JP2006180317A - Ultrasonic wave transmitter receiver and flow measuring instrument for fluid using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of an ultrasonic wave transmitter receiver such that a case having a piezoelectric body fixed to a top wall internal surface and a terminal plate are joined together by electric welding by preventing the piezoelectric body fixed to the top wall internal surface of the case and the terminal plate from short-circuiting by preventing welding dust from scattering. <P>SOLUTION: A flange 9 extending outward from a lower open end of the conductive cap-shaped case 6 is formed in one body, the outer periphery of the conductive terminal plate 10 is electrically welded, and then an airtight space 11 is formed in the case 6. A welding projection 17 is annularly provided on a top surface 16 nearby the outer periphery of the terminal plate 10 and a welding dust diffusion preventive projection 18 as a welding dust diffusion preventing means is annularly provided inside it. The case 6 and the terminal plate 10 are electrically welded through the welding projection 17, but welding dust is never diffused into the case 6 in this case because of the welding dust diffusion preventing projection 18. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic transducer and a flow measuring device that measures the flow velocity and flow rate of a gas or a liquid using the ultrasonic transducer.

  In this type of ultrasonic transducer, as shown in FIG. 7, the upper electrode surface 52a of the piezoelectric body 52 is fixed to the inner surface of the top wall of the conductive cap-like case 51 by means such as bonding, and the top wall An acoustic matching layer 53 was attached to the outer surface.

  A flange 54 extending outwardly from the lower open end of the case 51 is integrally formed, and the outer peripheral upper surface of the conductive terminal board 55 is welded to the lower surface thereof. The sealed space 56 is set. Normally, the sealed space 56 is filled with an inert gas such as nitrogen gas.

  A conductive elastic material 57 is elastically connected to the lower electrode surface 52b of the piezoelectric body 52, and one terminal 58 passing through the terminal plate 55 in an electrically insulating manner is connected thereto. The other terminal 59 is connected to a part of the terminal plate 55 at a predetermined interval.

  That is, one terminal 58 is connected to the lower electrode surface 52 b of the piezoelectric body 52 via the conductive elastic material 57, and the other terminal 59 is connected to the upper electrode surface 52 a of the piezoelectric body 52 via the terminal plate 55 and the case 51. Are connected to each other.

A glass insulating portion 60 is interposed in a penetrating portion of the terminal 58 with respect to the terminal plate 54 so that the insulating relationship between the two is maintained (for example, see Patent Document 1).
JP 2001-50785 A

  However, the conventional ultrasonic transducer has a configuration in which the flange 54 of the case 51 and the terminal plate 55 are joined by welding means such as electric welding. Depending on the fitting state of the terminal plate 55 to the case 51, In some cases, discharge occurs at the contact portion between the case 51 and the terminal plate 55, and thread-like weld dust is generated in the sealed space 60.

  The generated weld dust is confined in the sealed space 56. As a result, the welding dust is attached to the piezoelectric body 52, the inner surface of the case 51, and the outer periphery of the elastic member 57. In such a case, when both ends of the thread-like weld dust are brought into contact with the lower electrode surface 52a of the piezoelectric body 52 and the terminal plate 55, they are short-circuited, and the function of the piezoelectric body 52 is stopped.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to eliminate the influence of thread-like welding dust generated during electric welding and to always maintain the performance as an ultrasonic transducer.

  In order to achieve the above object, according to the present invention, welding dust diffusion preventing means is disposed in the vicinity of the welded portion of the case and the terminal plate.

  When the case and the terminal plate are welded to each other, the ultrasonic transducer of the present invention is prevented from being diffused and mixed into the case even if thread-like welding dust is generated. There is no short circuit with the terminal board. Thereby, the ultrasonic transducer excellent in reliability can be provided.

  In the embodiment of the present invention, a conductive case in which a piezoelectric body is attached to the inner surface of the top wall and an acoustic matching layer is attached to the outer surface of the top wall, and a conductive material that is fixed to the case by welding and closes the open portion. And a welding dust diffusion preventing means is disposed in the vicinity of the welded portion between the case and the terminal plate.

  As a result, even when thread-like weld dust is generated when the case and the terminal plate are electrically welded, the weld dust is prevented from entering the inside of the case by the welding dust diffusion preventing means provided near the welded portion. The short circuit between the electrode surface and the terminal plate is eliminated.

  Specifically, an outward flange is formed on the open end side of the case, and the upper surface of the terminal plate is welded to the lower surface of the flange, and diffused in the welded part, in the vicinity of the outer periphery, or on the inner peripheral side. Preventive means were arranged. If diffusion prevention means is installed near the outer periphery of the welded part, diffusion of weld dust to the outside of the case will also be prevented, and there will be no deposit of weld dust around the electrodes of the welder, and its work efficiency and reliability Will not be damaged.

  The specific structure of the diffusion preventing means is that a welding projection is formed from one of the lower surface of the flange and the upper surface of the terminal plate in the case, and the welding projection is formed on the inner periphery side or in the vicinity of the outer periphery. A welding dust diffusion prevention protrusion was protruded from either the lower surface of the flange or the upper surface of the terminal plate, and the diffusion prevention protrusion was set lower than the welding protrusion.

  As a result, the welding projection is surely brought into contact with the object to be welded, and the welding fixing of the case and the terminal plate is ensured, and there is a slight gap between the welding dust diffusion prevention projection and the mating portion. Yes, but not until the weld dust passes.

  As a welding dust diffusion prevention configuration, as another embodiment, a welding projection is formed from either the lower surface of the flange in the case or the upper surface of the terminal plate, and each of the welding projections in the vicinity of the outer periphery, Alternatively, a seal ring may be interposed between the lower surface of the flange and the upper surface of the terminal plate located on the inner peripheral side.

  Then, at least one pair of these ultrasonic transducers is arranged with an interval between the upstream side and the downstream side of the fluid passage, and the flow velocity of the fluid flowing through the fluid passage based on the ultrasonic propagation time between the ultrasonic transducers If the flow rate is measured, the fluid flow can be measured with high accuracy.

(Embodiment 1)
FIG. 1 shows a fluid flow measuring apparatus using an ultrasonic transducer, and at least 1 is provided at a predetermined interval between an upstream side and a downstream side of a fluid flow path 1 through which a fluid such as LP gas or natural gas flows. A pair of ultrasonic transducers 2 and 3 are arranged.

  These ultrasonic transducers 2 and 3 are configured such that ultrasonic waves transmitted from one side are received by the other across the fluid flow obliquely.

  The ultrasonic propagation time between the ultrasonic transducers 2 and 3 is measured by the measurement circuit 4, and the flow rate of the fluid is measured based on the result, and the flow rate is measured as necessary.

  The temporary action and operation of the flow measuring apparatus configured as described above will be described.

  The distance connecting the centers of the ultrasonic transducers 2 and 3, that is, the ultrasonic propagation distance is L, and the angle with the fluid flow direction is θ. In addition, it is assumed that the speed of sound in a windless state of the fluid is C and the fluid flow velocity is V.

The ultrasonic wave transmitted from the ultrasonic transducer 2 arranged on the upstream side crosses the fluid flow path 1 obliquely and is received by the ultrasonic transducer 3 arranged on the downstream side. The propagation time t1 at this time is
t1 = L / C + V cos θ (1)
Indicated by

Next, an ultrasonic wave is transmitted from the ultrasonic transducer 3 and received by the ultrasonic transducer 2. The propagation time t2 at this time is
t2 = L / C−Vcos θ (2)
Indicated by

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

  If L and θ are known, the flow velocity V can be obtained by measuring t1 and t2 in the measurement circuit 4. If necessary, the flow rate Q can be obtained by multiplying the flow velocity V by the cross-sectional area S of the fluid flow path 1 and the correction coefficient K. The flow rate calculation circuit 5 calculates Q = KSV.

  Next, the ultrasonic transducers 2 and 3 will be described with reference to FIGS.

  In the figure, the upper electrode surface 7a of the piezoelectric body 7 is fixed to the inner surface of the top wall of the conductive cap-like case 6 by means such as adhesion, and the acoustic matching layer 8 is attached to the outer surface of the top wall. .

  A flange 9 extending outward from the lower open end of the case 6 is integrally formed, and the upper surface of the outer periphery of the conductive terminal board 10 is electrically welded to the lower surface thereof. Is set in a sealed space 11. Normally, the sealed space 11 is filled with an inert gas such as nitrogen gas.

  A conductive elastic material 12 is elastically connected to the lower electrode surface 7b of the piezoelectric body 7, and one terminal 13 passing through the terminal plate 10 in an electrically insulating manner is connected. The other terminal 14 is connected to a part of the terminal plate 10 with a predetermined interval.

  That is, one terminal 13 is connected to the lower electrode surface 7 b of the piezoelectric body 7 via the conductive elastic material 12, and the other terminal 14 is connected to the upper electrode surface 7 a of the piezoelectric body 7 via the terminal plate 10 and the case 6. Are connected to each other.

  A glass insulating portion 15 is interposed in the penetrating portion of the terminal 13 with respect to the terminal plate 10 so that the insulating relationship between them is maintained.

  A welding projection 17 is provided in an annular shape on the upper surface 16 near the outer periphery of the terminal board 10, and a welding dust diffusion prevention projection 18, which is a welding dust diffusion prevention means, is provided in an annular shape. The height of the weld dust diffusion preventing projection 18 is set lower than that of the welding projection 17.

  In the above configuration, the case 6 and the terminal plate 10 are electrically welded via the welding projections 17. In this case, the welding projections 17 are set higher than the welding dust diffusion prevention projections 18. Reliable welding at a predetermined location is possible.

  As shown in FIG. 3, after the case 6 and the terminal plate 10 are welded, a minute gap 19 remains between the lower surface of the flange 9 of the case 6 and the weld dust diffusion prevention protrusion 18, but the weld dust passes. It won't be as good.

  Therefore, even when thread-like weld dust is generated when the case 6 and the terminal plate 10 are electrically welded, the weld dust is prevented from being formed on the case 6 by the weld dust diffusion prevention projection 18 provided inside the welding projection 17. It is possible to prevent the inside from entering, and it is possible to eliminate the short circuit between the lower electrode surface 7b of the piezoelectric body 7 and the terminal plate 10 and improve the reliability.

  Even if the cross-sectional shape of the diffusion preventing projection 18 is a semicircular shape, a triangular shape, a quadrangular shape, or the like, there is no difference in the effect.

(Embodiment 2)
In FIG. 4, another welding dust diffusion preventing projection 20 is provided in an annular shape on the outer peripheral side of the welding projection 17. In addition, the same code | symbol is attached | subjected to the part same as Embodiment 1, and the thing of Embodiment 1 is used for description of a structure, an effect | action, operation | movement, etc.

  This welding dust diffusion prevention protrusion 20 is also set slightly lower than the welding protrusion 17, and is between the bottom surface of the flange 9 of the case 6 remaining after the case 6 and the terminal plate 10 are welded and the welding dust diffusion prevention protrusion 20. The minute gap 21 is not so large as to allow welding dust to pass through.

  In this configuration, even if welding dust is generated, it is possible to prevent the case 6 from being diffused to the outside as well as the inside. Therefore, it is not necessary to clean the welding dust around the electrodes of the welding machine during the welding operation, and the production efficiency can be improved accordingly.

  The cross-sectional shape of the welding dust diffusion preventing projection 20 is not limited by a semicircular shape, a triangular shape, a quadrangular shape, or the like.

(Embodiment 3)
In FIG. 5, a seal ring 22, which is a welding dust diffusion preventing means, is disposed inside the welding projection 17. The seal ring 22 is made of rubber or a foamed resin in which low-foamed and low-density closed cells are formed, and is sandwiched between the forming base point of the flange 9 in the case 6 and the terminal plate 10 in a compressed state.

  In addition, the same code | symbol is attached | subjected to the part same as Embodiment 1, and the thing of Embodiment 1 is used for description of a structure, an effect | action, operation | movement, etc.

  In the above configuration, the case 6 and the terminal plate 10 are electrically welded via the welding projections 17, but welding dust generated at this time is prevented from passing by the seal ring 22, and the lower electrode surface 7 b of the piezoelectric body 7 is The short circuit of the terminal board 10 can be eliminated and the reliability can be improved.

(Embodiment 4)
6 shows not only the inside of the welding projection 17 but also the outside, and seal rings 22 and 23 which are welding dust diffusion preventing means are arranged respectively. The seal rings 22 and 23 are made of rubber or a foamed resin in which low foamed and low density closed cells are formed, and are sandwiched between the upper surface of the flange 9 and the terminal plate 10 in the case 6 in a compressed state.

  In addition, the same code | symbol is attached | subjected to the part same as Embodiment 1, and the thing of Embodiment 1 is used for description of a structure, an effect | action, operation | movement, etc.

  In the above configuration, the case 6 and the terminal plate 10 are electrically welded via the welding projections 17, but welding dust generated at this time is prevented from diffusing into the case 6 by the inner seal ring 22, The outer seal ring 23 can also prevent diffusion outside.

  Therefore, the short circuit between the lower electrode surface 7b of the piezoelectric body 7 and the terminal plate 10 can be eliminated to improve reliability, and welding dust cleaning around the electrodes of the welding machine becomes unnecessary, and the production efficiency is improved accordingly. I can plan. In addition, since the inner and outer circumferences of the welding projection 17 are insulated by the seal rings 22 and 23, the welding projection 17 is reliably energized, and as a result, the welding quality can be greatly improved.

  In the above embodiment, instead of forming the welding projection on the terminal plate, it may be formed on the flange side of the case, and the weld dust diffusion prevention projection may be formed on the flange side of the case as well. .

  As described above, the ultrasonic transducer according to the present invention is an ultrasonic transducer excellent in reliability without a short circuit between the piezoelectric body and the terminal plate due to welding dust generated in the electric welding part at the time of manufacture. For example, it can be used for fluid measurement such as a gas meter.

Schematic configuration diagram of ultrasonic flow measurement device Sectional drawing before welding of the ultrasonic transducer in Embodiment 1 of this 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 Sectional drawing of the ultrasonic transducer in Embodiment 3 of this invention Sectional drawing of the ultrasonic transducer in Embodiment 4 of this invention Sectional view showing a conventional ultrasonic transducer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid flow path 2,3 Ultrasonic transmitter / receiver 6 Case 7 Piezoelectric body 8 Acoustic matching layer 9 Flange 10 Terminal board 17 Welding protrusion 18,20 Welding dust diffusion prevention protrusion 22,23 Seal ring

Claims (5)

A conductive case having a piezoelectric body attached to the inner surface of the top wall and an acoustic matching layer attached to the outer surface of the top wall, and a conductive terminal plate fixed to the case by welding and closing the opening, An ultrasonic transducer having welding dust diffusion preventing means disposed in the vicinity of the welded portion between the case and the terminal plate. An outward flange is formed on the open end side of the case, and the upper surface of the terminal plate is welded to the lower surface of the flange, and a diffusion preventing means is disposed in the welded portion, in the vicinity of the outer periphery, or on the inner peripheral side. The ultrasonic transducer according to claim 1. A welding projection is formed from one of the lower surface of the flange and the upper surface of the terminal plate in the case, and the lower surface of the flange and the terminal are located in the vicinity of the outer periphery or on the inner peripheral side of the welding projection. The ultrasonic transducer according to claim 1 or 2, wherein a welding dust diffusion prevention projection is provided so as to project from either one of the upper surface of the plate and the diffusion prevention projection is set lower than the welding projection. A welding projection is formed from one of the lower surface of the flange and the upper surface of the terminal plate in the case, and the lower surface of the flange and the terminal are located in the vicinity of the outer periphery or on the inner peripheral side of the welding projection. The ultrasonic transducer according to claim 1 or 2, wherein a seal ring is interposed between the upper surface of the plate. 5. The ultrasonic wave propagation time between the ultrasonic transducers according to claim 1, wherein at least one pair of the ultrasonic transducers according to any one of claims 1 to 4 is arranged on the upstream side and the downstream side of the fluid passage at an interval. A fluid flow measuring device for measuring the flow velocity and / or flow rate of the fluid flowing through the fluid passage based on the above.

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