JP4026798B2 - Flame detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flame detector that detects a fire and detects ultraviolet rays, infrared rays, and the like that generate flames.
[0002]
[Prior art]
Conventionally, when a fire related to a flame is detected, in order to prevent a malfunction at the time of detecting the fire, a method of performing a time delay and confirming whether or not it is a fire has been adopted.
[0003]
That is, the detection element detects ultraviolet rays, infrared rays, or the like that generate flames, and the detection signal detected by the detection element reaches a predetermined fire discrimination level, and the detection signal is fired even if a predetermined delay time elapses. If the discriminating level or higher is maintained, it is determined that a fire has occurred.
[0004]
[Problems to be solved by the invention]
FIG. 6 is a diagram illustrating the operation of the conventional example.
[0005]
As shown in FIG. 6, when noise occurs even once, the state exceeding the fire discrimination level continues due to periodic sampling and malfunctions. In other words, in the conventional method, if noise (external light noise or thermal noise) higher than the fire determination level occurs, the detection signal may exceed the fire determination level, and the flame detector may malfunction. There's a problem.
[0006]
In this case, if the delay time is set longer than the predetermined time, the malfunction state can be prevented. However, if the delay time is increased in this way, another problem that the timing of fire detection is delayed. Occurs.
[0007]
Furthermore, in the conventional method, an internal light source and an external light source are provided inside and outside the light receiving glass that houses the detection element, and the output signal (detection signal) of the smoothing circuit is stabilized after irradiating the internal light source during the function test. Since the external light source is irradiated after that, there is a problem that the time required for the function test is long.
[0008]
An object of the present invention is to provide a flame detector that does not cause the flame detector to malfunction even when noise of a fire discrimination level or higher occurs, and that does not slow down the fire detection.
[0009]
In the present invention, an internal light source and an external light source are respectively provided inside and outside the light receiving glass that houses the detection element. When the external light source is irradiated after the internal light source is irradiated during the function test, the time required for the functional test It aims at providing the flame detector which can shorten.
[0010]
[Means for Solving the Problems]
In the present invention, a detection element for detecting ultraviolet rays or infrared rays generated by a flame, a narrow band filter for extracting a necessary frequency component from signals output from the detection element, and an output signal of the narrow band filter are charged. A smoothing means for outputting a signal as a detection signal, and a flame occurrence determining means for determining that a flame is generated when the detection signal output by the smoothing means exceeds a preset fire discrimination level; When the flame occurrence determination means determines that a flame has occurred, the discharge means for forcibly discharging the charged detection signal to return to the monitoring state, and the flame occurrence has occurred that fire occurrence determination means has determined, counting means for counting by periodic sampling, the said count value reaches a predetermined value, fire determination hand determines that fire occurs If, when the detection signal does not exceed the fire discrimination level, a flame detector and a count reset means for said count value to zero.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing a flame detector FD1 according to an embodiment of the present invention.
[0012]
The flame detector FD1 includes a long wavelength side detection element 10, a narrow band filter 20, an amplification circuit 30, a smoothing circuit 40, a short wavelength side detection element 10a, a narrow band filter 20a, an amplification circuit 30a, The smoothing circuit 40a, the discharge circuit 50, the CPU 60, the transmission unit 70, and the constant voltage unit 80 are included.
[0013]
The long wavelength side detection element 10 and the short wavelength side detection element 10a are detection elements that detect ultraviolet rays, infrared rays, and the like generated by the flame.
[0014]
The narrow-band filters 20 and 20a are filters that pass a signal of 1 to 20 Hz that is a flame fluctuation component among signals detected by the detection elements 10 and 10a.
[0015]
The smoothing circuits 40 and 40a are examples of smoothing means that smoothes the output signals of the narrowband filters 20 and 20a and outputs a detection signal.
[0016]
The CPU 60 is an example of flame occurrence determination means that determines that a flame has occurred when the detection signal exceeds a preset fire determination level.
[0017]
The discharge circuit 50 is an example of a discharge unit that discharges the detection signal when the flame generation detection unit determines that a flame is generated.
[0018]
The CPU 60 is an example of a counting unit that counts the number of discharges, and is an example of a fire determination unit that determines that a fire has occurred when the count value reaches a predetermined value. This is an example of count value resetting means for setting the count value to 0 if the fire discrimination level is not exceeded.
[0019]
The CPU 60 also includes a ROM that stores a program, a fire discrimination level, a RAM that temporarily stores detection signals output from the detection elements 10 and 10a, and an A / D that converts the detection signals from analog signals to digital signals. It has a conversion part.
[0020]
FIG. 2 is a circuit diagram showing a specific example of the flame detector FD1, and is a circuit diagram centering on the long wavelength side detection element 10. As shown in FIG.
[0021]
The detection element 10 includes a detection element 11 such as a pyroelectric element and a load resistance 12 thereof.
[0022]
In the narrowband filter 20, infrared light received by the detection element 10 is input to the narrowband filter amplifier 25. The filter 20 includes an amplifier 25, capacitors 21 and 23, and resistors 22 and 24, and allows flame fluctuations of 1 to 20 Hz to pass through. A stable voltage is supplied as a reference voltage of the amplifier 25 by the Zener diode 82 and the capacitor 83 as the constant voltage circuit 15. The resistor 81 is a current limiting resistor.
[0023]
In the amplifier circuit 30, a signal of 1 to 20 Hz is input to the amplifier 31, and the signal is amplified by an amplifier circuit configured by the amplifier 31 and the resistors 32, 33, and 34.
[0024]
In the smoothing circuit 40, the signal that has passed through the coupling capacitor 41 is impedance-converted by the FET 42 and the resistor 43, and the capacitor 45 is charged through the resistor 44 and smoothed. The resistor 46 is a discharge resistor that discharges a signal, and is slowly discharged so that the signal remains stable.
[0025]
In the CPU 60, this signal is input to the A / D converter of the CPU 60 via the protective resistor 54, and fire determination is performed.
[0026]
The discharge circuit 50 includes a base resistor 52, a transistor 51, and a discharge resistor 53. The transistor 51 is turned on / off by the presence / absence of an output from the CPU 60 via the base resistor 52, and discharges a signal from the smoothing circuit 40. By doing so, unless there is a light source in front of the detection element 11, the detection signal does not reach a level at which a fire is detected.
[0027]
The circuit centering on the short wavelength side detection element 10a is also configured similarly to the circuit shown in FIG.
[0028]
FIG. 4 is a diagram illustrating the detection wavelength characteristics of the detection elements 10 and 10a and the wavelength characteristics of light generated from various light sources.
[0029]
In FIG. 4, the detection region of the long wavelength side detection element 10 has a wavelength of 1.6 to 1.8 μm, and the region is formed by the characteristics of the pyroelectric element as the element and the optical filter on the front surface thereof. Further, the detection region of the short wavelength side detection element 10a has a wavelength of 0.9 to 1.1 μm, which is the characteristic of the photodiode as the element itself. The spectral characteristics of the flame centered on gasoline and the characteristics of misreporting factors of various electric lamps and sunlight are shown for both elements 10 and 10a. When judging from such a relationship, the long wavelength side This is based not only on a predetermined level of the detection element 10 but also on a predetermined output ratio with the output of the short wavelength side element 10a at that time. In addition, the detection area of both elements as a two-wavelength type is not limited, and it may have a width centering on each wavelength.
[0030]
Next, the operation of the above embodiment will be described.
[0031]
FIG. 3 is a flowchart showing the operation of the above embodiment.
[0032]
Here, steps S1 to S5 are fire monitoring operations, steps S11 to S13 are operations for discriminating fire and noise, and steps S21 to S27 are functional tests.
[0033]
When the fire is determined (S1), first, the value of the fire counter, which is a function of the CPU 60, is reset to “0” (S2). The output signal of the detection element 10 on the long wavelength side is smoothed and sampled (S3), and the output signal of the detection element 10a on the short wavelength side is smoothed and sampled (S4).
[0034]
Then, it is determined whether or not the sampled value (detection signal) exceeds the fire discrimination level (S5). For example, the value of the output signal of the long wavelength side detection element 10 is equal to or higher than a first predetermined level, and the value of the output signal of the long wavelength side detection element 10 and the value of the output signal of the short wavelength side detection element 10a If the ratio is greater than or equal to the second predetermined level, it is determined that the fire determination level is exceeded, and the process proceeds to step S11.
[0035]
If the detection signal exceeds the fire discrimination level (S5), the discharge circuit 50 is turned on (S11), the output signals of the smoothing circuits 40, 40a are set to 0, and the fire counter is incremented by "1" (S12).
[0036]
Here, the value of the fire counter is used to count the number of times it is determined that a flame has occurred. If the value of the fire counter has not reached 3 (S13), the process returns to step S3. If the value of the fire counter has reached 3 (S13), a fire signal is transmitted to a fire receiver (not shown) (S14). Note that the value of the fire counter as a condition for transmitting the fire signal to the fire reception may be set to a value other than 3.
[0037]
In FIG. 3, “Noise 1” is noise having a value equal to or higher than the fire determination level, and “Noise 2” is noise that does not satisfy the fire determination level. As “noise 1”, for example, headlight noise of a truck passing through a tunnel, thermal noise due to a muffler, and the like can be considered, and the level is often much higher than the fire determination level.
[0038]
In the above embodiment, since the detection signal (the output signal of the smoothing circuits 40 and 40a) is discharged in step S11, even if the detection signal at that time is noise and its level is considerably high, Since the battery is discharged, the flame detector FD1 does not malfunction due to the noise and is not determined to be a fire when the next fire is determined, and the fire detection is not delayed.
[0039]
On the other hand, when the output signals of the detection elements 10 and 10a do not include a signal exceeding the fire discrimination level (S5), and a function test needs to be performed (S21), the light receiving glass is provided inside. An internal light source not shown in detail is applied to the detection elements 10 and 10a (S22), the detection signal is sampled (S23), and discharged by the discharge circuit 50 (S24), and the detection signal is stabilized by the discharge. After that, an external light source (not shown in detail) provided outside the light receiving glass is irradiated to the detection elements 10 and 10a (S25), the detection signal is sampled (S26), and the test result is transmitted to a receiver (not shown). (S27).
[0040]
As described above, the level of light emitted from the internal light source to the detection elements 10 and 10a is high, and if the detection signal remains high as in the case of noise 1, it is necessary to wait for the detection signal to stabilize. However, after the detection signal is stabilized by the discharge, the detection elements 10 and 10a are irradiated from the external light source, so that the time required for the function test can be shortened. In an actual system, since a large number of flame detectors FD1 are connected to a receiver (not shown), the reduction in individual test time is very large when converted to the test time of the entire system.
[0041]
FIG. 5 is a diagram showing an input signal of the CPU 60 when the fire detection is performed without the presence of noise and when the fire detection is performed under the presence of the noise in the embodiment.
[0042]
That is, FIG. 5 shows detection signals output from the smoothing circuits 40 and 40a when no noise occurs and when noise occurs.
[0043]
When the signal output is amplified by noise, the fire discrimination level is exceeded by periodic sampling, but the transistor 51 of the discharge circuit 50 is temporarily turned on, and the charge of the capacitor 45 is forcibly discharged by the discharge resistor 53. And returning to the monitoring state, it is possible to prevent malfunction and immediately enable fire detection.
[0044]
On the other hand, at the time of a fire, since a detection signal equal to or higher than the fire determination level is continuously generated after the discharge, a fire is determined.
[0045]
According to the above embodiment, in the flame detector, when the detection signal reaches the fire discrimination level due to the single noise, the detection signal is discharged so as not to malfunction, and the fire and noise are discriminated to detect fire early. can do. In other words, the embodiment immediately enters the fire monitoring state due to the discharge, and can detect fire early.
[0046]
The timing at which the discharge circuit 50 discharges the detection signal does not have to be limited to the case where the fire determination level is exceeded. The discharge circuit 50 is driven after sampling (S3 and S4 in FIG. 3) to always discharge. It may be. Usually, a false alarm source similar to a flame is often generated in a pulsed manner, but it is preferable to drive the discharge circuit 50 for each sampling when low level steady noise accumulates. Further, driving the discharge circuit 50 for each sampling has an advantage that the 0 level of the detection signal is stabilized.
[0047]
In the above embodiment, the case where the detection elements 10 and 10a are used as the two-wavelength type is shown. However, even in the case of a single infrared detection element targeting a wide or narrow wavelength in the infrared region. Of course, an ultraviolet detecting element for the ultraviolet region may be used.
[0048]
【The invention's effect】
According to the present invention, even if noise exceeding the fire discrimination level occurs, the flame detector does not malfunction and fire detection is not delayed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a flame detector FD1 according to an embodiment of the present invention.
FIG. 2 is a circuit diagram showing a specific example of a flame detector FD1, and is a circuit diagram centering on a long wavelength side detection element 10. FIG.
FIG. 3 is a flowchart showing the operation of the embodiment.
FIG. 4 is a diagram illustrating wavelength characteristics of light generated from various light sources.
FIG. 5 is a diagram showing an input signal of the CPU 60 when fire detection is performed without noise in the embodiment and when fire detection is performed under the presence of noise.
FIG. 6 is a diagram illustrating an operation of a conventional example.
[Explanation of symbols]
FD1 ... Flame detector,
10 ... long wavelength side detection element,
10a ... short wavelength side detection element,
20, 20a ... narrow band filter,
30, 30a ... amplifier circuit,
40, 40a: smoothing circuit,
50 ... discharge circuit,
60 ... CPU.

Claims (1)

A detection element for detecting ultraviolet rays or infrared rays generated by flames;
A narrowband filter for extracting a necessary frequency component from signals output from the detection element;
Smoothing means for outputting a signal obtained by charging the output signal of the narrow band filter as a detection signal;
Flame occurrence determination means for determining that a flame is generated when the detection signal output from the smoothing means exceeds a preset fire determination level;
Discharging means for forcibly discharging the charged detection signal and returning it to a monitoring state when the flame occurrence determining means determines that a flame has occurred;
Counting means for counting by periodic sampling that the flame occurrence judging means judges that a flame has occurred;
Fire determining means for determining that a fire has occurred when the count value reaches a predetermined value;
Count value resetting means for setting the count value to 0 if the detection signal does not exceed the fire discrimination level;
A flame detector characterized by comprising:

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