JP5397051B2 - Ultrasonic transducer and ultrasonic flowmeter using the same - Google Patents

Description

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

  Conventional ultrasonic transducers of this type include those shown in FIGS. 8 and 9, for example. An upper electrode surface 57 of the piezoelectric body 56 is fixed to the inner surface of the top wall 55a of the conductive cap-like case 55 by means such as adhesion, and an acoustic matching 58 is attached to the outer surface of the top wall 55a. A flange 59 extending outward from the lower open end of the case 55 is integrally formed, and the outer peripheral upper surface of the conductive terminal plate 60 and the lower surface of the flange 59 are electrically welded. As a result, the inside of the case 55 is set in a sealed space 61. Normally, the sealed space 61 is filled with an inert gas such as nitrogen gas. A conductive elastic material 63 is elastically connected to the lower electrode surface 62 of the piezoelectric body 56, and a first terminal 64 that electrically penetrates the terminal plate 60 is connected thereto. A second terminal 65 is connected to a part of the terminal plate 60 spaced from the terminal 64 by a predetermined distance. That is, the first terminal 64 is connected to the lower electrode surface 62 of the piezoelectric body 56 via the conductive elastic material 63, and the second terminal 65 is connected to the upper electrode of the piezoelectric body 56 via the terminal plate 60 and the case 55. Each is connected to the surface 57. A glass insulating portion 66 is interposed in the penetrating portion of the first terminal 64 with respect to the terminal plate 60 so that the insulating relationship between them is maintained.

  A welding projection 68 is annularly provided on the upper surface 67 near the outer periphery of the terminal plate 60, and a weld dust diffusion prevention projection 69, which is a welding dust diffusion prevention means, is provided annularly on the inner side. The height of the weld dust diffusion prevention projection 69 is set lower than that of the welding projection 68. The case 55 and the terminal plate 60 are joined by melting the welding projection 68 by electric welding.

  In this device, a welding projection 68 is provided in an annular shape on the upper surface 67 near the outer periphery of the terminal plate 60, and a welding dust diffusion prevention projection 69, which is a welding dust diffusion preventing means, is provided in an annular shape on the inner side. Therefore, even if dust is generated during welding, dust can be prevented from entering the sealed space 61 (see, for example, Patent Document 1).

JP 2006-180317 A

  However, the above-described conventional configuration aims to prevent the entry of dust into the sealed space 61 even when dust is generated by providing the welding dust diffusion prevention protrusion 69 that is a weld dust diffusion prevention means in a ring shape. However, since there is a gap between the welding dust diffusion preventing projection 69 and the lower surface of the flange 59 at the moment when the welding projection 68 is energized to melt the welding projection 68, the welding projection 68 is melted. When dust occurs at an instant, there is a problem that dust enters the sealed space 61 through the gap.

  Therefore, when dust enters the sealed space 61, the weld dust contacts the lower electrode surface 62 and the terminal plate 60 of the piezoelectric body 56, and a short circuit occurs between the lower electrode surface 62 and the terminal plate 60 to generate ultrasonic waves. It had the problem of not being done.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems. By using a laser welding joining means for joining a tight contact portion when welding a case and a terminal plate, the piezoelectric body and the terminal are prevented from entering dust in the sealed space. It is an object of the present invention to provide an ultrasonic flowmeter using an ultrasonic transducer that is excellent in reliability, while realizing an ultrasonic transducer that does not cause a short circuit between plates.

In order to solve the above-described conventional problems, an ultrasonic transducer according to the present invention has a bottomed cylindrical case, a first electrode surface and a second electrode surface facing each other, and the first electrode A piezoelectric body whose surface is electrically connected to the top wall of the case, a terminal plate that covers the open end of the case and is electrically connected to the outer periphery of the case, and a first external member provided on the terminal plate An electrode terminal; a second external electrode terminal provided on the terminal plate in an insulated state from the first external electrode terminal; and provided between the second electrode surface and the second external electrode terminal. In an ultrasonic transducer comprising a conductor and an acoustic matching layer bonded and fixed to the outer surface of the top wall of the case, the corner of the outer peripheral portion of the terminal plate is inclined with respect to the cylindrical axis direction of the case constitutes a stepped portion having an inclined surface, wherein the case, the inclined surface and the same angle of the step portion on the outer peripheral edge portion An inclined surface, said that contact has a contact constituting the inclined surface characterized in, in a state where the case and the terminal plate is joined by adhesion contact adhesion, for example, a laser contact portions, and the case The terminal plate is in close contact with the two sides of the coaxial direction and at a right angle with respect to the fitting direction, so that the accuracy of the central axis when the case and the terminal plate are fitted is improved, and the processing accuracy of laser bonding is improved. Further, the contact distance between the case 10 and the terminal plate 12 is increased, and dust can be prevented from entering the case. There is no short circuit between the electrode surface and the terminal plate due to dust.

  The ultrasonic transducer according to the present invention has a configuration in which the case is fitted in contact with two surfaces of the coaxial direction and the perpendicular direction with respect to the fitting direction when the case is fitted to the terminal board, and the tight contact portion is formed by laser welding joining means. In the case of joining, the generation of weld dust in the sealed space is eliminated. Thereby, the penetration of dust into the case is eliminated, there is no short circuit between the electrode surface and the terminal plate, and an ultrasonic flowmeter using an ultrasonic transducer having excellent reliability can be provided.

1 is a schematic configuration diagram showing an ultrasonic flowmeter according to Embodiment 1 of the present invention. Sectional drawing of the ultrasonic transducer in Embodiment 1 of this invention Sectional drawing of the ultrasonic transducer in Embodiment 2 of this invention The expanded sectional view of the ultrasonic transducer in Embodiment 2 of the present invention The expanded sectional view after ultrasonic transducer welding in Embodiment 2 of the present invention Sectional drawing of the ultrasonic transducer in Embodiment 3 of this invention The expanded sectional view of the ultrasonic transducer in Embodiment 3 of the present invention Sectional view showing the conventional ultrasonic transducer before welding Sectional view showing the conventional ultrasonic transducer after welding

1st invention has a bottomed cylindrical case, the 1st electrode surface and 2nd electrode surface which oppose, The said 1st electrode surface was electrically connected to the top wall of the said case A piezoelectric body, a terminal plate that covers the open end of the case and is electrically connected to the outer periphery of the case, a first external electrode terminal provided on the terminal plate, and an insulating state from the first external electrode terminal And a second external electrode terminal provided on the terminal plate, a conductor provided between the second electrode surface and the second external electrode terminal, and an outer surface of the top wall of the case. In the ultrasonic transmitter / receiver provided with the acoustic matching layer , a step portion having an inclined surface inclined with respect to the cylindrical axis direction of the case is formed at a corner portion of the outer peripheral portion of the terminal plate , an inclined surface of the inclined plane the same angle of the step portion the outer peripheral end portion, configured contact abutting on the inclined surface And characterized in that it has, in a state where the case and the terminal plate is joined by adhesion contact adhesion, for example, a laser contact portions, the case and the terminal plate are in close contact in contact with the inclined surface, case and terminal The accuracy of the center axis when the plates are fitted is improved, and the processing accuracy of laser bonding is improved. In addition , the contact distance becomes longer and dust can be prevented from entering the case. There is no short circuit between the electrode surface and the terminal plate due to dust.

In addition, the greater the force applied, the smaller the gap between the case and the terminal plate on the contact surface. By performing laser irradiation on this tight contact surface, welding can be reliably performed, so that welding defects can be eliminated.

A second invention is, in particular, by configuring the ultrasonic flow meter using the first inventions of the ultrasonic transducer, is obtained with high reliability measurement accuracy.

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

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of an ultrasonic flowmeter using an ultrasonic transducer according to the first embodiment of the present invention.

  In FIG. 1, 1 is a flow path through which a fluid such as LP gas or natural gas flows, 2 is a flow rate measuring unit that measures the flow rate of the fluid flowing through the flow path 1, and 3 and 4 are upstream of the flow path 1. An ultrasonic transducer for transmitting and receiving ultrasonic waves disposed opposite to the downstream side and the downstream side, 5 is a measurement circuit for measuring the ultrasonic propagation time between the ultrasonic transducers 3 and 4, and 6 is from the measurement circuit 5. It is an arithmetic circuit for obtaining a flow velocity and / or flow rate based on a signal.

The operation and action of the ultrasonic flowmeter in the flow rate measuring unit 2 configured as described above will be described. The distance connecting the center of the ultrasonic transducer 3 and the ultrasonic transducer 4 is L, and the angle between this straight line and the longitudinal direction of the flow path 1 which is the flow direction is θ. Also, C is the speed of sound in a windless state of the fluid, and V is the flow velocity of the fluid in the flow path 1. The ultrasonic wave transmitted from the ultrasonic transducer 3 arranged on the upstream side of the flow rate measuring unit 2 crosses the flow path 1 obliquely and is received by the ultrasonic transducer 4 arranged on the downstream side. The propagation time t1 at this time is
t1 = L / C + V cos θ
Indicated by Next, an ultrasonic wave is transmitted from the ultrasonic transducer 4 and received by the ultrasonic transducer 3. The propagation time t2 at this time is
t2 = L / C−Vcos θ
Indicated by
Then, if the sound speed C of the fluid is eliminated from the expressions t1 and t2,
V = L / 2 cos θ (1 / t1-1 / t2)
The following equation is obtained.

  If L and θ are known, the flow velocity V can be obtained by measuring t1 and t2 in the measurement circuit 5. From the flow velocity V, the flow rate Q can be obtained by calculating Q = KSV by the arithmetic circuit 6 if the cross-sectional area of the flow path 1 is S and the correction coefficient is K.

  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 transducer according to the first embodiment of the present invention.

  In FIG. 2, the ultrasonic transducers 3 and 4 have a case 10 formed in a bottomed cylindrical shape whose lower side is open, and a first electrode surface 7 and a second electrode surface 8 that face each other. A piezoelectric body 9 in which the first electrode surface 7 is electrically connected to the inside of the top wall 10a of the case 10, and a terminal plate 12 in which the case outer peripheral vicinity portion 11 is fitted and the open end 10b of the case 10 is sealed. A first external electrode terminal 13 electrically connected to the terminal plate 12, a second external electrode terminal 14 fixed to a through hole 12a provided in the terminal plate 12 via an insulator 12b, Acoustic matching which is bonded to the outer surface of the top wall 10a of the case 10 opposite to the piezoelectric body 9 and the conductive rubber 15 having the conductor 15a provided between the second electrode surface 8 and the second external electrode terminal 14; And the layer 16.

  The case outer periphery vicinity part 11 and the terminal board outer periphery vicinity part 17 are fitted. The fitting portion 18 includes a stepped portion 17a constituted by two surfaces, a surface 19 parallel to the fitting direction of the case 10 and the terminal plate 12 (direction of arrow B in FIG. 2) and a surface 20 perpendicular to the fitting direction. The outer peripheral end portion 11b of the case 10 is in close contact with the stepped portion 17a. The outer diameter of the outer periphery 21 of the case and the outer periphery 22 of the terminal board is configured so that the terminal board is larger.

  An arrow 23 indicates the laser to be irradiated. FIG. 2 shows a state before the case 10 and the terminal plate 12 are laser welded.

  As described above, in the present embodiment, the case 10 and the terminal plate 12 are in close contact with each other on the two surfaces of the coaxial direction and the perpendicular direction with respect to the fitting direction, and the case 10 and the terminal plate 12 are fitted. As a result, the accuracy of the center axis of the case 10 and the terminal plate 12 is improved, and the processing accuracy of laser bonding is improved. Moreover, the contact distance between the case 10 and the terminal plate 12 is increased by fitting the two surfaces, so that dust can be prevented from entering the case.

(Embodiment 2)
3 to 5 are sectional views of an ultrasonic transducer according to the second embodiment of the present invention. 3 and 4, the ultrasonic transducer 24 is electrically connected to the piezoelectric body 27 having the first electrode surface 25 and the second electrode surface 26 facing each other, and the first electrode surface 25 of the piezoelectric body 27. The case 28 connected to the terminal plate 30, the terminal plate 30 fitted to the case outer peripheral vicinity 29, the first external electrode terminal 31 provided on the terminal plate 30, and the first external electrode terminal 31 in an insulated state. A second external electrode terminal 32 provided on the terminal plate 30; a conductive rubber 33 which is a conductor provided between the second electrode surface 26 of the piezoelectric body 27 and the second external electrode terminal 32; The acoustic matching layer 34 is opposed to the body 27 and bonded and fixed to the case 28.

The case outer peripheral portion 29 and the terminal plate outer peripheral portion 35 are fitted, and when a force is applied to the fitting direction in a state where the case 28 is fitted to the terminal plate 30, it is coaxial with the fitting direction. The contact contact surface 37 is configured with a certain inclination with respect to the direction. The outer diameter of the case outer periphery 38 and the terminal plate outer periphery 39 is configured such that the terminal plate 39 is larger by the dimension a. That is, when the case 28 is fitted to the terminal plate 30, the terminal plate outer periphery 39, which is the outermost surface of the fitting portion of the case 28 and the terminal plate 30, is not flush with the case outer periphery 38. An arrow 40 indicates a laser to be irradiated. 3 and 4 show a state before the case 28 and the terminal plate 30 are laser welded, and FIG. 5 shows a state after the laser welding.

  As described above, in the present embodiment, the case 28 and the terminal plate 30 apply a force in the fitting direction so that the case 28 and the terminal plate 30 come into contact with each other at a constant inclination, so that the contact of the close contact surface 37 is achieved. Length increases. Further, as the applied force is increased, the gap between the case 28 and the terminal plate 30 on the contact contact surface 37 is further reduced. By performing laser irradiation on this tight contact surface, welding can be reliably performed, so that welding defects can be eliminated. Further, when the laser irradiation is performed, the metal on the outer periphery 39 of the terminal plate with the higher surface melts and moves to the outer periphery 38 of the case with the lower surface to solidify, so that the welding surface may protrude from the surface of the terminal plate. In addition, an ultrasonic transducer with good dimensional accuracy can be obtained after laser welding. The outer diameter of the case 28 may be larger than the outer diameter of the terminal plate 30 and has the same effect.

(Embodiment 3)
6 and 7 are sectional views of an ultrasonic transducer according to the third embodiment of the present invention.

  6 and 7, the ultrasonic transducer 41 is electrically connected to the piezoelectric body 44 having the first electrode surface 42 and the second electrode surface 43 facing each other, and the first electrode surface 42 of the piezoelectric body 44. A case 45 connected to the terminal, a terminal plate 47 fitted with the case outer peripheral vicinity 46, a first external electrode terminal 48 provided on the terminal plate 47, and the first external electrode terminal 48 in an insulated state. A second external electrode terminal 49 provided on the terminal plate 45; a conductive rubber 50 which is a conductor provided between the second electrode surface 43 of the piezoelectric body 44 and the second external electrode terminal 49; The acoustic matching layer 51 is opposed to the body 44 and is fixed to the case 45 by adhesion.

  The case outer periphery vicinity portion 46 and the terminal plate outer periphery vicinity portion 52 are fitted, and when the case 45 is fitted to the terminal plate 47, the case outer periphery vicinity portion 46 covers the terminal plate outer periphery vicinity portion 52, and the outermost periphery. A surface 53 is formed. An arrow 54 indicates the laser to be irradiated. 6 and 7 show a state before the case 45 and the terminal plate 47 are laser-welded.

  As described above, in the form of the present embodiment, the welded portion of laser welding does not appear on the outermost peripheral surface, and when the vicinity of the outermost periphery of the ultrasonic receiver is a sealing surface, the ultrasonic receiver is When attached to the flow path 1, reliable sealing performance can be obtained. In the present invention, the terminal plate 47 may constitute the outermost peripheral surface, and the same effect can be obtained.

  As described above, the ultrasonic transducer and the ultrasonic flowmeter according to the present invention are a short circuit of the ultrasonic transducer due to welding dust generated at the joining of the case and the terminal plate when the ultrasonic transducer is manufactured. This is useful as an ultrasonic flowmeter using an ultrasonic transducer with excellent reliability.

7, 25, 42 First electrode surface 8, 26, 43 Second electrode surface 9, 27, 44 Piezoelectric body 10, 28, 45 Case 10a, 28a, 45a Top wall 10b Open end 11, 29, 46 Case outer periphery Near part (case outer periphery)
11b Outer peripheral edge 12, 30, 47 Terminal plate 13, 31, 48 First external electrode terminal 14, 32, 49 Second external electrode terminal 15a, 33a, 50a Conductor 16, 34, 51 Acoustic matching layer 17, 35, 52 Terminal board outer periphery vicinity (terminal board outer periphery)
17a Step part 18 Fitting part

Claims (2)

A cylindrical case with a bottom;
A piezoelectric body having first and second electrode surfaces facing each other, wherein the first electrode surface is electrically connected to a top wall of the case;
A terminal plate covering the open end of the case and electrically connected to the outer periphery of the case;
A first external electrode terminal provided on the terminal plate;
A second external electrode terminal provided on the terminal plate in an insulated state from the first external electrode terminal;
A conductor provided between the second electrode surface and the second external electrode terminal;
In the ultrasonic transmitter / receiver including an acoustic matching layer bonded and fixed to the outer surface of the top wall of the case, the terminal plate has an inclined surface inclined with respect to the cylindrical axis direction of the case at the corner of the outer peripheral portion. Configure the step,
The ultrasonic transducer according to claim 1, wherein the case has an inclined surface having the same angle as the inclined surface of the stepped portion at an outer peripheral end portion , and is in close contact with the inclined surface . The flow rate measuring unit for measuring the flow rate of the fluid flowing through the flow path, the at least one pair of ultrasonic transducers according to claim 1 provided in the flow rate measuring unit, and the ultrasonic propagation time between the ultrasonic transducers An ultrasonic flowmeter comprising a measurement circuit for measuring the flow rate and a flow rate calculation circuit for obtaining a flow rate based on a signal from the measurement circuit.