WO2017150455A1 - Ultrasonic cutting element and ultrasonic treatment tool - Google Patents

Ultrasonic cutting element and ultrasonic treatment tool Download PDF

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Publication number
WO2017150455A1
WO2017150455A1 PCT/JP2017/007515 JP2017007515W WO2017150455A1 WO 2017150455 A1 WO2017150455 A1 WO 2017150455A1 JP 2017007515 W JP2017007515 W JP 2017007515W WO 2017150455 A1 WO2017150455 A1 WO 2017150455A1
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vibrator
cutting element
main body
ultrasonic cutting
vibration
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PCT/JP2017/007515
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French (fr)
Japanese (ja)
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崇幸 直野
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富士フイルム株式会社
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/32—Surgical cutting instruments

Definitions

  • the present invention relates to an ultrasonic cutting element and an ultrasonic treatment tool for cutting an object by ultrasonically vibrating a blade edge, and in particular, an ultrastructure capable of realizing a small size that can be stored in a forceps port of a flexible endoscope.
  • the present invention relates to a sonic cutting element and an ultrasonic treatment device.
  • An ultrasonic scalpel used as an endoscopic treatment tool is superior to conventional laser scalpels, high-frequency knives, etc. in that it has tissue selectivity and is capable of hemostasis. Widely used in the field.
  • Non-Patent Document 1 proposes an ultrasonic knife having a drive unit including a PZT thin film formed by a hydrothermal synthesis method. This device is equipped with a horn as in the conventional product having the Langevin element described above, and is cut using the longitudinal vibration amplified by the horn. Miniaturization is realized.
  • the ultrasonic cutting element having the configuration described in Non-Patent Document 1 has a problem in that sufficient cutting performance cannot be obtained because sufficient vibration speed cannot be obtained.
  • an object of the present invention is to provide an ultrasonic cutting element and an ultrasonic treatment instrument that can realize a small size that can be applied to a flexible endoscope and that can obtain a sufficiently high vibration speed.
  • An ultrasonic cutting element includes a thin plate-shaped main body, a blade portion fixed to one end of the main body, a vibrator having a drive unit provided on at least one main surface of the main body, and the vibrator as the main body.
  • An ultrasonic cutting element comprising a holding member that holds a part of The drive unit is a piezoelectric actuator in which a lower electrode, a piezoelectric film, and an upper electrode are stacked in this order from the main surface side of the thin plate-like main body.
  • the vibrator is driven at both ends in the main surface direction by driving by the drive unit. It is a flexural vibrator that performs free bending vibration, and the holding member supports the vibrator only at a node position in a resonance mode of free bending vibration at both ends.
  • the main surface of the main body is a surface having the maximum area of the thin plate-shaped main body. Since the main body is a thin plate, the main surface exists on the front and back.
  • the main surface direction is a direction perpendicular to the main surface in a stationary state (a state where the main surface is not driven).
  • the piezoelectric film means a film-like piezoelectric body having a thickness of 10 ⁇ m or less.
  • the ultrasonic cutting element of the present invention is preferably provided with a flexible wire having one end connected to the holding member and guiding the vibrator to a cutting target.
  • the holding member supports the vibrator only on the long side surface of the main body.
  • the main body of the vibrator and the holding member are preferably formed from a single plate.
  • the vibrator includes a vibration detection unit that detects vibration of the vibrator on the main surface of the main body.
  • the piezoelectric film used in the drive unit is preferentially oriented to the tetragonal c-axis, Pb (Zr y , Ti z , Nb 1-yz ) O 3 , 0 ⁇ y ⁇ 1,0 ⁇ z ⁇ 1 It is preferable to consist of the perovskite type oxide represented by these.
  • Pb is an A site element in a perovskite structure generally represented by ABO 3
  • Zr, Ti, and Nb are B site elements.
  • the molar ratio of Pb: (Zr y , Ti z , Nb 1-yz ): O is 1: 1: 3 as a standard, but may be deviated as long as a perovskite structure can be obtained.
  • the main body is preferably made of a material having a thermal expansion coefficient larger than that of the piezoelectric film.
  • the ultrasonic treatment device of the present invention applies a resonance mode drive voltage signal that causes free bending vibration at both ends to the ultrasonic cutting device of the present invention and the upper electrode and lower electrode of the drive unit of the ultrasonic cutting device. And a signal control unit.
  • the ultrasonic cutting element of the present invention uses a flexural vibrator as a vibrator, it is possible to use a resonance frequency of a low-order mode even if the ultrasonic vibrator is downsized as compared with the case where a longitudinal vibrator is used.
  • the low-order mode since wide detuning can be taken, a stable vibration can be obtained even at a large amplitude.
  • the holding member since the holding member has a structure in which the vibrator is bent and held by a vibration node, vibration energy can be confined in the vibrator, and the resonance frequency is lowered even when a flexible catheter wire or the like is connected. Stable vibration can be obtained.
  • the ultrasonic cutting element of the present invention can obtain a sufficiently large vibration speed even if it is miniaturized, and can also be applied to a flexible endoscope.
  • FIG. 2 is a cross-sectional view taken along the lines IIA-IIA ′ and IIB-IIB ′ of the ultrasonic cutting element shown in FIG. It is sectional drawing of the design modification of the ultrasonic cutting element drive part of 1st Embodiment. It is a simulation figure of the displacement shape and node position of an ultrasonic cutting element based on the resonance analysis result by a finite element method. It is a figure which shows the displacement amount in a vibrator longitudinal direction position based on the resonance analysis result by a finite element method.
  • FIG. 6 is a plan view showing a structure A of an ultrasonic cutting element of Comparative Example 1.
  • FIG. 6 is a plan view showing a structure B of an ultrasonic cutting element of Comparative Example 2.
  • FIG. 3 is a plan view showing a structure C of the ultrasonic cutting element according to Embodiment 1.
  • FIG. It is a schematic diagram by the simulation which shows the displacement state of the ultrasonic cutting element of the comparative example 1.
  • 6 is a schematic diagram by simulation showing a displacement state of an ultrasonic cutting element of Comparative Example 2.
  • FIG. 3 is a schematic diagram by simulation showing a displacement state of the ultrasonic cutting element of Example 1.
  • FIG. 1 is a schematic configuration diagram schematically illustrating a configuration of an ultrasonic cutting treatment instrument including the ultrasonic cutting element according to the first embodiment of the present invention.
  • 2 is a cross-sectional view taken along the lines IIA-IIA ′ and IIB-IIB ′ of the ultrasonic cutting element shown in FIG. 1, and
  • FIG. 3 is a cross-sectional view of the ultrasonic cutting element according to the design change example.
  • the ultrasonic cutting element 1 includes a thin plate-like main body 10, a blade portion 15 fixed to one end of the main body 10, and a main body 10.
  • a vibrator 30 having a drive unit 20 provided on the surface and a holding member 40 for holding the vibrator 30 by a part of the main body 10 are provided.
  • the ultrasonic cutting element 1 includes a flexible wire 45 that is connected at one end to the holding member 40 and guides the vibrator 30 to a cutting target.
  • the ultrasonic treatment tool 100 provided with this ultrasonic cutting element 1 is a signal for inputting a driving voltage signal in a resonance mode to be described later to the driving unit 20 of the ultrasonic cutting element 1 in addition to the ultrasonic cutting element 1.
  • a control unit 50 is provided.
  • the vibrator 30 is a bending vibrator that freely bends and vibrates at both ends in the principal surface direction when driven by the driving unit 20.
  • the driving unit 20 causes the vibrator 30 to generate ultrasonic vibrations.
  • the drive unit 20 is a piezoelectric actuator in which a lower electrode 22, a piezoelectric film 23, and an upper electrode 24 are laminated in this order on at least one main surface 11 of the main body 10.
  • “lower” and “upper” do not mean top and bottom.
  • the pair of electrodes provided with the piezoelectric film interposed therebetween one electrode disposed on the main body side with respect to the main body 10 is simply referred to as a lower electrode, and the other electrode is simply referred to as an upper electrode.
  • the drive unit 20 may be provided on each of the two main surfaces 11 and 12 of the main body 10.
  • the piezoelectric film 23 by making the piezoelectric film 23 into two layers, the area of the portion that generates force can be doubled compared to the case of only one layer, so the generated force per unit voltage is doubled. be able to. Therefore, the cutting property as a cutting element is improved.
  • the lower electrode 22 and the piezoelectric film 23 may also be formed on the holding member 40. The piezoelectric film 23 provided on the holding member 40 does not contribute to driving.
  • the piezoelectric film 23 expands and contracts, and the drive unit 20 is formed on the main body 10 and the blade unit 15 integrated with the main body 10. Ultrasonic vibration can be generated.
  • the lower electrode 22 may be provided as necessary.
  • the main body 10 is formed of a conductive material such as metal
  • the piezoelectric film 23 may be formed directly on the main body 10 without providing the lower electrode 22.
  • the main component of the lower electrode 22 is not particularly limited, and examples thereof include metals or metal oxides such as Au, Pt, Ir, IrO 2 , RuO 2 , LaNiO 3 , and SrRuO 3 , and combinations thereof.
  • the main component of the upper electrode 24 is not particularly limited, and the materials exemplified for the lower electrode 22, electrode materials generally used in semiconductor processes such as Al, Ti, Ta, Cr, and Cu, and combinations thereof include Can be mentioned.
  • perovskite oxides represented by the following general formula (P) can be used as the piezoelectric film 23.
  • ABO 3 (P) (In the formula, A is an A site element and at least one element including Pb, B is an element of a B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, At least one element selected from the group consisting of Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and a lanthanide element, O: an oxygen atom.
  • the molar ratio of A: B: O is 1: 1: 3 as a standard, but this molar ratio may be deviated within a range where a perovskite structure can be taken.
  • Nb-PZT having a Nb / (Zr + Ti + Nb) molar ratio of 0.06 or more and 0.20 or less is preferable.
  • a film preferentially oriented to the tetragonal c-axis is preferable.
  • c-axis orientation means that the c-axis in a tetragonal crystal having a perovskite structure has a direction parallel to the film thickness direction. Whether or not the c-axis preferred orientation is determined can be determined by performing an X-ray structural analysis on the piezoelectric film. When the (001) peak indicating the c-axis orientation is larger than the (100) peak indicating the a-axis orientation, it can be regarded as “c-axis preferred orientation”.
  • the thickness of the lower electrode 22 and the upper electrode 24 is not particularly limited and is, for example, about 200 nm.
  • the film thickness of the piezoelectric film 23 is not particularly limited as long as it is 10 ⁇ m or less, and is usually 1 ⁇ m or more, for example, 1 to 5 ⁇ m.
  • the drive unit uses a piezoelectric film with a thickness of 10 ⁇ m or less, so the size can be reduced especially in the thickness direction, and it can be incorporated into a flexible endoscope. Can be designed.
  • the constituent material of the main body 10 Ti, Al or those alloys, stainless steel, an alumina, tungsten, a silicon etc. can be mentioned.
  • PZT or Nb-doped PZT it is preferable to use a material having a thermal expansion coefficient larger than that of the piezoelectric film such as titanium, titanium alloy, stainless steel, or alumina. Thereby, the orientation of the piezoelectric film can be easily set to the preferential orientation in the c-axis direction.
  • the holding member 40 supports the vibrator 30 only at the node position in the resonance mode of the free bending vibration at both ends.
  • the holding member 40 is connected to the main body 10 of the vibrator 30 by a support portion 42.
  • the support portion 42 is connected to the main body 10 at the node position of the vibrator 30.
  • the support portion 42 of the holding member 40 is connected to the main body 10 only on the long side surface of the main body 10 and is supported only on the long side surface (longitudinal side surface perpendicular to the main surface). .
  • the main body 10 is supported so as to be sandwiched from both sides at a node position from two long side surfaces.
  • the holding member 40 is supported at at least two points opposed to each other with the vibrator 30 interposed therebetween at one node position of the vibrator 30.
  • FIG. 4 is a schematic perspective view showing a displacement shape and a node position based on a resonance analysis result of a finite element method (FEM).
  • FIG. 5 is a graph showing the displacement amount for each position in the longitudinal direction of the vibrator based on the resonance analysis result. 4 and 5, as an example, when the longitudinal length L of the main body is 8.0 mm, the lateral length 1.2 mm, the blade length 1.5 mm, and the blade root portion width 0.3 mm An example is shown.
  • the shape of the vibrator is a thin plate having no blade and having a longitudinal dimension L
  • the blade portion 15 is provided at the tip of the thin plate-like main body 10
  • the mass balance in the longitudinal direction is lost. Therefore, the node position is different from the case of only the main body of the thin plate.
  • the node position when the blade is applied is a position where the amount of displacement is 0 in the longitudinal position shown in FIG.
  • the node position for supporting the vibrator 30 by the holding member 40 is not strictly limited to the node where the displacement amount is 0, but includes the vicinity of the node.
  • the vicinity of this node means a range in which the displacement amount is 5% or less of the displacement amount at the maximum displacement point of the resonator in the resonance mode.
  • the higher-order mode having three or more nodes is used than the lowest-order mode having two nodes, thereby improving vibration energy and performing a large work on the cutting target. It can be carried out.
  • FIG. 6 is a diagram schematically showing the vibration shape of the flexure vibrator when the number of nodes is 2, 3, and 4.
  • the number of nodes 2 described above is the resonance mode with the lowest order.
  • Table 1 below shows the result of calculating the vibration energy by FEM resonance analysis for each number of nodes.
  • the vibration frequency was set to approximately 30.7 kHz, which was substantially the same, the length of the vibrator was designed, and the vibration energy per blade speed of 1 m / s was obtained.
  • the blade length in the vibrator of each example was unified to 1.5 mm, and the width of the blade root portion was unified to 0.3 mm.
  • the vibration energy increases as the number of nodes increases.
  • the vibration energy is large, a decrease in vibration speed when a load is applied to the blade tip can be suppressed, so that the cutting characteristics can be stably maintained. That is, when a design using a flexural vibration mode with a large number of nodes is made, the cutting characteristics can be maintained even when a large load is applied during cutting.
  • the length of the vibrator becomes large.
  • the number of node positions supported by the holding member may be only one, but it is preferable that the node is supported at two or more node positions.
  • the ultrasonic cutting element of the present invention includes a flexural vibrator. Therefore, the resonance frequency can be realized in a lower order mode as compared with the longitudinal vibration. For this reason, the degree of detuning with the adjacent mode can be widened, and stable vibration can be obtained even during vibration with a large amplitude.
  • the degree of detuning is small, adjacent vibration modes are mixed when driving in the target vibration mode. In this case, non-linearity occurs due to dimensional changes due to mutual vibrations, which becomes the main factor that the vibration speed is sluggish. Furthermore, this phenomenon becomes more prominent as the vibration speed increases. From such a viewpoint, flexural vibration with a large degree of detuning can easily obtain a high vibration speed. In order to obtain a sufficient vibration speed, the degree of detuning is preferably 5% or more.
  • the flexural vibrator when applying an ultrasonic cutting element equipped with a flexural vibrator to a flexible endoscope, the flexural vibrator has a large vibration amplitude. Therefore, if the support method is not properly applied, vibration energy leaks to the soft catheter wire. As a result, the problem arises that the resonance frequency is greatly lowered and the driving becomes impossible.
  • the present inventor has found the problem. This is a problem that occurs for the first time when applied to a flexible endoscope, and cannot be generated without considering application to a flexible endoscope. Since the ultrasonic transducer according to the present invention has a structure in which the transducer is bent and held in the vicinity of the node of vibration, vibration energy can be confined in the transducer. Therefore, even when a flexible catheter wire or the like is connected, the resonance frequency does not decrease and the vibration speed does not decrease. That is, cutting characteristics such as the resonance frequency and vibration speed can be maintained.
  • the ultrasonic cutting element of the present invention is not limited to the one provided with a flexible wire, and the holding member may be connected to a strong fixing member.
  • the effect of not letting vibration energy escape to the outside of the vibrator is particularly remarkable when connected to a flexible wire.
  • the ultrasonic cutting element 1 of this embodiment shown in FIGS. 1 and 2 includes the main body 10 and the holding member 40 formed from a single plate.
  • the outer shape of the holding member 40 and the main body 10 is cut out from a single substrate by laser processing, and the support portion 42 of the holding member 40 is left, and a gap is formed between the holding member 40 and the main body 10. can do.
  • a complicated assembly process can be eliminated and manufacturing can be performed at low cost.
  • FIG. 7 is a plan view schematically showing the configuration of the ultrasonic cutting element 2 of the second embodiment.
  • the ultrasonic cutting element 2 of the present embodiment is the ultrasonic cutting element of the first embodiment described above in that the vibration detection unit 25 that detects the vibration state is provided on a part of the main surface 11 of the main body 10. Different from 1.
  • the same components as those of the ultrasonic cutting element 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
  • the upper electrode 24 of the drive unit 20 in the ultrasonic cutting element 1 of the first embodiment is partly divided and used as the detection electrode 27 of the vibration detection unit 25.
  • the configuration of the vibration detection unit 25 is the same as that of the drive unit 20, and has a laminated structure of the lower electrode 22, the piezoelectric film 23, and the detection electrode 27.
  • a voltage corresponding to the amount of stress is generated between both electrodes by a positive piezoelectric effect when stress is applied. It is possible to monitor whether the vibrator is in a resonance state by using the voltage generated when the stress is generated as a detection signal.
  • the vibration detection unit 25 is preferably provided in a region where stress is likely to occur.
  • the signal control unit 50 inputs to the drive unit 20 a drive voltage signal having a resonance frequency that causes the vibrator 30 to vibrate in the resonance mode of flexural vibration.
  • the cutting process by the ultrasonic cutting element is performed in a resonance state.
  • the ultrasonic cutting element 2 of the present embodiment has a configuration in which a detection signal from the vibration detection unit 25 is fed back to the signal control unit.
  • the signal control unit 50 calculates the deviation from the resonance state based on the phase difference between the detection signal and the drive voltage signal or the amplitude of the detection signal. Further, a drive voltage signal corrected so that the deviation from the calculated resonance state is always in the resonance state is generated.
  • the corrected drive voltage signal is applied to the drive unit 20. That is, the configuration of the ultrasonic cutting element 2 of the present embodiment makes it possible to easily operate in a state where the resonance state is always maintained.
  • the vibration detection unit 25 is separately provided on the other main surface side where the drive unit 20 is not formed, in addition to a configuration in which a part of the drive unit 20 is divided as in the above embodiment. May be. That is, as shown in the cross-sectional view of FIG. 3, each main surface of the main body 10 has a piezoelectric element structure of a lower electrode, a piezoelectric film, and an upper electrode, and the piezoelectric element on one main surface side is used as a drive unit. In addition, the piezoelectric element on the other main surface side may be used as the vibration detection unit.
  • FIG. 8A, FIG. 8B, and FIG. 8C show the structures A to C of the small ultrasonic scalpels of the comparative example 1, comparative example 2, and example 1 of the ultrasonic cutting element of the present invention, respectively.
  • 8A, 8B, and 8C also show the dimensions of each part of each element.
  • t is the thickness of each main body. In either case, the unit is [mm].
  • FIGS. 9A, 9B, and 9C are schematic perspective views showing displacement states in the vibration modes of the vibrators of FIGS. 8A, 8B, and 8C, respectively.
  • the ultrasonic cutting element (structure A) of Comparative Example 1 shown in FIGS. 8A and 9A is a conventional longitudinal vibration ultrasonic knife having a horn portion at the tip. The blade tip is pierced and cut by the vibration direction indicated by the double arrow in FIG.
  • the ultrasonic cutting element (Structure B) of Comparative Example 2 and the ultrasonic cutting element (Structure C) of Comparative Example 3 are vibrations that bend in the thickness direction (main surface direction) of the main body, that is, super vibrations that use flexural vibration. Sonic scalpel. 9B and 9C, the object is cut by vibrating the vibration direction indicated by the double arrow, that is, the blade in the thickness direction of the main body.
  • Comparative Examples 1 and 2 and Example 1 A manufacturing procedure of the elements of Comparative Examples 1 and 2 and Example 1 will be described.
  • a substrate constituting the main body and the holding member two types of 64 titanium alloy plate materials of 0.4 mm thickness (Comparative Example 1, Example 1) and 1.0 mm thickness (Comparative Example 2) (Standard: ASTM Gr.5, ASTM) F136) was used.
  • 30 nm of Ti was formed as an adhesion layer on the substrate surface by a sputtering method at a substrate temperature of 350 ° C., and then a lower electrode made of Ir was formed to 150 nm on the Ti film.
  • a piezoelectric film of about 3 ⁇ m was formed on the obtained lower electrode by Rf (radio frequency) sputtering.
  • the deposition gas used was a mixed gas of 97.5% Ar + 2.5% O 2 , and a target material having a composition of Pb 1.3 (Zr 0.52 Ti 0.48 ) 0.88 Nb 0.12 ) O 3 was used.
  • An upper electrode having a two-layer structure of Au (300 nm) / Ti (30 nm) was formed by patterning on the obtained piezoelectric film (hereinafter referred to as Nb-PZT film) by a lift-off method. Finally, the substrate was trimmed by laser processing to obtain the shapes shown in FIGS. 8A, 8B and 8C.
  • the resonance mode frequency, the mode order, and the degree of detuning are calculated by a finite element method (FEM) simulation. did.
  • Table 2 below shows the results of calculating the resonance frequency and detuning degree of the vibration mode used for cutting in each structure by FEM simulation.
  • the longitudinal vibration mode of the structure A is a 36th-order mode and a higher order, and the degree of detuning is as very low as 0.4%.
  • the bending vibrations of the structures B and C are the first and third modes, respectively, and the detuning degrees are 17% and 35%, which are sufficiently large values, which is advantageous for obtaining a high vibration speed. I can say that.
  • Table 2 also shows the experimental results of the vibration speed of the blade tip for each element.
  • the method for measuring the vibration speed was as follows. For each of the ultrasonic cutting elements of the structures A, B, and C, wiring was drawn from the upper electrode and lower electrode of the drive unit by wire bonding and connected to a function generator that was a signal control unit. The vibrator was vibrated by applying a sine voltage waveform corresponding to each resonance frequency between the upper electrode and the lower electrode by a function generator, and the maximum vibration velocity at the tip of the blade was measured by a laser Doppler meter. The excitation was performed at the resonance frequencies of the resonance modes shown in Table 1.
  • the ultrasonic cutting element of each example as the form which fixes the edge part opposite to the braid
  • the maximum driving speed at the tip of the blade was measured.
  • strong fixation gravity fixation was performed by an object having a sufficiently large weight with respect to each ultrasonic cutting element.
  • fixation via wire a catheter was assumed, and one end of a titanium wire having a diameter of 1 mm and the end of the holding member were joined with an adhesive, and the other end of the wire was strongly fixed.
  • a cantilever vibrator like the structure B shown in Comparative Example 2 receives a reaction force from the holding member fixed end when vibrating. That is, since vibration energy leaks out of the vibrator, the vibration speed is remarkably lowered when the vibration is caused to be fixed via a wire. On the other hand, since the element of Example 1 supports the vibrator at the node position of the bending vibration, almost no reaction force is generated in the holding member, and energy can be confined in the vibrator. Therefore, even if it was made to vibrate by fixing via a wire, a decrease in vibration speed was not confirmed.
  • the ultrasonic cutting element of the present invention can be applied to excision of a tumor or the like under a flexible endoscope, for example.
  • the elements of Examples 2 to 5 were manufactured by changing the substrate, and an experiment for comparing the driving durability was performed.
  • the devices of Examples 2 to 5 were manufactured by the same manufacturing method as in Example 1 except that the substrate was as shown in Table 3 below.
  • Table 3 shows the materials of the respective substrates (hereinafter referred to as substrate materials), their thermal expansion coefficients, and evaluation of the orientation, dielectric constant, and driving durability of the Nb-PZT film.
  • the orientation of the Nb-PZT film was analyzed by X-ray structural analysis, and the (001) peak was compared with the (100) peak, and the surface with the higher peak intensity was shown.
  • the dielectric constant of the Nb-PZT film was calculated from the value obtained by measuring the capacitance at a frequency of 1 kHz using an impedance analyzer.
  • the crystal orientation of the Nb-PZT film changes. This is caused by a difference in thermal expansion coefficient between the piezoelectric film and the substrate.
  • the piezoelectric film is an Nb-PZT film having a thermal expansion coefficient of 6.7 ppm / ° C.
  • the substrate material is silicon or tungsten.
  • a substrate made of a material having a thermal expansion coefficient larger than that of the piezoelectric film such as alumina, stainless steel (SUS430 in this case), or titanium alloy is used, a residual stress in the compressive direction is applied to the piezoelectric film.
  • a driving durability test was performed on the elements of Examples 1 to 5. Specifically, the time T [time (h)] from the start of driving to the stop of the function was measured, and the driving durability was evaluated according to the following criteria.
  • rubber was brought into contact with the tip of the blade portion as a cutting load, and a 30 Vpp sine wave was applied to the drive portion while maintaining the resonance frequency to drive the blade for a long time.
  • the function stop time is defined as the point at which the vibration speed drops below 10% due to dielectric breakdown of the piezoelectric film.

Abstract

Provided are an ultrasonic cutting element and an ultrasonic treatment tool that are small enough to be used in a flexible endoscope and that can achieve a sufficiently high vibration speed. An ultrasonic cutting element (1) that comprises: a vibrator (30) that has a thin-plate-shaped main body (10), a blade part (15) that is fixed to one end of the main body (10), and a drive part (20) that is provided upon at least one main surface (11) of the main body (10); and a holding member (40) that holds the vibrator (30) at one part of the main body (10). The drive part (20) comprises a piezoelectric actuator that is formed by layering, in order from the main surface (11) side of the main body (10), a lower electrode (22), a piezoelectric film (23), and an upper electrode (24). The vibrator (30) is driven by the drive part (20) and is a flexural vibrator that undergoes both-end free bending vibration in a main surface direction. The holding member (40) supports the vibrator (30) only in a node position for a resonance mode that is for both-end free bending vibration.

Description

超音波切断素子および超音波処置具Ultrasonic cutting element and ultrasonic treatment device
　本発明は、刃先を超音波振動させて被対象を切断する超音波切断素子および超音波処置具に関し、特に、軟性内視鏡の鉗子口に収納可能な小型サイズを実現可能な構造とした超音波切断素子および超音波処置具に関する。 The present invention relates to an ultrasonic cutting element and an ultrasonic treatment tool for cutting an object by ultrasonically vibrating a blade edge, and in particular, an ultrastructure capable of realizing a small size that can be stored in a forceps port of a flexible endoscope. The present invention relates to a sonic cutting element and an ultrasonic treatment device.
　内視鏡処置具として利用される超音波メスは、従来のレーザーメス、高周波ナイフ等に対し、組織選択性がある、および止血が可能である等の点で優れているため、硬性内視鏡の分野で広く用いられている。 An ultrasonic scalpel used as an endoscopic treatment tool is superior to conventional laser scalpels, high-frequency knives, etc. in that it has tissue selectivity and is capable of hemostasis. Widely used in the field.
　従来の超音波メスおよび超音波カッターなどの超音波切断素子は、圧電セラミックスのランジュバン素子を用いて縦振動を発生させる振動発生源（駆動部）と、発生した縦振動の速度を増幅するホーンとを機械的に組み合わせた構成となっている。しかしながら、ランジュバン素子とホーンとを組み合わせた大型の構成となるため、経口内視鏡や大腸内視鏡など、軟性内視鏡の鉗子口に収納可能なサイズのものは存在しない。 Conventional ultrasonic cutting elements such as ultrasonic scalpels and ultrasonic cutters use a piezoelectric ceramic Langevin element to generate a vibration (drive unit) that generates longitudinal vibration, and a horn that amplifies the speed of the generated vertical vibration. Are mechanically combined. However, since it has a large configuration combining a Langevin element and a horn, there is no size that can be accommodated in a forceps port of a flexible endoscope, such as an oral endoscope or a colonoscope.
　超音波切断素子の小型化の試みとして、非特許文献１では、水熱合成法によって成膜したＰＺＴ薄膜を備えた駆動部を有する超音波メスが提案されている。このデバイスは、上述のランジュバン素子を備えた従来品と同様にホーンを備え、ホーンにより増幅された縦振動を利用して切断するものであるが、圧電体を薄膜化することによりデバイスとして大幅な小型化を実現している。 As an attempt to reduce the size of the ultrasonic cutting element, Non-Patent Document 1 proposes an ultrasonic knife having a drive unit including a PZT thin film formed by a hydrothermal synthesis method. This device is equipped with a horn as in the conventional product having the Langevin element described above, and is cut using the longitudinal vibration amplified by the horn. Miniaturization is realized.
特開２０１２－１７９１０２号公報JP 2012-179102 A
　しかしながら、非特許文献１に記載の構成の超音波切断素子では、十分な振動速度が得られないため、十分な切断性能が得られないという問題があった。 However, the ultrasonic cutting element having the configuration described in Non-Patent Document 1 has a problem in that sufficient cutting performance cannot be obtained because sufficient vibration speed cannot be obtained.
　本発明は、上記事情に鑑み、軟性内視鏡に適用できるレベルの小型サイズを実現でき、かつ十分大きい振動速度が得られる超音波切断素子および超音波処置具を提供することを目的とする。 In view of the above circumstances, an object of the present invention is to provide an ultrasonic cutting element and an ultrasonic treatment instrument that can realize a small size that can be applied to a flexible endoscope and that can obtain a sufficiently high vibration speed.
　本発明者は、鋭意検討の結果、縦振動を用いた非特許文献１に記載のデバイスの振動速度不足の主原因は、隣接モードとの周波数差（＝離調度）が小さいためであることを突き止め、この知見に基づいて本発明を想到した。 As a result of intensive studies, the inventor has found that the main cause of insufficient vibration speed of the device described in Non-Patent Document 1 using longitudinal vibration is that the frequency difference (= detuning degree) from the adjacent mode is small. Based on this finding, the present inventors have conceived the present invention.
　本発明の超音波切断素子は、細板状の本体、本体の一端に固定されたブレード部、および本体の少なくとも一方の主面上に設けられた駆動部を有する振動子と、振動子を本体の一部で保持する保持部材とを備えた超音波切断素子であって、
　駆動部は、細板状の本体の主面側から下部電極、圧電体膜および上部電極がこの順に積層されてなる圧電アクチュエータであり、振動子は、駆動部による駆動により、主面方向に両端自由屈曲振動する撓み振動子であり、保持部材は、両端自由屈曲振動の共振モードにおける節位置でのみ振動子を支持していることを特徴とする。 An ultrasonic cutting element according to the present invention includes a thin plate-shaped main body, a blade portion fixed to one end of the main body, a vibrator having a drive unit provided on at least one main surface of the main body, and the vibrator as the main body. An ultrasonic cutting element comprising a holding member that holds a part of
The drive unit is a piezoelectric actuator in which a lower electrode, a piezoelectric film, and an upper electrode are stacked in this order from the main surface side of the thin plate-like main body. The vibrator is driven at both ends in the main surface direction by driving by the drive unit. It is a flexural vibrator that performs free bending vibration, and the holding member supports the vibrator only at a node position in a resonance mode of free bending vibration at both ends.
　ここで、本体の主面とは、細板状の本体の最大面積を有する面である。本体は細板であるため、主面は表裏に存在する。また、主面方向とは、静止状態（駆動されていない状態）の主面に垂直な方向をいう。
　本明細書において、圧電体膜とは１０μｍ以下の厚みの膜状の圧電体をいうものとする。 Here, the main surface of the main body is a surface having the maximum area of the thin plate-shaped main body. Since the main body is a thin plate, the main surface exists on the front and back. The main surface direction is a direction perpendicular to the main surface in a stationary state (a state where the main surface is not driven).
In this specification, the piezoelectric film means a film-like piezoelectric body having a thickness of 10 μm or less.
　本発明の超音波切断素子は、一端が保持部材に接続され、切断対象に振動子を導くための可撓性ワイヤを備えていることが好ましい。 The ultrasonic cutting element of the present invention is preferably provided with a flexible wire having one end connected to the holding member and guiding the vibrator to a cutting target.
　本発明の超音波切断素子は、保持部材が振動子を、本体の長側面でのみ支持していることが好ましい。 In the ultrasonic cutting element of the present invention, it is preferable that the holding member supports the vibrator only on the long side surface of the main body.
　本発明の超音波切断素子は、振動子の本体と保持部材とが一枚板から形成されてなることが好ましい。 In the ultrasonic cutting element of the present invention, the main body of the vibrator and the holding member are preferably formed from a single plate.
　本発明の超音波切断素子は、振動子が、本体の主面に、振動子の振動を検出する振動検出部を備えていることが好ましい。 In the ultrasonic cutting element according to the present invention, it is preferable that the vibrator includes a vibration detection unit that detects vibration of the vibrator on the main surface of the main body.
　本発明の超音波切断素子は、駆動部に用いられる圧電体膜が、正方晶ｃ軸に優先配向した、Ｐｂ（Ｚｒｙ，Ｔｉｚ，Ｎｂ1－ｙ－ｚ）Ｏ３，０＜ｙ＜１，０＜ｚ＜１
で表されるペロブスカイト型酸化物からなることが好ましい。 In the ultrasonic cutting element of the present invention, the piezoelectric film used in the drive unit is preferentially oriented to the tetragonal c-axis, Pb (Zr y , Ti z , Nb 1-yz ) O 3 , 0 <y < 1,0 <z <1
It is preferable to consist of the perovskite type oxide represented by these.
　ここで、Ｐｂは一般にＡＢＯ３で表されるペロブスカイト構造におけるＡサイト元素であり、Ｚｒ，Ｔｉ，ＮｂはＢサイト元素である。Ｐｂ：（Ｚｒｙ，Ｔｉｚ，Ｎｂ1－ｙ－ｚ）：Ｏのモル比は１：１：３が標準であるが、ペロブスカイト構造を取りうる範囲でずれていてもよい。 Here, Pb is an A site element in a perovskite structure generally represented by ABO 3 , and Zr, Ti, and Nb are B site elements. The molar ratio of Pb: (Zr y , Ti z , Nb 1-yz ): O is 1: 1: 3 as a standard, but may be deviated as long as a perovskite structure can be obtained.
　本発明の超音波切断素子は、本体が、圧電体膜の熱膨張係数よりも大きい熱膨張係数を有する材料からなることが好ましい。 In the ultrasonic cutting element of the present invention, the main body is preferably made of a material having a thermal expansion coefficient larger than that of the piezoelectric film.
　本発明の超音波処置具は、本発明の超音波切断素子と、超音波切断素子の駆動部の上部電極および下部電極に対して、両端自由屈曲振動を生じさせる共振モードの駆動電圧信号を付与する信号制御部とを備えている。 The ultrasonic treatment device of the present invention applies a resonance mode drive voltage signal that causes free bending vibration at both ends to the ultrasonic cutting device of the present invention and the upper electrode and lower electrode of the drive unit of the ultrasonic cutting device. And a signal control unit.
　本発明の超音波切断素子は、振動子として撓み振動子を用いているため、縦振動子を用いる場合と比較して小型にしても低次モードの共振周波数を用いることができる。低次モードの場合、離調を広く取ることができるため、大振幅での振動時も安定した振動が得られる。また、保持部材が振動子を撓み振動の節で保持する構造を有しているので、振動エネルギーを振動子に閉じ込めることができ、フレキシブルなカテーテルワイヤなどが接続された際でも共振周波数が低下したり、振動速度が落ちたりすることがなく、安定した振動を得ることができる。 Since the ultrasonic cutting element of the present invention uses a flexural vibrator as a vibrator, it is possible to use a resonance frequency of a low-order mode even if the ultrasonic vibrator is downsized as compared with the case where a longitudinal vibrator is used. In the case of the low-order mode, since wide detuning can be taken, a stable vibration can be obtained even at a large amplitude. In addition, since the holding member has a structure in which the vibrator is bent and held by a vibration node, vibration energy can be confined in the vibrator, and the resonance frequency is lowered even when a flexible catheter wire or the like is connected. Stable vibration can be obtained.
　したがって、本発明の超音波切断素子は、小型化しても十分大きい振動速度を得ることができ、軟性内視鏡にも適用することができる。 Therefore, the ultrasonic cutting element of the present invention can obtain a sufficiently large vibration speed even if it is miniaturized, and can also be applied to a flexible endoscope.
第１の実施形態における超音波切断素子および超音波切断素子を備えた超音波処置具の概略構成を示す図である。It is a figure which shows schematic structure of the ultrasonic treatment tool provided with the ultrasonic cutting element and ultrasonic cutting element in 1st Embodiment. 図１に示した超音波切断素子のIIA-IIA'断面図およびIIB-IIB'断面図である。FIG. 2 is a cross-sectional view taken along the lines IIA-IIA ′ and IIB-IIB ′ of the ultrasonic cutting element shown in FIG. 第１の実施形態の超音波切断素子駆動部の設計変形例の断面図である。It is sectional drawing of the design modification of the ultrasonic cutting element drive part of 1st Embodiment. 有限要素法による共振解析結果に基づく、超音波切断素子の変位形状および節位置のシミュレーション図である。It is a simulation figure of the displacement shape and node position of an ultrasonic cutting element based on the resonance analysis result by a finite element method. 有限要素法による共振解析結果に基づく、振動子長手方向位置における変位量を示す図である。It is a figure which shows the displacement amount in a vibrator longitudinal direction position based on the resonance analysis result by a finite element method. 異なるノード数の撓み振動子の振動形状を模式的に示す図である。It is a figure which shows typically the vibration shape of the bending vibrator of a different number of nodes. 第２の実施形態における超音波切断素子および超音波切断素子を備えた超音波処置具の概略構成を示すである。It is a schematic configuration of an ultrasonic treatment device including an ultrasonic cutting element and an ultrasonic cutting element according to a second embodiment. 比較例１の超音波切断素子の構造Ａを示す平面図である。6 is a plan view showing a structure A of an ultrasonic cutting element of Comparative Example 1. FIG. 比較例２の超音波切断素子の構造Ｂを示す平面図である。6 is a plan view showing a structure B of an ultrasonic cutting element of Comparative Example 2. FIG. 実施例１の超音波切断素子の構造Ｃを示す平面図である。3 is a plan view showing a structure C of the ultrasonic cutting element according to Embodiment 1. FIG. 比較例１の超音波切断素子の変位状態を示すシミュレーションによる模式図である。It is a schematic diagram by the simulation which shows the displacement state of the ultrasonic cutting element of the comparative example 1. 比較例２の超音波切断素子の変位状態を示すシミュレーションによる模式図である。6 is a schematic diagram by simulation showing a displacement state of an ultrasonic cutting element of Comparative Example 2. FIG. 実施例１の超音波切断素子の変位状態を示すシミュレーションによる模式図である。FIG. 3 is a schematic diagram by simulation showing a displacement state of the ultrasonic cutting element of Example 1.
　以下、図面を参照して本発明の超音波切断素子および超音波切断素子を備えた超音波処置具の実施の形態について説明する。
　図１は、本発明の第１の実施形態の超音波切断素子を備えた超音波切断処置具の構成を模式的に示す概略構成図である。図２は、図１に示す超音波切断素子のIIA－IIA'断面図およびIIB-IIB'断面図であり、図３は設計変更例の超音波切断素子の断面図である。 DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an ultrasonic treatment device including an ultrasonic cutting element and an ultrasonic cutting element according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram schematically illustrating a configuration of an ultrasonic cutting treatment instrument including the ultrasonic cutting element according to the first embodiment of the present invention. 2 is a cross-sectional view taken along the lines IIA-IIA ′ and IIB-IIB ′ of the ultrasonic cutting element shown in FIG. 1, and FIG. 3 is a cross-sectional view of the ultrasonic cutting element according to the design change example.
　超音波切断素子１は、図１に示すように、細板状の本体１０、その本体１０の一端に固定された、切断対象を切断するためのブレード部１５、および本体１０の少なくとも一方の主面上に設けられた駆動部２０を有する振動子３０と、振動子３０を本体１０の一部で保持する保持部材４０とを備えている。また、超音波切断素子１は、一端が保持部材４０に接続され、切断対象に振動子３０を導くための可撓性ワイヤ４５を備えている。 As shown in FIG. 1, the ultrasonic cutting element 1 includes a thin plate-like main body 10, a blade portion 15 fixed to one end of the main body 10, and a main body 10. A vibrator 30 having a drive unit 20 provided on the surface and a holding member 40 for holding the vibrator 30 by a part of the main body 10 are provided. In addition, the ultrasonic cutting element 1 includes a flexible wire 45 that is connected at one end to the holding member 40 and guides the vibrator 30 to a cutting target.
　そして、本超音波切断素子１を備えた超音波処置具１００は、超音波切断素子１に加え、超音波切断素子１の駆動部２０に対して後述する共振モードの駆動電圧信号を入力する信号制御部５０を備えている。 And the ultrasonic treatment tool 100 provided with this ultrasonic cutting element 1 is a signal for inputting a driving voltage signal in a resonance mode to be described later to the driving unit 20 of the ultrasonic cutting element 1 in addition to the ultrasonic cutting element 1. A control unit 50 is provided.
　振動子３０は、駆動部２０による駆動により主面方向に両端自由屈曲振動する撓み振動子である。 The vibrator 30 is a bending vibrator that freely bends and vibrates at both ends in the principal surface direction when driven by the driving unit 20.
　駆動部２０は、振動子３０に超音波振動を生じさせるものである。図２に示すように、駆動部２０は本体１０の少なくとも一方の主面１１上に下部電極２２、圧電体膜２３および上部電極２４がこの順に積層されてなる圧電アクチュエータである。ここで、「下部」および「上部」は天地を意味するものではない。圧電体膜を挟んで設けられる一対の電極に関し、本体１０を基準として本体側に配置される一方の電極を下部電極、他方の電極を上部電極と称しているに過ぎない。 The driving unit 20 causes the vibrator 30 to generate ultrasonic vibrations. As shown in FIG. 2, the drive unit 20 is a piezoelectric actuator in which a lower electrode 22, a piezoelectric film 23, and an upper electrode 24 are laminated in this order on at least one main surface 11 of the main body 10. Here, “lower” and “upper” do not mean top and bottom. Regarding the pair of electrodes provided with the piezoelectric film interposed therebetween, one electrode disposed on the main body side with respect to the main body 10 is simply referred to as a lower electrode, and the other electrode is simply referred to as an upper electrode.
　なお、図３に示すように、駆動部２０は本体１０の２つの主面１１、１２のそれぞれに設けられていてもよい。図３に示すように圧電体膜２３を二層にすることで、一層のみの場合に比べて力を発生させる部分の面積を２倍にできるため、単位電圧あたりの発生力を２倍にすることができる。そのため、切断素子としての切断性が向上する。また、図３に示すように、保持部材４０にも下部電極２２および圧電体膜２３が形成されていても構わない。保持部材４０に設けられている圧電体膜２３は駆動には寄与しない。 In addition, as shown in FIG. 3, the drive unit 20 may be provided on each of the two main surfaces 11 and 12 of the main body 10. As shown in FIG. 3, by making the piezoelectric film 23 into two layers, the area of the portion that generates force can be doubled compared to the case of only one layer, so the generated force per unit voltage is doubled. be able to. Therefore, the cutting property as a cutting element is improved. Further, as shown in FIG. 3, the lower electrode 22 and the piezoelectric film 23 may also be formed on the holding member 40. The piezoelectric film 23 provided on the holding member 40 does not contribute to driving.
　上部電極２４－下部電極２２間に駆動電圧が印加されることにより、圧電体膜２３に伸縮が生じて駆動部２０が形成されている本体１０および本体１０と一体となっているブレード部１５に超音波振動を生じさせることができる。 When a drive voltage is applied between the upper electrode 24 and the lower electrode 22, the piezoelectric film 23 expands and contracts, and the drive unit 20 is formed on the main body 10 and the blade unit 15 integrated with the main body 10. Ultrasonic vibration can be generated.
　下部電極２２は必要に応じて設ければよい。例えば、本体１０が金属などの導電性を有する材料で形成されている場合は、下部電極２２を設けず、本体１０上に直接圧電体膜２３を成膜してもよい。下部電極２２の主成分としては、特に制限はなく、Ａｕ、Ｐｔ、Ｉｒ、ＩｒＯ２、ＲｕＯ２、ＬａＮｉＯ３、およびＳｒＲｕＯ３等の金属または金属酸化物、および、これらの組合せが挙げられる。上部電極２４の主成分としては特に制限なく、下部電極２２で例示した材料、Ａｌ、Ｔｉ、Ｔａ、Ｃｒ、およびＣｕ等の一般的に半導体プロセスで用いられている電極材料、およびこれらの組合せが挙げられる。 The lower electrode 22 may be provided as necessary. For example, when the main body 10 is formed of a conductive material such as metal, the piezoelectric film 23 may be formed directly on the main body 10 without providing the lower electrode 22. The main component of the lower electrode 22 is not particularly limited, and examples thereof include metals or metal oxides such as Au, Pt, Ir, IrO 2 , RuO 2 , LaNiO 3 , and SrRuO 3 , and combinations thereof. The main component of the upper electrode 24 is not particularly limited, and the materials exemplified for the lower electrode 22, electrode materials generally used in semiconductor processes such as Al, Ti, Ta, Cr, and Cu, and combinations thereof include Can be mentioned.
　圧電体膜２３としては、下記一般式（Ｐ）で表される１種または複数種のペロブスカイト型酸化物を用いることができる。 As the piezoelectric film 23, one or more perovskite oxides represented by the following general formula (P) can be used.
　一般式ＡＢＯ３・・・（Ｐ）
（式中、Ａ：Ａサイト元素であり、Ｐｂを含む少なくとも１種の元素、Ｂ：Ｂサイトの元素であり、Ｔｉ、Ｚｒ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｓｃ、Ｃｏ、Ｃｕ、Ｉｎ、Ｓｎ、Ｇａ、Ｚｎ、Ｃｄ、Ｆｅ、Ｎｉ、およびランタニド元素からなる群より選ばれた少なくとも１種の元素、Ｏ：酸素原子。
Ａ：Ｂ：Ｏのモル比は１：１：３が標準であるが、このモル比はペロブスカイト構造を取り得る範囲内でずれてもよい。） General formula ABO 3 (P)
(In the formula, A is an A site element and at least one element including Pb, B is an element of a B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, At least one element selected from the group consisting of Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and a lanthanide element, O: an oxygen atom.
The molar ratio of A: B: O is 1: 1: 3 as a standard, but this molar ratio may be deviated within a range where a perovskite structure can be taken. )
　特には、Ｐｂ（Ｚｒｙ，Ｔｉｚ，Ｎｂ1－ｙ－ｚ）Ｏ３，０＜ｙ＜１，０＜ｚ＜１で表される、所謂ＰＺＴ（lead zirconate titanate）、あるいはＮｂ－ＰＺＴ(Nb doped lead zirconate titanate)と称される、ペロブスカイト型酸化物であることが好ましい。特には、Ｎｂ／（Ｚｒ＋Ｔｉ＋Ｎｂ）モル比が０．０６以上０．２０以下であるＮｂ－ＰＺＴが好ましい。また、圧電体膜が、ＰＺＴもしくはＮｂ－ＰＺＴである場合、正方晶ｃ軸に優先配向した膜であることが好ましい。このＰＺＴもしくはＮｂ－ＰＺＴからなる圧電体膜はｃ軸優先配向の場合、誘電率が小さくなり、駆動時の発熱を抑え、耐久性を向上することができるからである。
　なお、ここで、「ｃ軸配向」とは、ペロブスカイト構造の正方晶におけるｃ軸が、膜厚方向に平行な向きを持つことを意味する。ｃ軸優先配向であるか否かは、圧電体膜についてＸ線構造解析を行って判断することができる。ｃ軸配向を示す（００１）のピークがａ軸配向を示す（１００）のピークよりも大きい場合、「ｃ軸優先配向」と看做すことができる。 Particularly, Pb (Zr y, Ti z , Nb 1-y-z) O 3, 0 <y <1,0 <z < represented by 1, so-called PZT (lead zirconate titanate), or Nb-PZT ( A perovskite oxide called Nb doped lead zirconate titanate is preferable. In particular, Nb-PZT having a Nb / (Zr + Ti + Nb) molar ratio of 0.06 or more and 0.20 or less is preferable. Further, when the piezoelectric film is PZT or Nb-PZT, a film preferentially oriented to the tetragonal c-axis is preferable. This is because the piezoelectric film made of PZT or Nb-PZT has a low dielectric constant in the c-axis preferential orientation, can suppress heat generation during driving, and can improve durability.
Here, “c-axis orientation” means that the c-axis in a tetragonal crystal having a perovskite structure has a direction parallel to the film thickness direction. Whether or not the c-axis preferred orientation is determined can be determined by performing an X-ray structural analysis on the piezoelectric film. When the (001) peak indicating the c-axis orientation is larger than the (100) peak indicating the a-axis orientation, it can be regarded as “c-axis preferred orientation”.
　下部電極２２と上部電極２４の厚みは特に制限なく、例えば２００ｎｍ程度である。圧電体膜２３の膜厚は１０μｍ以下であれば特に制限なく、通常１μｍ以上であり、例えば、１～５μｍである。駆動部に厚み１０μｍ以下である圧電体膜を用いているので、従来のランジュバン振動子を用いた構造に比べて、特に厚み方向でのサイズダウンが可能であり、軟性内視鏡に組み込めるサイズでの設計が可能となる。 The thickness of the lower electrode 22 and the upper electrode 24 is not particularly limited and is, for example, about 200 nm. The film thickness of the piezoelectric film 23 is not particularly limited as long as it is 10 μm or less, and is usually 1 μm or more, for example, 1 to 5 μm. Compared to the structure using a conventional Langevin vibrator, the drive unit uses a piezoelectric film with a thickness of 10 μm or less, so the size can be reduced especially in the thickness direction, and it can be incorporated into a flexible endoscope. Can be designed.
　なお、本体１０の構成材料についても特に制限はないが、Ｔｉ、Ａｌあるいはそれらの合金、ステンレス鋼、アルミナ、タングステン、シリコンなどを挙げることができる。ＰＺＴあるいはＮｂドープＰＺＴを圧電体膜とする場合、チタン、チタン合金、ステンレス鋼あるいはアルミナなどの圧電体膜の熱膨張係数より大きい熱膨張係数を有する材料を用いるのが好ましい。これにより、圧電体膜の配向を容易にｃ軸方向への優先配向とすることができる。 In addition, although there is no restriction | limiting in particular also about the constituent material of the main body 10, Ti, Al or those alloys, stainless steel, an alumina, tungsten, a silicon etc. can be mentioned. When PZT or Nb-doped PZT is used as the piezoelectric film, it is preferable to use a material having a thermal expansion coefficient larger than that of the piezoelectric film such as titanium, titanium alloy, stainless steel, or alumina. Thereby, the orientation of the piezoelectric film can be easily set to the preferential orientation in the c-axis direction.
　保持部材４０は、両端自由屈曲振動の共振モードにおける節（ノード）位置でのみ振動子３０を支持している。保持部材４０は支持部４２で振動子３０の本体１０と接続されている。この支持部４２は振動子３０の節位置で本体１０と接続されている。
　特に、本実施形態においては、保持部材４０の支持部４２は、本体１０の長側面でのみ本体１０に接続されて、長側面（主面に垂直な長手方向の側面）でのみ支持されている。本体１０の２つの長側面から節位置で両側から挟むようにして支持される。このように、保持部材４０は、振動子３０の１つの節位置において振動子３０を挟んで対向する少なくとも２点で支持する。 The holding member 40 supports the vibrator 30 only at the node position in the resonance mode of the free bending vibration at both ends. The holding member 40 is connected to the main body 10 of the vibrator 30 by a support portion 42. The support portion 42 is connected to the main body 10 at the node position of the vibrator 30.
In particular, in the present embodiment, the support portion 42 of the holding member 40 is connected to the main body 10 only on the long side surface of the main body 10 and is supported only on the long side surface (longitudinal side surface perpendicular to the main surface). . The main body 10 is supported so as to be sandwiched from both sides at a node position from two long side surfaces. As described above, the holding member 40 is supported at at least two points opposed to each other with the vibrator 30 interposed therebetween at one node position of the vibrator 30.
　両端自由屈曲振動の共振モードにおける節とは、振動子３０が撓み振動を行う際、変位が０となる地点である。節位置は、有限要素法を用いた共振解析による求めることができる。図４は有限要素法（Finite Element Method：FEM）の共振解析結果に基づく変位形状および節位置を示す斜視模式図である。図５は共振解析結果に基づく、振動子の長手方向位置毎の変位量を示すグラフである。図４および図５においては、一例として、本体の長手方向長さＬ＝８．０ｍｍ、短手方向長さ１．２ｍｍ、ブレード長さ１．５ｍｍ、ブレード根元部の幅０．３ｍｍとした場合における例を示している。 The node in the resonance mode of free bending vibration at both ends is a point where the displacement becomes zero when the vibrator 30 performs flexural vibration. The node position can be obtained by resonance analysis using a finite element method. FIG. 4 is a schematic perspective view showing a displacement shape and a node position based on a resonance analysis result of a finite element method (FEM). FIG. 5 is a graph showing the displacement amount for each position in the longitudinal direction of the vibrator based on the resonance analysis result. 4 and 5, as an example, when the longitudinal length L of the main body is 8.0 mm, the lateral length 1.2 mm, the blade length 1.5 mm, and the blade root portion width 0.3 mm An example is shown.
　ここでは、節の数（ノード数）が２となる最低次数の振動の場合について検討している。振動子の形状がブレードを備えていない、長手方向寸法がＬの細板である場合、長手方向の両端からそれぞれ約Ｌ／４の位置に節が存在する。しかしながら、図４に示すように、ブレード部１５が細板状の本体１０の先端に設けられているため、長手方向の質量バランスが崩れる。そのため、節位置は細板の本体のみの場合とは異なる。ブレードが付与されている場合の節位置は、図５に示す長手方向位置において、変位量が０となる位置である。 Here, we consider the case of vibration of the lowest order where the number of nodes (number of nodes) is 2. When the shape of the vibrator is a thin plate having no blade and having a longitudinal dimension L, there are nodes at positions of about L / 4 from both ends in the longitudinal direction. However, as shown in FIG. 4, since the blade portion 15 is provided at the tip of the thin plate-like main body 10, the mass balance in the longitudinal direction is lost. Therefore, the node position is different from the case of only the main body of the thin plate. The node position when the blade is applied is a position where the amount of displacement is 0 in the longitudinal position shown in FIG.
　なお、保持部材４０による振動子３０を支持する節位置とは、厳密に上記の変位量が０となる節に限定されるものではなく、節近傍を含む。この節近傍とは、変位量が共振モードの振動子最大変位点における変位量の５％以下である範囲をいうこととする。 Note that the node position for supporting the vibrator 30 by the holding member 40 is not strictly limited to the node where the displacement amount is 0, but includes the vicinity of the node. The vicinity of this node means a range in which the displacement amount is 5% or less of the displacement amount at the maximum displacement point of the resonator in the resonance mode.
　撓み共振モードとしては、ノードの数が２である最低次モードよりも、ノードの数が３以上である高次モードを使用することにより、振動エネルギーを向上させ、切断対象に対して大きな仕事を行うことができる。 As the flexural resonance mode, the higher-order mode having three or more nodes is used than the lowest-order mode having two nodes, thereby improving vibration energy and performing a large work on the cutting target. It can be carried out.
　図６は、ノード数２、３および４の場合の撓み振動子の振動形状を模式的に示す図である。先に説明したノード数２が最も次数の低い共振モードである。各ノード数の場合について、振動エネルギーをＦＥＭの共振解析によって計算した結果を下記表１に示す。ここでは、振動周波数がほぼ同等の３０．７ｋＨｚ程度となるようにした上で、振動子長さを設計し、ブレード速度１ｍ／ｓ当たりの振動エネルギーを求めた。なお、各例の振動子におけるブレード長さは１．５ｍｍ、ブレード根元部の幅は０．３ｍｍで統一した。 FIG. 6 is a diagram schematically showing the vibration shape of the flexure vibrator when the number of nodes is 2, 3, and 4. The number of nodes 2 described above is the resonance mode with the lowest order. Table 1 below shows the result of calculating the vibration energy by FEM resonance analysis for each number of nodes. Here, the vibration frequency was set to approximately 30.7 kHz, which was substantially the same, the length of the vibrator was designed, and the vibration energy per blade speed of 1 m / s was obtained. In addition, the blade length in the vibrator of each example was unified to 1.5 mm, and the width of the blade root portion was unified to 0.3 mm.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示す通り、ノード数が大きくなるにつれて、振動エネルギーが大きいことが分かる。振動エネルギーが大きい場合、ブレード先端に負荷がかかった際の振動速度の低下を抑制することができるため、切断特性を安定して維持することができる。つまり、ノード数の多い撓み振動モードを用いた設計がされた場合、切断時に大きな負荷がかかっても、切断特性を維持することができる。但し、ノード数が大きい共振モードを採用した場合、振動子の長さが大きくなってしまう。ノード数の増加による切断特性の向上と小型化とはトレードオフの関係にあるので、用途に応じて適宜設定すればよい。
　なお、保持部材により支持される節位置は、１つのみでも構わないが、２以上の節位置で支持されていることが好ましい。 As shown in Table 1, it can be seen that the vibration energy increases as the number of nodes increases. When the vibration energy is large, a decrease in vibration speed when a load is applied to the blade tip can be suppressed, so that the cutting characteristics can be stably maintained. That is, when a design using a flexural vibration mode with a large number of nodes is made, the cutting characteristics can be maintained even when a large load is applied during cutting. However, when a resonance mode with a large number of nodes is adopted, the length of the vibrator becomes large. There is a trade-off relationship between improvement in cutting characteristics and size reduction due to an increase in the number of nodes, and therefore it may be set as appropriate according to the application.
Note that the number of node positions supported by the holding member may be only one, but it is preferable that the node is supported at two or more node positions.
　上記の通り、本発明の超音波切断素子は撓み振動子を備えている。よって、縦振動に比べて共振周波数が低次モードで実現できる。そのため、隣接モードとの離調度を広く取ることができ、かつ、大振幅での振動時も安定した振動を得ることができる。離調度が小さい場合、目的の振動モードでの駆動時に、隣接した振動モードが混入する。この場合、互いの振動による寸法変化が影響して非線形性が発生し、振動速度が伸び悩む主要因となる。さらに、この現象は振動速度が大きくなるほど顕著となる。このような観点から、離調度の大きい撓み振動は、高い振動速度を容易に得ることができる。十分な振動速度を得るためには、離調度を５％以上とすることが好ましい。 As described above, the ultrasonic cutting element of the present invention includes a flexural vibrator. Therefore, the resonance frequency can be realized in a lower order mode as compared with the longitudinal vibration. For this reason, the degree of detuning with the adjacent mode can be widened, and stable vibration can be obtained even during vibration with a large amplitude. When the degree of detuning is small, adjacent vibration modes are mixed when driving in the target vibration mode. In this case, non-linearity occurs due to dimensional changes due to mutual vibrations, which becomes the main factor that the vibration speed is sluggish. Furthermore, this phenomenon becomes more prominent as the vibration speed increases. From such a viewpoint, flexural vibration with a large degree of detuning can easily obtain a high vibration speed. In order to obtain a sufficient vibration speed, the degree of detuning is preferably 5% or more.
　一方で、撓み振動子を備えた超音波切断素子を軟性内視鏡に適用する場合、撓み振動子は振動振幅が大きいため、支持方法を適切に行わないと、柔らかいカテーテルワイヤに振動エネルギーが漏れ、共振周波数が大幅に低下して駆動不可能となってしまうという課題が発生する。本発明者はその課題を見出した。これは、軟性内視鏡に適用する際に初めて発生する課題であり、軟性内視鏡への適用を検討しなければ生じ得ない。本発明の超音波振動子は、振動子を撓み振動の節近傍で保持する構造を有しているので、振動エネルギーを振動子に閉じ込めることができる。よって、可撓性のあるカテーテルワイヤなどが接続された際でも共振周波数が低下したり、振動速度が落ちたりすることがない。つまり、共振周波数や振動速度等の切断特性を保つことができる。 On the other hand, when applying an ultrasonic cutting element equipped with a flexural vibrator to a flexible endoscope, the flexural vibrator has a large vibration amplitude. Therefore, if the support method is not properly applied, vibration energy leaks to the soft catheter wire. As a result, the problem arises that the resonance frequency is greatly lowered and the driving becomes impossible. The present inventor has found the problem. This is a problem that occurs for the first time when applied to a flexible endoscope, and cannot be generated without considering application to a flexible endoscope. Since the ultrasonic transducer according to the present invention has a structure in which the transducer is bent and held in the vicinity of the node of vibration, vibration energy can be confined in the transducer. Therefore, even when a flexible catheter wire or the like is connected, the resonance frequency does not decrease and the vibration speed does not decrease. That is, cutting characteristics such as the resonance frequency and vibration speed can be maintained.
　なお、本発明の超音波切断素子は可撓性のワイヤを備えているものに限らず、保持部材が強固な固定部材に接続されていてもよい。しかし、既述の通り、振動子の外に振動エネルギーを逃がさないとう効果は、可撓性ワイヤに接続されている場合に特に顕著である。 Note that the ultrasonic cutting element of the present invention is not limited to the one provided with a flexible wire, and the holding member may be connected to a strong fixing member. However, as described above, the effect of not letting vibration energy escape to the outside of the vibrator is particularly remarkable when connected to a flexible wire.
　なお、図１および図２に示す本実施形態の超音波切断素子１は、本体１０および保持部材４０が一枚板から形成されてなることが好ましい。例えば、レーザー加工により、一枚の基板から保持部材４０および本体１０の外形を切り出すと共に、保持部材４０の支持部４２を残し、保持部材４０と本体１０との間に隙間を形成することにより作製することができる。このように、一体構造として作製することにより、複雑な組み上げプロセスを無くし、低コストで製造することができる。 In addition, it is preferable that the ultrasonic cutting element 1 of this embodiment shown in FIGS. 1 and 2 includes the main body 10 and the holding member 40 formed from a single plate. For example, the outer shape of the holding member 40 and the main body 10 is cut out from a single substrate by laser processing, and the support portion 42 of the holding member 40 is left, and a gap is formed between the holding member 40 and the main body 10. can do. Thus, by producing as a monolithic structure, a complicated assembly process can be eliminated and manufacturing can be performed at low cost.
　図７は、第２の実施形態の超音波切断素子２の構成を模式的に示す平面図である。
　本実施形態の超音波切断素子２は、本体１０の主面１１の一部に振動状態を検出する振動検出部２５を設けている点で先に説明した第１の実施形態の超音波切断素子１と異なる。第１の実施形態の超音波切断素子１と同一構成要素には同一符号を付し、詳細な説明は省略する。 FIG. 7 is a plan view schematically showing the configuration of the ultrasonic cutting element 2 of the second embodiment.
The ultrasonic cutting element 2 of the present embodiment is the ultrasonic cutting element of the first embodiment described above in that the vibration detection unit 25 that detects the vibration state is provided on a part of the main surface 11 of the main body 10. Different from 1. The same components as those of the ultrasonic cutting element 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
　本実施形態においては、第１の実施形態の超音波切断素子１における駆動部２０の上部電極２４を一部分割し、振動検出部２５の検出用電極２７として用いている。振動検出部２５の構成は、駆動部２０と同様であり、下部電極２２、圧電体膜２３および検出用電極２７の積層構造となっている。振動検出部２５の検出用電極２７および下部電極２２間を電気的に開放状態とすることで、応力が印加された際に正圧電効果によって応力量に応じた電圧が両電極間に発生する。この応力発生時に生じる電圧を検出信号として利用して、振動子が共振状態にあるかどうかをモニタすることができる。なお、振動検出部２５は応力が生じやすい領域に備えられていることが好ましい。 In the present embodiment, the upper electrode 24 of the drive unit 20 in the ultrasonic cutting element 1 of the first embodiment is partly divided and used as the detection electrode 27 of the vibration detection unit 25. The configuration of the vibration detection unit 25 is the same as that of the drive unit 20, and has a laminated structure of the lower electrode 22, the piezoelectric film 23, and the detection electrode 27. By electrically opening the detection electrode 27 and the lower electrode 22 of the vibration detection unit 25, a voltage corresponding to the amount of stress is generated between both electrodes by a positive piezoelectric effect when stress is applied. It is possible to monitor whether the vibrator is in a resonance state by using the voltage generated when the stress is generated as a detection signal. Note that the vibration detection unit 25 is preferably provided in a region where stress is likely to occur.
　共振状態にあるか否かの判断方法には、駆動信号と検出信号の位相差を利用する方法と、検出信号の大きさを利用する方法とがある。前者の場合、駆動用電圧信号と検出信号の位相差が９０°であれば共振状態にあると判断できる。また、後者の場合、共振状態において検出信号の振幅が最大値を示すことを利用する。 There are two methods for determining whether or not a resonance state exists: a method using the phase difference between the drive signal and the detection signal and a method using the magnitude of the detection signal. In the former case, if the phase difference between the driving voltage signal and the detection signal is 90 °, it can be determined that the resonance state exists. In the latter case, the fact that the amplitude of the detection signal shows the maximum value in the resonance state is used.
　信号制御部５０は駆動部２０に対して、振動子３０を撓み振動の共振モードで振動させる共振周波数の駆動電圧信号を入力する。超音波切断素子による切断処理は共振状態で行う。ところで、切断対象を切断する際にブレード部１５の先端部に負荷がかかると、共振周波数が変化する。本実施形態の超音波切断素子２においては、振動検出部２５からの検出信号が信号制御部にフィードバックされる構成を備える。信号制御部５０は検出信号と駆動電圧信号との位相差もしくは検出信号の振幅に基づいて、共振状態からのずれを算出する。さらに、算出された共振状態からのずれを常に共振状態となるように補正された駆動電圧信号を生成する。この補正された駆動電圧信号を駆動部２０に付与する。すなわち、本実施形態の超音波切断素子２の構成により、常に共振状態を保った状態で動作させることが容易に可能となる。 The signal control unit 50 inputs to the drive unit 20 a drive voltage signal having a resonance frequency that causes the vibrator 30 to vibrate in the resonance mode of flexural vibration. The cutting process by the ultrasonic cutting element is performed in a resonance state. By the way, when a load is applied to the tip of the blade portion 15 when cutting the object to be cut, the resonance frequency changes. The ultrasonic cutting element 2 of the present embodiment has a configuration in which a detection signal from the vibration detection unit 25 is fed back to the signal control unit. The signal control unit 50 calculates the deviation from the resonance state based on the phase difference between the detection signal and the drive voltage signal or the amplitude of the detection signal. Further, a drive voltage signal corrected so that the deviation from the calculated resonance state is always in the resonance state is generated. The corrected drive voltage signal is applied to the drive unit 20. That is, the configuration of the ultrasonic cutting element 2 of the present embodiment makes it possible to easily operate in a state where the resonance state is always maintained.
　なお、振動検出部２５は、上記実施形態のように駆動部２０の一部を分割して構成される形態の他、駆動部２０が形成されていない他方の主面側に別途に設けられていてもよい。
すなわち、図３に示す断面図のように、本体１０の両方の主面にそれぞれ下部電極、圧電体膜および上部電極の圧電素子構造を備え、一方の主面側の圧電素子を駆動部として、かつ、他方の主面側の圧電素子を振動検出部として利用してもよい。 The vibration detection unit 25 is separately provided on the other main surface side where the drive unit 20 is not formed, in addition to a configuration in which a part of the drive unit 20 is divided as in the above embodiment. May be.
That is, as shown in the cross-sectional view of FIG. 3, each main surface of the main body 10 has a piezoelectric element structure of a lower electrode, a piezoelectric film, and an upper electrode, and the piezoelectric element on one main surface side is used as a drive unit. In addition, the piezoelectric element on the other main surface side may be used as the vibration detection unit.
　以下、実施例および比較例を挙げて本発明をより詳細に説明する。
　本発明の超音波切断素子の具体的な比較例１、比較例２および実施例１の小型超音波メスの構造Ａ～Ｃを図８Ａ、図８Ｂおよび図８Ｃにそれぞれ示す。
　図８Ａ、８Ｂおよび８Ｃには、各素子の各部の寸法を併せて示している。各図中ｔはそれぞれの本体の板厚である。いずれも単位は[ｍｍ]である。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
8A, FIG. 8B, and FIG. 8C show the structures A to C of the small ultrasonic scalpels of the comparative example 1, comparative example 2, and example 1 of the ultrasonic cutting element of the present invention, respectively.
8A, 8B, and 8C also show the dimensions of each part of each element. In each figure, t is the thickness of each main body. In either case, the unit is [mm].
　また、図９Ａ、９Ｂおよび９Ｃは、それぞれ図８Ａ、図８Ｂおよび図８Ｃの各振動子の振動モードにおける変位状態を示す模式的な斜視図である。図９Ａ、９Ｂおよび９Ｃにおいては色が薄いほど静止状態（図中細実線）からの変位量が大きいことを示している。
　図８Ａおよび図９Ａに示す比較例１の超音波切断素子（構造Ａ）は、先端にホーン部を備えた従来型縦振動の超音波メスである。図９Ａに両矢印で示す振動方向、すなわちブレードの長手方向に振動する縦振動によって、ブレード先端を対象に突き刺して切断する。 9A, 9B, and 9C are schematic perspective views showing displacement states in the vibration modes of the vibrators of FIGS. 8A, 8B, and 8C, respectively. In FIGS. 9A, 9B and 9C, the lighter the color, the greater the displacement from the stationary state (thin solid line in the figure).
The ultrasonic cutting element (structure A) of Comparative Example 1 shown in FIGS. 8A and 9A is a conventional longitudinal vibration ultrasonic knife having a horn portion at the tip. The blade tip is pierced and cut by the vibration direction indicated by the double arrow in FIG.
　一方、比較例２の超音波切断素子（構造Ｂ）および比較例３の超音波切断素子（構造Ｃ）は、本体の厚み方向（主面方向）に屈曲する振動、つまり撓み振動を利用する超音波メスである。図９Ｂおよび図９Ｃにおいて両矢印で示す振動方向、即ちブレードを本体の厚み方向に振動させて対象を切断する。 On the other hand, the ultrasonic cutting element (Structure B) of Comparative Example 2 and the ultrasonic cutting element (Structure C) of Comparative Example 3 are vibrations that bend in the thickness direction (main surface direction) of the main body, that is, super vibrations that use flexural vibration. Sonic scalpel. 9B and 9C, the object is cut by vibrating the vibration direction indicated by the double arrow, that is, the blade in the thickness direction of the main body.
　比較例１、２および実施例１の素子の作製手順について説明する。
　本体および保持部材を構成する基板として、０．４ｍｍ厚（比較例１、実施例１）、１．０ｍｍ厚（比較例２）の２種類の６４チタン合金板材（規格：ASTM Gr.5，ASTM F136）を用いた。
　まず、基板表面にスパッタ法で基板温度３５０℃にて密着層としてＴｉを３０ｎｍ成膜し、引き続きＴｉ膜上にＩｒからなる下部電極を１５０ｎｍ形成した。得られた下部電極上に、Ｒｆ（radio frequency）スパッタ法によって圧電体膜を約３μｍ成膜した。成膜ガスは９７．５％Ａｒ＋２．５％Ｏ２の混合ガスを用い、ターゲット材料としてＰｂ1.3（Ｚｒ0.52Ｔｉ0.48）0.88Ｎｂ0.12）Ｏ3の組成のものを用いた。得られた圧電体膜（以下においてＮｂ－ＰＺＴ膜という。）上に、リフトオフ法によってＡｕ(３００ｎｍ)／Ｔｉ(３０ｎｍ)の二層構造の上部電極をパターニング形成した。最後に、レーザー加工によって基板を外形加工して図８Ａ、８Ｂおよび８Ｃに示す形状とした。 A manufacturing procedure of the elements of Comparative Examples 1 and 2 and Example 1 will be described.
As a substrate constituting the main body and the holding member, two types of 64 titanium alloy plate materials of 0.4 mm thickness (Comparative Example 1, Example 1) and 1.0 mm thickness (Comparative Example 2) (Standard: ASTM Gr.5, ASTM) F136) was used.
First, 30 nm of Ti was formed as an adhesion layer on the substrate surface by a sputtering method at a substrate temperature of 350 ° C., and then a lower electrode made of Ir was formed to 150 nm on the Ti film. A piezoelectric film of about 3 μm was formed on the obtained lower electrode by Rf (radio frequency) sputtering. The deposition gas used was a mixed gas of 97.5% Ar + 2.5% O 2 , and a target material having a composition of Pb 1.3 (Zr 0.52 Ti 0.48 ) 0.88 Nb 0.12 ) O 3 was used. An upper electrode having a two-layer structure of Au (300 nm) / Ti (30 nm) was formed by patterning on the obtained piezoelectric film (hereinafter referred to as Nb-PZT film) by a lift-off method. Finally, the substrate was trimmed by laser processing to obtain the shapes shown in FIGS. 8A, 8B and 8C.
　まず、図８Ａ、８Ｂおよび８Ｃに示した構造Ａ，Ｂ，Ｃの超音波切断素子について、共振モード周波数、モード次数およびその際の離調度を有限要素法（Finite Element Method：FEM）シミュレーションによって計算した。
　下記表２に、各構造における切断に用いる振動モードの共振周波数、離調度をＦＥＭシミュレーションによって計算した結果を示す。
　表２に示すように、構造Ａの縦振動モードは３６次モードと高次であり、その離調度は０．４％と非常に小さい。一方、構造Ｂおよび構造Ｃの曲げ振動はそれぞれ１次、３次モードであり、離調度はそれぞれ１７％、３５％と十分大きな値が得られているため、高い振動速度を得るのに有利と言える。 First, for the ultrasonic cutting elements having the structures A, B, and C shown in FIGS. 8A, 8B, and 8C, the resonance mode frequency, the mode order, and the degree of detuning are calculated by a finite element method (FEM) simulation. did.
Table 2 below shows the results of calculating the resonance frequency and detuning degree of the vibration mode used for cutting in each structure by FEM simulation.
As shown in Table 2, the longitudinal vibration mode of the structure A is a 36th-order mode and a higher order, and the degree of detuning is as very low as 0.4%. On the other hand, the bending vibrations of the structures B and C are the first and third modes, respectively, and the detuning degrees are 17% and 35%, which are sufficiently large values, which is advantageous for obtaining a high vibration speed. I can say that.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　上記表２には、各素子についてのブレード先端の振動速度についての実験結果を併せて示した。振動速度の測定方法は以下の通り行った。
　構造Ａ，Ｂ，Ｃの各超音波切断素子について、駆動部の上部電極および下部電極からワイヤボンディングによって配線を引き出し、信号制御部であるファンクションジェネレータに接続した。上部電極および下部電極間にファンクションジェネレータによってそれぞれの共振周波数に該当する周波数の正弦電圧波形を印加することで振動子を加振し、レーザードップラー計によってブレード部先端の最大振動速度を測定した。なお、加振はそれぞれ、表１に示す共振モードの共振周波数で行った。 Table 2 also shows the experimental results of the vibration speed of the blade tip for each element. The method for measuring the vibration speed was as follows.
For each of the ultrasonic cutting elements of the structures A, B, and C, wiring was drawn from the upper electrode and lower electrode of the drive unit by wire bonding and connected to a function generator that was a signal control unit. The vibrator was vibrated by applying a sine voltage waveform corresponding to each resonance frequency between the upper electrode and the lower electrode by a function generator, and the maximum vibration velocity at the tip of the blade was measured by a laser Doppler meter. The excitation was performed at the resonance frequencies of the resonance modes shown in Table 1.
　各例の超音波切断素子について、図８Ａ、８Ｂおよび８Ｃにおける保持部材のブレードとは反対の端部を「強固定」および「ワイヤ経由固定」の２種類の方法にて固定する形として、それぞれの場合のブレード部先端の最大駆動速度を測定した。
　ここで、強固定としては、各超音波切断素子に対して十分に大きい重量を持つ物体によって重力固定した。また、ワイヤ経由固定としては、カテーテルを想定し、直径１ｍｍのチタン製ワイヤの一端と保持部材の端部とを接着剤によって接合した上でワイヤの他端を強固定した。 About the ultrasonic cutting element of each example, as the form which fixes the edge part opposite to the braid | blade of the holding member in FIG. 8A, 8B and 8C by two types of "strong fixing" and "fixing via a wire", respectively In this case, the maximum driving speed at the tip of the blade was measured.
Here, as strong fixation, gravity fixation was performed by an object having a sufficiently large weight with respect to each ultrasonic cutting element. As for fixation via wire, a catheter was assumed, and one end of a titanium wire having a diameter of 1 mm and the end of the holding member were joined with an adhesive, and the other end of the wire was strongly fixed.
　表２に示す実駆動結果に関し、まず、強固定の場合について言及する。比較例１の素子については、駆動電圧の上昇とともに振動速度は上昇したが、１．７ｍ／ｓ以上の速度は振動が不安定になって得られなかった。離調度が小さいため、振動振幅が大きくなるにつれて隣接振動モードが混入し、振動が不安定になったと考えられる。これに対し、比較例２および実施例１の素子ではいずれも２０ｍ／ｓ以上の振動速度が得られた。比較例２および実施例１の素子では、振動速度の上限は振動の不安定性ではなく、圧電体の絶縁破壊によって引き起こされた。つまり、離調度の大きい撓み振動を用いることで、振動振幅が大きくなっても安定して振動させることができるため、大きい振動速度が得られた。 Referring to the actual driving results shown in Table 2, first, the case of strong fixation will be mentioned. With respect to the element of Comparative Example 1, the vibration speed increased as the drive voltage increased, but a speed of 1.7 m / s or more was not obtained because the vibration became unstable. Since the degree of detuning is small, it is considered that the adjacent vibration mode is mixed as the vibration amplitude increases, and the vibration becomes unstable. On the other hand, the vibration speed of 20 m / s or more was obtained in the devices of Comparative Example 2 and Example 1. In the devices of Comparative Example 2 and Example 1, the upper limit of the vibration velocity was not caused by vibration instability but was caused by dielectric breakdown of the piezoelectric material. That is, by using a flexural vibration with a large degree of detuning, it is possible to stably vibrate even when the vibration amplitude increases, and thus a large vibration speed is obtained.
　次に、カテーテルへの組み込みを想定したワイヤ経由固定の場合について言及する。比較例２に示す構造Ｂのような片持ち梁振動子は、振動する際に保持部材固定端から反力を受ける。つまり、振動エネルギーが振動子の外に漏れるため、ワイヤ経由固定で振動させた際に振動速度が著しく低下する結果となった。これに対して実施例１の素子は、撓み振動の節位置にて振動子を支持しているため、保持部材に反力はほとんど発生せず、振動子にエネルギーを閉じ込めることができる。したがって、ワイヤ経由固定で振動させても、振動速度の低下は確認されなかった。 Next, mention is made of the case of fixing via a wire that is assumed to be incorporated into a catheter. A cantilever vibrator like the structure B shown in Comparative Example 2 receives a reaction force from the holding member fixed end when vibrating. That is, since vibration energy leaks out of the vibrator, the vibration speed is remarkably lowered when the vibration is caused to be fixed via a wire. On the other hand, since the element of Example 1 supports the vibrator at the node position of the bending vibration, almost no reaction force is generated in the holding member, and energy can be confined in the vibrator. Therefore, even if it was made to vibrate by fixing via a wire, a decrease in vibration speed was not confirmed.
　一般的に、ブレード部先端の最大振動速度が３ｍ/ｓを上回れば、超音波メスとして良好な切断特性が得られる。本発明の実施例１の素子は、強固定の場合およびワイヤ経由固定の場合ともに２５ｍ/ｓの最大振動速度を達成しており、比較例１および比較例２の素子に比べて切断特性も良好であった。すなわち、節近傍で撓み振動子を保持することにより、カテーテル先端においても高い振動速度を得ることが可能であることが明らかになった。したがって、本発明の超音波切断素子は、例えば、軟性内視鏡下での腫瘍などの切除に適用可能である。 Generally, when the maximum vibration speed of the blade tip exceeds 3 m / s, good cutting characteristics can be obtained as an ultrasonic knife. The element of Example 1 of the present invention achieves a maximum vibration speed of 25 m / s in both the case of strong fixation and the case of fixation via wire, and the cutting characteristics are better than the elements of Comparative Example 1 and Comparative Example 2. Met. That is, it has been clarified that a high vibration speed can be obtained even at the distal end of the catheter by holding the bending vibrator in the vicinity of the node. Therefore, the ultrasonic cutting element of the present invention can be applied to excision of a tumor or the like under a flexible endoscope, for example.
　上述のように、節支持の撓み振動子を用いた本発明の超音波切断素子の構造を採用することにより、カテーテル先端で高い振動速度が得られた。 As described above, by adopting the structure of the ultrasonic cutting element of the present invention using a node-supported flexural vibrator, a high vibration speed was obtained at the catheter tip.
　ところで、超音波切断素子は、物体を切断している最中は、駆動部に強い応力と駆動電圧が組み合わさって印加される上に、誘電損失による発熱が発生する。そのため、繰り返し駆動を行うと絶縁破壊が起きやすくなる。超音波切断素子の実用性を高めるには、絶縁破壊を抑制し、駆動寿命を伸ばすことが課題となる。 Incidentally, while the ultrasonic cutting element is cutting an object, a strong stress and a driving voltage are applied to the driving unit in combination, and heat is generated due to dielectric loss. For this reason, dielectric breakdown tends to occur when the driving is repeated. In order to improve the practicality of the ultrasonic cutting element, it is necessary to suppress dielectric breakdown and extend the driving life.
　そこで、実施例１の超音波切断素子の構造Ｃにおいて、基板を変えて実施例２～５の素子を作製し、駆動耐久性を比較する実験を行った。
　実施例２～５の素子は、基板を下記表３に示す通りとした以外は、上記の実施例１と同様の製造方法にて作製した。表３には、各基板の材料（以下において、基板材料）とその熱膨張係数およびＮｂ－ＰＺＴ膜の配向性、誘電率並びに駆動耐久性の評価を併せて示す。 Therefore, in the structure C of the ultrasonic cutting element of Example 1, the elements of Examples 2 to 5 were manufactured by changing the substrate, and an experiment for comparing the driving durability was performed.
The devices of Examples 2 to 5 were manufactured by the same manufacturing method as in Example 1 except that the substrate was as shown in Table 3 below. Table 3 shows the materials of the respective substrates (hereinafter referred to as substrate materials), their thermal expansion coefficients, and evaluation of the orientation, dielectric constant, and driving durability of the Nb-PZT film.
　各基板材料の熱膨張係数は、電子材料ハンドブック（朝倉書店）、ステンレス協会ホームページ(http://www.jssa.gr.jp/contents/faq-article/q6/)、株式会社神戸製鋼所ホームページ(http://www.kobelco.co.jp/titan/characteristic/)、株式会社アライドマテリアルホームページ(http://www.allied-material.co.jp/products/tungsten/processed/)、京セラ株式会社ホームページ(http://www.kyocera.co.jp/fcworld/charact/heat/thermaexpan.html)を参照した。
　Ｎｂ－ＰＺＴ膜の配向性はＸ線構造解析を行い、（００１）ピークと（１００）ピークとを比較してピーク強度が大きかった方の面を示した。
　Ｎｂ－ＰＺＴ膜の誘電率は、インピーダンスアナライザを用いて周波数1kHzに対するキャパシタンスを測定した値から算出した。 The coefficient of thermal expansion of each substrate material can be found in the Electronic Materials Handbook (Asakura Shoten), the Stainless Steel Association website (http://www.jssa.gr.jp/contents/faq-article/q6/), Kobe Steel Corporation website ( http://www.kobelco.co.jp/titan/characteristic/), Allied Materials website (http://www.allied-material.co.jp/products/tungsten/processed/), Kyocera Corporation website (http://www.kyocera.co.jp/fcworld/charact/heat/thermaexpan.html) was referred to.
The orientation of the Nb-PZT film was analyzed by X-ray structural analysis, and the (001) peak was compared with the (100) peak, and the surface with the higher peak intensity was shown.
The dielectric constant of the Nb-PZT film was calculated from the value obtained by measuring the capacitance at a frequency of 1 kHz using an impedance analyzer.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表３に示す通り、基板材料が異なるとＮｂ－ＰＺＴ膜の結晶配向性が変化する。これは、圧電体膜と基板の熱膨張係数の差に起因して生じる。一般的に、圧電体膜よりも小さい熱膨張係数を持つ材料からなる基板を用いると、高温成膜後の冷却過程において圧電体膜に引っ張り方向の残留応力が印加され、結晶格子の長軸が面内方向を向く(１００)方向（＝ａ軸配向）となる。例えば、圧電膜を熱膨張係数が６．７ｐｐｍ／℃であるＮｂ－ＰＺＴ膜とし、基板材料をシリコンやタングステンとした場合である。一方、アルミナ、ステンレス鋼（ここではＳＵＳ４３０）、チタン合金のように圧電体膜よりも大きい熱膨張係数を持つ材料からなる基板を用いると、圧電体膜に圧縮方向の残留応力が印加され、結晶格子の長軸が垂直方向を向く（００１）方向（＝ｃ軸配向）となる。 As shown in Table 3, when the substrate material is different, the crystal orientation of the Nb-PZT film changes. This is caused by a difference in thermal expansion coefficient between the piezoelectric film and the substrate. Generally, when a substrate made of a material having a smaller thermal expansion coefficient than that of a piezoelectric film is used, a residual stress in the tensile direction is applied to the piezoelectric film during the cooling process after high-temperature film formation, and the long axis of the crystal lattice is The (100) direction (= a-axis orientation) faces the in-plane direction. For example, the piezoelectric film is an Nb-PZT film having a thermal expansion coefficient of 6.7 ppm / ° C., and the substrate material is silicon or tungsten. On the other hand, when a substrate made of a material having a thermal expansion coefficient larger than that of the piezoelectric film such as alumina, stainless steel (SUS430 in this case), or titanium alloy is used, a residual stress in the compressive direction is applied to the piezoelectric film. The major axis of the lattice is the (001) direction (= c-axis orientation) in the vertical direction.
　＜駆動耐久性＞
　実施例１～５の素子についての駆動耐久性の試験を行った。具体的には、駆動開始から機能停止までの時間Ｔ[時間（ｈ）]を計測し、以下の基準で駆動耐久性を評価した。
Ａ：１２０ｈ＜Ｔ
Ｂ：２４ｈ＜Ｔ≦１２０ｈ
Ｃ：Ｔ≦２４ｈ
このとき、ブレード部先端に切断負荷としてゴムを接触させ、共振周波数を維持しながら３０Ｖｐｐの正弦波を駆動部に印加して長期駆動させた。機能停止の時間の定義は、圧電膜の絶縁破壊により振動速度が１０％以下に落ち込んだ時点である。 <Driving durability>
A driving durability test was performed on the elements of Examples 1 to 5. Specifically, the time T [time (h)] from the start of driving to the stop of the function was measured, and the driving durability was evaluated according to the following criteria.
A: 120h <T
B: 24h <T ≦ 120h
C: T ≦ 24h
At this time, rubber was brought into contact with the tip of the blade portion as a cutting load, and a 30 Vpp sine wave was applied to the drive portion while maintaining the resonance frequency to drive the blade for a long time. The function stop time is defined as the point at which the vibration speed drops below 10% due to dielectric breakdown of the piezoelectric film.
　表３に示す通り、ｃ軸方向に配向したＮｂ－ＰＺＴを備えた実施例１～３はａ軸配向したＮｂ－ＰＺＴを備えた実施例４および５に比べて耐久性がよいという結果が得られた。Ｎｂ－ＰＺＴがｃ軸配向することにより、誘電率が低くなる。そのために、駆動時の発熱が小さくなる。その駆動時の発熱が小さくなる効果により、耐久性が改善したと考えられる。
　上記の通り、本発明の超音波切断素子において、ＰＺＴ膜を圧電体膜に用いる場合には、ｃ軸方向に優先配向した膜を用いることが、耐久性の観点から好ましいことが明らかになった。 As shown in Table 3, the results of Examples 1 to 3 having Nb-PZT oriented in the c-axis direction are superior to those in Examples 4 and 5 having Nb-PZT oriented to the a-axis. It was. When Nb-PZT is c-axis oriented, the dielectric constant is lowered. Therefore, heat generation during driving is reduced. It is thought that durability was improved by the effect of reducing heat generation during the driving.
As described above, in the ultrasonic cutting element of the present invention, when using the PZT film as the piezoelectric film, it has become clear that it is preferable from the viewpoint of durability to use a film preferentially oriented in the c-axis direction. .
　１、２　　超音波切断素子
　１０　　本体
　１１、１２　　主面
　１５　　ブレード部
　２０　　駆動部
　２２　　下部電極
　２３　　圧電体膜
　２４　　上部電極
　２５　　振動検出部
　２７　　検出用電極
　３０　　振動子
　４０　　保持部材
　４２　　支持部
　４５　　可撓性ワイヤ
　５０　　信号制御部
　１００　　超音波処置具 DESCRIPTION OF SYMBOLS 1, 2 Ultrasonic cutting element 10 Main body 11, 12 Main surface 15 Blade part 20 Drive part 22 Lower electrode 23 Piezoelectric film 24 Upper electrode 25 Vibration detection part 27 Detection electrode 30 Vibrator 40 Holding member 42 Support part 45 Flexible Wire 50 Signal control unit 100 Ultrasonic treatment instrument

Claims (8)

  1. 　細板状の本体、該本体の一端に固定されたブレード部、および前記本体の少なくとも一方の主面上に設けられた駆動部を有する振動子と、該振動子を前記本体の一部で保持する保持部材とを備えた超音波切断素子であって、
    　前記駆動部は、前記本体の前記主面側から下部電極、圧電体膜および上部電極がこの順に積層されてなる圧電アクチュエータであり、
    　前記振動子は、前記駆動部による駆動により、主面方向に両端自由屈曲振動する撓み振動子であり、
    　前記保持部材は、前記両端自由屈曲振動の共振モードにおける節位置でのみ前記振動子を支持している超音波切断素子。     A vibrator having a thin plate-like main body, a blade portion fixed to one end of the main body, and a drive unit provided on at least one main surface of the main body, and holding the vibrator by a part of the main body An ultrasonic cutting element comprising a holding member that
    The drive unit is a piezoelectric actuator in which a lower electrode, a piezoelectric film, and an upper electrode are laminated in this order from the main surface side of the main body,
    The vibrator is a flexural vibrator that freely bends and vibrates at both ends in a principal surface direction by driving by the driving unit,
    The ultrasonic cutting element in which the holding member supports the vibrator only at a node position in a resonance mode of the free bending vibration at both ends.
  2. 　一端が前記保持部材に接続され、切断対象に前記振動子を導くための可撓性ワイヤを備えた請求項１記載の超音波切断素子。 The ultrasonic cutting element according to claim 1, further comprising a flexible wire having one end connected to the holding member and guiding the vibrator to a cutting target.
  3. 　前記保持部材が前記振動子を、該本体の長側面でのみ支持している請求項１または２に記載の超音波切断素子。 The ultrasonic cutting element according to claim 1 or 2, wherein the holding member supports the vibrator only on a long side surface of the main body.
  4. 　前記振動子の前記本体と前記保持部材とが一枚板から形成されてなる請求項１から３いずれか１項記載の超音波切断素子。 The ultrasonic cutting element according to any one of claims 1 to 3, wherein the main body of the vibrator and the holding member are formed from a single plate.
  5. 　前記振動子が、前記本体の主面に、該振動子の振動を検出する振動検出部を備えている請求項１から４いずれか１項記載の超音波切断素子。 The ultrasonic cutting element according to any one of claims 1 to 4, wherein the vibrator includes a vibration detection unit that detects vibration of the vibrator on a main surface of the main body.
  6. 　前記駆動部に用いられる圧電体膜が、正方晶ｃ軸に優先配向した、
    Ｐｂ（Ｚｒｙ，Ｔｉｚ，Ｎｂ1－ｙ－ｚ）Ｏ３，０＜ｙ＜１，０＜ｚ＜１
    で表されるペロブスカイト型酸化物からなる請求項１から５いずれか１項記載の超音波切断素子。     The piezoelectric film used for the drive unit is preferentially oriented to the tetragonal c-axis,
    Pb (Zr y , Ti z , Nb 1-yz ) O 3 , 0 <y <1, 0 <z <1
    The ultrasonic cutting element according to claim 1, comprising a perovskite oxide represented by:
  7. 　前記本体が前記圧電体膜の熱膨張係数よりも大きい熱膨張係数を有する材料からなる請求項６記載の超音波切断素子。 The ultrasonic cutting element according to claim 6, wherein the main body is made of a material having a thermal expansion coefficient larger than that of the piezoelectric film.
  8. 　請求項１から７のいずれか１項に記載の超音波切断素子と、
    　前記駆動部の前記上部電極および前記下部電極に対して、前記両端自由屈曲振動を生じさせる共振モードの駆動電圧信号を付与する信号制御部とを備えた超音波処置具。     The ultrasonic cutting element according to any one of claims 1 to 7,
    An ultrasonic treatment instrument comprising: a signal control unit that applies a drive voltage signal in a resonance mode that causes the free bending vibration at both ends to the upper electrode and the lower electrode of the drive unit.
PCT/JP2017/007515 2016-03-03 2017-02-27 Ultrasonic cutting element and ultrasonic treatment tool WO2017150455A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010084160A (en) * 2008-09-29 2010-04-15 Fujifilm Corp Film deposition method of lead-containing perovskite-type oxide film, piezoelectric device, and liquid ejecting device
JP2012179102A (en) * 2011-02-28 2012-09-20 Fujifilm Corp Resonant transducer, method of producing the resonant transducer, and ultrasonic treatment tool including the resonant transducer
JP2013099418A (en) * 2011-11-08 2013-05-23 Olympus Corp Ultrasonic treatment instrument and ultrasonic treatment apparatus
JP2014079424A (en) * 2012-10-17 2014-05-08 Olympus Corp Ultrasonic treatment device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010084160A (en) * 2008-09-29 2010-04-15 Fujifilm Corp Film deposition method of lead-containing perovskite-type oxide film, piezoelectric device, and liquid ejecting device
JP2012179102A (en) * 2011-02-28 2012-09-20 Fujifilm Corp Resonant transducer, method of producing the resonant transducer, and ultrasonic treatment tool including the resonant transducer
JP2013099418A (en) * 2011-11-08 2013-05-23 Olympus Corp Ultrasonic treatment instrument and ultrasonic treatment apparatus
JP2014079424A (en) * 2012-10-17 2014-05-08 Olympus Corp Ultrasonic treatment device

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