JP4995608B2 - smoke detector - Google Patents

Description

  The present invention relates to a smoke detector that optically detects contaminants such as smoke floating in the air.

Smoke detectors are used as a fire prevention and fire detection system, or in semiconductor manufacturing plants and food factories that require a certain level of environmental protection.
Conventionally, various smoke detectors have been proposed. As an example, an outline of a “particle detection method and apparatus” disclosed in Japanese Patent Laid-Open No. 63-9845 will be described below.
JP 63-9845 A

  That is, the fine particle detection method and apparatus guides a gas to be measured to a detection unit of an optical system, and receives scattered light from fine particles suspended in the gas by a pair of projectors and light receivers installed in the detection unit. In the fine particle detection device for detecting the presence and concentration of fine particles, a first supply system for supplying a gas to be measured to the detection unit, and a second supply system for supplying clean air to the detection unit And a switching mechanism for alternately switching between the first supply system and the second supply system.

According to this configuration, by performing the supply of the gas to be measured and the supply of clean air alternately, the light receiver output when the fine particles are present in the gas to be measured, and when the fine particles are not present Both of the light receiver outputs can be detected immediately, and by obtaining the difference between the two detection values, only the detection values due to the scattered light of the fine particles, excluding fluctuations, can be obtained.

However, according to the study of the present inventor, a new problem has been revealed regarding smoke detection.
That is, in the smoke detector, the gas of the first supply system and the gas of the second supply system may be mixed. In this case, the difference between the receiver output when the microparticles are present and the receiver output when the microparticles are not present is small, and only the detection values due to the scattered light of the microparticles excluding fluctuations are detected. Is difficult to obtain.

Moreover, an on-off valve for switching between the first supply system and the second supply system, a control circuit for switching control, and the like are required, and the entire apparatus is complicated.
Furthermore, when the smoke detection device is used for a long period of time, the wall surface inside the device may become dirty, and the attached fine dust may float near the smoke detection unit. When this phenomenon occurs, the same scattered light as in smoke detection is generated, which may be mistaken for a fire if it is severe.

  The present invention has been made in view of the above problems, and an object thereof is to provide a smoke detector that can accurately detect smoke and has a simple structure.

According to the present invention, an optical case having a dark box inside and air sucked from a monitoring space are filtered through a first filter , and flowed into the optical case as a gas to be detected, and a smoke detecting unit And a path for filtering the air sucked from the monitoring space through the second filter and circulating it as a clean gas. A second air passage surrounding the periphery in an annular manner, a light emitting element disposed in the optical case, and a light receiving element for receiving scattered light generated by smoke particles existing in the smoke detecting section by light emitted from the light emitting element An optical trap that is disposed opposite to the light emitting element to attenuate stray light, a light receiving amplification circuit that amplifies the output signal of the light receiving element, and a detection level obtained by A / D converting the amplified output signal is equal to or higher than a threshold value Fire A determination unit, characterized in that the provided.

The fire determination unit includes a control unit that adjusts a gas supply amount of the first air passage or the second air passage when a smoke concentration increase or contamination of the smoke detection unit is detected. And

Since the present invention is configured as described above, the following various effects can be obtained.
That is, the light emitted from the light emitting element is condensed in the vicinity of the optical trap by the condenser lens, and the smoke to be sensed is transmitted through the smoke detecting section that flows in along with the air. In the smoke detector, the sampling air obtained by the first filter and the clean air obtained by re-filtering the sampling air by the second filter so as to surround the outer periphery, or the clean air obtained by another system Allow air to pass through.

When detecting fire, the laser beam is transmitted to the smoke detector, but clean air acts as an air curtain for sampling air, so that the diffusion of sampling air containing smoke particles is prevented, Mixing of dust other than smoke particles can be prevented. In the event of a fire, the laser light strikes and scatters the smoke particles, and the scattered light is received by the light receiving element to detect the fire, but the suspended air other than the smoke particles does not enter the sampling air in the optical case. Therefore, the fire detection can be performed accurately and with high sensitivity, and the reliability of the smoke detector is improved.
In addition, there is no need to switch the light-receiving element and the on-off valve, and the operation of the configuration can be greatly simplified. Can be achieved.

As a result of repeated research and experiments in order to solve the above problems, the present inventor has found that the following may be performed.
In order to prevent the sampling air from diffusing and mixing in undesired floating substances, clean air is introduced so as to surround the outside of the sampling air flowing into the smoke detector. As a result, clean air acts on the sampling air like an air curtain. In the event of a fire, the sampling air contains smoke particles, but since the smoke particles do not diffuse, the fire occurrence can be detected accurately and with high sensitivity.

Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS.
The overall configuration of the smoke detector 1 will be described with reference to FIG. 1. In an optical case 2 configured in a substantially cylindrical shape, for example, a light emitting element 3 that emits infrared light, and a stray light unit at a position facing the light emitting element 2. 4, a condensing lens 5 for condensing the light L emitted between them on the stray light portion 4, a smoke detecting portion 6 for allowing air to be detected to pass through, a light receiving element 7 for receiving scattered light, etc. It is provided. Apertures 8 are provided at appropriate intervals so as to limit light shielding and diffracted light by irradiation light.

The output signal S of the light receiving element 7 is supplied to the fire determination unit 11. The fire discriminating unit 11 includes an amplification circuit that amplifies the output signal S of the light receiving element 7, an A / D converter that converts the detection signal to a detection level, a comparison circuit that discriminates a fire when the detection level exceeds a preset threshold value, and the like. The integrated control is performed by the CPU.
Although not shown in FIG. 1, a power supply unit for supplying power to the light emitting element 3, the light receiving element 7, and the fan 31 shown in FIG. 4 is also provided.

Next, the smoke detector 6 in the present embodiment will be described.
The smoke detector 6 not only circulates air (sampling air) a to be detected, that is, a gas containing smoke at the time of a fire, but also circulates the sampling air a in the center and surrounds the circumference in an annular shape. In this way, clean air is circulated.
This configuration will be described in more detail. As shown in FIG. 2, the air A sucked from the monitoring space is supplied to the first filter 21, and a part of the roughly filtered air is supplied to the smoke detector 6 as sampling air a. Circulate. Further, a part of the air filtered by the first filter 21 is supplied to the second filter 22 and subjected to double filtration to obtain a relatively clean air b with respect to the sampling air a. Then, clean air b is circulated around the sampling air a in an annular shape. Note that a HEPA filter or the like may be applied as the first and second filters 21 and 22.

  The configuration of the first and second filters 21 and 22 is a configuration in which a second filter 22 formed in an annular shape is stacked on a first filter 21 formed in a disk shape as shown in FIG. Good. An annular gap G is formed between the outer surface of the first filter 21 and the inner surface of the second filter 22.

  According to this configuration, an annular gap g as shown in FIG. 2 is generated between the sampling air a and the double filtered clean air b in the smoke detector 6. The sampling air a is roughly filtered, but the clean air b is double-filtered, so that there is a difference between the flow rates of both. That is, in this embodiment, the flow rate of clean air b is slower than the flow rate of sampling air a. Therefore, the clean air b does not disturb the flow of the sampling air a.

Both the sampling air a and the clean air b are sucked out of the optical case 2 from the suction unit 23 after passing through the smoke detector 6.
Here, the circulation of the air A in the fire monitoring space will be described. As shown in FIG. 4, the air A is sucked by the fan 31 and blown to the exhaust side through the pipe 32. As indicated by the arrow A1, the air is sucked to the first filter 21 side. Then, it is filtered by the first filter 21 to obtain the sampling air a, and at the same time, the clean air b is obtained from the second filter 22 and supplied to the smoke detector 6 as described above.

  When smoke detection is performed, as indicated by an arrow L in FIGS. 1 to 3, light emitted from the light emitting element 3, for example, laser light L is allowed to pass. In the steady state, no smoke particles are contained in the sampling air a, so the laser light L is not scattered in the smoke detector 6. Therefore, the output signal S is not obtained from the light receiving element 7, and the fire determination unit 11 does not perform fire notification.

On the other hand, when a fire occurs in the fire monitoring area, the sampling air a contains smoke particles. In this case, the laser light L collides with the smoke particles and is scattered, and a part of the scattered light is received by the light receiving element 7. Accordingly, an output signal S is obtained from the light receiving element 7, and the fire determination unit 11 operates to notify the occurrence of a fire.
When the fire determination unit 11 detects an increase in the smoke concentration in the optical case 2, the detection level quickly reaches the threshold value or more when the supply amount of the sampling air a is increased. On the other hand, when the fire determination unit 11 detects dirt in the optical case 2, the sampling air a is stopped and the amount of clean air b supplied is increased to blow away dust or the like remaining in the optical case 2. Can do. These are controlled by the fire determination unit 11.

The first embodiment has the following various effects.
Since the clean air b acts on the sampling air a like an air curtain, the sampling air a does not diffuse and fire detection is performed accurately.
In addition, dirt in the optical case 2 can be reduced.
Furthermore, even if dust or the like adhering to the wall surface in the optical case 2 floats in the air, it is not mixed into the sampling air a, and the S / N ratio for fire detection can be improved.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the present embodiment, clean air b is obtained in a separate system from the sampling air a.
That is, a part A1 of the air A in the monitoring area exhausted to the secondary side of the fan 31 and the other outside air C are sucked and mixed by the pump or the fan 32 and supplied to the second filter 22. Configured. Further, the clean air b may be supplied from only one of the part A1 or the outside air C of the air A in the monitoring area.
The clean air b obtained from the second filter 22 is discharged to the outer periphery of the sampling air a in the optical case 2 as described above.

Even with this configuration, it is possible to reliably detect the occurrence of a fire in the same manner as described above, and to obtain an effect of preventing dirt in the optical case 2 and the like.
In addition, the flow rate of clean air b can be freely changed with respect to the flow rate of sampling air a. For example, it can be used for multiple purposes such as temporarily increasing the flow rate to set the cleaning mode and blowing away dust accumulated in the optical case 2. Can also be planned. Also in this case, since the sampling air a is prevented from diffusing, no malfunction occurs in smoke detection.

  As mentioned above, although the Example of this invention was described, this invention is not limited to each said Example. For example, the flow shape of the sampling air a and the clean air b is not limited to a cylinder or an annular shape, and may be an ellipse or a rectangle. Then, since the light scattering region increases by making the long direction follow the laser light L, the amount of scattered light received by the light receiving element 7 increases, and fire detection can be performed more quickly and accurately.

It is a block diagram of the smoke detector which shows 1st Example of this invention. It is sectional drawing which shows the structure of a filter. It is a perspective view which shows the structure of a filter. It is a systematic diagram which shows the flow of air. It is a systematic diagram which shows 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Smoke detector 2 Optical case 3 Light emitting element 4 Stray light part 5 Condensing lens 6 Smoke detection part 7 Light receiving element 11 Fire judgment part 21 First filter 22 Second filter 23 Suction part 31 Fan 32 Pump or fan a Sampling air b Clean air L Light

Claims (2)

An optical case with a dark box inside,
A first air passage that filters the air sucked from the monitoring space through the first filter and flows into the optical case as a gas to be detected to form a smoke detector ;
A second air passage for filtering the air sucked from the monitoring space through a second filter and circulating it as a clean gas, and surrounding the first air passage in an annular shape When,
A light emitting device disposed in the optical case;
A light receiving element that receives scattered light generated by smoke particles present in the smoke detector, and the light emitted from the light emitting element;
An optical trap disposed to face the light emitting element to attenuate stray light;
A light receiving amplification circuit for amplifying the output signal of the light receiving element;
A fire determination unit for performing a fire determination when a detection level obtained by A / D converting the amplified output signal is equal to or higher than a threshold;
Smoke detector characterized by providing.   The fire determination unit includes a control unit that adjusts a gas supply amount of the first air passage or the second air passage when a smoke concentration increase or contamination of the smoke detection unit is detected. The smoke detector according to claim 1.

Images