Fire Detection Methods

Abstract

To provide a fire sensor capable of reliably detecting a fire without introducing smoke.SOLUTION: A sensor 1 for detecting a fire occurring in a target area comprises a fire detection unit 141 that detects the fire occurring in the target area based on sound speed information in the target area and an attenuation coefficient indicating a degree of attenuation of a sound wave in the target area, and further comprises: a wave transmitting unit 111 that transmits a sound wave to the target area; and a first sound receiving unit 112A and a second sound receiving unit 112B that receive the sound wave, wherein based on the sound waves received by the first sound receiving unit 112A and the second sound receiving unit 112B, the fire detection unit 141 performs first processing for calculating the sound speed information and the attenuation coefficient, second processing for specifying a temperature of the target area based on the calculated sound speed information and attenuation coefficient, and third processing for detecting the fire occurring in the target area based on the specified temperature.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, fire detectors that detect fires based on smoke generated in a target area have been known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-126700 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional fire detectors require smoke to be introduced into the detector, but there has been a demand for a technology that can detect fires without introducing smoke.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a fire detector that can reliably detect fires without introducing smoke. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the fire detection method according to claim 1 is a fire detection method for detecting a fire occurring in a target area, and includes a wave transmitting step in which a wave transmitting means transmits sound waves to the target area, a wave receiving step in which a wave receiving means receives the sound waves, and a fire detection step in which a fire detection means detects a fire occurring in the target area based on sound speed information in the target area and an attenuation coefficient indicating the degree of attenuation of sound waves in the target area, wherein the fire detection means performs, in the fire detection step, a first process of calculating the sound speed information and the attenuation coefficient based on the sound waves received by the wave receiving means, a second process of specifying the temperature of the target area based on the calculated sound speed information and the attenuation coefficient, and a third process of detecting a fire occurring in the target area based on the specified temperature. The wave transmitting step and the wave receiving step are repeatedly performed, and the fire detection means performs the fire detection step when the propagation time and amplitude of the sound wave transmitted and received at a first timing differ from the propagation time and amplitude of the sound wave transmitted and received at a second timing that is earlier than the first timing. In addition, the fire detection method described in claim 2 is the fire detection method described in claim 1, in which the fire detection means performs the fire detection step when the propagation time of a sound wave transmitted and received in a time period after the first timing changes by more than a first width and then fluctuates within a second width that is smaller than the first width.

[0007] Also, claims 3 The fire detection method according to claim 1 or 2 In the fire detection method described above, the fire detection means identifies the temperature and humidity of the target area in the second process, and detects a fire occurring in the target area based on the identified temperature and humidity in the third process.

[0008] Also, claims 4 The fire detection method according to claim 1 Any one of the items from to 3 In the fire detection method described above, the wave receiving means comprises a first wave receiving means provided in the vicinity of the wave transmitting means and a second wave receiving means provided at a position farther away from the wave transmitting means than the first wave receiving means, and the fire detection means calculates at least the attenuation coefficient based on the sound waves received by the first wave receiving means and the second wave receiving means in the first processing.

[0009] Also, claims 5 The fire detection method according to claim 1 to 4In the fire detection method described in any one of the above, the fire detection means calculates the sound speed information based on the propagation distance over which the sound waves transmitted from the transmitting means propagate until they are received by the receiving means in the first processing, and the fire detection method further includes a correction step in which a correction means corrects the propagation distance. [Effects of the Invention]

[0010] According to the fire detection method set forth in claim 1, the object of the present application can be achieved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing an example of installation of a sensor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing a sensor. [Figure 3] 10 is a flowchart of a fire detection process. [Figure 4] FIG. 10 is a diagram illustrating an example of a change in propagation time over time. [Figure 5] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fire detector 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.

[0013] [Basic Concept of the Embodiment] First, the basic concept of this embodiment will be explained. This embodiment generally relates to a fire detector.

[0014] A "fire detector" is a device that detects fires occurring in a target area, and is a concept that includes, for example, reflective fire detectors and opposing fire detectors. The fire detector's fire detection method may be, for example, a quantitative type or a differential type.

[0015] The "target area" is an area in which fire is to be detected, and is a concept that includes any area, such as a parking space in a parking lot or a room in a building.

[0016] The term "reflection-type fire detector" refers to a concept that includes, for example, a detector that detects fires by using sound waves reflected by a reflective surface within a target area. The term "opposing-type fire detector" refers to a concept that includes, for example, a detector that has a transmitting device and a receiving device that are separated from each other and are placed on either side of a target area, and that detects fires by using sound waves that are output from the transmitting device and then directly received by the receiving device.

[0017] The "quantitative method" is a concept that includes methods for detecting fires based on the values ​​of physical quantities in the target area (for example, temperature, humidity, etc.). The "differential method" is a concept that includes methods for detecting fires based on the time change in physical quantities in the target area (for example, gradient, etc.).

[0018] In the embodiment described below, the "target area" is a parking space in a parking lot, and a quantitative system is used in a reflective fire detector. Other matters will be described in modified examples.

[0019] [Specific details of the embodiment] Next, specific details of the embodiment will be described.

[0020] (composition) First, the configuration of a sensor according to this embodiment will be described. Fig. 1 is a diagram showing an installation example of a sensor according to this embodiment, and Fig. 2 is a block diagram showing the sensor. In Fig. 1, some components of the sensor 1 are shown as rectangles, and the overall shape of the sensor 1 is shown enlarged.

[0021] Detector 1 in Fig. 1 is a reflective fire detector, and is a device for detecting fires that occur in, for example, a parking space in a parking lot (i.e., a target area). Detector 1 is a quantitative type (more specifically, a constant temperature type) that detects fires based on the temperature value of the parking space itself, and is installed, for example, on the ceiling, transmits sound waves toward the floor surface, and receives the sound waves reflected by the floor surface.

[0022] As shown in FIG. 2, the detector 1 includes, for example, a sound wave unit 11, an alarm unit 12, a recording unit 13, and a control unit 14.

[0023] (Configuration - Sound wave part) The sonic unit 11 transmits or receives sonic waves, and includes, for example, a wave transmitting unit 111, a first wave receiving unit 112A, and a second wave receiving unit 112B. Note that in the present application, sonic waves of any frequency band may be used, but for example, a case where sonic waves of a frequency band corresponding to ultrasonic waves are used will be described.

[0024] (Configuration - sound wave part - transmitting part) The wave transmitting unit 111 is a wave transmitting means that transmits sound waves to a target area, and is provided at a predetermined position in the housing of the sensor 1, for example, as shown in Fig. 1. As this wave transmitting unit 111, for example, a known ultrasonic wave transmitter using a piezoelectric ceramic vibrator can be used.

[0025] (Configuration - Sound wave section - First receiving section) The first wave receiving unit 112A is a wave receiving means that receives sound waves, and is, for example, as shown in Fig. 1, a first wave receiving means that is provided near the wave transmitting unit 111. As this first wave receiving unit 112A, for example, a known ultrasonic receiver using a piezoelectric ceramic vibrator can be used (the same applies to the second wave receiving unit 112B).

[0026] (Configuration - Sound wave section - Second receiving section) The second wave receiving section 112B is a wave receiving means that receives sound waves, and is, for example, as shown in FIG. 1, a second wave receiving means that is provided at a position farther away from the wave transmitting section 111 than the first wave receiving section 112A.

[0027] (Configuration-Alarm part) The alarm unit 12 is an alarm means for outputting an alarm, and may be, for example, an indicator light or a speaker (neither of which are shown).

[0028] (Configuration - Recording Department) The recording unit 13 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, etc. The recording unit 13 stores distance information.

[0029] (Configuration - Recording section - Distance information) "Distance information" is information for identifying the distance over which sound waves propagate (i.e., the propagation distance); specifically, as illustrated by the dotted line in Figure 1, it is information for identifying the distance over which sound waves transmitted from the transmitting unit 111 propagate when the sound waves reach the second receiving unit 112B after being reflected by a reflecting object within the target area (i.e., an object from which the sound waves are reflected).

[0030] In this embodiment, the distance information is explained by taking as an example a case where information corresponding to the length of the distance L between the ceiling and the floor in the vertical direction (up and down in the drawing) is stored as the initial value of the distance information.

[0031] (Configuration - Control Unit) The control unit 14 in Figure 2 is also 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 a RAM for storing programs and various data.

[0032] The control unit 14 conceptually includes, for example, a fire detection unit 141 and a correction unit 142. The fire detection unit 141 is a fire detection means that detects a fire occurring in a target area based on sound speed information in the target area and an attenuation coefficient that indicates the degree of attenuation of sound waves in the target area. The correction unit 142 is a correction means that corrects the propagation distance. The processing performed by each unit of the control unit 14 will be described later.

[0033] The "sound speed information" is information indicating the sound speed in the target area. The "attenuation coefficient" is information indicating the degree of attenuation of the sound wave in the target area, and is determined, for example, according to the ratio between the amplitude of the sound wave before propagation in the target area and the amplitude of the sound wave after propagation in the target area.

[0034] (process) Next, the fire detection process executed by the detector 1 configured as above will be described. Figure 3 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 in a parking space. This fire detection process can be executed at any timing, but for example, when the detector 1 is powered on, repeated execution will be started, and the description will begin from the point where execution of the fire detection process has started.

[0035] 3, the fire detection unit 141 transmits sound waves from the wave transmitting unit 111 and receives the sound waves at the first wave receiving unit 112A and the second wave receiving unit 112B. Here, for example, the first wave receiving unit 112A receives, in the target area, sound waves before propagation (hereinafter also referred to as "pre-propagation sound waves") transmitted from the wave transmitting unit 111. Furthermore, the second wave receiving unit 112B receives, in the target area, sound waves after propagation (hereinafter also referred to as "post-propagation sound waves") transmitted from the wave transmitting unit 111 and reflected by a reflecting object (for example, a floor surface).

[0036] 3, the fire detection unit 141 measures the propagation time and amplitude and stores the measurement results. Note that the "propagation time" is a concept that indicates the time it takes for a sound wave transmitted by a sensor 1 to return to the sensor 1, and is a concept that corresponds to, for example, TOF (Time of Flight).

[0037] Specifically, the propagation time is measured as the time from when the wave transmitting unit 111 transmits the sound wave to when the second wave receiving unit 112B receives the "propagation sound wave." The amplitude of the "pre-propagation sound wave" received by the first wave receiving unit 112A and the amplitude of the "propagation sound wave" received by the second wave receiving unit 112B are also measured. These measurement results are then stored in the recording unit 13.

[0038] 3, the fire detection unit 141 determines whether the propagation time and amplitude values ​​measured in the most recent SA2 are different from the propagation time and amplitude values ​​measured in the past SA2. If it is determined that they are different (YES in SA3), the process proceeds to SA4. On the other hand, if it is determined that they are not different (i.e., they are the same) (NO in SA3), the process proceeds to SA1 and the above-mentioned process is repeated.

[0039] Here, for example, there may be a change in the temperature or humidity of the parking space in Fig. 1, or a car may be parked in the parking space, causing the sound wave reflecting surface to be located higher (for example, on the top of the parked car) than in Fig. 1, changing the propagation distance. In such cases, the propagation time and amplitude values ​​measured in the most recent SA2 will differ from the propagation time and amplitude values ​​measured in the previous SA2, so it is determined that they are different (YES in SA3), and the process moves to SA4.

[0040] 3, the fire detection unit 141 measures the propagation time and amplitude N times (for example, 5 to 10 times, or 50 to 100 times, etc.) and stores the N measurement results (that is, N sets of measurement results) in the recording unit 13. Note that the specific processing is the same as the processing in SA1 and SA2.

[0041] 3, the fire detection unit 141 determines whether the propagation time has stabilized after a sudden change in time for the N sets of measurement results measured in SA4. If it is determined that the propagation time has stabilized after a sudden change in time (YES in SA5), the process proceeds to SA6. On the other hand, if it is determined that the propagation time has not stabilized after a sudden change in time (i.e., if the result is other than YES in SA5) (NO in SA5), the process proceeds to SA7.

[0042] Figure 4 is a diagram illustrating the change in propagation time over time. For example, if a car parks in an empty parking space at time t1, as shown in Figure 4(a), the propagation time changes relatively significantly at time t1, and then becomes a constant value. Also, if a fire breaks out at time t1 and the temperature in the parking space gradually rises, the propagation time will continue to change gradually from time t1, as shown in Figure 4(b).

[0043] In the processing of SA5, for example, a method is applied in which a determination is made as "SA5 YES" when the propagation time transitions as shown in Fig. 4(a), and a determination is made as "SA5 NO" when the propagation time transitions other than as shown in Fig. 4(a) (for example, when the propagation time transitions as shown in Fig. 4(b)). More specifically, for example, a method may be applied in which a determination is made as "SA5 YES" when the propagation time transitions within a second width (a width that is much smaller than the first width) after the propagation time has changed by more than a first width, and a determination is made as "SA5 NO" in other cases.

[0044] Next, in SA6 of Fig. 3, the correction unit 142 performs a distance information correction process. The "distance information correction process" is a process of correcting and updating the distance information stored in the recording unit 13 of Fig. 2, that is, a process of correcting the propagation distance.

[0045] In the processing of SA6, for example, the propagation time when the measurement result of SA5 becomes stable after a sudden change over time is used to calculate the propagation distance based on a predetermined calculation (the calculation is based on the fact that the propagation distance is obtained from the product of the sound speed value (here, for example, a predetermined value) and the propagation time), and information for identifying the calculated propagation distance is stored in the recording unit 13 as distance information indicating the corrected propagation distance and updated.

[0046] The propagation time used in this calculation is the propagation time that remains stable after a sudden change in the N propagation times in the N sets of measurement results measured by SA4. In other words, in the example of Figure 4(a), the propagation time measured after timing t1 is used. After this, the process moves to SA1, where the above-mentioned processes are repeatedly performed.

[0047] Next, in SA7 after NO in SA5 in Fig. 3, the fire detection unit 141 identifies the temperature based on the N sets of measurement results (i.e., N sets of propagation times, amplitudes of "pre-propagation sound waves", and amplitudes of "post-propagation sound waves"). Any specific method may be used to identify the temperature here, but for example, the following first to third methods may be used.

[0048] <First method> The first method uses the first equation, which calculates the speed of sound using temperature and humidity as variables, and the second equation, which calculates the attenuation coefficient using temperature and humidity as variables.

[0049] When using this first method, first, the distance information from the recording unit 13 is acquired, and then the propagation distance (the propagation distance specified by the acquired distance information) is divided by the propagation time (measurement result), and the calculation result is calculated as the speed of sound.

[0050] Next, the attenuation coefficient is calculated by calculating "(20 ÷ distance) × log (amplitude of "sound wave before propagation" ÷ amplitude of "sound wave after propagation")" (note that the base of log is "10"). Note that the "distance" in this formula indicates the propagation distance of the sound wave from the first wave receiving unit 112A to the second wave receiving unit 112B, with respect to the sound wave reflected by the reflecting object as shown in Figure 1. This "distance" may be calculated by subtracting a predetermined distance (for example, a predetermined propagation distance of the sound waves transmitted from the wave transmitting unit 111 until they reach the first wave receiving unit 112A directly) (hereinafter also referred to as "the distance from the wave transmitting unit 111 to the first wave receiving unit 112A") from the distance indicated by the distance information recorded in the recording unit 13 in Fig. 2 (i.e., the distance the sound waves transmitted from the wave transmitting unit 111 propagate from the time they are reflected by a reflecting object in the target area until they reach the second wave receiving unit 112B) (hereinafter also referred to as "the distance from the wave transmitting unit 111 to the second wave receiving unit 112B"). Note that this predetermined distance may be a numerical value determined by performing a predetermined experiment or simulation.

[0051] Alternatively, as a variant, since the "distance from the wave transmitting unit 111 to the second wave receiving unit 112B" is much longer than the "distance from the wave transmitting unit 111 to the first wave receiving unit 112A," the "distance from the wave transmitting unit 111 to the first wave receiving unit 112A" can be ignored, and the "distance from the wave transmitting unit 111 to the second wave receiving unit 112B" can be used as the "distance" in the formula for calculating the attenuation coefficient described above.

[0052] Next, by substituting the calculated sound speed value into Equation 1 and substituting the calculated attenuation coefficient into Equation 2, two mutually independent equations are derived that use the two variables temperature and humidity. Next, the temperature and humidity are calculated based on these two derived equations, and the calculated temperature is identified.

[0053] It should be noted that the first and second formulas may be publicly known formulas, or formulas defined based on predetermined experiments or simulations.

[0054] <Second method> The second method uses another equation that shows the relationship between temperature and the speed of sound. When using this second method, the speed of sound is calculated in the same manner as in the previous method, and the temperature is calculated by applying the calculation result to the other equation, and the calculated temperature is identified.

[0055] <Third Method> The third method uses predetermined table information that shows the relationship between temperature and humidity and the speed of sound and attenuation coefficient. When using this third method, the speed of sound and attenuation coefficient are calculated in the same manner as in the previous method, and the table information is referenced to obtain the temperature and humidity corresponding to the calculated speed of sound and attenuation coefficient, and the obtained temperature is identified.

[0056] Next, in SA8 of Fig. 3, the fire detection unit 141 determines whether or not a fire has occurred based on the temperature identified in SA7. Specifically, it is assumed that a temperature threshold serving as a criterion for determining whether or not a fire has occurred is set in advance. If the temperature identified in SA7 is below the temperature threshold, it is determined that no fire has occurred (NO in SA8), and the process ends without detecting a fire. On the other hand, if the temperature identified in SA7 is equal to or higher than the temperature threshold, it is determined that a fire has occurred (YES in SA8), and a fire is detected, and the process proceeds to SA9.

[0057] Here, for example, in SA7, N temperatures are identified based on N sets of measurement results, and if a predetermined number or more of the N temperatures are above a temperature threshold, it may be determined that a fire has occurred, or if the average value of the N temperatures is above a temperature threshold, it may be determined that a fire has occurred.

[0058] Next, at SA9 in FIG. 3, the fire detection unit 141 notifies the occurrence of a fire by transmitting a fire signal indicating that a fire has occurred to a disaster prevention receiver (not shown) or by outputting an alarm via the alarm unit 12.

[0059] Next, in SA10 of Fig. 3, when the fire detection unit 141 receives a restoration signal (i.e., a signal for restoring to a state for notifying the occurrence of a fire) transmitted from the disaster prevention receiver side, the fire detection unit 141 ends the notification of the occurrence of a fire and restores itself. This concludes the explanation of the fire detection process.

[0060] (Effects of the embodiment) According to this embodiment, by detecting a fire occurring in a target area based on sound speed information and attenuation coefficient, it is possible to reliably detect a fire without introducing smoke into the detector 1, for example.

[0061] Furthermore, by detecting a fire occurring in a target area based on the temperature within the target area, it becomes possible to reliably detect a fire, for example.

[0062] Furthermore, by calculating at least the attenuation coefficient based on the sound waves received by the first wave receiving section 112A and the second wave receiving section 112B, it is possible to improve the calculation accuracy of the attenuation coefficient, for example, thereby making it possible to reliably detect fires.

[0063] [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.

[0064] (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.

[0065] (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.

[0066] (Regarding the receiving unit) In the above embodiment, the first wave receiving unit 112A is provided, but this component may be omitted. In this case, for example, a predetermined value may be used as the amplitude value of the "pre-propagation sound wave."

[0067] (Fire Determination) In the above embodiment, the occurrence of a fire is determined (i.e., a fire is detected) based on temperature in SA8 of Fig. 3, but this is not limiting. For example, SA7 may be configured to specify humidity in addition to temperature, and SA8 may be configured to determine the occurrence of a fire using humidity in addition to temperature. In such a configuration, a fire occurring in a target area can be detected based on the temperature and humidity within the target area, thereby making it possible to reliably detect a fire, for example.

[0068] (Regarding the correction section) The correction unit 142 may be configured to perform the following first to third correction processes. Each of these correction processes may be performed, for example, when the detector 1 is installed, or at any other timing.

[0069] <First correction process> The first correction process is a process of performing correction based on a user's operation. In this case, for example, when an operation means (e.g., a DIP switch or the like) for inputting distance information to the detector 1 is provided and the user inputs distance information through the operation of the operation means, the correction unit 142 acquires the input distance information and stores it in the recording unit 13 to perform correction.

[0070] <Second Correction Process> The second correction method is a method of correction based on communication. In this case, for example, when distance information is transmitted to the detector 1 from an external device (such as a user's terminal device or a disaster prevention receiver), the correction unit 142 receives the distance information and stores it in the recording unit 13, thereby correcting the distance. Note that the method of transmitting the distance information here is arbitrary, and it may be transmitted, for example, by a signal in wired communication, radio waves in wireless communication, or sound wave communication.

[0071] <Third correction process> The third correction method is a method of correction using a correction jig. Fig. 5 is a diagram showing the correction jig. The correction jig 900 is a device used to correct distance information, and includes a reflector 901 that reflects sound waves that are a predetermined distance from the sensor 1. Correction propagation distance information for specifying the propagation distance of sound waves when the correction jig 900 is installed is stored in advance in the recording unit 13.

[0072] Then, when the user presses the correction operation button (not shown) on the detector 1 after installing the correction jig 900, the correction unit 142 measures N sets of propagation times and amplitudes by performing processing similar to SA4 in Fig. 3 and stores the measurement results. Next, the correction unit 142 performs a calculation of the propagation distance specified by the correction propagation distance information in the recording unit 13 divided by the measured propagation time (more specifically, the average value of the N measured propagation times), and calculates the calculation result as the speed of sound in the current environment. Next, when the user removes the correction jig 900 and presses the correction operation button (not shown) on the detector 1 again, the correction unit 142 measures N sets of propagation times and amplitudes by performing processing similar to SA4 in Fig. 3 and stores the measurement results. Next, the correction unit 142 performs a calculation of the calculated sound speed value multiplied by the measured propagation time (more specifically, the average value of N measured propagation times), calculates the calculation result as the propagation distance of the target area (for example, the parking space in Figure 1), and corrects the calculated propagation distance by storing information specifying the calculated propagation distance in the recording unit 13 as distance information.

[0073] When configured in this manner, by correcting the propagation distance, it is possible to calculate sound speed information using a propagation distance appropriate for the environment in which the detector 1 is installed, thereby making it possible to reliably detect fires.

[0074] (Differential type) The above-described sensor 1 may also be configured as a differential type. In this case, for example, fire detection is possible even if the absolute value of the propagation distance is deviated, so SA6 in FIG. 3 may be omitted. In this case, after YES in SA5, SA6 may not be executed and the process may proceed to SA1. In addition, when configured in this way, in SA8, for the N temperatures identified in SA7, the slope of a line showing the change in temperature with the horizontal axis representing the passage of time and the vertical axis representing the temperature value may be calculated, and the calculated slope may be compared with a predetermined slope for fire detection, and whether or not a fire has occurred may be determined based on the comparison result.

[0075] (For facing types) The sensor 1 described above may also be configured as an opposed type. In this case, for example, the sensor 1 is separated into a first device having at least the wave transmitting unit 111 and the first wave receiving unit 112A, and a second device having the second wave receiving unit 112B, and these devices are arranged facing each other across the target area, so that the devices communicate with each other. In this configuration, after YES at SA3 in Figure 3, SA4 to SA6 may be omitted and SA7 to SA10 may be executed.

[0076] (Other application examples) Furthermore, the detection of an object in a target area or the distance to the object may be performed based on the measurement results of the propagation time or amplitude.

[0077] (Features) Furthermore, the features of the above-described embodiments and modifications may be combined in any manner.

[0078] (Addendum) The fire detector of Appendix 1 is a fire detector that detects a fire that occurs in a target area, and is equipped with fire detection means that detects a fire that occurs in the target area based on sound speed information in the target area and an attenuation coefficient that indicates the degree of attenuation of sound waves in the target area.

[0079] The fire detector of Appendix 2 is the fire detector of Appendix 1, further comprising a wave transmitting means for transmitting sound waves to the target area and a wave receiving means for receiving the sound waves, wherein the fire detection means performs a first process of calculating the sound speed information and the attenuation coefficient based on the sound waves received by the wave receiving means, a second process of identifying the temperature of the target area based on the calculated sound speed information and the attenuation coefficient, and a third process of detecting a fire occurring in the target area based on the identified temperature.

[0080] The fire detector of Appendix 3 is the fire detector of Appendix 2, wherein the fire detection means identifies the temperature and humidity of the target area in the second process, and detects a fire occurring in the target area based on the identified temperature and humidity in the third process.

[0081] The fire detector of Appendix 4 is the fire detector of Appendix 2 or 3, wherein the receiving means comprises a first receiving means provided near the transmitting means and a second receiving means provided at a position farther from the transmitting means than the first receiving means, and the fire detection means calculates at least the attenuation coefficient in the first processing based on the sound waves received by the first receiving means and the second receiving means.

[0082] The fire detector of Supplementary Note 5 is a fire detector according to any one of Supplementary Notes 2 to 4, wherein the fire detection means, in the first processing, calculates the sound speed information based on a propagation distance over which the sound wave transmitted from the transmitting means propagates until it is received by the receiving means, and the fire detector further comprises a correction means for correcting the propagation distance.

[0083] (Effect of supplementary notes) According to the fire detector described in Appendix 1, by detecting a fire occurring in a target area based on sound speed information and an attenuation coefficient, it is possible to reliably detect a fire without introducing smoke into the fire detector, for example.

[0084] According to the fire detector described in Supplementary Note 2, it is possible to reliably detect a fire, for example, by detecting a fire occurring in a target area based on the temperature within the target area.

[0085] According to the fire detector described in Supplementary Note 3, it is possible to reliably detect a fire, for example, by detecting a fire occurring in a target area based on the temperature and humidity within the target area.

[0086] According to the fire detector described in Appendix 4, by calculating at least the attenuation coefficient based on the sound waves received by the first wave receiving means and the second wave receiving means, it is possible to improve the calculation accuracy of the attenuation coefficient, for example, and thereby make it possible to reliably detect fires.

[0087] According to the fire detector described in Supplementary Note 5, by correcting the propagation distance, it is possible to calculate sound speed information using, for example, a propagation distance appropriate for the environment in which the fire detector is installed, thereby making it possible to reliably detect fires. [Explanation of symbols]

[0088] 1 sensor 11. Sound wave section 12 Alarm section 13 Recording section 14 Control Unit 111 Transmitting unit 112A 1st wave receiver 112B 2nd wave receiver 141 Fire detection unit 142 Correction unit 900 Correction jig 901 Reflector L distance

Claims

1. A fire detection method for detecting a fire occurring in a target area, a wave transmitting step in which a wave transmitting means transmits a sound wave to the target area; a wave receiving step in which the wave receiving means receives the sound wave; a fire detection step in which the fire detection means detects a fire occurring in the target area based on sound speed information in the target area and an attenuation coefficient indicating the degree of attenuation of sound waves in the target area; In the fire detection step, the fire detection means a first process of calculating the sound speed information and the attenuation coefficient based on the sound waves received by the wave receiving means; a second process of identifying a temperature of the target region based on the calculated sound speed information and the attenuation coefficient; and a third process of detecting a fire occurring in the target area based on the identified temperature. The wave transmitting step and the wave receiving step are repeatedly performed, The fire detection means performs the fire detection step when a propagation time and an amplitude of a sound wave transmitted and received at a first timing are different from a propagation time and an amplitude of a sound wave transmitted and received at a second timing that is earlier than the first timing. Fire detection methods.

2. The fire detection means performs the fire detection step when the propagation time of a sound wave transmitted and received in a time period after the first timing changes by more than a first width and then changes within a second width smaller than the first width. The fire detection method according to claim 1 .

3. The fire detection means In the second process, the temperature and humidity of the target area are identified; In the third process, a fire occurring in the target area is detected based on the identified temperature and humidity.

3. The fire detection method according to claim 1 or 2.

4. The wave receiving means is a first wave receiving means provided in the vicinity of the wave transmitting means; a second wave receiving means provided at a position farther from the wave transmitting means than the first wave receiving means, The fire detection means In the first processing, at least the attenuation coefficient is calculated based on the sound waves received by the first wave receiving means and the second wave receiving means. A fire detection method according to any one of claims 1 to 3.

5. The fire detection means In the first processing, the sound speed information is calculated based on a propagation distance over which the sound wave transmitted from the wave transmitting means propagates until it is received by the wave receiving means, The fire detection method includes: The method further includes a correction step in which the correction means corrects the propagation distance. A fire detection method according to any one of claims 1 to 4.

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