JPH07234140A - Fluidic flowmeter - Google Patents

Abstract

PURPOSE:To reduce the effect of pressure fluctuations on an upstream side by stabilizing fluidic oscillation. CONSTITUTION:The gas received from the inlet part 11 of a fluidic flowmeter passes-through a first gas passage 14 and an opening part 16 to reach the nozzle 21 within a second gas passage 15. The gas ejected from the nozzle 21 is branched by the end part on the upstream side of a target part 51 to be guided to feedback passages 27, 28 by guide walls 51a, 51b to alternately flow through the feedback passages 27, 28. The frequency of the changeover in the flow directions of the gas is detected on the basis of the outputs of pressure sensors 33, 34 and a flow rate is measured on the basis of this frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidic flowmeter used for gas meters and the like, and more particularly to a fluidic flowmeter having means for reducing the influence of pressure fluctuations on the upstream side.

[0002]

2. Description of the Related Art A fluidic flow meter has a flow passage expanding portion formed by a pair of side walls on the downstream side of a nozzle for generating a jet flow, and a fluid passing through the nozzle by a return guide provided on the outside of the side wall. Forming a pair of feedback flow paths that lead to the jet outlet side of the nozzle along the outer side of each side wall, and a fluid that has passed through the nozzle alternately flows through the pair of feedback flow paths (hereinafter referred to as fluidic oscillation). The flow rate of the fluid is measured based on the frequency of switching of the flow direction of the fluid that has passed through the nozzle (hereinafter referred to as oscillation frequency).

By the way, in a flow meter used as a gas meter, fluctuation (pulsation) of gas pressure generated by a device connected to the downstream side of the flow meter is prevented from being transmitted to the metering section of the flow meter or the upstream side of the flow meter. , At the outlet of the flowmeter, a diaphragm or punching metal (a metal plate with a large number of holes),
A porous plate made of sintered metal or the like, or a plate provided with a buffer channel such as a rubber tube has been proposed.

[0004]

However, when a flow meter is used as a gas meter, pressure fluctuations occur on the upstream side of the flow meter depending on the state of the nearby gas meter and the usage status of the nearby gas. Conventionally, the pressure fluctuation on the upstream side of the flowmeter has not been considered. When the flow rate of gas with pressure fluctuation on the upstream side is measured by a fluidic flow meter, the oscillation frequency of the fluidic flow meter is disturbed by the pressure fluctuation on the upstream side, for example, the oscillation frequency of the fluidic flow meter is on the upstream side. There is a case where the frequency of the pressure fluctuation at 1 or the frequency of half of the pressure fluctuation changes. Therefore, the error of the measured flow rate becomes large,
There was a problem that the flow rate could not be measured.

As a method of reducing the influence of such pressure fluctuations on the upstream side, it is conceivable to stabilize the fluidic oscillation by devising the internal structure of the fluidic flowmeter. For example, Japanese Patent Laid-Open No. 1-25072
As shown in Japanese Patent Publication No. 5, in front of the nozzle outlet,
It is possible to stabilize the fluidic oscillation by providing a target that branches the fluid ejected from the nozzle.

FIG. 5 shows an essential part of an example of a fluidic flowmeter having such a target. In this fluidic flow meter, a pair of side walls 23 and 24 that form an enlarged flow path are provided on the downstream side of the nozzle 21, and a predetermined space is provided between the side walls 23 and 24 to upstream side. The first target 25 and the second target 26 are disposed on the downstream side. In addition, a pair of feedback flow paths 27 and 28 are formed outside the side walls 23 and 24 to return the fluid passing through the nozzle 21 to the ejection port side of the nozzle 21 along the outer peripheral portions of the side walls 23 and 24. A guide 29 is provided. In addition, the 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. Further, pressure sensors 33 and 34 for detecting switching of the flowing direction of the fluid that has passed through the nozzle 21 are provided near the ejection ports, respectively.

However, in the fluidic flowmeter having such a structure, there are spaces between the first target 25 and the second target 26 and between the second target 26 and the return guide 29, so that the side walls 23, Two
A part of the fluid flowing along 4 flows into these spaces, and the flow returning to the ejection port side of the nozzle 21 becomes weak. As a result, there is a problem that the fluidic oscillation tends to become unstable when there is a pressure fluctuation on the upstream side of the fluidic flow meter.

The present invention has been made in view of the above problems, and an object thereof is to stabilize fluidic oscillation,
An object of the present invention is to provide a fluidic flow meter capable of reducing the influence of pressure fluctuation on the upstream side.

[0009]

A fluidic flowmeter according to the present invention is provided with an inlet portion for receiving a fluid, a nozzle for passing a fluid received from the inlet portion to generate a jet flow, and a downstream side of the nozzle. A pair of side walls forming an enlarged flow path, and a pair of feedback flow paths provided outside the side walls for returning the fluid that has passed through the nozzles to the ejection port side of the nozzles along the outer side of each side wall. A return guide that is formed, an outlet that discharges the fluid that has passed through the feedback channel, a detection unit that detects the switching of the flowing direction of the fluid that has passed through the nozzle, and a pair of side walls that are provided between the side wall and the nozzle. Provided between the target for branching the fluid and the pair of side walls and on the downstream side of the target, and guiding the fluid branched by the target to the feedback channel. It is obtained and two of the guide wall of the eye.

In this fluidic flow meter, the fluid that has passed through the nozzle is branched by the target and guided to the feedback channel by the guiding wall. Thereby, fluidic oscillation is stably performed.

The fluidic flowmeter according to claim 2 is
In the fluidic flow meter according to claim 1, the guide wall is continuously provided between the target and the return guide.

[0012]

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 fluidic flow meter according to the first embodiment of the present invention. The present embodiment is an example of a fluidic flow meter used as a gas meter. As shown in FIG. 1, the fluidic flow meter of this embodiment 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 the partition wall 13
The first gas flow path 14 is formed between the inlet 11 and
A second 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 a valve 1 capable of closing the opening 16 in the first gas flow path 14.
7 is provided. 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 and is joined to the valve 17. When the solenoid 18 is demagnetized, the valve 1
7 is separated from the opening 16, the opening 16 is opened, and when the solenoid 18 is in the excited state, the plunger 19 projects and the valve 17 closes the opening 16.

In the second gas passage 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. A rectifying member 22 that regulates the flow of gas is provided on the upstream side of the nozzle 21. On the downstream side of the nozzle 21, a pair of side walls 23, 24 forming an enlarged flow path are provided. This side wall 23, 24
A target portion 51 that acts as a target and a guiding wall is provided between the two. Also, the side walls 23, 2
The gas that has passed through the nozzle 21 is provided outside each of the side walls 2
A return guide 29 is provided along the outer peripheral portions of 3, 24 to form a pair of feedback flow paths 27, 28 for returning to the ejection port side of the nozzle 21. 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.

The target section 51 includes a return guide 29.
In addition to being integrated, the width gradually increases from the upstream end to the return guide 29. Then, the upstream end of the target portion 51 acts as a target, and from this end, the return guide 2
Two wall surfaces up to 9 serve as two guide walls 51a and 51b for guiding the gas branched by the target to the feedback flow paths 27 and 28.

In addition, pressure sensors 33 and 34 as detecting means for detecting the switching of the flow direction of the gas passing through the nozzle 21 are provided in the vicinity of the ejection port of the nozzle 21.

FIG. 2 is a block diagram showing the configuration of the circuit portion of the fluidic flow meter of this embodiment. As shown in this figure, the fluidic flowmeter is provided with each pressure sensor 33,
Flow rate calculator 41 that inputs the output of 34 and calculates the flow rate
And a display unit 42 that displays the flow rate calculated by the flow rate calculation unit 41, and is controlled by the flow rate calculation unit 41.
And a solenoid drive circuit 43 for driving the solenoid 18. The flow rate calculation unit 41 uses, for example, each pressure sensor 3
The outputs of 3 and 34 are binarized and pulsed, the number of pulses per unit time is counted, the switching frequency of the flowing direction of the gas passing through the nozzle 21 is obtained, and this frequency is converted into a flow rate. Further, the fluidic flow meter of the present embodiment has a safety function when used as a gas meter, for example, when the flow rate calculation unit 41 detects a flow rate of a predetermined amount or more, or when a predetermined flow rate is detected for a predetermined time or more, etc. In addition, the solenoid drive circuit 43 is operated to excite the solenoid 18, and the valve 17 closes the opening 16 to shut off the gas. The flow rate calculation unit 41 is realized by, for example, a microcomputer.

Next, the operation of the fluidic flow meter of this embodiment will be described.

The gas received from the inlet portion 11 of the fluidic flow meter is the first gas flow path 14 and the opening portion 16.
To enter the second gas flow path 15. The gas that has entered the second gas flow path 15 passes through the rectifying member 22 and the nozzle 2
1, and becomes a jet flow and is ejected from the nozzle 21.
The gas ejected from the nozzle 21 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 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. This gas is further fed back to the feedback channel 28.
Through the discharge path 32 of the nozzle 21.
And then discharged from the outlet section 12. Then, the nozzle 21
The gas ejected from the feedback flow channel 2 this time.
The gas flowing in 8 changes its direction and again flows along the side wall 23 and the feedback flow path 27. By repeating the above operation, the gas passing through the nozzle 21 alternately flows through the pair of feedback flow paths 27 and 28. The switching frequency of the gas flow direction has a correspondence with the flow rate. The frequency at which the flow direction of the gas passing through the nozzle 21 is switched is determined by the pressure sensor 3
It is calculated by the flow rate calculation unit 41 based on the outputs of 3 and 34. The flow rate calculation unit 41 calculates the flow rate from the obtained frequency and displays it on the display unit 42. In addition, the flow rate calculation unit 41
Is the solenoid drive circuit 43 when a flow rate of a predetermined amount or more is detected, or when a predetermined flow rate is detected for a predetermined time or more.
Is operated to excite the solenoid 18, the opening 16 is closed by the valve 17, and the supply of gas to the downstream side of the fluidic flow meter is stopped.

By the way, in the fluidic flow meter of this embodiment, the target portion 51 is provided between the two side walls 23 and 24.
The gas that has passed through the nozzle 21 is branched at the upstream end of the target portion 51, and the side wall 2
3, 24 and guide walls 51a and 51b of the target unit 51
And are guided to the feedback channels 27 and 28.
In the present embodiment, the side walls 23, 24 are provided between the upstream end of the target portion 51 and the return guide 29.
There is no space for a part of the fluid flowing along to flow into. Therefore, according to the fluidic flowmeter of the present embodiment, the flow returning to the ejection port side of the nozzle 21 via the feedback flow paths 27 and 28 becomes strong, and fluidic oscillation is stably performed. Therefore, even if the gas pressure fluctuates on the upstream side of the fluidic flow meter, it is possible to accurately measure the flow rate.

Further, in the fluidic flowmeter of this embodiment, since fluidic oscillation is stably performed, accurate flowrate can be measured even when the flowrate is small.

FIG. 3 is a sectional view showing the structure of the essential part of the fluidic flow meter of the second embodiment of the present invention. In this embodiment, in the fluidic flowmeter of the first embodiment, a target 52 separate from the return guide 29 is provided instead of the target portion 51, and the target 52 is also provided.
Two guiding walls 53 and 54 are provided between the first and the second guides. Two guide walls 5
The interval between 3 and 54 gradually increases from the upstream side to the downstream side. Other configurations, actions and effects are first
It is similar to the embodiment.

FIG. 4 is a sectional view showing the structure of the essential part of a fluidic flowmeter according to the third embodiment of the present invention. In this embodiment, in the fluidic flowmeter of the first embodiment, a target portion 56 separate from the return guide 29 is provided instead of the target portion 51. The target portion 56 has a shape in which the width gradually increases from the upstream end portion to the downstream end portion. The upstream end of the target portion 56 acts as a target, and the two wall surfaces from the upstream end to the downstream end feed the gas branched by the target to the feedback flow path 27. Two guiding walls 56 for leading to 28
a and 56b.

In this embodiment, although there is a space between the target portion 56 and the return guide 29, the guide wall 56 is provided.
As compared with the example shown in FIG. 5, due to the actions of a and 56b, the flow returning to the ejection port side of the nozzle 21 via the feedback flow paths 27 and 28 becomes stronger, and the fluidic oscillation is stabilized. Other configurations, operations and effects are similar to those of the first embodiment.

The present invention is not limited to the above-described embodiments, and for example, instead of the pressure sensors 33 and 34, the difference between the pressure at the position of the pressure sensor 33 and the pressure at the position of the pressure sensor 34 is obtained. A pressure sensor may be provided.

In each of the above embodiments, the fluidic flowmeter for measuring the flow rate of gas such as gas has been described. However, the fluidic flowmeter of the present invention serves as a flowmeter for measuring the flow rate of not only gas but also liquid. Can also be used.

[0027]

As described above, according to the fluidic flow meter of the present invention, the fluid that has passed through the nozzle is branched by the target and guided to the feedback flow path by the guiding wall, so that fluidic oscillation is stable. Therefore, it is possible to reduce the influence of the pressure fluctuation on the upstream side.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a fluidic flow meter according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a circuit portion of the fluidic flow meter according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a configuration of a main part of a fluidic flow meter according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a main part of a fluidic flow meter according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a main part of an example of a fluidic flowmeter having a target.

[Explanation of symbols]

 11 inlet part 12 outlet part 21 nozzle 23, 24 side wall 27, 28 feedback channel 29 return guide 33, 34 pressure sensor 51 target part 51a, 51b guiding wall

Claims (2)

[Claims] 1. An inlet part for receiving a fluid, a nozzle for passing the fluid received from the inlet part to generate a jet flow, and a pair of side walls provided on the downstream side of the nozzle and forming an enlarged flow path. And a return guide that is provided on the outside of the side wall and forms a pair of feedback flow paths for returning the fluid that has passed through the nozzles to the ejection port side of the nozzle along the outside of each side wall, and the feedback flow path. An outlet for discharging the fluid that has passed through, a detection unit that detects switching of the flowing direction of the fluid that has passed through the nozzle, a target that is provided between the pair of sidewalls, and that branches the fluid that has passed through the nozzle, It is provided between the pair of side walls and downstream of the target, and guides the fluid branched by the target to the feedback channel. A fluidic flowmeter characterized by comprising the two guiding walls of the. 2. The fluidic flow meter according to claim 1, wherein the guide wall is continuously provided between the target and the return guide.