JPS63283477A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To reduce loss accompanying driving, by providing predetermined slits on the elastic body of an oscillating body radially at equal intervals. CONSTITUTION:The oscillating body 9 of an ultrasonic motor is constituted by bonding a piezoelectric body of an annular piezoelectric ceramics 8 to one of the main surfaces of an annular elastic body 7. Further slits 10 having a given width are formed on the other main surface of the elastic body 7. The bending rigidity in the traveling direction of bending oscillation is reduced in appearance by the slits 10. A moving body 13 is constituted by bonding the friction member 11 of an abrasion resistant material to an elastic body 12. The moving body 13 is pushed to come into contact with the oscillation body 9 by pressure through the friction member 11. According to this constitution, a traveling wave is excited in the oscillating body 9 and the moving body 13 rotates when electric field is impressed on the piezoelectric body 8. Further, an ideal traveling wave may be obtained when the number of the slits 10 is the integral multiplies of four (4) per one wave length of the traveling wave of the circumferential bending oscillation.

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.

BACKGROUND OF THE INVENTION In recent years, ultrasonic motors have attracted attention, in which a vibrating body made of a piezoelectric material such as a piezoelectric ceramic is excited with elastic motion, and this is used as a driving force.

Hereinafter, the conventional technology of an ultrasonic motor will be explained with reference to the drawings.

FIG. 6 is a perspective view of a conventional toroidal ultrasonic motor, in which a vibrating body 3 is constructed by pasting a toroidal piezoelectric ceramic 2 as a piezoelectric body to one of the toric surfaces of a toroidal elastic body 1. There is.

Reference numeral 4 indicates a friction material made of a wear-resistant material, and reference numeral 5 indicates an elastic body, which are pasted together to form a moving body 6. The moving body 6 is in contact with the vibrating body 3 via the friction material 4. When an electric field is applied to the piezoelectric body 2, a traveling wave for bending and imaging is excited in the circumferential direction of the vibrating body 3, thereby driving the movable body 6. Note that the arrow in the figure indicates the rotation direction of the moving body 6.

FIG. 7 shows an example of the electrode structure of the piezoelectric ceramic 2 used in the ultrasonic motor of FIG. In the figure, nine elastic waves are placed in the circumferential direction. In the same figure,
A and B are electrode groups each consisting of a small area corresponding to one wavelength of 25), C is an electrode with a length of three-quarters of a wavelength, and D is an electrode with a length of one-quarter of a wavelength. Electrodes C and D create a positional phase difference of 1/4 wave length (90 degrees) between electrode groups A and B.

Adjacent small electrode portions in electrodes A and B are polarized oppositely to each other in the thickness direction. The adhesive surface of the piezoelectric body 2 with the elastic body 1 is the opposite surface to the surface shown in FIG. 7, and the electrode is a solid electrode. During use, electrode groups A and B are short-circuited, as indicated by diagonal lines in the figure.

V t-Voxsin (ωt) at the electrodes A and B of the piezoelectric body 2 of the ultrasonic motor configured as above.
(1) V2-Vo×cos(ωt) −
--(2) However, if vo: instantaneous value of voltage ω; angular frequency t: voltages v1 and v2 expressed in time are applied,
The vibrating body 3 has ξ−ξox(cos(ωt)xcos(kx)+5in
(ωt)xsin(kx)) −ξ□ xcos(ωt−kx) −−−(
3) However, ξ: amplitude value of bending vibration ξ0: instantaneous value of bending vibration k: wave number (2π/λ) λ: wavelength

Fig. 8 shows that point A on the surface of the vibrating body 3 moves in an ellipse with a long axis 2W and a short axis 2u due to the excitation of the traveling wave, and the movable body 6 placed under pressure on the vibrating body 3 moves in an ellipse. The figure shows how the waves move at a speed of V-ωx14 in a direction opposite to the direction of wave travel due to frictional force due to contact near the apex.

Problems to be Solved by the Invention FIG. 9 shows the radial displacement distribution of the vibrating body of the annular ultrasonic motor. In order to increase the output of the ultrasonic motor,
The kinetic energy can be increased by increasing the displacement or mass of the vibrating body. Once the outer diameter of the vibrating body is determined, the inner diameter can be made as small as possible, the thickness can be increased, or the displacement can be increased. However, even if the inner diameter is made smaller, as the inner diameter becomes smaller, the amplitude value suddenly decreases as shown in FIG. 8, and even if the hole in the vibrating body is made smaller, the kinetic energy does not increase much. Then, increase the thickness (the bending rigidity of the vibrating body will increase and the displacement will increase ()).
I can't. Further, the upper limit of the increase in displacement is determined by the fracture limit. Therefore, there is a problem in that the conventional ultrasonic motor using annular bending imaging cannot increase its output.

The present invention has been made in view of these points, and an object of the present invention is to provide an ultrasonic motor that can increase output with the same volume and is highly efficient.

Means for solving the problem A piezoelectric body is formed by inserting slits with a width that is a multiple of 4 per wavelength of bending vibration at equal intervals in the radial direction in the elastic body that constitutes the vibrating body. Either a drive electrode is provided only in the vicinity of the slit, or a piezoelectric body is provided only in the vicinity of the slit, and drive signals time-divided according to the number of slits per wavelength of bending vibration are applied to the piezoelectric body.

By providing a working slit, the mass of the vibrating body can be increased without increasing the bending rigidity too much, and it is also possible to drive by providing a drive electrode only near the slit or a piezoelectric body only near the slit. As a result, loss associated with driving can be reduced.

EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cutaway perspective view showing the configuration of the ultrasonic motor of the present invention. A vibrating body 9 is constructed by bonding a toroidal piezoelectric ceramic 8 as a piezoelectric body to one of the main surfaces of the toroidal elastic body 7. Furthermore, a slit 10 having a constant width is formed on the other main surface of the elastic body 7. This slit 10
As a result, the apparent bending rigidity in the direction of upward bending vibration can be reduced. 11 is a friction material made of a wear-resistant material, and 12 is an elastic body, which are pasted together to form a moving body 13. The moving body 13 is in pressure contact with the vibrating body 9 via the friction material 11. When an electric field is applied to the piezoelectric body 8 and the piezoelectric body 8 is driven, a traveling wave of bending vibration is excited in the circumferential direction of the vibrating body 9, and the movable body 13 is driven by a frictional force, and the movable body 13 starts rotating.

If the number of slits is an integer multiple of 4 per wavelength of the traveling wave of bending vibration in the circumferential direction, and if they are placed at equal intervals in the radial direction, the positional relationship can be seen from either of the two standing waves that make up the traveling wave. are the same, and an ideal traveling wave is obtained.

FIG. 2 is a side view of the vibrating body 9 of one embodiment.

The thickness of the vibrating body 9 is greatly different between the part with the slit 10 and the part without the slit 10, so the bending rigidity is greatly different between the two parts, and most of the bending vibration is caused by the slit 10.
It is displaced in the part. The slit 10 formed in the radial direction of the elastic body 7 has a constant width. As a result, the drive at the slit section operates in the same way as a rectangular bonding element, and the mechanical loss is lower than in the case where the slits on the inner and outer peripheries can be regarded as equidistant fan-shaped bonding elements with different widths. Can be driven small.

Further, 14 in FIG. 2 is a drive electrode provided on the piezoelectric body 8. As mentioned above, the portion without the slit 10 has a large bending rigidity, so it can hardly be deformed, and even if this portion is driven, there will only be a loss. Therefore, the drive electrode 14 is provided only in the area where the slit 10 is inserted, so that it is driven only in the vicinity of the slit 10. This makes it possible to excite traveling waves with low loss.

FIG. 3 is a side view of another specific example of a vibrating body that is driven only in the vicinity of the slit. In the figure, in order to drive the vibrating body only in the vicinity of the slit 10, the piezoelectric body 15 is installed only in the vicinity of the slit 10.

FIG. 4 is a plan view of the piezoelectric body to show the driving method;
The shaded portions in the same figure may be regarded as drive electrode portions as shown in FIG. 2 or as piezoelectric body portions as shown in FIG. 3. In this example, nine wavelengths of bending vibration are excited in the circumferential direction, and eight slits are provided for each wavelength, for a total of 72 slits. Lead wires are taken out from each drive electrode, and drive signals numbered as shown in the figure are applied.

FIG. 5 is a timing chart of drive signals applied to each drive electrode shown in FIG. Numbers in both figures correspond to each other, and drive signals are applied to electrodes with the same number. The drive signal is obtained by dividing the drive wavelength into eight parts as described above. The drive signal can be easily obtained by inputting a frequency signal eight times the drive frequency to the shift register. When a drive signal is applied to each electrode, a traveling wave is synthesized on the vibrating body, and the moving body 1
Drive 3.

Effects of the Invention According to the present invention, it is possible to provide an ultrasonic motor that can increase the output per volume and is highly efficient.

[Brief explanation of the drawing]

FIG. 1 is a cutaway perspective view of an annular ultrasonic motor according to an embodiment of the present invention, FIG. 2 is a side view of a main part of a vibrating body according to the same embodiment, and FIG. 3 is a vibrating body according to another embodiment. 4 is a plan view of the piezoelectric body for explaining the driving method, 5 is a timing chart of the drive signal, and 6 is a cutaway perspective view of a conventional annular ultrasonic motor. Figure 7 is a plan view showing the shape and electrode structure of the piezoelectric body used in the ultrasonic motor in Figure 6, Figure 8 is an explanatory diagram of the operating principle of the ultrasonic motor, and Figure 9 is the bending of the vibrating body. It is a vibration state of vibration and a radial displacement distribution diagram. 7...Elastic body, 8...Piezoelectric body, 9...
... Vibrating body 10 ... Slit, 11 ...
...Friction material, 12...Elastic body, 13...
...Moving body, 14... Drive electrode, 15...
...Piezoelectric body. Name of agent: Patent attorney Toshio Nakao and 1 other person Figure 1 Figure 2 O Attack on Titan Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 3 of the moving body 7#1 ); wave difference Jtemanyo Figure 9 11

Claims (1)

[Claims] A piezoelectric body is driven by an alternating current voltage to excite an elastic traveling wave in a vibrating body composed of the piezoelectric body and an elastic body, thereby moving a movable body placed in contact with the vibrating body. In the sonic motor, an annular vibrating body is used as the vibrating body, a bending vibration is used as the traveling wave, and the elastic body constituting the vibrating body is provided with vibrations per wavelength of the bending vibration at equal intervals in the radial direction. Either a multiple of 4 slits with a constant width are provided and a drive electrode is provided only in the vicinity of the slit of the piezoelectric material, or the piezoelectric material is provided only in the vicinity of the slit, and the number of slits per wavelength of the bending vibration is An ultrasonic motor characterized in that the vibrating body is driven by applying a drive signal time-divided according to the number of slits to the piezoelectric body.