JP4238971B2

JP4238971B2 - Manufacturing method of radial anisotropic sintered magnet

Info

Publication number: JP4238971B2
Application number: JP2002310880A
Authority: JP
Inventors: 孝治佐藤; 光雄川端; 武久美濃輪
Original assignee: Shin Etsu Chemical Co Ltd
Current assignee: Shin Etsu Chemical Co Ltd
Priority date: 2001-10-31
Filing date: 2002-10-25
Publication date: 2009-03-18
Anticipated expiration: 2022-10-25
Also published as: JP2004153867A

Description

【０００１】
【発明の属する技術分野】
本発明は、ラジアル異方性焼結磁石の製造方法に関する。
【０００２】
【従来の技術】
フェライトや希土類合金のような結晶磁気異方性材料を粉砕し、特定の磁場中でプレス成形を行って作製される異方性磁石は、スピーカ、モータ、計測器、その他の電気機器等に広く使用されている。このうち特にラジアル方向に異方性を有する磁石は、磁気特性に優れ、自由な着磁が可能であり、またセグメント磁石のような磁石固定用の補強の必要もないため、ＡＣサーボモータ、ＤＣブラシレスモータ等に使用されている。特に近年はモータの高性能化にともない、長尺のラジアル異方性磁石が求められてきた。
【０００３】
ラジアル配向を有する磁石は、垂直磁場垂直成形法又は後方押し出し法により製造される。垂直磁場垂直成形法は、プレス方向より、コアを介して磁場を対抗方向から印加し、ラジアル配向を得ることを特徴とするものである。即ち、垂直磁場垂直成形法は、図２に示されるように、配向磁場コイル２において発生させた磁場をコア４及び５を介して対抗させ、コアよりダイス３を通過し、成形機架台１を経て循環するような磁気回路にて、充填磁石粉８をラジアル配向させるものである。なお、図中６は上パンチ、７は下パンチである。
【０００４】
このように、この垂直磁場垂直成形装置において、コイルにより発生した磁界はコア、ダイス、成形機架台、コアとなる磁路を形成させている。この場合、磁場漏洩損失低下のため、磁路を形成する部分の材料には強磁性体を用い、主に鉄系金属が使われる。しかし、磁石粉を配向させるための磁場強度は、以下のようにして決まってしまう。コア径をＢ（磁石粉充填内径）、ダイス径をＡ（磁石粉充填外径）、磁石粉充填高さをＬとする。上下コアを通過した磁束がコア中央でぶつかり対抗し、ダイスに至る。コアを通った磁束量はコアの飽和磁束密度で決定され、鉄製コアで磁束密度が２０ｋＧ程度である。従って磁石粉充填内外径での配向磁場は、上下コアの通った磁束量を磁石粉充填部の内面積及び外面積で割ったものとなり、
２・π・（Ｂ／２）²・２０／（π・Ｂ・Ｌ）＝１０・Ｂ／Ｌ…内周、
２・π・（Ｂ／２）²・２０／（π・Ａ・Ｌ）＝１０・Ｂ²／（Ａ・Ｌ）…外周
となる。外周での磁場は内周より小さいので、磁石粉充填部すべてにおいて良好な配向を得るには、外周で１０ｋＯｅ以上必要であり、このため、１０・Ｂ²／（Ａ・Ｌ）＝１０となり、従って、Ｌ＝Ｂ²／Ａとなる。成形体高さは充填粉の高さの約半分で、焼結時、更に８割程度になるので、磁石の高さは非常に小さくなる。このようにコアの飽和が配向磁界の強度を決定するためコア形状により配向可能な磁石の大きさ即ち高さが決まってしまい、円筒軸方向に長尺品を製造することが困難であった。特に、径が小さな円筒磁石では非常に短尺品しか製造することができなかった。
【０００５】
また、後方押し出し法は設備が大掛かりで、歩留まりが悪く、安価な磁石を製造することが困難であった。
【０００６】
このようにラジアル異方性磁石は、いかなる方法においても製造が困難であり、安く大量に製造することは更に難しく、ラジアル異方性磁石を用いたモータも非常にコストが高くなってしまうという不利があった。
【０００７】
焼結磁石でラジアル異方性リング磁石を製造する場合、異方性化に伴い、焼結及び時効冷却過程において、磁石のＣ軸方向とＣ軸垂直方向との線膨張係数の差により発生する応力が磁石の機械的強度より大きい場合、割れやクラックが発生し問題となる。このため、Ｒ−Ｆｅ−Ｂ系焼結磁石では内外径比０．６以上の磁石形状でのみ製造が可能であった（日立金属技報Ｖｏｌ．６，ｐ３３〜３６）。更に、Ｒ−（Ｆｅ，Ｃｏ）−Ｂ系焼結磁石では、Ｆｅを置換したＣｏは合金組織中主相の２−１４−１相に含まれるだけでなく、Ｒリッチ相中でＲ₃Ｃｏを形成し、機械的強度を著しく低減する。しかもキュリー温度が高いため、冷却時のキュリー温度〜室温間におけるＣ軸方向及びＣ軸垂直方向の熱膨張率変化量も大きくなり、割れ、クラックの発生原因である残留応力が増大する。このためＲ−（Ｆｅ，Ｃｏ）−Ｂ系ラジアル異方性リング磁石はＣｏの入らないＲ−Ｆｅ−Ｂ系磁石より更に形状制限が厳しく、内外径比０．９以上の形状でしか、安定した磁石生産が行えなかった。また、フェライト磁石、Ｓｍ−Ｃｏ系磁石においても同じ理由により、割れ、クラックが発生し、安定生産できていない状態である。
【０００８】
ラジアル異方性化に伴う焼結及び時効冷却過程で発生する割れ又はクラックの原因となる周方向の残留応力は、フェライト磁石に関するＫｏｏｌｓの検討結果（Ｆ．Ｋｏｏｌｓ：ＳｃｉｅｎｃｅｏｆＣｅｒａｍｉｃｓ．Ｖｏｌ．７，（１９７３），２９−４５）に示され、式（１）のように表される。
σ_θ＝ΔＴΔαＥＫ²／（１−Ｋ²）・（Ｋβ_Kη^K-1−Ｋβ_-Kη^-K-1−１）‥‥‥（１）
σ_θ：周方向の応力
ΔＴ：温度差
Δα：線膨張係数の差（α‖−α⊥）
Ｅ：配向方向のヤング率
Ｋ² ：ヤング率の異方性比（Ｅ⊥／Ｅ‖）
η ：位置（ｒ／外径）
β_k ：（１−ρ^1+K）／（１−ρ^2K）
ρ ：内外径比（内径／外径）
【０００９】
上記式のうち、割れ又はクラックの原因に最も大きな影響を与える項は、Δα：線膨張係数の差（α‖−α⊥）であり、フェライト磁石、Ｓｍ−Ｃｏ系希土類磁石、Ｎｄ−Ｆｅ−Ｂ系希土類磁石では、結晶方向による熱膨張率の差（熱膨張異方性）はキュリー温度より発現し、冷却時の温度低下により増大する。このとき、残留応力が磁石の機械強度以上となり、割れに至る。
【００１０】
上記式による、配向方向と配向方向に垂直な方向における熱膨張の違いによる応力は、円筒磁石が、径方向にラジアル配向するがゆえに発生する。従って、一部がラジアル配向と異なる配向を有する円筒磁石を製造すれば割れが発生することはない。例えば、水平磁場垂直成形法によって作製された、円筒軸に垂直な一方向に配向された円筒磁石は、フェライト磁石、Ｓｍ−Ｃｏ系希土類磁石、Ｎｄ−Ｆｅ（Ｃｏ）−Ｂ系希土類磁石のどのタイプの磁石においても割れることはない。
【００１１】
個々のラジアル異方性磁石を用いずとも円筒磁石に多極着磁が行え、磁束密度が高く、かつ極間における磁束密度のばらつきが小さければ、高性能の永久磁石モータ用の磁石となりうる。水平磁場垂直成形法により円筒軸に垂直な一方向に配向させた磁石を、着磁のみを多極にすることにより、ラジアル異方性磁石を用いずに永久磁石モータ用円筒多極磁石を作製する方法が提案されている（電気学会マグネティクス研究会資料ＭＡＧ−８５−１２０、１９８５）。水平磁場垂直成形法により製造された、円筒軸に垂直な一方向に配向された磁石（以下、径方向配向円筒磁石と呼ぶ）は、プレス機のキャビティが許すかぎりの長尺化（５０ｍｍ以上）に加えて多連プレスが行えるので、１度のプレスで多数個の成形体が得られ、高価なラジアル異方性磁石の代わりに廉価にモータ用円筒磁石を供給することができる。
【００１２】
しかし、実際には水平磁場垂直成形法により作製された径方向配向の円筒磁石に多極着磁を行った磁石は、配向磁場方向近傍の極では磁束密度が高く、配向磁場方向に垂直な極では磁束密度が小さいため、モータに組みモータを回転させると、極間の磁束密度のばらつきを反映したトルクむらが生じてしまい、実用に耐えうるモータ用磁石とはいえなかった。
【００１３】
この課題を解決するために、特許文献１では、水平磁場垂直成形法によって作製された、円筒軸に垂直な一方向に配向された円筒磁石における周方向の着磁極数が２ｎ（ｎは１より大きく５０より小さい正の整数）個のとき、この円筒磁石と組み合わせるステータの歯の数が３ｍ（ｍは１より大きく３３より小さい正の整数）個とする提案がなされている。特許文献２では、着磁極数がｋ（ｋは４以上の正の偶数）個のとき、この円筒磁石と組み合わせるステータの歯数が３ｋ・ｊ／２（ｊは１以上の正の整数）個とする提案がなされている。また、特許文献３では、円筒軸に垂直な一方向に配向された円筒磁石で角度をずらして段積みすることでトルクむらを軽減する提案がなされている。
【００１４】
しかし、特許文献１〜３とも、トルクむらは低減するものの、リング磁石内で径方向に配向した部分が少なく、同じ磁気特性を有するラジアル磁石に対し、モータにした際のトータルトルクが７０％と小さく、実用化されていない。
【００１５】
【特許文献１】
特開２０００−１１６０８９号公報
【特許文献２】
特開２０００−１１６０９０号公報
【特許文献３】
特開２０００−１７５３８７号公報
【非特許文献１】
日立金属技報Ｖｏｌ．６，ｐ．３３−３６
【非特許文献２】
Ｆ．Ｋｏｏｌｓ：ＳｃｉｅｎｃｅｏｆＣｅｒａｍｉｃｓ．
Ｖｏｌ．７，（１９７３），ｐ．２９−４５
【非特許文献３】
電気学会マグネティクス研究会資料
ＭＡＧ−８５−１２０，１９８５
【００１６】
【発明が解決しようとする課題】
従って、本発明の目的は、多連、長尺品が容易に生産可能で、高性能の永久磁石モータを安価に実現することができるラジアル異方性焼結磁石の製造方法を提供することにある。
【００１７】
【課題を解決するための手段及び発明の実施の形態】
本発明は、円筒状に形成され、ラジアル方向に対し３０°以上傾いた方向に配向した部位を磁石体積の２％以上５０％以下含有し、磁石体積の残りの部位がラジアル方向乃至ラジアル方向に対する傾きが３０°未満に配向したものであることを特徴とする周方向に２ｎ（ｎは２以上５０以下の正の整数）の多極に着磁したラジアル異方性焼結磁石を提供する。また、かかる磁石を得る方法として、円筒磁石用成形金型のコアの少なくとも一部の材質に飽和磁束密度５ｋＧ以上を有する強磁性体を用い、金型キャビティ内に充填した磁石粉を水平磁場垂直成形法により磁石粉に０．５〜１２ｋＯｅの磁場で配向磁界を印加して成形することを特徴とするラジアル異方性焼結磁石の製造方法を提供する。
【００１８】
即ち、本発明者らは、上記目的を達成するために鋭意努力を重ねた結果、円筒磁石の径方向への配向を、全体的にラジアル配向とし、一部分意図的に乱すことで、焼結・時効時の冷却過程において、割れ・クラックの発生のない安定した生産を実現でき、尚且つモータに組み込んだ際、大きなトルクを得ることができることを見出したものである。
【００１９】
本発明によれば、磁場が均一で内外径比の小さな形状においても、焼結及び時効冷却時の割れ、クラックのない、優れた磁石特性を有するＲ−Ｆｅ（Ｃｏ）−Ｂ系ラジアル異方性焼結磁石を安定して生産でき、これはＡＣサーボモータ、ＤＣブラシレスモータ、スピーカ用磁石等の高性能化、ハイパワー化、小型化等に有用であり、特に、自動車用スロットルバルブ等に使用される径方向２極着磁磁石の生産においても有効であり、性能の優れた同期式磁石モータ用円筒磁石を安価かつ大量に供給することができる。
【００２０】
また、本発明は、上記の目的を達成するため、上記製造方法として、金型キャビティ内に充填した磁石粉を水平磁場垂直成形法により磁石粉に配向磁界を印加して成形することにより、ラジアル異方性焼結磁石を製造するに際し、金型キャビティ内に充填した磁石粉をコイルによる発生磁場方向に対し相対的に回転させる操作を、下記（ｉ）〜（ｖ）
（ｉ）磁場印加中、磁石粉を金型周方向に所定角度回転させる、
（ｉｉ）磁場印加後、磁石粉を金型周方向に所定角度回転させ、その後再び磁場を印加する、
（ｉｉｉ）磁場印加中、磁場発生コイルを磁石粉に対し金型周方向に所定角度回転させる、
（ｉｖ）磁場印加後、磁場発生コイルを磁石粉に対し金型周方向に所定角度回転させ、その後再び磁場を印加する、
（ｖ）磁場発生コイルを２対以上配置し、１対のコイルが磁場を印加した後、別のコイル対が磁場を印加する
の操作のうち少なくとも一の操作により行うことを特徴とするラジアル異方性焼結磁石の製造方法を提供する。ここで、充填磁石粉を回転させる際、コア、ダイス及びパンチのうち少なくとも１つを周方向に回転させることで充填磁石粉を回転せしめることができる。また、磁場印加後充填磁石粉を回転させる際、強磁性コア又は磁石粉の残留磁化の値が５０Ｇ以上であり、コアを周方向に回転させることで磁石粉を回転せしめることができる。
【００２１】
この発明によれば、生産性が低く高価なラジアル異方性磁石を用いずに、多連、長尺品が容易に生産可能で、磁場が均一で安価で大量に安定して供給できる、水平磁場垂直成形法で製造される径方向配向円筒磁石を用いて高性能の永久磁石モータを実現することができ、ＡＣサーボモータ、ＤＣブラシレスモータ等の高性能モータの低価格化に有用である。
【００２２】
本発明は、複数個のステータ歯を有するモータにラジアル異方性円筒磁石を組み込んでなる永久磁石モータにおいて、前記円筒磁石が、上記製造方法によって成形作製されたラジアル異方性円筒磁石であって、周方向の着磁極数が２ｎ（ｎは２以上５０以下の正の整数）個のとき、この円筒磁石と組み合わせるステータの歯数が３ｍ（ｍは２以上３３以下の正の整数）個であり、かつ２ｎ≠３ｍであることを特徴とする周方向に多極に着磁した永久磁石モータを提供する。この場合、円筒磁石における周方向の着磁極数がｋ（ｋは４以上の正の偶数）個のとき、この円筒磁石と組み合わせるステータの歯数が３ｋ・ｊ／２（ｊは１以上の正の整数）個であることが好ましく、また、円筒磁石のＮ極とＳ極との境界がラジアル方向に対し３０°以上傾いた方向に配向した部位の中央部に対し、１０°以内にあることが好ましい。更に、円筒磁石のスキュー角度が円筒磁石の１極分の角度の１／１０〜２／３で、多極スキュー着磁するのが好ましく、特にステータ歯のスキュー角度が円筒磁石の１極分の角度の１／１０〜２／３のスキュー歯をもつことが好ましい。
【００２３】
本発明によれば、性能の優れた同期式磁石モータに用いる円筒磁石を、特に長尺でかつ廉価で大量に供給することができる。
【００２４】
本発明は、上記製造方法によって成形作製されたラジアル異方性円筒磁石の複数個を軸方向に２段以上積み重ねてなることを特徴とする多段長尺多極着磁円筒磁石ロータを提供する。この場合、円筒磁石の積み重ね数をｉ（ｉは２以上１０以下の正の整数）とするとき、各円筒磁石の配向磁場方向と同一方向を１８０／ｉ°の角度だけずらしてｉ個積み重ねることが好ましく、また、多極着磁の極数をｎ（ｎは４以上５０以下の正の整数）とするとき、積み重ね数ｉと極数ｎとがｉ＝ｎ／２の関係にあることが好ましい。更に、円筒磁石の外周面にｎ（ｎは４以上５０以下の正の整数）極の多極着磁を行うに際し、１極の角度を３６０／ｎ°とし、この角度の１／１０〜２／３の角度でスキュー着磁されてなることが好ましい。本発明は、上記多段長尺多極着磁円筒磁石ロータを用いた永久磁石式モータをも提供する。
【００２５】
即ち、上記構成とすることにより、極間の磁束密度のばらつきを大きく軽減し、高トルクでトルクむらのないスムーズな回転を実現できるモータ用磁石、即ち、多段長尺多極着磁円筒磁石ロータ及びこれを用いた永久磁石式モータの製造を可能としたものである。
【００２６】
以下、本発明につき更に詳しく説明する。
本発明に係るラジアル異方性焼結磁石は、円筒磁石であって、全体的にはラジアル方向（径方向）に配向され、但し、磁石体積の２％以上５０％以下の部位がラジアル方向に対し３０°以上９０°以下配向するようにしたものである。
【００２７】
本発明のラジアル異方性焼結磁石は、このようにラジアル方向に対し３０〜９０°傾いた方向に配向された部位が磁石体積の２〜５０％であるものである。
【００２８】
即ち、上述した式（１）で示される応力は、径方向にラジアル配向した周方向への連続体、つまり、円筒磁石であるがゆえに発生する。従って、一部分連続的な配向が阻害されれば応力は減少する。そこで、ラジアル方向に対し３０°以上傾いた方向に配向した部位を磁石体積の２％以上５０％以下含有せしめることにより、割れずに生産できる磁石である。３０°以上傾いた部分が２％より小さい場合、割れを防ぐ効果が小さく、３０°以上傾いた部分が５０％より多い場合は、モータ用ロータとした際のトルク不足を招き実用的でない。より好ましくは３０°以上傾いた部分を５〜４０％、更に好ましくは１０〜４０％含有することがよい。
【００２９】
なお、残りの磁石体積部位、即ち５０〜９８％、より好ましくは６０〜９５％の磁石体積の部分は、ラジアル方向乃至ラジアル方向に対する傾きが３０°未満であるように配向せしめられているものである。
【００３０】
図１は、円筒磁石の成形時、磁場中配向を行うための水平磁場垂直成形装置の説明図であり、特にモータ用磁石の水平磁場垂直成形装置である。ここで、図２の場合と同様、１は成形機架台、２は配向磁場コイル、３はダイスを示し、また５ａはコアを示す。６は上パンチ、７は下パンチ、８は充填磁石粉であり、また９はポールピースを示す。
【００３１】
本発明においては、上記コア５ａの少なくとも一部、好ましくは全体を飽和磁束密度５ｋＧ以上、好ましくは５〜２４ｋＧ、更に好ましくは１０〜２４ｋＧの強磁性体にて形成する。かかるコア材質としては、Ｆｅ系材料、Ｃｏ系材料及びそれらの合金材料等の素材を用いた強磁性体が挙げられる。
【００３２】
このように、飽和磁束密度５ｋＧ以上有する強磁性体をコアに使用すると、磁石粉に配向磁界を印加する場合、磁束は強磁性体に垂直に入ろうとするためラジアルに近い磁力線を描く。従って、図３ａに示されるように、磁石粉充填部の磁界方向をラジアル配向に近づけることができる。これに対し、従来はコア５ｂ全体を非磁性又は磁石粉と同等の飽和磁束密度を有した材料を用いており、この場合、磁力線は図３ｂに示したように、互いに平行で、図において中央付近はラジアル方向であるが、上側及び下側に向うにつれてコイルによる配向磁場方向となる。コアを強磁性体で形成してもコアの飽和磁束密度が５ｋＧ未満の場合、コアは容易に飽和してしまい、強磁性コアを用いたにもかかわらず、磁場は図３ｂに近い状態となる。加えて、５ｋＧ未満では充填磁石粉の飽和密度（磁石の飽和磁束密度×充填率）と等しくなり、充填磁石粉及び強磁性コア内での磁束の方向はコイルの磁界方向に等しくなってしまう。
【００３３】
また、コアの一部に５ｋＧ以上の強磁性体を用いた際も上記と同様な効果が得られ有効であるが、全体が強磁性体であることが好ましい。一部（中央部）が強磁性体及び外周部が弱い強磁性体（ＷＣ−Ｎｉ−Ｃｏ系）である一例を図４に示す。図４において、５ａ'は弱い強磁性体超硬合金部、１１はパーメンジュールを示す。
【００３４】
上記方法によると、円筒磁石内の径方向でのラジアル配向に対する乱れは、配向磁場方向に垂直な部分のみの配向の乱れとなるため、着磁後、各極の磁束量減少はわずかに抑えることができ、モータのトルクむら及びトルク劣化のないモータロータ用円筒磁石を製造することができる。
【００３５】
また、上記のように成形を行う際、水平磁場垂直成形装置で発生する磁場は０．５〜１２ｋＯｅであることが好ましい。このように水平磁場垂直成形装置で発生する磁場を定めた理由としては、磁場が大きい場合、図３ａのコア５ａが飽和してしまい、図３ｂに近い状態になり、円筒磁石の磁場垂直方向での配向がラジアル配向とはならなくなるため、磁場は１２ｋＯｅ以下が好ましい。強磁性コアを用いると磁束がコアに集中するため、コア周辺では、コイルによる磁場より大きな磁場が得られる。しかし、磁場があまり小さいと、コア周辺においても配向に十分な磁場が得られなくなるため、０．５ｋＯｅ以上が好ましい。前述のように強磁性体周辺では磁束が集まり、磁場が大きくなるため、ここでいう水平磁場垂直成形装置で発生する磁場とは、強磁性体から十分に離れた場所における磁場又は強磁性コアを取り除いて測定したときの磁場の値を意味する。従って、更に好ましくは１〜１０ｋＯｅであることがよい。
【００３６】
更に、本発明においては、図２に示したような垂直磁場垂直成形装置において、円筒磁石用成形金型のダイス材に非磁性体をトータル角度２０°以上１８０°以下、特に３０〜１２０°の領域に亘り少なくとも１つ以上配することが好ましい。
【００３７】
図５は垂直磁場垂直成形装置におけるラジアル円筒磁石用成形金型のダイス材に非磁性体（例えば非磁性超硬材等）１０を、角度θ＝３０°の領域（ダイス円筒３６０°のうち３０°にあたる領域）で対称に２個配した垂直磁場垂直成形装置を示す。なお、非磁性体近傍の磁力線は強磁性体に向かって曲げられる。特に非磁性体と強磁性体の境に存在する強磁性体エッジの方向に曲げられる。磁石粉は曲げられた磁力線の方向に配向するため、求める磁石が得られる。このときの非磁性体配置角度が２０°未満であると磁力線が曲げられる効果が小さく、加えて配向方向が径方向に対し３０°以上傾いた領域が少なくなり、割れを抑える効果が小さい。また、１８０°より大きい場合はラジアル配向が阻害され、目的にたる磁石とはならない。
この場合、図５において、１は成形機架台、３はダイス、４はコア、８は充填磁石粉であることは、図２の場合と同様である。また、ダイス３における上記非磁性体１０以外の材質は、５ｋＧ以上の強磁性体にて形成する。更に、コア材は１０ｋＧ以上の強磁性体にて形成することができる。
【００３８】
ところで、金型のコア５ａの少なくとも一部、好ましくは全体を飽和磁束密度５ｋＧ以上の強磁性体で形成し、上記のように水平磁場垂直成形を行う場合、なお、この方法では、コイルによる配向磁場方向に対し９０°である方向では、ラジアル配向とならない場合がある。磁場中に強磁性体がある場合、磁束は強磁性体に垂直に入ろうとし強磁性体に引き寄せられるため、強磁性体の磁場方向面では磁束密度が上昇し、垂直方向では磁束密度が低下する。このため、金型内に強磁性コアを配した場合、充填磁石粉において強磁性コアの磁場方向部では強い磁場により良好な配向が得られ、垂直方向部ではあまり配向しない。これを補うために磁石粉をコイルによる発生磁場に対し相対的に回転させ、不完全配向部を磁場方向の強い磁場部で再度配向することで良好な磁石が得られる。
【００３９】
ここで、磁石粉をコイルによる発生磁場に対し、相対的に回転させる方法としては、下記（ｉ）〜（ｖ）
（ｉ）磁場印加中、磁石粉を金型周方向に所定角度回転させる、
（ｉｉ）磁場印加後、磁石粉を金型周方向に所定角度回転させ、その後再び磁場を印加する、
（ｉｉｉ）磁場印加中、磁場発生コイルを磁石粉に対し金型周方向に所定角度回転させる、
（ｉｖ）磁場印加後、磁場発生コイルを磁石粉に対し金型周方向に所定角度回転させ、その後再び磁場を印加する、
（ｖ）磁場発生コイルを２対以上配置し、１対のコイルが磁場を印加した後、別のコイル対が磁場を印加する
の操作のうち少なくとも一の操作を一回又は繰り返して複数回行うものである。
【００４０】
なお、充填磁石粉の回転については、図６で示すように磁石粉をコイルによる発生磁場方向に対し、相対的に回転できれば、コイル２、コア５ａ、ダイス３、パンチ６、７のいずれかを回転させてもよい。このうち特に、磁場印加後、充填磁石粉を回転させる際、強磁性コア又は磁石粉の残留磁化を５０Ｇ以上、特に２００Ｇ以上存在させておけば、磁石粉は強磁性コアとの間に磁気的な吸引力が発生するため、強磁性コアを回転させるだけで磁石粉も回転させることができる。
【００４１】
回転角度については適宜選定されるが、当初の位置を０°とした場合、好ましくは１０〜１７０°、特に６０〜１２０°の範囲、典型的には９０°前後で、磁場印加中に回転させる場合は、徐々に所定角度回転させ、磁場印加後に回転させる場合は、所定角度回転させた後に再度磁場を印加するものである。
【００４２】
本発明は、上記のように成形するものであるが、それ以外は通常の垂直成形法により磁石粉に配向磁界を印加して、一般的な成形圧０．５〜２．０ｔ／ｃｍ²で成形し、更に焼結、時効処理、加工処理等を施し、焼結磁石を得ることができる。
【００４３】
なお、磁石粉としては、特に制限されるものではなく、Ｎｄ−Ｆｅ−Ｂ系の円筒磁石を製造する場合に好適であるほか、フェライト磁石、Ｓｍ−Ｃｏ系希土類磁石、各種ボンド磁石等の製造においても有効であるが、いずれも平均粒径０．１〜１００μｍ、特に０．３〜５０μｍの合金粉を用いて成形するものである。
【００４４】
本発明においては、このようにして得られた円筒磁石に対し、その外周面を多極着磁する。ここで、図７は、着磁機２２を用いて円筒磁石２１の着磁を行う様子を示している。なお、符号２３は着磁機磁極歯であり、符号２４は着磁機コイルである。
【００４５】
本発明による水平磁場垂直成形にて製造されるラジアルライクな径方向配向円筒磁石を図７の着磁機にて６極着磁を行った際の表面磁束密度を図１１に示す。また、図１２は従来の製法で作られた径方向配向円筒磁石に図７の着磁機により６極着磁を行った際の表面磁束密度図である。従来の水平磁場垂直成形法により径方向配向円筒磁石を作製し、配向磁場方向がＮ、Ｓ極となるように６極着磁を行うと、配向方向のＡ、Ｄでは表面磁束密度が大きく、配向方向と９０°の角度をなす方向に近いＢ、Ｃ、Ｅ、Ｆの配向方向では小さな表面磁束密度となる。そればかりか、同じ角度幅を持つ着磁機具を用いて着磁を行ったにもかかわらず、着磁幅は方向により大きく異なる。これに対し、本発明品では、Ｂ、Ｃ、Ｅ、Ｆのピーク値において上昇がみられ、表面磁束が０となるところでの着磁幅もほぼ一定となる。しかし、表面磁化が、ピークの位置でＡ、Ｄに比べＢ、Ｃ、Ｅ、Ｆはとがった形状となっている。磁束量はピーク面積が大きいほど大きいので、Ａ、Ｄに比べＢ、Ｃ、Ｅ、Ｆは小さくなってしまう。各極間における磁束量のばらつきはモータに組みこまれた際の回転むらになり、振動、騒音の原因となる。従って、この各極間の磁束量のばらつきを低減することで、むらの無いスムーズな回転が行える。
【００４６】
図１０は、９個のステータ歯（ステータティース）を有する３相モータの平面図を示したものである。３相モータ３０はα、β、γのステータ歯３１がα、β、γの順に配列し、その配線がステータ歯をコイル状に巻きながらつながり、Ｕ、Ｖ、Ｗ相としてモータの入力線となる。このＵ、Ｖ、Ｗ相に電流を流してコイル３２に磁場を発生させ、コイルによる磁場と円筒磁石２１との間に働く斥力及び引力によりモータは回転する。Ｕ−Ｖ、Ｖ−Ｗ、Ｗ−Ｕはそれぞれ総ステータ歯数の１／３の数の歯を周っており、Ｕ−Ｖに電流が流れるとステータコアのαより磁場が発せられ、同様にＶ−Ｗによりβ、Ｗ−Ｕによりγにそれぞれ磁場が発生する。図１０は、このような歯数９個のステータを有する３相モータに、６極に着磁を行った径方向配向円筒磁石２１を組み込んだものである。なお、図中３３はモータロータ軸である。
【００４７】
図中において、Ｕ−Ｖ（α）が磁石の極の中心に位置し、モータトルクのピークとなる。この際、Ｕ−Ｖ（α）と作用し、回転力を生じる極はＡ、Ｃ、Ｅ極であり、Ａ極は配向磁場方向極であり、磁束量が大きく、Ｃ及びＥは配向磁場方向とはずれた角度に位置する極であり、磁束量は小さい。次に、磁石が回転し、Ｕ−Ｖ（α）にＤ、Ｆ、Ｂ極が近づく。Ｄ極は配向磁場方向の極であり、磁束量が大きく、Ｆ及びＢは配向磁場方向とはずれた角度に位置する極であり、磁束量は小さい。しかし、磁石極数６の３／２倍の９個の歯を有するがために、Ｕ−Ｖ（α）のコイルに鎖交する磁束量はＡ、Ｃ、Ｅ極分合わせたものとＤ、Ｆ、Ｂ極分合わせたものでは常に等しくなる。この関係はＶ−Ｗ（β）、Ｗ−Ｕ（γ）においても同様である。この場合、円筒磁石における着磁極数がｋ（ｋは４以上の正の偶数）個のとき、この円筒磁石と組み合わせるステータの歯数が３ｋ・ｊ／２（ｊは１以上の正の整数）個であることがよく、特に上記のように、磁石の極とモータのステータの歯数の組み合わせを磁石極数ｋ＝６、歯数３ｋ・ｊ／２＝９（ｋ＝６、ｊ＝１）の組み合わせとすることで、磁石に配向磁場方向の極と配向磁場方向からずれた極が存在し、磁束量にばらつきがある円筒磁石においても、磁束ばらつきが緩和され、回転むらのないモータを得ることができる。なお、ｋは好ましくは５０以下、更に好ましくは４０以下の偶数であり、ｊは好ましくは１０以下、更に好ましくは５以下の整数である。極数ｋが多くなりすぎると、１極の幅が小さくなり、配向磁場方向に垂直方向では極が明確にならない場合がある。
【００４８】
このうち磁石極数２ｎ（ｎは２以上５０以下の正の整数）に対し、ステータ歯数を３ｍ（ｍは２以上３３以下の正の整数）とした際に、常に上記関係が維持され、回転むらのないモータを得ることができる。但し、２ｎ≠３ｍである。特に、径方向配向円筒磁石に多極着磁を行い、ステータ歯数を着磁極数の３ｎ倍としたものは、特に回転むらのない優れたモータ特性を有するモータを生産できる。
【００４９】
本発明に係る円筒磁石に多極着磁を行ったものは、ラジアル異方性リング磁石に多極着磁を行った場合に比べ、極間付近の着磁性及び磁気特性が低いので磁束密度の極間部の変化が滑らかであり、モータのコギングトルクは小さいが、スキュー着磁又はステータ歯にスキューを施すことで、更にコギングトルクを低減することができる。円筒磁石及びステータ歯のスキュー角度が、円筒磁石１極分の角度の１／１０未満であるとスキュー着磁によるコギングトルク低下の効果が小さく、円筒磁石１極分の角度の２／３より大きいとモータのトルクの低下が大きくなるため、スキュー角度は円筒磁石１極分の角度の１／１０〜２／３の角度が好ましく、特に１／１０〜２／５の角度が好ましい。
なお、本発明の永久磁石モータは、上記した構成とする以外は、公知の構成として製造し得る。
【００５０】
この場合、図７は円筒磁石の配向方向を図８に対し９０°回転させて着磁を行ったものであるが、図９に示されるように、円筒磁石のＮ極とＳ極の境界がラジアル方向に対し±３０°以上傾いた方向に配向した部位の中央部４０に対し、±１０°以内にあることが好ましい。そして、このように設定したＮ極とＳ極との境界から周方向に互いに等間隔ずつ離間してＮ極とＳ極との境界を設けるように、周方向に多極に着磁することが好ましい。一方、図８による着磁に比べ、図７による着磁は、ラジアル方向からずれた部位を４極（片側２極ずつ）で分担するため、コギングが少なく、トルクが上昇する。
【００５１】
また、図８は、円筒磁石の配向方向を図７に対して９０°回転させて着磁を行う様子を示す着磁模式図である。図７に対して配向方向を９０°回転させて６極着磁を行った図８に示されるものは、配向磁場方向付近のＢ、Ｃ、Ｅ、Ｆ極からは比較的大きな磁束量が得られ、Ａ、Ｄ極の配向方向に垂直な方向の部分では磁束量は小さくなる。図７及び８にて着磁した磁石を２段積みして９０°ずらして着磁してモータ用ロータ磁石とすると、図７で着磁した大きな磁束量のＡ、Ｄが図８で着磁した場合は少ない磁束量となるため、合わせると図７での着磁ではやや小さな磁束量であるが、図８での着磁では比較的大きな磁束量が得られるＢ、Ｃ、Ｅ、Ｆ極とほぼ同じ磁束量となる。このため、各極間の磁束量のばらつきを低減することで、むらの無いスムーズな回転が行える。
【００５２】
同様に、水平磁場垂直成形装置にて製造されるラジアルライクな配向を有する円筒磁石を輪切りして円筒軸方向に２等分割し、一方に対しもう片方を徐々に回転させて段積みを行い、はじめは図７の配置で着磁されるが、徐々に向きが変わり、９０°回転後は図８の配置での着磁となる。これを次々に９０°まで回転させて段積みし、その後着磁をしていくと、Ａ、Ｄ極では回転角が増えるにつれ徐々に総磁束量が減少し、Ｂ、Ｃ、Ｅ、Ｆ極では総磁束量は増加する。
【００５３】
このように該成形機にて製造されるラジアルライクな径方向配向円筒磁石を、軸方向に２段以上積み重ねて多極着磁を行うことにより、各極間の磁束量のばらつきを低減することができ、モータとして用いた際のトルクむらを抑えることができる。なお、積層数の上限は特に制限はないが、１０段程度が好ましい。
【００５４】
分割した磁石の配向方向を相対的に所定の角度回転させて多段（２段以上）積みして多極着磁することにより、配向方向とこれに垂直な方向との磁束量のばらつきを均一化し、極間の磁束量のばらつきを低減させることができる。このとき、積み重ねる各磁石の配向方向を１８０／ｉ°（ｉは積み重ね数）だけ角度をずらして積み重ね、多極着磁を行うことが好ましい。
【００５５】
また、分割数は配向方向を各極に均一に分布させるために、ｉ＝ｎ／２段（ｎは極数）とすることで、配向方向の磁束量の多い部分と、これに垂直な方向で磁束量の少ない部分とをそれぞれ各極に均一に分布でき、これを１８０／ｉ°だけ角度をずらして積み重ね、多極着磁することで各極の総磁束量を等しくすることができる。
【００５６】
なお、ｎは４〜５０の正の整数で、ｎが多くなると着磁極間が狭くなり、十分な着磁が困難となるので、ｎは特に４〜３０が好ましい。
【００５７】
また、ｉは２〜１０の正の整数で、ｉが大きく積み重ね数が多くなると、コストが高くなるので、特に２〜６が好ましい。
【００５８】
水平磁場垂直成形装置により一方向異方性を有する円筒磁石に多極着磁を行ったものは、ラジアル異方性リング磁石に多極着磁を行った場合に比べ、極間付近の着磁性及び磁気特性が低いので磁束密度の極間部の変化が滑らかであり、モータのコギングトルクは小さい。なお、磁石をスキュー着磁するか、ステータ歯にスキューを施すことで更にコギングトルクを低減することができる。
【００５９】
スキュー角度は、磁石ステータともに磁石１極分（３６０／ｎ°）の角度の１／１０以下であると、スキュー着磁によるコギングトルク低下の効果が小さく、２／３より大きいと、モータのトルクの低下が大きくなるため、スキュー角は、磁石１極分の角度の１／１０〜２／３の角度が好ましい。
【００６０】
本発明の永久磁石式モータは、例えば図１０に示したように、モータ、特に複数個のステータ歯を有するモータにロータとして上記の多段長尺多極着磁円筒磁石ロータを組み込めばよく、この場合、該ステータ歯を有するモータの構成は公知のものとすることができる。
【００６１】
【発明の効果】
本発明のラジアル異方性焼結磁石は、内外径比の小さな形状においても焼結及び時効冷却時の割れ、クラックのない優れた磁石特性を有する。
【００６２】
【実施例】
以下、実施例及び比較例を示し、本発明を具体的に説明するが、本発明は下記の実施例に制限されるものではない。
【００６３】
［参考例１］
それぞれ純度９９．７重量％のＮｄ、Ｄｙ、Ｆｅ、Ｃｏ、Ｍ（ＭはＡｌ、Ｓｉ、Ｃｕ）と純度９９．５重量％のＢを用い、Ｎｄ₂₉Ｄｙ_2.5Ｆｅ₆₄Ｃｏ₃Ｂ₁Ａｌ_0.2Ｃｕ_0.1Ｓｉ_0.2の合金を真空溶解炉で溶解鋳造してインゴットを作製した。このインゴットをジョウクラッシャー及びブラウンミルで粗粉砕し、更に窒素気流中ジェットミル粉砕により平均粒径３．５μｍの微粉末を得た。この粉末を飽和磁束密度２０ｋＧの強磁性体（Ｓ５０Ｃ：Ｆｅ鋼）コアを配置した水平磁場垂直成形装置にて８ｋＯｅの磁場中において０．５ｔ／ｃｍ²の成形圧にて成形した。このとき、磁石粉の充填密度は２５％であった。この成形体はＡｒガス中１０９０℃で１時間焼結を行い、引き続き５８０℃で１時間の時効熱処理を行った。その後加工を行い、φ３０ｍｍ×φ２５ｍｍ×Ｌ３０ｍｍの円筒磁石を得た。上記円筒磁石を図７の着磁機にて６極着磁し、着磁後の磁石を磁石と同一高さの図１０に示す構成のステータ内に組み込んだモータを作製した。磁石内径にはモータ軸となる強磁性コアが挿入接着されている。銅細線を各歯それぞれ１５０ターン巻きとした。モータを１０００ｒｐｍで回転させた際の誘起電圧及び同モータを１〜５ｒｐｍで回転させた際の荷重計によるトルクリップルの大きさを測定した。
【００６４】
［参考例２］
図８の着磁配置により着磁した以外は参考例１と同様にして得た磁石を同様にモータに組み込んだ際の誘起電圧とトルクリップルの大きさを測定した。結果を表１に示す。
【表１】

【００６５】
［参考例３］
コア断面積の６０％の面積を占める飽和磁束密度１８ｋＧの強磁性体（ＳＫ５：Ｆｅ鋼）をコア外周と同心円状に配置し、残りは非磁性体材で作成したコアを用い、その他は参考例１と同様にして作製した円筒磁石をモータに組み込み、モータ特性を測定した。
【００６６】
［参考例４］
参考例１と同じ成形機を用い、発生磁場を６ｋＯｅとし、他は参考例１の条件で磁石を作製し、モータに組み込みモータ特性を測定した。
【００６７】
［比較例１］
参考例１と同様の磁石粉を用い、図２に示される垂直磁場垂直成形装置を用い、コイルの発生磁界２０ｋＯｅで磁石粉充填深さ３０ｍｍとし、磁場中成形後の成形体を下方に移動させ、成形体の上に先ほどと同様に３０ｍｍ磁石粉を乗せ、磁場中成形後の磁石を参考例１と同様の条件で焼結時効を行い、φ３０ｍｍ×φ２５ｍｍ×Ｌ３０ｍｍの円筒磁石を得た。これをモータに組み込みモータ特性を測定した。
【００６８】
［比較例２］
非磁性体（非磁性超硬材ＷＣ−Ｎｉ−Ｃｏ）をコア材に用いた以外は、参考例１と同じ条件で磁石を作製し、モータに組み込みモータ特性を測定した。
【００６９】
［比較例３］
飽和磁束密度２ｋＧの強磁性体（磁性超硬材ＷＣ−Ｎｉ−Ｃｏ）コアを配置した成形機にて、他は参考例１と同じ条件で磁石を作製し、モータに組み込みモータ特性を測定した。
【００７０】
［参考例５］
図５に示すように、非磁性体（非磁性超硬材ＷＣ−Ｎｉ−Ｃｏ）をダイス内角度３０°の部分で２個対称になるように配置し（トータル６０°）、その他は比較例１と同様な条件で磁石を作製し、同様にモータ特性を測定した。
【００７１】
偏光顕微鏡観察により、ラジアル配向に対し、３０°以上傾いた部分の体積（配向乱れ体積）を算出し、表２に示す。また、これらの円筒磁石をそれぞれの条件で１００個製造した際の割れの数もあわせて記載する。
【００７２】
【表２】

【００７３】
表２より、参考例は大きな起電力が得られ、かつトルクリップルが小さく、クラックの発生がないためモータ用磁石として優れた特性を有する磁石の量産化に有効である。
【００７４】
また、参考例４の条件で作製した磁石を偏光顕微鏡観察した結果を図１３、１４、１５に示す。即ち、図１３、１４、１５は強磁性材をコアとして用いた水平磁場垂直成形装置により作製された磁石において、配向磁場方向に対し、３０°方向、６０°方向、９０°方向での磁石の配向の様子を示したもので、これらからわかるように本発明による円筒磁石では、配向磁場方向に対し６０°方向で初めてラジアル方向とのずれが３０°となり、これより３０体積％で３０°以上ずれていることがわかる。
【００７５】
［実施例１〜４、参考例６］
それぞれ純度９９．７重量％のＮｄ、Ｄｙ、Ｆｅ、Ｃｏ、Ｍ（ＭはＡｌ、Ｓｉ、Ｃｕ）と純度９９．５重量％のＢを用い、Ｎｄ₂₉Ｄｙ_2.5Ｆｅ_63.8Ｃｏ₃Ｂ₁Ａｌ_0.3Ｓｉ_0.3Ｃｕ_0.1の合金を真空溶解炉で溶解鋳造してインゴットを作製した。このインゴットをジョウクラッシャー及びブラウンミルで粗粉砕し、更に窒素気流中ジェットミル粉砕により平均粒径３．５μｍの微粉末を得た。この粉末を図１に示すような飽和磁束密度２０ｋＧの鉄製の強磁性体コアを配置した水平磁場垂直成形装置にて、コイルの発生磁場４ｋＯｅの磁場中において配向させた後、実施例１として、コイルを９０°回転させ、次いで同様に４ｋＯｅの磁場中において再び配向させ、１．０ｔ／ｃｍ²の成形圧にて成形した。
【００７６】
実施例２としては、水平磁場垂直成形装置にてコイルの発生磁場４ｋＯｅの磁場中において配向させた後、ダイスとコア及びパンチを９０°回転させ、次いで同様に４ｋＯｅの磁場中において再び配向させ、１．０ｔ／ｃｍ²の成形圧にて成形した以外は実施例１と同様に成形した。
【００７７】
実施例３としては、水平磁場垂直成形装置にてコイルの発生磁場４ｋＯｅの磁場中において配向させた後、残留磁化４ｋＧのコアを９０°回転させた。このときの磁石粉の残留磁化は８００Ｇであった。次いで同様に４ｋＯｅの磁場中において再び配向させ、その後、１．０ｔ／ｃｍ²の成形圧にて成形した以外は実施例１と同様に成形した。
【００７８】
これらの成形体はＡｒガス中１０９０℃で１時間焼結を行い、引き続き５８０℃で１時間の時効熱処理を行った。その後、加工を行い、φ２４ｍｍ×φ１９ｍｍ×Ｌ３０ｍｍの円筒磁石を得た。なお、本円筒磁石と同一磁石粉を用い、水平磁場垂直成形装置にて１２ｋＯｅの磁場中において１．０ｔ／ｃｍ²の成形圧にて成形し、Ａｒガス中１０９０℃で１時間焼結を行い、引き続き５８０℃で１時間の熱処理をして本円筒磁石と同一条件で作製したブロック磁石の特性は、Ｂｒ：１２．５ｋＧ、ｉＨｃ：１５ｋＯｅ、（ＢＨ）ｍａｘ：３６ＭＧＯｅであった。上記の円筒磁石を、図７に示す着磁機にて６極、２０°でスキュー着磁し、着磁後の磁石を磁石と同一高さの図１０に示す構成のステータ内に組み込んだモータを作製した。また、上記実施例のモータを５０００ｒｐｍで回転させた際の誘起電圧及び同モータを５ｒｐｍで回転させた際の荷重計によるトルクリップルの大きさを測定した。更に、上記と同様に成形、焼結、熱処理して得た円筒磁石を図８の着磁機にて着磁し、モータに組み込んで、誘起電圧及びトルクリップルを測定した（実施例３ａ）。表３に誘起電圧の絶対値の最大及びトルクリップルの最大最小の差を示す。
【００７９】
実施例４として、実施例１と同じ水平磁場垂直成形装置を用い、１２ｋＯｅの磁場中において９０°回転させながら配向を行い、１．０ｔ／ｃｍ²の成形圧にて成形した。他は実施例１と同様にして作製した磁石を用いたモータのモータ特性を測定した。
【００８０】
一方、参考例６として、実施例１において４ｋＯｅの磁場で配向させた際、回転させずそのまま磁界中１．０ｔ／ｃｍ²の成形圧にて成形した。他は実施例１と同様にして作製した磁石を用いたモータのモータ特性を測定した。これらの結果を表３に示す。
【００８１】
【表３】

【００８２】
表３より、参考例６に対し実施例ではトルクに相応する誘起電圧が大きく改善されており、本発明がモータ用磁石の製造方法として優れた方法であることがわかる。
【００８３】
なお、実施例１の着磁後のロータ磁石の表面磁束を測定した結果は図１１と同様の結果で各極が均一化しており、かつ極の面積が大きくなっており、実施例は大きな磁場が均一に発生できることがわかる。
【００８４】
［参考例７］
それぞれ純度９９．７重量％のＮｄ、Ｄｙ、Ｆｅ、Ｃｏ、Ｍ（ＭはＡｌ、Ｓｉ、Ｃｕ）と純度９９．５重量％のＢを用い、Ｎｄ₂₉Ｄｙ_2.5Ｆｅ₆₄Ｃｏ₃Ｂ₁Ａｌ_0.2Ｓｉ_0.2Ｃｕ_0.1の合金を真空溶解炉で溶解鋳造してインゴットを作製した。このインゴットをジョウクラッシャー及びブラウンミルで粗粉砕し、更に窒素気流中ジェットミル粉砕により平均粒径３．５μｍの微粉末を得た。この粉末を飽和磁束密度２０ｋＧのＦｅ製の強磁性体コアを配置した図１に示す水平磁場垂直成形装置にて１０ｋＯｅの磁場中において１．０ｔ／ｃｍ²の成形圧にて成形した。この成形体はＡｒガス中１０９０℃で１時間焼結を行い、引き続き５８０℃で１時間の熱処理を行った。その後加工を行い、φ３０ｍｍ×φ２５ｍｍ×Ｌ３０ｍｍの円筒磁石を得た。本円筒磁石と同一磁石粉を用い、水平磁場垂直成形装置にて１０ｋＯｅの磁場中において１．０ｔ／ｃｍ²の成形圧にて成形し、Ａｒガス中１０９０℃で１時間焼結を行い、引き続き５８０℃で１時間の熱処理をして、本円筒磁石と同一条件で作製したブロック磁石の特性は、Ｂｒ：１３．０ｋＧ、ｉＨｃ：１５ｋＯｅ、（ＢＨ）ｍａｘ：４０ＭＧＯｅであった。
【００８５】
上記の径方向配向円筒磁石を、着磁機にて６極着磁し、着磁後の磁石を磁石と同一高さの図１０に示す構成の９個のステータ内に組み込んだモータを作製した。磁石内径にはモータ軸となる強磁性コアが挿入接着されている。銅細線を各歯それぞれ１００ターン巻きとした。Ｕ−Ｖ相間の磁束量をフラックスメータを用いて測定した。
【００８６】
［比較例４］
本ステータ歯のうちの一つだけに参考例７と同じ銅細線を１００ターン巻き、磁束量をフラックスメータにて測定した。磁石を１周させたときのピークの値を表４に示す。表に示されるように、比較例ではピークによる磁束量が、小さいピークに対し大きなピークでは１．５倍程度と非常に大きいにもかかわらず、参考例７ではピーク値がほとんど変わらない。
【００８７】
［参考例８］
コア断面積の６０％の面積を占める飽和磁束密度１８ｋＧの強磁性体をコア外周と同心円状に配置し、残りは非磁性体材で作製したコアを用い、その他は参考例７と同様にして作製したモータのＵ−Ｖ相間の磁束量を測定した。
【００８８】
［比較例５］
非磁性体（非磁性超硬材ＷＣ−Ｎｉ−Ｃｏ）をコア材に用いた他は参考例７と同様にして作製したモータのＵ−Ｖ相間の磁束量を測定した。
【００８９】
［比較例６］
Ｆｅ製の強磁性体コアの飽和磁束密度を２ｋＧとした他は参考例７と同様にして作製したモータのＵ−Ｖ相間の磁束量を測定した。配置した際のモータのＵ−Ｖ相間の磁束量をそれぞれフラックスメータを用いて測定した。
これらの結果を表４に示す。
【００９０】
【表４】

【００９１】
［参考例９］
参考例７のモータを１０００ｒｐｍで回転させた際の誘起電圧及び同モータを１〜５ｒｐｍで回転させた際の荷重計によるトルクリップルの大きさを測定した。表５に誘起電圧の絶対値の最大及びトルクリップルの最大最小の差を示す。表５より、本モータは使用上十分な誘起電圧量を有し、十分小さなトルクリップルであることがわかる。
【００９２】
［参考例１０］
参考例７の径方向配向円筒磁石を着磁する際、スキュー角度を磁石１極分の角度の１／３の２０°でスキュー着磁を行い、該磁石を参考例７のモータに組み込み、参考例９と同様に誘起電圧及びトルクリップルを測定した値を表５に示す。表５よりトルクリップルの量がスキュー無し品より更に小さく、誘起電圧の低下はわずかであることがわかる。
【００９３】
［参考例１１］
参考例７の径方向配向円筒磁石を着磁する際、スキュー角度磁石１極分の角度の５／６の５０°でスキュー着磁を行い、該磁石を参考例７のモータに組み込み、参考例９と同様に誘起電圧及びトルクリップルを測定した値を表５に示す。表５よりトルクリップルの量はスキュー無し品より小さいが、誘起電圧の低下が大きく、実用に適さない場合があることがわかる。
【００９４】
［参考例１２］
径方向配向円筒磁石を参考例７と同様に着磁し、スキュー角度が磁石１極分の角度の１／３の２０°であるステータ歯をもつ参考例７と同寸法のモータに組み込み、参考例９と同様に誘起電圧及びトルクリップルを測定した値を表５に示す。表５より、トルクリップルの量がスキュー無し品より更に小さく、誘起電圧の低下はわずかであることがわかる。
【００９５】
【表５】

【００９６】
［参考例１３］
それぞれ純度９９．７重量％のＮｄ、Ｄｙ、Ｆｅ、Ｃｏ、Ｍ（ＭはＡｌ、Ｓｉ、Ｃｕ）と純度９９．５重量％のＢを用い、Ｎｄ₂₉Ｄｙ_2.5Ｆｅ₆₄Ｃｏ₃Ｂ₁Ａｌ_0.2Ｓｉ_0.2Ｃｕ_0.1の合金を真空溶解炉で溶解鋳造し、インゴットを作製した。このインゴットをジョウクラッシャー及びブラウンミルで粗粉砕し、更に、窒素気流中でのジェットミル粉砕により平均粒径３．５μｍの微粉末を得た。この粉末を飽和磁束密度２０ｋＧのＦｅ製の強磁性体コアを配置した図１に示す如き水平磁場垂直成形装置にて６ｋＯｅの磁場中において１．０ｔ／ｃｍ²の成形圧にて成形した。この成形体は、Ａｒガス中１０９０℃で１時間焼結を行い、引き続き５８０℃で１時間の熱処理を行った。その後、加工して外径３０ｍｍ、内径２５ｍｍ、厚さ１５ｍｍの円筒磁石を得た。
【００９７】
参考例１３は、作製した円筒磁石を、配向方向を６０°ずらして積み重ね、１段目の磁石配向方向が図８の関係（極ＡがＮ極となる）になるように配置し、６極着磁３段積みを行った。
【００９８】
［参考例１４］
参考例１４は、ずらし角を９０°とし、参考例１３と同様に６極着磁２段積みを行った。
【００９９】
［参考例１５］
参考例１３と同じ磁石粉末を用い、成形体高さを変え、段積みをしないこと以外は参考例１３と同一条件で外径３０ｍｍ、内径２５ｍｍ、厚さ３０ｍｍの円筒磁石を作製し、６極着磁を行った。
【０１００】
［参考例１６］
参考例１３と同じ磁石粉末を用い、同一条件で外径３０ｍｍ、内径２５ｍｍ、厚さ１０ｍｍの円筒磁石を作製し、配向方向を６０°ずらして３段積み重ね、各段の円筒磁石の配向方向がそれぞれ図７の配置になるようにし、６極着磁を行った。この様子を図１６に示す。図中の大矢印は、円筒磁石の各段の配向時の磁場方向を示している。なお、符号３３はモータロータ軸である。
【０１０１】
これらの磁石を評価するために、横１０．５ｍｍ、縦３０ｍｍの四角形に銅細線を５０ターン巻き、コイルを作製した。このコイルを円筒磁石に接した状態から磁石の磁力の影響を受けない遠方まで遠ざけ、この間のコイルを横切る磁束量を円筒磁石の外周方向にフラックスメータを用いて測定し、ピーク値を表６に示す。
【０１０２】
【表６】

【０１０３】
［参考例１７，１８，１９、比較例７］
図１０は、９個のモータステータ歯３１を有する３相の永久磁石モータ３０の平面図を示したものである。着磁した円筒磁石をこの磁石と同一高さのステータ内に組み込んでモータを作製した。円筒磁石の内径部にはモータ軸となる強磁性コアが挿入接着されている。各ティースに銅細線をそれぞれ１５０ターン巻きした。このモータを１０００ｒｐｍで回転させ、このときの誘起電圧の絶対値の最大で、かつ１〜５ｒｐｍで回転させ、荷重計を用いてトルクリップルの大きさを測定した。
【０１０４】
ここで、参考例１７は、参考例１４と同様にずらし角９０°で磁石を２段に重ね合わせ、スキュー角を磁石１極分の角度の１／３の２０°でスキュー着磁を行い、この磁石をモータに組み込んだものである。
【０１０５】
参考例１８は、参考例１６と同じ寸法の円筒磁石を用い、図１６に示すようにずらし角６０°で磁石を３段に重ねてスキューなしに着磁し、スキュー角が磁石１極分の角度の１／３の２０°であるスキューステータ歯を有するモータに組み込んだものである。
【０１０６】
また、段積みをしない円筒磁石を参考例１９とし、また成形金型のコアを非磁性（非磁性超硬材ＷＣ−Ｎｉ−Ｃｏ）で作製して成形機に配置し、その他は参考例１３と同様に磁石を作製し、これを参考例１７と同様にしてモータに組み込み、比較例７とした。これらの誘起電圧、トルクリップルを測定し、誘起電圧とともにトルクリップルの最大最小の差を表７に示した。
【０１０７】
表７から、各実施例は実用に十分耐える誘起電圧を有し、トルクリップルも十分小さいが、参考例１９はトルクリップルが大きいことが認められる。比較例７は誘起電圧が低く、実用に適さない。
【０１０８】
［参考例２０］
参考例１７の径方向配向円筒磁石を着磁する際、スキュー角磁石１極分の角度の５／６の５０°でスキュー着磁を行い、この磁石を図１０のモータに組み込み、参考例１７と同様にして誘起電圧及びトルクリップルを測定し、表７に示した。
【０１０９】
表７から、トルクリップルの量は小さいが、誘起電圧の低下が大きく実用に適さないことが認められる。
【０１１０】
［参考例２１，２２］
参考例１３のＮｄ磁石合金を用いて、水平磁場垂直成形法により一軸配向のリング磁石を作製した。磁石寸法は外径２５ｍｍ、内径２０ｍｍ、厚さ１５ｍｍである。配向方向を６０°ずつ変化させながら６段積み重ねて６極にストレート着磁し磁石ロータを作製した。これを７°のスキュー角のステータに組み込みモータにした。
【０１１１】
更に参考例２２として、参考例２１と同じ磁石を用いて配向方向を一方向にそろえ、６極にストレート着磁し磁石ロータを作製した。これを無スキューのステータに組み込みモータにした。これらにおいて誘起電圧とともにトルクリップルを測定した。
【０１１２】
その結果は、表７に示したとおりであり、参考例２１では参考例２２に比べてトルクリップルが大きく低下しており、本発明による磁石の配向方向分散の効果が顕著であることがわかる。
【０１１３】
【表７】

【図面の簡単な説明】
【図１】円筒磁石を製造する際に使用する水平磁場垂直成形装置の一実施例を示す説明図であり、（ａ）は平面図、（ｂ）は縦断面図である。
【図２】ラジアル異方性円筒磁石を製造する際に使用する従来の垂直磁場垂直成形装置を示す説明図であり、（ａ）は縦断面図、（ｂ）は（ａ）図におけるＡ−Ａ’線の断面図である。
【図３】円筒磁石を製造する際に使用する水平磁場垂直成形装置で磁場発生時の磁力線の様子を模式的に示す説明図であり、（ａ）は本発明に係る成形装置の場合、（ｂ）は従来の成形装置の場合である。
【図４】円筒磁石を製造する際に使用する水平磁場垂直成形装置の他の実施例を示す説明図であり、（ａ）は平面図、（ｂ）は縦断面図である。
【図５】ラジアル異方性円筒磁石を製造する際に使用するダイス部に一部非磁性材を配置した垂直磁場垂直成形装置を示す説明図であり、（ａ）は図２（ｂ）と同様の断面図、（ｂ）は（ａ）図におけるＢ１〜Ｂ４部の拡大図である。
【図６】円筒磁石を製造する際に使用する成形装置で、回転式水平磁場垂直成形装置の一例を示す説明図である。
【図７】着磁機を用いて円筒磁石の着磁を行う様子を示す着磁模式図である。
【図８】着磁機を用いて円筒磁石の着磁を行う様子を示す着磁模式図で、円筒磁石の配向方向を図７に対して９０°回転させて着磁を行う様子を示す。
【図９】円筒磁石のＮ極とＳ極との境界を説明する平面図である。
【図１０】６極に多極着磁した円筒磁石と９個のステータ歯を組み合わせた３相モータの平面図を示したものである。
【図１１】本発明に係る水平磁場垂直成形装置により作製したＮｄ−Ｆｅ−Ｂ系円筒磁石に６極着磁を行った際の表面磁束密度を示した図である。
【図１２】従来の水平磁場垂直成形装置（コア材として非磁性材を使用）により作製したＮｄ−Ｆｅ−Ｂ系円筒磁石に６極着磁を行った際の表面磁束密度を示した図である。
【図１３】円筒磁石を製造する際に使用する強磁性材をコアとして用いた水平磁場垂直成形装置により作製された磁石の配向磁場方向に対し、３０°方向での磁石の配向を示す顕微鏡写真である。
【図１４】円筒磁石を製造する際に使用する強磁性材をコアとして用いた水平磁場垂直成形装置により作製された磁石の配向磁場方向に対し、６０°方向での磁石の配向を示す顕微鏡写真である。
【図１５】円筒磁石を製造する際に使用する強磁性材をコアとして用いた水平磁場垂直成形装置により作製された磁石の配向磁場方向に対し、９０°方向での磁石の配向を示す顕微鏡写真である。
【図１６】径方向配向円筒磁石を各６０°ずらして３段に積層した本発明の永久磁石式モータ用ロータを示す斜視図である。
【符号の説明】
１成形機架台
２配向磁場コイル
３ダイス
４コア
５コア
５ａコア
５ａ’ 弱い強磁性体超硬合金部
６上パンチ
７下パンチ
８充填磁石粉
９ポールピース
１０ダイス非磁性体
１１パーメンジュール
２１円筒磁石
２２着磁機
２３着磁機磁極歯
２４着磁機コイル
３０３相モータ
３１ステータ歯
３２コイル
３３モータロータ軸[0001]
BACKGROUND OF THE INVENTION
The present invention, LaThe present invention relates to a method for manufacturing a dial anisotropic sintered magnet..
[0002]
[Prior art]
Anisotropic magnets produced by crushing magnetocrystalline anisotropic materials such as ferrite and rare earth alloys and performing press molding in a specific magnetic field are widely used in speakers, motors, measuring instruments, and other electrical devices. in use. Among these, magnets having anisotropy in the radial direction are particularly excellent in magnetic properties, can be freely magnetized, and do not require reinforcement for fixing magnets like segment magnets. Used in brushless motors. In particular, in recent years, with the improvement in performance of motors, long radial anisotropic magnets have been demanded.
[0003]
A magnet having a radial orientation is manufactured by a vertical magnetic field vertical forming method or a backward extrusion method. The vertical magnetic field vertical forming method is characterized in that a radial orientation is obtained by applying a magnetic field from the opposing direction through the core in the pressing direction. That is, in the vertical magnetic field vertical forming method, as shown in FIG. 2, the magnetic field generated in the orientation magnetic field coil 2 is opposed through the

cores

4 and 5, and passes through the die 3 from the core. In the magnetic circuit that circulates through, the filled magnet powder 8 is radially oriented. In the figure, 6 is an upper punch and 7 is a lower punch.
[0004]
Thus, in this vertical magnetic field vertical forming apparatus, the magnetic field generated by the coil forms the core, the die, the molding machine base, and the magnetic path that becomes the core. In this case, in order to reduce the magnetic field leakage loss, a ferromagnetic material is used as the material of the part forming the magnetic path, and iron-based metal is mainly used. However, the magnetic field strength for orienting the magnet powder is determined as follows. The core diameter is B (magnet powder filling inner diameter), the die diameter is A (magnet powder filling outer diameter), and the magnet powder filling height is L. The magnetic flux that has passed through the upper and lower cores collides with each other in the center of the core and reaches the dice. The amount of magnetic flux passing through the core is determined by the saturation magnetic flux density of the core, and the magnetic flux density of the iron core is about 20 kG. Therefore, the orientation magnetic field at the inner and outer diameters of the magnet powder filling is obtained by dividing the amount of magnetic flux passed through the upper and lower cores by the inner area and the outer area of the magnet powder filling part,
2 · π · (B / 2)²20 / (π · B · L) = 10 · B / L ... inner circumference,
2 · π · (B / 2)²20 / (π · A · L) = 10 · B²/(AL)...outer periphery
It becomes. Since the magnetic field at the outer periphery is smaller than the inner periphery, in order to obtain good orientation in all the magnet powder filling portions, it is necessary to have 10 kOe or more at the outer periphery.²/ (A · L) = 10, so L = B²/ A. The height of the compact is about half of the height of the filling powder and is about 80% during sintering, so the height of the magnet is very small. As described above, since the saturation of the core determines the strength of the orientation magnetic field, the size of the magnet that can be oriented, that is, the height is determined depending on the core shape, and it is difficult to manufacture a long product in the cylindrical axis direction. In particular, only a very short product could be manufactured with a cylindrical magnet having a small diameter.
[0005]
Also, the backward extrusion method requires a large amount of equipment, has a low yield, and it is difficult to produce an inexpensive magnet.
[0006]
As described above, the radial anisotropic magnet is difficult to manufacture by any method, and it is further difficult to manufacture in large quantities at a low cost, and the motor using the radial anisotropic magnet is very disadvantageous in that the cost becomes very high. was there.
[0007]
When a radial anisotropic ring magnet is manufactured with a sintered magnet, it is generated due to the difference in linear expansion coefficient between the C-axis direction and the C-axis vertical direction of the magnet in the sintering and aging cooling process due to anisotropy. When the stress is greater than the mechanical strength of the magnet, cracks and cracks occur, which is a problem. For this reason, R-Fe-B based sintered magnets could only be manufactured in a magnet shape having an inner / outer diameter ratio of 0.6 or more (Hitachi Metals Technical Report Vol. 6, p33-36). Furthermore, in the R— (Fe, Co) —B based sintered magnet, Co substituted for Fe is not only contained in the 2-14-1 phase of the main phase in the alloy structure, but also in the R rich phase._ThreeCo is formed and the mechanical strength is significantly reduced. Moreover, since the Curie temperature is high, the amount of change in the coefficient of thermal expansion in the C-axis direction and the C-axis vertical direction between the Curie temperature at the time of cooling and the room temperature also increases, and the residual stress that causes cracks and cracks increases. For this reason, R- (Fe, Co) -B-based radial anisotropic ring magnets are more restrictive in shape than R-Fe-B-based magnets that do not contain Co, and are stable only in shapes with an inner / outer diameter ratio of 0.9 or more. Magnet production was not possible. In addition, ferrite magnets and Sm-Co magnets are in a state where cracks and cracks have occurred for the same reason, and stable production has not been achieved.
[0008]
The residual stress in the circumferential direction that causes cracking or cracking in the sintering and aging cooling processes associated with radial anisotropy is the result of the study by Kools on ferrite magnets (F. Schools: Science of Ceramics. Vol. 7, (1973), 29-45), and is expressed as in equation (1).
σ_θ= ΔTΔαEK²/ (1-K²) ・ (Kβ_Kη^K-1-Kβ_-Kη^-K-1-1) ... (1)
σ_θ: Circumferential stress
ΔT: temperature difference
Δα: Difference in linear expansion coefficient (α‖−α⊥)
E: Young's modulus in orientation direction
K²  : Anisotropy ratio of Young's modulus (E⊥ / E‖)
η: position (r / outer diameter)
β_k  : (1-ρ^{1 + K}) / (1-ρ^2K)
ρ: Inner / outer diameter ratio (inner diameter / outer diameter)
[0009]
Of the above formulas, the term that has the greatest influence on the cause of cracking or cracking is Δα: difference in linear expansion coefficient (α‖−α⊥), which is a ferrite magnet, Sm—Co rare earth magnet, Nd—Fe—. In the B-based rare earth magnet, the difference in thermal expansion coefficient (thermal expansion anisotropy) depending on the crystal direction is expressed from the Curie temperature, and increases due to a temperature decrease during cooling. At this time, the residual stress exceeds the mechanical strength of the magnet, leading to cracking.
[0010]
The stress due to the difference in thermal expansion between the orientation direction and the direction perpendicular to the orientation direction according to the above formula is generated because the cylindrical magnet is radially oriented in the radial direction. Therefore, cracks do not occur if a cylindrical magnet having a partially different orientation from the radial orientation is manufactured. For example, the cylindrical magnets oriented in one direction perpendicular to the cylindrical axis produced by the horizontal magnetic field vertical forming method are ferrite magnets, Sm—Co rare earth magnets, Nd—Fe (Co) —B rare earth magnets. Even the type of magnet does not break.
[0011]
Even if individual radial anisotropic magnets are not used, multipolar magnetization can be performed on the cylindrical magnet, and if the magnetic flux density is high and the variation in magnetic flux density between the poles is small, it can be a magnet for a high-performance permanent magnet motor. Cylindrical multipolar magnets for permanent magnet motors are produced without using radial anisotropic magnets by magnetizing magnets oriented in one direction perpendicular to the cylindrical axis by the horizontal magnetic field vertical forming method. Has been proposed (Electrical Society Magnetics Study Group Material MAG-85-120, 1985). Magnets oriented in one direction perpendicular to the cylinder axis (hereinafter referred to as radial orientation cylindrical magnets) manufactured by the horizontal magnetic field vertical forming method are made as long as the cavity of the press machine allows (50 mm or more). In addition, since multiple presses can be performed, a large number of compacts can be obtained by one press, and a cylindrical magnet for a motor can be supplied at a low price instead of an expensive radial anisotropic magnet.
[0012]
However, in practice, a magnet with multipolar magnetization applied to a radially oriented cylindrical magnet manufactured by the horizontal magnetic field vertical forming method has a high magnetic flux density in the pole near the orientation magnetic field direction, and the pole perpendicular to the orientation magnetic field direction. However, since the magnetic flux density is small, when the motor is assembled in a motor and the motor is rotated, torque unevenness reflecting the variation in the magnetic flux density between the poles is generated, which cannot be said to be a motor magnet that can withstand practical use.
[0013]
In order to solve this problem, in Patent Document 1, the number of magnetic poles in the circumferential direction in a cylindrical magnet oriented in one direction perpendicular to the cylindrical axis produced by the horizontal magnetic field vertical forming method is 2n (n is 1). There is a proposal that the number of teeth of the stator combined with the cylindrical magnet is 3 m (m is a positive integer smaller than 33 and larger than 1). In Patent Document 2, when the number of magnetic poles is k (k is a positive even number of 4 or more), the number of teeth of the stator combined with this cylindrical magnet is 3k · j / 2 (j is a positive integer of 1 or more). A proposal has been made. In Patent Document 3, there is a proposal for reducing torque unevenness by stacking the cylinder magnets at different angles with a cylindrical magnet oriented in one direction perpendicular to the cylindrical axis.
[0014]
However, in Patent Documents 1 to 3, although the torque unevenness is reduced, there are few portions oriented in the radial direction in the ring magnet, and the total torque when the motor is used is 70% with respect to a radial magnet having the same magnetic characteristics. It is small and not put into practical use.
[0015]
[Patent Document 1]
JP 2000-116089 A
[Patent Document 2]
JP 2000-116090 A
[Patent Document 3]
JP 2000-175387 A
[Non-Patent Document 1]
Hitachi Metals Technical Report Vol. 6, p. 33-36
[Non-Patent Document 2]
F. Kools: Science of Ceramics.
Vol. 7, (1973), p. 29-45
[Non-Patent Document 3]
IEEJ Magnetics Study Group
MAG-85-120, 1985
[0016]
[Problems to be solved by the invention]
  Therefore,BookinventionEyesThe objective is to provide a method for manufacturing a radial anisotropic sintered magnet that can easily produce multiple and long products and can realize a high-performance permanent magnet motor at low cost..
[0017]
Means for Solving the Problem and Embodiment of the Invention
  The present inventionIsA portion formed in a cylindrical shape and oriented in a direction inclined by 30 ° or more with respect to the radial direction contains 2% or more and 50% or less of the magnet volume, and the remaining portion of the magnet volume has a gradient from the radial direction to the radial direction of 30 °. Provided is a radially anisotropic sintered magnet that is magnetized in 2n (n is a positive integer not less than 2 and not more than 50) in the circumferential direction, characterized in that it is oriented below. As a method for obtaining such a magnet, a ferromagnetic material having a saturation magnetic flux density of 5 kG or more is used as a material of at least a part of a core of a cylindrical magnet molding die, and magnet powder filled in the mold cavity is used in a horizontal magnetic field vertical direction. Provided is a method for manufacturing a radially anisotropic sintered magnet, which is formed by applying an orientation magnetic field to a magnetic powder by a forming method at a magnetic field of 0.5 to 12 kOe.
[0018]
That is, as a result of intensive efforts to achieve the above object, the present inventors made the radial orientation of the cylindrical magnet entirely radial, and partially deliberately disturbed the sintering and It has been found that stable production without cracks and cracks can be realized in the cooling process during aging, and that a large torque can be obtained when incorporated in a motor.
[0019]
According to the present invention, even in a shape having a uniform magnetic field and a small inner / outer diameter ratio, the R-Fe (Co) -B radial anisotropy has excellent magnet characteristics without cracks and cracks during sintering and aging cooling. Stable magnets can be produced stably, which is useful for high performance, high power, miniaturization, etc. of AC servo motors, DC brushless motors, speaker magnets, etc. It is also effective in the production of the radial direction dipole magnet used, and it is possible to supply a large amount of a cylindrical magnet for a synchronous magnet motor having excellent performance.
[0020]
  The present invention also provides:the aboveIn order to achieve the above object, a radial anisotropic sintered magnet is obtained by forming the magnet powder filled in the mold cavity by applying an orientation magnetic field to the magnet powder by a horizontal magnetic field vertical molding method. When manufacturing, the operation of rotating the magnet powder filled in the mold cavity relative to the direction of the magnetic field generated by the coil is described below (i) to (v).
(I) While applying a magnetic field, rotate the magnet powder by a predetermined angle in the circumferential direction of the mold,
(Ii) After applying the magnetic field, rotate the magnet powder by a predetermined angle in the circumferential direction of the mold, and then apply the magnetic field again.
(Iii) During magnetic field application, the magnetic field generating coil is rotated by a predetermined angle in the circumferential direction of the mold with respect to the magnet powder.
(Iv) After applying the magnetic field, the magnetic field generating coil is rotated by a predetermined angle in the mold circumferential direction with respect to the magnet powder, and then the magnetic field is applied again.
(V) Two or more pairs of magnetic field generating coils are arranged, and after one pair of coils applies a magnetic field, another pair of coils applies a magnetic field.
A method for producing a radially anisotropic sintered magnet is provided, which is performed by at least one of the above operations. Here, when rotating the filling magnet powder, the filling magnet powder can be rotated by rotating at least one of the core, the die and the punch in the circumferential direction. Further, when rotating the filled magnet powder after applying the magnetic field, the value of the residual magnetization of the ferromagnetic core or the magnet powder is 50 G or more, and the magnet powder can be rotated by rotating the core in the circumferential direction.
[0021]
  ThisDepartureAccording to Ming, a horizontal magnetic field that can easily produce multiple and long products without using low-productivity and expensive radial anisotropic magnets, and can stably supply a large amount of magnetic fields uniformly, inexpensively A high-performance permanent magnet motor can be realized using a radially oriented cylindrical magnet manufactured by a vertical forming method, and is useful for reducing the price of high-performance motors such as AC servo motors and DC brushless motors.
[0022]
  The present invention, DoubleIn a permanent magnet motor in which a radial anisotropic cylindrical magnet is incorporated in a motor having several stator teeth, the cylindrical magnet is a radial anisotropic cylindrical magnet formed and manufactured by the manufacturing method described above, and has a circumferential direction. When the number of magnetic poles is 2n (n is a positive integer of 2 to 50), the number of teeth of the stator combined with this cylindrical magnet is 3m (m is a positive integer of 2 to 33), and 2n There is provided a permanent magnet motor magnetized in multiple directions in the circumferential direction, characterized in that ≠ 3 m. In this case, when the number of magnetic poles in the circumferential direction of the cylindrical magnet is k (k is a positive even number of 4 or more), the number of stator teeth combined with this cylindrical magnet is 3k · j / 2 (j is a positive number of 1 or more). The boundary between the north pole and the south pole of the cylindrical magnet is preferably within 10 ° with respect to the central portion of the portion oriented in a direction inclined by 30 ° or more with respect to the radial direction. Is preferred. Furthermore, it is preferable that the skew angle of the cylindrical magnet is 1/10 to 2/3 of the angle of one pole of the cylindrical magnet, and the multi-pole skew is preferably magnetized. In particular, the skew angle of the stator teeth is equivalent to one pole of the cylindrical magnet. It is preferable to have skew teeth of 1/10 to 2/3 of the angle.
[0023]
According to the present invention, a large number of cylindrical magnets used for a synchronous magnet motor having excellent performance can be supplied in a particularly long and inexpensive manner.
[0024]
  The present invention,UpA multi-stage long multi-pole magnetized cylindrical magnet rotor is provided, wherein a plurality of radial anisotropic cylindrical magnets formed and manufactured by the manufacturing method are stacked in two or more stages in the axial direction. In this case, when the number of cylindrical magnets to be stacked is i (i is a positive integer not less than 2 and not more than 10), i are stacked by shifting the same direction as the orientation magnetic field direction of each cylindrical magnet by an angle of 180 / i °. In addition, when the number of poles of multipolar magnetization is n (n is a positive integer of 4 to 50), the stacking number i and the number of poles n may have a relationship of i = n / 2. preferable. Further, when performing multipolar magnetization of n (n is a positive integer of 4 to 50) poles on the outer peripheral surface of the cylindrical magnet, the angle of one pole is set to 360 / n °, and 1/10 to 2 of this angle. It is preferable that skew magnetization is performed at an angle of / 3. The present invention also provides a permanent magnet motor using the multistage long multipole magnetized cylindrical magnet rotor.
[0025]
In other words, by adopting the above-described configuration, the magnet for a motor that can greatly reduce the variation in magnetic flux density between the poles and realize smooth rotation without torque unevenness with high torque, that is, a multistage long multipole magnetized cylindrical magnet rotor. In addition, a permanent magnet motor using the same can be manufactured.
[0026]
Hereinafter, the present invention will be described in more detail.
The radially anisotropic sintered magnet according to the present invention is a cylindrical magnet, and is generally oriented in the radial direction (radial direction), provided that a portion of 2% to 50% of the magnet volume is in the radial direction. In contrast, the orientation is 30 ° or more and 90 ° or less.
[0027]
The radially anisotropic sintered magnet of the present invention is such that the portion oriented in the direction inclined by 30 to 90 ° with respect to the radial direction is 2 to 50% of the magnet volume.
[0028]
That is, the stress represented by the above-described formula (1) is generated because it is a continuous body in the circumferential direction radially oriented in the radial direction, that is, a cylindrical magnet. Therefore, the stress decreases if partial continuous orientation is disturbed. Therefore, the magnet can be produced without cracking by including a portion oriented in a direction inclined by 30 ° or more with respect to the radial direction in an amount of 2% to 50% of the magnet volume. When the portion inclined by 30 ° or more is smaller than 2%, the effect of preventing cracking is small, and when the portion inclined by 30 ° or more is more than 50%, the torque for the motor rotor is insufficient, which is not practical. More preferably, a portion inclined by 30 ° or more is contained in an amount of 5 to 40%, more preferably 10 to 40%.
[0029]
The remaining magnet volume portion, that is, the magnet volume portion of 50 to 98%, more preferably 60 to 95% is oriented so that the inclination with respect to the radial direction or the radial direction is less than 30 °. is there.
[0030]
FIG. 1 is an explanatory diagram of a horizontal magnetic field vertical forming apparatus for performing orientation in a magnetic field at the time of forming a cylindrical magnet, in particular, a horizontal magnetic field vertical forming apparatus for a motor magnet. Here, as in FIG. 2, 1 is a molding machine base, 2 is an oriented magnetic field coil, 3 is a die, and 5a is a core. 6 is an upper punch, 7 is a lower punch, 8 is a filling magnet powder, and 9 is a pole piece.
[0031]
In the present invention, at least a part, preferably the whole, of the core 5a is formed of a ferromagnetic material having a saturation magnetic flux density of 5 kG or more, preferably 5 to 24 kG, more preferably 10 to 24 kG. Examples of the core material include ferromagnetic materials using materials such as Fe-based materials, Co-based materials, and alloy materials thereof.
[0032]
As described above, when a ferromagnetic material having a saturation magnetic flux density of 5 kG or more is used for the core, when an orientation magnetic field is applied to the magnet powder, the magnetic flux tends to enter perpendicularly to the ferromagnetic material and draws magnetic lines close to radial. Therefore, as shown in FIG. 3a, the magnetic field direction of the magnet powder filling portion can be brought close to radial orientation. In contrast, conventionally, the entire core 5b is made of a nonmagnetic material or a material having a saturation magnetic flux density equivalent to that of magnet powder. In this case, the lines of magnetic force are parallel to each other as shown in FIG. The vicinity is the radial direction, but the direction of the magnetic field is oriented by the coil toward the upper side and the lower side. Even if the core is made of a ferromagnetic material, if the saturation magnetic flux density of the core is less than 5 kG, the core is easily saturated, and the magnetic field is in a state close to FIG. . In addition, if it is less than 5 kG, it becomes equal to the saturation density of the filled magnet powder (magnet saturation magnetic flux density × filling rate), and the direction of the magnetic flux in the filled magnet powder and the ferromagnetic core becomes equal to the magnetic field direction of the coil.
[0033]
Further, when a ferromagnetic material of 5 kG or more is used for a part of the core, the same effect as described above is obtained and effective, but the whole is preferably a ferromagnetic material. FIG. 4 shows an example in which a part (central part) is a ferromagnetic body and a peripheral part is a weak ferromagnetic body (WC-Ni-Co system). In FIG. 4, 5a 'indicates a weak ferromagnetic cemented carbide part, and 11 indicates permendur.
[0034]
According to the above method, since the disturbance to the radial orientation in the radial direction in the cylindrical magnet becomes the disturbance of the orientation only in the part perpendicular to the orientation magnetic field direction, the decrease in the amount of magnetic flux of each pole should be suppressed slightly after magnetization. It is possible to manufacture a cylindrical magnet for a motor rotor that is free from torque unevenness and torque deterioration of the motor.
[0035]
Moreover, when shaping | molding as mentioned above, it is preferable that the magnetic field which generate | occur | produces with a horizontal magnetic field vertical shaping | molding apparatus is 0.5-12 kOe. The reason why the magnetic field generated by the horizontal magnetic field vertical forming apparatus is determined in this way is that when the magnetic field is large, the core 5a in FIG. 3a is saturated and becomes close to FIG. Therefore, the magnetic field is preferably 12 kOe or less. When a ferromagnetic core is used, magnetic flux concentrates on the core, so that a magnetic field larger than the magnetic field generated by the coil can be obtained around the core. However, if the magnetic field is too small, a magnetic field sufficient for orientation cannot be obtained even around the core, so 0.5 kOe or more is preferable. As described above, magnetic flux gathers around the ferromagnet and the magnetic field becomes large. Therefore, the magnetic field generated by the horizontal magnetic field vertical forming apparatus referred to here is a magnetic field or a ferromagnetic core in a place sufficiently away from the ferromagnet. It means the value of the magnetic field when it is removed and measured. Therefore, it is more preferable that it is 1 to 10 kOe.
[0036]
Furthermore, in the present invention, in the vertical magnetic field vertical molding apparatus as shown in FIG. 2, a nonmagnetic material is applied to the die material of the cylindrical magnet molding die at a total angle of 20 ° to 180 °, particularly 30 to 120 °. It is preferable to arrange at least one over the region.
[0037]
FIG. 5 shows a nonmagnetic material (for example, nonmagnetic cemented carbide) 10 as a die material of a radial cylindrical magnet molding die in a vertical magnetic field vertical molding apparatus, and an area of an angle θ = 30 ° (30 of 360 ° of the die cylinder). 2 shows a vertical magnetic field vertical forming apparatus arranged symmetrically in a region corresponding to °. The magnetic field lines near the nonmagnetic material are bent toward the ferromagnetic material. In particular, it is bent in the direction of the ferromagnetic material edge existing at the boundary between the nonmagnetic material and the ferromagnetic material. Since the magnet powder is oriented in the direction of the bent magnetic field lines, the desired magnet is obtained. If the non-magnetic material arrangement angle at this time is less than 20 °, the effect of bending the lines of magnetic force is small, and in addition, the region in which the orientation direction is inclined by 30 ° or more with respect to the radial direction is reduced, and the effect of suppressing cracking is small. On the other hand, when the angle is larger than 180 °, the radial orientation is hindered and the intended magnet is not obtained.
In this case, in FIG. 5, 1 is a molding machine base, 3 is a die, 4 is a core, and 8 is a filled magnet powder, as in FIG. Further, the material other than the non-magnetic material 10 in the die 3 is formed of a ferromagnetic material of 5 kG or more. Furthermore, the core material can be formed of a ferromagnetic material of 10 kG or more.
[0038]
By the way, in the case where the mold core 5a is formed of a ferromagnetic material having a saturation magnetic flux density of 5 kG or more and at least a part, preferably the whole, is formed by horizontal magnetic field vertical molding as described above, this method uses an orientation by a coil. In a direction that is 90 ° with respect to the direction of the magnetic field, the radial orientation may not be achieved. When there is a ferromagnet in the magnetic field, the magnetic flux tries to enter the ferromagnet perpendicularly and is attracted to the ferromagnet, so the magnetic flux density increases in the magnetic field direction plane of the ferromagnet and decreases in the vertical direction. To do. For this reason, when a ferromagnetic core is disposed in the mold, good orientation can be obtained by a strong magnetic field in the magnetic field direction portion of the ferromagnetic core in the filled magnet powder, and not so much in the vertical direction portion. In order to compensate for this, a good magnet can be obtained by rotating the magnet powder relative to the magnetic field generated by the coil and reorienting the imperfectly oriented portion with a magnetic field portion having a strong magnetic field direction.
[0039]
Here, as a method of rotating the magnet powder relative to the magnetic field generated by the coil, the following (i) to (v)
(I) While applying a magnetic field, rotate the magnet powder by a predetermined angle in the circumferential direction of the mold,
(Ii) After applying the magnetic field, rotate the magnet powder by a predetermined angle in the circumferential direction of the mold, and then apply the magnetic field again.
(Iii) During magnetic field application, the magnetic field generating coil is rotated by a predetermined angle in the circumferential direction of the mold with respect to the magnet powder.
(Iv) After applying the magnetic field, the magnetic field generating coil is rotated by a predetermined angle in the mold circumferential direction with respect to the magnet powder, and then the magnetic field is applied again.
(V) Two or more pairs of magnetic field generating coils are arranged, and after one pair of coils applies a magnetic field, another pair of coils applies a magnetic field.
Of these operations, at least one of the operations is performed once or repeated a plurality of times.
[0040]
As for the rotation of the filled magnetic powder, as shown in FIG. 6, if the magnetic powder can be rotated relative to the direction of the magnetic field generated by the coil, any one of the coil 2, the core 5a, the die 3, and the

punches

6 and 7 is used. It may be rotated. Among these, in particular, when the filled magnet powder is rotated after the magnetic field is applied, if the residual magnetization of the ferromagnetic core or the magnet powder is 50 G or more, particularly 200 G or more, the magnet powder is magnetic between the ferromagnetic core. Therefore, the magnet powder can be rotated only by rotating the ferromagnetic core.
[0041]
The rotation angle is appropriately selected. When the initial position is 0 °, the rotation angle is preferably 10 to 170 °, particularly 60 to 120 °, typically around 90 °, and is rotated during application of the magnetic field. In this case, the magnetic field is gradually rotated by a predetermined angle, and when rotating after applying the magnetic field, the magnetic field is applied again after rotating by a predetermined angle.
[0042]
The present invention is formed as described above. Otherwise, a normal forming pressure is applied to the magnet powder by a normal vertical forming method, and a general forming pressure of 0.5 to 2.0 t / cm is applied.²And then subjected to sintering, aging treatment, processing, etc. to obtain a sintered magnet.
[0043]
The magnet powder is not particularly limited, and is suitable for producing Nd—Fe—B cylindrical magnets, and also producing ferrite magnets, Sm—Co rare earth magnets, various bonded magnets, and the like. However, all are formed using an alloy powder having an average particle size of 0.1 to 100 μm, particularly 0.3 to 50 μm.
[0044]
In the present invention, the outer peripheral surface of the cylindrical magnet thus obtained is multipolarized. Here, FIG. 7 shows a state in which the cylindrical magnet 21 is magnetized using the magnetizer 22. Reference numeral 23 denotes a magnetizer magnetic pole tooth, and reference numeral 24 denotes a magnetizer coil.
[0045]
FIG. 11 shows the surface magnetic flux density when a radial-like radially oriented cylindrical magnet manufactured by the horizontal magnetic field vertical molding according to the present invention is magnetized with 6 poles by the magnetizer shown in FIG. FIG. 12 is a surface magnetic flux density diagram when 6-pole magnetization is performed on a radially oriented cylindrical magnet made by a conventional manufacturing method using the magnetizer shown in FIG. When a radially oriented cylindrical magnet is produced by a conventional horizontal magnetic field vertical forming method and subjected to 6-pole magnetization so that the orientation magnetic field directions are N and S, the surface magnetic flux density is large in the orientation directions A and D. In the B, C, E, and F alignment directions close to the direction forming an angle of 90 ° with the alignment direction, the surface magnetic flux density is small. In addition, the magnetization width varies greatly depending on the direction, even though magnetization is performed using a magnetizing device having the same angular width. On the other hand, in the product of the present invention, an increase is observed in the peak values of B, C, E, and F, and the magnetization width where the surface magnetic flux becomes zero is substantially constant. However, B, C, E, and F have a sharp shape in the surface magnetization as compared with A and D at the peak positions. Since the amount of magnetic flux is larger as the peak area is larger, B, C, E, and F are smaller than A and D. Variation in the amount of magnetic flux between the poles causes uneven rotation when incorporated in a motor, causing vibration and noise. Therefore, by reducing the variation in the amount of magnetic flux between the poles, smooth rotation without unevenness can be performed.
[0046]
FIG. 10 is a plan view of a three-phase motor having nine stator teeth (stator teeth). In the three-phase motor 30, the α, β, and γ stator teeth 31 are arranged in the order of α, β, and γ, and the wiring is connected while winding the stator teeth in a coil shape, and the U, V, and W phases are connected to the motor input line. Become. A current is passed through the U, V, and W phases to generate a magnetic field in the coil 32, and the motor rotates due to repulsive and attractive forces acting between the magnetic field generated by the coil and the cylindrical magnet 21. U-V, V-W, and W-U go around 1/3 of the total number of stator teeth, and when a current flows through U-V, a magnetic field is generated from α of the stator core. Magnetic fields are generated in β by V-W and γ by W-U, respectively. FIG. 10 shows an example in which a radially oriented cylindrical magnet 21 magnetized with 6 poles is incorporated into a three-phase motor having a stator with 9 teeth. In the figure, 33 is a motor rotor shaft.
[0047]
In the figure, U-V (α) is located at the center of the pole of the magnet and becomes the peak of the motor torque. At this time, the poles that act with U-V (α) and generate a rotational force are the A, C, and E poles, the A pole is the orientation magnetic field direction pole, the amount of magnetic flux is large, and C and E are the orientation magnetic field directions. The pole is located at an angle deviating from the above, and the amount of magnetic flux is small. Next, the magnet rotates and the D, F, and B poles approach U-V (α). The D pole is a pole in the orientation magnetic field direction and has a large amount of magnetic flux, and F and B are poles located at an angle deviating from the orientation magnetic field direction, and the amount of magnetic flux is small. However, since it has 9 teeth, which is 3/2 times the number of magnet poles 6, the amount of magnetic flux interlinked with the coil of U-V (α) is D, It is always the same for the F and B poles. This relationship is the same for VW (β) and WU (γ). In this case, when the number of magnetic poles in the cylindrical magnet is k (k is a positive even number of 4 or more), the number of teeth of the stator combined with this cylindrical magnet is 3k · j / 2 (j is a positive integer of 1 or more). In particular, as described above, the combination of the number of magnet poles and the number of teeth of the stator of the motor is the number of magnet poles k = 6, the number of teeth 3k · j / 2 = 9 (k = 6, j = 1). ), The magnets have a pole in the orientation magnetic field direction and a pole deviated from the orientation magnetic field direction, and even in a cylindrical magnet with a variation in the amount of magnetic flux, a magnetic flux variation is alleviated and a motor with no rotation unevenness is achieved. Obtainable. Note that k is preferably an even number of 50 or less, more preferably 40 or less, and j is preferably an integer of 10 or less, more preferably 5 or less. If the number of poles k is too large, the width of one pole becomes small, and the pole may not be clear in the direction perpendicular to the orientation magnetic field direction.
[0048]
Among these, when the number of stator teeth is 3 m (m is a positive integer of 2 to 33) with respect to the number of magnet poles 2n (n is a positive integer of 2 to 50), the above relationship is always maintained, A motor without uneven rotation can be obtained. However, 2n ≠ 3m. In particular, when a multi-pole magnet is applied to a radially oriented cylindrical magnet and the number of stator teeth is 3n times the number of magnetized poles, a motor having excellent motor characteristics with no rotation unevenness can be produced.
[0049]
Compared to the case where multipolar magnetization is performed on a radial anisotropic ring magnet, the cylindrical magnet according to the present invention has a lower magnetic magnetization and magnetic properties than the case where multipolar magnetization is performed on a radial anisotropic ring magnet. Although the change in the inter-polar part is smooth and the cogging torque of the motor is small, the cogging torque can be further reduced by applying skew to the skew magnetization or the stator teeth. When the skew angle of the cylindrical magnet and the stator teeth is less than 1/10 of the angle of one pole of the cylindrical magnet, the effect of lowering the cogging torque due to skew magnetization is small, and it is larger than 2/3 of the angle of one pole of the cylindrical magnet. Therefore, the skew angle is preferably 1/10 to 2/3 of the angle corresponding to one pole of the cylindrical magnet, and more preferably 1/10 to 2/5.
In addition, the permanent magnet motor of this invention can be manufactured as a well-known structure except having the above-mentioned structure.
[0050]
In this case, FIG. 7 shows the magnetization performed by rotating the orientation direction of the cylindrical magnet by 90 ° with respect to FIG. 8, but the boundary between the north pole and the south pole of the cylindrical magnet is shown in FIG. It is preferable that the angle is within ± 10 ° with respect to the central portion 40 of the portion oriented in a direction inclined by ± 30 ° or more with respect to the radial direction. Then, it is possible to magnetize multiple poles in the circumferential direction so as to provide a boundary between the N pole and the S pole spaced apart from each other at equal intervals in the circumferential direction from the boundary between the N pole and S pole set in this way. preferable. On the other hand, compared with the magnetization according to FIG. 8, the magnetization according to FIG. 7 shares the part shifted from the radial direction with 4 poles (2 poles on each side), so that cogging is less and the torque increases.
[0051]
FIG. 8 is a magnetization schematic diagram showing a state where magnetization is performed by rotating the orientation direction of the cylindrical magnet by 90 ° with respect to FIG. The one shown in FIG. 8 in which the orientation direction is rotated by 90 ° with respect to FIG. 7 and the 6-pole magnetization is performed provides a relatively large amount of magnetic flux from the B, C, E, and F poles in the vicinity of the orientation magnetic field direction. In addition, the amount of magnetic flux is small in the portion in the direction perpendicular to the alignment direction of the A and D poles. When the magnets magnetized in FIGS. 7 and 8 are stacked in two stages and magnetized by shifting by 90 ° to form a rotor magnet for a motor, the large magnetic flux amounts A and D magnetized in FIG. 7 are magnetized in FIG. In this case, since the amount of magnetic flux is small, when combined, the amount of magnetic flux is slightly small in the case of magnetization in FIG. 7, but a relatively large amount of magnetic flux can be obtained in the case of magnetization in FIG. And almost the same magnetic flux. For this reason, smooth rotation without unevenness can be performed by reducing the variation in the amount of magnetic flux between the poles.
[0052]
Similarly, a cylindrical magnet having a radial-like orientation manufactured by a horizontal magnetic field vertical molding apparatus is cut into two equal parts in the cylindrical axis direction, and the other one is gradually rotated to perform stacking. Initially, the magnet is magnetized in the arrangement shown in FIG. 7, but the direction gradually changes, and after 90 ° rotation, the magnetism is obtained in the arrangement shown in FIG. When these are rotated one by one to 90 ° and stacked, and then magnetized, the total magnetic flux gradually decreases as the rotation angle increases in the A and D poles, and the B, C, E, and F poles Then, the total magnetic flux increases.
[0053]
By reducing the amount of magnetic flux between each pole by stacking two or more radial-like radially oriented cylindrical magnets manufactured in this way in the axial direction and performing multipolar magnetization in this way. Torque unevenness when used as a motor can be suppressed. The upper limit of the number of layers is not particularly limited, but is preferably about 10 steps.
[0054]
By rotating the orientation direction of the divided magnets relatively by a predetermined angle and stacking in multiple stages (two or more stages) and multi-pole magnetizing, the variation in the amount of magnetic flux between the orientation direction and the direction perpendicular thereto is made uniform. The variation in the amount of magnetic flux between the poles can be reduced. At this time, it is preferable to perform multipolar magnetization by stacking the magnets to be stacked while shifting the orientation direction of the magnets by 180 / i ° (i is the number of stacks).
[0055]
Further, in order to uniformly distribute the orientation direction to each pole, the number of divisions is set to i = n / 2 stages (n is the number of poles), so that the portion having a large amount of magnetic flux in the orientation direction and the direction perpendicular thereto Thus, a portion with a small amount of magnetic flux can be evenly distributed to each pole, and these can be stacked by shifting the angle by 180 / i °, and the total magnetic flux amount of each pole can be made equal by multipolar magnetization.
[0056]
In addition, n is a positive integer of 4 to 50, and when n increases, the gap between the magnetized magnetic poles becomes narrow and it becomes difficult to sufficiently magnetize. Therefore, n is particularly preferably 4 to 30.
[0057]
In addition, i is a positive integer of 2 to 10, and when i is large and the number of stacks is large, the cost is high, so 2 to 6 is particularly preferable.
[0058]
When a multi-pole magnet is applied to a cylindrical magnet with unidirectional anisotropy using a horizontal magnetic field vertical forming device, the magnetism in the vicinity of the gap is larger than when a multi-pole magnet is applied to a radial anisotropic ring magnet. In addition, since the magnetic characteristics are low, the change between the pole portions of the magnetic flux density is smooth, and the cogging torque of the motor is small. The cogging torque can be further reduced by skew magnetizing the magnet or by skewing the stator teeth.
[0059]
If the skew angle is 1/10 or less of the angle of one magnet (360 / n °) for both the magnet stator, the effect of lowering the cogging torque due to skew magnetization is small, and if it is greater than 2/3, the torque of the motor Therefore, the skew angle is preferably 1/10 to 2/3 of the angle of one magnet.
[0060]
For example, as shown in FIG. 10, the permanent magnet type motor of the present invention may incorporate the above-mentioned multistage long multipole magnetized cylindrical magnet rotor as a rotor in a motor, particularly a motor having a plurality of stator teeth. In this case, the configuration of the motor having the stator teeth can be a known one.
[0061]
【The invention's effect】
The radial anisotropic sintered magnet of the present invention has excellent magnet characteristics free from cracks and cracks during sintering and aging cooling even in a shape having a small inner / outer diameter ratio.
[0062]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
[0063]
    [referenceExample 1]
  Nd, Dy, Fe, Co, and M (M is Al, Si, Cu) having a purity of 99.7% by weight and B having a purity of 99.5% by weight are used.₂₉Dy_2.5Fe₆₄Co_ThreeB₁Al_0.2Cu_0.1Si_0.2An ingot was prepared by melting and casting the above alloy in a vacuum melting furnace. The ingot was coarsely pulverized with a jaw crusher and a brown mill, and further finely pulverized with an average particle size of 3.5 μm by jet mill pulverization in a nitrogen stream. This powder was 0.5 t / cm in a magnetic field of 8 kOe in a horizontal magnetic field vertical forming apparatus in which a ferromagnetic (S50C: Fe steel) core having a saturation magnetic flux density of 20 kG was arranged.²Molding was performed at a molding pressure of At this time, the packing density of the magnet powder was 25%. This molded body was sintered in Ar gas at 1090 ° C. for 1 hour, and subsequently subjected to aging heat treatment at 580 ° C. for 1 hour. Thereafter, processing was performed to obtain a cylindrical magnet of φ30 mm × φ25 mm × L30 mm. The above-mentioned cylindrical magnet was magnetized in 6 poles by the magnetizer shown in FIG. 7, and a motor was produced in which the magnet after magnetizing was incorporated in a stator having the same height as that shown in FIG. A ferromagnetic core serving as a motor shaft is inserted and bonded to the inner diameter of the magnet. The copper thin wire was wound with 150 turns for each tooth. The induced voltage when the motor was rotated at 1000 rpm and the magnitude of torque ripple by a load meter when the motor was rotated at 1 to 5 rpm were measured.
[0064]
    [referenceExample 2]
  Except for being magnetized by the magnetizing arrangement of FIG.referenceThe magnitude of the induced voltage and torque ripple when a magnet obtained in the same manner as in Example 1 was similarly incorporated into a motor was measured. The results are shown in Table 1.
[Table 1]

[0065]
    [referenceExample 3]
  A ferromagnetic body (SK5: Fe steel) with a saturation magnetic flux density of 18 kG occupying an area of 60% of the core cross-sectional area is arranged concentrically with the outer periphery of the core, and the rest is made of a core made of a non-magnetic material.referenceA cylindrical magnet produced in the same manner as in Example 1 was incorporated into a motor, and the motor characteristics were measured.
[0066]
    [referenceExample 4]
  referenceUsing the same molding machine as in Example 1, the generated magnetic field was 6 kOe,referenceA magnet was manufactured under the conditions of Example 1, and incorporated in a motor to measure the motor characteristics.
[0067]
    [Comparative Example 1]
  referenceUsing the same magnetic powder as in Example 1, using the vertical magnetic field vertical molding apparatus shown in FIG. 2, the magnet generated magnetic field 20 kOe and the magnet powder filling depth 30 mm, the molded body after molding in the magnetic field is moved downward, Place the 30mm magnet powder on the compact as before, and place the magnet after molding in the magnetic field.referenceSintering aging was performed under the same conditions as in Example 1 to obtain a cylindrical magnet of φ30 mm × φ25 mm × L30 mm. This was incorporated into a motor and the motor characteristics were measured.
[0068]
    [Comparative Example 2]
  Except for using a non-magnetic material (non-magnetic cemented carbide WC-Ni-Co) as a core material,referenceA magnet was manufactured under the same conditions as in Example 1, and incorporated in a motor to measure the motor characteristics.
[0069]
    [Comparative Example 3]
  In a molding machine in which a ferromagnetic (magnetic carbide WC-Ni-Co) core with a saturation magnetic flux density of 2 kG is placed,referenceA magnet was manufactured under the same conditions as in Example 1, and incorporated in a motor to measure the motor characteristics.
[0070]
    [referenceExample 5]
  As shown in FIG. 5, two nonmagnetic materials (nonmagnetic cemented carbide WC-Ni-Co) are arranged so as to be symmetrical at a portion with an angle of 30 ° in the die (total 60 °), and the others are comparative examples. A magnet was produced under the same conditions as in No. 1, and the motor characteristics were measured in the same manner.
[0071]
The volume of the portion tilted by 30 ° or more with respect to the radial orientation (orientation disorder volume) was calculated by polarizing microscope observation and shown in Table 2. In addition, the number of cracks when 100 cylindrical magnets are manufactured under the respective conditions is also described.
[0072]
[Table 2]

[0073]
  From Table 2,referenceThe example is effective for mass production of magnets having excellent characteristics as motor magnets because a large electromotive force is obtained, torque ripple is small, and cracks are not generated.
[0074]
  Also,referenceThe results of observation with a polarizing microscope of the magnet produced under the conditions of Example 4 are shown in FIGS. That is, FIGS. 13, 14, and 15 show magnets produced by a horizontal magnetic field vertical forming apparatus using a ferromagnetic material as a core, in directions of 30 °, 60 °, and 90 ° with respect to the orientation magnetic field direction. As can be seen from these, in the cylindrical magnet according to the present invention, the deviation from the radial direction is 30 ° for the first time in the direction of 60 ° with respect to the direction of the magnetic field, and more than 30 ° at 30% by volume. You can see that it is shifted.
[0075]
    [Example1~4Reference examples6]
  Nd, Dy, Fe, Co, and M (M is Al, Si, Cu) having a purity of 99.7% by weight and B having a purity of 99.5% by weight are used.₂₉Dy_2.5Fe_63.8Co_ThreeB₁Al_0.3Si_0.3Cu_0.1An ingot was prepared by melting and casting the above alloy in a vacuum melting furnace. The ingot was coarsely pulverized with a jaw crusher and a brown mill, and further finely pulverized with an average particle size of 3.5 μm by jet mill pulverization in a nitrogen stream. Example 1 This powder was oriented in a horizontal magnetic field vertical molding apparatus in which an iron ferromagnetic core having a saturation magnetic flux density of 20 kG as shown in FIG.1Rotate the coil 90 ° and then re-orientate again in a 4 kOe magnetic field, 1.0 t / cm²Molding was performed at a molding pressure of
[0076]
  Example2In the horizontal magnetic field vertical forming apparatus, the coil is generated in the magnetic field of 4 kOe, and then the die, the core and the punch are rotated by 90 °, and then again oriented in the magnetic field of 4 kOe. / Cm²Example other than molding with molding pressure of1Molded in the same way as
[0077]
  Example3As described above, after orientation in a magnetic field of 4 kOe generated by a coil using a horizontal magnetic field vertical forming apparatus, a core having a residual magnetization of 4 kG was rotated by 90 °. The residual magnetization of the magnet powder at this time was 800G. Then, it is similarly oriented again in a magnetic field of 4 kOe, and then 1.0 t / cm.²Example other than molding with molding pressure of1Molded in the same way as
[0078]
  These compacts were sintered in Ar gas at 1090 ° C. for 1 hour, followed by aging heat treatment at 580 ° C. for 1 hour. Thereafter, processing was performed to obtain a cylindrical magnet of φ24 mm × φ19 mm × L30 mm. In addition, using the same magnet powder as this cylindrical magnet, it is 1.0 t / cm in a magnetic field of 12 kOe with a horizontal magnetic field vertical molding apparatus.²The block magnet produced under the same conditions as the present cylindrical magnet after molding at 1090 ° C. for 1 hour in Ar gas and subsequently heat-treated at 580 ° C. for 1 hour has the following characteristics: Br: 12 0.5 kG, iHc: 15 kOe, (BH) max: 36 MGOe. A motor in which the above-mentioned cylindrical magnet is skew magnetized at 6 poles and 20 ° by the magnetizer shown in FIG. 7, and the magnet after magnetizing is incorporated in a stator having the same height as that of the magnet shown in FIG. Was made. Further, the induced voltage when the motor of the above example was rotated at 5000 rpm and the magnitude of torque ripple by a load meter when the motor was rotated at 5 rpm were measured. Further, a cylindrical magnet obtained by molding, sintering, and heat treatment in the same manner as described above was magnetized by the magnetizer shown in FIG. 8, and incorporated in the motor, and the induced voltage and torque ripple were measured (Example).3a). Table 3 shows the difference between the maximum absolute value of the induced voltage and the maximum and minimum of the torque ripple.
[0079]
  Example4As an example1Using the same horizontal magnetic field vertical forming apparatus as in the above, orientation is performed while rotating 90 ° in a magnetic field of 12 kOe, and 1.0 t / cm²Molding was performed at a molding pressure of Other examples1The motor characteristics of the motor using the magnet produced in the same manner as above were measured.
[0080]
  On the other hand, a reference example6As an example1In the magnetic field of 4 kOe in the magnetic field without rotation, 1.0 t / cm²Molding was performed at a molding pressure of Other examples1The motor characteristics of the motor using the magnet produced in the same manner as above were measured. These results are shown in Table 3.
[0081]
[Table 3]

[0082]
  From Table 3, reference examples6On the other hand, in the embodiment, the induced voltage corresponding to the torque is greatly improved, and it can be seen that the present invention is an excellent method for manufacturing a motor magnet.
[0083]
  Examples1As a result of measuring the surface magnetic flux of the rotor magnet after magnetizing, the poles are uniform and the area of the poles is large, and the embodiment can generate a large magnetic field uniformly. I understand.
[0084]
    [Reference Example 7]
  Nd, Dy, Fe, Co, and M (M is Al, Si, Cu) having a purity of 99.7% by weight and B having a purity of 99.5% by weight are used.₂₉Dy_2.5Fe₆₄Co_ThreeB₁Al_0.2Si_0.2Cu_0.1An ingot was prepared by melting and casting the above alloy in a vacuum melting furnace. The ingot was coarsely pulverized with a jaw crusher and a brown mill, and further finely pulverized with an average particle size of 3.5 μm by jet mill pulverization in a nitrogen stream. This powder is 1.0 t / cm in a magnetic field of 10 kOe in a horizontal magnetic field vertical molding apparatus shown in FIG. 1 in which a ferromagnetic core made of Fe having a saturation magnetic flux density of 20 kG is arranged.²Molding was performed at a molding pressure of This molded body was sintered in Ar gas at 1090 ° C. for 1 hour, and subsequently heat-treated at 580 ° C. for 1 hour. Thereafter, processing was performed to obtain a cylindrical magnet of φ30 mm × φ25 mm × L30 mm. Using the same magnetic powder as this cylindrical magnet, 1.0 t / cm in a magnetic field of 10 kOe with a horizontal magnetic field vertical forming apparatus.²The block magnet produced under the same conditions as the present cylindrical magnet after molding at 1090 ° C. for 1 hour in Ar gas and subsequently heat-treated at 580 ° C. for 1 hour has the following characteristics: 13.0 kG, iHc: 15 kOe, (BH) max: 40 MGOe.
[0085]
The above-mentioned radially oriented cylindrical magnet was magnetized with 6 poles by a magnetizer, and a motor was prepared by incorporating the magnetized magnets into nine stators having the same height as the magnet and having the configuration shown in FIG. . A ferromagnetic core serving as a motor shaft is inserted and bonded to the inner diameter of the magnet. The copper thin wire was wound 100 turns for each tooth. The amount of magnetic flux between the U-V phases was measured using a flux meter.
[0086]
    [Comparative Example 4]
  Only one of the stator teethReference Example 7The same copper fine wire as 100 was wound 100 turns, and the amount of magnetic flux was measured with a flux meter. Table 4 shows the peak values when the magnet is rotated once. As shown in the table, in the comparative example, although the amount of magnetic flux due to the peak is as large as about 1.5 times in the large peak with respect to the small peak,Reference Example 7Then, the peak value hardly changes.
[0087]
    [Reference Example 8]
  A ferromagnetic material with a saturation magnetic flux density of 18 kG occupying an area of 60% of the core cross-sectional area is arranged concentrically with the outer periphery of the core, and the rest is a core made of a non-magnetic material.Reference Example 7The amount of magnetic flux between the U and V phases of the motor produced in the same manner as above was measured.
[0088]
    [Comparative Example 5]
  Other than using non-magnetic material (non-magnetic cemented carbide WC-Ni-Co) as the core materialReference Example 7The amount of magnetic flux between the U and V phases of the motor produced in the same manner as above was measured.
[0089]
    [Comparative Example 6]
  Other than changing the saturation magnetic flux density of the ferromagnetic core made of Fe to 2 kGReference Example 7The amount of magnetic flux between the U and V phases of the motor produced in the same manner as above was measured. The amount of magnetic flux between the U and V phases of the motor at the time of placement was measured using a flux meter.
  These results are shown in Table 4.
[0090]
[Table 4]

[0091]
    [Reference Example 9]
  Reference Example 7The induced voltage when the motor was rotated at 1000 rpm and the magnitude of torque ripple with a load meter when the motor was rotated at 1 to 5 rpm were measured. Table 5 shows the difference between the maximum absolute value of the induced voltage and the maximum and minimum of the torque ripple. From Table 5, it can be seen that this motor has a sufficient amount of induced voltage in use and has a sufficiently small torque ripple.
[0092]
    [Reference Example 10]
  Reference Example 7When magnetizing a radially oriented cylindrical magnet, the skew angle is set to 20 °, which is 1/3 of the angle of one pole of the magnet.Reference Example 7Built into the motorReference Example 9Table 5 shows values obtained by measuring the induced voltage and torque ripple in the same manner as described above. It can be seen from Table 5 that the amount of torque ripple is smaller than that of the product without skew and the induced voltage is only slightly reduced.
[0093]
    [Reference example11]
  Reference Example 7When magnetizing a radially oriented cylindrical magnet, skew magnetization is performed at 50 °, which is 5/6 of the angle of one pole of the skew angle magnet.Reference Example 7Built into the motorReference Example 9Table 5 shows values obtained by measuring the induced voltage and torque ripple in the same manner as described above. It can be seen from Table 5 that the amount of torque ripple is smaller than that of the product without skew, but the induced voltage is greatly reduced and may not be suitable for practical use.
[0094]
    [Reference Example 12]
  A radially oriented cylindrical magnetReference Example 7With a stator tooth that is 20 ° which is 1/3 of the angle of one magnet.Reference Example 7Built into a motor of the same dimensions asReference Example 9Table 5 shows values obtained by measuring the induced voltage and torque ripple in the same manner as described above. From Table 5, it can be seen that the amount of torque ripple is smaller than that of the product without skew, and the induced voltage is only slightly reduced.
[0095]
[Table 5]

[0096]
    [Reference Example 13]
  Nd, Dy, Fe, Co, and M (M is Al, Si, Cu) having a purity of 99.7% by weight and B having a purity of 99.5% by weight are used.₂₉Dy_2.5Fe₆₄Co_ThreeB₁Al_0.2Si_0.2Cu_0.1The alloy was melted and cast in a vacuum melting furnace to produce an ingot. The ingot was coarsely pulverized with a jaw crusher and a brown mill, and further fine powder having an average particle size of 3.5 μm was obtained by jet mill pulverization in a nitrogen stream. This powder is 1.0 t / cm in a magnetic field of 6 kOe in a horizontal magnetic field vertical molding apparatus as shown in FIG. 1 in which a ferromagnetic core made of Fe having a saturation magnetic flux density of 20 kG is arranged.²Molding was performed at a molding pressure of This molded body was sintered in Ar gas at 1090 ° C. for 1 hour, and subsequently heat-treated at 580 ° C. for 1 hour. Thereafter, it was processed to obtain a cylindrical magnet having an outer diameter of 30 mm, an inner diameter of 25 mm, and a thickness of 15 mm.
[0097]
  Reference Example 13The stacked cylindrical magnets are stacked with the orientation direction shifted by 60 °, and the first-stage magnet orientation direction is arranged as shown in FIG. 8 (pole A becomes N pole). Stacked up.
[0098]
    [Reference Example 14]
  Reference Example 14Has a shift angle of 90 °,Reference Example 13In the same manner as above, two-stage stacking of 6 poles was performed.
[0099]
    [Reference example15]
  Reference Example 13Use the same magnet powder, change the height of the compact, and do not stackReference Example 13A cylindrical magnet having an outer diameter of 30 mm, an inner diameter of 25 mm, and a thickness of 30 mm was produced under the same conditions as described above, and hexapole magnetization was performed.
[0100]
    [Reference Example 16]
  Reference Example 13The cylindrical magnets having the outer diameter of 30 mm, the inner diameter of 25 mm, and the thickness of 10 mm are manufactured under the same conditions using the same magnet powder, and the orientation direction is shifted by 60 ° and stacked in three stages. 6 pole magnetization was performed. This is shown in FIG. Large arrows in the figure indicate the direction of the magnetic field during the orientation of each stage of the cylindrical magnet. Reference numeral 33 denotes a motor rotor shaft.
[0101]
In order to evaluate these magnets, copper thin wires were wound 50 turns around a square of 10.5 mm in width and 30 mm in length to produce a coil. The coil is moved away from the state where it is in contact with the cylindrical magnet and is not affected by the magnetic force of the magnet. The amount of magnetic flux crossing the coil is measured using a flux meter in the outer circumferential direction of the cylindrical magnet. Show.
[0102]
[Table 6]

[0103]
    [Reference Examples 17, 18, 19Comparative Example 7]
  FIG. 10 is a plan view of a three-phase permanent magnet motor 30 having nine motor stator teeth 31. A magnet was produced by incorporating a magnetized cylindrical magnet into a stator having the same height as the magnet. A ferromagnetic core serving as a motor shaft is inserted and bonded to the inner diameter portion of the cylindrical magnet. A thin copper wire was wound around each tooth for 150 turns. The motor was rotated at 1000 rpm, the maximum value of the induced voltage at this time was rotated at 1 to 5 rpm, and the magnitude of torque ripple was measured using a load meter.
[0104]
  here,Reference Example 17IsReference Example 14In the same manner as described above, the magnets are stacked in two stages at a shift angle of 90 °, and skew magnetization is performed at 20 °, which is 1/3 of the angle of one pole of the magnet, and this magnet is incorporated in the motor.
[0105]
  Reference Example 18IsReference Example 16As shown in FIG. 16, the magnets are stacked in three stages at a shift angle of 60 ° and magnetized without skew, and the skew angle is 20 °, which is 1/3 of the angle of one pole of the magnet. It is incorporated in a motor having a skew stator tooth.
[0106]
  In addition, a cylindrical magnet without stacking is a reference example.19In addition, the core of the molding die is made of non-magnetic (non-magnetic cemented carbide WC-Ni-Co) and placed on the molding machine.Reference Example 13Make a magnet in the same way asReference Example 17In the same manner as described above, it was incorporated in a motor to obtain Comparative Example 7. These induced voltages and torque ripples were measured, and the maximum and minimum differences in torque ripple along with the induced voltages are shown in Table 7.
[0107]
  From Table 7, each example has an induced voltage that can withstand practical use and torque ripple is sufficiently small.19It is recognized that the torque ripple is large. Comparative Example 7 has a low induced voltage and is not suitable for practical use.
[0108]
    [Reference example20]
  Reference Example 17When magnetizing a radially oriented cylindrical magnet, skew magnetization is performed at 50 ° which is 5/6 of an angle corresponding to one pole of a skew angle magnet, and this magnet is incorporated into the motor of FIG.Reference Example 17The induced voltage and torque ripple were measured in the same manner as shown in Table 7.
[0109]
From Table 7, it is recognized that the amount of torque ripple is small, but the decrease in induced voltage is large and is not suitable for practical use.
[0110]
    [Reference Examples 21 and 22]
  Reference Example 13Using this Nd magnet alloy, a uniaxially oriented ring magnet was produced by a horizontal magnetic field vertical forming method. The magnet dimensions are an outer diameter of 25 mm, an inner diameter of 20 mm, and a thickness of 15 mm. The magnet rotor was manufactured by stacking six stages while changing the orientation direction in increments of 60 ° and magnetizing straight to 6 poles. This was incorporated into a stator having a skew angle of 7 ° to be a motor.
[0111]
  Further reference examples22AsReference Example 21Using the same magnet, the orientation direction was aligned in one direction and magnetized straight to 6 poles to produce a magnet rotor. This was built into a skew-free stator and used as a motor. In these, torque ripple was measured together with induced voltage.
[0112]
  The results are as shown in Table 7.Reference Example 21In the reference example22The torque ripple is greatly reduced as compared with the above, and it can be seen that the effect of dispersion in the orientation direction of the magnet according to the present invention is remarkable.
[0113]
[Table 7]

[Brief description of the drawings]
1A and 1B are explanatory views showing an embodiment of a horizontal magnetic field vertical forming apparatus used when manufacturing a cylindrical magnet, wherein FIG. 1A is a plan view and FIG. 1B is a longitudinal sectional view.
2A and 2B are explanatory views showing a conventional vertical magnetic field vertical forming apparatus used when manufacturing a radial anisotropic cylindrical magnet, wherein FIG. 2A is a longitudinal sectional view, and FIG. It is sectional drawing of an A 'line.
FIG. 3 is an explanatory view schematically showing a state of magnetic lines of force when a magnetic field is generated by a horizontal magnetic field vertical forming apparatus used when manufacturing a cylindrical magnet, and FIG. 3 (a) is a case of a forming apparatus according to the present invention; b) is the case of a conventional molding apparatus.
FIGS. 4A and 4B are explanatory views showing another embodiment of a horizontal magnetic field vertical forming apparatus used when manufacturing a cylindrical magnet, wherein FIG. 4A is a plan view and FIG. 4B is a longitudinal sectional view.
FIG. 5 is an explanatory view showing a vertical magnetic field vertical forming apparatus in which a non-magnetic material is partially arranged in a die part used when manufacturing a radial anisotropic cylindrical magnet. FIG. 5 (a) is a view similar to FIG. A similar cross-sectional view, (b) is an enlarged view of B1 to B4 in FIG.
FIG. 6 is an explanatory view showing an example of a rotary horizontal magnetic field vertical forming apparatus, which is a forming apparatus used when manufacturing a cylindrical magnet.
FIG. 7 is a magnetization schematic diagram showing how a cylindrical magnet is magnetized using a magnetizer.
FIG. 8 is a magnetization schematic diagram showing how a cylindrical magnet is magnetized using a magnetizer, and shows how magnetization is performed by rotating the orientation direction of the cylindrical magnet by 90 ° with respect to FIG.
FIG. 9 is a plan view for explaining a boundary between a north pole and a south pole of a cylindrical magnet.
FIG. 10 is a plan view of a three-phase motor in which a cylindrical magnet magnetized with 6 poles and 9 stator teeth are combined.
FIG. 11 is a diagram showing a surface magnetic flux density when hexapolar magnetization is performed on an Nd—Fe—B cylindrical magnet produced by a horizontal magnetic field vertical forming apparatus according to the present invention.
FIG. 12 is a diagram showing the surface magnetic flux density when N pole-Fe-B cylindrical magnets produced by a conventional horizontal magnetic field vertical forming apparatus (using a non-magnetic material as a core material) are subjected to 6-pole magnetization. is there.
FIG. 13 is a photomicrograph showing the orientation of a magnet in a 30 ° direction with respect to the orientation magnetic field direction of a magnet produced by a horizontal magnetic field vertical forming apparatus using a ferromagnetic material used as a core for manufacturing a cylindrical magnet. It is.
FIG. 14 is a photomicrograph showing the orientation of a magnet in a 60 ° direction with respect to the orientation magnetic field direction of a magnet produced by a horizontal magnetic field vertical forming apparatus using a ferromagnetic material used as a core for manufacturing a cylindrical magnet. It is.
FIG. 15 is a photomicrograph showing the orientation of a magnet in a 90 ° direction with respect to the orientation magnetic field direction of a magnet produced by a horizontal magnetic field vertical forming apparatus using a ferromagnetic material used as a core for manufacturing a cylindrical magnet. It is.
FIG. 16 is a perspective view showing a rotor for a permanent magnet motor according to the present invention in which radially oriented cylindrical magnets are stacked in three stages with a shift of 60 ° each.
[Explanation of symbols]
1 Molding machine base
2 Oriented magnetic field coil
3 dice
4 cores
5 cores
5a core
5a 'Weak ferromagnetic cemented carbide part
6 Top punch
7 Lower punch
8 Filling magnet powder
9 pole piece
10 Non-magnetic dice
11 permendur
21 Cylindrical magnet
22 Magnetizer
23 Magnetic pole teeth
24 Magnetizer coil
30 3-phase motor
31 Stator teeth
32 coils
33 Motor rotor shaft

Claims

By molding by applying an orientation magnetic field to the magnet powder by a magnet powder packed into a cylindrical magnet forming mold cavity horizontal magnetic field vertical molding method, when producing a radial anisotropic sintered magnet, molding cylindrical magnet A ferromagnetic material having a saturation magnetic flux density of 5 kG or more is used as at least a part of the material of the mold core, and the magnetic powder filled in the mold cavity is formed into a magnetic powder of 0.5 to 12 kOe by horizontal magnetic field vertical forming The operation of rotating the magnet powder filled in the mold cavity relative to the direction of the magnetic field generated by the coil while applying an orientation magnetic field in the following (i) to (v)
(I) While applying a magnetic field, rotate the magnet powder by a predetermined angle in the circumferential direction of the mold,
(Ii) After applying the magnetic field, rotate the magnet powder by a predetermined angle in the circumferential direction of the mold, and then apply the magnetic field again.
(Iii) During magnetic field application, the magnetic field generating coil is rotated by a predetermined angle in the circumferential direction of the mold with respect to the magnet powder.
(Iv) After applying the magnetic field, the magnetic field generating coil is rotated by a predetermined angle in the mold circumferential direction with respect to the magnet powder, and then the magnetic field is applied again.
(V) A cylindrical shape characterized in that two or more pairs of magnetic field generating coils are arranged, and after one pair of coils applies a magnetic field, another coil pair applies a magnetic field by at least one operation. 2% or more and 50% or less of the magnet volume, and the remaining part of the magnet volume has an inclination with respect to the radial direction or the radial direction of less than 30 °. A method for producing a radially anisotropic sintered magnet that is oriented and has 2n (n is a positive integer of 2 to 50) magnetized in the circumferential direction .

When rotating the filled magnetic powder, the core, the radial anisotropic sintered magnet according to claim 1, wherein a for rotating the filling magnet powder by rotating at least one of the die and punch in the circumferential direction Production method.

When rotating the magnetic field applying after filling the magnet powder, the value of residual magnetization of the ferromagnetic core or the magnet powder is not less than 50G, claim 1, characterized in that for rotating the magnet powder by rotating the core in the circumferential direction The manufacturing method of the radial anisotropic sintered magnet of description.