JP5184764B2 - Electronic gas meter - Google Patents

Description

  The present invention relates to an electronic gas meter, and in particular, an electronic gas meter having at least a function of cutting off gas supply from the viewpoint of ensuring safety when a change in gas flow rate does not exceed a predetermined threshold value continues for a certain period of time. It relates to a gas meter.

  An electronic gas meter with a safety function that judges that an abnormality such as gas leakage has occurred and shuts off the gas flow path when the flow rate of the gas flowing through the flow path has been substantially constant for a predetermined time. Are known. More specifically, this type of electronic gas meter is provided with a correspondence table showing correspondence between gas consumption classification (flow rate) and safe continuous use time (cutoff time). The safety is ensured by setting it long in the region where the gas consumption is small and short in the region where the gas consumption is large. A change in the gas flow rate exceeds a predetermined threshold value (for example, 51.82 L / h) within the time limit for continued safe use set in accordance with the current gas flow rate (gas consumption amount). When this happens, the control unit judges that the user has consciously changed the usage conditions of the gas consuming equipment, resets the timer and restarts the safe continuous use time (blocking time) from 0, The gas supply is prevented from being cut off even though the gas consuming device is functioning normally.

  When the target gas consuming equipment is a gas stove, a gas water heater, a bathtub, etc., a large change in gas flow rate will occur during use of the equipment due to changes in combustion conditions intentionally made by the user. A gas flow rate change that exceeds a threshold value is likely to occur within a certain period of time. For this reason, the safety mechanism described above functions properly, and when the gas consuming equipment is used properly for a long time, the gas meter side will continue to operate safely even though there is no abnormality such as gas leakage. There is no inconvenience that the gas flow path is shut off when it is determined that (the shut-off time) has been exceeded.

  By the way, in recent years, a gas consuming device such as a heat source machine, a gas fan heater, or a fuel cell in a hot water circulation type floor heating system is frequently used, and this kind of gas consuming device is a proportional control type gas consuming device. For this reason, even if normal operation is continued, the speed of the gas flow rate change that occurs there is often very slow. In this case, if the conventional electronic gas meter is used as it is, it cannot recognize that the gas flow rate has changed beyond a predetermined threshold value, and the gas consuming equipment is functioning normally. When a predetermined time limit for continued safe use elapses, it may be determined that an abnormality such as a gas leak has occurred and the gas flow path is blocked.

  In order to eliminate the inconvenience, Patent Document 1 or Patent Document 2 states that the gas combustion amount continuously varies over a preset time on the gas consuming device side disposed downstream of the electronic gas meter. A technique is disclosed that includes gas combustion amount forced change means for forcibly changing the gas combustion amount in the gas combustion section when it is detected that the change has not been exceeded. By providing the gas consuming device with this means, the control unit of the electronic gas meter allows the gas flow rate to exceed a predetermined threshold value within a predetermined time limit corresponding to the current gas flow rate (gas consumption amount). Recognizing that a change has occurred, it is possible to prevent the gas supply from being cut off even though the gas consuming device is functioning normally.

  On the other hand, in the electronic gas meter, for the purpose of detecting the total flow rate excess and the individual maximum flow rate excess, a technique for determining whether there is an instantaneous gas flow rate change flowing in the meter is disclosed in Patent Document 3 or Patent Document 4 or the like. It is described in. There, the flow rate measured by the flow rate measurement unit is stored at regular time intervals, and the latest n (n is an integer) number average is calculated therefrom, and the latest n times average flow rate and the immediately preceding ( n-1 times), or the difference between the latest n times average flow rate and the n times average flow rate before n times is compared with a predetermined threshold, and based on the comparison result, Whether or not there is a change in flow rate is determined.

Japanese Patent No. 3532757 JP 2004-258767 A JP-A-8-327415 JP 2005-241405 A

  By adopting the technology described in Patent Document 1 or Patent Document 2, in a gas consuming device such as a gas fan heater or a fuel cell where the rate of change of the gas consumption flow rate is slow, the device functions normally. Nevertheless, it is possible to reliably prevent the gas supply from being interrupted on the way. However, all of the techniques described in Patent Document 1 and Patent Document 2 are provided with a means for forcibly changing the amount of gas combustion on the gas consuming device side, and an equipment load that is not originally required on the gas consuming device side. Can be said to impose.

  The present invention has been made in view of the above circumstances, and does not impose a special equipment burden on the gas consuming equipment side, and the gas supply shut-off despite the above-described gas consuming equipment functioning normally. An object of the present invention is to provide an electronic gas meter capable of avoiding occurrence of the above.

  An electronic gas meter according to the present invention includes a flow rate calculation unit that calculates a flow rate of gas at measurement points at regular time intervals, a flow rate storage unit that stores a flow rate measured by the flow rate calculation unit for a plurality of measurement points, A comparison unit that takes a difference between a flow rate at a measurement point of the current point and a flow rate at a reference measurement point that is a measurement point that has been traced a certain time before the previous measurement point, and compares the difference value with a predetermined threshold value; And a flow rate change determination unit that determines the presence or absence of a change in the flow rate of the gas based on a comparison result by the comparison unit.

  In the electronic gas meter according to the present invention, the flow rate at the latest measurement point is not compared with the immediately preceding measurement point, but the measurement point that is traced back for a certain time before the immediately preceding measurement point is used as the reference measurement point, and the flow rate is And the difference between the flow rate at the latest measurement point and the difference value is compared with a predetermined threshold value. For this reason, the gas consumption flow rate per unit time during normal operation is slow due to the operating characteristics of the gas consuming equipment, and the flow rate change between adjacent measurement points, that is, the flow rate at the latest measurement point. Even if a flow rate change exceeding a predetermined threshold value (for example, 51.82 L / h) does not occur between the flow rate at the previous measurement point, the flow rate change determination unit is within the predetermined measurement measurement time. It is possible to reliably detect that a change in the flow rate that exceeds the threshold value has occurred in the latest measurement point and within a time that has been traced back by a certain time before that, and determine that there is a change in the flow rate.

  When the flow rate change determination unit determines that there is a flow rate change, for example, by taking measures such as not shutting off the gas supply even after the initially set safe continuous use time has elapsed, It is possible to avoid such a disadvantage that the gas supply is shut off despite functioning.

  Basically, how much time the reference measurement point is set to be a point that is back from the latest measurement point depends on the gas consumption characteristics of the gas consuming device arranged downstream of the electronic gas meter. Preferably, a time for causing a flow rate change equal to or greater than the predetermined threshold value in an operating state where the flow rate change amount per unit time of the gas consuming device arranged at the downstream of the electronic gas meter is the smallest is the reference measurement point. Set as a reference. When arranging multiple gas consuming devices downstream of an electronic gas meter, select the device that changes the gas flow rate most slowly among the flow control methods of the multiple gas consuming devices, and select the most It is set with reference to a time for causing a flow rate change equal to or greater than the predetermined threshold value in an operating state where the flow rate change amount per unit time is small. In any case, the time for causing the flow rate change equal to or greater than the predetermined threshold value may be calculated from the design value of the gas consuming device or may be actually measured and measured.

  In a preferred aspect of the electronic gas meter according to the present invention, the electronic gas meter further includes a continuous use time setting unit that sets a safe continuous use time corresponding to the gas flow rate, and the continuous use time setting unit includes the flow rate change determination unit. When it is determined that there is a change in flow rate, the safe continuous use time corresponding to the gas flow rate at the latest measurement point is reset and the timer is reset.

  In the above electronic gas meter, when the control unit determines that there is a flow rate change, the safe continuous use time is reset according to the flow rate at the measurement point at that time, and a new time measurement starts from the point of determination. Therefore, the safe continuous use time according to the actual driving | running state of the said gas consumption apparatus can be ensured reliably.

  A flow rate difference exceeding a predetermined threshold value does not occur on the downstream side of the electronic gas meter between the latest measurement point and the measurement point that is a predetermined time before the previous measurement point. When a gas consuming device with a very slow flow rate change per unit time is connected, the flow rate change determination unit shall repeatedly determine that there is no flow rate change for the set safe continuous use time. Even though the gas consuming device is functioning normally, a gas shut-off can occur at the end of the safe continuous use time.

  In another aspect of the electronic gas meter according to the present invention to cope with this, the comparison unit selects the start point of the set safe continuous use time as the reference measurement point, and the end point or the previous measurement point is the latest measurement point. It is set to be selected as a point.

  In the above-mentioned electronic gas meter, the flow rate difference value at a long time interval between the start and end of the set continuous use time can be compared with the threshold value. It is possible to more reliably avoid the occurrence of blocking.

  In a preferred aspect of the electronic gas meter according to the present invention, the gas flow rate calculation unit includes an n-time average flow rate calculation unit that calculates n (n is an integer) times average at the time of n consecutive measurements, and at each measurement point. Is the n-time average flow rate calculated by the n-time average flow rate calculation unit. Of course, the intended purpose can be achieved even if the gas flow rate measured at the measurement point is an instantaneous flow rate, but the average flow rate n times as described in Patent Document 3 or Patent Document 4 described above is obtained at each measurement point. By adopting it as a flow rate, it is possible to eliminate the influence of a temporary sudden flow rate change. Note that the integrated flow rate can be used n times instead of the average flow rate n times.

  By using the electronic gas meter according to the present invention, the gas supply is interrupted even though the gas consuming device is functioning normally without giving a special equipment burden to the gas consuming device. Can surely be avoided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an electronic gas meter according to the present invention, FIG. 2 is a block diagram showing a control unit thereof, and FIG. 3 is a gas flow rate (gas consumption) when a certain gas consuming device is functioning normally. L / h) a graph showing the relationship between change and time (seconds), FIG. 4 is a flowchart for explaining the first embodiment of the processing procedure of the electronic gas meter according to the present invention, and FIGS. It is a flowchart for demonstrating the 2nd aspect of the process sequence of the electronic gas meter by.

  As shown in the block diagram of FIG. 1, the electronic gas meter 10 includes a flow rate sensor 11 used for measuring the flow rate of the gas G flowing in the pipe H inside the metal housing 1, and the gas G A pressure sensor 12 for detecting the pressure of the battery, a clock 13 used for measuring time, a memory 14 for storing various information, a lithium battery 15 for supplying power to the entire meter, and a control for controlling the entire meter. And a shutoff valve 17 for switching the supply state of the gas G to the downstream side of the gas meter 10. A display panel 18 for displaying various information is attached to the casing 1 of the gas meter 10.

  The flow rate sensor 11 is an ultrasonic flow rate sensor (refer to Japanese Patent Application Laid-Open No. 2004-212288, for example) that measures the flow rate of the gas G using, for example, a conventionally known ultrasonic wave. Is output as a measurement signal S1. The pressure sensor 12 is, for example, a piezoelectric film sensor that generates a voltage corresponding to a strain generated according to a conventionally known pressure. The pressure sensor 12 detects the pressure of the gas G flowing through the pipe H and applies pressure to the control unit 16. Output a signal. The clock 13 includes a crystal oscillator, and outputs a clock signal S2 to the control unit 16 using the operation characteristics of the crystal oscillator.

  The memory (storage unit) 14 stores various data required by the control unit 16, and is configured by a RAM, for example. Specifically, the instantaneous flow rate QM of the gas G calculated by the control unit 16, the n-time average flow rate QI at a plurality of measurement points at regular time intervals, and the n-time integrated flow rate QP when necessary are stored. Further, a correspondence table Ta of threshold value Rz, gas flow rate classification (flow rate) U, and safe continuous use time (cutoff time) T, which is a basic value for determining that there is a flow rate change, is also stored.

  The control unit 16 is configured by, for example, a CPU, and has functions corresponding to the “flow rate calculation unit”, “comparison unit”, “flow rate change determination unit”, “continuous use time setting unit”, and the like in the present invention. Run. Each will be described below with reference to FIG.

(1) Flow rate calculation function (flow rate calculation unit 21)
The flow rate calculation unit 21 measures the time based on the clock signal S2 output from the clock 13, and the flow rate V of the gas G at every predetermined measurement time interval s based on the measurement signal S1 output from the flow rate sensor 11. And the instantaneous flow rate QM of the gas G is calculated by multiplying the flow velocity V of the gas G by the cross-sectional area A of the pipe H. In addition, the n-time average flow rate calculation unit 22 calculates the n-time average flow rate QIi at each measurement point Pi and the n-time integrated flow rate QP, if necessary, from the continuous n times of the instantaneous flow rate QM. The calculation result is sent to the memory 14.

(2) Comparison function (comparison unit 23)
The n-time average flow rate QIp at the latest measurement point Pp stored in the memory 14 and the n-time average flow rate QIs at the measurement point (reference measurement point) Ps that goes back by a predetermined time M (M> s × n) Is calculated from the memory 14 and the absolute value of the obtained difference value Rp is compared with a predetermined threshold value Rz (for example, 51.82 L / h). The comparison result is sent to the flow rate change determination unit 24. In addition, in order to calculate the difference value Rp, the n times integrated flow rate QP may be adopted instead of the n times average flow rate QI. In that case, the value of the threshold value Rz corresponding to that is stored in the memory 14.

(3) Flow rate change determination function (flow rate change determination unit 24)
This is a function for determining the presence or absence of a change in the gas flow rate based on the comparison result by the comparison unit 23. If the absolute value of the obtained difference value Rp is greater than or equal to a predetermined threshold value Rz, there is a flow rate change. If it is smaller than the predetermined threshold value Rz, it is determined that there is no change in the flow rate. The determination result is sent to the continuous use time setting unit 25.

(4) Continuous use time setting function (continuous use time setting unit 25)
The safe continuous use time T corresponding to the current gas flow rate Up is fetched from the correspondence table Ta between the gas flow rate classification (flow rate) U and the safe continuous use time (cutoff time) T stored in the memory 14, and the safe continuous use time T And a shutoff signal S3 is output to the shutoff valve 17 when the safe continuous use time T elapses. When the flow rate change determination unit 24 determines that there is a flow rate change, the safe continuous use time Tp corresponding to the n-time average flow rate QIp at the measurement point Pp at the time of determination is read from the correspondence table Ta, and is used as a new continuous use time Tp. Reset it. At the same time, the timer is reset to 0, and a cutoff signal S3 is output to the cutoff valve 17 when a new continuous use time Tp has elapsed.

  Next, the first aspect of the processing procedure of the electronic gas meter according to the present invention will be described more specifically with reference to FIGS. In this aspect, the “continuous use time setting function” described above is not used. The graph of FIG. 3 shows the relationship between the change in gas flow rate (gas consumption) (L / h) and time (seconds) when a certain gas consuming device is functioning normally. In the example, it is assumed that the aforementioned threshold value Rz is 51.82 L / h.

  In S101, the flow rate calculation unit 21 calculates the instantaneous flow rate QM at every measurement time (in this example, every 5 seconds) at a constant interval s, and the storage unit 14 stores the same sequentially (S102). The flow rate calculation unit 21 reads the latest n (for example, 5) instantaneous flow rates QM from the storage unit 14, and calculates the n times average flow rate QI as the flow rate at the measurement point P (S103). The flow rate calculation unit 21 calculates the average flow rate QI n times continuously at a constant time interval S (s × n = 5 seconds × 5 times = 25 seconds), and a plurality of measurement points Pi (i = 1 to k). The storage unit 14 sequentially stores (S104).

  The comparison unit 23 compares the flow rate QIp at the latest measurement point Pp with the flow rate QIs at the reference measurement point Ps, which is a measurement point that is traced by a predetermined time M before the measurement point immediately before the latest measurement point Pp. Then, the difference value Rp is calculated (S105). Further, the absolute value of the difference value Rp is compared with the threshold value Rz (S106). The comparison result is sent to the flow rate change determination unit 24.

  When the comparison result is Rp <Rz, the flow rate change determination unit 24 determines that there is no flow rate change (S107), and the flow rate calculation unit 21 continues to calculate the average flow rate QI n times during the measurement time ( S108). When the comparison result is Rp ≧ Rz, the flow rate change determination unit 24 determines that there is a change in flow rate (S109).

  A specific example will be described with reference to FIG. 3. For example, when the predetermined time M is set so that the reference measurement point Ps is any one of Pp-6 to Pp-2, the value of QIs-QIp is set. Is smaller than the threshold value Rz (51.82 L / h), and it is determined that there is no change in the flow rate. When the predetermined time M is set so that the reference measurement point Ps becomes Pp-7, the value of Qs-QIp is equal to or exceeds the threshold value Rz (51.82 L / h) for the first time, It is determined that there is a change in flow rate. Therefore, by using the electronic gas meter 10 according to the present invention, even if the change in the gas consumption flow rate per unit time during normal operation is very gradual due to the operation characteristics of the gas consuming equipment connected to the downstream side. It is possible to reliably detect that the change in the flow rate exceeds a predetermined threshold value.

  As described above, in the actual machine, the fixed time M has a flow rate change greater than or equal to the predetermined threshold value Rz in an operating state in which the flow rate change amount per unit time of the gas consuming device arranged downstream of the electronic gas meter is the smallest. Set the generation time as a reference. The setting may be calculated from a design value of the gas consuming device or may be actually operated to obtain an optimum value.

  5 and 6 illustrate a second embodiment of the processing procedure of the electronic gas meter according to the present invention. In this aspect, the “continuous use time setting function” described above is used. In FIG. 5, S101 to S104 are the same as those shown in FIG.

  In S200, the continuous use time setting unit 25 changes the flow rate QIs at the reference measurement point Ps from the correspondence table Ta of the gas flow rate classification (flow rate) U and the safe continuous use time (cutoff time) T stored in the storage unit 14. The corresponding safe continuous use time (blocking time) T is read and set as the reference safe continuous use time Ts, and the timer is reset to zero.

  Next, in the same manner as the processing procedure shown in FIG. 4, the comparison unit 23 goes back by a certain time M before the flow rate QIp at the latest measurement point Pp and the measurement point immediately before the latest measurement point Pp. A difference value Rp is calculated by comparing the flow rate QIs at the reference measurement point Ps, which is a measurement point (S201). Further, the absolute value of the difference value Rp is compared with the threshold value Rz (S202). The comparison result is sent to the flow rate change determination unit 24.

  When Rp <Rz, the flow rate change determination unit 24 determines that there is no flow rate change (S203), and the flow rate calculation unit 21 calculates the average flow rate QI n times until the set safe continuous use time Ts elapses. (S204). After the time Ts elapses, the continuous use time setting unit 25 outputs a cutoff signal S3 to the cutoff valve 17 (S205).

  When Rp ≧ z, the flow rate change determination unit 24 determines that there is a change in flow rate (S210), and outputs it to the continuous use time setting unit 25. The continuous use time setting unit 25 reads the safe continuous use time Tp corresponding to the latest measurement point Pp when it is determined that there is a change in the flow rate from the correspondence table Ta stored in the storage unit 14 and the previous safe continuous use time. At the same time as rewriting Ta to Tp, the timer is reset to 0 (S211). Thereafter, the calculation of the instantaneous flow rate is continued until a new safe continuous use time Tp set by the continuous use time setting unit 25 elapses (S212). After the elapse of time, the continuous use time setting unit 25 outputs a cutoff signal S3 to the cutoff valve 17 (S213).

  In this processing procedure, when the control unit 16 (continuous use time setting unit 25) determines that there is a change in flow rate, the safe continuous use time (blocking time) corresponding to the flow rate at the measurement point at that time is reset, And since new time measurement starts from the time of a judgment, the safe continuation use time (cutoff time) according to the actual operating condition of the said gas consumption apparatus can be ensured reliably.

  In the processing procedure described above, the value of “a fixed time M that goes back before the measurement point immediately before the latest measurement point Pp” for setting the reference measurement point Ps is set as the time of the set safety continuous use time T. You may make it substantially correspond with length. Specifically, the comparison unit 23 is set so as to select the start point of the currently set safe continuous use time T as the reference measurement point Ps and the end point or the immediately preceding measurement point Pp as the latest measurement point. To. By setting in this way, even when a gas consuming device with a very slow flow rate change is connected, the flow rate change exceeding the threshold at the end point of the set safe continuous use time T It is possible to reliably detect the occurrence of gas shut-off, and it is possible to reliably avoid the occurrence of gas shutoff at the end of the safe continuous use time even though the gas consuming device is functioning normally.

The block diagram which shows an electronic gas meter. The block diagram which shows a control part. The graph which shows the relationship between gas flow rate (gas consumption) (L / h) change and time (second) when a certain gas consumption apparatus is functioning normally. The flowchart for demonstrating the 1st aspect of the process sequence of an electronic gas meter. The flowchart for demonstrating the 2nd aspect of the process sequence of an electronic gas meter. The flowchart following FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electronic gas meter, 11 ... Flow rate sensor, 12 ... Pressure sensor, 13 ... Clock, 14 ... Memory | storage part (memory), 16 ... Control part, 17 ... Shut-off valve, 21 ... Flow rate calculating part, 22 ... n times average flow rate Calculation unit, 23: comparison unit, s: instantaneous flow rate measurement time interval, n: instantaneous flow rate measurement count, M: predetermined time, Ps: reference measurement point, Pp: latest measurement point, QM: instantaneous flow rate, QI ... n times average flow rate, QR ... n times integrated flow rate, Rz ... threshold value that is determined to be flow rate change, Rp ... difference value, Ta ... gas flow rate classification and safe continuous use time (interruption time) table

Claims (3)

A flow rate calculation unit that calculates the flow rate of gas at measurement points at regular time intervals, a flow rate storage unit that stores a flow rate measured by the flow rate calculation unit for a plurality of measurement points, a flow rate at the latest measurement point, and its flow rate A comparison unit that takes a difference from a flow rate at a reference measurement point, which is a measurement point that is traced a certain time before the previous measurement point, and compares the difference value with a predetermined threshold value, and a comparison result by the comparison unit A flow rate change determination unit for determining the presence or absence of a change in the flow rate of the gas based on the electronic gas meter,
The reference measurement point is set on the basis of a time for causing a flow rate change equal to or greater than the predetermined threshold in an operation state in which the flow rate change amount per unit time of a gas consuming device attached downstream of the electronic gas meter is the smallest. In addition,
A continuous use time setting unit for setting a safe continuous use time corresponding to the gas flow rate, and the continuous use time setting unit at the latest measurement point when the flow rate change determination unit determines that there is a flow rate change. An electronic gas meter characterized by resetting a continuous safe use time corresponding to a gas flow rate and resetting a timer . 2. The electronic gas meter according to claim 1 , wherein the comparison unit is set to select a start point of a set safe continuous use time as a reference measurement point and an end point or a measurement point immediately before as a latest measurement point. An electronic gas meter characterized by being made. The gas flow rate calculation unit includes an n-time average flow rate calculation unit that calculates an average of n (n is an integer) times during n consecutive measurements, and the flow rate at each measurement point is an n-time average flow rate. The electronic gas meter according to claim 1 or 2 .

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