JPH01311878A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase the mechanical output of an ultrasonic motor and to stably enhance its efficiency by employing as a vibration mode a radial secondary, circumferential tertiary or higher order bending vibrations. CONSTITUTION:In an ultrasonic motor, a groove 15 is formed to a neutral plane 14 near the nodal circular part 21 of a vibrator 9, and the vibrator 9 is supported fixedly by a base 17 having a protrusion 16 to be engaged with the groove 15. Further, a moving element 13 is attached to the lower part of the base 17 through a bearing, and brought into pressure contact with the vibrator 9 by means of a leaf spring 19 and a pressure regulator 20. A disclike vibrator is employed as the vibrator 9, and radial secondary, circumferential tertiary or higher order, e.g., quaternary bending vibration is employed as its vibration mode. Thus, the inside of the vibrator 9 contributes to an effective kinetic energy thereby to increase its output.

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. 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 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. 7, and the electrode is a solid electrode. During use, electrode groups A and B are short-circuited, as indicated by diagonal lines in FIG. 7.

The electrodes A and B of the piezoelectric body 2 of the ultrasonic motor configured as described above have V+-Vo x 5 in (ωt)---(1) V2-Vox
eos(ωt) ---(2) However,
vo: instantaneous value of voltage ω・angular frequency t: voltage V expressed in time; and if v2 are applied respectively,
The vibration body 3 has ξ−ξox(eos(ωt)xcos(kx)+5
in(ωt)x sin(kx)) −ξ oxeos(ωt, −kx)
--- (3) where ξ: amplitude value of bending vibration ξ0: instantaneous value of bending vibration k: wave number (2π/λ) λ: wavelength Excited.

Figure 8 shows that point A on the surface of the vibrating body 3 moves in an ellipse with major axis 2w and minor 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-ωX11 in the direction opposite to the direction of wave propagation due to frictional force due to contact near the apex.

In order to increase the output of an ultrasonic motor, the kinetic energy of the vibrating body should be increased. Kinetic energy is proportional to the square of the mass and velocity of the vibrating body, so
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 made smaller to increase the mass, and the amplitude of the vibration can be increased to increase the speed. However, the amplitude of vibration is limited by the allowable strain of the piezoelectric body. In addition, since conventional ultrasonic motors use circular bending vibration of the first order in the radial direction and the third order in the circumferential direction, the amplitude value suddenly decreases near the inner circumference, as shown in Figure 9. Even if the hole in the vibrating body is made small, the kinetic energy does not increase very much.Therefore, conventional ultrasonic motors that use circular bending vibrations of the first order in the radial direction and the third order in the circumferential direction have a lower output. The problem is that it is not possible to increase the

In addition, since the vibrating body of an annular ultrasonic motor vibrates entirely as shown in Figure 9, it is difficult to fix the vibrating body in position, and mechanical output loss due to fixed support is unavoidable. .

Problems to be Solved by the Invention Conventionally, ultrasonic motors that use annular bending vibrations of first order in the radial direction, third order in the circumferential direction or more have a large output (not possible, and mechanical There is a problem that efficiency decreases due to output loss.

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 the output with the same volume and reduce mechanical output loss due to support and fixation.

A solution to the problem is to use a disc-shaped vibrator as the vibrator, use bending vibrations of 2nd order in the radial direction, 3rd order or higher in the circumferential direction as the vibration mode, and use a neutral surface near the nodal part of the vibrator. Then, a base having a convex portion for fixing the position of the vibrating body is provided.

By using a disk-shaped vibrating body as the working vibrating body and using bending vibration of 2nd order in the radial direction, 3rd order or more in the circumferential direction as the vibration mode, even the inversion of the photographing body can be effectively converted into kinetic energy of the vibrating body. At the same time, by supporting and fixing the vibrating body on a neutral surface near the nodal part where the vibrating body does not vibrate, the mechanical output loss due to fixation is reduced and the system is stable and efficient. A sound wave motor can be realized.

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

Embodiment 1 Embodiment 1 aims to support and fix a vibrating body to realize a stable and efficient ultrasonic motor.

FIG. 1 is a cross-sectional view of Embodiment 1 of the ultrasonic motor of the present invention, and FIG. 2 shows the photographed displacement state of the vibrating body 9 when radial second-order and circumferential fourth-order bending vibrations are excited. It is a figure showing displacement distribution. In the same figure, the inside 21 of the part is shown at a non-reduced plate thickness (hereinafter referred to as a neutral surface). As shown in FIG.
The vibrating body 9 is supported and fixed on a base 17 having a convex portion 16 that fits into the groove 15. Furthermore, the movable body 13 is attached to the lower part of the base 17 via a bearing 18, and the movable body 13 is attached by a leaf spring 19 and a pressure adjustment tool 20.
is brought into pressure contact with the vibrating body 9.

FIG. 3 is a cutaway perspective view showing the configuration of the ultrasonic motor. A disk-shaped piezoelectric ceramic 8 as a piezoelectric body is bonded to one of the main surfaces of a disk-shaped elastic body 7 to form a moving body 9 . 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 motion 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 about the 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 the electrode groups E and F are short-circuited and voltages with temporally different phases of 90 degrees are applied between them and the solid electrodes on the back surface, bending vibrations of the second order in the radial direction and the fourth order in the circumferential direction are generated in the camera body 9. traveling waves are excited.

In addition, as shown in Figure 2, by exciting the radial second-order and circumferential fourth-order bending vibration modes, unlike the conventional annular ultrasonic motor that uses the radial first-order vibration mode,
Even in the inner circumference, the imaging displacement does not become suddenly smaller. Therefore, when the ultrasonic motor occupies the same volume, the kinetic energy of the vibrating body 9 can be made thicker than when using the first-order vibration mode in the radial direction. In addition, since the neutral surface 14 near the inside 21 of the unit is not capable of photographing in principle, by supporting and fixing the vibrating body 9 via the convex portion 16 of the base 17, the mechanical (Moreover, the stress concentration in the radial direction is alleviated by the grooves 15,
Vibration excitation is easy, stable and efficient (the moving body 13 can be driven).

According to the present invention, it is possible to provide an ultrasonic motor with stable motor characteristics, high efficiency, and high output.

Embodiment 2 Embodiment 2 aims at supporting and fixing a vibrating body to realize a stable and efficient ultrasonic motor.

FIG. 5 is a sectional view of a vibrating body and a base of a second embodiment of the ultrasonic motor of the present invention. In the figure, the interior 2 of the camera body 9
A groove 15 having a triangular or trapezoidal cross-sectional shape in the radial direction is provided near the neutral surface 14, and the vibrating body 9 is supported and fixed by a base 17 having a protrusion 16 having a triangular or trapezoidal cross-sectional shape that fits into the groove 15. It is structured like this.

According to the present invention, the contact area between the convex part and the vibrating body can be made as small as possible, so the inside of the part can be supported and fixed with a wire, and
The strength of the convex portion can also be ensured by making it triangular or trapezoidal. Therefore, since support can be provided only near the nodal portion, efficiency can be further improved.

Example 3 In Example 3, by supporting and fixing the vibrating body and the base,
The purpose is to prevent the generation of audible sounds.

Normally, the vibrating body has a high mechanical Q (low-cost Fe-based or stainless steel materials are used. Due to the vibration misalignment with the vibrating body, co-turbation is likely to occur and audible sound is likely to be generated.Therefore, the mechanical Q of the base material that supports and fixes the vibrating body is made sufficiently smaller than the mechanical Q of the vibrating body.
An ultrasonic motor that does not generate unnecessary audible sounds can be realized by using a highly rigid material such as ABS resin, fluoride resin, polystyrene resin, or the like.

According to the present invention, by making the mechanical Q of the base material that supports and fixes the vibrating body sufficiently smaller than the mechanical Q of the vibrating body material, an ultrasonic motor that rotates stably without generating audible noise can be achieved. Can be provided.

Effects of the Invention According to the present invention, the mechanical output is large by using bending vibration of the second order in the radial direction and the third order in the circumferential direction as the vibration mode, and the neutral surface near the nodal part where the vibrating body does not vibrate is By supporting and fixing with a base with convex parts, vibration displacement is not inhibited, and the grooves provided in the vibrating body alleviate stress concentration in the radial direction, providing a stable and efficient ultrasonic motor. can.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a disc-shaped ultrasonic motor according to an embodiment of the present invention, and Fig. 2 shows the vibration state of the vibrating body when radial secondary and circumferential tertiary bending vibrations are used as vibration modes. and a 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 sectional view of Example 2 of the disc-shaped ultrasonic motor of the present invention, FIG. 6 is a cutaway perspective view of the annular ultrasonic motor, and FIG. 7 is a piezoelectric diagram used in the ultrasonic motor of FIG. 6. A plan view showing the shape of the body and the electrode structure, Figure 8 is an explanatory diagram of the operating principle of the ultrasonic motor, and Figure 9 shows the vibration when using bending vibration of the first order in the radial direction and the eighth order in the circumferential direction as the vibration mode. It is a vibration state of the body and a displacement distribution diagram in the radial direction. 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... Protrusion, 17... Base, 1
8... Hair ring, 19... Leaf spring,
20... Pressure adjustment tool, 21... Inside the joint. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1, Figure 3 8 Figure 9

Claims (3)

[Claims] (1) Driving a piezoelectric body with an alternating current voltage to excite a traveling wave of bending vibration of second order in the radial direction, third order in the circumferential direction or higher in a disc-shaped vibrating 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, a groove is provided near the nodal part of the vibrating body,
An ultrasonic motor comprising a base having a convex portion for fixing the vibrating body near a neutral plane. (2) The ultrasonic motor according to claim 1, wherein the base having the convex portion and the groove provided near the nodal portion of the vibrating body have a triangular or trapezoidal cross-sectional shape. (3) The ultrasonic motor according to claim 1, wherein the base having the convex portion is made of a material whose mechanical Q is smaller than that of the vibrating body.