JPH09314054

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DESCRIPTION JPH09314054
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic apparatus such as an ultrasonic cutter and an ultrasonic welding machine equipped
with a handpiece for emitting ultrasonic energy, and more particularly to an ultrasonic oscillator
for driving these.
[0002]
2. Description of the Related Art FIG. 4 is a block diagram showing a first prior art example of an
ultrasonic oscillator. FIG. 5 is a schematic view showing a hand piece as a vibration system driven
by the ultrasonic oscillation device. Hereinafter, it demonstrates based on these drawings.
[0003]
The ultrasonic wave oscillation device 50 incorporates an oscillator (not shown) and controls the
oscillator so that the frequency and phase of the output signal always coincide with the
frequency and phase of the input signal, and the PLL module 52 And an electromagnetic coil 58
that feeds back the vibration of the ultrasonic transducer 54 to the PLL module 52 as an input
signal.
[0004]
The drive circuit 56 outputs FETs 561 and 562 alternately turned on in accordance with the
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output signal of the PLL module 52, and an output transformer 563 for converting the primary
voltage amplified by the FETs 561 and 562 at a predetermined ratio into secondary voltage. And
a choke coil 564 for improving the power factor.
[0005]
The handpiece 60 is a bolted Langevin type transducer (hereinafter referred to as "LBT") in
which the ultrasonic transducer 54 is held between the metal plates 601 and 602.
And a horn 604 whose base end is fixed to the LBT 603, a magnetic core 605 which vibrates
together with the LBT 603 and is inserted into the electromagnetic coil 58, and a housing 606
indicated by a virtual line.
A tool or the like (not shown) is attached to the tip of the horn 604.
[0006]
The output signal of the PLL module 52 is amplified by the drive circuit 56 and supplied to the
ultrasonic transducer 54. Then, the ultrasonic transducer 54 vibrates, and the vibration is
detected by the electromagnetic coil 58 and is fed back to the PLL module 52 as an input signal.
The PLL module 52 controls the oscillator so that the frequency and phase of the output signal
match the frequency and phase of the input signal. Thus, it is possible to automatically track a
change in the vibration frequency of the ultrasonic transducer 54 due to a change in load or the
like. Also, in place of the electromagnetic coil 58 and the magnetic core 605, a piezoelectric
element or the like may be attached to or embedded in the horn 604 to detect the vibration of
the ultrasonic transducer 54.
[0007]
FIG. 6 is a block diagram showing a second conventional example of the ultrasonic wave
oscillation apparatus. FIG. 7 is a block diagram showing a third conventional example of the
ultrasonic wave oscillation apparatus. Hereinafter, it demonstrates based on these drawings.
However, the same parts as those in FIG.
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[0008]
In the ultrasonic wave oscillation device 70 of FIG. 6, means for feeding back the vibration of the
ultrasonic transducer 54 to the PLL module 52 as an input signal (hereinafter referred to as
"feedback signal detection means"). Voltage divider resistors 701 and 702 for detecting a voltage
applied to the ultrasonic transducer 54 are used. In the ultrasonic wave oscillation device 80 of
FIG. 7, a secondary side detection coil 801 for detecting the secondary side voltage of the output
transformer 563 is used as a feedback signal detection means.
[0009]
However, in the ultrasonic oscillation device 50 according to the first prior art, since it is
necessary to incorporate the electromagnetic coil 58 etc. into the handpiece 60, the handpiece
60 has been complicated and enlarged. This problem hinders the cost reduction, weight
reduction and miniaturization of the handpiece 60.
[0010]
In addition, although it is not necessary to provide any feedback signal detection means in the
handpiece 60 in the ultrasonic oscillation devices 70 and 80 of the second or third conventional
example, as will be described below, the actual practice of the ultrasonic transducer 54 The
ultrasonic transducer 54 is driven at a phase slightly shifted from the vibration. As a result, a
power loss based on the phase difference between the vibration frequency and the drive
frequency is generated, and it is necessary to provide each component with a margin in order to
absorb the power loss. This problem has been a hindrance to reducing the power consumption,
reducing the cost, reducing the weight and reducing the size of the ultrasonic oscillator.
[0011]
FIG. 8 is an equivalent circuit diagram showing a part of the ultrasonic wave oscillation device
70. As shown in FIG. FIG. 9 is a vector diagram for explaining voltages detected by voltage
dividing resistors 701 and 702. Referring to FIG. Hereinafter, description will be made with
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reference to FIGS. 6, 8 and 9.
[0012]
The ultrasonic transducer 54 can be represented as a series circuit of a capacitor 541 and a
resistor 542. Here, assuming that the capacitance value of the capacitor 541 is Cs and the
resistance value of the resistor 542 is Rs, a voltage V2 applied to the ultrasonic transducer 54
(the same phase as the voltage detected by the voltage dividing resistors 701 and 702) Is delayed
from the voltage VR (= Rs × I 2) across the resistor 542 by the phase θ 2. On the other hand,
the vibration of the ultrasonic transducer 54 matches the voltage VR. Therefore, the ultrasonic
oscillation device 70 drives the ultrasonic transducer 54 at a phase slightly deviated from the
actual vibration of the ultrasonic transducer 54.
[0013]
FIG. 10 is an equivalent circuit diagram showing a part of the ultrasonic wave oscillation device
80. As shown in FIG. FIG. 11 is a vector diagram for explaining the voltage detected by the
secondary side detection coil 801. As shown in FIG. Hereinafter, description will be made with
reference to FIGS. 7, 10 and 11.
[0014]
Assuming that the inductance value of the choke coil 564 is L, the secondary side voltage V3 of
the output transformer 563 (the same phase as the voltage detected by the secondary side
detection coil 801) is the voltage VR (= Rs × I3) across the resistor 542 ) Delayed by the phase
θ3. Strictly speaking, if the resonant frequency determined by L and Cs matches the vibration
frequency of the ultrasonic transducer 54, then θ3 = 0, but due to the variation of L and Cs and
the frequency variation of the ultrasonic transducer 54, θ3 ≠ 0 Therefore, like the ultrasonic
oscillation device 70, the ultrasonic oscillation device 80 drives the ultrasonic transducer 54 with
a phase slightly deviated from the actual vibration of the ultrasonic transducer 54.
[0015]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic
oscillator which can achieve low power consumption, low cost, light weight and miniaturization
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of the handpiece and the ultrasonic oscillator.
[0016]
The ultrasonic oscillation apparatus according to the present invention has a built-in oscillator
and controls the oscillator so that the frequency and the phase of the output signal always
coincide with the frequency and the phase of the input signal. A module, a drive circuit for
amplifying the output signal of the PLL module and supplying the amplified signal to an
ultrasonic transducer, and a motional bridge circuit for feeding back the vibration of the
ultrasonic transducer as the input signal to the PLL module It is
Further, the free-running frequency of the oscillator may be set in the vicinity of the resonant
frequency of a vibration system including the ultrasonic transducer.
[0017]
The output signal of the PLL module is amplified by the drive circuit and supplied to the
ultrasonic transducer. The vibration of the ultrasonic transducer is fed back as an input signal to
the PLL module by the motional bridge circuit. Here, when the vibration frequency of the
ultrasonic transducer changes due to load fluctuation or the like, the change is fed back to the
PLL module via the motional bridge circuit. Then, the PLL module controls the oscillator so that
the frequency and phase of the output signal match the frequency and phase of the input signal.
Thus, the ultrasonic oscillation device automatically tracks the change in the vibration frequency
of the ultrasonic transducer.
[0018]
At this time, the motional bridge circuit cancels out the capacitance component of the ultrasonic
transducer, and detects the voltage across the resistance component of the ultrasonic transducer.
On the other hand, the vibration of the ultrasonic transducer coincides with the change in voltage
across the motional bridge circuit. Therefore, the ultrasonic oscillation device drives the
ultrasonic transducer in the same phase as the actual vibration of the ultrasonic transducer.
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[0019]
Further, since the PLL module incorporates an oscillator, it oscillates at a free-running frequency
even without an input signal. Therefore, the ultrasonic oscillator operates even if it can not obtain
an input signal of a sufficient level from the motional bridge circuit. At this time, if the freerunning frequency is set around the resonant frequency of the vibration system including the
ultrasonic transducer, tracking of the vibration frequency becomes easier.
[0020]
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an
embodiment of an ultrasonic oscillator according to the present invention. FIG. 2 is a block
diagram showing an example of a PLL module in the ultrasonic oscillation apparatus of FIG. FIG.
3 is an equivalent circuit diagram showing a motional bridge circuit in the ultrasonic oscillation
apparatus of FIG. Hereinafter, it demonstrates based on these drawings. However, the same parts
as those in FIG.
[0021]
The ultrasonic wave oscillation device 10 incorporates the oscillator 12 and controls the
oscillator 12 such that the frequency and phase of the output signals OUT1 and OUT2 always
coincide with the frequency and phase of the input signal IN1, and the PLL module 14 A drive
circuit 56 for amplifying the output signals OUT1 and OUT2 of the above and supplying the
same to the ultrasonic transducer 54, and a motional bridge circuit 16 for feeding back the
vibration of the ultrasonic transducer 54 to the PLL module 14 as the input signal IN1. There is.
[0022]
The PLL module 14 generates a phase comparator 141 that generates an output voltage
corresponding to the phase difference between the input signals IN1 and IN2, and unnecessary
harmonic components and noises included in the output voltage of the phase comparator 141 to
remove the control signal voltage. The generated filter 142, an oscillator (VCO) 12 whose
oscillation frequency is determined by the control signal voltage output from the filter 142, FET
drivers 143 and 144 for amplifying or inverting amplifying the output signal OUT0 of the
oscillator 12, and the oscillator 12 And an external resistor 144 and a capacitor 145.
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Further, the output signal OUT0 is the input signal IN2 as it is. The PLL-IC 146 includes a phase
comparator 141, a filter 142, and an oscillator 12, and is, for example, a trade name LM565
manufactured by National Semiconductor Company. The external resistor 144 and capacitor 145
set the free-running frequency of the oscillator 12. The free-running frequency is set around the
resonance frequency of the vibration system including the ultrasonic transducer 54.
[0023]
The motional bridge circuit 16 is a bridge circuit composed of capacitors 161 to 163 and an
ultrasonic transducer 54, and by canceling out the capacitive component of the ultrasonic
transducer 54, the resistance component of the ultrasonic transducer 54 is selected. Detect the
voltage at both ends. The principle is described below. The ultrasonic transducer 54 can be
represented as a series circuit of a capacitor 541 and a resistor 542. Here, the capacitance value
of the capacitor 541 is Cs, the resistance value of the resistor 542 is Rs, the capacitance values of
the capacitors 161 to 163 are C1 to C3, the impedance of the ultrasonic transducer 54 is Z, and
the impedance of the capacitors 161 to 163 is Z1. .About.Z3, let the input and output voltages of
the motional bridge circuit 16 be VIN and VOUT. Then, for example, assuming that C1 = 10 ×
Cs, C2 = 300 × Cs, and C3 = 30 × Cs, since Z >> Z3, Z1 >> Z2, VOUT ((Z · Z 2 −Z 1 · Z 3) · VIN /
It becomes (Z1 · Z). Therefore, if Z = Cs (Rs = 0), then VOUT becomes 0, and if Rs ≠ 0, a VOUT
proportional to Rs is obtained. Thereby, the motional bridge circuit 16 detects the voltage VR
across the resistor 542 as the output voltage VOUT, and feeds back the output voltage VOUT to
the PLL module 14 as the input signal IN1.
[0024]
Next, the operation of the ultrasonic wave oscillation device 10 will be described.
[0025]
The output signals OUT1 and OUT2 of the PLL module 14 are amplified by the drive circuit 56
and supplied to the ultrasonic transducer 54.
The vibration of the ultrasonic transducer 54 is fed back as an input signal IN 1 of the PLL
module 14 by the motional bridge circuit 16. Here, when the vibration frequency of the
ultrasonic transducer 54 changes due to load fluctuation or the like, the change is fed back to the
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PLL module 14 via the motional bridge circuit 16. Then, the PLL module 14 controls the
oscillator 12 so that the frequency and phase of the output signals OUT1 and OUT2 coincide
with the frequency and phase of the input signal IN1. For example, when the phase of the input
signal IN2 in phase with the output signals OUT1 and OUT2 is delayed with respect to the input
signal IN1, the oscillator 12 raises the frequency of the output signal OUT0. Conversely, when
the phase of the input signal IN2 is advanced with respect to the input signal IN1, the oscillator
12 lowers the frequency of the output signal OUT0. In this manner, the ultrasonic oscillation
device 10 automatically tracks the change in the vibration frequency of the ultrasonic transducer
54.
[0026]
At this time, as described above, the motional bridge circuit 16 cancels the capacitance
component of the ultrasonic transducer 54 and detects the voltage VR across the resistance
component of the ultrasonic transducer 54. On the other hand, the vibration of the ultrasonic
transducer 54 coincides with the change of the voltage VR. Therefore, the ultrasonic oscillation
device 10 drives the ultrasonic transducer 54 in the same phase as the actual vibration of the
ultrasonic transducer 54.
[0027]
Further, since the PLL module 14 incorporates the oscillator 12, it oscillates at a free-running
frequency even without the input signal IN1. Therefore, the ultrasonic wave oscillation device 10
operates even if the motional bridge circuit 16 can not obtain the input signal IN1 of a sufficient
level. At this time, if the free-running frequency is set in the vicinity of the resonance frequency
of the vibration system including the ultrasonic transducer 54, tracking of the vibration
frequency becomes easy.
[0028]
Needless to say, the present invention is not limited to the above embodiment. For example, since
it is sufficient that the drive circuit can amplify the output signal of the PLL module and supply it
to the ultrasonic transducer, the output transformer or choke transformer may be omitted, or a
bipolar transistor may be used instead of the FET. .
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[0029]
According to the ultrasonic oscillator of the present invention, the same phase as the actual
vibration of the ultrasonic transducer is obtained by feeding back the vibration of the ultrasonic
transducer to the PLL module through the motional bridge circuit. Can drive the ultrasonic
transducer. Therefore, the power loss based on the phase difference between the vibration
frequency and the drive frequency can be eliminated without providing any feedback signal
detection means in the handpiece. Therefore, low power consumption, low cost, light weight and
miniaturization of the handpiece and the ultrasonic oscillator can be achieved.
[0030]
Also, since the PLL module incorporates an oscillator, it oscillates at a free-running frequency
even without an input signal. Therefore, when operating with a load such as an ultrasonic
welding machine, it is possible to operate even if an input signal of a sufficient level can not be
obtained from the motional bridge circuit. Therefore, combined with the above effects, the
application of the ultrasound device can be expanded more than ever. Furthermore, at this time,
when the free-running frequency of the oscillator is set around the resonance frequency of the
vibration system including the ultrasonic transducer, tracking of the vibration frequency can be
made easier.
[0031]
Brief description of the drawings
[0032]
1 is a block diagram showing an embodiment of the ultrasonic wave oscillation device according
to the present invention.
[0033]
2 is a block diagram showing an example of a PLL module in the ultrasonic oscillation device of
FIG.
[0034]
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3 is an equivalent circuit diagram showing a motional bridge circuit in the ultrasonic oscillation
device of FIG.
[0035]
4 is a block diagram showing a first conventional example of the ultrasonic wave oscillation
device.
[0036]
5 is a schematic view showing a handpiece driven by the ultrasonic oscillation device.
[0037]
6 is a block diagram showing a second conventional example of the ultrasonic wave oscillation
device.
[0038]
7 is a block diagram showing a third conventional example of the ultrasonic wave oscillation
device.
[0039]
8 is an equivalent circuit diagram showing a part of the ultrasonic wave oscillation device of FIG.
[0040]
9 is a vector diagram for explaining the voltage detected by the voltage dividing resistor in the
ultrasonic oscillation device of FIG.
[0041]
10 is an equivalent circuit diagram showing a part of the ultrasonic oscillation device of FIG.
[0042]
11 is a vector diagram for explaining the voltage detected by the secondary side detection coil in
the ultrasonic oscillation device of FIG.
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[0043]
Explanation of sign
[0044]
DESCRIPTION OF REFERENCE NUMERALS 10 ultrasonic oscillator 12 oscillator 14 PLL module
16 motional bridge circuit 54 ultrasonic vibrator 56 driving circuit IN1 input signal OUT1, OUT2
output signal
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