JPS62193574A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase energy stored in a driving unit and increase mechanical output, by using a disc with a hole or a holeless disc for a driving unit, and by generating specified progressive wave on the driving unit. CONSTITUTION:An elastic unit 7 is bonded to a piezoelectric unit 8 to compose a driving unit. An abrasion-proof slider 11 is put on an elastic unit 12 to compose a mover 13. For the driving unit 14, a disc with a hole bored through the central section or a holeless disc is used. On the driving unit, the progressive waves of bending oscillation mode tertiary or more in the circumferential direction and secondary in the diameter direction are excited, and the mover set in contact with the upper section of the driving unit is moved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic motor that generates driving force using a piezoelectric material.

2. Description of the Related Art In recent years, ultrasonic motors have attracted attention, in which elastic vibrations are excited in a driving body using a piezoelectric body such as a piezoelectric ceramic, and this vibration is used as a driving force.

The principle of the ultrasonic motor will be explained below with reference to the drawings.

Figure 3 shows an example of an ultrasonic motor, with an annular elastic body 1
An annular piezoelectric ceramic 2 is pasted on one of the annular surfaces of the
It constitutes a piezoelectric drive body 3. 4 is a slider made of a wear-resistant material, and 6 is an elastic body, which are pasted together to form the moving body 6. The moving body 6 is in contact with the driving body 3 via the slider 4.

When an electric field is applied to the piezoelectric ceramic 2, a traveling wave of bending vibration is excited in the circumferential direction of the driving body 30, thereby driving the moving body 6. Note that the arrow in the figure indicates the direction of recirculation of the moving object 6.

FIG. 4 shows an example of the electrode structure of the RF electroceramic 2 used in the ultrasonic motor of FIG. In the figure, the bending vibration is applied in the circumferential direction at 9V. In the figure, A and B are electrode groups each consisting of a small region corresponding to a half wavelength, and C and D are electrodes having a length of three-quarter wavelength and a quarter wavelength, respectively. Therefore, there is a phase shift of a quarter wavelength (=90 degrees) between the electrode group of the person and the electrode group of B in the circumferential direction. Adjacent small electrode portions in electrode groups A and B are polarized in mutually opposite directions in the thickness direction. The bonding surface of the piezoelectric ceramic 2 with the elastic body 1 is the surface opposite to the surface shown in FIG. 4, and the electrode is a solid electrode. When in use, electrode groups A and B are short-circuited, as indicated by diagonal lines in FIG. 4, and the peta electrode is used as a common electrode.

The operation of the ultrasonic motor configured as above will be described below. Voltage V = VO-sin (wt) -=-(
When 1) is applied, the driver 3 performs bending motion in the circumferential direction. FIG. 5 is a perspective view of the drive body of the ultrasonic motor shown in FIG. 3 when it is approximated by a straight line. The situation when a voltage is applied to the piezoelectric body 2 is shown.

FIG. 6 is an enlarged depiction of the contact situation between the moving body 6 and the first driving body 3. Vo-sin is applied to the electrode group A of the piezoelectric body 2.
(wt), and Vg-cos (wt), which are mutually shifted in phase by π/1, are applied to the electrode group B.1, it is possible to create a traveling wave of bending vibration in the circumferential direction of the small moving body 3.

Generally speaking, if the amplitude of a traveling wave is ξ, then ξ=ξ(3-cos
(wt-kx) −・・・・ (Can be expressed as 2. (
2) The formula is ξ=ξO−(cos(wt) −cosQcx)+si
n (wt) −sin (kx) )・・・・・・
Equation (3) can be rewritten as (3), where the traveling wave is composed of waves cos(wt) and 5in (wt) whose phase is shifted by π/2 in time, and cos(wt) whose phase is shifted by π/2 in position. kx) and s
It shows that it can be obtained by the sum of the respective products with in (kx). From the above explanation, the piezoelectric body 2 is a group of electrodes whose phase is shifted from each other by π/2 (=λ/4).

B, a traveling wave of bending vibration can be created in the driving body 3 by applying voltages with a phase shift of π/2 to each of the polarization groups.

Figure 6 shows that the front entry point of moving body 3 is caused by the excitation of traveling waves.
It shows an elliptical motion with a long axis 2W and a short axis 2u,
It shows how the moving body 6 placed on the driving body 3 comes into contact with the ellipse at point m and moves at a speed of v=w−u in the opposite direction to the direction of wave propagation. That is, the moving body 6 is pressed against the driving body 3 with an arbitrary static pressure, contacts the surface of the sounding body 3, and is moved at a speed V in the direction opposite to the direction of wave propagation due to the frictional force between the moving body 6 and the driving body 3. Driven. When there is slippage between the two, the velocity will be smaller than the above V.

Problems to be Solved by the Invention The conventional ultrasonic motor described above, as shown in FIG. 7, uses a bending vibration mode of third or higher order in the circumferential direction and first order in the radial direction. FIG. 7 shows a bending vibration mode of ninth order in the circumferential direction and first order in the radial direction.

In this way, in the radial direction [first-order bending vibration mode], the amplitude ξG is maximum at the outer circumference. The speed V of the moving object 6 is V = W-u cc W-ξo-h −・
- Since it can be expressed as (4), the velocity V of the moving body 6 is maximum when it is placed in contact with the outer circumference. However, since such a vibration mode is a mode when the outer peripheral portion is a free end, it is difficult to design because the vibration mode changes when the moving body 6, which is a load, is placed in contact with it.

Further, in this mode, the smaller the width of the driving body 3, the more efficiently the driving can be performed, but when the width of the driving body 3 is made smaller, the mass of the driving body 3 decreases, and the energy that can be stored decreases.

Therefore, it is not possible to obtain a large output to the outside.

The present invention has been made in view of these points, and an object of the present invention is to provide an ultrasonic motor with a simple configuration, easy to design, and a large mechanical output.

Means for resolving the problem A circular disk with a hole in the center or a disk without a hole is adopted as the small moving body, and the driving body has three vibration modes in the circumferential direction.
A moving body placed in contact with a driving body is moved by exciting a traveling wave in a bending vibration mode of second or higher order in the radial direction.

By using a point other than near the outer periphery with the thickest amplitude of the traveling wave of 3rd order or higher order bending vibration in the circumferential direction and 2nd order or higher order in the radial direction excited in the action 111 body, it is also possible to use a driving body with or without a hole. By using a disc, the weight can be increased with the same volume, the energy stored in the drive body can be increased, and the drive body can be resistant to loads and has a high mechanical output. I will explain about it. FIG. 1 is a cutaway perspective view of an ultrasonic motor according to an embodiment of the present invention. In the figure, 01o, which is an elastic body and is bonded to the piezoelectric body 8 and constitutes the driving body 9, is a rotation axis and becomes the center of rotational movement. Reference numeral 11 denotes a slider made of a wear-resistant material, which is attached to the elastic body 12 to constitute a moving body 13. The moving body 13 is installed in contact with the driving body 9 via the slider 11. When an alternating voltage near the resonance of the piezoelectric 8vC sounding body 9 is applied, a traveling wave in a bending vibration mode is excited in the driving body 3, giving a lateral velocity to the slider 11, and the moving body 13 moves in the direction of the arrow in the figure. Rotate and move in the direction of.

FIG. 2 is a displacement distribution diagram of the driving body 3 of the ultrasonic motor of the embodiment shown in FIG. 1, in which a third-order vibration mode in the circumferential direction and a second-order vibration mode in the radial direction are used in the four south.

From the figure, the point of maximum amplitude is located at the radius rQO, and in FIG. 1, in order to maximize the rotational speed of the moving object 13, the slider 11 is brought into contact with this point to extract the mechanical output.

FIG. 8 shows the electrode structure of the piezoelectric body 9 of the embodiment shown in FIG. Electrode groups A and B consist of two electrodes having a circumferential length of half the length, polarized in opposite directions in the thickness direction, and are short-circuited when in use. Electrode C
, D are electrodes with a length of 1/4 length and 3/4 length in the circumferential direction, respectively, and the electrode group and B are shifted by 1/4 wavelength (π/2) in position. It is set up for the purpose. By applying sine wave and COS wave voltages to electrode groups B and B, respectively, a traveling wave of bending vibration can be excited.

However, with this electrode structure, third-order vibration modes in the circumferential direction and first-order vibration modes in the radial direction can also be excited. However, in the first-order mode in the radial direction, the amplitude decreases rapidly toward the center, so
The stored energy within the drive body is reduced. (This means that in the first-order radial imaging mode, the inside acts as a load on the outer circumference.) In the second-order radial vibration mode, the inside Since the amplitude can be increased, the energy stored in the driving body can be increased. Therefore, the external drive frequency must be set close to the resonance frequency of third-order bending vibration in the circumferential direction and second-order bending vibration in the radial direction. In other words, the higher-order mode is selected by selecting the external drive frequency.

Bending vibration modes of 3rd order or higher in the circumferential direction and 2nd or higher order in the radial direction can also be excited in the same manner. In the vibration mode described above, the maximum point of amplitude is no longer at the free end of the outer periphery, and therefore,
By extracting the mechanical output near the maximum amplitude point, the influence of the load on the driving body can be reduced. In addition, since the volume and mass can be made larger than the annular shape within the same space, a large amount of elastic energy can be fused into the driving body, and the mechanical output can be increased.

It should be noted that the disk to be used may have a hole in the upper middle portion or not, as long as it can be driven in a mode of second order or higher in the radial direction.

Effects of the Invention According to the present invention, it is possible to provide an ultrasonic motor that has a simple configuration, is less affected by load, and has a large mechanical output.

[Brief explanation of drawings]

FIG. 1 is a cutaway perspective view of an ultrasonic motor according to an embodiment of the present invention, FIG. 2 is a displacement distribution diagram of a driving body in the embodiment of FIG.
Fig. 3 is a cutaway perspective view of a conventional annular ultrasonic motor, Fig. 4 is a plan view showing the piezoelectric electrode structure used in the ultrasonic motor of Fig. 3, and Fig. 6 is an ultrasonic motor. Fig. 6 is a diagram explaining the principle of the ultrasonic motor, Figs. FIG. 3 is a plan view showing an electrode structure of a piezoelectric body used in an ultrasonic motor. 7...Elastic body, 8...Piezoelectric body, 9...
...Driver, 10...Rotation 11Ql+, 11
...Slider, 12...Elastic body, 13
...Moving body. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Section Figure 3 Figure 4 C Figure 5 Bay Figure 6

Claims (1)

[Claims] (1) In an ultrasonic motor that moves a moving body placed in contact with the driving body by exciting elastic traveling waves in the driving body made of an elastic body and a piezoelectric body, the shape of the driving body is circular. An ultrasonic motor having a plate shape, wherein the vibration mode of the elastic traveling wave is a third-order or higher-order vibration mode in the circumferential direction, and a second-order or higher-order bending vibration mode in the radial direction.