JPH0589385A - Fire detecting device - Google Patents

Abstract

PURPOSE:To discover fire at an early stage and also to suppress erroneous information to a min. by jointly using a hydrocarbon gas sensor with a combus tion gas sensor. CONSTITUTION:A fire alarming device 3 is provided with a pre-alarm judging part 4, a pre-alarm output part 5, a fire judging part 6, a fire alarm part 7 and an environment state alarm part 8. When the pre-alarm judging part 4 judges the detection of hydrocarbon gas by a hydrocarbon gas sensor 1, pre- alarm judgement output is generated in the pre-alarm output part 5 so that pre-alarm is outputted by the turning-on of a display lamp or the ring of a buzzer. The pre-alarm judging part 4 simultaneously set a pre-alarm flag on for the fire judging part 6. The fire judging part 6 judges fire when the gas density of CO2 gas detected by a CO2 sensor 2 rapidly increases in a state where the pre-alarm flag is set on so that the judgement output is generated in the fire alarm part 7 and fire alarm is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detection device for detecting a gas generated during a fire to judge the fire.

[0002]

2. Description of the Related Art Conventionally, in a device for detecting a gas by detecting a gas generated during a fire, the CO generated during a combustion
_A fire alarm is output by detecting combustion gas such as ₂ gas or CO gas.

[0003]

However, in such a conventional fire detection device, since the CO ₂ gas or CO gas generated in the combustion state after ignition is the detection target, the CO ₂ gas is not detected. Alternatively, in order for the CO gas to reach a threshold concentration at which it can be determined that a fire has occurred, it is when the flame spreads and the fire progresses sufficiently, and there is a problem that the discovery of the fire is delayed.

When the sensitivity of fire detection is increased for early detection of a fire, it is impossible to distinguish an increase in CO ₂ gas due to an artificial cause such as tobacco and an increase in CO ₂ gas due to a fire. , There was a problem that it is easy to cause false alarms. The present invention has been made in view of such conventional problems,
An object of the present invention is to provide a fire detection device capable of detecting a fire early by monitoring gas and minimizing false alarms.

[0005]

Means for Solving the Problems The inventors of the present invention repeated a combustion experiment for identifying a fire phenomenon,
In the process of analyzing the fire phenomenon on a microscopic level, it was found that the sample had a slight weight loss at the very early stage of the fire before ignition. When the cause of this slight weight loss before ignition was further investigated, it was thought that some gas was released during the temperature rise before ignition, and the gas generated in the initial state of the fire was measured by a mass spectrometer. When analyzed, the mass number 1 which is not seen under normal conditions
A distribution of mass spectrum having a wide width of 140 and a peak periodically appearing at every mass number of about 14 was observed.

It is clear that such a mass spectrum distribution is not a CO ₂ gas generated after ignition having a spectrum concentrated at a mass number of 44, and as a result, it is a hydrocarbon gas having about 1 to 10 carbon atoms. It has been found.
The generation of hydrocarbon gas in the process of increasing the temperature before ignition is a novel fact that has not been recognized in the conventional fire monitoring field, and the present invention is based on this point. It is configured as follows.

That is, the fire detection device of the present invention comprises a hydrocarbon gas sensor for detecting a hydrocarbon gas generated in the very initial state of a fire before ignition and a combustion gas sensor for detecting a gas generated or changed by combustion due to ignition. And a pre-alarm determination unit that determines the detection of hydrocarbon gas by the hydrocarbon gas sensor and outputs a pre-alarm, and an increase or decrease of the detection gas by the combustion gas sensor after the detection of hydrocarbon gas is determined by the pre-alarm determination unit And a fire determination unit that outputs a fire alarm by determining a fire.

Here, as the combustion gas sensor, one that detects CO ₂ gas, CO gas or O ₂ gas is used, and the fire determination unit detects the CO detected by the combustion gas sensor after the detection of hydrocarbon gas is determined. _A fire is judged when the ₂ gas or CO gas sharply increases, while a fire is judged when the O ₂ gas detected by the combustion gas sensor sharply decreases.

Further, the fire judging section changes the gas (CO ₂ or CO ₂₎ due to combustion by the combustion gas sensor in a state where the detection of the hydrocarbon gas is not judged by the pre-alarm judging section.
Gas increase or O ₂ gas decrease),
Notify the deterioration of the environment.

[0010]

According to the fire detecting apparatus of the present invention having such a structure, attention is paid to the fact that a flammable hydrocarbon gas is generated as a precursor of ignition, and a hydrocarbon gas is detected, so that a fire can be started early. Can be found in. Further, since the generation of hydrocarbon gas is not observed due to an artificial cause such as tobacco, detection of hydrocarbon gas and, for example, CO ₂ gas or CO
By deciding a fire from the temporal continuity of gas detection, even if the detection sensitivity is increased, it is possible to distinguish between a fire and an increase in CO ₂ gas or CO gas due to a cause other than a fire. Can be reduced and the reliability of fire judgment can be improved.

[0011]

FIG. 1 is a block diagram of an embodiment showing a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a hydrocarbon gas sensor, which detects a flammable hydrocarbon gas generated in a heated state before ignition. Reference numeral 2 denotes a CO ₂ sensor as a combustion gas sensor, which detects CO ₂ gas generated by combustion.

A fire alarm device 3 includes a pre-alarm determination unit 4, a pre-alarm output unit 5, a fire determination unit 6, a fire alarm unit 7, and an environmental condition alarm unit 8. When the pre-alarm determination unit 4 determines that the hydrocarbon gas sensor 1 has detected the hydrocarbon gas, a pre-alarm determination output is generated at the pre-alarm output unit 5, and a pre-alarm is output by turning on an indicator lamp or ringing a buzzer. At the same time, the pre-alarm determination unit 4 sets the pre-alarm flag for the fire determination unit 6 to ON.

The fire determination unit 6 detects a fire when the gas concentration of the CO ₂ gas detected by the CO ₂ sensor 2 is rapidly increased while the pre-alarm flag from the pre-alarm determination unit 4 is set to ON. Judgment is made, and the fire alarm unit 7 outputs a judgment output to give a fire alarm. On the other hand, when the fire determination unit 6 determines that the gas concentration of the CO ₂ gas has rapidly increased while the pre-alarm flag from the pre-alarm determination unit 4 is reset to off, no hydrocarbon gas is generated. Therefore, not the increase in CO ₂ gas due to a fire but the increase due to an artificial cause such as a cigarette causes a judgment output to the environmental condition alarm unit 8 to issue an alarm or display indicating deterioration of the environmental condition.

Here, the reason why the hydrocarbon gas is generated before the ignition which is the basis of the present invention will be explained with reference to the characteristic diagram of the measurement data of FIG. 2 obtained by the combustion experiment. Figure 2 is a polyethylene as a sample (p-CH ₂ CH
₂ ) It is the experimental data when heated, and as shown in the temperature curve 4, polyethylene as a sample is heated from room temperature to 500
The change in weight of the sample shown by the weight curve 5 and the thermal reaction of the sample shown by the thermal reaction curve 6 are shown when the sample is heated to 0 ° C. with a constant temperature gradient.

In FIG. 2, when polyethylene as a sample is started to be heated, an endothermic reaction 7 occurs in which the thermal reaction curve falls when heated to around 120 ° C. This endothermic reaction 7
Is generated because polyethylene as a sample is melted and transferred from a solid to a liquid. When the temperature was further increased, the sample ignited at 400 ° C. shown at time tf,
Therefore, the weight is greatly reduced by the combustion as shown from the point B to the point C of the weight curve corresponding to 400 ° C to 500 ° C. At the ignition time tf, the thermal reaction curve 6 has a peak of the exothermic reaction 8 due to ignition.

Although such a change in the measured data is observed in a normal combustion experiment, the inventors of the present application further examined the experimental data in detail, and as a result, point B in the weight curve 5 before ignition at time tf. Up to 300 ℃ to 400 ℃
It was found that there was a slight, but reduced weight loss of the sample during the temperature rise to ° C. The weight reduction from point A to point B in the first stage is about 10%. On the other hand, when the thermal reaction curve 6 corresponding to the points A to B in the weight curve 5 is seen, it does not show an exothermic reaction, and therefore it is understood that combustion does not occur during this period.

Therefore, when the gas produced during the first stage weight loss period in which the temperature changes from 310 ° C. to 400 ° C. is supplied to the mass spectrometer for mass spectrometry, the mass spectrum shown in FIG. 3 is obtained. The results of analysis were obtained. Here, the carrier gas is helium He80%,
Oxygen O ₂ 20% is used. Looking at the measurement result of the mass spectrum in FIG. 3, the spectrum is widely distributed with the mass number of 1 to 140, and the peak change appears periodically at intervals of the mass number of about 14.

FIG. 4 shows the analysis result of the mass spectrum of the produced gas obtained in the combustion state after the time tf. A peak appears at the mass number 44, which is the CO ₂ gas produced by the combustion. Is shown. However, regarding the product gas before combustion in FIG. 3, there is no peak of only the spectrum of the mass number 44 showing the CO ₂ gas during combustion in FIG. 4, which is quite different from CO ₂ gas.

A gas having such a mass spectrum distribution as shown in FIG. 3 is considered to be a combustible gas having about 1 to 10 carbon atoms, and it was finally proved to be a combustible hydrocarbon gas. As described above, it is not known at all in the field of fire detection that hydrocarbon gas is generated in a heated state before ignition, and it can be confirmed for the first time by mass analysis of the generated gas conducted by the inventors of the present application through a combustion experiment. It is a thing.

Therefore, in the present invention, it is possible to detect a fire at an early stage by detecting the carbonized gas produced before the ignition, and C as a combustible gas generated after the ignition.
A more accurate fire judgment can be made by detecting a rapid increase in O ₂ gas or CO gas or a sharp decrease in O ₂ gas and capturing the temporal continuity between the detection of hydrocarbon gas and the detection of combustion product gas. It is a thing.

FIG. 5 is a flow chart showing the processing operation of the fire alarm device 3 provided in the first embodiment of FIG. Figure 5
First, in step S1, it is checked whether or not hydrocarbon gas is detected. If the pre-alarm determination unit 4 detects hydrocarbon gas, the process proceeds to step S2 to turn on the pre-alarm flag, and the pre-alarm output unit Output a pre-alarm from 5.

Subsequently, the CO ₂ gas concentration detected by the CO ₂ sensor 2 in the fire determination unit 6 is set to a threshold value D1 set in two stages.
Check whether or not the lower threshold value D1 of D2 is greater than or equal to
When the threshold D1 is exceeded, the process proceeds to step S4, and it is checked whether the higher threshold D2 is exceeded. If it is less than the higher threshold value D2 in step S4, the process proceeds to step S5 to check whether the pre-alarm flag is on or off. At this time, if hydrocarbon gas is detected and the pre-alarm flag is on, hydrocarbon gas is detected. Then, the time continuity that CO ₂ gas is detected is obtained, so that it is judged as a fire, and the process proceeds to step S6 to issue a fire alarm.

On the other hand, in an explosive fire, hydrocarbon gas cannot be detected because there is almost no heating time before ignition,
In this case, the process proceeds from step S1 to S3, and since the CO ₂ gas concentration exceeds the lower threshold value D1, the process proceeds to step S4, and at the same time, the CO ₂ gas concentration higher threshold value D2.
Since it also exceeds the limit, the process immediately goes to step S6 to give a fire alarm.

Further, since the hydrocarbon gas is not detected when the CO ₂ gas concentration is artificially increased by cigarettes or the like, the process proceeds from step S1 to S3, and when the CO ₂ gas concentration exceeds the lower threshold D1, the step is performed. The process proceeds to S4, and since it is less than the higher threshold value D2, the process proceeds to step S5. In step S5, since the pre-alarm flag indicating the detection of hydrocarbon gas is off, the process proceeds to step S7 to warn that the environmental condition has deteriorated.

In the first embodiment shown in FIG. 1, the CO ₂ sensor 2 is used as the combustion gas sensor.
A CO sensor that detects CO gas may be used instead of the _two sensors. Further, in the embodiment of FIG. 1, a plurality of hydrocarbon gas sensors 1 and CO ₂ sensors 2 provided for each warning area are connected to the fire alarm device 3, but for simplicity of the drawing, The sensors provided in the two warning areas are shown as representatives.

FIG. 6 shows an embodiment showing the second embodiment of the present invention.
FIG. 2 is a configuration diagram showing the CO provided in the first embodiment of FIG. 1.₂ Sensor
O as a combustion gas sensor instead of 2₂ Provide the sensor 9
The other configuration is the same as that of FIG.
Therefore, the same reference numerals are given and description thereof is omitted. Of this FIG.
In the second embodiment, O₂ The fuel after ignition by the sensor 9
O in baked state ₂ Because of the sharp decrease in gas,
In the disaster determination unit 6, the hydrocarbon gas of the pre-alarm determination unit 4
ON state of the pre-alarm flag set by the detection of the
On the condition of, for example, step S3 of the flowchart of FIG.
As shown in, the higher of the two thresholds
When it falls below the threshold of
U Also, hydrocarbon gas is detected like an explosive fire.
Otherwise, the higher threshold is followed by the lower threshold.
When it falls below the value, it is immediately judged to be a fire and a fire alarm is issued.
You Furthermore, due to artificial causes such as cigarettes, O₂ Gas decreased
If the pre-alarm flag is off
If the condition falls below the higher threshold, the environmental deterioration warning is issued.
Will be done.

In the above embodiment, the fire is judged by using a predetermined threshold for the increase of CO ₂ gas or CO gas generated in the combustion state or the decrease of O ₂ gas. The rate of increase or decrease per hour, that is, the differential value may be used to judge the fire. Furthermore, a plurality of data may be sampled, and a coefficient of a quadratic function may be obtained to predict an increase or decrease in gas concentration to judge a fire.

[0028]

As described above, according to the present invention, a fire phenomenon which could not be detected until combustion has been detected by the CO ₂ gas sensor, the CO gas sensor, and the O ₂ sensor has hitherto been detected. When used together, it is possible to detect a pre-alarm before ignition at the very early stage of the fire and to detect the fire early. Further, by using the detection of hydrocarbon gas in combination with the detection of CO ₂ gas, it is possible to distinguish a change in only the CO ₂ concentration due to cigarettes or the like from a fire and treat it as a deterioration of the environmental condition.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing measurement data of a combustion experiment showing generation of hydrocarbon gas occurring before ignition.

FIG. 3 is a characteristic diagram showing an analysis result of a mass spectrum of a produced gas generated by weight reduction before ignition.

FIG. 4 is a characteristic diagram showing the analysis result of the mass spectrum of the produced gas generated in the combustion state after ignition.

5 is a flowchart showing the processing of the embodiment of FIG.

FIG. 6 is a block diagram of an embodiment showing a second embodiment of the present invention.

[Explanation of symbols]

1: Hydrocarbon gas sensor 2: CO ₂ sensor 3: Fire alarm device 4: Pre-alarm determination unit 5: Pre-alarm output unit 6: Fire determination unit 7: Fire alarm unit 8: Environmental condition alarm unit 9: O ₂ sensor

Claims (3)

[Claims] 1. A hydrocarbon gas sensor for detecting a hydrocarbon gas generated in a very initial state of a fire before ignition, a combustion gas sensor for detecting a gas generated or changed by combustion due to ignition, and a carbonization by the hydrocarbon gas sensor. A pre-alarm determination unit that determines the detection of hydrogen gas and outputs a pre-alarm, and a fire is determined from the increase or decrease of the detection gas by the combustion gas sensor after the detection of hydrocarbon gas is determined by the pre-alarm determination unit. A fire detection device comprising: a fire determination unit that outputs a fire alarm. 2. The fire detection device according to claim 1, wherein the combustion gas sensor detects CO ₂ gas, CO gas or O ₂ gas, and the fire / fire determination unit determines that hydrocarbon gas is detected. After that, when the CO ₂ gas or CO gas detected by the combustion gas sensor suddenly increases, a fire is judged,
Further, the fire detection device is characterized in that a fire is judged when the O ₂ gas detected by the combustion gas sensor sharply decreases. 3. The fire detection device according to claim 1, wherein the fire determination unit determines a change in gas due to combustion by the combustion gas sensor in a state where detection of hydrocarbon gas by the pre-alarm determination unit is not determined. A fire detection device that informs the user of the deterioration of the environment.