JPH09117168A - Supersonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a supersonic motor only with one type of piezoelectric element and at the same time reduce a drive voltage by arranging at least one sheet-shaped piezoelectric element which is polarized in thickness direction with a specific inclination for the height direction of a vibrator. SOLUTION: Piezoelectric elements 4, 5, 6, and 7 are held between elastic bodies 1 and 2 which are generated by cutting a cylindrical elastic body into two portions while they are inclined from a side surface, a hole at the center of the elastic body 2 is cut, a screw 8 is inserted, and piezoelectric elements 4, 5, 6, and 7 are fed through and fixed, where the piezoelectric elements 4, 5, 6, and 7 are in elliptical shape, are polarized in thickness direction, these polarization directions are alternately in opposite directions before lamination, thus exciting vertical and twisting vibration by the piezoelectric elements 4, 5, 6, and 7 which are polarized in thickness direction and making thin the sheet- shaped piezoelectric elements 4, 5, 6, and 7 for laminating a number of sheets, and hence achieving a large amplitude.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor for moving a driven body using ultrasonic vibration as a driving force source.

[0002]

2. Description of the Related Art As an example of an ultrasonic motor for moving a driven body using ultrasonic vibration as a driving force source, see New Actuator Manual for Precision Control, "Vertical-torsion compound vibrator type ultrasonic motor", pages 956 to 966. The listed ultrasonic motor is known.

As shown in FIG. 15, the structure of this ultrasonic motor uses a bolted Langevin structure vibrator, and a piezoelectric element (piezoelectric ceramic block L) 51 for exciting longitudinal vibration and a torsional vibration are excited. The piezoelectric element (piezoelectric ceramic block T) 52 that operates is sandwiched between the head mass 61 and the rear mass 62. Piezoelectric element 51,
52 is polarized in the thickness direction for longitudinal vibration and is polarized in the circumferential direction for torsional vibration. This ultrasonic motor is driven by applying a two-phase voltage having an appropriate phase difference to each piezoelectric element 51, 52.
The magnitude of the voltage is a few + Vrms.

[0004]

However, the ultrasonic motor requires separate piezoelectric elements 51 and 52 to generate longitudinal vibration and torsional vibration. Furthermore, the piezoelectric elements 51, 52 polarized in the circumferential direction to generate torsional vibrations.
Is required, which is more complicated in manufacturing method and more expensive than a piezoelectric element polarized in the thickness direction. Further, if the piezoelectric elements 51 and 52 polarized in the circumferential direction are used, a high voltage is required to obtain a necessary vibration amplitude, which is disadvantageous for use in driving an ultrasonic motor with a low voltage source such as a battery. There was a flaw.

The present invention has been made in order to solve the above problems, and provides an ultrasonic motor which can be constituted by only one kind of piezoelectric element polarized in the thickness direction and can further reduce the driving voltage. It is provided.

[0006]

An ultrasonic motor according to a first aspect of the present invention is a vibrator and a vibrator, which is sandwiched so as to occupy a part of the vibrator in the height direction, and the vibrator. Of the plate-like piezoelectric element, which is arranged with a predetermined inclination with respect to the height direction, is polarized in the thickness direction, and is provided with divided electrodes, and is brought into pressure contact with the vibrator. It has a driven body.

An ultrasonic motor according to a second aspect of the present invention is a state in which the ultrasonic motor is sandwiched so as to occupy a part of the vibrator in the height direction, and the ultrasonic motor with respect to the height direction of the vibrator. It has a plurality of plate-shaped piezoelectric elements which are arranged at substantially orthogonal angles and which are polarized in the thickness direction and each of which has a slightly different electrode position, and a driven body which is brought into pressure contact with the vibrator. It is characterized by that.

An ultrasonic motor according to a third aspect of the present invention is the ultrasonic motor according to the first or second aspect, in which the phase difference of the applied voltage with respect to a pair of electrode phases provided on the plate-shaped piezoelectric element is 90 degrees, It is characterized in that the driven body is rotationally driven by utilizing the bending resonance vibration of which the phase is shifted by 90 degrees when the vibrator is set to -90 degrees.

According to the ultrasonic motor of the first aspect, by arranging one or a plurality of the plate-like piezoelectric elements with an inclination so as to occupy a part of the vibrator in the height direction, , A plate-shaped piezoelectric element polarized in the thickness direction can excite both longitudinal vibration and torsional vibration or bending vibration in two directions with different vibration directions to drive a driven body, and a piezoelectric element polarized in the circumferential direction can be used. The manufacturing method is simplified and the manufacturing cost can be reduced as compared with the case of using.

According to the ultrasonic motor of the present invention, the position of the electrode is changed little by little, and the plurality of plate-shaped piezoelectric elements are laminated to form a plurality of plate-shaped piezoelectric elements polarized in the thickness direction. Both the longitudinal vibration and the torsional vibration, or the bending vibration in two directions having different vibration directions can be excited by only the type to drive the driven body, and the manufacturing method is different from the case where the piezoelectric element polarized in the circumferential direction is used. Is simplified and the manufacturing cost can be reduced, and a plurality of plate-shaped piezoelectric elements are arranged at an angle substantially orthogonal to the height direction of the vibrator. It is more simplified than the ultrasonic motor described in 1.

According to the ultrasonic motor of the third aspect of the present invention, in the ultrasonic motor of the first or second aspect, the phase difference of the applied voltage with respect to the pair of electrode phases provided on the plate-shaped piezoelectric element is 90. , -90 degrees of the vibrator, which occurs when the angle is set to -90 degrees, is used to rotationally drive the driven body by utilizing flexural resonance vibration with a phase difference of -90 degrees.
It is not necessary to match the resonance frequencies of the longitudinal vibration and the torsional vibration, and the degree of freedom in designing the vibrator can be increased.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS.

The vibrator 1 of the ultrasonic motor shown in FIGS. 1 and 2.
0 has the following configuration. That is, an elastic body made of brass and having a cylindrical shape with a hole in the center is cut into two pieces with an inclination from the side surface to divide into two elastic bodies 1 and 2. A groove 3 is provided in the middle of one of the elastic bodies 1.

Between the elastic bodies 1 and 2, piezoelectric elements 4, 5 and
It sandwiches 6 and 7. A screw is cut in the hole 2a at the center of the elastic body 2. As shown in FIG.
The piezoelectric elements 4, 5, 6, 7 are inserted from the side, and further protruded upward through the screw of the elastic body 2 to fix the piezoelectric elements 4, 5, 6, 7 between the elastic bodies 1, 2. It is like this. At this time, if an adhesive is used together to fix the piezoelectric bodies 4 to 7, the piezoelectric bodies 4 to 7 can be more firmly fixed. A wear resistant material 9 is adhered and fixed to the upper surface of the elastic body 2.

Next, as shown in FIG. 3, a rotor 11 is mounted on a wear resistant member 9 of a vibrator 10 via a bearing 12 so as to be rotatable around a screw 8, and a spring 13 and a spring 13 are provided. With the nut 14, the rotor 11 and the wear resistant material 9
It is designed to be pressed to the side.

The piezoelectric elements 4 to 7 are shown in FIG.
As shown in (b), it has an elliptical shape, and the positive electrodes 15 are provided in a two-divided arrangement on each surface except for the central portion a. Negative electrodes 16 are provided on the back surface except for parts b and c which are parts on both sides. Polarization is performed in the thickness direction. The piezoelectric elements 4 to 7 are laminated such that the polarization directions are alternately opposite to each other as shown by arrows in FIG.

Then, on the side surface of the portion a of the negative electrode 16 on the back surface side shown in FIG. 4, the layers laminated as shown in FIG. 5A are bonded to each other with a conductive paste and used as a GND terminal. It In addition, on the positive electrode 15 side of the surface of the piezoelectric elements 4 to 7, since the electrode portion does not exist in the portion a, the positive electrode 15 and the negative electrode 16 are not short-circuited by the conductive paste.

On the side surfaces of portions b and c of the positive electrode 15 on the surface of the piezoelectric elements 4 to 7 shown in FIG. 4, (b) of FIG.
As shown in (c), the laminated layers are bonded to each other with a conductive paste and used as an A-phase terminal and a B-phase terminal, respectively. In this case, since there is no electrode portion on the back surface of the piezoelectric elements 4 to 7 in the portion b and the portion c of the negative electrode 16, the positive electrode 15 and the negative electrode 16 are not short-circuited by the conductive paste.

Next, the operation of the above-described first embodiment will be described. Consider a case where in-phase AC voltages are applied to the A phase and the B phase. The piezoelectric elements 4 to 7 have A phase and B phase in the polarization direction.
The phases are displaced in the same phase and vibrate. Using the displacement of the piezoelectric elements 4 to 7 as a driving source, the vibrator 10 causes longitudinal resonance vibration or bending resonance vibration as shown in the left and middle columns of FIG. The frequencies of these vibrations are determined by the natural frequency of the vibrator 10. Since the resonance frequencies of the two vibrations are different from each other, it is possible to excite only one of the longitudinal resonance vibration and the bending resonance vibration by selecting the drive frequency.

Next, when AC voltages of opposite phases are applied to the A phase and the B phase, the piezoelectric element 10 vibrates in the opposite phases of the A phase and the B phase, and when one extends in the thickness direction, the other extends in the thickness direction. Shrink. Then, depending on the natural frequency of the vibrator 10, torsional resonance vibration or bending resonance vibration as shown in the right column or the middle column of FIG. 6 is generated. Since these two resonance frequencies are different from each other, it is possible to excite only one of the torsion resonance vibration and the bending resonance vibration by selecting the drive frequency.

By devising the shape of the vibrator 10, the frequencies of the longitudinal resonance vibration and the torsional resonance vibration are matched. For this reason, the groove 3 is provided in the vibrator 10. Groove 3 as shown in FIG.
There is a groove position L where the frequencies of the longitudinal resonance and the torsional resonance coincide with each other depending on the position of the vibrator end, and the groove 3 is formed here.

In this way, the longitudinal resonance frequency and the torsional resonance frequency are matched, and the voltage of this frequency is set to the intermediate phase difference of 90 degrees between the in-phase (phase difference of 0 degrees) and the opposite phase (phase difference of 180 degrees). Then, two resonance vibrations can be generated at the same time.

In this state, the rotor 11 can be driven to rotate by abutting it on the end face of the vibrator 10 as shown in FIG. The rotation direction of the rotor 11 is A
Phase difference between applied voltage of phase B and phase B is +90 degrees or -90
It is decided by the degree.

The first embodiment has an effect that longitudinal vibration and torsional vibration can be excited only by the piezoelectric elements 4 to 7 polarized in the thickness direction. Further, by thinning the plate-shaped piezoelectric elements 4 to 7 and stacking a large number of them, the required amplitude can be obtained even at a low voltage. In the first embodiment, the plate-shaped piezoelectric elements 4 to 7 are stacked and laminated, but a laminated piezoelectric element having the same structure, which is integrally fired in advance, may be used.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 8, the vibrator 33 according to the second embodiment has the following structure. That is, the elastic body 21 having a convex side surface and a circular cross section has a groove 23 in the middle thereof, and a screw 21a is cut on the protruding portion at the center. Further, in the inner cavity of the cylindrical elastic body 22, the screw 21 a of the convex portion of the elastic body 21 is provided.
The screw 22a for engaging with is cut.

Between the elastic body 21 and the cylindrical elastic body 22,
The piezoelectric elements 24 to 29 are sandwiched. Elastic body 21
And the cylindrical elastic body 22 are tightened by screwing the screws 21a and 22a to fix the piezoelectric elements 24 to 29. At this time, if the piezoelectric elements 24 to 29 are fixed together with an adhesive, they can be fixed firmly. A wear resistant material 30 is bonded to the cylindrical elastic body 22.

A hole 3 is formed in the center of the elastic body 21.
1 is bored, and a screw (not shown) is provided in the hole 31 at substantially the center of the elastic body 21 in the height direction. A shaft 32 provided with a screw on the outer periphery is screwed into this. Elastic body 21
The diameter of the hole 31 is set to be slightly larger than the diameter of the shaft 32 so that the shaft 32 and the shaft 32 do not come into contact with each other except for the threaded portion at the center thereof.

As shown in FIG. 10, a rotor 34 is rotatably held by a wear-resistant material 30 of the vibrator 33 around a shaft 32 via a bearing 35.
Further, the rotor 34 is pressed against the wear resistant material 30 by the spring 36 and the nut 37.

As shown in FIGS. 11 (a) to 11 (f), the piezoelectric elements 24 to 29 have a positive electrode 38 divided into two parts on the front surface and a position facing the positive electrode 38 on the back surface. There is a negative electrode 39 at. The electrodes 38 and 39 are formed so that the positions of the piezoelectric elements 24 to 29 are slightly different. The positive electrode 38 is formed so that the end portion is exposed on the outer surface of the ring shape and the end portion is not exposed on the inner surface. On the contrary, the negative electrode 39 is formed such that the end portion does not extend to the outer side surface of the ring shape and the end portion extends to the inner side surface. All polarization is done in the thickness direction.

These piezoelectric elements 24 to 29 are shown in FIG.
As shown by arrows, the layers are laminated so that the polarization directions are alternately opposite to each other.

The laminated layers of the piezoelectric elements 24 to 29 are bonded to each other by a conductive paste, and the positive electrode 38 is used as an A-phase terminal and a B-phase terminal, respectively, as shown in FIG. Further, the negative electrodes 39 on the back surfaces of the piezoelectric elements 24 to 29 are similarly bonded to each other on the ring-shaped inner side surface with a conductive paste, and are bonded to the elastic body 21 to be used as a GND terminal.

According to the second embodiment, the same longitudinal resonance vibration or bending resonance vibration as that shown in FIG. 6 is generated by the same principle as that of the first embodiment. Since these two resonance frequencies are different from each other, only one of them can be excited by selecting the drive frequency.

When an AC voltage of opposite phase is applied to the A phase and the B phase, torsional resonance vibration or bending resonance vibration similar to the case shown in FIG. 6 is caused. Since these two resonance frequencies are different from each other, only one of them can be excited by selecting the drive frequency.

Further, similarly to the case of the first embodiment, the frequencies of the longitudinal resonance and the torsional resonance can be made to coincide with each other by placing the groove 23 in the oscillator 33 at an appropriate position.

In this way, the longitudinal resonance frequency and the torsional resonance frequency are made to coincide with each other, and the applied voltage is the same phase (phase difference 0).
Degree) and the opposite phase (phase difference 180 degrees), the phase difference is 90 degrees, so that the two resonance vibrations described above can be simultaneously generated.

In this state, the rotor 34 can be rotationally driven by pressing the rotor 34 against the end face of the vibrator 33 as shown in FIG. The rotation direction of the rotor 34 is determined by whether the phase difference between the applied voltages of the A phase and the B phase is +90 degrees or −90 degrees.

The second embodiment has an effect that longitudinal vibration and torsional vibration can be excited only by the piezoelectric elements 24 to 29 polarized in the thickness direction. Further, by making the plate-shaped piezoelectric elements 24 to 29 thin and laminating a large number of them, the required amplitude can be obtained even at a low voltage. In the present second embodiment, the plate-shaped piezoelectric elements 24 to 29 are laminated, but a laminated piezoelectric element of the same structure that is integrally fired in advance may be used as in the case of the first embodiment. . In the second embodiment, the elastic body 2 is different from the first embodiment.
Since there is no need to give a slope to 1 and to cut, there is an effect that it can be processed only by a lathe and the like, and the production is easy.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. The structure of the ultrasonic motor of the third embodiment is the same as that of the first and second embodiments.
Any of the above may be used and is not shown here. However, the groove 3 or the groove 23 in the case of the first embodiment or the second embodiment may be omitted.

The ultrasonic motor of the third embodiment is different from the first or second embodiment only in the operating principle.

That is, when the in-phase or anti-phase voltage is applied to the A-phase and the B-phase of the vibrator 41 shown in FIGS. 13 and 14, bending resonance vibration occurs in the first and second embodiments.
Said. FIG. 13 shows a case where voltages are applied in phase at this time.
In the case of the opposite phase, the directions are 90 ° and the directions are β and δ in FIG.

When the vibrator 41 is symmetric with respect to the vibration direction like a cylinder, the bending resonance frequencies in the two directions coincide with each other without any special measures. A voltage having a frequency approximately matching the bending resonance frequency is applied to the A phase and the B phase. When the applied voltage has a phase difference of 90 degrees between the in-phase (phase difference of 0 degrees) and the opposite phase (phase difference of 180 degrees) described above, two bending resonance vibrations occur in a state where the phases are shifted by 90 degrees.

At this time, as shown in FIG.
When the rotor 42 is pressed, the contact position between the oscillator 41 and the rotor 42 changes one after another, and the rotor 42 rotates due to the frictional force between the oscillator 41 and the rotor 42.

The order in which the vibrator 41 and the rotor 42 contact each other changes as shown in FIG. 14I depending on whether the phase difference between the A-phase voltage and the B-phase voltage is +90 degrees or -90 degrees. The rotation direction of is also switched.

In the third embodiment, compared to the first and second embodiments, it is not necessary to make a special effort to match the resonance frequencies of the longitudinal vibration and the torsional vibration, and the bending resonance frequencies in the two directions are the same. Therefore, the degree of freedom in designing the vibrator 41 is relatively large. It is also possible to switch the drive frequency with the ultrasonic motors of the first and second embodiments and select whether to use the vertical-twist mode or the bending-bending mode.

In the third embodiment, as in the first and second embodiments, there is an effect that the piezoelectric element polarized in the thickness direction can excite bending vibrations in which the vibration directions differ by 90 degrees. In addition, by reducing the thickness of the plate-shaped piezoelectric element and stacking a large number of piezoelectric elements, the required amplitude can be obtained even at a low voltage.

[0047]

According to the invention described in claim 1, it is possible to reduce the cost because it can be constituted by only one kind of piezoelectric element polarized in the thickness direction, and further, the driving voltage can be lowered. A sonic motor can be provided.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, it is possible to provide an ultrasonic motor which is easy to manufacture.

According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, it is possible to provide an ultrasonic motor capable of increasing the degree of freedom in designing the vibrator.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a vibrator of an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2 is a front view showing a vibrator of the ultrasonic motor according to the first embodiment of the present invention.

FIG. 3 is a front view showing the ultrasonic motor according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an electrode arrangement of the plate-shaped piezoelectric element according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a laminated structure and electrode phases of the plate-shaped vibrator according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing longitudinal vibration, bending vibration, and torsional vibration according to the first embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the resonance frequency and the length from the vibrator end to the groove in the first embodiment of the present invention.

FIG. 8 is an exploded perspective view showing a vibrator of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 9 is a front view showing a vibrator of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 10 is a front view showing an ultrasonic motor according to a second embodiment of the present invention.

FIG. 11 is an explanatory diagram showing an electrode arrangement of the plate-shaped piezoelectric element according to the second embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a laminated structure and an electrode phase of a plate-shaped vibrator of a plate-shaped piezoelectric element according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a driving principle of the vibrator according to the third embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a rotor driving state by phase switching of bending vibration of the vibrator according to the third embodiment of the present invention.

FIG. 15 is a partial cross-sectional view showing a conventional ultrasonic motor.

[Explanation of symbols]

 1 Elastic Body 2 Elastic Body 3 Groove 4 Piezoelectric Element 5 Piezoelectric Element 6 Piezoelectric Element 7 Piezoelectric Element 8 Screw 9 Wear Resistant Material 10 Vibrator 11 Rotor 13 Spring 14 Nut

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoki Funakubo 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (3)

[Claims] 1. A vibrator and a vibrator which are sandwiched so as to occupy a part of the vibrator in the height direction and are arranged with a predetermined inclination with respect to the height direction of the vibrator. At the same time, an ultrasonic motor comprising: one or a plurality of plate-shaped piezoelectric elements each polarized in the thickness direction and provided with a divided electrode; and a driven body brought into pressure contact with the vibrator. 2. The vibrator, the vibrator being disposed so as to be sandwiched so as to occupy a part of the vibrator in the height direction, arranged at an angle substantially orthogonal to the height direction of the vibrator, and having a thickness. An ultrasonic motor comprising: a plurality of plate-shaped piezoelectric elements each of which is polarized in a direction and provided with divided electrodes whose electrode positions are slightly different from each other; and a driven body which is brought into pressure contact with the vibrator. 3. A flexural resonance vibration of 90 degrees out of phase of the vibrator, which occurs when the phase difference of applied voltages to a pair of electrode phases provided on the plate-shaped piezoelectric element is 90 degrees and −90 degrees, is utilized. The ultrasonic motor according to claim 1 or 2, wherein the driven body is driven to rotate.