JPH03158754A - Oxygen sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an oxygen sensor for measuring oxygen concentration in the environment, and particularly to a limiting current type oxygen sensor using an oxygen ion conductive solid electrolyte.

Conventionally, as shown in FIG. 2, this type of oxygen sensor has been equipped with metal electrode films 2 (anode 2a, cathode 2a, cathode, 2b), and further the cathode 2
A U-shaped lid 3 is placed on the solid electrolyte plate l on the b side to create a sealed space.
The lid body 3 is further provided with an oxygen diffusion hole 4 that communicates the external space with the closed space.

In this configuration, when a DC voltage is applied between the electrodes 2 after heating the oxygen sensor to an operable temperature, the cathode 2b
An ionization reaction of oxygen molecules occurs, and the ionized oxygen ions move positively towards the anode 2a in the solid electrolyte.
At 2a, a molecularization reaction of oxygen ions occurs and is discharged to the external space. On the other hand, the inflow of oxygen into the closed space is restricted by the diffusion chamber 4 provided on the lid 3, and the inflow of oxygen into the cathode 2b is diffusion-controlled. As a result, the current generated by the movement of oxygen ions in the solid electrolyte t+&1 shows a constant value after a certain voltage as the applied voltage increases, and this constant current is the limiting current.

Since this is approximately proportional to the oxygen concentration in the atmospheric gas, the oxygen concentration can be measured by detecting the limiting current. (For example, JP-A-59-192953, JP-A-60-252254) Problem to be Solved by the Invention The size of the diffusion hole 4 can be set arbitrarily depending on the operating temperature of the oxygen sensor and the magnitude of the limiting current. be done. However, in order to ensure the long-term reliability of the oxygen sensor, it is desirable to keep the operating temperature as low as possible. In the case of a zirconia-based ceramic solid electrolyte, the minimum operating temperature is about 400°C from the viewpoint of oxygen ion transport ability.

In order to obtain a practical limit current value at this operating temperature, the diffusion hole 4 must have a diameter of several μm and an extremely small length. Therefore, when the oxygen sensor is manufactured, there is a concern that dust, foreign matter, etc. may enter the diffusion hole 4 and block it during actual use. As a result, there is a problem that the oxygen sensor becomes inoperable.

The present invention has been made to solve such conventional problems, and an object of the present invention is to provide an oxygen sensor in which the diffusion hole is less likely to be clogged by foreign matter or dust.

Means for Solving the Problems In order to solve the above problems, the oxygen sensor of the present invention includes: a solid electrolyte plate having oxygen ion conductivity; a cathode electrode film formed on one surface of the solid electrolyte plate; A plurality of pairs of an anode electrode film formed on the other surface of the solid electrolyte plate and a pair of starting ends and terminal ends surrounding the cathode electrode film and in contact with the surrounding space are arranged at intervals on the solid electrolyte plate. a spacer, a seal plate disposed on the spacer so as to face the solid electrolyte plate, and a plurality of spacers surrounded by the opposing partition walls of the spacer, the solid electrolyte plate, and the seal plate. It is equipped with a spiral diffusion hole.

Function In the above structure of the present invention, a plurality of spiral diffusion holes each consisting of a pair of starting ends and a terminal end are formed, and the diffusion hole is formed between the solid electrolyte 1rvi and the seal plate, so that a plurality of the plurality of diffusion holes In practical terms, it is almost impossible for all the starting ends to be blocked by foreign matter or dust.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, and FIG. 1(a) is an exploded perspective view of an oxygen sensor, and FIG. 1(a) is a partially cutaway perspective view of an oxygen sensor.

In FIG. 1(a), et al., electrode films 2 are formed on both sides of a solid electrolyte plate 1 having oxygen ion conductivity. Two pairs of spiral spacers 5 are arranged on one surface of the solid electrolyte plate 1, surrounding the electrode membrane 2, and having a pair of starting ends 5I and a terminal end 52 and a ground pair starting ff1i 53 and a terminal end 54 spaced apart from each other. 6 is placed.

The two diffusion holes 71 and 72 are formed in a spiral space surrounded by the opposite partition walls of the spiral spacer 5, the solid electrolyte plate 1, and the seal 6, and oxygen flows through this space to the electrode 1112.
spread to.

For the solid electrolyte plate 1, zirconia-based ceramics, especially zirconia doped with ittria, are often used. The electrode film 2 is composed of platinum, gold, palladium, silver, etc.
It is not particularly limited.

The helical spacer 5 is required to have sufficient heat resistance to withstand the operating temperature of the oxygen sensor and to maintain airtightness between the solid electrolyte plate I and the seal plate 6, and its materials include glass and metal. For the seal [6, a ceramic plate made of zirconia ceramic, forsterite, or the like is used. In addition, solid electrolyte
The thermal expansion coefficients of IrFil, helical spacer 5, and seal plate 6 are selected to have similar values as much as possible.

Although two starting edges 51, 53 are shown in the embodiment shown in FIG. 1, more than two starting edges can easily be formed. As described above, since the oxygen sensor of the present invention has a plurality of starting ends, it is virtually impossible for all the starting ends to be blocked by foreign matter or dust. Furthermore, instead of the circular seal plate 6 shown in FIG. 1, a seal #Ii6 having the same shape as the solid electrolyte plate 1 is used, and the starting end 51. It is preferable to place it on the inside, starting fi51.5
Foreign matter and dust may enter solid electrolyte foreign matter 1 and seal plate 6.
This is because it is reduced by Although the above explanation uses a rectangular solid electrolyte Fit, it is not limited to a rectangular shape as long as the starting ends 51 and 53 are arranged inside the ends of the solid electrolyte plate 1 and the seal plate 6. That should be obvious.

Some of the plurality of starting ends may be blocked by foreign matter or dust. In this case, although the limiting current value decreases, a constant limiting current is obtained through the remaining diffusion hole consisting of the starting end and the ending end. This limiting current value changes with respect to oxygen concentration at the same rate as before occlusion. Therefore, if the oxygen concentration in the atmosphere can be used as a standard state, it can be put to practical use by calibrating in the atmosphere. For example, when used in tunnel construction, it can be easily calibrated in the atmosphere before entering the tunnel. In this way, the oxygen sensor of the present invention can have a long service life.

Effects of the Invention As described above, the oxygen sensor of the present invention provides the following effects.

(1) Since it has a plurality of starting ends, clogging of the starting ends due to foreign matter or dust can be reduced.

(2) Even if some of the multiple starting ends are blocked by foreign matter or dust, a constant limiting current can be obtained through the diffusion holes made up of the remaining starting ends and ending ends. Longer service life can be achieved.

[Brief explanation of the drawing]

FIG. 1a is an exploded perspective view of an oxygen sensor showing an embodiment of the present invention, and FIG. 2 is a partially cutaway perspective view of the same, and FIG. 2 is a sectional view of a conventional oxygen sensor. 5...Solid electrolyte
... Termination, 71.72 ... Diffusion hole.

Claims (2)

[Claims] (1) a solid electrolyte plate having oxygen ion conductivity; a cathode electrode film formed on one surface of the solid electrolyte plate;
A plurality of pairs of an anode electrode film formed on the other surface of the solid electrolyte plate and a pair of start and end ends surrounding the cathode electrode film and in contact with the surrounding space are spaced apart from each other on the solid electrolyte plate. a plurality of spacers, a seal plate disposed on the spacer so as to face the solid electrolyte plate, a plurality of spacers surrounded by the opposed partition walls of the spacer, the solid electrolyte plate, and the seal plate; Oxygen sensor consisting of a helical diffusion hole. (2) The oxygen sensor according to claim 1, wherein the starting end is located inside the ends of the solid electrolyte plate and the seal plate.