JP3812926B2

JP3812926B2 - Rare earth bonded magnet compound, method for producing the same, and R-T-B bonded magnet

Info

Publication number: JP3812926B2
Application number: JP08270699A
Authority: JP
Inventors: 克典岩崎; 一憲田原
Original assignee: Neomax Co Ltd
Current assignee: Proterial Ltd
Priority date: 1998-04-06
Filing date: 1999-03-26
Publication date: 2006-08-23
Anticipated expiration: 2019-03-26
Also published as: JPH11354363A

Description

【０００１】
【発明の属する技術分野】
本発明は良好な寸法精度と高い磁気特性とを具備するＲ−Ｔ−Ｂ系ボンド磁石、特に薄肉または薄肉長尺形状のものに関する。また本発明は、前記ボンド磁石を実現可能な原料コンパウンドならびにその製造方法に関する。
【０００２】
【従来の技術】
希土類ボンド磁石に多用されている磁石粉末は、Ｎｄ_２Ｆｅ_１４Ｂ型金属間化合物を主相とする合金組成に調整した溶湯を、溶湯急冷法により超急冷しいったん非晶質合金を得る。続いて必要に応じて粉砕後、熱処理を施して結晶化したＮｄ_２Ｆｅ_１４Ｂ型金属間化合物を主相とする等方性の磁石粉末である。その他、前記合金組成に調整後、ストリップキャスト法または高周波溶解法等により溶解、鋳造して得られた合金を粉砕し、続いていわゆる水素化、相分解、脱水素、再結合処理法（特許第１９４７３３２号参照）を適用して異方性を有する微細再結晶組織のＮｄ_２Ｆｅ_１４Ｂ型金属間化合物を主相とするボンド磁石用粉末としたものがある。あるいは前記非晶質合金の薄片をホットプレス等により温間で加圧成形し高密度化後さらに温間で据込み加工等の塑性加工を施すことにより異方性を有する微細結晶組織のＮｄ_２Ｆｅ_１４Ｂ型金属間化合物を主相とするボンド磁石用粉末としたものがある。
昨今の希土類ボンド磁石には高性能化（薄肉化）とともに厳しい寸法精度が求められつつある。例えば移動体通信用の電子ブザーに用いる場合、振動板とのギャップ調整により音質を調整する方法が採用される。組立工程も自動化ラインで行われるため、希土類ボンド磁石を含めた電子ブザー用部品の寸法精度を向上することが性能向上に必須である。また、例えばコンピュータのハードディスクドライブを構成するスピンドルモーター用、ＣＤ−ＲＯＭ駆動装置のモーター用、さらには今後ＤＶＤ（デジタルビデオディスク）用の希土類ボンド磁石に対して、特に高い磁気特性（薄肉化）および厳しい寸法精度の要求が見込まれる。接着剤による継ぎ目をなくすことで組立工数の削減とともに高性能化を実現できるため、長尺でかつ一体ものの希土類ボンド磁石のニーズがある。さらに薄肉長尺品形状の希土類ボンド磁石を求めるニーズもある。ここで、本発明における長尺とは高さ寸法が１０ｍｍ以上のもの、薄肉とは肉厚が３ｍｍ以下のものをいう。このように、昨今の希土類ボンド磁石には薄肉化、長尺化または薄肉長尺化とともに磁気特性および寸法精度のさらなる向上が求められている。
【０００３】
薄肉または薄肉長尺形状の希土類ボンド磁石は、成形方法および使用するコンパウンドの性状等により磁気特性および寸法精度が大きく影響を受ける。前記希土類ボンド磁石の成形方法として、圧縮成形、射出成形または押出成形の採用が一般的である。圧縮成形法による場合は、希土類ボンド磁石用のコンパウンドを所定の成形金型のキャビティに充填後加圧成形して成形体を作製する。その後加熱硬化して希土類ボンド磁石を得る。近年、メカプレスあるいはロータリープレスといった圧縮成形技術の進展により高速成形が可能となった。しかし、ボンド磁石の製品形状が薄肉化または薄肉長尺化するに従い、キャビティへの給粉が困難になる他、特に充填深さ方向（加圧方向）への圧力伝達が不十分になり、１成形品内において加圧力を直接受ける両端部に比べて中央部付近の密度が低くなるという問題がある。この密度ばらつきは磁気特性、製品寸法のばらつきを招来する。
【０００４】
【発明が解決しようとする課題】
本発明の課題は、良好な寸法精度と高い磁気特性とを具備するＲ−Ｔ−Ｂ系ボンド磁石、特に薄肉または薄肉長尺形状のものを提供することである。また本発明は、前記ボンド磁石を実現可能な原料コンパウンドならびにその製造方法を提供することである。
【０００５】
【課題を解決するための手段】
上記課題を解決した本発明の希土類ボンド磁石用コンパウンドの製造方法は、希土類磁石粉末と熱硬化性樹脂とから実質的になる（但し、熱硬化性樹脂の含有量は０．５重量％以上２０重量％未満である。）混合物を押出装置に投入し、押出しの加圧力により押出装置に設けた直径５０〜３００μｍのノズル穴から押出して押出物を得る工程、得られた押出物を、最大径ａと最小径ｂの比（ａ／ｂ）が１．００を超えて３以下であり、かつ（ａ＋ｂ）／２で定義する平均粒径が５０〜３００μｍである丸みを帯びた形状に整粒する工程、および得られた整粒を９０〜１５０℃で加熱する工程を有することを特徴とする。９０〜１５０℃で加熱する処理を施した後の整粒に対し、０．０１〜０．５重量％の潤滑剤を添加することが好ましい。
前記ノズル穴から強制的に押出されたものはノズル穴の直径と略同一の断面積を有する略円柱状細粒形状を呈する。その後、切断力と遠心力の作用下で整粒する方式の整粒装置（マルメライザーまたはドライスプレー等）で整粒して丸みを帯びたコンパウンドの粒にする。このコンパウンド粒を用いて圧縮成形法により薄肉品または薄肉長尺品を成形した場合、１成形品における密度のばらつきが非常に小さくなるとともに、従来に比べて良好な磁気特性および寸法精度を実現できる。従来より、希土類磁石粉末と樹脂との混練（後述の予備混練に相当）には二軸混練機等を用いて、さらにペレタイジングしてペレット状のコンパウンドを得ている。この従来のコンパウンド（ペレット）は空隙をかなり含み、角張った不定形状のため流動性（成形性）に乏しいという欠点を有する。従来のペレットを用いて、圧縮成形法により、薄肉または薄肉長尺形状の希土類ボンド磁石を作製すると、１成形品において大きな密度のばらつきを発生し、加圧力の直接作用する両端部に比べて中心部の密度が大きく低下するという問題がある。同時に中実円筒状の場合は外径真円度が、リング形状の場合は外径／内径真円度が劣化する。真円度不良のリング磁石を用いて回転子を構成し、回転機に組み込んだ場合は、前記リング磁石の真円度不良を反映して回転子の偏芯量が大きくなり、回転時の回転子と固定子との間隔（エアギャップ間隔）の不均一性が増大する。エアギャップ間隔の不均一性の増大は回転機の出力ばらつきを招来する。また、回転子と固定子の接触事故を未然に防ぐために、回転子の偏芯量を加味したエアギャップ間隔を採用せざるを得ず、高効率の回転機を構成できないという問題がある。本発明者らは、従来のペレットを前記穴径に形成したノズル穴を付設した押出装置に投入し、ノズル穴から混練物を強制的に押出すことにより押出物の密度を高め、続いて押出物を切断と整粒とが同時に行える整粒装置に投入して丸みを帯びた粒状のコンパウンドを得た。このコンパウンドを用いて圧縮成形法により希土類ボンド磁石を作製すると、１成形品内での密度のばらつきが小さく抑えられ、同時に高い磁気特性と良好な寸法精度が得られることを知見した。特に、マルメライザーを用いてその回転盤の回転速度と回転盤上面に設けた溝部の形状、配置、寸法との相関から最適な整粒条件を設定すると、回転盤の回転とともに前記略円柱状細粒物がほぼその直径と等しい長さで切断されつつ回転力により丸められ、比表面積の小さなコンパウンドになった。このコンパウンドに対して潤滑剤（ステアリン酸カルシウム等）を０．０１〜０．５ｗｔ％相当分添加したものは良好な流動性および圧力伝達性を示す。潤滑剤の添加量が０．０１ｗｔ％未満では潤滑効果が得られず、０．５ｗｔ％超では添加効果が飽和する。
【０００６】
本発明において、最大径とはコンパウンド、磁石粉末またはノズル穴断面を撮影した写真において、その最大長を最大径と定義する。最小径とは最大径に直交する方向の最大長をいう。このことを模式的に図１４に示す。
【０００７】
本発明の希土類ボンド磁石用コンパウンドは、希土類磁石粉末と熱硬化性樹脂および潤滑剤とから実質的になる（但し、熱硬化性樹脂の含有量は０．５重量％以上２０重量％未満であり、潤滑剤が０．０１〜０．５重量％添加されている。）、圧縮成形法による希土類ボンド磁石用コンパウンドであって、最大径ａと最小径ｂの比（ａ／ｂ）が１．００を超えて３以下であり、かつ（ａ＋ｂ）／２で定義する平均粒径が５０〜３００μｍである丸みを帯びた粒状であり、ＪＩＳ規格（Ｚ２５０２）に基づく流動性が１．８４〜２．４３ｇ／秒の範囲内にあることを特徴とする。前記コンパウンドは、９０〜１５０℃で加熱する処理を施すことにより良好な流動性を具備することができる。
前記コンパウンドの一粒内に最小径が３〜４０μｍの希土類磁石粉末の粒子が平均値で１０個以上含まれる。本発明のコンパウンドは軟化状態で前記穴径のノズル穴を強制的に通過する際に高い加圧力を受けるので希土類磁石粉末が結着樹脂中に密に充填される。よって、個々のコンパウンド粒内には少なくとも最小径が３〜４０μｍの希土類磁石粉末の粒子が平均値で１０個以上充填される。充填個数が１０個未満では従来よりも磁気特性、寸法精度を改善することが困難である。コンパウンドの形態は走査型電子顕微鏡（ＳＥＭ）により確認することができる。（ａ／ｂ）が３を超えると長細の形状になり流動性（給粉性）が大きく低下し、（ａ／ｂ）が１．００のものは工業生産上作製が困難である。平均粒径（ａ＋ｂ）／２はノズル穴の径寸法により制約されるため、５０〜３００μｍが適当である。５０μｍ未満では前記Ｒ_２Ｔ_１４Ｂ型金属間化合物を主相とする磁石粉末を分散したコンパウンドの押出しが困難な場合があり、３００μｍ超ではコンパウンドの流動性が大きく低下する。
ノズル穴の作製はドリル加工によるのが実用的である。直径３００μｍ以下のノズル穴はレーザー加工または電子ビーム加工により形成することがより好ましく、ノズル穴の寸法精度を高められる。コンパウンドの平均粒径に対応してノズル穴の直径は５０〜３００μｍにされる。ノズル穴の直径が５０μｍ未満では磁石粉末の詰まりにより押出が困難な場合が発生し、３００μｍ超では従来に比べてコンパウンドの流動性、圧力伝達性、さらには希土類ボンド磁石の磁気特性および寸法精度を改善することが困難になる。ノズル穴の断面形状は楕円、矩形または不定形であってもよいが、いずれにしろノズル穴の断面形状において最大径を３００μｍ以下、最小径を５０μｍ以上とすることがコンパウンドの流動性、圧力伝達性を改善するために必要である。コンパウンドの一粒内に平均値で１０個以上含まれる希土類磁石粉末粒子の最小径の上限は、溶湯急冷法によるＲ_２Ｔ_１４Ｂ型金属間化合物を主相とする磁石粉末を用いる場合、溶湯急冷法による非晶質合金薄片の厚みの最大値（約４０μｍ）に相当し、最小径の下限は３μｍである。３μｍ未満では酸化劣化が顕著になる。
【０００８】
本発明のＲ−Ｔ−Ｂ系ボンド磁石は、Ｒ_２Ｔ_１４Ｂ型金属間化合物を主相とする平均結晶粒径が０．０１〜０．５μｍのＲ−Ｔ−Ｂ系合金の粉末（ＲはＹを含む希土類元素の１種または２種以上、ＴはＦｅまたはＦｅとＣｏ）と熱硬化性樹脂及び潤滑剤とから実質的になる（但し、熱硬化性樹脂の含有量は０．５重量％以上２０重量％未満であり、潤滑剤が０．０１〜０．５重量％添加されている。）Ｒ−Ｔ−Ｂ系コンパウンドを、圧縮成形し、加熱硬化したもので、前記コンパウンドは、最大径ａと最小径ｂの比（ａ／ｂ）が１．００を超えて３以下であり、かつ（ａ＋ｂ）／２で定義する平均粒径が５０〜３００μｍである丸みを帯びた粒状であり、ＪＩＳ規格（Ｚ２５０２）に基づく流動性が１．８４〜２．４３ｇ／秒の範囲内にあり、前記ボンド磁石は、（外径寸法−内径寸法）／２で定義する肉厚が０．３〜３ｍｍでありかつ高さ寸法が５０ｍｍ以下（より好ましくは５〜５０ｍｍ）のリング形状を有し、１成形品の密度が６．０ｇ／ｃｍ^３以上であるとともに１成形品の高さ方向における両端部の密度が高く中心部の密度が低い密度分布を有し、かつ１成形品における密度の最大値と最小値の差が０．３ｇ／ｃｍ^３以下（より好ましく０．２ｇ／ｃｍ^３以下）であり、外径寸法の真円からのずれが１０μｍ未満になっている。また内径寸法の真円からのずれが１０μｍ未満になっている。
よって、この薄肉または薄肉長尺リング磁石を用いて回転子を構成し、回転機に組み込んだ場合、エアギャップの間隔を従来より狭めることが可能で、高効率の回転機を構成することができる。なお、前記リング形状範囲を外れると、従来に比べて高い磁気特性および良好な寸法精度を実現困難な場合が発生する。
【０００９】
また、本発明のＲ−Ｔ−Ｂ系ボンド磁石は、Ｒ_２Ｔ_１４Ｂ型金属間化合物を主相とする平均結晶粒径が０．０１〜０．５μｍのＲ−Ｔ−Ｂ系合金の粉末（ＲはＹを含む希土類元素の１種または２種以上、ＴはＦｅまたはＦｅとＣｏ）と熱硬化性樹脂および潤滑剤とから実質的になる（但し、熱硬化性樹脂の含有量は０．５重量％以上２０重量％未満であり、潤滑剤が０．０１〜０．５重量％添加されている。）Ｒ−Ｔ−Ｂ系コンパウンドを、圧縮成形し、加熱硬化したもので、前記コンパウンドは、最大径ａと最小径ｂの比（ａ／ｂ）が１．００を超えて３以下であり、かつ（ａ＋ｂ）／２で定義する平均粒径が５０〜３００μｍである丸みを帯びた粒状であり、ＪＩＳ規格（Ｚ２５０２）に基づく流動性が１．８４〜２．４３ｇ／秒の範囲内にあり、前記ボンド磁石は、外径寸法が５０ｍｍ以下（より好ましくは３０ｍｍ以下、さらに好ましくは２５ｍｍ以下）、高さ寸法が５０ｍｍ以下の中実円筒形状を有し、１成形品の密度が６．０ｇ／ｃｍ^３以上であるとともに１成形品の高さ方向における両端部の密度が高く中心部の密度が低い密度分布を有しており、さらに１成形品における密度の最大値と最小値の差が０．３ｇ／ｃｍ^３以下（より好ましくは０．２ｇ／ｃｍ^３以下）であり、かつ外径寸法の真円からのずれが１０μｍ未満になっている。なお、前記中実円筒形状範囲を外れると、従来に比べて高い磁気特性および良好な寸法精度を実現困難な場合が発生する。
【００１０】
本発明に用いる磁石粉末として、例えばＲ_２Ｔ_１４Ｂ型金属間化合物を主相とするＲ−Ｔ−Ｂ系合金の粉末（ＲはＹを含む希土類元素の１種または２種以上、ＴはＦｅまたはＦｅとＣｏ）を用いる。この磁石粉末は、Ｒ：８〜１６ａｔ％、Ｂ：４〜１１ａｔ％、残部Ｆｅ（Ｆｅの一部を３０ａｔ％以下のＣｏで置換してもよい）の主成分および不可避不純物からなる組成に調整したＲ−Ｔ−Ｂ系合金を溶解後、溶湯急冷法により超急冷しいったん非晶質合金を作製する。その後、必要に応じて粉砕後、熱処理して得られる。熱処理は真空中または不活性ガス雰囲気で５５０〜８００℃×１〜５時間加熱する条件で行う。５５０℃×１時間未満では結晶化が十分でなく、８００℃×５時間超では結晶粒が粗大化する。熱処理により、平均結晶粒径が０．０１〜０．５μｍの微細な多結晶体であり、Ｒ_２Ｔ_１４Ｂ型金属間化合物を主相とする等方性のボンド磁石用希土類磁石粉末が得られる。平均結晶粒径が０．０１μｍ未満および０．５μｍ超ではボンド磁石の保磁力ｉＨｃ、不可逆減減率が大きく低下する。主相の定義は磁石粉末の断面を電子顕微鏡や光学顕微鏡により撮影した断面写真において主相の面積比率が５０％以上のものをいう。磁気特性を改善するために、前記磁石粉末に添加元素ＭとしてＮｂ、Ｗ、Ｖ、Ｔａ、Ｍｏ、Ｓｉ、Ａｌ、Ｚｒ、Ｈｆ、Ｐ、Ｃ、Ｚｎの１種または２種以上を０．００１〜５ａｔ％含むことがよい。含有量が０．００１ａｔ％未満では添加効果が認められず、５ａｔ％超では残留磁束密度Ｂｒおよび／またはｉＨｃが低下する。
【００１１】
また、Ｓｍ_２Ｔｍ_１７（ＴｍはＣｏ、Ｆｅ、Ｃｕを必ず含み、さらにＺｒ、Ｈｆ、Ｔｉの１種または２種以上を含む）および／またはＳｍＣｏ_５を主相とする希土類磁石粉末を用いることができる。
また、Ｔｈ_２Ｚｎ_１７型、Ｔｈ_２Ｎｉ_１７型、ＴｂＣｕ_７型の結晶構造相のいずれかを磁石主相とするＳｍ−Ｔｎ−Ｎ系合金粉末（ＴｎはＦｅまたはＦｅとＣｏ）を用いることができる。また、ＴｈＭｎ_１２型の結晶構造相を磁石主相とするＮｄ−Ｔｎ’−Ｎ系合金粉末（Ｔｎ’はＦｅまたはＦｅとＣｏ）を用いてもよい。
【００１２】
本発明のコンパウンドに配合する希土類磁石粉末は、前記ノズルの穴寸法より細かく粉砕した後、結着樹脂と混合（混練）する。粉砕は不活性ガス雰囲気に保持したバンタムミル、ディスクミル、振動ミル、アトライターあるいはジェットミル等で行なう。コンパウンドの押出時のノズル穴の詰まり防止のために、粉砕後の希土類磁石粉末を前記ノズル穴の寸法より細かい目開きの篩いで篩分するかあるいは前記ノズルの穴寸法より細かい粒径分布に分級しておくことが必要である。
【００１３】
樹脂として、熱硬化性樹脂を用いる。押出混練および圧縮成形には熱硬化性液状樹脂が特に適している。
具体例を挙げれば、エポキシ樹脂、ポリイミド樹脂、ポリエステル樹脂、フェノール樹脂、フッ素樹脂またはケイ素樹脂の液状樹脂がよい。特に、液状エポキシ樹脂は取り扱いが容易で良好な耐熱性を示し、安価であるため最もよい。固形（粉末状）樹脂では粘性が無いため前記穴径のノズル穴を通過させることが容易ではない。
コンパウンドに占める樹脂量は重量比で０.５％以上でかつ２０％未満が好ましい。樹脂量が０.５％未満では希土類磁石粉末の周囲を十分に覆うことができず前記穴径のノズル穴を通過させることが容易ではない。押出条件を選択すれば強制的に前記穴径のノズル穴を通過させることができるが、樹脂分が乏しいので結着作用が弱く押出物から希土類磁石粉末が分離、飛散することが多い。樹脂量が２０％以上では結着樹脂の占める体積比率が大きくなり希土類ボンド磁石の磁気特性が大きく低下する。
成形体に加熱硬化のための熱処理を施し、経時的な製品寸法の劣化および／または磁気特性の劣化を抑えることが好ましい。加熱硬化の加熱条件は大気中または不活性ガス雰囲気で１００〜２００℃×０．５〜５時間が好ましい。１００℃×０．５時間未満では加熱硬化の重合反応が不十分であり、２００℃×５時間超では熱処理の効果が飽和する。特に、Ａｒガス雰囲気中で加熱硬化処理を行うと、高い（ＢＨ）ｍａｘを得られるので好ましい。
【００１４】
【発明の実施の形態】
以下、実施例により本発明を説明するが、これら実施例により本発明が限定されるものではない。
【００１５】
（実施例１）
希土類磁石粉末として、平均結晶粒径が０．０６〜０．１１μｍであり、ａｔ％でＮｄ_１１．７Ｆｅ_８２．３Ｂ_６の主成分組成を有するＭＱＩ（マグネクエンチインターナショナル）社製の等方性ＭＱＰ−Ｂ材を用いた。この磁石粉末は厚さが２０〜４０μｍで平板の大きさが最長部分で約５００〜６００μｍの不定形平板状の形態を有する。前記磁石粉末を窒素ガス雰囲気中でバンタムミルにより粉砕した後、１２５μｍアンダーに分級した。分級後の磁石粉末に対して２.５ｗｔ％相当の液状エポキシ樹脂を添加し混合した。続いて、約９０℃に加熱した二軸混練機に投入し、予備混練してペレットを得た。
次に、予備混練したペレットを、図１３の上側に示す押出装置に投入した。投入したペレットは軟化状態でスクリュー２の回転とともに押出装置の先端に設置されたノズル４に向かって練られつつ搬送される。ノズル４は押出圧力を効率良く伝達するために半球のドーム形状に形成してある。スクリュー２により搬送された混練物は押出力によって最終的にノズル４に多数設けた直径０.２ｍｍの穴７から押出された。押出物は略円柱状細粒形状を呈し、その直径はほぼノズルの穴７の直径寸法になっていた。
次に、押出された略円柱状細粒物を図１３の下側に示すマルメライザーに回収し整粒した。この整粒に際し、押出された直後の略円柱状細粒物は適当な長さで自然に切れて、その直径に対し長さ方向の寸法が１００〜５００倍の細長い形状になっている。これらをマルメライザーの回転盤１１上に乗せて１００r.p.m.で回転すると、回転盤１１の上面に設けた溝部（図示省略）およびシールド１２の内面に接触または衝突しながら回転移動して行き、最終的に長さ寸法がその略円柱状細粒物のほぼ直径寸法に切断されつつ丸められた粒状になった。この整粒後のコンパウンド粒は若干粘性を帯びているので、１２０℃×１時間の加熱処理を施した後、さらに潤滑剤としてステアリアン酸カルシウムを０.０５ｗｔ％相当分添加し圧縮成形用のコンパウンドとした。前記加熱処理は９０〜１５０℃×０．５〜１．５時間が好ましく、９０〜１２０℃×０．５〜１．５時間がより好ましい。９０℃×０．５時間未満では粘性の除去が十分でなく、１５０℃×１．５時間超では重合が進んでボンド磁石の密度が低下する。
上記製造工程を図１に示す。また、押出後の代表的な略円柱状細粒物の外観を図２に示す。また、整粒後の代表的な圧縮成形用のコンパウンドの外観を図３に示す。
（比較例１）
実施例１の予備混練ペレット（従来のコンパウンド）を比較例１のペレットとする。その外観を図４に示す。
図２より、押出された略円柱状細粒物は表面に若干凹凸を有するもののほぼノズルの穴７に対応した直径寸法に押出されていることがわかる。
次に、図３と図４の比較から、本発明のコンパウンドはマルメライザーによる整粒によって完全な球形ではないが丸みを帯びていることがわかる。実施例１の丸みを帯びた粒状コンパウンドのうち２００個を任意にサンプリングしてＳＥＭ写真に撮影し、評価したところ、各コンパウンド粒の最大径ａと最小径ｂとの比（ａ／ｂ）はいずれも１．００を超えて３以内であり、（ａ＋ｂ）／２で定義した平均粒径は１７０μｍだった。
また図３から、本発明のコンパウンドは多数の磁石粉末粒子の集合体であることがわかる。本発明のコンパウンドの一粒に含まれる磁石粉末粒子の充填個数を調べるために、実施例１のコンパウンドの任意のものをアセトン中に浸して樹脂分を除いた後、磁石粒子の充填数をカウントした。その結果、コンパウンド一粒に含まれる磁石粒子の最小径は３〜２０μｍであり、コンパウンド一粒あたり１２〜５３個含まれていた。
【００１６】
（比較例２）
実施例１において、分級後のＭＱＰ−Ｂ材粉末に対し０．４５ｗｔ％相当の液状エポキシ樹脂を添加した以外は実施例１と同様にして圧縮成形用のボンド磁石用コンパウンドを作製した。このコンパウンドの作製に際し、図１３の押出装置を用いてコンパウンドを押出す工程が困難を極め、実施例１の押出条件に比べて押出温度を高める等の調整を施してようやく押出すことができた。しかし、押出直後のものから磁石粉末が分離または飛散する現象が観察された。このコンパウンドの外観を図５に示す。
【００１７】
（実施例２）
実施例１において、押出時のノズル穴７の直径を５０、１００、１５０、３００μｍに各々変えた以外は実施例１と同様にして本発明のコンパウンドを作製した。
（比較例３）
実施例１において、押出時のノズル穴７の直径を４００μｍとした以外は実施例１と同様にしてコンパウンドを作製した。
次に、実施例１のコンパウンド（ノズル穴７の直径２００μｍの場合）とノズル穴７の直径を５０、１００、１５０、３００μｍとして作製した実施例２の４種のコンパウンドについて、金型キャビティへの給粉性を評価した。給粉性の評価にはＪＩＳ規格（Ｚ２５０２）に基づく流動率測定装置を用いた。まず各々のコンパウンドを８０ｇずつ秤量した後、流動率測定装置に設けた直径２ｍｍの貫通穴を、各コンパウンドの所定量が通過する時間を測定した。次いで、単位時間当たりに前記貫通穴から落下するコンパウンドの重量に換算して評価した。同様にして、比較例１のペレット、比較例３のコンパウンドの流動性を評価した。結果を表１に示す。表１より、ノズル穴７の直径が５０〜３００μｍの場合にコンパウンドの流動性が改善されることがわかる。
【００１８】
【表１】

【００１９】
（実施例３）
次に、実施例１のコンパウンドを用いて圧縮成形法により等方性ボンド磁石を作製し、評価した結果を説明する。
実施例１のコンパウンドはほぼ球形であり、圧力伝達性に優れていると予想されたため、直径が１０ｍｍのキャビティを有する圧縮成形金型を用い、充填深さ（加圧方向のキャビティの深さ）を変えることにより、圧縮成形圧力６トン／ｃｍ^２の条件で、コンパウンドの充填量を変化させて、高さ（Ｌ）がＬ＝３〜３０ｍｍの中実円筒形状の成形体を得た。次いで加熱硬化し、等方性の希土類ボンド磁石を得た。得られた希土類ボンド磁石の２０℃における最大エネルギー積（ＢＨ）maxと高さ（Ｌ）との関係を図６（ａ）の（○）に示す。図６（ａ）の（○）で示す等方性ボンド磁石の密度はいずれも６．１（ｇ/ｃｍ^３）超であり、外径寸法の真円からのずれ（真円度）は４〜７μｍであり小さかった。
次に、前記希土類ボンド磁石のうちＬ＝１０ｍｍのものを、図６（ｂ）に示すようにＬ方向に略等長に３分割して、密度の分布を調べた。その結果、Ｎｏ．２１（左端部）が６．１９（ｇ/ｃｍ^３）、Ｎｏ．２２（中央部）が６．０２（ｇ/ｃｍ^３）、Ｎｏ．２３（右端部）が６．１８（ｇ/ｃｍ^３）だった。続いて、Ｌ＝３０ｍｍのものを、Ｌ方向に略等長に１０分割して、密度の分布を調べた。その結果、左端部が６．１７（ｇ/ｃｍ^３）で最も高く、中央部の２切断片が６．０１〜６．０２（ｇ/ｃｍ^３）で最も低く、右端部が６．１６（ｇ/ｃｍ^３）で２番めに高かった。
（比較例４）
比較例１のペレットを用いた以外は実施例３と同様にして、Ｌ＝３〜３０ｍｍの等方性ボンド磁石を作製し、評価した。結果を図６（ａ）の（●）に示す。
図６（ａ）の（●）で示す等方性ボンド磁石の密度はいずれも６．０（ｇ/ｃｍ^３）未満であり、外径寸法の真円からのずれは１６〜２６μｍであり大きかった。
次に、実施例３と同様にして、図６（ａ）の（●）で示すＬ＝１０ｍｍのボンド磁石を３分割し、密度分布を調べた。その結果、Ｎｏ．３１（左端部）が５．９８（ｇ/ｃｍ^３）、Ｎｏ．３２（中央部）が５．４１（ｇ/ｃｍ^３）、Ｎｏ．３３（右端部）が５．９６（ｇ/ｃｍ^３）だった。続いて、図６（ａ）の（●）で示すＬ＝３０ｍｍのものを、Ｌ方向に略等長に１０分割して、密度の分布を調べた。その結果、左端部が５．９７（ｇ/ｃｍ^３）で最も高く、中央部の２切断片が５．３８〜５．４０（ｇ/ｃｍ^３）で最も低く、右端部が５．９６（ｇ/ｃｍ^３）で２番めに高かった。
図６（ａ）に示すように、実施例１のコンパウンドを用いた場合、Ｌ＝５〜１０ｍｍのときに１１．１ＭＧＯｅという最高特性が得られ、Ｌ＝３０ｍｍでも１０．７ＭＧＯｅが得られた。この（ＢＨ）maxの低下は３．６％であり小さい。これに対し、比較例１のペレットを用いた場合、Ｌが大きくなる（長尺になる）と（ＢＨ）maxが激減することがわかる。例えばＬ＝５ｍｍで１０．１ＭＧＯｅを得たが、Ｌ＝３０ｍｍでは８．７ＭＧＯｅに低下した。この（ＢＨ）maxの低下は約１４％であり、大きい。実施例３と比較例４との（ＢＨ）max、外径寸法の真円度、密度、密度分布の顕著な差は、実施例１のコンパウンドと比較例１のペレットの差である。
次に、本発明者らは、実施例１のコンパウンドおよび比較例１のペレットを、各々、圧縮成形金型の直径５０ｍｍのキャビティに充填し、加圧して、直径（Ｄ）が５０ｍｍ、高さ（Ｌ）が５０ｍｍの等方性の中実円筒状ボンド磁石を圧縮成形した。加熱硬化後、Ｌ方向に１０分割し、両端部および中央部の密度分布を調べた。その結果、いずれも両端部の密度が最も高く中央部の密度が最も低かった。また、両端部と中央部の密度の差は、実施例１のコンパウンドを用いた場合は０．３（ｇ/ｃｍ^３）未満だったが、比較例１のペレットを用いた場合では０．３（ｇ/ｃｍ^３）を大きく超えており密度のばらつきが大きかった。また、前記加熱硬化後のものの外形寸法の真円からのずれは、実施例１のコンパウンドを用いた場合では１０μｍ未満だったが、比較例１のペレットを用いた場合は１５μｍ超だった。
以上から、比較例１のペレットに比べて本発明のコンパウンドが圧縮成形時の給粉性、圧力伝達性に優れていることがわかる、また本発明によれば、Ｄ≦５０ｍｍでかつＬ≦５０ｍｍ、より好ましくはＤ≦３０ｍｍでかつＬ＝３〜５０ｍｍという等方性の中実円筒形状の希土類ボンド磁石とした場合、従来に比べて１成形品内の密度ばらつきを小さく抑えられるので高い磁気特性と良好な外径寸法の真円度を実現することができる。
【００２０】
（実施例４）
実施例１のコンパウンドを用いて、外径２２ｍｍ、内径２０ｍｍ、高さ寸法規格が１１．８〜１２．０ｍｍの等方性の薄肉長尺リング磁石を圧縮成形した。径方向の寸法精度は金型でほぼ決まるが、高さ寸法はコンパウンドの給粉性（充填性）、圧力伝達性により大きく変動する。したがって、複数の成形体を成形し、成形体の高さ寸法の変動程度からコンパウンドの給粉性（充填性）、圧力伝達性を評価することができる。メカプレスを用いて、成形圧力が約５.５トン／ｃｍ^２になるように充填深さ、加圧力を調整した後、連続して圧縮成形した。連続成形回数（成形体個数）と得られた成形体の高さ寸法の関係を図７に示す。
（比較例５）
比較例１のペレットを用いた以外は、実施例４と同様にして連続成形し、図７の結果が得られた。
図７に示すように、比較例１のペレットを用いて作製した比較例５の連続成形体の高さ寸法のばらつきが大きく、高さ寸法規格を満たしていないことがわかる。このため、比較例５の連続成形体のうち、高さ寸法が１１．８ｍｍ未満のものを除外した。さらに高さ寸法が１２．０ｍｍ超のものを選別後、続いて加熱硬化した後に研磨して高さ寸法規格内に仕上げる工程を要した。これに対し、実施例１のコンパウンドを用いて作製した実施例４の連続成形体は全て高さ寸法規格内に入っており、加熱硬化後も高さ寸法規格を満たしていた。
【００２１】
実施例４、比較例５の連続成形体の高さ寸法、密度の測定結果を表２に示す。
表２より、実施例４の連続成形体の平均密度は６．０９ｇ／ｃｍ^３だったが、比較例５の連続成形体の平均密度は５．５７ｇ／ｃｍ^３であり、低かった。
次に、実施例４および比較例５の連続成形体の密度分布を調べたところ、いずれも１成形品における両端部の密度が高く中心部の密度が低い密度分布を有していた。実施例４の連続成形体の、１成形品における密度の最大値と最小値の差はいずれも０．２ｇ／ｃｍ^３以下だった。これに対し、比較例５の連続成形体の、１成形品における密度の最大値と最小値の差はいずれも０．３ｇ／ｃｍ^３超だった。
次に、実施例４で作製した高さ１１．９０ｍｍ、密度６．１０ｇ／ｃｍ^３の成形体および比較例５で作製した高さ１１．９０ｍｍ、密度５．５６ｇ／ｃｍ^３の成形体を加熱硬化した。その後、磁束量が飽和する条件で着磁して磁束量を測定した結果、両者の密度差に比例した磁束量の差が認められた。
【００２２】
【表２】

【００２３】
（実施例５）
実施例４の薄肉長尺リング磁石を加熱硬化後、外径の真円度を測定した結果を図８に示す。また、比較例５の薄肉長尺リング磁石を加熱硬化後、外径の真円度を測定した結果を図９に示す。測定に供した薄肉長尺リング磁石は実施例４および比較例５で作製したうちの、それぞれ、（高さ、最短）寸法品および（高さ、最長）寸法品の２個である。
図９より、比較例５の薄肉長尺リング磁石の外径寸法はいずれも真円から大きくずれており、外径寸法の真円からのずれは１６〜２８μｍに達した。
これに対し、図８に示すように、実施例４の薄肉長尺リング磁石はいずれも外径寸法の真円からのずれが最大８μｍ（６〜８μｍ）であり、小さい。
このように、本発明のコンパウンドを用いて等方性の薄肉長尺リング形状のボンド磁石を作製した場合、外形寸法の真円からのずれを従来に比べて約１／２以下（１０μｍ以下）に低減できることがわかる。この外径寸法の真円度の差は実施例１のコンパウンドと比較例１のペレットの給粉性、圧力伝達性の差に起因する圧縮成形体のスプリングバックによるものと判断する。
（実施例６）
図８に示す実施例４の薄肉長尺リング磁石の（高さ、最長）寸法品および（高さ、最短）寸法品の２個について、内径の真円度を測定した結果を図１０に示す。また、図９に示す比較例５の薄肉長尺リング磁石の（高さ、最長）寸法品および（高さ、最短）寸法品の２個について、内径の真円度を測定した結果を図１１に示す。
図１０より、実施例４の薄肉長尺リング磁石の内径寸法の真円からのずれは５〜６μｍであり小さかった。これに対し、図１１より、比較例５の薄肉長尺リング磁石の内径寸法の真円からのずれは１６〜２５μｍであり、大きい。
次に、本発明者らは、実施例１のコンパウンドおよび比較例１のペレットを用いて、外径２０ｍｍ、内径１９．４ｍｍ（肉厚０．３ｍｍ）、高さ５ｍｍの等方性薄肉リングおよび外径２５ｍｍ、内径１９ｍｍ（肉厚３ｍｍ）、高さ５０ｍｍの等方性薄肉長尺リングを圧縮成形した。続いて加熱硬化後、前記と同様にして外径および内径の真円度を測定した。その結果、実施例１のコンパウンドを用いた場合はいずれも外径および内径寸法の真円からのずれは１０μｍ以下だった。これに対し、比較例１のペレットを用いた場合は外径および内径寸法の真円からのずれは１５μｍ超であり大きかった。
【００２４】
（実施例７）
上パンチおよび下パンチで加圧する方式の圧縮成形機に設けた成形用金型のキャビティに実施例１のコンパウンドを充填し、成形圧力５．８トン／ｃｍ^２で、外径３０ｍｍ、内径２５ｍｍ（肉厚２．５ｍｍ）、高さ（Ｌ）が３０ｍｍの等方性の薄肉長尺リング磁石を成形した。加熱硬化後、図１２（ｂ）に示すように、Ｌ方向に略等長に１０分割して、各切断片（Ｎｏ．４１〜５０）の密度を測定した。結果を図１２（ａ）に示す。図１２（ａ）および図１２（ｂ）中のＮｏ．は符合する。
（比較例６）
比較例１のペレットを用いた以外は実施例７と同様にして外径３０ｍｍ、内径２５ｍｍ（肉厚２．５ｍｍ）、高さ（Ｌ）が３０ｍｍの等方性の薄肉長尺リング磁石を成形した。加熱硬化後、図１２（ｂ）に示すように、Ｌ方向に略等長に１０分割して、各切断片（Ｎｏ．５１〜６０）の密度を測定した。結果を図１２（ａ）に示す。図１２（ａ）および図１２（ｂ）中のＮｏ．は符合する。
図１２（ａ）より、実施例１のコンパウンドを用いた実施例７の薄肉長尺リング磁石の密度は、上パンチ側の端部（Ｎｏ．４１）が６．１３（ｇ/ｃｍ^３）で最も高く、下パンチ側の端部（Ｎｏ．５０）が６．１２（ｇ/ｃｍ^３）で２番目に高く、中央部（Ｎｏ．４５、４６）が５．９５（ｇ/ｃｍ^３）で最も低かった。これに対し、比較例１のペレットを用いた比較例６の薄肉長尺リング磁石の密度は、上パンチ側の端部（Ｎｏ．５１）が５．９５（ｇ/ｃｍ^３）、下パンチ側の端部（Ｎｏ．６０）が５．９４（ｇ/ｃｍ^３）、中央部のＮｏ．５５で５．３１（ｇ/ｃｍ^３）、Ｎｏ．５６で５．２９（ｇ/ｃｍ^３）となり低かった。
次に、実施例７で作製した薄肉長尺リング磁石の内径および外径の真円度を測定した結果、内径および外径寸法の真円からのずれは１０μｍ未満だった。これに対し、比較例６で作製した薄肉長尺リング磁石の内径および外径寸法の真円からのずれは１５μｍ超だった。
次に、実施例７および比較例６のＬ＝３０ｍｍの薄肉長尺リング状ボンド磁石に、磁束量が飽和する条件で外周面に対称４極着磁を施し、磁束量を測定した。その結果、実施例７の薄肉長尺リング状ボンド磁石は比較例６のものに比較して磁束量が約３％高かった。
次に、前記の対称４極着磁した実施例７および比較例６のＬ＝３０ｍｍの薄肉長尺リング状ボンド磁石を用いて回転子を構成し、ブラシレスＤＣモータに組み込んで最高効率を評価した。このブラシレスＤＣモータは、回転子と固定子間の平均のエアギャップ間隔を０．３ｍｍに調整してある。ブラシレスＤＣモータの最高効率は下記式で定義する。
最高効率＝回転数１５００r.p.m.以下で評価した、
｛（出力）／（入力）×１００（％）｝の最大値
入力（Ｗ）＝固定子巻線に通電される、印加電流Ｉ（Ａ）×印加電圧（Ｖ）
出力（Ｗ）＝トルク（ｋｇｆ・ｃｍ）×回転数（r.p.m.）×0.01027
その結果、比較例６のＬ＝３０ｍｍの薄肉長尺リング状ボンド磁石を用いた場合に比べて、実施例７のＬ＝３０ｍｍの薄肉長尺リング状ボンド磁石を用いた場合の方がブラシレスＤＣモータの最高効率が１．３％大きかった。この最高効率の差は回転子に用いたリング状ボンド磁石における磁束量の差および外径／内径の真円度の差によるものである。
【００２５】
上記実施例では等方性の希土類ボンド磁石およびそれに用いるコンパウンドならびにその製法を記載した。磁気等方性の希土類磁石粉末に替えて、例えば異方性を有する平均（再）結晶粒径が０．０１〜０．５μｍのＲ_２Ｔ_１４Ｂ型金属間化合物を主相とする希土類磁石粉末を用いて、上記実施例と同様の押出、整粒処理を施せば流動性、圧力伝達性の良好な異方性のコンパウンドが得られる。この異方性のコンパウンドを用いて磁場中圧縮成形すれば、従来よりも密度分布の不均一性が改善されて、磁気特性および真円度を向上した異方性の中実円筒状またはリング状の希土類ボンド磁石を実現することができる。
【００２６】
【発明の効果】
以上記述の通り、本発明によれば、良好な寸法精度と高い磁気特性とを具備するＲ−Ｔ−Ｂ系ボンド磁石、特に薄肉または薄肉長尺形状のものを提供することができる。また、前記ボンド磁石を実現可能な原料コンパウンドならびにその製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明のコンパウンドの製造工順を示す図である。
【図２】本発明のコンパウンドに係わる押出後の外観を走査型電子顕微鏡で観察した写真の一例を示す図である。
【図３】本発明のコンパウンドの外観を走査型電子顕微鏡で観察した写真の一例を示す図である。
【図４】比較例のコンパウンドの外観を走査型電子顕微鏡で観察した写真を示す図である。
【図５】比較例のコンパウンドの外観を走査型電子顕微鏡で観察した写真を示す図である。
【図６】長尺化に伴う（ＢＨ）maxの変化の一例を示す図（ａ）、および切断片の位置を示す図（ｂ）である。
【図７】薄肉長尺リング磁石を連続成形した場合の高さ寸法のばらつきを示す図である。
【図８】本発明による薄肉長尺リング磁石の外径寸法の真円度の一例を示す図である。
【図９】比較例の薄肉長尺リング磁石の外径寸法の真円度を示す図である。
【図１０】本発明による薄肉長尺リング磁石の内径寸法の真円度の一例を示す図である。
【図１１】比較例の薄肉長尺リング磁石の内径寸法の真円度を示す図である。
【図１２】本発明の薄肉長尺リング状ボンド磁石の密度分布の一例を示す図（ａ）、および切断片の位置を示す図（ｂ）である。
【図１３】本発明に用いる押出装置および整粒装置の一例を示す断面図である。
【図１４】最大径、最小径を定義する模式図である。
【符号の説明】
２スクリュー、４ノズル、７ノズル穴、１１回転盤、
１２シールド。[0001]
BACKGROUND OF THE INVENTION
  The present invention has good dimensional accuracy and high magnetic properties.R-T-B systemBond magnet, especially thin wallOrThin long shapethingAbout. The present invention also providesBond magnetThe present invention relates to a raw material compound capable of realizing
[0002]
[Prior art]
Magnet powder frequently used for rare earth bonded magnets is Nd.₂Fe₁₄The melt adjusted to the alloy composition containing the B-type intermetallic compound as the main phase is super-quenched by the melt quenching method to obtain an amorphous alloy once. Subsequently, after pulverization as necessary, Nd crystallized by heat treatment₂Fe₁₄It is an isotropic magnet powder having a B-type intermetallic compound as a main phase. In addition, after adjusting to the above alloy composition, the alloy obtained by melting and casting by a strip casting method or a high frequency melting method is pulverized, followed by a so-called hydrogenation, phase decomposition, dehydrogenation, recombination treatment method (patent no. Nd of a fine recrystallized structure having anisotropy by applying No. 1947332)₂Fe₁₄There are powders for bonded magnets whose main phase is a B-type intermetallic compound. Alternatively, the amorphous alloy flakes are hot-pressed by hot pressing or the like, densified to be densified, and further subjected to plastic working such as upsetting after warming, so that Nd having an anisotropic fine crystal structure₂Fe₁₄There are powders for bonded magnets whose main phase is a B-type intermetallic compound.
Recent rare-earth bonded magnets are demanding strict dimensional accuracy as well as higher performance (thinning). For example, when used for an electronic buzzer for mobile communication, a method of adjusting sound quality by adjusting a gap with a diaphragm is employed. Since the assembly process is also performed on an automated line, it is essential to improve the dimensional accuracy of electronic buzzer parts including rare earth bonded magnets. In addition, for example, for a spindle motor constituting a hard disk drive of a computer, a motor for a CD-ROM drive device, and a rare earth bonded magnet for a DVD (digital video disk) in the future, particularly high magnetic characteristics (thinning) and Strict dimensional accuracy is expected. There is a need for a long and integral rare-earth bonded magnet because it eliminates the joints made of adhesives, thereby reducing assembly steps and improving performance. There is also a need for a rare-earth bonded magnet with a thin and long shape. Here, the long in the present invention refers to those having a height dimension of 10 mm or more, and the thin wall refers to those having a thickness of 3 mm or less. As described above, recent rare-earth bonded magnets are required to be further reduced in magnetic properties and dimensional accuracy along with reduction in thickness, length, or lengthening.
[0003]
  ThinOrThin-walled long-shaped rare earth bonded magnets are greatly affected in magnetic properties and dimensional accuracy by the molding method and the properties of the compound used. As a method for forming the rare earth bonded magnet, compression molding, injection molding or extrusion molding is generally employed. In the case of the compression molding method, a rare earth bonded magnet compound is filled into a cavity of a predetermined molding die and then press-molded to produce a molded body. Thereafter, it is cured by heating to obtain a rare earth bonded magnet. In recent years, high-speed molding has become possible with the development of compression molding technologies such as mechanical presses and rotary presses. However, the product shape of the bond magnet has become thinner.OrAs the wall becomes thinner and longer, powdering into the cavity becomes difficult, and in particular, pressure transmission in the filling depth direction (pressure direction) becomes insufficient.1There is a problem that the density in the vicinity of the center portion is lower than both end portions that are directly subjected to the applied pressure in the molded product. This density variation leads to variations in magnetic characteristics and product dimensions.
[0004]
[Problems to be solved by the invention]
  The object of the present invention is to provide good dimensional accuracy and high magnetic properties.R-T-B systemBond magnet, especially thin wallOrThin long shapethingIs to provide. The present invention also providesBond magnetThe raw material compound which can implement | achieve, and its manufacturing method are provided.
[0005]
[Means for Solving the Problems]
  The present invention that solves the above problemsMethod for manufacturing rare earth bonded magnet compoundsWith rare earth magnet powderThermosetting resinAnd essentially consists of(However, the content of the thermosetting resin is 0.5% by weight or more and less than 20% by weight.)The diameter that the mixture was put into the extrusion equipment and the extrusion equipment was provided by the pressure applied to the extrusion50-300 μmExtrude from the nozzle holeThe step of obtaining the extrudate, the ratio of the maximum diameter a to the minimum diameter b (a / b) is more than 1.00 and 3 or less, and the average defined by (a + b) / 2 The particle size is 50-300 μmResize to a rounded shapeIt has the process and the process of heating the obtained granulated powder at 90-150 degreeC. It is preferable to add 0.01 to 0.5% by weight of the lubricant with respect to the sized particles after the heating at 90 to 150 ° C..
  The product forcedly extruded from the nozzle hole has a substantially cylindrical fine particle shape having a cross-sectional area substantially the same as the diameter of the nozzle hole. Thereafter, the particles are sized by a sizing device (malmerizer, dry spray, etc.) that sizing under the action of cutting force and centrifugal force to form round compound particles. Thin-walled products by compression molding using this compound grainOrWhen a thin long product is molded, the density variation in one molded product is very small, and better magnetic properties and dimensional accuracy can be realized compared to the conventional one. Conventional kneading of rare earth magnet powder and resin (See belowFor the preliminary kneading), a pellet compound is obtained by further pelletizing using a twin-screw kneader or the like. This conventional compound (pellet) has a defect that it contains a considerable amount of voids and has poor fluidity (moldability) due to its angular irregular shape. Thin walled by compression molding method using conventional pelletsOrWhen a thin-walled long-shaped rare earth bonded magnet is produced, there is a problem that a large density variation occurs in one molded product, and the density of the central portion is greatly reduced as compared with both end portions to which the pressing force directly acts. At the same time, the outer diameter roundness deteriorates in the case of a solid cylindrical shape, and the outer diameter / inner diameter roundness deteriorates in the case of a ring shape. When a rotor is constructed using a ring magnet with poor roundness and incorporated in a rotating machine, the eccentricity of the rotor increases to reflect the poor roundness of the ring magnet, and rotation during rotation The non-uniformity of the distance between the child and the stator (air gap distance) increases. Increased non-uniformity of the air gap spacing results in output variations of the rotating machine.In addition, in order to prevent a contact accident between the rotor and the stator, an air gap interval that takes into account the eccentricity of the rotor must be adopted, and there is a problem that a highly efficient rotating machine cannot be configured. The inventors put conventional pellets into an extrusion apparatus provided with nozzle holes formed in the above-mentioned hole diameter, and forcibly extrude the kneaded material from the nozzle holes to increase the density of the extrudate, followed by extrusion. The product was put into a sizing device capable of cutting and sizing at the same time to obtain a rounded granular compound. It has been found that when a rare earth bonded magnet is produced by compression molding using this compound, the variation in density within one molded product can be suppressed to a small level, and at the same time, high magnetic properties and good dimensional accuracy can be obtained. In particular, when the optimal sizing conditions are set by using a Malmerizer based on the correlation between the rotational speed of the rotating disk and the shape, arrangement, and dimensions of the grooves provided on the upper surface of the rotating disk, the above-mentioned substantially cylindrical fineness is increased with the rotation of the rotating disk. The granules were rounded by a rotational force while being cut to a length substantially equal to the diameter, resulting in a compound having a small specific surface area. What added the lubrication agent (calcium stearate etc.) equivalent to 0.01 to 0.5 wt% with respect to this compound shows good fluidity and pressure transmission. If the addition amount of the lubricant is less than 0.01 wt%, the lubrication effect cannot be obtained, and if it exceeds 0.5 wt%, the addition effect is saturated.
[0006]
In the present invention, the maximum diameter is defined as the maximum diameter in a photograph of a compound, magnet powder or nozzle hole cross section. The minimum diameter means the maximum length in the direction orthogonal to the maximum diameter. This is schematically shown in FIG.
[0007]
  The compound for rare earth bonded magnet of the present invention comprises rare earth magnet powder andThermosetting resin and lubricantAnd essentially consists of(However, the content of the thermosetting resin is 0.5 wt% or more and less than 20 wt%, and a lubricant is added in an amount of 0.01 to 0.5 wt%.)A compound for a rare earth bonded magnet, wherein the ratio (a / b) of the maximum diameter a to the minimum diameter b is more than 1.00 and 3 or less, and the average particle size defined by (a + b) / 2 is 50 to 50 300μm rounded grainThe fluidity based on JIS standard (Z2502) is in the range of 1.84 to 2.43 g / sec. The compound can have good fluidity by applying a treatment of heating at 90 to 150 ° C.
  In one grain of the compound, 10 or more particles of rare earth magnet powder having a minimum diameter of 3 to 40 μm are contained on average. Since the compound of the present invention is subjected to a high pressing force when forcibly passing through the nozzle hole having the above diameter in a softened state, the rare earth magnet powder is closely packed in the binder resin. Therefore, at least 10 particles of rare earth magnet powder having a minimum diameter of 3 to 40 μm are filled in each compound grain at an average value. If the number of fillings is less than 10, it is difficult to improve the magnetic characteristics and dimensional accuracy as compared with the prior art. The form of the compound can be confirmed by a scanning electron microscope (SEM). When (a / b) exceeds 3, the shape becomes long and fluidity (powder feeding property) is greatly reduced, and those having (a / b) of 1.00 are difficult to produce in industrial production. Since the average particle diameter (a + b) / 2 is restricted by the diameter of the nozzle hole, 50 to 300 μm is appropriate. R is less than 50 μm.₂T₁₄It may be difficult to extrude a compound in which magnet powder containing a B-type intermetallic compound as a main phase is dispersed, and if it exceeds 300 μm, the fluidity of the compound is greatly reduced.
  It is practical to make the nozzle holes by drilling. The nozzle hole with a diameter of 300 μm or less is more preferably formed by laser processing or electron beam processing, and the dimensional accuracy of the nozzle hole can be increased. Corresponding to the average particle diameter of the compound, the nozzle hole diameter is set to 50 to 300 μm. If the diameter of the nozzle hole is less than 50 μm, extrusion may be difficult due to clogging of the magnetic powder, and if it exceeds 300 μm, the fluidity of the compound, the pressure transferability, and the magnetic properties and dimensional accuracy of the rare earth bonded magnet will be improved. It becomes difficult to improve. The cross-sectional shape of the nozzle hole may be oval, rectangular, or indefinite, but in any case, the maximum diameter in the cross-sectional shape of the nozzle hole is 300 μm or less, and the minimum diameter is 50 μm or more. It is necessary to improve sex. 10 or more on average in a single compoundRare earth magnet powder particlesThe upper limit of the minimum diameter is R by the molten metal quenching method.₂T₁₄In the case of using magnet powder having a B-type intermetallic compound as the main phase, this corresponds to the maximum value (about 40 μm) of the thickness of the amorphous alloy flakes by the molten metal quenching method, and the lower limit of the minimum diameter is 3 μm. If it is less than 3 μm, the oxidative deterioration becomes remarkable.
[0008]
  The R-T-B based bonded magnet of the present invention is R₂T₁₄Powder of an R-T-B type alloy having an average crystal grain size of 0.01 to 0.5 μm mainly containing a B-type intermetallic compound (R is one or more of rare earth elements including Y, T is Fe or Fe and Co) and a thermosetting resin and a lubricant (provided that the thermosetting resin content is 0.5 wt% or more and less than 20 wt%, and the lubricant is 0.01 0.5 wt% is added.) R-T-B compound is compression-molded and heat-cured,The compound has a roundness in which the ratio (a / b) of the maximum diameter a to the minimum diameter b exceeds 1.00 and is 3 or less, and the average particle diameter defined by (a + b) / 2 is 50 to 300 μm. It has a granular shape, and the fluidity based on JIS standard (Z2502) is in the range of 1.84 to 2.43 g / sec.(Outer diameter dimension−Inner diameter dimension) / 2 The thickness defined by 0.3 is 3 to 3 mm and the height dimension is 50 mm or less (more preferably 5 to 50 mm), and the density of one molded product Is 6.0 g / cm³In addition to the above, there is a density distribution in which the density of both ends in the height direction of one molded product is high and the density of the central portion is low, and the difference between the maximum value and the minimum value of one molded product is 0.3 g / cm³The following (more preferably 0.2 g / cm³The deviation from the perfect circle of the outer diameter is less than 10 μm. Further, the deviation of the inner diameter from a perfect circle is less than 10 μm.
  Therefore, when a rotor is configured using this thin or thin long ring magnet and incorporated in a rotating machine, the air gap can be narrower than before and a highly efficient rotating machine can be configured. . In addition, when it is out of the ring shape range, there are cases where it is difficult to realize high magnetic characteristics and good dimensional accuracy as compared with the conventional case.
[0009]
  In addition, the R-T-B type bonded magnet of the present invention has R₂T₁₄Powder of an R-T-B type alloy having an average crystal grain size of 0.01 to 0.5 μm mainly containing a B-type intermetallic compound (R is one or more of rare earth elements including Y, T is Fe or Fe and Co) and a thermosetting resin and a lubricant (however, the content of the thermosetting resin is 0.5 wt% or more and less than 20 wt%, and the lubricant is 0.01 wt%). 0.5 wt% is added.) R-T-B compound is compression-molded and heat-cured,The compound has a roundness in which the ratio (a / b) of the maximum diameter a to the minimum diameter b exceeds 1.00 and is 3 or less, and the average particle diameter defined by (a + b) / 2 is 50 to 300 μm. It has a granular shape, and the fluidity based on JIS standard (Z2502) is in the range of 1.84 to 2.43 g / sec.It has a solid cylindrical shape with an outer diameter of 50 mm or less (more preferably 30 mm or less, more preferably 25 mm or less) and a height dimension of 50 mm or less, and the density of one molded product is 6.0 g / cm.³In addition to the above, it has a density distribution in which the density of both end portions in the height direction of one molded product is high and the density of the central portion is low, and the difference between the maximum value and the minimum value of one molded product is 0.3 g / Cm³The following (more preferably 0.2 g / cm³And the deviation of the outer diameter from the perfect circle is less than 10 μm. When the solid cylindrical shape range is not satisfied, it may be difficult to achieve high magnetic characteristics and good dimensional accuracy as compared with the conventional case.
[0010]
As the magnet powder used in the present invention, for example, R₂T₁₄An RTB-based alloy powder containing R type intermetallic compound as a main phase (R is one or more rare earth elements including Y, T is Fe or Fe and Co) is used. This magnet powder is adjusted to a composition comprising R: 8 to 16 at%, B: 4 to 11 at%, the main component of the balance Fe (a part of Fe may be replaced with 30 at% or less Co) and inevitable impurities. After the R-T-B alloy is melted, it is ultra-quenched by a molten metal quenching method to once produce an amorphous alloy. Thereafter, it is obtained by heat treatment after pulverization as necessary. The heat treatment is performed under a condition of heating in a vacuum or in an inert gas atmosphere at 550 to 800 ° C. for 1 to 5 hours. If it is less than 550 ° C. × 1 hour, crystallization is not sufficient, and if it exceeds 800 ° C. × 5 hours, the crystal grains become coarse. It is a fine polycrystal having an average crystal grain size of 0.01 to 0.5 μm by heat treatment, and R₂T₁₄An isotropic rare earth magnet powder for a bond magnet having a B-type intermetallic compound as a main phase is obtained. When the average crystal grain size is less than 0.01 μm and more than 0.5 μm, the coercive force iHc and the irreversible reduction rate of the bonded magnet are greatly reduced. The definition of the main phase means that the area ratio of the main phase is 50% or more in a cross-sectional photograph obtained by photographing a cross section of the magnet powder with an electron microscope or an optical microscope. In order to improve the magnetic properties, 0.001 or more of Nb, W, V, Ta, Mo, Si, Al, Zr, Hf, P, C, Zn as the additive element M is added to the magnet powder as 0.001. It is good to contain ~ 5at%. If the content is less than 0.001 at%, the effect of addition is not observed, and if it exceeds 5 at%, the residual magnetic flux density Br and / or iHc decreases.
[0011]
Sm₂Tm₁₇(Tm always contains Co, Fe, Cu, and further contains one or more of Zr, Hf, Ti) and / or SmCo₅It is possible to use rare earth magnet powder having a main phase of.
Th₂Zn₁₇Type, Th₂Ni₁₇Mold, TbCu₇Sm—Tn—N-based alloy powder (Tn is Fe or Fe and Co) in which any one of the types of crystal structure phases is a magnet main phase can be used. ThMn₁₂Nd-Tn'-N-based alloy powder (Tn 'is Fe or Fe and Co) may be used in which the main crystal structure phase is a magnet main phase.
[0012]
The rare earth magnet powder to be blended in the compound of the present invention is pulverized more finely than the hole size of the nozzle and then mixed (kneaded) with the binder resin. The pulverization is performed with a bantam mill, a disk mill, a vibration mill, an attritor, a jet mill or the like maintained in an inert gas atmosphere. In order to prevent clogging of nozzle holes during compound extrusion, the pulverized rare earth magnet powder is sieved with a sieve having openings smaller than the nozzle hole dimensions or classified to a particle size distribution finer than the nozzle hole dimensions. It is necessary to keep it.
[0013]
  As resinA thermosetting resin is used.Thermosetting liquid resins are particularly suitable for extrusion kneading and compression molding.
  Specific examples include a liquid resin such as an epoxy resin, a polyimide resin, a polyester resin, a phenol resin, a fluororesin, or a silicon resin. In particular, liquid epoxy resins are best because they are easy to handle, exhibit good heat resistance, and are inexpensive. Since solid (powdered) resin has no viscosity, it is not easy to pass through the nozzle hole having the hole diameter.
  The amount of resin in the compound is preferably 0.5% or more and less than 20% by weight. If the amount of resin is less than 0.5%, the periphery of the rare earth magnet powder cannot be sufficiently covered, and it is not easy to pass through the nozzle hole having the hole diameter. If the extrusion conditions are selected, the nozzle hole having the hole diameter can be forcibly passed. However, since the resin content is low, the binding action is weak and the rare earth magnet powder is often separated and scattered from the extrudate. When the amount of resin is 20% or more, the volume ratio occupied by the binder resin is increased, and the magnetic properties of the rare earth bonded magnet are greatly deteriorated.
  It is preferable to subject the molded body to heat treatment for heat-curing to suppress deterioration of product dimensions and / or deterioration of magnetic properties over time. The heating conditions for heat curing are preferably 100 to 200 ° C. × 0.5 to 5 hours in the air or in an inert gas atmosphere. If it is less than 100 ° C. × 0.5 hours, the heat curing polymerization reaction is insufficient, and if it exceeds 200 ° C. × 5 hours, the effect of heat treatment is saturated. In particular, it is preferable to perform heat curing in an Ar gas atmosphere because a high (BH) max can be obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these Examples.
[0015]
(Example 1)
The rare earth magnet powder has an average crystal grain size of 0.06 to 0.11 μm and Nd at at%._11.7Fe_82.3B₆An isotropic MQP-B material manufactured by MQI (Magnequench International) having a main component composition of The magnet powder has an amorphous plate shape with a thickness of 20 to 40 μm and a flat plate size of about 500 to 600 μm at the longest portion. The magnet powder was pulverized with a bantam mill in a nitrogen gas atmosphere, and then classified into under 125 μm. A liquid epoxy resin equivalent to 2.5 wt% was added to and mixed with the magnet powder after classification. Subsequently, the mixture was put into a biaxial kneader heated to about 90 ° C. and preliminarily kneaded to obtain pellets.
Next, the pre-kneaded pellets were put into an extruder shown on the upper side of FIG. The charged pellets are conveyed in a softened state while being kneaded toward the nozzle 4 installed at the tip of the extrusion device as the screw 2 rotates. The nozzle 4 is formed in a hemispherical dome shape in order to efficiently transmit the extrusion pressure. The kneaded material conveyed by the screw 2 was finally extruded from a hole 7 having a diameter of 0.2 mm provided in the nozzle 4 by pushing force. The extrudate had a substantially cylindrical fine grain shape, and its diameter was approximately the diameter of the hole 7 of the nozzle.
Next, the extruded substantially columnar fine particles were collected in a Malmerizer shown on the lower side of FIG. At the time of the sizing, the substantially cylindrical fine particles immediately after being extruded are naturally cut into appropriate lengths, and have a lengthwise dimension of 100 to 500 times the diameter. When these are placed on the rotary plate 11 of the Malmerizer and rotated at 100 rpm, the rotary part 11 rotates and moves while contacting or colliding with the groove (not shown) provided on the upper surface of the rotary plate 11 and the inner surface of the shield 12. In particular, the length dimension was cut into the diameter of the substantially cylindrical fine particles and the particles were rounded. Since the compounded particles after the sizing are slightly viscous, after heat treatment at 120 ° C. for 1 hour, 0.05 wt% of calcium stearate is further added as a lubricant for compression molding. It was a compound. The heat treatment is preferably 90 to 150 ° C. × 0.5 to 1.5 hours, more preferably 90 to 120 ° C. × 0.5 to 1.5 hours. If it is less than 90 ° C. × 0.5 hours, the viscosity is not sufficiently removed, and if it exceeds 150 ° C. × 1.5 hours, the polymerization proceeds and the density of the bonded magnet decreases.
The said manufacturing process is shown in FIG. Moreover, the external appearance of the typical substantially cylindrical fine particle after extrusion is shown in FIG. Moreover, the external appearance of the compound for typical compression molding after sizing is shown in FIG.
(Comparative Example 1)
The pre-kneaded pellet of Example 1 (conventional compound) is used as the pellet of Comparative Example 1. The appearance is shown in FIG.
From FIG. 2, it can be seen that the extruded substantially columnar fine particles are extruded to a diameter dimension substantially corresponding to the nozzle hole 7 although the surface has some irregularities.
Next, it can be seen from the comparison between FIG. 3 and FIG. 4 that the compound of the present invention is not perfectly spherical but rounded due to the sizing by the Malmerizer. Of the rounded granular compounds of Example 1, 200 samples were arbitrarily sampled and photographed on SEM photographs and evaluated. The ratio (a / b) between the maximum diameter a and the minimum diameter b of each compound grain was as follows. In all cases, the average particle size defined by (a + b) / 2 was 170 μm, exceeding 1.00 and within 3.
Further, FIG. 3 shows that the compound of the present invention is an aggregate of a large number of magnet powder particles. In order to examine the number of magnet powder particles contained in one compound of the present invention, any of the compounds of Example 1 was immersed in acetone to remove the resin component, and then the number of magnet particles filled was counted. did. As a result, the minimum diameter of the magnet particles contained in one compound grain was 3 to 20 μm, and 12 to 53 particles were contained per compound grain.
[0016]
(Comparative Example 2)
In Example 1, a bonded magnet compound for compression molding was prepared in the same manner as in Example 1 except that 0.45 wt% of the liquid epoxy resin was added to the classified MQP-B material powder. In the production of this compound, the process of extruding the compound using the extrusion apparatus of FIG. 13 was extremely difficult, and it was finally possible to extrude by adjusting the extrusion temperature as compared with the extrusion conditions of Example 1. . However, a phenomenon was observed in which the magnetic powder was separated or scattered from that immediately after extrusion. The appearance of this compound is shown in FIG.
[0017]
(Example 2)
In Example 1, the compound of the present invention was produced in the same manner as in Example 1 except that the diameter of the nozzle hole 7 during extrusion was changed to 50, 100, 150, and 300 μm, respectively.
(Comparative Example 3)
In Example 1, a compound was produced in the same manner as in Example 1 except that the diameter of the nozzle hole 7 during extrusion was 400 μm.
Next, with respect to the compound of Example 1 (in the case of the nozzle hole 7 having a diameter of 200 μm) and the four types of compounds of Example 2 prepared with the nozzle hole 7 having a diameter of 50, 100, 150, and 300 μm, Powdering property was evaluated. A flow rate measuring device based on JIS standard (Z2502) was used for evaluation of the powder feeding property. First, 80 g of each compound was weighed, and then the time required for a predetermined amount of each compound to pass through a 2 mm diameter through hole provided in the flow rate measuring device was measured. Subsequently, the weight of the compound dropped from the through hole per unit time was evaluated. Similarly, the fluidity of the pellets of Comparative Example 1 and the compound of Comparative Example 3 was evaluated. The results are shown in Table 1. From Table 1, it can be seen that the fluidity of the compound is improved when the diameter of the nozzle hole 7 is 50 to 300 μm.
[0018]
[Table 1]

[0019]
(Example 3)
Next, an isotropic bonded magnet is produced by the compression molding method using the compound of Example 1, and the evaluation results are described.
Since the compound of Example 1 was almost spherical and was expected to have excellent pressure transferability, a compression mold having a cavity with a diameter of 10 mm was used, and the filling depth (depth of the cavity in the pressing direction) By changing the compression molding pressure 6 ton / cm²Under these conditions, the filling amount of the compound was changed to obtain a solid cylindrical shaped body having a height (L) of L = 3 to 30 mm. Next, heat curing was performed to obtain an isotropic rare earth bonded magnet. The relationship between the maximum energy product (BH) max at 20 ° C. and the height (L) of the obtained rare earth bonded magnet is shown in (◯) of FIG. The density of the isotropic bonded magnet shown by (◯) in FIG. 6A is 6.1 (g / cm).³) And the deviation of the outer diameter from the perfect circle (roundness) was 4 to 7 μm, which was small.
Next, among the rare earth bonded magnets, those with L = 10 mm were divided into three substantially equal lengths in the L direction as shown in FIG. 6B, and the density distribution was examined. As a result, no. 21 (left end) is 6.19 (g / cm³), No. 22 (central part) is 6.02 (g / cm³), No. 23 (right end) is 6.18 (g / cm³)was. Subsequently, a sample with L = 30 mm was divided into 10 approximately equal lengths in the L direction, and the density distribution was examined. As a result, the left end was 6.17 (g / cm³), And the two cut pieces at the center are 6.01 to 6.02 (g / cm³) Is the lowest and the right end is 6.16 (g / cm³) Was the second highest.
(Comparative Example 4)
An isotropic bonded magnet with L = 3 to 30 mm was prepared and evaluated in the same manner as in Example 3 except that the pellet of Comparative Example 1 was used. The results are shown in (●) of FIG.
The density of the isotropic bonded magnet shown by (●) in FIG. 6A is 6.0 (g / cm).³) And the deviation of the outer diameter from the perfect circle was 16 to 26 μm, which was large.
Next, in the same manner as in Example 3, the bond magnet with L = 10 mm indicated by (●) in FIG. 6A was divided into three, and the density distribution was examined. As a result, no. 31 (left end) is 5.98 (g / cm³), No. 32 (central part) is 5.41 (g / cm³), No. 33 (right end) is 5.96 (g / cm³)was. Subsequently, a sample having L = 30 mm indicated by (●) in FIG. 6A was divided into 10 approximately equal lengths in the L direction, and the density distribution was examined. As a result, the left end was 5.97 (g / cm³) Is the highest, and the two cut pieces at the center are 5.38 to 5.40 (g / cm³) And the right end is 5.96 (g / cm³) Was the second highest.
As shown in FIG. 6A, when the compound of Example 1 was used, the highest characteristic of 11.1 MGOe was obtained when L = 5 to 10 mm, and 10.7 MGOe was obtained even when L = 30 mm. This decrease in (BH) max is as small as 3.6%. On the other hand, when the pellet of the comparative example 1 is used, it turns out that (BH) max reduces drastically when L becomes large (it becomes long). For example, 10.1 MGOe was obtained at L = 5 mm, but decreased to 8.7 MGOe at L = 30 mm. This decrease in (BH) max is about 14%, which is large. The remarkable difference in (BH) max, roundness of outer diameter, density, and density distribution between Example 3 and Comparative Example 4 is the difference between the compound of Example 1 and the pellet of Comparative Example 1.
Next, the inventors of the present invention filled the compound of Example 1 and the pellet of Comparative Example 1 into a cavity having a diameter of 50 mm of a compression molding die and pressed them, and the diameter (D) was 50 mm and the height was increased. An isotropic solid cylindrical bonded magnet (L) of 50 mm was compression molded. After heat curing, it was divided into 10 in the L direction, and the density distribution at both ends and the center was examined. As a result, the density of both end portions was the highest and the density of the central portion was the lowest. Further, the difference in density between the both end portions and the central portion is 0.3 (g / cm) when the compound of Example 1 is used.³), But 0.3 (g / cm) when the pellet of Comparative Example 1 was used.³) Was greatly exceeded, and the variation in density was large. Moreover, the deviation from the perfect circle of the outer dimension of the heat-cured product was less than 10 μm when the compound of Example 1 was used, but was more than 15 μm when the pellet of Comparative Example 1 was used.
From the above, it can be seen that the compound of the present invention is superior in the powder feeding property and pressure transmission property during compression molding as compared with the pellet of Comparative Example 1, and according to the present invention, D ≦ 50 mm and L ≦ 50 mm. More preferably, when a rare earth bonded magnet having an isotropic solid cylindrical shape with D ≦ 30 mm and L = 3 to 50 mm is used, the density variation in one molded product can be suppressed to be small as compared with the conventional one, and thus high magnetic characteristics. And a good roundness of the outer diameter can be realized.
[0020]
(Example 4)
Using the compound of Example 1, an isotropic thin long ring magnet having an outer diameter of 22 mm, an inner diameter of 20 mm, and a height dimension of 11.8 to 12.0 mm was compression molded. The dimensional accuracy in the radial direction is almost determined by the mold, but the height dimension varies greatly depending on the powder feedability (fillability) and pressure transferability of the compound. Therefore, a plurality of molded bodies can be molded, and the powder feedability (fillability) and pressure transferability of the compound can be evaluated from the degree of variation in the height dimension of the molded body. Using a mechanical press, the molding pressure is about 5.5 tons / cm.²After adjusting the filling depth and pressurizing force so as to become, it was continuously compression molded. FIG. 7 shows the relationship between the number of continuous moldings (number of molded bodies) and the height dimension of the obtained molded bodies.
(Comparative Example 5)
Except for using the pellet of Comparative Example 1, continuous molding was performed in the same manner as in Example 4, and the result of FIG. 7 was obtained.
As shown in FIG. 7, it can be seen that the variation in the height dimension of the continuous molded body of Comparative Example 5 produced using the pellets of Comparative Example 1 is large and does not satisfy the height dimension standard. For this reason, among the continuous molded bodies of Comparative Example 5, those having a height dimension of less than 11.8 mm were excluded. Further, after selecting a material having a height dimension of more than 12.0 mm, it was necessary to carry out a process of polishing after heat curing and finishing within the height dimension standard. On the other hand, all the continuous molded bodies of Example 4 produced using the compound of Example 1 were within the height dimension standard, and satisfied the height dimension standard even after heat curing.
[0021]
Table 2 shows the measurement results of the height dimension and density of the continuous molded bodies of Example 4 and Comparative Example 5.
From Table 2, the average density of the continuous molded body of Example 4 is 6.09 g / cm.³However, the average density of the continuous molded body of Comparative Example 5 was 5.57 g / cm.³It was low.
Next, when the density distribution of the continuous molded bodies of Example 4 and Comparative Example 5 was examined, both had a density distribution in which the density of both end portions in one molded product was high and the density of the central portion was low. The difference between the maximum value and the minimum value of density in one molded product of the continuous molded body of Example 4 is 0.2 g / cm.³It was below. On the other hand, the difference between the maximum value and the minimum value of the density in one molded product of the continuous molded body of Comparative Example 5 is 0.3 g / cm.³It was super.
Next, the height produced in Example 4 was 11.90 mm, and the density was 6.10 g / cm.³The height of 11.90 mm and the density of 5.56 g / cm prepared in Comparative Example 5³The molded body was heat-cured. Thereafter, the magnetic flux amount was measured under the condition that the magnetic flux amount was saturated. As a result, a difference in magnetic flux amount proportional to the density difference between the two was observed.
[0022]
[Table 2]

[0023]
(Example 5)
FIG. 8 shows the results of measuring the roundness of the outer diameter after heat curing the thin long ring magnet of Example 4. Moreover, the result of having measured the roundness of an outer diameter after heat-hardening the thin long ring magnet of the comparative example 5 is shown in FIG. The thin long ring magnets used for the measurement are two (height, shortest) dimension product and (height, longest) dimension product of Example 4 and Comparative Example 5, respectively.
From FIG. 9, the outer diameter of the thin long ring magnet of Comparative Example 5 is greatly deviated from the perfect circle, and the deviation of the outer diameter from the perfect circle has reached 16 to 28 μm.
On the other hand, as shown in FIG. 8, all the thin long ring magnets of Example 4 have a small deviation of the outer diameter from a perfect circle of 8 μm (6 to 8 μm) at maximum.
Thus, when an isotropic thin-walled long ring-shaped bonded magnet is produced using the compound of the present invention, the deviation of the outer dimension from a perfect circle is about ½ or less (10 μm or less) compared to the conventional one. It can be seen that it can be reduced. It is determined that the difference in the roundness of the outer diameter is due to the springback of the compression molded body resulting from the difference in the powder feeding property and the pressure transmission property between the compound of Example 1 and the pellet of Comparative Example 1.
(Example 6)
FIG. 10 shows the results of measuring the roundness of the inner diameter of two thin (height, longest) dimension products and (height, shortest) dimension products of the thin long ring magnet of Example 4 shown in FIG. . Further, the results of measuring the roundness of the inner diameter of two (height, longest) dimension product and (height, shortest) dimension product of the thin long ring magnet of Comparative Example 5 shown in FIG. 9 are shown in FIG. Shown in
From FIG. 10, the deviation from the perfect circle of the inner diameter dimension of the thin long ring magnet of Example 4 was as small as 5 to 6 μm. On the other hand, from FIG. 11, the deviation from the perfect circle of the inner diameter of the thin long ring magnet of Comparative Example 5 is 16 to 25 μm, which is large.
Next, the inventors used the compound of Example 1 and the pellets of Comparative Example 1 to obtain isotropic thin rings having an outer diameter of 20 mm, an inner diameter of 19.4 mm (thickness of 0.3 mm), and a height of 5 mm, and An isotropic thin-walled long ring having an outer diameter of 25 mm, an inner diameter of 19 mm (wall thickness: 3 mm), and a height of 50 mm was compression-molded. Subsequently, after heat curing, the roundness of the outer diameter and inner diameter was measured in the same manner as described above. As a result, when the compound of Example 1 was used, the deviation of the outer diameter and inner diameter from the perfect circle was 10 μm or less. On the other hand, when the pellet of Comparative Example 1 was used, the deviation of the outer diameter and inner diameter from the perfect circle was greater than 15 μm and was large.
[0024]
(Example 7)
The compound of Example 1 is filled in the cavity of the molding die provided in the compression molding machine of the type that pressurizes with the upper punch and the lower punch, and the molding pressure is 5.8 tons / cm.²Thus, an isotropic thin long ring magnet having an outer diameter of 30 mm, an inner diameter of 25 mm (wall thickness of 2.5 mm), and a height (L) of 30 mm was formed. After the heat curing, as shown in FIG. 12 (b), the cut pieces (Nos. 41 to 50) were measured in density by dividing the cut piece into approximately equal lengths in the L direction. The results are shown in FIG. In FIG. 12 (a) and FIG. Matches.
(Comparative Example 6)
An isotropic thin long ring magnet having an outer diameter of 30 mm, an inner diameter of 25 mm (wall thickness of 2.5 mm), and a height (L) of 30 mm was formed in the same manner as in Example 7 except that the pellets of Comparative Example 1 were used. did. After the heat curing, as shown in FIG. 12 (b), the cut pieces (Nos. 51 to 60) were measured in density by dividing the L pieces into 10 substantially equal lengths. The results are shown in FIG. In FIG. 12 (a) and FIG. Matches.
From FIG. 12 (a), the density of the thin long ring magnet of Example 7 using the compound of Example 1 is 6.13 (g / cm) at the end (No. 41) on the upper punch side.³) And the lower punch side end (No. 50) is 6.12 (g / cm³) Is the second highest, and the central part (No. 45, 46) is 5.95 (g / cm³) Was the lowest. In contrast, the density of the thin long ring magnet of Comparative Example 6 using the pellets of Comparative Example 1 is 5.95 (g / cm) at the end (No. 51) on the upper punch side.³), The lower punch side end (No. 60) is 5.94 (g / cm³), No. in the center. 55, 5.31 (g / cm³), No. 56. 5.29 (g / cm³It was low.
Next, as a result of measuring the roundness of the inner diameter and the outer diameter of the thin long ring magnet produced in Example 7, the deviation of the inner diameter and the outer diameter from the perfect circle was less than 10 μm. On the other hand, the deviation of the inner and outer diameters of the thin long ring magnet produced in Comparative Example 6 from a perfect circle was more than 15 μm.
Next, symmetrical thin 4-pole magnetization was performed on the outer peripheral surface of the thin long ring-shaped bonded magnet of L = 30 mm in Example 7 and Comparative Example 6 under the condition that the amount of magnetic flux was saturated, and the amount of magnetic flux was measured. As a result, the amount of magnetic flux of the thin long ring-shaped bonded magnet of Example 7 was about 3% higher than that of Comparative Example 6.
Next, a rotor was constructed using the thin long ring-shaped bonded magnets of L = 30 mm of Example 7 and Comparative Example 6 which were magnetized in the above-mentioned symmetric quadrupole and incorporated in a brushless DC motor to evaluate the maximum efficiency. . In this brushless DC motor, the average air gap distance between the rotor and the stator is adjusted to 0.3 mm. The maximum efficiency of a brushless DC motor is defined by the following equation.
Maximum efficiency = Evaluated at a rotational speed of 1500 r.p.m. or less,
Maximum value of {(output) / (input) x 100 (%)}
Input (W) = applied current I (A) × applied voltage (V) energized to the stator winding
Output (W) = Torque (kgf · cm) x Number of revolutions (r.p.m.) x 0.01027
As a result, compared to the case of using the thin long ring-shaped bonded magnet of L = 30 mm in Comparative Example 6, the case of using the thin long ring-shaped bonded magnet of L = 30 mm in Example 7 is the brushless DC. The maximum efficiency of the motor was 1.3% greater. This difference in maximum efficiency is due to the difference in the amount of magnetic flux in the ring-shaped bonded magnet used in the rotor and the difference in the roundness of the outer diameter / inner diameter.
[0025]
In the above embodiment, an isotropic rare earth bonded magnet, a compound used therefor, and a method for producing the compound were described. In place of magnetically isotropic rare earth magnet powder, for example, R having an anisotropy average (re) crystal grain size of 0.01 to 0.5 μm₂T₁₄An anisotropic compound having good fluidity and pressure transferability can be obtained by performing extrusion and sizing treatment in the same manner as in the above-mentioned examples using a rare earth magnet powder having a B-type intermetallic compound as a main phase. If this anisotropic compound is used for compression molding in a magnetic field, the non-uniformity of density distribution will be improved compared to the conventional one, and the anisotropic solid cylindrical or ring shape with improved magnetic properties and roundness The rare earth bonded magnet can be realized.
[0026]
【The invention's effect】
As described above, according to the present invention, it has good dimensional accuracy and high magnetic properties.R-T-B systemBond magnet, especially thin wallOrThin long shapethingCan be provided. Also,Bond magnetIt is possible to provide a raw material compound and a method for producing the same.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a manufacturing process for a compound of the present invention.
FIG. 2 is a view showing an example of a photograph obtained by observing the appearance after extrusion related to the compound of the present invention with a scanning electron microscope.
FIG. 3 is a view showing an example of a photograph of the appearance of the compound of the present invention observed with a scanning electron microscope.
FIG. 4 is a view showing a photograph of the appearance of a compound of a comparative example observed with a scanning electron microscope.
FIG. 5 is a view showing a photograph of the appearance of a compound of a comparative example observed with a scanning electron microscope.
FIG. 6A is a diagram showing an example of a change in (BH) max associated with an increase in length, and FIG. 6B is a diagram showing a position of a cut piece.
FIG. 7 is a diagram showing variation in height dimension when a thin long ring magnet is continuously formed.
FIG. 8 is a diagram showing an example of roundness of the outer diameter of a thin long ring magnet according to the present invention.
FIG. 9 is a diagram showing the roundness of the outer diameter of the thin long ring magnet of the comparative example.
FIG. 10 is a diagram showing an example of the roundness of the inner diameter of a thin long ring magnet according to the present invention.
FIG. 11 is a diagram showing the roundness of the inner diameter of the thin long ring magnet of the comparative example.
FIG. 12A is a diagram showing an example of a density distribution of a thin long ring-shaped bonded magnet according to the present invention, and FIG. 12B is a diagram showing a position of a cut piece.
FIG. 13 is a cross-sectional view showing an example of an extrusion apparatus and a sizing apparatus used in the present invention.
FIG. 14 is a schematic diagram defining a maximum diameter and a minimum diameter.
[Explanation of symbols]
2 screws, 4 nozzles, 7 nozzle holes, 11 turntable,
12 Shield.

Claims

The mixture consisting essentially of rare earth magnet powder and a thermosetting resin (however, the content of the thermosetting resin is not less than 0.5% by weight and less than 20% by weight) is put into an extruder and subjected to extrusion. A step of obtaining an extrudate by extruding from a nozzle hole having a diameter of 50 to 300 μm provided in an extrusion device by pressure,
The obtained extrudate has a ratio (a / b) of maximum diameter a to minimum diameter b of more than 1.00 and 3 or less, and an average particle size defined by (a + b) / 2 is 50 to 300 μm. The process of sizing into a rounded shape,
And a method for producing a compound for a rare earth bonded magnet, comprising a step of heating the obtained sized particles at 90 to 150 ° C.

The process for adding 0.01 to 0.5% by weight of a lubricant to the sized particles after being heated at 90 to 150 ° C in the method for producing a compound for rare earth bonded magnet according to claim 1. A method for producing a compound for a rare earth bonded magnet, comprising:

It consists essentially of rare earth magnet powder, a thermosetting resin, and a lubricant (however, the content of the thermosetting resin is 0.5 wt% or more and less than 20 wt%, and the lubricant is 0.01 to 0.00%). 5% by weight)), a compound for rare earth bonded magnets by compression molding,
The ratio (a / b) of the maximum diameter a to the minimum diameter b is more than 1.00 and 3 or less, and the average particle diameter defined by (a + b) / 2 is a rounded granule having a diameter of 50 to 300 μm. A rare-earth bonded magnet compound characterized by having a fluidity based on JIS standard (Z2502) in a range of 1.84 to 2.43 g / sec.

The compound for rare earth bonded magnet according to claim 3, wherein the compound is heated at 90 to 150 ° C.

One or two of the rare earth element powder (R a R ₂ T ₁₄ B-type average crystal grain size of the intermetallic compound as the main phase is 0.01~0.5μm R-T-B-based alloy containing Y As described above, T is substantially composed of Fe or Fe and Co), a thermosetting resin, and a lubricant (provided that the content of the thermosetting resin is 0.5 wt% or more and less than 20 wt%, and the lubricant R-T-B type bonded magnet formed by compression-molding an R-T-B type compound and heat-curing,
The compound has a roundness in which the ratio (a / b) of the maximum diameter a to the minimum diameter b exceeds 1.00 and is 3 or less, and the average particle diameter defined by (a + b) / 2 is 50 to 300 μm. It has a granular shape and fluidity based on JIS standard (Z2502) is in the range of 1.84 to 2.43 g / sec.
The bonded magnet has a ring shape with a thickness defined by (outer diameter dimension−inner diameter dimension) / 2 of 0.3 to 3 mm and a height dimension of 50 mm or less, and the density of one molded product is 6. The density distribution is 0 g / cm ³ or more, the density of both ends in the height direction of one molded product is high, and the density of the central portion is low, and the difference between the maximum value and the minimum value of one molded product is 0 An R-T-B type bonded magnet having a diameter of ³ g / cm ³ or less and a deviation of the outer diameter from a perfect circle of less than 10 μm.

6. The RTB-based bond magnet according to claim 5, wherein a deviation of the inner diameter from a perfect circle is less than 10 μm.

One or two of the rare earth element powder (R a R ₂ T ₁₄ B-type average crystal grain size of the intermetallic compound as the main phase is 0.01~0.5μm R-T-B-based alloy containing Y As described above, T is substantially composed of Fe or Fe and Co), a thermosetting resin, and a lubricant (provided that the content of the thermosetting resin is 0.5 wt% or more and less than 20 wt%, and the lubricant R-T-B type bonded magnet formed by compression-molding an R-T-B type compound and heat-curing,
The compound has a roundness in which the ratio (a / b) of the maximum diameter a to the minimum diameter b exceeds 1.00 and is 3 or less, and the average particle diameter defined by (a + b) / 2 is 50 to 300 μm. It has a granular shape and fluidity based on JIS standard (Z2502) is in the range of 1.84 to 2.43 g / sec.
The bonded magnet has a solid cylindrical shape with an outer diameter of 50 mm or less and a height of 50 mm or less, and the density of one molded product is 6.0 g / cm ³ or more and the height direction of the one molded product. The density of both end portions is high and the density of the center portion is low, and the difference between the maximum value and the minimum value of one molded product is 0.3 g / cm ³ or less, and the outer diameter dimension The R-T-B type bond magnet is characterized in that the deviation from the perfect circle is less than 10 μm.