DESCRIPTION JP2011015264

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DESCRIPTION JP2011015264
To provide an ultrasonic transducer which does not mix in the case the welding dust generated
when joining the case and the terminal plate by electric welding. An inclined portion (17) is
formed in an outer peripheral vicinity portion (11) of a case (10), and an outer peripheral vicinity
portion (19) of a terminal plate (12) and an outer peripheral vicinity portion (11) of the case are
brought into close contact. With the configuration of joining by the joining means, the generation
of welding dust in the enclosed space is eliminated. As a result, a short circuit between the
electrode surface 8 and the terminal plate 12 is eliminated, and an ultrasonic flowmeter using an
ultrasonic transducer excellent in reliability can be provided. [Selected figure] Figure 2
Ultrasonic transducer and ultrasonic flowmeter using the same
[0001]
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 or liquid using ultrasonic
waves generated using the ultrasonic transducer.
[0002]
A conventional ultrasonic transducer of this type is, for example, as shown in FIGS.
The upper electrode surface 65 of the piezoelectric body 64 is fixed to the inner surface of the
top wall 63a of the conductive cap-like case 63 using a means such as bonding, and an acoustic
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matching 66 is attached to the outer surface of the top wall 63a. . An outwardly extending flange
67 is integrally formed from the lower open end of the case 63, and the outer peripheral upper
surface of the conductive terminal plate 68 and the lower surface of the flange 67 are electrically
welded. Thus, the inside of the case 63 is set as the sealed space 63b. Usually, the closed space
63b is filled with an inert gas such as nitrogen gas. A conductive elastic material 70 is resiliently
conductive to the lower electrode surface 69 of the piezoelectric body 64, and a first terminal 71
penetrating the terminal plate 68 in an electrically insulating manner is connected. Further, a
second terminal 72 is connected to a part of the terminal plate 68 which has a predetermined
distance from the terminal 71. That is, the first terminal 71 is on the lower electrode surface 69
of the piezoelectric body 64 via the conductive elastic material 70, and the second terminal 72 is
on the upper electrode of the piezoelectric body 64 via the terminal plate 68 and the case 63.
Each is connected to the surface 65. A glass insulating portion 73 is interposed in the penetrating
portion of the first terminal 71 with respect to the terminal plate 68 so that the insulation
relationship between the both can be maintained.
[0003]
A welding projection 75 is annularly provided on the upper surface 74 in the vicinity of the outer
periphery of the terminal plate 68, and a welding dust diffusion preventing projection 76 serving
as a welding dust diffusion preventing means is annularly provided on the inner side thereof. The
height of the welding dust diffusion preventing projection 76 is set to be lower than that of the
welding projection 75. The joining of the case 63 and the terminal plate 68 is performed by
melting the welding projection 75 by electric welding.
[0004]
In this embodiment, the welding projection 75 is annularly provided on the upper surface 74 in
the vicinity of the outer periphery of the terminal plate 68, and the welding dust diffusion
preventing projection 76 serving as welding dust diffusion preventing means is annularly
provided inside thereof. Therefore, even when dust is generated at the time of welding, it is
possible to prevent dust from entering the sealed space 63a (see, for example, Patent Document
1).
[0005]
JP, 2006-180317, A
[0006]
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However, the above-described conventional configuration aims at providing the welding dust
diffusion preventing projection 76, which is a welding dust diffusion preventing means, annularly
to prevent the invasion of dust into the sealed space 63a even when dusting occurs. However,
since there is a gap between the welding dust diffusion preventing protrusion 76 and the lower
surface of the flange 67 at the moment when the welding protrusion 75 is energized to melt the
welding protrusion 75, the welding protrusion 75 is melted. When dust is generated in an
instant, there is a problem that the dust passes through the gap and intrudes into the sealed
space 63a.
[0007]
Therefore, when dust enters into the sealed space 63a, the welding dust contacts the lower
electrode surface 69 of the piezoelectric body 64 and the terminal plate 68, causing a short
circuit between the lower electrode surface 69 and the terminal plate 68 and generating
ultrasonic waves. I had the problem of not doing.
[0008]
The present invention solves the above-mentioned conventional problems, and when using laser
welding / joining means for joining the contact abutment portion when welding the case and the
terminal plate, dust does not intrude into the sealed space and a piezoelectric body is formed. An
object of the present invention is to provide an ultrasonic flowmeter using an ultrasonic
transducer excellent in reliability, as well as realizing an ultrasonic transducer in which a short
circuit does not occur between terminal plates.
[0009]
In order to solve the above-mentioned conventional problems, an ultrasonic transducer according
to the present invention has a cylindrical case with a bottom, and a first electrode surface and a
second electrode surface facing each other. A piezoelectric body electrically connected to the
inside of the top wall of the case, a terminal plate covering the open end of the case and
electrically conducted to the case outer peripheral portion, and a first external 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 the second
external electrode terminal provided between the second electrode surface and the second
external electrode terminal In an ultrasonic transducer including a conductor and an acoustic
matching layer adhesively fixed to the top wall outer surface of the case, an inclined portion is
formed on at least one of the terminal plate outer peripheral portion and the case outer
peripheral end. Bonding the contact contact portion where the terminal plate outer peripheral
portion and the case outer peripheral portion are in close contact contact In a state in which the
contact contact portion where the case and the terminal plate are in close contact with each
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other is joined by, for example, a laser, the terminal plate is formed from the outer peripheral
surface of the contact contact portion irradiated with the laser. As it is gradually melted toward
the central part, there is no generation of dust in the molten part on the central part side and
there is no penetration of dust into the case, so there is no short circuit between the electrode
surface and the terminal plate by the dust It is.
[0010]
The ultrasonic transducer according to the present invention closely contacts the outer
peripheral portion of the terminal plate and the outer peripheral portion of the case, and joins
the close contact portion by laser welding and bonding means to generate welding dust in the
sealed space. It has been eliminated.
As a result, the entry of dust into the case is eliminated, and a short circuit between the electrode
surface and the terminal plate is eliminated, whereby an ultrasonic flowmeter using an ultrasonic
transducer excellent in reliability can be provided.
[0011]
The schematic block diagram which shows the ultrasonic flowmeter in Embodiment 1 of this
invention The cross section figure of the ultrasonic transducer in Embodiment 1 of this invention
The cross section figure of the ultrasonic transducer in this embodiment 2 of this invention
Sectional view of the ultrasonic transducer according to the third embodiment of the present
invention Sectional view after ultrasonic transducer welding according to the third embodiment
of the present invention sectional view showing the conventional ultrasonic transducer before
welding Sectional view showing the ultrasonic transducer after welding
[0012]
According to a first aspect of the present invention, there is provided a cylindrical case having a
bottom, a first electrode surface and a second electrode surface facing each other, and the first
electrode surface is electrically connected to the inside of the top wall of the case. A piezoelectric
body, a terminal plate covering the open end of the case and electrically conducted to the case
outer peripheral portion, a first external electrode terminal provided on the terminal plate, and
an insulating state from the first external electrode terminal 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 adhesively fixed to the outer surface of the top wall
of the case. In the ultrasonic transducer including the acoustic matching layer, an inclined
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portion is formed on at least one of the terminal plate outer peripheral portion or the case outer
peripheral end portion, and the terminal plate outer peripheral portion and the case outer
peripheral portion are in close contact with each other. And a contact contact portion that is in
contact with the case. For example, in a state where the close contact portion in which the sub
plates are in close contact is joined by a laser, for example, the outer peripheral surface of the
close contact portion irradiated with the laser is gradually melted toward the central portion of
the terminal plate. Since there is no generation of dust in the molten part on the part side and
there is no penetration of dust into the case, the short circuit between the electrode surface and
the terminal plate due to the dust is eliminated.
[0013]
Specifically, the flange portion of the case is inclined and the case outer peripheral portion is in
close contact with the terminal plate.
By irradiating the laser to the portion in close contact with the terminal plate by closely
contacting the case outer peripheral portion to the terminal plate, no gap is formed between the
case and the terminal plate at the time of welding, so welding defects can be eliminated. is there.
[0014]
According to a second aspect of the present invention, in particular, in the first aspect, the
terminal plate outer peripheral portion has an inclined portion in which the surface facing the
case is inclined toward the case bonding direction. By performing laser irradiation to the close
contact portion, welding can be performed reliably, and welding defects can be eliminated.
When the terminal plate is thicker than the case, the flatness of the outer periphery of the
terminal plate can be machined with high precision when the terminal plate is machined.
[0015]
In the third invention, particularly in the third invention, the terminal plate is a flat surface
opposite to the joint surface with the case, and the laser is moved to the close contact portion
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where the terminal plate outer peripheral portion and the terminal plate are in close contact By
performing the irradiation, welding can be performed reliably, so that defects in welding can be
eliminated.
At the same time, by forming the opposite surface on the side of the close contact contact portion
as a flat surface, reliable sealing performance can be obtained when the outer peripheral portion
of the terminal plate and the case is used as a seal surface.
[0016]
According to a fourth aspect of the present invention, particularly in any of the first to third
aspects, the case and the terminal plate are in close contact by the laser welding means
configured to bond the close contact portion between the terminal plate and the case by the laser
welding means. In the processing state in which the contact contact portion is melted, the contact
contact portion irradiated with the laser is gradually melted from the outer peripheral surface
toward the central portion of the terminal plate. There is no generation of dust, and it is possible
to eliminate the occurrence of a problem due to a short circuit between the electrode surface and
the terminal plate due to the intrusion of dust.
[0017]
A fifth aspect of the present invention is a flow rate measuring unit for measuring the flow rate
of fluid flowing through a flow path, and at least a pair of ultrasonic transducers according to any
one of claims 1 to 4 provided in the flow rate measuring unit. And a measuring circuit for
measuring the ultrasonic wave propagation time between the ultrasonic transducers and the
ultrasonic flowmeter having a flow rate calculating circuit for obtaining the flow rate based on
the signal from the measuring circuit. High measurement accuracy can be obtained.
[0018]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
The present invention is not limited by the present embodiment.
[0019]
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Embodiment 1 FIG. 1 is a view showing the configuration of an ultrasonic flowmeter using an
ultrasonic transducer according to a first embodiment of the present invention.
[0020]
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 for measuring 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 arranged opposite to the side
and the downstream side to transmit and receive ultrasonic waves, 5 is a measurement circuit for
measuring an ultrasonic wave propagation time between the ultrasonic transducers 3 and 4, and
6 is a measurement circuit from the measurement circuit 5 It is an arithmetic circuit which
calculates | requires the flow velocity and / or flow rate based on a signal.
[0021]
The operation and action of the ultrasonic flowmeter in the flow rate measuring unit 2
configured as described above will be described.
A distance connecting the centers of the ultrasonic transducer 3 and the ultrasonic transducer 4
is L, and an angle between the straight line and the longitudinal direction of the flow path 1
which is the flow direction is θ.
Further, the velocity of sound in a windless state of the fluid is denoted by C, and the flow
velocity of the fluid in the flow passage 1 is denoted by V.
The ultrasonic waves transmitted from the ultrasonic transducer 3 disposed on the upstream side
of the flow rate measuring unit 2 obliquely cross the flow path 1 and are received by the
ultrasonic transducer 4 disposed on the downstream side.
The propagation time t1 at this time is represented by t1 = L / C + V cos θ.
Next, ultrasonic waves are transmitted from the ultrasonic transducer 4 and received by the
ultrasonic transducer 3.
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The propagation time t2 at this time is represented by t2 = L / C-V cos θ.
Then, if the sound velocity C of the fluid is eliminated from the equations of t1 and t2, the
equation of V = L / 2 cos θ (1 / t1-1 / t2) is obtained.
[0022]
If L and θ are known, the flow velocity V can be obtained by measuring t1 and t2 in the
measuring circuit 5. From the flow velocity V, assuming that the cross-sectional area of the flow
channel 1 is S and the correction coefficient is K, the calculation circuit 6 can calculate Q = KSV
to obtain the flow rate.
[0023]
The ultrasonic transducer used for the ultrasonic flowmeter which performs a flow measurement
by the above principle of operation is demonstrated using FIG. FIG. 2 is a cross-sectional view of
the ultrasonic transducer according to the first embodiment of the present invention.
[0024]
In FIG. 2, the ultrasonic transducers 3 and 4 have a case 10 formed in a bottomed cylindrical
shape whose lower side is opened, and have a first electrode surface 7 and a second electrode
surface 8 facing each other. The piezoelectric body 9 electrically connected to the inside of the
top wall 10a of the case 10, and the terminal plate 12 which is in close contact with the outer
peripheral portion 11 of the case 10 and seals the open end of the case 10 , The first external
electrode terminal 13 provided on the terminal plate 12, the second external electrode terminal
14 provided on the terminal plate 12 in an insulated state from the first external electrode
terminal 13, and the second external electrode terminal 14 of the piezoelectric body 9.
Conductive rubber 15 having a conductor 15a provided between the second electrode surface 8
and the second external electrode terminal 14, and an acoustic matching layer 16 facing the
piezoelectric body 9 and adhesively fixed to the outside of the case 10 It is configured.
[0025]
The outer peripheral portion 11 of the case 10 is formed in a flange shape and the inclined
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portion 17 is formed. The outer peripheral portion 18 of the inclined portion 17 of the case 10
abuts on the outer peripheral portion 19 of the terminal plate 12 The contact portion 20 is
configured.
[0026]
An arrow 21 indicates a laser irradiated to the close contact portion 20.
FIG. 2 shows the state before the case 10 and the terminal plate 12 are laser-welded.
[0027]
As described above, in the embodiment, the close contact portion 20 where the case 10 and the
terminal plate 12 are in close contact by the laser welding means is melted from the outer
peripheral side.
Since the laser is gradually melted from the outer peripheral surface of the close contact portion
20 irradiated with the laser toward the central portion of the terminal plate 12, generation of
dust is eliminated in the molten portion on the central portion side.
[0028]
Second Embodiment FIG. 3 is a cross-sectional view of an ultrasonic transducer according to a
second embodiment of the present invention. In FIG. 3, the ultrasonic transducer 22 is
electrically connected to the piezoelectric body 25 having the first electrode surface 23 and the
second electrode surface 24 opposed to each other and to the first electrode surface 23 of the
piezoelectric body 25. The case 26, the terminal plate 28 in close contact with and in contact
with the outer peripheral portion 27 of the case 26, the first external electrode terminal 29
provided on the terminal plate 28, and the first external electrode terminal 29 are insulated. A
second external electrode terminal 30 provided on the terminal plate 28, and a conductive
rubber 31 having a conductor 31a provided between the second electrode surface 24 of the
piezoelectric body 25 and the second external electrode terminal 30; It is composed of an
acoustic matching layer 32 facing the piezoelectric body 25 and adhesively fixed to the case 26.
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FIG. 3 shows the state before the case 26 and the terminal plate 28 are laser-welded.
[0029]
An inclined portion 34 inclined toward the joining direction of the case 26 is formed in the outer
peripheral portion 33 of the terminal plate 28, and the outer peripheral portion 35 of the
inclined portion 34 of the terminal plate 28 is an outer peripheral portion 27 of the case 26. It
abuts and constitutes the close contact portion 36. The arrow 37 shows the laser irradiated to
the close contact portion 36.
[0030]
As described above, in the embodiment of the present invention, welding by laser irradiation can
be reliably performed by closely contacting the outer periphery of the terminal plate 28 with the
case 26, so that welding defects can be eliminated. When the terminal plate 28 is made thicker
than the case 26, for example, when pressing the terminal plate 28, the flatness of the contact
surface of the terminal plate 28 with the outer peripheral vicinity portion 27 of the case 26 is
processed with high accuracy. There is an effect of eliminating the gap between the close contact
portion 36 of the outer peripheral portion 27 of the case 26 and the outer peripheral portion 35
of the terminal plate 28.
[0031]
Third Embodiment FIG. 4 is a cross-sectional view of an ultrasonic transducer according to a
third embodiment of the present invention. In FIG. 4, the ultrasonic transducer 38 is electrically
connected to the piezoelectric body 41 having the first electrode surface 39 and the second
electrode surface 40 facing each other and to the first electrode surface 39 of the piezoelectric
body 41. Case 42, the terminal plate 44 to which the outer peripheral vicinity portion 43 of the
case 42 is electrically connected, the first external electrode terminal 45 provided on the
terminal plate 44, the first external electrode terminal 45, and the insulating state And a
conductive rubber 47 having a conductor 47 a provided between the second electrode surface
40 of the piezoelectric body 41 and the second external electrode terminal 46. And an acoustic
matching layer 77 opposed to the piezoelectric body 41 and adhesively fixed to the case 42.
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[0032]
The inclined portion 50 is formed on the contact contact portion side 49 with the case 42 of the
outer peripheral vicinity portion 48 of the terminal plate 44, and the outer peripheral portion 51
of the inclined portion 50 of the terminal plate 44 is the outer peripheral vicinity portion 43 of
the case 42. And a close contact portion 52 is formed. An arrow 53 indicates a laser irradiated to
the close contact portion 52. The opposite surface 54 of the contact contact portion side 49 of
the terminal plate 44 and the vicinity 43 of the outer peripheral portion of the case 42 are
parallel to each other. FIG. 4 shows the state before the case 42 and the terminal plate 44 are
laser-welded.
[0033]
As described above, in the present embodiment, welding by laser irradiation can be reliably
performed by closely contacting the outer peripheral portion 51 of the terminal plate 44 to the
vicinity 43 of the outer peripheral portion of the case 42 so that welding defects can be
eliminated. It is a thing. Furthermore, when the ultrasonic transducer 38 is attached to the flow
rate measuring unit by forming the opposite surface 54 of the close contact contact portion 49 in
a parallel plane with respect to the outer peripheral portion vicinity 43 of the case 42, the
opposite side of the terminal plate 44 Since the surface 54 and the outer peripheral vicinity 43 of
the case 42 are configured to be parallel to each other, reliable sealing performance can be
obtained.
[0034]
FIG. 5 shows a cross-sectional view of the ultrasonic transducer after laser welding in the third
embodiment of the present invention. In FIG. 5, the outer peripheral vicinity portion 57 of the
case 56 of the ultrasonic transducer 55 and the outer peripheral portion 59 of the terminal plate
58 constitute a fusion portion 61 by laser irradiated to the close contact portion 60 and are
integrally joined. There is. The range of the melting portion 61 extends from the round outer
peripheral portion 57 to the inner melting portion 62. 62 denotes a piezoelectric body.
[0035]
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As described above, in the embodiment of the present embodiment, since the outer peripheral
vicinity portion 57 of the melting portion 61 is rounded and individualized, when the ultrasonic
transducer 38 is attached to the flow rate measuring portion, an O-ring or sealing means is used.
When a molded rubber material is used, reliable sealing performance can be obtained without
causing damage to the rubber material. Further, the laser irradiated to the close contact portion
60 melts the outer peripheral portion 57 and the outer peripheral portion 59, and the melting
range reaches the inner melting portion 62 while moving in the central direction of the terminal
plate 58. In the inner melting portion 62, since the laser does not directly hit and is melted by
heat, no dust is generated in the direction of the piezoelectric body 62.
[0036]
Further, in the ultrasonic transducer, the welding means of the close contact portion where the
vicinity of the outer periphery of the terminal plate and the vicinity of the outer periphery of the
case are in close contact with each other is laser welding.
[0037]
Thereby, in a state where the close contact portion where the case and the terminal plate are in
close contact is melted by the laser welding means, the outer circumferential surface of the close
contact portion irradiated with the laser is gradually directed toward the central portion of the
terminal plate. Since it is melted, generation of dust does not occur in the melted portion on the
central portion side, and a short circuit between the electrode surface and the terminal plate can
be eliminated.
[0038]
Then, at least one pair of this ultrasonic transducer with no contamination of dust in the enclosed
space is arranged upstream and downstream of the flow path through which the fluid to be
measured flows, based on the ultrasonic wave propagation time between both ultrasonic
transducers. By setting the flow velocity and / or flow rate of the fluid to be measured to be
ultrasonic waves, it is possible to obtain highly reliable measurement without short circuit due to
dust.
[0039]
As described above, in the ultrasonic transducer and ultrasonic flow meter according to the
present invention, when the ultrasonic transducer is manufactured, a short circuit of the
ultrasonic transducer due to welding dust generated at the joining of the case and the terminal
plate It is useful as an ultrasonic flowmeter using an ultrasonic transducer with excellent
reliability.
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[0040]
3, 4, 22, 38, 55 ultrasonic transducer 7, 23, 39 first electrode surface 8, 24, 40 second electrode
surface 9, 25, 41 piezoelectric body 10, 26, 42 case 10a, 26a , 63a top wall 11, 27, 43 outer
periphery of the case (case outer peripheral portion) 12, 28, 44, 58 terminal plate 13, 29, 45
first external electrode terminal 14, 30, 46 second external electrode terminal 15a, 31a, 47a
Conductor 16, 32, 77 Acoustic matching layer 17, 34, 50 Inclined portion 19, 33, 48 Adjacent
portion of outer periphery of terminal plate (terminal plate outer peripheral portion) 20, 36, 52,
60 Close contact portion
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