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JPS54148129

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DESCRIPTION JPS54148129
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 3 are perspective views showing the main
part of a conventional ultrasonic electro-acoustic transducer, and FIG. 4 is an ultrasonic electroacoustic transducer according to an embodiment of the present invention. FIG. 5 is a crosssectional view showing a converter, and FIG. 5 is a side view of the main part thereof. '10 · · · · · · ·
· Bimorph oscillator, 11 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 14 · · ·
Conical resonators 15, composite resonators.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic
electroacoustic transducer using a piezoelectric ceramic vibrator, and in particular, a bimorph
vibrator in which a piezoelectric ceramic resonator and a diaphragm made of metal or resin are
bonded. The present invention relates to an ultrasonic electroacoustic transducer to be used.
Heretofore, as an ultrasonic electroacoustic transducer using a piezoelectric ceramic vibrator,
there has been one shown in FIG. 1 to FIG. To use the bimorph oscillator in which the ones
shown in FIG. 1 (size, two piezoelectric ceramic oscillators 1 ′ ′: G) are bonded to each other G!
The conical resonator 2 is attached to the central portion of the vibrator with l 夛-/ '-'- 2 and the
conical resonator 2 is mounted to improve the acoustic conversion efficiency. Further, in FIG. 2
(in the case of tζ, a bimorph vibrator is used in which a metal diaphragm 4 having one or more
holes 3 provided in one piezoelectric ceramic vibrator 1 is bonded. It was easy to pull out.
However, in the case shown in FIGS. 1 and 2, the frequency adjustment of the bimorph oscillator
can not be performed, and therefore the frequency adjustment can be performed unless the
center value and accuracy of each component are adjusted. Although the structure shown in FIG.
3 has been considered to solve this drawback, the structure shown in FIG. 3 is an improvement to
the bimorph oscillator shown in FIG. A hole is provided in the center of the vibrator 1 in advance,
and when bonding two piezoelectric ceramic vibrators 1 into a bimorph vibrator, the coupling
shaft 5 is passed through the hole. In the structure shown in FIG. 3, the three resonance
frequencies can be adjusted by adjusting the length of the coupling shaft 5. However, on the
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other hand, the mechanical-acoustic conversion efficiency is likely to fluctuate, and the structure
is complicated and expensive. The present invention has been made in view of such conventional
problems. It is an object of the present invention to provide an ultrasonic electroacoustic
transducer in which frequency adjustment is easy and sound conversion efficiency is stable.
Hereinafter, the present invention will be described with reference to FIGS. 4 and 5 showing an
embodiment of the present invention. In the figure, 10 is a bimorph oscillator, and this bimorph
oscillator 10 is configured by bonding a diaphragm 11 made of metal or resin and a piezoelectric
ceramic oscillator 12. The diaphragm 11 (in which one or more cut-and-raised portions 13 are
provided (one in the figure), the piezoelectric material is provided on the side opposite to the side
on which the cut-and-raised portions 13 are provided. A porcelain vibrator 12 is attached. The
piezoelectric ceramic vibrator 12 is constructed by providing counter electrodes on both sides of
the piezoelectric ceramic plate and polarization.
The bimorph vibrator 1o performs electro-acoustic conversion, and when an electric signal is
applied due to the bimorph structure, flexural vibration is performed to perform acoustic
conversion. The resonance frequency (J'r) in this case is determined by the following equation:
fAny · F4 shell (Hz) r'3 ((1σ) r: radius, t: thickness, E: Young's modulus. p: density, σ: polyan
ratio, α: mode and Biaso) Mr. J Uo J 5 several 4 straight one ·, when adjusting the resonance
frequency to one side of the collar, make r and t strange It is done by making a noise. In this case,
the resonance frequency varies due to the influence of the finish variation and the misalignment
of each component of the bimorph oscillator. In order to reduce the variation of the frequency,
the resonator structure having the adjusting function is eight effective. The cut-and-raised
portion 13 corresponds to T in the above-mentioned equation, and in particular, it is installed so
that the mass of the vibrator can be varied. Therefore, the above-mentioned ぢ 351 "" 30-"110
'It-' □ t,!: Tc J: Lt'iW [彪 彪 ノ 5 波 can be adjusted to a high wave number. Even if it is added,
since it is integrated in the diaphragm 11, the degree of coupling between the cut-and-raised part
13 and the diaphragm 11 does not change, and unlike the structure in which the coupling axis is
adhered to the conventional bimorph oscillator Because they are integrated, there is little
additional resistance and mechanical resistance due to vibration can be reduced, and 14 is a
resin or metal conical resonator, which is located at the center of the tip of the conical resonator
14. A through hole is provided, and the cut and raised portion 13 of the diaphragm 11 is inserted
into the through hole, and the tip end of the conical resonator 14 is fixed to the cut and raised
portion 13 to obtain conical resonance. The element 14 is attached to the diaphragm 11 to
provide complex resonance The child 15 is configured. The vibration of the bimorph oscillator
10 is transmitted to this conical resonator 14 through the cut-and-raised portion 13 to perform
acoustic conversion efficiently. Also, the material of the conical resonator 14 is a characteristic
acoustic resistance of air. The one that matches to is selected. The reference numeral 16
designates a terminal for holding the composite resonator 15). The piezoelectric ceramic vibrator
12 of the composite resonator 15 is fixed to the terminal plate 16 by an elastic adhesive agent.
Although the bonding position is a circumferential portion corresponding to a node on the
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vibration mode of the bimorph oscillator 10, it is possible to change the supporting position
according to the required sensitivity-frequency characteristics. 18.19 is a terminal pin / disposed
on the terminal board 16. The lead pin of the bimorph oscillator 1o is connected to the terminal
pin 18.19. The terminal board 16 is of the metal case 20. The opening end is closed, and a metal
plate 21 for obtaining a shielding effect together with the metal case 20 is disposed outside the
terminal plate 16.
Further, an opening is provided on the side of the conical resonator 14 of the metal case 2o, and
the opening is closed by a screen 22 for preventing mechanical impact and obtaining a shielding
effect. In the case of the metal case 20, a plurality of holes may be provided to constitute the
screen 22. As apparent from the above description, the ultrasonic electro-acoustic transducer
according to the present invention is provided on the diaphragm. The frequency adjustment is
performed by (a raised portion) a, and the frequency adjustment is facilitated, and the adhesion
strength of the connection portion between the conical resonator and the bimorph oscillator for
improving the acoustic conversion efficiency is increased. And the degree of coupling can be
made tight. As a result, it is possible to obtain a high-sensitivity ultrasonic electroacoustic
transducer having high vibration transmission efficiency and high electro-acoustic conversion
efficiency (and conical resonance in the cut-and-raised portion integrated with the diaphragm).
Since a child is attached, it is possible to obtain a characteristic with a small rate of temperature
change, rather than using an adhesive with a large contribution to change in temperature
characteristics as compared to the conventional structure in which a bonding shaft is attached to
a bimorph oscillator by bonding. It has a very high practical value.
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