JP3576672B2 - R-Fe-B permanent magnet with excellent electrical insulation, heat resistance and corrosion resistance, and method for producing the same - Google Patents
R-Fe-B permanent magnet with excellent electrical insulation, heat resistance and corrosion resistance, and method for producing the same Download PDFInfo
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- 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
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Description
【０００１】
【発明の属する技術分野】
この発明は、Ｒ−Ｆｅ−Ｂ系永久磁石の改良とその製造方法に係り、Ｒ−Ｆｅ−Ｂ系永久磁石表面に所定膜厚みのカーボン膜層を介して、蒸着重合法によりポリイミド樹脂層を被履し、自動車モーター用永久磁石等に求められる電気絶縁性、耐熱性並びに耐食性を達成したＲ−Ｆｅ−Ｂ系永久磁石とその製造方法に関する。
【０００２】
【従来の技術】
Ｒ−Ｆｅ−Ｂ系永久磁石は、実用化されている磁石の中で最もすぐれた磁気特性を有するが、これを多磁極型の自動車用モーターの永久磁石に用いるためには、まず、前記永久磁石に発生する渦電流発生を防止するために、電気絶縁性のすぐれた被膜で被履する必要があり、また、自動車は走行中にかかるモーターを配置するエンジンルーム温度が２００℃になることより、使用する磁石には耐熱性とともに耐食性を兼備した被膜が要求される。
【０００３】
Ｒ−Ｆｅ−Ｂ系永久磁石は、耐食性及び磁気特性の温度特性が悪いという欠点があり、そのため耐食性改善のため磁石表面に樹脂を被履することが提案（特開昭６０−６３９０２号）されているが、前記方法では耐食性は改善されても、耐熱性が十分でなく、かつ電気絶縁性が悪いという問題があり、磁気特性のすぐれたＲ−Ｆｅ−Ｂ系永久磁石が自動車モーター用に使用できない原因となっている。
【０００４】
【発明が解決しようとする課題】
最近、耐摩耗性の改善のために、鉄心の磁極面とアクチュエータの磁極面にそれぞれＮｉめっき層上に高耐摩耗性被膜としてポリイミド樹脂を蒸着重合法にて被履することが提案（特開平３−２７６５３２号）されているが、リレーの対向磁極面の耐摩耗性の改善向上効果は得られるが、多磁極型の自動車用モーターのＲ−Ｆｅ−Ｂ系永久磁石に必要な被膜強度に優れ、かつ電気絶縁性、耐熱性、耐食性を満足するものではない。
【０００５】
この発明は、特に、多磁極型の自動車用モーターの永久磁石に求められる電気絶縁性、耐熱性を満足し、かつ耐食性にすぐれたＲ−Ｆｅ−Ｂ系永久磁石とその製造方法の提供を目的としている。
【０００６】
【課題を解決するための手段】
発明者らは、磁気特性のすぐれたＲ−Ｆｅ−Ｂ系永久磁石を自動車用モーターに使用するため、耐食性のほか、電気絶縁性および耐熱性を改善向上するため、種々検討した結果、磁石表面をポリイミド樹脂により被履することにより、すぐれた磁気特性を具備するとともに、耐食性はもちろん、電気絶縁性および耐熱性を大きく改善向上することを知見した。
【０００７】
しかしながら、磁石表面にポリイミド樹脂を直接蒸着重合法にて被履する場合、重合反応時及びイミド化処理時に磁石表面に水分を生成して、前記水分と磁石表面が反応して磁石表面へのポリイミド樹脂の密着性を阻害する問題があることを知見し、さらに検討を加えた結果、磁石表面をイオンスパッター法等により清浄化した後、前記磁石体表面に真空蒸着法、プラズマスパッター法、イオンプレーティング等のＰＶＤ薄膜形成法により、カーボン膜層を形成すると、ポリイミド樹脂の蒸着重合時またはイミド化処理時の加熱により、カーボンがＲ−Ｆｅ−Ｂ系永久磁石表面に拡散し、特に、Ｒ−Ｆｅ−Ｂ系永久磁石表面のＢの一部とカーボンが置換するものと考えられ、また、カーボン膜層とポリイミド樹脂がＣ−Ｃ反応を生じて、ポリイミド樹脂膜の密着性が大きく改善されることにより、目的とする電気絶縁性・耐熱性・耐食性にすぐれたＲ−Ｆｅ−Ｂ系永久磁石が得られることを知見し、この発明を完成した。
【０００８】
すなわち、この発明は、
主相が正方晶からなるＲ−Ｆｅ−Ｂ系永久磁石体表面に、膜厚０．００５μｍ〜０．１μｍのカーボン膜層を介して膜厚２．０μｍ〜１０μｍのポリイミド膜層を有することを特徴とする電気絶縁性・耐熱性・耐食性にすぐれたＲ−Ｆｅ−Ｂ系永久磁石である。
【０００９】
また、この発明は、上記のＲ−Ｆｅ−Ｂ系永久磁石の製造方法として、
主相が正方晶からなるＲ−Ｆｅ−Ｂ系永久磁石体表面を清浄化した後、真空蒸着、スパッタ、イオンプレーティングのＰＶＤ薄膜形成法により前記磁石体面に膜厚０．００５μｍ〜０．１μｍのカーボン膜を形成後、前記磁石体を蒸着重合法により膜厚２．０μｍ〜１０μｍのポリイミド膜層を形成することを特徴とする電気絶縁性・耐熱性・耐食性にすぐれたＲ−Ｆｅ−Ｂ系永久磁石の製造方法を提案する。
【００１０】
さらに、この発明は、上記の製造方法において、
蒸着重合法は、真空度１Ｐａ〜１０−３Ｐａの真空容器でポリイミド膜の原料となる２種類のモノマーを２００℃〜２５０℃で加熱蒸着してポリアミック酸膜を形成後、常圧下、２８０℃〜３８０℃でイミド化処理を行ってポリイミド膜を生成する電気絶縁性・耐熱性・耐食性にすぐれたＲ−Ｆｅ−Ｂ系永久磁石の製造方法であり、また、
蒸着重合法に用いる２種類の原料モノマーは、芳香族カルボン酸二無水物と芳香族ジアミンである電気絶縁性・耐熱性・耐食性にすぐれたＲ−Ｆｅ−Ｂ系永久磁石の製造方法、を併せて提案する。
【００１１】
【発明の実施の形態】
この発明において、清浄化した磁石表面に設けるカーボン膜の厚みを０．００５μｍ〜０．１μｍに限定した理由は、０．００５μｍ未満では磁石表面との密着性が十分でなく、０．１μｍを越えると効果的には問題ないが、カーボン膜としてコスト上昇を招来して、実用的でなく好ましくないので、カーボン膜厚は０．００５μｍ〜０．１μｍとする。
また、下地金属膜の成膜方法は、真空蒸着、スパッタ、イオンプレーティングのＰＶＤ薄膜形成法がよい。
【００１２】
この発明においてポリイミド樹脂の厚みを２．０μｍ〜１０μｍに限定した理由は、２．０μｍ未満では被覆が十分でなく、電気絶縁性、耐熱性、耐食性にすぐれた被膜が得られず、１０μｍを越えると効果上は問題ないが、製造コスト上昇を招来するので実用的でなく、好ましくない。
【００１３】
この発明において、蒸着重合する真空容器の真空度を１Ｐａ〜１０−３Ｐａに限定した理由は、１Ｐａを越えると重合反応が不均一となり膜質が劣化し、また、１０−３Ｐａ未満ではモノマーの蒸発がきわめて少なく、安定した重合反応が生じないので好ましくないことによる。
【００１４】
また、蒸着重合時の基板磁石の温度は、１５０℃〜２００℃に設定するのが好ましく、１５０℃未満では磁石基板との密着が十分でなく、２００℃を越えると磁石基板上での蒸着重合反応がすみやかに進行しないため、基板磁石の温度は１５０℃〜２００℃に設定するとよい。
【００１５】
この発明において、蒸着重合に用いる２種類の原料モノマーは、芳香族カルボン酸二無水物、芳香族ジアミンであり、芳香族カルボン酸二無水物としてはピロメリット酸二無水物等があり、芳香族ジアミンとしてはジアミノジフェニルエーテル、ｐ−フェニレンジアミン等が用いられる。
【００１６】
また、真空容器内で２種類の原料モノマーを２００℃〜２５０℃で加速蒸着する理由は、２００℃未満では蒸発量が十分でなく、２５０℃を越えると蒸発速度が大きすぎて膜厚制御が難しく、好ましくない。
【００１７】
また、この発明において、ポリイミド樹脂を生成するイミド化温度は、２８０℃未満ではイミド化反応が十分に進行せず、下地膜との密着性が十分でなく、３８０℃を越えるとポリイミド樹脂が劣化して脆くなり亀裂等が生じて剥離を発生するため２８０℃〜３８０℃とする。
【００１８】
この発明の永久磁石に用いる希土類元素Ｒは、組成の１０原子％〜３０原子％を占めるが、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。
【００１９】
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（ミッシュメタル、ジジム等）を入手上の便宜等の理由により用いることができる。なお、このＲは純希土類元素でなくてもよく、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支えない。
【００２０】
Ｒは、Ｒ−Ｆｅ−Ｂ系永久磁石における必須元素であって、１０原子％未満では結晶構造がα−鉄を同一構造の立方晶組織となるため、高磁気特性、特に高保磁力が得られず、３０原子％を越えるとＲリッチな非磁性相が多くなり、残留磁束密度（Ｂｒ）が低下してすぐれた特性の永久磁石が得られない。よって、Ｒはｌ０原子％〜３０原子％の範囲が望ましい。
【００２１】
Ｂは、上記系永久磁石における必須元素であって、２原子％未満では菱面体構造が主相となり高い保磁力（ｉＨｃ）は得られず、２８原子％を越えるとＢリッチな非磁性相が多くなり、残留磁束密度（Ｂｒ）が低下するため、すぐれた永久磁石が得られない。よって、Ｂは２原子％〜２８原子％の範囲が望ましい。
【００２２】
Ｆｅは、上記系永久磁石において必須元素であり、６５原子％未満では残留磁束密度（Ｂｒ）が低下し、８０原子％を越えると高い保磁力が得られないので、Ｆｅは６５原子％〜８０原子％の含有が望ましい。
【００２３】
また、Ｆｅの一部をＣｏで置換することは、得られる磁石の磁気特性を損うことなく、温度特性を改善することができるが、Ｃｏ置換量がＦｅの２０％を越えると、逆に磁気特性が劣化するため好ましくない。Ｃｏの置換量がＦｅとＣｏの合計量で５原子％〜１５原子％の場合は、（Ｂｒ）は置換しない場合に比較して増加するため、高磁束密度を得るために好ましい。
【００２４】
また、Ｒ、Ｂ、Ｆｅの他、工業的生産上不可避的不純物の存在を許容でき、例えば、Ｂの一部を４．０ｗｔ％以下のＣ、２．０ｗｔ％以下のＰ、２．０ｗｔ％以下のＳ、２．０ｗｔ％以下のＣｕのうち少なくとも１種、合計量で２．０ｗｔ％以下で置換することにより、永久磁石の製造性改善、低価格化が可能である。
【００２５】
さらに、Ａｌ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｂｉ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｓｂ、Ｇｅ、Ｓｎ、Ｚｒ、Ｎｉ、Ｓｉ、Ｚｎ、Ｈｆ、のうち少なくとも１種は、Ｒ−Ｆｅ−Ｂ系永久磁石に対してその保磁力、減磁曲線の角型性を改善あるいは製造性の改善、低価格化に効果があるため添加することができる。なお、添加量の上限は、磁石材料の（ＢＨ）ｍａｘを２０ＭＧＯｅ以上とするには、（Ｂｒ）が少なくとも９ｋＧ以上必要となるため、該条件を満す範囲が望ましい。
【００２６】
また、この発明の永久磁石は平均結晶粒径が１〜８０μｍの範囲にある正方晶系の結晶構造を有する化合物を主相とし、体積比で１％〜５０％の非磁性相（酸化物相を除く）を含むことを特徴とする。
この発明による永久磁石は、保磁力ｉＨｃ≧１ｋＯｅ、残留磁束密度Ｂｒ＞４ｋＧ、を示し、最大エネルギー積（ＢＨ）ｍａｘは、（ＢＨ）ｍａｘ≧１０ＭＧＯｅを示し、最大値は２５ＭＧＯｅ以上に達する。
【００２７】
この発明は、磁石表面をイオンスパッター法等により清浄化した後、前記磁石体表面に真空蒸着、スパッタ、イオンプレーティングのＰＶＤ薄膜形成法により、Ｒ−Ｆｅ−Ｂ系永久磁石との密着性及びポリイミド樹脂との密着性の良好な特定膜厚のカーボン膜を形成後、その上にポリイミド樹脂を蒸着重合により形成することにより、目的とする電気絶縁性、耐熱性、耐食性にすぐれ、特に自動車用モーターに使用可能な高性能Ｒ−Ｆｅ−Ｂ系永久磁石が得られることを特徴とする。
【００２８】
【実施例】
１５Ｎｄ−７７Ｆｅ−８Ｂ（ａｔ％）組成の鋳造インゴットを粉砕し、微粉砕後に成形、焼結、熱処理後に径１２ｍｍ×２ｍｍ寸法の磁石体試験片を得た。その磁石特性を表１に示す。
真空容器内を１×１０−３Ｐａ以下に真空排気し、Ａｒガス圧１０Ｐａ、−５００Ｖで１５分間表面スパッターを行って、磁石体表面を清浄化した後、再度、真空容器内を１×１０−３Ｐａ以下に真空排気し、１００Ｖ、４０Ａでカーボン棒を加熱して蒸発させ、磁石表面に０．０２μｍ厚にカーボン膜を形成した。
【００２９】
真空容器内を１×１０−２Ｐａの真空度に設定し、１つの蒸発源としてピロメリット酸二無水物を２２０℃で加熱するとともに、もう１つの蒸発源としてジアミノジフエニルエーテルを２１０℃で加熱して、さらに磁石基板を１７０℃に加熱して、１時間処理を行い、原料モノマーを磁石表面に蒸着重合させてポリアミック酸被膜を生成させる。
【００３０】
次に常圧下、窒素雰囲気で３００℃で１時間加熱してイミド化処理を行い、ポリイミド樹脂膜を生成させることにより、ポリイミド樹脂膜を５μｍ厚に形成した。
【００３１】
その後、得られたポリイミド樹脂膜を表面に有する永久磁石試験片を、温度８０℃、相対湿度９０％の条件下で５００時間放置後に、その磁気特性および体積抵抗率、熱変形温度を測定した。その測定結果を表２に示す。
なお、体積抵抗率は電気絶縁性を評価するものであり、電極付けを行い、被膜表面と磁石間の抵抗を測定し、下記（１）式から求める。
【００３２】
ρ＝Ｒ・Ｓ／ｌ （１）式
ただし、ρ：体積抵抗率Ω・ｃｍ、Ｒ：抵抗Ω、Ｓ：電極面積ｃｍ２、ｌ：ポリイミド膜厚さｃｍ
また、熱変形温度は耐熱性を評価するものであり、大気中２０時間その温度に放置して被膜の変色、亀裂等が生じる温度とした。
【００３３】
比較例１
実施例１と同一組成の磁石体試験片を実施例１と同一条件にて表面清浄化した後、実施例１と同一条件にて磁石表面に直接ポリイミド樹脂膜を５μｍ厚形成した。
その後、実施例１と同一の温度８０℃、相対湿度９０％の条件下で５００時間放置後の磁気特性および体積抵抗率、熱変形温度を測定し、その結果を表３に示す。
【００３４】
【表１】
【表２】
【発明の効果】
この発明によるＲ−Ｆｅ−Ｂ系永久磁石は、本系永久磁石表面に特定の所定膜厚みのカーボン層を介して、蒸着重合法によりポリイミド樹脂層にて被履したことにより、実施例に示すごとく、すぐれた電気絶縁性、耐熱性並びに十分な耐食性を達成しており、Ｒ−Ｆｅ−Ｂ系永久磁石が本来有するすぐれた磁石特性を、多磁極型自動車モーター用永久磁石等の苛酷な用途に提供でき、モーターの小型軽量化に寄与することが可能である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement of an R-Fe-B-based permanent magnet and a method of manufacturing the same. A polyimide resin layer is formed by vapor deposition polymerization on a surface of a R-Fe-B-based permanent magnet through a carbon film layer having a predetermined thickness. The present invention relates to an R-Fe-B-based permanent magnet that is worn and achieves electrical insulation, heat resistance, and corrosion resistance required for a permanent magnet for an automobile motor and the like, and a method of manufacturing the same.
[0002]
[Prior art]
R-Fe-B permanent magnets have the best magnetic properties among magnets that have been put to practical use, but in order to use them as permanent magnets for multi-pole motors for automobiles, first, the permanent magnets are used. In order to prevent the generation of eddy currents generated in the magnets, it is necessary to wear a coating with excellent electrical insulation properties. The magnet used is required to have a coating having both heat resistance and corrosion resistance.
[0003]
R-Fe-B permanent magnets have the drawback of poor corrosion resistance and poor temperature characteristics of magnetic properties. Therefore, it has been proposed to wear a resin on the magnet surface to improve the corrosion resistance (Japanese Patent Application Laid-Open No. 60-63902). However, even though the corrosion resistance is improved by the above method, there is a problem that the heat resistance is not sufficient and the electrical insulation is poor, and R-Fe-B-based permanent magnets having excellent magnetic properties are used for automobile motors. The cause is that it cannot be used.
[0004]
[Problems to be solved by the invention]
Recently, in order to improve wear resistance, it has been proposed to apply a polyimide resin as a highly wear-resistant coating on a Ni-plated layer on a magnetic pole surface of an iron core and a magnetic pole surface of an actuator by a vapor deposition polymerization method, respectively (Japanese Patent Laid-open No. Although the effect of improving and improving the abrasion resistance of the opposed magnetic pole surface of the relay can be obtained, the coating strength required for the R-Fe-B permanent magnet of the multi-pole motor for automobile is improved. It is not excellent and does not satisfy electrical insulation, heat resistance and corrosion resistance.
[0005]
An object of the present invention is to provide an R-Fe-B-based permanent magnet which satisfies the electrical insulation and heat resistance required for a permanent magnet of a multi-pole type motor for an automobile and has excellent corrosion resistance, and a method for producing the same. And
[0006]
[Means for Solving the Problems]
The present inventors have conducted various studies to use R-Fe-B-based permanent magnets having excellent magnetic properties in motors for automobiles and to improve and improve electrical insulation and heat resistance in addition to corrosion resistance. It has been found that, by wearing a polyimide resin with a polyimide resin, excellent magnetic properties are provided, and not only corrosion resistance, but also electrical insulation and heat resistance are greatly improved.
[0007]
However, when a polyimide resin is directly applied to the magnet surface by vapor deposition polymerization, moisture is generated on the magnet surface during the polymerization reaction and during the imidization treatment, and the moisture reacts with the magnet surface to cause polyimide on the magnet surface. After finding out that there is a problem of inhibiting the adhesion of the resin, and further studying the results, after cleaning the magnet surface by an ion sputtering method or the like, a vacuum evaporation method, a plasma sputtering method, an ion When a carbon film layer is formed by a PVD thin film forming method such as a heating method, carbon is diffused on the surface of the R-Fe-B permanent magnet by heating during vapor deposition polymerization of a polyimide resin or imidization treatment. It is considered that a part of B on the surface of the Fe-B-based permanent magnet is replaced by carbon, and the carbon film layer and the polyimide resin cause a C-C reaction to cause By adhesion bromide resin film is greatly improved, and found that R-Fe-B permanent magnets with excellent electrical insulation, heat resistance and corrosion resistance of interest is obtained, and have completed the present invention.
[0008]
That is, the present invention
On the surface of the R-Fe-B permanent magnet body whose main phase is tetragonal, a polyimide film layer having a thickness of 2.0 μm to 10 μm is provided via a carbon film layer having a thickness of 0.005 μm to 0.1 μm. R-Fe-B-based permanent magnets with excellent electrical insulation, heat resistance and corrosion resistance.
[0009]
Further, the present invention provides a method for producing the above R-Fe-B permanent magnet,
After cleaning the surface of the R-Fe-B-based permanent magnet body whose main phase is a tetragonal crystal, a film thickness of 0.005 μm to 0.1 μm is formed on the magnet body surface by a PVD thin film forming method of vacuum deposition, sputtering, or ion plating. R-Fe-B having excellent electrical insulation, heat resistance and corrosion resistance, characterized in that after forming the carbon film, a polyimide film layer having a thickness of 2.0 μm to 10 μm is formed on the magnet body by vapor deposition polymerization. We propose a method of manufacturing permanent magnets.
[0010]
Further, the present invention provides the above-mentioned production method,
In the vapor deposition polymerization method, two kinds of monomers as a raw material of a polyimide film are heated and vapor-deposited at 200 ° C. to 250 ° C. in a vacuum vessel having a degree of vacuum of 1 Pa to 10 −3 Pa to form a polyamic acid film. A method for producing an R-Fe-B-based permanent magnet having excellent electrical insulation, heat resistance, and corrosion resistance by performing an imidization treatment at ~ 380 ° C to produce a polyimide film;
The two types of raw material monomers used in the vapor deposition polymerization method are an aromatic carboxylic acid dianhydride and an aromatic diamine, a method for producing an R-Fe-B-based permanent magnet having excellent electrical insulation, heat resistance, and corrosion resistance. To suggest.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the reason for limiting the thickness of the carbon film provided on the cleaned magnet surface to 0.005 μm to 0.1 μm is that if the thickness is less than 0.005 μm, the adhesion to the magnet surface is not sufficient, and the thickness exceeds 0.1 μm. Although this is not a problem, the carbon film increases the cost and is not practical and not preferable. Therefore, the carbon film thickness is set to 0.005 μm to 0.1 μm.
As a method for forming the underlying metal film, a PVD thin film forming method of vacuum deposition, sputtering, or ion plating is preferable.
[0012]
The reason for limiting the thickness of the polyimide resin to 2.0 μm to 10 μm in the present invention is that if the thickness is less than 2.0 μm, the coating is not sufficient, and a film excellent in electric insulation, heat resistance, and corrosion resistance cannot be obtained, and the thickness exceeds 10 μm. Although there is no problem in terms of effect, the production cost is increased, which is not practical and is not preferable.
[0013]
In the present invention, reasons for limiting the degree of vacuum in the vacuum chamber to deposit polymerization 1Pa~10 -3 Pa, the excess of 1Pa and polymerization reaction deteriorates the film quality becomes uneven, also monomers is less than 10 -3 Pa This is because the evaporation is extremely low and a stable polymerization reaction does not occur, which is not preferable.
[0014]
Further, the temperature of the substrate magnet during vapor deposition polymerization is preferably set to 150 ° C. to 200 ° C. If the temperature is lower than 150 ° C., the adhesion to the magnet substrate is not sufficient, and if it exceeds 200 ° C., the vapor deposition polymerization on the magnet substrate is performed. Since the reaction does not proceed promptly, the temperature of the substrate magnet is preferably set to 150 ° C to 200 ° C.
[0015]
In the present invention, two kinds of raw material monomers used for vapor deposition polymerization are an aromatic carboxylic dianhydride and an aromatic diamine. Examples of the aromatic carboxylic dianhydride include pyromellitic dianhydride and the like. As the diamine, diaminodiphenyl ether, p-phenylenediamine and the like are used.
[0016]
In addition, the reason why the two kinds of raw material monomers are acceleratedly vapor-deposited at 200 ° C. to 250 ° C. in a vacuum vessel is that the evaporation amount is not sufficient below 200 ° C. Difficult and undesirable.
[0017]
In the present invention, if the imidization temperature at which the polyimide resin is formed is lower than 280 ° C., the imidization reaction does not proceed sufficiently, the adhesion to the underlying film is not sufficient, and if the temperature exceeds 380 ° C., the polyimide resin deteriorates. The temperature is set to 280 ° C. to 380 ° C. because the brittle material is brittle, cracks and the like occur, and peeling occurs.
[0018]
The rare earth element R used in the permanent magnet of the present invention accounts for 10 to 30 atomic% of the composition, and at least one of Nd, Pr, Dy, Ho, and Tb, or further, La, Ce, Sm, and Gd. , Er, Eu, Tm, Yb, Lu, and Y are preferable.
[0019]
Usually, one kind of R is sufficient, but in practice, a mixture of two or more kinds (mish metal, dymium, etc.) can be used for reasons such as convenience in obtaining. Note that R may not be a pure rare earth element, and may contain impurities that are unavoidable in production within the industrially available range.
[0020]
R is an essential element in the R-Fe-B permanent magnet, and if it is less than 10 atomic%, the crystal structure has the same cubic structure as that of α-iron, so that high magnetic properties, particularly high coercive force, can be obtained. On the other hand, if it exceeds 30 atomic%, the number of R-rich non-magnetic phases increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R is desirably in the range of 10 at% to 30 at%.
[0021]
B is an essential element in the above-mentioned permanent magnet. When the content is less than 2 atomic%, the rhombohedral structure becomes a main phase, and a high coercive force (iHc) cannot be obtained. When the content exceeds 28 atomic%, a B-rich nonmagnetic phase is formed. As the residual magnetic flux density (Br) decreases, an excellent permanent magnet cannot be obtained. Therefore, B is desirably in the range of 2 to 28 atomic%.
[0022]
Fe is an essential element in the above-mentioned permanent magnet. When the content is less than 65 at%, the residual magnetic flux density (Br) decreases, and when it exceeds 80 at%, a high coercive force cannot be obtained. Atomic% is desirable.
[0023]
Further, by replacing part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet. However, when the amount of Co exceeds 20% of Fe, the conversely occurs. It is not preferable because the magnetic properties deteriorate. When the substitution amount of Co is 5 atomic% to 15 atomic% in the total amount of Fe and Co, (Br) increases as compared with the case where the substitution is not performed, so that it is preferable to obtain a high magnetic flux density.
[0024]
Further, in addition to R, B, and Fe, the presence of unavoidable impurities in industrial production can be tolerated. For example, a part of B may be 4.0 wt% or less of C, 2.0 wt% or less of P, 2.0 wt%. By substituting at least one of the following S and Cu of 2.0 wt% or less, with a total amount of 2.0 wt% or less, it is possible to improve the productivity of the permanent magnet and reduce the price.
[0025]
Further, at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, and Hf is R-Fe-B It can be added to the system permanent magnet because it has an effect of improving the coercive force and the squareness of the demagnetization curve, improving the productivity, and reducing the price. Note that the upper limit of the addition amount is desirably in a range that satisfies the condition because (Br) must be at least 9 kG or more in order to make (BH) max of the magnet material 20 MGOe or more.
[0026]
Further, the permanent magnet of the present invention comprises a compound having a tetragonal crystal structure having an average crystal grain size in a range of 1 to 80 μm as a main phase, and a nonmagnetic phase (oxide phase 1% to 50% by volume ratio). ).
The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe and a residual magnetic flux density Br> 4 kG, the maximum energy product (BH) max shows (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.
[0027]
According to the present invention, after the magnet surface is cleaned by an ion sputtering method or the like, the magnet body surface is vacuum-deposited, sputtered, and adhered to an R-Fe-B-based permanent magnet by a PVD thin film forming method of ion plating. After forming a carbon film of a specific thickness with good adhesion to the polyimide resin, by forming the polyimide resin on the carbon film by vapor deposition polymerization, the intended electrical insulation, heat resistance, excellent corrosion resistance, especially for automobiles A high-performance R-Fe-B permanent magnet usable for a motor is obtained.
[0028]
【Example】
A cast ingot having a composition of 15Nd-77Fe-8B (at%) was pulverized, molded, sintered, and heat-treated after fine pulverization to obtain a magnet test piece having a diameter of 12 mm x 2 mm. Table 1 shows the magnet characteristics.
The inside of the vacuum vessel was evacuated to 1 × 10 −3 Pa or less, the surface was sputtered at an Ar gas pressure of 10 Pa and −500 V for 15 minutes to clean the surface of the magnet body. Vacuum was exhausted to -3 Pa or less, and the carbon rod was heated and evaporated at 100 V and 40 A to form a carbon film having a thickness of 0.02 μm on the magnet surface.
[0029]
The inside of the vacuum vessel was set to a degree of vacuum of 1 × 10 −2 Pa, and pyromellitic dianhydride was heated at 220 ° C. as one evaporation source, and diaminodiphenyl ether was heated at 210 ° C. as another evaporation source. After heating, the magnet substrate is further heated to 170 ° C., and the treatment is performed for 1 hour, and a raw material monomer is vapor-deposited and polymerized on the magnet surface to form a polyamic acid film.
[0030]
Next, the polyimide resin film was heated at 300 ° C. for 1 hour under a normal pressure under a normal pressure to perform an imidization treatment to form a polyimide resin film, thereby forming a polyimide resin film having a thickness of 5 μm.
[0031]
Thereafter, the permanent magnet test piece having the polyimide resin film on the surface was allowed to stand at a temperature of 80 ° C. and a relative humidity of 90% for 500 hours, and then its magnetic properties, volume resistivity, and heat distortion temperature were measured. Table 2 shows the measurement results.
The volume resistivity is used to evaluate the electrical insulation. The electrode is attached, the resistance between the coating surface and the magnet is measured, and the volume resistivity is determined from the following equation (1).
[0032]
ρ = RS · l (1) where ρ: volume resistivity Ω · cm, R: resistance Ω, S: electrode area cm 2 , l: polyimide film thickness cm
The heat distortion temperature is used to evaluate heat resistance, and is set to a temperature at which the film is left at that temperature for 20 hours in the air to cause discoloration, cracks and the like of the film.
[0033]
Comparative Example 1
After a magnet body test piece having the same composition as in Example 1 was cleaned under the same conditions as in Example 1, a polyimide resin film having a thickness of 5 μm was formed directly on the magnet surface under the same conditions as in Example 1.
Thereafter, the magnetic properties, the volume resistivity, and the heat distortion temperature after being left for 500 hours under the same conditions as in Example 1 at a temperature of 80 ° C. and a relative humidity of 90% were measured, and the results are shown in Table 3.
[0034]
[Table 1]
[Table 2]
【The invention's effect】
The R-Fe-B-based permanent magnet according to the present invention is shown in Examples by being covered with a polyimide resin layer by a vapor deposition polymerization method via a carbon layer having a specific predetermined film thickness on the surface of the permanent magnet. As described above, excellent electrical insulation, heat resistance and sufficient corrosion resistance have been achieved, and the excellent magnet properties inherent in R-Fe-B permanent magnets are used in severe applications such as permanent magnets for multi-pole type automobile motors. To contribute to the reduction in size and weight of the motor.
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35467495A JP3576672B2 (en) | 1995-03-03 | 1995-12-25 | R-Fe-B permanent magnet with excellent electrical insulation, heat resistance and corrosion resistance, and method for producing the same |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7-70896 | 1995-03-03 | ||
| JP7089695 | 1995-03-03 | ||
| JP35467495A JP3576672B2 (en) | 1995-03-03 | 1995-12-25 | R-Fe-B permanent magnet with excellent electrical insulation, heat resistance and corrosion resistance, and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08306517A JPH08306517A (en) | 1996-11-22 |
| JP3576672B2 true JP3576672B2 (en) | 2004-10-13 |
Family
ID=26412019
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35467495A Expired - Lifetime JP3576672B2 (en) | 1995-03-03 | 1995-12-25 | R-Fe-B permanent magnet with excellent electrical insulation, heat resistance and corrosion resistance, and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3576672B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112662939B (en) * | 2020-12-16 | 2022-03-25 | 太原理工大学 | Ultrathin permanent magnet with surface deposited coating |
-
1995
- 1995-12-25 JP JP35467495A patent/JP3576672B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08306517A (en) | 1996-11-22 |
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