JPH074996A - Fluid vibration detection sensor in fluid vibration type flow meter - Google Patents

Abstract

PURPOSE:To provide a fluid vibration detection sensor in a fluid vibration type flow meter wherein sensor sensitivity is improved and reduction in size is possible. CONSTITUTION:The fluid vibration detection sensor in a fluid vibration type flow meter for measuring a flow rate detects a change in pressure by a piezoelectric film 222 for displacing first and second vibration pressures which are caused by binary-switching a flow path of a gushed stream and which are equal in fluctuation frequency and in a relation of reverse phases to each other by means of vibration pressure. Voltage and electric charge generated by the piezoelectric film 222 is proportional to its displacement. The piezoelectric film 222 is formed by together vapor-depositing electrodes 2222, 2224 and a layer of a piezoelectric material (poly-urea) 2223 onto a substrate 2221 made of a fluorine compound-based film whose modulus of elasticity is much smaller than that of the piezoelectric material 2223. The piezoelectric film 222 has a multilayered structure. The substrate 2221 is semispherical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a fluid vibration type flow meter such as a Karman vortex flow meter or a fluidic flow meter for detecting the frequency of pressure vibration in a fluid and measuring the flow velocity and flow rate of the fluid. The present invention relates to a fluid vibration detection sensor that detects pressure vibration.

[0002]

2. Description of the Related Art Conventionally, as this type of fluid vibration detection sensor, one applied to a fluidic flowmeter has been known. In this detection sensor, a part of the jet flow of the fluid flowing along the side wall due to the Counder effect is returned to the base of the jet flow by the return flow passage, so that the flow passage of the jet flow is binary-switched. Two oscillating pressures having the same fluctuation period and opposite phases to each other are introduced into the piezoelectric film, and the piezoelectric film is displaced in the thickness direction by the both pressures, so that the voltage or the charge corresponding to the two pressures is applied to the piezoelectric film. Since the frequency of the voltage or charge generated between the front and back surfaces of the piezoelectric film is proportional to the flow velocity or flow rate of the fluid, the voltage or charge frequency should be measured. The flow velocity or the flow rate is measured by.

By the way, this fluid vibration detection sensor has an advantage that an external power source is not required because a voltage is generated from the piezoelectric film itself. In the conventional fluid vibration detection sensor, PVDF (polyvinylidene fluoride) is used as the piezoelectric film. Ride) or TrFE (trifluoroethylene) was stretched to form a film and then subjected to poling treatment, and a pressure sensor was formed by forming electrodes on both surfaces of the film.

[0004]

However, the conventional fluid vibration detection sensor has the following various problems.
Incidentally, the relationship between the pressure P applied to the piezoelectric film and its displacement ζ is expressed by the following equation.

[0005]

[Equation 1]

In the equation, a is the area of the piezoelectric film, T ₀ is the tension of the piezoelectric film, and k is the elastic coefficient. In the equation, paying attention only to the second term,

[0007]

[Equation 2]

Therefore, the sensor output (sensor sensitivity) proportional to the displacement ζ is proportional to the sensor area a and inversely proportional to the elastic coefficient k of the piezoelectric film. The elastic coefficient k is the product of the elastic modulus C of the piezoelectric film and the film pressure D, that is, k = C · D.

By the way, the elastic modulus C of PVDF used as a piezoelectric film as described above is, for example, 3 × 10 ⁹ N
/ M ² , but in the case of PVDF, the thickness is actually 9μ
Since it is as thick as m, the elastic coefficient k obtained by multiplying the elastic modulus by the thickness becomes very large, and the sensor sensitivity inversely proportional to the elastic coefficient k is poor, resulting in a problem that the output is small.

Therefore, there is a problem that the sensor cannot be downsized because the sensor area must be increased in order to secure the output of the pressure sensor. In addition, an amplifier for amplifying a small output is burdened, and a battery-driven type consumes a large amount of current and shortens the battery life, which causes a problem in maintenance.

In the case of PVDF, the piezoelectric film is formed by poling after stretching as described above.
There was also a problem that it could not be molded into a highly sensitive special shape.

Therefore, in view of the above-mentioned conventional problems, it is an object of the present invention to provide a fluid vibration detecting sensor in a fluid vibration type flow meter which has improved sensor sensitivity and can be miniaturized.

[0013]

In order to achieve the above object, a fluid vibration detecting sensor in a fluid vibration type flow meter according to the present invention returns a part of a jet flow of a fluid flowing along a side wall by a Counder effect. By returning the jet flow to the base of the jet flow by the flow passage, the first and second oscillating pressures having the same fluctuation period and opposite phase to each other, which are generated by binary switching the flow passage of the jet flow, are generated. A fluid vibration detection sensor in a fluid vibration type flow meter for detecting a pressure change by a piezoelectric film displaced by the vibration pressure and measuring a frequency of a voltage or an electric charge generated by the piezoelectric film by the detection to measure a flow rate, The piezoelectric film is characterized in that it is formed by depositing a layer of an electrode and a piezoelectric material on a substrate having a smaller elastic modulus than the piezoelectric material.

The piezoelectric material is polyurea, the substrate is made of a fluorine-based film, the piezoelectric film has a multi-layer structure in which an electrode and the polyurea layer are vapor-deposited a plurality of times, or the substrate is semi-finished. It is further characterized by being spherical.

[0015]

In the above structure, the fluid vibration detecting sensor in the fluid vibration type flow meter for measuring the flow rate has the same fluctuation period and opposite phase to each other, which occurs when the jet flow passage is binary-switched. A pressure change is detected by a piezoelectric film that is displaced by the first and second oscillating pressures. The voltage or charge generated by the piezoelectric film is proportional to its displacement. An electrode and a layer of a piezoelectric material forming a piezoelectric film are co-deposited on a substrate to be formed very thin, and a substrate having a smaller elastic modulus than that of the piezoelectric material is used for the substrate.
Therefore, the elastic coefficient of the entire piezoelectric film is reduced, and the piezoelectric film is displaced by that amount to generate a large output. Polyurea that can be deposited is used as the piezoelectric material.

The fluorine-based film forming the substrate has a very small elastic modulus, and even if the thickness required for the substrate is large, the elastic modulus is negligible as compared with the polyurea layer. Since the piezoelectric film has a multi-layered structure, the area is correspondingly increased and a large output can be obtained. In addition, since the substrate has a semi-spherical shape, it is easily stretched and deformed by pressure, and a large output can be obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a fluid vibration type flow meter to which the fluid vibration detection sensor according to the present invention is applied. In FIG. 1, a fluidic oscillator constituting the fluid vibration type flow meter is provided, for example, in the middle of a gas pipe (not shown). Is formed in the duct 1 having a rectangular cross section. Inside the pipe 1, a pair of flow path forming members 4a, 4 forming the pipe contracting portion 2 and the jet nozzle 3 are formed.
b is arranged symmetrically with respect to the pipe center axis P, the gas is smoothly guided to the ejection nozzle 3 by the action of the pipe contracting portion 2, and the gas is ejected from the ejection nozzle 3 with the pipe center line P as the ejection center. It is supposed to be done.

Further, symmetrically with respect to the central axis P of the pipe, the pipe expanding part 5, the pair of control nozzles 6a and 6b, and the pipe expanding part 5 are provided.
Pair of return flow passages 7a, 7b, and a pair of return flow passages 7a, 7b for communicating the downstream side of the control nozzles 6a, 6b with each other.
A pair of partition walls 8a and 8b that define the partition are arranged. A target 9 for stabilizing the switching of the flow direction is arranged on the pipe central axis P of the pipe expanding portion 5. The pair of control nozzles 6a and 6b are arranged to face each other in a direction substantially perpendicular to the ejection direction of the ejection nozzle 3.

A partition wall 11 forming a pair of discharge paths 10a, 10b in cooperation with the pair of partition walls 8a, 8b is provided in a state of blocking the downstream side of the conduit expanding portion 5, and both discharge paths 1 are provided.
The inlets of 0a and 10b are separately communicated with the inlet sides of both return flow paths 7a and 7b. In addition, in the partition wall 11,
Recesses 11a and 11b are formed. Also, in the figure,
The conduit 1, the flow path forming members 4a and 4b, the partition walls 8a and 8b, the target 9 and the partition wall 11 are shown as separate members, but they can be integrally formed by die casting, for example, and a lid not shown. It is completed by attaching the body from above.

With the above construction, when the gas ejection from the ejection nozzle 3 is started, the ejected gas flows along one partition wall 8a due to the Counder effect, and a vortex is generated thereby, so that the gas is positioned on the partition wall 8a side. Control nozzle 6
Large fluid energy is supplied to a from the return flow path 7a. This acts on the ejection gas ejected from the ejection nozzle 3 to cause the ejection gas to flow along the partition wall 8b on the opposite side, thereby generating a vortex. Therefore, this time, the jet gas comes to flow again along the first partition wall 8a by the fluid energy from the control nozzle on the opposite side, and thereafter, the jet gas from the jet nozzle 3 alternately flows along the partition walls 8a and 8b. It comes to flow. The fluid vibration due to the switching of the flow direction of the ejected gas has a shorter cycle with a quantitative correlation with the increase in the ejected gas amount.

The flow rate can be measured by causing a pressure change in the flow passage in the pipe expanding portion 5 which reaches the return flow passage by the above-mentioned fluid vibration, and the flow rate can be measured by detecting the pressure change. The pressure derivation holes 12a and 12b are opened at positions symmetrical with respect to the pipe center axis P in which the above-mentioned flow path of the portion 5 is formed, and the pressure derived from the pressure derivation holes 12a and 12b is fluidized through the pressure guiding paths 13a and 13b. Vibration sensor 1
Leading to 4. The detection sensor 14 includes pressure guiding paths 13a, 1
A pulsed electric signal is generated according to the pressure introduced through 3b and is sent to the flow rate measuring device 15. The flow rate measuring device 15 calculates the flow rate from the frequency of the pulsed electric signal from the detection sensor 14 and displays it.

FIG. 2 shows a fluid vibration detecting sensor according to the present invention.
An example incorporated in the lid 21 is shown in FIG.
, The pressure lead-out holes 12a and 12b, the pressure guiding path 13a,
13b is formed on the lid 21. The lid 21
Also, the pressure introduced through the pressure guiding paths 13a and 13b is guided.
Pressure detection chambers 22a and 22b are formed. pressure
In the detection chambers 22a and 22b, the pressure guiding paths 13a and 13b are at the bottom.
22a formed in the lid 21 by communicating with the₁, 22
b₁Pressure sensor 22a made of a piezoelectric film ₂, 2
2b₂Formed by being mounted fluid-tight
ing. Pressure sensor 22a made of piezoelectric film₂, 22b₂
Recessed portion 22a partitioned by₁, 22b₁Outside of
The flow path is not affected by pressure changes due to the conduit not shown.
A void S of constant pressure is formed which communicates with the
It

FIG. 3A shows the pressure sensor 22.₂Of the concrete
An example of the configuration is shown in FIG._{twenty one}Is a low modulus
The substrate has a modulus of elasticity of 49 kgf.
/ Mm²Fluorine-based polymer materials such as those from Toray
Fluorine film sold under the trade name of Yofron FEP
(Copolymerization of tetrafluoroethylene and propylene hexafluoride
The body is made of, for example, 12.5 μm thick electrically insulating film.
Rum is used. 22 _{twenty two}Is the substrate 22_{twenty one}On the upper surface of
For example, a layer with a thickness of 0.1 μm formed by vapor deposition
It is an electrode layer made of, for example, aluminum. 22_{twenty three}Is the electrode layer
22_{twenty two}Formed on the upper surface of the substrate by vapor deposition, for example, with a thickness of 1
Elasticity of 2.2 × 10 with piezoelectric characteristics of μm ⁹N / m²of
It is a polyurea layer. 22_{twenty four}Is the polyurea layer 22_{twenty three}Across
Electrode layer 22 _{twenty two}Formed by, for example, vapor deposition so as to face
Made from, for example, aluminum with a thickness of 0.1 μm
Is an electrode layer.

Polyurea layer 22 ₂₃ having the above-mentioned piezoelectric characteristics
Is, for example, by evaporating the raw material monomers consisting of diamine and diisocyanate in a vacuum, and then applying these to the electrode layer 22 ₂₂
And a predetermined area on the substrate 22 ₂₁ to form a polyurea film by vapor deposition polymerization, and the polyurea film is subjected to poling treatment. The poling treatment is performed by heating the polyurea film to a high temperature at a temperature of 100 to 20
An electric field of about 0 MV / m is applied for a predetermined time and then gradually cooled to room temperature.

As described above, the substrate 22 having a small elastic modulus
_{Since the} extremely thin polyurea layer 22 ₂₃ is formed on ₂₁ by vapor deposition to form the pressure sensor 22 ₂ , the elastic modulus of the pressure sensor obtained by multiplying the elastic modulus by the thickness becomes small. Therefore, the output of the detection sensor, which is in inverse proportion to the elastic coefficient, that is, the sensitivity is increased.

The pressure sensor 2 described above with reference to FIG.
In 2 ₂ , the polyurea layer 22 ₂₃ is a single layer, but FIG.
As shown in (b), the electrode layer 22 ₂₂ and the polyurea layer 22 ₂₃
The electrode layers 22 ₂₄ and the electrode layers 22 ₂₄ are alternately and repeatedly formed by vapor deposition to form a multilayer structure.
In the case of this structure, since the area of the polyurea layer 2 ₂₃ is tripled, the thickness of the polyurea layer 22 _{23 for} the three layers is adjusted to be as small as possible, and the elastic coefficient is suppressed so that the output is reduced. Can be significantly increased. Note that FIG.
3C shows the upper surface of the pressure sensor 22 ₂ shown in FIGS. 3A and 3B.

In the above-described embodiment, the piezoelectric film of the pressure sensor is attached in a flat shape, but as shown in FIG. 3 (d), a larger output can be obtained by forming the piezoelectric film in a hemispherical shape in advance. Like This is because the output is obtained by stretching the membrane, and in the case of a hemispherical shape, when the pressure p due to fluid vibration is applied, the lateral stretching of the membrane is transmitted in all directions as shown in FIG. 3 (e). Is. Since the polyurea layer 2 ₂₃ is formed by vapor deposition, the substrate 22 ₂₁ can be preliminarily formed into a hemispherical shape, but PVDF which requires stretching cannot obtain such a shape.

The piezoelectric film forming the pressure sensor 22 ₂ is attached to the pressure detection chambers 22a and 22b by using a fixture 23 as shown in FIG. A specific example will be described below in the case where a fluorine-based polymer film is used as a substrate having a modulus of elasticity sufficiently smaller than that of polyurea. First, as shown in FIG. 5A, the metal ring 23a
The thick fluorine film 23b is heat-welded by heating for several minutes, and then the thin fluorine film to be the substrate 22 ₂₁ is heat-welded by heating for several seconds on the thick fluorine film 23b to form a film ring. To get

Thereafter, an electrode layer 22 ₂₂ , a polyurea layer 22 ₂₃ and an electrode layer 22 ₂₄ are formed by vapor deposition on a substrate 22 _{21 made of} a thin fluorine film to obtain a pressure sensor assembly. Then, as shown in FIG. 5 (b), the pressure sensor assembly is fluid-tightly fitted into the outer ring 23c, and subsequently the electrode rings 24a and 24b are brought into electrical contact with the electrode layers 22 ₂₂ and 22 ₂₄ , respectively. Mating, this electrode ring 2
This is completed by connecting lead wires to 4a and 24b, respectively.

The reason why the substrate 22 ₂₁ is fixed by heat welding and the thick fluorine-based film 23b is used for the heat-welding is that an adhesive cannot be used for this fluorine-based film and thin fluorine-containing film is used. This is because if the substrate 22 ₂₁ made of a system film is directly heat-welded to the metal ring 23a, it takes a long time to melt the film.

FIG. 6 is a graph showing the fluid vibration frequency-output characteristics of the detection sensor constructed by using the piezoelectric film having the three-layer structure described above with reference to FIG. 3 (b) in comparison with that using the conventional PVDF. It was found that the output level could be improved by at least 5 dB or more in the range of 1 to 1 kHz.

[0032]

As described above, according to the present invention, an electrode and a layer of a piezoelectric material composed of polyurea are deposited together,
The substrate is made very thin and its elastic modulus is smaller than that of the piezoelectric material, and the piezoelectric film as a whole has a small elastic coefficient and can be displaced by that amount to generate a large output. .

The fluorine-based film forming the substrate is suitable as a substrate because it has an extremely small elastic modulus and can be ignored as compared with a layer of a piezoelectric material made of polyurea. Since the electrode and the layer of polyurea, which is the piezoelectric material, are formed by vapor deposition on the substrate together, the multilayer structure of the piezoelectric film can be obtained, and the hemispherical shape of the substrate can be taken, so that a large output can be obtained. Become.

Therefore, the sensor sensitivity is improved, and the sensor can be downsized.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a fluid vibration type flow meter to which a fluid vibration detection sensor according to the present invention is applied.

FIG. 2 is a diagram showing an embodiment of a fluid vibration detection sensor according to the present invention.

FIG. 3 is a diagram showing various examples of a pressure sensor of the fluid vibration detection sensor according to the present invention.

FIG. 4 is a diagram schematically showing a mounting structure of a pressure sensor of a fluid vibration detection sensor according to the present invention.

5 is a diagram showing a specific example of the mounting structure of FIG.

FIG. 6 is a graph showing the output characteristics of the fluid vibration detection sensor according to the present invention in comparison with a conventional example.

[Explanation of symbols]

22 ₂ Piezoelectric film (pressure sensor) 22 ₂₁ Substrate (fluorine film) 22 ₂₂ , 22 ₂₄ Electrode layer 22 ₂₃ Piezoelectric material layer (polyurea layer)

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

By the way, this fluid vibration detection sensor has an advantage that an external power source is not required because a voltage is generated from the piezoelectric film itself. In the conventional fluid vibration detection sensor, PVDF (polyvinylidene fluoride) is used as the piezoelectric film. Ride) or P (VDF / TrFE) (vinylidene fluoride)
And a film made of a trifluoroethylene copolymer) and then subjected to a poling treatment, and a pressure sensor was formed by forming electrodes on both surfaces of the film.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

Where a is the radius of the piezoelectric film and T ₀ is the piezoelectric film.
Initial tension, k is a two-dimensional elastic coefficient. In the equation, paying attention only to the second term,

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

[Equation 2]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

Therefore, the sensor output (sensor sensitivity) proportional to the conversion ζ is proportional to the sensor area a and inversely proportional to the elastic coefficient k of the piezoelectric film. The two-dimensional elastic coefficient k is the product of the elastic modulus C of the piezoelectric film and the film pressure D, that is, k = C · D
Is.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

By the way, the elastic modulus C of PVDF used as a piezoelectric film as described above is, for example, 3 × 10 ⁹ N
/ M ² , but in the case of PVDF, the thickness is actually 9μ
Since it is as thick as m, the two-dimensional elastic coefficient k obtained by multiplying the elastic modulus by the thickness becomes very large, and the sensor sensitivity inversely proportional to the elastic coefficient k is poor, resulting in a small output. Was occurring.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

Polyurea layer 22 ₂₃ having the above-mentioned piezoelectric characteristics
Is, for example, 4,4'-diaminodiphenylmethene in vacuum.
Starting material consisting of tan and 4,4'-diphenylmethane diisocyanate is evaporated, and these are converted into an electrode layer 22.
₂₂ and by vapor deposition polymerization on a predetermined region on the substrate 22 ₂₁ to form a polyurea film is formed by performing a polling process on the polyurea membrane. In the poling treatment, the polyurea film is heated to a high temperature at a temperature of 100 to 2
It is performed by applying an electric field of about 00 MV / m for a predetermined time and then gradually cooling to room temperature.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

As described above, the substrate 22 having a small elastic modulus
_{Since the} extremely thin polyurea layer 22 ₂₃ is formed on ₂₁ by vapor deposition to form the pressure sensor 22 ₂ , the two-dimensional elastic coefficient of the pressure sensor obtained by multiplying the elastic modulus by the thickness becomes small.
Therefore, the output of the detection sensor, which is in inverse proportion to the two-dimensional elastic coefficient, that is, the sensitivity is increased.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

The reason why the substrate 22 ₂₁ is fixed by heat welding and the thick fluorine-based film 23b is used for the heat-welding is that an adhesive cannot be used for this fluorine-based film and thin fluorine-containing film is used. When thermal welding directly the metal ring 23a of the substrate 22 ₂₁ consisting of system film, because would become dissolved off Lee <br/> Lum.

[Procedure amendment]

[Submission date] November 12, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (5)

[Claims] 1. The flow path of the jet flow is binary-switched to cause a part of the jet flow of the fluid flowing along the side wall by the Counder effect to return to the base of the jet flow by the return flow passage, The first and second oscillating pressures having the same fluctuation period and the mutually opposite phases are detected by the piezoelectric film displaced by the oscillating pressure, and the voltage or charge generated by the piezoelectric film is detected by the detection. In a fluid vibration detection sensor in a fluid vibration type flow meter which measures a frequency to measure a flow rate, the piezoelectric film is formed by depositing an electrode and a layer of a piezoelectric material on a substrate having a smaller elastic modulus than the piezoelectric material. And a fluid vibration detecting sensor in a fluid vibration type flow meter. 2. The fluid vibration detecting sensor in a fluid vibration type flowmeter according to claim 1, wherein the piezoelectric material is polyurea. 3. The fluid vibration detection sensor in a fluid vibration type flow meter according to claim 1, wherein the substrate is made of a fluorine film. 4. The fluid vibration detecting sensor in a fluid vibration type flow meter according to claim 1, wherein the piezoelectric film has a multilayer structure in which the electrode and the polyurea layer are vapor-deposited a plurality of times. 5. The fluid vibration detecting sensor in a fluid vibration type flow meter according to claim 1, wherein the substrate has a semi-spherical shape.