JP2003172719A - Gas sensor and gas detector for preventing fat and oil fire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor capable of detecting a small amount of gas using a simple gas detection element. <P>SOLUTION: This gas sensor is provided with a gas suction member F changeable into a suction condition in which it sucks the gas to be detected and an elimination condition in which the gas to be detected is eliminated due to changes of temperature, a heater 7 for heating the gas suction member F, the gas detection element 3 arranged at a position where the gas to be detected eliminated from the gas suction member F reaches and capable of detecting the gas to be detected, and a drive means for heating and driving the heater 7 so that a temperature of the gas suction member F is alternately changed to a low temperature side set temperature and a high temperature side set temperature. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor capable of detecting a small amount of gas to be detected while using a simple gas detection element, and a fire caused by overheating of oils and fats such as tempura oil using this gas sensor. The present invention relates to a gas detector for preventing oil and fire for preventing fire.

[0002]

2. Description of the Related Art Conventionally, smoke detection type or heat detection type fire alarms have been used as means for detecting oil and fat fires such as tempura oil. Among them, the smoke detection type uses the light attenuation effect of smoke generated from the flame at the time of fire occurrence, and therefore has sensitivity to smoke from grilled fish and the like generated during normal cooking, There are many false alarms. On the other hand, the heat detection type has a low possibility of false alarm, but since it detects a temperature rise in the progress of the fire, it cannot be used as a means for preventing the occurrence of the fire. On the other hand, various techniques have been proposed for fire detectors that detect smoky gas generated in the early stages of a fire. As a general fire detection, in Japanese Patent No. 2890205, a technology of a fire detector using two sensors having different relative ratios of sensitivity to burning odor and alcohol odor is disclosed, and the sensor detection unit responds to aliphatic alcohol. It is described that a sensor that easily reacts and a sensor that easily responds to aromatics including aromatic alcohol and aldehyde can be used to detect the gas generated during heating of acetate, wood, glass epoxy resin, decorative plywood, and the like. Regarding detection of oil fire such as tempura oil, Japanese Patent Laid-Open No. 4-155132 discloses a method for preventing false alarm due to smoke from grilled fish.
A technique relating to a flue gas hood in which a gas detection unit is combined with a conventional smoke detection unit is disclosed, and further it is described that a large amount of acetaldehyde is generated when edible oil and fat is heated. Further, Japanese Patent Application Laid-Open No. 8-170955 discloses a material technology of a detection unit which is particularly sensitive to acetaldehyde and formaldehyde in order to detect acetaldehyde generated when smoking tobacco or heating edible oil and fat. .

[0003]

However, as a result of the analysis by the inventors of the gases generated during heating of various edible oils and fats, the main component of the pyrolysis gas generated during heating of oils and fats such as cooking oil is C2-C8 alkanes (C5-C5 pentane, C7-heptane, C8
Octane, etc.) and aldehydes having 3 to 9 carbon atoms (propionaldehyde having 3 carbon atoms, butyraldehyde having 4 carbon atoms, pentanal having 5 carbon atoms, hexanal having 6 carbon atoms, heptenal having 7 carbon atoms, etc.). Although it was found to be a gas group, when the applicability of the prior art to a fat and oil fire was examined in view of the detection characteristics for these gas species, it was found that the following problems were encountered.

First, in the combination of sensors for gas species shown in Japanese Patent No. 2890205, that is, the sensor which is responsive to aliphatic alcohol is combined with the sensor which is responsive to aromatic compounds including aromatic alcohol and aldehyde. It is not possible to deal with oil fire such as tempura oil. Further, even in the technique disclosed in Japanese Patent Laid-Open No. 4-155132, the reliability of gas detection generated when heating fats and oils is poor, and alcohol is generated by cooking with grilled fish and cooking liquor at the same time. In addition, there is a possibility of erroneous detection, and in the technique of detecting a lower aldehyde (acetaldehyde) as disclosed in JP-A-8-170955, a low linolenic acid content, for example, oleic acid-rich beni flower oil is used. Almost lower aldehydes are not generated when such edible oils and fats are used, and thus it is difficult to obtain sufficient sensitivity to a fire when such oils and fats are used.

On the other hand, it has a specific high sensitivity to the gas species in the gas group consisting of the alkane having 2 to 8 carbon atoms and the aldehyde having 3 to 9 carbon atoms, or only in these gas groups. There is no simple gas detection element having a specific high sensitivity. Moreover, the amount of the pyrolysis gas that is generated by heating the oil and fat and reaches the position of the gas detection element is very small. Therefore, the temporal change pattern peculiar to the gas species of the gas group appearing in the output of the gas detection element is identified, or the output of a plurality of gas detection elements having different detection characteristics for the gas species of the gas group is combined. It is possible to detect the gas to be detected by determining the type of gas to be detected, etc., but in this case, there is a problem that the configuration of the detection process becomes complicated.

The present invention has been made in view of the above circumstances, and a first object thereof is to provide a gas sensor capable of detecting a trace amount of gas to be detected by using a simple gas detection element. It is to be. A second object is to provide a grease fire prevention gas detector that can detect a grease fire before the occurrence of the grease fire using the gas sensor.

[0007]

A first characteristic configuration of a gas sensor according to the present invention is, as described in claim 1 of the scope of claims, an adsorption state in which a gas to be detected is adsorbed by a change in temperature. And a gas adsorbing member that can be changed to a desorption state in which the detection target gas is desorbed, a heater for heating the gas adsorption member, and a position where the detection target gas desorbed from the gas adsorption member reaches And a gas detection element capable of detecting the gas to be detected, and a driving means for heating and driving the heater so that the temperature of the gas adsorbing member is alternately changed between the low temperature side set temperature and the high temperature side set temperature. It is in the point of being prepared.

The second characteristic constitution is, in addition to the first characteristic constitution, the low temperature side preset temperature is in a range from room temperature to 130 ° C., as described in claim 2 of the scope of claims. In point.

The third characteristic constitution is, in addition to the first or second characteristic constitution, as described in claim 3 of the scope of claims, the gas detecting element is used as the gas to be detected. , An aldehyde having 3 to 9 carbon atoms, and 2 to 8 carbon atoms
Is sensitive to at least one gas component of the alkane.

In the fourth characteristic constitution, as described in claim 4 of the scope of the claims, in addition to any one of the first to third characteristic constitutions, the gas adsorbing member is activated carbon. In point.

A characteristic configuration of the oil and fat fire prevention gas detector according to the present invention is provided with the gas sensor of any one of the first to fourth characteristic configurations as described in claim 5 of the scope of claims. A point is provided for determining whether or not the oil or fat is in an overheated state, based on the output information of the gas detection element output at the timing of the heating drive by the drive unit.

The operation and effect will be described below. According to the first characteristic configuration of the gas sensor according to the present invention, the gas adsorption member that can be changed between the adsorption state in which the detection target gas is adsorbed and the desorption state in which the detection target gas is desorbed due to the change in temperature is set to the low temperature side. When the driving means heats and drives the heater for heating the gas adsorbing member so as to change to the temperature, the gas adsorbing member is changed to the adsorbed state and adsorbs the gas to be detected, and then the gas adsorbing member is heated to a high temperature. When the driving means drives the heater so as to change to the side set temperature, the gas adsorbing member is changed to the desorption state to desorb the adsorbed detection target gas, and the detection target gas desorbed from the gas adsorption member is It reaches the position of the gas detection element and is detected. That is, first, the gas to be detected is adsorbed to the gas adsorbing member that has been heated to the low temperature side set temperature and changed to the adsorbed state, and then heated to the high temperature side set temperature and changed to the desorbed state. Since the adsorbed detection target gas is desorbed and detected by the gas detection element, the generated detection target gas is in a very small amount, and the gas detection element has high specific sensitivity to the detection target gas. Even if it does not, the gas detection element can detect the detection target gas that has accumulated and increased in amount in the process of adsorbing to the gas adsorbing member. Therefore, there is provided a gas sensor capable of detecting a small amount of a detection target gas by using a simple gas detection element having no specific high sensitivity to the detection target gas.

According to the second characteristic configuration, the gas adsorbing member is heated to the low temperature side preset temperature in the range of room temperature to 130 ° C. and changed to the adsorbed state. That is, when the set temperature on the low temperature side is set in the range of room temperature to 130 ° C., the gas adsorbing member has 3 to 3 carbon atoms, which is the main component of the pyrolysis gas of edible oil and fat.
Since any of the 9 aldehydes can be adsorbed, any of the above aldehydes is surely adsorbed to the gas adsorbing member at an appropriate low temperature side set temperature, desorbed at the high temperature side set temperature, and detected by the gas detection element. be able to. Further, for example, in a situation where alcohol is used heavily, setting the low temperature side set temperature in the range of around 85 ° C. to 130 ° C. impairs the adsorption of hexanal, which is a thermal decomposition gas component of edible fats and oils, to the gas adsorption member. Therefore, the adsorption of ethanol, which is a false alarm, can be reduced, and thus the selectivity of the edible fat and oil to the pyrolysis gas component can be increased with respect to the ethanol, which is a false alarm. In addition, in the situation where it is important to distinguish from methane and propane, if the low temperature setting temperature is set to near room temperature, pentane, which is one of the pyrolyzed gas components of edible fats and oils, aggregates at 36 ° C or lower, so that gas is well While it can be adsorbed on the adsorption member, the adsorption of methane or propane, which is a false alarm, is reduced, and the selectivity of the cooking oil to the pyrolysis gas component can be increased with respect to methane or propane, which is a false alarm. Therefore, by setting the low temperature side set temperature in the range of room temperature to 130 ° C., an embodiment of a gas sensor suitable for a case where the pyrolysis gas of edible oil and fat is to be detected can be obtained.

According to the third characteristic constitution, among the aldehyde having 3 to 9 carbon atoms and the alkane having 2 to 8 carbon atoms, which are the gas to be detected desorbed from the gas adsorbing member at the high temperature side set temperature, The gas detection element detects at least one gas component of That is, the main component of the pyrolysis gas generated when heating fats and oils such as edible oil, regardless of the type of fats and oils,
It is known to be a gas group consisting of an alkane having 2 to 8 carbon atoms and an aldehyde having 3 to 9 carbon atoms. The gas detection element having the above characteristics causes the oil and fat to be generated when heated, and is adsorbed and desorbed by the gas adsorbing member. The separated pyrolysis gas component can be appropriately detected. Therefore, an embodiment of the gas sensor suitable for the case where the pyrolysis gas of oil or fat such as edible oil is to be detected regardless of the type of oil or fat can be obtained.

According to the fourth characteristic structure, the activated carbon is the gas adsorbing member which can be changed between the adsorption state in which the gas to be detected is adsorbed and the desorption state in which the gas to be detected is desorbed by the change in temperature. That is, activated carbon has a large specific surface area, is advantageous for adsorbing various gases, and is an easily available and inexpensive material. In addition, activated carbon easily adsorbs hydrophobic molecules, and is suitable for adsorbing gas species of a gas group consisting of the alkane and aldehyde, which are the main components of the thermal decomposition gas of fats and oils. Therefore, by using activated carbon for the gas adsorbing member, good adsorbing characteristics can be realized with an inexpensive structure, and particularly, a gas sensor suitable for the case where a pyrolysis gas of an oil or fat such as edible oil is to be detected. Embodiment is obtained.

According to the characteristic construction of the oil and fire prevention gas detector of the present invention, in the gas sensor having any one of the first to fourth characteristic constructions, the heater for heating the gas adsorbing member is driven by the driving means. Based on the output information of the gas detection element output in accordance with the timing,
The determination means determines whether or not the oil or fat is in an overheated state. That is, when the gas adsorbing member is heated to the low temperature side set temperature, the pyrolysis gas component generated by heating the oil and fat is adsorbed to the gas adsorbing member, and the gas adsorbing member is heated to the high temperature side set temperature. In addition, the pyrolysis gas component desorbed from the gas adsorbing member is detected by the gas detection element, and it is determined whether or not the oil or fat is overheated based on the output information of the gas detection element. Further, since the thermal decomposition gas generated when the oil and fat is heated is detected to determine the overheated state of the oil and fat, it is possible to appropriately determine the possibility of fire occurrence before the oil and fat fire occurs. Therefore, a grease fire prevention gas detector capable of detecting a grease fire before it occurs is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a gas sensor and a fat and oil fire prevention gas detector according to the present invention will be described with reference to the drawings. [First Embodiment] First, the configuration of a gas sensor 1 according to the present invention will be described. As shown in FIG. 1 (a), the gas sensor 1 is provided with a semiconductor type gas detection element 3 which is supported by a substrate 10 and is surrounded by a housing 8A. Passage 9
A is formed. Further, the filter housing 8B, which is adjacent to the housing 8A and communicates with the inside of the housing 8A through the gas passage port 9A, is
It is provided in a state of being supported by A. A gas inlet 9B for taking in the detection target gas G is formed in the upper part of the filter housing 8B, and the inside of the filter housing 8B detects the adsorption state in which the detection target gas G is adsorbed due to a change in temperature. The gas adsorbing member F, which can be changed into a desorbed state for desorbing the target gas G, is filled, and
A heater 7 for heating the gas adsorbing member F is built in. The gas adsorption member F is specifically granular activated carbon.

The gas detection element 3 is a gas detection element which is arranged at a position where the detection target gas G desorbed from the gas adsorbing member F reaches and which can detect the detection target gas G. That is, the gas to be detected G that has flowed into the filter housing 8B from the gas inlet 9B is once adsorbed by the gas adsorbing member F that is maintained at the adsorbing temperature condition (the set temperature on the low temperature side), and then desorbed. Of the gas to be detected G that has been desorbed from the gas adsorbing member F that has been changed to the temperature condition for use (high temperature side setting temperature), and the desorbed detection target gas G flows into the housing 8A through the gas passage port 9A. 3 detected.

The gas detection element 3 is sensitive to at least one gas component of the aldehyde having 3 to 9 carbon atoms and the alkane having 2 to 8 carbon atoms as the gas G to be detected. In particular, it is desirable to have sensitivity to any of pentane (C5), octane (C8), heptane (C7), pentanal (C5), and hexanal (C6). However, the gas detection element 3 is
It is also sensitive to combustible gases other than the above-mentioned aldehydes and alkanes, for example, alcohols such as ethanol and component gases of city gas (methane, propane, butane).

FIG. 4 shows the composition of the pyrolysis gas of two kinds of edible oils and fats (normal salad oil and oleic acid rich safflower oil) at 250 ° C. In the figure, the unit of gas concentration is an arbitrary unit. According to the figure, acetaldehyde (carbon number 2) is about double (concentration ratio 0.5
In contrast to 6), there is a small difference in the concentration of hexanal (6 carbon atoms) depending on the type of fat and oil, and also in the total sum of the aldehydes having 3 to 9 carbon atoms. On the other hand, for alkanes, the concentration of methane (carbon number 2) generated is low regardless of the type of edible oil and fat, and depending on the type of edible oil and fat, pentane (carbon number 5) has a concentration ratio of about 0.7 times that of carbon. Even in the sum of alkanes of several 2 to 8, there is only a 1.3-fold change in concentration ratio. From the above, it can be seen that the aldehyde having 3 to 9 carbon atoms and the alkane having 2 to 8 carbon atoms are suitable as detection targets for the thermal decomposition gas of edible oil and fat.

The gas detecting element 3 is specifically shown in FIG.
As shown in (b), it has a structure in which a gas sensitive layer 5 containing an oxide semiconductor as a main component is provided on an alumina substrate 4.
Although the drawing shows a substrate type detection element structure, a spherical element structure or the like may be used. Further, a heater 6 for heating the gas sensitive layer 5 is attached to the lower surface of the substrate 4, and the influence of heat from the heater 6 on the gas adsorbing member F can be neglected from the arrangement shown in the drawing. The gas sensitive layer 5 is composed of tin oxide SnO ₂ , zinc oxide ZnO, indium oxide In ₂ O ₃ or the like.
a and a catalyst in which 0.1 to 10% by weight of a metal such as W or Mo is supported on an Al ₂ O ₃ carrier, for example, which is laminated so as to cover the gas sensitive portion 5a and suppresses the sensitivity of alcohol. And layer 5b. With this configuration, the gas detection characteristics of the gas-sensitive layer 5 are changed by the catalyst layer 5b, and the carbon number of 3 to
It is configured to have sensitivity to the aldehyde of 9 and the gas component contained in the alkane having 2 to 8 carbon atoms.

From the gas detecting element 3, a total of four lead wires are taken out for energizing the heater 6 and for taking out the signal of the gas sensitive layer 5, and these lead wires are taken out from the bottom surface of the substrate 10. As shown in FIG. 2, the gas detection element 3 is connected to a pin and is further connected to the control unit 2 including a microcomputer by the lead wire. The gas sensitive layer 5 is heated to a temperature range of 400 to 550 ° C. during the detection operation.

Next, a circuit for detecting the output of the gas detecting element 3 is shown in FIG. In FIG. 3, Rs is the gas detection element 3
Is a resistance of the gas sensitive section 5a, a fixed resistance Ro is connected in series to the resistance Rs of the gas sensitive section 5a, and the voltage Vt is applied to the series arrangement of the resistance Rs and the fixed resistance Ro of the gas sensitive section 5a. Then, the voltage Vo across the fixed resistor Ro is measured. The air level voltage when the resistance Rs decreases due to the increase in the concentration of the gas G to be detected with reference to the voltage Vo in the state of only clean air (air level) in which the pyrolysis gas of oil and fat does not exist. The increment of the measured voltage Vo from is taken out as the output of the sensor. still,
The resistance value of the fixed resistance Ro is a value when the resistance value Rs is most decreased by the thermal decomposition gas of oil and fat, that is,
The resistance value Rs at the time when the oil temperature exceeds 300 ° C. is selected to be approximately the same value.

A driving means 100 for heating and driving the heater 7 is constructed in the control unit 2 so that the temperature of the gas adsorbing member F alternates between the low temperature side setting temperature and the high temperature side setting temperature. ing. Specifically, the temperature of the gas adsorption member F is changed in a cycle of a low temperature side set temperature of 85 ° C. for 25 seconds and a high temperature side set temperature of 250 ° C. for 5 seconds.
The heating drive pattern of the heater 7 is set.

Therefore, the gas adsorbing member F is heated to the high temperature side preset temperature (250 ° C.) of 150 ° C. or higher and is changed to the desorption state. That is, by setting the high temperature side set temperature to 150 ° C. or higher, the gas adsorbing member F for the aldehyde having 3 to 9 carbon atoms, which is the main component of the pyrolysis gas of edible oil and fat.
Is promoted. Accordingly, the aldehyde adsorbed on the gas adsorbing member F at the low temperature side set temperature can be reliably desorbed from the gas adsorbing member F at the appropriate high temperature side set temperature and detected by the gas detection element 3.
The gas sensor 1 suitable for the case where the thermally decomposed gas of edible oil is to be detected can be obtained. The high temperature side set temperature is not particularly limited to the upper limit temperature from the viewpoint of action and effect, but from the viewpoint of low power consumption, it is desirable to set the temperature to 150 ° C. or higher to the minimum required temperature.

Next, in addition to the configuration of the gas sensor 1, the oil and fat fire prevention gas detector according to the present invention is output in the control section 2 in synchronization with the heating drive timing of the drive means 100. A determination unit 101 that determines whether or not the oil and fat is in an overheated state is configured based on the output information of the gas detection element 3.

Next, measurement by the gas sensor 1 will be described. The gas sensor 1 was installed in a chamber having an internal volume of 30 L, and 10 cc of salad oil was placed in a glass container on a hot plate in the chamber, and the sensor output when continuously heated was measured. In addition, about the same about 3 sake
The sensor output was measured when cc was heated and the entire amount was evaporated. FIG. 5 shows the response of the sensor output before and after heating the gas adsorbing member F. In the figure, the high temperature side set temperature (2
The temperature is maintained at 50 ° C.

As can be seen from FIG. 5, in the heating period of the gas adsorbing member F, an increase and a decrease in the sensor output due to desorption from the gas adsorbing member F can be confirmed for both salad oil and sake, but the maximum value of the sensor output Salad oil is bigger than sake. Therefore, by setting the heating conditions of the gas adsorbing member F as described above, the gas sensor 1 that can detect the pyrolysis gas of salad oil with higher sensitivity than the evaporative gas of sake (such as ethanol) is configured. Also, focusing on the difference (change amount) between the sensor output before heating the gas adsorbing member F (low temperature side set temperature) and the maximum value during heating, the sensor output at the low temperature side set temperature is Is lower than that of sake, so the above-mentioned change is larger in the case of salad oil than in sake. Therefore, the difference (change amount) between the sensor output before heating the gas adsorbing member F and the sensor output after a predetermined time (2 to 3 seconds) has elapsed after the heater is turned on, which is the maximum value during the heating period, is calculated. By determining the magnitude, the gas sensor 1 with improved detection selectivity for the pyrolysis gas of salad oil is configured.

Further, in FIG. 6, as a comparative example, only the gas detecting element 3 from which the gas adsorbing member F and the heater 7 are removed from the gas sensor 1 is installed in the above chamber, and salad oil and sake are heated in the same manner. The sensor output is shown. It should be noted that 0 on the time axis in FIG. 6 is the time when the evaporation of the liquid in the chamber is completed. From FIG. 6, since the detection characteristic of the gas detection element 3 itself appears in the method of the comparative example,
The detection output level reaching saturation after evaporation of salad oil is relatively lower than the detection output level reaching saturation after evaporation of sake, and the pyrolysis gas of salad oil can be detected separately from the evaporation gas of sake (such as ethanol). I find it difficult.

Then, in the oil and fire prevention gas detector,
The determination means 101 determines whether or not the oil or fat is in an overheated state based on the output of the gas sensor 1 when the gas adsorbing member F is heated. For example, when the maximum value of the sensor output exceeds the predetermined value even once, it is determined that the fat or oil is overheated, or when the maximum value of the sensor output continuously exceeds the predetermined value a plurality of times. The determination conditions can be set as appropriate in order to secure the reliability of detection and avoid false alarms such as determining that the oil or fat is overheated.

The determination means 101 is provided with an alarm means 11 which activates an alarm when an overheated state of oil or fat is determined, and the alarm means 11 can be set to either an operable state or an inoperable state. It is configured. Specifically, the alarm means 11 is configured by a buzzer connected to the control unit 2 for generating an alarm sound, a speaker for issuing an alarm by voice, or a lamp for displaying blinking light or the like. Then, by turning on or off the manual switch 12 connected to the control unit 2, it is possible to change and set the alarm means 11 between an operable state and an inoperable state.

Further, based on the output information of the gas detection element 3 output at the timing of the heating drive by the drive means 100, it is determined whether or not the oil is overheated by using an external measuring device or the like. It is also possible to judge. Specifically, the output of the gas detecting element 3 shown in FIG. 1 is input to an external measuring device, and the measuring device analyzes the output signal of the gas detecting element 3 to determine the overheated state of the oil and fat. In this case, there is an advantage that the user who uses the gas detection element 3 can freely set the analysis content for analyzing the output signal of the gas detection element 3 in consideration of the conditions of the oil and fat to be detected. .

[Second Embodiment] Next, a second embodiment of the gas sensor and the oil / fat fire prevention gas detector according to the present invention will be described. In the second embodiment, this occurs when cooking liquor or the like is heated. The low temperature side preset temperature of the gas adsorbing member F is set to 30 to 40 ° C. for the purpose of detecting fats and oils such as salad oil in distinction from city gas (methane, propane, butane, etc.) instead of alcohol. Different from the first embodiment. The differences will be described below.

Similar to the first embodiment, the gas sensor 1 is installed in a chamber having an internal volume of 30 L, 10 cc of salad oil is put in a glass container on a hot plate in the chamber, and the sensor output when continuously heated is displayed. It was measured. In addition, 0.3cc (about 10pp
The sensor output when (corresponding to m) was introduced was also measured. FIG. 7 shows the response of the sensor output before and after heating the gas adsorbing member F with the low temperature side preset temperature being 35 ° C. and the high temperature side preset temperature being 250 ° C. In FIG. 7, the high temperature side preset temperature (250 ° C.) is maintained between the position of 5 seconds on the horizontal axis and the position of 10 seconds.

As can be seen from FIG. 7, the maximum value of the sensor output during the heating period of the gas adsorbing member F is larger when the salad oil is heated than when the methane is introduced. Therefore, by setting the heating conditions of the gas adsorbing member F as described above, a gas sensor that can detect the thermally decomposed gas of salad oil with higher sensitivity than city gas such as methane is configured.

In FIG. 8, as a comparative example, when only the gas detecting element 3 from which the gas adsorbing member F and the heater 7 are removed from the gas sensor 1 is installed in the chamber and the salad oil is similarly heated. , And sensor output when methane is introduced. From FIG. 8, in the method of the comparative example, the detection output level reaching saturation after the evaporation of salad oil is relatively lower than the detection output level when methane gas is 10 ppm, and the pyrolysis gas of salad oil is separated from city gas such as methane. It turns out that it is difficult to detect separately.

[Other Embodiment] Another embodiment will be described below. In the above-described embodiment, the heater 7 for heating the gas adsorbing member F is arranged inside the gas adsorbing member F, but if the gas adsorbing member F can be heated, other than this, it is illustrated in FIG. Thus, it may be arranged on the side surface of the gas adsorbing member F or on the bottom surface of the gas adsorbing member F.

In the above embodiment, the gas adsorbing member F is made of activated carbon. However, in addition to this, the gas adsorbing member F has a large specific surface area which is advantageous for adsorbing gas and has a characteristic of enduring a heating cycle for adsorption / desorption. It can be composed of various adsorbents.

In the above embodiment, the fixed resistance Ro is connected in series to the resistance Rs of the gas detection element 3, and the increment of the voltage Vo across the fixed resistance Ro from the air level voltage is taken out as the output of the gas detection element 3. However, conversely, the decrease amount of the voltage across the resistor Rs of the gas detection element 3 from the air level voltage may be taken out as the output of the gas detection element 3.
Further, a fixed resistor R is connected in series with the resistor Rs of the gas detection element 3.
Instead of connecting o, a well-known bridge circuit may be configured to take out the sensor output.

In the above embodiment, the oxide semiconductor, which is the main component of the gas sensitive portion 5a constituting the gas detecting element 3, is n.
Although it is composed of a p-type semiconductor, it may be composed of a p-type semiconductor.

In the above embodiment, the driving means 100 is used.
However, as the low temperature side preset temperature and the high temperature side preset temperature, respectively,
It is configured to set three temperature conditions and change the temperature of the gas adsorbing member F between these two temperatures, but set three or more temperature conditions to change the temperature between them. You may comprise.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a structure of a gas sensor according to the present invention.

FIG. 2 is a block diagram of a gas sensor and a fat and fire prevention gas detector according to the present invention.

FIG. 3 is a diagram showing an equivalent circuit of a gas detector.

FIG. 4 is a diagram showing characteristics of gas generated when fats and oils are overheated.

FIG. 5 is a graph showing gas detection characteristics according to the first embodiment.

FIG. 6 is a graph showing gas detection characteristics of a comparative example according to the first embodiment.

FIG. 7 is a graph showing gas detection characteristics according to the second embodiment.

FIG. 8 is a graph showing gas detection characteristics of a comparative example according to the second embodiment.

FIG. 9 is a side sectional view showing a structure of a gas sensor according to another embodiment.

[Explanation of symbols]

3 Gas detection element 7 heater 100 driving means 101 determination means F gas adsorption member (activated carbon)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hirokazu Sasaki             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. F term (reference) 2G046 AA19 AA20 AA21 AA22 AA24                       AA25 BA01 BA02 BA04 BA09                       BB02 BB04 BD01 BE02 BE03                       BF05 BG01 BH02 BJ08 DB05                       DB09 DC09 DC14 DC16 DC17                       DC18 EB06 FB02 FE03 FE15                       FE22 FE39 FE46 FE48                 2G060 AA01 AB16 AB17 AB18 AB21                       AB22 AE19 AF07 BA01 BB02                       BB09 BB13 BB14 BB16 BB18                       HB06 HC07 HC13 HC19 HC21                       HC22 HD01 HD02 HD07 KA01                 5C085 AA05 AB01 BA40 CA30

Claims (5)

[Claims] 1. A gas adsorbing member which is changeable between an adsorbing state for adsorbing a gas to be detected and a desorbing state for desorbing a gas to be detected by a temperature change, and a heater for heating the gas adsorbing member. A gas detection element which is arranged at a position where the gas to be detected desorbed from the gas adsorbing member reaches and which can detect the gas to be detected, and the temperature of the gas adsorbing member is set to a low temperature side and a high temperature side set temperature. And a drive means for heating and driving the heater so as to alternately change to and. 2. The low temperature side preset temperature is from room temperature to 130 ° C.
The gas sensor according to claim 1, wherein 3. The gas detection element uses an aldehyde having 3 to 9 carbon atoms and 2 to 2 carbon atoms as the gas to be detected.
The gas sensor according to claim 1 or 2, wherein the gas sensor has sensitivity to at least one gas component of the alkane of 8. 4. The gas sensor according to claim 1, wherein the gas adsorption member is activated carbon. 5. The oil sensor is provided with the gas sensor according to any one of claims 1 to 4, and the oil and fat is brought into an overheated state based on the output information of the gas detection element output at the timing of the heating drive by the drive means. A gas detector for preventing oil and fat fires, which is provided with a determination means for determining whether or not there is such a gas.