JPH02142366A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase the output by providing a groove near the nodal circle section of a disc-shaped oscillating body and by pressing an oscillation-proof material to the oscillating body for supporting with a spring. CONSTITUTION:In an ultrasonic motor a groove 15 is provided up to the neutral surface 14 near a nodal circle section 20 of an oscillating body 9. An oscillating- proof material 16 is provided to this groove 15 and with a diaphragm spring 17 fitted into the groove 15 the oscillating body 9 is supported and fixed. Under this spring 17 a moving body 13 is installed through a bearing 18 and with a pressure adjuster 19 the oscillation-proof material 16 is pressed to and brought into contact with the oscillating body 9. Stress concentration in the diametrical direction can thereby be moderated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to supporting and fixing an ultrasonic motor that generates driving force using a piezoelectric body.

BACKGROUND OF THE INVENTION In recent years, ultrasonic motors have attracted attention in which elastic imaging is excited in a vibrating body using a piezoelectric material such as a piezoelectric ceramic, 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. 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 moving 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. When in use, electrode groups A and B are short-circuited, as indicated by diagonal lines in FIG.

Vt-VoXsin(ωt) ---<
1) V2-Voxcos(ωt) --
-(2) However, if vo: instantaneous value of voltage ω: angular frequency t: voltage expressed in time, and v2 are applied, respectively,
The vibration body 3 has ξ−ξox(cos(ωt)×cos(kx)+5
in(ωt)xsin(kx)) −ξoxcos(ωt−kx) ---(3
) where ξ: amplitude value of bending imaging ξ0: instantaneous value of bending vibration k: wave number (2π/λ) λ: wavelength

FIG. 7 shows that point A on the surface of the photographing 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 photographing body 3 moves in an ellipse. This figure shows how the waves move at a speed of V-ω×u in the direction opposite to the direction of wave travel due to frictional force due to contact near the apex.

In order to increase the output of the ultrasonic motor, the kinetic energy of the vibrating body can be greatly shifted. Since kinetic energy is proportional to the square of the mass and speed of the vibrating body, the output can be increased by increasing the mass or speed of the vibrating body. Once the external shape of the ultrasonic motor is determined, the size of the hole in the vibrating body can be reduced to increase the mass (and the amplitude of the imaging can be increased to increase the speed. However, the allowable distortion of the piezoelectric body The amplitude of imaging is limited by , the amplitude value suddenly becomes small (becomes) near the inner circumference, and even if the hole in the object is made small, the kinetic energy does not become very large (does not become so large). Ultrasonic motors that use ring bending vibration have a problem in that they cannot produce large output.

Further, since the entire vibrating body of the annular ultrasonic motor is photographed as shown in FIG. 8, it is difficult to fix the position of the vibrating body. Further, by fixing the vibrating part, noise due to mechanical loss and vibration misalignment between the support material and the vibrating body cannot be avoided.

Problems to be Solved by the Invention Conventionally, ultrasonic motors that use circular bending imaging with primary radial direction, tertiary or higher circumferential direction cannot increase the output, and are fixed due to mechanical loss. Accordingly, there is a problem that efficiency decreases.

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

Means for Solving the Problem A piezoelectric body is driven with an alternating current voltage, and a traveling wave of bending vibration of second order in the radial direction, third order in the circumferential direction or more is generated in a disc-shaped moving body composed of the piezoelectric body and an elastic body. In an ultrasonic motor that moves a movable body placed in contact with the vibrating body by exciting the vibrating body, a groove is provided in the vicinity of the nodal part of the vibrating body, and a vibration-proofing material is installed in the groove. The vibrating body is fixed by pressurizing and supporting the vibration isolating material with a diaphragm spring.

By using a disk-shaped vibrating body as the moving body and using bending vibration of 2nd order in the radial direction, 3rd order or more in the circumferential direction as the vibration mode, the internal energy of the vibrating body can be effectively converted into kinetic energy of the vibrating body. By installing a vibration isolating material on the neutral surface near the nodal part where the vibrating body does not vibrate, and directly fixing the imaging body with a diaphragm spring through the vibration isolating material, Loss due to support and fixation can be reduced, the pressurizing mechanism can be simplified, and noise caused by unnecessary resonance can be prevented by the vibration isolating material, making it possible to realize a stable and efficient ultrasonic motor.

EXAMPLE Hereinafter, an example aimed at a stable and efficient support and pressurizing method of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the ultrasonic motor of the present invention. FIG. 2 is a diagram showing the vibration displacement state and displacement distribution of the vibrating body 9 when radial second order and circumferential direction fourth order bending vibrations are excited.

In the figure, a nodal portion 20 on the neutral surface 14 is shown. As shown in FIG. 1, a groove 15 is provided up to the neutral surface 14 in the vicinity of the nodal part 20 of the photographing body 9, a vibration isolating material 16 is installed in the groove 15, and a diaphragm spring 17 fitted in the groove 15 is attached to the photographing body 9.
is supported and fixed. Furthermore, the diaphragm spring 17
A moving body 13 is attached to the lower part of the moving body 9 via a bearing 18 , and the moving body 13 is pressed into contact with the moving body 9 by a pressure adjustment tool 19 .

FIG. 3 is a cutaway perspective view showing the configuration of the ultrasonic motor. A vibrating body 9 is constructed by pasting a disk-shaped piezoelectric ceramic 8 as a piezoelectric body to one of the main surfaces of the disk-shaped elastic body 7. Further, on the other main surface of the elastic body 7, a protrusion 10 for extracting mechanical output is formed. 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 includes the friction material 11
It is in pressurized contact with a protrusion 10 installed on the vibrating body 9 via. When an electric field is applied to the piezoelectric body 8, a traveling wave of bending vibration is excited in the circumferential direction of the moving body 9, and the movable body 13 is driven by a frictional force. The moving body 13 starts rotating around the central axis.

FIG. 4 is a plan view showing the electrode structure of the disc-shaped piezoelectric ceramic 8. As shown in FIG. In the figure, E and F are electrode groups each having a length equivalent to a half wavelength in the circumferential direction, and consisting of small electrode portions in which the polarization directions of adjacent electrode portions are opposite in the thickness direction. The electrode groups E and F have a phase of 4 in the circumferential direction.
They are configured to be shifted by an amount equivalent to one-tenth of a wavelength (90 degrees).

Therefore, if electrode groups E and F are short-circuited and voltages with a temporal phase difference of 90 degrees are applied between them and the solid electrodes on the back surface, the vibrating body 9 will be subjected to bending vibrations of second order in the radial direction and fourth order in the circumferential direction. traveling waves are excited.

In addition, as shown in Figure 2, by exciting bending vibrations in the 2nd order in the radial direction and the 4th order in the circumferential direction, unlike the conventional annular ultrasonic motor that uses the 1st order imaging mode in the radial direction, The vibration displacement at the periphery also suddenly becomes small (it does not become small). Therefore, when the ultrasonic motor occupies the same volume, the kinetic energy of the vibrating body 9 can be used more than when using the first-order vibration mode in the radial direction. It is possible to realize an ultrasonic motor that can increase the size of the motor and generate a large output.In addition, in principle, the neutral surface 14 near the nodal portion 20 does not vibrate, so it is possible to realize an ultrasonic motor that can generate a large output.
By directly supporting and fixing the vibrating body 9 with the diaphragm spring 17 via the diaphragm spring 17 and pressurizing it with the pressure adjustment tool 19, there is no mechanical loss caused by supporting and fixing the vibrating body, and the pressurizing mechanism can be simplified and vibration-proofing can be achieved. The material 16 absorbs the vibration misalignment between the imaging body 9 and the diaphragm spring 17 and prevents the generation of noise. Furthermore, the grooves 15 relieve stress concentration in the radial direction, making excitation for imaging easy and stable. Efficient (can drive the moving body 13).

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

Effects of the Invention According to the present invention, by using bending vibrations of 2nd order in the radial direction, 3rd order in the circumferential direction or higher as the imaging mode, the mechanical output is large, and the vibration is achieved in the vicinity of the nodal part of the imaging object where the vibration does not occur. By installing a vibration isolator on the surface of the camera and directly pressurizing and supporting the vibration isolator with a diaphragm spring, it does not impede the imaging displacement, simplifies the pressure mechanism, and prevents noise generation. Since stress concentration in the radial direction is alleviated by the grooves 15 provided in the vibrating body, a stable and efficient ultrasonic motor can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of one embodiment of the disc-shaped ultrasonic motor of the present invention, and Fig. 2 shows the vibration of the vibrating body when the vibration mode is 2nd order in the radial direction and 3rd order in the circumferential direction. Condition and radial displacement distribution diagram, Figure 3 is a cutaway perspective view to explain the operation of the disc-shaped ultrasonic motor, Figure 4 is a plan view of the piezoelectric ceramic used in the ultrasonic motor of Figure 1, Fig. 5 is a cutaway perspective view of the annular ultrasonic motor, Fig. 6 is a plan view showing the shape and electrode structure of the piezoelectric body used in the ultrasonic motor of Fig. 5, and Fig. 7 is the operation of the ultrasonic motor. FIG. 8, which is an explanatory diagram of the principle, is a vibration state and a radial displacement distribution diagram of the imaging body when bending vibration of first order in the radial direction and eighth order in the local direction is used as the imaging mode. 7...Elastic body, 8...Piezoelectric body, 9...
... Vibrating body 10 ... Protrusion, 11 ...
...Friction material, 12...Elastic body, 13...
- Moving body, 14... Neutral surface, 15...
Groove, 16... Damaging material, 17... Diaphragm spring, 18... Bearing, 19... Pressure adjustment tool, 20...・Inside the knot. Name of agent: Patent attorney Shigetaka Awano and 1 other list

Claims (1)

[Claims] By driving the piezoelectric body with an alternating current voltage and exciting a traveling wave of bending vibration of second order in the radial direction, third order in the circumferential direction or higher in the disc-shaped vibrating body composed of the piezoelectric body and the elastic body, In an ultrasonic motor that moves a movable body installed in contact with a vibrating body, a groove is provided near the nodal part of the vibrating body, a vibration isolating material is installed in the groove, and the vibration isolating material is connected with a diaphragm spring. An ultrasonic motor characterized in that the vibrating body is fixed by being supported under pressure.