Fire detection system

Abstract

To provide a fire detection system that enables enhancing detection accuracy of a fire.SOLUTION: A disaster prevention system, which detects a fire occurring in an object area, comprises: a wave transmission unit 11 that transmits a sound wave to an object area; a wave reception unit 12 that receives the sound wave; temperature identification means of identifying a temperature of the object area on the basis of time until the sound reception unit 12 receives the sound wave the wave transmission unit 11 transmits; and fire detection means of detecting the fire occurring in the object area on the basis of the temperature of the object area the temperature identification means identifies. The temperature identification means is configured to: identify mutual correlation information; identify a plurality of deviation times in which a degree of correlation in the correlation information is greater; identify a plurality of temperature candidates corresponding to the plurality of deviation times on the basis of a plurality of identified deviation times; and identify a temperature of the object area on the basis of a plurality of identified temperature candidates.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a fire detection system. [Background technology]

[0002] BACKGROUND ART Conventionally, a technique for detecting a fire using sound waves has been known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-117536 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, there has been a demand for a technology that can improve the accuracy of fire detection when detecting fires using sound waves.

[0005] The present invention has been made in view of the above problems, and has an object to provide a fire detection system that can improve the accuracy of fire detection. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the fire detection system described in claim 1 is a fire detection system that detects a fire that occurs in a target area, and comprises: a transmitting means for transmitting sound waves to the target area; a receiving means for receiving the sound waves; a temperature determining means for determining the temperature of the target area based on the time it takes for the sound waves transmitted by the transmitting means to be received by the receiving means; and a fire detection means for detecting a fire that occurs in the target area based on the temperature of the target area determined by the temperature determining means, wherein the temperature determining means determines cross-correlation information that determines the degree of correlation between the transmitted signal and the received signal with respect to a delay time when either the transmitted signal corresponding to the sound waves transmitted by the transmitting means or the received signal corresponding to the sound waves received by the receiving means is shifted in time, identifies a plurality of delay times at which the degree of correlation in the cross-correlation information is large, identifies a plurality of temperature candidates corresponding to the plurality of delay times based on the identified plurality of delay times, and determines the temperature of the target area based on the identified plurality of temperature candidates.

[0007] In addition, the fire detection system described in claim 2 is the fire detection system described in claim 1, wherein the temperature identification means is configured to repeatedly identify the temperature of the target area, and the temperature identification means selects from the plurality of temperature candidates a temperature candidate that is closest to the temperature of the target area identified last time, and identifies the selected temperature candidate as the temperature of the target area.

[0008] Furthermore, the fire detection system described in claim 3 is the fire detection system described in claim 1, wherein the temperature identification means identifies the delay time belonging to a second time period that is earlier than a first time period to which the delay time corresponding to the maximum correlation degree in the cross-correlation information belongs, or the delay time belonging to a third time period that is later than the first time period.

[0009] Furthermore, the fire detection system described in claim 4 is the fire detection system described in claim 1, further comprising a frequency control means for controlling the frequency of the sound waves transmitted from the transmitting means, wherein the frequency control means causes the transmitting means to transmit sound waves of a frequency in a first frequency band when it has not detected the possibility of a fire occurring in the target area, and causes the transmitting means to transmit sound waves of a frequency in a second frequency band when it has detected the possibility of a fire occurring in the target area, the second frequency band being a frequency band lower than the first frequency band.

[0010] Furthermore, the fire detection system described in claim 5 is the fire detection system described in claim 1, wherein the fire detection means detects a fire occurring in the target area based on the temperature variation in the target area identified by the temperature identification means.

[0011] In addition, the fire detection system described in claim 6 is the fire detection system described in claim 1, and further comprises a scattering detection means for detecting fire-caused scattering, which is scattering of sound waves caused by a fire occurring in the target area, based on the transmitted signal and the received signal, and the fire detection means detects a fire occurring in the target area based on the temperature of the target area identified by the temperature identification means and the detection result of the scattering detection means. [Effects of the Invention]

[0012] According to the fire detection system described in claim 1, by identifying multiple temperature candidates corresponding to multiple delay times based on the delay times in the cross-correlation information and identifying the temperature, it is possible to improve the accuracy of temperature identification, for example, and thereby improve the accuracy of fire detection.

[0013] According to the fire detection system of claim 2, by selecting the temperature candidate that is closest to the previously identified temperature from among a plurality of temperature candidates, it becomes possible to appropriately identify the temperature, for example.

[0014] According to the fire detection system described in claim 3, by identifying a delay time belonging to a second time period that is earlier than the first time period to which the delay time corresponding to the maximum correlation belongs, or a delay time belonging to a third time period that is later than the first time period, it is possible to appropriately identify the temperature, taking into account, for example, scattering of sound waves by flames and reverberation of sound waves within the target area.

[0015] According to the fire detection system described in claim 4, if the possibility of a fire has not been detected, sound waves of a frequency in the first frequency band are transmitted, and if the possibility of a fire has been detected in the target area, sound waves of a frequency in the second frequency band (a frequency band lower than the first frequency band) are transmitted.This makes it possible to use sound waves of an appropriate frequency depending on the situation regarding the fire, for example, thereby improving the accuracy of fire detection.

[0016] According to the fire detection system of claim 5, by detecting a fire based on temperature variations, it is possible to improve the accuracy of fire detection, for example.

[0017] According to the fire detection system of claim 6, by detecting a fire based on the temperature of the target area and fire-caused scattering, it is possible to improve the accuracy of fire detection, for example. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing an example of installation of a sensor according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing an example of installation of a sensor according to an embodiment of the present invention; [Figure 3] FIG. 2 is a block diagram showing a sensor. [Figure 4] FIG. 1 is an explanatory diagram of a sound wave. [Figure 5] FIG. 2 is an explanatory diagram of a transmitting-side acoustic signal. [Figure 6] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 7] FIG. 10 is an explanatory diagram of a delay time and a correlation degree. [Figure 8]10 is a flowchart of a temperature detection process. [Figure 9] FIG. 1 is a side view showing the interior of the target area. [Figure 10] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 11] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 12] 10 is a flowchart of a first fire detection process. [Figure 13] 10 is a flowchart of a second fire detection process. [Figure 14] 10 is a flowchart of a third fire detection process. [Figure 15] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 16] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 17] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 18] FIG. 1 is a side view showing the interior of the target area. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fire detection system according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the embodiment.

[0020] [Basic Concept of the Embodiment] First, the basic concept of this embodiment will be explained. This embodiment generally relates to a fire detection system.

[0021] The term "fire detection system" refers to a system that detects fires occurring in a target area, and is a concept that includes, for example, systems that have reflective fire detectors and opposing fire detectors. Note that the fire detection system may also be interpreted as a concept that includes, for example, other devices (e.g., disaster prevention receiving devices, server devices, or terminal devices) in addition to fire detectors.

[0022] A "target area" is an area in which a fire is to be detected, and is a concept that includes, for example, a specified area indoors or outdoors, and as an example, a concept that includes any area such as a room in a building or a parking space in a parking lot.

[0023] In the following embodiment, the case where the "target area" is a room will be described.

[0024] [Specific details of the embodiment] Next, specific details of the embodiment will be described.

[0025] (composition) First, the configuration of a disaster prevention system according to this embodiment will be described. Figures 1 and 2 are diagrams showing an example of installation of sensors according to this embodiment.

[0026] In this embodiment, the case where the interior shape of the room, which is the target area, is a rectangular parallelepiped will be described. That is, the case where the floor and ceiling of the target area are parallel to each other and there are four walls that are perpendicular to these floor and ceiling surfaces (all adjacent walls are perpendicular to each other) will be described. As a variation, the target area may have any other shape, or may be a space that is not covered by a ceiling or walls.

[0027] 1 is a side view showing the inside of the target area, and Fig. 2 is a plan view showing the inside of the target area. In each figure, the X, Y, and Z axes are assumed to be mutually orthogonal, the Z axis indicates the vertical direction, and the X and Y axes indicate the horizontal direction.

[0028] The disaster prevention system 100 in FIG. 1 is a fire detection system, and includes a detector 1, for example.

[0029] Although the number of sensors 1 is arbitrary, the following description focuses on sensors 101 and 102, which are opposite each other based on a common acoustic axis 901. Sensors 101 to 102 have similar configurations, and will be referred to as sensor 1 when there is no need to distinguish between them.

[0030] (Configuration-sensor) Fig. 3 is a block diagram showing a detector, and Fig. 4 is an explanatory diagram of sound waves. Detector 1 in Fig. 1 is a fire detector that detects fires in a target area, for example, a device that detects fires using sound waves, and an example is detector 101 and detector 102 that have a common sound axis 901.

[0031] The sensor 1 in FIG. 3 includes, for example, a wave transmitting unit 11, a wave receiving unit 12, a recording unit 13, and a control unit 14.

[0032] (Configuration - Sensor - Transmitter) 3 is a wave transmitting means for transmitting sound waves to a target area, and for example, outputs sound waves along a self-set sound axis 901. This wave transmitting unit 11 can be configured using a known sound wave transmitter (for example, one using a piezoelectric ceramic vibrator, a signal processing circuit, etc.).

[0033] 1 is configured to output a sound wave having a predetermined directivity along the acoustic axis 901 toward one side (+X direction).

[0034] The sound waves from this sensor 101 then reach sensor 102, and among these arriving sound waves, there are assumed to be "direct waves" that reach the sensor without being reflected within the target area, and "reflected waves" that reach the sensor after being reflected within the target area, as shown in Fig. 4. Note that the assumptions here are merely examples, and other sound waves can also be assumed if specifically stated.

[0035] In reality, reflected waves include those reflected by walls, floors, etc., but for the sake of convenience, this embodiment will focus on those reflected by the ceiling. Also, reflected waves can be primary reflected waves that are reflected once, secondary reflected waves that are reflected twice, tertiary reflected waves that are reflected three times, etc., but for the sake of convenience, this embodiment will focus on primary reflected waves.

[0036] 1 is also configured in the same way, that is, to output sound waves having a predetermined directivity along the sound axis 901 toward the other side (−X direction).

[0037] (Configuration - Sensor - Receiver) 3 is a receiving means for receiving sound waves, for example, a device for receiving sound waves that have reached the receiving unit 12. The receiving unit 12 can be configured using a known sound wave receiver (for example, one using a piezoelectric ceramic vibrator, a signal processing circuit, etc.).

[0038] The wave receiving unit 12 of the sensor 101 in FIG. 1 is configured to receive the sound waves output from the sensor 102, and is also configured to receive sound waves corresponding to the sound waves output by the sensor 101 itself.

[0039] Note that the sound waves received by the sensor 101 in response to the sound waves output by the sensor 101 itself may include "direct waves" that arrive without being reflected within the target area (propagating only the extremely short distance between the components of the wave transmitting unit 11 and the components of the wave receiving unit 12), and "reflected waves" that arrive after being reflected. Note that the assumptions here are merely examples, and other sound waves may also be assumed if specifically stated.

[0040] The same is true for the wave receiving unit 12 of the sensor 102 in Figure 1, that is, it is configured to receive the sound waves output from the sensor 101, and also to receive sound waves corresponding to the sound waves output by the sensor 102 itself.

[0041] (Configuration - Sensor - Recording unit) The recording unit 13 in FIG. 3 is a recording means for recording programs and various data required for the operation of the sensor 1, and can be configured using, for example, a flash memory.

[0042] (Configuration - Sensor - Control Unit) The control unit 14 in Figure 3 is a control means for controlling the sensor 1, and specifically, is a computer comprising a CPU, various programs that are interpreted and executed on the CPU (including basic control programs such as an OS, and application programs that are started on the OS and realize specific functions), and an internal memory such as a RAM for storing programs and various data.

[0043] The control unit 14 conceptually functions as, for example, a temperature specifying means, a fire detecting means, a frequency controlling means, and a scattering detecting means.

[0044] ===Temperature identification means=== The temperature determination means is a means for determining the temperature of the target area based on the time it takes for the sound waves transmitted by the wave transmitting means to be received by the wave receiving means.

[0045] The temperature determination means, for example, determines cross-correlation information that determines the degree of correlation between the transmitted signal and the received signal relative to the delay time when either the transmitted signal corresponding to the sound waves transmitted by the transmitting means or the received signal corresponding to the sound waves received by the receiving means is shifted in time, determines multiple delay times at which the degree of correlation in the cross-correlation information is large, determines multiple temperature candidates corresponding to the multiple delay times based on the determined multiple delay times, and determines the temperature of the target area based on the determined multiple temperature candidates.

[0046] The temperature identification means is configured, for example, to repeatedly identify the temperature of the target area, select a temperature candidate from among multiple temperature candidates that is closest to the temperature of the target area identified last time, and identify the selected temperature candidate as the temperature of the target area.

[0047] The temperature identification means, for example, identifies a delay time belonging to a second time period that is earlier than a first time period to which the delay time corresponding to the maximum correlation degree in the cross-correlation information belongs, or a delay time belonging to a third time period that is later than the first time period.

[0048] ===Fire Detection Methods=== The fire detection means is a means for detecting a fire occurring in a target area based on the temperature of the target area identified by the temperature identification means.

[0049] The fire detection means detects a fire occurring in the target area, for example, based on the variation in temperature of the target area identified by the temperature identification means.

[0050] The fire detection means detects a fire occurring in the target area, for example, based on the temperature of the target area identified by the temperature identification means and the detection result of the scattering detection means.

[0051] ===Frequency Control Method=== The frequency control means is a means for controlling the frequency of the sound waves transmitted from the wave transmitting means.

[0052] For example, the frequency control means causes the wave transmitting means to transmit sound waves of a first frequency band when it has not detected the possibility of a fire occurring in the target area, and causes the wave transmitting means to transmit sound waves of a second frequency band when it has detected the possibility of a fire occurring in the target area, the second frequency band being a frequency band lower than the first frequency band.

[0053] ===Scattering detection means=== The scattering detection means is a means for detecting fire-induced scattering, which is scattering of sound waves caused by a fire occurring in a target area, based on the transmitted wave signal and the received wave signal. The processing performed by each part of the control unit 14 will be described later.

[0054] (sound signal on the transmitting side, sound signal on the receiving side) Next, the transmitting-side acoustic signal and the receiving-side acoustic signal will be described.

[0055] ===Transmitting side acoustic signal=== Figure 5 is an explanatory diagram of the transmitting-side acoustic signal. Note that the signal waveform in Figure 5 is for convenience of explanation (the same applies to other figures). The "transmitting-side acoustic signal" is a transmitting signal corresponding to the acoustic wave to be transmitted (transmitted) from the transmitting unit 11 (Figure 3), and more specifically, is an electrical signal generated by the transmitting unit 11.

[0056] The specific content of this transmitting-side acoustic signal is the same as that of known signals, and for example, as shown in Fig. 5, a signal that is continuously output for a period of time T92 (for example, about 1 millisecond) and is repeatedly output at intervals of time T91 (for example, about 5 seconds) will be used as an example. Note that, hereinafter, unless otherwise specified, the description will be focused on acoustic waves corresponding to one transmitting-side acoustic signal (a signal that is continuously output for a period of time T92).

[0057] The frequency of the transmitting side acoustic signal (more specifically, the signal that is continuously output for only the time T92 in Figure 5) is arbitrary, and for example, a fixed frequency may be used, or a frequency that is varied (swept) within a predetermined frequency band may be used. In this embodiment, the case where the latter (varied (swept) frequency) is used will be described.

[0058] Then, the transmitting unit 11 generates a transmitting-side acoustic signal in response to a command from the control unit 14, and outputs an acoustic wave corresponding to the generated acoustic signal.

[0059] === Receiver side sound signal === The "receiving-side acoustic signal" is a received signal corresponding to the acoustic wave received by the receiving unit 12 (FIG. 3), and more specifically, is an electrical signal generated by the receiving unit 12.

[0060] The wave receiving section 12 then generates a receiving-side sound wave signal corresponding to the sound wave that it has received.

[0061] (Cross-correlation information) Next, the cross-correlation information will be described.

[0062] ===Prerequisite configuration=== 1 are connected by wire or wirelessly so as to be able to electrically communicate with each other, and one of these two sensors can also grasp the electrical signals (transmitting-side acoustic signal and receiving-side acoustic signal) of the other sensor. Note that any communication method can be applied as a specific communication method here, and therefore a description thereof will be omitted.

[0063] 1 transmits sound waves and the sensor 102 receives sound waves, unless otherwise specified. That is, for example, the sensor 102 generates a receiving-side sound signal and transmits it to the sensor 101, and the sensor 101 performs various processes (including a process for identifying cross-correlation information) using both the transmitting-side sound signal and the corresponding receiving-side sound signal.

[0064] ===Cross-correlation information=== 6 is an explanatory diagram of cross-correlation information. "Cross-correlation information" is information for determining the degree of correlation between the transmitting-side sound signal and the receiving-side sound signal with respect to the time lag (information that can identify the degree of correlation), and is information indicating, for example, how similar (or different) the waveforms of the two signals are. Note that this correlation information is a concept that corresponds to, for example, known cross-correlation techniques. "Time lag" is a concept that indicates the time shifted when, for example, either the transmitting-side sound signal or the receiving-side sound signal is shifted in time.

[0065] The cross-correlation information may be expressed in any format, for example, it may be expressed in the form of a graph as shown in FIG. 6, and the explanation will be given using this format.

[0066] The horizontal axis of Fig. 6 indicates the time lag, with "0" at the left end of the drawing, indicating that there is no time lag (the transmitting-side sound signal and the receiving-side sound signal are not lag-shifted in time), and the time lag increases as one moves to the right side of the drawing. Note that the numerical values ​​exemplified in Fig. 6 (such as "8", "+10", and "-10") are given for convenience of explanation.

[0067] The vertical axis in Figure 6 indicates the degree of correlation, with "0" representing the reference point. Moving above "0" indicates greater similarity, and moving below "0" indicates greater deviation (dissimilarity).

[0068] Fig. 7 is an explanatory diagram of the time lag and the degree of correlation. In Fig. 7, time T81 indicates the time when the sensor 101 transmits a sound wave, and time T82 indicates the time when the sensor 102 receives the sound wave from the sensor 101. In other words, the elapsed time from time T81 to time T82 (i.e., the difference time between time T81 and time T82) corresponds to the time from when the sound wave is transmitted to when the sound wave is received.

[0069] 7A shows the acoustic signals when the delay time is "0" (i.e., there is no delay and there is no delay time). Also, in FIG. 7B and FIG. 7C, the acoustic signals when the delay times are time T71 and time T72 are shown.

[0070] In the cross-correlation information of Fig. 6, point P91 indicates the correlation value when the delay time is "0", for example, as shown in Fig. 7(a). In this case, when the time period of the receiving-side sound signal in Fig. 7(a) is used as a reference, the transmitting-side sound signal does not exist, and only the receiving-side sound signal exists, so the correlation degree in Fig. 6 is "0".

[0071] In the cross-correlation information of Fig. 6, point P92 indicates the correlation value when the delay time is time T71, as shown in Fig. 7(b), for example. In this case, when the time period of the receiving-side sound signal in Fig. 7(b) is used as a reference, the transmitting-side sound signal does not exist, and only the receiving-side sound signal exists, so the correlation degree in Fig. 6 is "0".

[0072] In the cross-correlation information of Fig. 6, point P93 indicates the correlation value when the delay time is time T72 (the difference time between time T81 and time T82), as shown in Fig. 7(c), for example. In this case, when the time period of the receiving-side sound signal in Fig. 7(c) is used as a reference, the transmitting-side sound signal and the receiving-side sound signal are similar, so the correlation degree in Fig. 6 is a relatively large positive value (maximum value).

[0073] (process) Next, a description will be given of the processes executed by the disaster prevention system 100 configured as described above. Here, for example, a temperature detection process, a first fire detection process, a second fire detection process, and a third fire detection process will be described.

[0074] (Processing - Temperature detection processing) First, the temperature detection process will be explained. Figure 8 is a flowchart of the temperature detection process (in the following explanation of each process, steps will be abbreviated as "S"). The "temperature detection process" is a process for identifying and detecting the temperature of a target area. This temperature detection process will be explained from the point where it starts to be executed, assuming that repeated execution has started (the same applies to other processes).

[0075] Here, for example, a case will be described in which the temperature is determined by focusing on the propagation time of a direct wave. As a variation, the temperature may be determined by focusing on the propagation time of a reflected wave.

[0076] Also, for example, as described above, a case will be described in which processing is performed on the sensor 101 side using both the transmitting-side sound signal and the corresponding receiving-side sound signal (the same applies to other processing).

[0077] ===SA1=== In SA1 of FIG. 8, the control unit 14 of the sensor 101 identifies cross-correlation information based on the transmitting-side sound signal and the receiving-side sound signal corresponding to the transmitting-side sound signal.

[0078] Specifically, although the method is arbitrary, for example, the transmitting side acoustic signal and the receiving side acoustic wave corresponding to the direct wave and reflected wave in Figure 4 are acquired, and cross-correlation information is determined by performing known processing related to cross-correlation on each acquired acoustic signal.

[0079] =When there is no scattering of sound waves by flames= For example, if there is no fire within the target area as shown in Figure 4, there is no scattering of sound waves due to flames within the target area, so the cross-correlation information in Figure 6 is identified.

[0080] In this case, in the cross-correlation information, as shown in FIG. 6, the correlation degree is specified in the order of the direct wave and the reflected wave in the direction in which the delay time becomes longer (that is, toward later time periods).

[0081] Furthermore, since the receiving-side sound wave signal corresponding to a direct wave that propagates directly without reflection is more similar to the transmitting-side sound wave signal than the receiving-side sound wave signal corresponding to a reflected wave that propagates after reflection, in the cross-correlation information, the maximum value of the correlation degree corresponding to the direct wave (point P93 in Figure 6) is greater than the maximum value of the correlation degree corresponding to the reflected wave (point P94 in Figure 6), and the maximum value of the correlation degree corresponding to the direct wave (point P93 in Figure 6) becomes the overall maximum value.

[0082] =When sound waves are scattered by flames= Fig. 9 is a side view showing the inside of the target area, and Fig. 10 is an explanatory diagram of cross-correlation information. Fig. 9 illustrates a state in which a fire has broken out within the target area and the flames of the fire have reached sound axis 901. Note that "the flames have reached sound axis 901" is a concept that includes cases in which a fire has broken out on sound axis 901, cases in which a fire that has broken out in another location has reached sound axis 901, and cases in which a flame has reached the vicinity of sound axis 901 (for example, within 1 meter).

[0083] For example, when flames of a fire reach sound axis 901 within the target region as shown in FIG. 9, scattering of sound waves occurs due to the flames within the target region, and the cross-correlation information of FIG. 10 is identified.

[0084] In this case, in the cross-correlation information, as shown in FIG. 10, the correlation degree is specified in the order of the direct wave and the reflected wave in the direction in which the delay time becomes longer (that is, toward later time periods).

[0085] Furthermore, because part of the direct wave is scattered by the flame, the receiving-side acoustic signal corresponding to the reflected wave that is reflected and propagates is more similar to the sending-side acoustic signal than the receiving-side acoustic signal corresponding to the direct wave that propagates directly without being reflected.Therefore, in the cross-correlation information, the maximum value of the correlation degree corresponding to the reflected wave (point P84 in Figure 10) is greater than the maximum value of the correlation degree corresponding to the direct wave (point P83 in Figure 10), and the maximum value of the correlation degree corresponding to the reflected wave (point P84 in Figure 10) becomes the overall maximum value.

[0086] ===SA2=== At SA2 in FIG. 8, the control unit 14 of the sensor 101 identifies the propagation time of the direct wave.

[0087] Specifically, although this is optional, the process is performed assuming that cross-correlation information (FIG. 6) in the absence of scattering of sound waves by flames has been identified by SA1. In other words, the process is performed assuming that the maximum value of the correlation degree corresponding to the direct wave (point P93 in FIG. 6) is the overall maximum value.

[0088] Specifically, the time lag at which the degree of correlation is maximum in the cross-correlation information is identified, and the identified time lag is determined as the propagation time of the direct wave.

[0089] =When there is no scattering of sound waves by flames= Here, for example, if there is no scattering of sound waves by flames, the delay time corresponding to point P93 in Fig. 6 is identified as the propagation time of the direct wave. In other words, it becomes possible to correctly identify the propagation time of the direct wave.

[0090] =When sound waves are scattered by flames= On the other hand, if there is scattering of sound waves due to a flame, for example, the delay time corresponding to point P84 in Figure 10 will be identified as the propagation time of the direct wave. In other words, the propagation time of the reflected wave will be erroneously identified, and the propagation time of the direct wave will not be correctly identified.

[0091] ===SA3=== In SA3 of FIG. 8, the control unit 14 of the sensor 101 identifies the temperature in the target area.

[0092] Specifically, although the details are arbitrary, for example, it is assumed that target area identification information indicating the configuration (shape, size, etc.) of the target area in Fig. 1 is stored in the recording unit 13 of the sensor 101. For example, it is assumed that the distance between the wall surfaces in the horizontal direction (X axis) on the sound axis 901 in Fig. 1 (i.e., the distance between the sensors 101 and 102) (hereinafter also referred to as "separation distance") and the like are recorded as the target area identification information.

[0093] Regarding the processing, the distance is identified by referring to the target area identification information of the recording unit 13, and the propagation velocity, which is the speed of the sound wave, is identified based on the identified distance and the propagation time identified by SA2, and the temperature is identified using a predetermined method (such as a method of identifying the temperature using a known arithmetic formula that shows the relationship between velocity and temperature) based on the identified propagation velocity.

[0094] Here, for example, the calculation result of "separation distance" divided by "propagation time" is taken as the propagation speed of the direct wave, and the temperature is determined based on this propagation speed.

[0095] =When there is no scattering of sound waves by flames= For example, if there is no scattering of sound waves by a flame, the propagation time of the direct wave can be correctly determined, and the temperature can be correctly determined.

[0096] =When sound waves are scattered by flames= On the other hand, if the sound wave is scattered by a flame, the propagation time of the direct wave cannot be determined correctly, and the temperature cannot be determined correctly. That is, for example, the delay time corresponding to point P84 in Figure 10 will be erroneously determined as the propagation time of the direct wave, so the propagation time will be longer than the actual one, the propagation speed will be slower, and as a result, the determined temperature value will be lower.

[0097] ===SA4=== At SA4 in FIG. 8, the control unit 14 of the sensor 101 determines whether or not to correct the temperature identified at SA3.

[0098] Specifically, the process is arbitrary, but for example, the process is performed with the intention of determining that correction should be performed when "sound waves are scattered by a flame" as described above. For example, the temperature detection process (FIG. 8) is repeatedly executed, and the temperature of the target area is identified and detected each time the temperature detection process is executed, so when the state changes from "when sound waves are not scattered by a flame" to "when sound waves are scattered by a flame," the temperature identified by SA3 will fluctuate relatively greatly compared to the temperature detected the previous time the temperature detection process was executed (hereinafter also referred to as the "previous temperature"), and processing is performed with attention to this point.

[0099] In detail, if the temperature determined in SA3 does not fluctuate by more than a threshold value (for example, 5 to 10 degrees) from the "previous temperature," it is determined that this does not correspond to "the case where sound waves are scattered by a flame," and it is determined not to correct the temperature determined in SA3 (NO in SA4), and the process ends. In this case, the temperature determined in SA3 is detected as the temperature of the target area. Then, the temperature detection process (Figure 8) is repeatedly executed.

[0100] On the other hand, if the temperature determined in SA3 fluctuates from the "previous temperature" by more than a threshold value (for example, the threshold value is 5 to 10 degrees, and the time interval for the temperature detection process in Figure 8 is approximately 5 to 20 seconds), it is determined that this is an unrealistic temperature change and corresponds to "when sound waves are scattered by flames," and it is determined that the temperature determined in SA3 should be corrected (YES in SA4), and the process proceeds to SA5.

[0101] ===SA5=== At SA5 in FIG. 8, the control unit 14 of the sensor 101 identifies the propagation time of the direct wave by the first method.

[0102] Fig. 11 is an explanatory diagram of cross-correlation information. In Fig. 11, a first time period T61, a second time period T62, and a third time period T63 are shown in the same cross-correlation information as in Fig. 10.

[0103] The first time period T61 is the time period that serves as the basis for processing, and is, for example, the time period to which point P84 (the point with the highest correlation) that is the basis for determining the propagation time in SA2 belongs.As an example, it is a time period that corresponds to the temporal spread of the correlation related to the reflected wave (a time period that corresponds to a predetermined amount of time lag centered on the lag time of point P84).

[0104] The second time period T62 is a time period earlier than the first time period T61 (i.e., a time period corresponding to a smaller delay time), for example, a time period corresponding to the temporal spread of the correlation degree associated with the direct wave (a time period corresponding to a delay time a predetermined time away from the delay time of point P84).

[0105] The third time zone T63 is a time zone that is later than the first time zone T61 (that is, a time zone that corresponds to a larger delay time), and is, for example, a time zone that corresponds to a delay time that is a predetermined time away from the delay time of point P84.

[0106] The "first method" is a method for identifying propagation times by identifying delay times that meet a predetermined condition related to the degree of correlation in all time periods in the cross-correlation information. "All time periods" is a concept that refers to time periods including the first time period T61, the second time period T62, and the third time period T63 in Fig. 11. The content of the "predetermined condition" is arbitrary, but for example, a case will be described in which a condition is adopted that identifies delay times corresponding to a predetermined number (e.g., 5 to 10) of maximum values ​​with the highest correlation degree values.

[0107] Here, for example, from among many maximum values ​​including points P84 and P83 in Fig. 11, point P84, which is the maximum value corresponding to the largest value, the point with the second largest value, the point with the third largest value, etc. are identified, and the delay times corresponding to these identified points are identified as the propagation times. For example, a number of propagation times are identified.

[0108] By performing this processing, it becomes possible to specify the propagation time, for example, taking into account the correlation degree of all time periods.

[0109] ===SA6=== At SA6 in FIG. 8, the control unit 14 of the sensor 101 identifies the propagation time of the direct wave by the second method.

[0110] The "second method" is a method for identifying the propagation time by identifying the delay time that meets a predetermined condition related to the correlation degree in the second time period T62 in the cross-correlation information. The content of the "predetermined condition" is arbitrary, and may be the same as the content of the first method, or the number of conditions may be changed (the same applies to the predetermined condition of the third method).

[0111] Here, for example, from among many maximum values ​​including point P83 in Fig. 11, point P83, which is the maximum value corresponding to the largest value, the point with the second largest value, the point with the third largest value, etc. are identified, and the delay times corresponding to these identified points are identified as the propagation times. For example, b propagation times are identified.

[0112] By performing this processing, it becomes possible to identify the propagation time taking into consideration the degree of correlation in the time period assumed to correspond to the direct wave, for example.

[0113] ===SA7=== At SA7 in FIG. 8, the control unit 14 of the sensor 101 identifies the propagation time of the direct wave by the third method.

[0114] The "third method" is a method for identifying the propagation time by identifying a delay time that meets a predetermined condition regarding the degree of correlation in a third time period T63 in the cross-correlation information.

[0115] By processing in this manner, even when a propagation time corresponding to the reverberation sound of a previously output sound wave is identified, it is possible to identify the propagation time by taking into consideration the correlation of the time period assumed to correspond to the direct wave. In particular, when the size of the target region is relatively small, it is assumed that SA2 in Fig. 8 may identify a propagation time corresponding to the reverberation sound of a previously output sound wave, and in this case, it is assumed that the delay time corresponding to the correlation of the intended direct wave belongs to a time period with a larger delay time (third time period T63 in Fig. 11). Even in such a case, it is possible to identify the intended propagation time.

[0116] As a variation, one or two of the processes of SA5 to SA7 may be omitted, and the following processes related to the omitted processes may also be omitted or changed as appropriate.

[0117] ===SA8=== At SA8 in FIG. 8, the control unit 14 of the sensor 101 identifies the temperature corresponding to the propagation time identified at SA5 to SA7.

[0118] Specifically, although this is optional, for example, the same process as that of SA3 is performed. That is, the propagation speed is determined based on the separation distance and the propagation time determined in SA5 to SA7, and then the temperature corresponding to the propagation speed is determined.

[0119] Here, for example, a temperatures corresponding to each of the a propagation times identified in SA5, b temperatures corresponding to each of the b propagation times identified in SA6, and c temperatures corresponding to each of the c propagation times identified in SA7 are identified.

[0120] The temperature identified in SA8 may be interpreted as corresponding to a "temperature candidate" that is a candidate for the temperature of the target region.

[0121] ===SA9=== In SA9 of FIG. 8, the control unit 14 of the sensor 101 selects one temperature from the multiple temperatures identified in SA8 that is closest to the "previous temperature" (see the explanation of SA4), identifies and detects the selected temperature as the temperature of the target area, and then terminates the processing.

[0122] Here, for example, the temperature identified from the delay time corresponding to point P83 in Fig. 11 is detected as the temperature of the target area. In this way, by performing the processes SA5 to SA9, the identified temperature is corrected, and it becomes possible to appropriately identify the temperature of the target area.

[0123] (Processing - First Fire Detection Processing) Next, the first fire detection process will be described. Fig. 12 is a flowchart of the first fire detection process. The "first fire detection process" is a process for detecting a fire occurring in a target area, and is, for example, a process for detecting a fire by appropriately changing the frequency of sound waves.

[0124] Here, for example, by repeatedly executing the temperature detection process of Figure 8, the temperature of the target area can be detected at a predetermined time interval (e.g., every 5 to 20 seconds), and the temperature is used appropriately for processing (the same applies to other processes).

[0125] ===SB1=== In SB1 of Figure 12, the control unit 14 of the sensor 101 causes the transmitting unit 11 to generate a transmitting-side acoustic signal for generating an acoustic wave of a frequency in the first frequency band, output the acoustic wave, and then identifies the temperature repeatedly detected in the temperature detection process (Figure 8).

[0126] Since the first frequency band is a higher frequency band than the second frequency band, the frequencies of this first frequency band (frequencies belonging to the first frequency band) are also referred to as "high frequencies," and the frequencies of the second frequency band (frequencies belonging to the second frequency band) are also referred to as "low frequencies."

[0127] In this embodiment, a frequency-swept signal is used as the transmitting side acoustic signal (more specifically, a signal that is continuously output for only the time T92 in Figure 5), so high frequencies refer to multiple frequencies belonging to the first frequency band (the same applies to low frequencies).

[0128] Furthermore, the specific frequency widths of the first frequency band and the second frequency band are arbitrary, but for example, the first frequency band may correspond to frequencies within a typical inaudible range for humans, and the second frequency band may correspond to frequencies within a typical audible range for humans.

[0129] ===SB2=== 12, the control unit 14 of the sensor 101 processes the temperature identified in SB1 depending on whether the rate of temperature rise is equal to or greater than a first threshold (e.g., 6°C / min). If the rate of temperature rise is equal to or greater than the first threshold (YES in SB2), the process proceeds to SB6, and if the rate of temperature rise is not equal to or greater than the first threshold (NO in SB2), the process proceeds to SB3.

[0130] The "temperature rise rate" is the rate at which the temperature rises, and is a concept that indicates, for example, the temperature rise per unit time (1 minute).

[0131] The "first threshold" is a predetermined value that is compared with the rate of temperature rise, and is, for example, a value used for various judgments (such as determining whether a fire has occurred), and is a value greater than the second threshold, such as "6°C / min."

[0132] The "second threshold" is a predetermined value that is compared with the rate of temperature rise, and is, for example, a value used for various judgments (such as determining whether a fire may occur), and is a value smaller than the first threshold, such as "2°C / min."

[0133] ===SB3=== 12, the control unit 14 of the sensor 101 performs processing based on whether the rate of temperature rise identified in SB1 is equal to or greater than a second threshold (e.g., 2°C / min). If the rate of temperature rise is equal to or greater than the second threshold (YES in SB3), the control unit 14 detects the possibility of a fire and then proceeds to SB4, whereas if the rate of temperature rise is not equal to or greater than the second threshold (NO in SB3), the control unit 14 does not detect the possibility of a fire and proceeds to SB1.

[0134] ===SB4=== At SB4 in FIG. 12, the control unit 14 of the sensor 101 causes the transmitting unit 11 to generate a transmitting-side acoustic signal for generating an acoustic wave of a frequency in the second frequency band, outputs the acoustic wave, and then identifies the temperature repeatedly detected in the temperature detection process (FIG. 8).

[0135] In this case, the frequency of the sound waves is switched from high to low, improving the sound wave propagation performance and enabling the temperature to be determined with higher accuracy than in the case of high frequencies.

[0136] ===SB5=== 12, the control unit 14 of the sensor 101 performs processing for the temperature identified in SB4 depending on whether the rate of temperature rise has reached or exceeded a first threshold value (e.g., 6°C / min) within a predetermined time (e.g., 5 minutes) since the start of execution of SB4. If the rate of temperature rise has reached or exceeded the first threshold value within the predetermined time (YES in SB5), the process proceeds to SB6, and if the rate of temperature rise has not reached or exceeded the first threshold value within the predetermined time (NO in SB5), the process proceeds to SB1.

[0137] ===SB6=== At SB6 in FIG. 12, the control unit 14 of the detector 101 detects that a fire has occurred in the target area, outputs an alarm signal (a signal notifying of the occurrence of a fire) or issues a fire alarm, and then terminates the processing.

[0138] (Processing - Secondary Fire Detection Processing) Next, the second fire detection process will be described. Fig. 13 is a flowchart of the second fire detection process. The "second fire detection process" is a process for detecting a fire that occurs in a target area, and is a process for detecting a fire based on, for example, temperature variations in the target area.

[0139] In the second fire detection process, when the flames of a fire reach the sound axis 901 (FIG. 9), it is assumed that the temperature will fluctuate and vary due to the flames, and this assumption is used to detect the fire.

[0140] ===SC1~SC3=== In SC1 to CS3 in FIG. 13, the control unit 14 of the sensor 101 performs the same processes as those in SB1 to SB3 in FIG.

[0141] ===SC4=== In SC4 of FIG. 13, the control unit 14 of the sensor 101 determines the degree of temperature variation determined in SC1 and performs processing depending on whether the determined degree of variation is equal to or greater than a threshold. Temperature-related statistical values ​​(e.g., variance, standard deviation, etc.) may be used to determine the variation here. The "temperature variation" here refers to the variation in temperature over time. For example, if temperatures are detected in the order Te1°C, Te2°C, Te3°C, etc., and the temperatures are identified, the variation corresponding to Te1°C, Te2°C, Te3°C, etc. is indicated. Temperature variation using variance, standard deviation, etc. can occur both when the temperature rises uniformly and when the temperature fluctuates randomly up and down. Both of these occur during a fire, and therefore can be used to detect fires. Since the tendency of the temperature change is determined in SC3 of FIG. 13, the variation in temperature change (for example, the variance or standard deviation of the temperature change) may be used for the determination.

[0142] If the degree of temperature variation is greater than or equal to the threshold (more variation) (YES in SC4), the process proceeds to SC5, and if the degree of temperature variation is not greater than or equal to the threshold (not very variable) (NO in SC4), the process proceeds to SC1.

[0143] ===SC5=== At SC5 in Figure 13, the control unit 14 of the detector 101 detects that a fire has occurred in the target area, similar to SB6 in Figure 12, and then outputs an alarm signal and issues a fire alarm, and then terminates the processing.

[0144] (Processing - Third Fire Detection Processing) Next, the third fire detection process will be described. Fig. 14 is a flowchart of the third fire detection process. The "third fire detection process" is a process for detecting a fire that occurs in a target area, and is, for example, a process for detecting a fire based on fire-caused scattering in the target area.

[0145] ===Fire-induced scattering=== First, fire-induced scattering will be explained. Figures 15 to 17 are explanatory diagrams of cross-correlation information, and Figure 18 is a side view showing the inside of the target area. Figures 15 to 17 show cross-correlation information corresponding to the case where the detector 101 transmits a wave and receives a sound wave corresponding to the transmitted sound wave.

[0146] If there is no fire When no fire has broken out, immediately after the detector 101 in Fig. 1 outputs a sound wave from its own wave transmitting unit 11, the detector 101 receives the sound wave (direct wave) at its own wave receiving unit 12, so the waveforms of the transmitting-side sound wave signal at the wave transmitting unit 11 and the receiving-side sound wave signal at the wave receiving unit 12 become similar at almost the same time. Therefore, as shown in Fig. 15, the correlation degree corresponding to the direct wave is identified when the delay time is near "0".

[0147] =When the flame reaches the sound axis= When a fire breaks out and the flames of the fire reach the acoustic axis 901 (Fig. 18), a portion of the sound waves output by the sensor 101 is returned to the sensor 101 due to scattering of the sound waves by the flames (fire-induced scattering), and this returned portion of the sound waves (hereinafter also referred to as "scattered waves") is received by the sensor 101. Therefore, when cross-correlation information is determined based on the transmitting-side sound wave signal in the transmitting unit 11 of the sensor 101 and the receiving-side sound wave signal in the receiving unit 12 of the sensor 101, the correlation degree corresponding to the scattered waves will also be determined in addition to the correlation degree corresponding to the direct waves described above, as shown in Fig. 16.

[0148] =Scattering detection= By calculating the difference between the correlation degree at each delay time in the cross-correlation information in Fig. 16 (information when a flame reaches the sound axis) and the correlation degree at each delay time in the cross-correlation information in Fig. 15 (information when no fire has occurred), it is possible to extract only the correlation degree corresponding to the scattered waves shown in Fig. 17. Then, depending on whether or not there is a correlation degree greater than a predetermined value in the correlation degree mutual information in Fig. 17, it is possible to detect the presence of a correlation degree corresponding to the scattered waves (i.e., scattering of sound waves by a flame).

[0149] The third fire detection process uses the items corresponding to these to detect fires, etc.

[0150] ===SD1=== In SD1 of FIG. 14, the control unit 14 of the sensor 101 performs the same process as in SB1 of FIG. 12 to identify the temperature repeatedly detected in the temperature detection process (FIG. 8).

[0151] ===SD2=== In SD2 of Figure 14, the control unit 14 of the sensor 101 performs processing similar to that in SB2 of Figure 12, and if the rate of temperature rise for the temperature identified in SD1 is equal to or greater than the first threshold (YES in SD2), it proceeds to SD11, and if the rate of temperature rise is not equal to or greater than the first threshold (NO in SD2), it proceeds to SD3.

[0152] ===SD3=== In SD3 of Figure 14, the control unit 14 of the sensor 101 acquires the most recent transmitting side acoustic signal and the receiving side acoustic signal corresponding to the transmitting side acoustic signal, and performs well-known cross-correlation processing on each acquired acoustic signal to determine cross-correlation information (hereinafter also referred to as "most recent cross-correlation information").

[0153] The transmitting-side acoustic signal used here corresponds to the acoustic waves output by the sensor 101 from its own transmitting unit 11, and the receiving-side acoustic signal corresponds to the acoustic waves received by the sensor 101 at its own receiving unit 12 (the same applies to SD4 described below).

[0154] =When there is no scattering of sound waves by flames= For example, if no fire has occurred within the target area as shown in FIG. 4, no scattering of sound waves occurs due to flames within the target area, and therefore the cross-correlation information of FIG. 15 is identified.

[0155] =When sound waves are scattered by flames=

[0156] For example, if the flames of a fire reach the sound axis 901 within the target area as shown in Figure 18, the flames will scatter sound waves (i.e., scattered waves) within the target area, and the cross-correlation information of Figure 16 will be identified.

[0157] ===SD4=== In SD4 of FIG. 14, the control unit 14 of the detector 101 determines a moving average of the cross-correlation information corresponding to each previous acoustic signal.

[0158] Specifically, the method is arbitrary, but for example, the previous X number of transmitting-side acoustic signals and the receiving-side acoustic signals corresponding to those transmitting-side acoustic signals are acquired, and known cross-correlation processing is performed on each acquired acoustic signal to identify each piece of cross-correlation information, and then cross-correlation information corresponding to the average of the identified pieces of cross-correlation information (hereinafter also referred to as "average cross-correlation information") is identified.

[0159] The "previous X sending-side acoustic signals" is a concept that indicates, for example, X consecutive sending-side acoustic signals that were used before the sending-side acoustic signal (i.e., the most recent sending-side acoustic signal) used in the processing of SD3 among a plurality of sending-side acoustic signals used sequentially in time for acoustic output. For example, if X is 3, and the sending-side acoustic signals are used in the order of W(n-4), W(n-3), W(n-2), W(n-1), and W(n), and W(n) is the most recent sending-side acoustic signal, then the three signals W(n-3), W(n-2), and W(n-1) are the "previous X sending-side acoustic signals."

[0160] Here, for example, if no fire has occurred, each piece of cross-correlation information will be similar to the example shown in Figure 15, and the "average cross-correlation information" corresponding to this average will be similar to the example shown in Figure 15.

[0161] ===SD5=== In SD5 of Figure 14, the control unit 14 of the detector 101 performs processing similar to that of SB3 of Figure 12, and if the rate of temperature rise for the temperature identified in SD1 is equal to or greater than the second threshold (YES in SD5), it detects the possibility of a fire and proceeds to SD9, and if the rate of temperature rise is not equal to or greater than the second threshold (NO in SD5), it does not detect the possibility of a fire and proceeds to SD6.

[0162] ===SD9=== In SD9 of FIG. 14 after YES in SD5, the control unit 14 of the sensor 101 calculates the difference between the correlation degree for each delay time between the “most recent cross-correlation information” identified in SD3 and the “average cross-correlation information” identified in SD4, and thereby identifies the “difference cross-correlation information” corresponding to these differences.

[0163] Here, for example, if the "most recent cross-correlation information" is the information illustrated in FIG. 16 and the "average cross-correlation information" is information corresponding to the information illustrated in FIG. 15, the information illustrated in FIG. 17 is identified as the "differential cross-correlation information."

[0164] Furthermore, for example, if the "most recent cross-correlation information" is the information illustrated in FIG. 15 and the "average cross-correlation information" is information corresponding to the information illustrated in FIG. 15, then the "differential cross-correlation information" will be information (not shown) in which the correlation degree is close to "0" at all delay times.

[0165] ===SD10=== In SD10 of Fig. 14, the control unit 14 of the detector 101 processes the "differential cross-correlation information" identified in SD9 depending on whether or not there is a correlation greater than or equal to a threshold value (a predetermined value such as "+5", for example). If there is a correlation greater than or equal to the threshold value (YES in SD10), fire-induced scattering is detected and the process proceeds to SD11. If there is no correlation greater than or equal to the threshold value (NO in SD10), fire-induced scattering is not detected and the process proceeds to SD1.

[0166] ===SD11=== At SD11 in FIG. 13, the control unit 14 of the detector 101 detects that a fire has occurred in the target area, similar to SB6 in FIG. 12, and then outputs an alarm signal or issues a fire alarm, and then terminates the processing.

[0167] ===SD6=== In SD6 of FIG. 14 after NO in SD5, the control unit 14 of the sensor 101 performs the same process as in SD9.

[0168] ===SD7=== In SD7 of Fig. 14, the control unit 14 of the sensor 101 processes the "differential cross-correlation information" identified in SD6 depending on whether or not there is a correlation degree equal to or greater than a threshold value (e.g., a predetermined value such as "+5"). If there is a correlation degree equal to or greater than the threshold value (YES in SD7), the process proceeds to SD8. If there is no correlation degree equal to or greater than the threshold value (NO in SD7), the process proceeds to SD1.

[0169] The processing here focuses on the fact that, for example, if an obstacle (such as temporarily placed luggage) rather than a flame is placed on the sound axis 901 in Figure 1, the sound waves will be scattered or reflected by the obstacle, causing the "differential cross-correlation information" to become information corresponding to the information exemplified in Figure 17, and that if a correlation level equal to or greater than a threshold exists (YES in SD7), the obstacle can be detected.

[0170] ===SD8=== In SD8 of FIG. 13, the control unit 14 of the sensor 101 detects the presence of an obstacle in the target area, issues an obstacle alarm, and then ends the process.

[0171] (Effects of the embodiment) Thus, according to this embodiment, by identifying multiple temperature candidates corresponding to multiple delay times based on the delay times in the cross-correlation information and identifying the temperature, it is possible to improve the accuracy of temperature identification, thereby improving the accuracy of fire detection, for example.

[0172] Furthermore, by selecting the temperature candidate that is closest to the previously specified temperature from among a plurality of temperature candidates, it becomes possible to appropriately specify the temperature, for example.

[0173] Furthermore, by identifying a delay time belonging to a second time period that is earlier than the first time period to which the delay time corresponding to the maximum correlation belongs, or a delay time belonging to a third time period that is later than the first time period, it becomes possible to appropriately identify the temperature, taking into account, for example, scattering of sound waves by flames and reverberation of sound waves within the target area.

[0174] Furthermore, if the possibility of a fire has not been detected, sound waves of a frequency in the first frequency band are transmitted, and if the possibility of a fire has been detected in the target area, sound waves of a frequency in the second frequency band (a frequency band lower than the first frequency band) are transmitted. This makes it possible to use sound waves of an appropriate frequency depending on the situation regarding the fire, thereby improving the accuracy of fire detection.

[0175] Furthermore, by detecting a fire based on temperature variations, it is possible to improve the accuracy of fire detection, for example.

[0176] Furthermore, by detecting a fire based on the temperature of the target area and fire-caused scattering, it is possible to improve the accuracy of fire detection, for example.

[0177] [Modifications to the embodiment] Although the embodiments of the present invention have been described above, the specific configurations and means of the present invention can be modified and improved as desired within the scope of the technical ideas of the inventions set forth in the claims. Such modifications will be described below.

[0178] (About the problem to be solved and the effects of the invention) First, the problems that the invention aims to solve and the effects of the invention are not limited to those described above, and may vary depending on the implementation environment of the invention and the details of the configuration, and may solve only some of the problems described above or achieve only some of the effects described above.

[0179] (Regarding decentralization and integration) Furthermore, the above-described configuration is a functional concept, and does not necessarily have to be physically configured as shown in the drawings. In other words, the specific form of distribution or integration of each part is not limited to that shown in the drawings, and all or part of it can be functionally or physically distributed or integrated in any unit.

[0180] (Fire detection processing) Furthermore, the first to third fire detection processes described in the above embodiment may be configured to be executed by all of the sensors 1, or only one or two of the processes may be executed. Alternatively, for example, a plurality of sensors 1 provided in the target area may each be configured to execute a predetermined process.

[0181] (Functional layout) Furthermore, the implementation targets of the means described in the above embodiments are merely examples, and each means may be configured to be provided in any device of the disaster prevention system 100 and perform processing.

[0182] (About the numbers) Furthermore, the numerical values ​​shown in the above embodiments are merely examples, and any other numerical values ​​may be used as long as they correspond to the characteristics of the present application.

[0183] (Features) Furthermore, the features of the above-described embodiments and modifications may be combined in any manner.

[0184] (Addendum) The fire detection system of Appendix 1 is a fire detection system that detects a fire that occurs in a target area, and comprises: a wave transmitting means that transmits sound waves to the target area; a wave receiving means that receives the sound waves; a temperature determining means that determines the temperature of the target area based on the time it takes for the sound waves transmitted by the wave transmitting means to be received by the wave receiving means; and a fire detection means that detects a fire that occurs in the target area based on the temperature of the target area determined by the temperature determining means, wherein the temperature determining means determines cross-correlation information that determines the degree of correlation between the transmitted signal and the received signal with respect to a delay time when either the transmitted signal corresponding to the sound waves transmitted by the wave transmitting means or the received signal corresponding to the sound waves received by the wave receiving means is shifted in time, identifies a plurality of delay times at which the degree of correlation in the cross-correlation information is large, identifies a plurality of temperature candidates corresponding to the plurality of delay times based on the identified plurality of delay times, and determines the temperature of the target area based on the identified plurality of temperature candidates.

[0185] The fire detection system of Appendix 2 is the fire detection system described in Appendix 1, wherein the temperature identification means is configured to repeatedly identify the temperature of the target area, and the temperature identification means selects a temperature candidate from the plurality of temperature candidates that is closest to the temperature of the target area identified last time, and identifies the selected temperature candidate as the temperature of the target area.

[0186] The fire detection system of Appendix 3 is the fire detection system described in Appendix 1, wherein the temperature identification means identifies the delay time belonging to a second time period that is earlier than a first time period to which the delay time corresponding to the maximum correlation degree in the cross-correlation information belongs, or the delay time belonging to a third time period that is later than the first time period.

[0187] The fire detection system of Appendix 4 is the fire detection system of Appendix 1, further comprising a frequency control means for controlling the frequency of the sound waves transmitted from the transmitting means, wherein the frequency control means causes the transmitting means to transmit sound waves of a frequency in a first frequency band when it has not detected the possibility of a fire occurring in the target area, and causes the transmitting means to transmit sound waves of a frequency in a second frequency band when it has detected the possibility of a fire occurring in the target area, the second frequency band being a frequency band lower than the first frequency band.

[0188] The fire detection system of Appendix 5 is the fire detection system described in Appendix 1, wherein the fire detection means detects a fire occurring in the target area based on the temperature variation in the target area identified by the temperature identification means.

[0189] The fire detection system of Appendix 6 is the fire detection system described in Appendix 1, and further comprises a scattering detection means for detecting fire-caused scattering, which is scattering of sound waves caused by a fire occurring in the target area, based on the transmitted signal and the received signal, and the fire detection means detects a fire occurring in the target area based on the temperature of the target area identified by the temperature identification means and the detection result of the scattering detection means.

[0190] (Effect of supplementary notes) According to the fire detection system described in Appendix 1, by identifying multiple temperature candidates corresponding to multiple delay times based on the delay times in the cross-correlation information and identifying the temperature, it is possible to improve the accuracy of temperature identification, for example, and thereby improve the accuracy of fire detection.

[0191] According to the fire detection system described in Appendix 2, by selecting the temperature candidate closest to the previously identified temperature from among a plurality of temperature candidates, it is possible to appropriately identify the temperature, for example.

[0192] According to the fire detection system described in Appendix 3, by identifying a delay time belonging to a second time period that is earlier than the first time period to which the delay time corresponding to the maximum correlation belongs, or a delay time belonging to a third time period that is later than the first time period, it is possible to appropriately identify the temperature, taking into account, for example, scattering of sound waves by flames and reverberation of sound waves within the target area.

[0193] According to the fire detection system described in Appendix 4, if the possibility of a fire has not been detected, sound waves of a frequency in the first frequency band are transmitted, and if the possibility of a fire has been detected in the target area, sound waves of a frequency in the second frequency band (a frequency band lower than the first frequency band) are transmitted.This makes it possible to use sound waves of an appropriate frequency depending on the fire situation, for example, thereby improving the accuracy of fire detection.

[0194] According to the fire detection system described in Supplementary Note 5, by detecting a fire based on temperature variations, it is possible to improve the accuracy of fire detection, for example.

[0195] According to the fire detection system described in Supplementary Note 6, by detecting a fire based on the temperature of the target area and fire-caused scattering, it is possible to improve the accuracy of fire detection, for example. [Explanation of symbols]

[0196] Below, in parentheses, the matters specifying the invention in the claims that correspond to the terms used in the embodiments are written, but the correspondence between the two is not limited to this. 1 sensor 11 Wave transmitter (wave transmitter) 12 Wave receiving section (wave receiving means) 13 Recording section 14 control unit (temperature determination means, fire detection means, frequency control means, scattering detection means) 100 Disaster prevention system (fire detection system) 101 Sensor 102 Sensor 901 sound axis P91 points P92 points P93 points P94 points T61 1st time slot T62 2nd Time Zone T63 3rd Time Zone T71 hours T72 hours T81 hours T82 hours T91 hours T92 hours

Claims

1. 1. A fire detection system for detecting a fire occurring in a target area, comprising: a wave transmitting means for transmitting a sound wave to the target area; wave receiving means for receiving sound waves; a temperature determination means for determining the temperature of the target area based on the time it takes for the sound waves transmitted by the wave transmitting means to be received by the wave receiving means; a fire detection means for detecting a fire occurring in the target area based on the temperature of the target area identified by the temperature identification means, The temperature specifying means When either a transmission signal corresponding to the sound wave transmitted by the transmitting means or a reception signal corresponding to the sound wave received by the receiving means is shifted in time, cross-correlation information is identified to determine the degree of correlation between the transmission signal and the reception signal with respect to the shift time, Identifying a plurality of the delay times at which the degree of correlation in the cross-correlation information becomes large; Identifying a plurality of temperature candidates corresponding to the plurality of delay times based on the plurality of identified delay times; identifying a temperature of the target area based on the identified plurality of temperature candidates; Fire detection systems.

2. the temperature determining means is configured to repeatedly determine the temperature of the target area; The temperature specifying means selecting a temperature candidate that is closest to the previously identified temperature of the target area from the plurality of temperature candidates, and identifying the selected temperature candidate as the temperature of the target area; The fire detection system of claim 1 .

3. The temperature specifying means identifying the delay time belonging to a second time period that is earlier than a first time period to which the delay time corresponding to the maximum correlation degree in the cross-correlation information belongs, or the delay time belonging to a third time period that is later than the first time period; The fire detection system of claim 1 .

4. a frequency control means for controlling the frequency of the sound wave transmitted from the transmitting means; The frequency control means If it is not detected that a fire may have occurred in the target area, the wave transmitting means transmits sound waves having a frequency in a first frequency band; When detecting a possibility of a fire occurring in the target area, the wave transmitting means transmits sound waves having a frequency in a second frequency band, the second frequency band is a frequency band lower than the first frequency band; The fire detection system of claim 1 .

5. the fire detection means detects a fire occurring in the target area based on the temperature variation in the target area identified by the temperature identification means. The fire detection system of claim 1 .

6. a scattering detection means for detecting, based on the transmitted wave signal and the received wave signal, fire-induced scattering, which is scattering of sound waves caused by a fire occurring in the target area; the fire detection means detects a fire occurring in the target area based on the temperature of the target area identified by the temperature identification means and the detection result of the scattering detection means. The fire detection system of claim 1 .

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