JPH0322875A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric torsional oscillator, simple in working, having no bonding process and small in variability, by providing a piezoelectric torsional oscillation unit and a piezoelectric longitudinal oscillation unit. CONSTITUTION:A piezoelectric composite longitudinal-torsional oscillator 21 is provided with diagonal electrodes 22, 23, formed at the central part of a piezoelectric ceramics pipe 20' so as to have an angle of 45 deg. with respect to the longitudinal direction of the pipe, whereby a piezoelectric torsional oscillation unit 21a is constituted. Circumferential electrodes 24, 25 are formed at one end of the piezoelectric torsional oscillator unit 21a whereby a piezoelectric torsional oscillator unit 21b is constituted. The circumferential electrodes 26, 27 are also formed at the other end of the piezoelectric oscillation unit 21a whereby another piezoelectric oscillation unit 21b' is constituted. When an AC voltage is impressed on the piezoelectric composite longitudinal-torsional oscillator 21, the piezoelectric ceramics pipe 20' is resonated so that both ends thereof are twisted whereby the pipe can be utilized as an ultrasonic motor. According to this method, the ultrasonic motor, simple in structure and small in the variability of characteristics, may be obtained.

Description

[Detailed Description of the Invention] Field of Industrial Application] The present invention relates to a so-called ultrasonic motor using ultrasonic vibration of a piezoelectric vibrator used in OAi''a, etc., and in particular to a vertical torsional vibrator with a simple structure. Regarding type ultrasonic motor.

[Prior Art] FIG. 7 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, in which a piezoelectric torsional vibrator 102 and a piezoelectric longitudinal vibration Child 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 an example of the structure of an ultrasonic motor configured using the vertical single-twist composite vibrator 101 shown in FIG. axis 1
07 is erected, and a rotor 109 rotatably supported by a bearing 8 is passed through the shaft 107 and is pressed against the end face of the single vertical 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 disc-shaped piezoelectric torsional vibrator 102 is constructed by joining four fan-shaped piezoelectric ceramic plates 112. Each fan-shaped piezoelectric ceramic plate 112 is polarized in the chord direction 112a of the fan, as shown in FIG. When a DC voltage is applied between the electrodes, a sliding strain parallel to the plate thickness occurs 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, a fan-shaped piezoelectric ceramic plate is formed by ultrasonic processing from a piezoelectric ceramic plate 113 that has been polarized in the width direction. Punch out a fan-shaped piezoelectric ceramic plate 112 polarized in the direction of the chord of the fan as shown in FIG. 10, and then glue four pieces together to form a disk-like structure, as shown in FIG. 12(a). From the piezoelectric ceramic block 114 polarized in the thickness direction as shown in FIG.
), cut out a regular square prism 115 with the polarization direction diagonal, and stack four regular square prisms 115 so that the polarization direction forms a closed loop, as shown in FIG. 12(c). The outer periphery is polished into a pipe shape as shown in FIG. 12(d), and then cut into a disk shape as shown in FIG. 12(e).

FIG. 13 shows an example of a conventional piezoelectric vertical vibrator 103 made of Hitotsubashi construction, in which a voltage is applied to a piezoelectric ceramic disk 116 that has electrodes on both sides and is polarized in the thickness direction. ).

In order to obtain a large vibration amplitude with a low applied voltage, a plurality of thin piezoelectric ceramic discs 116' may be laminated to form a structure as shown at 103' in FIG. 14.

[Problems to be Solved by the Invention] Since the conventional piezoelectric torsional vibrator 102 shown in FIG. 9 is constructed 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 vibration and longitudinal vibration 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 press 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.

[Means for Solving the Problems] According to the present invention, a piezoelectric torsional vibrator section that torsionally vibrates around a central axis, and a piezoelectric torsional vibrator section that is continuous with one end and the other end of the torsional vibrator section in the direction of the central axis. A composite vibrator having first and second piezoelectric vertical vibrator sections that perform stretching and contraction vibrations, a pair of metal materials each having one end joined to both ends of the composite vibrator, and a pair of metal materials other than the pair of metal materials. a pair of rotors that are press-contacted at respective ends, the composite vibrator includes piezoelectric ceramics having an outer scrap surface, and the piezoelectric torsion vibrator section has a center portion of the outer circumferential surface that is disposed relative to the central axis. It has a plurality of first diagonal electrodes and a plurality of second diagonal electrodes arranged alternately in intersecting directions, and the first piezoelectric vertical vibrator section has a plurality of first diagonal electrodes arranged alternately in the circumferential direction at one end of the outer peripheral surface. a plurality of first circumferential electrodes and a plurality of second circumferential electrodes arranged on the outer circumferential surface; An ultrasonic motor characterized by having a plurality of third circumferential electrodes and a plurality of fourth circumferential electrodes is obtained.

[Function] The piezoelectric longitudinal single-torsion composite vibrator used in the present invention includes a piezoelectric torsional vibrator portion formed at the center of the outer circumferential surface of the piezoelectric ceramic, and a piezoelectric torsional vibrator portion formed at one end and the other end of the outer circumferential surface of the piezoelectric ceramic. It has first and second piezoelectric vertical vibrator parts each having a shape.

The piezoelectric torsional vibrator section has two terminals by forming first and second diagonal electrodes in a direction preferably 45'' with respect to the length direction of the piezoelectric ceramic, and then attaching the first and second diagonal electrodes. The piezoelectric ceramic is polarized in a direction perpendicular to the length direction of the first and second diagonal electrodes.In this state, a voltage is applied to the first and second diagonal electrodes. When applied, if the polarity of the voltage is the same as the polarity of the voltage during polarization, stretching will occur in the direction of polarization, and if the polarity of the voltage is opposite to the polarity of the voltage during polarization, contraction will occur in the direction of polarization. When an elongation or contraction strain occurs in the polarization direction, a contraction or expansion strain occurs in the direction perpendicular to the polarization direction, respectively, in the opposite direction.

As a result of the above, torsional displacement occurs in the piezoelectric ceramic.

Further, the first piezoelectric vertical vibrator section is formed by applying first and second circumferential electrodes in the circumferential direction of the piezoelectric ceramic to form two terminals, and then using the first and second circumferential electrodes. The piezoelectric ceramic is polarized in a direction perpendicular to the length direction of the first and second electrodes, that is, in the length direction of the piezoelectric ceramic.

When a voltage is applied to the first and second circumferential electrodes in this state, if the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, an elongation strain will occur in the direction of polarization, and the polarity of the voltage will change to the voltage at the time of polarization. If the polarity is opposite to that of , shrinkage distortion occurs in the direction of polarization.

That is, an expansion/contraction displacement is generated in the length direction of the piezoelectric ceramic.

Further, in the 12 piezoelectric vertical vibrator sections, third and fourth circumferential electrodes are applied in the circumferential direction of the piezoelectric ceramic to form two terminals, similarly to the first piezoelectric longitudinal vibrator section. The third and fourth electrodes are attached to the piezoelectric ceramic using four circumferential electrodes.
Polarization treatment is performed in a direction perpendicular to the length direction of the electrode, that is, in the long direction of the piezoelectric ceramic.

When a voltage is applied to the third and fourth circumferential electrodes in this state, if the polarity of the voltage is the same as the polarity of the voltage during polarization, an elongation strain will occur in the direction of polarization (2. In the case where the polarity is opposite to the electric field, shrinkage distortion occurs in the direction of polarization.

That is, an expansion/contraction displacement is generated in the length direction of the piezoelectric ceramic.

Therefore, at both ends of such a piezoelectric vertical single-torsion composite vibrator,
By joining metal materials with the same cross-section in the direction orthogonal to the central axis of the piezoelectric ceramics, and further press-fitting a rotor to the ends, the piezoelectric vertical single-twist composite vibrator can be made along the central axis of the metal materials at both ends. The combined vibration of torsional vibration and stretching vibration within the city can be converted into rotational vibration of the rotor.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

Embodiment 1 FIG. 1 is a perspective view showing the structure of an ultrasonic motor according to a first embodiment of the present invention. Metal circular tubes 5 and 6 are joined to both sides of the hollow piezoelectric single-torsion composite vibrator 21 shown in FIG. A single-torsion vibrator 31 is used. A shaft 7 is passed through the hollow part of the Langevin type vertical single-torsion vibrator 31, and bearings 8, 8 are attached to both ends of the shaft 7.
A rotor 9.9 rotatably supported by springs 1.0, . 1 0” through nut 11.11
- are configured by being pressed against the end faces of the Langevin-type vertical single-torsion vibrator 31, respectively.

This Langevin-type vertical torsional vibrator 31 can be stably supported by supporting it with a ring-shaped support frame 3 on which a resonance node of torsional vibration is attached.

FIGS. 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 crossed electrodes 18 and 19 are formed on one surface of the piezoelectric ceramic plate 17, and the first and second crossed electrodes are arranged every other electrode. The common electrode 18'19' is connected to the common electrode 18'19', forming an interdigital electrode.

In Fig. 2(b), the dashed arrow indicates the direction of polarization when polarization processing is performed using such interdigital electrodes, and Fig. 2(c) and (d) indicate the direction of polarization in Fig. 2(c) and (d). It shows the state of distortion that occurs when a DC voltage is applied to the polarized piezoelectric ceramic plate 17 as shown in b), and the solid arrow indicates 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 pipe 20 when both end surfaces of the piezoelectric ceramic pipe 20 are twisted as shown by the solid arrows in the figure. 45 for the direction
Expansion and contraction occur in the direction of the angle 9, moreover in the direction of the arrow indicated by the broken torsional line, and shrinkage distortion occurs in the direction perpendicular to this as indicated by the dashed-dotted line.

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

Furthermore, a second
First and second interdigital electrodes as shown in the figure are formed so that the direction of the interdigital fingers is parallel to the circumferential direction of the piezoelectric ceramic 20, and polarization processing is performed using the first and second interdigital electrodes. When a DC voltage is applied to the same interdigital electrode, the piezoelectric ceramic will elongate in the length direction if the polarity of the voltage is the same as the polarity of the voltage during polarization, and if the polarity of the voltage is opposite to the polarity of the voltage during polarization. On the contrary, it shrinks in the length direction.

FIG. 4 is a perspective view showing an example 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 21 has a plurality of first and second oscillators that intersect with each other at an angle of 45° with respect to the length direction at the center of the outer peripheral surface of the piezoelectric ceramic vibrator 20'. Two oblique electrodes 22 and 23 are formed and connected to first and second common electrodes 22' and 23', respectively, to constitute a piezoelectric torsional vibration section 21a. Further, a plurality of first and second circumferential electrodes 24 and 25 are formed on the outer circumferential surface of one end side of the piezoelectric torsional vibrator section 21a, and are arranged parallel to the circumferential direction and intersect with each other. are electrically connected by third and fourth common electrodes 24' and 25' to constitute a first piezoelectric torsional vibrator section 21b. On the other hand, a plurality of third
and fourth circumferential electrodes 26 and 27 are formed, and the electrodes with the same numbers in the figure are the fifth and sixth common electrodes 26', respectively.
and 27' to form a second piezoelectric torsional vibrator section 21e.

In FIG. 4, first and second common electrodes 22' and 2
After performing polarization by applying a DC high voltage between the piezoelectric ceramic pipes 20' and 3', if an AC voltage with a frequency equal to the resonant frequency of this composite vibrator is applied, the piezoelectric ceramic pipe 20' resonates so that both ends are twisted. .

Similarly, between the first and second circumferential electrodes 24 and 25. After applying a DC high voltage between the third and fourth circumferential electrodes 26 and 27 to perform polarization treatment, the piezoelectric ceramic pipe 20- is twisted by applying an AC voltage equal to the resonance frequency of the twist. This piezoelectric ceramic vibrator undergoes stretching vibration (longitudinal vibration) in the length direction at a resonance frequency of . 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 vibrator-shaped Langevin type piezoelectric vertical single-torsion composite vibrator used in an ultrasonic motor according to an embodiment of the present invention. In this figure, a vib-shaped Langevin type piezoelectric single-torsion composite vibrator 31 is constructed by joining metal vipes 5 and 6 of equal length to both sides of the piezoelectric single-torsion vertical composite vibrator 21 shown in FIG. It is constructed by providing a ring-shaped support frame 3 in the central part. As shown in FIG. 5, the piezoelectric longitudinal single-torsion composite vibrator 21 is located at a position where the center of the torsional vibrator portion is approximately half of the total length of the Langevin type vibrator 31. In this case, the vibration state of the Langevin type vibrator 31 is as shown in FIG. In other words, for torsional vibration, the Langevin type oscillator 3
The central part of 1 becomes the node of vibration.

6(a) and 6(b) are diagrams showing the vibration state when an AC voltage equal to the resonance frequency is applied to this Langevin type vibrator 31, and the horizontal axis represents the torsional vibration of the Langevin type vibrator. The position is shown from the center of the child toward both ends.

As can be seen from FIG. 6(a), both ends of the Langevin type vibrator 31 are twisted in opposite directions, both in the case of clockwise rotation as shown by the solid line and in the case of counterclockwise rotation as shown by the broken line.

Furthermore, as can be seen from FIG. 6(b), for longitudinal vibration (i), if the frequency of the applied voltage is the same as the torsion resonance frequency, both ends of the Langevin type vibrator 31 will be affected by the torsion. Extends and contracts in the length direction in synchronization with resonance.

At this time, if the polarities of the voltages applied to the stretching strain generation parts formed on both sides of the piezoelectric vertical single-torsion composite vibrator 21 are reversed, the direction of the stretching strain will be the same as that shown in FIG. become.

(7) Therefore, when the ends of the Langevin-type vertical single-torsion oscillator 31 extend from the vibration node position to both sides, the direction of displacement of torsional vibration is the same, and the end of the Langevin-type vertical single-torsion oscillator 31 In this case, if the voltage applied to the torsional vibration or the phase of the applied longitudinal vibration is changed by 180°, the direction of the elliptical 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. The piezoelectric torsional vibrator and the piezoelectric longitudinal vibrator can be obtained as an integrated piece by using a piezoelectric ceramic and printing electrodes on their outer peripheral surfaces, which is also a common technique. It is possible to obtain a piezoelectric longitudinal single-torsion composite vibrator with less variation in characteristics due to complicated processing steps.

Further, according to the present invention, when the piezoelectric longitudinal single-torsion composite vibrator is configured in the shape of a vibrator, an ultrasonic motor of a type in which a shaft penetrates a hollow portion and rotates two rotors simultaneously can be obtained.

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 the drawing]

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 how distortion occurs when a piezoelectric ceramic vibrator is twisted. FIG. 4 is an illustration of how distortion occurs when a piezoelectric ceramic vibrator is twisted. FIG. FIG. 5 is a perspective view showing a structure of a composite vibrator; FIG.
FIG. 6(a) is a diagram showing the relative magnitude of torsional displacement of the pipe-shaped Langevin oscillator in FIG. FIG. 7 is a perspective view showing the structure of a conventional vertical single-twist Lilangevin type vibrator; FIG. 8 is a perspective view showing the structure of a conventional vertical single-twist ultrasonic motor; Figure 9 is a perspective view showing the structure of a conventional torsional vibrator, Figures 10 and 11.
The figure is an explanatory diagram of the manufacturing process of a conventional torsional oscillator, and Figure 12 (
a), (b), (C). (d) and (e) are explanatory diagrams 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 shows another structure of a conventional longitudinal oscillator. This is a perspective view. :7a {・Must, 3...Support frame, 4,5,6,...Metal cylinder, 7...Shaft, 8.8''...Bearing, 9.9'...
Rotor 10.10'...Spring, 11.11'
... Nut, 17 ... Piezoelectric ceramic thin plate, 1
8.19: Interdigital electrode, 18'. 19'... Common electrode, 20... Piezoelectric ceramic pipe, 21... Piezoelectric vertical single torsion composite vibrator, 21a... Piezoelectric torsional vibrator section,
2lb22c... Piezoelectric longitudinal vibration part, 22.23... Oblique electrode, 23, 24, 25.26... Circumferential electrode, 22'
23'24'.25', 26-, 27=...Common electrode, two...Piezoelectric torsional vibrator section, 30...Piezoelectric longitudinal vibrating section, 101...Piezoelectric longitudinal one-torsion composite vibrator, 102
...Piezoelectric torsional vibrator, 103,103-...Piezoelectric longitudinal vibrator, 104,105,106...Metal cylinder, 10
7... Shaft, 108... Bearing, 109... Rotor, 110... Spring, 111... Nut, 11
2...Fan-shaped piezoelectric ceramic plate, 113, 114...
- Piezoelectric ceramic plate, 115... piezoelectric ceramic plate prism, 116, 116-... piezoelectric ceramic disc. Figure 3 Figure 8 Figure 5 Figure 6 Circle Figure 9 Figure 10 Figure 11 Figure 13 Figure 14 Figure k103

Claims (1)

[Claims] 1. A piezoelectric torsional vibrator section that performs torsional vibration around a central axis, and first and second piezoelectric longitudinal vibrator sections that continuously perform stretching vibration in the direction of the central axis at one end and the other end of the torsional vibrator section, respectively. a pair of metal materials each having one end joined to both ends of the composite vibrator, and a pair of rotors press-welded to the other ends of the pair of metal materials, respectively; The composite vibrator includes a piezoelectric ceramic having an outer circumferential surface, and the piezoelectric torsion vibrator section includes a plurality of first electrodes arranged alternately in a direction intersecting the central axis at the center of the outer circumferential surface.
a diagonal electrode and a plurality of second diagonal electrodes;
The piezoelectric vertical vibrator section has a plurality of first circumferential electrodes and a plurality of second circumferential electrodes arranged alternately in the circumferential direction at one end of the outer circumferential surface, and the second piezoelectric longitudinal vibration An ultrasonic motor characterized in that the child part has a plurality of third circumferential electrodes and a plurality of fourth circumferential electrodes arranged alternately in the circumferential direction at the other end of the outer circumferential surface.