JPS6165153A - Sensor for combustion safety device - Google Patents

Abstract

PURPOSE:To make possible the detection of incomplete combustion, etc., even if heat power fluctuates by providing >=2 pieces of heat-resistant electrodes on the outside peripheral surface of a tubular or blind pipe-shaped oxygen ion-conductive solid electrolyte sintered body and 1 piece of electrode on the inside peripheral surface thereof. CONSTITUTION:Zirconia, thoria, etc. stabilized by yttria, calcia, magnesia, etc. are used as a material for the oxygen ion-conductive solid electrolyte sintered body 3. Said body is formed by molding such material into a tubular or blind pipe shape having a circular or square sectional shape and sintering the molding. >=2 Pieces of the outside peripheral electrodes 4, 5 and 1 piece of the inside peripheral electrode 1 are provided to such body 3. The respective electrodes are heat resistant and are formed by using a metal such as platinum, rhodium, palladium, etc. or the alloy thereof as the material, forming the material into a paste, coating the paste on the inside and outside peripheral surface of the body 3 by printing method, etc. and calcining the same. The detection is made possible even if the heat power fluctuates by making use of the electromotive force by the oxygen partial pressure generated between the electrodes 1 and 4 in the stage of strong combustion and the electromotive force generated between the electrodes 1 and 5 in the stage of weak combustion when the combustion stops as a result of putting out of the flame or when the incomplete combustion arises as a result of oxygen deficiency.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a household combustion appliance that detects when combustion stops due to flame extinguishing, or when incomplete combustion occurs due to lack of oxygen. This invention relates to an improvement of a senna for a combustion safety device that operates the device.

(Prior Art) Conventionally, as a senna for a combustion safety device in a combustion appliance, a sintered body of an oxygen ion conductive solid electrolyte in the shape of a tube or a bag tube, with heat-resistant T& formed on the inner and outer circumferential surfaces, has been used.

Figure 4 shows an example, where a) is a front view, and (b) is a front view.
This is a sensor in which a heat-resistant inner circumferential electrode and an outer circumferential electrode 2 are formed on a tubular sintered body 3 of an oxygen ion conductive solid electrolyte. This sensor generates an electromotive force E based on the well-known Nernst equation due to the difference in oxygen partial pressure between the inner circumferential electrode and the outer circumferential electrode via the partition wall of the oxygen ion conductive solid electrolyte. That is, the electromotive force is E= (RT/4F)In
It is expressed by the formula (P1/P2.). Here, R is a gas constant, F is Faraday's constant + Pt is the oxygen partial pressure at the inner circumferential electrode, Pz is the oxygen partial pressure at the outer circumferential electrode, and T is the absolute temperature of the detection part.

When the above-mentioned sensor is installed in a burner 11 such as a gas or oil heater/heater that has a fire power adjustment function such as strong and weak combustion as shown in Fig. 5, the inner electrode 1 comes into contact with the atmosphere through its lower end, and the amount of oxygen increases. Under normal conditions, as shown in FIG. 5(a), the outer peripheral electrode 2 comes into contact with the combustion flame 6, and the partial pressure of oxygen between both electrodes increases, generating an electromotive force. In the same figure, 7 is the inner flame, 8 is the outer flame when the firepower is low (weak combustion), and 10
is the external flame when the firepower is high (during strong twist firing), and the length of the combustion flame changes depending on the magnitude of the firepower. In addition, when an oxygen-deficient state occurs due to strong combustion, the outer flame further extends as shown in Fig. 5(b), and the inner flame also extends, resulting in a mixture of unburned gas and primary air. 9 and the outer peripheral electrode, the difference in oxygen partial pressure between the inner and outer peripheral electrodes becomes smaller, and the electromotive force decreases. As described above, the length of the combustion flame varies due to fluctuations in thermal power, and the change in electromotive force relative to the indoor oxygen concentration differs depending on fluctuations in thermal power, which often makes it difficult to detect incomplete combustion. In FIG. 5 (al, (bl), 13 and 14 are lead wires for connection to external instruments.

(Objective of the Invention) It is an object of the present invention to provide a sensor for a combustion safety device that can solve the above-mentioned problems and detect incomplete combustion, etc. even under fluctuations in thermal power.

(Structure of the Invention) The present invention provides a combustion safety device comprising two or more heat-resistant electrodes on the outer peripheral surface of a tubular or bag-shaped oxygen ion conductive solid electrolyte sintered body and a heat-resistant electrode on the inner peripheral surface. related to sensors for

In the present invention, the oxygen ion conductive solid electrolyte sintered body (hereinafter referred to as sintered body) is made of zirconia, doria, etc. stabilized with yttoria, calcia, magnesia, ceria, strontea, etc., and has a circular or square cross section. It is formed into a tubular or bag tubular shape and sintered. Heat-resistant electrode (hereinafter referred to as electrode).

Metals such as platinum, rhodium, palladium, or alloys thereof are used as materials, and are made into a paste and applied to the inner and outer peripheral surfaces of the sintered body by a printing method or the like.

Burned. Two or more electrodes on the outer circumferential surface and one on the inner circumferential surface.
(hereinafter referred to as outer circumferential electrodes and inner circumferential electrodes).

The size, shape, and positional relationship of the electrodes are selected by considering the fuel used, the burner, the performance of the combustion equipment, etc., and there is no limit to the percentage. It is preferable to provide the terminal portion to be connected to the outer circumferential surface so as not to contact the outer circumferential electrode, since this facilitates connection with the lead wire. For example, in the case of a cylindrical sintered body, the outer circumferential electrode is placed at the opposite position 180° in the circumferential direction, and the other electrode is placed at the opposite position to the tip that comes in contact with the combustion flame, as shown at 5 in Fig. 2. As shown in 4 in the same figure, it is preferable to provide it halfway so that it is in contact with the exhaust gas but not with the combustion flame.

Further, it is preferable to provide a protective film formed by spraying zirconia powder or the like on the electrode surface, since this improves the corrosion resistance of the electrode.

(Function) The function of the sensor configured as described above will be explained using FIG. 2 as an example. As shown in Figure 2, the inner electrode 1 is placed on the sintered body 3.
When the sensor formed with the two outer circumferential electrodes 4.5 is placed on a burner, the inner circumferential electrode 1 comes into contact with the atmosphere. When the amount of oxygen is normal, the outer electrode 4 is in contact with the combustion exhaust gas and the other outer electrode 5 is in contact with the combustion flame, as shown in Fig. 2 (a), and the oxygen partial pressure difference between the electrodes 1 and 4 is Although the electromotive force is low because it is small, the difference in oxygen partial pressure between the electrodes 3.5 is large, and the electromotive force is high.As shown in Figure 2 (bl), both the outer electrodes 4.5 and 4.5 come into contact with the combustion flame during combustion. The oxygen partial pressure difference between the electrode and the inner peripheral electrode 1 is large, and a high electromotive force is exhibited.

On the other hand, when an oxygen-deficient state occurs, part of the primary air in the combustion flame comes into contact with the outer peripheral electrode 5 as in the case shown in FIG. 5 (bl).

During strong twist firing, the oxygen concentration in the room is 18 to 19 degrees.

The electromotive force generated between the electrodes 1.5 rapidly decreases, and incomplete combustion is detected at the room oxygen degree i. When the oxygen concentration in the room further decreases, a part of the primary air in the combustion flame comes into contact with the outer peripheral electrode 4, and when the oxygen concentration in the room is 17-18%, the electrode 1.4
The electromotive force generated between the two ends suddenly drops, and incomplete combustion is detected. In addition, when an oxygen deficiency occurs during weak combustion, the electromotive force generated between electrodes 1.5 rapidly decreases when the indoor oxygen concentration is 17 to 18%, and the electromotive force generated between electrodes 1.4 decreases rapidly when the indoor oxygen concentration is 17% to 18%. It decreases rapidly at 15 to 16 inches.

From the above, by using the electromotive force generated between electrodes 1 and 4 during strong twist firing and the electromotive force generated between electrodes 1.5 during 2-low combustion, even when the thermal power fluctuates such as 9-strong/low combustion, there is no problem due to oxygen deficiency. Complete combustion can be detected.

(Example) The present invention will be explained in detail below.

FIG. 1 shows a senna for a combustion safety device according to an embodiment of the present invention; (a) l'j front view, fb) #'if, i) sectional view h.

3 is made of zirconia powder stabilized with Ittria with an outer diameter of 4 mm,
A cylindrical sintered body is molded and fired to have an inner diameter of 2 un and a length of 35 on, and platinum paste (◆8103 manufactured by Tokuriki Chemical Co., Ltd.) is coated on the outer periphery at positions 180° apart from each other and on the entire inner periphery and then baked to form an outer peripheral electrode. 4.5 and 1 tl of inner peripheral electrodes were formed, and zirconia powder was thermally sprayed on the outer peripheral surface to form a 100 μm protective film (not shown).

This is a sensor. The structure outer electrode 5 is provided with its tip end up to the left end of the sintered body 3, the outer electrode 4 is provided with its tip shifted from the left end of the sintered body to the right side, and a part of the inner electrode 1 is provided as shown in FIG.
As shown in a), a lead wire connection portion was provided continuously from the inner circumference to the outer circumference.

This sensor was placed on the burner 11 of the oil fan heater installed inside the combustion chamber as shown in Figure 2 (al).

The outer electrode 5 is installed so that its tip contacts the combustion flame 6 and the outer electrode 4 contacts the combustion exhaust gas, and the lead wires 13 and 1
After connecting to the external instrument using 4.

When the oxygen concentration in the room was changed and the resulting electromotive force was measured, as shown in Figure 3, during normal combustion with an oxygen concentration of 20% or more, 0.7 parts or more was generated in both cases of strong combustion and weak combustion. It shows a high electromotive force, and as the oxygen concentration in the room decreases, the electromotive force decreases, resulting in 2-strong twist firing.

In both cases of weak combustion, the oxygen concentration suddenly decreased between 17 and 19%, and incomplete combustion was detected.

(Effects of the Invention) According to the present invention, incomplete combustion due to lack of oxygen, flame extinction, etc. can be detected even when the fire power fluctuates, such as when firing with a high twist or burning with a low twist. In addition, if the sensor deteriorates or is damaged, the electromotive force decreases, so abnormalities in the sensor can be detected by the sensor without relying on other sensors.

[Brief explanation of the drawing]

Fig. 1 shows a sensor for a combustion safety device according to an embodiment of the present invention (al is a front view, (b) is a sectional view of (al), and Fig. 2 is a sensor for a combustion safety device shown in Fig. 1. A schematic diagram showing the state, Figure 3 is a graph showing the relationship between indoor oxygen concentration and electromotive force,
FIG. 4 shows a conventional combustion safety device sensor (al is a front view, (b) is a sectional view of (al), and FIG. 5 is a schematic diagram showing the usage state of the combustion safety device sensor of FIG. 4. Explanation of symbols 1...Inner circumferential electrode 2...Outer circumferential electrode 3...Sintered body 4...Outer circumferential electrode 5...Outer circumferential electrode
6... Combustion flame 7... Inner flame 8...
External flame (during weak combustion) 9... Mixed gas of unburned gas and primary air 10... External flame (during strong combustion) 11... Burner 12
... External flame (at the time of lack of oxygen) 13 ... Lead wire 14 ... Lead wire length α Escape indoor sacrifice (separate)

Claims (1)

[Claims] 1. A sensor for a combustion safety device comprising two or more heat-resistant electrodes on the outer peripheral surface and a heat-resistant electrode on the inner peripheral surface of a tubular or bag-shaped oxygen ion conductive solid electrolyte sintered body.