JP3654807B2 - Manufacturing method of R-Fe-B permanent magnet excellent in electrical insulation - Google Patents
Manufacturing method of R-Fe-B permanent magnet excellent in electrical insulation Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/026—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets protecting methods against environmental influences, e.g. oxygen, by surface treatment
Description
【０００１】
【発明の属する技術分野】
本発明は、電気絶縁性に優れたＲ−Ｆｅ−Ｂ系永久磁石及びその製造方法に係り、とくに自動車用のモーター用永久磁石等に求められる電気絶縁性、耐食性及び耐熱性に優れたＲ−Ｆｅ−Ｂ系永久磁石の製造方法に関する。
【０００２】
【従来の技術】
この種の電気絶縁性を有するＲ−Ｆｅ−Ｂ系永久磁石（Ｒ：希土類元素）としては、特開平８−２７９４０７号公報に開示されているものがある。ここで開示されているＲ−Ｆｅ−Ｂ系永久磁石は、Ｒ−Ｆｅ−Ｂ系永久磁石素体表面に、膜厚１．０〜３．０μｍの下地金属層を介して、膜厚２．０〜１０μｍのポリイミド膜を有するものである。これにより、優れた電気絶縁性、耐熱性並びに十分な耐食性を達成し、自動車モーター用永久磁石等の苛酷な環境に対応可能である旨述べられている。
【０００３】
【発明が解決しようとする課題】
ところで、近年の環境問題からエネルギーの高効率化が求められており、とりわけ自動車においてはＥＶモーターの開発が盛んに行われている。これに伴い、使用される磁石の温度特性向上は勿論のこと、モーター効率を向上させるために磁石自体の絶縁性が求められるようになってきた。
【０００４】
従来のＲ−Ｆｅ−Ｂ系永久磁石は防錆処理として、Ｎｉメッキが広く採用されている。しかしながら、最表面が金属であるため磁石自身が高い導電性を示し、永久磁石に発生する渦電流がモーター効率を低下させる要因となっていた。これを解決するために、下地層として金属皮膜を形成し、さらにポリイミド皮膜を形成する方法が検討されている。
【０００５】
特開平８−２７９４０７号公報の例ではポリイミド皮膜を蒸着法で形成しており、成膜時に３００℃以上の加熱処理が行われている。このため、加熱時に磁石素体と金属皮膜の膨張係数の違いから、界面にマイクロクラック等が発生することがあり、高温加熱処理に伴う歪みに起因して磁気特性が劣化してしまうことがあった。また、最表面のポリイミド皮膜は摺動性が小さいため、モーター組み込み時のハンドリングで皮膜が傷つくことがあった。さらに、単にポリイミド皮膜の膜厚を厚くしたのでは、ガスピンホールが発生するきらいがあった。
【０００６】
本発明は、上記の点に鑑み、絶縁皮膜の加熱硬化処理に伴う磁気特性の劣化がなく、ハンドリング時の絶縁皮膜損傷で電気絶縁性が損なわれることのない電気絶縁性に優れたＲ−Ｆｅ−Ｂ系永久磁石の製造方法を提供することを目的とする。
【０００７】
本発明のその他の目的や新規な特徴は後述の実施の形態において明らかにする。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明の電気絶縁性に優れたＲ−Ｆｅ−Ｂ系永久磁石の製造方法は、Ｒ（希土類元素の少なくとも１種）−Ｆｅ−Ｂ系永久磁石素体表面に、下地金属層を形成した後、該下地金属層上に電気絶縁皮膜を形成する場合において、
前記下地金属層を膜厚２〜１５μｍで形成後に、多官能エポキシ樹脂、付加反応タイプのポリイミド樹脂又は付加反応タイプのポリアミドイミド樹脂に絶縁性固体潤滑剤粒子を混入した塗料を塗布し、１２０℃〜２００℃で加熱硬化処理して耐熱性電気絶縁皮膜を膜厚５〜５０μｍで形成したことを特徴としている。
【００１３】
前記電気絶縁性に優れたＲ−Ｆｅ−Ｂ系永久磁石の製造方法において、前記下地金属層は、メッキ又は気相蒸着法によって形成するとよい。
【００１４】
前記下地金属層はＮｉ，Ｓｎ，Ｃｕ，Ｚｎ，Ａｌであるか、あるいはＮｉ，Ｓｎ，Ｃｕ，Ｚｎ又はＡｌを含む合金であるとよい。
前記塗料は全樹脂量に対して２〜５０重量％の前記絶縁性固体潤滑剤粒子を混入したものであるとよい。
前記絶縁性固体潤滑剤粒子はフッ素樹脂、窒化ホウ素のいずれか１種類以上であり、平均粒子径が１０μｍ以下であるとよい。
前記多官能エポキシ樹脂は、フェノールノボラック又はｏ−クレゾールノボラック樹脂をエポキシ変性させたものであるとよい。
【００１５】
【発明の実施の形態】
以下、本発明に係る電気絶縁性に優れたＲ−Ｆｅ−Ｂ系永久磁石の製造方法の実施の形態を説明する。
【００１６】
希土類磁石であるＲ−Ｆｅ−Ｂ系永久磁石素体の表面に下地金属層として２〜１５μｍの金属皮膜を形成した後、さらに電気絶縁皮膜として固体潤滑剤粒子が分散された５〜５０μｍの樹脂皮膜を形成する。
【００１７】
前記金属皮膜はＮｉ，Ｓｎ，Ｃｕ，Ｚｎ，Ａｌ等の金属、あるいはＮｉ，Ｓｎ，Ｃｕ，Ｚｎ，Ａｌを主に含む合金を、メッキ又は気相蒸着法（イオンプレーティング、スパッタ等）で被着、形成したものである。但し、アルミ（Ａｌ）又はアルミ合金は気相蒸着法の場合のみ使用可能である。
【００１８】
前記固体潤滑剤粒子が分散された樹脂皮膜は、樹脂をベースとした塗料のディップ又はスプレーコーティングによって形成する。コーティングに使用する樹脂はポリイミド、ポリアミドイミド又はエポキシ樹脂である。ポリイミド、ポリアミドイミドは付加反応タイプのポリイミド、ポリアミドイミドであり、エポキシ樹脂はフェノールノボラック、ｏ−クレゾールノボラック樹脂をエポキシ変性したものを代表とする多官能エポキシ樹脂である。さらに、前記樹脂をベースとした塗料には全樹脂量に対し２〜５０ｗｔ％（重量％）のフッソ樹脂、窒化ホウ素等の絶縁性を有する固体潤滑剤粒子を混入している。これら固体潤滑剤粒子の粒径は１０μｍ以下である。前記樹脂をベースとし、絶縁性の固体潤滑剤粒子を混入した塗料を下地金属層上にコーティング後、加熱（好ましくは１２０℃〜２００℃の温度範囲）して塗膜の硬化処理を行い、電気絶縁皮膜を形成する。
【００１９】
この実施の形態において、下地層として２〜１５μｍの金属皮膜を形成する理由は、磁石素体表面に直接樹脂塗装しても樹脂自体に透湿性があるため、十分な耐食性を得るためには厚膜化しなければならないからであり、あまり厚膜化すると磁石自体の体積比率が低下するため磁気特性が低下する。このため、下地層としては耐食性に優れたＮｉ，Ｓｎ，Ｃｕ，Ｚｎ等の金属、あるいはＮｉ，Ｓｎ，Ｃｕ又はＺｎを主に含む合金からなる金属皮膜が好ましい。金属皮膜の膜厚を２〜１５μｍとしたのは必要最低限の耐食性を発揮でき、さらに樹脂コートしても磁気特性の損失が少ない範囲であることによる。つまり、膜厚２μｍ未満では防湿性、耐食性に不安があり、１５μｍあれば耐湿性は充分であり、後工程で樹脂コートすることを考慮すると１５μｍを越える膜厚とすることは必要ない。
【００２０】
また、電気絶縁皮膜として５〜５０μｍの樹脂皮膜を形成するのは、優れた電気絶縁性を発揮し、磁気特性を損なわず均一な皮膜を形成できる膜厚は５〜５０μｍであるからであり、ディップ又はスプレーコーティングで膜厚５μｍ未満になると、塗装されていない箇所が生じ、絶縁性の低下につながる。膜厚が５０μｍを越えると下地に金属層を介しているため磁気特性の低下が大きくなるばかりでなく、膜厚が不均一になりやすい。
【００２１】
また、金属皮膜をメッキで形成するのは、希土類磁石の防錆処理として最も実績があり、安価であることによる。特にＮｉメッキは耐食性に優れ高い密着性を示し、小物形状では低コストである。
【００２２】
樹脂をベースとした塗料をディップ又はスプレーコーティングするのは、特開平８−２７９４０７号公報の例にある蒸着法が均一で緻密な塗膜が得られる反面、顔料を添加することができないため着色や塗膜潤滑性等の機能を付加することができないからである。また、蒸着法に比べて製造コストが安価である。
【００２３】
樹脂として付加反応型ポリイミド又はポリアミドイミドを使用するのは以下の理由による。一般にポリイミド樹脂の反応は縮合反応、又は付加反応の２種類に分けることができる。前者は特開平８−２７９４０７号公報にある蒸着法や耐熱電線用コーティングで広く使用されている。縮合反応タイプのポリイミドはイミド構造を形成するのに３００℃以上の加熱を必要とするため磁気特性を損なうことがある。また、反応時に水が生成するため塗膜にピンホールが発生するおそれがある。これに対し付加反応タイプは予めイミド構造を有するものを原料としており、塗膜硬化時に縮合反応タイプのものほど高温加熱する必要がない。また、硬化反応の際、水等の揮発成分が生成しないためピンホールが発生しにくい。
【００２４】
樹脂として多官能エポキシ樹脂を使用するのは以下の理由による。一般に多官能エポキシ樹脂は耐熱性が必要とされる用途に使用されている。とくにフェノールノボラックやｏ−クレゾールノボラックをエポキシ変性したものは半導体の封止材として使用されており、耐熱性、電気絶縁性に優れる。塗料用の樹脂成分とした場合、耐食性、耐熱性、電気絶縁性に優れた塗膜を与える。
【００２５】
絶縁性を有する固体潤滑剤粒子を樹脂中に分散する理由は、固体潤滑剤としてフッソ樹脂、窒化ホウ素の他に、グラファイト、二硫化モリブデンが多く使用されているが、二硫化モリブデンは半導体であり、グラファイトは導体であるため樹脂中にこれらを分散しても高い電気抵抗性が得られないからである。また、全樹脂量に対し、２〜５０ｗｔ％の固体潤滑剤粒子を混入する理由は、２〜５０ｗｔ％の潤滑成分を添加することで塗膜に適度な潤滑性を与え、塗膜に空隙を作らないためである。また、固体潤滑剤粒子は塗料に使用する樹脂成分と接着しにくい。このため塗膜硬化時に溶剤が揮発するとき固体潤滑剤粒子と樹脂成分との界面を通過するため、溶剤を除去しやすくガスピンホールが発生しにくい。さらに、固体潤滑剤粒子の平均粒径を１０μｍ以下とするのは、１０μｍを越えると５０μｍ以下の膜厚で均一な塗膜を得ることが困難であるからである。
【００２６】
この実施の形態によれば、Ｒ−Ｆｅ−Ｂ系永久磁石素体表面に、膜厚２〜１５μｍの下地金属層を形成し、該下地金属層上に膜厚５〜５０μｍの電気絶縁皮膜を形成してＲ−Ｆｅ−Ｂ系永久磁石を作製し、かつ前記電気絶縁皮膜は多官能エポキシ樹脂、ポリイミド樹脂又はポリアミドイミド樹脂を樹脂皮膜成分とし、さらに該樹脂皮膜中に固体潤滑剤粒子が分散されている構成としたので、耐食性、電気絶縁性に優れた磁石を提供できる。特に、前記電気絶縁皮膜となる塗膜硬化温度が従来の縮合反応タイプのポリイミド樹脂の蒸着法に比べて低いため、磁石素体に対するメッキ膜の密着性を損なわず優れた磁気特性を示す。また、前記電気絶縁皮膜となる塗料自体の耐熱性が高いため高温下での連続使用に耐え、固体潤滑剤粒子が分散されているため塗膜表面の摺動性が高く、ハンドリング時等において塗膜に傷が発生しにくい。
【００２７】
なお、ポリイミド、ポリアミドイミド樹脂のうち、ポリイミドの方が耐熱性が優れているのでいっそう好ましい。
【００２８】
また、樹脂塗膜を設ける前に化成処理、カップリング剤による処理を施すとよい。
【００２９】
【実施例】
次に本発明を実施例で詳述する。
【００３０】
Ｒ−Ｆｅ−Ｂ系永久磁石としてのＮｄＦｅＢ焼結磁石を加工して、直方体のサンプルを作製した。得られた磁石素体をアルカリ溶液で脱脂し、３％−ＨＮＯ３でエッチング後、スルファミン酸Ｎｉメッキ浴中で電気メッキを行い下地金属層として膜厚が約１０μｍのＮｉメッキ皮膜を得た。メッキした磁石をＩＰＡ（イソプロパノール）で洗浄し、ＰＴＦＥ（四フッ化エチレン樹脂）粒子を分散したポリイミド系（付加反応タイプ）又は多官能エポキシ系（変性エポキシ系）塗料をスプレーコーティングし、１８０℃１時間の加熱硬化処理を施して厚さ約１５μｍの樹脂塗膜を作製したものを以下の表１のように実施例１，２のサンプルとした。また、以下の表１に示す条件で比較例１乃至４のサンプルを作製した。
【００３１】
【表１】
表面処理した実施例１，２及び比較例１，２，３，４の各サンプルについて、体積抵抗率、磁気特性（磁束量）、及び耐食性を評価した。
【００３３】
体積抵抗率は実際の測定値から、次の式で算出した。
ρ＝Ｒ・Ｓ／Ｌ
但し、ρ：体積抵抗率（Ω・cm）、Ｒ：電気抵抗（Ω）、Ｓ：電極面積（cm２）、Ｌ：塗膜の膜厚（cm）
測定は直径９mm×１．２mmの円板形状の磁石サンプルを作製して行った。電気抵抗は電極にサンプルを挟み、２５Ｖで２０秒チャージ後、放電したときの抵抗値を測定した（但しサンプル数５）。データはサンプル５個の平均を示した。
【００３４】
磁気特性は上記サンプルと同一形状の磁石を使用し、磁束を測定した。なお、塗膜未硬化品及び塗膜硬化品についてそれぞれ１０個ずつサンプルを用意し、それぞれＨ＝２４００（ｋＡ／ｍ）で着磁を行い磁束計（fluxメーター）で磁束を測定した。データはサンプル１０個の測定値の平均を示した。
【００３５】
耐食性は８５℃、湿度８５％の条件下で１０００時間放置後の外観変化及び電気抵抗を測定した。また、塩水噴霧試験を行い、錆の発生時間を調査した。
【００３６】
さらに、コーティングしたサンプルについては摩擦係数も測定した。
【００３７】
各サンプルについて、塗膜硬化前後の磁気特性を測定した。結果を表２に示す。
【００３８】
【表２】
表２より、実施例１，２においては、通常の１８０℃１時間の加熱硬化処理を施した場合の塗膜硬化前後の磁束低下率は実質零であることがわかる。一方、下地にＮｉメッキ皮膜を有する比較例３は、塗膜硬化温度が３００℃と高いため、硬化前後で明らかに磁気特性が低下しているのがわかる。また、実施例１，２及び比較例４についても下地にＮｉメッキ皮膜を有しているため、必要以上に加熱すると（３００℃で加熱すると）比較例３と同様に磁気特性が低下している。これは、磁石とメッキ皮膜の熱膨張係数の違いから、磁石とメッキ界面に歪みが生じた事による。なお、比較例１，２の樹脂塗膜単体では金属に比べて樹脂塗膜が柔らかいために、磁石と樹脂塗膜界面に歪みが発生せず磁気特性の劣化が非常に少ない。
【００４０】
次に、耐湿試験前後の体積抵抗率を表３に示す。
【００４１】
【表３】
表３より実施例１，２では体積抵抗率の変化が少なく絶縁性は良好に保たれ、比較例４では体積抵抗率の変化が大きく絶縁性が劣化していることが判る。なお、比較例１，２では、発錆により樹脂皮膜が破れて測定不能となった。
【００４３】
さらに塩水噴霧１６８時間後の表面の状態を表４、塗膜の摩擦係数を表５に示す。
【００４４】
【表４】
表４より実施例１，２、比較例４では表面状態に変化がないのに対し、比較例１，２，３では全面又は部分的に発錆していることがわかる。
【００４６】
【表５】
表５より実施例１，２、比較例１，４では塗膜の摩擦係数が小さい状態に保たれているが、比較例２，３では摩擦係数がかなり増加していることが判る。
【００４８】
以上の表２乃至表５の結果を見ると、実施例１，２の場合、磁束量、体積抵抗率、耐食性、摩擦係数の全ての点において問題がないのに反し、比較例１乃至４はいずれかの点で問題が発生しており、実施例１，２が優れていることが判る。
【００４９】
このＲ−Ｆｅ−Ｂ系永久磁石に用いる希土類元素Ｒは、Ｎｄ，Ｐｒ，Ｄｙ，Ｈｏ，Ｔｂのうち少なくとも１種、あるいはさらにＬａ，Ｃｅ，Ｓｍ，Ｇｄ，Ｅｒ，Ｅｕ，Ｔｍ，Ｙｂ，Ｌｕ，Ｙのうち少なくとも１種を含むものが好ましい。また、通常Ｒのうち１種をもって足りるが、実用上は２種以上の混合物を用いることもできる。また、このＲは純希土類元素でなくともよく、工業上入手可能な範囲で製造上不可避な不純物を含有するものでも差し支えない。
【００５０】
以上本発明の実施の形態及び実施例について説明してきたが、本発明はこれに限定されることなく請求項の記載の範囲内において各種の変形、変更が可能なことは当業者には自明であろう。
【００５１】
【発明の効果】
以上説明したように、本発明によりＲ−Ｆｅ−Ｂ系磁石素体表面に金属皮膜を形成し、さらに潤滑剤粒子を含む樹脂皮膜を電気絶縁皮膜として形成したものは電気絶縁性、耐食性、磁気特性いずれについても優れた性能を有していることがわかる。また、摩擦係数が小さいため塗膜にこすり傷等が発生しにくく、ハンドリング時等に電気絶縁性が損なわれるおそれがない。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an R—Fe—B permanent magnet excellent in electrical insulation and a method for producing the same, and in particular, R— excellent in electrical insulation, corrosion resistance and heat resistance required for motor permanent magnets for automobiles and the like. The present invention relates to a method for producing an Fe-B permanent magnet .
[0002]
[Prior art]
An R-Fe-B permanent magnet (R: rare earth element) having this type of electrical insulation is disclosed in Japanese Patent Laid-Open No. 8-279407. The R—Fe—B permanent magnet disclosed here has a film thickness of 2. on the surface of the R—Fe—B permanent magnet body with a base metal layer of 1.0 to 3.0 μm in thickness. It has a 0-10 μm polyimide film. Thus, it is stated that excellent electrical insulation, heat resistance and sufficient corrosion resistance can be achieved, and that it can cope with severe environments such as permanent magnets for automobile motors.
[0003]
[Problems to be solved by the invention]
By the way, in recent years, there has been a demand for higher energy efficiency due to environmental problems, and in particular, EVs have been actively developed in automobiles. As a result, not only the temperature characteristics of the magnet used but also the insulation of the magnet itself has been required to improve the motor efficiency.
[0004]
Conventional R-Fe-B permanent magnets are widely used for Ni plating as an antirust treatment. However, since the outermost surface is a metal, the magnet itself exhibits high conductivity, and the eddy current generated in the permanent magnet is a factor that reduces motor efficiency. In order to solve this, a method of forming a metal film as a base layer and further forming a polyimide film has been studied.
[0005]
In the example of JP-A-8-279407, a polyimide film is formed by a vapor deposition method, and a heat treatment at 300 ° C. or higher is performed at the time of film formation. For this reason, a microcrack or the like may occur at the interface due to the difference in expansion coefficient between the magnet body and the metal film during heating, and the magnetic characteristics may be deteriorated due to distortion caused by high-temperature heat treatment. It was. In addition, since the polyimide film on the outermost surface has low slidability, the film may be damaged by handling when the motor is incorporated. Further, simply increasing the film thickness of the polyimide film tends to cause gas pinholes.
[0006]
In view of the above points, the present invention does not cause deterioration of magnetic properties due to heat curing treatment of an insulating film, and R-Fe excellent in electric insulation without damaging the electric insulation due to damage to the insulating film during handling. It aims at providing the manufacturing method of -B type permanent magnet .
[0007]
Other objects and novel features of the present invention will be clarified in embodiments described later.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a method for producing an R—Fe—B permanent magnet excellent in electrical insulation according to the present invention is provided on the surface of an R (at least one rare earth element) —Fe—B permanent magnet body. In the case of forming an electrical insulating film on the underlying metal layer after forming the underlying metal layer,
After the base metal layer is formed with a film thickness of 2 to 15 μm, a polyfunctional epoxy resin, an addition reaction type polyimide resin, or an addition reaction type polyamideimide resin is applied with a paint mixed with insulating solid lubricant particles, and 120 ° C. It is characterized in that a heat-resistant electrical insulating film is formed at a film thickness of 5 to 50 μm by heat curing at ˜200 ° C.
[0013]
In the method for producing an R—Fe—B permanent magnet excellent in electrical insulation, the base metal layer may be formed by plating or vapor deposition.
[0014]
The base metal layer may be Ni, Sn, Cu, Zn, Al, or an alloy containing Ni, Sn, Cu, Zn, or Al.
The coating material may contain 2 to 50% by weight of the insulating solid lubricant particles based on the total resin amount.
The insulating solid lubricant particles may be at least one of fluororesin and boron nitride, and the average particle size may be 10 μm or less.
The polyfunctional epoxy resin may be a phenol novolac or o-cresol novolac resin that is epoxy-modified.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a method for producing an R—Fe—B permanent magnet having excellent electrical insulation according to the present invention will be described below.
[0016]
A resin of 5 to 50 μm in which a solid lubricant particle is dispersed as an electric insulation film after forming a metal film of 2 to 15 μm as a base metal layer on the surface of an R—Fe—B permanent magnet element body which is a rare earth magnet. Form a film.
[0017]
The metal film is coated with a metal such as Ni, Sn, Cu, Zn, Al or an alloy mainly containing Ni, Sn, Cu, Zn, Al by plating or vapor deposition (ion plating, sputtering, etc.). It has been formed. However, aluminum (Al) or an aluminum alloy can be used only in the case of vapor deposition.
[0018]
The resin film in which the solid lubricant particles are dispersed is formed by dipping or spray coating a resin-based paint. The resin used for coating is polyimide, polyamideimide or epoxy resin. Polyimide and polyamideimide are addition reaction type polyimides and polyamideimides, and epoxy resins are polyfunctional epoxy resins typified by epoxy-modified phenol novolac and o-cresol novolac resins. Further, the resin-based coating material contains 2-50 wt% (weight%) of a solid resin particle having insulating properties such as fluorine resin, boron nitride, etc. with respect to the total resin amount. These solid lubricant particles have a particle size of 10 μm or less. After coating the base metal layer with a paint based on the resin and mixed with insulating solid lubricant particles, the coating is cured by heating (preferably in a temperature range of 120 ° C. to 200 ° C.). An insulating film is formed.
[0019]
In this embodiment, the reason why a metal film of 2 to 15 μm is formed as the underlayer is that the resin itself has moisture permeability even if it is directly coated on the surface of the magnet body. This is because the film must be formed into a film, and if the film is made too thick, the volume ratio of the magnet itself is reduced, so that the magnetic characteristics are deteriorated. For this reason, as the underlayer, a metal film made of a metal such as Ni, Sn, Cu, or Zn having excellent corrosion resistance or an alloy mainly containing Ni, Sn, Cu, or Zn is preferable. The reason why the thickness of the metal film is set to 2 to 15 μm is that the minimum necessary corrosion resistance can be exhibited, and even if the resin is coated, the loss of magnetic properties is small. That is, if the film thickness is less than 2 μm, there is anxiety about moisture resistance and corrosion resistance, and if it is 15 μm, the moisture resistance is sufficient.
[0020]
Moreover, the reason why the 5-50 μm resin film is formed as the electric insulation film is that the film thickness is 5-50 μm, which exhibits excellent electric insulation and can form a uniform film without impairing magnetic properties, When the film thickness is less than 5 μm by dip or spray coating, an unpainted portion is generated, leading to a decrease in insulation. If the film thickness exceeds 50 μm, the metal layer is interposed in the underlayer, so that the magnetic properties are not only greatly deteriorated, but the film thickness tends to be non-uniform.
[0021]
In addition, the metal film is formed by plating because it has the most proven track record as a rust preventive treatment for rare earth magnets and is inexpensive. In particular, Ni plating is excellent in corrosion resistance and exhibits high adhesion, and a small shape is low in cost.
[0022]
The dip or spray coating of a resin-based paint can be performed because the vapor deposition method in the example of JP-A-8-279407 can obtain a uniform and dense coating film, but it cannot be added with pigments. This is because functions such as coating film lubricity cannot be added. Moreover, the manufacturing cost is low compared with the vapor deposition method.
[0023]
The reason why the addition reaction type polyimide or polyamideimide is used as the resin is as follows. In general, the reaction of the polyimide resin can be divided into two types, a condensation reaction or an addition reaction. The former is widely used in the vapor deposition method and the coating for heat-resistant electric wires described in JP-A-8-279407. Condensation reaction type polyimide requires a heating of 300 ° C. or more to form an imide structure, which may impair magnetic properties. Moreover, since water is generated during the reaction, pinholes may be generated in the coating film. In contrast, the addition reaction type uses a material having an imide structure as a raw material in advance, and does not need to be heated at a higher temperature than the condensation reaction type when the coating film is cured. In addition, since a volatile component such as water is not generated during the curing reaction, pinholes are hardly generated.
[0024]
The reason why the polyfunctional epoxy resin is used as the resin is as follows. In general, polyfunctional epoxy resins are used for applications that require heat resistance. In particular, phenol novolac or o-cresol novolac modified with epoxy is used as a semiconductor sealing material and is excellent in heat resistance and electrical insulation. When used as a resin component for paints, it provides a coating film with excellent corrosion resistance, heat resistance, and electrical insulation.
[0025]
The reason why the solid lubricant particles having insulating properties are dispersed in the resin is that, in addition to fluororesin and boron nitride, graphite and molybdenum disulfide are often used as the solid lubricant, but molybdenum disulfide is a semiconductor. This is because, since graphite is a conductor, high electrical resistance cannot be obtained even if these are dispersed in the resin. The reason for mixing 2-50 wt% solid lubricant particles with respect to the total resin amount is to add 2-50 wt% of the lubricating component to give the coating film appropriate lubricity and to form voids in the coating film. This is because it is not made. Further, the solid lubricant particles are difficult to adhere to the resin component used in the paint. For this reason, when the solvent is volatilized when the coating film is cured, the solvent passes through the interface between the solid lubricant particles and the resin component, so that the solvent is easily removed and gas pinholes are hardly generated. Furthermore, the reason why the average particle size of the solid lubricant particles is 10 μm or less is that when it exceeds 10 μm, it is difficult to obtain a uniform coating film with a film thickness of 50 μm or less.
[0026]
According to this embodiment, a base metal layer having a film thickness of 2 to 15 μm is formed on the surface of the R—Fe—B permanent magnet body, and an electric insulation film having a film thickness of 5 to 50 μm is formed on the base metal layer. An R—Fe—B permanent magnet is formed to form a polyfunctional epoxy resin, polyimide resin or polyamideimide resin as a resin film component, and solid lubricant particles are dispersed in the resin film. Since it is configured as described above, a magnet having excellent corrosion resistance and electrical insulation can be provided. In particular, since the coating temperature for forming the electrical insulating film is lower than that of the conventional condensation reaction type polyimide resin deposition method, excellent magnetic properties are exhibited without impairing the adhesion of the plating film to the magnet body. In addition, since the paint itself that forms the electrical insulating film has high heat resistance, it can withstand continuous use at high temperatures, and since the solid lubricant particles are dispersed, the coating surface is highly slidable. The film is less likely to be damaged.
[0027]
Of polyimide and polyamideimide resin, polyimide is more preferable because of its excellent heat resistance.
[0028]
Moreover, it is good to give a chemical conversion process and the process by a coupling agent before providing a resin coating film.
[0029]
【Example】
Next, the present invention will be described in detail with reference to examples.
[0030]
A NdFeB sintered magnet as an R—Fe—B permanent magnet was processed to prepare a rectangular parallelepiped sample. The obtained magnet body was degreased with an alkaline solution, etched with 3% -HNO 3 , and then electroplated in a sulfamic acid Ni plating bath to obtain a Ni plating film having a thickness of about 10 μm as a base metal layer. The plated magnet is washed with IPA (isopropanol) and spray-coated with a polyimide (addition reaction type) or polyfunctional epoxy (modified epoxy) paint in which PTFE (tetrafluoroethylene resin) particles are dispersed. Samples of Examples 1 and 2 as shown in Table 1 below were obtained by applying a time-hardening treatment to produce a resin coating having a thickness of about 15 μm. Samples of Comparative Examples 1 to 4 were produced under the conditions shown in Table 1 below.
[0031]
[Table 1]
About each sample of Examples 1 and 2 and Comparative Examples 1, 2, 3, and 4 which were surface-treated, volume resistivity, a magnetic characteristic (magnetic flux amount), and corrosion resistance were evaluated.
[0033]
The volume resistivity was calculated from the actual measurement value by the following formula.
ρ = R · S / L
However, ρ: Volume resistivity (Ω · cm), R: Electric resistance (Ω), S: Electrode area (cm 2 ), L: Film thickness (cm)
The measurement was performed by preparing a disk-shaped magnet sample having a diameter of 9 mm × 1.2 mm. The electrical resistance was measured by sandwiching a sample between the electrodes, charging at 25 V for 20 seconds, and then discharging the battery (however, the number of samples was 5). The data showed the average of 5 samples.
[0034]
Magnetic characteristics were measured using a magnet having the same shape as the above sample. In addition, 10 samples were prepared for each of the uncured film and the cured film, respectively, magnetized at H = 2400 (kA / m), and the magnetic flux was measured with a flux meter. The data showed the average of 10 sample measurements.
[0035]
Corrosion resistance was measured by changing appearance and electrical resistance after leaving for 1000 hours under conditions of 85 ° C. and 85% humidity. Moreover, the salt spray test was done and the generation | occurrence | production time of rust was investigated.
[0036]
In addition, the coefficient of friction was also measured for the coated samples.
[0037]
About each sample, the magnetic characteristic before and behind coating-film hardening was measured. The results are shown in Table 2.
[0038]
[Table 2]
From Table 2, it can be seen that in Examples 1 and 2, the rate of decrease in magnetic flux before and after curing the coating film when subjected to the usual heat curing treatment at 180 ° C. for 1 hour is substantially zero. On the other hand, it can be seen that Comparative Example 3 having a Ni plating film on the base has a coating film curing temperature as high as 300 ° C., and thus the magnetic properties are clearly deteriorated before and after curing. In addition, since Examples 1 and 2 and Comparative Example 4 also have a Ni plating film on the underlayer, when heated more than necessary (when heated at 300 ° C.), the magnetic properties are lowered as in Comparative Example 3. . This is because the magnet and the plating interface are distorted due to the difference in thermal expansion coefficient between the magnet and the plating film. In addition, since the resin coating film of Comparative Examples 1 and 2 is softer than the metal, the interface between the magnet and the resin coating film is not distorted, and the magnetic characteristics are hardly deteriorated.
[0040]
Next, Table 3 shows the volume resistivity before and after the moisture resistance test.
[0041]
[Table 3]
From Table 3, it can be seen that in Examples 1 and 2, the change in volume resistivity is small and the insulation is kept good, and in Comparative Example 4, the change in volume resistivity is large and the insulation is deteriorated. In Comparative Examples 1 and 2, the resin film was torn due to rusting, making measurement impossible.
[0043]
Furthermore, Table 4 shows the surface state after 168 hours of salt spray, and Table 5 shows the friction coefficient of the coating film.
[0044]
[Table 4]
From Table 4, it can be seen that in Examples 1 and 2 and Comparative Example 4, there is no change in the surface state, whereas in Comparative Examples 1, 2 and 3, rusting occurs entirely or partially.
[0046]
[Table 5]
From Table 5, it can be seen that in Examples 1 and 2 and Comparative Examples 1 and 4, the friction coefficient of the coating film is kept small, but in Comparative Examples 2 and 3, the friction coefficient is considerably increased.
[0048]
Looking at the results of Table 2 to Table 5 above, in the case of Examples 1 and 2, there are no problems in all aspects of magnetic flux amount, volume resistivity, corrosion resistance, and friction coefficient, but Comparative Examples 1 to 4 are It can be seen that there is a problem at any point, and Examples 1 and 2 are excellent.
[0049]
The rare earth element R used in this R—Fe—B permanent magnet is at least one of Nd, Pr, Dy, Ho, and Tb, or La, Ce, Sm, Gd, Er, Eu, Tm, Yb, and Lu. , Y containing at least one kind is preferable. In addition, one type of R is usually sufficient, but a mixture of two or more types can be used in practice. The R may not be a pure rare earth element, and may contain impurities that are inevitable in production within a commercially available range.
[0050]
Although the embodiments and examples of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited thereto and various modifications and changes can be made within the scope of the claims. I will.
[0051]
【The invention's effect】
As described above, according to the present invention, a metal film is formed on the surface of an R-Fe-B magnet body, and a resin film containing lubricant particles is formed as an electric insulating film. It turns out that it has the outstanding performance about all the characteristics. In addition, since the friction coefficient is small, the coating film is less likely to be scratched, and there is no possibility that the electrical insulation is impaired during handling.
Claims (6)
前記下地金属層を膜厚２〜１５μｍで形成後に、多官能エポキシ樹脂、付加反応タイプのポリイミド樹脂又は付加反応タイプのポリアミドイミド樹脂に絶縁性固体潤滑剤粒子を混入した塗料を塗布し、１２０℃〜２００℃で加熱硬化処理して耐熱性電気絶縁皮膜を膜厚５〜５０μｍで形成したことを特徴とする電気絶縁性に優れたＲ−Ｆｅ−Ｂ系永久磁石の製造方法。R (at least one kind of rare earth element) -Fe-B-based permanent magnet An R-Fe-B-based permanent magnet in which an underlying metal layer is formed on the surface of a permanent magnet body and then an electric insulating film is formed on the underlying metal layer. In the manufacturing method,
After the base metal layer is formed with a film thickness of 2 to 15 μm, a polyfunctional epoxy resin, an addition reaction type polyimide resin, or an addition reaction type polyamideimide resin is applied with a paint mixed with insulating solid lubricant particles , and 120 ° C. A method for producing an R-Fe-B permanent magnet having excellent electrical insulation, wherein a heat-resistant electrical insulation film is formed at a film thickness of 5 to 50 µm by heat curing at ~ 200 ° C.
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| JP2000013616A JP3654807B2 (en) | 2000-01-24 | 2000-01-24 | Manufacturing method of R-Fe-B permanent magnet excellent in electrical insulation |
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| JP2007158030A (en) * | 2005-12-05 | 2007-06-21 | Neomax Co Ltd | Rare-earth permanent magnet and its manufacturing method |
| CN102936455B (en) * | 2012-10-31 | 2015-05-13 | 沈阳中北通磁科技股份有限公司 | Neodymium iron boron rare earth permanent magnet surface anti-corrosion coating and preparation method thereof |
| JP6246500B2 (en) * | 2013-05-28 | 2017-12-13 | 日本電産サンキョー株式会社 | Rare earth magnet manufacturing method |
| CN104454852B (en) * | 2014-11-28 | 2016-05-18 | 烟台首钢磁性材料股份有限公司 | A kind of permanent magnet ndfeb magnet steel insulate bonding method and dedicated extruded frock |
| CN104674169A (en) * | 2015-02-12 | 2015-06-03 | 烟台首钢磁性材料股份有限公司 | Method for electroplating surface of permanent magnet neodymium iron boron magnetic steel with composite coating |
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| JP2546990B2 (en) * | 1986-04-30 | 1996-10-23 | 株式会社 トーキン | Permanent magnet with excellent oxidation resistance |
| JPS63110708A (en) * | 1986-10-29 | 1988-05-16 | Hitachi Metals Ltd | Permanent magnet |
| JPS63307214A (en) * | 1987-06-05 | 1988-12-14 | Tokin Corp | Manufacture of oxidation-resistant permanent magnet |
| JPH02310395A (en) * | 1989-05-26 | 1990-12-26 | Johoku Riken Kogyo:Kk | Method for preventing corrosion of neodymium-iron-boron sintered magnet |
| JPH0311714A (en) * | 1989-06-09 | 1991-01-21 | Kanegafuchi Chem Ind Co Ltd | Resin-bonded type magnet and manufacture thereof |
| JPH05156207A (en) * | 1991-11-30 | 1993-06-22 | Nitto Denko Corp | Paint composition |
| JPH06257613A (en) * | 1993-03-03 | 1994-09-16 | Toyota Motor Corp | Bearing structure for connecting rod |
| JPH08199116A (en) * | 1995-01-26 | 1996-08-06 | Shikoku Chem Corp | Resin composition for coating |
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