JP3051513B2 - Fire detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detecting device for detecting a gas generated at the time of a fire and judging a fire.

[0002]

2. Description of the Related Art Conventionally, in an apparatus for detecting a gas generated at the time of fire and judging a fire, CO
_A fire alarm is output by detecting combustion product gas such as ₂ gas or CO gas.

[0003]

[SUMMARY OF THE INVENTION However, in such a conventional fire detection system, since the CO ₂ gas or CO gas generated in the combustion state after the firing is set to the detection target, CO ₂ gas or CO The gas reaches the threshold concentration at which the fire can be judged to be a fire when the flame spreads and the fire has sufficiently proceeded, and there has been a problem that the detection of the fire is delayed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a fire detecting device which can detect a fire early by monitoring gas and minimize a false alarm. Aim.

[0005]

Means for Solving the Problems The inventors of the present invention have repeatedly conducted a combustion experiment to find out a fire phenomenon.
In the process of analyzing the fire phenomena on a microscopic level, it was found that the sample slightly lost its weight at the very early stage of the fire before ignition. When the cause of this slight weight loss before ignition was further investigated, it is considered that some gas was released at the stage of temperature rise before ignition, and mass analysis was performed with a mass spectrometer. Mass number 1 to 140 which is not seen is wide and mass number 1
The distribution of the mass spectrum in which peaks appeared periodically at about every four 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, is a hydrocarbon gas having about 1 to 10 carbon atoms. It has been found.
The generation of hydrocarbon gas during the process of increasing the temperature before ignition is a novel fact that was not recognized at all in the field of conventional fire monitoring, and the present invention is based on this point. It is configured as follows.

That is, the fire detecting device according to the present invention has about 1 to 10 carbon atoms generated in an extremely initial state of a fire before ignition.
Of the hydrocarbon gas sensor for detecting the hydrocarbon gas, detecting the radiant heat emitted by the exothermic reaction by combustion, radiant heat
Sending out the first output when the first level is reached,
Reaches a second level higher than the first level
2, and a fire determination unit that determines a detection output of hydrocarbon gas by the hydrocarbon gas sensor and a detection output of heat radiation by the heat ray sensor and outputs a fire alarm. I do.

[0008] The fire determining unit detects that the hydrocarbon gas has been detected.
Output a pre-alarm, and the hot-wire sensor
Or when the hot wire sensor sends the first output
To output a fire alarm when the pre-alarm is being output .

[0009]

According to the fire detecting device of the present invention having the above-described structure, attention is paid to the fact that flammable hydrocarbon gas is generated as a precursor of ignition, and the detection of hydrocarbon gas enables early detection of a fire. Can be found in Further, by judging a fire from the detection of hydrocarbon gas and the detection of radiant heat, false alarms can be reduced and the reliability of fire judgment can be improved.

[0010]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a hydrocarbon gas sensor, which detects a combustible hydrocarbon gas generated in a heated state before ignition. Reference numeral 2 denotes a heat ray sensor, for example, a pyroelectric element having a detection sensitivity in an infrared region, and detects radiant heat due to an exothermic reaction at the time of combustion.

Reference numeral 3 denotes a fire alarm device, which includes a pre-alarm judgment unit 4, a pre-alarm output unit 5, a fire judgment unit 6, and a fire alarm unit 7. The pre-alarm determination unit 4 determines the detection of hydrocarbon gas by the hydrocarbon gas sensor 1 and causes the pre-alarm output unit 5 to output a pre-alarm. Also,
The pre-alarm determining unit 4 sets a pre-alarm flag for the fire determining unit 6 to ON when determining the detection of the hydrocarbon gas.

The fire judging section 6 judges the intensity of the radiant heat detected by the heat ray sensor 2, and the radiant heat detected by the heat ray sensor 2 in a state where the pre-alarm flag is set to ON by the pre-alarm judgment section 4. If the intensity exceeds the threshold value, an increase in radiant heat is obtained following the detection of the hydrocarbon gas, so that it is determined that a fire has occurred, and the fire alarm unit 7 outputs a fire alarm.

Here, the grounds for the generation of hydrocarbon gas in the heating stage before ignition, which is the basis of the fire judgment in the present invention, will be described as follows. FIG. 2 is a characteristic diagram showing experimental data of a combustion experiment when polyethylene (p-CH ₂ CH ₂ ) was heated as a sample. In FIG. 2, reference numeral 4 denotes a temperature curve, in which polyethylene as a sample is heated at a constant temperature gradient from room temperature to 500 ° C. 5 is a weight curve, which shows the weight change of the sample in percent. Further, 6 is a thermal reaction curve showing endothermic and exothermic of the sample.

First, when polyethylene as a sample is heated from normal temperature, an endothermic reaction 7 occurs in which the thermal reaction curve 6 sharply drops near 120 ° C. This endothermic reaction 7 occurs when the polyethylene changes from a solid to a liquid. When the temperature was further increased and reached 400 ° C. at time tf, polyethylene as a sample ignited, and 400 ° C. at the time of ignition at time tf.
During heating from 500 to 500 ° C., the weight curve 5 shows a sharp weight loss due to combustion as shown from the point B to the point C.

At the ignition time tf, an exothermic reaction 8 occurs in which the thermal reaction curve 6 sharply rises, and radiant heat is released.
Such characteristics from heating to ignition have been known in the past. However, when the inventors of the present application examined the measurement data shown in FIG. 2 in more detail, the heating data before the ignition time tf of the weight curve 5 was found. Heating temperature 400 from point A of temperature 310 ° C
There is a slight weight loss between point B up to ° C. The weight loss from point A to point B is about 10%. That is, there is a slight, but first, weight loss before ignition, and a two-stage weight loss after ignition, a second weight loss.

At the first stage of the weight reduction from the point A to the point B before the ignition time tf, as is clear from the thermal reaction curve 6, no combustion occurs because there is no exothermic reaction. Then, when the gas generated by the first-stage weight reduction was applied to the mass spectrometer, the analysis result of the mass spectrum shown in FIG. 3 was obtained. Note that helium He 80% and oxygen O ₂ 20% are used as carrier gases.

As is apparent from the mass spectrum analysis result shown in FIG. 3, the spectrum of the product gas obtained by the first stage weight reduction before combustion is dispersed in a wide range of mass numbers 1 to 140, and A peak change appears periodically at a mass number of about 14. The peak of the mass number 32 is that of the O ₂ gas used as the carrier. Figure 4 shows a second step gravimetric decrease the mass spectrum of the gas produced during combustion of causing in Figure 2, the peak level appears only in the mass number 44, CO ₂ gas generated by the combustion It turns out that it is. However, the gas generated in the heated state before ignition in FIG. 3 is considerably different from the spectrum of the CO ₂ gas having a mass number of 44 generated during the combustion in FIG.

A gas having 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 has turned out to be a hydrocarbon gas after all. The fact that hydrocarbon gas is generated in the heating stage before ignition in this way has not been recognized at all in the field of fire detection, and has been newly confirmed by the present inventors. Therefore, in the present invention, an accurate fire judgment is made by detecting the hydrocarbon gas generated before the ignition and detecting the radiant heat radiated by the ignition.

FIG. 5 is a flowchart showing the processing operation of the fire alarm device 3 of FIG. In FIG. 5, first, in step S1, the presence or absence of detection of hydrocarbon gas by the hydrocarbon gas sensor 1 is checked.
When the detection of hydrocarbon gas is determined in step S2, the process proceeds to step S2, where the pre-alarm flag for the fire determination unit 6 is turned on,
The pre-alarm is output from the pre-alarm output unit 5.

Then, the process proceeds to a step S3, wherein the fire judging section 6
And the intensity of the radiant heat detected by the hot-wire sensor 2, that is, the hot-wire level, is compared with the lower threshold H1 set in two steps. I do. If it is less than the threshold value H2, the process proceeds to step S5, and if the pre-alarm flag is turned on by the detection of the hydrocarbon gas, the process proceeds to step S6 to issue a fire alarm.

On the other hand, in the case of an explosive fire, there is no process of generating hydrocarbon gas, and no hydrocarbon gas is detected, so that the process proceeds from step S1 to step S3. And exceeds the lower threshold H1 and at the same time exceeds the higher threshold H2,
Therefore, the process immediately proceeds to S6 via S3 and S4 to issue a fire alarm.

Further, in step S1, no hydrocarbon gas is detected, and in step S3, the threshold value H1 of the lower heat ray level is set.
When the process goes to step S5 via step S4, the pre-alarm flag is off, and in this case, a fire alarm is issued because, for example, an increase in radiant heat due to an oil stove or the like does not result in a fire. And return to step S1 again.

In the embodiment shown in FIG. 1, a pre-alarm judgment section 4 and a pre-alarm output section 5 are provided so that a pre-alarm is issued when the hydrocarbon gas sensor 1 detects a hydrocarbon gas. However, when a hydrocarbon gas is detected without issuing a pre-alarm, and then a temporal relationship is obtained in which the intensity of radiant heat exceeding the threshold is detected, a fire may be determined. Good.

Although the fire is judged by comparing the intensity of the radiant heat from the heat ray sensor 2 with a threshold value, the fire may be judged from the increase (differential value) of the radiant heat per unit time, or the radiant heat may be judged. A plurality of points may be sampled at a plurality of points, a coefficient of a quadratic function may be obtained, and a change in radiant heat may be predicted to determine a fire. Further, when the hydrocarbon gas is generated before the ignition, the temperature is sufficiently high, so that the hydrocarbon gas is detected even before the ignition, and the intensity of the radiant heat exceeding a predetermined threshold value is further increased. When a pre-alarm or a fire alarm is performed when a is detected, a fire can be found early.

[0025]

As described above, according to the present invention, it is possible to detect a fire at an early stage by detecting hydrocarbon gas generated at an extremely early stage of a fire before ignition, and to reduce the increased radiant heat. By monitoring and determining by detecting hydrocarbon gas and detecting an increase in radiant heat, a reliable fire determination can be made, and false alarms can be greatly reduced.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a flowchart showing processing of the embodiment of FIG. 1;

[Explanation of symbols]

 1: hydrocarbon gas sensor 2: heat ray sensor 3: fire alarm device 4: pre-alarm judgment unit 5: pre-alarm output unit 6: fire judgment unit 7: fire alarm unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-110395 (JP, A) JP-A 3-82487 (JP, U) JP-A 61-30193 (JP, U) JP-A 61-193 180393 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G08B 17/02-17/12

Claims (1)

(57) [Claims] (1) Charcoal generated in an extremely initial state of a fire before ignition
A hydrocarbon gas sensor for detecting a prime 1 to 10 about the hydrocarbon gas, to detect the radiant heat emitted by the exothermic reaction by combustion, radiation
Sending a first output when the heat reaches the first level;
When the heat reaches a second level higher than the first level
A hot-wire sensor that sends out a second output, and a detection output of hydrocarbon gas by the hydrocarbon gas sensor and a detection output of heat radiation by the hot-wire sensor.
Outputs a pre-alarm when detecting hydrocarbon gas,
When the hot-wire sensor sends out the first output and the second output
Or, the hot wire sensor sends out the first output and the pre-alarm
And a fire determining unit for outputting a fire alarm when the signal is output.