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JPS57196699

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DESCRIPTION JPS57196699
Description 1 and title of the invention acoustic transducer (1) metal container, acoustic
conversion piezoelectric element provided in the wave transmitting / receiving unit in the metal
container, facing 1rK between the metal container and the acoustic conversion piezoelectric
element 11. An acoustic transducer having an adhesive layer for integrating a metal container
and an acoustic conversion piezoelectric element, wherein the adhesive layer is made of Ag and
Li.
2, the scope of claims
3. Detailed Description of the Invention The present invention relates to an acoustic transducer
for catching abnormal noise in, for example, a high temperature (600 ° C.) reactor using an
acoustic conversion piezoelectric element 1 such as LiNbO5. This type of acoustic transducer
generally has the structure shown in FIG. That is, a metal container (1), an acoustic conversion
piezoelectric element LjNbOs13) provided in the transmission / reception unit (2) in the metal
container, the transmission / reception unit (2) and the acoustic conversion piezoelectric element
(3) AC voltage is applied to the adhesive layer (4), which is located on the opposite side of the
surface, and integrates the wave transmitting / receiving unit (2) and the acoustic conversion
piezoelectric element (3), and the acoustic piezoelectric element (3) and the wave transmitting /
receiving unit (2). It has a metal-coated cable (8) and a core wire (9) to be introduced, a
conductor (6) for transmitting the potential of the core wire (8) to the acoustic conversion
piezoelectric element (3), and an electrode (5). For the adhesive layer (4), an Ag paste containing
Bi, Pb, etc. of low melting point metals is used. An acoustic transducer of such a configuration is
used, for example, as a sodium-permeable device for confirming abnormal noise and abnormal
conditions in a nuclear reactor. In operation, when an AC voltage is first applied from the
external power supply (not shown) to the connection between the metal-coated cable (8) and the
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core wire (9), both surfaces of the acoustic conversion piezoelectric element (3), that is, the
electrode (5) and the adhesive layer (4) An alternating voltage is applied to the Under this
electric field EndPage: 1 energy, acoustic energy, that is, ultrasonic waves are generated from the
acoustic conversion piezoelectric element (3). The ultrasonic waves of the veins are transmitted
through the adhesive layer (4) and the wave transmitting / receiving unit (2) into the furnace,
and the echoes of the ultrasonic waves rang to the subject are caught by the other acoustic
transducer. At that time, analyze the input signal by echo to confirm the presence or absence of
abnormality in the reactor. The adhesive layer will be described in detail with and. . In the
adhesive layer based on the conventional Ag paste K, Bi; -Pb etc. contain 5 lQwtIs of the whole
adhesive layer. When this adhesive layer is formed, Ag paste is applied to both the container and
the piezoelectric element, and there is a step to heat and bake, and it is necessary to bake K at
700 ° to 900 ° C to make an acoustic transducer for high temperature is there. In this firing
step, as shown in FIG. 2, the Ag paste adhesive layer (4) shows that Bi is LiNb0. Segregation
occurs on the side to form a segregation layer (4). According to the inventor's experiments, it was
found that this phenomenon is particularly likely to occur when Bi is contained. It is considered
that the segregated Bi reacts with the special KLi of the piezoelectric element so that the
conversion efficiency from electrical energy to ultrasonic energy is reduced.
The formation of the segregation layer (4) is confirmed by EPMA analysis. The present invention
has been made to eliminate such conventional drawbacks, and it is an object of the present
invention to provide a highly efficient acoustic transducer free of segregation. The configuration
is the same as in FIG. 1, and a metal container, an acoustic conversion piezoelectric element
provided in the wave transmitting / receiving unit in the metal container, and an opposing
surface of the metal container and the acoustic conversion piezoelectric element In an acoustic
transducer having an adhesive layer for integrating a metal container and an acoustic conversion
piezoelectric element, the adhesive layer is made of Ag and L &. The acoustic conversion
piezoelectric element is a sheet of LiNb 0 °, and the compounding ratio of adhesive layer Ag to
Li is about 3 wt% of Li.
2, the scope of claims
The following is a detailed description of the present invention by way of examples: ig-3 I, i paste
(Li 3 wt qb, remaining 1 p Ag), 20 φ × 3.6 t LiNbO, piezoelectric element (3) on both sides Coat
one more layer. After drying at room temperature, it is further coated. After drying, it is coated
and placed on the 8U8304L transmission / reception unit (2) before drying, and then the
electrode (5) of 5U8304L is placed on the acoustic conversion piezoelectric element (3) through
the adhesive layer. It is put into an electric furnace as it is, and ai is heated to 700 to 900 ° C. in
ai (the temperature is raised with a second and then fired to obtain an acoustic transducer of an
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adhesive layer (3) having a thickness of 50 μm. Take the oxide layer outside the metal container.
Thereafter, a conductor (6), a core wire (7), a metal-coated cable (8) and the like are formed in
the same manner as in the conventional example to complete an acoustic transducer. As a result
of disassembling the completed acoustic transducer and analyzing the adhesive layer (4), no
segregation of Ll was observed. A friend comparing the characteristics of this acoustic transducer
with that of a conventional acoustic transducer. The measurement method is a method in which a
constant output is oscillated from one PZT oscillator, and the respective outputs when received
by an acoustic transducer which is an object to be measured on the other side are read at the
voltage level of the synchroscope. The results are shown in FIG. 3. It is confirmed that the
sensitivity of the present invention shown by b is higher than that of the conventional acoustic
transducer shown by a. It was done. 'In addition, after 10 oO hours of the life test at high
temperature 600 ° C, the reception power of the * following acoustic transducer decreased to
half of the 0 hour, but that of the present invention was hardly reduced. As a result of
experimenting for the concentration of Ll, it was found that about 3 wtlll (2.51 to 3.5%) of Li is
optimum. If the amount of LA is too large, the melting point decreases, so it can not withstand
use under high temperature conditions. 9 If the amount of Li is too small, the melting point will
be high, but the metallurgical container (SUS) will oxidize and the adhesion strength of the
adhesive layer will decrease. . The above-mentioned acoustic transducer of the present invention
is characterized in that the adhesive layer is composed of Ag and Ll, and the receiving sensitivity
is extremely high as compared with the conventional acoustic transducer (and further higher
temperature) It has the special effect of enduring long-term use at the same time.
4. Brief description of the drawings. FIG. 1 is a schematic cross-sectional view of the acoustic
transducer, EndPage: 2 FIG. 2 is a diagram for explaining the defect of the adhesive layer of the
conventional acoustic transducer, and FIG. It is the figure which compared and measured the
receiving sensitivity of and this invention. 2 °° · ° wave transceiver section 3 ...... acoustic
transducer piezoelectric element 4 ----- adhesive layer (7317) Charge 1 person Attorney law near
KenYu (and one other) Figure 1 EndPage: 3
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