JP2007201993A - Ultrasonic transducer and ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic transducer which estimates a direction of a piezoelectric material having an anisotropy sealed by a case and a terminal strip from an appearance of the ultrasonic transducer. <P>SOLUTION: In the ultrasonic transducer 9 comprised of the piezoelectric material 21 having the anisotropy and the terminal strip 19 connected to a flange portion 18a as sealing the piezoelectric material 21, the direction of the piezoelectric material 21 is estimated from the appearance of the ultrasonic transducer 9, a deterioration of a transceiver sensitivity is prevented, and a reduction of a measuring accuracy is prevented, by arranging the terminal strip 19 so as to suit a line to join external electrode terminals 22 and 23 to the direction of the piezoelectric material 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic transducer that performs transmission and reception of ultrasonic pulses and an ultrasonic flowmeter that measures the flow rate and flow velocity of gas and liquid using the ultrasonic transducer.

Conventionally, as shown in FIGS. 9 and 10, the ultrasonic transducer used in this type of ultrasonic flowmeter is the inner wall surface of the top portion 3 of the celestial cylindrical case 2. The piezoelectric body 4 is bonded and fixed, and the terminal plate 6 is joined to the flange portion 5 to seal the piezoelectric body 4, so that the safety and the reliability of the piezoelectric body are measured when the flow rate of the flammable fluid is measured. (For example, refer to Patent Document 1). Further, the case 2 is provided with a bent portion 7 so that the direction of the piezoelectric body 4 can be seen, and it has been devised so that the direction of the piezoelectric body 4 that cannot be observed can be seen from the appearance.
JP 2000-298045 A

  However, in the conventional configuration, when a pair of ultrasonic transducers are mounted facing each other on the flow rate measurement unit of the ultrasonic flowmeter, for example, the bent portion cannot be observed from the outside, the piezoelectric flow meter is assembled in the ultrasonic flowmeter assembly process. The direction of the body cannot be estimated. For this reason, the piezoelectric body 4 cannot be set in a predetermined direction, and the transmission / reception sensitivity is lowered, so that the measurement accuracy is lowered.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides an ultrasonic transducer capable of estimating the direction of an anisotropic piezoelectric body sealed with a case and a terminal plate from the appearance of the ultrasonic transducer. It is intended to provide.

  In order to solve the above-described conventional problems, an ultrasonic transducer according to the present invention includes a ceiling-shaped case having a top portion, a side wall portion, and a flange portion, and an anisotropic body connected to the inner wall surface of the top portion. In an ultrasonic transducer comprising a piezoelectric body having a property and a terminal plate connected to a flange so as to seal the piezoelectric body, the direction of the piezoelectric body can be estimated from the appearance of the ultrasonic transducer It constitutes a direction identification means.

  Thus, when a pair of ultrasonic transducers are used facing each other, the direction of the piezoelectric body can be arranged in a predetermined direction by using the direction identification means of the ultrasonic transducer.

  It is possible to estimate the orientation of the anisotropic piezoelectric body sealed with the case and terminal board from the appearance of the ultrasonic transducer, and the orientation of the piezoelectric body sealed inside the ultrasonic transducer By controlling this, it is possible to prevent a decrease in transmission / reception sensitivity and a decrease in measurement accuracy.

  1st invention is the ultrasonic transducer which sealed the piezoelectric material which has anisotropy of shape in a case, Comprising: The arrangement | positioning information of a piezoelectric material can be estimated from the external appearance of an ultrasonic transducer Since the direction identification means is provided, it is possible to prevent a decrease in transmission / reception sensitivity by controlling the direction of the piezoelectric body sealed inside the ultrasonic transducer, and it is possible to prevent a decrease in measurement accuracy. .

  In particular, the second invention is characterized in that the ultrasonic transducer according to the first invention has an anisotropy connected to a ceiling-like case having a top portion, a side wall portion, and a flange portion, and an inner wall surface of the top portion. Since the piezoelectric body having the terminal plate connected to the flange portion so as to seal the piezoelectric body is provided, the piezoelectric body can be sealed, and the long-term reliability of the ultrasonic transducer can be improved.

  In the third invention, in particular, since the direction identification means of the ultrasonic transducer of the first or second invention is provided on the outer surface of the terminal plate, the piezoelectric body sealed inside the ultrasonic transducer is provided. It becomes easy to control the direction, can prevent the transmission / reception sensitivity from decreasing, and can prevent the measurement accuracy from decreasing.

  In the fourth invention, in particular, the direction identification means of the ultrasonic transducer of the first or second invention is a straight line formed by connecting predetermined two of the plurality of external electrode terminals provided on the terminal plate, Since the direction indicated by the direction identification means and the direction of the piezoelectric body are set at a predetermined angle, the direction of the piezoelectric body sealed inside the ultrasonic transducer is easily controlled, and the transmission / reception sensitivity is reduced. Therefore, it is possible to prevent a decrease in measurement accuracy.

  The fifth invention is particularly the case where three or more external electrode terminals are provided on the terminal plate of the ultrasonic transducer of the fourth invention, and the two external electrode terminals used for the direction identification means are other Because it has a shape different from that of the external electrode terminal, it becomes easy to control the orientation of the piezoelectric body sealed inside the ultrasonic transducer, and it can prevent a decrease in transmission and reception sensitivity and prevent a decrease in measurement accuracy. Is possible.

  In the sixth invention, in particular, the direction identification means of the ultrasonic transducer of the first or second invention is a line or symbol provided on the outer surface of the terminal plate of the ultrasonic transducer, and the direction identification means The direction of the piezoelectric body and the direction of the piezoelectric body are set so as to have a predetermined positional relationship. Therefore, the orientation of the piezoelectric body sealed inside the ultrasonic transducer can be easily controlled, and deterioration of transmission / reception sensitivity is prevented. Therefore, it is possible to prevent a decrease in measurement accuracy.

  In the seventh aspect of the invention, in particular, since the piezoelectric body is sealed with the case and the terminal plate of the ultrasonic transducer according to the sixth aspect of the invention, the direction identification means consisting of a line or a symbol is provided on the outer surface of the terminal plate. Control of the direction of the piezoelectric body sealed inside the ultrasonic transducer is facilitated, and it is possible to prevent a decrease in transmission / reception sensitivity and a decrease in measurement accuracy.

  In the eighth invention, in particular, at least one surface of the piezoelectric body of the ultrasonic wave transmitter / receiver of the first or second invention is at least one of the transmitting / receiving surface or the surface facing the transmitting / receiving surface. Since a groove is provided and the arrangement information of the piezoelectric body is the direction of at least one groove of the groove, it becomes easy to control the direction of the piezoelectric body sealed inside the ultrasonic transducer, and the transmission / reception sensitivity is lowered. Therefore, it is possible to prevent a decrease in measurement accuracy.

  The ninth invention is the ultrasonic transducer according to any one of the second to eighth inventions provided with a matching layer on the outer wall surface of the top of the case, so that the transmission / reception sensitivity can be improved and the measurement accuracy can be improved. Can be improved.

A tenth aspect of the invention is a flow rate measurement unit through which a fluid to be measured flows, a pair of ultrasonic transmission / reception units according to any one of the first to ninth aspects that are provided in the flow rate measurement unit and transmit / receive ultrasonic waves, A driving circuit for driving the ultrasonic transducer, a reception detection circuit for detecting an ultrasonic pulse connected to the other ultrasonic transducer, a timer for measuring a propagation time of the ultrasonic pulse, An ultrasonic flowmeter comprising a drive circuit, a control unit for controlling the timer, and a calculation unit for calculating a flow rate from an output of the timer, wherein the ultrasonic flowmeter includes the ultrasonic transducer It is arranged so that only the outer surface of the terminal plate can be observed, and the mounting angle of the ultrasonic transducer is the direction indicated by the direction identification means of one ultrasonic transducer and the direction of the other ultrasonic transducer The direction indicated by the identification means is a predetermined angle Therefore, it becomes easy to control the direction of the piezoelectric body sealed inside the ultrasonic transducer, can prevent a decrease in transmission / reception sensitivity, and can prevent a decrease in measurement accuracy. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attaches | subjects the same code | symbol in drawing is the same thing, and abbreviate | omits detailed description. Further, the present invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of an ultrasonic flowmeter using the ultrasonic transducer according to the first embodiment of the present invention. In FIG. 1, 8 is a flow rate measuring unit through which a fluid to be measured flows, 9, 10 are ultrasonic transducers arranged obliquely with respect to the flow direction of the flow rate measuring unit 8, and 11 is an ultrasonic transducer. Reference numerals 9 and 10 denote oscillation circuits that transmit operating frequencies, reference numeral 12 denotes a drive circuit that is connected to the oscillation circuit 11 and drives the ultrasonic transducers 9 and 10, reference numeral 13 denotes a switching circuit that switches the ultrasonic transducers to be transmitted and received, and reference numeral 14 A reception detection circuit for detecting an ultrasonic pulse, 15 is a timer for measuring the propagation time of the ultrasonic pulse, 16 is a calculation unit for calculating a flow rate from the output of the timer 15, and 17 is a control signal output to the drive circuit 12 and the timer 15 It is a control part.

  The operation of the ultrasonic flowmeter configured as described above will be described. In the present embodiment, the gas to be measured is assumed to be a city gas and a household gas meter is assumed to be an ultrasonic flow meter, and the material constituting the flow rate measuring unit 8 is an aluminum alloy die casting.

  In addition, about 500 kHz is selected as the operating frequency of the ultrasonic transducers 9 and 10. The oscillation circuit 11 is composed of, for example, a capacitor and a resistor, and transmits a square wave of about 500 kHz. The drive circuit 11 drives the ultrasonic transducer 9 from the signal of the oscillation circuit 11, and the square wave is composed of a burst signal of three waves. A drive signal can be output. The measuring means uses a single-around method to improve the resolution of the measured flow rate.

  The control unit 17 outputs a transmission start signal to the drive circuit 12 and starts time measurement of the timer 15 at the same time. When receiving the transmission start signal, the drive circuit 12 drives the ultrasonic transducer 9 and transmits an ultrasonic pulse. The transmitted ultrasonic pulse propagates through the flow rate measuring unit 8 and is received by the ultrasonic transducer 10. The received ultrasonic pulse is converted into an electrical signal by the ultrasonic transducer 10 and output to the reception detection circuit 14. The reception detection circuit 14 determines the reception timing of the reception signal and outputs the reception detection signal to the control unit 17. Upon receipt of the reception detection signal, the control unit 17 outputs a transmission start signal to the drive circuit 12 again after a preset delay time td has elapsed, and performs the second measurement. After repeating this operation N times, the timer 15 is stopped. The calculation unit 16 calculates the propagation time t1 by dividing the time measured by the timer 15 by the number of times N and subtracting the delay time td.

  Subsequently, the ultrasonic transducer connected to the drive circuit 12 and the reception detection circuit 14 is switched by the switching circuit 13, and the control unit 17 again outputs a transmission start signal to the drive circuit 12 and simultaneously starts time measurement of the timer 15. Contrary to the measurement of the propagation time t1, an ultrasonic pulse is transmitted by the ultrasonic transducer 10 and the measurement received by the ultrasonic transducer 9 is repeated N times, and the propagation time t2 is calculated by the calculation unit 16.

Here, the distance connecting the centers of the ultrasonic transducer 9 and the ultrasonic transducer 10 is L, the speed of sound in an airless state is C, the flow velocity in the flow rate measuring unit 8 is V, and the flow of the non-measurement fluid The propagation time t1 and t2 are expressed as follows, where θ is the angle between the direction of and the line connecting the centers of the ultrasonic transducer 9 and the ultrasonic transducer 10.
t1 = L / (C + V cos θ) (1)
t2 = L / (C−Vcos θ) (2)
Indicated by (1) When sonic velocity C is eliminated from equation (2) and flow velocity V is obtained, V = L / 2 cos θ (1 / t1−1 / t2) (3)
Is obtained. Since L and θ are known, the flow velocity V can be obtained by measuring t1 and t2. If the flow velocity V and the area of the flow rate measuring unit 8 are S and the correction coefficient is K, the flow rate Q is Q = KSV (4)
It can be calculated with.

  An ultrasonic transducer used in an ultrasonic flowmeter that performs flow measurement based on the above operation principle will be described with reference to FIGS.

  2 is an external view of the ultrasonic transducer according to the first embodiment, FIG. 3 is a cross-sectional view of the ultrasonic transducer, and FIG. 4 is an external view of a piezoelectric body used in the ultrasonic transducer.

  In FIG. 2, the ultrasonic transducer 9 (the ultrasonic transducer 9 and the ultrasonic transducer 10 have the same configuration) are provided on the outer side of the top 18 a of the cylindrical case 18 and the top 18 a of the case 18. It consists of a matching layer 20 and a terminal plate 19 connected to the flange portion 18 b of the case 18. 3, the ultrasonic transducer 9 includes a piezoelectric body 21 connected to the inside of the top 18a of the case 18, a terminal plate 19 having external electrode terminals 22 and 23, an external electrode terminal 22, and a piezoelectric element. It consists of a conductive rubber 24 that pressurizes and connects the body 21. As shown in FIG. 4, the piezoelectric body 21 used in the ultrasonic transducer 9 has two surfaces 21a and 21b as electrode surfaces, a length L, a width W, and a thickness T.

  For example, when the length of the piezoelectric body 21 used in the ultrasonic transducer 9 is L = 8 mm and the width is W = 3, the electrode surface 21a (the electrode surface 21a and the electrode surface 21b have the same configuration) has a rectangular shape. The piezoelectric body has anisotropy. When the electrode surfaces 21a of the piezoelectric bodies 21 used in the ultrasonic transducers 9 and 10 are opposed to each other in parallel, the transmission / reception sensitivity is maximized. However, since the piezoelectric body 21 is sealed by the case 18 and the terminal plate 19, the direction of the electrode surface 21a cannot be observed. Furthermore, since the case 19 is cylindrical, the direction of the electrode surface 21a rotates like a clock hand, and the direction cannot be estimated from the appearance.

  Therefore, as shown in FIG. 5, the long side of the electrode surface 21a is AA ', the line connecting the centers of the external electrode terminals 21 and 22 provided on the terminal plate 19 is BB', and the line connecting the long side AA 'and the external electrode terminal The ultrasonic transducer 9 is configured so that BB ′ is parallel. With this configuration, the direction of the electrode surface 21a can be controlled by controlling the direction of the line BB 'connecting the external electrode terminals of the ultrasonic transducers 9 and 10.

  Here, a case where ultrasonic transducers 9 and 10 are attached to the flow rate measuring unit 8 will be considered. As described above, the direction of the line BB 'connecting the external electrode terminals is controlled in order to make the electrode surfaces 21a of the piezoelectric body 21 face each other in parallel. However, when the ultrasonic transducers 9 and 10 are attached to the flow rate measuring unit 8, it is difficult to observe the external electrodes 22 and 23 of the two ultrasonic transducers 9 and 10 at the same time. Therefore, a reference line CC ′ is set on the top surface 8a (or bottom surface 8b) of the flow rate measuring unit 8, and the ultrasonic transducer 9 is set so that the line BB ′ connecting the reference line CC ′ and the external electrode is parallel. 10 is attached. As a result, the electrode surfaces 21a of the piezoelectric body 21 can be made to face each other in parallel, the transmission / reception sensitivity is increased, and the flow rate measurement accuracy is improved.

In the first embodiment, the piezoelectric body 21 is a rectangular parallelepiped having a length of L = 8 mm and a width of W = 3 mm. However, the piezoelectric body 21 is a piezoelectric body having an anisotropic shape such as an elliptical column or a triangular column. It doesn't matter if it exists. In addition, the line BB ′ connecting the external electrode terminals and the long side AA ′ of the electrode surface 21a are configured to be parallel to each other. However, the line BB ′ may be a right angle, and may be set to any angle as long as it can be managed. The long side of the electrode surface 21a is AA ′, but the short side may be AA ′. Further, although the ultrasonic transducer 9 is configured to include the matching layer 20, it is not necessary to include the matching layer 20 depending on the fluid to be measured.

(Embodiment 2)
FIG. 6 is an external view of the ultrasonic transducer viewed from the terminal board side of the second embodiment. 8 is a flow measurement unit, 8a is a top surface of the flow measurement unit 9, 8b is a bottom surface of the flow measurement unit 8, 19 is a terminal plate, 21a is an electrode surface of the sealed piezoelectric body 21, and 22 and 23 are terminal plates 19. The above is the same as the configuration of FIG. The difference from the configuration of FIG. 5 is that a third external electrode terminal 25 is provided on the terminal plate 19.

  For example, if there are three external electrode terminals on the terminal plate 9, three lines BB ′ connecting the external electrode terminals can be drawn, so the line BB ′ connecting the external electrode terminals and the long side AA ′ of the electrode surface 21a are set in parallel. It becomes difficult to do. Therefore, the thickness of the external electrode terminals 22 and 23 is increased, and the external electrode terminal 25 is decreased. By using the external electrode terminals 22, 23, and 25 having different thicknesses as described above, if the line connecting the thick external electrode terminals 22 and 23 is BB ′, the direction of the piezoelectric body 21 can be controlled. .

  The method of attaching the ultrasonic transducer configured as described above to the flow rate measuring unit 8 and the operation principle of the ultrasonic flow meter are the same as those in the first embodiment, and therefore will be omitted.

  In the second embodiment, the external electrode terminals 22 and 23 are thick and the external electrode terminal 25 is thin. However, if the external electrode terminals 22 and 23 and the external electrode terminal 25 can be distinguished, the external electrode terminals 22 and 23 are used. You may change the shape and color of the glass hermetic. Although the number of external electrode terminals is three, the number of external electrode terminals may be four or more as long as two external electrode terminals 22 and 23 can be distinguished from other external electrode terminals.

(Embodiment 3)
FIG. 7 is an external view of an ultrasonic transducer viewed from the terminal board side according to the third embodiment. 8 is a flow measurement unit, 8a is a top surface of the flow measurement unit 8, 8b is a bottom surface of the flow measurement unit 8, 19 is a terminal plate, 21a is an electrode surface of the sealed piezoelectric body 21, and 22 and 23 are terminal plates 19. The above is the same as the configuration of FIG. 5 is different from the configuration of FIG. 5 in that a direction indicating line 26 is provided on the terminal board 19 as direction identification means.

  After the terminal plate 19 is arranged so that the long side AA ′ of the electrode surface 21 a and the direction indicating line 26 are parallel, the piezoelectric body 21 is sealed with the terminal plate 19. If the terminal plate 19 is arranged so as to have such a positional relationship, the direction of the piezoelectric body 21 can be controlled.

  The method of attaching the ultrasonic transducer configured as described above to the flow rate measuring unit 8 and the operation principle of the ultrasonic flow meter are the same as those in the first embodiment, and therefore will be omitted.

  In the third embodiment, the direction identifying means is the direction indicating line 26. However, a symbol such as a character or a two-dimensional bar code may be used if the direction can be specified. Further, the long side AA 'of the electrode surface 21a and the direction indicating line 26 are configured to be parallel to each other, but may be a right angle, or may be set to an arbitrary angle as long as it can be managed.

  In the first to third embodiments, the piezoelectric body 21 has dimensions different from each other in length L and width W. However, if the electrode provided on the electrode surface 21a has a shape anisotropy such as a rectangle, the length L and width Squares having the same W may be used, or a shape in which the groove 27 is provided on the electrode surface 21a as shown in FIG.

  As described above, since the ultrasonic transducer according to the present invention can estimate the direction of the piezoelectric body from the appearance of the ultrasonic transducer, it is possible to prevent a decrease in transmission / reception sensitivity and to measure accuracy. Therefore, it can be applied to applications such as measurement of hydrogen gas flow rate in household gas meters, water meters, and fuel cells.

1 is a schematic configuration diagram of an ultrasonic flow meter according to Embodiment 1 of the present invention. External view of the ultrasonic transducer of the first embodiment Sectional view of the ultrasonic transducer of the first embodiment External view of piezoelectric body of embodiment 1 FIG. 3 is a diagram showing a configuration of attaching the ultrasonic transducer according to the first embodiment to a flow rate measuring unit. External view of ultrasonic transducer viewed from terminal plate side of embodiment 2 External view of ultrasonic transducer as seen from terminal plate side of embodiment 3 External view showing an example of a piezoelectric body Cross-sectional view of a conventional ultrasonic transducer External view of conventional ultrasonic transducer

Explanation of symbols

8 Flow measurement unit 9 Ultrasonic transducer
DESCRIPTION OF SYMBOLS 10 Ultrasonic transducer 12 Drive circuit 14 Reception detection circuit 15 Timer 16 Calculation part 17 Control part 18 Case 18a Top part 18b Flange part 19 Terminal board 20 Matching layer 21 Piezoelectric body 22 External electrode terminal 23 External electrode terminal 25 External electrode terminal 26 Direction indicator 27 Groove

Claims (10)

An ultrasonic transducer in which a piezoelectric body having a shape anisotropy is sealed in a case, and direction identification means that can estimate the arrangement information of the piezoelectric body from the appearance of the ultrasonic transducer Ultrasonic transducer equipped. A cylindrical case having a top part, a side wall part, and a flange part, a piezoelectric body having anisotropy connected to the inner wall surface of the top part, and the flange part so as to seal the piezoelectric body 2. The ultrasonic transducer according to claim 1, comprising a connected terminal plate. 3. The ultrasonic transducer according to claim 1, wherein the direction identification means is provided on the outer surface of the terminal board. The direction identification means is a straight line formed by connecting predetermined two of the plurality of external electrode terminals provided on the terminal plate, and the direction indicated by the direction identification means and the direction of the piezoelectric body are set at a predetermined angle. The ultrasonic transducer according to claim 1 or 2. 5. The ultrasonic transducer according to claim 4, wherein three or more external electrode terminals are provided on the terminal plate, and the two external electrode terminals used for the direction identification means have different shapes from the other external electrode terminals. . The direction identification means is a line or symbol provided on the outer surface of the terminal plate of the ultrasonic transducer, and is set so that the direction indicated by the direction identification means and the direction of the piezoelectric body have a predetermined positional relationship. Or the ultrasonic transducer according to 2. The ultrasonic transducer according to claim 6, wherein after the piezoelectric body is sealed with the case and the terminal plate, linear or symbol direction identification means is provided on the outer surface of the terminal plate. One or more grooves are provided on at least one of the transmitting / receiving surface of the piezoelectric body or the surface facing the transmitting / receiving surface, and the arrangement information of the piezoelectric body includes the direction of at least one of the grooves The ultrasonic transducer according to claim 1 or 2. The ultrasonic transducer according to any one of claims 2 to 8, wherein a matching layer is provided on an outer wall surface of a top portion of the case. A flow rate measurement unit through which a fluid to be measured flows, a pair of ultrasonic transducers according to any one of claims 1 to 9 provided in the flow rate measurement unit and transmitting / receiving ultrasonic waves, and one of the ultrasonic transmission / reception units A drive circuit for driving a wave detector, a reception detection circuit for detecting an ultrasonic pulse connected to the other ultrasonic transducer, a timer for measuring a propagation time of the ultrasonic pulse, the drive circuit and the timer An ultrasonic flow meter comprising a control unit for controlling the flow rate and a calculation unit for calculating a flow rate from an output of the timer, wherein the ultrasonic flow meter has an outer surface of the terminal plate of the ultrasonic transducer Are arranged so that only the ultrasonic transducer can be observed, and the mounting angle of the ultrasonic transducer is the direction indicated by the direction identification means of one ultrasonic transducer and the direction indicated by the direction identification means of the other ultrasonic transducer Is set at a predetermined angle. Ultrasonic flow meter was.

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