JP2019179919A - Method for manufacturing powder-compact magnetic core - Google Patents

Abstract

To provide a method for manufacturing a powder-compact magnetic core which is low in loss and superior in direct current superposing property, and which is arranged so as to suppress the increase in hysteresis loss caused by distortion and the decrease in magnetic permeability by increasing a thermal treatment temperature.SOLUTION: The method for manufacturing a powder-compact magnetic core comprises: a silicone oligomer layer-forming step of mixing soft magnetic powder with a silicone oligomer, followed by drying; a silicone resin layer-forming step of mixing a silicone resin in the resultant soft magnetic powder with a silicone oligomer layer formed thereon, followed by drying; a compacting step of press-compacting the soft magnetic powder having gone through the respective steps into a compact; and a thermal treatment step of performing a thermal treatment on the compact at 600°C or higher to manufacture the powder-compact magnetic core. In the method, the soft magnetic powder is Fe-Si alloy; an addition amount of the silicone oligomer is 0.15-3.5 wt% to the soft magnetic powder; the temperature of drying the silicone oligomer is over 160°C up to 350°C; and the silicone oligomer is a methyl-based or methylphenyl-based silicone oligomer.SELECTED DRAWING: Figure 1

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 in energy exchange efficiency and low heat generation. Specifically, the magnetic characteristic relating to the magnetic flux density is magnetic permeability (μ). Specifically, the magnetic characteristic regarding energy loss is 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. When the hysteresis loss increases, the loss as a whole increases, and the saturation magnetic flux density decreases, so that the direct current superimposition characteristics deteriorate. Therefore, it is preferable to apply a heat treatment for removing this, and for sufficient removal, a heat treatment at a high temperature of about 700 ° C. or higher is preferable.

  On the other hand, if the heat treatment temperature is raised too much, the insulating coating between the soft magnetic powders is broken or disappeared, thereby causing dielectric breakdown between the soft magnetic powders. Therefore, in order to realize heat treatment at a high temperature, it is necessary that the insulating coating between the soft magnetic powders is maintained without being destroyed or lost even at a high temperature. For that purpose, as described below, it was considered that the mechanical bonding force and the film thickness of the insulating coating were important.

  The soft magnetic powder used for the dust core is a soft powder, and the particles are crushed and flattened during molding at a high pressure. If the insulating coating of the dust core has a weak mechanical coupling force, it is crushed together with the soft magnetic powder during molding, and the insulating coating is damaged or torn. When the powder magnetic core is heat-treated at a high temperature while the insulating coating is damaged or lacerated, the insulating coating is destroyed or lost, and the dielectric breakdown occurs between the soft magnetic powders. Thus, in order to raise the heat treatment temperature, it is preferable to use an insulating film having a strong mechanical bonding force.

  A thin film of the insulating coating is easily destroyed or lost by thermal decomposition in the heat treatment step, and the dielectric breakdown is liable to occur between the soft magnetic powders. That is, heat treatment must be performed at a low temperature that is not thermally decomposed, and the heat treatment temperature cannot be increased. From the above, it is preferable that the insulating coating formed on the dust core has a strong mechanical coupling force and a large film thickness.

  Conventionally, for example, a coating made of a silicone resin and a silane coupling agent described in Patent Document 1 has been used as the insulating coating. The silicone resin is a polymer having a siloxane bond as a main skeleton, has a strong mechanical bonding force, and forms a thick film. However, the silane coupling agent layer inside the silicone resin layer has a small molecular weight and a thin film thickness. In addition, the silane coupling agent layer has a weak mechanical bonding force and cannot withstand high pressure molding. For this reason, the heat treatment temperature cannot be increased with the coating of the silicone resin and the silane coupling agent described in Patent Document 1.

  Patent Document 2 proposes a film in which an insulating film containing hydrated water and a silicone resin film are combined. In the coating of Patent Document 2, an insulating layer having a strong mechanical bonding force and a large film thickness is not formed inside the silicone resin coating. Therefore, the method for producing a soft magnetic material disclosed in Patent Document 2 cannot increase the heat treatment temperature of the dust core. Actually, in the example of Patent Document 2, the heat treatment temperature is set to 600 ° C., which is not sufficiently high.

Patent Document 3 describes an anti-aggregation powder composed of at least one of magnesium oxide (MgO), titanium oxide (TiO ₂ ), or alumina (Al ₂ O ₃ ), and an insulating coating composed of a binder (alkoxy oligomer). Has been. The insulating coating of Patent Document 3 uses an inorganic insulating powder, but its purpose is to prevent aggregation of the magnetic powder and does not form an insulating coating. In addition, a thick silicone resin layer is not formed on the outside of the metal powder. Therefore, the thickness of the insulating coating is thin as a whole. Therefore, the heat treatment temperature cannot be increased with the insulating film made of the powder for pressure molding disclosed in Patent Document 3.

  The present invention has been made to solve the above-described problems, and its purpose is to realize a high heat treatment temperature in the heat treatment process, to reduce hysteresis loss by removing strain in the soft magnetic powder, and to achieve saturation. It is to increase the magnetic flux density. Thereby, the manufacturing method of the powder magnetic core which reduced the loss and improved the direct current superposition characteristic can be provided.

  The inventor of the present invention has found a silicone oligomer as a material for an insulating film having a strong mechanical bonding force and a large film thickness. Silicone oligomers have a main skeleton that is a siloxane bond and a strong mechanical bond. 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.

  The method of manufacturing a dust core according to the present invention includes a step of mixing a silicone oligomer with a soft magnetic powder and drying to form a silicone oligomer layer, and a mixing of a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon. A step of forming a silicone resin layer, a molding step of forming the molded body by pressure-molding the soft magnetic powder that has undergone the respective steps, and a molded body that has undergone the molding step of 600 ° C. A heat treatment step for heat treatment, wherein the soft magnetic powder is an Fe-Si alloy, and the addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder, The drying temperature of the silicone oligomer is higher than 160 ° C. and lower than 350 ° C., and the silicone oligomer is a methyl or methylphenyl silicone oligomer. It is characterized by.

  The method of manufacturing a dust core according to the present invention includes a step of mixing a silicone oligomer with a soft magnetic powder and drying to form a silicone oligomer layer, and a mixing of a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon. A step of forming a silicone resin layer, a molding step of forming the molded body by pressure-molding the soft magnetic powder that has undergone the respective steps, and a molded body that has undergone the molding step of 600 ° C. A heat treatment step for heat treatment, wherein the soft magnetic powder is pure iron, and the addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder, and the silicone oligomer The drying temperature is higher than 160 ° C. and lower than 300 ° C., and the silicone oligomer is a methyl or methylphenyl silicone oligomer. , Characterized by.

  The method of manufacturing a dust core according to the present invention includes a step of mixing an inorganic insulating powder in a soft magnetic powder and attaching the inorganic insulating powder to the surface of the soft magnetic powder, and the inorganic insulating powder attached to the surface. A step of mixing a silicone oligomer with a soft magnetic powder and drying to form a silicone oligomer layer, and a step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer A step of forming a molded body by subjecting the soft magnetic powder that has undergone the respective steps to a pressure molding process, and a heat treatment step of heat-treating the molded body that has undergone the molding step at 700 ° C. or higher. The soft magnetic powder is an Fe-Si alloy, and the amount of the silicone oligomer added is 0.15 to 3.5 wt% with respect to the soft magnetic powder. Drying temperature of mer is not less 160 ° C. Ultra 350 ° C. or less, the silicone oligomer, it is a silicone oligomer methyl-based or methylphenyl system, characterized by.

  The method of manufacturing a dust core according to the present invention includes a step of mixing an inorganic insulating powder in a soft magnetic powder and attaching the inorganic insulating powder to the surface of the soft magnetic powder, and the inorganic insulating powder attached to the surface. A step of mixing a silicone oligomer with a soft magnetic powder and drying to form a silicone oligomer layer, and a step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer A step of forming a molded body by subjecting the soft magnetic powder that has undergone the respective steps to a pressure molding process, and a heat treatment step of heat-treating the molded body that has undergone the molding step at 700 ° C. or higher. The soft magnetic powder is pure iron, and the addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder. Temperature is at 160 ° C. Ultra 300 ° C. or less, the silicone oligomer, it is a silicone oligomer methyl-based or methylphenyl system, characterized by.

  According to the present invention as described above, even if the heat treatment is performed at a high temperature of 600 ° C. or higher, the insulating film is not broken or burned out. By realizing a high heat treatment temperature, strain in the soft magnetic powder can be removed, hysteresis loss can be reduced, and saturation magnetic flux density can be increased. 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.

The flowchart which shows the manufacturing method of the powder magnetic core which concerns on one Embodiment of this invention. In Examples 1-7 of this invention and Comparative Examples 1-4, the graph which showed the relationship between the heat processing temperature at the time of changing the kind of material which comprises a 2nd insulating layer, and loss. The graph which showed the ratio of the magnetic permeability with respect to the intensity | strength of a magnetic field about Examples 2-6 and Comparative Example 16 of this invention. The graph which showed the relationship between the silicone oligomer addition amount and loss when the addition amount of a silicone oligomer was changed in Examples 8-11 and Comparative Examples 5-8 of this invention. The graph which showed the relationship between the drying temperature and loss of a silicone oligomer at the time of changing the drying temperature of a silicone oligomer in Examples 8-11 of this invention, and Comparative Examples 5-8. The graph which showed the relationship between the drying temperature of a silicone resin, and loss when the drying temperature of a silicone resin was changed in Examples 12-15 of this invention, and Comparative Examples 9 and 10. FIG. In Examples 16-18 of this invention, and the comparative example 11, the graph which showed the ratio of the magnetic permeability with respect to the intensity | strength of a magnetic field in the case of changing the drying temperature of a silicone resin. In Examples 19-21 of this invention, and the comparative example 14, the graph which showed the relationship between the specific surface area and loss at the time of changing the specific surface area of an inorganic insulating powder. In Example 22 of this invention and Comparative Example 15, the graph which showed the ratio of the magnetic permeability with respect to the intensity | strength of a magnetic field at the time of changing classification of a sieve. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Example 23 and Comparative Example 16. The graph which shows the ratio of the magnetic permeability with respect to the magnetic field intensity of Example 24 and Comparative Example 17. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Example 25 and Comparative Example 18. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Examples 23, 26, and 27 and Comparative Example 16. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Examples 24, 28, and 29 and Comparative Example 17. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Examples 25, 30, and 31 and Comparative Example 18. The graph which shows the ratio of the magnetic permeability with respect to the intensity | strength of the magnetic field of Examples 23 and 32-36 and the comparative example 16. FIG. The graph which shows the ratio of the magnetic permeability with respect to the intensity | strength of the magnetic field of Example 25, 37-41, and the comparative example 18. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Examples 23, 42-45, and the comparative example 16. FIG. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Example 25, 45-48, and the comparative example 18. FIG. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Examples 23 and 49. FIG. The graph which shows the ratio of the magnetic permeability with respect to the strength of the magnetic field of Examples 24 and 50. FIG.

[1. 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 inorganic insulating powder adhering step (step 1) in which an inorganic insulating powder is mixed with an inorganic insulating powder to the soft magnetic 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 inorganic 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) A molding step (step 4) in which the soft magnetic powder that has undergone the above-described step is subjected to pressure molding treatment to produce a molded body.
(5) A heat treatment step (step 5) of heat-treating the molded body that has undergone the molding step at 700 ° C. or higher.
Hereafter, each process is demonstrated concretely.

(1) Inorganic insulating powder adhering step In the inorganic insulating powder adhering step, soft magnetic powder and inorganic insulating powder are mixed. Mixing is performed using a mixer (W type, V type), a pot mill or the like, and at this time, mixing is performed so that internal strain does not enter the powder. As described above, the inorganic insulating powder layer can be adhered to the surface of the soft magnetic powder. By attaching the inorganic insulating powder to the surface of the soft magnetic powder, the soft magnetic powder can be insulated and the heat treatment temperature can be increased.

  The inorganic insulating powder may be attached in the form of dots dispersed on the surface of the soft magnetic powder, or in the case of being dispersed and attached in a lump on the surface of the soft magnetic powder. The case where it adheres, forming the layer of an inorganic insulating powder so that the surface or 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.

(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 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.

(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 0.5 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 the magnetic properties other than the eddy current loss are deteriorated. If these problems do not occur, the inorganic insulating powder deposition step is not necessarily required.

(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 to which the inorganic insulating powder is adhered, 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.

(Silicone oligomer)
Silicone oligomers can be methyl-based or methylphenyl-based having alkoxysilyl groups and no reactive functional groups, and epoxy-based, epoxymethyl-based, mercapto-based, mercapto-based compounds having alkoxysilyl groups and reactive functional groups. Methyl-based, acrylmethyl-based, methacrylmethyl-based, vinylphenyl-based, alicyclic epoxy-based compounds having a reactive functional group without having an alkoxysilyl group can be used. In particular, a thick and hard insulating layer can be formed by using a methyl or methylphenyl silicone oligomer. In view of the ease of the silicone oligomer layer forming step, methyl or methylphenyl having a relatively low viscosity may be used. More specifically, silicone oligomers A to E shown in Table 8 below can be used as silicone oligomers having a relatively low viscosity.

  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 between the soft magnetic powders is likely. For example, when inorganic insulating powder is adhered to the surface of Fe-Ni alloy powder, Fe-Si alloy powder or pure iron powder, even if the distribution is uniform before the heat treatment step, the distribution varies after the heat treatment step. It is thought that has occurred. 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 to 3.5 wt% with respect to the soft magnetic powder, and 0.5 to 1.25 wt% when the soft magnetic powder is Fe—Ni alloy powder. It is more preferable that When the soft magnetic powder is Fe-Si alloy powder or pure iron powder, it is more preferably 0.15 to 3.5 wt%. If the addition amount is less than 0.15 wt%, it does not function as an insulating film, and eddy current loss increases, resulting in deterioration of magnetic characteristics. When the addition amount is more than 3.5 wt%, the core expands to lower the density of the molded body and lower the magnetic permeability.

  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 2 hours.

(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.

(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 1.0 to 1.5 wt% with respect to the soft magnetic powder. If the addition amount is less than 1.0 wt%, it will not function as an insulating film, and eddy current loss will increase, resulting in deterioration of 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 300 ° 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.

(4) Molding step In the molding step, a compact is formed by pressure molding soft magnetic powder having an insulating coating formed on the surface. 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, an insulating film coated with soft magnetic powder at 700 ° C. or higher in N ₂ gas or N ₂ + H ₂ gas non-oxidizing atmosphere is applied to the molded body that has undergone the molding step. A powder magnetic core is produced by performing a heat treatment at a temperature at which the material is destroyed (for example, 850 ° C.) or less. 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 to 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 1 to 22 and Comparative Examples 1 to 15 of the present invention will be described below with reference to Tables 1 to 6 and FIGS.
[1. Measurement item]
As measurement items, permeability and loss were measured by the following methods. The magnetic permeability was calculated from the inductance at 10 kHz and 0.5 V by applying a primary winding (20 turns) to the produced dust core and using an impedance analyzer (Agilent Technology: 4294A).

  Loss is determined by applying a primary winding (20 turns) and a secondary winding (3 turns) to the dust core, and using a BH analyzer (Iwatori Measurement Co., Ltd .: SY-8232) as a magnetic measurement device. Iron loss (Pcv) was measured under the conditions of 100 kHz and maximum magnetic flux density Bm = 0.1T. And hysteresis loss (Ph) and eddy current loss (Pe) were calculated from the loss. This calculation was performed by calculating a hysteresis loss coefficient (Kh) and an eddy current loss coefficient (Ke) by the least square method using the following frequency equations (1) to (3).

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

In this example, the average particle diameter and the circularity of each powder are the average values of 3000 using the following apparatus, and the powder is dispersed on a glass substrate, and a powder photograph is taken with a microscope. It was measured automatically from the image every time.
Company name: Malvern
Device name: morphologic G3S
The specific surface area was measured by the BET method.

[2. First characteristic comparison (comparison of dielectric breakdown temperature depending on the type of material constituting the insulating layer)]
In the first characteristic comparison, dielectric breakdown temperatures were compared by changing the type of material constituting the insulating layer. In Examples 1 to 7, a silicone oligomer layer was formed as an insulating layer. In Comparative Examples 1 to 4, a silane coupling agent layer was formed as the insulating layer.

Samples used in Examples 1 to 7 were prepared as follows. In the following description, “wt%” indicates a weight ratio with respect to the soft magnetic powder.
(1) Soft magnetic powder made of permalloy (Fe50Ni) having an average circularity of 0.97 was produced by a water atomization method. Thereafter, sieving was performed with a 200-th sieve (aperture 75 μm), and the average particle size was set to 33.2 μm.
(2) with respect to the soft magnetic powder prepared, the specific surface area was mixed 0.75 wt% of alumina powder of 130m ² / g.
(3) 1 wt% of the methyl-based silicone oligomer A shown in Table 8 was mixed with these, followed by heat drying at 300 ° C. for 2 hours.
(4) 1.5 wt% of methylphenyl silicone resin (product name: TSR-108) was mixed with the dried powder, followed by heat drying at 300 ° C. for 2 hours in an air atmosphere.
(5) 30 th meshes (aperture 500 μm) were passed through for the purpose of crushing the lump generated after heat drying. Thereafter, 0.6 wt% of ethylene bis stearate amide was mixed as a lubricant.
(6) The soft magnetic powder with the insulating coating formed by the above process was filled into a toroidal container having an outer diameter of 17 mm, an inner diameter of 11 mm, and a height of 8 mm, and a molded body was produced at a molding pressure of 15 ton / cm ² .
(7) Finally, the compact was heat-treated in a nitrogen atmosphere at different heat treatment temperatures of 550 ° C. to 850 ° C. to produce a dust core.

The samples used in Comparative Examples 1 to 4 were subjected to the following steps in place of the steps (2), (3) and (4) of the above-mentioned Example.
(1) The produced soft magnetic powder was mixed with 0.75 wt% of alumina powder having a specific surface area of 65 m ² / g.
(2) 0.5 wt% of silane coupling agent (γ-aminopropyltriethoxysilane) and 1.5 wt% of methylphenyl silicone resin (product name: TSR-108) are mixed with these in the atmosphere. And heat drying at 150 ° C. for 2 hours.

  Table 1 is a table showing the magnetic properties of the dust cores when the dust cores of Examples 1 to 7 and Comparative Examples 1 to 4 were processed at different heat treatment temperatures of 550 ° C to 850 ° C. FIG. 2 is a graph showing the relationship between heat treatment temperature and loss for Examples 1 to 7 and Comparative Examples 1 to 4. FIG. 3 is a graph showing the ratio of magnetic permeability to magnetic field strength for Examples 2 to 6 and Comparative Example 16 treated at a heat treatment temperature of 600 ° C. to 800 ° C. The strength of the magnetic field is obtained by measuring the strength of the magnetic field generated when a coil is wound around the dust core and a current is passed. The magnetic permeability is the amplitude magnetic permeability, and was calculated from the inductance of the strength of each magnetic field at 20 kHz and 1.0 V by using the impedance analyzer described above. The magnetic permeability ratio is defined as the magnetic permeability at 0H (A / m) in each magnetic field, where the magnetic permeability is 100% when DC is not superimposed (when the magnetic field strength is 0H (A / m)). Shows the rate of change. In Comparative Example 16, the heat treatment temperature was set to 500 ° C., and the other temperature was the same as Comparative Examples 1 to 4.

  As shown in Table 1 and FIG. 2, the eddy current loss (Pe) of Examples 1 to 7 tends to increase slightly until the heat treatment temperature reaches 800 ° C., but increases significantly when the heat treatment temperature reaches 850 ° C. I understood it. This is thought to be due to dielectric breakdown occurring between the powder particles when the heat treatment temperature reaches 850 ° C. It was also found that the hysteresis loss (Ph) tends to decrease as the heat treatment temperature is increased. This is considered to be due to the fact that the distortion inside the soft magnetic powder is removed by heat treatment at a high temperature. Also, as shown in FIG. 3, for Examples 2 to 4 where the heat treatment temperature is relatively low, Comparative Example 19 is higher on the low magnetic field side, but becomes the same as the higher magnetic field side, and the heat treatment temperature is the same. In comparatively high Examples 5 and 6, the ratio of magnetic permeability is higher than that of Comparative Example 19 at all magnetic field strengths.

  On the other hand, it was found that the eddy current loss (Pe) of Comparative Examples 1 to 4 significantly increased when the heat treatment temperature reached 700 ° C. That is, in Comparative Examples 1-4, it turned out that the dielectric breakdown between powder particles has occurred at 700 degreeC.

  From the first characteristic comparison, it was found that Examples 1 to 7 in which the silicone oligomer layer was formed can realize a higher heat treatment temperature. This is considered to be due to the fact that the insulating coating is retained even at a high heat treatment temperature by forming a silicone oligomer layer having a strong mechanical bonding force and a large film thickness as the insulating coating. By increasing the heat treatment temperature to 800 ° C., the hysteresis loss of the core is reduced and the saturation magnetic flux density can be increased. Thereby, it is possible to provide a dust core having low loss and excellent direct current superposition characteristics.

[3. Second characteristic comparison (comparison according to the amount of silicone oligomer added)]
In the second characteristic comparison, the magnetic characteristics of the dust cores were compared by changing the amount of silicone oligomer added to the soft magnetic powder. Examples 8 to 11 and Comparative Examples 5 to 8 were prepared in which the amount of silicone oligomer added was 0.00 wt% to 1.50 wt%.

The samples used in Examples 8 to 11 and Comparative Examples 5 to 8 are replaced with the production steps (2), (3), (4), and (7) of Examples 1 to 7 in the first characteristic comparison. The following steps were performed.
(1) 0.75 wt% of alumina powder having a specific surface area of 100 m ² / g was mixed with the produced soft magnetic powder.
(2) To these, 0.001 to 1.50 wt% of a methyl silicone oligomer A shown in Table 8 below was mixed, followed by heat drying at 300 ° C. for 2 hours in an air atmosphere.
(3) 1.0 wt% of methylphenyl silicone resin (product name: TSR-108) was mixed with the dried powder, followed by heat drying at 250 ° C. for 2 hours in an air atmosphere.
(4) Finally, the compact was heat-treated at a heat treatment temperature of 800 ° C. to produce a dust core.

  Table 2 shows the relationship between the amount of the silicone oligomer added to the soft magnetic powder and the magnetic properties of the dust core in this example. In FIG. 4, the horizontal axis indicates the amount of silicone oligomer added, and the vertical axis indicates loss (Pcv, Ph, Pe).

As shown in Table 2, it was found that the loss was reduced as the amount of silicone oligomer added increased. Further, as shown in FIG. 4, it has been found that the loss is reduced particularly when the addition amount of the silicone oligomer is 0.5 wt% or more. It was found that when the amount of the silicone oligomer added was 0.5 wt% or more, the eddy current loss (Pe) was 390 (kW / m ³ ) or less, which was sufficiently reduced. This means that insulation between powder particles is ensured without causing dielectric breakdown even under high temperature conditions.

  It was also found that when the amount of silicone oligomer added was 1.50 wt%, the density was lowered. When the density is lowered, the magnetic permeability is lowered and the magnetic properties are lowered. This is considered to be that when the silicone oligomer is excessively added, the density of the molded body is lowered due to expansion of the core.

  From the above, it was found that the addition amount of the silicone oligomer is preferably 0.50 wt% to 1.25 wt%. By setting the addition amount in the above range, it is possible to provide a dust core having a reduced loss and a high density and magnetic permeability of the molded body and a method for producing the same.

[4. Third characteristic comparison (comparison by drying temperature of silicone oligomer)]
In the third characteristic comparison, the magnetic characteristics of the dust cores were compared by changing the drying temperature of the silicone oligomer. As Examples 12 to 15 and Comparative Examples 9 and 10, the magnetic properties of dust cores having a silicone oligomer drying temperature of 150 to 400 ° C. were measured.

The samples used in Examples 12 to 15 and Comparative Examples 9 and 10 were subjected to the following steps in place of the production steps (3) and (7) of Examples 1 to 7 in the first characteristic comparison.
(1) 1 wt% of silicone oligomer (methyl) was mixed with these, and heat drying was performed at 150 ° C. to 400 ° C. shown in Table 3 for 2 hours in an air atmosphere.
(2) Finally, the compact was heat-treated at a heat treatment temperature of 800 ° C. to produce a dust core.

  Table 3 is a table showing the relationship between the drying temperature of the silicone oligomer and the magnetic properties of the dust core in this example. FIG. 5 is a graph showing the relationship between the drying temperature and loss of the silicone oligomer.

As shown in Table 3 and FIG. 5, compared to Examples 12 to 15 where the drying temperature of the silicone oligomer is 200 ° C. to 350 ° C., Comparative Example 9 which is 150 ° C. and Comparative Example 10 which is 400 ° C. It turns out that the loss has increased. In particular, for Comparative Example 10 at 400 ° C., the hysteresis loss (Ph) has increased significantly to 600 (kW / m ³ ). For this reason, it has been found that the drying temperature of the silicone oligomer is preferably 200 ° C to 350 ° C.

  From the above, it has been found that the drying temperature of the silicone oligomer is preferably 200 ° C to 350 ° C. By setting the drying temperature within the above range, it is possible to provide a dust core capable of reducing loss and a method for manufacturing the same.

[5. Fourth characteristic comparison (comparison by drying temperature of silicone resin)]
In the fourth characteristic comparison, the magnetic characteristics of the dust cores were compared by changing the drying temperature of the silicone resin. As Examples 16 to 18 and Comparative Examples 11 to 13, the magnetic properties of the dust cores in which the drying temperature of the silicone resin was 175 ° C. to 400 ° C. were measured.

The samples used in Examples 16 to 18 were subjected to the following steps in place of the production step (4) of Examples 1 to 7 in the first characteristic comparison.
(1) 1.5 wt% of methylphenyl silicone resin was mixed and heat-dried at 150 ° C. to 400 ° C. shown in Table 4 for 2 hours in an air atmosphere.
(2) Finally, the compact was heat-treated at a heat treatment temperature of 800 ° C. to produce a dust core.

  Table 4 is a table showing the relationship between the drying temperature of the silicone resin and the magnetic properties of the dust core in this example. FIG. 6 is a graph showing the relationship between the drying temperature and loss of the silicone resin. FIG. 7 is a graph showing the ratio of magnetic permeability to magnetic field strength for a silicone resin having a drying temperature of 175 ° C. to 300 ° C.

As shown in Table 4 and FIG. 6, it was found that the loss of Comparative Example 11 at 175 ° C. was increased compared to Examples 16 to 18 where the drying temperature of the silicone oligomer was 200 ° C. to 300 ° C. . Moreover, about the comparative example 13 whose drying temperature is 400 degreeC, it turned out that the loss has increased significantly to 720 (kW / m < ³ >). In particular, it has been found that the loss is most reduced when the drying temperature is 300 ° C. For this reason, it has been found that the drying temperature of the silicone resin is preferably 200 ° C to 300 ° C.

  As shown in FIG. 7, the magnetic permeability ratio tends to decrease as the magnetic field increases, but Examples 16 to 18 having a drying temperature of 200 ° C. or higher as compared with Comparative Example 11 having a drying temperature of 175 ° C. It has been found that the lowering of the permeability ratio is suppressed.

  From the above, it was found that the drying temperature of the silicone resin is preferably 200 ° C to 300 ° C. By setting the drying temperature within the above range, it is possible to provide a dust core that can reduce loss and suppress a decrease in the magnetic permeability ratio and a method for manufacturing the same.

[6. Fifth characteristic comparison (comparison by specific surface area of inorganic insulating powder)]
In the fifth characteristic comparison, the magnetic characteristics of the dust cores were compared by changing the specific surface area of the inorganic insulating powder added to the soft magnetic powder. In this characteristic comparison, magnetic characteristics were measured for Examples 19 to 21 and Comparative Example 14 to which alumina powders having different specific surface areas were added.

The samples used in Examples 19 to 21 and Comparative Example 14 were subjected to the following steps in place of the production steps (2) and (7) of Examples 1 to 7 in the first characteristic comparison.
(1) The produced soft magnetic powder was mixed with 0.75 wt% of alumina powder having a specific surface area of 50 to 130 m ² / g.
(2) Finally, the compact was heat-treated at a heat treatment temperature of 800 ° C. to produce a dust core.

  Table 5 shows the relationship between the specific surface area of the inorganic insulating powder added to the soft magnetic powder and the magnetic properties of the dust core in this example. FIG. 8 is a graph showing the relationship between the specific surface area of the inorganic insulating powder added to the soft magnetic powder and the loss.

As shown in Table 5 and FIG. 8, it was found that the loss of the powder magnetic core was smaller as the specific surface area of the inorganic insulating powder was larger. In particular, in Examples 19 to 21 The specific surface area was added an inorganic insulating powder 65~130m ² / g, as compared with Comparative Example 14 in which the specific surface area was added an inorganic insulating powder ^{50 m} 2 / g, hysteresis loss (Ph ) And eddy current loss (Pe) are reduced, and iron loss (Pcv) is reduced. For this reason, it turned out that 65-130 m < ² > / g is good for the specific surface area of the inorganic insulating powder mixed with soft-magnetic powder. The reason for this is considered that the larger the specific surface area of the inorganic insulating powder, the smaller the particle diameter, and the inorganic insulating powder enters between the soft magnetic powders without any gaps, and the strain at the time of compacting the magnetic core is reduced. .

From the above, it has been found that the specific surface area of the inorganic insulating powder added to the soft magnetic powder is preferably 65 to 130 m ² / g. By setting the specific surface area within the above range, it is possible to provide a low-loss powder magnetic core with reduced hysteresis loss (Ph) and eddy current loss (Pe) and a method for manufacturing the same.

[7. Sixth characteristic comparison (comparison by sieve classification)]
In the sixth characteristic comparison, the magnetic characteristics of the dust cores were compared by changing the classification of the sieves for sieving the soft magnetic powder produced by the gas atomization method. The classification was 150 (mesh 106 μm) as Comparative Example 15, and 200 (mesh 75 μm) was used as Example 22.

The samples used in Example 22 and Comparative Example 15 were subjected to the following steps in place of the production steps (1) and (7) of Examples 1 to 7 in the first characteristic comparison.
(1) A soft magnetic powder made of Fe50Ni having an average particle diameter of 45.4 μm and an average circularity of 0.99 was prepared by a gas atomization method.
(2) Thereafter, classification was performed at 150 (106 μm) or 200 (75 μm), and 0.6 wt% ethylene bis-stearate amide was mixed as a lubricant.
(3) Finally, the compact was heat-treated at a heat treatment temperature of 800 ° C. to produce a dust core.

  Table 6 is a table showing the relationship between classification and magnetic properties of the dust core in this example. FIG. 9 is a graph showing the ratio of magnetic permeability to magnetic field strength for Example 22 and Comparative Example 15.

As shown in Table 6, it was found that the loss was reduced in Example 22 in which the classification was 200 (75 μm) than in Comparative Example 15 in which the classification was 150 (106 μm). Further, as shown in FIG. 9, it was found that when the sieve classification is 200 (75 μm), the decrease in the ratio of the permeability in the strong magnetic field is suppressed. Further, when the sieve classification is 200 (75 μm), the increase in iron loss (Pcv) is suppressed as a whole, and in particular, the eddy current loss (Pe) is 273 (kW / m ³ ), and the increase is suppressed. I found out. Further, it has been found that even when a soft magnetic powder produced by the gas atomization method is used, magnetic characteristics equivalent to those of the soft magnetic powder produced by the water atomization method can be realized.

  From the above, it was found that the sieve classification is preferably 200 (75 μm). As a result, it is possible to provide a dust core in which loss is reduced and a decrease in the ratio of permeability in a strong magnetic field is suppressed, and a method for manufacturing the same.

[8. Seventh characteristic comparison (characteristic comparison by the difference in the kind of material of the insulating layer comprised with respect to Fe-Si alloy powder or pure iron powder)
In the seventh characteristic comparison, the iron loss and DC superposition characteristics of the dust cores were compared by changing the type of material constituting the insulating layer formed on the surface of the soft magnetic powder. In Examples 23 to 25, a silicone oligomer layer was formed as an insulating layer on the surface of the soft magnetic powder, and in Comparative Examples 16 to 18 a silane coupling agent layer was formed as an insulating layer on the surface of the soft magnetic powder.

The sample used in Example 23 was prepared as follows.
(1) A soft magnetic powder made of an Fe-6.5% Si alloy having an average circularity of 0.97 was produced by a gas atomization method. Thereafter, sieving was carried out with a sieve having 250 meshes (aperture 63 μm), and the average particle diameter (D50) was 40 μm.
(2) 0.75 wt% of alumina powder having a specific surface area of 130 m ² / g was mixed with the produced soft magnetic powder.
(3) 1 wt% of the methyl-based silicone oligomer A shown in Table 8 below was mixed with these, followed by heat drying at 300 ° C. for 2 hours.
(4) Methylphenyl silicone resin (product name: TSR-108) was mixed with 1.4 wt% of the dried powder, and heat-dried at 150 ° C. for 2 hours in an air atmosphere.
(5) 30 th meshes (aperture 500 μm) were passed through for the purpose of crushing the lump generated after heat drying. Thereafter, 0.6 wt% of ethylene bis stearate amide was mixed as a lubricant.
The soft magnetic powder insulation coating formed by (6) above step, the outer diameter of 17 mm, an inner diameter of 11 mm, filled in a container of toroidal shape of height 8 mm, to produce a molded body at a molding pressure of 15 ton / cm ^2.
(7) Finally, the compact was heat-treated in a nitrogen atmosphere at a heat treatment temperature of 850 ° C. for 2 hours to produce a dust core.

The sample used in Example 24 was subjected to the following process in place of the manufacturing process (1) of Example 23.
(1) A soft magnetic powder made of an Fe-3.5% Si alloy having an average circularity of 0.95 was prepared by a water atomization method. Thereafter, sieving was carried out with a sieve having 150 meshes (aperture 106 μm), and the average particle diameter (D50) was set to 70 μm.

The sample used in Example 25 was subjected to the following steps instead of the manufacturing steps (1) and (7) of Example 23.
(1) Soft magnetic powder made of pure iron powder having an average circularity of 0.9 was produced by a water atomization method. Thereafter, sieving was carried out with a sieve having 250 meshes (aperture 63 μm), and the average particle diameter (D50) was 40 μm.
(7) Finally, the compact was heat-treated in a hydrogen atmosphere at a heat treatment temperature of 625 ° C. for 2 hours to produce a dust core.

The samples used in Comparative Examples 16 to 18 were subjected to the following steps in place of the production steps (3) and (4) of Examples 23 to 25, respectively.
(3 ′) 1 wt% of a silane coupling agent (product name: A1100) and 1.4 wt% of a methylphenyl silicone resin (product name: TSR-108) are mixed with these, and the mixture is kept at 150 ° C. for 2 hours in an air atmosphere. Was dried by heating.

表７は、本実施例２３〜２５及び比較例１６〜１８の鉄損（Ｐｃｖ）の算出結果を示す。表７の「絶縁層の第１層目」は、軟磁性粉末の表面に形成する樹脂の種類を示し、「絶縁層の第２層目」は、軟磁性粉末の表面の第１層目の絶縁層の外側に形成される絶縁層の樹脂の種類を示す。鉄損は、周波数１００ｋＨｚ、最大磁束密度１００ｍＴの条件で算出したものである。表７に示すように、絶縁層の第１層目にシリコーンオリゴマーを使用した本実施例２３〜２５の鉄損が、シランカップリング剤を使用した比較例１６〜１８と比べて同程度又は低くなっていることが分かる。 (Iron loss and DC superposition characteristics)

Table 7 shows the calculation results of the iron loss (Pcv) of Examples 23 to 25 and Comparative Examples 16 to 18. In Table 7, “first layer of insulating layer” indicates the type of resin formed on the surface of the soft magnetic powder, and “second layer of insulating layer” indicates the first layer on the surface of the soft magnetic powder. The kind of resin of the insulating layer formed in the outer side of an insulating layer is shown. The iron loss is calculated under the conditions of a frequency of 100 kHz and a maximum magnetic flux density of 100 mT. As shown in Table 7, the iron loss of Examples 23 to 25 using a silicone oligomer in the first layer of the insulating layer is the same or lower than that of Comparative Examples 16 to 18 using a silane coupling agent. You can see that

  FIG. 10 is a graph showing the ratio of the magnetic permeability to the magnetic field strength of Example 23 and Comparative Example 16. FIG. 11 is a graph showing the ratio of the magnetic permeability to the magnetic field strength in Example 24 and Comparative Example 17. FIG. 12 is a graph showing the ratio of the magnetic permeability to the magnetic field strength of Example 25 and Comparative Example 18. The magnetic permeability is the amplitude magnetic permeability, and was calculated from the inductance of the strength of each magnetic field at 20 kHz and 1.0 V by using the impedance analyzer described above. The magnetic permeability ratio is defined as the magnetic permeability at 0H (A / m) in each magnetic field, where the magnetic permeability is 100% when DC is not superimposed (when the magnetic field strength is 0H (A / m)). Shows the rate of change.

  As shown in FIGS. 10 to 12, the magnetic permeability ratios of Examples 23 to 25 are higher than the magnetic permeability ratios of Comparative Examples 16 to 18 in the strength of each magnetic field, and the DC superimposition characteristics are high. It can be seen that it has improved. One reason for the improved DC superimposition characteristics is that the inorganic insulating powder (alumina powder) is uniformly distributed.

[9. Eighth characteristic comparison (comparison based on different types of silicone oligomer)]
In the eighth characteristic comparison, the iron loss and DC superposition characteristics of the dust cores were compared by changing the type of silicone oligomer added to the Fe—Si alloy powder or pure iron powder. As Examples 26 to 29, the soft magnetic powder was Fe-6.5% Si alloy powder, Fe-3.5% Si alloy powder, and the steps other than the type of silicone oligomer were the same as in Examples 23 and 24. The types of silicone oligomers were as shown in oligomers B and D in Table 8 below. In Examples 30 and 31, the soft magnetic powder is pure iron powder, the steps other than the type of silicone oligomer are the same as in Example 25, and the types of types of silicone oligomer are the types B and D in Table 8 below. It was as follows.

In addition, the silicone oligomer A of Table 8 is a silicone oligomer containing 40 to 50% of alkoxysilane, and the silicone oligomer B is a silicone oligomer containing 100% of organopolysiloxane. Silicone oligomer C is a silicone oligomer containing 100% of organopolysiloxane, and silicone oligomer D is a silicone oligomer containing 100% of alkoxysiloxane. Silicone oligomer E is a silicone oligomer comprising a methoxy functional methyl-phenyl-polysiloxane.

表９は、実施例２３、２６、２７及び比較例１６の鉄損（Ｐｃｖ）の算出結果を示す。図１３は、実施例２３、２６、２７及び比較例１６の磁界の強さに対する透磁率の比率を示すグラフである。表９に示すように、実施例２３、２６、２７及び比較例１６間で鉄損は同程度であることが分かる。一方、図１３に示すように、実施例２３、２６、２７の透磁率の比率は、各磁界の強さにおいて、比較例１６の透磁率の比率よりも上回っており、直流重畳特性が向上していることが分かる。実施例２３、２６、２７のうち、実施例２６、２７の透磁率の比率は同程度であり、実施例２３が最も直流重畳特性が向上していることが確認できる。 (Iron loss and DC superposition characteristics)

Table 9 shows the calculation results of the iron loss (Pcv) of Examples 23, 26, and 27 and Comparative Example 16. FIG. 13 is a graph showing the ratio of the magnetic permeability to the magnetic field strength of Examples 23, 26, and 27 and Comparative Example 16. As shown in Table 9, it can be seen that the iron loss is comparable between Examples 23, 26, and 27 and Comparative Example 16. On the other hand, as shown in FIG. 13, the magnetic permeability ratio of Examples 23, 26, and 27 is higher than the magnetic permeability ratio of Comparative Example 16 in the strength of each magnetic field, and the DC superposition characteristics are improved. I understand that Among Examples 23, 26, and 27, the ratios of the magnetic permeability of Examples 26 and 27 are approximately the same, and it can be confirmed that Example 23 has the most improved DC superposition characteristics.

表１０は、実施例２４、２８、２９及び比較例１７の鉄損（Ｐｃｖ）の算出結果を示す。図１４は、実施例２４、２８、２９及び比較例１７の磁界の強さに対する透磁率の比率を示すグラフである。表１０に示すように、実施例２４、２８、２９が比較例１７と比べて鉄損が低くなっていることが分かる。一方、図１４に示すように、実施例２４、２８、２９の透磁率の比率は、各磁界の強さにおいて、比較例１７の透磁率の比率よりも上回っており、直流重畳特性が向上していることが分かる。実施例２４、２８、２９のうち、実施例２８、２９の透磁率の比率は同程度であり、実施例２４が最も直流重畳特性が向上していることが確認できる。

Table 10 shows the calculation results of the iron loss (Pcv) of Examples 24, 28, and 29 and Comparative Example 17. FIG. 14 is a graph showing the ratio of the magnetic permeability to the magnetic field strengths of Examples 24, 28, and 29 and Comparative Example 17. As shown in Table 10, it can be seen that Examples 24, 28, and 29 have lower iron loss than Comparative Example 17. On the other hand, as shown in FIG. 14, the magnetic permeability ratios of Examples 24, 28, and 29 are higher than the magnetic permeability ratio of Comparative Example 17 in the strength of each magnetic field, and the DC superposition characteristics are improved. I understand that Among Examples 24, 28, and 29, the magnetic permeability ratios of Examples 28 and 29 are approximately the same, and it can be confirmed that Example 24 has the most improved DC superposition characteristics.

  Table 11 shows the calculation results of the iron loss (Pcv) of Examples 25, 30, and 31 and Comparative Example 18. FIG. 15 is a graph showing the ratio of the magnetic permeability to the magnetic field strength of Examples 25, 30, and 31 and Comparative Example 18. As shown in Table 11, it can be seen that the iron loss in Examples 25, 30, and 31 is lower than that in Comparative Example 18. On the other hand, as shown in FIG. 15, the magnetic permeability ratio of Examples 25, 30, and 31 is higher than the magnetic permeability ratio of Comparative Example 18 in the strength of each magnetic field, and the DC superposition characteristics are improved. I understand that Among Examples 25, 30, and 31, the ratios of the magnetic permeability of Examples 30 and 31 are approximately the same, and it can be confirmed that Example 25 has the most improved DC superposition characteristics.

  As described above, it can be seen from FIGS. 13 to 15 and Table 8 that when the oligomer A whose organic substituent is methyl is used, the direct current superposition characteristics tend to show good results.

[10. Ninth characteristic comparison (comparison according to the amount of silicone oligomer added)]
(1) When the soft magnetic powder is Fe-Si alloy powder In the ninth characteristic comparison, the iron loss and DC superposition characteristics of the powder magnetic core are compared by changing the amount of silicone oligomer added to the Fe-Si alloy powder. Went. As Examples 32-36, the steps other than the addition amount of the silicone oligomer were the same as those in Example 23, and the addition amount of the silicone oligomer was prepared from 0.15 wt% to 3.5 wt%.

表１２は、実施例２３、３２〜３６及び比較例１６の鉄損（Ｐｃｖ）の算出結果を示す。図１６は、実施例２３、３２〜３６及び比較例１６の磁界の強さに対する透磁率の比率を示すグラフである。表１２に示すように、シリコーンオリゴマーの添加量が０．１５ｗｔ％〜３．５ｗｔ％の範囲で鉄損が比較例１６と同程度であることが分かった。添加量が０．１５ｗｔ％未満であると、絶縁被膜として機能せず、渦電流損失が増加することにより磁気特性が低下する。添加量が３．５ｗｔ％を超えると、圧粉磁心の強度が低下する場合がある。図１６に示すように、シリコーンオリゴマーの添加量が０．１５ｗｔ％の場合、他の実施例と比べて直流重畳特性が比較例１６よりも低下する。一方、シリコーンオリゴマーの添加量が０．５ｗｔ％〜３．５ｗｔ％である実施例２３、３３〜３６の場合、直流重畳特性が良好な結果であることが分かった。特に、シリコーンオリゴマーの添加量が２ｗｔ％〜３．５ｗｔ％の実施例３４〜３６において、直流重畳特性が比較例１６と比べて、格段に向上していることが分かった。 (Iron loss and DC superposition characteristics)

Table 12 shows the calculation results of the iron loss (Pcv) of Examples 23, 32-36 and Comparative Example 16. FIG. 16 is a graph showing the ratio of the magnetic permeability to the magnetic field strength of Examples 23, 32-36 and Comparative Example 16. As shown in Table 12, it was found that the iron loss was about the same as that of Comparative Example 16 when the addition amount of the silicone oligomer was in the range of 0.15 wt% to 3.5 wt%. If the addition amount is less than 0.15 wt%, it does not function as an insulating film, and eddy current loss increases, resulting in a decrease in magnetic properties. If the amount added exceeds 3.5 wt%, the strength of the dust core may be reduced. As shown in FIG. 16, when the addition amount of the silicone oligomer is 0.15 wt%, the direct current superimposition characteristic is lower than that of the comparative example 16 as compared with the other examples. On the other hand, in Examples 23 and 33 to 36 in which the addition amount of the silicone oligomer was 0.5 wt% to 3.5 wt%, it was found that the direct current superposition characteristics were good results. In particular, in Examples 34 to 36 in which the addition amount of the silicone oligomer was 2 wt% to 3.5 wt%, it was found that the direct current superposition characteristics were remarkably improved as compared with Comparative Example 16.

(2) When the soft magnetic powder is pure iron powder Further, the iron loss and DC superposition characteristics of the dust cores were compared by changing the amount of the silicone oligomer added to the pure iron powder. As Examples 37 to 41, processes other than the addition amount of the silicone oligomer were the same as those in Example 25, and the addition amount of the silicone oligomer was prepared from 0.15 wt% to 3.5 wt%.

表１３は、実施例２５、３７〜４１及び比較例１８の鉄損（Ｐｃｖ）の算出結果を示す。図１７は、実施例２５、３７〜４１及び比較例１８の磁界の強さに対する透磁率の比率を示すグラフである。表１３に示すように、シリコーンオリゴマーの添加量が０．１５ｗｔ％〜３．５ｗｔ％の範囲で比較例１８と比べて良好な結果であることが分かった。添加量が０．１５ｗｔ％未満であると、絶縁被膜として機能せず、渦電流損失が増加することにより磁気特性が低下する。添加量が３．５ｗｔ％を超えると、圧粉磁心の強度が低下する場合がある。従って、シリコーンオリゴマーの添加量は０．１５ｗｔ％〜３．５ｗｔ％であることが、より好ましい。図１７に示すように、実施例２５、３７〜４１は比較例１８と比べて、全ての各磁界の強さにおいて直流重畳特性が良好な結果であることが分かった。特に、シリコーンオリゴマーの添加量が２ｗｔ％〜３．５ｗｔ％の実施例３９〜４１において、直流重畳特性が比較例１６と比べて、格段に向上していることが分かった。 (Iron loss and DC superposition characteristics)

Table 13 shows the calculation results of the iron loss (Pcv) of Examples 25, 37 to 41, and Comparative Example 18. FIG. 17 is a graph showing the ratio of magnetic permeability to the magnetic field strength of Examples 25, 37 to 41, and Comparative Example 18. As shown in Table 13, it was found that the addition amount of the silicone oligomer was better than that of Comparative Example 18 in the range of 0.15 wt% to 3.5 wt%. If the addition amount is less than 0.15 wt%, it does not function as an insulating film, and eddy current loss increases, resulting in a decrease in magnetic properties. If the amount added exceeds 3.5 wt%, the strength of the dust core may be reduced. Therefore, the addition amount of the silicone oligomer is more preferably 0.15 wt% to 3.5 wt%. As shown in FIG. 17, it was found that Examples 25 and 37 to 41 had better DC superposition characteristics at all the magnetic field strengths than Comparative Example 18. In particular, in Examples 39 to 41 in which the addition amount of the silicone oligomer was 2 wt% to 3.5 wt%, it was found that the direct current superposition characteristics were remarkably improved as compared with Comparative Example 16.

[11. Tenth characteristic comparison (comparison by drying temperature of silicone oligomer)]
(1) When the soft magnetic powder is Fe-Si alloy powder In the tenth characteristic comparison, the iron loss and DC superposition characteristics of the powder magnetic core are compared by changing the amount of silicone oligomer added to the Fe-Si alloy powder. Went. As Examples 42 to 44 and Comparative Example 19, the steps other than the drying temperature of the silicone oligomer were the same as those in Example 23, and the drying temperature of the silicone oligomer was from 25 ° C to 400 ° C.

表１４は、実施例２３、４２〜４４及び比較例１６、１９の鉄損（Ｐｃｖ）の算出結果を示す。図１８は、実施例２３、４２〜４５及び比較例１６の磁界の強さに対する透磁率の比率を示すグラフである。表１４に示すように、鉄損は、実施例２３、４２〜４４が比較例１６と比べて同程度であり、比較例１９より低くなることが分かった。一方、図１８に示すように、実施例２３、４２〜４４は、比較例１８と比べて、全ての各磁界の強さにおいて直流重畳特性が良好な結果であることが分かった。特に、実施例４２〜４４は、直流重畳特性が比較例１６と比べて格段に良好である。乾燥温度が２５℃未満であると膜の形成が不完全となり、渦電流損失が高くなりやすいが、２５℃前後であると乾燥のための特別な設備を設けなくて済むという利点がある。一方、乾燥温度３５０℃より大きいと粉末が酸化することによりヒステリシス損失が高くなり、鉄損が増大する傾向にある。また、圧粉磁心の強度が低下する場合がある。 (Iron loss and DC superposition characteristics)

Table 14 shows the calculation results of the iron loss (Pcv) of Examples 23 and 42 to 44 and Comparative Examples 16 and 19. FIG. 18 is a graph showing the ratio of magnetic permeability to magnetic field strength in Examples 23, 42 to 45, and Comparative Example 16. As shown in Table 14, it was found that the iron loss in Examples 23 and 42 to 44 was comparable to that in Comparative Example 16 and was lower than that in Comparative Example 19. On the other hand, as shown in FIG. 18, it was found that Examples 23 and 42 to 44 had better DC superposition characteristics than the comparative example 18 in all the magnetic field strengths. In particular, Examples 42 to 44 have much better direct current superimposition characteristics than Comparative Example 16. If the drying temperature is less than 25 ° C., the film formation is incomplete and eddy current loss tends to increase, but if it is around 25 ° C., there is an advantage that no special equipment for drying is required. On the other hand, when the drying temperature is higher than 350 ° C., the powder is oxidized, resulting in an increase in hysteresis loss and an increase in iron loss. Further, the strength of the dust core may be reduced.

(2) When the soft magnetic powder is pure iron powder Further, the iron loss and DC superposition characteristics of the dust cores were compared by changing the amount of the silicone oligomer added to the pure iron powder. As Examples 45 to 48 and Comparative Example 20, the steps other than the drying temperature of the silicone oligomer were the same as those of Example 25, and the drying temperature of the silicone oligomer was from 25 ° C to 350 ° C.

表１５は、実施例２５、４５〜４８及び比較例１８、２０の鉄損（Ｐｃｖ）の算出結果を示す。図１９は、実施例２５、４５〜４８及び比較例１８の磁界の強さに対する透磁率の比率を示すグラフである。表１５に示すように、実施例２５、４５〜４８は、比較例１８、２０と比べて低鉄損であることが分かった。乾燥温度が３５０℃である比較例２０では、実施例２５、４５〜４８と比べて、約２倍程度鉄損が増大している。これは、乾燥温度が３５０℃を超えると、粉末が酸化することによりヒステリシス損失が高くなることが要因を考えられる。また、図１９に示すように、実施例２５、４５〜４８は、比較例１８と比べて、全ての各磁界の強さにおいて直流重畳特性が良好な結果であることが分かった。特に、実施例４５、４６、４７で比較例１８と比べて直流重畳特性が格段に向上していることが分かった。その中でも実施例４６が最も良好な結果を示している。なお、比較例２０の透磁率の比率のグラフは図２０に示していない。比較例２０は鉄損が大きく、直流重畳特性を得るための有効な透磁率が得られなかったからである。 (Iron loss and DC superposition characteristics)

Table 15 shows the calculation results of the iron loss (Pcv) of Examples 25, 45 to 48 and Comparative Examples 18 and 20. FIG. 19 is a graph showing the ratio of magnetic permeability to the magnetic field strength of Examples 25, 45 to 48 and Comparative Example 18. As shown in Table 15, it was found that Examples 25 and 45 to 48 had lower iron loss than Comparative Examples 18 and 20. In Comparative Example 20 in which the drying temperature is 350 ° C., the iron loss is increased about twice as much as in Examples 25 and 45 to 48. This may be due to the fact that when the drying temperature exceeds 350 ° C., the hysteresis loss increases due to the oxidation of the powder. Further, as shown in FIG. 19, it was found that Examples 25 and 45 to 48 had better DC superposition characteristics at all magnetic field strengths than Comparative Example 18. In particular, it was found that the direct current superposition characteristics in Examples 45, 46, and 47 were significantly improved as compared with Comparative Example 18. Among them, Example 46 shows the best result. In addition, the graph of the ratio of the magnetic permeability of the comparative example 20 is not shown in FIG. This is because Comparative Example 20 has a large iron loss, and an effective magnetic permeability for obtaining the DC superposition characteristics cannot be obtained.

[12. Eleventh characteristic comparison (comparison of presence or absence of inorganic insulating powder)]
In the eleventh characteristic comparison, the iron loss and direct current superposition characteristics of the dust cores were compared depending on the presence or absence of the inorganic insulating powder added to the Fe—Si alloy powder. In Example 49, the soft magnetic powder was made of Fe-6.5% Si alloy powder, the inorganic insulating powder adhering step was eliminated, and the others were made in the same manner as in Example 23. In Example 50, the soft magnetic powder was Fe-3.5% Si alloy powder, and the other steps were the same as in Example 24 except that the inorganic insulating powder adhesion step was omitted. That is, Examples 49 and 50 are obtained by eliminating the step (2) of Examples 23 and 24 and performing the steps (3) to (7) after the step (1).

  Table 16 shows the calculation results of the iron loss (Pcv) of Examples 23 and 49. Table 17 shows the calculation results of the iron loss (Pcv) of Examples 24 and 50. FIG. 20 is a graph showing the ratio of magnetic permeability to magnetic field strength in Examples 23 and 49. FIG. 21 is a graph showing the ratio of magnetic permeability to magnetic field strength in Examples 24 and 50. As shown in Tables 16 and 17, it was found that the iron loss in Example 49 was the same as that in Example 23, and that in Example 50 was about the same as that in Example 24. As shown in FIGS. 20 and 21, Examples 23 and 49 and Examples 24 and 50 showed no difference in direct current superposition characteristics. When Si is contained in the soft magnetic powder, it is considered that even if there is no inorganic insulating powder, DC superimposition characteristics equivalent to those obtained can be obtained.

[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. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

Claims (5)

Mixing a silicone oligomer with soft magnetic powder and drying to form a silicone oligomer layer;
A step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer;
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
A heat treatment step of heat-treating the molded body that has undergone the molding step at 600 ° C. or higher;
Have
The soft magnetic powder is an Fe-Si alloy;
The addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder,
The drying temperature of the silicone oligomer is more than 160 ° C and not more than 350 ° C,
The silicone oligomer is a methyl or methylphenyl silicone oligomer;
A method for producing a dust core, characterized by comprising: Mixing a silicone oligomer with soft magnetic powder and drying to form a silicone oligomer layer;
A step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer;
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
A heat treatment step of heat-treating the molded body that has undergone the molding step at 600 ° C. or higher;
Have
The soft magnetic powder is pure iron;
The addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder,
The drying temperature of the silicone oligomer is more than 160 ° C. and 300 ° C. or less,
The silicone oligomer is a methyl or methylphenyl silicone oligomer;
A method for producing a dust core, characterized by comprising: Mixing the inorganic insulating powder with the soft magnetic powder and attaching the inorganic insulating powder to the surface of the soft magnetic powder;
A step of mixing a silicone oligomer with the soft magnetic powder having the inorganic insulating powder attached to the surface, and drying to form a silicone oligomer layer;
A step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer;
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
A heat treatment step of heat-treating the molded body that has undergone the molding step at 700 ° C. or higher;
Have
The soft magnetic powder is an Fe-Si alloy;
The addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder,
The drying temperature of the silicone oligomer is more than 160 ° C and not more than 350 ° C,
The silicone oligomer is a methyl or methylphenyl silicone oligomer;
A method for producing a dust core, characterized by comprising: Mixing the inorganic insulating powder with the soft magnetic powder and attaching the inorganic insulating powder to the surface of the soft magnetic powder;
A step of mixing a silicone oligomer with the soft magnetic powder having the inorganic insulating powder attached to the surface, and drying to form a silicone oligomer layer;
A step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer;
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
A heat treatment step of heat-treating the molded body that has undergone the molding step at 700 ° C. or higher;
Have
The soft magnetic powder is pure iron;
The addition amount of the silicone oligomer is 0.15 to 3.5 wt% with respect to the soft magnetic powder,
The drying temperature of the silicone oligomer is more than 160 ° C. and 300 ° C. or less,
The silicone oligomer is a methyl or methylphenyl silicone oligomer;
A method for producing a dust core, characterized by comprising:   The method for producing a dust core according to any one of claims 1 to 4, wherein the silicone oligomer has a molecular weight of 100 to 4000.

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