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DESCRIPTION JPH0328756

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DESCRIPTION JPH0328756
[0001]
[Industrial field of application] The present invention relates to an ultrasonic probe, for example,
used for ultrasonic wave transmission and reception to detect defects in a test material and
measure the thickness of a test material, particularly in a short distance region. It relates to the
improvement of the signal to noise ratio. 1 [Prior Art] A piezoelectric vibrator made of quartz,
lithium niobate, or a single crystal piezoelectric material is used for an ultrasonic probe. The
single-crystal piezoelectric vibrator is provided over the entire surface on one side or the other
side (the other electrode is also used for the test material) of the single-crystal piezoelectric
vibrator as an electrode by a method such as baking of silver or the like. For example, when a
disk-like single crystal piezoelectric vibrator is used for an ultrasonic probe and a pulse signal is
applied between the two electrodes and energized, vibration of a predetermined moment in the
thickness direction of the single crystal piezoelectric vibrator occurs. It is generated and an
ultrasonic pulse is thrown out. At the same time, parasitic vibration is generated at the peripheral
edge of the single crystal piezoelectric vibrator and propagates in the radial direction of the
vibrator to reach the opposing peripheral edge where it is converted into an electrical signal by
the piezoelectric effect. Therefore, an interference signal due to the odd vibration appears in the
short distance region after the ultrasonic pulse transmission. Fig. 8 is an operation waveform
showing an example of conventional detection of defects in a test material, open in Fig. 8 for
transmitted waves, ? for bottom surface echoes countered from the bottom of the test material,
and ? for defects in the test material 2 Defective echoes reflected from the surface, ? are
interference signals, and interference signals due to strange vibration ? also change the level
etc. depending on the contact state of the ultrasonic probe with the test material in ultrasonic
flaw detection and thickness measurement Do. The interference signal is close to the timing of
the appearance of the respective signals used for defect detection and defect evaluation near the
surface of the test material and thickness measurement of the thin test material. In particular, in
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the case of micro defect detection and thickness measurement of a material with remarkable
attenuation, the signal level becomes small, and therefore the effect of the interference signal
becomes noticeable as the gain of the reception signal is increased. [Problems to be Solved by the
Invention] In the conventional ultrasonic probe as described above, when the single crystal
piezoelectric transducer is energized to emit ultrasonic waves, the vibration caused by the
vibration is generated in the single crystal piezoelectric transducer at the same time. In the short
range area after ultrasonic wave transmission, the disturbance signal which is caused by the
strange vibration appears. When detecting defects in the vicinity of the surface of the test
material using an ultrasonic probe or measuring the thickness of a thin test material, the 3 defect
echoes, the thickness measurement signal and the interference signal are close in timing of their
appearance In an extreme case, the timings coincide and the signal-to-noise ratio degrades and
the respective signals can not be identified. Therefore, the minimum flaw detection distance
increases because it is impossible to detect minute defects in the vicinity of the surface or to
make a correct defect evaluation, and in thickness measurement, the reproducibility decreases
and the measurement accuracy also decreases.
Moreover, since the level etc. of a disturbance signal are fluctuate | varied according to the
contact state to the to-be-tested material of an ultrasonic probe, there existed a problem that the
identification became still difficult. The present invention has been made to solve such problems,
and can suppress the influence of an odd vibration generated in a single crystal piezoelectric
vibrator to improve the signal-to-noise ratio, so that minute defects in the vicinity of the surface
of a test material It is an object of the present invention to obtain an ultrasonic probe which is
improved in the detection or correct defect evaluation as well as the minimum flaw detection
distance and in which the reproducibility of thickness measurement of a thin test material is
improved to improve measurement accuracy. [Means for Solving the Problems] The ultrasonic
probe according to the present invention has a shape similar to the outer shape of a single
crystal piezoelectric vibrator and having a large number of irregularities along a small outline. An
electrode is provided on one surface of a single crystal piezoelectric vibrator. [Operation] In the
present invention, the ultrasonic probe has a shape similar to the outer shape of the singlecrystal piezoelectric vibrator on one surface of the single-crystal piezoelectric vibrator and
having a large number of asperities along a small outline. Since the electrodes are provided,
when the single crystal piezoelectric vibrator is energized through the electrodes, the
interference signal due to the odd vibration generated simultaneously with the emission of the
required mode ultrasonic wave is the electrode and the single crystal piezoelectric vibrator
Depending on the relative size of the as well as its shape, the occurrence can be suppressed.
Therefore, the signal-to-noise ratio in the short range region is improved, and minute defects
detection and correct defect evaluation near the surface of the test material can be performed,
and the minimum flaw detection distance is improved. Also, the repeatability of the thickness
measurement of the thin test material can be improved to improve the measurement accuracy. 5
[Embodiment] An embodiment of the present invention will be described in detail with reference
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to the attached drawings. 1 is a front view showing an embodiment of the present invention, and
FIG. 2 is a sectional view taken along the line A-A of FIG. 1. In the figure, U indicates an ultrasonic
wave generating unit, 2 indicates a single crystal piezoelectric transducer, 3 indicates An
electrode for energizing the single crystal piezoelectric vibrator 2; a back plate 4 for attenuating
an ultrasonic wave emitted toward the single crystal piezoelectric vibrator 21; and 5 for
correcting the impedance of the single crystal piezoelectric vibrator 2. Matching coil, 6 is a sound
absorbing rod, 7 is a case, 8 is a conductor ring provided around the outer peripheral surface of
the case 7, 9 is a terminal, 10 is a moving piece made of a conductive material that moves the
test material 1 11 shows an elastic member connected to the sliding piece 10, 12 a container
made of a metal material, 13 a retainer for attaching the ultrasonic wave generating unit 1 to the
container 12, 14 a connector, and 15 a cable. In the case of the ultrasonic probe configured as
described above, the ultrasonic wave generating unit 1 is made of, for example, a single crystal
piezoelectric material such as quartz or lithium tin oxide which has the electrode 3 deposited on
one side. A disk-shaped piezoelectric vibrator 2 is housed in a case 7 made of a non-metallic
crucible, around which a conductive ring 8 is provided on the outer peripheral surface via a
sound absorbing material 6 such as rubber.
Further, the matching coil 5 is disposed between the electrode 3 to which the back plate 4 is
attached and the terminal 9 provided to the case 7. The ultrasonic wave generating unit 1 is
attached to the container 12 of metal material to which the connector 4 is attached by means of
the pressing member 13 together with the moving piece 10 to which the elastic member 11 is
connected. As a result, the terminal 9 is pressed to the pin of the connector 4 and the mass 10 is
electrically connected to the shell of the connector 4 via the elastic member 11 and the
conductor ring 8 and the container 12. The single-crystal piezoelectric transducer 2 Hekaplan 1
иии of the ultrasonic probe is coated and pressed onto a test material of a metallic material to be
subjected to defect detection or thickness measurement, the electrical signal transmitted by the
cable 15 is an electrode 3. The single crystal piezoelectric transducer 2 which is supplied with
electricity to the test material constituting the other electrode and is designed to be impedancematched is energized to generate vibration of a predetermined mode in the thickness direction,
and 7 ultrasonic wave search Ultrasonic waves are emitted from the feeler. Fig. 3 is a front view
showing an example of a disk-shaped single crystal piezoelectric vibrator, Fig. 4 shows a B-B
cross-sectional view of Fig. 3, and in the figure, 2 and 3 are the same as the above example. An
electrode 3 on which silver or the like is baked is provided on one surface of the plate-like single
crystal piezoelectric vibrator 2. As for the shape of the electrode 3, a large number of
irregularities are formed on a concentric circle having a diameter smaller than the external
dimension of the single crystal piezoelectric vibrator 2. When the single crystal piezoelectric
vibrator 2 is energized, at the same time as the throwing of the ultrasonic wave by the vibration
of the predetermined mode in the thickness direction, the odd vibration generated toward the
peripheral direction forms a contour or an uneven shape of the electrode 3 Therefore, the
distance to the peripheral edge of the single crystal piezoelectric vibrator 2, that is, the
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propagation path changes depending on the direction or the direction. Therefore, the signals
thrown out from the periphery are different in phase from each other, and the received signal
level due to the above-mentioned parasitic vibration received by the electrode 3 is reduced
equivalently and the level of the disturbing signal appearing in the short distance region is
significantly reduced. Do. By determining the size of the unevenness of the eight electrodes 3 in
accordance with the natural frequency of the single crystal piezoelectric vibrator 2, the
interference signal suppressing effect can be further improved. For example, when a crystal
oscillator with an outer diameter size of ? 32 2 M port Z is arranged on a concentric circle
slightly smaller than the above-mentioned external dimension, many irregularities of the size
related to the oscillator specific wavelength are disturbed. Level is improved by more than 15 dB.
Fig. 5 is a front view showing an example of a rectangular single crystal piezoelectric vibrator,
and Fig. 6 shows a cross sectional view taken along the line C-C in Fig. 5, and 2 and 3 are the
same as the above example. Even if the electrode 3 is steamed on one surface of the rectangular
single-crystal piezoelectric vibrator 2 and a large number of irregularities are formed along the
square contour of a size smaller than the external dimension of the piezoelectric vibrator 2 as the
shape of the electrode 3 You can do the same thing.
Although the dimensions of the electrode 3 are slightly reduced and the area is also reduced, the
sensitivity is hardly reduced. FIG. 7 is an operation waveform showing one example of defect
detection of the test material according to the present invention, and the symbols .box-solid.,
.Box-solid., .Box-solid. Has a different shape depending on the direction of the propagation path
with the peripheral edge of the single crystal piezoelectric vibrator 2, and as shown in the figure,
a disturbing signal that appears in a short distance region due to the odd vibration generated in
the single crystal piezoelectric vibrator 2. The level of ? can be significantly reduced. The signal
to noise ratio in this area can be improved by reducing the level of the disturbance signal
appearing in the near area, the reception gain is increased, and the defect detection near the
surface of the test material can detect even smaller defects. And defect assessment can be done
correctly. Therefore, the minimum flaw detection distance can be used for flaw detection of a test
material with a significantly improved thickness. In addition, even when used for measuring the
thickness of a thin test material, the reproducibility is excellent and the measurement accuracy
can be improved. Although the electrode 3 is disposed on one side of the single crystal
piezoelectric vibrator 2 in the above example, the same effect can be obtained even if the
electrodes are disposed on both sides and the above-described invention is applied to one of the
electrodes 3. 10 [Effect of the Invention] As described above, according to the simple structure in
which the outline of the electrode baked up to the single crystal piezoelectric vibrator is formed
into the predetermined shape as described above, the single crystal piezoelectric vibration is
generated simultaneously with the generation of the predetermined mode vibration. The signalto-noise ratio can be improved in the near range because the level of the interference signal
caused by the strange vibration generated in the child can be significantly suppressed. The effect
of being able to be used to perform minute defects detection and defect evaluation in the vicinity
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of the surface of the test material correctly, that is, to improve the minimum flaw detection
distance, and to improve the reproducibility in measuring the thickness of a thin test material is
there.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a front view showing one embodiment of the present invention, FIG. 2 is a sectional view
taken along the line AA of FIG. 1, FIG. 3 is a front view showing one example of a circular single
crystal piezoelectric vibrator, FIG. 3 is a cross-sectional view taken along the line B-B in FIG. 3,
FIG. 5 is a front view showing an example of the square single-crystal piezoelectric vibrator, FIG.
6 is a cross-sectional view taken along the line C-C in FIG. 5, and FIG. 11 is an operation
waveform showing an example of defect detection in a test material, and FIG. 8 is an operation
waveform showing an example of defect detection in a conventional material.
In the figure, Y is an ultrasonic wave generating unit, 2 is a single crystal piezoelectric vibrator, 3
is an electrode, 4 is a back plate, 5 is a matching coil, 6 is a sound absorbing rod, 7 is a case, 8 is
a conductor ring, 9 is a terminal, 10 is a sliding piece, 11 is an elastic member, 12 is a container,
13 is a retainer, 14 is a connector, and 15 is a cable. The same reference numerals in the
drawings indicate the same or corresponding parts.
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