JP2004039949A

JP2004039949A - Superconductive member and magnetic levitation device

Info

Publication number: JP2004039949A
Application number: JP2002196817A
Authority: JP
Inventors: Mitsuru Morita; 森田　充; Hidekazu Tejima; 手嶋　英一
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2002-07-05
Filing date: 2002-07-05
Publication date: 2004-02-05
Anticipated expiration: 2022-07-05
Also published as: CN1299302C; CN1476024A; JP4220733B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconductive member and a magnetic levitation device wherein loss is little in rotation and translational movement. <P>SOLUTION: The superconductive member is composed of a plurality of superconductors. A part of a surface joining the superconductors of the superconductive member mutually is not orthogonal to any surface in contact with the junction surface of the superconductor. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、磁気浮上用超伝導部材及び超伝導磁気浮上装置に関し、特に、電力貯蔵用フライホイールや高速回転機器等に用いられる超伝導軸受及びリニアモータ等の搬送機器等の磁気浮上装置に関する。
【０００２】
【従来の技術】
超伝導軸受は、超伝導体と磁石との間のピンニング効果を利用したものであり、物体を制御なしで非接触で安定に浮上・回転できる機能を有する軸受である。超伝導軸受における超伝導体と磁石の位置関係には、主にアキシャル軸受型配置とラジアル軸受型配置がある。図１に示すように、アキシャル軸受型配置では、超伝導体と磁石は軸方向に対向している。一方、図２に示すように、ラジアル軸受型配置では、超伝導体と磁石は動径方向に対向している。
【０００３】
超伝導軸受には、単結晶状に作製された大型の酸化物系超伝導体が用いられる。しかし、単結晶状の酸化物系超伝導体には結晶方位による異方性があり、結晶の　ｃ軸に平行な方向と、結晶の　ｃ軸に垂直な方向、すなわち結晶の　ａ軸と　ｂ軸で形成する　ａ−ｂ面内に平行な方向との間で、超伝導特性が大きく異なる。その結果、磁石に対する超伝導体の結晶方位をどちらに向けるかによって浮上力が大きく異なる。従来は、浮上力を大きくするため、超伝導体の　ｃ軸を磁石の方に向ける、すなわち超伝導体の　ｃ軸が磁石の面に垂直になるような結晶配置で用いられるのが一般的であった。すなわち、アキシャル軸受型配置では、超伝導体の　ｃ軸は軸方向に向いたアキシャル配向であり、ラジアル軸受型配置では、超伝導体の　ｃ軸は動径方向を向いたラジアル配向であった。
【０００４】
アキシャル軸受型配置では、軸受を構成する超伝導体全体の　ｃ軸をアキシャル配向させることは可能である。しかしながら、ラジアル軸受型配置では、軸受を構成する超伝導体の　ｃ軸を軸受全周にわたってラジアル配向させることは、単一の結晶では不可能である。従って、従来技術としては、図２に示すように、いくつかの試料を作製し、それぞれを扇形状に加工し、それらを組み合わせて１つの軸受を構成する超伝導体とし、軸受を構成する個々の要素部材の　ｃ軸をラジアル配向させる手法がとられている。このとき、個々の扇形状部材間の接合方法は、個々の部材を単に冷却容器に収納することによって物理的に接合しているだけか、あるいは冷却容器に収納する際にお互いに接着剤で接合固定しているだけである。上記従来技術は、特開２００１−２４８６４２号公報に記載されている。
また、回転運動する軸受に対し、並進運動する磁気浮上装置には、リニアモータ搬送装置等がある。図３に超伝導搬送装置の基本構造を示す。
【０００５】
【発明が解決しようとする課題】
しかしながら、図１、図２及び図３のように複数の超伝導体で超伝導軸受を作製すると、個々の超伝導要素部材は単に物理的に結合されているだけであり、各要素部材間の境界では超伝導電流は流れない。しかも、ラジアル型軸受の場合、厳密には個々の要素部材の　ｃ軸がラジアル配向している部分は要素部材の中央部だけであり、中央部からずれるにつれて　ｃ軸と動径方向とのずれは大きくなる。そのため、軸受全体としての超伝導体の　ｃ軸が動径方向へ配向している度合いを改善するには、要素部材の数を多くすることになるが、このことは逆に超伝導電流の流れない要素部材間の境界の数も増やすことになる。従って、ラジアル軸受型配置においては、従来の方法では、軸受全体の結晶の配向性を向上させることと、超伝導電流が流れない境界面の数を低減させることが、相反する性質を有しているため、浮上力及び回転損失を改善することが難しいという問題があった。
【０００６】
また、アキシャル軸受型配置でも、軸受サイズが大きくなると、単結晶状の超伝導体を一体もので作製することは困難なので、複数の超伝導体を組み合わせることになる。この場合にも、個々の超伝導体間に超伝導電流が流れないので、浮上力及び回転損失を改善することが難しいという問題があった。
【０００７】
このような課題に対し、図４及び図５に示すように、超伝導体を積層構造にし、かつ、隣り合う層毎に超伝導部材同士の境界面の位置がずれるようにすることによって、全体としての超伝導体の特性の均一化を図ることが、特開２００１−２４８６４２号公報に記載されている。
【０００８】
複数の超伝導部材からなる超伝導磁気軸受において、個々の部材の継ぎ目、及び個々の超伝導体内の特性不均質は、全体としての超伝導体の不均一性として現れる。軸受または搬送装置に荷重等の負荷が加えられた時、超伝導体は実質的に超伝導磁石として機能し、載荷力（又は反発力、又は浮上力）を発生する。この全体としての不均質は、不均質な超伝導磁石の原因になり、たとえ永久磁石の本来の特性が均質であったとしても、回転又は並進運動時には永久磁石内に誘導電流を誘起し、エネルギー損失をもたらす。　また、さらには、永久磁石の見掛けの磁場分布均質性を低下させる。このようなエネルギー損失は、超伝導フライホイールエネルギー貯蔵装置用軸受の場合、特に低減する必要がある。
【０００９】
本発明は、上記の問題を解決し、より簡便でかつ経済的に回転及び並進運動時に損失の少ない超伝導部材及び磁気浮上装置を提供することである。
【００１０】
【課題を解決するための手段】
本願発明は、以下のとおりである。
（１）複数の超伝導体からなる超伝導部材であって、該超伝導部材の超伝導体同士を接合した面の少なくとも一部が、該超伝導体の接合面に接する面の何れかの面と、直交しないことを特徴とする超伝導部材。
（２）前記超伝導部材がリング形状を有する部材である（１）記載の超伝導部材。
（３）前記超伝導体接合面の少なくとも一部が、前記超伝導体の接合面に接する面の何れかと、０°超４５°以下の交差角度を有する（１）又は（２）に記載の超伝導部材。
（４）前記超伝導体接合面の少なくとも一部が平面である（１）〜（３）の何れかに記載の超伝導部材。
（５）磁石と（１）〜（４）の何れかに記載の超伝導部材を少なくとも有する超伝導磁気浮上装置。
（６）磁石と超伝導部材とが動径方向に対向するラジアル型配置の超伝導磁気軸受であって、前記超伝導部材が（１）〜（４）の何れかに記載の磁気浮上用超伝導部材である超伝導磁気軸受。
（７）前記超伝導部材を構成する個々の超伝導体が単結晶状であり、かつ、該超伝導体の結晶学的　ｃ軸と回転軸とのなす角度が９０°±３０°の範囲内にある（６）記載の超伝導磁気軸受。
（８）前記　ｃ軸と回転軸とのなす角度が９０°である（７）記載の超伝導磁気軸受。
（９）前記超伝導部材を構成する個々の超伝導体が単結晶状であり、かつ、該超伝導体の結晶学的　ｃ軸と回転軸とのなす角度が０°±３０°の範囲内にある（６）記載の超伝導磁気軸受。
（１０）前記　ｃ軸と回転軸とのなす角度が０°である（９）記載の超伝導磁気軸受。
（１１）磁石と超伝導部材とが軸方向に対向するアキシャル型配置の超伝導磁気軸受であって、前記超伝導部材が（１）〜（４）の何れかに記載の磁気浮上用超伝導部材である超伝導磁気軸受。
（１２）前記超伝導部材を構成する個々の超伝導体が単結晶状であり、かつ、該超伝導体の結晶学的　ｃ軸と回転軸とのなす角度が０°±３０°の範囲内にある（１１）記載の超伝導磁気軸受。
（１３）前記　ｃ軸と回転軸とのなす角度が０°である（１２）記載の超伝導磁気軸受。
【００１１】
【発明の実施の形態】
永久磁石と超伝導体との自立安定型の超伝導磁気浮上を例に、本発明の内容を詳述する。超伝導体が永久磁石の磁場中で超伝導状態に冷却され、その安定点で、永久磁石から発する磁束が超伝導体中に捕捉されている状況を考える。永久磁石が安定点から変位しようとした場合、永久磁石が安定点から変位するときに発生する磁束変化を打ち消すように、超伝導体内で超伝導電流が誘起される。この超伝導電流により超伝導体は磁石となり、永久磁石と超伝導磁石との間に力が作用する。この力が載荷力（反発力又は浮上力）と呼ばれるもので、安定点への復元力であり、安定磁気浮上の原理である。すなわち、磁気浮上において、超伝導体は永久磁石との変位に応じて強度を変化させる制御磁石として機能する。
【００１２】
したがって、超伝導磁気浮上状態において、永久磁石と超伝導体との相対的変位が発生する場合、永久磁石の磁場分布が均一であっても、超伝導体の特性が不均一な場合は、超伝導磁石の不均一磁場により永久磁石内で誘導電流が発生し、エネルギー損失が生じる。このような、エネルギー損失を軽減するには、均質な永久磁石を用い、かつ全体としてより均一な超伝導体を用いる必要がある。超伝導体の不均質の要因には、個々の超伝導体の不均質と、個々の超伝導体間の継ぎ目による不均質がある。本発明は、主に、超伝導体間の継ぎ目による不均質を比較的簡便に改善するものである。
【００１３】
超伝導体は磁石として機能することから、磁場中冷却等で着磁された個々の超伝導体及び継ぎ目の磁束分布を均質にすることが、相対運動を伴う磁気浮上におけるエネルギー損失の低減に寄与する。
【００１４】
図６に十分に着磁された２つの超伝導体について、超伝導体内の超伝導電流の流れ、矢印の方向から見た磁束分布、超伝導体表面での磁束密度を、図６（ａ）、図６（ｂ）、図６（ｃ）にそれぞれ模式的に示す。図６から、磁石と対向する超伝導体の面と超伝導体同士の接合面の全部が直交している場合は、接合面で極性が反転する等、磁束密度分布は大きく変化しており、きわめて不均質な超伝導磁石になることが分かる。
【００１５】
これに対して、磁石と対向する超伝導体の面と超伝導体同士の接合面の全部が直交せず、例えば、斜めに重なり合うようにして接合されている場合は、図７に示すように、接合面での磁場分布は、かなり改善される。本発明における超伝導部材の磁石との対向面と超伝導体接合面との交差角度とは、図７の場合、９０°以下の狭い方の角度を意味し、３０°となる。
【００１６】
通常、磁気浮上において、上述した十分に着磁された状態は、安定点から完全離れた状態に対応する。実際には、磁気浮上状態においては、比較的小さな変位に対し、超伝導体の一部にのみ電流が流れる状態で機能している。図６と図７の比較において、このような場合の磁場分布は、図７の接合がより均質な磁場分布を形成する。
【００１７】
上記原理に基づき、アキシャル型超伝導磁気軸受、ラジアル型超伝導磁気軸受、並進型搬送装置等を構成する場合、図１、図２、図３に示す従来の超伝導体に対し、図８ないし図１０に記載の超伝導体の接合構造が、エネルギー損失の面からより優れていることが分かる。
【００１８】
磁石と対向する超伝導体の面と超伝導体同士の接合面とが必ずしも斜めの平面接合である必要はない。図１１に接合面の形状の例を示す。図１１（ａ）のような曲面でもよいが、加工の容易さの点からは図１１（ｂ）の平面が好ましい。また、図１１（ｃ）ように磁石の対向面のみ接合し、反対面は接合面を形成しない方法は、均質性を大きく損なうことなく、より小型の超伝導材料で実現できることから、経済的に優れている。超伝導体間の接合界面には、非超伝導物質又はギャップ等が存在しない方が望ましいが、補強等の観点から必要な場合は、最小限にとどめることが望ましい。なお、本発明における対向面との交差角度は、接合面全部で直交していなければ良く、図１１（ｄ）及び図１１（ｅ）のように、一部に直交した部分を有する場合でも、他の接合面による改善効果により、全体として磁場分布が改善できる。
【００１９】
本発明に用いる超伝導体は、ピンニング効果を発揮し得るものであれば特に制限されるものではないが、好ましくは、ピンニング力の強い超伝導体が望ましい。後述する本実施例で用いた超伝導体は、ＱＭＧ材と呼ばれるもので、単結晶状のＲＥＢａ_２Ｃｕ_３Ｏ_ｘ相（ＲＥはＹを含む希土類元素及びその組み合わせ）中にＲＥ_２ＢａＣｕＯ_５相が微細分散している酸化物系超伝導体で、液体窒素温度でピンニング力の強い材料である（特許登録番号第１８６９８８４号）。
【００２０】
ＱＭＧ材は、超伝導相であるＲＥＢａ_２Ｃｕ_３Ｏ_ｘ相の結晶学的方位における　ｃ軸に垂直な面（ａ−ｂ面）間に劈開性が有り、ミクロなクラックが発生しやすい。そのため、図８ないし図１０及び図１２に示すような、ａ−ｂ面内に超伝導電流を誘起する軸受構造又は搬送装置構造をとることが望ましい。図９及び図１２は　ｃ軸と回転軸とのなす角度が０°の位置関係を示し、図８は、　ｃ軸と回転軸とのなす角度が９０°の場合を示す。また、図１０は、　ｃ軸と磁石の移動方向とが直交している場合を示す。
【００２１】
一方、「Ｐｒｏｃｅｅｄｉｎｇｓ　ｏｆ　ｔｈｅ　ｆｉｆｔｈ　Ｕ．Ｓ．−Ｊａｐａｎ　Ｗｏｒｋｓｈｏｐ　ｏｎ　ｈｉｇｈ　Ｔｃ　Ｓｕｐｅｒｃｏｎｄｕｃｔｏｒ（Ｎｏｖｅｍｂｅｒ　１０，１９９２，　ｐ９５，　Ｔｓｕｋｕｂａ，　Ｊａｐａｎ）」　にも記載されているように、単結晶状のＱＭＧ材の超伝導相には、結晶方位の揺らぎがある。　ｃ軸方向の揺らぎに関して、数ｍｍの範囲内では、±６°程度ある。また、数ｃｍの範囲内では、±３０°程度ある場合がある。この揺らぎは、隣り合う亜粒界の方位差は数°以内であるため、臨界電流密度を極端に低下させる弱結合とはならない。上記の理由から請求項７〜１３の超伝導体と　ｃ軸と軸受の回転軸との方位関係を限定した。
【００２２】
また、本発明に用いる磁石は、軸受構造が簡単になるので永久磁石が望ましいが、電磁石や超伝導磁石でもよい。超伝導体と対向する表面の磁束密度が大きいほど浮上力も大きくなるので、永久磁石を用いる場合には、希土類系の永久磁石のように表面磁束密度の大きい材料、例えば、Ｎｄ−Ｆｅ−Ｂ系や　Ｐｒ−Ｆｅ−Ｂ系、Ｓｍ−Ｃｏ系等の永久磁石が望ましい。
【００２３】
超伝導体を用いた磁気浮上装置や磁気軸受は、一般に、ギャップを適宜調整した上で、超伝導体が常伝導状態で永久磁石と対向させた後、液体窒素等の冷媒又は冷凍機等を用いて超伝導状態に冷却される。所定の温度に超伝導体が冷却された後、永久磁石の質量及びフライホイール等の質量が加わり、負荷が加わると超伝導体と磁石との無負荷での平衡状態から変位し、超伝導体中には超伝導電流が流れ、新たな平衡点に達する。
【００２４】
リニアモーターの場合は、並進運動を行うが、レールに対応する側が超伝導体であっても磁石であってもどちらでもよい。本発明の超伝導部材を用いたリニアモーターは、より均質な磁場分布を発生できるので、揺れの少ない安定した走行が可能となる。また、軸受においても、超伝導体の機械的強度の観点から回転子側が永久磁石である方が望ましいが、回転子側が超伝導体であってもよい。
【００２５】
【実施例】
（実施例１）
図１３（ａ）に示すように、厚さ５ｍｍ、幅２５ｍｍ、長さ約５０ｍｍの平面状の接合面を有する超伝導材料を２本、物理的に接合し、交差角度の異なる４組の超伝導部材を作製した。交差角度は９０°、４５°、３０°、２０°の４種類であり、図１３（ａ）は９０°の場合を示す。これらの超伝導体に対して、１Ｔ及び０．１４Ｔの磁場中で７７Ｋに冷却した後、外部磁場を取り除いたときの接合界面付近における超伝導材料表面の磁束密度分布を測定した。用いた超伝導材料は、単結晶状のＹＢａ_２Ｃｕ_３Ｏ_ｘ相中に１μｍ程度の　Ｙ_２ＢａＣｕＯ_５相が２０体積％程度分散している酸化物系超伝導体（ＱＭＧ材）で、　ＹＢａ_２Ｃｕ_３Ｏ_ｘ相の結晶学的方位におけるｃ軸が板面に垂直であるように作製した。磁場印加方向は、　ｃ軸と平行であり、主に超伝導材料のａ−ｂ面内に流れる超伝導電流による　ｃ軸方向の磁場を測定した。
【００２６】
図１３（ｂ）に、交差角度９０°の材料について、図１３（ａ）中の点線が示す接合部付近の超伝導磁束密度分布を矢印が示す方向から見た様子を示す。接合部分で磁極が反転し、最低値を示す。表１及び表２に、同様に、各交差角度で接続した超伝導材料に対し、１Ｔ及び　０．１４Ｔ中で冷却した場合の磁束密度分布を示す。交差角度が４５°でも磁場分布を均一化する効果があり、３０°以下では、極めて大きな均一化効果があることが分かる。さらに、１Ｔ中で十分な着磁を行った場合よりも、比較的弱い磁場中　（０．１４Ｔ）で、超伝導体が十分に磁化していない着磁を行った場合の方が、均一化効果が大きく現れることが分かる。
【００２７】
以上のように、交差角度を小さくすることによって、超伝導磁石の均質化が図られ、並進及び回転運動を伴う磁気浮上装置において、磁石との相対運動による損失が低減できることが明らかになった。
【００２８】
【表１】

【００２９】
【表２】

【００３０】
（実施例２）
図１４に示すように、外径１８０ｍｍ、内径１００ｍｍ、厚さ１５ｍｍの８分割された超伝導バルク材料と外径１７０ｍｍ、内径１２０ｍｍ、厚さ１０ｍｍのＳｍ−Ｃｏ系永久磁石を対向させ、アキシャル型超伝導磁気軸受を構成し、回転数の減衰率を測定した。超伝導材料は、単結晶状のＹＢａ_２Ｃｕ_３Ｏ_ｘ相中に１μｍ程度のＹ_２ＢａＣｕＯ_５相が２０体積％程度分散している酸化物系超伝導体（ＱＭＧ材）で、ＹＢａ_２Ｃｕ_３Ｏ_ｘ相の　ｃ軸が回転軸と平行であるように作製した。交差角度は３０°である。永久磁石は継ぎ目を有しない一体ものであり、着磁は、回転軸と平行に磁場が発生するように行った。
【００３１】
真空チャンバー内において、永久磁石と超伝導材料とを１０ｍｍ離した状態で超伝導体を液体窒素中（７７Ｋ）に冷却した。３０００ｒｐｍまで高速回転させた後、２５００ｒｐｍまでに減衰する時間から、減衰率を評価したところ　２．０％／ｈであった。
比較材として、交差角度が９０°の上記８分割された超伝導バルク材料を作製し、同様の実験を行ったところ、減衰率は、４．０％／ｈであった。
これらの比較から、交差角度が３０°の場合、９０°の場合と比べ、極めて減衰率が低くなり、損失が低下することが明らかになった。
【００３２】
（実施例３）
図１５に示すような、外径１２０ｍｍ、内径１００ｍｍ、高さ５０ｍｍの８分割された超伝導バルク材料と、外径１４６ｍｍ、内径１２６ｍｍ、厚さ４０ｍｍの　Ｓｍ−Ｃｏ系永久磁石を対向させ、アキシャル型超伝導磁気軸受を構成し、回転数の減衰率を測定した。超伝導材料は、単結晶状のＧｄＢａ_２Ｃｕ_３Ｏ_ｘ相中に１μｍ程度のＧｄ_２ＢａＣｕＯ_５相が２０体積％程度分散し、かつ数百μｍの銀粒子が１５体積％程度分散している酸化物系超伝導体（ＱＭＧ材）で、ＧｄＢａ_２Ｃｕ_３Ｏ_ｘ相の　ｃ軸が回転軸と垂直であるように作製した。交差角度は３５°である。永久磁石は継ぎ目を有しない一体ものであり、着磁は、回転軸と垂直に磁場が発生するように行った。
【００３３】
真空チャンバー内において、永久磁石と超伝導材料と隙間を３ｍｍ離した状態で超伝導体を液体窒素温度（７７Ｋ）に冷却した。３０００ｒｐｍまで高速回転させた後、２５００ｒｐｍまでに減衰する時間から減衰率を評価したところ　２．８％／ｈであった。比較材として、交差角度が９０°の上記８分割された超伝導バルク材料を作製し、同様の実験を行ったところ、減衰率は、４．６％／ｈであった。
これらの比較から、交差角度が３５°の場合、９０°の場合と比べ、極めて減衰率が低くなり、損失が低下することが明らかになった。
【００３４】
【発明の効果】
以上で述べたように、本願発明の超伝導部材や超伝導磁気浮上装置は、回転又は平行移動にともなう損失が小さく、電力貯蔵用フライホイールや高速回転機器等に用いられる超伝導軸受及びリニアモータ等の搬送機器等の磁気浮上装置に好適に用いることができ、その工業的効果は甚大である。
【図面の簡単な説明】
【図１】従来のアキシャル型超伝導磁気軸受の永久磁石と超伝導部材の配置例と、これに用いる超伝導部材の例
【図２】従来のラジアル型超伝導磁気軸受の永久磁石と超伝導部材の配置例と、これに用いる超伝導部材の例
【図３】従来の並進浮上型装置の永久磁石と超伝導部材の配置例と、これに用いる超伝導部材の例
【図４】継ぎ目を覆うように超伝導材料を配置した従来技術の例
【図５】継ぎ目を覆うように超伝導材料を配置した従来のラジアル型超伝導磁気軸受の用超伝導部材の例
【図６】（ａ）十分に着磁された２つの超伝導体（交差角度＝９０°）及び超伝導電流の流れと（ｂ）これの矢印方向から見た磁束分布、（ｃ）超伝導体表面での磁束密度
【図７】（ａ）十分に着磁された２つの超伝導体（交差角度＝３０°）及び超伝導電流の流れと、（ｂ）これの矢印の方向から見た磁束分布、（ｃ）超伝導体表面での磁束密度
【図８】本発明のラジアル型超伝導磁気軸受の用超伝導部材の例
【図９】本発明のアキシャル型超伝導磁気軸受の用超伝導部材
【図１０】本発明の並進浮上型装置の超伝導部材の例
【図１１】（ａ）〜（ｅ）はそれぞれ本発明における超伝導部材の接合面の例を示す図
【図１２】超伝導材料の　ｃ軸が軸方向と平行なラジアル型超伝導磁気軸受の超伝導部材の例
【図１３】（ａ）実施例１で用いた超伝導体の一例と、これにおける（ｂ）磁束密度分布
【図１４】実施例２で用いたアキシャル型磁気軸受用超伝導体
【図１５】実施例３で用いたラジアル型磁気軸受用超伝導体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic levitation superconducting member and a superconducting magnetic levitation device, and more particularly to a magnetic levitation device such as a superconducting bearing used in a power storage flywheel or a high-speed rotating device, or a conveying device such as a linear motor.
[0002]
[Prior art]
A superconducting bearing uses a pinning effect between a superconductor and a magnet, and has a function of stably floating and rotating an object without contact and without control. The positional relationship between the superconductor and the magnet in the superconducting bearing mainly includes an axial bearing type arrangement and a radial bearing type arrangement. As shown in FIG. 1, in the axial bearing type arrangement, the superconductor and the magnet face each other in the axial direction. On the other hand, as shown in FIG. 2, in the radial bearing type arrangement, the superconductor and the magnet face each other in the radial direction.
[0003]
A large oxide superconductor made in a single crystal form is used for the superconducting bearing. However, single crystal oxide superconductors have anisotropy due to crystal orientation, and the direction parallel to the c-axis of the crystal and the direction perpendicular to the c-axis of the crystal, that is, the a-axis and b-axis of the crystal The superconducting characteristics are greatly different from those in the direction parallel to the ab plane. As a result, the levitation force varies greatly depending on the orientation of the crystal orientation of the superconductor relative to the magnet. Conventionally, in order to increase the levitation force, it is common to use a crystal arrangement in which the c-axis of the superconductor is directed toward the magnet, that is, the c-axis of the superconductor is perpendicular to the surface of the magnet. there were. That is, in the axial bearing type arrangement, the c axis of the superconductor was axially oriented in the axial direction, and in the radial bearing type arrangement, the c axis of the superconductor was in the radial orientation oriented in the radial direction.
[0004]
In the axial bearing type arrangement, it is possible to orient the c-axis of the entire superconductor constituting the bearing. However, in the radial bearing type arrangement, it is not possible with a single crystal to radially orient the c-axis of the superconductor constituting the bearing over the entire circumference of the bearing. Therefore, as shown in FIG. 2, as a conventional technique, several samples are produced, each is processed into a fan shape, and they are combined to form a superconductor constituting one bearing, and individual bearings are constituted. A method is employed in which the c-axis of the element member is radially oriented. At this time, the method of joining the individual fan-shaped members is to physically join the individual members by simply storing them in the cooling container, or to bond them together with an adhesive when they are stored in the cooling container. It is only fixed. The above prior art is described in Japanese Patent Laid-Open No. 2001-248642.
Further, examples of the magnetic levitation device that translates with respect to the bearing that rotates include a linear motor conveyance device. FIG. 3 shows the basic structure of the superconducting transport device.
[0005]
[Problems to be solved by the invention]
However, when a superconducting bearing is made of a plurality of superconductors as shown in FIGS. 1, 2 and 3, the individual superconducting element members are merely physically coupled, and each element member Superconducting current does not flow at the boundary. In addition, in the case of radial type bearings, strictly speaking, the portion where the c-axis of each element member is radially oriented is only the central portion of the element member, and the deviation between the c-axis and the radial direction as it deviates from the center portion. growing. Therefore, in order to improve the degree of orientation of the c-axis of the superconductor as the entire bearing in the radial direction, the number of element members must be increased. The number of boundaries between missing element members will also increase. Therefore, in the radial bearing type arrangement, the conventional method has the contradictory properties of improving the crystal orientation of the entire bearing and reducing the number of boundary surfaces through which no superconducting current flows. Therefore, there is a problem that it is difficult to improve the flying force and the rotation loss.
[0006]
Further, even in the axial bearing type arrangement, when the bearing size is increased, it is difficult to produce a single crystal superconductor as a single body, and thus a plurality of superconductors are combined. Also in this case, since a superconducting current does not flow between the individual superconductors, there is a problem that it is difficult to improve the levitation force and the rotation loss.
[0007]
As shown in FIGS. 4 and 5, the superconductor has a laminated structure, and the boundary surface position between the superconductor members is shifted for each adjacent layer as shown in FIGS. Japanese Patent Laid-Open No. 2001-248642 discloses that the characteristics of the superconductor as described above are made uniform.
[0008]
In superconducting magnetic bearings composed of a plurality of superconducting members, the joints of the individual members and the characteristic inhomogeneities within the individual superconductors appear as non-uniformities in the superconductor as a whole. When a load such as a load is applied to the bearing or the conveying device, the superconductor substantially functions as a superconducting magnet and generates a loading force (or repulsive force or levitation force). This overall inhomogeneity causes inhomogeneous superconducting magnets, which induce induced currents in the permanent magnets during rotational or translational motions, even if the original properties of the permanent magnets are homogeneous. Cause loss. Furthermore, the apparent magnetic field distribution homogeneity of the permanent magnet is reduced. Such energy losses need to be reduced especially in the case of superconducting flywheel energy storage device bearings.
[0009]
The present invention solves the above-mentioned problems and provides a superconducting member and a magnetic levitation apparatus that are simpler and more economical and have less loss during rotation and translation.
[0010]
[Means for Solving the Problems]
The present invention is as follows.
(1) A superconducting member composed of a plurality of superconductors, wherein at least a part of a surface of the superconducting member joined to each other is in contact with the joining surface of the superconductor. A superconducting member that is not perpendicular to the surface.
(2) The superconducting member according to (1), wherein the superconducting member is a member having a ring shape.
(3) The superconductor joint surface according to (1) or (2), wherein at least a part of the superconductor joint surface has an intersection angle greater than 0 ° and 45 ° or less with any of the surfaces in contact with the superconductor joint surface. Superconducting member.
(4) The superconducting member according to any one of (1) to (3), wherein at least a part of the superconductor bonding surface is a flat surface.
(5) A superconducting magnetic levitation device having at least a magnet and the superconducting member according to any one of (1) to (4).
(6) A superconducting magnetic bearing having a radial arrangement in which a magnet and a superconducting member oppose each other in a radial direction, wherein the superconducting member is a magnetic levitation superconductor according to any one of (1) to (4) Superconducting magnetic bearing which is a conductive member.
(7) Each superconductor constituting the superconductor member is in a single crystal form, and the crystallographic c-axis of the superconductor and the angle formed by the rotation axis are within a range of 90 ° ± 30 °. The superconducting magnetic bearing according to (6).
(8) The superconducting magnetic bearing according to (7), wherein an angle formed between the c-axis and the rotating shaft is 90 °.
(9) Each superconductor constituting the superconducting member is in a single crystal form, and the crystallographic c-axis of the superconductor and the angle formed by the rotation axis are within the range of 0 ° ± 30 °. The superconducting magnetic bearing according to (6).
(10) The superconducting magnetic bearing according to (9), wherein an angle formed between the c-axis and the rotating shaft is 0 °.
(11) A superconducting magnetic bearing having an axial arrangement in which a magnet and a superconducting member face each other in the axial direction, wherein the superconducting member is the superconducting magnetic levitation according to any one of (1) to (4) Superconducting magnetic bearing as a member.
(12) Each superconductor constituting the superconductor member is in a single crystal form, and the crystallographic c-axis of the superconductor and the angle formed by the rotation axis are within a range of 0 ° ± 30 °. The superconducting magnetic bearing according to (11).
(13) The superconducting magnetic bearing according to (12), wherein an angle formed between the c-axis and the rotating shaft is 0 °.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The content of the present invention will be described in detail by taking a self-supporting and stable superconducting magnetic levitation of a permanent magnet and a superconductor as an example. Consider a situation where a superconductor is cooled to a superconducting state in a magnetic field of a permanent magnet, and a magnetic flux emitted from the permanent magnet is trapped in the superconductor at its stable point. When the permanent magnet is about to be displaced from the stable point, a superconducting current is induced in the superconductor so as to cancel the magnetic flux change that occurs when the permanent magnet is displaced from the stable point. With this superconducting current, the superconductor becomes a magnet, and a force acts between the permanent magnet and the superconducting magnet. This force is called loading force (repulsive force or levitation force), is a restoring force to a stable point, and is a principle of stable magnetic levitation. That is, in magnetic levitation, the superconductor functions as a control magnet that changes its strength in accordance with the displacement from the permanent magnet.
[0012]
Therefore, when the relative displacement between the permanent magnet and the superconductor occurs in the superconducting magnetic levitation state, even if the magnetic field distribution of the permanent magnet is uniform, the characteristics of the superconductor are not uniform. An inductive current is generated in the permanent magnet due to the non-uniform magnetic field of the conductive magnet, resulting in energy loss. In order to reduce such energy loss, it is necessary to use a homogeneous permanent magnet and to use a more uniform superconductor as a whole. Superconductor inhomogeneities include inhomogeneities of individual superconductors and inhomogeneities due to seams between individual superconductors. The present invention mainly improves the inhomogeneity caused by the joint between the superconductors relatively easily.
[0013]
Since superconductors function as magnets, making the magnetic flux distribution of individual superconductors and joints magnetized by cooling in a magnetic field etc. contribute to reducing energy loss in magnetic levitation with relative motion. To do.
[0014]
For the two superconductors sufficiently magnetized in FIG. 6, the flow of superconducting current in the superconductor, the magnetic flux distribution seen from the direction of the arrow, and the magnetic flux density on the superconductor surface are shown in FIG. FIG. 6B and FIG. 6C schematically show each. From FIG. 6, when the superconductor surface facing the magnet and the joint surface of the superconductors are all orthogonal, the magnetic flux density distribution is greatly changed, such as the polarity being reversed at the joint surface, It turns out that it becomes a very heterogeneous superconducting magnet.
[0015]
On the other hand, when the superconductor surface facing the magnet and the joint surface of the superconductors are not orthogonal to each other, for example, when they are joined so as to be obliquely overlapped, as shown in FIG. The magnetic field distribution at the joint surface is considerably improved. In the case of FIG. 7, the crossing angle between the surface of the superconducting member facing the magnet and the superconductor joint surface in the present invention means the narrower angle of 90 ° or less, and is 30 °.
[0016]
Usually, in the magnetic levitation, the above sufficiently magnetized state corresponds to a state completely separated from the stable point. Actually, in the magnetically levitated state, the current functions only in a part of the superconductor with respect to a relatively small displacement. In comparison between FIG. 6 and FIG. 7, the magnetic field distribution in such a case forms a more uniform magnetic field distribution in the junction of FIG.
[0017]
Based on the above principle, when an axial type superconducting magnetic bearing, a radial type superconducting magnetic bearing, a translational conveying device, or the like is constructed, the conventional superconductor shown in FIGS. It can be seen that the superconductor junction structure shown in FIG. 10 is superior in terms of energy loss.
[0018]
The surface of the superconductor facing the magnet and the joint surface between the superconductors do not necessarily have to be an oblique plane joint. FIG. 11 shows an example of the shape of the joint surface. Although a curved surface as shown in FIG. 11A may be used, the plane shown in FIG. 11B is preferable from the viewpoint of ease of processing. Moreover, as shown in FIG. 11 (c), the method in which only the opposing surfaces of the magnet are joined and the opposite surface is not formed can be realized with a smaller superconducting material without greatly impairing the homogeneity. Are better. It is desirable that a non-superconducting material or a gap or the like does not exist at the bonding interface between the superconductors, but it is desirable to minimize it when necessary from the viewpoint of reinforcement. It should be noted that the crossing angle with the facing surface in the present invention is not required to be orthogonal to the entire bonding surface, and even when it has a portion orthogonal to a part as shown in FIGS. 11 (d) and 11 (e), The magnetic field distribution can be improved as a whole due to the improvement effect of other joint surfaces.
[0019]
The superconductor used in the present invention is not particularly limited as long as it can exhibit a pinning effect, but a superconductor having a strong pinning force is preferable. The superconductor used in this example to be described later is called a QMG material, and a RE ₂ BaCuO ₅ phase in a single-crystal REBa ₂ Cu ₃ O _x phase (RE is a rare earth element including Y and a combination thereof). Is a finely dispersed oxide-based superconductor, which is a material having a strong pinning force at a liquid nitrogen temperature (Patent Registration No. 1869884).
[0020]
The QMG material has a cleavage property between planes (ab planes) perpendicular to the c-axis in the crystallographic orientation of the REBa ₂ Cu ₃ O _x phase, which is a superconducting phase, and micro cracks are likely to occur. Therefore, it is desirable to adopt a bearing structure or a transport device structure that induces a superconducting current in the ab plane as shown in FIGS. 8 to 10 and 12. 9 and 12 show the positional relationship where the angle between the c-axis and the rotation axis is 0 °, and FIG. 8 shows the case where the angle between the c-axis and the rotation axis is 90 °. FIG. 10 shows a case where the c-axis and the moving direction of the magnet are orthogonal.
[0021]
On the other hand, it is also described in "G-like material of Proceedings of the fifty US-Japan Workshop on high Tc Superconductor (November 10, 1992, p95, Tsukuba, Japan)". Has fluctuations in crystal orientation. The fluctuation in the c-axis direction is about ± 6 ° within a range of several mm. Further, within a range of several centimeters, there may be about ± 30 °. This fluctuation does not become a weak coupling that drastically lowers the critical current density because the orientation difference between adjacent subgrain boundaries is within several degrees. For the above reason, the azimuth relationship between the superconductor of claims 7 to 13, the c-axis and the rotation axis of the bearing is limited.
[0022]
The magnet used in the present invention is preferably a permanent magnet because the bearing structure is simplified, but an electromagnet or a superconducting magnet may be used. Since the levitation force increases as the magnetic flux density on the surface facing the superconductor increases, when a permanent magnet is used, a material having a high surface magnetic flux density such as a rare earth permanent magnet, for example, an Nd-Fe-B system Or, permanent magnets such as Pr—Fe—B and Sm—Co are desirable.
[0023]
In general, a magnetic levitation device or a magnetic bearing using a superconductor generally adjusts a gap, and after a superconductor is opposed to a permanent magnet in a normal state, a refrigerant such as liquid nitrogen or a refrigerator is used. Used to cool to a superconducting state. After the superconductor is cooled to a predetermined temperature, the mass of the permanent magnet and the mass of the flywheel are added. When a load is applied, the superconductor and the magnet are displaced from the unloaded equilibrium state, and the superconductor A superconducting current flows inside and reaches a new equilibrium point.
[0024]
In the case of a linear motor, translational motion is performed, but the side corresponding to the rail may be either a superconductor or a magnet. Since the linear motor using the superconducting member of the present invention can generate a more homogeneous magnetic field distribution, stable running with less shaking is possible. In the bearing, the rotor side is preferably a permanent magnet from the viewpoint of the mechanical strength of the superconductor, but the rotor side may be a superconductor.
[0025]
【Example】
Example 1
As shown in FIG. 13 (a), two superconducting materials having a planar joining surface having a thickness of 5 mm, a width of 25 mm, and a length of about 50 mm are physically joined to form four sets of superconductors having different crossing angles. A conductive member was produced. There are four types of crossing angles of 90 °, 45 °, 30 °, and 20 °, and FIG. 13A shows the case of 90 °. After these superconductors were cooled to 77K in 1T and 0.14T magnetic fields, the magnetic flux density distribution on the surface of the superconductive material in the vicinity of the junction interface when the external magnetic field was removed was measured. The superconducting material used is an oxide-based superconductor (QMG material) in which a Y ₂ BaCuO ₅ phase of about 1 μm is dispersed in a single crystal YBa ₂ Cu ₃ O _x phase by about 20% by volume. YBa The c-axis in the crystallographic orientation of the ₂ Cu ₃ O _x phase was made perpendicular to the plate surface. The magnetic field application direction was parallel to the c-axis, and the magnetic field in the c-axis direction due to the superconducting current flowing mainly in the ab plane of the superconducting material was measured.
[0026]
FIG. 13B shows the superconducting magnetic flux density distribution in the vicinity of the junction indicated by the dotted line in FIG. 13A viewed from the direction indicated by the arrow for the material having an intersection angle of 90 °. The magnetic pole reverses at the joint and shows the lowest value. Similarly, Table 1 and Table 2 show magnetic flux density distributions when the superconducting materials connected at each crossing angle are cooled in 1T and 0.14T. It can be seen that even when the crossing angle is 45 °, there is an effect of homogenizing the magnetic field distribution, and when it is 30 ° or less, there is an extremely large homogenizing effect. Furthermore, it is more uniform when magnetization is performed in a relatively weak magnetic field (0.14T) and the superconductor is not sufficiently magnetized than when magnetization is sufficiently performed in 1T. It turns out that the effect appears greatly.
[0027]
As described above, it has been clarified that by reducing the crossing angle, the superconducting magnet can be homogenized, and in the magnetic levitation apparatus with translational and rotational motion, loss due to relative motion with the magnet can be reduced.
[0028]
[Table 1]

[0029]
[Table 2]

[0030]
(Example 2)
As shown in FIG. 14, an eight-part superconducting bulk material having an outer diameter of 180 mm, an inner diameter of 100 mm, and a thickness of 15 mm is opposed to an Sm—Co-based permanent magnet having an outer diameter of 170 mm, an inner diameter of 120 mm, and a thickness of 10 mm. A superconducting magnetic bearing was constructed and the damping rate of the rotational speed was measured. The superconducting material is an oxide-based superconductor (QMG material) in which a Y ₂ BaCuO ₅ phase of about 1 μm is dispersed in a single crystal YBa ₂ Cu ₃ O _x phase by about 20% by volume, and YBa ₂ Cu. The c-axis of the ₃ O _x phase was prepared so as to be parallel to the rotation axis. The crossing angle is 30 °. The permanent magnet is an integral part having no seam, and magnetization was performed so that a magnetic field was generated in parallel with the rotation axis.
[0031]
In the vacuum chamber, the superconductor was cooled in liquid nitrogen (77K) with the permanent magnet and the superconductive material separated by 10 mm. When the rate of decay was evaluated from the time of decay to 2500 rpm after high-speed rotation to 3000 rpm, it was 2.0% / h.
As a comparative material, the above eight-divided superconducting bulk material having a crossing angle of 90 ° was produced, and the same experiment was performed. As a result, the attenuation factor was 4.0% / h.
From these comparisons, it was found that when the crossing angle is 30 °, the attenuation rate is extremely low and the loss is reduced as compared with the case of 90 °.
[0032]
(Example 3)
As shown in FIG. 15, an eight-part superconducting bulk material having an outer diameter of 120 mm, an inner diameter of 100 mm, and a height of 50 mm is opposed to an Sm-Co permanent magnet having an outer diameter of 146 mm, an inner diameter of 126 mm, and a thickness of 40 mm. A type superconducting magnetic bearing was constructed, and the decay rate of the rotational speed was measured. In the superconducting material, about 1 μm of Gd ₂ BaCuO ₅ phase is dispersed about 20% by volume in a single crystal GdBa ₂ Cu ₃ O _x phase, and several hundreds of μm silver particles are dispersed about 15% by volume. An oxide-based superconductor (QMG material) was prepared so that the c-axis of the GdBa ₂ Cu ₃ O _x phase was perpendicular to the rotation axis. The crossing angle is 35 °. The permanent magnet is an integral part without a seam, and magnetization was performed so that a magnetic field was generated perpendicular to the rotation axis.
[0033]
In the vacuum chamber, the superconductor was cooled to liquid nitrogen temperature (77 K) with a gap of 3 mm between the permanent magnet and the superconductive material. When the rate of decay was evaluated from the time of decay to 2500 rpm after high-speed rotation to 3000 rpm, it was 2.8% / h. As a comparative material, the above eight-divided superconducting bulk material having a crossing angle of 90 ° was produced and the same experiment was performed. As a result, the attenuation factor was 4.6% / h.
From these comparisons, it was found that when the crossing angle is 35 °, the attenuation rate is extremely low and the loss is reduced as compared with the case of 90 °.
[0034]
【The invention's effect】
As described above, the superconducting member and the superconducting magnetic levitation device of the present invention have a small loss due to rotation or parallel movement, and are used in power storage flywheels, high-speed rotating devices, and the like. It can be suitably used for a magnetic levitation device such as a transport device, and the industrial effect is enormous.
[Brief description of the drawings]
FIG. 1 shows an arrangement example of permanent magnets and superconducting members of a conventional axial type superconducting magnetic bearing and an example of superconducting members used therefor. FIG. 2 shows permanent magnets and superconducting parts of a conventional radial superconducting magnetic bearing. Example of arrangement of members and example of superconducting member used for this [Fig. 3] Example of arrangement of permanent magnet and superconducting member of conventional translational levitation type device, and example of superconducting member used for this [Fig. 4] Seam Example of prior art in which superconducting material is arranged to cover [FIG. 5] Example of superconducting member for conventional radial superconducting magnetic bearing in which superconducting material is arranged to cover seam [FIG. 6] (a) Two sufficiently superconductors (crossing angle = 90 °) and the flow of superconducting current, (b) magnetic flux distribution viewed from the direction of the arrow, (c) magnetic flux density on the superconductor surface FIG. 7 (a) Two fully magnetized superconductors (crossing angle = 30 °) and superconducting current. (B) Magnetic flux distribution viewed from the direction of the arrow, (c) Magnetic flux density on the surface of the superconductor [FIG. 8] Example of superconducting member for the radial superconducting magnetic bearing of the present invention FIG. 9 is a superconducting member for an axial superconducting magnetic bearing of the present invention. FIG. 10 is an example of a superconducting member of a translational levitation device of the present invention. FIG. 12 is a diagram showing an example of a joining surface of a superconducting member in FIG. 12. FIG. 13 is an example of a superconducting member of a radial superconducting magnetic bearing in which the c-axis of the superconducting material is parallel to the axial direction. FIG. 14 shows an example of a superconductor used in Example 2 and (b) magnetic flux density distribution in the superconductor. FIG. 14 shows a superconductor for an axial type magnetic bearing used in Example 2. FIG. 15 shows a radial type magnetic bearing used in Example 3. Superconductor

Claims

A superconducting member composed of a plurality of superconductors, wherein at least a part of a surface of the superconducting member joined to each other is in contact with the joining surface of the superconductor; A superconducting member that is not orthogonal.

The superconducting member according to claim 1, wherein the superconducting member is a member having a ring shape.

3. The superconducting member according to claim 1, wherein at least a part of the superconductor bonding surface has an intersecting angle of more than 0 ° and 45 ° or less with any of the surfaces in contact with the bonding surface of the superconductor.

The superconductor member according to claim 1, wherein at least a part of the superconductor joint surface is a flat surface.

A superconducting magnetic levitation apparatus having at least a magnet and the superconducting member according to claim 1.

A superconducting magnetic bearing having a radial arrangement in which a magnet and a superconducting member oppose each other in a radial direction, wherein the superconducting member is a superconducting member for magnetic levitation according to any one of claims 1 to 4. Conductive magnetic bearing.

The individual superconductors constituting the superconducting member are in a single crystal form, and the crystallographic c-axis and rotation axis of the superconductor are within a range of 90 ° ± 30 °. Item 7. The superconducting magnetic bearing according to Item 6.

The superconducting magnetic bearing according to claim 7, wherein an angle formed between the c-axis and the rotating shaft is 90 °.

The individual superconductors constituting the superconducting member are in a single crystal form, and the crystallographic c-axis and the rotation axis of the superconductor are within a range of 0 ° ± 30 °. Item 7. The superconducting magnetic bearing according to Item 6.

The superconducting magnetic bearing according to claim 9, wherein an angle formed between the c-axis and the rotating shaft is 0 °.

A superconducting magnetic bearing having an axial arrangement in which a magnet and a superconducting member face each other in the axial direction, wherein the superconducting member is the superconducting member for magnetic levitation according to any one of claims 1 to 4. Magnetic bearing.

The individual superconductors constituting the superconducting member are in a single crystal form, and the crystallographic c-axis and the rotation axis of the superconductor are within a range of 0 ° ± 30 °. Item 12. The superconducting magnetic bearing according to Item 11.

The superconducting magnetic bearing according to claim 12, wherein an angle formed between the c-axis and the rotating shaft is 0 °.