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JPH06269077

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DESCRIPTION JPH06269077
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
horn type high frequency ultrasonic transducer used for atomization and atomization of liquids,
bonding of metals and plastics, cleaning of precision parts and the like.
[0002]
2. Description of the Related Art Ultrasonic atomizers and cleaners of the type which directly
immerses ultrasonic transducers or diaphragms in a frequency range of 200 kHz or higher and
do not involve expansion of the vibration amplitude by the horn are put to practical use. There is.
On the other hand, an ultrasonic wire bonder and an ultrasonic plastic welder have been put to
practical use, in which the vibration amplitude is increased by the horn in a region of a frequency
of 120 kHz or less.
[0003]
However, in the case of an ultrasonic atomizer in which the ultrasonic transducer is directly
immersed in the liquid, the efficiency is low because the entire liquid vibrates, and depending on
the liquid, there is a problem of causing a change in physical properties of the liquid due to
ultrasonic vibration and heat generation. is there. Furthermore, the application to the ultrasonic
atomization of the molten metal can not be used because the liquid temperature often exceeds
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the Curie temperature of the ultrasonic transducer. On the other hand, atomization of metal with
a horn type ultrasonic transducer of 40kHz or less has been experimented, but since the particle
size is inversely proportional to the 2/3 power of the frequency, the high frequency for
ultrafinerization Is expected. When the frequency of the ultrasonic wire bonder for IC is
increased, the crushing width of the wire to the object to be bonded is reduced, the effective
bonding area and the surge current are increased, and the bonding condition can be increased to
improve the reliability. A higher frequency can be expected for a workpiece that is easily
damaged, and the same effect can be expected for bonding metal foils and thin metal wires.
When the frequency of the plastic welder is increased, there is no hardening of the welded
portion of the chemical fiber, and welding with a maintained feel can be expected. Therefore,
development of a horn type high frequency ultrasonic transducer with a frequency of 100 kHz or
more is an important issue.
[0004]
From the foregoing, the present invention provides a horn type high frequency ultrasonic
transducer by utilizing high frequency flexural vibration (hereinafter referred to as elongation
flexural vibration) accompanied by the extension of a conical shell-like horn. It is.
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the abovementioned point, and a tool is installed on the small end face of a conical-shell horn, and an
ultrasonic vibration element is fixed on the large end face side. The conical vibrating horn drives
in phase with the flexural vibration of the horn by the sonic vibration element.
The required vibration amplitude is obtained from structural analysis (finite element method) of
the shapes of the horn and the tool.
[0006]
[Operation] By bolting the vibration nodes of the conical horn and the ultrasonic vibration
element, the bolt can be handled in the same manner as a conventional bolted Langevin type
vibrator (frequency: 20 to 100 kHz). It is possible to install a flange using the vibration node of In
the present situation, simulation by finite element method is required for extension deflection
vibration mode analysis of conical shell horn, but the tool can be designed according to the
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purpose, and conventional methods such as longitudinal vibration mode and vertical → bending
vibration mode are available. Applicable
[0007]
Embodiments of the high frequency ultrasonic transducer according to the present invention will
be described with reference to the drawings.
[0008]
FIG. 1 is an assembled sectional view showing an embodiment of the present invention.
In the figure, 1 is a tool, 2 is a conical horn, 3 to 7 are vibrating elements, 3 is a front body, 4 is a
PZT oscillator, 5 is an electrode, 6 is a surface, 7 and 71 are 2 to 6 Fastening bolts and nuts, 8
and 9 are the respective vibration modes of the same horn and vibrating element.
[0009]
A detailed view of the conical shell horn and its vibration mode is shown in FIG. In the figure, the
reference numeral 20 denotes the central axis of the conical horn, which comprises an integral
structure of the conical shell 22 and the solid cylinder 21 and the hollow cylinder 23. The conical
horn includes many harmonic vibration modes, one of which is an example of the desired
vibration mode shown in FIG. FIG. 8 shows a simulation of vibration by the finite element method
of the target vibration mode, in which 82 and 83 corresponding to the conical shell 22 and the
hollow cylinder 23 are extended and the flexural vibration mode (the vibration component in the
radial direction perpendicular to the axis is the diameter The figure shows that 81 corresponding
to the solid cylinder 21 (not parallel to the direction but with elongation) vibrates in the
longitudinal vibration mode (the vibration component in the radial direction is parallel to the
radial direction). In the example of FIG. 2, the mean lengths of the conical shell and the hollow
cylinder are adjusted to be four times the mean wavelength of the elongation-deflection
vibration. A fixing flange 24 is installed on the circumference of the hollow cylindrical outer
surface node line 84.
[0010]
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Arrows X1 and X2 on the end face of the hollow cylinder 23 in FIG. 2 indicate that the vibration
modes of the inner and outer surfaces of the large end face of the conical shell horn are in
antiphase relation to the plane perpendicular to the central axis. Arrows Y1 and Y2 indicate that
the vibration modes of the inner surface of the hollow cylinder 23 are in antiphase with respect
to a side line parallel to the central axis. Therefore, when the large horn end face is driven by the
driving element for longitudinal direction, the contact face is a local hollow circular face
corresponding to the arrow X1 near the horn outer side or the arrow X2 near the horn side, and
the arrows X1 and X2 are simultaneously made the same. It avoids longitudinal driving in the
direction and realizes in-phase driving of the horn. Specifically, a ring-shaped projection 31 is
provided on the contact surface of the front body 3 and the horn in FIG. 1 to drive the horn in
phase. Similarly, by making the contact surfaces of the radial drive vibration element and the
inner surface of the hollow cylindrical inner surface of the conical shell horn into local short
cylindrical surfaces corresponding to the portions Y1 or Y2 of the arrows, the portions of the
arrows Y1 and Y2 simultaneously and in the same direction It is also possible to achieve in-phase
drive of the horn, avoiding driving. In conventional ultrasonic transducers, various measures
have been taken to reduce the influence of longitudinal and radial vibration mode coupling so
that radial vibration is parallel to the radial direction. The present invention is intended to
amplify a high frequency vibration by the horn by applying the vibration mode which has been
avoided as the unintended vibration (spurious vibration) to the conical-shell horn and driving the
vibration in phase. In FIG. 1, at the tip of the conical shell horn, a disc tool 1 that vibrates and
vibrates in a two-node circle and a vibration converter 11 have a one-piece structure with the
same horn.
[0011]
Each of the elements constituting the longitudinal driving vibration element is installed at a
length at which longitudinal and half-wave resonance occurs in the axial direction at the
extension flexural resonance frequency of the target horn. A flange 61 is installed on the nodal
surface of the vibration of the spine 6 in the same manner as the conical-shell horn, and both the
flanges 24 and 61 are fastened with a bolt 7 and a nut 71. The two PZT vibrators 4 are arranged
in the same polarization direction (plus electrode side) with respect to the electrode 5 (in FIG. 1,
only one place is shown and the other is omitted). When a flange 51 is installed on the nodal
plane of the vibration of the electrode 5 and an electrical signal (not shown) equal to the
resonant frequency of the conical cone-shaped horn 2 aimed between the flange and the front
body and spine is applied, the same electrical signal Is electrically-mechanically converted by the
PZT vibrator 4 to be elastic vibration, and the vibration elements 3 to 6 vibrate in the
longitudinal vibration mode 9 to drive the horn. The longitudinal vibration input to the horn 2
undergoes extension deflection vibration, and then mode conversion is again performed to the
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longitudinal vibration, and finally the tool 1 is driven in the bending vibration mode.
[0012]
FIG. 3 shows another embodiment of the conical shell horn. FIG. 25 is an example of a conical
shell horn in which a cross section in which inner and outer lines are formed by a combination of
arcs is constituted by a rotating body with the axis 20 as a central axis. The center of the arc is
perpendicular to the central axis passing through the end faces of the hollow portion of the
conical horn on the plane including the central axis 20 of rotation. Assuming that the radius of
the arc is R1 and R2, respectively, R1 and R2 are the central axis length (height) of the hollow
portion of the conical horn, and the inner radius and thickness of the large end face are y and t1,
respectively Assuming that the radius on the end face side is t0, it is expressed by the relational
expression of Equation 1.
[0013]
In the equation (1), χ and y are set to satisfy the equation (2), where λ is an average
wavelength of the elongation-deflection vibration and n is a positive integer. In the actual design
of the conical-shell horn, the shape of the roughing is determined by Equations 1 and 2, and fine
adjustment is repeatedly performed by simulating trials of vibration analysis by the finite
element method of the same shape and its improved shape. Do.
[0014]
The simulation of the intended vibration mode by the finite element method of the conical-shell
horn 25 designed through the above-mentioned course is shown at 85. The vibration mode 85
corresponds to the extension deflection vibration of 8 in FIG.
[0015]
FIG. 4 shows still another embodiment of the conical shell horn. In FIG. 26, the inner and outer
surfaces of the horn are constituted by spherical shells, and the center of the arc is on the
rotation center axis, which is different from the case of FIG. Assuming that the average thickness
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of the spherical shell is t, the inner and outer surface radii R3 and R4 of the spherical shell can be
expressed by the following equation (3).
[0016]
Based on the size of the roughing determined by Equation 3, fine adjustment of the conical-shell
horn is performed by repeatedly simulating trials of vibrational breakup by the finite
requirement method in the same manner as in the case of FIG.
[0017]
A simulation based on the finite element method of the desired vibration mode of the conicalshell horn 26 designed through the above-mentioned course is shown at 86.
The vibration mode 86 corresponds to the extension deflection vibration of 8 in FIG.
[0018]
One embodiment of a method of driving a conical-shell horn different from the vibration method
of FIG. 1 is shown in FIG. This figure shows an example of driving the arrow Y1 or Y2 in FIG. 2
when the conical-shell horn is driven by the vibration element for radial direction drive. Although
there is no problem in principle even if the arrow Y1 or Y2 is driven in phase from FIG. 2 in
principle, the contact surface of the cylindrical PZT vibrator 41 and the horn has a small area,
and the efficiency is low. Therefore, in FIG. 5, in the conical shell horn having the horn 2 and the
front body 32 integrally formed, a gap 33 is provided to drive the portion 31 corresponding to
the contact surface of the front body and the horn in phase. Therefore, the axial direction of the
front body 32 is the longitudinal vibration mode, and the radial direction is the in-phase
thickness vibration mode. The front body 32 whose inner side surface is slightly tapered is
shrink-fit, fixed to the cylindrical PZT vibrator 41 by press fitting, adhesion or the like. The tool
12 vibrates in a longitudinal vibration mode. The vibration modes from the cylindrical PZT
vibrator 41 to the front body 32, the horn 2, and the tool 12 in FIG. 5 are thickness vibration →
thickness · longitudinal vibration → elongation deflection · longitudinal vibration → longitudinal
vibration.
[0019]
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In the present embodiment, three cases have been described as conical-shell-like horns, but as an
extension flexural vibrator, the inner and outer cross sections including the central axis are
constituted by conical curves or a collection thereof, and the cross section perpendicular to the
axis is from the large end face A cup-shaped axisymmetric oscillator gradually decreasing toward
the small end face is a conical horn.
[0020]
The effects of the present invention are shown below in the case of FIG.
A titanium alloy (6Al4V) is used as the vibration element excluding the conical shell horn and the
PZT vibrator, and the elongation flexural vibration resonance frequency 400k Hz, the large horn
end face inside diameter 14mm, outer diameter 14mm, tool disc thickness 1mm, same diameter
The simulation results in the case of 11 mm show that the cross-sectional area ratio of the horn
tip to the large end face 1:23 the vibration amplitude ratio of the horn tip to the vibrating
element end face 8: 1 disk tool to the cross section ratio of the horn tip 13: 1 disk tool and horn
The tip vibration amplitude ratio was 4: 1. As described above in detail, according to the present
invention, the conical-shell-like horn having a very simple structure can realize the expansion of
the vibration amplitude, and can provide a horn type ultrasonic transducer for high frequency of
100 kHz or more. The
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