JPH08136302A - Flowmeter - Google Patents

Abstract

PURPOSE: To measure a small flow-rate region with less amount of power consumption and without being affected by dust and moisture excessively by providing a fluidic oscillation detection sensor, a connecting hole, a differential pressure sensor, and a flow-rate operation means. CONSTITUTION: Connecting holes 41 and 42 are provided at the upstream/ downstream sides of a nozzle 21 and at the same time a throttle part 43 is provided near the entrance of the nozzle 21. The differential pressure between the connecting holes 41 and 42 is detected by a second piezoelectric film sensor. Then, the flow-rate at a small flow-rate region is calculated by a second flow- rate operation part based on the output of the sensor and the throttle part 43, thus measuring the flow rate at a small flow-rate region with a flowmeter using a fluidic flowmeter. The second piezoelectric film sensor consumes extremely less power as compared with a flow sensor and is not directly exposed in the flow of gas and hence is in a structure for achieving a stable operation without excessively affected by dust and water, thus improving reliability and durability without excessively affected by dust and moisture.

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 flow meter, and more particularly to a flow meter capable of measuring in a small flow range.

[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).

Since this fluidic flow meter has a very small measuring area, as shown in, for example, Japanese Patent Application Laid-Open No. 4-315916, a fluidic flow meter and a thermal type flow velocity sensor suitable for measuring a minute flow rate (hereinafter , 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. Then, the flow rate in a small flow rate range that cannot be measured by the fluidic flow meter is obtained from the relationship between the flow velocity and the flow rate obtained from the result of measurement in advance.

[0004]

However, in a flowmeter using such a fluidic flowmeter and a flow sensor together, the flow sensor consumes a relatively large amount of power, and therefore a large-scale power supply is required for long-term use. There is a problem that it is necessary to use it, or it is necessary to devise such as intermittently driving the flow sensor in order to save power, which is costly and troublesome.

Further, since the main part of the flow sensor is exposed in the flow of fluid, there is a problem that a flow meter for measuring the flow rate of gas is vulnerable to dust and humidity in the gas.

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 flow meter, which consumes less power and is less affected by dust and humidity. It is to provide a flow meter capable of measuring a small flow range.

[0007]

According to a first aspect of the present invention, there is provided a flowmeter, wherein the flowmeter main body forms a flow path from an inlet portion of a fluid to an outlet portion, and a flowmeter is provided in the main body of the flowmeter to eject the fluid. A fluidic oscillation generation unit that generates a fluidic oscillation by a fluid ejected from this nozzle, a fluidic oscillation detection sensor that detects the fluidic oscillation generated by this fluidic oscillation generation unit, and a nozzle Based on the output of the fluid pressure oscillation detection sensor and the differential pressure sensor that detects the differential pressure between the pressure guiding holes, and the flow rate in the large flow rate range. And a second flow rate calculation means for calculating the flow rate in the small flow rate range based on the output of the differential pressure sensor.

In this flow meter, the fluidic oscillation detection sensor detects the fluidic oscillation, and the first flow rate calculation means calculates the flow rate in the large flow rate region based on the output of the fluidic oscillation detection sensor. Further, the differential pressure sensor detects the differential pressure between the pressure guiding holes provided on the upstream side and the downstream side of the nozzle,
The second flow rate calculation means calculates the flow rate in the small flow rate range based on the output of the differential pressure sensor.

A flowmeter according to a second aspect is the flowmeter according to the first aspect, further comprising a throttle mechanism capable of changing a throttle opening degree corresponding to a cross-sectional area with an inlet portion of the nozzle. The second flow rate calculating means is configured to calculate the flow rate based on the throttle opening degree by the throttle mechanism and the output of the differential pressure sensor.

[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
The gas flow path 14 is formed between the inlet 3 and the inlet portion 11, and the gas flow path 15 is formed between the partition wall 13 and the outlet portion 12. An opening 16 is provided in the partition wall 13, and the gas flow path 14
A shutoff valve 17 capable of closing the opening 16 is provided therein. A solenoid 18 is fixed to the outside of the body 10, and a plunger 19 of the solenoid 18 is
Is penetrated through the side wall and is joined to the shutoff valve 17. Also,
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 16.

In the gas flow path 15, there is provided a nozzle 21 which allows the gas received from the inlet portion 11 to pass therethrough to generate a jet flow. On the downstream side of the nozzle 21, a pair of side walls 23, 24 forming an enlarged flow path are provided. A first target 25 is arranged on the upstream side and a second target 26 is arranged on the downstream side, with a predetermined space between the side walls 23 and 24. The gas that has passed through the nozzle 21 is provided outside the side walls 23 and 24, respectively.
A return guide 29 that forms a pair of feedback flow paths 27 and 28 that returns to the ejection port side of the nozzle 21 is provided along the outer peripheral portion of the nozzle 4. Feedback channel 2
A pair of discharge passages 31 and 32 are formed between the outlet portions of 7 and 28 and the outlet portion 12 by the back surface of the return guide 29 and the main body 10. The portions from these nozzles 21 to the discharge paths 31 and 32 correspond to the fluidic oscillation generator of the present invention.

A pressure guide hole 3 is provided in the vicinity of the nozzle 21 outlet.
3, 34 are provided outside the bottom of the main body 10 to communicate with the pressure guiding holes 33, 34 via pressure guiding paths (not shown) and detect the pressure difference between the pressure guiding holes 33 and 34. First piezoelectric film sensor 35 as a Dick oscillation detection sensor
(Not shown in FIG. 1) is provided.

Pressure guide holes 41 and 42 are provided on the upstream side and the outlet part 12 of the nozzle 21, respectively, and communicated with the pressure guide holes 41 and 42 on the outer side of the bottom of the main body 10 via a pressure guide path (not shown). Then, a second piezoelectric film sensor 50 (not shown in FIG. 1) is provided as a differential pressure sensor that detects the differential pressure between the pressure guiding hole 41 and the pressure guiding hole 42.

In the vicinity of the inlet of the nozzle 21, the nozzle 21
A throttle portion 43 for changing the throttle opening degree corresponding to the cross-sectional area between the inlet and the inlet is provided. This throttle 43
One end of a shaft 44 is connected to. Shaft 4
The other end side of 4 penetrates the side wall of the main body 10 and is connected to an actuator 45 provided outside the side wall of the main body 10. The actuator 45 drives the shaft 4
4 by advancing and retracting, the throttle portion 43 and the nozzle 21
The throttle opening corresponding to the cross-sectional area between the inlet and the inlet can be changed.

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 flowmeter includes an analog amplifier 51 for amplifying the output signal of the first piezoelectric film sensor 35, and a waveform shaping circuit 52 for shaping the output of the analog amplifier 51 to generate a pulse. ,
A first flow rate calculation unit 53 that calculates the flow rate in a large flow rate range based on the output of the waveform shaping circuit 52, and an analog amplifier 5 that amplifies the output signal of the second piezoelectric film sensor 50.
4 and a second flow rate calculator 55 that calculates the flow rate in the small flow rate range based on the output of the analog amplifier 54.

The flow meter further includes an integrated flow rate calculation section 56 for calculating an integrated flow rate based on one of the output of the first flow rate calculation section 53 and the output of the second flow rate calculation section 55, and this integrated flow rate calculation section. A display unit 57 that displays the integrated flow rate calculated by 56, and a shutoff valve control unit that is controlled by the first flow rate computing unit 53 and the second flow rate computing unit 55 to drive the solenoid 18 and control the shutoff valve 17. And 58.
The shutoff valve control unit 58, for example, when the flow rate calculation unit 53 or the flow rate calculation unit 55 detects a flow rate of a predetermined amount or more, or a predetermined flow rate for a predetermined time or more, the solenoid 1
8 is operated so that the opening 16 is closed by the shutoff valve 17 to shut off the gas.

The second flow rate calculation unit 55 drives the actuator 45 according to the calculated flow rate, and the throttle opening degree by the throttle unit 43 is stepwise or continuously so that the throttle opening degree becomes smaller as the flow rate becomes smaller. And the flow rate in the small flow rate range is calculated based on the throttle opening and the output of the second piezoelectric film sensor 50 (output of the analog amplifier 54).

The first flow rate calculation unit 53, the second flow rate calculation unit 55, the integrated flow rate calculation unit 56, and the shutoff valve control unit 5 are provided.
8 is constituted by, 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 flowmeter enters the nozzle 21 through the gas passage 14, the opening 16 and the gas passage 15 in this order. The gas that has passed through the nozzle 21 becomes a jet 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 returned to the ejection port side of the nozzle 21 via the feedback flow path 27, and is discharged from the outlet portion 12 via the discharge path 31. At this time, the direction of the gas ejected from the nozzle 21 is changed by the gas flowing through the feedback channel 27,
This time it will flow along the other side wall 24. This gas further passes through the feedback flow path 28, and the nozzle 2
1 is returned to the jet outlet side, passes through the discharge passage 32, and exit portion 12
Is more exhausted. Then, the direction of the gas ejected from the nozzle 21 is changed by the gas flowing through the feedback channel 28, and the gas flows again along the side wall 23 and the feedback channel 27. 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 first piezoelectric film sensor 35. First
The flow rate calculation unit 53 calculates the flow rate in the large flow rate range based on the period of the pulse output from the waveform shaping circuit 52.

Further, a pressure loss occurs due to the gas passing through the nozzle 21, and a differential pressure is generated between the upstream side and the downstream side of the nozzle 21. This differential pressure is proportional to the square of the flow rate.
Therefore, if the relationship between the differential pressure and the flow rate is measured and grasped in advance, the flow rate can be obtained from the differential pressure. In the present embodiment, the second piezoelectric film sensor 50 detects the pressure difference between the pressure guiding holes 41 and 42 provided on the upstream side and the downstream side of the nozzle 21, respectively. The second flow rate calculation unit 55 calculates the flow rate in the small flow rate range based on the output.

When the pressure loss in the nozzle 21 becomes small, the measurement accuracy of the flow rate deteriorates. The throttle unit 43 is provided near the inlet, and the second flow rate calculation unit 55 drives the actuator 45 in accordance with the calculated flow rate, so that the throttle opening degree becomes smaller as the flow rate becomes smaller. The diaphragm opening by the diaphragm unit 43 is changed.
Further, when the throttle opening degree by the throttle unit 43 changes, the output of the second piezoelectric film sensor 50 changes even if the flow rate is the same, so the second flow rate calculation unit 55 causes the throttle opening degree and the second piezoelectric film sensor 50 to change. The flow rate is calculated based on the output of the membrane sensor 50 (output of the analog amplifier 54). The relationship between the throttle opening and the output of the second piezoelectric film sensor 50 and the flow rate is measured and obtained in advance.

The integrated flow rate calculation unit 56 includes a large flow rate measurement area by the first flow rate calculation unit 53 and a second flow rate calculation unit 55.
A measurement area on the small flow rate side is set in advance, and based on one of the flow rate calculated by the first flow rate calculation section 53 and the flow rate calculated by the second flow rate calculation section 55 in accordance with this measurement area. To calculate the integrated flow rate. The display unit 57 displays the integrated flow rate calculated by the integrated flow rate calculation unit 56. In addition, the shutoff valve control unit 58 uses the first flow rate calculation unit 53.
Alternatively, when the second flow rate calculation unit 55 detects a flow rate equal to or higher than a predetermined amount, or when the predetermined flow rate is detected for a predetermined time or longer, the solenoid 18 is operated and the shutoff valve 17 closes the opening 16 to change the flow rate. The supply of gas to the downstream side of the meter is stopped.

As described above, according to this embodiment,
The pressure guide holes 41, 4 are provided on the upstream side and the downstream side of the nozzle 21, respectively.
2 is provided, and the throttle portion 43 is provided near the inlet of the nozzle 21.
Is provided and the differential pressure between the pressure guiding holes 41 and 42 is detected by the second piezoelectric film sensor 50. Based on the output of the second piezoelectric film sensor 50 and the diaphragm opening by the diaphragm unit 43, Since the flow rate calculator 55 calculates the flow rate in the small flow rate range, it is possible to measure the flow rate in the small flow rate range in the flow meter using the fluidic flow meter.

Further, since the second piezoelectric film sensor 50 for detecting the differential pressure consumes much less power than the flow sensor, continuous measurement is possible with a small-scale power source, and the flow sensor has a Since it is not necessary to intermittently drive, it is possible to reduce cost and labor.

Further, in this embodiment, the second piezoelectric film sensor 50 communicates with the pressure guiding holes 41 and 42 through the pressure guiding path and is not directly exposed in the gas flow, so that the gas is not exposed. Since the second piezoelectric film sensor 50 itself has a structure that allows stable operation without being much influenced by dust, moisture, etc., while being less attached by dust, moisture, etc., it is much influenced by dust and humidity. Without any increase in reliability and durability.

Further, in the vicinity of the inlet of the nozzle 21, the throttle 4 is provided.
By providing 3, the pressure guiding hole 41,
Since the differential pressure between 42 can be increased, the measurement range can be expanded.

The present invention is not limited to the above embodiment,
For example, the throttle unit 43 is fully opened when the flow rate is in the measurement region of the first flow rate calculation unit 53, and the flow rate is the second flow rate calculation unit 5.
In the case of the measurement area of 5, the switching may be performed in two steps so that the predetermined aperture is opened.

The position of the pressure guide hole 41 on the upstream side of the nozzle 21 is the nozzle 2 if the flow is stable.
It can be anywhere on the upstream side of 1. Further, the position where the pressure guiding hole 42 is provided on the downstream side of the nozzle 21 is preferably the outlet portion 12 where the flow is stable.

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

[0032]

As described above, according to the flowmeter of the first aspect, pressure guide holes are provided on the upstream side and the downstream side of the nozzle, and the differential pressure between the pressure guide holes is detected by the differential pressure sensor. However, since the flow rate in the small flow rate range is calculated by the second flow rate calculating means based on the output of the differential pressure sensor, the flow meter using the fluidic flow meter consumes less power and generates less dust. There is an effect that the flow rate can be measured in a small flow rate range without being affected by the humidity and humidity.

According to a second aspect of the flowmeter, a throttle mechanism capable of changing the throttle opening corresponding to the cross-sectional area between the nozzle and the inlet portion is provided, and the second flow rate calculating means is provided. Since the flow rate is calculated based on the throttle opening degree by this throttle mechanism and the output of the differential pressure sensor, in addition to the above effect, it is possible to increase the differential pressure between the pressure guiding holes at a small flow rate, There is an effect that the measurement range can be expanded.

[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 a flow meter according to an embodiment of the present invention.

[Explanation of symbols]

 21 Nozzle 33, 34 Pressure Guide Hole 35 First Piezoelectric Membrane Sensor 41, 42 Pressure Guide Hole 43 Restrictor 44 Shaft 45 Actuator 50 Second Piezoelectric Membrane Sensor 53 First Flow Rate Calculation Section 55 Second Flow Rate Calculation Section

Claims (2)

[Claims] 1. 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 that ejects a fluid. A fluidic oscillation generation unit that generates a fluidic oscillation, a fluidic oscillation detection sensor that detects a fluidic oscillation generated by the fluidic oscillation generation unit, and 2 provided on the upstream side and the downstream side of the nozzle, respectively. One pressure guide hole, a differential pressure sensor for detecting a differential pressure between the pressure guide holes, and a first flow rate calculation means for calculating a flow rate in a large flow rate range based on the output of the fluidic oscillation detection sensor, A second flow rate calculating means for calculating a flow rate in a small flow rate range based on the output of the differential pressure sensor. 2. A throttle mechanism capable of changing a throttle opening degree corresponding to a cross-sectional area between the nozzle and the inlet portion, wherein the second flow rate calculating means is configured by the throttle mechanism. The flowmeter according to claim 1, wherein the flowrate is calculated based on the output of the differential pressure sensor.