JPH0411166Y2 - - Google Patents
Info
- Publication number
- JPH0411166Y2 JPH0411166Y2 JP1984198279U JP19827984U JPH0411166Y2 JP H0411166 Y2 JPH0411166 Y2 JP H0411166Y2 JP 1984198279 U JP1984198279 U JP 1984198279U JP 19827984 U JP19827984 U JP 19827984U JP H0411166 Y2 JPH0411166 Y2 JP H0411166Y2
- Authority
- JP
- Japan
- Prior art keywords
- gas detection
- detection piece
- temperature
- heater
- bridge circuit
- 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
Links
- 238000001514 detection method Methods 0.000 claims description 40
- 239000000446 fuel Substances 0.000 claims description 7
- 239000004065 semiconductor Substances 0.000 claims description 5
- 229910044991 metal oxide Inorganic materials 0.000 claims description 4
- 150000004706 metal oxides Chemical class 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 35
- 230000035945 sensitivity Effects 0.000 description 14
- 238000010438 heat treatment Methods 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 229910002367 SrTiO Inorganic materials 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000003990 capacitor Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 229910006404 SnO 2 Inorganic materials 0.000 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
Landscapes
- Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
Description
〔考案の利用分野〕
この考案は、ガス検出装置の改良に関し、自動
車エンジンやボイラー、ストーブの空燃比制御等
に適したもので有る。
〔従来技術〕
特公昭57−37824号は、ｐ形ガス検出片とｎ形
ガス検出片とを直列に接続して、センサの温度補
償とＳ／Ｎの向上とを図つた装置を提案している
（第３図参照）。図において、ｎはｎ形ガス検出
片、ｐはｐ形ガス検出片、Ａ１は差動増幅器、Ｉ
１は空燃比コントローラで有る。
考案者が、この装置について改良せんとする点
は、
(1) ヒータにより各ガス検出片ｎ，ｐの温度を一
定にし、ガス検出片ｎ，ｐの特性のマツチング
を容易にする。
(2) 各ガス検出片ｎ，ｐの抵抗値が異なる場合に
も、検出感度が低下しないようにする、
ことに有る。
〔考案の課題〕
この考案の課題は、ガス検出片の抵抗値から温
度を検出してヒータをコントロールする技術を確
立すること、ガス検出片の抵抗値が異なる場合に
も検出感度が低下しないようにすること、に有
る。
〔考案の構成〕
この考案の特徴は、ｎ形ガス検出片とｐ形ガス
検出片とを並列にブリツジ回路に組み込み、ガス
検出片の抵抗値のマツチングを不要とし、ブリツ
ジ回路のインピーダンスから各ガス検出片の温度
を検出してヒータをコントロールするようにした
ことに有る。
〔実施例〕
第１図において、ｎはBaSnO3，TiO2，SnO2
等のｎ形金属酸化物半導体の焼結体に一対の電極
を接続したｎ形ガス検出片、ｐはSrTiO3，Sr2
TiO4，Sr3Ti2O7，Sr4Ti3O10，C0Ｏ，NiO、等の
ｐ形金属酸化物半導体の焼結体に一対の電極を接
続したｐ形ガス検出片で有る。
Rn，Rpはそれぞれ抵抗で、これらとガス検出
片ｎ，ｐとによりブリツジ回路を構成する。抵抗
Rn，Rpの抵抗値は、所定の排ガス中で、ガス検
出片ｎ，ｐの平均加熱温度Tmと最高加熱温度
Thの間の温度TBで、ガス検出片ｎ，ｐの抵抗値
と一致するように定める。
ブリツジ回路には、直列に小さな温度検出抵抗
RTと、直流安定化電源等の電源EBを接続する。
また電源EBの出力（＋VCC）を各部の電源に用い
る。
Ａ１は差動増幅器、Ｉ１は空燃比コントローラ
で、周知で有る。
温度検出抵抗RTへの印加電位VTにより、ヒー
タＨをコントロールする。コントロールは図示の
ものに限らず、例えばブリツジ回路とアース点の
間に反転増幅型の演算増幅器を設けてブリツジ回
路の全インピーダンスをそのまま取り出すもの
等、任意のものを用い得る。即ち２つの直列片で
のガスによるインピーダンス変化が打ち消し合
い、全インピーダンスが温度の関数となる。
実施例にもどつて、Ａ２は基準電位と電圧VT
との差を求める差動増幅器、Ｃ１は比較器、Ｉ２
は発振回路、Ｉ３，Ｉ４はフリツプフロツプ回路
をなすノア回路、Tr１はトランジスタ、２，４
はＣ−Ｒタイマとしてのコンデンサと抵抗で有
る。これらによりヒータコントローラを構成す
る。
Ｈはガス検出片ｎ，ｐを均一に加熱するための
ヒータで、Tr２はスイツチングトランジスタ、
EHはヒータ電源で電源EBと兼用しても良い。
表と第２図とにより、実施例の動作を述べる。
図において、TSはガス検出片ｎ，ｐの加熱温度
で、Ｔは最低加熱温度、Thは最高加熱温度、
ThとＴとの差はガス検出片ｎ，ｐの温度変動
幅を現わし、Tmは平均加熱温度、TBはブリツジ
感度が最大となる温度で有る。曲線２１は電圧
VTを、破線２２は基準電位を、実線２３はヒー
タＨへの電圧印加のデユーテイ比を、２４はブリ
ツジ回路の感度を、２５はガス検出片ｎ，ｐの酸
素感度を示す。
電圧VTにより近似的にガス検出片ｎ，ｐの温
度を一定にコントロールする。もしガス検出片
ｎ，ｐの抵抗値とガス感度とが完全に一致すれ
ば、電圧VTは温度のみに依存する。しかしこの
ような条件は現実には得られず、両者の抵抗値が
異なると電圧VTには空燃比が影響する。このよ
うな影響は設定値からの空燃比のシフトが大きい
程、例えばリーン領域で設定した回路がリツチ領
域や空燃比の当量点でも動作を求められる場合
に、大きくなる。
差動増幅器Ａ２で基準電位と電圧VTの差を求
め、それに比例したデユーテイ比でヒータＨに電
圧を印加する。差は平均加熱温度Tmとガス検出
片ｎ，ｐの温度TSの差を意味する。発振回路Ｉ
２から正のパルスが加わると、ノア回路Ｉ４の出
力がハイとなりトランジスタTr２がオンする。
同時にトランジスタTr１がオフし、コンデンサ
２への充電が始まり、充電電圧が増幅器Ａ２の出
力に一致するまで、ノア回路Ｉ４の出力はハイと
なる。２つの電圧が一致するとノア回路Ｉ４の出
力がロウとなり、トランジスタTr２がオフする。
なお電圧VTが基準電位より高い時は、ヒータＨ
への電圧印加のデユーテイ比は０となる。
このようなデユーテイ比制御を行う理由は、出
力可変電源を不要とし、電源での電圧ドロツプに
よる電力損失を解消するためで有る。
ブリツジ回路の出力は、ガス検出片ｎ，ｐの抵
抗値と、抵抗Rn，Rpの抵抗値が一致する時に最
大となる。ところでガス検出片ｎ，ｐの酸素感度
は、温度とともに少しずつ減少する性質をもつ。
このことは前記に例示した半導体に対しては全て
あてはまる。そこでブリツジ感度が、平均加熱温
度Tmと最高加熱温度Thの間で最高になるよう
にすれば、ブリツジ感度の温度依存性と酸素感度
の温度依存性の間で補償が行われる。
ｎ形ガス検出片ｎとしてBaSnO3を、ｐ形ガス
検出片ｐとしてSrTiO3を用いた際の結果を表に
示す。なおSr2TiO4，Sr3Ti2O7，Sr4Ti3O10の特
性は、SrTiO3に酷似する。750℃を平均温度Tm
とし、700〜800℃で温度が変化する系で、例えば
780℃にブリツジ感度最大の温度TBを設定する。
温度低下によるブリツジ感度の低下は、酸素感度
の上昇により捕われる。なお抵抗値やブリツジ等
の感度は780℃を基準に示した。
[Field of application of the invention] This invention relates to the improvement of gas detection devices, and is suitable for controlling the air-fuel ratio of automobile engines, boilers, and stoves. [Prior art] Japanese Patent Publication No. 57-37824 proposes a device in which a p-type gas detection piece and an n-type gas detection piece are connected in series to compensate for the temperature of the sensor and improve the S/N ratio. (See Figure 3). In the figure, n is an n-type gas detection piece, p is a p-type gas detection piece, A1 is a differential amplifier, and I
1 is an air-fuel ratio controller. The points that the inventor intends to improve on this device are: (1) The temperature of each gas detection piece n, p is made constant by the heater, and the matching of the characteristics of the gas detection pieces n, p is made easier. (2) The purpose is to prevent the detection sensitivity from decreasing even when the resistance values of each gas detection piece n and p are different. [Challenges of the invention] The challenges of this invention are to establish a technology to control the heater by detecting the temperature from the resistance value of the gas detection piece, and to prevent the detection sensitivity from decreasing even when the resistance value of the gas detection piece is different. There is something to do. [Configuration of the device] The feature of this device is that it incorporates an n-type gas detection piece and a p-type gas detection piece in a bridge circuit in parallel, eliminates the need for matching the resistance values of the gas detection pieces, and detects each gas from the impedance of the bridge circuit. The reason is that the heater is controlled by detecting the temperature of the detection piece. [Example] In Fig. 1, n is BaSnO 3 , TiO 2 , SnO 2
An n-type gas detection piece in which a pair of electrodes are connected to a sintered body of an n-type metal oxide semiconductor such as, p is SrTiO 3 , Sr 2
This is a p-type gas detection piece in which a pair of electrodes are connected to a sintered body of p-type metal oxide semiconductor such as TiO 4 , Sr 3 Ti 2 O 7 , Sr 4 Ti 3 O 10 , C 0 O, NiO, etc. Rn and Rp are resistors, respectively, and these and gas detection pieces n and p constitute a bridge circuit. resistance
The resistance values of Rn and Rp are the average heating temperature Tm and the maximum heating temperature of gas detection pieces n and p in the specified exhaust gas.
The temperature T B between Th is determined to match the resistance value of the gas detection pieces n and p. The bridge circuit has a small temperature sensing resistor in series.
Connect R T and power supply E B such as a DC stabilized power supply.
In addition, the output of power supply E B (+V CC ) is used as a power source for each part. A1 is a differential amplifier, and I1 is an air-fuel ratio controller, both of which are well known. The heater H is controlled by the potential V T applied to the temperature detection resistor R T. The control is not limited to the one shown in the drawings, but any other control may be used, such as one in which an inverting operational amplifier is provided between the bridge circuit and the ground point and the entire impedance of the bridge circuit is taken out as is. That is, the impedance changes due to gas in the two series pieces cancel each other out, and the total impedance becomes a function of temperature. Returning to the example, A2 is the reference potential and voltage V T
A differential amplifier that calculates the difference between , C1 is a comparator, and I2
is an oscillation circuit, I3 and I4 are NOR circuits forming a flip-flop circuit, Tr1 is a transistor, 2, 4
is a capacitor and a resistor as a C-R timer. These constitute a heater controller. H is a heater for uniformly heating the gas detection pieces n and p, Tr2 is a switching transistor,
E H is the heater power supply and may also be used as the power supply E B. The operation of the embodiment will be described with reference to the table and FIG.
In the figure, T S is the heating temperature of gas detection pieces n and p, T is the minimum heating temperature, Th is the maximum heating temperature,
The difference between Th and T represents the temperature fluctuation range of the gas detection pieces n and p, Tm is the average heating temperature, and T B is the temperature at which the bridge sensitivity is maximum. Curve 21 is the voltage
VT , the broken line 22 shows the reference potential, the solid line 23 shows the duty ratio of voltage application to the heater H, 24 shows the sensitivity of the bridge circuit, and 25 shows the oxygen sensitivity of the gas detection pieces n and p. The temperature of the gas detection pieces n and p is approximately controlled to be constant by the voltage V T . If the resistance values and gas sensitivities of the gas detection pieces n and p completely match, the voltage V T depends only on the temperature. However, such conditions cannot be achieved in reality, and if the resistance values of the two are different, the air-fuel ratio will affect the voltage VT . Such effects become greater as the air-fuel ratio shifts from the set value, for example when a circuit set in a lean region is required to operate in a rich region or at an equivalence point of the air-fuel ratio. The difference between the reference potential and the voltage V T is determined by the differential amplifier A2, and a voltage is applied to the heater H at a duty ratio proportional to the difference. The difference means the difference between the average heating temperature Tm and the temperature T S of the gas detection pieces n and p. Oscillation circuit I
When a positive pulse is applied from Tr2, the output of the NOR circuit I4 goes high, turning on the transistor Tr2.
At the same time, transistor Tr1 is turned off, charging of capacitor 2 begins, and the output of NOR circuit I4 becomes high until the charging voltage matches the output of amplifier A2. When the two voltages match, the output of the NOR circuit I4 becomes low and the transistor Tr2 is turned off.
Note that when the voltage V T is higher than the reference potential, the heater H
The duty ratio of voltage application to is 0. The reason for performing such duty ratio control is to eliminate the need for a variable output power supply and eliminate power loss due to voltage drop in the power supply. The output of the bridge circuit becomes maximum when the resistance values of the gas detection pieces n and p match the resistance values of the resistors Rn and Rp. Incidentally, the oxygen sensitivity of the gas detection pieces n and p has a property of decreasing little by little with temperature.
This applies to all of the semiconductors exemplified above. Therefore, if the bridge sensitivity is set to be the highest between the average heating temperature Tm and the maximum heating temperature Th, compensation will be performed between the temperature dependence of the bridge sensitivity and the temperature dependence of the oxygen sensitivity. The table shows the results when BaSnO 3 was used as the n-type gas detection piece n and SrTiO 3 was used as the p-type gas detection piece p. Note that the characteristics of Sr 2 TiO 4 , Sr 3 Ti 2 O 7 , and Sr 4 Ti 3 O 10 are very similar to those of SrTiO 3 . 750℃ average temperature Tm
In a system where the temperature changes between 700 and 800℃, for example,
Set the maximum bridge sensitivity temperature T B to 780°C.
The decrease in bridge sensitivity due to temperature decrease is captured by the increase in oxygen sensitivity. The sensitivity of resistance values and bridges is shown based on 780°C.
この考案では、ガス検出片の温度を一定にして
特性のマツチングを容易にし、また抵抗が異なる
ガス検出片をも使用可能にしている。
This invention makes it easier to match the characteristics by keeping the temperature of the gas detection piece constant, and also allows the use of gas detection pieces with different resistances.
第１図は実施例の回路図、第２図はその特性
図、第３図は従来例の回路図で有る。
Ａ１，Ａ２……差動増幅器、Ｈ……ヒータ。
FIG. 1 is a circuit diagram of the embodiment, FIG. 2 is a characteristic diagram thereof, and FIG. 3 is a circuit diagram of a conventional example. A1, A2...Differential amplifier, H...Heater.
Claims (1)
たｎ形ガス検出片ｎと、ｐ形金属酸化物半導体の
抵抗値の変化を利用したｐ形ガス検出片ｐと、各
ガス検出片ｎ，ｐにそれぞれ直列に接続した抵抗
Rn，Rpとで構成したブリツジ回路と、 このブリツジ回路の出力により動作する空燃比
コントローラＩ１と、 ブリツジ回路の全インピーダンスの変化により
動作して、各ガス検出片ｎ，ｐを加熱するための
ヒータへの印加電力をコントロールするヒータコ
ントローラ、 とを有するガス検出装置。[Claims for Utility Model Registration] An n-type gas detection piece n that utilizes a change in resistance value of an n-type metal oxide semiconductor, and a p-type gas detection piece p that uses a change in resistance value of a p-type metal oxide semiconductor. and a resistor connected in series to each gas detection piece n and p, respectively.
Rn and Rp, an air-fuel ratio controller I1 that operates based on the output of this bridge circuit, and a heater that operates based on changes in the total impedance of the bridge circuit to heat each gas detection piece n and p. A gas detection device comprising: a heater controller that controls power applied to the gas detector;
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1984198279U JPH0411166Y2 (en) | 1984-12-28 | 1984-12-28 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1984198279U JPH0411166Y2 (en) | 1984-12-28 | 1984-12-28 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61114353U JPS61114353U (en) | 1986-07-19 |
| JPH0411166Y2 true JPH0411166Y2 (en) | 1992-03-19 |
Family
ID=30757138
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1984198279U Expired JPH0411166Y2 (en) | 1984-12-28 | 1984-12-28 |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0411166Y2 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5237494A (en) * | 1975-09-20 | 1977-03-23 | Matsushita Electric Works Ltd | Gas, smoke detection device |
| JPS567056B2 (en) * | 1973-10-03 | 1981-02-16 | ||
| JPS5737824A (en) * | 1980-08-20 | 1982-03-02 | Seiko Epson Corp | Method and device for impurity diffusion |
| JPS5796248A (en) * | 1980-12-05 | 1982-06-15 | Matsushita Electric Ind Co Ltd | Detecting method for gas using superparticulate gas sensor |
| JPS5842960A (en) * | 1981-09-08 | 1983-03-12 | Matsushita Electric Works Ltd | Detection apparatus of combustible gas |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6123789Y2 (en) * | 1979-06-28 | 1986-07-16 |
-
1984
- 1984-12-28 JP JP1984198279U patent/JPH0411166Y2/ja not_active Expired
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS567056B2 (en) * | 1973-10-03 | 1981-02-16 | ||
| JPS5237494A (en) * | 1975-09-20 | 1977-03-23 | Matsushita Electric Works Ltd | Gas, smoke detection device |
| JPS5737824A (en) * | 1980-08-20 | 1982-03-02 | Seiko Epson Corp | Method and device for impurity diffusion |
| JPS5796248A (en) * | 1980-12-05 | 1982-06-15 | Matsushita Electric Ind Co Ltd | Detecting method for gas using superparticulate gas sensor |
| JPS5842960A (en) * | 1981-09-08 | 1983-03-12 | Matsushita Electric Works Ltd | Detection apparatus of combustible gas |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61114353U (en) | 1986-07-19 |
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