JPS59131159A - Detecting element of oxygen concentration - Google Patents

Abstract

PURPOSE:To obtain a detecting element of oxygen concn. which is inexpensive and mass produceable by punching fine holes inthe thick part of a pipe-shaped base body consisting of a solid electrolyte, inserting metallic wires therein and connecting the top ends thereof to noble metal electrodes. CONSTITUTION:Fine holes 9a, 9b are punched in the thick part of a pipe-shaped base body 7 consisting of a solid electrolyte and heat resistant metallic wires 10a, 10b are inserted therein. The wire 10a is connected at its top end 11a to an inside platinum electrode 12 and the wire 10b is connected at its top end 11b to an outside platinum electrode 13. The induced voltage corresponding to the difference between the oxygen concn. in the gas near a gas burner that contacts with the electrode 13 and the oxygen concn. in the air 15 from the outside that contacts with the electrode 12 is generated between the wires 14a and 14b. Since the provision of the electrodes 12, 13 at about 10mm. length on the side face of the body 7 suffices, the element is not so costly and the stage of applying platinum is easy.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an oxygen concentration sensing element having a function of detecting oxygen concentration inside gas combustion equipment.

Conventional structure and its problems Currently, solid electrolytes such as stabilized zirconia or cerium oxide doped with calcia are processed into a pipe shape and used as a substrate for oxygen concentration detection elements installed in gas combustion equipment. Pipe-shaped oxygen concentration sensing elements are often used.

This oxygen concentration sensing element utilizes the properties of a solid electrolyte such as stabilized zirconia, and has many potential applications in gas combustion equipment.

As shown in FIG. 1, the conventional oxygen concentration detection element has a base 1 made of a pipe-shaped solid electrolyte, with a platinum electrode 2a provided on the outer surface and a platinum electrode 2b provided on the inner surface. Further, a lead wire 3a is connected to the platinum electrode 2a on the outer surface by soldering 4a, and a lead wire 3b is connected to the platinum electrode 2b on the inner surface by soldering 4a.
electrically and mechanically connected by b.

When the above-mentioned element is used in a gas combustion device, the detection section 6 on one end side is used at a temperature of about 860°C. Therefore, the lead wire attachment portion 6 on the other end side
The total length of the base 1 is set to 70mm to 100mm so that the temperature of the base body 1 is kept below 200°C and the solders 4a and 4b are not melted.
And it's long. When the element is long like this, the dielectric 3 that composes it,
.

Since materials such as cerium oxide and cerium oxide are expensive, the price of the substrate 1 becomes high. In addition, since the platinum electrodes 2a and 2b must be coated over the entire length of the base 1, the number of man-hours increases, and the resistance between the detection part 6 of the platinum electrodes 2a and 2b and the lead wire attachment part 6 increases, resulting in measurement errors. will occur. Furthermore, since a large amount of material for the platinum electrodes 2a, 2b to be coated is required, the price becomes high. Further, since the pipe-shaped substrate 1 is manufactured by extrusion molding, there is a drawback that the substrate 1 is easily bent.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an oxygen concentration sensing element that is inexpensive and easy to mass-produce by eliminating many of the drawbacks of the conventional devices.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a pipe-shaped base made of a solid electrolytic material with a pipe inner hole penetrating in the longitudinal direction of the base and a pair of parallel pores formed in the thickness part of the base. A metal wire is inserted into each of these pores, the tips of the metal wires are connected to noble metal electrodes provided on the inner and outer surfaces of the base, and the other ends of the metal wires are taken out from the pores. It is composed of

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 2a and 2b, a pipe-shaped base 7 made of a solid electrolyte has pores 9a and 9b parallel to the pipe inner hole 8 in its thickness, and these pores Heat-resistant metal wires 10a and 10b made of tungsten or the like are inserted into the wires 9a and 9b, respectively. The metal wire 10a is electrically connected at one tip 11a to an inner platinum electrode 12 provided only on a portion of the inside of the base 7. On the other hand, the metal wire 10b is electrically connected at one tip 11b to an outer platinum electrode 13 provided only on a portion of the outer surface of the substrate 7.

Also, the other end 14 of each of the metal wires 10a and 10b
a and 14b are connected to a measuring device such as a voltage measuring device (not shown in the figure).

Next, the operation of the above oxygen concentration detection element will be explained.
The gas near the gas burner of gas combustion equipment is connected to the outer platinum electrode 1.
3, the one-way platinum electrode 12 comes into contact with air 16 flowing in through the pipe inner hole 8 from the outside. An electromotive force is generated between the metal wires 14a and 14b according to the difference between the oxygen concentration of the gas near the gas burner that touches the outer platinum electrode 13 and the oxygen concentration of the air 16 from the outside that touches the inner platinum electrode 12.
A user can detect the oxygen concentration of the gas near the gas burner by reading the measured value of a voltage measuring device connected between the metal wires 14a and 14b.

Note that, in addition to the platinum electrode, a noble metal such as palladium is used for the electrode provided on the base 7.

In the above oxygen concentration detection element, it is sufficient to provide the inner platinum electrode 12 and the outer platinum electrode 13 on the inner and outer surfaces of the base 7, respectively, to a length of about 10 cm, so even if platinum is used, the cost is low. The process of applying platinum is simplified. Further, an inner electrode 12 is formed by vapor deposition or the like so as to contact the tip 11a of the metal wire 14a fixed by the pore 9a, and an inner electrode 12 is formed by vapor deposition or the like so as to contact the tip 11a of the metal wire 14b fixed by the pore 9b. Since the outer electrodes 13 are formed so as to be in contact with each other, soldering unlike the conventional method is not required. Therefore, since the base body 7 may be much shorter than the conventional one, the cost of expensive raw materials such as zirconia or cerium oxide is reduced, and defects such as bending of the base body 7 during the manufacturing process do not occur. Further, each of the metal wires 14a and 14b has a pore 9a.

Since the metal wires 14a and 14b are protected by the base 7 while inserted into the metal wires 14a and 14b, breakage is extremely rare.
It has various advantages, such as a short length and very small measurement errors.

As described in detail, the oxygen concentration sensing element of the present invention requires less precious metal and solid electrolyte, so it is extremely inexpensive compared to conventional products. Ru. And solid 7;.

Since the length of the electrolyte base is short, bending does not occur during manufacturing, and since the metal wire is protected by the base, there is no risk of wire breakage, making it extremely reliable.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional pipe-shaped oxygen concentration sensing element.
FIGS. 2a and 2b are a cross-sectional front view and a side view, respectively, of an oxygen concentration sensing element according to an embodiment of the present invention. 7...Base body, 8...Pipe inner hole, 9a
, 9b... Pore, 10a, 1ob...
...Metal wire, 12...Inner platinum electrode, 13
・・・・・・Outer platinum electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] A pair of pores are drilled in the thickness of a pipe-shaped base made of a solid electrolytic material in parallel with the pipe inner hole passing through the base in the longitudinal direction, and metal wires are inserted into each of these pores. An oxygen concentration sensing element characterized in that the tips of the wires are connected to noble metal electrodes provided on the inner and outer surfaces of the base, and the other ends of the metal wires are taken out from the pores.