JP2014072245A - Powder magnetic core, electromagnetic component, and manufacturing method of powder magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder magnetic core including soft magnetic particles and exhibiting excellent corrosion resistance.SOLUTION: A powder magnetic core comprises: a compact containing multiple coated soft magnetic particles produced by coating the surface of soft magnetic particles with an insulating layer; and a rustproof layer for rustproofing the compact by covering the entire surface thereof. The rustproof layer contains a resin, and multiple metal pieces dispersed into the resin. The powder magnetic core has excellent corrosion resistance because it includes a rustproof layer. Since the metal pieces themselves in the resin divide a pinhole extending in the thickness direction of the rustproof layer, a rustproof layer having very small number of pinholes or not having any pinhole can be obtained.

Description

  The present invention relates to a dust core that can be used for a magnetic core of an electromagnetic component, an electromagnetic component including the dust core, and a method for manufacturing a dust core. In particular, the present invention relates to a dust core having soft magnetic particles and excellent in corrosion resistance.

  A circuit that converts energy, such as a switching power supply or a DC / DC converter, uses an inductor (electromagnetic component) such as a choke coil as a representative example. As a configuration example of an electromagnetic component, one having a dust core obtained by using a plurality of soft magnetic particles and a coil formed by winding a winding around the outer periphery of the dust core is known. For example, Patent Document 1 discloses a dust core in which an Fe—Si—Al alloy, that is, a so-called Sendust alloy is used as soft magnetic particles.

JP 2012-9825 A

  It has been considered that the electromagnetic component including the above-described dust core is used as an alternative to an electromagnetic component including a ferrite core, particularly an electromagnetic component that is housed and arranged in a small space. This is because a dust core having soft magnetic particles is easier to miniaturize than a ferrite core when obtaining magnetic properties equivalent to those of a ferrite core. As the electromagnetic component, for example, there is an antenna coil for opening and closing a door housed in a door handle of an automobile. However, when a dust core containing soft magnetic particles is used in a place where it is exposed to wind and rain for a long time, such as a door handle of an automobile, further corrosion resistance is required by the dust core.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a dust core having soft magnetic particles and having excellent corrosion resistance.

  Another object of the present invention is to provide an electromagnetic component having the above-described dust core.

  Another object of the present invention is to provide a method for producing the above-described dust core.

  In order to achieve the above object, the inventors of the present invention applied a resin to the surface of the molded body, resulting in insufficient improvement in corrosion resistance. This is considered to be due to the fact that the occurrence of resin pinholes cannot be sufficiently suppressed, and that when the resin is applied, the resin at the corners tends to be thinner than the flat part of the molded body. Therefore, as a result of studying the elimination of the above cause, the present inventors have found that when a specific solid material is contained in the resin, it is easy to suppress the generation of pinholes, and the resin thickness is limited (particularly the molded body). It was found that it was easy to prevent the film from becoming extremely thin at the corners). Based on this finding, the present invention is defined below.

  The dust core of the present invention comprises a molded body comprising a plurality of coated soft magnetic particles whose surfaces are covered with an insulating layer, and a rust preventive layer that covers the entire surface of the molded body and rusts the molded body. Prepare. The rust prevention layer includes a resin and a plurality of metal pieces dispersed in the resin.

  The dust core of the present invention is excellent in corrosion resistance by including the rust-proof layer. By having the metal piece in the resin, the metal piece itself divides the pinhole extending in the thickness direction of the antirust layer, so that the antirust layer having very few or no pinholes can be obtained. In addition, since the metal piece itself does not permeate rust-causing substances (water, oxygen, etc.), the invasion path of the rust-causing substance entering through the resin is made non-linear by dispersing multiple metal pieces in the resin. Therefore, the penetration path can be made longer than the thickness of the rust prevention layer itself. Therefore, it is difficult for the rust-causing substance to reach the molded body.

  As one form of the powder magnetic core of the present invention, the material of the metal piece is at least one of stainless steel and zinc.

  Since the metal piece is at least one of stainless steel and zinc, the metal piece itself is excellent in corrosion resistance, which contributes to an improvement in the rust prevention effect of the molded body.

  One form of the dust core of the present invention is that the shape of the metal piece is at least one of a thin piece and a particle.

  Since the shape of the metal piece is at least one of the thin piece and the particle, it is easy to disperse in the resin constituting the rust prevention layer, so that the deviation of the metal piece in the resin can be reduced, and the entire rust prevention layer is excellent. Corrosion resistance is provided.

  As one form of the powder magnetic core of the present invention, the metal piece includes a thin piece made of stainless steel, and the content of the stainless steel thin piece in the anticorrosive layer is 25% by mass to 50% by mass.

  By setting the content of the stainless steel flakes to 25% by mass or more, there are many pieces of stainless steel flakes in the resin, and the corrosion resistance of the rust preventive layer itself can be improved. When the content is 50% by mass or less, the number of thin pieces of stainless steel in the resin does not increase, and it is easy to ensure the insulation between the soft magnetic particles on the surface of the molded body and the surface of the rust-preventing layer.

  As one form of the powder magnetic core of the present invention, the metal piece contains zinc particles, and the content of zinc particles in the anticorrosive layer is 65% by mass to 90% by mass.

  By setting the content of zinc particles to 65% by mass or more, there are many zinc particles in the resin, and the corrosion resistance of the rust preventive layer itself can be improved. When the content is 90% by mass or less, the amount of zinc particles in the resin does not increase excessively, and it is easy to ensure insulation between the soft magnetic particles on the surface of the molded body and the surface of the rust prevention layer.

  As one form of the powder magnetic core of the present invention, the thickness of the flakes is 1 μm to 5 μm, the width is 5 μm to 20 μm, and the length is 5 μm to 20 μm.

  By setting the thickness of the flakes to 1 μm or more, the width to 5 μm or more, and the length to 5 μm or more, it is easy to lengthen the penetration path of the rust-causing substance that enters through the resin. On the other hand, since the thickness of the flakes is 5 μm or less, the width is 20 μm or less, and the length is 20 μm or less, the flakes are not too large and the flakes are easily dispersed in the resin, so that the thickness is thin and the corrosion resistance is excellent. It can be a rust layer.

  As one form of the powder magnetic core of the present invention, the average particle diameter of the particles may be 0.1 μm to 10 μm.

  By setting the average particle size of the particles to 0.1 μm or more, it is easy to lengthen the penetration path of the rust-causing substance that enters through the resin, and by setting the average particle size of the particles to 10 μm or less, the particles are large. Since it does not become too much and it is easy to disperse | distribute particle | grains in resin, it can be set as the rust prevention layer which is thin and excellent in corrosion resistance.

  As one form of the powder magnetic core of this invention, it is mentioned that the said resin is either an epoxy resin, a urethane resin, and an acrylic resin.

  Since these resins are excellent in corrosion resistance and can hold the metal piece, the formation of rust in the molded product can be suppressed.

  As one form of the powder magnetic core of the present invention, it is mentioned that the molded body has corner portions, and the thickness of the rust preventive layer formed at the corner portions is 5 μm or more.

  By setting the thickness of the rust-preventing layer formed at the corners to 5 μm or more, a rust-preventing layer having a thickness greater than that is formed on the flat surface where the resin is more easily formed than the corners. As a result, since the rust preventive layer has a sufficient thickness over the entire surface of the molded body, the occurrence of rust in the molded body can be suppressed.

  The electromagnetic component of the present invention includes the magnetic core having the dust core of the present invention and a coil that is formed by winding a winding and is disposed on the outer periphery of the magnetic core.

  The electromagnetic component of the present invention can be used for a long time even in places exposed to wind and rain because the magnetic core has a dust core having excellent corrosion resistance.

  The method for producing a dust core according to the present invention includes a molded body preparing step of preparing a molded body including a plurality of coated soft magnetic particles whose surfaces are covered with an insulating layer, a resin, and the resin is dispersed in the resin. A rust prevention step of forming a rust prevention layer including a plurality of metal pieces.

  The method for producing a dust core according to the present invention can produce a dust core having excellent corrosion resistance. Since there are metal pieces in the resin of the rust preventive layer, if there are no corners in the molded product, there is little variation over the entire surface of the molded product and a rust preventive layer with sufficient thickness to have corrosion resistance. Can be formed. On the other hand, even when the molded body has corner portions, by having metal pieces in the resin, a rust preventive layer having a sufficient thickness can be formed not only on the plane portions but also on the corner portions.

  The dust core of the present invention is excellent in corrosion resistance.

  The electromagnetic component of the present invention can be suitably used for an electromagnetic component used in a place where it is exposed to wind and rain for a long time.

  The method for producing a dust core according to the present invention can produce a dust core having excellent corrosion resistance.

  Embodiments of the present invention will be described below. First, a dust core will be described, and then a method for manufacturing the dust core and an electromagnetic component including the dust core will be described in this order.

<Dust core>
The feature of the powder magnetic core of the present invention is that a molded body containing soft magnetic particles is covered with a rust preventive layer, and the rust preventive layer is that a plurality of metal pieces are dispersed in the resin. Hereinafter, the rust preventive layer will be described first, and the specific configuration of the dust core other than the rust preventive layer will be described later when the method for manufacturing the dust core is described later.

(Rust prevention layer)
It is preferable that the resin constituting the rust preventive layer is a resin excellent in corrosion resistance. Specifically, it can be any of an epoxy resin, a urethane resin, and an acrylic resin.

  A plurality of metal pieces are dispersed in the resin and suppress the rust of the molded body. Specifically, pinholes extending in the thickness direction of the rust prevention layer are divided to suppress the occurrence of pinholes penetrating in the thickness direction from the surface of the rust prevention layer to the surface of the molded body in the resin. In addition, since the metal piece itself does not permeate rust-causing substances (water, oxygen, etc.), the intrusion path of the rust-causing substance that penetrates from the surface of the rust-preventing layer to the surface of the molded body through the resin is made non-linear and the penetration distance is increased. Make it longer than the thickness of the rust prevention layer. Moreover, when a molded object has a corner | angular part, it is easy to suppress the movement of uncured resin from a corner | angular part to a plane part at the time of rust prevention layer formation.

  Examples of the material of the metal piece include a metal having excellent corrosion resistance. This metal may be either magnetic or nonmagnetic, but is preferably nonmagnetic. Specifically, at least one of stainless steel and zinc can be used. Examples of the stainless steel include SUS316L.

  Here, the metal piece includes particles as well as the thin piece. That is, examples of the shape of the metal piece include thin pieces and particles. When the metal piece is a thin piece, the thickness is preferably 1 μm to 5 μm, the width is 5 μm to 20 μm, and the length is preferably 5 μm to 20 μm. Moreover, when a metal piece is particle | grains, it is preferable that the average particle diameter is 0.1 micrometer-10 micrometers. When the thickness of the flakes is 1 μm or more, the width is 5 μm or more, the length is 5 μm or more, or the average particle diameter of the particles is 0.1 μm or more, the invasion path of the rust-causing substance can be easily lengthened. On the other hand, when the thickness of the flakes is 5 μm or less, the width is 20 μm or less, the length is 20 μm or less, or the average particle size of the particles is 10 μm or less, the metal pieces do not become too large and the metal pieces are contained in the resin. Since it is easy to disperse, it can be set as the antirust layer which is thin and excellent in corrosion resistance.

  The content of the metal piece depends on the constituent material and shape of the metal piece. For example, when the metal piece is a thin piece of stainless steel, if the rust-proof layer is 100% by mass, the content is 25% by mass to 50% by mass. When the metal piece is zinc particles, it is preferably 65% by mass to 90% by mass. By setting the content of the stainless steel flakes in the rust prevention layer to 25% by mass or more, or by setting the content of zinc particles in the rust prevention layer to 65% by mass or more, there are many metal pieces in the resin. Further, the corrosion resistance of the rust preventive layer itself can be improved. On the other hand, by ensuring that the content of the flakes is 50% by mass or less and the content of the particles is 90% by mass or less, the insulation between the soft magnetic particles on the surface of the molded body and the surface of the rust prevention layer is ensured. Easy to do.

  When the molded body has corners, the thickness of the rust preventive layer (hereinafter sometimes referred to as the rust preventive layer corner) formed at the corners of the molded body is preferably as thick as possible from the viewpoint of the corrosion resistance of the molded body. For example, it is preferably 5 μm or more, more preferably 10 μm or more. If it does so, naturally the rust prevention layer (henceforth a rust prevention layer plane part) formed in places (plane part) other than the corner | angular part of a molded object is naturally thicker than the thickness of a rust prevention layer corner part. Since it is formed, a sufficient rust prevention layer can be formed over the entire surface of the molded body. That is, in other words, the thickness of the anticorrosive layer formed on the molded body is preferably 10 μm or more regardless of the presence or absence of the corners of the molded body. If it does so, the rusting of the molded object surface can be suppressed. The upper limit of the thickness of the corner portion of the rust prevention layer is preferably about 500 μm. On the other hand, the preferable thickness of the rust-preventing layer flat portion is about 1 to 100 times the thickness of the corner portion of the rust-preventing layer.

  Here, the corner portion of the rust preventive layer is defined as a ridge portion composed of two surfaces forming the corner portion. The thickness of the corner portion of the anticorrosion layer is the thickness of the anticorrosion layer in the normal direction to the curve when the chamfer is rounded in the cross section of the molded body when the corner portion of the molded body is R chamfered. When the chamfered corner is chamfered, the thickness of the anticorrosive layer in the direction perpendicular to the straight line when chamfered in the cross section of the molded body is taken. In particular, when the corners are chamfered, the average thickness of the rust prevention layers in a plurality of normal directions may be the thickness of the rust prevention layer corners. On the other hand, when there is no chamfered portion, the thickness of the rust-preventing layer in the direction that bisects between the extended surfaces of each surface in the two surfaces forming the corner of the molded body Of thickness. The thickness of the corner portion of the anticorrosive layer can be measured, for example, by observing a cross section of the dust core with an optical microscope or a scanning electron microscope (SEM).

<Effect>
According to the above-described dust core, the corrosion resistance is excellent by providing the rust prevention layer having a plurality of metal pieces dispersed in the resin. Since the metal piece in the resin itself divides the pinhole extending in the thickness direction of the rust prevention layer, the rust prevention layer having very few or no pinholes can be obtained. In addition, since the metal piece itself does not permeate the rust-causing substance, the intrusion path of the rust-causing substance entering through the resin can be made non-linear by dispersing a plurality of metal pieces in the resin. The intrusion path can be made longer than the thickness of the rust layer itself. Therefore, it is difficult for the rust-causing substance to reach the molded body. Since the rust-causing substance adheres to the metal piece and corrodes from the metal piece before reaching the formed body, rust can hardly be generated in the formed body.

<Production method of dust core>
The manufacturing method of the powder magnetic core of the present invention includes a molded body preparation process for preparing a molded body and a rust prevention process for forming the above-described rust preventive layer over the entire surface of the molded body. Each process will be described in turn.

[Molded body preparation process]
In the molded body preparation step, a coated soft magnetic powder constituting the powder magnetic core is prepared, and the powder is pressure-molded to form a molded body, or a previously molded molded body is purchased in advance. prepare. In the former case, a raw material preparation step and a forming step of forming a molded body from the raw material are provided. As a raw material preparation step, a coated soft magnetic powder constituting a dust core is prepared. The coated soft magnetic powder includes a plurality of coated soft magnetic particles in which an insulating layer is coated on the outer periphery of the soft magnetic particles.

[Raw material preparation process]
In the raw material preparation step, a coated soft magnetic powder is prepared. In this step, soft magnetic particles having the composition described later are prepared or manufactured, and the outer periphery of the soft magnetic particles is coated with an insulating layer having the composition described later to produce a coated soft magnetic powder. Alternatively, a coated soft magnetic powder manufactured in advance may be purchased. When the soft magnetic particles are manufactured among the former, the coated soft magnetic powder can be manufactured through the soft magnetic particle manufacturing method and the insulating layer coating method described below.

(Soft magnetic particles)
Examples of the composition of the soft magnetic particles include metals such as pure iron and iron alloys. An iron alloy is particularly preferable because it has higher corrosion resistance than pure iron and can improve the corrosion resistance of the molded body. Specifically, Fe-Si alloy, Fe-Al alloy, Fe-N alloy, Fe-Ni alloy, Fe-C alloy, Fe-B alloy, Fe-Co alloy, Fe-P It is preferable to use at least one selected from a base alloy, a Fe—Ni—Co alloy, a Fe amorphous alloy, and a Fe—Al—Si alloy.

  The average particle diameter of the soft magnetic particles is preferably in the range of about 40 to 150 μm. Use of powder having such a particle size is effective in suppressing increase in eddy current loss when the obtained dust core is used as an electromagnetic component in a high frequency range of 1 kHz or higher.

  Examples of the production of soft magnetic particles include atomizing methods such as a water atomizing method and a gas atomizing method. Since the soft magnetic particles produced by the water atomization method have many irregularities on the particle surface, it is easy to obtain a high-strength molded product by meshing the irregularities. On the other hand, the soft magnetic particles produced by the gas atomization method are preferable because the particle shape is almost spherical, and there are few irregularities that break through the insulating layer.

(Insulating layer)
The insulating layer is coated on the outer periphery of the soft magnetic particles in order to insulate adjacent soft magnetic particles. By covering the soft magnetic particles with the insulating layer, the contact between the soft magnetic particles can be suppressed, and the relative permeability of the molded body can be suppressed low. In addition, the presence of the insulating layer can suppress the eddy current from flowing between the soft magnetic particles, thereby reducing the eddy current loss of the dust core.

  The constituent material of the insulating layer is not particularly limited as long as it is a material excellent in insulation to such an extent that insulation between soft magnetic particles can be secured.

[Molding process]
In the molding step, a molded body is produced using the coated soft magnetic powder comprising a plurality of coated soft magnetic particles prepared in the raw material preparation step.

(Pressure process)
The coated soft magnetic powder is pressure molded to obtain a molded body. Typically, the coated soft magnetic powder is filled in a molding die composed of a punch and die having a predetermined shape corresponding to the type of electromagnetic component (the shape of the dust core) described later, and pressed and pressed. At this time, in the case where the soft magnetic particles are made of an iron alloy, a resin (for example, acrylic resin, polyvinyl alcohol, polyvinyl butyral, polyethylene resin, etc.) for retaining the shape before forming is coated with the soft magnetic powder. It is preferable to mix them. The pressure to pressurize can be selected as appropriate, and is preferably about 500 to 1500 MPa, and more preferably about 980 to 1180 MPa. By setting the pressure to 500 MPa or more, a high-density molded body can be obtained, and by setting the pressure to 1500 MPa or less, damage to the insulating layer can be suppressed.

(Heat treatment process)
The molded body is preferably subjected to a heat treatment for heating in order to remove strains and dislocations introduced into the soft magnetic particles in the pressing step. The temperature of the heat treatment is preferably 300 ° C. or higher and 1000 ° C. or lower, more preferably 400 ° C. or higher and 900 ° C. or lower. With such a heat treatment temperature, the strain can be sufficiently removed. What is necessary is just to select suitably the time which heat-processes according to the said heat processing temperature and the volume of a molded object, so that the distortion, dislocation, etc. which were introduced into the soft-magnetic particle at the pressurization process may fully be removed. For example, in the case of the above temperature range, it is preferably 10 minutes to 180 minutes, more preferably 30 minutes to 120 minutes. The atmosphere for performing the heat treatment may be air, but is preferably an inert gas atmosphere or a reduced pressure atmosphere. Thereby, oxidation of a molded object can be prevented.

  Through this molding step, a molded body having the above-described soft magnetic particles and an insulating layer covering the outer periphery of the soft magnetic particles, that is, an insulating layer interposed between the soft magnetic particles is obtained.

[Rust prevention process]
The above-mentioned rust preventive layer is formed on the entire surface of the molded body prepared in the molded body preparation step. Specifically, the method includes an application step of applying a resin solution containing the above-described metal piece, and a baking step of baking the applied solution to cure the resin. The method for applying the solution to the entire surface of the molded body is not particularly limited, and for example, a brush or a spray can be used. Application by spraying is preferable because it can be applied over the entire surface in a short time. After applying the solution, the powder is heated to cure the resin, whereby a dust core having a rust prevention layer formed on the entire surface of the molded body is obtained.

<Electromagnetic parts>
The electromagnetic component of the present invention includes a magnetic core and a coil. A magnetic core consists of a powder magnetic core mentioned above. Examples of the shape of the magnetic core include an annular shape (toroidal or torus), a rod shape (a rectangular bar such as a rectangular parallelepiped or a cylinder), and the like. The coil is configured by winding a winding having an insulating coating on the surface of a conductive wire. Examples of the end face shape of the coil include a circular shape, an elliptical shape, a track shape, and a rectangular shape. As the cross-sectional shape of the winding, various shapes such as a circle and a rectangle can be used.

  This electromagnetic component may be configured by winding a winding around the outer periphery of the magnetic core, or may be configured by fitting an air-core coil formed in advance into a spiral into the outer periphery of the magnetic core.

  Specific examples of the electromagnetic component include a high-frequency choke coil, a high-frequency tuning coil, a bar antenna coil, a power choke coil, a power transformer, a switching power transformer, and a reactor.

<Effect>
According to the method for manufacturing a dust core described above, a dust core having excellent corrosion resistance can be manufactured. Since the resin has metal pieces, when there is no corner in the molded body, there is little variation over the entire surface of the molded body, and a rust preventive layer having a sufficient thickness can be formed. On the other hand, even when the molded body has corner portions, by having a metal piece in the resin, a rust prevention layer having a sufficient thickness can be formed not only on the plane portion but also on the corner portion when forming the rust prevention layer. In addition, the molded body has corners, and even if chamfers such as R chamfering and C chamfering are not formed in advance at the corners, the rust prevention layer formed at the corners is naturally curved and formed. Is done. Therefore, when this dust core is used for an electromagnetic component, it is possible to prevent damage to the insulation coating of the winding due to contact between the corners and the winding when the coil is formed by winding the winding around the dust core.

  According to the above-described electromagnetic component, since it has a magnetic core composed of a dust core having excellent corrosion resistance, an electromagnetic component used in a place exposed to wind and rain for a long time, for example, a door stored in a door handle of an automobile. It can be suitably used for an antenna coil for opening / closing a lock (bar antenna coil). Further, since the dust core is made of soft magnetic particles, it can be made smaller than a magnetic core made of a magnetic material such as ferrite when obtaining magnetic properties equivalent to those of a magnetic core made of a magnetic material such as ferrite. For this reason as well, it can be suitably used for an antenna coil used in a small storage space such as in the door handle.

《Test example》
A compact was prepared, and various rust prevention layers were formed on the surface of the compact to produce a plurality of dust core samples. The magnetic property test and the environmental resistance test shown below were performed on each sample. .

[Sample No. 1]
First, a molded body is prepared. A soft magnetic powder obtained by a gas atomization method using an alloy having a composition of Fe-9.5 mass% Si-5.5 mass% Al is prepared. Next, an insulating layer made of an inorganic material containing Si and O was formed on the surface of the soft magnetic powder. The thickness of the insulating layer is about 120 nm.

  Next, the obtained coated soft magnetic powder and an acrylic resin as a molding resin were mixed, supplied to a mold, compressed, and then heat treated to produce a molded body. The pressure during the pressure molding was 980 MPa. The heat treatment was performed at 800 ° C. for 1 hour in a nitrogen atmosphere. Through the above steps, two types of molded bodies having a rectangular cross section (outer diameter 34 mm, inner diameter 20 mm, thickness 5 mm) and plate shape (thickness 5 mm, width 10 mm, length 55 mm) were produced. The corner of the annular molded body is formed with an R chamfer of 0.5 mm, and the corner of the plate-shaped molded body is also formed with an R chamfer of 0.5 mm.

  A rust preventive layer is formed over the entire surface of the two types of molded bodies. Here, a thin piece (thickness: about 2 μm, width: about 10 μm, length: about 10 μm) of stainless steel (Fe-14Ni-18Cr-2Mo (mass%)) is 16 mass%, an epoxy resin is 30 mass%, The remaining solvent solution is applied to the entire surface of the compact by spraying. Thereafter, the molded body to which this solution was applied was heated to 120 ° C. to cure the resin, and test pieces of ring-shaped and plate-shaped powder magnetic cores having a rust preventive layer coated on the surface of the molded body were produced. In any shape of the test piece, the content of the stainless steel thin piece in the anticorrosive layer is 35% by mass, and the thickness of the anticorrosive layer formed on the flat part of the formed body is 200 μm, and is formed at the corner of the formed body. The thickness of the rust preventive layer was 50 μm.

[Sample No. 2]
Sample No. 2 is Sample No. 1 is different from the constituent material of the rust prevention layer. Here, Sample No. A molded body similar to 1 was prepared, and a rust-proof layer made of an epoxy resin was applied to the entire surface of the molded body. The thickness of the epoxy resin formed on the flat portion of the molded body was 200 μm, and the thickness of the epoxy resin formed on the corner of the molded body was 10 μm.

[Sample No. 3]
Sample No. 3 is sample No. 1 is different from the constituent material of the rust prevention layer. Sample No. 1 is prepared, and 39% by mass of zinc particles (average particle size: about 1 μm), 6% by mass of epoxy resin, and the rest is applied to the entire surface of the molded product by spraying a solvent solution. . Thereafter, sample No. In the same manner as in No. 1, the resin was cured by heating to 120 ° C., and ring-shaped and plate-shaped dust core test pieces were produced. In any of the test pieces, the zinc content in the anticorrosive layer is 79% by mass, the thickness of the anticorrosive layer formed on the flat portion of the molded body is 200 μm, and the anticorrosive layer formed on the corner of the molded body is formed. The thickness was 40 μm.

[Sample No. 4]
Sample No. 4 is sample No. The difference from 1 is that a rust preventive layer is not formed on the surface of the molded body. That is, sample no. 4 remains a molded body.

[Magnetic property test]
With respect to the ring-shaped test piece in each sample produced as described above, the magnetic properties were measured by the following procedure. First, a winding was applied to a ring-shaped test piece, and a measurement member for measuring the magnetic properties of the test piece was produced. About this measurement member, iron loss at IFUTSU measurement Co., Ltd. BH / microanalyzer SY-8258, excitation magnetic flux density Bm: 1kG (= 0.1T), measurement frequency: 100kHz, environmental temperature: 25 degreeC W1 / 100k @ 25 ° C. was measured. The results are shown in Table 1.

[Environmental resistance test]
An environmental resistance test was performed on the plate-like test pieces in each sample prepared as described above in the following order and under test conditions. Here, the following <1> to <5> were set as one cycle and repeated up to 60 cycles. Table 1 shows the number of cycles until rusting.

(Test conditions)
<1> Salt spray: Salt water concentration: 5%, temperature: 50 ° C., time: 4 h
<2> Forced drying: Humidity: 30%, Temperature: 70 ° C., Time: 5h
<3> High temperature and high humidity: Humidity: 65%, temperature: 80 ° C., time: 12 h
<4> Forced drying: Humidity: 30%, Temperature: 70 ° C., Time: 2h
<5> Natural drying: Humidity: 60%, Temperature: 20 ° C., Time: 1h

〔result〕
Sample No. in which a rust prevention layer having a resin and a plurality of metal pieces dispersed in the resin was formed on the entire surface of the molded body. In Nos. 1 and 3, no rust was observed in the molded article even after the environmental resistance test was repeated 60 cycles. On the other hand, sample no. Sample No. 2 was rusted on the molded product in 31 cycles and remained as a molded product. No. 4 rusted in 3 cycles. From this result, sample no. 1 and 3 are sample No. It can be said that it is excellent in corrosion resistance compared with 2 and 4. In addition, the iron loss of sample Nos. It was the same as 2 and 4, and no deterioration of the magnetic properties due to having a metal piece in the anticorrosive layer was observed.

  Thus, sample No. Samples Nos. 1 and 3 are sample Nos. As a result, the corrosion resistance of the resin rust layer is improved by providing a rust preventive layer in which a plurality of metal pieces are dispersed in the resin. It is because generation | occurrence | production path | route of the rust causative substance from the surface of a rust prevention layer to the surface of a molded object was able to be lengthened while generating could be suppressed. Further, by having a plurality of metal pieces dispersed in the resin, a rust preventive layer having a thickness of 5 μm or more could be formed at the corner of the molded body. This is considered to be because it was possible to suppress the occurrence of rust from the corners of the molded body.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention. For example, the metal piece in the resin can be both stainless steel flakes and zinc particles, or one or both of stainless steel particles and zinc flakes.

  The dust core of the present invention can be suitably used for a magnetic core used in various inductors. Moreover, the manufacturing method of the powder magnetic core of this invention can be utilized suitably for obtaining the powder magnetic core used for various inductors. Furthermore, the electromagnetic component of the present invention can be suitably used for a high frequency choke coil, a high frequency tuning coil, a bar antenna coil, a power choke coil, a power transformer, a switching power transformer, a reactor, and the like. In particular, it can be suitably used for an antenna coil housed in a door handle of an automobile that is exposed to wind and rain for a long time.

Claims (11)

A molded body comprising a plurality of coated soft magnetic particles, wherein the surface of the soft magnetic particles is covered with an insulating layer;
Covering the entire surface of the molded body, provided with a rust prevention layer to rust the molded body,
The antirust layer is a dust core including a resin and a plurality of metal pieces dispersed in the resin.   The dust core according to claim 1, wherein a material of the metal piece is at least one of stainless steel and zinc.   The dust core according to claim 1 or 2, wherein the shape of the metal piece is at least one of a thin piece and a particle.   The pressure according to any one of claims 1 to 3, wherein the metal piece includes a stainless steel flake, and the content of the stainless steel flake occupying the rust prevention layer is 25 mass% to 50 mass%. Powder magnetic core.   The dust core according to any one of claims 1 to 4, wherein the metal piece includes zinc particles, and the content of the zinc particles in the antirust layer is 65% by mass to 90% by mass. .   5. The dust core according to claim 3, wherein the thin piece has a thickness of 1 μm to 5 μm, a width of 5 μm to 20 μm, and a length of 5 μm to 20 μm.   The powder magnetic core according to claim 3 or 5, wherein an average particle diameter of the particles is 0.1 µm to 10 µm.   The dust core according to any one of claims 1 to 7, wherein the resin is any one of an epoxy resin, a urethane resin, and an acrylic resin. The molded body has corners;
The dust core according to any one of claims 1 to 8, wherein a thickness of the anticorrosive layer formed at the corner is 5 µm or more. A magnetic core having the dust core according to any one of claims 1 to 9,
An electromagnetic component comprising a coil wound around a winding and disposed on an outer periphery of the magnetic core. A molded body preparation step of preparing a molded body including a plurality of coated soft magnetic particles in which the surface of the soft magnetic particles is covered with an insulating layer;
A method for producing a dust core comprising a rust-preventing step for forming a rust-preventing layer comprising a resin and a plurality of metal pieces dispersed in the resin over the entire surface of the molded body.