JPH0715410B2 - Radiant fire detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiant fire detector that detects 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. 2 wavelength type fire detector that distinguishes
It was known by the publication such as 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. A single-wavelength radiation fire detector using a pyroelectric element is also known as a simple one.

<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 Problems> The present invention is based on the drawbacks of the above-mentioned conventional fire detectors, and a radiant fire for notifying a fire in which flicker of low-frequency radiation emitted from a flame is detected by a pyroelectric element In the detector,
Of the AC output from the pyroelectric element, an amplifier for amplifying a low frequency and an amplifier for amplifying a high frequency are provided, and a predetermined output from an amplifier for amplifying a low frequency is generated when a predetermined output is generated from the amplifier for amplifying a high frequency. The feature is that the operation of the operating switching circuit is prohibited.

<Operation> When a fire occurs, the fire detector configured as described above generates an 8 Hz AC output in the pyroelectric element due to flicker of radiant light, which is amplified by the low-frequency amplifier, and the switching circuit is activated by the predetermined output. Operates and fire signal is emitted. On the other hand, if low frequency popcorn noise similar to the case of the above fire occurs in the pyroelectric element due to deterioration of the pyroelectric element,
This noise is amplified by the low frequency amplifier and tries to operate the switching circuit. However, since this popcorn noise contains 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 type fire detector of the present invention will be described below with reference to the circuit diagram of FIG. 1 and the output waveform diagram of the pyroelectric element of FIG. In FIG. 1, 11 and 12 are optical filters for transmitting a long-wavelength spectrum 1.0 to 2.2 μm and a short-wavelength spectrum 0.8 to 1.0 μm of a flame emitted from the same place, 21 is a pyroelectric element, and 22 is a solar cell. , Provided corresponding to the filters 11 and 12, respectively. 31 and 32 are peculiar to flame flicker,
For example, a bandpass filter having a peak value at 8 Hz is provided corresponding to the pyroelectric element 21 and the solar cell 22, respectively. Reference numeral 33 is a bandpass filter having a peak value at 170 Hz, which is a high-frequency component included in the popcorn noise generated in the pyroelectric element 21, and is provided corresponding to the pyroelectric element 21. 41, 42, 43 are AC amplifiers,
Reference numerals 51, 52 and 53 are smoothing circuits, which are composed of diodes and capacitors and convert the AC outputs of the amplifiers 41, 42 and 43 into DC.

Reference numeral 6 denotes a comparator, the in-phase input of which is connected to the output of the smoothing circuit 51, and the non-in-phase input of which is connected to the output of the smoothing circuit 52. When the long wavelength spectrum component> the short wavelength spectrum component, the output becomes high level. Is configured. Reference numerals 71 and 72 denote integrating circuits provided corresponding to the comparator 6 and the smoothing circuit 53, respectively. The integrating circuit 71 has a longer integration time than 72, and has a charging resistor R ₁ , a capacitor C ₁ and a transistor Tr for rapid discharge Tr.
It is composed of On the other hand, an integration circuit with a short integration time
72 is composed of a charging resistor R ₂ and a capacitor C ₂ .
81 and 82 are 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 the output of the integrating circuit 71, and the input of the switching circuit 82 is The output of the integration circuit 72, and the output is the transistor Tr of the integration circuit 71.
Connected to the base of.

Next, the operation of the radiant fire detector will be described. While the detector is illuminated by sunlight or ambient light such as an illumination lamp, even if low-frequency flicker near 8 Hz occurs, similar to a flame, the spectral components of these lights are short-wavelength spectral components> long-wavelength spectral components. Pyroelectric element 21 which has a relationship of spectral components and is normal
Does not generate high frequency output around 170Hz. Therefore, the outputs of the pyroelectric element 21 and the solar cell 22 are amplified by the amplifiers 41 and 42 via the filters 31 and 32 and smoothed by the smoothing circuits 51 and 52, but the smoothing circuit 51 that smoothes long-wavelength spectrum components. And the output relationship of the smoothing circuit 52 for smoothing the short wavelength vector component 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 the low level,
The integrating circuit 71 and the switching circuit 81 do not operate and continue the monitoring state.

When the radiant light of the flame caused by the fire is applied to the fire detector, there is a relationship of long-wavelength spectrum component> short-wavelength spectrum component, unlike the case of ambient light, and the pyroelectric element 21 and the solar cell 22 are A low-frequency AC output having a peak value at 8 Hz is generated as shown in FIG. Therefore, the output relationship between the smoothing circuits 51 and 52 in this case is the output of the smoothing circuit 51> the output of the smoothing circuit 52, and the comparator 6 becomes high level. As a result, the integration circuit 71 operates after a predetermined time, and the switching circuit 81 operates, so that a fire signal is issued to a receiver (not shown). In the case of the above-mentioned fire, the high frequency output near 170 Hz is the same as in the case of the monitoring state.
Therefore, the switching circuit 82 does not operate and the transistor Tr for rapid discharge of the integrating circuit 71 is not turned on.

On the other hand, if a low-frequency AC output near 8 Hz occurs as shown by the dotted line in FIG. 2 (b) due to deterioration of the pyroelectric element 21, the output of the smoothing circuit 51> smoothing circuit as in the case of a fire.
It becomes the output of 52, the comparator 6 becomes high level and the integration circuit
71 starts its integration operation. However, since the low-frequency output also includes a high-frequency output near 170 Hz as shown by the solid line in FIG. 2 (b), this output is amplified by the amplifier 43 via the filter 33 and the smoothing circuit 53. And the switching circuit 82 is operated. As a result, the transistor of the integration circuit 71 with a long integration time is
The Tr is turned on, the operation of the integrating circuit 71 is prohibited, the switching circuit 81 does not operate, and a fire signal as a false alarm is not sent to the receiver.

Although the above-mentioned embodiment is the case of the two-wavelength type fire detector,
In the case of a single-wavelength radiant fire detector, the output of the smoothing circuit 51 is directly connected to the integrating circuit 71, and the comparator 6, the optical filter 12, the solar cell 22, the filter 32, the amplifier 42 and the smoothing circuit 52. Should be omitted.

Further, in the above embodiment, the filters 31, 32, 33 for passing the AC signals of 8 Hz and 170 Hz, respectively, are provided on the input side of the amplifiers 41, 42, 43, but the amplifier itself amplifies only such frequencies. As an amplifier, the above filters 31,3
2,33 may be omitted.

Further, in the above embodiment, a monostable multivibrator is used instead of the integrating circuit 72 to inhibit the operation of the detector when noise occurs for a certain period of time, or a bistable multivibrator is used to inhibit it continuously thereafter. Good. In such a case, it is further purposeful if the switching circuit 82 lights the lamp to indicate that a failure has occurred.

<Effect> The radiant fire detector of the present invention has an effect of obtaining a radiant fire detector that does not malfunction even if a low-frequency output similar to that in the case of fire occurs due to deterioration of the pyroelectric element.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a radiation type fire detector of the present invention, and FIG. 2 is an output waveform diagram of a pyroelectric element. 11,12 ...... 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 …… Switching circuit, Tr …… Transistor.

Claims (3)

[Claims] 1. A radiation-type fire detector for detecting a flicker of low-frequency radiation emitted from a flame by a pyroelectric element to notify a fire, of which low frequency is amplified among the AC output from the pyroelectric element. And an amplifier for amplifying high frequency,
A radiation-type fire detector characterized in that when a predetermined output is generated from an amplifier that amplifies a high frequency, the operation of a switching circuit that operates at a predetermined output from an amplifier that amplifies a low frequency is prohibited. 2. The radiant fire detector according to claim 1, wherein the amplifier for amplifying the low frequency and the high frequency is provided with band filters having peak values of 8 Hz and 170 Hz on the input side thereof. 3. An amplifier for amplifying low frequency and high frequency,
The radiant fire detector according to claim 1, which itself is an AC amplifier having peak values at 8 Hz and 170 Hz, respectively.