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DESCRIPTION JP2008193539

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DESCRIPTION JP2008193539
The present invention provides an acoustic matching member, an ultrasonic transducer, and an
ultrasonic flow velocity flowmeter that more effectively suppress dust generation due to
exfoliated particles and the like generated from an acoustic matching member, and that do not
contaminate a measurement system. SOLUTION: The ultrasonic transducer 4 is provided with an
acoustic matching member 3 having a dustproof layer 2 on the outer peripheral portion, so that
the dustproof layer effectively emits dust due to exfoliated particles or the like generated from
the acoustic matching member. Since it is possible to suppress the contamination of the
measurement system, it is possible to perform the flow rate measurement with high accuracy and
to prevent the leakage when the measurement fluid is shut off. [Selected figure] Figure 2
Acoustic matching member and ultrasonic transducer and ultrasonic flow meter using it
[0001]
The present invention relates to an acoustic matching member for use in an ultrasonic
transducer that transmits ultrasonic waves in a fluid such as gas or liquid or receives ultrasonic
waves propagating in the fluid, and an ultrasonic transducer using the same. It relates to an
acoustic flow meter.
[0002]
The conventional ultrasonic transducer 50 of this type has a configuration as shown in FIG.
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In the figure, the ultrasonic transducer 50 is composed of an acoustic matching member 51, a
piezoelectric body 52 and lead wires 53, 54. The acoustic matching member 51 and the
piezoelectric body 52 are joined via the joining means 55. The electrodes 56 and 57 of the
piezoelectric body 52 and the lead wires 53 and 54 are electrically connected. In order to
efficiently propagate the vibration generated by the piezoelectric body 52 to the gas, it is
necessary to take acoustic impedance into consideration.
[0003]
The acoustic impedance Z of the object is defined by the speed of sound C and the density ρ as
shown in equation (1).
[0004]
Z = ρ × C (1) The acoustic impedance ZP of the piezoelectric body 52 which is a vibration
generating means is 30 × 106 kg / (m <2> s), and the acoustic impedance of a gas which is a
radiation medium of ultrasonic waves, for example, air. ZA is about 400 kg / (m <2> s) and
largely different.
The ultrasonic waves are reflected on such interfaces of different acoustic impedances, the
intensity of the transmitted ultrasonic waves is reduced, and the ultrasonic waves are not
efficiently propagated.
[0005]
The acoustic matching member 51 is used to solve this problem, and is formed between the
piezoelectric body 52 and the radiation medium. When the acoustic impedance ZM of the
acoustic matching member 51 satisfies the relationship of the following expression (2), ultrasonic
waves are efficiently propagated to the radiation medium.
[0006]
ZM = (ZP × ZA) <(1/2)> (2) This optimal value is about 11 × 10 <4> kg / (m <2> s). As
understood from the equation (2), the acoustic matching member 51 is required to be solid, low
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in density and low in sound velocity. Conventionally, in order to reduce the weight of the acoustic
matching member 51, a porous body is used. For example, as described in Patent Document 1,
the porous body is a sintered porous body of ceramic or a mixture of ceramic and glass.
Unexamined-Japanese-Patent No. 2004-45389
[0007]
However, in the conventional configuration, the porous body used to make the acoustic matching
member 51 low in density and low in sound velocity is vulnerable to external stress such as
impact and friction, so partial peeling from the acoustic matching member Dust is generated.
Therefore, when it used for an ultrasonic flow velocity flowmeter, it had the subject of
contaminating a measurement system.
[0008]
The present invention solves the above-mentioned conventional problems, and an object of the
present invention is to provide an acoustic matching member that does not contaminate the
measurement system, and an ultrasonic transducer and ultrasonic flow meter using the same.
[0009]
In order to solve the above-mentioned conventional problems, the ultrasonic transducer
according to the present invention has a structure in which a dustproof layer is provided on an
outer peripheral portion of an acoustic matching member which is a component.
[0010]
As a result, the dustproof layer can solve the problem of dust generation due to exfoliated
particles and the like generated from the acoustic matching member, and contamination of the
measurement system can be prevented.
[0011]
The ultrasonic transducer according to the present invention solves the dusting property of the
acoustic matching member, and does not contaminate the measurement system, and realizes an
ultrasonic transducer and an ultrasonic velocity flowmeter that realize high-accuracy flow
velocity measurement. be able to.
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[0012]
According to the first aspect of the present invention, by using an acoustic matching member
having a dustproof layer on the outer peripheral portion of the acoustic matching body, the
dustproof layer solves dust generation due to exfoliated particles and the like generated from the
acoustic matching member In this case, it is possible to use an ultrasonic transducer and an
ultrasonic flow velocity flowmeter that realize highly accurate flow velocity flow measurement.
[0013]
According to a second aspect of the present invention, the dustproof layer solves dust generation
due to exfoliated particles or the like generated from the acoustic matching member by using the
acoustic matching member provided with a dustproof layer on the side wall portion and top wall
surface of the acoustic matching body. In the case of an ultrasonic flow velocity flow meter, an
ultrasonic transducer and an ultrasonic flow velocity flow meter that realize high-accuracy flow
velocity flow measurement can be used.
[0014]
In the third invention, the dustproof layer has a higher density than the acoustic matching body,
and the dustproof layer becomes a denser layer by using the acoustic matching member
according to claim 1 or 2, so that the acoustic matching is achieved. Dust generation due to
exfoliated particles and the like generated from members can be more effectively suppressed.
[0015]
According to a fourth aspect of the present invention, there is provided an ultrasonic transducer
by using the acoustic matching member according to claim 1 or 2, wherein the dustproof layer
on the top outer wall surface of the acoustic matching body is thinner than the side wall portion.
Dust generation due to exfoliated particles and the like generated from the acoustic matching
member can be more effectively suppressed without deteriorating the characteristics at the time.
[0016]
According to a fifth aspect of the present invention, the thickness of the dustproof layer on the
top outer wall surface of the acoustic matching body is one-fifth to one-fifth of one-fifth to onefifth of ultrasonic wavelength λ propagating through the acoustic matching member. By setting
it as the acoustic matching member of the above, it is possible to more effectively suppress
dusting due to exfoliated particles and the like generated from the acoustic matching member
without degrading the characteristics of the ultrasonic transducer.
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[0017]
A sixth aspect of the present invention is the acoustic matching member according to any one of
claims 1 to 5, wherein the acoustic matching body is a porous body, whereby a higher output can
be obtained when an ultrasonic transducer is used. can do.
[0018]
According to a seventh invention, by using the acoustic matching member according to claim 6,
in which the porous body is a second porous body formed in the void portion of the first porous
body, it is possible to use an ultrasonic transducer more It can be high output.
[0019]
In the eighth invention, by using the acoustic matching member according to claim 7, wherein
the dustproof layer is made of the same material as the first porous body, the difference in
thermal expansion coefficient between the dustproof layer and the first porous body is small.
Since the adhesion is good, dust generation due to exfoliated particles and the like generated
from the acoustic matching member can be more effectively suppressed stably in a wide
temperature range when the ultrasonic transducer is used.
[0020]
In the ninth invention, by using the acoustic matching member according to claim 7, wherein the
first porous body is a ceramic material, the aging is small because it is an inorganic material, and
when it is used as an ultrasonic transducer, it takes a long time Can operate stably.
[0021]
In the tenth invention, by using the acoustic matching member according to claim 7, wherein the
second porous body is a porous organic glass, higher power can be obtained when it is used as
an ultrasonic transducer, and inorganic Since it is a material, its aging is small and it can operate
stably over a long period.
[0022]
In the eleventh invention, the porous organic glass is a silica dry gel obtained by polymerizing
and drying an organosilane compound, and by using the acoustic matching member according to
claim 10, the polymerization reaction can be easily controlled. It is possible to reduce the
characteristic variation when it is used as an acoustic transducer.
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[0023]
The twelfth invention is the acoustic matching member according to any one of claims 1 to 5,
wherein the dustproof layer is a member which shrinks by heat, whereby the dustproof layer can
be easily formed by heating. it can.
[0024]
A thirteenth invention is an ultrasonic transducer including the acoustic matching member
according to any one of claims 1 to 12 and a piezoelectric body, whereby emission from peeling
particles or the like generated from the acoustic matching member Dustiness can be suppressed
more effectively.
[0025]
In a fourteenth aspect of the present invention, the piezoelectric body is disposed on the inner
surface of the closed container, and the acoustic matching member according to any one of
claims 1 to 12 is disposed on the outer surface of the closed container at a position facing the
piezoelectric body. By forming the ultrasonic transducer as described above, it is possible to
reduce the deterioration of the electrode provided on the piezoelectric body and the deterioration
of the joint between the piezoelectric body and the closed container.
[0026]
A fifteenth invention is an ultrasonic flow velocity flowmeter comprising the ultrasonic
transducer according to claim 13 or 14, wherein a flow rate measuring unit through which a
fluid to be measured flows and the flow rate measuring unit Based on the propagation time, a
pair of ultrasonic transducers arranged opposite to each other on the upstream side and the
downstream side of the fluid flow, an ultrasonic wave propagation time measuring circuit
between the pair of ultrasonic transducers, and By using an ultrasonic flow velocity flowmeter
comprising calculation means for calculating the flow rate of the fluid to be measured, the dustproof layer does not contaminate the measurement system, and highly accurate measurement
can be performed.
[0027]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
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The present invention is not limited by the embodiments of the present invention.
[0028]
(First Embodiment) FIG. 1 is a cross-sectional view of an acoustic matching member 3 provided
with a dustproof layer 2 according to a first embodiment of the present invention, and FIG. 2 is
an ultrasonic transducer according to the first embodiment of the present invention. 4 shows a
cross-sectional view of FIG.
[0029]
In FIG. 1, an acoustic matching member 3 in which a dustproof layer 2 is formed on the outer
peripheral portion of the acoustic matching body 1 is provided.
In FIG. 2, the ultrasonic transducer 4 has a configuration in which the acoustic matching member
3 provided with the dustproof layer 2 and the piezoelectric body 5 are joined by the joining
means 6.
The piezoelectric body 5 is provided with the electrodes 7 facing each other, the electrodes 7 and
the lead wires 8 and 9 are electrically joined, and an electric signal is transmitted through the
lead wires 8 and 9.
[0030]
The operation and action of the ultrasonic transducer 4 configured as described above will be
described below.
[0031]
First, the ultrasonic transducer 4 vibrates the piezoelectric body 4 by applying an electric signal
adjusted to a rectangular wave of 200 to 600 kHz or a sine wave to the piezoelectric body 5
through the lead wires 8 and 9.
For the vibration, the acoustic matching member 3 provided with the dustproof layer 2 is
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previously adjusted to a thickness of 1⁄4 of the ultrasonic wavelength (λ) propagating through
the acoustic matching member 3. The acoustic matching member 3 resonates, and ultrasonic
waves propagate to the gas whose flow velocity or flow rate is to be measured.
As seen from the equations (1) and (2), the acoustic matching member 3 is required to be solid
and have a low density and a low sound velocity.
[0032]
Usually, in order to satisfy such a requirement, for example, 1) an acoustic matching member in
which a thermosetting epoxy resin is poured into a gap in which a hollow body of glass is densely
filled, and 2) a porous portion in a void portion of a ceramic porous body An acoustic matching
member in which organic glass is formed, or 3) A ceramic porous body is used as an acoustic
matching member, and an acoustic matching member in which a surface dense layer is formed
on an ultrasonic radiation surface is used.
When these acoustic matching members are reduced in weight to improve their characteristics,
they become vulnerable to external stress and dust is generated by particles exfoliating from the
acoustic matching members to contaminate the measurement system, resulting in a decrease in
measurement accuracy or measurement. There has been a problem that leakage occurs when the
flow of fluid is interrupted.
[0033]
The acoustic matching body 1 provided with the dustproof layer 2 on the outer peripheral
portion of the acoustic matching body 1 does not scatter into the measurement system by the
dustproof layer 2 even if particles etc. are separated from the acoustic matching body 1 High
performance ultrasonic transducers can be used for measurements without
Therefore, the dustproof layer 2 is denser than the particles etc. which exfoliate from the
acoustic matching body 1, and is usually formed of a material having a higher density than the
acoustic matching member.
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[0034]
For example, in the acoustic matching member in which the thermosetting resin is poured into
the void portion in which the hollow body of 1) glass is densely filled, a layer of the
thermosetting resin alone can be formed on the outer peripheral portion as the dustproof layer 2.
At this time, it is preferable that the thermosetting resin be of the same kind as the resin filled in
the void portion of the hollow sphere.
For this dustproof layer 2, for example, it is possible to use many printing methods such as spray
application, screen printing, gravure printing, metal mask printing, transfer, potting and the like.
[0035]
Examples of the material of the dustproof layer include phenol resin, urea resin, melamine resin,
furan resin, unsaturated polyester resin, epoxy resin, diallyl phthalate resin, guanamine resin,
ketone resin, polyimide, silicone resin and the like.
These resins and a curing agent are mixed, coated by the forming method described above, and
then heated to form the dustproof layer 2.
Here, a dilution solvent or the like may be used to adjust the viscosity according to the formation
method.
Usually, a thermosetting resin is often selected, but any thermoplastic resin having a glass point
transfer at 60 ° C. or higher, which is the maximum use temperature in the case of an ultrasonic
transducer, can be used.
[0036]
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In addition, as a method of forming the dustproof layer 2, the acoustic matching member 3
whose thickness is adjusted is disposed in a heat-shrinkable tube such as a heat-shrinkable tube
and formed by heating.
The dustproof layer 2 can also be formed of an elastic material such as silicon, and in this case, it
also has a function of suppressing unnecessary vibration when the ultrasonic transducer 4 is
used.
[0037]
The acoustic matching member in which the porous organic glass is formed in the void of the 2)
ceramic porous body, or 3) the acoustic matching member in which the ceramic porous body is
the acoustic matching member and the surface dense layer is formed on the ultrasonic radiation
surface The method of applying the thermosetting resin described above is effective, and it is
possible to form the dustproof layer 2.
[0038]
The acoustic matching member in which the porous organic glass is formed in the void portion of
the 2) ceramic porous body will be described below.
[0039]
FIG. 3 shows an enlarged cross-sectional view of the acoustic matching body 10 in which the
porous organic glass 12 is formed in the void portion of the ceramic porous body 11 in the first
embodiment of the present invention.
[0040]
In FIG. 3, the acoustic matching body 10 is formed by forming the porous organic glass 12
having a pore diameter smaller than that of the ceramic porous body 11 in the pores of the
ceramic porous body 11 and the ceramic porous body 11. It is arranged to hold the glass 12.
[0041]
The ceramic porous body 11 of the acoustic matching body 10 of the present invention is
preferably formed as follows.
[0042]
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The ceramic porous body 11 is made of at least an oxide-based or non-oxide-based ceramic, a
clay mineral, or the like.
Examples of oxide ceramics include alumina, mullite and zirconia. Non-oxide ceramics include
silicon carbide, silicon nitride, aluminum nitride, boron nitride and graphite. It can be mentioned.
The ceramic porous body 11 is preferably composed of a hard-fired ceramic, and more
preferably composed of a glass ceramic that is an oxide material selected from aluminum
titanate, corduleite, and lithia-alumina-silica compounds. .
When the ceramic porous body 11 is made of glass ceramic, the coefficient of thermal expansion
is small. Therefore, when the ceramic porous body 11 is used as an acoustic matching member of
the ultrasonic wave transmitter-receiver, sound waves are stably transmitted and received in a
wide temperature range. It is preferable in that it can be done.
[0043]
FIG. 4 shows a manufacturing process flow of the ceramic porous body 11.
The process comprises the steps of: grinding a non-sinterable ceramic; adding an additive to the
ceramic powder to form a slurry; introducing a bubble; introducing the slurry into a mold;
forming the slurry; and firing.
Details will be described below.
[0044]
(Sintering-resistant ceramic pulverizing step) Pulverization of ceramic can be obtained by mixing,
pulverizing or the like with a ball mill, pot mill or the like.
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The average particle size of the ceramic powder is not particularly limited, but is preferably 10
μm or less.
When the ceramic having an average particle diameter in this range is used, the powder
dispersibility in the slurry is improved, and the sinterability is also improved.
[0045]
(Slurrying Step of Ceramic Powder) In the ceramic slurry, water, an organic solvent, a mixed
solvent thereof, or the like can be used as a medium for suspending the ceramic powder.
Preferably water is used.
In order to uniformly contain the ceramic powder in the ceramic slurry, it is preferable to use a
suitable dispersant.
As a dispersing agent, a polycarboxylic acid-based dispersing agent (anionic dispersing agent)
can be used, and specifically, ammonium polycarboxylate and sodium polycarboxylate can be
used.
Preferably, a dispersant having a large change in slurry viscosity with the added amount of
dispersant is used.
The amount of the dispersant used is preferably 5% by weight or less, more preferably 1% by
weight or less, based on the weight of the ceramic powder.
[0046]
The ceramic slurry is removed before introducing the ceramic slurry bubbles, and the bubbles
are introduced while stirring the slurry.
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When bubbles are introduced into the ceramic slurry, a gelling agent, and a polymerizable
material comprising a monomer and a polymerization initiator are added in order to form the
desired shape. When a gelling agent is used, the slurry is gelled by temperature control, pH
control, and the like. Examples of the gelling agent include gelatin, agarose, agar, sodium alginate
and the like.
[0047]
When a polymerizable material is used, a monomer of the polymerizable material is used.
Specifically, monomers provided with one or more vinyl groups, allyl groups and the like can be
mentioned. When the slurry is composed of water or an aqueous solvent, it is preferable to use a
monofunctional or bifunctional polymerizable monomer. Moreover, when a slurry is comprised
with an organic solvent, it is preferable that it is a bifunctional polymerizable monomer. In
particular, when water is prepared as a solvent in the slurry, preferably at least one
monofunctional (meth) acrylamide and at least one difunctional (meth) acrylamide are used. Use
in combination. When the slurry is prepared with an organic solvent, preferably, at least two
difunctional (meth) acrylic acids are used in combination.
[0048]
When a monofunctional monomer or a bifunctional monomer is used, ammonium persulfate,
potassium persulfide and the like are preferable. Moreover, when using the functional group
monomer which has a 2 or more functional group, Preferably, an organic peroxide, a hydrogenperoxide compound, an azo or a diazo compound is used. Specifically, it is benzoyl peroxide.
[0049]
The introduced gas is preferably retained in the slurry as bubbles by a surfactant or the like. The
surfactant is preferably added to the ceramic slurry prior to the introduction of air bubbles by
stirring or the like in the air bubble introduction step. Examples of the surfactant include anionic
surfactants such as alkyl benzene sulfonic acid and cationic surfactants such as higher alkyl
amino acids. Specifically, n-dodecylbenzene sulfonic acid, polyoxyethylene sorbitan monolaurate,
polyoxyethylene monooleate, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether,
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and alkali metal salts such as sodium and potassium thereof It can be mentioned. In addition,
triethanolamine lauryl ether and the like and their halogenated salts, sulfates, acetates,
hydrochlorides and the like can be mentioned. Moreover, diethylhexyl succinic acid and its alkali
metal salt etc. can be mentioned.
[0050]
(Air Bubble Introduction Step) Air bubbles are introduced into the slurry produced as described
above. In the case of using a polymerizable material as the gelling material in this bubble
introducing step, it is preferable to add a polymerization initiator or a polymerization initiator
and a polymerization catalyst together with the polymerizable material. If a polymerization
catalyst is added, the time of the gelation step can be adjusted by the gelation temperature and
the addition amount thereof. Usually, when a polymerization catalyst is added, gelation
(polymerization) is rapidly started at around room temperature.
[0051]
Therefore, the use and type of the polymerization catalyst are selected in consideration of the
bubble introduction method, the bubble introduction amount, and the like. As a polymerization
catalyst, N, N, N ', N'- tetramethyl ethylene diamine etc. can be mentioned, for example.
[0052]
(Slurry Forming Step) The cell-containing ceramic slurry thus prepared is injected into a forming
die or the like and gelated to form a gel-like porous formed body. The slurry is poured into a
cylindrical mold containing a bubble-containing ceramic slurry and subjected to a polymerization
reaction or a gelation reaction to solidify. When the slurry solidifies, the bubbles present in the
slurry are also stored in the gel-like body.
[0053]
As a result, the solidified body becomes porous, and a gel-like porous molded body is obtained. It
is demolded, dried, degreased and fired. Drying is carried out to evaporate the water and solvent
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contained in the gel-like porous molded body. The drying conditions (temperature, humidity,
time, etc.) are appropriately adjusted according to the type of solvent used for slurry preparation
and the component (gelling agent or polymer) constituting the skeleton of the gel porous molded
body. Usually, the temperature is 20 ° C. or more, preferably 25 ° C. or more and 80 ° C. or
less, and more preferably 25 ° C. or more and 40 ° C. or less.
[0054]
(Firing Step) Next, in order to remove the organic component from the dried product, the heating
is further performed at a high temperature. The temperature and time for degreasing are
adjusted according to the amount and type of organic component used. For example, in the case
of a gel-like porous molded body prepared from a slurry using methacrylamide and N, Nmethylenebisacrylamide as a material for gelation, degreasing is performed at 700 ° C. for 2
days.
[0055]
After degreasing, a firing step is performed. The conditions for firing are set in consideration of
the type of ceramic material used and the like. By these steps, the ceramic porous body 11 of the
present invention can be obtained.
[0056]
The ceramic porous body 11 is a porous body, and a plurality of voids exist. The voids are
preferably dispersed in the ceramic porous body 11. The voids may exist independently, may be
present continuously with other voids, and may be in communication with the outside. In the
acoustic matching body 10, it is preferable that the holes be continuously present.
[0057]
The ceramic porous body 11 as a whole means a porosity of 60% to 90% (here, a total porosity
including open pores and closed pores). Is preferred. More preferably, it is 80% or more and 90%
or less. The total porosity is determined by the following formula (3).
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[0058]
Total porosity (%) = (1-bulk density / true density) x 100 (3) However, bulk density = weight of
sample / bulk volume of sample. True density, for example, an arbitrary amount of extremely
micronized sample is charged into a pycnometer, water is injected until a predetermined volume
is reached, and boiling is performed to eliminate voids, and from the relationship between weight
and volume, It can be asked.
[0059]
When the total porosity is 60% or less, the density 11 of the acoustic matching body 1 becomes
large, and when the pore diameter exceeds 90%, the mechanical strength significantly decreases.
The open porosity is more preferably 65% or more and 85% or less. The above materials and
manufacturing conditions are optimized, and the density of the ceramic porous body 11 of the
acoustic matching body 1 in the embodiment of the present invention is adjusted by adjusting it
at 200 kg / m <3> or more and less than 400 kg / m <3>. A ceramic porous body 11 of low
strength and high strength could be realized. The porous organic glass 12 of the acoustic
matching body 10 of the present invention is preferably formed as follows.
[0060]
FIG. 5 shows a flow of steps for producing a dried silica gel used as the porous organic glass in
the first embodiment of the present invention.
[0061]
In FIG. 5, the silica dry gel production process is formed by the I raw material preparation
process 13, the II gelation process 14, the III reconstruction process 15, the IV hydrophobization
process 16, and the V drying process 17.
Each step will be described in detail below.
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[0062]
(I Raw Material Preparation Step 13) In this step, an organosilane compound as a main raw
material of silica dry gel, water for hydrolyzing the same, a reaction solvent and a catalyst are
added to make a mixed solution as a starting raw material. is there. The organosilane compound
has, for example, a structure as shown in FIGS. In the molecule shown in FIG. 7, the nonhydrolyzable organic group 19 is directly bonded to silicon 20, and hydrolysis is not performed
with other organosilane compounds. The hydrolyzable organic group 21 is also directly bonded
to the silicon 20, and is hydrolyzed and polymerized with other organosilane compounds by
hydrolysis. The organosilane compounds 18 and 22 shown in FIGS. 6 and 7 may be used singly
or in combination of two or more.
[0063]
Although a non-hydrolyzed organic group is not specifically limited, For example, a C1-C8
substituted or unsubstituted monovalent hydrocarbon group is mentioned. Specifically, alkyl
groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl; cycloalkyls such as
cyclopentyl and cyclohexyl; 2-phenylethyl Aralkyl groups such as 3-phenylpropyl group; aryl
groups such as phenyl group and tolyl group; alkenyl groups such as vinyl group and allyl group;
chloromethyl group, γ-chloropropyl group, 3,3,3-trifluoropropyl And halogen-substituted
hydrocarbon groups such as groups; substituted hydrocarbon groups such as γmethacryloxypropyl group, γ-glycidoxypropyl group, 3,4-epoxycyclohexylethyl group, γmercaptopropyl group, etc. Can. Among them, alkyl groups having 1 to 4 carbon atoms and
phenyl groups are preferable in terms of easiness of synthesis, easiness of availability, and
hardness does not excessively decrease.
[0064]
Therefore, as the organotrialkoxysilanes of the formula (2), methyltrimethoxysilane,
methyltriethoxysilane, methyltriisopropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane,
3,3,3-trifluoropropyltriol A methoxysilane etc. can be illustrated.
[0065]
Further, as the diorganodialkoxysilane of the formula (3), dimethyldimethoxysilane,
dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane,
methylphenyldimethoxysilane and the like can be exemplified.
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[0066]
In addition, the starting material for obtaining the dry gel according to the present invention is,
for example, tetramer represented by the formula (1) composed of only the hydrolyzable organic
group 21 as shown in FIG. It may contain an alkoxysilane.
Examples of these include tetramethoxysilane, tetraethoxysilane and the like.
[0067]
All the molecules corresponding to the molecular conceptual diagram of FIG. 6 exemplified above
are components which soften the dried gel and make it difficult to cause breakage.
[0068]
As the catalyst, general organic acids, inorganic acids, organic bases and inorganic bases are
used.
Organic acids include acetic acid, citric acid and the like, inorganic acids include sulfuric acid,
hydrochloric acid, nitric acid, organic bases, piperidine and the like as inorganic bases, ammonia
and the like as inorganic bases.
In addition, it is more preferable from the viewpoint of capillary force reduction because the use
of an imine-based one such as piperidine has an effect of increasing the pore diameter.
[0069]
Examples of the solvent include lower alcohols such as methanol, ethanol, propanol, butanol,
ethylene glycol and diethylene glycol, mono- or diethers of ethylene glycol and diethylene glycol,
lower ketones such as acetone, lower ethers such as tetrahydrofuran and 1,3-dioxolane Water
soluble organic solvents are used. In addition, when a gel is formed by hydrolysis and
condensation polymerization of the first gel raw material, water necessary for hydrolysis is also
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added.
[0070]
The compounds shown above are stirred and mixed to prepare raw materials. These organosilane
compounds are hydrolyzed by a catalyst and polymerized.
[0071]
(II gelation step 14) In this step, after the raw material preparation step 13, a catalyst is added to
the prepared mixed solution to promote hydrolysis polymerization to form a solid skeleton of gel,
and a state in which the gel contains a solvent Is a process of making a wet gel. In order to
accelerate gelation, the catalyst is added and the solution temperature is raised as needed. The
catalyst is omitted because it is exemplified in the raw material preparation step.
[0072]
The catalyst may not be divided and added in particular in the raw material preparation step 13
and the gelation step 14, and the raw material preparation step 13 and the gelation step 14 may
be performed at once.
[0073]
(III Reconstruction Step 15) In this step, a new solid skeleton is formed in this step, while a part
of the solid skeleton of the wet gel formed in the gelling step 14 is decomposed.
Specifically, first, a reconstruction raw material solution is prepared by adding and mixing a
reconstruction raw material for a reconstruction step, a reconstruction catalyst and water, and a
solvent as necessary, and the solution is obtained in the gelation step. Soak the wet gel. The
treatment time of this step and the treatment temperature can adjust the density of the silica dry
gel.
[0074]
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As the reconstruction catalyst or organosilane compound used in the reconstruction step, those
exemplified in the raw material adjustment step 13 can be used, but it is not particularly
necessary to be the same as in the gelation step. After reinforcing the gel skeleton, the reaction is
stopped by replacing the reconstruction raw solution with, for example, isopropyl alcohol for the
purpose of stopping the reaction.
[0075]
(IV hydrophobization step 16) In this step following the reconstitution step 15, the surface of the
wet gel obtained up to the reconstitution step 15 is reacted with a hydrophobization solution in
which a hydrophobizing agent is dissolved in a solvent, Introduce a hydrophobic group.
[0076]
The hydrophobizing agent used in the present invention is preferably a silylating agent from the
viewpoint of high reactivity, and examples thereof include silazane compounds, chlorosilane
compounds, alkylsilanol compounds and alkylalkoxysilane compounds.
[0077]
These silylating agents, in the case of silazane compounds, chlorosilane compounds, and alkyl
alkoxysilane compounds, react directly or by hydrolysis to corresponding alkyl silanols and then
react with silanol groups on the gel surface.
In addition, when alkylsilanol is used as a silylating agent, it reacts with silanol groups on the
surface as it is.
[0078]
Among these, chlorosilane compounds and silazane compounds are particularly preferable in
view of high reactivity at the time of hydrophobization and availability, and easiness of
availability and not generating a gas such as hydrogen chloride and ammonia at the time of
hydrophobization. Alkyl alkoxysilanes are particularly preferably used.
[0079]
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20
Specifically, chlorosilane compounds such as trimethylchlorosilane, methyltrichlorosilane and
dimethyldichlorosilane, silazane compounds such as hexamethyldisilazane,
methoxytrimethylsilane, ethoxytrimethylsilane, dimethoxydimethylsilane, dimethoxydiethylsilane
and diethoxydimethylsilane And silylating agents represented by silanol compounds such as
trimethylsilanol and triethylsilanol.
If these are used, hydrophobization can be advanced by introducing an alkylsilyl group such as a
trimethylsilyl group on the surface of the wet gel.
[0080]
Also, if a fluorinated silylating agent is used as the hydrophobizing agent, the hydrophobicity
becomes strong and it is very effective.
[0081]
Further, as the hydrophobizing agent, in addition to alcohols such as ethanol, propanol, butanol,
hexanol, heptanol, octanol, ethylene glycol and glycerol, carboxylic acids such as formic acid,
acetic acid, propionic acid and succinic acid can be used. .
These react with hydroxyl groups on the gel surface to form an ether or ester to promote
hydrophobization, but since the reaction is relatively slow, high temperature conditions are
required.
[0082]
The hydrophobization step is a treatment to prevent moisture absorption in the finally obtained
dried gel, and after the gel is added to the silane coupling treatment solution, the solution is
replaced with, for example, isopropyl alcohol to stop the silanization reaction. Let
[0083]
(V Drying Step 17) In this step, the solvent is removed from the wet gel obtained up to the
hydrophobization step to obtain a silica dry gel which is a porous organic glass.
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21
[0084]
As a drying method for removing the solvent from the wet gel, there are (1) natural drying
method and (2) special drying method.
[0085]
(1) The natural drying method is the most common and convenient drying method, in which the
solvent in the liquid state is vaporized and removed by leaving the wet gel containing the solvent,
and this drying method is costly. Most preferable from the viewpoint.
From the viewpoint of productivity, heat drying for heating the wet gel or vacuum drying for
reducing the pressure of the wet gel to a pressure lower than atmospheric pressure is also
included in the natural drying method.
[0086]
The heating temperature is not particularly limited as long as the solvent evaporates.
[0087]
When dry, if the density of the gel is low, the gel may temporarily shrink and crack due to
capillary forces proportional to the surface tension of the solvent in the gel.
For this reason, the solvent at the time of drying is preferably a hydrocarbon solvent having a
small surface tension at the boiling point, and particularly inexpensive hexane, pentane or a
mixture thereof.
On the other hand, from the viewpoint of safety, drying from alcohols such as isopropanol,
ethanol, butanol, or a mixed solvent of water and an organic solvent is preferable.
Therefore, the stress at the time of drying can be reduced by replacing the solvent shown above
according to the purpose with the solvent used at the time of wet gel formation, and the wet gel
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22
becomes difficult to be broken at the time of drying.
[0088]
(2) There are two special drying methods: supercritical drying and lyophilization.
[0089]
Supercritical drying can remove the solvent as a supercritical state without passing through a
liquid state, so there is no generation of capillary force that forms a gas-liquid interface.
This makes the wet gel less likely to break when it is dried.
As a supercritical fluid used for drying, there are water, alcohol, carbon dioxide and the like. The
supercritical state is obtained at the lowest temperature, and carbon dioxide which is harmless is
often used.
[0090]
Specifically, first, liquefied carbon dioxide is introduced into the pressure container, and the wet
gel solvent in the pressure container is replaced with liquefied carbon dioxide. Next, the pressure
and temperature are raised above the critical point and brought into a supercritical state, and
carbon dioxide is gradually released while maintaining the temperature to complete drying.
[0091]
Lyophilization is a drying method in which the solvent in the wet gel is frozen and then the
solvent is removed by sublimation. Since it does not go through a liquid state and a gas-liquid
interface does not occur in the gel, capillary force does not work. For this reason, shrinkage of
the gel at the time of drying can be suppressed.
[0092]
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23
The solvent used for the lyophilization method is preferably one having a high vapor pressure at
the freezing point, and examples thereof include tertiary butanol, glycerin, cyclohexane,
cyclohexanol, para-xylene, benzene, phenol and the like. Among them, particularly preferred is
tertiary butanol or cyclohexane, from the viewpoint that the vapor pressure at the melting point
is high.
[0093]
At the time of lyophilization, it is effective to replace the solvent in the wet gel with a solvent
having a high vapor pressure at the above-mentioned freezing point. Further, it is more
preferable to use a solvent used at the time of gelation as a solvent having a high vapor pressure
at the freezing point, since the solvent substitution can be omitted to enable efficient production.
[0094]
Drying may be performed after the hydrophobization step or may be performed before the
hydrophobization step. In the case of hydrophobization after the drying step, the dried gel is not
in solution but is exposed to the vapor of the hydrophobizing agent to introduce hydrophobic
groups on the surface of the dried gel. Therefore, the amount of solvent used can be reduced.
[0095]
As the hydrophobizing agent to be used at this time, the above-mentioned hydrophobizing agents
can be used, but chlorosilane compounds such as trimethylchlorosilane and
dimethyldichlorosilane are most preferable in view of high reactivity. When a hydrophobizing
agent other than a chlorosilane compound is used, it is also effective to use a catalyst which can
be introduced in a gaseous state such as ammonia or hydrogen chloride.
[0096]
Moreover, when performing hydrophobization in a gaseous phase, the temperature at the time of
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24
hydrophobization can be raised without being restricted by the boiling point of the solvent or the
hydrophobizing agent. Thus, hydrophobization in the gas phase is effective to accelerate the
reaction. Further, if the wet gel is a thin film or a powder, it is more preferable because the
penetration of the hydrophobizing agent vapor is easy, and the thin film has a large effect of
reducing the amount of solvent.
[0097]
The acoustic matching body containing the silica dry gel formed as mentioned above is obtained.
[0098]
The method 3 for manufacturing an acoustic matching member in which the ceramic porous
body is the acoustic matching body 10 and the surface dense layer is formed on the ultrasonic
radiation surface is the same as that described in Patent Document 1 and thus will be omitted.
[0099]
When a part of the ceramic porous body 11 described above is used as the acoustic matching
body 10, the dustproof layer 2 is described with respect to a forming method of applying and
curing a thermosetting resin, but in this case, the ceramic porous body 11 and Since the thermal
expansion coefficient differs from that of the organic material, a method of forming an inorganic
material of the same type as the ceramic porous body 11 is preferable.
[0100]
When the ceramic porous body 11 is used as the acoustic matching body 10, it is preferable to
prepare a slurry containing the same kind of material as the acoustic matching body 10 to form
the dustproof layer 2, and the affinity between the dustproof layer 2 and the ceramic porous
body 11 It is easy to form by using the same material, and by using the same kind of material,
the same coefficient of linear expansion can realize stable dust resistance in a wide temperature
range.
Hereinafter, the ceramic material formed as the dustproof layer 2 will be described.
[0101]
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25
The ceramic material used as the dustproof layer 2 is usually formed by coating, sintering and
forming a ceramic rally.
The ceramic powder to be used is made of, for example, a known oxide or non-oxide ceramic, a
clay mineral or the like.
Examples of oxide ceramics include alumina, mullite and zirconia. Non-oxide ceramics include
silicon carbide, silicon nitride, aluminum nitride, boron nitride and graphite. be able to. The
average particle size of the ceramic powder is not particularly limited, but preferably 10 μm or
less. The use of the ceramic powder in this region improves the dispersibility of the ceramic
powder in the slurry.
[0102]
In the ceramic rally, the solvent for suspending the ceramic powder is water, an organic solvent,
or a mixture of these. A dispersing agent may be added to uniformly disperse the ceramic
powder. For example, ammonium polycarboxylate and sodium polycarboxylate can be
mentioned.
[0103]
Also, lubricants and thickeners can be added. For example, methyl cellulose, polyvinyl alcohol,
sucrose, molasses etc. can be illustrated.
[0104]
The ceramic rally can be obtained by mixing and grinding these exemplified materials in a ball
mill, pot mill or the like. In the obtained slurry, the acoustic matching body 1 is formed by
immersion treatment, metal mask printing, screen printing, application by spray, potting and the
like, and the dustproof layer 2 can be formed by firing and the dusting property is effectively
achieved. It can be suppressed.
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[0105]
The formed thickness of the dustproof layer 2 described above will be described.
[0106]
The thickness of the dustproof layer 2 is limited by the dustproof performance and the ultrasonic
characteristics, the thickness of the top portion 23 corresponding to the radiation surface of
ultrasonic waves.
Table 1 shows the relationship between the thickness of the dustproof layer on the outer wall
surface of the top portion of the acoustic matching body, the dustproof performance, and the
ultrasonic characteristics. A dustproof layer 2 was formed on several types of acoustic matching
bodies 1 to evaluate dustproofness and ultrasonic characteristics. The dustproofness is evaluated
by immersing the acoustic matching member 3 having the dustproof layer 2 formed in alcohol,
and the weight loss before and after the application of the ultrasonic wave, and the ultrasonic
characteristic is as shown in FIG. The waver 4 is disposed to face the flat plate 24 made of metal,
and the electric signal shown in FIG. 9 is applied to the ultrasonic transducer 4, and the reflected
ultrasonic wave at that time is transmitted by the ultrasonic transducer 4. The magnitude of the
reception output A of the received signal waveform was evaluated. As a result, it was possible to
satisfy the dustproofness and the ultrasonic characteristics when it was set to one-fifth to onefifth of the propagating ultrasonic wavelength (λ).
[0107]
Table 1 shows the relationship between the dustproof layer thickness of the acoustic matching
body top portion, the dustproof performance, and the ultrasonic characteristics.
[0108]
[0109]
In the first embodiment of the present invention, as described above, by forming the dustproof
layer 2, even if particles separated from the acoustic matching body 1 are scattered to the
measurement system by the dustproof layer 2, measurement can be performed. High
performance ultrasonic transducers can be used for measurement without any loss in accuracy.
14-04-2019
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[0110]
Further, in the present embodiment, when the acoustic matching body 1 formed entirely of
porous bodies is used, the adhesive penetrates into the acoustic matching body 1 so far at the
time of bonding with the piezoelectric body 5, and depending on the penetration state. Although
the ultrasonic characteristics varied, the ultrasonic characteristics can be stabilized by stably
forming the thickness of the dustproof layer 2 of the bonding surface formed before bonding.
[0111]
Second Embodiment FIG. 10 is a cross-sectional view of an ultrasonic transducer 29 according to
a second embodiment of the present invention.
[0112]
In FIG. 10, the ultrasonic transducer 29 has a structure in which the acoustic matching member
3 provided with the dustproof layer 2 and the piezoelectric body 5 are joined by the joining
means 6.
The piezoelectric body 5 is provided with electrodes 7 facing each other, is electrically joined to
the lead wires 8 and 9, and an electrical signal is transmitted to the electrode 7 through the lead
wires 8 and 9.
[0113]
The operation of the ultrasonic transducer 29 configured as described above is the same as that
of the first embodiment of the present invention, so only the operation will be described.
[0114]
FIG. 6 is a cross-sectional view of manufacturing steps of the ultrasonic transducer 11 in the
second embodiment.
In FIG. 6 (a), first, the adhesive 6 is applied to the piezoelectric body 5, and the acoustic matching
member 3 is attached. In FIG.
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In FIG. 6 (c), the dustproof layer 2 is formed by spraying or printing, and in FIG. 6 (d), a lead is
formed.
By manufacturing by such a manufacturing process, only the dust-proof layer forming process is
different, so that the current manufacturing process can be used.
[0115]
In the second embodiment of the present invention, as described above, by forming the dustproof
layer 2, even if particles separated from the acoustic matching body 1 are scattered to the
measurement system by the dustproof layer 2, measurement High performance ultrasonic
transducers can be used for measurement without any loss in accuracy.
[0116]
Third Embodiment FIG. 12 shows a cross-sectional view of an ultrasonic transducer 30 according
to a third embodiment of the present invention, and FIG. 13 is a manufacturing process diagram
of the ultrasonic transducer 30. As shown in FIG.
Hereinafter, the manufacturing process of the ultrasonic transducer 30 will be described.
The step (a) is a step of forming the acoustic matching member 3 provided with the dustproof
layer 2 and is omitted because it is the same as in the first and second embodiments.
The step (b) is a step of printing the adhesive used as the bonding members 34, 35 on the
surface of the electrode 32 formed of baked silver of the piezoelectric body 5 and the top outer
wall surface of the hollow cylindrical metal case 33. . The printing is not limited as long as the
adhesive can be printed to a predetermined thickness, such as screen printing, gravure printing,
and transfer. The hollow cylindrical metal case 33 may be made of a material having
conductivity, such as iron, brass, copper, aluminum, stainless steel, an alloy thereof, or a metal
obtained by plating the surface of these metals.
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29
[0117]
The piezoelectric body 5 printed with an adhesive, which is the bonding member 34, is opposed
to the piezoelectric body 5 with the acoustic matching member 3 provided with the dustproof
layer 2 on the top outer wall surface on the top inner wall surface of the hollow cylindrical metal
case 33 Paste on In such a state, heating is performed while applying pressure to cure the
adhesive. The adhesive is not particularly limited as long as it is a thermosetting resin such as an
epoxy resin, a phenol resin, or a cyanoacrylate resin. In some cases, even if it is a thermoplastic
resin, it can be used as an adhesive if the glass point transfer is 70 ° C. or less, which is the high
temperature use temperature.
[0118]
In the step (c), the cylindrical cylindrical metal case 33 joined by an adhesive and the terminal
plate 37 into which the conductive means 36 is inserted are joined by welding. The terminal
plate 37 includes an electrode terminal 38 and an electrode terminal 39, and is electrically
insulated by the terminal plate insulator 40. The conductive means 36 is composed of an elastic
body such as silicone rubber, butadiene rubber, elastomer or the like and a conductor, and
electrically connects the electrode 33 and the electrode terminal 39. The electrode 32 and the
electrode terminal 38 are electrically connected via the hollow cylindrical metal case 33.
[0119]
An inert gas is injected into the sealed space 41 formed by the cylindrical cylindrical metal case
33 and the terminal plate 37 when welding the cylindrical cylindrical metal case 33 and the
terminal plate 37, and the ultrasonic transducer 30 is manufactured. did. The inert gas is not
limited as long as it is a gas that does not react with the silver electrode, such as helium gas and
nitrogen gas. By inserting an inert gas into the hollow cylindrical metal case 33 at the time of
welding, the piezoelectric body 5 provided with the silver electrode is isolated from the external
environment, the electrical connection is stabilized over a long period, and the long-term
reliability is ensured. .
[0120]
Since the ultrasonic transducer 30 configured as described above includes the acoustic matching
member 3 provided with the dustproof layer 2, even if particles or the like separated from the
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30
acoustic matching body 1 are generated, the dustproof layer 2 There is no scattering, and a highperformance ultrasonic transducer can be used for measurement without reducing measurement
accuracy.
[0121]
Fourth Embodiment FIG. 14 is a cross-sectional view of an ultrasonic flow velocity / flow meter
according to a fourth embodiment of the present invention.
[0122]
In FIG. 14, ultrasonic transducers 43 and 44 having an acoustic matching member 3 provided
with a dustproof layer 2 are disposed in a diagonally arranged manner in the flow rate measuring
unit 42 in which the fluid flows.
L1 indicates the propagation path of the ultrasonic wave propagating from the ultrasonic
transducer 43 disposed on the upstream side, and L2 indicates the propagation path of the
ultrasonic wave of the ultrasonic transducer 44 disposed on the downstream side ing.
[0123]
Let V be the flow velocity of the fluid flowing through the tube, C be the velocity of the ultrasonic
waves in the fluid (not shown), and θ be the angle between the fluid flow direction and the
ultrasonic pulse propagation direction.
When the ultrasonic transducer 43 is used as an ultrasonic wave transmitter and the ultrasonic
transducer 44 is used as an ultrasonic wave receiver, ultrasonic pulses emitted from the
ultrasonic transducer 43 are ultrasonic wave transducers 44. The propagation time t1 to arrive
at is given by: t1 = L / (C + V cos θ) (4)
[0124]
Next, the propagation time t2 for the ultrasonic pulse emitted from the ultrasonic transducer 44
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31
to reach the ultrasonic transducer 43 is expressed by the following equation: t2 = L / (C−V cos
θ) (5) Then, if the sound velocity C of the fluid is eliminated from the equations (1) and (2), the
equation V = (L / 2 cos θ) ((1 / t1) − (1 / t2)) (6) is obtained.
[0125]
If L and θ are known, the flow velocity V can be obtained by measuring t1 and t2 in the
measuring circuit 45. If necessary, the flow rate Q can be determined by multiplying the flow
velocity V by the cross-sectional area S of the flow rate measurement unit 42 and the correction
coefficient K. The calculating means 46 calculates the above Q = KSV.
[0126]
Since the ultrasonic transducers 43 and 44 configured as described above are provided with the
acoustic matching member 3 provided with the dustproof layer, even if particles separated from
the acoustic matching body 1 are scattered to the measurement system by the dustproof layer 2.
It is possible to use a high-performance ultrasonic transducer for measurement without reducing
the measurement accuracy.
[0127]
As described above, the acoustic matching member provided with the dustproof layer according
to the present invention, the ultrasonic transducer using the same, and the ultrasonic flow meter
are high performance acoustic matching members and ultrasonic waves that do not contaminate
the measurement system. Since it can be a transducer, it is possible to perform highly accurate
measurement without contaminating the measurement system, and can be applied to
applications such as household gas meters which require long-term reliability.
[0128]
Acoustic matching member sectional view provided with a dustproof layer according to the first
embodiment of the present invention Ultrasonic transducer cross sectional view according to the
first embodiment of the present invention porous in the void portion of the ceramic porous body
according to the first embodiment Cross-sectional enlarged view of acoustic matching member
formed with organic glass Process chart of manufacturing process of ceramic porous body in the
first embodiment of the present invention Formation process of porous organic glass in the first
embodiment of the present invention Organosilane compound conceptual diagram in the silica
dry gel production process in 1 Organosilane compound conceptual diagram in the silica dry gel
production process in the first embodiment of the present invention Ultrasonic wave transducer
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characteristics evaluation schematic diagram in the first embodiment of the present invention
Ultrasonic transducer characteristic evaluation explanation diagram in the first embodiment of
the invention Ultrasonic transducer cross section diagram in the second embodiment of the
present invention Process flowchart showing a method of manufacturing an ultrasonic
transducer in mode 2 Ultrasonic transducer cross section in the third embodiment of the present
invention Ultrasonic transducer cross section in the third embodiment of the present invention
Ultrasonic velocity flowmeter sectional view in mode 4 Cross sectional view of conventional
ultrasonic transducer
Explanation of sign
[0129]
DESCRIPTION OF SYMBOLS 1 acoustic matching member 2 dust-proof layer 3 acoustic matching
member 3 provided with dust-proof layer 42 flow measurement part 43, 44 ultrasonic
transducer 45 measuring circuit 46 calculating means
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