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The present invention relates to a magnetostrictive vibrator used for generating ultrasonic waves,
and the cleaning effect is remarkable when the vibrator according to the present invention is
used for ultrasonic cleaning. First, conventional general magnetostrictive vibration Explain the
child. In general, the magnetostrictive vibrator is made of a magnetostrictive material having a
half wavelength (2/2) resonance length. The magnetostrictive material that is stretched or
contracted by a magnetic field is strained beforehand by giving a constant DC magnetic field
oHoc as a bias magnetic field, and superimposing the high frequency AC magnetic field HAC on it
causes the material to expand and contract following the AC magnetic field. It occurs around a
pre-set strain. FIG. 1 is a diagram showing this characteristic. If the length of the material in the
expansion and contraction direction is equal to half of the elastic resonance wavelength λ
corresponding to the frequency of the high frequency, a large strain larger than the given strain
is generated. The magnetostrictive vibrator utilizes this phenomenon, and FIG. 2 is an excitation
method and an amplitude-darkness characteristic diagram in the case of longitudinal vibration
which is vibrated in the length direction. As shown in FIG. 2 (a), a direct current (DC) bias current
■ Dc is allowed to flow through the exciting coil 2 wound around the magnetostrictive vibrator 1
and a magnetic field 0HDC given to the vibrator is a high frequency (abbreviated as AC) current
IAC. It is well known that when the magnetic field HAC is superimposed, the distribution of
amplitude and strain is generated on the direction axis of the magnetic field as shown in (b). FIG.
3 is a diagram showing an example of the structure of an actual vibrator, in which the so-called
rectangular vibrator 3 has a small magnetic resistance of DC and AC, and has a form easy to flow
−1, 1D and IAc. Particularly, (b) and (c) are those in which a DC magnetic field is generated by
the permanent magnet 4 in order to facilitate the application of the magnetic field and the AC
magnetic field. The point to be noted here is that in the relationship between the direction of
strain generated in the magnetostrictive material (i.e., a small strain of elongation e1 or a large
strain of contraction 2) and the direction of the alternating magnetic field, (l) one is + or- In this
case, the other is always + or-, and (2) the length of λ / 2 resonance, and hence the relationship
of (1) is established over the entire length. Next, the conditions of harmonic vibration will be
described. The above description is for the case where the vibrator is made to have λ / 2
resonance, but it is also possible to use a magnetostrictive material as a resonant vibrator having
a length of nλ / 2 (n is an integer of 2 or more). However, high frequency drive by DC bias
limited to one like λ / 2 resonance is impossible in relation to DC bias. Assuming that this is
possible, the following disadvantages occur. FIG. 4 is a relationship diagram of amplitude and
distortion at resonance due to longitudinal vibration in the transducer axial direction assuming a
λ resonance and assuming DC bias oHD (a constant, but the problem here is distortion If a half
of the distribution generates distortion in the + direction and the other half in the − direction,
the direction of the corresponding alternating magnetic field HAC can be seen from the
relationship in FIG. Since the strain corresponding to point b is point b ', the former I (the
direction of Ac should be +, the direction of the latter HAc should be-, and the positive and
negative directions of the HAC as shown in FIG. 4) Need to co-exist.
However, in order to provide this more HAC, it is impossible to do so unless the magnetic path is
divided into two and HACs of opposite directions are simultaneously given to each. On the other
hand, a method of simultaneously providing 0 HDe in two split magnetic paths in opposite
directions and simultaneously adding HAC is also conceivable but is not practical. That is, in the
conventional usage, excitation can be performed only at a single resonance frequency (a
frequency of approximately 2/2 resonance), and there is no method of driving at two or more
resonance frequencies with a single oscillator. The strain transducer is characterized in that it
enables excitation drive separately at multiple resonance frequencies, which is highly effective in
the field of ultrasonic cleaning 0, that is, the cleaning effect by the standing wave field in general
ultrasonic cleaning Uneven cleaning due to the constant standing wave distribution can not be
avoided. As a method of eliminating this drawback, for example, ultrasonic waves of two
frequencies are temporally shifted and alternated to obtain a uniform cleaning effect by different
standing wave distributions. However, since it is necessary to distribute two different transducers
at different positions, it is necessary to generate separate sound fields in spatially different parts
in the cleaning tank, and the effect is uniform in relation to each other. Is not always sufficient. In
order to improve this point, it is necessary to generate sound fields of different frequencies in the
same space. The present invention is a means for this purpose and will be described in more
detail below. The present invention applies a DC bias to a resonator having a length of n × λ / 2
resonance limited to the λ / 2 resonance part of strain and superimposes an AC magnetic field
at that point. 2, 2 (λ / 2), 3 (λ / 2), ················ n / (λ / 2) / t s / s s / s + · · · ...... Propose how to
make and use a vibrator having n resonance frequencies of In. FIG. 5 is a diagram for explaining
the principle of the present invention, in which n is an even number 4; Select the one j / 2 long
point (only one direction) of distortion when exactly 4 (λ / 2) resonance is generated, for
example, form a U-shaped excitation magnetic path 5 as shown in the figure, and use IDC as a
bias When the high frequency current IAC is superimposed while causing the current to flow
through the exciting coil in advance, distortion generating the driving force of the longitudinal
wave is generated at the 2/2 position, and resonance can be performed at the frequency ft
corresponding to λ / 2 over the entire length. Moreover, the relationship between amplitude and
distortion as shown in FIG. 5 is maintained. Here, the same resonance occurs at either frequency
f or f4 corresponding to Fi2λ / 2; λ '/ 2 or 4λ / 2 = λ' / 2.
FIG. 6 is a strain distribution diagram of each resonance mode over the entire length of the
vibrating body shown based on the minimum frequency and the number of two vibrations in
order to facilitate the above understanding and focusing on the strain distribution. In this figure,
the λ / 2 resonant half wavelength and the resonant frequency with respect to the total length t
of the vibrating body are λ1 / 2 and f +, respectively, and the nodes (nodes) of the strain
distribution are IAI + 2A1 as shown. Similarly, for a resonance whose half wavelength is 1/2 of
the total length t, λ * / ′ ′ + 7211A2 +212 + 312 is given, and λ8 / 2sfs... f4 "" "" 'IA4 + 214 +
8 A4 * 4 A4 + 5 A4 [lambda] s "+" "" IAII + 3 As + sA1 4 AS + 5 A5 + A5. Here, the following
relationship holds: 00J, / 2 = 2 (λg / 2) = 3 (us / 2) = 4 (λ4 / 2) = 5 (As / 2) ′ ′.... ··· · · · · · · fl =
f2 / 2 = fs / 3 = fa / 4 = fs 15 ■ IAI + IA! +IA! + IA4 + IAI are in the same position. ■ 2 AI +
3 A 2 + 4 A 3 + 5 A 4 + a As are at the same position. Now, in the section of u (lAt-zAs) and
(5A52A1) which can reasonably be excited for any of the above five resonance frequencies, this
is the section where the section length is the longest. The excitable section is the section in which
the phase of distortion is, for each resonance of any frequency, the same phase, that is to say, for
example, only one of expansion and contraction. The invention will now be described by way of
example. In a practical vibrator, the number of resonance frequencies can be limited due to the
structural limitation and asymmetry, and the above-mentioned {circle over (1)} and {circle over
(1)} signs do not hold and only approximately holds. FIG. 7 (a) shows 281d (a pi-type ferrite
vibrator for z bonded to a top concentrated load (Top-toad) at 281 d which is one of the
commercially available standard products, and the resonance frequency f! Is a cross-sectional
view of 26 jets, in which 6 is a π-type ferrite vibrator, 7 is an intermediate metal plate, 8 is a
permanent magnet for biasing, and 9 is a coil for excitation. The strain distribution diagram of
the vibrator in the case where the vibration is radiated into water through the intermediate metal
plate 7 using this vibrator is as shown in FIG. 7 (b). In the figure, 10 represents a strain
distribution of 26 kHz, and 11 represents a strain distribution of 57 × 2, respectively, which are
obtained by estimating the strain distribution from the amplitude measurement value and
plotting the strain distribution.
Here, the nodal part of the amplitude distribution at 26 kHz is the abdomen of the strain
distribution, but its position is about 56- from the end of the leg. Therefore, the permanent
magnet 8 was placed on the side of the head from the position and then driven at a frequency of
57 kHz, which is about twice 26 kHz, to cause the oscillator to resonate. In an example in which
eight such transducers were placed at the bottom of an ultrasonic bath and used as an ultrasonic
cleaning bath, it was possible to drive at a synthetic output of 150 W at each frequency of 26
kHz and 57 kHz. In actual driving,%) cHz and 57 kHz drive sources are used to alternately
establish two-frequency sound fields by alternately exciting the vibrators from the respective
driving sources. In the conventional two-frequency alternating drive system, two sets of
oscillators are prepared according to the resonance frequency of the magnetic field and
distributed at different locations, so that the sound field of each frequency is spatially effective.
There was a drawback that the range was divided. On the other hand, in the present invention,
since two-frequency vibration is possible with the same vibrator, there is no division of the sound
field due to the frequency and it is suitable for the purpose of obtaining a uniformed sound field.
FIG. 8 is a perspective view (a), a side view (b), and a strain distribution chart (e) at each
resonance frequency according to another embodiment of the present invention. A cylindrical (or
prismatic) metallic resonator is bonded as a concentrated load 17. The reference numeral 18
denotes a bias permanent magnet, and 19 denotes an excitation coil. In this example, excitation
drive can be performed at multiple frequencies, for example, 20 kHz, 40 kHz, and 60 kHz. In this
case, since the value of Q of the metal resonator is high, the frequency of the composite or
coupled resonance of the vibrator 16 and the resonator 17 becomes a value close to the
harmonic frequency of the metal resonator. The legs of the 20 kHz oscillator had a length
sufficient to wind the 3-frequency coil. Figure 20 (c) shows 20 cities. 401d (z, strain distribution
of the vibrator at each frequency of 60 kHz is shown by curves of 20, 21 and 22, respectively.
FIG. 9 shows a side view (a) of still another embodiment of the present invention and a strain
distribution chart (6) at each resonance frequency. This example shows a structure in which the
winding position of the excitation coil is separated from the head, and two permanent magnets
8a and 8b are attached in opposite directions to each other as shown. The mounting position of
the permanent magnet may be set to the same phase part of the strain distribution. As described
above in detail, in the present invention, when the magnetostrictive vibrator is configured to have
at least two or more resonance frequencies, distribution characteristics of distortion of the
vibrator at all resonance frequencies to be used, that is, vibration. Focusing on the mode, DC bias
and high frequency excitation are applied to a part of the common section in the vibrator having
the same phase in the strain distribution map along the vibrator at each resonance frequency, for
any resonance frequency. Can also obtain an oscillator that can be excited.
As described above, the use of such switching of the excitation frequency of the vibrator has a
remarkable effect on cleaning particularly for practical use.
Brief description of the drawings
Fig. 1 is a characteristic side view of a general magnetostrictive vibrator, Fig. 2 is a structure of a
vibrator for generating longitudinal vibration (a) and a strain characteristic view (b), and Fig. 3 is
an actual vibrator side Fig. 4 is a characteristic diagram of amplitude and distortion at one
wavelength resonance, Fig. 5 is an explanatory view of the principle of the present invention, and
Fig. 6 is a resonant wave whose half length is the total length of the vibrating body and its
harmonics. FIG. 7 is a cross-sectional view (a) of the π-type ferrite magnetic vibrator according
to the present invention, FIG. 7 is a strain distribution map (b) of the vibrator, and FIG. 8 is
another magnetostriction according to the present invention. An appearance view (a), a side view
(b) and a strain distribution view (C) of the vibrator, and FIG. 9 are a side view (a) and a strain
distribution view (b) of another embodiment of the present invention.
1.3 · · · oscillator, 2, 9.19 · · · excitation coil, 4, 8.8a, 8b, 18-permanent magnet, 5, 6, 16 · · · ferrite
oscillator, 7.17 · · · Top load, 10, 11, 20, 21, 22 ... strain distribution characteristics. 1 Flash
Figure 2 + 01 Tbl 3rd η 4 Flash ¥ 75 Flash A