JPS61296262A - Air/fuel ratio sensor - Google Patents

Abstract

PURPOSE:To enable a sufficient preventing measure by simple preventing treatment, by exposing the terminal surface of a leak resistor part to measuring gas. CONSTITUTION:An internal reference oxygen source R is formed by an electrode a1 constituted by forming an embedded porous electrode to the superposed part of a first element A and a blocking body 7 and a leak resistor part (porous layer) G of which the terminal surface is exposed to measuring gas and, by always flowing a current to the first element A, oxygen is generated in the oxygen source R and used as reference oxygen to enable the measurement of an air/fuel ration with the same measuring accuracy as that when the open air was introduced into the first element A, a second element B and the electrode a1 in the non-opposed side. Therefore, the opening par for introducing the open air becomes unnecessary and a sufficient preventing measure is enabled by simple preventing treatment.

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、各種燃焼機器の排気中の酸素濃度
に基づき空燃比を検出する空燃比センサーに関するもの
である。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an air-fuel ratio sensor that detects an air-fuel ratio based on the oxygen concentration in the exhaust gas of various combustion devices such as internal combustion engines.

［従来の技術］ 内燃機関等、各種燃焼機器に供給される混合気の空燃比
を排気中の酸素濃度より検出する空燃比検出装置の一つ
として、板状の酸素イオン伝導性固体電解質の両面に多
孔質電極が設（ブられた２枚の素子を、間隙を介して対
向配設し、一方の素子を間隙内の酸素を周囲に汲み出す
酸素ポンプ素子、他方の素子を周囲雰囲気と間隙との酸
素濃度差によって電圧を生ずる酸素濃淡電池素子として
、少なくとも空燃比のリーン域において空燃比に対応し
た信号を検出し得るよう構成されたものがある（特開昭
５９−１７８３５４）。[Prior Art] As an air-fuel ratio detection device that detects the air-fuel ratio of a mixture supplied to various combustion devices such as an internal combustion engine based on the oxygen concentration in exhaust gas, a plate-shaped oxygen ion-conducting solid electrolyte is used on both sides. A porous electrode is installed in the area (two cut-out elements are placed facing each other with a gap in between, one element is an oxygen pump element that pumps oxygen in the gap to the surroundings, and the other element is an oxygen pump element that pumps oxygen from the gap to the surrounding atmosphere. There is an oxygen concentration battery element that generates a voltage based on the difference in oxygen concentration between the two oxygen concentration cells, and is constructed so as to be able to detect a signal corresponding to the air-fuel ratio at least in the lean range of the air-fuel ratio (Japanese Patent Laid-Open No. 59-178354).

ところがこの種の空燃比センサーの場合、空燃比のリー
ン域、即ら排気中に残留酸素が存在する　−場合だけで
なく、空燃比のリッチ域、即ち排気中に残留酸素が極め
て少量しか存在しない場合にでも、排気中のＣｏ、ＣＯ
２、Ｈ２０等の反応により、リーン域における信号と同
様の信号を発生する特性を有することがわかった。つま
り検出信号に対して２つの空燃比が対応するようになる
ため、この種の空燃比センサーを用いて空燃比制御を実
行する場合、空燃比がリーン域にあるのか、あるいはリ
ッチ域にあるのかをはつきりさせる必要が生じてくるの
でおる。However, in the case of this type of air-fuel ratio sensor, it is possible to detect not only the lean range of the air-fuel ratio, that is, when there is residual oxygen in the exhaust gas, but also the rich range of the air-fuel ratio, that is, when there is only a very small amount of residual oxygen in the exhaust gas. Even if Co, CO in the exhaust
2. It was found that the reaction of H20 etc. has the characteristic of generating a signal similar to that in the lean region. In other words, two air-fuel ratios correspond to the detection signal, so when performing air-fuel ratio control using this type of air-fuel ratio sensor, it is difficult to determine whether the air-fuel ratio is in the lean region or in the rich region. There will be a need to measure the temperature.

そこで、酸素濃淡電池素子の酸素ポンプ素子に対向しな
い面に大気を導入し、検出信号が理論空燃比近傍で反転
することを防止するようにしたものが提案されている。Therefore, a method has been proposed in which the atmosphere is introduced into the surface of the oxygen concentration battery element that does not face the oxygen pump element to prevent the detection signal from inverting near the stoichiometric air-fuel ratio.

［発明が解決しようとする問題点］ しかしながら、酸素濃淡電池素子の一面に大気を導入す
るため、空燃比センサーを密閉化できず、防水対策が必
要となり、構造が複雑になってしまう。[Problems to be Solved by the Invention] However, since the atmosphere is introduced to one side of the oxygen concentration cell element, the air-fuel ratio sensor cannot be sealed, waterproofing measures are required, and the structure becomes complicated.

［問題点を解決するための手段］ 本発明の空燃比センサーは、大気を酸素濃淡電池素子の
一面に導入することなく、大気を導入した場合と同等の
効果を得るようにしたものであり、その構成は、 酸素イオン伝導性固体電解質板の表裏面に一対の多孔質
電極ａ、ｂを有する第１の素子と、酸素イオン伝導性固
体電解質板の表裏面に一対の多孔質電極ｃ、ｄを有する
第２の素子と、上記第１の素子の電極ａと接し、漏出抵
抗部を介して外部に連通する内部ＷＱ酸素源と、上記第
１の素子の電極す及び上記第２の素子の電極Ｃの両者と
接し、ガス拡散制限部を介して測定ガス雰囲気と連通ず
る測定ガス室と からなることを特徴とする。[Means for Solving the Problems] The air-fuel ratio sensor of the present invention is designed to obtain the same effect as when atmospheric air is introduced without introducing atmospheric air into one surface of the oxygen concentration cell element, Its configuration includes: a first element having a pair of porous electrodes a, b on the front and back surfaces of an oxygen ion conductive solid electrolyte plate; and a pair of porous electrodes c, d on the front and back surfaces of the oxygen ion conductive solid electrolyte plate. an internal WQ oxygen source that is in contact with electrode a of the first element and communicates with the outside via a leakage resistance part; It is characterized by comprising a measurement gas chamber that is in contact with both electrodes C and communicates with the measurement gas atmosphere via a gas diffusion restriction section.

第１の素子及び第２の素子に使用される酸素イオン伝導
性固体電解質としては、ジルコニアとイツトリアの固溶
体、おるいはジルコニアとカルシアとの固溶体等が代表
的なものであり、その他二酸化セリウム、二酸化トリウ
ム、二酸化ハフニウムの各固溶体、ペロブスカイト型酸
化物固溶体、３価金属酸化物固溶体等も使用可能である
。またその固体電解質両面に設けられる多孔質電極ａ。Typical oxygen ion conductive solid electrolytes used in the first element and the second element include a solid solution of zirconia and yttria, or a solid solution of zirconia and calcia, and others such as cerium dioxide, Thorium dioxide, hafnium dioxide solid solutions, perovskite oxide solid solutions, trivalent metal oxide solid solutions, etc. can also be used. Further, porous electrodes a are provided on both sides of the solid electrolyte.

ｂ、ｃ、ｄとしては、酸化反応の触媒作用を有する白金
やロン１クム等を用いればよく、その形成方法としては
、これらの金属粉末を主成分としてこれに固体電解質と
同じセラミック材料の粉末を混合してペースト化し、厚
膜技術を用いて印刷後、焼結して形成する方法、あるい
はフレーム溶射、化学メッキ、蒸着等の薄膜技術を用い
て形成する。For b, c, and d, platinum, ronium cum, etc., which have a catalytic effect on oxidation reactions may be used, and the method for forming them is to use these metal powders as the main component and add powder of the same ceramic material as the solid electrolyte. The paste is mixed into a paste, printed using thick film technology, and then sintered, or formed using thin film technology such as flame spraying, chemical plating, or vapor deposition.

ざらに排ガスにざらされる電極す、ｃ、ｄはその電極層
に更に、アルミナ、スピネル、ジルコニア、ムライト等
の多孔質保護層を厚膜技術を用いて形成することが好ま
しい。It is preferable that the electrodes S, C, and D, which are exposed to rough exhaust gas, further have a porous protective layer of alumina, spinel, zirconia, mullite, etc. formed on the electrode layer using a thick film technique.

内部基準酸素源は、例えば第１の素子に、該素子の電極
ａに対応する凹部を有するＡｇ２Ｏ３、スピネル、フォ
ルステライト、ステアタイト、ジルコニア等からなる遮
蔽体を積層し、一端面が上記凹部内に露出し、他の端面
が第１の素子と上記遮蔽体との接合部の端にまで達して
測定ガス側に露出した漏出抵抗部となる多孔質層とから
形成する。またこの漏出抵抗部は多孔質層に代えて例え
ば上記凹部から排ガス側に達する微孔であってもよい。The internal reference oxygen source is, for example, a first element laminated with a shield made of Ag2O3, spinel, forsterite, steatite, zirconia, etc., which has a recess corresponding to the electrode a of the element, and one end surface is placed inside the recess. and a porous layer whose other end face reaches the end of the joint between the first element and the shield and becomes a leak resistance part exposed to the measurement gas side. Further, instead of the porous layer, the leakage resistance portion may be, for example, fine pores reaching from the recessed portion to the exhaust gas side.

さらに上記凹部を設けずに電極ａ自体を内部基準酸素源
としてもよい。また漏出抵抗部は大気側に露出させても
よいが測定ガスに対して露出するようにするとこの空燃
比センサーの防水が容易となり好ましい。Furthermore, the electrode a itself may be used as an internal reference oxygen source without providing the recess. Further, the leak resistance portion may be exposed to the atmosphere, but it is preferable to expose it to the measurement gas because this makes it easier to waterproof the air-fuel ratio sensor.

測定ガス室は、例えば第１の素子と第２の素子との間に
Ａｇ２Ｏ３、スピネル、フォルステライト、ステアタイ
ト、ジルコニア等からなる層状中間部材としてのスペー
サを第１の素子の電極すと第２の素子の電極Ｃ間に偏平
な閉鎖状の室が形成されるようにして挟むことによって
設けられる。In the measurement gas chamber, for example, a spacer as a layered intermediate member made of Ag2O3, spinel, forsterite, steatite, zirconia, etc. is placed between the first element and the second element. The device is provided by sandwiching the device so that a flat closed chamber is formed between the electrodes C of the device.

そしてガス拡散制限部としてこのスペーサの一部に測定
ガス雰囲気と測定ガス室とを連通させる孔を設ける。こ
のガス拡散制限部は、上記スペーサの一部あるいは全部
を多孔黄体で置き換えたり、スペーサ（厚膜コートを含
む）に孔を設置ブたり、更には、スペーサを第１の素子
と第２の素子の端子側にのみに設けて第１の素子と第２
の素子との間に空隙を形成し、この空隙を測定ガス室と
一体のガス拡散制限間隙として設けることができる。A hole is provided in a part of this spacer as a gas diffusion restricting portion to communicate the measurement gas atmosphere with the measurement gas chamber. This gas diffusion restriction section may be achieved by replacing part or all of the spacer with a porous corpus luteum, by installing holes in the spacer (including a thick film coating), or by connecting the spacer to the first element and the second element. The first element and the second element are provided only on the terminal side of the
A gap can be formed between the measuring gas chamber and the measuring gas chamber, and this gap can be provided as a gas diffusion limiting gap integrated with the measuring gas chamber.

また上記空隙の全体に、電気絶縁性であることが望まし
い多孔質材を配してもよい。Further, a porous material which is preferably electrically insulating may be disposed throughout the void.

［作用］ 第１の素子は酸素発生及び酸素濃淡電池素子、第２の素
子は酸素ポンプ素子としての作用をもつ。[Function] The first element functions as an oxygen generation and oxygen concentration battery element, and the second element functions as an oxygen pump element.

即ら、 第１の索子の−っの作用は酸素発生であって、適当な温
度条件（例えば固体電解質が安定化ジルコニアの場合に
は４００’Ｃ以上）において固体電解質板の両面間に電
圧をかけることにより固（［ｉ解質仮中を酸素イオンが
移動する性質を利用している。この素子は、測定ガス室
に接する電極すと、内部基準酸素源に接する電極ａとの
間に酸素イオンが電極すから電極ａに向かって流れるよ
うに、即ち、電極すを負、電極ａ＠正とするよう電圧を
かけることにより、測定ガス室中の酸素を電極ａ近傍に
輸送し、内部基準酸素源に酸素を発生させる。That is, the action of the first cable is oxygen generation, and under appropriate temperature conditions (for example, 400'C or higher when the solid electrolyte is stabilized zirconia), a voltage is generated between both sides of the solid electrolyte plate. By multiplying the By applying a voltage so that oxygen ions flow from the electrode to the electrode a, that is, by applying a voltage so that the electrode is negative and the electrode a is positive, the oxygen in the measurement gas chamber is transported to the vicinity of the electrode a, and the internal Generate oxygen in a reference oxygen source.

第１の素子は又酸素濃淡電池としての作用を持ち適当な
温度条件において、固体電解質板の両面間にそれぞれの
表面における酸素ガス分圧の比に対応した電圧（起電力
）が生じる性質を利用している。この素子は、前述の内
部基準酸素源の酸素を基準酸素源として測定ガス室内の
酸素ガス分圧を測定する。The first element also functions as an oxygen concentration battery, and utilizes the property that under appropriate temperature conditions, a voltage (electromotive force) is generated between both surfaces of the solid electrolyte plate corresponding to the ratio of the oxygen gas partial pressure on each surface. are doing. This element measures the oxygen gas partial pressure in the measurement gas chamber using the aforementioned internal reference oxygen source as the reference oxygen source.

第２の素子は酸素ポンプ素子であって第１の素子と同様
、適当な温度条件において固体電解質板の両面間に電圧
をかけることにより固体電解質板中を酸素イオンが移動
する性質を利用している。The second element is an oxygen pump element, and like the first element, it utilizes the property that oxygen ions move within the solid electrolyte plate by applying a voltage between both sides of the solid electrolyte plate under appropriate temperature conditions. There is.

この酸素ポンプ素子は、２つの電極ｃ、ｄ間に電圧をか
けることによりガス拡散室内の酸素を汲み出したり、又
場合によってはガス拡散室内に酸素を汲み入れる。This oxygen pump element pumps oxygen out of the gas diffusion chamber by applying a voltage between the two electrodes c and d, or in some cases pumps oxygen into the gas diffusion chamber.

この空燃比センサーの動作は次の通りである。The operation of this air-fuel ratio sensor is as follows.

先ず、第１の素子の電極間に電極ａを正、電極すを負と
するよう所定電圧（例えば５Ｖ）を抵抗（例えば５００
にΩ）を介してかけることにより所定電流を流して測定
ガス室内から内部基？ｊＬ酸素源に酸素を輸送する。こ
の時の電流は数〜数十μＡ（例えば１０μＡ）程度であ
り、この電流による第１の素子の固体電解板における電
圧降下は数〜数十ｍＶ（例えば１０ｍＶ＞である。First, a predetermined voltage (e.g. 5V) is applied to a resistor (e.g. 500V) between the electrodes of the first element so that electrode a is positive and electrode A is negative.
A predetermined current is applied to the internal group from the measurement gas chamber by applying it through Ω). jL transports oxygen to the oxygen source. The current at this time is about several to several tens of μA (for example, 10 μA), and the voltage drop across the solid electrolyte plate of the first element due to this current is several to several tens of mV (for example, 10 mV>).

次いで、内部基準酸素源の酸素ガス分圧が測定ガス室内
の酸素ガス分圧より高くなると、この酸素ガス分圧差に
よって電極ａ、ｂ間の起電力が生じる。内部基準酸素源
が、漏出抵抗部の作用によってほぼ一定の酸素ガス分圧
となった時の上記起電力は、数百ｍＶ（例えば４００〜
６００ｍＶ＞であって、又リッヂ域とリーン域での変化
も数百ｍＶ小単位ある。Next, when the oxygen gas partial pressure of the internal reference oxygen source becomes higher than the oxygen gas partial pressure in the measurement gas chamber, an electromotive force is generated between electrodes a and b due to this oxygen gas partial pressure difference. When the internal standard oxygen source has a substantially constant partial pressure of oxygen gas due to the action of the leakage resistor, the electromotive force is several hundred mV (for example, 400 to 400 mV).
600 mV>, and there is also a small change of several hundred mV between the ridge region and the lean region.

従って第１の素子の端子間電圧は、内部基準酸素源に酸
素を輸送するための電圧（数〜数＋ｍｖ＞と、内部基準
酸素源の酸素ガス分圧と測定ガス室内の酸素ガス分圧と
の差による起電力（数百ｍＶ）との和となり、測定ガス
がリッチ域の場合とり一ン域の場合とで数百ｍＶの変化
が生じる。Therefore, the voltage across the terminals of the first element is determined by the voltage (several to several + mv) for transporting oxygen to the internal reference oxygen source, the oxygen gas partial pressure of the internal reference oxygen source, and the oxygen gas partial pressure in the measurement gas chamber. This is the sum of the electromotive force (several hundred mV) due to the difference between the two, and a change of several hundred mV occurs between when the measured gas is in the rich range and when it is in the one-gas range.

第２の素子はこの変化によって、測定カス室内の状態か
理論空燃比となるように測定ガス室内に外部から酸素を
汲み入れたり、汲み出したりする。Depending on this change, the second element pumps oxygen into or out of the measurement gas chamber from the outside so that the condition in the measurement gas chamber becomes the stoichiometric air-fuel ratio.

前述の通り、内部基準酸素源の酸素は測定ガス室内から
供給されているために、測定ガス室内の酸素ガス分圧は
測定ガスと全く同じではない。しかし測定ガス室内を理
論空燃比となるように、第２の素子に加える電流は通常
数〜数十ｍＡであり、前述の内部基準酸素発生に用いら
れた電流（数〜数十μＡ）に比べて十分大きいので、こ
の差は実際上、無視できる。このため、従来の空燃比セ
ンサーと同様測定ガス室内を理論空燃比とするための電
流から測定ガスの空燃比を知ることができる。As mentioned above, since the oxygen of the internal reference oxygen source is supplied from within the measurement gas chamber, the oxygen gas partial pressure within the measurement gas chamber is not exactly the same as that of the measurement gas. However, in order to maintain the stoichiometric air-fuel ratio in the measurement gas chamber, the current applied to the second element is usually several to several tens of mA, compared to the current (several to several tens of μA) used for internal reference oxygen generation described above. is sufficiently large that this difference can be ignored in practice. Therefore, as with conventional air-fuel ratio sensors, the air-fuel ratio of the measurement gas can be determined from the current that is used to bring the inside of the measurement gas chamber to the stoichiometric air-fuel ratio.

即ち、例えば第１の素子の端子間の電圧が所定の一定値
になるよう、第２の素子を用いて拡散室の酸素を汲み出
したり汲み入れたりし、その時第２の素子に流れる電流
（以下、ポンプ電流ともいう。）を検出するとか、おる
いは、その逆に第２の素子のポンプ電流を一定ｆａに制
御して測定ガス室の酸素を所定量だけ汲み出すが汲み入
れ、その時第１の素子の端子間の電圧を検出することに
よって、排ガスの空燃比に応じた信号を検出することが
できる。That is, for example, the second element is used to pump out or pump oxygen into the diffusion chamber so that the voltage between the terminals of the first element becomes a predetermined constant value, and at that time, the current flowing through the second element (hereinafter referred to as , pump current), or conversely, the pump current of the second element is controlled to a constant fa to pump out a predetermined amount of oxygen from the measurement gas chamber. By detecting the voltage between the terminals of one element, a signal corresponding to the air-fuel ratio of exhaust gas can be detected.

Ｕ実施例］ 第１図の部分破断図及び第２図の分解説明図によって本
発明の一実施例について説明する。尚、説明上、各図の
部分ごとの縮尺は異なる。Embodiment] An embodiment of the present invention will be described with reference to a partially cutaway view in FIG. 1 and an exploded explanatory view in FIG. 2. For convenience of explanation, the scale of each part of each figure is different.

本実施例の空燃比センサーは第１図及び第２図に示す如
く、 測定ガス側に延長された部分の一ψｔ；が露出する電４
４ａ１と電極ｂ２と固体電解質板３とからなる第１の素
子Ａと、 電極Ｃ４と電極ｄ５と固体電解質板６とからなる第２の
素子Ｂと、 第１の素子Ａと遮蔽体７との重ね合せ部分に、ここでは
埋設多孔質電極として形成された電極ａ１と電極ａ１か
ら延長されて端面を排ガスに露出する漏出抵抗部である
多孔質層Ｇとからなる内部基準酸素＠ｉＲと、 第１の素子Ａと第２の素子Ｂとが層状中間部材としての
スペー＋＃８を介して積層されてそれらの対向する電極
ｂ２、電極０４間に形成される測定ガス室９とからなる
。尚、本実施例ではスペーサ８の３カ所を切り欠いて孔
とじガス拡散制限部Ｔとした。As shown in Figs. 1 and 2, the air-fuel ratio sensor of this embodiment has an electric current 4 whose part ψt; which extends toward the measurement gas side is exposed.
4a1, electrode b2, and solid electrolyte plate 3, second element B consisting of electrode C4, electrode d5, and solid electrolyte plate 6, and first element A and shielding body 7. In the overlapping part, there is an internal reference oxygen @iR consisting of an electrode a1 formed here as a buried porous electrode and a porous layer G which is a leak resistance part extending from the electrode a1 and whose end face is exposed to exhaust gas; The first element A and the second element B are laminated with a spacer #8 as a layered intermediate member interposed therebetween, and a measurement gas chamber 9 is formed between the opposing electrodes b2 and electrodes 04. In this embodiment, the spacer 8 is cut out at three locations to form hole-filled gas diffusion restricting portions T.

電極ｄ５は端子１０に、電極ａ１、電極ｂ２、電極Ｃ４
は各々スルーホールを介して端子１１゜１２．１３に接
続される。尚、第２図において１点鎖線はスルーホール
の対応を示し、又、２点鎖線は各部の対応を示している
。Electrode d5 is connected to terminal 10, electrode a1, electrode b2, electrode C4
are connected to terminals 11, 12, and 13 through through holes, respectively. In FIG. 2, the one-dot chain line indicates the correspondence between through holes, and the two-dot chain line indicates the correspondence between each part.

各部の寸法は、固体電解質板３．６は厚さ０゜５ｍｍｘ
幅４ｍｍｘ長さ２５ｍｍ、電極ｂ２、電極Ｃ４、電極ｄ
５は２．４ｍｍｘ７．２ｍｍ、電極ａ１は２．４ｍｍｘ
７．８ｍｍであって、一端が固体電解質板３の測定部側
の端と一致している。The dimensions of each part are: Solid electrolyte plate 3.6 has a thickness of 0°5mm x
Width 4mm x length 25mm, electrode b2, electrode C4, electrode d
5 is 2.4mmx7.2mm, electrode a1 is 2.4mmx
The length is 7.8 mm, and one end coincides with the end of the solid electrolyte plate 3 on the measuring section side.

スペーサ８は厚さ６０μｍｘ幅４．　ｍ　ｍ　Ｘ長さ２
５ｍｍであって２．４ｍｍｘ７．７ｍｍの測定ガス室９
を有し、三方向に幅Ｑ、５ｍｍの孔からなるガス拡散制
限部Ｔを有する。遮蔽体７は厚さ０゜５ｍｍＸ幅４ｍｍ
Ｘ長さ２５ｍｍである。Spacer 8 has a thickness of 60 μm and a width of 4. mm x length 2
Measuring gas chamber 9 of 5 mm and 2.4 mm x 7.7 mm
It has a gas diffusion restricting portion T consisting of a hole having a width Q and 5 mm in three directions. The shielding body 7 has a thickness of 0°5mm and a width of 4mm.
X length is 25 mm.

本実施例の各素子の固体電解質板３，６はいずれもＹ２
０３−Ｚｒ　０２固体電解貿である。各素子の電極１，
２，４．５は白金に１０重蛋％のＹ２０３−Ｚｒ　０２
を添加した多孔質体である。遮蔽体７及びスペーサ８は
ジルコニアである。The solid electrolyte plates 3 and 6 of each element in this example are both Y2
03-Zr 02 solid electrolyte trade. Electrode 1 of each element,
2,4.5 is platinum with 10% heavy protein Y203-Zr 02
It is a porous body with added . The shield 7 and spacer 8 are made of zirconia.

本実施例の使用法の一例について第３図の構成図によっ
て説明する。尚、本図の空燃比センサーＳは説明上端子
１０．１１．１２．１３を省略し、電極１，２，４．５
に直接回路へのリード線が接続するよう描いである。An example of how to use this embodiment will be explained with reference to the configuration diagram in FIG. Note that in the air-fuel ratio sensor S in this figure, terminals 10, 11, 12, 13 are omitted for explanation purposes, and electrodes 1, 2, 4, 5
The lead wires are drawn to connect directly to the circuit.

この空燃比センサーＳは排気管１００に、ネジ部１０１
．固定部１０２によって取り付ける。This air-fuel ratio sensor S is attached to the exhaust pipe 100 at a threaded portion 101.
．． It is attached by the fixing part 102.

第１の索子Ａ及び第２の素子Ｂの電極１，２゜４．５は
空燃比信号検出回路２０１に接続される。Electrodes 1, 2°4.5 of the first cord A and the second element B are connected to an air-fuel ratio signal detection circuit 201.

空燃比信号検出回路２０１は、第１の素子によって内部
基準酸素源Ｒに酸素を発生させ、該基準酸素分圧と測定
ガス室９内の酸素ガス分圧比に応じた電極ａ１、電極ｂ
２間の出力が、所定の一定電圧となるよう、即ちガス拡
散至９内の空燃比が一定となるよう、第２の素子Ｂに流
れるポンプ電流を双方向に制御し、その電流値を空燃比
信号Ｖλとして検出する。The air-fuel ratio signal detection circuit 201 generates oxygen in the internal reference oxygen source R using a first element, and selects electrodes a1 and b according to the reference oxygen partial pressure and the oxygen gas partial pressure ratio in the measurement gas chamber 9.
The pump current flowing through the second element B is bidirectionally controlled so that the output between the elements B becomes a predetermined constant voltage, that is, the air-fuel ratio in the gas diffusion chamber 9 becomes constant. It is detected as a fuel ratio signal Vλ.

この空燃比信号検出回路２０１は、例えば、第４図に示
す如く、５個の演算増幅器ＯＰ１ないしＯＦ２を中心に
構成され、第１の素子Ａの出力ＶＳを増幅してから基準
電圧Ｖｃと比較し、その差を電圧によってポンプ電流を
双方向に制御し、このポンプ電流をＯＦ２によって空燃
比信号Ｖλを出力するものを用いればよい。For example, as shown in FIG. 4, this air-fuel ratio signal detection circuit 201 is configured around five operational amplifiers OP1 to OF2, and amplifies the output VS of the first element A and then compares it with the reference voltage Vc. However, the pump current may be bidirectionally controlled using the voltage based on the difference, and the pump current may be outputted as the air-fuel ratio signal Vλ by OF2.

又、本実施例の空燃比セン４ノー−は、電極ｂ２と電４
ｆＩＣ４との電位が同じとなるような回路を用いて、空
燃比を測定することも可能でおり、その場合には仮に電
極す、ｃが接触しても測定に影響を与えない。そのため
電極す、ｃを共通の一枚の電極とすることもできる。In addition, the air-fuel ratio sensor 4 NO in this embodiment is connected to the electrode b2 and the electrode 4.
It is also possible to measure the air-fuel ratio using a circuit that has the same potential as fIC4, and in that case, even if electrodes A and C come into contact, the measurement will not be affected. Therefore, electrodes A and C can be made into a common electrode.

このような空燃比信号検出回路２０１を使用することに
よって第５図に示す如ぎ、空燃比信号Ｖλが、λ−１の
点での設定電圧ＶＣを通り、リッチから１ノーンにかけ
て連続的に変化する特性が得られる。尚、この空燃比信
号Ｖλの特性は第１の素子Ａ及ｄ第２の素子Ｂと空燃比
信号検出回路２０１の各接続端子Ｐ１ないしＰ４との接
続方向を変更することによって、破線で示す傾きの特性
とすることができる。By using such an air-fuel ratio signal detection circuit 201, as shown in FIG. The characteristics that can be obtained are as follows. The characteristics of this air-fuel ratio signal Vλ can be changed to the slope shown by the broken line by changing the connection direction of the first element A and second element B and each connection terminal P1 to P4 of the air-fuel ratio signal detection circuit 201. It can be a characteristic of

［発明の効果］ 本発明の空燃比センサーは、第１の素子Ａに常に電流を
流すことによって内部基準酸素源に酸素を発生させ、こ
の酸素を基準酸素として用いることにより、第１の素子
の第２の素子と対向しない側の電極ａに大気を導入した
時と同じ効果を与えるものである。[Effects of the Invention] The air-fuel ratio sensor of the present invention generates oxygen in the internal reference oxygen source by constantly passing a current through the first element A, and uses this oxygen as the reference oxygen to increase the temperature of the first element. This provides the same effect as when air is introduced into the electrode a on the side not facing the second element.

本発明の空燃比センサーは大気導入のための開口部が不
用となり、簡単な防水処理で充分な防水対策を行うこと
ができる。The air-fuel ratio sensor of the present invention does not require an opening for introducing the atmosphere, and can provide sufficient waterproofing with a simple waterproofing treatment.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の第１実施例を説明する部分破断斜視図
、 第２図はその分解斜視図、 第３図はその使用例を説明する構成図、第４図はその使
用例における回路図、 第５図はその使用例の空燃比に対する信号の特性図であ
る。 Ａ・・・第１の素子 Ｂ・・・第２の素子 Ｇ・・・漏出抵抗部 Ｒ・・・内部基準酸素源 Ｔ・・・ガス拡散制限部 １．２，４．５−・・電極ａ、ｂ、ｃ、ｄ３．６・・・
固体電解質板 ９・・・測定ガス卒Fig. 1 is a partially cutaway perspective view illustrating the first embodiment of the present invention, Fig. 2 is an exploded perspective view thereof, Fig. 3 is a configuration diagram illustrating an example of its use, and Fig. 4 is a circuit in the example of its use. FIG. 5 is a characteristic diagram of the signal with respect to the air-fuel ratio in an example of its use. A...First element B...Second element G...Leakage resistance section R...Internal reference oxygen source T...Gas diffusion restriction section 1.2, 4.5-...Electrode a, b, c, d3.6...
Solid electrolyte plate 9...Measurement gas

Claims (1)

【特許請求の範囲】 　酸素イオン伝導性固体電解質板の表裏面に一対の多孔
質電極ａ、ｂを有する第１の素子と、酸素イオン伝導性
固体電解質板の表裏面に一対の多孔質電極ｃ、ｄを有す
る第２の素子と、上記第１の素子の電極ａと接し、漏出
抵抗部を介して外部に連通する内部基準酸素源と、 上記第１の素子の電極ｂ及び上記第２の素子の電極ｃの
両者と接し、ガス拡散制限部を介して測定ガス雰囲気と
連通する測定ガス室と からなることを特徴とする空燃比センサー。[Claims] A first element having a pair of porous electrodes a and b on the front and back surfaces of an oxygen ion conductive solid electrolyte plate, and a pair of porous electrodes c on the front and back surfaces of the oxygen ion conductive solid electrolyte plate. , d; an internal reference oxygen source that is in contact with electrode a of the first element and communicates with the outside via a leakage resistance section; An air-fuel ratio sensor comprising a measurement gas chamber that is in contact with both electrodes c of the element and communicates with a measurement gas atmosphere via a gas diffusion restriction section.