JPH0425755A - Oxygen sensor - Google Patents
Oxygen sensorInfo
- Publication number
- JPH0425755A JPH0425755A JP2132028A JP13202890A JPH0425755A JP H0425755 A JPH0425755 A JP H0425755A JP 2132028 A JP2132028 A JP 2132028A JP 13202890 A JP13202890 A JP 13202890A JP H0425755 A JPH0425755 A JP H0425755A
- Authority
- JP
- Japan
- Prior art keywords
- layer
- exhaust gas
- outermost layer
- protective layer
- platinum
- 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.)
- Pending
Links
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 44
- 239000001301 oxygen Substances 0.000 title claims abstract description 44
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 239000010410 layer Substances 0.000 claims abstract description 58
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000007789 gas Substances 0.000 claims abstract description 26
- 239000011241 protective layer Substances 0.000 claims abstract description 21
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 241000872198 Serjania polyphylla Species 0.000 claims abstract description 3
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 74
- 238000001514 detection method Methods 0.000 claims description 10
- 239000003054 catalyst Substances 0.000 claims description 8
- 150000004706 metal oxides Chemical class 0.000 claims description 7
- 229910052697 platinum Inorganic materials 0.000 abstract description 15
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 abstract description 14
- 239000000203 mixture Substances 0.000 abstract description 6
- 239000002904 solvent Substances 0.000 abstract description 4
- 230000003197 catalytic effect Effects 0.000 abstract description 2
- 239000011248 coating agent Substances 0.000 abstract description 2
- 238000000576 coating method Methods 0.000 abstract description 2
- 235000011837 pasties Nutrition 0.000 abstract 1
- 239000000446 fuel Substances 0.000 description 11
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 6
- 239000011133 lead Substances 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 230000001012 protector Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000007784 solid electrolyte Substances 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- -1 oxygen ions Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野〕
本発明は、例えば自動車等の排気管等に取付けられ、排
気ガス中の酸素濃度を検出するのに好適に用いられる酸
素センサに関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oxygen sensor that is attached to, for example, an exhaust pipe of an automobile or the like and is suitably used to detect the oxygen concentration in exhaust gas.
一般に、自動車等のエンジンにあっては、空燃比を最適
にフィードバック制御するため、排気管等に酸素センサ
（０２センサ）を取付けて、排気ガス中の酸素濃度を逐
一検出するようにしている。Generally, in engines such as automobiles, an oxygen sensor (02 sensor) is attached to the exhaust pipe or the like to detect the oxygen concentration in the exhaust gas in order to optimally feedback control the air-fuel ratio.
そこで、第３図ないし第６図に従来技術によるチューブ
型の酸素センサを示す。Therefore, FIGS. 3 to 6 show tube-type oxygen sensors according to the prior art.
図中、１は段付筒状のセンサ本体を示し、該センサ本体
１は、一端側外周におねじ部２Ａが形成され、他端側が
筒状の嵌合部２Ｂとなったホルダ２と、一端側が該ホル
ダ２の嵌合部２Ｂにカシメ部３Ａ、３Ａ、・・・により
固着され、他端側に環状の段部３Ｂ、縮径部３Ｃが形成
されたキャップ３とからなり、これらはステンレス鋼等
の金属材料によって形成されている。そして、該センサ
本体１は後述のジルコニアチューブ５を排気管（図示せ
ず）内に突出させるべ（、ホルダ２のおねじ部２Ａが排
気管に螺着されるようになっている。４はセンサ本体１
内に配設された絶縁筒体を示し、該絶縁筒体４はアルミ
ナ等のセラミック材料により形成されている。In the figure, reference numeral 1 indicates a stepped cylindrical sensor body, and the sensor body 1 includes a holder 2 having a threaded portion 2A formed on the outer periphery of one end and a cylindrical fitting portion 2B on the other end. Consisting of a cap 3, one end of which is fixed to the fitting part 2B of the holder 2 by caulking parts 3A, 3A, . It is made of metal material such as stainless steel. The sensor main body 1 has a zirconia tube 5, which will be described later, protruding into an exhaust pipe (not shown).The male threaded portion 2A of the holder 2 is screwed into the exhaust pipe. Sensor body 1
It shows an insulating cylinder disposed within the insulating cylinder 4, which is made of a ceramic material such as alumina.
５は基端側かホルダ２の肩部２Ｃにリング状のワッシャ
６を介して取付けられ、先端側がホルダ２外に突出した
酸素濃度検出素子としてのジルコニアチューブを示し、
該ジルコニアチューブ５は、例えば単斜晶相に対する正
方晶相の重量比が所定比率となったジルコニア（Ｚｒ
０２ 、重量比８８、７６％）の粉体にイツトリア（Ｙ
２Ｏ２、重量比８．８４％）の粉体およびバインダを混
合して焼成することにより、第４図等にも示す如（断面
Ｕ字形状に形成され、焼成時にはジルコニアとイツトリ
アとからなる立方晶相７５％程度の固体電解質層を構成
し、水浸入等に対する耐熱衝撃性を高めるようになって
いる。そして、該ジルコニアチューブ５の基端側は大径
の開口部５Ａとなり、先端側は閉塞端５Ｂとなっている
。5 indicates a zirconia tube as an oxygen concentration detecting element, which is attached to the proximal end or the shoulder 2C of the holder 2 via a ring-shaped washer 6, and whose distal end protrudes outside the holder 2;
The zirconia tube 5 is made of zirconia (Zr) in which the weight ratio of the tetragonal phase to the monoclinic phase is a predetermined ratio.
02, weight ratio 88, 76%) was added to the powder of Ittria (Y
2O2, weight ratio 8.84%) and a binder are mixed together and fired to form a U-shaped cross section (as shown in FIG. The zirconia tube 5 has a solid electrolyte layer with a phase content of approximately 75%, and is designed to enhance thermal shock resistance against water intrusion, etc.The proximal end of the zirconia tube 5 is a large diameter opening 5A, and the distal end is closed. The end is 5B.
７．８はジルコニアチューブ５の内、外面にそれぞれ設
けられた内側電極、外側電極を示し、該電極７．８は白
金（重量比９０％）とジルコニア（重量比１０％）とか
らなるペースト状の材料をジルコニアチューブ５の内１
外面に塗布することにより、帯状に伸長して形成されて
いる。そして、内側電極７はジルコニアチューブ５の開
口部５Ａ端面まで引出し部７Ａとなって伸び、該引出し
部７Ａは後述のコンタクトプレート１１と接続されてい
る。また、外側電極８はホルダ２の肩部２Ｃにワッシャ
６を介して接続され、アースされるようになっている。Reference numeral 7.8 indicates an inner electrode and an outer electrode provided on the inner and outer surfaces of the zirconia tube 5, respectively, and the electrode 7.8 is a paste-like material made of platinum (90% by weight) and zirconia (10% by weight). The material of 1 out of 5 zirconia tubes
By applying it to the outer surface, it is formed into an elongated band shape. The inner electrode 7 extends to the end face of the opening 5A of the zirconia tube 5 as a lead-out portion 7A, and the lead-out portion 7A is connected to a contact plate 11, which will be described later. Further, the outer electrode 8 is connected to the shoulder portion 2C of the holder 2 via a washer 6, and is grounded.
９は外側電極８の上側からジルコニアチューブ５の外面
に全周に亘ってコーティングされた触媒層としての白金
蒸着層を示し、該白金蒸着層９は、第４図、第５図中に
示す如（ジルコニアチューブ５と外側電極８を覆うよう
にジルコニアチューブ５の外面に全周に設けられている
。そして、該白金蒸着層９はジルコニアチューブ５の内
、外での酸素濃度の差により、外側電極８と内側電極７
との間に発生する起電力を触媒作用で増幅させ、この起
電力は内側電極７からコンタクトブレート１２等を介し
て外部に検８信号として出力するようになっている。１
０は多孔質のスピネル層等からなる保護層を示し、該保
護層１０は、前記白金蒸着層９の外面に全周に設けられ
、該白金蒸着層９の保護を行うようになっている。１１
は最外層を示し、該最外層１１は、前記保護層１０を覆
うように保護層１０の外面に全周に設けられ、該最外層
１１は、排気ガス中の鉛（Ｐｂ）。Reference numeral 9 indicates a platinum vapor deposited layer as a catalyst layer coated over the entire circumference of the outer surface of the zirconia tube 5 from the upper side of the outer electrode 8. (It is provided all around the outer surface of the zirconia tube 5 so as to cover the zirconia tube 5 and the outer electrode 8.The platinum vapor deposited layer 9 is formed on the outer surface of the zirconia tube 5 due to the difference in oxygen concentration inside and outside the zirconia tube Electrode 8 and inner electrode 7
The electromotive force generated between the inner electrode 7 and the inner electrode 7 is amplified by a catalytic action, and this electromotive force is outputted from the inner electrode 7 to the outside via the contact plate 12 and the like as a detection signal. 1
0 indicates a protective layer made of a porous spinel layer or the like, and the protective layer 10 is provided around the entire outer surface of the platinum vapor-deposited layer 9 to protect the platinum vapor-deposited layer 9. 11
indicates the outermost layer, and the outermost layer 11 is provided all around the outer surface of the protective layer 10 so as to cover the protective layer 10, and the outermost layer 11 is composed of lead (Pb) in the exhaust gas.
リン（Ｐ）、ケイ素（Ｓｉ）等の不純物による被毒対策
としてアルミナ（Ａρ２０３）に白金（Ｐｔ）を担持さ
せた白金担持のγ−アルミナ等により形成されている。As a measure against poisoning by impurities such as phosphorus (P) and silicon (Si), it is formed of platinum-supported γ-alumina, which is made by supporting platinum (Pt) on alumina (Aρ203).
なお、白金蒸着層９は０．５μｍ程度の薄膜によって形
成され、２ｍｍ程度の肉厚のジルコニアチューブ５．２
０μｍ程度の電極７．８および５０μｍ程度の保護層１
０に比較して非常に薄く形成されるから、第４図中では
省略しているものの、保護層１０と同様にジルコニアチ
ューブ５の全周に亘って設けられている。The platinum vapor deposited layer 9 is formed of a thin film of about 0.5 μm, and the zirconia tube 5.2 has a wall thickness of about 2 mm.
Electrode 7.8 of about 0 μm and protective layer 1 of about 50 μm
Although it is omitted in FIG. 4 because it is formed very thinly compared to the protective layer 10, it is provided over the entire circumference of the zirconia tube 5 like the protective layer 10.
また、第３図中では該保護層１０．白金蒸着層９および
最外層１１を省略して示している。In addition, in FIG. 3, the protective layer 10. The platinum vapor deposited layer 9 and the outermost layer 11 are omitted from the illustration.
１２は絶縁筒体４内に配設されたコンタクトプレートを
示し、該コンタクトプレート１２は導電性の金属板を曲
げ加工することにより形成され、その一端側には円板状
のコンタクト部１２Ａが、他端側には外部に導畠される
リード線１３と接続された接続部１２Ｂがそれぞれ設け
られている。Reference numeral 12 denotes a contact plate disposed within the insulating cylinder 4. The contact plate 12 is formed by bending a conductive metal plate, and a disk-shaped contact portion 12A is provided at one end of the contact plate 12. The other end side is provided with a connecting portion 12B connected to a lead wire 13 led to the outside.
そして、該コンタクトプレート１２のコンタクト部１２
Ａはジルコニアチューブ５の開口部５Ａ端面と絶縁筒体
４との間にディスクスプリング１４のばね荷重で挟持さ
れ、内側電極７の引出し部７Ａと接続されている。さら
に、１５はキャップ３の縮径部３Ｃ内に配設され、リー
ド線１３の周囲をシールしているシール部材、１６はジ
ルコニアチューブ５を保護すべく、ホルダ２に固着され
たプロテクタを示し、該プロテクタ１６には排気ガス導
入用の長孔１６Ａ、１６Ａ、・・・が形成されている。Then, the contact portion 12 of the contact plate 12
A is held between the end surface of the opening 5A of the zirconia tube 5 and the insulating cylindrical body 4 by the spring load of the disc spring 14, and is connected to the lead-out portion 7A of the inner electrode 7. Furthermore, 15 is a seal member disposed within the reduced diameter portion 3C of the cap 3 and seals around the lead wire 13, 16 is a protector fixed to the holder 2 to protect the zirconia tube 5, The protector 16 is formed with elongated holes 16A, 16A, . . . for introducing exhaust gas.
このように構成される従来技術の酸素センサでは、セン
サ本体１をおねじ部２Ａを介して排気管等に螺着するこ
とにより、ジルコニアチューブ５の先端側をプロテクタ
１６と共に排気管内に突出させて、排気ガス中の酸素濃
度の検出を行うようになっている。即ち、排気ガスは空
気と燃料との混合気を燃焼させた廃ガスであるから、排
気ガス中の酸素濃度はジルコニアチューブ５の内側の大
気に比較して低下し、ジルコニアチューブ５の内側と外
側とには大きな酸素濃度差が生じる。In the conventional oxygen sensor configured as described above, the sensor main body 1 is screwed onto the exhaust pipe etc. via the male threaded portion 2A, so that the distal end side of the zirconia tube 5 is projected into the exhaust pipe together with the protector 16. , the oxygen concentration in exhaust gas is detected. That is, since the exhaust gas is waste gas from burning a mixture of air and fuel, the oxygen concentration in the exhaust gas is lower than that of the atmosphere inside the zirconia tube 5, and the oxygen concentration in the exhaust gas is lower than that of the atmosphere inside the zirconia tube 5. There is a large difference in oxygen concentration between the two.
このため、固体電解質からなるジルコニアチューブ５に
は内側から外側へと酸素イオンが通り抜けるようになり
、内側電極７と外側電極８との間には起電力が生じる。Therefore, oxygen ions pass through the zirconia tube 5 made of a solid electrolyte from the inside to the outside, and an electromotive force is generated between the inner electrode 7 and the outer electrode 8.
そして、この起電力は排気ガス中の酸素濃度に応じて増
減するから、第６図に示す如（酸素濃度の検出信号とし
て、コンタクトプレート１２、リード線１３等を介して
外部のコントロールユニット（図示せず）に８力され、
該コントロールユニットではこの検出信号に基づいて燃
料噴射量等を補正し、空燃比をフィードバック制御する
ようになっている。Since this electromotive force increases or decreases depending on the oxygen concentration in the exhaust gas, as shown in FIG. (without showing) was given 8 power,
The control unit corrects the fuel injection amount, etc. based on this detection signal, and performs feedback control of the air-fuel ratio.
［発明が解決しようとする課題］
ところで、上述した従来技術の酸素センサは、一般に排
気管内に設けられ、高温の排気ガス中におかれるから、
最外層１１の材料である白金担持のγ−アルミナはジル
コニアチューブ５の製造時に８００℃位で焼成すること
により最外層１１を形成するようになっている。しかし
、実際の使用時には排気ガスの温度が焼成温度（８００
℃）以上になることがあり、最外層１１は高温に長時間
さらされると、白金担持のγ−アルミナがα−アルミナ
に相転位して、割れ等が生じてしまい、排気ガス中の鉛
、リン、ケイ素等の不純物が最外層１１から保護層１０
を介して白金蒸着層９へと侵入し、この白金蒸着層９を
劣化させて、酸素センサによる空燃比の制御特性が変化
してしまうという問題がある。[Problems to be Solved by the Invention] By the way, the above-mentioned conventional oxygen sensor is generally installed in an exhaust pipe and placed in high-temperature exhaust gas.
Platinum-supported γ-alumina, which is the material of the outermost layer 11, is fired at about 800° C. during the production of the zirconia tube 5 to form the outermost layer 11. However, in actual use, the temperature of the exhaust gas is the firing temperature (800
℃), and if the outermost layer 11 is exposed to high temperatures for a long time, the platinum-supported γ-alumina undergoes a phase transition to α-alumina, causing cracks, etc., and the lead in the exhaust gas, Impurities such as phosphorus and silicon are removed from the outermost layer 11 to the protective layer 10.
There is a problem in that the oxygen penetrates into the platinum vapor deposited layer 9 through the oxygen sensor, deteriorates the platinum vapor deposition layer 9, and changes the control characteristics of the air-fuel ratio by the oxygen sensor.
即ち、第７図に示す如く排気ガス温度８００℃の状態で
酸素センサの耐久試験を行った結果、特性線１４のよう
に経過時間が３００時間までの間に最外層１１が劣化し
、さらに経過時間が３００時間以上になると白金蒸着層
９の劣化が生じて制御特性が変化してしまい、これによ
っても酸素センサによる空燃比の制御特性が変化してい
ることが分かる。このため、常に酸素センサから正確な
酸素濃度の検出が不可能になり、適確な燃料噴射量等の
補正、空燃比のフィードバック制御が不可能になるとい
う問題が生じる。That is, as shown in FIG. 7, as a result of carrying out a durability test on the oxygen sensor at an exhaust gas temperature of 800°C, the outermost layer 11 deteriorated over a period of 300 hours as shown by characteristic line 14, and When the time exceeds 300 hours, the platinum vapor deposited layer 9 deteriorates and the control characteristics change, and it can be seen that this also changes the control characteristics of the air-fuel ratio by the oxygen sensor. Therefore, a problem arises in that it is impossible to always accurately detect the oxygen concentration from the oxygen sensor, and it becomes impossible to accurately correct the fuel injection amount, etc., and to perform feedback control of the air-fuel ratio.
本発明は上述した従来技術の問題点に鑑みなされたもの
で、本発明は高温の排気ガス中でも長時間に亘り安定し
て酸素濃度の検出ができ、耐久性を大幅に向上できるよ
うにした酸素センサを提供するものである。The present invention has been made in view of the problems of the prior art described above.The present invention provides an oxygen sensor that can stably detect oxygen concentration over a long period of time even in high-temperature exhaust gas and greatly improves durability. It provides a sensor.
〔課題を解決するための手段〕
上述した問題点を解決するために本発明が採用する構成
の特徴は、最外層を高温で安定な金属酸化物に白金ブラ
ックを混合して形成したことにある。[Means for Solving the Problems] The feature of the structure adopted by the present invention in order to solve the above-mentioned problems is that the outermost layer is formed by mixing platinum black with a metal oxide that is stable at high temperatures. .
［作用］
上記構成により、白金ブラックを含む金属酸化物からな
る最外層は高温に強いために、高温排気ガス中でも最外
層の劣化を防止することができ、排気ガス中の不純物が
触媒層へと侵入するのを長期に亘り防止することができ
、触媒層の劣化を長時間に亘って阻止することが可能と
なる。[Function] With the above configuration, the outermost layer made of metal oxide containing platinum black is resistant to high temperatures, so it is possible to prevent deterioration of the outermost layer even in high-temperature exhaust gas, and prevent impurities in the exhaust gas from reaching the catalyst layer. Intrusion can be prevented for a long period of time, and deterioration of the catalyst layer can be prevented for a long period of time.
Ｃ実施例Ｊ
以下、本発明の実施例を第１図および第２図に基づいて
説明する。なお、実施例では前述した従来技術と同一の
構成要素に同一の符号を付し、その説明を省略するもの
とする。C Example J Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2. In the embodiment, the same components as those in the prior art described above are given the same reference numerals, and their explanations will be omitted.
図中、２１は従来技術で述べた最外層１１と同様に、ジ
ルコニアチューブ５の外周面側に保護層１０を覆うよう
に設けらた最外層を示し、該最外層２１は高温で安定な
金属酸化物、例えばチタニア（ＴｉＯ２）に白金ブラッ
クを混合した混合物により形成されている。In the figure, 21 indicates the outermost layer provided on the outer peripheral surface side of the zirconia tube 5 so as to cover the protective layer 10, similar to the outermost layer 11 described in the related art, and the outermost layer 21 is made of a metal that is stable at high temperatures. It is formed from a mixture of an oxide such as titania (TiO2) and platinum black.
ここで、前記最外層２１のジルコニアチューブ５への形
成方法を第２図に示し説明する。Here, a method for forming the outermost layer 21 on the zirconia tube 5 will be described with reference to FIG. 2.
図中、２２は容器、２３は該容器２２内に収容され、チ
タニアに白金ブラックを混合して有機溶剤によりペース
ト状にした溶剤で、該溶剤２３は、例えば５０重量％の
白金ブラックをチタニアの粉体に添加し、これを有機溶
媒によりペースト状に溶かすことにより形成されている
。そして、この溶剤２３は前記ジルコニアチューブ５の
保護層１０を被覆するように該保護層１０の表面に二点
鎖線で示す如く塗布され、その後１０００℃以上、望ま
しくは１２００℃〜１４００℃程度の温度下でジルコニ
アチューブ５と共に焼成することにより最外層２１を安
定した状態に形成するようになっている。In the figure, 22 is a container, and 23 is a solvent contained in the container 22, which is made by mixing titania with platinum black and making it into a paste with an organic solvent. It is formed by adding it to powder and dissolving it into a paste with an organic solvent. Then, this solvent 23 is applied to the surface of the protective layer 10 of the zirconia tube 5 as shown by the two-dot chain line so as to cover the protective layer 10, and then heated to a temperature of 1000°C or more, preferably about 1200°C to 1400°C. By firing the outermost layer 21 together with the zirconia tube 5 at the bottom, the outermost layer 21 is formed in a stable state.
本実施例による酸素センサは上述の如き構成を有するも
ので、その基本的動作については従来技術によるものと
格別差異はない。The oxygen sensor according to this embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.
然るに本実施例では、保護層１０の外側に白金ブラック
とチタニアの混合物からなるペースト状の溶剤２３を塗
布した後、これを１２００℃〜１４００℃程度の温度下
で焼成することにより最外層２１を形成し、該最外層２
１で保護層１０を覆う構成としているから、該最外層２
１の表面は白金ブラックの粒子により凸凹の形状となっ
て、その比表面積を大幅に拡大できると共に、高温度下
での耐久性を向上でき、排気ガス中に含まれる鉛、リン
、ケイ素等の不純物が白金蒸着層９へと侵入するのを長
期に亘り効果的に防止することができる。However, in this embodiment, after coating the outside of the protective layer 10 with a paste-like solvent 23 made of a mixture of platinum black and titania, the outermost layer 21 is baked at a temperature of about 1200°C to 1400°C. forming the outermost layer 2
1 covers the protective layer 10, the outermost layer 2
The surface of 1 has an uneven shape due to platinum black particles, which can greatly expand its specific surface area, improve durability under high temperatures, and eliminate lead, phosphorus, silicon, etc. contained in exhaust gas. Impurities can be effectively prevented from entering the platinum deposited layer 9 over a long period of time.
即ち、従来技術のものと同様に高温の排気ガスにより当
該酸素センサの耐久試験を行った結果、第７図中に点線
で示す特性線２４の如く、６００時間に及ぶ耐久時間で
もその制御特性が殆ど変化せず、高温排気ガスにより最
外層２１に割れ等が全（発生せず、白金蒸着層９の劣化
を効果的に防止できることが確認された。That is, as a result of carrying out an endurance test of the oxygen sensor using high-temperature exhaust gas in the same manner as the prior art, it was found that its control characteristics remained unchanged even after an endurance period of 600 hours, as shown by the characteristic line 24 shown by the dotted line in FIG. There was almost no change, and no cracks or the like occurred in the outermost layer 21 due to the high-temperature exhaust gas, confirming that deterioration of the platinum vapor deposited layer 9 could be effectively prevented.
従って、本実施例によれば長期に亘り安定して酸素濃度
の検出行うことができ、酸素センサの寿命を延ばすこと
ができると共に、燃料噴射量等の補正、空燃比のフィー
ドバック制御を適確に長期に亘って行うことができる。Therefore, according to this embodiment, the oxygen concentration can be detected stably over a long period of time, the life of the oxygen sensor can be extended, and the correction of the fuel injection amount, etc., and the feedback control of the air-fuel ratio can be accurately performed. This can be done over a long period of time.
なお、前記実施例では最外層２１の金属酸化物にチタニ
アを用いた場合を例に挙げて説明したが、これに替えて
ジルコニア（ＺｒＯ２）等の高温で安定な金属酸化物を
用いることも可能である。In addition, in the above embodiment, the case where titania was used as the metal oxide of the outermost layer 21 was explained as an example, but instead of this, it is also possible to use a metal oxide that is stable at high temperatures such as zirconia (ZrO2). It is.
また、前記実施例では酸素濃度検出素子としてジルコニ
アチューブ５を用いるチューブ型を例に挙げて説明した
が、本発明はこれに限らず、例えばジルコニアにより平
板状に形成されたプレート型の酸素濃度検出素子を用い
てもよく、この場合には外側電極側、即ち排気ガスに直
接接触する最外層を白金ブラックとチタニア等の金属酸
化物とで形成すればよい。Further, in the above embodiment, a tube type oxygen concentration detection element using a zirconia tube 5 was explained as an example, but the present invention is not limited to this, and for example, a plate type oxygen concentration detection element formed in a flat plate shape from zirconia In this case, the outer electrode side, that is, the outermost layer that comes into direct contact with the exhaust gas, may be formed of platinum black and a metal oxide such as titania.
〔発明の効果］
以上詳述した通り、本発明によれば、酸素濃度検出素子
の保護層の外側を覆う最外層を、白金ブラックと高温で
安定な金属酸化物との混合物で形成するようにしたから
、高温度下で最外層に割れ等が生じるのを防止でき、排
気ガス中に含まれる不純物が触媒層へと侵入するのを確
実に防止することができ、高温耐久性を大幅に向上でき
る。従って、酸素センサの特性不良を防止でき、高温排
気ガス中での長期間の使用にも安定した酸素濃度の検出
を行うことができ、酸素センサの寿命を延ばすことがで
きる。[Effects of the Invention] As detailed above, according to the present invention, the outermost layer covering the outside of the protective layer of the oxygen concentration detection element is formed of a mixture of platinum black and a metal oxide that is stable at high temperatures. This prevents the outermost layer from cracking under high temperatures, reliably prevents impurities contained in exhaust gas from entering the catalyst layer, and greatly improves high-temperature durability. can. Therefore, defective characteristics of the oxygen sensor can be prevented, stable oxygen concentration can be detected even during long-term use in high-temperature exhaust gas, and the life of the oxygen sensor can be extended.
第１図および第２図は本発明の実施例を示し、第１図は
ジルコニアチューブの先端側要部を拡大して示す詳細断
面図、第２図は最外層の形成工程を示す説明図、第３図
ないし第７図は従来技術を示し、第３図は酸素センサの
全体構成を示す縦断面図、第４図はジルコニアチューブ
の縦断面図、第５図は第４図中のジルコニアチューブの
先端側要部を拡大して示す詳細断面図、第６図は検出信
号の特性線図、第７図は酸素センサによる空燃比制御の
耐久試験結果を、従来技術と本実施例と対比して示す特
性線図である。
１・・・センサ本体、５・・・ジルコニアチューブ（酸
素濃度検出素子）、７・・・内側電極、８・・・外側電
極、９・・・白金蒸着層（触媒層）、１０・・・保護層
、２１・・・最外層。
特許出願人 日本電子機器株式会社
代理人 弁理士 広 瀬 和 彦
第
図
第
図
７Δ
第
図
第
図
第
図
而寸 久 ｇ今 間 （ｈ）1 and 2 show an embodiment of the present invention, FIG. 1 is a detailed cross-sectional view showing an enlarged main part of the front end of the zirconia tube, FIG. 2 is an explanatory view showing the process of forming the outermost layer, 3 to 7 show the prior art, FIG. 3 is a vertical cross-sectional view showing the overall configuration of an oxygen sensor, FIG. 4 is a vertical cross-sectional view of a zirconia tube, and FIG. 5 is a zirconia tube in FIG. 4. 6 is a characteristic diagram of the detection signal, and FIG. 7 is a comparison of the durability test results of air-fuel ratio control using an oxygen sensor with the conventional technology and this example. FIG. DESCRIPTION OF SYMBOLS 1... Sensor main body, 5... Zirconia tube (oxygen concentration detection element), 7... Inner electrode, 8... Outer electrode, 9... Platinum vapor deposition layer (catalyst layer), 10... Protective layer, 21...outermost layer. Patent Applicant Japan Electronics Co., Ltd. Agent Patent Attorney Kazuhiko Hirose
Claims (1)
端側が該センサ本体外に突出し、ジルコニアにより形成
された酸素濃度検出素子とからなり、該酸素濃度検出素
子の内、外面には内側電極、外側電極を設けると共に、
該酸素濃度検出素子の外面には、該外側電極を外側から
覆う触媒層と、該触媒層を外側から覆う保護層と、該保
護層を外側から覆い、排気ガス中の不純物が前記触媒層
に向けて侵入するのを防止する最外層とを設けてなる酸
素センサにおいて、前記最外層は高温で安定な金属酸化
物に白金ブラックを混合して形成したことを特徴とする
酸素センサ。It consists of a sensor body, and an oxygen concentration detection element made of zirconia, the base end side of which is attached to the sensor body, the distal end side of which protrudes outside the sensor body, and the oxygen concentration detection element has inner and outer electrodes on its inner and outer surfaces. Along with providing an outer electrode,
The outer surface of the oxygen concentration detection element includes a catalyst layer that covers the outer electrode from the outside, a protective layer that covers the catalyst layer from the outside, and a protective layer that covers the protective layer from the outside to prevent impurities in the exhaust gas from reaching the catalyst layer. 1. An oxygen sensor comprising an outermost layer for preventing intrusion into the oxygen sensor, wherein the outermost layer is formed by mixing platinum black with a metal oxide that is stable at high temperatures.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2132028A JPH0425755A (en) | 1990-05-22 | 1990-05-22 | Oxygen sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2132028A JPH0425755A (en) | 1990-05-22 | 1990-05-22 | Oxygen sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0425755A true JPH0425755A (en) | 1992-01-29 |
Family
ID=15071812
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2132028A Pending JPH0425755A (en) | 1990-05-22 | 1990-05-22 | Oxygen sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0425755A (en) |
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| US5925076A (en) * | 1995-05-19 | 1999-07-20 | Inoue; Kanji | Appliance to be implanted, method of collapsing the appliance to be implanted and method of using the appliance to be implanted |
| US6270520B1 (en) | 1995-05-19 | 2001-08-07 | Kanji Inoue | Appliance to be implanted, method of collapsing the appliance to be implanted and method of using the appliance to be implanted |
| US6273917B1 (en) | 1998-03-27 | 2001-08-14 | Kanji Inoue | Transplantation device |
| US6364901B1 (en) | 1996-12-20 | 2002-04-02 | Kanji Inoue | Appliance collapsible for insertion into a human organ and capable of resilient restoration |
| US6436132B1 (en) * | 2000-03-30 | 2002-08-20 | Advanced Cardiovascular Systems, Inc. | Composite intraluminal prostheses |
| US6514282B1 (en) | 1999-10-04 | 2003-02-04 | Kanji Inoue | Method of folding transplanting instrument and transplanting instrument |
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-
1990
- 1990-05-22 JP JP2132028A patent/JPH0425755A/en active Pending
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| US5728158A (en) * | 1991-10-28 | 1998-03-17 | Advanced Cardiovascular Systems, Inc. | Expandable stents |
| US5735893A (en) * | 1991-10-28 | 1998-04-07 | Advanced Cardiovascular Systems, Inc. | Expandable stents and method for making same |
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