JP2832614B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a so-called ultrasonic motor using ultrasonic vibration of a piezoelectric vibrator used for office automation equipment and the like, and particularly to a longitudinal-torsional vibrator type having a simple structure. It relates to an ultrasonic motor.

[Prior Art] FIG. 7 is a perspective view of a structural example of a longitudinal-torsional combined vibrator 101 used in a conventional longitudinal-torsional vibrator type ultrasonic motor, and illustrates a piezoelectric torsional vibrator 102 and a piezoelectric longitudinal vibration. The child 103 is joined via a metal cylinder 104, and metal cylinders 105 and 106 are joined on both sides of the metal 103. In this case, a metal cylinder
A metal cylinder can be used instead of 105.

FIG. 8 is a perspective view showing an example of the structure of an ultrasonic motor constituted by using the vertical-torsion composite vibrator 101 shown in FIG. Axis 107
And the rotor 109 rotatably supported by the bearing 8 is moved vertically by the coil spring 110 and the nut 111.
It is pressed against the end face of the torsional composite vibrator 101.

FIG. 9 shows an example of the structure of the piezoelectric torsional vibrator shown in FIG. 7, in which a cylindrical piezoelectric torsional vibrator 102 is formed by joining four quadrant fan-shaped piezoelectric ceramic plates 112. As shown in FIG. 10, each shape of the piezoelectric ceramic plate 112 is polarized in the direction of the chord of the fan 112a, and electrodes are formed on the upper and lower surfaces of the fan-shaped piezoelectric ceramic plate 112. When a DC voltage is applied to the fan, slip distortion occurs parallel to the thickness of the fan-shaped piezoelectric ceramic plate.

As shown in FIG. 9, when four fan-shaped piezoelectric ceramic plates 112 are joined in a disk shape, the slip strain generated in each of the fan-shaped piezoelectric ceramic plates 112 is synthesized, and The torsional distortion is such that the lower surface is twisted. When an AC voltage is applied, such a vibration causing torsional distortion (referred to as torsional vibration) is excited.

When the conventional piezoelectric torsional vibrator shown in FIG. 9 is manufactured, first, as shown in FIG. 1, a sector-shaped piezoelectric ceramics plate is ultrasonically processed from a piezoelectric ceramics plate 113 polarized in the width direction. A sector-shaped piezoelectric ceramic plate 112 which is punched and polarized in the direction of the chord of the sector as shown in FIG.
And glue them together to form a disk, or
As shown in FIG. 12A, a square prism 115 whose polarization direction is a diagonal direction is cut out from the piezoelectric ceramic block 114 polarized in the thickness direction as shown in FIG. 12 As shown in Figure (c), four square prisms
115 is overlapped and bonded so as to form a closed loop of the polarization direction, and the outer periphery is polished into a pipe shape as shown in FIG. 12 (d), and then is formed into a disk shape as shown in FIG. 12 (e). It is formed by cutting.

FIG. 13 is a structural example of a conventional piezoelectric longitudinal vibrator 103,
Electrodes are applied to both sides, and a voltage is applied to the piezoelectric ceramics ring 116 polarized in the thickness direction to obtain vibration in the thickness direction (called longitudinal vibration).

In order to obtain a large vibration amplitude at a low applied voltage, a plurality of thin piezoelectric ceramic rings 116 'may be laminated to form a piezoelectric longitudinal vibrator 103' as shown in FIG.

[Problems to be Solved by the Invention] In the conventional piezoelectric torsional vibrator 102 shown in FIG. 9, since a plurality of piezoelectric ceramics are bonded, the characteristic variation due to the bonding is large. Also,
As shown in FIG. 10, FIG. 11, and FIG. 12, the processing for obtaining the piezoelectric torsional vibrator 102 was complicated and very costly. Further, when the torsional vibration and the longitudinal vibration are to be simultaneously obtained, the piezoelectric torsional vibrator 102 shown in FIG. 9 and the piezoelectric longitudinal vibrator 103 shown in FIG. 13 or 14 are bonded together. However, there has been a problem that the bonding cost is high due to the variation in the adhesion.

Therefore, a technical problem of the present invention is to eliminate the drawbacks of the conventional piezoelectric torsional vibrator and the longitudinal-torsional composite vibrator described above, and to simplify the processing, eliminate the bonding process, and reduce the variation in the piezoelectric torsional vibrator. And an ultrasonic motor using a piezoelectric vertical-torsion composite vibrator in which a vertical vibrator is formed on the same piezoelectric element.

Another technical problem of the present invention is that a hollow piezoelectric vertical
An object of the present invention is to provide a two-rotor type ultrasonic motor in which two rotors are pressed against both ends of the piezoelectric longitudinal-torsion composite vibrator by means of a shaft penetrating through the hollow portion by using the torsional composite vibrator.

[Means for Solving the Problems] According to the present invention, there is provided a piezoelectric torsional vibrator portion formed at a central portion in a direction of the central axis of a rod-shaped piezoelectric ceramic having a central axis and an outer peripheral surface around the central axis. A piezoelectric longitudinal-torsional composite vibrator having a pair of longitudinal vibrators formed on both sides of the piezoelectric torsional vibrator section and exciting longitudinal-torsional composite vibrations at both ends of the rod-shaped piezoelectric ceramic; A rotor that is pressed against at least one end of the composite vibrator and converts the longitudinal-torsional composite vibration into rotational motion, wherein the piezoelectric torsional vibrator portion is formed on the outer peripheral surface so as to intersect the central axis and be parallel to each other. A plurality of oblique electrodes, the central portion is polarized using the plurality of oblique electrodes, and a first AC drive voltage having a first frequency is applied to apply torsional vibration to both ends of the rod-shaped piezoelectric ceramic. Excited and the husband of the longitudinal vibrator part Each has a plurality of peripheral electrodes formed on the outer peripheral surface in a direction perpendicular to and parallel to the central axis, and polarizes both sides of the piezoelectric torsional vibrator using the plurality of peripheral electrodes, An ultrasonic motor characterized by applying a second AC drive voltage having a frequency equal to the frequency of (1) to excite stretching vibration at both ends of the rod-shaped piezoelectric ceramics is obtained.

[Operation] An ultrasonic motor of the present invention includes a piezoelectric longitudinal-torsion composite vibrator and a rotor.

The piezoelectric longitudinal-torsional composite vibrator includes a piezoelectric torsional vibrator formed at a central portion in a central axis direction of a rod-shaped piezoelectric ceramic having a central axis and an outer peripheral surface around the central axis, and both sides of the piezoelectric torsional vibrator. And a pair of longitudinal vibrators formed to excite longitudinal and torsional combined vibrations at both ends of the rod-shaped piezoelectric ceramic.

On the other hand, the rotor is pressed against at least one end of the piezoelectric longitudinal-torsional composite vibrator to convert the longitudinal-torsional composite vibration into rotary motion.

The piezoelectric torsional vibrator portion has a plurality of oblique electrodes formed on the outer peripheral surface thereof, which cross the center axis and are formed in parallel with each other. The central portion of the rod-shaped piezoelectric ceramic is polarized by using the plurality of oblique electrodes. Is given.

Each of the piezoelectric longitudinal vibrator portions has a plurality of peripheral electrodes formed on the outer peripheral surface of the rod-shaped piezoelectric ceramic in a direction perpendicular to the central axis and in parallel with the piezoelectric torsional vibration using the plurality of peripheral electrodes. Both sides of the child part are polarized.

When a first AC drive voltage having a first frequency is applied to such oblique electrodes, longitudinal vibrations are excited at both ends of the rod-shaped piezoelectric ceramic.

When a second AC drive voltage having a frequency equal to the first frequency is applied to the peripheral electrodes, stretching vibrations are excited at both ends of the rod-shaped piezoelectric ceramics.

Accordingly, when the first AC drive voltage and the second AC drive voltage are respectively applied to the corresponding electrodes, longitudinal-torsional vibration in which torsional vibration and expansion / contraction vibration are combined at both ends of the rod-shaped piezoelectric ceramics is excited. This longitudinal-torsional vibration is converted by the rotor into rotational movement about the axis of the rotor.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an ultrasonic motor according to an embodiment of the present invention. Piezoelectric longitudinal-torsional composite vibrator 28 described later
The shaft 7 is penetrated through the hollow portion of the piezoelectric vibrator 28, and is fixed at the resonance node inside the piezoelectric longitudinal-torsional composite vibrator 28. Rotor rotatably supported by bearings 8, 8 'at both ends of shaft 7
9, 9 'are pressed against the end faces of the piezoelectric longitudinal-torsional vibrator 28 by nuts 11, 11' via springs 10, 10 '.

The piezoelectric longitudinal-torsional vibrator 28 can support a central portion where a node of resonance of torsional vibration is attached by a ring-shaped support frame 30. In this case, stable support can be achieved.

FIGS. 2 (a), (b), (c) and (d) are diagrams showing the operating principle of a piezoelectric longitudinal-torsion composite vibrator used in an ultrasonic motor according to an embodiment of the present invention.

In FIG. 2 (a), a plurality of first and second cross electrodes 18 and 19, which cross each other, are formed on one surface of a piezoelectric ceramic plate 17, and the first and second cross electrodes 18 and 19 are provided every other one.
Are connected to the common electrodes 18 'and 19' to form interdigital electrodes.

2 (b), the dashed arrows indicate the direction of polarization when the polarization process is performed using such interdigital electrodes, and FIGS. 2 (c) and 2 (d) show the directions of polarization in FIG. The state of the distortion generated when a DC voltage is applied to the piezoelectric ceramic plate 17 subjected to the polarization treatment as shown in b) is shown, and the solid arrow indicates the direction of the electric field. As shown in FIG. 2 (c), when the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, stretching strain occurs in the direction of the polarization, while the polarity of the voltage as shown in FIG. 2 (d). Is opposite to the polarity of the voltage at the time of polarization, contraction distortion occurs in the direction of polarization.

FIG. 3 shows a state of distortion generated on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20 when both end surfaces of the piezoelectric ceramic hollow cylinder 20 are twisted as indicated by solid arrows in the figure. 45 for 20 axial directions
The expansion and contraction occur in the direction of the angle ゜, and in the direction of the arrow indicated by the dashed broken line, and the compression distortion occurs in the direction perpendicular to the direction indicated by the dashed line arrow.

Therefore, the first and second interdigital electrodes as shown in FIG. 2 are provided on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20 shown in FIG. When formed at an angle of 45 ° with respect to the length direction of the hollow cylinder 20, polarization processing is performed using the first and second interdigital electrodes, and a DC voltage is applied to the same interdigital electrode. If the polarity of the voltage is the same as the polarity of the voltage during polarization,
The piezoelectric ceramic hollow cylinder 20 is twisted in one direction, and is twisted in the opposite direction when the polarity of the voltage is opposite to the polarity of the voltage at the time of polarization.

Further, on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20, first and second interdigital electrodes as shown in FIG. 2 are formed so that the direction of the intersecting fingers is parallel to the circumferential direction of the piezoelectric ceramic hollow cylinder 20. When a polarization process is performed using the first and second interdigital electrodes and a DC voltage is applied to the same interdigital electrode,
When the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, the piezoelectric ceramic hollow cylinder 20 extends in the length direction, and when the polarity of the voltage is opposite to the polarity of the voltage at the time of polarization, it contracts in the length direction.

FIG. 4 is a perspective view showing an example of a piezoelectric vertical-torsion composite vibrator used in the ultrasonic motor according to the embodiment of the present invention. In this figure, the piezoelectric longitudinal-torsion composite vibrator section 21
A plurality of first and second oblique electrodes 22 and 23 intersecting each other are formed on the outer peripheral surface of the central portion of the piezoelectric ceramic hollow cylinder 20 'at an angle of 45 ° with respect to the length direction. The torsional vibrator portion 21a is formed by being connected to the first and second common electrodes 22 'and 23'.

Further, a plurality of first and second peripheral electrodes 24 and 25 are provided on the outer peripheral surface of both sides of the 45 ° interdigital electrode in parallel with the circumferential direction.
And 26 and 27 are formed, and the electrodes of the same number are electrically connected to each other to form a pair of longitudinal vibrator portions 21b and 21c.

In FIG. 4, the first and second common electrodes 22 'and
After applying a DC high voltage between 23 'and applying a polarization process, if an AC voltage having a frequency equal to the resonance frequency of this composite vibrator is applied, the piezoelectric ceramic hollow cylinder 20' resonates so that both ends are twisted. I do.

Similarly, after applying a DC high voltage between the first and second peripheral electrodes 24 and 25 and between the third and fourth peripheral electrodes 26 and 27 to perform polarization processing, the torsional resonance is performed. If an AC voltage equal to the frequency is applied, the piezoelectric ceramic hollow cylinder 2
Numeral 0 'indicates a torsional resonance frequency, which causes expansion and contraction vibration (longitudinal vibration) in the length direction of the hollow column 20'. Since the longitudinal vibration has a frequency different from the resonance frequency, the longitudinal vibration amplitude is considerably smaller than the amplitude at the time of resonance, but a practically sufficient amplitude can be obtained.

FIG. 5 is a perspective view showing an example of the structure of a piezoelectric longitudinal-torsion composite vibrator used in the ultrasonic motor according to the embodiment of FIG. In this figure, the piezoelectric longitudinal-torsional composite vibrator is
Abrasion-resistant members 29, 29 'are joined to both sides of a piezoelectric longitudinal-torsion composite vibrator 28 made of rod-shaped piezoelectric ceramics having a piezoelectric longitudinal-torsion composite vibrator portion 21 substantially at the center shown in FIG. It is composed. In this case, the vibration state of the piezoelectric longitudinal-torsion composite vibrator 28 is as shown in FIG. That is, for torsional vibration, the central portion of the piezoelectric longitudinal-torsional composite vibrator 28 becomes a node of the vibration.

As can be seen from FIG. 6 (a), both ends of the piezoelectric longitudinal-torsion composite vibrator 28 are twisted in opposite directions. When the frequency of the applied voltage is the same as the resonance frequency of the torsional vibration, both ends of the piezoelectric longitudinal-torsional composite vibrator 28 are twisted in opposite directions. As for the longitudinal vibration, when the frequency of the applied voltage is the same as the resonance frequency of the torsional vibration, both ends of the piezoelectric longitudinal-torsional composite vibrator 28 oscillate in the longitudinal direction in synchronization with the torsional resonance. do. At this time, if the polarity of the voltage applied to each of the longitudinal torsional vibrator portions formed on both sides of the piezoelectric longitudinal-torsion composite vibrator 21 is reversed, the direction of the expansion / contraction strain is as shown in FIG. 6 (b). become. Therefore,
The direction of displacement of the torsional vibration when the end of the piezoelectric longitudinal-torsional composite vibrator 28 extends to both sides from the position of the vibration node becomes the same. Motion vibration occurs. In this case, when the phase of the applied voltage of the torsional vibration or the applied voltage of the longitudinal vibration is changed by 180 °, the direction of the elliptical vibration is reversed.

[Effects of the Invention] As described above, according to the present invention, a piezoelectric vertical vibrator for an ultrasonic motor and a torsional vibrator can be easily manufactured by a press molding technique generally applied generally. By applying electrode printing, which is also a common technique, to these outer peripheral surfaces using rod-shaped piezoelectric ceramics, a piezoelectric torsional vibrator and a piezoelectric longitudinal vibrator can be obtained in an integrated shape, making it easy to manufacture and a bonding process. And a piezoelectric longitudinal-torsional composite vibrator with less variation in characteristics due to complicated processing steps.

Further, according to the present invention, when the shape of the piezoelectric longitudinal-torsion composite vibrator is a pipe shape, the shaft is penetrated through the hollow portion,
An ultrasonic motor of a type in which two rotors are simultaneously rotated can be obtained.

As described above, if the ultrasonic motor is constituted by using the piezoelectric longitudinal-torsion composite vibrator, an ultrasonic motor having a simple structure and little variation in characteristics can be obtained, and the practical effect is large.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structural example of an ultrasonic motor according to an embodiment of the present invention, and FIGS. 2 (a), (b), (c) and (d) show polarization and voltage using interdigital electrodes. FIG. 3 is an explanatory diagram of a state of occurrence of distortion when application is performed, FIG. 3 is an explanatory diagram of a state of occurrence of distortion when a hollow cylinder of piezoelectric ceramics is twisted, and FIG. FIG. 5 is a perspective view showing the structure of a torsional composite vibrator, FIG. 5 is a perspective view showing a structural example of a pipe-shaped Langevin vibrator used in the ultrasonic motor of the present invention, and FIG. FIG. 6 (b) is a diagram showing the relative magnitude of the torsional displacement of the torsional composite vibrator, and FIG. 6 (b) is a diagram showing the relative magnitude of the elongation displacement of the piezoelectric longitudinal-torsional composite vibrator of FIG. FIG. 7 is a perspective view showing the structure of a conventional longitudinal-twist type Langevin type vibrator, and FIG. 8 is the structure of a conventional longitudinal-twist type ultrasonic motor. Perspective view, FIG. 9 is a perspective view showing a structure of a conventional torsional vibrator, FIGS. 10 and 11 are explanatory views of manufacturing steps of a conventional torsional vibrator, Figure 12 showing (a),
(B), (c), (d) and (e) are explanatory views of the manufacturing process of a conventional torsional vibrator, FIG. 13 is a perspective view showing the structure of a conventional vertical vibrator, and FIG. It is a perspective view which shows other structures of a vertical vibrator. In the figure, 1 ... piezoelectric vertical-torsional oscillator, 2 ... piezoelectric torsional oscillator, 3 ... piezoelectric vertical-oscillator, 4,5,6 ... metal hollow cylinder, 7 ... shaft, 8,8 '... Bearing, 9,9' ... Rotor, 1
0,10 '... Spring, 11,11' ... Nut, 17 ... Piezoelectric ceramic thin plate, 18,19 ... Cross finger electrode, 18 ', 19'
... common electrode, 20 ... hollow cylindrical elastic body, 20 '... piezoelectric ceramic hollow cylinder, 21 ... vertical-torsion composite vibrator part,
21a: torsional vibrator, 21b, 21c: vertical vibrator, 22, 23
…… intersecting finger electrodes for torsional vibrators, 22 ′, 23 ′ …… common electrodes, 24,25,26,27 …… intersecting finger electrodes for longitudinal vibrators, 28 …… piezoelectric longitudinal-torsional composite vibrators, 29, 29 '…… Abrasion resistant material, 30 ……
Support frame, 101: piezoelectric longitudinal-torsional composite vibrator, 102: piezoelectric torsional vibrator, 103, 103 ': piezoelectric longitudinal-vibrator, 104, 105, 1
06 ... Metal hollow cylinder, 107 ... Shaft, 108 ... Bearing, 109 ...
... rotor, 110 ... spring, 111 ... nut, 112
…… Fan type piezoelectric ceramics plate, 113,114 …… Piezoelectric ceramics plate, 115 …… Piezoelectric ceramics plate prism, 116,116 ′
... Piezoelectric ceramic rings.

Continuation of the front page (56) References JP-A-3-22875 (JP, A) JP-A-3-22877 (JP, A) JP-A-3-40765 (JP, A) JP-A-3-40766 (JP) , A) Patent 2691617 (JP, B2) Patent 2729828 (JP, B2) Patent 2729829 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02N 2/00

Claims (1)

(57) [Claims] 1. A piezoelectric torsional vibrator portion formed at a center portion of a rod-shaped piezoelectric ceramic having a central axis and an outer peripheral surface around the central axis in the central axis direction, and formed on both sides of the piezoelectric torsional vibrator portion. A pair of longitudinal vibrators, a piezoelectric longitudinal-torsional composite vibrator that excites longitudinal-torsional composite vibration at both ends of the rod-shaped piezoelectric ceramics, and is pressed against at least one end of the piezoelectric longitudinal-torsional composite vibrator; A rotor that converts the longitudinal-torsional composite vibration into a rotational motion, the piezoelectric torsional vibrator portion has a plurality of oblique electrodes formed on the outer peripheral surface so as to intersect with the central axis and be formed in parallel with each other. The central portion is polarized using a plurality of oblique electrodes, a first AC drive voltage having a first frequency is applied to excite torsional vibration at both ends of the rod-shaped piezoelectric ceramic, and Each is perpendicular to the central axis on the outer peripheral surface A plurality of peripheral electrodes formed in parallel with each other, and using the plurality of peripheral electrodes to polarize both sides of the piezoelectric torsional vibrator portion, to form a second AC drive having a frequency equal to the first frequency. An ultrasonic motor, wherein a voltage is applied to excite stretching vibration at both ends of the rod-shaped piezoelectric ceramic.