JP3122881B2 - 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
The rotor 109 rotatably supported by the bearing 108 is pressed against the end face of the composite longitudinal-torsion oscillator 101 by the coil spring 110 and the nut 111.

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. Each of the fan-shaped piezoelectric ceramic plates 112 is subjected to a polarization process in the chord direction 112a of the fan as shown in FIG. 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 manufacturing the conventional piezoelectric torsional vibrator shown in FIG. 9, first, as shown in FIG. 11, 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 formed from a piezoelectric ceramic block 114 polarized in the thickness direction (arrow) as shown in FIG. 12B. As shown in FIG. 12 (c), four square prisms 115 are overlapped and bonded so as to form a closed loop of the polarization direction, as shown in FIG. 12 (c), and the outer periphery is formed into a pipe shape as shown in FIG. 12 (d). After polishing, it is formed by cutting into a disk shape as shown in FIG. 12 (e).

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.

[Problem 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.

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.

[Means for Solving the Problems] According to the present invention, a piezoelectric torsional vibrator including a first piezoelectric ceramic having an outer peripheral surface and performing torsional vibration around a central axis, and the central axis of the piezoelectric torsional vibrator And a second piezoelectric ceramic which is provided with a central axis at both ends on the extension of the piezoelectric ceramic and which is arranged symmetrically with respect to the center of the piezoelectric torsional vibrator via a metal material. A piezoelectric torsional composite vibrator provided with two piezoelectric longitudinal vibrators respectively arranged to perform stretching vibration, and arranged to perform longitudinal-torsional vibration in which the torsional vibration and the stretching vibration are combined. A wear-resistant member joined to an end of the piezoelectric longitudinal-torsional vibrator; and the piezoelectric longitudinal-
A rotor rotatably pressed against the torsional vibrator, wherein the piezoelectric torsional vibrator comprises a plurality of first oblique electrodes and a plurality of first oblique electrodes alternately arranged on the outer peripheral surface in a direction intersecting the central axis. The ultrasonic motor is characterized in that it is provided with the second oblique electrode and is polarized by using the first oblique electrode and the second oblique electrode.

[Operation] An ultrasonic motor of the present invention includes a piezoelectric longitudinal-torsion composite vibrator, a wear-resistant member, and a rotor. Piezoelectric vertical
The torsional composite vibrator has a piezoelectric torsional vibrator and at least one piezoelectric longitudinal vibrator. The piezoelectric torsional vibrator includes a first piezoelectric ceramic having an outer peripheral surface, and generates torsional vibration around a central axis. Do. That is, the piezoelectric torsional vibrator is provided with a plurality of first diagonal electrodes and a plurality of second diagonal electrodes alternately arranged on the outer peripheral surface in a direction intersecting with the central axis, and Using the oblique electrode and the second oblique electrode, this piezoelectric ceramic
Polarization is performed in a direction perpendicular to the length direction of the plurality of first oblique electrodes and the plurality of second oblique electrodes.

When a voltage is applied to the first and second oblique electrodes in this state, if 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, and the polarity of the voltage becomes When the polarity is opposite to the polarity of the voltage, shrinkage distortion occurs in the direction of polarization.

When an elongation or contraction strain is generated in the polarization direction, a contraction or elongation strain is generated in the direction perpendicular to the polarization direction, respectively.

Therefore, when an AC voltage is applied to the piezoelectric torsional vibrator, torsional vibration occurs in which both end faces are twisted.

Further, the piezoelectric longitudinal vibrator includes a second piezoelectric ceramic and performs expansion and contraction vibration in the direction of the central axis.

Accordingly, in the piezoelectric longitudinal-torsional composite vibrator, a node portion of the longitudinal-torsional composite vibration becomes a central portion of the piezoelectric torsional vibrator so as to perform a longitudinal-torsional composite vibration in which the torsional vibration and the stretching vibration are combined. The piezoelectric torsional vibrator and the piezoelectric longitudinal vibrator are arranged so that their respective central axes coincide.

Further, a wear-resistant member is joined to an end of the piezoelectric vertical-torsion composite vibrator.

The rotor is rotatably pressed to the piezoelectric longitudinal-torsion composite vibrator via the wear-resistant member.

Therefore, the rotor is pressed into contact with one of the two ends of the piezoelectric longitudinal-torsional composite vibrator having at least one piezoelectric longitudinal vibrator and the piezoelectric torsional vibrator via a wear-resistant member. Thereby, the combined vibration of the torsional vibration and the expansion-contraction vibration in the plane along the central axis of the piezoelectric longitudinal-torsional composite vibrator can be converted into the rotational vibration of the rotor.

[Example] Hereinafter, an example of the present invention will be described 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 24 described later
Through the shaft 7, and fixed to the piezoelectric longitudinal-torsional composite vibrator 24 at the portion of the resonance inside the piezoelectric longitudinal-torsional composite vibrator 24, and further, wear-resistant members 31, 31 'on both sides. Rotors 9, 9 rotatably supported by bearings 8, 8 '
The piezoelectric longitudinal and torsional vibrator 28 is configured to be pressed against both end faces of the piezoelectric longitudinal torsion vibrator 28 by 10 'and nuts 11 and 11'.

The piezoelectric longitudinal-torsional vibrator 24 can support a central portion where a node of resonance of torsional vibration is attached by a ring-shaped support frame 32. In this case, stable support can be achieved.

2 (a), 2 (b), 2 (c) and 2 (d) are explanatory views of 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 polarization,
On the other hand, when the polarity of the voltage is opposite to the polarity of the voltage at the time of polarization as shown in FIG. 2 (d), 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 of し か も and in the direction of the arrow indicated by the one-dot chain line, and the contraction distortion occurs in the direction perpendicular to the direction indicated by the one-dot chain arrow.

Accordingly, 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, first and second interdigital electrodes as shown in FIG. 2 are formed on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 20 so that the direction of the interdigital finger is parallel to the circumferential direction of the piezoelectric ceramic 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 extends in the length direction, 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 the piezoelectric torsional vibrator 21 used in the ultrasonic motor according to the embodiment of the present invention.

In this figure, the piezoelectric torsional vibrator 21 includes a plurality of first and second piezoelectric vibrators 21 that intersect with each other at an angle of 45 ° with respect to the length direction over substantially the entire outer peripheral surface of the piezoelectric ceramic hollow cylinder 21 ′. Second oblique electrodes 22 and 23 are formed and connected to the first and second common electrodes 22 'and 23', respectively.

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 21' resonates so that both ends are twisted. I do.

FIG. 5 is a perspective view showing one structural example of a piezoelectric longitudinal-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 is
One ends of piezoelectric vertical vibrators 25 and 26 having the same structure as the piezoelectric vertical vibrator 103 'shown in FIG. 14 are joined via metal materials 28 and 29. Further, metal members 27 and 30 are joined to the other ends of the piezoelectric longitudinal vibrators 25 and 26, respectively.

These metallic materials 27, 28, 29, 30
7 ', 28', 29 ', 30' are connected.

When a voltage having a frequency of one wavelength resonance in the torsional mode of the piezoelectric longitudinal-torsion composite vibrator 24 is applied between the electric terminals 22 'and 23' for driving torsional vibration of the piezoelectric longitudinal-torsion composite vibrator 24 of FIG. -The torsional vibrator 24 resonates such that both ends are twisted in opposite directions. Similarly, drive terminals 2 of piezoelectric longitudinal vibrators 25 and 26
When an AC voltage equal to the resonance frequency of the torsional mode is applied to 7 ', 28' and 29 ', 30', the composite vibrator 24 vibrates longitudinally at the torsional resonance frequency. Since the longitudinal vibration has a frequency different from the resonance frequency, the vibration amplitude in the vertical direction is considerably smaller than the amplitude at the time of resonance, so that a practically sufficient amplitude can be obtained. As shown in FIG. 5, piezoelectric longitudinal vibrators 25 and 26 are provided symmetrically with respect to the center of piezoelectric torsion vibrator 21 via metal members 28 and 29 at both ends in the central axis direction of piezoelectric torsion vibrator 21. When arranged, the node of the piezoelectric composite vibration is formed at the center of the piezoelectric torsional vibrator 21.

FIG. 6A is a diagram showing the vibration displacement of the piezoelectric longitudinal-torsional vibrator 24 at the time of torsional mode resonance.

As can be seen from FIG. 6 (a), both ends of the piezoelectric longitudinal-torsion composite vibrator 24 are twisted in opposite directions.

When the frequency of the applied voltage is equal to the resonance frequency of the torsional vibration, both ends of the piezoelectric longitudinal-torsional composite vibrator 24 are twisted in opposite directions. For longitudinal vibration, if the frequency of the applied voltage is the same as the resonance frequency of torsion, both ends of the piezoelectric longitudinal-torsion composite vibrator 24
It oscillates in the longitudinal direction in synchronization with the torsional resonance. At this time, when the polarity of the voltage applied to each of the piezoelectric longitudinal vibrators formed on both sides of the piezoelectric longitudinal-torsion composite vibrator 24 is reversed, the direction of the stretching strain becomes as shown in FIG. 6 (b). Become. Accordingly, the direction of displacement of the torsional vibration when the end of the piezoelectric longitudinal-torsional composite vibrator 24 extends to both sides from the position of the vibration node becomes the same, and the same direction is applied to the end of the piezoelectric longitudinal-torsional composite vibrator 24. Of the elliptical motion occurs. In this case, if the phase of the torsional vibration applied voltage or the longitudinal vibration applied voltage is changed by 180 °, the direction of the elliptical vibration is reversed.

[Effects of the Invention] As described above, according to the present invention, as a piezoelectric torsional vibrator for an ultrasonic motor, a rod-shaped piezoelectric element that can be easily manufactured by a generally used press molding technique. A piezoelectric torsional vibrator can be obtained by applying electrode printing, which is also a common technique, to these outer peripheral surfaces using ceramics, which makes it easy to manufacture, and makes it easy to manufacture products with variations in characteristics due to bonding and complicated processing. A small piezoelectric longitudinal-torsion composite vibrator can be obtained. Accordingly, since the ultrasonic motor is configured using the piezoelectric longitudinal-torsion composite vibrator, an ultrasonic motor having a simple structure and small variations 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 view of a state of occurrence of distortion when application is performed, FIG. 3 is an explanatory view of a state of occurrence of distortion when a hollow cylindrical piezoelectric ceramic is twisted, and FIG. 4 is a piezoelectric torsional vibration according to an embodiment of the present invention. FIG. 5 is a perspective view showing a structure example of a piezoelectric longitudinal-torsion composite vibrator used in the ultrasonic motor of the present invention, and FIG. FIG. 6B shows the relative magnitude of the torsional displacement of the torsional composite vibrator. FIG. 6B shows the relative magnitude of the elongation displacement of the piezoelectric longitudinal-torsional composite vibrator of FIG. FIG. 1 is a perspective view showing the structure of a conventional longitudinal-twisted Langevin type vibrator, and FIG. 8 is a perspective view showing the structure of a conventional longitudinal-twisted ultrasonic motor. Figure 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 (a), (b),
(C), (d) and (e) are explanatory views of the manufacturing process of the conventional torsional vibrator, FIG. 13 is a perspective view showing the structure of the conventional vertical vibrator, and FIG. It is a perspective view showing other structures. In the figure, 1 ... piezoelectric longitudinal-torsional oscillator, 2 ... piezoelectric torsional oscillator, 3 ... piezoelectric longitudinal oscillator, 4,5,6 ... hollow metal 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, 21 ... piezoelectric ceramic hollow cylinder, 22, 23 ... interdigital electrode for torsional vibrator, 22 ', 23' ... common electrode, 24 ... piezoelectric vertical -Torsional composite vibrator, 25, 26 ... piezoelectric longitudinal vibrator, 27, 28, 29, 30 ... metal material, 27 ', 28', 29 ', 30' ... electric terminal for driving piezoelectric longitudinal vibrator, 31, 31 ': abrasion-resistant material, 32: support frame, 101: piezoelectric longitudinal-torsion composite vibrator, 102: piezoelectric torsion vibrator, 103, 1
03 ': Piezoelectric longitudinal-vibrator, 104, 105, 106: Metal hollow cylinder, 107: Shaft, 108: Bearing, 109: Rotor, 110
… Spring, 111… Nut, 112… Fan-shaped piezoceramic plate, 113,114… Piezoceramic plate, 115… Piezoelectric plate prism, 116,116 ′… Piezoceramic ring.

Continuation of the front page (56) References JP-A-2-13282 (JP, A) JP-A-2-174573 (JP, A) JP-A-63-164477 (JP, A) JP-A-63-202191 (JP, A) , U) Patent 2729829 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00-2/18 H01L 41/00-41/09

Claims (1)

(57) [Claims] 1. A piezoelectric torsional vibrator including a first piezoelectric ceramic having an outer peripheral surface and performing torsional vibration around a central axis;
Second ends of the piezoelectric torsional vibrator which are provided at both ends on an extension of the central axis and which are arranged via a metal material so as to be symmetrical with respect to the center of the piezoelectric torsional vibrator are provided with central axes coinciding with the extension. Comprising two piezoelectric longitudinal vibrators each including a piezoelectric ceramic and arranged to perform stretching vibration in the direction of the central axis, and performing a torsional vibration in which the torsional vibration and the stretching vibration are combined. A piezoelectric torsional composite vibrator, a wear-resistant member joined to an end of the piezoelectric vertical-torsional vibrator, and a rotatable pressure contact with the piezoelectric vertical-torsional vibrator via the wear-resistant member. The piezoelectric torsional vibrator is provided with a plurality of first oblique electrodes and a plurality of second oblique electrodes alternately arranged on the outer peripheral surface in a direction intersecting with the central axis. Using the first oblique electrode and the second oblique electrode. Ultrasonic motor, characterized in that it is polarized.