JPS6031259B2 - 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 constantly vibrated and exposed to high-temperature exhaust gas while driving.
Conventional oxygen sensors gradually lose their seal during use,
If the inside of the solid electrolyte container is exposed to exhaust gas, water, dust, etc., the internal standard material and internal electrodes will be 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 maintain a high degree of sealing for a long period of time. The main idea is to heat and soften the high melting point glass, thereby improving its throwing power and adhesion to the ceramic layer, internal electrodes, etc. of the high melting point glass.

The present invention will be described with reference to an embodiment shown in the drawings. Reference numeral 1 denotes a solid electrolyte container, which is mainly made of zirconia, and preferably has 8 to 10 mol % of yttrium oxide added to the zirconia as a stabilizer.

A thin film of platinum, 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 plating. The solid electrolyte container 1 contains a metal-metal oxide, such as Ni-Ni○, Cu-Cu0, Co-Coo, as an internal standard substance 2.
A mixed powder of Fe-Fe○ is filled. A high melting point glass layer 4 is placed on top of the internal standard material 2 via a ceramic lower layer 3A. The material used for the ceramic layer is alumina. Zirconia, chromium, zircon, titanium, etc., and the material used for the high melting point glass layer is glass containing silica, lime, silicic acid, lead, borosilicate, aluminum silicate, etc. is selected to have a coefficient of thermal expansion substantially equal to that of the solid electrolyte container and the ceramic layer. 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. It is intended to prevent A ceramic upper layer 3B is further placed on top of the high melting point glass layer 4.

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. However, in order to improve the sealing performance of the oxygen sensor, it is preferable that the ceramic upper layer Make the vertical length of 3B larger than the horizontal length. Thus, the effective sealing thickness increases and the degree of sealing improves. The ceramic upper and lower layers 3A and 3B are
In order to further improve the adhesion with the high melting point glass layer 4, it is desirable to wet at least the supporting surface with the high melting point glass layer 4 with the same type of glass as the high melting point glass layer 4.

In order 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 failure through the ceramic upper layer 3B.

Heating can be done by placing the entire oxygen sensor in a furnace, but this method heats the entire oxygen sensor, so
The solid electrolyte container 1 may be deformed or cracked. In order to prevent this, the heating rate must be sufficiently slowed down or two-stage heating must be performed, which is a cumbersome process. A preferred method is to heat only the high melting glass portion with a torch. Since the entire solid electrolyte container is not heated in this manner, the high melting point glass can be softened and sealed quickly and easily without fear of deformation or cracking. Third
As shown in the figure, in the case of heating with the torch 5, the high melting point glass itself is also partially heated, so the gas does not form with the high melting point glass layer until the high melting point glass layer completely seals the solid electrolyte container. It can pass through the gap between the solid electrolyte container and the inner wall. Therefore, the moisture, carbon dioxide, etc. in the solid electrolyte container can be forced out by heating and pressing force with a torch, and the air bubbles contained in the high melting point glass layer can be extinguished. In this way, the high melting point glass layer 4 flows by being heated and softened while being pressed, and as shown in FIG. The components of the high melting point glass layer 4 permeate and diffuse through these surfaces, making it possible to obtain extremely high adhesion.

[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.
FIG. 3 is a cross-sectional view of a state in which the seal is being sealed by torch heating. In the diagram: 1... Solid electrolyte container, 2...
Internal standard substance, 3A...ceramic lower layer, 3
B...Ceramic upper layer, 4...High melting point glass layer, 6...Torch. 1 figure, 2 figures, 3 figures

Claims (1)

[Scope of Claims] 1. An internal standard substance is filled in a solid electrolyte container provided with inner and outer electrodes on the inner and outer surfaces, and a high melting point glass layer is placed on top of it with a ceramic lower layer interposed therebetween. By placing the upper layer and heating and softening the high melting point glass layer while pressing it through the ceramic upper layer, 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 are improved. A method for sealing an oxygen sensor characterized by improving performance. 2 Fill a solid electrolyte container with inner and outer electrodes on its inner and outer surfaces, place a high melting point glass layer on top of it through a ceramic lower layer, and then place a ceramic upper layer on top of it. , an oxygen sensor that 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 a solid electrolyte container by heating and softening the high melting point glass layer while pressing it through the ceramic upper layer. A method for sealing an oxygen sensor, characterized in that the vertical length of the ceramic upper layer is larger than the horizontal length. 3 Fill a solid electrolyte container with inner and outer electrodes on its inner and outer surfaces, place an internal standard substance on top of it, place a high melting point glass layer through a ceramic lower layer, and then place a ceramic upper layer on top of it. , an oxygen sensor that 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 a solid electrolyte container by heating and softening the high melting point glass layer while pressing it through the ceramic upper layer. A method for sealing an oxygen sensor, characterized in that only a portion of the high melting point glass layer is heated and softened with a torch.