JP2001004419A - Flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure stably and precisely a flow rate value when change is generated, by detecting change information and performing measurement when the flow rate of gas or liquid having flow rate change or pressure change is measured. SOLUTION: This flowmeter is equipped with a flow rate detecting means 28 detecting a flow rate by measuring the propagation time of a sound wave transmitted and received by a first vibrating means 23 and a second vibrating means 25 which transmit and receive the sound wave, a change detecting means 29 measuring pressure change in a flow channel with at least one out of the first and second vibrating means 23 and 25, and a measurement controlling means 30 beginning measurement synchronously with the timing of pressure change of the change detecting means. Thereby a pressure sensor is made unnecessary, miniaturization and simplification of a flow channel are enabled, and a flow rate can be measured stably in a short time when pressure change is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring a flow rate of a liquid or a gas, and more particularly to a means for accurately measuring a flow rate value even when a flow rate fluctuation occurs.

[0002]

2. Description of the Related Art Conventionally, this type of flow meter is disclosed in
Japanese Patent Application Laid-Open No. 5006 and Japanese Patent Application Laid-Open No. 11-44563 have been known. The configuration is described below with reference to FIG.
This will be described with reference to FIG.

As shown in FIG. 16, a sampling program 2 for reading a measurement value from an analog flow sensor 1 for measuring a gas flow rate at every predetermined first sampling time, and a gas consumption calculation for calculating a gas consumption flow rate for a predetermined time. A program 3, an average value calculation program 4 for reading a measured value of the analog flow sensor every second sampling time within a predetermined time within the first sampling time and calculating an average value thereof, and a cycle of pressure fluctuation from an output of the flow sensor. And a RAM 6 as a memory. Here, 7 is a ROM of a memory for storing the programs, and 8 is a CPU for executing the programs. With this configuration, the measurement process is performed so that the predetermined measurement time is at least one cycle of the vibration cycle of the pump or a multiple of the cycle. Even if the flow rate fluctuates due to averaging, the measured flow rate is affected. It is configured to be difficult to perform.

As shown in FIG. 17, a flow rate detecting means 9 for detecting a flow rate, a fluctuation detecting means 10 for detecting a fluctuation waveform of a fluid, and a measurement of the flow rate detecting means are performed near zero of an AC component of the fluctuation waveform. The configuration includes a pulsation measuring unit 11 to be started and a flow rate calculating unit 12 for processing a signal of the flow rate detecting unit. Here, 13 is a signal processing circuit, 14 is a clock circuit,
15 is a trigger circuit, 16 is a transmission circuit, 17 is a comparison circuit,
Reference numeral 18 denotes an amplification circuit, 19 denotes a switch, 20 denotes a measurement start signal circuit, 21 denotes a starting unit, and 22 denotes a flow path. With this configuration, the flow rate around the average of the fluctuation waveform is measured, and accurate flow rate measurement is performed in a short time.

[0005]

However, in the above-mentioned prior art, in the first reference, the gas flow rate is measured using the average value, and a long time measurement is required to obtain a stable average value. There was a problem that instantaneous flow rate measurement was difficult. Further, in the second reference, the method of measuring the flow rate is changed without pressure fluctuation, and there is a problem that two means of the pressure measuring means and the flow rate measuring means must be provided.

[0006]

According to the present invention, there is provided a transmitting / receiving means provided in a flow path for transmitting / receiving a sound wave, and a time measuring means for measuring a propagation time of the sound wave transmitted / received by the transmitting / receiving means. And, a flow rate detecting means for detecting a flow rate based on the value of the time measuring means, a fluctuation detecting means for measuring a fluctuation in the flow path by the transmitting and receiving means, and a measurement synchronized with a fluctuation timing of the fluctuation detecting means. And a control unit for starting the measurement.

According to the above invention, the fluctuation in the flow path can be measured in at least one of the first vibrating means and the second vibrating means, so that it is not necessary to provide another sensor for detecting fluctuation, and it is possible to reduce the size and the size. The flow path and the like can be simplified, and even when a change occurs, the flow rate can be measured stably and accurately in a short time.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a transmitting / receiving means provided in a flow path for transmitting and receiving a sound wave, a time measuring means for measuring a propagation time of a sound wave transmitted and received by the transmitting / receiving means, and a value based on the value of the time measuring means. Flow detecting means for detecting the flow rate, fluctuation detecting means for measuring fluctuations in the flow path in the transmitting and receiving means,
Measurement control means for starting measurement in synchronization with the timing of the fluctuation of the fluctuation detecting means. Since the fluctuation in the flow path can be measured in at least one of the first vibration means and the second vibration means, there is no need to provide another sensor for detecting fluctuation, and the size and the flow path are simplified. In addition, the flow rate can be measured stably and accurately in a short time even when the fluctuation occurs.

A first vibrating means and a second vibrating means provided in the flow path for transmitting and receiving a sound wave; a switching means for switching the transmitting and receiving operations of the first vibrating means and the second vibrating means; A fluctuation detecting means for detecting a pressure fluctuation in the flow path of at least one of the means and the second vibrating means; a time measuring means for measuring a propagation time of a sound wave transmitted and received by the first vibrating means and the second vibrating means; When the output of the fluctuation detecting means changes by a predetermined amount, the time measuring means measures a first time T1 which propagates from the first vibrating means on the upstream side of the flow path to the second vibrating means on the downstream side, and the fluctuation detecting means When the output of the first time changes in reverse to the predetermined change, the time measuring means controls the second time measuring time T2 propagating from the second vibrating means on the downstream side of the flow path to the first vibrating means on the upstream side. Means and the first total Time said the T1 second measured time T2
And a flow rate detecting means for calculating a flow rate by using the above. The measurement is performed at the timing when the change in the pressure fluctuation is reversed, so that the phase of the pressure fluctuation and the timing of the measurement can be shifted, and the measurement error due to the pressure fluctuation can be canceled.

When the output of the fluctuation detecting means changes by a predetermined amount, the measurement of the first clocking time T1 is started, and when the output of the fluctuation detecting means changes in a direction opposite to the predetermined change, the measurement of the second clocking time T2 is started. At the start of measurement control and the next measurement,
When the output of the fluctuation detecting means changes in reverse to the predetermined change, the measurement of the first clock time T1 is started, and when the output of the fluctuation detecting means changes by the predetermined time, the measurement of the second clock time T2 is started. The measurement control means and the first flow rate obtained by using the previous first time measurement time T1 and the second time measurement time T2 while alternately changing the measurement start, and the next first time measurement time T1 and second time measurement time T2. The flow rate detecting means for calculating the flow rate by successively averaging the second flow rates obtained by using the above-mentioned configuration is provided. By changing the measurement timing as described above and performing the first time measurement time T1 and the second time measurement time T2, even if the pressure fluctuation is asymmetric on the high pressure side and the low pressure side, the influence of the pressure fluctuation is offset. can do.

Further, the apparatus is provided with a repetition means for performing transmission and reception by a sound wave a plurality of times. Then, averaging can be performed by increasing the number of times of measurement, and stable flow rate measurement can be performed.

Further, the apparatus is provided with a repetition means for performing transmission and reception a plurality of times over an integral multiple of the fluctuation period. The pressure fluctuation is averaged by measuring in a fluctuation cycle, and a stable flow rate can be measured.

[0013] Further, a repetition means for starting transmission / reception measurement of sound waves when the output of the fluctuation detection means changes by a predetermined amount, and repeatedly performing transmission / reception measurement of sound waves until the output of the fluctuation detection means changes in the same manner as the predetermined change. Equipped. Since the start and the stop of the measurement can be made to coincide with the cycle of the pressure fluctuation, the measurement can be performed at the fluctuation cycle, and the pressure fluctuation can be averaged and a stable flow rate can be measured.

Further, the first vibration means and the second vibration means are provided with a selection means for switching between a case where the first vibration means is used for transmitting and receiving sound waves and a case where the first vibration means is used for detecting pressure fluctuation. Then, at least one of the first vibrating means and the second vibrating means can be used for pressure detection, and both flow rate measurement and pressure measurement can be achieved.

Further, the apparatus is provided with fluctuation detecting means for detecting the vicinity of zero of the AC component of the pressure fluctuation waveform. And
By detecting the fluctuation near the zero component of the pressure fluctuation, the time range for the flow rate measurement can be started from near the fluctuation zero, and the measurement at the time of the pressure fluctuation can be started by measuring the flow rate within the time where the fluctuation is small. Can be stabilized.

Further, a plurality of bits of counting means for counting the variation of the output signal of the variation detecting means, and counting is performed such that the count value of the counting means is different between the first time and the second time, and all of the plurality of bits are measured. The configuration provided with a flow rate detecting means for measuring the flow rate when the same combination is realized the same number of times. Since the measurement can be performed at all the fluctuation timings, the averaging is performed and the flow rate can be stably measured.

[0017] Further, the apparatus is provided with a cycle detecting means for detecting a cycle of a signal of the fluctuation detecting means, and a measuring control means for starting measurement only when the cycle detected by the cycle detecting means is a predetermined cycle. Then, by starting the measurement only at the predetermined period, the measurement can be performed at the time of the predetermined fluctuation, and the stable flow rate can be measured.

In addition, when a signal from the fluctuation detecting means cannot be detected, a detection canceling means for automatically starting measurement after a predetermined time is provided. Then, even if there is no fluctuation, the flow rate can be automatically measured after a predetermined time.

The first vibrating means and the second vibrating means are constituted by piezoelectric vibrators. By using a piezoelectric vibrator, pressure fluctuation can be detected while using ultrasonic waves for transmission and reception.

[0020]

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

(Embodiment 1) FIG. 1 is a block diagram of a flow meter according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 23 denotes a channel 2
4, a first piezoelectric vibrator as a first vibrating means of a transmitting / receiving means for transmitting / receiving ultrasonic waves, a second piezoelectric vibrator as a second vibrating means of a transmitting / receiving means for transmitting / receiving ultrasonic waves, and 26 A changeover switch 27 as a switching means for switching the transmission / reception operation of the first piezoelectric vibrator and the second piezoelectric vibrator. The switch 27 sets the propagation time of the sound wave repeatedly transmitted and received by the first piezoelectric vibrator 23 and the second piezoelectric vibrator 25. Time measuring means for measuring by the sing-around method, 28 is a flow rate detecting means for detecting a flow rate based on the value of the time measuring means, 29 is the first piezoelectric vibrator 23 and the second piezoelectric vibrator 25 for pressure fluctuation in the flow path. Is a measurement control unit that starts measurement in synchronization with the pressure fluctuation timing of the fluctuation detection unit.

Here, the measurement control means 30 starts measuring the first clocking time T1 when the output of the fluctuation detecting means 29 rises, and starts measuring the first time T1 when the output of the fluctuation detecting means 29 falls.
(2) Measurement control for starting measurement of the clocking time T2, and for the next measurement, measurement of the first clocking time T1 is started when the output of the fluctuation detecting means falls, and second measurement is performed when the output of the fluctuation detecting means rises. The measurement of the clocking time T2 is started and measurement control is performed. The flow rate measuring means 28 changes the first flow rate obtained by using the previous first clocking time T1 and the second clocking time T2 while alternately changing the measurement start and the next flow rate. The flow rate is calculated by sequentially averaging the second flow rate obtained by using the first clock time T1 and the second clock time T2. Reference numeral 31 denotes a selection switch as selection means for selecting whether to transmit / receive ultrasonic waves to the second piezoelectric vibrator or to detect pressure fluctuation, 32 denotes an ultrasonic signal transmitter, and 33 denotes an ultrasonic signal receiver. , 34 are repetition means for performing sing-around measurement, and 35 is operation check means for the first piezoelectric vibrator and the second piezoelectric vibrator.

Next, the operation and operation will be described with reference to FIGS. In the flow path configured as shown in FIG.
When the time T1 for propagation from the piezoelectric vibrator 23 to the second piezoelectric vibrator 25 is measured, T1 = L / (C + Vcos)
θ). When the time T2 for propagation from the second piezoelectric vibrator 25 to the first piezoelectric vibrator 23 is measured,
2 = L / (C−Vcos θ). Here, V is the flow velocity in the flow channel, C is the speed of sound, and θ is the inclination angle. And T
Taking the difference between the reciprocals of 1 and T2 gives T1,
The flow velocity V is obtained from T2.

1 / T1-1 / T2 = 2Vcosθ / LV V = (L / 2cosθ) ・ (1 / T1-1 / T2) Here, if there is a pressure fluctuation in the flow path, The flow rate changes. Therefore, assuming a fluctuating frequency f and a fluctuating flow velocity u, T1 and T2 are as follows: T1 = L / (C + Vcos θ + u · sin (2πf
t)) T2 = L / (C−Vcos θ−u · sin (2πft +
ψ)). Here, ψ is a time difference (phase difference) between the start of the T1 measurement and the start of the T2 measurement. Then, by taking the reciprocal difference between T1 and T2, 1 / T1-1 / T2 = (2Vcos θ + u · (sin
Since (2πft) + sin (2πft + ψ))) / L, when ψ = π, sin (2πft + ψ))
= −sin (2πft), and the influence of the fluctuation is cancelled. Therefore, assuming that V = (L / 2 cos θ) · (1 / T1-1 / T2), the flow velocity V can be measured even in the case of fluctuation, and the flow rate can be calculated in consideration of the cross-sectional area of the flow path and the like. . Although the above description has been given of the measurement of one transmission / reception, the integration time can also be obtained by the following formula in the case where the integration time is obtained by the sing-around method of repeatedly measuring the propagation time by the repeating means 34.

T1 = Σ [L / (C + Vcosθ + u · sin (2πfti))] = ΣL / (Σ (C + Vcosθ) + Σ (u · sin (2πfti))) T2 = Σ [L / (C−Vcosθθ-u · sin) (2πfti + ψ))] == L / (Σ (C + Vcosθ) + Σ (u · sin (2πfti + ψ))) where subscript i is the number of sing-arounds and Σ is i =
Shows the integration from 1 to N times. Although a detailed description of the measurement processing of the sing-around method is omitted, this method is a method of repeating transmission and reception of ultrasonic waves to increase the total propagation time and increase measurement accuracy.

From the reciprocal difference between T1 and T2, 1 / T1-1 / T2 = ({[2Vcos θ] + {[u ·
(Sin (2πft)) + Σ [u · sin (2πft +
ψ))]) / ΣL And when ψ = π, sin (2πft + ψ)) = −
sin (2πft), and the influence of the fluctuation is canceled even if the sing-around method is used. Therefore, assuming that V = (L / 2 cos θ) · (1 / T1-1 / T2), the flow velocity V can be measured even in the case of fluctuation, and the flow rate can be calculated in consideration of the cross-sectional area of the flow path and the like. .

Here, the start timing of measurement at which the time difference と becomes π will be described with reference to FIG. The output signal of the fluctuation detecting means 29 is realized by comparing and detecting the zero cross point of the AC component of the pressure fluctuation with a comparator. That is, the measurement of T1 is started at the rise of the output signal of the fluctuation detecting means, and the integration time T is calculated at a predetermined number of sing-around times.
Measure 1. On the other hand, the start of T2 measurement is performed at the fall of the output signal of the fluctuation detecting means 29, and the integrated time T2 is measured at the same predetermined number of sing-arounds. As shown in FIG. 3, T1 measures between A, B, and C of the pressure waveform, and T2 measures between F, G, and H having amplitudes opposite to those of A, B, and C.
Therefore, the pressure fluctuation is canceled.

In addition, in the case of a positive-negative symmetric pressure fluctuation as shown in FIG. 3, the measurement can be canceled by one measurement of T1 and T2. However, in the case of a positive-negative asymmetric as shown in FIG. Can be canceled by That is, the T1 measurement is started at the rising edge of the output signal of the fluctuation detecting means 29, and the integrated time T1 is measured at a predetermined number of sing-arounds. On the other hand, the start of T2 measurement is performed at the fall of the output signal of the fluctuation detecting means 29, and the integrated time T2 is measured at the same predetermined number of sing-arounds. And
In the next measurement, the start of the T1 measurement is determined by the fluctuation detecting means 29.
And the integration time T1 is measured at a predetermined number of sing-arounds. On the other hand, T2 measurement is started at the rise of the output signal of the fluctuation detecting means 29, and the integrated time T2 is measured at the same predetermined number of sing-arounds. As shown in FIG. 4, the first T1 is A,
B and C are measured, and T2 is measured between D, E and F. In this case, since the waveforms of C and F are different, the difference between C and F is the error C
− (− F), but at the time of the second measurement, T1
Is measured by H, I, and J of the reverse waveform, and T2 is measured by K, L, and M. Again, the waveforms of J and M are different and remain as errors, but in the second measurement, M
And J when measured from the downstream, and the sign is inverted, so that J and M remain as an error (−J−M).
Then, since C = M and F = J, C − (− F)
And (−J−M) are added and averaged, it becomes zero,
The pressure fluctuation will be canceled. When the direction of transmission and reception of ultrasonic waves is alternately inverted every time measurement is performed, it is apparent that the measurement start timing may be constant. In addition, although the description has been given of two measurements here, when the waveform of the pressure fluctuation is asymmetric and complicated, the start of the measurement is averaged by sequentially changing and repeating the start of the measurement according to the periodicity of the waveform, and the error is reduced. Can be minimized.

Next, the flow of measurement will be described with reference to the flowcharts of FIGS. First, it is determined whether or not the signal of the fluctuation detecting means has risen. If it does not rise, the determination is repeated until the output signal of the fluctuation detecting means 29 rises.
Here, when the rise does not occur even after standing for a predetermined time, the processing as the detection canceling means stops the rise detection, and assuming that there is no pressure fluctuation, the first clock time T1 and the second clock time T1 are determined.
2 is measured. When a rising is detected, the first
The time T1 is measured. Then, it is determined whether or not the signal of the fluctuation detecting means 29 falls. Here, when the fall is detected, the second time T2 is measured. Also, if the fall is not detected even after standing for a predetermined time, the processing as the detection canceling means stops the fall detection, and measures the second time T2 assuming that there is no pressure fluctuation. The flow rate Q (j) is calculated from T1 and the second time T2.

At the time of the next measurement, as shown in FIG. 6, this time, the falling detection is started, and after the falling detection,
After measuring the first clock time T1, a rise is detected, a second clock time T2 is measured, and the first clock time T1 is measured.
And the second time T2, the flow rate Q (j + 1) is calculated.
The measurement start is repeated while changing the measurement alternately, and the flow rate Q is calculated by measuring the first flow rate Q (j) and the second flow rate Q (j + 1) and sequentially averaging them, thereby averaging the errors. Can be eliminated in principle.

As described above, since the pressure fluctuation in the flow path can be measured by the second piezoelectric vibrator 25, there is no need to provide a pressure sensor, and the size and the flow path can be simplified. Even when pressure fluctuations occur, the instantaneous flow rate can be measured stably and accurately. The measurement is performed at the timing when the change in the pressure fluctuation is reversed, so that the phase of the pressure fluctuation and the timing of the measurement can be shifted, and the measurement error due to the pressure fluctuation can be canceled. Then, by setting the timing to be opposite for each measurement, even if the pressure fluctuation is asymmetric on the high pressure side and the low pressure side, the influence of the pressure fluctuation can be canceled. Then, by repeating the measurement in the sing-around, the measurement can be averaged in one measurement, and the stable flow measurement can be performed. By using the selecting means, at least one of the first vibrating means and the second vibrating means can be used for pressure detection, and both flow rate measurement and pressure measurement can be achieved. And by detecting the fluctuation near the zero component of the pressure fluctuation, the period of the fluctuation can be accurately grasped,
The flow rate can be offset. Then, even if there is no fluctuation, the flow rate can be automatically measured after a predetermined time. And, by using the piezoelectric vibrator as the fluctuation detecting means, it is possible to detect the pressure fluctuation while using the ultrasonic wave for transmission and reception, and further, it is not necessary to provide a dedicated pressure detecting means, and the leakage is prevented. There is an effect that a part which becomes a factor can be reduced.

The same effect can be obtained functionally by detecting the pressure fluctuation described in the present embodiment by using a dedicated pressure detecting means. Further, the case where the downstream second piezoelectric vibrator is used has been described, but the same effect can be obtained when the upstream first piezoelectric vibrator is used. In addition, upstream,
The same effect can be obtained by alternately using the piezoelectric vibrators on the downstream side. However, by using the piezoelectric vibrators alternately, it is also possible to check the operation state of each piezoelectric vibrator. That is, when the signal of the fluctuation detecting means is a signal of the same cycle in both of the signals from the piezoelectric vibrators, it can be determined that both are operating normally.

Although the flow meter has been described as a general instrument, the use of the present flow meter in a gas meter allows the flow meter to be used in a flow path pipe in which pulsation occurs, such as a pipe system using a gas engine heat pump. It is possible. Further, although the description has been made with reference to the pressure fluctuation, it is clear that a similar effect can be obtained even when there is a flow rate fluctuation.

(Embodiment 2) FIG. 8 is a timing chart showing the operation of a flow meter according to Embodiment 2 of the present invention. Example 1
A different point from the first embodiment is that a repetition means 34 for transmitting and receiving a sing-around a plurality of times over an integral multiple of the fluctuation period is provided. The configuration is shown in FIG.

As shown in FIG. 9, a predetermined time (for example, 2
When the measurement is started at intervals of a (second cycle), when a predetermined time has elapsed, the cycle of the fluctuation detected by the fluctuation detecting means 29 is measured. Then, the number of sing-arounds substantially matching the cycle is set. For example, one propagation time can be calculated by dividing the distance between the piezoelectric vibrators of ultrasonic waves by the speed of sound. Then, the number of necessary sing-arounds can be calculated by dividing the measured cycle by the propagation time. The flow rate is measured repeatedly by the number of sing-arounds. The circle 1 in the figure indicates that the processing of the circle 1 in FIG. 5 is performed.

As described above, by adjusting the number of sing-arounds to the fluctuation cycle, one cycle of the fluctuation can be measured, and the pressure fluctuation can be averaged and a stable flow rate can be measured. By measuring the number of times of pressure synchronization and the number of sing-arounds in accordance with an integral multiple of the cycle, the flow rate can be measured more stably. Furthermore, since the pressure synchronization can be detected by the signal of the piezoelectric vibrator,
There is a synergistic effect that the period can be detected and the flow rate can be measured stably.

FIG. 8 shows a case where two cycles are measured. When the propagation distance is short, sing-arounds of a predetermined number or more are required in order to increase the measurement accuracy, so when the number of sing-arounds obtained from the fluctuation cycle is smaller than the predetermined number, the sing-around is set to a multiple of the cycle. The number of sing-arounds may be determined in advance.

(Embodiment 3) FIG. 10 is a timing chart showing the operation of a flow meter according to Embodiment 3 of the present invention. The difference from the first embodiment is that when the output of the fluctuation detecting means 29 changes by a predetermined amount (for example, at the time of falling), the measurement of the sound wave transmission / reception is started, and the output of the fluctuation detecting means changes by the same amount as the predetermined change (for example, (At the time of falling) and a repeating means 34 for repeating transmission and reception measurements of sound waves. The configuration is shown in FIG.

As shown in FIG. 11, the rising of the fluctuation detection signal is detected at the start of the measurement, and the sing-around is started. Then, when the fluctuation detection signal rises again, the sing-around is stopped and the first time measurement time T1 is measured. Next, at the start of measurement, the falling of the fluctuation detection signal is detected, and sing-around is started. When the signal of the fluctuation detection signal falls again, the sing-around is stopped and the second time T2 is measured. Their T1
And the flow rate is calculated from T2.

As described above, the start and the stop of the measurement can be made to coincide with the cycle of the pressure fluctuation. Therefore, the measurement can be performed at the fluctuation cycle, and the pressure fluctuation can be averaged and a stable flow rate can be measured.

(Embodiment 4) FIG. 12 is a block diagram showing a flow meter according to Embodiment 4 of the present invention. The difference from the first embodiment is that the 2-bit counting unit 36 that counts the fluctuation of the output signal of the fluctuation detecting unit 29 and the count value of the counting unit 36 are different between the first time and the second time. The flow rate detecting means 28 is configured to measure the flow rate and measure the flow rate when all the combinations of 2 bits are realized the same number of times. FIG. 13 shows the timing chart.

As shown in FIG. 13, when the fluctuation is repeated in two cycles with positive and negative symmetry, for example, T1 measurement is performed when the output of the counting means is (1, 0) and the output of the fluctuation detecting means is a rising edge. Then, the T2 measurement is started at the fall of the fluctuation detecting means. The measured flow rate at this time is conceptually expressed as Q (i) = (A−B + C) − (− B
+ CD) = A + D. Then, the next measurement is T1
The measurement starts when the output of the counting means is (1, 1) and the fluctuation detecting means falls, and the T2 measurement starts at the subsequent rising. The measured flow rate at this time is conceptually expressed,
Q (i + 1) = (− B + CD) − (CD + A) = −
AB. Repeated measurement in this way gives Q
(I + 2) = (CD + A)-(-D + AB) = C +
B, Q (i + 3) = (-D + AB)-(AB + C)
= −CD. Here, Q (i) + Q (i + 1) +
Q (i + 2) + Q (i + 3) = 0, and the pressure fluctuation is cancelled. Although the description has been given of four measurements here, when the waveform of the pressure fluctuation is asymmetric and complicated, the start of the measurement is averaged by sequentially changing and repeating the start of the measurement according to the periodicity of the waveform, and the error is reduced. Can be minimized. Since measurement can be performed at all fluctuation timings, averaging is performed and the flow rate can be measured stably.

(Embodiment 5) FIG. 14 shows Embodiment 5 of the present invention.
FIG. 3 is a configuration diagram showing a flow meter of FIG. The difference from the first embodiment is
The cycle detecting means 37 for detecting the cycle of the signal of the fluctuation detecting means 29 and the measurement control means 30 for starting the measurement only when the cycle detected by the cycle detecting means 37 is a predetermined cycle are provided.

That is, as shown in FIG. 15, by starting the measurement only when the signal of the fluctuation detecting means 29 has the predetermined period Tm, the measurement can be performed at the predetermined fluctuation period even when the period fluctuates. Even in the case of the pressure waveform as shown in FIG. 13, if the cycle is detected, the flow rate can be measured only at a specific pressure fluctuation. Therefore, a stable flow rate can be measured in a short time even when the cycle of the pressure fluctuation is changed. The detection of the cycle is performed with a predetermined time width (for example, 2 milliseconds) so that the measurement is continued and the measurement is continued without interruption.

[0045]

As apparent from the above description, the flow meter according to the present invention has the following advantages.

According to the present invention, there is provided transmitting / receiving means provided in a flow path for transmitting / receiving a sound wave, time-measuring means for measuring a propagation time of the sound wave transmitted / received by the transmitting / receiving means, and detecting a flow rate based on the value of the time-measuring means. Flow rate detecting means, a fluctuation detecting means for measuring pressure fluctuations in the flow path by the transmitting and receiving means, and a measurement control means for starting measurement in synchronization with the timing of pressure fluctuations of the fluctuation detecting means, Since the pressure fluctuation in the flow path can be measured in at least one of the first vibration means and the second vibration means, there is no need to provide a pressure sensor, and the size and the flow path can be simplified. Even when pressure fluctuation occurs, a stable flow rate can be measured in a short time.

The first vibration means and the second vibration means provided in the flow path for transmitting and receiving a sound wave, the switching means for switching the transmission and reception operations of the first vibration means and the second vibration means, and the first vibration means A fluctuation detecting means for detecting a pressure fluctuation in the flow path of at least one of the means and the second vibrating means; a time measuring means for measuring a propagation time of a sound wave transmitted and received by the first vibrating means and the second vibrating means; When the output of the fluctuation detecting means changes by a predetermined amount, the time measuring means measures a first time T1 which propagates from the first vibrating means on the upstream side of the flow path to the second vibrating means on the downstream side, and the fluctuation detecting means When the output of the first time changes in reverse to the predetermined change, the time measuring means controls the second time measuring time T2 propagating from the second vibrating means on the downstream side of the flow path to the first vibrating means on the upstream side. Means and the first total Time said the T1 second measured time T2
With the flow rate detecting means for calculating the flow rate by using the pressure fluctuation, the phase of the pressure fluctuation and the timing of the measurement can be shifted by measuring at the timing when the change of the pressure fluctuation is reversed, and the measurement error due to the pressure fluctuation can be obtained. Can be offset.

When the output of the fluctuation detecting means changes by a predetermined amount, the measurement of the first clock time T1 is started, and when the output of the fluctuation detecting means changes in a direction opposite to the predetermined change, the measurement of the second clock time T2 is started. At the start of measurement control and the next measurement,
When the output of the fluctuation detecting means changes in reverse to the predetermined change, the measurement of the first clock time T1 is started, and when the output of the fluctuation detecting means changes by the predetermined time, the measurement of the second clock time T2 is started. The measurement control means and the first flow rate obtained by using the previous first time measurement time T1 and the second time measurement time T2 while alternately changing the measurement start, and the next first time measurement time T1 and second time measurement time T2. By providing the flow rate detecting means for calculating the flow rate by sequentially averaging the second flow rates obtained by using the above, the measurement timing is changed as described above to perform the first clock time T1 and the second clock time T2. Therefore, even if the pressure fluctuation is asymmetric on the high pressure side and the low pressure side, the influence of the pressure fluctuation can be canceled.

Further, by providing the repetition means for performing the transmission and reception by the sound wave a plurality of times, the number of times of measurement can be increased and the average can be obtained, so that the flow rate can be stably measured.

Further, by providing a repetition means for performing transmission and reception a plurality of times over an integral multiple of the fluctuation cycle, pressure fluctuations are averaged by measuring at the fluctuation cycle, and a stable flow rate can be measured.

A repetition means for starting transmission / reception measurement of sound waves when the output of the fluctuation detection means changes by a predetermined amount, and repeatedly performing transmission / reception measurement of sound waves until the output of the fluctuation detection means changes in the same manner as the predetermined change. By preparing, the start and stop of measurement can be matched with the cycle of pressure fluctuation,
Measurement can be performed in a fluctuation cycle, pressure fluctuations are averaged, and a stable flow rate can be measured.

Further, by providing the first vibrating means and the second vibrating means with a selecting means for switching between a case where the first vibrating means is used for transmitting and receiving a sound wave and a case where the first vibrating means is used for detecting a pressure fluctuation, the first vibrating means and the second vibrating means are provided. At least one can be used for pressure detection, and both flow measurement and pressure measurement can be achieved.

Further, by providing the fluctuation detecting means for detecting the vicinity of the zero of the AC component of the pressure fluctuation waveform, the range of the time for performing the flow measurement by detecting the fluctuation near the zero component of the pressure fluctuation is from the vicinity of the fluctuation near zero. Measurement can be started,
By performing the flow rate measurement within a time period in which the fluctuation is small, the measurement at the time of the pressure fluctuation can be stabilized.

Also, a plurality of bits of counting means for counting the variation of the output signal of the variation detecting means, and counting is performed so that the count value of the counting means is different between the first timekeeping and the second timekeeping. By providing the flow rate detecting means for measuring the flow rate when the combination of the above is realized the same number of times, the measurement can be performed at all the fluctuation timings, so that the averaging is performed and the flow rate can be stably measured.

Further, a cycle detecting means for detecting a cycle of a signal of the fluctuation detecting means, and a measuring control means for starting measurement only when the cycle detected by the cycle detecting means is a predetermined cycle is provided. By starting the measurement only at the time of, measurement can be performed at the time of a predetermined fluctuation, and a stable flow rate can be measured.

Further, when a signal from the fluctuation detecting means cannot be detected, a detection canceling means for automatically starting measurement after a predetermined time is provided. The flow rate can be measured.

Further, since the first vibrating means and the second vibrating means are constituted by piezoelectric vibrators, it is possible to detect pressure fluctuations by using the piezoelectric vibrator while using ultrasonic waves for transmission and reception.

[Brief description of the drawings]

FIG. 1 is a block diagram of a flow meter according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of the flow meter.

FIG. 3 is a timing chart showing the operation of the flow meter.

FIG. 4 is another timing chart showing the operation of the flow meter.

FIG. 5 is a flowchart showing the operation of the flow meter.

FIG. 6 is another flowchart showing the operation of the flow meter.

FIG. 7 is a block diagram showing the flow meter.

FIG. 8 is a timing chart showing the operation of the flow meter according to the second embodiment of the present invention.

FIG. 9 is a flowchart showing the operation of the flow meter.

FIG. 10 is a timing chart showing the operation of the flow meter according to the third embodiment of the present invention.

FIG. 11 is a flowchart showing the operation of the flow meter.

FIG. 12 is a block diagram illustrating a flow meter according to a fourth embodiment of the present invention.

FIG. 13 is a timing chart showing the operation of the flow meter.

FIG. 14 is a block diagram showing a flow meter according to a fifth embodiment of the present invention.

FIG. 15 is a flowchart showing the operation of the flow meter.

FIG. 16 is a block diagram showing a conventional flow meter.

FIG. 17 is a block diagram showing another conventional flow meter.

[Explanation of symbols]

 23 first piezoelectric vibrator (transmitting / receiving means, first vibrating means) 24 flow path 25 second piezoelectric vibrator (transmitting / receiving means, second vibrating means) 26 switching means 27 clocking means 28 flow detecting means 29 fluctuation detecting means 30 Measurement control means 31 selection means 34 repetition means 35 operation check means 36 counting means 37 cycle detection means

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shuji Abe 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 2F031 AC03 AD10 2F035 DA14 DA16 DA19 GA02

Claims (12)

[Claims] 1. A transmitting / receiving means provided in a flow path for transmitting and receiving a sound wave, a time measuring means for measuring a propagation time of a sound wave transmitted and received by the transmitting / receiving means, and a flow rate detecting means for detecting a flow rate based on a value of the time measuring means. A flowmeter comprising: means, a fluctuation detecting means for measuring fluctuations in the flow path by the transmission / reception means, and a measurement control means for starting measurement in synchronization with the fluctuation timing of the fluctuation detecting means. 2. A first vibration means and a second vibration means provided in a flow path for transmitting and receiving a sound wave, a switching means for switching transmission and reception operations of the first vibration means and the second vibration means, and the first vibration means A fluctuation detecting means for detecting a pressure fluctuation in the flow path in at least one of the first means and the second vibrating means;
A timer for measuring the propagation time of a sound wave transmitted and received by the vibration means and the second vibration means, and a second vibration downstream from the first vibration means on the upstream side of the flow path when the output of the fluctuation detecting means changes by a predetermined amount. The first time measuring time T1 propagating to the means is measured by the time measuring means, and when the output of the fluctuation detecting means changes in reverse to the predetermined change, the first vibrating means on the downstream side of the flow path from the first vibrating means on the upstream side Second time T that propagates to the vibration means
2. A flowmeter comprising: a measurement control means for controlling the measurement of the second time by the time measurement means; and a flow rate detection means for calculating a flow rate using the first time measurement time T1 and the second time measurement time T2. 3. When the output of the fluctuation detecting means changes by a predetermined amount,
(1) The measurement of the time measurement time T1 is started, and when the output of the fluctuation detecting means changes in reverse to the predetermined change, the second time measurement time T2
And measurement control for starting the measurement of the first time, and at the next measurement, the measurement of the first timed time T1 is started when the output of the fluctuation detecting means changes in reverse to the predetermined change, and the output of the fluctuation detecting means The measurement of the second time T2 is started when the measurement is started. The measurement control means performs measurement control, and the first flow rate obtained by using the previous first time T1 and the second time T2 while changing the measurement start alternately. 3. The flowmeter according to claim 2, further comprising a flow rate detecting means for calculating a flow rate by sequentially averaging a second flow rate obtained using the next first time measurement time T1 and second time measurement time T2. 4. The flowmeter according to claim 1, further comprising a repetition means for performing transmission and reception by a sound wave a plurality of times. 5. The flow meter according to claim 4, further comprising a repetition means for performing transmission and reception a plurality of times over an integral multiple of the fluctuation period. 6. A repetition means for starting transmission / reception measurement of a sound wave when the output of the fluctuation detection means changes by a predetermined amount, and repeatedly performing transmission / reception measurement of a sound wave until the output of the fluctuation detection means changes the same as the predetermined change. The flow meter according to claim 4, further comprising: 7. A method according to claim 1, further comprising a selecting means for switching between a case where the first vibrating means and the second vibrating means are used for transmitting and receiving a sound wave and a case where the first vibrating means is used for detecting a pressure fluctuation.
Flow meter according to the item. 8. The flowmeter according to claim 2, further comprising a fluctuation detecting means for detecting a vicinity of zero of an AC component of the pressure fluctuation waveform. 9. A multi-bit counting means for counting fluctuations of an output signal of a fluctuation detecting means, and measuring the count value of said counting means so as to be different between a first clock and a second clock. The flowmeter according to any one of claims 1 to 8, further comprising a flow rate detecting means for measuring a flow rate when the combination of the above is realized the same number of times. 10. A cycle detecting means for detecting a cycle of a signal from a fluctuation detecting means, and a measuring control means for starting measurement only when the cycle detected by the cycle detecting means is a predetermined cycle. 9. The flow meter according to any one of 8 above. 11. The flowmeter according to claim 1, further comprising detection canceling means for automatically starting measurement after a predetermined time when a signal from the fluctuation detecting means cannot be detected. 12. The flowmeter according to claim 1, wherein the transmitting / receiving means and the first and second vibrating means comprise a piezoelectric vibrator.