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DESCRIPTION JPS63250999

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DESCRIPTION JPS63250999
[0001]
The present invention relates to a piezoelectric vibrator for generating an ultrasonic wave by
utilizing an electrostrictive phenomenon, and more specifically, an electrode pattern is
appropriately formed on two opposing faces of a rectangular solid ■ type vibrator. The present
invention relates to a piezoelectric vibrator that makes it possible to significantly suppress the
side lobes generated in relation to the radiation pattern of ultrasonic waves by applying an
alternating voltage between the both electrodes. Background of the Invention A co-piezoelectric
transducer is an electroacoustic transducer having a so-called transceiving function, which
converts an electrical signal into an acoustic signal or converts an acoustic signal into an
electrical signal. Among them, piezoelectric vibrators that generate ultrasonic waves have
relatively little signal attenuation in liquid, especially in water, for ultrasonic waves, or it is
relatively easy to select the size of the sound source larger than the wavelength. 1. It is widely
adopted in sounding sounders, particularly fish finders, because it is possible to sharpen the
directivity of sound waves. Here, the directional characteristics of the sound wave represent the
characteristics of the range to which the sound wave is transmitted from the piezoelectric
vibrator having the transmission / reception function and the range of the sound wave received,
and the practical use of a fish finder It can be said that it is an extremely important factor in view
of sex. FIG. 1 shows an example of the directivity characteristic of a sound wave generated from a
piezoelectric vibrator. As can be easily understood from the figure, the sound pressure on the
central axis 4 in the direction orthogonal to the piezoelectric vibrator 2 is the strongest, and the
sound pressure decreases with the increase of the displacement angle θ from the central axis. In
this case, the acoustic beam on the central axis 4 is referred to as the main lobe M, and the
lateral acoustic beam is referred to as the side lobe S. When transmission and reception are
performed using the same piezoelectric vibrator, the directivity characteristic times is multiplied
by a square, so that the angle θ-3d8 at which the sound pressure in the main lobe M is 3 dBK
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smaller than the value of the central axis 4 It is important as an index that represents directional
characteristics. By the way, among the directivity characteristics of the sound wave shown in FIG.
1, the presence of the side lobe S is a reflection signal related to the side lobe S when the
piezoelectric vibrator for generating the sound wave is adopted for a fish finder. It may be
mistaken that the reflected signal is a reflected signal from the main lobe M. In this case, there is
no fish school in the throwing net area even if it starts throwing in a state where the direction of
the fish displayed on the display of the fish finder is relied upon, that is, it is misidentified The
disadvantages of lowering In order to suppress the unnecessary side lobes S, it is known to form
an electrode pattern of the facing surface of the rectangular ultrasonic piezoelectric transducer in
a special shape. Before describing the conventional technical concept of this measure, in order to
clarify the location of the problems of the prior art, first, the basic electrode pattern of the
piezoelectric vibrator and the side generated accompanying the electrode pattern The
relationship with the size of the lobe S will be described.
Usually, the suppression amount of the side lobe S is expressed as a side rope suppression ratio
R; R = 201 og B / A. Here, the reference symbol A is the maximum sound pressure level of the
main lobe M, and the reference symbol B is the maximum sound pressure level of the side lobe S
(see FIG. 1). Now, as shown in FIG. 2, the electrode pattern of the rectangular piezoelectric
vibrator 6 is the ultrasonic wave of the rectangular piezoelectric vibrator 6 in the most basic case
where the entire two opposing surfaces are the electrode patterns 8a and 8b. On the surface of
the radiation surface Us, as shown in FIG. 3a, an amplitude characteristic curve is obtained in
which the generated sound pressure level is equal to the major axis l. The side rope suppression
ratio R in this case is known to be approximately 13.5 dB. In order to make the side rope
suppression ratio R infinite, for example, as shown in FIG. 3, if the amplitude characteristic curve
related to the sound pressure is made a characteristic curve similar to the substantially cos
square characteristic curve Good things are being elucidated. Next, from this viewpoint, let us
consider an example of forming an electrode pattern according to the prior art. This technical
idea is disclosed, for example, in Japanese Patent Publication No. 58-32558. That is, in this
example, as shown in FIG. 4, of the two opposing electrode patterns of the rectangular
piezoelectric vibrator, the electrode pattern on one surface is cut in the oblique direction to excite
the excitation electrode C and the damping electrode. The vibration energy is divided into E, E,
and E2, and the vibration energy is suppressed at both ends. Therefore, it is described that the
ultrasonic wave emitted from the ultrasonic radiation surface U is most strongly emitted from the
central part of the radiation surface U, and is emitted so as to be gradually weakened as the end
part is approached. However, in this case, as apparent from the detailed examination of the
pattern shape, the arrangement shapes of the excitation electrode C and the damping electrodes
E, E, and E2 are linear, so it is possible to The effect of suppressing the side lobe S is insufficient.
That is, in this prior art, since the shape of the amplitude characteristic curve related to the
sound pressure is a substantially isosceles triangle, the side rope suppression ratio R is
approximately 20 dB, and the reflected signal of a fish school etc. related to the side lobe S There
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is no possibility that the risk of being mistaken as a reflected signal related to the main lobe M
has been eliminated. Furthermore, since the electrode pattern shape of the piezoelectric vibrator
disclosed in the present invention does not satisfy the condition of vertical and horizontal
symmetry with respect to the center of the vibrator, it causes unnecessary vibration and
disturbance of the radiation pattern occurs. It also exposes various drawbacks, including a fear
and a reduction in the efficiency of electric / ultrasonic conversion.
Therefore, in order to eliminate these defects, a large number of rectangular ultrasonic
piezoelectric vibrators are stacked to form vertically and horizontally symmetrical electrodes, and
on top of that, each piezoelectric vibrator is arranged to follow a substantially CO3 square
voltage distribution. Although attempts have been made to obtain a multilayer piezoelectric
vibrator configured to supply a voltage, in such a configuration, it takes time to manufacture the
piezoelectric vibrator as a final product, and as a result, the manufacturing cost is increased. It
exposes new inconveniences. SUMMARY OF THE INVENTION The present invention has been
made to overcome the above-mentioned problems. The present invention is directed to the
electrode patterns of the rectangular parallel piezoelectric vibrator facing each other on opposite
sides in a vertically symmetrical manner and in accordance with a substantially cos square curve.
The excitation electrode and the damping electrode are disposed. Therefore, by applying an
alternating voltage between the both electrodes, it becomes possible to suppress the side lobe S
generated in the radiation pattern of the ultrasonic wave in a substantially atmosphere, and in
addition, the formation of the electrode is extremely easy in manufacturing An object of the
present invention is to provide an ultrasonic piezoelectric vibrator. [Means for achieving the
object] In order to achieve the above object, the present invention is a rectangular parallelepiped
piezoelectric vibrator for generating ultrasonic waves, in which mutually opposing electrode
surfaces are substantially congruent in shape. The center of each surface is formed into an
electrode shape including one excitation electrode and a pair of damping electrodes that are
vertically and horizontally symmetrical with respect to an axis orthogonal to each other, and
excitation per unit length in the longitudinal direction of each surface The area of the electrode is
formed to be gradually narrowed from the center to both ends, and the area of the damping
electrode per unit length in the longitudinal direction is gradually reduced from the ends to the
center It is characterized in that the damping electrode on one side is electrically connected to
the excitation electrode on the other facing electrode surface. Embodiments Next, preferred
embodiments of the piezoelectric vibrator according to the present invention will be listed and
described in detail below with reference to the attached drawings. The same components as
those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and the detailed
description thereof will be omitted. In FIG. 5, reference numeral 10 denotes a rectangular
parallelepiped piezoelectric vibrator including an electric circuit drive unit according to the
present invention. The shape of the piezoelectric vibrator 10 is exactly a single rectangular
parallelepiped shape, and electrode patterns are formed substantially congruently on its two
opposing surfaces. In this case, in the figure, in the front part 12 and the back part 14, one
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excitation electrode 16.18 extending from the center part of the surface to the both ends over
the whole surface and each part from the both ends to the center part A pair of damping
electrodes 20a, 20b and 22a, 22b extending in a directed manner are disposed, and the
circumferential surfaces of the excitation electrode 16.18 and the damping electrodes 20a, 20b
and 22a, 22b are mutually insulated. It is formed.
In this case, the electrode area per unit length in the longitudinal direction of the excitation
electrode 16.18 is defined as an area distribution gradually decreasing corresponding to the cos
square curve, with the center part as the origin and directed to both ends. As an area distribution
in which the electrode area per unit length in the longitudinal direction of the damping
electrodes 20a, 20b and 22a, 22b gradually decreases in proportion to the curve (1-cos square)
from the both ends toward the central part It is formed. In addition, it is possible to print-form
each electrode by the silk screen method, Therefore, it can be set as the electrode shape suitable
for mass productivity, maintaining the accuracy of curvilinear shape. In such a configuration, the
excitation electrode 16 defined in the front part 12 is electrically connected to the pair of
damping electrodes 22 a and 22 b defined in the back part 14 and defined in the front part 12.
The pair of damping electrodes 20a and 20b and the excitation electrode 18 defined on the back
surface portion 14 are electrically connected to each other. An AC power supply E is connected
between the excitation electrode 16 of the front part 12 and the excitation electrode 18 of the
back part 14. The rectangular piezoelectric vibrator according to the present invention is
basically configured as described above. Next, its operation and effects will be described. In
general, it is said that excitation is performed to a piezoelectric vibrator utilizing an
electrostriction phenomenon by applying an alternating voltage, and in fact, the piezoelectric
vibrator IO is radiated by the application of an alternating current power supply E relating to a
resonance frequency. Ultrasonic waves are emitted upward from the surface U, or from the
opposite surface of the radiation surface Us. In this case, the directivity characteristics of the
ultrasonic waves are opposite to each other because the damping electrodes 20a, 20b and 22a,
22b of the same potential are opposed to each other on both end sides of the piezoelectric
vibrator 10 in the longitudinal direction. On the part side, it is damped and directed in the
longitudinal direction so that it is strongly excited as it goes to the central part. And in this case,
as described above, since the electrode area per unit length of the excitation electrode 16.18 is
formed to be, for example, approximately proportional to the cos square characteristic, the
ultrasonic wave emitted from the radiation surface Us Can be a radiation pattern almost free of
side lobes S. At this time, in order to make the directional pattern of the main lobe M
substantially the same as the piezoelectric vibrator of the basic electrode configuration shown in
FIG. Under the same condition as the basic piezoelectric vibrator, the length in the longitudinal
direction! , 1. It is preferable to form> 1. FIG. 6 shows another embodiment of the piezoelectric
vibrator according to the present invention.
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In FIG. 6, reference numeral 24 denotes an excitation electrode disposed in the front part 12, and
reference numerals 26a to 26d denote damping electrodes. In this case, the excitation electrode
28 and the damping electrodes 30a to 30d are formed on the back surface 14 substantially in a
congruent manner with the front surface 12, and the excitation electrode 24 of the front surface
12 and the damping electrodes 30a to 30d of the back surface 14 Are electrically connected, and
the damping electrodes 26a to 26d of the front part 12 and the excitation electrode 28 of the
back part 14 are electrically connected. Therefore, by applying an AC power source E between
the excitation electrodes 24 and 28, sound waves are emitted from the radiation surface U. Also
in this case, the electrode area per unit length in the longitudinal direction of the excitation
electrode 24.28 is directed to both end sides with the point at the center in the longitudinal
direction as the origin to be an area division proportional to the substantially cos square curve,
The vibrating electrodes 26a to 26d and 30a to 30d are shaped to have an area distribution
proportional to a (1 cos square) curve from the both end sides in the longitudinal direction
toward the central part. This makes it possible to obtain an ultrasonic radiation pattern that can
suppress side lobes. [Effects of the Invention] As described above, according to the present
invention, the excitation electrode and the damping electrode disposed on the front and back of
the piezoelectric vibrator are formed in the electrode pattern of upper, lower, left, and right
objects, and the electrode area is cos squared. It forms in the pattern shape which follows a
curve. Therefore, the directivity characteristic of the ultrasonic wave to be emitted becomes
sharp, and it becomes possible to suppress the side lobe generated in the radiation pattern of the
ultrasonic wave to substantially zero. In addition, since the method of forming the electrode is a
silk screen printing method, it is possible to extremely easily realize the formation of an electrode
pattern having a complicated shape without increasing the manufacturing cost. The present
invention has been described above by way of preferred embodiments, but the present invention
is not limited to these embodiments, and various improvements and design changes can be made
without departing from the scope of the present invention. Of course.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is an explanatory view of directivity characteristics of an ultrasonic wave generated from a
piezoelectric vibrator, FIG. 2 is a perspective explanatory view of a rectangular piezoelectric
vibrator having a conventional basic electrode shape, and FIG. 3 a is shown in FIG. Amplitude
characteristic curve diagram of the piezoelectric vibrator, FIG. 3 is a cos square amplitude
characteristic curve diagram, FIG. 4 is a perspective explanatory view of the piezoelectric vibrator
according to the prior art, and FIG. 5 is an electric circuit driver according to the present
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invention FIG. 6 is a perspective view showing another embodiment of the piezoelectric vibrator
according to the present invention.
DESCRIPTION OF SYMBOLS 10 ... Piezoelectric vibrator 12 ... Front part 14 ... Back part 16.18 ...
Excitation electrode 20a, 20b, 22a, 22b ... Damping electrode 24 ... Excitation electrode 26a-26d
... Damping electrode 28 ... Excitation electrode 30a to 30d ... Damping electrode E ... AC power
supply M ... Main lobe S ... Side lobe U9 ... Ultrasonic wave radiation surface F [G Longitudinal
direction of three piezoelectric vibrators-Longitudinal direction of one rod piezoelectric vibratorone-
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