JPS63240381A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To improve the efficiency and to increase the output of an ultrasonic motor by radially forming a slit having a constant width on an elastic unit which forms a circular vibrator. CONSTITUTION:An ultrasonic motor constructs a vibrator 9 by bonding a circular piezoelectric ceramic 8 as a piezoelectric element to one main surface of a circular elastic unit 7. A slit 10 having a constant width is composed on the other main surface of the unit 7. The bending rigidity of bending vibration advancing direction can be apparently reduced by the slit 10. A frictional material 11 of a wear resistant material and an elastic unit 12 are bonded to construct a moving body 13, and contacted under pressure with the vibrator 9. When an electric field is applied to the ceramics 8, a traveling wave is excited at the vibrator 9 to rotatably drive the body 13 by a frictional force.

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 vibrating body using a piezoelectric material such as a piezoelectric ceramic, and this vibration is used as a driving force.

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

FIG. 5 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 of bending vibration 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. 6 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 region corresponding to a half wavelength, C is an electrode group having a length of three-quarters of a wavelength, and D is an electrode having a length of a quarter of a wavelength. Electrodes C and D create a positional phase difference of 1/4 wavelength (=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. 6, 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 1−V ox sin(ωt) − at electrodes A and B of the piezoelectric body 2 of the ultrasonic motor configured as described above.
--(1) V2-Voxcos(ωt)
---(2) However, if vo: instantaneous value of voltage ω, diagonal frequency t: time, voltages v1 and v2 are respectively applied,
The vibrating body 3 has ξ−ξox(cos(ωt)xcos(kx)+5in
(ωt)xsin(kx)) −ξ o xcos(ωt−kx)
---(3) However, ξ: Amplitude value of bending vibration ξ0: Instantaneous value of bending vibration k: Wave number (2π/λ) λ: Wavelength Excited.

Fig. 7 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. This figure shows how the waves move at a speed of V-ωxu 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. 8 shows the radial displacement distribution of the vibrating body of the annular vibrating body 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 must be made as small as possible, the thickness must be increased, or the displacement must be increased. However, even if the inner diameter is made smaller, as the inner diameter becomes smaller, the As shown in the figure, the amplitude value suddenly decreases, and even if the hole in the vibrating body is made smaller, the kinetic energy does not increase much. (
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 bending vibration of an annular ring cannot increase its output.

The present invention has been made in view of this point, and an object of the present invention is to provide an ultrasonic motor that has the same volume and high output and is highly efficient.

Means for Solving the Problems A plurality of slits of constant width are made in the radial direction in the elastic body constituting the annular vibrating body, and the vibrator is driven only in the vicinity of the slits.

By keeping the width of the slit in the elastic body that makes up the annular vibrating body constant and driving it only in the vicinity of the slit, bending vibration can be excited efficiently, allowing a large displacement and reducing the mechanical strength of the vibrating body. It is possible to reduce loss, and as a result, realize a high-efficiency ultrasonic motor with a large output.

EXAMPLE Hereinafter, an example 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.

FIG. 2 is a side view of the vibrating body 9. The thickness of the vibrating body 9 is thicker (different) between the part with the slit 10 and the part without it, so the bending rigidity is greatly different between the two parts, and most of the bending imaging is caused by displacement in the part with the slit 10. The slit 10 made in the radial direction of the elastic body 7 has a constant width.As a result, the driving at the slit portion operates in the same way as a rectangular bonding element, and the inner and outer peripheries Drive with smaller mechanical loss can be achieved than in the case where the slits have different widths and can be regarded as equivalent fan-shaped bonding elements.

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 plan view of the elastic body 7 and piezoelectric body 8 that constitute the vibrating body 9 of one specific example that is driven only in the vicinity of the slit. Drive electrodes are formed on the piezoelectric body 8 to correspond to the slits in the elastic body 7. The back side of the piezoelectric body 8 is a solid electrode, and the symbol 10- in the figure indicates the direction of polarization. The elastic body 7 has eight slits each having a length equivalent to one wavelength. Therefore, four small electrodes correspond to one-half wavelength. small electrode,
If the wires are connected as shown in the figure, two drive electrode groups E and F can be formed which have different phases in position by an amount equivalent to a quarter wavelength. By applying two voltage sine waves and a cosine wave having temporally different phases by 90 degrees to this electrode group, a traveling wave of bending vibration can be excited in the vibrating body. Since the vibrating body is driven only in the vicinity of the slit, which handles most of the bending imaging, efficient driving is possible.

FIG. 4 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 provided only in the vicinity of the slit 10.

According to the present invention, it is possible to provide an ultrasonic motor that is efficient and has a large output.

Effects of the Invention According to the present invention, a slit with a constant width is provided in the radial direction in the elastic body constituting the annular vibrating body, and the vibrating body is driven only in the vicinity of the slit, thereby achieving high efficiency and output. We can provide large ultrasonic motors.

[Brief explanation of the drawing]

Fig. 1 is a cutaway perspective view of the annular ultrasonic motor of the present invention, Fig. 2 is a side view of the vibrating body that is driven only in the vicinity of the slit, and Fig. 3 is a plan view of the elastic body and the corresponding piezoelectric body. ,
Figure 4 is a side view of another vibrating body that is driven only in the vicinity of the slit, Figure 5 is a cutaway perspective view of a conventional annular ultrasonic motor, and Figure 6 is a vibrator used in the ultrasonic motor of Figure 5. FIG. 7 is a plan view showing the shape and electrode structure of the piezoelectric body, FIG. 7 is an explanatory diagram of the operating principle of the ultrasonic motor, and FIG. 8 is a diagram of the vibration state of the bending vibration of the vibrating body and the 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 one other person, Figure 1 Figure 3 Figure 4 [ ] /n Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] A superstructure that moves a moving body placed in contact with the vibrating body by driving a piezoelectric body with an alternating current voltage and exciting an elastic traveling wave in a vibrating body composed of the piezoelectric body and an elastic body. In the sonic motor, a ring-shaped vibrating body is used as the vibrating body, bending vibration is used as the traveling wave, and a plurality of slits having a constant width are provided in the radial direction in the elastic body constituting the vibrating body, An ultrasonic motor characterized in that it is driven only in the vicinity of the slit.