JP3256827B2 - Incomplete combustion detection sensor and incomplete combustion detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incomplete combustion detection sensor and an incomplete combustion detection device used in a combustion device.

[0002]

2. Description of the Related Art "Incomplete combustion" refers to combustion in which fuel does not completely change into water and carbon dioxide when it is burned, and hydrocarbons such as carbon monoxide, hydrogen, and aldehyde, which are intermediate products, are generated. State. The most harmful of these intermediates is CO, which can cause toxic effects in the human body and even death. Therefore, it is effective to use the CO concentration as an index indicating the degree of incomplete combustion in a combustion device, from the viewpoint of preventing poisoning accidents.

Therefore, it is desired that the incomplete combustion detection sensor detects CO as selectively as possible.

Therefore, an infrared absorption type CO analyzer has been conventionally used as an incomplete combustion detection sensor, and a contact combustion type sensor or a tin oxide sensor has been developed as a small sensor.

[0005]

In order to obtain sufficient sensitivity to CO in the above-mentioned CO analyzer, it is necessary to secure a sufficient optical path length of the infrared absorption chamber of the CO analyzer.
The size of the CO analyzer cannot be reduced below a predetermined size. In addition, components such as an infrared light emitting device, a light receiving device, and a pump used for the device are expensive, and there is a possibility that a long-term change in sensitivity may occur due to contamination of the absorption chamber.

Accordingly, the CO analyzer is too large in size as a sensor for preventing incomplete combustion of a combustion device such as a water heater, a fan heater, and a stove, and cannot be easily incorporated therein. It is also unsuitable in terms of cost, long-term durability and the like.

On the other hand, catalytic combustion type sensor and tin oxide sensor is a small, albeit incomplete combustion detecting sensor is excellent in long-term stability at low cost, it has a sensitivity in H ₂ or more CO. For this reason, in some cases, the degree of incomplete combustion is determined to be severe even in a safe combustion region in response to H ₂ even though CO is not generated.

[0008] Therefore, if such a malfunction occurs, a fire extinguishing in the combustion device or the like is caused, which causes a trouble.

In view of the above problems, the present invention provides a small-sized, low-cost sensor, an incomplete combustion detection sensor having good selectivity for CO, and a detection device using the same.

[0010]

According to a first aspect of the present invention, there is provided an incomplete combustion detecting sensor according to the first aspect of the present invention , wherein a pair of electrodes are provided on a gas detecting portion made of indium oxide,
Addition of potassium metal or alkali metal compound
This forms a detection unit .

According to a second aspect of the present invention, there is provided the incomplete combustion detection sensor according to the first aspect , wherein the alkali metal is Na, K,
Rb and Cs .

According to a third aspect of the present invention, there is provided the incomplete combustion detection sensor according to the first aspect , wherein the amount of the alkali metal added is 30.
% By weight or less.

According to a fourth aspect of the present invention, there is provided an incomplete combustion detection sensor according to the first aspect, further comprising a heating unit for heating the gas detection unit to a predetermined temperature.

According to a fifth aspect of the present invention, there is provided an incomplete combustion detection device, comprising: a resistance measuring means for measuring a resistance value between a pair of electrodes of the incomplete combustion detection sensor according to the first aspect; And sensing means for sensing the concentration.

[0015]

The incomplete combustion detection sensor according to claim 1 uses indium oxide for the gas detection part, so that the resistance value between the pair of electrodes is measured, and the change in the measured value detects the CO concentration. it can.

[0016] Then, indium oxide, because it is adding an alkali metal or alkali metal compound, C
The sensitivity to O is improved.

In the incomplete combustion detection sensor according to the second aspect , since the alkali metals are Na, K, Rb , and Cs , particularly,
Sensitivity is improved.

According to a third aspect of the present invention, in the incomplete combustion detection sensor, the amount of the alkali metal added to the indium oxide is 30% by weight.
Because of the following, the sensitivity to CO is particularly improved.

The incomplete combustion detection sensor according to claim 4, by heating to a predetermined temperature by the heating portion of the gas sensing portion and the sensitivity is raised to more sensitive temperature for CO in indium oxide, the selectivity for CO Can be improved.

According to a fifth aspect of the present invention, there is provided an incomplete combustion detecting device for measuring a resistance value between a pair of electrodes of an incomplete combustion detecting sensor by a resistance measuring means. Sense.

[0021]

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

The structure of an incomplete combustion detection sensor (hereinafter simply referred to as "sensor") 10 according to one embodiment of the present invention will be described.

FIG. 1 is an external view of the sensor 10, and FIG.
FIG. 3 is a diagram showing a state where the sensor 10 is attached to the combustion device 12.

The sensor 10 includes a gas detector 14 made of sintered indium oxide or the like, a pair of electrodes 16 made of platinum or the like provided on the gas detector 14, and a heater wire embedded inside the gas detector 14. Consists of eighteen.

The electrodes 16, 16 are connected to a resistance measuring device 20 for measuring a resistance value between them.

The heater wire 18 is connected to a power supply 22 for heating.

The following materials are suitable for the gas detecting section 14.

That is, a material obtained by adding an alkali metal or a compound of an alkali metal to indium oxide is used . This sensor 10 is, as shown in FIG.
The second exhaust unit 24 is provided. In addition, the combustion device 12
Generally, it comprises a combustion section 26 using gas, a heat exchanger 28 receiving heat from the combustion section 26, and the exhaust section 24.

When the combustion device 12 operates, the concentration of CO in the exhaust portion 24 is detected by the sensor 10, and the resistance value between the electrodes 16, 16 changes.
0 senses it. When the temperature of the air from the exhaust unit 24 is low (for example, 100 ° C. or less), the gas detecting unit 14 is heated to around 300 ° C. by the heater wire 18. The heating temperature is controlled by the power supply unit 22 so as to be always 300 ° C.

In the case of the sensor 10, since the gas detecting portion 14 is formed of indium oxide or the like, the size can be reduced and the cost can be reduced. In addition, CO in combustion exhaust gas
The allows detection with higher sensitivity than H _2, water heaters for domestic, available water heaters, fan heaters, in a stove or the like, it is possible to detect reliably incomplete combustion.

As the sensor 10, a thick film or a thin film printed on a substrate having electrodes attached thereto may be used.

As means for heating the gas detecting section 14, a heater wire may be wound around the gas detecting section 14, or the gas detecting section 14 may be provided on a substrate having a built-in heater.

The feature of the sensor 10 of the present embodiment resides in that the above-mentioned materials are used as the material of the gas detecting section 14. The following describes the suitability of these materials based on experimental data.

First, various materials (sintered sensor elements) used in the next experiment were placed on an alumina tube at 700.degree.
It was made by sintering for a time. As an environment for the experiment, the resistance of this element was adjusted to 300 to 700 under the flow of a test gas containing 1.5 vol% of water vapor (200 cm ³ / min).
The gas detection characteristics were investigated by measuring at ° C. The test gas contains 1,000 ppm of CO diluted in air.
And _{H 2} is used mainly. The gas sensitivity was represented by the ratio (Ra / Rg) of the element resistance (Ra) in the synthetic wet air and the resistance (Rg) in the test gas. Hereinafter, this ratio is referred to as sensitivity.

During the experiment, the measurement temperature was 300 ° C.
When the temperature was set to 600 ° C., the gas detector 14 was heated to this temperature by heating the heater wire 18.

Although not an example of the present invention, the fact that a single sample of indium oxide has much higher sensitivity to CO than other samples will be described with reference to FIG.

In the graph of FIG. 3, the vertical axis represents the voltage value (hereinafter referred to as output) (V) of the electrodes 16 and 16, and the horizontal axis represents the measurement time (minutes).

Then, CO was used as a test gas for the first 8 minutes, and H2 was used as a test gas for 15 to 23 minutes.

According to this, indium oxide has a very high sensitivity to CO as compared with other samples such as SnO 2 and ZnO. In addition, indium oxide alone
, In this temperature range, H ₂ pairs for CO have a sensitivity comparable
It was confirmed that.

[0040] When the addition of alkali metal to indium oxide are examples of the present invention will be described with reference to FIGS. 4 to 7 for the selective than H ₂ CO is improved.

4 to 6 , the ordinate represents the sensitivity, and the abscissa represents the added substances.

FIG . 4 is a bar graph showing the sensitivities to CO and H2 when sodium oxide was added from 1% to 20% and when sodium oxide was not added at all.

[0043] According to this, the case of adding sodium oxide, always sensitivity of CO has exceeded the sensitivity of H _2. Then, the sensitivity of CO only when no oxide is added sodium quite is below the sensitivity of the H _2. Then, it can be determined that the case where the addition amount is 30% by weight or less is preferable.

5 and 6 , the sensitivity of CO is always H when potassium oxide or rubidium oxide is added.
_It exceeds the sensitivity of ₂ .

FIG . 7 is a graph when cesium is added. The vertical axis indicates the output (V), and the horizontal axis indicates the measurement time.

According to this, the output is always higher when CO is the test gas than when H ₂ is the test gas, that is, the sensitivity of CO is higher than that of H ₂ . It is also good.

[0047]

As described above, according to the incomplete combustion detecting sensor of the present invention, since the gas detecting portion is formed of indium oxide or the like, the size can be reduced and the cost can be reduced. Further, since CO in the flue gas, can be detected with higher sensitivity than H _2, water heaters for domestic, water heaters, fan heaters,
It can be used in stoves and the like, and can reliably detect incomplete combustion.

Further, in the incomplete combustion detection device using the incomplete combustion detection sensor, incomplete combustion can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a plan view of a sensor showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a combustion device using a sensor.

FIG. 3 is a graph showing a comparison of sensor sensitivity when using indium oxide and when using another sample.

FIG. 4 is a graph showing sensitivity when sodium oxide is added to indium oxide.

FIG. 5 is a graph when potassium oxide is added.

FIG. 6 is a graph in the case where rubidium oxide is added.

FIG. 7 is a graph when cesium is added.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sensor 12 Combustion device 14 Gas detection part 16 Electrode 18 Heater wire 20 Resistance measuring device 22 Power supply part 24 Exhaust part 26 Combustion part 28 Heat exchanger

Continuation of the front page (56) References JP-A-7-72107 (JP, A) JP-A-7-55745 (JP, A) JP-A-59-38642 (JP, A) JP-A-60-89624 (JP) , A) JP-A-60-20024 (JP, A) JP-A 52-6687 (JP, U) JP-B 50-22435 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB (Name) G01N 27/12

Claims (5)

(57) [Claims] To 1. A consisting of indium oxide gas detector, a pair of electrodes, said indium oxide, an alkali metal or an alkali metal
An incomplete combustion detection sensor, wherein the gas detection unit is formed by adding a compound belonging to the genus . 2. The method according to claim 1, wherein said alkali metal is Na, K, Rb , C
incomplete combustion detection sensor according to claim 1, characterized in that the s. 3. incomplete combustion detection sensor according to claim 1, wherein the amount of the alkali metal is 30 wt% or less. 4. The incomplete combustion detection sensor according to claim 1, further comprising a heating section for heating the gas detection section to a predetermined temperature. 5. A resistance measuring means for measuring a resistance value between a pair of electrodes of the incomplete combustion detecting sensor according to claim 1, and a sensing means for detecting a concentration of CO from a measured value of the resistance measuring means. An incomplete combustion detection device, characterized in that: