JP2000241206A - Fluid vibration type flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid vibration type flow meter wherein the sensitivity is raised at a very low flow rate range with possibly minimizing influences of fluid vibrations on oscillations in a fluidic element. SOLUTION: A fluid entrance 1 located at the upstream of a nozzle unit 6 forming a nozzle 7 of a fluidic element is provided with a channel 2 for measuring a low flow rate having a smaller are than the flow cross sectional area of the nozzle 7, a flow sensor 16 capable of measuring the flow rate of a fluid flowing in the channel 2 is disposed at this channel 2, the opening width the channel 2 is set greater than the opening width of the nozzle 7, the opening height the channel 2 is set less than the opening height of the nozzle 7, and a detection end 16a of the flow sensor 16 is disposed facing a passage on a larger plane in the width or height direction of the channel 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid vibration type flow meter, mainly a gas meter for measuring a fluid flow rate using a fluidic element.

[0002]

2. Description of the Related Art Conventionally, in a fluid vibration type flow meter, a fluid element does not oscillate or oscillates in a small flow rate region, making it difficult to measure a small flow rate. To compensate for this, a device provided with a thermal flow sensor is used. In such a fluid vibration type flow meter, the flow sensor is disposed on one inner wall surface in the height direction in the flow path of the nozzle forming the jet of the fluidic element. And the lower limit flow rate in the micro flow rate area could not be reduced sufficiently. This is because the cross section of the nozzle cut at right angles to the flow direction of the nozzle is a rectangle having a large aspect ratio. For example, the ratio of the length of the long side (that is, the opening length of the nozzle) of the flow path cross section to the length of the short side (that is, the opening width of the nozzle) is about 10. As shown schematically in FIG. 8, the flow velocity of the fluid along the side wall surface in such a flow path is determined by the long side L and the short side S of the flow path cross section of the nozzle.
The problem is that the detection level of the flow velocity that can be detected at the side wall portion on the short side S side is extremely low.

As a countermeasure for solving this problem, a recess is formed at one end of the nozzle 7 in the height direction, as shown in FIG. It has been proposed to provide an enlarged flow path portion 7c formed to increase the flow path width (see Japanese Patent Application Laid-Open No. 4-326016). In the enlarged flow path portion 7c, the detection end 16a of the flow sensor 16 is disposed on the side wall surface 9 on the one end side so as to face the flow path, and is respectively recessed into the end of the opposed nozzle forming surface 7a. An arcuate surface is formed, and the opening width at the one end is about twice the nozzle opening width. This is a measure against the fact that the width of the flow sensor 16 occupies more than half of the nozzle opening width.
Although the sensitivity of No. 6 is said to have increased, there is a problem in that the nozzle forming surface 7a is not flat over the entire height. That is, the oscillation of the fluid vibration may be hindered due to the uneven width of the jet of the fluid ejected from the nozzle ejection surface 7b.

Therefore, as shown in FIG. 10 which shows a plane cross section along the flow path axis of the nozzle portion 6, the flow sensor 16 is provided on one side wall surface 9 in the height direction in the nozzle 7 of the fluidic element 5.
It has been proposed to dispose the nozzle and divide the flow path of the nozzle 7 into two parts so as to make the respective flow path resistances different (for example, see Japanese Utility Model Laid-Open No. 6-74925). In the fluid vibration type flow meter shown in FIG.
A partition 6b for dividing the flow path of the nozzle 7 in the height direction is provided, and divided into a large flow area flow path section 7e having a large height and a small flow area flow path section 7d having a small height. The flow sensor 16 is arranged on the side wall surface 9 on the side of the small flow rate channel 7d. That is, the aspect ratio of the small flow rate channel 7d is close to 1. Further, the large flow rate channel section 7
In e, a wire mesh 8 is placed on the inlet side to increase the flow path resistance. In this manner, by increasing the flow resistance of the large flow rate flow path 7e at the small flow rate, the flow velocity of the fluid in the small flow rate area at the small flow rate flow path 7d is increased, and the flow sensor 16 for the small flow rate is increased. In this case, the sensitivity to a very small flow rate is improved. When the flow rate becomes large, the pressure loss in the small flow rate flow path 7d increases, so that the flow rate of the fluid in the large flow rate flow path 7e increases in the large flow rate range. The flow rate of is approached.

[0005]

However, in the above-mentioned conventional structure, the nozzle portion 6 is formed so as to be divided into the two flow passage portions 7d and 7e.
Is covered with a wire mesh 8 on the inlet side, so that the nozzle 6
Was not easy to assemble, and there was a problem with workability. Further, since the flow distribution of the two flow paths 7d and 7e depends on the flow rate, the flow rate of the fluid increases even if the sensitivity of the flow sensor 16 can be maintained in a minute flow rate range. Accordingly, when the main flow shifts to the large flow rate flow path 7e side, there is a possibility that a difference occurs in the flow velocity of the jet flow from the flow paths 7d and 7e, and the fluid vibration in the fluidic element 5 Occasionally, oscillation may be hindered. Therefore, there is a problem that it is difficult to maintain the measurement accuracy of the fluidic element 5.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fluid vibration type flowmeter which has an improved sensitivity in a minute flow rate region while minimizing the influence of fluid vibration on oscillation in a fluidic element.

[0007]

[Means for Solving the Problems] A first feature of the fluid vibration type flow meter according to the present invention according to the first aspect is that the fluid oscillation type flowmeter has a structure upstream of a nozzle portion forming a nozzle of a fluidic element. The fluid introduction portion located on the side, the small cross-sectional flow portion for measuring a small flow rate of the cross-sectional area smaller than the flow cross-sectional area of the nozzle, and facing the small cross-sectional flow portion, the small cross-section It is configured to include a flow sensor capable of measuring a flow rate of a fluid flowing in the flow path portion, and an opening width of the small cross-section flow path portion,
Wider than the opening width of the nozzle, the opening height of the small-section flow path portion is set smaller than the opening height of the nozzle,
The detection end of the flow sensor is located on the large-side surface in the width direction or the height direction of the small-section flow path portion, facing the flow path.

A second characteristic configuration of the fluid vibration type flow meter according to the present invention according to claim 2 is that the flow sectional area S2 of the small sectional flow path portion and the flow sectional area S2 of the nozzle in the first characteristic structure are different.
The relationship with n is such that 0.35 ≦ S2 / Sn ≦ 0.50 is satisfied.

A third aspect of the fluid vibration type flowmeter according to the present invention according to the third aspect is the fluid oscillation type flow meter according to the first aspect or the second aspect, wherein the small cross section is provided in the fluid introduction portion provided with the small section flow path section. Separate from the flow path, formed coaxially with the nozzle,
The point is that a slit-shaped flow path portion in the height direction of the opening of the nozzle is formed.

According to a fourth aspect of the fluid vibration type flow meter of the present invention, the two flow paths are provided between the slit-shaped flow path and the small-section flow path in the third characteristic. The point is that a separating wall portion is formed.

According to the first feature configuration of the fluid vibration type flow meter according to the present invention, the sensitivity of the flow sensor in a very small flow rate region is minimized while minimizing the influence on the fluidic element. Can be increased. In other words, by forming a small-section flow passage portion having a smaller flow passage cross-sectional area than the flow passage cross-sectional area of the nozzle in the fluid introduction portion on the upstream side of the nozzle portion, while avoiding the influence on the fluid flow in the nozzle, By increasing the flow velocity of the fluid in the small cross-section flow path portion, it becomes possible to increase the sensitivity of the flow sensor disposed there. In addition, by disposing the flow sensor facing the flow path on the wall surface on the side of either the opening width or the opening height of the small cross-section flow path portion, the position where the flow velocity distribution along the wall surface is maximized The flow velocity can be measured by the above, and the sensitivity of the flow sensor can be increased. In addition, since the distance between the opening of the small-section flow path portion and the opening of the nozzle is large, the flow velocity distribution in the direction of the opening width of the nozzle does not expand at the position of the nozzle outlet. The adverse effects can be reduced.

According to the second characteristic configuration of the fluid vibration type flow meter according to the present invention, while exerting the effects of the first characteristic configuration, the influence of the fluidic element on the oscillation of the fluid vibration can be suppressed. It is possible to increase the sensitivity of the flow measurement in the minute flow range. That is, by forming the relationship between the flow path cross-sectional area S2 of the small cross-section flow path portion and the flow path cross-sectional area Sn of the nozzle so as to satisfy 0.35 ≦ S2 / Sn ≦ 0.50, It is possible to prevent the uniformity of the jet from the nozzle from being affected, while maintaining the detected flow velocity of the fluid in the flow path portion sufficiently high. For example, the flow path cross-sectional area S2 and the flow path cross-sectional area S
If the relationship with n is S2 / Sn <0.35, the flow of the fluid to the nozzle is too biased,
If the relationship between the flow path cross-sectional area S2 and the flow path cross-sectional area Sn satisfies S2 / Sn> 0.50, the jet flow may be partially non-uniform. In some cases, the effect of increasing the sensitivity of the flow sensor may be somewhat diminished due to the shortage of the flow velocity in the micro flow rate region.

According to the third characteristic configuration of the fluid vibration type flowmeter according to the present invention, the oscillation of the fluid vibration in the fluidic element can be stabilized while exhibiting the operation and effect of the first characteristic configuration or the second characteristic configuration. Can be done. That is,
Even though the fluid introduction unit has a small-section flow path that can increase the sensitivity of the flow sensor, the flow of the fluid from the slit upper flow path can eliminate the bias of the fluid reaching the nozzle. . Therefore, the jet flow from the nozzle can have a flat flow velocity distribution in the height direction of the opening of the nozzle.

According to the fourth aspect of the fluid vibration type flow meter according to the present invention, it is possible to further enhance the sensitivity of the flow sensor in a minute flow rate range while exhibiting the operation and effect of the third aspect. Become. In other words, by dividing the small cross-section flow path portion and the slit upper flow path portion by the partition wall portion, the small cross-section flow path portion can be formed into a flow path having an independent rectangular flow path cross section. It is possible to form a fluid flow that is not deviated in the height direction. Therefore, the flow sensor arranged on the large-sized wall surface can measure the flow velocity at the position of the maximum flow velocity. In particular, according to the third characteristic configuration, since the detection end of the flow sensor can be arranged on the side wall surface of the nozzle portion, the adverse effect on the flow velocity distribution of the jet from the nozzle due to the arrangement of the detection end is minimized. And the nozzle section can be easily assembled, and the workability in assembling the fluid vibration type flowmeter can be prevented while reducing the accuracy and sensitivity of the flow rate measurement in the minute flow rate range. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fluid vibration type flow meter according to the present invention will be described. FIG. 1 is a plan view sectional view showing an example of a gas meter using the fluid vibration type flow meter according to the present invention. FIG. 2 is a plan view sectional view of the fluid vibration type flow meter shown in FIG. FIG. 4 is a partially cutaway perspective view of the fluid introduction part, and FIG. 4 is an exploded perspective view of the fluid introduction part. 9 and FIG. 10 used in the above-described conventional technique are denoted by the same reference numerals as those shown in FIG. 9 and FIG. And a part of the detailed description is omitted.

A gas meter which is an example of the above flow meter is shown in FIG.
As shown in FIG. 1, a fluid vibration type flow meter 26 for measuring a flow rate using a fluidic element 5 is used. In this gas meter 20, the inflow direction I of the fluid f to be measured is
It is configured to be 180 ° opposite to the outflow direction O. That is, the fluid f such as gas, water, etc.
Path 2 having a pressure fluctuation absorbing mechanism 25
2 to the shutoff valve section 23. And this shutoff valve part 2
The fluid f having passed through 3 flows into the reservoir 24. The fluid f that has flowed into the storage unit 24 is configured to flow out of the device outlet 27 via the fluid vibration type flow meter 26. The fluid f flowing into the fluid vibration type flow meter 26 flows into the nozzle 7 from the fluid introduction path 6a via the fluid introduction section 1 of the nozzle section 6 forming the nozzle 7 of the fluidic element 5. The fluid f ejected from the nozzle 7 into the fluidic element 5 changes the direction of the jet and vibrates, and the fluid expanding portion 13 provided on the downstream side of the nozzle ejection surface 7b, the throttle Channel section 1
4 and flows out toward the device outlet 27. In the fluid vibration type flow meter 26, a pair of fluid vibration detection ends 10 for detecting the vibration of the jet flow are arranged on both sides of the nozzle 7 and near the nozzle ejection surface 7b. The fluid vibration detecting end 10 is an opening formed with a small diameter, and communicates with a fluid vibration detecting sensor having a pair of pressure introducing portions to detect fluid vibration.

As shown in FIG. 2, for example, the shape of the fluidic element 5 is such that the enlarged channel portion 13 is formed between the enlarged channel forming members 12 arranged with the channel axis Z as the axis of symmetry. A target 11 is provided at the center of the flow path of the flow path expanding section 13 to prevent the jet flowing from the nozzle 7 from going straight, and the throttle flow path section 1 is provided downstream of the flow path expanding section 13.
4 are provided. In the nozzle 7, both inner side surfaces in the nozzle width direction are formed by a nozzle forming surface 7a parallel to the flow channel axis Z, and the nozzle ejection surface 7b is formed in a state orthogonal to the flow channel axis Z. I have. The enlarged flow path forming member 1
2 has a center on a parallel straight line separated by a predetermined distance downstream from the nozzle ejection surface 7b, and a center spaced equidistantly from the flow channel axis Z. The sub-arc portion 12a formed by a pair of sub-arcs having a flat surface portion 12b formed by a tangent to the outside of the sub-arc and having a tangent approaching the flow axis Z on the nozzle ejection surface 7b side. Connected to form the inner surface. The sub-arc part 1
The rear end portion 2a is formed as a discharge arc portion 12c that smoothly connects the sub-arc portion 12a to the throttle channel portion 14. The target 11 is arranged at a position separated from the nozzle ejection surface 7b by a predetermined distance, and has an effect of stably switching the flow direction of the jet flow in the micro flow region.

By the way, in the flow rate region on the small flow rate side, the fluid f of the return flow tends to accumulate near the nozzle ejection surface 7b in response to the ejection from the nozzle 7 of the fluidic element 5, and this causes the fluid vibration. In order to avoid obstruction, the enlarged flow path forming member 12 forms a relief path 15 on the back side of the enlarged flow path forming member 12 by partially removing the vicinity of the nozzle ejection surface 7b, and forms the return flow. By branching near the nozzle ejection surface 7b, a part of the return flow is
It is made to flow out of the relief path 15 as a branch flow.

In the fluidic element 5, the jet flow jetted from the nozzle jetting surface 7 b branches off from the main flow of the jet flowing out of the throttle channel portion 14 bypassing the side of the target 11, It collides with a downstream portion of the flow channel expanding portion 13 or a reduced cross-sectional portion forming the throttle flow channel portion 14, and returns inside the flow channel along the inner surface of the expanded flow channel forming member 12 to the nozzle 7 side. When the return flow flows back toward the nozzle ejection surface 7b, the return flow flows in the vicinity of the nozzle ejection surface 7b in a direction orthogonal to the straight traveling direction of the jet and opposite to the swing direction of the jet. Directional fluid energy is applied, causing the jet to swing in the opposite direction. By repeating this, fluid oscillation occurs, and the oscillation cycle is inversely proportional to the fluid flow rate. Therefore, since the pressure difference between the pair of fluid vibration detection ends 10 arranged near the nozzle ejection surface 7b is proportional to the square of the flow velocity of the jet, the fluid vibration is measured by the capacitance type pressure vibration sensor. By detecting and measuring the frequency, an attempt is made to measure the flow rate of the fluid f flowing through this flow path.

As shown in FIG. 3 in which the nozzle portion 6 is viewed obliquely from the nozzle forming surface 7a side, a fluid introduction portion 1 is provided in a fluid introduction passage 6a located on the upstream side of the nozzle portion 6.
A small flow rate having a smaller cross-sectional area than the cross-sectional area of the flow path of the nozzle 7 is provided in the fluid introduction section 1 (in the figure, a part of a side wall of the fluid introduction path 6a is cut away as shown). A small-section flow path portion 2 for measurement is formed, and the flow rate of the fluid flowing through the small-section flow path portion 2 facing the small-section flow path portion 2 is reduced to a level at which oscillation of the fluid vibration becomes unstable. A flow sensor 16 capable of measuring a flow rate in a flow rate region is provided. The opening width of the small-section flow path section 2 is wider than the opening width of the nozzle section 6, and the opening height of the small-section flow path section 2 is The nozzle section 6
Is set to be smaller than the opening height of the flow sensor 1.
The six detection ends 16a are arranged on the side wall surface 9 in the height direction of the small-section flow path portion 2 so as to face the flow path.

As shown in FIG. 4, the fluid introduction unit 1
It is formed separately from the main body of the nozzle section 6, and is configured to be fitted into a fluid introduction passage 6 a to the nozzle 7 of the nozzle section 6 and to be integrally assembled with the main body of the nozzle section 6. In order to simplify the configuration, FIG. 4 shows the shape of the main body of the nozzle portion 6 and the shape of the fluid introduction portion 1 so as to be a simple shape different from the shapes shown in FIGS. Shown in shape. In the fluid introduction part 1, one slit-shaped flow path part 3 is formed coaxially with the nozzle 7 and is different from the small cross-section flow path part 2, in the height direction of the opening of the nozzle 7. I have. Further, a partition wall portion 4 for separating the two flow passage portions 2 and 3 is formed between the slit flow passage portion 3 and the small cross-section flow passage portion 2. Since the two flow paths 2 and 3 are separated from each other by the partition wall 4, both of the flow paths 2 and 3 have a rectangular cross section. The small cross-section channel portion 2 has an opening width larger than the opening height and at the same time, equal to or smaller than the flow channel width of the fluid introduction portion 6a, so that the cross-sectional area S2 of the channel and the flow path cutoff The relationship with the area Sn is formed so as to satisfy 0.35 ≦ S2 / Sn ≦ 0.50, and the opening width of the slit-shaped flow path portion 3 is made equal to the opening width of the nozzle 7. The relationship between the cross-sectional area S1 and the flow-path cross-sectional area Sn of the nozzle 7 is defined as 0.65 ≦ S1 / Sn ≦ 0.80.

By satisfying the above dimensional relationship, the flow path cross-sectional area (S1 + S2) of the entire fluid introduction section 1 is reduced by the nozzle 7
The flow direction of the fluid to the nozzle 7 in the height direction of the nozzle 7 is increased without increasing the flow resistance of the nozzle portion 6 to the fluid by increasing the flow channel cross-sectional area (Sn) by 1 to 1.3 times. Is made almost flat. As a result, the fluid vibration of the jet from the nozzle 7 in the fluidic element 5 can be stably maintained. The partition wall 4
Functions also as a connecting structure member between the constituent members of the fluid introduction unit 1 located on both sides of the small-section flow path unit 2 and the slit-shaped flow path unit 3. Therefore, when the fluid introduction unit 1 is inserted into the fluid introduction passage 6a of the nozzle unit 6, the fluid introduction unit 1 can be integrally handled,
The workability in assembling the fluid vibration type flow meter 26 can be improved while stabilizing the mounting of the fluid introduction unit 1 to the nozzle unit 6.

In the fluid vibration type flow meter 26 configured as described above, the fluid introduction part 1 is provided on the upstream side of the nozzle 7, and the small cross-section flow path part 2 is provided under the condition of the flow path cross-section area. And to satisfy the dimensional relationship between the width and height,
Since the flow sensor 16 is provided in the fluid introduction unit 1, the flow rate of the fluid in the minute flow rate region can be accurately measured using the flow sensor 16 as described above. In addition, the nozzle 7 passes through the two flow paths 2 and 3 of the fluid introduction section 1.
Flows into the fluid introduction passage 6a having an increased flow channel width, the main flow is diffused before reaching the nozzle 7, and the bias of the fluid introduced into the nozzle 7 is reduced from the nozzle 7 Can be reduced to such an extent that it does not affect the jet flow.

To explain an actual example, the flow path cross-sectional area Sn of the nozzle in the fluid vibration type flow meter of the conventional No. 3 meter is described.
Was 70 mm ² and that of the No. 6 meter was 140 mm ² . FIG. 5 shows a comparison between the two output levels when the detection data from the detection end of the flow sensor is pulsed with respect to the flow rate of 1 to 5 liter / h using the city gas (13A) as the fluid to be measured. As shown by the dotted line (a), the output level of the detection data at the No. 6 meter is about 1/3 of that at the No. 3 meter indicated by the dashed line (b), / H
Does not reach the output level of 1 liter / h in the No. 3 meter. As described at the beginning of the description of the prior art, this flow sensor has a detection end disposed on an inner wall surface at one end in the height direction of a nozzle. On the other hand, as shown by the solid line (c), the output level of the No. 6 meter in which the fluid inlet according to the present invention is arranged is almost uniformly increased by a factor of two or more, and is 1 liter / h. Output level is 3 liters /
h approaching the power level for the conventional one for 2 l / h. That is,
In the conventional No. 6 meter, for a fluid flow rate of 1 liter / h, the output level was close to the noise level indicated by the dashed line (n) and could not be measured at all. Depending on the configuration, detection is possible even at 1 liter / h. The specific dimensions are as follows: No. 3 meter No. 6 meter No. 6 meter (Invention product) Nozzle: Height 36 mm 36 mm 36 mm Width 1.94 mm 3.89 mm 3.89 mm Channel cross-sectional area Sn 70 mm ² 140 mm ² 140 mm ² small cross-sectional flow portion: aspect ratio - - 1.8 channel sectional area S2 - - 60 mm ² slit-like passage portions: the channel width - - 3.89Mm flow path cross-sectional area S1 - - is 112 mm ^2.

[Alternative Embodiment] <1> The configuration of the fluid introduction unit 1 is not limited to the type of the fluidic element 5 shown in FIGS. 1 and 2, but a fluid vibration type flow rate using a different type of fluidic element. The same operation and effect can be obtained for the total meter, and the present invention is not limited to the illustrated example. Of course, the shape of the fluid introduction unit 1 or the shape of the nozzle unit 6 is also modified according to the fluid vibration type flow meter to be applied. If the basic configuration is satisfied, the shape is not limited. The present invention can be applied to any type of fluid vibration type flow meter, and has an effect.

<2> In the above embodiment, the detection end 16a of the flow sensor 16 is arranged on the side wall surface 9 in the height direction of the small-section flow path portion 2 so as to face the flow path. Has been described, but the detection end 16 of the flow sensor 16 has been described.
a may be disposed on a surface facing the width direction of the small-section flow path portion 2, in short, on a large-size surface in the width direction or the height direction of the small-section flow path portion 2, What is necessary is just to arrange | position so as to face a flow path.

<3> In the above-described embodiment, the relationship between the cross-sectional area S2 of the small-section channel section 2 and the cross-sectional area Sn of the nozzle 7 is 0.35 ≦ S2 / Sn ≦ Although an example of forming the flow sensor so as to satisfy 0.50 has been described, this is a preferable range, and the flow sensor may be out of the above range depending on the combination with the slit-shaped flow path portion 3 and the dimensions thereof. The effect of improving the detection sensitivity is exhibited.

<4> In the above embodiment, one slit-shaped portion formed in the fluid introduction portion 1 coaxially with the nozzle 7 and formed in the opening height direction, which is separate from the small-section flow passage portion 2. Although the example in which the flow path section 3 is formed has been described, the slit-shaped flow path section 3 does not have to be single, and for example, as shown in FIG. 6 or FIG. A plurality of symmetrically arranged slit-shaped flow passages 3 may be formed, or four or more slit-shaped flow passages 3 may be formed. In the example shown in FIG. 7, the cross-sectional area of the center slit-shaped flow path 3 is
May be different from the cross-sectional area of the flow path. In addition, in the figure, each slit-shaped flow path portion 3 is used as a reinforcing material for the partition wall.
In addition, a channel partition wall arranged in the channel Z direction is provided which also functions as a connection structure member between constituent members of the fluid introduction unit 1 located on both sides of the slit-shaped channel unit 3. In short, it is sufficient that there is no deviation in the flow velocity distribution in the width direction in the fluid introduction path 6a. In any case, if the relationship between the cross-sectional area S1 of the entire slit-shaped flow path section 3 and the cross-sectional area Sn of the nozzle 7 is 0.65 ≦ S1 / Sn ≦ 0.80. Even better.

<5> In the above embodiment, the cross-sectional area S1 of the slit-shaped flow path 3 is set with respect to the cross-sectional area Sn of the flow path of the nozzle 7. Is described with respect to the flow path cross-sectional area S2 of the nozzle 7 and the flow path cross-sectional area S1 of the slit-shaped flow path section 3 and the flow cross-sectional area S1 of the small cross-section flow path section 2. If the sum of the cross-sectional area S2 of the passage satisfies the relationship of 1 ≦ (S1 + S2) /Sn≦1.3 with respect to the cross-sectional area Sn of the flow path of the nozzle 7, the fluid in the micro flow rate region with high sensitivity and accuracy. Can be measured, and at the same time, the influence of the fluid vibration in the fluidic element 5 on the oscillation can be suppressed.
That is, even if 0.95 ≦ (S1 + S2) / Sn <1, the sensitivity and accuracy of the flow sensor can be maintained sufficiently high if the increase in the pressure loss of the fluid vibration type flowmeter is somewhat tolerated. If 1.3 <(S1 + S2) /Sn≦1.5, while maintaining the sensitivity of the flow sensor,
An adverse effect on the oscillation of the fluid vibration can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional plan view showing an example of a gas meter according to the present invention.

FIG. 2 is a cross-sectional plan view illustrating a specific configuration of the fluid vibration type flow meter shown in FIG.

FIG. 3 is a partially cutaway perspective view showing an example of the configuration of a nozzle section according to the present invention.

FIG. 4 is an exploded perspective view of the nozzle unit shown in FIG. 3;

FIG. 5 is a diagram for explaining the operation of an example of the fluid vibration type flow meter according to the present invention.

FIG. 6 is an exploded perspective view showing another example of the nozzle section according to the present invention.

FIG. 7 is an exploded perspective view showing another example of the nozzle unit according to the present invention.

FIG. 8 is a schematic diagram illustrating a detection state of a fluid flow velocity in a flow path.

FIG. 9 is a longitudinal sectional view of a main part illustrating an example of a conventional minute flow rate measuring unit.

FIG. 10 is a longitudinal sectional view of a main part illustrating another example of a conventional minute flow rate measuring unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluid introduction part 2 Small cross section flow path part 3 Slit-shaped flow path part 4 Partition wall part 5 Fluidic element 6 Nozzle part 7 Nozzle 10 Flow sensor S2 Flow cross section area of small cross section flow path Sn nozzle flow cross section area

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Okabayashi 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. (72) Shuichi Okada 4-chome, Hirano-cho, Chuo-ku, Osaka-shi, Osaka No. 1-2 Inside Osaka Gas Co., Ltd. (72) Inventor Eiji Nakamura 2-10-16 Higashi Kobashi, Higashi-Nari-ku, Osaka-shi, Osaka Inside Kansai Gas Meter Co., Ltd. (72) Inventor Masanobu Namimoto Higashi-Nari-ku, Osaka-shi, Osaka 2-10-16 Kobashi Kansai Gas Meter Co., Ltd. (72) Inventor Kazuichi Tomoda 4-7-131 Nishiiwata, Higashiosaka-shi, Osaka Inside Kinmon Manufacturing Co., Ltd. (72) Masanari Imazaki Higashiosaka, Osaka 4-7-31, Nishi-Iwata-shi F-term (reference) in Kinmon Manufacturing Co., Ltd. 2F030 CA05 CA10 CC13 CD13 CE04 CF05 CF11

Claims (4)

[Claims] 1. A small cross-sectional flow for measuring a small flow rate having a smaller cross-sectional area than a cross-sectional area of a flow passage of a nozzle portion in a fluid introduction portion located upstream of a nozzle portion forming a nozzle of a fluidic element. With a path portion, facing the small cross-section flow path portion, it is configured to include a flow sensor capable of measuring a fluid flow rate flowing in the small cross-section flow path portion, the opening width of the small cross-section flow path portion, The opening height of the small-section flow path portion is set to be smaller than the opening height of the nozzle, the detection end of the flow sensor being wider than the opening width of the nozzle, and the width direction or the height of the small-section flow path portion being set. A fluid vibration type flow meter that is arranged on the surface on the large side in the vertical direction so as to face the flow path. 2. A flow path cross-sectional area S2 of the small cross-section flow path portion,
2. The fluid vibration type flow meter according to claim 1, wherein the relationship with the flow path cross-sectional area Sn of the nozzle is formed so as to satisfy 0.35 ≦ S2 / Sn ≦ 0.50. 3. 3. A slit formed in the fluid introduction portion provided with the small-section flow path portion and coaxially with the nozzle in a direction different from the small-section flow path portion in the opening height direction of the nozzle. 3. The fluid vibration type flow meter according to 1 or 2, wherein the flow path portion is formed. 4. The fluid vibration type flow meter according to claim 3, wherein a partition wall portion separating the two flow passage portions is formed between the slit-shaped flow passage portion and the small cross-section flow passage portion.