JP3580650B2

JP3580650B2 - Power resistor, method of manufacturing the same, and power circuit breaker

Info

Publication number: JP3580650B2
Application number: JP24741596A
Authority: JP
Inventors: 基真今井; 直樹首藤; 文雄上野
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1995-09-21
Filing date: 1996-09-19
Publication date: 2004-10-27
Anticipated expiration: 2016-09-19
Also published as: JPH09148111A

Description

【０００１】
【発明の属する技術分野】
本発明は、電力用抵抗体、その製造方法及び電力用遮断器に関し、具体的には、例えば高電圧装置、大容量コンデンサの充放電装置に用いられている中性点接地抵抗器、固定抵抗器、可変抵抗器、巻線抵抗器又は抵抗器アレーとして好適な電力用抵抗体、その製造方法及びその電力用抵抗体を投入抵抗体として備えた電力用遮断器に関する。
【０００２】
【従来の技術】
一般に、電力用抵抗器の材料は、金属系抵抗材料、金属酸化物系抵抗材料および非金属系抵抗材料に大別される。これらのうち、金属酸化物系抵抗材料は、他の材料に比べて耐熱性、耐電圧電流性および高電気エネルギーを吸収する耐エネルギー量が高いという特徴を有する。
【０００３】
代表的な金属酸化物系抵抗体としては、特開昭５８−１３９４０１号公報および特開昭５９−２１７６６８号公報に開示されている。
特開昭５８−１３９４０１号公報には、絶縁性の酸化アルミニウム結晶中に導電性のカーボン粉末を分散させ、粘土で焼き固めた炭素粒子分散型セラミック抵抗体が記載されている。かかる抵抗体としては、カーボン含有量が１．５〜２．０重量％であることが記載されている。
【０００４】
また、特開昭５９−２１７６６８号公報には、酸化アルミニウム、ムライト、焼成粘土の絶縁性無機質材料粉末に炭素粉末及び結合材を加え、混合、混練、加熱処理した原料を主原料として用いた炭素系電力用抵抗対について記載されており、このときの炭素粉末が０．１μｍ以下の微粉で、１．５〜５重量％の含有量であることが記載されている。
【０００５】
また、特開昭５７−５２１０１号公報には、酸化アルミニウムを主成分とし、他に酸化珪素、酸化マグネシウムなどの粘土材、さらに導電材としてのカーボンを３〜１０重量％含有量する抵抗部材について記載されている。
【０００６】
ところで、一般的に、酸化アルミニウム粉末にカーボン粉末を添加し焼結体を製造しようとすると、酸化アルミニウムの焼結性が阻害される。このため、前述した炭素粒子分散型セラミック抵抗体は、酸化アルミニウム粉末にカーボン粉末を添加しているため、酸化アルミニウムの焼結性が阻害される。このため、前述した炭素粒子分散型セラミック抵抗体は、酸化アルミニウム粉末にカーボン粉末を添加し、さらに酸化アルミニウム粉末の焼結性を補う目的で粘土を加えて焼結している。しかしながら、粘土の添加は単に酸化アルミニウムとカーボン粉末を結合させるが、焼結性を向上させないため、得られた抵抗体の気孔率は１０〜３０％と高く緻密性が低下しているため、次のような問題を招く。
【０００７】
すなわち、抵抗体の開閉時に発生するサージを吸収したり、遮断容量を増加させるために遮断接点と並列に接続される遮断器の投入抵抗体として用いた場合、抵抗体の緻密性の低下に起因して体積当りの熱容量が２Ｊ／ｃｍ^３・Ｋ程度と小さくなるために、サージ等のエネルギーの吸収に伴って抵抗体の温度上昇が著しくなる。また通電時にカーボン粉末が気孔内で放電を起こし、貫通放電が発生する。したがって、前述した炭素粒子分散型セラミック抵抗体を用い遮断器は、抵抗体の格納スペースが大きくなるとともに信頼性を確保するたには遮断容量を低く抑える必要があった。
【０００８】
さらに、このような抵抗体において、１０^３・Ω・ｃｍを超える高抵抗率の焼結体を得たい場合に、導電性をもたらすカーボン粒子がわずかな数で接続されることから製造条件の変動が敏感に反映されるため、優れた均一性をもつ焼結体を歩留まり良く製造することが困難であった。
【０００９】
また、米国特許第４４１８３２７号公報には、酸化アルミニウムとカーボンおよび焼結助材としての酸化マグネシウムを添加した抵抗体についての記載がある。しかしながら、このような抵抗体においても、十分緻密な焼結体を得ることは容易でなく、また、優れた均一性をもつ焼結体を歩留まり良く製造することは困難であった。
【００１０】
【発明が解決しようとする課題】
以上のように電力用抵抗体には、十分緻密でかつ高均一性を有する焼結体を歩留まりよく製造することが困難であるという問題がある。
また、特に緻密性の低下に伴い、熱容量の低下、顕著な温度上昇、貫通放電、格納スペースの増大、遮断容量の低下などの諸問題が発生する。
【００１１】
本発明は上記事情を考慮してなされたもので、単位体積あたりの熱容量が大きく、適切かつ安定した電気抵抗値を有し、サージ吸収による抵抗値の経時変化が小さく、焼結体の均一性に優れ、再現性良く製造可能な電力用抵抗体及びその製造方法を提供することを目的とする。
本発明の第２の目的は、遮断容量が大きく、遮断性能の安定した投入抵抗ユニットを備え、小型、高性能化を達成した電力用遮断器を提供することにある。
【００１２】
【課題を解決するための手段】
請求項１に対応する発明は、酸化アルミニウム及びカーボンを含む焼結体と、前記焼結体の対向する２つの面に形成された一対の電極とを具備した電力用抵抗体であって、前記焼結体としては、カーボン含有量が少ないかもしくはカーボンを含まない第１領域と、この第１領域よりカーボン含有量が多く、かつ前記一対の電極につながるように配置された第２領域とを有し、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを０．１〜５重量％の範囲で含んでいる電力用抵抗体である。
【００１３】
また請求項２に対応する発明は、酸化アルミニウム及びカーボンを含む焼結体と、前記焼結体の対向する２つの面に形成された一対の電極とを具備した電力用抵抗体であって、
前記焼結体は、
カーボン含有量が少ないかもしくはカーボンを含まない第１領域と、
この第１領域よりカーボン含有量が多く、かつ前記一対の電極に繋がるように配置された第２領域とを有し、
且つ二酸化珪素（ＳｉＯ_２）、酸化カルシウム（ＣａＯ）、酸化マグネシウム（ＭｇＯ）を二酸化珪素／酸化カルシウム／，酸化マグネシウムの含有比がモル比で３５〜６０／３０〜４５／５〜２５で合計量が０．１〜５重量％の範囲で含んでいることを特徴とする電力用抵抗体である。
【００１４】
また、請求項３に対応する発明は、請求項１に対応する電力用抵抗体において、前記第１の領域はカーボン含有量が１重量％未満であり、前記第２の領域はカーボン含有量が１〜１０重量％の範囲にある電力用抵抗体である。
【００１５】
さらに、請求項４に対応する発明は、請求項１に対応する電力用抵抗体において、前記第１の領域を形成する第１の造粒粉末に対し、前記第２の領域を形成する第２の造粒粉末が２０〜６０重量％の範囲で混合された電力用抵抗体である。
【００１６】
また、請求項５に対応する発明は、請求項１に対応する電力用抵抗体において、前記第２の領域の酸化アルミニウム粒子は平均粒径が０．４〜１μｍの範囲にあり、前記第１の領域の酸化アルミニウム粒子は前記第２の領域の酸化アルミニウム粒子の２〜５倍の大きさを有する電力用抵抗体である。
【００１７】
そして請求項６に対応する発明は、酸化アルミニウム及びカーボンを含む焼結体と、この焼結体の対向する２つの面に形成された一対の電極とを具備した電力用抵抗体であって、
前記焼結体は、
酸化アルミニウムの粒界に少なくとも二酸化珪素、酸化カルシウム及び酸化マグネシウムを含み
カーボン粒界には二酸化珪素、酸化カルシウム及び酸化マグネシウムを酸化アルミニウムの粒界より少ないか又は含まないように構成したことを特徴とする電力用抵抗体である。
【００１８】
さらに、請求項７に対する発明は、カーボン粉末が少ないかもしくはカーボン粉末を含まず、酸化アルミニウム粉末を含み、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを含有する第１の領域を形成する第１の造粒粉末を調整する工程と、前記第１の領域よりも多くカーボン粉末を含むと共に、酸化アルミニウムの粉末を含み、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを含有する第２の領域を形成する第２の造粒粉末を調整する工程と、前記第１の造粒粉末と前記第２の造粒粉末とを混合した後、成形、焼結することにより焼結体を作成する工程と、前記焼結体の対向する主面に一対の電極を形成する工程とを含んでいる電力用抵抗体の製造方法である。なおこの発明における焼結体は請求項２又は６のようなものであっても良い。
【００１９】
また、請求項８に対応する発明は、電流経路に配置される主開閉手段と前記電流経路に前記主開閉手段に対して電気的に並列に接続され、前記主開閉手段の閉状態への切替えよりも先行して閉状態に切替えられる補助開閉手段と、前記補助開閉手段に電気的に直列に接続され、焼結体及びこの焼結体の対抗する２つの面に形成された一対の電極を有する抵抗体が組み込まれ、前記焼結体としては、カーボン量が少ないかもしくはカーボンを含まない第１領域とこの第１領域よりカーボン量が多く含まれ、かつ前記一対の電極に繋がるように配置された第２領域とを有し、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを含む電力用遮断器である。
【００２０】
従って、請求項１に対応する発明は以上のような手段を講じたことにより、焼結体としては、カーボン含有量が少ないかもしくはカーボンを含まない第１領域と、この第１領域よりカーボン含有量が多く、かつ一対の電極に繋がるように配置された第２領域とを有し、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを０．１〜５重量％の範囲で含んでいるので、焼結体の緻密性及び均一性を向上できることにより、単位体積あたりの熱容量が大きく、適切かつ安定した電気抵抗値を有し、サージ吸収による抵抗値の経時変化が小さく、焼結体の均一性に優れ、再現性良く製造することができる。又請求項２に対応する発明のように第１の領域に含む二酸化珪素、酸化カルシウム、酸化マグネシウムのモル比を規定すれば、その効果はなお顕著である。
【００２１】
また、請求項３に対応する発明は、第１の領域はカーボン含有量が１重量％未満であり、第２の領域はカーボン含有量が１〜１０重量％の範囲にあるので、請求項１に対応する作用に加え、電力用抵抗体として好適な抵抗率と十分な緻密性とを確保することができる。
【００２２】
さらに請求項４に対応する発明は、第１の領域を形成する第１の造粒粉末に対し、第２の領域を形成する第２の造粒粉末が２０〜６０重量％の範囲で混合されているので、請求項１に対応する作用に加え、第２の領域どうしの電気的接続が容易な程度に含有される一方、第１の領域を無視するほどには含有されないので、容易に抵抗率を制御することができる。
【００２３】
また、請求項５に対応する発明は、第２の領域の酸化アルミニウム粒子は平均粒径が０．４〜１μｍの範囲にあり、第１の領域の酸化アルミニウム粒子は第２の領域の酸化アルミニウム粒子の２〜５倍の大きさを有するので、請求項１に対応する作用に加え、良好な焼結性を確保でき、且つ第２の造粒粉末の混合割合を、第１及び第２の造粒粉末の平均粒子径が等しい場合に比べて小さくすることができる。
【００２４】
さらに、請求項７に対応する発明は、カーボン粉末がすくないかもしくはカーボン粉末を含まず、酸化アルミニウム粉末を含み、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを含有する第１の領域を形成する第１の造粒粉末を調整する工程と、第１の領域よりも多くカーボン粉末を含むと共に、酸化アルミニウム粉末を含み、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを含有する第２の領域を形成する第２の造粒粉末を調整する工程と、第１の造粒粉末と第２の造粒粉末とを混合した後、成形、焼結することにより焼結体を作成する工程と、焼結体の対向する主面に一対の電極を形成する工程とを含んでいるので、請求項１に対応する作用と同様の作用を奏することができる。
【００２５】
また、請求項８に対応する発明は、請求項１に対応する焼結体からなる抵抗体を有しているので、遮断容量が大きく、遮断性能の安定した投入抵抗ユニットを備え、小型、高性能化を達成することができる。
【００２６】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参照しながら説明する。
図１は、本発明の実施の形態に係る電力用抵抗体の構成を示す断面図、図２は図１の焼結体の微構造を模式的に示す図、図３は図２の第２領域を拡大して模式的に示す図である。抵抗体１は、円板上の焼結体２と、焼結体２の円形両面に形成された一対の電極３と、焼結体２の外周面に被覆された絶縁層４とから構成されている。
【００２７】
焼結体２は、酸化アルミニウムおよびカーボン、二酸化珪素、酸化カルシウム、酸化マグネシウムを含む組成を有する。
焼結体２は、図２に示すように、カーボン量が少ないかもしくはカーボンを含まない第１領域５と、この第１領域５よりカーボン量の多い第２領域６とからなり、第１領域５は実質的に絶縁性を示し、第２領域６は導電性を示す。焼結体２において、第２領域６は３次元的なネットワーク構造で互いに接続されると共に、一対の電極３に繋がるように配置される。第２領域６の接続状態及び抵抗率により、焼結体２の抵抗値が制御される。
【００２８】
第２領域６は、図３に示すように、絶縁性の酸化アルミニウム粒子７の粒界に導電性のカーボン８が存在する形態を有し、カーボン８により複数の第２領域６を相互に電気的に接続している。
【００２９】
第２領域６では、該領域のカーボン含有量と、二酸化珪素（ＳｉＯ_２）、酸化カルシウム（ＣａＯ）、酸化マグネシウム（ＭｇＯ）を含む粉末原料の添加量とにより、該領域の抵抗率が制御可能となっている。比較的高抵抗率をもつ焼結体を得る場合、第２領域６の抵抗率を適度に大きくして第２の領域６間の接続数を十分大きくとることが可能となる。これにより、製造時の焼結雰囲気、温度分布等による焼結体内部の均一性への悪影響を相対的に小さくでき、製造歩留まりを向上できる。焼結体は、第１の領域の酸化アルミニウム粒子の会合部９と第２の領域のカーボン８の部分には、ＳｉＯ_２、ＣａＯ、ＭｇＯが存在し、焼結途中で液相を形成する。このため、焼結体にＳｉＯ_２、ＣａＯ、ＭｇＯを含む粉末原料の所定量の添加により、焼結が容易で、均一性良く、安定的に製造可能となっている。
【００３０】
本発明の電力抵抗体は、例えば以下のようにして作製可能である。
酸化アルミニウムは、平均粒子径が１μｍ以下であり、焼結性を良くするために好ましくは粒子径が０．５μｍ以下のものが原料粉末とされる。
【００３１】
カーボン粉末は、０．１μｍ以下の粒子径が焼結性の確保のために好ましく、微粉になる程好ましい。
このような酸化アルミニウム原料粉末と平均粒子径が０．１μｍ以下のカーボン粉末、およびＳｉＯ_２、ＣａＯ、ＭｇＯを含む粉末原料を水又は有機溶媒を用い、ボールミル中で混合し、第１及び第２の混合粉末をそれぞれ得る。
【００３２】
焼結体のカーボン含有量の異なる第１又は第２領域を形成する際に該領域のカーボン含有量は電機的性質に合わせて制御可能である。
すなわち、実質的に絶縁性の第１の領域を形成するためのカーボン含有量が少ない第１の混合粉末と、導電性の第２の領域を形成するためのカーボン含有量が多い第２の混合粉末とは、それぞれの電気的性質を表す範囲でカーボン含有量を制御可能である。第１領域及び第２領域におけるＳｉＯ_２、ＣａＯ、ＭｇＯを含む粉末原料についても同様に、電気的性質を表わす範囲内でその含有量を制御可能である。
【００３３】
これらカーボン含有量の異なる夫々の混合粉末に、成形体を作成するときのために所望により適宜パラフィン、ポリビニルアルコール等の成形用バインダーが添加可能であるが、この場合、これら成形用バインダーも焼結体中のカーボン原になるため、それを考慮し、予めカーボン粉末量の調整の必要がある。
【００３４】
成型用バインダーを添加混合後、メッシュを通過する等により造粒し、第１及び第２の造粒粉末が調整される。
夫々の造粒粉末を得る方法として、カーボン含有量の異なる第１の混合粉末と第２の混合粉末とを、夫々有機溶媒、成型用バインダーとともに混合し、スラリー化し、スプレードライヤー等を用いて、溶媒を除去することにより、第１の造粒粉末及び第２の造粒粉末とすることができる。
【００３５】
各造粒粉末は、所定の比率により、例えばＶ型ミキサーにより混合され、混合造粒粉末となる。混合造粒粉末を形成し、焼結し、焼結体とする。
成形は金型プレス、押出し及び射出成形などが適用可能である。金型成形を用いる場合、焼結体の密度を高めるために２００ｋｇ／ｃｍ^２以上の形成圧力が望ましい。なお、これ以下の成形圧力だと焼結体の相対密度が低く、単位体積当たりの熱容量が低下する。
【００３６】
焼成は非酸化ガス中で行なわれる脱脂の熱処理に続けて真空中または不活性ガス中、１３００〜１８００℃で１〜４時間保持することによって行われる。但し、脱脂の熱処理後、一度室温まで降温したのち再度昇温し焼成してもよい。
【００３７】
得られた焼結体の両主面を研磨し、溶射、焼き付け、スパッタリングなどの手段により一対の電極を形成する。この電極は、アルミニウムまたはニッケルなどから構成することが望ましい。
【００３８】
この後、焼結体の外周面および中空部の内周面に所望により、酸化アルミニウム、酸化ケイ素、ホウ珪酸ガラスの如き絶縁性セラミック、またはポリイミドのような樹脂を焼き付け、溶射または塗布、乾燥等により絶縁層を形成して抵抗体を製造する。
【００３９】
焼結体のカーボン含有量は０．３〜５重量％の範囲にあることが望ましい。カーボン含有量が０．３重量％以下であると、抵抗率が１０^５ Ω・ｃｍ以上となり電力用抵抗体としては抵抗率が高すぎる。カーボン含有率が５重量％以下では抵抗率が１０Ω・ｃｍ以下と低下するとともに、焼結体が緻密性に欠け、やはり電力用抵抗体には不適となる。
【００４０】
第１領域を形成する混合粉末は第１領域が実質的に絶縁性を示す観点から、第２の領域よりもオーダー的に抵抗率が高くなるカーボン含有量が好ましい。
第２領域を形成する混合粉末はカーボン含有量が１．１〜１０重量％の範囲にあることが好ましい。カーボン含有量が１．０重量％未満であると、抵抗率が１０^５ Ω・ｃｍを超え電力用抵抗体として抵抗率が高すぎる。また、カーボン含有量が１０重量％を超えると、焼結体の緻密性にかけ、本発明の効果が得られにくくなる。
【００４１】
第１の領域を形成する第１の造粒粉末に対し、第２の領域を形成する第２の造粒粉末の混合割合が２０重量％以上、６０重量％以下が好ましい。第２の造粒粉末の混合割合が１０重量％以下の場合には、第２の領域どうしの電気的な接続が困難になり、焼結体の抵抗率制御が困難になる。第２の造粒粉末の混合割合が６０重量％を超えると抵抗率は実質的に第２領域の抵抗率に近くなり、本発明の効果が得られにくくなる。第１及び第２領域におけるＳｉＯ_２、ＣａＯ、ＭｇＯを含む粉末原料の添加量は０．１〜５重量％の範囲にあることが好ましい。これら粉末原料の添加量が０．１重量％未満あるいは５重量％を超えると焼結体を均一に、再現性良く作成可能な効果がなくなる。
【００４２】
なお、第２の造粒粉末の平均粒子径は、第１の造粒粉末の平均粒子径よりも小さくしてもよい。この場合、第２の造粒粉末の混合割合は、第１及び第２の造粒粉末の平均粒子径が等しい場合に比べ、小さくすることができる。
【００４３】
なお、本発明に係る電力用抵抗体は前述した円板形状を有する構造に限定されない。例えば、図５および図６に示すように環状の焼結体１１と、焼結体１１の対向する環状両面に形成された電極１２と、焼結体１１の外周面および円周面に被覆された絶縁層１３，１４とから電力用抵抗体１５を構成してもよい。
【００４４】
また、本発明に係る電力用抵抗体を後述する電力用遮断器の投入抵抗体や高電圧装置、大容量コンデンサの充放電装置等に用いられる固定抵抗器、可変抵抗器、抵抗器アレーに適用することができる。
【００４５】
次に、本発明に係る電力用遮断器を図７および図８を参照して説明する。
図７は、本発明に係る遮断器の構成図、図８は投入抵抗体を示す斜視図である。遮断器２１は、消弧室２２内に配置され電流経路に接続された主接点２３を備えている。補助接点２４は、電流経路に主接点２３に対して並列に接続されている。投入抵抗ユニット２５は、補助接点２４に直列に接続されている。上下動する絶縁ロッド２６は、傾動するレバー２７に連結されている。
【００４６】
このような構成の電力用遮断器において、前記絶縁ロッド２６が上方に駆動されると、主接点２３のＯＮに先立って補助接点２４がＯＮされる。この際、投入抵抗ユニット２５は補助接点２４に直列に接続されているため、補助接点２４が介装された電流経路を流れる電流の電圧を投入抵抗ユニット２５に下げられる。主接点２３がＯＮされる直前においては電流は投入抵抗ユニット２５および補助接点２４が介装された電流経路を流、主接点２３が介装された電流経路に電流が流れていないため、主接点２３がＯＮした時にその接点に高電圧がかからない。その結果、主接点２３のＯＮ時にアークが発生するのを防止できる。
【００４７】
投入抵抗ユニット２５は、例えば図８に示すような主に絶縁性支持棒２８と、一対の絶縁性支持板２９ａ，２９ｂと、複数の中空円筒状の抵抗体３０と、弾性体３１とから構成されている。一対の絶縁性支持板２９ａ、２９ｂは、支持棒２８に嵌入されている。複数の中空円筒状の抵抗体３０は、支持板２９ａ，２９ｂ間に位置する支持棒２８部分に嵌入されている。弾性体３１は、一方（右端）の支持板２９ａと複数の抵抗体３０の間に配置されると共に、支持棒２８に嵌入されている。弾性体３１は、複数の抵抗体３０に弾性力を付与してそれらを支持棒２８に積層するために用いられる。ナット３２ａ，３２ｂは、支持棒２８の両端に螺合されている。ナット３２ａ，３２ｂは、支持板２９ａ，２９ｂ間に配置された弾性体３１を押圧するために用いられる。絶縁性支持棒２８は、高強度、軽量化、易加工性などの理由から有機系の材料が用いられる。一般に、投入抵抗体は開閉サージ吸収時に温度上昇を生じる。このため、耐熱性が劣る有機系材料からなる支持棒は強度を維持することが困難になる。ただし、後述する組成の投入抵抗体は熱容量が大きいために開閉サージ吸収時における温度上昇を一定温度以下に抑制することが可能になる。その結果、有機系材料からなる支持棒の使用が可能になる。また、熱容量の大きな投入抵抗体ほど容積を小さくすることが可能になる。
【００４８】
投入抵抗ユニット２５に組込まれた抵抗体（電力用抵抗体）３０は、前述した図５および図６に示すように環状の焼結体１１と、焼結体１１の環状両面に形成された一対の電極１２と、焼結体１１の外周面および内周面に被覆された絶縁層１３，１４とから構成されている。
【００４９】
上述したように本実施の形態に係る電力用遮断器は、前述した構成の焼結体を含み、単位体積当たりの熱容量が大きく、経時的な抵抗値変動が小さく、かつ所期目的の抵抗値を有する抵抗体が組み込まれた投入抵抗ユニットを備えている。このような投入抵抗ユニットは、遮断容量が大きく、従来のカーボン分散型セラミック抵抗体が組込まれた投入抵抗ユニットに比べて容積を小さくでき、さらに安定した遮断性能を有する。したがって、投入抵抗ユニットを備えた電力用遮断器は小型化および高性能化を図ることができる。
その他、本発明はその要旨を逸脱しない範囲で種々変形して実施できる。
【００５０】
【実施例】
以下、本発明の実施例について説明する。
［実施例１〜１４］
本発明の電力用抵抗体は以下の様に製造された。
【００５１】
図４中の点ＡＢＣＤで囲まれた成分比範囲のＳｉＯ_２、ＣａＯ、ＭｇＯ粉末原料の所定量に１０〜３０重量％のＡｌ_２Ｏ_３粉末原料を加え、混合した後、１２００℃〜１５００℃の温度で加熱・反応させた後、粉砕し、ＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末をあらかじめ作製した。ここに各点の成分比をモル比で（ＳｉＯ_２、ＣａＯ、ＭｇＯ）の順に、Ａは（３５，４５，２０）、Ｂは（３５，４０，２５）、Ｃは（４５，３０，２５）、Ｄは（６０，３０，１０）、Ｅは（６０，３５，５）、Ｆは（５０，４５，５）で表される。
【００５２】
Ｇ点は同様に（４，９，３８，１４）のモル比で表され、さらに１７重量％のＡｌ_２Ｏ_３を含むことで、これら成分系の共晶点（共晶温度１２３０℃）をなす。
【００５３】
平均粒径０．４μｍの酸化アルミニウム粉末にＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末を所定量加え、エタノールを溶媒とし、Ａｌ_２Ｏ_３製ポットおよびアルミナ製ボールを用いて混合、粉砕を行い、第１の混合粉末を得る。これを乾燥後、さらに成型用バインダーとしてパラフィンを固形分として５ｗｔ％加え、キシレンを溶媒としてスラリー化した後、乾燥を行い、第１の造粒粉末を得た。また、第１の造粒粉末に使用したものと同じ酸化アルミニウム粉末を出発原料として、平均粒子型５０ｎｍのカーボン粉末、および、ＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末を所定量加え、さらにエタノールを溶媒とし、アルミナ製ポットおよびアルミナ製ボールを用いて混合、粉砕を行い、第２の混合粉末を得て、これを乾燥後、さらに成型用バインダーとしてパラフィンを固形分として５ｗｔ％加え、第１の造粒粉末と同じ方法で、第２の造粒粉末を得た。第１の造粒粉末に対して第２の造粒粉末を４０ｗｔ％の割合でＶ型混合器により混合し、混合造粒粉末を得た。
【００５４】
なお、ＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末を添加量はＡｌ_２Ｏ_３、ＳｉＯ_２、ＣａＯ、ＭｇＯ成分のうち、ＳｉＯ_２、ＣａＯ、ＭｇＯ成分に換算した量を用いた。
【００５５】
これらの混合造粒粉末は鋼鉄製金型を用いてシリンダ型の円板状に形成され、窒素中６００℃の脱脂過程を経て、アルゴン中１５００℃で２時間の焼成を行った。この焼結体の側面に、ホウケイ酸ガラス粉末を塗布、焼き付けて絶縁層を形成した。その後、この焼結体の両端面を研削後、外径１２０ｍｍ、内径３５ｍｍ、高さ２５ｍｍの寸法とし、両端面にアルミニウム電極を溶射により形成して、抵抗素子を得た。
【００５６】
また、第１と第２の領域を持たない、すなわち、焼結体全体にカーボン濃度が均一になるように、上記酸化アルミニウム粉末に、実施例と同じカーボン粉末、およびＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末をＳｉＯ_２、ＣａＯ、ＭｇＯ成分に換算して０．５ｗｔ％加え、一括して混合し、造粒、成形し、以降、上記実施例と同様な方法で比較例の抵抗素子を得た。
表１に、第２の領域におけるカーボン添加量、焼結体中の第２の領域の割合、抵抗率、素子内及び素子間の抵抗比、抵抗変化率を比較例と合わせて示した。
【００５７】
【表１】

【００５８】
抵抗素子の製造安定性を調べるために、同一ロットの抵抗素子２０個の抵抗値を測定し、その最大値と最小値の比を素子間抵抗比とした。また、焼結体内部の抵抗率の均一性を評価するために、抵抗素子の一方の面の電極を除去し、直径３ｍｍのアルミニウム電極を２０個、溶射により電極面に均等に配置、形成した。これらの電極と他方の面の電極との間の抵抗を測定し、その最大値と最小値の比を素子内抵抗比とした。実用上、素子間抵抗比は５以下が好ましく、素子内抵抗分布は１０以下が好ましい。
【００５９】
抵抗変化率は、抵抗素子に２００Ｊ／ｃｍ^３のエネルギーに相当するサージ電圧を素子冷却を考慮した一定間隔の時間をおいて１０回繰り返し印加し、発生した抵抗変化を初期値に対する百分率で示した。実用上、抵抗変化率は１０％以下が好ましい。
【００６０】
表１によれば、カーボン含有量の異なる第１の領域と第２の領域を備えた抵抗体において、抵抗率が１０^３ Ω・ｃｍを超える場合においても、素子内抵抗比は１０以下の値を示し、均一性に優れるとともに、素子間抵抗比も５以下であり、安定に製造できることが明かである。さらに、サージ電圧を繰り返し印加したときの電圧変化率は５％以下であり、抵抗特性が良好な安定性を有しているものであった。また、ＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末をＳｉＯ_２／ＣａＯ／ＭｇＯの含有比がモル比で３５〜６０／３０〜４５／５〜２５で合計量が０．１〜５重量％の範囲で添加することにより、抵抗分布の均一性に優れ、素子間ばらつきも十分小さく、耐サージ性に優れた安定な抵抗特性を示すものであった。なお、第１および第２の領域構造を持たない比較例１〜３の場合には、均一な抵抗体が得られにくくなるとともに、製造安定性に劣るものであった。
【００６１】
［実施例１５〜２１］
平均粒径０．２μｍの酸化アルミニウム粉末にＳｉＯ_２、ＣａＯ、ＭｇＯの少なくとも一種の粉末原料を所定量加え、エタノールを溶媒とし、アルミナ製ポットおよびアルミナ製ボールを用いて混合、粉砕を行い、第１の混合粉末を得る。これを乾燥後、さらに成型用バインダーとしてパラフィンを固形分として５ｗｔ％加え、キシレンを溶媒としてスラリー化した後、乾燥を行い、第１の造粒粉末を得た。また、第１の造粒粉末に使用したものと同じ酸化アルミニウム粉末を出発原料として、平均粒子型５０ｎｍのカーボン粉末、および、ＳｉＯ_２、ＣａＯ、ＭｇＯを含む加熱反応粉末を所定量加え、さらにエタノールを溶媒とし、アルミナ製ポットおよびアルミナ製ボールを用いて混合、粉砕を行い、第２の混合粉末を得て、これを乾燥後、さらに成型用バインダーとしてパラフィンを固形分として５ｗｔ％加え、第１の造粒粉末と同じ方法で、第２の造粒粉末を得た。第１の造粒粉末に対して第２の造粒粉末を２０〜６０ｗｔ％の割合でＶ型混合器により混合し、混合造粒粉末を得た。この後実施例１〜１４と同様な方法で抵抗素子を作製した。結果を実施例１５〜２１として表２に示す。
【００６２】
【表２】

【００６３】
表２に示すように、素子内および素子間の抵抗比、さらに電圧変化率はいずれも良好な値を示し、第１の造粒粉末に対する第２の造粒粉末の割合が２０〜６０ｗｔ％の範囲で良好な値を示し、ＳｉＯ_２、ＣａＯ、ＭｇＯの加熱反応粉末の添加効果が発揮されている。
【００６４】
本発明に係る電力用抵抗体の相対密度は９２％以上と緻密に焼結されているため、従来例とは異なり、熱容量はほぼ３Ｊ／ｃｍ^３と大きな値を有しており、電力用抵抗体として好適である。
【００６５】
本発明により得られた抵抗体において、透過型電子顕微鏡で観察した焼結体の微構造を図２及び図３に示す。カーボン粒子は第１の領域にはほとんど見られず、第２の領域に多く見られ、領域構造を示していることがわかる。第２の領域の酸化アルミニウムの粒径は０．４〜１μｍと非常に細かく、また、カーボン粒子は酸化アルミニウム粒子の粒界の会合部（３重点）に平均粒子径５０ｎｍ程度の粒子が多数集まった構造をしており、このような構造が電流経路となるカーボン粒子同志の接続を安定に形成しているものと考えられる。また、第１の領域に見られるように、酸化アルミニウムの粒子は２〜５μｍと粒成長しており、焼結体の組織は緻密である。焼結体に見られる様な領域構造にすることにより、カーボンを含むことで難焼結性となる酸化アルミニウムに対して焼結性を向上させていることがわかる。さらに、第１の領域の酸化アルミニウム粒子の会合部および第２の領域のカーボン粒子が多数集まっている構造にはＳｉＯ_２、ＣａＯ、ＭｇＯ成分が存在していることがＥＤＳ（エネルギー分散型Ｘ線スペクトル分光）分析により確認される。図４のＡＢＣＤで囲まれた成分比のＳｉＯ_２、ＣａＯ、ＭｇＯに所定量のＡｌ_２Ｏ_３を加え加熱して得られる反応物は成分比に応じて１２３０℃またはこれ以上の温度で液相を生ずるため、焼結時にこれら反応物が酸化アルミニウム粒子の会合部で液相を生じ焼結をさらに向上させているものと理解される。
【００６６】
（遮断器の評価例）
前述した実施例２、３、７、９、１３、１５および比較例１の電力用抵抗体を前述した図８に示すように所定枚数積み重ね、各抵抗体３０の中心部を貫通する樹脂からなる絶縁性支柱棒２８と弾性体３１により支持し、円筒状容器に収めて投入抵抗ユニット２５を構成した。これら投入抵抗ユニットを前述した図６に示すように組込んで７種の電力用遮断器４１を組み立てた。
【００６７】
得られた７種の電力用遮断器について、それらの投入抵抗体に脱調投入し、抵抗体の温度上昇が８０℃以内になるときの抵抗体に注入可能なエネルギー（エネルギー容量）を測定した。また、実施例２、３、７、９、１３、１５の電力用抵抗体を組み込んだ電力用遮断器について、比較例１の電力用抵抗体を組み込んだ電力用遮断器に対する体積縮小率を測定した。これらの結果を下記表３に示す。
【００６８】
【表３】

【００６９】
表３のＮｏ．２〜７の電力用遮断器について、遮断性能の安定性を調べるために脱調投入相当のエネルギーを２０回印加し、投入抵抗体の抵抗率変化を測定した。その結果、いずれの電力用遮断器も抵抗率変化が１０％以下であり、十分に遮断性能の安定性が高いことが確認された。
【００７０】
【発明の効果】
以上説明したように請求項１の発明によれば、焼結体としては、カーボン含有量が少ないかもしくはカーボンを含まない第１領域と、この第１領域よりカーボン含有量が多く、かつ一対の電極に繋がるように配置された第２領域とを有し、且つ二酸化珪素、酸化カルシウム又は酸化マグネシウムのうち少なくとも一種を０．１〜５重量％の範囲で含んでいるので、焼結体の緻密性及び均一性を向上できることにより、単位体積あたりの熱容量が大きく、適切かつ安定した電気抵抗値を有し、サージ吸収による抵抗値の経時変化が小さく、焼結体の均一性に優れ、再現性良く製造電力用抵抗体を提供できる。請求項６によっても同様な効果が得られる。
【００７１】
また請求項１の発明によれば、焼結体としては、カーボン含有量が少ないかもしくはカーボンを含まない第１領域と、この第１領域よりカーボン含有量が多く、かつ一対の電極に繋がるように配置された第２領域とを有し、且つ二酸化珪素、酸化カルシウム、酸化マグネシウムを二酸化珪素／酸化カルシウム／，酸化マグネシウムの含有比がモル比で３５〜６０／３０〜４５／５〜２５で合計量が０．１〜５重量％の範囲で含んでいるので、焼結体の緻密性および均一性を向上でき、より単位体積あたりの熱容量が大きく、適切かつ安定した電気抵抗値を有し、サージ吸収による抵抗値の経時変化が小さく、焼結体の均一性に優れ、再現性良く製造できる電力用抵抗体を提供できる。
【００７２】
また、請求項３の発明によれば、第１の領域はカーボン含有量が１重量％未満であり、第２の領域はカーボン含有量が１〜１０重量％の範囲にあるので、請求項１の効果に加え、電力用抵抗体として好適な抵抗率と十分な緻密性を確保できる電力用抵抗体を提供できる。
【００７３】
さらに、請求項４の発明によれば、第１の領域を形成する第１の造粒粉末に対し、前記第２の領域を形成する第２の造粒粉末が２０〜６０重量％の範囲で混合されているので、請求項１の効果に加え、第２の領域どうしの電気的接続が容易な程度に含有される一方、第１の領域を無視するほどには含有されないので、容易に抵抗率を制御できる電力用抵抗体を提供できる。
【００７４】
また、請求項５の発明によれば、第２の領域の酸化アルミニウム粒子は平均粒径が０．４〜１μｍの範囲にあり、第１の領域の酸化アルミニウム粒子は第２の領域の酸化アルミニウム粒子の２〜５倍の大きさを有するので、請求項１の効果に加え、良好な焼結性を確保でき、かつ第２の造粒粉末の混合割合を、第１及び第２の造粒粉末の平均粒子径が等しい場合に比べて小さくできる電力用抵抗体を提供できる。
【００７５】
さらに、請求項７の発明によれば、カーボン粉末が少ないかもしくはカーボン粉末を含まず、酸化アルミニウム粉末を含み、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを二酸化珪素／酸化カルシウム／酸化マグネシウムの含有比がモル比で３５〜６０／３０〜４５／５〜２５で合計量が０．１〜５重量％の範囲で含有する第１の領域を形成する第１の造粒粉末を調整する工程と、第１の領域よりも多くカーボン粉末を含むと共に、酸化アルミニウム粉末を含み、かつ二酸化珪素、酸化カルシウム、酸化マグネシウムを二酸化珪素／酸化カルシウム／酸化マグネシウムの含有比がモル比で３５〜６０／３０〜４５／５〜２５で合計量が０．１〜５重量％の範囲で含有する第２の領域を形成する第２の造粒粉末を調整する工程と、第１の造粒粉末と第２の造粒粉末とを混合した後、成形、焼結することにより焼結体を作成する工程と、焼結体の対向する主面に一対の電極を形成する工程とを含んでいるので、請求項１の同様の効果を奏することができる電力用抵抗体の製造方法を提供できる。
【００７６】
また、請求項８の発明によれば、請求項１に対応する焼結体からなる抵抗体を有しているので、遮断容量が大きく、遮断性能の安定した投入抵抗ユニットを備え、小型、高性能化を達成できる電力用遮断器を提供できる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る電力用抵抗体の構成を示す断面図、
【図２】同実施の形態における焼結体の微構造を模式的に示す図、
【図３】同実施の形態における第２領域を拡大して模式的に示す図、
【図４】同実施に係わる二酸化珪素、酸化カルシウム、酸化マグネシウムを含む加熱反応物の成分比範囲を示す図、
【図５】本発明の他の実施の形態に係る電力用抵抗体の構成を示す斜視図、
【図６】図４の電力用抵抗体のＶ−Ｖ線矢視断面図、
【図７】本発明の実施の形態に係る電力用遮断器を示す構成図、
【図８】同実施の形態における電力用遮断器の投入抵抗ユニットを示す構成図。
【符号の説明】
１，１５…抵抗体
２，１１…焼結体
３，１２…電極
４…側面高抵抗層
５…第１領域
６…第２領域、
７…酸化アルミニウム粒子
８…カーボン
９…二酸化珪素、酸化カルシウム、酸化マグネシウムを含む相
２１…遮断器
２２…消弧室
２３…主接点
２４…補助接点
２５…投入抵抗体
２６…絶縁ロッド
３０…抵抗体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power resistor, a method of manufacturing the same, and a power circuit breaker, and more specifically, for example, a high-voltage device, a neutral ground resistor used in a large-capacity capacitor charging / discharging device, and a fixed resistor. TECHNICAL FIELD The present invention relates to a power resistor suitable as a device, a variable resistor, a wound resistor, or a resistor array, a method for manufacturing the same, and a power circuit breaker including the power resistor as a closing resistor.
[0002]
[Prior art]
In general, the materials of power resistors are roughly classified into metal-based resistance materials, metal-oxide-based resistance materials, and non-metal-based resistance materials. Among them, the metal oxide-based resistance material is characterized in that it has higher heat resistance, higher withstand voltage and current, and higher energy resistance to absorb high electric energy than other materials.
[0003]
Representative metal oxide-based resistors are disclosed in JP-A-58-139401 and JP-A-59-217668.
JP-A-58-139401 describes a carbon particle-dispersed ceramic resistor in which conductive carbon powder is dispersed in insulating aluminum oxide crystals and baked with clay. It is described that such a resistor has a carbon content of 1.5 to 2.0% by weight.
[0004]
JP-A-59-217668 discloses a method of adding carbon powder and a binder to an insulating inorganic material powder of aluminum oxide, mullite, and calcined clay, mixing, kneading, and heat-treating the raw material as a main raw material. A description is given of a resistance pair for system power, in which the carbon powder at this time is a fine powder of 0.1 μm or less and has a content of 1.5 to 5% by weight.
[0005]
JP-A-57-52101 discloses a resistance member containing aluminum oxide as a main component, a clay material such as silicon oxide and magnesium oxide, and 3 to 10% by weight of carbon as a conductive material. Has been described.
[0006]
By the way, in general, when carbon powder is added to aluminum oxide powder to produce a sintered body, sinterability of aluminum oxide is hindered. For this reason, in the above-described carbon particle dispersed ceramic resistor, since the carbon powder is added to the aluminum oxide powder, the sinterability of the aluminum oxide is hindered. For this reason, the carbon particle-dispersed ceramic resistor described above is obtained by adding carbon powder to aluminum oxide powder and further adding clay for the purpose of supplementing the sinterability of the aluminum oxide powder and sintering. However, the addition of clay merely binds the aluminum oxide and the carbon powder, but does not improve the sinterability. Therefore, the porosity of the obtained resistor is as high as 10 to 30% and the denseness is reduced. Such a problem is caused.
[0007]
In other words, when used as a closing resistor of a circuit breaker connected in parallel with a breaking contact to absorb surge generated when the resistor is opened and closed, or to increase the breaking capacity, it causes a decrease in the denseness of the resistor. And the heat capacity per volume is 2 J / cm ³ ・ Since the temperature is reduced to about K, the temperature of the resistor increases significantly due to the absorption of energy such as surge. Further, at the time of energization, the carbon powder causes a discharge in the pores, and a through discharge occurs. Therefore, in the circuit breaker using the above-described carbon particle dispersed ceramic resistor, the storage space for the resistor has to be large, and the breaking capacity has to be kept low in order to ensure reliability.
[0008]
Further, in such a resistor, 10 ³ ・ When it is desired to obtain a sintered body having a high resistivity exceeding Ω · cm, since a small number of carbon particles that bring about conductivity are connected, fluctuations in manufacturing conditions are sensitively reflected. It has been difficult to produce a sintered body having good properties with good yield.
[0009]
U.S. Pat. No. 4,418,327 describes a resistor in which aluminum oxide, carbon, and magnesium oxide as a sintering aid are added. However, even with such a resistor, it is not easy to obtain a sufficiently dense sintered body, and it has been difficult to produce a sintered body having excellent uniformity with a high yield.
[0010]
[Problems to be solved by the invention]
As described above, the power resistor has a problem that it is difficult to manufacture a sufficiently dense sintered body having high uniformity with a high yield.
In addition, various problems, such as a decrease in heat capacity, a remarkable rise in temperature, a through discharge, an increase in storage space, and a decrease in cut-off capacity, occur particularly with the decrease in denseness.
[0011]
The present invention has been made in consideration of the above circumstances, has a large heat capacity per unit volume, has an appropriate and stable electric resistance, has a small change in resistance with time due to surge absorption, and has a uniform sintered body. It is an object of the present invention to provide a power resistor which is excellent in reproducibility and can be manufactured with good reproducibility, and a method for manufacturing the same.
A second object of the present invention is to provide a power circuit breaker that has a large breaking capacity, has a closing resistance unit with stable breaking performance, and is small and has high performance.
[0012]
[Means for Solving the Problems]
The invention corresponding to claim 1 is a power resistor comprising a sintered body containing aluminum oxide and carbon, and a pair of electrodes formed on two opposing surfaces of the sintered body, As the sintered body, a first region having a low carbon content or containing no carbon, and a second region having a higher carbon content than the first region and arranged so as to be connected to the pair of electrodes are included. It is a power resistor which has silicon dioxide, calcium oxide and magnesium oxide in the range of 0.1 to 5% by weight.
[0013]
An invention corresponding to claim 2 is a power resistor comprising a sintered body containing aluminum oxide and carbon, and a pair of electrodes formed on two opposing surfaces of the sintered body,
The sintered body is
A first region having a low or no carbon content,
A second region having a higher carbon content than the first region and arranged to be connected to the pair of electrodes;
And silicon dioxide (SiO ₂ ), Calcium oxide (CaO) and magnesium oxide (MgO) in a silicon dioxide / calcium oxide / magnesium oxide content ratio of 35-60 / 30-45 / 5-25 in a molar ratio and a total amount of 0.1-5. It is a power resistor characterized by being contained in the range of weight%.
[0014]
According to a third aspect of the present invention, in the power resistor according to the first aspect, the first region has a carbon content of less than 1% by weight, and the second region has a carbon content of less than 1% by weight. A power resistor in the range of 1 to 10% by weight.
[0015]
Further, the invention according to claim 4 is the power resistor according to claim 1, wherein the second region forming the second region is formed with respect to the first granulated powder forming the first region. Is a power resistor in which the granulated powder is mixed in the range of 20 to 60% by weight.
[0016]
According to a fifth aspect of the present invention, in the power resistor according to the first aspect, the aluminum oxide particles in the second region have an average particle size in a range of 0.4 to 1 μm, and The aluminum oxide particles in the region are power resistors having a size two to five times as large as the aluminum oxide particles in the second region.
[0017]
The invention corresponding to claim 6 is a power resistor comprising a sintered body containing aluminum oxide and carbon, and a pair of electrodes formed on two opposing surfaces of the sintered body,
The sintered body is
At least silicon dioxide, calcium oxide and magnesium oxide at the grain boundaries of aluminum oxide
A power resistor characterized in that the carbon grain boundaries are configured such that silicon dioxide, calcium oxide and magnesium oxide are less than or not included in the grain boundaries of aluminum oxide.
[0018]
Furthermore, the invention according to claim 7 is characterized in that the carbon powder is low or does not contain carbon powder, contains aluminum oxide powder, and forms a first region containing silicon dioxide, calcium oxide and magnesium oxide. Adjusting the granular powder; and forming a second region that contains more carbon powder than the first region, contains aluminum oxide powder, and forms silicon dioxide, calcium oxide, and magnesium oxide. Adjusting the granulated powder of the above, mixing the first granulated powder and the second granulated powder, forming and sintering to form a sintered body; Forming a pair of electrodes on opposing main surfaces of the body. The sintered body according to the present invention may be as described in claim 2 or 6.
[0019]
According to an eighth aspect of the present invention, there is provided a main switching unit disposed on a current path and electrically connected to the current path in parallel with the main switching unit to switch the main switching unit to a closed state. An auxiliary opening / closing unit that is switched to a closed state earlier than the other, and a pair of electrodes that are electrically connected in series to the auxiliary opening / closing unit and that are formed on a sintered body and two opposing surfaces of the sintered body. And a first region having a small amount of carbon or containing no carbon and a large amount of carbon contained in the first region and connected to the pair of electrodes. A power circuit breaker having a second region and silicon dioxide, calcium oxide, and magnesium oxide.
[0020]
Therefore, the invention corresponding to claim 1 has taken the above-described means, so that the sintered body has a first region having a small carbon content or containing no carbon and a first region having a low carbon content. A large amount, a second region arranged so as to be connected to a pair of electrodes, and containing silicon dioxide, calcium oxide, and magnesium oxide in a range of 0.1 to 5% by weight; By improving the compactness and uniformity of the body, the heat capacity per unit volume is large, it has an appropriate and stable electric resistance value, the change over time in the resistance value due to surge absorption is small, and the uniformity of the sintered body is excellent , And can be manufactured with good reproducibility. If the molar ratio of silicon dioxide, calcium oxide and magnesium oxide contained in the first region is defined as in the invention corresponding to claim 2, the effect is still remarkable.
[0021]
In the invention corresponding to claim 3, the first region has a carbon content of less than 1% by weight and the second region has a carbon content of 1 to 10% by weight. In addition to the action corresponding to the above, it is possible to secure a resistivity suitable for the power resistor and a sufficient denseness.
[0022]
Further, the invention according to claim 4 is that the second granulated powder forming the second region is mixed with the first granulated powder forming the first region in a range of 20 to 60% by weight. Therefore, in addition to the action corresponding to claim 1, while the electrical connection between the second regions is contained to the extent that it is easy, the electrical resistance between the second regions is not so large as to be ignored. The rate can be controlled.
[0023]
According to a fifth aspect of the present invention, the aluminum oxide particles in the second region have an average particle size in a range of 0.4 to 1 μm, and the aluminum oxide particles in the first region are aluminum oxide particles in the second region. Since the particles have a size of 2 to 5 times the size of the particles, in addition to the action corresponding to claim 1, good sinterability can be ensured, and the mixing ratio of the second granulated powder is adjusted to the first and second ratios. It can be smaller than when the average particle diameter of the granulated powder is equal.
[0024]
Further, the invention according to claim 7 is characterized in that the carbon powder is short or does not contain carbon powder, contains aluminum oxide powder, and forms a first region containing silicon dioxide, calcium oxide and magnesium oxide. And a second step of forming a second region containing aluminum oxide powder and containing silicon dioxide, calcium oxide and magnesium oxide while containing more carbon powder than the first region. Adjusting the granulated powder, mixing the first granulated powder and the second granulated powder, forming and sintering to form a sintered body, and opposing the sintered body. And a step of forming a pair of electrodes on the main surface to perform the same operation as the first embodiment.
[0025]
Further, since the invention according to claim 8 has the resistor made of the sintered body according to claim 1, the invention has a closing resistance unit having a large breaking capacity and a stable breaking performance, and is small in size and high in height. Performance can be achieved.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing a configuration of a power resistor according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing a microstructure of the sintered body of FIG. 1, and FIG. It is a figure which expands an area | region and shows typically. The resistor 1 includes a sintered body 2 on a disk, a pair of electrodes 3 formed on both surfaces of the sintered body 2, and an insulating layer 4 coated on the outer peripheral surface of the sintered body 2. ing.
[0027]
The sintered body 2 has a composition containing aluminum oxide and carbon, silicon dioxide, calcium oxide, and magnesium oxide.
As shown in FIG. 2, the sintered body 2 includes a first region 5 having a small amount of carbon or containing no carbon, and a second region 6 having a larger amount of carbon than the first region 5. Reference numeral 5 indicates substantially insulating property, and second region 6 indicates conductive property. In the sintered body 2, the second regions 6 are arranged so as to be connected to each other in a three-dimensional network structure and to be connected to the pair of electrodes 3. The resistance of the sintered body 2 is controlled by the connection state and the resistivity of the second region 6.
[0028]
As shown in FIG. 3, the second region 6 has a form in which conductive carbon 8 exists at the grain boundaries of the insulating aluminum oxide particles 7, and the plurality of second regions 6 are electrically connected to each other by the carbon 8. Connected.
[0029]
In the second region 6, the carbon content of the region and silicon dioxide (SiO 2) ₂ ), The amount of powdered material containing calcium oxide (CaO) and magnesium oxide (MgO) can control the resistivity of the region. When obtaining a sintered body having a relatively high resistivity, it is possible to increase the resistivity of the second region 6 appropriately and to increase the number of connections between the second regions 6 sufficiently. Thereby, the adverse effect on the uniformity inside the sintered body due to the sintering atmosphere, the temperature distribution, and the like during the production can be relatively reduced, and the production yield can be improved. The sintered body has a structure in which a portion 9 of the aluminum oxide particles in the first region and a portion of the carbon 8 in the second region have SiO 2. ₂ , CaO and MgO are present and form a liquid phase during sintering. Therefore, the sintered body is made of ₂ By adding a predetermined amount of a powder raw material containing CaO and MgO, sintering is easy, uniform, and stable.
[0030]
The power resistor of the present invention can be manufactured, for example, as follows.
Aluminum oxide has an average particle diameter of 1 μm or less, and preferably has a particle diameter of 0.5 μm or less in order to improve sinterability.
[0031]
The carbon powder preferably has a particle diameter of 0.1 μm or less for securing sinterability, and is more preferably a fine powder.
Such aluminum oxide raw material powder, carbon powder having an average particle diameter of 0.1 μm or less, and SiO 2 ₂ , CaO and MgO are mixed in a ball mill using water or an organic solvent to obtain first and second mixed powders, respectively.
[0032]
When forming the first or second region having a different carbon content of the sintered body, the carbon content of the region can be controlled according to the electrical properties.
That is, a first mixed powder having a low carbon content for forming a substantially insulating first region and a second mixed powder having a large carbon content for forming a conductive second region. With the powder, the carbon content can be controlled within a range showing the respective electrical properties. SiO in the first region and the second region ₂ Similarly, the content of powder raw materials containing CaO, MgO and MgO can be controlled within a range showing electrical properties.
[0033]
To each of the mixed powders having different carbon contents, a molding binder such as paraffin or polyvinyl alcohol can be appropriately added as required for forming a molded body. In this case, these molding binders are also sintered. Since it becomes a carbon source in the body, it is necessary to adjust the amount of carbon powder in advance in consideration of the carbon source.
[0034]
After adding and mixing the molding binder, the mixture is granulated by passing through a mesh or the like, and the first and second granulated powders are adjusted.
As a method of obtaining each granulated powder, a first mixed powder and a second mixed powder having different carbon contents are mixed with an organic solvent and a molding binder, respectively, and slurried, using a spray drier or the like, By removing the solvent, a first granulated powder and a second granulated powder can be obtained.
[0035]
Each granulated powder is mixed at a predetermined ratio by, for example, a V-type mixer to form a mixed granulated powder. A mixed granulated powder is formed and sintered to obtain a sintered body.
Molding can be applied by die pressing, extrusion, injection molding and the like. When using mold forming, 200 kg / cm is used to increase the density of the sintered body. ² The above forming pressure is desirable. If the molding pressure is lower than this, the relative density of the sintered body is low, and the heat capacity per unit volume is reduced.
[0036]
The calcination is carried out by holding at 1300 to 1800 ° C. for 1 to 4 hours in a vacuum or an inert gas, following the heat treatment for degreasing performed in a non-oxidizing gas. However, after the heat treatment for degreasing, the temperature may be once lowered to room temperature, then raised again and fired.
[0037]
Both main surfaces of the obtained sintered body are polished, and a pair of electrodes is formed by means such as thermal spraying, baking, sputtering, or the like. This electrode is preferably made of aluminum or nickel.
[0038]
Thereafter, an insulating ceramic such as aluminum oxide, silicon oxide, or borosilicate glass, or a resin such as polyimide is baked, if necessary, on the outer peripheral surface of the sintered body and the inner peripheral surface of the hollow portion, and sprayed or coated, dried, or the like. To form a resistive element.
[0039]
The carbon content of the sintered body is desirably in the range of 0.3 to 5% by weight. When the carbon content is 0.3% by weight or less, the resistivity becomes 10%. ⁵ Ω · cm or more, and the resistivity is too high for a power resistor. When the carbon content is 5% by weight or less, the resistivity decreases to 10 Ω · cm or less, and the sintered body lacks denseness, which is also unsuitable for a power resistor.
[0040]
The mixed powder forming the first region preferably has a carbon content at which the resistivity is orderly higher than that of the second region, from the viewpoint that the first region exhibits substantially insulating properties.
The mixed powder forming the second region preferably has a carbon content in the range of 1.1 to 10% by weight. If the carbon content is less than 1.0% by weight, the resistivity becomes 10%. ⁵ The resistivity exceeds Ω · cm and the resistivity is too high as a power resistor. On the other hand, if the carbon content exceeds 10% by weight, the denseness of the sintered body is reduced, and the effect of the present invention is hardly obtained.
[0041]
The mixing ratio of the second granulated powder forming the second region to the first granulated powder forming the first region is preferably 20% by weight or more and 60% by weight or less. If the mixing ratio of the second granulated powder is 10% by weight or less, it becomes difficult to electrically connect the second regions, and it becomes difficult to control the resistivity of the sintered body. If the mixing ratio of the second granulated powder exceeds 60% by weight, the resistivity becomes substantially close to the resistivity of the second region, and the effect of the present invention is hardly obtained. SiO in the first and second regions ₂ The amount of the powdery raw material containing CaO, MgO is preferably in the range of 0.1 to 5% by weight. If the amount of these powdered raw materials is less than 0.1% by weight or more than 5% by weight, the effect of making the sintered body uniform and with good reproducibility is lost.
[0042]
The average particle size of the second granulated powder may be smaller than the average particle size of the first granulated powder. In this case, the mixing ratio of the second granulated powder can be smaller than that in the case where the average particle diameters of the first and second granulated powders are equal.
[0043]
The power resistor according to the present invention is not limited to the above-described disk-shaped structure. For example, as shown in FIGS. 5 and 6, an annular sintered body 11, electrodes 12 formed on both opposed annular surfaces of the sintered body 11, and an outer peripheral surface and a peripheral surface of the sintered body 11 are covered. The power resistor 15 may be composed of the insulating

layers

13 and 14 thus formed.
[0044]
In addition, the power resistor according to the present invention is applied to a fixed resistor, a variable resistor, and a resistor array used in a closing resistor, a high-voltage device, a large-capacity capacitor charging / discharging device, and the like of a power circuit breaker described later. can do.
[0045]
Next, a power circuit breaker according to the present invention will be described with reference to FIGS.
FIG. 7 is a configuration diagram of a circuit breaker according to the present invention, and FIG. 8 is a perspective view showing a closing resistor. The circuit breaker 21 has a main contact 23 arranged in the arc-extinguishing chamber 22 and connected to a current path. The auxiliary contact 24 is connected to the current path in parallel with the main contact 23. The closing resistance unit 25 is connected to the auxiliary contact 24 in series. The insulating rod 26 that moves up and down is connected to a lever 27 that tilts.
[0046]
In the power circuit breaker having such a configuration, when the insulating rod 26 is driven upward, the auxiliary contact 24 is turned on before the main contact 23 is turned on. At this time, since the closing resistance unit 25 is connected in series to the auxiliary contact 24, the voltage of the current flowing through the current path in which the auxiliary contact 24 is provided can be reduced to the closing resistance unit 25. Immediately before the main contact 23 is turned on, the current flows through the current path in which the closing resistance unit 25 and the auxiliary contact 24 are interposed, and no current flows in the current path in which the main contact 23 is interposed. When 23 is turned on, no high voltage is applied to its contact. As a result, it is possible to prevent an arc from being generated when the main contact 23 is turned on.
[0047]
The closing resistance unit 25 mainly includes, for example, an insulating support rod 28, a pair of insulating

support plates

29a and 29b, a plurality of hollow cylindrical resistors 30, and an elastic body 31 as shown in FIG. Have been. The pair of insulating

support plates

29a and 29b are fitted into the support rod 28. The plurality of hollow cylindrical resistors 30 are fitted into portions of the support rod 28 located between the

support plates

29a and 29b. The elastic body 31 is arranged between one (right end) support plate 29 a and the plurality of resistors 30, and is fitted into the support rod 28. The elastic body 31 is used to apply elastic force to the plurality of resistors 30 and stack them on the support rod 28. The nuts 32a and 32b are screwed to both ends of the support rod 28. The nuts 32a and 32b are used to press the elastic body 31 disposed between the

support plates

29a and 29b. The insulating support rod 28 is made of an organic material for reasons such as high strength, light weight, and easy workability. Generally, the temperature of the closing resistor increases when the switching surge is absorbed. For this reason, it becomes difficult to maintain the strength of the support rod made of an organic material having poor heat resistance. However, since the input resistor having the composition described later has a large heat capacity, it is possible to suppress the temperature rise during absorption of the switching surge to a certain temperature or less. As a result, it is possible to use a support rod made of an organic material. Further, the capacity can be reduced as the input resistor has a larger heat capacity.
[0048]
The resistor (power resistor) 30 incorporated in the closing resistor unit 25 includes an annular sintered body 11 as shown in FIG. 5 and FIG. Of the sintered body 11 and insulating

layers

13 and 14 coated on the outer and inner peripheral surfaces of the sintered body 11.
[0049]
As described above, the power circuit breaker according to the present embodiment includes the sintered body having the above-described configuration, has a large heat capacity per unit volume, a small variation in resistance value over time, and a desired resistance value. And a closing resistor unit in which a resistor having Such a closing resistance unit has a large breaking capacity, can have a smaller volume than a closing resistance unit in which a conventional carbon dispersed ceramic resistor is incorporated, and has more stable breaking performance. Therefore, the power circuit breaker provided with the closing resistance unit can be reduced in size and improved in performance.
In addition, the present invention can be variously modified and implemented without departing from the gist thereof.
[0050]
【Example】
Hereinafter, examples of the present invention will be described.
[Examples 1 to 14]
The power resistor of the present invention was manufactured as follows.
[0051]
SiO in a component ratio range surrounded by a point ABCD in FIG. ₂ , CaO, MgO powder raw material to a predetermined amount of 10-30% by weight of Al ₂ O ₃ After adding and mixing the powder raw materials, the mixture is heated and reacted at a temperature of 1200 ° C. to 1500 ° C., and then pulverized, ₂ , CaO and MgO were prepared in advance. Here, the component ratio of each point is represented by a molar ratio (SiO 2 ₂ , CaO, MgO), A is (35, 45, 20), B is (35, 40, 25), C is (45, 30, 25), D is (60, 30, 10), and E is (60, 35, 5) and F are represented by (50, 45, 5).
[0052]
Point G is also represented by the molar ratio of (4,9,38,14), and 17% by weight of Al ₂ O ₃ , The eutectic point (eutectic temperature 1230 ° C.) of these component systems.
[0053]
Aluminum oxide powder with an average particle size of 0.4 μm ₂ , CaO, and MgO are added in a predetermined amount, and ethanol is used as a solvent. ₂ O ₃ Using a pot made of alumina and balls made of alumina, mixing and grinding are performed to obtain a first mixed powder. After this was dried, paraffin as a molding binder was further added at 5 wt% as a solid content, and after slurrying with xylene as a solvent, drying was performed to obtain a first granulated powder. In addition, starting from the same aluminum oxide powder as that used for the first granulated powder, carbon powder having an average particle type of 50 nm and SiO ₂ , CaO, added a predetermined amount of heat reaction powder containing MgO, further using ethanol as a solvent, mixing and pulverizing using an alumina pot and alumina balls to obtain a second mixed powder, after drying, Further, paraffin was added as a molding binder at a solid content of 5 wt%, and a second granulated powder was obtained in the same manner as the first granulated powder. The second granulated powder was mixed with the first granulated powder at a ratio of 40 wt% by a V-type mixer to obtain a mixed granulated powder.
[0054]
Note that SiO ₂ Heated powder containing CaO, MgO, MgO ₂ O ₃ , SiO ₂ , CaO and MgO components, SiO ₂ , CaO and MgO components were used.
[0055]
These mixed granulated powders were formed into cylinder-shaped discs using a steel mold, fired in argon at 1500 ° C. for 2 hours through a degreasing process at 600 ° C. in nitrogen. Borosilicate glass powder was applied to the side surface of the sintered body and baked to form an insulating layer. Then, after grinding both end surfaces of this sintered body, dimensions of an outer diameter of 120 mm, an inner diameter of 35 mm, and a height of 25 mm were obtained, and aluminum electrodes were formed on both end surfaces by thermal spraying to obtain a resistance element.
[0056]
In addition, the same aluminum powder as in the example and the same carbon powder and SiO 2 were added to the aluminum oxide powder so as not to have the first and second regions, that is, to make the carbon concentration uniform throughout the sintered body. ₂ The heat reaction powder containing CaO, MgO, ₂ , CaO, and MgO components were added in an amount of 0.5 wt%, mixed at once, granulated, and molded. Thereafter, a resistance element of a comparative example was obtained in the same manner as in the above-described example.
Table 1 shows the amount of added carbon in the second region, the ratio of the second region in the sintered body, the resistivity, the resistance ratio in the element and between the elements, and the resistance change rate together with the comparative example.
[0057]
[Table 1]

[0058]
In order to examine the manufacturing stability of the resistance elements, the resistance values of 20 resistance elements of the same lot were measured, and the ratio between the maximum value and the minimum value was defined as the resistance ratio between elements. Further, in order to evaluate the uniformity of the resistivity inside the sintered body, the electrode on one surface of the resistance element was removed, and 20 aluminum electrodes having a diameter of 3 mm were uniformly arranged and formed on the electrode surface by thermal spraying. . The resistance between these electrodes and the electrode on the other surface was measured, and the ratio between the maximum value and the minimum value was defined as the in-element resistance ratio. In practice, the resistance ratio between elements is preferably 5 or less, and the resistance distribution in the element is preferably 10 or less.
[0059]
The resistance change rate is 200 J / cm ³ A surge voltage corresponding to the above energy was repeatedly applied 10 times at regular intervals in consideration of element cooling, and the generated resistance change was shown as a percentage of the initial value. In practice, the resistance change rate is preferably 10% or less.
[0060]
According to Table 1, in the resistor including the first region and the second region having different carbon contents, the resistivity is 10%. ³ Even when the resistance exceeds Ω · cm, the resistance ratio in the device shows a value of 10 or less, which is excellent in uniformity and the resistance ratio between the devices is 5 or less. Further, the voltage change rate when the surge voltage was repeatedly applied was 5% or less, and the resistance characteristics had good stability. In addition, SiO ₂ The heat reaction powder containing CaO, MgO, ₂ By adding in a molar ratio of 35/60/30 to 45/5 to 25 / CaO / MgO and a total amount of 0.1 to 5% by weight, the resistance distribution is excellent in uniformity, and the The variation between them was sufficiently small, and a stable resistance characteristic excellent in surge resistance was exhibited. In the case of Comparative Examples 1 to 3 having no first and second region structures, it was difficult to obtain a uniform resistor and the production stability was poor.
[0061]
[Examples 15 to 21]
Aluminum oxide powder with an average particle size of 0.2 μm ₂ , A predetermined amount of at least one powder material of CaO and MgO is added, and mixed and pulverized using ethanol as a solvent and an alumina pot and alumina balls to obtain a first mixed powder. After this was dried, paraffin as a molding binder was further added at 5 wt% as a solid content, and after slurrying with xylene as a solvent, drying was performed to obtain a first granulated powder. In addition, starting from the same aluminum oxide powder as that used for the first granulated powder, carbon powder having an average particle type of 50 nm and SiO ₂ , CaO, added a predetermined amount of heat reaction powder containing MgO, further using ethanol as a solvent, mixing and grinding using an alumina pot and alumina balls to obtain a second mixed powder, after drying, Further, paraffin as a molding binder was added at 5 wt% as a solid content, and a second granulated powder was obtained in the same manner as the first granulated powder. The second granulated powder was mixed with the first granulated powder at a ratio of 20 to 60 wt% by a V-type mixer to obtain a mixed granulated powder. Thereafter, a resistance element was manufactured in the same manner as in Examples 1 to 14. The results are shown in Table 2 as Examples 15 to 21.
[0062]
[Table 2]

[0063]
As shown in Table 2, the resistance ratio in the element and between the elements, and the voltage change rate all show good values, and the ratio of the second granulated powder to the first granulated powder is 20 to 60 wt%. Good value in the range ₂ , CaO and MgO, the effect of adding the heat-reacted powder is exhibited.
[0064]
Since the power resistor according to the present invention is densely sintered at a relative density of 92% or more, unlike the conventional example, the heat capacity is approximately 3 J / cm. ³ It is suitable as a power resistor.
[0065]
FIGS. 2 and 3 show the microstructure of the sintered body of the resistor obtained according to the present invention, as observed by a transmission electron microscope. Carbon particles are hardly found in the first region, but are often found in the second region, indicating that the carbon particles have a region structure. The particle size of the aluminum oxide in the second region is as fine as 0.4 to 1 μm, and a large number of carbon particles having an average particle size of about 50 nm gather at the junction (triple point) of the grain boundary of the aluminum oxide particles. It is considered that such a structure stably forms a connection between carbon particles serving as a current path. Further, as can be seen in the first region, the aluminum oxide particles have a grain growth of 2 to 5 μm, and the structure of the sintered body is dense. It can be seen that the region structure as seen in the sintered body improves the sinterability of aluminum oxide, which becomes difficult to sinter by containing carbon. Further, a structure in which a large number of carbon particles in the second region and the associated portion of the aluminum oxide particles in the first region are aggregated with SiO 2 ₂ , CaO and MgO components are confirmed by EDS (energy dispersive X-ray spectroscopy) analysis. SiO2 having a component ratio surrounded by ABCD in FIG. ₂ , CaO, MgO with a predetermined amount of Al ₂ O ₃ The reaction product obtained by adding and heating forms a liquid phase at a temperature of 1230 ° C. or higher, depending on the component ratio. It is understood that it has been further improved.
[0066]
(Example of circuit breaker evaluation)
As shown in FIG. 8 described above, a predetermined number of the power resistors of Examples 2, 3, 7, 9, 13, 15 and Comparative Example 1 are stacked and made of resin penetrating the center of each resistor 30. It was supported by an insulating support rod 28 and an elastic body 31 and housed in a cylindrical container to form a closing resistance unit 25. As shown in FIG. 6 described above, these closing resistance units were assembled to assemble seven types of power circuit breakers 41.
[0067]
With respect to the obtained seven types of power circuit breakers, step-out input was performed to the input resistors, and energy (energy capacity) that could be injected into the resistors when the temperature rise of the resistors was within 80 ° C. was measured. . Further, for the power circuit breakers incorporating the power resistors of Examples 2, 3, 7, 9, 9, 13 and 15, the volume reduction ratio of the power circuit breaker incorporating the power resistors of Comparative Example 1 was measured. did. The results are shown in Table 3 below.
[0068]
[Table 3]

[0069]
No. 3 in Table 3. For the power circuit breakers 2 to 7, energy equivalent to step-out input was applied 20 times to check the stability of the interrupting performance, and the change in resistivity of the input resistor was measured. As a result, each of the power circuit breakers had a change in resistivity of 10% or less, and it was confirmed that the stability of the breaking performance was sufficiently high.
[0070]
【The invention's effect】
As described above, according to the first aspect of the present invention, the sintered body includes a first region having a low carbon content or containing no carbon, a carbon region having a higher carbon content than the first region, and a pair of the first region. A second region disposed so as to be connected to the electrode and containing at least one of silicon dioxide, calcium oxide and magnesium oxide in a range of 0.1 to 5% by weight, so that the density of the sintered body is high. The heat capacity per unit volume is large, the electric resistance value is appropriate and stable, the change in resistance value over time due to surge absorption is small, the uniformity of the sintered body is excellent, and the reproducibility is improved. A resistor for manufacturing power can be provided well. A similar effect can be obtained by the sixth aspect.
[0071]
According to the first aspect of the present invention, the sintered body has a first region having a low carbon content or no carbon, and a carbon content higher than the first region, and is connected to a pair of electrodes. And a silicon dioxide, calcium oxide, and magnesium oxide having a silicon dioxide / calcium oxide / magnesium oxide content ratio of 35 to 60/30 to 45/5 to 25 in molar ratio. Since the total amount is in the range of 0.1 to 5% by weight, the compactness and uniformity of the sintered body can be improved, the heat capacity per unit volume is larger, and the sintered body has an appropriate and stable electric resistance value. In addition, it is possible to provide a power resistor that has a small change over time in resistance due to surge absorption, has excellent uniformity of the sintered body, and can be manufactured with good reproducibility.
[0072]
According to the third aspect of the present invention, the first region has a carbon content of less than 1% by weight and the second region has a carbon content of 1 to 10% by weight. In addition to the effects described above, it is possible to provide a power resistor that can secure a resistivity suitable for a power resistor and sufficient density.
[0073]
Further, according to the invention of claim 4, the second granulated powder forming the second region is contained in the range of 20 to 60% by weight based on the first granulated powder forming the first region. Since the second region is mixed, in addition to the effect of claim 1, the electrical connection between the second regions is contained to the extent that it is easy, but the first region is not contained so as to be neglected. It is possible to provide a power resistor capable of controlling the rate.
[0074]
According to the invention of claim 5, the aluminum oxide particles in the second region have an average particle size in the range of 0.4 to 1 μm, and the aluminum oxide particles in the first region are aluminum oxide particles in the second region. Since it has a size of 2 to 5 times as large as the particles, in addition to the effect of claim 1, good sinterability can be ensured, and the mixing ratio of the second granulated powder can be adjusted to the first and second granules. It is possible to provide a power resistor that can be made smaller than when the average particle diameter of the powder is equal.
[0075]
Further, according to the invention of claim 7, the carbon powder is low or does not contain carbon powder, contains aluminum oxide powder, and contains silicon dioxide, calcium oxide and magnesium oxide in a silicon dioxide / calcium oxide / magnesium oxide content ratio. Adjusting the first granulated powder that forms the first region containing a molar ratio of 35 to 60/30 to 45/5 to 25 and a total amount of 0.1 to 5% by weight; It contains more carbon powder than the first region, contains aluminum oxide powder, and contains silicon dioxide, calcium oxide and magnesium oxide in a silicon dioxide / calcium oxide / magnesium oxide molar ratio of 35-60 / 30-. Adjusting a second granulated powder forming a second region containing 45/5 to 25 in a total amount of 0.1 to 5% by weight; After mixing the granulated powder and the second granulated powder, molding and sintering to form a sintered body; and forming a pair of electrodes on opposing main surfaces of the sintered body. Therefore, a method for manufacturing a power resistor that can achieve the same effect as the first aspect can be provided.
[0076]
According to the eighth aspect of the present invention, since a resistor made of a sintered body according to the first aspect is provided, a closing resistance unit having a large breaking capacity and a stable breaking performance is provided. A power circuit breaker that can achieve high performance can be provided.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a power resistor according to an embodiment of the present invention;
FIG. 2 is a diagram schematically showing a microstructure of a sintered body in the embodiment.
FIG. 3 is a diagram schematically showing an enlarged second region in the embodiment.
FIG. 4 is a view showing a component ratio range of a heated reactant containing silicon dioxide, calcium oxide, and magnesium oxide according to the embodiment;
FIG. 5 is a perspective view showing a configuration of a power resistor according to another embodiment of the present invention;
6 is a sectional view of the power resistor shown in FIG. 4 taken along line VV.
FIG. 7 is a configuration diagram showing a power circuit breaker according to an embodiment of the present invention;
FIG. 8 is a configuration diagram showing a closing resistance unit of the power circuit breaker according to the embodiment.
[Explanation of symbols]
1,15 ... resistor
2,11 ... Sintered body
3,12 ... electrode
4: Side high resistance layer
5 ... first area
6: second area,
7 ... Aluminum oxide particles
8 ... Carbon
9: Phase containing silicon dioxide, calcium oxide and magnesium oxide
21 ... Circuit breaker
22 ... arc extinguishing chamber
23 ... Main contact
24 ... Auxiliary contact
25 ... closing resistor
26 ... Insulated rod
30 ... resistor

Claims

A power resistor comprising: a sintered body containing aluminum oxide and carbon; and a pair of electrodes formed on two opposing surfaces of the sintered body,
The sintered body is
A first region having a low or no carbon content,
A second region having a higher carbon content than the first region and arranged to be connected to the pair of electrodes;
A power resistor comprising at least one of silicon dioxide, calcium oxide and magnesium oxide in a range of 0.1 to 5% by weight.

A power resistor comprising: a sintered body containing aluminum oxide and carbon; and a pair of electrodes formed on two opposing surfaces of the sintered body,
The sintered body is
A first region having a low or no carbon content,
A second region having a higher carbon content than the first region and arranged to be connected to the pair of electrodes;
The total amount of silicon dioxide (SiO ₂ ), calcium oxide (CaO), and magnesium oxide (MgO) is 35 to 60/30 to 45/5 to 25 in a molar ratio of silicon dioxide / calcium oxide / magnesium oxide. A power resistor comprising 0.1 to 5% by weight.

The power resistor according to claim 1,
The first region has a carbon content of less than 1% by weight;
The power resistor according to claim 2, wherein the second region has a carbon content in a range of 1 to 10% by weight.

The power resistor according to claim 1,
The second granulated powder forming the second region is mixed with the first granulated powder forming the first region in a range of 20 to 60% by weight. Resistor.

The power resistor according to claim 1,
The aluminum oxide particles in the second region have an average particle size in the range of 0.2 to 0.5 μm,
The power resistor according to claim 1, wherein the aluminum oxide particles in the first region have a size two to eight times as large as the aluminum oxide particles in the second region.

A power resistor comprising a sintered body containing aluminum oxide and carbon, and a pair of electrodes formed on two opposing surfaces of the sintered body,
The sintered body is
The grain boundary of aluminum oxide contains at least silicon dioxide, calcium oxide and magnesium oxide, and the carbon grain boundary contains silicon dioxide, calcium oxide and magnesium oxide less or less than the grain boundary of aluminum oxide. Power resistor.

Low or no carbon powder,
Adjusting a first granulated powder containing aluminum oxide powder and forming a first region containing silicon dioxide, calcium oxide, and magnesium oxide;
Adjusting a second granulated powder containing a carbon powder more than the first region, containing an aluminum oxide powder, and forming a second region containing silicon dioxide, calcium oxide, and magnesium oxide; ,
After mixing the first granulated powder and the second granulated powder, forming and sintering to form a sintered body;
Forming a pair of electrodes on opposing main surfaces of the sintered body.

Main switching means arranged in the current path;
An auxiliary switching unit electrically connected to the current path in parallel with the main switching unit, the auxiliary switching unit being switched to a closed state prior to the switching of the main switching unit to a closed state; Are connected in series, a sintered body and a resistor having a pair of electrodes formed on two opposing surfaces of the sintered body are incorporated.
The sintered body is
A first region having a small amount of carbon or containing no carbon, and a second region containing a large amount of carbon than the first region and arranged so as to be connected to the pair of electrodes; A power circuit breaker containing calcium oxide and magnesium oxide.