JPH08136296A - Flowmeter - Google Patents

Abstract

PURPOSE: To accurately measure a flow rate even in the state that a pressure change occurs due to disturbance in a flowmeter using a fluidic element. CONSTITUTION: A correction processor 55 obtains the frequency of a pressure change by using the output of a flow sensor 30 provided in the passage of a nozzle when a flow rate calculator 45 calculates the flow rate based on the pulse of a fluidic oscillation detected by a first piezoelectric film sensor 35, and compares the frequency of the change with that of the fluidic oscillation to judge whether the frequency of the oscillation is varied or not due to disturbance. When a change is recognized, it obtains a flowing velocity change width by using the output of the sensor 30, and corrects the flow rate calculated based on the output of the sensor 35 according to the varying width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter using a fluidic element, and more particularly to a flow meter capable of reducing the influence of disturbance.

[0002]

2. Description of the Related Art A fluidic flowmeter is known as a flowmeter used for gas meters and the like. This fluidic flow meter, on the downstream side of the nozzle that generates the jet flow, while forming a flow path expansion portion by a pair of side walls,
The return guides provided outside the side walls form a pair of feedback flow paths that guide the fluid that has passed through the nozzles along the outside of each side wall to the jet outlet side of the nozzles. The flow rate of the fluid is measured based on the frequency and period of the fluidic oscillation by utilizing the phenomenon of alternating flow in the path (referred to as fluidic oscillation in the present application). In this fluidic flow meter, for example, fluidic oscillation is detected by a piezoelectric film sensor, the output of this piezoelectric film sensor is pulsed, and for each pulse, the pulse period that is the time interval with the preceding pulse is obtained, The flow rate and the integrated flow rate are obtained from this pulse cycle.

FIG. 6 shows a pulse generated based on the output of the piezoelectric film sensor (hereinafter referred to as a pulse of the piezoelectric film sensor).
In the figure, reference symbols A to E represent pulse periods. In the fluidic flow meter, the reciprocal of the pulse period is multiplied by a correction coefficient to integrate the values to obtain the integrated flow rate.

Since this fluidic flowmeter has a not so wide measuring area, as shown in, for example, Japanese Patent Laid-Open No. 4-315916, a fluidic flowmeter and a thermal type flow velocity sensor (hereinafter referred to as a flow velocity sensor suitable for measuring a minute flow rate) are used. , And a flow sensor) have also been proposed. The flow sensor is a sensor that obtains the flow velocity by utilizing the fact that the movement of heat in the pipe is related to the flow velocity of the fluid flowing in the pipe. This flow sensor is arranged, for example, in the passage of the nozzle of the fluidic flow meter and detects the flow velocity in this passage.

[0005]

However, in such a fluidic flowmeter, due to disturbance such as pressure fluctuation on the upstream side, pressure fluctuation occurs in the fluid passing through the nozzle as shown in FIG. 7A. As a result, FIG. 7 (b)
As shown in, the frequency of the pulse of the piezoelectric film sensor is partially or wholly the frequency of the pressure fluctuation or ½ thereof.
Phenomenon that changes to. Then, there is a problem that an accurate flow rate and flow rate integration cannot be measured.

The present invention has been made in view of the above problems, and an object thereof is to provide a flow meter using a fluidic element, which is capable of accurately measuring the flow rate even when there is a pressure fluctuation due to a disturbance. It is to provide a flow meter.

[0007]

According to a first aspect of the present invention, there is provided a flowmeter having a flowmeter main body which forms a flow path extending from an inlet portion of a fluid to an outlet portion, and a flowmeter provided in the main body of the flowmeter. Including a nozzle that ejects, a fluidic oscillation generation unit that generates fluidic oscillation by the fluid ejected from this nozzle, and a fluidic oscillation detection sensor that detects the fluidic oscillation generated by this fluidic oscillation generation unit, A flow velocity sensor that detects the flow velocity of the fluid passing through the nozzle, a flow rate calculation unit that calculates the flow rate based on one of the output of the fluidic oscillation detection sensor and the output of the flow velocity sensor according to the flow rate, and the flow rate calculation unit. When calculating the flow rate based on the output of the fluidic oscillation detection sensor, the frequency of pressure fluctuation is calculated using the output of the flow velocity sensor. Obtained, comparing the frequency of this pressure fluctuation and the frequency of the fluidic oscillation to determine whether the frequency of the fluidic oscillation is changing due to disturbance, and when it is determined that the frequency of the fluidic sensor is changing, The flow rate fluctuation range is obtained using the output, and the correction processing means is provided for correcting the flow rate calculated based on the output of the fluidic oscillation detection sensor according to the flow rate fluctuation range.

In this flow meter, the fluidic oscillation detection sensor detects the fluidic oscillation, and the flow velocity sensor detects the flow velocity of the fluid passing through the nozzle. The calculation means calculates the flow rate based on one of the output of the fluidic oscillation detection sensor and the output of the flow velocity sensor according to the flow rate. Further, the correction processing means, when the flow rate calculation means is calculating the flow rate based on the output of the fluidic oscillation detection sensor, obtains the frequency of pressure fluctuation using the output of the flow velocity sensor, and determines the frequency of this pressure fluctuation. By comparing with the frequency of fluidic oscillation to determine whether the frequency of fluidic oscillation is changing due to disturbance, if it is determined to be changing, obtain the flow velocity fluctuation range using the output of the flow velocity sensor. , The flow rate calculated based on the output of the fluidic oscillation detection sensor is corrected according to the flow velocity fluctuation range. When there is pressure fluctuation due to disturbance, the error that occurs in the flow rate calculated based on the output of the fluidic oscillation detection sensor changes according to the flow speed fluctuation range.
Accurate measurement of the flow rate becomes possible by performing the correction according to the fluctuation range of the flow velocity.

A flowmeter according to a second aspect is the flowmeter according to the first aspect, wherein the flow velocity sensor is intermittently driven,
Further, the drive cycle of the flow velocity sensor when obtaining the frequency of pressure fluctuation and the flow velocity fluctuation range by the correction processing means is more than the drive cycle of the flow velocity sensor when the flow rate calculating means calculates the flow rate based on the output of the flow rate sensor. Is configured to be small.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a flow meter according to an embodiment of the present invention. The flowmeter according to the present embodiment is used as a gas meter. As shown in FIG. 1, the flow meter includes a main body 10 having an inlet portion 11 for receiving gas (gas) and an outlet portion 12 for discharging gas. A partition wall 13 is provided in the main body 10, and this partition wall 1
3 and the inlet portion 11 are formed with a first gas passage 14, and the partition wall 13 and the outlet portion 12 are provided with a second gas passage 15.
Are formed. An opening 16 is provided in the partition wall 13, and a shutoff valve 17 capable of closing the opening 16 is provided in the first gas flow path 14. A solenoid 18 is fixed to the outside of the main body 10, and a plunger 19 of the solenoid 18 penetrates a side wall of the main body 10 to shut off the shutoff valve 1.
It is joined to 7. Further, a spring 20 is provided around the plunger 19 between the shutoff valve 17 and the main body 10, and the spring 20 biases the shutoff valve 17 toward the opening portion 16 side.

In the second gas passage 15, there is provided a nozzle 21 which allows the gas received from the inlet 11 to pass therethrough to generate a jet flow. A rectifying member 22 for regulating the flow of gas is provided on the upstream side of the nozzle 21. In addition, a flow sensor 30, which is a thermal type flow velocity sensor, is arranged in the passage of the nozzle 21. Although not shown, the flow sensor 30 has a heat generating portion and two temperature sensors arranged upstream and downstream of the heat generating portion,
Two temperature sensors are used to obtain the flow rate corresponding to the flow velocity from the power supplied to the heat generating part required to keep the difference in temperature detected by the two temperature sensors constant, or to heat the heat generating part with a constant current or constant power. The flow rate is obtained from the difference in temperature detected by.

On the downstream side of the nozzle 21, a pair of side walls 23 and 24 forming an enlarged flow path are provided. A predetermined space is provided between the side walls 23, 24 so that the first target 25 is located upstream and the second target 26 is located downstream.
Are arranged respectively. The gas that has passed through the nozzle 21 is provided outside the side walls 23 and 24.
A return guide 29 that forms a pair of feedback flow paths 27, 28 for returning to the ejection port side of the nozzle 21 is provided along the outer peripheral portion of the. A pair of discharge passages 31 and 32 are formed between the outlet portions of the feedback flow passages 27 and 28 and the outlet portion 12 by the back surface of the return guide 29 and the main body 10. These nozzles 21
The portions from the discharge paths 31 and 32 correspond to the fluidic oscillation generation section in the present invention.

A pressure guiding hole 3 is provided in the vicinity of the jetting port of the nozzle 21.
3, 34 are provided. Further, on the outside of the bottom of the main body 10, as a fluidic oscillation detection sensor that communicates with the pressure guiding holes 33 and 34 via a pressure guiding path (not shown) and detects the differential pressure between the pressure guiding hole 33 and the pressure guiding hole 34. The piezoelectric film sensor 35 (not shown in FIG. 1) is provided.

FIG. 2 is a block diagram showing the configuration of the circuit portion of the flow meter shown in FIG. As shown in this figure, the flow meter has an A / D converter 4 for converting the output signal of the flow sensor 30 from analog to digital (hereinafter referred to as A / D).
2, an analog amplifier 43 that amplifies the output signal of the piezoelectric film sensor 35, a waveform shaping circuit 44 that waveform-shapes the output of the analog amplifier 43 to generate a pulse, and an output of the flow sensor 30 according to the flow rate ( A flow rate calculation unit 45 that calculates a flow rate and an integrated flow rate based on one of the output of the A / D converter 42) and the output of the piezoelectric film sensor 35 (output of the waveform shaping circuit 44), and the flow rate calculation unit 45. The display unit 46 for displaying the accumulated flow rate and the flow rate calculation unit 45 drive the solenoid 18 to drive the shutoff valve 17
And a shutoff valve control unit 47 for controlling the. The shutoff valve control unit 47 operates the solenoid 18 when the flow rate calculation unit 45 detects a flow rate of a predetermined amount or more, or detects a predetermined flow rate for a predetermined time or more, and causes the shutoff valve 17 to open the opening 16. To block the gas.

The flow meter further comprises a flow sensor 30, A /
D converter 42, waveform shaping circuit 44, and flow rate calculation unit 45
The correction processing unit 55 connected to the. The correction processing unit 55, when the flow rate calculation unit 45 calculates the flow rate based on the output of the piezoelectric film sensor 35, the flow sensor 3
The frequency of the pressure fluctuation is obtained using the output of 0, and the frequency of the pressure fluctuation is compared with the frequency of the fluidic oscillation to determine whether or not the frequency of the fluidic oscillation is changed by the disturbance, When it is determined that the flow rate fluctuation range is obtained using the output of the flow sensor 30, the flow rate calculated based on the output of the piezoelectric film sensor 35 is corrected according to the flow rate fluctuation range. There is. In order to reduce power consumption, the flow sensor 30 is normally driven intermittently at a cycle of, for example, 8 seconds. However, when the correction processing unit 55 obtains the pressure fluctuation frequency and the flow velocity fluctuation width, the correction processing unit By the control of 55, intermittent driving is performed at a minimum cycle, for example, a 0.1 second cycle.

The flow rate calculator 45 and the shutoff valve controller 47
The correction processing unit 55 is composed of, for example, a microcomputer.

Next, the operation of the flowmeter according to this embodiment will be described.

The gas received from the inlet portion 11 of the flow meter enters the nozzle 21 through the first gas passage 14, the opening 16, the second gas passage 15 and the rectifying member 22 in this order.
Then, the flow sensor 30 arranged in the passage of the nozzle 21 detects the flow velocity of the gas passing through the nozzle 21.

The gas passing through the nozzle 21 becomes a jet stream and is jetted from the jet outlet. The gas ejected from the ejection port flows along one side wall due to the Coanda effect. Here, it shall first flow along the side wall 23. The gas flowing along the side wall 23 is further fed back to the feedback channel 2
After returning to the ejection port side of the nozzle 21, the discharge passage 3
It is discharged from the outlet portion 12 via 1 At this time, the gas ejected from the nozzle 21 is changed in direction by the gas flowing through the feedback flow path 27, and now flows along the other side wall 24. The gas is further returned to the ejection port side of the nozzle 21 via the feedback flow path 28, and is discharged from the outlet section 12 via the discharge path 32. Then, the direction of the gas ejected from the nozzle 21 is changed by the gas flowing through the feedback flow passage 28, and the side wall 23 and the feedback flow passage 2 again.
It comes to flow along 7. By repeating the above operation, the gas passing through the nozzle 21 performs fluidic oscillation which alternately flows through the pair of feedback flow paths 27 and 28. The frequency and period of this fluidic oscillation have a correlation with the flow rate. The fluidic oscillation is detected by the piezoelectric film sensor 35.

The flow rate calculator 45 outputs the output (A / D) of the flow sensor 30 in the flow rate range on the small flow rate side where the range is set in advance.
The flow rate and the integrated flow rate are calculated based on the output of the converter 42, and the flow rate and the integrated flow rate are calculated based on the output of the piezoelectric film sensor 35 (the output of the waveform shaping circuit 44) in the flow rate range on the large flow rate side where the range is set in advance. Calculate the flow rate. The display unit 46 displays the integrated flow rate calculated by the flow rate calculation unit 45. Further, the shutoff valve control unit 47 operates the solenoid 18 to operate the shutoff valve 17 when the flow rate calculation unit 45 detects a flow rate of a predetermined amount or more, or when a predetermined flow rate is detected for a predetermined time or more.
The opening 16 is closed by the above, and the supply of gas to the downstream side of the flow meter is stopped.

Next, the operation of the correction processing section 55 will be described with reference to the flowchart of FIG. The correction processing unit 55 first determines whether or not the flow rate calculation unit 45 is measuring by the piezoelectric film sensor 35 (step S101), and when it is not measuring (N), shifts to another process (return). During measurement (Y), the drive cycle of the flow sensor 30 is set to 0.1 second (step S102), and the flow sensor 30 is operated for several seconds.
Find the measured value of. Then, the frequency of pressure fluctuation is obtained from the measurement value of the flow sensor 30 (step S103).
Since the flow velocity and the pressure have a corresponding relationship, the frequency of pressure fluctuation is the same as the frequency of flow velocity fluctuation. Correction processing unit 55
Next, the frequency of the pressure fluctuation obtained from the measurement value of the flow sensor 30 is compared with the frequency of the pulse input from the waveform shaping circuit 44, that is, the frequency of the fluidic oscillation, and the frequency of the fluidic oscillation due to disturbance is determined. It is determined whether or not it has changed (step S104). In addition,
Here, when the frequency of the fluidic oscillation is the same as or half of the frequency of the pressure fluctuation, it is determined that the frequency of the fluidic oscillation is changing due to disturbance. When it is determined that there is no change (N), the correction process is not performed, and the flow rate calculation unit 45 is made to calculate the flow rate and the integrated flow rate based on the pulse period of the piezoelectric film sensor 35 as usual (step S105). , Shift to other processing.

On the other hand, when it is determined that the frequency of the fluidic oscillation is changing due to the disturbance (step S10)
4; Y), the correction processing unit 55 obtains the flow velocity fluctuation width in the passage of the nozzle 21 from the measurement value of the flow sensor 30. The flow velocity fluctuation range can be obtained as a difference between the maximum value and the minimum value of the flow velocity. The correction processing unit 55 then
The measured flow rate based on the pulse period of the piezoelectric film sensor 35 calculated by the flow rate calculation unit 45 is corrected according to the flow velocity fluctuation width to obtain a corrected flow rate (step S107), and the process proceeds to another process. In this case, in the flow rate calculation unit 45, the correction processing unit 55
The integrated flow rate is calculated based on the corrected flow rate obtained by The operation shown in FIG. 3 is repeatedly executed in the operation of the entire flow meter.

Here, the correction method in the correction processing section 55 will be described with reference to FIGS. 4 and 5. FIG.
As shown in FIG. 5, when there is a pressure fluctuation due to a disturbance, the error generated in the measured flow rate based on the pulse period of the piezoelectric film sensor 35 calculated by the flow rate calculation unit 45 changes according to the flow velocity fluctuation width in the passage of the nozzle 21. To do. The larger the fluctuation range of the flow velocity, the larger the error is because the ratio of the pulse generated by the pressure fluctuation to the pulse generated by the fluidic oscillation increases. When the fluctuation width of the flow velocity exceeds the predetermined value W, the frequency of the pulse of the piezoelectric film sensor 35 completely changes to the frequency of the pressure fluctuation or ½ thereof, so that the error becomes constant. When the measured flow rate based on the pulse period of the piezoelectric film sensor 35 is Q _d and the correction coefficient is k, the correction processing unit 55 calculates the corrected flow rate Q _c as Q _c = k × Q _d.
Ask as. In this case, from the relationship shown in FIG.
As shown in, the correction coefficient k depends on the flow velocity fluctuation range. If it obtained in advance by measuring the relationship between the velocity variation range and the correction coefficient k, obtain a correction coefficient k from velocity fluctuation range, it is possible to obtain the correction flow rate Q _c from the above equation.

As described above, according to this embodiment,
In the state where there is pressure fluctuation due to disturbance, the measured flow rate based on the pulse period of the piezoelectric film sensor 35 calculated by the flow rate calculation unit 45 is corrected according to the flow velocity fluctuation width.
Accurate flow rate and integrated flow rate can be measured even when there is pressure fluctuation due to disturbance.

The present invention is not limited to the above embodiment, and for example, the flow sensor 30 is not limited to the one having a heat generating portion and two temperature sensors, and for example,
The temperature of the heat generating part is calculated by calculating the flow velocity from the power supplied to the heat generating part required to keep the temperature (resistance) of the heat generating part constant, or by heating the heat generating part with a constant current or constant power. It is also possible to obtain the flow velocity from (resistance).

The present invention can also be applied to a flow meter for measuring the flow rate of liquid as well as gas.

[0028]

As described above, according to the flow meter of the present invention, when the flow rate calculation means calculates the flow rate based on the output of the fluidic oscillation detection sensor, the correction processing means causes the flow rate sensor Determine the frequency of pressure fluctuations using the output, compare the frequency of this pressure fluctuation with the frequency of the fluidic oscillation, determine whether the frequency of the fluidic oscillation is changing due to disturbance, and determine that it is changing. When judged, the flow velocity fluctuation range is calculated using the output of the flow velocity sensor, and the flow rate calculated based on the output of the fluidic oscillation detection sensor is corrected according to the flow velocity fluctuation range. There is an effect that an accurate flow rate can be measured even when there is a pressure fluctuation due to.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a flow meter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of the flow meter of FIG.

FIG. 3 is a flowchart showing an operation of a correction processing unit in FIG.

4 is a characteristic diagram showing the relationship between the flow velocity fluctuation width in the nozzle passage of FIG. 1 and the error in the measured flow rate based on the pulse period of the piezoelectric film sensor.

5 is a characteristic diagram showing a relationship between a correction coefficient used in the correction processing unit in FIG. 2 and a flow velocity fluctuation range.

FIG. 6 is a waveform diagram showing pulses of a piezoelectric film sensor in a fluidic flow meter.

FIG. 7 is a waveform diagram for explaining a phenomenon in which the pulse frequency of the piezoelectric film sensor changes due to disturbance.

[Explanation of symbols]

 21 nozzle 30 flow sensor 33, 34 pressure guide hole 35 piezoelectric film sensor 45 flow rate calculation unit 55 correction processing unit

Claims (2)

[Claims] 1. A fluid ejected from this nozzle, which includes a flowmeter main body that forms a flow path from a fluid inlet to an outlet, and a nozzle that is provided in the flowmeter main body and ejects the fluid. A fluidic oscillation generator that generates a fluidic oscillation by the fluidic oscillation detector, a fluidic oscillation detection sensor that detects the fluidic oscillation generated by the fluidic oscillation generator, and a flow velocity sensor that detects the flow velocity of the fluid passing through the nozzle. A flow rate calculation means for calculating a flow rate based on one of the output of the fluidic oscillation detection sensor and the output of the flow velocity sensor according to the flow rate; and the flow rate calculation means based on the output of the fluidic oscillation detection sensor. When calculating the flow rate by using the output of the flow velocity sensor, calculate the frequency of pressure fluctuation and calculate the frequency of this pressure fluctuation. Number and the frequency of the fluidic oscillation is compared to determine whether the frequency of the fluidic oscillation is changing due to disturbance, and when it is determined that the frequency is changing, the output of the flow velocity sensor is used to change the flow velocity. Find the width,
A flowmeter, comprising: a correction processing unit that corrects the flow rate calculated based on the output of the fluidic oscillation detection sensor in accordance with the flow velocity fluctuation range. 2. The flow rate sensor is driven intermittently, and the drive cycle of the flow rate sensor when the frequency of pressure fluctuation and the width of flow rate fluctuation are obtained by the correction processing means is such that the flow rate calculation means outputs the flow rate sensor. The flowmeter according to claim 1, wherein the flowmeter is smaller than a drive cycle of the flow velocity sensor when the flow rate is calculated based on.