JP3551635B2 - Ceramic resistance heating element and method of manufacturing the same - Google Patents
Ceramic resistance heating element and method of manufacturing the same Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、セラミックス抵抗発熱体に関する。本発明のセラミックス抵抗発熱体は、自動車用酸素センサー及びグロープラグ、半導体加熱用ヒーター並びに石油ファンヒーター等の各種燃焼機器の点火用ヒーターまたは石油気化器用熱源などに利用される。
【０００２】
【従来技術及びその問題点】
一般家庭用や業務用として使用されるガスや灯油を用いた給湯器や暖房器等の各種燃焼機器の点火用ヒーターとしては、従来より高電圧の火花放電を利用した放電点火方式の各種点火器具が広く利用されており、最近では小型の電子制御装置が搭載され、加熱時の温度制御や燃焼状態の安定化が図られている。
しかしながら、放電点火方式の各種点火器具は、点火時の放電に伴う電波障害により、搭載された電子制御装置を誤動作させる他、周囲の通信機器に雑音を発生させるなど、点火信頼性、未着火の場合の安全性に問題があった。
【０００３】
そこで、前記のような電波障害を解消し、確実に点火して安全性、信頼性を向上させ、耐久性に優れた高性能な点火用ヒーターとして、従来の放電点火方式の各種点火器具に代わり、無機導電物質より成る抵抗発熱体を電気絶縁性セラミックス中に埋設したセラミックス抵抗発熱体が注目されている。
また、ディーゼルエンジンの始動を容易にするために、燃焼室内にセラミックス製のグロープラグを装着し発熱部に通電加熱して燃料の着火、燃焼を促すことが行われている。この発熱部を構成するセラミックス抵抗発熱体としては、例えば、特開昭６１−２３５６１３号に示されたようなタングステン、モリブデン等の高融点金属のコイル状発熱抵抗体を電気絶縁性セラミックス中に埋設した構造のグロープラグが使用されてきた。
【０００４】
しかしながら、近年、グロープラグのコストダウンを目的として、無機導電物質より成る抵抗発熱体を電気絶縁性セラミックス中に埋設したセラミックス抵抗発熱体が注目されている。
セラミックス抵抗発熱体に使用される電気絶縁性セラミックスとしては、酸化物、窒化物、酸窒化物等の種々の材料が使用される。セラミックス抵抗発熱体の用途、要求性能により、マグネシア−アルミナ−シリカ系化合物から窒化ケイ素まで、種々の材料が検討されているが、いづれの材料においても耐熱衝撃性と耐久性の改善が技術開発の主要課題となっている。
【０００５】
最高の性能が要求される用途に対しては、耐熱衝撃性及び高温強度が他の材料よりも優れている窒化ケイ素質焼結体や窒化アルミニウム質焼結体等の非酸化性セラミックスを基体部または電気絶縁性物質として使用し、タングステン（Ｗ）、モリブデン（Ｍｏ）等の高融点金属もしくはこれらの化合物が抵抗発熱体または導電性物質として使用されている。例えば、抵抗発熱体のペーストを基体上にパターン印刷したり、パターン印刷した抵抗発熱体を基体中に埋設して焼成一体化したものが利用されている。
もう少し穏和な条件で使用される用途に対しては、アルミナ、アルミナ−シリカ系化合物、またはマグネシア−アルミナ−シリカ系化合物が基体部または電気絶縁性物質として使用されている。
【０００６】
しかしながら、いずれの材料においても、基体部と抵抗発熱体部とでは、その部位を構成する成分の種類、組成が異なるため、熱膨張係数に差異を生じ、昇降温の熱サイクルの際の熱応力により、基体部と抵抗発熱体部との界面にクラックが発生するという問題があった。
この熱膨張係数のミスマッチは、セラミックス抵抗発熱体の開発において、解決すべき最重要課題の一つである。
【０００７】
例えば、ガスや灯油を用いた各種燃焼機器の点火用ヒーターにおいては、確実な点火という観点から、ヒーターの表面温度は１０００℃以上である必要がある。特に、天然ガスや噴霧された石油を点火する場合には、前記の表面温度は最低１１５０℃以上に上昇している必要がある。
また、ディーゼルエンジンの始動に使用されるグロープラグにおいても、近年、グロープラグの速熱性をさらに向上させ、エンジン始動までの待ち時間を短縮させたいという要求が高まっており、プラグ温度を従来の１０００〜１１００℃から１２００〜１３００℃に高める必要が生じている。このため、熱膨張係数のミスマッチに起因する熱応力の発生の問題は、更に深刻なものとなっている。
【０００８】
このような要求に対して、例えば、特開昭６３−９６８８３号公報や特開平５−３６４７０号公報に見られるように、基体部に使用される電気絶縁性の窒化ケイ素質焼結体中にケイ化モリブデン（ＭｏＳｉ２）等の導電性物質を分散させて、基体部と抵抗発熱体部との熱膨張係数のミスマッチを低減しようとする試みが提案されている。
しかしながら、このような試みも、必ずしもセラミックス抵抗発熱体の抵抗変化や断線という問題を解決して、十分に耐久性を向上させたという成果をもたらしているとは言い難い。
【０００９】
【発明の目的】
本発明は、上記課題を解決し、１０００℃以上の高温に発熱させるセラミックスヒーター用として、長時間の反復使用が可能である高耐久性のセラミックス抵抗発熱体を提供することを目的としている。
また、本発明はこのような高特性の要求に対して、基体部を構成する各材料毎に各材料の特性を十分に発揮し、できるだけ低価格の材料で、できるだけ高特性なヒーター性能を発揮できるような普遍的原理を提案することにより、セラミックス抵抗発熱体を製造する際における微細構造制御の指針を明示することにある。
【００１０】
【問題点を解決するための手段】
本発明は、体積固有抵抗が１０６Ω・ｃｍ以上である窒化物、酸化物及び酸窒化物から選ばれる少なくとも一種の絶縁性物質と体積固有抵抗が０．１Ω・ｃｍ以下である金属単体又は合金、炭化物、窒化物、珪化物、硼化物及びそれらの複合化合物から選ばれる少なくとも一種の導電性物質から構成され、かつ電気絶縁性を示す基体中に、基体と同一の絶縁性物質と導電性物質から構成され、かつ導電性を示す抵抗発熱体が埋設されて、一体に成形、焼結されてなるセラミックス抵抗発熱体であって、基体中の導電性物質の含有量（体積分率）（Ａ）と抵抗発熱体中の導電性物質の含有量（体積分率）（Ｂ）との比率（Ａ）／（Ｂ）が０．７５〜１．１０であり、かつ基体中に分散した導電性物質の単位断面積当たりの存在個数（Ｃ）と抵抗発熱体中に分散した導電性物質の単位断面積当たりの存在個数（Ｄ）との比率（Ｃ）／（Ｄ）が２．５〜３０の範囲に制御されており、かつ基体部の抵抗率（Ｅ）と抵抗発熱体部の抵抗率（Ｆ）との比率（Ｅ）／（Ｆ）が１０２以上であることを特徴とするセラミックス抵抗発熱体に関する。
【００１１】
また、本発明は、体積固有抵抗が１０６Ω・ｃｍ以上である窒化物、酸化物及び酸窒化物から選ばれる少なくとも一種の絶縁性物質と体積固有抵抗が０．１Ω・ｃｍ以下である金属単体又は合金、炭化物、窒化物、珪化物、硼化物及びそれらの複合化合物から選ばれる少なくとも一種の導電性物質から構成され、かつ電気絶縁性を示す基体中に、基体と同一の絶縁性物質と導電性物質から構成され、かつ導電性を示す抵抗発熱体が埋設されてなるセラミックス抵抗発熱体を製造するに際し、基体に用いる絶縁性物質の原料粉末のメジアン平均粒径（Ｇ）と抵抗発熱体に用いる絶縁性物質の原料粉末のメジアン平均粒径（Ｈ）との比率（Ｇ）／（Ｈ）が１／２０〜１／８となるように調整された２種類の粒度の原料粉末を用い、これらに導電性物質を添加、混合した後、一体に成形、焼結することを特徴とするセラミックス抵抗発熱体の製造方法に関する。
【００１２】
本発明のセラミックス抵抗発熱体は、体積固有抵抗が１０６Ω・ｃｍ以上である絶縁性物質と体積固有抵抗が０．１Ω・ｃｍ以下である導電性物質から構成され、かつ電気絶縁性を示す基体中に、基体と同一の絶縁性物質と導電性物質から構成され、かつ導電性を示す抵抗発熱体が埋設されている。
【００１３】
絶縁性物質としては、窒化ケイ素、窒化アルミニウム、窒化ホウ素等の窒化物、α−サイアロン（Ｌｎｘ（Ｓｉ，Ａｌ）１２（Ｏ，Ｎ）１６；Ｌｎは希土類元素、０＜ｘ≦２）、β−サイアロン（Ｓｉ６−ｚＡｌｚＯｚＮ８−ｚ；０＜ｚ＜４．２）、酸窒化ケイ素（Ｓｉ２ＯＮ２）等の酸窒化物、アルミナ等の単一酸化物、及びムライト（３Ａｌ２Ｏ３ ２ＳｉＯ２）、長石質磁器（ＳｉＯ２−Ａｌ２Ｏ３系）等のアルミナ−シリカ系化合物、コージェライト（２ＭｇＯ ２Ａｌ２Ｏ３ ５ＳｉＯ２）、スピネル（ＭｇＡｌ２Ｏ４）、ステアタイト（ＭｇＳｉＯ３）、フォルステライト（Ｍｇ２ＳｉＯ４）、サフィリン（４ＭｇＯ ５Ａｌ２Ｏ３ ２ＳｉＯ２）等のマグネシア−アルミナ−シリカ系化合物、サンボナイト（ＢａＯ ２ＳｉＯ２）、セルシアン（ＢａＯ Ａｌ２Ｏ３ ２ＳｉＯ２）等の酸化バリウム−アルミナ−シリカ系化合物などの複合酸化物を主成分とする各種のセラミックス材料が挙げられる。
【００１４】
また、導電性物質としては、タングステン（Ｗ；熱膨張係数５．０×１０−６／℃（ＲＴ〜１５００℃））、モリブデン（Ｍｏ；熱膨張係数６．０×１０−６／℃（ＲＴ〜１５００℃））、レニウム（Ｒｅ）、鉄（Ｆｅ）、ニッケル（Ｎｉ）、クロム（Ｃｒ）、Ｗ−Ｍｏ合金、Ｗ−Ｒｅ合金、Ｗ−Ｃｏ合金、Ｗ−Ｚｒ合金、Ｎｉ−Ｃｒ合金（８０％Ｎｉ−２０％Ｃｒ）、カンタル合金（Ｃｒ２２％、Ａｌ５．５％、Ｎｉ７２．５％）、ＭＣｒＡｌＹ合金（Ｍ；Ｆｅ、Ｎｉ、Ｃｏ、ＮｉＣｏ）等の金属単体又は合金、炭化タングステン（ＷＣ）、炭化タンタル（ＴａＣ）、炭化チタン（ＴｉＣ）等の金属炭化物、窒化チタン（ＴｉＮ）、窒化ジルコニウム（ＺｒＮ）、窒化ニオブ（ＮｂＮ）等の金属窒化物、ケイ化モリブデン（ＭｏＳｉ２、Ｍｏ５Ｓｉ３、Ｍｏ４．８Ｓｉ３Ｃ０．６）、ケイ化タングステン（ＷＳｉ２、Ｗ５Ｓｉ３）、ケイ化タンタル（ＴａＳｉ２）等の金属珪化物、ホウ化チタン（ＴｉＢ２）、ホウ化ジルコニウム（ＺｒＢ２）等の金属硼化物及びこれらの固溶体や複合化合物が挙げられる。
【００１５】
基体中の導電性物質の含有量（体積分率）（Ａ）と抵抗発熱体中の導電性物質の含有量（体積分率）（Ｂ）との比率（Ａ）／（Ｂ）は、０．７５〜１．１０、好ましくは、０．８５〜１．００である。
（Ａ）／（Ｂ）が０．７５よりも小さくなると、一般に導電性物質として使用する金属単体又は合金、金属炭化物、金属窒化物、金属珪化物、金属硼化物等の熱膨張係数は、絶縁性物質として使用する窒化物、酸化物、酸窒化物等の熱膨張係数よりもかなり大きいため、基体部と抵抗発熱体部の熱膨張係数の差が大きくなり、熱応力が発生して、両者の界面にクラックが発生するので好ましくない。また、（Ａ）／（Ｂ）が１．１０よりも大きくなると、基体部の電気抵抗値が低くなり、本発明の微細構造制御によっても、基体部と抵抗発熱体部の体積固有抵抗の比率を調整することが困難となる。
【００１６】
また、基体中に分散した導電性物質の単位断面積当たりの存在個数（Ｃ）と抵抗発熱体中に分散した導電性物質の単位断面積当たりの存在個数（Ｄ）との比率（Ｃ）／（Ｄ）が２．５〜３０の範囲に制御されている。
（Ｃ）／（Ｄ）が２．５よりも小さくなると、基体部中の導電性物質の存在形態と抵抗発熱体中の導電性物質の存在形態とが類似なものとなり、両者の間の電気抵抗値が近づいて、もはや絶縁性部分と抵抗発熱部分とを作り分けることが困難となって、本発明の目的とするセラミックス抵抗発熱体は得られなくなる。また、（Ｃ）／（Ｄ）を３０よりも大きくするには、原料として使用する粉末の粒度に大きな差をつけねばならず、微細粒と粗大粒の焼結速度の差を考慮すれば、カプセルＨＩＰ、高圧焼結（印加圧力５０００ｋｇ／ｃｍ２以上）等の手段を採用しない限り、セラミックス抵抗発熱体を作製することが困難であるため、実際的でない。
【００１７】
また、基体部の抵抗率（Ｅ）と抵抗発熱体部の抵抗率（Ｆ）との比率（Ｅ）／（Ｆ）が１０２以上、好ましくは、１０３以上である必要がある。（Ｅ）／（Ｆ）が１０２よりも小さくなると、基体部の電気抵抗値と抵抗発熱体部の電気抵抗値が近づいて、もはや本発明の目的とするセラミックス抵抗発熱体としては機能しなくなる。
【００１８】
本発明においては、基体は微細な絶縁性物質と微細な導電性物質との複合組織体とし、抵抗発熱体はやや粗大な絶縁性物質とやや粗大な導電性物質との複合組織体とすることが望ましい。基体を構成する絶縁性物質のメジアン平均粒径は０．１〜３．０μｍ、導電性物質のメジアン平均粒径は０．３〜５．０μｍが好ましい。また、抵抗発熱体を構成する絶縁性物質のメジアン平均粒径は０．３〜１０μｍ、導電性物質のメジアン平均粒径は０．８〜２０μｍが好ましい。
【００１９】
また、基体中の導電性物質の含有量は９〜１８ｖｏｌ％、抵抗発熱体中の導電性物質の含有量は１２〜２４ｖｏｌ％であることが好ましい。
抵抗発熱体中の導電性物質の含有量が１２ｖｏｌ％よりも少なくなると、現状では電気抵抗値が高くなりすぎ、発熱体として使用することが難しくなる。また、基体中の導電性物質の含有量が１８ｖｏｌ％よりも多くなると、現状では電気抵抗値が低くなりすぎて絶縁体層として使用しづらくなる。ただし、抵抗発熱体中の絶縁性物質を顆粒状に造粒した後、導電性物質と混合すれば、１２ｖｏｌ％よりも少ない添加量でも所望の電気抵抗値を得ることができる。また、基体中の導電性物質を顆粒状に造粒した後、絶縁性物質と混合すれば、１８ｖｏｌ％よりも多い添加量でも絶縁体層として使用できる。このように、絶縁性物質または導電性物質を造粒して使用すれば、前記の制約は解除されるが、製造工程が増えるため、コストアップの要因となる。
したがって、基体中の導電性物質の含有量９〜１８ｖｏｌ％、抵抗発熱体中の導電性物質の含有量１２〜２４ｖｏｌ％という条件は、絶対的なものではないが、本発明のセラミックス抵抗発熱体を容易に製造しうる、ひとつの目安となりうる。
なお、基体中の導電性物質の含有量が９ｖｏｌ％よりも少ない場合、抵抗発熱体中の導電性物質の含有量が２４ｖｏｌ％よりも多い場合、前記の基体中及び抵抗発熱体中の導電性物質の含有量の比率（Ａ）／（Ｂ）が０．７５〜１．１０という条件を満足できなくなる。
【００２０】
本発明のセラミックス抵抗発熱体は、前記した絶縁性物質と導電性物質を原料粉末として用い、基体に用いる絶縁性物質の原料粉末のメジアン平均粒径（Ｇ）と抵抗発熱体に用いる絶縁性物質の原料粉末のメジアン平均粒径（Ｈ）との比率（Ｇ）／（Ｈ）が１／２０〜１／８となるように調整し、これらに導電性物質を添加、混合した後、一体に成形、焼結することにより製造される。
原料粉末として用いる絶縁性物質と導電性物質は、高度に粒度調整さたものを使用する。特に絶縁性物質については、基体部用には微細粒の粉末を、抵抗発熱体部用には粗大粒の粉末を使用する。その際、基体部用の微細粒のメジアン平均粒径（Ｇ）と抵抗発熱体部用の粗大粒のメジアン平均粒径（Ｈ）との比率（Ｇ）／（Ｈ）を１／２０〜１／８となるように調整することにより、成形焼結後の微細構造を変化させて、基体部及び抵抗発熱体部中に分散した導電性物質の分散状態を制御することができる。なお、本発明におけるメジアン平均粒径は、すべてレーザー回折散乱法により測定した粒度分布に基づく値である。
【００２１】
（Ｇ）／（Ｈ）が１／８よりも大きくなると、基体中に分散した導電性物質の単位断面積当たりの存在個数（Ｃ）と抵抗発熱体中に分散した導電性物質の単位断面積当たりの存在個数（Ｄ）との比率（Ｃ）／（Ｄ）が２．５よりも小さくなってしまうので好ましくない。また、（Ｇ）／（Ｈ）が１／２０よりも小さくなると、微細粒と粗大粒との平均粒径の差が大きく異なってくるため、両者の焼結速度に著しい差異を生じ、基体部は高密度になるものの、抵抗発熱体部には多数のボイド、ポアが残存して緻密化できないという問題が発生する。このような状態では、抵抗発熱体部が著しく低強度となり、通電中にクラックが発生して、セラミックスヒーターとしての寿命が短くなる。
【００２２】
また、基体に用いる絶縁性物質の原料粉末のメジアン平均粒径は１μｍ以下で、粒度分布曲線における１０％径と９０％径との比率が１０以下であり、抵抗発熱体に用いる絶縁性物質の原料粉末の平均粒径は５μｍ以上で、粒度分布曲線における１０％径と９０％径との比率が２０以下であることが好ましい。
抵抗発熱体に用いる絶縁性物質の原料粉末の平均粒径が５μｍよりも小さくなると、セラミックス抵抗発熱体にした場合に高抵抗となりすぎて、発熱特性が悪くなる。また、抵抗を下げるために導電性物質の添加量を増やしても、発熱体間のバラツキが大きくなる。
また、基体に用いる導電性物質の原料粉末のメジアン平均粒径は０．２〜３．０μｍで、粒度分布曲線における１０％径と９０％径との比率が２０以下であり、抵抗発熱体に用いる導電性物質の原料粉末のメジアン平均粒径は０．３〜８．０μｍで、粒度分布曲線における１０％径と９０％径との比率が２０以下であることが好ましい。
【００２３】
本発明において、絶縁性物質として使用される窒化物、酸窒化物、及びアルミナ、アルミナ−シリカ系化合物、マグネシア−アルミナ−シリカ系化合物、酸化バリウム−アルミナ−シリカ系化合物等の酸化物の原料粉末は、金属不純物量が１０００ｐｐｍ以下、好ましくは、５００ｐｐｍ以下であることが望ましい。特に、周期律表ＩＡ族のアルカリ金属不純物は２００ｐｐｍ以下であることが望ましい。さらに、５０μｍ以上の金属異物量が、粉末１ｃｍ３当たり１００個以下、好ましくは、１０個以下であることが望ましい。
金属不純物量が１０００ｐｐｍより多い場合、または５０μｍ以上の金属異物量が、粉末１ｃｍ３当たり１００個より多い場合には、セラミックス抵抗発熱体を作製した場合に、電流−電圧特性が一定レベルとならず、一定品質で高信頼性の部品を製造することが難しい。
【００２４】
本発明で使用する絶縁性物質のうち、窒化ケイ素及び窒化アルミニウムは難焼結性であり、多量の焼結助剤を添加しないと緻密体の作製が難しい。また、これらの材料を使用した抵抗発熱体の使用温度は１２００〜１４００℃であるため、高温強度の高いことが要求される。このため、焼結助剤として、希土類元素酸化物を絶縁性物質の総量に対して２〜１５重量％と、必要に応じて、酸化アルミニウム、酸化ハフニウム、シリカのうち少なくとも一種を絶縁性物質の総量に対して０．５〜１０重量％添加し、ホットプレス等を行って高密度焼結体を作製する。絶縁性物質が窒化ケイ素の場合には、０．５〜１０重量％の窒化アルミニウムの添加も有効である。
希土類元素酸化物の添加量が２重量％よりも少なくなると、高密度なセラミックス抵抗発熱体の作製が困難となり、添加量が１５重量％よりも多くなると、得られるセラミックス抵抗発熱体の耐熱衝撃性が低下し、ヒーター寿命、耐久性が悪化する。
酸化アルミニウム、酸化ハフニウム、シリカ、及び絶縁性物質が窒化ケイ素の場合にはさらに窒化アルミニウムの添加は、焼結を容易にし、得られるセラミックス抵抗発熱体の強度、耐熱衝撃性を向上させる。しかしながら、これらの物質の添加量が１０重量％よりも多くなると、高温強度が低下するため、結果としてセラミックス抵抗発熱体の寿命、耐久性が悪化する。
【００２５】
【実施例】
以下に実施例と比較例を挙げて更に具体的に本発明を説明する。
なお、原料粉末の粒度分布は、レーザー回折散乱法により測定した。測定に際しては、超音波ホモジナイザーを使用して分散を行った。
実施例１〜２０及び比較例１〜１１
表１に示す各種の粒度の窒化けい素粉末を用意した。これらの窒化ケイ素粉末に、表２及び表３に示す配合組成の焼結助剤と導電性物質を添加して、エタノールを溶媒として４８時間湿式混合を行った。得られたスラリーを乾燥後、３５０μｍ以下の顆粒に調粒した。抵抗発熱体用に調製した顆粒については、アミノアルキド樹脂ワニス等の粘結剤と希釈用の有機溶媒を添加して混練し、ペースト化した。
基体部用に調製した顆粒を平板状に成形し、その表面に抵抗発熱体用ペーストを使用して、Ｕ字状の抵抗発熱体パターンをスクリーン印刷法により厚膜印刷した。
抵抗発熱体パターンを乾燥固化した後、電子マイクロメーターを使用して実効発熱部の断面積を測定し、断面積の最大値と最小値との差が断面積の平均値の１０％以下となるように管理した。
次に、抵抗発熱体パターンを形成した平板状の窒化ケイ素質成形体の上面に、基体部用に調製した顆粒で作製した平板状の窒化ケイ素質成形体を重ね、ホットプレス法により、２００〜５００ｋｇ／ｃｍ２の加圧下、１５５０〜１８００℃の温度で焼結して、発熱体素子を作製した。
得られた発熱体素子の端部を研削加工して、端子部を露出させ、端子部にメタライズ層を被着させて、リード線を取り付け、セラミックスヒーターを作製した。
【００２６】
作製したセラミックスヒーターの初期抵抗値を測定し、初期抵抗値が３０Ωとなるように抵抗発熱体パターンの厚さを調整して、再度、同様のプロセスにてセラミックスヒーターを作製した。（添加する導電性物質の種類、添加量等によって抵抗発熱部の初期抵抗値が変化するため、実際にセラミックスヒーターを作製して、抵抗発熱体パターンの厚さを決定するという方法を採用した。）このようにして、厚さを決定した後、評価試験用のセラミックスヒーターを作製した。
同一条件で作製したセラミックスヒーター１０本につき、まず初期抵抗値のバラツキを調べた。
次に、発熱部の先端の温度が電圧印加２０秒後に１４００℃に達する直流電圧（３５〜６５Ｖ）を２０秒間印加し、その後３０秒間圧縮空気を噴き付けて強制的に冷却し、再び通電して１４００℃まで昇温するという繰り返し試験を行って、耐久性を調べた。５０００サイクル後の抵抗値を測定し、初期抵抗値と比較して抵抗変化率を調べた。
また、セラミックスヒーターに通電して所定の飽和温度に発熱させた後、０℃の水中にヒーター先端部を浸漬させ、ヒーター表面に発生するクラックの有無を調べるというスポーリング試験を行った。なお、クラックの発生は、蛍光探傷法により検出した。
セラミックスヒーターの性能試験の結果を表４及び表５に示す。
また、実施例６で得られたセラミックスヒーターについて、基体部及び抵抗発熱体部の窒化ケイ素粒子及び導電性物質の粒度分布を測定した結果を図１及び図２に示す。
【００２７】
【表１】
【表２】
【表３】
【表４】
【表５】
実施例２１及び比較例１２〜１３
表６に示す窒化アルミニウム粉末を使用し、表７に示す製造条件で窒化ケイ素の場合と同様にしてセラミックスヒーターを作製した。
同一条件で作製したセラミックスヒーター１０本につき、まず初期抵抗値のバラツキを調べた。
次に、発熱部の先端の温度が電圧印加１０秒後に１０００℃に達する直流電圧（２０〜５０Ｖ）を１０秒間印加し、その後１５秒間圧縮空気を噴き付けて強制的に冷却し、再び通電して１０００℃まで昇温するという繰り返し試験を行って、耐久性を調べた。５０００サイクル後の抵抗値を測定し、初期抵抗値と比較して抵抗変化率を調べた。結果を表８に示す。
【００３３】
実施例２２〜２６及び比較例１４〜２１
表６に示す原料粉末を使用し、表７に示す製造条件で窒化ケイ素の場合と同様にしてセラミックスヒーターを作製した。ただし、ホットプレスは以下の条件で行った。
次に、発熱部の先端の温度が電圧印加２０秒後に１２００℃に達する直流電圧（２０〜５０Ｖ）を１０秒間印加し、その後２０秒間圧縮空気を噴き付けて強制的に冷却し、再び通電して１２００℃まで昇温するという繰り返し試験を行って、耐久性を調べた。５０００サイクル後の抵抗値を測定し、初期抵抗値と比較して抵抗変化率を調べた。結果を表８に示す。
【００３４】
【表６】
【表７】
【表８】
【図面の簡単な説明】
【図１】図１は、実施例６で得られたセラミックスヒーターの基体部及び抵抗発熱体部についての窒化ケイ素粒子の粒度分布を示す図である。
【図２】図２は、実施例６で得られたセラミックスヒーターの基体部及び抵抗発熱体部についての導電性物質の粒度分布を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ceramic resistance heating element. INDUSTRIAL APPLICABILITY The ceramic resistance heating element of the present invention is used as an oxygen sensor for automobiles, a glow plug, a heater for heating semiconductors, an ignition heater for various combustion devices such as an oil fan heater, or a heat source for an oil vaporizer.
[0002]
[Prior art and its problems]
As ignition heaters for various combustion appliances such as water heaters and heaters using gas or kerosene that are used for general household or business use, various ignition devices of the discharge ignition type using spark discharge of higher voltage than before Is widely used, and recently, a small-sized electronic control device is mounted to control temperature during heating and stabilize a combustion state.
However, various ignition devices of the discharge ignition system may cause malfunctions of the mounted electronic control unit due to radio interference caused by discharge at the time of ignition, and may generate noise in surrounding communication devices, such as ignition reliability, unignited, etc. There was a problem with safety in case.
[0003]
Therefore, as a high-performance ignition heater that eliminates the above-mentioned radio wave interference, reliably ignites, improves safety and reliability, and has excellent durability, it can replace various conventional ignition devices of the discharge ignition type. Attention has been focused on a ceramic resistance heating element in which a resistance heating element made of an inorganic conductive material is embedded in an electrically insulating ceramic.
Further, in order to facilitate starting of a diesel engine, a glow plug made of ceramics is mounted in a combustion chamber, and a heating portion is energized and heated to promote ignition and combustion of fuel. As the ceramic resistance heating element constituting the heating section, for example, a coil-shaped heating resistor made of a high melting point metal such as tungsten or molybdenum as disclosed in JP-A-61-235613 is embedded in an electrically insulating ceramic. Glow plugs with different structures have been used.
[0004]
However, in recent years, for the purpose of reducing the cost of the glow plug, a ceramic resistance heating element in which a resistance heating element made of an inorganic conductive material is embedded in an electrically insulating ceramic has attracted attention.
Various materials such as oxides, nitrides, and oxynitrides are used as the electrically insulating ceramic used for the ceramic resistance heating element. Various materials, from magnesia-alumina-silica compounds to silicon nitride, are being studied depending on the application and required performance of the ceramic resistance heating element, but improvement in thermal shock resistance and durability is required for any material. It is a major issue.
[0005]
For applications requiring the highest performance, use non-oxidizing ceramics such as silicon nitride-based sintered bodies and aluminum nitride-based sintered bodies that have better thermal shock resistance and high-temperature strength than other materials. Alternatively, a refractory metal such as tungsten (W) or molybdenum (Mo) or a compound thereof is used as a resistance heating element or a conductive substance. For example, a pattern in which a paste of a resistance heating element is printed on a substrate or a pattern in which a resistance heating element with a pattern printed is embedded in a substrate and fired and integrated are used.
For applications that are used under milder conditions, alumina, alumina-silica-based compounds, or magnesia-alumina-silica-based compounds are used as the base portion or the electrically insulating material.
[0006]
However, in any of the materials, since the types and compositions of the components constituting the base portion and the resistance heating element portion are different from each other, a difference occurs in the coefficient of thermal expansion, and the thermal stress during the thermal cycle of temperature rise and fall. Accordingly, there is a problem that cracks occur at the interface between the base portion and the resistance heating element portion.
This mismatch in the coefficient of thermal expansion is one of the most important issues to be solved in the development of a ceramic resistance heating element.
[0007]
For example, in the case of an ignition heater for various combustion devices using gas or kerosene, the surface temperature of the heater needs to be 1000 ° C. or higher from the viewpoint of reliable ignition. In particular, when igniting natural gas or atomized petroleum, the above-mentioned surface temperature needs to rise to at least 1150 ° C. or more.
In recent years, with regard to glow plugs used for starting diesel engines, there has been an increasing demand for further improving the quick heating property of the glow plugs and reducing the waiting time until the engine is started. It is necessary to increase the temperature from 1100 ° C. to 1200 to 1300 ° C. For this reason, the problem of the generation of thermal stress due to the mismatch in the coefficient of thermal expansion has become more serious.
[0008]
In response to such demands, for example, as disclosed in JP-A-63-96883 and JP-A-5-36470, an electrically insulating silicon nitride sintered body used for a base portion is used. Attempts have been made to disperse a conductive material such as molybdenum silicide (MoSi 2 ) to reduce the mismatch in the coefficient of thermal expansion between the base and the resistance heating element.
However, it is hard to say that such an attempt has always brought about a result of solving the problems of resistance change and disconnection of the ceramic resistance heating element and sufficiently improving the durability.
[0009]
[Object of the invention]
An object of the present invention is to solve the above problems and to provide a highly durable ceramic resistance heating element that can be used repeatedly for a long time for a ceramic heater that generates heat at a high temperature of 1000 ° C. or higher.
In addition, the present invention, in response to the demand for such high characteristics, fully demonstrates the characteristics of each material for each material constituting the base portion, and exhibits the highest possible heater performance with the lowest possible price of the material. An object of the present invention is to propose a universal principle that can be used to clarify a guideline for microstructure control when manufacturing a ceramic resistance heating element.
[0010]
[Means for solving the problem]
The present invention provides at least one insulating material selected from nitrides, oxides, and oxynitrides having a volume resistivity of 10 6 Ω · cm or more, and a metal element having a volume resistivity of 0.1 Ω · cm or less. In a substrate which is composed of at least one kind of conductive material selected from alloys, carbides, nitrides, silicides, borides and composite compounds thereof, and which exhibits electrical insulation, the same insulating material as the substrate and the same conductivity A ceramic resistance heating element which is formed of a substance and is embedded and molded and sintered integrally with a resistance heating element exhibiting conductivity, wherein the content of the conductive substance in the substrate (volume fraction) ( The ratio (A) / (B) of (A) to the content (volume fraction) (B) of the conductive substance in the resistance heating element is 0.75 to 1.10. Number (C) and resistance per unit cross-sectional area of conductive material The ratio (C) / (D) of the number of conductive substances dispersed in the heat body per unit cross-sectional area (D) is controlled in the range of 2.5 to 30, and the resistivity of the base portion relates ceramic resistive heating element ratio of (E) and the resistance heating element resistivity and (F) (E) / ( F) is characterized in that 10 2 or more.
[0011]
In addition, the present invention provides at least one insulating material selected from nitrides, oxides and oxynitrides having a volume resistivity of 10 6 Ω · cm or more and a metal having a volume resistivity of 0.1 Ω · cm or less. Simple substance or alloy, carbide, nitride, silicide, boride and at least one kind of conductive material selected from composite compounds thereof, and in a substrate showing electrical insulation, the same insulating substance as the substrate, In producing a ceramic resistance heating element comprising a conductive substance and embedded with a resistance heating element exhibiting conductivity, the median average particle size (G) of the raw material powder of the insulating substance used for the base and the resistance heating element Using two types of raw material powders adjusted so that the ratio (G) / (H) to the median average particle size (H) of the raw material powder of the insulating material used in the present invention is 1/20 to 1/8. , These are conductive Adding quality, after mixing, integrally molded, a method of manufacturing a ceramic resistive heating element, characterized in that the sintering.
[0012]
The ceramic resistance heating element of the present invention is composed of an insulating material having a volume resistivity of 10 6 Ω · cm or more and a conductive material having a volume resistivity of 0.1 Ω · cm or less, and exhibits electrical insulation. A resistance heating element, which is made of the same insulating material and conductive material as the substrate and has conductivity, is embedded in the substrate.
[0013]
The insulating material, silicon nitride, aluminum nitride, nitrides such as boron nitride, alpha-sialon (Ln x (Si, Al) 12 (O, N) 16; Ln is a rare earth element, 0 <x ≦ 2), β- sialon (Si 6-z Al z O z N 8-z; 0 <z <4.2), oxynitrides such as silicon oxynitride (Si 2 ON 2), a single oxide such as alumina, and mullite (3Al 2 O 3 2SiO 2) , feldspathic porcelain (SiO 2 -Al 2 O 3 system) or the like of the alumina - silica compound, cordierite (2MgO 2Al 2 O 3 5SiO 2 ), spinel (MgAl 2 O 4) , steatite (MgSiO 3), forsterite (Mg 2 SiO 4), sapphirine (4MgO 5Al 2 O 3 2SiO 2 ) magnesia such as - alumina - silica compounds, Sambo Ito (BaO 2SiO 2), barium oxide such celsian (BaO Al 2 O 3 2SiO 2 ) - alumina - Various ceramic material composed mainly of compound oxide such as silica-based compounds.
[0014]
In addition, as the conductive material, tungsten (W; coefficient of thermal expansion 5.0 × 10 −6 / ° C. (RT to 1500 ° C.)), molybdenum (Mo; coefficient of thermal expansion 6.0 × 10 −6 / ° C. (RT ~ 1500 ° C), rhenium (Re), iron (Fe), nickel (Ni), chromium (Cr), W-Mo alloy, W-Re alloy, W-Co alloy, W-Zr alloy, Ni-Cr alloy (80% Ni-20% Cr), Kanthal alloy (Cr22%, Al5.5%, Ni72.5%), MCrAlY alloy (M; Fe, Ni, Co, NiCo), etc. WC), tantalum carbide (TaC), metal carbide such as titanium carbide (TiC), titanium nitride (TiN), metal nitride such as zirconium nitride (ZrN), niobium nitride (NbN), molybdenum silicide (MoSi 2) Mo 5 Si 3, Mo 4.8 Si 3 C 0.6), tungsten silicide (WSi 2, W 5 Si 3 ), a metal silicide such as tantalum silicide (TaSi 2), titanium boride (TiB 2) And metal borides such as zirconium boride (ZrB 2 ), and solid solutions and composite compounds thereof.
[0015]
The ratio (A) / (B) of the content (volume fraction) (A) of the conductive substance in the substrate and the content (volume fraction) (B) of the conductive substance in the resistance heating element is 0. 0.75 to 1.10, preferably 0.85 to 1.00.
When (A) / (B) is less than 0.75, the coefficient of thermal expansion of a simple metal or alloy, a metal carbide, a metal nitride, a metal silicide, a metal boride, and the like generally used as a conductive substance is insulated. Is considerably larger than the thermal expansion coefficients of nitrides, oxides, oxynitrides, etc. used as the conductive material, so that the difference between the thermal expansion coefficients of the base and the resistance heating element becomes large, and thermal stress is generated. This is not preferred because cracks occur at the interface. Further, when (A) / (B) is larger than 1.10, the electric resistance of the base decreases, and the ratio of the volume resistivity of the base to the resistance heating element can be controlled by the fine structure control of the present invention. Is difficult to adjust.
[0016]
The ratio (C) / (C) of the number of conductive substances present in the substrate per unit cross-sectional area (C) and the number of conductive substances present in the resistive heating element per unit cross-sectional area (D) / (D) is controlled in the range of 2.5 to 30.
When (C) / (D) is smaller than 2.5, the form of the conductive substance in the base portion and the form of the conductive substance in the resistance heating element become similar, and the electric current between the two becomes similar. As the resistance value approaches, it becomes difficult to separately form an insulating portion and a resistance heating portion, and the ceramic resistance heating element of the present invention cannot be obtained. Further, in order to make (C) / (D) larger than 30, the particle size of the powder used as a raw material must be greatly different. Considering the difference in the sintering speed between the fine particles and the coarse particles, Unless a means such as capsule HIP or high-pressure sintering (applied pressure of 5000 kg / cm 2 or more) is adopted, it is not practical because it is difficult to produce a ceramic resistance heating element.
[0017]
Further, the resistivity of the base portion (E) and the resistance of the resistance heating element (F) the ratio of the (E) / (F) is 10 2 or more, preferably, should be 10 3 or more. (E) / (F) If is smaller than 10 2, and the electric resistance value of the electric resistance value and the resistance heating element of the base portion is close, not function anymore as a ceramic resistance heating element which is an object of the present invention .
[0018]
In the present invention, the substrate is a composite structure of a fine insulating material and a fine conductive material, and the resistance heating element is a composite structure of a slightly coarse insulating material and a slightly coarse conductive material. Is desirable. The median average particle size of the insulating material constituting the base is preferably 0.1 to 3.0 μm, and the median average particle size of the conductive material is preferably 0.3 to 5.0 μm. Further, the median average particle size of the insulating material constituting the resistance heating element is preferably 0.3 to 10 μm, and the median average particle size of the conductive material is preferably 0.8 to 20 μm.
[0019]
The content of the conductive substance in the base is preferably 9 to 18 vol%, and the content of the conductive substance in the resistance heating element is preferably 12 to 24 vol%.
When the content of the conductive substance in the resistance heating element is less than 12 vol%, the electric resistance value is too high at present, and it is difficult to use the heating element as a heating element. On the other hand, when the content of the conductive substance in the base is more than 18 vol%, the electric resistance value is too low at present, and it is difficult to use it as an insulator layer. However, if the insulating substance in the resistance heating element is granulated into granules and then mixed with a conductive substance, a desired electric resistance value can be obtained with an addition amount of less than 12 vol%. Further, if the conductive material in the base is granulated into granules and then mixed with an insulating material, even an added amount of more than 18 vol% can be used as an insulator layer. As described above, if the insulating material or the conductive material is granulated and used, the above restriction is released, but the number of manufacturing steps is increased, which causes a cost increase.
Therefore, the condition that the content of the conductive substance in the base is 9 to 18 vol% and the content of the conductive substance in the resistance heating element is 12 to 24 vol% is not absolute, but the ceramic resistance heating element of the present invention is not absolute. Can be easily manufactured, and can be a guide.
In addition, when the content of the conductive substance in the base is less than 9 vol%, and when the content of the conductive substance in the resistance heating element is more than 24 vol%, the conductivity in the base and the resistance heating element is reduced. It becomes impossible to satisfy the condition that the ratio (A) / (B) of the substance contents is 0.75 to 1.10.
[0020]
The ceramic resistance heating element of the present invention uses the above-mentioned insulating substance and conductive substance as a raw material powder, the median average particle diameter (G) of the raw material powder of the insulating substance used for the substrate, and the insulating substance used for the resistance heating element. Is adjusted so that the ratio (G) / (H) of the raw material powder to the median average particle size (H) is 1/20 to 1/8, and a conductive substance is added thereto, mixed, and then integrated. It is manufactured by molding and sintering.
As the insulating substance and the conductive substance used as the raw material powders, those having a highly adjusted particle size are used. In particular, as for the insulating material, fine-grained powder is used for the base portion, and coarse-grained powder is used for the resistance heating element portion. At this time, the ratio (G) / (H) of the median average particle size (G) of the fine particles for the base portion and the median average particle size (H) of the coarse particles for the resistance heating element portion is 1/20 to 1 By adjusting so as to be / 8, the fine structure after molding and sintering can be changed to control the dispersion state of the conductive substance dispersed in the base portion and the resistance heating element portion. The median average particle diameter in the present invention is a value based on a particle size distribution measured by a laser diffraction scattering method.
[0021]
When (G) / (H) is larger than ８, the number of conductive substances dispersed in the base per unit cross-sectional area (C) and the unit cross-sectional area of the conductive substance dispersed in the resistance heating element The ratio (C) / (D) to the number of hits per unit (D) becomes smaller than 2.5, which is not preferable. When (G) / (H) is smaller than 1/20, the difference in average particle diameter between the fine particles and the coarse particles is significantly different, so that there is a remarkable difference in the sintering speed between the two. However, although the density becomes high, there is a problem that a large number of voids and pores remain in the resistance heating element portion so that it cannot be densified. In such a state, the resistance heating element portion has extremely low strength, cracks occur during energization, and the life of the ceramic heater is shortened.
[0022]
Further, the median average particle diameter of the raw material powder of the insulating substance used for the substrate is 1 μm or less, and the ratio of the 10% diameter to the 90% diameter in the particle size distribution curve is 10 or less. The average particle diameter of the raw material powder is preferably 5 μm or more, and the ratio of the 10% diameter to the 90% diameter in the particle size distribution curve is preferably 20 or less.
If the average particle diameter of the raw material powder of the insulating substance used for the resistance heating element is smaller than 5 μm, the resistance heating element becomes too high in the case of a ceramic resistance heating element, and the heat generation characteristics deteriorate. Further, even if the amount of the conductive substance added is increased to reduce the resistance, the variation between the heating elements increases.
The median average particle diameter of the raw material powder of the conductive substance used for the substrate is 0.2 to 3.0 μm, and the ratio of 10% diameter to 90% diameter in the particle size distribution curve is 20 or less. It is preferable that the raw material powder of the conductive substance used has a median average particle size of 0.3 to 8.0 μm and a ratio of 10% diameter to 90% diameter in the particle size distribution curve is 20 or less.
[0023]
In the present invention, raw material powders of nitrides, oxynitrides, and oxides such as alumina, alumina-silica-based compounds, magnesia-alumina-silica-based compounds, and barium oxide-alumina-silica-based compounds used as insulating materials It is desirable that the metal impurity amount be 1000 ppm or less, preferably 500 ppm or less. In particular, the content of alkali metal impurities in Group IA of the periodic table is desirably 200 ppm or less. Further, it is desirable that the amount of foreign metal particles having a size of 50 μm or more is 100 or less, preferably 10 or less per 1 cm 3 of the powder.
When the amount of metal impurities is more than 1000 ppm, or when the amount of foreign metal particles having a size of 50 μm or more is more than 100 per 1 cm 3 of powder, the current-voltage characteristics are not at a constant level when a ceramic resistance heating element is manufactured. It is difficult to manufacture high quality parts with high reliability.
[0024]
Among the insulating materials used in the present invention, silicon nitride and aluminum nitride are difficult to sinter, and it is difficult to produce a dense body without adding a large amount of a sintering aid. Further, since the working temperature of the resistance heating element using these materials is 1200 to 1400 ° C., high strength at high temperature is required. Therefore, as a sintering aid, the rare earth element oxide is 2 to 15% by weight based on the total amount of the insulating substance, and if necessary, at least one of aluminum oxide, hafnium oxide, and silica is used as the insulating substance. 0.5 to 10% by weight of the total amount is added, and hot pressing is performed to produce a high-density sintered body. When the insulating material is silicon nitride, the addition of 0.5 to 10% by weight of aluminum nitride is also effective.
When the amount of the rare earth element oxide is less than 2% by weight, it is difficult to produce a high-density ceramic resistance heating element, and when the amount is more than 15% by weight, the resulting ceramic resistance heating element has thermal shock resistance. And heater life and durability deteriorate.
When aluminum oxide, hafnium oxide, silica, and the insulating substance are silicon nitride, the addition of aluminum nitride facilitates sintering and improves the strength and thermal shock resistance of the resulting ceramic resistance heating element. However, when the addition amount of these substances is more than 10% by weight, the high-temperature strength decreases, and as a result, the life and durability of the ceramic resistance heating element deteriorate.
[0025]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
The particle size distribution of the raw material powder was measured by a laser diffraction scattering method. At the time of measurement, dispersion was performed using an ultrasonic homogenizer.
Examples 1 to 20 and Comparative Examples 1 to 11
Silicon nitride powders of various particle sizes shown in Table 1 were prepared. To these silicon nitride powders, a sintering aid and a conductive substance having the composition shown in Tables 2 and 3 were added, and wet mixing was performed for 48 hours using ethanol as a solvent. After the obtained slurry was dried, it was sized to granules of 350 μm or less. The granules prepared for the resistance heating element were kneaded by adding a binder such as an aminoalkyd resin varnish and an organic solvent for dilution to form a paste.
The granules prepared for the base were molded into a flat plate, and a U-shaped resistive heating element pattern was printed on the surface of the granule by a screen printing method using a resistive heating element paste.
After the resistance heating element pattern is dried and solidified, the sectional area of the effective heating section is measured using an electronic micrometer, and the difference between the maximum value and the minimum value of the sectional area becomes 10% or less of the average value of the sectional area. Managed as follows.
Next, on the upper surface of the flat silicon nitride-based molded body on which the resistance heating element pattern was formed, the flat silicon nitride-based molded body made of granules prepared for the base portion was overlaid, and hot press method was performed. Sintering was performed at a temperature of 1550 to 1800 ° C. under a pressure of 500 kg / cm 2 to produce a heating element.
An end portion of the obtained heating element was ground to expose a terminal portion, a metallized layer was applied to the terminal portion, a lead wire was attached, and a ceramic heater was produced.
[0026]
The initial resistance value of the produced ceramic heater was measured, the thickness of the resistance heating element pattern was adjusted so that the initial resistance value became 30Ω, and a ceramic heater was produced again by the same process. (Since the initial resistance value of the resistance heating portion changes depending on the type of the conductive substance to be added, the amount added, and the like, a method of actually producing a ceramic heater and determining the thickness of the resistance heating element pattern was adopted. After the thickness was determined in this way, a ceramic heater for an evaluation test was manufactured.
First, for 10 ceramic heaters manufactured under the same conditions, variations in the initial resistance value were examined.
Next, a DC voltage (35 to 65 V) at which the temperature at the tip of the heat generating portion reaches 1400 ° C. after 20 seconds from the application of the voltage is applied for 20 seconds, and then the compressed air is blown for 30 seconds to forcibly cool down, and energized again. The temperature was raised to 1400 ° C. to test the durability. The resistance value after 5000 cycles was measured and compared with the initial resistance value to determine the rate of change in resistance.
Further, after a ceramic heater was energized to generate heat to a predetermined saturation temperature, a spalling test was performed in which the heater tip was immersed in water at 0 ° C. to check for cracks generated on the heater surface. The occurrence of cracks was detected by a fluorescent flaw detection method.
Tables 4 and 5 show the results of the performance test of the ceramic heater.
1 and 2 show the results of measuring the particle size distribution of the silicon nitride particles and the conductive substance in the base and the resistance heating element for the ceramic heater obtained in Example 6.
[0027]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
Example 21 and Comparative Examples 12 to 13
Using the aluminum nitride powder shown in Table 6, a ceramic heater was produced under the production conditions shown in Table 7 in the same manner as in the case of silicon nitride.
First, for 10 ceramic heaters manufactured under the same conditions, variations in the initial resistance value were examined.
Next, a DC voltage (20 to 50 V) at which the temperature at the tip of the heat generating portion reaches 1000 ° C. after 10 seconds from the application of the voltage is applied for 10 seconds, and then compressed air is blown for 15 seconds to forcibly cool, and the power is supplied again. The temperature was raised to 1000 ° C. to test the durability. The resistance value after 5000 cycles was measured and compared with the initial resistance value to determine the rate of change in resistance. Table 8 shows the results.
[0033]
Examples 22 to 26 and Comparative Examples 14 to 21
Using the raw material powders shown in Table 6, a ceramic heater was produced under the production conditions shown in Table 7 in the same manner as in the case of silicon nitride. However, hot pressing was performed under the following conditions.
Next, a DC voltage (20 to 50 V) at which the temperature at the tip of the heating portion reaches 1200 ° C. after 20 seconds from the application of the voltage is applied for 10 seconds, and then the compressed air is blown for 20 seconds to forcibly cool, and the power is supplied again. The temperature was raised to 1200 ° C. to test the durability. The resistance value after 5000 cycles was measured and compared with the initial resistance value to determine the rate of change in resistance. Table 8 shows the results.
[0034]
[Table 6]
[Table 7]
[Table 8]
[Brief description of the drawings]
FIG. 1 is a view showing a particle size distribution of silicon nitride particles in a base portion and a resistance heating element portion of a ceramic heater obtained in Example 6.
FIG. 2 is a view showing a particle size distribution of a conductive substance in a base portion and a resistance heating element portion of a ceramic heater obtained in Example 6.
Claims (12)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19342596A JP3551635B2 (en) | 1996-07-23 | 1996-07-23 | Ceramic resistance heating element and method of manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19342596A JP3551635B2 (en) | 1996-07-23 | 1996-07-23 | Ceramic resistance heating element and method of manufacturing the same |
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| Publication Number | Publication Date |
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| JPH1041052A JPH1041052A (en) | 1998-02-13 |
| JP3551635B2 true JP3551635B2 (en) | 2004-08-11 |
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| JP19342596A Expired - Lifetime JP3551635B2 (en) | 1996-07-23 | 1996-07-23 | Ceramic resistance heating element and method of manufacturing the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP5030630B2 (en) * | 2007-03-20 | 2012-09-19 | 日本特殊陶業株式会社 | Ceramic heater |
| JP4996283B2 (en) * | 2006-05-18 | 2012-08-08 | 日本特殊陶業株式会社 | Ceramic heater and glow plug |
| CN101455118B (en) * | 2006-05-18 | 2011-08-17 | 日本特殊陶业株式会社 | Ceramic heater and glow plug |
| CN112385901A (en) * | 2019-10-23 | 2021-02-23 | 湖北中烟工业有限责任公司 | Heating element and preparation method and application thereof |
| CN112573926A (en) * | 2020-12-28 | 2021-03-30 | 无锡海古德新技术有限公司 | Aluminum nitride conductor material and aluminum nitride full-ceramic heating structure device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS60254586A (en) * | 1984-05-30 | 1985-12-16 | 株式会社デンソー | Ceramic heater |
| JPS6396883A (en) * | 1986-10-09 | 1988-04-27 | 株式会社デンソー | Ceramic heater |
| JP2616931B2 (en) * | 1987-09-01 | 1997-06-04 | 株式会社デンソー | Glow plug heater support |
| JP3575624B2 (en) * | 1994-04-04 | 2004-10-13 | 株式会社デンソー | Heating element |
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