JPH02266876A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To simplify the structure of an ultrasonic motor by employing a rod type elliptic motion vibrator and a vibration-rotation conversion member. CONSTITUTION:An ultrasonic motor is constituted of a piezo-electric elliptic motion vibrator 11', consisting of a piezo-electric ceramics column 11 and metallic rings connected to both terminals of the column 11, annular supporting frames 12, provided at the nodes of the vibration of the vibrator 11', and a cup type rotor 13, arranged with a vibration-rotation conversion member 13b and a driving shaft 13a. As a result, contact between the end of the vibrator 11' and the conversion member 13 comes on the same circumference with respect to the rotary shaft whereby a contacting area may be reduced and affection to the vibration may also be reduced.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a small motor used in electronic equipment, etc.
In particular, it relates to a small ultrasonic motor with a small rotor diameter.

(Conventional technology) Compared to conventional electromagnetic motors, ultrasonic motors can obtain high torque at low rotation speeds and have stopping power.
It has advantages such as low electromagnetic noise, and is used for camera autofocus, automobile power motors, etc.

FIGS. 7 and 8 are schematic diagrams showing the structure of a conventional ultrasonic motor, in which a metal disk 51 is provided with tooth-like protrusions on a ring, and the back side of the surface on which the protrusions are formed. It has a structure in which a disc-shaped rotor 54 is pressed onto a stator 51 having a structure in which two piezoelectric ceramic discs 52 and 53 are bonded together. The piezoelectric ceramic disks 52 and 53 are divided into even numbers with polarization directions opposite to each other in the thickness direction, and these two piezoelectric ceramic plates are adhered with an angle shifted by half the dividing angle.

(Problem to be Solved by the Invention) As shown in Figure 8, in conventional ultrasonic motors, two piezoelectric ceramic disks and a metal disk are bonded to form the stator. The disadvantages are that the process is difficult and the characteristics vary widely due to variations in bonding conditions. Furthermore, since the rotation axis of the rotor is provided at the center of the disk, it is necessary to increase the diameters of the stator and rotor. Therefore, the practical minimum diameter of conventional ultrasonic motors has been limited to 15 to 20 fins.

An object of the present invention is to provide an ultrasonic motor with a simple structure in which the diameter of the rotor is reduced and the number of bonding steps is reduced.

Another object of the present invention is to provide an ultrasonic motor with a rotor diameter of 15 degrees or less.

(Means for Solving the Problems) According to the present invention, a piezoelectric elliptical motion vibrator having an end portion that performs elliptical motion vibration, and a piezoelectric elliptical motion vibrator disposed in contact with the inner circumferential surface so as to cover the end portion, In an ultrasonic motor having a vibration-to-rotation conversion member that converts kinetic vibration into rotational movement around a rotational axis, the end portion is located on the same circumference with respect to the rotational axis on the inner circumferential surface. There is obtained an ultrasonic motor characterized in that it has a contact portion that contacts only a plurality of portions located in the inner peripheral surface, and that the contact area with respect to the inner circumferential surface is reduced.

(Function) In the ultrasonic motor of the present invention, a piezoelectric elliptical motion vibrator whose end face performs an elliptical motion including a circle is used, and the end of the piezoelectric elliptical motion vibrator and the inner circumferential surface of the vibration one-rotation conversion member are connected to each other. Since the contact is made at the contact portion that contacts only multiple parts located on the same circumference with respect to the rotation axis of the piezoelectric vibrator, the contact area with the inner peripheral surface of this vibration rotation conversion member is small (piezoelectric ellipse It is possible to obtain an ultrasonic motor that has less influence on the vibration of the motion vibrator and less changes in resonance frequency.

(Example) The ultrasonic motor of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an ultrasonic motor according to an embodiment of the present invention.

In FIG. 1, the ultrasonic motor includes a metal ring 10 or a metal disc 10' attached to both ends of a piezoelectric ceramic cylinder 11.
a piezoelectric elliptic motion vibrator 11' constructed by joining together, a ring-shaped support frame 12 provided at the vibration node of the piezoelectric elliptic motion vibrator 11', and a vibration one-rotation conversion member 13b;
It has a cup-shaped rotor 13 on which a drive shaft 13a is arranged.

FIG. 2 is a perspective view showing an example of the configuration of a piezoelectric elliptic motion vibrator 11' used in the ultrasonic motor of the present invention. In this figure, the piezoelectric ceramic cylinder 11 has electrodes 32, 34, 31.3 arranged parallel to its length at positions dividing the circumference into four.
3 is provided. On the other hand, this piezoelectric ceramic cylinder 1
A metal ring 10 or a metal disk 10= is provided at both ends of the metal ring 1.

FIG. 3 is a sectional view of the piezoelectric ceramic cylinder 11 used in the ultrasonic motor of the present invention, and FIG. 3(a) shows the electrode 32.
The direction of polarization when a voltage is applied with 34 set to (+) and electrodes 31 and 33 set to (-) is shown by a broken arrow 21.

FIG. 3(b) shows electrodes 33 and 34 (+) in a piezoelectric ceramic cylinder polarized as shown in FIG. 3(a).
1.32 is set to (-) and a voltage is applied as shown by a solid arrow 22, which shows the distortion in the cross section.

In FIG. 3(b), the voltage is applied to electrodes 34 to 31, electrode 3
3 to 32. For this purpose, the electrode 3 is placed along the circumferential surface of the piezoelectric ceramic cylinder 11 depending on the polarization direction.
The area between the electrodes 4 and 31 expands, and the area between the electrodes 33 and 32 contracts. As a result, as shown in FIG. 3(b), it is bent so that the lower side bulges in the length direction.

Furthermore, if the polarity of the applied voltage is reversed, the bending will also be reversed.

FIGS. 4(a) and 4(b) are explanatory diagrams of the vibration state when an alternating current voltage is applied to the piezoelectric ceramic cylinder 11. FIG.

When an AC voltage equal to the resonant frequency of the vibrator is applied between the electrodes 33, 34 and 31, 32, bending vibration is generated in the direction of the white arrow 23 as shown in FIG. 4(a). When electrodes 31, 34 and 32° 33 are connected and an alternating current voltage with a frequency equal to the resonant frequency of the vibrator is similarly applied, the direction of the bending vibration is perpendicular to the direction of the white arrow 23 in Fig. 4(a). direction.

Therefore, by shifting the phases of the bending vibrations in the above two directions by 90', specifically by shifting the phases of the applied voltages of each drive voltage by 90', the vibrations at both ends of the piezoelectric ceramic cylinder 11 are , it is possible to excite elliptical motion including circular motion as shown by arrow 24 in FIG. 4(b).

When actually constructing an ultrasonic motor, a metal ring 10 or a metal disk 10' is bonded to at least one end face of the piezoelectric ceramic cylinder 11 to improve the efficiency of contact with the rotor, and a piezoelectric elliptic motion vibrator is formed. 11' in many cases.

FIG. 5 is a perspective view showing an example of the shape of the end face of the piezoelectric elliptic motion vibrator 11' used in the ultrasonic motor of the present invention. A conical groove is formed along the length toward the center.

These minute protrusions and grooves may be provided on the metal cylinder or may be provided all the way to the piezoelectric ceramic inside the metal cylinder, in short, they are formed from the end surface of the piezoelectric elliptic motion vibrator 11' toward the center. That's fine.

FIG. 6 is a sectional view showing a state in which a cup-shaped roller 13 is combined with the end of the piezoelectric elliptic motion vibrator 11'.

As shown in FIG. 6, the inner wall surface of the cup-shaped roller 13 has an opening diameter slightly larger than the outer diameter of the end portion of the piezoelectric elliptic motion vibrator 11', and a bottom diameter that is slightly larger than the outer diameter of the end portion of the piezoelectric elliptic motion vibrator 11'. 11' is formed to be slightly smaller than the outer diameter of the end. The piezoelectric elliptical motion vibrator 11' and the vibration one-rotation conversion member 13b are pressed together in the axial direction 15.

When the piezoelectric elliptic motion vibrator 11' having the end face shape shown in FIG. 5 is used, only the conical minute protrusions 14 come into contact with the piezoelectric elliptic motion vibrator 11' and the cup-shaped roller 13. Therefore, compared to the case where the piezoelectric elliptical motion vibrator 11' is in contact with the entire circumference, the stiffness due to the contact is smaller, the load on the vibration of the piezoelectric elliptical motion vibrator 11' is lighter, and the deviation of the resonance frequency is reduced. Become.

Further, according to the present invention, the piezoelectric ceramic cylinder has a plurality of pairs of longitudinally parallel electrodes provided on the side surfaces of the piezoelectric ceramic cylinder or the piezoelectric ceramic vibrator, and the end face of the piezoelectric ceramic cylinder moves in an elliptical motion including a circle. Since an elliptical motion vibrator is used, the piezoelectric elliptical motion vibrator itself can be constructed without any bonding process, and therefore stable elliptical motion excitation with small variations in vibration characteristics is possible.

(Effects of the Invention) As shown above, in the ultrasonic motor of the present invention, the shape of the vibrator for generating driving force is simple, and the two vibration modes for generating rotational or elliptical vibration are the same. Since it is a bending mode, the structure is simple.

In addition, since a rod-shaped elliptical motion vibrator and a vibration one-rotation converting member are used, it is easy to reduce the rotor diameter, that is, the diameter of the vibration one-rotation converting member, and it is possible to obtain an ultrasonic motor with a small rotor diameter. can. The diameter of the motor varies depending on the required torque, but in principle 1
0m+e or less is also possible.

Furthermore, in the ultrasonic motor of the present invention, the end portion of the piezoelectric elliptical motion vibrator and the inner circumferential surface of the vibration one-rotation conversion member are in contact only at a plurality of portions located on the same circumference with respect to the rotation axis. The contact area is designed to have a small contact area with the inner circumferential surface, so it has less influence on the vibration of the piezoelectric elliptical vibrator, and has less change in the resonant frequency. A sonic motor is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an ultrasonic motor according to an embodiment of the present invention, FIG. 2 is a perspective view showing a piezoelectric elliptic motion vibrator used in the ultrasonic motor according to an embodiment of the present invention, and FIG. 4 is an explanatory diagram for explaining the operating principle of an elliptical motion vibrator using a cross-sectional view of a piezoelectric ceramic cylinder used in an ultrasonic motor according to an embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. FIG. 6 is a perspective view showing the end face shape of a piezoelectric elliptic motion vibrator used in an ultrasonic motor according to an embodiment of the present invention, and FIG. 7 and 8, which are cross-sectional views showing a combined state, are diagrams for explaining a structural example of a conventional ultrasonic motor. In the figure, 10 is a metal ring, 10' is a metal disk, 11 is a piezoelectric ceramic cylinder, 11' is a piezoelectric elliptical motion vibrator, 1
2 is a ring-shaped support frame, 13 is a cup-shaped roller 13a
is a drive shaft, 13b is a vibration one-rotation conversion member, 14 is a minute projection, 15 is a slit, 31, 32, 33, 34 is an electrode,
51 is a metal disk, and 52 and 53 are piezoelectric ceramic disks.

Claims (1)

[Claims] 1. A piezoelectric elliptical motion vibrator having an end portion that performs elliptical motion vibration, and a piezoelectric elliptical motion vibrator disposed in contact with the inner peripheral surface so as to cover the end portion, and converting the elliptic motion vibration into rotational motion around a rotation axis. In the ultrasonic motor having a conversion member, the end portion has a contact portion that contacts only a plurality of portions of the inner circumferential surface that are located on the same circumference with respect to the rotation shaft, and An ultrasonic motor characterized by having a small contact area with an inner peripheral surface.