JP6716082B2 - Excitation method of longitudinal and torsional vibration of Langevin type ultrasonic transducer - Google Patents

Description

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

Ultrasonic transducers that use a piezoelectric element as an ultrasonic wave generation source are known to have various configurations. 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 vibrator having a structure in which a polarized piezoelectric element is clamped and fixed at a high pressure by a bolt between a pair of metal blocks is capable of generating high-energy ultrasonic vibration. The use of ultrasonic processing, which is attached to a tool for cutting, plastic working, and abrasive processing of various materials, is being studied. Furthermore, for various ultrasonic transducers, ultrasonic vibration generated by the ultrasonic transducers is transmitted through a diaphragm or vibrating means to perform ultrasonic cleaning, metal bonding, plastic welding, ultrasonic fog. Consideration of ultrasonic wave processing such as emulsification, emulsification and dispersion, and application to underwater acoustic equipment (sonar) such as fish finder, ultrasonic flaw detector, medical echo diagnostic device, flow meter and other communication application equipment. Have been used in many fields.

The configuration of various ultrasonic transducers including the bolted Langevin type ultrasonic transducer is already known, but as a precaution, an example of the configuration of a typical bolted Langevin type ultrasonic transducer and its usage form A brief description is given below with reference to the accompanying FIGS. 1 and 2.

FIG. 1 is a diagram showing an example of a typical structure of a bolted Langevin type ultrasonic transducer. The bolted Langevin type ultrasonic transducer 1 includes a pair of metal blocks 2a and 2b between which a polarized piezoelectric element (eg, a piezoelectric ceramic sheet such as a PZT sheet) 3a and 3b is sandwiched and a bolt 4 is used to form the metal block. It has a structure in which 2a and 2b are fastened together. In FIG. 1, the arrow on the piezoelectric element indicates the polarization direction. It should be noted that the piezoelectric elements 3a and 3b are connected to electrode pieces 5a and 5b (usually using an electrode piece such as phosphor bronze) 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 device using a bolted Langevin type ultrasonic vibrator as an ultrasonic vibration source. In FIG. 2, an ultrasonic polishing machine 10 accommodates an ultrasonic transducer 1 having a polishing tool 13 connected to a lower end portion thereof via a horn 12 in a housing 11, and the ultrasonic transducer 1 is a bearing. It is rotatably supported by 14. The rotation of the ultrasonic transducer 1 is driven by an AC spindle motor 16 connected to the servo unit 15. In the apparatus of FIG. 2, the electric energy for ultrasonic vibration of the ultrasonic vibrator 1 is a contact type power supply including a carbon brush and a slip ring connected to an electric energy supply source 17 provided outside. It is supplied via the 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 the piezoelectric element 2a. 2b shows a vibration mode in a longitudinal direction (corresponding to the longitudinal direction in FIG. 1) having vibration nodes near the position 2b (called longitudinal primary vibration). Vibrations commonly used in the ultrasonic processing equipment shown in Fig. 2, ultrasonic cleaning, underwater acoustic devices (sonar) such as fish finder, ultrasonic flaw detector, medical echo diagnostic device, flow meter, etc. Is the vibration of the vibration mode of this vertical primary vibration.

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

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

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

Patent Document 1 discloses an improved invention of an ultrasonic motor that utilizes the longitudinal/torsional vibration mode of a conventionally known ultrasonic vibrator, and discloses a conventional ultrasonic motor targeted for the improvement. The ultrasonic motor having the configuration shown in FIG. 4 is shown and its description is described. That is, referring to FIG. 4, the ultrasonic motor 20 includes a stator 32 having a bottom nut 22, a piezoelectric element 24 for torsional vibration, a hollow holder 26, a piezoelectric element 28 for longitudinal vibration, and a hollow stator head 30, and a stator 32 thereof. It includes a center bolt 38 rotatably arranged on the shaft center of the rotor and a rotor 34 supported by the center bolt 38. 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 is incorporated inside the rotor 34 to ensure smooth rotation around the center bolt 40. In the inside of the ultrasonic vibrator, 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. And a 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 in the rotor 34, and the vertical vibration piezoelectric element 28 controls contact between the stator 32 and the rotor 34. More specifically, when a voltage is applied to the piezoelectric element for torsional vibration while the stator head 30 and the rotor 34 are in contact with each other under pressure by the spring force of the spring member 42, the torsional vibration generated by the piezoelectric element for torsional vibration 24 causes The rotor 34 rotates at a minute angle. After the rotation of this minute angle, when the pressing force of the rotor 34 against the stator head 30 is weakened by exciting the longitudinal vibration piezoelectric element 28, the torsional vibration of the torsional vibration piezoelectric element 24 disappears. Then, when a voltage is again applied to the piezoelectric element 24 for torsional vibration, the rotor 34 rotates again at a minute angle. By repeating the elliptic vibration generated by the combination of the torsional vibration of the piezoelectric element for torsional vibration 24 and the longitudinal vibration of the piezoelectric element for longitudinal vibration 28, the rotor 34 can be continuously rotated in a fixed direction. Then, the spokes are inserted into the coupling holes 46 and 56 formed by intersecting the rotor 34, and the rotary motion bodies are attached to the spokes, thereby rotating the rotary motion bodies.

The ultrasonic motor having the above-described configuration easily realizes low-speed and high-torque rotation, and the operation sound is quiet. Therefore, the ultrasonic motor is particularly useful as a motor to be mounted on small precision equipment and electric equipment.

By the way, the effects expected by applying ultrasonic vibrations to various tools in the above-mentioned ultrasonic processing apparatus are reduction of electric energy required for processing work by the tools and improvement of processing accuracy. With the ultrasonic processing apparatus that has been manufactured and used in actual processing operations, the expected effects have not been sufficiently obtained. For this reason, it cannot be said that the ultrasonic processing apparatus has been sufficiently spread at the present time. Therefore, in order to promote the further spread of ultrasonic machining, the amount of electrical energy required to excite the vibration of the ultrasonic transducer during the execution of ultrasonic machining work has been significantly reduced, and sufficient machining accuracy has been achieved. It is necessary to make improvements so that

The inventor of the present invention has hitherto devised various improved inventions of ultrasonic vibrators, which can be expected to improve the processing accuracy commensurate with the amount of electric energy required to excite vibrations of the ultrasonic vibrators during ultrasonic processing. , Have applied for a patent. For example, among the improved inventions, the invention disclosed in Patent Document 2 can be given as the latest invention.

In Patent Document 2, a vibration complex of a tool and an ultrasonic vibration body is supported with high stability, and a support body (fixed support body) of the vibration complex of ultrasonic energy generated in the ultrasonic vibration body. As a support structure that enables application of vibration energy to the tool with high efficiency by suppressing leakage to the low level, a flange is attached to the ultrasonic vibrator equipped with the tool, and one side of the flange is A supporting structure that engages and supports by contacting a flange supporting surface formed on a separately prepared fixed body under stress (however, the flange of the ultrasonic vibrator is not joined to the flange supporting surface of the fixed body. And the flange of the ultrasonic vibrating body which is engaged with and supported by contacting the supporting surface of the fixed body is structured to vibrate ultrasonically in the thickness direction of the flange when the ultrasonic vibrating body is in a vibrating state). Is disclosed.

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

Regarding the problem of the ultrasonic machining apparatus using the ultrasonic transducer that excites the longitudinal vibration of the conventionally known structure by the ultrasonic machining apparatus that uses the new ultrasonic transducer support structure described in Patent Document 2 There were some resolutions. However, also in the ultrasonic processing apparatus using the support structure of the ultrasonic oscillator described in Patent Document 2, it is possible to reduce the required amount of electric energy and improve the processing accuracy at a level that is practically sufficiently satisfactory. Has not been done.

On the other hand, when the Langevin type ultrasonic transducer is used as a means for exciting the ultrasonic vibrations in the longitudinal/torsional vibration modes used in the ultrasonic motors described above, for example, reduction of the electrical energy required for exciting the ultrasonic vibrations. In addition to that, there is another problem. This other problem will be described in detail below.

When a Langevin type ultrasonic transducer is combined with a piezoelectric element for longitudinal vibration excitation and a piezoelectric element for torsional vibration excitation to cause longitudinal/torsional vibration in the Langevin type ultrasonic transducer, Patent Document 1 As described in, the position which becomes the node of the longitudinal vibration mode excited by the piezoelectric element for longitudinal vibration excitation and the position which becomes the node of the torsional vibration mode excited by the piezoelectric element for torsional vibration excitation inside the ultrasonic transducer. And should be approximately the same. In addition, in order to downsize the Langevin type ultrasonic transducer for longitudinal and torsional vibrations, the electrical energy used for the vibrational excitation of the piezoelectric element for longitudinal vibration excitation and the vibrational excitation of 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 the torsional primary vibration (also the same as that for the excitation of longitudinal primary vibration (vibration in which a single node of longitudinal vibration appears in the oscillator) used in a Langevin-type ultrasonic transducer for ordinary longitudinal vibration excitation (also: The resonance frequency for excitation of vibration (where one torsional vibration node appears in the oscillator) does not match. Generally, the resonance frequency for torsional primary vibration excitation is about 2 times the resonance frequency for longitudinal primary vibration excitation. It is known that it becomes from /3 to about 1/2. For example, when the Langevin type ultrasonic transducer is manufactured from a steel material, the resonance frequency for exciting the torsional primary vibration is about 0.6 to 0.65 when the resonance frequency for exciting the longitudinal primary vibration is 1. Therefore, in order to excite the longitudinal primary vibration and the torsional primary vibration in the Langevin type ultrasonic transducer for longitudinal/torsional vibration, it is necessary to use two electric energy supply systems in principle. The installation of the electric energy supply system of is not practical and has not been adopted in practice.

On the other hand, torsional vibrations such as torsional secondary vibrations and torsional tertiary vibrations in which a plurality of torsional vibration nodes such as two or three are formed in a vibrator are also known. Is higher than the resonance frequency for exciting the torsional primary vibration. Then, using this knowledge, for example, a method of generating longitudinal/torsional vibrations by combining longitudinal primary vibrations and torsional secondary vibrations can be considered. Therefore, it is necessary to increase the length of the vibrator, which is disadvantageous for downsizing the ultrasonic motor. Furthermore, the amplitude of the torsional vibration generated by the torsional secondary vibration or the torsional tertiary vibration is smaller than that of the torsional vibration generated by the torsional primary vibration. This is also not practical because it decreases.

Therefore, an object of the present invention is to provide a Langevin-type ultrasonic transducer capable of simplifying the ultrasonic vibration excitation system and further realizing both practical miniaturization and a sufficient reduction in electric energy. It is to provide a method of exciting longitudinal/torsional vibration.

The inventor of the present invention aims to develop a method for exciting longitudinal/torsional vibrations of a Langevin-type ultrasonic transducer, which can realize both miniaturization of a practically satisfactory level and reduction of the required amount of electric energy. First, the mechanism of ultrasonic vibration generation of longitudinal vibration in the ultrasonic vibrator was examined again. Then, at the time of the examination, a supporting structure shown in FIG. 5 was devised as a model of a structure for firmly supporting the ultrasonic transducer. That is, in the support structure of FIG. 5, when assembling the bolted Langevin type ultrasonic transducer 1, first, an annular shape is formed around the upper end of the metal block (generally called “front mass”) 2b arranged on the front side. The support frame 6 is integrally formed with a metal block, and a flat plate-shaped piezoelectric element vertically polarized between the front mass 2b and a metal block (generally called "rear mass") 2a arranged on the rear side. The bolts 4 were tightened to fix 3a and 3b. Then, after preparing the bolted Langevin type ultrasonic transducer 1 configured as described above, the edge portion of the annular support frame 6 is provided with a housing 11 having a male screw (a support structure not shown in the housing itself). (Which is connected to a base, which is fixed), and a nut 7 having a female screw are engaged with each other by a fitting structure, and restrained and fixed. The bolted Langevin type ultrasonic transducer 1 is supplied with electric energy to the piezoelectric element 3 through a hole formed in the housing 11 at a predetermined frequency from an ultrasonic oscillation circuit 8 provided outside the housing. The voltage which it has was applied.

Next, as an ultrasonic vibrator supported and fixed by the support structure shown in FIG. 5, in order to observe its vibration characteristics by experiments, bolt tightening for longitudinal vibration excitation of the shape and size (unit: mm) shown in FIG. The Langevin type ultrasonic transducer 1 was produced. In the bolted Langevin type ultrasonic transducer 1 shown in FIG. 6, the plate-shaped piezoelectric elements (PZT piezoelectric elements) 3a and 3b, which have been vertically polarized, are annularly supported by using stainless steel as the rear mass 2a. It is arranged between the frame body 6 and the front mass 2b integrally formed with the frame body 6, and is fixed by tightening with the bolt 4 also integrally formed with the front mass 2b. Then, a taper-shaped recess for fitting a collet with a tool is formed in the lower portion of the front mass 2b.

In order to observe the ultrasonic vibration characteristics of the bolted Langevin type ultrasonic transducer having the shape and size shown in FIG. 6 by an experiment, first, using an impedance analyzer, the ultrasonic transducer in an unconstrained state The frequency characteristic was measured, and then the frequency characteristic was similarly measured with the same ultrasonic transducer supported and fixed (restricted) by the support structure shown in FIG. FIG. 7 shows an admittance curve showing the frequency characteristic of the bolted Langevin type ultrasonic transducer in the unconstrained state shown in FIG. 6, and an admittance curve showing the frequency characteristic of the bolted Langevin type ultrasonic transducer restrained by the support structure shown in FIG. 8 shows.

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

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

The existence of the two admittance peaks shown in the admittance curve in FIG. 8 means that the longitudinal ultrasonic vibration of the bolted Langevin type ultrasonic transducer to be measured can be excited at any frequency. To be understood. That is, both of these two frequencies are considered to correspond to the resonance frequency that enables the excitation of ultrasonic longitudinal vibration. In the admittance curve of the constrained ultrasonic transducer shown in FIG. 8, the longitudinal primary vibration in the admittance curve of the ultrasonic transducer in the unconstrained state shown in FIG. Although shifted 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 admittance peaks appearing at these two different frequency positions, and shows in FIG. 5 a voltage having a frequency close to two resonance frequencies found from the admittance curve of FIG. Applying to the bolted Langevin type ultrasonic vibrator of Fig. 6 under the restraint conditions to excite ultrasonic vibration and measure the vertical vibration displacement amount of the upper end surface of the rear mass 2a under vibration with a laser Doppler vibrometer did.

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

Therefore, the ultrasonic vibration (longitudinal primary vibration) appearing in the ultrasonic transducer and the relative appearing in the low frequency side due to the voltage application of the frequency corresponding to the relatively large admittance peak appearing on the high frequency side of the admittance curve in FIG. Comparing with the ultrasonic vibration that appears in the ultrasonic transducer 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 amount of longitudinal vibration displacement, and the ultrasonic vibration is further excited. It can be seen that the electric power required for this is about 1/7 of the former (0.5 W/3.5 W). That is, the power required to excite ultrasonic vibrations in the state where the bolted Langevin type ultrasonic transducer having the configuration shown in FIG. 6 is supported and restrained by using the support structure shown in FIG. By using the vibration when the voltage of the resonance frequency on the frequency side is applied, the vibration is significantly reduced compared to the former case where the vibration (the primary longitudinal vibration) when the voltage of the resonance frequency on the high frequency side is applied is used. It has been found.

Next, a collet equipped with a tool is attached to the recessed portion of the front mass 2b on the lower side of the bolted Langevin type ultrasonic transducer having the configuration shown in FIG. 6, and the vibration displacement amount of the tip of the tool is also measured. An experiment was conducted in which measurements were made in both the vertical and horizontal directions. In this experiment, as a model of a drill assumed as a tool, a rod body having a length of 40 mm and a diameter of 3 mm and a circular cross section was selected, and the rod body was protruded to the lower end of the collet and mounted with a length of 14.8 mm. A tool model was manufactured, and the amount of vibration displacement at the tip (lower end) of the circular rod was measured using this ultrasonic machining tool model.

In the above-mentioned measurement experiment of the vibration displacement amount of the tool tip part, by the measurement using the impedance analyzer for the ultrasonic machining tool model configured by mounting the collet and the tool on the bolted Langevin type ultrasonic vibrator of the configuration of 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 a voltage having each frequency was applied to the Langevin type ultrasonic transducer by bolting. ..

As a result of the above measurement experiment, the vertical vibration displacement amount of the tip of the tool mounted on the ultrasonic vibrator vibrated 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 vertical vibration displacement amount of the tip of the tool mounted on the ultrasonic vibrator vibrated by applying the voltage of the resonance frequency on the low frequency side is 7.70 μmp-p, and the horizontal vibration displacement amount is Was 0.248 μmp-p, and the power required for the vibration was 0.31 W.

Therefore, from the results of the above measurement experiment, the longitudinal vibration displacement amount of ultrasonic vibration at the resonance frequency on the low frequency side is compared with the longitudinal vibration displacement amount of ultrasonic vibration at the resonance frequency on the high frequency side. On the other hand, with respect to the amount of vibration displacement in the horizontal direction, the vibration due to the application of the resonance frequency voltage on the low frequency side is higher than the vibration due to 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). In addition, the amount of power consumption is about 1/4 (0.31) in the vibration due to the application of the voltage of the resonance frequency on the low frequency side, compared with the vibration due to the application of the voltage of the resonance frequency on the high frequency side (longitudinal primary vibration). /1.17), it was confirmed that the amount of power used to excite ultrasonic vibrations was significantly reduced.

From the experimental results described above, a vibration excitation method for an ultrasonic transducer by applying a voltage having a resonance frequency corresponding to an admittance peak appearing on a lower frequency side than the resonance frequency for exciting longitudinal primary vibration of the ultrasonic transducer. It has been found that by utilizing the above, not only the electric power required for the vibration excitation but also the transverse vibration (horizontal vibration) excited accompanying the longitudinal vibration is significantly reduced.

Next, the inventor of the present invention next investigates the nature of the vibration of the ultrasonic transducer generated by the application of 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 transducer. In order to clarify the above, using the commercially available finite element method analysis software ANSYS (registered trademark, distributor: Ansys Japan Co., Ltd.), the Langevin type ultrasonic transducer of FIG. The ultrasonic vibration excited when constrained under the constraint condition of the ultrasonic transducer for which the admittance curve of FIG. 8 was obtained was analyzed.

As a result of the analysis of ultrasonic vibrations by the finite element method described above, ultrasonic waves generated by applying a voltage of a 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. 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 vertical direction (long-axis direction of the ultrasonic vibrator). It has been found that this is ultrasonic vibration (in this specification, this vibration is referred to as pseudo-longitudinal zero-order vibration or para-longitudinal zero-order vibration) in which there is no portion that serves as a vibration node. According to the image of FIG. 9, in this pseudo-vertical zero-order vibration, a node of vibration appears at the portion where the annular support frame contacts the base, and the annular support frame itself also has the same ultrasonic vibration. It was also found to carry out ultrasonic vibration of the phase. That is, the ultrasonic vibration of the pseudo vertical zero-order vibration is a reciprocating motion in which the entire ultrasonic vibrator vibrates in the same vertical direction, and has one portion that serves as a node of vibration inside the ultrasonic vibrator. This is a vibration that is clearly different from the longitudinal primary vibration, which is a mode that shows vibrations that are opposite to each other in the longitudinal direction with the node serving as a boundary, and therefore the loss of applied electric energy is small and inevitable. It is presumed that this may result in the advantage of less lateral vibration.

On the other hand, 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, as is clear from the ANSYS analysis image of FIG. This is a mode in which there is one node of, and vibrations in the vertical directions are opposite to each other with the node serving as a boundary.

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

Therefore, according to the present invention, a metal block, a metal block provided with a supporting frame body projecting annularly on the side surface, and a vertically polarized disk-shaped piezoelectric element fixed between these metal blocks and a circumference A Langevin type ultrasonic transducer including a disc-shaped piezoelectric element polarized in a direction was prepared, and the Langevin type ultrasonic transducer was connected to a base through the support frame and supported in a restrained state. After that, both the disk-shaped piezoelectric element polarized in the longitudinal direction and the disk-shaped piezoelectric element polarized in the circumferential direction of the ultrasonic vibrator have vibration nodes inside the ultrasonic vibrator. The Langevin-type ultrasonic vibration is applied by applying a voltage having a frequency capable of exciting longitudinal vibration consisting of non-reciprocating vibration and torsional primary vibration having one node of vibration inside the ultrasonic vibrator. A composite vibration of ultrasonic vibration (quasi-longitudinal zero-order vibration) and torsion primary vibration, which is a reciprocating vibration having no vibration node inside the ultrasonic vibrator in a direction perpendicular to the plane of the piezoelectric element The present invention provides a novel method for exciting a Langevin type ultrasonic transducer, which comprises exciting longitudinal/torsional ultrasonic vibrations.

Further, according to the present invention, the frequency (resonance frequency) used in the method of exciting longitudinal and torsional vibrations of the ultrasonic vibrator is included in a frequency range lower than the resonance frequency for exciting the vibration of the vibrator in the first longitudinal vibration mode. Also provided is a vibrational excitation method, which is the frequency used.

Further, according to the present invention, in the method for exciting longitudinal/torsional vibration of an ultrasonic transducer as described above, an ultrasonic wave having the same phase as the ultrasonic vibration has a node of longitudinal vibration at a portion where the annular support frame is in contact with the base. A vibration excitation method for vibrating is also provided.

By utilizing the method for exciting the Langevin type ultrasonic transducer in the longitudinal and torsional vibrations of the present invention, the ultrasonic transducer is miniaturized, and even if the ultrasonic transducer is made small, the output of the longitudinal and torsional vibrations is high. Can be output. Furthermore, the electric energy required to excite longitudinal and torsional vibrations of the ultrasonic vibrator can be significantly reduced. Furthermore, since the torsional vibration to be 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 is realized. Even in the longitudinal and torsional vibrations used in the present invention, spurious (unnecessary vibration) is less likely to occur.
The method for exciting longitudinal-torsional vibration of the Langevin type ultrasonic transducer of the present invention is particularly effective for driving a small ultrasonic motor, but also in performing ultrasonic machining using a grinding tool or a polishing tool such as a drill. In addition, it has an advantage that it can be processed with high precision with low power energy. Then, the removal of chips generated during grinding or polishing is performed concurrently during the execution of grinding or polishing due to the action of the torsional vibration that is generated along with the pseudo vertical zero-order vibration, so that the processing efficiency is improved. There is also the advantage of improving.

It is a figure which shows the structure of a typical bolted Langevin type ultrasonic transducer. It is a figure which shows the example of a structure of the ultrasonic processing apparatus which utilizes a bolting Langevin type ultrasonic 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 fixing (restriction) structure of the ultrasonic transducer which can be utilized for the excitation of the longitudinal vibration which becomes the basis of the excitation method of the longitudinal-torsional vibration of the ultrasonic transducer of this invention. It is a figure which shows the example of a structure of the ultrasonic transducer which can be utilized for the excitation of the longitudinal vibration which becomes the basis of the excitation method of the longitudinal-torsional vibration of the ultrasonic transducer of this invention. FIG. 7 is a diagram showing an admittance curve representing frequency characteristics of the ultrasonic transducer shown in FIG. 6 in an unrestrained state. It is a figure which shows the admittance curve showing the frequency characteristic of the ultrasonic transducer of FIG. 6 restrained by the support structure shown in FIG. It is a figure which shows the vibration mode (quasi-longitudinal zero-order vibration) generated by the longitudinal vibration excitation method which is the basis of the longitudinal-torsional vibration excitation method of the ultrasonic oscillator 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 based on the evaluation result by the finite element method. It is a figure which shows typically the vibration mode of the pseudo-longitudinal zero order vibration which becomes the basis of the longitudinal-torsional vibration generated by the excitation method of the longitudinal-torsional vibration of the ultrasonic vibrator of this invention. FIG. 6A is a diagram showing a vibration mode of longitudinal primary vibration of the ultrasonic transducer, and FIG. 7B is an enlarged diagram showing the behavior of the piezoelectric element portion. It is a figure which shows the other shape of the ultrasonic vibrator utilized for the excitation of the longitudinal vibration which becomes the basis of the excitation method of the longitudinal-torsional vibration of the ultrasonic oscillator of this invention, and other examples of a support fixing structure. It is a figure which shows the ultrasonic vibration (pseudo vertical zero-order vibration) generated by the excitation in the support fixing structure of the ultrasonic vibrator shown in FIG. 13 as an image by the finite element method. Concept of a bolted Langevin-type ultrasonic transducer incorporating a piezoelectric element for longitudinal vibration excitation and a piezoelectric element for torsional vibration excitation used in carrying out a method for exciting longitudinal/torsional vibration of a bolted Langevin-type ultrasonic transducer of the present invention It is a figure. It is a figure which shows the structural example of the grinding|polishing apparatus used for enforcing the longitudinal-torsion vibration excitation method of the bolting Langevin type ultrasonic vibrator of this invention.

The resonance frequency used to excite the pseudo longitudinal zero-order vibration, which is the basis of the method for exciting the longitudinal and torsional vibrations of the ultrasonic oscillator of the present invention (corresponding to the resonance frequency for exciting the vibration of the ultrasonic oscillator in the longitudinal first-order vibration mode) The resonance frequency corresponding to the admittance peak appearing on the lower frequency side than the admittance peak is expressed as a resonance frequency for exciting the pseudo longitudinal zero-order vibration in the present specification. Has never been recognized by a person skilled in the art. Further, as far as the present inventor knows, the vibration excitation method for the ultrasonic vibrator utilizing the pseudo vertical zeroth order vibration has never been implemented so far.

In order to carry out the method for exciting longitudinal and torsional vibrations of an ultrasonic vibrator of the present invention by utilizing the resonance frequency for exciting the pseudo longitudinal zero-order vibration, which is discovered by the present inventor, first, as shown in FIG. It is necessary to fabricate a bolted Langevin type ultrasonic transducer incorporating a piezoelectric element for longitudinal vibration excitation and a piezoelectric element for torsional vibration excitation, which have various basic configurations.

The bolted Langevin type ultrasonic transducer 1a shown in FIG. 15 has a vertically polarized vertical space between a rear mass 2a and a front mass 2b each having an annular support frame (flange) 6 formed around the bottom. It is manufactured by sandwiching the vibration exciting piezoelectric elements 3a, 3b and the circumferentially polarized torsion vibration exciting piezoelectric elements 3c, 3d, and stacking and fixing under high pressure by bolting.

In addition, in FIG. 15, the annular support frame body 6 is formed on the rear mass 2a, but the annular support frame body may be formed on the front mass. Further, it is desirable that the annular support frame is formed integrally with the front mass or the rear mass, but the independently formed annular or disc-shaped support frame is mounted and fixed to the front mass or the rear mass, or It can also be attached and fixed between the rear and the rear mass.

FIG. 16 shows a structural example of an ultrasonic polishing apparatus incorporating the bolted Langevin type ultrasonic vibrator 1a having the basic structure shown in FIG. In FIG. 16, an ultrasonic polishing apparatus 10a accommodates an ultrasonic vibrator 1a having a polishing tool 13a, which is connected to a lower end portion thereof via a collet 12a, inside a housing (also a supporting body) 8. The sound wave oscillator 1a is rotatably supported by a bearing (not shown). In addition, inside the housing (also supporting body) 8 of the ultrasonic polishing apparatus 10a of FIG. 16, a battery 50 serving as a power source and an ultrasonic oscillation circuit 51 utilizing electric energy obtained from the battery are provided. A voltage having a common resonance frequency is applied to the piezoelectric elements 3a and 3b for exciting longitudinal vibration and the piezoelectric elements 3c and 3d for exciting torsional vibration through a lead wire (not shown) of the ultrasonic vibrator. .. In order to excite the vibration of an elliptical locus at the tip of the polishing tool 13a, the phase difference between the voltage applied to the longitudinal vibration excitation piezoelectric element and the voltage applied to the torsional vibration excitation piezoelectric element is 90°.

Next, as shown in FIG. 16, the vibration characteristics of the ultrasonic transducer supported and fixed by using an annular support frame are measured by an impedance analyzer to obtain an admittance curve as shown in FIG. If two peaks (admittance peaks) as shown in FIG. 8 appear on the admittance curve, the frequency of the peak appearing on the high frequency side is usually the resonance frequency of the longitudinal primary vibration excitation, and the frequency of the peak appearing on the low frequency side is pseudo. It can be determined that this is a resonance frequency that can be used to excite longitudinal zero-order vibration. If necessary, obtain the admittance curve by using an impedance analyzer after making the ultrasonic transducer unconstrained, and then the frequency corresponding to the admittance peak appearing in the admittance curve (exciting the 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 resonance frequency) 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 the longitudinal 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 the frequency of the pseudo longitudinal zero-order vibration. It is also possible to excite the longitudinal/torsional composite ultrasonic vibration including the intended 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 adjacent positions in the region on the lower wavelength side than the resonance frequency. With the admittance peak frequency as the frequency of the pseudo longitudinal zero-order vibration, it is possible to excite the longitudinal and torsion 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. ..

The ultrasonic vibrator having the configuration shown in FIG. 15 is equipped with a tool as shown in FIG. 16 to form an ultrasonic machining vibration tool, and the ultrasonic machining vibration tool has the pseudo-vertical zero-order determined by the above method. By applying the voltage of the resonance frequency for vibration excitation, it is possible to excite the longitudinal/torsional composite ultrasonic vibration including the pseudo longitudinal zero-order vibration in the tool. However, the resonance frequency for the pseudo longitudinal zero-order vibration excitation determined by the above method is the resonance frequency confirmed by the measurement without the tool and the tool mounting tool such as the collet, so the pseudo longitudinal There may be some deviation from the optimum resonance frequency at which the zero-order vibration can be excited. Further, even a slight deviation of the constraint condition (supporting and fixing condition) of the ultrasonic machining vibration tool may cause an optimum resonance frequency deviation. Therefore, in determining the resonance frequency for the pseudo longitudinal zero-order vibration excitation of the ultrasonic vibrator with the tool attached and constrained to the base, the optimum resonance frequency can be determined while checking the ultrasonic vibration to be excited. It is desirable to use an ultrasonic oscillator circuit capable of tracking the resonance frequency.

Even if an ultrasonic transducer having a structure as shown in FIG. 15 is manufactured, and an admittance curve is obtained using an impedance analyzer in a state where the ultrasonic transducer is constrained by the supporting and fixing structure as shown in FIG. When a plurality of (usually two) admittance peaks as shown in FIG. 8 do not appear, the constraint condition of the ultrasonic transducer is adjusted so that the admittance having two peaks as shown in FIG. Sometimes a curve can be obtained. However, if the admittance curve having two peaks as shown in FIG. 8 cannot be obtained even by adjusting the constraint conditions of the ultrasonic transducer, setting of the shape of the ultrasonic transducer or Since the supporting and fixing structure of the ultrasonic transducer is considered to be unsuitable for the excitation of the intended pseudo longitudinal zero-order vibration, the constraint conditions of the ultrasonic transducer of FIG. 5 and the ultrasonic transducer of FIG. It is necessary to redesign the ultrasonic transducer and reconsider the supporting and fixing structure, referring to the shape and size. It should be noted that the constraint conditions of the ultrasonic transducer of FIG. 5 and the shape and size of the ultrasonic transducer of FIG. 6 are merely representative examples of the method for carrying out the present invention, and the ultrasonic vibration of the present invention is not limited thereto. This is not a condition for limiting the embodiment of the method for exciting the pseudo vertical zero-order vibration of the child.

Further, by incorporating the ultrasonic transducer for exciting longitudinal/torsional vibration configured as shown in FIG. 15 into the ultrasonic motor as shown in FIG. 4, the longitudinal/torsional vibration (longitudinal/torsional composite) is combined according to the method of the present invention. (Vibration) makes it possible to obtain a compact and high-performance ultrasonic motor.

As described above, the present inventor has found that the longitudinal vibration that constitutes the combined longitudinal/torsional ultrasonic vibration generated by the vibration excitation method for the ultrasonic vibrator of the present invention is “the vertical vibration in the direction perpendicular to the plane of the piezoelectric element. It is an ultrasonic vibration consisting of reciprocating vibration without vibration nodes inside the vibrator." Next, the data on which this conclusion was based will be explained again.

As described above, the existence of the admittance peak appearing on the low frequency side of the admittance curve of FIG. 8 is not known to the inventor of the present invention. For this reason, the present inventors could not initially determine what the frequency corresponding to the frequency position where the admittance peak on the low frequency side 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 voltage of the resonance frequency is applied. It was confirmed that the longitudinal ultrasonic vibration excited by the ultrasonic transducer in the restrained state was generated with low power consumption, and the horizontal vibration was small.

Therefore, in order to analyze the vibration mode of the ultrasonic vibration confirmed this time, the inventor uses the commercially available calculation software based on the finite element method, ANSYS, and uses the ultrasonic wave used in the experiment. The vibration mode of the ultrasonic vibration generated in the ultrasonic transducer was analyzed under the conditions of the shape, size, material of the transducer and the fixed condition (constraint condition) of the ultrasonic transducer. The analysis results of the vibration mode are shown in FIGS. 9 and 10.

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 the ultrasonic transducer under the constraint condition. The vibration that appears is a 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, but the outer end of the annular support frame of the ultrasonic transducer. It can be seen that it exists (corresponding to the connection part 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 of the vibration mode according to the present invention, the ultrasonic vibrator as a whole repeats the reciprocating vibration vibrating in one direction. The annular support frame that supports and fixes the ultrasonic transducer to the base has a node at the 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 a reciprocating vibration in synchronization with the ultrasonic transducer. This vibration mode corresponds to the pseudo longitudinal 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 where the piezoelectric element exists (a position where the piezoelectric element exists), and repeats a vibration that vertically expands and contracts (longitudinal primary vibration). .. Since the longitudinal primary vibration is such a stretching vibration, when exciting the longitudinal vibration of the surface (lower side surface) on one side where the tool is mounted, the lower side surface realized in the pseudo longitudinal zero-order vibration mode shown in FIG. It is estimated that relatively large electric power is required to obtain a vibration amount (displacement amount) equivalent to the longitudinal vibration of.

FIG. 12(B) is a diagram schematically showing an enlarged view of the vibration of the ultrasonic transducer shown in FIG. 12(A), showing the deformation of the piezoelectric element 3 caused by the application of electric energy. It is a figure which shows a condition (estimated condition) typically. That is, the piezoelectric element 3 repeats expansion and contraction due to fluctuations in the applied electric energy, but at the time of expansion, as shown in the figure, the central portion expands against the pressure applied to the piezoelectric element. It is thought that it transforms so that it appears. Therefore, if the deformation of this piezoelectric element does not occur in a completely symmetrical shape at its center, the upper and lower end faces of the ultrasonic transducer are not completely parallel to the center plane of the stretching vibration, and therefore It is presumed that lateral vibration is likely to occur on the upper and lower end faces of the sound wave vibrator.

FIG. 13 shows the shape and size of an ultrasonic vibrator that can be used in the vibration exciting method of the ultrasonic vibrator, which is the basis of the longitudinal/torsional vibration generated by the method of exciting longitudinal/torsional vibration of the ultrasonic vibrator of the present invention ( FIG. 14 is a diagram showing another example of the supporting and fixing structure (unit: mm), and FIG. 14 is an ultrasonic vibration (quasi-longitudinal zero-order vibration) generated by excitation in the supporting and fixing structure of the ultrasonic vibrator shown in FIG. It is a figure which shows as an image obtained by the finite element method. Similar to the image shown in FIG. 9, the vibration that appears in the ultrasonic vibrator is reciprocating vibration in which the entire ultrasonic vibrator moves in one direction, and the node of the vibration must not exist inside the ultrasonic vibrator. Instead, it exists at the outer end (corresponding to the connection to the base) of the annular support frame of the ultrasonic transducer.

1 Bolting Langevin type ultrasonic transducer 2a Metal block (rear mass)
2b Metal block (front mass)
3a, 3b Piezoelectric element for exciting longitudinal vibration 3c, 3d Piezoelectric element for exciting torsional vibration 4 Bolt 5a Copper electrode 5b Copper electrode 6 Annular support frame 7 Nut 10 Ultrasonic grinding machine 11 Housing 12 Horn 13 Polishing tool 20 Ultrasonic wave Motor 22 Bottom nut 24 Piezoelectric element for torsional vibration 26 Holder 28 Piezoelectric element for longitudinal vibration 30 Stator head 32 Stator 34 Rotor 36 Friction material 38 Center bolt 40 Center bolt 42 Spring member 44 Bearing 48 Flange

Claims (3)

A metal block, a metal block with a support frame protruding in a ring shape on the side surface, and a vertically polarized disk-shaped piezoelectric element fixed between these metal blocks and a circle polarized in the circumferential direction. A Langevin-type ultrasonic transducer including a plate-shaped piezoelectric element is prepared, the Langevin-type ultrasonic transducer is connected to a base through the support frame and supported in a restrained state, and then the ultrasonic vibration is applied. Both the longitudinally polarized disk-shaped piezoelectric element and the circumferentially polarized disk-shaped piezoelectric element are composed of reciprocating vibrations without vibration nodes inside the ultrasonic vibrator. By applying a voltage having a frequency capable of exciting the vibration and the torsional primary vibration having one node of the vibration inside the ultrasonic vibrator, the piezoelectric element is applied to the Langevin type ultrasonic vibrator. To excite longitudinal and torsional ultrasonic vibrations, which are composite vibrations of ultrasonic vibrations consisting of reciprocating vibrations without vibration nodes inside the ultrasonic vibrators in a direction perpendicular to the plane of A method for exciting longitudinal/torsional vibration of a Langevin type ultrasonic transducer. A Langevin type ultrasonic vibrator in which the frequency used in the method for exciting longitudinal and torsional vibrations of the ultrasonic vibrator is a frequency included in a frequency range lower than a resonance frequency for exciting the vibration of the vibrator in the first longitudinal vibration mode. A new method of exciting longitudinal and torsional vibrations. In the method of exciting longitudinal and torsional vibrations of the ultrasonic vibrator, a Langevin type supersonic wave having a longitudinal vibration node at a portion where the annular support frame is in contact with the base and performing ultrasonic vibration in the same phase as the ultrasonic vibration A new method for exciting longitudinal and torsional vibrations of acoustic wave oscillators.

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