JP3237688B2 - Edge tone flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention can avoid clogging of a measurement fluid, can easily extract a measurement signal, and can reduce the size.
The present invention relates to an edge tone flowmeter capable of improving an S / N ratio.

[0002]

2. Description of the Related Art FIG. 8 is a diagram for explaining the configuration of a conventional example generally used in the prior art. For example, the title of a paper entitled "Flowmeter Using Edge Tone Oscillation"
Vol. 0, No. 4, published in August 1974 Published by the Society of Instrument and Control Engineers P92 to P93.

[0003] Reference numeral 11 denotes a pipe through which the measurement fluid flows, and 12 denotes an internal space provided in the middle of the pipe 111. Reference numeral 13 denotes a slit-shaped nozzle which is provided upstream of the internal space 12 and ejects a measurement fluid into the internal space 12. Reference numeral 14 denotes a columnar edge having a triangular cross section.

In the above configuration, the measurement fluid is supplied to the pipe 11
Flows through the nozzle 13 and gushes from the nozzle 13 and causes edge tone oscillation under certain conditions. Generally, there is a proportional range in the relationship between the oscillation frequency and the average flow rate of the jet flow.

[0005] By detecting the pressure fluctuation of the measuring fluid based on the oscillation frequency by the pressure fluctuation detecting means, the flow rate and flow rate of the measuring fluid can be measured. Such an edge tone type flow meter is characterized by a higher oscillation frequency and stable oscillation than other oscillation type flow meters.

[0006]

However, in such an apparatus, as shown in FIG. 9, there is a jump in the oscillation frequency indicating the discontinuity and a hysteresis phenomenon in the oscillation characteristics. Therefore, there is a problem that the dynamic range is narrow.

As a solution to this problem, there is Japanese Patent Application No. 6-102737, entitled "Edge Tone Flowmeter", which is a prior application filed by the present applicant. FIG. 10 is an explanatory diagram of a main part configuration of an embodiment of Japanese Patent Application No. 6-102737. In the figure, the configuration of the same symbol as in FIG. 8 represents the same function. Hereinafter, only differences from FIG. 8 will be described.

[0008] 21 is provided downstream of the internal space 12,
This is a throttle for restricting the flow of the measurement fluid from the internal space 12.
Reference numeral 22 denotes a thin plate-like edge in which a plane is arranged in the interior space 12 in parallel with the pipe line 11.

Reference numeral 23 denotes a pressure fluctuation detecting means which is disposed in the internal space 12 and detects a pressure fluctuation due to edge tone oscillation of the measurement fluid. In this case, it comprises a pressure introducing hole 231 and a pressure detector 232 (not shown) for detecting a pressure fluctuation of the measurement fluid guided from the pressure introducing hole 231.

The reference numeral 31 indicates that the minimum cross-sectional area B formed with the downstream end of the edge is equal to or larger than the cross-sectional area A of the nozzle 13 perpendicular to the measurement flow path direction. , A tapered portion provided at the upstream end of the stop 21.

In the above configuration, the measurement fluid is supplied to the pipe 11
The jet flow that flows through the nozzle 13 and jets from the nozzle 13 collides with the tip of the edge 22 and causes edge tone oscillation. By detecting the pressure fluctuation of the measuring fluid based on the oscillation frequency by the pressure fluctuation detecting means 23, the flow velocity and flow rate of the measuring fluid can be measured.

As a result, (1) Since the edge 22 is a thin plate and the throttle 21 is provided downstream of the edge 22, an oscillation area is widened and an edge tone flow meter having a large dynamic range can be obtained.

(2) The edge 22 is a thin flat plate,
Since the throttle 21 is provided downstream of 2, the fluctuating pressure of the edge tone oscillation is increased, and an edge tone flowmeter capable of ensuring stable edge tone oscillation is obtained.

[0014]

However, in such an apparatus, the pressure fluctuation of the measurement fluid based on the oscillation frequency of the edge 22 is measured by detecting the differential pressure of the pressure introducing hole 231. In this case, the pressure introduction hole 23
1 is easily clogged with the measurement fluid.

It is necessary to connect a lead tube for leading the pressure from the pressure introducing hole 231 and the like, which complicates the structure. Since the structure is complicated, it is not suitable for miniaturization.
Further, since the edge tone flow meter is directly mounted on the measurement pipe, noise due to external vibrations caused by a pump or the like is easily picked up, and the S / N ratio is not good.

The present invention solves this problem. SUMMARY OF THE INVENTION An object of the present invention is to provide an edge tone flowmeter capable of avoiding clogging of a measurement fluid, facilitating extraction of a measurement signal, reducing the size, and improving the S / N ratio.

[0017]

In order to achieve this object, the present invention relates to an edge tone flowmeter for measuring a flow rate by detecting an oscillation frequency based on an edge tone oscillation of a measurement fluid. And a slit-shaped nozzle provided upstream of the internal space and ejecting a measurement fluid to the internal space; and a measurement provided from the internal space provided downstream of the internal space. A restrictor for restricting the flow of fluid, a thin plate-shaped edge having a plane parallel to the direction of the measurement flow path in the internal space, and an edge tone of the measurement fluid provided upstream of the thin plate-shaped edge Distortion detecting means for detecting an oscillation frequency due to oscillation, distortion detecting means for detecting external vibration provided on the thin plate-shaped edge downstream of the distortion detecting means for detecting oscillation, and detecting external vibration noise; Distortion detection for oscillation detection It is obtained by constituting the edge tone flow meter, characterized by comprising an external vibration noise compensation circuit for removing the calculated external vibration noise signal from the stage and the external vibration detection distortion detecting means.

[0018]

In the above construction, the measurement fluid flows through the pipe, and the jet flow from the nozzle causes edge tone oscillation. The flow rate flow rate of the measurement fluid is measured by detecting the pressure fluctuation of the measurement fluid based on the oscillation frequency by the strain detecting means. Hereinafter, a detailed description will be given based on embodiments.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG.
It is B sectional drawing. In the figure, the configuration of the same symbol as in FIG. 10 indicates the same function. Hereinafter, only differences from FIG. 10 will be described.

Reference numeral 41 denotes an oscillation detecting strain gauge which is provided on the upstream side of the thin plate-shaped edge 22 and detects an oscillation frequency due to edge tone oscillation of the measurement fluid. 42
Is an external vibration detecting strain gauge provided on the thin plate-shaped edge 22 downstream of the oscillation detecting strain gauge 41 to detect external vibration noise.

In this case, the strain gauge 41 for detecting oscillation and the strain gauge 42 for detecting external vibration are arranged near the fixed end of the edge 22, as shown in FIG. The edge 22 has a fixed end and a support end because both ends of the edge 22
If it is fixed to 1, thermal expansion due to the temperature of the pipe line 11,
Since it is completely affected by shrinkage, one end is used as a support end to avoid the influence of a temperature change in the pipeline 11.

Reference numeral 43 denotes an external vibration noise compensation circuit (not shown) for calculating signals from the oscillation detection strain gauge 41 and the external vibration detection strain gauge 42 and removing external vibration noise. As shown in FIG. 4, the oscillation detecting strain gauge 41 and the external vibration detecting strain gauge 42 are attached to both sides of the edge 22 by two each.

Reference numeral 44 denotes a notch groove provided on the edge 22 to escape a protrusion due to the attachment of the strain gauges 41 and 42. Reference numeral 45 denotes a filler filled in the notch groove 44. In this case, an epoxy resin is used. 46
Is a cover plate that covers the strain gauges 41 and 42.

In the above configuration, the measurement fluid is supplied to the pipe 11
The jet flow that flows through the nozzle 13 and jets from the nozzle 13 causes edge tone oscillation. The pressure fluctuation of the measurement fluid based on the oscillation frequency is detected by the strain gauges 41 and 42 to measure the flow rate and flow rate of the measurement fluid.

FIG. 5 is an example of a stress analysis diagram in which stress analysis of the edge 22 is performed using the generated pressure distribution obtained by the simulation. Here, the experiment was performed under the conditions that the edge thickness was 0.4 mm and the flow rate of the measurement fluid was 0.4 m / s.

In the figure, the distribution of the difference in stress is shown separately for a black portion, a gray portion, and a white portion. The black portion shows the maximum distortion of about 0.5 μs. This confirmed that there was a difference in stress between the upstream side and the downstream side of the edge 22. The present invention focuses on this point.

In this case, the displacement generated at the edge 22 is
As shown in FIG. In the figure, x indicates the horizontal direction of the edge 22. y represents the displacement of the edge 22. A indicates a signal component, and the upstream side of the edge 22 is larger than the downstream side. B is a component based on external vibration, and shows a constant value in the horizontal direction of the edge 22 as shown.

Accordingly, the difference between the detection signal of the oscillation detection strain gauge 41 and the detection signal of the external vibration detection strain gauge 42 is obtained by the external vibration noise compensating circuit 43, so that the external vibration noise is removed. An edge tone flowmeter that can obtain a measurement signal with a good / N ratio is obtained.

As a result, since the pressure introducing hole 231 does not need to be used, there is no danger of clogging with the measurement fluid. Since it is not necessary to use the pressure introduction hole 231, it is not necessary to connect a lead tube for leading the pressure from the pressure introduction hole 231, and the structure can be simplified. Since the structure can be simplified, the size can be reduced.

Since the external vibration noise is canceled by the oscillation detecting strain gauge 41, the external vibration detecting strain gauge 42, and the external vibration noise compensating circuit 43, an edge tone flow meter having a good S / N ratio can be obtained. .

FIG. 7 is a relationship diagram showing the relationship between the flow rate of the measurement fluid and the detected oscillation frequency between the present invention and the conventional example of FIG. From FIG. 7, it can be seen that the strain detection method of the present invention and the pressure detection method of the conventional example in FIG. 10 show similar detection characteristics, and the apparatus of the present invention can be sufficiently replaced with the conventional apparatus in FIG. Things are confirmed.

Although the oscillation-detecting strain gauge 41 and the external-vibration detecting strain gauge 42 are arranged close to the fixed end in the embodiment of FIG. 2, the present invention is not limited to this. It may be placed where possible.

In the above-described embodiment, the strain detecting means is described as being constituted by a strain gauge. However, the present invention is not limited to this. For example, lead zirconate titanate (PZT) or polyvinylidene fluoride (PVDF) may be used. good. In short, what is necessary is just to be able to detect distortion.

The thickness of the edge 22 is not limited to the one shown in FIG. Preferably, the nozzle 13
If the width is equal to or less than the width, the same edge tone oscillation can be obtained.

Further, the shape of the internal space 12 is not limited to that shown in FIG. In short, internal space 1
It suffices if the edge 22 can be arranged in the area 2. Anything should come.

[0036]

As described above, the present invention relates to an edge tone flow meter for measuring a flow rate by detecting an oscillation frequency based on an edge tone oscillation of a measurement fluid, and has an internal space provided in the middle of a measurement flow path. , A slit-shaped nozzle provided upstream of the internal space and ejecting the measurement fluid into the internal space, and a throttle provided downstream of the internal space and restricting the flow of the measurement fluid from the internal space And a thin plate-shaped edge in which a plane is arranged in the internal space in parallel with the measurement flow path direction,
Oscillation detecting strain detecting means provided on the upstream side of the thin plate-shaped edge and detecting an oscillation frequency due to edge tone oscillation of the measurement fluid, and provided on the thin plate-shaped edge downstream of the oscillation detecting strain detecting means. External vibration noise detecting means for detecting external vibration noise, and an external vibration noise compensating circuit for calculating signals from the oscillation detecting distortion detecting means and the external vibration detecting distortion detecting means and removing external vibration noise. And an edge tone flowmeter characterized by comprising:

As a result, since the pressure introducing hole does not need to be used, there is no danger of clogging with the measurement fluid. Since it is not necessary to use the pressure introducing hole, there is no need to connect a deriving tube for deriving pressure from the pressure introducing hole, and the structure can be simplified. Since the structure can be simplified, the size can be reduced.

Since the external vibration noise is canceled by the oscillation detecting distortion detecting means, the external vibration detecting distortion detecting means, and the external vibration noise compensating circuit, an edge tone flow meter having a good S / N ratio can be obtained.

Therefore, according to the present invention, a clogging of the measurement fluid can be avoided, the measurement signal can be easily taken out, the size can be reduced, and the edge tone flowmeter which can improve the S / N ratio can be realized. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a detailed view of a main part of FIG. 1;

FIG. 5 is an operation explanatory diagram of FIG. 1;

FIG. 6 is an operation explanatory diagram of FIG. 1;

FIG. 7 is an operation explanatory diagram of FIG. 1;

FIG. 8 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 9 is an operation explanatory diagram of FIG. 8;

FIG. 10 is an explanatory diagram of a main configuration of an embodiment of Japanese Patent Application No. 6-102737.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Pipeline 12 Internal space 13 Nozzle 21 Throttle 22 Edge 31 Tapered part 41 Strain gauge for oscillation detection 42 Strain gauge for external vibration detection 43 External vibration noise compensation circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-161526 (JP, A) JP-A-63-163116 (JP, A) JP-A 8-261806 (JP, A) JP-A 7-161 234139 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 1/00-9/02

Claims (1)

(57) [Claims] An edge tone flowmeter for measuring a flow rate by detecting an oscillation frequency based on an edge tone oscillation of a measurement fluid, comprising: an internal space provided in the middle of a measurement flow path; A slit-shaped nozzle provided to eject a measurement fluid into the internal space; a throttle provided downstream of the internal space to restrict the flow of the measurement fluid from the internal space; A thin plate-like edge having a plane parallel to the road direction, an oscillation detecting strain detecting means provided upstream of the thin plate-like edge and detecting an oscillation frequency of the measurement fluid due to edge tone oscillation of the measurement fluid; An external vibration detecting distortion detecting means provided on the thin plate-shaped edge downstream of the detecting distortion detecting means to detect external vibration noise, the oscillation detecting distortion detecting means and the external vibration detecting distortion detecting means, Signal from Calculated by the edge tone flow meter, characterized by comprising an external vibration noise compensation circuit for removing the external vibration noise.