JPH03246700A - Fire detector - Google Patents

Abstract

PURPOSE:To make it possible to detect the generation of a fire in a wide detection area by using an circular scanning optical system as a scanning optical system for scanning the visual field of an infrared ray detecting element and constituting the optical system so that the visual field of the detecting element is included on a scanning axis. CONSTITUTION:The fire detector has the infrared ray detecting element 2, the circular scanning optical system 1 for circularly scanning the visual field of the element 2 and a judging part 5 for judging a fire generation direction based on the scanning direction of the system 1. The system 1 is constructed so that a member for interrupting a visual field is not arranged under a mirror M1 for scanning the visual field. Since the system 1 is used for scanning the visual field of the element 2, frames due to fire generation can be detected in the wide detection area by the simple and inexpensive constitution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is capable of determining the occurrence and direction of a fire by detecting the power of a unique infrared wavelength emitted from the flames of a fire occurring within a monitoring area. This invention relates to an infrared-receiving fire detection device that can detect fires.

[Prior Art] Many infrared receiving type fire detection devices have been proposed in the past. This type of device detects infrared rays characteristic of flames to determine the occurrence of a fire. Figure 7 shows the spectral characteristics of sunlight, illumination light, and flame.
There is a peak created by the resonant emission of O2. On the other hand, sunlight and illumination light have little radiant energy at wavelengths around 4.3 μm. Therefore, if fire occurrence is determined by infrared rays around this wavelength, the sensitivity for detecting flames can be set high. Convenient and specific methods for detecting flames include detecting only the flickering frequency characteristic of flames, or determining the amount of energy of infrared rays around the wavelength of 4.3μ, which is characteristic of flames. Detection methods and the like have been proposed (see Japanese Patent Publication No. 56-28544, Japanese Patent Publication No. 55-25862, Japanese Utility Model Application No. 61-8398, Japanese Patent Application Publication No. 62255832, and Japanese Patent Application Publication No. 62-157580).

[Problems to be Solved by the Invention] However, conventional infrared-receiving fire detection devices may malfunction if strong sunlight is directly incident on the infrared detection element, or if it is reflected by a metal or other object and enters with flickering light. there were. It also sometimes malfunctioned in response to things like the shaking of leaves coming in through the window. Furthermore, a flame that is not a fire, such as a flame from a stove or gas stove, may be determined to be a fire.

If a system is configured that uses such conventional detection devices to detect the occurrence of a fire or the direction of fire occurrence, and then automatically releases extinguishing agent in that direction, it may result in false detection of fire occurrence or incorrect direction of fire occurrence. If detected, there was a risk of damage caused by the extinguishing agent. Furthermore, if the detection sensitivity of infrared rays is set low to prevent false detection, the radiation of extinguishing agent may be delayed and the fire may not be extinguished.

Furthermore, in the fire detection device of Japanese Patent Application No. 1-119485, as shown in FIG. Since it is located between the viewing plane U and the cylindrical mirror M, when the cylindrical mirror M passes over the arm 9 that supports the infrared detection element 2 and the preamplifier 3, the instantaneous field of view F created by the cylindrical mirror M is may be blocked.

For this reason, as shown in FIG. 4, non-detection areas A 2 and A s may occur on the detection area S. The width wA of the non-detection area A is the distance d between the infrared detection element 2 and the mirror M, as shown in FIG. 3(b).
If, for example, 10CIl and the distance dx from the infrared detection element 2 to the detection surface U is 10 rings, there is a problem that a non-detection area A having a width W of 50e- will be created. In the figure, P2 is the position of the infrared detection element 2, PM is the position of the mirror M, and P is the position of the armrest. The distance d from the element position P2 to the arm 9 is twice the distance dM.

In order to prevent the non-detection area A shown in FIG. 4 from occurring, it is necessary to make the arm 9 thin or to make it of a member transparent to infrared rays. Further, even in that case, there is a problem that the non-detection area A2 on the scanning center axis remains.

The present invention has been made in view of these points, and its purpose is to provide an infrared-receiving fire detection device with a simple and inexpensive configuration that can determine the occurrence of fire and the direction of fire occurrence using an algorithm with fewer malfunctions. It is about providing.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, an infrared detection element 2, a circular scanning optical system 1 that circularly scans the field of view of the infrared detection element 2, and a preamplifier 3 that amplifies the output signal of the infrared detection element 2.
, a signal processing unit 4 that converts the output of the preamplifier 3 into a signal for flame detection, and a signal processing unit 4 that determines the occurrence of a fire based on the output of the signal processing unit 4 and scans the circular scanning optical system 1. This apparatus is characterized by comprising a determining section 5 that determines the direction of fire occurrence based on the direction, and an output section 6 that outputs a fire occurrence signal and a fire occurrence direction signal based on the signal from the determining section 5.

Here, the judgment unit 5 detects that the level of the signal for flame detection gradually increases and judges that a fire has occurred.
It is preferable to include at least one of the following algorithm and a second algorithm that determines that a fire has occurred by detecting that the scanning range where the signal for flame detection becomes high level gradually expands.

Further, the determining unit 5 is a means for determining flame detection prior to determining whether a fire has occurred due to increase or expansion of the flame when the signal for flame detection exceeds a predetermined level, and the output unit 6 It is more preferable if the means outputs the flame detection signal prior to outputting the fire occurrence signal.

Further, the circular scanning optical system 1 preferably has a structure in which there is no member blocking the field of view below the mirror that scans the field of view, as shown in the embodiments described later.

In the present invention, since the circular scanning optical system 1 is used to scan the field of view of the infrared detection element 2, flames caused by a fire can be detected within a wide detection area, although the configuration is simple and inexpensive. In addition, the direction of fire occurrence can be easily detected as the direction from the rotation center of the field of view.

Note that if the occurrence of a fire is determined using at least one, preferably both, of flame increase and flame expansion, it is possible to reliably determine whether a fire has occurred. Further, by outputting a flame detection signal prior to a fire occurrence signal, residents can be alerted to check whether a fire has occurred.

This can prevent non-fire flames, reflections of sunlight, etc. from being misinterpreted as a fire outbreak and extinguishing agent being emitted. Also,
Even in the event of a fire, residents can extinguish the flames while they are still small, and prevent fire extinguishing agents from being emitted from so-called "small fires."

[Embodiment] FIG. 2 shows a circular scan in a fire detection device according to an embodiment of the present invention. The detection device is placed on the ceiling and monitors the occurrence of fire on the floor. In the figure, F
is the field of view, Q is the scanning direction, and Fo is the total effective field of view. Further, 11 is the rotation center of the viewing plane F, which coincides with the viewing center C of the infrared detection element 2. As is clear from the figure, the flame H of the fire seen from above becomes an image extending in the radial direction from the visual field center C, except when it occurs at the visual field center C. Taking the above points into consideration, a rectangular slit-shaped field of view is provided and a circular scanning method is used in which the field of view is rotated around its end point to effectively and efficiently detect a fire and to determine its direction. can be determined. In FIG. 2, Dv indicates the instantaneous field of view width. Dv is set in the optical system so as to have an optimum size, taking into consideration the width of the flame to be detected. Generally, it is set to be slightly smaller than the minimum width of the flame that you want to detect.

By the way, when using an optical system as shown in FIG. 3(a), it is necessary to position an infrared detecting element between the rotating plate and the detection surface, which creates a non-detection area as shown in FIG. 3(b). This is not preferable in practical use. A means for solving this problem is shown below.

FIG. 13 shows the first embodiment. In this embodiment, infrared rays from the band-shaped instantaneous visual field (see F in FIG. 4) created by the concave-convex mirror M1 shown in FIG. ,
The light is guided to the condenser lens 14 via the plane mirror M and is incident on the infrared detecting element 2 through the hollow motor shaft 11 as an optical path.

The focal length of the lens 14 may be set to an appropriate value so that the light is focused on the optical surface of the infrared detection element 2.

FIG. 14 shows the second embodiment. In this embodiment, the infrared rays from the band-shaped instantaneous field of view (see F in FIG. 4) created by the concave-convex mirror M1 shown in FIG. M,
The infrared detecting element 2 is transmitted through the condensing mirror M2 in FIG.
The focal length of the zero-focus mirror M, which is incident on the infrared rays, is set to an appropriate value so that the light is focused on the element surface of the infrared detecting element 2.

FIG. 15 shows a third embodiment. In this embodiment, a band-shaped instantaneous visual field (
The infrared rays from the infrared rays (see F in FIG. 4) are guided to the condensing lens 14 via the concave-convex mirror M and the plane mirror M, and are passed through the motor shaft 11, which is hollow and has a mirror-finished inner surface, as an optical path. The light is incident on the detection element 2. 15 is a lens boulder.

In the motor shaft 11 whose inner surface is mirror-finished, infrared rays propagate like light passing through an optical fiber, so the motor shaft may be thin, and the motor 12 used may also be small and thin. The focal length of 14 is set to an appropriate value so that the light is focused on the lower entrance of the motor shaft 11.

FIG. 16 shows a fourth embodiment. In this embodiment, infrared rays from the strip-shaped instantaneous field of view (see F in FIG. 4) created by the concave-convex mirror M shown in FIG. M1
and guided to the condensing lens 14 via the plane mirror M,
The light enters the infrared detection element 2 through this lens 14.

The focal length of the condensing lens 14 is set to an appropriate value so as to condense the light onto the element surface of the infrared detection element 2.
Since the driving force is applied from the motor 12 attached to the outer periphery of the rotary plate 10 via the decelerator 16, the rotational torque may be small, and a small motor can be used.

Also, since there is no need to place the motor on the central axis,
Another effect is that the device can be made thinner.

FIG. 17 shows a fifth embodiment. In this embodiment, infrared rays from the band-shaped instantaneous visual field (see F in FIG. 4) created by the concave-convex mirror M1 shown in FIG.
through the condensing mirror M of FIG.

The light is incident on the infrared detecting element 2 through the hole in the center of the rotary plate 1o. The focal length of the condensing mirror M2 is set to an appropriate value so that the light is focused on the element surface of the infrared detection element 2.The driving force of the zero-rotation plate 1o is decelerated by a motor 12 attached to the outer periphery of the rotation plate 10. Since the rotational torque is applied through the device 16, the rotational torque can be small, and a small motor can be used. Furthermore, since there is no need to arrange a motor on the central axis, there is also the effect that the device can be made thinner.

In each of the embodiments described above, the concavo-convex mirror M is attached to the rotating plate 1o so that the direction of the line AA' shown in FIG. 5 coincides with the radial direction. Also, the first to fifth
A common point to note in each of the embodiments is that unless the reflectance of the surface of the rotary plate 1o is considerably lower than that of the mirror M, infrared rays from outside the instantaneous field of view will also be infrared rays. Care must be taken because the flame may enter the detection element 2 and the S/N ratio as a flame detection signal will be poor.

For example, the surface of the rotating plate 10 other than the mirror M is black,
If the difference in reflectance with the surface of mirror M is increased, S
A received light signal with a good /N ratio can be obtained.

Reference numeral 13 denotes a rotation period detection section, which is configured using, for example, a photo sensor, a magnetic sensor, etc., and generates a synchronization signal every time the rotating disk IO rotates once. The rotation period detection section 13 is attached near the outer periphery of the rotary plate 10, as shown in FIGS. 13 to 17.

The mounting position may be near the rotating shaft, but since the circumferential speed is higher near the outer periphery of the rotary plate 10, there is an advantage that a synchronization signal with a sharp rise can be obtained.

Here, the circuit configuration of a fire detection device using the optical system will be explained based on FIG. 9. The output of the infrared detection element 2 is amplified by the preamplifier 3 and then input to the bandpass filter 41. As the infrared detection element 2, a pyroelectric element that does not require cooling and is inexpensive is used.

Since this pyroelectric element contains many low frequency components as background noise, the bandpass filter 41 cuts out unstable low frequency components and also cuts unnecessary high frequency components to improve the S/N ratio. . The output of the bandpass filter 41 is A
/D converter 42 and A/D converter 42
The signal is A/D converted and output to the microcomputer 51 constituting the determination section 5. microcomputer 5
The motor drive unit 12 is operated by the control signal from 1, and the 0 rotation period detection unit 13 is controlled to rotate at a predetermined constant speed.
A synchronizing signal is output to the microcomputer 51 every rotation. The microcomputer 51 is the rotation period detection section 1
The A/D converter 42 is operated based on the synchronization signal from the A/D converter 3, and waveforms are sequentially captured from the A/D converter 42 every rotation. The microcomputer 51 provides signals indicating non-fire (normal state), fire expansion, fire increase, flame detection, fire direction, fire range, etc. to the output unit 6 using an algorithm to be described later. The output unit 6 displays these signals, controls an automatic fire extinguishing system according to these signals, and broadcasts evacuation guidance.

By the way, as shown in FIG. 7, infrared rays radiated from flames when a fire breaks out are characterized by the presence of a peak due to the resonance radiation of CO2 around a wavelength of 4.3 .mu.-. Therefore, the infrared detection element 2 has a wavelength of 4.3 as shown in FIG.
A bandpass filter is added and used to pass infrared rays around μm.

Next, we will explain the algorithm for determining fire occurrence.
The first feature of this algorithm is that it judges the occurrence of a fire based on both criteria: an increase in the power of the flame and an increase in the area of the flame.

Here, an increase in the area of the flame is determined by an increase in the width of the flame when viewed from the center of the circular scan. The second feature is that, as a step before issuing a fire signal, when a signal exceeding a certain predetermined level is detected, a warning signal indicating "flame detection" is output.

The third feature is that when fire flames are detected, the direction from the center of the rotational scanning field of view is output as a fire direction signal.

This algorithm will be explained in detail below.

Fire flames are generally characterized by a small area at first. In other words, as shown in Figure 2, there is a flame H within the effective field of view.
occurs, the width of flame H seen from the center of rotation is small,
The infrared radiation power from the flame H is also small, but as the fire progresses, the area of the flame H increases and the radiation power also increases. The principle of this algorithm is to distinguish between flames and non-fire flames.

First, as shown in FIG. 2, when the instantaneous field of view F crosses the flame H within the effective field of view, a waveform as shown in FIG. This is the time when the synchronization signal is obtained from the rotation period detection section 13. The maximum value of this waveform is ``H1'', the minimum value is ``L'', the time when the maximum value is obtained, tH1, and the time when the minimum value is obtained is tL.

These detection times tH and tL are based on the synchronization signal from the rotation period detection section 13, so when the rotating plate 10 is controlled at a constant speed, the time tH+tL
can be converted into a direction or a scanning angle from the center of rotation when the mounting position of the rotation period detection unit 13 is set as a reference.

FIG. 11 shows how the flame gradually increases in size and the detected waveform at that time. FIG. 11(a) shows the case where the flame is small. In this case, the microcomputer 51
As shown in the flowchart of FIG. 12, in program step #1, the synchronization signal is used as a trigger to convert the detected waveform accumulated in the input buffer from the A/D converter 42 into one signal.
The scanned amount is stored in the memory, and in program step #2, the maximum value ■H and minimum value ■shi of the detected waveform and their detection times tH and tL are determined. And program step #3
is compared with the flame detection threshold Vs. Maximum value V of detected waveform,
If is less than the flame detection threshold ■s, it is determined in program step #4 that VH≦Vs, and the program proceeds to step #5, where a normal state signal indicating no fire is output. Thereafter, the process returns to #1 and the same process is repeated for the detected waveform obtained in the next scan.

FIG. 11(b) shows a case where the fire progresses and the flames do not grow large. In this case, in program step 1 #3, the maximum value VH of the detected waveform becomes larger than the flame detection threshold Vs for the first time, so the maximum value V of the detected waveform obtained in this scan and the detection times tH and tL are used. So, V H5=V
H, T s = tl - tH are determined and these are stored as reference values for the following fire judgment. In scanning at this time, VH>Vs is determined in program step #4.
Therefore, the program moves to step #6.
Find flame detection time T=tL-LH. This flame detection time T
indicates the width of the flame when viewed from the center of the field of view. And program step #7. After the determination in #8, a flame detection signal is output in program step #9, a scanning time TF indicating the direction of fire occurrence is calculated in program step #10, and the process returns to #1.

Figure 11(c) shows that the fire has spread and the flame detection time T = tL.
-t, is longer. At this time, since the power of the flame has not become very large, the maximum value VH of the detected waveform is smaller than M times the reference value VH5, and the determination in program step #7 is that VH<M・VH5.
Proceeding to program step #8, the flame detection time T is compared with twice the reference value TS. If it is determined in program step #8 that T≧K −'rs, the process moves to #program step #11 and a fire expansion signal is output.

FIG. 11(d) shows a case where the fire progresses further, the radiant power of the flame increases, and the width of the flame also increases. At this time, 782M・VH' at program step #8.
3 and moves to program step #12,
Here, it is determined that T≧-Ts, and the program moves to step #14, so both the fire increase and fire expansion signals are output.

In addition, in program step #8, the fire spreads (T≧ -T
Before determining S), program step #7
If it is determined that the fire has increased (VH≧M−VHs), program step #12 to program step #
13, only the fire increase signal is output.

Here, K is a fire expansion determination coefficient, which is a coefficient that determines how wide the flame width must be to determine that there is a fire. Further, M is a fire increase determination coefficient, which is a coefficient that determines how much the flame radiation power should increase to determine a fire when the output signal of the infrared detection element 2 is increased. The value of these coefficients M varies depending on the environment in which the fire detection device is installed, the size of the monitoring range, the installation height, etc., so by setting it to the optimal value according to the installation condition, Effective Fire Detection 6 Finally, the method of calculating the scanning time TF indicating the direction of fire occurrence in program step #10 will be explained.

As is clear from FIG. 11, the direction of the center of the flame caused by the fire is determined as the scanning angle seen from the scanning center by using the synchronization signal from the rotation period detection section 13 as a reference. When the rotating plate 10 is rotating at a constant speed, the scanning angle corresponds to the scanning time. As a result of repeated experiments, we have found that the scanning time TF from the time when the synchronization signal is generated to the direction of the center of the fire flame can be approximated by the following equation.

Tp='rH+ a-T b-Ts c The third and fourth terms in the above equation are as follows: Even if the flame is the same size, if the radial distance from the scanning center is different, the speed at which the instantaneous field of view crosses the flame will be different. , is a correction term for correcting an error in the detection time T due to the fact that the detected waveform becomes dull when the flame is close and becomes sharp when the flame is far away. The values of constants a, b, and e in the above equation can be determined by selecting appropriate values according to the height above the floor where the fire detection device is installed, the length of the field of view in the radial direction, etc. The scanning time TF can be determined with high accuracy.For example, when the height is 15-1
If the radius is 7 mm, a=0.5, b=0.315
, c=0.025, good results were obtained.

In the above equation, the direction of fire occurrence is expressed by the scanning time TF, but if the rotation period of the field of view is, for example, 10 seconds, and the direction of the center of the flame is expressed by the angle θ from the rotation period detection unit 13, then θ=360 (TH+a -Tb-Ts e)/
10f:degll If a plurality of fire detection devices capable of detecting the direction of fire occurrence are used, the position of fire occurrence can be determined based on the plurality of fire direction signals.

[Effects of the Invention] As described above, the present invention provides an infrared receiving type fire detection device that detects infrared rays emitted from fire flames to determine the occurrence of a fire. Since it uses a scanning optical system, it has the effect of being able to detect fire outbreaks within a wide detection area while having a simple and inexpensive configuration.In addition, the direction of fire outbreak can be easily determined from the rotation center of the field of view. It has the effect of being detectable. Furthermore, since the field of view of the infrared detection element is included on the scanning axis of the circular scanning optical system, there is an effect that no non-detection area occurs on the detection surface.

Furthermore, if the occurrence of a fire is determined by detecting at least one of the expansion and increase of flames, which are characteristics of fire flames, there is an effect that the determination of the occurrence of a fire can be made reliably.

Furthermore, by making it possible to output the fire detection signal prior to the fire occurrence signal, it is possible to prevent the automatic fire extinguishing system from malfunctioning due to non-fire flames, sunlight, etc.

Note that by installing a plurality of fire detection devices of the present invention, it is possible to detect not only the direction but also the position of a fire outbreak.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the basic configuration of the present invention, Fig. 2 is a plan view showing the scanning situation of the field of view in the present invention, and Fig. 3 (
(a) is a schematic diagram of the optical system used in the conventional example, and (b) is a schematic diagram of the optical system used in the conventional example.
4 is a plan view of the detection area according to the above, FIG. 5(a) is a perspective view of the concave-convex mirror used in the present invention, and FIG. 5(b) is a line AA' in the same as above. Cross-sectional view, same figure (
c) is a sectional view taken along line B-B' of the same as above, FIG. 6(a) is a perspective view of the condensing mirror used in the present invention, and FIG.
A' line sectional view, the same figure (c) is the same B-B' line sectional view,
Fig. 7 is a diagram showing the spectral radiant energy characteristics of flame, which is the detection target of the present invention, and illumination light and sunlight, which are not the detection targets, and Fig. 8 is the spectral transmittance of the bandpass filter included in the infrared detection element used in the present invention. 9 is a block diagram of an embodiment of the present invention, FIG. 10 is a waveform diagram showing the detection waveform of the same as above, and FIG. 11 is an operation explanatory diagram showing the algorithm of fire occurrence detection as above. Figure 12 is a flowchart showing the processing contents of the microcomputer used in the above.
3 to 17 are longitudinal sectional views of optical systems used in different embodiments of the present invention. 1 is a circular scanning optical system, 2 is an infrared detection element, 3 is a preamplification section, 4 is a signal processing section, 5 is a judgment section, and 6 is an output section.

Claims (6)

[Claims] (1) An infrared detection element, a circular scanning optical system that circularly scans the field of view of the infrared detection element, a preamplifier that amplifies the output signal of the infrared detection element, and flame detection for the output of the preamplification unit. a signal processing unit that converts the signal into a signal for the determination, a determination unit that determines the occurrence of a fire based on the output of the signal processing unit and determines the direction of fire occurrence based on the scanning direction of the circular scanning optical system; and an output section that outputs a fire occurrence signal and a fire occurrence direction signal in response to a signal from the section, and the circular scanning optical system is configured such that the field of view of the infrared detection element is included on the scanning center axis. Characteristic fire detection device. (2) The circular scanning optical system uses a hollow motor shaft, which is the central axis of the rotary plate, as an optical path, and the infrared light from the fire is collected at the center of rotation by a concave-convex mirror, and then transferred to the motor using a flat mirror and a condensing lens. 2. The fire detection device according to claim 1, wherein the fire detection device is configured so that the light passes through the shaft and is focused on the surface of the infrared detection element. (3) The circular scanning optical system uses the motor shaft, which is the central axis of the rotary plate, as a hollow light path, and the infrared light from the fire is collected at the center of rotation by a concave-convex mirror, and is passed through the motor shaft by a concave mirror to the infrared detection element. The fire detection device according to claim 1, wherein the fire detection device is configured to condense light onto a surface. (4) In the circular scanning optical system, the motor shaft, which is the center axis of the rotary plate, is made into a hollow space with a mirrored inner wall, and is used as an optical fiber-like optical path. 2. The fire detection device according to claim 1, wherein the light is condensed at the end of the shaft by a mirror and a condensing lens, and is condensed onto an infrared detection element through the shaft of the optical fiber. (5) The circular scanning optical system has a condensing lens at the center of the rotating plate, and the infrared light from the fire that is collected at the center of rotation by the concave-convex mirror is reflected by the flat mirror, and the infrared detection element is detected by the condensing lens. 2. The fire detection device according to claim 1, wherein the fire detection device is configured so that the light is focused on the rotary plate and the rotational driving force is applied from the outer periphery of the rotary plate. (6) A circular scanning optical system has a hole in the center of a rotating plate, and infrared light from a fire is collected at the center of rotation by a concave-convex mirror, and is passed through the center of the rotating plate by a concave condensing mirror to an infrared detection element. 2. The fire detection device according to claim 1, wherein the fire detection device is configured so that the light is focused on the rotary plate and the rotational driving force is applied from the outer periphery of the rotary plate.