JPH11242014A - Nitrogen oxide sensor - Google Patents
Nitrogen oxide sensorInfo
- Publication number
- JPH11242014A JPH11242014A JP10060628A JP6062898A JPH11242014A JP H11242014 A JPH11242014 A JP H11242014A JP 10060628 A JP10060628 A JP 10060628A JP 6062898 A JP6062898 A JP 6062898A JP H11242014 A JPH11242014 A JP H11242014A
- Authority
- JP
- Japan
- Prior art keywords
- sensor
- oxide
- electrode
- electrodes
- nitrogen oxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims abstract description 310
- 239000007789 gas Substances 0.000 claims abstract description 30
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 18
- AHKZTVQIVOEVFO-UHFFFAOYSA-N oxide(2-) Chemical compound [O-2] AHKZTVQIVOEVFO-UHFFFAOYSA-N 0.000 claims abstract description 9
- YDZQQRWRVYGNER-UHFFFAOYSA-N iron;titanium;trihydrate Chemical group O.O.O.[Ti].[Fe] YDZQQRWRVYGNER-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000000203 mixture Substances 0.000 claims abstract description 5
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 4
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 3
- 238000012360 testing method Methods 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 238000002485 combustion reaction Methods 0.000 abstract description 12
- 230000008859 change Effects 0.000 description 26
- 230000035945 sensitivity Effects 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 11
- 238000000034 method Methods 0.000 description 10
- 229910000510 noble metal Inorganic materials 0.000 description 10
- 238000001514 detection method Methods 0.000 description 9
- 241000627951 Osteobrama cotio Species 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 6
- 238000002844 melting Methods 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
- 230000008018 melting Effects 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000003411 electrode reaction Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- -1 for example Inorganic materials 0.000 description 2
- 239000010416 ion conductor Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 229910052727 yttrium Inorganic materials 0.000 description 2
- RUDFQVOCFDJEEF-UHFFFAOYSA-N yttrium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Y+3].[Y+3] RUDFQVOCFDJEEF-UHFFFAOYSA-N 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 1
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 229910052688 Gadolinium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 229910052769 Ytterbium Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910000416 bismuth oxide Inorganic materials 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- 235000012255 calcium oxide Nutrition 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 150000002826 nitrites Chemical class 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 229940116411 terpineol Drugs 0.000 description 1
Landscapes
- Measuring Oxygen Concentration In Cells (AREA)
Abstract
(57)【要約】
【課題】 高温の燃焼排気ガス中でも使用可能な安定性
を有し、数百ｐｐｍ以下の低濃度のＮＯx を測定可能で
あり、且つＮＯとＮＯ2 が共存する被検ガス雰囲気中に
おいても全ＮＯx 濃度を測定可能な窒素酸化物センサを
提供する。
【解決手段】 二つで一対となる電極が表面に形成され
た酸化物イオン導電性固体電解質からなるセンサ素子
と、対をなす二つの電極間に電流を印加可能な電流源と
から構成され、前記二つの電極のうちの少なくとも一方
の電極が次式（Ｉ）：ＭＴｉＯ3 （Ｉ）〔式中、ＭはＦ
ｅ，Ｃｏ，Ｎｉ，Ｃｒ及びＭｎを表わす〕で表わされる
組成のイルメナイト型構造の酸化物であり、前記電極間
に電流を印加した時の電極間の電圧から被検ガス中の全
窒素酸化物濃度を検出する窒素酸化物センサ。
(57) Abstract: have stability that is available in high-temperature combustion exhaust gas, can be measured several hundred ppm or lower concentrations of NO x, and subject to NO and NO 2 coexist also provides a nitrogen oxide sensor capable of measuring the total concentration of NO x in the gas atmosphere. SOLUTION: The sensor element is composed of a sensor element made of an oxide ion conductive solid electrolyte having two pairs of electrodes formed on the surface thereof, and a current source capable of applying a current between two pairs of electrodes, At least one of the two electrodes has the following formula (I): MTiO 3 (I) [where M is F
e, Co, Ni, Cr and Mn], which is an oxide having an ilmenite structure having a composition represented by the following formula: Nitrogen oxide sensor to detect concentration.
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車のエンジン
やボイラーなどから出る燃焼排気ガス中に含まれる全窒
素酸化物（ＮＯx ）濃度、すなわち一酸化窒素（ＮＯ）
濃度と二酸化窒素（ＮＯ2 ）濃度との和を直接検知する
ことができる窒素酸化物センサに関するものである。The present invention relates to the total nitrogen oxides contained in the combustion exhaust gas from automobile engines and boilers (NO x) concentration, i.e. nitric oxide (NO)
The present invention relates to a nitrogen oxide sensor capable of directly detecting the sum of a concentration and a nitrogen dioxide (NO 2 ) concentration.
【０００２】[0002]
【従来の技術及び発明が解決しようとする課題】自動車
のエンジンやボイラーなどから発生する燃焼排気ガス中
に含まれるＮＯx の低減のために、ＮＯx センサを用い
たＮＯx 濃度モニタ及びその結果に基づく燃焼機器の燃
焼状態の制御，触媒浄化装置の制御等が検討されてい
る。ＮＯxを有効に検知するために、高温の燃焼排気ガ
ス中でも安定して作動する小型の窒素酸化物センサの開
発が望まれている。排気ガス中のＮＯx はＮＯとＮＯ2
とからなるが、ＮＯが７割以上を占めるため、ＮＯ2 よ
りもＮＯに対する感度の高いセンサが好ましい。また、
排気規制はＮＯとＮＯ2 との和であるＮＯx が対象とな
るので、ＮＯに対する感度とＮＯ2 に対する感度とが同
じで、両者を区別せずにＮＯx として直接検知すること
ができるセンサがあれば更に好ましい。For reduction of the NO x contained in the combustion exhaust gas generated from such engines and boilers automobile BACKGROUND OF 0006], NO x concentration monitoring and the results using the NO x sensor The control of the combustion state of combustion equipment, the control of a catalyst purification device, and the like based on the above are being studied. To effectively detect the NO x, it has been desired development of a small nitrogen oxide sensor operating stably even during high-temperature combustion exhaust gases. NO x in the exhaust gas is NO and NO 2
However, since NO accounts for 70% or more, a sensor having higher sensitivity to NO than NO 2 is preferable. Also,
Since emission regulations is the sum of NO and NO 2 NO x are of interest, sensitivity and NO 2 sensitivity and are the same for the relative NO, a sensor can be directly detected as NO x without distinction both It is more preferable if there is.
【０００３】これまでＮＯx センサとしては、酸化物半
導体を用いた抵抗変化式、固体電解質を用いた電流式及
び起電力式の種々のセンサが提案され又は文献に開示さ
れているが、ＮＯ／ＮＯ2 比が任意に変わる条件下でＮ
ＯとＮＯ2 とを区別せずにＮＯx として直接検知するこ
とができる実用レベルのＮＯx センサは無い。以下各Ｎ
Ｏx センサについて、検出原理と実用上の問題とを述べ
る。Various types of NO x sensors have been proposed or disclosed in the literature, such as a resistance change type sensor using an oxide semiconductor, a current type sensor using a solid electrolyte, and an electromotive force type sensor. Under conditions where the NO 2 ratio changes arbitrarily, N
NO x sensor at a practical level, which can and O and NO 2 without distinguishing directly detected as NO x is not. Below N
The detection principle and practical problems of the O x sensor will be described.
【０００４】抵抗変化式の窒素酸化物センサは、半導体
表面にＮＯx が吸着した場合に前記半導体の電気抵抗が
変化することを利用したセンサである。しかし、抵抗変
化式の窒素酸化物センサは還元性ガスに対しても感度を
有するため、ガス選択性に乏しい。また、６００℃を越
える高温では半導体表面へのガス吸着が起こりにくいた
め、抵抗変化式の窒素酸化物センサでは高温で充分な感
度が得られない。更に、ＮＯx のうちＮＯに対する感度
が小さくＮＯ2 に対する感度が大きいため、全ＮＯx 濃
度を検知するために使用することはできない。[0004] Nitrogen oxides of the resistance change type sensor is a sensor utilizing the electrical resistance of the semiconductor is changed when the NO x is adsorbed on the semiconductor surface. However, the nitrogen oxide sensor of the resistance change type has sensitivity to reducing gas, and thus has poor gas selectivity. At a high temperature exceeding 600 ° C., gas adsorption to the semiconductor surface is unlikely to occur, so that a resistance change type nitrogen oxide sensor cannot provide sufficient sensitivity at a high temperature. Furthermore, the sensitivity sensitivity for smaller NO 2 to NO out of the NO x is large, it can not be used to detect the total concentration of NO x.
【０００５】電流式の窒素酸化物センサはジルコニアの
ような酸化物イオン導電体を用い、ＮＯx を電気化学的
に分解し、電解質中をＯ2-として流れる電流値からＮＯ
x 量を検知する。しかし、排気ガス中に共存するＯ2 も
Ｏ2-として電解質中を流れるので、ＮＯx とＯ2 とを分
離して検知することが困難である。その解決法として、
２セル式のＮＯx センサが提案されている（特開平８−
２７１４７６号公報）。２セル式のＮＯx センサにおい
ては、第一セルでＯ2 の分離とＮＯ2 からＮＯへの変換
を行い、第二セルでＮＯを分解する際に流れる電流の値
からＮＯを検知する。それ故、原理的にはＮＯx とＯ2
とを分離して検知すること及び全ＮＯx濃度（＝ＮＯ濃
度＋ＮＯ2 濃度）を検知することが可能であるが、前記
電流の値がガス温度に比例するので、数百ｐｐｍ以下の
ＮＯx を検知しようとする場合、電流出力が極めて微小
になるという欠点がある。A current-type nitrogen oxide sensor uses an oxide ion conductor such as zirconia, electrochemically decomposes NO x, and obtains NO 2 from the current value flowing as O 2− in the electrolyte.
Detect x amount. However, since O 2 coexisting in the exhaust gas also flows in the electrolyte as O 2− , it is difficult to separate and detect NO x and O 2 . As a solution,
A two-cell NO x sensor has been proposed (Japanese Patent Laid-Open No. 8-
271476). In a two-cell NO x sensor, O 2 is separated and NO 2 is converted to NO in a first cell, and NO is detected from a value of a current flowing when NO is decomposed in a second cell. Therefore, in principle, NO x and O 2
And the total NO x concentration (= NO concentration + NO 2 concentration) can be detected, but since the value of the current is proportional to the gas temperature, NO x of several hundred ppm or less can be detected. However, there is a drawback that the current output becomes extremely small when attempting to detect the current.
【０００６】起電力式の窒素酸化物センサは、固体電解
質を隔壁とした電気化学セル間に発生する起電力からＮ
Ｏx を検知する方式のセンサである。この方式では、電
極の一方に硝酸塩又は亜硝酸塩を塗布した固体素子型の
センサ素子を備えた窒素酸化物センサが主に検討され、
多数公開されている（特開昭６１−１８４４５０号公
報）。この方式のセンサは数百ｐｐｍ以下の低濃度のＮ
Ｏx に対しても数十〜数百ｍＶ以上の大きい起電力変化
を示し、その起電力がネルンストの式に一致するという
利点がある。しかし、これらのセンサ素子は構成要素と
して水溶性且つ低融点の硝酸塩又は亜硝酸塩を含むた
め、その融点によって動作温度が制限される。すなわ
ち、硝酸塩及び亜硝酸塩の中で最も融点が高いＢａ（Ｎ
Ｏ3 ）2 でも融点が５９２℃のため、前記窒素酸化物セ
ンサは、６００℃以上の高温では使用不可能である。[0006] An electromotive force type nitrogen oxide sensor uses an electromotive force generated between electrochemical cells having a solid electrolyte as a partition.
This is a sensor that detects O x . In this method, a nitrogen oxide sensor having a solid element type sensor element coated with nitrate or nitrite on one of the electrodes is mainly studied,
Many have been published (JP-A-61-184450). This type of sensor has a low N concentration of several hundred ppm or less.
O x also shows a large electromotive force variation of several tens to several hundreds mV with respect, there is an advantage that the electromotive force coincides with the Nernst equation. However, since these sensor elements contain a water-soluble and low-melting nitrate or a nitrite as a component, the operating temperature is limited by the melting point. That is, Ba (N) having the highest melting point among nitrates and nitrites
Since the melting point of O 3 ) 2 is 592 ° C., the nitrogen oxide sensor cannot be used at a high temperature of 600 ° C. or higher.
【０００７】起電力式の窒素酸化物センサにおける前記
問題を解決するために、電極の一方に各種酸化物を用い
る方式が提案されている。これらのセンサの特性は酸化
物材料に大きく依存することが知られており、良好な特
性を示す電極材料としてＫ2ＮｉＦ4 型及びペロブスカ
イト型酸化物（特開平７−１９８６７１号公報）、VIIa
族又はVIIIa 族元素を含む酸化物（特開平８−２４７９
９２号公報）等が開示されている。これらの酸化物電極
は、融点や分解温度が硝酸塩より高いため耐熱性は優れ
ている。しかし、ＮＯx 検知機構が混成電位機構に基づ
くため、ＮＯとＮＯ2 に対して起電力の変化方向が原理
的に逆向きになる。燃焼排気ガス中のＮＯx はＮＯを主
成分として一部ＮＯ2 を含み、ＮＯとＮＯ2 の混合状態
となっている。そのためＮＯとＮＯ2 に対する起電力の
変化方向が逆向きのセンサを排気ガス中で用いると、起
電力の出力が互いに打ち消されて正確なＮＯx 濃度の測
定ができなくなる。[0007] In order to solve the above-mentioned problem in the nitrogen oxide sensor of the electromotive force type, there has been proposed a system in which various oxides are used for one of the electrodes. It is known that the characteristics of these sensors greatly depend on the oxide material, and K 2 NiF 4 type and perovskite type oxides (JP-A-7-198671) and VIIa as electrode materials exhibiting good characteristics.
Oxide containing an element of group IIIa or group VIIIa (JP-A-8-2479)
No. 92) is disclosed. These oxide electrodes have excellent heat resistance because their melting points and decomposition temperatures are higher than those of nitrates. However, since the NO x detection mechanism is based on the hybrid potential mechanism, the change direction of the electromotive force is opposite to NO and NO 2 in principle. NO x in the combustion exhaust gas comprises a portion NO 2 as a main component NO, has a mixed state of NO and NO 2. When the direction of change of the electromotive force for that reason NO and NO 2 is using a sensor in the opposite direction in the exhaust gas, can not be accurate measurement of concentration of NO x is canceled output electromotive force with each other.
【０００８】前記の型のセンサにおいて、酸化物電極を
スピネル型酸化物とすることでＮＯ2 選択性を高める方
法（特開平９−８００１４号公報）も開示されている
が、ＮＯに対する起電力変化がＮＯ2 に対する起電力変
化と逆向きであることに変わりはなく、例えばＮＯがＮ
Ｏ2 に対して大過剰になるエンジン排気ガス中の使用で
も、依然として起電力の出力が互いに打ち消される可能
性がある。従って、酸化物電極をスピネル型酸化物とし
たセンサを用いても、排気ガス中の使用で求められるＮ
Ｏ，ＮＯ2 の独立測定や全ＮＯx 濃度の測定は不可能で
ある。In a sensor of the type described above, a method of increasing NO 2 selectivity by using an oxide electrode of a spinel type oxide (Japanese Patent Application Laid-Open No. 9-80014) is disclosed. Is still in the opposite direction to the electromotive force change with respect to NO 2 , for example, NO becomes N
Also the use of the engine exhaust gas becomes large excess with respect to O 2, there is still a possibility that the output of the electromotive force are canceled each other. Therefore, even if a sensor using a spinel-type oxide as the oxide electrode is used, the N required for use in exhaust gas can be reduced.
It is impossible to measure O and NO 2 independently or to measure the total NO x concentration.
【０００９】以上述べた通り、従来の窒素酸化物センサ
は、高温の燃焼排気ガス中で使用できない、数百ｐ
ｐｍ以下の低濃度のＮＯx を検知できない、全ＮＯx
濃度（＝ＮＯ濃度＋ＮＯ2 濃度）を検知することができ
ない、のうちの少なくとも一つ以上の欠点を有してい
る。As described above, the conventional nitrogen oxide sensor cannot be used in a high temperature combustion exhaust gas, and has a capacity of several hundred p.
pm can not be detected below the low concentration of NO x, the total NO x
It has at least one of the disadvantages that the concentration (= NO concentration + NO 2 concentration) cannot be detected.
【００１０】本発明は前記従来技術の問題点を解決する
ためのものであり、その目的とするところは、高温の燃
焼排気ガス中でも使用可能な安定性を有し、数百ｐｐｍ
以下の低濃度のＮＯx を測定可能であり、且つＮＯとＮ
Ｏ2 が共存する被検ガス雰囲気中においても全ＮＯx 濃
度を測定可能な窒素酸化物センサを提供することにあ
る。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art.
The following low concentration of NO x can be measured, and NO and N
Also in a test gas atmosphere O 2 coexist is to provide a nitrogen oxide sensor capable of measuring the total concentration of NO x.
【００１１】[0011]
【課題を解決するための手段】すなわち、本発明の窒素
酸化物センサは、二つで一対となる電極が表面に形成さ
れた酸化物イオン導電性固体電解質からなるセンサ素子
と、対をなす二つの電極間に電流を印加可能な電流源と
から構成され、前記二つの電極のうちの少なくとも一方
の電極が次式（Ｉ）： ＭＴｉＯ3 （Ｉ） 〔式中、ＭはＦｅ，Ｃｏ，Ｎｉ，Ｃｒ及びＭｎを表わ
す〕で表わされる組成のイルメナイト型構造の酸化物で
あり、前記電極間に電流を印加した時の電極間の電圧か
ら被検ガス中の全窒素酸化物濃度を検出することを特徴
とする。That is, a nitrogen oxide sensor according to the present invention has a pair of a sensor element made of an oxide ion conductive solid electrolyte having two pairs of electrodes formed on the surface thereof. And a current source capable of applying a current between the two electrodes, wherein at least one of the two electrodes has the following formula (I): MTiO 3 (I) wherein M is Fe, Co, Ni , Cr and Mn] in which the concentration of total nitrogen oxides in the test gas is detected from the voltage between the electrodes when a current is applied between the electrodes. It is characterized by.
【００１２】＜作動原理＞本発明のセンサにおいて電極
間に電流を印加しない状態では、酸化物電極を有する固
体電解質セルの電極間の起電力からＮＯx を検知する窒
素酸化物センサ（例えば、特開平７−１９８６７１号公
報，特開平９−８００１４号公報記載の窒素酸化物セン
サ）と同様に、酸化物電極上でＮＯ2 に対して以下の
（１），（２）の反応が起こっていると考えられる。 ＮＯ2 ＋２ｅ- →ＮＯ＋Ｏ2- （１） Ｏ2-→１／２Ｏ2 ＋２ｅ- （２） また、ＮＯに対しては以下の（３），（４）の反応が起
こっていると考えられる。 １／２Ｏ2 ＋２ｅ- →Ｏ2- （３） ＮＯ＋Ｏ2-→ＮＯ2 ＋２ｅ- （４） すなわち、ＮＯ2 に対してはＮＯ2 がＮＯに還元される
反応（１）が、また、ＮＯに対してはＮＯがＮＯ2 に酸
化される反応（４）が起こる。したがって、電極間に電
流を印加せずに、電極間に発生する起電力からＮＯx を
検知しようとすると、原理的にＮＯとＮＯ2 とで起電力
の変化方向が逆になり、ＮＯとＮＯ2 との総和を直接検
知することができない。[0012] In a state of not applying current between the electrodes in the sensor of <working principle> present invention, the nitrogen oxide sensor for detecting the NO x from the electromotive force between the electrodes of the solid electrolyte cell having an oxide electrode (for example, Japanese In the same manner as in the nitrogen oxide sensor described in Japanese Unexamined Patent Publication No. Hei 7-198167 and Japanese Unexamined Patent Publication No. Hei 9-80014, the following reactions (1) and (2) occur for NO 2 on the oxide electrode. it is conceivable that. NO 2 + 2e − → NO + O 2− (1) O 2− → 1 / 2O 2 + 2e − (2) It is considered that the following reactions (3) and (4) have occurred for NO. 1 / 2O 2 + 2e - → O 2- (3) NO + O 2- → NO 2 + 2e - (4) i.e., the reaction NO 2 is reduced to NO for NO 2 (1), but also, the NO On the other hand, a reaction (4) in which NO is oxidized to NO 2 occurs. Therefore, if an attempt is made to detect NO x from the electromotive force generated between the electrodes without applying a current between the electrodes, the direction of change of the electromotive force is reversed between NO and NO 2 in principle, and NO and NO The sum of 2 cannot be detected directly.
【００１３】本発明の窒素酸化物センサにおいては、電
流源を用いてＭＴｉＯ3 電極（酸化物電極）が＋となる
ように電極間に電流を印加する（すなわち、酸化物電極
をアノード分極する）。この電流印加の極性は、前記従
来の文献に多数開示されている電流式ＮＯx センサと逆
である。このように電流を印加（アノード分極）する
と、Ｏ2 が存在する雰囲気ではＭＴｉＯ3 電極側では
（２）の反応が、もう一方の電極（例えば、貴金属電
極）では（３）の反応が起こり、固体電解質中を酸化物
イオン（Ｏ2-）が貴金属電極側から酸化物電極側へ流れ
る。雰囲気にＮＯとＮＯ2 とが共存する場合、このＯ2-
の流れにより（１）の反応が抑制され、（４）の反応が
促進される。更に電流値を上げると、ＭＴｉＯ3 電極で
は電極触媒反応により、次式（５）： ＮＯ2 ＋Ｏ2-→ＮＯ＋１／２Ｏ2 ＋２ｅ- （５） で表わされるＮＯ2 の酸化的分解反応が起こるようにな
る。そのためＮＯとＮＯ2 共に検知反応は酸化反応とな
り、電圧の変化方向を同一にすることができる。本発明
の窒素酸化物センサにおいて、印加電流を適当に選ぶと
ＮＯに対する感度とＮＯ2 に対する感度とを同一にする
ことができるので、その電流値を印加した場合の電圧変
化をセンサ出力とすれば、ＮＯとＮＯ2 とを区別せずに
ＮＯx として検知することが可能となる。ＮＯに対する
感度とＮＯ2 に対する感度とを同一にすることができる
印加電流の値は、電極として用いるＭＴｉＯ3 の種類と
センサ温度に依存する。In the nitrogen oxide sensor of the present invention, a current is applied between the electrodes using a current source so that the MTiO 3 electrode (oxide electrode) becomes positive (that is, the oxide electrode is anodically polarized). . The polarity of this current application is opposite to that of the current-type NO x sensor disclosed in many of the above-mentioned conventional documents. When a current is applied (anode polarization) in this manner, the reaction (2) occurs on the MTiO 3 electrode side in the atmosphere where O 2 exists, and the reaction (3) occurs on the other electrode (for example, a noble metal electrode). Oxide ions (O 2− ) flow from the noble metal electrode side to the oxide electrode side in the solid electrolyte. When NO and NO 2 coexist in the atmosphere, this O 2-
The reaction (1) is suppressed by the flow (1), and the reaction (4) is promoted. When the current value is further increased, an oxidative decomposition reaction of NO 2 represented by the following formula (5): NO 2 + O 2− → NO + 1 / 2O 2 + 2e − (5) occurs by an electrode catalytic reaction in the MTiO 3 electrode. become. Therefore, the detection reaction of both NO and NO 2 is an oxidation reaction, and the direction of voltage change can be made the same. In nitrogen oxide sensor of the present invention, since the pick applied current appropriately and sensitivity to sensitivity and NO 2 to NO can be the same, if a voltage change in the case of applying the current between the sensor output , NO and NO 2 can be detected as NO x without distinction. The value of the applied current that can make the sensitivity to NO and the sensitivity to NO 2 the same depends on the type of MTiO 3 used as an electrode and the sensor temperature.
【００１４】[0014]
【発明の実施の形態】本発明の窒素酸化物センサにおい
て、センサ素子の固体電解質材料としては酸化物イオン
導電性を示すものを使用することができる。具体的に
は、例えばジルコニウム系固体電解質（ＺｒＯ2 −Ｍ2
Ｏ3 固溶体又はＺｒＯ2 −ＭＯ固溶体、Ｍ＝Ｙ，Ｙｂ，
Ｇｄ，Ｃａ，Ｍｇなど）、セリア系固体電解質（ＣｅＯ
2 −Ｍ2Ｏ3 固溶体又はＣｅＯ2 −ＭＯ固溶体、Ｍ＝
Ｙ，Ｓｍなど）、酸化ビスマス系固体電解質（Ｂｉ2 Ｏ
3 −ＷＯ3 固溶体など）を使用することができる。排気
ガス中での安定性の観点から、ジルコニウム系固体電解
質が好ましく、特に熱衝撃抵抗と酸化物イオン導電率と
の兼ね合いで、５〜８ｍｏｌ％のＹ2 Ｏ3 を固溶させた
ＺｒＯ2 が最も好ましい。BEST MODE FOR CARRYING OUT THE INVENTION In the nitrogen oxide sensor of the present invention, a material having oxide ion conductivity can be used as a solid electrolyte material of a sensor element. Specifically, for example, a zirconium-based solid electrolyte (ZrO 2 -M 2
O 3 solid solution or ZrO 2 -MO solid solution, M = Y, Yb,
Gd, Ca, Mg, etc.), ceria-based solid electrolyte (CeO
2 -M 2 O 3 solid solution or CeO 2 -MO solid solution, M =
Y, Sm, etc.), bismuth oxide solid electrolyte (Bi 2 O
3, such as -WO 3 solid solution) can be used. From the viewpoint of stability in exhaust gas, a zirconium-based solid electrolyte is preferable. Particularly, ZrO 2 in which 5 to 8 mol% of Y 2 O 3 is dissolved in consideration of thermal shock resistance and oxide ion conductivity is preferable. Most preferred.
【００１５】本発明の窒素酸化物センサにおいて、二つ
の電極のうちの少なくとも一方の電極の材料としては、
ＭＴｉＯ3 〔式中、ＭはＦｅ，Ｃｏ，Ｎｉ，Ｃｒ及びＭ
ｎを表わす〕で表わされる組成のイルメナイト型構造の
酸化物を用いる。前記酸化物からなる電極は、アノード
分極時にＮＯ，ＮＯ2 の電極反応〔上記（４），（５）
の反応〕の活性が高く且つ排気ガス中での安定性が高
い。もう一方の電極の材料は特に限定されるものではな
いが、Ｏ2 の電極反応〔上記（２），（３）の反応〕の
活性が著しく高いものが好ましく、例えば、ＬａＭＯ3
〔Ｍ＝Ｃｏ，Ｍｎ，Ｃｒ〕系の電子導電性酸化物やＰ
ｔ，Ｐｄ等の貴金属材料を利用することができる。特に
高温での耐久性を考えると、もう一方の電極の材料とし
ては、Ｐｔ，Ｐｄ及びそれらを主成分とする合金が最も
適している。In the nitrogen oxide sensor of the present invention, the material of at least one of the two electrodes is
MTiO 3 [where M is Fe, Co, Ni, Cr and M
n is used. An oxide having an ilmenite structure having a composition represented by the following formula is used. The electrode made of the oxide reacts with the electrode reaction of NO and NO 2 during anodic polarization [(4) and (5) above].
Reaction) and high stability in exhaust gas. The material of the other electrode is not particularly limited, but it is preferable that the activity of the electrode reaction of O 2 [the reaction of the above (2) and (3)] is extremely high. For example, LaMO 3
[M = Co, Mn, Cr] -based electronic conductive oxides and P
Noble metal materials such as t and Pd can be used. In particular, considering durability at high temperatures, Pt, Pd and alloys containing these as main components are most suitable as the material of the other electrode.
【００１６】本発明の窒素酸化物センサにおけるセンサ
素子及び電極は、この分野における慣用の方法を用いて
製造してよく、例えば、焼成法，印刷法，スパッタ法，
ＣＶＤ法などの既存の方法を全て用いることができる。
センサ素子及び電極の大きさや形状は、窒素酸化物セン
サの大きさや形状に応じて適宜選択する。また、本セン
サ素子をＯ2 ポンプセルと組み合わせて２セル型の構造
としてもよい。この場合、Ｏ2 ポンプセルはＮＯx 検知
部の雰囲気を一定のＯ2 濃度にするために用いられ、Ｎ
Ｏx の検出精度の向上に寄与する。The sensor element and the electrodes in the nitrogen oxide sensor of the present invention may be manufactured by using a conventional method in this field, for example, a firing method, a printing method, a sputtering method,
All existing methods such as the CVD method can be used.
The size and shape of the sensor element and the electrode are appropriately selected according to the size and shape of the nitrogen oxide sensor. The sensor element may be combined with an O 2 pump cell to form a two-cell structure. In this case, the O 2 pump cell is used to bring the atmosphere of the NO x detection unit to a constant O 2 concentration,
This contributes to improvement in the detection accuracy of O x .
【００１７】本発明の窒素酸化物センサにおける電流源
としては、好適な直流電流電源を選択する。また、前記
電流源を制御・管理したり、又はセンサ素子からの信号
を処理するために、パーソナルコンピューターなどの装
置を使用することができる。As a current source in the nitrogen oxide sensor of the present invention, a suitable direct current power supply is selected. Further, a device such as a personal computer can be used to control and manage the current source or to process a signal from the sensor element.
【００１８】本発明の窒素酸化物センサにおけるセンサ
素子を他の機能を有するセンサ素子、例えば酸素センサ
素子と組み合わせて使用することもできる。機能を異に
する複数のセンサ素子において、その構成要素、例えば
酸化物イオン導電性固体電解質を共有することができる
場合には、一つの酸化物イオン導電性固体電解質上に本
発明の窒素酸化物センサ素子を含む複数のセンサ素子を
形成して複合型センサを構成してもよい。The sensor element in the nitrogen oxide sensor of the present invention can be used in combination with a sensor element having another function, for example, an oxygen sensor element. In the case where a plurality of sensor elements having different functions can share a component thereof, for example, an oxide ion conductive solid electrolyte, the nitrogen oxide of the present invention is placed on one oxide ion conductive solid electrolyte. A composite sensor may be formed by forming a plurality of sensor elements including a sensor element.
【００１９】[0019]
【実施例】以下の実施例により、本発明を更に詳細に説
明する。実施例１ 図１は本発明の実施例１の窒素酸化物センサの概略構成
図である。固体電解質１は酸化物イオン導電体であり、
特に安定性の点でイットリア，カルシア，マグネシア等
で安定化したジルコニアが好ましい。本実施例では６ｍ
ｏｌ％イットリアで安定化したジルコニアを用いた。丸
板状の固体電解質１の対向する面には酸化物電極２及び
貴金属電極３が設けられている。酸化物電極２及び貴金
属電極３はそれぞれＮｉＴｉＯ3 及びＰｔで形成されて
いる。酸化物電極２（ＮｉＴｉＯ3 電極）は市販のＮｉ
ＴｉＯ3 粉末をテルピネオールに懸濁し、この懸濁液を
固体電解質上に塗布，乾燥後、大気中で１０００℃で１
時間の熱処理を行い焼き付けて形成した。貴金属電極３
（Ｐｔ電極）はスパック法により形成した。それぞれの
電極には集電用のＰｔメッシュ４，５を被せ、Ｐｔリー
ド線６，７を取り付け、定電流源８及び電圧計９に接続
した。被検ガス中のＮＯx の測定に際しては、本センサ
のセンサ素子部を６５０℃に加熱し、貴金属電極３側に
空気を、酸化物電極２側にＮＯx を含む被検ガスを各々
１リットル／分の流速で流した。図２に、酸化物電極２
側を＋とし、被検ガスを５％Ｏ2 −Ｎ2 ，５００ｐｐｍ
ＮＯ−５％Ｏ2 −Ｎ2 ，５００ｐｐｍＮＯ2 −５％Ｏ2
−Ｎ2 とした時の電流（Ｉ）−電圧（Ｖ）特性を示す。
図２を見ると、電圧がある値以上になると、ＮＯ又はＮ
Ｏ2 が共存した場合の方がＯ2 −Ｎ2 のみの場合よりも
電流値が大きくなっていることが判る。また、５００ｐ
ｐｍＮＯ−５％Ｏ2 −Ｎ2 ，５００ｐｐｍＮＯ2 −５％
Ｏ2 −Ｎ2 に対するＩ−Ｖ曲線が交わるところがある
（図２のＡ点）。すなわち、Ａ点に相当する電流値（約
０．５μＡ）を印加した場合の電圧変化をセンサ出力と
すればＮＯとＮＯ2 とに同一の感度を持たせることがで
きる。図３に、同一の素子を用いて０．５μＡの定電流
を印加し、それぞれＮＯ，ＮＯ2 （５００ｐｐｍ導入）
に対する電圧変化を測定した結果を示す。ＮＯ，ＮＯ2
の何れの変化に対しても電圧は減少する方向に変化して
おり、それらの値は完全に一致はしないものの同程度で
あることがあることが判る。したがって、ＮＯとＮＯ2
とを区別せずにＮＯx として同時に検知することができ
る。The present invention will be described in more detail with reference to the following examples. Embodiment 1 FIG. 1 is a schematic configuration diagram of a nitrogen oxide sensor according to Embodiment 1 of the present invention. The solid electrolyte 1 is an oxide ion conductor,
In particular, zirconia stabilized with yttria, calcia, magnesia or the like is preferable from the viewpoint of stability. 6m in this embodiment
zirconia stabilized with ol% yttria was used. An oxide electrode 2 and a noble metal electrode 3 are provided on opposing surfaces of the round plate-shaped solid electrolyte 1. The oxide electrode 2 and the noble metal electrode 3 are formed of NiTiO 3 and Pt, respectively. The oxide electrode 2 (NiTiO 3 electrode) is a commercially available Ni
TiO 3 powder is suspended in terpineol, and this suspension is applied on a solid electrolyte, dried, and then dried at 1000 ° C. in air for 1 hour.
A heat treatment was performed for a long time, followed by baking. Noble metal electrode 3
(Pt electrode) was formed by the Spack method. Each electrode was covered with Pt meshes 4 and 5 for current collection, Pt lead wires 6 and 7 were attached, and connected to a constant current source 8 and a voltmeter 9. When measuring NO x in the test gas, the sensor element portion of the present sensor was heated to 650 ° C., and air was supplied to the noble metal electrode 3 side, and the test gas containing NO x was supplied to the oxide electrode 2 side each 1 liter. / Min flow rate. FIG. 2 shows the oxide electrode 2
And the test gas was 5% O 2 -N 2 , 500 ppm
NO-5% O 2 -N 2 , 500ppmNO 2 -5% O 2
Current when the -N 2 (I) - shows the voltage (V) characteristics.
Referring to FIG. 2, when the voltage exceeds a certain value, NO or N
It can be seen that the current value is larger when O 2 coexists than when only O 2 -N 2 is present. Also, 500p
pmNO-5% O 2 -N 2 , 500ppmNO 2 -5%
There are places where the IV curves for O 2 -N 2 intersect (point A in FIG. 2). That is, if a voltage change when a current value (approximately 0.5 μA) corresponding to the point A is applied is used as the sensor output, NO and NO 2 can have the same sensitivity. In FIG. 3, a constant current of 0.5 μA is applied using the same element, and NO and NO 2 (500 ppm introduced) are respectively applied.
3 shows the results of measuring the voltage change with respect to NO, NO 2
It can be understood that the voltage changes in the decreasing direction with respect to any of the changes, and that the values do not completely match but may be similar. Therefore, NO and NO 2
DOO can be detected simultaneously as NO x without distinction.
【００２０】実施例２ 電極２をＦｅＴｉＯ3 で形成すること以外は実施例１と
同様の方法により、実施例２の窒素酸化物センサを作製
した。ＦｅＴｉＯ3 は市販のＦｅ2 Ｏ3 粉末とＴｉＯ2
粉末とをＦｅ／Ｔｉ比が１となるように混合し、１２０
０℃で１０時間焼成することにより合成した。本センサ
のセンサ素子部を実施例１と同様に６５０℃に加熱し、
貴金属電極３（Ｐｔ電極）側に空気を、酸化物電極２
（ＦｅＴｉＯ3 電極）側にＮＯx を含む被検ガスを各々
１リットル／分の流速で流した。図４に、２μＡの定電
流を印加した時のＮＯ濃度変化及びＮＯ2 濃度変化に対
する電圧出力の変化を示す。本実施例の印加電流は実施
例１と同様に特性の測定結果に基づいて選定した。ＮＯ
濃度変化，ＮＯ2 濃度変化に対応した電圧変化が認めら
れ、ＦｅＴｉＯ3 電極の場合にもＮＯとＮＯ2 とをほぼ
同一感度で検知できることが判る。[0020] By the same method as in Example 1 except for forming the embodiment 2 electrodes 2 FeTiO 3, to prepare a nitrogen oxide sensor of Example 2. FeTiO 3 is commercially available Fe 2 O 3 powder and TiO 2
And powder so that the Fe / Ti ratio becomes 1.
It was synthesized by firing at 0 ° C. for 10 hours. The sensor element of this sensor was heated to 650 ° C. in the same manner as in Example 1,
Air is applied to the noble metal electrode 3 (Pt electrode) side, and the oxide electrode 2
A test gas containing NO x was flowed at a flow rate of 1 liter / minute to the (FeTiO 3 electrode) side. FIG. 4 shows a change in voltage output with respect to a change in NO concentration and a change in NO 2 concentration when a constant current of 2 μA is applied. The applied current in the present embodiment was selected based on the measurement results of the characteristics as in the first embodiment. NO
Voltage changes corresponding to the concentration change and the NO 2 concentration change are recognized, and it is understood that NO and NO 2 can be detected with almost the same sensitivity even in the case of the FeTiO 3 electrode.
【００２１】実施例３ 電極２をＣｏＴｉＯ3 で形成すること以外は実施例１と
同様の方法により、実施例３の窒素酸化物センサを作製
した。ＣｏＴｉＯ3 は市販のＣｏＴｉＯ3 粉末を用い
た。本センサのセンサ素子部を実施例１と同様に６５０
℃に加熱し、貴金属電極３（Ｐｔ電極）側に空気を、酸
化物電極２（ＣｏＴｉＯ3 電極）側にＮＯx を含む被検
ガスを各々１リットル／分の流速で流した。図５にはＮ
Ｏ2 共存時のＮＯ濃度変化に対する電圧の出力変化を、
また図６にはＮＯ共存時のＮＯ2 濃度変化に対する電圧
変化を示す。印加電流は前述の方法と同じくＩ−Ｖ特性
から選定し、共に５μＡである。ＣｏＴｉＯ3 電極では
特に出力が大きくなっていること、及びＮＯとＮＯ2 と
が共存する場合でもＮＯ濃度変化，ＮＯ2 濃度変化に対
応した電圧変化を示していることが判る。図５，図６の
結果から、全ＮＯx （＝ＮＯ＋ＮＯ2 ）と電圧変化との
関係をプロットした結果を図７に示す。ＮＯ，ＮＯ2 の
何れがが変化しても、ＮＯx 濃度変化として検知できる
ことが判る。[0021] By the same method as in Example 1 except for forming the embodiment 3 electrodes 2 in CoTiO 3, to prepare a nitrogen oxide sensor of Example 3. As CoTiO 3, a commercially available CoTiO 3 powder was used. The sensor element portion of this sensor is 650 in the same manner as in the first embodiment.
℃ heated to the air in the noble metal electrode 3 (Pt electrode) side, flushed with oxide electrode 2 (CoTiO 3 electrode) side to the test gas containing NO x, respectively at 1 liter / min flow rate. FIG.
The change in voltage output with respect to the change in NO concentration when O 2 is present
FIG. 6 shows a voltage change with respect to a change in NO 2 concentration when NO coexists. The applied current is selected from the IV characteristics in the same manner as in the above-described method, and is 5 μA in both cases. It can be seen that the output is particularly large in the CoTiO 3 electrode, and that even when NO and NO 2 coexist, the NO concentration change and the voltage change corresponding to the NO 2 concentration change are shown. FIG. 7 shows the result of plotting the relationship between the total NO x (= NO + NO 2 ) and the voltage change from the results of FIGS. NO, any NO 2 is even changed, it can be seen that can be detected as a concentration of NO x changes.
【００２２】ＭＴｉＯ3 で表わされる組成のイルメナイ
ト型構造の酸化物として、実施例１ではＮｉＴｉＯ
3 を、実施例２ではＦｅＴｉＯ3 を、実施例３ではＣｏ
ＴｉＯ3を各々使用したが、ＭＴｉＯ3 で表わされる組
成のイルメナイト型構造の酸化物としてＣｒＴｉＯ3 や
ＭｎＴｉＯ3 を使用しても、実施例１〜３と同様に優れ
た性質を有する本発明の窒素酸化物センサを得ることが
できる。In Example 1, NiTiO 3 was used as an oxide having an ilmenite structure having a composition represented by MTiO 3.
3 in Example 2, FeTiO 3 in Example 2, and Co in Example 3
Although TiO 3 was used, even when CrTiO 3 or MnTiO 3 was used as an oxide having an ilmenite structure having a composition represented by MTiO 3 , the nitrogen of the present invention having excellent properties as in Examples 1 to 3 An oxide sensor can be obtained.
【００２３】[0023]
【発明の効果】以上説明したように、本発明の窒素酸化
物センサは、印加電流を適切な値に選定することにより
ＮＯ及びＮＯ2 に対する電圧出力の変化の方向と大きさ
を同一にすることができる。したがって、燃焼排気ガス
のようにＮＯとＮＯ2 とが共存し且つその濃度比が任意
に変わる雰囲気でも、両者を区別せずに全ＮＯx 濃度
（ＮＯ濃度とＮＯ2 濃度との和）を検知することができ
る。また、本センサの出力は従来の電流式のＮＯx セン
サよりも遥かに大きく、排気規制の対象である全ＮＯx
を簡便に高感度で検知することができるため、燃焼排気
ガス浄化触媒の状態監視，劣化検知や燃焼制御に大きな
威力を発揮する。更に、本発明のセンサは熱的及び化学
的に安定な材料から構成されているので燃焼排気ガス中
での安定性に優れており、また７００℃近い高温でも使
用できるため、排気管などの高温排ガス雰囲気中に直接
挿入することが可能であり、小型化や軽量化も容易であ
る。As described above, in the nitrogen oxide sensor of the present invention, the direction and magnitude of the change in the voltage output with respect to NO and NO 2 can be made equal by selecting the applied current to an appropriate value. Can be. Therefore, even in an atmosphere in which NO and NO 2 coexist and the concentration ratio changes arbitrarily as in the case of combustion exhaust gas, the total NO x concentration (the sum of the NO concentration and the NO 2 concentration) is detected without distinguishing between the two. can do. The output of this sensor is much larger than that of the conventional current-type NO x sensor, and the total NO x
Can be detected easily and with high sensitivity, and it exerts great power in monitoring the state of the combustion exhaust gas purifying catalyst, detecting deterioration, and controlling combustion. Further, since the sensor of the present invention is made of a thermally and chemically stable material, it has excellent stability in combustion exhaust gas, and can be used even at a high temperature close to 700 ° C. It can be directly inserted into the exhaust gas atmosphere, and it is easy to reduce the size and weight.
【図１】本発明の窒素酸化物センサの概略構成図であ
る。FIG. 1 is a schematic configuration diagram of a nitrogen oxide sensor of the present invention.
【図２】酸化物電極をＮｉＴｉＯ3 電極とした場合の本
センサのＩ−Ｖ特性を示す図である。FIG. 2 is a diagram showing IV characteristics of the present sensor when an oxide electrode is a NiTiO 3 electrode.
【図３】ＮｉＴｉＯ3 電極の本センサのＮＯx 検知特性
を示す図である。3 is a diagram illustrating a NO x detection characteristics of the sensor NiTiO 3 electrodes.
【図４】ＦｅＴｉＯ3 電極の本センサのＮＯx 検知特性
を示す図である。FIG. 4 is a diagram showing the NO x detection characteristics of the present sensor using an FeTiO 3 electrode.
【図５】ＣｏＴｉＯ3 電極の本センサのＮＯ2 共存時の
ＮＯ検知特性を示す図である。FIG. 5 is a diagram showing the NO detection characteristics of the present sensor of the CoTiO 3 electrode when NO 2 is present;
【図６】ＣｏＴｉＯ3 電極の本センサのＮＯ共存時のＮ
Ｏ2 検知特性を示す図である。FIG. 6 shows N in the presence of NO in the present sensor having a CoTiO 3 electrode.
It is a figure showing O 2 detection characteristics.
【図７】ＣｏＴｉＯ3 電極の本センサの電圧出力のＮＯ
x 濃度依存性を示す図である。FIG. 7 shows the NO of the voltage output of the present sensor using a CoTiO 3 electrode.
FIG. 4 is a diagram showing x concentration dependency.
１：固体電解質 ２：酸化物電
極 ３：貴金属電極 ４，５：Ｐｔ
メッシュ ６，７：Ｐｔリード線 ８：定電流電
源 ９：電圧計1: solid electrolyte 2: oxide electrode 3: noble metal electrode 4, 5: Pt
Mesh 6, 7: Pt lead wire 8: Constant current power supply 9: Voltmeter
Claims (1)
た酸化物イオン導電性固体電解質からなるセンサ素子
と、対をなす二つの電極間に電流を印加可能な電流源と
から構成され、 前記二つの電極のうちの少なくとも一方の電極が次式
（Ｉ）： ＭＴｉＯ3 （Ｉ） 〔式中、ＭはＦｅ，Ｃｏ，Ｎｉ，Ｃｒ及びＭｎを表わ
す〕で表わされる組成のイルメナイト型構造の酸化物で
あり、 前記電極間に電流を印加した時の電極間の電圧から被検
ガス中の全窒素酸化物濃度を検出することを特徴とする
窒素酸化物センサ。1. A sensor element comprising an oxide ion conductive solid electrolyte having two pairs of electrodes formed on the surface thereof, and a current source capable of applying a current between two pairs of electrodes. Wherein at least one of the two electrodes has an ilmenite structure having a composition represented by the following formula (I): MTiO 3 (I), wherein M represents Fe, Co, Ni, Cr and Mn. A nitrogen oxide sensor for detecting a total nitrogen oxide concentration in a test gas from a voltage between the electrodes when a current is applied between the electrodes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06062898A JP3526000B2 (en) | 1998-02-25 | 1998-02-25 | Nitrogen oxide sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06062898A JP3526000B2 (en) | 1998-02-25 | 1998-02-25 | Nitrogen oxide sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11242014A true JPH11242014A (en) | 1999-09-07 |
| JP3526000B2 JP3526000B2 (en) | 2004-05-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06062898A Expired - Fee Related JP3526000B2 (en) | 1998-02-25 | 1998-02-25 | Nitrogen oxide sensor |
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| Country | Link |
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| JP (1) | JP3526000B2 (en) |
Cited By (5)
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| JP2008139294A (en) * | 2006-11-08 | 2008-06-19 | Honda Motor Co Ltd | Detection apparatus and method |
| JP2012504237A (en) * | 2008-09-30 | 2012-02-16 | イルジン カッパー ホイル カンパニー リミテッド | Nitrogen oxide gas sensor |
| JP2012504235A (en) * | 2008-09-30 | 2012-02-16 | イルジン カッパー ホイル カンパニー リミテッド | Nitrogen oxide gas sensor with long-term signal stability |
| JP2012504236A (en) * | 2008-09-30 | 2012-02-16 | イルジン カッパー ホイル カンパニー リミテッド | Nitrogen oxide gas sensor |
| JP2015147166A (en) * | 2014-02-05 | 2015-08-20 | トヨタ自動車株式会社 | Exhaust gas purification catalyst |
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|---|---|
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