JPH037812Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an oxygen concentration detector that detects the oxygen concentration of automobile exhaust gas using an oxygen ion conductive solid electrolyte.

Conventional configuration and problems thereof Conventionally, this type of oxygen concentration detector has been configured as shown in FIG. That is, a crucible-shaped solid electrolyte tube 1 having a stepped portion on the outside is provided with an inner electrode 2 and an outer electrode 3 made of catalytic material such as platinum on the inner and outer surfaces, and the outer electrode 3 is coated with a ceramic coating 4 for the purpose of protection. Electrical conduction is established between the casing 6 and the inner electrode 2 and the terminal 10 through graphite powder 7 in the uncoated body. The graphite powder 7 is then applied to the solid electrolyte tube 1.
The exhaust gas from the automobile that touches the outer electrode 3 of the terminal 3 is prevented from entering the inner side, and the air flows into the inner electrode 2 as a reference gas through the air hole 11 of the terminal 10 and contacts the outer electrode 3. 2, a voltage is generated according to the difference in oxygen concentration between the gases that come into contact with the two. In the figure, 8 and 9 are metal rings.

In this case, the shape of the solid electrolyte tube 1 requires a complicated manufacturing process, and also requires a large investment in manufacturing equipment such as a hydrostatic press and a polishing machine using diamond. Due to manufacturing problems regarding the inner diameter and wall thickness of the solid electrolyte tube 1, there is a limit to miniaturization including low cost, which is a market demand.

Purpose of the Invention The present invention aims to eliminate such conventional drawbacks, and to provide an oxygen concentration detector that reduces the manufacturing cost of a solid electrolyte tube and facilitates miniaturization.

Structure of the invention In order to achieve this purpose, the oxygen concentration sensor of the invention uses a straight tube with both ends open, which can be manufactured by extrusion molding as a solid electrolyte tube, and the open end on the exhaust gas side is bonded with heat-resistant ceramic. The structure is such that the sealing agent is used to cover a part of the ceramic coating that protects the outer electrode.

With this configuration, solid electrolyte tubes can be manufactured using an extrusion molding method, increasing mass productivity.
Low cost. Sealing agents such as ceramic adhesives that prevent exhaust gas from entering the solid electrolyte tube inner pores are strong adhesives that can withstand loads such as thermal cycles and vibrations when they are configured to cover a portion of the uneven ceramic coating. It will have power.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 2. Note that parts in FIG. 2 that are the same as those in FIG. 1 are given the same numbers.

In FIG. 2, the oxygen ion conductive solid electrolyte tube 12 has a straight tube shape made by extrusion molding, and has inner electrodes 2 made of platinum on the inner and outer surfaces.
An outer electrode 3 is provided, and the portion of the outer electrode 3 that comes into contact with exhaust gas is coated with a ceramic coating 4 by plasma spraying. The inner electrode 2 is electrically connected to the terminal 10 with high-temperature solder 14, and the outer electrode 3 is electrically electrically connected to the casing 6 using graphite powder 7. In order to prevent the exhaust gas from entering the inner electrode 2, the end face of the solid electrolyte tube 12 on the exhaust gas side is sealed with a ceramic adhesive 13, which also partially covers the ceramic coating 4. Furthermore, the atmosphere is introduced into the inside of the solid electrolyte tube 12 through the air hole 11 of the terminal 10.
is fixed by a ceramic adhesive 15.

By using the straight solid electrolyte tube 12 in this manner, the manufacturing process of the solid electrolyte tube 12 is simplified by the extrusion molding method, and the investment in equipment is also reduced. Further, strong adhesion can be obtained by sealing the end face of the solid electrolyte tube 12 by covering a portion of the uneven ceramic coating 4 with the ceramic adhesive 13.

In addition, heat-resistant ceramic adhesive 1
3 and 15 may be a sealant such as glass.

Effects of the invention As described above, according to the oxygen concentration detector of the invention, by sealing the open end of the solid electrolyte tube on the exhaust gas side with a heat-resistant sealant, it is possible to Solid electrolyte tubes can be used, significantly lowering manufacturing costs. Furthermore, by using a tube with both ends open, it is possible to use thermal decomposition methods such as immersion instead of sputtering or vapor deposition when forming electrodes, making it possible to form electrodes even in solid electrolyte tubes with small inner pores. Therefore, we can expect greater miniaturization than before. Moreover, by covering a portion of the uneven ceramic coating with this sealant, the adhesive force is increased, and a highly reliable sealing can be achieved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional oxygen concentration detector.
FIG. 2 is a sectional view showing an embodiment of the oxygen concentration detector according to the present invention. 2...Inner electrode, 3...Outer electrode, 4...Ceramic coating, 12...Solid electrolyte tube, 1
3... Sealant (ceramic adhesive).

Claims (1)

[Scope of utility model registration request] A catalytic electrode such as platinum is provided on the surface of a straight oxygen ion conductive solid electrolyte tube with both ends open.
The outer electrode is protected with a ceramic coating, and the open end surface of the solid electrolyte tube on the exhaust gas side is sealed with a sealant such as a heat-resistant ceramic adhesive, and a part of the ceramic coating is sealed with the sealant. An oxygen concentration detector characterized by covering.