JP5585402B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures a flow rate of gas or the like using ultrasonic waves.

  Conventionally, in this type of flow rate measuring device, as shown in FIG. 3, a first ultrasonic transducer 19 and a second ultrasonic transducer 20 are arranged in a fluid line 18 relative to the fluid flow direction. Yes. Then, after the ultrasonic wave is detected by the transmission circuit 21 to the first ultrasonic transducer 19, the reception circuit 22 that performs signal processing on the ultrasonic wave received by the second ultrasonic transducer 20, Repeating means 23 for repeating transmission from one ultrasonic transducer and reception by the second ultrasonic transducer 3 a plurality of times, the number of repetitions by the repeating unit 23, that is, resolution setting means 24 for setting measurement resolution, intermittent measurement Trigger means 25 for instructing the start, period setting means 26 for setting the output period of the trigger means 25, measuring means 27 for measuring the time required for multiple times of ultrasonic propagation performed by the repeating means 23, and measured values of the measuring means 27 The flow rate calculating means 28 for obtaining the flow rate from the above and the measurement control means 29 for controlling each of the above-mentioned elements are provided. Normal measurement means 30 for obtaining the measured flow rate based on the value obtained as a result, and a period shorter than that of the normal measurement means 30 is set in the period setting means 26, and the coarse resolution is resolved. A search and measurement unit 31 that estimates the flow rate based on a value obtained by setting the setting unit 24, a determination unit 32 that sets a measurement cycle or a measurement resolution from the difference between the measured flow rate and the estimated flow rate, and a flow rate calculation It is comprised from the integrating | accumulating means 33 which calculates | requires integrated flow volume by integrating the flow volume value calculated | required by the means 28 (for example, refer patent document 1).

Japanese Patent No. 3432210

  However, in the conventional flow rate measuring device, the search measurement is performed with a shorter period and with a coarser resolution than that of the normal measuring means, so the flow rate measurement accuracy is lowered. Therefore, when the flow rate of the fluid that needs to be determined from the fluid conduit is small, it is not possible to determine the fluid leakage by the search measurement. In addition, since the resolution of the normal measuring means is made finer by decreasing the measurement flow rate, there is a problem that the power consumption cannot be reduced when the flow rate is small.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to make it possible to determine fluid leakage and reduce power consumption.

In order to solve the conventional problem, a flow rate measuring device according to the present invention includes a first vibrator and a second vibrator that transmit and receive an ultrasonic signal provided in a fluid pipe through which a fluid to be measured flows, Time measuring means for measuring the propagation time of the ultrasonic signal between the vibrators, switching means for switching transmission / reception of the first vibrator and the second vibrator every time measurement by the time measuring means is completed, and the vibrator Repetitive means for performing ultrasonic propagation between the plurality of times, repetitive setting means for setting the number of repetitive means, time calculating means for calculating an average value of propagation times from the outputs of the time measuring means and the repetitive means, A flow rate calculation means for calculating a flow rate from the propagation time calculated by the time calculation means, a number of repetitions set in the repetition setting means, and a normal measurement means for calculating a measured flow rate at a predetermined measurement cycle; A flow rate estimating unit that calculates an estimated flow rate with a larger number of repetitions and a longer measurement cycle than the normal measurement unit, and the repeat setting unit performs the normal measurement according to a difference between the measured flow rate and the estimated flow rate. The number of repetitions by means is set.

  As a result, even when the flow rate is small, the estimated flow rate is calculated with high measurement accuracy, and if the estimated flow rate is less than a predetermined value that may cause fluid leakage, fluid leakage can be reduced by increasing the number of repetitions of the normal measurement means. Can be determined. In addition, the frequency of the normal measurement means can be reduced by reducing the number of repetitions of the normal measurement means above a predetermined value that may cause fluid leakage. As a result, power consumption can be reduced.

  The flow measuring device of the present invention can reduce power consumption while discriminating fluid leakage even at low flow rates.

Block diagram of a flow rate measuring device in Embodiment 1 of the present invention Flow chart showing a method for changing the number of repetitions of the flow rate measuring device Block diagram of a conventional flow measurement device

1st invention measures the propagation time of the ultrasonic signal between the 1st vibrator and the 2nd vibrator which transmit and receive the ultrasonic signal provided in the fluid channel through which the fluid under measurement flows, and the vibrator Clocking means, switching means for switching transmission / reception of the first vibrator and second vibrator every time measurement by the timekeeping means is completed, and repeating means for performing ultrasonic propagation between the vibrators a plurality of times A repetition setting means for setting the number of repetition means, a time calculation means for calculating an average value of the propagation time from the outputs of the timing means and the repetition means, and a flow rate from the propagation time calculated by the time calculation means. A flow rate calculation means to calculate, a repeat count set in the repeat setting means, a normal measurement means to calculate a measured flow rate at a predetermined measurement cycle, a repeat count greater than the normal measurement means, and A flow rate estimating means for calculating an estimated flow rate with a long measurement cycle, wherein the repeat setting means sets the number of repetitions in the normal measurement means according to the difference between the measured flow rate and the estimated flow rate. is there.

  Thereby, the estimated flow rate can be calculated with high measurement accuracy. As a result, it is possible to determine fluid leakage and reduce the frequency of normal measurement.

  In a second aspect of the invention, in particular, in the first aspect of the invention, when the measured flow rate is equal to or greater than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is less than a predetermined value, the number of repetitions set in the repetition setting unit is set. It's something to reduce.

  Thereby, the operation frequency of a normal measurement means can be reduced and power consumption can be reduced.

  In a third aspect of the invention, in particular, in the first aspect of the invention, when the measured flow rate is equal to or greater than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is equal to or greater than a predetermined value, the number of repetitions set in the repetition setting unit is set. To do more.

  As a result, when the change in the measured flow rate is large, the measurement accuracy for the flow rate measurement is improved by increasing the number of repetitions of the normal measurement means.

According to a fourth aspect of the invention, in particular, in the first aspect of the invention, the determination unit is configured to repeat the setting unit when the measured flow rate is less than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is less than a predetermined value. The number of repetitions set to is reduced.

  Thereby, when the measured flow rate is small and the difference between the measured flow rate and the estimated flow rate is small, i.e., the error in measurement accuracy is small, the possibility of fluid leakage is low, so the operation frequency of the normal measurement means can be reduced, Power consumption can be reduced.

In a fifth aspect of the invention, in particular, in the first aspect of the invention, the determination unit is configured to repeat the setting unit when the measured flow rate is less than a predetermined flow rate and a difference between the measured flow rate and the estimated flow rate is a predetermined value or more. The number of repetitions set to is increased.

  As a result, when the measured flow rate is small and the difference between the measured flow rate and the estimated flow rate is large, that is, when the measurement accuracy error is large, the possibility of fluid leakage is high, so the number of repetitions of the normal measurement means should be increased. Improve measurement accuracy for flow rate measurement.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a flow rate measuring apparatus showing Embodiment 1 of the present invention, and FIG. 2 is a flowchart showing the operation of the apparatus. In FIG. 1, a first ultrasonic transducer 2 and a second ultrasonic transducer 3 are arranged in a fluid conduit 1 through which a fluid to be measured flows in a flow direction, and the first ultrasonic transducer is arranged. Transmitting means 4 to 2 or the second ultrasonic transducer 3, receiving means 5 for receiving and detecting the ultrasonic waves received by the first ultrasonic transducer 2 or the second ultrasonic transducer 3, the first ultrasonic After receiving by the time measuring means 6 and the receiving means 5 for measuring the time until transmission / reception of ultrasonic waves between the ultrasonic transducer 2 and the second ultrasonic transducer 3, the first ultrasonic transducer 2 and the second ultrasonic transducer are received. Repeating means 7 for repeating transmission / reception of ultrasonic waves between the sound wave oscillators 3 multiple times, switching means 8 for switching between transmission and reception of ultrasonic waves when repeating the transmission / reception of ultrasonic waves by the repeating means 7, timing means 6 and repeating means 7 Time to calculate the average value of propagation time from multiple transmission / reception of ultrasonic waves Calculation means 9, the flow rate calculating unit 10 for calculating the flow rate from the measured value of the time calculating means 9 comprises measurement control means 11 for controlling each element.

  The measurement control unit 11 includes a normal measurement unit 12 and a flow rate estimation unit 13, and a determination unit 14 that determines the measurement values of the normal measurement unit 12 and the flow rate estimation unit 13.

  Further, there are provided a leakage determination means 15 for determining a fluid leakage from the measurement value of the normal measurement means 12 and an integration means 16 for integrating the amount of fluid that has passed through the fluid pipe 1. The normal measuring unit 12 and the flow rate estimating unit 13 output the number of repetitions set in the repetition unit 7 to the repetition setting unit 17 according to the determination unit 14.

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

  First, the switching means 8 sets the first ultrasonic transducer 2 to the transmission side and the second ultrasonic transducer 3 to the reception side. Then, the ultrasonic wave transmitted from the first ultrasonic transducer 2 by the burst signal transmitted by the transmission means 4 propagates through the fluid to be measured in the fluid pipe line 1, and is transmitted by the second ultrasonic transducer 3. Received and detected by the receiving means 5, the time measuring means 6 measures the propagation time (forward propagation time t 1) until transmission / reception of ultrasonic waves.

Next, the switching means 8 sets the first ultrasonic transducer 2 to the receiving side and the second ultrasonic transducer 3 to the transmitting side. Then, the burst signal is transmitted again from the transmission means 4 via the repetition means 7, and the ultrasonic waves are transmitted from the second ultrasonic transducer 3, propagated through the fluid to be measured in the fluid conduit 1, and the first Received by the ultrasonic transducer 2 and detected by the receiving means 5, the time measuring means 6 measures the propagation time (reverse direction propagation time t 2), and calculates the difference between the two measured propagation times (t 1, t 2). . At this time, the repetition means 7 repeats a predetermined number of times, and the time calculation means 9 calculates the average value of the propagation time differences.

Here, assuming that the sound velocity of the fluid to be measured 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 (C−V). . When the distance between the first ultrasonic transducer 2 and the second ultrasonic transducer 3 is L and the angle between the ultrasonic propagation axis and the central axis of the pipe is θ, the forward propagation time t1. The propagation time t2 in the reverse direction is
t1 = L / (C + V cos θ) Equation (1)
t2 = L / (C−V cos θ) Equation (2)
It becomes. Here, the difference between t1 and t2 is a small value, and it is difficult to obtain sufficient resolution for measurement as a single phenomenon. Therefore, a method is adopted in which transmission / reception of ultrasonic waves is repeated a plurality of times and the average value is obtained. If the number of repetitions by the repetition means 7 is n, the propagation times T1 and T2 are
T1 = n × L / (C + V cos θ) Equation (3)
T2 = n × L / (C−V cos θ) Equation (4)
From Equations (3) and (4)
V = n × L / 2 cos θ (1 / T1-1 / T2) Equation (5)
If L and θ are known, the flow velocity V can be obtained by measuring T1 and T2. From this flow velocity V, if the flow rate Q is S and the correction coefficient is K,
Q = K × S × V Formula (6)
It becomes.

  Then, as apparent from the equations (3) and (4), the resolution of the flow rate Q can be increased by increasing the number of repetitions n. The flow rate calculation means 10 calculates the flow rate by executing the calculation processes of (T1-T2), the expressions (5), and (6) in the time calculation means 9.

  The flow rate calculated for each predetermined cycle ti and the number of repetitions ni by the above-described flow rate calculation in accordance with the instruction from the normal measurement means 12 is referred to as a measured flow rate. The number of repetitions in the normal measuring unit 12 is set to m as an initial value, and the number of repetitions can be set by the repetition setting unit 17 and can be changed according to the situation. Furthermore, the flow rate calculated by the flow rate estimation unit 13 for each interval 2ti longer than the cycle ti of the normal measurement unit 12 and a large number of repetitions ni + a is referred to as an estimated flow rate. The initial value of the number of repetitions in the flow rate estimation means 13 is determined as m + a times and the period is defined as ti + b. That is, the number of repetitions set by the flow rate estimation means 13 is larger and the period is set longer.

  The procedure for calculating the estimated flow rate by the flow rate estimation means 13 is basically the same as the method by the normal measurement means 12. The flow rate estimation means 13 has a high measurement accuracy in order to prevent the measurement accuracy from dropping when the measurement flow rate is small and the number of repetitions ni in the normal measurement means 12 is reduced, and the leakage discrimination means 15 cannot discriminate fluid leakage. Since the purpose is to estimate the flow rate, the flow is executed with a number of repetitions larger than that of the normal measurement means 12, and is executed with a longer cycle than the normal measurement means 12 in order to reduce power consumption.

  The determination unit 14 determines whether or not normal measurement is performed with the number of repetitions corresponding to a predetermined flow rate from the measured flow rate calculated by the normal measurement unit 12 and the estimated flow rate calculated by the flow rate estimation unit 13, and the repetition setting unit 17. Output the number of repetitions to. The accumulating unit 16 accumulates the amount of fluid that flows when the amount of fluid flowing in the fluid pipe line 1 is equal to or greater than a predetermined flow rate, and stores the accumulated amount as an accumulated value.

  Here, the predetermined flow rate of the measured flow rate is a threshold value for determining whether or not the amount of fluid passing through the fluid conduit 1 is integrated, and the fluid flow rate region is defined as a flow rate of 0 when the measured flow rate is equal to or lower than the predetermined flow rate. The flow rate is divided into a first flow rate region in which the amount is not integrated and a second flow region in which the measured flow rate is equal to or higher than a predetermined flow rate and the fluid amount is integrated.

  When the flow rate is small, the difference between the propagation time t1 and the propagation time t2 is small and the measurement error becomes large. Therefore, measurement with high measurement accuracy is required in the first flow rate region.

  Therefore, from the difference between the measured flow rate by the normal measurement unit 12 and the estimated flow rate by the flow rate estimation unit 13 and the measured flow rate, the determination unit 14 outputs the number of repetitions to the repetition setting unit 17 by the following method.

  FIG. 2 is a flowchart showing a method of increasing / decreasing the number of repetitions. First, an initial value is set as the number of repetitions as the number of repetitions (S1).

  Next, it is determined whether or not the measured flow rate is equal to or higher than the predetermined flow rate (S2). If the measured flow rate is equal to or higher than the predetermined flow rate, the difference between the measured flow rate and the estimated flow rate is compared with a predetermined value (S3). If it is less, the measurement accuracy by the normal measurement unit 12 may be somewhat reduced, so the determination unit 14 reduces the number of repetitions output to the repetition setting unit 17 (S4). Conversely, when the difference between the measured flow rate and the estimated flow rate is greater than or equal to a predetermined value, there is a possibility that the measurement accuracy of the measured flow rate is low, so the determination unit 14 increases the number of repetitions output to the repetition setting unit 17 ( S5).

  If the measured flow rate is less than the predetermined flow rate, the difference between the measured flow rate and the estimated flow rate is compared with a predetermined value (S6). If this difference is less than the predetermined value, the estimated flow rate by the flow rate estimating means 13 is high in measurement accuracy. Since measurement is being performed, the determination unit 14 determines that the possibility of fluid leakage is low, thereby reducing the number of repetitions output to the repetition setting unit 17 (S7). Conversely, if the difference between the measured flow rate and the estimated flow rate is greater than or equal to a predetermined value, the determination unit 14 determines that the possibility of fluid leakage is high, thereby increasing the number of repetitions output to the repetition setting unit 17 (S8). ).

  In addition, since the measurement accuracy in the flow rate estimation unit 13 that measures the estimated flow rate may be higher than the measurement accuracy of the normal measurement unit 12, the number of repetitions in the flow rate estimation unit 13 is greater than the number of repetitions set in the normal measurement unit 12. A large number may be set, and the number may be changed according to the number of repetitions set in the normal measurement unit 12.

  In addition, when the upper limit of the number of repetitions is set and the number of repetitions set in the normal measurement unit 12 exceeds the upper limit, it is more than necessary if the number of repetitions of the normal measurement unit 12 and the flow rate estimation unit 13 is set to the upper limit number. Can be prevented, and power saving can be achieved. When the flow rate is large, the accuracy is high even if the number of repetitions is small. Therefore, by setting the upper limit of the number of repetitions as the measurement flow rate is increased, further power saving can be achieved.

  As a result, the power consumption can be reduced by changing the operation frequency of the normal measuring means 12 according to a predetermined flow rate as described above.

  As described above, the flow rate measuring device according to the present invention can reduce power consumption while discriminating fluid leakage by setting the number of repetitions according to the flow rate, and therefore can be applied to all ultrasonic gas meters. It can be done.

DESCRIPTION OF SYMBOLS 1 Fluid line 2 1st ultrasonic transducer | vibrator (1st transducer | vibrator)
3 Second ultrasonic transducer (second transducer)
4 Transmitting means 5 Receiving means 6 Timing means 7 Repeating means 8 Switching means 9 Time calculating means 10 Flow rate calculating means 12 Normal measuring means 13 Flow rate estimating means 17 Repeat setting means

Claims (5)

A first vibrator and a second vibrator for transmitting and receiving an ultrasonic signal provided in a fluid pipe through which a fluid to be measured flows;
Time measuring means for measuring the propagation time of the ultrasonic signal between the vibrators;
Switching means for switching transmission and reception of the first vibrator and the second vibrator every time measurement by the time measuring means is completed;
Repeating means for performing ultrasonic propagation between the vibrators a plurality of times,
Repetition setting means for setting the number of repetition means;
Time calculating means for calculating an average value of propagation time from outputs of the time measuring means and the repeating means;
Flow rate calculation means for calculating a flow rate from the propagation time calculated by the time calculation means;
Normal measurement means for calculating the measurement flow rate at a predetermined number of times and the number of repetitions set in the repetition setting means;
A flow rate estimating means for calculating an estimated flow rate with a larger number of repetitions and a longer measurement cycle than the normal measuring means,
The repetitive setting unit is a flow rate measuring device that sets the number of repetitions in the normal measurement unit in accordance with a difference between the measured flow rate and the estimated flow rate. The flow rate measuring apparatus according to claim 1, wherein when the measured flow rate is equal to or higher than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is less than a predetermined value, the number of repetitions set in the repetition setting unit is reduced. The flow rate measuring device according to claim 1, wherein when the measured flow rate is equal to or higher than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is equal to or higher than a predetermined value, the number of repetitions set in the repetition setting unit is increased. The flow rate measuring device according to claim 1, wherein when the measured flow rate is less than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is less than a predetermined value, the number of repetitions set in the repetition setting unit is reduced. The flow rate measuring device according to claim 1, wherein when the measured flow rate is less than a predetermined flow rate and the difference between the measured flow rate and the estimated flow rate is greater than or equal to a predetermined value, the number of repetitions set in the repetition setting unit is increased.

Images