Gas meter and control method therefor

Abstract

To provide a gas meter capable of specifying a cause of pressure drop and its control method.SOLUTION: A gas meter includes a pressure sensor 13, a storage part 15e, a flow sensor 14, a flow determination part 15b for determining the existence / nonexistence of a flow on the basis of a signal from the flow sensor 14, and a control part 15 for determining pressure drop abnormality to close a shutoff valve 12 when pressure indicated by the pressure sensor 13 is abnormal pressure or less, and the control part 15 determines whether the cause of the pressure drop is a closed state on a gas container side or a shortage state of fuel gas in a gas container on the basis of pressure information stored by the storage part 15e until the time earlier by a predetermined time than the time of determination of the pressure drop abnormality in the case of determining the pressure drop abnormality in a state in which the flow determination part 15b determines that the flow exists.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas meter and a control method thereof. [Background technology]

[0002] Conventionally, gas meters have been known that are equipped with a pressure sensor for detecting the pressure on the gas supply side, and that have a pressure drop shut-off function that determines that an abnormal drop in pressure has occurred when the pressure value indicated by the pressure sensor falls below a predetermined level and closes the shut-off valve (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-189853 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the gas meter described in Patent Document 1 merely closes the shutoff valve when there is an abnormal drop in pressure, and is unable to identify the cause of the drop in pressure.

[0005] The present invention has been made to solve the above-mentioned conventional problems, and its object is to provide a gas meter and a control method thereof that are capable of identifying the cause of a pressure drop. [Means for solving the problem]

[0006] The gas meter of the present invention comprises a pressure sensor for measuring the pressure of fuel gas supplied from the gas container side, a memory means for chronologically storing pressure information based on a signal from the pressure sensor, a flow sensor for measuring the flow rate of fuel gas supplied to a consumer side, a flow rate determination means for determining whether or not there is a flow rate based on the signal from the flow rate sensor, and a control means for determining that there is a pressure drop abnormality when the pressure indicated by the pressure sensor is below a predetermined level and for closing a shut-off valve.When the control means determines that there is a flow rate and that there is a pressure drop abnormality, the control means determines that the cause of the pressure drop is a blockage on the gas container side if the pressure value based on the pressure information stored in the memory means from the time of determining the pressure drop abnormality until a predetermined time ago is equal to or greater than a pressure threshold value that is higher than the predetermined level, and determines that the cause of the pressure drop is a shortage of fuel gas in the gas container if the pressure value is below the pressure threshold.

[0007] Furthermore, a gas meter according to the present invention comprises a pressure sensor for measuring the pressure of fuel gas supplied from the gas container side, storage means for chronologically storing pressure information based on a signal from the pressure sensor, a flow rate sensor for measuring the flow rate of fuel gas supplied to a consumer side, flow rate determination means for determining whether or not there is a flow rate based on the signal from the flow rate sensor, and control means for determining that a pressure drop has occurred abnormally when the pressure indicated by the pressure sensor is below a predetermined level and for closing a shut-off valve, wherein when the control means determines that there is a flow rate and that there is a pressure drop abnormality, it calculates a pressure decrease rate based on the pressure information stored in the storage means from the time when the pressure drop abnormality was determined to be present until a predetermined time ago, and if the decrease rate is equal to or greater than a decrease rate threshold, determines that the cause of the pressure drop is a blockage on the gas container side, and if the decrease rate is less than the decrease rate threshold, determines that the cause of the pressure drop is a shortage of fuel gas in the gas container.

[0008] The gas meter control method of the present invention is a control method for a gas meter equipped with a pressure sensor for measuring the pressure of fuel gas supplied from a gas container side, a memory means for chronologically storing pressure information based on a signal from the pressure sensor, and a flow sensor for measuring the flow rate of fuel gas supplied to a consumer side, and comprises: a flow rate determination step for determining whether or not there is a flow rate based on the signal from the flow rate sensor; and a control step for determining a pressure drop abnormality when the pressure indicated by the pressure sensor is below a predetermined level and closing a shut-off valve. In the control step, when it is determined that there is a flow rate in the flow rate determination step and it is determined that there is a pressure drop abnormality, if the pressure value based on the pressure information stored in the memory means from the time when the pressure drop abnormality was determined until a predetermined time ago is equal to or greater than a pressure threshold value higher than the predetermined level, it determines that the cause of the pressure drop is a blockage on the gas container side, and if the pressure value is below the pressure threshold, it determines that the cause of the pressure drop is a shortage of fuel gas in the gas container.

[0009] Furthermore, a gas meter control method according to the present invention is a method for controlling a gas meter equipped with a pressure sensor for measuring the pressure of fuel gas supplied from a gas container side, a memory means for chronologically storing pressure information based on a signal from the pressure sensor, and a flow sensor for measuring the flow rate of fuel gas supplied to a consumer side, and comprises: a flow rate determination step for determining whether or not there is a flow rate based on the signal from the flow rate sensor; and a control step for determining that there is a pressure drop abnormality when the pressure indicated by the pressure sensor is below a predetermined level and closing a shut-off valve. In the control step, when it is determined that there is a flow rate in the flow rate determination step and it is determined that there is a pressure drop abnormality, the control step calculates a pressure decrease rate based on pressure information stored in the memory means from the time when the pressure drop abnormality was determined until a predetermined time ago, and if the decrease rate is equal to or greater than a decrease rate threshold, determines that the cause of the pressure drop is a blockage on the gas container side, and if the decrease rate is less than the decrease rate threshold, determines that the cause of the pressure drop is a shortage of fuel gas in the gas container. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a gas meter and a control method thereof that are capable of identifying the cause of a pressure drop. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing a fuel supply system including a gas meter according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of the gas meter shown in FIG. [Figure 3] FIG. 1 is a first diagram showing pressure changes. [Figure 4] FIG. 2 is a second diagram showing pressure changes. [Figure 5] 3 is a flowchart showing a method for controlling a gas meter according to the first embodiment. [Figure 6] 10 is a flowchart showing a gas meter control method according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and the embodiments can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments shown below, some components are omitted from illustration and description, but for the details of the omitted technologies, publicly known or well-known technologies are applied as appropriate within the scope of not causing any contradiction with the content described below.

[0013] Fig. 1 is a configuration diagram showing a fuel supply system including a gas meter according to a first embodiment of the present invention. As shown in Fig. 1, the fuel supply system 100 supplies fuel gas in a gas container B to a consumer side via a gas meter 1, and includes the gas container B, the gas meter 1, and gas pipes L1 and L2.

[0014] The gas container B stores high-pressure fuel gas. The gas container B is provided with a gas valve B1 at the fuel gas outlet. The gas valve B1 is connected to the gas meter 1 via a first gas pipe L1. The fuel supply system 100 is not limited to having only one gas container B, and may have a plurality of gas containers B. Although not shown in FIG. 1, a pressure regulator is provided between the gas container B and the gas meter 1.

[0015] The gas meter 1 measures the flow rate of fuel gas passing through it. The gas meter 1 displays the integrated value of the measured fuel gas on a display unit 11 on the front. The gas meter 1 is also connected to a second gas pipe L2. The second gas pipe L2 supplies fuel gas to the consumer side, and is connected to a gas appliance in a home, for example.

[0016] Fig. 2 is a block diagram showing a schematic configuration of the gas meter 1 shown in Fig. 1. As shown in Fig. 2, the gas meter 1 is an ultrasonic gas meter that measures flow rate using, for example, ultrasonic waves, and includes a shutoff valve 12, a pressure sensor 13, a flow rate sensor 14, and a control unit (control means) 15.

[0017] The shutoff valve 12 is provided on a substantially U-shaped flow path R formed inside the gas meter 1, and opens or closes the flow path R in response to an instruction from the control unit 15. The pressure sensor 13 measures the pressure of the fuel gas supplied from the gas container B (see FIG. 1). The pressure sensor 13 is provided on the flow path R upstream of the shutoff valve 12.

[0018] The flow rate sensor 14 is provided in a flow path R formed within the gas meter 1 and measures the flow rate of fuel gas flowing through the flow path R, i.e., the flow rate of fuel gas supplied to the consumer side. In this embodiment, the flow rate sensor 14 is configured by an ultrasonic sensor, and has an upstream ultrasonic sensor and a downstream ultrasonic sensor. The flow rate sensor 14 determines the gas flow velocity based on the propagation time when these sensors transmit and receive ultrasonic signals, and calculates the flow rate based on the gas flow velocity and the cross-sectional area of ​​the flow path R. The flow rate sensor 14 also transmits information on the calculated flow rate to the control unit 15.

[0019] The control unit 15 controls the entire gas meter 1, and includes a pressure measurement unit 15a, a flow rate determination unit (flow rate determination means) 15b, a decrease determination unit 15c, a cause determination unit 15d, and a memory unit (memory means) 15e.

[0020] The pressure measurement unit 15a receives a signal from the pressure sensor 13 and measures the pressure of the fuel gas. The pressure measurement unit 15a measures the pressure of the fuel gas, for example, at a specified time interval (for example, every few seconds, specifically every 2 seconds). The memory unit 15e stores pressure information and the like obtained at specified time intervals based on the signal from the pressure sensor 13. In this embodiment, the memory unit 15e stores pressure information for the most recent specified time (for example, about several seconds to several tens of seconds, specifically 16 seconds), and discards pressure information for times exceeding the specified time. The flow rate determination unit 15b determines whether or not there is a flow rate based on the information on the flow rate measured by the flow rate sensor 14.

[0021] The drop determination unit 15c determines that a pressure drop has occurred abnormally when the pressure indicated by the signal from the pressure sensor 13 is equal to or lower than a predetermined abnormal pressure (predetermined level). The fuel gas in the gas container B is adjusted to an appropriate pressure via a pressure regulator (not shown) and supplied to the gas meter 1. When the pressure of the fuel gas falls below the abnormal pressure, it can be determined that some abnormality has occurred in the fuel supply system 100. Therefore, when the drop determination unit 15c determines that a pressure drop has occurred abnormally, the control unit 15 closes the shutoff valve 12.

[0022] The cause determination unit 15d determines the cause of the pressure drop when the pressure drop determination unit 15c determines that a pressure drop abnormality has occurred. In this embodiment, the cause determination unit 15d determines whether the cause is 1) upstream blockage (blockage on the gas container B side), 2) gas shortage (insufficient fuel gas in the gas container B), or 3) upstream leakage (gas leakage on the gas container B side).

[0023] First, when the flow rate determination unit 15b determines that there is a flow rate and that there is a pressure drop abnormality, the cause determination unit 15d determines whether the abnormality is 1) or 2) based on the pressure information stored in the memory unit 15e from the time of the determination until a predetermined time ago.

[0024] 3 and 4 are diagrams showing pressure changes when an abnormal pressure drop occurs, where Fig. 3 shows pressure changes when the upstream side is blocked, and Fig. 4 shows pressure changes when there is a gas shortage.

[0025] First, 1) upstream blockage refers to a state in which, for example, gas container B has been replaced but the gas valve B1 remains closed. In such a case, as shown in Figure 3, the gas pressure exceeds the normal pressure (e.g., 2.0 kPa) a predetermined time before the pressure drop is determined to be abnormal, and then drops rapidly from this state to below the abnormal pressure (e.g., 0.68 kPa). This is because the only fuel gas available for supply to the consumer is that remaining in the first gas pipe L1.

[0026] A more detailed explanation will be given below. First, let us assume that the gas pressure after a unit time has elapsed is ΔP, the volume inside gas container B is V1, the volume from gas container B to gas meter 1 is V2, the gas flow rate passing through gas meter 1 per unit time is Q1, and the original pressure is P0. In this case, the gas pressure ΔP after a unit time has elapsed can be expressed by the following formula. Note that V1 also includes the volume inside gas container B. ΔP=P0×{(V1+V2)-(Q1)} / (V1+V2)

[0027] Also, for example, suppose the internal volume of the first gas pipe L1 is 0.2 L / m (equivalent to a 15A steel pipe) and the length of the first gas pipe L1 is 4 m. Here, when the upstream side is blocked, no fuel gas is supplied from the gas container B, and V1 = 0. Therefore, if the current gas pressure P0 is, for example, 2.8 kPa and the gas flow rate Q1 is 100 mL / sec, the gas pressure will drop to below the abnormal pressure in approximately 6 seconds. Furthermore, if the gas flow rate Q1 is the maximum flow rate (1111 mL / sec) of the residential gas meter, the gas pressure will drop to below the abnormal pressure within 1 second. Therefore, when the upstream side is blocked, the gas pressure exceeds the normal pressure a predetermined time before the pressure drop is determined to be abnormal, and then it rapidly drops from this state to below the abnormal pressure.

[0028] Note that the upstream blockage is not limited to a state in which the gas valve B1 remains closed, but may also be a state in which the flow of gas is blocked due to, for example, an abnormality in the pressure regulator.

[0029] Furthermore, 2) gas shortage refers to a state in which, for example, fuel gas in gas container B has been consumed and needs to be replaced, but the container continues to be used. In this case, as shown in Figure 4, the gas pressure does not exceed the normal pressure a predetermined time before a pressure drop abnormality is detected. In other words, the gas pressure gradually decreases as the fuel gas in gas container B is consumed, and therefore does not exceed the normal pressure a predetermined time before a pressure drop abnormality is detected.

[0030] A more detailed explanation follows. For example, suppose the internal volume of the first gas pipe L1 is 0.2 L / m and the length of the first gas pipe L1 is 4 m. Furthermore, suppose that gas container B is a 20 kg container (47 L per container). Assume that the fuel gas in gas container B is not all in a high-pressure liquefied state, but is at 2.8 kPa after pressure adjustment. In this case, if the gas flow rate Q1 is 100 mL / sec, it takes approximately six minutes for the gas pressure to drop below the abnormal pressure. Furthermore, even if the gas flow rate Q1 is the maximum flow rate of the residential gas meter, it takes approximately 32 seconds for the gas pressure to drop below the abnormal pressure. Therefore, during a gas shortage, the gas pressure does not exceed the normal pressure even before the predetermined time when a pressure drop is determined to be abnormal.

[0031] Referring again to FIG. 2, as described above, the pressure drop behavior differs significantly between upstream blockage and gas shortage. Therefore, the cause determination unit 15d utilizes this pressure drop trend to determine whether the cause is 1) upstream blockage or 2) gas shortage. That is, when the cause determination unit 15d determines that there is a flow rate in a state where the flow rate determination unit 15b determines that there is a pressure drop abnormality, the cause determination unit 15d refers to a pressure value based on pressure information stored in the memory unit 15e from the time of determination until a predetermined time ago. If the pressure value is equal to or greater than a normal pressure (an example of a pressure threshold) that exceeds the abnormal pressure, the cause determination unit 15d determines that there is 1) upstream blockage. On the other hand, if the pressure value is less than the normal pressure, the cause determination unit 15d determines that there is 2) gas shortage.

[0032] Here, the cause determination unit 15d preferably divides the pressure information stored in the memory unit 15e into two halves, one for the newest and one for the oldest, into two halves in time series, and compares the pressure value based on the older pressure information with the normal pressure. As described with reference to FIG. 3, it is possible that the gas pressure may take approximately six seconds to drop below the abnormal pressure. For this reason, for example, if the gas pressure is measured at two-second intervals and the pressure value two seconds before the pressure drop is determined to be abnormal is determined to be normal, the pressure may not be higher than the normal pressure even when the upstream side is blocked. However, by comparing the pressure value based on the older pressure information divided into two halves as described above with the normal pressure, the cause determination unit 15d can reduce the possibility of such an erroneous determination and more accurately determine the cause.

[0033] Although the cause determination unit 15d determines whether the pressure value is equal to or greater than the normal pressure, the pressure value to be compared with is not limited to the normal pressure. For example, the cause determination unit 15d may set a threshold value (an example of a pressure threshold value) other than the normal pressure separately, and determine whether the pressure value is equal to or greater than this threshold value to determine whether 1) upstream blockage or 2) gas shortage exists.

[0034] Furthermore, when the flow rate determining unit 15b determines that there is no flow rate and a pressure drop abnormality occurs, the cause determining unit 15d determines that the cause is 3) an upstream leak. For example, if the high-pressure hose connected to the gas valve B1 is disconnected, the gas meter 1 detects that the pressure inside the flow path R becomes atmospheric pressure, resulting in a pressure drop abnormality. In this case, no fuel gas is being used and the gas pressure measured by the pressure sensor 13 falls below the abnormal pressure. Therefore, when the flow rate determining unit 15b determines that there is no flow rate and a pressure drop abnormality occurs, the cause determining unit 15d determines that there is 3) an upstream leak.

[0035] The upstream leakage is not limited to the disconnection of the high-pressure hose connected to the gas valve B1, but may be the leakage caused by, for example, a crack in the first gas pipe L1 or a break in the pressure regulator.

[0036] Fig. 5 is a flowchart showing a method for controlling the gas meter 1 according to the first embodiment. The flowchart shown in Fig. 5 is repeatedly executed until the power supply to the gas meter 1 is turned off.

[0037] 5, the pressure measurement unit 15a measures the pressure of the fuel gas based on a signal from the pressure sensor 13 (S1). Next, the flow rate sensor 14 measures the gas flow rate (S2). The storage unit 15e then stores the pressure information obtained by the measurement in step S1 and the flow rate information obtained by the measurement in step S2 (S3).

[0038] Thereafter, the decrease determination unit 15c determines whether the pressure value based on the pressure information obtained by the measurement in step S1 is equal to or less than the abnormal pressure (S4). If the pressure value is not equal to or less than the abnormal pressure (S4: NO), the process proceeds to step S1.

[0039] On the other hand, if the pressure value is equal to or less than the abnormal pressure (S4: YES), the drop determination unit 15c determines that a pressure drop abnormality has occurred, and the control unit 15 closes the shutoff valve 12 (S5). Thereafter, the cause determination unit 15d determines whether there was a flow rate when the pressure drop abnormality was determined (S6). In this process, the cause determination unit 15d determines whether there was a flow rate by referring to the flow rate information stored in the memory unit 15e.

[0040] If there is no flow rate when determining the pressure drop abnormality (S6: NO), it can be said that the pressure drop abnormality occurred even though no fuel gas was being used. Therefore, the cause determination unit 15d determines that the cause of the pressure drop is an upstream leak (S7). Then, the process proceeds to step S12.

[0041] If there is a flow rate when determining that a pressure drop abnormality has occurred (S6: YES), the cause determination unit 15d uses one of the oldest pressure values ​​among the pressure values ​​based on pressure information within a predetermined time period stored in the storage unit 15e (S8). In this embodiment, the cause determination unit 15d uses, for example, the pressure value based on the oldest pressure information within the predetermined time period.

[0042] Next, the cause determination unit 15d determines whether the pressure value adopted in step S8 is equal to or greater than the normal pressure (S9). If the pressure value is equal to or greater than the normal pressure (S9: YES), the cause determination unit 15d determines that the cause of the pressure drop is an upstream blockage (S10). Then, the process proceeds to step S12.

[0043] If the pressure value is not equal to or greater than the normal pressure (S9: NO), the cause determining unit 15d determines that the cause of the pressure drop is a gas shortage (S11), and the process proceeds to step S12.

[0044] In step S12, the control unit 15 causes the display unit 11 to display the cause of the pressure drop determined by the cause determination unit 15d. After that, the process shown in Fig. 5 ends.

[0045] In this way, the gas meter 1 and its control method according to this embodiment determine whether the cause of the pressure drop is an upstream blockage or a gas shortage based on pressure information from the time when the pressure drop abnormality was determined until a predetermined time before. Here, assume a case where the upstream blockage occurs, such as when gas container B is replaced while the gas valve B1 is closed. In this case, the fuel gas in gas container B cannot be supplied to the consumer side, and the only fuel gas that can be supplied to the consumer side is that remaining in the first gas pipe L1 extending from gas container B, which is very small. Therefore, when there is a flow rate such that fuel gas is being used by the consumer, the fuel gas is consumed early, and the pressure measured by the pressure sensor 13 suddenly drops from normal pressure to below the abnormal pressure. Therefore, it is highly likely that the pressure values ​​from the time when the pressure drop abnormality was determined until the predetermined time before include values ​​above normal pressure.

[0046] On the other hand, if the pressure drop abnormality occurs due to a lack of gas in gas container B, the pressure will gradually drop and reach or fall below the abnormal pressure. Therefore, it is highly likely that the pressure value from the time the pressure drop abnormality was determined until a certain time before was below the normal pressure.

[0047] In this way, because the process leading to the pressure drop abnormality differs between upstream blockage and gas shortage, it is possible to identify the cause of the pressure drop by comparing the pressure value from the time the pressure drop abnormality was determined until a predetermined time ago with the normal pressure. Therefore, it is possible to provide a gas meter 1 and a control method thereof that can identify the cause of the pressure drop.

[0048] Furthermore, the gas meter 1 and its control method according to this embodiment divide pressure information within a predetermined time period into two parts, new and old, and compare the pressure value based on the older pressure information with the normal pressure. Therefore, the newer pressure information within the predetermined time period is discarded. Here, if the cause of the pressure drop is an upstream blockage, the pressure may drop suddenly, but the newer pressure may be below the normal pressure. However, the older pressure is less likely to be such a case and may be above the normal pressure. On the other hand, if the cause of the pressure drop is a gas shortage, the pressure will gradually decrease, making it highly likely that the pressure at any point within the predetermined time period will be below the normal pressure. Therefore, by comparing the pressure value based on the older pressure information within the predetermined time period with the normal pressure, the accuracy of identifying the cause of the pressure drop can be improved.

[0049] Furthermore, the gas meter 1 and its control method according to this embodiment determine that the cause of the pressure drop is an upstream leak when a pressure drop abnormality is detected in a state where it is determined that there is no flow rate. Here, when there is no flow rate, the pressure does not normally drop. Furthermore, when a leak occurs on the consumer side of the gas meter 1, the leaking fuel gas passes through the gas meter 1, which indicates that there is a flow rate. In this situation, when there is a pressure drop without a flow rate, it can be said that a leak is occurring on the gas container B side of the gas meter 1. Therefore, it is possible to provide a gas meter 1 and its control method that are more capable of identifying the cause of the pressure drop.

[0050] Next, a second embodiment of the present invention will be described. The gas meter according to the second embodiment is similar to that of the first embodiment, but the configuration and control method are partially different. The differences from the first embodiment will be described below.

[0051] First, the cause determination unit 15d shown in Fig. 2 determines whether the cause of the abnormal pressure drop is 1) upstream blockage, 2) gas shortage, or 3) upstream leakage. Here, the gas meter 1 according to the first embodiment determines whether the cause is 1) upstream blockage or 2) gas shortage based on whether the pressure value is equal to or higher than the normal pressure. This is because, as described with reference to Figs. 3 and 4, the rate of pressure drop differs between 1) upstream blockage and 2) gas shortage.

[0052] In the second embodiment, the cause determination unit 15d calculates the rate of pressure decrease in order to directly determine the rate of such pressure decrease, and determines whether the cause is 1) upstream blockage or 2) gas shortage based on whether the rate of decrease is greater than or equal to a predetermined decrease rate threshold.

[0053] Fig. 6 is a flowchart showing a method for controlling the gas meter 1 according to the second embodiment. The flowchart shown in Fig. 6 is similar to Fig. 5, and is repeatedly executed until the power supply to the gas meter 1 is turned off. In the flowchart shown in Fig. 6, the same processes as those in Fig. 5 are assigned the same reference numerals, and their explanations will be omitted.

[0054] 6, if there is a flow rate when determining that a pressure drop abnormality has occurred (S6: YES), the cause determining unit 15d calculates the pressure decrease rate based on the pressure information within a predetermined time period stored in the storage unit 15e (S13). Here, the cause determining unit 15d may calculate the decrease rate from only two pieces of pressure information among the multiple pieces of pressure information within the predetermined time period, or may calculate multiple decrease rates from three or more pieces of pressure information and use a representative value such as an average value or an average value excluding abnormal values.

[0055] Thereafter, the cause determination unit 15d determines whether the decrease rate calculated in step S13 is equal to or greater than the decrease rate threshold (S14). Here, as shown in FIGS. 3 and 4, the pressure decrease rate is large when the upstream side is blocked, and is small when there is a gas shortage. Therefore, if the decrease rate is equal to or greater than the decrease rate threshold (S14: YES), the cause determination unit 15d determines that the cause of the pressure drop is upstream blockage (S10). Then, the process proceeds to step S12.

[0056] On the other hand, if the decrease rate is not equal to or greater than the decrease rate threshold (S14: NO), the cause determining unit 15d determines that the cause of the pressure drop is a gas shortage (S11), and the process proceeds to step S12.

[0057] In this way, the gas meter 1 and control method thereof according to the second embodiment determine that the cause of the pressure drop is an upstream blockage when the rate of pressure decrease based on pressure information from the time of determining the pressure drop abnormality until a predetermined time ago is equal to or greater than the decrease rate threshold. Furthermore, the gas meter 1 and control method thereof determine that the cause of the pressure drop is a lack of gas in the gas container B when the rate of pressure decrease is less than the decrease rate threshold. Here, the rate of pressure decrease differs between when the cause of the pressure drop is an upstream blockage and when the cause is a gas shortage. Therefore, the gas meter 1 and control method thereof can determine whether the cause is an upstream blockage or a gas shortage by calculating the decrease rate and comparing it with the decrease rate threshold. Therefore, it is possible to provide a gas meter 1 and control method thereof that can identify the cause of the pressure drop.

[0058] Furthermore, the gas meter 1 and its control method according to the second embodiment determine that the cause of the pressure drop is an upstream leak when a pressure drop abnormality is detected in a state where no flow rate is determined, so that the cause of the pressure drop can be more easily identified, as in the first embodiment.

[0059] The present invention has been described above based on the above embodiment, but the present invention is not limited to the above embodiment, and modifications may be made within the scope of the spirit of the present invention, publicly known or well-known technologies may be combined as appropriate, or embodiments may be combined with each other.

[0060] For example, in the above embodiment, the cause determination unit 15d may determine the cause of the pressure drop based on both whether the pressure is above the normal pressure and whether the pressure is above the decrease rate threshold. In this case, for example, the cause determination unit 15d may determine that the upstream side is blocked when both of these are judged to be "YES," and may determine that there is a gas shortage when both of these are judged to be "NO." Furthermore, the cause determination unit 15d may determine that the cause is unknown when one of these is "YES" and the other is "NO."

[0061] In the above embodiment, the flow rate determining unit 15b determines whether or not there is a flow rate based on the flow rate measured by the ultrasonic flow rate sensor 14. However, this is not particularly limited, and the flow rate determining unit 15b may determine whether or not there is a flow rate without relying on information from the flow rate sensor 14, for example, by inputting a usage signal from a gas appliance.

[0062] Furthermore, in the above embodiment, the memory unit 15e stores pressure information, etc. within a predetermined time period and discards information that exceeds the predetermined time period, but this is not limited to this, and the memory unit 15e may be configured not to discard information, or may be configured to discard information in response to an operation by a user, worker, etc. [Explanation of symbols]

[0063] 1: Gas meter 12:Shut-off valve 13: Pressure sensor 14: Flow sensor 15: Control unit (control means) 15a: Pressure measurement section 15b: Flow rate judgment unit (flow rate judgment means) 15c: Decrease judgment part 15d: Cause determination department 15e: Storage unit (storage means) B: Gas bottle

Claims

1. a pressure sensor for measuring the pressure of the fuel gas supplied from the gas container; a storage means for storing pressure information based on a signal from the pressure sensor in chronological order; a flow rate sensor for measuring the flow rate of fuel gas supplied to a consumer; a flow rate determining means for determining whether or not there is a flow rate based on a signal from the flow rate sensor; a control means for determining that a pressure drop abnormality occurs when the pressure indicated by the pressure sensor is equal to or lower than a predetermined level, and for closing the shutoff valve; When the control means determines that there is a pressure drop abnormality in a state in which the flow rate determination means determines that there is a flow rate, if a pressure value based on pressure information stored in the storage means from the time of determination of the pressure drop abnormality until a predetermined time ago is equal to or greater than a pressure threshold value that is higher than the predetermined level, the control means determines that the cause of the pressure drop is a blockage on the gas container side, and if the pressure value is less than the pressure threshold value, the control means determines that the cause of the pressure drop is a shortage of fuel gas in the gas container. A gas meter characterized by:

2. The storage means stores pressure information for a recent predetermined time period, The control means divides the pressure information stored in the storage means for a predetermined time period into two parts, new and old, in chronological order, and compares a pressure value based on the older pressure information with the pressure threshold value.

2. The gas meter according to claim 1 .

3. a pressure sensor for measuring the pressure of the fuel gas supplied from the gas container; a storage means for storing pressure information based on a signal from the pressure sensor in chronological order; a flow rate sensor for measuring the flow rate of fuel gas supplied to a consumer; a flow rate determining means for determining whether or not there is a flow rate based on a signal from the flow rate sensor; a control means for determining that a pressure drop abnormality occurs when the pressure indicated by the pressure sensor is equal to or lower than a predetermined level, and for closing the shutoff valve; When the control means determines that there is a pressure drop abnormality in a state where the flow rate determination means determines that there is a flow rate, the control means calculates a pressure drop rate based on pressure information stored in the storage means from the time when the pressure drop abnormality was determined to have occurred until a predetermined time ago, and if the pressure drop rate is equal to or greater than a drop rate threshold, determines that the cause of the pressure drop is a blockage on the gas container side, and if the pressure drop rate is less than the drop rate threshold, determines that the cause of the pressure drop is a shortage of fuel gas in the gas container. A gas meter characterized by:

4. When the control means determines that there is no flow based on the signal from the flow sensor, and determines that the pressure drop is abnormal, it determines that the cause of the pressure drop is gas leakage on the gas container side.

4. The gas meter according to claim 1 or 3.

5. a pressure sensor for measuring the pressure of the fuel gas supplied from the gas container; a storage means for storing pressure information based on a signal from the pressure sensor in chronological order; A method for controlling a gas meter equipped with a flow rate sensor for measuring the flow rate of fuel gas supplied to a consumer side, comprising: a flow rate determination step of determining whether or not there is a flow rate based on a signal from the flow rate sensor; a control step of determining that a pressure drop abnormality occurs when the pressure indicated by the pressure sensor is equal to or lower than a predetermined level and closing the shutoff valve; In the control step, when it is determined that there is a flow in the flow rate determination step and it is determined that there is a pressure drop abnormality, if a pressure value based on the pressure information stored in the storage means from the time when the pressure drop abnormality was determined until a predetermined time ago is equal to or greater than a pressure threshold value that is higher than the predetermined level, it is determined that the cause of the pressure drop is a blockage on the gas container side, and if the pressure value is less than the pressure threshold value, it is determined that the cause of the pressure drop is a shortage of fuel gas in the gas container. A gas meter control method comprising:

6. a pressure sensor for measuring the pressure of the fuel gas supplied from the gas container; a storage means for storing pressure information based on a signal from the pressure sensor in chronological order; A method for controlling a gas meter equipped with a flow rate sensor for measuring a flow rate of fuel gas supplied to a consumer side, comprising: a flow rate determination step of determining whether or not there is a flow rate based on a signal from the flow rate sensor; a control step of determining that a pressure drop abnormality occurs when the pressure indicated by the pressure sensor is equal to or lower than a predetermined level and closing the shutoff valve; In the control step, when it is determined that there is a flow rate in the flow rate determination step and it is determined that there is a pressure drop abnormality, a pressure drop rate is calculated based on pressure information stored in the storage means from the time when the pressure drop abnormality was determined until a predetermined time ago, and if the drop rate is equal to or greater than a drop rate threshold, it is determined that the cause of the pressure drop is a blockage on the gas container side, and if the drop rate is less than the drop rate threshold, it is determined that the cause of the pressure drop is a shortage of fuel gas in the gas container. A gas meter control method comprising:

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