JPH049258B2 - - Google Patents
Info
- Publication number
- JPH049258B2 JPH049258B2 JP57055813A JP5581382A JPH049258B2 JP H049258 B2 JPH049258 B2 JP H049258B2 JP 57055813 A JP57055813 A JP 57055813A JP 5581382 A JP5581382 A JP 5581382A JP H049258 B2 JPH049258 B2 JP H049258B2
- Authority
- JP
- Japan
- Prior art keywords
- oxygen concentration
- gas
- measured
- oxygen
- voltage
- 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.)
- Expired - Lifetime
Links
- 229910052760 oxygen Inorganic materials 0.000 claims description 119
- 239000001301 oxygen Substances 0.000 claims description 118
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 105
- 239000007789 gas Substances 0.000 claims description 51
- 239000007784 solid electrolyte Substances 0.000 claims description 7
- 238000001514 detection method Methods 0.000 claims description 4
- 238000000034 method Methods 0.000 description 19
- 239000010410 layer Substances 0.000 description 9
- 238000005259 measurement Methods 0.000 description 9
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 8
- 239000000919 ceramic Substances 0.000 description 8
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 239000012212 insulator Substances 0.000 description 5
- -1 oxygen ion Chemical class 0.000 description 5
- 238000002485 combustion reaction Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000001771 impaired effect Effects 0.000 description 2
- 229910052573 porcelain Inorganic materials 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 1
- 206010021143 Hypoxia Diseases 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 1
- 229910052839 forsterite Inorganic materials 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000006104 solid solution Substances 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
- 239000003381 stabilizer Substances 0.000 description 1
- 239000000454 talc Substances 0.000 description 1
- 229910052623 talc Inorganic materials 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
- 229910052845 zircon Inorganic materials 0.000 description 1
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/406—Cells and probes with solid electrolytes
- G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Molecular Biology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Measuring Oxygen Concentration In Cells (AREA)
Description
【発明の詳細な説明】
本発明は酸素濃度検出方法に関し、さらに詳し
くは、酸素イオン透過性固体電解質製基板の両面
に電極を形成してなる酸素センサを用いて、被測
定ガス中における酸素濃度が非常に低い場合にお
いてさえも、その酸素濃度を精度良く検出するこ
とができる方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting oxygen concentration, and more specifically, to a method for detecting oxygen concentration in a gas to be measured using an oxygen sensor having electrodes formed on both sides of a substrate made of an oxygen ion-permeable solid electrolyte. The present invention relates to a method that can accurately detect the oxygen concentration even when the oxygen concentration is very low.
従来より、被測定ガス中の酸素濃度を検出する
ための酸素濃度検出器として、ジルコニア等の固
体電解質を用いた濃淡電池型酸素センサが知られ
ている。この濃淡電池型酸素センサは、例えばジ
ルコニア等のような酸素イオン透過性固体電解質
で形成された試験管状素子本体の内外両面に耐熱
性金属からなる電極層を形成してセンサ素子と
し、このセンサ素子の内側電極に酸素濃度既知の
基準ガスを接触させ、外側電極に被測定ガスを接
触させたとき、両極間には、基準ガスと被測定ガ
ス中の酸素濃度差により起電力が生じ、この起電
力を測定することにより被測定ガス中の酸素濃度
を知ることができる。 Conventionally, a concentration cell type oxygen sensor using a solid electrolyte such as zirconia has been known as an oxygen concentration detector for detecting the oxygen concentration in a gas to be measured. This concentration cell type oxygen sensor has a test tube-like element body made of an oxygen ion-permeable solid electrolyte such as zirconia, and electrode layers made of heat-resistant metal are formed on both the inner and outer surfaces of the sensor element. When a reference gas with a known oxygen concentration is brought into contact with the inner electrode and a gas to be measured is brought into contact with the outer electrode, an electromotive force is generated between the two electrodes due to the difference in oxygen concentration between the reference gas and the gas to be measured. By measuring the electric power, the oxygen concentration in the gas to be measured can be determined.
しかしながら、上記濃淡電池型酸素センサにお
いては、基準ガスと被測定ガス中の酸素濃度が近
い場合は起電力が小さいため測定精度が悪く、ま
た基準ガスが必要なためセンサ素子を大型にした
り、あるいはセンサの構造自体が複雑になるとい
う欠点があつた。 However, in the above-mentioned concentration cell type oxygen sensor, when the oxygen concentration in the reference gas and the gas to be measured are close, the electromotive force is small, resulting in poor measurement accuracy, and since the reference gas is required, the sensor element must be made large, or The drawback was that the sensor structure itself was complicated.
上記欠点を有しない酸素濃度検出器として、酸
素イオン透過性固体電解質基板の両面に電極を設
け少なくとも一方の極板を多孔性セラミツクで被
覆した素子を、被測定ガスに接触させ、両極板に
一定電圧を印加して、このとき酸素濃度に応じて
素子に生ずる限界電流を測定し、これにより被測
定ガス中の酸素濃度を検出する、いわゆる限界電
流型酸素センサが知られている。この限界電流型
酸素センサは、上記濃淡電池型酸素センサに比較
して、基準ガスが不要であるので構造的に簡単で
あり、また、被測定ガス中の酸素濃度を連続的に
精度良く検出することができるという利点を有す
る。 As an oxygen concentration detector that does not have the above drawbacks, an element in which electrodes are provided on both sides of an oxygen ion permeable solid electrolyte substrate and at least one plate is covered with porous ceramic is brought into contact with the gas to be measured. A so-called limiting current type oxygen sensor is known that applies a voltage and measures the limiting current generated in the element according to the oxygen concentration, thereby detecting the oxygen concentration in the gas to be measured. This limiting current type oxygen sensor has a simpler structure than the above-mentioned concentration cell type oxygen sensor because it does not require a reference gas, and can continuously and accurately detect the oxygen concentration in the gas to be measured. It has the advantage of being able to
従来から行なわれている酸素濃度検出方法を第
１図を用いてさらに詳しく説明する。 The conventional oxygen concentration detection method will be explained in more detail with reference to FIG.
第１図は上記限界電流型酸素センサにおける印
加電圧と出力電流との関係を示すグラフで、図中
ａは、被測定ガス中の酸素濃度１％、ｂは酸素濃
度２％、ｃは酸素濃度５％、ｄは酸素濃度10％の
ときのそれぞれの電圧−電流特性曲線を示す。 Figure 1 is a graph showing the relationship between the applied voltage and the output current in the limiting current type oxygen sensor. 5% and d indicate the respective voltage-current characteristic curves when the oxygen concentration is 10%.
前記構成の限界電流型酸素センサの両極板に電
圧を印加すると、被測定ガス中の酸素が陰極でイ
オン化され、この酸素イオンが陽極へ向かつて透
過する。センサ印加電圧を上げるとこれに比例し
て出力電流が増加する（図中、a1，b2，c1，d1は
それぞれ各酸素濃度における特性曲線の第１の立
上り部分を示す）。印加電圧がある一定値以上に
なると、素子の陰極は多孔性セラミツク層で被覆
されているため酸素イオン透過量が制限されて、
印加電圧を増加しても出力電流がほぼ一定とな
り、特性曲線ａ，ｂ，ｃ，ｄはフラツト部a2，
b2，c2，d2を形成する。このフラツト部における
出力電流値が限界電流値である。この限界電流値
は各酸素濃度に比例して異なり、また限界電流値
を発生する印加電圧の範囲も各酸素濃度により異
なる。印加電圧を所定範囲よりさらに増加する
と、印加電圧の増加に伴なつて出力電流が増加し
はじめ、特性曲線ａ，ｂ，ｃ，ｄは第２の立上り
部a3，b3，c3，d3を示す。このような特性曲線を
有する限界電流型酸素センサに、ある一定電圧、
例えば1V（図中、垂直直線Ｂで示す）を印加する
と、各酸素濃度の特性曲線ａ，ｂ，ｃ，ｄと垂直
直線Ｂとの交点における電流値が素子から出力さ
れる。出力された電流値を各酸素濃度ごとに読み
取り、第３図に示す出力電流と酸素濃度との関係
を直線Ａとして求め、これに基づいて被測定ガス
中の酸素濃度を検出する。 When a voltage is applied to both electrode plates of the limiting current type oxygen sensor configured as described above, oxygen in the gas to be measured is ionized at the cathode, and the oxygen ions pass toward the anode. When the voltage applied to the sensor is increased, the output current increases in proportion to this (in the figure, a 1 , b 2 , c 1 , and d 1 each indicate the first rising portion of the characteristic curve at each oxygen concentration). When the applied voltage exceeds a certain value, the cathode of the device is covered with a porous ceramic layer, which limits the amount of oxygen ion permeation.
Even if the applied voltage is increased, the output current remains almost constant, and the characteristic curves a, b, c, and d have flat parts a 2 ,
Form b 2 , c 2 , d 2 . The output current value at this flat portion is the limit current value. This limiting current value varies in proportion to each oxygen concentration, and the range of applied voltage that generates the limiting current value also varies depending on each oxygen concentration. When the applied voltage is further increased beyond the predetermined range, the output current begins to increase as the applied voltage increases, and the characteristic curves a, b, c, and d show second rising portions a 3 , b 3 , c 3 , d Showing 3 . A limiting current type oxygen sensor with such a characteristic curve has a certain constant voltage,
For example, when 1V (indicated by vertical straight line B in the figure) is applied, current values at the intersections of the characteristic curves a, b, c, and d of each oxygen concentration with vertical straight line B are output from the element. The output current value is read for each oxygen concentration, the relationship between the output current and the oxygen concentration shown in FIG. 3 is obtained as a straight line A, and based on this, the oxygen concentration in the gas to be measured is detected.
しかしながら、この方法には次のような問題点
があつた。 However, this method has the following problems.
例えば、被測定ガス中の成分がN2−O2系の場
合には、酸素センサは第１図で示す電流−電圧特
性曲線を示すが、被測定ガス中にH2O，CO2等が
存在する場合には、第２図に示すように、センサ
素子部の電圧−電流特性曲線のフラツト部の幅が
狭くなる。このため電圧1V（図中、垂直直線Ｂで
示す）をセンサに印加したとき、曲線ａ及びｂ
（酸素低濃度側）では第２の立上り部a3，b3から
出力されるので限界電流値より高くなり、第３図
に示す出力電流−酸素濃度関係線A′の低濃度側
での直線性が損なわれる。したがつて、酸素低濃
度領域例えば酸素濃度２％以下の場合には測定精
度が悪く誤差が生じやすくなる。 For example, if the component in the gas to be measured is N 2 - O 2 , the oxygen sensor will show the current-voltage characteristic curve shown in Figure 1, but if the gas to be measured contains H 2 O, CO 2 , etc. If it exists, as shown in FIG. 2, the width of the flat portion of the voltage-current characteristic curve of the sensor element becomes narrow. Therefore, when a voltage of 1V (indicated by vertical straight line B in the figure) is applied to the sensor, curves a and b
(low oxygen concentration side), the output is output from the second rising portions a 3 and b 3 , so the current is higher than the limit current value, and the output current-oxygen concentration relationship line A' shown in Fig. 3 is a straight line on the low concentration side. Sexuality is impaired. Therefore, in a low oxygen concentration region, for example, when the oxygen concentration is 2% or less, the measurement accuracy is poor and errors are likely to occur.
この低濃度側での測定誤差を避ける方法として
は、印加電圧を特性曲線ａのフラツト部a2及び特
性曲線ｂのフラツト部b2の範囲内になるように制
御することも考えられるが、これに適合するよう
に印加電圧を下げる（すなわち、垂直直線Ｂを図
中左方向へ移動させる）と、被測定ガス中の酸素
濃度が10％（特性曲線ｄ）の場合には印加電圧が
フラツト部d2から外れてしまうので限界電流値よ
り低い電流値を出力する。このため、酸素高濃度
側の出力電流−酸素濃度関係線の直線性が損なわ
れ好ましくない。 One possible way to avoid this measurement error on the low concentration side is to control the applied voltage so that it falls within the range of flat part a2 of characteristic curve a and flat part b2 of characteristic curve b. If the applied voltage is lowered to match (that is, the vertical straight line B is moved to the left in the figure), if the oxygen concentration in the measured gas is 10% (characteristic curve d), the applied voltage will change to a flat portion. Since it deviates from d 2 , a current value lower than the limit current value is output. For this reason, the linearity of the output current-oxygen concentration relationship line on the high oxygen concentration side is impaired, which is not preferable.
限界電流型酸素センサの特性曲線は、被測定ガ
ス中のガス成分の種類のほか、センサ素子部の温
度や素子部の構造等によつても影響され、いずれ
にしても各酸素濃度における電圧−電流特性曲線
のフラツト部内の電圧値を広い範囲にわたつて満
足するように、印加電圧値を設定することは困難
である。 The characteristic curve of a limiting current type oxygen sensor is affected not only by the type of gas component in the gas to be measured, but also by the temperature of the sensor element, the structure of the element, etc., and in any case, the voltage - It is difficult to set the applied voltage value so as to satisfy the voltage value within the flat portion of the current characteristic curve over a wide range.
本発明は、限界電流型酸素センサを用い、酸素
濃度が非常に低い被測定ガスを測定する場合は、
センサ素子に一定電流を流して出力電圧を測定
し、この出力電圧値より酸素濃度を検出する方法
を提供するものである。 The present invention uses a limiting current type oxygen sensor to measure a gas with a very low oxygen concentration.
A method is provided in which a constant current is passed through a sensor element, an output voltage is measured, and an oxygen concentration is detected from this output voltage value.
すなわち、本発明の酸素濃度検出方法は、酸素
イオン透過性固体電解質からなる素子本体表面に
１対の電極が対向して形成された酸素センサの素
子を、被測定ガスと接触させて該被測定ガス中の
酸素濃度を検出するに当たり、
センサ素子に一定電圧を印加し、この場合の出
力電流値が一定値を越えていれば該出力電流値か
ら前記被測定ガス中の酸素濃度を検出し、
前記出力電流値が一定値以下であれば、前記セ
ンサ素子に一定電流を流し、この場合の出力電圧
値が一定値を越えていれば該出力電圧値から前記
被測定ガス中の酸素濃度を検出し、
前記出力電圧値が一定値以下であれば、前記セ
ンサ素子に再度一定電圧を印加する工程を繰り返
すことにより前記被測定ガス中の酸素濃度を検出
するというを特徴を有している。 That is, in the oxygen concentration detection method of the present invention, an oxygen sensor element, which has a pair of electrodes facing each other on the surface of the element body made of an oxygen ion-permeable solid electrolyte, is brought into contact with a gas to be measured. In detecting the oxygen concentration in the gas, a constant voltage is applied to the sensor element, and if the output current value in this case exceeds a constant value, the oxygen concentration in the gas to be measured is detected from the output current value, If the output current value is below a certain value, a certain current is passed through the sensor element, and if the output voltage value in this case exceeds a certain value, the oxygen concentration in the measured gas is detected from the output voltage value. However, if the output voltage value is below a certain value, the oxygen concentration in the gas to be measured is detected by repeating the process of applying a certain voltage to the sensor element again.
以下、本発明方法をさらに詳しく図面に基づい
て説明する。 Hereinafter, the method of the present invention will be explained in more detail based on the drawings.
第４図は本発明で使用する酸素センサの一例を
示す模式図である。 FIG. 4 is a schematic diagram showing an example of an oxygen sensor used in the present invention.
第４図中、１は酸素イオン透過性固体電解質か
らなる円板状素子本体である。素子本体１は、
ZrO2、HfO2、ThO2、Bi2O3等にCaO、MgO、
Y2O3、Yb2O3等を安定剤として固溶させた緻密
な円板状焼結体である。円板状素子本体１の両面
には、Pt、Rh、Ir、Pd、Ag等またはこれらの合
金からなる耐熱性電極層２，３が、スパツタリン
グ、蒸着、メツキ等により、または上記金属もし
くは合金のペーストを塗布後焼付ける等の方法に
よつて形成される。前記内外両電極層２，３は、
被測定ガス中のカーボン等の付着による電極の短
絡または高温下での両電極のシンタリングを防止
するために、多孔性セラミツク層４，５で被覆さ
れる。多孔性セラミツクとしては、ケイ石質、シ
ヤモツト、アルミナ質、クロミア質、ホルステラ
イト質、スピネル質、ジルコン質、ジルコニア質
等である。前記多孔性セラミツク層のうち前記両
電極２，３のうち陰極となる電極２を被覆するセ
ラミツク層４は、陽極３側を被覆するセラミツク
層５よりも厚くしておくのが好ましい。６，７
は、一端が前記両電極２，３に接続するリード線
で、その他端は電源９に接続し、測定回路を構成
する。素子１で出力される電圧は、電圧計８で測
定される。 In FIG. 4, reference numeral 1 denotes a disk-shaped element body made of an oxygen ion permeable solid electrolyte. The element body 1 is
CaO, MgO, etc. to ZrO 2 , HfO 2 , ThO 2 , Bi 2 O 3 etc.
It is a dense disc-shaped sintered body containing Y 2 O 3 , Yb 2 O 3 , etc. as a solid solution as a stabilizer. Heat-resistant electrode layers 2 and 3 made of Pt, Rh, Ir, Pd, Ag, etc. or alloys thereof are formed on both sides of the disc-shaped element body 1 by sputtering, vapor deposition, plating, etc., or by coating the above metals or alloys. It is formed by a method such as applying a paste and then baking it. Both the inner and outer electrode layers 2 and 3 are
The electrodes are covered with porous ceramic layers 4 and 5 in order to prevent short-circuiting of the electrodes due to adhesion of carbon or the like in the gas to be measured or sintering of both electrodes at high temperatures. Examples of porous ceramics include silica, syamoto, alumina, chromia, forsterite, spinel, zircon, and zirconia. Of the porous ceramic layers, the ceramic layer 4 that covers the cathode 2 of the electrodes 2 and 3 is preferably thicker than the ceramic layer 5 that covers the anode 3 side. 6,7
is a lead wire whose one end is connected to both the electrodes 2 and 3, and whose other end is connected to the power source 9, forming a measurement circuit. The voltage output by element 1 is measured by voltmeter 8.
上記酸素センサは、具体的には第５図に示すよ
うな構成で使用される。第５図において、１１は
略円筒状アルミナ碍管で、その内部には長手軸方
向に貫通する中空部１１ａ，１１ａが設けられ、
外周には外方へ突出する肩部１１ｂが設けられて
いる。この中空部１１ａ，１１ａ中に貫装された
リード線１２，１２の先端を前記酸素センサ素子
Ａのリード線６，７に接続することにより、素子
Ａをアルミナ碍管１１の先端に取付ける（図中、
１３，１３は接合部を示す）。前記アルミナ碍管
１１は、その肩部１１ｂをグラフアイトリング２
６を介してハウジング２５のテーパ部２５ａに当
接することによりハウジング２５に係止される。
素子Ｓの外周にはコイル状発熱体１０が位置し、
さらにその外周には通気孔１４，１４……を設け
た保護カバー１５が配設されている。発熱体１０
は、アルミナ碍管１１に設けられた中空部１１
ａ，１１ａと別の図示しない軸方向貫通孔に装入
されたリード線と接続しており、外部からの電圧
印加により発熱する。 Specifically, the oxygen sensor described above is used in a configuration as shown in FIG. In FIG. 5, reference numeral 11 denotes a substantially cylindrical alumina insulator tube, in which hollow portions 11a, 11a penetrating in the longitudinal axis direction are provided.
A shoulder portion 11b projecting outward is provided on the outer periphery. By connecting the tips of the lead wires 12, 12 passed through the hollow parts 11a, 11a to the lead wires 6, 7 of the oxygen sensor element A, the element A is attached to the tip of the alumina insulator tube 11 (in the figure). ,
13, 13 shows the joint part). The alumina insulator 11 has a shoulder portion 11b attached to a graphite ring 2.
6, and is locked to the housing 25 by contacting the tapered portion 25a of the housing 25.
A coiled heating element 10 is located on the outer periphery of the element S,
Furthermore, a protective cover 15 provided with ventilation holes 14, 14, . . . is disposed around its outer periphery. heating element 10
is the hollow part 11 provided in the alumina insulator tube 11
a, 11a and a lead wire inserted into another axial through hole (not shown), and generates heat when voltage is applied from the outside.
前記アルミナ碍管１１の肩部１１ｂの上面とハ
ウジング２５との間隙にタルク２７を充てんし、
その上に押さえ板２８を設け、押さえ板２８の上
面に下部ホルダ２４の下端部を当接させたのち、
このホルダ２４の外周に位置決めリング２９を設
け、ハウジング２５の先端をかしめる。下部ホル
ダ２４の上端部には上部ホルダ１９を接続させ
る。図中、１６は下部ホルダ２４を排気管に取付
けるためのフランジ、１７は、フランジ１６に設
けられたネジ穴、１８はアルミナ碍管１１上部に
設けられた第２の円筒状アルミナ碍管である。ま
た、２０は前記リード線１２，１２を内部に収納
した絶縁管、２１はコネクタ、２２はリード線固
定用の内部ホルダ、２３は絶縁性材料からなるブ
ツシユである。 Filling the gap between the upper surface of the shoulder portion 11b of the alumina insulator tube 11 and the housing 25 with talc 27,
A presser plate 28 is provided on top of the presser plate 28, and the lower end of the lower holder 24 is brought into contact with the upper surface of the presser plate 28.
A positioning ring 29 is provided on the outer periphery of this holder 24, and the tip of the housing 25 is caulked. The upper holder 19 is connected to the upper end of the lower holder 24. In the figure, 16 is a flange for attaching the lower holder 24 to the exhaust pipe, 17 is a screw hole provided in the flange 16, and 18 is a second cylindrical alumina porcelain tube provided above the alumina porcelain tube 11. Further, 20 is an insulating tube in which the lead wires 12, 12 are housed, 21 is a connector, 22 is an internal holder for fixing the lead wires, and 23 is a bush made of an insulating material.
上記構成の酸素センサを用いて非常に低い酸素
濃度を測定するには、フランジ１６を例えば自動
車内燃機関の排気管（図示せず）に取付け、外部
から電圧を印加して発熱体１０を発熱させ、素子
Ｓを作動温度、例えば700℃に加温する。排気管
を流れる被測定ガスは保護カバー１５の通気孔１
４を通つて素子Ｓに接触する。また、リード線１
２，１２を介して素子Ｓに一定電流を流す。素子
Ｓに流す電流が0.2mA／mm2のとき酸素濃度変化に
応じて素子Ｓに生ずる電圧変化を、第６図中実線
ａで示し、0.4mA／mm2のときに生ずる電圧変化を
第６図中破線ｂで示す。第６図から明らかなよう
に、被測定ガス中の酸素濃度が５％以下の領域で
は、各酸素濃度における出力電圧値の変化率が大
きいため、素子Ｓで起こる電圧変化をリード線１
２，１２を介して外部へ導びき、電圧計で測定す
れば、被測定ガス中の酸素濃度を精度良く検出す
ることができる。 To measure a very low oxygen concentration using the oxygen sensor configured as described above, the flange 16 is attached to, for example, an exhaust pipe (not shown) of an automobile internal combustion engine, and a voltage is applied from the outside to cause the heating element 10 to generate heat. , the element S is heated to an operating temperature, for example 700°C. The gas to be measured flowing through the exhaust pipe is passed through the vent hole 1 of the protective cover 15.
4 to contact the element S. Also, lead wire 1
A constant current is caused to flow through the element S via 2 and 12. The voltage change that occurs in the element S in response to changes in oxygen concentration when the current flowing through the element S is 0.2 mA/mm 2 is shown by the solid line a in Figure 6, and the voltage change that occurs when the current flowing through the element S is 0.4 mA/mm 2 is shown in the 6th line. It is indicated by a broken line b in the figure. As is clear from FIG. 6, in the region where the oxygen concentration in the gas to be measured is 5% or less, the rate of change in the output voltage value at each oxygen concentration is large.
2 and 12 to the outside and measured with a voltmeter, the oxygen concentration in the gas to be measured can be detected with high accuracy.
素子Ｓに流す電流はなるべく低く、例えば
1mA／mm2以下とするのが好ましい。1mA／mm2以
上とすると素子Ｓの両極板２，３間で短絡が生
じ、素子Ｓ自体の耐久性が損なわれるので好まし
くない。具体的には１×10-3mA／mm2〜1mA／
mm2、特に0.1mA／mm2〜0.4mA／mm2が好ましい。 The current flowing through the element S is as low as possible, for example
It is preferable to set it to 1 mA/mm 2 or less. If it is 1 mA/mm 2 or more, a short circuit will occur between the two electrode plates 2 and 3 of the element S, which will impair the durability of the element S itself, which is not preferable. Specifically, 1×10 -3 mA/mm 2 ~1mA/
mm 2 , especially 0.1 mA/mm 2 to 0.4 mA/mm 2 is preferred.
本発明方法において、センサ素子に一定電流を
流し、この場合の出力電圧値から被測定ガス中の
酸素濃度を検出する工程が適用可能な被測定ガス
は酸素低濃度領域のもので、具体的には５％以
下、特に３％以下のものが好ましい。５％以上に
なると第６図から明らかなように、酸素濃度に対
応する出力電圧値の変化率が小さく測定精度が低
下する。また、酸素濃度が0.1％以下になると出
力電圧値の変化率が大きくなり過ぎ好ましくな
い。したがつて、本発明方法において、センサ素
子に一定電流を流し、この場合の出力電圧値から
被測定ガス中の酸素濃度を検出する工程は、酸素
濃度0.1〜５％、特に0.1〜３％の被測定ガスの測
定に適する。 In the method of the present invention, the gas to be measured to which the process of flowing a constant current through the sensor element and detecting the oxygen concentration in the gas to be measured from the output voltage value in this case is in a low oxygen concentration region, is specifically is preferably 5% or less, particularly 3% or less. As is clear from FIG. 6, when it exceeds 5%, the rate of change in the output voltage value corresponding to the oxygen concentration is small and the measurement accuracy is reduced. Furthermore, if the oxygen concentration is 0.1% or less, the rate of change in the output voltage value becomes too large, which is not preferable. Therefore, in the method of the present invention, the step of flowing a constant current through the sensor element and detecting the oxygen concentration in the gas to be measured from the output voltage value in this case is performed when the oxygen concentration is 0.1 to 5%, particularly 0.1 to 3%. Suitable for measuring gases to be measured.
本発明方法を用いて、自動車内燃機関から排出
される排ガス中の酸素濃度を連続的に検出するに
は例えば次のように行なう。 For example, the method of the present invention can be used to continuously detect the oxygen concentration in exhaust gas discharged from an automobile internal combustion engine as follows.
第７図は本実施例で用いる酸素センサ（第５図
に示す構成のもの）における電圧−電流特性曲線
から求められた出力電流−酸素濃度関係線Ｉを示
すグラフ、第８図は前記特性曲線から求められた
出力電圧−酸素濃度関係線を示すグラフであ
り、また、第９図は本実施例のシステム図であ
る。センサ素子には、定電圧回路と定電流回路と
が切換え可能に接続されている。 FIG. 7 is a graph showing the output current-oxygen concentration relationship line I obtained from the voltage-current characteristic curve of the oxygen sensor used in this example (having the configuration shown in FIG. 5), and FIG. 8 is a graph showing the characteristic curve I. 9 is a graph showing the output voltage-oxygen concentration relationship line obtained from FIG. 9, and FIG. 9 is a system diagram of this embodiment. A constant voltage circuit and a constant current circuit are switchably connected to the sensor element.
まず、酸素センサに所定電圧を印加し、このと
き素子から出力される電流値が一定レベル以下で
あるかないかを検知する。電流値が一定レベル以
上であれば出力電流を測定し、第７図に示す関係
線Ｉから排ガス中の酸素濃度を検出する。出力電
流値が一定レベル以下であると、酸素センサに一
定電流を流す。酸素センサからの出力電圧が一定
レベル以上であると出力電圧を測定し、第８図に
示す関係線から排ガス中の酸素濃度を検出す
る。出力電圧値が一定レベル以下であると、酸素
センサに一定電圧を印加する。この出力電圧また
は出力電流測定を連続的に繰り返すことにより排
ガス中の酸素濃度を検出することができる。本実
施例では、排ガス中の酸素濃度が２％以上のとき
には出力電流を測定して第７図に示す関係線Ｉか
ら酸素濃度を検知し、また酸素濃度２％以下のと
きには出力電圧を測定して関係線から酸素濃度
を検知するようにする。この場合、一定電圧及び
一定電流は、センサ素子の構造及び排ガス中の成
分等により選択される。 First, a predetermined voltage is applied to the oxygen sensor, and it is detected whether the current value output from the element at this time is below a certain level or not. If the current value is above a certain level, the output current is measured, and the oxygen concentration in the exhaust gas is detected from the relationship line I shown in FIG. When the output current value is below a certain level, a certain current is passed through the oxygen sensor. When the output voltage from the oxygen sensor is above a certain level, the output voltage is measured, and the oxygen concentration in the exhaust gas is detected from the relationship line shown in FIG. When the output voltage value is below a certain level, a certain voltage is applied to the oxygen sensor. By continuously repeating this output voltage or output current measurement, the oxygen concentration in the exhaust gas can be detected. In this embodiment, when the oxygen concentration in the exhaust gas is 2% or more, the output current is measured and the oxygen concentration is detected from the relationship line I shown in FIG. 7, and when the oxygen concentration is 2% or less, the output voltage is measured. The oxygen concentration is detected from the relationship line. In this case, the constant voltage and constant current are selected depending on the structure of the sensor element, the components in the exhaust gas, etc.
センサ素子の形状は第４図及び第５図に示した
ような円板状のもの以外にも、一端が閉じた円筒
形状、すなわちカツプ形状のものでもよい。 The shape of the sensor element is not limited to the disk shape shown in FIGS. 4 and 5, but may also be a cylindrical shape with one end closed, that is, a cup shape.
なお、本発明方法は、上記実施例で示した限界
電流を利用する連続酸素濃度検出方法に限定され
ず、被測定ガス中に微少割合で酸素が混入する被
測定ガス中の酸素濃度を検出する場合に適用可能
である。この場合には、素子の陰極を被覆するコ
ーテイング層を陽極側に比べて厚くするというこ
とは必要ない。 Note that the method of the present invention is not limited to the continuous oxygen concentration detection method using the limiting current shown in the above embodiment, but also detects the oxygen concentration in a gas to be measured in which oxygen is mixed in a small proportion in the gas to be measured. Applicable to cases. In this case, it is not necessary to make the coating layer covering the cathode of the device thicker than the anode side.
本発明方法は、上述のように、それほど低くな
い濃度から非常に低濃度の酸素含有被測定ガス中
の酸素濃度を精度良く測定することができるとい
う利点を有する。また、本発明方法には従来使用
されている限界電流型酸素センサを用いることが
できるので、本発明方法を実施するための新たな
装置を必要とせず、単に測定回路を切替えること
によつて出力電圧を測定すれば良いのでコスト的
に安価ですむ。なお、本発明方法は、自動車内燃
機関の排ガス酸素濃度を連続的に測定する以外
に、他の種々の酸素濃度測定方法として、例えば
室内等の酸欠測定、各種工業用雰囲気制御システ
ム等に利用可能である。 As described above, the method of the present invention has the advantage that it is possible to accurately measure the oxygen concentration in an oxygen-containing gas to be measured at a not-so-low concentration to a very low concentration. In addition, since the method of the present invention can use a conventionally used limiting current type oxygen sensor, there is no need for new equipment to carry out the method of the present invention, and output can be achieved by simply switching the measurement circuit. Since it is only necessary to measure the voltage, the cost is low. In addition to continuously measuring the oxygen concentration of exhaust gas from automobile internal combustion engines, the method of the present invention can be used for various other oxygen concentration measurement methods, such as oxygen deficiency measurement in indoor rooms, various industrial atmosphere control systems, etc. It is possible.
第１図は限界電流型酸素センサの各酸素濃度に
おける印加電圧−出力電流特性曲線を表わすグラ
フ、第２図は限界電流型酸素センサの第１図と異
なる種類の被測定ガス中の各酸素濃度における印
加電圧−出力電流特性曲線を表わすグラフ、第３
図は、第１図及び第２図の特性曲線から得られる
出力電流−酸素濃度関係線を示すグラフ、第４図
は本発明方法による電圧測定状態を示す断面模式
図、第５図は本発明方法で使用する限界電流型酸
素センサの一例を示す断面模式図、第６図は第５
図の構成の酸素センサに一定電流を加えたときの
出力電圧−酸素濃度関係線を示すグラフ、第７図
は実施例で使用する酸素センサにおける出力電流
−酸素濃度関係線、第８図は実施例で使用する酸
素センサにおける出力電圧−酸素濃度関係線、第
９図は本発明の一実施例を示すシステム図、であ
る。
図中、１……素子本体、２，３……金属電極、
４，５……多孔性セラミツク層、８……電圧計、
９……電源。
Figure 1 is a graph showing the applied voltage-output current characteristic curve for each oxygen concentration of a limiting current type oxygen sensor, and Figure 2 is a graph showing each oxygen concentration in a different type of gas to be measured for the limiting current type oxygen sensor. Graph representing the applied voltage-output current characteristic curve at
The figure is a graph showing the output current-oxygen concentration relationship line obtained from the characteristic curves of FIGS. 1 and 2, FIG. 4 is a cross-sectional schematic diagram showing the voltage measurement state according to the method of the present invention, and FIG. A schematic cross-sectional diagram showing an example of a limiting current type oxygen sensor used in the method, FIG.
A graph showing the output voltage-oxygen concentration relationship line when a constant current is applied to the oxygen sensor configured as shown in the figure. Figure 7 is the output current-oxygen concentration relationship line for the oxygen sensor used in the example. Figure 8 is the graph showing the relationship line between the output voltage and oxygen concentration when a constant current is applied to the oxygen sensor configured as shown in the figure. The output voltage-oxygen concentration relationship line in the oxygen sensor used in the example, and FIG. 9 is a system diagram showing one embodiment of the present invention. In the figure, 1... element body, 2, 3... metal electrode,
4, 5... Porous ceramic layer, 8... Voltmeter,
9...Power supply.
Claims (1)
体表面に１対の電極が対向して形成された酸素セ
ンサの素子を、被測定ガスと接触させて該被測定
ガス中の酸素濃度を検出するに当たり、 センサ素子に一定電圧を印加し、この場合の出
力電流値が一定値を越えていれば該出力電流値か
ら前記被測定ガス中の酸素濃度を検出し、 前記出力電流値が一定値以下であれば、前記セ
ンサ素子に一定電流を流し、この場合の出力電圧
値が一定値を越えていれば該出力電圧値から前記
被測定ガス中の酸素濃度を検出し、 前記出力電圧値が一定値以下であれば、前記セ
ンサ素子に再度一定電圧を印加する工程を繰り返
すことにより前記被測定ガス中の酸素濃度を検出
することを特徴とする酸素濃度検出方法。[Claims] 1. An oxygen sensor element, in which a pair of electrodes are formed facing each other on the surface of an element body made of an oxygen ion permeable solid electrolyte, is brought into contact with a gas to be measured to remove oxygen in the gas to be measured. In detecting the concentration, a constant voltage is applied to the sensor element, and if the output current value in this case exceeds a constant value, the oxygen concentration in the gas to be measured is detected from the output current value, and the output current value is is below a certain value, a certain current is passed through the sensor element, and if the output voltage value in this case exceeds a certain value, the oxygen concentration in the measured gas is detected from the output voltage value, and the output An oxygen concentration detection method characterized in that, if the voltage value is below a certain value, the oxygen concentration in the gas to be measured is detected by repeating the step of applying a certain voltage to the sensor element again.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57055813A JPS58172542A (en) | 1982-04-03 | 1982-04-03 | Detection of oxygen concentration |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57055813A JPS58172542A (en) | 1982-04-03 | 1982-04-03 | Detection of oxygen concentration |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS58172542A JPS58172542A (en) | 1983-10-11 |
| JPH049258B2 true JPH049258B2 (en) | 1992-02-19 |
Family
ID=13009367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP57055813A Granted JPS58172542A (en) | 1982-04-03 | 1982-04-03 | Detection of oxygen concentration |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58172542A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0640094B2 (en) * | 1986-03-17 | 1994-05-25 | 日本碍子株式会社 | Electrochemical device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5562349A (en) * | 1978-11-02 | 1980-05-10 | Nissan Motor Co Ltd | Measuring method for air fuel ratio |
| JPS55166039A (en) * | 1979-06-12 | 1980-12-24 | Nissan Motor Co Ltd | Air fuel ratio detector |
-
1982
- 1982-04-03 JP JP57055813A patent/JPS58172542A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5562349A (en) * | 1978-11-02 | 1980-05-10 | Nissan Motor Co Ltd | Measuring method for air fuel ratio |
| JPS55166039A (en) * | 1979-06-12 | 1980-12-24 | Nissan Motor Co Ltd | Air fuel ratio detector |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58172542A (en) | 1983-10-11 |
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