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JP4341782

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DESCRIPTION JP4341782
Abstract: To provide an ultrasonic transducer capable of performing normal measurement
without being affected by moisture. A clearance 39 is formed at an interval such that moisture
escapes due to its own weight even if dew condensation occurs, and an interval such that it
escapes due to a negative pressure received from a fluid to be measured flowing through a
measuring pipe. . The gap 39 is in communication with the transmission / reception space 41
that transmits / receives ultrasonic waves. On the outer surface of the other end 45, in order to
maintain the state of the gap 39, a plurality of convex portions are disposed and formed at an
equal pitch. A plurality of housing through holes 42 are formed in the inner housing 35 so as to
penetrate the inner and outer surfaces. [Selected figure] Figure 2
Ultrasonic transducer
[0001]
The present invention relates to an ultrasonic transducer, and more particularly to an ultrasonic
transducer used in an ultrasonic flowmeter for gas.
[0002]
The following technology is disclosed in Patent Document 1 below.
In FIG. 8A, the ultrasonic flowmeter 1 includes a measurement pipe 2 in which a fluid to be
measured flows at a flow velocity F. The measuring tubes 2 are provided with supporting tubes 3
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and 4 which face each other at an angle β with respect to the tube axis OO. An ultrasonic
transducer 5 is fixed to the support tube 3 and an ultrasonic transducer 6 is coaxially fixed to the
support tube 4.
[0003]
The ultrasonic flowmeter 1 emits ultrasonic waves from the ultrasonic transducer 6 in a forward
direction for a predetermined time as indicated by the arrow Ua, and receives the ultrasonic
waves at the ultrasonic transducer 5 as indicated by arrow Ua. It has become. The ultrasonic
transducer 5 receives ultrasonic waves and then emits ultrasonic waves in the opposite direction
to the flow as shown by the arrow Ub, that is, toward the ultrasonic transducer 6. The ultrasonic
transducers 5 and 6 have the same structure. The ultrasonic transducers 5 and 6 alternately
repeat transmission and reception of ultrasonic waves.
[0004]
In the section of the ultrasonic transducers 5 and 6, the time difference between the propagation
time of the ultrasonic wave in the arrow Ua direction and the propagation time of the arrow Ub is
a time difference proportional to the flow velocity in the arrow F direction of the fluid to be
measured It has been known. Therefore, the ultrasonic flowmeter 1 obtains the flow rate
obtained by performing Reynolds number correction on the flow pattern of the fluid to be
measured in the above time difference, and obtains the flow rate by multiplying this flow rate by
the pipe cross-sectional area of the measurement pipe 2 It can be done.
[0005]
In FIG. 8B, the ultrasonic transducer 5 has a substantially cylindrical shape in which an elastic
body 7, an ultrasonic wave transmitting / receiving element (not shown) embedded in the elastic
body 7, and a portion of the elastic body 7 adhere. And the inner side housing 8 (The ultrasonic
transducer 6 is also the same, so the description here is omitted). The ultrasonic transducer 5 is
fixed by inserting the inner housing 8 into the support pipe 3 formed in the measurement pipe 2
without a gap. The elastic body 7 has one end 9 of a substantially cylindrical shape, the other end
10 of a substantially cylindrical shape, and a narrow portion 11 of a small diameter located
therebetween. One end 9 is fixed to the inner housing 8. At the other end 10, an ultrasonic wave
transmitting / receiving element is embedded.
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[0006]
A gap 12 is provided between the outer surface of the other end portion 10 and the inner surface
of the inner housing 8. Further, a damping action space 13 is provided between the constricted
portion 11 and the inner surface of the inner side housing 8. The gap 12 between the outer
surface of the other end 10 and the inner surface of the inner housing 8 is formed in such a way
that a very small space is created. Between the end face 14 of the other end 10 and the end face
15 of the inner housing 8, a seal for preventing the gap 12 from communicating with the
transmission / reception space 16 in the measurement tube 2 for transmitting / receiving
ultrasonic waves. A member 17 is provided. The sealing member 17 is provided to prevent
moisture (liquid) from the fluid to be measured from entering the gap 12. Although the space 12
is a very small space, it is a space sufficient for water to enter.
[0007]
The reason why the sealing member 17 is provided is that if the elastic body 7 is encased by the
water from the fluid to be measured, the elastic body 7 will be in a crosslinked state with respect
to the inner side housing 8 as well. The ultrasonic wave does not propagate in the gas, but
propagates to the inner housing 8 which is more easily transmitted. As a result, there is a risk
that the transmission and reception of the ultrasonic wave may be disturbed to cause a
measurement failure. . Patent No. 3639570 gazette
[0008]
By the way, in the above-mentioned prior art, since the sealing member 17 is provided between
the end surface 14 of the other end 10 of the elastic body 7 and the end surface 15 of the inner
housing 8, the following problems are caused. have. That is, when, for example, dew
condensation or the like occurs inside the inner housing 8, the moisture can not be extracted by
the presence of the sealing member 17, and as a result, transmission and reception of the
ultrasonic wave is hindered. I have a point.
[0009]
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If dew condensation or the like occurs on the inner side, the ultrasonic transducer 5 must be
removed from the support tube 3 to remove moisture, which requires a troublesome operation.
In addition, good measurement results can not be obtained until this troublesome work is done.
The inventor of the present application has found that the received waveform is disturbed and
normal measurement can not be performed.
[0010]
The present invention has been made in view of the above-described circumstances, and an
object of the present invention is to provide an ultrasonic transducer which can perform normal
measurement without being affected by moisture.
[0011]
The ultrasonic transducer according to claim 1 of the present invention, which was made to solve
the above problems, has a substantially cylindrical or substantially discoid end, a substantially
cylindrical other end, and a position between them. Ultrasonic wave comprising: an elastic body
having a small diameter neck portion, an ultrasonic wave transmitting / receiving element
embedded in the elastic body, and a substantially cylindrical inner housing to which the elastic
body is fixed via the one end portion It is a transducer, wherein the inner housing and the elastic
body have a damping action space between the inner surface of the inner housing and the
narrow portion, and between the inner surface of the inner housing and the other end. In an
ultrasonic transducer having a gap, a plurality of convex portions are provided on the outer
surface of the other end, the diameter of the other end is adjusted to positively form the gap, and
ultrasonic waves are generated. Transmitting and receiving space in the measuring tube to
transmit and receive And between said inner housing so as to communicate the said elastic
member is disposed is formed, and, wherein the inner housing, is characterized in that a plurality
of locations forming a housing through hole through the internal housing.
[0012]
According to the present invention having such a feature, even if, for example, dew condensation
occurs or water from the fluid to be measured enters between the inner housing and the elastic
body, the water naturally comes out. .
[0013]
The ultrasonic transducer according to the second aspect of the present invention is the
ultrasonic transducer according to the first aspect, wherein the housing through holes are
formed at four positions at equal pitches in the circumferential direction of the inner housing. It
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is characterized by being set to.
[0014]
According to the present invention having such a feature, the housing through hole is disposed
and formed at a position that is not easily influenced by the mounting direction of the ultrasonic
transducer.
The housing through hole is preferably arranged and formed in consideration of, for example, the
position of the screw hole when supporting and fixing the inner housing to the support pipe of
the measurement pipe through which the fluid to be measured flows (for example, screw hole If
there are four, place and form it so as to be located between adjacent screw holes).
[0015]
The ultrasonic transducer according to the third aspect of the present invention is characterized
in that, in the ultrasonic transducer according to the first aspect or the second aspect, the
application is gas measurement.
[0016]
According to the present invention having such a feature, even if water is temporarily contained
in the gas, the water naturally comes out, so that it becomes an ultrasonic transducer suitable for
gas measurement.
[0017]
According to the present invention, it is possible to provide an ultrasonic transducer which is not
affected by moisture.
In addition, the ultrasonic transducer according to the present invention has an effect that
normal measurement can be performed.
[0018]
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Hereinafter, description will be made with reference to the drawings.
FIG. 1 is a view schematically showing the measurement principle of the ultrasonic flowmeter.
2 is a front view showing an embodiment of the ultrasonic transducer according to the present
invention, FIG. 3 is a sectional view taken along the line AA of FIG. 2, and FIG. 4 is a perspective
view of the ultrasonic transducer.
[0019]
In FIG. 1, an ultrasonic flowmeter 21 is for measuring gas, and includes a measurement pipe 22
through which a fluid to be measured (for example, gas) flows at a flow velocity V.
The measuring tubes 22 are provided with ultrasonic transducers A and B via the support tubes
23 and 23, respectively.
The ultrasonic flowmeter 21 is configured to obtain a flow rate from the difference in
propagation time of ultrasonic waves transmitted and received alternately between the ultrasonic
transducers A and B. The ultrasonic flowmeter 21 is not susceptible to rotational flow in the
transmission and reception of ultrasonic waves, and can achieve high measurement resolution,
"reflection (single reflection) method", and "propagation of the propagation time, which does not
relate to the speed of sound. By adopting the difference method , it becomes possible to
measure the gas flow rate with high accuracy and stability. The principle of measurement will be
briefly described below.
[0020]
Let "Tab" be the propagation time (s) from ultrasonic transducer A to B, "Tba" be the propagation
time (s) from ultrasonic transducer B to A, "L" be the propagation of ultrasonic waves The
distance (m), "C" is the velocity of sound (m / s) in the measurement gas, "V" is the flow velocity
of the measurement gas (m / s), "φ" is the path of the ultrasonic wave and the measurement tube
22 When it is an angle with the central axis of the conduit, when gas is flowing, it is expressed by
the following equation.
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[0021]
[0022]
From equations (1) and (2),
[0023]
[0024]
Assuming that the cross-sectional area of the measurement pipe 22 is A (m <2>), the flow rate Q
(m <3> / h) is expressed by the following equation (4).
[0025]
[0026]
That is, the flow velocity is obtained from the difference of the reciprocal of the ultrasonic wave
propagation time (see the above equation (3)), and as a result, the flow rate can be obtained (see
the above equation (4)).
[0027]
Next, the ultrasonic transducer 31 of the present invention corresponding to the abovementioned ultrasonic transducers A and B will be described with reference to FIGS. 2 to 4.
[0028]
In FIG. 2 to FIG. 4, the ultrasonic transducer 31 of the present invention comprises a housing 32
supported and fixed to the support tube 23 by screwing.
The ultrasonic transducer 31 also includes an elastic body 33 housed in the housing 32 and an
ultrasonic wave transmitting / receiving element 34 embedded in the elastic body 33.
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[0029]
The housing 32 is manufactured by cutting a material made of, for example, stainless steel.
The housing 32 has an inner housing 35 inserted into the support pipe 23, a flange 36 screwed
to the support pipe 23, and an outer housing 38 exposed to the outside of the support pipe 23 to
lead out the wire 37. ing.
[0030]
The ultrasonic transducer 31 according to the present invention is characterized by an inner
housing 35, an elastic body 33 accommodated in the inner housing 35, and a gap 39 formed
therebetween (see FIG. The other configuration is basically the same as the conventional one, and
the detailed description will be omitted).
[0031]
The inner housing 35 has a substantially cylindrical shape and is formed so that the tip end
portion 40 is exposed to the pipe of the measuring tube 22, that is, the transmission / reception
space 41 (see FIG. 1) for transmitting and receiving ultrasonic waves. It is done.
The inner housing 35 has a predetermined length, and an annular flange 36 is coupled to the
proximal end.
The inner surface and the outer surface of the inner housing 35 are formed to be concentric with
the central axis (not shown) of the housing 32 when viewed in cross section.
A plurality of housing through holes 42 are formed in such an inner housing 35 so as to
penetrate the inner and outer surfaces.
[0032]
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The housing through holes 42 are disposed and formed at four locations at equal pitches (90degree pitch) in the circumferential direction of the inner housing 35 (the number is an example.
The number may be one or more than one).
The housing through hole 42 is disposed at a position shifted by 45 degrees with respect to the
screw hole 43 of the flange 36.
The housing through hole 42 is formed to extend along the central axis.
In the present embodiment, it is formed in an oval shape (this is an example. For example, it may
be formed in a substantially rectangular shape or an elliptical shape. In addition, a plurality of
circular holes may be arranged in a line.
[0033]
Although the inner housing 35 has a shape in which a plurality of housing through holes 42 are
provided, sufficient rigidity is secured.
[0034]
The elastic body 33 has a substantially disc-shaped end 44, a substantially cylindrical other end
45, and a small-diameter constricted portion 46 located therebetween, and is formed into a
shape as illustrated. It is done.
The elastic body 33 is fixed to the inner housing 35 via the one end 44 (the fixing position in the
figure is an example). The other end 45 is slightly smaller in diameter than the other end 11 (see
FIG. 8B) of the conventional example. That is, the other end 45 is formed such that the distance
between the outer surface of the other end 45 and the inner surface of the inner housing 35 is
wider than that of the conventional example. Thus, the gap 39 is positively formed larger than
the conventional example.
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[0035]
The gap 39 is formed in a space in which moisture escapes due to its own weight even if dew
condensation occurs, and in a space which escapes due to a negative pressure received from the
fluid to be measured flowing through the measuring pipe 22. The gap 39 is in communication
with the transmission / reception space 41 that transmits / receives ultrasonic waves. In the
present invention, no sealing member as in the prior art is present between the end surface 47 of
the other end 45 and the end surface 48 of the inner housing 35.
[0036]
On the outer surface of the other end portion 45, in order to maintain the state of the gap 39, a
plurality of convex portions 49 are arranged and formed at an equal pitch. The convex part 49 is
formed in four places by the shape used as a protrusion in this form (a shape shall be an
example). The convex portion 49 is formed such that its tip is in contact with the inner surface of
the inner housing 35. The other end 45 is formed in a tapered shape in a portion continuous with
the constricted portion 46. It is difficult for water to stay in the tapered portion. A damping
action space 50 is formed between the constricted portion 46 and the inner surface of the inner
housing 35.
[0037]
The ultrasonic wave transmitting / receiving element 34 is configured to include a disc-like
piezoelectric element 51 having a predetermined piezoelectric constant, an impedance matching
layer 52, and a lead wire (not shown). The ultrasonic wave transmitting / receiving element 34 is
the same as the ultrasonic wave transmitting / receiving element (not shown) of the conventional
example. The ultrasonic transducer 34 is disposed such that the impedance matching layer 52 is
exposed at the central position of the end face 47 of the other end 45.
[0038]
In the above configuration and structure, when the piezoelectric element 51 is driven by the fall
of the drive pulse, it is compressed in the direction of the central axis (not shown) by the
vibration system consisting of the spring force of the elastic body 33 and the mass of the other
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end 45 An expanding piezoelectric alternating strain is generated, the acoustic impedance with
the external medium transmitting and receiving the ultrasonic wave is matched via the
impedance matching layer 52, and the ultrasonic wave is efficiently emitted. At the same time,
the other end 45 of the elastic body 33 also vibrates, and this vibration propagates to the central
neck 46. This vibration is damped due to the small cross sectional area of the constricted portion
46 and the large internal friction, and the damping action by the damping action space 50, and
the piezoelectric alternating strain is rapidly damped.
[0039]
If moisture enters the gap 39, or if moisture is generated due to condensation, the gap 39 is
larger than that of the conventional example, and the plurality of housing through holes 42 allow
the moisture to naturally escape. Therefore, according to the present invention, the ultrasonic
transducer 31 is not affected by moisture. Since the ultrasonic transducer 31 of the present
invention is not affected by moisture, it has an effect that normal measurement can be
performed. This effect is described below.
[0040]
Fig. 5 is a block diagram of the water inclusion influence test device to see the water influence in
the actual flow, Fig. 6 is a graph showing the result of the water inclusion influence test, and Fig.
7 is a diagram related to the received wave of the ultrasonic transducer. is there.
[0041]
In FIG. 5, the water inclusion influence test device 61 flows air of 15 m / s from the upstream of
the ultrasonic flowmeter 62 through the bellows pipe 63 and the pipe 64, and pressurizes the
pressure feeding tank 65 at 0.1 MPa to produce water. The flow rate is set to 0.7 to 1.0 L / min,
and the apparatus is configured to look at the influence of moisture in the actual flow.
Reference numeral 66 indicates a volumetric flow meter. The ultrasonic flowmeter 62 is provided
with either the ultrasonic transducer 31 of the present invention or the conventional ultrasonic
transducers 5 and 6 (see FIG. 8). The water inclusion influence test device 61 is configured to be
a test under much more severe conditions than actual usage conditions where water flows in the
lower part of the pipe 64. The ultrasonic flowmeter 62 is configured to measure the flow rate
with a diameter of 50 mm (numerical values of the diameter and the like are an example).
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[0042]
In the graph of FIG. 6, the ordinate represents the flow velocity (m / s) and the abscissa
represents the time (s), and the ordinate of the flow velocity is omitted below 12 m / s. The solid
line in the graph is the result when the ultrasonic transducer 31 of the present invention is used,
and in a state of flowing air at 15 m / s, 1.0 L / min of water is enclosed at the point of arrow P1,
Water supply is stopped at the point of From the graph, it can be seen that in the case of using
the ultrasonic transducer 31 of the present invention, it is not affected by moisture. In other
words, normal measurement can be performed.
[0043]
On the other hand, the broken line in the graph is the result in the case of using the ultrasonic
transducers 5 and 6 of the conventional example, and in the state of flowing air of 15 m / s, the
moisture is 1.0 L at the point of the arrow P3. Immediately after this, it is understood that the
flow velocity drops rapidly to 0 m / s and becomes immeasurable when / min is enclosed. In
addition, I tried to stop the water filling but it did not return.
[0044]
In FIG. 7, the steady received wave in the state of not containing water has a waveform as shown
in FIG. 7 (a). On the other hand, in the case where the ultrasonic transducer 31 of the present
invention is used in the state where the water is sealed, the received wave has a waveform as
shown in FIG. 7 (b). However, in the case where the conventional ultrasonic transducers 5 and 6
are used in a state in which water is sealed, the received wave has a waveform as shown in FIG. 7
(c). Therefore, it is natural that the result shown in the graph of FIG. 6 is obtained.
[0045]
As described above with reference to FIGS. 1 to 7, according to the present invention, it is
possible to provide an ultrasonic transducer 31 which is not affected by moisture. Further, the
ultrasonic transducer 31 of the present invention has an effect that normal measurement can be
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performed.
[0046]
It goes without saying that the present invention can be variously modified without departing
from the spirit of the present invention.
[0047]
It is a figure which shows typically the measurement principle of an ultrasonic flowmeter.
It is a front view showing one embodiment of an ultrasonic transducer of the present invention. It
is the sectional view on the AA line of FIG. It is a perspective view of an ultrasonic transducer. It
is a block diagram of the water inclusion influence examination device for seeing the water
influence in a real flow. It is a graph which shows the result of a water inclusion influence test. It
is a figure which concerns on the received wave of an ultrasonic transducer. (A) is a figure which
shows the ultrasonic flowmeter of a prior art example, (b) is a figure which shows the ultrasonic
transducer of a prior art example.
Explanation of sign
[0048]
Reference Signs List 21 ultrasonic flow meter 22 measurement tube 23 support tube 31
ultrasonic transducer 32 housing 33 elastic body 34 ultrasonic transducer 35 inner housing 36
flange 37 wiring 38 external housing 39 gap 40 tip 41 wave receiving space 42 housing
Through hole 43 screw hole 44 one end 45 other end 46 constricted part 47, 48 end face 49
convex part 50 damping space 51 piezoelectric element 52 impedance matching layer
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