JPS6296849A - Improved scattered light type smoke detector - Google Patents

Abstract

PURPOSE:To make it possible to ensure the issuance of warning at a specified smoke concentration and to make it possible to detect time deterioration of a light emitting element, by setting the lightness of the inner surface of a black box, which detects the intrusion of smoke and issues warning, in a specified range. CONSTITUTION:A fault signal detecting circuit 8 is provided. A black box 5 has a labyrinth structure, into which smoke can intrude. In the black box 5, a light emitting element 3 and a light receiving element 4, into which the beam from the light emitting element does not directly enter, are provided. When smoke invades into the black box 5, scattering of light due to smoke particulates is detected by the light receiving element 4, and the presence of the smoke is detected. Then warning and the like are generated. The inner surface of the black box 5 of this scattered light type smoke detector is set in the range of Munsell values 2-5. The issuance of warning is ensured at the smoke concentration of about 10%/m in this smoke detector having such a black box 5. Time deterioration of the light emitting element 3, which cannot be detected in the conventional detector, can also be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a novel scattered light type smoke detector. More specifically, a smoke detector that is a scattered light type smoke detector and can detect a base level noise light (Bank-Gouland) in the absence of smoke to check for malfunction of the smoke detector. Regarding.

<Prior art and its problems> Scattered light smoke detectors are equipped with a light-emitting element and a light-receiving element in a dark box that allows smoke to enter so that the beam from the light-emitting element does not directly enter the light-receiving element. This is a device that uses a light receiving element to sense the scattering of light caused by smoke particles when smoke enters, detects the presence of smoke, and generates a fire alarm. Such a device is set to be able to detect the base level noise light (background) when no smoke is present, and when it is not detected, a fault signal is detected.In general, the lower the noise light is, the better. °The inner surface of the dark box that allows entry (usually has a labyrinth structure) is painted matte black.

Therefore, the bank round is extremely low.

Even with such a low background, it is possible to sufficiently detect damage to the light emitting element, disconnection, etc., but phenomena such as weakening of the light emitting element over time are difficult to detect with such a low background.

In this case, if you increase the brightness of the inside of the dark box, in other words,
If you brighten the color tone on the inside of the dark box, the background (base level noise light) will increase and it will be easier to detect functional deterioration of parts, but the noise value will increase.
This time, the difference with the signal will not decrease, which will lead to a decrease in the accuracy of the alarm.

<Means for solving the problem> The inventor of the present invention clarified the relationship between the increase in smoke concentration and the change in the output of the photodetector when the brightness of the inside wall of the dark box was increased, and found that, contrary to expectations, the brightness of the inside wall of the dark box , Munsell lightness is 2~
The present invention was completed after confirming that increasing the value within the range of 5 does not affect actual smoke detection. Until now, no one had thought of intentionally increasing the brightness of the inner wall of a dark box.

<Structure of the Invention> The present invention provides a dark box having a labyrinth structure that has a failure detection circuit and allows smoke to enter, a light emitting element, and a light emitting element provided in the dark box so that a beam from the light emitting element does not directly enter the dark box. A scattered light smoke detector consists of a light-sensing element that detects the scattering of light caused by smoke particles when smoke enters a dark box, detects the presence of smoke, and generates an alarm. To provide a scattered light type smoke detector characterized in that the inner surface of a dark box is set to have a Munsell brightness in the range of 2 to 5.

<Specific description of the invention> The present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of an example of a light scattering smoke detector with a failure detection circuit according to the above-described principle. As shown in this figure, the detector includes a pulse generating circuit 1, a light emitting element 3 installed in a dark box 5 having a labyrinth structure, and a light emitting element 3 installed in the dark box so as not to directly receive the beam from the light emitting element 3. A light-receiving element 4, an amplifier 6 that amplifies the output of the light-receiving element, a fire signal generation circuit 7 that generates a signal output when an output of a predetermined level or higher is applied to the amplifier 6, and an output of a predetermined level or lower applied to the amplifier 6. Fault signal generating circuits 8 which sometimes produce signal outputs, A which is output by the logical product of the outputs of these signal generating circuits 7 and 8 and the outputs of the pulse generating circuit 1, respectively.
It consists of ND gates 9 and 10. Note that the pulse generation circuit is not essential in terms of the technical idea of the present invention. Alternatively, the output of the amplifier 6 may be sent directly to the receiver via a transmission circuit, and the receiver may determine whether it is smoke or a malfunction.

Normally, this type of smoke detector has a smoke density of 6 to 6 attenuation rate.
It is set to issue an alarm at a concentration of 15%/m (a concentration that attenuates the light beam by 10 points per meter of optical path), and the S/N ratio is set to be around 4 or more.

Generally, when the Munsell brightness of the inner wall of the dark box of a scattered light smoke detector is increased, the output of the light receiving element increases parabolically. Figure 2 shows the change in the output of the light-receiving element when the Munsell brightness of the inner wall of the dark box is increased in the absence of smoke in a smoke detector (Model 2KC manufactured by Tutan Co., Ltd.). This means a sharp rise in the noise (background) value.

However, the presence of smoke is expected to cancel out the bank ground.

When both background and smoke are present in the dark box,
Although there is no method for distinguishing and detecting these, the inventors quantitatively studied the relationship between the two as much as possible. Regarding the smoke detectors that obtained the data in Figure 2, the Munsell brightness was 1.5, 2.2,
3.0, 3.6, and 4.5 dark boxes are prepared, and the light receiving element output when each dark box is attached, and the light receiving element when smoke with a concentration of 10 chi/m is present in each case. The output was measured.

Table 1 0 0 2,. 40 0 2.40 1.5 0.20 Z60 0.20 2.4012
0.60 3,00 0.59 2,393.0 1
．． 60 3.87 1,57 2,373.6 3.0
O5,302,942,365724,411 4,0'4. Now 06 # □ 23ki 5.0 60.00 61.20 58.81 1.2
0 In the above table, brightness 0 corresponds to the case where the sensor without a dark box is placed in a truly dark room, that is, when there is no dark background at all. Noise (background) value (C
) is approximately 0.98 to the light receiving element output value (A) in the absence of smoke.
It is the value multiplied by The reason is as follows. It is not possible to directly distinguish how much of the output of the photodetector when smoke is present is due to the scattering effect of the smoke itself, and how much is due to the background (noise) attenuated by the smoke. However, it is calculated that the background attenuation effect of smoke at a smoke density of 10%/m is about 2%. The basis for this is as follows. The dark box of the smoke detector used has a diameter of about 5 cm, and the light beam from the light emitting element is reflected three to four times before entering the light receiving element, so the optical path length is about 20 cm. Applying this to Lambert's law to find the attenuation effect, x 100 = 2.085 cm/20 cm #2
%/20cm.

(Note: 0.11: smoke concentration at path distance α, α: optical path length (
20cm), smoke density at Ou: 1m) In other words, the effect of background attenuation due to smoke is smaller than expected up to a lightness of around 5 and a smoke density of around 10%/m, and in cases where the SZN ratio is further increased. turns out to be largely negligible.

FIG. 3 shows the results of measuring the output of the light-receiving element at various densities using dark boxes with different brightnesses. Straight line 0 corresponds to brightness O, straight line 1.5 corresponds to brightness 1.5 (2KC type smoke detector currently used by Kanto Toyama's company), straight line 2.
2 is the brightness of 2.2, straight line 3 is the brightness of 3, straight line 3
．． 6 is a case where the brightness is 3.6, straight line 4 is a case where the brightness is 4, and straight line 5 is a case where the brightness is 5.

As the brightness increases, the slope of the straight lines gradually decreases, and the distance between the straight lines becomes a dog in terms of geometric progression, but until the brightness is around 5, it maintains a substantially parallel relationship with the case of brightness 1 and 5,
It has been found that by adjusting the alarm output, it is possible to increase the brightness without changing the system of the smoke detector currently in use.

<Example> Light emitting element (light emitting diode OL D-2 manufactured by Oki Electric Co., Ltd.)
203), when installing a dark box with a brightness of z2 in a smoke detector using a photodiode (photodiode NJL612B manufactured by New Japan Radio Co., Ltd.), a dark box with a brightness of 1.5 was conventionally used), 10%/m The smoke density has been changed to output 92.4 mv as usual.

The smoke detector adjusted in this manner reliably issued an alarm at a smoke density of 10%/m, and was also able to detect deterioration over time of the light emitting element, which could not be detected conventionally.

<Effects of the Invention> Although the present invention is a simple technology, it must be praised for its achievements in expanding the conventional fault detection capability by changing the way of thinking.

[Brief explanation of drawings]

FIG. 1 is a simplified circuit diagram showing the concept of an example of a scattered light type smoke detector with a failure detection circuit. FIG. 2 is a graph showing the relationship between the change in brightness of the inner wall of the dark box and the output of the light receiving element of one detector. FIG. 3 shows the relationship between the change in brightness of the inner wall of the dark box, the smoke density, the output of the light receiving element, and the brightness of the inner wall of the dark box for the same detector. In these drawings, 3: light emitting element, 4: light receiving element, 5: dark box.

Claims (1)

[Claims] It consists of a dark box with a labyrinth structure that has a fault detection circuit, a light emitting element, and a light receiving element installed in the dark box so that the beam from the light emitting element does not directly enter the dark box. This is a scattered light type smoke detector that detects the presence of smoke by sensing the scattering of light caused by fine particles using a light receiving element, and generates an alarm etc. A scattered light type smoke detector characterized by being set within a range.