JPS632056B2 - - Google Patents
Info
- Publication number
- JPS632056B2 JPS632056B2 JP15713479A JP15713479A JPS632056B2 JP S632056 B2 JPS632056 B2 JP S632056B2 JP 15713479 A JP15713479 A JP 15713479A JP 15713479 A JP15713479 A JP 15713479A JP S632056 B2 JPS632056 B2 JP S632056B2
- Authority
- JP
- Japan
- Prior art keywords
- iridium
- sensing element
- platinum
- air
- response characteristics
- 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
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 17
- 229910052741 iridium Inorganic materials 0.000 claims description 12
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- 229910052697 platinum Inorganic materials 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 229910000314 transition metal oxide Inorganic materials 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 230000004044 response Effects 0.000 description 16
- 239000000446 fuel Substances 0.000 description 10
- 239000007789 gas Substances 0.000 description 9
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 5
- 238000002485 combustion reaction Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000000567 combustion gas Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 229910001020 Au alloy Inorganic materials 0.000 description 1
- 241000872198 Serjania polyphylla Species 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007606 doctor blade method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
Landscapes
- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
Description
【発明の詳細な説明】
本発明は、遷移金属酸化物からなり、ガス中の
酸素濃度を検知して排気ガス浄化システムに使用
される酸素濃度検知素子の製造方法に関するもの
である。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an oxygen concentration sensing element made of a transition metal oxide and used in an exhaust gas purification system by sensing the oxygen concentration in a gas.
本発明の目的は排気ガス中の酸素濃度変化に対
して良好な応答性を示し、空燃比を精度良く制御
するシステムに有用な検知素子の製造方法を提供
するものである。 An object of the present invention is to provide a method for manufacturing a sensing element that exhibits good responsiveness to changes in oxygen concentration in exhaust gas and is useful for a system that accurately controls the air-fuel ratio.
一般に内燃機関あるいは燃焼機器において、そ
れらに供給されるガス混合物中の空燃比（Ａ／
Ｆ）が化学量論点近傍にある時、燃焼後の平衡状
態におけるガス中の酸素分圧が急変する。そし
て、車載用の内燃機関において、排気ガス中の
NOx，CO，HC等の有害成分の排出量を最小限
に抑えるためには、それらに供給されるガス混合
物中の空燃比（Ａ／Ｆ）を敏速に化学量論点に非
常に近い範囲に制御する必要がある。さらに、空
燃比を精度良く且つ正確に制御するためには、空
気過剰雰囲気（Lean）から燃料過剰雰囲気
（Rich）あるいはその逆の方向にガス雰囲気が変
化する場合、一定の空燃比において制御できる検
知素子が要望される。前述の目的で使用される検
知素子の１つとして、酸化チタン焼結体としたい
わゆる電気抵抗体型素子がある。これは基本的に
は検出ガス中の酸素濃度に依存した電気抵抗値を
示す事を利用したものであるが、さらに応答速度
を速めるためにこれに貴金属系触媒を担持させた
ものが実用上有用である。通常この種の検知素子
の電極線としては、Pt線あるいはPt―Au合金線
が使用されている。しかしながら、従来の検知素
子の場合、燃焼ガス雰囲気においてLean状態か
らRich状態に変化した場合とその逆の方向に変
化した場合とでは応答性においてヒステリシスを
生じ、一定の空燃比で制御できずいわゆる検知素
子として空燃比を精度良く且つ正確藩に制御する
上で問題であつた。 In general, in internal combustion engines or combustion equipment, the air-fuel ratio (A/
When F) is near the stoichiometric point, the partial pressure of oxygen in the gas in the equilibrium state after combustion changes suddenly. In automotive internal combustion engines, the exhaust gas
In order to minimize the emissions of harmful components such as NOx, CO, and HC, the air-fuel ratio (A/F) in the gas mixture supplied to them must be quickly controlled within a range very close to the stoichiometric point. There is a need to. Furthermore, in order to control the air-fuel ratio with high precision and accuracy, it is necessary to detect the air-fuel ratio so that it can be controlled at a constant air-fuel ratio when the gas atmosphere changes from an air-excess atmosphere (Lean) to a fuel-excess atmosphere (Rich) or vice versa. element is required. One of the sensing elements used for the above-mentioned purpose is a so-called electric resistance type element made of a titanium oxide sintered body. This basically takes advantage of the fact that it shows an electrical resistance value that depends on the oxygen concentration in the detected gas, but in order to further speed up the response speed, it is practically useful to support a noble metal catalyst on it. It is. Usually, a Pt wire or a Pt--Au alloy wire is used as the electrode wire of this type of sensing element. However, in the case of conventional sensing elements, hysteresis occurs in response when the combustion gas atmosphere changes from a lean state to a rich state and when the state changes in the opposite direction, making it impossible to control the air-fuel ratio at a constant level. As an element, there was a problem in controlling the air-fuel ratio with high precision and accuracy.
本発明者らは、かかる問題の解決にあたり、
種々検討を重ねた結果、イリジウムの微量成分を
焼結体中に存在させる事によつて、燃焼ガス雰囲
気の酸素濃度変化に対してヒステリシスのないす
ぐれた応答特性を示す検知素子を得る事ができる
事を見い出した。 In solving this problem, the present inventors
As a result of various studies, it was possible to obtain a sensing element that exhibits excellent response characteristics without hysteresis to changes in oxygen concentration in the combustion gas atmosphere by including a trace amount of iridium in the sintered body. I found out something.
本発明はこれに基づくものであり、白金とイリ
ジウムからなる一対のの合金線を電極線とし、該
電極線の端部を埋設する形で半導体酸化物粉末成
形体を設け、該成形体を高温で焼成して酸化物焼
結すると同時に該電極線に含有するイリジウム成
分の一部を焼結体中に拡散させる事を特徴とする
ものである。 The present invention is based on this, in which a pair of alloy wires made of platinum and iridium are used as electrode wires, a semiconductor oxide powder molded body is provided with the ends of the electrode wires buried, and the molded body is heated at a high temperature. The method is characterized in that a part of the iridium component contained in the electrode wire is diffused into the sintered body at the same time as the electrode wire is fired to sinter the oxide.
以下、本発明につき実施例をあげ説明する。 Hereinafter, the present invention will be described with reference to examples.
＜実施例＞
純度99％以上の酸化チタン生原料を1000℃で６
時間仮焼後、ボールミルで20時間湿式粉砕して乾
燥する。こうして得られた酸化チタン粉末40ｇと
平均粒経0.5μ以下の白金黒0.8ｇと有機バインダ
ーとをボールミルで10時間混練し、スラリーを作
り、ドクターブレード法により厚みが800μのイ
ートを作成する。このシートから直径４mmの円板
を打ち抜く。この円板２枚の間に相対重量比が白
金90重量％、イリジウム10重量％の線径250μの
合金線の一対を互に1.5mm離してその端部が円板
に埋設するようにはさみ込んで、２枚の円板を加
圧接合して成形体を作製する。この時、円板の接
合されるべき面に少量の有機溶媒を施した。この
ようにして得られた成形体を1250℃で１時間、空
気中焼成して検知素子を作製した。この検知素子
につき、Ｘ線マイクロアナライザーにより解析し
た結果、明らかにイリジウム成分が素子内に拡散
している事が確認された。<Example> Titanium oxide raw material with a purity of 99% or more was heated at 1000°C.
After calcination for an hour, it is wet ground in a ball mill for 20 hours and dried. 40 g of the titanium oxide powder thus obtained, 0.8 g of platinum black with an average particle size of 0.5 μm or less, and an organic binder are kneaded in a ball mill for 10 hours to form a slurry, and a slurry is prepared using a doctor blade method to create an eat product with a thickness of 800 μm. Punch out a disk with a diameter of 4 mm from this sheet. A pair of alloy wires with a relative weight ratio of 90% platinum and 10% iridium and a wire diameter of 250μ are sandwiched between these two discs with a distance of 1.5 mm so that their ends are embedded in the discs. Then, the two discs are joined together under pressure to produce a molded body. At this time, a small amount of organic solvent was applied to the surfaces of the disks to be joined. The thus obtained molded body was baked in air at 1250° C. for 1 hour to produce a sensing element. As a result of analyzing this detection element using an X-ray microanalyzer, it was confirmed that an iridium component was clearly diffused within the element.
＜比較例＞
実施例のうち一対の電極線が250μ白金線であ
り、他はすべて実施例と同方法で検知素子を作製
した。<Comparative Example> In the example, a pair of electrode wires was a 250μ platinum wire, and a sensing element was fabricated in the same manner as in the example except for the other electrode wires.
このようにして得られた検知素子の応答特性
は、混合ガス（N2＋H2）が毎分1000c.c.の割合で
流入出している装置内に検知素子を組み込み、こ
の混合ガス中に空気を０c.c.から100c.c.の範囲で流
した時の出力電圧の変化（Rich雰囲気→Lean雰
囲気）と、逆に空気を100c.c.から０c.c.の範囲で流
した時の出力電圧の変化（Lean雰囲気→Rich雰
囲気）を比較する事によつて調べられた。なお、
測定温度は450℃である。 The response characteristics of the sensing element obtained in this way were determined by incorporating the sensing element into a device in which a mixed gas (N 2 + H 2 ) flows in and out at a rate of 1000c.c. The change in output voltage when air is flowed in the range of 0 c.c. to 100 c.c. (Rich atmosphere → Lean atmosphere) and conversely when air is flowed in the range of 100 c.c. to 0 c.c. This was investigated by comparing the change in output voltage (lean atmosphere → rich atmosphere). In addition,
The measurement temperature is 450℃.
その結果を第１図及び第２図に示す。第１図は
比較例により作製された従来の検知素子の応答特
性を示すものであり、１はRich雰囲気からLean
雰囲気に変化した場合の応答性を示し、２は逆の
方向に雰囲気を変えた場合の応答特性を示したも
のである。第１図より明らかなように従来の検知
素子ではRich雰囲気からLean雰囲気あるいはそ
の逆の方向に雰囲気が変化した場合、応答特性に
おいてヒステリシスを生じ、空燃比を正確に制御
する上で実用上好ましくない。 The results are shown in FIGS. 1 and 2. Figure 1 shows the response characteristics of the conventional sensing element fabricated as a comparative example.
2 shows the response characteristics when the atmosphere changes, and 2 shows the response characteristics when the atmosphere changes in the opposite direction. As is clear from Figure 1, in conventional sensing elements, when the atmosphere changes from rich to lean or vice versa, hysteresis occurs in the response characteristics, which is not practical for accurately controlling the air-fuel ratio. .
これに対し、第２図からも明らかなように本発
明により得られた検知素子の場合、応答特性にお
いてヒステリシスがほとんどなく、正確に空燃比
を制御でき、検知素子として実用性に富んでいる
事が明白である。 On the other hand, as is clear from Figure 2, the sensing element obtained by the present invention has almost no hysteresis in its response characteristics, can accurately control the air-fuel ratio, and is highly practical as a sensing element. is obvious.
第２図において、１はRich雰囲気からLean雰
囲気に変化した場合の応答特性を示し、２はその
逆の方向に変化した場合の応答特性を示すもので
ある。 In FIG. 2, 1 shows the response characteristics when changing from a rich atmosphere to a lean atmosphere, and 2 shows the response characteristics when changing in the opposite direction.
なお、本発明の製造方法において、白金とイリ
ジウムの相対重量比を白金95〜80重量％、イリジ
ウム５〜20重量％と限定したのは、イリジウム含
有量が５重量％未満の場合は応答特性において効
果がなく、また20重量％を越えると応答速度が遅
くなり、検知素子としては好ましくないためであ
る。なお、本発明の実施例において、遷移金属酸
化物として二酸化チタンを用いた場合を説明した
が、他の遷移金属酸化物、たとえば、酸化コバル
ト、酸化セリウムなどについても応答特性の向上
を確認した。 In addition, in the manufacturing method of the present invention, the relative weight ratio of platinum and iridium is limited to 95 to 80% by weight of platinum and 5 to 20% by weight of iridium because if the iridium content is less than 5% by weight, the response characteristics will be affected. This is because there is no effect, and if it exceeds 20% by weight, the response speed becomes slow, making it undesirable as a sensing element. In the examples of the present invention, a case was explained in which titanium dioxide was used as the transition metal oxide, but improvement in response characteristics was also confirmed with other transition metal oxides, such as cobalt oxide and cerium oxide.
第１図は比較例における従来の検知素子の応答
特性を示す特性図、第２図は本発明の製造方法に
より作製された検知素子の応答特性を示す特性図
である。
FIG. 1 is a characteristic diagram showing the response characteristics of a conventional sensing element in a comparative example, and FIG. 2 is a characteristic diagram showing the response characteristics of a sensing element manufactured by the manufacturing method of the present invention.
Claims (1)
極線とし、該電極線の端部を埋設する形で遷移金
属酸化物粉末成形体を設け、該成形体を高温で焼
成して酸化物焼結すると同時に上記電極線に含有
するイリジウム成分の一部を焼結体中に拡散させ
ることを特徴とする酸素濃度検知素子の製造方
法。 ２ 白金とイリジウムの相対重量比が白金95〜80
重量％に対しイリジウム５〜20重量％であること
を特徴とする特許請求の範囲第１項記載の酸素濃
度検知素子の製造方法。[Claims] 1. A pair of alloy wires made of platinum and iridium are used as electrode wires, a transition metal oxide powder molded body is provided with the ends of the electrode wires buried, and the molded body is fired at a high temperature. A method for manufacturing an oxygen concentration sensing element, characterized in that at the same time as the oxide is sintered, a part of the iridium component contained in the electrode wire is diffused into the sintered body. 2 The relative weight ratio of platinum and iridium is platinum 95 to 80
2. The method for manufacturing an oxygen concentration sensing element according to claim 1, wherein the content of iridium is 5 to 20% by weight.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15713479A JPS5679243A (en) | 1979-12-03 | 1979-12-03 | Preparation of oxygen concentration sensing element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15713479A JPS5679243A (en) | 1979-12-03 | 1979-12-03 | Preparation of oxygen concentration sensing element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5679243A JPS5679243A (en) | 1981-06-29 |
| JPS632056B2 true JPS632056B2 (en) | 1988-01-16 |
Family
ID=15642940
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15713479A Granted JPS5679243A (en) | 1979-12-03 | 1979-12-03 | Preparation of oxygen concentration sensing element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5679243A (en) |
-
1979
- 1979-12-03 JP JP15713479A patent/JPS5679243A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5679243A (en) | 1981-06-29 |
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