WO2017082350A1

WO2017082350A1 - Method for exciting longitudinal/torsional vibration of langevin-type ultrasonic vibrator

Info

Publication number: WO2017082350A1
Application number: PCT/JP2016/083374
Authority: WO
Inventors: 大西　一正
Original assignee: 有限会社Ｕｗａｖｅ
Priority date: 2015-11-10
Filing date: 2016-11-10
Publication date: 2017-05-18
Also published as: JPWO2017082350A1; JP6716082B2

Abstract

[Problem] To provide a method for exciting an ultrasonic vibration excited by a Langevin-type ultrasonic transducer, wherein the ultrasonic vibration is a longitudinal/torsional composite ultrasonic vibration of a novel vibration mode. [Solution] A method for: preparing a metal block, a metal block provided with a support frame body projecting in an annular shape on a side surface, and a Langevin-type ultrasonic transducer including a disc-shaped piezoelectric element which has been polarized-processed in the vertical direction and a disc-shaped piezoelectric element polarized in the circumferential direction, the Langevin-type ultrasonic transducer being fixed between the metal blocks; connecting the Langevin-type ultrasonic transducer to a base via the support frame body to support the Langevin-type ultrasonic transducer in a restrained state; thereafter applying, to both the disc-shaped piezoelectric element which has been polarization-processed in the vertical direction and the disc-shaped piezoelectric element polarized in the circumferential direction of the ultrasonic transducer, a voltage having a frequency capable of exciting a longitudinal vibration, which comprises a reciprocating vibration having no vibration nodes inside the ultrasonic transducer, and a torsional primary vibration having one vibration node inside the ultrasonic transducer; and thereby exciting, in the Langevin-type ultrasonic transducer, a longitudinal/torsional ultrasonic vibration which is a composite vibration of a torsional primary vibration and an ultrasonic vibration comprising a longitudinal reciprocating vibration having no vibration nodes inside the ultrasonic transducer.

Description

Excitation method of longitudinal and torsional vibration of Langevin type ultrasonic transducer

The present invention relates to a method for exciting longitudinal and torsional vibrations of a Langevin type ultrasonic transducer, and more particularly to a method for exciting longitudinal and torsional vibrations of ultrasonic vibrations in a novel vibration mode.

Various types of ultrasonic transducers using piezoelectric elements as ultrasonic wave generation sources are known. A typical configuration is a pair of metal blocks and a polarization fixed between these metal blocks. A Langevin type ultrasonic transducer composed of a processed piezoelectric element is known. Among them, the bolted Langevin type ultrasonic transducer with a structure in which a piezoelectric element that has been subjected to a polarization treatment is fastened and fixed with a bolt between a pair of metal blocks at a high pressure can generate high-energy ultrasonic vibrations. The use in ultrasonic machining attached to a tool that performs cutting, plastic processing, abrasive processing, etc. of various materials has been studied. Furthermore, for various types of ultrasonic vibrators, ultrasonic vibrations generated by the ultrasonic vibrators are transmitted via a vibration plate or vibration means, thereby performing ultrasonic cleaning, metal bonding, plastic welding, ultrasonic fogging. Consideration of ultrasonic processing such as emulsification, emulsification and dispersion, and use in communication application equipment such as underwater acoustic instruments (sonar) such as fish detectors, ultrasonic flaw detectors, medical echo diagnostic equipment, and flow meters And is actually used in many fields.

The configurations of various types of ultrasonic transducers including bolted Langevin type ultrasonic transducers are already known, but just in case, examples of typical bolted Langevin type ultrasonic transducer configurations and their usage forms A brief description will be given below with reference to FIGS.

FIG. 1 is a diagram showing an example of a typical structure of a bolted Langevin type ultrasonic transducer. The bolt-clamped Langevin type ultrasonic vibrator 1 includes a pair of

metal blocks

2a and 2b sandwiched between polarized piezoelectric elements (eg, piezoelectric ceramic sheets such as PZT sheets) 3a and 3b, and a metal block using bolts 4 2a and 2b are clamped together. In FIG. 1, the arrow written in the piezoelectric element indicates the polarization direction. The

piezoelectric elements

3a and 3b are connected to electrode pieces (usually using electrode pieces such as phosphor bronze) 5a and 5b used as terminals for applying electric energy.

FIG. 2 is a diagram showing a configuration example of an ultrasonic polishing machine as an ultrasonic processing apparatus using a bolted Langevin type ultrasonic transducer as an ultrasonic vibration source. In FIG. 2, an ultrasonic polishing machine 10 accommodates an ultrasonic vibrator 1 having a polishing tool 13 connected to a lower end portion thereof via a horn 12 in a housing 11, and this ultrasonic vibrator 1 is used as a bearing. 14 is rotatably supported. The rotation of the ultrasonic vibrator 1 is driven by an AC spindle motor 16 connected to the servo unit 15. In the apparatus of FIG. 2, the electrical energy for ultrasonic vibration of the ultrasonic vibrator 1 is a contact-type power supply composed of a carbon brush and a slip ring connected to an electric energy supply source 17 provided outside. Supplied via device 18.

The bolted Langevin type ultrasonic transducer 1 shown in FIG. 1 has a configuration in which

piezoelectric elements

2a and 2b are polarized in a direction perpendicular to the element plane. In this case, the ultrasonic transducer is usually a piezoelectric element 2a. 2b shows a vibration mode of vibration (referred to as longitudinal primary vibration) in the length direction (corresponding to the longitudinal direction in FIG. 1) having a vibration node near the position 2b. Vibrations commonly used in the ultrasonic processing apparatus shown in FIG. 2, ultrasonic cleaning, underwater acoustic instruments (sonar) such as fish detectors, ultrasonic flaw detectors, medical echo diagnostic equipment, flow meters, etc. Is the vibration in the vibration mode of the longitudinal primary vibration.

On the other hand, a torsional vibration piezoelectric element 3c in which a disk-shaped piezoelectric element is polarized in the circumferential direction as shown in FIG. 3 is also known. This torsional vibration piezoelectric element 3c is obtained by once dividing a disk-shaped piezoelectric element into element pieces, then polarizing each element piece in the plane direction of the disk (in the direction of the arrow), and then using an adhesive. It can be produced by recombining the polarized element pieces into a disc shape.

The torsional vibration piezoelectric element polarized in the circumferential direction having the configuration shown in FIG. 3 is incorporated into a Langevin type ultrasonic vibrator and used to excite ultrasonic vibration in the torsional vibration mode.

In addition, the piezoelectric element for torsional vibration is combined with the longitudinally polarized piezoelectric element for longitudinal vibration excitation shown in FIG. 1 and incorporated into a Langevin type ultrasonic vibrator, and combined vibration (longitudinal / torsional vibration) It is also used to excite ultrasonic vibrations in torsional vibration) mode. An ultrasonic motor is known as a typical usage form of ultrasonic vibration in such a longitudinal / torsional vibration mode.

Patent Document 1 discloses an improved invention of an ultrasonic motor that uses the longitudinal and torsional vibration modes of a conventionally known ultrasonic vibrator, and as a conventional ultrasonic motor that is the object of the improvement. FIG. 4 shows an ultrasonic motor having the configuration shown in FIG. That is, in FIG. 4, an ultrasonic motor 20 includes a bottom nut 22, a torsional vibration piezoelectric element 24, a hollow holder 26, a longitudinal vibration piezoelectric element 28, and a stator 32 configured by connecting a hollow stator head 30, and the stator. A center bolt 38 rotatably disposed on the shaft core portion of the shaft and a rotor 34 supported by the center bolt 38 are included. The ultrasonic motor 20 is further provided with another center bolt 40. By connecting the center bolt 40 and the center bolt 38, the stator head 30 of the stator 32 and the rotor 34 are connected in a sliding state. It will be. A friction material 36 is provided between the stator head 30 and the rotor 34. A spring member 42 is attached to the center bolt 40 and presses the rotor 34 against the stator head 30 via the friction material 36. A bearing 44 for assuring smooth rotation around the center bolt 40 is incorporated in the rotor 34. In the ultrasonic transducer, the position of the node of the longitudinal vibration mode excited by the piezoelectric element for longitudinal vibration and the position of the node of the torsional vibration mode excited by the piezoelectric element for torsional vibration are substantially the same. The flange 48 is provided at this position. When the ultrasonic motor 20 is installed on the base, the flange 48 is fixed to the base.

In the ultrasonic motor 20 having the configuration shown in FIG. 4, the torsional vibration piezoelectric element 24 generates a rotational driving force on the rotor 34, and the longitudinal vibration piezoelectric element 28 performs contact control between the stator 32 and the rotor 34. More specifically, when a voltage is applied to the torsional vibration piezoelectric element while the stator head 30 and the rotor 34 are in contact with each other by the spring force of the spring member 42, the torsional vibration generated by the torsional vibration piezoelectric element 24 causes the torsional vibration. The rotor 34 rotates at a minute angle. If the pressing force against the stator head 30 of the rotor 34 is weakened by the excitation of the longitudinal vibration piezoelectric element 28 after the rotation of the minute angle, the torsional vibration of the torsional vibration piezoelectric element 24 disappears. Then, when a voltage is applied again to the torsional vibration piezoelectric element 24, the rotor 34 again rotates by a small angle. The rotor 34 can be continuously rotated in a certain direction by repeatedly performing the elliptical vibration generated by the combination of the torsional vibration of the torsional vibration piezoelectric element 24 and the longitudinal vibration of the longitudinal vibration piezoelectric element 28. Then, spokes are inserted into coupling holes 46 and 56 formed so as to perforate the rotor 34, and the rotary motion body is mounted on the spokes, thereby rotating the rotary motion body.

The ultrasonic motor having the above-described configuration is particularly useful as a motor to be mounted on a small precision device or electric device because it can easily rotate at a low speed and with a high torque and has a quiet operation sound.

By the way, the effects expected by applying ultrasonic vibration to various tools in the above-described ultrasonic processing apparatus are reduction of electrical energy required for the processing work by the tool and improvement of processing accuracy. In the ultrasonic processing apparatus that has been manufactured and used for actual processing operations, the expected effect is not sufficiently obtained. For this reason, it cannot be said that the spread of ultrasonic processing apparatuses is sufficiently advanced at the present time. Therefore, in order to further promote the use of ultrasonic machining, the amount of electrical energy required for exciting the vibration of the ultrasonic transducer in the implementation of ultrasonic machining work has been greatly reduced, and sufficient machining accuracy has been achieved. It is necessary to improve such that the improvement is obtained.

The inventor of the present invention has devised various inventions for improving ultrasonic transducers that can be expected to improve the machining accuracy commensurate with the amount of electrical energy required for exciting the vibration of the ultrasonic transducers during ultrasonic machining. Have filed patent applications. For example, the invention disclosed in Patent Document 2 can be cited as a recent invention among the improved inventions.

In Patent Document 2, a vibration composite of a tool and an ultrasonic vibrator is supported with high stability, and the support of the vibration composite of ultrasonic energy generated in the ultrasonic vibrator (fixed support) is disclosed. As a support structure that enables high-efficiency application of vibrational energy to the tool by suppressing leakage to the low level, a flange is attached to the ultrasonic vibrator provided with the tool, and one side of the flange is A support structure that engages and supports a flange support surface formed on a separately prepared fixed body in a stressed state (however, the flange of the ultrasonic vibrator is joined to the flange support surface of the fixed body). In addition, the flange of the ultrasonic vibrator that is engaged with and supported by the support surface of the fixed body is structured to vibrate ultrasonically in the thickness direction of the flange when the ultrasonic vibrator is in a vibrating state. Open It is.

JP-A-5-146172 International publication WO 2014/017460 A1

Problems of an ultrasonic processing apparatus using an ultrasonic vibrator that excites a longitudinal vibration of a conventionally known structure by an ultrasonic processing apparatus that uses a new support structure of an ultrasonic vibrator described in Patent Document 2. There were not a few solutions. However, the ultrasonic processing apparatus using the support structure of the ultrasonic transducer described in Patent Document 2 can still reduce the required amount of electric energy and improve the processing accuracy to a level that is sufficiently satisfactory for practical use. It is not done.

On the other hand, when the Langevin type ultrasonic vibrator is used as an excitation means for ultrasonic vibration in the longitudinal / torsional vibration mode used in the above-described ultrasonic motor, for example, the electrical energy required for exciting the ultrasonic vibration is reduced. In addition to there is another problem. This additional problem is described in detail below.

In the case where a Langevin type ultrasonic transducer is combined with a piezoelectric element for exciting longitudinal vibration and a piezoelectric element for exciting torsional vibration to cause longitudinal and torsional vibration in the Langevin type ultrasonic transducer, Patent Document 1 As described in the above, the position of the longitudinal vibration mode node excited by the longitudinal vibration excitation piezoelectric element and the position of the torsional vibration mode node excited by the torsional vibration excitation piezoelectric element inside the ultrasonic vibrator Must be substantially the same. In order to reduce the size of Langevin ultrasonic transducers for longitudinal and torsional vibration, the electrical energy used for vibration excitation of the piezoelectric element for longitudinal vibration excitation and the piezoelectric element for torsional vibration excitation is the same resonance. It is desired to be realized by applying a frequency voltage. However, the resonance frequency and torsional primary vibration (same for the excitation of longitudinal primary vibration (vibration in which a single longitudinal vibration node appears in the vibrator) used in a Langevin type ultrasonic vibrator for normal longitudinal vibration excitation) The resonance frequency for excitation of a vibration in which a single torsional vibration node appears in the vibrator does not coincide with the resonance frequency. In general, the resonance frequency for torsional primary vibration excitation is about 2 times the resonance frequency for longitudinal primary vibration excitation. It is known that from / 3 to about 1/2. For example, when a Langevin type ultrasonic vibrator is manufactured from a steel material, the resonance frequency for torsional primary vibration excitation is approximately 0.6 to 0.65, where 1 is the resonance frequency for longitudinal primary vibration excitation. Accordingly, in order to excite the longitudinal primary vibration and the torsional primary vibration in the Langevin type ultrasonic vibrator for longitudinal and torsional vibration, it is necessary to use two electric energy supply systems in principle. The installation of the electrical energy supply system is not practical and has not been adopted.

On the other hand, torsional vibrations such as torsional secondary vibration and torsional tertiary vibration in which a plurality of torsional vibration nodes such as two or three are formed in the vibrator are also known. Therefore, the resonance frequency is higher than the resonance frequency for exciting the torsional primary vibration. Using this knowledge, for example, a method of generating longitudinal and torsional vibrations by combining longitudinal primary vibration and torsional secondary vibration is also conceivable, but each vibration node is located at substantially the same position in the vibrator. Therefore, it is necessary to increase the length of the vibrator, which is disadvantageous for miniaturization of the ultrasonic motor. Furthermore, since the amplitude of torsional vibration generated by torsional secondary vibration or torsional tertiary vibration is smaller than that of torsional vibration generated by torsional primary vibration, ultrasonic motors using such combined vibration modes are This is also not practical.

Accordingly, an object of the present invention is to provide a Langevin type ultrasonic transducer capable of simplifying an ultrasonic vibration excitation system and realizing both a miniaturization at a level that is sufficiently satisfactory for practical use and a reduction in the required amount of electric energy. The object is to provide a method for exciting longitudinal and torsional vibrations.

The inventor of the present invention aims to develop a method for exciting longitudinal and torsional vibrations of a Langevin type ultrasonic transducer capable of realizing both a reduction in size that is sufficiently satisfactory for practical use and a reduction in the required amount of electrical energy. First, the mechanism of ultrasonic vibration generation of longitudinal vibration in the ultrasonic vibrator was examined again. And in the examination, the support structure shown in FIG. 5 was devised as a model of the structure that firmly supports the ultrasonic transducer. That is, in the support structure of FIG. 5, when assembling the bolted Langevin type ultrasonic transducer 1, first, an annular ring is formed around the upper end portion of the metal block (generally called “front mass”) 2b disposed on the front side. A plate-shaped piezoelectric element in which a support frame 6 is formed integrally with a metal block, and is polarized in the vertical direction between the front mass 2b and a metal block (generally called “rear mass”) 2a disposed on the rear side. 3a and 3b were fastened with bolts 4 and fixed. Then, after preparing the bolted Langevin type ultrasonic transducer 1 configured in this way, the edge of the annular support frame 6 is attached to a housing 11 having a male screw (a support structure not shown in the figure). And is fixed by being engaged by a fitting structure of a nut 7 provided with a female screw. The electric energy supplied to the piezoelectric element 3 of the bolted Langevin type ultrasonic transducer 1 is set at a predetermined frequency from an ultrasonic oscillation circuit 8 provided outside the housing through a hole formed in the housing 11. The voltage which has is made to apply.

Next, in order to observe the vibration characteristics of the ultrasonic vibrator supported and fixed by the support structure shown in FIG. 5 by experiments, the bolts for longitudinal vibration excitation having the shape and size (unit: mm) shown in FIG. 6 are used. A Langevin type ultrasonic transducer 1 was produced. The bolt-clamped Langevin type ultrasonic transducer 1 shown in FIG. 6 has a plate-like piezoelectric element (PZT piezoelectric element) 3a and 3b polarized in the vertical direction and is annularly supported using stainless steel as a material similar to the rear mass 2a made of stainless steel. It arrange | positions between the front mass 2b shape | molded integrally with the frame 6, and it is set as the structure fixed by the bolt 4 similarly shape | molded integrally with the front mass 2b. And the taper-shaped recessed part for fitting the collet equipped with the tool was formed in the lower part of the front mass 2b.

In order to observe the ultrasonic vibration characteristics of the bolt-clamped Langevin type ultrasonic vibrator having the shape and size shown in FIG. 6 through experiments, an impedance analyzer is first used to make the ultrasonic vibrator unconstrained. The frequency characteristics were measured, and then the frequency characteristics were measured in the same manner with the same ultrasonic transducer being supported and fixed (restrained) by the support structure shown in FIG. FIG. 7 shows an admittance curve representing the frequency characteristics in the unconstrained state of the bolted Langevin type ultrasonic transducer of FIG. 6, and FIG. 7 is a diagram illustrating the admittance curves representing the frequency characteristics in the state restrained by the support structure shown in FIG. It is shown in FIG.

In the admittance curve of FIG. 7, when the bolted Langevin type ultrasonic transducer to be measured is in an unconstrained state, one admittance peak appears at a frequency position of 42.125 KHz. This admittance peak frequency (42.125 KHz) is understood to be a resonance frequency that excites the longitudinal primary vibration of the ultrasonic transducer of FIG. 6 in an unconstrained state.

On the other hand, the admittance curve of the bolted Langevin type ultrasonic transducer in the constrained state of FIG. 8 has one frequency close to the resonance frequency (44.375 KHz) that excites the longitudinal primary vibration seen in the admittance curve of FIG. It has been found that an admittance peak appears, and an admittance peak slightly smaller than the admittance peak at the resonance frequency appears at a frequency position of 24.250 KHz in a lower frequency region than the frequency of the admittance peak.

The presence of the two admittance peaks appearing in the admittance curve of FIG. 8 means that the ultrasonic longitudinal vibration of the bolted Langevin type ultrasonic transducer to be measured can be excited at any frequency. Understood. That is, it is considered that these two frequencies correspond to resonance frequencies that enable excitation of ultrasonic longitudinal vibration. In the admittance curve of FIG. 8 for the constrained ultrasonic transducer, the longitudinal primary vibration in the admittance curve of FIG. 7 of the ultrasonic transducer in the unconstrained state is changed from where the ultrasonic transducer is in the constrained state. Although it shifts from the peak corresponding to the resonance frequency to be excited, it can be understood that the admittance peak on the high frequency side in FIG. 8 should correspond to the resonance frequency for longitudinal primary vibration excitation. Next, the present inventor pays attention to the existence of these two admittance peaks appearing at different frequency positions, and shows voltages having frequencies approximate to the two resonance frequencies found from the admittance curve of FIG. 6 is applied to the bolted Langevin type ultrasonic vibrator of FIG. 6 under the restricted condition, and the ultrasonic vibration is excited, and the vertical vibration displacement amount of the upper end surface of the rear mass 2a under vibration is measured by a laser Doppler vibrometer. did.

According to the measurement result of the longitudinal vibration displacement of the upper end surface of the rear mass 2a using a laser Doppler vibrometer, the frequency approximated to the frequency of the relatively large admittance peak on the high frequency side shown in FIG. The amount of vibration displacement of the upper end surface of 2a of the front mass of the ultrasonic vibrator excited by ultrasonic vibration (so-called longitudinal primary vibration) by applying a voltage of 43.86 KHz is about 33 μm. It was found that the electric power required for this was about 3.5W. On the other hand, the rear mass of an ultrasonic transducer in which ultrasonic vibration is excited by applying a voltage (23.64 KHz) approximate to the frequency of the relatively small admittance peak on the low frequency side shown in FIG. It has been found that the vibration displacement amount of the upper end surface of 2a is slightly reduced to about 30 μm, and the electric power required for the ultrasonic vibration is remarkably reduced to about 0.5 W.

Therefore, the ultrasonic vibration (vertical primary vibration) that appears in the ultrasonic vibrator by applying a voltage having a frequency corresponding to a relatively large admittance peak that appears on the high frequency side of the admittance curve in FIG. 8 and the relative that appears on the low frequency side. Compared with the ultrasonic vibration that appears in the ultrasonic vibrator by applying a voltage with a frequency corresponding to a small admittance peak, the latter is slightly smaller than the former in terms of the longitudinal vibration displacement, further exciting the ultrasonic vibration It can be seen that the power required for the latter is about 1/7 (0.5 W / 3.5 W) of the former. That is, the electric power required for exciting the ultrasonic vibration in a state where the bolted Langevin type ultrasonic transducer having the configuration shown in FIG. 6 is supported and restrained using the support structure shown in FIG. By using the vibration when applying the voltage of the resonance frequency on the frequency side, the vibration is greatly reduced compared to the case of using the vibration (vertical primary vibration) when applying the voltage of the resonance frequency on the high frequency side. It has been found.

Next, a collet provided with a tool is attached to the recess of the front mass 2b on the lower side of the bolt-clamped Langevin type ultrasonic vibrator having the configuration shown in FIG. Experiments were conducted to measure in both the vertical and horizontal directions. In this experiment, a rod model with a length of 40 mm and a diameter of 3 mm was selected as a drill model assumed as a tool, and this rod was projected to the lower end of the collet and mounted with a length of 14.8 mm. A tool model was prepared, and the vibration displacement amount of the tip (lower end) of the circular rod was measured using this ultrasonic machining tool model.

In the measurement experiment of the vibration displacement amount of the tool tip portion described above, by using an impedance analyzer for an ultrasonic machining tool model configured by mounting a collet and a tool on a bolted Langevin type ultrasonic transducer having the configuration shown in FIG. Based on the obtained admittance curve, the resonance frequency on the high frequency side was set to 30.20 KHz and the resonance frequency on the low frequency side was set to 21.09 KHz, and voltages having the respective frequencies were applied to the bolted Langevin type ultrasonic transducer. .

As a result of the above measurement experiment, the longitudinal vibration displacement of the tip of the tool attached to the ultrasonic vibrator oscillated by applying the voltage of the resonance frequency on the high frequency side is 8.33 μmp-p, It was found that the amount of vibration displacement in the direction was 0.787 μmp-p, and the power required for the vibration was 1.17 W. On the other hand, the longitudinal vibration displacement amount of the tip portion of the tool mounted on the ultrasonic vibrator oscillated by applying the resonance frequency voltage on the low frequency side is 7.70 μmp-p, and the transverse vibration displacement amount. Was 0.248 μmp-p, and the power required for the vibration was found to be 0.31 W.

Therefore, from the result of the above measurement experiment, the longitudinal vibration displacement of the ultrasonic vibration at the resonance frequency on the low frequency side is compared with the vibration displacement in the longitudinal direction of the ultrasonic vibration at the resonance frequency on the high frequency side. On the other hand, with regard to the amount of vibration displacement in the lateral direction, the vibration caused by the application of the resonance frequency voltage on the low frequency side is larger than the vibration caused by the application of the resonance frequency voltage on the high frequency side (longitudinal primary vibration). It was confirmed that it was about 1/3 (0.248 / 0.787). Also, the amount of power used is about 1/4 (0.31) in vibration caused by application of a voltage having a resonance frequency on the low frequency side, compared with vibration caused by application of a voltage on the resonance frequency on the high frequency side (vertical primary vibration). /1.17), it was confirmed that the amount of power used for exciting ultrasonic vibrations was also significantly reduced.

From the experimental results described above, the vibration excitation method of the ultrasonic vibrator by applying the voltage of the resonance frequency corresponding to the admittance peak appearing on the lower frequency side than the resonance frequency for exciting the longitudinal primary vibration of the ultrasonic vibrator described above. It has been found that by using, a significant reduction in the power required for vibration excitation and a significant reduction in lateral vibration (rolling) excited accompanying longitudinal vibration are realized.

Next, the inventor of the present invention describes the nature of the vibration of the ultrasonic vibrator generated by applying a voltage having a resonance frequency corresponding to an admittance peak that appears on the lower frequency side than the resonance frequency that excites the longitudinal primary vibration of the ultrasonic vibrator. In order to solve the problem, ANSYS (distributor: Ansys Japan Co., Ltd.), which is a commercially available finite element method analysis software, is used to change the Langevin type ultrasonic transducer of FIG. 6 into the constraint condition of FIG. The ultrasonic vibration excited when restrained by the restraint condition of the ultrasonic transducer from which the admittance curve was obtained was analyzed.

As a result of the above-mentioned analysis of ultrasonic vibration by the finite element method, ultrasonic waves generated by applying a voltage having a resonance frequency corresponding to an admittance peak appearing on the lower frequency side than the resonance frequency that excites the longitudinal primary vibration of the ultrasonic vibrator. As is clear from the ANSYS analysis image of FIG. 9, the vibration of the vibrator is a reciprocating motion in which the entire ultrasonic vibrator vibrates in the same longitudinal direction (long axis direction of the ultrasonic vibrator). It has been found that the vibration is an ultrasonic vibration in which there is no vibration node (in this specification, this vibration is called pseudo longitudinal zero-order vibration or para-longitudinal zero-order vibration). According to the image of FIG. 9, in this pseudo longitudinal zero-order vibration, a vibration node appears at a portion where the annular support frame is in contact with the base, and the annular support frame itself is also the same as the ultrasonic vibration. It has also been found to perform phase ultrasonic vibration. In other words, the ultrasonic vibration of the pseudo longitudinal zero-order vibration is a reciprocating motion in which the entire ultrasonic vibrator vibrates in the same vertical direction, and has one portion that becomes a vibration node inside the ultrasonic vibrator, This is a vibration that is clearly different from the longitudinal primary vibration, which is the mode that shows the vibrations that are opposite to each other in the longitudinal direction with the node part as the boundary.Therefore, the loss of applied electric energy is small and inevitably It is presumed that this will result in the advantage that the vibration in the lateral direction is reduced.

On the other hand, as is apparent from the ANSYS analysis image of FIG. 10, the vibration generated by the voltage of the resonance frequency that excites the longitudinal primary vibration of the ultrasonic vibrator vibrates in a portion close to the flange inside the ultrasonic vibrator. This mode has a single node and exhibits vibrations that are opposite to each other in the vertical direction from the part that becomes the node.

The present invention is based on the above-mentioned novel finding by the present inventor regarding the excitation of ultrasonic longitudinal vibration of pseudo longitudinal zero order vibration in a Langevin type ultrasonic transducer, and ultrasonic waves by pseudo longitudinal zero order vibration newly found. This invention has been completed by obtaining the knowledge that a new combined ultrasonic / vibration vibration, which is a longitudinal / torsional vibration, can be obtained by combining a vibration with a conventionally known ultrasonic vibration by a torsional primary vibration.

Therefore, according to the present invention, a metal block, a metal block having a support frame projecting annularly on the side surface, and a vertically polarized disk-shaped piezoelectric element fixed between these metal blocks and the circumference A Langevin type ultrasonic transducer including a disk-shaped piezoelectric element polarized in a direction is prepared, and the Langevin type ultrasonic transducer is connected to a base via the support frame and supported in a restrained state. After that, both the disk-shaped piezoelectric element polarized in the longitudinal direction of the ultrasonic transducer and the disk-shaped piezoelectric element polarized in the circumferential direction have vibration nodes inside the ultrasonic transducer. The Langevin type ultrasonic vibration by applying a voltage having a frequency capable of exciting a longitudinal vibration consisting of no reciprocating vibration and a torsional primary vibration having one node of vibration inside the ultrasonic vibrator The piezoelectric element Longitudinal and torsional ultrasonic waves, which are a combination of ultrasonic vibrations (pseudo-longitudinal zero-order vibrations) and torsional primary vibrations, which are reciprocating vibrations that do not have vibration nodes in the direction perpendicular to the plane. A novel longitudinal / torsional vibration excitation method for a Langevin type ultrasonic transducer characterized by exciting vibration is provided.

Further, according to the present invention, the frequency (resonance frequency) used in the above-described ultrasonic / vibration longitudinal / torsional vibration excitation method is included in a frequency range lower than the resonance frequency for exciting the vibration in the longitudinal primary vibration mode of the vibrator. Also provided is a vibration excitation method that is at a frequency that can be reduced.

Further, according to the present invention, in the longitudinal and torsional vibration excitation method of the ultrasonic vibrator described above, the annular support frame has a longitudinal vibration node at a portion contacting the base, and an ultrasonic wave having the same phase as the ultrasonic vibration is provided. A vibration excitation method for performing vibration is also provided.

By utilizing the longitudinal and torsional vibration excitation method of the Langevin type ultrasonic vibrator of the present invention, the ultrasonic vibrator is miniaturized, and even with a small-sized ultrasonic vibrator, high output longitudinal and torsional vibration Can be output. Furthermore, it is possible to significantly reduce the power energy necessary for exciting the longitudinal and torsional vibrations of the ultrasonic vibrator. Furthermore, since the torsional vibration used is the torsional primary vibration, which is the basic mode, torsional vibration with less spurious (unnecessary vibration) is realized, and therefore, the combined vibration of the torsional primary vibration and the pseudo longitudinal zero-order vibration Even in the longitudinal and torsional vibrations used in the present invention, spurious (unnecessary vibration) is hardly generated.
The longitudinal and torsional vibration excitation method of the Langevin type ultrasonic vibrator of the present invention is particularly effective for driving a small ultrasonic motor, but also in ultrasonic processing using a grinding tool such as a drill or a polishing tool. There is an advantage that high-precision processing is possible with low power energy. In addition, the removal of chips generated in grinding and polishing processes is performed in parallel with the grinding and polishing processes by the action of torsional vibration generated in combination with the pseudo longitudinal zeroth order vibration. There is also an advantage of improvement.

It is a figure which shows the structure of a typical bolting Langevin type ultrasonic transducer | vibrator. It is a figure which shows the example of a structure of the ultrasonic processing apparatus using a bolting Langevin type ultrasonic transducer | vibrator. It is a figure which shows the example of the piezoelectric element for torsional vibration excitation. It is a figure which shows the example of an ultrasonic motor. It is a figure which shows the example of the support fixation (restraint) structure of the ultrasonic transducer | vibrator which can be utilized for excitation of the longitudinal vibration used as the foundation of the excitation method of the longitudinal / torsional vibration of the ultrasonic transducer | vibrator of this invention. It is a figure which shows the example of a structure of the ultrasonic transducer | vibrator which can be utilized for excitation of the longitudinal vibration used as the foundation of the excitation method of the longitudinal / torsional vibration of the ultrasonic transducer | vibrator of this invention. It is a figure which shows the admittance curve showing the frequency characteristic in the unconstrained state of the ultrasonic transducer | vibrator shown in FIG. FIG. 6 is a diagram showing an admittance curve representing frequency characteristics of the ultrasonic transducer of FIG. 6 constrained by the support structure shown in FIG. 5. It is a figure which shows the vibration mode (pseudo longitudinal zero order vibration) generate | occur | produced with the excitation method of the longitudinal vibration used as the foundation of the excitation method of the longitudinal / torsional vibration of the ultrasonic transducer | vibrator of this invention based on the evaluation result by a finite element method. . It is a figure which shows the vibration mode generate | occur | produced by the longitudinal primary vibration of an ultrasonic transducer | vibrator based on the evaluation result by a finite element method. It is a figure which shows typically the vibration mode of the pseudo longitudinal zero order vibration used as the foundation of the longitudinal and torsional vibration which generate | occur | produces with the excitation method of the longitudinal and torsional vibration of the ultrasonic transducer | vibrator of this invention. FIG. 4A is a diagram showing a vibration mode of longitudinal primary vibration of an ultrasonic vibrator, and FIG. 5B is an enlarged view showing the behavior of the piezoelectric element portion. It is a figure which shows the other example of the shape and size of an ultrasonic transducer | vibrator utilized for excitation of the longitudinal vibration used as the foundation of the excitation method of the longitudinal / torsional vibration of the ultrasonic transducer | vibrator of this invention, and a support fixing structure. It is a figure which shows the ultrasonic vibration (pseudo longitudinal zero order vibration) which generate | occur | produces by the excitation in the support fixing structure of the ultrasonic transducer | vibrator shown in FIG. 13 as an image by a finite element method. Concept of a bolt-clamped Langevin type ultrasonic transducer incorporating a longitudinal vibration excitation piezoelectric element and a torsional vibration excitation piezoelectric element for use in the implementation of the longitudinal and torsional vibration excitation method of the bolted Langevin type ultrasonic transducer of the present invention FIG. It is a figure which shows the structural example of the grinding | polishing apparatus used for implementation of the excitation method of the longitudinal and torsional vibration of the bolting Langevin type ultrasonic vibrator of this invention.

Resonant frequency used to excite pseudo longitudinal zeroth order vibration that is the basis of the excitation method of longitudinal and torsional vibration of ultrasonic transducer of the present invention (corresponding to resonant frequency that excites vibration of longitudinal primary vibration mode of ultrasonic transducer) As far as the present inventor knows, the existence of a resonance frequency corresponding to an admittance peak appearing on a lower frequency side than the admittance peak to be expressed (represented as a resonance frequency for exciting pseudo longitudinal zero-order vibration in this specification) Has never been recognized by those skilled in the art. In addition, as far as the present inventor is aware, the vibration excitation method of the ultrasonic vibrator using the pseudo longitudinal zeroth order vibration has never been implemented.

In order to implement the method for exciting the longitudinal and torsional vibrations of the ultrasonic transducer of the present invention using the resonance frequency for exciting the pseudo-longitudinal zeroth order vibration discovered by the present inventor, first, as shown in FIG. It is necessary to produce a bolt-clamped Langevin type ultrasonic vibrator incorporating a piezoelectric element for exciting longitudinal vibration and a piezoelectric element for exciting torsional vibration having a basic structure.

The bolted Langevin type ultrasonic transducer 1a shown in FIG. 15 has a vertically polarized vertical polarization between a rear mass 2a in which an annular support frame (flange) 6 is formed around the bottom and a front mass 2b. The vibration exciting

piezoelectric elements

3a and 3b and the circumferentially polarized torsional vibration exciting

piezoelectric elements

3c and 3d are sandwiched and laminated and fixed under high pressure by bolting.

In FIG. 15, the annular support frame 6 is formed on the rear mass 2a, but the annular support frame may be formed on the front mass. The annular support frame is preferably formed integrally with the front mass or the rear mass, but an annular or disc-shaped support frame formed independently is mounted and fixed to the front mass or the rear mass, or the front mass. It can also be fixed between the rear mass.

FIG. 16 shows a configuration example of an ultrasonic polishing apparatus incorporating the bolted Langevin type ultrasonic transducer 1a having the basic configuration shown in FIG. In FIG. 16, an ultrasonic polishing apparatus 10a accommodates an ultrasonic transducer 1a having a polishing tool 13a connected to the lower end portion thereof via a collet 12a inside a housing (also a support) 8. The sound wave oscillator 1a is rotatably supported by a bearing (not shown). Note that a battery 50 serving as a power source and an ultrasonic oscillation circuit 51 that uses electric energy obtained from the battery are provided inside the housing (also supporting body) 8 of the ultrasonic polishing apparatus 10a of FIG. A voltage having a common resonance frequency is applied to the longitudinal vibration exciting

piezoelectric elements

3a and 3b and the torsional vibration exciting

piezoelectric elements

3c and 3d via lead wires (not shown) of the ultrasonic vibrator. . In order to excite the vibration of the elliptical locus at the tip of the polishing tool 13a, the phase difference between the voltage applied to the longitudinal vibration exciting piezoelectric element and the voltage applied to the torsional vibration exciting piezoelectric element is 90 °.

Next, as shown in FIG. 16, the vibration characteristics of the ultrasonic vibrator supported and fixed using the annular support frame are measured by an impedance analyzer, and an admittance curve as shown in FIG. 8 is obtained. If two peaks (admittance peak) as shown in FIG. 8 appear in the admittance curve, the peak frequency appearing on the high frequency side is usually the resonance frequency of the longitudinal primary vibration excitation, and the peak frequency appearing on the low frequency side is pseudo. It can be determined that the resonance frequency can be used for excitation of longitudinal zeroth order vibration. If necessary, an admittance curve is obtained using an impedance analyzer after placing the ultrasonic transducer in an unconstrained state, and a frequency corresponding to an admittance peak appearing in the admittance curve (exciting longitudinal primary vibration). It is also possible to confirm that the resonance frequency on the high frequency side corresponds to the resonance frequency of longitudinal primary vibration excitation based on the comparison between the frequency of the admittance peak on the high frequency side and the frequency of the admittance peak on the high frequency side.

∙ Depending on the shape of the ultrasonic transducer, a clear admittance peak of vertical primary vibration may not appear in the admittance curve. In that case, according to a method using a known calculation formula, the resonance frequency for exciting the longitudinal primary vibration is estimated, and the frequency of the admittance peak appearing in the region on the lower wavelength side than the resonance frequency is set to the frequency of the pseudo longitudinal zero-order vibration. Therefore, it is possible to excite the longitudinal / torsional composite ultrasonic vibration including the target pseudo longitudinal zero-order vibration by applying a voltage having the frequency of the pseudo longitudinal zero-order vibration.

On the other hand, even when three or more admittance peaks appear on the admittance curve, the resonance frequency that excites the longitudinal primary vibration is estimated by the above method, and appears at a position adjacent to the region on the lower wavelength side than the resonance frequency. Using the frequency of the quasi-longitudinal vibration as the frequency of the quasi-vertical zero-order vibration, the longitudinal and torsional composite ultrasonic vibration including the desired pseudo-longitudinal zero-order vibration can be excited by using the frequency of the quasi-longitudinal zero-order vibration. .

A tool as shown in FIG. 16 is attached to the ultrasonic vibrator having the configuration shown in FIG. 15 to form a vibration tool for ultrasonic machining, and the ultrasonic vertical vibration tool determined by the above method is used for the ultrasonic machining vibration tool. By applying a voltage having a resonance frequency for vibration excitation, it is possible to excite longitudinal / torsional composite ultrasonic vibration including pseudo longitudinal zero-order vibration on the tool. However, since the resonance frequency for excitation of the pseudo vertical zeroth order vibration determined by the above method is the resonance frequency confirmed by the measurement in a state where no tool mounting tool such as a tool or a collet is mounted, the pseudo vertical vibration of the tool is determined. There may be a slight deviation from the optimum resonance frequency that can excite the zero-order vibration. Further, even when the restraint condition (support fixing condition) of the vibration tool for ultrasonic machining is slightly shifted, an optimal resonance frequency shift may occur. Therefore, the determination of the resonance frequency for excitation of the pseudo vertical zeroth order vibration of the ultrasonic vibrator that is attached to the base and restrained by the base is such that the optimum resonance frequency can be determined while checking the excited ultrasonic vibration. It is desirable to use an ultrasonic oscillation circuit capable of tracking the resonance frequency.

Even if an ultrasonic transducer having a configuration as shown in FIG. 15 is manufactured and the ultrasonic transducer is restrained by the support fixing structure as shown in FIG. 5, an admittance curve is obtained using an impedance analyzer. When a plurality of (usually two) admittance peaks as shown in FIG. 8 do not appear, the admittance having two peaks as shown in FIG. 8 is adjusted by adjusting the constraint condition of the ultrasonic transducer. A curve may be obtained. However, if an admittance curve having two peaks as shown in FIG. 8 cannot be obtained even by adjusting the constraint condition of the ultrasonic transducer, the ultrasonic transducer shape setting, Since it is considered that the support fixing structure of the ultrasonic vibrator is inappropriate for excitation of the target pseudo longitudinal zero-order vibration, the constraint condition of the ultrasonic vibrator of FIG. 5 and the ultrasonic vibrator of FIG. With reference to the shape and size, it is necessary to change the design of the ultrasonic transducer and review the support fixing structure. Note that the constraint conditions of the ultrasonic transducer in FIG. 5 and the shape and size of the ultrasonic transducer in FIG. 6 are merely representative examples of the implementation method of the present invention. It is not a condition that limits the embodiment of the excitation method of the pseudo longitudinal zeroth order vibration of the child.

15 is incorporated into an ultrasonic motor as shown in FIG. 4, and longitudinal and torsional vibrations (longitudinal and torsional composites are combined) according to the method of the present invention. By generating vibration, a small and high performance ultrasonic motor can be obtained.

As described above, the present inventor has described that the longitudinal vibration constituting the combined longitudinal and torsional ultrasonic vibration generated by the vibration excitation method of the ultrasonic vibrator of the present invention is “the direction perpendicular to the plane of the piezoelectric element”. “Ultrasonic vibration consisting of reciprocating vibration with no vibration node inside the vibrator”. Next, the data on which this conclusion is based will be explained again.

As described above, the existence of the admittance peak appearing on the low frequency side of the admittance curve in FIG. 8 is not known as far as the present inventors know. For this reason, the present inventor was unable to judge at first what the frequency corresponding to the frequency position where the low frequency side admittance peak appears is. However, as is clear from the experimental facts described so far, the frequency corresponding to the frequency position where the admittance peak on the low frequency side appears is also the resonance frequency of the ultrasonic transducer, and the application of the voltage at the resonance frequency is applied. As a result, it was confirmed that the longitudinal ultrasonic vibration excited by the ultrasonic transducer in the constrained state was generated with low power consumption, and further the horizontal vibration was small.

For this reason, in order to analyze the vibration mode of the ultrasonic vibration confirmed this time, the present inventor used ANSYS, which is calculation software based on a commercially available finite element method, as described above, and used the ultrasonic wave used in the experiment. The vibration mode of the ultrasonic vibration generated in the ultrasonic vibrator was analyzed under the shape, size, material of the vibrator and the support fixing condition (constraint condition) of the ultrasonic vibrator. The analysis result of the vibration mode is shown in FIG. 9 and FIG.

As described above, FIG. 9 is an image showing a vibration mode that appears when a voltage having a resonance frequency on the low frequency side is applied to an ultrasonic transducer under a constraint condition. The vibration that appears is a vibration in which the entire ultrasonic vibrator is directed in one direction, and the node of the vibration does not exist inside the ultrasonic vibrator, and the outer end of the annular support frame of the ultrasonic vibrator It can be seen that it is present (corresponding to the connection to the base). Next, FIG. 10 is an image showing a vibration mode that appears when a voltage having a resonance frequency on the high frequency side is applied to the ultrasonic transducer under the constraint condition. From this image, the vibration that appears in the ultrasonic transducer is shown. Is a stretching vibration that has a node inside the ultrasonic transducer and vibrates up and down with the node as a boundary.

FIG. 11 is a diagram schematically illustrating the vibration mode represented by the image shown in FIG. That is, in the ultrasonic vibration in the vibration mode according to the present invention, the ultrasonic vibrator repeats reciprocating vibration that vibrates in one direction as a whole. The annular support frame that supports and fixes the ultrasonic transducer to the base has a node at a connection portion with the base (corresponding to the peripheral portion of the annular support frame), and corresponds to the connection portion of the ultrasonic transducer. The inner peripheral portion of the annular support frame also exhibits vibration that repeats reciprocating motion synchronized with the ultrasonic transducer. This vibration mode corresponds to the pseudo vertical zeroth-order vibration mode described in this specification.

12A is a diagram schematically illustrating the vibration mode represented by the image shown in FIG. That is, in the ultrasonic vibration of FIG. 10, the ultrasonic vibrator has a node at a substantially central portion (position where the piezoelectric element is present) where the piezoelectric element exists, and repeats vibration (vertical primary vibration) that expands and contracts vertically. . Since the vertical primary vibration is such a stretching vibration, the lower side surface realized in the pseudo vertical zero-order vibration mode shown in FIG. 11 when exciting the vertical vibration on one side (lower side surface) on which the tool is mounted. It is presumed that relatively large electric power is required to obtain a vibration amount (displacement amount) equivalent to the vertical vibration.

12B is a schematic enlarged view showing the vibration state of the ultrasonic vibrator shown in FIG. 12A, and the deformation that appears in the piezoelectric element 3 due to the application of electrical energy. It is a figure which shows a condition (estimated condition) typically. In other words, the piezoelectric element 3 repeats expansion and contraction due to fluctuations in the applied electric energy, but at the time of expansion, the central portion expands against the pressure applied to the piezoelectric element as shown in the figure. It is considered to be deformed so as to be put out. Therefore, if the deformation of the piezoelectric element does not occur in a shape that is completely symmetric with respect to the center thereof, the upper and lower end faces of the ultrasonic transducer are not completely parallel to the center plane of the stretching vibration. It is presumed that lateral vibration is likely to occur on the upper and lower end faces of the acoustic wave vibrator.

FIG. 13 shows the shape and size of an ultrasonic vibrator that can be used in the vibration excitation method of the ultrasonic vibrator that is the basis of the longitudinal and torsional vibration generated by the method of exciting ultrasonic and vertical vibrations of the present invention. FIG. 14 is a diagram showing another example of the support and fixing structure, and FIG. 14 is a diagram illustrating ultrasonic vibration (pseudo longitudinal zeroth order vibration) generated by excitation in the support and fixing structure of the ultrasonic transducer shown in FIG. Is shown as an image obtained by the finite element method. Similar to the image shown in FIG. 9, the vibration appearing in the ultrasonic transducer is a reciprocating vibration in which the entire ultrasonic transducer is directed in one direction, and the node of the vibration does not exist inside the ultrasonic transducer. It is present at the outer end of the annular support frame of the ultrasonic transducer (corresponding to the connection to the base).

1 Bolt-clamped Langevin type ultrasonic transducer 2a Metal block (rear mass)
2b Metal block (front mass)
3a, 3b Longitudinal vibration

excitation piezoelectric element

3c, 3d Torsional vibration excitation piezoelectric element 4 Bolt

5a Copper electrode

5b Copper electrode 6 Annular support frame 7 Nut 10 Ultrasonic grinding apparatus 11 Housing 12 Horn 13 Polishing tool 20 Ultrasonic Motor 22 Bottom nut 24 Torsional vibration piezoelectric element 26 Holder 28 Longitudinal vibration piezoelectric element 30 Stator head 32 Stator 34 Rotor 36 Friction material 38 Center bolt 40 Center bolt 42 Spring member 44 Bearing 48 Flange

Claims

Metal block, metal block having a support frame projecting in an annular shape on the side surface, and a vertically polarized disk-shaped piezoelectric element fixed between these metal blocks and a circumferentially polarized circle A Langevin type ultrasonic transducer including a plate-like piezoelectric element is prepared, and after the Langevin type ultrasonic transducer is connected to a base via the support frame and supported in a restrained state, the ultrasonic vibration Both the disk-shaped piezoelectric element polarized in the longitudinal direction of the child and the disk-shaped piezoelectric element polarized in the circumferential direction are longitudinal vibrations composed of reciprocating vibrations having no vibration nodes inside the ultrasonic vibrator. By applying a voltage having a frequency capable of exciting vibration and a torsional primary vibration having one node of vibration inside the ultrasonic vibrator, the Langevin type ultrasonic vibrator is applied to the piezoelectric element. In a direction perpendicular to the plane of A Langevin-type ultrasonic transducer that excites longitudinal and torsional ultrasonic vibrations, which are a combination of ultrasonic vibrations consisting of reciprocating vibrations with no vibration nodes inside the ultrasonic vibrators and torsional primary vibrations. Excitation method for vertical and torsional vibration.
The Langevin type ultrasonic transducer in which the frequency used in the longitudinal and torsional vibration excitation method of the ultrasonic transducer is a frequency included in a frequency range lower than the resonance frequency for exciting the vibration of the longitudinal primary vibration mode of the transducer New vertical and torsional vibration excitation method.
In the above-described ultrasonic vibrator longitudinal / torsional vibration excitation method, a Langevin type supersonic wave having an ultrasonic vibration in the same phase as the ultrasonic vibration has a node of the vertical vibration at the portion where the annular support frame contacts the base. A novel longitudinal and torsional vibration excitation method for acoustic wave vibrators.