JP2591637Y2 - Fluidic flow meter - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fluidic flow meter.

[0002]

2. Description of the Related Art Since a vibration frequency of a fluid flowing through a fluid oscillation element corresponds to a flow rate of a fluid, a flow meter for measuring the vibration frequency to obtain a flow rate of gas or the like is disclosed in Japanese Patent Laid-Open No. 4-326014. It is.

In this flow meter, a piezoelectric membrane sensor is used to detect fluid vibration. The measurable range of a fluidic flow meter using this piezoelectric membrane sensor is about 1/50 of the maximum used flow rate. Yes, it is impossible to measure in a very small flow rate range. Therefore, in the large flow rate region, the fluid vibration of the fluid oscillation element is detected by the piezoelectric film sensor, and in the minute flow rate area, the flow rate is detected from the flow velocity by the flow sensor provided on the nozzle wall surface of the fluid oscillation element.

This fluidic flow meter is shown in FIGS.
It is configured as shown in FIG. That is, 101 is a case, in which a flow path main body 103 constituting a flow path 102 is provided inside the case 101.

[0005] A nozzle 104 is provided upstream of the flow path 102.
Downstream of the nozzle 104, first and second targets 105
And 106, and further downstream thereof, a return wall 107 is provided. 108 and 109 are side walls. A so-called fluidic oscillating element is constituted by the flow path 102 to the side wall 109.

Reference numeral 110 denotes a fluid outlet. The first target 105 to the side wall 109 are integrally formed with the flow path main body 103 so as to protrude forward from the rear wall of the flow path main body 103,
In front of this, as shown in FIG. 11 in particular, a metal lid 11 is provided via an elastic gasket 111 for gas sealing.
2 is fixed.

A straightening plate made of a wire mesh (not shown) is provided upstream of the nozzle 104. Nozzle 10
4 has a rectangular cross-sectional shape perpendicular to the flow direction (vertical direction in the drawing), the width W of the jet port in the left-right direction is narrowed down to the length L of the nozzle 104, and the depth (depth) D is The length is set to be longer than the length L of the nozzle 104.

The right and left walls 104a and 104b of the nozzle 104 are, as shown in FIG.
The nozzle width was gradually narrowed from the upstream end (upper end in the figure) to the downstream end (lower end in the figure). That is,
The nozzle entrances of the right wall 104a and the left wall 104b were formed on a so-called R surface.

However, the wall surfaces 10 before and after the nozzle 104
4c and 104d were formed as planes parallel to each other as shown in FIG. 12B, and the depth D of the nozzle 104 was the same from the upper end to the lower end of the nozzle.

Therefore, the turbulence of the flow velocity distribution in the left-right direction when viewed from the front is caused by the nozzle 10 as shown by the arrow in FIG.
No. 4 could be eliminated. This is because, as described above, the ratio between the length L and the width W of the nozzle 104 is sufficient, and the left and right wall surfaces 104b and 1
This is because the particularly upstream portion (the nozzle inlet portion) of the nozzle 04a has a curved surface shape that gradually narrows the nozzle width.

[0011]

In the above prior art, the front wall 104c and the rear wall 104d of the nozzle 104 are formed by planes parallel to each other, and the depth of the nozzle 104 is from the upstream end to the downstream end of the nozzle 104. (B), even if a rectifier such as a wire mesh is provided upstream of the nozzle 104, the flow velocity distribution in the front-rear direction at the nozzle outlet is biased as shown by the arrow in FIG. Occurs. This deviation has a problem that the state changes depending on the flow velocity through the meter, and the instrumental error characteristic has a large fluctuation.

Further, the gasket 111 shown in FIG. 11 may be deformed and protrude into the nozzle 104 or the flow path 102, which may cause a flow of the flow velocity distribution on the nozzle front wall 104c. Further, there is a problem that the instrumental difference changes due to a change in the nozzle cross-sectional area due to such protrusion of the gasket 111.

FIG. 13 shows an example of the instrumental error characteristics of such a prior art fluidic flowmeter. The instrumental error is ± 1.3.
%. Therefore, an object of the present invention is to provide a fluidic flow meter capable of solving such a problem.

[0014]

According to a first aspect of the present invention, there is provided a fluid flow meter according to the first aspect, wherein at least one of a front wall and a rear wall of a nozzle of the fluid oscillation element goes from upstream to downstream. It is characterized in that the nozzle is formed with a curved surface with a reduced depth.

According to a second aspect of the present invention, in the fluidic flow meter of the first aspect, the front wall and the rear wall of the nozzle are made of a material having high rigidity. The invention of claim 3 is based on claim 1 or 2
One of the front wall and the rear wall of the nozzle was formed as a curved surface, and the other was formed as a flat surface, and a flow sensor for detecting a minute flow rate was disposed on the other.

[0016]

[Function] By the curved surface formed on the front wall or the rear wall of the nozzle,
Since the depth of the nozzle is narrowed, the bias of the flow velocity distribution in the front-rear direction at the nozzle ejection port described with reference to FIG.

Further, since the front and rear walls of the nozzle are made of a material having high rigidity, the gasket does not protrude as in the prior art. Further, it is effective to provide a flow sensor on the flat wall of the front and rear walls of the nozzle.

[0018]

1 (a) and 1 (b) show a first embodiment of the present invention, wherein 1 is a main body of a flow path 2 which is an inlet 3, a room 4, a nozzle 5, a target 6, a side wall 7a. , 7b, return wall 8 and outlet 9. Reference numeral 10 denotes a metal lid attached to the front surface of the flow path main body 1 via a gasket 11.

The cross section perpendicular to the vertical flow of the nozzle 5 is rectangular, and the wall surfaces thereof are indicated by left and right walls 5a and 5b, and front and rear walls by 5c and 5d, respectively. Left and right wall 5
As shown in FIG. 1A, a and 5b are formed on the R surface at an upstream portion of the nozzle 5 and narrow the width of the nozzle 5 (this is the same as the conventional case). The front wall 5c and the rear wall 5d are formed on the R surface at an upstream portion of the nozzle 5, and reduce the depth of the nozzle 5.

FIG. 2 shows a second embodiment of the present invention.
The second embodiment differs from the first embodiment in that the target 6, the return wall 8, and the left and right walls (7a) and (7b) (not shown) are integrally formed with the lid 10 by die casting.

FIG. 3 shows a third embodiment of the present invention, in which a metal plate 12 is provided on the inside (rear side) of the lid 10, and the front wall 5c of the nozzle and the front wall 12a of the fluid oscillation element are provided on the plate 12. Is formed.

In the first to third embodiments, the room 4
(Depth in the front-back direction) is set to be greater than the depth D of the downstream end ejection port of the nozzle 4. In the above-described first to third embodiments, since the upstream portion of the front wall 5c and the rear wall 5d of the nozzle 5 is set as an R surface, the depth of the nozzle 5 in the front-rear direction is reduced, and as shown in FIG. The front / rear wall 5 shows that the flow velocity distribution (arrow A) in the front-rear direction in FIG.
The flow is narrowed at c and 5d, so that the nozzle outlet has an unbiased flow velocity distribution as shown by arrow B.

As described above, the function of eliminating the deviation of the flow velocity distribution in the front-rear (depth) direction due to the restricting action of the front and rear walls 5c and 5d may be achieved by simply setting one of the front and rear walls to the R-plane. The embodiment is shown in FIGS.

In the fourth embodiment shown in FIGS. 5 to 8, only the front wall 5c of the nozzle 5 is formed on the R surface at the upstream portion thereof to reduce the depth of the nozzle 5. The rear wall 5d of the nozzle 5 is flat as in the prior art, and a thermal flow sensor 13 for detecting a flow rate at a minute flow rate is provided on the rear wall. Note that 14
Is the second target, 15 and 16 are the first and second, respectively.
The current plate is made of wire mesh. The plate 12 is placed in contact with the front ends of the targets 6, 14, the side walls 7a, 7b, the return wall 8, and the like in a manner that covers the flow path 2 of the fluidic oscillation element and the front surface of the nozzle 5.

In the fourth embodiment shown in FIGS. 5 to 8, the effect that the depth of the nozzle is reduced on the R surface of the front wall 5c of the nozzle 5, the front wall of the nozzle is not a gasket, but a metal plate 12 is used.
The fluctuation of the instrumental error as a flow meter is reduced due to the effect that there is no protrusion and so on, as shown in FIG.

This instrumental error characteristic is suppressed to a variation width of about 38% as compared with the instrumental error characteristic of the prior art of FIG.
The improvement is clear.

[0027]

Since the fluidic flow meter of the present invention is constructed as described above, the depth in the front-rear direction is reduced by the nozzle (5), and the variation of the instrumental characteristic with respect to the flow rate is reduced.

Further, since the gasket does not protrude into the nozzle (5) and the flow path (2), disturbance of the flow velocity distribution due to the protruding gasket is eliminated. The result also improves the instrumental characteristics.

Further, since one of the front and rear walls of the nozzle (5) is a curved surface and the other is a flat surface, and a flow sensor for detecting the flow velocity is disposed on the side of the flat surface, the restriction by the curved surface is restricted. There is no loss of effect.

[Brief description of the drawings]

FIG. 1A is a front view of a first embodiment of the present invention with a cover removed, and FIG. 1B is a cross-sectional view taken along the line AA of FIG.

FIG. 2 is a longitudinal sectional side view of a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional side view of a third embodiment of the present invention.

FIG. 4 is a view for explaining the operation of the embodiment of the present invention.

FIG. 5 is a front view of a main part of a fourth embodiment of the present invention.

FIG. 6 is a sectional view taken along the line BB in FIG. 5;

FIG. 7 is a sectional view taken along the line CC of FIG. 5;

8 is a front view of the plate 12 of FIG.

FIG. 9 is a flow rate versus instrument difference diagram.

FIG. 10 is a front view in which a part of a conventional technique is cut longitudinally.

FIG. 11 is a longitudinal sectional side view of a conventional technique.

FIG. 12 is a diagram illustrating a flow velocity distribution of a nozzle ejection port.
(A) shows the distribution in the left-right direction, and (b) shows the distribution in the front-back direction.

FIG. 13 is a flow rate versus instrument difference diagram.

[Explanation of symbols]

 5 Nozzle 5c Front wall 5d Rear wall D: Depth 13: Flow sensor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigenori Okamura 4-1-2, Hirano-cho, Chuo-ku, Osaka City Inside Osaka Gas Co., Ltd. No. 2 70 Inside Aichi Watch Electric Co., Ltd. (72) Inventor Tadao Shibuya 2-10-16 Higashi Kobashi, Higashi-Nari-ku, Osaka-shi Kansai Gas Meter Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) ) G01F 1/20 G01F 1/68 G01F 7/00

Claims (3)

(57) [Scope of request for utility model registration] 1. A fluid flow meter characterized in that at least one of a front wall and a rear wall of a nozzle of a fluidic oscillation element is formed with a curved surface whose depth decreases from upstream to downstream. 2. The fluid flow meter according to claim 1, wherein the front wall and the rear wall of the nozzle are made of a material having high rigidity. 3. A fluidic according to claim 1, wherein one of the front wall and the rear wall of the nozzle is formed as a curved surface and the other is formed as a flat surface, and the other is provided with a flow sensor for detecting a minute flow rate. Flowmeter.