JP2989320B2 - Flame 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 flame detecting device for notifying a fire by detecting radiation emitted from a flame in the infrared region by a pyroelectric element.

[0002]

2. Description of the Related Art Conventionally, as this kind of flame detecting apparatus, for example, Japanese Patent Application Laid-Open Nos. 63-204397 and 63-217
231 and JP-A-48-90030. In these conventional devices, each of the short-wavelength and long-wavelength spectrums of the emitted light from the flame is detected by a plurality of detection elements (a combination of a solar cell and a pyroelectric element or a combination of pyroelectric elements, etc.). It is configured to emit a fire signal when the level difference between the two wavelength signals is inverted and the signal output of one element is equal to or higher than a predetermined level. And
For example, even if popcorn noise occurs due to non-uniform crystal of the semiconductor element from the pyroelectric element provided on the long wavelength side, the element output on the short wavelength side becomes lower than a predetermined level, so that malfunction due to popcorn noise can be prevented. It has become.

[0003]

However, in an apparatus using such a conventional semiconductor element (pyroelectric element) for detecting a flame, a popcorn generated from the semiconductor element used for this detection is used. There is a problem that even if the probability of erroneous detection of a flame due to noise can be reduced, it cannot be basically prevented. That is, as described above, in the conventional apparatus, even if popcorn noise is generated from the semiconductor element (pyroelectric element) on the long wavelength side, the element output on the short wavelength side is below a predetermined level, so that malfunction due to noise is prevented. However, the output of short-wavelength devices is not always increased only by the flame in a fire.In fact, even if there is a sudden irradiation of sunlight, an increase in radiation from car lights or indoor lighting equipment, etc. The signal output increases. On the other hand, when the radiated light energy is increased rapidly in this way, popcorn noise from the detection semiconductor element is likely to be generated due to the non-uniformity of the crystal of the semiconductor element. The probability that popcorn noise is generated from a semiconductor detection element for detecting a signal output on the long wavelength side near 4.4 μm, particularly a pyroelectric element, increases. Therefore, even if popcorn noise is generated from the semiconductor element on the long wavelength side, the output of the element on the short wavelength side is not necessarily lower than a predetermined level, and it is impossible to completely prevent malfunction. Further, in the conventional device, there is a device in which transient popcorn noise is absorbed by an integrating circuit. However, popcorn noise is transient short-time vibration noise, but its voltage is large and integration of CR or the like is large. It is difficult to absorb in the circuit, and even if it is absorbed in the integrating circuit, the signal converted from the actual radiated light from the flame into an electric signal is also absorbed by the integrating circuit. There was a problem that it became impossible to do.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. Popcorn noise generated from a semiconductor element is, as the word implies, a transient low-frequency noise generated by non-uniformity of a semiconductor crystal. By paying attention to vibration noise and non-persistent noise that rapidly attenuates, by checking the non-persistence due to vibration attenuation, which is the basic property of popcorn noise, it is possible to completely eliminate malfunctions due to popcorn noise occurrence It is an object of the present invention to provide a flame detecting device which can prevent the energy of a small fire and detect the energy of a very small fire with high sensitivity.

[0005]

According to the present invention, there is provided a flame detecting apparatus using a pyroelectric element as a detecting means for detecting radiation in a wavelength in the infrared region emitted from a flame. A counting means for counting the number of vibrations of the detection signal from the pyroelectric element within a predetermined time; a gate means for passing the detection signal when the number of vibrations counted by the counting means is equal to or more than a predetermined number; And a fire judging means for issuing a fire signal when the detection signal passing through the means is equal to or higher than a reference level. According to a second aspect of the present invention, there are provided two pyroelectric elements for separately detecting short-wavelength and long-wavelength spectral components of emitted light, and a means for counting the number of vibrations of a signal from each pyroelectric element within a predetermined time. And vibrates through the gate means when the number of vibrations is equal to or greater than a predetermined number.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a flame detection device according to one embodiment of the present invention. This flame detection device
An optical filter 1 that transmits radiation near 4.4 μm, which is CO2 resonance radiation from a fire, a pyroelectric element 2, and a band-pass filter 3 that transmits a signal of, for example, 1 to 20 Hz, which is specific to flicker of flame. An AC amplifier 4, a rectifier 5 for converting an AC signal into DC, an analog switch 6,
A level discriminator 7 that turns on and off by discriminating whether a predetermined voltage level of the AC signal is higher than or lower than a predetermined level, a counter 8 that counts a signal from the level discriminator 7, and a signal from the level discriminator 7 A one-shot multivibrator 9 which is turned on for several seconds by a signal, a one-shot multivibrator 10 which is turned on only for a predetermined time by a signal from the counter 8 when the counter 8 has counted a predetermined number of times, and an output of the analog switch 6 is a reference voltage And a comparator 11 that outputs a fire signal when the number is 12 or more.

[0007] The detection operation of the present flame detection device configured as described above in the event of a fire will be described. When a fire occurs, only light having an energy having a wavelength of around 4.4 μm out of the light emitted from the flame is selectively transmitted by the optical filter 1 and is incident on the pyroelectric element 2 to be converted into an electric signal. Then, only the flicker component of 1 to 20 Hz unique to the flame passes through the band-pass filter 3 and is amplified by the AC amplifier 4 and output to the rectifier 5 and the level discriminator 7, respectively. Level discriminator 7
Turns on when the signal from the AC amplifier 4 is higher than a predetermined level, and turns off when the signal is lower than the predetermined level, thereby repeatedly turning on and off and outputting a signal to the counter 8 and the one-shot multivibrator 9. The one-shot multivibrator 9 outputs a pulse having a time width determined by the first signal input from the level discriminator 7 to a reset terminal of the counter 8 to enable the counter 8. Although the counter 8 is normally reset, the reset is released by an enable signal of the one-shot multivibrator 9 and counts the number of clock pulses from the level discriminator 7, and the number of counts is determined by the one-shot multivibrator 9. If the number of times exceeds a predetermined number within a predetermined time, the one-shot multivibrator 10 is triggered. The one-shot multivibrator 10 outputs a pulse of a predetermined width to the analog switch 6 and turns on the analog switch 6 for the time. At this time, the AC amplifier signal converted to DC by the rectifier 5 is turned on by the analog switch 6 so that the comparator 1
1 and is compared with a predetermined reference voltage. If the AC amplifier signal is equal to or higher than the reference voltage 12, the comparator 11 turns on and sends out a fire signal to the next circuit. As described above, flame detection is performed.

Next, the operation of the present flame detecting apparatus when popcorn noise occurs will be described. When popcorn noise is generated from the pyroelectric element 2, the transient vibration AC signal passes through the band-pass filter 3, is amplified by the AC amplifier 4, and is output to the rectifier 5 and the level discriminator 7.
The level discriminator 7 repeats ON and OFF according to the signal of the AC amplifier 4 as described above, and outputs a clock pulse to the counter 8 and the one-shot multivibrator 9. The one-shot multivibrator 9 outputs a pulse to the reset terminal of the counter 8 according to the first signal to enable the counter 8. The reset of the counter 8 is released by the enable signal of the one-shot multivibrator 9, and the counter 8 counts the clock pulse from the level discriminator 7. The popcorn noise signal is a transient rapid attenuating signal, and is caused by several vibrations. Since it disappears, the count value of the counter 8 does not exceed the set predetermined number of times. That is, the one-shot multivibrator 10 at the next stage is not triggered by the counter 8. Accordingly, since no pulse is output from the one-shot multivibrator 10 to the analog switch 6, the analog switch 6 does not operate and the AC amplifier signal converted to DC by the rectifier 5 for fire detection has a high level even if the AC amplifier signal has a large level. Is never entered. Thereby, malfunction due to popcorn noise is completely prevented.

As shown in FIG. 2, an analog switch 6 may be arranged in front of the rectifier 5. In this case, even if popcorn noise of the pyroelectric element 2 is generated, the counter 8
Is less than that frequency, the analog switch 6 is not turned on and no noise is input to the rectifier 5, so that the reference voltage 1
2 can be reduced, so that a flame detection device with higher sensitivity can be realized. Further, the input to the level discriminator 7 does not necessarily need to be connected from the output of the AC amplifier 4 and may be directly connected to the output of the pyroelectric element 2. Further, the analog switch 6 may be arranged in a stage preceding the AC amplifier 4.

FIG. 3 shows the structure of a flame detecting device according to another embodiment of the present invention. The flame detecting device shown in FIG. 3 includes two optical filters 1 and 21 that respectively transmit radiation light in different transmission wavelength bands, for example, near 3.8 μm and near 4.4 μm.
Accordingly, two pyroelectric elements 2 and 22 for detecting emitted light, two band-pass filters 3 and 23, and two AC amplifiers 4 and 24 are arranged. The output of each of the AC amplifiers 4 and 24 is connected to a differential amplifier 25 for amplifying a difference between the outputs, and further connected to an analog switch 6, a rectifier 5, and a comparator 11. The AC amplifiers 4 and 24 are connected to a level discriminator 7, a counter 8, and one-shot multivibrators 9 and 10 via an OR circuit 26. Two sets of optical filters 1 and 21 to AC amplifiers 4 and 24 are provided.
5 and an OR circuit 26, except for the configuration shown in FIG.

Here, in the case of ordinary ambient light, a short wavelength of 3.
A longer wavelength of 4.4 μm for spectral components around 8 μm
The spectral component around m is smaller or slightly larger, but the radiation emitted from the flame due to the occurrence of a fire is 4.4 μm different from ordinary ambient light.
It has the property that nearby spectral components are larger than those near 3.8 μm. Therefore, when radiated light from a fire is irradiated, the spectrum component around 4.4 μm becomes large unlike ordinary ambient light. The apparatus detects the increase and judges that it is a flame, and issues a fire signal. If popcorn noise is generated from the pyroelectric element 2 on the short wavelength side or the pyroelectric element 22 on the long wavelength side, the vibration signal is amplified by the AC amplifiers 4 and 24 and sent to the level discriminator 7 via the OR circuit 26. Although output, the vibration signal attenuates rapidly, so that the counter 8 cannot count more than a predetermined number of times within a predetermined time set by the one-shot multivibrator 9, and the one-shot multivibrator 10 Since the trigger cannot be performed, the analog switch 6 does not turn on. Therefore, even if the signals of the pyroelectric elements 2 and 22 are amplified by the AC amplifiers 4 and 24, the analog switch 6 is turned off. No fire signal will be issued.

On the other hand, when radiation is emitted from the flame to the flame detection device due to the occurrence of a fire, the short-wavelength spectrum around 3.8 μm by the optical filter 1 is applied to the pyroelectric element 2, and the short-wave spectrum around 4.4 μm by the optical filter 21. Is irradiated on the pyroelectric element 21 and converted into electric signals, respectively.
After passing through 24, the signal is amplified, and the difference is amplified by the differential amplifier 25 and input to the analog switch 6. In case of fire, unlike popcorn noise, its 1-20Hz
Since the flicker continues, the counter 8 counts a predetermined number of times or more within a predetermined time set by the one-shot multivibrator 9, and triggers the one-shot multivibrator 10. While the one-shot multivibrator 10 is on, the output signal of the differential amplifier 25 passes through the analog switch 6, is converted to direct current by the rectifier 5, and is input to the comparator 11. When the voltage is equal to or higher than the reference voltage 12, the comparator 11 turns on and emits a fire signal.

[0013]

As described above, according to the present invention, the counting means for counting the number of vibrations of the detection signal from the detecting element within a predetermined time period, and when the number of vibrations counted by the counting means is equal to or more than the predetermined number of times, By providing the gate means for passing the detection signal, the non-persistence due to the attenuation of the vibration signal, which is the basic property of popcorn noise, is checked by the counting means, and the signal due to the popcorn noise is cut off by the gate means, Malfunction due to generation of popcorn noise can be completely prevented. Also, since there is no need to use an integrating circuit to absorb popcorn noise as in the prior art, there is no possibility that the signal due to the actual light emitted from the flame is absorbed by the integrating circuit and the sensitivity is degraded. It can detect small fire energy with high sensitivity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a flame detection device according to the present invention.

FIG. 2 is a block diagram showing a modification of the embodiment shown in FIG.

FIG. 3 is a block diagram showing a configuration of another embodiment of the flame detection device of the present invention.

[Explanation of symbols]

 Reference Signs List 1,21 Optical filter 2,22 Pyroelectric element 3,23 Bandpass filter 4,24 AC amplifier 5 Rectifier 6 Analog switch 7 Level discriminator 8 Counter 9,10 One-shot multivibrator 11 Comparator 25 Differential amplifier

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G08B 17/12

Claims (2)

(57) [Claims] 1. A flame detecting apparatus using a pyroelectric element as a detection means for detecting radiation in an infrared region emitted from a flame, wherein the number of vibrations of a detection signal from the pyroelectric element within a predetermined time is counted. Counting means, a gate means for passing the detection signal when the number of vibrations counted by the counting means is equal to or more than a predetermined number, and a fire judgment for issuing a fire signal when the detection signal passing through the gate means is equal to or more than a reference level Means for providing a flame. 2. A pyroelectric element for separately detecting short-wavelength and long-wavelength spectral components of emitted light, and the number of vibrations of a signal from each pyroelectric element within a predetermined time is counted by a counting means. 2. The flame detecting apparatus according to claim 1, wherein the gate is passed when the number of vibrations is equal to or more than a predetermined number.