JP2006105706A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detection part excellent in operability, manufacturing, transporting, moreover in workability at the time of installation, and easy of keeping reliability and in securing of accuracy in an ultrasonic flow meter of sound tube type. <P>SOLUTION: The ultrasonic flowmeter comprises: a measurement tube made of synthetic resin; a 1st ultrasonic transducer made to close contact with the measurement tube; a 2nd ultrasonic transducer made to close contact with the measurement tube at the point apart from the 1st ultrasonic transducer along the tube axis of the measurement tube to be measured; the sound source for supplying an electric signal only to either transducer of the 1st ultrasonic transducer and the 2nd ultrasonic transducer; the delay measuring part for measuring the delay time between the electric signal and the reproduced electric signal which is converted by receiving the ultrasonic wave transmitted by converting the electric signal into mechanical vibration by another oscillator; and the operation unit for operating the flow of the object fluid flowing in the measurement tube on the basis of the difference of delay time observed at the time of switching either oscillator and another oscillator alternately. The 1st ultrasonic oscillator and the 2nd ultrasonic oscillator are provided on the flexible band which is formed in a sheet provided with a polymer piezoelectric film on the contact surface with the measurement tube. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a configuration of a detection unit of an acoustic tube type ultrasonic flowmeter.

  As a measuring instrument using an ultrasonic sensor typified by an annular piezoelectric ceramic, for example, there is the following document as a prior art of an ultrasonic flowmeter.

JP-A-10-122923 JP-A-11-264750 JP 2000-180228 A

  FIG. 2 is a block diagram showing an example of such a conventional acoustic tube type ultrasonic flowmeter.

  The conventional ultrasonic flowmeter of FIG. 2 includes a measurement tube 1 that is a straight fluororesin pipe, piezoelectric ceramics 2A and 2B that are formed into an annular shape with a fixed width when mounted on the measurement tube 1, and a signal source 3 The delay measuring units 4 and 4B, the arithmetic circuit 5, and the control switches 6A and 7 are configured.

  Piezoelectric ceramics 2A and 2B are arranged at a predetermined distance from the measurement tube 1 through which the fluid to be measured flows. At this time, the piezoelectric ceramics 2A and 2B are in close contact with the entire circumference along the outer circumference of the measuring tube 1, and are connected to the common signal source 3 via control switches 6A and 6B, respectively, at the respective signal input ends. is doing.

The delay measuring units 4A and 4B are connected to signal output terminals of the piezoelectric ceramics 2A and 2B in addition to the signal source 3, respectively.
Each measurement value output from the delay measurement units 4A and 4B is connected to the calculation unit 5, respectively.

  Next, the operation of the conventional example shown in FIG. 2 will be described.

  Piezoelectric ceramics 2A and 2B are elements having an interconversion action between electric energy and mechanical vibration energy, and transmit and receive ultrasonic waves using a fluid to be measured in the measuring tube 1 as a medium.

At this time, the piezoelectric ceramics 2A and 2B exclusively execute an ultrasonic wave transmission operation. That is, the control switches 6A and 6B are alternately opened and closed to connect one of the piezoelectric ceramics to the signal source 3, and only the piezoelectric ceramic on the connected side transmits ultrasonic waves.
On the other hand, in the piezoelectric ceramic on the receiving side, the ultrasonic wave propagated using the fluid to be measured in the measuring tube 1 as a medium is regenerated into an electrical signal.

  The delay measurement unit 4A or 4B corresponding to the piezoelectric ceramic on the receiving side measures the time difference between the electric signal of the signal source 3 used on the transmitting side and the reproduced electric signal reproduced from the received ultrasonic wave.

  However, the ultrasonic wave received by the piezoelectric ceramic downstream of the fluid to be measured arrives faster than the case where it propagates through the stationary medium by the addition of the moving speed of the medium. On the contrary, the ultrasonic wave received by the piezoelectric ceramics located on the upstream side of the fluid to be measured arrives with a delay corresponding to the subtraction of the moving speed of the medium.

  The computing unit 5 computes the moving speed of the fluid to be measured corresponding to the medium moving speed with reference to the time difference required for the arrival of the ultrasonic waves obtained by the observation by the delay measuring units 4A and 4B.

  However, in the conventional acoustic tube type ultrasonic flow meter shown in FIG. 2, the piezoelectric ceramics generally used have the following problems.

  The first problem is that since the material is ceramics, it is difficult to process when it is formed into an annular shape, which requires a lot of labor and cost.

  The second problem is that ceramics are heavy and bulky when mounted on a measuring tube, and are difficult to handle on site. For example, when installing an ultrasonic flow meter, to place the measuring tube in the hole in the center of the ring-shaped ceramic, divide it into two semicircular shapes, bring it into the field, and then assemble it with the measuring tube in between. In addition, it is necessary to remove a part of the measuring tube, pass it through the annular hole, and return it to the pipe line again.

  As described above, when the ultrasonic flowmeter is moved, installed, or removed, the construction work procedure becomes complicated, and it takes time for test adjustment and inspection after the installation.

  The third problem is that, particularly when the material of the measuring tube is a resin pipe, the thermal expansion coefficients of ceramics and fluororesin are greatly different. For this reason, the repeated stresses of expansion and compression accompanying temperature changes have caused problems such as permanent peeling on the bonding surface between the piezoelectric ceramics and the measuring tube and the occurrence of temporary bonding failure sites due to temperature changes. .

  As described above, in the conventional ultrasonic flowmeter in operation, a lot of maintenance man-hours have been expended for periodic inspection and the like because it is necessary to ensure reliability and maintain accuracy.

  The present invention has been made to solve the above-mentioned problems, and the object thereof is an acoustic tube type ultrasonic flowmeter, which is excellent in handling, manufacturing transportation and workability during installation, and maintaining reliability and accuracy. An object of the present invention is to provide a detection unit that can be easily secured.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
A measurement tube made of resin, a first ultrasonic transducer closely attached to the measurement tube, and the measurement tube at a predetermined distance from the first ultrasonic transducer along the tube axis of the tube to be measured A second ultrasonic transducer in close contact with the first ultrasonic transducer, a signal source for applying an electrical signal to only one of the first ultrasonic transducer and the second ultrasonic transducer, and transmitting the electrical signal by converting it into mechanical vibration A delay measuring unit that measures a delay time in which the reproduced electrical signal converted by the other receiving the received ultrasonic wave is delayed from the electrical signal, and the delay observed when the one and the other are alternately switched In an ultrasonic flowmeter provided with a calculator that calculates the flow velocity of the fluid to be measured flowing through the measurement tube based on the difference in time,
The ultrasonic wave characterized in that the first ultrasonic vibrator and the second ultrasonic vibrator are provided on a flexible band having a polymer piezoelectric film on the contact surface side with the measurement tube and processed into a sheet shape. It is a flow meter.

The invention according to claim 2
The ultrasonic flowmeter according to claim 1, wherein the flexible band further includes a flexible printed board and has a first fitting portion that accommodates the electrode of the polymer piezoelectric film at one end thereof. The other end portion has a second fitting portion that interfaces with the signal source and the delay measuring portion.

  The invention according to claim 3 is the ultrasonic flowmeter according to claim 1 or 2, characterized in that the flexible band is wound around and fixed to the measuring tube within a predetermined outer peripheral dimension standard. .

  The invention according to claim 4 is characterized in that the flexible band further comprises a hook-and-loop fastener that is wound around and fixed to the measuring tube within a predetermined outer peripheral dimension standard. This is an ultrasonic flowmeter.

The present invention has the following effects.
According to the first, second, third, and fourth aspects of the present invention, the first ultrasonic transducer and the second ultrasonic transducer of the ultrasonic flowmeter corresponding to the detection unit of the acoustic tube type are respectively connected to the flexible band. Mounted on top.

  Compared with conventional piezoelectric ceramics molded into an annular shape, it is possible to provide an ultrasonic vibrator with a soft and flexible material. For this reason, the measurement location can be freely selected without being restricted by the cross-sectional shape of the measurement tube.

  That is, it is not necessary to have a circular cross section if the outer peripheral length of the measurement pipe line is within a predetermined range. Furthermore, since the ultrasonic transducer has the second fitting portion, connection and assembly work with the main body portion relating to the calculation such as the signal source and the delay measurement portion can be easily performed. The first fitting portion can be exchanged with another polymer piezoelectric film in the same series having a film-like electrode.

  For this reason, the polymer piezoelectric film accommodated in the flexible band can be separated from the first fitting portion as necessary, and replaced with a polymer piezoelectric film having another rated value. That is, the detection unit can be easily upgraded and maintained.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a detection unit of an ultrasonic flowmeter according to the present invention. FIG. 1A shows a surface corresponding to the front side of the measurement tube, and FIG. 1B shows a contact surface with the measurement tube, that is, a surface on the back side.

  In FIG. 1, a flexible sheet 10 constitutes a main body of a first or second ultrasonic transducer that is a detection unit of an ultrasonic flowmeter. The polymer piezoelectric film 11 is a rectangular film processed into a sheet shape, and includes a pair of electrodes 12.

  The flexible printed board 13 is electrically and mechanically fixed to the two electrodes 12 via the first fitting portion 15. Three rivets 18 are used for the polymer piezoelectric film 11, the flexible sheet 10 and the flexible printed board 13.

  The other end of the flexible printed board is provided with a second fitting portion 16 that is a connector. The flexible sheet 10 has a through hole 14 on the opposite side of the flexible printed board 13. Further, hook fasteners 17 are provided at both ends of the front side.

  Next, the operation of the embodiment shown in FIG. 1 will be described.

  The flexible sheet 10 is made of a low-rigidity material that is highly durable and can be bent and twisted and does not cause an extreme change in shape due to temperature and humidity. On the back side thereof, that is, on the contact surface with the measurement tube, the polymer piezoelectric film 11 is used. Are mechanically held and follow the shape change of the flexible sheet 10 to have an action of integration.

  For this reason, only the sheet film-like polymer piezoelectric film 11 can be replaced and repaired and maintained as necessary, or the rated value of the polymer piezoelectric film 11 serving as a vibrator can be easily changed by replacement. it can. Such an effect cannot be expected in the prior art using a piezoelectric ceramic vibrator processed into an annular shape.

  The second fitting unit 16 as a connector has an action of interfacing electrically with an external delay measurement unit and a calculation unit (not shown). Therefore, when the ultrasonic flowmeter is installed in the measurement tube, an electrical interface with the detection unit can be easily performed, and the assembling workability is improved.

  When the through hole 14 provided in the flexible sheet 10 is wound around the measuring tube and attached, the second fitting portion 16 side is passed through the hole and the whole is fastened to bond the hook-and-loop fasteners 17 such as Velcro (registered trademark). .

  Further, if necessary, it is fastened and fixed with a fixing band or the like from the outside of the flexible sheet 10 to improve the close contact with the measurement tube and to prevent the measurement tube from dropping off or being displaced.

  According to Example 1 having such a configuration, an ultrasonic vibrator can be mounted by winding a soft belt-like flexible sheet around a measurement tube instead of the annular piezoelectric ceramic. For this reason, even if the cross-sectional shape of the measuring tube is not a circle that perfectly matches the inner diameter of the ceramics, the ultrasonic transducer can be attached with the entire surface in close contact as a result of changing the curvature freely according to the cross-sectional shape of the measuring tube. There is an effect that can be done.

  Further, even when the fluororesin pipe as a measurement tube and the polymer piezoelectric film have close thermal expansion coefficients and are exposed to a temperature cycle or the like, peeling at the contact surface can be prevented. For this reason, it is not necessary to add a filler such as packing or grease, which has been conventionally supplemented when the piezoelectric ceramic is attached to the measuring tube, to the contact surface.

  Furthermore, compared to conventional piezoelectric ceramics that are bulky and bulky, the first embodiment of the present invention employs a sheet film-like ultrasonic vibrator, so it is extremely easy to carry and handle during assembly. It is.

  In addition, since the material of the ultrasonic transducer is changed from piezoelectric ceramic to polymer piezoelectric film, the acoustic impedance value is close to that of resin piping and measurement fluid, and the detection sensitivity is improved, and the mechanical Q value is extremely small and packed. A single-pulse transmission / reception waveform with good crispness can be obtained without requiring the insertion of a member or the like, and the advantage that the signal processing of the arithmetic unit can be simplified can be obtained.

  As described above, according to the present invention, in the acoustic tube type ultrasonic flow meter, the use of the polymer piezoelectric film makes it easy to handle, manufacture, transport, and install, and is reliable. Can provide an ultrasonic flowmeter capable of ensuring and improving accuracy.

  Furthermore, according to the present invention, even if the cross section of the measuring tube is not circular but irregular, it can be flexibly changed in shape and installed.

  When installing the ultrasonic flowmeter of the present invention, the outer surface of the flexible tube is wound around the measurement tube, and then the surface to be contacted with the measurement tube is tightened with a metal or plastic fixing band. It can be securely fixed with the mechanical pressure applied to ensure the necessary and sufficient durability.

It is a 2nd figure which shows the Example of this invention. It is a block diagram which shows an example of the conventional acoustic tube type ultrasonic flowmeter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flexible sheet 11 Polymer piezoelectric film 12 Electrode 13 Flexible printed board 17 Surface fastener 18 Rivet

Claims (4)

A measurement tube made of resin, a first ultrasonic transducer closely attached to the measurement tube, and the measurement tube at a predetermined distance from the first ultrasonic transducer along the tube axis of the tube to be measured A second ultrasonic transducer in close contact with the first ultrasonic transducer, a signal source for applying an electrical signal to only one of the first ultrasonic transducer and the second ultrasonic transducer, and transmitting the electrical signal by converting it into mechanical vibration A delay measuring unit that measures a delay time in which the reproduced electrical signal converted by the other receiving the received ultrasonic wave is delayed from the electrical signal, and the delay observed when the one and the other are alternately switched In an ultrasonic flowmeter provided with a calculator that calculates the flow velocity of the fluid to be measured flowing through the measurement tube based on the difference in time,
The ultrasonic wave characterized in that the first ultrasonic vibrator and the second ultrasonic vibrator are provided on a flexible band having a polymer piezoelectric film on the contact surface side with the measurement tube and processed into a sheet shape. Flowmeter.   The flexible band further includes a flexible printed board and has a first fitting portion that accommodates the electrode of the polymer piezoelectric film at one end thereof, and the signal source and the delay measurement portion at the other end. The ultrasonic flowmeter according to claim 1, further comprising a second fitting portion that interfaces.   The ultrasonic flowmeter according to claim 1 or 2, wherein the flexible band is wound around and fixed to the measurement tube within a predetermined outer peripheral dimension standard. The ultrasonic flowmeter according to any one of claims 1 to 3, wherein the flexible band further includes a hook-and-loop fastener that is wound around and fixed to the measurement tube within a predetermined outer peripheral dimension standard.

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