JPH07159372A - Limit current type oxygen sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a limit current type oxygen sensor, wherein an oxygen diffusing path for limiting the movement of oxygen molecules can be manufactured by a simple method. CONSTITUTION:A pair of electrode films 2a and 2b are formed on both surface of an oxygen-ion conductive solid electrolyte body 1. A diffusion-rate determining body 4 having an oxygen diffusing path 3 is tightly fixed on the upper part of one side of the oxygen-ion conductive solid electrolyte plate 1 through an adhesion member 5. In the diffusion-rate determining body 4, a sealing plate 8a having a small hole 7a and a sealing plate 8b having a small hole 7b are laminated through a bonding member 9. A plurality of the sealing plates 8a and 8b are laminated so that the positions of the small holes 7a and 7b are different. A communicating groove 10 for connecting the small hole 7a and the small hole 7b is formed in the bonding member 9. The oxygen diffusing path 3 is mainly constituted of the communicating groove 10 so that the length is long and the cross-sectional area is broad. Since the communicating groove 10 can be formed by the thick film printing of the bonding member 9 using glass paste, the oxygen diffusing path 3 can be simply formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limiting current type oxygen sensor for measuring the oxygen concentration in an atmosphere, and more particularly to a limiting current type oxygen sensor capable of manufacturing an oxygen diffusion passage for limiting movement of oxygen molecules by a simple manufacturing method. The present invention relates to a sensor and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 4 showing a conventional limiting current type oxygen sensor.
At the cathode-side and anode-side surfaces of the solid electrolyte plate 41 exhibiting oxygen ion conductivity,
And 42b are formed. A diffusion rate controlling member 44 is arranged on one surface of the solid electrolyte plate 41 so as to surround the electrode film 42a and has an oxygen diffusion passage 43 that restricts the movement of inflowing oxygen molecules. Oxygen diffusion passage 43
Is a micropore having a diameter of several tens of μm and a length of several mm. Oxygen passes through the oxygen diffusion passage 43 and the electrode film 42
diffuse to a. A heating unit 45 is formed in the diffusion rate controlling member 44 to heat the solid electrolyte plate 41 to improve the conduction of oxygen ions.

Next, the operation will be described. A predetermined voltage is applied to the heating unit 45 using a heating voltage source (not shown), and the solid electrolyte plate 41 is heated to about 500 ° C. via the heating unit 45.
Heat to the temperature of. On the other hand, a predetermined voltage is also applied to the electrode films 42a and 42b formed on both sides of the solid electrolyte plate 41 by using a DC voltage source (not shown). Then, oxygen in the air flows in through the oxygen diffusion passage 43, and oxygen ions move from the cathode side electrode film 42a toward the anode electrode film 42b by the oxygen pumping action so that oxygen moves in the solid electrolyte plate 41. However, since the oxygen diffusion passage 43 restricts the inflow of oxygen molecules, a saturation current (referred to as a limiting current) corresponding to the oxygen concentration is generated. The oxygen concentration is determined by measuring this limiting current value.

Then, in Japanese Patent Laid-Open No. 5-133934,
By using a spiral spacer and an auxiliary spacer, the oxygen diffusion passage in the spiral space can be formed as designed without being blocked, so that the sensor manufacturing yield is improved and the productivity is improved. Oxygen sensor technology is disclosed.

[0005]

In the structure of the conventional limiting current type oxygen sensor, the oxygen diffusion passage 43 for restricting the movement of inflowing oxygen molecules has a diameter of several tens of μm and a length of several mm.
A sensor having an oxygen diffusion passage 43 of this size can obtain a limiting current of several hundred μA in the atmosphere. However, since the oxygen diffusion passages 43 having a fine dimension with a diameter of several tens of μm are manufactured by firing a ceramic containing an organic material, it is difficult to manufacture the oxygen diffusion paths 43 with no dimensional variation. Since the oxygen diffusion passage 43 having a large size cannot be obtained, there is a problem that the yield is low.

The present invention solves such a conventional problem, and provides a limiting current type oxygen sensor having a structure capable of easily manufacturing an oxygen diffusion passage for restricting movement of oxygen molecules with high yield, and a manufacturing method thereof. The purpose is to do.

[0007]

In order to achieve the above object, a limiting current type oxygen sensor of the present invention comprises an oxygen ion conductive solid electrolyte body having electrode films formed on both surfaces, and the oxygen ion conductive solid electrolyte. A diffusion-controlled body which is located on one side of the body and is arranged so as to surround the electrode film on the one side, and which has an oxygen diffusion passage for limiting the movement of inflowing oxygen molecules, the oxygen-ion-conductive solid electrolyte body, and the diffusion-controlled body. And, in an element composed of an adhesive material that closely fixes and fixes a gap between the outlet of the oxygen diffusion passage and the electrode film formed on one side of the oxygen ion conductive solid electrolyte, the diffusion-controlling body,
A plurality of sealing plates having small holes are arranged and laminated so that the small holes are located at different positions, and a bonding material having a communicating groove with the small holes is arranged between the plurality of sealing plates. Is.

Further, the above-mentioned means is a method for manufacturing a limiting current type oxygen sensor in which the electrode film, the adhesive material and the bonding material are manufactured by thick film printing.

[0009]

The limiting current is proportional to the ratio of the cross-sectional area of the oxygen diffusion passage to its length. Therefore, in order to obtain the limiting current with the same value as that of the conventional component, if the length of the oxygen diffusion passage is increased, the cross-sectional area thereof should be increased accordingly.

In the limiting current type oxygen sensor element of the present invention, the diffusion-controlling body is formed by laminating a plurality of sealing plates having small holes so that the small holes are arranged at different positions, and between the plurality of sealing plates. This is a structure in which a bonding material having a communication groove with the small hole is arranged. That is, a plurality of sealing plates are laminated so that the small holes are arranged at different positions, and the small holes are connected to each other by the communication groove formed in the bonding material arranged therebetween. Therefore, the oxygen diffusion passage is formed from the small hole to the communication groove, and further from the communication groove to the small hole, and oxygen moves from the small hole to the communication groove and further from the communication groove to the small hole. Since the small holes are arranged at different positions, the communication groove can be lengthened, and the size of the small holes can be increased accordingly.

It is easy to form the small holes in the seal plate, for example, by pressing a green sheet to open the small holes,
A small hole having a diameter of 0.1 mm or more can be easily formed by firing thereafter. On the other hand, a bonding material having a communicating groove is formed by printing a printing pattern having a communicating groove to a small hole on a sealing plate with a glass paste by using a thick film printing technique, stacking another sealing plate, and then firing it. It can be formed, and as a result, a bonding material having a communication groove with the small hole can be arranged between the two sealing plates. For example, if a small amount of heat-resistant particles having a predetermined particle size is contained in the glass paste, an oxygen diffusion passage having a height of several tens of μm and a cross section of 0.4 mm in width can be obtained, and a printing pattern of meandering communication grooves is formed. Then, an oxygen diffusion passage having a length of several tens of mm can be easily obtained.

From the above, with this structure, an oxygen diffusion passage having a fine diameter and a long length can be easily formed by using thick film printing.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A limiting current type oxygen sensor according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1 showing a cross section of a limiting current type oxygen sensor which is an embodiment of the present invention, a pair is formed on each of the cathode side and the anode side of a plate-shaped oxygen ion conductive solid electrolyte body 1. Electrode film 2a on the cathode side and the anode side
And 2b are formed. A diffusion rate-controlling body 4, which is arranged so as to surround the electrode film 2a on one side and has an oxygen diffusion passage 3 for restricting the movement of inflowing oxygen molecules, is adhered to the upper part of one side of the solid electrolyte plate 1 through an adhesion material 5. It is fixed. When the solid electrolyte body 1 and the diffusion-controlling body 4 are closely fixed, the close-contact material 5 is tightly fixed so that a gap 6 is formed between the outlet of the oxygen diffusion passage 3 and the electrode 2a.

On the other hand, the diffusion-controlling body 4 has a construction in which a seal plate 8a having a small hole 7a and a seal plate 8b having a small hole 7b are laminated via a bonding material 9. This diffusion-controlled body 4
The seal plate 8a and the seal plate 8b are laminated so that the small hole 7a and the small hole 7b are located at different positions. Further, the bonding material 9 arranged between the seal plate 8a and the seal plate 8b has a small size. A communication groove 10 that connects the hole 7a and the small hole 7b is formed. Therefore, the oxygen diffusion passage 3 is formed from the small hole 7a to the communication groove 10 and then to the small hole 7b, and oxygen moves from the small hole 7a to the communication groove 10 and further from the communication groove 10 to the small hole 7b. Since the small holes 7a and the small holes 7b are arranged at different positions, the communication groove 10 can be lengthened, and the sizes of the small holes 7a and the small holes 7b can be increased accordingly.

A heating part 11 is formed in the diffusion-controlling body 4 to heat the oxygen ion conductive solid electrolyte plate 1 to improve the conduction of oxygen ions.

Next, a description will be given based on a specific embodiment.
In FIG. 2 showing an exploded view of the limiting current type oxygen sensor of the present embodiment, the oxygen ion conductive solid electrolyte plate 1 has a size of 10 × 10 × 0.4 mm ZrO ₂ · Y ₂ O ₃
(8 mol% of Y ₂ O ₃ added) was used to form platinum electrode films 2a and 2b having an area of 8 × 8 mm on both surfaces thereof. Further, the sealing plate 8a having the small holes 7a is formed on the heating portion 11 of the platinum heater by using the thick film printing technique and the firing technique.
Was formed. Then, the bonding material 9 in which the communication groove 10 was formed was formed on the seal plate 8b having the small holes 7b by using the thick film printing technique. Then, the seal plate 8a having the small holes 7a was laminated and heat-melted so that the small holes 7a and the small holes 7b were arranged at different positions. Since the small holes 7a and the small holes 7b are communicated with each other through the communication groove 10, the oxygen diffusion passage 3 is formed by the heat melting from the small hole 7a to the communication groove 10 and from the communication groove 10 to the small hole 7b. Finally, the diffusion-controlling body 4 of this laminated product and the oxygen ion conductive solid electrolyte body 1 are adhered and fixed to each other via the adhesion material 5, whereby the limiting current type oxygen sensor of this embodiment is completed. Seal plate 8a and seal plate 8b
Is forsterite, and the bonding material 9 and the adhesive material 5 are made of glass (coefficient of thermal expansion is approximately the same as ZrO ₂ · Y ₂ O ₃
A small amount of heat-resistant particles having a predetermined particle size) was used.

This limiting current type oxygen sensor has an average particle size of 1
By using a glass paste containing a small amount of 5 μm heat-resistant particles, the bonding material 9 having the meandering communication groove 10 is printed on the seal plate 8b, and the seal plate 8a is laminated and fired to obtain 15 μm. An oxygen diffusion passage 3 having a height of 30 mm and a cross-sectional area of 0.4 mm and a length of 30 mm was obtained. In addition,
The seal plate 8a and the seal plate 8b are 0.2 mm thick forsterite plates (10 mm square) having one small hole with a diameter of 0.1 mm. Also, the total size of the sensor is 10 ×
It is 10 × 0.8 mm.

FIG. 3, which shows an effect characteristic diagram of the limiting current type oxygen sensor of the present embodiment, measures the voltage-current characteristic at an operating temperature of 500.degree.

The current shows a constant current value regardless of the applied voltage when the applied voltage is about 0.5 V or more, and the limiting current is obtained, and the limiting current has a characteristic that it is approximately proportional to the oxygen concentration.

[0021]

As is apparent from the above description, according to the diffusion limiting body of the limiting current type oxygen sensor of the present invention, a plurality of sealing plates with small holes are laminated so that the small holes are arranged at different positions. The small holes and the small holes are made to communicate with each other by a communication groove formed in the bonding material arranged therebetween. Therefore, the following effects occur. (1) Since the oxygen diffusion passage can be formed from the small hole to the communication groove and further from the communication groove to the small hole, the communication groove can be lengthened accordingly, and the size of the small hole can be increased accordingly. . (2) An adhesion material for closely fixing the oxygen ion conductive solid electrolyte body and the diffusion rate controlling body, a bonding material arranged between a plurality of seal plates, and electrode films formed on both surfaces of the oxygen ion conductive solid electrolyte body, Since all are manufactured by thick film printing, the manufacturing method is simple, the manufacturing cost is low, and the mass productivity is excellent. (3) Since the diffusion-controlling body is laminated on the oxygen-ion-conducting solid electrolyte body, the electrode film can occupy a large area in the oxygen-ion-conducting solid-electrolyte body, resulting in a large ionic current. The reliability can be improved by reducing the current density.

[Brief description of drawings]

FIG. 1 is a sectional view of a limiting current type oxygen sensor according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the same limiting current type oxygen sensor.

FIG. 3 is a graph showing the effect characteristics of the same limiting current type oxygen sensor.

FIG. 4 is a sectional view of a conventional limiting current type oxygen sensor.

[Explanation of symbols]

 1 Oxygen Ion Conducting Solid Electrolyte Body 2a Electrode Membrane (Cathode Side) 2b Electrode Membrane (Anode Side) 3 Oxygen Diffusion Passage 4 Diffusion Rate Controlling Material 5 Adhesive Material 6 Gap 7a, 7b Small Hole 8a, 8b Seal Plate 9 Bonding Material 10 Communication groove

Claims (2)

[Claims] 1. An oxygen ion conductive solid electrolyte body having electrode films formed on both sides thereof, and the oxygen ion conductive solid electrolyte body is located on one side of the oxygen ion conductive solid electrolyte body and is disposed so as to surround the electrode film on one side and flows into the oxygen ion conductive solid electrolyte body. A diffusion-controlling body having an oxygen diffusion passage for limiting the movement of oxygen molecules, the oxygen ion-conducting solid electrolyte body and the diffusion-controlling body, the outlet of the oxygen diffusion passageway and one side of the oxygen ion-conducting solid electrolyte body. In the element composed of an adhesive material which is closely adhered and fixed to the electrode film formed on the substrate, the diffusion-controlling body is configured such that a plurality of sealing plates having small holes are provided at different positions of the small holes. A limiting current type oxygen sensor in which a bonding material having a communicating groove with the small hole is arranged between the plurality of sealing plates. 2. An oxygen ion conductive solid electrolyte body having electrode films formed on both sides thereof, and the oxygen ion conductive solid electrolyte body is located on one side of the oxygen ion conductive solid electrolyte body and is disposed so as to surround the electrode film on one side and flows in. A diffusion-controlling body having an oxygen diffusion passage for limiting the movement of oxygen molecules, the oxygen ion-conducting solid electrolyte body and the diffusion-controlling body, the outlet of the oxygen diffusion passageway and one side of the oxygen ion-conducting solid electrolyte body. A space is provided between the diffusion control body and the electrode film formed on the substrate, and the diffusion control body is laminated by arranging a plurality of sealing plates having small holes so that the small holes are located at different positions. A method for manufacturing a limiting current type oxygen sensor, further comprising: arranging a bonding material having a communication groove with the small holes between the plurality of sealing plates, and manufacturing the electrode film, the adhesive material, and the bonding material by thick film printing.