Gas shutoff device

Abstract

To provide a gas cutoff device capable of more precisely detecting shift of a flow rate on a negative side by monitoring whether an actual flow rate shifts to the negative side at regular intervals.SOLUTION: A gas cutoff device is configured so that a flow rate calculation unit calculates a flow rate value from an instantaneous flow rate measured by a flow rate measurement unit, and an integration unit integrates the calculated flow rate value to an accumulation buffer for a unit accumulation period. When the unit accumulation period, which is a predetermined period, has passed, a first determination unit counts the number of times the integrated flow rate value is determined to be less than a predetermined value. When the cumulative number of times is greater than or equal to a predetermined number of times and when the certain number of times succeeds a predetermined number, the gas cutoff device determines that the flow rate shifts to the negative side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas shutoff device that detects whether or not there is a flow rate shift. [Background technology]

[0002] Conventionally, gas shutoff devices have the function of detecting gas leaks and issuing an alarm or shutting off the gas.

[0003] For example, a typical operation is to monitor the flow rate in a gas pipe, determine whether there is gas flow or not based on specified conditions, clear the leak determination timer if it determines that there is no flow, and count the leak determination timer if it determines that there is flow, and when the leak determination timer has reached a specified period (e.g., 30 days), it determines that there is a leak and issues an alarm or shuts off the gas.

[0004] In addition, with city gas, the zero point of the flow rate can shift, causing the overall flow rate to shift to the positive or negative side, due to fluctuations in gas supply pressure, pressure fluctuations (hereinafter referred to as pulsation) caused by the use of gas appliances such as gas engines, heat pumps, or air conditioners, long-term gas flow (hereinafter referred to as breathing) caused by pressure fluctuations in the gas pipes due to factors such as temperature changes (rises and falls) during the day, or changes in sensor characteristics and electronic circuit characteristics over time.

[0005] If the overall flow rate shifts to the positive side, it becomes easier to exceed the threshold for determining a leak (for example, 1.1 L / h), making it impossible to accurately determine that there is no flow, and it may be determined that there is a leak even when there is no leak, resulting in a false alarm and shutdown. Also, if the overall flow rate shifts to the negative side, it becomes harder to exceed the threshold for determining a leak, making it impossible to accurately determine that there is a flow, and it may be determined that there is no leak even when there is actually a leak, resulting in no alarm and shutdown, which may be unsafe.

[0006] In this way, in leak detection, it is important to correctly determine whether the zero point of the flow rate or the entire flow rate has shifted, and this is being studied.

[0007] For example, in Patent Document 1, a moving average flow rate within a predetermined interval (e.g., 20 minutes) is calculated from an interval average flow rate (e.g., an average flow rate over a 2-minute period). Then, when the difference between the maximum and minimum moving average flow rates within the predetermined interval is within a predetermined range (e.g., 0.5 L / h), the interval average flow rate is within a predetermined range (e.g., ±11 L / h), and the difference between the maximum and minimum instantaneous flow rates from which the interval average flow rate was calculated is within a predetermined range (e.g., 50 L / h), a cumulative average flow rate is acquired by accumulating and averaging M interval average flow rates (e.g., 30) included in the moving average flow rate. If the acquired cumulative average flow rate falls below a predetermined flow rate (e.g., −3.5 L / h) a predetermined number of times (e.g., 10 times) within a predetermined period (e.g., 30 days), it is determined that the flow rate has shifted to the negative side. If it is determined that the flow rate has shifted to the negative side, the leak detection timer is not cleared.

[0008] By not clearing the leak detection timer, if a predetermined period of time has passed, it will be determined that there is a leak and an alarm will be issued and the system will be shut off, improving safety. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-205245 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in Patent Document 1, when the flow rate is shifted to the negative side, if large variations occur due to fluctuations in the instantaneous flow rate caused by pulsation, the difference between the maximum and minimum instantaneous flow rates used to calculate the section average flow rate may fall outside a predetermined range, or the difference between the maximum and minimum moving average flow rates may fall outside a predetermined range. Therefore, if either the difference between the maximum and minimum instantaneous flow rates or the difference between the maximum and minimum moving average flow rates falls outside a predetermined range, there is a problem in that it may not be possible to correctly determine whether the flow rate has shifted.

[0011] The present invention solves the above-mentioned conventional problems and aims to provide a gas shutoff device that can more accurately detect a negative shift in flow rate by monitoring at predetermined time intervals whether the actual flow rate is shifting to the negative side. [Means for solving the problem]

[0012] The gas shutoff device of the present invention comprises a flow rate measuring unit connected to a gas supply pipe and measuring an instantaneous gas flow rate at predetermined intervals; a flow rate calculation unit calculating a flow rate value from the instantaneous flow rate measured by the flow rate measuring unit; an integration unit integrating the flow rate values ​​of the flow rate calculation unit at predetermined intervals; a first determination unit determining whether the integrated flow rate value integrated by the integration unit over a first predetermined period is less than a predetermined flow rate; a second determination unit determining whether the number of times the first determination unit has determined that the integrated flow rate value is less than the predetermined flow rate is equal to or greater than a first predetermined number; and a flow rate shift determination unit determining that the flow rate over the second predetermined period has shifted to the negative side if it determines that the number of times counted by the second determination unit within a second predetermined period is equal to or greater than the first predetermined number, and confirming the flow rate shift if the flow rate shift determination is established the second predetermined number of times.

[0013] This allows the flow rate measurement unit to measure at predetermined intervals whether gas in the pipe is moving in the forward or reverse direction from upstream to downstream due to pressure fluctuations caused by pulsation, even when no gas is actually being used. Even if the measured instantaneous flow rate has positive or negative fluctuations or variations, the instantaneous flow rate (L / h) measured by the flow rate measurement unit is converted into a flow rate value (L) by the flow rate calculation unit, and this flow rate value is then calculated as an integrated flow rate value by the integration unit, making it possible to determine the actual volume of gas moving in the pipe. This allows for more accurate determination of flow rate shifts. [Effects of the Invention]

[0014] By using the gas shutoff device of the present invention, even if gas in the pipe moves upstream or downstream and then returns due to pressure fluctuations caused by pulsation despite no actual gas being used, it is possible to grasp the volume of gas that has actually moved in the pipe.Then, by using the first determination unit, second determination unit, and flow rate shift determination unit to determine whether the flow rate has shifted to the negative side based on the integrated flow rate value integrated by the integrating unit, it is possible to more accurately determine a flow rate shift. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram of a gas meter according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a diagram showing an operation procedure for determining whether or not there is a flow rate shift in the first embodiment of the present invention. [Figure 3] FIG. 10 is a block diagram of a gas meter according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a diagram showing an operation procedure for determining whether or not there is a flow rate shift in the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The first invention comprises a flow rate measuring unit connected to a gas supply pipe and measuring an instantaneous flow rate of gas at predetermined intervals; a flow rate calculation unit calculating a flow rate value from the instantaneous flow rate measured by the flow rate measuring unit; an integrating unit integrating the flow rate values ​​of the flow rate calculation unit at predetermined intervals; a first judgment unit determining whether the integrated flow rate value integrated by the integrating unit over a first predetermined period is less than a predetermined flow rate; a second judgment unit determining whether the number of times the first judgment unit has determined that the integrated flow rate value is less than the predetermined flow rate is equal to or greater than a first predetermined number; and a flow rate shift judgment unit determining that the flow rate over the second predetermined period has shifted to the negative side if it is determined that the number of times counted by the second judgment unit within a second predetermined period is equal to or greater than the first predetermined number, and confirming the flow rate shift if the flow rate shift judgment is established the second predetermined number of times.

[0017] As a result, even when there is no actual flow rate, the flow rate measuring unit measures the movement of gas in the pipe in the forward or reverse direction from the upstream to the downstream due to pressure fluctuations caused by pulsation at predetermined time intervals, and can measure the movement even if the measured instantaneous flow rate has positive or negative fluctuations or variations.The measured instantaneous flow rate (L / h) is then converted to a flow rate value (L) by the flow rate calculation unit, and this flow rate value is integrated in an integration buffer by the integration unit, making it possible to determine the actual volume of gas that has moved in the pipe.Based on the buffer value integrated by the integration unit, the first determination unit, second determination unit, and flow rate shift determination unit determine whether the flow rate has shifted to the negative side, making it possible to more accurately determine a flow rate shift.

[0018] A second invention is characterized in that, particularly in the first invention, the flow rate shift determination unit confirms the flow rate shift when the determination of the flow rate shift is established a second predetermined number of times in succession.

[0019] A third invention is characterized in that, particularly in the first invention, the flow rate shift determination unit confirms the flow rate shift when the flow rate shift determination is established a second predetermined number of times within a third predetermined period.

[0020] A fourth invention is characterized in that, in the first to third inventions, the flow rate shift determination unit and at least one flow rate shift determination unit that determines a flow rate shift using a determination method different from that of the flow rate shift determination unit are included, and the flow rate shift determination unit and the at least one flow rate shift determination unit each determine whether the flow rate has shifted to the negative side. This makes it possible to optimize the flow rate shift determination depending on the installation situation.

[0021] The fifth invention is the fourth invention, wherein the flow rate shift determination unit is provided with a determination method selection unit that switches the execution of the determinations of the multiple flow rate shift determination units under predetermined conditions or sets them to be performed in parallel.

[0022] This allows multiple flow rate shift determination units to be switched under specified conditions or set to process in parallel, making it possible to select a determination method that suits the environment and situation on the market.

[0023] Hereinafter, with reference to the drawings, an embodiment will be described in detail, taking a gas meter as an example of a gas shutoff device. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0024] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0025] (Embodiment 1) FIG. 1 shows a block diagram of a gas meter according to a first embodiment of the present invention.

[0026] 1, gas meter 1 is installed on gas supply pipe a, and one or more gas appliances installed in each user's home are connected to the downstream piping (not shown). Gas meter 1 is also composed of a shutoff unit 2, a flow rate measurement unit 3, a flow rate calculation unit 4, an integrating unit 5, a first determination unit 6, a second determination unit 7, a flow rate shift determination unit 8, a control unit 9, and an external communication unit 10.

[0027] The flow rate measuring unit 3 is installed in the gas supply pipe a, and uses ultrasonic signals to determine a propagation time difference caused by the gas flow rate in the gas supply pipe a, and detects the instantaneous gas flow rate based on the propagation time difference.

[0028] The flow rate calculation unit 4 calculates the gas flow rate based on the instantaneous flow rate detected at regular time intervals by the flow rate measurement unit 3. The flow rate measurement unit 3 and the flow rate calculation unit 4 realize the flow rate measurement function.

[0029] The integrating unit 5 integrates the flow rate values ​​calculated by the flow rate calculating unit 4 in an integration buffer (not shown) that the integrating unit 5 has, to obtain an integrated flow rate value.

[0030] The first judgment unit 6 measures the time accumulated in the accumulation buffer by the accumulation unit 5, and when the accumulated time has passed the unit accumulation period, judges whether the accumulated flow rate value accumulated by the accumulation unit 5 is less than a predetermined flow rate.

[0031] The second determination unit 7 determines whether the number of times that the integrated flow rate value is less than the predetermined flow rate, as determined by the first determination unit 6, is equal to or greater than a predetermined number.

[0032] The flow rate shift determining section 8 determines whether or not the flow rate has shifted to the negative side based on the determination result of the second determining section 7, and details will be described later.

[0033] The control unit 9 controls the operation of each unit in the gas meter 1, and also performs safety processing such as issuing a warning and cutting off gas depending on the result of the determination by the flow rate shift determination unit 8 as to whether or not a flow rate shift has occurred.

[0034] The external communication unit 10 notifies the outside of the predetermined cumulative judgment value by the first judgment unit 6, the predetermined number of times by the second judgment unit 7, and the predetermined period by the flow rate shift judgment unit 8, as well as issuing warnings or shut-off information when a negative flow rate shift is confirmed.

[0035] The cutoff unit 2 is connected to the middle of the gas supply pipe a, and based on an instruction from the control unit 9, closes the gas supply pipe a to cut off the supply of gas.

[0036] 2 is a schematic flowchart for determining whether or not a flow rate shift is to be performed by the gas meter 1 in embodiment 1. Hereinafter, the operation of determining whether or not a flow rate shift is to be performed by the gas meter 1 will be described with reference to FIGS.

[0037] 1 and 2, the measurement interval of the instantaneous flow rate by the flow rate measurement unit 3 is set to, for example, 2 seconds.

[0038] First, the flow rate measuring unit 3 measures the instantaneous flow rate of gas flowing through the gas supply pipe a (step S1).

[0039] Next, the flow rate calculation unit 4 calculates a flow rate value from the instantaneous flow rate measured by the flow rate measurement unit 3 (step S2).

[0040] Next, the accumulation unit 5 has the accumulation buffer described above for accumulating flow rate values ​​over a unit accumulation period (e.g., 60 minutes), which is a first predetermined period, and accumulates the flow rate values ​​from the flow rate calculation unit 4 in the accumulation buffer to obtain an accumulated flow rate value (step S3).

[0041] Next, the first determination unit 6 has a timer T1 (not shown) that measures a unit integration period, which is a first predetermined period, and determines whether the time measured by the timer T1 has passed the unit integration period (step S4).

[0042] If the time counted by timer T1 has not elapsed the unit integration period (step S4: No), the integration unit 5 continues integrating the integration buffer, and the process returns to flow rate measurement (step S1). On the other hand, if the time counted by timer T1 has elapsed the unit integration period (step S4: Yes), the first determination unit 6 determines whether the integrated flow rate value in the integration buffer is less than a predetermined flow rate (e.g., −3.5 L) that is a shift determination value (step S5).

[0043] If the integrated flow rate value of the integration buffer is equal to or greater than the predetermined flow rate (step S5: No), the integration unit 5 clears the integration buffer to zero and the first judgment unit 6 restarts the timer T1, and the process returns to flow rate measurement (step S1).

[0044] On the other hand, when the first determination unit 6 determines that the integrated flow rate value of the integrating buffer is less than the predetermined flow rate (step S5: Yes), the second determination unit 7 counts it as one occurrence (step S6).Then, the second determination unit 7 determines whether the count value C1 is equal to or greater than a predetermined number of times determination value (for example, 2 times) (step S7).

[0045] If the count value C1 does not reach the predetermined number of judgment value during the second predetermined period, which is the flow rate shift judgment period (for example, 30 days) (step S7: No), the accumulator 5 clears the accumulation buffer to zero and the first judgment unit 6 restarts the timer T1, and the process returns to flow rate measurement (step S1).

[0046] On the other hand, if the count value C1 reaches a predetermined number of times during the flow rate shift determination period (step S7: Yes), as described below, the flow rate shift determination unit 8 determines that there is a negative flow rate shift during that flow rate shift determination period, and sets the number of times C2 that a flow rate shift has occurred to 1.

[0047] If the second determination unit 7 determines that there is a negative flow rate shift during the flow rate shift determination period (step S7: Yes), the flow rate shift determination unit 8 clears the count value C1 to zero (step S8). Then, the flow rate shift determination unit 8 determines whether the number of determinations C2 that there is a negative flow rate shift has occurred a predetermined number of times (for example, twice) in succession (step S9).

[0048] If it is not determined that a negative flow rate shift has occurred a predetermined number of times in a row (step S9: No), the flow rate shift determination unit 8 determines that a flow rate shift has occurred within the immediately preceding determination period (not shown), the integrating unit 5 clears the integration buffer to zero, and the first determination unit 6 restarts the timer T1, and the process returns to flow rate measurement (step S1). On the other hand, if it is determined that a negative flow rate shift has occurred a predetermined number of times in a row (step S9: Yes), the flow rate shift determination unit 8 confirms a negative flow rate shift (step S10).

[0049] Here, the unit accumulation period in the accumulation unit 5, the flow rate shift judgment value in the first judgment unit 6, the predetermined number of judgment values ​​of the count value C1 in the second judgment unit 7, and the predetermined number of judgment times C2 in the flow rate shift judgment unit 8 are not limited to the exemplified values, but can be set to optimal values, and may be set externally by the external communication unit 10.

[0050] As described above, in the first embodiment, even though there is no actual flow rate, the flow rate measurement unit can measure at predetermined time intervals whether gas in the pipe moves in the forward or reverse direction from the upstream side to the downstream side due to pressure fluctuations caused by pulsation. Even if the measured instantaneous flow rate has positive or negative fluctuations or variations, the instantaneous flow rate (L / h) measured by the flow rate measurement unit 3 is converted into a flow rate value (L) by the flow rate calculation unit 4, and the flow rate value is integrated in an integration buffer by the integration unit 5, thereby making it possible to determine the actual volume of gas moving in the pipe. Based on the buffer value integrated by the integration unit 5, the first determination unit 6, the second determination unit 7, and the flow rate shift determination unit 8 determine whether the flow rate has shifted to the negative side, thereby enabling more accurate determination of a flow rate shift.

[0051] In this embodiment, a negative flow rate shift is determined when it is determined that a negative flow rate shift has occurred a predetermined number of times in succession, but this is not limiting.A negative flow rate shift may also be determined when it is determined that a negative flow rate shift has occurred multiple times (for example, twice) within multiple periods (for example, three periods) of the flow rate shift determination period.

[0052] (Embodiment 2) FIG. 3 shows a block diagram of a gas meter according to the second embodiment of the present invention.

[0053] 3, the gas meter 1 further includes a determination method selection unit 11, a first flow rate shift determination unit 12, and a second flow rate shift determination unit 13 in addition to the configuration shown in FIG.

[0054] The first flow rate shift determination unit 12 is composed of an integrating unit 5, a first determination unit 6, a second determination unit 7, and a flow rate shift determination unit 8, and performs the operations described in Figures 1 and 2 of embodiment 1.

[0055] On the other hand, the second flow rate shift determination unit 13 determines whether or not there is a flow rate shift using a method different from that of the first flow rate shift determination unit 12. Specifically, as described in Patent Document 1, for example, the second flow rate shift determination unit 13 is composed of an interval calculation means, a moving average flow rate calculation means, a corresponding flow rate determination means, a first determination means, a second determination means, and a flow rate shift determination means (none of which are shown).

[0056] Both the first flow rate shift determining unit 12 and the second flow rate shift determining unit 13 are configured to notify the control unit 9 of the determination result as to whether or not there is a flow rate shift.

[0057] The determination method selection unit 11 switches between using either the first flow rate shift determination unit 12 or the second flow rate shift determination unit 13 for processing, or sets whether to use the first flow rate shift determination unit 12 and the second flow rate shift determination unit 13 in parallel for processing, based on predetermined conditions set externally by the external communication unit 10. Note that the above-mentioned predetermined conditions are, for example, quantified for each gas meter 1 based on the likelihood of pulsation occurring in the installation environment of the gas meter 1, and defined based on a comparison between the quantized value and a threshold value.

[0058] The processing in the second flow rate shift determining unit 13 of this embodiment will be described below with reference to FIG.

[0059] In FIG. 3, the second flow rate shift determination unit 13 first accumulates the instantaneous flow rates measured by the flow rate measurement unit 3 for a first predetermined interval using an interval calculation means to calculate an interval average flow rate, and then calculates a moving average from N consecutive interval average flow rates using a moving average flow rate calculation means and holds it for a second predetermined interval.

[0060] Next, the relevant flow rate determining means determines whether the difference between the maximum and minimum values ​​of the moving average flow rate in the second predetermined section is less than a threshold value, and holds the section average flow rate determined to be less than the threshold value.

[0061] Next, a first determination means determines whether the difference between the maximum and minimum instantaneous flow rates used to calculate the section average flow rate is within a first predetermined range, and a second determination means determines whether the section average flow rate held by the corresponding flow rate determination means is within a second predetermined range.

[0062] Next, the flow rate shift determination means accumulates the section average flow rates that are determined by the first determination means to be within the first predetermined range and by the second determination means to be within the second predetermined range, and when M section average flow rates have been accumulated by the flow rate shift determination means, the flow rate shift determination means calculates an accumulated average flow rate from the accumulated section average flow rates.Then, when the number of times that the accumulated average flow rate has fallen below the average determination flow rate exceeds a predetermined number of times consecutively, the flow rate shift determination means determines that a negative flow rate shift has occurred.

[0063] 4 is a schematic flowchart of the determination of the presence or absence of a flow rate shift performed by the gas meter 1 in embodiment 2. Hereinafter, the operation of the determination of the presence or absence of a flow rate shift performed by the gas meter 1 will be described with reference to FIGS.

[0064] First, the determination method selection unit 11 determines whether or not to perform processing by the first flow rate shift determination unit 12 (step S11) based on predetermined conditions externally set by the external communication unit 10. If the processing by the first flow rate shift determination unit 12 is to be performed (step S11: Yes), the first flow rate shift determination unit 12 performs a first shift determination (step S12). On the other hand, if the processing by the first flow rate shift determination unit 12 is not to be performed (step S11: No), the process proceeds to step S15 described below.

[0065] Next, the first flow rate shift determination unit 12 determines whether or not there is a flow rate shift (step S13), and if the first flow rate shift determination unit 12 determines that there is a minus flow rate shift (step S13: Yes), the flow rate shift determination unit 8 performs processing to confirm that there is a minus flow rate shift (step S14).On the other hand, if the first flow rate shift determination unit 12 determines that there is no minus flow rate shift (step S13: No), the determination method selection unit 11 determines whether or not to perform processing by the second flow rate shift determination unit 13 (step S15).

[0066] If the processing of the second flow rate shift determination unit 13 is to be performed (step S15: Yes), the second flow rate shift determination unit 13 performs a second shift determination (step S16). On the other hand, if the processing of the second flow rate shift determination unit 13 is not to be performed (step S15: No), the processing ends.

[0067] Next, the second flow rate shift determination unit 13 determines whether or not there is a flow rate shift (step S17), and if the second flow rate shift determination unit 13 determines that there is a minus flow rate shift (step S17: Yes), it performs a process to confirm that there is a minus flow rate shift (step S18).On the other hand, if the second flow rate shift determination unit 13 determines that there is no minus flow rate shift (step S17: No), the process ends.

[0068] In the above explanation, the process of determining whether there is a flow rate shift means a process that is performed when a negative flow rate shift is determined to exist consecutively, or based on the number of negative flow rate shift determinations made within a specified period, as explained in embodiment 1.

[0069] As described above, in the second embodiment, two flow rate shift determination units are provided, namely, the first flow rate shift determination unit 12 and the second flow rate shift determination unit 13, and these two flow rate shift determination methods can be switched under predetermined conditions or processed in parallel, so that it becomes possible to determine that there is a negative flow rate shift in either one of them. This makes it possible to determine that there is a negative flow rate shift overall, and more accurately warn of and shut off the sensor abnormality.

[0070] In addition, since the judgment methods can be switched or set in parallel, it becomes possible to select a judgment method that suits the environment and situation on the market.

[0071] For example, in an environment where pulsation is likely to occur, large variations in instantaneous flow rate occur, and the difference between the maximum and minimum instantaneous flow rate is likely to fall outside the specified range in the processing of the second flow rate shift determination unit 13, which may result in the failure to determine whether or not a flow rate shift has occurred. Therefore, by setting the determination method selection unit 11 to process the first flow rate shift determination unit 12, it becomes possible to convert the variations in positive and negative instantaneous flow rate into flow rate values ​​and integrate them. This makes it possible to cancel out positive and negative fluctuations and variations, making it possible to more accurately determine whether or not a negative flow rate shift has occurred.

[0072] Furthermore, in the case of a respiratory phenomenon in which gas flows for a long period of time, it is possible to monitor a stable flow rate for a long period of time by selecting the second flow rate shift determination unit 13. This makes it possible to more accurately determine whether or not there is a negative flow rate shift.

[0073] Furthermore, when the first flow rate shift determination unit 12 and the second flow rate shift determination unit 13 are executed in parallel, even if one of them erroneously determines that there is no flow rate shift, the other determines that there is a flow rate shift, making it possible to more accurately determine whether there is a flow rate shift.

[0074] In this embodiment, two flow rate presence / absence determination units, the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11, have been described. However, it is also possible to add another flow rate presence / absence determination unit that uses a different determination method from these two, and configure the determination method selection unit 12 to select or combine these multiple flow rate presence / absence determination units. [Industrial Applicability]

[0075] As described above, the gas shutoff device of the present invention can determine a negative flow rate shift even in an environment where pulsation is occurring, and therefore the subject matter of the present invention is not limited to this, but also includes other flammable gases, non-flammable gases, etc., and can also be applied to methods for detecting water or gas leaks. [Explanation of symbols]

[0076] 1 Gas meter 2. Breaker 3 Flow measurement section 4 Flow rate calculation section 5. Integration section 6 First Judgment Department 7 Second judgment section 8 Flow rate shift determination unit 9 Control Unit 10 External Communications Department 11 Judgment method selection section 12 First flow rate shift determination unit (flow rate shift determination unit) 13 Second flow rate shift determination unit (flow rate shift determination unit)

Claims

1. a flow rate measuring unit connected to the gas supply pipe and configured to measure an instantaneous flow rate of the gas at predetermined intervals; a flow rate calculation unit that calculates a flow rate value from the instantaneous flow rate measured by the flow rate measurement unit; an integrating unit that integrates the flow rate value of the flow rate calculation unit at predetermined intervals; a first determination unit that determines whether or not an integrated flow rate value integrated by the integration unit over a first predetermined period is less than a predetermined flow rate; a second determination unit that determines whether the number of times that the first determination unit has determined that the integrated flow rate value is less than the predetermined flow rate is equal to or greater than a first predetermined number of times; a flow rate shift determination unit that determines that the flow rate within the second predetermined period has shifted to the negative side when it is determined that the number of times counted by the second determination unit within the second predetermined period is equal to or greater than a first predetermined number of times, and that the flow rate shift is confirmed when the determination of the flow rate shift is established a second predetermined number of times; A gas shutoff device comprising:

2. The gas shutoff device according to claim 1 , wherein the flow rate shift determination unit confirms the flow rate shift when the determination of the flow rate shift is established a second predetermined number of times in succession.

3. 2. The gas shutoff device according to claim 1, wherein the flow rate shift determination unit determines the flow rate shift when the determination of the flow rate shift is satisfied a second predetermined number of times within a third predetermined period.

4. The flow rate shift determination unit and at least one flow rate shift determination unit that determines a negative flow rate shift by a determination method different from that of the flow rate shift determination unit, The gas shutoff device according to any one of claims 1 to 3, characterized in that a negative flow rate shift is determined using one or more determination results determined by the flow rate shift determination unit and the at least one flow rate shift determination unit.

5. 5. The gas shutoff device according to claim 4, further comprising a determination method selection unit that switches the execution of determination by the plurality of flow rate shift determination units under a predetermined condition or sets the determinations to be performed in parallel.

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