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(Industrial field of application) The present invention relates to an ultrasonic transducer excellent
in vibration conversion efficiency. [Background Art] Conventionally, a bolt-clamped Langevin
type transducer is well known as one of ultrasonic transducers, and is widely used in medical
devices such as ultrasonic surgical tools. More than one annular electrode plate (31) and two
metal blocks (32) disposed at both ends thereof, the central holes of the electrostrictive element
(30) and the electrode plate (31) The whole is fixed and fixed with the screw hole of the metal
block (32) and the bolt through the bolt. In addition, an insulator may be disposed between the
electrode plate (31) and the metal block (32), which is preferable from the viewpoint of safety.
The ultrasonic transducer generates ultrasonic vibration on the end face (35) by passing a high
frequency current of a predetermined frequency from the conducting wires (33) and (34) to each
electrode plate. However, the processing distortion of the surface roughness and flatness of the
surfaces adjacent to each other between the electrostrictive element (30), the electrode plate (31)
and the metal block (32) causes the electrostrictive effect of the electrostrictive element (30). The
efficiency of converting expansion and contraction of 0, 5 to 10 μm into vibration generated at
the end face of the vibrator (35) is likely to vary, and it is also easy to reduce with use. When
firmly tightened, the distribution of rJ repulsive force on each pressure contact surface between
each of the electrostrictive elements (30), the electrode plate (31) and the metal block (32) is
radial toward the outer periphery from the central hole Expansion and contraction that occurred
around the central hole and expansion and contraction that occur near the outer periphery are
different, and can not be efficiently converted to vibration at the transducer end face (35).
Electrostrictive element Fever been misaligned in and the electrode plate, may become
impossible vibrations, difficult to set the fastening force. As a parameter proportional to these
vibration conversion efficiencies, there is a dynamic admittance value. In a conventional
ultrasonic transducer, when a low voltage, for example, a voltage of about 1 to 10 V at a
resonance frequency, is applied to a transducer having a diameter of 10 to 30 mφ and 4 to 10
electrostrictive elements, the dynamic admittance value is When vibration is applied by applying
a practical voltage of about 50 to 500 V, usually 5 to 10 m5, abnormal heat may be generated
from the vibrator or the vibration may stop without maintaining the resonance state. However, as
these solutions, it was lent extra time to adjust the fastening force for each individual vibrator.
SUMMARY OF THE INVENTION The present invention solves the problem that the vibration
conversion efficiency of the conventional ultrasonic transducer is low and the adjustment of the
fastening force is difficult, and the fastening force by bolting An object of the present invention is
to provide an ultrasonic transducer excellent in workability in manufacturing by improving the
vibration conversion efficiency by uniformly applying it to the entire pressure contact surface,
eliminating the process of adjusting the fastening force, and achieving excellent manufacturing
According to the present invention, one or more annular electrostrictive elements and an annular
electrode plate having a number larger than that of the electrostrictive elements are alternately
connected in parallel. A bolt-clamped Langevin type ultrasonic transducer in which a metal block
is disposed at each end with or without an insulator, and the whole is fastened with a bolt in the
center hole. It is an ultrasonic transducer characterized in that a hard elastic layer is provided
between pressure-welding surfaces in which two selected from an element, a metal block and an
insulator are adjacent to each other. Hereinafter, the present invention will be described in detail
with reference to the drawings. FIG. 1 is a view showing an ultrasonic transducer according to an
embodiment of the present invention. In the ultrasonic vibrator of the present invention, an
annular electrostrictive element (1) and an annular electrode plate (2) having a number more
than that of the electrostrictive element are alternately stacked, and metal blocks (3) are disposed
at both ends thereof. A hard elastic layer (4) is provided between the mutually adjacent pressure
contact surfaces of the electrostrictive element (1), the electrode plate (2) and the metal block
(3). Bolts are inserted into the center holes of the (1) and the electrode plate (2), and the whole is
fastened and fixed with the screw holes and bolts of the metal block (3). In addition, as shown in
FIG. 2, an insulator (8) may be disposed between the electrode plate (2) and the metal block (3)
via the hard elastic layer (4). When using for medical devices, such as a tool, it is preferable also
from a safety viewpoint. Each electrode plate is electrically connected to each other by the leads
(5) and (6) as shown in FIG. It is connected to the IJ and causes an electrostrictive effect in the
electrostrictive element (1) by passing a high frequency current of a predetermined frequency,
which is transmitted and converted to an end face of the ultrasonic transducer (the ultrasonic
vibration Occur. The material of the electrostrictive element (1) is not particularly limited as long
as it can withstand the clamping pressure, but it is preferable to use ceramics such as PZT (lead
zirconate titanate). The material of the metal block (3) may be stainless steel, titanium alloy,
aluminum alloy or the like, or may be a combination of metal blocks of different kinds of bases,
and is not particularly limited. Further, the insulator (8) is not limited as long as it is a ceramic
having an electrical resistance of 10 13 Ωcm or more and a relative dielectric constant of 20 or
less, for example, an Al 1 property. The hard elastic layer (4) in the present invention has a
hardness (stiffness) that can withstand the clamping force by bolting for assembly of the
ultrasonic transducer, the electrostrictive element (1) on both sides thereof, and the electrode
plate ( 2) It is required to have an elasticity that can uniformly transmit the ultrasonic vibration
to the entire press-contacting surface by absorbing the processing variation of the interface
roughness and flatness of the metal or ceramic forming the metal block (3 g) etc. Ru.
If the elastic modulus is too small, it acts to absorb ultrasonic vibration and the efficiency of
ultrasonic vibration transmission is low, so the elastic modulus on the order of 1/10 to 1/100
compared to metal and ceramic Is appropriate. In addition, it is necessary that the rigidity and
the elastic modulus do not greatly decrease not only at the normal operation (30 to 40'C) of the
ultrasonic transducer but also at the abnormal temperature (70 to 80'C). Furthermore, when it is
used for medical equipment such as ultrasonic surgical instruments, it has recently been required
that it can be autoclaved (vapor sterilization at 110 ° C. or higher) as a sterilization method.
Even at a high temperature of at least about 110 to 135 ° C., it is necessary not to lose the
rigidity against the pressure by the bolting. Examples of such materials include epoxy resins,
polyimide resins, polyamideimide resins, polybenzimidazole resins, and cross-linked curing types
such as composite resins of epoxy resins and polyimide resins or phenol resins for the edges.
Resins are suitable. The thickness of the hard elastic layer (4) is suitably 5 to 200 μm, preferably
20 to 100 μm, and when thinner than 5 μm, the effect as an elastic body can not be obtained,
while on the other hand, if it exceeds 200 μm There is a tendency for the transmission efficiency
of ultrasonic vibration to decrease. According to the structure of the present invention, the
dynamic admittance value shows 20 to 50 m5 more than twice that of the conventional one, and
the deterioration (the decrease in the dynamic admittance value) due to the use of the ultrasonic
transducer also decreases. For example, FIG. 3 shows the change of the dynamic admittance
value after generating a practical level of vibration of the ultrasonic transducer according to the
present invention and the conventional ultrasonic transducer. The vertical axis represents the
dynamic admittance value, the horizontal axis represents the vibration time, and the vibrator has
a structure in which the number of electrostrictive elements is six, and the vibration condition is
to connect the same vibrator (horn) to the vibrator. As a result of applying a liquid load to the tip
of the vibrator and repeating the cycle of stopping for 10 seconds with vibration applied for 10
seconds with a vibrator applied voltage of 100 to 300 V, the dynamic admittance value of the
vibrator according to the present invention is 20 m5 or more In contrast to this, there is no
change with respect to the initial value of 23 m5, while the conventional vibrator has a low initial
value of 10 m5, and the dynamic admittance value tends to decrease as the vibration time
increases. In the case of vibration, abnormal heat generation and vibration stop due to load
fluctuation occur. According to the present invention, the clamping pressure of the pressure
contact surfaces of the respective elements constituting the vibrator becomes uniform, and the
expansion and contraction of the entire pressure surface by the electrostrictive effect can be
converted into the vibration of the ultrasonic vibrator. A high soot of 20 m5 or more can be
obtained as the dynamic admittance value at low voltage, the vibration conversion efficiency is
improved, the number of steps for adjusting the adhesion to individual vibrators can be omitted,
and the manufacturing cost can be reduced. Thus, it is possible to absorb minute vibrations
generated in the diametrical direction, and to take out only axial vibrations at the end face of the
required ultrasonic transducer.
Furthermore, since the parallelism of the pressure-contacting surface of each component and the
variation in the surface roughness can be absorbed by the thickness of the hard elastic layer, the
cost can be reduced and the yield can be improved, and medical devices such as ultrasonic
surgical tools etc. It is suitable as an ultrasonic transducer used.
Brief description of the drawings
1 and 2 are diagrams showing the configuration of an ultrasonic transducer according to an
embodiment of the present invention, and FIG. 3 is a diagram showing a change in dynamic
admittance value according to the vibration time of the ultrasonic transducer. .
FIG. 4 is a view showing an example of the configuration of a conventional ultrasonic transducer.
Patent applicant Sumitomo Bakelite Co., Ltd. Fig. 1 rli Fig. 2