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JPH01160299

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DESCRIPTION JPH01160299
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer, and more particularly to an electroacoustic transducer of an azimuth
measuring sonar used in water. [Prior Art] Conventionally, an electro-acoustic transducer of this
type has internal electrodes 92a-92d of a cylindrical piezoelectric vibrator 91, as described in, for
example, Japanese Patent Application No. 61-16286, as shown in FIG. As shown in <>, it had
become 4 division electrodes divided into 4 parts. Reference numeral 93 denotes an outer
surface electrode. Also, as shown in FIG. 9 (b), the output obtained by reverse connection
between the opposing electrodes is a transformer 96a. By passing it through 96b, the output
components of the zero-order longitudinal vibration shown in FIG. 8 (a) of the cylindrical
piezoelectric vibrator 91 and the primary vibration shown in FIG. 8 (b) are extracted, FIG. 9 (c),
The omnidirectionality and dipole directivity shown in (d) and (e) were obtained and used as an
electroacoustic transducer of a direction measurement sonar. [Problems to be Solved] The abovedescribed conventional electroacoustic transducer has zero-order longitudinal vibration and
primary longitudinal vibration generated on the circumference of a cylindrical piezoelectric
vibrator 91 as shown in FIG. 8 (a> <b>). Vibration is used to obtain the required omni directivity
and dipole directivity. When using dipole directivity obtained by primary longitudinal vibration
for azimuth measurement, it can be used only in a frequency range lower than the resonance
frequency of primary longitudinal vibration. However, another vibration mode exists in this
frequency range, and when the output is superimposed, there is a problem that directivity error
occurs, and accurate dipole directivity can not be obtained. Assuming that the resonance
frequency of zero-order longitudinal vibration for obtaining an omni signal is f0, it is represented
by the resonance frequency 4iHto of primary vibration for obtaining dipole characteristics. The
zero-order vibration has a resonant frequency at a frequency lower than that of the first-order
vibration. However, since the opposing partial electrodes are reversely connected, the charges
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cancel each other out and can not be used as an output voltage. On the other hand, the resonance
frequency of the flexural vibration is 0. 0. -8Xt / aXfO, the resonance frequency of the third
bending vibration is 2.2Xt / aXfo, the fourth bending vibration is 4.2Xt / aXfo, the fifth bending
vibration is 6, 8Xt / aXfO etc. Be done. Here, t is the thickness of the cylindrical piezoelectric
vibrator 91, and a is the average radius. In cylindrical piezoelectric vibrators that are generally
used, since t / a = about 0.1 to 0.2, bending vibration of the 7th or higher order has a resonance
frequency higher than that of primary longitudinal vibration, so it is especially considered You
don't have to. Further, even-order bending vibration has no influence on the dipole
characteristics because the generated charges are canceled by reverse connection of the
opposing partial electrodes and can not be used as an output voltage.
However, the third-order flexural vibration shown in FIG. 8 (c) and the fifth-order flexural
vibration shown in FIG. 8 (d) have resonance in a frequency range lower than the resonance
frequency of the first-order flexural vibration. Then, the generated charge can not be canceled
out, and this output affects the dipole characteristic, and there is a problem of becoming an error
in the direction measurement. Moreover, in the case of the purpose of using in the state with few
errors, there existed a problem that the usable frequency was restricted to the narrow range.
Therefore, an object of the present invention is to solve the above-mentioned conventional
problems, to remove the disturbance of the dipole characteristics, and to provide an
electroacoustic transducer capable of accurate direction measurement over a wide range.
[Solution to the Problems] The present invention is an electroacoustic transducer having
electrodes on the inner and outer surfaces and having a cylindrical piezoelectric vibrator
polarized in the radial direction, in which at least one of the inner and outer surfaces is subjected
to third order deflection It is a partial electrode with a central angle that can remove the
influence of vibration or fifth deflection vibration, and it is formed as eight divisions or sixteen
divisions, and the remaining surface is a full surface electrode. Next, an embodiment of the
present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional
view of a cylindrical piezoelectric vibrator showing a first embodiment of the present invention.
In the figure, the cylindrical piezoelectric vibrator 11 is provided with inner electrodes 12 a to 12
h and an outer electrode 13. As the inner electrodes 12a to 12h, partial electrodes having a
central angle of 60 degrees and 30 degrees are alternately provided, and a total of eight divided
electrodes are provided. Here, as shown in FIG. 8 (C), since the third-order bending vibration is a
vibration that bends at a cycle of 120 degrees at the central angle, if the electrode is provided at
a central angle of 120 degrees, it occurs in the electrode Charge cancels each other out and does
not appear as an output voltage. Although it is necessary to reversely connect opposite
electrodes to obtain dipole characteristics, only one pair of partial electrodes with a central angle
of 120 degrees can be provided in one cylindrical vibrator, and it is independent in the
overlapping portion with the orthogonal electrode pairs. Partial electrode 12b. 12d, 12f, 12h are
provided and used as common electrodes for obtaining orthogonal dipole characteristics and
omni characteristics. By passing the outputs obtained from the cylindrical piezoelectric vibration
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of this structure through addition circuits 54a to 54e and subtraction circuits 55a and 55b as
shown in FIG. 5, an output VX (θ of the orthogonal dipole characteristics as in the prior art is
obtained. ), Vy (θ), and omni-characteristic VO (θ) can be obtained. FIG. 2 is a cross-sectional
view showing a second embodiment of the present invention. As the inner electrodes 22a to 22h,
partial electrodes having a central angle of 72 degrees and 18 degrees are alternately provided,
which is a structure of an 8-divided electrode.
Here, as shown in FIG. 8 (d), the fifth order flexural vibration is a vibration that bends at a period
of 72 degrees when the central angle is set, so if the electrode is provided at a central angle of 72
degrees, it will occur in the electrode The charges cancel each other out and do not appear as an
output electrode. In order to obtain orthogonal dipole characteristics, partial electrodes with a
width of 72 degrees at a central angle may be provided at intervals of 90 degrees, and opposite
partial electrodes may be reversely connected as in the conventional case. However, if an interval
between the four partial electrodes 22a, 22c, 22e, and 22g is an electrodeless portion, the output
of the fourth-order bending vibration can be obtained when the connection is to obtain an omni
characteristic, and thus the partial electrodes 22b and 22d are independent. , 22f and 22h, and
as shown in FIG. 6, the omni characteristic output Vo (θ) is obtained using the output from the
entire inner surface. FIG. 3 is a cross-sectional view showing a third embodiment of the present
invention. In the second embodiment, the central angle of the electrode for obtaining the dipole
characteristic is 72 degrees, but since the impedance becomes high in inverse proportion to the
electrode area, it is necessary to make the input impedance of the circuit or the like higher than
before. In the third embodiment, the central angle of the opposing electrodes is 144 degrees so
as to cancel generated charges for two cycles of the fifth bending vibration. However, in this
structure, as shown in FIG. 5, common electrodes 32b, 32d, 32f, and 32h are provided because a
part of the electrodes overlaps if two pairs of opposite electrodes orthogonal to each other are
provided as in the first embodiment. By connecting it, the output which removed the influence of
the 5th order flexural vibration is obtained. FIG. 4 is a cross-sectional view showing a fourth
embodiment of the present invention. In the first embodiment, an electrode structure capable of
removing the influence of the third flexural vibration and the third flexural vibration in the third
embodiment is used. Here, the central angles of 36 degrees, 12 degrees, 30 degrees, and 12
degrees are used. The electrodes are repeatedly provided in this order to form a 16-segment
divided electrode structure. By proper combination of the partial electrodes 42a to 42P, an
electrode pair orthogonal to the central angle 120 degrees and an electrode pair orthogonal to
the central angle 144 degrees similar to the first embodiment and the third embodiment are
obtained. 7 using the adder circuit 74 and the subtractor circuit 75 as shown in FIG. 7 to remove
the influence of the third-order deflection signal and remove the influence of the die bow
movement (X5 (.theta.) And * Y5 (* 5)). θ) and omni characteristics * 0 (θ) can be obtained
simultaneously. The present invention is not limited to the above embodiments, and various
modifications can be made within the scope of the present invention. For example, in FIG. 1 to
FIG. 3, when the inner surface is a divided electrode, FIGS. 4 to 6 show cross sections of the
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cylindrical piezoelectric vibrator in the case where the outer surface is a divided electrode. It may
be an electrode.
Also, although an example using an adder circuit and a subtractor circuit to obtain dipole
characteristics and omni characteristics is shown, similar characteristics can be obtained using a
transformer or the like. It can also be used for transmission. As described above, according to the
present invention, in the cylindrical piezoelectric vibrator having the electrodes on the inner and
outer surfaces and polarized in the radial direction, at least one of the inner and outer surfaces is
subjected to the third flexural vibration or the fifth deflection vibration. The electrode structure
has a central angle of 8 or 16 divided so that the next deflection vibration can be removed, and
for example, an 8-divided electrode in which partial electrodes of 60 ° and 30 ° are alternately
provided or a central angle of 72 ° Or 18 divisional electrodes are alternately provided, or 8
division electrodes are alternately provided with a central angle of 36 degrees or 54 degrees, or a
partial angle of a central angle of 36 degrees or 54 degrees A structure in which electrodes are
alternately provided in eight divided electrodes or in which partial electrodes of center angles of
36 degrees, 12 degrees, 30 degrees, and 12 degrees are repeatedly provided in this order, and
the remaining surfaces are all over electrodes 3rd order flexural vibration or 5th order by It is
possible to eliminate the disturbance of the dipole characteristics due to the output voltage
generated by the saw vibration, the effect of enabling accurate azimuth measurements over a
wide frequency range.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a sectional view of a cylindrical piezoelectric vibrator showing a first embodiment of the
present invention, FIG. 2 is a sectional view showing a second embodiment of the present
invention, and FIG. 3 is a third embodiment of the present invention FIG. 4 is a cross sectional
view showing a fourth embodiment of the present invention, and FIGS. 5 to 7 show outputs of
dipole characteristics and omni characteristics from the cylindrical piezoelectric vibrator shown
in the embodiment. FIG. 8 is an explanatory view showing a vibration mode of the vibrator, and
FIG. 9 is an explanatory view showing a conventional electro-acoustic transducer.
11.21, 31, 51 degree 61.71, 91: Piezoelectric vibrators 12a to 12h, 22a to 22h. 32a to 32h, 42a
to 42p, 52 ° 62.72.92a to 92d: inner electrodes 13.23.33, 43.53a to 53h. 63a∼63h、
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73a∼73p。 93: outer surface electrodes 54a to 54e, 64. 74a to 74i: addition circuits 55a,
55b, 65a, 65b. 75a to 75d: subtraction circuits 96a, 96b: transformers
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