JPH0476624B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a smoke sensor, and particularly to a smoke sensor that can accurately detect the occurrence of an initial fire in a clean room, distinguishing it from operational dust.

[Conventional technology] A clean room in a semiconductor factory is a room in which the air is kept at a high level of cleanliness at a constant temperature and humidity.
There are many manufacturing devices that use large amounts of electric power and combustion gas. For this reason, the Fire Service Act requires that clean rooms be equipped with various types of fire prevention equipment, and for example, photoelectric detectors, ionization detectors, and the like are used as smoke detectors.

FIG. 3 is a diagram showing an example of the configuration of a conventional fire detection device used in a clean room.

First, the configuration of this fire detection device will be explained. In the figure, a photoelectric smoke detector 23 is provided on the ceiling 16, and this smoke detector 23 is connected to an alarm 25. To explain this smoke detector 23, a main body 18 is provided on a common base 17 that houses an output terminal for outputting a signal to the outside. A dark box 19 having a plurality of openings 19a is provided on the main body 18, and an indicator light 20 is provided around the dark box 19. Inside the dark box 19, a light emitting element 21 and a light receiving element 2 are placed on the main body 18.
2 is provided.

Next, the operation of this fire detection device will be explained. Air containing suspended particles such as smoke particles and dust generated by a fire in the clean room flows through the opening 19a.
Enter dark box 19 from here. At this time, the light emitting element 21
The light from the fire is scattered by the floating particles 24, and this scattered light is received by the light receiving element 22 and converted into an electrical signal, thereby detecting the occurrence of a fire. The light receiving element 22 output is the indicator light 18 and the common base 17
The signal is sent to the alarm device 25 through the output terminal of the device, and the fact that a fire has been detected is indicated by the lighting of the indicator light 18, and the alarm device 25 issues an alarm to indicate that a fire has occurred. Let me know.

[Problems to be solved by the invention] By the way, a large amount of highly clean air is constantly circulated and supplied to a clean room, so the smoke generated from an initial fire that occurs inside the clean room is diluted. However, because conventional smoke detectors have low detection sensitivity for smoke particles, it is difficult to accurately detect the initial occurrence of a fire, and the problem is that an alarm is only issued after the fire has become large. It was hot.

In addition, the cleanliness of the air in a clean room may change over time due to operational dust generated from manufacturing equipment or workers.
Although smoke detectors are known to vary spatially, there is a problem in that conventional smoke detectors cannot distinguish between the initial occurrence of a fire and operational dust, and often issue false alarms. .

This invention was made to solve the above-mentioned problems, and it has a simple structure that has high detection sensitivity for floating particles, and can accurately detect the occurrence of an initial fire by distinguishing it from operational dust. The purpose is to obtain a sensor.

[Means for Solving the Problems] The smoke sensor according to the present invention allows air containing suspended particles to pass through a container having an inlet and an outlet using an air moving means, irradiates the air in the container with a light source, and receives light. The element receives scattered light from suspended particles and converts it into an electrical signal, the particle size threshold setting means sets a predetermined particle size threshold regarding the particle size of the suspended particles, and the comparing means determines the light receiving element output. is compared with a predetermined particle size threshold, and a pulse is generated when the light receiving element output is larger than the predetermined particle size threshold, thereby detecting suspended particles (hereinafter referred to as large particles) with a particle size larger than the predetermined particle size threshold. Detecting large-diameter suspended particles), setting a predetermined period by a period setting means, counting the number of pulses at each predetermined period by a pulse counting means, and thereby detecting the particle concentration of large-diameter suspended particles, The particle concentration threshold setting means sets a predetermined first particle concentration threshold and a predetermined second particle concentration threshold larger than the first particle concentration threshold regarding the particle concentration of large-diameter suspended particles, and the number of times setting means sets a predetermined number of times. , the control means compares the particle concentration of the large-diameter suspended particles with predetermined first and second particle concentration thresholds, and when the particle concentration matches the predetermined first particle concentration threshold, the alarm issuing means operates the first particle concentration threshold. The alarm issuing means is controlled to issue a second alarm when the particle concentration matches a predetermined second particle concentration threshold a predetermined number of times. This is what I did.

[Function] In this invention, the floating particle detection section has JIS
Since it uses a light scattering particle counter as specified in B9921, the detection sensitivity for airborne particles is increased.

Further, the comparison means compares the light receiving element output with a predetermined particle size threshold, and generates a pulse when the light receiving element output is larger than the predetermined particle size threshold. Detects suspended particles of particle size (large-diameter suspended particles). Detecting the particle concentration of large-diameter suspended particles by counting the number of pulses from the comparison means at predetermined intervals using the pulse counting means, and comparing this particle concentration with predetermined first and second particle concentration thresholds. When this particle concentration matches a predetermined first particle concentration threshold, the alarm issuing means issues a first alarm, and when this particle concentration matches a predetermined second particle concentration threshold a predetermined number of times. Since the second alarm is issued by the alarm issuing means at the same time, it is possible to accurately detect the occurrence of an initial fire, distinguishing it from operational dust generation.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

It is generally known that the concentration of suspended particles in an initial fire increases at an accelerating rate before the fire develops, whereas the concentration of suspended particles in operational dust generation increases suddenly. , after which it rapidly decreases due to the functioning of the clean room. This invention focuses on the characteristic differences between the two, and uses a light scattering particle counter as specified in JIS B9921 to increase the detection sensitivity for suspended particles, and to distinguish it from operational dust and detect the occurrence of initial fires. can be detected accurately.

Furthermore, it is known that there is a similar relationship between the particle concentration distribution characteristics of suspended particles in relation to the particle size in a clean room where the air is highly clean and the particle concentration distribution characteristics of suspended particles in relation to the particle size in a fire state. ing. Therefore, in order to detect the occurrence of an initial fire, it is sufficient to be able to detect large smoke particles with a particle size of about 1 to 2 μm without detecting very small suspended particles, and this invention also takes advantage of this point. Compared to the light scattering type particle counter, the sensor structure is simplified and the lamp can be lit at low brightness, resulting in a longer life.

FIG. 1 is a diagram showing the configuration of a smoke sensor that is an embodiment of the present invention.

First, the configuration of this smoke sensor will be explained. In the figure, a detection cell 1 has an inlet 1a and an outlet 1
b, and the detection cell 1 is provided with a suction pump 2. The suction pump 2 sucks air containing suspended particles such as smoke particles and dust into the detection cell 1 from an inlet 1a, and discharges the air from an outlet 1b. 3 indicates floating particles in the air within the detection cell 1. Further, a lamp 4 and a lens 6a are provided on one side of the detection cell 1, and a light receiving element 5 and a lens 6b are provided on the other side. Light from the lamp 4 is irradiated onto the air within the detection cell 1 through the lens 6a. The light receiving element 5 receives scattered light from the floating particles 3 through a lens 6b, and converts this scattered light into an electrical signal. The light receiving element 5 is connected to a comparator 9 via an amplifier 7, and a particle size threshold setting device 8 made of a DC power source is connected between the comparator 9 and ground. The amplifier 7 amplifies the output of the light receiving element 5. The particle size threshold setting device 8 is
A predetermined particle size threshold for the particle size of suspended particles is set. The comparator 9 compares the 7 output with a predetermined particle size threshold, and generates a pulse when the light receiving element 7 output is larger than the predetermined particle size threshold. Detects suspended particles (large-diameter suspended particles). Comparator 9 is connected to pulse counter 10 , and counting period setting timer 11 is connected to pulse counter 10 . The counting period setting timer 11 has a predetermined counting period T.
Set. The pulse counter 10 counts the number of pulses from the comparator 9 every predetermined counting period T, thereby detecting the particle concentration of large-diameter suspended particles. The pulse counter 10 is connected to an alarm 15 via a control device 12. The particle concentration threshold setter 13 and the number of times setter 14 are connected to the control device 12 . The particle concentration threshold setting device 13 sets a two-stage first particle concentration threshold and a second particle concentration threshold regarding the particle concentration of large-diameter suspended particles. The number of times setter 14 sets a predetermined number of times.
The alarm device 15 issues an alarm. The control device 12 is
The particle concentration of large-diameter suspended particles, which is the output of the pulse counter 10, is compared with the first and second particle concentration thresholds, and when the particle concentration of the large-diameter suspended particles matches the first particle concentration threshold, the alarm 15 is activated. The alarm device 15 is configured to issue a second alarm when the particle concentration of large-diameter suspended particles matches the second particle concentration threshold a predetermined number of times. control.

Next, the operation of this smoke sensor will be explained.
Air containing suspended particles such as smoke particles and dust in the clean room enters the detection cell 1 as a thin air stream from the inlet 1a by the suction pump 2, and is discharged from the outlet 1b. At this time, the light from the lamp 4 is irradiated onto this thin airflow through the lens 6a. Floating particles 3 in the airflow scatter the light from the lamp 4, and this scattered light is received by the light receiving element 5. The light receiving element 5 converts the scattered light into an electrical signal, and this electrical signal is provided to the amplifier 7. The amplifier 7 amplifies the output of the light receiving element 5, and the output of the amplifier 7 is given to the comparator 9. The comparator 9 compares the output of the amplifier 7 with a particle size threshold set by the particle size threshold setter 8, for example, a particle size of 1.5 μm, and when the output of the amplifier 7 is larger than this particle size threshold, A pulse is output, thereby detecting large-diameter suspended particles among the suspended particles. The comparator 9 output is given to a pulse counter 10. The pulse counter 10 outputs a comparator 9 every counting period T set by the counting period setting timer 11.
The number of pulses is counted, and the particle concentration (pieces/unit volume) of large-diameter suspended particles is thereby detected.
The pulse counter 10 output is given to the control device 12. The control device 12 compares the particle concentration of large-diameter suspended particles, which is the output of the pulse counter 10, with first and second particle concentration thresholds set by the particle concentration threshold setting device 13, and determines whether this particle concentration is the first particle concentration. 1 When the particle concentration reaches the threshold value, the controller 12 output causes the alarm 15 to issue the first alarm (for example, "There is a lot of dust, so please check"), and this particle concentration becomes the second particle concentration. When the threshold value matches the predetermined number of times set by the number setter 14, for example three times, the alarm 15 issues a second alarm (for example, "There is a fire. Please evacuate") by the output of the control device 12. .

Next, an example of the operation of issuing the first alarm and the second alarm will be explained using FIG.

In FIG. 2, the horizontal axis shows time, and the vertical axis shows the particle concentration of diameter-shaped suspended particles in the air in the clean room detected every counting period T of, for example, 6 seconds. From time 0 to _t6 , the particle concentration changes from _C1 to _C6 , the particle concentration suddenly increases, and then rapidly decreases, and this type of change is due to operational dust generation. In this case, the particle concentration at points M ₂ and M ₃ coincides with the first particle concentration threshold C _TH1 of, for example, 1 × 10 ⁴ particles/foot ³ , and at each time point corresponding to these points, The first alarm is issued. Time t ₈ ~ t ₁₃
In this case, the particle concentration changes from _C9 to _C13 , and the particle concentration increases at an accelerating rate, and this type of change is due to the occurrence of the initial fire. In this case,
The particle concentration matches the first particle concentration threshold C _TH1 at M ₁₀ points, M ₁₁ points, M ₁₂ points, and M ₁₃ points, and the first alarm is issued at each point corresponding to each of these points, _N11
For example, the particle concentration at the point, _N12 point, and _N13 point is 4×
10 The second particle concentration threshold C _TH2 of ⁴ particles/foot ³ is met, and the second alarm is activated at the point corresponding to the N ₁₃ point where the particle concentration matches the second particle concentration threshold C _TH2 for the third time. Reported.

In this way, by using a light scattering particle counter as specified in JIS B9921 in the suspended particle detection section, the detection sensitivity for suspended particles can be increased compared to conventional smoke detectors. In addition, since large-diameter suspended particles among suspended particles are detected, it is possible to extend the life of the lamp 4 by lighting it at a lower brightness than in the case of the light scattering type particle counter described above. For example, an incandescent lamp with a lighting life of about 10,000 hours can be used. Furthermore, by detecting large-diameter suspended particles, the structure of the smoke sensor can be simplified, and the smoke sensor can be manufactured at low cost. In addition, the particle concentration of large-diameter suspended particles is compared with the first and second particle concentration thresholds, and when this particle concentration matches the first particle concentration threshold, a first alarm is issued, and the particle concentration Since the second alarm is issued when the particle concentration matches the second particle concentration threshold three times, it is possible to accurately detect the occurrence of an initial fire, distinguishing it from operational dust generation.

In the above embodiment, the counting period T is set to 6 seconds, the first particle concentration threshold is set to 1×10 ⁴ particles/ft ³ , and the second particle concentration threshold is set to 4×10 ⁴ particles/ft ^{3 .} Although shown for the case, the invention is not limited thereto, and the characteristics of the clean room (e.g. ventilation circuit, particle concentration during cleaning, etc.)
The counting period T etc. may be appropriately selected according to the above. In addition, in the above embodiment, the second alarm is issued when the particle concentration of large-diameter suspended particles matches the second particle concentration threshold three times.
It is also possible to further reduce the probability of false fire alarms by issuing a second alarm when the particle concentration threshold is met a number of times greater than three times.

In addition, although the above embodiment shows a case in which the smoke sensor is used for fire prevention in a clean room, the present invention can also be used for fire prevention in other equipment, and can also be used for simple dust detection such as dusty air or exhaust gas. It can also be used for measuring quantities.

[Effects of the Invention] As described above, according to the present invention, a light scattering particle counter as specified in JIS B9921 is used in the suspended particle detection unit to detect large-diameter suspended particles among suspended particles. and when the particle concentration of large-diameter suspended particles matches a predetermined first particle concentration threshold, the first alarm is issued, and when this particle concentration matches the predetermined second particle concentration threshold a predetermined number of times. Since the second alarm is issued, it is possible to obtain an inexpensive smoke sensor with a simple structure that has high detection sensitivity for suspended particles and can accurately detect the occurrence of an initial fire by distinguishing it from operational dust. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a smoke sensor that is an embodiment of the present invention. FIG. 2 is a diagram for explaining the operation of issuing a first alarm and a second alarm in the smoke sensor of FIG. 1. FIG. 3 is a diagram showing an example of the configuration of a conventional fire detection device. In the figure, 1 is a detection cell, 1a is an entrance, 1b
is an outlet, 2 is a suction pump, 3 is floating particles, 4 is a lamp, 5 is a light receiving element, 6a, 6b are lenses, 7 is an amplifier, 8 is a particle size threshold setter, 9 is a comparator, 10 is a pulse counter , 11 is a counting period setting timer, 12 is a control device, 13 is a particle concentration threshold setting device, 14 is a frequency setting device, and 15 is an alarm device. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A container having an inlet and an outlet, an air moving means for passing air containing suspended particles in the container, a light source for irradiating the air in the container, and scattering from the suspended particles. a light receiving element that receives light and converts it into an electrical signal; a particle size threshold setting means that sets a predetermined particle size threshold regarding the particle size of the suspended particles; A pulse is generated when the light-receiving element output is larger than the predetermined particle size threshold when compared with a threshold value, and thereby the suspended particles (hereinafter referred to as large diameter particles) whose particle size is larger than the predetermined particle size threshold are generated. a period setting means for setting a predetermined period; and a period setting means for counting the number of pulses for each predetermined period;
pulse counting means for detecting the particle concentration of the large-diameter suspended particles by this; and a particle concentration for setting a predetermined first particle concentration threshold and a predetermined second particle concentration threshold larger than the predetermined first particle concentration threshold with respect to the particle concentration. threshold setting means; number setting means for setting a predetermined number of times; alarm issuing means for issuing an alarm; and comparing the particle concentration with the predetermined first and second particle concentration thresholds, The particle concentration matches the predetermined second particle concentration threshold the predetermined number of times, such that the alarm issuing means issues a first alarm when the concentration matches the predetermined first particle concentration threshold. and control means for controlling the alarm issuing means so that the alarm issuing means issues a second alarm when the alarm issuing means issues a second alarm.