JP6713018B2 - Soft magnetic material, dust core, and method for manufacturing dust core - Google Patents

Description

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

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

A powder magnetic core is required to have a magnetic characteristic that a large magnetic flux density can be obtained with a small applied magnetic field and a magnetic characteristic that an energy loss due to a change in the magnetic flux density is small in order to improve energy exchange efficiency and generate less heat. The magnetic characteristic relating to the magnetic flux density is specifically the magnetic permeability (μ). The magnetic characteristic relating to energy loss is specifically iron loss (Pcv). The iron loss (Pcv) is represented by the sum of the hysteresis loss (Ph) and the eddy current loss (Pe).

JP, 2008-305823, A JP, 2010-001561, A JP2012-129217A

In recent years, there has been a demand for a dust core which is excellent in reliability with little increase in iron loss and little decrease in magnetic permeability even when exposed to an environment of high temperature and high humidity for a long time. The dust core is made of a soft magnetic material containing soft magnetic powder. In order to manufacture a dust core with high reliability, a method of using a soft magnetic material having a soft magnetic powder and an insulating layer made of a silicone oligomer (hereinafter referred to as a silicone oligomer layer) formed around the soft magnetic powder can be considered.

The silicone oligomer layer has excellent mechanical strength and covers the circumference of the soft magnetic powder. By using the soft magnetic powder having the silicone oligomer layer formed therein, it is possible to suppress the breakage of the silicone oligomer layer due to the pressure applied during the production of the powder magnetic core and the strain generated in the soft magnetic powder. Thereby, the gap between the soft magnetic powders can be kept uniform. Therefore, even if it is exposed to a high temperature and high humidity environment for a long time, it is possible to suppress an increase in iron loss and a decrease in magnetic permeability, and it is possible to manufacture a highly reliable dust core. However, there is a demand for the production of a highly reliable dust core that suppresses an increase in iron loss and a decrease in magnetic permeability.

The present invention has been proposed in order to solve the above-mentioned problems of the prior art. An object of the present invention is to provide a soft magnetic material, a dust core, and a method for manufacturing a dust core, which are capable of obtaining a dust core having excellent reliability even when exposed to an environment of high temperature and high humidity for a long time. Especially.

As a result of earnest research, the present inventor has found that, in the step of forming a layer of silicone oligomer around the soft magnetic powder in the step of manufacturing the soft magnetic material, not only the silicone oligomer is added to the soft magnetic powder, but also the silicone oligomer. It is said that a dust core using a soft magnetic material containing titanium phosphate or titanium oligomer in an amount of 10 wt% or more of the addition amount of is low loss, excellent in DC superposition characteristics, and excellent in high temperature and high humidity environment. I got the knowledge.

Therefore, in order to achieve the above object, the soft magnetic material according to the present invention has a soft magnetic powder and an insulating layer that covers the surface of the soft magnetic powder, and the insulating layer includes a silicone oligomer and titanium phosphate. And a silicone oligomer layer containing a mixture of the above, and the addition amount of the titanium phosphate is 10 wt% or more of the addition amount of the silicone oligomer.

The addition amount of the titanium phosphate may be 11.1 wt% to 400 wt% of the addition amount of the silicone oligomer.

The soft magnetic material of the present invention has a soft magnetic powder and an insulating layer covering the surface of the soft magnetic powder, and the insulating layer is a silicone oligomer layer containing a mixture of a silicone oligomer and a titanium oligomer. The amount of the titanium oligomer added is 11.1 wt% to 400 wt% of the amount of the silicone oligomer added.

The insulating layer may include a silicone resin layer covering the silicone oligomer layer.

The insulating layer may include insulating fine powder that covers the soft magnetic powder.

A dust core using the above soft magnetic material and a method for manufacturing the dust core are also one aspect of the present invention.

According to the present invention, there is provided a soft magnetic material, a dust core, and a method for manufacturing a dust core, which are capable of obtaining a dust core excellent in reliability with little deterioration in characteristics even under an environment of high temperature and high humidity. be able to.

It is a flow chart for explaining the manufacturing method of the dust core concerning an embodiment. It is a graph which shows the relationship between temperature and weight loss in a silicone oligomer. It is a graph which shows the relationship between the addition amount of titanium phosphate and the density of the dust core of Examples 1-4 and Comparative Examples 1-3. It is a graph which shows the relationship between the amount of titanium phosphate added and the DC superimposition characteristic of the dust cores of Examples 1 to 4 and Comparative Examples 1 to 3. It is a graph which shows the relationship of the amount of titanium phosphate addition of the powder magnetic cores of Examples 1-4 and Comparative Examples 1-3 in a high temperature high humidity test, and the magnetic permeability and the rate of change of iron loss. 5 is a graph showing the relationship between the amount of titanium phosphate added and the density of the dust cores of Examples 8 to 13 and Comparative Example 1. It is a graph which shows the relationship between the amount of titanium phosphate addition of the dust core of Examples 8-13, and the comparative example 1, and a direct current superposition characteristic. It is a graph which shows the relationship of the amount of titanium phosphate addition of the dust core of Examples 8-13 and the comparative example 1 in a high temperature and high humidity test, the magnetic permeability, and the rate of change of iron loss.

[1. Manufacturing method of dust core]
The soft magnetic material, the dust core, and the manufacturing method thereof according to the embodiment will be described along with the method for manufacturing the dust core. The soft magnetic material according to the embodiment is a dust core obtained by forming a silicone oligomer layer by adding titanium phosphate or titanium oligomer to the silicone oligomer and mixing them to form the silicone oligomer layer. That is, it is a soft magnetic material obtained through the process of step 2 described later. Therefore, the soft magnetic material obtained by the steps 1, 2, 4 to 6 and the soft magnetic material obtained by the steps 2, 4 to 6 not including the following step 1 and/or step 3 The soft magnetic material obtained through the steps 2 to 6 is also included in the soft magnetic material of the present invention.

The method for manufacturing a dust core of the present embodiment has the following steps. This process is shown in the flowchart of FIG.
(1) Insulating fine powder adhering step (step 1) of adhering insulating fine powder by mixing insulating fine powder with soft magnetic powder.
(2) A silicone oligomer layer forming step (step 2) of forming a silicone oligomer layer by adding and mixing a silicone oligomer and titanium phosphate or a titanium oligomer to the soft magnetic powder having the insulating fine powder adhered to the surface thereof.
(3) A silicone resin layer forming step (step 3) of forming a silicone resin layer by mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon.
(4) A lubricant mixing step of adding and mixing a lubricant to the soft magnetic powder obtained through the steps 1 to 3 (step 4).
(5) A molding step (step 5) in which the soft magnetic powder that has been subjected to the lubricant mixing step is subjected to pressure molding processing to produce a molded body.
(6) A heat treatment step (step 6) of heat-treating the molded body that has undergone the molding step.

Hereinafter, each step will be specifically described.
(1) Insulating fine powder adhering step In the insulating fine powder adhering step, the soft magnetic powder and the insulating fine powder are mixed. Mixing is performed by using a mixer (W type, V type), a pot mill, or the like, and at this time, the powder is mixed so as not to cause distortion. By mixing the soft magnetic powder and the insulating fine powder, the insulating fine powder can be attached to the surface of the soft magnetic powder. The insulating fine powder attached to the surface of the soft magnetic powder has a constant thickness. Since the insulating fine powder adheres to the surface of the soft magnetic powder, the soft magnetic powders do not come into direct contact with each other. Further, since the insulating fine powder has an insulating property, it is possible to insulate between the soft magnetic powders.

The insulating fine powder may be adhered to the surface of the soft magnetic powder in a dot-like manner, or to the surface of the soft magnetic powder in a lump-like manner. This includes the case where the insulating fine powder is adhered while being formed so as to cover the surface or a part of the surface. Further, it includes a case where not only the particles adhere to the surface of the soft magnetic powder but also the particles are mixed with the silicone oligomer layer formed on the outside of the soft magnetic powder and dispersed in the silicone oligomer layer. Depending on the conditions such as the stirring time by the mixer, it may not be dispersed in the 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, and Mn. When using permalloy (Fe-Ni alloy), the ratio of Ni to Fe is preferably 50:50 or 25:75, but other ratios may be used. For example, Fe-80Ni or Fe-36Ni may be used. In addition to Fe and Ni, Si, Cr, Mo, Cu, Nb, Ta, etc. may be contained. 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% and 6.5%. May be The pure iron powder contains 99% or more of Fe. The soft magnetic powder is not limited to one type, and may be a mixed powder of two or more types.

The average particle size of the soft magnetic powder is preferably 20 μm to 80 μm. This is because the loss reduction effect can be obtained by setting it within this range. In addition, in this specification, an "average particle diameter" means a median diameter (D50).

The manufacturing method of the soft magnetic powder does not matter. It may be produced by a pulverizing method or by an atomizing method. The atomizing method may be any of a water atomizing method, a gas atomizing method and a water gas atomizing method. At present, the water atomization method is the most available and has the lowest cost. When the water atomizing method is used, since the particle shape is distorted, it is easy to improve the mechanical strength of the powder compact obtained by pressure molding it.

(Insulating fine powder)
The insulating fine powder to be mixed with the soft magnetic powder is preferably at least one of alumina powder, magnesia powder, silica powder, titania powder and zirconia powder, which are inorganic insulating powders 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 due to the heat applied in the heat treatment step performed for the purpose of removing the strain due to the pressure applied at the time of molding described later. This is to prevent it from becoming unusable.

The specific surface area of the insulating fine powder is preferably 65 to 130 m ² /g (7 nm to 200 nm in particle size), and more preferably 100 to 130 m ² /g (7 nm to 50 nm in particle size). The larger the specific surface area of the insulating fine powder, the smaller the particle size. The smaller the particle size, the finer the insulating powder will enter between the soft magnetic powders without a gap, and the denser insulating layer will be formed, thus alleviating the strain at the time of molding the dust core. On the other hand, if the specific surface area of the insulating fine powder is too large, the particle size becomes too small, which makes production difficult.

The addition amount of the insulating fine powder is 0.2 wt% to 2.0 wt% with respect to the soft magnetic powder. If the added amount is less than 0.2 wt %, the insulation performance cannot be sufficiently exhibited, and the eddy current loss may remarkably increase at a high heat treatment temperature. On the other hand, if the added amount is more than 2.0 wt %, the insulating performance can be exhibited, but the molding density becomes low, and there may be a problem that magnetic properties other than eddy current loss deteriorate. If these problems do not occur, the insulating fine powder adhesion step is not always necessary.

(2) Silicone Oligomer Layer Forming Step In the silicone oligomer layer forming step, a predetermined amount of the silicone oligomer and titanium phosphate or titanium oligomer is added to the soft magnetic powder, and dried at a predetermined temperature in the air atmosphere. The silicone oligomer layer forming step forms a strong and dense silicone oligomer layer on the outer side of the soft magnetic powder.

The drying temperature of the silicone oligomer layer is preferably 25°C to 350°C, and more preferably 100°C to 200°C. If the drying temperature is lower than 25° C., the insulating layer will be incompletely formed, resulting in high eddy current loss and increased loss. On the other hand, when the drying temperature is higher than 350° C., the powder is oxidized to increase the hysteresis loss and increase the loss. Moreover, when the drying temperature is 100° C. or higher, the drying time can be shortened, and when the drying temperature is 200° C. or lower, the oxidation of the powder can be further suppressed. The drying time is about 1 hour. Since the reaction is promoted by adding titanium phosphate or titanium oligomer, the drying time can be shortened as compared with the case where titanium phosphate or titanium oligomer is not added.

(Titanium phosphate)
Titanium phosphate is a monomer.

(Titanium oligomer)
The titanium oligomer is a compound that condenses titanium alkoxide (Ti-OR) or titanium chelate and contains a multimeric structure (-Ti-O-Ti-) in the molecule.

The addition amount of titanium phosphate and titanium oligomer is preferably 10 wt% or more of the addition amount of silicone oligomer. The addition of titanium phosphate and titanium oligomer accelerates the curing of the silicone oligomer during drying, as compared with the case where titanium phosphate and titanium oligomer are not added. The upper limit of the amount of titanium phosphate and titanium oligomer added is preferably 400% of the amount of silicone oligomer added. Even if 400% or more of titanium phosphate and titanium oligomer are added, the magnetic properties of the dust core cannot be improved by the silicone oligomer layer and the dense silicone oligomer layer. Further, titanium phosphate and titanium oligomer are expensive materials. Therefore, by limiting the addition amount, it is possible to suppress the manufacturing cost of the dust core.

(Titanium phosphate suppresses weight reduction of silicone oligomer)
It is necessary to cure the silicone oligomer when forming the silicone oligomer layer at a temperature of 25° C. or higher. In addition, the curing speed increases when the temperature is higher. On the other hand, the silicone oligomer is a volatile substance. At high temperatures, the amount of silicone oligomers that volatilize and decompose increases. FIG. 2 is a graph showing the relationship between the drying temperature and the weight loss of silicone oligomers. The broken line in FIG. 2 is a comparative example (Comparative Example 1 described below) in which the silicone oligomer layer is formed only by 0.50 wt% of the silicone oligomer, and the solid line is 0.25 wt% of the silicone oligomer and 0.25 wt% of phosphoric acid. It is an example of forming a silicone oligomer layer with titanium (Example 3 described later). The weight reduction rate was calculated by the following formula (1), where W0 before drying and W1 after drying were used.

[Formula (1)]
(W1-W0)/W0*100=weight reduction rate (%) (1)

As shown in FIG. 2, in the comparative example, the weight loss rate at 50° C. is almost zero. However, when the temperature changes to a high temperature and reaches 150°C, the weight loss rate becomes -11.5%. When the temperature further reaches 350°C, the weight loss rate becomes -45.6%. On the other hand, in the example, the weight loss rate at 150° C. was −2.8%, and when dried at 150° C., the example reduced the decomposition of the silicone oligomer by heating by about 30% as compared with the comparative example. It becomes possible to suppress to. Further, the weight loss rate at 350° C. is -17.5%. That is, the weight reduction rate of the example at 150° C. is (2.8%÷11.5%×100=)24.3% as compared with the weight reduction rate of the comparative example, and the weight of the example at 350° C. The reduction rate is (17.5%÷45.6%×100=)38.4% as compared with the weight reduction rate of the comparative example, and when dried at 350° C., the example compares with the comparative example. The decomposition of the silicone oligomer due to heating can be suppressed to about 30/8 minutes.

That is, when forming the silicone oligomer layer, the silicone oligomer is cured by the high temperature during drying, while the decomposition also progresses due to the influence of the high temperature. When the curing speed of the silicone oligomer is slow, a large amount of the silicone oligomer decomposes. By adding titanium phosphate or a titanium oligomer, decomposition of the silicone oligomer due to heat can be suppressed. Therefore, by adding titanium phosphate and titanium oligomer, it becomes possible to reduce the amount of silicone oligomer required when forming a silicone oligomer layer having the same thickness.

(Ensuring reliability of dust core with durable silicone oligomer layer)
When the same amount of silicone oligomer is dried at the same temperature, by adding titanium phosphate, a layer of silicone oligomer formed on the surface of the soft magnetic powder as compared with the case where titanium phosphate is not added. Becomes thicker. Thicker silicone oligomer layers can be formed. The thick silicone oligomer layer exhibits high mechanical strength against pressure during the subsequent molding step, and is unlikely to cause distortion or breakage. Therefore, inside the manufactured dust core, the soft magnetic powder is uniformly arranged with a certain gap. The uniform arrangement of the soft magnetic powder suppresses the decrease in the magnetic permeability μ and the increase in the iron loss Pcv due to the high temperature and high humidity.

(Ensuring reliability of dust core by uniform silicone oligomer layer)
As described above, the decomposition of the silicone oligomer proceeds during drying. This is no exception to the silicone oligomer which is attached to the periphery of the soft magnetic powder and is being cured. When a part of the silicone oligomer is decomposed in the silicone oligomer being hardened around the soft magnetic powder, the thickness of the silicone oligomer layer formed after drying becomes uneven. When a soft magnetic material having a silicone oligomer layer having a non-uniform thickness is used to manufacture a dust core, the arrangement of the soft magnetic powder inside becomes non-uniform. Therefore, the uniform arrangement of the soft magnetic powder suppresses the decrease in the magnetic permeability μ and the increase in the iron loss Pcv due to the high temperature and high humidity.

(Silicone oligomer)
The main skeleton of the silicone oligomer is a siloxane bond, and the mechanical bond strength is strong. In addition, a silane coupling agent that is a monomer having one Si atom uses a silicone oligomer having a low molecular weight and a dimer or trimer with a molecular weight of about 1000. It can be thickened. That is, by forming the silicone oligomer layer as the intermediate layer of the insulating coating, the mechanical strength of the insulating coating as a whole can be increased and the film thickness can be increased.

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

The molecular weight of the silicone oligomer is preferably 100 to 4000. When the molecular weight is less than 100, the soft magnetic powders are likely to be destroyed or disappeared by thermal decomposition in the heat treatment step, and dielectric breakdown between soft magnetic powders is likely to occur. For example, when a silicone oligomer layer is formed around the Fe-Si alloy powder and the molecular weight is less than 100, even if the film thickness distribution is uniform before the heat treatment process, the film thickness distribution after the heat treatment process varies. Is considered to have occurred. On the other hand, when the molecular weight is more than 4000, the film thickness becomes too thick and the magnetic properties deteriorate. In other words, the presence of the silicone oligomer makes it possible to maintain the gap between the soft magnetic powders, contribute to a decrease in magnetic permeability, and obtain a dust core having a low magnetic permeability.

The addition amount of the silicone oligomer is preferably 1.0 wt% to 5.0 wt% with respect to the soft magnetic powder, and when it is 3.5 wt% or more, the insulating coating becomes thick and the magnetic permeability decreases. Cheap. Further, more than 3.5 wt% and 5.0 wt% or less is more preferable. If the amount added is less than 1.0 wt %, the insulating film does not function and the eddy current loss increases, resulting in an increase in loss. If the addition amount is more than 5.0 wt %, the dust core expands, resulting in a decrease in strength.

(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 the atmosphere. The silicone resin layer forming step forms a silicone resin layer on the outside of the silicone oligomer layer.

(Silicone resin)
Silicone resin is a resin having a siloxane bond (Si-O-Si) as a main skeleton. By using a silicone resin, it is possible to form a film having excellent flexibility. As the silicone resin, methyl type, methyl phenyl type, propyl phenyl type, epoxy resin modified type, alkyd resin modified type, polyester resin modified type, rubber type and 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 having a small heat loss and excellent heat resistance.

The addition amount of the silicone resin is preferably 1.0 wt% to 4.0 wt% with respect to the soft magnetic powder. If the added amount is less than 1.0 wt %, the insulating film does not function and the eddy current loss increases, resulting in increased loss. If the addition amount is more than 4.0 wt %, the powder magnetic core expands and the density decreases. By adjusting the addition amount of the silicone resin to the silicone oligomer appropriately, it is possible to form a strong and highly insulating insulating film, especially when the weight ratio of the silicone resin to the silicone oligomer is 0.4 to 1.4. , Excellent in strength and insulation performance. Further, the silicone resin has lubricity, and the amount of lubricant added can be reduced.

The drying temperature of the silicone resin layer is preferably 100°C to 400°C. If the drying temperature is lower than 100° C., the film formation is incomplete, the eddy current loss increases, and the loss increases. On the other hand, if the drying temperature is higher than 400° C., the powder is oxidized to increase the hysteresis loss, which causes an increase in the loss. The drying time is about 2 hours.

(4) Lubricant Mixing Step The lubricant mixing step is a step of adding and mixing a lubricant to the obtained soft magnetic material. By this mixing step, the outermost surface of the insulating coating, that is, the surface of the silicone resin layer is coated with the lubricant. As the lubricant, stearic acid and metal salts thereof and waxes such as ethylene bis-stearamide, ethylene bis-stearamide and ethylene bis-stearate amide can be used. By mixing the lubricant, the slip between the powders can be improved, so that the density at the time of mixing can be improved and the molding density can be increased. Furthermore, it is possible to reduce the drawing pressure of the upper punch during molding and prevent the generation of vertical stripes on the core wall surface due to the contact between the die and the powder. The addition amount of the lubricant is preferably about 0.1 wt% to 0.6 wt% with respect to the soft magnetic material.

(5) Molding Step In the molding step, a soft magnetic powder having an insulating coating formed on its surface is pressure-molded to form a molded body. The pressure during molding is 10 to 20 ton/cm ² , and preferably 12 to 15 ton/cm ^{2 on} average.

(6) Heat Treatment Step In the heat treatment step, the molded body that has been subjected to the molding step is an insulating film coated with soft magnetic powder at 750° C. or higher in a non-oxidizing atmosphere such as N ₂ gas or N ₂ +H ₂ gas. The powder magnetic core is manufactured by performing a heat treatment at a temperature (eg, 850° C. or 950° C.) at which is destroyed. The heat treatment is performed below the temperature at which the insulating coating is destroyed in order to release the strain in the molding process and to prevent the insulating coating around the soft magnetic powder from being broken by the heat during the heat treatment. On the other hand, if the heat treatment temperature is raised too high, the insulating coating coated with this soft magnetic powder is broken, and the eddy current loss greatly increases due to the deterioration of the insulating performance. This causes a problem that the magnetic characteristics deteriorate.

[2. Action/effect]
The soft magnetic material of the present embodiment includes a soft magnetic powder and an insulating layer that covers the surface of the soft magnetic powder, and the insulating layer includes a silicone oligomer and titanium phosphate of 10% or more of the addition amount of the silicone oligomer. Or a silicone oligomer layer comprising a mixture with a titanium oligomer. In this soft magnetic material, a strong and dense silicone oligomer layer is formed.

When the strength of the silicone oligomer layer is low, the pressure in the molding step destroys the silicone oligomer layer, and the gap between the soft magnetic powders cannot be maintained. Due to this cause, the arrangement of the soft magnetic powder in the manufactured dust core becomes non-uniform. Also, when the denseness of the silicone oligomer layer is low, the arrangement of the soft magnetic powder in the formed dust core becomes non-uniform. The non-uniform arrangement of the soft magnetic powder leads to an increase in iron loss and a decrease in magnetic permeability under high temperature and high humidity. These reduce the reliability of the dust core. On the other hand, in the dust core of the present embodiment using the soft magnetic material having a strong and dense silicone oligomer layer formed, the arrangement of the soft magnetic powder inside can be made uniform, so that the reliability is excellent. A dust core can be obtained.

Examples 1 to 13 and Comparative Examples 1 to 3 of the present invention will be described below with reference to FIGS. 3 to 8 and Tables 1 to 5.

[1. Measurement item]
As the measurement items, the magnetic permeability and the 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 manufactured dust core and using an LCR meter (Agilent Technology: 4294A).

Loss was measured by applying a primary winding (20 turns) and a secondary winding (3 turns) to the manufactured dust core and using a BH analyzer (Iwatsu Measurement Co., Ltd.: SY-8219), which is a magnetic measuring instrument. The loss (Pcv) was measured under the conditions of a frequency of 50 kHz and a maximum magnetic flux density Bm=0.1T. Then, the hysteresis loss (Ph) and the eddy current loss (Pe) were calculated from the loss. This calculation was performed by calculating the hysteresis loss coefficient (Kh) and the eddy current loss coefficient (Ke) by the least squares method using the following frequency curves of the losses (2) to (4).

[Formulas (2) to (4)]
Pcv=Kh×f+Ke×f ² (2)
Ph=Kh×f (3)
Pe=Ke×f ² (4)
Pcv: 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 obtained by averaging 3000 particles using the following apparatus. The powder is dispersed on a glass substrate and a powder photograph is taken with a microscope. Each time, it was automatically measured from the image.
Company Name: Malvern
Device name: morphologi G3S
The specific surface area was measured by the BET method.

[2. First characteristic comparison (titanium phosphate)]
In the first characteristic comparison, a silicone oligomer layer was formed for 0.5 wt% of soft magnetic fine powder. At that time, the addition amounts of the silicone oligomer and the titanium phosphate were adjusted so that the total amount was 0.50 wt %, and the powder magnetic cores to be the samples of Examples 1 to 4 and Comparative Examples 1 to 3 were obtained. It was made. Table 1 is a table|surface which shows the compounding conditions of the soft magnetic material used for manufacture of the powder magnetic cores of Examples 1-4 and Comparative Examples 1-3.

Table 1 shows the addition amount of insulating fine powder, the addition amount of silicone oligomer, the addition amount of titanium phosphate, and the ratio of the addition amount of silicone oligomer to the addition amount of titanium phosphate. The B/A ratio was calculated by B/A×100, where A is the addition amount of the silicone oligomer and B is the addition amount of titanium phosphate.

つまり、実施例１〜４、比較例１〜３で使用した軟磁性微粉末は、表２の円形度を有し、Ｓｉ含有量を６．５ｗｔ％とするＦｅ−Ｓｉ合金粉末からなる軟磁性粉末をガスアトマイズ法で作製した粉末である。 In addition, in Examples 1 to 4 and Comparative Examples 1 to 3, Fe-6.5Si gas atomized powder having the particle size distribution, circularity, and holding power shown in Table 2 was used as the soft magnetic fine powder.

That is, the soft magnetic fine powders used in Examples 1 to 4 and Comparative Examples 1 to 3 have the circularity shown in Table 2 and are made of Fe-Si alloy powder having a Si content of 6.5 wt%. It is a powder produced by a gas atomizing method.

(Example 1)
Using the produced soft magnetic powder, the dust core of Example 1 was produced as follows.
(1) 0.5 wt% of alumina powder having a specific surface area of 100 m ² /g was mixed with the produced soft magnetic powder.
(2) 0.45 wt% of a silicone oligomer and 0.05% of titanium phosphate were added to and mixed with the soft magnetic powder mixed with the alumina powder. The B/A ratio is 11.1. After mixing, heat drying was performed at 150° C. for 1 hour.
(5) 0.8 wt% of methylphenyl-based silicone resin (product name: TSR-108) was mixed with the dried powder, and heated and dried at 150° C. for 2 hours in the air atmosphere.
(6) For the purpose of crushing the lumps generated after heating and drying, a sieve having a mesh size of 500 μm was passed. Then, 0.5 wt% of ethylenebisstearamide was mixed as a lubricant.
(7) The soft magnetic powder having the insulating layer formed in the above step was filled in a toroidal-shaped 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 .
(8) 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.

(Example 2)
In Example 2, the step (2) of Example 1 was used as the following step, and the same steps as (1) to (8) were sequentially performed (2) to the soft magnetic powder mixed with the alumina powder. Then, 0.40 wt% of the silicone oligomer and 0.10% of titanium phosphate were added and mixed. In Example 2, the B/A ratio is 25. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 3)
In Example 3, the step (2) of Example 1 was used as the following step, and the same steps as (1) to (8) were sequentially performed (2) with respect to the soft magnetic powder mixed with the alumina powder. Then, 0.25 wt% of the silicone oligomer and 0.25% of titanium phosphate were added and mixed. The B/A ratio is 100. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 4)
In Example 4, the step (2) of Example 1 was used as the following step, and the same steps as (1) to (8) were sequentially performed (2) to the soft magnetic powder mixed with the alumina powder. Then, 0.10 wt% of the silicone oligomer and 0.40% of titanium phosphate were added and mixed. The B/A ratio is 400. After mixing, heat drying was performed at 150° C. for 1 hour.

(Comparative Example 1)
In Comparative Example 1, the step (2) of Example 1 was used as the following step, and the same steps as the above (1) to (8) were sequentially performed (2) to the soft magnetic powder mixed with the alumina powder. Then, 0.50 wt% of a silicone oligomer was added and mixed. The B/A ratio is 0. After mixing, heat drying was performed at 150° C. for 1 hour.

(Comparative example 2)
In Comparative Example 2, the step (2) of Example 1 was used as the following step, and the same steps as (1) to (8) were sequentially performed (2) to the soft magnetic powder mixed with the alumina powder. Then, 0.48 wt% of the silicone oligomer and 0.02% of titanium phosphate were added and mixed. The B/A ratio is 4.2. After mixing, heat drying was performed at 150° C. for 1 hour.

(Comparative example 3)
In Comparative Example 3, the step (2) of Example 1 was used as the following step, and the same steps as (1) to (8) were sequentially performed (2) to the soft magnetic powder mixed with the alumina powder. Then, 0.5 wt% of titanium phosphate was added and mixed, and heated and dried at 150° C. for 1 hour.

Table 3 shows the magnetic permeability and loss calculation results of Examples 1 to 4 and Comparative Examples 1 to 3, the change rate of the iron loss Pc in the high temperature and high humidity test for 100 hours, and the permeability in the high temperature and high humidity test for 100 hours. The change rate of magnetic susceptibility μ is shown. In the 100-hour high temperature and high humidity test, the dust core was left for 100 hours in an environment of a temperature of 85° C. and a humidity of 85%. FIG. 3 is a graph showing the relationship between the amount of titanium phosphate added and the density of the dust cores of Examples 1 to 4 and Comparative Examples 1 to 3, and FIG. 4 is Examples 1 to 4 and Comparative Examples 1 to 1. 3 is a graph showing the relationship between the amount of titanium phosphate added to the powder magnetic core of Example 3 and the DC superimposition characteristics, and FIG. 5 is a powder magnetic core of Examples 1 to 4 and Comparative Examples 1 to 3 in a 100-hour high temperature and high humidity test 5 is a graph showing the relationship between the amount of titanium phosphate added, the magnetic permeability, and the rate of change in iron loss.

It can be confirmed from Table 3 that the rate of change of iron loss and the rate of change of magnetic permeability of Examples 1 to 4 are less than ±5.5% in the high temperature and high humidity test for 100 hours. The rate of change in iron loss was calculated by the following equation (5), with iron loss Pc0 before the 100-hour high temperature and high humidity test and iron loss Pc1 after the 100-hour high temperature and high humidity test.

[Formula (5)]
(Pc1-Pc0)÷Pc0×100=Change rate of iron loss (%) (5)

Further, the rate of change in magnetic permeability is expressed by the following formula (1) for magnetic permeability μ0 (0 kA/m) before the high temperature and high humidity test for 100 hours and after the high temperature and high humidity test for 100 hours. Calculated according to 6).

[Formula (6)]
(Μ1-μ0)÷μ0×100=change rate of magnetic permeability (%) (6)

The rate of change of iron loss of Examples 1 to 4 is less than 5.5%, and the rate of change of iron loss of Comparative Examples 1 to 3 is 5.5% or more. Further, of Comparative Examples 1 to 3, Comparative Example 2 having the smallest change rate of iron loss is 7.8%, whereas, in Examples 1 to 4, the largest change rate of iron loss is. The example was 5.1%. The rate of change in iron loss of Example 4 was about 65% as compared with Comparative Example 2, and Examples 1 to 4 had iron loss of 100 hours in a high temperature and high humidity test as compared with Comparative Examples 1 to 3. It can be seen that there is little change. Further, the rate of change of magnetic permeability of Examples 1 to 4 is less than −5.5%, and the rate of change of magnetic permeability of Comparative Examples 1 to 3 is −5.5% or more. From this, it can be seen that Examples 1 to 4 have less change in magnetic permeability in the 100-hour high temperature and high humidity test as compared with Comparative Examples 1 to 3.

The ratio of titanium phosphate to silicone oligomer in Examples 1 to 4 (titanium phosphate/silicone oligomer) is 11.1 to 400. 3 to 5, the rate of change in iron loss and the rate of change in magnetic permeability are less than ±5% even when the ratio of titanium phosphate to silicone oligomer is 10. As described above, by using the soft magnetic material having the silicone oligomer layer containing the silicone oligomer and the mixture of titanium phosphate of 10% or more of the addition amount of the silicone oligomer, the soft magnetic material is exposed to a high temperature and high humidity environment for a long time. However, it is possible to obtain a dust core with less deterioration of characteristics and excellent reliability.

Further, the magnetic permeability in Table 3 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 above-mentioned impedance analyzer. “Μ(0 kA/m)” in Table 3 indicates the initial magnetic permeability when no direct current is superposed, that is, when the magnetic field strength is 0 H(A/m). “Μ (10 kA/m)” in Table 3 indicates the magnetic permeability when the magnetic field strength is 10 kH (kA/m). “Μ(10k)/μ0” in Table 3 indicates the DC superposition characteristic calculated from the initial permeability and the magnetic permeability when the magnetic field strength is 10 kHz (kA/m). As shown in Table 3, in Examples 1 to 4, the DC superposition characteristic μ (10 kA/m)/μ0 was 53% or more, and excellent DC superposition characteristics were obtained.

[3. Second characteristic comparison (amount of silicone oligomer added)]
In the second characteristic comparison, a silicone oligomer layer was formed for 0.5 wt% of soft magnetic fine powder. In the first characteristic comparison, the addition amount of the silicone oligomer and the addition amount of titanium phosphate at that time were 0.50 wt% in total, but in this characteristic comparison, the addition amount of the silicone oligomer and the addition amount of titanium phosphate were The powder magnetic cores were prepared as samples of Examples 5 to 8 by adjusting the total amount to be other than 0.50 wt %. Table 4 is a table showing the compounding conditions of the soft magnetic materials used for producing the dust cores of Examples 5 to 8.

Table 4 shows the addition amount of insulating fine powder, the addition amount of silicone oligomer, the addition amount of titanium phosphate, and the ratio of the addition amount of silicone oligomer to the addition amount of titanium phosphate.

(Example 5)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.50 wt% of a silicone oligomer and 0.50% of titanium phosphate were added and mixed. The B/A ratio is 100. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 6)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. 0.90 wt% of a silicone oligomer and 0.10% of titanium phosphate were added to and mixed with the mixed soft magnetic powder. The B/A ratio is 11.1. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 7)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. 1.00 wt% of a silicone oligomer and 0.50% of titanium phosphate were added to and mixed with the mixed soft magnetic powder. The B/A ratio is 50. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 8)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.05 wt% of a silicone oligomer and 0.05% of titanium phosphate were added and mixed. The B/A ratio is 100. After mixing, heat drying was performed at 150° C. for 1 hour.

Table 5 shows the magnetic permeability of Examples 5 to 8, the calculation results of the loss, the change rate of the iron loss Pc in the 100-hour high temperature and high humidity test, and the change rate of the magnetic permeability μ in the 100-hour high temperature and high humidity test. ..

As shown in Table 5, in the 100-hour high temperature and high humidity test, it can be confirmed that in Examples 5 to 8, the rate of change in iron loss and the rate of change in magnetic permeability were less than ±5.5%. That is, a soft magnetic material having a silicone oligomer layer containing 0.05 to 1.00 wt% of a silicone oligomer with respect to the soft magnetic powder and a mixture of 10 wt% or more of the amount of the silicone oligomer added with titanium phosphate is used. By doing so, even if exposed to an environment of high temperature and high humidity for a long time, the characteristics are less deteriorated, and a dust core having excellent reliability can be obtained.

[4. Third characteristic comparison (titanium oligomer)]
In the third characteristic comparison, powder magnetic cores as samples of Examples 9 to 13 and Comparative Example 1 were produced by changing the addition amount of the titanium oligomer when forming the silicone oligomer layer. Table 6 is a table showing the compounding conditions of the soft magnetic materials used for producing the dust cores of Examples 9 to 13 and Comparative Example 1.

Table 6 shows the addition amount of insulating fine powder, the addition amount of silicone oligomer, the addition amount of titanium phosphate, and the ratio of the addition amount of silicone oligomer to the addition amount of titanium phosphate. The C/A ratio was calculated by C/A×100, where A is the addition amount of the silicone oligomer and C is the addition amount of the titanium oligomer.

(Example 9)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.45 wt% of silicone oligomer and 0.05% of titanium oligomer were added and mixed. In Example 9, when the addition amount of the silicone oligomer is A and the addition amount of the titanium oligomer is C, the ratio of the silicone oligomer and the titanium oligomer is represented by C/A. In Example 9, the C/A ratio is 11.1. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 10)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.40 wt% of silicone oligomer and 0.10% of titanium oligomer were added and mixed. In Example 10, the C/A ratio is 25. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 11)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.25 wt% of a silicone oligomer and 0.25% of a titanium oligomer were added and mixed. The C/A ratio is 100. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 12)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.50 wt% of a silicone oligomer and 0.50% of a titanium oligomer were added and mixed. The C/A ratio is 100. After mixing, heat drying was performed at 150° C. for 1 hour.

(Example 13)
Using the soft magnetic powder used in the first characteristic comparison, the step (2) of Example 1 was set as the following step, and the same steps as (1) to (8) were sequentially performed. To the mixed soft magnetic powder, 0.10 wt% of a silicone oligomer and 0.40% of a titanium oligomer were added and mixed. The C/A ratio is 400. After mixing, heat drying was performed at 150° C. for 1 hour.

Table 7 shows the magnetic permeability of Examples 5 to 8, the calculation results of the loss, the change rate of the iron loss Pc in the 100-hour high temperature and high humidity test, and the change rate of the magnetic permeability μ in the 100-hour high temperature and high humidity test. .. 6 is a graph showing the relationship between the addition amount of titanium oligomer and the density of the dust cores of Examples 8 to 13 and Comparative Example 1, and FIG. 7 is the dust core of Examples 8 to 13 and Comparative Example 1. FIG. 8 is a graph showing the relationship between the amount of titanium oligomer added and the DC superposition characteristic, and FIG. It is a graph which shows the relationship of the change rate of loss.

As shown in Table 7, in the 100-hour high-temperature high-humidity test, it can be confirmed that in Examples 9 to 13, the change rate of iron loss and the change rate of magnetic permeability are less than ±5.5%. In other words, even when a titanium oligomer is used in place of titanium phosphate, the rate of change in iron loss and the rate of change in magnetic permeability are small in a 100-hour high-temperature high-humidity test, and high reliability is ensured.

Moreover, the C/A ratio of titanium phosphate and titanium oligomer in Examples 9 to 13 is 11.1 to 400. Further, from FIGS. 6 to 8, even when the ratio of titanium phosphate to titanium oligomer is 10, the rate of change in iron loss and the rate of change in magnetic permeability are less than ±5%. As described above, by using the soft magnetic material having the silicone oligomer layer containing the silicone oligomer and the mixture of the titanium oligomer of 10% or more of the addition amount of the silicone oligomer, the soft magnetic material can be exposed to a high temperature and high humidity environment for a long time. Also, it is possible to obtain a dust core with excellent reliability and less deterioration in characteristics.

[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 within a range not departing from the gist of the invention in an implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements of different embodiments may be combined appropriately.

For example, in the present embodiment, when forming the silicone oligomer layer, one of titanium phosphate and titanium oligomer is added to the silicone oligomer, but the present invention is not limited to this. Titanium phosphate and titanium oligomer may be mixed as long as the addition amount of one of titanium phosphate and titanium oligomer is 10% or more of the addition amount of silicone oligomer.

Claims (10)

Soft magnetic powder,
An insulating layer covering the surface of the soft magnetic powder,
Have
The insulating layer comprises a silicone oligomer layer containing a mixture of a silicone oligomer and titanium phosphate,
The soft magnetic material, wherein the addition amount of the titanium phosphate is 10 wt% or more of the addition amount of the silicone oligomer. The soft magnetic material according to claim 1, wherein the addition amount of the titanium phosphate is 11.1 wt% to 400 wt% of the addition amount of the silicone oligomer. Soft magnetic powder,
An insulating layer covering the surface of the soft magnetic powder,
Have
The insulating layer comprises a silicone oligomer layer containing a mixture of a silicone oligomer and a titanium oligomer,
The soft magnetic material, wherein the addition amount of the titanium oligomer is 11.1 wt% to 400 wt% of the addition amount of the silicone oligomer. Soft magnetic powder,
An insulating layer covering the surface of the soft magnetic powder,
Have
The insulating layer comprises a silicone oligomer layer containing a mixture of a silicone oligomer and a titanium oligomer,
The amount of titanium oligomer, Ri 10 wt% or more der addition amount of the silicone oligomer,
The insulating layer is
A soft magnetic material comprising insulating fine powder covering the soft magnetic powder . The insulating layer is
The soft magnetic material according to claim 1, further comprising a silicone resin layer that covers the silicone oligomer layer. The insulating layer is
The soft magnetic material according to any one of claims 1 to 3 , further comprising insulating fine powder that covers the soft magnetic powder. A dust core using the soft magnetic material according to claim 1. A step of forming a silicone oligomer layer, in which a silicone oligomer and titanium phosphate of 10 wt% or more of the addition amount of the silicone oligomer are added to and mixed with the soft magnetic powder;
A silicone resin layer forming step of adding and mixing a silicone resin to the mixture obtained in the silicone oligomer layer forming step,
A molding step in which the mixture obtained in the silicone resin layer forming step is put into a predetermined container and pressure-molded,
A heat treatment step of heat treating the molded body obtained in the molding step,
Be equipped with,
A method for manufacturing a dust core, comprising: A step of forming a silicone oligomer layer in which a silicone oligomer and a titanium oligomer of 11.1 wt% to 400 wt% of the addition amount of the silicone oligomer are added to and mixed with the soft magnetic powder;
A silicone resin layer forming step of adding and mixing a silicone resin to the mixture obtained in the silicone oligomer layer forming step,
A molding step in which the mixture obtained in the silicone resin layer forming step is put into a predetermined container and pressure-molded,
A heat treatment step of heat treating the molded body obtained in the molding step,
Be equipped with,
A method for manufacturing a dust core, comprising: The method for producing a powder magnetic core according to claim 8 or 9, wherein in the step of forming the silicone oligomer layer, drying is performed at 100°C to 200°C.

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