FIRE DETECTION SYSTEM AND FIRE DETECTION METHOD

Abstract

A fire detection system includes a transmitter including a light source that sends an optical signal and a receiver including a detector that detects the optical signal sent from the light source through a predetermined light propagation section, a signal processing unit that calculates at least one of a first gas concentration, a first smoke concentration, and a first temperature in the light propagation section based on the optical signal, a sensor that acquires at least one of a second gas concentration, a second smoke concentration, and a second temperature in the surroundings, and a determiner that determines whether there is a fire by comparing at least one of the first gas concentration, the first smoke concentration, and the first temperature with at least one of the second gas concentration, the second smoke concentration, and the second temperature in the surroundings.

Claims

1. A fire detection system comprising: a transmitter including a light source configured to send an optical signal; and a receiver comprising: a detector configured to detect the optical signal sent from the light source through a predetermined light propagation section; a signal processing unit configured to calculate at least one of a first gas concentration, a first smoke concentration, and a first temperature in the light propagation section based on the optical signal detected by the detector; a sensor configured to acquire at least one of a second gas concentration, a second smoke concentration, and a second temperature in the surroundings; and a determiner configured to determine whether or not there is a fire by comparing at least one of the first gas concentration, the first smoke concentration, and the first temperature calculated by the signal processing unit with at least one of the second gas concentration, the second smoke concentration, and the second temperature in the surroundings acquired by the sensor.

2. The fire detection system according to claim 1, wherein the transmitter and the receiver are integrated as a transceiver, the fire detection system further comprises a first reflection unit disposed at a predetermined distance from the transceiver, the predetermined light propagation section is formed between the transceiver and the first reflection unit, and the optical signal sent from the light source of the transceiver reciprocates in the predetermined light propagation section between the transceiver and the first reflection unit.

3. The fire detection system according to claim 1, wherein the sensor includes at least one of a gas sensor configured to measure the second gas concentration around the receiver, a smoke detector configured to measure the second smoke concentration around the receiver, and a temperature sensor configured to measure the second temperature around the receiver.

4. The fire detection system according to claim 2, wherein the signal processing unit and the sensor are integrated as a hybrid processing unit, and the transceiver further includes a second reflection unit configured to reflect the optical signal sent from the light source and an optical switch configured to switch between a direction of the first reflection unit and a direction of the second reflection unit and then emit the optical signal sent from the light source, and the hybrid processing unit is configured to calculate at least one of the first gas concentration, the first smoke concentration, and the first temperature in the light propagation section based on the optical signal reflected from the first reflection unit and detected by the detector, and at least one of the second gas concentration, the second smoke concentration, and the second temperature in the surroundings based on the optical signal reflected from the second reflection unit and detected by the detector.

5. The fire detection system according to claim 1, wherein the determiner is configured to calculate a difference between at least one of the first gas concentration, the first smoke concentration, and the first temperature in the predetermined light propagation section of the optical signal calculated by the signal processing unit and at least one of the second gas concentration, the second smoke concentration, and the second temperature in the surroundings acquired by the sensor, respectively, and determine that the fire has occurred when each difference is greater than a threshold.

6. The fire detection system according to claim 5, wherein the determiner is configured to calculate an amount of change in the difference per unit time and determine that the fire has occurred when the calculated amount of change is greater than a threshold.

7. A fire detection method comprising: sending an optical signal from a light source; detecting the optical signal sent from the light source through a predetermined light propagation section; calculating at least one of a first gas concentration, a first smoke concentration, and a first temperature in the light propagation section based on the detected optical signal; acquiring at least one of a second gas concentration, a second smoke concentration, and a second temperature in the surroundings; and determining whether or not there is a fire by comparing at least one of the calculated first gas concentration, the calculated first smoke concentration, and the calculated first temperature with at least one of the acquired second gas concentration, the acquired second smoke concentration, and the acquired second temperature in the surroundings.

Description

EFFECT OF THE FIRST EXAMPLE EMBODIMENT

[0029] According to the first example embodiment, the following effects can be achieved.

[0030] A first effect is that a fire can be accurately detected when a environmental change occurs while, for example, vehicles travel under a condition where there can be a large environmental change such as in a road tunnel. A reason for this is that, in the related art, a determination of whether there is a fire is made based only on the gas concentration and smoke concentration in the long distance light propagation section. For this reason, when the environmental change is large, erroneous identification is often caused. On the other hand, in the first example embodiment, as described above, the local second gas concentration, the local second smoke concentration, and the local second temperature around the receiver (12) are incorporated into the flow of determining whether there is a fire as environmental reference values, so that the influence of the environmental change can be canceled.

[0031] The first example embodiment is not limited to the above configuration. For example, in the first example embodiment, the light source (111) is configured as a laser light source and instead the light source (111) may be configured as a broadband light source such as an LED (Light Emitting Diode) or an SLD (Super Luminescent Diode). The signal processing unit (123) may measure the gas concentration by DOAS accordingly.

[0032] An optical amplifier may be inserted into an output stage of the light source (111) or an input stage of the detector (122). By doing so, the signal-to-noise ratio of the received optical signal can be improved, and the accuracy of the measurement result can be improved.

[0033] The determiner (127) uses the carbon monoxide (CO) concentration as an indicator for determining a fire state but the indicator of determining the fire state is not limited to this. The determiner (127) may use, as the indicator for determining the fire state, a carbon dioxide (CO.sub.2) concentration, a water vapor (H.sub.2O) concentration, or a ratio of the CO concentration to the CO.sub.2 concentration as described in Non Patent Literature 4, etc. The output wavelength λ.sub.1 of the light source (111) may be set as the absorption wavelength of CO.sub.2 or H.sub.2O accordingly. A plurality of kinds of gas concentrations may be measured using a plurality of light sources.

[0034] In the first example embodiment, CO is selected as the gas species to be measured, and 10 [ppm] is set as a gas concentration threshold, but the present disclosure is not limited thereto. Another value may be set as the threshold, or the determination may be made using another gas concentration. Further, although 0.4 [1/m] is set as a smoke concentration threshold, another value may be set as this threshold.

[0035] In the first example embodiment, the signal processing unit (123) measures the average space temperature in the predetermined light propagation section based on the spread of the spectral width of the absorption spectrum, but the present disclosure is not limited thereto. The signal processing unit (123) may measure the average space temperature on an optical axis based on two line thermometry as shown in Non Patent Literature 5.

[0036] In the first example embodiment, the determiner (127) determine whether theres is a fire using the difference between measured values of the gas concentrations, the smoke concentrations, and the temperatures, but the present disclosure is not limited thereto. The determiner (127) may determine whether there is a fire based on an amount of change in the difference between the measured values per unit time. The determiner (127) determines that a fire has occurred when the amount of change in the difference between the measured values per unit time is greater than a threshold.

[0037] In the first example embodiment, the determiner (127) determines whether there is a fire by referring to all the measured values of the gas concentration, the smoke concentration, and the temperature, but the present disclosure is not limited thereto. The determiner (127) may determine whether there is a fire by referring to one or two of the gas concentration, the smoke concentration, and the temperature.

SECOND EXAMPLE EMBODIMENT

[0038] A second example embodiment of the present disclosure will be described with reference to FIGS. 3 and 4. In the first example embodiment, the transmitter (11) and the receiver (12) are placed at spatially separated positions, and the first gas concentration, the first smoke concentration, and the first temperature in the space of the light propagation section are measured. On the other hand, in the second example embodiment, the optical signal from a transceiver (42) is returned at a first reflection unit (41), and the first gas concentration, the first smoke concentration, and the first temperature in the light propagation section are measured.

Configuration of the Second Example Embodiment

[0039] FIG. 4 is a block diagram showing the configuration of the second example embodiment. A fire detection system (2) according to the second example embodiment of the present disclosure includes the first reflection unit (41) and the transceiver (42). The transceiver (42) includes the transmitter (11) and the receiver (12) described above, which are accomodated in one housing and are integrated. The first reflection unit (42) is disposed at a predetermined distance from the transceiver (41). A predetermined light propagation section is formed between the transceiver (42) and the first reflection unit (41). The optical signal transmitted from the transceiver (42) reciprocates between the transceiver (42) and the first reflection unit (41). The fire detection system (2) propagates the optical signal between the transceiver (42) and the first reflection unit (41), and measures the first gas concentration, the first smoke concentration, and the first temperature in the space of the light propagation section. The transceiver (42) includes a light source (4201), condensers (4202, 4205), multiplexers/demultiplexers (4203, 4204), a detector (4206), a signal processing unit (4207), a gas sensor (4208), a smoke detector (4209), a temperature sensor (4210), and a determiner (4211).

Operation of the Second Example Embodiment

[0040] The light source (4201) outputs the optical signal having a wavelength λ.sub.1 μm. The condenser (4202) converts the optical signal from the light source (4201) into a quasi-parallel beam. The multiplexers/demultiplexers (4203, 4204) emit the quasi-parallel beam from the condenser (4202) into space. The optical signal emitted from the transceiver (42) is reflected by the first reflection unit (41) and returned to the transceiver (42). Here, the first reflection unit (41) is a retroreflector. The first reflection unit (41) reflects the optical signal in a direction parallel to the propagation direction of the optical signal propagated from the transceiver (42). Thus, the optical signal accurately returns to the transceiver (42).

[0041] The returned optical signal passes through the multiplexer/demultiplexer (4204), condensed by the condenser (4205), and photoelectrically converted by the detector (4206). The signal processing unit (4207) processes the electric signal photoelectrically converted by the detector (4206) to thereby calculate the first gas (CO) concentration, the first smoke concentration, and the first temperature between the transceiver (42) and the first reflection unit (41). Since the method of calculating the measured values is the same as the method of calculating the measured value described in the first example embodiment, a detailed description thereof is omitted.

[0042] The gas sensor (4208) measures the second gas concentration around the transceiver (42). The smoke detector (4209) measures the second smoke concentration around the transceiver (42). The temperature sensor (4210) measures the second temperature around the transceiver (42).

[0043] The determiner (4211) determines a fire state using the above measurement results of the first and second gas concentrations, the first and second smoke concentrations, and the first and second temperatures as parameters based on the flowchart shown in FIG. 3.

EFFECT OF THE SECOND EXAMPLE EMBODIMENT

[0044] According to the second example embodiment, the following effects can be achieved.

[0045] A first effect is that, in a manner similar to the first example embodiment, a fire can be accurately detected when a environmental change occurs while, for example, vehicles travel under a condition where there can be a large environmental change such as in a road tunnel. A reason for this is that, in the related art, a determination of whether there is a fire is made based only on the gas concentration and smoke concentration in the long distance light propagation section.

For this reason, when the environmental change is large, erroneous determination is often caused. On the other hand, in the second example embodiment, as described above, the local second gas concentration, the local second smoke concentration, and the local second temperature around the transceiver (42) are incorporated into the flow of determining whether there is a fire as environmental reference values, so that the influence of the environmental change can be canceled.

[0046] A second effect is that the work at the time of the sensor installation can be facilitated. A reason for this is that, in Patent Literature 1 and the first example embodiment, the transmitter (11) and the receiver (12), which require power supplies, are separated at two places, and thus power supply installation work is required at each place. On the other hand, the configuration according to the second example embodiment is such that the parts requiring the power supply are integrated into one transceiver (42), and another part not requiring the power supply is a passive component, i.e., the first reflection unit 41, so that the power supply installation work is required in only one place.

[0047] The second example embodiment is not limited to the above configuration. For example, in the second example embodiment, the light source (4201) is configured as a laser light source and instead the light source (4201) may be configured as a broadband light source such as an LED (Light Emitting Diode) or an SLD (Super Luminescent Diode). The signal processing unit (4207) may measure the gas concentration by DOAS accordingly.

[0048] In the second example embodiment, as shown in FIG. 4, a driver for driving the light source (4201) is not explictly specified, but it is assumed that the laser wavelength and intensity are appropriately controlled.

[0049] An optical amplifier may be inserted into an output stage of the light source (4201) or an input stage of the detector (4206). By doing so, the signal-to-noise ratio of the received optical signal can be improved, and the accuracy of the measurement result can be improved.

[0050] The determiner (4211) uses the CO concentration as an indicator for determining a fire state but the indicator of determining the fire state is not limited to this. The determiner (4211) may use, as the indicator for determining the fire state, a carbon dioxide (CO.sub.2) concentration, a water vapor (H.sub.2O) concentration, or a ratio of the CO concentration to the CO.sub.2 concentration as described in Non Patent Literature 4, etc. The output wavelength λ.sub.1 of the light source (4201) may be set as the absorption wavelength of CO.sub.2 or H.sub.2O accordingly. A plurality of kinds of gas concentrations may be measured using a plurality of light sources.

[0051] In the second example embodiment, CO is selected as the gas species to be measured, and 10 [ppm] is set as a gas concentration threshold, but the present disclosure is not limited thereto. Another value may be set as the threshold, or the determination may be made using another gas concentration. Further, although 0.4 [1/m] is set as the smoke concentration threshold, another value may be set as this threshold.

[0052] In the second example embodiment, the signal processing unit (4207) measures the average space temperature in the predetermined light propagation section based on the spread of the spectral width of the absorption spectrum, but the present disclosure is not limited thereto. The signal processing unit (4207) may measure the average space temperature on an optical axis based on two line thermometry as shown in Non Patent Literature 5.

[0053] In the second example embodiment, the determiner (4211) determines whether there is a fire using the difference between measured values of the gas concentrations, the smoke concentrations, and the temperatures, but the present disclosure is not limited thereto. The determiner (4211) may determine whether there is a fire based on an amount of change in the difference between the measured values per unit time.

[0054] In the second example embodiment, the first reflection unit (41) is configured as a retroreflective reflector to reflect spatially propagated optical signals, but the present disclosure is not limited thereto. The first reflection unit (41) may be configured as a simple plane mirror.

[0055] In the second example embodiment, the determiner (4211) determines whether there is a fire by referring to all the measured values of the gas concentration, the smoke concentration, and the temperature, but the present disclosure is not limited thereto. The determiner (4211) may determine whether there is a fire by referring to one or two of the gas concentration, the smoke concentration, and the temperature.

THIRD EXAMPLE EMBODIMENT

[0056] A third example embodiment of the present disclosure will be described with reference to FIGS. 3, 5, and 6. The fire detection systems (1) and (2) according to the first and second example embodiments use individual point sensors to measure the local second gas concentration, the local second smoke concentration, and the local second temperature around the receiver (12) and the transceiver (42). On the other hand, a fire detection system (3) according to the third example embodiment measures the local second gas concentration, the local second smoke concentration, and the local second temperature using an optical signal.

Configuration of the Third Example Embodiment

[0057] FIG. 5 is a block diagram showing the configuration of the third example embodiment. The fire detection system (3) according to the third example embodiment of the present disclosure includes a first reflection unit (51) and a transceiver (52). The fire detection system (3) transmits the optical signal between the transceiver (52) and the first reflection unit (51), and measures the first gas concentration, the first smoke concentration and the first temperature in a space between the transceiver (52) and the first reflection unit (51). The transceiver (52) includes a light source (5201), condensers (5202, 5205), multiplexer/demultiplexer (5203), an optical switch (5204), a detector (5206), a hybrid processing unit (5207), a second reflection unit (5208), and a determiner (5209). cl Operation of the Third Example Embodiment

[0058] The light source (5201) outputs the optical signal having a wavelength λ.sub.1 μm. The condenser (5202) converts the optical signal from the light source (5201) into a quasi-parallel beam. The quasi-parallel beam passes through the multiplexer/demultiplexer (5203) and enters the optical switch (5204). As shown in FIG. 6, the optical switch (5204) emits the optical signal to discharge paths 1 or 2 depending on the time.

[0059] During a time T1, the optical switch (5204) emits the optical signal input from the multiplexer/demultiplexer (5203) in a direction (hereinafter referred to as the discharge path 1) of the first reflection unit (51), and outputs the optical signal input from the discharge path 1 in a direction of the condenser (5205). The optical signal emitted from the transceiver (52) is reflected by the first reflection unit (51) and returned to the transceiver (52). Here, the first reflection unit (51) is a retroreflector. The first reflection unit (51) reflects the optical signal in a direction parallel to the propagation direction of the optical signal propagated from the transceiver (52). Thus, the optical signal accurately returns to the transceiver (52). The returned optical signal passes through the optical switch (5204), condensed by the condenser (5205), and photoelectrically converted by the detector (5206). The hybrid processing unit (5207) performs predetermined processing on the electric signal photoelectrically converted by the detector 5206 to thereby calculate the first gas (CO) concentration, the first smoke concentration, and the first temperature between the transceiver (52) and the first reflection unit (51). Since the method of calculating the measured values is the same as the method of calculating the measured value described in the first example embodiment, a detailed description thereof is omitted.

[0060] During a time T2, the optical switch (5204) emits the optical signal input from the multiplexer/demultiplexer (5203) in a direction (hereinafter referred to as the discharge path 2) of the second reflection unit (5205), and outputs the optical signal input from the discharge path 2 in a direction of the condenser (5208). The optical signal emitted from the optical switch (5204) is reflected by the second reflection unit (5208) and returned to the optical switch (5204). Here, the second reflection unit (5208) is a retroreflector. The second reflection unit (5208) reflects the optical signal in a direction parallel to the propagation direction of the optical signal propagated from the optical switch (5204). Thus, the optical signal accurately returns to the optical switch (5204). The returned optical signal passes through the optical switch (5204), condensed by the condenser (5205), and photoelectrically converted by the detector (5206). The hybrid processing unit (5207) performs predetermined processing on the electric signal photoelectrically converted by the detector 5206 to thereby calculate the second gas (CO) concentration, the second smoke concentration, and the second temperature around the transceiver (52). Since the method of calculating the measured values is the same as the method of calculating the measured value described in the first example embodiment, a detailed description thereof is omitted.

[0061] The determiner (5209) determines a fire state using the above measurement results of the first and second gas concentrations, the first and second smoke concentrations, and the first and second temperatures as parameters based on the flowchart shown in FIG. 3.

EFFECT OF THE THIRD EXAMPLE EMBODIMENT

[0062] According to the third example embodiment, the following effects can be achieved.

[0063] A first effect is that, in a manner similar to the first and second example embodiments, a fire can be accurately detected when a environmental change occurs while, for example, vehicles travel under a condition where there can be a large environmental change such as in a road tunnel. A reason for this is that, in the related art, a determination of whether there is a fire is made based only on the gas concentration and smoke concentration in the long distance light propagation section. For this reason, when the environmental change is large, erroneous determination is often caused. On the other hand, in the third example embodiment, as described above, the local second gas concentration, the local second smoke concentration, and the local second temperature around the transceiver (52) are incorporated into the flow of determining whether there is a fire as environmental reference values, so that the influence of the environmental change can be canceled.

[0064] A second effect is that, in a manner similar to the second example embodiment, the work at the time of the sensor installation can be facilitated. A reason for this is that, in Patent Literature 1 and the first example embodiment, the transmitter (11) and the receiver (12), which require power supplies, are separated at two places, and thus power supply installation work is required at each place.

On the other hand, the configuration according to the third example embodiment is such that the parts requiring the power supply are integrated into one transceiver (52), and another part not requiring the power supply is a passive component, i.e., the first reflection unit (51), so that the power supply installation work is required in only one place.

[0065] A third effect is that the sensor configuration can be simplified and the number of parts can be reduced. A reason for this is that, in the first and second example embodiments, the gas sensor, the smoke detector, and the temperature sensor are used to acquire local environmental information, so that the number of parts is increased. On the other hand, in the third example embodiment, peripheral environmental information is acquired by utilizing the optical signal for measuring the long distance section. For this reason, the sensor configuration can be simplified and the number of parts can be reduced.

[0066] The third example embodiment is not limited to the above configuration. For example, in the third example embodiment, the light source (5201) uses a laser light source and instead a broadband light source such as an LED (Light Emitting Diode) or an SLD (Super Luminescent Diode) may be used. The hybrid processing unit (5207) may measure the gas concentration by DOAS accordingly.

[0067] In the third example embodiment, as shown in FIG. 5, a driver for driving the light source (5201) is not explictly specified, but it is assumed that the laser wavelength and intensity are appropriately controlled.

[0068] An optical amplifier may be inserted into an output stage of the light source (5201) or an input stage of the detector (5206). By doing so, the signal-to-noise ratio of the received optical signal can be improved, and the accuracy of the measurement result can be improved.

[0069] The determiner (5209) uses the CO concentration as an indicator for determining a fire state but the indicator of determining the fire state is not limited to this. The determiner (5209) may use, as the indicator for determining the fire state, a carbon dioxide (CO.sub.2) concentration or a water vapor (H.sub.2O) concentration. The determiner (5209) may use, the the indicator for determining the fire state, a ratio of the CO concentration to the CO.sub.2 concentration as described in Non Patent Literature 4, etc. The output wavelength λ.sub.1 of the light source (5201) may be set as the absorption wavelength of CO.sub.2 or H.sub.2O accordingly. A plurality of kinds of gas concentrations may be measured using a plurality of light sources.

[0070] In the third example embodiment, CO is selected as the gas species to be measured, and 10 [ppm] is set as a gas concentration threshold, but the present disclosure is not limited thereto. Another value may be set as the threshold, or the determination may be made using another gas concentration. Further, although 0.4 [1/m] is set as a smoke concentration threshold, another value may be set as this threshold.

[0071] In the third example embodiment, the hybrid processing unit (5207) measures the average space temperature in the light propagation section based on the spread of the spectral width of the absorption spectrum, but the present disclosure is not limited thereto. The hybrid processing unit (5207) may measure the average space temperature on an optical axis based on two line thermometry as shown in Non Patent Literature 5.

[0072] In the third example embodiment, the determiner (5209) determines whether there is a fire using the difference between measured values of the gas concentrations, the smoke concentrations, and the temperatures, but the present disclosure is not limited thereto. The determiner (5209) may determine whether there is a fire based on an amount of change in the difference between the measured values per unit time.

[0073] In the third example embodiment, the first reflection unit (51) is configured as a retroreflective reflector to reflect spatially propagated optical signals, but the present disclosure is not limited thereto. The first reflection unit (51) may be configured as a simple plane mirror.

[0074] In the third example embodiment, the determiner (5209) determines whether there is a fire by referring to all the measured values of the gas concentration, the smoke concentration, and the temperature, but the present disclosure is not limited thereto. The determiner (5209) may determine whether there is a fire by referring to one or two of the gas concentration, the smoke concentration, and the temperature.

[0075] Although the present disclosure has been described with reference to the above example embodiments, the present disclosure is not limited by the above. Various changes that can be understood by a person skilled in the art within the scope of the disclosure may be made to the configurations and details of the present disclosure.

[0076] The present disclosure can also be realized by causing the CPU to execute the processing shown in FIG. 3 by a computer program.

[0077] The program can be stored and provided to a computer using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (Read Only Memory), CD-R, CD-R/W, and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory), etc.).

[0078] The program may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g. electric wires, and optical fibers) or a wireless communication line.

INDUSTRIAL APPLICABILITY

[0079] The present disclosure is applicable to fire detection in a wide space. In particular, the present disclosure is applicable to fire detection in a situation where various ignition sources such as a road tunnel are present and various gases such as exhaust gas are present.

REFERENCE SIGNS LIST

[0080] 1, 2, 3 FIRE DETECTION SYSTEM

[0081] 11, 71 TRANSMITTER

[0082] 12, 72 RECEIVER

[0083] 111, 4201, 5201, 711 LIGHT SOURCE

[0084] 112, 712 DRIVER

[0085] 115, 121, 4202, 4205, 5202, 5205, 713, 721 CONDENSER

[0086] 122, 4206, 5206, 723 DETECTOR

[0087] 123, 4207, 725 SIGNAL PROCESSING UNIT

[0088] 5207 HYBRID PROCESSING UNIT

[0089] 124, 4208 GAS SENSOR

[0090] 125, 4209 SMOKE DETECTOR

[0091] 126, 4210 TEMPERATURE SENSOR

[0092] 127, 4211, 5209, 727 DETERMINER

[0093] 41, 51 FIRST REFLECTION UNIT

[0094] 5208 SECOND REFLECTION UNIT

[0095] 42, 52 TRANSCEIVER

[0096] 4203, 4204, 5203 MULTIPLEXER/DEMULTIPLEXER

[0097] 5204 OPTICAL SWITCH