JP2007317007A - Fire alarm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fire alarm capable of preventing a fire alarm from being issued, when there is no fire, while issuing the fire alarm immediately when a fire breaks out. <P>SOLUTION: The fire alarm comprises: a smoke detection part 3 for detecting smoke; an alarm part 4 for issuing the fire alarm; and a control unit 2 in which an accumulation time starts to be measured from, when smoke density based on an output detected by the smoke detection part 3 has reached a prescribed threshold or larger, and the alarm part 4 issues the fire alarm when the smoke density has continued to be equal to the threshold or larger for a prescribed accumulation time. Before the accumulation time has come, the control unit 2 discriminates between fire and non-fire, on the basis of a behavior of change due to aging of smoke density amount at a prescribed time, from the time at least the smoke density reaches the threshold or becomes larger, and performs control either by reducing the accumulation time, when the fire is identified or prolonging the accumulation time, when non-fire is identified. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention starts the measurement of the accumulation time from the time when the smoke concentration based on the output detected by the smoke detection unit detecting the smoke and the smoke detection unit becomes a predetermined threshold or more, and the smoke concentration is The present invention relates to a fire alarm including a control unit that controls an alarm unit to emit a fire alarm when a state equal to or greater than a threshold value continues for a predetermined accumulation time.

  In this type of fire alarm, for example, as disclosed in Patent Document 1, even if the detection result of the smoke detector exceeds a preset detection level, a fire alarm is not immediately issued. In other words, the accumulation time from when the detection result of the smoke detection unit exceeds a predetermined threshold so that a fire alarm is not issued in the event of a non-fire in response to a phenomenon unrelated to fire such as cigarette smoke or steam. And a fire alarm is issued when a predetermined accumulation time is reached with the detection result exceeding a predetermined threshold.

JP-A-7-182573

  By the way, from the viewpoint of preventing issuing a fire alarm at the time of non-fire, it is preferable that the above accumulation time is long. On the other hand, in order to issue a warning quickly in the event of a fire, it is preferable that the above accumulation time is short.

  However, in the above-described fire alarm, regardless of whether the fire is fire or non-fire, the fire alarm is issued after a predetermined accumulation time has elapsed when the smoke concentration exceeds a predetermined threshold. For this reason, from the viewpoint of quickly issuing an alarm in the event of a fire, it is necessary to set the accumulation time short, and there has been a problem that it may not be possible to sufficiently prevent the fire alarm from being issued in the event of a non-fire.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a fire alarm capable of generating a fire alarm quickly in the event of a fire and preventing a fire alarm in the event of a non-fire. There is.

  The first characteristic configuration of the present invention is that the smoke detection unit that detects smoke, the alarm unit that issues a fire alarm, and the smoke concentration based on the output detected by the smoke detection unit is accumulated from the time when the smoke concentration becomes a predetermined threshold or more. A control unit that starts time measurement and controls the alarm unit to emit a fire alarm when the smoke concentration is equal to or higher than the threshold value for a predetermined accumulation time, and the control unit However, before reaching the accumulation time, a fire and a non-fire are distinguished based on the behavior of the change in the smoke density over time at a predetermined time from the time when the smoke density becomes equal to or higher than the threshold. In addition, at least one of the shortening of the accumulation time when identified as a fire and the extension of the accumulation time when identified as a non-fire is performed.

According to this configuration, the control unit discriminates between fire and non-fire based on the behavior of the temporal change at least during a predetermined time during the accumulation time, and shortens the accumulation time when it is identified as a fire. And control of at least one of the extension of the accumulation time when it is identified as non-fire is performed. As a result, when the possibility of fire is high, the accumulation time is shortened to quickly issue a fire alarm, and when the possibility of fire is low, the accumulation time is lengthened to prevent the fire alarm from being issued. It will have at least one of them.
Moreover, according to this configuration, the accumulation time is controlled based on at least the behavior of the change in smoke density over time during the accumulation time. For this reason, for example, compared with the case where the accumulation time is controlled only based on the smoke concentration before the start of the accumulation time, the fire and the non-fire are distinguished at a time when the behavior of the temporal change is different between the fire and the non-fire. Will be. As a result, fire and non-fire can be reliably identified and the accumulation time can be controlled appropriately.
As a result, it is possible to provide a fire alarm capable of appropriately controlling the accumulation time, quickly issuing a fire alarm at the time of a fire, and preventing issuing a fire alarm at the time of a non-fire.

  The second characteristic configuration of the present invention is that the accumulation time control unit controls the accumulation time based on a correlation between an average value of the change amount and a standard deviation.

  With this configuration, the time control unit can reliably identify fire and non-fire based on the correlation between the average value of the change amount and the standard deviation, and can appropriately control the accumulation time.

  A third characteristic configuration of the present invention is that a control unit controls the accumulation time based on a frequency spectrum of the change amount.

  With this configuration, the control unit can reliably identify fire and non-fire based on the frequency spectrum of the change amount, and can appropriately control the accumulation time.

(Fire alarm)
FIG. 1 is a block diagram showing a configuration of a fire alarm 1 according to the present embodiment.
The fire alarm 1 includes a smoke detector 3 that detects smoke concentration, a controller 2 that controls the fire alarm 1, and an alarm unit 4 that issues a fire alarm.

As the smoke detection unit 3, for example, a scattered light type smoke sensor having a smoke detection function can be used. The scattered light type smoke sensor has a light emitting part and a light receiving part (both not shown), and the light receiving element of the light receiving part receives scattered light by utilizing a scattering phenomenon that occurs when light from the light emitting part hits smoke particles. Changes in photocurrent are detected.
The smoke detection unit 3 is not limited to the above-described one, and for example, a transmitted light type smoke sensor may be used. The transmitted light type smoke sensor detects a change in photocurrent generated when a light receiving element of a light receiving unit receives transmitted light.

  The control unit 2 starts measuring the accumulation time t from when the smoke density based on the output detected by the smoke detection unit 3 becomes equal to or higher than a predetermined threshold (hereinafter also referred to as “alarm level” as appropriate) When the state where the smoke concentration is equal to or higher than the alarm level continues for a predetermined accumulation time T, the alarm unit 4 is controlled to issue a fire alarm. Further, the control unit 2 performs the accumulation time based on the behavior of the change in smoke concentration over time for a predetermined time (hereinafter also referred to as “analysis time” as appropriate) from the time when the smoke concentration becomes equal to or higher than the alarm level. Before reaching T, distinguish between fire and non-fire. Then, at least one of the shortening of the accumulation time T when it is identified as a fire and the extension of the accumulation time T when it is identified as a non-fire is performed.

  The control unit 2 includes a concentration determination unit 21, a time measurement unit 22, an accumulation time control unit 23, a fire / non-fire determination unit 24, and a display management unit 25. The density determination means 21 determines whether or not the smoke density based on the detection result of the smoke detector 3 is equal to or higher than the alarm level. The time measuring means 22 measures the accumulation time t. The accumulation time control means 23 controls the accumulation time based on the behavior of change with time. In addition, the display management unit 25 issues a fire signal to the alarm unit 4 when the fire / non-fire determination unit 24 determines that there is a fire.

  The alarm unit 4 includes, for example, a speaker and an LED. When the fire / non-fire judgment means 24 judges that the fire is a fire, the alarm section 4 uses an alarm signal from the display management means 25 to hear an audio / visual fire alarm such as a sound from a speaker or blinking of an LED. To emit.

(Operation of fire alarm)
Next, operation | movement of this fire alarm 1 is demonstrated based on FIG.
When the smoke detector 3 detects smoke (Y branch of # 1), the smoke density determination means 21 determines whether or not the smoke density based on the detection level is equal to or higher than a predetermined threshold (alarm level) (# 2). If the smoke density is less than the alarm level (N branch of # 2), the accumulation time t and a flag F described later are set to 0 (# 8), and the detection level is read again (# 1). On the other hand, when the smoke density is equal to or higher than the alarm level (Y branch of # 2), measurement of the accumulation time t is started (# 3).

Thereafter, it is determined whether or not the flag F is 0 (# 4). Here, the flag F = 0 indicates that an accumulation time control process described later has not yet been performed, and the flag F = 1 indicates that an accumulation time control process has already been performed.
When the flag F = 0 (Y branch of # 4), since the accumulation time control process has not been performed yet, the accumulation time control process is performed, and the accumulation time T is shortened or extended (# 5). On the other hand, when flag F = 1 (N branch of # 4), since the accumulation time control process has already been performed, the accumulation time control process is not performed, and the measurement of the accumulation elapsed time t is continued (see FIG.

  When the accumulation time t reaches a predetermined accumulation time T (Y branch of # 6), a fire alarm is issued. On the other hand, when the accumulation time t has not reached the predetermined accumulation time T (N branch of # 6), the above-described processes of # 1 to # 4 and # 6 are repeated. If the smoke concentration falls below the alarm level before the accumulation time t reaches the predetermined accumulation time T (N branch of # 2), the accumulation time t and the flag F are set to 0 (# 8). The smoke is detected again (# 1).

(Accumulation time control processing)
Next, the accumulation time control process will be described with reference to FIG. The accumulation time control process identifies whether it is a fire or a non-fire based on the behavior of the change in smoke concentration over time, and if it is identified as a fire, the accumulation time T is shortened and the fire is non-fire. In the case of identification, the accumulation time T is extended.
When the accumulation time control process is started, measurement of analysis time is started (# 51), and the smoke density is read and stored. For example, the change in smoke density is calculated by obtaining the difference from the smoke density read last time, and the change over time in the change in smoke density is stored (# 52). If the analysis time is less than the predetermined analysis time Ta (N branch at # 53), the above operation is repeated until the analysis time Ta is reached, and the change over time in the amount of change in smoke density is stored. When the analysis time Ta is reached (Y branch of # 53), a preliminary determination is made as to whether it is a fire or non-fire based on the behavior of the change over time (# 54). If it is determined in the preliminary determination that there is a fire (Y branch of # 55), the accumulation time T is shortened to T-dT1 (# 56). On the other hand, if the non-fire is identified (N branch of # 55), the accumulation time T is extended to T + dT2 (# 57). Further, flag F is set to 1 to indicate that the accumulation time control process has been performed (# 58).

By performing the accumulation time control process described above, the accumulation time can be shortened when the possibility of fire is high, and the accumulation time can be lengthened when the possibility of fire is low. As a result, it is possible to quickly issue a fire alarm in the event of a fire, and to prevent issuing a fire alarm in the event of a non-fire.
In addition, since the accumulation time is controlled based on the behavior of the change in the smoke concentration during the accumulation time over time, for example, compared to the case where the accumulation time is controlled only based on the smoke concentration before the start of the accumulation time. Thus, when the difference between the smoke concentration behavior in the case of a fire and the smoke concentration behavior in the case of a non-fire is more prominent, a fire and a non-fire are distinguished. As a result, fire and non-fire can be reliably identified and the accumulation time can be controlled appropriately. As a result of the above, it is possible to appropriately control the accumulation time, to quickly issue a fire alarm in the event of a fire, and to prevent issuing a fire alarm in the event of a non-fire.

In the above example, the example in which the accumulation time T is both extended and shortened has been shown, but only one of them may be performed. Further, the shortening time dT1 and the extending time dT2 may be the same time or different times.
In addition, although an example of performing accumulation time control processing based on the amount of change in smoke density after the start of the accumulation time has been shown, accumulation is performed based on the amount of change in smoke density over the accumulation time from the start of the accumulation time. Time control processing may be performed. In this case, for example, the accumulation time control process may be started when the concentration determination unit 21 determines that the smoke concentration is equal to or higher than a predetermined value lower than the alarm level. Also, the temporal change in smoke density (or the amount of change in smoke density) is stored before the smoke concentration reaches the alarm level, and after the smoke concentration reaches the alarm level, the change over time is called to control the accumulation time. Processing may be performed.

  Further, when the accumulation time control process is performed based on the change amount of the smoke density after the accumulation time starts, the accumulation time control process does not necessarily have to be performed from the time when the smoke density reaches the alarm level. However, it is necessary to distinguish between fire and non-fire before the accumulation time elapses. For this reason, it is preferable to start the accumulation time control process early after the smoke concentration reaches the alarm level.

(Example of accumulation time control processing)
Next, a specific example of the accumulation time control process will be described. The initial accumulation time is not particularly limited, but is set to 40 seconds in this embodiment. The alarm level was 10% / m. In this measurement, a scattered light type smoke sensor was used as the smoke detector 3, and the measurement was performed with a detection period of 1 s.
In this embodiment, the smoke concentration change analysis time is set to 20 seconds from the start of the accumulation time (that is, when the smoke concentration reaches the alarm level), and a fire or non-fire is detected after 20 seconds. to decide.

Experiments were conducted with futon fires and tempura oil fires as examples of fires and steam as an example of non-fires. FIG. 4 shows the time-dependent change in the smoke concentration in each case, assuming that the time when the smoke concentration exceeded the fire alarm level is zero. FIG. 5 shows the change over time in the amount of change in smoke density, with the time when the smoke density exceeds the fire alarm level being represented as zero.
In these figures, the solid line indicates the result of futon fire, the dotted line indicates the result of tempura oil fire, and the alternate long and short dash line indicates the result of steam. In the case of a futon firewood fire, the smoke concentration increased slowly at a substantially constant rate. In the case of a tempura oil fire, the smoke concentration rapidly increased at a substantially constant increasing rate, and fired after about 20 seconds, and the smoke concentration became substantially constant. In the case of steam, the smoke concentration increased and decreased repeatedly.
From the above figure, it can be seen that the smoke concentration and the amount of change are larger in the case of non-fire due to steam compared with fires such as futon fire and tempura oil fires. Therefore, it is possible to make a preliminary determination for distinguishing between a fire and a non-fire based on a change over time in the amount of change in smoke density.

FIG. 6 is a graph in which the same measurement as in FIG. 1 is performed 6 times in each case, and the average value and standard deviation of the smoke density change amount between 0 and 20 s at each measurement are plotted.
As is clear from the above-mentioned figure, the correlation between the average value and the standard deviation differs between fire and non-fire. That is, in the futon firewood that is a fire, the average standard deviation shows a small value. Moreover, in the tempura oil fire which is a fire, the average value shows a relatively large value, and the standard deviation shows a relatively small value. On the other hand, in the case of steam that is not fire, the average value shows a small value, and the standard deviation shows a large value. From this result, it is understood that if the standard deviation is small, the possibility of fire is high, and if the standard deviation is large and the average value is small, the possibility of non-fire is high.
For this reason, in FIG. 5, it is divided into a fire area and a non-fire area, and the average value and standard deviation of the smoke concentration change during the analysis time exist in either the fire area or the non-fire area in the figure. Whether fire or non-fire can be distinguished.

  In the above-described example, the analysis time of the smoke concentration change amount is set to 20 seconds from the start of alarm accumulation, and when 20 seconds have elapsed, it is determined whether fire or non-fire has occurred. For this reason, for example, in the case of a tempura oil fire, it is possible to quickly issue a fire alarm by shortening the accumulation time, for example, 20 seconds, and issuing an alarm immediately after the preliminary determination. On the other hand, in the case of steam, for example, by extending the accumulation time for 20 seconds, it can be expected that steam will disappear naturally without issuing a fire alarm.

  In this way, it is possible to distinguish between fire and non-fire by evaluating the behavior of the change in smoke concentration over time within the accumulation time. In the case of a fire, the accumulation time can be shortened to give an alarm early. In the case of a non-fire, the accumulation time can be extended to prevent the fire alarm from being issued.

  In the above-described embodiment, the accumulation time control process does not necessarily have to be performed from the time when the smoke concentration reaches the alarm level. However, in the case of a tempura fire, as is clear from FIG. 4, the smoke concentration becomes a substantially constant value after ignition (after about 20 seconds), and it is determined whether a fire is fired or not fired based on the change over time in the amount of smoke concentration change. Becomes difficult. Therefore, it is preferable to start the accumulation time control process early.

(Another example of accumulation time control)
FIG. 7 is a frequency spectrum obtained by performing frequency analysis for 0 to 20 seconds in FIG. In FIG. 7, the solid line indicates the result of the futon fire, the dotted line indicates the result of the tempura oil fire, and the alternate long and short dash line indicates the result of steam.
The difference between a fire (tempura oil fire / futon fire) and a non-fire (steam) is remarkable in the frequency range of 0.20 to 0.45 Hz. That is, in the case of steam that is not a fire, the amplitude is larger than in the case of futon firewood and tempura oil fires that are fires. Therefore, for example, the frequency spectrum is integrated in the region where the frequency is 0.20 to 0.45 Hz, and if the integrated value is equal to or higher than a predetermined value, it is identified as non-fire, and the integrated value is equal to or lower than the predetermined value. Can be identified as a fire.

  In the above-described specific example of the accumulation time control process, the example based on the average value and standard deviation of the smoke density and the example based on the frequency spectrum have been described. However, the accumulation time control process is not limited to the above example. For example, if the change amount is within a predetermined range (in this embodiment, for example, -20 to + 20% / m / s), the accumulation time T is shortened from the change over time in the change amount of the smoke density shown in FIG. However, if the amount of change exceeds the above range, it may be other than the above, such as extending the accumulation time T.

The block diagram which shows the fire alarm which concerns on this invention Flow chart showing fire alarm operation Flow chart showing accumulation time control processing Figure showing the change in smoke concentration over time A diagram showing the change over time in the amount of smoke density change Figure showing the correlation between the mean value of the change in smoke density and the standard deviation Frequency spectrum of change in smoke density

Explanation of symbols

1 Fire alarm 2 Control unit 3 Smoke detection unit 4 Alarm unit T Accumulation time

Claims (3)

A smoke detector for detecting smoke;
An alarm unit for issuing a fire alarm;
The measurement of the accumulation time starts when the smoke density based on the output detected by the smoke detector becomes equal to or higher than a predetermined threshold, and the state where the smoke density is equal to or higher than the threshold continues for the predetermined accumulation time. And a control unit that controls the alarm unit to issue a fire alarm when
Based on the change over time of the amount of change in the smoke concentration in a predetermined time from the time when the smoke concentration becomes equal to or higher than the threshold, the control unit determines whether the fire and non-fire before reaching the accumulation time. A fire alarm that controls at least one of the shortening of the accumulation time when it is identified as a fire and the extension of the accumulation time when it is identified as a non-fire.   The fire alarm according to claim 1, wherein the control unit performs the control based on a correlation between an average value of the change amount and a standard deviation.   The fire alarm according to claim 1, wherein the control unit performs the control based on a frequency spectrum of the change amount.

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