JPH03218454A - Threshold current type 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 Industrial Application The present invention relates to an oxygen sensor for measuring the oxygen concentration in an atmospheric gas, and particularly relates to a limiting current type oxygen sensor using an oxygen ion conductive solid electrolyte. .

2. Description of the Related Art Conventionally, this type of oxygen sensor has electrodes lII2 (an anode 2a, a cathode 2b), furthermore, a U-shaped lid body 3 for forming a sealed space is arranged on the solid electrolyte plate l on the side of the cathode 2b, and furthermore, an external space and a sealed space are connected to the bud body 3. The structure includes an expansion hole 4 for oxygen. Note that the diffusion holes 4 are formed in a size that allows a smaller amount of oxygen to be diffused than the oxygen delivery capacity of the cathode 2b. In this configuration, after heating the oxygen sensor to an operable temperature, when an Ilf current voltage is applied between the electrodes 2, the cathode 2
An ionization reaction of oxygen molecules occurs at b, and the ionized oxygen ions move toward the anode 28 in the solid electrolyte plate l, and a molecularization reaction of oxygen ions occurs at the anode 2a, and is discharged to the outside space. On the other hand, the inflow of oxygen into the closed space is prevented by the lid 3.
The diffusion hole 4 provided in the # electrode 2b restricts the oxygen flow into the # electrode 2b, and the flow of oxygen into the # electrode 2b becomes diffusion-controlled. As a result, the isoelectrolytic T plate l
The electric current generated by the movement of oxygen ions in
As the applied voltage increases, it shows a constant value after a certain voltage. This constant 1 current is the limiting current. Is this oxygen in the atmospheric gas? Since it is approximately proportional to 111 degrees, the limit 1Ii. Oxygen concentration can be measured by detecting the flow. (For example, JP-A-59-192953, JP-A-60-252254) The diffusion hole 4
Ceramic materials are often used for the material of the lid body 3 from the viewpoint of heat resistance and corrosion resistance. The size of the diffusion hole 4 is arbitrarily set depending on the operating temperature of the oxygen sensor and the magnitude of the limiting current. However, to ensure long-term reliability of oxygen sensors, it is desirable to keep the operating temperature as low as possible. A solid electrolyte made of zirconia ceramic has a minimum recommended temperature of about 400° C. from the viewpoint of oxygen ion transport ability.

In order to obtain a practical limiting current value at this operating temperature, the diffusion hole 4 must have an extremely small diameter of several +17 m and a length of 100 m. Therefore, it is difficult in practice to accurately drill diffusion holes 4 in ceramic materials, and the disadvantages are that variations in characteristics become large, and that productivity is poor due to micromachining, resulting in high costs. was there. In order to solve this drawback, the inventors have developed an oxygen ion conductive solid electrolyte plate having electrode films formed on both sides, and a starting end and a terminal end that surround one of the electrode films and are spaced apart from each other on the solid electrolytic T-plate. a helical spacer disposed so as to have the solid electrolytic W plate; and a sealing plate disposed on the helical spacer to face the solid electrolytic W plate; We have developed a limiting current type oxygen sensor with a configuration in which a diffusion hole is formed surrounded by an electrolyte plate and the seal plate. In this limit current type oxygen sensor, the spiral diffusion hole is formed at the same time when the a-helical spacer, the solid electrolyte T#Fi, and the seal plate are attached, so the diffusion hole of the conventional limit current type oxygen sensor is different from that of the conventional limit current type oxygen sensor. Like this, there is no need for complicated hole drilling, and it is suitable for mass production. In addition, since the spiral diffusion hole is formed around the electrode membrane, the diffusion hole can be designed with a large length and features such as excellent dimensional accuracy. Problem to be Solved by the Invention By the way, as in the limiting current type oxygen sensor invented by the inventors, the diffusion hole is formed by adhering the screw*a spacer, the solid electrolytic plate, and the sealing plate, and the bonding Good or bad influences the characteristics. In other words, if the diffusion hole is well formed, the limit current can be obtained, but if the filling is bad and there is a partial contact failure, the limit tura cannot be obtained, and in the case of IIklm, the diffusion hole is closed and the ion current is reduced. This results in a situation where the flow does not flow. The present invention provides a new configuration for the shape of the helical spacer in order to eliminate the above-mentioned bonding defects.

Means for Solving the Problems In order to solve vI#4 above, the oxygen sensor of the present invention has the following features:
an oxygen ion conductive solid electrolyte plate having an electrode film formed on both sides; a spiral spacer surrounding one of the electrode films and disposed such that a starting end and a terminal end thereof are spaced apart from each other on the electrolyte plate; a seal plate disposed on a shaped spacer so as to face the solid electrolyte plate, and the solid electrolyte is surrounded by the opposite partition wall of the spiral spacer, the solid electrolyte thin plate, and the seal plate, A hole is formed, the helical spacer is a protrusion made of a mixture of a hardening material and heat-resistant fine particles of a predetermined particle size, and the hardening material is made of a hardening material in which a portion facing the electrode film and the diffusion hole flow path population is formed as a void. The solid electrolyte plate and the seal plate are closely fixed together via a membrane. Effect: With this configuration, the heat-resistant fine particles of a predetermined size mixed in the hardening material prevent the solid electrolyte plate and the seal plate from settling when they are bonded, and the helical spacer closes the gap between the solid electrolyte plate and the seal plate. (distance) can be maintained with good dimensional accuracy. In addition, when the protrusion, which is a spiral spacer, is closely fixed to a seal plate, etc., sufficient adhesion cannot be obtained by direct bonding to the seal plate, etc. due to the effect of heat-resistant fine particles dispersed in the hardened material of the protrusion. However, in the present invention, since the solid electrolytic w plate and the sealing plate are closely fixed together through a single piece made of a hardened material, the vf?
The adhesion can be achieved perfectly by using both hardening materials. Moreover, since the membrane body has a void in the part facing the electrode membrane, there is a risk that part of the hardening material may accidentally fall onto the electrode membrane during close fixation, causing a decrease in the activity of the electrode. This can be significantly reduced. Also, the one thing is diffusion hole cleaning. Since there is a void in the area facing the road surface, it is possible to prevent part of the hardening material of the membrane from accidentally concentrating on the diffusion hole entrance and blocking the diffusion hole entrance when the membrane is tightly fixed. EXAMPLES Hereinafter, examples of the present invention will be explained based on the attached drawings. FIG. 1 shows an embodiment of the limiting current type oxygen sensor of the present invention, and FIG. 1(a) is an exploded perspective view of the oxygen sensor, and FIG.
) is a partially cutaway perspective view of the oxygen sensor. Figure 1(a)
, (b), l is a solid electrolyte plate having oxygen ion conductivity, and electrodes W2 are formed on both sides of the solid electrolyte plate. A spirally carved spacer 5, which surrounds the electrode film 2 and whose starting and ending ends are spaced apart from each other, is arranged on one surface of the solid electrolytic IR plate 1, and a sealing plate 6 is further arranged. The diffusion hole 7 of the present invention is formed in a spiral space surrounded by the opposing partition walls of the spiral spacer 5, the isoelectrolyte '1@1, and the seal plate 6, and oxygen diffuses into the electrode 11112 through the space. ．． On the other hand, the spiral spacer 5 is a protrusion 5a made of a mixture of a hardening material and heat-resistant fine particles of a predetermined particle size, and closely identifies the solid electrolyte plate 1 and the sealing plate 6 through a film body 5b made of a hardening material. There is. In the membrane body 5b, a portion 7 facing the electrode 112 and a portion 9 facing the expanded hole channel population 8 are voids, and these portions are formed as voids. I4P
The material for i1 is zirconia (ZrO,}-based ceramic, which is the most practical in terms of long-term reliability and stability of properties, among which yttria (Yt ox )
Zirconia with added is good.

Materials for the electrode IIII2 include platinum, gold, palladium,
Examples include silver, but are not particularly limited.

The hardened material used as the material for the protrusion 5a and the membrane 5b, which are the helical spacer 5, has heat resistance sufficient to withstand the operating temperature of the oxygen sensor, and achieves airtightness between the solid electrolyte plate 1 and the seal plate 6. Adhesive properties are required, and glass is an example of this material. When the glass material is passed through a zirconia thread ceramic as a solid electrolyte, the coefficient of mature expansion is ±10.
It is desirable that the PbO
ZnO Bt oN S jot series, KtO-
PbO-Sin. Thread, Nag O Kg O P
bO-SiOg yarn, Nag O-CaO-S ion system, K,O-CaO-S 40, system, BaO-Sin. −
Examples include NaO-based glass. By the way, when the spiral spacer 5 is made of only glass, when the seal plate 6 is placed on top and heated and fired, the seal plate 6 sinks due to the softening of the glass, and the gap of the AA type spacer 5, that is, the diffusion hole 4 The variation in the dimensions of will increase. In the present invention, in order to prevent this, heat-resistant particles having a higher melting point than the glass component are dispersed in the glass component. As the material for the seal plate 6, zirconia diameter ceramics and forstellite are used in consideration of thermal expansion coefficient and heat resistance. Next, we will explain its function and effects based on specific experimental examples. ! The constituent materials and manufacturing method of the oxygen sensor in the embodiment of the present invention shown in llfi are as follows. In addition, limit 1II
．． Ryusei designed the spiral expansion hole 7 to have a current of 200uA (in air).・Solid electrolyte plate I ZrO dew ・Y, 0, ceramic (Y*Os 8mo
n! %) and has dimensions 12xl2x O. 4t ■.
? Electrode 11#2 Form a film with PT paste with an electrode diameter of 6- and a thickness of about 5 μ-. It was coated on both sides of the solid electrolyte plate 1 by screen printing and baked at 820°C for lθ minutes.

・Helical spacer 5 Glass-BaO S tit Nag O-based glass paste heat-resistant particles-B a O-T i O. -S i O
T-type glass powder average particle size 50u 1 Moeki glass space}Ig, the glass powder is
A spiral spacer protrusion 5a surrounding the electrode film 2 was coated on one surface of the solid electrolytic plate 1 by screen printing using a mixture of Omg and M, and heated at 820°C for 10 minutes.
Separate firing. The protrusion 5a of the helical spacer has the shape shown in FIG.
m (width of mu-shaped diffusion hole 7) x 40Hm (height of spiral-shaped expansion hole 7), length is 11 cm x X-shaped expansion hole 7
The distance from the starting point to the ending point is (gill). On the other hand, its width is 0.8 mm.

[Membrane body 5bl Using BaO-NatO-S iOz-based glass paste, a film of about 10 μl was coated on one surface of the sealing plate 6 by screen printing, and baked at 820° C. for 10 minutes. In contrast, the membrane body 5b has voids in a portion 7 facing the electrode membrane 2 and a portion 9 facing the diffusion hole channel population 8.

[Seal plate 6} It is made of forsterite and its dimensions are 12Xl2XO.
5L Pavilion.

The solid electrolyte plate 1 and the seal plate 6 are tightly fixed together by heating and melting (820° CXlO) the protrusion 5a of the spiral spacer and the membrane 5b. Regarding the oxygen sensor thus produced, a lead &l+ (Pt) was attached to the electrode [2, and the voltage-current characteristics were evaluated by heating at 400°C in air. The results are shown in FIG. At each oxygen concentration, the saturation current, that is, the limit east current, is obtained. Next, the configurations of the protrusion 5a and the membrane 5b were changed, and the manufacturing conditions at which the manufacturing yield was evaluated were the same as above, 20 prototypes were manufactured for each loft, and the limiting current was 200±.
100 A (# element concentration 20%, operating temperature 400°C)
The following table shows the results expressed as the percentage of non-defective products.

It can be seen that the present invention has a non-defective product rate of 100%. The reason for this is thought to be the following.

(Margins below.) (1) Heat-resistant fine particles of a predetermined size mixed in the hardening material prevent the solid electrolyte plate and seal plate from settling when they are bonded, and the a-circular spacer seals the solid electrolyte t@. The gap (distance) to the plate can be maintained with good dimensional accuracy. (2) Connect the protrusion, which is a spiral spacer, to a seal plate, etc.
When determining the adhesion, direct bonding to a seal plate, etc. using heat-resistant fine particles dispersed in the hardening material of the protrusion does not provide sufficient adhesion, but the present invention Since they are closely fixed, the solid electrolyte plate and the seal plate can be perfectly bonded by the hardening material.

(3) Since the membrane body has a void in the part facing the electrode membrane, there is a risk that part of the hardening material may accidentally fall onto the electrode membrane during close identification, causing a decrease in the activity of the electrode membrane. It can be significantly reduced.

141 Since the till body has a void in the part facing the diffusion pore flow path population, a part of the hardening material of the membrane body may accidentally concentrate on the diffusion pore population and block the diffusion pore population when tightly fixed. can be prevented. Effects of the Invention As shown below, the oxygen sensor of the present invention provides the following effects. (1) The helical spacer is a protrusion made of a hardened material in which heat-resistant fine particles of a predetermined #I diameter are dispersed, and the solid electrolytic II plate and the sealing plate are closely fixed together through a film made of the hardened material. As a result, the two plates are brought into close contact with each other by the hardening material on both sides, and the dimensional accuracy of the gap (diffusion hole) between the two plates is improved to a certain extent. In particular, the diffusion hole dimensional accuracy is maintained using heat-resistant fine particles of a predetermined particle size, and the adhesion method by heating and melting the glass used for the protrusion and membrane body is resistant to bonding deviation between the solid electrolyte plate and the seal plate, and improves manufacturing yield. It is effective in greatly improving

Moreover, since the membrane body has voids in the portion facing the electrode membrane and the diffusion pore flow path population, it prevents a decrease in the activity of the electrode membrane and the clogging of the diffusion pore flow path population that may occur accidentally due to the hardening material, and improves manufacturing yield. It is extremely effective in improving (2) The diffusion hole is tightly fixed by heating and melting the spiral spacer made of a glass printed film, the identification electrolyte plate, and the seal plate, so it can be formed by an extremely simple method, and is easy to manufacture and low cost. becomes. <<3>> Since the diffusion holes are formed parallel to the solid electrolyte plate, dust and foreign matter are prevented from entering the diffusion holes! It is possible to stabilize the characteristics and improve long-term reliability.

(4) Since the size of the oxygen diffusion hole can be made larger than before, the relative variation in the diffusion can be reduced, and the variation in the critical wealth i1J4M can be reduced.

{5) By forming the body into a homogeneous electrode tube plate and forming the body into an elbow like a seal, it is possible to create a rich electrode on the homogeneous electrode tube plate.
can secure a large amount of leverage, and along with that, the W polar single {
The electric blasphemy charges around I7 Mukai will be reduced.

Therefore, the interfacial resistance in the electrode film is reduced, and the durability and durability of the electrode film are improved accordingly.

[Brief explanation of drawings]

Figure 1 (fat) is an exploded perspective view of a limit 'f 2 alcohol sensor which is an example of the present invention, Figure 1 (fb) is a partially cutaway perspective view of the same oxygen sensor, FIG. 3 is a cross-sectional view of a conventional limit-actual oxygen sensor, which shows the effects of the invention. 1...Dotai Army Kaiyoitei~, 2...■1#
, 5...screw h7 cedar spacer, 5a...
Projection body, 5b... Membrane body, 6... Seal plate, 7... Portion facing the electrode film, 8...
... Expansion hole flow path population, 9... Part opposite to the diffusion hole flow path population.

Claims (3)

[Claims] (1) An oxygen ion conductive solid electrolyte plate having electrode films formed on both sides, and a spiral spacer surrounding one of the electrode films so that its starting end and ending end are spaced apart from each other on the solid electrolyte board. , a seal plate disposed on the helical spacer so as to face the solid electrolyte plate, and is surrounded by the opposite partition walls of the helical spacer, the solid electrolyte plate, and the seal plate, and is surrounded by the solid electrolyte plate and the seal plate. pores are formed,
The spiral spacer is a protrusion made of a mixture of a hardening material and heat-resistant fine particles of a predetermined particle size, and the spiral spacer is a protruding body made of a mixture of a hardening material and heat-resistant fine particles of a predetermined particle size. and a limiting current type oxygen sensor in which the solid electrolyte plate and the seal plate are closely fixed. (2) The limiting current type oxygen sensor according to claim 1, wherein the protrusion is formed on a solid electrolyte plate and the membrane body is formed on a seal plate. (3) The limiting current type oxygen sensor according to claim 1, wherein the hardening material is glass.