JPH11148916A - Gas sensor - Google Patents
Gas sensorInfo
- Publication number
- JPH11148916A JPH11148916A JP9329638A JP32963897A JPH11148916A JP H11148916 A JPH11148916 A JP H11148916A JP 9329638 A JP9329638 A JP 9329638A JP 32963897 A JP32963897 A JP 32963897A JP H11148916 A JPH11148916 A JP H11148916A
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- Prior art keywords
- gas
- electrode
- detection
- solid electrolyte
- detection electrode
- Prior art date
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- Measuring Oxygen Concentration In Cells (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ガスセンサ、特に
燃焼ガス中の窒素酸化物濃度を検出するガスセンサに関
するものである。また、本発明の原理は窒素酸化物以外
のガス検知にも広く適用することができる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor, and more particularly to a gas sensor for detecting the concentration of nitrogen oxides in combustion gas. Further, the principle of the present invention can be widely applied to detection of gases other than nitrogen oxides.
【０００２】[0002]
【従来の技術】自動車を初めとした内燃機関と火力発電
所、プラント等の燃焼機器から排出されるＮＯｘが光化
学スモックや酸性雨の原因になるほか、人間の呼吸器に
有害であり、地球環境にも大きな汚染源とされている。
このため、ＮＯｘ等の有害ガスの検知は重要な課題とな
り、測定機器の小型化、低コスト化、さらに、各種使用
環境に対応できるガスセンサが求められている。2. Description of the Related Art NOx emitted from internal combustion engines such as automobiles and combustion equipment such as thermal power plants and plants causes photochemical smocks and acid rain, and is harmful to human respiratory organs. It is also a major source of pollution.
For this reason, detection of harmful gases such as NOx has become an important issue, and there has been a demand for a gas sensor that can be reduced in size and cost, and that can respond to various use environments.
【０００３】近年、自動車排ガス中に直接挿入して連続
検知が行える全固体型ＮＯｘセンサが注目を集め、幾つ
かの研究結果を報告されている。例えば、自動車の高温
排ガス中のＮＯｘ濃度を検出できるセンサとして電流型
のセンサが報告されている（SAE TECHNICAL PARER 9603
34）。このセンサはイオン伝導体に２室を設け、第一室
で酸素ポンプにより測定雰囲気内の酸素濃度をほぼゼロ
にしてＮＯｘ中のＮＯ2をガス平衡に従いＮＯに還元
し、そのＮＯを第二室に設けた電極に電圧を印加して更
に分解する。その時に生じる酸素をイオン化して電流を
検出しＮＯｘ濃度を検出するセンサである。このセンサ
においてもＮＯｘ濃度を検出するためにＮＯ2をＮＯに
還元する酸素ポンプが適用されているため、検出される
ＮＯｘ濃度は、酸素ポンプの性能と残存する酸素濃度に
大きく左右され、測定対象ガス濃度に比べて充分に小さ
い濃度に制御しなければならない難点がある。さらに、
根本的には、ＮＯとＮＯ2の個々の濃度を測定できない
欠点がある。[0003] In recent years, all-solid-state NOx sensors that can be inserted directly into automobile exhaust gas for continuous detection have attracted attention, and some research results have been reported. For example, a current-type sensor has been reported as a sensor capable of detecting the NOx concentration in high-temperature exhaust gas from automobiles (SAE TECHNICAL PARER 9603).
34). The sensor provided a two-chamber to the ion conductor, substantially to zero the NO 2 in NOx oxygen concentration in the measurement atmosphere by the oxygen pump in the first chamber is reduced to NO accordance gas equilibrium, the NO second chamber Is further decomposed by applying a voltage to the electrode provided in the above. This sensor detects the current by ionizing oxygen generated at that time and detects the NOx concentration. Since this sensor also employs an oxygen pump that reduces NO 2 to NO in order to detect the NOx concentration, the detected NOx concentration largely depends on the performance of the oxygen pump and the remaining oxygen concentration. There is a drawback that the concentration must be controlled to be sufficiently smaller than the gas concentration. further,
Fundamentally, there is the disadvantage that the individual concentrations of NO and NO 2 cannot be measured.
【０００４】これとは別に、特開平４−１４２４５５号
公報では、イオン伝導体に感知電極と参照電極を設置
し、被検ガス中で電極間の起電力を測定するセンサが提
案されている。このセンサでは、ＮＯやＮＯ2に対して
感度を示すものの、ＮＯとＮＯ2に対する感度極性が相
反するために、ＮＯとＮＯ2が共存する被検ガスにおい
てはお互いの出力がキャンセルしあい、ＮＯとＮＯ2が
共存する場合はそれらを個々に正確に検出することはで
きない。また、ＮＯ感度がＮＯ2感度に比して小さく、
ＮＯ検知時には出力が小さい欠点がある。また、このた
めに、このままのセンサ構成では総ＮＯｘ検知もできな
いことは明白である。[0004] Separately, Japanese Patent Application Laid-Open No. 4-142455 proposes a sensor in which a sensing electrode and a reference electrode are provided on an ion conductor and an electromotive force between the electrodes in a test gas is measured. In this sensor, while indicating sensitivity to NO and NO 2, for sensitivity polarity to NO and NO 2 is reciprocal, mutually canceled output of each other in the subject gas NO and NO 2 coexist, and NO When NO 2 coexists, they cannot be individually detected accurately. Also, the NO sensitivity is smaller than the NO 2 sensitivity,
There is a disadvantage that the output is small at the time of NO detection. In addition, it is obvious that the total NOx cannot be detected with the sensor configuration as it is.
【０００５】[0005]
【発明が解決しようとする課題】このようにこれまでに
提案されているガスセンサは、測定雰囲気中のＮＯやＮ
Ｏ2を個別に検知することができず、また総ＮＯｘ濃度
を検出する場合には、ＮＯの感度が小さい欠点があっ
た。さらに、触媒や酸素ポンプなどを用いてＮＯの酸化
あるいはＮＯ2の還元を前処理として必須であり、変換
能力もかなり高いものが必要であった。本発明はＮＯあ
るいはＮＯ2に対する感度を要求に応じて大きく、且つ
他ガスに対する選択性の高いセンサを提供することを解
決すべき課題とする。As described above, the gas sensors that have been proposed so far are designed to measure NO or N in a measurement atmosphere.
In the case where O 2 cannot be detected individually and the total NOx concentration is detected, there is a disadvantage that the sensitivity of NO is low. Further, oxidation of NO or reduction of NO 2 using a catalyst, an oxygen pump, or the like is indispensable as a pretreatment, and a material having a considerably high conversion capacity is required. It is an object of the present invention to provide a sensor having a high sensitivity to NO or NO 2 as required and a high selectivity to other gases.
【０００６】[0006]
【課題を解決するための手段】本発明者らは、前述の課
題に鑑み鋭意な研究を行った結果、以下のような解決方
策を提案する。すなわち、検知対象ガスに活性な検知極
と、対極と検知対象ガスに不活性な参照極とを同一の固
体電解質上に固定し、少なくとも検知極を被検ガス中に
配し、該検知極と対極に検知極が正あるいは負のバイア
ス電圧となるように定電圧を印加し分極させ、該基準極
と対極間に流れる電流を測定する方式であって、検知対
象ガスの検知極での酸化電流の大きさから検知対象ガス
の濃度を検知するガスセンサを提案するものである。こ
の方式は、後述するごとく測定ガス濃度を正確に測定す
ることができる方式である。Means for Solving the Problems The present inventors have made intensive studies in view of the above-mentioned problems, and as a result, propose the following solutions. That is, a detection electrode active in the detection target gas, a counter electrode and a reference electrode inactive in the detection target gas are fixed on the same solid electrolyte, at least the detection electrode is arranged in the test gas, and the detection electrode is This method measures the current flowing between the reference electrode and the counter electrode by applying a constant voltage so that the detection electrode has a positive or negative bias voltage at the counter electrode and polarizing the electrode. The present invention proposes a gas sensor that detects the concentration of a detection target gas from the size of the gas. This method is a method capable of accurately measuring the measurement gas concentration as described later.
【０００７】また前述の方法の簡易型としては以下のも
のを提案する。すなわち、測定検知対象ガスに活性な検
知極と、検知対象ガスに不活性な対極とを同一の固体電
解質上に固定し、少なくとも検知極を被検ガス中に配
し、該検知極と対極間に検知極が正あるいは負のバイア
ス電圧となるように定電圧を印加し分極させ、当該電極
間に流れる電流を測定する方式であって、検知対象ガス
の検知極での酸化電流の大きさから検知対象ガスの濃度
を検知するものである。 The following is proposed as a simplified version of the above method. That is, the detection electrode active in the measurement detection target gas and the counter electrode inactive in the detection target gas are fixed on the same solid electrolyte, and at least the detection electrode is arranged in the test gas, and the detection electrode and the counter electrode are interposed. A method of measuring the current flowing between the electrodes by applying a constant voltage so that the detection electrode has a positive or negative bias voltage and measuring the current flowing between the electrodes. It detects the concentration of the gas to be detected.
【０００８】本発明のより具体的な手段としては、被検
ガス中の酸素濃度が０.１ｖｏｌ％以上であり、且つ該
固体電解質がジルコニアを主体とする酸素イオン伝導体
からなるガスセンサを提示する。すなわち、酸素イオン
伝導性のジルコニア固体電解質を用いることにより、被
検ガス中の酸素濃度が０.１ｖｏｌ％以上、より好もし
くは１ｖｏｌ％以上の高濃度で且つ広範囲の雰囲気中に
て用いることができる。As a more specific means of the present invention, there is provided a gas sensor in which the oxygen concentration in a test gas is 0.1 vol% or more and the solid electrolyte is an oxygen ion conductor mainly composed of zirconia. . That is, by using the oxygen ion conductive zirconia solid electrolyte, the oxygen concentration in the test gas can be 0.1 vol% or more, more preferably 1 vol% or more, and it can be used in a wide range of atmospheres. .
【０００９】より具体的な手段として、検知対象ガスが
窒素酸化物であり、且つ固体電解質上に固定された検知
極と対極間に印加するバイアス電圧が０Ｖより高く４０
０ｍＶより低い正の定電圧にてＮＯを選択的に検知する
方式、あるいは０Ｖより低く−１Ｖより高い負の定電圧
バイアスを用いてＮＯ2を選択的に検知するガスセンサ
を提供する。As a more specific means, the gas to be detected is nitrogen oxide and the bias voltage applied between the detection electrode fixed on the solid electrolyte and the counter electrode is higher than 0 V
Providing selectively detect that the gas sensor of NO 2 with selective detection to scheme negative constant voltage bias or higher than -1V lower than 0V, the NO in lower positive constant voltage 0 mV.
【００１０】本発明のより好ましい検知極材料はＮｉま
たはＣｒを構成元素として含む酸化物、あるいはＮｉま
たはＣｒを構成元素として含む酸化物とジルコニア固体
電解質との混合体からなる検知極を用いた窒素酸化物ガ
スセンサ、あるいはＩｒ電極、Ｒｈ電極、ＰｔとＩｒと
の合金電極、ＰｔとＲｈとの合金電極である貴金属電
極、あるいは前記貴金属とジルコニア固体電解質との混
合体とからなる検知極を用いた窒素酸化物ガスセンサを
提示する。A more preferred sensing electrode material of the present invention is an oxide containing Ni or Cr as a constituent element, or a nitrogen containing a mixture of an oxide containing Ni or Cr as a constituent element and a zirconia solid electrolyte. An oxide gas sensor, or an Ir electrode, a Rh electrode, an alloy electrode of Pt and Ir, a noble metal electrode that is an alloy electrode of Pt and Rh, or a detection electrode made of a mixture of the noble metal and a zirconia solid electrolyte was used. A nitrogen oxide gas sensor is presented.
【００１１】本発明の総ＮＯｘ検知センサへの適用につ
いては、酸素イオン伝導性を有するジルコニア固体電解
質体に一室あるいは二室の測定ガス雰囲気に連通する内
部空所を設け、少なくとも前記検知極を該内部空所に設
置し、さらに該内部空所にＮＯｘを変換するための電気
化学的酸素ポンプあるいは触媒体を形成した構成であっ
て、前記検知極が設置される内部空所にて検知対象ガス
のＮＯｘがＮＯの単体ガス、あるいはＮＯ2及びＮＯ2以
上の過酸化窒素に変換されるように酸素ポンプあるいは
触媒体を機能させ、検知極とその対極間に検知極が正あ
るいは負のバイアス電圧となるように定電圧を印加し、
前記電極間に流れる電流を測定するガスセンサにて総Ｎ
Ｏｘセンサの検知精度を向上するものである。In the application of the present invention to a total NOx detection sensor, one or two internal voids communicating with a measurement gas atmosphere are provided in a zirconia solid electrolyte having oxygen ion conductivity, and at least the detection electrode is provided. A structure in which an electrochemical oxygen pump or a catalyst for converting NOx is formed in the internal space, and a detection target is formed in the internal space in which the detection electrode is installed. single gas NOx is NO gas or to function oxygen pump or catalyst body as converted NO 2 and NO 2 or more in nitrogen peroxide, the detection electrode and the detection electrode positive or negative bias between its counter electrode Apply a constant voltage so that it becomes a voltage,
The gas sensor that measures the current flowing between the electrodes
This is to improve the detection accuracy of the Ox sensor.
【００１２】[0012]
【発明の実施の形態】図１に本発明の最も基本的な実施
形態のセンサ構成および原理を窒素酸化物センサ１を用
いて示す。ジルコニア基板２の片面にＮＯｘに対して活
性な検知極３とＯ2のみに対して活性な参照極４を形成
し、これの反対面に電流を流すための対極５を形成す
る。検知極３はＯ2に対して活性であっても構わない
が、この活性は低いことが望ましい。但し、全く不活性
であると、ＮＯｘ濃度がゼロのとき、電位が不安定にな
るので好ましくない。また、参照極４はＮＯｘに対して
不活性で、Ｏ2のみに対しての活性な金属材料を使用す
ることが望ましいが、これを被検ガスの空間と別の大気
中に設ける場合には、活性であっても構わない。対極５
についてはＮＯｘに対して活性であっても不活性であっ
ても構わないが、対極側の過電圧を高くなり過ぎないよ
うにするため、Ｏ2にのみ活性な電極が望ましい。この
ように作製したセンサ素子１を図１に示すように、ポテ
ンシオスタット６に接続し、参照極４に対して所定電圧
を検知極３に印加して、この際の検知極３に流れる電流
を測定する。この場合、ポテンシオスタットによって電
位が安定な参照極４に対して検知極３の電位が厳密に所
定値に制御され、電極電流は検知極３の表面近傍のＯ2
濃度に依存する。さらに、被検ガス中にＮＯｘが共存す
れば、検知極３の電流がＮＯｘの濃度に依存して増加す
る。このことは図２に示す検知極３の分極曲線から説明
できる。FIG. 1 shows a sensor configuration and principle of a most basic embodiment of the present invention using a nitrogen oxide sensor 1. A detection electrode 3 active for NOx and a reference electrode 4 active only for O 2 are formed on one surface of the zirconia substrate 2, and a counter electrode 5 for flowing a current is formed on the opposite surface. Although the sensing electrode 3 may be active with respect to O 2 , it is desirable that this activity is low. However, it is not preferable to be completely inactive because the potential becomes unstable when the NOx concentration is zero. It is desirable that the reference electrode 4 be made of a metal material which is inert to NOx and active only to O 2. It may be active. Counter electrode 5
May be active or inactive with respect to NOx, but an electrode that is active only on O 2 is desirable in order to prevent the overvoltage on the counter electrode side from becoming too high. As shown in FIG. 1, the sensor element 1 thus manufactured is connected to a potentiostat 6, a predetermined voltage is applied to the reference electrode 4 to the detection electrode 3, and a current flowing through the detection electrode 3 at this time is applied. Is measured. In this case, the potential of the detection electrode 3 is strictly controlled to a predetermined value with respect to the reference electrode 4 whose potential is stable by the potentiostat, and the electrode current is reduced to O 2 near the surface of the detection electrode 3.
Depends on concentration. Further, if NOx coexists in the test gas, the current of the detection electrode 3 increases depending on the NOx concentration. This can be explained from the polarization curve of the sensing electrode 3 shown in FIG.
【００１３】以上、説明したのは基本的な三電極方式Ｎ
Ｏｘセンサであるが、センサの製造と使用の面を考慮す
れば、図３に示すような構成に簡略する事ができる。ジ
ルコニア基板２の片面にＮＯｘとＯ2に対して活性な検
知極３を形成し、反対面に参照極４の作用を兼ねる対極
５を形成する。検知極３のＯ2に対する活性が低いこと
が望ましく、対極５のＯ2に対する活性が高く、ＮＯｘ
に対して不活性であることが望ましい。この素子を定電
圧電源に検知極３が正あるいは負になるように接続し、
所定電圧を印加する。また、回路中に電流測定手段を設
け、ＮＯｘ濃度に依存する電流変化を検出するようにす
る。バイアス電圧及びＯ2濃度に依存して検知極３の電
流が有る一定値に安定するが、ＮＯｘが共存すると、バ
イアス電圧によってＮＯｘが酸化或いは還元され、検知
極の電流が変化し、ＮＯｘ濃度が検出される。また、印
加電圧によって、ＮＯ2或いはＮＯのどちらか一方のみ
を選択的に検出することができ、両方に同方向の電流変
化を得ることもできる。従って、総ＮＯｘセンサとして
用いることも可能である。What has been described above is the basic three-electrode type N
Although it is an Ox sensor, the structure as shown in FIG. 3 can be simplified in consideration of manufacturing and use of the sensor. On one surface of the zirconia substrate 2, a detection electrode 3 active for NOx and O 2 is formed, and on the other surface, a counter electrode 5 also serving as a reference electrode 4 is formed. It is desirable that the activity of the detection electrode 3 against O 2 be low, the activity of the counter electrode 5 against O 2 be high, and NOx
It is desirable to be inert to This element is connected to a constant voltage power supply so that the detection electrode 3 is positive or negative,
Apply a predetermined voltage. Further, a current measuring means is provided in the circuit to detect a current change depending on the NOx concentration. The current of the detection electrode 3 is stabilized to a certain constant value depending on the bias voltage and the O 2 concentration. However, when NOx coexists, the NOx is oxidized or reduced by the bias voltage, the current of the detection electrode changes, and the NOx concentration decreases. Is detected. Further, only one of NO 2 and NO can be selectively detected by the applied voltage, and a current change in the same direction can be obtained for both. Therefore, it can be used as a total NOx sensor.
【００１４】本発明センサは、基本的に酸素共存下にお
ける混成電位型検知極及び対極の酸化電流あるいは還元
電流を測定する方式であって、単に起電力を測定する方
式や酸素が除去された雰囲気中でのガス分解で生じる酸
素の電解電流ではない。その結果として、１％以上の高
酸素濃度雰囲気にても感度の酸素濃度依存性が小さいこ
とや、ＮＯとＮＯ2での感度比はそのバイアス電圧の値
で広範囲に制御することができる。以上ＮＯｘ検知を例
に原理的な説明を行ったが、以下に具体的な実施例を上
げて、より詳細に説明する。The sensor of the present invention is basically a method of measuring the oxidation current or reduction current of the mixed potential type detection electrode and the counter electrode in the presence of oxygen, and is a method of simply measuring an electromotive force or an atmosphere from which oxygen is removed. It is not the electrolytic current of oxygen generated by gas decomposition in the atmosphere. As a result, even in an atmosphere having a high oxygen concentration of 1% or more, the dependence of sensitivity on oxygen concentration is small, and the sensitivity ratio between NO and NO 2 can be controlled in a wide range by the value of the bias voltage. Although the principle has been described above with reference to NOx detection as an example, a more specific example will be described below in more detail.
【００１５】[0015]
【実施例】（実施例１）図１に示すような構造を有する
ＮＯｘセンサを下記の方法により作製して、本測定原理
を実証した。酸素イオン伝導性を有するジルコニア固体
電解質基板２の表面にＰｔの集電体付きのＣｄＣｒ2Ｏ4
検知極３と、大気側にＰｔ参照極４とＰｔ対極５をそれ
ぞれのペーストを作製し塗布し、１２００℃で焼成して
形成した。センサを５００℃に加熱し、空気組成のガス
とこれに２００ｐｐｍのＮＯを添加した場合にて、ポテ
ンシオスタットを用いて分極曲線を測定した。その結果
を図２に示す。０〜０.２Ｖの電位領域にＮＯの濃度に
依存する酸化電流が明確に観測された。通常電流を流さ
ない場合では、ＣｄＣｒ2Ｏ4電極はＮＯに対して電極電
位の応答は全く示さないが、一定の電圧を検知極３に印
加すると、電極電流が大きく変化することが図２から分
かる。すなわち、空気のみの時の電極電流とNOを添加し
た場合の電極電流値の差(ΔＩ)が生じる領域が本発明に
よる検知の範囲となる。また電流差(ΔＩ)が無くなる上
限電圧は酸素濃度に依存し酸素濃度０.１％では０.４Ｖ
となった。(Example 1) A NOx sensor having a structure as shown in FIG. 1 was manufactured by the following method, and the principle of the present measurement was verified. CdCr 2 O 4 with a Pt current collector on the surface of a zirconia solid electrolyte substrate 2 having oxygen ion conductivity
The detection electrode 3 and a Pt reference electrode 4 and a Pt counter electrode 5 were formed and applied to the atmosphere side, respectively, and formed by baking at 1200 ° C. When the sensor was heated to 500 ° C., and a gas having an air composition and 200 ppm of NO were added thereto, a polarization curve was measured using a potentiostat. The result is shown in FIG. An oxidation current depending on the NO concentration was clearly observed in the potential range of 0 to 0.2 V. When a normal current is not applied, the CdCr 2 O 4 electrode does not show any response of the electrode potential to NO, but when a constant voltage is applied to the detection electrode 3, the electrode current changes significantly from FIG. I understand. That is, the region where the difference (ΔI) between the electrode current when only air is used and the electrode current value when NO is added is the range of detection according to the present invention. The upper limit voltage at which the current difference (ΔI) disappears depends on the oxygen concentration, and is 0.4 V at an oxygen concentration of 0.1%.
It became.
【００１６】（実施例２）実施例１と同様にして検知極
３にＰｔペーストを塗布し、１２００℃にて焼成して電
極を形成した。実施例１と同様にしてポテンシオスタッ
トを用いて分極曲線を測定した。結果を図６に示す。こ
のように検知極３にＰｔを用いた場合には、ＮＯに対し
て殆ど電流変化がないことが分かる。すなわち、検知極
３には検知対象ガスに活性な検知材料を用いることが、
本発明には有効であることが分かる。Example 2 A Pt paste was applied to the detection electrode 3 in the same manner as in Example 1, and baked at 1200 ° C. to form an electrode. A polarization curve was measured using a potentiostat in the same manner as in Example 1. FIG. 6 shows the results. As described above, when Pt is used for the detection electrode 3, it can be seen that there is almost no change in current with respect to NO. That is, for the detection electrode 3, it is necessary to use an active detection material for the detection target gas.
It is found that the present invention is effective.
【００１７】（実施例３）ジルコニア固体電解質基板２
の片面にＣｄＣｒ2Ｏ4検知極３とＰｔ参照極４を形成
し、基板２の反対面に白金対極５を形成し、図１のよう
な構造を有するセンサを作製した。検知極３と対極５の
間に検知極３の方が正となるように安定な参照極４の電
位を基準に電圧をかけた。また測定回路中に電流測定用
の負荷抵抗を挿入し、検知電流を検出した。バイアス電
圧は＋１００ｍＶと−１５０ｍＶとした。このときに、
空気にＮＯとＮＯ2を各種濃度となるように添加し、セ
ンサ温度５００℃にて電流変化を測定した。図４にバイ
アス電圧＋１００ｍＶの時のＮＯ出力を、図５にバイア
ス電圧−１５０ｍＶの時のＮＯ2出力をそれぞれ示す。
ここに示されるようにＮＯあるいはＮＯ2濃度に対して
ほぼリニアな検知出力が得られた。(Example 3) Zirconia solid electrolyte substrate 2
A CdCr 2 O 4 detection electrode 3 and a Pt reference electrode 4 were formed on one surface of the substrate, and a platinum counter electrode 5 was formed on the opposite surface of the substrate 2 to produce a sensor having a structure as shown in FIG. A voltage was applied between the detection electrode 3 and the counter electrode 5 based on the stable potential of the reference electrode 4 so that the detection electrode 3 was more positive. In addition, a load resistor for current measurement was inserted into the measurement circuit, and the detection current was detected. The bias voltage was +100 mV and -150 mV. At this time,
NO and NO 2 were added to the air at various concentrations, and the current change was measured at a sensor temperature of 500 ° C. FIG. 4 shows the NO output when the bias voltage is +100 mV, and FIG. 5 shows the NO 2 output when the bias voltage is -150 mV.
As shown here, a detection output almost linear with respect to the NO or NO 2 concentration was obtained.
【００１８】（実施例４）実施例３と同様にして他ガス
の干渉特性を測定した。バイアス電圧が＋１００ｍＶの
時は、２００ｐｐｍＮＯ，２００ｐｐｍＮＯ2，２００
ｐｐｍＣＯ，２００ｐｐｍＨ2，２００ｐｐｍＣＨ4，２
０００ｐｐｍＣＯ2および７００ＰａのＨ2Ｏを個別に測
定した。結果を表１に示す。ここに示されるように他ガ
スからの干渉は非常に小さく、ＮＯガスを選択的に検知
できることが分かる。Example 4 In the same manner as in Example 3, the interference characteristics of other gases were measured. When the bias voltage is +100 mV, 200 ppm NO, 200 ppm NO 2 , 200 ppm
ppmCO, 200 ppm H 2 , 200 ppm CH 4 , 2
000 ppm CO 2 and 700 Pa H 2 O were measured separately. Table 1 shows the results. As shown here, the interference from other gases is very small, and it can be seen that the NO gas can be selectively detected.
【００１９】[0019]
【表１】 [Table 1]
【００２０】（実施例５）図３に示すようにジルコニア
基板２の片面にＣｄＣｒ2Ｏ4ペーストを塗布し検知極３
を形成し、その反対面にＰｔペーストを塗布し対極５と
して形成した。この電極間にポテンシオスタットにて定
電圧を印加し、その間に流れる電流を測定した。空気組
成ガスにＮＯ濃度を変えて測定ガスとした。その他の条
件は実施例１と同様とした。結果を図４に比較例１とし
て記入してある。実用上２電極構造でも殆ど差がないこ
とが分かる。Embodiment 5 As shown in FIG. 3, a CdCr 2 O 4 paste is applied to one surface of a zirconia
Was formed, and a Pt paste was applied to the opposite surface to form a counter electrode 5. A constant voltage was applied between the electrodes by a potentiostat, and the current flowing during the period was measured. The measurement gas was obtained by changing the NO concentration to an air composition gas. Other conditions were the same as in Example 1. The results are shown in FIG. 4 as Comparative Example 1. It can be seen that there is almost no difference even in a two-electrode structure in practical use.
【００２１】（実施例６）実施例５と同様にして検知極
材料のみを変えて、ＮＯ感度を測定した。各種検知極酸
化物および貴金属粉に固体電解質のジルコニア粉を添加
し、多孔化を図ることは通常行われる。結果を表２に示
す。ここに見られるようにＮｉあるいはＣｒを含む単体
あるいは複合酸化物、もしくはＩｒ電極、Ｒｈ電極、Ｐ
ｔとＩｒとの合金電極、ＰｔとＲｈとの合金電極が大き
な感度を有することが分かる。(Example 6) The NO sensitivity was measured in the same manner as in Example 5, except that only the material of the detection electrode was changed. It is common practice to add zirconia powder as a solid electrolyte to various detection electrode oxides and precious metal powders to make them porous. Table 2 shows the results. As seen here, a simple or complex oxide containing Ni or Cr, or an Ir electrode, Rh electrode, P
It can be seen that the alloy electrode of t and Ir and the alloy electrode of Pt and Rh have great sensitivity.
【００２２】[0022]
【表２】 [Table 2]
【００２３】[0023]
【発明の効果】本発明によりＮＯあるいはＮＯ2の相互
干渉や還元性ガスなどの他ガス干渉をきわめて少なくす
ることができる。バイアス電圧を調整することで、ＮＯ
とＮＯ2の感度比を任意に調整することができ、等感度
にすることで総ＮＯx検知が、簡単なセンサ構成にて可
能となる。According to the present invention, the mutual interference of NO or NO 2 and the interference of other gases such as reducing gas can be extremely reduced. By adjusting the bias voltage, NO
And the sensitivity ratio of NO 2 can be adjusted arbitrarily, and by making the sensitivity equal, the total NOx detection can be performed with a simple sensor configuration.
【図１】第１図は本発明の一例の断面図である。FIG. 1 is a sectional view of an example of the present invention.
【図２】第２図は検知極の分極曲線を示す図である。FIG. 2 is a diagram showing a polarization curve of a sensing electrode.
【図３】第３図は本発明の他の例の断面図である。FIG. 3 is a sectional view of another example of the present invention.
【図４】第４図はバイアス電圧を１００ｍｖとするとき
のＮＯの出力を示す図である。FIG. 4 is a diagram showing an output of NO when the bias voltage is set to 100 mv.
【図５】第５図はバイアス電圧を１５０ｍｖとするとき
のＮＯ2の出力を示す図である。FIG. 5 is a diagram showing the output of NO 2 when the bias voltage is set to 150 mv.
【図６】第６図はＰｔを用いた検知極の分極曲線を示す
図である。FIG. 6 is a diagram showing a polarization curve of a detection electrode using Pt.
１ ガスセンサ ２ 固体電解質基板 ３ 検知極 ４ 参照極 ５ 対極 DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Solid electrolyte substrate 3 Detection electrode 4 Reference electrode 5 Counter electrode
Claims (7)
るガスセンサにおいて、検知対象ガスに活性な検知極及
び対極と、検知対象ガスに不活性な参照極とを同一の固
体電解質上に固定し、少なくとも検知極を被検ガス中に
配し、該検知極と対極に検知極が正あるいは負のバイア
ス電圧となるように定電圧を印加し分極させ、該参照極
と対極間に流れる電流を測定し、検知対象ガスの検知極
での酸化電流の大きさから検知対象ガスの濃度を検知す
ることを特徴とするガスセンサ。In a gas sensor for measuring the concentration of a gas component in a gas to be detected, a detection electrode and a counter electrode active in the gas to be detected and a reference electrode inactive to the gas to be detected are fixed on the same solid electrolyte. Arranging at least the detection electrode in the test gas, applying a constant voltage to the detection electrode and the counter electrode so that the detection electrode has a positive or negative bias voltage, and polarizing the current; and flowing the current flowing between the reference electrode and the counter electrode. A gas sensor which measures and detects the concentration of a gas to be detected from the magnitude of an oxidation current at a detection electrode of the gas to be detected.
るガスセンサにおいて、検知対象ガスに活性な検知極
と、検知対象ガスに不活性な対極とを同一の固体電解質
上に固定し、少なくとも検知極を被検ガス中に配し、該
検知極と対極間に検知極が正あるいは負のバイアス電圧
となるように定電圧を印加し分極させ、当該電極間に流
れる電流を測定し、検知対象ガスの検知極での酸化電流
の大きさから検知対象ガスの濃度を検知することを特徴
とするガスセンサ。2. A gas sensor for measuring a gas component concentration in a gas to be detected, wherein a detection electrode active in the gas to be detected and a counter electrode inactive to the gas to be detected are fixed on the same solid electrolyte, and at least detection is performed. A pole is arranged in the test gas, a constant voltage is applied between the detection pole and the counter electrode so that the detection pole has a positive or negative bias voltage, the polarization is performed, the current flowing between the electrodes is measured, and the detection target is measured. A gas sensor which detects the concentration of a gas to be detected from the magnitude of an oxidation current at a gas detection electrode.
質上に固定し、少なくとも検知極を被検ガス中に配し、
当該電極間に検知極が正あるいは負のバイアス電圧とな
るように定電圧を印加し分極させ、当該電極間に流れる
電流を測定し、被検ガス中の酸素濃度が０.１ｖｏｌ％
以上であり、且つ該固体電解質がジルコニアを主体とす
る酸素イオン伝導体からなることを特徴とする請求項１
項および２項記載のガスセンサ。3. A detection electrode and a counter electrode or a reference electrode are fixed on a solid electrolyte, and at least the detection electrode is disposed in a test gas.
A constant voltage is applied between the electrodes so that the detection electrode has a positive or negative bias voltage, and polarization is performed. The current flowing between the electrodes is measured, and the oxygen concentration in the test gas is 0.1 vol%.
2. The solid electrolyte according to claim 1, wherein the solid electrolyte comprises an oxygen ion conductor mainly composed of zirconia.
Item 3. The gas sensor according to Item 2.
固体電解質上に固定された検知極と対極間に印加するバ
イアス電圧が０Ｖより高く４００ｍＶより低い正の定電
圧、あるいは０Ｖより低く−１Ｖより高い負の定電圧で
あることを特徴とする請求項１項乃至３項記載の何れか
のガスセンサ。4. The detection target gas is a nitrogen oxide, and a bias voltage applied between a detection electrode and a counter electrode fixed on a solid electrolyte is a positive constant voltage higher than 0 V and lower than 400 mV, or lower than 0 V. The gas sensor according to any one of claims 1 to 3, wherein the gas sensor has a negative constant voltage higher than 1V.
またはＣｒを構成元素として含む酸化物、あるいはＮｉ
またはＣｒを構成元素として含む酸化物とジルコニア固
体電解質との混合体からなることを特徴とする請求項１
項乃至４項記載の何れかの窒素酸化物のガスセンサ。 5. The detection electrode fixed on a solid electrolyte is Ni
Or an oxide containing Cr as a constituent element, or Ni
Or a mixture of an oxide containing Cr as a constituent element and a zirconia solid electrolyte.
Item 5. The nitrogen oxide gas sensor according to any one of Items 1 to 4.
電極、Ｒｈ電極、ＰｔとＩｒとの合金電極、ＰｔとＲｈ
との合金電極である貴金属電極、あるいは前記貴金属と
ジルコニア固体電解質との混合体とからなることを特徴
とする請求項１項乃至４項記載の何れかの窒素酸化物の
ガスセンサ。6. The detection electrode fixed on the solid electrolyte is Ir
Electrode, Rh electrode, alloy electrode of Pt and Ir, Pt and Rh
The nitrogen oxide gas sensor according to any one of claims 1 to 4, comprising a noble metal electrode that is an alloy electrode of the above and a mixture of the noble metal and a zirconia solid electrolyte.
体電解質体に一室あるいは二室の測定ガス雰囲気に連通
する内部空所を設け、少なくとも検知極を該内部空所に
設置し、さらに該内部空所にＮＯｘを変換するための電
気化学的酸素ポンプあるいは触媒体を形成した構成であ
って、前記検知極が設置される内部空所にて検知対象ガ
スのＮＯｘがＮＯの単体ガス、あるいはＮＯ2及びＮＯ2
以上の過酸化窒素に変換されるように該酸素ポンプある
いは触媒体を機能させ、該検知極とその対極間に検知極
が正あるいは負のバイアス電圧となるように定電圧を印
加し、当該電極間に流れる電流を測定することを特徴と
する窒素酸化物のガスセンサ。7. A zirconia solid electrolyte body having oxygen ion conductivity is provided with one or two internal spaces communicating with a measurement gas atmosphere, and at least a detection electrode is installed in said internal space. a structure forming the electrochemical oxygen pump or catalyst body for converting NOx at, single gas NOx is NO detection target gas in the internal space of the sensing electrode is placed, or NO 2, And NO 2
The oxygen pump or the catalyst is operated so as to be converted into the above-mentioned nitrogen peroxide, and a constant voltage is applied between the detection electrode and the counter electrode such that the detection electrode has a positive or negative bias voltage, and A nitrogen oxide gas sensor characterized by measuring a current flowing therebetween.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9329638A JPH11148916A (en) | 1997-11-14 | 1997-11-14 | Gas sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9329638A JPH11148916A (en) | 1997-11-14 | 1997-11-14 | Gas sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH11148916A true JPH11148916A (en) | 1999-06-02 |
Family
ID=18223586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9329638A Pending JPH11148916A (en) | 1997-11-14 | 1997-11-14 | Gas sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH11148916A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009092501A (en) * | 2007-10-09 | 2009-04-30 | Yazaki Corp | Gas sensor and gas detector |
| JP2012098068A (en) * | 2010-10-29 | 2012-05-24 | Kyocera Corp | Nitrogen oxide sensor element and nitrogen oxide detection method |
| JP2020003264A (en) * | 2018-06-26 | 2020-01-09 | 株式会社Ｓｏｋｅｎ | Nitrous oxide concentration detector |
-
1997
- 1997-11-14 JP JP9329638A patent/JPH11148916A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009092501A (en) * | 2007-10-09 | 2009-04-30 | Yazaki Corp | Gas sensor and gas detector |
| JP2012098068A (en) * | 2010-10-29 | 2012-05-24 | Kyocera Corp | Nitrogen oxide sensor element and nitrogen oxide detection method |
| JP2020003264A (en) * | 2018-06-26 | 2020-01-09 | 株式会社Ｓｏｋｅｎ | Nitrous oxide concentration detector |
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