JP2011043366A - Fluid flow measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic fluid flow measuring apparatus which allows stable measurement even for a high-pressure fluid and a fluid with pressure fluctuations. <P>SOLUTION: The fluid flow measuring apparatus includes: a pair of ultrasonic vibrators 3, 4 which are placed on the upstream and downstream side of a measuring part 2 through which a fluid under measurement flows; a measuring circuit 18 for measuring ultrasonic wave propagation time between the ultrasonic vibrators 3, 4; and an arithmetic means 19 for calculating a flow rate and/or flow on the basis of a signal from the measuring circuit 18. The internal pressure of a sealed container 8 having a piezoelectric body 9 of the ultrasonic vibrators 3, 4 therewithin is set to be within the fluctuation range of the pressure P1 of the measuring part 2, thereby surely preventing deformation of the sealed container 8, destruction of the piezoelectric body, and destruction of the connecting part between the piezoelectric body and the sealed container, and allowing stable measurement even for a high-pressure fluid and a fluid with pressure fluctuations. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fluid flow measurement device that measures the flow velocity and / or flow rate of a gas or liquid using ultrasonic waves.

  Conventionally, as shown in FIG. 8, an ultrasonic transducer 101 used in this type of fluid flow measuring device has a piezoelectric body 103 bonded and fixed to the inner surface of the top wall of a conductive celestial cylindrical case 102. The acoustic matching layer 104 is bonded and fixed to the outer wall surface.

  Electrodes 105 and 106 are formed on the upper and lower surfaces of the piezoelectric body 103, and the upper electrode 105 is electrically connected to the celestial tubular case 102.

  A flange 107 is integrally formed outward from the lower opening of the celestial tubular case 105, and the outer peripheral upper surface of the conductive terminal plate 108 is welded to the lower surface thereof. Is set to

  Normally, the sealed space 109 is filled with an inert gas such as nitrogen gas so that the internal pressure is maintained at about 10 to 50 kpa.

  A conductive elastic material 110 is elastically contacted with the electrode 106 below the piezoelectric body 103, and one terminal 112 penetrating the terminal plate 108 through an electrical insulating portion 111 such as a hermetic seal is the elastic material 110. Is electrically connected.

  On the other hand, the other terminal 113 is directly attached to the terminal board 108 (see, for example, Patent Document 1).

JP 2003-270013 A

  However, in the conventional ultrasonic transducer, when measuring a low-pressure fluid of about 1 to 5 kpa, the measurement is not hindered even if the pressure in the sealed container 109 is not considered so much. When measuring a high-pressure fluid of a certain level, if a pressure difference occurs between the pressure in the ultrasonic vibrator and the measurement fluid, the sealed container in the ultrasonic vibrator is deformed, and the piezoelectric body contained in the container is There has been a problem that the measurement or the measurement itself cannot be performed due to the destruction or the joining portion between the piezoelectric body and the sealed container, which eventually breaks the ultrasonic vibrator.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an ultrasonic threshold flow measuring device capable of stably measuring even a high-pressure fluid and a fluid with pressure fluctuation.

In order to achieve the above object, the present invention provides a pair of ultrasonic transducers disposed on the upstream and downstream sides of a measurement unit through which a fluid to be measured flows and transmits and receives ultrasonic signals, and an ultrasonic wave between the ultrasonic transducers. An internal pressure of a sealed container provided with a measurement circuit for measuring a propagation time and a calculation means for calculating a flow velocity and / or a flow rate based on a signal from the measurement circuit, in which a piezoelectric body of the ultrasonic transducer is provided, It is set within the fluctuation range of the pressure P1 of the measuring unit.

  As a result, the pressure difference between the pressure in the measurement unit and the pressure in the ultrasonic transducer is reduced, and deformation of the sealed container in the ultrasonic transducer can be suppressed to a small level. Breakage of the joint between the piezoelectric body and the hermetic container can be suppressed, and as a result, stable measurement can be performed even for high-pressure fluid and fluid with pressure fluctuation.

  The fluid flow measuring device of the present invention can stably measure even a high-pressure fluid and a fluid with pressure fluctuation, and can also suppress damage to an ultrasonic transducer.

The block diagram of the flow measurement apparatus in Embodiment 1 of this invention Main part enlarged sectional view of the same flow measuring device Time variation diagram of pressure fluctuations at the measurement part during high-pressure fluid measurement Manufacturing process diagram of the ultrasonic transducer The block diagram of the flow measuring device in Embodiment 2 of this invention The block diagram of the flow measuring device in Embodiment 3 of this invention The block diagram of the flow measurement apparatus in Embodiment 4 of this invention Cross-sectional view of a conventional ultrasonic transducer

  1st invention measures the ultrasonic propagation time between a pair of ultrasonic transducers which are disposed on the upstream and downstream sides of the measurement unit through which the fluid to be measured flows and transmits and receives ultrasonic signals. An internal pressure of a sealed container provided with a measurement circuit and a calculation means for calculating a flow velocity and / or a flow rate based on a signal from the measurement circuit, wherein the piezoelectric body of the ultrasonic transducer is provided is a pressure of the measurement unit It is set within the fluctuation range of P1, the pressure difference between the pressure of the measurement unit and the pressure in the ultrasonic transducer is reduced, the deformation of the sealed container in the ultrasonic transducer can be suppressed, and the contained piezoelectric body Or destruction of the joint between the piezoelectric body and the hermetic container can be prevented, and as a result, stable measurement can be performed even for high-pressure fluid and fluid with pressure fluctuation.

  According to a second aspect of the present invention, in the first aspect of the invention, the internal pressure P2 of the sealed container is set to a substantially average value of the pressure P1 in the measurement unit, so that the measurement pressure can be measured even in the measurement of a high-pressure fluid and a fluid with pressure fluctuation The pressure difference between the pressure in the airtight container and the pressure in the airtight container is reduced, and the deformation of the airtight container can be further suppressed.

  According to a third aspect of the present invention, a pair of ultrasonic transducers that are disposed on the upstream and downstream sides of a measurement unit through which a fluid to be measured flows and transmits and receives ultrasonic signals, and an ultrasonic propagation time between the ultrasonic transducers are measured. A measurement circuit; a calculation unit that calculates a flow velocity and / or a flow rate based on a signal from the measurement circuit; and a pressure detection unit that detects the pressure of the measurement unit. If the internal pressure P2 of the closed container installed is compared with the measurement part pressure P1 detected by the pressure detection means and the pressure abnormality determination is performed, an abnormality is detected when a pressure higher than the pressure assumed for the ultrasonic transducer is applied. Can be displayed to protect it.

4th invention is arrange | positioned in the upstream and downstream of the measurement part through which the fluid to be measured flows, and measures the ultrasonic propagation time between the ultrasonic transducer and a pair of ultrasonic transducers that transmit and receive ultrasonic signals. A measurement circuit; a calculation unit that calculates a flow velocity and / or a flow rate based on a signal from the measurement circuit; and a pressure estimation unit that estimates a pressure of the measurement unit based on a characteristic change of an ultrasonic transducer. By comparing the internal pressure P2 of the sealed container in which the piezoelectric body of the ultrasonic vibrator is installed and the measurement part pressure P1 estimated by the pressure estimating means, and performing pressure abnormality determination, the pressure exceeds the pressure assumed for the ultrasonic vibrator. When high pressure is applied, the abnormality is displayed and the ultrasonic transducer can be protected.

  In a fifth aspect of the invention, in particular, in any one of the first to fourth aspects of the invention, the ultrasonic transducer includes a conductive sealed container having a bottomed cylindrical shape and an open portion closed by a terminal plate, and the sealed container. A piezoelectric body having one electrode side bonded to the inner surface of the top wall, one terminal penetrating the terminal plate while maintaining electrical insulation and connected to the other electrode side of the piezoelectric body, and With the configuration consisting of the other terminal directly fixed to the same terminal plate, it can be measured safely even when measuring flammable fluid, and the chemical change of the piezoelectric electrode contained in the sealed container can be suppressed. Highly reliable measurement.

  In a sixth aspect of the invention, in particular, in any one of the first to fifth aspects of the invention, by setting the Young's modulus of the sealed container to 150 GPa or more, deformation due to the pressure of the celestial cylindrical case can be reduced, It is possible to suppress the destruction of the piezoelectric body contained in the sealed container, or the breakage of the joined portion between the piezoelectric body and the sealed container.

  In the seventh invention, in particular, in any one of the first to sixth inventions, the thickness of the top wall of the sealed container is set larger than the thickness of the side wall, so that the side wall is larger than the top wall due to pressure. It is possible to suppress the deformation of the piezoelectric body that is deformed and contained, or the breakage of the joint portion between the piezoelectric body and the sealed container.

  In the eighth invention, in particular, in the fifth invention, the thickness t of the top wall of the sealed container is in the range of λ / 30 <t <λ / 10, where λ is the wavelength used for the acoustic matching body. By doing so, it is possible to suppress the destruction of the piezoelectric body contained in the sealed container, or the breakage of the joined portion between the piezoelectric body and the sealed container.

  In the ninth aspect of the invention, in particular, in the fifth aspect of the invention, the setting of the internal pressure P2 of the sealed container in the ultrasonic vibrator is performed when the sealed container is sealed with the terminal plate, so that the high pressure can be more easily achieved. An ultrasonic transducer capable of measuring fluid can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 and 2, the flow measuring device 1 according to the present embodiment includes a pair of ultrasonic transducers 3 and 4 on the upstream and downstream sides of the measuring unit 2 through which the fluid to be measured flows, and the measuring unit 2 A configuration is adopted in which ultrasonic waves propagate so as to cross the flowing fluid diagonally.

  The ultrasonic transducer 4 is inserted into the opening 6 of the measurement unit 2 through the insulating elastic body 5 and fixed with a presser 7 or the like, and one ultrasonic transducer 3 is similarly fixed.

  Since the configurations of the ultrasonic transducers 3 and 4 are the same, a specific description will be given using the ultrasonic transducer 4.

  A piezoelectric body 9 is bonded and fixed to the inner surface of the top wall of the conductive celestial cylindrical sealed container 8, and an acoustic matching layer 10 is bonded and fixed to the outer surface of the top wall.

  Electrodes are formed on the upper and lower surfaces of the piezoelectric body 9, and the upper electrodes are electrically connected to the sealed container 8.

A flange is integrally formed outwardly from the lower opening of the sealed container 8, and the outer peripheral upper surface of the conductive terminal plate 11 is welded to the lower surface thereof, whereby the interior is set as a sealed space 12. Yes.

  Normally, the sealed space 12 is filled with an inert gas such as nitrogen gas.

  A conductive elastic material is elastically contacted with an electrode below the piezoelectric body 9, and one terminal 13 penetrating the terminal plate 11 through an electrical insulating portion such as a hermetic seal is electrically connected to the elastic material. ing. On the other hand, the other terminal 14 is directly attached to the terminal plate 11.

  When the pressure difference between the pressure in the sealed space 12 and the pressure in the measurement unit 2 is large, the sealed container 8 is greatly deformed, and the joint portion with the piezoelectric body 9 is destroyed.

  Therefore, it is necessary to reduce the pressure difference between the sealed space 12 and the measurement unit 2.

  FIG. 3 shows the change over time of the pressure fluctuation of the measuring unit 2 during high-pressure fluid measurement.

  That is, at the start of measurement, there is a rising portion A in which the pressure changes abruptly, and the pressure stabilizing portion B becomes smaller in pressure change with time.

  The pressure of the pressure stabilizing part B is Pa, the pressure increase of the rising part A is Pb, and the pressure in the sealed space 12 of the ultrasonic transducer is preferably within the range of Pa. More preferably, by making the pressure within the range of the approximate pressure average value in the pressure stabilization part B of the measurement fluid, the pressure difference of the measurement part 2 can be reduced, and the deformation of the sealed container 8 can be further suppressed.

  The manufacturing method of the ultrasonic transducer described above will be described with reference to FIG.

  FIG. 4A shows the acoustic matching body 10 adjusted to a predetermined thickness. The manufacturing method is, for example, a state in which a glass balloon used as a void forming material is vibrated and filled in a fixed container, and then impregnated with an epoxy resin used as a thermosetting resin, and the epoxy resin is cured by heat and then sliced. Is shown.

  Slicing is performed by dicing or lapping, and the thickness is adjusted to resonate with the piezoelectric body at a predetermined frequency.

  In (b), a joining means 15 made of a thermosetting adhesive or the like used as a joining means is applied to the piezoelectric body 9, and the joining means 16 is similarly applied to the top surface of the sealed container 8.

  Here, the closed container 8 preferably has a Young's modulus of 150 GPa or more.

  Table 1 shows the pressure test results when an ultrasonic vibrator with a material thickness of 200 μm of the sealed container 8 is used. As shown in Table 1, when the sealed container 8 was an iron-based metal and nickel, good results in pressure-proofing were obtained.

  More preferably, it is desirable to use a metal material having a Young's modulus of 200 GPa or more.

  The thermosetting adhesive used as the joining means is not particularly limited as long as it is a thermosetting resin such as an epoxy resin, a phenol resin, a polyester resin, or a melamine resin. Depending on the case, even if it is a thermoplastic resin, if it is 70 degrees C or less whose glass point transfer is high temperature use temperature, it can be used as an adhesive agent.

  In FIG. 4C, the piezoelectric body 9, the sealed container 8, and the acoustic matching body 10 are positioned and bonded together so as to be laminated. At this time, the piezoelectric body 9, the sealed container 8, and the acoustic matching body 10 are fixed in a state where a pressure of about 1 to 10 kg / cm 2 is applied, and the thermosetting adhesive used as the joining means 15 and 16 is cured.

  Curing of the joining means 15 and 16 is performed in a general heating tank. The joining means 15 and 16 are cured and joined by the above-described process, and the terminal plate 11 to which the terminals 13 and 14 are fixed is welded to the sealed container 8 of the semi-finished product 17 that is integrated.

  FIG. 4D shows a completed state of the ultrasonic transducer 4 manufactured through the above steps. Here, at the time of welding, argon gas, nitrogen gas, helium gas or the like, which is an inert gas, is sealed in the sealed space 12 to deteriorate the electrode of the piezoelectric body 9 and the bonded portion of the piezoelectric body 9 and the sealed container 8. It is desirable to reduce

  If the top wall of the sealed container 8 is made thicker than the side wall part, the side wall part is greatly deformed by pressure, and the piezoelectric body 9 contained therein is broken or the piezoelectric body 9 and the sealed container 8 are It is possible to suppress the joint portion from being broken, and as a result, the flow velocity and / or flow rate can be stably measured even with a high-pressure fluid and a fluid with pressure fluctuation.

  The airtight container 8 can be manufactured by forming a cylindrical side wall part, joining it so as to cover the circular top wall part, and integrating the periphery by laser welding or the like.

  Further, if the thickness of the top wall of the sealed container 8 is t and the wavelength used for the acoustic matching layer 10 is λ, the envelope is contained in the sealed container 8 by setting within the range of λ / 30 <t <λ / 10. It is possible to suppress the destruction of the piezoelectric body 9 or the joined portion between the piezoelectric body 9 and the sealed container 8, and as a result, the flow velocity can be stably stabilized even in a high-pressure fluid and a fluid with pressure fluctuation. And / or the flow rate can be measured.

  If the thickness of the sealed container 8 is increased in order to improve the pressure resistance, the balance of acoustic matching is lost, and the propagation efficiency of ultrasonic waves to the measurement fluid is reduced.

  Therefore, from λ / 30 at which the withstand voltage can be ensured to λ / 10 in which the decrease in the ultrasonic wave propagation efficiency is within an allowable range, both withstand voltage and high sensitivity can be achieved.

  When an electrical signal is applied to both electrodes of the piezoelectric body 9, the piezoelectric body 9 vibrates, the acoustic matching layer 10 adjusted so as to resonate with this vibration resonates, and this vibration is transmitted to the measurement fluid.

  This is the operation when transmitting an ultrasonic wave, but in the case of reception, the opposite action is that the ultrasonic wave propagating from the measurement fluid is converted into an electrical signal by the piezoelectric body 10 and the time when the signal arrives. Is used for measurement.

  The measurement method will be described below.

As shown in FIG. 1, the ultrasonic transmission path between the ultrasonic transducers 3 and 4 is L, the flow velocity of the fluid flowing through the measurement unit 2 is V, the ultrasonic velocity of the ultrasonic fluid to be measured is C, the direction of fluid flow and the superfluidity When the angle of the propagation direction of the ultrasonic pulse is θ, the ultrasonic transducer 3 is used as a transmitter, and the ultrasonic transducer 4 is used as a receiver, the ultrasonic pulse from the ultrasonic transducer 3 is converted into an ultrasonic wave. The propagation time t1 reaching the vibrator 4 is
t1 = L / (C + V cos θ) (1)
Indicated by

Next, the propagation time t2 at which the ultrasonic pulse from the ultrasonic transducer 4 reaches the ultrasonic transducer 3 is:
t2 = L / (C−Vcos θ) (2)
Indicated by

And if the sound velocity C of the fluid is eliminated from the equations (1) and (2),
V = L / 2 cos θ (1 / t1-1 / t2) (3)
The following equation is obtained.

  If L and θ are known, the flow velocity V can be obtained via the calculation means 19 if the measurement circuit 18 measures t1 and t2. If necessary, the calculation means 19 can obtain the flow rate Q by multiplying the flow velocity V by the cross-sectional area S and the correction coefficient K of the measuring unit 2.

  As described above, in the present embodiment, the pair of ultrasonic transducers 3 and 4 that are provided in the measurement unit 2 through which the fluid to be measured flows and transmits and receives an ultrasonic signal are connected between the ultrasonic transducers 3 and 4. A measurement circuit 18 for measuring the ultrasonic propagation time and a calculation means 19 for calculating the flow velocity and / or flow rate of the fluid based on the signal from the measurement circuit 18 are provided. The internal pressure P2 of the airtight container 8 is set within the fluctuation range of the pressure P1 of the measurement unit 2, and thus the high pressure fluid and the fluid with pressure fluctuation are measured. The pressure difference between the measured pressure and the internal pressure of the ultrasonic vibrator is reduced, and the deformation of the sealed container 8 in the ultrasonic vibrators 3 and 4 can be suppressed to a small level. 9 destruction or piezoelectric body 9 Can junction between the sealed container 8 is prevented from being destroyed, with the result that it can be measured stably even in high-pressure fluid, and a fluid with a pressure variation.

In the present embodiment, the pressure P2 in the sealed container 8 of the ultrasonic transducers 3 and 4 is approximately the average value of the pressure stabilizing portion of the pressure P1 of the measurement unit 2, thereby allowing high pressure fluid and Even in the measurement of fluid with pressure fluctuation, the pressure difference between the measured pressure and the internal pressure of the ultrasonic transducer is reduced, and the deformation of the closed vessel 8 in the ultrasonic transducers 3 and 4 can be suppressed to a smaller level. It is possible to suppress the destruction of the piezoelectric body 9 included in the body 8 or the joint portion between the piezoelectric body 9 and the sealed container 8, and as a result, it is stable even with a high-pressure fluid and a fluid with pressure fluctuation. Can be measured.

  Further, since the Young's modulus of the sealed container 8 of the present embodiment is 150 GPa or more, deformation due to pressure can be reduced, and the piezoelectric body 9 included in the sealed container 8 is broken or the piezoelectric body 9 is broken. And the sealed container 8 can be prevented from being broken, and as a result, high-pressure fluid and fluid with pressure fluctuation can be stably measured.

  In addition, since the thickness of the top wall of the sealed container 8 of the present embodiment is larger than the thickness of the side wall part, the side wall part is greatly deformed by pressure, and the piezoelectric body included in the sealed container 8 is used. 9 or the joint portion between the piezoelectric body 9 and the sealed container 8 can be suppressed, and as a result, high-pressure fluid and fluid with pressure fluctuation can be stably measured.

  In addition, the thickness of the top wall of the sealed container 8 of the present embodiment is in the range of λ / 30 <t <λ / 10 when the wavelength used for the acoustic matching layer 10 is λ. It is possible to suppress the destruction of the piezoelectric body 9 included in the body 8 or the joint portion between the piezoelectric body 9 and the sealed container 8, and as a result, it is stable even with a high-pressure fluid and a fluid with pressure fluctuation. Can be measured.

(Embodiment 2)
FIG. 5 shows a second embodiment, in which the fluid flow measuring device 1 is arranged so that the ultrasonic transducers 3 and 4 are diagonally opposed to the measuring unit 2 through which the fluid to be measured flows at a predetermined interval. It becomes the composition.

  At the time of measuring the flow velocity and / or flow rate, a pressure detection means 20 is attached to detect an abnormality in the pressure of the measurement unit 2, and the pressure in the sealed container set in advance in the ultrasonic transducers 3 and 4 An abnormality is detected when the pressure of the measuring unit 2 exceeds the assumed withstand pressure and becomes a large pressure, and the detected signal is compared with a preset pressure limit value by the abnormality determination means 21 and exceeds the pressure limit. In this case, a signal is sent to the warning unit 22 and a pressure abnormality is displayed on the display means 23 to notify that an overload, that is, a pressure exceeding the design is applied to the ultrasonic transducers 3 and 4.

  As a result, replacement of the ultrasonic transducers 3 and 4 is promoted, and replacement with a higher pressure resistance, that is, a pressure set in the sealed space of the ultrasonic transducer is increased.

  As described above, the present embodiment is characterized in that the pressure abnormality determination is performed by comparing the pressure in the sealed container of the ultrasonic transducers 3 and 4 with the pressure detected by the pressure detecting means 20. When a pressure higher than the pressure assumed for the ultrasonic vibrators 3 and 4 is applied, an abnormality is displayed and the ultrasonic vibrators 3 and 4 are protected, and the damage due to the pressure can be prevented. it can.

(Embodiment 3)
6 shows the third embodiment, the configuration of the measurement part is the same as in FIG. 1, the same reference numerals are given for convenience, and the specific description of the first embodiment is used.

  The difference is that attention is paid to the characteristic change of the ultrasonic transducers 3 and 4 in order to detect an abnormality in the pressure of the measurement unit 2.

In the characteristic change, for example, the ultrasonic vibrators 3 and 4 are originally vibrators that vibrate in the ultrasonic region. Therefore, when the pressure of the measurement unit 2 increases, the frequency of vibration changes due to distortion due to pressure. Use to detect pressure abnormalities.

  Alternatively, the voltage generated by the piezoelectric effect may be detected when the pressure of the measuring unit 2 increases by using the piezoelectric effect of the piezoelectric body included in the ultrasonic vibrators 3 and 4.

  It is possible to measure the pressure change and pressure abnormality of the measuring unit 2 more accurately by combining numerical values with these alone or in combination.

  As described above, when the pressure of the measuring unit 2 exceeds the assumed withstand pressure and becomes a large pressure, an abnormality is detected, and the detected signal is compared with a pressure limit value set in advance by the abnormality determination unit 21 to determine the pressure limit. When it exceeds, a signal is sent to the warning unit 22 and a pressure abnormality is displayed on the display means 23 to notify that an overload, that is, a pressure exceeding the design is applied to the ultrasonic transducers 3 and 4.

  As a result, replacement of the ultrasonic transducers 3 and 4 is promoted, and replacement with a higher pressure resistance, that is, replacement of the ultrasonic transducers 3 and 4 with a high pressure in the sealed space is promoted.

  As described above, in the present embodiment, the pressure of the measurement unit detected by the characteristic change of the ultrasonic transducers 3 and 4 is estimated, and pressure abnormality determination is performed. Since it is performed by the ultrasonic transducers 3 and 4 themselves, it is very useful in terms of cost.

(Embodiment 4)
FIG. 7 shows the fourth embodiment. In other words, this embodiment is a combination of the ideas of the previous embodiments 2 and 3, and the same reference numerals are given to the components that perform the same operations as in FIGS. Use a few.

  That is, in order to detect the pressure abnormality of the measurement unit 2 with higher accuracy, the pressure abnormality is more accurately performed using the pressure detection means 20 and the characteristic changes of the ultrasonic transducers 3 and 4.

  As described above, in the embodiment of the present invention, the measurement unit 2 through which the fluid to be measured flows, the pair of ultrasonic vibrators 3 and 4 provided in the measurement unit 2, and the pressure detection means 20 of the measurement unit 2 The pressure abnormality determination means 21 of the measurement unit 2, the measurement circuit 18 that measures the ultrasonic propagation time between the ultrasonic transducers 3 and 4, and the flow velocity and / or flow rate based on the signal from the measurement circuit 18 Is provided with a calculation means 19 and a display means 23, and the pressure P2 in the sealed container 8 of the ultrasonic transducers 3 and 4 and the pressure P1 of the measuring unit 2 detected by the pressure detection means 20 are calculated. Combining the means for comparing with the means for estimating the internal pressure P2 of the sealed container 8 of the ultrasonic transducers 3 and 4 and the measurement unit pressure P1 detected by the characteristic change of the ultrasonic transducers 3 and 4 results in abnormal pressure. It is characterized by making a judgment Therefore, when a pressure higher than the pressure assumed by the ultrasonic transducers 3 and 4 is accurately applied, an abnormality is displayed and the ultrasonic transducers 3 and 4 are protected. Destruction can be prevented.

  As described above, the fluid flow measurement device according to the present invention is suitable for measuring the flow velocity and / or flow rate of a high-pressure measurement fluid, and can measure a high-pressure fluid over a long period of time. For back sonar, or a level meter in a tank, household gas meter, water meter, etc. can be applied.

2 Measurement unit 3, 4 Ultrasonic transducer 8 Sealed container 9 Piezoelectric body 10 Acoustic matching layer 11 Terminal plate 13, 14 Terminal 18 Measurement circuit 19 Calculation unit 20 Pressure detection unit 21 Abnormality determination unit 22 Warning unit 23 Display unit

Claims (9)

A pair of ultrasonic transducers that are arranged on the upstream and downstream sides of the measurement unit through which the fluid to be measured flows, transmits and receives ultrasonic signals, a measurement circuit that measures ultrasonic propagation time between the ultrasonic transducers, and the measurement Calculating means for calculating the flow velocity and / or flow rate based on the signal from the circuit, and the internal pressure of the sealed container in which the piezoelectric body of the ultrasonic transducer is provided is within the fluctuation range of the pressure P1 of the measurement unit. Set fluid flow measuring device. The fluid flow measuring device according to claim 1, wherein the internal pressure P2 of the sealed container is a substantially average value of the pressure P1 in the measuring unit. A pair of ultrasonic transducers that are arranged on the upstream and downstream sides of the measurement unit through which the fluid to be measured flows, transmits and receives ultrasonic signals, a measurement circuit that measures ultrasonic propagation time between the ultrasonic transducers, and the measurement An internal pressure of an airtight container having a calculation means for calculating a flow velocity and / or a flow rate based on a signal from a circuit and a pressure detection means for detecting the pressure of the measurement unit, in which a piezoelectric body of the ultrasonic vibrator is provided A fluid flow measuring device characterized in that P2 and a measuring section pressure P1 detected by the pressure detecting means are compared to determine pressure abnormality. A pair of ultrasonic transducers that are arranged on the upstream and downstream sides of the measurement unit through which the fluid to be measured flows, transmits and receives ultrasonic signals, a measurement circuit that measures ultrasonic propagation time between the ultrasonic transducers, and the measurement A calculation unit that calculates a flow velocity and / or a flow rate based on a signal from the circuit; and a pressure estimation unit that estimates a pressure of the measurement unit based on a characteristic change of the ultrasonic transducer, the piezoelectric body of the ultrasonic transducer A fluid flow measuring device characterized in that pressure abnormality determination is performed by comparing an internal pressure P2 of an airtight container provided with a measuring portion pressure P1 estimated by the pressure estimating means. The ultrasonic vibrator has a cylindrical shape with a bottom and an open portion closed by a terminal plate, a piezoelectric body housed in the closed vessel, and one electrode side bonded to the inner surface of the top wall, The terminal plate penetrates the terminal plate while maintaining electrical insulation, and includes one terminal connected to the other electrode side of the piezoelectric body and the other terminal directly fixed to the terminal plate, and the top of the sealed container. The fluid flow measuring device according to any one of claims 1 to 4, wherein an acoustic matching body is provided on the outer wall surface. The fluid flow measuring device according to claim 1, wherein the Young's modulus of the sealed container is set to 150 GPa or more. The fluid flow measuring device according to any one of claims 1 to 6, wherein the thickness of the top wall of the sealed container is set to be thicker than the thickness of the side wall. 6. The fluid flow measuring device according to claim 5, wherein the thickness t of the top wall of the sealed container is set to λ / 30 <t <λ / 10, where λ is a wavelength used for the acoustic matching body. 6. The fluid flow measuring device according to claim 5, wherein the setting of the internal pressure P2 of the sealed container in the ultrasonic vibrator is performed when the sealed container is sealed with a terminal plate.