JP2006217002A - Ultrasonic transducer and ultrasonic flowmeter using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic transmitter-receiver with high reliability wherein stable electric continuity is attained by configuring conduction parts of an elastic body with conductor wires located in an axial direction. <P>SOLUTION: The conduction parts 11a of the conductive elastic body 11 sandwiched between electrode faces 12a, 12b of a piezoelectric body 12 and external electrode terminals 13a, 13b are configured by the conductor wires located in the axial direction. As a result, continuity failure of the ultrasonic transmitter-receivers 2, 3 can be prevented and the measurement of a flow rate with high reliability can be attained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Conventionally, this type of ultrasonic transducer generally used has soldered lead wires to the electrode surface in order to electrically connect the electrode surface of the piezoelectric body and the external electrode. However, in the electrical connection method using soldering, variation in the frequency characteristics and transmission / reception sensitivity of the ultrasonic transmitter / receiver occurs due to the thermal influence on the soldered location and the amount of solder attached, and this ultrasonic transmitter / receiver. When used in an ultrasonic flowmeter, there was a problem of affecting the measurement system.

Therefore, as a method not using soldering for the electrical connection, for example, there is one disclosed in Patent Document 1. As shown in FIG. 8, this ultrasonic transducer is electrically connected by pressing an elastic body 11 having conductivity between the electrode surface 12a of the piezoelectric body 12 and the terminal 13a of the terminal plate 13. I am trying. Specifically, a conductive rubber made of silicon rubber rubber, or an elastic body 11 configured to hold elasticity by alternately arranging conductive layers 11 a and insulating layers 11 b as shown in the figure, is formed on the terminal plate 13. The flange 15a of the case 15 containing the outer peripheral portion 13c of the terminal plate 13 and the piezoelectric body 7 in this state is electrically welded. Are joined together. The terminals 13 a and 13 b provided on the terminal plate 13 are electrically insulated by a glass (insulating part) 17. As a result, the electrode surface 12a and the terminal 13a are electrically connected, and the other electrode surface 12b is electrically connected to the terminal 13b via the case 15 also serving as an external electrode, the outer peripheral portion 13c of the terminal plate 13, A sealed space 16 formed by the case 15 and the terminal plate 13 is filled with nitrogen gas.
JP 2001-50785 A

  However, in the above conventional configuration, an elastic body in which conductive layers and insulating layers are alternately arranged in layers is provided in the concave portion of the terminal plate and is sandwiched between the piezoelectric body and the terminal. In the configuration in which the elastic body is dropped into the recess of the terminal plate and then sandwiched between the piezoelectric body and the terminal, the inside of the recess is easily moved in the lateral direction. As a countermeasure against this, it is conceivable that a holding hole is provided in the terminal board, and the elastic body 11 is held while being compressed by the holding hole. In this case, when the conductive layer is compressed, it spreads to the wall surface side of the holding hole and may cause a short circuit by contacting the holding hole. In addition, when the conduction resistance value of the elastic body 11 is changed, the conduction layer is increased or decreased, so that there is a problem that a minute conduction resistance value cannot be adjusted.

  Further, the elastic body 11 is provided with a height higher than the maximum dimension of the cross section so that the conductive layer 11a arranged in layers is not buckled by pressurization during assembly. Since the insertion is possible even if they are different, there is also a problem that an insertion failure is likely to occur during assembly.

  The present invention solves the above-mentioned problem, and by configuring the conductive portion of the elastic body with a conductive wire in the axial direction, stable conduction is possible, and a highly reliable ultrasonic transmission / reception wave that suppresses problems during assembly. It is an object to provide a blood vessel and an ultrasonic flow meter using the same.

  In order to solve the above problems, the present invention provides a terminal plate having a pair of electrode surfaces on a piezoelectric body and two external electrode terminals that are in electrical contact with the respective electrode surfaces. The conductive part of the elastic body having conductivity sandwiched between the outer electrode terminal and one of the external electrode terminals is constituted by a conductive wire in the axial direction.

  According to the above invention, even when the holding hole is provided in the terminal plate and the elastic body is compressed by the holding hole, the conductive portion does not come into contact with the wall surface side of the holding hole. Since the electrode is bitten into one of the external electrode terminals, poor conduction can be prevented. Further, the conduction resistance value can be controlled by varying the number of conductive wires. Furthermore, since the conduction direction of the conductive wire provided in the axial center of the elastic body can be confirmed from the outer peripheral direction of the elastic body, it is possible to prevent poor insertion during assembly.

  The ultrasonic transducer according to the present invention and the ultrasonic flowmeter using the ultrasonic transducer have a conductive portion of a conductive elastic body as a conductive wire, and the conductive wire penetrates into the electrode surface of the piezoelectric body and the external electrode terminal. Therefore, poor conduction can be prevented and the conduction resistance value can be controlled, so that a highly reliable ultrasonic transducer can be obtained and the flow measurement of the fluid to be measured can be measured stably. can do.

  According to a first aspect of the present invention, there is provided a piezoelectric body having a pair of opposing electrode surfaces, a terminal plate having two external electrode terminals that are in electrical contact with the electrode surfaces, one electrode surface of the piezoelectric body, and one of the electrode surfaces. And an elastic body having conductivity sandwiched between the external electrode terminals.

  According to the present invention, the conductive portion has a size that fits in a plane in contact with the terminal, so that the conductive portion contacts the periphery of the terminal even when the elastic body is sandwiched between the piezoelectric body and the external electrode terminal. Therefore, short circuit can be prevented.

  The second invention is characterized in that the conductive portion of the elastic body has conductivity of the piezoelectric body and the terminal plate within a bending elastic limit range of the conductive wire.

  According to the present invention, the elastic body is sandwiched between the piezoelectric body and the external electrode terminal and compressed to obtain a spring property by bending the conductive portion composed of a plurality of the piezoelectric body and the external electrode terminal. It is possible to ensure conduction.

  The third invention is characterized in that the conductive portion of the elastic body has conductivity by biting the end portion of the conductive wire into the electrode surface of the piezoelectric body.

  According to the present invention, since the conductive portion is provided with a convex portion from the surface of the insulating portion, the conductive portion is pierced into the electrode surface of the piezoelectric body and is sandwiched between the electrical contact surfaces of the external electrode terminals. As a result, poor conduction can be prevented.

  According to a fourth aspect of the present invention, the elastic body is constituted by an insulating portion capable of confirming a conduction direction of the conductive portion from the outer peripheral direction.

  According to the present invention, since the elastic body is colorless and visible so that the state of bending of the conductive portion can be seen even from the side, the state of the conductive portion can be confirmed. Since the conduction direction of the conductive wire provided in the shaft center of the elastic body can be confirmed, it is possible to prevent unnecessary insertion during assembly.

  In addition, this makes it possible to easily confirm the problem of the bending use limit when pinched and the deterioration of the conductive portion.

  Then, by applying these ultrasonic transducers to an ultrasonic flow meter, highly reliable flow measurement that enables stable conduction is possible.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiment. Moreover, what attaches | subjects the same code | symbol in drawing is the same, and detailed description is abbreviate | omitted.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of an ultrasonic flowmeter using an ultrasonic transducer shown in each embodiment described later of the present invention. In FIG. 1, 1 is a flow rate measuring unit through which a fluid to be measured flows, 2 and 3 are ultrasonic transducers disposed obliquely opposite to the flow direction of the flow rate measuring unit 1, and 4 is an ultrasonic transducer. 2 and 3, an oscillation circuit for transmitting the used frequency, 5 is a drive circuit for driving the ultrasonic transducers 2 and 3 connected to the oscillation circuit 4, 6 is a switching circuit for switching an ultrasonic transducer for transmission and reception, and 7 A reception detection circuit for detecting an ultrasonic pulse, 8 is a timer for measuring the propagation time of the ultrasonic pulse, 9 is a calculation unit for calculating a flow rate from the output of the timer 8, and 10 is a control signal output to the drive circuit 5 and the timer 8 It is a control part.

  The operation of the ultrasonic flowmeter configured as described above will be described. In this embodiment, assuming that the fluid to be measured is city gas and a household gas meter is assumed as an ultrasonic flow meter, the material constituting the flow rate measuring unit 1 is aluminum alloy die casting.

  In addition, about 500 kHz is selected as the operating frequency of the ultrasonic transducers 2 and 3. The oscillation circuit 4 is composed of a capacitor and a resistor, for example, and transmits a square wave of about 500 kHz. The drive circuit 7 drives the ultrasonic transducer 2 from the signal of the oscillation circuit 4, and the square wave is composed of a burst signal having 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 10 outputs a transmission start signal to the drive circuit 5 and starts time measurement of the timer 8 at the same time. When receiving the transmission start signal, the drive circuit 5 drives the ultrasonic transducer 2 and transmits an ultrasonic pulse. The transmitted ultrasonic pulse propagates through the flow rate measurement 1 and is received by the ultrasonic transducer 3. The received ultrasonic pulse is converted into an electrical signal by the ultrasonic transducer 3 and output to the reception detection circuit 7. The reception detection circuit 7 determines the reception timing of the reception signal and outputs the reception detection signal to the control unit 10. When receiving the reception detection signal, the control unit 10 outputs a transmission start signal to the drive circuit 5 again after a preset delay time td has elapsed, and performs the second measurement. After repeating this operation N times, the timer 8 is stopped. The calculating unit 10 calculates the propagation time t1 by dividing the time measured by the timer 8 by the number of times N and subtracting the delay time td.

  Subsequently, the ultrasonic transducer connected to the drive circuit 5 and the reception circuit 7 is switched by the switching circuit 6, and the control unit 10 again outputs a transmission start signal to the drive circuit 5 and simultaneously starts time measurement of the timer 8. Contrary to the measurement of the propagation time t1, an ultrasonic pulse is transmitted by the ultrasonic transducer 3 and the measurement received by the ultrasonic transducer 2 is repeated N times, and the calculation unit 9 calculates the propagation time t2.

Here, the distance connecting the centers of the ultrasonic transducer 2 and the ultrasonic transducer 3 is L, the speed of sound in an airless state is C, the flow velocity in the flow rate measuring unit 1 is V, and the flow of the non-measurement fluid The propagation times t1 and t2 are as follows: θ and the angle between the direction of the line and the line connecting the centers of the ultrasonic transducer 2 and the ultrasonic transducer 3 are θ.
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 1 are S and the correction coefficient is K, the flow rate Q is Q = KSV (4)
It can be calculated with.

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

  FIG. 2 is a sectional view of the ultrasonic transducers 2 and 3 of the present invention. 3A and 3B show an elastic body 11 having conductivity used in the ultrasonic transducers 2 and 3 of the present invention. FIG. 3A is a plan view when viewed from above, and FIG. 3B is a perspective view thereof.

  In FIG. 2, ultrasonic transducers 2 and 3 include a piezoelectric body 12 having a pair of opposed electrode surfaces 12a and 12b, and external electrode terminals 13a and 13b that are electrically connected to the electrode surfaces 12a and 12b, respectively. And a conductive elastic body that is held in a holding hole 14 formed in the center of the terminal plate 13 between the electrode surface 12a of the piezoelectric body 12 and the external electrode terminal 13a for electrical connection. 11. The piezoelectric body 12 is bonded to the inner surface of the top portion of a case 15 made of stainless steel having a flange with an epoxy resin adhesive. In addition, 12c provided in the piezoelectric body 12 is a groove | channel for making thickness longitudinal vibration the main mode in order to transmit and receive an ultrasonic wave efficiently. In addition, by reducing the thickness of the adhesive to the case 15, the piezoelectric body 12 can achieve electrical connection between the electrode surface 12 b and the case 15 at the same time as adhesive fixation.

  The conductive elastic body 11 may be formed of another elastic material as long as it is a conductive elastic body such as a conductive rubber made of silicon rubber, but in this embodiment, the center in the axial direction is used. A columnar shape composed of a conductive portion 11a composed of a plurality of conductive wires arranged in the vicinity and an insulating portion 11b arranged around the conductive portion 11a is used. The elastic body 11 is held in the holding hole 14 of the terminal board 13 and processed between the piezoelectric body 12 and the external electrode terminal 13a. In this state, the outer peripheral portion 13c of the terminal board 13 and the case 15 are processed. The flange portion 15a is joined by electric welding. Then, the sealed space 16 is formed by the case 15 and the terminal plate 13, and the sealed space 16 is exhausted and replaced with an inert gas such as nitrogen gas.

  The terminal plate 13 is made of metal, and a terminal 13b is provided in the vicinity of the outer peripheral portion 13c, and a terminal 13a is provided in the central portion, but glass (insulating portion) is provided around the terminal 13a (inside the holding hole 14). ) 17 is provided, the terminals 13a and 13b are electrically insulated from each other. As a result, the electrode surface 12a of the piezoelectric body and the terminal 13b are electrically connected, and the electrode surface 12b of the piezoelectric body is electrically connected to the terminal 13b via the case 15 also serving as an external electrode and the outer peripheral portion 13c of the terminal plate 13. Connected. In addition, when the elastic body 11 is formed of conductive rubber that entirely constitutes a conducting portion, it is electrically connected to the terminal plate 13 when held in the holding hole 14, so that the position where the glass 17 is provided is the holding hole 14. It is necessary to provide insulation between both terminal plates 13a and 13b by providing the outer peripheral side from the periphery.

  The elastic body 11 is a plan view of FIG. 3A (showing the boundary surface with the piezoelectric body 12 as viewed from above), and FIG. 3B is a perspective view of FIG. The figure is shown. As shown in FIG. 3A, the cross-sectional shape is circular, and the conductive portions 11a are also arranged circularly in the axial direction. The size d of the circle of the conductive portion 11a is set so as to be within a plane in contact with the terminal 13a, so that the conductive portion 11a can be formed even when the elastic body 11 is narrow between the piezoelectric body 12 and the external electrode terminal 13a. Since there is no contact with the periphery of the terminal 13a (inside the holding hole 14), there is no short circuit. The compression amount when the elastic body 11 is narrowed by the piezoelectric body 12 and the external electrode terminal 13a may be compressed in a wide range of 5 to 50% from the height H of the elastic body 11, but 10 to 40 It is preferable to use in the range of%. In the present embodiment, the compression amount is used around 25%. In addition, the elastic body 11 is narrowed by the piezoelectric body 12 and the external electrode terminal 13a and compressed to obtain a spring property by bending the conductive portion 11a composed of a plurality of the piezoelectric body 12 and the external electrode terminal. Connection with 13a is ensured.

  Furthermore, since the conductive portion 11a in the enlarged view of the conductive elastic body shown in FIG. 4 is provided with the convex portion 11c from the surface of the insulating portion 11b, the conductive portion 11a pierces the electrode surface 12a of the piezoelectric body 12, and the external electrode terminal It will be narrowed in the form of biting into the electrical contact surface of 13a.

  Colored silicon rubber may be used for the insulating portion 11b of the elastic body 11, but in this embodiment, it is colorless and visible so that the conductive portion 11a can be bent even from the side surface of the elastic body 11. I am using something. Since the state of the conductive portion 11a can be confirmed, the conduction direction of the conductive wire provided in the axial center of the elastic body can be confirmed from the outer peripheral direction of the elastic body, so that poor insertion during assembly can also be prevented. In addition, it is possible to easily confirm the malfunction due to the bend usage limit when it is narrowed, deterioration of the conductive portion 11a, and the like.

  Moreover, it becomes easy to vary the conduction resistance value by varying the number of conductive lines of the conductive portion 11a configured by a plurality of conductive lines. Any conductive wire material and wire diameter may be used as the conductive portion 11a of the elastic body 11 as long as it has conductivity, but in this embodiment, a nickel-plated wire is used.

  As described above, the embodiment of the present invention has been described with reference to FIG. 3 showing the conductive portions 11a arranged in a circular shape, but the present invention is not limited to this, as shown in FIG. 5, FIG. 6, and FIG. Various modifications and applications are possible.

  FIG. 5 is a plan view of the elastic body 11 (showing the boundary surface with the piezoelectric body 12 as viewed from above). The cross-sectional shape is circular, and the conductive portion 11a is in the axial direction. Are arranged in a hexagonal shape. The longitudinal dimension A of the conductive portion 11a is set to a size that fits in a plane in contact with the terminal 13a. Here, a hexagon is used, but a polygon may be used.

  FIG. 6 is a plan view of the elastic body 11 (showing the boundary surface with the piezoelectric body 12 as viewed from above). The cross-sectional shape is circular, and the conductive portion 11a is in the axial direction. The length L and the width W of the conductive part 11a are sized to fit within the surface in contact with the terminal 13a. Here, although two rows are used, a plurality of rows may be used.

  FIG. 7 is a plan view of the elastic body 11 (showing the boundary surface with the piezoelectric body 12 as viewed from above). The cross-sectional shape is circular, and the conductive portion 11a is in the axial direction. Are arranged in a first circular shape and a second circular shape outside the first circular shape, and the size D of the second circle of the conductive portion 11a is set to be within a plane in contact with the terminal 13a. In addition, although it was set to the 2nd circle here, multiple circles may be sufficient.

  As described above, since the ultrasonic transducer according to the present invention and the ultrasonic flowmeter using the ultrasonic transducer can achieve efficient electrical connection without causing poor conduction, the flow rate of the fluid to be measured can be measured. Measurement with high accuracy is possible. Furthermore, the present invention can be applied to applications such as an ultrasonic flowmeter that measures the flow rate and flow velocity of gas and liquid by ultrasonic waves.

Configuration diagram including a partial cross-sectional view of an ultrasonic flowmeter using the ultrasonic transducer of the present invention Sectional drawing of the ultrasonic transducer in Embodiment 1 of this invention (A) The top view which shows the structure by which the elastic body which has electroconductivity in Embodiment 1 of this invention is hold | maintained at the holding hole of a terminal board (b) The elastic body which has electroconductivity in Embodiment 1 of this invention Is a perspective view showing a configuration in which is held in the holding hole of the terminal board The enlarged view of the elastic body which has electroconductivity in Embodiment 1 of this invention The top view of the elastic body which has electroconductivity in Embodiment 1 of this invention The top view of the elastic body which has electroconductivity in Embodiment 1 of this invention The top view of the elastic body which has electroconductivity in Embodiment 1 of this invention Perspective view of a conventional ultrasonic transducer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow measurement part 2, 3 Ultrasonic transducer 4 Transmission circuit 5 Drive circuit 6 Switching circuit 7 Reception detection circuit 8 Timer 9 Calculation part 10 Control part 11 Elastic body 11a Conductive part 11b Insulating part 11c Convex part 12 of the conductive part 11a Piezoelectric body 12a, 12b Electrode surface 13 Terminal plate 13a, 13b External electrode terminal 14 Holding hole

Claims (5)

Between a piezoelectric body having a pair of opposing electrode surfaces, a terminal plate having two external electrode terminals that are in electrical contact with the respective electrode surfaces, and between one electrode surface of the piezoelectric body and one external electrode terminal An ultrasonic transmitter / receiver comprising an elastic body having conductivity sandwiched between two conductors, wherein the conductive portion of the elastic body is formed of a conductive wire in an axial direction. 2. The ultrasonic transducer according to claim 1, wherein the conductive portion of the elastic body has conductivity between the piezoelectric body and the terminal plate within a bending elastic limit range of the conductive wire. 2. The ultrasonic transducer according to claim 1, wherein the conductive portion of the elastic body has conductivity by biting an end portion of the conductive wire into the electrode surface of the piezoelectric body. The ultrasonic transducer according to claim 1, wherein the elastic body is configured by an insulating portion capable of confirming a conduction direction of the conductive portion from an outer peripheral direction. A flow rate measurement unit through which a fluid to be measured flows, a pair of ultrasonic transducers provided in the flow rate measurement unit for transmitting and receiving ultrasonic waves, and a propagation time between the ultrasonic transducers are measured. An ultrasonic flowmeter comprising a measurement circuit and a flow rate calculation means for calculating a flow rate based on a signal from the measurement circuit.

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