JP3857356B2 - Manufacturing method of magnetic powder for dust cores - Google Patents
Manufacturing method of magnetic powder for dust cores Download PDFInfo
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- JP3857356B2 JP3857356B2 JP13323996A JP13323996A JP3857356B2 JP 3857356 B2 JP3857356 B2 JP 3857356B2 JP 13323996 A JP13323996 A JP 13323996A JP 13323996 A JP13323996 A JP 13323996A JP 3857356 B2 JP3857356 B2 JP 3857356B2
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- Prior art keywords
- magnetic powder
- insulating layer
- forming solution
- iron
- powder
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
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Description
【0001】
【発明の属する技術分野】
本発明は、高周波用変圧器,リアクター,チョークコイル等の高周波用圧粉磁心に好適な磁性粉の製法に関する。
【0002】
【従来の技術】
高周波用変圧器、リアクター、チョークコイル等の高周波用のコイルに用いられる磁心は低鉄損であり、かつ、高磁束密度であると同時に、それらの磁気特性が高周波領域(1〜10MHz)においても低下しないことが求められる。鉄損の内、渦電流損は周波数の二乗に比例して大きくなるので、高周波領域における特性を向上するためには、渦電流損を下げることが重要になる。
【0003】
渦電流損を下げるには、渦電流を小さな領域に閉じ込める必要がある。そのためには、磁性粉が圧縮成形された圧粉磁心の個々の磁性粉粒子が、絶縁されているのがよい。
【0004】
渦電流の大きさは磁性粉の大きさに依存するために、渦電流損を減らすには磁性粉の粒径を小さくするのが効果的である。しかし、粒径を小さくしすぎると、磁心を作製するときの密度が上がらず、結果的に磁束密度が低下してしまう。また無理に密度を上げようとして高圧で圧縮すると、成型時の歪みが大きくなりヒステリシス損が増大し、その結果鉄損の増大を招いてしまう。
【0005】
また、渦電流損を下げるために絶縁被覆層(以下、絶縁層と云う)の厚みを厚くしすぎると、磁心中の磁性粉の割合が低下し、その結果磁束密度が低下してしまう。
【0006】
従って、良好な特性を有する圧粉磁心を作るためには、適正な粒径の磁性粉粒子に薄くて絶縁性の良好な絶縁層を形成することが必要である。
【0007】
【発明が解決しようとする課題】
圧粉磁心の製造には、従来、特開昭61−154014号、特開昭59−50138号、特開昭51−89198号公報に示されるようなエポキシ樹脂、フッ素樹脂等の有機結着剤、または、水ガラス等の無機結着剤を絶縁層とする方法が用いられていた。
【0008】
しかし、これらの方法では十分な絶縁性を得るには絶縁層を厚くする必要があった。これを解決するために、特開昭62−247005号、特開昭63−70504号、特開昭63−6809号、特開昭62−71202号、特開昭61−296704号、特開昭61−82402号公報に示されているような有機、無機の絶縁層を予め磁性粉粒子にコーティングする方法が提案されている。
【0009】
磁性粉の絶縁層としてP,Mg,B,Feを必須成分とする絶縁層が優れた特性を有することが特開平6−260319号公報に示されている。
【0010】
上記の無機絶縁層を磁性粉の表面に形成する方法としては、混合、蒸着と云ったファンデルワールス力を利用する方法、噴霧,湿式混合と云った水分による毛管力を利用する方法、電着と云った電気力等を利用する方法など物理的に付着させる方法がある。しかし、こうした方法では絶縁層の厚みが厚くなると云う問題があった。
【0011】
こうした磁性粉では、圧粉磁心にしたとき鉄損が高くなるか、あるいは、磁束密度を十分に高くできない。
【0012】
これに対し、磁性粉の表面に化学的に形成する方法は、分子レベルの現象であり、その反応を適度に制御してやればより薄い絶縁層を形成することが可能である。即ち、磁性粉と反応性の絶縁層形成溶液とを接触させ、その界面での化学反応を制御して絶縁層を形成する方法が簡便で実用的である。
【0013】
こうした絶縁層形成溶液としては、例えば、リン酸を含む溶液があり、これを用いた場合、磁性粉としては鉄、ニッケルと云ったイオン化傾向の大きな金属を含有する磁性粉を用いると、金属とリン酸が反応して絶縁性のリン酸塩が表面に形成され、これが絶縁層となる。こうした反応では界面での表面自由エネルギーが反応に大きく影響する。
【0014】
即ち、溶液の表面張力が磁性粉の表面張力よりも大きいと、溶液は表面ではじかれて液滴状になり、その結果、磁性粉表面と絶縁層形成溶液との接触部分が小さくなり、表面での反応にムラが出易くなる。こうしたムラを無くすためには、絶縁層形成溶液の量を多くすることが考えられるが、これの増加は絶縁層が厚くなることにつながる。
【0015】
また、絶縁層形成溶液の濃度を下げると云うことが考えられるが、反応速度が遅くなりすぎて絶縁層の形成に時間がかかり実用的でない。また、絶縁層形成溶液に水などの酸化性の溶液を用いた場合には、磁性粉の表面で酸化反応が起こり好ましくない。
【0016】
従って、適切な濃度、適切な量の絶縁層形成溶液で、磁性粉の表面でムラなく化学反応を起こさせるためには、磁性粉の表面張力を大きくするか、絶縁層形成溶液の表面張力を相対的に小さくするのがよい。
【0017】
金属の表面は高エネルギー表面で理想的には非常に濡れ易い表面であることが知られている。しかし、通常、磁性粉の表面は製造工程中、工程間での汚染は避けられず、磁性粉の表面を完全に清浄な状態にすることは殆ど不可能である。
【0018】
従って、一般に磁性粉の表面張力は理想的な値より小さく、かつ、磁性粉表面での表面張力の分布には、ムラがあると考えなければいけない。こうしたことが、絶縁層形成溶液による絶縁層が不均一になる原因になっていた。
【0019】
本発明の目的は、圧粉磁心、特に、高周波用圧粉磁心に好適な圧粉磁心用磁性粉の製法を提供することにある。
【0020】
【課題を解決するための手段】
我々は上記目的を達成するため、磁性粉の表面に絶縁層を形成させる際、磁性粉と絶縁層との界面の化学反応を、磁性粉表面で均一に起こさせるよう制御することにより、薄く、かつ、絶縁性の優れた絶縁層の形成方法について検討を重ねた結果、絶縁層形成溶液の表面張力を下げればよいことを見出した。こうした知見に基づき本発明に至ったが、その要旨は次のとおりである。
【0021】
リン酸、ほう酸、マグネシウムイオンおよび分子の骨格が炭素数3〜15のパーフルオロアルキル基で、かつ、アニオン性またはカチオン性の官能基を有する界面活性剤を含む絶縁層形成溶液を磁性粉と混合し、乾燥することにより絶縁層を磁性粉の表面に形成することを特徴とする圧粉磁心用磁性粉の製法にある。
【0022】
【発明の実施の形態】
本発明の磁性粉の表面に薄く均一な絶縁層を形成する絶縁層形成溶液としては、リン酸、ほう酸、マグネシウムイオンを含み、さらに界面活性剤として式〔1〕に示した炭素数3〜15のパーフルオロアルキル基を骨格とするアニオン性、または、カチオン性の界面活性剤を含む溶液を用いる。
【0023】
【化2】
【0024】
絶縁層形成溶液の溶媒としては水が望ましいが、リン酸、ほう酸、マグネシウムイオン、界面活性剤の各成分が溶解できる範囲で、水と相溶するアルコールなどの有機溶媒を混合してもよい。
【0025】
リン酸の量は1〜163g/lが望ましく、163g/lを超えると磁束密度の低下を招き、1g/lよりも少なくなると絶縁性が悪くなる。
【0026】
ほう酸の量は0.3〜30g/lが望ましく、この範囲外では絶縁層の安定性が悪くなる。
【0027】
マグネシウムイオン/リン酸の比率は1/9〜1/200(重量比)が望ましく、1/9よりも大きくなると磁性粉と絶縁層形成溶液の反応性が低下し、1/200よりも小さくなると絶縁層の熱安定性が悪くなる。
【0028】
前記式〔1〕で示す界面活性剤としては、炭素数が3〜15のパーフルオロアルキル基の骨格にカルボキシル基、スルホニル基、硫酸エステル基、リン酸エステル基を有するアニオン性の界面活性剤、または、アンモニウム基、ピリジニウム基、イミダゾリニウム基を有するカチオン性の界面活性剤であればいずれでもよい。
【0029】
界面活性剤の量は、溶液に対して0.01〜1重量%が望ましく、0.01重量%未満では表面張力を下げて界面を濡れ性を向上させる効果が不十分となり、1重量%より多くしても効果の増大はそれほど望めないので経済的でない。
【0030】
磁性粉に対する絶縁層形成溶液の添加量は、磁性粉1kg当り25〜400mlが望ましく、400mlより多いと圧粉磁心に加工したときの磁束密度の低下およびヒステリシス損の増加を招き、25mlより少ないと絶縁性が悪くなり、磁心内での渦電流損が増加する。
【0031】
上記磁性粉としては、軟磁性体である純鉄、Fe−Si合金、Fe−Al合金、パーマロイ、センダストなどの鉄系磁性合金の粉末が用いられるが、磁束密度が高く、成形性が良好で低コストの純鉄粉が好ましい。
【0032】
以下に本発明を実施例に基づきさらに詳しく説明する。
【0033】
【実施例】
〔実施例1〜6〕
純水1lにリン酸20g、ほう酸5g、酸化マグネシウム5g(溶解してマグネシウムイオン3gになる)を溶解し、アニオン性界面活性剤(新秋田化学製、エフトップEF−104)、または、カチオン性界面活性剤(エフトップEF−132)を表1の割合で加え、絶縁層形成溶液とした。
【0034】
この絶縁層形成溶液を平均粒径100μmのアトマイズ鉄粉1kgに対し80ml添加し、V型ミキサーを用いて1時間混合し、温風循環型恒温槽中で180℃,30分間乾燥し、鉄粉粒子表面の絶縁層形成処理を行ない、本発明の圧粉磁心用磁性粉を得た。
【0035】
上記磁性粉に、結着剤として市販の熱硬化型エポキシ樹脂を1重量%添加し、離型剤としてステアリン酸リチウムを0.1重量%添加して混合した後、金型に投入し、700MPaの圧力で圧縮成形して150℃,4時間硬化反応を行い、外形50mm×内径30mm×厚み25mmのリング状試験片を作製し、鉄損および磁束密度を測定した。鉄損の測定は、15kHz,0.5Tで行い、磁束密度の測定は50Hz,30kA/mで行った。これらの結果を表2に示す。
【0036】
【表1】
【0037】
【表2】
【0038】
〔比較例1〕
実施例1〜6で作製した絶縁層形成溶液のリン酸、ほう酸、酸化マグネシウムの量は同じで、界面活性剤を含まない溶液を絶縁層形成溶液とした他は、実施例1〜6と同様の方法で試験片を作製した。鉄損および磁束密度の測定結果を表2に併せて示す。
【0039】
〔実施例7〕
上記実施例2で用いたのと同じ組成の絶縁層形成溶液をアトマイズ鉄粉1kgに対して1〜500mlの割合で変化させ、V型ミキサーを用いて1時間混合し、温風循環型恒温槽中で180℃,30分間乾燥し、鉄粉表面の絶縁処理を行った。
【0040】
製造した絶縁処理磁性粉を実施例1〜6と同じ方法でリング状試験片を作製した。鉄損および磁束密度の測定結果を図1に示す。
【0041】
図1から分かるように、鉄粉に対する絶縁層形成溶液の割合が25〜400ml/kgの範囲が好ましい。
【0042】
【発明の効果】
本発明によれば、表2に示すよう界面活性剤の効果は絶大で、磁性粉表面での反応をむらなく行うことができ、絶縁層を薄く均一に形成できる。これにより、鉄損が小さく磁性特性の優れた圧粉磁心用磁性粉を提供することができる。
【図面の簡単な説明】
【図1】磁性粉1kg当りの絶縁層形成溶液量と、圧縮成形した磁心試験片の鉄損および磁束密度との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing magnetic powder suitable for high-frequency powder magnetic cores such as high-frequency transformers, reactors, and choke coils.
[0002]
[Prior art]
Magnetic cores used in high-frequency coils such as high-frequency transformers, reactors, and choke coils have low iron loss and high magnetic flux density, and at the same time their magnetic properties are also in a high-frequency region (1 to 10 MHz). It is required not to decrease. Since the eddy current loss increases in proportion to the square of the frequency among the iron losses, it is important to reduce the eddy current loss in order to improve the characteristics in the high frequency region.
[0003]
In order to reduce the eddy current loss, it is necessary to confine the eddy current in a small area. For this purpose, the individual magnetic powder particles of the powder magnetic core obtained by compression-molding the magnetic powder are preferably insulated.
[0004]
Since the size of the eddy current depends on the size of the magnetic powder, it is effective to reduce the particle size of the magnetic powder in order to reduce the eddy current loss. However, if the particle size is made too small, the density at which the magnetic core is produced does not increase, and as a result, the magnetic flux density decreases. In addition, when the compression is performed at a high pressure in order to increase the density forcibly, the strain at the time of molding increases and the hysteresis loss increases, resulting in an increase in iron loss.
[0005]
Further, if the thickness of the insulating coating layer (hereinafter referred to as the insulating layer) is made too thick in order to reduce the eddy current loss, the ratio of the magnetic powder in the magnetic core decreases, and as a result, the magnetic flux density decreases.
[0006]
Therefore, in order to make a dust core having good characteristics, it is necessary to form a thin insulating layer with good insulating properties on magnetic powder particles having an appropriate particle size.
[0007]
[Problems to be solved by the invention]
For the production of a dust core, conventionally, organic binders such as epoxy resins and fluororesins as disclosed in JP-A-61-154014, JP-A-59-50138, and JP-A-51-89198 are used. Alternatively, a method of using an inorganic binder such as water glass as an insulating layer has been used.
[0008]
However, in these methods, it is necessary to increase the thickness of the insulating layer in order to obtain sufficient insulation. In order to solve this problem, Japanese Patent Laid-Open Nos. 62-247005, 63-70504, 63-6809, 62-71202, 61-296704, 61-296704, There has been proposed a method of previously coating an organic or inorganic insulating layer on magnetic powder particles as disclosed in JP-A-61-82402.
[0009]
JP-A-6-260319 discloses that an insulating layer containing P, Mg, B, and Fe as essential components as an insulating layer of magnetic powder has excellent characteristics.
[0010]
Methods for forming the inorganic insulating layer on the surface of the magnetic powder include methods using van der Waals force such as mixing and vapor deposition, methods utilizing capillary force due to moisture such as spraying and wet mixing, and electrodeposition. There is a physical attachment method such as a method using an electric force or the like. However, such a method has a problem that the thickness of the insulating layer is increased.
[0011]
With such magnetic powder, the iron loss becomes high when the powder magnetic core is formed, or the magnetic flux density cannot be sufficiently increased.
[0012]
On the other hand, the method of chemically forming on the surface of the magnetic powder is a phenomenon at the molecular level, and if the reaction is appropriately controlled, a thinner insulating layer can be formed. That is, a method of forming an insulating layer by bringing a magnetic powder and a reactive insulating layer forming solution into contact with each other and controlling a chemical reaction at the interface is simple and practical.
[0013]
As such an insulating layer forming solution, for example, there is a solution containing phosphoric acid, and when this is used, when magnetic powder containing a metal having a large ionization tendency such as iron or nickel is used as the magnetic powder, Phosphoric acid reacts to form an insulating phosphate on the surface, which becomes an insulating layer. In such a reaction, the surface free energy at the interface greatly affects the reaction.
[0014]
That is, when the surface tension of the solution is larger than the surface tension of the magnetic powder, the solution is repelled on the surface and forms droplets. As a result, the contact portion between the magnetic powder surface and the insulating layer forming solution is reduced, and the surface It becomes easy to produce unevenness in the reaction. In order to eliminate such unevenness, it is conceivable to increase the amount of the insulating layer forming solution, but this increase leads to an increase in the thickness of the insulating layer.
[0015]
In addition, it can be considered that the concentration of the insulating layer forming solution is lowered, but the reaction rate becomes too slow, and it takes time to form the insulating layer, which is not practical. Further, when an oxidizing solution such as water is used as the insulating layer forming solution, an oxidation reaction occurs on the surface of the magnetic powder, which is not preferable.
[0016]
Therefore, in order to cause a uniform chemical reaction on the surface of the magnetic powder with an appropriate concentration and an appropriate amount of the insulating layer forming solution, increase the surface tension of the magnetic powder or increase the surface tension of the insulating layer forming solution. It should be relatively small.
[0017]
It is known that metal surfaces are high energy surfaces and ideally very wettable surfaces. However, usually, the surface of the magnetic powder is inevitably contaminated during the manufacturing process, and it is almost impossible to completely clean the surface of the magnetic powder.
[0018]
Therefore, in general, the surface tension of the magnetic powder is smaller than an ideal value, and the distribution of the surface tension on the surface of the magnetic powder must be considered uneven. This has been a cause of non-uniformity of the insulating layer formed by the insulating layer forming solution.
[0019]
The objective of this invention is providing the manufacturing method of the magnetic powder for dust cores suitable for a dust core, especially the dust core for high frequency.
[0020]
[Means for Solving the Problems]
In order to achieve the above objective, when forming an insulating layer on the surface of the magnetic powder, by controlling the chemical reaction at the interface between the magnetic powder and the insulating layer to occur uniformly on the surface of the magnetic powder, And as a result of repeating examination about the formation method of the insulating layer excellent in insulation, it discovered that the surface tension of the insulating layer formation solution should be lowered. Based on these findings, the present invention has been achieved, and the gist thereof is as follows.
[0021]
An insulating layer forming solution containing phosphoric acid, boric acid, magnesium ions, and a surfactant having a C3-C15 perfluoroalkyl group and an anionic or cationic functional group is mixed with the magnetic powder. And forming an insulating layer on the surface of the magnetic powder by drying.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The insulating layer forming solution for forming a thin and uniform insulating layer on the surface of the magnetic powder of the present invention contains phosphoric acid, boric acid and magnesium ions, and further has 3 to 15 carbon atoms represented by the formula [1] as a surfactant. A solution containing an anionic or cationic surfactant having a perfluoroalkyl group as a skeleton is used.
[0023]
[Chemical 2]
[0024]
As a solvent for the insulating layer forming solution, water is desirable, but an organic solvent such as alcohol compatible with water may be mixed within a range in which each component of phosphoric acid, boric acid, magnesium ion, and surfactant can be dissolved.
[0025]
The amount of phosphoric acid is preferably from 1 to 163 g / l. If it exceeds 163 g / l, the magnetic flux density is lowered, and if it is less than 1 g / l, the insulation properties are deteriorated.
[0026]
The amount of boric acid is preferably 0.3 to 30 g / l, and the stability of the insulating layer is deteriorated outside this range.
[0027]
The ratio of magnesium ion / phosphoric acid is desirably 1/9 to 1/200 (weight ratio). When the ratio is greater than 1/9, the reactivity between the magnetic powder and the insulating layer forming solution is decreased, and when the ratio is less than 1/200. The thermal stability of the insulating layer is deteriorated.
[0028]
As the surfactant represented by the formula [1], an anionic surfactant having a carboxyl group, a sulfonyl group, a sulfate ester group, or a phosphate ester group in the skeleton of a C 3-15 perfluoroalkyl group, Alternatively, any cationic surfactant having an ammonium group, a pyridinium group, or an imidazolinium group may be used.
[0029]
The amount of the surfactant is desirably 0.01 to 1% by weight with respect to the solution. If the amount is less than 0.01% by weight, the effect of lowering the surface tension and improving the wettability of the interface becomes insufficient. Even if it increases, the increase in the effect cannot be expected so much, so it is not economical.
[0030]
The amount of the insulating layer forming solution added to the magnetic powder is preferably 25 to 400 ml per 1 kg of the magnetic powder. When the amount is more than 400 ml, the magnetic flux density is decreased and the hysteresis loss is increased when processed into a dust core, and the amount is less than 25 ml. Insulation is deteriorated, and eddy current loss in the magnetic core increases.
[0031]
As the above-mentioned magnetic powder, soft magnetic materials such as pure iron, Fe-Si alloy, Fe-Al alloy, permalloy, sendust and other iron-based magnetic alloy powders are used, but the magnetic flux density is high and the moldability is good. Low cost pure iron powder is preferred.
[0032]
Hereinafter, the present invention will be described in more detail based on examples.
[0033]
【Example】
[Examples 1 to 6]
Dissolve 20 g of phosphoric acid, 5 g of boric acid, 5 g of magnesium oxide (dissolved to 3 g of magnesium ions) in 1 l of pure water, an anionic surfactant (manufactured by Shin-Akita Chemical Co., Ltd., EFtop EF-104), or cationic Surfactant (F-top EF-132) was added at the ratio shown in Table 1 to obtain an insulating layer forming solution.
[0034]
80 ml of this insulating layer forming solution is added to 1 kg of atomized iron powder having an average particle size of 100 μm, mixed for 1 hour using a V-type mixer, and dried in a hot air circulating thermostat at 180 ° C. for 30 minutes. An insulating layer forming process was performed on the particle surface to obtain a magnetic powder for a dust core according to the present invention.
[0035]
1% by weight of a commercially available thermosetting epoxy resin as a binder is added to the above magnetic powder, and 0.1% by weight of lithium stearate is added as a release agent and mixed. A compression test was conducted at 150 ° C. for 4 hours to form a ring-shaped test piece having an outer diameter of 50 mm, an inner diameter of 30 mm and a thickness of 25 mm, and the iron loss and magnetic flux density were measured. The iron loss was measured at 15 kHz and 0.5 T, and the magnetic flux density was measured at 50 Hz and 30 kA / m. These results are shown in Table 2.
[0036]
[Table 1]
[0037]
[Table 2]
[0038]
[Comparative Example 1]
The amounts of phosphoric acid, boric acid, and magnesium oxide in the insulating layer forming solutions prepared in Examples 1 to 6 are the same, and the insulating layer forming solution is a solution that does not contain a surfactant. A test piece was prepared by the method described above. The measurement results of iron loss and magnetic flux density are also shown in Table 2.
[0039]
Example 7
The insulating layer forming solution having the same composition as used in Example 2 above was changed at a rate of 1 to 500 ml per 1 kg of atomized iron powder, mixed for 1 hour using a V-type mixer, and a hot-air circulating thermostat Inside, it was dried at 180 ° C. for 30 minutes to insulate the iron powder surface.
[0040]
A ring-shaped test piece was produced from the manufactured insulated magnetic powder by the same method as in Examples 1-6. The measurement results of iron loss and magnetic flux density are shown in FIG.
[0041]
As can be seen from FIG. 1, the ratio of the insulating layer forming solution to the iron powder is preferably in the range of 25 to 400 ml / kg.
[0042]
【The invention's effect】
According to the present invention, as shown in Table 2, the effect of the surfactant is enormous, the reaction on the surface of the magnetic powder can be performed uniformly, and the insulating layer can be formed thinly and uniformly. Thereby, the magnetic powder for dust cores with small iron loss and excellent magnetic properties can be provided.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the amount of an insulating layer forming solution per kg of magnetic powder and the iron loss and magnetic flux density of a compression molded magnetic core test piece.
Claims (4)
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13323996A JP3857356B2 (en) | 1996-05-28 | 1996-05-28 | Manufacturing method of magnetic powder for dust cores |
EP01108424A EP1113465A3 (en) | 1996-05-28 | 1997-05-26 | Soft-magnetic powder composite core having particles with insulating layers |
DE69717718T DE69717718T2 (en) | 1996-05-28 | 1997-05-26 | Soft magnetic powder composite core made of particles with insulating layers |
EP97108473A EP0810615B1 (en) | 1996-05-28 | 1997-05-26 | Soft-magnetic powder composite core having particles with insulating layers |
US08/863,627 US6054219A (en) | 1996-05-28 | 1997-05-27 | Process for forming insulating layers on soft magnetic powder composite core from magnetic particles |
US09/448,475 US6344273B1 (en) | 1996-05-28 | 1999-11-24 | Treatment solution for forming insulating layers on magnetic particles process for forming the insulating layers, and electric device with a soft magnetic powder composite core |
Applications Claiming Priority (1)
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JP13323996A JP3857356B2 (en) | 1996-05-28 | 1996-05-28 | Manufacturing method of magnetic powder for dust cores |
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JPH09320830A JPH09320830A (en) | 1997-12-12 |
JP3857356B2 true JP3857356B2 (en) | 2006-12-13 |
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JP4850764B2 (en) | 2007-03-19 | 2012-01-11 | 日立粉末冶金株式会社 | Manufacturing method of dust core |
JP5417074B2 (en) * | 2009-07-23 | 2014-02-12 | 日立粉末冶金株式会社 | Powder magnetic core and manufacturing method thereof |
US9646756B2 (en) | 2010-03-26 | 2017-05-09 | Hitachi Powdered Metals Co., Ltd. | Powder magnetic core and method for producing the same |
CN102319895A (en) * | 2011-10-12 | 2012-01-18 | 长沙市杰冠电子科技有限公司 | Clad powder for powdered iron core and preparation process for clad powder |
JP6478107B2 (en) | 2015-03-30 | 2019-03-06 | 日立化成株式会社 | Powder magnetic core and reactor using the powder magnetic core |
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