JP2005037251A - Apparatus for measuring fluid flow - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently detect very small leakages in a short time, without increasing the electric power consumption. <P>SOLUTION: A switchover determination means 15 switches the operation of a flow velocity detecting means 9 between two different procedures, a flow measurement procedure having a long action time for measuring the quantity of flow of a fluid and a leakage verification procedure, having a long-acting time for determining a very small leakage, by changing an acting time set at a repeating means 7, the number of times of sing arounds. Since a leakage deciding means 17 discriminates between a leakage and a zero point, on the basis of a flow value determined in the leakage verification procedure and is constituted in such a way that leakage decision is not to restart, when at least a prescribed period of time has not elapsed, efficient decision on leakage can be made in a short time, without causing electric power consumption to be increased excessively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fluid flow measurement apparatus that intermittently samples and measures a fluid flow state using a detection method such as an ultrasonic meter or a hot-wire meter.

  Conventionally, various types of measuring devices have been proposed. Among them, a so-called reciprocal difference method is widely known as a measuring principle of an ultrasonic flow rate measuring device. The flow rate measuring device based on the reciprocal difference method has a configuration as shown in FIG. 7, for example.

  In FIG. 7, a first vibrator 31 and a second vibrator 32 that receive and transmit ultrasonic waves are arranged in the flow direction of the flow path 33 in the middle of the fluid flow path 1. Controls transmission / reception of the second vibrators 31 and 32.

  When the ultrasonic wave propagates in the flow, it is influenced by the flow of the fluid, the forward direction of the flow, that is, the propagation time when transmitted from the first vibrator 31 to the second vibrator 32, and the flow The propagation time in the reverse direction, that is, when transmitting from the second vibrator 32 to the first vibrator 31, becomes a different value, and the difference increases as the flow rate increases.

  It is possible to measure the flow rate of the fluid using this property, the ultrasonic wave propagation time is measured by the flow velocity detection means 35, and the flow rate calculation means 36 calculates the flow rate using this value.

Next, the measurement principle will be described. When the velocity of sound in the static fluid is c and the velocity of the fluid flow is v, the propagation velocity of the ultrasonic wave in the forward direction is (c + v) and the propagation velocity in the reverse direction is (cv). The distance between the transducers 2 and 3 is L, the angle between the ultrasonic wave propagation axis and the central axis of the flow path is θ, the propagation time of the ultrasonic wave transmitted in the forward direction of the flow is t _f , and the reverse of the flow When the time for propagation of the ultrasonic wave transmitted in the direction and t _r,
t _f = L / (c + v cos θ) (Formula 1)
_{t r = L / (c-} vcosθ) ( Equation 2)
It becomes.

  Although it is possible to determine the flow velocity v directly from one of the above (Equation 1) or (Equation 2), the sound velocity c needs to be known.

In general, the speed of sound c depends on the fluid temperature, so the fluid temperature needs to be known. However, by assuming that the fluid temperatures at the time when the forward direction and the reverse direction are measured are equal, the flow velocity v can be obtained from (Equation 1) and (Equation 2) even if the sound velocity c is unknown. Is possible. That is, when (Formula 1) and (Formula 2) are transformed and solved for v,
_{v = (L / 2cosθ) ·} (1 / t f -1 / t r) ( Equation 3)
If L and θ are known, t _f and _tr are measured to determine the flow velocity v. Here, if the channel cross-sectional area is S and the correction coefficient is K, the flow rate Q is Q = K · S · v (Equation 4)
It becomes.

  As is clear from the above (Formula 3) and (Formula 4), the flow rate Q is obtained by obtaining the propagation time.

Here, when attempting to detect up to minute flow rates, it is necessary to increase the detection accuracy of the t _f, t _r, it is difficult to improve the accuracy when measured as a single phenomenon repeated a plurality of times and receives A method of ensuring accuracy by measuring and averaging the total time is generally adopted in ultrasonic measurement and is called a single-around method.

In the sing-around method, if the set number of repetitions is M and the total value of the propagation times in the forward and reverse directions of the flow is T _f and T _r , the propagation times t _f and _tr are T _f and T _r. Can be obtained by averaging the number of times. Therefore, the flow velocity v can be obtained from the equation (Equation 5) by modifying (Equation 3).

v = M (L / 2 cos θ) · (1 / T _f −1 / T _r ) (Formula 5)
In this type of flow rate measuring device, it is required to accurately determine the total amount of gas used, but it is also required to have high performance in the security function for monitoring the usage status of gas appliances.

  A meter with a security function is generally called a microcomputer meter, which estimates the use state of a gas appliance from the transition of the amount of gas used, and shuts off the gas supply when an abnormal use state is detected.

  For example, the microcomputer meter needs to obtain an accurate instantaneous flow rate in a very wide use range as long as 10,000 times. When an ultrasonic flow meter is applied to a microcomputer meter, if the number of times of sing-around is increased by adjusting the measurement accuracy to the minimum flow rate, the power consumption of the entire apparatus is increased.

  As a technique for solving this, a method of changing the number of times of single-around and the measurement cycle according to the measured flow rate has been proposed (see, for example, Patent Document 1).

In other words, at a small flow rate that is less likely to be an error as the total amount used, the resolution is improved by increasing the number of times of single-around, but the measurement cycle is lengthened so as not to increase the total power consumption. .
Republished Patent No. 96/12933

  As a function to be realized by the microcomputer meter, there is a function of detecting a minute leak generated due to a crack or the like generated in the pipe.

  When the measurement resolution is increased in consideration of this minute leak, natural convection in the pipe is also detected in the pipe, and even though the use of gas appliances is actually stopped, The flow rate value may be detected as if the gas is flowing temporarily.

  In order to prevent this, the measurement values obtained by the flow velocity detection means 9 can be averaged relatively easily.

  However, in recent years, air conditioners (floor heating, gas air conditioners) using gas heat sources have become widespread, but these appliances operate intermittently throughout the day, and in a short period of time when they are not in use. It is necessary to make a correct leak judgment.

  In order to obtain a sufficient averaging effect in this short time, the intermittent drive cycle cannot be set as long as expected, and as a result, it is difficult to reduce current consumption when measuring a small flow rate. there were.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to enable detection of minute leaks efficiently in a short time without causing an increase in power consumption.

  In order to solve the above-described conventional problems, a fluid flow measuring device according to the present invention includes a measurement procedure with a short operation time for measuring a fluid flow, and a leak with a long operation time for determining a minute leak in a fluid supply path. The leak determination means determines whether or not there is a leak based on a value obtained by driving the leak check procedure. The leak determination means is configured not to restart unless at least a predetermined time has elapsed.

  Therefore, since the frequency of leak determination with high power consumption can be reduced, it is possible to detect minute leaks without causing an increase in power consumption.

  According to the flow measuring apparatus of the present invention, since the operation frequency of leakage determination with high power consumption is reduced, leakage determination can be performed efficiently and in a short time without excessively increasing power consumption. .

  An embodiment of the present invention includes a measuring unit that measures a flow rate and / or a flow rate of a fluid by intermittently executing a predetermined series of measuring procedures, and a control unit that controls the operation of the measuring unit, The measurement means includes two different measurement procedures, a flow measurement procedure with a short operation time and a leak check procedure with a long operation time for determining a minute leak in the fluid supply path, and the control means has the flow A switching determination means for switching between a measurement procedure and a leakage confirmation procedure, and a leakage determination means for determining the presence or absence of leakage by comparing the value obtained by driving the leakage confirmation procedure with a threshold, the leakage determination means, At least a predetermined time has not passed before the system is restarted.

  Therefore, since the operation frequency of leakage determination with large power consumption is reduced, leakage determination can be performed efficiently and in a short time without excessively increasing power consumption.

  If the leakage determination means is configured to execute leakage determination by continuously driving the leakage confirmation procedure a plurality of times and comparing the output average value and the threshold value, it is less susceptible to disturbance, The reliability of leak determination can be improved.

  If the leakage determination means is configured to operate only when the flow rate value obtained by the flow measurement procedure and the variation in the flow rate value are small, the leakage determination can be performed by looking for an appropriate timing with a small flow disturbance, and the probability of erroneous determination. Can be reduced.

  If the leakage determination means is configured to set the operation time of the leakage determination procedure to be shorter as the variation in the flow value obtained by the flow measurement procedure becomes smaller, an appropriate measurement condition can be set according to the flow value. it can.

  If the leak determination means is configured to set the number of times the leak determination procedure is driven to be smaller as the variation in the flow value obtained by the flow measurement procedure becomes smaller, it is possible to set an appropriate measurement condition according to the flow value. it can.

  If the leakage determination means is configured not to operate when the number of detections of “no leakage” reaches a predetermined number, it is possible to reduce wasteful power consumption after safety is confirmed.

  If the leak determination means is configured to initialize the number of detections of “no leak” every time a predetermined period elapses and restart the operation, periodic leak check can be performed while reducing power consumption. It becomes possible.

  Embodiments of the present invention will be described below with reference to FIGS.

(Example 1)
In FIG. 1, a first vibrator 2 and a second vibrator 3 that transmit and receive ultrasonic waves are arranged in the flow direction in the middle of a fluid flow path 1. Reference numeral 4 denotes transmission means, reference numeral 5 denotes reception means for performing signal processing on the ultrasonic waves received in step 6, and reference numeral 6 denotes switching means for switching transmission / reception between the first vibrator 2 and the second vibrator 3.

  7 is a repeating unit that repeats transmission from one transducer and reception by the other transducer a plurality of times after the ultrasonic wave is detected by the receiving circuit 5, and 8 is a plurality of ultrasonic propagations performed by the repeating unit 7. It is a time measuring means for measuring the required time.

  Reference numeral 9 denotes flow velocity detection means using a power source 10 such as a battery or a commercial power source as a power source. The first vibrator 2, the second vibrator 3, the transmission means 4, the reception means 5, the switching means 6, and the repetition means 7 described above. The time measuring means 8 is constituted by each element.

  Reference numeral 11 denotes a control means, a flow rate calculation means 12 for calculating a flow rate based on the propagation time of the ultrasonic wave obtained by the time measuring means 8 and a flow rate based on the flow velocity, and an average value of the flow rate calculated by the flow rate calculation means 12. The average value calculating means 13 to be obtained, the variation calculating means 14 for calculating the variation in flow rate obtained by the flow rate calculating means 12, the series of measurements performed by the flow velocity detecting means 9 from the outputs of the average value calculating means 13 and the variation calculating means 14 Determination of switching of operating time of the procedure, that is, switching determination means 15 for setting the number of times of sing around, measurement period setting means 16 for setting the intermittent period and operating the power supply 10 according to the set period, average value It is constituted by a leakage determination means 17 for determining the presence or absence of leakage from the output of the calculation means 13.

  Next, a measurement procedure in the flow velocity detection means 9 will be described. In the control means 11, when the switch circuit of the power supply 10 is closed and the supply of power to the flow velocity detection means 9 is started, a trigger signal for starting measurement is output to the repetition means 7.

  In response to the trigger signal, the switching unit 6 connects the first transducer 2 to the transmission unit 4 and the second transducer 3 to the reception unit 5 to measure the propagation time during which ultrasonic waves are transmitted in the forward direction of the flow. It constitutes a circuit.

  Then, at the same time as the transmission signal is output from the transmission means 4, the time measurement means 8 starts measuring the time required for transmission / reception.

When the reception unit 5 completes the first reception, a transmission signal is output from the transmission unit 4 again. Similarly, the forward / reverse flow of the flow is performed for a predetermined number of times of singing, and when the predetermined number of times is finished, the time measuring means 8 stops measuring the propagation time, and the measurement result Tf is used as the flow rate calculating means. 12 is output.
Subsequently, the switching unit 6 connects a first transducer 2 to the receiving unit 5 and a second transducer 3 to the transmitting unit 4, and measures a propagation time for transmitting an ultrasonic wave in the reverse direction of the flow. Constitute.

  Then, at the same time as the transmission signal is output from the transmission means 4, the time measurement means 8 starts measuring the time required for transmission / reception.

  When the reception unit 5 completes one reception, a transmission signal is output from the transmission unit 4 again. In the same manner, transmission / reception in the reverse direction of the flow is performed for a predetermined number of times of sing-around, and when the predetermined number of times ends, the time measuring means 8 stops measuring the propagation time, and the measurement result Tr is sent to the flow rate calculating means 12. Output.

  As described above, a series of measurement procedures is completed with a sing-around number of times determined in the order of flow and reverse, and the control means 11 opens the circuit of the power supply 10 and stops supplying power to the flow velocity detection means 9. .

  If the number of repetitions determined in the measurement procedure is M, the flow rate can be obtained based on (Expression 4) and (Expression 5).

  As described above, a series of measurement procedures is executed each time the measurement cycle determined by the measurement cycle setting unit 16 elapses.

  The relationship between the measurement variation obtained by the flow rate calculation means 12 and the number of sing-arounds will be described with reference to FIGS.

  Even if it is assumed that a constant flow rate (including zero) is generated in the pipe, slight measurement variations occur due to disturbance and detection accuracy. Therefore, in order to obtain the true value, it is necessary to obtain the flow value by averaging.

  One method for increasing the averaging effect is to increase the number of times of single-around.

  That is, by increasing the number of times of sing-around, the operation time per measurement becomes longer, and as a result, it is possible to suppress the variation in the flow rate value.

  FIG. 2 shows the standard deviation of the flow rate value when the number of times of sing-around is changed under the same conditions.

  As shown in FIG. 2, it has been experimentally confirmed that the standard deviation σ decreases in inverse proportion to the square root of the number of times of sing-around M. This can be expressed as (Expression 6).

(K is a proportional constant)
In FIG. 3, distribution A is a density distribution of the occurrence probability of the flow rate when the use of the gas appliance is stopped, that is, the flow rate is zero (hereinafter referred to as zero point) and the number of times of sing around is M. The distribution B is a density distribution of the flow rate generation probability under the condition that the minute flow rate value Qs [L / h] is generated.

  Here, it is assumed that the standard deviation σ of the measured values of the flow rate = 0 and the flow rate = Qs is equal. Assuming that Qs is the lower limit value of minute leakage that can actually occur, if the distributions A and B do not overlap, it is possible to identify the leakage and the zero point.

  Here, in order to facilitate the identification, the number of times of single-around M may be increased so as to reduce the standard deviation σ.

  Furthermore, if a technique is used to average the results of multiple measurements continuously without determining leakage by only one measurement, the variation in the average value becomes smaller in inverse proportion to the square root of the averaging count. Therefore, the determination accuracy can be further increased.

  On the other hand, considering the usage pattern of gas appliances in general households, the time when the gas appliances are not used is much longer than the time when the gas appliances are used. Therefore, when the flow rate is small, simply increasing the number of sing-arounds results in an increase in power consumption and is not practical.

  Therefore, if it is determined that leak detection is performed only once every fixed period (for example, one hour), power consumption does not increase significantly even if the number of times of single-around during the leak detection period is set.

  In view of the above, the control means 11 operates as follows. The operation of the control means 11 will be described with reference to FIG. The normal number of sing-around times is set to 40 times (STEP 1), 30 times in a measurement cycle of 2 seconds, that is, 1 minute measurement is performed (STEP 2), and the average value of the flow rate value during that time is the average value calculation means 13. The standard deviation of the flow value is calculated by the variation calculating means 14 (STEP 3).

  Here, if the obtained average value is smaller than the reference value Q1 (STEP 4) and the standard deviation is smaller than the threshold value Q2 (STEP 5), the switching determination unit 15 switches the operation of the flow velocity detection unit 9 to the leakage determination operation.

  In response to this, the number of times of single-around set in the repeater is set to 800 (STEP 6).

  At the time of leakage determination, sampling is performed intensively for a short time (5 times or 10 seconds) determined by a measurement cycle of 2 seconds (STEP 7), and the average value calculation means 13 obtains the average flow rate value during that period (STEP 8).

  A comparison between the average flow rate obtained at this time and the threshold value Qs for leakage determination is performed by the leakage determination means 17 (STEP 9). If it is smaller than the threshold, it is determined that there is no zero point, that is, no leakage (STEP 10). (STEP 11).

  After the leakage determination is performed once, the switching determination unit 15 determines the end of the leakage determination, and returns the number of times to be set in the repetition unit 7 to 40 (STEP 12).

  Until one hour elapses, no leakage determination is performed regardless of the flow rate (STEP 13).

  Therefore, the leakage determination can be performed efficiently and in a short time without excessively increasing the power consumption.

  The number of sing-around times set in STEP 6 in FIG. 4 is set to 800. However, in order to suppress the required minimum power consumption, as shown in FIG. It may be configured to be variable according to the standard deviation σp of the flow rate measurement value.

  Since σp is a standard deviation at 40 times of sing-around, the standard deviation σs when the number of times of sing-around is changed to Ms times can be obtained as (Equation 7).

  In order to determine the measurement conditions at the time of leak determination without excess or deficiency according to the situation at that time, the value of (Equation 7) should be a value that can withstand leak determination and be constant. When (Equation 7) is solved for Ms, it can be transformed as (Equation 8).

Ms = 40 (σp / σs) ² (Formula 8)
Considering σs as a constant in (Equation 8), Ms is proportional to the square of σp. Actually, since Ms is an integer value, the value obtained by (Equation 8) is rounded up after the decimal point, and when the value obtained by using (Equation 8) is less than 40 times of sing-around at the time of flow measurement. , Ms = 40.

  This relationship can be illustrated as shown in FIG. 5, and as the standard deviation of the flow rate measurement value for 1 minute immediately before the leak determination becomes smaller, the number of sing-around times at the leak determination may be reduced. Recognize.

  In addition, the number of times of measurement at the time of leak determination set in STEP 7 of FIG. 4 is set to 5, but the number of times of sing-around is fixed at 800 times, and as shown in FIG. Even in a configuration in which Ls is variable according to the standard deviation σp of the flow rate measurement value for the previous minute, the required power consumption can be suppressed.

  Since σp is the standard deviation when the singaround is 40 times, the standard deviation σs when the number of singarounds is changed to 800 can be obtained as in (Equation 9).

  Furthermore, when the standard deviation σss of the average value of Ls times, which is the number of measurements at the time of leakage determination, is obtained, (Expression 10) is obtained.

  In order to determine the measurement conditions at the time of leakage determination without excess or deficiency according to the situation at that time, the value of (Equation 10) may be a value that can withstand leakage determination and be constant. When (Equation 10) is solved for Ls, it can be transformed as (Equation 11).

Ls = 0.05 (σp / σss) ² (Formula 11)
Considering σss as a constant in (Equation 11), Ls is proportional to the square of σp. Actually, since Ls is an integer value, it is obtained by rounding up the decimal point of the value obtained in (Equation 11).

  This relationship can be illustrated as shown in FIG. 6, and it can be seen that the number of measurements at the time of leak determination may be reduced as the standard deviation of the flow rate measurement value for one minute immediately before the leak determination becomes smaller.

  Furthermore, if a steady leak has occurred, the zero point should not be detected, so once the zero point, that is, “no leak” is confirmed for a predetermined number of times (for example, 5 times) or more. If possible, it may be configured not to perform subsequent leakage determination.

  In this case, for example, after a certain period (for example, one month) or more has elapsed, it is possible to clear all zero point detection histories and perform leakage determination again, while further saving power consumption. Since a steady leak can be detected, safety is not impaired.

  As described above, according to the present embodiment, the leakage determination unit having a long operation time is configured not to be restarted unless at least a predetermined time has elapsed, so that it can be efficiently performed without excessively increasing power consumption. Leakage determination can be performed in a short time. In particular, in the case of using a battery as a device power source like a household gas meter, safety can be ensured without increasing the battery capacity or sacrificing the product life.

  Moreover, since the leak determination is performed based on the average value of a plurality of consecutive measurements, it is difficult to be affected by disturbances, and the determination reliability can be further improved.

  In addition, since the leak determination is performed only when the flow rate value and its variation are small, the leak determination can be performed at an appropriate timing, so that the reliability of the determination can be improved.

  Further, since the leakage determination time is set to be shorter as the variation in the flow rate value becomes smaller, it is possible to set an appropriate measurement condition depending on the situation.

  When the number of detections of “no leakage” reaches a predetermined number, the leakage determination unit does not operate, and thus it is possible to reduce wasteful power consumption after confirming safety.

  Furthermore, since the operation of the leakage determination unit is restarted every time a predetermined period elapses, it is possible to periodically check for leakage and ensure safety.

  In this embodiment, the ultrasonic wave propagation speed has been described. However, for example, a method of controlling the sampling time during flow rate measurement is used even for a configuration using a hot-wire flow sensor. The same effect can be obtained.

  In addition, the leakage determination is not limited to the flow rate, and it is needless to say that the determination can be made in the same manner even at a flow velocity that is a base for obtaining the flow rate.

  As described above, according to the flow measuring device of the present invention, it is possible to reduce power consumption by reducing the operation frequency of leakage determination with large power consumption, and can be widely applied from gas fluid such as gas to liquid fluid. Is.

1 is a block diagram of a flow rate measuring apparatus according to a first embodiment of the present invention. Characteristic diagram showing the relationship between the number of sing-arounds during measurement and the standard deviation of the measured value Characteristic diagram showing the relationship between standard deviation of measured values and leak judgment Flow chart explaining operation of the apparatus Characteristic diagram showing the relationship between the standard deviation of the measured value of the device and the number of times of sing-around when determining leakage Characteristic diagram showing the relationship between the standard deviation of the measured value of the device and the number of measurements at the time of leak judgment Block diagram of a conventional flow measurement device

Explanation of symbols

9 Measuring means 13 Flow rate calculating means 14 Variation calculating means 15 Switching judgment means 17 Leakage judgment means

Claims (7)

A measuring means for measuring the flow rate and / or flow velocity of the fluid by intermittently executing a set of measurement procedures, and a control means for controlling the operation of the measuring means, the measuring means having an operating time The flow measurement procedure and the leak check procedure with a long operation time for determining micro leaks in the fluid supply path, and the control means includes the flow measurement procedure and the leak check procedure. A switching determination means for switching, and a leakage determination means for determining the presence or absence of leakage by comparing a value obtained by driving the leakage confirmation procedure with a threshold value, and the leakage determination means must be at least a predetermined time elapsed. This is a fluid flow measurement device that does not restart. The fluid flow measuring device according to claim 1, wherein the leakage determination means performs the leakage determination by continuously driving the leakage confirmation procedure a plurality of times and comparing the output average value with a threshold value. The fluid flow measuring device according to claim 1 or 2, wherein the leakage determining means is operated only when the measured value obtained by the flow measuring procedure and the variation of the measured value are small. The fluid flow measurement device according to any one of claims 1 to 3, wherein the operation time of the leakage determination procedure is set to be shorter as the variation in the measured value obtained by the flow measurement procedure becomes smaller. The fluid flow measuring device according to any one of claims 1 to 3, wherein the number of times the leakage determination procedure is driven is set to be smaller as the variation in the measured value obtained by the flow measuring procedure is smaller. The fluid flow measuring device according to any one of claims 1 to 5, wherein the leakage determination means does not operate when the number of detections without leakage reaches a predetermined number. 7. The fluid flow measuring device according to claim 6, wherein the number of times of detection without leakage is initialized and the operation of the leakage determination means is restarted each time a predetermined period elapses.

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