JPS5919310B2 - Gas component detection element - Google Patents
Gas component detection elementInfo
- Publication number
- JPS5919310B2 JPS5919310B2 JP12074176A JP12074176A JPS5919310B2 JP S5919310 B2 JPS5919310 B2 JP S5919310B2 JP 12074176 A JP12074176 A JP 12074176A JP 12074176 A JP12074176 A JP 12074176A JP S5919310 B2 JPS5919310 B2 JP S5919310B2
- Authority
- JP
- Japan
- Prior art keywords
- gas component
- detection element
- component detection
- sintering
- gas
- 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
Description
【発明の詳細な説明】
本発明は、例えば三元触媒を使用したフィードバック方
式の排気ガス浄化システムに採用されるガス成分検出素
子に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas component detection element employed in, for example, a feedback type exhaust gas purification system using a three-way catalyst.
自動車排気ガス中の有害成分を減少または除去するため
には、エンジンに吸入される吸入空気量と燃料との比、
いわゆる空燃比を精度よく制御する必要がある。In order to reduce or eliminate harmful components in automobile exhaust gas, the ratio of the intake air amount to the fuel taken into the engine,
It is necessary to accurately control the so-called air-fuel ratio.
特に、三元触媒を用いて有害成分を同時に減少するため
には、空燃比を理論空燃比に非常に近い範囲にｆ５ｌ脚
しなければならない。そのためにはこの空燃比を精度よ
く制御でき、且つ耐久性のある検出器が必要である。従
来この種の検出器としては、酸化ジルコニウム等の酸素
イオン伝導性金属酸化物よりなる酸素濃度検出素子、な
らびに酸化チタン等の酸素分圧に依存した電気抵抗変化
を示す金属酸化物を用いたガス成分検出素子が公知であ
る。従来、金属酸化物として酸化チタンを用いたガス成
分検出素子は耐久実験を行なうと理論空燃比点における
電気抵抗変化幅ならびに電気抵抗値が変化する現象があ
りガス成分検出素子の安定性に欠けている。In particular, in order to simultaneously reduce harmful components using a three-way catalyst, the air-fuel ratio must be adjusted to a range very close to the stoichiometric air-fuel ratio. For this purpose, a durable detector is required that can accurately control the air-fuel ratio. Conventional detectors of this type include oxygen concentration detection elements made of oxygen ion conductive metal oxides such as zirconium oxide, and gas sensors using metal oxides such as titanium oxide that exhibit electrical resistance changes depending on oxygen partial pressure. Component detection elements are known. Conventionally, gas component detection elements that use titanium oxide as a metal oxide have a phenomenon in which the range of electrical resistance change and the electrical resistance value change at the stoichiometric air-fuel ratio point during durability tests, resulting in a lack of stability of the gas component detection element. There is.
ガス成分検出素子の不安定な原因の一つとしては、セン
サー取付け場所が比較的高温であるため、ガス成分検出
素子の熱劣化が実験的に確認されている。ガス成分検出
素子の熱劣化を防ぐには、このガス成分検出素子が使用
される温度よりも更に高温で焼成（製造時の焼成）すれ
ば耐熱性が良好となつて熱劣化が防止できる。しかしな
がら、高温で焼成すれば焼結度が高まつて緻密な構造と
なり、検出ガスがガス成分検出素子の内部に容易に浸透
せず、ガス成分の濃度変化に対する応答時間が遅くなる
つまり感度が低下するという問題が生じる。本発明は上
記の点に鑑み、酸化チタンに、酸化クロム、酸化ナトリ
ウムの群から選択した少なくも１つの金属酸化物を添加
して焼結することでガス成分検出素子を構成したことに
より、上記混合金属酸化物の焼成時には酸化クロム、酸
化ナトリウムが焼結阻止剤として作用し、高温下で焼成
しても焼結度は酸化チタン単独に比べて低くでき、従つ
て耐熱性を向上するために高温下で焼成しても十分に多
孔質であり、耐熱性、応答性ともに良好なガス成分検出
素子を提供しようとするものである。It has been experimentally confirmed that one of the causes of instability of the gas component detection element is thermal deterioration of the gas component detection element due to the relatively high temperature of the sensor mounting location. In order to prevent thermal deterioration of the gas component detection element, if the gas component detection element is fired at a higher temperature than the temperature at which it is used (firing during manufacturing), the heat resistance will be improved and thermal deterioration can be prevented. However, if fired at a high temperature, the degree of sintering will increase and a dense structure will result, which prevents the detection gas from penetrating easily into the interior of the gas component detection element, slowing down the response time to changes in the concentration of gas components, and reducing sensitivity. The problem arises. In view of the above points, the present invention comprises a gas component detection element by adding at least one metal oxide selected from the group of chromium oxide and sodium oxide to titanium oxide and sintering the same. When firing mixed metal oxides, chromium oxide and sodium oxide act as sintering inhibitors, and even when fired at high temperatures, the degree of sintering can be lower than that of titanium oxide alone. The object is to provide a gas component detection element that is sufficiently porous even when fired at high temperatures and has good heat resistance and responsiveness.
本発明のガス成分検出素子の形状例を第１図に示す。An example of the shape of the gas component detection element of the present invention is shown in FIG.
ガス成分検出素子１は細長の形状を有しており、２本の
電極２が互いに間隔を保持してガス成分検出素子１に端
部側を埋設されている。本発明のガス成分検出素子は次
のような方法で製造できる。即ち、１２００℃で仮焼し
た純酸化チタン粉末（ルチル型）をボールミル等によつ
て粉砕し粒子径を比較的細かく例えば平均粒径０．１〜
１．０μ、好ましくは０．１〜３μに揃える。本実施例
では平均粒径０．５μである。その粉末に組成比にして
１ａｔｍ％になるように正確に秤量された金属酸化物（
Ｃｒ２Ｏ３、Ｎａ２Ｏ）を加え、有機バインダー溶液と
ともに二ーダ一で混練しスラリーを形成する。次に、ド
クターブレード法を使用して０．２１１位のシートを作
成し、数枚重ねて厚さを制御する。電極はシートの重ね
合わせた間に挿入し、一体型で圧縮成形、焼成を行なつ
てガス成分検出素子を得る。第２図にＴｉＯ２＋添加物
（１ａｔｍ％）焼結体のかさ比重一焼成温度特性を示す
。The gas component detection element 1 has an elongated shape, and two electrodes 2 are embedded at their ends in the gas component detection element 1 with a distance maintained between them. The gas component detection element of the present invention can be manufactured by the following method. That is, pure titanium oxide powder (rutile type) calcined at 1200°C is ground using a ball mill or the like, and the particle size is relatively fine, for example, the average particle size is 0.1 to 0.1.
The thickness is adjusted to 1.0μ, preferably 0.1 to 3μ. In this example, the average particle size is 0.5μ. Metal oxide (
Cr2O3, Na2O) are added and kneaded together with an organic binder solution in a kneader to form a slurry. Next, a 0.211 sheet is created using a doctor blade method, and several sheets are stacked to control the thickness. The electrodes are inserted between the stacked sheets, and the sheet is compression molded and fired to obtain a gas component detection element. FIG. 2 shows the bulk specific gravity versus sintering temperature characteristics of a TiO2+additive (1 atm %) sintered body.
かさ比重は焼成密度／理論密度×１００％の式から求め
た。平均粒径０．５μの純ＴｉＯ２粉末にそれぞれ１ａ
ｔｍ％のＣｒＯ３．Ｍａ２Ｏを混合し、１００ｋｆ１／
Ｃｄで成形した円板（直径１０ｍｍ、厚さ２１１）で測
定した。第２図かられかるように、Ｃｒ２Ｏ３．Ｎａ２
Ｏを添加した方が純ＴｉＯ２よりもかさ比重が少なく換
言すれば焼結度が低く、Ｃｒ２Ｏ３．Ｎａ２Ｏは焼結阻
止剤として効果があることがわかる。なお、Ｃｒ２Ｏ３
とＮａ２Ｏとを同時に添加したものにおいて、それらの
混合割合は各々０．５ａｔｍ％づつである。また、Ｚｎ
Ｏ．ＣｕＯを純ＴｉＯ２に添加した場合には焼結促進剤
として働らき添加物により特性が異なることがわかる。
第３図に前記の要領で作成したシート状のガス成分検出
素子（幅２１！』長さ５ｎ，厚さ１１１）を１１００℃
、１２００℃で焼成した際の応答時間を示す。Ｒ（空燃
比１３）ヰＬ（空燃比１６）に空燃比を変えた時の応答
時間はＭａ２Ｏ，．ｃｒ２Ｏ３の焼結阻止剤を添加した
方が速く、ＺｎＯ．ＣｕＯの焼結促進剤を添加すると遅
くなつている。例えば、ＴｉＯ２を１１００℃で焼成し
てなるガス成分検出素子の応答時間は０．３８（Ｓｅｃ
）であるのに対し、ＴｉＯ２にＣｒ２Ｏ３を添加して１
２００℃で焼成しても応答時間は０．３３（Ｓｅｃ）で
ある。つまり、ＴｉＯ２にＣｒ２Ｏ３、Ｎａ２Ｏを添加
して焼成したガス成分検出素子は、ＴｉＯ２単独あるい
はＴｉＯ２にＺｎＯ、ＣｕＯを添加して焼成したガス成
分検出素子に比べて同一焼成温度では、焼結度が低く多
孔質であるために、検出ガスが内部に侵透しやすくなり
、旧ガスが速やかに排出されるので、応答時間が速くな
るのである。なお、第４図に示すように、例゛えばＣｒ
２Ｏ３をＴｉＯ２に添加する場合、５ａｔｍ％以上では
効果があまり変わらず、０．５〜５ａｔｍ％ が好まし
い。The bulk specific gravity was determined from the formula: fired density/theoretical density x 100%. 1a each to pure TiO2 powder with an average particle size of 0.5μ
tm% CrO3. Mix Ma2O, 100kf1/
Measurements were made using a disk (diameter 10 mm, thickness 211 mm) made of Cd. As shown in Fig. 2, Cr2O3. Na2
Adding O has a lower bulk specific gravity than pure TiO2, in other words, the degree of sintering is lower, and Cr2O3. It can be seen that Na2O is effective as a sintering inhibitor. In addition, Cr2O3
and Na2O are added at the same time, the mixing ratio of each is 0.5 atm%. Also, Zn
O. It can be seen that when CuO is added to pure TiO2, it acts as a sintering accelerator and the properties vary depending on the additive.
Figure 3 shows a sheet-shaped gas component detection element (width 21!, length 5n, thickness 111) prepared in the above manner at 1100°C.
, shows the response time when fired at 1200°C. The response time when changing the air-fuel ratio from R (air-fuel ratio 13) to L (air-fuel ratio 16) is Ma2O, . It is faster to add cr2O3 sintering inhibitor, and ZnO. Addition of CuO sintering accelerator slows down the process. For example, the response time of a gas component detection element made by firing TiO2 at 1100°C is 0.38 (Sec.
), whereas by adding Cr2O3 to TiO2, 1
Even when fired at 200° C., the response time is 0.33 (Sec). In other words, a gas component detection element fired by adding Cr2O3 and Na2O to TiO2 has a lower degree of sintering than a gas component detection element fired by adding TiO2 alone or adding ZnO and CuO to TiO2 at the same firing temperature. Because it is porous, the detection gas can easily penetrate inside, and the old gas can be expelled quickly, resulting in a faster response time. In addition, as shown in FIG. 4, for example, Cr
When adding 2O3 to TiO2, the effect does not change much if the amount is 5 atm% or more, and 0.5 to 5 atm% is preferable.
なお、Ｎａ２Ｏの場合も同じであつた。以上述べたよう
に本発明によれば、ガス成分検出素子を、酸化チタンに
、酸化クロム、酸化ナトリウムの群から選択された少な
くも１種を添加して焼成した焼結金属酸化物により構成
したから、ガス成分検出素子の耐熱性を向上させるため
に製造時において上記組成を高温度で焼成しても上記酸
化クロム、酸化ナトリウムが焼結阻止剤として作用し、
十分な多孔性が得られるため、従来のように耐熱性を向
上させると多孔性が失なわれ、ガス成分濃度変化に対す
る応答性が遅くなるという問題を解決することができ、
従つて耐熱性がよく、しかも応答性もよいガス成分検出
素子を得ることができる。The same was true for Na2O. As described above, according to the present invention, the gas component detection element is made of a sintered metal oxide obtained by adding at least one selected from the group of chromium oxide and sodium oxide to titanium oxide and firing the mixture. Therefore, in order to improve the heat resistance of the gas component detection element, even if the above composition is fired at high temperature during manufacturing, the chromium oxide and sodium oxide act as sintering inhibitors,
Since sufficient porosity can be obtained, it is possible to solve the problem of conventional methods in which porosity is lost when heat resistance is improved, resulting in slow response to changes in gas component concentration.
Therefore, it is possible to obtain a gas component detection element with good heat resistance and good response.
第１図は本発明ガス成分検出素子の形状例を示す斜視図
、第２図ならびに第３図は本発明の効果の説明に供する
特性図であつて、第２図は焼成温度とかさ比重との関係
を示す特性図、第３図は焼成温度と応答時間との関係を
示す特性図、第４図はＴｉＯ２に添加するＣｒ２Ｏ３の
量と焼結度との関係を示す特性図である。
１・・・・・・ガス成分検出素子。FIG. 1 is a perspective view showing an example of the shape of the gas component detection element of the present invention, FIGS. 2 and 3 are characteristic diagrams for explaining the effects of the present invention, and FIG. 2 shows the relationship between firing temperature and bulk specific gravity. FIG. 3 is a characteristic diagram showing the relationship between firing temperature and response time, and FIG. 4 is a characteristic diagram showing the relationship between the amount of Cr2O3 added to TiO2 and the degree of sintering. 1... Gas component detection element.
Claims (1)
ス成分検出素子において、酸化チタンに、酸化クロムお
よび酸化ナトリウムの群から選択された少なくとも１種
を添加して焼結してなることを特徴とするガス成分検出
素子。1. A gas component detection element that exhibits an electrical resistance value depending on the gas component in the detected gas is made by adding at least one kind selected from the group of chromium oxide and sodium oxide to titanium oxide and sintering it. Characteristic gas component detection element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12074176A JPS5919310B2 (en) | 1976-10-06 | 1976-10-06 | Gas component detection element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12074176A JPS5919310B2 (en) | 1976-10-06 | 1976-10-06 | Gas component detection element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5345596A JPS5345596A (en) | 1978-04-24 |
| JPS5919310B2 true JPS5919310B2 (en) | 1984-05-04 |
Family
ID=14793826
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12074176A Expired JPS5919310B2 (en) | 1976-10-06 | 1976-10-06 | Gas component detection element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5919310B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6310084U (en) * | 1986-07-07 | 1988-01-22 | ||
| JPH0450883B2 (en) * | 1985-03-11 | 1992-08-17 | Shachihata Industrial | |
| JPH0537484U (en) * | 1991-10-18 | 1993-05-21 | 太陽鉄工株式会社 | Adsorption device |
-
1976
- 1976-10-06 JP JP12074176A patent/JPS5919310B2/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0450883B2 (en) * | 1985-03-11 | 1992-08-17 | Shachihata Industrial | |
| JPS6310084U (en) * | 1986-07-07 | 1988-01-22 | ||
| JPH0537484U (en) * | 1991-10-18 | 1993-05-21 | 太陽鉄工株式会社 | Adsorption device |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5345596A (en) | 1978-04-24 |
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