JPH0522965A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To reduce the dispersion of characteristics by providing a piezoelectric longitudinal-torsional composite vibrator, which has a torsional vibrating section and a longitudinal vibrating section and one end of which is fixed, and rotor pressure-welded to the other end of the vibrator and supported rotatably. CONSTITUTION:When AC voltage having frequency approximately equal to the resonance frequency of a torsional motion is applied to the torsional- vibration driving electrode of a longitudinal-torsional composite vibrator 1, the rotor 4 of the vibrator 1 is vibrated so that an end on the pressure welding side is twisted. When AC voltage synchronized with the torsional vibrations is applied to a longitudinal vibration driving electrode, composite vibrations obtained by synthesizing torsional vibrations by a torsional vibrating section 10 and stretching vibrations by a longitudinal vibrating section 20 are excited at an end section on the rotor 4 pressure-welding side of the vibrator 1. Consequently, when the rotor 4 is pressure-welded to the end section, composite vibrations are converted into the revolution of the rotor 4. Accordingly, the dispersion of characteristics can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor used in office automation equipment and toys, and more particularly to an ultrasonic motor having a large torque despite its small rotor diameter.

[0002]

2. Description of the Related Art Generally, an ultrasonic motor has advantages that an electromagnetic motor can obtain a high torque at a low rotation speed, a stop holding force, and a small electromagnetic noise, as compared with an electromagnetic motor. It is used for auto focus of cameras and automobile power motors. 3 and 4 are exploded views schematically showing the structure of a conventional ultrasonic motor. 3 and 4, the conventional ultrasonic motor has a metal disc 1 having a ring-shaped and comb-teeth-shaped protrusion on one surface.
Two piezoelectric ceramic discs 107 and 108 which are laminated and bonded to the back side of the surface on which the projecting portion of 06 is formed.
And constitute a stator, and the rotor 109 is pressed onto the stator. The piezoelectric ceramic discs 107 and 108 are polarized in opposite directions evenly evenly.
7 and 108 are bonded by being rotated by an angle that is half the dividing angle.

[0003]

In the conventional ultrasonic motor shown in FIGS. 3 and 4, since the ultrasonic vibration of the stator is transmitted to the rotor in a plane around the central axis, it is inevitable. Since the diameter is large, it is difficult to obtain a motor with a small diameter. Therefore, the practical minimum diameter of the conventional ultrasonic motor is limited to the range of 20 to 30 mm. Further, as can be seen from FIG. 4, in the conventional ultrasonic motor, since the stator is composed of many parts, the manufacturing error of each part is prosperous, resulting in large variation in characteristics. There is a drawback that the manufacturing cost of the motor becomes high. Therefore, one technical problem of the present invention is to provide a small-sized ultrasonic motor having a reduced rotor diameter, particularly an ultrasonic motor having a rotor diameter of 20 mm or less. Further, another technical problem of the present invention is to provide an ultrasonic motor having a small number of components and a low manufacturing cost.

[0004]

According to the present invention, a pair of polarization and driving members extending in the direction of 45 ° with respect to the lengthwise direction are provided on the outer peripheral surface of the piezoelectric ceramic hollow cylinder approximately half the lengthwise direction. A torsional vibrating portion having interdigitated electrodes for applying torsional vibration to the piezoelectric ceramic cylinder, and a circumferential half of the piezoelectric ceramic hollow cylinder adjacent to the torsional vibration portion on the outer peripheral surface of the remaining approximately half of the length of the piezoelectric ceramic hollow cylinder. Piezoelectric longitudinal-torsion composite vibration having one end fixed, which has a longitudinal vibrating portion having a pair of interdigital electrodes for polarization and driving extending parallel to the longitudinal direction and imparting longitudinal vibration to the piezoelectric ceramic hollow cylinder An ultrasonic motor including a child and a rotatably supported rotor that is pressed against the other end of the piezoelectric vertical-torsion composite oscillator is obtained.

[0005]

In the ultrasonic motor of the present invention, the piezoelectric longitudinal-torsional composite oscillator has a torsional vibration portion which is substantially half of the piezoelectric ceramic hollow cylinder and a longitudinal vibration portion which is the other half. The torsional vibration part has a pair of interdigital electrodes formed on the outer peripheral surface in a direction of 45 ° with respect to the length direction of the piezoelectric ceramic hollow cylinder. The piezoelectric ceramic hollow cylinder is polarized by using the pair of interdigital electrodes, and when an alternating voltage is applied with the pair of interdigital electrodes as two terminals, both ends of the piezoelectric ceramic hollow cylinder vibrate torsionally. On the other hand, in the longitudinal vibrating portion, a pair of interdigital electrodes are formed on the outer peripheral surface of the remaining piezoelectric ceramic hollow cylinder parallel to the circumferential direction or the length direction. The piezoelectric ceramic hollow cylinder is polarized by using the pair of interdigital electrodes, and when the pair of interdigital electrodes is used as two terminals and an AC voltage is applied, the longitudinal vibration part expands and contracts in the length direction of the piezoelectric ceramic hollow cylinder. Vibrate. Therefore, when an AC voltage synchronized with the torsional vibration is applied to the longitudinal vibrating portion, the piezoelectric ceramic hollow cylinder is excited with a composite vibration that is a combination of torsional vibration and stretching vibration. When one of the ends of the piezoelectric longitudinal-torsion composite oscillator is fixed to a fixed base and a rotor rotatably supported at one end is pressed, the composite vibration is converted into rotation of the rotor.

[0006]

EXAMPLES Next, examples of the present invention will be described. FIG. 1 is a perspective view showing a structural example of a vertical-torsion type ultrasonic motor of the present invention. In FIG. 1, a torsional vibration generating electrode side end of a vertical-torsion composite vibrator 1 is fixed to a fixed base 2, and a rotor 4 rotatably supported by a bearing 3 is pressed against the other end. . The bearing 3 is fixed to the fixed base 2 by a fixed frame 5. FIG. 2 is a schematic diagram showing a structural example of the vertical-torsion composite vibrator 1 used in the vertical-torsion composite vibrator pressure contact type ultrasonic motor of the present invention. In FIG.
A torsional vibrating portion 10 is provided in approximately half the area of the outer peripheral surface of the piezoelectric ceramic hollow cylinder 1'with respect to the lengthwise direction, and a longitudinally vibrating portion 20 is continuously provided in the other half area along the lengthwise direction of the ceramic cylinder. . The piezoelectric ceramic hollow cylinder 1'is manufactured by ordinary press molding, and the electrode portion is manufactured by electrode printing. The torsional vibration part 10 includes the first and second oblique electrodes 11 in the direction of 45 ° with respect to the length direction of the cylinder.
a and 12a are formed, and the first and second diagonal electrodes 1 are formed.
1a and 12a are first and second common electrodes 11b and 12b
To form two terminals, and first and second diagonally intersecting finger electrodes 11 and 12 are formed. When the piezoelectric ceramic hollow cylinder 1 ′ is polarized by using the first and second diagonal interdigital electrodes 11, 12, the polarization direction of the surface of the piezoelectric ceramic hollow cylinder is the first and second diagonal electrodes. 1
The direction is perpendicular to the length direction of 1a and 12a.
When an AC voltage is applied to the first and second diagonal interdigitated electrodes 11 and 12 in such a polarized state, elongation strain of polarization occurs when the polarity of the voltage is the same as the polarity of the voltage during polarization. However, if the polarity of the voltage is opposite to the polarity of the voltage during polarization, shrinkage distortion occurs in the direction of polarization. When elongation or contraction strain occurs in the polarization direction, contraction or elongation strain occurs in the direction orthogonal to the polarization direction, opposite to these. Therefore, torsional displacement occurs in the torsional vibration part 10 of the piezoelectric ceramic hollow cylinder 1 '.

Further, the piezoelectric ceramic hollow cylinder 1 shown in FIG.
A longitudinal vibrating portion 20 is formed in the other half area of the outer peripheral surface of the ‘′ in the length direction. The longitudinal vibrating portion 20 has first and second peripheral electrodes extending parallel to the circumferential direction, respectively, and is connected to a first connection electrode and a second connection electrode 22c (not shown) and has two terminals. The first and second vertical interdigitated electrodes 2
1, 22 are formed. A piezoelectric ceramic hollow cylinder 1'is formed by using the first and second vertical crossing finger electrodes 21 and 22.
When the polarization treatment is performed on, the polarization direction becomes a direction perpendicular to the length directions of the first and second peripheral electrodes on the surface of the piezoelectric ceramic hollow cylinder. When an AC voltage is applied to the first and second longitudinal interdigitated electrodes 21 and 22 in this state, if the voltage polarity is the same as the voltage polarity during polarization, extension strain occurs in the polarization direction and the voltage polarity Is opposite to the polarity of the voltage during polarization,
Shrinkage distortion occurs in the polarization direction. Therefore, the longitudinal vibration part 20 of the piezoelectric ceramic hollow cylinder 1'expands and contracts in the length direction.

Returning to FIG. 1, when an AC voltage having a frequency substantially equal to the resonance frequency of torsional vibration is applied to the torsional vibration drive electrode of the longitudinal-torsional composite vibrator 1, the rotor 4 of the longitudinal-torsional composite vibrator 1 is pressure-contacted. It vibrates so that the side end is twisted.
When an AC voltage synchronized with the torsional vibration is applied to the longitudinal vibration driving electrode, the torsional vibration due to the torsional vibration part and the longitudinal vibration part are formed at the end portion of the longitudinal-torsion composite vibrator 1 on the rotor 4 pressure contact side. A composite vibration that is a combination of the stretching vibration due to is excited. Therefore, when the rotor 4 is pressed against this end, the composite vibration is converted into rotation of the rotor 4. The rotation direction of the rotor 4 can be changed by changing the phase of the torsional vibration driving voltage or the phase of the longitudinal vibration driving voltage by 180 °.

[0009]

As described above, in the ultrasonic motor of the present invention, the shape of the piezoelectric vibrator for generating the driving force is simple, and it is easy to use the press molding technique which is generally applied. Piezoelectric torsional oscillators and piezoelectric longitudinal oscillators can be obtained by using piezoelectric ceramic hollow cylinders that can be manufactured and by applying electrode printing, which is also a general technique, to the outer peripheral surface of the cylinders. Therefore, an ultrasonic motor with less variation in characteristics due to the bonding process and complicated processing process can be obtained, and its practical value is really great. Furthermore, in the ultrasonic motor of the present invention, the vertical
Since the torsion composite oscillator has a cylindrical shape, it is possible to provide an ultrasonic motor having a small diameter.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structural example of a vertical-torsion ultrasonic motor of the present invention.

FIG. 2 is a perspective view showing a configuration example of a vertical-torsion composite vibrator used in the vertical-torsion composite vibrator pressure contact type ultrasonic motor of FIG.

FIG. 3 is an exploded perspective view showing the structure of a conventional ultrasonic motor.

FIG. 4 is an exploded perspective view schematically showing the structure of the ultrasonic motor shown in FIG.

[Explanation of symbols]

 1 Vertical-Torsion Composite Oscillator 1'Piezoelectric Ceramic Hollow Cylinder 2 Fixed Base 3 Bearing 4 Rotor 10 Torsional Vibration Part 11a First Oblique Electrode 12a Second Oblique Electrode 11 First Oblique Interdigitated Finger Electrode 12 Second Oblique Intersection Finger electrode 20 Longitudinal vibrating part 21a First peripheral electrode 22a First peripheral electrode 21 First vertical crossing finger electrode 22 Second vertical crossing finger electrode 22c Second connection electrode 106 Metal disk 107 Piezoelectric ceramic disk 108 Piezoelectric ceramic disc 109 rotor

Claims (1)

Claim: What is claimed is: 1. A pair of interdigital electrodes for polarization and driving, which extend in a direction of 45 ° with respect to the lengthwise direction, are provided on an outer peripheral surface of the piezoelectric ceramic hollow cylinder approximately half the lengthwise direction. A torsional vibrating portion which applies torsional vibration to the piezoelectric ceramic cylinder, and a circumferential or longitudinal direction adjacent to the torsional vibrating portion on the outer peripheral surface of the remaining approximately half of the length of the piezoelectric ceramic hollow cylinder. A piezoelectric longitudinal-torsion composite oscillator having a pair of interdigitated electrodes for polarization and driving extending in parallel, and a longitudinal vibrating portion for longitudinally vibrating the piezoelectric ceramic hollow cylinder, and one end of which is fixed, An ultrasonic motor, comprising: a rotatably supported rotor that is pressed against the other end of the piezoelectric vertical-torsion composite oscillator.