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JPS6385355

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DESCRIPTION JPS6385355
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electric 81 foot acoustic wave transducer capable of generating an oblique SH wave, which is
used, for example, in an ultrasonic flaw detector. [Prior Art] FIG. 6 is a perspective view showing
the construction of a conventional electromagnetic ultrasonic transducer capable of generating
SH waves for oblique angles. As shown in FIG. 6, the conventional im ultrasonic transducer has a
single magnet on one side of a magnet block in which a plurality of magnets 1 are sequentially
arranged such that their magnetization directions are opposite to each other. The rectangular coil
2 is mounted. FIG. 7 is a view showing a state of use of the conventional electromagnetic
ultrasonic transducer of the above construction. That is, in the state where the electromagnetic
ultrasonic transducer is disposed close to the subject 3 as shown, the high frequency 1! When
the current flows, an eddy current J is generated near the surface of the subject 3 and a magnetic
field B in the vertical direction is applied by the magnet 1 at the same time. Then, due to the
interaction between the eddy current J and the magnetic field B, a force in a direction orthogonal
to the paper surface acts on the subject 3. Since this force is alternately 180 ° different in
direction at the width pitch of the magnet 1, the imaging dynamic phase of the ultrasonic wave
generated by the above force is also 18 ° different. Therefore, the synthesized wavefront W by
the ultrasonic waves propagates in the oblique direction as illustrated. Thus, the SH wave picked
up in the direction orthogonal to the paper can be transmitted as an ultrasonic wave incident in
the oblique direction. Delivery is performed by the reverse process of the above. [Problems to be
Solved by the Invention] The above-mentioned conventional electromagnetic ultrasonic
transducers have the following problems. Since the magnetization directions of adjacent magnets
are alternately different, the magnetic flux emitted from the N pole of one magnet 1 enters the S
pole of the adjacent magnet. As a result, the magnetic flux does not spread far beyond the end
face of the magnet, and the magnetic field component in the vertical direction is extremely small.
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For this reason, when the gap between the electromagnetic ultrasonic transducer and the subject
3 increases, the sensitivity drops sharply. Therefore, for example, if the surface of the subject 3 is
uneven, the sensitivity significantly decreases due to the influence thereof, and the required
function can not be exhibited. Therefore, according to the present invention, the magnetic flux
spreads to a position far from the end face of the magnet, the magnetic field component in the
vertical direction becomes sufficiently large, and even if the gap with the object is large, the
decrease in sensitivity is relatively insignificant. An object of the present invention is to provide
an electromagnetic ultrasonic transducer capable of stably exhibiting a required function. [Means
for Solving the Problems] In order to solve the above problems and achieve the object, the
present invention takes the following means.
That is, a plurality of pairs of magnets in which a pair of magnets are combined and arranged
such that the magnetization directions are opposite to each other are arranged with the
magnetization directions aligned such that the magnetization directions are the same between
adjacent magnet pairs. Then, rectangular coils are mounted, for example, in a letter shape so as
to cover the respective magnetic pole surfaces of the respective magnet pairs, and pulse-like
excitation currents are sequentially supplied to the respective rectangular coils with a phase
shift. . [Function] By taking the above means, the following function is exhibited. That is, since the
magnetization directions of adjacent magnet pairs are arranged to be the same, the magnetic flux
spreads to a position far from the end face of the magnet and the perpendicular magnetic field
component increases, so that the sensitivity decrease is small even if the gap with the object is
large. It can be done. In addition, since a rectangular coil is attached to each magnet pair, and
pulse-like excitation current having a short time width is sequentially supplied to each
rectangular coil with a phase shift, each coil is adjacent to the object surface. Due to the current
flowing through the eddy currents, eddy currents flow sequentially. As a result, a force is
sequentially generated in the subject due to the interaction with the magnetic field, and the
ultrasonic waves generated by this force propagate obliquely. FIG. 1 (a) <b) is a front view and a
side view showing an embodiment of an electromagnetic ultrasonic transducer according to the
present invention. FIG. 2 is a perspective view showing a part of the embodiment cut away. In (a),
(b) and (b) and (b) in FIG. 2, a plurality of (+ 'r, 11a and 11b, 12a and 12b, 13a and It is a pair of
magnet pairs (three pairs in this embodiment). A spacer 14 intervenes between the magnets in
each pair of magnet pairs 11a and 11b 112a and 12b, and 13a and 13b. Then, as shown in FIG.
1 (a), each magnet pair is disposed and fixed relative to the support plate 15 in a state where the
magnetization directions are aligned so that the magnetization directions are the same between
adjacent magnet pairs. . In each set of magnet pairs, a rectangular coil 21.22 ° 23 is bent in a
letter shape and attached so as to cover the respective pole faces. FIG. 3 shows a configuration of
a transmitting / receiving circuit for generating an ultrasonic wave by supplying a pulse-like
excitation current to each coil 21.22.23 of the electromagnetic ultrasonic transducer and for
receiving a reflected ultrasonic wave. It is a block diagram. In FIG. 3, reference numeral 30
denotes a pulse generator. The high frequency pulses generated by the pulse generator 30 are
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delayed by a predetermined time each by a delay circuit 41.42.43 and then pulsed by a pulser
51.52.53. It is converted into an excitation current and supplied to each coil 21. 22.23.
Thus, ultrasonic waves are generated and transmitted into the subject. The reflected ultrasonic
waves from the subject are respectively received by the coils 21 ° 22.23, amplified by the
amplifiers 61 ° 62.63, and then delayed by the delay circuits 71.72. Phased and added /
combined by the adding circuit 80. The received and combined signal is displayed by the display
90. The generated pulse signal from the pulse generator 30 is also given to the display 90, and is
simultaneously displayed. Next, the operation of this embodiment configured as described above
will be described. When the pulse generator 30 of the transmission / reception circuit is
operated, pulse-like excitation currents of different phases having a predetermined time delay are
sequentially supplied to the coils 21. 22. 23 as shown in FIG. 4. Now, focusing attention on the
point of time when the excitation current is supplied to the rectangular coil 23, as shown in FIG.
5, an eddy current J is generated in the vicinity of the surface of the object 3 corresponding to
the position of the rectangular coil 23. A perpendicular magnetic field B by the magnets 13a and
13b acts on this portion. Therefore, due to the interaction between the eddy current J and the
magnetic field B, a force F in the direction orthogonal to the paper surface is generated, and an
SH oscillation wave is generated. The same vibration occurs when the excitation current flows
through the other coils 21 and 22. However, since the generation time point of each vibration is
deviated, coil 21 ° is generated when vibration is generated by the coil 23 as illustrated. The
wave front of the imaging movement by 22 is W1. It is shown as W2. Therefore, the combined
wavefront W of these wavefronts travels obliquely as shown. Delivery is done in the reverse
process. As described above, according to the present embodiment, since the magnetization
polarities of adjacent magnet pairs are aligned in the same direction, magnetic flux does not flow
between adjacent magnet pairs. Therefore, the perpendicular magnetic field exists relatively far
from the end face of the magnet. As a result, even when the gap between the object 3 and the
subject 3 is relatively large, the significant decrease in sensitivity due to the gap is suppressed.
Then, since pulse-like excitation currents whose phases are shifted are sequentially supplied to
each coil, ultrasonic waves can be generated in the inclined direction even if the magnetization
polarities of adjacent magnet pairs are aligned in the same direction. And the above pulse-like
excitation? Since the four currents are short in time width, there is no interference between the
currents flowing to the other coils, and there is no influence of the interference, and the synthetic
wave itself becomes a pulse with short time width. There is an advantage that the temporal
resolution is high.
The present invention is not limited to the above-described embodiment, and it goes without
saying that various modifications can be made without departing from the scope of the present
invention. According to the present invention, a plurality of magnet pairs in which a pair of
magnets are combined and arranged such that the magnetization directions are opposite to each
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other are magnetized so that the magnetization directions are the same between adjacent magnet
pairs. The rectangular coils are mounted, for example, in the shape of a letter so as to cover the
respective pole faces of the respective magnet pairs, and the pulse-like excitation current is
sequentially phase-shifted in these rectangular coils. The magnetic flux spreads to a position far
from the end face of the magnet, and the magnetic field component in the vertical direction
becomes sufficiently large. Even if the gap with the object is large, the sensitivity decrease is
relatively small. It is possible to provide an electromagnetic ultrasonic transducer that can exhibit
the required functions stably.
[0002]
Brief description of the drawings
[0003]
1 (a) (b) to 5 (a) to 5 (c) are views showing an example of the seat according to the present
invention, and FIGS. 1 (a) and (b) are front and side views of an electromagnetic ultrasonic
transducer, 2 is a perspective view showing the electromagnetic ultrasonic transducer partially
cut away, FIG. 3 is a block diagram showing the configuration of the transmission / reception
circuit, and FIG. 4 is a diagram showing an excitation current waveform to each coil, The figure is
a figure for demonstrating an effect ¦ action.
FIG. 6 is a perspective view showing the structure of the conventional example, and FIG. 7 is an
operation explanatory view of the conventional example. 11a and 11b, 12a and 12b, 13a and
13b: magnet pair, 14: spacer, 15: support plate, 21.22.23: rectangular coil, J: eddy current, B ···
Magnetic field, F: force, W: combined wave front, W1, W2: wave front. Patent Reinforcement
Agent Patent attorney Suzue Takehiko (a) (b) Fig. 1 Fig. 2 Fig. 2 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 1
Case display JP Patent Application No. 61-231919 2, Patent application (620) Mitsubishi Heavy
Industries, Ltd. 4, re-agent 5, spontaneous correction 7, contents of correction (1) Correct
"Invention Name" to "Electromagnetic Ultrasonic Transducer" to match that of the request. (2) As
indicated in the written statement and attached sheet of the specification attached at the
beginning of the application (no change in the contents) 1, the display of the case No. Patent
applicant (620) Mitsubishi Heavy Industries, Ltd. 4 back agent, Chiyoda-ku, Tokyo 3-7-2 UBE
Building 6, correction target 2, claim magnetizing magnet pair A plurality of pairs of magnet
pairs arranged in a direction opposite to each other are arranged with their magnetization
directions aligned so that the magnetization direction is identical between adjacent magnet pairs,
and the respective pole faces of the respective magnet pairs A rectangular ultrasonic transducer
is mounted so as to cover each of the rectangular coils, and pulse-like excitation currents are
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sequentially supplied to the respective rectangular coils with a phase shift.
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