JPH0322876A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric torsional oscillator, simple in working, having no bonding process and small in variability, by a method wherein an ultrasonic motor is provided with a piezoelectric torsional oscillation unit and a piezoelectric longitudinal oscillation unit while a first AC driving voltage and a second AC driving voltage are impressed on corresponding electrodes respectively. CONSTITUTION:A piezoelectric composite longitudinal-torsional oscillation unit 21 is provided with diagonal electrodes 22, 23, formed on the outer peripheral surface of the central part of a piezoelectric ceramics hollow column 20' so as to have the angle of 45 deg. with respect to the longitudinal direction of the column 20' whereby a torsional oscillation unit 21a is formed. A plurality of circumferential electrodes 24, 25 as well as the circumferential electrodes 26, 27 are formed on the outer peripheral surfaces of both end sides of the diagonal electrodes 22, 23 in parallel to the circumferential direction of the column 20' whereby longitudinal oscillation units 21c, 21c are formed. When an AC driving voltage having a first frequency is impressed on the diagonal electrodes 22, 23 and another AC driving voltage having a second frequency is impressed on the circumferential electrodes 24, 25 as well as the circumferential electrodes 26, 27, expanding oscillation is excited in the piezoelectric ceramics hollow column 20'.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a so-called ultrasonic motor that uses ultrasonic vibration of a piezoelectric vibrator used in OA equipment, etc., and particularly relates to a so-called ultrasonic motor that uses ultrasonic vibration of a piezoelectric vibrator used in OA equipment, etc. Regarding ultrasonic motors.

[Prior Art] FIG. 17 is a perspective view of a structural example of a vertical single-torsion composite vibrator 101 used in a conventional vertical single-torsion vibrator type ultrasonic motor, and includes a piezoelectric torsional vibrator 102 and a piezoelectric longitudinal vibrator. 103
are joined via a metal cylinder 104, and metal cylinders 105 and 106 are further joined to both sides thereof. In this case, a metal cylinder can be used instead of the metal cylinder 105.

FIG. 8 is a perspective view showing a structural example of an ultrasonic motor constructed using the vertical single-torsion composite vibrator 101 shown in FIG. axis 1
07 is erected, and a rotor 109 rotatably supported by a bearing 8 is pressed against the end surface of the longitudinal single-twist composite vibrator 101 by a coil spring 110 and a nut 111.

FIG. 9 shows an example of the structure of the piezoelectric torsional vibrator shown in FIG. 7, and the cylindrical piezoelectric torsional vibrator 102 is constructed by joining four sector-shaped piezoelectric ceramic plates 112 divided into quarters. Each fan-shaped piezoelectric ceramic plate 112 has 11
As shown in FIG.
When electrodes are applied to the upper and lower surfaces of the piezoelectric ceramic plate and a DC voltage is applied between the upper and lower electrodes, a sliding strain parallel to the thickness of the piezoelectric ceramic plate is generated in 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 sliding strain generated in each sector-shaped piezoelectric ceramic plate 112 is combined and This results in torsional distortion such that the lower surface is twisted.

When an alternating current voltage is applied, such vibrations that cause torsional distortion (referred to as torsional vibrations) are excited.

When manufacturing the conventional piezoelectric torsional vibrator shown in FIG. 9, first, as shown in FIG. 11, piezoelectric ceramic plates 11, . A fan-shaped piezoelectric ceramic plate 112 polarized in the direction of the chord of the fan as shown in FIG. 10 is made by punching out a fan-shaped piezoelectric ceramic plate 112 using ultrasonic processing from step 3, and four of these are glued together to form a disc-shaped piezoelectric ceramic plate 112. Alternatively, as shown in FIG. 12(a), from a piezoelectric ceramic block 114 polarized in the thickness direction, a regular square is formed such that the polarization direction is diagonal as shown in FIG. 12(b). A square prism 115 is cut out, and as shown in FIG. 12(c), four regular square prisms 115 are stacked and glued together so that the polarization direction forms a closed loop, and the outer periphery is shaped as shown in FIG. 12(d). After polishing into a vibrator shape, it is formed by cutting into a disk shape as shown in FIG. 12(e).

Figure M13 is an example of a conventional piezoelectric longitudinal vibrator 103 made of Hitotsubashi construction, in which a voltage is applied to a piezoelectric ceramic ring 116 that has electrodes on both sides and is polarized in the thickness direction to generate vibrations in the thickness direction (
(called longitudinal vibration).

In order to obtain a large vibration amplitude with a low applied voltage, a piezoelectric longitudinal vibrator 103' may be constructed by laminating a plurality of thin piezoelectric ceramic rings 116- as shown in FIG.

[Problems to be Solved by the Invention] Since the conventional piezoelectric torsional vibrator 102 shown in FIG. 9 is configured by bonding a plurality of piezoelectric ceramics, there are large variations in characteristics due to bonding. Furthermore, as shown in FIGS. 10, 11, and 12, the processing to obtain the piezoelectric torsional vibrator 102 is complicated and extremely expensive. Furthermore, when trying to obtain torsional and longitudinal vibrations at the same time, the piezoelectric torsional vibrator 102 shown in FIG. 9 and the piezoelectric longitudinal vibrator 103 shown in FIG. There was a problem with the variation in the amount of adhesive and the high cost of adhesion.

Therefore, the technical problem of the present invention is to eliminate the drawbacks of the conventional piezoelectric torsional vibrator and vertical single-torsion composite vibrator as described above, and to create a piezoelectric torsional vibrator that is easy to process, does not require a bonding process, and has little variation. Furthermore, it is an object of the present invention to provide an ultrasonic motor using a piezoelectric vertical single-torsion composite vibrator in which a longitudinal vibrator is formed in the same piezoelectric element.

Another technical problem of the present invention is to use a hollow piezoelectric vertical-torsional composite vibrator, and to connect two rotors to both ends of the piezoelectric vertical-torsional composite vibrator by means of a shaft penetrating the hollow part. An object of the present invention is to provide a two-rotor type ultrasonic motor that is pressed into contact with each other.

[Means for Solving the Problems] According to the present invention, a piezoelectric torsional vibrator portion formed at the center in the direction of the central axis of a rod-shaped piezoelectric ceramic having a central axis and an outer circumferential surface around the central axis; A piezoelectric vertical single-torsion composite vibrator that has a pair of vertical vibrator parts formed on both sides of a piezoelectric torsional vibrator part and excites longitudinal single-torsion composite vibrations at both ends of the rod-shaped piezoelectric ceramic; a rotor that is press-contacted to at least one end of the composite vibrator and converts the vertical torsional composite vibration into rotational motion; The central part is polarized using the plurality of diagonal electrodes, and a first AC driving voltage having a first frequency is applied to generate torsional vibration at both ends of the rod-shaped piezoelectric ceramic. Each of the vertical vibrator parts has a plurality of circumferential electrodes formed on the outer circumferential surface in parallel with orthogonal to the central axis, and the piezoelectric torsion vibrator is excited by using the plurality of circumferential electrodes. There is provided an ultrasonic motor characterized in that both sides of the rod-shaped piezoelectric ceramic are polarized and a second AC driving voltage having a frequency equal to the first frequency is applied to excite stretching vibrations at both ends of the rod-shaped piezoelectric ceramic. It will be done.

1 Effect] The ultrasonic motor of the present invention includes a piezoelectric vertical single-torsion composite vibrator and a rotor.

A piezoelectric longitudinal single-torsion composite vibrator includes a piezoelectric torsional vibrator section formed at the center in the direction of the central axis of a bar-shaped piezoelectric ceramic having a central axis and an outer peripheral surface around the central axis, and a piezoelectric torsional vibrator section on both sides of this piezoelectric torsional vibrator section. It has a pair of vertical vibrator parts formed in
A vertical torsional complex vibration is excited at both ends of this rod-shaped piezoelectric ceramic.

On the other hand, the rotor is pressed against at least one end of the piezoelectric longitudinal single-torsion compound vibrator, and converts the longitudinal single-torsion compound vibration into rotational motion.

This piezoelectric torsional vibrator section has a plurality of diagonal electrodes formed parallel to each other and intersecting the central axis on the outer circumferential surface,
The central portion of this rod-shaped piezoelectric ceramic is polarized using the plurality of oblique electrodes.

Furthermore, each of the piezoelectric vertical vibrator sections has a plurality of circumferential electrodes formed on the outer peripheral surface of the rod-shaped piezoelectric ceramic in parallel and orthogonal to the central axis, and uses the plurality of circumferential electrodes to generate the piezoelectric torsional vibration. Both sides of the child part are polarized respectively.

When a first AC driving voltage having a first frequency is applied to such an oblique electrode, longitudinal vibration is excited at both ends of the rod-shaped piezoelectric ceramic.

Furthermore, when a second AC drive voltage having a frequency equal to the first frequency is applied to the circumferential electrode, stretching vibrations are excited at both ends of the rod-shaped piezoelectric ceramic.

Therefore, when the first AC drive voltage and the second AC drive voltage are respectively applied to the corresponding electrodes, longitudinal torsional vibration, which is a combination of torsional vibration and stretching vibration, is excited at both ends of the rod-shaped piezoelectric ceramic. This longitudinal torsional vibration is converted by the rotor into rotational motion around the axis of the rotor.

[Examples] Examples of the present invention will be described in detail below 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 vertical single-torsion extraction vibrator 28 to be described later
The shaft 7 is passed through the hollow part of the piezoelectric vertical single-torsion composite vibrator 28, and is fixed at the resonance node inside the piezoelectric vertical single-torsion composite vibrator 28. A rotor 9.9'' rotatably supported by bearings 8 and 8' at both ends of the shaft 7 is pressed onto the end face of the piezoelectric vertical single-torsion vibrator 28 by nuts 11 and 11 through springs 10 and 10, respectively. It is constructed by

The piezoelectric vertical torsional vibrator 28 can be supported by a ring-shaped support frame 30 at the center portion where the resonance node of torsional vibration is placed, and in this case, stable support can be achieved.

Figure 2(a). (b). (c) and (d) are explanatory diagrams of the operating principle of a piezoelectric vertical single-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 intersecting electrodes 18 and 19 are formed on one surface of the piezoelectric ceramic plates 1 and 7, and the first and second intersecting electrodes 18 and 19 intersect with each other. It is connected to two common electrodes 18'19' to form interdigital electrodes.

In Fig. m2 (b), the dashed arrow indicates the direction of polarization when polarization processing is performed using such interdigital electrodes, and Fig. 2 (c) and (d) show the direction of polarization in Fig. 2 (b). ) shows the state of distortion that occurs when a DC voltage is applied to the polarized piezoelectric ceramic plate 17, and solid arrows indicate the direction of the electric field. As shown in Figure 2 (C), when the polarity of the voltage is the same as the polarity of the voltage during polarization, an elongation strain occurs in the direction of polarization, while as shown in Figure 2 (d), the polarity of the voltage If the polarity is opposite to the polarity of the voltage during polarization, shrinkage distortion occurs in the direction of polarization.

FIG. 3 shows the state of distortion that occurs 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 shown by the solid arrows in the figure. Expansion and contraction occurs in the direction of an angle of 45'' with respect to the axial direction of 20, and in the direction of the arrow indicated by the broken torsional line, and shrinkage distortion occurs in the direction perpendicular to this indicated by the dashed-dotted arrow. .

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

Furthermore, first and second interdigital electrodes as shown in FIG. When a polarization process is performed using the first and second interdigital electrodes and a DC voltage is applied to the same interdigital electrodes, when the polarity of the voltage is the same as the polarity of the voltage during polarization, the piezoelectric ceramic hollow cylinder 20 It extends in the length direction, and conversely contracts in the length direction when the polarity of the voltage is opposite to the polarity of the voltage during polarization.

FIG. 4 is a 7T perspective view of an example of the piezoelectric longitudinal single-torsion composite vibrator section used in the ultrasonic motor according to the embodiment of the present invention. In this figure, piezoelectric vertical twist? Standing vibrator section 2
1, a plurality of first and second oblique electrodes 22 and 23 are formed on the outer circumferential surface of the central portion of a piezoelectric ceramic hollow cylinder 20'' at an angle of 45'' with respect to the length direction, and intersect with each other. , first and second common electrodes 22, respectively.
' and 23' to form a torsional vibrator section 21a.

Furthermore, a plurality of first and second circumferential electrodes 24 are arranged parallel to the circumferential direction on the outer circumferential surface of the portions on both sides of this 45° interdigital electrode.
25, 26, and 27 are formed, and electrodes having the same number are electrically connected to form a pair of vertical vibrator parts 21b and 21c.

In FIG. 4, after polarization treatment is performed by applying a DC high voltage between the first and second common electrodes 22' and 23',
When an alternating current voltage having a frequency equal to the resonant frequency of this composite vibrator is applied, the piezoelectric ceramic hollow cylinder 20' resonates so that both ends thereof are twisted.

Similarly, after polarization treatment is performed by applying a DC high voltage between the first and second circumferential electrodes 24 and 25 and between the first and third and fourth circumferential electrodes 26 and 27, the torsional resonance When an alternating current voltage equal to the frequency is applied, the piezoelectric ceramic hollow cylinder 20' undergoes stretching vibration (longitudinal vibration) in the length direction of the piezoelectric ceramic hollow cylinder 20' at the torsional resonance frequency.

For longitudinal vibration, the frequency is different from the resonance frequency, so the vibration amplitude in the longitudinal direction is considerably smaller than the amplitude at resonance, but a sufficient amplitude can be obtained for practical use.

FIG. 5 is a perspective view showing an example of a hitotsubashi structure of a piezoelectric vertical single-torsion composite vibrator used in an ultrasonic motor according to an embodiment of the present invention. In this figure, the piezoelectric longitudinal single-torsion composite vibrator has the fourth
It is constructed by bonding wear-resistant members 29 and 29- to both sides of a piezoelectric vertical single-torsion composite vibrator 28 made of rod-shaped piezoelectric ceramics having a piezoelectric vertical single-torsion composite vibrator portion 21 shown in the figure approximately in the center. be done. In this case, the vibration state of the piezoelectric vertical single-torsion composite vibrator 28 is as shown in FIG. 6(a). That is, for torsional vibration, the piezoelectric longitudinal single-torsion composite vibrator 28
The center part becomes the node of vibration.

As can be seen from FIG. 6(a), both ends of the piezoelectric vertical single-torsion composite vibrator 28 are twisted in opposite directions.

Regarding longitudinal vibration, if the frequency of the applied voltage is the same as the torsion resonance frequency, both ends of the piezoelectric longitudinal single-torsion composite vibrator 28 are twisted in opposite directions.

Regarding longitudinal vibration, if the frequency of the applied voltage is set to the same frequency as the torsional resonance frequency, both ends of the piezoelectric longitudinal single-torsion composite vibrator 28 will undergo stretching vibration in the longitudinal direction in synchronization with the torsional resonance. do. At this time, the piezoelectric vertical single-torsion composite vibrator 21
When the polarities of the voltages applied to the longitudinal helical vibrator portions formed on both sides of the oscillator are reversed, the direction of expansion/contraction strain becomes as shown in FIG. 6(b). Therefore, when the end of the piezoelectric vertical single-torsion composite vibrator 28 extends from the vibration node position to both sides, the direction of displacement of torsional vibration is the same, and the end of the piezoelectric vertical single-torsion composite vibrator 28 is directed in the same direction. An elliptical motion vibration occurs. In this case, if the phase of the voltage applied to the torsional vibration or the voltage applied to the longitudinal vibration is changed by 180'', the direction of the elliptic vibration is reversed.

[Effects of the Invention] As shown above, according to the present invention, piezoelectric longitudinal vibrators and torsional vibrators for ultrasonic motors can be easily manufactured using commonly used press molding techniques. By using rod-shaped piezoelectric ceramics and printing electrodes on their outer peripheral surfaces, which is also a common technique, a piezoelectric torsional vibrator and a piezoelectric longitudinal vibrator can be obtained as an integrated structure, which is easy to manufacture and requires no adhesives. A piezoelectric longitudinal single-torsion composite vibrator with little variation in characteristics due to process or complicated processing steps can be obtained.

Further, according to the present invention, when the shape of the piezoelectric longitudinal single-torsion composite vibrator is pipe-like, the shaft is penetrated through the hollow part, and two
An ultrasonic motor that rotates two rotors simultaneously can be created.

In this way, if an ultrasonic motor is constructed using a piezoelectric vertical single-torsion composite vibrator, an ultrasonic motor with a simple structure and less variation in characteristics can be obtained, which has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a structural example of an ultrasonic motor according to an embodiment of the present invention, and FIG. 2(a). (b). (c) and (d) are illustrations of how distortion occurs when polarization and voltage are applied using interdigital electrodes, and Figure 3 shows how distortion occurs when a piezoelectric ceramic hollow cylinder is twisted. An explanatory diagram, FIG. 4 is a perspective view showing the structure of a piezoelectric vertical single-torsion composite vibrator according to an embodiment of the present invention, and FIG. FIG. 6(a) is a diagram showing the relative magnitude of torsional displacement of the piezoelectric vertical single-torsion composite vibrator of FIG. 5, and FIG.
Figure 7 is a perspective view showing the structure of a conventional vertical single-torsion Lilangevin type vibrator, and Figure 8 is a conventional vertical single-torsion composite vibrator. FIG. 9 is a perspective view showing the structure of a conventional torsional oscillator; FIGS. 10 and 11 are explanatory diagrams of the manufacturing process of a conventional torsional oscillator; Figure 12(a).
(b). (c), (d). (e) is an explanatory diagram of the manufacturing process of a conventional torsional oscillator, FIG. 13 is a perspective view showing the structure of a conventional longitudinal oscillator, and FIG. 14 is a perspective view showing another structure of the conventional longitudinal oscillator. be. In the figure, 1... Piezoelectric vertical single torsion composite vibrator, 2... Piezoelectric torsional vibrator, 3... Piezoelectric vertical single vibrator, 4, 5, 6...
・Metal hollow cylinder, 7...shaft, 8.8"...bearing, 9
,9...Rotor 10.10-...Spring,
11.11'... Nut, 17... Piezoelectric ceramic thin plate, 18.19... Interdigital electrode, 18-, 19-
... Common electrode, 20 ... Hollow cylindrical elastic body, 20'
. . . Piezoelectric ceramic hollow cylinder, 21 . . . Vertical one-torsion composite oscillator portion, 21a . . . Torsional oscillator portion, 21b, 2
1c...Longitudinal vibrator part, 22.23...Interdigital electrode for torsional vibrator, 22''.23゛...Common electrode, 24,2
5.26.27... Interdigital electrode for vertical vibrator, 28...
・Piezoelectric vertical single-twist composite vibrator, 29.29=... Wear-resistant material, 30... Support frame, 101... Piezoelectric vertical single-twist composite vibrator, 〕02... Piezoelectric torsional vibrator, 103 ,103
'...Piezoelectric vertical single vibrator, 104, 105, 106...
・Metal hollow cylinder, 107...shaft, 108...bearing,
109...Rotor 110...Spring, 11
DESCRIPTION OF SYMBOLS 1... Nut, 112... Fan-shaped piezoelectric ceramic plate, 113, 114... Piezoelectric ceramic plate, 115.
・Piezoelectric ceramic plate prismatic column, 116.116-...
Piezoelectric ceramic sling. }Rokumachi Figure 3 Figure 4 Figure 5 Figure 9 Figure 10 Figure 11 [Shrinkage] Figure 8

Claims (1)

[Claims] 1. A piezoelectric torsional vibrator portion formed at the center in the direction of the central axis of a rod-shaped piezoelectric ceramic having a central axis and an outer peripheral surface around the central axis, and a pair of longitudinal vibrations formed on both sides of the piezoelectric torsional vibrator portion. a piezoelectric longitudinal-torsional composite vibrator which excites longitudinal-torsional composite vibration at both ends of the rod-shaped piezoelectric ceramic; a rotor that converts vibration into rotational motion; the piezoelectric torsional vibrator section has a plurality of diagonal electrodes on the outer circumferential surface that intersect with the central axis and are formed parallel to each other; and applying a first alternating current driving voltage having a first frequency to excite torsional vibration at both ends of the rod-shaped piezoelectric ceramic, and each of the longitudinal vibrator parts The plane has a plurality of circumferential electrodes formed perpendicularly and parallel to the central axis, and the plurality of circumferential electrodes are used to polarize both sides of the piezoelectric torsional vibrator section, and the frequency is equal to the first frequency. An ultrasonic motor characterized in that a second AC driving voltage having a certain frequency is applied to excite stretching vibrations at both ends of the rod-shaped piezoelectric ceramic.