JPH0226278A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To lengthen the lifetime of a motor and to improve its reliability either by keeping trapezoidal inclination to a projected body of an oscillating body in the circumferential direction or in the diametrical direction, or by keeping curvature to the contact surface of the projected body with the frictional material. CONSTITUTION:An oscillating body 22 of a disc type ultrasonic motor is composed of an elastic body 20 and a piezoelectric body 21. On this occasion, projected bodies 23 are provided to the oscillating body 22 which have trapezoidal inclinations in the circumferential direction. The width of the vertex of each trapezoidal projected body 23 therefore becomes narrow, so that the contact state of a friction material with the trapezoidal projected body 23 is always constant. There will be no scratch caught by the angles of the projected body 23 even in a low speed rotation and the motor can rotate stably. Flexural rigidity can also be reduced. By the way, a projected body 23 may have a trapezoidal inclination in the diametrical direction or may have a curvature to the contact surface with the friction material.

Description

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

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 the vibrations are used as a driving force.

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

FIG. 4 is a cutaway perspective view of an annular ultrasonic motor with primary order in the radial direction and tertiary or higher order in the circumferential direction. are doing. 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. 5 shows an example of the electrode structure of the piezoelectric body 2 used in the ultrasonic motor of FIG. In the figure, nine elastic waves are placed in the circumferential direction. A and B are each 2
This is an electrode group consisting of a small region corresponding to one-quarter wavelength, where C is an electrode corresponding to three-quarter wavelength and D is an electrode corresponding to one-quarter wavelength. Electrodes C and D are positionally 1/4 wave longer than electrode groups A and B =
This is provided to create a phase difference of 90 degrees. Electrodes A and B
Adjacent small electrode portions within the electrode are polarized in opposite directions 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. 5, 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) -- to the electrodes A and B of the piezoelectric body 2 of the ultrasonic motor configured as above.
-(1)V2-V○xcos(ωt)---(2) However, vo: Instantaneous value of voltage ω: Angular frequency t: If voltages v1 and v2 expressed in time are respectively applied,
The vibration body 3 has ξ−ξo×(cos(ωt)xcos(kx)+5i
n(ωt)xsin(kx)) −vo xcos(ωt−kx) ---
(3) where ξ: amplitude value of bending vibration ξ0: instantaneous value of bending vibration k: wave number (2π/λ) λ: wavelength .

FIG. 6 shows that point A on the surface of the vibrating body 3 moves in an ellipse with the long axis 2w and the 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-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 mechanical output, the displacement component U in the traveling direction of the vibrating body should be made thicker.For this purpose, as shown in FIG. 7, a columnar protrusion 7 is provided on the vibrator. 7
As a result, the component U in the traveling direction due to bending vibration is expanded, so that the mechanical output can be increased.

FIG. 8 is a cutaway perspective view of a disc-shaped ultrasonic motor using a bending imaging mode of 2nd order in the radial direction, 3rd order or more in the circumferential direction. A vibrating body 10 is constructed by bonding a disk-shaped piezoelectric body 9 to a disk-shaped elastic body 8. 11 is a friction material made of wear-resistant material; 1
Reference numeral 2 denotes an elastic body, which is pasted together to form the movable body 13.

The movable body 13 is in pressure contact with a columnar protrusion 15 provided on the vibrating body 10 via the friction material 11 .

When an electric field is applied to the piezoelectric body 9, a traveling wave of bending vibration is excited in the circumferential direction of the vibrating body 10, and the movable body 13 rotates about the rotation axis 14.

FIG. 9 is a diagram showing the vibration state of the vibrating body 10 of the disc-shaped ultrasonic motor and the photographed displacement distribution in the radial direction. In order to obtain a large mechanical output, it is sufficient to extract the output from a location where the displacement is large, so a columnar protrusion 15 is provided at the point of maximum displacement.

FIG. 10 is a model diagram of the operation of the ultrasonic motor in the vicinity of the columnar protrusion 16. The tip of the columnar protrusion 16 is the friction material 1
7 and drives the moving body 18 by frictional force. The contact surface of the tip of the columnar protrusion 16 is not always parallel to the friction material 17 (it comes into contact with it from its corner, but the contact surface of the columnar protrusion 16
The contact between the friction material 17 and the circumferential width 18 of the protrusion 16
has a considerable value (e.g. 2-5 mm), so
It's not always in a constant state. Furthermore, if the contact surface of the columnar protrusion 16 has protruding corners or burrs, the friction material 17 will come into contact with the corner of the protrusion 16 at a certain moment.
There are problems in that the contact area may be mechanically damaged or the contact area may become small, resulting in inefficient power transmission.

In addition, since the contact state between the columnar protrusion 16 and the friction material 17 is not constant, the influence is greater during low speed rotation (,
There is a problem that the characteristics become unstable.

Problems to be Solved by the Invention In conventional ultrasonic motors, the mechanical output is extracted using the columnar protrusions 16, so the contact state cannot be kept constant, which may damage the friction material 17 or reduce the efficiency of power transmission. (There is a problem that the output efficiency is low.

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 has a large output, high efficiency, long life, and high reliability.

Means for Solving the Problem A trapezoidal protrusion is provided in the circumferential direction on the contact surface of the vibrating body with the movable body, and the movable body placed in contact with the contact surface is driven.

Function By configuring as described above, the contact state is kept constant, the friction material is not mechanically damaged, and it is efficient (the vibration of the vibrating body can be transmitted to the moving body, allowing low-speed rotation This makes it possible to realize an ultrasonic motor that is stable, has a large output, is highly efficient, has a long life, and is highly reliable.

Embodiments Embodiment 1 Hereinafter, embodiment ff1l1 of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a vibrating body of a disc-shaped ultrasonic motor of the present invention. In the figure, an elastic body 20 and a piezoelectric body 21 constitute a vibrating body 22. 23 is a protrusion provided on the vibrating body 22 and having a trapezoidal slope in the circumferential direction. Therefore, the width of the apex of the trapezoidal protrusion 23 becomes narrower, and the friction material 1
The contact state between the trapezoidal protrusion 23 and the trapezoidal protrusion 7 is always constant, and even when rotating at low speed, there is no catch by the corners of the protrusion 23 (stable rotation is possible.
3, the bending rigidity can be reduced (as a result, the velocity component U in the traveling direction due to bending vibration can be expanded, so a large mechanical output can be obtained.Furthermore, at the corner of the protrusion 23, the friction material 1
7 will not be mechanically damaged. Further, although not described in detail here, the same applies to the annular ultrasonic motor.

Example 2 Example 2 of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a perspective view of the vibrating body of the disc-shaped ultrasonic motor of the present invention. In the figure, the difference from Example 1 is that the protrusion 24 having a trapezoidal slope in the circumferential direction is also provided with a trapezoidal slope in the radial direction. This further stabilizes the characteristics by keeping constant the uneven contact state in the radial direction between the friction material 17 and the protrusion 24 due to static deflection that occurs in the vibrating body 22 during processing or piezoelectric bonding. This is something that can be achieved.

Example 3 Hereinafter, Example 3 of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a perspective view of the vibrating body of the disc-shaped ultrasonic motor of the present invention. In the figure, an elastic body 20 and a piezoelectric body 21 constitute a vibrating body 22. And the friction material 1 of the protrusion
A protrusion 25 having a curvature smaller than 1/2 wavelength of the elastic vibration of the vibrating body 22 is provided on the surface in contact with the vibrating body 7 .

As a result, the friction material and the protrusion 25 with curvature are always located at one point.
contact, the influence of the initial deflection of the vibrating body and the friction material 17
It is almost unaffected by the surface accuracy of the surface, and stable characteristics can be changed. Furthermore, the friction material 17 is not damaged and its life can be extended.

Here, we have described the protrusion 23 having a trapezoidal inclination in the circumferential direction with a curvature, but the shape of the protrusion is not limited to this. It goes without saying that the body 24 may be used (and it goes without saying that it may also have curvature in the radial direction at the same time).

Effects of the Invention In the present invention, the bending rigidity can be reduced by giving the protrusions of the vibrating body a trapezoidal inclination in the circumferential or radial direction, and by giving the protrusions a curvature to the surface in contact with the friction material. At the same time, since the contact state can always be kept constant, vibrations can be efficiently transmitted to the moving object, resulting in large output and high efficiency, as well as a long life by minimizing mechanical damage to the friction material. This makes it possible to provide a highly reliable ultrasonic motor that rotates stably even at low speeds.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a vibrating body of a disc-shaped ultrasonic motor in an embodiment of the present invention, and FIG. 2 is a perspective view of a vibrating body of a disc-shaped ultrasonic motor in a second embodiment of the present invention. FIG. 3 is a perspective view of a vibrating body of a disc-shaped ultrasonic motor according to a third embodiment of the present invention, FIG. 4 is a cutaway perspective view of a conventional annular ultrasonic motor, and FIG. A plan view showing the shape and electrode structure of the piezoelectric body used in the ultrasonic motor, Fig. 6 is an explanatory diagram of the operating principle of the ultrasonic motor, and Fig. 7 shows an annular ultrasonic motor with protrusions on the vibrating body. 8 is a cutaway perspective view of a conventional disk-shaped ultrasonic motor, FIG. 9 is a radial displacement distribution diagram of a disk-shaped vibrating body, and FIG. 10 is a cutout perspective view of a conventional disc-shaped ultrasonic motor. FIG. 3 is a model diagram of the operation of a sonic motor. 20...Elastic body, 21...Piezoelectric body, 2
2... Vibrating body, 23... Protrusion body having a trapezoidal inclination in the circumferential direction 24... Protrusion body having a trapezoidal inclination also in the radial direction, 25. ...Protrusion with curvature. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1 Figure 2 Figure 25 Protrusion with a base and mark Figure Figure Figure Figure Figure C

Claims (3)

[Claims] (1) 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, a moving body placed in contact with the vibrating body can be moved. In the ultrasonic motor for moving, a trapezoidal protrusion is provided in the circumferential direction on a contact surface side of the vibrating body with the movable body, and the movable body installed in contact with the protrusion is driven. Features an ultrasonic motor. (2) The ultrasonic motor according to claim 1, characterized in that the trapezoidal protrusion in the circumferential direction is further provided with a trapezoidal inclination in the radial direction. (3) 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, a moving body placed in contact with the vibrating body can be moved. In the ultrasonic motor for moving, a protrusion is provided on the side of the contact surface of the vibrating body with the movable body, and the surface of the protrusion has a curvature on the side of the contact surface with the movable body. sonic motor.