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JP2000295695

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2000295695
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
Langevin type ultrasonic transducer used as a vibration source of ultrasonic application
equipment such as an ultrasonic cleaner.
[0002]
2. Description of the Related Art As shown in FIG. 6, a Langevin ultrasonic transducer a is
disposed between a front plate c consisting of a pair of upper and lower cylindrical metal blocks
equal in diameter to a piezoelectric element b and a backing plate d. There is known one in which
a piezoelectric element b is disposed and these are integrally connected by a central bolt e.
[0003]
The total length of the ultrasonic transducer a is set to substantially coincide with the length of a
half wavelength of a predetermined resonance frequency, as can be understood from the
resonance waveform illustrated on the side of FIG.
[0004]
The ultrasonic transducer a having such a configuration is used by being incorporated into an
ultrasonic cleaner or the like for cleaning metal parts that operates at a low frequency of 20 kHz
to 50 kHz.
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[0005]
By the way, for cleaning glass substrates such as liquid crystal display panels and hard disks,
ultrasonic cleaners that generate strong ultrasonic waves at resonance frequencies in the 70 kHz
to 200 kHz band are suitable, and ultrasonic waves of such ultrasonic cleaners are suitable.
Although a high frequency resonance frequency is achieved as a vibrator, the ultrasonic vibrator
a having the above-described conventional configuration is designed to operate at a resonance
frequency of 70 kHz or more, and its total length is about 30 mm. It will be shorter.
As a result, not only the piezoelectric element b can not be firmly connected tightly to the front
plate c and the backing plate d, but it also becomes difficult to hold the ultrasonic transducer a
during mounting, and the electric input power can be up to 10 W at most. Due to the limit,
various problems such as high output can not be obtained.
[0006]
Therefore, in order to cope with such a problem, the overall length of the ultrasonic transducer is
formed to substantially coincide with the length of the 3/2 wavelength of the resonance
frequency, whereby the total length as compared with the half wavelength wavelength. Can be
approximately tripled, and an ultrasonic transducer usable at a resonance frequency of 70 kHz or
more can be obtained.
[0007]
By the way, in an ultrasonic cleaner using a plurality of ultrasonic transducers, the ultrasonic
transducers are arranged in a lattice form at a predetermined interval with respect to the
vibrating plate.
Therefore, if the diameter of each ultrasonic transducer is increased, the outer end area of the
front plate which is the ultrasonic radiation surface is increased, the number of ultrasonic
transducers used is reduced, and the manufacturing cost can be reduced. However, the larger the
diameter of the ultrasonic transducer, the larger the radial vibration due to the Poisson's ratio,
and the smaller the admittance representing the vibration efficiency.
And even if it is an ultrasonic transducer for a 70 kHz to 200 kHz band, which has a resonance
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length of 3/2 wavelength, this is a big problem.
[0008]
The present invention relates to an ultrasonic transducer operating at a resonance frequency in
the 70 kHz to 200 kHz band, and provides a Langevin-type ultrasonic transducer that can widen
the area of ultrasonic radiation without reducing its vibration efficiency. It is the purpose.
[0009]
SUMMARY OF THE INVENTION According to the present invention, a piezoelectric element is
disposed and integrally coupled between a front plate and a backing plate, which are a pair of
upper and lower cylindrical metal blocks, and 70 kHz is applied to the piezoelectric element. In
the Langevin-type ultrasonic transducer to which a high frequency voltage of ~ 200 kHz band is
applied, the overall length is formed to substantially match the resonance length of 3/2
wavelength, and the diameters of the backing plate and the front plate are approximately the
same diameter. An axial blind end hole is formed in the center of the outer end face of the
backing plate.
[0010]
In this configuration, it may be proposed as a preferred embodiment that the diameter of the
blind end hole is approximately 1/3 of the diameter of the backing plate.
[0011]
As described above, when a blind end hole is formed in the backing plate and the admittance
representing the vibration efficiency is measured, the admittance is small even if the diameter of
the front plate becomes large, as is apparent from the measurement results described later In
addition, it was found that the vibration efficiency did not decrease.
In addition, when the diameter of the blind end hole was made approximately 1/3 of the
diameter of the backing plate, it was found that no spurious (unnecessary vibration) was
generated near the resonance frequency.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a Langevin-type ultrasonic
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transducer according to the present invention will be described below with reference to FIG.
[0013]
The Langevin ultrasonic transducer 1 comprises a piezoelectric element pair 2, a pair of upper
and lower front plates 5 sandwiching the piezoelectric element pair 2, and a backing plate 6.
The piezoelectric element pair 2 is formed by laminating two annularly formed piezoelectric
elements 3a and 3b with an electrode plate 4a interposed therebetween, and arranging the
electrode plate 4b on the upper portion of the upper annular piezoelectric element 3b. Is
configured.
Further, the front plate 5 and the backing plate 6 are made of cylindrical metal blocks formed
using iron or aluminum as a material.
The piezoelectric element pair 2 is disposed between the front plate 5 and the backing plate 6
and is integrally coupled by a central bolt 7.
[0014]
The front plate 5 and the backing plate 6 are both formed larger in diameter with respect to the
diameter of the piezoelectric elements 3a and 3b, and the contact end with the piezoelectric
elements 3a and 3b is reduced in diameter via the conical portions 8 and 9 And the diameters of
the piezoelectric elements 3a and 3b are substantially equal.
The diameter R2 of the backing plate 6 and the diameter R1 of the front plate 5 are set to have
substantially the same dimensions, and the outer end face of the front plate 5 is the ultrasonic
radiation surface 10. A blind end hole 11 having a diameter R3 along the axial direction is
formed at the center of the outer end face of the backing plate 6. Then, the total length of the
ultrasonic transducer 1 having such a configuration is set to substantially match the resonance
length of the 3/2 wavelength of the predetermined resonance frequency, as can be seen from the
resonance waveform illustrated on the side of FIG. ing.
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[0015]
As described above, by configuring the ultrasonic transducer 1, even in the high frequency band
of 70 kHz to 200 kHz, the total length is almost tripled compared to that formed in the
resonance length of 1⁄2 wavelength. It can be long. As a result, the piezoelectric element pair 2,
the front plate 5, and the backing plate 6 can be firmly connected tightly by the center bolt 7,
and the holding of the ultrasonic transducer 1 at the time of mounting becomes easy. The
ultrasonic transducer 1 is obtained.
[0016]
Further, by forming the blind end hole 11 in the axial direction in the central portion of the outer
end surface of the backing plate 6 as described above, the vibration efficiency is improved as
apparent from the following experimental example.
[0017]
As an experimental sample, the resonance frequency is 75 kHz, the total length of the ultrasonic
transducer 1 determined by the resonance frequency is 88.4 mm, the diameter R2 of the backing
plate 6 is set to 45 mm and 50 mm, and each backing The ratio R3 / R2 of the diameter R3 of
the blind end hole 11 to the diameter R2 of the backing plate 6 is set to 2/9, 2.5 / 9, 3/9, 3.5 / 9,
4/9 for each size of the plate 6 And those without the blind end hole 11 (R3 = 0) were prepared.
Incidentally, the dimensions of the diameter R3 of each blind end hole 11 in the above ratio are
R3 = 10, 12.5, 15, 17.5, 20 mm when the diameter R2 of the backing plate 6 is 45 mm, and R3
≒ 11.1 when R2 is 50 mm. , 13.9, 16.7, 19.4, 22.2 mm.
[0018]
In the case where the blind end hole 11 is not formed in the backing plate 6, since the diameters
R1 and R2 of the front plate 5 and the backing plate 6 exceed about 40 mm, the admittance
representing the vibration efficiency rapidly increases as shown in FIG. Since it is known in
advance that the diameter R1 of the front plate 5 is 40 mm and the ultrasonic radiation surface
10 is narrow, the diameter R2 of the backing plate 6 provided in substantially the same
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dimension as the diameter R1 of the front plate 5 The ultrasonic radiation surface 10 is made
wide by 45 mm and 50 mm, which are 5 mm larger than 40 mm as in FIG. Further, the depth of
the blind end hole 11 in each sample is set to about 10 mm.
[0019]
Then, a high frequency voltage of 75 kHz band was applied to the piezoelectric elements 3a and
3b through the electrode plates 4a and 4b to measure the admittance representing the vibration
efficiency of each sample. The measured values are shown in FIG.
[0020]
FIG. 4 is a graph showing the relationship between admittance and R3 = 0 and each ratio R3 / R2
based on the measured values of FIG. Here, the plot mark ◆ indicates that the diameter R2 of the
backing plate 6 is 45 mm, and the plot mark は indicates that the R2 is 50 mm. From this result,
when the blind end hole 11 is formed, the ratio R3 / R2 is 2/9 to 3.5 / 9 as compared with the
back plate 6 without the blind end hole 11 (R3 = 0). It is understood that when the admittance is
higher, especially when the diameter R2 of the backing plate 6 is 45 mm, the admittance
becomes the largest when the ratio R3 / R2 is around 3/9 (1/3). Thereby, by forming the blind
end hole 11 of the required ratio in the backing plate 6, the ultrasonic radiation area 10 can be
widened without reducing the vibration efficiency, and the ratio R3 / R2 is approximately 1/3. It
was confirmed that the vibration efficiency is most improved when
[0021]
Although not shown, several types of ultrasonic transducers 1 are formed so that the entire
length of the ultrasonic transducer 1 substantially matches the resonance length of 3/2
wavelength at a resonance frequency of 70 kHz to 200 kHz except 75 kHz. 11 and the ratio R3 /
R2 of the diameter R3 of the blind end hole 11 to the diameter R2 of the backing plate 6 is
changed by the above ratio to measure the admittance, the result is substantially the same as
above, and the vibration efficiency is It has been confirmed that the ultrasonic radiation area 10
can be increased without lowering.
[0022]
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Further, for the case where the diameter R2 of the backing plate 6 is 45 mm, the relationship
between the ratio R3 / R2 and the resonance characteristic is investigated and the result is
shown in FIG.
Here, FIGS. 5A to 5C show waveform diagrams of three representative examples, in which R / R2
is 2/9, R is 3/9, and C is 4/9. In each waveform diagram, the vertical axis represents the
admittance, and the horizontal axis represents the frequency scaled at intervals of 200 Hz, and
the display frequency band is the 75 kHz band.
[0023]
Comparing the respective waveform diagrams in FIG. 5A to FIG. 5B, two spurious noises
(unnecessary vibrations) are generated between the resonance point x and the antiresonance
point y in a, and the antiresonance point y in c. Large spurious emissions occur in the vicinity. On
the other hand, in B, there is no generation of spurious noise near the resonance frequency, and
it is recognized that the vibration is stable. From this, it is understood that by setting R3 / R2 to
about 3/9 (1/3), the electrical loss is small and the vibration efficiency is excellent.
[0024]
As described above, according to the present invention, the piezoelectric element is disposed
between the front plate and the backing plate made of cylindrical metal blocks and integrally
coupled, and a high frequency voltage of 70 kHz to 200 kHz band is applied. In the Langevin
type ultrasonic transducer, the entire length is formed so as to substantially match the resonance
length of 3/2 wavelength, and the diameters of the backing plate and the front plate are made
substantially the same diameter, and the outer end face of the backing plate Since an axial blind
end hole is formed in the central portion of the above, as is clear from the experiment, the
ultrasonic radiation area can be widened without reducing the vibration efficiency. As a result,
when arranging a plurality of ultrasonic transducers at a predetermined interval on a vibrating
plate such as an ultrasonic cleaner, the number of ultrasonic transducers per unit area can be
reduced, and the manufacturing cost is reduced. It will be possible.
[0025]
Further, in the above configuration, by setting the diameter of the blind end hole to about 1/3 of
the diameter of the backing plate, generation of spurious is suppressed, vibration is stabilized,
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and vibration efficiency is improved. Have an effect.
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