JPH0660843B2 - Radiant fire detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiant fire detector that detects a radiant light emitted from a flame to notify a fire.

<Prior Art> Conventionally, as a radiant fire detector, two different spectral components in infrared rays are detected, and by comparing these radiation amounts, light such as flame and sunlight or lighting (hereinafter referred to as ambient light) is detected. A two-wavelength type fire detector that distinguishes between the two is known from Japanese Patent Publication No. 58-16238. According to this publication, the short-wavelength spectrum component and the long-wavelength spectrum component are detected by the two solar cells through the filter, but there is a risk of malfunction due to a blue rotating light of a car, In order to avoid this, the range in which the long-wavelength spectrum component is detected is shifted to a range that does not include these, whereby a pyroelectric element is used as an element. Under normal ambient light, the output is short-wavelength spectrum> long-wavelength spectrum, whereas radiation emitted from the flame has short-wavelength <long-wavelength spectrum. I was trying to inform you. As a simple one, a short-wavelength radiant fire detector using a pyroelectric element is also known.

<Problems of the prior art> A detector using a pyroelectric element is excellent in that a detector that does not malfunction with a blue rotating lamp or the like is obtained, but changes in ambient temperature, shock, element deterioration, or lead wire High-frequency noise around 170Hz caused by poor contact, so-called popcorn noise, sometimes triggered a fire alarm even though it was not a fire.

<Means for Solving the Problems> The present invention is conceived in view of the drawbacks of the conventional fire detectors described above, and does not malfunction even if high frequency noise such as popcorn noise is generated from the pyroelectric element. The purpose is to obtain a fire detector that will perform a normal fire detection operation even if a fire occurs.A radiation type that detects the flicker of low-frequency radiation emitted from the flame with a pyroelectric element and notifies the fire. In the fire detector, corresponding to the pyroelectric element,
A first low-frequency amplifier for amplifying a low-frequency output from a pyroelectric element caused by flicker of flame, a high-frequency amplifier for amplifying a high-frequency output caused by high-frequency noise generated when the pyroelectric element fails, and this amplifier A second low-frequency amplifier for amplifying a low-frequency output among the outputs of the first and second low-frequency amplifiers, and a differential amplifier for outputting the difference between the outputs of the first and second low-frequency amplifiers, respectively. A fire signal is emitted when a predetermined output is generated in the dynamic amplifier.

<Operation> In the fire detector configured as described above, when a fire occurs, an AC output having a peak value at 8 Hz due to flicker of radiant light is generated in the pyroelectric element and no high-frequency noise output is generated. The output amplified by the low frequency amplifier is output from the differential amplifier, and a fire signal is emitted by the predetermined output. On the other hand, when a high frequency noise output due to popcorn noise is generated in the pyroelectric element, the low frequency output generated by this noise is simultaneously amplified by the first and second low frequency amplifiers and input to the differential amplifier. Due to the action, these inputs cancel each other out, the noise components are canceled out, the output is not generated from the differential amplifier, and a malfunction is prevented.

<Embodiment> An embodiment of the radiant fire detector according to the present invention will be described below with reference to the circuit diagram of FIG. 1 and the output waveforms at points A to F in the circuit diagram when a fire occurs (a) and a noise occurs (b). ) And fire when noise occurs
The output waveform diagram of FIG. 2 showing (c) will be described.
In FIG. 1, 11 and 12 are filters for transmitting the long-wavelength spectrum 1.0 to 2.2 μm and the short-wavelength spectrum 0.8 to 1.0 μm of the flame emitted from the same place, 21 is a pyroelectric element, and 22 is a solar cell. The filters 11 and 12 are provided respectively.

Reference numerals 31 and 32 are low-frequency amplifiers, which are provided corresponding to the pyroelectric element 21 and the solar cell 22, respectively, and are OP for amplifying an AC signal peculiar to the flickering of the flame, for example, having a peak value at 8 Hz.
The feedback circuit of the amplifier is adjusted. A high frequency amplifier 33 is provided corresponding to the pyroelectric element 21 together with the low frequency amplifier 31 and amplifies a noise output having a peak value at 170 Hz, for example, due to popcorn noise generated when the pyroelectric element 21 fails. Thus, the feedback circuit of the OP amplifier is adjusted. Reference numeral 34 is a low frequency amplifier, and the feedback circuit of the OP amplifier is adjusted so as to amplify the low frequency output having a peak value at 8 Hz generated by the high frequency output from the high frequency amplifier 33 when noise occurs.

Reference numeral 4 is a phase matching circuit that outputs the output of the pyroelectric element 21 to a high frequency amplifier.
It is provided corresponding to the low frequency amplifier 31 so as to match the phase of the output of the low frequency amplifier 34 that amplifies via 33 with the output that is amplified only by the low frequency amplifier 31, and the phase with suppressed gain It is executed by an amplifier mainly for adjustment. 5
Is a differential amplifier set to detect the difference between a pair of inputs, and the output of the phase matching circuit 4 and the output of the low frequency amplifier 34 are connected to the pair of inputs, respectively. The smoothing circuits 61 and 62 are composed of rectifying diodes and capacitors, and the smoothing circuit 61 converts the AC output of the differential amplifier 5 and the smoothing circuit 62 converts the AC output of the low frequency amplifier 32 into DC.

Reference numeral 7 is a comparator, the in-phase input of which is connected to the output of the smoothing circuit 61, and the non-in-phase input of which is connected to the output of the smoothing circuit 62. When the long wavelength spectrum component> the short wavelength spectrum component, the output becomes high level. Is configured. Further, an offset circuit 71 is provided on the non-in-phase input side so as to stably attain a low level in the monitoring state. Reference numeral 8 denotes an integrating circuit, which is composed of, for example, a charging resistor and a capacitor, and is provided so as to detect only a long-lasting signal in case of a fire. A switching circuit 9 is configured to emit a fire signal to a receiver (not shown).

Next, the operation of the radiant fire detector will be described. During normal operation when the detector is exposed to ambient light such as sunlight or lighting, and the pyroelectric element does not fail, the light does not flicker, and high-frequency noise output near 170 Hz produces a pyroelectric element. Since the outputs of the low-frequency amplifiers 31 and 32 and the high-frequency amplifier 33 are almost zero, and the outputs of the differential amplifier are almost zero, the output of the comparator 7 is forced by the action of the offset circuit 71. Is maintained at a low level. Further, even if low-frequency flicker near 8 Hz occurs in the ambient light similar to a flame, the spectral components of these lights have a relationship of short-wavelength spectral component> long-wavelength spectral component. Therefore, no output is generated from the low frequency amplifier 34, and the output of the pyroelectric element 21 smoothed by the smoothing circuit 61 through the low frequency amplifier 31, the phase matching circuit 4 and the differential amplifier 5 is the low frequency amplifier 32.
Is smaller than the output of the solar cell 22 smoothed by the smoothing circuit 62 through, the comparator 7 maintains a low level, and the integrating circuit 8 and the switching circuit 9 do not operate.

When the fire detector irradiates the fire detector with radiant light from a fire, unlike the case of ambient light, the pyroelectric element 21 and solar cell
At 22, an AC output with a peak value at 8 Hz is generated due to flame flicker. And those outputs have a relation of long-wavelength spectrum component> short-wavelength spectrum component,
Further, no high frequency noise output having a peak value at 170 Hz is generated from the normal pyroelectric element 21. Therefore, in such a state, the output of the differential amplifier 5 is only the output of the low frequency amplifier 31 due to the output from the low frequency amplifier 34, and the output of the smoothing circuit 61> the output of the smoothing circuit 62. The container 7 becomes high level. By this inversion to the high level, the integration circuit 8 operates and the switching circuit 9 operates after a predetermined time, and a fire signal is sent to a receiver (not shown). Therefore, the output waveforms at points A to F in FIG. 1 are shown in FIG.
It becomes like (a).

When a high frequency noise output having a peak value at 170 Hz as shown by the solid line in A of FIG. 2 (b) is generated due to deterioration of the pyroelectric element 21, this output is amplified by the high frequency amplifier 33, and this output The resulting low frequency output having a peak value at 8 Hz is amplified by the low frequency amplifier 34 and input to the differential amplifier 5. On the other hand, the low frequency output having a peak value at 8 Hz shown by the dotted line in A of FIG. 2 (b) caused by the high frequency output is also amplified by the low frequency amplifier 31 and is output by the phase matching circuit 4 to the output of the low frequency amplifier 34. It is adjusted to have the same phase and input to the differential amplifier 5. The signal input here has the same frequency, phase, and its amplitude as shown by D and E in FIG. 2 (b), so the output of the differential amplifier 5 becomes zero and the output of the smoothing circuit 61 also. It becomes almost zero, and at this time, the signals that cause the malfunction are canceled. Therefore, similarly to the time of monitoring, the comparator 7 maintains the low level by the action of the offset circuit 71, the integrating circuit 8 and the switching circuit 9 do not operate, and the fire signal is not emitted.

Further, if a fire occurs while noise output is being generated in the pyroelectric element 21, the pyroelectric element 21 will be affected by a fire as shown by A in FIG. 2 (c).
A flicker noise output of the flame produces a composite output. This combined output has a low-frequency component generated by the amplifier.
The signal is amplified by 31 and input to the differential amplifier 5 via the phase matching circuit 4. On the other hand, in the high frequency amplifier 33, only the high frequency component that is the noise output is amplified, and the low frequency output generated by this output is amplified by the low frequency amplifier 34 and input to the differential amplifier 5. Therefore, the outputs of the phase matching circuit 4 and the low-frequency amplifier 34 input to the differential amplifier 5 are outputs as shown in D and E of FIG. 2 (c), and only the difference, that is, the fire component is present. As shown by F in FIG. 2 (c), it is output from the differential amplifier 5 and smoothed by the smoothing circuit 61. In the case of a fire, the output of the smoothing circuit 61 naturally becomes larger than the output from the smoothing circuit 62 obtained by smoothing the output from the solar cell 22, so that the comparator 7 becomes high level, and the integrating circuit 8 and the switching circuit 9 Activates and fire signal is emitted.

Although the above-mentioned embodiment is the case of the two-wavelength type fire detector,
In the case of a single-wavelength radiation fire detector, the output of the smoothing circuit 61 is directly connected to the integrating circuit 8, and the comparator 7 and its offset circuit 71, the filter 12, the solar cell 22, the low-frequency amplifier 32 and The smoothing circuit 62 may be omitted.

<Effect> Since the radiant fire detector of the present invention is configured and operates as described above, it does not malfunction even if high frequency noise such as popcorn noise is generated from the pyroelectric element, and a fire occurs in such a state. In that case, there is an effect that a fire detector that normally performs a fire detection operation can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the radiant fire detector of the present invention, and FIG. 2 is an output waveform diagram at points A to F in the circuit diagram of FIG. 11,12 ... Filter, 21 ... Pyroelectric element, 22 ... Solar cell, 31, 32
... low-frequency amplifier, 33 ... high-frequency amplifier, 4 ... phase matching circuit, 5 ... differential amplifier, 61, 62 ... smoothing circuit, 7 ... comparator,
8 ... Integrator circuit, 9 ... Switching circuit.

Claims (1)

[Claims] 1. A radiant fire detector for detecting a flicker of low-frequency radiant light emitted from a flame by a pyroelectric element to report a fire. A first low-frequency amplifier for amplifying a low-frequency output from the electric element, a high-frequency amplifier for amplifying a high-frequency output generated by high-frequency noise generated when the pyroelectric element fails, and a low-frequency output of the amplifier. A second low frequency amplifier that amplifies the output and a differential amplifier that outputs the outputs of the first and second low frequency amplifiers and outputs the difference between them are provided. A radiation-type fire detector characterized by emitting a fire signal when it occurs.