JPS551705

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DESCRIPTION JPS551705
Description 1, title of the invention
'Tht magnetic acoustic transceiver
3. Detailed Description of the Invention The present invention relates to an electromagnetic
acoustic transducer, particularly suitable for transmitting a sound wave to a medium of a high
temperature atmosphere or a high radiation atmosphere and for receiving a sound wave from
such a medium. It relates to a wave device. For example, in a device such as Na) IJ um
fluoroscope, ultrasonic flow velocity meter, □□□□ ultrasonic flaw detector, or abnormal sound
detector, the sound wave emitted to the medium, the sound wave from the medium is detected
Needs a so-called acoustic-electrical converter. Heretofore, a piezoelectric element has been used
as this type of acoustic-electrical conversion device. That is, a piezoelectric element having
electrodes formed on both sides is adhered to a diaphragm by silver brazing or the like, and
transmission is performed by thickness vibration generated by applying a high frequency voltage
to both electrode surfaces, or conversely pressure The induced voltage generated by the change
was detected and received. However, when it is necessary to use it in a high temperature
atmosphere or a place where the temperature change is severe (d1 piezoelectric element may be
damaged due to the difference in thermal expansion with the diaphragm, or it may be used in a
high radiation atmosphere) However, there is a disadvantage that the characteristics of the
piezoelectric element change due to high radiation. An object of the present invention is to solve
such drawbacks of the prior art and to provide an acoustic transducer which can be used in a
high temperature atmosphere, a medium with rapidly changing temperature or a medium with a
high radiation atmosphere. That is, the present invention relates to an electromagnetic acoustic
transducer, wherein a magnetic pole pair and an electrode pair are provided so as to be
orthogonal to each other in the conductive medium storage unit, and the conductive medium in
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the storage unit is placed in a magnetic field. It is configured to interconvert the longitudinal
wave vibration of the conductive medium in the direction perpendicular to both directions of the
pole pair and EndPage: 1 electrode pair and the electrical signal between the electrode pair, and
convert the acoustic vibration into an electrical signal. There are acoustic receivers, and
conversely, acoustic transmitters that convert electrical signals into acoustic vibrations.
Hereinafter, the present invention will be described in detail based on the drawings. The acoustic
receiver and the acoustic transmitter have almost the same structure and can be used either
depending on the usage. FIG. 1 is a structural explanatory view of an embodiment of an acoustic
transmitting and receiving device according to the present invention, and FIGS. 2 and 3 show
cross sections thereof. The openings 2a and 2b are provided in a pair of opposing surfaces of the
case 1, and the peripheral portions of both the openings 2a and 2b are connected by a pipeline 3.
The inside of the pipe 3 and the outside of the case 1 are in communication. The inside of such a
conduit 3 corresponds to the conductive medium storage unit 4. A pair of pole pieces 5 a and 5 b
are provided at right angles to the axial direction of the conduit 3 so as to sandwich the
conductive medium storage unit 4. In this embodiment, the excitation winding 6 is applied to the
substantially U-shaped magnetic core 5 so that the tip of the magnetic core 5 is located in the
vicinity of the outer wall of the conduit 3.
The pole pieces 5a and 5b are formed in a narrow shape, and the width d thereof is about half
the wavelength of the sound wave. Furthermore, a pair of electrodes 7a and 7b are provided so
as to sandwich the conductive medium storage portion 4 in the direction perpendicular to the
axial direction of the conduit 3 and the direction connecting the pole pieces 5a and 5b. The
excitation cable 8 and the signal cable 9 are connected to both ends of the excitation winding 6
and the electrodes 7a and 7b, respectively, and are drawn out of the case 1. Next, the operation,
usage, etc. of this device will be described. Case 1 is placed in a conductive medium. The
conductive medium is freely accessible in and out of the conduit 3. When a current is supplied
from the excitation cable 8 to the excitation winding 6 to excite the magnetic core 5, a magnetic
field is formed in the conductive medium storage portion 4 between the pole pieces 5a and 5b.
Now, when used as an acoustic receiver, the voltage appearing between the electrodes 7a and 7b
may be detected. Generally, when a conductive object vibrates in a magnetic field, an
electromotive force is generated in a direction perpendicular to both the direction of the
magnetic field and the vibration direction of the object. Since the sound wave is also a vibration
of the object, an electromotive force is generated, and the sound wave can be detected by
extracting the electromotive force to the outside by the signal cable 9 and measuring it. The
current supplied to the excitation winding 6 may be direct current or alternating current. Also,
permanent magnets may be used instead of the electromagnets. As described above, the width d
of the magnetic pole should not be very wide. This is because the narrower the pole width d, the
wider the frequency range of the medium that can be received. For example, assuming that the
width d of the magnetic pole is about one wing, acoustic vibration at about I MHz can be
detected. Since the electrical signal obtained by the signal cable 9 also includes noise
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components due to the flow effect of the conductive medium and the low frequency vibration
phenomenon, only the desired acoustic vibration is separated and detected therefrom. Therefore,
the SN ratio is improved by passing a band pass filter that is at the frequency of the sound wave
to be detected. In addition, when the magnetic field is vibrated in the direction of strengthening
the electromotive force in synchronization with the vibration of the conductive medium, the SN
ratio is improved. Next, in the case of using as an acoustic transmitter, a current is caused to flow
between the electrodes 7a and 7b. Then, since the conductive medium vibrates in a direction
perpendicular to both the magnetic field and the current, that is, in the axial direction of the
conduit 3, sound waves can be emitted in the direction of the conduit 3. In this case, as in the
case of the acoustic receiver, a direct current or alternating current electromagnet or permanent
magnet may be used, and the current flowing between the electrodes may be direct current or
alternating current, but at least one of them is to be transmitted. It must be an alternating current
that was at the frequency of the sound wave.
The same applies to the shape of the magnetic pole 5ag 5b as in the case of the acoustic wave
receiver. Although the above embodiment is the case where the medium is conductive, the
present invention can be applied to the case where the medium is nonconductive or low in
conductivity. In such a case, as can be seen from the cross-sectional view of the fan 4, a sealed
space is formed by the partitions 10 a and 10 b at the center of the conduit 3, and the space is
used as the conductive medium storage unit 11 A conductive medium such as liquid sodium is
enclosed. The remaining configuration may be similar to that of the above embodiment. A pair of
magnetic pole pieces 5 a and 5 b and a pair of electric EndPage: two poles (not shown) are
provided in the conductive medium storage portion 11. The both ends of the conduit 3 (d
communicate with the outside of the case 1 so that the surrounding media can flow freely. The
operation as the acoustic transceiver is the same as that of the above embodiment. In the case of
an acoustic receiver, the acoustic vibration of the nonconductive or low conductive medium
outside the case 1 is transmitted to the conductive medium in the conductive medium container
11 through the partition walls 10a and 10b, and the conductive medium Also vibrate. Therefore,
by detecting the vibration of the conductive medium, the acoustic vibration of the non-conductive
or low conductive medium can be detected. Conversely, in the case of an acoustic transmitter, if
the liquid in the conductive medium container 11 is vibrated, the vibration is transmitted to the
external nonconductive or low conductive medium through the partition wall 10a and + Ob.
become. As described above, the acoustic transducer according to the present invention can be
used in high temperature, high radiation atmosphere because it can be backed by metal material
or inorganic material that can withstand high temperature, high radiation, not crystal material or
organic material. Also, it can sufficiently withstand sudden temperature changes. FIG. 1 is a
structural explanatory view showing an embodiment of the acoustic wave transmitting and
receiving apparatus according to the present invention, FIG. 2 is a sectional view of 1-n of FIG. 2
and FIG. 3 is a sectional view of 3-- FIG. Fig. 4 is a cross sectional view showing another
embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Case, 3 ... pipeline, 4, 11 ...
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electroconductive medium storage part, 5 ... magnetic core, 5a, 5b ... pole piece, 7a, 71) ...
electrode, 8 ... Excitation cable, 9 ... signal cable. Applicator of the Dynamic Agent Reactor for
Nuclear Fuel Development Corp. Atsuko Ohgaki Agent Atsushi Araki Figure 2 EndPage: ３
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