JP3627722B2 - Flowmeter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow meter that measures the flow rate of a liquid or gas, and more particularly to a flow meter that accurately measures a flow value even when a flow rate fluctuation occurs.
[0002]
[Prior art]
Conventionally, this type of flowmeter has been known as disclosed in JP-A-9-15006. The configuration will be described below with reference to FIG. As shown in FIG. 5, a sampling program 2 that reads a measured value every predetermined first sampling time from an analog flow sensor 1 that measures a gas flow rate, and a gas consumption calculation program 3 that calculates a gas consumption flow rate at a predetermined time, The average value calculation program 4 for reading the measurement value of the analog flow sensor every second sampling time within the predetermined time within the first sampling time and calculating the average value, and estimating the pressure fluctuation period from the output of the flow sensor It consists of a pressure fluctuation period estimation program 5 and a RAM 6 as a memory. Here, 7 is a ROM of a memory for storing each program, and 8 is a CPU for executing the program. With this configuration, the measurement process is performed so that the predetermined measurement time is one or more times the vibration period of the pump or a multiple of that period. It is hard to be configured.
[0003]
[Problems to be solved by the invention]
However, in the above-described prior art, it is necessary to estimate the period and change the measurement time every time the fluctuation period changes, and it is difficult to adapt when the fluctuation period changes, and a sophisticated CPU for complicated estimation program processing And the current consumption is increased.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a flow rate measuring means for measuring the flow rate in the flow path, and a measurement control means for measuring the flow rate a plurality of times in a cycle shorter than the pulsation cycle of the pressure pulsation generated in the flow path. And it was set as the structure provided with the flow volume detection means which calculates | requires an average flow volume from the said multiple times of measurement flow volume, and makes it a measurement flow volume.
[0005]
According to the above invention, even if the frequency of the pressure fluctuation generated in the flow path changes, measurement is performed in a short time that is equal to or longer than the fluctuation cycle, so that the influence can be reduced and stable flow measurement can be realized. it can.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a pair of sound wave transmission / reception means provided in a flow path for transmitting / receiving sound waves, and a first repetition of repeatedly performing a transmission / reception operation of transmitting sound waves from one of the sound wave transmission / reception means and receiving it by the other sound wave transmission / reception means A first time measuring means for measuring transmission / reception time measured by the first repeating means, and a transmission / reception operation in which a sound wave is transmitted from the other sound wave transmitting / receiving means and received by the one sound wave transmitting / receiving means. 2 repetition means, 2nd time measuring means for measuring the transmission / reception time measured by the 2nd repetition means, and the operation of the first repetition means and the second repetition means as one unit of measurement. A third repeating means for repeatedly performing, a switching means for switching the transmission / reception relationship between the first repeating means and the second repeating means, and the first time counting means after being repeated by the third repeating means. Measurement time and second time A flow rate detecting means for detecting a flow rate based on the value of the measurement time of the stage, and generating a measurement cycle determined in the flow path by the switching means and the first repeating means or the second repeating means It was set as the structure provided with the measurement control means to measure with a period shorter than the pulsation period of the pressure pulsation to do. Thereby, even if the frequency of the pressure fluctuation generated in the flow path changes, measurement is performed in a short time that is equal to or longer than the fluctuation cycle, so that the influence can be reduced and stable flow measurement can be realized.
[0007]
Further, the measurement control means controls so that the total measurement time when repeated by the third repeat means substantially coincides with the period width of the pressure pulsation change. By setting the total measurement time to be a predetermined time, when the pulsation period changes at a predetermined interval, stable flow rate measurement can be performed in any pulsation period.
[0008]
Further, by setting the measurement cycle by the measurement control means in the range of 0.002 seconds to 0.05 seconds, it is possible to accurately measure low frequency pulsations. Note that, by setting 0.005 seconds as the optimum setting, pulsations with a frequency lower than 200 Hz can be accurately measured.
Further, the measurement control means randomly controls the timing at which the first repeating means is first operated within a predetermined time. By controlling at random, it is possible to accurately measure pulsations with a constant period.
[0009]
Furthermore, the measurement control unit sets control to allow random operated within 3 seconds. By randomly measuring in the range of 3 seconds, low-frequency pulsations can be measured randomly, and the influence of pulsations can be suppressed and measured accurately. Note that 2 seconds is the optimum setting.
[0010]
Further, the first repeating means, the second repeating means, the first timing means, and the second timing means are also used, and the number of repetitions is set to the same number. And by setting to the same frequency | count, a measurement time interval is stabilized and a highly accurate flow volume measurement can be performed.
[0011]
Further, the number of repetitions of the first repeating unit and the second repeating unit was set to two. And by setting it twice, the influence of the reflected wave of the sound wave can be reduced, and the flow rate can be measured with higher accuracy.
[0012]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
Example 1
FIG. 1 is a block diagram of a flow meter according to a first embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a first vibrator as a sound wave transmitting / receiving unit provided in the flow path 9 to transmit / receive a sound wave, 11 a second vibrator as a sound wave transmitting / receiving unit, and 12 a first transducer 10 and the first vibrator. Switching means for alternately switching the transmission / reception relationship of the two vibrators 11, 13 is a first repeating means for repeatedly transmitting a signal received by the second vibrator 11 using the first vibrator 10 as a transmitting means, Second repeating means for repeatedly transmitting a signal received by the first vibrator 10 using the second vibrator 11 as a transmitting means, 15 is a first for measuring a transmission / reception time measured by the first repeating means 13. Time measuring means, 16 is a second time measuring means for measuring the transmission / reception time measured by the second repeating means, and 17 is an operation using the operations of the first repeating means and the second repeating means as one unit of measurement. 3rd repeating means to repeat, 18 is the front A flow rate detecting means for detecting a flow rate based on the value of time measured by the second time measuring means 16 and the measurement time of the first time counting means 15 after it has been repeated by the third repeating unit. Reference numeral 19 denotes measurement control means for measuring the measurement cycle determined by the switching means and the first repeat means or the second repeat means with a period shorter than the pulsation period of the pressure pulsation generated in the flow path. Here, the flow rate measuring means for measuring the flow rate from the propagation time of the sound wave is an ultrasonic flow rate measuring device and shows the whole.
[0014]
Next, operation | movement and an effect | action are demonstrated using FIGS. 2-4. As shown in FIG. 2, the flowmeter of the present invention starts measurement by the repeat start signal of the first repeater 13 and inputs the transmission signal to the first vibrator 10. And the 1st vibrator | oscillator 10 vibrates and radiates | emits an ultrasonic wave, and the 2nd vibrator | oscillator 11 receives. Then, the first time measuring means counts the propagation time during this period with a predetermined clock, and measures the time. The delay time in the figure is a waiting time for waiting for the sound wave to decay, and is set to a predetermined time. Then, after detecting a value obtained by counting the delay time and the propagation time, a transmission signal is input to the first transducer 10 again, an ultrasonic wave is transmitted, and repeated measurement received by the second transducer 11 is performed a predetermined number of times. Here, the number of repetitions will be described as two. And the 1st time measuring means measures the measurement time 1 of two transmission / reception operations. Here, by setting the number of repetitions to two times, there is an effect that the influence of the reflected wave which is reflected by the transducer on the receiving side and further reciprocated once can be removed.
[0015]
Then, the direction of transmission / reception is switched by the switching means 12. That is, measurement is started by the next repetition start signal of the second repetition means 14, and the transmission signal is input to the second vibrator 11. Then, the first vibrator 10 receives the ultrasonic wave that the second vibrator 11 vibrates and radiates the ultrasonic wave. Then, the time is measured while the second time measuring means counts the propagation time during this period with a predetermined clock. The measurement time 2 when this transmission / reception operation is repeated twice is measured.
[0016]
The third repeater 17 performs a plurality of measurements using the repeat operation of the first repeater 13 and the second repeater 14 as one measurement unit. Then, the flow rate is calculated based on a predetermined formula from the reciprocal difference between the measurement time 1 of the first time measuring means and the measurement time 2 of the second time measuring means after this repeated operation.
[0017]
Here, as shown in FIG. 3, the measurement period determined by the switching time of the switching means and the total time of the first repeating means or the second repeating means is the pulsation of pressure pulsation generated in the flow path. By measuring at a cycle shorter than the cycle, it is possible to follow the fluctuation speed of the pressure pulsation, and to measure the flow rate with high accuracy. The measurement cycle is preferably set to ½ or less of the pressure pulsation cycle, but can be measured with sufficient accuracy even with a cycle slightly smaller than the pressure pulsation cycle. For example, it is preferable to set the measurement cycle in the range of 0.002 seconds to 0.05 seconds, but if the optimum value is about 0.005 seconds (strictly, it is 0.00468 seconds, it varies depending on the flow rate) The pressure pulsation can be measured up to about 200 Hz. By changing the measurement cycle, there are cases where the measurement time can be reduced, and responding to the frequency of the generated pulsation has the effect of reducing power consumption. FIG. 4 shows a pressure pulsation waveform and a timing chart of measurement.
[0018]
Further, if it is known that the pressure pulsation changes with a predetermined period width, the flow rate can be accurately measured in any period by making the total measurement time coincide with the changing period width. This is because the total measurement time is an integral multiple of the pressure pulsation cycle, and the measurement time is a common multiple of the pressure pulsation cycle, so that measurement can be realized for each cycle. For example, when the rotational speed is controlled every 100 rpm as in the case of control of a gas engine, the pressure pulsation changes every 0.833 Hz. In this case, by setting the total measurement time to 1.2 seconds, the pressure pulsation can be measured in units of cycles at any number of rotations, so that the measurement accuracy during pulsation is greatly improved. In addition, the average time can be shortened, and highly accurate flow rate measurement can be realized in a short time.
[0019]
Next, measurement control means for randomly controlling the timing at which the first repeating means is first operated will be described. If the timing of the repetition start signal output at the beginning of the measurement is repeated at a predetermined time interval, the measurement is always performed at the same timing, and only a specific part of the pressure pulsation may be repeatedly measured. Therefore, by making the measurement start timing random, it is possible to avoid measurement of only a specific portion. Since the measured flow rate is averaged by starting at random, the measured flow rate value measured for a predetermined time is highly accurate. For example, when the pressure pulsation is 200 Hz, it may be random within a range of 0.005 seconds, and when it is 0.5 Hz, it is necessary to randomize within a range of 2 seconds. Therefore, when performing over a wide frequency range from low frequency to high frequency, it is desirable to perform random measurement in a range of 3 seconds considering a low frequency of about 0.3 Hz. And although the number which distributes at random is large, it can measure accurately, but there also exists the subject that measurement time takes long. Therefore, it is desirable to set from 8 to 256 values of 2 to the power of n, from the ability of the microcomputer or the like to operate the measurement control means. As the optimum value, 8 values, 64 values, 128 values, etc. are recommended.
[0020]
Here, the first repeating means and the second repeating means are described as separate means, but they do not operate at the same time, so if they are configured to be used by switching, one repeating means is used. Can also be used. As a result, the same number of repetitions can be set, and the measurement accuracy can be improved.
[0021]
In this way, by measuring with a cycle shorter than the pulsation cycle of the pressure pulsation generated in the flow path, pressure fluctuations generated in the flow path can be followed quickly, and even if the frequency changes, the effect Can be reduced, and stable flow rate measurement can be realized. By controlling the total measurement time to be a predetermined time, when the pulsation cycle changes at a predetermined interval, stable flow rate measurement can be performed in any pulsation cycle. And a pulsation can be measured more accurately by setting a measurement period to a period shorter than the pulsation period of the pressure pulsation which generate | occur | produces in a flow path. Further, by randomly controlling the timing at which the third repeating means is operated, it is possible to accurately measure pulsations with a constant period. Furthermore, by setting the number of repetitions of the first repetition unit and the second repetition unit to the same number, the measurement time interval can be stabilized and highly accurate flow rate measurement can be performed. This flow meter can measure the flow rate on pipes connected to devices that generate pressure pulsations such as gas engines, such as a gas meter, and is accurate even if pulsation occurs, and shortens the measurement cycle. Therefore, a short measurement time can be obtained, so that instantaneous measurement can be realized. As a result, a security function such as gas leak detection can be realized with high accuracy and in a fast time.
[0022]
【The invention's effect】
As described above, according to the flowmeter of the present invention, the following effects can be obtained.
[0023]
The present invention includes a flow rate measuring means for measuring a flow rate in a flow path, a measurement control means for performing flow rate measurement a plurality of times in a cycle shorter than a pulsation cycle of pressure pulsation generated in the flow path, and the plurality of measured flow rates. A flow rate detecting means for obtaining an average flow rate to obtain a measured flow rate was provided. And even if the frequency of the pressure fluctuation which generate | occur | produces in a flow path changes, the influence can be lessened by measuring with a short period, and the stable flow measurement can be implement | achieved.
[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 timing chart for explaining the operation of the flow meter. FIG. 3 is a timing explanatory diagram for explaining the operation of the flow meter. Pulsation waveform and measurement timing chart explaining flow meter operation [Fig. 5] Block diagram showing a conventional flow meter [Explanation of symbols]
9 Channel 10 First vibrator (Sound wave transmission / reception means)
11 Second vibrator (sound wave transmission / reception means)
12 switching means 13 first repeating means 14 second repeating means 15 first timing means 16 second timing means 17 third repeating means 18 flow rate detecting means 19 measurement control means

Claims (7)

A pair of sound wave transmitting / receiving means provided in the flow path for transmitting / receiving sound waves; a first repeating means for repeatedly transmitting / receiving sound waves from one of the sound wave transmitting / receiving means and received by the other sound wave transmitting / receiving means; A first timing unit for measuring a transmission / reception time measured by the first repeating unit; and a second repeating unit for repeatedly performing a transmission / reception operation in which a sound wave is transmitted from the other sound wave transmitting / receiving unit and received by the one sound wave transmitting / receiving unit. And a second time measuring means for measuring a transmission / reception time measured by the second repeating means, and a second measuring means for repeatedly performing the operations of the first repeating means and the second repeating means as one unit of measurement. 3 repeater means, switching means for switching the transmission / reception relationship between the first repeater means and the second repeater means, the measurement time of the first timer means after being repeated by the third repeater means, Measurement of the second timing means A flow rate detecting means for detecting a flow rate based on a value between them, and a pressure pulsation that generates a measurement cycle determined by the switching means and the first repeating means or the second repeating means in the flow path A flow meter provided with a measurement control means for measuring at a cycle shorter than the pulsation cycle. The flowmeter according to claim 1, wherein the measurement control unit further controls the total measurement time when the measurement is repeated by the third repeating unit so as to substantially match the period width of the pressure pulsation change . The flow meter according to claim 1 or 2, wherein a measurement cycle by the measurement control means is in a range of 0.002 seconds to 0.05 seconds. The flowmeter according to any one of claims 1 to 3 , wherein the measurement control unit randomly controls a timing at which the first repeating unit is first operated within a predetermined time. The flowmeter according to claim 4 , wherein the measurement control means can set a random operation within a range of 3 seconds. Shared with the first repeating unit and the second repeating unit and the first counting means and the second timing means, any one of claims 1 to 5 to set their number of repetitions to the same number of times The flow meter according to item 1. The flowmeter according to claim 6 , wherein the number of repetitions of the first repeating unit and the second repeating unit is set to two.

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