JP7754752B2 - fire detector - Google Patents

Description

This disclosure relates to a fire detector that extracts features that change in response to the occurrence of a fire and determines whether a fire has occurred by comparing the features with a fire threshold.

For example, some fire detectors use a light-emitting element in the light-receiving element to receive scattered light from smoke particles generated by a fire, and determine whether a fire has occurred based on the amount of light received.

Here, the amount of received light corresponds to a feature that changes when a fire occurs. Therefore, with such a fire detector, it is possible to determine that a fire has occurred when the feature exceeds a pre-set fire threshold.

Depending on the environment in which a fire detector is installed, steam, dust, cigarette smoke, etc. may cause the detector to mistakenly recognize a fire when there is no fire, resulting in a "false fire alarm."

There is therefore conventional technology that automatically identifies detectors that frequently emit non-fire alarms and provides guidance on countermeasures to reduce the number of non-fire alarms (see, for example, Patent Document 1). Specifically, Patent Document 1 has a function that, if the number of non-fire alarms from a single detector exceeds a certain level, displays or issues an alarm to that effect, allowing appropriate maintenance measures to be taken.

Furthermore, Patent Document 1 has the ability to compare and analyze the causes of non-fire alarms, which are accumulated as building-specific data for fire monitoring and common reference data based on legal standards, and to provide guidance on countermeasures such as optimal detectors to reduce non-fire alarms, thereby effectively reducing non-fire alarms.

Japanese Patent Application Publication No. 8-77483

However, the conventional techniques have the following problems.
As described above, according to Patent Document 1, the system automatically identifies detectors that frequently generate non-fire alarms when the number of non-fire alarms exceeds a certain number, and, if necessary, provides a function to notify countermeasures such as guidance on the optimal detector to reduce non-fire alarms.

However, although Patent Document 1 has a function to automatically identify detectors that frequently generate non-fire alarms, the only countermeasures to reduce non-fire alarms are to provide guidance.

As a result, specific mitigation measures depend on the operator who views the guidance, and those who can implement mitigation measures are limited to operators who are capable of doing so. Furthermore, until such an operator takes action, the situation of frequent non-fire alarms continues. Therefore, while the conventional technology described in Patent Document 1 can automatically identify detectors that frequently generate non-fire alarms, it is difficult to quickly implement mitigation measures.

Furthermore, Patent Document 1 merely determines after the fact whether the current installation environment is one in which non-fire alarms are likely to occur frequently. However, it would be more important to determine whether the current installation environment is one in which non-fire alarms are likely to occur before a non-fire alarm actually occurs, and to prevent unnecessary non-fire alarms from occurring in advance.

This disclosure has been made to solve the above-mentioned problems, and aims to provide a fire detector that can quantitatively determine whether the current installation environment is prone to false fire alarms, and can quickly implement measures to reduce false fire alarms without operator intervention.

The fire detector disclosed herein is a fire detector equipped with a control unit that extracts feature values that change in response to the occurrence of a fire and determines whether a fire has occurred when the feature value exceeds a fire threshold. The control unit sets an environmental judgment region defined by an upper limit value that is lower than the fire threshold and a lower limit value that is also lower than the upper limit value in order to monitor the occurrence of feature values that are lower than the fire threshold. The control unit generates time-series data by sequentially acquiring feature values, and counts the number of times that the feature value changes from a value below the lower limit value to within the environmental judgment region over a predetermined judgment period in relation to the transition state of the feature value in the time-series data as the environmental judgment count. If the environmental judgment count exceeds the predetermined environmental judgment threshold, the fire threshold is updated to an updated value higher than the initial value. The control unit is equipped with an environmental monitoring function that changes the fire detection sensitivity by dynamically changing the fire threshold according to the installation environment.

This disclosure makes it possible to obtain a fire detector that can quantitatively determine whether the current installation environment is prone to false fire alarms, and can quickly implement measures to reduce false fire alarms without operator intervention.

FIG. 1 is a functional block diagram of a fire detector according to a first embodiment of the present disclosure. 2 is a functional block diagram showing the internal configuration of a control unit included in the fire detector according to the first embodiment of the present disclosure. FIG. 10 is a flowchart showing a series of processes of an environment monitoring function for updating a fire threshold value executed by an environment monitoring processing unit according to the first embodiment of the present disclosure. FIG. 10 is an explanatory diagram relating to an environmental monitoring function for updating a fire threshold value in the first embodiment of the present disclosure. 10 is a flowchart illustrating a series of processes of an environment monitoring function for restoring a fire threshold value, which is executed by an environment monitoring processing unit according to the first embodiment of the present disclosure. FIG. 10 is an explanatory diagram relating to an environmental monitoring function for restoring a fire threshold value in the first embodiment of the present disclosure.

Preferred embodiments of the fire detector of the present disclosure will be described below with reference to the drawings. In the following embodiment 1, we will explain an example of a fire detector that receives scattered light caused by smoke particles generated by a fire, and determines whether a fire has occurred by comparing the amount of received light with a fire threshold.

However, the fire detector disclosed herein is not limited to this configuration and can be applied to fire detectors that determine whether a fire has occurred based on the results of comparing a feature that changes in response to the occurrence of a fire with a fire threshold.

The fire detector disclosed herein has a technical feature of being equipped with an environmental monitoring function that changes the fire detection sensitivity by dynamically changing the fire threshold according to the installation environment. This enables quantitative determination of whether the current installation environment is prone to generating false fire alarms, and by quickly implementing measures to reduce false fire alarms without operator intervention, it achieves the remarkable effect of preventing unnecessary false fire alarms from occurring.

Embodiment 1.
1 is a functional block diagram of a fire detector according to a first embodiment of the present disclosure. The fire detector 1 according to the first embodiment is configured to include a light-emitting element 11, a light-receiving element 12, an amplifier 20, a controller 30, and an alarm transmitter 40.

To detect smoke caused by a fire, the light-emitting element 11 emits light of a predetermined wavelength and intensity as a signal component at a predetermined timing. Meanwhile, the light-receiving element 12 is positioned so that the light emitted by the light-emitting element 11 does not directly strike it. The light-receiving element 12 receives the light emitted by the light-emitting element 11 and scattered by smoke particles, and outputs it as an electrical signal, specifically a voltage value.

An example of a light-emitting element 11 that emits light of a predetermined wavelength and intensity is an LED that emits a 20 kHz optical signal for fire detection, or an LED that emits light intermittently with a light pulse of 100 microseconds and a light emission cycle of 2 seconds.

The amplifier unit 20 amplifies the voltage value output from the light receiving element 12 and outputs it to the control unit 30.

When detecting smoke, the control unit 30 controls the light-emitting element 11 to emit light at a predetermined timing. The control unit 30 then receives the voltage value received via the light-receiving element 12 and amplifier unit 20 in response to the emission of light from the light-emitting element 11 as a feature value that changes due to the occurrence of a fire. Furthermore, the control unit 30 detects the occurrence of smoke when the feature value exceeds a preset fire threshold, and determines that a fire has occurred.

In addition, if the control unit 30 determines that a fire has occurred, it can report the occurrence of a fire to the outside via the alarm unit 40. By executing this series of processes, the control unit 30 executes the fire determination process.

Next, the environmental monitoring function, which is a technical feature of the fire detector of the present disclosure, will be described in detail. Figure 2 is a functional block diagram showing the internal configuration of the control unit 30 included in the fire detector 1 of embodiment 1 of the present disclosure. The control unit 30 includes a fire detection processing unit 31 and an environmental monitoring processing unit 32.

The fire detection processing unit 31 executes the series of fire detection processes described above during fire monitoring. Meanwhile, the environmental monitoring processing unit 32 executes an environmental monitoring function that changes the fire detection sensitivity by dynamically changing the fire threshold according to the installation environment.

Specific examples of installation environments include smoking rooms and hotel bathrooms, where steam, dust, cigarette smoke, etc. can cause the device to mistakenly recognize a fire when there is none, resulting in a "false fire alarm."

Figure 3 is a flowchart showing a series of processes of the environmental monitoring function for updating the fire threshold executed by the environmental monitoring processing unit 32 in embodiment 1 of the present disclosure. Figure 4 is an explanatory diagram of the environmental monitoring function for updating the fire threshold in embodiment 1 of the present disclosure. The environmental monitoring function for dynamically changing the fire threshold will be described in detail using Figures 3 and 4.

First, the technical meanings of the terms shown in FIG. 4 used in performing the environmental monitoring function for updating the fire thresholds are listed below.
"Time series data": A data sequence generated by the control unit 30 at predetermined intervals as feature data that changes as a fire breaks out. In the example of Fig. 1, the control unit 30 sequentially acquires, via the amplifier unit 20, voltage values corresponding to the intensity of light scattered by smoke particles as feature data.

It is also possible to generate time-series data of feature quantities within the control unit 30 based on physical quantities obtained from an external source. In other words, the feature quantities are extracted by the control unit 30 as values that change in response to the occurrence of a fire.

"Fire threshold (initial value)": This is an initially set value used to compare the magnitude of each feature in the time series data. If a feature greater than this value is detected, this is the threshold used to determine that a fire has occurred.

"Fire threshold (updated value)": This fire threshold is dynamically updated according to the installation environment in order to change the fire detection sensitivity by executing the environmental monitoring function for updating the fire threshold, described below.

"Upper limit value": A value for specifying the upper limit of the "environmental judgment region", which is a value that is set in advance as a value lower than the fire threshold value.
"Lower limit value": A value for specifying the lower limit of the "environment determination region", which is a value that is set in advance as a value lower than the upper limit value.

"Environmental Judgment Region": A range of values defined by an "upper limit" and a "lower limit". This region is used to monitor the occurrence of features with values lower than the fire threshold, and to count the number of times that a non-fire alarm does not actually occur, but quantitatively indicates that the environment is prone to non-fire alarms.

"Determination period": A pre-set value used to count the number of times that quantitatively indicate that the environment is prone to false fire alarms.

"Environmental Determination Threshold": Although not shown in Figure 4, this is a threshold used to determine whether to change from the "Fire Threshold (Initial Value)" to the "Fire Threshold (Updated Value)." Specifically, this is a threshold used for comparison with the number of environmental determinations described below.

Using these terms and the explanatory diagram of Figure 4, each step in the flowchart of Figure 3 will be explained in order. In step S301, the environment monitoring processing unit 32 generates time-series data by sequentially acquiring feature amounts. Figure 4 shows an example of time-series data related to feature amounts when the evaluation period is 25 days.

Figure 4 illustrates an example of a state in which the time-series data of the feature values transitions within values below the fire threshold over the judgment period, but also transitions within a range of environmental judgment regions established to prevent false fire alarms and quantitatively determine whether the current installation environment is prone to false fire alarms.

Next, in step S302, the environment monitoring processing unit 32 counts the number of times that the feature value changes from a value below the lower limit to within the environment determination range over a predetermined determination period, in relation to the transition state of the feature value from the time-series data. Based on the determination period shown in Figure 4 and the relationship between the transition state of the time-series data and the environment determination range, the number of environment determinations will be counted as four over the 25-day determination period.

In this way, the environmental monitoring processing unit 32 can quantitatively determine whether the current environment is prone to generating non-fire alarms by counting the number of times a feature value enters the environmental judgment area set up to monitor the occurrence of feature values lower than the fire threshold.

Next, in step S303, the environment monitoring processing unit 32 determines whether the number of environment determinations, which is the count result in step S302, exceeds a preset environment determination threshold. For simplicity's sake, let's assume that the environment determination threshold is set to three times, and the determination in step S303 will be YES.

If step S303 returns YES, the process proceeds to step S304, where the environmental monitoring processing unit 32 changes the fire threshold to an updated value higher than the initial value. Then, once step S304 has been completed, or if step S303 returns NO, the environmental monitoring processing unit 32 ends the series of processes.

By performing this series of processes, the environmental monitoring processing unit 32 can dynamically change the fire threshold according to the installation environment, thereby changing the fire detection sensitivity. In other words, by performing this series of processes, the environmental monitoring processing unit 32 quantitatively determines whether the installation environment is prone to false fire alerts, and if it determines that the installation environment is prone to false fire alerts, it can lower the fire detection sensitivity by changing the fire threshold to an updated value higher than the initial value, thereby making it possible to prevent false fire alerts from occurring.

When performing the update process in step S304, the environmental monitoring processing unit 32 can also change the fire threshold to a higher updated value depending on the count value of the number of environmental judgments during the judgment period, so that the more the number, the higher the update value.

In addition, although not shown in the flowchart of Figure 3, the environmental monitoring processing unit 32 within the control unit 30 has a function for changing the fire threshold that is different from the environmental monitoring function, and if the other function is set to a higher priority than the environmental monitoring function, it is possible to prevent the environmental monitoring function from changing the fire threshold setting during the period when the other function is enabled.

For example, if a separate function, a nighttime function for setting appropriate fire thresholds at night, is set as a higher priority than the environmental monitoring function, the environmental monitoring processing unit 32 will not change the setting of the fire thresholds using the environmental monitoring function during the period when the nighttime function is enabled.

The upper limit is set to a value that does not exceed the initial fire threshold. This is because if the upper limit were set to the same value or higher than the fire threshold, the feature would also exceed the fire threshold, preventing a situation that should normally be judged as a fire from being judged as a non-fire. In this case, by setting the upper limit to a level slightly lower than the fire threshold, if the feature is above the upper limit but below the fire threshold, the monitoring function can be changed to treat the situation as being close to a fire, such as strengthening fire monitoring while still allowing environmental monitoring to function, or judging the environment to be a non-fire environment close to a fire.

The series of processes shown in Figure 3 can be executed repeatedly during the period in which the environmental monitoring function for updating the fire threshold is enabled.

Next, we will explain the series of processes for restoring the fire threshold, which changes the fire threshold from the initial value to an updated value and then returns it to the initial value. Figure 5 is a flowchart related to the series of processes of the environmental monitoring function for restoring the fire threshold executed by the environmental monitoring processing unit 32 in embodiment 1 of the present disclosure. Figure 6 is also an explanatory diagram related to the environmental monitoring function for restoring the fire threshold in embodiment 1 of the present disclosure. The environmental monitoring function will be explained in detail using Figures 5 and 6.

First, the technical meanings of the terms shown in Figure 6, which are used when performing the environmental monitoring function for restoring fire thresholds, are listed below. Explanations of terms that are the same as those in Figure 4 will be omitted.

"Return Determination Period": A pre-set period for determining whether the "Fire Threshold (Updated Value)", which was changed from the "Fire Threshold (Initial Value)" as a result of executing the environmental monitoring function for updating the fire threshold shown in Figure 3, should be returned to the original "Fire Threshold (Initial Value)".

"Return Determination Threshold": This is the threshold used in the return determination process to return the "Fire Threshold (Updated Value)", which was changed from the "Fire Threshold (Initial Value)" as a result of executing the environmental monitoring function for updating the fire threshold shown in Figure 3, to the original "Fire Threshold (Initial Value)". Specifically, this is the threshold used for comparison with the return determination count described below.

Using these terms and the explanatory diagram of Figure 6, each step in the flowchart of Figure 5 will be explained in order. In step S501, the environment monitoring processing unit 32 generates time-series data by sequentially acquiring feature amounts. Figure 6 shows an example of time-series data related to feature amounts when a 30-day recovery determination period is used.

Figure 6 illustrates an example in which the time-series data for the feature value transitions at a value smaller than the return determination threshold value over the return determination period, and the feature value remains below the return determination threshold value.

Next, in step S502, the environment monitoring processing unit 32 counts the number of times that the feature value changes so as to exceed the recovery determination threshold value over a preset recovery determination period, in relation to the transition state of the feature value in the time-series data. Based on the recovery determination period shown in Figure 6 and the relationship between the transition state of the time-series data and the recovery determination threshold value, the number of recovery determinations over a 30-day recovery determination period will be counted as 0.

In this way, the environmental monitoring processing unit 32 can quantitatively determine whether the current environment is no longer prone to generating non-fire alarms by counting the number of times the feature exceeds the recovery determination threshold.

Next, in step S503, the environment monitoring processing unit 32 determines whether the number of recovery determinations, which is the count result from step S502, is 0. In this case, since the number of recovery determinations was counted as 0 in the previous step S502, the determination in step S503 is YES.

If step S503 returns YES, the process proceeds to step S504, where the environmental monitoring processing unit 32 resets the fire threshold to an initial value lower than the updated value. Then, if step S504 is completed, or if step S503 returns NO, the environmental monitoring processing unit 32 ends the series of processes.

By performing this series of processes, the environmental monitoring processing unit 32 can dynamically change the fire threshold according to the installation environment, thereby changing the fire detection sensitivity. In other words, by performing this series of processes, the environmental monitoring processing unit 32 quantitatively determines whether the installation environment is no longer one in which non-fire alarms are likely to occur, and if it determines that the installation environment has returned to the initial environment in which non-fire alarms are unlikely to occur, it re-sets the fire threshold to an initial value that is lower than the updated value, thereby improving the fire detection sensitivity to its original value and enabling highly accurate detection of fires.

In the process described using Figures 5 and 6, the recovery determination period is set to a period longer than the determination period, and the recovery determination threshold is set to a value lower than the lower limit. As a result, a hysteresis characteristic can be imparted when the fire threshold is reconfigured to an initial value lower than the updated value.

Note that in the judgment process in step S503, the number of recovery judgments was compared with 0, but it is also possible to compare it with a value greater than or equal to 1.

In addition, when executing the restoration process in step S504, the environment monitoring processing unit 32 can also change the setting depending on the count value of the number of restoration determinations during the restoration determination period, so that the fewer the number, the closer the fire threshold is to the initial value.

The series of processes shown in Figure 5 can be executed repeatedly in sequence during the period in which the environmental monitoring function for restoring the fire threshold is enabled.

In addition, in Figure 4, the judgment period is set to 25 days, and in Figure 6, the recovery judgment period is set to 30 days, but these settings are just examples, and appropriate periods can be set depending on the installation environment.

As described above, according to embodiment 1, by dynamically changing the fire threshold based on the transition state of the feature values that change in response to the occurrence of a fire, it is possible to automatically change the fire detection sensitivity to a level appropriate for the installation environment. In other words, it is possible to quantitatively determine whether the current installation environment is prone to the occurrence of non-fire alarms before a non-fire alarm actually occurs, and to realize a fire detector that can quickly implement measures to reduce non-fire alarms without operator intervention.

In this first embodiment, the fire threshold is changed based on the time series data of the fire detector, but similar control may also be performed on the fire receiver side. In this case, the fire detector outputs the time series data (analog data) along with its address to the receiver, and the receiver determines whether the time series data falls within the environment judgment area.

1 Fire detector, 11 Light-emitting element, 12 Light-receiving element, 20 Amplification unit, 30 Control unit, 31 Fire detection processing unit, 32 Environmental monitoring processing unit, 40 Alarm unit.

Claims (4)

A fire detector including a control unit that extracts a feature amount that changes in response to the occurrence of a fire and determines whether a fire has occurred when the feature amount exceeds a fire threshold,
The control unit
an environment determination area is set, the environment determination area being defined by an upper limit value that is a value lower than the fire threshold and a lower limit value that is a value lower than the upper limit value, in order to monitor occurrence conditions of feature quantities that are lower than the fire threshold;
generating time-series data by sequentially acquiring the feature amounts;
counting the number of times that the feature value changes from a value less than the lower limit value to within the environment determination range over a predetermined determination period, as an environment determination count, with respect to a transition state of the feature value according to the time-series data;
When the number of environmental determinations exceeds a preset environmental determination threshold, the fire threshold is changed to an updated value higher than the initial value;
A fire detector equipped with an environmental monitoring function that dynamically changes the fire threshold according to the installation environment, thereby changing the detection sensitivity for fire occurrence. The control unit
The fire detector according to claim 1 , wherein the fire threshold is changed to a higher updated value as the number of environmental determinations during the determination period increases according to a count value of the number of environmental determinations during the determination period. The control unit
In order to restore the fire threshold value, which has been changed to the updated value, to the initial value, a restoration determination period that is a period longer than the determination period and a restoration determination threshold value that is a value lower than the lower limit value are set in advance,
3. The fire detector according to claim 1, wherein, when a transition state of a feature based on the time series data remains below the recovery determination threshold for the recovery determination period, the fire threshold is changed to the initial value. The control unit
A fire detector as described in any one of claims 1 to 3, which is provided with a function different from the environmental monitoring function as a function for changing the fire threshold, and if the other function is set to a higher priority than the environmental monitoring function, the fire threshold setting change by the environmental monitoring function is not performed during a period in which the other function is enabled.