JP4646238B2 - Composite magnetic material and method for producing composite magnetic material - Google Patents

Description

  The present invention relates to a composite magnetic material comprising a mixture of a plurality of types of powders and a resin, and a method for producing the same.

  A composite magnetic material composed of a magnetic powder and a resin can be easily formed into a desired shape by molding. Therefore, it is used for various magnetic cores and various efforts have been made.

  As a molding method using the composite magnetic material, there are an atmospheric pressure casting method, a pressure casting method, a dry molding method, and the like. Here, in the normal pressure casting method, a product having a desired shape can be obtained simply by pouring a composite material before curing into a mold and curing it. Therefore, the degree of freedom in shape and configuration is high. For example, a winding and a magnetic body are integrated. It is also possible to easily form it. For example, Patent Document 1 describes a method of manufacturing a magnetic core by a normal pressure casting method.

  In comparison of these molding methods, the difference from the viewpoint of magnetic materials is that the final placement of individual magnetic particles is determined by external force due to pressure and compression in the pressure casting method and dry molding method, In the normal pressure casting method, after dispersion by mixing, it is determined by the rotation and sedimentation of particles due to gravity and resin viscosity.

  Here, the composite magnetic material composed of a plurality of magnetic particles is extremely in a state where there is one air gap between two magnetic bodies. In an actual composite magnetic material composed of a large number of particles, It is expected to be close to the process of subdividing the air gap into infinitesimal. Therefore, in order to control the magnetization characteristics of the composite magnetic material, it is important how to control the diameter and interval of individual particles.

  In the pressure casting method, the dry molding method, etc., the arrangement of the particles can be made relatively uniform by adjusting the external force. Therefore, in order to control the interval between the particles, the same applies to the case of two magnetic bodies. What is necessary is just to arrange | position the spacer of desired thickness between particle | grains, for example, after arrange | positioning or coating the powder of a desired magnitude | size, or an inorganic substance, and an organic substance layer on the magnetic particle surface, if it shape | molds to a desired density by pressure Good.

JP 2001-68324 A

  However, in the atmospheric pressure casting method, the above-described sedimentation occurs, and the degree of sedimentation varies depending on the location. Especially, when the depth is deep, the difference between the bottom and the top is large, and the arrangement of the particles becomes inhomogeneous. As a result, a magnetic core having uniform characteristics as a magnetic material cannot be obtained. Patent Document 1 describes a method of manufacturing a magnetic core by atmospheric pressure casting, but does not mention control of the interval between individual particles and non-uniformity between the top and bottom during casting.

  Specifically, the magnetic characteristics will be described. For example, one spherical particle has a demagnetizing factor of 1/3, and magnetization proceeds in accordance with the demagnetizing factor in a magnetic field. When another particle is adjacent to the magnetic field direction, the demagnetizing coefficient of the two composites takes an intermediate value between 0 and 1/3. This value changes depending on the interval between the two particles, and the closer it is, the closer it is to 0 and the smaller value. In other words, when a large number of approaching particles are magnetized, the magnetization process changes depending on the distance to the other adjacent particles, and the closer particles are magnetized early with respect to the external magnetic field, easily saturated, and separated. The particles are less likely to saturate.

  That is, in one magnetic core, there are a portion that is likely to be saturated with respect to the external magnetic field, and a portion that is not so, and as a result, the linear portion of the rise of the BH curve indicating the magnetization becomes unclear.

  This is not preferable because the linearity of the inductance with respect to the DC current deteriorates in a power choke that uses a DC current, that is, a DC magnetic field superimposed.

  Moreover, in order to reduce only the separation from the resin as the fluid due to the overall sedimentation of the particles, it is easily guessed that the particle space factor is increased and the resin space factor is decreased. Actually, it is difficult to prevent sedimentation of particles by itself, and if the space factor of the resin as a fluid is lowered too much, the fluidity necessary for casting is impaired and it is easy to cause adverse effects due to remaining bubbles.

  Moreover, even if the fluidity as a macro behavior decreases, there is no change in the viscosity of the resin itself, which is a fluid existing between the particles, and it is in a floating state due to particle size distribution, local bridging phenomenon, etc. A certain particle or group of particles settles and approaches at a sedimentation speed corresponding to the particle diameter. Moreover, even if fine particles of an appropriate size are dispersed in the fluid to control the particle interval, the particle interval is less likely to be uniform when movement due to sedimentation of particles in a floating state occurs. This leads to variations in magnetization characteristics.

  Therefore, the object of the present invention is macroscopically reduced in density difference between the top and bottom of the casting, that is, nonuniformity of the particle spacing, and is likely to occur in the top of the casting, which is an extreme situation of nonuniformity. It is to suppress the generation of a separation layer of only resin.

  Furthermore, it is an object of the present invention to improve the non-uniformity of particle spacing due to particle settling locally. Ultimately, it is an object of the present invention to provide a composite magnetic material having excellent magnetization characteristics and a method for producing the composite magnetic material by these improvements.

  In the composite magnetic material of the present invention, a mixture of a resin and a powder having an average particle size of 0.1 μm or less is interposed between magnetic particles to control the interval between the magnetic particles and reduce the separation layer in the magnetic core. High effect is obtained.

  In the composite magnetic material of the present invention, the powder having an average particle size of 0.1 μm or less surrounds other magnetic particles, and the viscosity of the fluid itself that governs the movement of the magnetic particles, in particular, the region where the shear rate is low. Thus, the thixotropy having a high shear stress and the action of suppressing the sedimentation can be improved, and as a result, the effect of reducing the separation layer in the magnetic core is obtained.

The present invention relates to a composite magnetic material in which a mixture of a plurality of types of powders and resins, each of which is a magnetic material having a particle size of 10 to 1000 μm, is molded and solidified by a normal pressure casting method. The powder having an average particle diameter of 0.1 μm or less is 1 vol% or more and 20 vol% under the condition that the total volume of the resin and the powder having the average particle diameter of 0.1 μm or less is 100%. It is a composite magnetic material included in the following range.

The present invention is the composite magnetic material, wherein the powder having an average particle size of 0.1 μm or less is an oxide or organic material such as SiO ₂ or Al ₂ O ₃ .

  Further, the present invention is a composite magnetic material in which, among the plurality of types of powders, a powder that is a magnetic substance is contained in an amount of 55 vol% or more with the volume of the composite magnetic substance being 100 vol%.

  The present invention is the composite magnetic material, wherein the magnetic body is at least one of an Fe—Si alloy, an Fe—Si—Al alloy, an iron amorphous alloy, and a cobalt amorphous alloy.

  The present invention also provides a magnetic core formed by molding any one of the above composite magnetic materials at normal pressure.

Further, the present invention provides a method for producing a composite magnetic material in which at least one kind is a magnetic substance having a particle size of 10 to 1000 μm and solidifies a mixture of a plurality of kinds of powders and a resin. The powder having an average particle size of 0.1 μm or less is an oxide or an organic substance such as SiO ₂ or Al ₂ O ₃ , and the powder having an average particle size of 0.1 μm or less is the resin and the average particle size is 0.00. In a method for producing a composite magnetic material, wherein the composite magnetic material is included in a range of 1 vol% or more and 20 vol% or less under the condition that the total volume of the powder with 1 μm or less is 100 vol%, and the composite magnetic material is molded and solidified at normal pressure is there.

  In addition, the present invention is a method for producing a composite magnetic material, wherein among the plurality of types of powders, a magnetic powder is contained in an amount of 55 vol% or more, with the composite magnetic body having a volume of 100 vol%.

  The present invention is also a method for producing a composite magnetic material, wherein the magnetic material is at least one of an Fe—Si alloy, an Fe—Si—Al alloy, an iron amorphous alloy, and a cobalt amorphous alloy.

  According to the present invention, nonuniformity of particle spacing due to macroscopic and local particle settling is improved, and a composite magnetic material having excellent magnetization characteristics suitable as a magnetic core material and the like A manufacturing method can be provided.

The composite magnetic material of the present invention is a composite magnetic material in which a mixture of a plurality of types of powder and resin, each of which is a magnetic substance having a particle size of 10 to 1000 μm, is molded and solidified by a normal pressure casting method. Among these types of powders, a powder having an average particle size of 0.1 μm or less is contained in an amount of 1 vol% or more and 20 vol% or less of the resin. Here, the volume fraction of the powder having an average particle diameter of 0.1 μm or less is defined as 100 vol% of the total volume of the powder having an average particle diameter of 0.1 μm or less and the resin. Further, unless otherwise specified, the particle diameter value of the powder described in the present application is a sphere equivalent diameter measured using an electron micrograph of the particle.

As the powder having an average particle size of 0.1 μm or less, an oxide powder such as SiO ₂ or Al ₂ O ₃ , or an organic powder such as a silicone resin powder or a fluororesin powder is used. As appropriate.

  The composite magnetic material of the present invention is preferably a magnetic substance among a plurality of types of powders, with the volume fraction being 55 vol% or more when the volume of the composite magnetic substance is 100 vol%. Here, when the magnetic substance powder is less than 55 vol%, when the composite magnetic material is used as the magnetic core, the magnetic permeability is low, which is not suitable for practical use.

  In addition, as a composite magnetic material used for a magnetic core or the like, the magnetic material has a high magnetic permeability, a high saturation magnetic flux density, a Fe-Si alloy, a Fe-Si-Al alloy, an iron amorphous alloy, a cobalt amorphous alloy, etc. It is preferable to use at least one. In addition, a magnetic powder having a particle size of 10 to 1000 μm can be used. However, if the particle size is large, the fluidity deteriorates and the overcurrent loss increases, so that the usable frequency band is narrowed and the particle size is reduced. If it becomes finer, the fluidity also deteriorates and the magnetic permeability decreases. Generally, it is desirable to use a magnetic powder having a particle diameter in the range of several tens to 200 μm.

  Here, the resin used for the composite magnetic material may be a resin that easily flows during molding, and an epoxy resin, a silicone resin, a phenol resin, a urethane resin, or the like can be used.

Further, the composite magnetic material of the present invention can be produced by mixing at least one kind of magnetic powder having a particle size of 10 to 1000 μm and a resin, and molding and solidifying by a normal pressure casting method. Good. At this time, the volume fraction of the powder having an average particle size of 0.1 μm or less among the plurality of types of powders is 1 vol% when the total volume of the powder having the average particle size of 0.1 μm or less and the resin is 100 vol%. As mentioned above, it is good to mix so that 20 vol% or less may be contained. At this time, the powder having an average particle size of 0.1 μm or less may be manufactured using an oxide powder such as SiO ₂ or Al ₂ O ₃ or an organic powder.

  Furthermore, among a plurality of types of powders, a powder that is a magnetic material may be produced by mixing so that the volume fraction is 55 vol% or more when the volume of the composite magnetic material is 100 vol%. .

  Here, when the magnetic core of the present invention is formed, it may be performed as follows. That is, a plurality of kinds of powders in a predetermined ratio and a liquid resin are kneaded with a mixer to prepare a slurry. As the resin, for example, a two-component mixed thermosetting epoxy resin may be used. The prepared slurry is cast (poured) into a predetermined mold, and if necessary, fluidity is improved by applying vibration or the like, and defoaming is performed by decompression. Then, for example, a magnetic core made of a composite magnetic material can be obtained by heating and curing under conditions of 150 ° C. × 3 hours and then removing from the mold.

Example 1
A composite magnetic material was prepared with the formulation shown in Table 1, and various characteristics were compared.

A gas atomized powder of Fe-6.5Si material having an average particle size of 120 μm was used as the magnetic powder, a thermosetting epoxy resin was used as the resin, and a SiO ₂ powder was used as the other powder. The volume percentage of the magnetic powder was 65 vol% when the composite magnetic material was 100 vol%, and the balance was resin and other powders. The volume percentage of the resin was about 34 vol%, and the volume percentage of the SiO ₂ powder was about 1 vol%.

Here, exactly the powder resin and SiO _2, the volume percentage of the SiO ₂ powder were blended volume percentage of the total of the resin and the SiO ₂ powder so as to be 3 vol% when the 100 vol%. At this time, the SiO ₂ powder was surface-treated with an appropriate amount of a coupling agent and then mixed with the resin.

As the SiO ₂ powder to be blended, those having various average particle diameters were selected. Here, as shown in Table 1, as the SiO ₂ powder, powder having an average particle diameter of 10 μm, 2.4 μm, 0.5 μm, 0.3 μm, and 0.1 μm was used.

In the above-mentioned mixing ratio shown in Table 1, magnetic substance powder, SiO ₂ powder and resin are mixed to prepare a slurry, poured into a casting mold, subjected to vacuum defoaming, heat-cured, and then taken out. A sample was prepared. Here, a casting for a toroidal core having an outer diameter of 27 mm, an inner diameter of 15 mm, and a depth of 12 mm and a casting for a cylindrical shape having an outer diameter of 23 mm and a depth of 50 mm were prepared, and two types of samples were prepared. Using a toroidal core, DC superposition characteristics were measured, and separation of particles and resin was examined using a cylindrical sample.

  The direct current superimposition characteristic was measured by winding a φ1.5 mm copper wire for 23 turns so as to be almost equal to a toroidal core having an outer diameter of 27 mm, an inner diameter of 15 mm, and a height of 12 mm, and measuring the inductance with an LCR meter. Here, the inductance value when the DC current is not superimposed and the inductance value when the constant DC current (5 A) is superimposed are measured, and the former is L0 and the latter is L1, and ΔL / L0 = (L0− L1) / L0 was defined as the DC current superimposition characteristic of the composite magnetic material.

  In addition, in the case of a columnar sample having a height of 50 mm, after measuring the thickness of the cured product separation layer in which the separation of the particles on the upper part of the magnetic core and the resin has progressed and removing the upper cured product separation layer, the top and bottom portions A sample having an outer diameter of 23 mm and a height of 8 mm was prepared by cutting at a portion having a height of 8 mm, and the density was measured for each of the two samples at the top and bottom. Furthermore, a through-hole having a diameter of 9 mm was formed in the center of each sample to form a toroidal shape, wound, and measured for initial permeability with an LCR meter.

  The DC current superposition characteristics of the magnetic core are generally 30% or less and more preferably 20% or less because the design allowable range is generally several tens of percent in a power choke coil. . In addition, the particle diameter of the powder was measured by a dry laser scattering method, and the average particle diameter was defined as the particle diameter at which the cumulative frequency was 50%. The results are shown in Table 1.

As is apparent from Table 1, when a powder having an average particle size of 0.1 μm is added as a SiO ₂ powder, no separation layer is generated, and the density difference between the top and bottom of the formed magnetic core is also observed. It is small and the difference in permeability between the top and bottom is also minimal. As a result, the direct current superimposition characteristic of the magnetic core, which is a magnetic characteristic reflecting the linearity of the magnetization characteristic, is also improved.

(Example 2)
A composite magnetic material was prepared with the formulation shown in Table 2 and various characteristics were compared.

A gas atomized powder of Fe-6.5Si material having an average particle size of 120 μm was used as the magnetic powder, a thermosetting epoxy resin was used as the resin, and a SiO ₂ powder was used as the other powder. The volume percentage of the magnetic powder was 65 vol% when the composite magnetic material was 100 vol%, and the balance was resin and other powders.

As the SiO ₂ powder to be blended, the same kind of powder having an average particle diameter of 0.1 μm was used, and samples were prepared by changing the blending ratio of the resin and the SiO ₂ powder. The mixing ratio of the resin and the SiO ₂ powder, the volume percentage of SiO ₂ powder, without the volume percentage of the total of the resin and the SiO ₂ powder when the 100vol%, 1vol%, 3vol% , 5vol%, 20vol % And 25 vol%. At this time, the SiO ₂ powder was surface-treated with an appropriate amount of a coupling agent and then mixed with the resin.

  The powder and resin in the mixing ratio shown in Table 2 are mixed to prepare a slurry, poured into a casting mold as in Example 1, vacuum defoamed, heat-cured, and then taken out to prepare a sample. did. Here, a casting for a toroidal core having an outer diameter of 27 mm, an inner diameter of 15 mm, and a depth of 12 mm and a casting for a cylindrical shape having an outer diameter of 23 mm and a depth of 50 mm were prepared, and two types of samples were prepared. Using a toroidal core, DC superposition characteristics were measured, and separation of particles and resin was examined using a cylindrical sample.

  The direct current superimposition characteristic was measured by winding a φ1.5 mm copper wire for 23 turns so as to be almost equal to a toroidal core having an outer diameter of 27 mm, an inner diameter of 15 mm, and a height of 12 mm, and measuring the inductance with an LCR meter. Here, the inductance value when the DC current is not superimposed and the inductance value when the constant DC current (5 A) is superimposed are measured, and the former is L0 and the latter is L1, and ΔL / L0 = (L0− L1) / L0 was defined as the DC current superimposition characteristic of the composite magnetic material.

  The DC current superimposition characteristics of the magnetic core is generally 30% or less, more preferably 20% or less, because the design allowable range is generally several tens of percent for power choke coils. Is desirable.

  In addition, in the case of a columnar sample having a height of 50 mm, after measuring the thickness of the cured product separation layer in which the separation of the particles on the upper part of the magnetic core and the resin has progressed and removing the upper cured product separation layer, the top and bottom portions A sample having an outer diameter of 23 mm and a height of 8 mm was prepared by cutting at a portion having a height of 8 mm, and the density was measured for each of the two samples at the top and bottom. Furthermore, a through-hole having a diameter of 9 mm was formed in the center of each sample to form a toroidal shape, wound, and measured for initial permeability with an LCR meter. The measurement results are shown in Table 2.

From the results shown in Table 2, in the magnetic core produced with the SiO ₂ powder blending ratio of 1 vol% or more, there is no separation layer, the difference in density between the top and bottom is small, and the initial permeability between the top and bottom is small. The difference in magnetic susceptibility is also small. As a result, the direct current superimposition characteristic of the magnetic core, which is a magnetic characteristic reflecting the linearity of the magnetization characteristic, is also improved.

Here, when there is no addition of the SiO ₂ powder, a cured product separation layer is generated, but as the addition amount of the SiO ₂ powder is increased, the generation of the cured product separation layer is reduced. From this aspect, it is considered that the larger the addition amount, the better. However, even if 1 vol% is added, a sufficient effect is recognized. Further, when the addition of SiO ₂ powder exceeds 20 vol%, the fluidity is lowered, and at 25 vol%, the density of the magnetic core is lowered and the magnetic permeability is also lowered. Therefore, the addition of the SiO ₂ powder is 20 vol% or less. It is desirable to do.

Claims (8)

In a composite magnetic material in which a mixture of a plurality of types of powders and resins, each of which is a magnetic substance having a particle size of 10 to 1000 μm, is molded and solidified by a normal pressure casting method , The powder having an average particle diameter of 0.1 μm or less is in the range of 1 vol% or more and 20 vol% or less under the condition that the total volume of the resin and the powder having the average particle diameter of 0.1 μm or less is 100%. A composite magnetic material characterized by being contained.   The composite magnetic material according to claim 1, wherein the powder having an average particle size of 0.1 μm or less is an oxide or an organic substance.   3. The composite according to claim 1, wherein among the plurality of types of powders, the magnetic powder is contained in an amount of 55 vol% or more when the volume of the composite magnetic body is 100 vol%. Magnetic material.   4. The magnetic material according to claim 1, wherein the magnetic material is at least one of an Fe—Si based alloy, an Fe—Si—Al based alloy, an iron based amorphous alloy, and a cobalt based amorphous alloy. 5. Composite magnetic material.   5. A magnetic core formed by molding the composite magnetic material according to claim 1 at normal pressure. In the method for producing a composite magnetic material in which at least one kind is a magnetic substance having a particle size of 10 to 1000 μm and a mixture of a plurality of kinds of powders and a resin is solidified, the average particle size of the plurality of kinds of powders is 0.00. The condition that the powder of 1 μm or less is an oxide or an organic substance, the powder having an average particle size of 0.1 μm or less, and the total volume of the resin and the powder having an average particle size of 0.1 μm or less is 100 vol% In the method of manufacturing a composite magnetic material, the composite magnetic material is included in a range of 1 vol% or more and 20 vol% or less, and the composite magnetic material is molded and solidified under normal pressure.   7. The method of producing a composite magnetic material according to claim 6, wherein among the plurality of types of powders, the magnetic powder is contained in an amount of 55 vol% or more with the volume of the composite magnetic body being 100 vol%.   8. The composite according to claim 6, wherein the magnetic body is at least one of an Fe—Si based alloy, an Fe—Si—Al based alloy, an iron based amorphous alloy, and a cobalt based amorphous alloy. Manufacturing method of magnetic material.