JPS63217231A - Radiation type fire detector - Google Patents

Abstract

PURPOSE:To obtain a fire detector which does not malfunction by inhibiting a switching circuit which operates with a specific output from an amplifier for low-frequency amplification from operating when an amplifier which performs high-frequency amplification is generates a specific output. CONSTITUTION:When a pyroelectric element 21 generates an AC output of about 8Hz low frequency owing to deterioration, the output of a smoothing circuit 51 becomes larger then the output of a smoothing circuit 52 as well as in case of a fire, a comparator 6 generates a high-level output, and an integration circuit 71 begins to perform its integrating operation. This low-frequency output, however, contains a high frequency voltage of 170Hz, so this output is passed through a filter 33, amplified by an AC amplifier 43, and smoothed by a smoothing circuit 53 to operate the switching circuit 82 through an integration circuit 72. Consequently, the transistor Tr of the integration circuit 71 with a long integration time is turned on, the integration circuit 71 is inhibited from operating, and the switching circuit 81 does not operate, so that no wrong fire signal is sent out to a receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a radiation-type fire detector that detects radiant light emitted from a flame to notify a fire.

<Prior art> Conventionally, radiation fire detectors detect two different spectral components in infrared rays, and by comparing their radiation amounts, they can distinguish flame from sunlight or light such as a lighting lamp (hereinafter referred to as environmental light). A two-wavelength fire detector that differentiates between According to this publication, the short wavelength spectral component and the long wavelength spectral component were detected using two solar cells through a filter, but there was a risk of malfunction due to the blue revolving lights of cars, etc. In order to avoid this, the range for detecting long wavelength spectral components was shifted to a range that did not include these components, and as a result, a pyroelectric element was used as the element. Under normal ambient light, the output is a short-wavelength spectrum > long-wavelength spectrum, whereas the radiant light from a flame has a short-wavelength, long-wavelength spectrum, and this reversal is detected and the occurrence of a fire is notified. I was trying to do that.

Furthermore, a simple single-wavelength radiation fire detector using a pyroelectric element is also known.

<Problems with the prior art> Detectors using pyroelectric elements are excellent in that they do not malfunction when exposed to blue rotating lights, etc., but they
High-frequency noise around 170 Hz, so-called popcorn noise, caused by changes in temperature, shock, element deterioration, poor contact of lead wires, etc., sometimes caused a fire alarm even though it was not a fire.

Means for Solving the Problems> In view of the above-mentioned drawbacks of the conventional fire detector, the present invention provides a radiation type fire detector that uses a pyroelectric element to detect flickers of low-frequency radiant light emitted from flames to notify the fire. The detector is provided with an amplifier that amplifies the low frequency and an amplifier that amplifies the high frequency of the AC output from the pyroelectric element, and when the amplifier that amplifies the high frequency generates a predetermined output, the amplifier that amplifies the low frequency The present invention is characterized in that the operation of a switching circuit that operates at a predetermined output is prohibited.

<Function> When a fire occurs in the fire detector configured as described above, an 8 Hz AC output is generated in the pyroelectric element due to the flicker of radiant light, which is amplified by a low frequency amplifier, and the predetermined output is used for switching. The circuit operates and a fire signal is emitted.

On the other hand, when low-frequency popcorn noise similar to that in the case of fire occurs in the pyroelectric element due to deterioration of the pyroelectric element, this noise is amplified by the low-frequency amplifier and attempts to operate the switching circuit. However, since this Bohubu Cove noise includes a high frequency component having a peak value at 170 Hz, the high frequency amplifier reaches a predetermined value and the operation of the switching circuit is prohibited.

Embodiment An embodiment of the radiation fire detector of the present invention will be described below with reference to the circuit diagram in FIG. 1 and the output waveform diagram of the pyroelectric element in FIG. 2. In Figure 1, 1). 12 is an optical filter that transmits a long wavelength spectrum of 1.0 to 2.2 μm and a short wavelength spectrum of 0.8 to 1.0 μm of flame emitted from the same location, 21 is a pyroelectric element, 22 is a solar cell, Each filter 1). 12. 31.
Reference numeral 32 denotes a bandpass filter having a peak value at, for example, 8 Hz, which is unique to flame flickering, and is connected to the pyroelectric element 21.32, respectively. It is provided corresponding to the solar cell 22. 33 is a high frequency component included in the popcorn noise generated in the pyroelectric element 21; 170
1) A bandpass filter with a peak value at z, and a pyroelectric element 21
It is set up correspondingly. Reference numerals 41, 42, and 43 are AC amplifiers, and 51, 52, and 53 are smoothing circuits, which are composed of diodes and capacitors, and convert the AC output of the amplifiers 41, 42, and 43 into DC.

6 is a comparator whose in-phase input is connected to the output of the smoothing circuit 51;
The non-in-phase input is connected to the output of the smoothing circuit 52, and is configured such that the output becomes high level when the long wavelength spectral component is greater than the short wavelength spectral component. 71
．． 72 is an integrating circuit provided corresponding to the comparator 6 and the smoothing circuit 53, respectively. The integrating circuit 71 has a longer integration time than 72, and is composed of a charging resistor R1, a capacitor C1, and a transistor Tr for rapid discharge. ing.

On the other hand, the integration circuit 72 having a short integration time is composed of a charging resistor R2 and a capacitor C2. 81 and 82 are switching circuits provided for generating a fire signal and for inhibiting the operation of the switching circuit 81, respectively.The input of the switching circuit 81 is connected to the output of the integrating circuit 71, and the input of the switching circuit 82 is connected to the output of the integrating circuit 71. to the output of the integrating circuit 72, and its output is connected to the transistor T of the integrating circuit 71.
connected to the base of r.

Next, the operation of the radiation type fire detector will be explained.

While the detector is illuminated with environmental light such as sunlight or illumination lights, even if a flicker of low frequency around 8Hz similar to a flame occurs, the spectral components of these lights will be different from the short wavelength spectral component>long wavelength. There is a relationship between spectral components, and a normal pyroelectric element 21 does not generate a high frequency output around 170 Hz.

Therefore, the pyroelectric element 21. The output of the solar cell 22 is amplified by an amplifier 41.42 via a filter 31.32, and smoothed by a smoothing circuit 51.52. The output relationship of the smoothing circuit 52 for smoothing is the output of the smoothing circuit 51 <the output of the smoothing circuit 52.

As a result, the comparator 6 is not inverted and maintains a low level, and the integrating circuit 71 and switching circuit 81 do not operate and continue the monitoring state.

When a fire detector is irradiated with flame radiation from a fire, unlike the case of environmental light, there is a relationship of long wavelength spectral component > short wavelength spectral component, and the pyroelectric element 21 and the solar cell 22 A low-frequency AC output having a peak value at 8 Hz as shown by +a+ in Fig. 2 is generated. Therefore, in this case, the output relationship of the smoothing circuits 51 and 52 is as follows: output of the smoothing circuit 51>output of the smoothing circuit 52, and the comparator 6 becomes high level. As a result, the integrating circuit 71 operates after a predetermined time, and then the switching circuit 81 operates, and a fire signal is issued to a receiver (not shown). In addition, in the case of the above-mentioned fire, high frequency output around 170 Hz will not be generated in the pyroelectric element 21, as in the case of the monitoring state.
The switching circuit 82 does not operate, and the rapid discharge transistor Tr of the integrating circuit 71 is not turned on.

On the other hand, if a low frequency AC output around 8 Hz occurs as shown by the dotted line in Figure 2 due to deterioration of the pyroelectric element 21, as in the case of a fire, the output of the smoothing circuit 51 > the smoothing circuit 52 The comparator 6 becomes high level and the integration circuit 71 starts its integration operation. However, for the above low frequency output, 170H is required as shown in the solid line in Figure 2.
Since the high frequency output near z is also included, this output is amplified by the amplifier 43 via the filter 33, and then the smoothing circuit 5
3, the integrating circuit 72 is operated, and the switching circuit 82 is operated. As a result, the transistor Tr of the integrating circuit 71 having a long integration time is turned on, and the integrating circuit 71
is prohibited from operating, the switching circuit 81 does not operate, and a fire signal as a false alarm is not sent to the receiver.

The above example was for a two-wavelength fire detector, but
In the case of a single-wavelength radiation fire detector, the output of the smoothing circuit 51 is directly connected to the integrating circuit 71, and the comparator 6
．． Optical filter 12. Solar cell 22. Filter 32. The amplifier 42 and the smoothing circuit 52 may be omitted.

Furthermore, in the above example, 8Hz and 170H, respectively.
The filters 31, 32, 33 that pass the AC signal of , 33 may be omitted.

Further, in the above embodiment, a monostable multi-pipe break is used instead of the integrating circuit 72 to prohibit the operation of the detector for a certain period of time when noise occurs, or a bi-stable multi-bi break is used to prohibit the operation continuously thereafter. However, in such a case, it would be more convenient if the switching circuit 82 turns on a lamp to indicate that a failure has occurred.

(Effects) The radiation type fire detector of the present invention has the effect of providing a radiation type fire detector that does not malfunction even if the pyroelectric element deteriorates and generates a low frequency output similar to that in the case of a fire. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the radiation type fire detector of the present invention, and FIG. 2 is an output waveform diagram of a pyroelectric element. 1), 12... optical filter, 21... pyroelectric element,
22...Solar cell, 31.32.33...Band filter, 41.42°43...AC amplifier, 51.52
．． 53... Smoothing circuit, 6... Comparator, 71.72.
・・Integrator circuit, 81.82・・Swissonching circuit,
Tr...°transistor. Patent issued by Nomi Disaster Prevention Industry Co., Ltd.

Claims (3)

[Claims] (1) In a radiation fire detector that uses a pyroelectric element to detect flickering low-frequency radiant light emitted from a flame to notify a fire, an amplifier that amplifies the low frequency of the AC output from the pyroelectric element. and an amplifier that amplifies high frequencies, and when a predetermined output is generated from the amplifier that amplifies high frequencies, the switching circuit that operates with the predetermined output from the amplifier that amplifies low frequencies is prohibited from operating. Radiant fire detector. (2) The radiation type fire detector according to claim 1, wherein the amplifier for amplifying low and high frequencies is provided with a bandpass filter having peak values of 8 Hz and 170 Hz, respectively, on its input side. (3) The radiation type fire detector according to claim 1, wherein the amplifiers that amplify the low frequency and high frequency are themselves AC amplifiers having peak values at 8 Hz and 170 Hz, respectively.