Fire detection system

Abstract

To provide a fire detection system that enables detecting a fire more securely.SOLUTION: A fire detection system, which detects a fire occurring in an object area, comprises: a wave transmission unit 11 that transmits a sound wave to the object area; a wave reception unit 12 that receives the sound wave; temperature identification means of identifying a temperature on a propagation path of the transmitted sound wave on the basis of the transmitted sound wave and received sound wave; and fire detection means of detecting a fire occurring in the object area on the basis of the temperature of the object area the temperature identification means identifies. The wave reception unit 12 is configured to receive a direct arrival wave and reflection wave, and the temperature identification means is configured to identify a temperature on propagation paths of the direct arrival wave and reflection wave transmitted from the wave transmission unit 11 on the basis of a transmission wave signal corresponding to the sound wave the transmission unit 11 transmits, and a wave reception signal corresponding to the direct arrival wave and reflection wave the wave reception unit 12 receives.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

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

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

[0004] However, there has been a demand for a technology that can more reliably detect fires using sound waves.

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

[0006] In order to solve the above-mentioned problems and achieve the object, the fire detection system according to claim 1 is a fire detection system for detecting a fire occurring in a target area, comprising: wave transmitting means for transmitting sound waves to the target area; wave receiving means for receiving the sound waves; temperature specifying means for specifying a temperature on a propagation path of the sound waves transmitted from the wave transmitting means based on the sound waves transmitted by the wave transmitting means and the sound waves received by the wave receiving means; and a fire detection system for detecting a fire occurring in the target area based on the temperature of the target area specified by the temperature specifying means. The wave receiving means receives direct waves, which are sound waves that are transmitted to the wave transmitting means and reach the wave receiving means directly without being reflected within the target area, and reflected waves, which are sound waves that are transmitted to the wave transmitting means and reach the wave receiving means after being reflected within the target area, and the temperature determination means determines the temperature on the propagation paths of the direct waves and the reflected waves transmitted from the wave transmitting means based on a transmitted wave signal corresponding to the sound waves transmitted by the wave transmitting means and a received wave signal corresponding to the direct waves and the reflected waves received by the wave receiving means.

[0007] Furthermore, the fire detection system described in claim 2 is the fire detection system described in claim 1, wherein the reflected waves include one or more of a first reflected wave reflected by the floor surface of the target area, a second reflected wave reflected by the wall surface of the target area, or a third reflected wave reflected by the ceiling surface of the target area, and the temperature identification means identifies the temperature on the propagation path of the sound wave transmitted from the transmitting means based on arrival order information indicating the order in which the direct wave and the one or more reflected waves arrive at the receiving means.

[0008] Furthermore, the fire detection system described in claim 3 is the fire detection system described in claim 1, wherein the temperature determination means performs a first process of determining cross-correlation information that determines the degree of correlation between the transmitted signal and the received signal relative to the shift time when either the transmitted signal or the received signal is shifted in time, and a second process of determining the temperature on the propagation path of the sound wave transmitted from the transmitting means based on the cross-correlation information determined in the first process.

[0009] The fire detection system according to claim 4 is the fire detection system according to claim 1, characterized in that the reflected waves include multiple reflections that are reflected at a plurality of locations. [Effects of the Invention]

[0010] According to the fire detection system described in claim 1, by determining the temperature based on the transmitted signal corresponding to the transmitted sound wave and the received signal corresponding to the received direct wave and reflected wave, and detecting a fire based on the determined temperature, it becomes possible to more reliably detect a fire, for example.

[0011] According to the fire detection system described in claim 2, by identifying the temperature on the propagation path of the transmitted sound wave based on arrival order information indicating the order in which the direct wave and one or more reflected waves arrive at the receiving means, it is possible to improve the accuracy of temperature identification, for example, and therefore the accuracy of fire detection.

[0012] According to the fire detection system described in claim 3, by identifying the temperature on the propagation path of the sound wave based on cross-correlation information, it is possible to improve the accuracy of temperature identification, for example, and therefore the accuracy of fire detection.

[0013] According to the fire detection system of claim 4, the reflected waves include multiple reflections from multiple locations, making it possible to more reliably detect fires at any position in the target area, for example. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing an example of installation of a sensor according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing an example of installation of a sensor according to an embodiment of the present invention; [Figure 3] FIG. 2 is a block diagram showing a sensor. [Figure 4] FIG. 1 is an explanatory diagram of a sound wave. [Figure 5] FIG. 1 is an explanatory diagram of a sound wave. [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 fire detection process. [Figure 10] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 11] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 12] FIG. 10 is an explanatory diagram of cross-correlation information. [Figure 13] FIG. 1 is a side view showing the interior of the target area. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] [Basic Concept of the Embodiment] First, the basic concept of this embodiment will be explained. This embodiment generally relates to a fire detection system.

[0017] The term "fire detection system" refers to a system that detects fires occurring in a target area, and is a concept that includes, for example, systems that have reflective fire detectors and opposing fire detectors. Note that the fire detection system may also be interpreted as a concept that includes, for example, other devices (e.g., disaster prevention receiving devices, server devices, or terminal devices) in addition to fire detectors.

[0018] A "target area" is an area in which a fire is to be detected, and is a concept that includes, for example, a specified area indoors or outdoors, and as an example, a concept that includes any area such as a room in a building or a parking space in a parking lot.

[0019] In the following embodiment, the case where the "target area" is a room will be described.

[0020] [Specific details of the embodiment] Next, specific details of the embodiment will be described.

[0021] (composition) First, the configuration of a disaster prevention system according to this embodiment will be described. Figures 1 and 2 are diagrams showing an example of installation of sensors according to this embodiment.

[0022] 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.

[0023] 1 is a side view showing the inside of the target area, and Fig. 2 is a plan view showing the inside of the target area. In each figure, the X, Y, and Z axes are assumed to be mutually orthogonal, the Z axis indicates the vertical direction, and the X and Y axes indicate the horizontal direction.

[0024] The disaster prevention system 100 in FIG. 1 is a fire detection system, and includes a detector 1, for example.

[0025] Although the number of sensors 1 is arbitrary, the following description focuses on sensors 101 and 102, which are opposite each other based on a common acoustic axis 901. Sensors 101 to 102 have similar configurations, and will be referred to as sensor 1 when there is no need to distinguish between them.

[0026] (Configuration-sensor) Fig. 3 is a block diagram showing a detector, and Figs. 4 and 5 are explanatory diagrams of sound waves. Fig. 4 is a side view similar to Fig. 1, and Fig. 5 is a plan view similar to Fig. 2. Detector 1 in Fig. 1 is a fire detector that detects a fire in a target area, for example, a device that detects a fire using sound waves, and one example is detector 101 and detector 102 that have a common sound axis 901.

[0027] 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.

[0028] (Configuration - Sensor - Transmitter) 3 is a wave transmitting means for transmitting sound waves to a target area, and for example, outputs sound waves along a self-set sound axis 901. This wave transmitting unit 11 can be configured using a known sound wave transmitter (for example, one using a piezoelectric ceramic vibrator, a signal processing circuit, etc.).

[0029] 1 is configured to output a sound wave having a predetermined directivity along the acoustic axis 901 toward one side (+X direction).

[0030] The sound waves from sensor 101 then reach sensor 102, and the sound waves that reach it are assumed to be direct waves and reflected waves. "Direct waves" are sound waves that reach the target area without being reflected within the target area, as shown in Figures 4 and 5. "Reflected waves" are sound waves that reach the target area after being reflected within the target area, as shown in Figures 4 and 5.

[0031] Reflected waves may include, for example, a primary reflected wave that is reflected once, a secondary reflected wave that is reflected twice, and a tertiary reflected wave that is reflected three times. However, for the sake of convenience, this embodiment will focus on the primary reflected wave.

[0032] The reflected waves are assumed to be waves reflected by the floor surface (FIG. 4), ceiling (FIG. 4), and wall surface (FIG. 5). Regarding the reflected waves reflected by the wall surface, the reflected waves reflected by the wall surface on the +Y side shown in FIG. 5 and the reflected waves reflected by the wall surface on the -Y side (not shown) are measured, but in this embodiment, the description will focus on the reflected waves reflected by the wall surface on the +Y side shown in FIG. 5.

[0033] The reflected waves reflected from the floor, ceiling, and wall surfaces will be referred to as "floor-side reflected waves," "ceiling-side reflected waves," and "wall-side reflected waves," respectively. Furthermore, the "wall-side reflected waves" may be interpreted as having the same height in the Z-axis direction as the direct waves, for example.

[0034] 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).

[0035] (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.).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] (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.

[0040] (Configuration - Sensor - Control Unit) The control unit 14 in Figure 3 is a control means for controlling the sensor 1, and specifically, is a computer comprising a CPU, various programs that are interpreted and executed on the CPU (including basic control programs such as an OS, and application programs that are started on the OS and realize specific functions), and an internal memory such as a RAM for storing programs and various data.

[0041] The control unit 14 conceptually functions as, for example, a temperature specifying means and a fire detecting means.

[0042] ===Temperature identification means=== The temperature specifying means is means for specifying the temperature on the propagation path of the sound wave transmitted from the wave transmitting means based on the sound wave transmitted by the wave transmitting means and the sound wave received by the wave receiving means.

[0043] The temperature determination means determines the temperature along the propagation path of the direct wave and reflected wave transmitted from the transmitting means, for example, based on a transmitting signal corresponding to the sound wave transmitted by the transmitting means and a receiving signal corresponding to the direct wave and reflected wave received by the receiving means.

[0044] The temperature specifying means specifies the temperature on the propagation path of the sound wave transmitted from the wave transmitting means based on, for example, arrival order information indicating the order in which the direct wave and one or more reflected waves arrive at the wave receiving means.

[0045] The temperature determination means performs a first process of determining cross-correlation information that determines the degree of correlation between the transmitted signal and the received signal relative to the shift time when, for example, either the transmitted signal or the received signal is shifted in time, and a second process of determining the temperature on the propagation path of the sound wave transmitted from the transmitting means based on the cross-correlation information determined in the first process.

[0046] ===Fire Detection Methods=== The fire detection means is a means for detecting a fire occurring in a target area based on the temperature of the target area identified by the temperature identification means.

[0047] (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.

[0048] ===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.

[0049] 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).

[0050] 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.

[0051] Then, the transmitting unit 11 generates a transmitting-side acoustic signal in response to a command from the control unit 14, and outputs an acoustic wave corresponding to the generated acoustic signal.

[0052] === 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 specifically, is an electrical signal generated by the receiving unit 21.

[0053] Then, the wave receiving section 21 generates a receiving-side sound wave signal corresponding to the sound wave that it has received.

[0054] (Cross-correlation information) Next, the cross-correlation information will be described.

[0055] ===Prerequisite configuration=== 1 are connected by wire or wirelessly so as to be able to electrically communicate with each other, and one of these two sensors can also grasp the electrical signals (transmitting-side acoustic signal and receiving-side acoustic signal) of the other sensor. Note that any communication method can be applied as a specific communication method here, and therefore a description thereof will be omitted.

[0056] 1 transmits sound waves and the sensor 102 receives sound waves, unless otherwise specified. That is, for example, the sensor 102 generates a receiving-side sound signal and transmits it to the sensor 101, and the sensor 101 performs various processes (including a process for identifying cross-correlation information) using both the transmitting-side sound signal and the corresponding receiving-side sound signal.

[0057] ===Cross-correlation information=== 7 is an explanatory diagram of cross-correlation information. "Cross-correlation information" is information for determining the degree of correlation between the transmitting-side sound signal and the receiving-side sound signal with respect to the time lag (information that can identify the degree of correlation), and is information 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 techniques. "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.

[0058] The cross-correlation information may be expressed in any format, for example, it may be expressed in the form of a graph as shown in FIG. 7, and the explanation will be given using this format.

[0059] 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.

[0060] 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).

[0061] Fig. 8 is an explanatory diagram of the time lag and the degree of correlation. In Fig. 8, time T81 indicates the time when the sensor 101 transmits a sound wave, and time T82 indicates the time when the sensor 102 receives the sound wave from the sensor 101. In other words, the elapsed time from time T81 to time T82 (i.e., the difference time between time T81 and time T82) corresponds to the time from when the sound wave is transmitted to when the sound wave is received.

[0062] 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.

[0063] 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. 7 is "0".

[0064] 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".

[0065] 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).

[0066] ===Order of sound wave arrival=== The order in which sound waves transmitted from sensor 101 in Figures 4 and 5 arrive at sensor 102 depends on the propagation distance, and in this embodiment, a case will be described in which the sound waves are configured to arrive in the order of direct wave, ceiling-side reflected wave, floor-side reflected wave, and wall-side reflected wave. In particular, a case will be described in which information relating to each sound wave is configured to be separable in terms of time, as shown in Figure 7.

[0067] Note that any specific method may be used for achieving this configuration, but for example, the installation positions of the sensors 101 and 102 (for example, the mutual distance L in the X-axis direction in FIG. 4, the distance between the sensors 101 and 102 in the Z-axis direction relative to the height H from the floor to the ceiling, the distance from the sensors 101 and 102 to the wall in the Y-axis direction in FIG. 5, etc.) may be determined so that the arrival time of the direct wave is shorter than the arrival time of the ceiling-side reflected wave, thereby satisfying the condition (first condition) that the corresponding information in FIG. 7 does not overlap with each other, the arrival time of the ceiling-side reflected wave is shorter than the arrival time of the floor-side reflected wave, thereby satisfying the condition (second condition) that the corresponding information in FIG. 7 does not overlap with each other, and the arrival time of the floor-side reflected wave is shorter than the arrival time of the wall-side reflected wave, thereby satisfying the condition (third condition) that the corresponding information in FIG. 7 does not overlap with each other) may be determined.

[0068] The installation positions can be changed arbitrarily. For example, as illustrated in Figures 4 and 5, sensors 101 and 102 may be installed on the wall surface itself, or may be installed at a position away from the wall surface in the X-axis direction. Furthermore, sensors 101 and 102 may be installed at the same height as each other in the Z-axis direction, or at different heights (similarly in the Y-axis direction).

[0069] Furthermore, as long as it is in line with the concept of the arrival order described above, the installation positions of the sensors 101 and 102 may be determined arbitrarily by conducting experiments or simulations, taking into consideration the internal shape of the target area or objects (furniture, etc.) installed within the target area.

[0070] (process) Next, the fire detection process executed by the disaster prevention system 100 configured as above will be described. FIG. 9 is a flowchart of the fire detection process (in the following description of each process, steps will be abbreviated as "S"). The "fire detection process" is a process for detecting a fire occurring in a target area. This fire detection process will be described from the point where it starts to be repeatedly executed, for example.

[0071] For example, immediately after the start of the fire detection process, the control unit 14 of the detector 101 causes the transmitting unit 11 to generate a transmitting-side sound wave signal for generating sound waves of a frequency in the first frequency band and output the sound waves.

[0072] 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."

[0073] 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).

[0074] 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.

[0075] Also, for example, as described above, a case will be described in which processing is performed on the sensor 101 side using both the transmitting-side sound signal and the corresponding receiving-side sound signal (the same applies to other processing).

[0076] ===SA1=== In SA1 of FIG. 9, the control unit 14 of the sensor 101 identifies cross-correlation information based on the transmitting-side acoustic signal and the receiving-side acoustic signal corresponding to the transmitting-side acoustic signal.

[0077] 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 Figures 4 and 5 are acquired, and cross-correlation information is determined by performing known cross-correlation processing on each acquired acoustic signal.

[0078] Here, for example, a sound wave output from sensor 101 reaches sensor 102 in the order of a direct wave, a ceiling-side reflected wave, a floor-side reflected wave, and a wall-side reflected wave, and therefore the cross-correlation information in Figure 7 is identified.

[0079] ===SA2=== 9, the control unit 14 of the sensor 101 identifies the temperature in the target area (i.e., the temperature on the propagation path of the floor-side reflected wave) based on the floor-side reflected wave. Specifically, although any step may be taken, for example, a first step and a second step may be performed.

[0080] =Step 1= In the first step, in the cross-correlation information identified in SA1, a group of correlation degrees corresponding to the floor-side reflected wave is identified, a delay time corresponding to the maximum correlation degree among the identified group of correlation degrees is identified, and the identified delay time is identified as the propagation time of the floor-side reflected wave.

[0081] Note that, with regard to the method for identifying the correlation group corresponding to the floor-side reflected wave, for example, arrival order information indicating the aforementioned arrival order (in the order of direct wave, ceiling-side reflected wave, floor-side reflected wave, and wall-side reflected wave) is stored in the recording unit 14 of the sensor 101. Then, the control unit 14 refers to the arrival order information and determines that the floor-side reflected wave is third in arrival order, and then identifies the correlation group with the third shortest delay time (shown as "floor-side reflected group" in FIG. 7) among the four correlation groups in FIG. 7 (four groups of information whose correlation is equal to or greater than a predetermined value) as the correlation group corresponding to the floor-side reflected wave.

[0082] As a variation, the range of delay times of each sound wave may be assumed in advance, and a correlation degree group corresponding to a corresponding time range within this assumed range of delay times may be identified.

[0083] Here, for example, the delay time corresponding to point P95 in FIG. 7 is identified as the propagation time of the floor-side reflected wave.

[0084] =Second Step= In the second step, the temperature in the target area (that is, the temperature on the propagation path of the floor-side reflected wave) is determined based on the propagation time determined in the first step.

[0085] 3 and 4 is stored in the recording unit 13 of the sensor 101. The control unit 14 then refers to the propagation distance information in the recording unit 13 to identify the propagation distance of the floor-side reflected wave, identifies the propagation velocity, which is the speed of the sound wave, based on the identified propagation distance and the propagation time identified in the first step, and identifies the temperature using a predetermined method (such as a method of identifying the temperature using a known arithmetic expression that indicates the relationship between velocity and temperature) based on the identified propagation velocity.

[0086] Here, for example, the calculation result of "propagation distance" divided by "propagation time" is used as the propagation speed of the floor-side reflected wave, and the temperature on the propagation path of the floor-side reflected wave is identified based on this propagation speed.

[0087] It should be noted that the processes of SA1 and SA2 in Figure 9 are basically executed repeatedly independently of each process described below, and the sensor 101 is capable of repeatedly identifying the temperature along the propagation path of the floor-side reflected wave (the same applies to SA8 and SA13 described below).

[0088] ===SA3=== 9, the control unit 14 of the sensor 101 processes the temperature identified in SA2 depending on whether the rate of temperature rise is equal to or greater than a first threshold (e.g., 6°C / min). If the rate of temperature rise is equal to or greater than the first threshold (YES in SA3), the process proceeds to SA7, and if the rate of temperature rise is not equal to or greater than the first threshold (NO in SA3), the process proceeds to SA4.

[0089] 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).

[0090] 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."

[0091] 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."

[0092] ===SA4=== 9, the control unit 14 of the sensor 101 performs processing based on whether the rate of temperature rise of the temperature identified in SA2 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 SA4), the process proceeds to SA5, and if the rate of temperature rise is not equal to or greater than the second threshold (NO in SA4), the process proceeds to SA8.

[0093] ===SA5=== In SA5 of Figure 9, the control unit 14 of the sensor 101 causes the transmitting unit 11 to generate a transmitting-side sound wave signal for generating sound waves of a frequency in the second frequency band, output the sound waves, and then performs processing similar to SA1 and SA2 to repeatedly identify the temperature on the propagation path of the floor-side reflected wave.

[0094] 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.

[0095] ===SA6=== 9, the control unit 14 of the sensor 101 performs processing for the temperature identified in SA5 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 starting execution of SA5. If the rate of temperature rise has reached or exceeded the first threshold value within the predetermined time (YES in SA6), the process proceeds to SA7, and if the rate of temperature rise has not reached or exceeded the first threshold value within the predetermined time (NO in SA6), the process proceeds to SA1.

[0096] When proceeding to SA1 after a NO in SA6, the frequency is returned to high frequency before proceeding to SA1. Therefore, in the subsequent SA1, sound waves in the first frequency band are output and processing is performed, just as immediately after the start of the fire detection process.

[0097] ===SA7=== 9, the control unit 14 of the sensor 101 detects that a fire has broken out in the target area, outputs an alarm signal (a signal notifying the occurrence of a fire), issues a fire alarm, and then terminates the processing. Note that here, for example, the configuration may be such that the propagation path of the floor-side reflected wave is identified as the location of the fire, and information indicating the identified location is also output.

[0098] ===SA8=== In SA8 after NO in SA4 in Figure 9, the control unit 14 of the sensor 101 determines the temperature within the target area based on the direct wave and the wall-side reflected wave (i.e., the temperature on the propagation path of the direct wave and the temperature on the propagation path of the wall-side reflected wave).

[0099] Specifically, the process is arbitrary, and for example, the same process as that of SA1 and SA2 is performed. Here, only the parts that are different from SA1 and SA2 will be explained in detail (the same applies to SA13 described later).

[0100] 7 is first identified, and correlation groups corresponding to the direct wave and the wall-side reflected wave are identified based on the arrival order information in the recording unit 14, and the delay times corresponding to points P93 and P96 in Fig. 7 are identified as the propagation times of the direct wave and the wall-side reflected wave. Then, the propagation distance of each of the direct wave and the wall-side reflected wave is identified by referring to the propagation distance information, and based on the identified propagation distances and the identified propagation times, the propagation velocities, which are the speed of sound waves, are identified, and based on the identified propagation velocities, the temperature on the propagation path of the direct wave (hereinafter also referred to as the "direct-side temperature") and the temperature on the propagation path of the wall-side reflected wave (hereinafter also referred to as the "wall-side temperature") are identified.

[0101] ===SA9=== 9, the control unit 14 of the sensor 101 performs processing for the temperature identified in SA8 depending on whether the rate of temperature rise of the direct-side temperature or the wall-side temperature is equal to or greater than a first threshold value (e.g., 6°C / min). If the rate of temperature rise of the direct-side temperature or the wall-side temperature is equal to or greater than the first threshold value (YES in SA9), the control unit 14 proceeds to SA12, and if the rate of temperature rise of the direct-side temperature or the wall-side temperature is not equal to or greater than the first threshold value (i.e., if both the rate of temperature rise of the direct-side temperature and the rate of temperature rise of the wall-side temperature are less than the first threshold value) (NO in SA9), the control unit 14 proceeds to SA10.

[0102] ===SA10=== 9, the control unit 14 of the sensor 101 performs processing for the temperature identified in SA8 depending on whether the rate of temperature rise of the direct-side temperature or the wall-side temperature is equal to or greater than a second threshold (e.g., 2°C / min). If the rate of temperature rise of the direct-side temperature or the wall-side temperature is equal to or greater than the second threshold (YES in SA10), the control unit 14 proceeds to SA11, and if the rate of temperature rise of the direct-side temperature or the wall-side temperature is not equal to or greater than the second threshold (i.e., if both the rate of temperature rise of the direct-side temperature and the rate of temperature rise of the wall-side temperature are less than the second threshold) (NO in SA11), the control unit 14 proceeds to SA13.

[0103] ===SA11=== 9, the control unit 14 of the sensor 101 determines whether or not a fire is detected. While any specific determination method may be used, for example, a case where processing similar to SA5 and SA6 is performed will be described, and variations will be described in modified examples.

[0104] For example, the processing involves causing the transmitting unit 11 to generate a transmitting side sound wave signal for generating sound waves of a frequency in the second frequency band, outputting the sound waves, and then performing processing similar to that of SA8 to repeatedly determine the direct side temperature and wall side temperature at low frequencies.

[0105] Then, the specified direct-side temperature and wall-side temperature are processed depending on whether the temperature rise rate of the direct-side temperature or the wall-side temperature rise rate becomes equal to or greater than a first threshold value (e.g., 6°C / min) within a predetermined time (e.g., 5 minutes) after switching the frequency of the second frequency band. If the temperature rise rate of the direct-side temperature or the wall-side temperature rise rate becomes equal to or greater than the first threshold value within the predetermined time, it is determined that a fire has been detected (YES in SA11), and the process proceeds to SA12. On the other hand, if the temperature rise rate of the direct-side temperature or the wall-side temperature rise rate does not become equal to or greater than the first threshold value within the predetermined time (in other words, if both the temperature rise rate of the direct-side temperature and the wall-side temperature rise rate are less than the first threshold value), it is determined that a fire has not been detected (NO in SA11), and the process proceeds to SA13.

[0106] After the NO at SA11, the frequency is returned to high frequency and the process moves to SA13. Therefore, at SA13, sound waves in the first frequency band are output and processed.

[0107] ===SA12=== 9, the control unit 14 of the sensor 101 detects that a fire has occurred in the target area, outputs an alarm signal, issues a fire alarm, and then terminates the processing. Note that here, for example, the control unit 14 may be configured to identify the location of the fire on the propagation path of the direct wave or the wall-side reflected wave, and output information indicating the identified location.

[0108] ===SA13=== At SA13 in FIG. 9, the control unit 14 of the sensor 101 identifies the temperature in the target area based on the ceiling-side reflected wave (that is, the temperature on the propagation path of the ceiling-side reflected wave).

[0109] Specifically, the method is arbitrary, and for example, first, the cross-correlation information in Fig. 7 is identified, and the correlation group corresponding to the ceiling-side reflected wave is identified based on the arrival order information in the recording unit 14, and the delay time corresponding to point P94 in Fig. 7 is identified as the propagation time of the ceiling-side reflected wave. Then, the propagation distance of the ceiling-side reflected wave is identified by referring to the propagation distance information, and the propagation velocity, which is the speed of the sound wave, is identified based on the identified propagation distance and the above-mentioned identified propagation time, and the temperature on the propagation path of the ceiling-side reflected wave is identified based on the identified propagation velocity.

[0110] ===S14=== 9, the control unit 14 of the sensor 101 performs processing based on whether the rate of temperature rise of the temperature identified in SA13 is equal to or greater than a first threshold (e.g., 6°C / min). If the rate of temperature rise is equal to or greater than the first threshold (YES in SA14), the process proceeds to SA15, and if the rate of temperature rise is not equal to or greater than the first threshold (NO in SA14), the process proceeds to SA1.

[0111] ===SA15=== 9, the control unit 14 of the sensor 101 detects that a fire has occurred in the target area, outputs an alarm signal, issues a fire alarm, and then terminates the processing. Note that here, for example, the configuration may be such that the location of the fire is identified on the propagation path of the ceiling-side reflected wave, and information indicating the identified location is also output.

[0112] (Effects of the embodiment) Thus, according to this embodiment, by determining the temperature based on the transmitted signal corresponding to the transmitted sound waves and the received signal corresponding to the received direct waves and reflected waves, and detecting a fire based on the determined temperature, it becomes possible to more reliably detect a fire, for example.

[0113] Furthermore, by identifying the temperature on the propagation path of the transmitted sound wave based on arrival order information indicating the order in which the direct wave and one or more reflected waves arrive at the receiving means, it is possible to improve the accuracy of temperature identification, thereby improving the accuracy of fire detection, for example.

[0114] Furthermore, by identifying the temperature on the propagation path of the sound waves based on the cross-correlation information, it is possible to improve the accuracy of identifying the temperature, for example, and therefore to improve the accuracy of detecting a fire.

[0115] Furthermore, since the reflected waves include multiple reflections from multiple locations, it becomes possible to more reliably detect fires at any location in the target area, for example.

[0116] [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.

[0117] (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.

[0118] (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.

[0119] (Fire detection processing (part 1)) Furthermore, the fire detection processing described in the above embodiment may be configured to be executed by all sensors 1, or may be configured to execute only one or two processes. Alternatively, for example, a configuration may be adopted in which each of a plurality of sensors 1 provided in a target area executes a predetermined process.

[0120] (Fire detection processing (part 2)) Furthermore, in SA11 of FIG. 9 of the above embodiment, the following first to third processes may be applied.

[0121] ===First Process===

[0122] The first process is a process that focuses on fire-induced scattering.

[0123] =Fire-induced scattering= First, fire-induced scattering will be explained. Figures 10 to 12 are explanatory diagrams of cross-correlation information, and Figure 13 is a side view showing the inside of the target area. Figures 10 to 12 show cross-correlation information corresponding to the case where the detector 101 transmits a wave and receives a sound wave corresponding to the transmitted sound wave.

[0124] If there is no fire When no fire has broken out, immediately after the detector 101 in Fig. 1 outputs a sound wave from its own wave transmitting unit 11, the detector 101 receives the sound wave (direct wave) at its own wave receiving unit 12, so the waveforms of the transmitting-side sound wave signal at the wave transmitting unit 11 and the receiving-side sound wave signal at the wave receiving unit 12 become similar at almost the same time. Therefore, as shown in Fig. 10, the correlation degree corresponding to the direct wave is identified when the delay time is near "0".

[0125] =When the flame reaches the sound axis= When a fire breaks out and the flames of the fire reach the acoustic axis 901 (Fig. 13), a portion of the sound waves output by the sensor 101 is returned to the sensor 101 side due to scattering of the sound waves by the flames (fire-induced scattering), and this returned portion of the sound waves (hereinafter also referred to as "scattered waves") is received by the sensor 101. Therefore, when cross-correlation information is determined based on the transmitting-side sound wave signal in the transmitting unit 11 of the sensor 101 and the receiving-side sound wave signal in the receiving unit 12 of the sensor 101, the correlation degree corresponding to the scattered waves will also be determined in addition to the correlation degree corresponding to the direct waves described above, as shown in Fig. 11.

[0126] =Scattering detection= By calculating the difference between the correlation degree at each delay time in the cross-correlation information in Fig. 11 (information when a flame reaches the sound axis) and the correlation degree at each delay time in the cross-correlation information in Fig. 10 (information when no fire has occurred), it is possible to extract only the correlation degree corresponding to the scattered waves shown in Fig. 12. Then, depending on whether or not there is a correlation degree greater than a predetermined value in the correlation degree mutual information in Fig. 12, it is possible to detect the presence of a correlation degree corresponding to the scattered waves (i.e., scattering of sound waves by a flame).

[0127] =Processing= The control unit 14 of the sensor 101 first acquires the most recent transmitting-side acoustic signal and the receiving-side acoustic signal corresponding to the transmitting-side acoustic signal, and then performs known cross-correlation processing on each acquired acoustic signal to identify cross-correlation information (hereinafter also referred to as "most recent cross-correlation information").

[0128] Next, the previous X number of transmitting-side acoustic signals and the receiving-side acoustic signals corresponding to those transmitting-side acoustic signals are acquired, and known cross-correlation processing is performed on each acquired acoustic signal to identify each piece of cross-correlation information, and then cross-correlation information corresponding to the average of the identified pieces of cross-correlation information (hereinafter also referred to as "average cross-correlation information").

[0129] Next, the difference between the correlation degree for each delay time in the above-specified "most recent cross-correlation information" and "average cross-correlation information" is calculated, thereby specifying "difference cross-correlation information" corresponding to these differences.

[0130] Next, the identified "difference cross-correlation information" is processed depending on whether or not there is a correlation greater than or equal to a threshold (a predetermined value such as "+5"). If there is a correlation greater than or equal to the threshold, fire-caused scattering is detected and it is determined that a fire has been detected. If there is no correlation greater than or equal to the threshold, fire-caused scattering is not detected and it is determined that a fire has not been detected.

[0131] ===Second Process===

[0132] The second process is a process that focuses on temperature fluctuations (variations) caused by a fire.

[0133] Specifically, although the specific method is arbitrary, for example, the control unit 14 of the detector 101 determines the variance of the temperature value determined in SA8 of FIG. 9, and if the determined variance is equal to or greater than a threshold value, it determines that there is temperature fluctuation due to a fire and determines that a fire has been detected, and if the determined variance is less than the threshold value, it determines that there is no temperature fluctuation due to a fire and determines that a fire has not been detected.

[0134] Here, the processing may be performed on either the direct side temperature or the wall surface side temperature, or on both.

[0135] ===Third Process===

[0136] The third process is a process that is performed by focusing on the temperature difference between the direct-side temperature and the wall-side temperature identified in SA8 of FIG.

[0137] Specifically, although the method is optional, for example, the control unit 14 of the detector 101 identifies the maximum value of the temperature difference between the direct side temperature and the wall side temperature identified in SA8 of Figure 9 within a predetermined time period, and if the identified maximum value is equal to or greater than a threshold value, it determines that a fire has been detected, and if the identified maximum value is less than the threshold value, it determines that a fire has not been detected.

[0138] ===Combination=== Furthermore, the process explained in SA11 of FIG. 9 in the embodiment and the first to third processes explained here may be arbitrarily combined to make the determination in SA11 of FIG.

[0139] (Multiple reflections) Furthermore, in the above embodiment, the case where the reflected wave in FIGS. 4 and 5 is reflected only once by a reflection object (wall, ceiling, floor, etc.) has been described, but the present invention is not limited to this.

[0140] For example, the processing may be configured to take into account multiple reflected waves (waves reflected multiple times) that are output from sensor 101 and then reflected multiple times (two or more times) at multiple different locations before reaching sensor 102 or sensor 101 itself.

[0141] Specifically, for example, in Fig. 5, it is assumed that after a sound wave is output from sensor 101, it is reflected by the wall surface on the +Y side, and then reflected by the wall surface on the -Y side before reaching sensor 102. In such an assumption, the correlation corresponding to the reflected wave that has been reflected twice will appear in a time period (on the right side of the drawing) with an even longer delay than the "wall-side reflected wave" in Fig. 7, and processing may be performed taking such information into consideration.

[0142] It should be noted that multiple reflections at multiple different locations may be interpreted as corresponding to "multiple reflections."

[0143] (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.

[0144] (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.

[0145] (Features) Furthermore, the features of the above-described embodiments and modifications may be combined in any manner.

[0146] (Addendum) The fire detection system of Supplementary Note 1 is a fire detection system for detecting a fire occurring in a target area, and includes: wave transmitting means for transmitting sound waves to the target area; wave receiving means for receiving the sound waves; temperature specifying means for specifying a temperature on a propagation path of the sound waves transmitted from the wave transmitting means based on the sound waves transmitted by the wave transmitting means and the sound waves received by the wave receiving means; and fire detection means for detecting a fire occurring in the target area based on the temperature of the target area specified by the temperature specifying means; The stage receives direct waves, which are sound waves sent to the transmitting means and reach the receiving means directly without being reflected within the target area, and reflected waves, which are sound waves sent to the transmitting means and reflected within the target area before reaching the receiving means, and the temperature determination means determines the temperature on the propagation paths of the direct waves and the reflected waves sent from the transmitting means based on a transmission signal corresponding to the sound waves sent by the transmitting means and a reception signal corresponding to the direct waves and the reflected waves received by the receiving means.

[0147] The fire detection system of Appendix 2 is the fire detection system described in Appendix 1, wherein the reflected waves include one or more of a first reflected wave reflected by the floor surface of the target area, a second reflected wave reflected by the wall surface of the target area, or a third reflected wave reflected by the ceiling surface of the target area, and the temperature identification means identifies the temperature on the propagation path of the sound wave transmitted from the transmitting means based on arrival order information indicating the order in which the direct wave and the one or more reflected waves arrive at the receiving means.

[0148] The fire detection system of Appendix 3 is the fire detection system described in Appendix 1, wherein the temperature determination means performs a first process of determining cross-correlation information that determines the degree of correlation between the transmitted signal and the received signal relative to the shift time when either the transmitted signal or the received signal is shifted in time, and a second process of determining the temperature on the propagation path of the sound wave transmitted from the transmitting means based on the cross-correlation information determined in the first process.

[0149] The fire detection system of Supplementary Note 4 is characterized in that in the fire detection system of Supplementary Note 1, the reflected waves include multiple reflections reflected at multiple locations.

[0150] (Effect of supplementary notes) According to the fire detection system described in Appendix 1, the temperature is determined based on the transmitted signal corresponding to the transmitted sound waves and the received signal corresponding to the received direct waves and reflected waves, and a fire is detected based on the determined temperature, thereby making it possible to more reliably detect fires, for example.

[0151] According to the fire detection system described in Appendix 2, the temperature on the propagation path of the transmitted sound wave can be determined based on arrival order information indicating the order in which the direct wave and one or more reflected waves arrive at the receiving means, thereby improving the accuracy of temperature determination, thereby making it possible to improve the accuracy of fire detection.

[0152] According to the fire detection system described in Appendix 3, by identifying the temperature on the propagation path of the sound wave based on cross-correlation information, it is possible to improve the accuracy of temperature identification, for example, and therefore the accuracy of fire detection.

[0153] According to the fire detection system described in Appendix 4, the reflected waves include multiple reflections from multiple locations, making it possible to more reliably detect fires at any position in the target area, for example. [Explanation of symbols]

[0154] Below, in parentheses, the matters specifying the invention in the claims that correspond to the terms used in the embodiments are written, but the correspondence between the two is not limited to this. 1 sensor 11 Wave transmitter (wave transmitter) 12 Wave receiving section (wave receiving means) 13 Recording section 14 Control unit (temperature determination means, fire detection means) 100 Disaster Prevention System 101 Sensor 102 Sensor 901 sound axis P91 points P92 points P93 points P94 points P95 points P96 points T71 hours T72 hours T81 hours T82 hours T91 hours T92 hours

Claims

1. 1. A fire detection system for detecting a fire occurring in a target area, comprising: a wave transmitting means for transmitting a sound wave to the target area; wave receiving means for receiving sound waves; a temperature determination means for determining a temperature on a propagation path of the sound wave transmitted from the wave transmitting means based on the sound wave transmitted by the wave transmitting means and the sound wave received by the wave receiving means; a fire detection means for detecting a fire occurring in the target area based on the temperature of the target area identified by the temperature identification means, the wave receiving means receives direct waves, which are sound waves that are transmitted to the wave transmitting means and reach the wave receiving means directly without being reflected within the target area, and reflected waves, which are sound waves that are transmitted to the wave transmitting means and reach the wave receiving means after being reflected within the target area; the temperature specifying means specifies the temperatures on the propagation paths of the direct wave and the reflected wave transmitted from the wave transmitting means based on a transmitted wave signal corresponding to the sound wave transmitted by the wave transmitting means and a received wave signal corresponding to the direct wave and the reflected wave received by the wave receiving means. Fire detection systems.

2. The reflected waves include one or more of a first reflected wave reflected by a floor surface of the target area, a second reflected wave reflected by a wall surface of the target area, or a third reflected wave reflected by a ceiling surface of the target area, the temperature specifying means specifies the temperature on the propagation path of the sound wave transmitted from the wave transmitting means based on arrival order information indicating the order in which the direct wave and the one or more reflected waves arrive at the wave receiving means. The fire detection system of claim 1 .

3. The temperature specifying means a first process for determining cross-correlation information for determining a degree of correlation between the transmitted wave signal and the received wave signal with respect to a time shift when either the transmitted wave signal or the received wave signal is shifted in time; and performing a second process of identifying the temperature on the propagation path of the sound wave transmitted from the wave transmitting means based on the cross-correlation information identified in the first process. The fire detection system of claim 1 .

4. The reflected wave includes multiple reflections reflected at multiple locations. The fire detection system of claim 1 .

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