JP4623486B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures the flow rate of a fluid by intermittently sampling the flow rate of the fluid using a method of detecting a flow velocity such as an ultrasonic flow meter or a thermal flow meter.

  Conventionally, many types of flowmeters using thermal flow sensors and ultrasonic sensors have been proposed as this type of flowmeter, and these have the characteristics of a highly sensitive flowmeter that can detect minute flows. .

  However, although a minute flow can be detected, there is a case in which the flow rate is detected in response to a local flow even though there is no fluid flow as a drawback because of high sensitivity. In particular, this phenomenon appears remarkably when a large pressure fluctuation occurs in the supply pipe. Therefore, by integrating the detected values as they are, the value of the integrated flow rate may increase even though the fluid use is stopped.

  In order to prevent this phenomenon, a method has been proposed in which the flow rate value detected by the sensor is once added to auxiliary integration means called a cancellation buffer (see, for example, Patent Document 1).

  The flow rate measuring device described in Patent Document 1 covers a wide measurement range (several [L / h] to several thousand [L / h]) like a household gas meter. The fluid oscillation phenomenon of the element is measured by a piezoelectric film sensor, and the small flow rate region where fluid oscillation hardly occurs is measured by using a thermal flow sensor.

  FIG. 6 shows the measurement processing contents of the small flow rate region of the conventional flow rate measuring device described in Patent Document 1, that is, the measurement region of the flow sensor.

  That is, the flow sensor 21, the conversion means 22, the cancellation buffer 23, the timer 24, the integration means 25, and the display means 26 are configured. The flow sensor 21 is driven every 6 seconds and outputs an electrical signal corresponding to the flow rate generated in the apparatus.

  Based on the output of the flow sensor, the conversion means 22 obtains the flow rate that has passed through the apparatus during the sensor drive interval of 6 seconds and outputs the flow rate to the cancellation buffer 23. The value added to the cancellation buffer outputs a signal every time it reaches 1 [L], and the accumulating means 25 receives the signal output and adds 1 [L] to the accumulated value. Then, the value of the integrating means 25 is displayed on the display means 26.

  In the flow rate measuring apparatus having the above configuration, for example, in the case where a large pressure fluctuation occurs under the condition where no gas is used, the output of the conversion means 22 has a large variation, and is instantaneously positive. In some cases, the value may be large, but on the contrary, a large negative value may be output.

  However, temporarily, the output may be biased to a positive value. If left as it is, there is a risk that the content of the cancellation buffer 23 reaches 1 [L] and the value of the display means 26 increases.

Therefore, the timer 24 periodically clears the accumulated value held in the cancellation buffer 23. For example, this time is determined as follows. If the judgment criterion of gas leakage is 3 [L / h], this value is considered as the detection lower limit flow rate of the apparatus. When a flow rate of 3 [L / h] is generated, the value of the cancellation buffer reaches 1 [L] in 20 minutes. Therefore, if the clear time set by the timer 24 is set to a value larger than 20 minutes, it is possible to detect 3 [L / h] and to prevent an increase in the integrated value when the gas is not used.
JP 2002-62179 A

  However, in the conventional configuration, when the predetermined time has elapsed, the contents of the cancellation buffer 23 are cleared, so that the value remaining in the cancellation buffer 23 when the use of the gas appliance is stopped is discarded. There is a problem that an integration error occurs.

  This phenomenon will be described with reference to FIG. FIG. 7 shows the movement of the instantaneous flow rate value of the gas appliance, the value of the cancellation buffer 23, and the display value of the display means 26. In FIG. 7, it is assumed that the gas appliance of 15 [L / h] has been used for 14 minutes, and in order to simplify the explanation, the value of the cancellation buffer 23 at the time T0, Both values are 0L.

  Since the value of the cancellation buffer exceeds 1 [L] at times T1, T2, and T3, 1 [L] is added to the integrating means 25 each time, and at the same time, the cancellation buffer 23 is cleared. At the same time, the timer 24 is restarted.

  Since the use of the gas appliance is stopped at time T4, the value of the buffer 23 remains almost unchanged at 0.5 [L] after T4. Next, the cancellation buffer 23 is cleared at time T5 when the clear time 20 minutes has elapsed from time T3 when the integrated flow rate value last increased. The total amount of gas used in T0 to T4 is 3.5 [L], but the value output to the integrating means 25 is actually 3 [L], and the remaining 0.5 [L] is It will be thrown away.

  Including the above case, since the flow rate retained in the offset buffer when the use of the gas appliance is stopped is an arbitrary value between 0 and 1 [L / h], an average of 0.5 [L ] Can be considered. Therefore, every time the use of the gas appliance is stopped for a time longer than the buffer clear time, the average flow rate of 0.5 [L] is discarded. Therefore, in the case where the small-sized gas appliance is used in small increments for a relatively short time, the relative error cannot be ignored.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to prevent an integrated value from increasing when a gas is not used and to reduce an integrated error when the gas is used.

  In order to solve the above-described conventional problems, the flow rate measuring device of the present invention includes an auxiliary integration unit that periodically clears the output of the passage flow rate calculation unit by the action of the clear unit when the determination unit determines that the flow rate is low. Since the output of the passage flow rate calculation means is directly output to the main integration means when the determination means determines that the flow rate is large, the flow rate detected when the fluid is not used is cleared. Thus, the flow rate detected when the fluid is used is not cleared but is added as an integrated value.

  The flow rate measuring device of the present invention can prevent the integrated value from increasing when the fluid is not used, and can also reduce the integrated error when the fluid is used.

According to a first aspect of the present invention, there is provided a measuring means for intermittently measuring a physical quantity correlated with a fluid flow rate, a computing means for calculating a fluid flow rate or a flow velocity from the output of the measuring means, and a passing flow rate from the output of the computing means. A passing flow rate calculating means for calculating, and an integrating means for calculating an integrated value by adding the outputs of the passing flow rate calculating means, and the integrating means compares the output of the calculating means with a threshold value to determine the flow rate. A determination unit that performs size determination, an auxiliary integration unit that calculates an auxiliary integrated value by adding the output of the passage flow rate calculation unit when the determination result of the determination unit is small, and a determination result of the determination unit is a flow rate In the case of large, it includes a main integration means for adding the output of the passage flow rate calculation means, and a clear means for clearing the auxiliary integration value of the auxiliary integration means every time a predetermined time elapses. Total When the output exceeds a predetermined capacity, the auxiliary integrated value is added to the main integrating means, so that the output of the measuring means detected when the fluid is not used is once added to the auxiliary integrating means, The output of the measuring means that is cleared by the clearing means and detected when using the gas is directly output to the main integrating means and integrated, so that the integrated value is prevented from increasing when the fluid is not used, and at the same time the fluid is used. The integration error at the time can also be reduced.
In addition, when the determination result of the determination means is switched from a low flow rate to a high flow rate, the auxiliary integration value integrated by the auxiliary integration unit is added to the main integration unit, so that a transient change in the flow rate can be obtained. It is possible to accumulate without missing. In addition, the clearing unit is configured to determine the elapse of a predetermined time from the time point when the determination result of the determining unit is switched from high flow rate to low flow rate, so that the flow rate is temporarily determined by the influence of disturbance. Even if it is less than, the flow rate during that time can be reliably reflected in the integrated value.

(Embodiment 1)
The one shown in FIG. 1 to FIG. 3 is assumed to be applied to a home gas meter, and a flow sensor 2 as a measuring means is disposed in the fluid flow path 1, and the flow velocity in the fluid pipe is measured. Detects and outputs an electrical signal corresponding to the flow velocity. The calculating means 3 calculates the instantaneous flow rate of the fluid from the output of the flow sensor 2, and the passing flow rate calculating means 4 calculates the passing flow rate of the fluid from the output of the calculating means 3 and outputs the result to the integrating means 5.

  Then, the display unit 6 displays the accumulated flow rate of the fluid obtained by the integrating unit 5. Further, the integrating means 5 has the following configuration.

  That is, the determination unit 7 performs a binary determination of the flow rate by comparing the output of the calculation unit 3 with the determination threshold set by the setting unit 8. The switching unit 9 receives the determination result of the determination unit 5 and switches the output destination of the flow rate obtained by the passing flow rate calculation unit 4.

  The auxiliary integrating means 10 is added with the passing flow rate obtained by the passing flow rate calculating means 4 when the determination result of the determining means 7 is small, and the clearing means 11 periodically clears the value of the auxiliary integrating means 10, 0 [L]. The main integrating means 12 is added with the passing flow rate via the two paths after the switching means 9. The main integration unit 12 integrates these values, and the display unit 6 displays the contents of the main integration unit 12 in units of 1 [L].

  The operation and action of the flow rate measuring apparatus configured as described above will be described below.

  First, an operation until the output of the flow sensor 2 is converted into a passage flow rate will be described. The flow sensor 2 is driven every predetermined time (for example, 2 seconds), and at that time, the flow velocity v generated in the fluid flow path is AD converted and output as a voltage signal E. The flow velocity v and the output of the flow sensor 2 are in a proportional relationship. If E is known, the flow velocity v can be obtained using (Equation 1).

v = K · E (Formula 1)
In (Expression 1), K is a proportionality constant. If the flow velocity distribution in the flow path is uniform, the flow rate of the fluid can be obtained by obtaining the product of the flow velocity and the cross-sectional area S. It is not uniform. Therefore, in order to convert the flow velocity v into the instantaneous flow rate Qs, it can be obtained by (Equation 2) using the correction coefficient M depending on the flow velocity v.

Qs = M · S · v = M · S · K · E (Formula 2)
It is the computing means 3 that obtains the fluid flow rate using (Equation 2). Further, the passage flow rate Qi in the apparatus for t seconds can be obtained by multiplying the flow rate obtained by (Equation 2) by the driving interval t of the flow sensor 2.

Qi = Qs · t (Formula 3)
For example, if Q is 180 [L / h], a value is substituted into (Expression 3), and it is obtained using (Expression 4).

Qi = 180 [L / h] × 2 [s] × (1 [h] / 3600 [s]) = 0.1 [L]
(Formula 4)
The passage flow rate calculation means 4 calculates the passage flow rate using (Equation 3).

  Next, the operation / action of the integrating means 5 will be described. The determination unit 7 compares the flow rate determination threshold Qth set by the setting unit 8 with the instantaneous flow rate Qs, and determines that “high flow rate” if Qs is larger, and “small flow” if Qth is larger. To do.

  “High flow rate” corresponds to a state where the gas appliance is used, and “Low flow rate” corresponds to a state where the use of the gas appliance is stopped. Therefore, the determination threshold value Qth can be rephrased as a threshold value for determining whether or not the gas appliance is used. This determination threshold value Qth is variable, and at the time of installation, the setting value of the setting means 8 can be changed using an external device such as a remote controller according to the situation of each home. For example, by setting a value smaller than the minimum flow rate of the installed gas appliance, it is possible to determine whether the gas appliance is used.

  Moreover, the system which changes a determination threshold value according to the measurement dispersion | variation at the time of gas appliance non-use may be used. For example, in an installation condition in which pressure fluctuation hardly occurs, the determination threshold value may be a value near 0 [L / h]. However, in an installation condition in which a large pressure fluctuation is predicted, the determination threshold value Is set to a value as far as possible from 0 [L / h], it is possible to prevent unnecessary integrated values when the gas is not used.

  Then, according to the determination result of the determination unit 7, the switching unit 9 switches the output path of the passage flow rate calculation unit 4. That is, if the determination result of the determination unit 5 is “low flow rate”, the output of the passage flow rate calculation unit 4 is added to the auxiliary integration unit 10, and if the determination result of the determination unit 5 is “high flow rate”, The output of the flow rate calculation means 4 is added to the main integration means 12.

  The value added to the auxiliary integrating means 10 is considered to be a value detected when the use of the gas appliance is stopped or a value detected when a gas leak is smaller than the flow rate of use of the gas appliance. If the lower limit flow rate assumed at the time of gas leak is 3 [L / h], the gas leak can be detected if the configuration is cleared every 20 minutes, as described in the background art. At the same time, an increase in integrated value when gas is not used can be prevented. Therefore, the clearing unit 11 clears the content of the auxiliary integrating unit 10 every 20 minutes to 0 [L].

  On the other hand, the value detected when the gas appliance is used is added directly to the main integrating means 12 and is therefore reflected in the display value of the display means 6 without being cleared. The operation of the integrating means 5 will be described with reference to FIG.

  FIG. 2 shows the content of the main integrating means 12, that is, the movement of the integrated flow rate when a 15 [L / h] gas appliance is used. The threshold value Qth for determining the flow rate in the determination means 7 is 12 [L / h]. In FIG. 2, since the instantaneous flow rate Qs is 0 [L / h] until immediately before time T0, it is determined that the flow rate is small, and the passing flow rate Qi is added to the auxiliary integration means 10.

  Since Qs exceeds Qthh = 10 [L / h] at time T0, Qi is added to the main integration means 12 from this point. Thereafter, the integrated value increases and reaches 3.5 [L] at time T4. Since the use of the gas appliance at time T4 is stopped, Q1 is added to the main integrating means 12 again.

  The use stop time of the gas appliance is 1 hour, and during this time, there is no output from the auxiliary integrating means 12, so the value of the main integrating means 12 is maintained at 3.5 [L]. Then, since the use of the gas appliance is resumed from time T5, the value of the main integrating means 12 begins to increase again starting from 3.5 [L].

  The total usage time of the gas appliances from time T0 to T4 and from T5 to T6 is 16 minutes, and during this time, the value of the main integrating means 12 increases by 4 [L]. Since there is a one hour rest period from T4 to T5, the auxiliary integration means is cleared a total of three times. However, since the flow rate measured during use of the gas appliance is directly added to the main integrating means 12 without passing through the auxiliary integrating means 10, even if the auxiliary integrating means 10 is cleared, Accurate integrated values can be obtained without any influence.

  By the way, the change in the flow rate is not necessarily a steep change as shown in FIG. 2, and the rising may be slow. In addition, the flow rate when the gas appliance is used is not always stable, and changes due to disturbance occur. Even if the gas flow rate falls below the threshold due to the influence of the change as described above, it is necessary to reliably reflect the integrated flow rate.

  Therefore, in consideration of such a transitional change, when the determination result of the determination unit 7 is switched from “low flow rate” to “high flow rate”, the value held in the auxiliary integration unit 10 is changed to the main integration unit. 12 is added to clear the contents of the auxiliary integration means 10.

  FIG. 3 shows the operation of the integrating means 5 when the gas appliance starts up and when a disturbance occurs. The gas flow rate, the integrated value of the main integrating means 12 (hereinafter simply referred to as the integrated value) and the integrated value of the auxiliary integrating means 10 ( Hereinafter, the sampling timing of the flow sensor 2 is shown. The flow rate when the gas is stable is 15 [L / h], and the magnitude determination threshold Qth is 12 [L / h].

  First, since the instantaneous flow rates at the time T1 and T2 at the time of rising of the instrument are less than Qth, the passing flow rate obtained at these points is added to the auxiliary integrating means 10.

  At time T3, since the flow rate Qi exceeds Qth, the auxiliary integrated value Qx [L] at this time is added to the main integrating means 12, and the auxiliary integrated value is cleared. Then, the sum of the passage flow rate obtained in T3 and Qx is added to the integrated value. Therefore, a transient value at the rise of the flow rate can be reflected in the integration.

  Next, during the period from T4 to T5, due to the influence of disturbance, the instantaneous flow rate temporarily falls below Qth, so the passing flow rate detected during this time is added to the auxiliary integration means 10. At time T6, since the flow rate again exceeds Qth, the auxiliary integrated value Qy [L] at this time is output to the main integrating means 12 and the auxiliary integrated value is cleared. Then, the passage flow rate and Qy obtained at T6 are added to the integrated value. Therefore, the passage flow rate during the time period temporarily below the threshold value Qth due to disturbance is reliably reflected in the integrated value.

  At this time, if the time T4 when the flow rate Qth falls below the flow rate Qth and is switched to “low flow rate” is set as a starting point for starting the measurement of the clear time in the auxiliary integrating means 10, the passing flow rate generated from T4 to T5 is cleared. Therefore, a more accurate integrated flow rate can be obtained.

  As described above, in the flow rate measuring device of the present invention, when the determination unit 7 determines that the flow rate is small, the passage flow rate Qi is passed through the auxiliary integration unit 10 that is periodically cleared by the action of the clear unit 11. When the addition means 7 determines that the flow rate is large, the passing flow rate Qi is directly added to the main integration means 10, so that the output of the flow sensor 2 when the gas is not used is the clear means 11. The output of the flow sensor 2 when the gas is used is directly added to the main integration means 12, so that the value of the display means 6 is prevented from increasing when the gas is not used, and at the same time, the integration error when the gas is used. Can also be reduced.

  In addition, since the determination threshold value Qth of the determination means 7 is variable by being set by the setting means 8, an appropriate threshold value can be determined according to the measurement installation status of the apparatus. The accuracy can be further improved. In particular, since the value is set in the vicinity of the assumed minimum flow rate of the gas appliance and smaller than this, the flow rate when using the gas appliance is not cleared.

  Further, when the determination result of the determination means 7 is switched from “low flow rate” to “high flow rate”, the integrated value of the auxiliary integration means 10 is added to the main integration means 12, so that a transient change in the flow rate can be achieved. It is possible to accumulate without missing.

  Further, the clearing unit 11 clears the integrated value of the auxiliary integrating unit 10 when a predetermined time has elapsed from the time when the determination result of the determining unit 7 is switched from “high flow rate” to “low flow rate”. Therefore, even if the flow rate temporarily falls below the threshold due to disturbance, the flow value during that time can be reflected in the integrated value.

  In the above configuration, the flow rate is determined using the instantaneous flow rate Qs. As is clear from (Equation 2), the instantaneous flow rate Qs is uniquely determined when the flow velocity v is determined. A configuration in which the size is determined by the flow velocity v may be used.

(Embodiment 2)
4 and 5 are time charts for explaining the operation of the integrating means 5 in Embodiment 2 of the present invention. In the second embodiment, the constituent elements of the invention are the same as those in the first embodiment, and only the flow rate determination method in the determination means 10 is different. Therefore, detailed description of the components is omitted.

  The difference from Embodiment 1 is that not only the instantaneous flow rate Qs but also the measurement result of a plurality of times is reflected in the flow size determination in consideration of the case where the variation in the measured flow rate becomes large due to the influence of pressure fluctuation or the like. This is the point to be judged. That is, the determination unit 7 performs the “low flow rate” determination when the value of the instantaneous flow rate Qs is continuously lower than the determination threshold value Qth a plurality of times (five times).

  In FIG. 4, the instantaneous flow rate Qs falls below the determination threshold value Qth at times T1, T2 to T3, but none of them reaches 5 times continuously, so it is determined that the flow rate is “high”. Therefore, since the passage flow rate detected during this time is continuously added directly to the main integrating means 12, it is not cleared by the clearing means 11, and an accurate integrated value can be obtained.

  Further, the “high flow rate” determination is performed when Qth is exceeded five times in succession, similarly to the “low flow rate” determination. That is, the determination means 7 performs the “high flow rate” determination when the value of the instantaneous flow rate Qs exceeds the determination threshold value Qth continuously for a plurality of times (five times).

  In FIG. 5, the instantaneous flow rate Qs exceeds the determination threshold value Qth at times T1 to T2, but does not reach five consecutive times, so it is determined as “low flow rate”.

  Therefore, the detected passing flow rate is integrated in the auxiliary integration means 10, and when the clear time 20 minutes elapses, the contents of the auxiliary integration means 10 are cleared, and therefore an unnecessary increase in the integrated value is caused. It is possible to prevent.

  In such a configuration, there is a delay until it is determined that the flow rate is determined to be “high flow rate” at the beginning of use of the gas appliance. Since the contents of the auxiliary integration means 10 are added to the main integration means 12 when the flow rate is switched to "high flow", the auxiliary integration value added to the auxiliary integration means 10 during the delay time is the main integration means. Since it is added to the integrated value of 12, the rising flow rate can be reliably integrated.

  As described above, in the flow rate measuring apparatus of the above embodiment, the determination unit 7 determines that “the flow rate is low” when the output Q1 of the calculation unit 7 continuously falls below the determination threshold value a plurality of times. Even when a large disturbance such as fluctuation occurs, the detected flow rate when using the gas appliance can be reliably reflected in the integrated flow rate.

  Further, since the determination means 7 determines that “the flow rate is large” when the output Qi of the calculation means 7 continuously exceeds the determination threshold value a plurality of times, this is a case where a large disturbance such as pressure fluctuation occurs. However, it is possible to prevent erroneously integrating the detected flow rate when the gas appliance is not used.

  Similarly, as another method for reducing the influence of the pressure fluctuation, a method of determining the flow rate magnitude determination based on an average value of Qi multiple times (for example, 5 times) may be used. By averaging, a value closer to the true value can be detected, so that the flow rate determination becomes more accurate, and a correct integrated value can be obtained.

  In addition, the above-described method in which threshold determination by a plurality of consecutive times and threshold determination by an average value are combined, that is, a determination threshold value is determined for a plurality of average values of the instantaneous flow rate Qi, and the result is determined a plurality of times. If it is the structure which determines the magnitude determination of a flow volume at the continuous time, the magnitude determination precision will be improved more.

  The flow rate measuring device of the present invention can prevent an increase in the value of the display means when the fluid is not used, and at the same time, can reduce the integrated error when the fluid is used. It can also be applied to uses such as meters.

Block diagram of a flow rate measuring device in Embodiment 1 of the present invention Time chart explaining the operation of the integration means Another time chart explaining the operation of the accumulating means Time chart for explaining the operation of the integrating means in Embodiment 2 of the present invention Another time chart explaining the operation of the accumulating means Block diagram of a conventional flow measurement device Time chart for explaining the operation

Explanation of symbols

2 Flow sensor 3 Computing means 4 Passing flow rate computing means 5 Accumulating means 7 Judging means 10 Auxiliary integrating means 11 Clearing means 12 Main integrating means

Claims (1)

A measuring means for intermittently measuring a physical quantity correlated with the flow rate of the fluid;
Arithmetic means for calculating a fluid flow rate or a flow velocity from the output of the measuring means;
Passing flow rate calculating means for calculating a passing flow rate from the output of the calculating means;
An integrating means for calculating an integrated value by adding the output of the passage flow rate calculating means,
The integrating means adds the output of the passing flow rate calculating means when the determination result of the determining means is a small flow rate, and a determining means for comparing the output of the calculating means with a threshold value to determine the magnitude of the flow rate. An auxiliary integrating means for calculating an auxiliary integrated value, a main integrating means for adding the output of the passing flow rate calculating means when the determination result of the determining means is large, and the auxiliary integrating means each time a predetermined time elapses. Clearing means to clear the auxiliary integrated value of
The auxiliary integration means is configured to add the auxiliary integration value to the main integration means when the auxiliary integration value exceeds a predetermined capacity,
When the determination result of the determination unit is switched from a small flow rate to a large flow rate, the auxiliary integration value integrated by the auxiliary integration unit is added to the main integration unit,
The clear means, said judging means the determination result of the flow rate measuring device for determining the elapse of a predetermined time starting from the switching time point to the flow rate small from the flow Univ.

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