JPS62196085A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase mechanical output, by forming a driving unit in the shape of a disc, and by exciting the progressive wave of a bending oscillation mode tertiary or more in the peripheral direction and secondary in the diameter direction, on the driving unit. CONSTITUTION:The piezo-electric unit 7 of piezo-electric ceramics or the like for exciting the progressive wave of a bending oscillation mode tertiary or more in the peripheral direction and secondary in the diameter direction is put on an elastic unit 8, to compose a disc-formed driving unit 9. At the position of the nodal circle of the oscillation of the driving unit 9, a projection 10 is set, and via the projection 10, the driving unit 9 is positioned and fixed on a base 13. Sliders 14, 17 in contact with projections 11, 12 arranged near the outer periphery of the driving unit 9 and on the web of oscillation are put together with elastic units 15, 18 to compose moving units 16, 19. When voltage is applied to the piezo-electric unit 7, then the progressive wave of higher bending oscillation is excited on the driving unit 9, and the moving units 16, 19 are rotated with a rotary shaft 22 for the center.

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 elastic vibrations are excited in a drive body using a piezoelectric body such as a piezoelectric ceramic, and this vibration is used as a driving force.

The principle of the ultrasonic motor will be explained below with reference to the drawings.

Figure 3 shows an example of an ultrasonic motor, with an annular elastic body 1
An annular piezoelectric ceramic 2 is pasted on one of the annular surfaces of the
It constitutes a piezoelectric drive body 3. 4 is a slider made of a wear-resistant material, and 6 is an elastic body, which are pasted together to form the moving body 6. The moving body 6 is in contact with the driving body 3 via the slider 4.

When an electric field is applied to the piezoelectric ceramic 2, a traveling wave of bending vibration is excited in the circumferential direction of the driving body 3, thereby driving the moving body 6. Note that the arrow in the figure indicates the direction of rotation of the moving body 6.

FIG. 4 shows an example of the electrode structure of the piezoelectric ceramic 2 used in the ultrasonic motor of FIG. In the figure, nine waves of bending vibration are applied in the circumferential direction. In the same figure,
Person and B are electrode groups each consisting of a small region corresponding to a half wavelength, and C and D are electrodes having a length of three-quarter wavelength and one-quarter wavelength, respectively. Therefore, there is a phase shift of a quarter wavelength (=90 degrees) between the electrode group M and the electrode group B in the circumferential direction. Adjacent small electrode portions in electrode group B are polarized in mutually opposite directions in the thickness direction. The bonding surface of the piezoelectric ceramic 2 with the elastic body 1 is the surface opposite to the surface shown in FIG. 4, and the electrodes are solid electrodes. When in use, the electrode groups B are short-circuited as shown by diagonal lines in FIG. 4, and the solid electrode is used as a common electrode.

The operation of the ultrasonic motor configured as above will be explained below.A voltage V = V (1-5 in (wt)) applied to the electrode group of the piezoelectric body 2.
When −(1) is applied, the driving body 3 bends and vibrates in the circumferential direction. FIG. 5 is a perspective view of the driving body of the ultrasonic motor shown in FIG. 3 when approximated by a straight line. This shows what happens when voltage is applied.

FIG. 6 is an enlarged depiction of the contact situation between the moving body 6 and the driving body 3. vo@Sin on the electrode group part of the piezoelectric body 2
(W t ), and by applying Vo-cos (wt) voltages whose phases are shifted by π/2 from each other to the electrode group B, a traveling wave of bending vibration can be created in the circumferential direction of the driving body 3. Generally speaking, if the amplitude of a traveling wave is ξ, then ξ=ξ(1-cos
It can be expressed as (wt-kx) -=-(2). (2)
The formula is ξ=ξ0@(cos(wt)−cos(kx)+s
Rewrite it as in(wt)-8in(kx))-(3),
Equation (3) shows that the traveling waves are composed of waves cos (wt) and sin (wt) whose phase is temporally shifted by π/2, and oos (kx) and sin (kx) whose phase is shifted positionally by π/2.
It shows that it can be obtained by the sum of the respective products. From the above explanation, the piezoelectric bodies 2 are positioned at π/
The electrode group has a phase shift of 2 (=λ/4).

B, a traveling wave of bending vibration can be created in the driving body 3 by applying voltages with a phase difference of π/2 to each of the electrode groups.

Figure 6 shows that the surface entry point of the driving body 3 is moving in an ellipse with the long axis 2W and the short axis 2u due to the excitation of the traveling wave, and the moving body 6 placed on the driving body 3 is at the apex of the ellipse. The figure shows how the waves move at a speed of Ma = w * u in the opposite direction to the direction of wave travel. That is, the moving body 6 is pressed against the driving body 3 with an arbitrary static pressure, contacts the surface of the driving body 3, and is driven by the frictional force between the moving body 6 and the driving body 3 at a speed in the direction opposite to the direction of wave propagation. be done. When there is slippage between the two, the velocity will be smaller than the above Ma.

Problems to be Solved by the Invention FIG. 7 is a radial displacement distribution diagram of the annular moving body of a conventional ultrasonic motor. The speed of the ultrasonic motor is 7 = W* ucx: Weξo @h
,, mark, ,,, ←). Therefore, when using the third-order or higher-order bending vibration mode in the circumferential direction and the first-order bending vibration mode in the radial direction shown in FIG. 7, if the moving body is installed so as to be in contact with the vicinity of the outer circumferential portion, the velocity ma will increase. However, a toroidal moving body has a small volume within the same occupied space and a small mass, so the amount of energy stored therein is small and the mechanical output cannot be increased. Even if the width of the ring is widened to increase the mass,
In the above vibration mode, the amplitude at the inner circumference becomes smaller as the width becomes wider, and as a result, the stored energy cannot be increased that much.

Means for Solving the Problems In the present invention, a disk having a hole in the center or having no hole is used as the driving body, and the driving body is bent by three degrees or more in the circumferential direction and second degree in the radial direction. A moving body is placed in contact with at least the outer peripheral portion of the driving body by exciting vibrations.

Using a disk as the driving body, the third order or more in the circumferential direction and the second order in the radial direction
By exciting the next higher order bending vibration, the energy stored in the same occupied space is increased and the mechanical output is increased. In addition, at the outer periphery, even if the order of the circumferential diameter and the driving frequency are changed, the maximum amplitude point always comes, so the output can be stably obtained from the maximum amplitude point.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an ultrasonic motor according to an embodiment of the present invention. In the figure, 7 is a piezoelectric body such as a piezoelectric ceramic that excites traveling waves in the bending vibration mode of 3rd order in the circumferential direction and 2nd order in the radial direction in the disk-shaped drive body, and is attached to the elastic body 8 and is driven. constitutes a body 9. A protrusion 1° is installed at the nodal circle of vibration of the drive body 9, and the drive body 9 is fixed to the base 13 via the protrusion 1o. Numerals 11 and 12 are protrusions provided near the outer periphery of the driving body 9 and at the antinode of vibration, and are provided to extract mechanical output from the two locations mentioned above. Reference numeral 14 denotes a wear-resistant slider, which is placed in contact with the protrusion 11 and bonded to the elastic body 16 to form the moving body 16. 17 is also a wear-resistant slider, which is placed in contact with the protrusion 12, and which is attached to the elastic body 1.
8 to form a moving object 19. Moving objects 16 and 19
are attached to a rotating shaft 22 installed on the base 13 via bearings 20 and 21, respectively. When a voltage is applied to the piezoelectric body 7, a traveling wave of high-order bending vibration is excited in the driving body 9, and the moving bodies 16 and 19 rotate around the rotation axis 22.

FIG. 2 is a plan view showing the electrode structure of the piezoelectric body used in the above embodiment. In the figure, the back surface is a solid electrode used as a common electrode, and is the adhesive surface to the elastic body 8. Electrode A
', B' have a length corresponding to the intestine wavelength in the circumferential direction, and are composed of small electrode parts that are polarized in opposite directions in the thickness direction. It is shifted by π/2 due to the intense wavelength region D'. C' is a % area and is generated by setting area D'. A sine wave is applied to electrodes M' and B' respectively.

If a coS wave voltage is applied, according to equation (3), the circumferential direction 3
A traveling wave that moves in the circumferential direction of second-order bending vibration in the radial direction is excited. Although the third order in the circumferential direction is used in the above embodiment, any order greater than or equal to the third order is sufficient in view of the operating principle.

Note that the bending vibration mode can be selected by appropriately setting the external drive frequency in relation to the electrode configuration.

Fig. 8 is a perspective view and a radial displacement distribution diagram showing the vibration mode of the disc-shaped drive body. From the figure, the radial secondary vibration mode has one nodal circle and is located at the position of this nodal circle. A fixed dowel projection 10 is attached to the drive body 9. Further, in the embodiment, in order to increase the speed, protrusions 12.degree. 11 are added to the antinode of the vibration and near the outer periphery. The projection 11.12 allows the velocity (
(according to equation (4)) can be extracted as a mechanical output. Here, since the phases of the amplitudes at the positions of the protrusions 11 and 12 are opposite, the movable bodies 16 and 19 rotate in opposite directions. If the mechanical output is taken from the point where the amplitude value is equal, both speeds will be equal, and the protrusion 12 will be adjusted so that the product of the reciprocal of the radius and the amplitude value is equal.
If you choose the position of , you can match the rotation speed of both.

FIG. 9 is a plan view of the drive body 9, showing the protrusions 11 and 12 provided on the drive body. The protrusions 11 and 12 are made of s'J as shown in the figure, so as not to increase the bending rigidity in the circumferential direction.
) is included. The protrusions 11 and 12 take out the mechanical output at that position and also calculate the speed in the traveling direction (4)
It also serves to increase the distance of the equation.

In this embodiment, a disk having a hole in the center is used as the driving body, but the same effect can be obtained even if a disk without a hole is used. Further, as shown in FIG. 8, since there is no vibration near the center of the disk, it is possible to extend the rotation axis from the center of the drive body. Further, it can be similarly inferred that the mechanical output is extracted only from the outer circumferential portion.

As described in detail, in the present invention, the shape of the driving body is a disk, and the driving body is excited by exciting a traveling wave in a bending vibration mode of third order or higher order in the circumferential direction and second order in the radial direction. By increasing the energy stored in the body, mechanical output can be increased.
In addition, since the phase of vibration is different inside and outside the vibration nodal circle, by extracting mechanical output from near the outer periphery, a completely new motor that achieves the above effects and can obtain various rotations with one drive body. can be realized.

[Brief explanation of drawings]

Fig. 1 is a sectional view of an ultrasonic motor according to an embodiment of the present invention, Fig. 2 is a plan view of a piezoelectric body used in the embodiment of Fig. 1, and Fig. 3 is a cutaway perspective view of a conventional ultrasonic motor. , Fig. 4 is a plan view of the piezoelectric body used in the ultrasonic motor of Fig. 3, Fig. 5 is a linear model diagram showing the vibration state of the driving body part of the ultrasonic motor, and Fig. 6 is an explanation of the principle of the ultrasonic motor. 7 is a diagram of the radial displacement distribution of the conventional annular drive body in the vibration state, and FIG.
The figure is a radial displacement distribution diagram of the vibration state of the disc-shaped moving body, and FIG. 9 is a plan view of the disc-shaped moving body. 7...Piezoelectric body, 8...Elastic body, 9...
...Driver, 10.11.12...Protrusion,
13...Base, 14°17...Slider, 15.18...Elastic body, 16°19...
...Moving object, 2o, 21...Bearing, 22
······Axis of rotation. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2D Figure 3 Figure 4 (cL) Figure 6 Figure 7 (1: Direction 1

Claims (1)

[Claims] In an ultrasonic motor that moves a moving body placed in contact with the driving body by exciting an elastic traveling wave in the driving body made of an elastic body and a piezoelectric body, a disk is used as the driving body, and the driving body Exciting third or higher order bending vibration modes in the circumferential direction and second order in the radial direction in the body as traveling waves, placing a moving body in contact with at least the vicinity of the outer periphery of the driving body, and moving the moving body. Features an ultrasonic motor.