A method for manufacturing a reactor, comprising a step of disposing a coil in the container before the injecting step.

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