JP2012199580A - Method of manufacturing soft magnetic composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a soft magnetic composite material suitable for a core of a reactor.SOLUTION: A method of manufacturing a soft magnetic composite material includes the steps of: preparing soft magnetic powder having a density ratio represented by (apparent density/true density)×100 of more than 45% and 70% or less; mixing the soft magnetic powder 10 with a resin 20 by adjusting viscosity of the resin 20 at a resin temperature at the mixing to 100 mPa s-100 Pa s; and filling the mixed material into a mold 3 at filling pressure of an atmospheric pressure or more and 1 MPa or less, and curing the resin to obtain a molded body. According to this method, the soft magnetic composite material having a certain degree of high filling rate can be obtained by using the soft magnetic powder having a predetermined density ratio.

Description

  The present invention relates to a method for producing a soft magnetic composite material and a method for producing a magnetic element. In particular, the present invention relates to a method for manufacturing a magnetic element suitable for manufacturing a reactor.

  In recent years, hybrid vehicles and electric vehicles have been put into practical use from the viewpoint of protecting the global environment. A hybrid vehicle is a vehicle that includes an engine and a motor as drive sources and travels using one or both of them. Such a hybrid vehicle or the like includes a booster circuit in a power supply system to a motor. A reactor that can store electric energy as magnetic energy is used as one of the components of the booster circuit.

The reactor includes a coil and a core having a gap, and a closed magnetic path passing through the gap is formed in the core by excitation of the coil. A typical core of the reactor R used in a booster circuit of a hybrid vehicle or the like is a ring-shaped core M as shown in FIG. The core M is configured by combining a plurality of core pieces as described below. The core M has a U-shaped core pieces m _u pair having a rectangular end face, made I-shaped core piece m _{i 4} bracts, so that the U-shaped core pieces m _u is between the end face of each other facing arranged, side by side one by 2 I-shaped core piece m _i between the end faces, are formed by joining respectively. A coil C is formed by winding a winding around a part of such a core M, and a closed magnetic circuit is formed in the core M by passing a current through the coil C. The material constituting the core M can be obtained by press-molding a soft magnetic powder having an insulating coating together with a resin powder (for example, Patent Documents 1 and 2 as documents showing similar techniques).

  In addition, the core M is provided with a gap in the closed magnetic path by arranging a spacer s at each joint portion of the core piece in order to avoid magnetic saturation. The inductance of the reactor is mainly defined by the total length of the gaps formed in the closed magnetic circuit (here, the total thickness of the spacers s). This total length needs to be maintained with high accuracy, and each spacer s uses a non-magnetic plate material such as alumina that is processed with high accuracy.

JP 2002-305108 A JP 2006-302958 A

  However, in order to maintain the total length of the gap with high accuracy, the thickness of each spacer s must be managed with high accuracy. For example, the thickness accuracy required for the alumina plate material as the spacer s is on the order of several hundredths of a millimeter. However, the accuracy control of the thickness is performed by polishing the alumina plate material, and in addition to the required high processing accuracy, alumina itself is a difficult-to-process material with high hardness, so that it can be easily performed. It is not a thing. Therefore, it takes a long time to adjust the total length of the gap, and there has been a demand for the development of a technique for producing the reactor more efficiently.

  As a countermeasure against this problem, as shown in Patent Document 1, if a coil is placed in a mold, and a mixed powder of soft magnetic powder and resin is filled in the mold and pressure-molded, a magnetic element without a gap is provided. Can be obtained. However, such a green compact is molded at a high pressure exceeding 10 MPa, usually several hundred MPa. For this reason, the soft magnetic powders may be pressed against each other and the insulating coating may be damaged. If the insulating coating is damaged, the eddy current loss of the molded body increases due to the electrical connection between the soft magnetic powders. Moreover, in the core without a gap, although it is necessary to make it low magnetic permeability, there exists a tendency for the relative magnetic permeability of a compacting body to become high by the electrical connection of soft magnetic powder. Here, if the volume ratio of the soft magnetic powder is reduced, the relative permeability of the core can be kept low, but the saturation magnetic flux density is also lowered. Therefore, if the cross-sectional area of the core perpendicular to the magnetic field lines passing through the core, that is, the core size is not increased, the necessary magnetic force cannot be secured, which is contrary to the need for downsizing and weight reduction of parts. Furthermore, when a coil is embedded in a mixed powder of soft magnetic powder and resin powder and pressure-molded at a high pressure, the coil itself may be deformed or the insulating coating of the coil may be damaged.

  The present invention has been made in view of the above circumstances, and one of its purposes is suitable for a reactor core without a gap, and a method for producing a soft magnetic composite material that can be obtained without being pressurized to a high pressure. Is to provide.

  Another object of the present invention is to provide a method for manufacturing a magnetic element in which an internal member such as a coil is difficult to deform.

  As a result of various studies on a method for producing a soft magnetic composite material suitable for forming a core and a coil in an integrated state, the present inventors have completed the present invention.

The method for producing a soft magnetic composite material of the present invention includes the following steps.
(Apparent density / true density) Preparatory step of preparing a soft magnetic powder having a density ratio represented by 100 and exceeding 45% and 70% or less.
A step of mixing the soft magnetic powder and the resin, wherein the mixing is performed by adjusting the viscosity of the resin at the resin temperature at the time of mixing to 100 mPa · s to 100 Pa · s.
A molding step of filling a mold with the mixed material at a filling pressure of atmospheric pressure to 1 MPa and curing the resin to obtain a molded body.

  According to the method of the present invention, a soft magnetic composite material having a relatively low relative permeability and a relatively high saturation magnetic flux density can be obtained by using a soft magnetic powder having a predetermined density ratio.

  In addition, since molding is performed under a predetermined low pressure, problems such as an increase in eddy current loss due to the pressure contact between soft magnetic powders or an increase in relative permeability can be reduced.

As one form of the production method of the present invention, the preparation step preferably uses a spherical powder having a maximum diameter / equivalent circle diameter of 1 to 1.3 as the soft magnetic powder.
However, the equivalent circle diameter is the diameter of a circle that specifies the contour shape of the soft magnetic powder particles and has the same area as the area surrounded by the contour, and the maximum diameter is the maximum length of the particles in the contour shape. It is.

  By using such a spherical powder, it is possible to obtain a soft magnetic composite material having a specific permeability and a saturation magnetic flux density suitable for a magnetic element while ensuring a predetermined filling rate without applying high pressure.

  As one form of this invention manufacturing method, it is preferable that the said spherical powder is the powder obtained by the gas atomization method.

  The soft magnetic powder obtained by the gas atomization method can easily obtain a powder having few surface irregularities and having a maximum diameter / equivalent circle diameter of 1 to 1.3.

  As one form of this invention manufacturing method, it is preferable that the said preparation process uses the powder which passed through the classification process which removes a predetermined coarse grain as a soft magnetic powder.

  By passing through the classification step, it is possible to remove coarse particles in which the contact area between the particles tends to be large, and it is possible to suppress the increase in the relative magnetic permeability and obtain a powder with a high apparent density.

  As an embodiment of the production method of the present invention, the soft magnetic powder is preferably a powder having no soft insulating coating on the surface of the soft magnetic metal particles.

  Even in a soft magnetic powder without an insulating coating, electrical connection due to contact between powder particles can be suppressed as much as possible by using particles having a predetermined apparent density, and the relative permeability of the composite material can be kept low.

  As one form of the production method of the present invention, the soft magnetic powder is preferably a powder having an insulating coating on the surface of soft magnetic metal particles.

  By using a soft magnetic powder having an insulating coating, electrical connection due to contact between powder particles can be suppressed, generation of eddy currents can be suppressed, and the relative permeability of the composite material can be suppressed low.

  As one form of this invention manufacturing method, it is preferable that the nonelectroconductive filler is further disperse | distributed and included in resin.

  By adding a non-conductive filler to the mixed material of the soft magnetic powder and the resin, the viscosity of the mixed material can be easily adjusted, and the soft magnetic powder can be prevented from being precipitated and separated in the resin. . Accordingly, a composite material in which soft magnetic powder is uniformly dispersed in the resin can be obtained.

  As one form of this invention manufacturing method, the said resin is an epoxy resin, It is preferable to use an acid anhydride as a hardening | curing agent of an epoxy resin.

  If an acid anhydride is used as a curing agent, the pot life can be secured by suppressing the increase in the viscosity of the mixed material in the process from mixing the resin and soft magnetic powder to pouring into the mold. Heat generation is mild and cracks are difficult to form in the molded product.

  As one form of this invention manufacturing method, the said resin is an epoxy resin, It is preferable to use a latent hardener as a hardening | curing agent of an epoxy resin.

  If a latent curing agent is used, the pot life can be secured by suppressing the increase in the viscosity of the mixed material from the mixing of the resin and soft magnetic powder to the injection into the mold, and heat generation during curing can be achieved. Loose and difficult to crack in the molded product.

On the other hand, the method for manufacturing a magnetic element of the present invention includes the following steps.
(Apparent density / true density) Preparatory step of preparing a soft magnetic powder having a density ratio represented by 100 and exceeding 45% and 70% or less.
A step of mixing the soft magnetic powder and the resin, wherein the mixing is performed by adjusting the viscosity of the resin at the resin temperature at the time of mixing to 100 mPa · s to 100 Pa · s.
A member arrangement step of arranging the inclusion member in the mold in advance.
A molding step in which a mixed material of the soft magnetic powder and the resin is filled in a mold in which an inclusion member is disposed at a filling pressure of atmospheric pressure to 1 MPa, and the resin is cured to obtain a molded body.

  By placing the inclusion member in the mold in advance and filling with a predetermined mixed material, the composite material and the inclusion can be formed without being pressure-molded at a high pressure and without combining the composite material and the inclusion member in a separate process. A magnetic element integrated with a member can be obtained. Since the molding pressure is low, it is possible to obtain a magnetic element in which there is substantially no pressure contact between the soft magnetic powders and the inner member is hardly deformed.

  As one form of the manufacturing method of the magnetic element of the present invention, when the inclusion member is previously arranged in the mold, the inclusion member is preferably a coil.

  If the enclosing member is a coil, a magnetic element in which a core and a coil made of a soft magnetic composite material are integrated can be obtained without applying high pressure.

  As one form of the manufacturing method of the magnetic element of the present invention, it is preferable that the molded body is a reactor including a core made of a soft magnetic composite material and a coil integrated and included in the core.

  By the manufacturing method of the present invention, a reactor having a core made of a soft magnetic composite material as a so-called pot-type core can be easily obtained.

  According to the method for producing a composite material of the present invention, a soft magnetic composite material having a relatively low relative permeability and a high saturation magnetic flux density can be obtained by using a soft magnetic powder having a predetermined density ratio. In addition, since the molding is performed under a predetermined low pressure, problems such as an increase in eddy current loss due to pressure contact between soft magnetic powders or an increase in relative permeability can be reduced.

  Furthermore, according to the method for manufacturing a magnetic element of the present invention, a magnetic element with little deformation of the encapsulating member can be obtained by molding at a low pressure using soft magnetic powder having a predetermined density ratio.

It is explanatory drawing of this invention manufacturing method, (I) shows a mixing process, (II) shows a casting process, (III) shows a hardening process. It is explanatory drawing which shows the circle equivalent diameter and the maximum diameter of soft-magnetic powder. It is a partial notch perspective view of the reactor which is a magnetic element obtained with this invention manufacturing method. It is explanatory drawing of another this invention manufacturing method. It is a graph which shows the relationship between the saturation magnetic flux density of the composite material obtained by this invention manufacturing method, and relative magnetic permeability. It is a microscope picture which shows the cross-sectional state of the composite material obtained by this invention manufacturing method. It is a partial notch perspective view of the conventional reactor.

  Hereinafter, the configuration requirements of the present invention will be described.

<Manufacturing method>
Briefly describing the production method of the present invention, it comprises a preparation step of soft magnetic powder, a mixing step of this powder and resin, and a molding step of filling the mixed material into a mold and curing.

(Preparation of powder)
The apparent density is a density determined based on JIS Z 2504 “Metal powder—apparent density test method”. The true density is a density in which only the volume occupied by the substance itself is a volume for density calculation. When there are no cavities inside individual particles, the true density can be regarded as the specific gravity of the constituent metal of the soft magnetic powder. The density ratio obtained from the apparent density and the true density is set to more than 45% and 70% or less. If this density ratio is 45% or less, it is difficult to obtain a composite material having a saturation magnetic flux density of 0.6 T or more without applying high pressure during molding. On the other hand, when the density ratio exceeds 70%, it is difficult to obtain a powder having such a high density ratio, and the relative permeability of the composite material tends to increase. Moreover, when mixed with a resin, the powder with a high density ratio precipitates easily and is difficult to disperse uniformly. The lower limit of the density ratio is preferably 50% or more. The upper limit of the density ratio is 65% or less, 60% or less. In order to make the density ratio more than 45% and 70% or less, for example, as described later, a predetermined spherical powder is used or the powder is classified. In particular, the powder produced by the gas atomization method can have a density ratio of more than 45% and 70% or less.

(mixture)
For example, as shown in FIG. 1I, the soft magnetic powder and the resin are mixed by putting the soft magnetic powder 10 and the resin 20 into the mixing container 1 and stirring with the stirrer 2. At that time, it is preferable to adjust the viscosity at the time of resin mixing to 100 mPa · s to 100 Pa · s. Below this lower limit, the soft magnetic powder is precipitated, the soft magnetic powder and the resin are separated, and the homogeneity of the resulting soft magnetic composite material is hindered. Conversely, when the upper limit is exceeded, it is difficult for the soft magnetic powder to be dispersed in the resin, and it is difficult to increase the filling rate of the soft magnetic powder. More preferably, the viscosity at the time of mixing the resin is 1 Pa · s to 50 Pa · s.

  This viscosity adjustment can be adjusted by changing the temperature of the resin according to the type of resin, or by adding the filler described above. For example, a thermosetting resin may satisfy a predetermined viscosity at room temperature, but may be heated to about 50 ° C. or lower to reduce the viscosity of the resin. If it is a thermoplastic resin, it adjusts to predetermined viscosity by heating to the temperature beyond the melting | fusing point of the resin, and reducing a viscosity.

(Arrangement of inclusion member)
If necessary, an inner member (coil C) is placed in the mold 3 before casting the mixed material of the soft magnetic powder 10 and the resin 20 (see FIG. 1 (II)). A member in which the composite material and the inclusion member are integrated can be obtained by placing the inclusion member in the mold and then casting and curing the mixed material. For example, when the inner member is a coil C, a reactor in which a core M made of a soft magnetic composite material and the coil C are integrated can be obtained (see FIG. 1 (III)). At this time, just by going through the process of placing the inclusion member in the mold → casting the mixed material → curing the resin, the core and the coil are individually manufactured, and the reactor can be obtained without performing the process of combining them. Can do. Of course, it is not necessary to adjust the inductance of the reactor by combining the gap material with the core. In addition, since it is necessary to draw the end of the winding out of the mold, the coil is provided with a lead-out hole for the winding end in a part of the mold, or the end of the winding is attached to the mold itself. It is conceivable to have a structure in which the parts are pulled out.

(Mixed material casting)
The mixed material of the soft magnetic powder 10 and the resin 20 is injected into the mold 3 and cured, for example, as shown in FIG. 1 (II), to form a composite material (core M). In the casting of the mixed material, the mixed material may simply be poured into the mold, or the inside of the mold may be pressurized or depressurized so as to have a predetermined low pressure. Even when the mixed material is filled in the reduced pressure mold, the mixed material is relatively pressurized. For example, if the closed mold is evacuated to a predetermined pressure and the mixed material is filled in the mold, the mixed material is held in the mold in a pressurized state.

  The filling pressure of the mixed material is set to atmospheric pressure or more and 1 MPa or less. When compacting a conventional soft magnetic powder material and a resin powder, the pressure was at least over 10 MPa. For this reason, the insulation coating of the soft magnetic powder and the inner member may be damaged or the inner member may be deformed by the pressure contact between the soft magnetic powders or the pressure member between the soft magnetic powder and the inner member. However, by setting the filling pressure of the mixed material into the mold to a low pressure of 1 MPa or less, damage to the insulating coating of the soft magnetic powder and the inner member and damage to the inner member can be greatly reduced. The upper limit of this pressure is 0.7 MPa or less, 0.5 MPa or less, or 0.3 MPa or less. Note that when the pressure is increased to a pressure equal to or higher than the atmospheric pressure within the range of 1 MPa or less, there is an effect of reducing the size of voids formed in the composite material and reducing the variation in magnetic properties of the composite material.

(Resin curing)
After casting the mixed material, as shown in FIG. 1 (III), the resin is cured by a curing method according to the type of the resin. If it is a thermosetting resin, it is cured by heating a mixed material of the cast resin and soft magnetic powder. If it is a photocurable resin, it will be hardened | cured by irradiating the light (ultraviolet ray) of a predetermined wavelength to the mixed material of cast resin and soft magnetic powder. If it is an electron beam curable resin, it will be hardened by irradiating the mixed material of cast resin and soft magnetic powder with an electron beam. If it is a moisture curable resin, it will harden | cure by arrange | positioning the mixed material of cast resin and soft-magnetic powder in a moisture atmosphere. In addition, it is preferable to use various curing agents for curing the resin. Among these, it is preferable to use a latent curing agent. If a latent curing agent is used, the pot life can be secured by suppressing the increase in the viscosity of the mixed material from the mixing of the resin and soft magnetic powder to the injection into the mold, and heat generation during curing can be achieved. Loose and difficult to crack in the molded product. Examples of the latent curing agent include a thermosetting latent curing agent, a microcapsule latent curing agent, and a photocurable latent curing agent. In addition, an acid anhydride curing agent can be used as a curing agent that can ensure pot life and can moderately generate heat during curing. Such latent curing agents and acid anhydride curing agents can be suitably used when an epoxy resin is used as the resin.

  Next, the soft magnetic composite material obtained by the production method of the present invention will be described. This composite material is a soft magnetic composite material having a soft magnetic powder and a resin containing the powder in a dispersed state.

<Soft magnetic powder>
The soft magnetic powder includes a powder composed of a single soft magnetic metal powder and a powder having an insulating coating formed on the surface of the soft magnetic metal powder.

(Soft magnetic metal powder)
Soft magnetic metal powders include Fe, Co or Ni, Fe-Si, Fe-Ni, Fe-Al, Fe-Co, Fe-Cr, Fe-N, Fe-C, Fe-B, Fe-P Fe-based alloy powders such as Fe-Al-Si, rare earth metal powders, and ferrite powders can be used.

(Insulation coating)
The insulating coating functions as an insulating layer between the soft magnetic metal powder particles. By covering the metal particles with an insulating coating, the contact between the soft magnetic metal powder particles can be suppressed, and the relative magnetic permeability of the composite material can be suppressed. In addition, the presence of the insulating coating can suppress the eddy current from flowing between the metal particles, thereby reducing the eddy current loss of the composite material. For the insulating coating, for example, an insulating material such as a metal oxide, a metal nitride, or a metal carbide, a metal phosphate compound, a metal borate compound, or a metal silicate compound can be used. As the metal here, Fe, Al, Ca, Mn, Zn, Mg, V, Cr, Y, Ba, Sr, rare earth elements, and the like can be used.

  The thickness of the insulating coating is preferably 10 nm or more and 1 μm or less. By setting the thickness of the insulating coating to 10 nm or more, it is possible to effectively suppress contact between metal particles and energy loss due to eddy current. Moreover, by setting the thickness of the insulating coating to 1 μm or less, the ratio of the insulating coating to the soft magnetic composite material does not become too large. For this reason, it can prevent that the magnetic flux density of this soft-magnetic composite material falls remarkably. If the particle diameter of the soft magnetic metal powder particles is small, the thickness of the insulating coating tends to be small.

(Particle shape)
The soft magnetic powder is preferably a spherical powder having a maximum diameter / equivalent circle diameter of 1.0 to 1.3. Here, the equivalent circle diameter is the diameter of a circle having the same area as the area surrounded by the contour of the soft magnetic powder particle P as shown in FIG. That is, the equivalent circle diameter = 2 × {the above-mentioned contour area S / π} ^1/2 . The maximum diameter is the maximum length of the particles P in the contour shape. Therefore, the closer this ratio is to 1.0, the closer the particle is to a true sphere. In order to obtain the area within the contour of the soft magnetic powder particles, for example, the powder particle is observed with a microscope, and the area within the contour is calculated from the particles in the observed image by image processing or the like.

  If such spherical particles are used, the filling rate of the soft magnetic powder in the composite material can be increased. If the powder has the same weight, the non-spherical particles, that is, the particles with many irregularities on the surface, have a larger bulk than the spherical particles. On the other hand, since spherical particles are smaller in volume than non-spherical particles, a composite material having a high filling rate can be easily obtained without applying high pressure during molding.

  In addition, spherical particles can suppress the generation of voids in the composite material as compared to non-spherical particles. Since the non-spherical particles have many irregularities on the surface, it may be difficult to spread the resin sufficiently in the irregularities even if the surface treatment is performed, and voids may be generated in the composite material. However, if the particles are spherical, the resin sufficiently surrounds the particles, so that the generation of voids can be reduced.

  In addition, in the case of spherical particles, even if the particles are adjacent to each other, they are substantially only in point contact and hardly in surface contact. If the number of soft magnetic metal powders dispersed in the resin increases, the relative magnetic permeability of the composite material tends to increase, and there is a problem that eddy current flows between particles. Therefore, as described above, it is preferable to use a soft magnetic powder having an insulating coating. However, if spherical particles are used, the occurrence of contact between soft magnetic metal powders can be reduced even for particles without an insulating coating. The relative permeability of the composite material can be suppressed. In this case, it is not necessary to form an insulating coating on the soft magnetic metal powder when obtaining the soft magnetic powder.

  Specific examples of the soft magnetic powder include a powder generated by a gas atomization method and a powder generated by a water atomization method. Among these, the former is a substantially spherical particle, and the latter is a non-spherical particle having irregularities formed on the surface. The maximum diameter / equivalent circle diameter may be 1.0 to 1.3 by pulverizing the surface portion of the powder produced by the water atomization method with a ball mill or the like to form a spherical shape.

  In addition, when using particles whose maximum diameter / equivalent circle diameter does not become 1.0 to 1.3, classification is preferable. This classification is performed, for example, by removing predetermined coarse particles with a sieve. More specifically, it is preferable to remove coarse particles whose diameter is 150% or more larger than the average particle diameter of the soft magnetic powder. By such classification, coarse particles in which the contact area between particles tends to be large can be removed, and an increase in relative permeability can be suppressed and a powder having a high apparent density can be obtained. More preferably, coarse grains having a diameter of 100% or more than the average particle diameter of the soft magnetic powder are removed, and particularly preferably coarse grains having a diameter of 50% or more are removed. Further, the fine particles of the soft magnetic powder may be removed. For example, it is preferable to remove fine particles having a diameter 50% or more smaller than the average particle diameter of the soft magnetic powder. By such classification, it is possible to obtain a composite material in which variation in particle size is suppressed and soft magnetic powder is uniformly dispersed. The fine particles may be removed using a sieve.

  As described above, the composite material obtained by the method of the present invention is obtained by casting and curing a mixed material under atmospheric pressure or a predetermined low pressure. Is not pressed and deformed. Therefore, the “maximum diameter / equivalent circle diameter” in the soft magnetic powder before molding is substantially the same as the “maximum diameter / equivalent circle diameter” in the soft magnetic powder after molding.

  The average particle size of the soft magnetic powder is preferably 5 to 500 μm. If the average particle size of the powder is too small, it is difficult to increase the filling rate. Conversely, if this average particle size is large, it will be difficult to uniformly disperse the soft magnetic powder in the resin. Examples of the lower limit of the average particle diameter of the powder include 10 μm, 15 μm, and 20 μm. Examples of the upper limit of the average particle diameter of the powder include 100 μm, 80 μm, 70 μm, 60 μm, and 50 μm. The average particle size of the soft magnetic powder is more preferably 10 to 100 μm.

(Filling rate)
According to the method of the present invention, a composite material in which the filling rate of the soft magnetic metal powder in the composite material is 70% by volume or less can be obtained. This filling rate is represented by {volume of soft magnetic powder / (volume of soft magnetic powder + volume of resin)} × 100. More specifically, the filling rate can be determined according to JIS K 7250 (2006) “Plastics—How to determine ash content”. The volume of the soft magnetic powder is, for example, by heating the composite material to 600 ° C. in a muffle furnace to remove the resin component, measuring the weight of the remaining soft magnetic powder, and dividing this weight by the true density of the soft magnetic powder. Is required. On the other hand, the volume of the resin is obtained by subtracting the weight of the soft magnetic powder from the weight of the composite material to obtain the weight of the resin and dividing the weight of the resin by the density of the resin. The filling rate can be calculated from the volume of the soft magnetic powder and the volume of the resin based on the above formula. In the case of a composite material containing a non-conductive filler, the filling rate is represented by {volume of soft magnetic powder / (volume of soft magnetic powder + volume of resin + volume of filler)} × 100. . If the soft magnetic powder and filler remaining after removing the resin of the composite material are selected with a magnet, the volume of the soft magnetic powder and the volume of the filler can be obtained.

  By setting the filling rate to 70% by volume or less, a composite material having a relatively low magnetic permeability can be easily obtained. As an upper limit of this filling rate, 65 volume%, 60 volume%, and 55 volume% are mentioned. The lower limit of the filling rate is preferably 30% by volume or more. By setting the filling rate to 30% by volume or more, it is possible to ensure appropriate permeability and saturation magnetic flux density as a composite material, and when a reactor is configured with this composite material, a suitable inductance value can be obtained. . Examples of the lower limit of the filling rate include 35% by volume, 40% by volume, and 45% by volume. A more preferable range of the filling rate is 40 to 60% by volume. In particular, when a reactor is manufactured by the method of the present invention, a reactor having an appropriate inductance value can be obtained without using a gap material.

<Resin>
The resin holds the soft magnetic powder in a dispersed state. As this resin, a thermosetting resin, a light (ultraviolet) curable resin, an electron beam curable resin, a moisture curable resin, or the like can be used.

  Examples of the thermosetting resin include phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, polyurethane, diallyl phthalate resin, and silicone resin.

  Examples of the oligomer of the photocurable resin include urethane acrylate, epoxy acrylate, ester acrylate, acrylate, epoxy, and vinyl ether resins.

  Examples of the electron beam curable resin oligomer include unsaturated polyester, unsaturated acrylic, epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, and polyene / polythiol.

  Examples of the moisture curable resin include a moisture curable epoxy resin and a moisture curable polyurethane resin.

  In addition, use of a thermoplastic resin is also conceivable. Examples of the thermoplastic resin include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyethylene terephthalate, acrylonitrile butadiene copolymer resin, polybutylene terephthalate, polyvinylidene chloride, polycarbonate, polyamide, polyacetal, polyimide, methacrylic resin, and fluorine resin. .

  When the composite material obtained by the method of the present invention is used in the field where heat resistance is required, it is preferable to use a thermosetting resin. It is expected to be used in the required fields.

<Relative permeability μ>
The relative magnetic permeability of the composite material obtained by the method of the present invention is preferably 5-30. Conventionally, the relative magnetic permeability of the electromagnetic steel sheet used for the core of the reactor is about 4000 to 8000, and the relative permeability of the green compact formed at high pressure is about 400 to 600. With such a high magnetic permeability material, it is difficult to configure the core without providing a gap. However, if it is a composite material obtained by the method of the present invention, a low permeability material having a relative permeability of 5 to 30 can be obtained, and the problem of magnetic saturation of the core can be solved without providing a gap. If a reactor is comprised with the composite material which has such a relative permeability, it can utilize suitably, for example as a reactor for the booster circuit of a motor vehicle. Examples of the upper limit of the relative permeability include 25, 20, 15, and 12.

<Saturation magnetic flux density Bs>
The saturation magnetic flux density Bs of the composite material obtained by the method of the present invention is preferably 0.6 T or more. By making such a composite material of saturation magnetic flux density, it can be made a saturation magnetic flux density higher than the ferrite conventionally used as a magnetic material, and when this composite material is used as a magnetic element such as a reactor, Magnetic saturation can be suppressed. A more preferable value of the saturation magnetic flux density is 0.8 T or more, a further preferable value is 1.0 T or more, and a particularly preferable value is 1.2 T or more. If a reactor is comprised using the composite material of such a preferable value, the reactor for a larger electric current use can be comprised.

<Magnetic flux density B ₁₀₀ >
The magnetic flux density B ₁₀₀ when a magnetic field of 7960 A / m (100 oersted (Oe)) is applied to the composite material obtained by the method of the present invention is preferably 0.05 T or more. When the core is formed of such a magnetic material, the magnetic permeability of a reactor or the like can be set to a target value without using a gap. A more preferable value of the magnetic flux density B ₁₀₀ is 0.07T or more, a further preferable value is 0.10T or more, and a particularly preferable value is 0.11T or more.

<Internal member>
The inner member is a member that generates a magnetic field, and is integrated with the soft magnetic composite material as necessary. A typical example of the internal member is an inductor (coil). The coil is usually constituted by a winding in which an insulating coating is applied to the surface of a metal wire. The metal wire is preferably highly conductive, and copper and copper alloys can be suitably used. The insulating coating can be a coating such as enamel. Examples of the cross-sectional shape of the winding include a circle, a rectangle, and a hexagon. Examples of the magnetic element in which the coil and the soft magnetic composite material are integrated include a choke coil, a transformer, a bar antenna, and a reactor.

  In particular, when the magnetic element is a reactor, the core is preferably a pot core. For example, as shown in FIG. 3, the pot core M includes an inner core Mi disposed on the inner side of the coil C, an outer core Mo disposed on the outer side of the coil C, and ends disposed on both ends of the coil C. Part core Me. Pot core M makes reactor R with coil C housed in core M, effectively suppressing noise caused by vibration accompanying excitation of coil C and mechanically protecting coil C You can do it. In particular, since the core M and the coil C made of the soft magnetic composite material are integrated, in addition to the noise suppression effect, the heat radiation of the coil C through the core M can be effectively performed.

<Filler>
The filler is mainly used to adjust the viscosity of the mixed material and suppress the precipitation of the soft magnetic powder when the soft magnetic powder and the resin are mixed.

Examples of the filler material include SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , BN, AlN, ZnO, and TiO ₂ . In particular, when a high thermal conductivity material such as Al ₂ O ₃ , BN, or AlN is used as the filler, the heat dissipation characteristics of the soft magnetic composite material can be improved. When a material having a low coefficient of thermal expansion such as SiO ₂ or BN is used for the filler, the thermal expansion of the soft magnetic composite material can be suppressed.

  The average particle size of the filler is preferably 1/5 or less of the average particle size of the soft magnetic powder. Thus, by using a finer filler than the soft magnetic powder, the filler particles can be dispersed and spread around the soft magnetic powder. Thereby, the probability that the soft magnetic powders come into contact with each other can be reduced, the magnetic permeability of the soft magnetic composite material can be kept low, and the magnetic and mechanical characteristics can be homogenized.

Examples of the shape of the filler include solid particles of various shapes such as a spherical shape and a non-spherical shape (a plate shape, a needle shape, a rod shape, etc.). In addition, hollow particles can be used. If it is a hollow filler, a soft magnetic composite material can be reduced in weight compared with the case where a solid filler is used. Examples of the commercially available hollow filler include SiO ₂ .

  The filler content may be adjusted mainly according to the viscosity of the resin. For example, when the total volume of the soft magnetic powder, the resin, and the filler is 100%, the filler content is about 5 to 30% by volume. Good.

<Insulator>
In the case of a magnetic element in which a core and a coil made of a soft magnetic composite material are integrated, an insulator may be interposed between the core and the coil. By using this insulator, insulation between the coil and the core can be ensured even if the insulation coating of the winding forming the coil is damaged. In order to provide this insulator, for example, a thin cylindrical body made of an insulating material is placed inside or outside the coil in advance, the coil and the cylindrical body are integrally placed in a mold, and the mixed material is filled and cured. You can do it. Alternatively, a coil hardened with an insulating resin may be placed in a mold, and the mixed material may be filled and cured.

  Soft magnetic powders and resins shown in Table 1 were prepared, and soft magnetic composite materials were produced from these raw materials. The outline of the manufacturing process is powder preparation → mixing of powder and resin → casting of mixed material → curing of resin → removal of molded product.

  First, a predetermined soft magnetic powder is prepared. Here, three types of powders of pure iron, Fe-6.5 mass% Si alloy, and Fe-3.0 mass% Si alloy were prepared. All are powders substantially made of metal powder, and no insulating coating is formed. Among these, about the powder of Fe-6.5 mass% Si alloy, what was produced | generated by the gas atomization method and what was produced | generated by the water atomization method were prepared. In Table 1, “gas” indicates a powder generated by the gas atomization method, and “water” indicates a powder generated by the water atomization method. Each powder was used after removing coarse particles with a sieve of 150 μm (ASTM # 100) of JIS Z 8801 (1994). The “diameter ratio” in Table 1 is a ratio represented by the maximum diameter / equivalent circle diameter. The equivalent circle diameter is the diameter of a circle having the same area as the area surrounded by the contour of the contour of the soft magnetic powder particles identified from the micrograph, and the maximum diameter is the maximum length of the particles in the contour shape. To do. Here, a cross section of the obtained molded body is observed with an optical microscope, and an observation image of a plurality of fields is binarized to extract 1000 or more soft magnetic powder particles. And the maximum diameter / equivalent circle diameter of each powder particle was calculated | required, and the average of the calculated value of each obtained particle | grain was made into diameter ratio. Since the soft magnetic composite material of this example is molded at a low pressure as will be described later, the maximum diameter / equivalent circle diameter of the raw material powder and the maximum diameter / equivalent circle diameter of the soft magnetic powder in the molded body are substantially the same. It is. Furthermore, the “density ratio” in Table 1 is represented by (apparent density / true density) × 100.

  The apparent density of the soft magnetic powder was determined based on JIS Z 2504 “Metal powder—apparent density test method”. “Average particle size” in the table is the particle size distribution measured using the Nitraso Nanotrac particle size distribution analyzer UPA-EX150. In the particle size distribution histogram, the sum of the masses from the smaller particle size is the total mass. The particle size was 50% of the particle size.

  Furthermore, the soft magnetic powders used were silane coupling treated. The silane coupling treatment was performed by adding 0.2% by mass of a silane coupling agent to the soft magnetic powder and stirring. By surface-treating the soft magnetic powder with a silane coupling agent, the dispersibility of the soft magnetic powder in the resin can be improved.

Sample 1 in Table 1 contains silica (SiO ₂ ) having an average particle diameter of 1 μm as a filler, 20% by volume of the total of soft magnetic powder, resin and filler as 100% by volume. 10% by volume of silica was contained. Other samples do not contain fillers.

Resin is mixed with such soft magnetic powder. Here, an epoxy resin composition containing the following materials was used.
Main agent: Bisphenol A type epoxy resin (Japan Epoxy Resin Co., Ltd. JER828)
Curing agent: Acid anhydride curing agent (YH300 manufactured by Japan Epoxy Resin Co., Ltd.)
Curing accelerator: Imidazole-based curing accelerator (2-ethyl-4 (5) -methylimidazole: EMI24 manufactured by Japan Epoxy Resin Co., Ltd.)

  The mixing ratio of the main agent: curing agent: curing accelerator is 100 parts by weight: 90 parts by weight: 0.5 parts by weight. The viscosity of such a resin at 30 ° C. is set to 34 Pa · s and mixed with soft magnetic powder (soft magnetic powder to which a filler is added if necessary). The viscosity was measured at a rotational speed of 10 rpm using a B-type viscometer BH manufactured by Toki Sangyo Co., Ltd.

The mixed material is filled in a mold and cured. More specifically, as shown in FIG. 4, a mixed material of soft magnetic powder 10 and resin 20 having a predetermined viscosity is prepared in a resin container 4. The resin container 4 can supply the internal mixed material to the mold 3 via the pipe 5 by filling the container 4 with N ₂ gas. There is a resin supply port 31 on the bottom side of the mold 3 and an exhaust port 32 connected to the vacuum pump 6 on the upper surface side of the mold. This vacuum pump 6 evacuates the mold 3. Then, by controlling the N ₂ gas pressure, the mixed material can be filled into the mold 3 at a predetermined pressure. Here, the filling pressure of the mixed material was set to 1 MPa.

  The resin in the mold was heated to 120 ° C. with a jacket (not shown) provided outside the mold 3 to cure the resin. After the resin was cured, the obtained molded body was taken out of the mold to obtain a soft magnetic composite material having a diameter of 40 mm and a height of 20 mm.

  The obtained composite material was cut into a ring shape having an outer diameter of 34 mm, an inner diameter of 20 mm, and a thickness of 5 mm. Using this ring-shaped member as a sample, the magnetic flux when a magnetic field of 100 oersted (Oe) is applied to the sample using the BH curve tracer “BHS-40S10K” manufactured by Riken Denshi Co., Ltd. Density was measured.

  The saturation magnetic flux density was determined as Bs by applying a magnetic field of 10,000 (Oe) to the sample with an electromagnet and sufficiently magnetically saturating the sample.

B ₁₀₀ is a sample with 300 windings on the primary side and 20 windings on the secondary side, the BH initial magnetization curve is measured in the range of H = 0 to 100 (Oe), and in the applied magnetic field of 100 (Oe) It reads the magnetic flux density of the samples was a B _100. Further, the maximum value of B / H of this BH initial magnetization curve was defined as relative permeability μ.

  These measurement results are shown together in Table 1. Further, in order to see the magnetic characteristics of the composite material with the change in the filler filling amount, the relationship between the saturation magnetic flux density Bs and the relative magnetic permeability μ of the samples 1 to 3 in Table 1 is shown in the graph of FIG.

  As is apparent from Table 1, Samples 1 to 4 and 6 using the soft magnetic powder produced by the gas atomization method have characteristics such as a low relative permeability of 11.0 or less and a saturation magnetic flux density of 0.9 T or more. Yes. In contrast, Sample 5 using soft magnetic powder produced by the water atomization method has a relative permeability of less than 5 and a saturation magnetic flux density of less than 0.6 T. Further, as is apparent from Table 1 and FIG. 5, it can be seen that as the filler filling amount increases, the filling rate of the soft magnetic powder decreases, and both the relative magnetic permeability and the saturation magnetic flux density tend to decrease.

  Further, the cross section of the composite material of Sample 2 was observed with an optical microscope. The micrograph is shown in FIG. The particles that appear white in this photograph are soft magnetic powder, and the black part of the background is resin. As is apparent from this photograph, it can be seen that the soft magnetic powders are not pressed and deformed even after molding, and the powder shape is maintained in a substantially spherical shape.

  The method for producing a composite material of the present invention can be suitably used for producing a reactor, more specifically, a reactor for a booster circuit such as a hybrid vehicle or a reactor for power generation / transforming equipment.

1 Mixing container 2 Stirrer 3 Type 4 Resin container 5 Piping 6 Vacuum pump
10 Soft magnetic powder 20 Resin 31 Supply port 32 Exhaust port
R reactor M core C coil
Mi inner core Mo outer core Me end core
m _u U-shaped core piece m _i I-shaped core piece s spacer
P soft magnetic powder particles

Claims (12)

A preparation step of preparing a soft magnetic powder having a density ratio represented by (apparent density / true density) × 100 and exceeding 45% and 70% or less;
A step of mixing the soft magnetic powder and the resin, the mixing step of adjusting the viscosity of the resin at the resin temperature at the time of mixing to 100 mPa · s to 100 Pa · s and mixing,
A molding step of filling the mixed material in a mold with a filling pressure of atmospheric pressure to 1 MPa, and curing the resin to obtain a molded body,
A method for producing a soft magnetic composite material, wherein a filling rate of the soft magnetic powder is set to 30% by volume or more and 65% by volume or less. The method for producing a soft magnetic composite material according to claim 1, wherein the preparing step uses a spherical powder having a maximum diameter / equivalent circle diameter of 1 to 1.3 as the soft magnetic powder.
However, the equivalent circle diameter is the diameter of a circle that specifies the contour shape of the soft magnetic powder particles and has the same area as the area surrounded by the contour, and the maximum diameter is the maximum length of the particles in the contour shape. It is.   3. The method for producing a soft magnetic composite material according to claim 2, wherein the spherical powder is a powder obtained by a gas atomizing method.   4. The method for producing a soft magnetic composite material according to claim 1, wherein the preparatory step uses, as the soft magnetic powder, a powder that has undergone a classification step for removing predetermined coarse particles.   5. The method for producing a soft magnetic composite material according to claim 1, wherein the soft magnetic powder is a powder having no insulating coating on the surface of the soft magnetic metal particles.   5. The method for producing a soft magnetic composite material according to claim 1, wherein the soft magnetic powder is a powder having an insulating coating on the surface of soft magnetic metal particles.   7. The method for producing a soft magnetic composite material according to claim 1, wherein a non-conductive filler is further mixed in the mixing step.   The method for producing a soft magnetic composite material according to any one of claims 1 to 7, wherein the resin is an epoxy resin, and an acid anhydride is used as a curing agent for the epoxy resin.   8. The method for producing a soft magnetic composite material according to claim 1, wherein the resin is an epoxy resin, and a latent curing agent is used as a curing agent for the epoxy resin. A preparation step of preparing a soft magnetic powder having a density ratio represented by (apparent density / true density) × 100 and exceeding 45% and 70% or less;
A step of mixing the soft magnetic powder and the resin, the mixing step of adjusting the viscosity of the resin at the resin temperature at the time of mixing to 100 mPa · s to 100 Pa · s and mixing,
A member arrangement step of arranging the inclusion member in the mold in advance;
Filling a mold in which an inclusion member is arranged at a filling pressure of atmospheric pressure to 1 MPa or less with a mixed material of the soft magnetic powder and the resin, and curing the resin to obtain a molded body,
A method of manufacturing a magnetic element, wherein a filling rate of the soft magnetic powder is 30% by volume or more and 65% by volume or less.   11. The method for manufacturing a magnetic element according to claim 10, wherein the enclosing member is a coil.   12. The method of manufacturing a magnetic element according to claim 11, wherein the molded body is a reactor including a core made of a soft magnetic composite material and a coil that is integrated and included in the core.