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DESCRIPTION JPH0865792

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DESCRIPTION JPH0865792
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer that performs electroacoustic conversion using the piezoelectric effect to
transmit, receive, and transmit sound waves, which is fired in a ring shape and has a diameter.
Ultrasonic transducer using a composite piezoelectric material of a ring-shaped piezoelectric
ceramic vibrator polarized in a direction and utilizing radial thickness vibration, and a ringshaped piezoelectric ceramic vibrator having a radial slit groove and in a groove portion In a
laminate in which a ring-shaped composite piezoelectric material filled with a polymer material
and a ring-shaped piezoelectric ceramic vibrator are stacked, formation of a cylindrical composite
piezoelectric material having radial slit grooves and filled with a polymer material in the groove
portion On the way.
[0002]
2. Description of the Related Art Conventionally, in order to form an ultrasonic transducer having
a directivity width of 360 degrees in general, as described in Japanese Patent Laid-Open No. 2273000, a pair of opposing surfaces of a rectangular parallelepiped is inclined. By placing a drive
electrode on another pair of parallel faces, a plurality of piezoelectric ceramic vibrators whose
planes are perpendicular to these four faces are arranged to form a cylinder. It is formed. As
described above, it is convenient to use a wedge-shaped piezoelectric ceramic vibrator to arrange
a plurality of cylinders at a constant interval, and there is a problem of durability when subjected
to vibration operation and structural distortion generated in the manufacturing process. I can
solve the problem.
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[0003]
Further, a cylindrical piezoelectric ceramic vibrator in which the piezoelectric ceramic vibrator
itself is sintered in a cylindrical shape and polarized in the radial direction is disclosed in
Japanese Patent Application Laid-Open Nos. 5-244691 and 60-112397. 60-112398.
[0004]
However, when the wedge-shaped piezoelectric ceramic vibrators are arranged in a cylindrical
shape as in the above-mentioned prior art, the arrangement accuracy has a great influence on the
directivity in the high frequency band. Exert.
In addition, since the piezoelectric ceramic vibrator becomes smaller in inverse proportion to the
frequency when the frequency becomes high, machining equipment with high accuracy is
required for processing into a bowl shape, resulting in cost increase. Further, in the cylindrical
piezoelectric ceramic vibrator, there is a problem that the sensitivity is lowered as the frequency
becomes higher due to the coupling vibration in the circumferential direction.
[0005]
In general, when a cylindrical piezoelectric ceramic vibrator is used as a wave transmitter, in
many cases a radial expansion / contraction mode (respiratory vibration) is used, and this wave
transmission frequency is the circumferential length of the position of the cylinder average
diameter. However, in the high frequency band, the average diameter of the cylinder becomes
small, and the range can not be manufactured as a cylindrical piezoelectric ceramic vibrator. In
addition, the acoustic radiation area is reduced, and the target sensitivity can not be achieved. On
the other hand, when the radial thickness vibration of the cylindrical piezoelectric ceramic
vibrator is used, the frequency is determined by the thickness, so that it does not depend on the
circumferential length of the cylinder. However, lateral vibration causes coupling vibration in the
circumferential direction of the cylinder, which lowers the sensitivity. As a countermeasure, a
method is adopted in which a plurality of grooves are provided radially and mechanically
separated, but there is a problem that the processing is complicated and it is not suitable for
small volume production.
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[0006]
The object of the present invention is to solve the above-mentioned problems and to provide a
composite piezoelectric material inexpensively suitable for small-volume production without the
need for large-scale machining equipment together with a 360-degree nondirectional ultrasonic
transducer. It is an object of the present invention to provide a method of forming, and
additionally to ensure cylindrical alignment accuracy, and at the same time to prevent sensitivity
deterioration due to circumferential coupled vibration.
[0007]
The above-mentioned object can be achieved by using a ring-shaped composite piezoelectric
material in which a ring-shaped piezoelectric ceramic vibrator is divided and filled with a
polymer material.
Further, in the ring-shaped composite piezoelectric material, the piezoelectric ceramic vibrator
fired in a ring shape is fixed with a thermoplastic wax to a jig formed of a material which is
highly brittle and extremely brittle and which is excellent in heat resistance. The groove is
machined with the machine tool to be used, and then a polymer material is poured into the
groove and molded, and only when the polymer material reaches a certain degree of hardness,
only the jig is broken to take out the composite piezoelectric material. To be achieved. In
addition, it is also achieved by processing the groove after laminating the ring-shaped
piezoelectric ceramic vibrator and pouring a polymer material into the groove to form a
composite piezoelectric material.
[0008]
Therefore, by using the means as described in the preceding paragraph, it is possible to form the
composite piezoelectric material relatively inexpensively without requiring large-scale machining
equipment, ensuring the alignment accuracy, It is possible to prevent the decrease in sensitivity
due to the coupled vibration. In addition, a plurality of ring-shaped piezoelectric ceramic
vibrators are stacked to form a laminate, and by forming a laminate of composite piezoelectric
materials using the means as described in the preceding paragraph, the alignment accuracy in
the circumferential direction and the cylinder central axis direction can be obtained. Can be
secured.
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[0009]
Embodiments of the present invention will be described below with reference to FIGS. 1 to 11.
FIG. 1 is a perspective view showing an outline of an ultrasonic transducer according to the
present invention. The ultrasonic transducer, generally designated 5, has a disk-shaped flange 4
to which the cylindrical composite piezoelectric element 2 is attached. A cylindrical acoustic
transmission / reception window 3 is disposed on the outer peripheral portion of the flange 4.
The acoustic transmission / reception window 3 fixes and protects the cylindrical composite
piezoelectric vibrator 2 and electrically insulates between the cylindrical composite piezoelectric
vibrator 2 and a medium for transmitting and receiving sound.
[0010]
The cylindrical composite piezoelectric vibrator 2 has a structure in which the ring-shaped
composite piezoelectric material 1 is stacked in the thickness direction, and the ring-shaped
composite piezoelectric material 1 divides the ring-shaped piezoelectric ceramic vibrator in the
radial direction. It has a configuration filled with a polymer material. Further, a cable 6 for
transmitting an electrical signal to and from an apparatus such as a signal transmitter / receiver
externally connected to the ultrasonic transducer 5 is connected and fixed to the flange 4.
[0011]
In the ultrasonic transducer 5, when transmitting a sound wave, the electric signal transmitted
from the cable 6 is electro-acoustically converted by the cylindrical composite piezoelectric
vibrator 2, and water is transmitted through the acoustic transmission / reception window 3. It
radiates as sound waves into the medium of Conversely, in the case of receiving a sound wave,
the sound wave propagating in the medium is received by the cylindrical composite piezoelectric
vibrator 2 through the acoustic transmission / reception window 3, and acoustic-electrical
conversion is performed by the cable 6. Transmit to external devices. In these cases, since the
cylindrical composite piezoelectric vibrator 2 is used as a piezoelectric vibrator for transmitting
and receiving sound waves, sound waves can be transmitted simultaneously in all directions of
360 degrees, and they come from all directions of 360 degrees It is possible to receive sound
waves. Furthermore, as the most excellent point of the ultrasonic transducer according to the
present invention, since the ring-shaped composite piezoelectric material 1 made by dividing the
ring-shaped piezoelectric ceramic vibrator is used, the coupled vibration due to the transverse
effect in the circumferential direction is As a result, it is possible to prevent 360 degree
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circumferential (horizontal) omnidirectionality and sensitivity deterioration.
[0012]
In the present invention, when electric signals are simultaneously input to all of the ring-shaped
composite piezoelectric members 1 of the cylindrical composite piezoelectric vibrator 2 to
transmit sound waves, the cylinder height is increased according to the number of laminated
ring-shaped composite piezoelectric members 1. Control the directivity width in the longitudinal
direction (vertical direction), and give directivity in any direction by controlling the number of
divisions of the ring-shaped piezoelectric ceramic vibrator, the number of laminated layers of the
ring-shaped composite piezoelectric material 1, and the electrical signal. Beam scan to investigate
is also possible. Next, a method of forming the ring-shaped composite piezoelectric material will
be described with reference to FIG.
[0013]
In FIG. 2, the jig 8 for holding the ring-shaped piezoelectric ceramic vibrator 7 is made of, for
example, a carbon material having high hardness, very brittle, and heat resistance, and the ringshaped piezoelectric ceramic vibrator 7 is It has an annular groove for receiving. Then, the
thermoplastic wax 9 is filled in the annular groove. First, heat is applied to the thermoplastic wax
9 to apply it to the annular groove of the jig 8 made of carbon, and the ring-shaped piezoelectric
ceramic vibrator 7 is bonded and fixed here. Since the thermoplastic wax 9 flows at about 60 °
C., the temperature is lower than the Curie point of the vibrator when the ring-shaped
piezoelectric ceramic vibrator 7 is fixed, which affects the characteristics of the ring-shaped
piezoelectric ceramic vibrator 7. do not do.
[0014]
In FIG. 3, a carbon jig 8 on which a ring-shaped piezoelectric ceramic vibrator 7 is fixed is
mounted on a table of a machine tool (not shown), and the diamond cutter 10 is rotated in the
direction of arrow 12 Advance to The table on which the head of the cutter 10 or the jig 8 is
attached is indexed at a constant angle, and the circumferential grooves 11 are formed in the
direction of the arrow 14 to form the radial grooves 11. By this groove processing, the groove 11
is formed integrally with the ring-shaped ceramic vibrator 7 and the jig 8 fixing the same.
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[0015]
As shown in FIG. 4, the groove 11 is filled with the polymeric material 15 by molding the entire
jig 2 processed as shown in FIG. The polymer material 15 is, for example, an epoxy resin, and has
a property of being hardened to such an extent as to be cut by a cutter or the like by leaving it
for about 3 days. Finally, the polymer material 15 such as epoxy resin has a hardness of about 90
and sufficient adhesion.
[0016]
FIG. 5 illustrates the machining of the fully cured polymeric material 15. The polymer material
15 including the entire carbon jig 8 is mounted on a suitable machine tool, and the polymer
material 15 is cut and processed to a state as shown in FIG. By this processing, the boss portion
16 of the carbon jig 8 is also removed. By this processing, the carbon jig 8 remains only on the
surfaces of the inner periphery and the outer periphery of the ring-shaped composite
piezoelectric material 1. In this state, the ring-shaped composite piezoelectric material 1 is held
by a cylindrical jig having the same outer shape as the ring-shaped composite piezoelectric
material 1, and a part 17 of the carbon jig 8 is released while heat is applied to take out the ringshaped composite piezoelectric material 1. Since the ring-shaped composite piezoelectric
material 1 produced by this method does not have positional deviation in the circumferential
direction, the arrangement accuracy is good and the directivity is good.
[0017]
In the process shown in FIG. 6, in order to take out the electrode from the ring-shaped composite
piezoelectric material 1 taken out in FIG. Next, the case where the ring-shaped piezoelectric
ceramic vibrator 7 is laminated to form a cylindrical composite piezoelectric material will be
described.
[0018]
FIG. 7 shows an embodiment in which two ring-shaped piezoelectric ceramic vibrators 7 are
stacked. In FIG. 7, two ring-shaped piezoelectric ceramic vibrators 7 are stacked to form a
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laminate 20, and the laminate 20 is fixed by a thermoplastic wax 9 to a carbon jig 21 whose
annular groove is made deeper by an amount equivalent to fixing the laminate 20. Thereafter, the
processing shown in FIGS. 3, 4 and 5 is performed to form a cylindrical composite piezoelectric
material 22.
[0019]
In the process shown in FIG. 8, in order to take out the electrode from the cylindrical composite
piezoelectric material 22 taken out, the metal foil 23 is stuck by the conductive adhesive 12. As
another method, a metal foil may be attached to the ring-shaped piezoelectric ceramic vibrator 7
to form a cylindrical composite piezoelectric material, and this method is suitable for beam
scanning. In addition to the arrangement accuracy in the circumferential direction, the cylindrical
composite piezoelectric material produced by this method can ensure the arrangement accuracy
in the cylinder center axis direction.
[0020]
Further, when the number of laminated layers of the ring-shaped piezoelectric ceramic vibrator 7
is large and it is difficult to carry out the same processing as in FIG. 3, as shown in FIG. Advance
in the direction of 24 while causing the diamond cutter 10 to rotate 12 in parallel. The radial
grooves 11 can also be processed by indexing this at a constant angle and performing processing
all around in the direction of 25. Thereafter, the same processing as in FIGS. 4 and 5 is
performed to form a cylindrical composite piezoelectric material. Furthermore, another method
of forming a cylindrical composite piezoelectric material will be described.
[0021]
In FIG. 10, a plurality of ring-shaped piezoelectric ceramic vibrators 7 are laminated, and then
molded with a polymer material 15. After the polymer material 15 is sufficiently cured, a holding
portion 26 can be held by a machine tool. Provide Next, the groove 11 is processed with respect
to the laminate molded with the polymer material 15 while making the diamond cutter 10 rotate
12 as in FIG. If the number of laminations of the ring-shaped piezoelectric ceramic vibrator 7 is
large and it causes a problem in performing the same processing as FIG. 3, the diamond cutter
10 is rotated parallel to the central axis of the cylinder on the acoustic radiation surface as in FIG.
Advance in the direction shown by arrow 24 while performing 12. This is indexed at a fixed
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angle to process the radial grooves 11. Then, a polymer material is injected into the groove 11 to
form a cylindrical composite piezoelectric material. When acrylic or the like is used as the
material of the mold, the acoustic matching layer can be formed simultaneously.
[0022]
That is, in this processing method, the jig for holding the ring-shaped piezoelectric ceramic
vibrator 7 is omitted, and the polymer material 15 is used as a jig. In this method, it is not
necessary to prepare a jig, and the production efficiency is also improved. As described above,
according to the present invention, since the machining process is carried out with a commonly
used surface grinding machine and no special large-sized machine tool is used, the cylindrical
composite piezoelectric material can be made relatively inexpensively and suitable for small
volume production It can be manufactured.
[0023]
According to the present invention, the composite piezoelectric material can be formed relatively
inexpensively without using equipment such as a large-sized machine tool. Further, in the
ultrasonic transducer using the composite piezoelectric material according to the present
invention, since the positions in the circumferential direction and in the direction of the cylinder
central axis in the laminated case are aligned, there is an effect that the accuracy of directivity is
good. Since the vibrator is divided, coupled vibration in the circumferential direction is less likely
to occur, and there is also an effect that a decrease in sensitivity can be prevented.
[0024]
Brief description of the drawings
[0025]
1 is an explanatory view showing an embodiment of the ultrasonic transducer according to the
present invention.
[0026]
2 is an explanatory view showing a process of attaching a ring-shaped piezoelectric vibration
ceramic moving element to a carbon jig with wax.
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[0027]
3 is an explanatory view showing a process of forming a groove by machining with a diamond
cutter.
[0028]
Fig. 4 is an external view after resin molding.
[0029]
Explanatory drawing which shows the detachment | leave process of the FIG. 5 jig | tool.
[0030]
6 is an explanatory view showing an attaching process of the metal foil for electrode.
[0031]
7 is an explanatory view showing a process of attaching the ring-shaped piezoelectric ceramic
vibrator laminate to a jig made of carbon.
[0032]
8 is an explanatory view showing a process of attaching the metal foil for electrode to the
cylindrical composite piezoelectric material.
[0033]
9 is an explanatory view showing another example of the groove processing step in the present
invention.
[0034]
10 is an external view of the ring-shaped piezoelectric ceramic vibrator laminate directly molded
with a polymer material for groove processing.
[0035]
Explanation of sign
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[0036]
Reference Signs List 1 ring-shaped composite piezoelectric material 2 cylindrical composite
piezoelectric vibrator 3 acoustic transmitting / receiving window 4 flange 5 ultrasonic transducer
6 cable 7 ring-shaped piezoelectric ceramic vibrator 8 carbon jig 9 thermoplastic wax 10
diamond cutter 15 polymer material 18 conductive Adhesive 19 Metal foil for electrode 22
Cylindrical composite piezoelectric material
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