JPS6138428A - Fire sensor - Google Patents

Abstract

PURPOSE:To contrive to reduce the occurrence an erroneous alarm issuing by discriminating noise due to external light, by detecting two wavelength lights in three specific mutually different infrared wavelength regions of radiant light by a flame. CONSTITUTION:Two wavelength lights in three wavelength regions of (1):1+ or - 0.2mum, (2):2+ or -0.2mum and (3):4.3+ or -0.2mum as relatively separated wavelengths are detected. For example, a band-pass filter for allowing a 1mum-region to pass is used as an optical fiber 1a while a band-pass filter for allowing a 4.3mum-region to pass is used as an optical filter 1b to detect lights which are, in turn, amplified by integrating amplifiers 3a, 3b through photoelectric converters 2a, 2b and, further, the intensities of two wavelength infrared rays by outputs A, B from the amplifiers 3a, 3b are compared by a comparing amplifier 4 and, if A<B, flame sensing output is generated to issue an alarm by an alarm output circuit 5. By this method, an erroneous alarm can be prevented by excluding noise due to external light.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a long-range fire detector that reduces false alarms.

[Background of the Invention] In general, long-range fire detectors that detect infrared light emitted from flames are used to detect flames over a relatively wide range, such as in factory buildings and expressway tunnels.

Conventionally, this type of fire detector detects light in two different infrared wavelength regions among the radiant light emitted from a flame, and distinguishes between the flame and noise caused by external light such as the sun or lights.
Wavelength type devices have been put into practical use.

However, this fire detector was still insufficient in terms of the risk of false alarms. In this fire detector, this is, for example, 0.8μm and 1.1μm or 3.3μm.
The system detects relatively close wavelengths in either the near-infrared region or the far-infrared region, such as 4.3 μm and 4.3 μm, and it is still difficult to distinguish between noise caused by flame and external light. It is enough.

In other words, as shown in Figure 2, the flame wavelength distribution (relative value) curve is completely different from external light such as sunlight or car headlights, and is relatively good as long as the influence of external light is small. Can distinguish between flame and external light. However, since the absolute value of sunlight is much larger than that of flame, and the absolute value of external light changes in various ways, it may not be possible to distinguish between flame and external light depending on two wavelengths that are close to each other.

In addition, in Fig. 2, the wavelength distribution curve of the flame is 4.3μ.
The peak of m is mainly due to combustion of gasoline and the like.

[Object of the Invention] The present invention has been made in view of the problems with the conventional type described above, and an object of the present invention is to provide a long-distance type fire detector that generates fewer false alarms.

[Structure of the Invention] In order to achieve the above object, the present invention uses a two-wavelength method that detects light in two different infrared wavelength regions among the radiant light generated from a flame and discriminates noise caused by the flame and external light. In a fire detector, each of the above two wavelengths is 1±0.2μ.
m, 2±0.2μm j3 and 4.3±0.2μm
It is characterized by being selected from among.

[Explanation of Examples] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a fire detector according to an embodiment of the present invention. In the figure, 1a and 1b are optical filters, 2a
, 2b is a photoelectric converter such as a pyroelectric sensor, 3a and 3b are integrating amplifiers, 4 is a comparison amplifier, and 5 is an alarm output circuit. Further, 6 is a flame to be detected by this fire detector.

In this fire detector, ■1±0.2μm, ■2±
It is characterized by detecting light of two wavelengths out of the three wavelength ranges of 0.2 μm and 4.3±0.2 μm to distinguish between flame and noise caused by external light. The optical filters 1a and 1b are for passing only the light of the wavelength to be detected. For example, when detecting wavelengths of 1μ and 4.3μ, a bandpass filter that passes the 1μ region is used as the optical filter 1a, and the optical filter A bandpass filter that passes through the 4.3μ region is used as 1b. Note that when using the 1μ region and 2μ region or the 2μ region and 4.3 region as the two detection wavelength regions, the optical filter 1a.

Of course, as 1b, one that passes through these wavelength ranges is used.

Pyroelectric sensors are normally used as the photoelectric converters 2a and 2b, but solar cells may be used if the detection wavelength is around 1 μm.

Integrating amplifiers 3a and 3b are photoelectric detectors 1a.

By amplifying the output of 1b, it is possible to suppress momentary fluctuations in incident light caused by automobile lights and the like.

In the comparator amplifier 4, the intensities of infrared light of two wavelengths are compared using the output A of the integrating amplifier 3a and the output B of the integrating amplifier 3b, and if A<B, a fire detection output is generated.

The alarm output circuit 5 is used to generate an alarm sound such as an emergency bell, a buzzer, or a siren when the comparison amplifier 4 generates a fire detection output, or to transmit an alarm signal to a road management center, local fire department, etc. It is.

[Effects of the Invention] As described above, according to the present invention, when detecting light in two infrared wavelength regions among radiation light generated from a flame and distinguishing noise caused by flame and external light, near-infrared light Since the sensor detects light of relatively distant wavelengths such as far-infrared light, it is relatively easy to realize a fire detector that outputs a signal only in the event of a fire and does not generate false alarms.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing a fire detector according to an embodiment of the present invention, and Fig. 12 is a graph showing the wavelength distribution of radiant light from flames, automobile headlight light, and sunlight in general fires. be. la, 1b...optical filter, 2a, 2b...photoelectric converter, 3a, 3b...integrating amplifier, 4...comparison amplifier, 5...alarm output circuit.

Claims (1)

[Claims] In a two-wavelength fire detector that detects light in two different wavelength regions of infrared light emitted from a flame and distinguishes between flame and noise caused by external light, each of the two wavelengths is 1±0. .2μm, 2±0.2μm and 4.3±0
．． A fire detector characterized in that it is selected from 2 μm.