JP3510050B2 - Electrode for oxygen sensor - Google Patents
Electrode for oxygen sensorInfo
- Publication number
- JP3510050B2 JP3510050B2 JP20117996A JP20117996A JP3510050B2 JP 3510050 B2 JP3510050 B2 JP 3510050B2 JP 20117996 A JP20117996 A JP 20117996A JP 20117996 A JP20117996 A JP 20117996A JP 3510050 B2 JP3510050 B2 JP 3510050B2
- Authority
- JP
- Japan
- Prior art keywords
- electrode
- powder
- oxygen sensor
- pump cell
- psz
- 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 - Fee Related
Links
- 239000001301 oxygen Substances 0.000 title claims description 67
- 229910052760 oxygen Inorganic materials 0.000 title claims description 67
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims description 61
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 86
- 239000000843 powder Substances 0.000 claims description 53
- 229910002077 partially stabilized zirconia Inorganic materials 0.000 claims description 37
- 239000000758 substrate Substances 0.000 claims description 37
- 239000002245 particle Substances 0.000 claims description 32
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 22
- 230000005484 gravity Effects 0.000 claims description 19
- 239000002994 raw material Substances 0.000 claims description 9
- 238000010304 firing Methods 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 description 29
- 229910052697 platinum Inorganic materials 0.000 description 18
- 238000012360 testing method Methods 0.000 description 17
- 238000002156 mixing Methods 0.000 description 13
- 239000007784 solid electrolyte Substances 0.000 description 11
- 238000009792 diffusion process Methods 0.000 description 10
- 239000007789 gas Substances 0.000 description 8
- 238000002485 combustion reaction Methods 0.000 description 7
- 238000000034 method Methods 0.000 description 7
- 238000000859 sublimation Methods 0.000 description 7
- 230000008022 sublimation Effects 0.000 description 7
- 239000000446 fuel Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 150000002926 oxygen Chemical class 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000007650 screen-printing Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- -1 oxygen ion Chemical class 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 239000010937 tungsten Substances 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000010344 co-firing Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000007750 plasma spraying Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000003232 water-soluble binding agent Substances 0.000 description 1
Landscapes
- Measuring Oxygen Concentration In Cells (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、センサ基板との密
着性に優れ、しかもその密着性が長期に渡って維持さ
れ、センサ基板との間の導電性の低下が抑えられる酸素
センサ用電極に関する。本発明の酸素センサ用電極は、
内燃機関、ガス燃焼装置等の空燃比を検出し、そのデー
タをフィードバックして空燃比を制御するための空燃比
検出センサなどの電極として使用することができる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an oxygen sensor which has excellent adhesion to a sensor substrate, which is maintained over a long period of time, and whose conductivity is prevented from decreasing with respect to the sensor substrate. . The oxygen sensor electrode of the present invention is
It can be used as an electrode of an air-fuel ratio detection sensor for detecting the air-fuel ratio of an internal combustion engine, a gas combustion device, etc. and feeding back the data to control the air-fuel ratio.
【０００２】[0002]
【従来の技術】ジルコニア等の酸素イオン伝導性に優れ
た固体電解質を隔壁とし、白金等の貴金属からなる電極
を設けた酸素濃淡電池（センシングセル）とか酸素ポン
プの原理によって酸素濃度を測定する酸素センサが実用
化されている。この酸素センサは自動車等の内燃機関、
又はガス燃焼装置などの排気ガス中に含まれる酸素の濃
度を検出し、内燃機関等の燃焼状態を把握し、その空燃
比を制御する等の用途において使用されている。2. Description of the Related Art Oxygen concentration battery (sensing cell) having a solid electrolyte such as zirconia or the like having excellent ion conductivity as a partition wall and an electrode made of a noble metal such as platinum, or oxygen for measuring oxygen concentration by the principle of an oxygen pump. Sensors are in practical use. This oxygen sensor is used for internal combustion engines of automobiles,
Alternatively, it is used in applications such as detecting the concentration of oxygen contained in exhaust gas of a gas combustion device, grasping the combustion state of an internal combustion engine, etc., and controlling the air-fuel ratio thereof.
【０００３】固体電解質の表面に電極を設ける方法とし
ては、スパッタ法、真空蒸着法、ペースト法等が挙げら
れるが、この他、固体電解質と電極とを同時焼成して、
固体電解質表面に電極を密着、接合させる方法もある。
この同時焼成の場合、白金又白金族金属を併用した電極
でも固体電解質と接合することはできるが、より好まし
くは、白金等の金属に、電極の導電性を損なわない程度
の量比のセラミックが配合されるとよい。そして、この
ように金属とセラミックによって構成される電極では、
固体電解質と電極とガスとをより十分に接触させるた
め、従来より、電極の気孔率を高くして３相界面を多数
形成するように設計されてきた。As a method for providing an electrode on the surface of the solid electrolyte, there may be mentioned a sputtering method, a vacuum deposition method, a paste method and the like. In addition to this, the solid electrolyte and the electrode are simultaneously fired,
There is also a method of adhering and bonding an electrode to the surface of the solid electrolyte.
In the case of this co-firing, an electrode using platinum or a platinum group metal in combination can also be joined to the solid electrolyte, but more preferably, a metal such as platinum is mixed with a ceramic in an amount ratio that does not impair the conductivity of the electrode. It is recommended to be blended. And in the electrode composed of metal and ceramic in this way,
In order to bring the solid electrolyte, the electrode and the gas into contact with each other more sufficiently, it has been conventionally designed to increase the porosity of the electrode to form a large number of three-phase interfaces.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、上記の
電極では、固体電解質と接合するのは主として該電極中
のセラミックであり、電極の気孔率が高い場合、接合さ
れる面積が減少するという問題がある。また、より確実
に密着、接合させるためにセラミックを増やした場合
は、その導電性が低下するとの問題がある。このように
当初より密着性に問題がある他、長期に渡る使用によっ
て、特に酸素ポンプを利用したリーン、リッチの領域で
空燃比を測定する酸素センサでは、電極が固体電解質表
面から徐々に剥離してくるという問題もある。However, in the above-mentioned electrode, it is mainly the ceramic in the electrode that is bonded to the solid electrolyte, and when the porosity of the electrode is high, there is a problem that the bonded area decreases. is there. In addition, when ceramics are added in order to more firmly adhere and bond, there is a problem that the conductivity decreases. In this way, there is a problem with adhesion from the beginning, and with long-term use, especially in oxygen sensors that measure the air-fuel ratio in the lean and rich regions using an oxygen pump, the electrodes gradually peel off from the solid electrolyte surface. There is also the problem of coming.
【０００５】本発明は、上記の問題を解決するものであ
り、固体電解質との密着性に優れ、且つ長期に渡って使
用しても、初期の密着性が維持され、固体電解質から剥
離することのない酸素センサ用電極を提供することを目
的とする。また、本発明の酸素センサ用電極では、セラ
ミックの量が電極の導電材に比べて１／１０以下と僅か
である従来の電極、或いは粒径の大きな白金をスパッタ
リングして形成した従来の電極に比べて多量のセラミッ
クが配合される。それによって密着性が向上し、且つそ
の密着性が使用中に渡って維持されるものであるが、セ
ラミックが多いにもかかわらず、同時に導電性にも優
れ、非常に優れた性能の酸素センサ用電極を得ることが
できる。The present invention solves the above problems and has excellent adhesion to a solid electrolyte, and even when it is used for a long period of time, the initial adhesion is maintained and it is peeled from the solid electrolyte. It is an object of the present invention to provide an electrode for an oxygen sensor that does not have a battery. Further, in the oxygen sensor electrode of the present invention, a conventional electrode in which the amount of ceramic is a little less than 1/10 of the conductive material of the electrode, or a conventional electrode formed by sputtering platinum having a large grain size is used. A large amount of ceramic is mixed in comparison. As a result, the adhesiveness is improved, and the adhesiveness is maintained throughout use. However, despite the large amount of ceramics, it is also excellent in conductivity and at the same time for oxygen sensors with excellent performance. An electrode can be obtained.
【０００６】[0006]
【課題を解決するための手段】上記の電極の固体電解質
からの剥離について、その原因等を検討した。その結
果、酸素ポンプとなるポンプセル基板の特に外側に設け
られた電極において、白金の一部が、この電極の該ポン
プセル基板との界面側に移動し、偏在していることが確
認された。そして、この界面における白金の増量によっ
て電極が徐々に剥離するものと考えられる。[Means for Solving the Problems] The cause of the above-mentioned peeling of the electrode from the solid electrolyte was examined. As a result, it was confirmed that, in the electrode provided particularly outside the pump cell substrate serving as the oxygen pump, part of platinum moved to the interface side of the electrode with the pump cell substrate and was unevenly distributed. Then, it is considered that the electrode is gradually peeled off due to the increase of platinum in this interface.
【０００７】このような白金の移動、偏在は、下記のよ
うにして生ずるものと考えられる。先ず、ポンプセル基
板の外側に配置されたセラミックヒータからの熱によっ
て、該ポンプセル基板の外側に設けられた雰囲気と直接
接触する電極中の白金が昇華し、拡散される。この昇
華、拡散が、ポンプセル基板中の酸素のポンピングによ
って酸素濃度の高いところで加速され、ポンプセル基板
との界面に達した白金の蒸気は、ここで再び固化し析出
する。このように白金の移動、偏在は、温度勾配によっ
て引き起こされ、酸素の存在によって促進されるものと
考えられる。It is considered that such movement and uneven distribution of platinum occur as follows. First, the platinum in the electrode that is in direct contact with the atmosphere provided outside the pump cell substrate is sublimated and diffused by the heat from the ceramic heater arranged outside the pump cell substrate. The sublimation and diffusion are accelerated by oxygen pumping in the pump cell substrate at a high oxygen concentration, and platinum vapor reaching the interface with the pump cell substrate is solidified and precipitated again here. Thus, it is considered that the migration and uneven distribution of platinum are caused by the temperature gradient and promoted by the presence of oxygen.
【０００８】本発明者は、電極が剥離する原因を上記の
ように推定し、従来の電極において使用されていた白金
粉末に比べて粒径の大きな白金粉末を使用し、且つ電極
中のセラミックを増量することにより、上記の問題を解
決した。即ち、白金の粒径を大きくすることにより、単
位体積当たりの白金粉末の表面積を小さくし、白金の昇
華を抑えることができる。また、粒径が大きいため、セ
ラミックが多くても白金粒子間の接触が比較的よく保た
れ、十分な導電性が確保される。しかもセラミックが多
いため、初期の密着性も向上し、長期に渡って優れた性
能が維持されるものである。The present inventor presumed the cause of the electrode peeling as described above, uses platinum powder having a larger particle size than the platinum powder used in the conventional electrode, and removes the ceramic in the electrode. The problem was solved by increasing the amount. That is, by increasing the particle size of platinum, the surface area of the platinum powder per unit volume can be reduced and the sublimation of platinum can be suppressed. Further, since the particle size is large, the contact between the platinum particles is relatively well maintained even if there are many ceramics, and sufficient conductivity is secured. Moreover, since there are many ceramics, the initial adhesion is improved, and excellent performance is maintained over a long period of time.
【０００９】第１発明の酸素センサ用電極は、白金粉末
及びジルコニア粉末を含む原料粉末を焼成してなる酸素
センサ用電極において、上記白金粉末を１００重量部と
した場合に、上記ジルコニア粉末は１４〜２５重量部で
あり、上記白金粉末の粒径は２〜２０μｍであって、且
つそのかさ比重は２．５〜４．２であることを特徴とす
る。The oxygen sensor electrode of the first invention is an oxygen sensor electrode obtained by firing a raw material powder containing platinum powder and zirconia powder, and when the platinum powder is 100 parts by weight, the zirconia powder is 14 parts by weight. .About.25 parts by weight, the particle size of the platinum powder is 2 to 20 .mu.m, and the bulk specific gravity thereof is 2.5 to 4.2.
【００１０】上記「酸素センサ用電極」（以下、電極と
いう。）は、排気ガス中の可燃成分の燃焼を促進する触
媒作用を有する白金（以下、Ｐｔという。）等の貴金属
元素を主成分とする。そして、これに酸素イオン導電性
を有し、センサ基板として多用されるジルコニア（以
下、ＺｒＯ2 という。）が配合される。このＰｔには、
ルテニウム、オスミウム、イリジウム、ロジウム及びパ
ラジウム等を少量併存させることもできる。「Ｐｔ粉
末」の「粒径」が「２μｍ」未満では、その単位体積当
たりの表面積が大きくなり、昇華、拡散し易くなり、初
期の導電性等には優れるものの、耐久性に劣った電極と
なる。The above "electrode for oxygen sensor" (hereinafter referred to as "electrode") is mainly composed of a noble metal element such as platinum (hereinafter referred to as "Pt") having a catalytic action for promoting combustion of combustible components in exhaust gas. To do. Then, zirconia (hereinafter, referred to as ZrO 2 ) which has oxygen ion conductivity and is widely used as a sensor substrate is mixed with this. In this Pt,
A small amount of ruthenium, osmium, iridium, rhodium, palladium and the like can be present together. When the “particle size” of the “Pt powder” is less than “2 μm”, the surface area per unit volume is large, sublimation and diffusion are easy, and the initial conductivity is excellent, but the electrode has poor durability. Become.
【００１１】一方、Ｐｔ粉末の粒径が「２０μｍ」を越
える場合は、例えばスクリーン印刷等によって電極の形
状や厚みを精度よく形成することが困難である。更に、
形成された電極の導電性も不安定となる。このＰｔ粉末
の粒径は、特に５〜１５μｍ程度とすることが好まし
い。Ｐｔ粉末の粒径がこの範囲であれば、適度なかさ比
重を有するものが得られ易く、より確実に優れた導電性
を有する電極を形成することができる。また、その昇
華、拡散も十分に抑えられ、電極とポンプセル基板との
優れた密着性が長期に渡って維持される。On the other hand, if the particle size of the Pt powder exceeds "20 μm", it is difficult to form the shape and thickness of the electrode with high precision by screen printing or the like. Furthermore,
The conductivity of the formed electrode also becomes unstable. The particle size of the Pt powder is preferably about 5 to 15 μm. When the particle diameter of the Pt powder is in this range, it is easy to obtain one having an appropriate bulk specific gravity, and it is possible to more reliably form an electrode having excellent conductivity. Further, the sublimation and diffusion thereof are sufficiently suppressed, and the excellent adhesion between the electrode and the pump cell substrate is maintained for a long time.
【００１２】更に、Ｐｔ粉末の「かさ比重」が「２．
５」未満では、たとえその粒径が望ましい範囲内であっ
ても、比較的少量の「ＺｒＯ2 粉末」の配合によって、
初期の導電性そのものが大きく低下する。そのため、Ｚ
ｒＯ2 粉末を多量に配合することができず、電極とポン
プセル基板との密着性も不十分となる。また、かさ比重
が「４．２」を越える場合は、初期の導電性は良好で、
また密着性も十分なものとすることができる。しかし、
Ｐｔ粉末の単位体積当たりの表面積が大きく、Ｐｔの昇
華、拡散を生じ易いためか、耐久性に劣り、比較的短時
間で導電性が低下する。このＰｔ粉末のかさ比重は、第
２発明のように「３．０〜４．０」の範囲がより好まし
く、このような電極であれば、優れた密着性と導電性と
が長期に渡って維持される。Further, the "bulk specific gravity" of Pt powder is "2.
If it is less than 5 ", even if the particle size is within the desired range, by blending a relatively small amount of" ZrO 2 powder ",
The initial conductivity itself is greatly reduced. Therefore, Z
It is not possible to mix a large amount of rO 2 powder, and the adhesion between the electrode and the pump cell substrate becomes insufficient. If the bulk specific gravity exceeds "4.2", the initial conductivity is good,
In addition, the adhesion can be sufficient. But,
Perhaps because the Pt powder has a large surface area per unit volume and Pt is easily sublimated and diffused, the durability is poor and the conductivity is reduced in a relatively short time. The bulk specific gravity of the Pt powder is more preferably in the range of "3.0 to 4.0" as in the second invention, and such an electrode has excellent adhesion and conductivity over a long period of time. Maintained.
【００１３】ＺｒＯ2 粉末が、Ｐｔ粉末１００重量部に
対して「１４重量部」未満では、電極とポンプセル基板
との初期の密着性も必ずしも十分ではなく、且つＰｔの
昇華、拡散にともなって、この密着性が経時とともに低
下し、同時に導電性も低下する。また、このＺｒＯ2 粉
末の配合量が「２５重量部」を越える場合は、初期の導
電性そのものが低下する。このＺｒＯ2 粉末の配合量
は、特に第３発明のように「１７〜２２重量部」の範囲
が好ましい。この範囲の配合量であれば、ほぼ一定した
優れた導電性が得られ、且つ密着性も従来の電極を大き
く上回る優れた性能の電極を得ることができる。If the amount of ZrO 2 powder is less than “14 parts by weight” with respect to 100 parts by weight of Pt powder, the initial adhesion between the electrode and the pump cell substrate is not always sufficient, and Pt sublimates and diffuses. This adhesion decreases with time, and at the same time, the conductivity also decreases. Further, when the amount of the ZrO 2 powder compounded exceeds “25 parts by weight”, the initial conductivity itself deteriorates. The blending amount of this ZrO 2 powder is particularly preferably in the range of “17 to 22 parts by weight” as in the third invention. When the blending amount is within this range, it is possible to obtain an electrode having excellent conductivity which is substantially constant and excellent in adhesion, which is far superior to that of a conventional electrode.
【００１４】また、ＺｒＯ2 粉末としては、特に第４発
明のように「部分安定化ジルコニア粉末」（この部分安
定化ジルコニアのことを、以下、ＰＳＺという。）を使
用することが好ましい。これは、酸素ポンプを利用した
酸素センサにおいて、ポンプセル基板として多用される
セラミックであるＰＳＺと同質のセラミックを使用する
ものである。これによって電極及びポンプセル基板と、
その他の構成部材とを同時焼成することができ、効率よ
く酸素センサを作製することができる。As the ZrO 2 powder, it is particularly preferable to use "partially stabilized zirconia powder" (this partially stabilized zirconia is hereinafter referred to as PSZ) as in the fourth invention. This uses a ceramic of the same quality as PSZ, which is a ceramic often used as a pump cell substrate in an oxygen sensor using an oxygen pump. With this, the electrode and the pump cell substrate,
The other constituent members can be co-fired, and the oxygen sensor can be efficiently manufactured.
【００１５】[0015]
【発明の実施の形態】以下、本発明を実施例によって詳
しく説明する。
(1) 電極の原料の調製
純度９９．９％のＺｒＯ2 粉末９５モル％と、純度９
９．９％のＹ2 Ｏ3 粉末５モル％とを湿式混合した後、
１３００℃の温度で仮焼した。この仮焼物に水を加え、
ボールミルによって粉砕した後、水溶性バインダを添加
し、スプレードライ法によって造粒した。このＰＳＺ粉
末の平均粒径は０．６μｍである。その後、特定の粒径
及びかさ比重のＰｔ粉末と、所定量のＰＳＺ粉末及び所
定粘度に調合された有機バインダビヒクルとを、ポット
ミルによって攪拌、混合した。尚、上記のＰＳＺ粉末の
平均粒径は光分散法により測定した。また、Ｐｔ粉末の
粒径は沈降法により測定し、かさ比重はＪＩＳ Ｚ２５
０４に基づき測定した。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples. (1) Preparation of electrode raw material 95 mol% of ZrO 2 powder having a purity of 99.9% and a purity of 9%
After wet mixing with 5 mol% of 9.9% Y 2 O 3 powder,
It was calcined at a temperature of 1300 ° C. Add water to this calcined product,
After crushing with a ball mill, a water-soluble binder was added and granulated by a spray dry method. The average particle size of this PSZ powder is 0.6 μm. Then, Pt powder having a specific particle size and bulk specific gravity, a predetermined amount of PSZ powder and an organic binder vehicle prepared to have a predetermined viscosity were stirred and mixed by a pot mill. The average particle size of the PSZ powder was measured by the light dispersion method. Further, the particle size of Pt powder is measured by a sedimentation method, and the bulk specific gravity is JIS Z25.
It was measured based on 04.
【００１６】上記のＰＳＺ粉末、Ｐｔ粉末及び有機バイ
ンダビヒクルの攪拌、混合においては、適宜の有機溶剤
を併用することもできる。また、この電極の原料をスク
リーン印刷に適した粘度となるように調整するため、使
用時に更に有機溶剤を加えてもよい。尚、上記のように
純度の高いＺｒＯ2 粉末とＹ2 Ｏ3 粉末とからなるＰＳ
Ｚを使用することによって、より導電性に優れた電極と
することができる。In the stirring and mixing of the above PSZ powder, Pt powder and organic binder vehicle, an appropriate organic solvent can be used together. Further, in order to adjust the raw material of this electrode to have a viscosity suitable for screen printing, an organic solvent may be further added during use. In addition, as described above, a PS containing ZrO 2 powder and Y 2 O 3 powder having high purity is used.
By using Z, an electrode having more excellent conductivity can be obtained.
【００１７】(2) 本発明の電極を用いて作製した酸素セ
ンサ
本発明の電極を用いて作製した酸素センサの概略を図１
及び図２に示す。図１は、本発明の電極を使用した酸素
センサを分解した状態の概略を表す斜視図である（但
し、セラミックヒータは図示していない。）。また、図
２は、この酸素センサのセンサ部分の縦断面図である。
図１において、１はポンプセル基板であり、上記の電極
用の原料に配合されているのと同じＰＳＺからなる。１
１はポンプセル外側電極、１２はポンプセル内側電極で
あり、ポンプセル基板１の両面の相対する位置に設けら
れている。また、２は測定室形成部材であり上記と同様
のＰＳＺによって形成されている。２１は測定室、２２
は拡散律速部であり、この拡散律速部２２によって排気
ガスの測定室２１への流入は制限される。尚、拡散律速
部２２に多孔質セラミックを配置することが好ましい。(2) Oxygen sensor produced using the electrode of the present invention An oxygen sensor produced using the electrode of the present invention is schematically shown in FIG.
And shown in FIG. Figure 1 is a perspective view showing an outline of a disassembled state oxygen sensor using the electrode of the present invention (however, the ceramic heater is not shown.). Further, FIG. 2 is a vertical cross-sectional view of the sensor portion of this oxygen sensor.
In FIG. 1, reference numeral 1 denotes a pump cell substrate, which is made of the same PSZ as that blended in the above-mentioned electrode raw material. 1
Reference numeral 1 denotes a pump cell outer electrode, and 12 denotes a pump cell inner electrode, which are provided at opposite positions on both surfaces of the pump cell substrate 1. Further, 2 is a measurement chamber forming member, which is formed of PSZ similar to the above. 21 is a measurement room, 22
Is a diffusion rate controlling part, and the diffusion rate controlling part 22 limits the inflow of exhaust gas into the measurement chamber 21. In addition, it is preferable to dispose a porous ceramic in the diffusion control part 22.
【００１８】３はセンシングセル基板であり、同様に上
記電極に配合されているのと同じＰＳＺからなる。３１
はセンシングセル感知電極、３２はセンシングセル酸素
基準電極であり、センシングセル基板の両面の相対する
位置に設けられている。４は補強基板であり、上記と同
様のＰＳＺからなり、センシングセル酸素基準電極３２
を保護するとともに、酸素センサ全体を補強している。
また、図２において、１１１は多孔質セラミックからな
るオーバーコーティングであり、ポンプセル外側電極１
１の全表面を覆って保護するとともに、この電極の表面
からのＰｔの昇華、拡散を抑えている。Reference numeral 3 denotes a sensing cell substrate, which is also made of the same PSZ as that blended in the above electrodes. 31
Is a sensing cell sensing electrode, and 32 is a sensing cell oxygen reference electrode, which are provided at opposite positions on both sides of the sensing cell substrate. Reference numeral 4 denotes a reinforcing substrate, which is made of PSZ similar to that described above, and has a sensing cell oxygen reference electrode 32.
And protects the entire oxygen sensor.
Further, in FIG. 2, reference numeral 111 denotes an overcoating made of porous ceramic, and the pump cell outer electrode 1
The entire surface of No. 1 is covered and protected, and the sublimation and diffusion of Pt from the surface of this electrode are suppressed.
【００１９】また、５はセラミックヒータ、５１は発熱
部材、５２はリード部材及び５３はセラミックヒータと
ポンプセル基板との接合材である。セラミックヒータ５
は、通常、アルミナ（Ａｌ2 Ｏ3 ）を主体とするセラミ
ック中に白金、タングステン等からなる発熱部材５１及
びリード部材５２が埋設されている。そして、セラミッ
クヒータ５の図２に表されていない端面には、リード部
材５２の両端部が露出している。このリード部材５２の
端部を利用して形成された端子に通電することにより、
発熱部材５１が発熱し、ポンプセル及びセンシングセル
が所要温度に局所的に加熱される。Reference numeral 5 is a ceramic heater, 51 is a heating member, 52 is a lead member, and 53 is a bonding material between the ceramic heater and the pump cell substrate. Ceramic heater 5
In general, a heat generating member 51 and a lead member 52 made of platinum, tungsten or the like are embedded in a ceramic mainly composed of alumina (Al 2 O 3 ). Both ends of the lead member 52 are exposed at the end surface of the ceramic heater 5 not shown in FIG. By energizing the terminal formed using the end portion of the lead member 52,
The heat generating member 51 generates heat, and the pump cell and the sensing cell are locally heated to the required temperature.
【００２０】(3) 酸素センサの作製方法
先ず、ポンプセル基板１を形成するためのＰＳＺからな
るグリーンシートの一表面にポンプセル外側電極１１
を、他表面にポンプセル内側電極１２を形成するため、
上記(1) において調製した電極の原料をスクリーン印刷
した。一方、センシングセル基板３を形成するための同
一組成のＰＳＺからなるグリーンシートの両面に、セン
シングセル感知電極３１及びセンシングセル酸素基準電
極３２を形成するため、上記の電極の原料を同様にスク
リーン印刷した。また、同一組成のＰＳＺからなる測定
室形成部材２及び補強基板４となるグリーンシートを準
備した。(3) Method of Manufacturing Oxygen Sensor First, the pump cell outer electrode 11 is formed on one surface of the green sheet made of PSZ for forming the pump cell substrate 1.
To form the pump cell inner electrode 12 on the other surface,
The electrode raw material prepared in (1) above was screen-printed. Meanwhile, in order to form the sensing cell sensing electrode 31 and the sensing cell oxygen reference electrode 32 on both sides of the green sheet made of PSZ having the same composition for forming the sensing cell substrate 3, the above electrode materials are similarly screen-printed. did. Further, a measurement chamber forming member 2 made of PSZ having the same composition and a green sheet to be the reinforcing substrate 4 were prepared.
【００２１】上記のようにして準備した各部材を図１の
構造となるように一体とし、これを１４５０℃〜１５０
０℃の温度において焼成した。次いで、ポンプセル外側
電極１１を保護するためのオーバーコーティング１１１
を設けた。このオーバーコーティング１１１は、ポンプ
セル外側電極１１の全表面にマグネシウムアルミネート
スピネル粉末をプラズマ溶射して設けたものであり、厚
さは２０μｍ程度とした。The respective members prepared as described above are integrated so as to have the structure shown in FIG.
Baking at a temperature of 0 ° C. Then, an overcoating 111 for protecting the pump cell outer electrode 11
Was set up. The overcoating 111 is formed by plasma spraying magnesium aluminate spinel powder on the entire surface of the pump cell outer electrode 11 and has a thickness of about 20 μm.
【００２２】一方、Ａｌ2 Ｏ3 粉末を主成分としたグリ
ートシートを準備した。そして、このグリーンシートの
一表面の所要箇所に、白金ペーストをスクリーン印刷法
により塗布し、発熱部材５１及びリード部材５２となる
塗膜を形成した。リード部材５２となる塗膜は、グリー
ンシートの端面にまで設けられており、このリード部材
５２の端部は端子に加工され通電に供される。また、同
様の組成のグリーンシートを更に一枚準備し、このグリ
ーンシートを、上記のグリーンシートの白金ペーストが
塗布された面に積層し、焼成し、一体化してセラミック
ヒータ５を作製した。尚、本実施例では導電材料として
白金を使用したが、耐熱性が低くてもよい場合はタング
ステンを用いてもよい。その後、リン酸セメントからな
るポンプセル基板とセラミックヒータとの接合材５３に
よって、両者を接合し、酸素センサを作製した。On the other hand, a greet sheet containing Al 2 O 3 powder as a main component was prepared. Then, a platinum paste was applied to a required portion on one surface of the green sheet by a screen printing method to form a coating film to be the heat generating member 51 and the lead member 52. The coating film to be the lead member 52 is provided up to the end surface of the green sheet, and the end portion of the lead member 52 is processed into a terminal and supplied with electricity. Further, another green sheet having the same composition was prepared, and this green sheet was laminated on the surface of the above green sheet to which the platinum paste was applied, fired, and integrated to manufacture the ceramic heater 5. Although platinum is used as the conductive material in this embodiment, tungsten may be used if the heat resistance may be low. After that, the pump cell substrate made of phosphate cement and the ceramic heater were joined together by the joining material 53 to fabricate an oxygen sensor.
【００２３】(4) 性能試験とその評価
耐久試験
粒径７．６μｍ、かさ比重２．２のＰｔ粉末１００重量
部に、１４重量部のＰＳＺを加えた試料ａ及び粒径１０
μｍ、かさ比重３．４のＰｔ粉末１００重量部に、２２
重量部のＰＳＺを加えた試料ｂを用いて形成された電極
を設けた酸素センサを使用した。この酸素センサを、排
気量２０００ｃｃのガソリンエンジンの排気管に取り付
け耐久性の試験を実施した。試験条件は、λ＝１付近に
制御しながら、７５０℃の温度で３０分間、その後リッ
チな状態で８５０℃の温度で１５分間、次いでリーンな
状態で１０００℃の温度で１５分間のパターンを１サイ
クルとするパターン耐久試験とした。尚、１サイクルは
約８０ｋｍの走行に相当する。また、酸素センサは、そ
のセンサ部分ではない端部の外周に酸素センサを排気管
に取り付けるための固定具を接合し、この固定具の外周
に設けられたネジによって排気管の所定位置に穿設され
た貫通孔に固定した。酸素センサのセンサ部分は排気管
中に突き出した状態となり、このセンサ部分に排気ガス
が当たるようにした。(4) Performance Test and Its Evaluation Durability Test Sample a prepared by adding 14 parts by weight of PSZ to 100 parts by weight of Pt powder having a particle size of 7.6 μm and a bulk specific gravity of 2.2 and a particle size of 10
22 parts per 100 parts by weight of Pt powder having a μm and a bulk specific gravity of 3.4
An oxygen sensor provided with an electrode formed by using the sample b added with parts by weight of PSZ was used. This oxygen sensor was attached to an exhaust pipe of a gasoline engine having a displacement of 2000 cc and a durability test was conducted. The test conditions are as follows: a temperature of 750 ° C. for 30 minutes, a rich condition of 850 ° C. for 15 minutes, and a lean condition of 1000 ° C. for 15 minutes while controlling the λ = 1. The cycle durability test was performed. It should be noted that one cycle corresponds to traveling of about 80 km. Further, the oxygen sensor has a fixture for attaching the oxygen sensor to the exhaust pipe joined to the outer periphery of the end portion which is not the sensor portion, and the oxygen sensor is provided at a predetermined position of the exhaust pipe with a screw provided on the outer periphery of the fixture. It was fixed in the through hole. The sensor portion of the oxygen sensor was in a state of protruding into the exhaust pipe, and the exhaust gas was made to hit this sensor portion.
【００２４】耐久試験中、酸素センサのセンシングセル
感知電極と酸素基準電極との間に、酸素基準電極を正極
として僅かな定電流（例えば２５μＡ）を加えた状態
で、酸素基準電極とセンシングセル感知電極との間の起
電力が０．４５Ｖと一定の値になるように、ポンプセル
外側電極と内側電極との間に電圧を印加し、またセラミ
ックヒータに１０Ｖの電圧を印加して稼働状態とした。
但し、エンジンの制御はこの酸素センサの出力信号を利
用せずに、別の制御装置により行った。During the endurance test, a slight constant current (for example, 25 μA) is applied between the sensing cell sensing electrode of the oxygen sensor and the oxygen reference electrode with the oxygen reference electrode as a positive electrode, and the oxygen reference electrode and the sensing cell sensing electrode are applied. A voltage was applied between the outer electrode and the inner electrode of the pump cell and a voltage of 10 V was applied to the ceramic heater so that the electromotive force between the electrode and the electrode was a constant value of 0.45 V, and the ceramic heater was put into an operating state. .
However, the engine was controlled by another control device without using the output signal of the oxygen sensor.
【００２５】上記の耐久試験の所定時間経過時、センサ
を８００℃の温度において、酸素濃度１６％のモデル気
体中に置き、且つ上記と同様の条件下、ポンプセル外側
電極と内側電極との間に電圧を印加した。また、同様に
セラミックヒータに１０Ｖの電圧を印加した。このよう
にして、所定の電流量を得るための電圧の変化、言い換
えればポンプセル外側電極と内側電極との間の内部抵抗
の変化を測定した。結果を図３に示す。After a lapse of a predetermined time in the above-mentioned durability test, the sensor was placed in a model gas having an oxygen concentration of 16% at a temperature of 800 ° C., and under the same conditions as described above, between the pump cell outer electrode and the inner electrode. A voltage was applied. Similarly, a voltage of 10 V was applied to the ceramic heater. In this way, a change in voltage for obtaining a predetermined amount of current, in other words, a change in internal resistance between the pump cell outer electrode and the inner electrode was measured. The results are shown in Fig. 3.
【００２６】図３の結果によれば、試料ａは、耐久性の
試験時間とともに徐々に内部抵抗が上昇しているのが分
かる。これは言い換えれば所定の電流量を確保するため
には、徐々に印加電圧を高くしていく必要があることを
意味しており、これは電極の耐久性等からみて好ましい
ことではない。一方、試料ｂの場合は、２０００時間経
過後も内部抵抗はほとんど変化しておらず、本発明の電
極が耐久性に優れた電極であることが分かる。尚、試料
ａのセンサでは、１０００時間経過後辺りから、ポンプ
セル基板との界面において、ポンプセル外側電極の表面
に徐々にＰｔ粒子が析出し始め、電極がポンプセル基板
から浮き上がって剥離してくる現象が観察された。From the results shown in FIG. 3, it can be seen that the internal resistance of the sample a gradually increases with the durability test time. In other words, this means that it is necessary to gradually increase the applied voltage in order to secure a predetermined current amount, which is not preferable from the viewpoint of the durability of the electrodes. On the other hand, in the case of the sample b, the internal resistance hardly changed even after 2000 hours, which shows that the electrode of the present invention has excellent durability. In the sensor of sample a, Pt particles gradually begin to deposit on the surface of the pump cell outer electrode at the interface with the pump cell substrate after about 1000 hours, and the electrode floats from the pump cell substrate and peels off. Was observed.
【００２７】ＰＳＺ配合量と電極の密着強度及び電流
量との相関
粒径１０μｍ、かさ比重３．４のＰｔ粉末１００重量部
に、７、１２、１４、１７、２０、２２、２５及び３０
重量部のＰＳＺを配合した電極の原料を、ポンプセル基
板となるグリーンシートの片面にスクリーン印刷し、同
時焼成して電極を形成した。その後、この電極の中央部
に電極が１ｍｍ角となるように切断部を設け、この切断
部に銀ロウペーストを印刷した。次いで、半田付けによ
ってこの切断部と測定器とを接続し、切断部を垂直方向
に引っ張ってポンプセル基板と電極との密着強度を測定
した。また、上記の電極の原料を用いて、ポンプセル基
板の両面の相対する位置に、幅２．４ｍｍ、長さ４ｍｍ
の一対の電極を設けた試片を準備した。その後、この試
片を大気中、８００℃に設定された炉中に挿入し、電極
間に１．５Ｖの直流電圧を印加して、ポンプセル基板を
通して流れる電流を測定した。結果を図４に示す。Correlation between PSZ blending amount and electrode adhesion strength and current amount 100 parts by weight of Pt powder having a particle size of 10 μm and a bulk specific gravity of 3.4, 7, 12, 14, 17, 20, 22, 25 and 30.
The electrode raw material containing parts by weight of PSZ was screen-printed on one surface of a green sheet to be a pump cell substrate and simultaneously fired to form an electrode. Then, a cut portion was provided in the center of the electrode so that the electrode was 1 mm square, and a silver wax paste was printed on the cut portion. Next, this cut portion was connected to a measuring device by soldering, and the cut portion was pulled in the vertical direction to measure the adhesion strength between the pump cell substrate and the electrode. Further, using the above electrode raw material, the width of 2.4 mm and the length of 4 mm are provided at opposite positions on both surfaces of the pump cell substrate.
A test piece provided with a pair of electrodes was prepared. Then, this test piece was inserted into a furnace set to 800 ° C. in the atmosphere, a DC voltage of 1.5 V was applied between the electrodes, and the current flowing through the pump cell substrate was measured. The results are shown in Fig. 4.
【００２８】図４の結果によれば、密着強度はＰＳＺの
配合量の増加とともに上昇を続けることが分かる。そし
て、ＰＳＺの配合量が１７重量部を越える辺りから密着
強度は２．０ｋｇを上回り、密着性に優れた電極が得ら
れることが分かる。一方、電流量はＰＳＺの配合量が２
２重量部までは高い値であって大きな変化はない。しか
し、ＰＳＺの配合量がそれ以上になると急激に低下し、
ＰＳＺの配合量が３０重量部では、電流量は０となって
しまうことが分かる。From the results shown in FIG. 4, it can be seen that the adhesion strength continues to increase as the PSZ compounding amount increases. Further, it can be seen that the adhesion strength exceeds 2.0 kg from the area where the amount of PSZ compounded exceeds 17 parts by weight, and an electrode having excellent adhesion can be obtained. On the other hand, the amount of current is 2 for PSZ.
The value is high up to 2 parts by weight, and there is no big change. However, when the amount of PSZ added exceeds that amount, it drops sharply,
It can be seen that the current amount becomes 0 when the blending amount of PSZ is 30 parts by weight.
【００２９】図５には、粒径及びかさ比重の異なる３種
類のＰｔ粉末を使用し、上記と同様にしてＰＳＺの配合
量と電流量との相関を評価した結果を示す。その結果に
よれば、粒径が０．５μｍと相当に微小な粒子であって
も、かさ比重が４．５と大きいＰｔ粉末を使用した場合
〔図５の（ｃ）〕は、Ｐｔ粒子相互が容易に連接される
ためか、ＰＳＺの配合量が３０重量部になっても相当な
電流量が確保されていることが分かる。しかし、この電
極では、単位体積当たりの表面積が大きいＰｔ粉末を使
用したため、Ｐｔの昇華、拡散を生じ易く、後記の図７
のように耐久性に劣ったものとなる。。FIG. 5 shows the results of evaluating the correlation between the amount of PSZ compounded and the amount of current in the same manner as above, using three types of Pt powders having different particle sizes and bulk specific gravities. According to the results, even if the particle size is as small as 0.5 μm and Pt powder having a bulk specific gravity as large as 4.5 [(c) in FIG. 5] is used, It can be understood that a considerable amount of current is ensured even if the amount of PSZ compounded is 30 parts by weight, probably because they are easily connected. However, in this electrode, since Pt powder having a large surface area per unit volume was used, sublimation and diffusion of Pt were likely to occur, and therefore, FIG.
The durability is inferior. .
【００３０】一方、粒径は７．６μｍと比較的大きいも
のの、そのかさ比重が２．２と小さいＰｔ粉末を使用し
た場合〔図５の（ｄ）〕は、ＰＳＺの配合量が１５重量
部前後から電流量は低下し始めることが分かる。この場
合、後記の図７において、耐久性に問題はない。これは
使用したＰｔ粉末の単位体積当たりの表面積が小さく、
Ｐｔの昇華、拡散が抑えられるためである。また、粒径
１０μｍ、かさ比重３．４のＰｔ粉末を使用した場合
〔図５の（ｅ）〕は、ＰＳＺの配合量が２５重量部にな
っても電流量は２０ｍＡとなっている。更に、その耐久
時間は後記の図７のように２０００時間を越えている。
このように、後記の図７の結果とも併せ考えれば、Ｐｔ
粉末の粒径及びかさ比重がともに第１発明に特定された
範囲にある場合に、密着性と電流量とのバランスのよ
い、且つ耐久性に優れた電極が得られることが分かる。On the other hand, when Pt powder having a relatively large particle diameter of 7.6 μm and a bulk specific gravity of 2.2 is used [(d) of FIG. 5], the PSZ content is 15 parts by weight. It can be seen that the amount of current begins to decrease from the front and back. In this case, there is no problem in durability in FIG. 7 described later. This is because the used Pt powder has a small surface area per unit volume,
This is because sublimation and diffusion of Pt can be suppressed. When Pt powder having a particle size of 10 μm and a bulk specific gravity of 3.4 is used [(e) in FIG. 5], the current amount is 20 mA even when the blending amount of PSZ is 25 parts by weight. Further, the durability time exceeds 2000 hours as shown in FIG. 7 described later.
Thus, in consideration of the result of FIG. 7 described later, Pt
It can be seen that when both the particle size and the bulk specific gravity of the powder are in the ranges specified in the first invention, an electrode having a good balance between adhesion and current amount and excellent durability can be obtained.
【００３１】ＰＳＺの配合量と耐久性との相関
粒径１０μｍ、かさ比重３．４のＰｔ粉末１００重量部
に、７、１２、１４、１７、２０、２２及び２５重量部
のＰＳＺを配合した原料によって電極が形成された酸素
センサを作製した。この酸素センサについて前記のと
同じ条件で耐久試験を行った。その結果を図６に表す。
尚、耐久性の限界は内部抵抗が初期の２倍になる時間と
した。その結果によれば、ＰＳＺの配合量が７〜２５重
量部の間では、耐久時間はＰＳＺの配合量とともにほぼ
直線的に長くなっていることが分かる。Correlation Between PSZ Blending Amount and Durability 7,12,14,17,20,22 and 25 parts by weight of PSZ were added to 100 parts by weight of Pt powder having a particle size of 10 μm and a bulk specific gravity of 3.4. An oxygen sensor having electrodes formed by the raw materials was produced. A durability test was conducted on this oxygen sensor under the same conditions as described above. The result is shown in FIG.
The limit of durability was the time at which the internal resistance doubled from the initial value. The results show that the durability time increases linearly with the PSZ blending amount when the PSZ blending amount is between 7 and 25 parts by weight.
【００３２】Ｐｔ粉末の粒径と耐久性との相関
粒径０．５、１、２、５、７．６及び１０μｍのＰｔ粉
末１００重量部に、ＰＳＺを２０重量部配合した原料に
よって電極が形成された酸素センサを作製した。この酸
素センサを、排気量２０００ｃｃのガソリンエンジンの
排気管に取り付け耐久性の試験を実施した。試験条件は
前記の場合と同様である。結果を図７に示す。その結
果によれば、Ｐｔ粉末の粒径が２μｍ未満と小さい場合
は、前記の図５に示すように、初期の電流量は十分確保
されることがあるものの、耐久試験の結果では必ずしも
この初期性能が維持されず、比較的短時間で内部抵抗が
高くなってしまうことが分かる。また、Ｐｔの粒径が１
μｍと２μｍとでは耐久時間に大きな差があり、Ｐｔ粒
径が２μｍ以上であれば耐久性に優れた電極が得られる
ことが分かる。Correlation Between Pt Powder Particle Size and Durability 100% by weight of Pt powder having a particle size of 0.5, 1, 2, 5, 7.6 and 10 μm was mixed with 20 parts by weight of PSZ to form an electrode. The formed oxygen sensor was produced. This oxygen sensor was attached to an exhaust pipe of a gasoline engine having a displacement of 2000 cc and a durability test was conducted. The test conditions are the same as above. The results are shown in Fig. 7. According to the result, when the particle diameter of the Pt powder is as small as less than 2 μm, the initial amount of current may be sufficiently secured as shown in FIG. It can be seen that the performance is not maintained and the internal resistance increases in a relatively short time. Also, the particle size of Pt is 1
It can be seen that there is a large difference in the durability time between μm and 2 μm, and an electrode having excellent durability can be obtained when the Pt particle size is 2 μm or more.
【００３３】尚、本発明においては、前記具体的実施例
に示すものに限られず、目的、用途に応じて本発明の範
囲内で種々変更した実施例とすることができる。即ち、
上記の実施例では、Ｙ2 Ｏ3 によって部分安定化された
ＺｒＯ2 を用いたが、Ｙ2 Ｏ3 の代わりに、又はＹ2 Ｏ
3 と共にＣａＯ、ＭｇＯを含有するＺｒＯ2 を使用して
もよい。また、実施例に示した酸素センサ以外の酸素ポ
ンプを利用した他の構成の酸素センサの電極として使用
することもできる。The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention according to the purpose and application. That is,
In the above examples, ZrO 2 partially stabilized by Y 2 O 3 was used, but instead of Y 2 O 3 or Y 2 O 3.
ZrO 2 containing CaO and MgO together with 3 may be used. Further, it can also be used as an electrode of an oxygen sensor having another configuration using an oxygen pump other than the oxygen sensor shown in the embodiment.
【００３４】[0034]
【発明の効果】第１発明の電極によれば、酸素センサの
電極として使用した場合に、温度勾配と酸素ポンプの影
響による電極中のＰｔの移動が抑えられ、長期に渡って
所望の電極性能が維持される。また、第１発明の電極
は、Ｐｔ粉末に特に第４発明のようにポンプセル基板と
同質のＰＳＺを適量配合することにより、同時焼成によ
って容易に全域空燃比センサ等の酸素センサの電極とし
て用いることができる。According to the electrode of the first invention, when it is used as an electrode of an oxygen sensor, the movement of Pt in the electrode due to the influence of a temperature gradient and an oxygen pump is suppressed, and the desired electrode performance is maintained for a long period of time. Is maintained. Further, the electrode of the first invention can be easily used as an electrode of an oxygen sensor such as a global air-fuel ratio sensor by simultaneous firing by mixing Pt powder with an appropriate amount of PSZ of the same quality as the pump cell substrate as in the fourth invention. You can
【図１】本発明の電極を使用した酸素センサを分解した
状態の概略を表す斜視図である（但し、セラミックヒー
タは図示していない。）。FIG. 1 is a perspective view schematically showing a state in which an oxygen sensor using an electrode of the present invention is disassembled (however, a ceramic heater is not shown).
【図２】図１の酸素センサのセンサ部分の縦断面図であ
る。FIG. 2 is a vertical sectional view of a sensor portion of the oxygen sensor of FIG.
【図３】実機による耐久試験において、特定雰囲気下で
測定した内部抵抗の経時変化の、ＰＳＺの配合量による
差異を表すグラフである。FIG. 3 is a graph showing a change in internal resistance with time, which is measured under a specific atmosphere, in a durability test using an actual machine, depending on a blending amount of PSZ.
【図４】電極中のジルコニアの量比と、電極の密着強度
及び電流量との相関を表すグラフである。FIG. 4 is a graph showing the correlation between the amount ratio of zirconia in the electrode and the adhesion strength of the electrode and the amount of current.
【図５】電極中のジルコニアの量比と、Ｐｔ粉末の粒径
及びかさ比重を変化させた場合の電流量との相関を表す
グラフである。FIG. 5 is a graph showing the correlation between the amount ratio of zirconia in the electrode and the amount of current when the particle size and bulk specific gravity of Pt powder are changed.
【図６】電極中のＰＳＺの量比と、実機による耐久試験
における試験時間との相関を表すグラフである。FIG. 6 is a graph showing a correlation between a PSZ amount ratio in an electrode and a test time in a durability test by an actual machine.
【図７】電極中のＰｔ粉末の粒径と、実機による耐久試
験における試験時間との相関を表すグラフである。FIG. 7 is a graph showing the correlation between the particle size of Pt powder in an electrode and the test time in a durability test using an actual machine.
１；ポンプセル基板、１１；ポンプセル外側電極、１１
１；オーバーコーティング、１２；ポンプセル内側電
極、２；測定室形成材、２１；測定室、２２；拡散律速
部、３；センシングセル基板、３１；センシングセル感
知電極、３２；センシングセル酸素基準電極、４；補強
基板、５；セラミックヒータ、５１；発熱部材、５２；
リード部材、５３；セラミックヒータとポンプセル基板
との接合材。1; Pump cell substrate, 11; Pump cell outer electrode, 11
1; Overcoating, 12; Pump cell inner electrode, 2; Measurement chamber forming material, 21; Measurement chamber, 22; Diffusion rate controlling part, 3; Sensing cell substrate, 31; Sensing cell sensing electrode, 32; Sensing cell oxygen reference electrode, 4; Reinforcement substrate, 5; Ceramic heater, 51; Heat generating member, 52;
Lead member, 53; Bonding material between ceramic heater and pump cell substrate.
Claims (4)
粉末を焼成してなる酸素センサ用電極において、上記白
金粉末を１００重量部とした場合に、上記ジルコニア粉
末は１４〜２５重量部であり、上記白金粉末の粒径は２
〜２０μｍであって、且つそのかさ比重は２．５〜４．
２であることを特徴とする酸素センサ用電極。1. An electrode for an oxygen sensor obtained by firing a raw material powder containing platinum powder and zirconia powder, wherein when the platinum powder is 100 parts by weight, the zirconia powder is 14 to 25 parts by weight. The particle size of platinum powder is 2
.About.20 .mu.m and its bulk specific gravity is 2.5 to 4.
2. The electrode for an oxygen sensor, which is 2.
０である請求項１記載の酸素センサ用電極。2. The bulk specific gravity of the platinum powder is 3.0 to 4.
The oxygen sensor electrode according to claim 1, which is 0.
に、上記ジルコニア粉末は１７〜２２重量部である請求
項１又は２記載の酸素センサ用電極。3. The electrode for an oxygen sensor according to claim 1, wherein the zirconia powder is 17 to 22 parts by weight when the platinum powder is 100 parts by weight.
外側電極として用いられる上記酸素センサ用電極におい
て、上記ジルコニア粉末として、上記ポンプセル基板を
形成する部分安定化ジルコニアと同質のジルコニア粉末
を使用した請求項１乃至３のいずれか１項に記載の酸素
センサ用電極。4. The zirconia powder of the same quality as the partially stabilized zirconia forming the pump cell substrate is used as the zirconia powder in the oxygen sensor electrode used as an outer electrode of a pump cell substrate constituting an oxygen sensor. The electrode for an oxygen sensor according to any one of 1 to 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20117996A JP3510050B2 (en) | 1996-07-10 | 1996-07-10 | Electrode for oxygen sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20117996A JP3510050B2 (en) | 1996-07-10 | 1996-07-10 | Electrode for oxygen sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1026603A JPH1026603A (en) | 1998-01-27 |
| JP3510050B2 true JP3510050B2 (en) | 2004-03-22 |
Family
ID=16436669
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20117996A Expired - Fee Related JP3510050B2 (en) | 1996-07-10 | 1996-07-10 | Electrode for oxygen sensor |
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| Country | Link |
|---|---|
| JP (1) | JP3510050B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20150056857A (en) * | 2012-09-25 | 2015-05-27 | 다나카 기킨조쿠 고교 가부시키가이샤 | Sensor electrode, manufacturing method thereof, and metal paste for electrode formation |
| US9245660B2 (en) | 2011-09-27 | 2016-01-26 | Tanaka Kikinzoku Kogyo K.K. | Electroconductive particle and metal paste, and electrode |
| US9556343B2 (en) | 2010-07-12 | 2017-01-31 | Tanaka Kikinzoku Kogyo K. K. | Conductive fine particle and metal paste for electrode formation and electrode |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4795874B2 (en) * | 2006-07-05 | 2011-10-19 | 日本特殊陶業株式会社 | Gas sensor element, gas sensor using the same, and method for manufacturing gas sensor element |
| JP4578556B2 (en) * | 2008-05-12 | 2010-11-10 | 日本特殊陶業株式会社 | Gas sensor and manufacturing method thereof |
| JP6131166B2 (en) | 2012-11-22 | 2017-05-17 | 株式会社デンソー | Electrode for gas sensor and gas sensor element using the same |
-
1996
- 1996-07-10 JP JP20117996A patent/JP3510050B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9556343B2 (en) | 2010-07-12 | 2017-01-31 | Tanaka Kikinzoku Kogyo K. K. | Conductive fine particle and metal paste for electrode formation and electrode |
| US9245660B2 (en) | 2011-09-27 | 2016-01-26 | Tanaka Kikinzoku Kogyo K.K. | Electroconductive particle and metal paste, and electrode |
| KR20150056857A (en) * | 2012-09-25 | 2015-05-27 | 다나카 기킨조쿠 고교 가부시키가이샤 | Sensor electrode, manufacturing method thereof, and metal paste for electrode formation |
| KR101706879B1 (en) * | 2012-09-25 | 2017-02-14 | 다나카 기킨조쿠 고교 가부시키가이샤 | Sensor electrode, manufacturing method thereof, and metal paste for electrode formation |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1026603A (en) | 1998-01-27 |
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