JPH02280043A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To reduce the measuring time of oxygen concn. by incorporating a ceramic having ionic conductivity into the calcined body of crystallized glass as a sealing member covering a cathode plate and electrically connecting the sealing member and the cathode plate. CONSTITUTION:The cathode plate 12 is provided on the front of an ionic conductor 10 and an anode plate 13 on the rear. The sealing member 16 forming a space 15 is furnished above the cathode plate 12 and brought into contact with a cathode conductive part 14. The member 16 is formed by the crystallized glass which has been heated and calcined above a specified temp. and contains a ceramic having specified ionic conductivity. Accordingly, when a voltage is impressed on the electrodes 12 and 13 and the oxygen concn. is measured by the limiting current value, the time until the limiting current value is reached is reduced, and the response characteristic in the concn. measurement is improved. The measuring time of oxygen concn. is reduced in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a limiting current type oxygen sensor, and particularly relates to the structure of an oxygen sensor with excellent response.

[Prior Art] In recent years, limiting current type oxygen sensors made of stabilized zirconia have been put into practical use, and their performance is being improved.

This limiting current type oxygen sensor will be explained with reference to FIG. In the figure, the symbol l is an ionic conductor. This ion conductor I is formed into a disk shape with a predetermined thickness, and a gas diffusion 42 is formed in the center thereof so as to penetrate from the front and back. Further, a negative electrode plate 3 is provided on the front surface of the ion conductor l, and a negative electrode plate 3 is provided on the back surface.
A positive electrode plate 4 is provided. A sealing member 6 is provided above the negative electrode plate 3 so that a space 5 having a predetermined capacity is formed. This sealing member 6 is about tot
Stabilized zirconia (with a volume resistivity of about oΩcm)
For example, it is made of a solid electrolyte material such as Z ro , -3mol%ytos).

Further, one end portion of the cathode conduction portion 7 is connected to the negative electrode plate 3, and the other end portion extends outside the sealing member 6 and extends along the outer surface of the sealing member 6. It has reached this point.

The sensor element having the above configuration is provided with a circuit 8 . The circuit 8 is connected to the outer end of the cathode conduction section 7 and the positive electrode plate 4, and applies a voltage between the negative electrode plate 3 and the positive electrode plate 4 by a power source.

When measuring oxygen concentration using the above oxygen sensor,
First, the oxygen sensor having the above configuration is installed at a measurement location, and a predetermined voltage is applied between the negative electrode plate 3 and the positive electrode plate 4 using a power source. In this way, oxygen molecules in the space 5 combine with electrons at the contact surface between the negative electrode plate 3 and the ion conductive plate 1, become oxygen ions, move inside the ion conductor 1, and circuit the circuit. A current flows through 8.

Then, the oxygen ions emit electrons at the contact surface between the ion conductor I and the positive electrode plate 4, turn into oxygen molecules, and flow out to the outside.

At this time, the space 5 also has gas diffusion holes 2, or the ionic conductor 1 and the negative electrode plate 3, due to the pumping action. External measurement air is allowed to flow in through the holes in the positive electrode plate 4.

By further increasing the voltage applied from the power supply, the current flowing through the circuit 8 reaches the limit current in accordance with the oxygen concentration, and the value of the ammeter A becomes constant, and the current of the ammeter A at this time
And the oxygen concentration is measured based on the data of the voltmeter V.

In order to improve the response of this oxygen sensor, various improvements have been attempted, such as lowering the operating temperature, making the ionic conductor zirconia a thinner film, and improving the gas diffusion holes, but there are ways to easily improve the response. Although the principle is unknown, as shown in FIG.
We have discovered that a phenomenon in which the response of the sensor improves can be observed by extracting the sensor's response to the outside.

[Problems to be Solved by the Invention] However, the oxygen sensor having the above configuration does not include the sealing member 6.
However, since the oxygen sensor itself cannot be easily fired into a predetermined shape, and the oxygen sensor itself is very small, it takes a lot of effort to process the cathode conduction part 7, making it difficult to mass-produce it. It had the disadvantage of being.

In this case, in order to solve the above-mentioned drawbacks, there is a method using crystallized glass that can be easily fired into a predetermined shape as a material for forming the sealing member 6, but this crystallized glass itself is The problem was that it was difficult to improve the concentration response characteristics of the oxygen sensor due to its high insulation properties.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an oxygen sensor that has excellent concentration response characteristics and that can be easily mass-produced.

[Means for solving the problem] On the front and back surfaces of a porous ionic conductor made of a solid electrolyte,
In an oxygen sensor comprising an electrode and a sealing member provided on one surface of the ionic conductor to cover one of the electrodes provided on the ionic conductor, the sealing member is a crystallized material containing an ionic conductive substance. It is characterized by the use of a fired body made of glass.

[Function] According to the present invention, a ceramic having low insulating properties (
In particular, by incorporating ion-conductive materials (mainly ion-conductive materials) and providing electrical continuity between the sealing member and each electrode plate, its action improves the response characteristics of oxygen concentration when measuring oxygen concentration. I can do that.

[Example] Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 10 is an ion conductor. The ionic conductor 10 is made of stabilized zirconia (for example, Z r
It is a porous material composed of a solid electrolyte such as ot-8mol%yto3). This ion conductor 10 is formed into a disk shape with a predetermined thickness,
A gas diffusion hole 11 is formed in the center thereof, passing through the front and back sides.

The above-mentioned ion conductor 10 is provided with a negative electrode plate 12 on the front side and a positive electrode plate I3 on the back side so as to cover the gas diffusion holes II.

These negative electrode plate 12 and positive electrode plate 13 are formed by applying platinum paste or the like, and are porous due to gaps between platinum particles.

As shown in FIG. 2, the negative electrode plate 12 has a cathode conduction portion 14 connected to a part of its outer periphery. Further, a sealing member 16 that forms a space 15 of a predetermined capacity is provided on the upper part of the negative electrode plate 12 by firing, and is in contact with the cathode conducting portion 14 so as to be electrically conductive.

The sealing member I6 uses crystallized glass that is fired by heating to a predetermined temperature or higher, and is made of ceramic (ionically conductive material) 16a, 16 with low insulation properties.
About 20 wt% of a... is contained. As these ceramics 16a, 16a..., for example, Z ro
Stabilized zirconia powder such as t-8not%Y, 03 is used. Moreover, this sealing member 16 is made of ceramic +
By containing 6a, 16a, etc., the volume resistivity ρ is approximately 10 3 to 1 OI 3 ΩCff1.

Here, in the manufacturing process of the main body of the oxygen sensor, there is a step in which a space 15 is formed at the upper part of the negative electrode plate 12 as described below. You can use it. According to this method, when firing the sealing member 16, a heat-resistant material such as carbon black that can be decomposed and volatilized is applied to the upper part of the negative electrode plate 12, and then the sealing member 16 is
Apply. Then, by heating the sealing member 16 to fire it, the sealing member 16 is fired, and the heat-resistant material (carbon black) is decomposed and volatilized, and is volatilized from the gas diffusion hole It to the negative electrode plate 12. A space 15 having a predetermined capacity is formed above the .

In the oxygen sensor having the above configuration, a circuit 17 is wired to the positive electrode plate 13 and the cathode conduction portion 14, as shown in FIG. This circuit I7 includes a voltmeter V and an ammeter A.
A predetermined voltage is applied between the negative electrode plate 12 and the positive electrode plate 13 by a power source.

When measuring oxygen concentration using the above oxygen sensor,
Measured using the same procedure as before, when the limiting current is reached,
The concentration of oxygen is measured based on the data of ammeter A and voltmeter V.

Here, the sealing member 16 is made of ceramic lubricant having low insulation properties.
Due to the inclusion of Ga and 16a, it has conductivity and is electrically connected to the negative electrode plate 12, so during the above measurement, the current limit is reached due to some action or effect of the above. The time required for this is significantly reduced, and oxygen concentration can be measured quickly.

The ceramics 16a, 16a, etc. contained in the sealing member 16 of the above embodiment may be ion-conductive metal oxides (for example, zirconia, ittria, bismuth oxide, etc.).

1 Effect of invention] According to this invention, the following effects can be obtained.

(2) By blending ion-conductive ceramic into highly insulating crystallized glass to increase ion conductivity, we were able to improve the response characteristics of the oxygen sensor's concentration measurement. This made it possible to significantly shorten the time required to measure oxygen concentration.

(2) Since crystallized glass, which can be easily fired by heating, is used, the production of the oxygen sensor itself becomes easy, and therefore mass production of oxygen sensors becomes possible.

[Brief explanation of drawings]

1 and 2 are views explaining the present invention in detail, FIG. 1 is a sectional view explaining the structure of the oxygen sensor of the present invention, and FIG. 2 is a top view of the oxygen sensor of the present invention. It is a diagram. FIG. 3 is a sectional view illustrating a conventional oxygen sensor. lO...Ion conductor, ■2...Negative electrode plate, 13...Positive electrode plate,

Claims (1)

[Claims] Electrodes are provided on the front and back surfaces of an ionic conductor made of a solid electrolyte, and a sealing member is provided on one surface of the ionic conductor to cover one of the electrodes provided on the ionic conductor. An oxygen sensor characterized in that the sealing member is a fired body made of crystallized glass containing an ion-conductive substance.