JPH05264302A - Fluid vibration detector - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the influence of external noise and expand the measurement range in the low-speed basin while increasing the durability. [Structure] Pressure chambers 61, 6 juxtaposed by diaphragms 70a, 70b in which inorganic piezoelectric bodies 72a, 72b are integrally attached to thin metal plates 71a, 71b, respectively.
Divide the center of 2. Two systems of fluid pressures P1 and P2 are respectively introduced into both sides of the partitioned pressure chambers 61 and 62 so as to intersect with each other, and the diaphragm 70a,
A displacement is generated in 70b and a voltage is generated in the piezoelectric bodies 72a and 72b. These voltages are taken out by the lead wires 76a and 76b and subjected to electrical processing to remove noise and measure the pressure vibration of the fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid vibration detecting device used in a Karman vortex flowmeter, a fluidic flowmeter or the like for measuring the flow rate by detecting the frequency of pressure vibration generated in a fluid.

[0002]

2. Description of the Related Art As a conventional fluid vibration detecting device, one disclosed in Japanese Patent Application Laid-Open No. 2-268230 is known.
As shown in FIG. 9, this fluid vibration detecting device has electrodes formed on both surfaces of a polymeric piezoelectric film 2, 3 having a pressure detecting portion stretched in a planar shape, and its peripheral portion from both sides of the housing 1.
1, 13 and 4,5 are pressed or adhered to maintain airtightness, and pressure chambers 6, 7 and 14, 19 for introducing the pressure of the fluid are formed on both sides of the polymeric piezoelectric films 2, 3, respectively, and then The two pressure detecting portions 21 and 22 thus configured are arranged so that the attachment directions and polarization polarities of the polymer piezoelectric films 2 and 3 are the same.

Further, the pressure chambers 6, 7 and 14, 19 respectively formed in the pressure detecting portions 21, 22 with the polymer piezoelectric films 2, 3 separated from each other are the pressure chambers on the opposite side of the other pressure detecting portions. It is in communication. These two sets of pressure chambers are connected to the inlet nozzles 23 and 24, respectively.
By taking out the difference in the fluid pressures sent via 3, 24 as an electric signal, the pressure vibration frequency can be measured. Moreover, this fluid vibration detection device can remove the influence of noise due to external vibration and obtain a measurement result with a good S / N ratio.

[0004]

By the way, in the conventional fluid vibration detecting device, the polymer piezoelectric film 2 is used as the piezoelectric film material.
3 is generally PVDF (polyvinylidene fluoride fi)
lm) piezoelectric film is used, but the PVDF polymer piezoelectric film has a small specific gravity of around 1.8, so when used as a diaphragm, the value of inertial force generated by external vibration becomes small, There is an advantage that the output of vibration noise is reduced accordingly. However, when a polymer material is used as the piezoelectric film material, there are the following problems.

(1) A piezoelectric material made of a polymer material loses or deteriorates its piezoelectric ability in a high temperature state. That is, the piezoelectric polymer film has a Curie point at which the piezoelectricity disappears at about 100 ° C, which is 1/3 of that of the inorganic piezoelectric material.
Cannot be used with high temperature fluids.

(2) In addition, even if it is used at room temperature but is exposed to direct sunlight outdoors, deterioration over time will be accelerated due to a rise in temperature during the day. Therefore, when it is used as a flow meter, the installation location is limited.

(3) In particular, in the case of a PVDF piezoelectric film,
Since it is produced by stretching in the uniaxial direction, the dimension changes with time (contraction), and the tension of the diaphragm changes. Since this change in tension changes the pressure sensitivity and the resonance frequency of the diaphragm, the response to external vibration, the seismic resistance, and the S / N ratio also change over time.

(4) Further, the PVDF piezoelectric film has anisotropy in various characteristics. Above all, the anisotropy of the coefficient of linear expansion makes it difficult to fix the diaphragm.

(5) Further, when used in a flow meter, the pressure difference at the measurement level is introduced and balanced on both sides of the diaphragm during steady operation, but in the event of abnormalities such as pipe leakage and breakage, sudden changes in load, etc. If there is, the fluid pressure fluctuates greatly. With respect to this abnormal fluctuation, the film made of a polymer material lacks strength and is inferior in durability.

The present invention has been made in order to solve the above problems, and its purpose is to reduce the influence of external noise to expand the measurement range in the low-speed basin and to provide excellent durability. Another object of the present invention is to provide a fluid vibration detecting device.

[0011]

In order to achieve the above object, the first aspect of the present invention introduces two systems of fluid pressure into two pressure chambers formed by partitioning the center by a diaphragm. In a fluid vibration detection device that detects the pressure vibration of the fluid by extracting the displacement of the diaphragm generated by the differential pressure of the fluid as an electric signal, the diaphragm is formed by integrally bonding an inorganic piezoelectric body to the surface of the central part of the metal thin film. Is formed.

According to a second aspect of the present invention, in the fluid vibration detecting device of the first aspect, the outer shape of the diaphragm is substantially circular, and on the concentric circumference outside the piezoelectric body and inside the diaphragm. It is characterized in that it is provided with a cylindrical supporting portion for closely supporting the diaphragm and partitioning the pressure chamber.

According to a third aspect of the present invention, two fluid vibration detecting devices according to the first or second aspect of the present invention are arranged in such a manner that the piezoelectric elements have the same polarization direction and the plane directions of the diaphragms coincide with each other. To the two pressure chambers on one side, and the fluid pressures introduced to the two pressure chambers on one side are branched and crossed before being introduced to the pressure chamber on the other side. It is characterized by

According to a fourth aspect of the present invention, in the fluid vibration detecting apparatus of the first, second or third aspect, the lead wire connected to the piezoelectric body is fixed to the surface of the diaphragm and the support portion of the diaphragm, and then the pressure chamber. It is characterized by being pulled out to the outside.

[0015]

In the first aspect of the present invention, the use of the inorganic piezoelectric material increases the heat resistance, stabilizes the thermal characteristics, and reduces the secular change in the piezoelectric characteristics and dimensions.
Further, since the diaphragm main body is made of metal, its strength is increased, and it can sufficiently withstand an excessive fluid pressure. Further, since the piezoelectric body is arranged in the central portion, the diaphragm itself becomes light in weight, and the influence of inertial force due to external vibration is reduced.

In the second aspect of the invention, since the outer shape of the diaphragm is substantially circular and the diaphragm is supported on a concentric circle inside the diaphragm, when the diameter of the supporting portion is set appropriately, vertical external force is applied. Therefore, even if a harmful inertial force that causes noise is generated in the diaphragm, the moment due to the inertial force generated in the diaphragm itself is balanced inside and outside the support portion. As a result, the flatness at the center is substantially maintained, and the strain generated in the piezoelectric body is minimized.

In the third aspect of the invention, since the two fluid vibration detecting devices are arranged side by side, after the noise signal due to the external force which could not be completely removed in the case of only one fluid vibration detecting device is taken out, It becomes possible to erase by adding electrical adjustment processing.

In the fourth aspect of the invention, the lead wire connected to the piezoelectric body is fixed to the surface of the diaphragm and the supporting portion of the diaphragm and then pulled out to the outside of the pressure chamber, so that the lead wire is exposed to fluid pressure in the pressure chamber. It will not move in response to fluctuations or external vibrations.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing an embodiment of the first, third and fourth inventions, and FIG. 2 is an enlarged sectional view showing an essential part of FIG.
FIG. 3 is a circuit diagram showing an electrical configuration of the same embodiment. In the figure, reference numeral 15 designates two congruent circular recesses 16 on its upper surface,
17 are formed side by side, and concave portions 16 and
It is a thick plate-shaped first housing provided with a first pressure guide port 8 and a second pressure guide port 9 communicating with 17 and introducing the fluid pressures P1 and P2 into these recesses. Reference numeral 18 is an O-ring that fluid-tightly guides the pressure P1 to the pressure guide port 8, and 19 is an O-ring that fluid-tightly guides the pressure P2 to the pressure guide port 9.

Reference numerals 70a and 70b are metal plates 71a and 71 made of lightweight metal such as titanium or duralumin and having a thickness of about 20 μm.
b and the PZT piezoelectric ceramic 72a, approximately in the center of one surface thereof,
The diaphragms 72b are integrally fixed to each other. The piezoelectric ceramic 72a is provided with electrodes 74a and 75a on both surfaces of a piezoelectric substrate 73a, and the metal plate 71a and the electrode 75a are electrically connected to each other so as to be bonded and fixed so as to have polarization polarities in the same direction. The piezoelectric ceramic 72b has the same structure. 76a and 76b are electrodes 74a and 74
It is a lead wire for taking out the outputs of b and 75a, 75b to the outside. The diaphragms 70a and 70b can have the piezoelectric ceramics 72a and 72b fixed to not only one surface but also both surfaces.

Reference numeral 27 denotes a circular concave portion 2 on one surface thereof at a position corresponding to the concave portions 16 and 17 formed in the housing 15.
It is a thick plate-shaped second housing in which 8, 29 are formed.
In FIG. 1, the recesses 16 and 17 and the recesses 28 and 29 all face inward, the recesses 16 and 28 face each other, and the recesses 17 and 29 face each other, so that the housing 15 and the diaphragm 70a, The contact portion with 70b and the contact portion between the housing 27 and the housing 15 are fluid-tightly bonded with an adhesive.

Recessed portion 1 formed in housings 15 and 27
The first pressure chamber 61 composed of 6 and the recess 28 and the second pressure chamber 62 composed of the recess 17 and the recess 29 are fluid-tightly divided into two by the diaphragms 70a and 70b, respectively.
The pressure chamber 35, the 12th pressure chamber 41, the 21st pressure chamber 40, and the 22nd pressure chamber 36 are formed.

The first communication hole 31 includes a through hole 32 formed in the housing 15 between the recess 16 and the recess 17, and a through hole 34 formed in the housing 27 between the recess 28 and the recess 29. By fixing the housings 15 and 27 as described above, the 11th pressure chamber 35 formed by the recess 16 and the diaphragm 70a and the 22nd pressure chamber 36 formed by the recess 29 and the diaphragm 70b are formed. Communicate. The second communication hole 37 includes a through hole 38 formed in the housing 15 as illustrated by a dotted line and a through hole 39 formed in the housing 27 as illustrated by a dotted line, and includes the recess 17 and the diaphragm 70b. The formed 21st pressure chamber 40, the recessed part 28, and the diaphragm 70a.
The 12th pressure chamber 41 formed by and is made to connect.

The above-mentioned lead wires 76a and 76b are provided with conductors 78a and 78b on both surfaces of a flexible insulator 77, where 78a is the electrode 74a and 78b is the electrode 7.
It is fixed so as to be electrically connected to the diaphragm 70a which is electrically connected to 5a. Thus, the tip portions of the lead wires 76a and 76b are integrated with the diaphragms 70a and 70b, respectively, and the intermediate portions thereof are recessed portions 28 and 29, respectively.
Since it is fixed to the inner wall of the housing and is taken out through the housing 27, the lead wires 76a and 76b do not vibrate and generate noise even when external vibration is applied. Further, 47 is a voltage detecting device composed of the non-inverting amplifier 12 and resistors R1, R2 and R3, and 48 is an oscillating pressure detecting device constituted by the above-mentioned respective parts.

FIG. 4 shows an example in which the above-mentioned device 48 is applied to a Karman vortex flowmeter or the like. Since the vortices 78 are alternately generated behind both side surfaces of the vortex generator 77, the pressures of the vortices have a phase relationship opposite to each other. Since this pressure is transmitted to the first pressure guiding port 8 and the second pressure guiding port 9 via the pressure guiding ports 79a and 79b, the diaphragm 7
0a and 70b receive the opposite forces and are displaced in the opposite directions.
Here, since the piezoelectric ceramics 72a and 72b are provided so as to be polarized in the same direction, the output voltages have opposite phases and the electrode 75
By connecting a and 75b, the sum of the outputs of the two piezoelectric ceramics 72a and 72b can be obtained.

On the other hand, since the diaphragms 70a and 70b are displaced in the same direction with respect to the external vibration applied in the direction perpendicular to the surface, the piezoelectric ceramics 72a and 72b generate the same phase output, but their magnitudes are equal. So electrode 74a,
No potential difference is generated between 74b. That is, noise output due to external vibration can be erased by electrical processing.

Further, a light weight material such as Ti or duralumin is used for the metal plates forming the diaphragms 70a, 70b, and the piezoelectric ceramics 72a, 7 for detecting the displacement.
By providing 2b only in the central portion where the strain is the largest, the weight of the diaphragms 70a and 70b can be reduced, and the displacement of the diaphragms 70a and 70b due to external vibration can be reduced.

As described above, according to the embodiment, in a device for detecting a fluid vibration pressure such as a Karman vortex or a fluidic flowmeter, unlike the conventional case where a diaphragm for detecting the pressure is formed of a polymer piezoelectric film. Since a light-weight metal substrate and an inorganic piezoelectric material are laminated and fixed on at least the center of at least one side of the substrate, even when applied to a high temperature fluid, a highly reliable characteristic with little change over time can be obtained. ..

Further, two pressure chambers are arranged side by side, and the diaphragms are installed in the same direction. When a fluid vibration pressure is applied, the diaphragms are displaced in opposite directions, while acting vertically to the diaphragm surface. The two diaphragms are displaced in the same direction with respect to the external vibration acceleration
The output of the piezoelectric body is obtained with the polarity corresponding to the direction of the displacement. By electrically taking the difference between these two output voltages, the noise output generated by the diaphragm displacement due to the external vibration acceleration is electrically erased. Thereby,
Even a small signal in the low flow velocity region can be detected without being affected by vibration.

Further, in the embodiment, the first chamber 61 supporting the diaphragm 70a and the second chamber 62 supporting the diaphragm 70b are arranged in parallel, but the diaphragm 70a and the first chamber 61 may be used alone. It is possible to obtain a fluid vibration detection device having excellent heat resistance and durability.

Next, an embodiment of the second invention will be described with reference to FIGS. 5, 6 and 7. FIG. 5 is a sectional view of the embodiment, and FIGS. 6 and 7 are explanatory views of the operation. The difference of this embodiment from the embodiment of FIG. 1 is that only one diaphragm is provided and the diaphragm is supported not at the outer peripheral end but at the inner side of the outer peripheral end. The same parts as those in the embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the figure, the diaphragm 70 is not fixed at its outer peripheral portion, but is supported on the circumference inside the outer circumference and outside the piezoelectric ceramic 72.
That is, the diaphragm 70 is pressed and supported from both sides by the concentric O-rings 80 and 81. This O-ring 8
0 and 81 are held and positioned by the tips of cylindrical protrusions 84 and 85 formed inside the housings 82 and 83, respectively.

Further, the housings 82 and 83 are positioned by a plurality of positioning pins 86 penetrating the abutting surfaces, and the relative positions of the protrusions 84 and 85 that support the O-rings 80 and 81 are held. Recesses 87 and 88 having a circular cross section are provided on the surfaces of the housings 82 and 83 facing the diaphragm 70 inside the protrusions 84 and 85, and pressure chambers 89 and 90 that are airtight to each other are formed.

Diaphragm 70 outside protrusions 84 and 85
The annular groove 9 is formed on the surface of the housing 82, 83 facing the
1, 92 are provided, and a cavity 93 is formed. The cavity 93 communicates with the outside air or the measurement fluid so as not to be a closed space. In this embodiment, the pressure introducing port 94 communicates with the pressure chamber 90. The pressure chamber 90 is provided through the pressure guide ports 95 and 96 provided in the housings 83 and 82, and the pressure chamber 89 is provided through the pressure guide port 97 provided in the housing 82, and the pressure guide port 9 is formed in the lid 98. And 8 respectively. Incidentally, 99 is a lid for keeping the pressure chamber 90 airtight.

Next, the operation will be described with reference to FIGS. The fluid vibration pressure of the Karman vortex flowmeter, etc.
It is transmitted to the pressure chambers 89 and 90 via 9. Since the transmitted pressures P1 and P2 have an inverse phase relationship in principle, the diaphragm 70 is deformed as shown by the dotted line in FIG.
In the piezoelectric ceramic 72, a sinusoidal output voltage corresponding to this deformation is generated. At this time, since the pressure P2 of the pressure introducing port 9 on one side is only guided to the cavity 93, no external force is applied to the portion 100 outside the diaphragm 70.

On the other hand, when external vibration is applied as shown in FIG. 7, the vibration acceleration acts on the entire diaphragm 70, so that the deformation is opposite between the inside and outside of the diaphragm 70. If acceleration is applied in the direction A in the figure, the inertial force of itself is generated in the direction A in the central portion 101 of the diaphragm 70, whereas the inertial force generated in the peripheral portion 100 of the diaphragm 70 is in the central direction. It acts so as to displace the portion 101 in the opposite direction.

Therefore, by optimally selecting the position of the O-rings 80 and 81 which are the mass or fulcrum of the peripheral portion 100, the deformation generated in the central portion 101 of the diaphragm 70 due to the vibration can be canceled, and the external It is possible to prevent generation of noise due to vibration. Further, the pressure acts evenly on both sides of the peripheral edge portion 100 of the diaphragm 70 in response to the fluctuation of the fluid pressure when there is no external vibration, and it is in a so-called free state, so that the central portion 101 of the diaphragm 70 is affected by the peripheral edge portion 100. Never receive.

As described above, according to the embodiment, the diaphragm 70 for detecting the pressure is constructed by laminating and fixing the metal substrate 71 and the piezoelectric ceramic 72, which is an inorganic piezoelectric material, on the substantially central portion of at least one surface thereof. At the same time, at least one side in the radial direction is airtightly supported by cylindrical protrusions 84, 85 and the like, and two pressure chambers are formed on both sides of the diaphragm 70. The Karman vortex and fluidic flowmeters are formed in these pressure chambers. Since the fluid oscillating pressures P1 and P2 are introduced,
The deformation of the central portion 101 of the diaphragm 70 due to external vibration can be canceled by the bending moment of the inertial force generated in the peripheral portion 100. As a result, there is an advantage that even a configuration using one diaphragm 70 can detect a low pressure minute flow pressure signal without being affected by external vibration.

Since only one diaphragm 70 is required, the structure is simple and the cost is reduced, which is a practical advantage. Further, since this method utilizes the bending moment of the inertial force applied to the diaphragm 70, the diaphragm 70
Requires rigidity. Therefore, the action and effect as described above cannot be obtained in principle with a film-like body such as a conventional device, and vibration can be eliminated only by using a metal diaphragm. Further, there is an advantage that it can be applied to medium and high temperature fluids, and also to applications where a large detected pressure is required and strength is required.

Next, an embodiment of the third invention will be described with reference to FIG. In the figure, the same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted. The present embodiment is provided with two pressure detecting elements configured as in the second embodiment of the present invention, and the output of the two elements is electrically adjusted to adjust the S / N of vibration noise and fluid vibration pressure. The ratio is further improved.

In the figure, on the lower surface side of the housing 83, cylindrical supports 102a and 102b for supporting the diaphragms 70a and 70b, and a concentric circular recess 88 inside thereof.
a and 88b and outer annular concave grooves 92a and 92b are formed. Further, on the upper surface side of the housing 82, circular recesses 87a facing the diaphragms 70a, 70b,
87b is provided. The housing 82 and the housing 83 are airtightly adhered and fixed to each other so that the diaphragm 7
0a and 70b on both sides of the pressure chambers 89a and 90a and 89
b and 90b are formed respectively.

Further, the pressure chamber 89a communicates with the pressure guide port 8 and the pressure chamber 90b through the pressure guide holes 103a and 104b.
Further, the pressure chamber 89b communicates with the pressure guide port 9 and also communicates with the pressure chamber 90a via the pressure guide holes 103b and 104a. In the second embodiment, the diaphragm 70 is O
Although the structure is such that the rings 80 and 81 are used for holding, the diaphragm 70 is attached to the supports 102a and 102b as in the present embodiment.
The same function can be obtained by adhesively fixing one side of a and 70b.

In the above structure, the fluid vibration pressure of the Karman vortex flowmeter or the like is introduced through the conduits 79a and 79b into the pressure guide port 8,
When guided to 9, the diaphragms 70a and 70b are displaced by receiving pressures in opposite directions. Piezoelectric ceramics 72a, 7
Since 2b has the same polarization direction and is fixed to the metal plates 71a and 71b, the output voltages have opposite phases. By connecting the electrodes 75a and 75b as in the case of FIG. 3, the outputs of the piezoelectric ceramics 72a and 72b are output. The sum of can be calculated.

On the other hand, the external vibration applied in the direction perpendicular to the surfaces of the diaphragms 70a and 70b is eliminated in the same manner as in the second embodiment of the present invention.
Since 72b has a finite size, it is theoretically impossible to completely eliminate the deformation of the diaphragms 70a and 70b due to the inertial force within this size, and there is a limit to noise removal. However, external vibration causes the diaphragm 7
Since 0a and 70b are displaced in the same direction, the unerased portions of the output caused by the sizes of the piezoelectric ceramics 72a and 72b have the same phase as described above, and the output lines are connected to each other as in the above-described first embodiment of the invention. The noise component can be canceled by connecting. That is, the signal component is doubled as compared with the case of using one diaphragm, and the vibration noise is eliminated, so that an output with a very high S / N ratio can be obtained.

In the third embodiment of the invention, two diaphragms according to the second embodiment of the invention are used to displace the diaphragms in opposite directions by fluid vibration pressure and to act perpendicularly to the diaphragm surface. For vibration acceleration, a piezoelectric body is placed so that an output with a polarity corresponding to the direction of displacement can be obtained by utilizing the fact that the diaphragms are displaced in the same direction, and the outputs of both diaphragms are electrically summed. , And the difference was taken. As a result, the signal of fluid vibration pressure is doubled, while the unbalanced component generated by the size of the piezoelectric body can be eliminated from the deformation component of the diaphragm due to external vibration, so it is not affected by external vibration. Therefore, there is an advantage that a low flow velocity region can be detected.

[0046]

As described above, according to the first invention,
By using the inorganic piezoelectric material, the heat resistance is increased, the thermal characteristics are stabilized, and the piezoelectric characteristics and the dimensional change are reduced, and the durability is improved. Similarly, since the diaphragm main body is made of metal, the strength is increased, and sufficient strength can be obtained even against an excessive pressure during a transition, and durability is increased. Further, by disposing the piezoelectric body only in the central portion,
The diaphragm itself becomes light in weight, the influence of inertial force is reduced, and the S / N ratio is improved accordingly, enabling high-precision measurement. In particular, when the diaphragm is made of lightweight metal, the measurement accuracy is further improved.

According to the second aspect of the present invention, the outer shape of the diaphragm is made substantially circular, and the diaphragm is supported on the concentric circumference, so that a vertical external force is applied to the diaphragm to generate a harmful inertial force. In this case, the moment due to the inertial force generated in the diaphragm itself is balanced inside and outside the support portion. As a result, the flatness at the central portion of the diaphragm is maintained, the strain generated in the piezoelectric body is minimized, and the generation of noise is suppressed to the minimum, enabling highly accurate measurement.

According to the third aspect of the invention, since the two fluid vibration detecting devices are arranged in parallel, the noise signal due to the external force, which is not removed by only one fluid vibration detecting device, can be electrically adjusted. It becomes possible to erase,
Enables more accurate measurement.

According to the fourth aspect of the present invention, the lead wire connected to the piezoelectric body is fixed in the pressure chamber, which may cause noise even if fluid pressure fluctuations or external vibrations are applied in the pressure chamber. It becomes possible to measure with higher accuracy. In each of the above inventions, when measuring the frequency of the fluid oscillating pressure, the generation of noise due to external vibration is reduced, and the generated noise is eliminated to improve the S / N ratio. It is possible to extend the measurement range in the low speed basin and increase the durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the first and fourth inventions.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a circuit diagram showing an electrical configuration of the embodiment shown in FIG.

FIG. 4 is a diagram showing a state in which the embodiment of FIG. 1 is applied to a Karman vortex flowmeter.

FIG. 5 is a sectional view showing an embodiment of the second invention.

FIG. 6 is a diagram for explaining the operation of the embodiment of FIG.

FIG. 7 is a diagram for explaining the operation of the embodiment of FIG.

FIG. 8 is a cross-sectional view showing a configuration of an example of the third invention.

FIG. 9 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 8 1st pressure port 9 2nd pressure port 31 1st communicating hole 32, 34 through hole 35 11th pressure chamber 36 22nd pressure chamber 37 2nd communicating hole 38, 39 through hole 40 21st pressure chamber 41 12th Pressure chamber 61 First pressure chamber 62 Second pressure chamber 70a, 70b Diaphragm 71a, 71b Metal plate 72a, 72b Piezoelectric ceramic 73a Piezoelectric substrate 74a, 74b, 75a, 75b Electrode 76a, 76b Lead wire 80, 81 O-ring 84, 85 Projection 89,90 Pressure chamber 94,95,96,97 Pressure guide port 100 Peripheral part 101 Central part 102a, 102b Support body 103a, 103b, 104a, 104b Pressure guide hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Noriyuki Hirayama Inventor Noriyuki Hirayama 1-1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (4)

[Claims] 1. Fluid pressures of two systems are respectively introduced into two pressure chambers formed by dividing the center by a diaphragm, and the displacement of the diaphragm generated by the differential pressure between the two fluid pressures is taken out as an electric signal to obtain the fluid. In the fluid vibration detecting apparatus for detecting the pressure vibration, the diaphragm is formed by integrally bonding an inorganic piezoelectric material to the surface of the central portion of the metal thin film. 2. The fluid vibration detection device according to claim 1, wherein the outer shape of the diaphragm is substantially circular, and the diaphragm is closely contacted on the outer circumference of the piezoelectric body and on the concentric circumference inside the outer circumference of the diaphragm. A fluid vibration detection device comprising a cylindrical support portion that supports and divides a pressure chamber. 3. The two fluid vibration detection devices according to claim 1 or 2, wherein the piezoelectric bodies have the same polarization direction and the diaphragms are arranged in parallel so that the surface directions of the diaphragms coincide with each other. It is characterized in that two systems of fluid pressures are respectively introduced into both pressure chambers, and the fluid pressures introduced into both pressure chambers on one side are branched and crossed before being introduced into the pressure chambers on the other side. Fluid vibration detector. 4. The fluid vibration detection device according to claim 1, 2, or 3, wherein the lead wire connected to the piezoelectric body is fixed to the surface of the diaphragm and the supporting portion of the diaphragm and then pulled out to the outside of the pressure chamber. Characteristic fluid vibration detection device.