JP2929038B2 - Air-fuel ratio sensor drive circuit - Google Patents
Air-fuel ratio sensor drive circuitInfo
- Publication number
- JP2929038B2 JP2929038B2 JP2339523A JP33952390A JP2929038B2 JP 2929038 B2 JP2929038 B2 JP 2929038B2 JP 2339523 A JP2339523 A JP 2339523A JP 33952390 A JP33952390 A JP 33952390A JP 2929038 B2 JP2929038 B2 JP 2929038B2
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- Japan
- Prior art keywords
- voltage
- cell
- pump
- fuel ratio
- air
- Prior art date
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- Expired - Lifetime
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- Measuring Oxygen Concentration In Cells (AREA)
- Fuel Cell (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は内燃機関等の排気ガス中の酸素濃度に基づき
空燃比を検出する空燃比センサーの駆動回路に関する。The present invention relates to a driving circuit for an air-fuel ratio sensor that detects an air-fuel ratio based on an oxygen concentration in exhaust gas of an internal combustion engine or the like.
従来、この種の空燃比センサーとして、ジルコニア等
の酸素イオン伝導性固体電解質材料を用い、板状の酸素
イオン伝導性固体電解質の両面に多孔質電極を設けた２
枚の素子を間隙を介して対向配置すると共に、該間隙と
測定ガス雰囲気との間にガス拡散制限部を設けて該間隙
を拡散室とし、一方の素子を拡散室と測定ガス雰囲気と
の間で酸素イオンを移動させるポンプセルとし、他方の
素子を拡散室と内部基準酸素室との酸素濃度差によって
起電力を発生する起電力セルとしたものが提案されてい
る（特開昭62−148849号）。Conventionally, an oxygen ion conductive solid electrolyte material such as zirconia has been used as an air-fuel ratio sensor of this type, and porous electrodes are provided on both sides of a plate-shaped oxygen ion conductive solid electrolyte.
The two elements are arranged to face each other with a gap therebetween, and a gas diffusion restricting portion is provided between the gap and the measurement gas atmosphere to make the gap a diffusion chamber, and one element is provided between the diffusion chamber and the measurement gas atmosphere. A pump cell has been proposed in which a pump cell is used to move oxygen ions, and the other element is an electromotive force cell which generates an electromotive force based on a difference in oxygen concentration between a diffusion chamber and an internal reference oxygen chamber (Japanese Patent Application Laid-Open No. 62-144889). ).
この空燃比センサーの駆動回路では、起電力セルで検
出される電圧が所定の一定電圧となるよう、即ち、拡散
室の空燃比が一定となるようにポンプセルに流す電流を
双方向に制御し、その電流値により測定ガス雰囲気の空
燃比を検出するようにしている。そして、内部基準酸素
室と拡散室とは漏出抵抗部を介して連通され、起電力セ
ルに僅かな電流を流すことにより拡散室から内部基準酸
素室に酸素イオンを運び、内部基準酸素室の酸素分圧が
測定ガス雰囲気の空燃比にかかわらず所定の基準酸素分
圧となるようにされている。In the drive circuit of this air-fuel ratio sensor, the current flowing through the pump cell is controlled bidirectionally so that the voltage detected by the electromotive force cell becomes a predetermined constant voltage, that is, the air-fuel ratio of the diffusion chamber becomes constant. The air-fuel ratio of the measurement gas atmosphere is detected based on the current value. The internal reference oxygen chamber and the diffusion chamber are communicated with each other through a leakage resistance portion, and a small amount of current flows through the electromotive force cell to carry oxygen ions from the diffusion chamber to the internal reference oxygen chamber. The partial pressure is set to a predetermined reference oxygen partial pressure regardless of the air-fuel ratio of the measurement gas atmosphere.
しかしながら、上記従来空燃比センサーの駆動回路で
は、一般に拡散室の空燃比が理論空燃比となるようにポ
ンプセルに電流を流すため、測定ガス雰囲気の空燃比が
余りにリッチであったりリーンであったりすると、ポン
プセルに印加される電圧が過大になり、ポンプセルを形
成するジルコニアZrO2がマイナス側電極近傍でジルコニ
ュウム金属Zrと酸素O2とに解離する、いわゆるブラック
ニング（黒化）を生じて破壊してしまうという問題点が
あった。However, in the drive circuit of the conventional air-fuel ratio sensor, since current is generally passed through the pump cell so that the air-fuel ratio of the diffusion chamber becomes the stoichiometric air-fuel ratio, if the air-fuel ratio of the measurement gas atmosphere is too rich or lean, When the voltage applied to the pump cell becomes excessive, the zirconia ZrO 2 forming the pump cell is dissociated into zirconium metal Zr and oxygen O 2 near the negative electrode, resulting in so-called blackening (blackening). There was a problem that it would.
本発明は、上記の問題点に鑑みなされたものであり、
その目的とするところは、ポンプセルに印加される電圧
を制限してポンプセルを形成するジルコニアのブラック
ニングを防止することができると共に、ポンプセル電圧
を制限し始めた状態でも正確な空燃比を検出することが
できる空燃比センサーの駆動回路を提供することにあ
る。The present invention has been made in view of the above problems,
The purpose is to limit the voltage applied to the pump cell to prevent blackening of the zirconia forming the pump cell, and to detect an accurate air-fuel ratio even when the pump cell voltage has begun to be limited. It is an object of the present invention to provide a driving circuit for an air-fuel ratio sensor that can perform the above.
上記の目的を達成するため、本発明では、 酸素イオン伝導性固体電解質板に一対の多孔質電極を
有し、その一の多孔質電極を測定ガス雰囲気に面するよ
うにされたポンプセルと、 酸素イオン伝導性固体電解質板に一対の多孔質電極を
有し、その一の多孔質電極を内部基準酸素質に面するよ
うにされた起電力セルと、 前記ポンプセルと起電力セルとに囲まれ、ガス拡散制
限部を経由して測定ガス雰囲気と連通するようにされた
拡散室と、 前記内部基準酸素室からガスが漏出するガス通路を構
成する漏出抵抗部とを備える空燃比センサーの駆動回路
であって、 前記起電力セルに所定電流を流す手段と、 前記起電力セルの電圧を前記拡散室の空燃比が理論空
燃比である時に前記起電力セルの電圧が示す電圧近傍の
所定制御電圧値とするべく前記ポンプセルに流す電流の
方向及び大きさを制御するポンプ電流制御手段と、 前記ポンプセルに流す電流値に対応した信号を出力す
る信号出力手段と、 前記ポンプセルに印加される電圧を検出し、該電圧の
絶対値が所定電圧を超えた場合に前記起電力セルの所定
制御電圧値を変化させる制御電圧変動手段と、 を備えることを特徴とする空燃比センサーの駆動回路が
提供される。In order to achieve the above object, according to the present invention, there is provided a pump cell having a pair of porous electrodes on an oxygen ion conductive solid electrolyte plate, wherein one of the porous electrodes faces a measurement gas atmosphere. An ion-conducting solid electrolyte plate has a pair of porous electrodes, an electromotive cell in which one of the porous electrodes faces the internal reference oxygen, and is surrounded by the pump cell and the electromotive cell, A driving circuit for an air-fuel ratio sensor including a diffusion chamber configured to communicate with a measurement gas atmosphere via a gas diffusion limiting unit, and a leakage resistance unit forming a gas passage through which gas leaks from the internal reference oxygen chamber. Means for flowing a predetermined current through the electromotive force cell; and a predetermined control voltage value near the voltage indicated by the voltage of the electromotive force cell when the air-fuel ratio of the diffusion chamber is the stoichiometric air-fuel ratio. Said to be Pump current control means for controlling the direction and magnitude of the current flowing through the pump cell; signal output means for outputting a signal corresponding to the value of the current flowing through the pump cell; detecting a voltage applied to the pump cell; And a control voltage changing means for changing a predetermined control voltage value of the electromotive force cell when an absolute value exceeds a predetermined voltage. A driving circuit for an air-fuel ratio sensor is provided.
上記のように構成された空燃比センサーでは、ポンプ
セルは両面の多孔質電極間に電流を流すことにより、測
定ガス雰囲気と拡散室との間で多孔質電極の負極側から
正極側に酸素イオンを移動させる酸素ポンプとしての作
用をする。In the air-fuel ratio sensor configured as described above, the pump cell causes oxygen ions to flow from the negative electrode side to the positive electrode side of the porous electrode between the measurement gas atmosphere and the diffusion chamber by flowing a current between the porous electrodes on both surfaces. It acts as a moving oxygen pump.
起電力セルは内部基準酸素室と拡散室との酸素分圧の
比に対応した起電力を発生する酸素濃淡電池として作用
すると共に、両面の多孔質電極間に流される所定電流に
より拡散室から内部基準酸素室に酸素イオンを運び、内
部基準酸素室の酸素分圧を所定値に維持する作用をす
る。The electromotive force cell functions as an oxygen concentration cell that generates an electromotive force corresponding to the ratio of the partial pressure of oxygen between the internal reference oxygen chamber and the diffusion chamber, and also has a predetermined current flowing between the porous electrodes on both sides to generate an internal power from the diffusion chamber. The oxygen ions are carried to the reference oxygen chamber, and serve to maintain the oxygen partial pressure in the internal reference oxygen chamber at a predetermined value.
ポンプ電流制御手段では拡散室の空燃比が理論空燃比
となるようにフィードバッグ制御をしながらポンプセル
に流す電流（以下ポンプ電流Ipという）を制御し、拡散
室から測定ガス雰囲気に酸素を汲み出したり、あるいは
逆に拡散室に酸素を汲み入れたりする。The pump current control means controls the current flowing through the pump cell (hereinafter referred to as pump current Ip) while performing feedback control so that the air-fuel ratio of the diffusion chamber becomes the stoichiometric air-fuel ratio, and pumps oxygen from the diffusion chamber into the measurement gas atmosphere. Or vice versa, pumping oxygen into the diffusion chamber.
ここで、ポンプセルに印加される電圧（以下ポンプ電
圧Vpという）は、ポンプセルの抵抗値Ripとポンプ電流I
pによる電圧降下分と、測定ガス雰囲気と拡散室との間
の酸素分圧の比に対応した起電力との和になる。即ち、
ポンプ電圧Vpは周知のネルンストの式から次式で示され
る。Here, the voltage applied to the pump cell (hereinafter referred to as pump voltage Vp) is determined by the resistance value Rip of the pump cell and the pump current Ip.
The sum of the voltage drop due to p and the electromotive force corresponding to the ratio of the oxygen partial pressure between the measurement gas atmosphere and the diffusion chamber is obtained. That is,
The pump voltage Vp is expressed by the following equation from the well-known Nernst equation.
Vp＝Rip×Ip＋（RT/4F）1n（Poe/Pe） 上式において、Ｒは気体定数、Ｔは絶対温度、Ｆはファ
ラデー定数、Poeは測定ガス雰囲気の酸素分圧、Peは拡
散室の酸素分圧である。Vp = Rip × Ip + (RT / 4F) 1n (Poe / Pe) In the above equation, R is a gas constant, T is an absolute temperature, F is a Faraday constant, Poe is an oxygen partial pressure of a measurement gas atmosphere, and Pe is a diffusion chamber. Oxygen partial pressure.
従って、制御電圧変動手段により起電力セルの所定制
御電圧値を変化させてフィードバック制御の動作点を変
化させ、拡散室の酸素分圧Peを変化させることにより、
ポンプ電流Ipを変えることなくポンプ電圧Vpを変化さ
せ、ポンプ電圧Vpを制限することができる。Therefore, by changing the predetermined control voltage value of the electromotive force cell by the control voltage changing means to change the operating point of the feedback control, and changing the oxygen partial pressure Pe of the diffusion chamber,
By changing the pump voltage Vp without changing the pump current Ip, the pump voltage Vp can be limited.
本発明の実施例について図面を参照し説明する。 Embodiments of the present invention will be described with reference to the drawings.
第２図はセンサー素子を断面で示した動作原理図であ
る。センサー素子は板状のヒータ板１と、スペーサ２
と、ポンプセル３と、スペーサ４と、起電力セル５と、
遮蔽体板６とを積層して構成される。ヒータ板１にはヒ
ータ７が埋設され、図示せぬ制御回路によりセンサー素
子を約800℃の温度に保持する。スペーサ２、４はアル
ミナからなる絶縁体である。FIG. 2 is an operation principle diagram showing a cross section of the sensor element. The sensor elements are a plate-like heater plate 1 and a spacer 2
A pump cell 3, a spacer 4, an electromotive force cell 5,
It is configured by laminating the shield plate 6. A heater 7 is embedded in the heater plate 1, and the sensor element is maintained at a temperature of about 800 ° C. by a control circuit (not shown). The spacers 2 and 4 are insulators made of alumina.
ポンプセル３は酸素イオン伝導性固体電解質材料であ
る安定化または部分安定化ジルコニアZrO2により形成さ
れ、その表面と裏面のそれぞれに白金で形成された多孔
質電極11、12を有している。ポンプセル３の一方の多孔
質電極11は直接測定ガス雰囲気に晒されるようにされて
いる。The pump cell 3 is made of stabilized or partially stabilized zirconia ZrO 2 , which is an oxygen ion conductive solid electrolyte material, and has porous electrodes 11 and 12 made of platinum on the front and back surfaces, respectively. One porous electrode 11 of the pump cell 3 is directly exposed to the measurement gas atmosphere.
起電力セル５も同様にジルコニアZrO2により形成さ
れ、その表面と裏面のそれぞれに白金で形成された多孔
質電極13、14を有している。ポンプセル３と起電力セル
５に囲まれて拡散室15が形成されている。拡散室15はガ
ス拡散制限部16を経由して測定ガス雰囲気と連通するよ
うにされている。ガス拡散制限部16は単なる小孔であっ
てもよいし、多孔質物質を充填してもよい。また、起電
力セル５の背面には内部基準酸素室17が設けられ、その
内部基準酸素室17は漏出抵抗部18を経由して拡散室15に
連通している。漏出抵抗部18も単なる小孔であってもよ
いし、多孔質物質を充填してもよい。The electromotive force cell 5 is also formed of zirconia ZrO 2, and has porous electrodes 13 and 14 formed of platinum on the front and back surfaces, respectively. A diffusion chamber 15 is formed surrounded by the pump cell 3 and the electromotive force cell 5. The diffusion chamber 15 communicates with the measurement gas atmosphere via the gas diffusion restricting section 16. The gas diffusion restricting portion 16 may be a simple pore or may be filled with a porous substance. An internal reference oxygen chamber 17 is provided on the back surface of the electromotive force cell 5, and the internal reference oxygen chamber 17 communicates with the diffusion chamber 15 via the leakage resistance portion 18. The leakage resistance portion 18 may also be a mere small hole, or may be filled with a porous material.
起電力セル５は内部基準酸素室17の拡散室15との酸素
分圧の比に対応した起電力を発生する酸素濃淡電池とし
て作用すると共に、両面の多孔質電極13、14間に流され
る所定電流Icpにより拡散室15から内部基準酸素室17に
酸素イオンを運び、内部基準酸素室17の酸素分圧を所定
値に維持する作用をする。The electromotive force cell 5 functions as an oxygen concentration cell that generates an electromotive force corresponding to the ratio of the oxygen partial pressure of the internal reference oxygen chamber 17 to that of the diffusion chamber 15 and flows between the porous electrodes 13 and 14 on both surfaces. Oxygen ions are carried from the diffusion chamber 15 to the internal reference oxygen chamber 17 by the current Icp, and the oxygen ions in the internal reference oxygen chamber 17 are maintained at a predetermined value.
内部基準酸素室17の酸素分圧を所定値に維持する作用
について説明する。内部基準酸素室17の酸素分圧をP0
2、拡散室15の酸素分圧をPe、漏出抵抗部18のコンダク
タンスをＣ、ファラデー定数をＦとすると、所定電流Ic
pにより拡散室15から内部基準酸素室17に汲み込む酸素
流量J1は、 J1＝Icp/4F また、漏出抵抗部18を通って内部基準酸素室17から拡散
室15に戻る酸素流量J2は、 J2＝Ｃ（P02−Pe） 一方、起電力セル５に生ずる電圧Vsは周知のネルンスト
の式から次式で示される。The operation of maintaining the oxygen partial pressure of the internal reference oxygen chamber 17 at a predetermined value will be described. Set the oxygen partial pressure of the internal reference oxygen chamber 17 to P0
2. Assuming that the oxygen partial pressure of the diffusion chamber 15 is Pe, the conductance of the leakage resistance portion 18 is C, and the Faraday constant is F, the predetermined current Ic
The oxygen flow rate J1 pumped from the diffusion chamber 15 into the internal reference oxygen chamber 17 by p is J1 = Icp / 4F. The oxygen flow rate J2 returning from the internal reference oxygen chamber 17 to the diffusion chamber 15 through the leakage resistance portion 18 is J2 = C (P02-Pe) On the other hand, the voltage Vs generated in the electromotive force cell 5 is expressed by the following equation from the well-known Nernst equation.
Vs＝Rvs×Icp＋（RT/4F）1n（P02/Pe） 上式において、Rvsは起電力セル５の抵抗値、Ｒは気体
定数、Ｔは絶対温度、Ｆはファラデー定数である。Vs = Rvs × Icp + (RT / 4F) 1n (P02 / Pe) In the above equation, Rvs is a resistance value of the electromotive force cell 5, R is a gas constant, T is an absolute temperature, and F is a Faraday constant.
ここで、素子温度が充分高く上式の第１項が無視で
き、電圧Vsが450mVの近傍であれば、内部基準酸素室17
の酸素分圧P02は拡散室15の酸素分圧Peに比べて充分に
高くPeを無視できる。従って定常状態では酸素流量J1＝
J2から、 Icp/4F＝Ｃ×P02 となり、大気を導入しなくても一定電流Icpを流すこと
により内部基準酸素室17の酸素分圧P02を所定値に維持
することができる。Here, if the element temperature is sufficiently high and the first term of the above equation can be ignored, and the voltage Vs is near 450 mV, the internal reference oxygen chamber 17
The oxygen partial pressure P02 is sufficiently higher than the oxygen partial pressure Pe in the diffusion chamber 15, and Pe can be ignored. Therefore, in the steady state, the oxygen flow rate J1 =
From J2, Icp / 4F = C × P02, and the oxygen partial pressure P02 in the internal reference oxygen chamber 17 can be maintained at a predetermined value by flowing the constant current Icp without introducing the atmosphere.
ポンプセル３は両面の多孔質電極11、12間に電流Ipを
流すことにより、測定ガス雰囲気と拡散室15との間で多
孔質電極11、12の負極側から正極側に酸素イオンを移動
させる酸素ポンプとしての作用をする。The pump cell 3 supplies oxygen I between the negative electrode side and the positive electrode side of the porous electrodes 11 and 12 between the measurement gas atmosphere and the diffusion chamber 15 by flowing a current Ip between the porous electrodes 11 and 12 on both surfaces. Acts as a pump.
起電力セル５に生ずる電圧Vsが一定となった定常状態
においては、測定ガス雰囲気がリーンの場合は、ポンプ
セル３の電流Ipにより運ばれる酸素流量と、拡散室15に
ガス拡散制限部16を経由して流入する酸素流量とが等し
くなる。一方、測定ガス雰囲気がリッチの場合は、ポン
プセル３の電流Ipにより運ばれる酸素流量と、拡散室15
にガス拡散制限部16を経由して流入する還元ガス流量と
が等しくなる。このことから、ポンプ電流Ipは次式で示
される。In a steady state in which the voltage Vs generated in the electromotive force cell 5 is constant, when the measurement gas atmosphere is lean, the flow rate of oxygen carried by the current Ip of the pump cell 3 and the diffusion chamber 15 pass through the gas diffusion limiting unit 16. And the flow rate of the incoming oxygen becomes equal. On the other hand, when the measurement gas atmosphere is rich, the flow rate of oxygen carried by the current Ip of the pump cell 3 and the diffusion chamber 15
And the flow rate of the reducing gas flowing through the gas diffusion restricting section 16 becomes equal. From this, the pump current Ip is expressed by the following equation.
測定ガス雰囲気がリーンの場合、 Ip＝〔4FDS/RTL〕×〔Poe−Pe〕 測定ガス雰囲気がリッチの場合、 Ip＝〔2FDHS/RTL〕×〔PHOe−PHe〕 ＋〔2FDcoS/RTL〕×〔Pcooe−Pcoe］ 上式において、Ｄは酸素の拡散係数、DHは水素の拡散係
数、Dco一酸化炭素COの拡散係数、Ｓはガス拡散制限部1
6の断面積、Ｌはガス拡散制限部16の長さ、Poeは測定ガ
ス雰囲気の酸素分圧、PHOeは測定ガス雰囲気の水素分
圧、Pcooeは測定ガス雰囲気の一酸化炭素分圧、Peは拡
散室15の酸素分圧、PHeは拡散室15の水素分圧、Pcoeは
拡散室15の一酸化炭素分圧である。If the measured gas atmosphere is lean, Ip = if [4FDS / RTL] × [Poe-Pe] measured gas atmosphere is rich, Ip = [2FD H S / RTL] × [P Hoe -P the He] + [2FDcoS / RTL] × [Pcooe-Pcoe] In the above equation, D is the diffusion coefficient of oxygen, D H is the diffusion coefficient of hydrogen, Dco is the diffusion coefficient of carbon monoxide CO, and S is the gas diffusion limiting unit 1.
6, L is the length of the gas diffusion restrictor 16, Poe is the oxygen partial pressure of the measurement gas atmosphere, P HOe is the hydrogen partial pressure of the measurement gas atmosphere, Pcooe is the carbon monoxide partial pressure of the measurement gas atmosphere, Pe Is the oxygen partial pressure in the diffusion chamber 15, P He is the hydrogen partial pressure in the diffusion chamber 15, and Pcoe is the carbon monoxide partial pressure in the diffusion chamber 15.
以上説明した各セル３、５の作用に基づき、駆動回路
の基本的な作動について説明する。起電力セル５には抵
抗R1を経由して一定電流Icpが流される。第１の増幅器A
1は起電力セル５に発生する電圧Vsを検出するバッファ
アンプである。第２の増幅器A2と第３の増幅器A3により
ポンプセル３にポンプ電流Ipが流される。第３の増幅器
A3は共通ライン30の電圧が所定の基準電圧となるように
制御し、第２の増幅器A2は起電力セル５の電圧Vsが所定
制御電圧値となるようにポンプ電流Ipを制御する。The basic operation of the drive circuit will be described based on the operation of each of the cells 3 and 5 described above. A constant current Icp flows through the electromotive force cell 5 via the resistor R1. First amplifier A
Reference numeral 1 denotes a buffer amplifier that detects a voltage Vs generated in the electromotive force cell 5. The pump current Ip flows through the pump cell 3 by the second amplifier A2 and the third amplifier A3. Third amplifier
A3 controls the voltage of the common line 30 to be a predetermined reference voltage, and the second amplifier A2 controls the pump current Ip so that the voltage Vs of the electromotive force cell 5 has a predetermined control voltage value.
所定制御電圧値は拡散室15の空燃比が理論空燃比とな
る450mVに設定される。これにより、測定ガス雰囲気の
酸素分圧にかかわらず拡散室15の空燃比が理論空燃比と
なるようにフィードバック制御をしながらポンプ電流Ip
を制御し、拡散室15から測定ガス雰囲気に酸素を汲み出
したり、あるいは逆に拡散室15に酸素を汲み入れたりす
る。そして、抵抗R3の電圧降下によりポンプ電流Ipを検
出し、ポンプ電流Ipに対応した信号として第２の増幅器
A2の出力電圧を出力端子40に出力する。The predetermined control voltage value is set to 450 mV at which the air-fuel ratio of the diffusion chamber 15 becomes the stoichiometric air-fuel ratio. Thus, the pump current Ip is controlled while performing feedback control so that the air-fuel ratio of the diffusion chamber 15 becomes the stoichiometric air-fuel ratio regardless of the oxygen partial pressure of the measurement gas atmosphere.
Is controlled to pump oxygen from the diffusion chamber 15 into the measurement gas atmosphere or vice versa. Then, the pump current Ip is detected by the voltage drop of the resistor R3, and the second amplifier is used as a signal corresponding to the pump current Ip.
The output voltage of A2 is output to the output terminal 40.
第１図は駆動回路の具体的内容を示す回路図である。
第１の増幅器A1は起電力セル５に発生する電圧Vsを検出
し、第２の増幅器A2と第３の増幅器A3によりポンプセル
３にポンプ電流Ipが流される。ここで、電源電圧Voは8V
に設定され、分圧抵抗R11、R12により与えられる結合点
31の基準電圧は4Vにされている。従って、共通ライン30
の電圧は基準電圧4Vに制御される。FIG. 1 is a circuit diagram showing the specific contents of the drive circuit.
The first amplifier A1 detects the voltage Vs generated in the electromotive force cell 5, and the pump current Ip flows through the pump cell 3 by the second amplifier A2 and the third amplifier A3. Here, the power supply voltage Vo is 8V
And is provided by the voltage dividing resistors R11 and R12.
The reference voltage of 31 is set to 4V. Therefore, common line 30
Is controlled to a reference voltage of 4V.
また、第２の増幅器A2に入力される比較電圧は、基本
的には、分圧抵抗R13、R14により与えられ、結合点32の
比較電圧は3.55Vにされている。この比較電圧は基準電
圧4Vから起電力セル５の所定制御電圧値450mVを差し引
いた電圧である。The comparison voltage input to the second amplifier A2 is basically given by the voltage dividing resistors R13 and R14, and the comparison voltage at the node 32 is set to 3.55V. This comparison voltage is a voltage obtained by subtracting a predetermined control voltage value 450 mV of the electromotive force cell 5 from the reference voltage 4 V.
起電力セル５には抵抗R1を経由して電源電圧Voから一
定電流Icpが流される。電流Icpの大きさは25〜30μＡ程
度の微弱なものである。しかし、この電流Icpがポンプ
電流Ip検出用の抵抗R3に流れ込むとポンプ電流検出に僅
かな誤差を生じ、ポンプ電流Ipが零となる理論空燃比
（空気過剰率λ＝１）の位置が電流Icp分だけシフトし
てしまう。A constant current Icp flows from the power supply voltage Vo to the electromotive force cell 5 via the resistor R1. The magnitude of the current Icp is as weak as about 25 to 30 μA. However, when this current Icp flows into the resistor R3 for detecting the pump current Ip, a slight error occurs in the pump current detection, and the position of the stoichiometric air-fuel ratio (excess air ratio λ = 1) at which the pump current Ip becomes zero is the current Icp Shift by minutes.
そこで、共通ライン30と接地との間に抵抗R5を挿入
し、電流Icp分を接地に逃すようにしている。抵抗R4は
微小であるからこれを無視すると、抵抗R5は次式を満た
す抵抗値であればよい。Therefore, a resistor R5 is inserted between the common line 30 and the ground so that the current Icp is released to the ground. Since the resistance R4 is very small, if this is neglected, the resistance R5 only needs to satisfy the following equation.
〔Vo−（0.45＋Va）〕/R1−0.45/R2 ＝Va/R5 上式でVoは電源電圧8V、Vaは基準電圧4Vである。上式の
右辺第１項は抵抗R1を流れる電流、第２項は抵抗R2に流
れる電流、左辺は抵抗R5に流れる電流である。[Vo− (0.45 + Va)] / R1−0.45 / R2 = Va / R5 In the above equation, Vo is a power supply voltage of 8V, and Va is a reference voltage of 4V. The first term on the right side of the above equation is the current flowing through the resistor R1, the second term is the current flowing through the resistor R2, and the left side is the current flowing through the resistor R5.
第４の増幅器A4及び第５の増幅器A5は、ポンプセル３
に印加されるポンプ電圧Vpを検出し、ポンプ電圧Vpの絶
対値が所定電圧2Vを超えた場合に起電力セル５の所定制
御電圧値450mVを変化させる制御電圧変動手段を構成し
ている。即ち、第３の増幅器A3の出力とポンプセル３と
を接続するライン33の電圧が第４の増幅器A4及び第５の
増幅器A5に入力され、分圧抵抗R15、R16、R17から与え
られる結合点34、35の電圧と比較するようにされてい
る。ライン33の電圧は共通ライン30の基準電圧4Vを基準
としたポンプセル３のポンプ電圧Vpを示している。ま
た、結合点34の電圧は6Vに、結合点35の電圧は2Vに設定
されている。第４の増幅器A4及び第５の増幅器A5の出力
はそれぞれダイオードD1、D2を介し、抵抗R18を経由し
て結合点32に接続されている。The fourth amplifier A4 and the fifth amplifier A5 are connected to the pump cell 3
And a control voltage changing means for changing the predetermined control voltage value 450 mV of the electromotive force cell 5 when the absolute value of the pump voltage Vp exceeds the predetermined voltage 2 V. That is, the voltage of the line 33 connecting the output of the third amplifier A3 and the pump cell 3 is input to the fourth amplifier A4 and the fifth amplifier A5, and the connection point 34 provided from the voltage dividing resistors R15, R16 and R17. , 35 voltage. The voltage on the line 33 indicates the pump voltage Vp of the pump cell 3 based on the reference voltage 4 V of the common line 30. The voltage at the node 34 is set to 6V, and the voltage at the node 35 is set to 2V. The outputs of the fourth amplifier A4 and the fifth amplifier A5 are connected to the junction 32 via the diodes D1 and D2 and the resistor R18, respectively.
ポンプセル３に印加されるポンプ電圧Vpの絶対値が2V
以下であるときは、ダイオードD1、D2に阻止され抵抗R1
8に電流が流れず、結合点32の比較電圧は3.55Vのままで
ある。ポンプ電圧Vpが＋2V以上になると、ライン33の電
圧が6V以上になり、第４の増幅器A4からダイオードD1を
経由して電流が結合点32に流れ込み、結合点32の電圧を
上昇させる。このことは、起電力セル５の所定制御電圧
値を450mVから下げることになる。一方、ポンプ電圧Vp
が−2V以下になると、ライン33の電圧が2V以下になり、
結合点32からダイオードD2を経由して電流が第５の増幅
器A5に流れ込み、結合点32の電圧を下降させる。このこ
とは、起電力セル５の所定制御電圧値を450mVから上げ
ることになる。The absolute value of the pump voltage Vp applied to the pump cell 3 is 2 V
If it is less than or equal to R1
No current flows through 8, and the comparison voltage at node 32 remains at 3.55V. When the pump voltage Vp rises above + 2V, the voltage on the line 33 rises above 6V, and current flows from the fourth amplifier A4 via the diode D1 to the junction 32, raising the voltage at the junction 32. This lowers the predetermined control voltage value of the electromotive force cell 5 from 450 mV. On the other hand, the pump voltage Vp
Is below −2V, the voltage on line 33 is below 2V,
Current flows from the node 32 via the diode D2 to the fifth amplifier A5, causing the voltage at the node 32 to drop. This means that the predetermined control voltage value of the electromotive force cell 5 is increased from 450 mV.
測定ガス雰囲気がリーンの場合の作用について説明す
る。ポンプ電圧Vpは周知のネルンストの式から次式で示
される。The operation when the measurement gas atmosphere is lean will be described. The pump voltage Vp is expressed by the following equation from the well-known Nernst equation.
Vp＝Rip×Ip ＋（RT/4F）1n（Poe/Pe） 上式において、Ｒは気体定数、Ｔは絶対温度、Ｆはファ
ラデー定数、Poeは測定ガス雰囲気の酸素分圧、Peは拡
散室15の酸素分圧である。Vp = Rip × Ip + (RT / 4F) 1n (Poe / Pe) In the above equation, R is a gas constant, T is an absolute temperature, F is a Faraday constant, Poe is an oxygen partial pressure of a measurement gas atmosphere, and Pe is a diffusion chamber. 15 oxygen partial pressure.
測定ガス雰囲気がリーンの場合、Poe＞Pe、Vp＞０で
あり、ポンプ電圧Vpが＋2V以上になろうとすると、起電
力セル５の所定制御電圧値Vsを450mVから下げることに
なる。この結果、拡散室15の酸素分圧Peを大きくし、上
式の第２項を小さくすることになるから、第１項が大き
くなっても、結果的にポンプ電圧Vpを＋2V近傍の所定値
以下に制限する。そのため、ポンプセル３を形成するジ
ルコニアZrO2のマイナス側電極12近傍のブラックニング
（黒化）を防止することができる。現象論的に言えば、
所定制御電圧値Vsを450mVから下げることにより、拡散
室15の酸素濃度が上昇するため、マイナス側の多孔質電
極12近傍に充分な酸素が供給され、ポンプセル３のブラ
ックニングを防止することになる。When the measurement gas atmosphere is lean, Poe> Pe, Vp> 0, and if the pump voltage Vp is going to be more than + 2V, the predetermined control voltage value Vs of the electromotive force cell 5 will be reduced from 450 mV. As a result, the oxygen partial pressure Pe of the diffusion chamber 15 is increased, and the second term of the above equation is decreased. Therefore, even if the first term is increased, the pump voltage Vp is eventually increased to a predetermined value near + 2V. Restrict to the following. Therefore, blackening (blackening) near the negative electrode 12 of zirconia ZrO 2 forming the pump cell 3 can be prevented. Phenomenologically speaking,
By lowering the predetermined control voltage value Vs from 450 mV, the oxygen concentration in the diffusion chamber 15 increases, so that sufficient oxygen is supplied to the vicinity of the porous electrode 12 on the negative side, and blackening of the pump cell 3 is prevented. .
測定ガス雰囲気がリッチの場合の作用も上記と略同様
である。測定ガス雰囲気がリッチの場合、Poe＜Pe、Vp
＜０であり、ポンプ電圧Vpが−2V以下になろうとする
と、起電力セル５の所定制御電圧値Vsを450mVから上げ
ることになる。この結果、拡散室15の酸素分圧Peを小さ
くし、上式の第２項を大きくすることになるから、第１
項が小さくなっても、結果的にポンプ電圧Vpを−2V近傍
の所定値以上に制限する。The operation when the measurement gas atmosphere is rich is substantially the same as above. When the measurement gas atmosphere is rich, Poe <Pe, Vp
<0, and when the pump voltage Vp is going to be −2 V or less, the predetermined control voltage value Vs of the electromotive force cell 5 is increased from 450 mV. As a result, the oxygen partial pressure Pe of the diffusion chamber 15 is reduced, and the second term of the above equation is increased.
Even if the term becomes smaller, the pump voltage Vp is consequently limited to a predetermined value near −2 V or more.
第３図は、上記の空燃比センサーにおける、空燃比
（A/F）をパラメータとした起電力セル５の制御電圧値V
sとポンプセル３のポンプ電流Ipとの関係を示す特性図
である。図から明らかなように、Ip/Vs特性は制御電圧
値Vsが300mVから600mVの範囲でほぼ平坦な特性を示して
いる。このため、制御電圧Vsを450mVから多少変化さ
せ、動作点を変えたとしても、ポンプ電流Ipは空燃比
（A/F）を正確に表現した値となり、ポンプ電圧Vpを制
限し始めた状態でも正確な空燃比を検出することができ
る。FIG. 3 shows a control voltage value V of the electromotive force cell 5 in the above-described air-fuel ratio sensor using the air-fuel ratio (A / F) as a parameter.
FIG. 7 is a characteristic diagram showing a relationship between s and a pump current Ip of the pump cell 3. As is clear from the figure, the Ip / Vs characteristic shows a substantially flat characteristic when the control voltage value Vs is in the range of 300 mV to 600 mV. Therefore, even if the control voltage Vs is slightly changed from 450 mV and the operating point is changed, the pump current Ip becomes a value that accurately represents the air-fuel ratio (A / F), and even when the pump voltage Vp starts to be limited. An accurate air-fuel ratio can be detected.
第４図は、上記の空燃比センサーにおける、空燃比
（A/F）とポンプ電流Ipとの関係を示す特性図である。
駆動回路において抵抗R5が共通ライン30の接地との間に
挿入されてないと、出力端子40で検出されるポンプ電流
Ipは、破線で示すように、起電力セル５の電流Icpだけ
シフトする。空燃比センサーではポンプ電流Ipが零とな
る理論空燃比（空気過剰率λ＝１）の状態の検出が重要
であるが、抵抗R5によるIcpの補正がなされないと検出
ポンプ電流Ipが零となる位置が空気過剰率λ＝１の位置
からリッチ側にシフトしてしまう。本実施例では抵抗R5
の挿入によりIcp分の補正がなされ、実線で示すような
正確なポンプ電流Ip出力を得ることができる。FIG. 4 is a characteristic diagram showing a relationship between an air-fuel ratio (A / F) and a pump current Ip in the above-described air-fuel ratio sensor.
If the resistor R5 is not inserted between the common line 30 and the ground in the drive circuit, the pump current detected at the output terminal 40
Ip shifts by the current Icp of the electromotive force cell 5 as shown by the broken line. It is important for the air-fuel ratio sensor to detect the state of the stoichiometric air-fuel ratio (excess air ratio λ = 1) at which the pump current Ip becomes zero, but if the Icp is not corrected by the resistor R5, the detected pump current Ip becomes zero. The position shifts from the position where the excess air ratio λ = 1 to the rich side. In this embodiment, the resistor R5
, The correction for Icp is made, and an accurate pump current Ip output as shown by the solid line can be obtained.
〔発明の効果〕 本発明は、上記の構成を有し、ポンプセルに印加され
る電圧を検出し、該電圧の絶対値が所定電圧を超えた場
合に起電力セルの所定制御電圧値を変化させる制御電圧
変動手段を備えるものであるから、ポンプセルに印加さ
れる電圧を制限してポンプセルを形成するジルコニアの
ブラックニングを防止することができると共に、ポンプ
セル電圧を制限し始めた状態でも正確な空燃比を検出す
ことができるという優れた効果がある。[Effects of the Invention] The present invention has the above configuration, detects a voltage applied to a pump cell, and changes a predetermined control voltage value of the electromotive force cell when an absolute value of the voltage exceeds a predetermined voltage. Since the control voltage fluctuation means is provided, it is possible to prevent the blackening of the zirconia forming the pump cell by limiting the voltage applied to the pump cell, and to provide an accurate air-fuel ratio even when the pump cell voltage has been limited. There is an excellent effect that can be detected.
第１図は本発明の実施例を示す空燃比センサーの駆動回
路の回路図、第２図はセンサー素子を断面で示した動作
原理図、第３図は空燃比をパラメータとした制御電圧値
Vsとポンプ電流Ipとの関係を示す特性図、第４図は空燃
比とポンプ電流Ipとの関係を示す特性図である。 ３……ポンプセル、５……起電力セル、11、12、13、14
……多孔質電極、15……拡散室、17……内部基準酸素
室、R3……ポンプ電流Ip検出用の抵抗、R5……Icp補正
用の抵抗、A4、A5……制御電圧変動手段を構成する増幅
器。FIG. 1 is a circuit diagram of a driving circuit of an air-fuel ratio sensor showing an embodiment of the present invention, FIG. 2 is an operation principle diagram showing a cross section of a sensor element, and FIG. 3 is a control voltage value using an air-fuel ratio as a parameter.
FIG. 4 is a characteristic diagram showing the relationship between Vs and the pump current Ip, and FIG. 4 is a characteristic diagram showing the relationship between the air-fuel ratio and the pump current Ip. 3 ... Pump cell, 5 ... Electromotive cell, 11, 12, 13, 14
... porous electrode, 15 ... diffusion chamber, 17 ... internal reference oxygen chamber, R3 ... resistance for detecting pump current Ip, R5 ... resistance for Icp correction, A4, A5 ... control voltage fluctuation means The amplifier to make up.
フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) G01N 27/419 Continuation of front page (58) Field surveyed (Int.Cl. 6 , DB name) G01N 27/419
Claims (1)
孔質電極を有し、その一の多孔質電極を測定ガス雰囲気
に面するようにされたポンプセルと、 酸素イオン伝導性固体電解質板に一対の多孔質電極を有
し、その一の多孔質電極を内部基準酸素室に面するよう
にされた起電力セルと、 前記ポンプセルと起電力セルとに囲まれ、ガス拡散制限
部を経由して測定ガス雰囲気と連通するようにされた拡
散室と、 前記内部基準酸素室からガスが漏出するガス通路を構成
する漏出抵抗部とを備える空燃比センサーの駆動回路で
あって、 前記起電力セルに所定電流を流す手段と、 前記起電力セルの電圧を前記拡散室の空燃比が理論空燃
比である時に前記起電力セルの電圧が示す電圧近傍の所
定制御電圧値とするべく前記ポンプセルに流す電流の方
向及び大きさを制御するポンプ電流制御手段と、 前記ポンプセルに流す電流値に対応した信号を出力する
信号出力手段と、 前記ポンプセルに印加される電圧を検出し、該電圧の絶
対値が所定電圧を超えた場合に前記起電力セルの所定制
御電圧値を変化させる制御電圧変動手段と、 を備えることを特徴とする空燃比センサーの駆動回路。A pump cell having a pair of porous electrodes on an oxygen ion conductive solid electrolyte plate, one of the porous electrodes facing a measurement gas atmosphere; An electromotive force cell having a pair of porous electrodes, one of the porous electrodes facing the internal reference oxygen chamber, surrounded by the pump cell and the electromotive force cell, via a gas diffusion restricting section A driving circuit for an air-fuel ratio sensor, comprising: a diffusion chamber configured to communicate with a measurement gas atmosphere; and a leakage resistance portion forming a gas passage through which gas leaks from the internal reference oxygen chamber. Means for flowing a predetermined current to the pump cell; and flowing the voltage of the electromotive force cell to the pump cell so as to have a predetermined control voltage value near the voltage indicated by the voltage of the electromotive cell when the air-fuel ratio of the diffusion chamber is the stoichiometric air-fuel ratio. Current direction Pump current control means for controlling the magnitude and magnitude of the current; signal output means for outputting a signal corresponding to the value of the current flowing through the pump cell; detecting a voltage applied to the pump cell; And a control voltage changing means for changing a predetermined control voltage value of the electromotive force cell when the voltage exceeds the control voltage, a driving circuit of the air-fuel ratio sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2339523A JP2929038B2 (en) | 1990-11-30 | 1990-11-30 | Air-fuel ratio sensor drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2339523A JP2929038B2 (en) | 1990-11-30 | 1990-11-30 | Air-fuel ratio sensor drive circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04204370A JPH04204370A (en) | 1992-07-24 |
| JP2929038B2 true JP2929038B2 (en) | 1999-08-03 |
Family
ID=18328286
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2339523A Expired - Lifetime JP2929038B2 (en) | 1990-11-30 | 1990-11-30 | Air-fuel ratio sensor drive circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2929038B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05203618A (en) * | 1992-01-23 | 1993-08-10 | Japan Electron Control Syst Co Ltd | Air-fuel ratio sensor |
| JP5062755B2 (en) * | 2007-05-07 | 2012-10-31 | 日本特殊陶業株式会社 | Sensor control device |
| EP2952714B1 (en) * | 2013-01-29 | 2020-05-06 | Toyota Jidosha Kabushiki Kaisha | Control device for internal combustion engine |
| CN104956057B (en) | 2013-01-29 | 2017-09-29 | 丰田自动车株式会社 | The control device of internal combustion engine |
| EP2952721B1 (en) | 2013-01-29 | 2018-03-21 | Toyota Jidosha Kabushiki Kaisha | Control device for internal combustion engine |
| AU2013376228B2 (en) | 2013-01-29 | 2016-01-14 | Toyota Jidosha Kabushiki Kaisha | Control device for internal combustion engine |
| CN104956053B (en) * | 2013-01-29 | 2020-07-24 | 丰田自动车株式会社 | Control device for internal combustion engine |
-
1990
- 1990-11-30 JP JP2339523A patent/JP2929038B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04204370A (en) | 1992-07-24 |
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