JPH06160323A - Co gas detector - Google Patents

Abstract

PURPOSE:To furnish a CO gas detector which has an increased precision in detection of CO and also which can be used for a long period and has high reliability, by preventing an activated carbon filter from being heated by a radiation heat of a sensor. CONSTITUTION:A CO gas detector which is equipped with a first case body 11 having an activated carbon filter 2 and being made of a material of high thermal conductivity and with a second case body 12 having a stem 4 disposed in the lower part, having, in the upper part, a heat-resistant porous resin plate 14 having a porous reflecting film 14a on the lower side, being provided with a sensor 6 for detecting a CO gas in a hollow chamber 5 formed between the porous resin plate 14 and the stem 4 and being made of a material of high thermal conductivity, and of which the first case body 11 and the second case body 12 are joined together integrally with an insulating material 15 of low thermal conductivity interposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CO gas detector for detecting CO (carbon monoxide) gas generated by incomplete combustion of fuel.

[0002]

2. Description of the Related Art There is a device disclosed in Japanese Utility Model Publication No. 2-20682 as an example of a CO gas detecting device equipped with a sensor for detecting CO gas and a filter for removing alcohol, NO _x gas and the like. FIG. 7 shows a configuration diagram of this CO gas detection device.

In the figure, 1 is a cylindrical casing made of synthetic resin such as plastic, 2 is an activated carbon filter disposed on the upper portion of the casing 1, and a metal mesh 3a made of corrosion resistant metal such as stainless steel, 3b holds the activated carbon. According to the activated carbon filter 2, as shown in FIG. 8, ethanol, NO, and NO ₂ contained in smoke, gas, etc. generated in the air or in a fire, for example.
NO _x such as is adsorbed and removed by passing through the activated carbon filter 2, but CO passes through as it is. Reference numeral 4 denotes a stem made of an insulating material disposed in the lower part of the housing 1. The stem 4 and the activated carbon filter 2 form a hollow chamber 5 in the housing 1.

6 is, for example, SnO ₂ (tin dioxide), S
This sensor 6 is composed of a compound semiconductor sintered by adding 3 mg of Pd (addition amount in terms of metal, the same applies below) per 1 g of nO _2, and has a coil for heating itself inside. The sensor 6 is heated to a certain temperature, that is, about 80 ° C., and when CO gas is adsorbed by the sensor 6, the electric resistance decreases, and CO is detected by the decrease in the electric resistance. Further, the sensor 6 is periodically heated up to about 500 ° C., and once CO or the like adsorbed on the sensor 6 is thermally decomposed to be desorbed and heat cleaned. Reference numeral 7 denotes an electrode terminal, one end of which is connected to the sensor 6 and the other end of which is connected to a power supply unit (not shown) that supplies power to the sensor 6, which is held by the stem 4 and is connected to the stem 4 and the electrode terminal 7. The sensor 6 is arranged substantially in the center of the hollow chamber 5.

The noble metal added to SnO ₂ of the sensor 6 is Pt, Rh, Ir, Os, Ru, A instead of Pd.
One or more members of noble metals such as u and Ag may be used, and the addition amount is 1 mg to 15 m per 1 g of SnO _2.
You may change in the range of g.

When the CO gas detecting apparatus constructed as described above detects the CO gas generated by the incomplete combustion of the fuel, the air mixed with the CO gas and the like passes through the activated carbon filter 2 and into the hollow chamber 5. Sent. At this time, ethanol, NO _x, etc. mixed in the air are adsorbed by the activated carbon filter 2 and removed, and only carbon dioxide gas such as CO is sent to the hollow chamber 5. The CO gas in the carbon dioxide gas sent into the hollow chamber 5 is adsorbed by the sensor 6 heated to 80 ° C. When CO is adsorbed, the electric resistance of the sensor 6 decreases with the change in the CO concentration, and therefore the presence or absence of CO gas and the CO gas concentration are detected by this decrease in electric resistance.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The O gas detection device removes alcohol and NO _{x of} air mixed with CO gas generated by incomplete combustion of fuel with the activated carbon filter 2 to obtain only CO gas, and sends this gas into the hollow chamber 5 to remove CO 2. Was adsorbed on the sensor 6, and CO gas was detected by the change in the electric resistance of the adsorbed sensor 6. However, as shown in FIG. 9, the activated carbon used in the activated carbon filter 2 generates CO gas, CO ₂ (carbon dioxide) gas, etc. as the temperature rises, so that the arrow X in FIG. As shown, 80 ~
The activated carbon of the activated carbon filter 2 is heated from below by the radiant heat of the sensor 6 heated to about 500 ° C. and becomes a high temperature state, and CO gas or the like is generated from the activated carbon. Therefore, CO gas from the activated carbon other than the CO gas to be actually detected is adsorbed on the sensor 6 to reduce the electric resistance,
Since CO gas is detected due to this change in electric resistance, the detection accuracy of the sensor 6 is lowered, and the reliability of the CO gas detection device is lowered.

Further, even though the sensor 6 is subjected to heat cleaning, the sensor 6 is always in an adsorbed state due to CO gas generated from the activated carbon.
There was a problem of long-term use due to the trapping effect.

Further, by detecting the CO gas generated from the activated carbon, there is a possibility that an erroneous operation may be caused, for example, a CO gas alarm device equipped with this CO gas detection device may be activated.

The present invention has been made in order to solve the above problems, and prevents the activated carbon filter from being heated by the radiant heat of the sensor to improve the CO detection accuracy and has high reliability for long-term use. The purpose is to provide a gas detector.

[0011]

A CO gas detector according to the present invention is provided with a first casing made of a material having a high thermal conductivity and provided with an activated carbon filter, a stem provided at a lower portion, and a lower surface provided at an upper portion. Has a heat-resistant porous resin plate having a porous reflective film on the inside thereof, and is provided with a sensor for detecting CO gas in the hollow chamber formed between the porous resin plate and the stem. A second housing made of a high material is provided, and the first housing and the second housing are integrally coupled via an insulating material having a low thermal conductivity.

Further, instead of the porous resin plate, a sintered plate of fine ceramic balls having a porous reflecting film on the lower surface is used.

[0013]

When air mixed with CO gas generated by incomplete combustion flows into the CO gas detector, the air passes through the activated carbon filter and further through the porous resin plate or the sintered plate of ceramic balls. It is sent to the hollow chamber.
At this time, alcohol and NO _x in the air are removed by the activated carbon filter, and only gas such as CO is left. Then, the CO gas in the incompletely combusted gas sent into the hollow chamber is adsorbed on the sensor, and the electric resistance of the sensor is lowered.
Then, the presence or absence of CO gas and the concentration of CO gas are detected by the electric resistance that decreases with the change in CO concentration.

During the CO gas detection, the activated carbon filter is prevented from being heated by the radiant heat of the sensor by the reflective film of the porous resin plate or the sintered plate or the insulating member, and the activated carbon filter is kept at room temperature to eliminate the influence of the activated carbon filter.

[0015]

【Example】

Example 1. FIG. 1 is a configuration explanatory view of a first embodiment of the present invention, and FIG. 2 is an enlarged view of the main part thereof. The same parts as those of the conventional example described with reference to FIG.

In the figure, 11 is a cylindrical first casing made of a material having a high thermal conductivity such as aluminum, and an activated carbon filter 2 is disposed between the metal meshes 3a and 3b. Reference numeral 12 is a second casing made of a material having a high thermal conductivity such as aluminum and having a plurality of heat radiation fins 13 provided around the stem 12, and a stem 4 made of an insulating material is disposed in the lower portion of the second casing. Hollow chamber 5 on top
Are formed. A sensor 6 for detecting CO, which is connected to an electrode terminal 7, is installed at substantially the center of the hollow chamber 5.

Reference numeral 14 denotes a heat shield plate provided on the upper part of the second housing 12, and is made of a heat-resistant porous resin such as porous Teflon which allows gas or air to pass therethrough, as shown by an arrow B in FIG. As shown by an arrow C in FIG. 2, a reflective film 14a formed by vapor-depositing porous gold that allows gas and air to pass but reflects heat is provided on one surface. The shield plate 14 is arranged such that the surface on which the reflection film 14a is provided faces the sensor 6. Reference numeral 15 is an insulating member which is interposed between the first housing 11 and the second housing 12 and integrally connects the two, and which is provided between the activated carbon filter 2 and the heat shield plate 13. The air layer 16 is formed. With this configuration, the heat in the second housing 12 heated by the radiant heat of the sensor 6 is not transferred to the first housing 11 in which the activated carbon filter 2 is housed.

Next, the operation of this embodiment will be described. For example, when incomplete combustion of fuel occurs, CO gas or the like generated by incomplete combustion is mixed with air, the air flows into the CO gas detector and passes through the activated carbon filter 2, and further the air layer 16 And it is sent to the hollow chamber 5 through the heat shield plate 14. At this time, ethanol, NO _{x and the} like mixed in the air are adsorbed and removed by the activated carbon filter 2, and only gas such as CO is sent into the hollow chamber 5.
Then, CO in the incomplete combustion gas sent into the hollow chamber 5
The gas is adsorbed by the sensor 6 heated to about 80 ° C. by the power source supplied from the power source section. When CO is adsorbed, C
The electrical resistance of the sensor 6 decreases as the concentration of O changes, and the presence or absence of CO gas and the concentration of CO gas are detected by this decrease in electrical resistance.

The radiant heat of the sensor 6 during CO gas detection is shown in FIG.
As indicated by an arrow A in FIG.
Radiate heat to these to radiate heat to the heat shield plate 14.
Since it is reflected by the reflective film 14a of the above, heating from below the activated carbon filter 2 can be prevented. Also, the second
The second fin 12 heated by the radiant heat of the sensor 6 can be air-cooled more quickly by the radiation fins 13 provided around the outer casing 12, and the insulating member 1
5 and the air layer 16 can almost block the conduction of heat to the first housing 11 and the activated carbon filter 2. Therefore, the activated carbon filter 2 can be prevented from being heated and kept at room temperature, and the generation of CO gas or the like from the activated carbon of the activated carbon filter 2 can be prevented. That is, it is possible to obtain a highly reliable CO gas detector that is not affected by the activated carbon filter 2.

The above-mentioned operation is clear from the experimental results shown in FIGS. 3 (a), 3 (b)
Is the electric resistance (KΩ) of the sensor 6 on the vertical axis and the CO gas concentration (ppm) in the air on the horizontal axis, and the gas-sensing characteristics of the conventional example of FIG. 7 and this example depending on the presence or absence of the activated carbon filter 2. It is shown. If the conventional CO gas detection device does not have the activated carbon filter 2, as shown by the broken line in FIG. 3 (a), it becomes a flat state with a high electric resistance in the clean atmosphere in which CO gas is not mixed, and the C
When the O gas concentration changes, the electric resistance decreases with the change. In addition, when the activated carbon filter 2 is provided, as shown in FIG.
As shown by the solid line in (a), in a clean atmosphere, the electric resistance is lower than in the case where the activated carbon filter 2 is not present and becomes flat, and when the CO gas concentration in the atmosphere changes, the electric resistance decreases with the change. This is because CO gas or the like is generated from the activated carbon filter 2 which has been in a high temperature state due to the radiant heat of the sensor 6 even in a clean atmosphere, and the CO gas is adsorbed to the sensor 6 to lower the electric resistance, thereby the activated carbon filter 2
It shows that there is a difference in electric resistance depending on the presence or absence of. That is, it can be seen that the sensor 6 is always affected by the activated carbon filter 2.

On the other hand, in the CO gas detector of this embodiment, as shown by the solid line in FIG. 3 (b), there is no change in the electric resistance with or without the activated carbon filter 2. That is,
The radiant heat of the sensor 6 is completely shielded by the reflective film 14a of the heat shield plate 14 and the insulating member 15, and it can be judged that a CO gas detector which is not affected by the activated carbon filter 2 and has excellent detection accuracy is obtained. .

In FIG. 4, the vertical axis represents the electrical resistance (K) of the sensor 6.
Ω), the horizontal axis is the years of use (years), and Fig. 5
In (a) and (b), the vertical axis indicates the gas sensitivity ratio (Rair / R).
g), CO gas concentration (ppm) in air for detecting the horizontal axis
7 shows the time-varying characteristics of the conventional example and this example of FIG. The gas sensitivity ratio is the electric resistance in the clean air divided by the electric resistance in the gas-mixed air.

Since the electric resistance of the conventional CO gas detection device is constantly changed by the CO gas generated from the activated carbon filter 2, as shown by the broken line in FIG. As a result, the detection accuracy also decreases. On the other hand, since the CO gas detector of this embodiment is not affected by the activated carbon filter 2 by the heat shield plate 14 and the like, as shown by the solid line in FIG. It can be seen that a CO gas detector having excellent reliability can be obtained without lowering the detection accuracy.

Further, the conventional CO gas inspection device is shown in FIG.
As shown in (a), it can be seen that the difference D in the gas sensitivity ratio increases with the lapse of years, and the sensor 6 is trapped. On the other hand, the CO gas detector of this embodiment is
As shown in FIG. 5B, it can be seen that there is almost no difference D in the gas sensitivity ratio even after the lapse of years, the sensor 6 maintains a state close to the initial state, and there is almost no change over time. In other words, it can be determined that a CO gas detector that can be used for a long period of time without being affected by the activated carbon filter 2 was obtained.

Example 2. FIG. 6 is an enlarged view of the essential parts of the second embodiment of the present invention. In this embodiment, instead of the heat shield plate 14 of the first embodiment, as shown by arrows B and C in FIG. Use a heat shield plate 17 that has a reflective film 17a on which vapor or air passes but reflects heat, which is vapor-deposited on one surface, and through which gas or air passes, for example, a ceramic ball fine-grained sintered body. It was what I had. The maximum heat resistant temperature of the heat shield plate 17 is 1500 ° C., and the heat shield plate 1 of the first embodiment is
Better heat resistance than No. 4.

Also in this embodiment having such a structure, as in the case described in the first embodiment, the radiant heat of the sensor 6 to the activated carbon filter 2 is blocked by the heat shield plate 17 to keep the activated carbon filter 2 at room temperature. It is possible to prevent the generation of CO gas and the like from activated carbon and to accurately detect the presence or absence of CO gas and the concentration of CO gas.

In the above embodiment, the case where the heat radiation fins 13 are provided around the second housing 12 is shown, but the present invention is not limited to this, and the surface area can be increased by providing unevenness, for example. Good.

[0028]

As described above, according to the present invention, the first casing made of a material having a high thermal conductivity and provided with the activated carbon filter, the stem arranged in the lower part, and the porous reflective film formed in the lower part on the upper part. Having a heat-resistant porous resin plate having, or a ceramic ball fine-grained sintered plate having a porous reflective film on the lower surface thereof, and being formed between the porous resin plate or sintered plate and the stem. And a second housing made of a material having a high thermal conductivity in which a sensor for detecting CO gas is provided in the hollow chamber, and the first housing and the second housing are insulated from each other with a low thermal conductivity. Since it is integrally connected through the member, the heat to the activated carbon filter is blocked by the porous resin plate or the sintered plate or the insulating member to keep the activated carbon filter at room temperature, and the CO from the activated carbon is removed.
It is possible to obtain a CO gas detector that can prevent the generation of gas and the like, can reduce the change over time of the sensor, and have excellent detection accuracy and reliability that are not affected by the activated carbon filter and that can be used for a long time. .

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3A is a diagram showing the gas-sensitive characteristics of a conventional CO gas inspection device. (B) is a diagrammatic graph showing gas-sensitive characteristics of the example of the present invention.

FIG. 4 is a diagram showing time-dependent change characteristics of an embodiment of the present invention and a conventional CO gas detection device in a clean atmosphere.

FIG. 5A is a diagram showing a time-dependent change characteristic of a conventional CO gas detector in a gas atmosphere. (B) is a diagram showing the time-dependent change characteristics of the example of the present invention in a gas atmosphere.

FIG. 6 is an enlarged view of a main part of the second embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional CO gas detection device.

FIG. 8 is a diagram showing a gas removal characteristic of activated carbon.

FIG. 9 is a diagram showing a gas generation characteristic of activated carbon.

[Explanation of symbols]

 2 Activated carbon filter 4 Stem 5 Hollow chamber 6 Sensor 7 Electrode terminal 11 First casing 12 Second casing 13 Radiating fins 14,17 Heat shield plate 14a, 17a Reflective film 15 Insulation member 16 Air layer

Claims (2)

[Claims] 1. A heat-resistant porous resin having a first housing made of a material having a high thermal conductivity and provided with an activated carbon filter, a stem arranged in a lower portion, and a porous reflective film in a lower portion on an upper portion. A second housing made of a material having a high thermal conductivity, having a plate, and a sensor for detecting CO gas provided in a hollow chamber formed between the porous resin plate and the stem, A CO gas detector characterized in that the first casing and the second casing are integrally coupled via an insulating member having a low thermal conductivity. 2. The CO gas detector according to claim 1, wherein, instead of the porous resin plate, a sintered plate of fine ceramic balls having a porous reflective film on the lower surface is used.