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JP2007117934

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DESCRIPTION JP2007117934
PROBLEM TO BE SOLVED: To provide a bolt-clamped Langevin type vibrator capable of
obtaining a large amplitude sufficient for occurrence of cavitation even at high frequency.
SOLUTION: The total thickness formed by the thickness of the first metal plate 7 and the second
metal plate 8 and the thickness of the piezoelectric element 3 is set to be one wavelength, and
the second metal plate 8 is set. And the piezoelectric element 3 is held so that the large surface of
the first metal plate 7 and the second metal plate 8 abut each other, and the central portion is
bolt 6 By configuring a bolt-clamped Langevin type vibrator by fastening at the same time, the
expanded amplitude is transmitted to the third metal plate 9 set to a half wavelength, and a high
frequency of 3/2 wavelength as a whole is obtained. High amplitude is obtained. [Selected figure]
Figure 4
Bolt tightening Langevin type vibrator
[0001]
The present invention relates to a piezoelectric element used in a vibration system of high
intensity ultrasonic wave application, and more particularly to a bolt-clamped Langevin type
vibrator suitable for a high frequency ultrasonic wave cleaning machine.
[0002]
At present, in ultrasonic cleaning machines, piezoelectric elements are used as a drive source for
generating ultrasonic waves.
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1
Among them, an industrial ultrasonic cleaner used for cleaning a product after machining has a
large ultrasonic output, so a vibrator for generating strong ultrasonic waves called a boltclamped Langevin type vibrator. Is used.
[0003]
FIG. 1 is a side view showing an example of a bolted Langevin type vibrator. The general bolted
Langevin type vibrator 1 has a pair of disc-shaped piezoelectric elements 3 having a through hole
at the center on both sides of the electrode plate 2 and further has the same diameter as the
piezoelectric elements 3 on both sides. A disk-shaped metal plate 4 and a metal plate 5 are
disposed, and are integrally coupled by a bolt 6 at a central portion.
[0004]
FIG. 2 is a graph showing the vibration characteristics of the bolt-clamped Langevin type
vibrator. When the center of the bolt-clamped Langevin type vibrator 1 shown in FIG. 1 is 0 and
the length in the longitudinal direction is 2 L, the horizontal axis is + L for the distance to the
right end surface and −L for the distance to the left end surface. , The distance from the center
with respect to the longitudinal direction of the bolted Langevin type vibrator 1 is shown. The
vertical axis indicates the amplitude generated in the longitudinal direction when the boltclamped Langevin-type vibrator 1 is driven at the resonance frequency, and the amplitude of the
bolt-clamped Langevin-type vibrator 1 shown in FIG. The amplitude in the left direction is
indicated as-(minus).
[0005]
Α shown in FIG. 2 indicates the maximum amplitude value when driven by a certain voltage.
Here, focusing only on the amplitude of the right end face of the bolt-clamped Langevin type
vibrator 1 shown in FIG. 1, the amplitude is proportional to the voltage, and the voltage value
changing with time at the resonance frequency is synchronized with the change of the amplitude.
The horizontal axis of the graph shown in is replaced with time T, and + L is + T and -L is the
same locus as the graph with -T. At this time, it is understood that time 2T is a half wavelength of
the resonance frequency, and the full length 2L of the bolt-clamped Langevin type vibrator is a
half wavelength of the resonance frequency.
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[0006]
As a bolt-clamped Langevin-type vibrator used for industrial ultrasonic cleaning machines, one
with a resonance low frequency of 20 kHz to 50 kHz that easily generates cavitation is generally
used, but in recent years, the degree of cleaning has been increased In order to improve, boltclamped Langevin type vibrators with a high resonance frequency of 50 kHz to 200 kHz have
also been used.
[0007]
In this high-frequency bolt-clamped Langevin-type vibrator, usually, a method of increasing the
frequency by shortening the total length is used.
For example, in a bolt-clamped Langevin type vibrator having a total length of 40 mm at 50 kHz,
when the resonance frequency is about 100 kHz, the total length is shortened to about 20 mm.
[0008]
However, in this case, it is not only difficult to integrally connect the piezoelectric element and
the metal plate with a bolt, but it also becomes necessary to reduce the thickness of the
piezoelectric element. Therefore, there is a problem that the electrical input is also limited and
high output can not be obtained. As a solution to this problem, a proposal has been made to solve
by setting the total length to be 1.5 wavelengths instead of half wavelengths, and setting the total
length to 3 times the length when designed with half wavelengths. ing. Such a bolted Langevin
type vibrator is disclosed in Patent Document 1.
[0009]
Japanese Patent Application Laid-Open No. 6-254493
[0010]
FIG. 3 is a graph showing the relationship between the sound wave intensity and the frequency
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3
for generating cavitation in the ultrasonic cleaning machine.
The horizontal axis shows frequency (Hz), and the vertical axis shows minimum sound intensity
(W / cm <2>) required for cavitation generation. Further, in the graph, two levels of water as a
medium are shown in the case of deaerated water and in the case of saturated water. As can be
seen from the graph, the higher the frequency, the higher the minimum sound intensity required
for cavitation generation, and the required minimum sound intensity several times higher at 50
kHz to 200 kHz than at 20 kHz to 50 kHz normally used. I understand.
[0011]
However, in the conventional bolt-clamped Langevin-type vibrator having a resonance frequency
of 50 kHz to 200 kHz, the amplitude obtained at the same electrical input is 1.5 KHz, and the
amplitude obtained at the same electrical input is 20 kg to 50 kHz. There is a problem that it
does not change much with the mold vibrator, and as described above, the lowest sound intensity
for obtaining cavitation at high frequency can not be obtained.
[0012]
Therefore, an object of the present invention is to solve the problems of the prior art.
Specifically, it is an object of the present invention to provide a bolt-clamped Langevin-type
vibrator capable of obtaining a large amplitude sufficient for cavitation even at high frequencies.
[0013]
The present invention adopts the following means in order to solve the problems. That is,
according to the present invention, the total thickness formed by the thickness of the first and
second metal plates and the thickness of the piezoelectric element is one wavelength, and the
third metal plate is expanded by expanding the amplitude with the second metal plate. The gist is
that a large amplitude can be obtained even at higher frequencies.
[0014]
According to the present invention, there is provided a bolt-clamped Langevin type vibrator
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comprising a first metal plate, a second metal plate, a third metal plate, a piezoelectric element
and a bolt, wherein the first metal plate has an upper surface portion And a bottom surface and a
side surface, and has a female screw at the center of the top surface or bottom surface, and the
second metal plate has a top surface, a bottom surface and a side surface. The area of the bottom
surface of the second metal plate is larger than that of the top surface, and the piezoelectric
element has a plate shape consisting of the top surface, the bottom surface, and the side surface,
and has one or more. The central portion has a hole which is held in contact with the top surface
of the first metal plate and the bottom surface of the second metal plate and penetrates from the
top surface to the bottom surface, and the bolt is made of piezoelectric material. The female
screw of the first metal plate and the female screw of the second metal plate are screwed through
the holes of the element, and the first metal plate and the second metal plate The third metal
plate comprises a top surface, a bottom surface and a side surface, and the bottom surface of the
third metal plate is in contact with the top surface of the second metal plate. The dimension
formed by the sum of the thickness of the first metal plate, the thickness of the second metal
plate, and the thickness of all the piezoelectric elements is one wavelength, and the thickness
dimension of the third metal plate is a half wavelength A bolt-clamped Langevin type vibrator
characterized by being a positive integer multiple is obtained.
[0015]
The total thickness of the thickness of the first and second metal plates and the thickness of all
the piezoelectric elements is set to be one wavelength, and the area of the bottom of the second
metal plate is the area of the upper surface A bolt-clamped Langevin-type vibrator is configured
by sandwiching the piezoelectric element such that a larger plate shape is formed and the first
metal block and the bottom surface portion of the second metal block abut, and the central
portion is fastened by the bolt. By doing this, the expanded amplitude is transmitted to the third
metal block set to the half wavelength, and a high amplitude at a high frequency which is 1.5
wavelengths as a whole can be obtained.
The third metal block may be a positive integer multiple of half wavelength.
[0016]
The external shape of the first metal plate and the piezoelectric element is preferably a disk
having the same diameter, but the first metal plate is a polygon or a surface larger than that
inscribed in the outer periphery of the piezoelectric element. It may be a rectangular plate. The
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bottom of the second metal plate has a circular shape with the same diameter as the outer shape
of the piezoelectric element, and preferably has a structure in which the diameter decreases
toward the upper surface or the shape of a truncated cone. It may be in the shape of a polygonal
frustum having a base of an inscribed polygon or a larger area. Furthermore, in the second metal
plate, the ridge line connecting the top surface and the bottom surface is preferably a curved line,
but a straight line or a combination of a straight line and a curved line may be formed.
[0017]
Further, according to the present invention, there can be obtained a bolted Langevin type
vibrator characterized in that the second metal plate and the third metal plate are integrally
formed. The second metal plate and the third metal plate may be mechanically coupled by
fastening with a bolt, bonding, welding or the like, but may be integrally formed by cutting or
casting from a single material Also good.
[0018]
Further, according to the present invention, there can be obtained a bolt-clamped Langevin type
vibrator characterized in that it has a recessed portion which circulates on the side surface
portion of the third metal plate.
[0019]
In the present invention, it is desirable that the third metal plate be a disk having the same outer
diameter as the piezoelectric element.
Furthermore, the surface on the side opposite to the surface to be joined to the second metal
plate is a vibration radiation surface, and by providing a circumferential recess in the side surface
portion of the third metal plate, the vibration distribution of the entire radiation surface is
uniformed. It is possible to
[0020]
Further, according to the present invention, there is provided a bolted Langevin type vibrator
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characterized in that the piezoelectric element is two or more and the fourth metal plate
sandwiched by the piezoelectric element is provided. When the thickness of the piezoelectric
element is reduced in order to lower the drive voltage, it is necessary to increase the number of
piezoelectric elements to compensate for the strength of the power resistance as much as the
thickness of the piezoelectric element is reduced. At this time, adjusting the frequency and
controlling the vibration mode can be performed by inserting the fourth metal plate between the
piezoelectric elements.
[0021]
As described above, according to the present invention, it is possible to provide a bolt-clamped
Langevin type vibrator capable of obtaining a large amplitude sufficient to generate cavitation
even at high frequencies.
[0022]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings.
[0023]
FIG. 4 is a side view showing the first embodiment.
The hatched portion in FIG. 4 indicates a cross section.
In the first embodiment, as shown in FIG. 4, using the first metal plate 7, the second metal plate
8, the third metal plate 9, the two piezoelectric elements 3, the bolts 6 and the electrode plate 2.
It was a bolt-clamped Langevin type vibrator.
[0024]
The first metal plate 7, the second metal plate 8 and the third metal plate 9 use an aluminum
alloy. The first metal plate 7 was a disc having a diameter of 35 mm and a thickness of 10 mm,
and was provided with a female screw of M10 (ISO standard) so as to penetrate through the
center of the disc. The second metal plate 8 is composed of a disc portion having a diameter of
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35 mm and a thickness of 5 mm and a horn-like portion having a thickness of 15 mm gradually
decreasing from 35 mm to 23 mm in diameter. A female screw with a depth of 15 mm was
attached to the surface. The third metal plate 9 is a disc having a diameter of 35 mm and a
thickness of 23 mm, and the third metal plate 9 and the second metal plate 8 are integrally
formed by cutting a single aluminum alloy material. And
[0025]
As the piezoelectric element 3, a lead zirconate titanate piezoelectric ceramic was used. Two
pieces of annular shape with an outer diameter of 35 mm, an inner diameter of 15 mm and a
thickness of 5 mm are used, the two piezoelectric elements 3 face each other with the same
polarity face, and sandwich the electrode plate 2 therebetween. Placed in Further, of the two
surfaces of the piezoelectric element 3 not in contact with the electrode plate 2, one surface is
disposed to abut the first metal plate 7, and the other surface has a diameter of the second metal
plate 8 It arrange | positioned so that it might contact | abut with the surface used as 35 mm.
Then, the bolt 6 was screwed into the female screw to fasten the first metal plate 7 and the
second metal plate 8. The third metal plate 9 is integrated with the second metal plate 8, and in
this state, a bolt-clamped Langevin type vibrator is formed.
[0026]
Here, the thickness (dimensions from A to D shown in FIG. 4) formed by the first metal plate 7,
the two piezoelectric elements 3 and the second metal plate 8 is a length of one wavelength at
the resonance frequency, Design and adjust the thickness from the speed of sound possessed by
each material used so that the thickness of the third metal plate 9 (dimensions D to E shown in
FIG. 4) is a half wavelength length at the resonance frequency The dimensions are not limited to
the above.
[0027]
FIG. 5 is a graph showing the vibration characteristics of the first embodiment.
In this graph, the vertical axis represents the amplitude, and the horizontal axis represents the
position in the longitudinal direction shown in FIG. 4, and shows the amplitude at each position
in the longitudinal direction of the bolted Langevin type vibrator according to the first
embodiment. . In the graph, the value of the amplitude when the amplitude in the left direction
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8
becomes maximum with respect to the longitudinal direction of the vibrating radiation surface
11 shown in FIG. The amplitude at each position is shown. Therefore, the display of + (plus) on
the vertical axis indicates that the amplitude is rightward with respect to the longitudinal
direction.
[0028]
From the vibration characteristics of Example 1 shown in FIG. 5, it is understood that the
absolute value of the amplitude is amplified from β1 to γ1 in the region of C to D of the graph,
that is, the portion of the second metal plate 8. Then, the value of γ1 appears as it is as the
amplitude at the vibrating radiation surface 11 shown in FIG. The amplification of this amplitude
is realized by providing the second metal plate 8 with two large and small surfaces having
different facing areas. Further, it can be seen that one wavelength is in the region of A to D and
half wavelength in the region of D to E of the graph.
[0029]
In Example 1, when a voltage of 100 Vpp at a frequency of 100 kHz was applied, an amplitude of
γ1 = 1.5 μm was obtained. This is a value corresponding to an amplitude 1.5 to 2 times the
amplitude conventionally obtained. Therefore, during ultrasonic cleaning, a large amplitude
sufficient to generate cavitation was obtained even at high frequencies.
[0030]
FIG. 6 is a side view showing the second embodiment. The basic configuration is the same as that
of the first embodiment, but in the second embodiment, the total volume of the piezoelectric
device 3 is increased more than that of the first embodiment by using four piezoelectric devices
3 with a thickness of 4 mm. It has a structure that can increase power. For this purpose, two sets
of two piezoelectric elements 3 facing each other with the same polarity face, and arranged so as
to sandwich the electrode plate 2 between them, are formed in an annular shape of 35 mm in
outer diameter, 15 mm in inner diameter and 3 mm in thickness Are arranged so as to sandwich
the fourth metal plate 10 made of aluminum alloy, which constitutes the first one, of the two
faces not in contact with the electrode plate 2 of the piezoelectric element 3 as in the first
embodiment. It arrange | positioned so that the metal plate 7 might be contact | abutted, and it
arrange | positioned so that the other surface might contact | abut with the surface used as the
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diameter of 35 mm of 2nd metal plate. Then, the bolt 6 was screwed into the female screw, and
the first metal plate 7 and the second metal plate 8 were fastened.
[0031]
Here, the thicknesses of the first metal plate 7 and the second metal plate 8 are thin so as to
offset the increase in the total thickness of the piezoelectric element 3 and the increase in the
fourth metal plate 10. did. In addition, a recess 12 having a width of 5 mm and a depth of 3.5
mm was provided all around the central portion of the side surface portion of the third metal
plate.
[0032]
FIG. 7 is a graph showing the vibration characteristic of the second embodiment. Similar to FIG.
5, in this graph, the vertical axis indicates amplitude, and the horizontal axis indicates the
position relative to the longitudinal direction shown in FIG. 6, and the amplitude at each position
relative to the longitudinal direction Is shown. In the graph, when the vibration radiation surface
11 shown in FIG. 6 has the maximum amplitude in the left direction with respect to the
longitudinal direction, the value of the amplitude is indicated by-(minus) on the vertical axis, The
amplitude at each position of Therefore, the display of + (plus) on the vertical axis indicates that
the amplitude is rightward with respect to the longitudinal direction.
[0033]
From the vibration characteristics of the second embodiment shown in FIG. 7, as in the first
embodiment, the absolute value of the amplitude is amplified from β2 to γ2 in the region from
C to D in the graph, that is, the second metal plate 8 portion. Understand that Then, the value of
γ2 appears as it is as the amplitude at the vibrating radiation surface 11 shown in FIG. The
amplification of the amplitude is also realized by providing the second metal plate 8 with two
large and small surfaces having different facing areas, as in the first embodiment.
[0034]
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In Example 1, when a voltage of 100 Vpp at a frequency of 100 kHz was applied, an amplitude of
γ2 = 1.3 μm was obtained. This is a slightly smaller value than that of the first embodiment.
This is because the piezoelectric element 3 and the fourth metal plate are increased, the
efficiency of vibration transmission is reduced, and the loss is increased.
[0035]
FIG. 8 is a view showing the vibration distribution of the vibration radiation surface. The
distribution of the amplitude in the oscillating radiation surface 11 from F to G shown in FIG. 6 is
shown. The dotted line indicates the vibration distribution 19 in the first embodiment, and the
solid line indicates the vibration distribution 20 in the second embodiment. As will be understood
from this figure, the vibration distribution 20 according to the second embodiment has equal
amplitude in a wider region than the vibration distribution 19 in the first embodiment. This is
due to the result that the vibration transmission is made uniform by the effect of the concave
groove provided in the third metal plate.
[0036]
Accordingly, also in the second embodiment, although the amplitude is smaller than that in the
first embodiment, the distribution of the vibration on the vibration radiation surface 11 becomes
uniform, and again, the large amplitude sufficient to generate cavitation even at high frequencies
during ultrasonic cleaning. It was obtained.
[0037]
In the first and second embodiments, the first metal plate, the second metal plate and the third
metal plate are disks, but the same effect can be obtained by using a square plate. .
Further, the material to be used is not limited to the aluminum alloy, and stainless steel, titanium
and other metals may be used.
[0038]
The bolt-clamped Langevin type vibrator according to the present invention can be used not only
for high frequency ultrasonic cleaning machines, but also for ultrasonic machines requiring high
output and large amplitude, medical machines utilizing ultrasonic waves, and the like.
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[0039]
The side view which shows an example of a bolting Langevin type | mold vibrator.
The graph which shows the oscillation characteristic of a bolting Langevin type | mold vibrator.
The graph which shows the relationship between the sound wave intensity and frequency for
generating cavitation in an ultrasonic cleaning machine. FIG. 2 is a side view showing Example 1;
6 is a graph showing vibration characteristics of Example 1; FIG. 7 is a side view showing
Example 2; 6 is a graph showing vibration characteristics of Example 2; The figure which shows
vibration distribution of a vibration radiation surface.
Explanation of sign
[0040]
Reference Signs List 1 bolt tightening Langevin type vibrator 2 electrode plate 3 piezoelectric
element 4 5 metal plate 6 bolt 7 first metal plate 8 second metal plate 9 third metal plate 10
fourth metal plate 11 vibration radiation surface 12 concave portion 19, 20 vibration
distribution
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