JP3071902B2 - Fire alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire alarm device for detecting the presence or absence of a fire and the type of smoke from light scattered by smoke generated during a fire.

[0002]

2. Description of the Related Art A scattered light type smoke detector is known as a device for judging a fire from light scattered by smoke generated in a fire. This is because, as shown in FIG. 4, a light emitting element 2 such as a light emitting diode for irradiating directional light toward the center X of a smoke detection chamber (smoke detection space) and an optical axis of the light emitting element 2 A light-receiving lens 4 and a light-receiving element 6, such as a photodiode, whose optical axes are aligned at a predetermined angle (hereinafter, referred to as a scattering angle) θ, and a fire signal is generated when an output signal of the light-receiving element 6 is larger than a predetermined threshold value. A comparator 8 for outputting a detection signal So is provided.

The principle that there is a correlation between the scattered light incident on the light receiving element 6 and the concentration of smoke in the smoke detection space, that is, the smoke 1
Since the intensity of the scattered light reaching the light receiving element 6 is small because 0 does not enter, the intensity of the scattered light reaching the light receiving element 6 increases when the smoke 10 invades due to a fire. By setting the threshold value of 8, the presence or absence of a fire is detected.

[0004]

However, such a conventional scattered light type smoke detector does not have a function of judging the type of smoke, but simply reduces the concentration of smoke entering the smoke detection space. Only the presence or absence of a fire is determined by comparing with a threshold level. However, in reality, smoke generated by combustion of gasoline and the like and smoke generated by combustion of wood and the like have various colors and particle diameters, so that the smoke concentration in the smoke detection space is equal. This also causes a phenomenon that the intensity of the scattered light detected by the light receiving element differs. From this,
Determining a fire based on a uniform threshold level regardless of the type of smoke determines that a non-fire is a fire,
There were problems such as delaying fire judgment.

[0005] Generally, such a fact is empirically found that, for example, a scattered light type smoke detector installed in a room filled with cigarette smoke malfunctions due to cigarette smoke even though it is not a fire. Are known. Further, there is a problem that the intensity of scattered light becomes small for black smoke generated by combustion of gasoline or the like, which delays a fire judgment. The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a fire alarm device that performs appropriate fire detection according to the type of smoke to be detected.

[0006]

In order to achieve the above object, the present invention irradiates light toward a smoke detection space, and scatters light from smoke existing in the smoke detection space to obtain different polarization directions. And the degree of polarization is calculated from these light intensities, the type of smoke is determined based on the degree of polarization, and a threshold set in accordance with the type of smoke determined thereby. By further comparing the values with these light intensities, the presence or absence of a fire was determined.

[0007]

According to the fire alarm device of the present invention having such a configuration, there is an inherent correlation between the degree of polarization obtained based on the scattered light having different degrees of polarization and the type of smoke, Can be determined. In addition, a threshold for determining the presence or absence of a fire is set according to the determined type of smoke, and the presence or absence of a fire is finally determined by comparing the threshold with the magnitude of the light intensity of the scattered light. Therefore, it is possible to improve the determination accuracy and prevent a false fire report, as compared with a conventional case where the presence or absence of a fire is determined using a uniform threshold value regardless of the type of smoke.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the invention is applied to a scattered light type fire detector will be described below with reference to the drawings. First, the structure will be described with reference to FIG. 1. Reference numeral 12 denotes a light-emitting element that irradiates directional light toward the center X of the smoke detection space, such as a halogen lamp that emits light having a plurality of wavelength components. Have been applied.

Reference numeral 14 denotes a first light receiving element such as a photodiode, which is provided so that its light receiving axis is at a predetermined scattering angle θ1 with respect to the optical axis direction of the light emitting element 12. 1
Reference numeral 6 denotes a first polarizing filter, which has a degree of polarization set so that the light receiving output of the light receiving element 14 that receives light scattered by smoke is maximized, and is provided in front of the light receiving surface of the first light receiving element 14. I have.

Reference numeral 18 denotes a second light receiving element such as a photodiode. The second light receiving element is provided such that its light receiving axis is at a predetermined scattering angle θ2 with respect to the optical axis direction of the light emitting element 12.
In this embodiment, the scattering angles θ1 and θ2 are both set to 30 °. 20 is the first polarizing filter 16 and 90
° a second polarization filter having a different polarization plane, the light reception output of the light receiving element 18 is set to be a minimum when scattered light is present, provided in front of the light receiving surface of the second light receiving element 18 Have been.

Reference numeral 22 denotes an arithmetic unit which receives the output signals S1 and S2 of the first and second light receiving elements 14 and 18 and calculates the following equation (1) based on the output levels of these signals. Thus, the degree of polarization C of the light passing through each of the polarization filters 16 and 20 is calculated. C = (S1−S2) / (S1 + S2) (1) Reference numeral 24 denotes a determination unit which compares the polarization degree C with a threshold value Tth for determining the type of smoke, and determines the polarization degree C as a threshold. Value T
Judgment of the type of smoke based on the relation of th. Further, a threshold value Tv for fire detection is set for each type of smoke, and the output signals S1 and S1 of the first and second light receiving elements 14 and 18 are set.
When it is detected that the output level of S2 has exceeded the threshold value Tv, it is determined that a fire has occurred, and a fire notification signal So is output.

That is, the threshold value Tth is set to determine the type of smoke, and the threshold value Tv is a unique threshold value corresponding to the type of smoke determined based on the threshold value Tth. This enables fire detection according to the type of smoke.
Reference numeral 26 denotes a reference data storage unit that stores in advance the data for the determination unit 24 to use as a reference for the fire occurrence condition. , The first and second light receiving elements 14 and 18
The data of a plurality of thresholds Tth and the data of the threshold Tv corresponding to the set angles of the scattering angles θ1 and θ2 are stored.

Then, although not shown, the types of combustibles and the data of the scattering angles θ1 and θ2 of the first and second light receiving elements 14 and 18 are initialized by an initialization switch or the like. Specific thresholds Tth and T
v is supplied to the determination unit 24, and the determination unit 24 determines the type of smoke and the presence or absence of a fire based on the threshold values Tth and Tv.

By providing the reference data storage unit 26 in this manner, it is possible to cope with various types of fires assumed in advance according to the situation in the monitored area. Next, the operation of the embodiment having such a configuration will be described together with the principle of fire detection. First, the principle of fire detection applied to this embodiment will be described. As a result of many experiments and researches, the inventor of the present application has found that the difference in the scattering angle θ and the degree of polarization C formed by the optical axis of the light emitting element and the light receiving element causes the smoke density in the smoke detection chamber of the scattered light smoke detector to be constant. Even so, it was confirmed that each type of smoke had unique characteristics.

FIG. 2 shows an example of the result of such an experiment. Here, the horizontal axis indicates the scattering angle θ, the vertical axis indicates the degree of polarization when the smoke detection space is filled with smoke of a predetermined concentration (1.0% / m), and the vertical axis indicates the logarithm. I have. It goes without saying that the degree of polarization does not change even if the smoke concentration changes. A characteristic curve a is a measurement result of smoke caused by kerosene (liquid fire), and a characteristic curve b is a measurement result of smoke caused by cotton wick (smoking fire).

As is apparent from FIG. 2, for each type of smoke,
It can be seen that there is an inherent correlation between the degree of polarization and the scattering angle θ. Therefore, the present inventor has determined the type of smoke from the value of the degree of polarization at a predetermined scattering angle. For example, the scattering angle θ1 = θ2 = 60 ° and the threshold value Tth is set to 0.
05 is set, and the type of smoke is determined by detecting the magnitude relationship between the polarization degree C and the threshold value Tth.

Next, the operation will be described. First, when the sensor is installed, the type of combustibles provided in the monitoring area and the scattering angle θ are initially set to specify the type of smoke that will be generated in the event of a fire. The light is emitted from the light emitting element 12, and the calculation unit 22 performs the calculation of the above equation (1) on the photoelectric conversion signals S1 and S2 output from the first light receiving element 14 and the second light receiving element 18 at every predetermined period τ. Then, the degree of polarization C is obtained.

The determining unit 24 compares the polarization degree C with the threshold value Tth in synchronization with the period τ. When the degree of polarization C is larger than the threshold value Tth, the first threshold value Tv1 for detecting smoke caused by a liquid fire is automatically read from the reference data storage unit 26. Is the threshold T
If the threshold value is smaller than th, the second threshold value Tv2 for detecting smoke caused by the smoke fire is automatically read out from the reference data storage unit 26, and the threshold value corresponding to the liquid fire or the smoke fire is obtained. The value Tv is set.

When the threshold value Tv1 is set, the photoelectric conversion outputs S of the first and second light receiving elements 14 and 18 are set.
If the output levels of S1 and S2 exceed the threshold value Tv1, it is determined that a liquid fire has occurred and a fire alarm signal So is output. If the output level does not exceed the threshold value Tv1, it is determined that a fire has not occurred. Thus, the monitoring operation is continued without outputting the fire alarm signal So. Also, when the threshold Tv2 is set,
The photoelectric conversion outputs S1, of the first and second light receiving elements 14, 18,
If the output level of S2 exceeds the threshold value Tv2, it is determined that the fire is a flammable fire, and a fire alarm signal So is output. If the output level does not exceed the threshold value Tv2, it is determined that there is no fire. The monitoring operation is continued without outputting the fire alarm signal So.

As described above, according to this embodiment, the type of smoke due to a fire is determined, and the presence or absence of a fire is determined for each type of smoke based on a specific threshold value Tv. Enable notification. In this embodiment, the arithmetic unit 22, the determination unit 24, and the reference data storage unit 26 have been described as being incorporated in the scattered light smoke detector. However, the light emitting element 12, the first and second light receiving elements 14, 18 and the optical filter 16,
Only the optical system of 20 is built in the scattered light smoke detector, and an arithmetic unit 22, a determination unit 24, and a reference data storage unit 26 for performing arithmetic and determination based on the photoelectric conversion outputs S1 and S2 include a so-called receiver or You may make it provide in a repeater. Further, the scattering angle θ can be determined as appropriate.

In this embodiment, the type of smoke is determined by calculating the degree of polarization C based on the above equation (1). As a simpler calculation method, the following equation (2) is used.
May be applied as an approximate value of the degree of polarization. C ′ = S1 / S2 (2) Next, another embodiment will be described with reference to FIG. In FIG. 3, the same or corresponding parts as those in FIG. 1 are indicated by the same reference numerals.

In FIG. 3, a light receiving element 28 in which the scattering angle of the light emitting element 12 with respect to the optical axis is set to θ is provided.
In front of the light receiving surface of the light receiving element 28, a polarizing filter 30 that rotates at a predetermined angular velocity about the optical axis of the light receiving element 28 is provided. A driving unit 32 such as a motor for rotating the polarization filter 30 at a constant speed rotates at a constant speed in synchronization with a synchronization signal from the timing control unit 34.

Accordingly, the degree of polarization changes as the rotation angle of the polarizing filter 30 changes, and the light receiving element 28 receives the scattered light according to the change in the degree of polarization. Further, the calculation unit 22 synchronizes with the synchronization signal from the timing control unit 34 and controls the light receiving element 1 when the polarization plane of the polarization filter 30 is 0 °.
4 and the photoelectric conversion output S2 of the light receiving element 14 when the polarization plane of the polarization filter 30 is 90 °, and the above formula (1) or (2) is applied every time the polarization filter 30 rotates 360 °. ) Is calculated to obtain the degree of polarization C.

Based on the degree of polarization C, the judgment unit 24 calculates
As in the first embodiment, the thresholds Tv1 and Tv2 are set, and the presence or absence of a fire is determined under each set condition. According to this embodiment, the number of polarizing filters can be reduced. In these examples, the difference in the degree of polarization was 90%.
°, the type of smoke was determined based on the degree of polarization, but is not particularly limited to 90 °, and the type of smoke may be determined based on the degree of polarization at another appropriate angle. Good.

[0025]

As described above, according to the present invention, light is radiated toward the smoke detection space, and the light intensity of light having different polarization directions is changed from the scattered light due to the smoke existing in the smoke detection space. At the same time, the degree of polarization is calculated from these light intensities, the type of smoke is determined based on the degree of polarization, and a threshold set according to the determined type of smoke and the light intensity are determined. Is determined by further comparing the number of smokes, based on the inherent correlation between the degree of polarization obtained based on the scattered light of different degrees of polarization and the type of smoke. Can be determined.

In addition, a threshold for determining the presence or absence of a fire is set in accordance with the determined type of smoke, and the threshold is compared with the magnitude of the light intensity of the scattered light to determine the presence or absence of the fire. Because the final judgment is, rather than judging the presence or absence of a fire with a uniform threshold regardless of the type of smoke as in the past,
The accuracy of the determination is improved, and a false alarm report can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the principle of smoke discrimination according to the present invention.

FIG. 3 is a configuration explanatory view showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a configuration explanatory view for explaining a configuration of a conventional scattered light type smoke detector.

[Explanation of symbols]

 12; light-emitting elements 14, 18, 28; light-receiving elements 16, 20, 30; polarizing filter 22; calculation section 24; determination section 26;

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G08B 17/02-17/12 G01N 21/00-21/01 G01N 21/17-21/61

Claims (2)

(57) [Claims] 1. A first polarizing filter having a light emitting means for irradiating light toward a smoke detection space, and a polarization plane for passing only light in a predetermined direction among light scattered by smoke existing in the smoke detection space. A second polarization filter having a polarization plane that allows only light in a direction different from the direction set by the first polarization filter out of scattered light due to smoke existing in the smoke detection space; and a first polarization filter. First light-receiving means for receiving light transmitted through the second light-receiving element; second light-receiving means for receiving light transmitted through the second polarizing filter; and a degree of polarization based on the output of the first light-receiving element and the second output. Calculating means for calculating the type of smoke from the magnitude relationship between the degree of polarization calculated by the calculating means and a preset threshold value for smoke detection; and
A fire alarm device comprising: a fire detector based on a fire detection threshold value corresponding to the determined type of smoke and a fire detector based on a magnitude relationship between outputs of the first and second light receiving devices. 2. A light emitting means for irradiating light toward a smoke detection space, a polarizing filter which transmits scattered light due to smoke existing in the smoke detection space and changes an angle of a polarization plane, and Light receiving means for receiving the transmitted light; a first output from the light receiving means when the polarization plane of the polarizing filter is at a first angle; and a light receiving means when the polarization plane of the polarizing filter is at a second angle. Calculating means for calculating the degree of polarization based on the second output from the means; determining the type of smoke from a magnitude relationship between the degree of polarization calculated by the calculating means and a preset threshold value for smoke detection And
A fire alarm device comprising: a fire detector based on a fire detection threshold value corresponding to the determined type of smoke and a fire detector based on a magnitude relationship between outputs of the first and second light receiving devices.