JPS6154443A - Oxygen concentration detecting element - Google Patents

Abstract

PURPOSE:To eliminate the need to separate reference gas and gas to be measured and simplify the structure by clamping both sides of oxygen ion conductive solid electrolytic ceramic between opposite electrodes and coating one electrode hermetically with ceramic made of the same material with the oxygen ion conductive solid electrolytic ceramic. CONSTITUTION:The oxygen ion conductive solid electrolytic ceramic 1 uses powder of zirconia, thoria, etc., and is shaped as part of a green sheet of a plane plate, rod, or pellet, etc., which is punched into a formed body 8 consisting of many parts. Electrodes 2 and 2' are formed on both surfaces of each part sectioned by a slit 9 through screen printing treatment by using, for example, platinum paste. Division pieces obtained by dividing the formed body 8 where no electrode is printed along slits 9 are stacked and pressed to a solid electrolyte 1 as a coating body 3, and further baked and sealed to obtain the oxygen thickness detecting element 3. A reduction flaw A and an oxidation flame B are separated from the detecting element 4 during normal combustion, and the reduction flame extends as shown by C in an oxygen deficient state to cover the detecting element 4. Consequently, it is not necessary to separate the reference gas and gas to be measured, and the structure is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an oxygen concentration detection element that detects incomplete combustion, extinction, etc. due to lack of oxygen in heating equipment and the like.

(Prior Art) Thermocouple type, flame rond type, or oxygen ion conductive solid electrolyte type detectors are known as conventional detectors for detecting incomplete combustion, overheating prevention, etc., for example, in oil heating equipment.

Among these, the oxygen ion conductive solid electrolyte method directly measures the oxygen concentration in the atmosphere to be measured, and has been widely used in recent years because it is more accurate than other methods and 1) does not require an external power source. ing. An example of this method is shown in Figure 4 (
a).

Shown in (b). In Fig. 4(a), when the reducing flame of the gas burner 5 extends from A to C and wraps around the detection element 6 during oxygen deficiency, a difference in oxygen concentration occurs inside and outside the detection element 6, and a change in output is detected. Raw gas (arrow) must be passed through the inside of the tubular detection element, and Fig. 4(b) shows the detection element t.
An L-shaped combustion exhaust gas introduction pipe 7 is connected to the open end of the combustion exhaust gas, and the combustion exhaust gas is sucked into this introduction pipe 7 (arrow), so that one side of the detection element 6 is always in contact with the reducing flame A, and the other side is kept in contact with the reducing flame A. Depending on the combustion state, the combustion chamber is exposed to an oxidizing atmosphere when it is normal, and a reducing atmosphere when there is a lack of oxygen. Furthermore, Figure 4 (al, (
In bl, B emits an oxidizing flame. As described above, in both cases (a) and (b) in FIG. 4, the problem of having to separate the reference gas and the gas to be measured frequently arises.

(Objective of the Invention) An object of the present invention is to provide an acid light concentration detection element that solves such conventional problems.

(Means for Solving the Problems) As a result of extensive studies, the inventors of the present invention sandwiched both sides of an oxygen ion conductive isoelectrolyte ceramic with band-shaped electrodes made of a catalytic metal, and one of the electrodes was It has been discovered that by covering and sealing with the same ceramic as the ion-sensitive solid electrolyte ceramic, there is no need to consider separating the reference gas and the gas to be measured, and the structure becomes simple. An oxygen concentration detection element comprising an ion-conductive solid electrolyte ceramic sandwiched between opposite electrodes, one electrode of which is covered and sealed with a ceramic made of the same material as the oxygen-ion conductive solid electrolyte ceramic. .

The oxygen ion conductive solid electrolyte ceramic (hereinafter referred to as solid electrolyte) used in the present invention is:

Although the material is not particularly limited, powders of zirconia, doria, etc. stabilized with ittria are used as the raw material powder, and the shape is flat, rod-like, pellet, etc.

Molding methods include a method in which an organic binder, etc. is added to the raw material powder and granulated and pressure molded, a method in which an organic binder, a plasticizer, etc. is added to the raw material powder and extrusion molding is carried out, and a method in which an organic binder, a solvent, etc. is added to the raw material powder. In addition, there is a green sheet method for molding, and the green sheet method is preferable in terms of mass productivity.

The electrode material may be a catalytic metal such as platinum or platinum-rhodium, and is not particularly limited. Electrodes are formed on the surface of a solid electrolyte in the form of a band, for example, by applying it to the solid electrolyte and forming it into a predetermined shape, or by applying a catalytic metal paste onto an adhesive film in the required shape and then transferring and adhering it to the solid electrolyte. Any method may be used.

In addition, in order to cover and seal one electrode with a ceramic made of the same material as the solid electrolyte (hereinafter referred to as a coating), the electrode is coated on the solid electrolyte formed body, the formed bodies of the coating are overlapped and crimped, and then The solid electrolyte and coating are fired. Electrodes are bonded to a solid electrolyte that has been pressure-molded and calcined, and a coating slurry is applied to the surface of one electrode, followed by firing.

(Example) Example 1 Butyral resin (manufactured by Denki Kagaku KL, trade name Denka 4000) 6% by weight, dioctyl phthalate (Wako Junkei) 2-8% by weight, butanol 23.2%
After adding weight% and mixing, pour it out onto a glass plate to a thickness of 0.7
A green sheet of m was obtained. After punching this green sheet into a mold into a large number of molded bodies 8 as shown in FIGS. The electrodes 2, 2' were formed by screen printing using platinum paste (Yairi Kagaku G+5x03) into a shape having terminal portions as shown in FIGS. 1 and 2 on both sides of each portion. Thereafter, the molded body 8 was divided along the slits 9 to obtain the solid electrolyte 1 shown in FIG. The molded body 8 on which no electrodes are printed is divided along the slits 9, and as shown in FIG. It was fired at 16500C and sealed to obtain an oxygen concentration detection element.

Example 2 100 parts of powder with the same composition as Example 1 and 5 parts of paraffin
Parts by weight were added and mixed under heating at 120°C to obtain granules of 32 mesh or less. This granule is molded into 1000 kg
/cm2 and calcined at 1100°C to obtain a solid electrolyte having the same shape as shown in FIG.

Next, 20% by weight of butyral resin having the same properties as in Example 1,
Mix and dissolve 8% by weight of dioctyl phthalate and 74% by weight of n-butanol, pour it onto Lumirror film (manufactured by Toshisha Co., Ltd.), and apply about 2 μm of resin (adhesive) on the Lumirror film.
A film was formed. The platinum paste used in Example 1 was applied onto the resin film in the shape shown in 2 in Figure 1, and the Lumirror film was pressed onto the upper and lower surfaces of the calcined solid electrolyte to form the solid electrolyte. Platinum was transferred onto the surface to form platinum electrodes 2.2' as shown in FIGS. 1 and 2.

Solid electrolyte powder having the same composition as in Example 1 was coated on one side of the electrode with a slurry dispersed in water, and then the temperature was gradually increased and baked at 1650°C to obtain an e-cord chain detection element. Ta.

(Function) Example 1. When the oxygen concentration detection element obtained as in Example 2 is inserted into a heating device, in the case of normal combustion, the reducing flame A and the oxidizing flame B move away from the detecting element 4 and move away from the sensor as shown in Fig. 3. When the combustion exhaust gas comes into contact with the electrode 2' having no enclosure as shown in FIG. 2, the oxygen partial pressure difference between the electrodes 2 and 2' is large and a high electromotive force of about 068 V is exhibited as shown in FIG. When an oxygen-deficient state occurs, the reducing flame extends as shown by C in FIG. 3 and covers the detection element 4, causing the electrode 2. As the oxygen partial pressure difference between the two groups becomes smaller, the electromotive force suddenly decreases as shown in FIG.

(Effects of the Invention) According to the present invention, since there is no need to separate the reference gas and the gas to be measured, the structure of the detection part is simple and the oxygen concentration detection element can be downsized. It can also be applied to equipment safety devices.

Furthermore, it is possible to mold a large number of plate-shaped solid electrolytes, thereby reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an oxygen concentration detection element according to an embodiment of the present invention, FIG. 2 is a side cross-sectional view of FIG. 1, and FIG. Figure 4 (a) (
bl is an explanatory diagram showing the action of a conventional oxygen concentration detection element,
FIG. 5 is a diagram illustrating the manufacturing method of a nutrient electrolyte for an oxygen concentration detection element in an embodiment of the present invention, and FIG. 6 is a graph showing the relationship between oxygen concentration and electromotive force. Explanation of symbols

Claims (1)

[Claims] 1. An oxygen concentration detection element comprising an oxygen ion conductive solid electrolyte ceramic sandwiched between opposite electrodes, one electrode of which is covered and sealed with ceramic of the same material as the oxygen ion conductivity solid electrolyte ceramic.