JP4215992B2

JP4215992B2 - Oxide magnetic powder and core manufacturing method, core molding method, magnetic component and coil component

Info

Publication number: JP4215992B2
Application number: JP2002056205A
Authority: JP
Inventors: 拓志明平; 裕斎藤; 卓也小野
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2002-03-01
Filing date: 2002-03-01
Publication date: 2009-01-28
Anticipated expiration: 2022-03-01
Also published as: JP2003257725A

Description

【０００１】
【発明の属する技術分野】
本発明は、酸化物磁性粉体とコアの製造方法と前記酸化物磁性粉体を用いたコアの成形方法と磁性部品とコイル部品に係り、特にドラム型コア形状のように、複雑な形状の磁性部品に好適なものに関する。
【０００２】
【従来の技術】
Ｎｉ−Ｚｎ系フェライト等の磁性酸化物粉体は、一般に、材料酸化物の混合−仮焼−粉砕−造粒−成形の各工程を経た後、適正に制御された高温下で焼成することによって製造されている。
【０００３】
前記工程のうち、粉砕は、湿式粉砕が一般的であるが、湿式粉砕後の粉体材料を成形する場合、一般的に成形体密度を高くすることが困難である。このため、成形圧力を高くする方法で成形体密度を上げると、成形時のひび割れや、成形体内部の密度の不均一さが原因で焼成後に変形やひび割れが発生することが知られている。
【０００４】
また、図１（Ａ）に示すドラムコア１のように、複雑な形状のコイル部品用コアを図１（Ｂ）に示す下型２と上型３により成形する際に、巻心部１ａの両端の鍔部１ｂの密度低下を防止する目的で過剰な圧力を加えた場合に、巻心部１ａの部分にのみ応力が集中して金型２、３が破損する事例が多数報告されている。特に、図１（Ａ）において、巻心部１ａの加圧方向の径（図示のようにコア１の巻心部が円柱形状の場合）または幅（コア１の巻心部が角柱形状の場合）ａが、鍔部１ｂの加圧方向の径（鍔部が円柱形状の場合）または幅（鍔部が多角柱形状の場合）ｂの６０％以下の形状である場合、図１（Ｂ）に示すように、巻心部１ａの巻心軸方向に対して垂直方向に加圧すると、巻心部１ａが相対的に密、鍔部１ｂが相対的に疎となる密度差が生じ、上述したひび割れ、変形、金型の破損が発生することが知られている。
【０００５】
これらの不具合を解決する手段として、特開平９−３０６７７４号公報に記載のように、円柱あるいは角柱状に一体成形した成形体の中間部を切削して巻心部１ａの径または幅を鍔部１ｂの６０％以下に加工する方法が用いられる場合がある。しかしこの切削による場合には、生産性が悪く、特に例えば１ｍｍ程度の長さの小型の形状になるほど寸法精度を含めた生産性が低下する。
【０００６】
この切削による方法以外に、成形時に全方位から比較的均一に成形圧力を加える冷間等方圧成形（ＣＩＰ）等が知られているが、比較的大型の成形体を造る場合は効果は大きいが、ドラムコア等のような複雑な成形体には効果が不十分であり、また、一度に成形できる能力にも限界があり、大量生産に適した方法ではない。
【０００７】
さらに、近年、各種電子機器の小型、軽量化が急速に進み、それに対応すべくこれらの電子機器の電気回路に用いられる電子部品の小型化、高性能化への要求も急速に高まってきている。このため、さらなる部品の小型化に対応するためには、限られた時間の中で大量に、しかも精密に成形できる成形法を開発することは勿論、粉体材料に関係する分野からの取り組みも不可欠になっている。
【０００８】
これらの要求に応じるべく、特開平５−４３２４８号公報には、粉体材料を乾式粉砕した後、湿式粉砕を行うことによって粒子の凝集状態を変化させることにより、成形体の圧縮密度を２．６ｇ／ｃｍ^３〜３．２ｇ／ｃｍ^３の範囲に連続的に制御する密度制御方法が記載されている。
【０００９】
【発明が解決しようとする課題】
前述のように、湿式粉砕のみで仮焼後の酸化物磁性粉体を粉砕すると、粉体を凝集させることができず、圧縮密度を高くすることはできない。また、粗粒子が残りやすい傾向がある。
【００１０】
一方、乾式粉砕のみでは、粗粒子を微細化し、粉体を凝集させることはできるものの、焼結体密度は高くならず、思うような電磁気特性が得られないという問題がある。また、目標とする平均粒子径に粉砕するまでに粉砕機の内壁やメディアから不純物が混入するという不具合がある。
【００１１】
そこで、前記特開平５−４３２４８号公報に記載のように、粉体材料を乾式粉砕した後、湿式粉砕を行うことが考えられるが、この方法によると、乾式粉砕によって作った凝集が僅かにほぐれる傾向を持ち、さらに圧縮密度が低下してしまう。その結果、成形体の圧縮密度として３．２ｇ／ｃｍ^３以上の高密度のものを得ることが難しく、このため、高い成形体強度のコア等を得ることが困難である。また、焼結体内部の密度差、変形等の不具合を抑制することも困難であり、寸法精度および電磁気特性の優れた磁性部品を安定して製造できないという問題点があった。
【００１２】
本発明は、このような従来技術の問題点に鑑み、磁性部品の成形体として高密度で、焼結体内部での密度差が小さく、もって変形を抑制でき、寸法精度、電磁気特性が優れたものを得ることができる酸化物磁性粉体とコアの製造方法を提供することを目的とする。また、本発明は、前記酸化物磁性粉体を用いたコアの成形方法と磁性部品とコイル部品を提供することを目的とする。
【００１３】
【課題を解決するための手段】
本発明のコアの製造方法は、磁性酸化物の材料となる複数種類の酸化物を秤量、配合した後仮焼し、仮焼後の磁性酸化物粉体に水を加えて湿式粉砕処理を施し、その後、乾燥し、乾燥後の磁性酸化物粉体に乾式粉砕処理を施して磁性酸化物粉体を微細化し、微細化した粉体をスラリー化し、乾燥造粒して圧縮密度が高い酸化物磁性粉体を得、この酸化物磁性粉体を成形してコアを得ることを特徴とする（請求項１）。
【００１４】
このように、湿式粉砕の後に乾式粉砕を行うことにより、単に湿式粉砕による場合に比較して凝集を起こし易くなり、圧縮密度を高くすることができ、しかも単に乾式粉砕による場合よりも湿式粉砕で前処理することにより、焼結体密度を高くし、コアの電磁気特性を良好とすることが可能になる。
【００１５】
また、湿式粉砕の後に乾式粉砕を行うことにより、乾式粉砕の時間を短縮できるので、粉砕機の内壁やメディアからの不純物の混入を少なくすることができ、コア内（ドラムコアであれば、巻心部と鍔部）の密度差を小さくすることとも相まって、コアの電磁気特性の向上が達成できる。
【００１６】
より詳しくは、湿式粉砕処理では充分に粉砕処理できなかった磁性酸化物粉体中の粗大粒子を短時間に粉砕し、平均粒子径が０．４〜１．８μｍ、より好ましくは０．６〜１．２μｍの尖鋭な粒子径分布の酸化物磁性粉体を得ることができる。
【００１７】
また、比表面積を２．４g／ｃｍ^３以上に処理しながら、酸化物磁性粉体を凝集させて成形体の圧縮密度を低圧成形下でも３．２g／ｃｍ^３以上に制御可能とし、これによって複雑な形状のコアを研削加工等をすることなく一体成形可能とするものである。
【００１８】
本発明において、湿式粉砕に用いる粉砕機として、湿式ボールミルやアトライター等を用いることができ、また、乾式粉砕に用いる粉砕機として、乾式ボールミル、振動式ミル等を用いることができる。
【００１９】
本発明のコアの製造方法としては、磁性酸化物がＭｎ−Ｚｎ系フェライトも対象となるが、特に電気抵抗が高く、コイルの直巻が行えるＮｉ−Ｚｎ系フェライトを用いたコアの製造方法（請求項２）として、好適に適用することができる。
【００２０】
また、本発明による製造方法を実施する場合、前記乾燥造粒により得た酸化物磁性粉体を成形することにより、０．１ＭＰａにおける成形体密度が３．２ｇ／ｃｍ^３以上の成形体を得る（請求項３）ように粉砕処理することが可能となる。
【００２１】
また、本発明の前記製造方法によって前記乾燥造粒により得られる酸化物磁性粉体をコア形状に加圧成形する際に、コアの加圧方向の最小幅を、加圧方向の最大幅の６５％以下にして成形する（請求項４）際に、焼結体製品としての歩留まりを高くして実施することができる。
【００２２】
また、本発明の前記製造方法によって前記乾燥造粒により得られる酸化物磁性粉体をドラム型コア形状に、その巻心軸方向に対して垂直方向に加圧成形する際に、巻心部の加圧方向の径または幅を、鍔部の加圧方向の径または幅の６０％以下にして成形する（請求項５）ことにより、焼結体製品としての歩留まりを高くして実施することができる。
【００２３】
また、本発明の前記製造方法によって前記乾燥造粒により得られる酸化物磁性粉体を成形する際の成形圧力の変化量ΔＰ（ＭＰａ）に対する成形体密度の変化量Δｄ（ｇ／ｃｍ^３）の比Δｄ／ΔＰが、０．０５ＭＰａ〜０．３ＭＰａの成形圧力範囲において、
Δｄ／ΔＰ≦１．６である酸化物磁性粉体（請求項６）を得ることができ、かつそのような特性を有することが、低い成形圧力で（すなわち焼結体製品におけるひび割れや変形を少なくして）高い圧縮密度を得、しかも均一な密度分布を得る上で好ましい。
【００２４】
また、本発明の前記製造方法により得られる酸化物磁性粉体の成形体密度の変化量Δｄ（ｇ／ｃｍ^３）に対する、焼結後の密度の変化量ΔＤ（ｇ／ｃｍ^３）の比ΔＤ／Δｄが
ΔＤ／Δｄ≦０．１３である酸化物磁性粉体（請求項７）を得ることができ、かつそのような特性を有することが、低い成形圧力で（すなわち焼結体製品におけるひび割れや変形を少なくして）高い焼結体密度を得る上において好ましい。
【００２５】
また、本発明の前記製造方法により得られる酸化物磁性粉体から成形、焼結されてなる磁性部品（請求項８）とすることにより、焼結体内部の密度差が小さく、変形の少ない歩留まりの良い電磁気特性の優れた磁性部品を得ることができる。
【００２６】
また、本発明の前記製造方法による磁性部品をコアとして備えたコイル部品（請求項９）を得ることにより、電磁気特性の優れたコイル部品を得ることができる。
【００２７】
【発明の実施の形態】
本発明の酸化物磁性粉体の製造方法は、インダクタ、トランス、アンテナ、テレビのブラウン管、その他、磁性を要する部品の材料を得る場合に好適なものであり、特に図１（Ａ）に示したようなドラムコアのような複雑な形状、すなわち成形時における金型の移動方向について、成形体の加圧方向の径または幅ａ、ｂが大幅に異なるような磁性部品を得る場合の酸化物磁性粉体として好適なものである。
【００２８】
図２は本発明による酸化物磁性粉体の製造方法の一実施の形態を示すブロック図である。図２に示すように、本実施の形態においては、所定の特性のフェライトが得られるように、個々の酸化物粉体を秤量し、水を加えて湿式配合する（工程ａ）。次にスプレー乾燥装置等を用いて乾燥造粒する（工程ｂ）。次にこの粉体を仮焼する（工程ｃ）。
【００２９】
次にこの焼結体に水を加え、湿式ボールミル等により湿式粉砕する（工程ｄ）。この粉砕したものを乾燥する（工程ｅ）。そしてこの湿式粉砕し、乾燥したものを乾式の振動式ボールミル等により乾式粉砕する（工程ｆ）。次に分散剤、結合剤等を適正量加え（工程ｇ）、スプレー乾燥装置等を用いて乾燥造粒する（工程ｈ）ことにより、酸化物磁性材粉体を得る。
【００３０】
【実施例】
（比較例１）−湿式粉砕
Ｆｅ_２Ｏ_３、ＺｎＯ、ＮｉＯ、およびＣｕＯからなる酸化物粉体を所定のモル比で湿式混合した後、９００℃で仮焼した。得られた酸化物組成は、
Ｆｅ_２Ｏ_３：ＺｎＯ：ＮｉＯ：ＣｕＯ＝６６．３：１９．６：９．３：４．８（重量％）であった。また、この仮焼後の材料の比表面積は１．２ｍ^２／ｇ、圧縮密度は２．４０ｇ／ｃｍ^３であった。次に、この仮焼体に水を加えて湿式粉砕処理した。この湿式粉砕は、ボール１５００ｇに対し、酸化物粉体１０００ｇとして湿式ボールミルにより２０時間行った。
【００３１】
次に、この粉砕された酸化物に結合剤、分散剤を適正量加えた後、スプレー乾燥装置を使用して乾燥造粒を行った。
【００３２】
（比較例２）−乾式粉砕
比較例１と同一の仮焼材を湿式粉砕することなく、乾式粉砕処理した。乾式粉砕は、乾式の振動式ボールミルにより行い、ボール４０００ｇに対し、酸化物粉体を６００ｇ加えて９０分行った。次にこの乾式粉砕したものを湿式工程でスラリー化した後、結合剤、分散剤等を適正量加え、スプレー乾燥装置を使用して乾燥造粒を行った。
【００３３】
（実施例１）−湿式粉砕＋乾式粉砕
比較例１のように湿式粉砕処理した後、これをさらに乾式粉砕処理した。乾式粉砕は、乾式の振動式ボールミルにより行い、ボール４０００ｇに対し、酸化物粉体を６００ｇ加えて６０分行った。次にこの乾式粉砕したものを湿式工程でスラリー化した後、結合剤、分散剤等を適正量加え、スプレー乾燥装置を使用して乾燥造粒を行った。
【００３４】
（実施例２）−湿式粉砕＋乾式粉砕
比較例１のように湿式粉砕処理した後、これを乾式粉砕処理した。乾式粉砕は、乾式の振動式ボールミルにより行い、ボール８０００ｇに対し、酸化物粉体を６００ｇ加えて６０分行った。次にこの乾式粉砕したものを湿式工程でスラリー化した後、結合剤、分散剤等を適正量加え、スプレー乾燥装置を使用して乾燥造粒を行った。
【００３５】
（特性等の測定）
上述のようにして作製した各粉体の粒度分布、種々の成形圧力における圧縮密度および成形圧力の変化に対する圧縮密度の変化を測定した。また、このような種々の粉体を用いて円環状に圧縮成形したものを焼成炉内で１０００〜１２００℃で焼成した。そして焼結体密度、電磁気特性（初期透磁率μ_ｉ、飽和磁束密度Ｂ_Ｓ）等を求めた。同様に、寸法精度、歩留まり等についてはドラム型コア形状にて求めた。
【００３６】
［粒度分布］
図３に前記各例における粒度分布を示す。図３に示すように、湿式粉砕のみによる比較例１の場合、乾式粉砕による比較例２や、湿式粉砕＋乾式粉砕による実施例１、２に比較して粒径が大きく、かつ粒度分布が尖鋭ではなく、粒径が広い範囲におよぶ。
【００３７】
比較例２や実施例１、２による場合には粒径や粒度分布にほとんど差がなく、湿式粉砕のみによる場合に比較して粒径を小さく、かつ粒径を揃えることができることが分かる。すなわち、実施例１、２による場合、乾式粉砕時間が短縮されたにもかかわらず（すなわち粉砕機の内壁やメディヤからの不純物の混入を少なくして）乾式粉砕のみによる比較例２とほぼ同様の粒度分布を得ることができる。
【００３８】
［圧縮密度］
表１のその１および図４に前記各例により得られた粉体を種々の成形圧力で成形した場合の圧縮密度を示す。表１のその１に示すように、湿式粉砕のみによる比較例１に比較し、乾式粉砕のみによる比較例２および湿式粉砕＋乾式粉砕による実施例１、２による場合、０．０５ＭＰａ〜０．３ＭＰａにおいて、高い圧縮密度を得ることができる。
【００３９】
【表１】

【００４０】
［Δｄ／ΔＰ］
表１のその２に、成形圧力（ＭＰａ）の変化量ΔＰに対する圧縮密度（ｇ／ｃｍ^３）の変化量Δｄの比Δｄ／ΔＰを、成形圧力の変化量が０．０５〜０．３、０．０５〜０．１、０．０５〜０．２、０．２〜０．３、０．１〜０．３（ＭＰａ）の各範囲について示す。
【００４１】
表１のその２から分かるように、湿式粉砕のみによる比較例１に比較し、乾式粉砕のみによる比較例２および湿式粉砕＋乾式粉砕による実施例１、２の場合、前記比Δｄ／ΔＰが小さくなり、低い圧力で高い圧縮密度が得られることが分かった。実施例１、２、比較例２においては、成形圧力の変化の範囲が０．０５〜０．３ＭＰａの範囲において、Δｄ／ΔＰ＝１．６以下の値が得られる。
【００４２】
［焼結体密度］
図５に実施例１、２と比較例１、２の成形体密度に対する焼結体密度を示す。実施例１、２による場合、成形体密度が３．２〜３．６ｇ／ｃｍ^３の範囲において、比較例１、２よりも高い焼結体密度が得られた。また、前記成形体密度の範囲において、成形体密度（ｇ／ｃｍ^３）の変化量Δｄに対する焼結体密度（ｇ／ｃｍ^３）の変化量ΔＤの比ΔＤ／Δｄは実施例１、２の場合０．１３以下となり、比較例１の場合の０．２５に比較して小さい値が得られ、成形体密度が低い場合でも焼結体密度が高いことが確認された。
【００４３】
［歩留まりおよび電磁気特性］
前記各例で得られた粉体を用いて成形圧０．１ＭＰａにより成形した場合の金型破損、有効成形数と歩留まりと電磁気特性（初期透磁率μ_ｉ、飽和磁束密度Ｂ_Ｓ）と焼結体密度を求めた結果を表２に示す。比較例１においては、５千個で摩耗が進行し、使用不可能となった。一方、比較例２および実施例１、２の場合には、２０万個の成形によっても使用不可能となる程の金型摩耗は生じなかった。
【００４４】
通常量産を考慮すると、８０％の以上の歩留まりが望ましい。比較例２の場合、２０万個の成形において、変形等のために寸法精度が悪く、６０〜７０％の歩留まりが得られたが、実施例１の場合、８５％以上の歩留まりが得られ、実施例２の場合、９０％以上の歩留まりが得られた。
【００４５】
また、表２に示すように、初透磁率μ_ｉ、飽和密度Ｂ_Ｓ、焼結体密度ｄについては、比較例１、２に比較し、実施例１、２による場合にはすべて優れた数値をあげることができた。これは実施例１、２の場合、焼結体の構成部分（巻心部、鍔部）の密度差が小さくすることができたためである。
【００４６】
【表２】

【００４７】
ドラムコア形状に成形したときの芯鍔比（巻心部の径または幅／鍔部の径または幅）と有効成形数（１セットの金型で成形できるコアの個数）との関係を表３に示す。表３に示すように、芯鍔比と有効成形数については、実施例１、２および比較例２による場合は、芯鍔比４５％までは有効成形数は２００，０００個以上得られており、実用上充分な成形数を得ている。また芯鍔比３５％では実施例１および比較例２で１００，０００個、実施例２で１５０，０００個と有効成形数は比較的減ってはいるが、実用的な成形数を得ている。比較例１においては、芯鍔比７０％までは実用上使用可能な成形数を得ているが、６５％を境界にして金型破損が発生し、有効成形数が激減する傾向にある。これは成形時に芯部に過剰な圧力がかかるため、金型が荷重に耐えられずに破損することによるものである。
【００４８】
【表３】

【００４９】
【発明の効果】
本発明によれば、湿式粉砕の後に乾式粉砕を行うため、粒径が小さい磁性酸化物粉体が得られ、低い成形圧で高い圧縮密度の成形体を得ることが可能となり、もって焼結体密度が高く、構成部分の密度差の小さい磁性部品およびコイル部品用のコアを得ることが可能となる。
【００５０】
また、単に乾式粉砕処理を行ったものに比較し、製品の歩留まりが向上する。このような歩留まりの向上は、低い成形圧で高い成形体密度を得ることができ、変形やひび割れを抑制することができる上、成形体の構成部分の密度差を極めて小さく抑えることができ、さらに不純物混入量を低下させて電磁気特性を向上させたことによる。
【００５１】
また、前記湿式粉砕、乾式粉砕後に、０．１ＭＰａにおける成形体密度が３．２ｇ／ｃｍ^３以上の成形体を得ることにより、焼結体密度が高く、電磁気特性が優れた磁性部品、コイル部品を得ることができる。
【００５２】
また、コアに加圧成形する際に、巻心部の加圧方向の最小幅を最大幅の６５％以下とするか、あるいはドラム型コア形状における巻心部の加圧方向の径または幅を、鍔の加圧方向の径または幅の６０％以下にしたもののように、複雑な形状の磁性部品を加工成形する際にも、構成部分の密度差が小さく、歩留まりの向上を達成することが可能となる。
【図面の簡単な説明】
【図１】（Ａ）は本発明により製造する磁性部品の一例であるドラムコアを示す側面図、（Ｂ）はその製造用金型を示す断面図である。
【図２】本発明による酸化物磁性粉体の製造方法の一実施の形態を示すブロック図である。
【図３】本発明の製造方法による酸化物磁性粉体と比較例の酸化物磁性粉体の粒度分布を示す図である。
【図４】本発明の製造方法による酸化物磁性粉体と比較例の酸化物磁性粉体の成形圧力と圧縮密度との関係を示す図である。
【図５】本発明の製造方法による酸化物磁性粉体と比較例の酸化物磁性粉体の成形体密度と焼結体密度との関係を示す図である。
【符号の説明】
１：ドラムコア、１a：巻心部、１ｂ：鍔部、２：下型、３：上型[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molding method and magnetic components and coil component of the core using the production method of the oxide magnetic powder and core and said oxide magnetic powder, as in particular a drum-type core shape, a complex shape The present invention relates to a material suitable for magnetic parts.
[0002]
[Prior art]
In general, magnetic oxide powders such as Ni-Zn-based ferrites are baked at appropriately controlled high temperatures after passing through the steps of mixing material oxides-calcining-grinding-granulating-forming. It is manufactured.
[0003]
Among the steps, the pulverization is generally wet pulverization. However, when the powder material after wet pulverization is formed, it is generally difficult to increase the density of the formed body. For this reason, it is known that when the compact density is increased by increasing the molding pressure, deformation and cracks occur after firing due to cracks during molding and non-uniform density inside the compact.
[0004]
Further, when the coil component core having a complicated shape, such as the drum core 1 shown in FIG. 1 (A), is formed by the lower die 2 and the upper die 3 shown in FIG. 1 (B), both ends of the core 1a. Many cases have been reported in which, when an excessive pressure is applied for the purpose of preventing a decrease in density of the flange portion 1b, the

molds

2 and 3 are damaged due to concentration of stress only in the core portion 1a. In particular, in FIG. 1A, the diameter in the pressing direction of the core 1a (when the core of the core 1 is cylindrical as shown) or the width (when the core of the core 1 is prismatic) ) When a is a shape that is 60% or less of the diameter (when the collar is cylindrical) or the width (when the collar is a polygonal column) b in the pressing direction of the collar 1b, FIG. 1 (B) As shown in FIG. 3, when the pressure is applied in the direction perpendicular to the direction of the core axis of the core portion 1a, a density difference is generated in which the core portion 1a is relatively dense and the flange portion 1b is relatively sparse. It is known that cracks, deformations, and mold damage occur.
[0005]
As means for solving these problems, as described in JP-A-9-306774, an intermediate portion of a molded body integrally formed into a cylinder or a prismatic shape is cut to reduce the diameter or width of the core portion 1a. A method of processing to 60% or less of 1b may be used. However, in the case of this cutting, the productivity is poor, and the productivity including the dimensional accuracy is lowered as the size becomes smaller, for example, about 1 mm.
[0006]
In addition to this cutting method, cold isostatic pressing (CIP) is known in which molding pressure is applied relatively uniformly from all directions at the time of molding, but the effect is great when producing relatively large shaped bodies. However, the effect is insufficient for a complex molded body such as a drum core, and the ability to be molded at one time is limited, which is not a method suitable for mass production.
[0007]
Furthermore, in recent years, various electronic devices have been rapidly reduced in size and weight, and in order to cope with this, demands for miniaturization and higher performance of electronic components used in the electric circuits of these electronic devices have also increased rapidly. . For this reason, in order to cope with further miniaturization of parts, not only the development of molding methods that can be molded in large quantities and precisely in a limited time, but also efforts from fields related to powder materials It has become essential.
[0008]
In order to meet these requirements, Japanese Patent Application Laid-Open No. 5-43248 discloses that the compression density of the compact is 2. by changing the agglomeration state of the powder by dry pulverizing the powder material and then performing wet pulverization. 6g ^/ cm ³ ~3.2g ^/ cm 3 range continuously controlled to the density control method is described.
[0009]
[Problems to be solved by the invention]
As described above, when the oxide magnetic powder after calcination is pulverized only by wet pulverization, the powder cannot be agglomerated and the compression density cannot be increased. In addition, coarse particles tend to remain.
[0010]
On the other hand, with only dry pulverization, coarse particles can be refined and powders can be agglomerated, but there is a problem that the sintered body density does not increase and the desired electromagnetic properties cannot be obtained. In addition, there is a problem that impurities are mixed in from the inner wall and media of the pulverizer before pulverization to the target average particle diameter.
[0011]
Therefore, as described in JP-A-5-43248, it is conceivable to perform wet pulverization after dry pulverization of the powder material, but according to this method, the aggregation formed by dry pulverization is slightly loosened. It has a tendency and the compression density further decreases. As a result, it is difficult to obtain a compact having a high density of 3.2 g / cm ³ or more as the compression density of the compact, and thus it is difficult to obtain a core having a high compact strength. In addition, it is difficult to suppress problems such as density difference and deformation inside the sintered body, and there is a problem that a magnetic component having excellent dimensional accuracy and electromagnetic characteristics cannot be manufactured stably.
[0012]
In view of such problems of the prior art, the present invention has a high density as a molded part of a magnetic part, a small density difference inside the sintered body, and can suppress deformation, and has excellent dimensional accuracy and electromagnetic characteristics. It is an object of the present invention to provide an oxide magnetic powder and a method for producing a core that can be obtained. Another object of the present invention is to provide a core molding method, a magnetic component and a coil component using the oxide magnetic powder .
[0013]
[Means for Solving the Problems]
The core manufacturing method of the present invention is a method of weighing and mixing a plurality of types of oxides used as magnetic oxide materials, calcining, adding water to the calcined magnetic oxide powder, and subjecting it to wet pulverization. Then, the dried magnetic oxide powder is dried and subjected to dry pulverization to refine the magnetic oxide powder. The refined powder is slurried, dried, granulated, and oxidized with high compression density. A magnetic material powder is obtained, and the oxide magnetic powder is molded to obtain a core (claim 1).
[0014]
Thus, by performing dry pulverization after wet pulverization, it becomes easier to cause agglomeration than in the case of simply using wet pulverization, the compression density can be increased, and wet pulverization can be performed more simply than in the case of simply using dry pulverization. By performing the pretreatment, the density of the sintered body can be increased and the electromagnetic characteristics of the core can be improved.
[0015]
In addition, by performing dry pulverization after wet pulverization, the dry pulverization time can be shortened, so that contamination from impurities from the inner wall of the pulverizer and media can be reduced. In combination with the reduction in the density difference between the part and the collar part, the electromagnetic characteristics of the core can be improved.
[0016]
More specifically, coarse particles in the magnetic oxide powder that could not be sufficiently pulverized by wet pulverization were pulverized in a short time, and the average particle size was 0.4 to 1.8 μm, more preferably 0.6 to An oxide magnetic powder having a sharp particle size distribution of 1.2 μm can be obtained.
[0017]
Further, while processing the specific surface area to 2.4 g / cm ³ or more, the oxide magnetic powder is agglomerated so that the compression density of the compact can be controlled to 3.2 g / cm ³ or more even under low pressure molding. A core having a complicated shape can be integrally formed without grinding or the like.
[0018]
In the present invention, a wet ball mill, an attritor, or the like can be used as a pulverizer for wet pulverization, and a dry ball mill, a vibration mill, or the like can be used as a pulverizer for dry pulverization.
[0019]
As a method for producing a core of the present invention, a magnetic oxide is also a Mn—Zn ferrite, but a core production method using a Ni—Zn ferrite that has a particularly high electrical resistance and can be wound directly on a coil ( Claim 2) can be preferably applied.
[0020]
Moreover, when the manufacturing method according to the present invention is carried out, a molded body having a molded body density of 0.1 g / cm ³ or more at 0.1 MPa is obtained by molding the oxide magnetic powder obtained by the dry granulation. (Claim 3) It becomes possible to perform the pulverization treatment.
[0021]
When the oxide magnetic powder obtained by the dry granulation by the production method of the present invention is pressed into a core shape, the minimum width in the pressing direction of the core is set to 65, the maximum width in the pressing direction. % Or less (Claim 4), the yield as a sintered product can be increased.
[0022]
Further, when the oxide magnetic powder obtained by the dry granulation by the production method of the present invention is pressed into a drum-shaped core shape in a direction perpendicular to the direction of the core axis, It is possible to increase the yield as a sintered product by forming the diameter or width in the pressing direction to 60% or less of the diameter or width in the pressing direction of the collar (Claim 5). it can.
[0023]
Further, the amount of change Δd (g / cm ³ ) in the compact density relative to the amount of change ΔP (MPa) in molding pressure when the oxide magnetic powder obtained by the dry granulation is formed by the production method of the present invention. In the molding pressure range where the ratio Δd / ΔP is 0.05 MPa to 0.3 MPa,
It is possible to obtain an oxide magnetic powder satisfying Δd / ΔP ≦ 1.6 (Claim 6) and to have such characteristics, so that cracking and deformation in a sintered product can be achieved at a low molding pressure. This is preferable in order to obtain a high compression density and a uniform density distribution.
[0024]
The ratio of the amount of change in green density of more resulting oxide magnetic powder in the production method of the present invention Δd for (g / cm ^3), the amount of change in density after sintering ΔD (g / cm ³⁾ It is possible to obtain an oxide magnetic powder (Claim 7) in which ΔD / Δd is ΔD / Δd ≦ 0.13 and to have such characteristics at a low molding pressure (that is, in a sintered product). This is preferable in order to obtain a high sintered body density (with fewer cracks and deformation).
[0025]
Further, molded from the more obtained in the production process oxide magnetic powder of the present invention, by a magnetic component comprising sintered (Claim 8), the density difference between the sintered body portion is small, less deformation A magnetic component having a good yield and excellent electromagnetic characteristics can be obtained.
[0026]
Moreover, a coil component having excellent electromagnetic characteristics can be obtained by obtaining a coil component having a magnetic component as a core according to the manufacturing method of the present invention (claim 9).
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The method for producing oxide magnetic powder of the present invention is suitable for obtaining materials for inductors, transformers, antennas, television cathode ray tubes, and other parts that require magnetism, and is particularly shown in FIG. Oxide magnetic powder for obtaining a magnetic part having a complicated shape such as a drum core, that is, with respect to the moving direction of the mold at the time of molding, in which the diameter or widths a and b of the molded body are significantly different It is suitable as a body .
[0028]
FIG. 2 is a block diagram showing an embodiment of a method for producing oxide magnetic powder according to the present invention. As shown in FIG. 2, in the present embodiment, individual oxide powders are weighed and added with water so as to obtain ferrite having predetermined characteristics (step a). Next, dry granulation is performed using a spray dryer or the like (step b). Next, this powder is calcined (step c).
[0029]
Next, water is added to the sintered body and wet pulverized by a wet ball mill or the like (step d). This pulverized product is dried (step e). The wet pulverized and dried product is then dry pulverized by a dry vibration ball mill or the like (step f). Next, an appropriate amount of a dispersant, a binder or the like is added (step g), and dry granulation is performed using a spray dryer or the like (step h) to obtain an oxide magnetic material powder .
[0030]
【Example】
(Comparative Example 1) - Wet grinding _{_{Fe 2 O 3, ZnO, NiO}} , and after wet mixing the oxide powder consisting of CuO in a predetermined molar ratio, and then calcined at 900 ° C.. The resulting oxide composition is
_{_{Fe 2 O 3: ZnO: NiO}} : CuO = 66.3: 19.6: 9.3: was 4.8 (wt%). The calcined material had a specific surface area of 1.2 m ² / g and a compression density of 2.40 g / cm ³ . Next, water was added to the calcined body and wet pulverized. This wet pulverization was carried out for 20 hours by using a wet ball mill as 1000 g of oxide powder with respect to 1500 g of balls.
[0031]
Next, after adding appropriate amounts of a binder and a dispersant to the pulverized oxide, dry granulation was performed using a spray dryer.
[0032]
(Comparative Example 2) -Dry pulverization The same calcined material as in Comparative Example 1 was dry pulverized without wet pulverization. Dry pulverization was performed by a dry vibration ball mill, and 600 g of oxide powder was added to 4000 g of the ball for 90 minutes. Next, after this dry pulverized product was slurried in a wet process, an appropriate amount of a binder, a dispersant, and the like were added, and dry granulation was performed using a spray drying apparatus.
[0033]
(Example 1)-Wet grinding + dry grinding After wet grinding as in Comparative Example 1, this was further dry ground. Dry pulverization was performed by a dry vibration ball mill, and 600 g of oxide powder was added to 4000 g of balls for 60 minutes. Next, after this dry pulverized product was slurried in a wet process, an appropriate amount of a binder, a dispersant, and the like were added, and dry granulation was performed using a spray drying apparatus.
[0034]
(Example 2)-Wet grinding + dry grinding After wet grinding as in Comparative Example 1, this was dry ground. Dry pulverization was performed by a dry vibration ball mill, and 600 g of oxide powder was added to 8000 g of balls for 60 minutes. Next, after this dry pulverized product was slurried in a wet process, an appropriate amount of a binder, a dispersant, and the like were added, and dry granulation was performed using a spray drying apparatus.
[0035]
(Measurement of characteristics etc.)
The particle size distribution of each powder produced as described above, the compression density at various molding pressures, and the change in the compression density with respect to the change in the molding pressure were measured. Moreover, what was compression-molded in the annular | circular shape using such various powder was baked at 1000-1200 degreeC in the baking furnace. Then, the sintered body density, electromagnetic characteristics (initial magnetic permeability μ _i , saturation magnetic flux density B _S ) and the like were determined. Similarly, dimensional accuracy, yield, and the like were obtained from the drum core shape.
[0036]
[Particle size distribution]
FIG. 3 shows the particle size distribution in each of the above examples. As shown in FIG. 3, in the case of Comparative Example 1 using only wet pulverization, the particle size is large and the particle size distribution is sharp compared to Comparative Example 2 using dry pulverization and Examples 1 and 2 using wet pulverization and dry pulverization. Rather, the particle size ranges over a wide range.
[0037]
In the case of Comparative Example 2 and Examples 1 and 2, there is almost no difference in particle size and particle size distribution, and it can be seen that the particle size can be made smaller and the particle size can be made uniform as compared with the case of only wet pulverization. That is, in the case of Examples 1 and 2, although the dry pulverization time was shortened (that is, mixing of impurities from the inner wall and media of the pulverizer was reduced), it was almost the same as Comparative Example 2 using only dry pulverization. A particle size distribution can be obtained.
[0038]
[Compression density]
Part 1 of Table 1 and FIG. 4 show the compression density when the powders obtained in the above examples were molded at various molding pressures. As shown in Part 1 of Table 1, 0.05 MPa to 0.3 MPa in the case of Comparative Example 2 only by dry grinding and Examples 1 and 2 by wet grinding + dry grinding as compared with Comparative Example 1 only by wet grinding. , A high compression density can be obtained.
[0039]
[Table 1]

[0040]
[Δd / ΔP]
Table 2 shows the ratio Δd / ΔP of the change amount Δd of the compression density (g / cm ³ ) to the change amount ΔP of the molding pressure (MPa). The change amount of the molding pressure is 0.05 to 0.3, It shows about each range of 0.05-0.1, 0.05-0.2, 0.2-0.3, 0.1-0.3 (MPa).
[0041]
As can be seen from Part 2 in Table 1 , the ratio Δd / ΔP is smaller in the case of Comparative Example 2 in which only dry pulverization is used and in Examples 1 and 2 in which wet pulverization and dry pulverization are used compared with Comparative Example 1 in which only wet pulverization is performed Thus, it was found that a high compression density can be obtained at a low pressure. In Examples 1 and 2 and Comparative Example 2, a value of Δd / ΔP = 1.6 or less is obtained when the range of change in molding pressure is 0.05 to 0.3 MPa.
[0042]
[Sintered body density]
FIG. 5 shows the sintered body density with respect to the molded body density of Examples 1 and 2 and Comparative Examples 1 and 2. In the case of Examples 1 and 2, a sintered body density higher than that of Comparative Examples 1 and 2 was obtained in the range where the green body density was 3.2 to 3.6 g / cm ³ . It is also in the scope of the green density, the ratio [Delta] D / [Delta] d of the variation [Delta] D of the sintered body density with respect to the change amount [Delta] d of the green density ^{(g / cm 3) (g} / cm 3) is the Examples 1 and 2 In the case of 0.13 or less, a small value was obtained compared to 0.25 in the case of Comparative Example 1, and it was confirmed that the sintered body density was high even when the compact density was low.
[0043]
[Yield and electromagnetic characteristics]
Die breakage, effective molding number and yield, electromagnetic characteristics (initial magnetic permeability μ _i , saturation magnetic flux density B _S ) and sintering when the powder obtained in each of the above examples is molded at a molding pressure of 0.1 MPa. Table 2 shows the results of the body density. In Comparative Example 1, the abrasion progressed after 5,000 pieces, making it unusable. On the other hand, in the case of Comparative Example 2 and Examples 1 and 2, there was no mold wear that could not be used even after molding 200,000 pieces.
[0044]
Considering normal mass production, a yield of 80% or more is desirable. In the case of Comparative Example 2, in 200,000 moldings, dimensional accuracy was poor due to deformation and the like, and a yield of 60 to 70% was obtained. In the case of Example 1, a yield of 85% or more was obtained, In the case of Example 2, a yield of 90% or more was obtained.
[0045]
As shown in Table 2, the initial permeability μ _i , the saturation density B _S , and the sintered body density d are all superior in comparison with Comparative Examples 1 and 2 and according to Examples 1 and 2. I was able to give. This is because in the case of Examples 1 and 2, the density difference between the constituent parts (the core part and the collar part) of the sintered body could be reduced.
[0046]
[Table 2]

[0047]
Table 3 shows the relationship between the core ratio (diameter or width of the core part / diameter or width of the collar part) and the number of effective moldings (number of cores that can be molded with one set of molds) when molded into a drum core shape. Show. As shown in Table 3, with respect to the core ratio and the number of effective moldings, in the case of Examples 1 and 2 and Comparative Example 2, the number of effective moldings of 200,000 or more was obtained up to a core ratio of 45%. A practically sufficient number of moldings has been obtained. Further, when the core ratio is 35%, the number of effective moldings is relatively reduced to 100,000 in Example 1 and Comparative Example 2 and 150,000 in Example 2, but a practical number of moldings is obtained. . In Comparative Example 1, the number of moldings that can be practically used is obtained up to a core ratio of 70%, but the mold breakage occurs at 65% as a boundary, and the number of effective moldings tends to decrease drastically. This is because an excessive pressure is applied to the core during molding, and the mold is damaged without being able to withstand the load.
[0048]
[Table 3]

[0049]
【The invention's effect】
According to the present invention, since the dry pulverization is performed after the wet pulverization, a magnetic oxide powder having a small particle size can be obtained, and a compact with a high compression density can be obtained with a low molding pressure. It is possible to obtain a magnetic component and a core for a coil component having a high density and a small density difference between constituent parts.
[0050]
Further, the yield of the product is improved as compared with the case where the dry pulverization process is simply performed. Such an improvement in yield can obtain a high molded body density with a low molding pressure, can suppress deformation and cracking, and can suppress the density difference of the constituent parts of the molded body to be extremely small. This is because the electromagnetic characteristics are improved by reducing the amount of impurities.
[0051]
In addition, after obtaining the above-mentioned wet pulverization and dry pulverization, by obtaining a molded body having a molded body density of 0.1 g / cm ³ or more at 0.1 MPa, a magnetic component and a coil component having a high sintered body density and excellent electromagnetic characteristics. Can be obtained.
[0052]
Further, when the core is pressure-molded, the minimum width in the pressing direction of the core is set to 65% or less of the maximum width, or the diameter or width in the pressing direction of the core in the drum core shape is set. Even when a magnetic part having a complicated shape, such as one having a diameter or width in the pressing direction of the ridge of 60% or less, is processed, the difference in density of the constituent parts is small, and the yield can be improved. It becomes possible.
[Brief description of the drawings]
FIG. 1A is a side view showing a drum core as an example of a magnetic component manufactured according to the present invention, and FIG. 1B is a cross-sectional view showing a mold for manufacturing the drum core.
FIG. 2 is a block diagram showing an embodiment of a method for producing an oxide magnetic powder according to the present invention.
3 is a diagram showing a particle size distribution of the oxide magnetic powder of Comparative Example and oxide magnetic powder according to the production method of the present invention.
FIG. 4 is a diagram showing the relationship between the compacting pressure and the compression density of the oxide magnetic powder produced by the production method of the present invention and the comparative oxide magnetic powder .
FIG. 5 is a graph showing the relationship between the density of a compact and the density of a sintered oxide magnetic powder produced by the production method of the present invention and a comparative oxide magnetic powder .
[Explanation of symbols]
1: drum core, 1a: winding core, 1b: collar, 2: lower mold, 3: upper mold

Claims

Weighing and blending multiple types of oxides as magnetic oxide materials, calcining, adding water to the calcined magnetic oxide powder and subjecting it to wet pulverization, then drying, and drying The magnetic oxide powder is subjected to dry pulverization to refine the magnetic oxide powder, the refined powder is slurried, and dry granulated to obtain an oxide magnetic powder having a high compression density. A method for producing a core , comprising molding a magnetic powder to obtain a core .

The method for producing a core , wherein the magnetic oxide according to claim 1 is Ni-Zn ferrite.

The method of manufacturing a core according to claim 1 or 2, by forming the oxide magnetic powder obtained by the dry granulation, the compact density of 3.2 g / cm ³ or more cores in 0.1MPa A method for producing a core , characterized in that it is obtained.

When the oxide magnetic powder used in the manufacturing method according to claim 1 or 2 is pressed into a core shape, the minimum width in the pressing direction of the core is set to 65% or less of the maximum width in the pressing direction. A core molding method characterized by molding.

When the oxide magnetic powder used in the manufacturing method according to claim 1 or 2 is pressed into a drum-shaped core shape in a direction perpendicular to the direction of the core axis, A method for forming a core, characterized in that the diameter or width is set to 60% or less of the diameter or width in the pressing direction of the collar portion.

The oxide magnetic powder used in the production method according to claim 1 or 2, wherein a ratio of a change amount Δd (g / cm ³ ) of a compact density to a change amount ΔP (MPa) of a molding pressure during molding. In a molding pressure range where Δd / ΔP is 0.05 MPa to 0.3 MPa,
Δd / ΔP ≦ 1.6 Oxide magnetic powder , characterized in that

An oxide magnetic powder used in the production method according to claim 1 or 2, with respect to the amount of change in green density Δd (g / cm ^3), after sintering density variation ΔD (g / cm ³ oxide magnetic powder the ratio [Delta] D / [Delta] d in) are characterized by a ΔD / Δd ≦ 0.13.

3. A magnetic component formed and sintered using the oxide magnetic powder used in the manufacturing method according to claim 1 or 2.

A coil component comprising the magnetic component according to claim 8 as a core.