JP2010087366A - Metal powder for soft magnetic composite material, and soft magnetic composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: metal powder for a soft magnetic composite material manufacturing a core or the like of a reactor having an excellent constant permeability characteristic even when a gap formed in the core is eliminated; and the soft magnetic composite material. <P>SOLUTION: This metal powder for the soft magnetic composite material includes: a metal powder body formed of iron-based alloy powder or pure iron powder; and an insulation coating film for coating the surface of the metal powder body. The film thickness of the insulation coating film is 1/100-1/2 of the average particle diameter of the metal powder body, and the insulation coating film is formed of a material without being melted or dissolved at a temperature to which it is exposed in a process of forming the metal powder into a completed product. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a soft magnetic composite material used when manufacturing a reactor or the like equipped in an inverter of a hybrid vehicle, and a metal powder for soft magnetic composite material for manufacturing the soft magnetic composite material.

  A hybrid vehicle has two or more power sources with different operating principles and can be driven by a single power source or a plurality of power sources depending on the situation. Its energy efficiency is the same as that of electric vehicles and fuel cell vehicles. In recent years, it has been attracting attention from the viewpoint that it has a low environmental impact and is practical.

  This hybrid vehicle is equipped with an inverter that controls the motor, and a boost converter reactor that drives the motor by converting the battery voltage to a high voltage by the boost converter in order to produce higher output is incorporated. .

  As shown in FIG. 1 and FIG. 2, the conventional reactor A includes a core 1 formed by integrally assembling a plurality of divided cores 1 a and 1 b laminated with electromagnetic steel plates via a gap 2, and an outer periphery of the core 1. It is formed from a coil 3 wound around. The reactor A is excited by the coil 3 to form a magnetic flux path through the core 1.

  The gap 2 adjusts the magnetic permeability so that no magnetic saturation occurs in the core 1 of the reactor A, and is provided to stabilize the inductance characteristics when DC is superimposed. The gap 2 is formed by, for example, sandwiching a spacer 4 made of a nonmagnetic material made of an inorganic material between the split cores 1a and 1a and between the split cores 1a and 1b, and joining the split cores 1a and 1b and the spacer 4. It is formed between adjacent divided cores 1a and 1a and between divided cores 1a and 1b.

  When excited by the coil 3, an electromagnetic attractive force acts on the core 1, but since the core 1 is divided by the gap 2 into divided cores 1a and 1b, when the electromagnetic attractive force acts, the core 1 is divided. Vibration will occur at the joint between the cores 1a and 1b and the spacer 4 for forming the gap 2. That is, when the gap 2 is formed in the reactor A, the inductance characteristic at the time of direct current superposition is stabilized. On the other hand, vibration is generated at the junction between the split cores 1a and 1b and the spacer 4 for forming the gap 2. And a problem arises that noise caused by the vibration is generated from the reactor A.

  Further, when the gap 2 is provided in the core 1, the nonmagnetic material spacer 4 that forms the gap 2 has a much smaller magnetic permeability than the laminated steel sheet that forms the core 1, so that the magnetic flux path is outside. It will leak. This leakage magnetic flux enters the coil 3 wound around the outer periphery and causes eddy current loss in the coil 3.

  The problem that this noise is generated and the problem that leakage magnetic flux is generated are both problems caused by the formation of the gap 2 in the core 1, and it is difficult to manage the length of the gap 2. It is desirable to eliminate gap 2 from 1. However, in the reactor A in which the electromagnetic steel sheets are laminated, there is a problem that it is impossible to obtain excellent constant magnetic permeability characteristics when the gap 2 is not formed.

  Under such circumstances, there has been a long-awaited development of a new material capable of obtaining excellent constant magnetic permeability characteristics even when a reactor core or the like is produced without forming a gap.

  On the other hand, a metal powder made of iron-based alloy powder or pure iron powder obtained by coating or mixing soft magnetic powder with an organic binder such as epoxy resin, imide resin, or silicone resin has been proposed as a material for the dust core. In addition, iron-based alloy powder or metal powder made of pure iron powder obtained by coating or mixing soft magnetic powder with an inorganic binder such as water glass containing sodium silicate as a main component has also been proposed as a material for a dust core.

  Conventional metal powders made from these soft magnetic powders were made by forming a very thin film on the surface or adding a small amount of additives for the purpose of high magnetic permeability. Although it has been used as a material for magnetic cores of electromagnetic parts such as motors used in alternating current, it causes magnetic saturation at a relatively low magnetic field, has poor constant permeability characteristics, and does not provide a gap as it is. It cannot be used as a reactor core material.

  Under such circumstances, recently proposed are magnetic cores made of metal powder that do not form gaps, and soft magnetic composite materials that can be used as materials such as reactor cores without forming gaps. Being started.

  As a magnetic core without forming a gap, an Fe-based constant magnetic permeability core made of an Fe-based alloy having an Fe-based crystal layer and an amorphous layer described in Patent Document 1 has been proposed. This magnetic core was developed not as a reactor core application, but as a choke coil or transformer application. Although it is described as a Fe-based constant magnetic permeability core, its constant permeability characteristic has a large current. It is not enough for use as a reactor core.

  Further, Patent Document 2 discloses a proposal regarding a soft magnetic composite material suitable for a reactor core without a gap, and Patent Document 3 discloses a proposal regarding a method for manufacturing the soft magnetic composite material.

  In Patent Document 2, a suitable relative magnetic permeability and saturation magnetic flux density are required for use as a core material of a reactor without a gap, and a soft magnetic shape and a filling rate in a composite material are required to cope with the problem. Is described. Patent Document 3 describes that in this method for producing a soft magnetic composite material, the viscosity of the resin at the time of mixing is adjusted to 100 mPa · s to 100 Pa · s. Accordingly, it is described that it is necessary to adjust by changing the temperature of the resin or to adjust by mixing a non-conductive filler. However, these adjustments must be made according to the type of resin, and it is very difficult to find the optimum value for each type of resin, and it takes a long time. Finding the mixing ratio was very difficult.

JP-A-6-181113 JP 2008-147403 A JP 2008-147405 A

  The present invention has been made as a solution to the above-described conventional problems, and can eliminate the gap formed in the core and can produce a reactor core having excellent constant magnetic permeability characteristics, etc. It is an object of the present invention to provide a metal powder and a soft magnetic composite material.

  The invention according to claim 1 is a metal powder for a soft magnetic composite material comprising a metal powder body made of iron-based alloy powder or pure iron powder, and an insulating film covering the surface of the metal powder body, wherein the insulating film The film thickness is 1/100 or more and 1/2 or less of the average particle diameter of the metal powder body, and the insulating coating does not melt or dissolve at a temperature exposed in the process of making the metal powder into a finished product. A metal powder for soft magnetic composite material, characterized in that it is made of a material.

  The invention according to claim 2 is characterized in that the insulating coating is formed of a thermosetting resin that does not melt or dissolve at a temperature exposed in the process of making the metal powder into a finished product. This is a metal powder for soft magnetic composite materials.

  The invention according to claim 3 is characterized in that the insulating coating is formed of a thermoplastic resin having a melting point higher than a temperature at which the metal powder is exposed in the step of making the metal powder into a finished product. It is a metal powder for magnetic composite materials.

  The invention according to claim 4 is a soft magnetic composite material formed by adding a resin to the metal powder for soft magnetic composite material according to any one of claims 1 to 3 or the metal powder for soft magnetic composite material. The soft magnetic composite material is characterized in that the change rate of the differential permeability in the excitation magnetic fields 10 Oe and 100 Oe is ± 5% or less.

  According to the metal powder for soft magnetic composite material of the present invention, the thickness of the insulating coating covering the surface of the metal powder body is sufficiently thick, and the insulating coating is melted at a temperature exposed in the process of making the powder into a finished product. Since it is formed of a resin that does not dissolve, the metal powder bodies are not in direct contact with each other, and a sufficient space can be secured between the metal powder bodies. Therefore, from this metal powder for a soft magnetic composite material, a reactor core having excellent constant magnetic permeability characteristics can be produced without a gap.

  According to the soft magnetic composite material of the present invention, since the rate of change in the differential magnetic permeability in the excitation magnetic fields 10 Oe and 100 Oe is ± 5% or less and excellent constant magnetic permeability characteristics, the soft magnetic composite material eliminates the gap. In addition, a reactor core having excellent constant magnetic permeability characteristics can be produced.

  The present inventors have advanced research and development to find a new material capable of producing a reactor core having excellent constant magnetic permeability characteristics even without a gap. As a result, in recent years, the present inventors have been used in alternating current. We paid attention to iron-base alloy powder or metal powder made of pure iron powder produced based on soft magnetic powder that has been used as a material for magnetic cores of electromagnetic parts such as motors. However, this metal powder is produced by forming a very thin film on the surface or adding a small amount of additives for the purpose of high magnetic permeability, and it is magnetic in a relatively low magnetic field. Saturation occurs and the constant magnetic permeability characteristics are poor, and it cannot be used as a reactor core material without a gap.

  The present inventors considered that the disadvantage that the constant magnetic permeability characteristic is poor lies in the thin film thickness of the insulating coating. The insulating coating formed on the conventional powder for soft magnetic composite material functions only as an insulating layer between metal powder bodies. With a coating thickness that functions only as an insulating layer, eddy current flowing between the metal powder bodies can be suppressed and eddy current loss can be suppressed, but the non-permeability cannot be controlled to obtain constant permeability characteristics. According to the study by the present inventors, it was found that a sufficient interparticle distance can be obtained and the constant magnetic permeability characteristics can be obtained by appropriately controlling the film thickness of the insulating coating.

  In the present invention, the thickness of the insulating coating is 1/100 or more and 1/2 or less of the average particle diameter of the metal powder body.

  By setting the film thickness of the insulating coating to 1/100 or more of the average particle diameter of the metal powder body, when the metal powder or the like is molded into a soft magnetic composite material, the soft magnetic composite material is further used as a reactor core or the like. When a finished product is used, even if the metal powders come into contact with each other, the interval between the metal powder bodies can be reliably ensured by the insulating coating. If the thickness of the insulating coating is less than 1/100 of the average particle diameter of the metal powder body, it is not possible to ensure a sufficient space between the metal powder bodies, and as a result, the metal powder body is isolated and dispersed. It becomes difficult to ensure excellent constant magnetic permeability characteristics.

  On the other hand, by setting the film thickness of the insulating coating to ½ or less of the average particle diameter of the metal powder body, the metal powder or the like is molded into a soft magnetic composite material, or the soft magnetic composite material is further used as a reactor core. The density of the magnetic body (metal powder body) and the magnetic flux density can be ensured when a finished product such as is used. If the film thickness of this insulating coating exceeds 1/2 of the average particle diameter of the metal powder body, the density of the magnetic body and magnetic flux density in the molded body such as the core of the reactor will decrease, and as a result, as the core of the reactor etc. It may be impossible to use.

  The insulating coating must be formed using a resin that does not melt or dissolve at a temperature exposed in the process of making the metal powder into a finished product. For this reason, it is recommended to use a thermosetting resin that does not melt or dissolve when heat is applied. If a thermosetting resin is used as a material for forming an insulating coating, an insulating coating that does not melt or dissolve in heat or a solvent can be formed, and the metal powder body can be reliably isolated and dispersed by the insulating coating.

  Further, even a thermoplastic resin can be used as a material for forming an insulating coating if its melting point is higher than the temperature exposed in the process of making the metal powder into a finished product. Even when such a thermoplastic resin is used as a material for forming an insulating film, it is possible to form an insulating film that does not melt or dissolve with respect to heat or a solvent, and the insulating film reliably isolates and disperses the metal powder body. Can do.

  The insulating coating may be a laminate of a plurality of different types of insulating coatings. In this case, the thickness of the insulating coating is the total thickness obtained by combining the thicknesses of the plurality of insulating coatings. Moreover, the same effect that the metal powder main body can be reliably isolated and dispersed can be obtained by fixing an inorganic compound on the surface of the metal powder instead of these resins.

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

  Examples of the thermoplastic resin having a high melting point that can be used for forming an insulating coating include polyethylene, polypropylene, polyamide, polystyrene, polycarbonate, methacrylic resin, fluororesin, PEEK, POM, PPE, PSU, PES, PPS, PAI, and TPX. It can be illustrated. In addition, when the maximum temperature exposed in the process which makes a metal powder a finished product is illustrated, it is about 250 degreeC, Comprising: As a thermoplastic resin, it is desirable to use the thermoplastic resin whose melting | fusing point is 280 degreeC or more.

  Examples of inorganic compounds include metal oxides, metal nitrides, metal carbides, metal phosphates, metal borate salts, metal silicate compounds, and silicon oxide.

  This metal powder is formed as a soft magnetic composite material by using a metal powder alone or by adding and mixing a resin. As a molding method, a molding method such as compacting, injection molding, or casting can be employed. Since the environment to which the metal powder is exposed varies depending on the molding method, it is necessary to select a resin or the like corresponding to each molding method as a material for forming the insulating film.

  In addition, when forming by adding a liquid resin to the metal powder and mixing, the powdered metal powder is mixed so as to be put in the liquid resin, but forms the surface of the metal powder. Since the specific gravity of the insulating coating is relatively light, the insulating coating causes buoyancy in the liquid resin, prevents precipitation of the metal powder, and makes it easier to disperse the metal powder body in isolation.

  Pure iron powder (Atomel 300NH manufactured by Kobe Steel, average particle size: about 100 μm) is used as a metal powder body, 3 to 18% by mass of silicone resin (SR2400 manufactured by Toray Dow Corning) is mixed, and 250 ° C. in the atmosphere. After drying for 30 minutes, it was pulverized to obtain a metal powder for soft magnetic composite material coated with an insulating film made of silicone resin. The silicone resin (SR2400 manufactured by Toray Dow Corning) used in this example is a thermosetting resin.

  The metal powder for soft magnetic composite material coated with this insulating coating is embedded in another resin and cut, and the cross section of the metal powder for soft magnetic composite material is observed with an SEM (scanning electron microscope). The film thickness of was measured. The measurement results are shown in Table 1.

  Next, 20-25% by mass of an unsaturated polyester resin (No. 105 made by Marumoto Struers) is mixed with the metal powder for soft magnetic composite material coated with this insulating film, and poured into a container of φ40 and solidified. Thus, a molded body (soft magnetic composite material) was produced and used as an invention example.

  On the other hand, pure iron powder (Atmel 300NH manufactured by Kobe Steel, average particle size: about 100 μm) is used as a metal powder body, 0.1% by mass silicone resin (SR2400 manufactured by Toray Dow Corning) is mixed in the atmosphere. After drying at 250 ° C. for 30 minutes, it was pulverized to obtain a metal powder coated with an insulating film.

  23 to 43% by mass of unsaturated polyester resin (No. 105 made by Marumoto Struers) is mixed with the metal powder coated with this insulating coating, poured into a container of φ40, and solidified to produce a molded body. It was set as a comparative example.

  The molded bodies of these inventive examples and the molded bodies of the comparative examples were observed from the side surfaces, and the presence or absence of segregation due to precipitation of metal powder was visually confirmed. The confirmation results are shown in Table 1.

  Further, the molded body of the invention example and the molded body of the comparative example were machined into a core of a reactor having an outer diameter: 36 mm, an inner diameter: 24 mm, and a height: 5 mm, and DC magnetic measurement was performed with a BH curve tracer. Differential permeability was measured at magnetic fields 10 (Oe) and 100 (Oe). The rate of change was determined from the difference in the differential permeability. The measurement results are shown in Table 1. In the present invention, the change rate of the differential magnetic permeability in the excitation magnetic fields 10 (Oe) and 100 (Oe) is in the range of ± 5% and has excellent constant magnetic permeability characteristics.

  According to Table 1, the measurement results of the film thickness of the insulating coating were 3 μm in Invention Example 1, 11 μm in Invention Example 2, 26 μm in Invention Example 3, and 0.1 μm in Comparative Example 1 and Comparative Example 2. The ratio of the film thickness of the insulating coating to the metal powder body having an average particle diameter of 100 μm is 3/100 in Invention Example 1, 11/100 in Invention Example 2, and 26/100 in Invention Example 3, and is compared with Comparative Example 1. In Example 2, it is 1/1000. That is, Invention Examples 1 to 3 are within the range of 1/100 or more and 1/2 or less as described in claim 1, but Comparative Example 1 and Comparative Example 2 are out of the range.

  Segregation due to precipitation of metal powder could not be confirmed in Invention Examples 1 to 3, but could be confirmed in Comparative Examples 1 and 2.

  Moreover, the change rate of the differential permeability in the excitation magnetic fields 10 (Oe) and 100 (Oe) is +3.1 in Invention Example 1, +2.1 in Invention Example 2, -2.7 in Invention Example 3, and Comparative Example 1 It was -49.7 and Comparative Example 2 was -7.5. That is, in the inventive examples 1 to 3, the change rate of the differential permeability could be within a range of ± 5%, but in the comparative examples 1 and 2, the change rate of the differential permeability was ± 5%. Could not be within range.

  From this result, by setting the film thickness of the insulating coating to 1/100 or more and 1/2 or less of the average particle diameter of the metal powder main body, there is no segregation, and a reactor core having excellent constant magnetic permeability characteristics, etc. It was confirmed that it could be produced.

It is a perspective view which shows arrangement | positioning of the split core of the reactor in which the conventional gap was formed. It is a cross-sectional view showing a conventional reactor.

Explanation of symbols

A ... Reactor 1 ... Core 1a, 1b ... Split core 2 ... Gap 3 ... Coil 4 ... Spacer

Claims (4)

A metal powder body made of iron-based alloy powder or pure iron powder, and a metal powder for soft magnetic composite material comprising an insulating coating covering the surface of the metal powder body,
The film thickness of the insulating coating is 1/100 or more and 1/2 or less of the average particle diameter of the metal powder body,
A metal powder for a soft magnetic composite material, wherein the insulating coating is formed of a material that does not melt or dissolve at a temperature exposed in the process of making the metal powder into a finished product.   2. The metal powder for a soft magnetic composite material according to claim 1, wherein the insulating coating is formed of a thermosetting resin that does not melt or dissolve at a temperature exposed in the process of making the metal powder into a finished product.   2. The metal powder for soft magnetic composite material according to claim 1, wherein the insulating coating is formed of a thermoplastic resin having a melting point higher than a temperature exposed in the step of making the metal powder into a finished product. The metal powder for soft magnetic composite material according to any one of claims 1 to 3, or a soft magnetic composite material formed by adding a resin to the metal powder for soft magnetic composite material,
A soft magnetic composite material characterized in that the change rate of differential permeability in exciting magnetic fields 10 Oe and 100 Oe is ± 5% or less.

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