JPS6057538B2 - How to seal the oxygen sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen sensor used primarily to measure the oxygen concentration of automobile engine exhaust gas.

This type of oxygen sensor has conductive inner and outer electrodes provided on the inner and outer surfaces of a solid electrolyte container made of an oxygen ion conductive material, an internal standard substance filled in the solid electrolyte container, and a ceramic layer placed on top of the internal standard substance. Many types are sealed with a glass layer.

However, this type of oxygen sensor is installed in a car and is used under extremely harsh conditions, such as being exposed to high-temperature exhaust gas while being subjected to constant vibrations while driving, and conventional oxygen sensors are not used. The degree of sealing gradually decreases, and the inside of the solid electrolyte container is exposed to exhaust gas, water, dust, etc., and the internal standard material and internal electrodes are denatured, making it difficult to accurately detect the oxygen concentration in the exhaust gas.

The purpose of the present invention is to improve the degree of sealing of an oxygen sensor and to maintain a high degree of sealing for a long period of time. The main idea is that the pressing force is applied directly to the inner wall of the solid electrolyte container when heating and softening the high melting point glass to improve its throwing power and adhesion to the ceramic layer, internal electrodes, etc. be.

To explain the present invention with reference to an embodiment shown in the drawing, 1 is a solid electrolyte container, and a step IC is provided at the inlet portion, and the material thereof is mainly based on zirconia, preferably zirconia. 8-10 mol % of yttrium oxide is added as a stabilizer.

A thin film of platinum or an alloy of platinum and gold, palladium, rhodium, etc. is provided on the inner and outer surfaces of the solid electrolyte container 1, and these are used as inner and outer electrodes IA and IB. The metal thin film is provided by means such as chemical plating, electroplating, and vapor deposition. The solid electrolyte container 1 contains a metal-metal oxide such as Ni-NiO, Cu-CuO, Fe-FeO as an internal standard substance 2.
The mixed powder is filled. On top of internal standard material 2,
A high melting point glass layer 4 is placed via the ceramic lower layer 3A. The materials used for the ceramic layer include alumina, zirconia, chromium, zircon, and titanium, and the materials used for the high melting point glass layer include silica, soda lime, silicic acid, lead, borosilicate, and aluminum silicate. A glass having a thermal expansion coefficient approximately equal to that of the solid electrolyte container and the ceramic layer is desirably selected. Here, the ceramic lower layer 3A prevents direct contact between the high melting point glass layer 4 and the internal standard substance 2, and prevents a reaction between the high melting point glass and the internal standard substance from denaturing the internal standard substance. There are things you can do to prevent it.
On top of the high melting point glass layer 4, there is further a ceramic upper layer 3B.
is placed.

The ceramic upper layer is also formed of the same material as the ceramic lower layer, and functions as a pressing surface for pressing the high melting point glass. On the bottom of the ceramic upper layer 3B,
It is desirable to weld or sandwich a glass layer 3C of the same quality as the high melting point glass layer 4. If you do this,
The adhesion between the ceramic upper layer 3B and the high melting point glass layer 4 becomes extremely good. Furthermore, the ceramic upper layer 3B may be wetted with a similar glass. To seal the oxygen sensor, the high melting point glass layer 4 is heated to a temperature higher than the softening point of the high melting point glass while being pressed in the direction of arrow A through the ceramic upper layer 3B.

In this way, the high melting point glass flows and surrounds the inner wall of the ceramic upper and lower layers 3A, 3B1 and the solid electrolyte container 1 as shown in FIG. Penetrate and diffuse. On this occasion,
Since a pressing force is directly applied to the stepped portion 1C of the solid electrolyte container 1, the high melting point glass spreads, wets, and permeates/diffuses extremely well in this portion. Furthermore, the stepped portion 1C
The adhesion can be further improved by removing the internal electrode 1A and performing a pretreatment of baking conductive glass thereon. In addition to this embodiment, in order to apply the pressing force directly to the inner wall of the solid electrolyte container 1, a tapered portion 1''.C may be formed at the entrance of the solid electrolyte container 1 as shown in FIG. .The present invention has the following features:
As described above, when filling the solid electrolyte container 1 with inner and outer electrodes on the inner and outer surfaces and sealing it with a high melting point glass layer through the ceramic lower layer, the solid electrolyte container 1 is pressed through the ceramic upper layer. A stepped or tapered part is provided at the entrance of the solid electrolyte container so that pressure is applied and the pressing force is applied directly to the inner wall of the solid electrolyte container, which prevents the high melting point glass from sticking to the inner wall of the solid electrolyte container and the upper and lower ceramic layers. The components of the high melting point glass layer smoothly permeate and diffuse into the inner wall of the solid electrolyte container, especially at the stepped or tapered portions, providing good adhesion.

Therefore, the sealability and sealability of the oxygen sensor are greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention before sealing, and FIG. 2 is a cross-sectional view of another embodiment after sealing.

Claims (1)

[Claims] 1. An internal standard substance is filled in a solid electrolyte container with inner and outer electrodes provided on the inner and outer surfaces, a high melting point glass layer is placed on top of it via a ceramic lower layer, and a ceramic upper layer is further placed on top of it. , oxygen which improves the throwing power and adhesion of the high melting point glass to the ceramic lower layer, the ceramic upper layer and the inner wall of the solid electrolyte container by heating and softening the high melting point glass layer while pressing it through the ceramic upper layer. In the sensor sealing method, a step or a tapered portion is provided at the inlet of the solid electrolyte container so that the pressing force is directly applied to the inner wall of the solid electrolyte container, and a shape that fits into the step or taper is provided in the upper ceramic layer. A method for sealing an oxygen sensor, comprising: providing a sealing method for an oxygen sensor;