JPH0347571

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DESCRIPTION JPH0347571
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of manufacturing a Langevin type vibrator used for an ultrasonic processing machine or
the like. [Conventional art] Conventionally, a Langevin-type vibrator of this type is made of lead
zirconate titanate or lead titanate ceramic, and an electrode plate of a piezoelectric element of 2
fl 1 or more which has been polarized in the thickness direction without load. An electrostrictive
element laminated through the above and a pair of metal blocks in contact with the upper and
lower end surfaces of the electrostrictive element are completed by integrally fastening them
with a fastening member consisting of a bolt and a nut. [Problems to be Solved by the Invention]
However, since the piezoelectric element incorporated in the Langevin-type vibrator is subjected
to mechanical compressive stress in the polarization axis direction only when it is incorporated,
90 ′ ′ domain inversion or Since a phase transition occurs and a decrease in remanent
polarization and a deterioration in piezoelectric characteristics occur, a Langevin-type vibrator
characteristic fully utilizing the characteristics of the piezoelectric element can not be obtained.
The present invention has been made to solve the above-mentioned problems, and the
piezoelectric element is subjected to mechanical compression stress once more than the final
fastening force before fastening, and subjected to polarization treatment as it is. By reassembling
in the shape of a vibrator using reversibility of area inversion, remanent polarization of the
piezoelectric element under mechanical compressive stress is improved, and a Langevin type
vibrator fully utilizing the characteristics of the piezoelectric element is provided. The purpose is
that. [Means for Solving the Problems] In order to achieve this object, in the method of
manufacturing a Langevin-type vibrator of the present invention, the piezoelectric element in the
electrostrictive element is subjected to polarization treatment using a jig which applies
mechanical compressive stress. And a step of integrally fastening the electrostrictive element and
a pair of metal blocks disposed on both end faces by a fastening member. [Operation] In the
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present invention having the above-described configuration, the pressure element is subjected to
the polarization process under the mechanical compressive stress higher than the final fastening
pressure by the polarization process. By the subsequent fastening process, the piezoelectric
element is put under mechanical compressive stress again, and is operated as a vibrator. An
embodiment of the present invention will now be described with reference to the drawings. FIG.
1 is a view showing a process of performing polarization treatment in silicon oil after assembling
an unpolarized piezoelectric element using a jig which applies mechanical compressive stress,
and is mainly composed of lead zirconate titanate. The ring-shaped unpolarized piezoelectric
elements 1a and 1b made of porcelain and having an outer diameter of 39 mm, an inner
diameter of 20 mm and a thickness of 6 mm are laminated via the copper electrode plate 2 to
form an electrostrictive element.
At both ends of the electrostrictive element, metal blocks 3a and 3b made of aluminum alloy and
having an outer diameter of 40 mm, an inner diameter of 17 mm, and a thickness of 20 m + a are
provided. A torque jig of 1500 kgf (d) was fastened by means of M16P1.0 fastening bolt 5 and
fastening nut 6 which are inserted in an insulating manner, to obtain a polarization jig. Lead wire
7 a for the copper electrode plate 2 and the fastening bolt 5. A direct current type 1IiX 8 is
connected through 7b, and polarization processing is performed for 60 minutes in a silicone oil 9
heated to 130 ° C., with an applied electric field of 300 kv / long. At this time, the annular
insulator 4 serves to prevent short circuit and discharge between the copper electrode plate 2
and the fastening bolt 5. FIG. 2 is a view in which the piezoelectric element obtained as described
above is assembled as a Langevin-type vibrator, and the piezoelectric elements 1a and 1b are
laminated through the copper electrode plate 2 in the same manner as in the previous process. It
is considered as a distortion element. An outer diameter of 40 m1 made of an aluminum alloy at
both ends of the electrostrictive element. The back plate 11 with an inner diameter of 17 mm
and a thickness of 32 mm and a screw part for fastening are provided, and the front plate 12
with an outer diameter of 40 mm and a length of 68 mm is abutted. After inserting both screw
bolts 13 of M16P1.0, the bolts were tightened with a tightening nut 6 to a torque of 1000 k 100
O) to obtain a bolt-clamped Langevin type vibrator. Electrically, a bolted Langevin type vibrator
obtained by the embodiment of the present invention and a bolted Langevin type vibrator having
a piezoelectric element subjected to polarization processing without applying stress as in the
prior art as an electrostrictive element As a result of measuring the characteristics, the boltclamped Langevin-type vibrator according to the present invention has resonance, while the boltclamped Langevin-type vibrator according to the conventional method exhibits the resonance
frequency fr 20.19 KHz, the resonance admittance Yr 160 mS, and the electroacoustic
conversion efficiency eaea 91%. The frequency fr 20.15 KHz, the resonant admittance Yr 220
mS, and the electroacoustic conversion efficiency eaea 95% are shown. As apparent from this, the
Langevin-type vibrator according to the present invention exhibits superior characteristic values
as compared to the Langevin-type vibrator according to the conventional method, and
polarization processing is performed in a state where mechanical compressive stress is applied to
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the piezoelectric element in advance. The effect to be done was confirmed. In the polarization
processing, it is also possible to assemble the final vibrator shape and perform polarization
without using a jig. [Effects of the Invention] As is apparent from the above detailed description,
according to the present invention, after subjecting a piezoelectric element which is an
electrostrictive element to a polarization treatment in a state in which a mechanical compressive
stress is applied in advance, As a result, it is possible to obtain a bolt-clamped Langevin-type
vibrator having excellent characteristics in which the characteristics of the piezoelectric element
are sufficiently utilized.
[0002]
Brief description of the drawings
[0003]
1 to 2 show an embodiment embodying the present invention, and FIG. 1 is a sectional view
showing a polarization treatment process of a piezoelectric element placed under compressive
stress, and FIG. 2 is a bolt. It is sectional drawing of a clamp Langevin type ¦ mold vibrator.
In the figure, 1 is a piezoelectric element, 3 is a metal block.
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