Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2001-07-31
2004-06-08
Olsen, Kaj K. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S424000
Reexamination Certificate
active
06746586
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a multi-layer gas sensor element and a gas sensor including the element. More particularly, the present invention relates to a multi-layer gas sensor element including a porous body, which element produces minimal warpage and does not suffer exfoliation, cracking, etc.; i.e., which element exhibits high durability; and a gas sensor including the gas sensor element, which sensor is highly resistant to poisoning by exhaust gas.
BACKGROUND OF THE INVENTION
Conventional multi-layer gas sensor elements (hereinafter referred to simply as “elements”) have been employed in a gas sensor (such as an oxygen sensor, an HC sensor, or an NO
x
sensor) for detecting a specific component contained in exhaust gas of, for example, an internal combustion engine, and measuring the concentration of the component. In some cases, such a gas sensor element includes a porous body for covering a detection electrode which is brought into contact with a gas to be detected, in order to protect the detection electrode from poisoning. However, warpage of conventional multi-layer gas sensor elements including a porous body has not heretofore been satisfactorily prevented. Therefore, conventional gas sensor elements have tended to suffer cracking due to such warpage.
SUMMARY OF THE INVENTION
The present invention contemplates solving the above-mentioned problems, and an object of the present invention is to provide a multi-layer gas sensor element including a porous body, which element produces minimal warpage and does not suffer exfoliation, cracking, etc.; i.e., which element exhibits high durability; and a gas sensor including the gas sensor element, which sensor exhibits high durability. Al
2
O
3
can be used as the ceramic component for realization of.
Accordingly, the present invention provides a multi-layer gas sensor element comprising a solid electrolytic member, a substrate, and a porous member, wherein each of the substrate and the porous member has a thickness greater than that of the solid electrolytic member with respect to a lamination direction; the substrate and the porous member face each other and sandwich the solid electrolytic member; a ceramic component constituting the substrate in the highest volume percent thereof is the same as the ceramic component constituting the porous member in the highest volume percent thereof; and the volume percent (R2) of the ceramic component contained in the porous member is 80% or more the volume percent (R1) of the ceramic component contained in the substrate. Characteristic features of the multi-layer gas sensor element reside in minimization of the differences in shrinkage percentage between the substrate and the porous member during firing and the difference in thermal expansion therebetween during use.
As another aspect of the invention, in the gas sensor element of the present invention, when the mean grain size of crystals constituting the substrate is referred to as “a1” and the mean grain size of crystals constituting the porous member is referred to as “a2,” the value A represented by the equation
A=a
1
/a
2 (1)
preferably falls within a range between 0.9 and 5 inclusive, more preferably 1.0≦A≦3.25, most preferably 1.0≦A≦2.0. When the value A falls outside a range between 0.9 and 5 inclusive, warpage of the gas sensor element may fail to be satisfactorily prevented.
REFERENCES:
patent: 4221650 (1980-09-01), Friese et al.
patent: 4595485 (1986-06-01), Takahashi et al.
patent: 4642174 (1987-02-01), Shibata
patent: 4661234 (1987-04-01), Takahashi et al.
patent: 4798693 (1989-01-01), Mase et al.
patent: 5522979 (1996-06-01), Tatumoto
patent: 0059933 (1982-09-01), None
patent: 0059933 (1985-08-01), None
patent: 0686847 (1995-12-01), None
Practical Handbook of Materials Sciene, Charles Lynch (ed.), pp. 299,310,and 311, 1989.
Awano Shinya
Hayashi Hiroyuki
Kuroki Yoshiaki
Mabuchi Tomohiro
Yanagi Kunio
NGK Spark Plug Co. Ltd.
Olsen Kaj K.
LandOfFree
Multi-layer gas sensor element and gas sensor comprising the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-layer gas sensor element and gas sensor comprising the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-layer gas sensor element and gas sensor comprising the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3321236