JP4730635B2 - Hydrocarbon gas sensor and hydrocarbon gas concentration measuring method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は炭化水素ガスセンサ及び炭化水素ガス濃度測定方法に関する。更に詳しくは、プロトン導電性を示す固体電解質体上に形成された電極間の電位差を測定することで対象ガスの濃度を測定する炭化水素ガスセンサ及び炭化水素ガス濃度の測定方法に関する。本発明の炭化水素ガスセンサは、各種ガスの濃度測定に用いることができるが、なかでも内燃機関の排気ガス中に含まれる炭化水素ガスの濃度測定に好適である。
【０００２】
【従来の技術】
近年、酸素イオン導電性を有する固体電解質体を利用したガスセンサが多く開発され、特表平８−５１０８４号公報及び特開２０００−１４６９０２号公報等に開示された技術が知られている。しかし、これらは何れも酸素イオンの導電を利用するため元来酸素濃度の影響を受け易く、更に、水素や一酸化炭素等と炭化水素ガスとを区別して濃度測定することは難しい。このため、酸素濃度の影響を小さくする特殊な技術及び水素や一酸化炭素等と炭化水素ガスとを区別するための特殊な技術等を必要とする。
一方、プロトン導電性を有する固体電解質体を利用したガスセンサとして、特開平６−２４２０６０号公報及び特開平９−１２７０５５号公報等が開示されている。
【０００３】
【発明が解決しようとする課題】
このうち特開平６−２４２０６０号公報に開示される炭化水素センサは、２つの電極の両方を被測定雰囲気に曝す必要がある。これは一方の電極の表面で炭化水素を燃焼させて水蒸気を発生させ、炭化水素を燃焼させない他方の電極との水蒸気分圧の差を測定することで炭化水素の濃度を測定しようとするものだからである。しかし、大量の水蒸気を含有する内燃機関の排気ガス中などでは使用することが困難である。
一方、特開平９−１２７０５５号公報には、ＢａＣｅＯ3系酸化物をプロトン導電性酸化物として用いた（１）特開平６−２４２０６０号公報と同様な両電極の水蒸気分圧差を測定する炭化水素センサ、（２）電流検知式の炭化水素センサ及び（３）水素ポンプ素子を備える起電力式の炭化水素センサが各々開示されている。更に、（４）ＳｒＣｅＯ3系酸化物を用いた電流検知式の炭化水素ガスセンサも上記公報には開示されている。しかし、実使用を鑑みると被測定ガスの有無による起電力差がより大きなガスセンサが望まれる。更に、制御性に優れる起電力式のガスセンサであることが望ましい。
【０００４】
本発明は上記問題点を解決するものであり、内燃機関等のように水蒸気が多い場所であっても使用することができ、更には水素、一酸化炭素及び一酸化窒素等を検知しない炭化水素ガスセンサ及び炭化水素ガス濃度測定方法を提供することを目的とする。更に、ＢａＣｅＯ３系酸化物と比較して測定時の電位差が大きい電位差測定式の炭化水素ガスセンサ及び炭化水素ガス濃度測定方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明の炭化水素ガスセンサは、炭素数３〜４の炭化水素ガスの濃度を測定する炭化水素ガスセンサであって、プロトン導電性を示す固体電解質体と、該固体電解質体の表面に形成された一対の電極とを備え、該電極のうちの一方は被測定雰囲気と接触し、他方は大気雰囲気と接触することを特徴とする。
また、本発明の炭化水素ガス濃度測定方法は、炭素数３〜４の炭化水素ガスの濃度を測定する炭化水素ガス濃度測定方法であって、プロトン導電性を示す固体電解質体の表面に形成された一対の電極の一方は被測定雰囲気と接触させ、他方は大気雰囲気と接触させ、該一対の電極間に生じる電位差を測定することを特徴とする。
【０００６】
上記「プロトン導電性を示す固体電解質体」（以下、単に「固体電解質体」という）は、特に限定されないが、例えば、ＳｒＣｅＯ3系プロトン導電性酸化物、ＳｒＺｒＯ3系プロトン導電性酸化物、ＢａＣｅＯ3系プロトン導電性酸化物、ＣａＺｒＯ3系プロトン導電性酸化物等（以下、これら「プロトン導電性酸化物」を単に「酸化物」ともいう）から構成することができる。
これらの酸化物には、各々のＢサイト（ＡＢＯ3系酸化物として表した場合のＢの位置）にＳｃ、Ｙ、Ｉｎ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｇｄ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ及びＬｕのうちの少なくとも１種が固溶された酸化物も含まれる。例えば、ＳｒＣｅＯ3系酸化物としてはＳｒ（Ｃｅ，Ｙｂ）Ｏ3系酸化物、ＳｒＺｒＯ3系酸化物としてはＳｒ（Ｚｒ，Ｙ）Ｏ3系酸化物及びＳｒ（Ｚｒ，Ｙｂ）Ｏ3系酸化物、ＢａＣｅＯ3系酸化物としてはＢａ（Ｃｅ，Ｙ）Ｏ3系酸化物及びＢａ（Ｃｅ，Ｎｄ）Ｏ3系酸化物、ＣａＺｒＯ3系酸化物としてはＣａ（Ｚｒ，Ｉｎ）Ｏ3系酸化物等を挙げることができる。
【０００７】
これらの酸化物を各々Ａ（Ｂ１，Ｂ２）Ｏ3系酸化物（ＡＢ１Ｏ3系酸化物のＢサイトにＢ２が固溶していることを表す）として表した場合に、Ｂ１元素及びＢ２元素の合計と、Ｏとの組成比は、Ｂ１元素、Ｂ２元素、Ｏ元素の組成比Ｂ１：Ｂ２：Ｏをｙ１：ｙ２：３−δとすると、０．８≦ｙ１≦０．９５、０．０５≦ｙ２≦０．２、０．０２５≦δ≦０．１であることが好ましい。
【０００８】
更に、Ｓｒ（Ｃｅ，Ｙｂ）Ｏ3系酸化物では０．９≦ｙ１≦０．９８、０．０２≦ｙ２≦０．１であることが好ましく、Ｓｒ（Ｚｒ，Ｙ）Ｏ3系酸化物では０．９≦ｙ１≦０．９８、０．０２≦ｙ２≦０．１であることが好ましく、Ｂａ（Ｃｅ，Ｙ）Ｏ3系酸化物では０．７≦ｙ１≦０．９、０．１≦ｙ２≦０．３であることが好ましく、Ｃａ（Ｚｒ，Ｉｎ）Ｏ3系酸化物では０．８５≦ｙ１≦０．９５、０．０５≦ｙ２≦０．１５であることが好ましい。
これらのプロトン導電性酸化物の中でも、上記のＳｒＣｅＯ3系酸化物及びＳｒＺｒＯ3系酸化物のうちの少なくとも一方を用いることが特に好ましい。これらの酸化物によると、被検知ガスとの接触により特に大きな電位差を生じさせることができる。
【０００９】
また、この固体電解質体の大きさ、形状等は特に限定されない。固体電解質体の形状は、例えば、有底円筒型、板型（長方形型、円盤型等、厚さ１０μｍ以上）、薄膜型（厚さ１０μｍ未満）などを適宜選択して用いることができる。
【００１０】
上記「一対の電極」のうち被測定雰囲気と接触する一方の電極（以下、単に「検知電極」という）は、固体電解質体の表面に形成され、被測定雰囲気に直接的又は間接的（被毒物質等から検知電極を保護する多孔性保護層等を介して）に接触する電極である。また、他方の電極（以下、単に「基準電極」という）は、固体電解質体の表面に形成されて基準ガスである大気雰囲気と接触する電極である。
【００１１】
これら検知電極及び基準電極は、電気抵抗率が１０−２Ω・ｃｍ以下（通常 Ω・ｃｍ以上、Ω・ｃｍとは試料の大きさにおいて１×１×１ｃｍ3当たりの抵抗値を示す）であることが好ましい。更に、耐熱性及び耐食性に優れ、また、固体電解質体上に被膜を形成した場合に密着性に優れることが好ましい。このため、貴金属及び貴金属を含有する導電材を検知電極及び基準電極として用いることが好ましい。更に、これらの導電材の種類によりガスセンサから取り出せる起電力にも差ができるため、より大きな起電力を取り出すことができるものを用いることが好ましい。
【００１２】
このような導電材としては、Ｏｓを除く貴金属の少なくとも１種を主成分（導電材全体の７０質量％以上、好ましくは８０質量％以上、更に好ましくは９０質量％以上含有する）とすることが好ましく、なかでも、Ｐｔ及びＰｄの少なくとも一方を主成分とすることが好ましい。尚、検知電極及び基準電極において導電材を同一にする必要はない。
【００１３】
また、検知電極及び基準電極の形状、大きさ及び厚さなどは特に限定されないが、その厚さは２μｍ以上（更には２〜１５μｍ、特に５〜１２μｍ）とすることが好ましい。２μｍ未満であると十分な導通を図ることが困難となる場合がある。また、検知電極においては、その厚さは５０μｍ以下とすることが好ましい。５０μｍを超えて厚い場合は被測定ガス（被測定雰囲気中に含まれる測定対象ガス）が、検知電極と固体電解質体とが接する三相界面（被測定ガスと検知電極と固体電解質体の３相）に達することが困難となり、感度の低下を招くことがある。
【００１４】
本発明の他の炭化水素ガスセンサは、炭素数３〜４の炭化水素ガスの濃度を測定する炭化水素ガスセンサであって、ＳｒＣｅＯ３系プロトン導電性酸化物及びＳｒＺｒＯ３系プロトン導電性酸化物のうちの少なくとも一方からなる固体電解質体と、該固体電解質体の表面に形成された一対の電極とを備え、該電極のうちの一方は被測定雰囲気と接触し、他方は水素ガスと接触することを特徴とする。
また、本発明の他の炭化水素ガス濃度測定方法は、炭素数３〜４の炭化水素ガスの濃度を測定する炭化水素ガス濃度測定方法であって、ＳｒＣｅＯ３系プロトン導電性酸化物及びＳｒＺｒＯ３系プロトン導電性酸化物のうちの少なくとも一方からなる固体電解質体の表面に形成された一対の電極の一方は被測定雰囲気と接触させ、他方は水素ガスと接触させ、該一対の電極間に生じる電位差を測定することを特徴とする。
【００１５】
上記「ＳｒＣｅＯ3系プロトン導電性酸化物」及び上記「ＳｒＺｒＯ3系プロトン導電性酸化物」は前述におけると同様である。
上記「一対の電極」のうち、被測定雰囲気と接触する電極は前記検知電極におけると同様である。また、他方の電極は水素ガスと接触すること以外は前記基準電極と同様である。
上記「水素ガス」は、基準電極が接触する雰囲気全体に対して９０体積％（尚、以下において割合を表す単位には単に「％」又は「ｐｐｍ」と記す）以上含有されることが好ましい。また、水素ガスの濃度の変化は１０％以下であることが好ましい。
【００１６】
この基準電極を水素と接触させる方法は特に限定されないが、例えば、密閉された空間内に保持された水素中に基準電極を曝すことで接触させることができる。また、別途用意された貯蔵器から流出させた水素が流通する空間内に基準電極をおくことによって接触させることができる。更に、本発明の炭化水素ガスセンサを構成する固体電解質体とは別体のプロトン導電性固体電解質体の表裏に一対の電極を設けた水素ポンプ素子を用い、この水素ポンプ素子により供給される水素に曝すことによって接触させることができる。また、本発明の固体電解質体の表面に形成された基準電極の固体電解質体に対向しない面を密封し、測定前に検知電極と基準電極との間に電圧を印加することにより固体電解質体と基準電極との間に水素を一定圧力まで充填することができる。このように固体電解質体と基準電極との間に貯めることで基準電極と水素を接触させることができる。
【００１７】
これら本発明の炭化水素ガスセンサを用いる温度は特に限定されないが、特に高い精度を必要とする場合は、固体電解質体（炭化水素ガスセンサとして用いる固体電解質）の温度は６００℃以下（より好ましくは５５０〜６００℃、更に好ましくは５６５〜５８５℃）に保持されることが好ましく、更に、狭い温度範囲（例えば温度差１０℃以内）に保たれることが好ましい。この固体電解質体が６００℃を超える高い温度ではその温度の上昇に伴い次第に起電力が小さくなる傾向にあるためである。
【００１８】
例えば、ＳｒＣｅＯ3系プロトン導電性酸化物及びＳｒＺｒＯ3系プロトン導電性酸化物のうちの少なくとも一方からなる固体電解質体を用いた場合、この固体電解質体を６００℃以下（通常５００℃以上）に保持することにより、プロペンが含有されない時と、プロペンが１０００ｐｐｍ含有される時との電位差を３０ｍＶ以上（好ましくは４０ｍＶ以上、好ましくは１００ｍＶ以下、通常２００ｍＶ以下）とすることができる。更に、この固体電解質体の温度を５５０〜６００℃に保持することで上記と同様な電位差の温度変化に伴う変動を小さく（絶対値で２０ｍＶ以下、更には１５ｍＶ以下）することができる。
【００１９】
また、このように６００℃以下であってもより適切な温度に固体電解質体を保つためにヒータ素子を別体又は一体に設けることが好ましい。更に、固体電解質体自体の抵抗は固体電解質体の温度に依存するため、その抵抗を測定し、これをフィードバックしてヒータの可動・停止を制御するヒータ制御手段を設けることもできる。これらにより更に精度のよいガス濃度測定を行うことができる。
【００２０】
これら本発明の炭化水素ガスセンサ及び本発明の炭化水素ガス濃度測定方法を用いると、水素、一酸化炭素及び一酸化窒素等に対する感度は非常に小さく（各成分ガスが含有されない時の起電力と、１０００ｐｐｍ含有される時の起電力との電位差が５ｍＶ未満）、ほとんど検知しない。これに対して、炭素数が３〜４の炭化水素｛脂肪族炭化水素、環状炭化水素及び芳香族炭化水素（これらの炭化水素が飽和、不飽和、直鎖、分枝を有するものはこれらも含む）など｝、ＣＨ２＝ＣＨＸ、ＣＨ２＝ＣＨＣＨ２Ｘ、Ｃ３Ｈ７Ｘ及びＣＨ３−ＣＨＸ−ＣＨ３等のハロゲン化炭化水素（但し、Ｘはハロゲン原子）、Ｃ２Ｈ５ＯＨ等のアルコール類、ＣＨ３ＮＯ２等のニトロ化合物類、ＣＨ３ＮＨ２等のアミン化合物類、ＣＨ３ＣＯＯＨ等のカルボン酸化合物類、ＣＨ３ＣＨＯ等のアルデヒド化合物類、アセトン等のケトン化合物類、ＣＨ３ＯＣＨ３等のエーテル化合物類及びＮＨ３等に対する起電力は十分に有するため各種可燃性ガスの検知及び濃度測定に好適である。本発明の炭化水素ガスセンサ及び炭化水素ガス濃度測定方法は、これらの中でも特に炭素数３〜４のアルケンに対する検知に優れている。
【００２４】
これら本発明の炭化水素ガスセンサ及び本発明の炭化水素ガス濃度測定方法を用いると、水素、一酸化炭素及び一酸化窒素等に対する感度は非常に小さく（各成分ガスが含有されない時の起電力と、１０００ｐｐｍ含有される時の起電力との電位差が絶対値で５ｍＶ未満）、ほとんど検知しない。これに対して、炭素数が３〜４の炭化水素、特に不飽和炭化水素に対する感応性に優れる｛各成分ガスが含有されない時と、１０００ｐｐｍ含有される時との電位差が絶対値で２０ｍＶ以上（更には３０ｍＶ以上、特に４０ｍＶ以上、通常２００ｍＶ以下）｝。
【００２５】
また、本発明の炭化水素ガスセンサ及び本発明の炭化水素ガス濃度測定方法において、プロペンを測定基準として使用した場合に、プロペンが含有されない時とプロペンが１０００ｐｐｍ含有される時のとの電位差を絶対値で２０ｍＶ以上（更には３０ｍＶ以上、特に４０ｍＶ以上、通常２００ｍＶ以下）｝とすることができる。
更に、１−ブテン（ｎ−ブテン）を測定基準として使用した場合に、１−ブテンが含有されない時と１−ブテンが１０００ｐｐｍ含有される時のとの電位差を絶対値で３０ｍＶ以上（更には３５ｍＶ以上、特に４０ｍＶ以上、通常２００ｍＶ以下）｝とすることができる。
【００２６】
【発明の実施の形態】
以下、実施例により本発明を具体的に説明する。
［１］炭化水素ガスセンサの製造
（１）本発明の炭化水素ガスセンサ及び炭化水素ガス濃度測定装置の製造
組成がＳｒＣｅ０．９５Ｙｂ０．０５Ｏ３−α（以下、単に「ＳＣＹ」と記す）で表され、直径１４ｍｍ、厚さ０．８ｍｍの円盤状プロトン導電性固体電解質体１の表裏面の中央部０．５ｃｍ２にＰｔ粉末を７１〜７６質量％含有する白金ペーストを塗布した。次いで、９００℃に１時間加熱して、円盤状プロトン導電性固体電解質体の表裏面に塗布した白金ペーストを焼き付けて厚さ５〜３０μｍの電極層２１、２２を形成した。次いで、この電極層の各々に金線３２が延設された金メッシュ３１（全体の７１〜７６質量％が金）を接触させてガスセンサを得た。その後、この金メッシュを接触させたプロトン導電性固体電解質体を、内部に細径の内管４１（直径９ｍｍ）を有するアルミナセラミック製の２本の二重管（外管４２直径１３ｍｍ）の間にガラスシール材５を介して挟み、金線を管外まで導出してガラスシール材を封着した。次いで、検知電極に接続された金線をプラスとして、基準電極及び検知電極に接続された金線にエレクトロメータ（北斗電工株式会社製、形式「ＨＥ−１０４」）を接続して炭化水素ガス濃度測定装置を得た。
【００２７】
同様にして、組成がＳｒＺｒ０．９Ｙ０．１Ｏ３−α（以下、単に「ＳＺＹ」と記す）、ＢａＣｅ０．８Ｙ０．２Ｏ３−α（以下、単に「ＢＣＹ」と記す）で各々表される円盤状プロトン導電性固体電解質体を用いた炭化水素ガスセンサと、炭化水素ガス濃度測定装置を製造した。
【００２８】
（２）炭化水素ガス濃度の測定
（１）で得られた本発明の炭化水素ガスセンサを備える炭化水素ガス濃度測定装置の各々を加熱炉内に表１に示す温度に保って載置した。次いで、基準電極側の二重管内に大気を毎分１００ｍｌの速度で流入させた。更に、検知電極側の二重管内には酸素を１０％含有するアルゴンガスからなる基ガスと、基ガス内での濃度が１０００ｐｐｍとなるプロペンとを各々別の貯蔵器から合わせて毎分１００ｍｌの速度で流入させた。このような各装置においてプロペンを流入させた時と流入させなかった時との電極間の電位差を測定し、その電位差の差異を算出し、表１に併記した。
【００２９】
【表１】
その結果、プロペンの流入の有無により、いずれの炭化水素ガスセンサを用いた場合にも起電力の差が生じており、各々プロペンに対する感応性を有することが分かる。特に、ＳＣＹ及びＳＺＹを用いた場合には起電力の差が３５ｍＶ以上と大きく、優れた感応性を有することが分かる。
【００３１】
（３）電極材料の検討
（１）と同様にして、ＳＣＹを用いて炭化水素ガスセンサを形成した。但し、電極となるペーストとして、（１）におけると同様の白金ペースト、Ｐｄ粉末を７１〜７６質量％％含有するパラジウムペースト、Ａｕ粉末を７１〜７６質量％％含有する金ペーストの３種を用い、電極材料の異なる３種類の炭化水素ガスセンサを得た。次いで、（１）と同様にして、炭化水素ガス濃度測定装置を得た。
その後、得られた炭化水素ガス濃度測定装置を用いて（２）と同様にして起電力の差を測定した。この結果を表２に示す。
【００３２】
【表２】
この結果より、いずれの電極を用いても起電力の差を検知することができるこことが分かるが、特にＰｔ又はＰｄを用い場合には３０ｍＶ以上の大きな起電力の差を生じていることが分かる。
【００３４】
（４）ガス種による感度差の検討
（１）で得られたＳＣＹを用い、検知電極及び基準電極ともに白金ペーストから形成された炭化水素ガスセンサを用いた炭化水素ガス濃度測定装置を用い、検知電極側の二重管内に酸素を１０％含有するアルゴンガスを基ガスとし、基ガスとは別にメタン、エタン、エテン、エチン、プロパン、プロペン、ブタン、１−ブテン、２−メチルプロペン、水素、一酸化炭素、一酸化窒素の各１種づつを次第に流入させる濃度を濃くしながら（２００ｐｐｍ、４００ｐｐｍ、６００ｐｐｍ、８００ｐｐｍ、１０００ｐｐｍ）流入させた。この時の各濃度における起電力を測定して図２及び図３に示した。
【００３５】
この結果より、水素、一酸化炭素及び一酸化窒素にはほとんど感応性を有しない一方、炭素数３〜４であるアルケンに対しては被測定ガスの濃度が２００ｐｐｍであっても４０ｍＶ以上の起電力を発生しており、アルケンに対する感応性には特に優れていることが分かる。
【００３６】
（５）測定温度の検討
（１）で得られたＳＣＹを備えるガス濃度測定装置を用い、この装置を保持する温度を５００、５５０、６００、６５０及び７００℃に変化させたこと以外は（２）と同様にして起電力の測定を行い、ＳＣＹの温度に対する依存性を検討した。この結果を図４に示す。
その結果、６００℃を超えると急激に起電力が低下し始めていることが分かる。従って、本発明の炭化水素ガスセンサは６００℃以下の温度において使用することが好ましいことが分かる。
【００３７】
（６）水蒸気依存性の検討
（１）で得られた白金から形成された検知電極及び基準電極を有するＳＣＹを備える炭化水素ガス濃度測定装置を用い、検知電極側の二重管内に酸素を１０％含有するアルゴンガスを基ガスとし、基ガスとは別にプロペンを常時１０００ｐｐｍ流入させ、更に、水蒸気を流入させる基体全体に対する割合が０．６％及び２．３％となるように変化させて流入させ、この時の起電力を測定して図５に示した。
この結果より、水蒸気の含有量に依存することなくガス濃度の測定が可能であることが分かる。特に、水蒸気の含有量が０．５％以上においては全く影響を受けることがない。
【００３８】
（７）酸素依存性の検討
（１）で得られた白金から形成された検知電極及び基準電極を有するＳＣＹを備える炭化水素ガス濃度測定装置を用い、検知電極側の二重管内にアルゴンガスを基ガスとし、基ガスとは別にプロペンを常時１０００ｐｐｍ流入させ、更に、酸素を流入させる基体全体に対する割合が１％、５％及び１０％となるように変化させて流入させ、この時の起電力を測定して図６に示した。尚、比較例としてＳＣＹの変わりに酸素イオン導電性のＹＳＺを用いて｛検知電極及び基準電極は（１）と同様の白金ペーストから形成｝形成した炭化水素ガス濃度測定装置を用いて同様な測定を行った結果を示した。
この結果より、酸素イオン導電性固体電解質体を用いる場合に比べて酸素濃度の影響を受け難いことが分かる。即ち、酸素濃度が１％以下では多少の変化が見られるが、実使用時の酸素濃度域ではほとんど変化していないことが分かる。
【００３９】
（８）比較のためのＹＳＺによる各種ガスに対する感応性
プロトン導電性固体電解質体を用いた場合と、酸素イオン導電性固体電解質体を用いた場合とで、水素、一酸化炭素及び一酸化窒素に対する感応性にどのような差がでるかを検討するために、比較例であるＹＳＺを用いて（１）と同様なガス濃度測定装置を製造した。このガス濃度測定装置を用いて、（２）と同様にして測定した水素、一酸化炭素及び一酸化窒素による電位差を測定し、図７に示した。
この結果より、酸素イオン導電性を有する固体電解質体に比べて、プロトン導電性を有する固体電解質体を用いることで、特に、水素及び一酸化炭素の影響を受けることなく被測定雰囲気に中に含有される所定の炭化水素ガス濃度を測定できることが分かる。
【００４１】
【発明の効果】
本発明の炭化水素ガスセンサ及び炭化水素ガス濃度測定方法によると、内燃機関等のように水蒸気量が多い場所であっても正確に目的の炭素数３〜４の炭化水素ガスの濃度を測定することができ、更には、水素、一酸化炭素及び一酸化窒素を検知しない濃度測定を行うことができる。また、電位差測定式の炭化水素ガスセンサ及び炭化水素ガス濃度測定方法において、測定時の電位差が大きいため感度が良好で精度の高い測定を行うことができる。
【図面の簡単な説明】
【図１】 本発明の炭化水素ガスセンサを用いた炭化水素ガス濃度測定装置の一例である。
【図２】 本発明の炭化水素ガスセンサにおける各種炭化水素ガスの濃度と起電力との相関である。
【図３】 本発明の炭化水素ガスセンサにおける各種炭化水素ガスの濃度と起電力との相関である。
【図４】 本発明の炭化水素ガスセンサにおける測定温度と起電力との相関である。
【図５】 本発明の炭化水素ガスセンサにおける水蒸気の濃度と起電力との相関である。
【図６】 本発明の炭化水素ガスセンサ及び比較例であるＹＳＺを用いた炭化水素ガスセンサにおける酸素の濃度と起電力との相関である。
【図７】 比較例であるＹＳＺを用いた炭化水素ガスセンサにおける各種ガスの濃度と起電力との相関である。
【符号の説明】
１；プロトン導電性固体電解質体、２１；検知電極、２２；基準電極、３１；金メッシュ、３２；金線、４１；内管、４２；外管、５；ガラスシール。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrocarbon gas sensor and a hydrocarbon gas concentration measuring method. More specifically, the present invention relates to a hydrocarbon gas sensor for measuring the concentration of a target gas by measuring a potential difference between electrodes formed on a solid electrolyte body showing proton conductivity, and a method for measuring the concentration of hydrocarbon gas. The hydrocarbon gas sensor of the present invention can be used for measuring the concentration of various gases, and is particularly suitable for measuring the concentration of hydrocarbon gas contained in the exhaust gas of an internal combustion engine.
[0002]
[Prior art]
In recent years, many gas sensors using a solid electrolyte body having oxygen ion conductivity have been developed, and techniques disclosed in JP-A-8-51084 and JP-A-2000-146902 are known. However, since these all use the conduction of oxygen ions, they are inherently affected by the oxygen concentration, and it is difficult to measure the concentration by distinguishing hydrogen, carbon monoxide, and the like from hydrocarbon gas. For this reason, a special technique for reducing the influence of the oxygen concentration and a special technique for distinguishing hydrogen, carbon monoxide, and the like from hydrocarbon gas are required.
On the other hand, as a gas sensor using a solid electrolyte body having proton conductivity, Japanese Patent Laid-Open Nos. 6-242060 and 9-127055 are disclosed.
[0003]
[Problems to be solved by the invention]
Of these, the hydrocarbon sensor disclosed in JP-A-6-242060 needs to expose both of the two electrodes to the atmosphere to be measured. This is because the hydrocarbon concentration is burned on the surface of one electrode to generate water vapor, and the concentration of the hydrocarbon is measured by measuring the difference in water vapor partial pressure with the other electrode that does not burn the hydrocarbon. It is. However, it is difficult to use in an exhaust gas of an internal combustion engine containing a large amount of water vapor.
On the other hand, in Japanese Patent Laid-Open No. 9-127055, BaCeO 3 -based oxide is used as a proton conductive oxide. (1) Hydrocarbon for measuring the water vapor partial pressure difference between both electrodes similar to Japanese Patent Laid-Open No. 6-242060 A sensor, (2) a current detection type hydrocarbon sensor, and (3) an electromotive force type hydrocarbon sensor including a hydrogen pump element are disclosed. Further, (4) a current detection type hydrocarbon gas sensor using SrCeO 3 oxide is also disclosed in the above publication. However, in view of actual use, a gas sensor with a larger electromotive force difference due to the presence or absence of the gas to be measured is desired. Furthermore, an electromotive force type gas sensor excellent in controllability is desirable.
[0004]
The present invention solves the above-mentioned problems, and can be used even in a place where there is a lot of water vapor such as an internal combustion engine, and further, hydrocarbons that do not detect hydrogen, carbon monoxide, nitrogen monoxide, etc. An object is to provide a gas sensor and a hydrocarbon gas concentration measuring method. It is another object of the present invention to provide a potential difference measurement type hydrocarbon gas sensor and a hydrocarbon gas concentration measurement method in which the potential difference at the time of measurement is larger than that of a BaCeO 3 oxide.
[0005]
[Means for Solving the Problems]
The hydrocarbon gas sensor of the present invention is a hydrocarbon gas sensor that measures the concentration of a hydrocarbon gas having 3 to 4 carbon atoms , and includes a solid electrolyte body showing proton conductivity and a pair formed on the surface of the solid electrolyte body. One of the electrodes is in contact with the atmosphere to be measured, and the other is in contact with the air atmosphere.
The hydrocarbon gas concentration measuring method of the present invention is a hydrocarbon gas concentration measuring method for measuring the concentration of a hydrocarbon gas having 3 to 4 carbon atoms, which is formed on the surface of a solid electrolyte body showing proton conductivity. One of the pair of electrodes is in contact with the atmosphere to be measured, and the other is in contact with the air atmosphere, and a potential difference generated between the pair of electrodes is measured.
[0006]
The "solid electrolyte body showing the proton conductivity" (hereinafter, simply "solid electrolyte body" hereinafter) is not particularly limited, for example, SrCeO 3 based proton conductive oxide, SrZrO 3 based proton conductive oxide, BaCeO It can be composed of a 3 type proton conductive oxide, a CaZrO 3 type proton conductive oxide or the like (hereinafter, these “proton conductive oxides” are also simply referred to as “oxides”).
These oxides include Sc, Y, In, Nd, Pm, Sm, Eu, Gd, Dy, Ho, Er, Tm at each B site (position of B when expressed as an ABO 3 oxide). , An oxide in which at least one of Yb and Lu is dissolved is also included. For example, Sr as SrCeO 3 based oxide (Ce, Yb) O 3 based oxide, Sr (Zr, Y) as SrZrO 3 based oxide O 3 based oxide and Sr (Zr, Yb) O 3 based oxide things, Ba (Ce, Y) as BaCeO 3 based oxide O 3 based oxide and Ba (Ce, Nd) O 3 based oxide, Ca as CaZrO 3 based oxide (Zr, in) O 3 based oxide And the like.
[0007]
When these oxides are expressed as A (B1, B2) O 3 -based oxides (representing that B2 is in solid solution at the B site of AB1O 3 -based oxides), the B1 element and the B2 element The composition ratio between the total and O is as follows: B1 element, B2 element, O element composition ratio B1: B2: O is y1: y2: 3-δ, 0.8 ≦ y1 ≦ 0.95, 0.05 It is preferable that ≦ y2 ≦ 0.2 and 0.025 ≦ δ ≦ 0.1.
[0008]
Furthermore, it is preferable that 0.9 ≦ y1 ≦ 0.98 and 0.02 ≦ y2 ≦ 0.1 in the Sr (Ce, Yb) O 3 oxide, and the Sr (Zr, Y) O 3 oxide In this case, 0.9 ≦ y1 ≦ 0.98 and 0.02 ≦ y2 ≦ 0.1 are preferable. In the case of a Ba (Ce, Y) O 3 -based oxide, 0.7 ≦ y1 ≦ 0.9,. It is preferable that 1 ≦ y2 ≦ 0.3, and in the case of a Ca (Zr, In) O 3 oxide, 0.85 ≦ y1 ≦ 0.95 and 0.05 ≦ y2 ≦ 0.15 are preferable.
Among these proton conductive oxides, it is particularly preferable to use at least one of the above-described SrCeO 3 -based oxide and SrZrO 3 -based oxide. According to these oxides, a particularly large potential difference can be generated by contact with the gas to be detected.
[0009]
Further, the size, shape and the like of the solid electrolyte body are not particularly limited. As the shape of the solid electrolyte body, for example, a bottomed cylindrical type, a plate type (rectangular type, disc type, etc., thickness of 10 μm or more), a thin film type (thickness of less than 10 μm), etc. can be appropriately selected and used.
[0010]
One electrode in contact with the atmosphere to be measured (hereinafter simply referred to as “detection electrode”) of the “pair of electrodes” is formed on the surface of the solid electrolyte body and is directly or indirectly (poisoned) to the atmosphere to be measured. The electrode is in contact with the detection electrode through a porous protective layer or the like that protects the detection electrode from a substance or the like. The other electrode (hereinafter simply referred to as “reference electrode”) is an electrode that is formed on the surface of the solid electrolyte body and is in contact with the atmospheric air that is the reference gas.
[0011]
These detection electrodes and reference electrodes have an electric resistivity of 10-2 Ω · cm or less (usually Ω · cm or more, where Ω · cm indicates a resistance value per 1 × 1 × 1 cm 3 in the size of the sample). It is preferable. Furthermore, it is excellent in heat resistance and corrosion resistance, and it is preferable that it is excellent in adhesiveness when a film is formed on the solid electrolyte body. For this reason, it is preferable to use the noble metal and the conductive material containing the noble metal as the detection electrode and the reference electrode. Furthermore, since the electromotive force that can be extracted from the gas sensor can be varied depending on the type of the conductive material, it is preferable to use a material that can extract a larger electromotive force.
[0012]
As such a conductive material, at least one precious metal other than Os is a main component (70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more of the entire conductive material). In particular, it is preferable that at least one of Pt and Pd is a main component. It is not necessary to use the same conductive material for the detection electrode and the reference electrode.
[0013]
Further, the shape, size, thickness and the like of the detection electrode and the reference electrode are not particularly limited, but the thickness is preferably 2 μm or more (more preferably 2 to 15 μm, particularly 5 to 12 μm). If it is less than 2 μm, it may be difficult to achieve sufficient conduction. Further, the thickness of the detection electrode is preferably 50 μm or less. If the thickness exceeds 50 μm, the gas to be measured (the gas to be measured contained in the atmosphere to be measured) is a three-phase interface where the detection electrode and the solid electrolyte body are in contact (the three phases of the gas to be measured, the detection electrode and the solid electrolyte body) ) May be difficult to achieve, leading to a decrease in sensitivity.
[0014]
Another hydrocarbon gas sensor according to the present invention is a hydrocarbon gas sensor that measures the concentration of a hydrocarbon gas having 3 to 4 carbon atoms, and is a SrCeO 3 proton conductive oxide or a SrZrO 3 proton conductive oxide. A solid electrolyte body comprising at least one of the above and a pair of electrodes formed on the surface of the solid electrolyte body, wherein one of the electrodes is in contact with the atmosphere to be measured and the other is in contact with hydrogen gas. Features.
Another hydrocarbon gas concentration measuring method of the present invention is a hydrocarbon gas concentration measuring method for measuring the concentration of a hydrocarbon gas having 3 to 4 carbon atoms, comprising: SrCeO 3 proton conductive oxide and SrZrO 3 One of the pair of electrodes formed on the surface of the solid electrolyte body made of at least one of the system proton conductive oxides is brought into contact with the atmosphere to be measured, and the other is brought into contact with hydrogen gas, and is generated between the pair of electrodes. It is characterized by measuring a potential difference.
[0015]
The “SrCeO 3 -based proton conductive oxide” and the “SrZrO 3 -based proton conductive oxide” are the same as described above.
Of the “pair of electrodes”, the electrode in contact with the atmosphere to be measured is the same as in the detection electrode. The other electrode is the same as the reference electrode except that it comes into contact with hydrogen gas.
The above-mentioned “hydrogen gas” is preferably contained in an amount of 90% by volume or more (hereinafter, simply expressed as “%” or “ppm” in a unit expressing a ratio) with respect to the entire atmosphere in contact with the reference electrode. The change in the concentration of hydrogen gas is preferably 10% or less.
[0016]
The method of bringing the reference electrode into contact with hydrogen is not particularly limited. For example, the reference electrode can be brought into contact with hydrogen held in a sealed space. Further, contact can be made by placing a reference electrode in a space where hydrogen flowed out from a separately prepared reservoir flows. Further, a hydrogen pump element provided with a pair of electrodes on the front and back sides of a proton conductive solid electrolyte body separate from the solid electrolyte body constituting the hydrocarbon gas sensor of the present invention is used to supply hydrogen supplied by this hydrogen pump element. Can be contacted by exposure. In addition, the surface of the reference electrode formed on the surface of the solid electrolyte body of the present invention is sealed against the solid electrolyte body, and a voltage is applied between the detection electrode and the reference electrode before the measurement. Hydrogen can be filled up to a certain pressure between the reference electrode. By storing between the solid electrolyte body and the reference electrode in this way, the reference electrode and hydrogen can be brought into contact with each other.
[0017]
The temperature at which these hydrocarbon gas sensors of the present invention are used is not particularly limited. However, when particularly high accuracy is required, the temperature of the solid electrolyte body (solid electrolyte used as a hydrocarbon gas sensor) is 600 ° C. or less (more preferably 550 to 500 ° C.). 600 ° C., more preferably 565 to 585 ° C.), and it is more preferable that the temperature be kept within a narrow temperature range (for example, a temperature difference within 10 ° C.). This is because when the solid electrolyte body has a high temperature exceeding 600 ° C., the electromotive force tends to gradually decrease as the temperature rises.
[0018]
For example, when a solid electrolyte made of at least one of SrCeO 3 -based proton conductive oxide and SrZrO 3 -based proton conductive oxide is used, the solid electrolyte is held at 600 ° C. or lower (usually 500 ° C. or higher). By doing this, the potential difference between when propene is not contained and when propene is contained at 1000 ppm can be made 30 mV or more (preferably 40 mV or more, preferably 100 mV or less, usually 200 mV or less). Further, by maintaining the temperature of the solid electrolyte body at 550 to 600 ° C., the variation due to the temperature change of the potential difference similar to the above can be reduced (absolute value is 20 mV or less, further 15 mV or less).
[0019]
Further, it is preferable that the heater element is provided separately or integrally in order to keep the solid electrolyte body at a more appropriate temperature even at 600 ° C. or lower. Further, since the resistance of the solid electrolyte body itself depends on the temperature of the solid electrolyte body, it is possible to provide a heater control means for measuring the resistance and feeding back this to control the movement / stopping of the heater. Thus, the gas concentration can be measured with higher accuracy.
[0020]
When using the hydrocarbon gas sensor of the present invention and the hydrocarbon gas concentration measurement method of the present invention, the sensitivity to hydrogen, carbon monoxide, nitrogen monoxide, etc. is very small (electromotive force when each component gas is not contained, The potential difference from the electromotive force when it is contained at 1000 ppm is less than 5 mV), and is hardly detected. On the other hand, hydrocarbons having 3 to 4 carbon atoms {aliphatic hydrocarbons, cyclic hydrocarbons and aromatic hydrocarbons (these hydrocarbons are saturated, unsaturated, straight chain, branched, etc. Etc.), halogenated hydrocarbons such as CH 2 = CHX, CH 2 = CHCH 2 X, C 3 H 7 X and CH 3 -CHX-CH 3 (where X is a halogen atom), C 2 H 5 OH Alcohols such as CH 3 NO 2 , amine compounds such as CH 3 NH 2 , carboxylic acid compounds such as CH 3 COOH, aldehyde compounds such as CH 3 CHO, and ketone compounds such as acetone Since it has sufficient electromotive force for ether compounds such as CH 3 OCH 3 and NH 3 , it is suitable for detection and concentration measurement of various combustible gases. Hydrocarbon gas sensor and hydrocarbon gas concentration measuring method of the present invention is particularly excellent in detection for alkene 3-4 carbons Of these.
[0024]
When using the hydrocarbon gas sensor of the present invention and the hydrocarbon gas concentration measurement method of the present invention, the sensitivity to hydrogen, carbon monoxide, nitrogen monoxide, etc. is very small (electromotive force when each component gas is not contained, The potential difference from the electromotive force when it is contained at 1000 ppm is less than 5 mV in absolute value), and is hardly detected. On the other hand, it has excellent sensitivity to hydrocarbons having 3 to 4 carbon atoms, particularly unsaturated hydrocarbons. The potential difference between when each component gas is not contained and when it is contained at 1000 ppm is 20 mV or more in absolute value ( Furthermore, 30 mV or more, particularly 40 mV or more, usually 200 mV or less)}.
[0025]
In the hydrocarbon gas sensor of the present invention and the hydrocarbon gas concentration measurement method of the present invention, when propene is used as a measurement standard, the potential difference between when propene is not contained and when propene is contained at 1000 ppm is an absolute value. 20 mV or more (further 30 mV or more, particularly 40 mV or more, usually 200 mV or less)}.
Further, when 1-butene (n-butene) is used as a measurement standard, the potential difference between when 1-butene is not contained and when 1-butene is contained at 1000 ppm is 30 mV or more in absolute value (more 35 mV). Above, in particular, 40 mV or more, usually 200 mV or less)}.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described specifically by way of examples.
[1] Manufacture of a hydrocarbon gas sensor (1) Manufacture of a hydrocarbon gas sensor and a hydrocarbon gas concentration measuring device of the present invention The composition is SrCe 0.95 Yb 0.05 O 3-α (hereinafter simply referred to as “SCY”) A platinum paste containing 71 to 76% by mass of Pt powder was applied to 0.5 cm 2 at the center of the front and back surfaces of the disc-shaped proton conductive
[0027]
Similarly, the composition is SrZr 0.9 Y 0.1 O 3-α (hereinafter simply referred to as “SZY”), BaCe 0.8 Y 0.2 O 3-α (hereinafter simply referred to as “BCY”). ), A hydrocarbon gas sensor using a discotic proton conductive solid electrolyte body, and a hydrocarbon gas concentration measuring device were manufactured.
[0028]
(2) it is placed keeping the temperature shown in Table 1 in the hydrocarbon gas concentration measurement of (1) to each of the hydrocarbon gas concentration measuring apparatus comprising a hydrocarbon gas sensor of the present invention obtained in the heating furnace. Next, air was introduced into the double tube on the reference electrode side at a rate of 100 ml per minute. Furthermore, in the double tube on the detection electrode side, a base gas composed of argon gas containing 10% oxygen and propene having a concentration of 1000 ppm in the base gas are combined from separate reservoirs, and 100 ml per minute. It was allowed to flow in at a speed. In each of these apparatuses, the potential difference between the electrodes when propene was introduced and when propene was not introduced was measured, and the difference in the potential difference was calculated and shown in Table 1.
[0029]
[Table 1]
As a result, it can be seen that there is a difference in electromotive force when any hydrocarbon gas sensor is used depending on the presence or absence of inflow of propene, and each has sensitivity to propene. In particular, when SCY and SZY are used, it can be seen that the difference in electromotive force is as large as 35 mV or more and has excellent sensitivity.
[0031]
(3) Examination of electrode material A hydrocarbon gas sensor was formed using SCY in the same manner as in (1). However, as the paste to be an electrode, the same platinum paste as in (1), a palladium paste containing 71 to 76% by mass of Pd powder, and a gold paste containing 71 to 76% by mass of Au powder were used. Three types of hydrocarbon gas sensors with different electrode materials were obtained. Subsequently, the hydrocarbon gas concentration measuring apparatus was obtained like (1).
Then, the difference in electromotive force was measured like (2) using the obtained hydrocarbon gas concentration measuring apparatus. The results are shown in Table 2.
[0032]
[Table 2]
From this result, it can be seen that the difference in electromotive force can be detected using any electrode, but in particular, when using Pt or Pd, a large electromotive force difference of 30 mV or more is generated. I understand.
[0034]
(4) using the SCY obtained in consideration of sensitivity difference due to the gas species (1), using the hydrocarbon gas concentration measuring device using a formed from the sensing electrode and the reference electrode both the platinum paste hydrocarbon gas sensor, sensing electrodes Argon gas containing 10% oxygen in the double tube on the side is used as a base gas, and separately from the base gas, methane, ethane, ethene, ethyne, propane, propene, butane, 1-butene, 2-methylpropene, hydrogen, one The carbon oxide and the nitric oxide were each introduced while gradually increasing the concentration (200 ppm, 400 ppm, 600 ppm, 800 ppm, 1000 ppm). The electromotive force at each concentration at this time was measured and shown in FIGS.
[0035]
From this result, hydrogen, carbon monoxide, and nitric oxide have little sensitivity, but for alkenes having 3 to 4 carbon atoms, even if the concentration of the gas to be measured is 200 ppm, the occurrence of 40 mV or more is caused. It can be seen that power is generated and sensitivity to alkenes is particularly excellent.
[0036]
(5) Examination of measurement temperature (2) Except that the gas concentration measurement device provided with SCY obtained in (1) was used and the temperature for holding this device was changed to 500, 550, 600, 650 and 700 ° C. (2 ), The electromotive force was measured, and the dependence of SCY on temperature was examined. The result is shown in FIG.
As a result, it can be seen that when the temperature exceeds 600 ° C., the electromotive force starts to rapidly decrease. Therefore, it can be seen that the hydrocarbon gas sensor of the present invention is preferably used at a temperature of 600 ° C. or lower.
[0037]
(6) Examination of water vapor dependency Using a hydrocarbon gas concentration measuring device equipped with SCY having a detection electrode and a reference electrode formed from platinum obtained in (1), oxygen was introduced into the double tube on the detection electrode side. Argon gas containing 1% is used as the base gas, and in addition to the base gas, propene is allowed to constantly flow in at 1000 ppm, and the ratio of the water vapor into the entire substrate is changed to 0.6% and 2.3%. The electromotive force at this time was measured and shown in FIG.
From this result, it is understood that the gas concentration can be measured without depending on the water vapor content. In particular, when the water vapor content is 0.5% or more, there is no influence at all.
[0038]
(7) Examination of oxygen dependence Using a hydrocarbon gas concentration measuring device equipped with SCY having a detection electrode and a reference electrode formed from platinum obtained in (1), argon gas was introduced into the double tube on the detection electrode side. In addition to the base gas, propene is always allowed to flow in at 1000 ppm, and oxygen is allowed to flow in such a way that the ratio of the total base to the base is 1%, 5%, and 10%. Was measured and shown in FIG. As a comparative example, the same measurement was performed using a hydrocarbon gas concentration measuring device formed using oxygen ion conductive YSZ instead of SCY {the detection electrode and the reference electrode are formed from the same platinum paste as in (1)}. The result of having performed was shown.
From this result, it can be seen that it is less susceptible to the influence of oxygen concentration than the case of using an oxygen ion conductive solid electrolyte body. That is, it can be seen that some change is seen when the oxygen concentration is 1% or less, but there is almost no change in the oxygen concentration range during actual use.
[0039]
(8) Sensitivity to various gases by YSZ for comparison When using a proton conductive solid electrolyte body and when using an oxygen ion conductive solid electrolyte body, the sensitivity to hydrogen, carbon monoxide and nitrogen monoxide In order to examine what kind of difference appears in sensitivity, a gas concentration measuring device similar to (1) was manufactured using YSZ as a comparative example. Using this gas concentration measuring apparatus, the potential difference due to hydrogen, carbon monoxide and nitrogen monoxide measured in the same manner as in (2) was measured and is shown in FIG.
From this result, compared with the solid electrolyte body having oxygen ion conductivity, the use of the solid electrolyte body having proton conductivity, particularly in the atmosphere to be measured without being affected by hydrogen and carbon monoxide. It can be seen that the predetermined hydrocarbon gas concentration can be measured.
[0041]
【The invention's effect】
According to the hydrocarbon gas sensor and hydrocarbon gas concentration measuring method of the present invention, the concentration of the target hydrocarbon gas having 3 to 4 carbon atoms can be accurately measured even in a place where the amount of water vapor is large such as an internal combustion engine. Furthermore, it is possible to perform concentration measurement without detecting hydrogen, carbon monoxide and nitric oxide. Further, in the potential difference measurement type hydrocarbon gas sensor and hydrocarbon gas concentration measurement method, since the potential difference at the time of measurement is large, it is possible to perform measurement with good sensitivity and high accuracy.
[Brief description of the drawings]
1 is an example of the hydrocarbon gas concentration measuring device using a hydrocarbon gas sensor of the present invention.
FIG. 2 is a correlation between the concentration of various hydrocarbon gases and electromotive force in the hydrocarbon gas sensor of the present invention.
FIG. 3 is a correlation between concentrations of various hydrocarbon gases and electromotive force in the hydrocarbon gas sensor of the present invention.
FIG. 4 is a correlation between measured temperature and electromotive force in the hydrocarbon gas sensor of the present invention.
FIG. 5 is a correlation between water vapor concentration and electromotive force in the hydrocarbon gas sensor of the present invention.
FIG. 6 is a correlation between oxygen concentration and electromotive force in a hydrocarbon gas sensor of the present invention and a hydrocarbon gas sensor using YSZ as a comparative example.
FIG. 7 is a correlation between concentrations of various gases and electromotive force in a hydrocarbon gas sensor using YSZ as a comparative example.
[Explanation of symbols]
DESCRIPTION OF
Claims (8)
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| JP3993122B2 (en) * | 2002-05-29 | 2007-10-17 | 株式会社デンソー | Gas sensor element and method for measuring hydrogen-containing gas |
| JP4912968B2 (en) * | 2007-06-27 | 2012-04-11 | 則雄 三浦 | Non-methane hydrocarbon gas detector |
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|---|---|---|---|---|
| JPS60263853A (en) * | 1984-06-11 | 1985-12-27 | Tokyo Yogyo Co Ltd | Detector for concentration of hydrogen or steam in gas |
| JPH0377055A (en) * | 1989-08-21 | 1991-04-02 | Tokyo Yogyo Co Ltd | Sensor for high-temperature exhaust gas |
| JPH03276056A (en) * | 1990-03-27 | 1991-12-06 | Tokyo Yogyo Co Ltd | Insertion type sensor probe |
| JPH06242060A (en) * | 1993-02-23 | 1994-09-02 | Tokyo Yogyo Co Ltd | Hydrocarbon sensor |
| JPH08278278A (en) * | 1995-04-03 | 1996-10-22 | Tokyo Yogyo Co Ltd | Hydrogen sensor probe and its manufacturing method |
| JPH09127055A (en) * | 1995-11-02 | 1997-05-16 | Matsushita Electric Ind Co Ltd | Hydrocarbon sensor |
| JPH10284108A (en) * | 1997-03-31 | 1998-10-23 | Toyota Motor Corp | Solid electrolyte, and fuel cell, hydrogen pump, oxygen concentration sensor, and steam concentration sensor using the electrolyte |
| JPH11337518A (en) * | 1998-05-25 | 1999-12-10 | Matsushita Electric Ind Co Ltd | Hydrocarbon sensor |
| JP2000131273A (en) * | 1998-10-22 | 2000-05-12 | Tokyo Yogyo Co Ltd | Hydrogen gas sensor |
| JP2000292409A (en) * | 1999-04-01 | 2000-10-20 | Matsushita Electric Ind Co Ltd | Hydrocarbon sensor |
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- 2001-03-21 JP JP2001081449A patent/JP4730635B2/en not_active Expired - Lifetime
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60263853A (en) * | 1984-06-11 | 1985-12-27 | Tokyo Yogyo Co Ltd | Detector for concentration of hydrogen or steam in gas |
| JPH0377055A (en) * | 1989-08-21 | 1991-04-02 | Tokyo Yogyo Co Ltd | Sensor for high-temperature exhaust gas |
| JPH03276056A (en) * | 1990-03-27 | 1991-12-06 | Tokyo Yogyo Co Ltd | Insertion type sensor probe |
| JPH06242060A (en) * | 1993-02-23 | 1994-09-02 | Tokyo Yogyo Co Ltd | Hydrocarbon sensor |
| JPH08278278A (en) * | 1995-04-03 | 1996-10-22 | Tokyo Yogyo Co Ltd | Hydrogen sensor probe and its manufacturing method |
| JPH09127055A (en) * | 1995-11-02 | 1997-05-16 | Matsushita Electric Ind Co Ltd | Hydrocarbon sensor |
| JPH10284108A (en) * | 1997-03-31 | 1998-10-23 | Toyota Motor Corp | Solid electrolyte, and fuel cell, hydrogen pump, oxygen concentration sensor, and steam concentration sensor using the electrolyte |
| JPH11337518A (en) * | 1998-05-25 | 1999-12-10 | Matsushita Electric Ind Co Ltd | Hydrocarbon sensor |
| JP2000131273A (en) * | 1998-10-22 | 2000-05-12 | Tokyo Yogyo Co Ltd | Hydrogen gas sensor |
| JP2000292409A (en) * | 1999-04-01 | 2000-10-20 | Matsushita Electric Ind Co Ltd | Hydrocarbon sensor |
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