Water leakage detection system

Abstract

This water leakage detection system is provided with a flow meter that includes: a flow rate measuring unit that measures the flow rate of water in a measurement flow passage on the basis of the propagation time of ultrasonic waves; a storage unit that stores, as water usage pattern information for each employed device, information that has been repeated a prescribed number of times, among information indicating the instantaneous flow rate of water measured by the flow rate measuring unit and the water usage time, using a prescribed period after the installation of the flow meter as a learning period; and a water pressure change rate estimating unit that estimates, as a rate of change in water pressure in a flow passage of a water supply network, the ratio of the average value of the instantaneous flow rate for the employed devices over a prescribed period to a prescribed instantaneous flow rate reference value, in accordance with the result of a comparison between the instantaneous flow rate and the usage time when water is being used, and the water usage pattern information for the employed devices, stored in the storage unit.

Description

Water Leak Detection System

[0001] The present disclosure relates to a water leak detection system for detecting water leaks in a flow path.

[0002] A water leak detection system has been known in the past that detects water leaks by linking a communication unit provided in each ultrasonic flowmeter with a centralized processing unit having a centralized communication unit (see Patent Document 1). In this water leak detection system, when all flow rates of the ultrasonic flowmeters in a target area and the flow rate upstream of the target area fall below a threshold, the propagation time of ultrasonic waves between two adjacent ultrasonic flowmeters is measured. The measured propagation time is then compared with the propagation time when there is no water leak to determine whether there is a water leak between the two adjacent ultrasonic flowmeters.

[0003] Japanese Patent Application Laid-Open No. 2022-169885

[0004] One method for determining whether or not a water leak exists is to use a pressure sensor to detect changes in water pressure. However, pressure sensors are expensive, which increases the cost of the entire water leak detection system. Another problem with the conventional water leak detection system is that there is a limit to the amount of water pressure change that can be detected based on the amplitude of the received ultrasonic waveform.

[0005] Therefore, an object of the present disclosure is to provide a water leakage detection system that is capable of determining the presence or absence of water leakage inexpensively and with high accuracy.

[0006] The water leakage detection system disclosed herein is a water leakage detection system including a plurality of flow meters provided in a water supply network and a central device that manages the plurality of flow meters, wherein the flow meters each include a pair of ultrasonic transmitters and receivers arranged in a measurement flow path, a propagation time measurement unit that measures a propagation time, which is the time it takes for an ultrasonic wave to be transmitted by one of the ultrasonic transmitters and receivers and to be received by the other of the ultrasonic transmitters and receivers, a flow rate measurement unit that measures the flow rate of water in the measurement flow path based on the propagation time, a memory unit that stores, as water usage pattern information for each device used, information indicating the instantaneous flow rate of water measured by the flow meter unit and the duration of water use, which information has been repeated a predetermined number of times over a predetermined period of time after installation of the flow meter, and a memory unit that stores, as water usage pattern information, the instantaneous flow rate and duration of water use and the duration of water use, which information has been repeated a predetermined number of times over a predetermined period of time after installation of the flow meter. and a communication unit that communicates with the center device. The center device comprises: a water pressure change rate estimation unit that estimates the ratio of the average instantaneous flow rate for the usage equipment over a predetermined period to a predetermined instantaneous flow rate reference value as the rate of change of water pressure in the flow path of the water supply network, based on the comparison result with the water usage pattern information for the usage equipment stored in a memory unit; and a communication unit that communicates with the center device. The center device comprises: a general communication unit that communicates with the communication unit; and a water leakage determination unit. When the water flow rates measured by each of the plurality of flow meters in the target area of ​​water leakage inspection are each below a threshold value and the flow rate flowing into the target area is below a threshold value, the water leakage determination unit determines whether or not there is a leak in the flow path of the water supply network based on a comparison of the rate of change of water pressure estimated by the flow meters with the water pressure reference value.

[0007] According to the present disclosure, water usage pattern information, which indicates the instantaneous water flow rate and usage time based on measurement results from the flow meter, is stored in advance in a storage unit. The water usage pattern information is information based on the use of appliances (e.g., toilets, bathtubs, washing machines, etc.) in the consumer's home and may be information obtained by learning the usage history for a predetermined period of time. Then, based on the results of comparing the instantaneous water flow rate and usage time during water usage with the water usage pattern information, a water pressure change rate estimation unit obtains a water pressure change rate in a flow path of the water supply network by comparing an average instantaneous water flow rate during water usage over a predetermined period with a predetermined instantaneous flow rate reference value. The water pressure change rate is estimated when the instantaneous water flow rate and usage time during water usage are the same as those in the water usage pattern information, i.e., when the same appliance is used as the appliance corresponding to the water usage pattern information. This increases the reliability of the water pressure change rate. A water leak determination unit in the central device then compares the highly reliable water pressure change rate with a predetermined water pressure reference value and determines the presence or absence of a water leak in the flow path based on the comparison result. This increases the accuracy of determining whether or not there is a water leak, and also reduces costs because a pressure sensor is not required.

[0008] In the above disclosure, the flow meter may further include a temperature acquisition unit that acquires the temperature of the water in the measurement flow path based on the propagation time, and a correction unit that corrects the instantaneous flow rate when the water is in use based on the temperature acquired by the temperature acquisition unit, and the water pressure change rate estimation unit may use the instantaneous flow rate corrected by the correction unit as the instantaneous flow rate when the water is in use.

[0009] When the temperature of the water changes, the instantaneous flow rate of the water also changes. According to the above configuration, the correction unit corrects the instantaneous flow rate based on the temperature, and the corrected accurate instantaneous flow rate is used in the water pressure change rate estimation unit.

[0010] According to the present disclosure, it is possible to provide a water leakage detection system that is capable of determining the presence or absence of water leakage inexpensively and with high accuracy.

[0011] It is a block diagram of a water supply network in one embodiment. It is a block diagram of an example of the configuration of an ultrasonic flow meter. It is a block diagram of a water leak detection system. It is a flowchart showing the processing flow in the ultrasonic flow meter.

[0012] A water leak detection system according to an embodiment of the present disclosure will be described below with reference to the drawings. The water leak detection system described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiment, and additions, deletions, and modifications are possible within the scope of the present disclosure.

[0013] As shown in FIG. 1, the water leak detection system 100 of this embodiment includes a water supply station 51, a water supply network 60, one or more customer homes 56 included in a target area 57 for water leak inspection, and a center device 20.

[0014] The water supply network 60 is the area surrounded by a dashed line in Fig. 1, and is a network that supplies water from the water supply plant 51 to each customer's home 56 (identified as 56A to 56D in Fig. 1). The water supply network 60 includes a main pipe 52, a branch section 53, a common pipe 54, and a service pipe 55.

[0015] A water supply plant 51 and a branching section 53 are connected by a main pipe 52. A common pipe 54 branches off from the branching section 53. One of the common pipes 54 extends toward a target area 57, and multiple inlet pipes 55 branch off from the common pipe 54. The downstream ends of the multiple inlet pipes 55 are connected to consumer homes 56. In this configuration, water from the water supply plant 51 is supplied to each consumer home 56 via the main pipe 52, the branching section 53, the common pipe 54, and the inlet pipe 55. Each consumer home 56 is equipped with an ultrasonic flowmeter 1 ( FIG. 2 ), which corresponds to a flow meter. FIG. 1 and FIG. 3 (described later) illustrate four consumer homes 56, namely, consumer homes 56A, 56B, 56C, and 56D, and in FIG. 3 , the ultrasonic flowmeters 1 for the consumer homes 56A, 56B, 56C, and 56D are identified as ultrasonic flowmeters 1A, 1B, 1C, and 1D, respectively. A detailed description will be given later of the configuration of the ultrasonic flowmeter 1. In this embodiment, the common pipe 54 and the intake pipe 55 correspond to the flow path of the water supply network.

[0016] The center device 20 manages a plurality of ultrasonic flowmeters 1. The center device 20 includes a water leakage determination unit 58 and a central communication unit 59. The center device 20 receives meter reading data such as measured flow rates by communicating with each ultrasonic flowmeter 1, and also has the function of issuing various instructions to each ultrasonic flowmeter 1. The communication method between the center device 20 and each ultrasonic flowmeter 1 is not particularly limited, and may be, for example, cellular communication, specified low-power wireless communication, or network communication via a relay station. The central communication unit 59 communicates with a communication unit 9 (described later) included in each ultrasonic flowmeter 1. The water leakage determination unit 58 determines the presence or absence of a water leakage based on the rate of change in water pressure obtained from the ultrasonic flowmeter 1 via the central communication unit 59. Details will be described later.

[0017] Next, the configuration of the ultrasonic flowmeter 1 will be described. As shown in Fig. 2, the ultrasonic flowmeter 1 includes a control unit 2, a flowmeter unit 3, a propagation time measurement unit 4, a first ultrasonic transmitter / receiver 5, a second ultrasonic transmitter / receiver 6, a first reflecting unit 7, a second reflecting unit 8, a communication unit 9, a temperature acquisition unit 10, a water pressure change rate estimation unit 11, a memory unit 12, a correction unit 13, an appliance use determination unit 14, and a measurement flow path 40. In Fig. 2, the symbol FD indicates the direction of water flow, and the symbol PP indicates the propagation path of the ultrasonic waves.

[0018] The control unit 2 includes at least one of a processor such as a CPU and an integrated circuit such as an ASIC. The control unit 2 controls the operations of the first ultrasonic transmitter / receiver 5 and the second ultrasonic transmitter / receiver 6. The control unit 2 is electrically connected to a communication unit 9 and a memory unit 12. In this embodiment, the flowmeter unit 3, the propagation time measurement unit 4, the temperature acquisition unit 10, the water pressure change rate estimation unit 11, the correction unit 13, and the device use determination unit 14 are functional components that are functionally realized when the control unit 2 executes a predetermined program.

[0019] The measurement flow path 40 is a water flow path that extends in one direction and is provided inside the ultrasonic flowmeter 1. The first ultrasonic transmitter / receiver 5 is disposed on the upstream side of the outer surface of the measurement flow path 40, and transmits ultrasonic waves in the radial direction of the measurement flow path 40 while receiving ultrasonic waves similarly transmitted by the second ultrasonic transmitter / receiver 6. The second ultrasonic transmitter / receiver 6 is disposed on the downstream side of the outer surface of the measurement flow path 40, and transmits ultrasonic waves in the radial direction of the measurement flow path 40 while receiving ultrasonic waves similarly transmitted by the first ultrasonic transmitter / receiver 5.

[0020] A first reflecting unit 7 and a second reflecting unit 8 are provided in the measurement flow path 40. The first reflecting unit 7 is disposed upstream in the measurement flow path 40 and deflects the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 5 by 90 degrees in their traveling direction and reflects them toward the second reflecting unit 8. The first reflecting unit 7 also deflects the ultrasonic waves from the second reflecting unit 8 by 90 degrees in their traveling direction and reflects them toward the first ultrasonic transmitter / receiver 5. Similarly, the second reflecting unit 8 is disposed downstream in the measurement flow path 40 and deflects the ultrasonic waves from the first reflecting unit 7 by 90 degrees in their traveling direction and reflects them toward the second ultrasonic transmitter / receiver 6. The second reflecting unit 8 also deflects the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 6 by 90 degrees in their traveling direction and reflects them toward the first reflecting unit 7.

[0021] 2 , ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 5 propagate through the measurement flow path 40 via the first reflecting unit 7 and the second reflecting unit 8 along the propagation path PP, and are then received by the second ultrasonic transmitter / receiver 6. Similarly, ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 6 propagate through the measurement flow path 40 via the second reflecting unit 8 and the first reflecting unit 7 along the propagation path PP, and are then received by the first ultrasonic transmitter / receiver 5.

[0022] The propagation time measurement unit 4 measures the propagation time, which is the time it takes for an ultrasonic wave to be transmitted by one ultrasonic transmitter / receiver and received by the other ultrasonic transmitter / receiver. Specifically, the propagation time measurement unit 4 measures the propagation time from the time the ultrasonic wave is transmitted from the first ultrasonic transmitter / receiver 5 to the time the ultrasonic wave is received by the second ultrasonic transmitter / receiver 6. The propagation time measurement unit 4 also measures the propagation time from the time the ultrasonic wave is transmitted from the second ultrasonic transmitter / receiver 6 to the time the ultrasonic wave is received by the first ultrasonic transmitter / receiver 5.

[0023] The flow meter unit 3 measures the flow rate of water in the measurement flow path 40 based on the propagation time. In this case, the flow meter unit 3 measures the flow rate of water as follows. Let V be the flow velocity of water flowing in the direction FD within the measurement flow path 40, and C be the speed of sound in water. Let L be the length of the straight portion of the propagation path PP of the ultrasonic waves propagating between the first ultrasonic transmitter / receiver 5 and the second ultrasonic transmitter / receiver 6. In this case, the propagation time t1, which is the propagation time for the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 5 to propagate a distance of length L until they reach the second ultrasonic transmitter / receiver 6, is given by the following equation 1. The propagation time measurement unit 4 obtains the propagation time t1 using the following equation 1.

[0024] (Math. 1) t1=L / (C+V)

[0025] Next, the propagation time t2 of the ultrasonic wave transmitted from the second ultrasonic transmitter / receiver 6 to reach the first ultrasonic transmitter / receiver 5 over a distance of length L is expressed by the following equation 2. The propagation time measurement unit 4 obtains the propagation time t2 using the following equation 2.

[0026] (Math. 2) t2=L / (CV)

[0027] By eliminating the sound velocity C of the fluid from the above formulas 1 and 2, the following formula 3 is obtained: As can be seen from the following formula 3, if L is known, the flow velocity V can be obtained using the above propagation times t1 and t2.

[0028] (Math. 3) V=L / 2 ((1 / t1)-(1 / t2))

[0029] Next, as shown in the following formula 4, the flow meter unit 3 can calculate the flow rate Q by multiplying the flow velocity V by the cross-sectional area S of the measurement flow path 40. Note that k in the following formula 4 is a correction coefficient for correcting various errors that occur in the measurement.

[0030] (Equation 4) Q = k × (V × S)

[0031] In this manner, the flow meter unit 3 obtains the flow rate of water in the measurement flow path 40. The flow meter unit 3 also obtains the instantaneous flow rate, which will be described later, in a similar manner. The propagation time between the first ultrasonic transmitter / receiver 5 and the second ultrasonic transmitter / receiver 6 includes the propagation time between the first ultrasonic transmitter / receiver 5 and the first reflecting unit 7 and the propagation time between the second ultrasonic transmitter / receiver 6 and the second reflecting unit 8. Since this propagation time basically does not depend on the flow velocity and can be calculated in advance, the propagation time measurement unit 4 calculates the sum of this propagation time and the propagation time obtained by the above formula as the propagation time of the ultrasonic waves between the first ultrasonic transmitter / receiver 5 and the second ultrasonic transmitter / receiver 6.

[0032] The storage unit 12 is composed of various types of memory, a hard disk, or the like. The storage unit 12 stores, as water usage pattern information, information indicating the instantaneous water flow rate measured by the flowmeter unit 3 and the duration of water usage, which is repeated a predetermined number of times during a learning period after installation of the ultrasonic flowmeter 1. In this case, the control unit 2 may be equipped with artificial intelligence, which may acquire water usage pattern information during the learning period through learning by the artificial intelligence, and store the water usage pattern information in the storage unit 12. The water usage pattern information is stored in the storage unit 12 for each appliance (e.g., toilet, bath, washing machine, etc.) used in each consumer's home 56. In this embodiment, the instantaneous flow rate in the water usage pattern information is corrected to be the instantaneous flow rate at a predetermined temperature (e.g., 20°C). The storage unit 12 also stores an instantaneous flow rate reference value and a water pressure reference value, which will be described later. The instantaneous flow rate may be, for example, the water flow rate every 1 to 2 seconds, or may be the water flow rate at each ultrasonic transmission interval by the ultrasonic transmitter / receiver.

[0033] The appliance-in-use determination unit 14 determines the appliance being used (e.g., a toilet, a bathtub, a washing machine, etc.) based on the instantaneous water flow rate measured by the flowmeter unit 3. The appliance-in-use determination unit 14 stores the determined instantaneous flow rate corresponding to the appliance being used in the memory unit 12 for each appliance being used.

[0034] The water pressure change rate estimation unit 11 estimates the rate of change of water pressure in the flow paths of the water supply network 60 by comparing the average instantaneous flow rate during use over a predetermined period of time with an instantaneous flow rate reference value, based on the results of comparing the instantaneous flow rate and usage time during water use at the consumer's home 56 with the water usage pattern information. Specifically, the water pressure change rate estimation unit 11 estimates the ratio of the average instantaneous flow rate for the device in use over a predetermined period of time to the predetermined instantaneous flow rate reference value as the rate of change of water pressure in the flow paths of the water supply network 60. In other words, the water pressure change rate estimation unit 11 recognizes changes in instantaneous flow rate for the same device in use as those registered in the memory unit 12 as changes in water pressure. In this embodiment, the water pressure change rate estimation unit 11 uses the instantaneous flow rate corrected by the correction unit 13 (described below) as the instantaneous flow rate during use. When the instantaneous flow rate and usage time during water usage at the consumer's home 56 are identical to the instantaneous flow rate and usage time in the water usage pattern information, the water pressure change rate estimation unit 11 estimates the rate of change of water pressure in the flow path of the water supply network 60 based on a comparison between the average value and the instantaneous flow rate reference value. Note that "same" does not necessarily mean "identical" but also means "approximate" within a predetermined range. The water pressure change rate estimation unit 11 may be provided with artificial intelligence, which determines whether the instantaneous flow rate and usage time during water usage are identical to the water usage pattern information. Note that the instantaneous flow rate reference value is a reference value for the instantaneous flow rate for each appliance used.

[0035] The temperature acquisition unit 10 acquires the temperature of the water in the measurement flow path 40 based on the propagation time measured by the propagation time measurement unit 4. In this case, information on the water temperature corresponding to the propagation time is pre-stored in the memory unit 12. The temperature acquisition unit 10 acquires the information on the water temperature corresponding to the propagation time from the memory unit 12.

[0036] The correction unit 13 corrects the instantaneous flow rate of water during use based on the temperature acquired by the temperature acquisition unit 10. In this case, the correction unit 13 corrects the instantaneous flow rate measured by the flowmeter unit 3 (i.e., the instantaneous flow rate corresponding to the temperature acquired by the temperature acquisition unit 10) to an instantaneous flow rate corresponding to a predetermined temperature (e.g., 20°C) using a predetermined calculation formula.

[0037] The communication unit 9 communicates with external devices such as the general communication unit 59 of the center device 20, and transmits and receives various data.

[0038] Next, the water leakage determination by the water leakage detection system 100 in the area 57 subject to water leakage inspection will be described with reference to the drawings.

[0039] In Figure 3, ultrasonic flowmeter 1A is an ultrasonic flowmeter corresponding to customer home A in target area 57 in Figure 1, ultrasonic flowmeter 1B is an ultrasonic flowmeter corresponding to customer home B, ultrasonic flowmeter 1C is an ultrasonic flowmeter corresponding to customer home C, and ultrasonic flowmeter 1D is an ultrasonic flowmeter corresponding to customer home D.

[0040] The ultrasonic flowmeter 1A is connected to the common pipe 54 by a lead-in pipe 55A, and the ultrasonic flowmeter 1B is connected to the common pipe 54 by a lead-in pipe 55B. The ultrasonic flowmeter 1C is connected to the common pipe 54 by a lead-in pipe 55C, and the ultrasonic flowmeter 1D is connected to the common pipe 54 by a lead-in pipe 55D. Branch points of the lead-in pipes 55A to 55C to the common pipe 54 are designated as P1 to P3. The lead-in pipe 55D is connected to the downstream end P4 of the common pipe 54.

[0041] The piping path from ultrasonic flowmeter 1A to ultrasonic flowmeter 1B is designated as Lab, the piping path from ultrasonic flowmeter 1B to ultrasonic flowmeter 1C is designated as Lbc, and the piping path from ultrasonic flowmeter 1C to ultrasonic flowmeter 1D is designated as Lcd. Furthermore, the flow rates through the lead-in pipes 55A to 55D measured by the flow rate measuring units 3 of the ultrasonic flowmeters 1A to 1D are designated as q1 to q4, respectively. Furthermore, the flow rate at branch point P1 of the common pipe 54 is designated as Q1. The flow rate Q1 is the sum of the flow rates q1 to q4.

[0042] The water leakage determination unit 58 of the center device 20 receives the flow rates q1 to q4 from the ultrasonic flow meters 1A to 1D via the integrated communication unit 59. The water leakage determination unit 58 then determines whether the flow rates q1 to q4 measured by the ultrasonic flow meters 1A to 1D are equal to or less than the respective thresholds, and determines whether the flow rate flowing into the target district 57 (i.e., flow rate Q1) is equal to or less than the threshold stored in the integrated communication unit 59. The water leakage determination unit 58 executes a process for determining whether or not there is a water leak when the flow rates q1 to q4 are equal to or less than the respective thresholds and are equal to or less than the flow rate Q1 threshold.

[0043] The water leakage determination unit 58 of the central device 20 acquires the water pressure change rate from the water pressure change rate estimation unit 11 of each of the water meters 1A-1D via the integrated communication unit 59. The water leakage determination unit 58 determines whether or not there is a water leak in the flow path of the water supply network 60 based on a comparison between the acquired water pressure change rate and a water pressure reference value (e.g., a threshold value set in advance for comparison with the water pressure change rate acquired in the target district 57 or a threshold value set in advance for comparison with the water pressure change rate acquired in another target district 57). In this case, the water leakage determination unit 58 can determine that a water leak is occurring near the ultrasonic flowmeter 1 where the difference between the acquired water pressure change rate and the water pressure reference value is the largest. For example, if the difference related to water meter 1A is the largest, it is estimated that there is a high possibility that a water leak is occurring in piping path Lab. If the difference related to water meter 1B or the difference related to water meter 1C is the largest, it is estimated that there is a high possibility that a water leak is occurring in piping path Lbc. Furthermore, if the difference relating to the water meter 1D is the largest, it is estimated that there is a high possibility that a water leak is occurring in the piping path Lcd.

[0044] Next, the processing flow in the ultrasonic flowmeter 1 will be described. As shown in Fig. 4, first, the flowmeter unit 3 in the ultrasonic flowmeter 1 measures the instantaneous flow rate of water in the measurement flow path 40 (step S1). Then, the flowmeter unit 3 determines whether or not a predetermined flow rate change has occurred based on a comparison between the measured instantaneous flow rate and a threshold value (step S2). If the predetermined flow rate change has occurred (Yes in step S2), the flowmeter unit 3 stores the instantaneous flow rate and the usage time associated with the instantaneous flow rate in the memory unit 12 (step S3). On the other hand, if the predetermined flow rate change has not occurred (No in step S2), the flowmeter unit 3 returns to the processing in step S1.

[0045] Next, the flowmeter unit 3 determines whether water use has stopped (step S4). If water use has stopped (Yes in step S4), the water pressure change rate estimation unit 11 compares the instantaneous flow rate and usage time with water use pattern information pre-stored in the memory unit 12 (step S5). If water use has not stopped (No in step S4), the flowmeter unit 3 continues the process of step S4.

[0046] If the instantaneous flow rate, usage time, and water usage pattern information are the same (Yes in step S6), the temperature acquisition unit 10 acquires the water temperature based on the propagation time measured by the propagation time measurement unit 4 (step S7). On the other hand, if the instantaneous flow rate, usage time, and water usage pattern information are not the same (No in step S6), the flowmeter unit 3 returns to the processing of step S1.

[0047] Next, the correction unit 13 corrects the instantaneous flow rate based on the temperature acquired by the temperature acquisition unit 10 (step S8). The water pressure change rate estimation unit 11 then determines whether a predetermined period has elapsed (step S9). If the predetermined period has elapsed (Yes in step S9), the water pressure change rate estimation unit 11 acquires the rate of change of water pressure in the flow path of the water supply network 60 by comparing the average value of the instantaneous flow rate over the predetermined period with the instantaneous flow rate reference value (step S10). On the other hand, if the predetermined period has not elapsed (No in step S9), the flowmeter unit 3 returns to the processing of step S1. After processing step S10, the water pressure change rate estimation unit 11 transmits information related to the rate of change of water pressure to the water leak determination unit 58 of the center device 20 via the communication unit 9 (step S11).

[0048] As described above, in the water leak detection system 100 of this embodiment, the storage unit 12 pre-stores water usage pattern information, which indicates the instantaneous water flow rate and usage time, based on the measurement results from the flowmeter unit 3. The water pressure change rate estimation unit 11 then compares the instantaneous water flow rate and usage time during water usage with the water usage pattern information, and estimates the rate of change of water pressure in the flow paths of the water supply network 60 by comparing the average value of the instantaneous water flow rate during water usage over a predetermined period with a predetermined instantaneous flow rate reference value. The rate of change of water pressure is estimated when the instantaneous water flow rate during water usage and usage time during water usage are the same as those in the water usage pattern information, i.e., when the same equipment is used as the equipment corresponding to the water usage pattern information. This increases the reliability of the rate of change of water pressure. The water leak determination unit 58 in the center device 20 then compares the highly reliable rate of change of water pressure with a predetermined water pressure reference value and determines the presence or absence of a water leak in the flow paths of the water supply network 60 based on the comparison results. This increases the accuracy of determining the presence or absence of a water leak and reduces costs because a pressure sensor is not required.

[0049] The present disclosure is not limited to the above-described embodiments, and various modifications are possible as described below without departing from the gist of the present disclosure.

[0050] In the above embodiment, the water leakage determination unit 58 is provided in the central device 20, but this is not limited to this, and the water leakage determination unit 58 may also be provided in one of the multiple ultrasonic flow meters 1 installed in the target area 57.

[0051] The installation location of the center device 20 is not particularly limited, and it may be installed next to the water supply station 51, for example.

[0052] In the above embodiment, the cross-sectional area of ​​the common pipe 54 is generally constant, and the flow rate decreases toward the downstream side. Therefore, the flow rate at the branch point P1 may be used as the flow rate of the common pipe 54.

[0053] In addition, in the above embodiment, four ultrasonic flow meters 1 are connected to the common pipe 54, but this is not limited to this, and the number of ultrasonic flow meters 1 connected to the common pipe 54 may be, for example, three or less, or five or more.

[0054] In addition, in the above embodiment, the ultrasonic flowmeter 1 has two reflecting sections, the first reflecting section 7 and the second reflecting section 8, but this is not limited to this, and the number of reflecting sections may be, for example, one or three or more.

[0055] Furthermore, in the above embodiment, water leakage has been described as an example, but the inclusion of air bubbles or foreign matter can also be detected in the same way.

[0056] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D Ultrasonic flowmeter 2 Control unit 3 Flowmeter side unit 4 Propagation time measurement unit 5 First ultrasonic transmitter / receiver 6 Second ultrasonic transmitter / receiver 9 Communication unit 10 Temperature acquisition unit 11 Water pressure change rate estimation unit 12 Memory unit 13 Correction unit 14 Equipment used determination unit 20 Center device 40 Measurement flow path 54 Common piping 55 Intake pipe 56 Customer's home 57 Target area 58 Water leak determination unit 59 Integrated communication unit 60 Water supply network 100 Water leak detection system

Claims

1. A water leak detection system comprising a plurality of flow meters provided in a water supply network and a central device that manages the plurality of flow meters, wherein the flow meters comprise: a pair of ultrasonic transmitters and receivers arranged in a measurement flow path; a propagation time measurement unit that measures the propagation time, which is the time it takes for an ultrasonic wave to be transmitted by one of the ultrasonic transmitters and receivers and received by the other of the ultrasonic transmitters and receivers; a flow measurement unit that measures the flow rate of water in the measurement flow path based on the propagation time; a memory unit that stores, as water usage pattern information for each device used, information indicating the instantaneous flow rate of water measured by the flow meter unit and the duration of water use, which is repeated a predetermined number of times, using a predetermined period after installation of the flow meter as a learning period; a water pressure change rate estimation unit that estimates the ratio of the average value of the instantaneous flow rate for the device used over a predetermined period to a predetermined instantaneous flow rate reference value as the rate of change of water pressure in the flow path of the water supply network, based on the comparison result of the instantaneous flow rate and duration of use when water is used with the water usage pattern information for the device used stored in the memory unit; and a communication unit that communicates with the central device, A water leak detection system comprising: a general communication unit that communicates with the communication unit; and a water leak determination unit that determines whether or not there is a leak in the flow path of the water supply network based on a comparison between the rate of change of the water pressure estimated by the flow meters and a water pressure reference value when the water flow rate measured by each of the plurality of flow meters in the target area of ​​the water leak inspection is below a threshold and the flow rate flowing into the target area is below a threshold.

2. The water leak detection system described in claim 1, wherein the flow meter further comprises: a temperature acquisition unit that acquires the temperature of the water in the measurement flow path based on the propagation time; and a correction unit that corrects the instantaneous flow rate when the water is in use based on the temperature acquired by the temperature acquisition unit; and the water pressure change rate estimation unit uses the instantaneous flow rate corrected by the correction unit as the instantaneous flow rate when the water is in use.

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