Fire detection system

Abstract

To provide a fire detection system which can identify a position of fire.SOLUTION: A fire detection system comprises: first wave transmitting means transmitting a sonic wave in a direction along a sound axis 901; first wave receiving means receiving a sonic wave along the sound axis 901; first temperature identification means identifying first temperature on a sound wave propagation route based on a first wave transmitting signal corresponding to the sonic wave transmitted by the first wave transmitting means and a first wave receiving signal corresponding to the sonic wave received by the first wave receiving means; second wave transmitting means transmitting a sonic wave in a direction along a sound axis 903 nearly orthogonal to the sound axis 901; second wave receiving means receiving a sonic wave along the sound axis 903; second temperature identification means identifying second temperature on the sonic wave propagation route based on a second wave transmitting signal corresponding to the sonic wave transmitted by the second wave transmitting means and a second wave receiving signal corresponding to the sonic wave received by the second wave receiving means; and fire position identification means identifying a fire position based on the identification results of the first and second temperature identification means.SELECTED DRAWING: Figure 2

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] However, there has been a demand for a technology to detect the location of a fire when it occurs.

[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 identify the location of a fire. [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 for identifying a fire location that is the location of a fire that has occurred in a target area, comprising: a first wave transmitting means for transmitting sound waves to the target area in a direction along a first sound axis; a first wave receiving means for receiving the sound waves transmitted from the first wave transmitting means, the first wave transmitting and receiving means being a combination of a first wave receiving means for receiving the sound waves that have propagated through the target area along the first sound axis; a first temperature identifying means for identifying a first temperature on a propagation path of the sound waves transmitted from the first wave transmitting means based on a first wave transmitting signal corresponding to the sound waves transmitted by the first wave transmitting means and a first wave receiving signal corresponding to the sound waves received by the first wave receiving means; a second wave transmitting means for transmitting sound waves to the target area in a direction along a second sound axis that is substantially perpendicular to the first sound axis; and a second wave receiving means for receiving the sound waves transmitted from the second wave transmitting means, the first wave receiving means being a combination of a first wave transmitting means and a first wave receiving means for receiving the sound waves that have propagated through the target area along the first sound axis. the target area is divided into a plurality of sections in a matrix by the plurality of first sound axes of the plurality of first wave transmitting and receiving means and the plurality of second sound axes of the plurality of second wave receiving means.

[0007] The fire detection system according to claim 2 is the fire detection system according to claim 1, wherein the fire location identification means, when a variance over time of the first temperatures for at least one of the plurality of first wave transmitting and receiving means exceeds a first threshold, identifies the fire location in the direction along the second sound axis based on a position along the second sound axis at which at least one of the first wave transmitting and receiving means is provided, and, when all of the variances over time of the plurality of first temperatures for each of the plurality of first wave transmitting and receiving means do not exceed the first threshold, identifies the fire location in the direction along the second sound axis based on a position along the second sound axis at which the first wave transmitting and receiving means corresponding to the highest temperature of the plurality of first temperatures is provided and a position along the second sound axis at which the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature of the plurality of first temperatures is provided. , the location of the fire in a direction along the second sound axis is identified; and if the variance over time of the second temperatures for at least one of the plurality of second wave-transmitting and receiving means exceeds a second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis at which at least one of the second wave-transmitting and receiving means is located; and if all of the variances over time of the plurality of second temperatures for each of the plurality of second wave-transmitting and receiving means do not exceed the second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis at which the second wave-transmitting and receiving means corresponding to the highest temperature among the plurality of second temperatures is located and the position along the first sound axis at which the second wave-transmitting and receiving means corresponding to the temperature next to the highest temperature among the plurality of second temperatures is located. [Effects of the Invention]

[0008] According to the fire detection system of claim 1, it is possible to identify the location of a fire by identifying the location of the fire based on the identification results of the first temperature identification means and the second temperature identification means. In particular, for example, since the target area is divided into a plurality of sections in a matrix by a plurality of first sound axes and a plurality of second sound axes, it is possible to reliably identify the location of the fire based on each section.

[0009] According to the fire detection system of claim 2, when the variance of the first temperature over time exceeds the first threshold, the position of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where at least one first wave transmitting and receiving means is provided; when all of the variances of the first temperature over time do not exceed the first threshold, the position of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the highest temperature is provided and the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature is provided; and when the variance of the second temperature over time exceeds the second threshold, at least The location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis where at least one second wave transmitting / receiving means is provided, and if all of the variances of the second temperatures over time do not exceed the second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis where the second wave transmitting / receiving means corresponding to the highest temperature is provided and the position along the first sound axis where the second wave transmitting / receiving means corresponding to the temperature next to the highest temperature is provided.This makes it possible to identify the location of the fire taking into account the variances of the first and second temperatures, for example, thereby improving the accuracy of identifying the location of the fire. [Brief explanation of the drawings]

[0010] [Figure 1] 1A to 1C are diagrams illustrating an example of installation of a sensor according to an embodiment of the present invention. [Figure 2] 1A to 1C are diagrams illustrating 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 a block diagram showing a disaster prevention receiver. [Figure 6] FIG. 2 is an explanatory diagram of a transmitting-side acoustic signal. [Figure 7] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 8] FIG. 10 is an explanatory diagram of a delay time and a correlation degree. [Figure 9] 10 is a flowchart of a temperature detection process. [Figure 10] FIG. 1 is a side view showing the interior of the target area. [Figure 11] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 12] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 13] 10 is a flowchart of a first fire detection process. [Figure 14] 10 is a flowchart of a second fire detection process. [Figure 15] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] [Basic Concept of the Embodiment] First, the basic concept of this embodiment will be explained. This embodiment generally relates to a fire detection system.

[0013] A "fire detection system" is a system that identifies the location of a fire that has occurred in a target area, and is a concept that includes, for example, systems that have reflective fire detectors, opposing fire detectors, and other devices (for example, disaster prevention receiving devices, server devices, or terminal devices). Note that a "disaster prevention receiving device" is a device for managing a target area, and specifically, is a concept that includes devices that are set up to be able to communicate with fire detectors, and is a concept that includes, for example, R-type or P-type receivers.

[0014] A "target area" is an area in which a fire is to be detected and in which the location of the fire is to be identified. It is a concept that includes, for example, a specified area indoors or outdoors, and as an example, any area such as a room in a building or a parking space in a parking lot.

[0015] In the following embodiment, the case where the "target area" is a room will be described.

[0016] [Specific details of the embodiment] Next, specific details of the embodiment will be described.

[0017] (composition) First, the configuration of a disaster prevention system according to this embodiment will be described. Figures 1 and 2 are diagrams showing examples of installation of sensors according to this embodiment.

[0018] 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.

[0019] 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. The disaster prevention receiver 9 may be installed at any position, for example, outside the target area.

[0020] In each drawing, the X, Y, and Z axes are assumed to be perpendicular to one another, the Z axis indicates the vertical direction, and the X and Y axes indicate the horizontal direction.

[0021] The disaster prevention system 100 in FIG. 1 is a fire detection system, and includes, for example, a detector 1 and a disaster prevention receiver 9.

[0022] (Configuration-sensor) Fig. 3 is a block diagram showing a detector, and Fig. 4 is an explanatory diagram of sound waves. The detector 1 in Fig. 1 is a fire detector that detects fires in a target area, and is, for example, a device that detects fires using sound waves.

[0023] The number and installation locations of the sensors 1 are arbitrary, but the following description focuses on 12 sensors 1 installed as shown in FIG. 2, for example. Sensors 101A to 101C, 102A to 102C, 103A to 103C, and 104A to 104C will be collectively referred to as "sensors 1" as appropriate. 101A to 101C will be collectively referred to as "sensors 101" (FIG. 1) as appropriate. 102A to 102C will be collectively referred to as "sensors 102" (FIG. 1) as appropriate. 103A to 103C will be collectively referred to as "sensors 103" (not shown) as appropriate. 104A to 104C will be collectively referred to as "sensors 104" (not shown) as appropriate.

[0024] 2 is an acoustic axis set in common to sensors 101A and 102A, and is along the X-axis direction, with sensors 101A and 102A facing each other with acoustic axis 901A as the reference. Acoustic axes 901B and 901C are similar to acoustic axis 901A. Note that acoustic axes 901A to 901A will be collectively referred to as "acoustic axis 901" where appropriate.

[0025] 2 is an acoustic axis set in common to sensors 103A and 104A, and is along the Y direction (i.e., perpendicular to acoustic axis 901A), with sensors 103A and 104A facing each other with acoustic axis 903A as the reference. Acoustic axes 903B and 903C are similar to acoustic axis 903A. Note that acoustic axes 903A to 903A will be collectively referred to as "acoustic axis 903" where appropriate.

[0026] The target area is divided into a plurality of sections in a matrix by acoustic axes 901 and 903 in a plan view as shown in FIG.

[0027] As a variation, the angle at which sound axis 901 and sound axis 903 intersect may be any angle other than a right angle, for example.

[0028] Furthermore, sensors 101A to 101C and sensors 102A to 102C are configured to transmit sound waves to a target area in a direction along acoustic axes 901A to 901C, and are a plurality of sensors 1 arranged in a direction along acoustic axis 903.

[0029] Furthermore, sensors 103A to 103C and sensors 104A to 104C are configured to transmit sound waves to the target area in a direction along acoustic axes 903A to 903C, and are a plurality of sensors 1 arranged in a direction along acoustic axis 901.

[0030] 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.

[0031] (Configuration - Sensor - Transmitter) 3 is a wave transmitting means for transmitting sound waves to a target region, and outputs sound waves along acoustic axes 901 and 903 set therein. This wave transmitting unit 11 can be configured using a known acoustic wave transmitter (for example, one using a piezoelectric ceramic vibrator, a signal processing circuit, etc.).

[0032] 1 is configured to output a sound wave having a predetermined directivity along the acoustic axis 901 toward one side (+X direction).

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 2 are also configured in the same way, that is, to output sound waves having a predetermined directivity along sound axis 903 toward one side (-Y direction).

[0037] Then, the sound waves from the sensors 103A to 103C reach the sensors 104A to 104C, and the sound waves that reach them are assumed to be "direct waves" and "reflected waves" as described above.

[0038] 1 are also configured to output sound waves having a predetermined directivity along the sound axis 903 toward the other side (+Y direction).

[0039] (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.).

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The same is true for the wave receiving units 12 of the sensors 103A to 103C in Figure 2, that is, they are configured to receive the sound waves output from the sensors 104A to 104C, and also to receive sound waves corresponding to the sound waves output by the sensors 103A to 103C themselves.

[0044] The same is true for the wave receiving units 12 of the sensors 104A to 104C in Figure 2, that is, they are configured to receive the sound waves output from the sensors 103A to 103C, and also to receive sound waves corresponding to the sound waves output by the sensors 104A to 104C themselves.

[0045] (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 or the like (the same applies to recording units of other devices).

[0046] (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 launched on the OS and realize specific functions), and an internal memory such as RAM for storing programs and various data (the same applies to control units of other devices).

[0047] The control unit 14 functions, for example, conceptually as a temperature specifying means.

[0048] ===Temperature identification means=== The temperature determination means is a means for determining a first temperature on the propagation path of the sound wave transmitted from the wave transmitting means based on a transmission signal corresponding to the sound wave transmitted by the wave transmitting means and a reception signal corresponding to the sound wave received by the wave receiving means. Note that the processing performed by each part of this control unit 14 will be described later.

[0049] ===Interpretation of Terms (First Wave Transmitting Means, First Wave Receiving Means, First Wave Transmitting and Receiving Means, First Temperature Identifying Means)=== In this embodiment, for example, sensors 1 that share a common acoustic axis 901A to 901C (for example, sensors 101A and 102A that face each other based on the common acoustic axis 901A) are configured to process in a mutually combined state.

[0050] In this case, for example, it may be interpreted that the wave transmitting unit 11 of one of the combined sensors, sensor 101A or sensor 102A, corresponds to the "first wave transmitting means," and the wave receiving unit 12 of the other sensor corresponds to the "first wave receiving means."

[0051] The "first wave transmitting means" refers to a means for transmitting sound waves to a target area in a direction along the first sound axis. The "first wave receiving means" refers to a means for receiving sound waves transmitted from the first wave transmitting means, and receives sound waves propagated through the target area along the first sound axis. The combination of the "first wave transmitting means" and the "first wave receiving means" is the "first wave transmitting and receiving means."

[0052] Furthermore, the "temperature determining means" in the control unit 14 of the sensor 101A or the sensor 102A may be interpreted as corresponding to the "first temperature determining means."

[0053] The "first temperature determination means" is a means for determining the first temperature on the propagation path of the sound wave transmitted from the first transmitting means based on the first transmitting-side sound signal corresponding to the sound wave transmitted by the first transmitting means and the first receiving-side sound signal corresponding to the sound wave received by the first receiving means.

[0054] ===Interpretation of Terms (Second Wave Transmitting Means, Second Wave Receiving Means, First Wave Transmitting and Receiving Means, Second Temperature Determining Means)=== In this embodiment, for example, sensors 1 that share a common acoustic axis 903A to 903C (for example, sensors 103A and 104A that face each other based on the common acoustic axis 903A) are configured to process in a mutually combined state.

[0055] In this case, for example, it may be interpreted that the wave transmitting unit 11 of one of the combined sensors, sensor 103A or sensor 104A, corresponds to the "second wave transmitting means," and the wave receiving unit 12 of the other sensor corresponds to the "second wave receiving means."

[0056] The "second wave transmitting means" refers to a means for transmitting sound waves to a target area in a direction along a second sound axis, which is a direction substantially perpendicular to the first sound axis. The "second wave receiving means" refers to a means for receiving sound waves transmitted from the second wave transmitting means, and receives sound waves propagated through the target area along the second sound axis. The combination of the "second wave transmitting means" and the "second wave receiving means" is the "second wave transmitting and receiving means."

[0057] Furthermore, the "temperature determining means" in the control unit 14 of the sensor 103A or the sensor 104A may be interpreted as corresponding to the "second temperature determining means."

[0058] The "second temperature determination means" is a means for determining the second temperature on the propagation path of the sound wave transmitted from the second transmitting means based on a second transmitting signal corresponding to the sound wave transmitted by the second transmitting means and a second receiving signal corresponding to the sound wave received by the second receiving means.

[0059] === Variations === As a variation, the terms "first" and "second" above may be interpreted interchangeably.

[0060] (Configuration - Disaster prevention receiver) Fig. 5 is a block diagram showing a disaster prevention receiver. The disaster prevention receiver 9 in Fig. 5 is a disaster prevention receiving device, and is a device for monitoring and managing a target area. The disaster prevention receiver 9 is connected to, for example, a sensor 1 so that they can communicate with each other.

[0061] The disaster prevention receiver 9 in FIG. 5 includes, for example, a communication unit 91, an operation unit 92, a display unit 93, an audio unit 94, a recording unit 95, and a control unit 96.

[0062] (Configuration - Disaster prevention receiver - Communication unit) 5 is a communication unit for communicating with an external device (for example, the sensor 1). The specific configuration is arbitrary, but it can be configured using, for example, a known communication circuit or the like.

[0063] (Configuration - Disaster prevention receiver - Operation unit) The operation unit 92 in Fig. 5 is an operation means for inputting operations to the disaster prevention receiver 9. The specific configuration is arbitrary, but it can be configured using, for example, various buttons or a touch panel.

[0064] (Configuration - Disaster prevention receiver - Display unit) 5 is a display unit that displays various information. The specific configuration is arbitrary, but it can be configured using a display or the like, for example.

[0065] (Configuration - Disaster prevention receiver - Sound section) 5 is an audio unit that outputs various types of audio information, etc. The specific configuration is arbitrary, but it can be configured using a speaker, for example.

[0066] (Configuration - Disaster prevention receiver - Recording unit) 5 is a recording unit that records programs and various data required for the operation of the sensor 1. The recording unit 95 stores, for example, area-related information.

[0067] "Area-related information" is information related to the target area to which the disaster prevention system 100 is applied, such as information that identifies the configuration of the target area (shape, size, etc.), the configuration of the detectors 1 installed in the target area (information indicating the installation location, etc.), etc.

[0068] (Configuration - Disaster prevention receiver - Control unit)

[0069] The control unit 96 in FIG. 5 is a control means for controlling the disaster prevention receiver 9, and conceptually functions as a fire location identification means, for example.

[0070] ===Fire location identification means=== The fire location identification means is a means for identifying the location of a fire based on the identification results of the first temperature identification means and the second temperature identification means.

[0071] The fire location identification means identifies the fire location in the direction along the second sound axis based on the position along the second sound axis at which at least one first transmitting and receiving means is located, for example, when the temporal dispersion of the first temperature for at least one first transmitting and receiving means among the plurality of first transmitting and receiving means exceeds a first threshold value.

[0072] For example, when all of the time-dependent variances of the multiple first temperatures for each of the multiple first transmitting and receiving means do not exceed a first threshold, the fire location identification means identifies the fire location in the direction along the second sound axis based on the position in the direction along the second sound axis at which the first transmitting and receiving means corresponding to the highest temperature among the multiple first temperatures is located, and the position in the direction along the second sound axis at which the first transmitting and receiving means corresponding to the temperature next to the highest temperature among the multiple first temperatures is located.

[0073] The fire location identification means identifies the fire location in the direction along the first sound axis based on the position along the first sound axis at which at least one second wave transmitting and receiving means is located, for example, when the temporal dispersion of the second temperature for at least one second wave transmitting and receiving means among the plurality of second wave transmitting and receiving means exceeds a second threshold value.

[0074] For example, when all of the variances over time of the multiple second temperatures for each of the multiple second wave transmitting and receiving means do not exceed the second threshold, the fire location identification means identifies the fire location in the direction along the first sound axis based on the position along the first sound axis at which the second wave transmitting and receiving means corresponding to the highest temperature among the multiple second temperatures is located and the position along the first sound axis at which the second wave transmitting and receiving means corresponding to the temperature next to the highest temperature among the multiple second temperatures is located. Note that the processing performed by each part of this control unit 96 will be described later.

[0075] (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.

[0076] ===Transmitting side acoustic signal=== Fig. 6 is an explanatory diagram of the transmitting-side acoustic signal. Note that the signal waveform in Fig. 6 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 (Fig. 3), and specifically, is an electrical signal generated by the transmitting unit 11.

[0077] The specific content of this transmitting-side acoustic signal is the same as that of known signals, and for example, as shown in Fig. 6, 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).

[0078] The frequency of the transmitting side acoustic signal (more specifically, the signal that is continuously output for the duration of time T92 in Figure 6) 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.

[0079] Then, the transmitting unit 11 in FIG. 3 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.

[0080] === 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.

[0081] Then, the wave receiving section 12 in FIG. 3 generates a receiving-side sound wave signal corresponding to the sound wave that it has received.

[0082] (Cross-correlation information) Next, the cross-correlation information will be described.

[0083] ===Prerequisite configuration=== Here, for example, two mutually combined sensors 1 (for example, a combination of sensor 101A and sensor 102A facing each other with common acoustic axis 901A as the reference in FIG. 3) are wired or wirelessly connected so as to be able to electrically communicate with each other, and one of these 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 the specific communication method here, and therefore a description thereof will be omitted.

[0084] Unless otherwise specified, the following description will be given taking as an example a case where the sensors 101A to 101C and 103A to 103C in Fig. 2 transmit sound waves and the sensors 102A to 102C and 104A to 104C in Fig. 2 receive sound waves. That is, for example, the sensors 102A to 102C and 104A to 104C generate receiving-side sound signals and transmit them to the sensors 101A to 101C and 103A to 103C, and various processes (including a process for identifying cross-correlation information) are performed on the sensors 101A to 101C and 103A to 103C side using both the transmitting-side sound signals and the corresponding receiving-side sound signals.

[0085] As a variation, the sensor 1 that transmits waves and the sensor 1 that receives waves may be changed as desired, for example, sensors 101A, 102B, 101C, etc. may transmit sound waves, and sensors 102A, 101B, 102C may receive sound waves.

[0086] ===Cross-correlation information=== FIG. 7 is an explanatory diagram of cross-correlation information. "Cross-correlation information" is information (information that can identify the degree of correlation) that determines the degree of correlation between the transmitting-side sound signal and the receiving-side sound signal (each sound signal of the sensor 1 that is combined with each other) with respect to the time lag, and is information that indicates, 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 technology. "Time lag" is a concept that indicates the time that is shifted when, for example, either the transmitting-side sound signal or the receiving-side sound signal is shifted in time.

[0087] The expression format of the cross-correlation information is arbitrary, and for example, it can be expressed in the graph format shown in Fig. 7, and the description will be made using this format. Here, the description will be made by focusing on the combination of the sensor 101A and the sensor 102A in Fig. 3, for example.

[0088] The horizontal axis of Fig. 7 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. 7 (such as "8", "+10", and "-10") are given for convenience of explanation.

[0089] The vertical axis in Figure 7 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).

[0090] Fig. 8 is an explanatory diagram of the time lag and the degree of correlation. In Fig. 8, time T81 indicates the time when sensor 101A transmits a sound wave, and time T82 indicates the time when sensor 102A receives the sound wave from sensor 101A. 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.

[0091] 8A 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. 8B and FIG. 8C, the acoustic signals when the delay times are time T71 and time T72 are shown.

[0092] In the cross-correlation information of Fig. 7, point P91 indicates the correlation value when the delay time is "0", for example, as shown in Fig. 8(a). In this case, when the time period of the receiving-side sound signal in Fig. 8(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. 8 is "0".

[0093] In the cross-correlation information of Fig. 7, point P92 indicates the correlation value when the delay time is time T71, as shown in Fig. 8(b), for example. In this case, when the time period of the receiving-side sound signal in Fig. 8(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. 7 is "0".

[0094] In the cross-correlation information of Fig. 7, 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. 8(c), for example. In this case, when the time period of the receiving-side sound signal in Fig. 8(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. 7 is a relatively large positive value (maximum value).

[0095] (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, a first fire location identification process, and a second fire location identification process will be described.

[0096] (Processing - Temperature detection processing) First, the temperature detection process will be described. Fig. 9 is a flowchart of the temperature detection process (in the following description 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, and is a process executed by the sensor 1, for example. This temperature detection process will be described from the point where it starts to be executed, assuming that it is repeatedly executed (the same applies to other processes).

[0097] 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.

[0098] Furthermore, the temperature detection process may be performed by, for example, the sensors 101A-101C and 103A-103C in Fig. 3, and here, focusing on the combination of sensor 101A and sensor 102A in Fig. 3, a case where sensor 101A performs the process will be described as an example (the same applies to the first fire detection process and the second fire detection process). Also, for example, as described above, a case where processing is performed on the sensor 101A side using both the transmitting-side sound signal and the corresponding receiving-side sound signal will be described (the same applies to the first fire detection process and the second fire detection process).

[0099] ===SA1=== At SA1 in FIG. 9, the control unit 14 of the sensor 101A identifies cross-correlation information based on the transmitting-side acoustic signal and the receiving-side acoustic signal corresponding to the transmitting-side acoustic signal.

[0100] 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.

[0101] =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 7 is identified.

[0102] In this case, in the cross-correlation information, as shown in FIG. 7, 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).

[0103] 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 7) is greater than the maximum value of the correlation degree corresponding to the reflected wave (point P94 in Figure 7), and the maximum value of the correlation degree corresponding to the direct wave (point P93 in Figure 7) becomes the overall maximum value.

[0104] =When sound waves are scattered by flames= Fig. 10 is a side view showing the inside of the target area, and Fig. 11 is an explanatory diagram of cross-correlation information. Fig. 10 illustrates a state in which a fire has broken out within the target area and the flames of the fire have reached acoustic axis 901A. Note that "the flames have reached acoustic axis 901A" is a concept that includes cases in which a flame has broken out on acoustic axis 901A, cases in which a flame that has broken out in another location has reached acoustic axis 901A, and cases in which a flame has reached the vicinity of acoustic axis 901A (for example, within 1 meter).

[0105] For example, when flames of a fire reach sound axis 901A within the target region as shown in FIG. 10, scattering of sound waves occurs due to the flames within the target region, and the cross-correlation information of FIG. 11 is identified.

[0106] In this case, in the cross-correlation information, as shown in FIG. 11, 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).

[0107] 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 11) is greater than the maximum value of the correlation degree corresponding to the direct wave (point P83 in Figure 11), and the maximum value of the correlation degree corresponding to the reflected wave (point P84 in Figure 11) becomes the overall maximum value.

[0108] ===SA2=== At SA2 in FIG. 9, the control unit 14 of the sensor 101A identifies the propagation time of the direct wave.

[0109] Specifically, although this is optional, the process is performed assuming that the cross-correlation information (Fig. 7) 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. 7) is the overall maximum value.

[0110] 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.

[0111] =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. 7 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.

[0112] =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 11 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.

[0113] ===SA3=== At SA3 in FIG. 9, the control unit 14 of the sensor 101A identifies the temperature in the target area.

[0114] 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 101A. For example, it is assumed that the distance between the wall surfaces in the horizontal direction (X axis) on the sound axis 901A in Fig. 1 (i.e., the distance between the sensors 101A and 102A) (hereinafter also referred to as "separation distance") and the like are recorded as the target area identification information.

[0115] 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.

[0116] 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.

[0117] =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.

[0118] =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 11 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.

[0119] ===SA4=== At SA4 in FIG. 9, the control unit 14 of the sensor 101 determines whether or not to correct the temperature identified at SA3.

[0120] Specifically, the process is arbitrary, but for example, the process is performed with the intention of determining that correction should be performed when "there is scattering of sound waves by a flame" as described above. For example, the temperature detection process (FIG. 9) is repeatedly executed, and the temperature of the target area is identified and detected each time the temperature detection process is executed, so when there is a change from "when there is no scattering of sound waves by a flame" to "when there is scattering of sound waves 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.

[0121] 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 9) is repeatedly executed.

[0122] On the other hand, if the temperature determined in SA3 fluctuates by more than a threshold value (for example, 5 to 10 degrees) from the "previous temperature," it is determined that this 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.

[0123] ===SA5=== At SA5 in FIG. 9, the control unit 14 of the sensor 101A identifies the propagation time of the direct wave by the first method.

[0124] Fig. 12 is an explanatory diagram of cross-correlation information. In Fig. 12, 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. 11.

[0125] 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).

[0126] 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).

[0127] 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.

[0128] 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. 12. 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.

[0129] Here, for example, from among many maximum values ​​including points P84 and P83 in Fig. 12, 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.

[0130] By performing this processing, it becomes possible to specify the propagation time, for example, taking into account the correlation degree of all time periods.

[0131] ===SA6=== At SA6 in FIG. 9, the control unit 14 of the sensor 101A identifies the propagation time of the direct wave by the second method.

[0132] 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).

[0133] Here, for example, from among many maximum values ​​including point P83 in Fig. 12, 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.

[0134] 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.

[0135] ===SA7=== At SA7 in FIG. 9, the control unit 14 of the sensor 101A identifies the propagation time of the direct wave by the third method.

[0136] 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.

[0137] 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. 9 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. 12). Even in such a case, it is possible to identify the intended propagation time.

[0138] 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.

[0139] ===SA8=== At SA8 in FIG. 9, the control unit 14 of the sensor 101A identifies the temperature corresponding to the propagation time identified at SA5 to SA7.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] ===SA9=== In SA9 of Figure 9, the control unit 14 of the sensor 101A 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.

[0144] Here, for example, the temperature identified from the delay time corresponding to point P83 in Fig. 12 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.

[0145] (Processing - First Fire Detection Processing) Next, the first fire detection process will be described. Fig. 13 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, for example, a process for detecting a fire by appropriately changing the frequency of sound waves, and is a process executed by the detector 1, for example.

[0146] Here, for example, by repeatedly executing the temperature detection process of Figure 9, 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).

[0147] ===SB1=== In SB1 of FIG. 13, the control unit 14 of the sensor 101A 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, outputs the acoustic wave, and then identifies the temperature repeatedly detected in the temperature detection process (FIG. 9).

[0148] 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."

[0149] 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 6), so high frequencies refer to multiple frequencies belonging to the first frequency band (the same applies to low frequencies).

[0150] 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.

[0151] ===SB2=== 13, the control unit 14 of the sensor 101 performs processing based on whether the rate of temperature increase identified in SB1 is equal to or greater than a first threshold (e.g., 6°C / min). If the rate of temperature increase is equal to or greater than the first threshold (YES in SB2), the process proceeds to SB6, and if the rate of temperature increase is not equal to or greater than the first threshold (NO in SB2), the process proceeds to SB3.

[0152] 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).

[0153] 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."

[0154] 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."

[0155] ===SB3=== 13, the control unit 14 of the sensor 101A processes the temperature identified in SB1 depending on whether the rate of temperature rise 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.

[0156] ===SB4=== At SB4 in FIG. 13, the control unit 14 of the sensor 101A 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. 9).

[0157] 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.

[0158] ===SB5=== 13, the control unit 14 of the sensor 101A 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.

[0159] ===SB6=== At SB6 in Figure 13, the control unit 14 of the detector 101A detects that a fire has occurred in the target area, outputs an alarm signal (a signal notifying of the occurrence of a fire) (transmits the alarm signal to the disaster prevention receiver 9), issues a fire alarm, and then terminates the processing.

[0160] (Processing - Secondary Fire Detection Processing) Next, the second fire detection process will be described. Fig. 14 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, for example, a process for detecting a fire based on temperature variations in the target area, and is a process executed by the detector 1, for example.

[0161] 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.

[0162] ===SC1~SC3=== In SC1 to CS3 in FIG. 14, the control unit 14 of the sensor 101 performs the same processes as those in SB1 to SB3 in FIG.

[0163] ===SC4=== In SC4 of Fig. 14, the control unit 14 of the sensor 101 identifies the degree of temperature variation identified in SC1 and performs processing depending on whether the identified degree of variation is equal to or greater than a threshold. Note that the variation here may be a statistical value related to temperature (e.g., variance, standard deviation, etc.). Note that 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.

[0164] 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.

[0165] ===SC5=== At SC5 in Figure 14, the control unit 14 of the detector 101 detects that a fire has occurred in the target area, similar to SB6 in Figure 13, and then outputs an alarm signal (transmits the alarm signal to the disaster prevention receiver 9) and issues a fire alarm, and then terminates the processing.

[0166] (Processing - First fire location processing) Next, the first fire location identification process will be described. Fig. 15 is an explanatory diagram of the process. In Fig. 15, fire sources F1 to F3 are illustrated in a plan view showing the inside of the target area.

[0167] The "first fire location identification process" is a process for identifying the location of a fire, for example, a process performed using the temperature identified by each detector 1, and is a process executed by the disaster prevention receiver 9.

[0168] The timing of execution of this first fire location identification process is arbitrary, but for example, execution is started when a fire is detected in the first fire detection process of Fig. 13 or the second fire detection process of Fig. 14. In other words, execution is started when the disaster prevention receiver 9 receives an alarm signal transmitted by the detector 1, for example.

[0169] Also, each detector 1 (more specifically, for example, detectors 101A-101C, 103A-103C, etc. in FIG. 3) is configured to repeatedly execute the temperature detection process (FIG. 9) and transmit temperature information indicating the temperature of the monitored area detected to the disaster prevention receiver 9. In this case, each detector 1 transmits the temperature information to the disaster prevention receiver 9 in a state where the detector ID (detector identification information for uniquely identifying the detector 1) set for itself is correlated with the temperature information.

[0170] Furthermore, the area-related information in the recording unit 95 (Fig. 5) of the disaster prevention receiver 9 includes information that correlates the detector ID of each detector 1 with installation location-related information of the detector 1 corresponding to that detector ID (information indicating the location where each detector 1 is installed within the target area, information indicating the sound axis set for each detector 1, etc.).The disaster prevention receiver 9 is then capable of ascertaining the temperature that has been identified and detected by each detector 1 within the target area, based on the detector ID and temperature information received from each detector 1 and the area-related information recorded in the recording unit 95.

[0171] Then, the control unit 96 of the disaster prevention receiver 9 identifies the temperature detected by each sensor 1 as the temperature on the acoustic axis in the monitoring area corresponding to each sensor 1. Specifically, for example, the control unit 96 regards the temperatures identified by sensors 101A to 101C and 103A to 103C in Fig. 15 as temperatures on the corresponding acoustic axes 901A to 901C and 903A to 903C, and performs the following position identification process.

[0172] Here, for example, the temperature etc. identified by the sensor 101A in FIG. 15 is regarded as the temperature etc. on the acoustic axis 901A in FIG. 15, and the position identification process is performed.

[0173] ===Location Identification Processing=== In the location identification process, the control unit 96 of the disaster prevention receiver 9 identifies the highest and second highest temperatures on the parallel sound axes, and if the difference between these temperatures (temperature difference) is equal to or greater than a predetermined temperature threshold (a predetermined value at which it can be determined that the highest temperature is clearly higher than the second temperature), the highest temperature is relatively higher than the other temperatures, and the control unit 96 identifies the position on the sound axis corresponding to the highest temperature as the location of the fire.On the other hand, if the temperature difference is less than the predetermined temperature threshold, the highest temperature and the second temperature are almost the same, and the control unit 96 identifies the position between the two sound axes corresponding to the highest and second temperatures as the location of the fire.

[0174] In the above, with regard to "identifying the highest temperature and the second highest temperature," if the two temperatures match, these two temperatures are identified, and the above-mentioned processing is performed based on the difference between these temperatures.

[0175] Then, by performing the above-mentioned processing on sound axes 901A to 901C along the X-axis direction, the position of the fire in the Y-axis direction is identified, and by performing the above-mentioned processing on sound axes 903A to 903C along the Y-axis direction, the position of the fire in the X-axis direction is identified.

[0176] Here, for example, a case where fire sources F1 to F3 in FIG. 15 are the locations of the fire will be described.

[0177] =Fire source F1= For example, if the fire source F1 in Figure 15 is the location of the fire, then for sound axes 901A to 901C along the X-axis direction, the "highest temperature" = "temperature of sound axis 901A" and the "second temperature" = "temperature of sound axis 901B" are identified, and since the difference between these temperatures is greater than or equal to a predetermined temperature threshold, the position of sound axis 901A corresponding to the highest temperature is identified as the location of the fire in the Y-axis direction.

[0178] In this case, for sound axes 903A to 903C along the Y-axis direction, the "highest temperature" is identified as "the temperature of sound axis 903A" and the "second temperature" is identified as "the temperature of sound axis 903B", and since the difference between these temperatures is greater than or equal to a predetermined temperature threshold, the position of sound axis 903A corresponding to the highest temperature is identified as the position of the fire along the X-axis direction.

[0179] In this case, the position corresponding to the position of the fire source F1 in FIG. 15 is identified as the position of the fire.

[0180] =Fire source F2= For example, if fire source F2 in Figure 15 is the location of the fire, then on sound axes 901A to 901C along the X-axis direction, the position of sound axis 901A is identified as the location of the fire in the Y-axis direction, in the same way as when fire source F1 is the location of the fire.

[0181] In this case, for sound axes 903A to 903C along the Y-axis direction, the "highest temperature" is determined to be the "temperature of sound axis 903B" and the "second temperature" is determined to be the "temperature of sound axis 903C." Since the difference between these temperatures is less than a predetermined temperature threshold, the position between the position of sound axis 903B corresponding to the highest temperature and the position of sound axis 903C corresponding to the second temperature (for example, the position corresponding to the midpoint in the X-axis direction) is determined to be the position of the fire in the X-axis direction.

[0182] In this case, the position corresponding to the position of the fire source F2 in FIG. 15 is identified as the position of the fire.

[0183] =Fire source F3= For example, if fire source F3 in Figure 15 is the location of the fire, then for sound axes 901A to 901C along the X-axis direction, the "highest temperature" = "temperature of sound axis 901A" and the "second temperature" = "temperature of sound axis 901B" are identified, and since the difference between these temperatures is less than a predetermined temperature threshold, the position between the position of sound axis 901A corresponding to the highest temperature and the position of sound axis 901B corresponding to the second temperature (for example, the position corresponding to the midpoint in the Y-axis direction) is identified as the location of the fire in the Y-axis direction.

[0184] In this case, for sound axes 903A to 903C along the Y-axis direction, the "highest temperature" is determined to be the "temperature of sound axis 903A" and the "second temperature" is determined to be the "temperature of sound axis 903B." Since the difference between these temperatures is less than a predetermined temperature threshold, the position between the position of sound axis 903A corresponding to the highest temperature and the position of sound axis 903B corresponding to the second temperature (for example, the position corresponding to the midpoint in the X-axis direction) is determined to be the position of the fire in the X-axis direction.

[0185] In this case, the position corresponding to the position of the fire source F3 in FIG. 15 is identified as the position of the fire.

[0186] (Processing - Second fire location processing) Next, the second fire location identification process will be described.

[0187] The "second fire location identification process" is a process for identifying the location of a fire, for example, a process performed using the variance over time of the temperature identified by each detector 1, and is a process executed by the disaster prevention receiver 9.

[0188] The "variance of temperature over time" is a concept that indicates the degree of variation when the temperature fluctuates and varies due to, for example, a flame.

[0189] The timing of execution of this second fire location identification process is arbitrary, but may be the same as that of the first fire location identification process, for example.

[0190] Furthermore, each detector 1 (more specifically, for example, detectors 101A-101C and 103A-103C in Fig. 3) performs processing similar to that described in the first fire location identification processing, and the control unit 96 of the disaster prevention receiver 9 identifies the temperature detected by each detector 1 as the temperature on the acoustic axis corresponding to each detector 1 in the monitored area. Specifically, for example, the following location identification processing is performed by regarding each temperature identified by detectors 101A-101C and 103A-103C in Fig. 15 as the temperature on the corresponding acoustic axis 901A-901C and 903A-903C.

[0191] ===Location Identification Processing=== In the location determination process, the control unit 96 of the disaster prevention receiver 9 determines the time-dependent variance of temperature on each of the sound axes that are parallel to each other, and performs processing depending on whether or not any of the determined variance values ​​exceeds a predetermined threshold value.

[0192] If there is a variance value that exceeds a predetermined threshold, the position on the sound axis that corresponds to that variance value (that is, the variance value that exceeds the predetermined threshold) is identified as the position of the fire.

[0193] On the other hand, if there is no variance value exceeding the predetermined threshold, the location of the fire is identified using the method described in the first fire location identification process.

[0194] Here, for example, a case where fire sources F1 to F3 in FIG. 15 are the locations of the fire will be described.

[0195] =Fire source F1= 15 is the location of the fire, the temperature variance over time (i.e., the temperature variance over time on sound axis 901A, the temperature variance over time on sound axis 901B, and the temperature variance over time on sound axis 901C) is identified. In this case, since only the temperature on sound axis 901A varies relatively greatly due to the flame of fire source F1, only the temperature variance value on sound axis 901A exceeds a predetermined threshold, and if there is a variance value that exceeds the predetermined threshold, the position of sound axis 901A corresponding to that variance value is identified as the location of the fire in the Y-axis direction.

[0196] In this case, the temperature variance over time is determined on sound axes 903A to 903C along the Y-axis direction (i.e., the temperature variance over time on sound axis 903A, the temperature variance over time on sound axis 903B, and the temperature variance over time on sound axis 903C). Note that in this case, only the temperature on sound axis 903A varies relatively greatly due to the flame of fire source F1, so only the temperature variance value on sound axis 903A exceeds a predetermined threshold, and if there is a variance value that exceeds the predetermined threshold, the position of sound axis 903A corresponding to that variance value is determined as the position of the fire in the X-axis direction.

[0197] In this case, the position corresponding to the position of the fire source F1 in FIG. 15 is identified as the position of the fire.

[0198] =Fire source F2= For example, if fire source F2 in Figure 15 is the location of the fire, then on sound axes 901A to 901C along the X-axis direction, the position of sound axis 901A is identified as the location of the fire in the Y-axis direction, in the same way as when fire source F1 is the location of the fire.

[0199] In this case, the temperature dispersion over time is identified on sound axes 903A to 903C along the Y-axis direction. Note that in this case, the degree of variation in all of these temperatures is relatively small, so all of the temperature dispersion values ​​on sound axes 903A to 903C are equal to or less than a predetermined threshold, and no dispersion value exceeds the predetermined threshold, and the location of the fire is identified using the method described in the first fire location identification process.

[0200] Specifically, for sound axes 903A to 903C along the Y-axis direction, the "highest temperature" is determined to be the "temperature of sound axis 903B" and the "second temperature" is determined to be the "temperature of sound axis 903C." Since the difference between these temperatures is less than a predetermined temperature threshold, the position between the position of sound axis 903B corresponding to the highest temperature and the position of sound axis 903C corresponding to the second temperature (for example, the position corresponding to the midpoint in the X-axis direction) is determined to be the position of the fire in the X-axis direction.

[0201] In this case, the position corresponding to the position of the fire source F2 in FIG. 15 is identified as the position of the fire.

[0202] =Fire source F3= For example, if fire source F3 in Fig. 15 is the location of the fire, the temperature variance over time is identified on sound axes 901A to 901C along the X-axis direction. In this case, the degree of variation in all of these temperatures is relatively small, so all of the temperature variance values ​​on sound axes 901A to 901C are below a predetermined threshold value and no variance value exceeds the predetermined threshold value, and the location of the fire is identified using the method described in the first fire location identification process.

[0203] Specifically, for sound axes 901A to 901C along the X-axis direction, the "highest temperature" is determined to be the "temperature of sound axis 901A" and the "second temperature" is determined to be the "temperature of sound axis 901B." Since the difference between these temperatures is less than a predetermined temperature threshold, the position between the position of sound axis 901A corresponding to the highest temperature and the position of sound axis 901B corresponding to the second temperature (for example, the position corresponding to the midpoint in the Y-axis direction) is determined to be the position of the fire in the Y-axis direction.

[0204] In this case, the temperature dispersion over time is identified on sound axes 903A to 903C along the Y-axis direction. Note that in this case, the degree of variation in all of these temperatures is relatively small, so all of the temperature dispersion values ​​on sound axes 903A to 903C are equal to or less than a predetermined threshold, and no dispersion value exceeds the predetermined threshold, and the location of the fire is identified using the method described in the first fire location identification process.

[0205] Specifically, for sound axes 903A to 903C along the Y-axis direction, the "highest temperature" is determined to be the "temperature of sound axis 903A" and the "second temperature" is determined to be the "temperature of sound axis 903B." Since the difference between these temperatures is less than a predetermined temperature threshold, the position between the position of sound axis 903A corresponding to the highest temperature and the position of sound axis 903B corresponding to the second temperature (for example, the position corresponding to the midpoint in the X-axis direction) is determined to be the position of the fire in the X-axis direction.

[0206] In this case, the position corresponding to the position of the fire source F3 in FIG. 15 is identified as the position of the fire.

[0207] The predetermined threshold value to be compared with the temperature variance value may be interpreted as corresponding to the "first threshold value" or "second threshold value" to be compared with the temperature variance over time. The predetermined threshold value to be compared with the variance value on the X-axis side and the predetermined threshold value to be compared with the variance value on the Y-axis side may be the same value or different values. The predetermined threshold value may be determined, for example, through experiments or simulations, to determine whether or not a fire is located on the sound axis, and this value may be used.

[0208] (Effects of the embodiment) As described above, according to this embodiment, it is possible to identify the location of a fire by identifying the location of the fire based on the identification results of the first temperature identifying means and the second temperature identifying means. In particular, for example, since the target area is divided into a plurality of sections in a matrix by a plurality of first sound axes and a plurality of second sound axes, it is possible to reliably identify the location of the fire based on each section.

[0209] Furthermore, when the variance of the first temperature over time exceeds the first threshold, the location of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where at least one first wave transmitting and receiving means is provided; when all of the variances of the first temperature over time do not exceed the first threshold, the location of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the highest temperature is provided and the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature is provided; when the variance of the second temperature over time exceeds the second threshold, the location of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature is provided; The location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis on which the wave-receiving means is provided, and if all of the time-dependent variances of the second temperature do not exceed the second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis on which the second wave-transmitting and receiving means corresponding to the highest temperature is provided and the position along the first sound axis on which the second wave-transmitting and receiving means corresponding to the temperature next to the highest temperature is provided.This makes it possible to identify the location of the fire taking into account, for example, the variances of the first and second temperatures, thereby improving the accuracy of identifying the location of the fire.

[0210] [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.

[0211] (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.

[0212] (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.

[0213] (Fire detection processing) Furthermore, the first fire detection process and the second fire detection process described in the above embodiment may be configured to be executed by all of the sensors 1, or only one process or only two 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.

[0214] (About processing) Furthermore, the system may be configured so that when a fire is detected in the first fire detection process of Fig. 13 described in the above embodiment, the first fire location identification process is executed, and on the other hand, when a fire is detected in the second fire detection process of Fig. 14, the second fire location identification process is executed. Alternatively, conversely, the system may be configured so that when a fire is detected in the first fire detection process of Fig. 13, the second fire location identification process is executed, and on the other hand, when a fire is detected in the second fire detection process of Fig. 14, the first fire location identification process is executed.

[0215] In addition, if a more effective combination of the first fire detection process or the second fire detection process and the first fire location identification process or the second fire location identification process can be expected depending on the type of fire that is expected, that effective combination may be implemented.

[0216] (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.

[0217] (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.

[0218] (Regarding sequential output of sound waves) Furthermore, in the multiple sensors 1 of FIG. 2, each sensor 1 may be configured to output sound waves in sequence so that the above processing is performed using sound waves output by one sensor 1.

[0219] (Features) Furthermore, the features of the above-described embodiments and modifications may be combined in any manner.

[0220] (Addendum) The fire detection system of Supplementary Note 1 is a fire detection system for identifying a fire location, which is the location of a fire that has occurred in a target area, comprising: a first wave transmitting means for transmitting sound waves to the target area in a direction along a first sound axis; a first wave receiving means for receiving the sound waves transmitted from the first wave transmitting means, the first wave transmitting and receiving means being a combination of a first wave receiving means for receiving the sound waves that have propagated through the target area along the first sound axis; a first temperature identifying means for identifying a first temperature on a propagation path of the sound waves transmitted from the first wave transmitting means based on a first wave transmitting signal corresponding to the sound waves transmitted by the first wave transmitting means and a first wave receiving signal corresponding to the sound waves received by the first wave receiving means; a second wave transmitting means for transmitting sound waves to the target area in a direction along a second sound axis that is substantially perpendicular to the first sound axis; and a second wave receiving means for receiving the sound waves transmitted from the second wave transmitting means, the second wave receiving means receiving the sound waves that have propagated through the target area along the second sound axis. a second temperature determining means for determining a second temperature on the propagation path of the sound waves transmitted from the second transmitting means based on a second transmitting signal corresponding to the sound waves transmitted by the second transmitting means and a second receiving signal corresponding to the sound waves received by the second receiving means; and a fire location determining means for determining the location of the fire based on the determination results of the first temperature determining means and the second temperature determining means, wherein the first sound axis and the second sound axis are approximately parallel to the floor surface of the target area, a plurality of the first transmitting and receiving means are arranged in a direction along the second sound axis, and a plurality of the second transmitting and receiving means are arranged in a direction along the first sound axis, and the target area is divided into a plurality of sections in a matrix by the plurality of first sound axes of the plurality of first transmitting and receiving means and the plurality of second sound axes of the plurality of second transmitting and receiving means.

[0221] The fire detection system of Supplementary Note 2 is the fire detection system of Supplementary Note 1, wherein the fire location identification means, when a variance over time of the first temperatures for at least one of the plurality of first wave transmitting and receiving means exceeds a first threshold, identifies the fire location in the direction along the second sound axis based on a position along the second sound axis at which at least one of the first wave transmitting and receiving means is provided, and, when all of the variances over time of the plurality of first temperatures for each of the plurality of first wave transmitting and receiving means do not exceed the first threshold, identifies the fire location in the direction along the second sound axis based on a position along the second sound axis at which the first wave transmitting and receiving means corresponding to the highest temperature of the plurality of first temperatures is provided and a position along the second sound axis at which the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature of the plurality of first temperatures is provided. The location of the fire in a direction along two sound axes is identified, and if the variance over time of the second temperatures for at least one of the plurality of second wave-transmitting and receiving means exceeds a second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis at which at least one of the second wave-transmitting and receiving means is located, and if all of the variances over time of the plurality of second temperatures for each of the plurality of second wave-transmitting and receiving means do not exceed the second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis at which the second wave-transmitting and receiving means corresponding to the highest temperature among the plurality of second temperatures is located and the position along the first sound axis at which the second wave-transmitting and receiving means corresponding to the temperature next to the highest temperature among the plurality of second temperatures is located.

[0222] (Effect of supplementary notes) According to the fire detection system described in Supplementary Note 1, it is possible to identify the location of a fire, for example, by identifying the location of a fire based on the identification results of the first temperature identification means and the second temperature identification means. In particular, for example, since the target area is divided into a plurality of sections in a matrix by a plurality of first sound axes and a plurality of second sound axes, it is possible to reliably identify the location of a fire based on each section.

[0223] According to the fire detection system described in Supplementary Note 2, when the variance of the first temperature over time exceeds the first threshold, the position of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where at least one first wave transmitting and receiving means is provided; when all of the variances of the first temperature over time do not exceed the first threshold, the position of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the highest temperature is provided and the position in the direction along the second sound axis where the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature is provided; and when the variance of the second temperature over time exceeds the second threshold, at least The location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis where at least one second wave transmitting / receiving means is provided, and if all of the variances of the second temperatures over time do not exceed the second threshold, the location of the fire in the direction along the first sound axis is identified based on the position along the first sound axis where the second wave transmitting / receiving means corresponding to the highest temperature is provided and the position along the first sound axis where the second wave transmitting / receiving means corresponding to the temperature next to the highest temperature is provided.This makes it possible to identify the location of the fire taking into account the variances of the first and second temperatures, for example, thereby improving the accuracy of identifying the location of the fire. [Explanation of symbols]

[0224] 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 9 Disaster prevention receiver 11 Wave transmitting unit (first wave transmitting means, second wave transmitting means, first wave transmitting / receiving means, second wave transmitting / receiving means) 12 wave receiving unit (first wave receiving means, second wave receiving means, first wave transmitting and receiving means, second wave transmitting and receiving means) 13 Recording section 14 control unit (first temperature determination means, second temperature determination means) 91 Communications Department 92 Operation section 93 Display section 94 Sound Department 95 Recording Department 96 Control Department (Fire Location Specific Means) 100 Disaster Prevention System (Fire Prevention System) 101 Perceptron 101A Sensor 101B Perceptron 101C Perceptron 102 Perceptron 102A Sensor 102B sensor 102C Perceptron 103 Perceptron 103A Sensor 103B Perceptron 103C Sensor 104 Perceptron 104A Sensor 104B Perceptron 104C Sensor 901 Sound Axis 901A tone axis 901B tone axis 901C tone axis 903 Sound Axis 903A tone axis 903B tone axis 903C tone axis F1 Fire Source F2 Fire Source F3 Fire Source P91 points P92 point P93 points P94 point T61 1st Time Band T62 2nd Time Band T63 3rd Time Band T71 Time T72 Time T81 Time T82 Time T91 Time T92 Time

Claims

1. A fire detection system for identifying a fire location, which is the location of a fire occurring in a target area, comprising: a first transmitting / receiving means that is a combination of a first transmitting means that transmits sound waves to the target area in a direction along a first sound axis, and a first receiving means that receives the sound waves transmitted from the first transmitting means and receives the sound waves that have propagated through the target area along the first sound axis; a first temperature determination means for determining a first temperature on a propagation path of the sound wave transmitted from the first wave transmitting means based on a first wave transmission signal corresponding to the sound wave transmitted by the first wave transmitting means and a first wave reception signal corresponding to the sound wave received by the first wave receiving means; a second wave transmitting means that transmits sound waves to the target area in a direction along a second sound axis that is a direction substantially perpendicular to the first sound axis; and a second wave receiving means that receives the sound waves transmitted from the second wave transmitting means and receives the sound waves that have propagated through the target area along the second sound axis; a second temperature determination means for determining a second temperature on a propagation path of the sound wave transmitted from the second wave transmitting means based on a second wave transmission signal corresponding to the sound wave transmitted by the second wave transmitting means and a second wave reception signal corresponding to the sound wave received by the second wave receiving means; a fire location identification means for identifying the fire location based on the identification results of the first temperature identification means and the second temperature identification means, the first sound axis and the second sound axis are substantially parallel to a floor surface of the target area, a plurality of the first wave transmitting and receiving means are arranged in a direction along the second sound axis, a plurality of the second wave transmitting and receiving means are arranged in a direction along the first sound axis, the target area is divided into a plurality of sections in a matrix by the plurality of first sound axes of the plurality of first wave transmitting and receiving means and the plurality of second sound axes of the plurality of second wave transmitting and receiving means, Fire detection systems.

2. The fire location identification means when the variance over time of the first temperature for at least one of the first wave transmitting and receiving means among the plurality of first wave transmitting and receiving means exceeds a first threshold value, the position of the fire in the direction along the second sound axis is identified based on the position in the direction along the second sound axis at which at least one of the first wave transmitting and receiving means is provided; when all of the variances over time of the plurality of first temperatures for each of the plurality of first wave transmitting and receiving means do not exceed the first threshold value, the position of the fire in the direction along the second sound axis is identified based on a position along the second sound axis at which the first wave transmitting and receiving means corresponding to the highest temperature among the plurality of first temperatures is provided and a position along the second sound axis at which the first wave transmitting and receiving means corresponding to the temperature next to the highest temperature among the plurality of first temperatures is provided; when the variance over time of the second temperature for at least one of the second wave transmitting and receiving means among the plurality of second wave transmitting and receiving means exceeds a second threshold value, the position of the fire in the direction along the first sound axis is identified based on the position in the direction along the first sound axis at which the at least one second wave transmitting and receiving means is provided; If all of the variances over time of the second temperatures for each of the second wave transmitting and receiving means do not exceed the second threshold value, the fire position in the direction along the first sound axis is identified based on a position in the direction along the first sound axis at which the second wave transmitting and receiving means corresponding to the highest temperature among the second temperatures is provided and a position in the direction along the first sound axis at which the second wave transmitting and receiving means corresponding to the temperature next to the highest temperature among the second temperatures is provided. The fire detection system of claim 1 .

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