JPH0522962A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To reduce the diameter of a rotor while providing a small-sized ultrasonic motor having large torque. CONSTITUTION:A torsional vibrator 6 composed of a piezoelectric ceramic hollow column conducting torsional vibrations in the circumferential direction, longitudinal vibrators 8, 8' consisting of piezoelectric ceramic hollow columns having one end sections oppositely faced to one end sections of the torsional vibrator and performing stretching vibrations in the longitudinal direction and rotors 12, 12' interposed among the torsional vibrator 6 and the longitudinal vibrators 8, 8' and pressure-welded to one end sections of each vibrator are provided.

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, toys, etc., and more particularly to an ultrasonic motor having a large torque despite its small rotor diameter.

[0002]

2. Description of the Related Art Generally, ultrasonic motors have advantages such as high torque at low rotation, stop holding force, and small electromagnetic noise, as compared with electromagnetic motors. It is used for auto focus and power motors for automobiles.

FIG. 5 is a perspective view showing a structural example of a conventional ultrasonic motor. In FIG. 5, the piezoelectric torsion composite oscillator 1
01 and a piezoelectric vertical oscillator 102, and a vertical-twisted composite oscillator 1
Rotor 10 rotatably supported on one end surface of 03
4 are brought into pressure contact with each other.

FIG. 6 is a perspective view showing one structural example of the piezoelectric torsion composite oscillator 101 used in the ultrasonic motor of FIG. In FIG. 6, a plurality of fan-shaped piezoelectric ceramic plates 105 polarized in the direction of the chord are joined in a disk or ring shape so that the respective polarization directions are closed.

FIG. 7 is an explanatory view of the operation principle of the vertical-twist type ultrasonic motor. In FIG. 7, the vertical-torsion composite oscillator 1
The state of the torsional vibration displacement ξ of No. 03, the expansion and contraction displacement ξ ′ in the length direction, and the rotating state of the rotor 104 are shown. The direction of each displacement is point-symmetrical as shown in FIG. 7, and has a vibration mode that gradually increases as it moves to both ends.

[0006]

As can be seen from FIG. 6, in the conventional piezoelectric torsion composite oscillator 101, a plurality of fan-shaped piezoelectric ceramic plates 105 are adhered, which complicates the assembling process and causes the adhesion. There is a drawback that the variations in characteristics are large. Generally, in a cylindrical vibrator as shown in FIG. 5, since the resonance frequency of torsional vibration does not match the resonance frequency of longitudinal vibration, the longitudinal vibration is non-resonant even when driven at the resonance frequency of torsional vibration. It will be driven in the state of. Therefore, there is a drawback that the vibration amplitude of the longitudinal vibration becomes small and it is difficult to increase the torque of the ultrasonic motor.

Therefore, a technical object of the present invention is to provide an ultrasonic motor which can reduce the diameter of the rotor and is small in size and has a large torque.

[0008]

According to the present invention, there is provided a torsional oscillator made of a piezoelectric ceramic hollow cylinder that vibrates in a torsional direction in the circumferential direction, and has a long end having one end facing the one end of the torsional oscillator. A vertical oscillator including a piezoelectric ceramic hollow cylinder that performs stretching vibration in the vertical direction, and a rotor that is interposed between the torsional oscillator and the vertical oscillator and is pressed against one end of each oscillator are provided. A characteristic ultrasonic motor is obtained.

According to the present invention, in the ultrasonic motor, the other end of the longitudinal oscillator that faces the one end is fixed, and the torsional oscillator is supported by the node of the torsional vibration. A characteristic ultrasonic motor is obtained.

According to the present invention, in the ultrasonic motor, a shaft that penetrates the vertical vibrator, the torsional vibrator, and the rotor arranged between them in a straight line is provided, and the torsional vibrator is An ultrasonic motor is obtained in which the longitudinal oscillator is supported by a support ring, the other end of the vertical oscillator facing the one end is fixed to a fixing member, and is housed in the fixing frame.

According to the present invention, in the ultrasonic motor, the torsional longitudinal oscillator has an interdigitated finger extending on an outer peripheral surface of the piezoelectric ceramic hollow cylinder in a direction forming an angle of 45 ° with a longitudinal direction. An ultrasonic motor is obtained which is characterized in that electrodes are formed.

According to the present invention, in the ultrasonic motor, the longitudinal vibrator is provided with interdigital electrodes extending parallel to a longitudinal direction or a circumferential direction on an outer peripheral surface of the piezoelectric ceramic hollow cylinder. An ultrasonic motor characterized in that it is obtained.

[0013]

In the ultrasonic motor of the present invention, when the length of one of the longitudinal vibrators is increased in synchronization with the displacement of the torsional vibrator, the rotor interposed therebetween is sandwiched by the two vibrators and the torsional displacement is suppressed. Rotate in the direction. At this time, the other longitudinal oscillator is contracted, and if the direction of the torsional displacement is reversed, the length of the longitudinal oscillator increases in synchronization with the displacement of the torsional oscillator, and the rotor is in the same torsional displacement direction as the previous rotation direction. Rotate to.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic motor of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view showing an example of the configuration of the ultrasonic motor of the present invention. In FIG. 1, the ultrasonic motor is a so-called vertical vibrator torsional vibrator pressure contact type ultrasonic motor, and one end face of the vertical vibrator 8 is fixed to the fixed base 1.
Piezoelectric torsional vibrations in which two fixed ones (1 and 8's) (the other is 8 ') are made to face each other and the contact point of the torsional vibration is fixed by the support ring 10 between these end faces. The child 6 is configured to be sandwiched with the two rotors 12 and 12 'interposed therebetween. The rotors 12 and 12 'are rotatably supported between both end faces of the torsional oscillator 6 and the end faces of the piezoelectric vertical oscillators 8 and 8'.

A shaft 13 which rotates integrally with the rotors 12 and 12 'penetrates the inside of the piezoelectric ceramic hollow cylindrical vertical vibrator and the torsional vibrator and is entirely housed in a fixed frame 16, and at least one of the fixed frames 16 is fixed. The nut 15 is pressed from the end side via the disc spring 14.

FIG. 2 is a perspective view showing the torsional vibrator 6 used in the ultrasonic motor of FIG. In FIG. 2, every other diagonal electrodes 6a, 6b, ... Which extend in the direction of 45 ° with respect to the length direction of the cylinder are formed on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 7, and the conductivity of opposite end portions of the electrodes is formed. Are connected to the flexible connecting portions 26a and 26b to form two terminals and form diagonal finger electrodes. These electrodes are formed by the common method of printing electrodes on a piezoelectric ceramic hollow cylinder. When polarization treatment is performed using the oblique electrodes 6a and 6b, the polarization direction becomes a direction perpendicular to the length direction of the oblique electrodes 6a and 6b. When an alternating voltage is applied to the diagonal interdigital electrodes in the polarized state, when the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, extension strain occurs in the direction of the polarization, and the polarity of the voltage becomes the polarity at the time of polarization. In the opposite case, contraction strain occurs in the direction of polarization. When elongation or contraction strain occurs in the polarization direction, contraction or elongation strain occurs in the direction perpendicular to the polarization direction, opposite to these. Therefore, torsional displacement is generated in the piezoelectric ceramic hollow cylinder 7 such that both end surfaces rotate in opposite directions and are twisted.

FIG. 3 is a perspective view showing a structural example of one vertical vibrator 8 used in the ultrasonic motor of the present invention, and another vertical vibrator 8'has the same structure. The peripheral electrodes 8a, 8b ... Are formed parallel to each other on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 9 shown in FIG.
8a and another common part (not shown) to form two terminals, forming interdigital electrodes 17. When a polarization process is performed using this cross electrode 17, the polarization direction becomes a direction perpendicular to the length direction of the cross finger electrode 17. When an AC voltage is applied to the interdigital electrode 17 in this state, when 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 that during polarization. In this case, shrinkage strain occurs in the polarization direction. Therefore, the piezoelectric ceramic hollow cylinder 9 expands and contracts in the length direction.

Returning to FIG. 1, when the length of the vertical vibrator 8 is increased in synchronization with the displacement of the torsional vibrator 6, the rotor 12 is twisted by being sandwiched between the end faces of the two vibrators 6 and 8. Rotate in the direction of displacement. At this time, the other vertical vibrator 8'is contracted, and when the direction of the torsional displacement is reversed, the length of the vertical vibrator 8'is extended in synchronization with the displacement of the torsional vibrator 6 and the rotor 12 'is rotated in the previous rotational direction. Rotates in the same torsional displacement direction as. In this case, the rotation speed and the torque are determined by the magnitudes of the torsional vibration and the longitudinal vibration when the driving frequency is constant.

In the ultrasonic motor of the present invention shown in FIG. 1, since the torsional vibrator 6 and the vertical vibrator 8 (8 ') are independent of each other, the respective resonance frequencies are independent of the size of the respective vibrators. The resonance frequencies can be matched by adjusting to. Therefore, the torsional oscillator 6 and the longitudinal oscillator 8 (8 ') can be driven at their respective resonance frequencies, and the vibration amplitude of the torsional vibration and the vibration amplitude of the longitudinal vibration can be increased. Further, by driving the longitudinal vibration having a high resonance frequency with respect to the torsional vibration by ¼λ, a longitudinal oscillator having a resonance frequency that matches the resonance frequency of the torsional vibration can be formed with a size shorter than that of the torsional oscillator. The rotation direction of the rotors 12 and 12 'can be changed by changing either the phase of the torsional vibration driving voltage or the phase of the longitudinal vibration driving voltage by 180 °.

In the above embodiment of the present invention, the vertical oscillator 8
As the structure (8 '), the interdigital electrodes 8a, 8b, 8 are formed on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 9 in a direction parallel to the circumferential direction.
Although the case where c ... Is formed has been described, FIG.
As shown in FIG. 4, the piezoelectric ceramic hollow cylinder 40 may have a crossed electrode 18 formed on the outer peripheral surface thereof in a direction parallel to the lengthwise direction of the cylinder to form a vertical vibrator. Further, as shown in FIG. The same effect can be obtained as a piezoelectric vertical vibrator configured by forming electrodes on substantially the entire outer peripheral surface and inner peripheral surface of the piezoelectric ceramic hollow cylinder 40 '.

[0021]

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 generally used press molding technique. Piezoelectric torsional oscillators and piezoelectric longitudinal oscillators can be obtained by applying electrode printing, which is also a general technique, to the outer peripheral surface of a piezoelectric ceramic hollow cylinder that can be produced, and thus easy to produce. It is possible to provide an ultrasonic motor with less variation in characteristics due to the bonding process and the complicated processing process.

Furthermore, in the ultrasonic motor of the present invention,
Since it is possible to adjust the resonance frequencies of the piezoelectric torsional oscillator and the piezoelectric longitudinal oscillator individually to match them, it is possible to increase the respective vibration amplitudes. Therefore, an ultrasonic motor with large torque can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration example of a vertical oscillator torsional oscillator pressure contact type ultrasonic motor of the present invention.

FIG. 2 is a torsion oscillator 6 used in the ultrasonic motor of FIG.
FIG.

FIG. 3 is a longitudinal oscillator 8 used in the ultrasonic motor of FIG.
It is a perspective view showing (8 ').

FIGS. 4A and 4B are perspective views showing a structural example of another type of vertical oscillator used in the ultrasonic motor of the present invention.

FIG. 5 is a perspective view showing a structure of a conventional ultrasonic motor.

6 is a perspective view showing the structure of a piezoelectric torsion composite oscillator used in the ultrasonic motor of FIG.

FIG. 7 is an explanatory diagram of an operating principle of the vertical-torsion ultrasonic motor of FIG.

[Explanation of symbols]

6 Torsional oscillator 7 Piezoelectric ceramic hollow cylinder 8 Vertical oscillator 8'vertical oscillator 8a Circumferential electrode 8b peripheral electrode 8c peripheral electrode 8d peripheral electrode 8e peripheral electrode 8f peripheral electrode 8g peripheral electrode 8h peripheral electrode 10 Support ring 11 fixed base 11 'fixed base 12 rotor 12 'rotor, 13 shaft 14 Belleville 15 nuts 17 Interdigital electrodes 18 Interdigital electrodes 40 Piezoelectric ceramic 40 'piezoelectric ceramic 41a cross finger electrode 41b Interdigital electrode 41c cross finger electrode 41d cross finger electrode 101 Piezoelectric torsion composite oscillator 102 Piezoelectric vertical oscillator 102 'piezoelectric vertical oscillator 103 Vertical-torsion compound oscillator 104 rotor 105 fan-shaped piezoelectric ceramic plate

Claims (5)

[Claims] 1. A torsion oscillator formed of a piezoelectric ceramic hollow cylinder that oscillates torsionally in a circumferential direction, and a piezoelectric ceramic hollow that has one end opposite to one end of the torsion oscillator and performs stretching vibration in a longitudinal direction. An ultrasonic motor comprising: a vertical oscillator formed of a cylinder; and a rotor interposed between the torsional oscillator and the vertical oscillator and being in pressure contact with one end of each oscillator. 2. The ultrasonic motor according to claim 1, wherein the other end of the vertical oscillator which faces one end is fixed, and the torsional oscillator is supported by a node of torsional oscillation. And ultrasonic motor. 3. The ultrasonic motor according to claim 1, further comprising a shaft penetrating through the longitudinal oscillator, the torsional oscillator, and the rotor arranged between the longitudinal oscillator, the torsional oscillator, and the torsional oscillator. The ultrasonic motor is characterized in that it is supported by a support ring at one end, and the other end of the vertical oscillator facing the one end is fixed to a fixing member and housed in the fixing frame. 4. The ultrasonic motor according to claim 1, wherein the torsional longitudinal oscillator extends on the outer peripheral surface of the piezoelectric ceramic hollow cylinder in parallel with a direction forming an angle of 45 ° with respect to the longitudinal direction. An ultrasonic motor characterized by being formed with. 5. The ultrasonic motor according to claim 1, wherein the longitudinal vibrator has cross finger electrodes extending parallel to a lengthwise direction or a circumferential direction on an outer peripheral surface of the piezoelectric ceramic hollow cylinder. An ultrasonic motor characterized by the above.