JP6571146B2 - Soft magnetic material, dust core using soft magnetic material, reactor using dust core, and method for manufacturing dust core - Google Patents

Description

  The present invention relates to a soft magnetic material, a powder magnetic core using the soft magnetic material, a reactor using the powder magnetic core, and a method for manufacturing the powder magnetic core.

  Reactors are used as part of the power supply system for motors, inverters, and converters. A powder magnetic core is used as the core of this reactor. The dust core is formed by press-molding a powder composed of a metal powder and an insulating film covering the metal powder.

  The powder magnetic core is required to have a magnetic characteristic capable of obtaining a large magnetic flux density with a small applied magnetic field and a magnetic characteristic such that an energy loss due to a change in the magnetic flux density is small due to demands such as improvement of energy exchange efficiency and low heat generation. Specifically, the magnetic characteristic relating to the magnetic flux density is the magnetic permeability (μ). Specifically, the magnetic characteristics relating to energy loss are iron loss (Pcv). The iron loss (Pcv) is represented by the sum of hysteresis loss (Ph) and eddy current loss (Pe).

JP 2008-305823 A JP 2010-001561 A JP 2012-129217 A

  The dust core using soft magnetic powder is required to improve the magnetic flux density as described above. For this purpose, it is necessary to increase the density of the dust core. For this reason, compacting is performed at a high pressure, but at that time, many distortions are generated in the particles of the soft magnetic powder. This distortion increases the coercive force of the dust core and increases hysteresis loss. Hysteresis loss leads to an increase in loss as a whole of the dust core, a decrease in saturation magnetic flux density, and a deterioration in DC superposition characteristics. Therefore, for the purpose of reducing distortion generated in the particles of the soft magnetic powder during compacting, a method of compacting by adding a lubricant to the soft magnetic powder is employed. Further, it is known that the dust core is deteriorated with time, and the magnetic loss and the iron loss (Pcv) are reduced due to the deterioration of hysteresis loss.

As a result of intensive studies, the present inventor used calcium stearate as a lubricant,
The present inventors have found that it is possible to suppress the permeability due to aging and the deterioration of hysteresis loss while suppressing the occurrence of distortion in the soft magnetic powder during compacting at high pressure. The object of the present invention is to use calcium stearate as a lubricant, and suppress the generation of distortion in the particles of soft magnetic powder even when compacted at high pressure, and magnetic properties of the dust core due to aging Is to provide a soft magnetic material with reduced deterioration, a powder magnetic core using the soft magnetic material, a reactor using the powder magnetic core, and a method for manufacturing the powder magnetic core.

In order to achieve the above object, the soft magnetic material of the present invention comprises a soft magnetic powder having a periphery coated with an insulating layer, and a lubricant added to the soft magnetic powder, the lubricant comprising: 0 with respect to the soft magnetic powder. Look containing a 5 wt% of calcium stearate, wherein the insulating layer comprises an insulating powder layer uniformly distributed around the soft magnetic powder, and the silicone oligomer layer covering the outside of the insulating powder layer, outside of the silicone oligomer layer A part of or all of the insulating powder layer is aluminum tripolyphosphate powder, and the amount of the aluminum tripolyphosphate powder added is 1.0 to 1 with respect to the soft magnetic powder. .5 wt% .

The addition amount of the lubricant may be 0.5 wt% with respect to the soft magnetic powder, and the ratio of the calcium stearate in the lubricant may be 100 %.

  The silicone oligomer layer may be a solidified methyl or methylphenyl silicone oligomer.

  In addition, a dust core using the soft magnetic material, a reactor in which a coil is wound around the dust core, and a method for manufacturing the dust core are also one aspect of the present invention.

  According to the present invention, by using calcium stearate as a lubricant, it is possible to suppress the occurrence of distortion in the particles of the soft magnetic powder even if compacted at a high pressure. Thereby, a hysteresis loss can be reduced and a saturation magnetic flux density can be raised. As a result, it is possible to provide a dust core with low loss and excellent direct current superposition characteristics and a method for manufacturing the same.

It is a flowchart which shows the manufacturing method of the powder magnetic core which concerns on one Embodiment of this invention. It is a graph which shows the correlation of the addition amount of calcium stearate in the 1st characteristic comparison, and magnetic permeability. It is a graph which shows the correlation of the addition amount of a calcium stearate in a 1st characteristic comparison, and an iron loss. It is a graph which shows the correlation of the addition amount of calcium stearate in a 1st characteristic comparison, and a density. It is a graph which shows the correlation of the addition amount of calcium stearate in the 1st characteristic comparison, and crushing strength. It is a graph which shows the correlation of the addition amount of tripoly aluminum phosphate and magnetic permeability in 2nd characteristic comparison. It is a graph which shows the correlation of the addition amount of an aluminum tripolyphosphate in a 2nd characteristic comparison, and an iron loss. It is a graph which shows the correlation of the addition amount of aluminum tripolyphosphate in a 2nd characteristic comparison, and a density.

[1. Embodiment]
[1-1. Constitution]
The soft magnetic powder material of the present embodiment is a powder magnetic core material. The soft magnetic powder material includes a soft magnetic powder whose periphery is covered with an insulating layer, and a lubricant added to the soft magnetic powder. As the lubricant, 0.1 to 0.5 wt% of calcium stearate is used with respect to the soft magnetic powder. In the present embodiment, a soft magnetic powder material to which a lubricant is added is pressed into a predetermined shape to produce a molded body. The shape of the molded body can be various shapes such as toroidal, I-type, U-type, θ-type, E-type, and EER-type. The powder magnetic core is molded by heat-treating the molded body arranged in a predetermined shape. In addition, an insulating layer can be arbitrarily selected according to the performance requested | required from an insulating powder layer, a silicone oligomer layer, and a silicone resin layer. In the present embodiment, for the sake of explanation, the insulating layer is described as being composed of three layers of an insulating powder layer, a silicone oligomer layer, and a silicone resin layer.

(1) Soft magnetic powder

  The soft magnetic powder used in the present embodiment is a soft magnetic powder containing iron as a main component, and is permalloy (Fe—Ni alloy), Si-containing iron alloy (Fe—Si alloy), Sendust alloy (Fe—Si—). Al alloy), pure iron powder, etc. are used. The iron alloy may further contain Co, Al, Cr, or Mn. When using permalloy (Fe—Ni alloy), the ratio of Ni to Fe is preferably 50:50 or 25:75, but may be other ratios. For example, Fe-80Ni and Fe-36Ni may be used. In addition to Fe and Ni, Si, Cr, Mo, Cu, Nb, Ta, or the like may be included. Examples of the Fe-Si alloy powder include Fe-3.5% Si alloy powder and Fe-6.5% Si alloy powder, but the ratio of Si to Fe is other than 3.5% or 6.5%. It may be. Pure iron powder contains 99% or more of Fe. The soft magnetic powder is not limited to one type but may be a mixed powder of two or more types.

  The average particle diameter (D50) of the soft magnetic powder is preferably 20 μm to 150 μm. In the present specification, the “average particle diameter” refers to D50, that is, the median diameter unless otherwise specified. The method for producing the soft magnetic powder is not limited. Those produced by a pulverization method or those produced by an atomization method may be used. The atomizing method may be any of a water atomizing method, a gas atomizing method, and a water gas atomizing method. The water atomization method is currently the most available and low cost. When the water atomization method is used, since the particle shape is irregular, it is easy to improve the mechanical strength of a powder molded body obtained by pressure molding.

  The soft magnetic powder is preferably spherical. The circularity of the first magnetic powder is preferably 0.90 or more. This is because by increasing the circularity, the gaps between the soft magnetic powders are reduced, and the density and permeability can be improved.

  Any method can be adopted as a method for producing the soft magnetic powder. For example, the average circularity of the particles is set to 0.90 or more by using a gas atomized method, a water atomized method, or a water gas atomized method. Further, when a powder having an average circularity of 0.90 or more cannot be formed only by various atomizing methods, a process for further increasing the average circularity of the particles may be performed. For example, the soft magnetic powder by the gas atomization method is a substantially spherical particle. Therefore, the powder formed by the gas atomization method can be used as it is without being processed. On the other hand, the soft magnetic powder produced by the water atomization method is non-spherical particles having irregularities formed on the surface thereof. In this case, the average circularity of the particles can be increased by leveling the surface irregularities using a ball mill, mechanical alloying, jet mill, attritor, or surface modification device.

(2) Insulating layer The insulating layer is a layer having insulating performance formed around the soft magnetic powder. In this embodiment, a plurality of types of layers are formed as the insulating layer. In this embodiment, the periphery of the soft magnetic powder is covered in order of the insulating powder layer and the insulating coating layer from the inside. The insulating coating layer includes a first insulating coating layer containing silicon (Si) provided on the surface of the soft magnetic powder, and a second insulation containing silicon (Si) provided on the surface of the first layer. A coating layer.

(2-1. Insulating powder layer)
The insulating powder layer is a layer in which the insulating powder is uniformly attached to the surface of the soft magnetic powder. As the insulating powder, condensed metal phosphate metal salt powder or inorganic insulating powder is used. The insulating powder is not limited to one type, and two or more types may be mixed.

(Condensed metal phosphate)
A condensed aluminum phosphate powder is suitable as the condensed metal phosphate powder that is an insulating powder mixed with the soft magnetic powder. Among them, aluminum tripolyphosphate powder, aluminum metaphosphate powder obtained by dehydration reaction by heating primary aluminum phosphate, or a powder obtained by mixing these powders is suitable. Aluminum tripolyphosphate is a white fine powder at room temperature, and the powder is hardly soluble in water. Aluminum tripolyphosphate is a layered compound in which plate-like crystals overlap. Specific examples of aluminum tripolyphosphate include aluminum dihydrogen phosphate. The average particle size of aluminum tripolyphosphate is more preferably 1.5 μm to 6.0 μm. Tripolyaluminum phosphate has an antirust effect, and when added to soft magnetic powder, it acts to prevent oxidation of the surface of soft magnetic powder. When the powder surface is oxidized, the distance between the soft magnetic powders increases. An increase in the distance between the soft magnetic powders leads to deterioration of the magnetic permeability. Further, when the surface of the soft magnetic powder is oxidized, the crystal structure in the soft magnetic powder is distorted. The distortion of the crystal structure leads to deterioration of hysteresis loss in the dust core. By uniformly distributing the aluminum tripolyphosphate on the surface of the soft magnetic powder, it is possible to prevent deterioration of the magnetic permeability of the dust core and deterioration of hysteresis loss.

(Inorganic insulating powder)
The inorganic insulating powder mixed with the soft magnetic powder is preferably at least one of alumina powder, magnesia powder, silica powder, titania powder, and zirconia powder, which is an inorganic insulating powder having a melting point of 1000 ° C. or higher. The inorganic insulating powder having a melting point of 1000 ° C. or higher is used as a material for the powder magnetic core by sintering the inorganic insulating powder by heat applied in the heat treatment process performed for the purpose of removing distortion due to the pressure applied during the molding described later. This is to prevent it from becoming unusable.

The specific surface area of the inorganic insulating powder is 65~130m ² / g (if the particle diameter 7～200Nm) are preferred, and more preferably 100~130m ² / g (7~50nm in particle size). The larger the specific surface area of the inorganic insulating powder, the smaller the particle size. When the particle diameter is smaller, the inorganic insulating powder enters between the soft magnetic powders without any gaps, and a dense insulating coating is formed, thereby reducing the strain at the time of forming the dust core. On the other hand, when the specific surface area of the inorganic insulating powder is too large, the particle diameter becomes too small and the production becomes difficult.

  The addition amount of the inorganic insulating powder is 0.25 to 2.0 wt% with respect to the soft magnetic powder. If it is less than this, insulation performance cannot fully be exhibited, and eddy current loss may increase remarkably at high heat treatment temperatures. On the other hand, if it is more than this, the insulation performance can be exhibited, but the molding density is lowered, and there may be a problem that magnetic properties other than eddy current loss are deteriorated. If these problems do not occur, the inorganic insulating powder layer is not always necessary.

(2-2. Insulating coating layer)
The soft magnetic powder on which the insulating powder layer is formed is covered with two types of insulating coating layers. That is, the first insulating coating layer of the first layer is formed outside the soft magnetic powder on which the insulating powder layer is formed with the soft magnetic powder as the center, and the first insulating coating layer of the first layer is formed outside the first insulating coating layer. A second insulating coating layer of the second layer is formed. The first insulating coating layer is a silica (Si) layer formed by polymerization reaction of a silicone oligomer through a heat treatment process. The second insulating coating layer is a silica (Si) layer added with a predetermined amount of silicone resin and dried at a predetermined temperature in the air atmosphere. When the insulating powder is attached around the soft magnetic powder, the first layer contains the insulating powder. In this case, the first insulating coating layer tends to have a lower Si density than the second layer. The first insulating coating layer and the second insulating coating layer can be identified by, for example, a difference in Si density. This is because the first layer contains an inorganic insulating powder, but the second layer does not contain or contains a small amount of inorganic insulating powder.

(Silicone oligomer)
A silicone oligomer has a siloxane bond as a main skeleton and a strong mechanical bonding force. In addition, it is better to use a silicone oligomer having a molecular weight of about 1000, which is a low molecular, dimer or trimer, with respect to the silane coupling agent which is a monomer having one Si atom. It can be thickened. That is, by forming the silicone oligomer layer as an intermediate layer of the insulating coating, the entire insulating coating has a strong mechanical bonding force and can be made thicker.

  Specifically, the silicone oligomer has an alkoxysilyl group. Alkoxysilyl groups include methoxy, ethoxy, and methoxy / ethoxy groups. If it is a silicone oligomer having an alkoxysilyl group, a methyl type or methylphenyl type having no reactive functional group, an epoxy type having an alkoxysilyl group and a reactive functional group, an epoxymethyl type, a mercapto type, a mercapto type Methyl, acrylmethyl, methacrylmethyl, vinylphenyl, and the like can be used. In particular, a thick and hard insulating layer can be formed by using a methyl or methylphenyl silicone oligomer.

  The content of the alkoxysilyl group with respect to the silicone oligomer is preferably 20 wt% to 45 wt%. When the content of the alkoxysilyl group is less than 20 wt%, the density is lowered, the direct current superimposition characteristics are deteriorated, and the hysteresis loss is increased. On the other hand, when the content of the alkoxysilyl group is more than 45 wt%, the density decreases and the hysteresis loss increases. More preferably, the content of alkoxysilyl groups is 28 wt% to 40 wt%. If it is this range, since there is little hysteresis loss and a density is high in the range whose content is 20 wt%-45 wt%, it is suitable. In addition, since the density is high, the magnetic permeability is high and the direct current superposition characteristics are good.

  The silicone oligomer is a silicone oligomer containing in its structure a T unit (trifunctional) represented by the following (formula 1). The silicone oligomer that forms the silicone oligomer layer preferably does not contain a monomer, that is, an M unit (monofunctional) represented by the following (formula 2). This is because when the silicone oligomer layer is formed, the M unit portion volatilizes and the volatilized portion becomes rough, and the magnetic properties deteriorate when exposed to high temperature and high humidity. That is, when the silicone oligomer contains an M unit, the M unit portion becomes rough when the silicone oligomer layer is formed, and the portion is easily exposed to the outside air. When exposed to a high temperature and high humidity environment in this state, outside air enters the roughened gap portion, and rust or the like is generated in that portion, causing deterioration of characteristics. For example, when a reactor sample is allowed to stand for 100 hours in an environment of high temperature and high humidity of 85 ° C. and 95%, in a conventional example in which a silicone oligomer layer is formed with a silicone oligomer containing M units, However, the magnetic permeability decreases by 10% and the hysteresis loss increases by 30%. On the other hand, in the case where the silicone oligomer layer is formed of only the T unit and does not contain the M unit under the same conditions, the magnetic permeability is only 3% lower than that before being left, and the hysteresis loss is also reduced. Will only increase by 5%.

(Formula 1)
RSiO _3/2 (Formula 1)
(R is an organic substituent.)
(Formula 2)
R ₃ SiO _1/2 ... (Formula 2)
(R is an organic substituent.)

As a silicone oligomer which does not contain M unit for forming a silicone oligomer layer, in addition to silicone oligomer consisting only of T unit and silicone oligomer containing T unit, D unit represented by the following (formula 3) ( It may be a silicone oligomer containing a Q unit (tetrafunctional) represented by (difunctional) or (formula 4). Even if these silicone oligomers are exposed to high temperature and high humidity for a long time, deterioration of magnetic permeability and hysteresis loss can be reduced.
(Formula 3)
R ₂ SiO _2/2 (Formula 3)
(R is an organic substituent.)
(Formula 4)
SiO _4/2 ... (Formula 4)

  The molecular weight of the silicone oligomer is preferably 100 to 4000. When the molecular weight is less than 100, it is likely to be destroyed or lost by thermal decomposition in the heat treatment step, and the dielectric breakdown is likely to occur between the soft magnetic powders. On the other hand, if the molecular weight is larger than 4000, the film thickness becomes too thick and the magnetic properties are deteriorated.

  The addition amount of the silicone oligomer is preferably 0.15 wt% to 3.5 wt% with respect to the soft magnetic powder. When the addition amount is less than 1.0 wt%, the direct current superposition characteristics deteriorate. When the added amount is more than 2.0 wt%, the density is lowered, whereby the initial permeability is lowered and the hysteresis loss is increased.

  The drying temperature of the silicone oligomer layer is preferably 25 ° C to 350 ° C, and more preferably 200 ° C to 350 ° C when the soft magnetic powder is an Fe-Ni alloy powder. When the soft magnetic powder is Fe-Si alloy powder or pure iron powder, 25 ° C to 350 ° C is more preferable. When the drying temperature is less than 25 ° C., film formation is incomplete and eddy current loss increases. On the other hand, when the drying temperature is higher than 350 ° C., the powder is oxidized to increase the hysteresis loss, and the density and magnetic permeability of the compact are reduced. The drying time is about several hours, for example, about 1 to 2 hours.

  In the case where the inorganic insulating powder adhering step is not provided, the silicone oligomer layer forming step adds a predetermined amount of the silicone oligomer to the soft magnetic powder and performs drying at a predetermined temperature in the air atmosphere. A silicone oligomer layer is formed on the surface of the soft magnetic powder by the silicone oligomer layer forming step.

(Silicone resin)
The silicone resin is a resin having a siloxane bond (Si—O—Si) as a main skeleton. By using a silicone resin, a film excellent in flexibility can be formed. As the silicone resin, methyl, methylphenyl, propylphenyl, epoxy resin-modified, alkyd resin-modified, polyester resin-modified, rubber or the like can be used. Among these, in particular, when a methylphenyl-based silicone resin is used, it is possible to form a silicone resin layer with little heat loss and excellent heat resistance.

  The addition amount of the silicone resin is preferably 0.5 to 1.5 wt% with respect to the soft magnetic powder. If the addition amount is less than 0.5 wt%, it does not function as an insulating film, and eddy current loss increases, resulting in a decrease in magnetic properties. If the addition amount is more than 1.5 wt%, the core expands to reduce the density of the molded body and the magnetic permeability. By appropriately adjusting the amount of the silicone resin added to the silicone oligomer, it is possible to form a strong insulating film having a high insulating performance, and particularly the weight ratio of the silicone resin to the silicone oligomer is 1: 0.8 to 1: 3. In case, strength and insulation performance are excellent.

  The drying temperature of the silicone resin layer is preferably 100 ° C to 400 ° C, and more preferably 200 ° C to 300 ° C when the soft magnetic powder is an Fe-Ni alloy powder. When the soft magnetic powder is an Fe—Si alloy powder, 100 ° C. to 400 ° C. is more preferable. When the soft magnetic powder is pure iron powder, 100 ° C. to 300 ° C. is more preferable. When the drying temperature is lower than 100 ° C., film formation is incomplete and eddy current loss increases. On the other hand, when the drying temperature is higher than 400 ° C., the powder is oxidized to increase the hysteresis loss, and the density and magnetic permeability of the compact are reduced. The drying time is about 2 hours.

(3) Lubricant Calcium stearate is used as a lubricant. By adding a lubricant to the soft magnetic powder, it is possible to improve the sliding between the soft magnetic powders, so that the density during mixing can be improved and the molding density can be increased. Furthermore, it is possible to reduce the punching pressure of the upper punch during molding and to prevent the vertical stripes on the core wall surface from being generated due to the contact between the mold and the powder. Further, through an annealing process described later, calcium stearate contained in the lubricant becomes calcium oxide and remains in the core. The calcium oxide in the core prevents the rust from being generated in the core due to the moisture absorption action of the calcium oxide, and prevents deterioration of the core characteristics due to rust.

  The addition amount of the lubricant is preferably about 0.1 wt% to 0.5 wt% with respect to the soft magnetic powder, and generally about 0.5 wt%. If it is less than this, a sufficient effect cannot be obtained, and if it is more than this, there arises a problem that the magnetic properties are deteriorated due to a decrease in the maximum magnetic flux density due to a decrease in density and an increase in hysteresis loss.

  In addition to calcium stearate, other waxes may be mixed and used as a lubricant. Other waxes include stearic acid and its metal salts and waxes such as ethylene bisstearamide. For example, ethylene bisstearamide, lithium stearate, aluminum stearate and the like. In addition to calcium stearate, the amount of addition of other waxes is preferably about 0.1 wt% to 0.5 wt% of the mixed lubricant with respect to the soft magnetic powder.

[1-2. Manufacturing method of powder magnetic core]
The manufacturing method of the powder magnetic core of the present embodiment includes the following steps. This process is shown in the flowchart of FIG.
(1) An insulating powder attaching step (step 1) in which insulating powder is mixed with the soft magnetic powder to attach the powder.
(2) A silicone oligomer layer forming step (step 2) in which a silicone oligomer layer is formed by mixing a silicone oligomer with a soft magnetic powder having an insulating powder adhered to the surface.
(3) A silicone resin layer forming step of forming a silicone resin layer by mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon (step 3).
(4) Lubricant mixing step of mixing calcium stearate with the soft magnetic powder that has undergone the above process (Step 4)
(5) A molding step (step 5) in which the soft magnetic powder that has undergone the above-described step is subjected to pressure molding treatment to produce a molded body.
(6) A heat treatment process (step 6) in which the molded body that has undergone the molding process is heat treated at 600 ° C. or higher.
Hereafter, each process is demonstrated concretely.

(1) Insulating powder adhering step In the insulating powder adhering step, soft magnetic powder and insulating powder are mixed. Mixing is performed using a mixer (W type, V type), a pot mill or the like, and at this time, the powder is mixed so that internal distortion does not enter. As described above, the insulating powder layer can be attached to the surface of the soft magnetic powder. By attaching the aluminum tripolyphosphate powder to the surface of the soft magnetic powder, rust generated in the soft magnetic powder can be prevented. On the other hand, by attaching an inorganic insulating powder to the surface of the soft magnetic powder, it is possible to insulate the soft magnetic powder and increase the heat treatment temperature.

  As for the manner of adhesion of the insulating powder, the surface of the soft magnetic powder is dispersed and adhered in the form of dots, the surface of the soft magnetic powder is dispersed and adhered to the surface of the soft magnetic powder, the entire surface of the soft magnetic powder Or the case where it adheres, forming the layer of inorganic insulating powder so that a part of surface may be covered is included. In addition to being attached to the surface of the soft magnetic powder, a case where it is mixed with a silicone oligomer layer formed on the outside of the soft magnetic powder and dispersed in the silicone oligomer layer is also included. In addition, depending on conditions, such as stirring time by a mixer, it may not disperse | distribute in a silicone oligomer layer.

(2) Silicone oligomer layer forming step In the silicone oligomer layer forming step, a predetermined amount of silicone oligomer is added to the soft magnetic powder, and drying is performed at a predetermined temperature in the air atmosphere. A silicone oligomer layer is formed outside the soft magnetic powder by the silicone oligomer layer forming step.

When the insulating powder adhering step is not provided, the silicone oligomer layer forming step adds a predetermined amount of the silicone oligomer to the soft magnetic powder and performs drying at a predetermined temperature in the air atmosphere. A silicone oligomer layer is formed on the surface of the soft magnetic powder by the silicone oligomer layer forming step.

(3) Silicone resin layer forming step In the silicone resin layer forming step, a predetermined amount of silicone resin is added to the soft magnetic powder on which the silicone oligomer layer is formed, and dried at a predetermined temperature in an air atmosphere. A silicone resin layer is formed outside the silicone oligomer layer by the silicone resin layer forming step.

  By such a mixing step, granulated powder that is a mixture of magnetic powder and resin can be obtained.

(4) Lubricant mixing step In the lubricant mixing step, a predetermined amount of calcium stearate is added to the soft magnetic powder on which the silicone resin layer is formed. As a mixing method, mixing is performed using a mixer (W type, V type), a pot mill or the like. If other lubricants are used in addition to calcium stearate, they can be mixed in this step. The timing of mixing other lubricants can be selected before the calcium stearate is charged, when the calcium stearate is charged, or after the calcium stearate is charged. Alternatively, calcium stearate and another lubricant may be mixed in advance, and the mixed lubricant may be added to the soft magnetic powder on which the silicone resin layer is formed.

(5) Molding step In the molding step, a compact is formed by pressure molding soft magnetic powder having an insulating coating formed on the surface mixed with a lubricant. The pressure at the time of molding is 10 to 20 ton / cm ^{2 and} is preferably about 15 ton / cm ^{2 on} average.

(5) Heat treatment step In the heat treatment step, the temperature at which the insulating coating coated with the soft magnetic powder is destroyed at 600 ° C. or higher in a N 2 gas or N 2 + H 2 gas non-oxidizing atmosphere with respect to the molded body that has undergone the molding step. The powder magnetic core is manufactured by performing a heat treatment below (for example, 850 ° C.). The reason why the heat treatment is performed at a temperature lower than the temperature at which the insulating film is broken is to release distortion in the molding process and prevent the insulating film coated around the soft magnetic powder from being broken by the heat during the heat treatment. is there. On the other hand, if the heat treatment temperature is increased too much, the insulating film coated with the soft magnetic powder is broken, and the eddy current loss is greatly increased due to the deterioration of the insulating performance. This causes a problem that the magnetic characteristics are deteriorated.

  Examples of the present invention will be described below with reference to Tables 1 and 2 and FIGS.

(1) Measurement items Measurement items are magnetic permeability, iron loss, and density. For measurement of magnetic permeability and calculation of iron loss, a primary winding (20 turns) was applied to each of the produced dust cores, and a reactor was produced. Moreover, the magnetic permeability and iron loss of the produced reactor were computed on condition of the following.

<Density>
The density of the core is the apparent density. That is, the outer diameter, inner diameter, and height of the sample of each core were measured, and the volume (cm ³ ) of the sample was calculated from these values based on π × (outer diameter ² −inner diameter ² ) × height. Then, the mass of the sample was measured, and the density of the core was calculated by dividing the measured mass by the calculated volume.

<Permeability and iron loss>
The measurement conditions for magnetic permeability and iron loss were secondary winding (3 turns), frequency 100 kHz, and maximum magnetic flux density Bm = 100 mT. The magnetic permeability was the amplitude magnetic permeability when the maximum magnetic flux density Bm was set when measuring the iron loss Pcv. The iron loss was calculated using a BH analyzer (Iwatori Measurement Co., Ltd .: SY-8232), which is a magnetic measurement device. This calculation was performed by calculating the hysteresis loss coefficient and the eddy current loss coefficient of the iron loss frequency curve by the following method (1) to (3) by the least square method.

Pcv = Kh × f + Ke × f2 (1)
Ph = Kh × f (2)
Pe = Ke × f2 (3)
Pcv: Iron loss Kh: Hysteresis loss coefficient Ke: Eddy current loss coefficient f: Frequency Ph: Hysteresis loss Pe: Eddy current loss

(2) First characteristic comparison: Comparison of characteristics when the insulating powder is an inorganic insulating powder In this characteristic comparison, a dust core using a soft magnetic powder coated with an inorganic insulating powder and a composite soft magnetic material using a lubricant is used. Samples were prepared and their characteristics were compared. In the sample dust core, the amount of lubricant was 0.5 wt% with respect to the soft magnetic powder. A plurality of samples were prepared by changing the ratio of calcium stearate in the lubricant and ethylene bis-stearide, and Examples 1 to 6 and Comparative Example 1 were used depending on the amount of calcium stearate. These production methods and the results are shown below in order.

  0.25 wt% of alumina powder (average particle diameter of about 7 nm) having a specific surface area of 100 m 2 / g was mixed as an insulating fine powder with Fe6.5Si powder having an average particle diameter of 27 μm. And as an insulation process, 0.4 wt% silicone oligomer was mixed with respect to the said mixture, and it heat-dried at 200 degreeC for 1 hour. Furthermore, 0.8 wt% silicone resin was mixed and heat-dried at 150 ° C. for 2 hours to prepare granulated powder.

  Next, 0.5 wt% lubricant was mixed with the granulated powder. As the lubricant, calcium stearate and ethylene bis-stearide were added. The ratio of calcium stearate in the lubricant was 0% in Comparative Example 1 and 20 to 100% in Examples 1-6.

The granulated powder mixed with a lubricant is pressure-molded at a pressure of 15 ton / cm ² at room temperature to produce a ring-shaped molded body having an outer diameter of 16.5 mm, an inner diameter of 11.0 mm, and a height of 5.0 mm, Heat treatment was performed at 850 ° C. for 2 hours in a nitrogen atmosphere to produce a dust core.

  With respect to these samples, as shown in the above “measurement item”, a reactor was prepared, and magnetic permeability, calculation of iron loss, density and crushing strength were measured. Thereafter, each sample was subjected to a high temperature and high humidity (85 ° C., 85%) test for 500 hours, and the magnetic permeability and iron loss were calculated again.

Table 1 shows the ratio of calcium stearate in Examples 1 to 6 and Comparative Example 1, the permeability μ and the iron loss change rate Pcv (%) after the high-temperature and high-humidity test for 500 hours, the density, and the crushing strength. The rate of change in permeability in Table 1 was calculated by the following equation, with the permeability (μ0) at the start of the test and the permeability (μ1) after 500 hours.
(Μ1−μ0) ÷ μ0 × 100 = change rate of permeability μ (%)
Moreover, the rate of change of the iron loss Pcv was calculated by the following formula, assuming the iron loss at the start of the test (Pcv0) and the iron loss after 500 hours (Pcv1).
(Pcv1-Pcv0) ÷ Pcv0 × 100 = rate of change of iron loss Pcv (%)
[Table 1]

  Moreover, from Table 1, the figure which shows the correlation of the addition amount of a calcium stearate, magnetic permeability, an iron loss, a density, and a crushing strength was created as FIGS.

  From Table 1 and FIG. 2, in the comparative example 1 which added 0.5 wt% of ethylene bis-stellaride with respect to the soft magnetic powder as a lubricant, the change rate μ of the magnetic permeability was −11.2%. The minus of the rate of change μ of the magnetic permeability indicates that the magnetic permeability μ1 after the test is lower than the magnetic permeability μ0 at the start of the test, and 11.2 indicates the ratio. That is, as a result of the high temperature and high humidity test for 500 hours, the magnetic permeability decreased by 10% or more. On the other hand, in the dust core produced by including 0.1 to 0.5 wt% of calcium stearate as a lubricant with respect to the soft magnetic powder, the permeability change rate μ is −7.0% to −3. 2%. It can be seen that the permeability change is less than 10% even after a 500 hour high temperature and high humidity test. Further, by adding 0.25 wt% or more of calcium stearate, the permeability change rate μ can be set to −5% or less.

  From Table 1 and FIG. 3, in Comparative Example 1 in which 0.5 wt% of ethylene bisstellaride was added to the soft magnetic powder as a lubricant, the iron loss change rate Pcv was 12.6%. On the other hand, in the powder magnetic core prepared by including 0.1 to 0.5 wt% calcium stearate as a lubricant with respect to the soft magnetic powder, the iron loss change rate Pcv is 4.1% to 8.9%. It became. It can be seen that the iron loss change is less than 10% even after a high temperature and high humidity test for 500 hours. Further, by adding 0.25 wt% or more of calcium stearate, the iron loss change rate μ can be set to 5% or less.

  Further, as shown by the density items in FIG. 4 and Table 1 focusing on the density, it can be seen that the density of Examples 1 to 6 is higher than that of Comparative Example 1. That is, by adding calcium stearate instead of ethylene bis-stellaride, a high-density powder magnetic core can be produced even at the same molding pressure.

  Further, as shown in FIG. 5 focusing on the crushing strength and the item of crushing strength in Table 1, it can be seen that the crushing strength is higher in Examples 1 to 6 than in Comparative Example 1. That is, by adding calcium stearate instead of ethylene bis-stellaride, it is possible to produce a dust core having a high crushing strength even at the same molding pressure.

  As described above, in a dust core made of a soft magnetic material using 0.1 to 0.5 wt% of calcium stearate as a lubricant, the permeability change rate μ and iron loss can be reduced even when used for a long time. It becomes possible to produce a dust core having a small change rate Pcv.

(3) Second characteristic comparison: Comparison of characteristics when the insulating powder is aluminum tripolyphosphate In this characteristic comparison, a compact powder using a soft magnetic powder coated with aluminum tripolyphosphate powder and a composite soft magnetic material using a lubricant is used. Magnetic core samples were prepared and their characteristics were compared. In the powder magnetic core as a sample, calcium stearate was used as a lubricant, and the addition amount was 0.5 wt% with respect to the soft magnetic powder. A plurality of samples were prepared by changing the amount of aluminum tripolyphosphate powder, and Examples 1 to 6 and Comparative Example 1 were used according to the amount of aluminum tripolyphosphate powder. These production methods and the results are shown below in order.

As an insulating fine powder, Fe0.25Si powder having an average particle diameter of 27 μm is 0.25 to 1. 50 wt% aluminum tripolyphosphate was mixed. And as an insulation process, 0.5 wt% silicone oligomer was mixed with respect to the said mixture, and heat drying was performed at 200 degreeC for 1 hour. Furthermore, 0.8 wt% silicone resin was mixed, heat-dried at 150 ° C. for 2 hours, and passed through a sieve having an opening of 300 μm to prepare granulated powder. And 0.5 wt% calcium stearate was mixed with the granulated powder as a lubricant.

  The granulated powder mixed with the lubricant is pressure-molded at a temperature of 15 ton / cm 2 at room temperature to produce a ring-shaped molded body having an outer diameter of 16.5 mm, an inner diameter of 11.0 mm, and a height of 5.0 mm. Heat treatment was performed at 850 ° C. for 2 hours in an atmosphere to prepare a dust core.

  With respect to these samples, as shown in the above “measurement item”, a reactor was prepared, and permeability, iron loss calculation, and density measurement were performed. Thereafter, each sample was subjected to a high temperature and high humidity (85 ° C., 85%) test for 500 hours, and the magnetic permeability and iron loss were calculated again.

Table 2 shows the percentage of definitive calcium stearate in Example 7 to 1, 500 hours of high-temperature high-humidity permeability through the test μ and iron loss of the rate of change Pcv (%), indicating the density.
[Table 2]

  Moreover, the table which shows the correlation of the addition amount of aluminum tripolyphosphate, magnetic permeability, iron loss, and density from Table 2 was created as FIGS.

From Table 2 and Figure 6, Oite in Example 7 to 1 using tripolyphosphate aluminum powder as a powder of the insulating powder layer, the rate of change of the magnetic permeability μ is -4.8～-2.4% I understand that. This is because, in all samples, by using aluminum tripolyphosphate powder of 0.25 wt% or more, the change rate μ of the permeability becomes −5.0% or less, and the change rate of the permeability even when used for a long time. It becomes possible to produce a dust core having a small μ.

Table from 2 and 7, Oite in Example 7 to 1 using tripolyphosphate aluminum powder as a powder of the insulating powder layer, the rate of change Pcv iron loss 2. It turns out that it will be 1-5.0. This is because the iron loss change rate Pcv becomes 5.0% or less by using aluminum tripolyphosphate powder of 0.25 wt% or more in all samples, and the iron loss change rate Pcv even when used for a long time. It is possible to produce a dust core with a small diameter.

  On the other hand, as shown by the density items in FIG. 8 and Table 2 focusing on the density, the density is lowered by increasing the amount of the aluminum tripolyphosphate powder added. For both the permeability change rate and the iron loss change rate, there is no difference in the change rate between the amount of aluminum tripolyphosphate powder of 1.00 wt% and that of 1.50 wt%, or the amount of aluminum tripolyphosphate powder is The case of 1.50 wt% is larger. That is, even if the amount of aluminum tripolyphosphate powder exceeds 1.50 wt, it is presumed that the rate of change in magnetic permeability and the rate of change in iron loss do not decrease. In other words, it can be seen that when the aluminum tripolyphosphate powder is added in order to reduce the rate of change of magnetic permeability and the rate of change of iron loss, the preferred range is 0.25 to 1.50.

  As described above, in the dust core made of the soft magnetic material using the aluminum tripolyphosphate powder as the powder of the insulating powder layer and using 0.5 wt% calcium stearate as the lubricant, 0.25 to 1.50 wt. By forming an insulating powder layer of aluminum tripolyphosphate powder, it is possible to produce a dust core having a small permeability change rate μ and iron loss change rate Pcv even when used for a long time.

[1-3. Action / Effect]
(1) The soft magnetic material of the present embodiment includes a soft magnetic powder whose periphery is covered with an insulating layer, and a lubricant added to the soft magnetic powder. The lubricant is 0 with respect to the soft magnetic powder. .1 to 0.5 wt% calcium stearate. The calcium stearate contained in the lubricant becomes calcium oxide and remains in the powder magnetic core through an annealing process at a high temperature. Calcium oxide in the powder magnetic core prevents rust from occurring in the core due to the hygroscopic action of calcium oxide, and prevents deterioration of the core characteristics due to rust. That is, calcium stearate not only serves as a lubricant during the molding process, but also becomes calcium oxide after molding and serves as a hygroscopic agent. If an additional additive is added to prevent rust, the density of the core decreases, but this problem does not occur when calcium stearate is used. As a result, in a dust core made of a soft magnetic material containing calcium stearate as a lubricant, it is possible to produce a dust core having a small iron loss change rate Pcv even when used for a long time.

(2) Even if calcium stearate is used alone or in combination with other lubricants, the effect of (1) can be achieved. That is, even if the proportion of calcium stearate in the lubricant in the soft magnetic material is 20 to 100%, it is possible to produce a dust core having a small iron loss change rate Pcv even when used for a long time. In addition, the amount of lubricant added to the soft magnetic material is one standard of 0.5 wt% with respect to the soft magnetic powder. Even when 0.5 wt% of this lubricant is added, calcium stearate in the lubricant is used. By making the ratio of 20 to 100%, it becomes possible to produce a dust core having a small change rate Pcv of iron loss even when used for a long time.

(3) The soft magnetic powder material of the present embodiment may include a silicone oligomer layer that covers the outside of the soft magnetic powder and a silicone resin layer that covers the outside of the silicone oligomer layer. By forming the silicone oligomer layer on the outside of the soft magnetic powder, it is possible to form a thick insulating coating layer having a strong mechanical bonding force. Moreover, the film excellent in flexibility can be formed by forming the silicone resin layer outside the silicone oligomer layer. The silicone oligomer layer may be a solidified methyl or methylphenyl silicone oligomer.

(4) An insulating powder layer distributed uniformly around the soft magnetic powder may be included, and the silicone oligomer layer and the silicone resin layer may cover the insulating powder layer. By using a part or all of the insulating powder as the inorganic insulating powder, it is possible to insulate between the soft magnetic powders and increase the heat treatment temperature. On the other hand, by using a part or all of the insulating powder as aluminum tripolyphosphate powder, it is possible to prevent deterioration of the magnetic permeability of the dust core and deterioration of hysteresis loss.

(5) When the insulating powder is an aluminum tripolyphosphate powder, the addition amount of the aluminum tripolyphosphate powder is preferably 0.25 to 1.50 wt% with respect to the soft magnetic powder. An insulating powder layer of 0.25 to 1.50 wt% aluminum tripolyphosphate powder is formed with respect to the soft magnetic powder, and a pressure produced from a soft magnetic material using 0.1 to 0.5 wt% calcium stearate as a lubricant. Even when the powder magnetic core is used for a long time, the magnetic permeability change rate μ and the iron loss change rate Pcv can be reduced.

[2. Other Embodiments]
The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment.

(1) In the present embodiment, soft magnetic powder having an average particle diameter (D50) of 20 μm to 150 μm is used. In addition, a plurality of magnetic powders having different average particle diameters may be used. For example, it may be composed of two kinds of magnetic powders having different average particle diameters, or three or more kinds of soft magnetic powders may be mixed. For example, when a soft magnetic powder of 20 μm to 150 μm is used as the first soft magnetic powder, a second soft magnetic powder having an average particle size smaller than that of the first soft magnetic powder is compared with the first soft magnetic powder. It can also be used as a mixture. The average particle diameter of the second soft magnetic powder is preferably 5 μm to 10 μm. By mixing two kinds of magnetic powders having different average particle diameters, the second magnetic powder having a small average particle diameter enters the gap between the first magnetic powders. Thereby, improvement of density and magnetic permeability and reduction of iron loss can be achieved. In addition, the second soft magnetic powder is preferably spherical, like the first magnetic powder, and the circularity of the second magnetic powder is preferably 0.94 or more. This is because more second magnetic powder can easily enter the gap between the first magnetic powders, and the density and permeability can be improved. The 2nd magnetic powder can use what was manufactured by the gas atomization method, the water atomization method, or the water gas atomization method. The average circularity of the particles formed by these methods is preferably 0.90 or more, and when a powder having an average circularity of 0.90 or more cannot be formed only by various atomization methods, the average circularity of the particles is further increased. You may give the process which raises a degree.

  (2) In the present embodiment, the soft magnetic powder on which the insulating powder layer is formed is covered with two types of insulating coating layers of a silicone oligomer and a silicone resin. However, the kind of the film forming the insulating film layer is not limited to this. For example, you may form two types of insulating coating layers other than a silicone oligomer and a silicone resin. In addition, the insulating coating layer is a double insulating coating layer composed of a silicone oligomer and a silicone resin, but it may be a triple or more insulating coating layer, or from either one of the silicone oligomer and the silicone resin insulating coating layer. It may be formed.

Claims (6)

Soft magnetic powder with an insulating layer around it,
A lubricant added to the soft magnetic powder;
With
The lubricant is to the soft magnetic powder 0. Look containing a 5 wt% of calcium stearate,
The insulating layer is
An insulating powder layer uniformly distributed around the soft magnetic powder;
A silicone oligomer layer covering the outside of the insulating powder layer;
A silicone resin layer covering the outside of the silicone oligomer layer;
Including
Part or all of the insulating powder layer is aluminum tripolyphosphate powder,
The amount of the aluminum tripolyphosphate powder added is 1.0 to 1.5 wt% with respect to the soft magnetic powder,
Soft magnetic material characterized by The addition amount of the lubricant is 0.5 wt% with respect to the soft magnetic powder,
The soft magnetic material according to claim 1, wherein a ratio of the calcium stearate in the lubricant is 100 %. The silicone oligomer layer is a soft magnetic material according to claim 1 or 2, characterized in that the solidified methyl-based or methyl phenyl-based silicone oligomer. A dust core using the soft magnetic material according to any one of claims 1 to 3 ,
A dust core containing calcium oxide. A reactor in which a coil is wound around the dust core according to claim 4 . The Rukoto to uniformly disperse the 1.0～1.5Wt% of tripolyphosphate aluminum powder with respect to the soft magnetic powder around the soft magnetic powder, an insulating powder layer forming step of forming an insulating powder layer,
A silicone oligomer layer forming step of mixing a silicone oligomer with a soft magnetic powder in which the insulating powder is uniformly dispersed and drying to form a silicone oligomer layer;
A silicone resin layer forming step of mixing a silicone resin with the soft magnetic powder on which the silicone oligomer layer is formed, and drying to form a silicone resin layer;
Calcium stearate is added to the soft magnetic powder having the silicone resin layer formed thereon in an amount of 0 . A lubricant mixing step of mixing 5 wt % ;
A molding step for producing a compact by subjecting the soft magnetic powder that has undergone each of the above steps to pressure molding, and
The manufacturing method of the powder magnetic core which has.

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