JP2583769B2 - Fire monitoring system - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improvement in a device that detects radiant infrared rays in a monitoring area using an infrared sensor and monitors the presence or absence of a fire through a signal discriminating circuit, and in particular, to an improvement in a device. An object of the present invention is to enable detection of smoke from an initial fire and to prevent occurrence of false alarm due to reduction of a reference value (threshold) to be compared.

(Prior Art) As means for detecting a smoldering state (smoldering state) in an initial fire in a monitoring area, a method disclosed in JP-A-60-83 is known.
No. 197 fire detector has been proposed.

This is a method in which radiant energy from within a predetermined area is collected by an optical system and converted into an electric signal, and is collected by the optical system in a fire detector that determines the presence or absence of a fire in the predetermined area based on the electric signal. Radiant energy detecting means for converting the radiant energy into an electric signal, and performing a predetermined calculation based on the electric signal output by the radiant energy detecting means, and determining whether there is a fire in the predetermined area based on the calculation result. Calculating means for detecting the amplified detection signal and the reference signal set in the oscillation circuit, and further demodulates the signal to obtain a demodulated signal. The average temperature Tmean (n) for each period is obtained by averaging for each time Δt, and the average temperature difference ΔTmean for each of these periods is obtained. n), i.e. ΔTmean (n) = Tmean (n + 1) -Tmean (n) (however, n: 1, 2, 3, positive integer representing the ......, Tmean (n):
The average temperature in the n-th period is calculated as follows: ΔTmean (n + m) −ΔTmean (n) ≧ K ₁ ΔTmean (n + m) ≧ K ₂ , Tmean (n) ≧ K ₂ (where m: 1,2, It is an integer representing 3 ..., usually 1 or 2.

(K ₁ , K ₂ : constant) When the conditions indicated by the following conditions are simultaneously satisfied, it is determined that a fire has occurred and linked to the subsequent measures.

(Problems to be Solved by the Invention) In theory, the above-described invention can prevent false alarms caused by, for example, the smoking of workers in the monitoring area. The flame fluctuates in the range of about 10 Hz or less with radiated infrared rays, and the fluctuations are accompanied by complex waveforms along the time axis. Our experiment revealed that it was not possible to determine whether a fire had occurred at this stage.

(Means for Solving the Problems) Therefore, the present invention solves the above-mentioned problems of the prior art,
In particular, it is designed to reliably determine the occurrence of an initial fire and to prevent the occurrence of false alarms to enable stable fire monitoring.Specifically, it detects radiated infrared rays in the monitoring area. , after converting it into an electrical signal, the signal discrimination circuit, measured up to ₁ -Dn th D radiation amount of infrared rays reference to the monitoring region a preset threshold for each unit time, the threshold after storing the first th measurements D ₁ exceeding, of the second measurement value D ₂ as compared with the D _1, measured value instead of the measured value D ₁ in the case of D ₁ ≦ D ₂
Together and stores the D _2, performs measurements compared by subsequent similar arithmetic expression, an alarm upon reaching a Dn-th and /
Or when starting fire extinguisher radiation etc.,
A fire monitoring system characterized in that, when comparing the above measured values, the next stage measured value with respect to the stored value of each stage is set to be determined as the same value as the previous stage stored value up to 90% or more of the previous stage stored value. About the method.

Hereinafter, the specific contents of the present invention will be described with reference to the embodiment of the drawings. FIG. 1 shows a block diagram of an infrared monitoring system used in the present invention.
A indicates a sensor unit, B indicates a main circuit unit, and C indicates a cable unit connecting the sensor unit A and the main circuit unit B.

The sensor unit A includes an infrared sensor 1 and a field effect transistor (FET) 2 attached thereto, an analog amplifier (OP.AMP) 3, and a voltage (V) / frequency (F) converter 4. This is an electronic amplifier circuit with a low output impedance.

Further, the electronic amplifier circuit having the low output impedance is not limited to the case where the analog amplifier 3 described above is used, but may be an analog (A) / digital (D) converter.
An electronic circuit having both functions of an analog amplifier and an A / D converter is more desirable.

Next, the main circuit B includes a signal discriminating circuit element (CPU) 8, a relay coil driving transistor 9, a relay coil 10, and a line separately connected to a fire alarm or the like via a contact 10a thereof, and a line of a power supply 11. Have.

A threshold value (set reference value) to be compared is set in the signal discriminating circuit element (CPU) 8 in advance, and the value of the amount of infrared rays sampled by the infrared sensor 1 in the sensor unit A after the start is set. When the value exceeds the threshold value as a result of comparison with the value When this value is stored as D _{1 and} the value of the infrared amount sampled next time is D ₂ and compared with the previously stored value D ₁ and D ₁ ≦ D ₂ to proceed to the stage of the next, so as thereafter perform the measurement sampling up D ₁ -Dn th by the same procedure, actuates an alarm and / or fire extinguishing agent activation start relay radiation such as when it reaches Dn th In this case, even if the sampling value of the next stage is slightly lower than the stored value of the previous stage, there is a certain allowable range so that the stored value of the next stage is equivalent to the stored value of the previous stage. It is constant. If this allowable range is less than 90% of the previous stored value, false alarms will increase, and if it is 100%, it will be the same as the case of the above-mentioned conventional technology, and eventually the judgment of fire occurrence in the initial stage of fire In the range of 90% to 99%, preferably 90% to
Experimental results have shown that a range of 97% is best.

Further, the cable unit C includes a signal conductor 5 for connecting between the electronic amplifier circuit having a low output impedance of the sensor unit A and the signal discriminating circuit element 8 of the main circuit unit B, and a power supply circuit of the sensor unit A and a main circuit. As shown in a cross section in FIG. 2, a plus-side power supply wire 6 connecting to a power supply 11 of the circuit unit B is buried in a rubber material or other insulator 12 so as to further surround the periphery thereof. A number of shielding wires 7 connecting the infrared sensor 1 of the sensor unit A and the main circuit B are connected to the insulating portion 12.
Buried inside.

The shield conductor 7 also serves as a power conductor for connecting the sensor unit A and the negative side of the main circuit B. Further, the outer peripheral surface of the insulator 12 is a cable jacket.
It is configured to be insulated by 13.

The cable unit C is connected to the sensor unit A and the main circuit unit B by using an appropriate connector such as a connector.

The main circuit unit B is installed in a place where the reliability is most easily secured, for example, near a fire extinguishing agent discharge operation valve or near a power supply thereof, and where maintenance is easy and inexpensive, and the sensor unit A is placed in a monitoring area. Set freely to face, and cable unit C
Thus, the sensor unit A and the main circuit B are connected to each other by penetrating a wall or a ceiling, and used.

(Operation) In the configuration of the above embodiment, the operation is shown in FIGS.
Referring to FIG. 4, FIG. 3 shows the signal discriminating circuit element 8 of the main circuit unit B.
The flow chart from the detection of radiated infrared radiation in the monitoring area to the determination of fire occurrence by
RY is a relay, SAMPLING D _{1 to} D ₃ are measured values per unit time, X is a threshold value to be compared, t is a sampling gate time (variable), α is a stored value of the preceding stage, The permissible range (per unit t) considered equivalent to this is shown below.

The value D ₁ sampled first from START is set to the threshold X
Compare to

If D ₁ <X · t, return to START as NO and return to D ₁
Together is stored as YES only if a ≧ X · t is compared with the D ₁ stored the D ₂ is the value of the next sampling.

If D ₂ <D ₁ -α · t, return to START as NO, and if D ₂ ≧ D ₁ -α · t, set to YES and store this in place of the storage value of D ₁ described above. Along with the next sampling.

Note After capturing this case D _2, likewise D ₂ ≧ the case of D ₁
X · t is essential, and if D ₂ <X · t
It is of course D ₁ is also erased stored back to SATRT.

D ₂ that further stores the sampled D ₃ value
Compare with

If D ₃ <X · t or D ₃ <D ₂ −α · t, return to START as NO. YES only if D ₃ > X · t and D ₃ ≧ D ₂ −α · t To send the first signal to the alarm generation relay RY1 and return to START again.

It repeats the same operation as described above up to D ₁ to D ₃ again through the above process, if the determination result is NO at any stage of the D _1, D _2, D ₃ is immediately OFF relays RY1 alarm Cancel.

When YES is maintained for all of D _{1 to} D ₃ , the second signal is sent to the relay RY 2 for extinguishing agent emission, the operation of extinguishing agent emission is automatically performed, and the operation is completed. Let it.

The fluctuation of the amount of radiated infrared rays due to the fluctuation of the flame described above
FIG. 4 shows the measurement state for each unit time.

(Effects of the Invention) As described above, when comparing the measured values of the amount of radiated infrared rays per unit time by the signal discriminating circuit, the minimum of the measured value of the next stage with respect to the stored value of each stage is 90 to 99% of the stored value of the preceding stage. It is set to the same value as the stored value in the previous stage up to the range, so it can sufficiently cope with fluctuations in the amount of radiated infrared radiation due to the fluctuation of the flame, including the smoke of the initial fire, and should be compared By reducing the reference value, it is possible to reliably realize the initial warning and extinguishing of a fire, and also to prevent false alarm and erroneous fire extinguishing operation due to the reduction of the reference value. Further, when the sampling gate time t is set to about 3 to 5 seconds by using this method, no chopper device is provided (there is no mechanically moving part), and therefore, a practical inexpensive pyroelectric infrared sensor element is used. It is also possible to economically provide a fire monitoring and automatic fire extinguishing system that is efficient, reliable and easy to maintain.

[Brief description of the drawings]

FIG. 1 is a block diagram of an infrared monitoring system for carrying out the present invention, FIG. 2 is an enlarged sectional view of a cable in the cable unit shown in FIG. 1, and FIG. 3 is a signal discrimination of a main circuit unit in FIG. FIG. 4 is a flow chart showing a process from detection of radiated infrared rays in the monitoring area by the circuit element to determination of fire occurrence, and FIG. 4 is a graph showing fluctuations in the amount of radiated infrared rays due to fluctuations of a flame and a measurement state per unit time. A ... Sensor unit, 1 ... Infrared sensor 2 ... Field effect transistor 3 ... Analog amplification element 4 ... Voltage / frequency conversion element C ... Cable unit, 5 ... Signal conductor 6 ... Positive power supply Conducting wire 7 Shield wire B Main circuit unit 8 Signal discriminating circuit element 9 Transistor for driving relay coil 10 Relay coil 10a Contact 11 Contact power

Claims (1)

(57) [Claims] 1. Sensing radiated infrared rays in a monitoring area,
After converting it into an electrical signal, the signal discrimination circuit, measured up to ₁ -Dn th D radiation amount of infrared rays preset criteria surveillance area threshold for each unit time, exceeds the threshold value after storing the first th measurements D _1, the second-th measured value D ₂ as compared with the D _1, measured values in the case of D ₁ ≦ D ₂
In the case where the measured value D ₂ is stored in place of D ₁ , the measured value is compared by the same calculation formula thereafter, and when the Dn-th order is reached, the activation of an alarm and / or fire extinguishing agent emission is started. A fire monitoring system wherein, when comparing the measured values, the next-stage measured value with respect to the stored value at each stage is set to be the same as the previous-stage stored value up to 90% or more of the preceding-stage stored value. .