JPS62193569A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase the speed of a mover, by enlarging a distance between a neutral surface and a contact surface without preventing two standing waves composing an elastic progressive wave excited on a driving unit, from being excited. CONSTITUTION:A surface side in contact with the mover 6 of an elastic unit 1 composing a driving unit 3 is provided with a projection unit 7. The mover 6 is set in pressure contact with the tip of the projection unit 7 via a slider 4. When an alternating electric field near the resonance frequency of the driving unit 3 is applied to a piezo-electric ceramics 2, then the progressive wave of bending oscillation is excited on the driving unit 3, and the mover 6 is moved by the projection unit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic motor that generates all of its driving force using piezoelectric body sound.

BACKGROUND OF THE INVENTION In recent years, ultrasonic motors have been attracting attention, in which elastic vibrations are fully excited in a drive body using a piezoelectric material such as a piezoelectric ceramic, and this 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 an abrasion-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 a full 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 and drives the moving body 6 . Note that the arrow in the figure indicates the direction of rotational force 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 area corresponding to 1/2 wavelength, and C and D are electrodes having a length of 3/4 wavelength and 1/4 V length, respectively. Therefore, there is a phase difference n of a quarter wavelength (=90 degrees) in the circumferential direction between the electrode group of the person and the electrode group of B. Adjacent small electrode portions in electrode groups A and B are polarized in the thickness direction in opposite force directions. The adhesive surface of the piezoelectric ceramic 2 with the elastic body 1 is the surface opposite to the surface shown in FIG. 4, and the electrode is a solid electrode. When in use, the electrode groups A and B are short-circuited, as indicated by diagonal lines in FIG. 4, and the solid electrode is not used as a common electrode.

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

Is Fig. 6 the contact situation between the moving body 6 and the driving body 3? This is an enlarged drawing. Vo-sin is applied to the electrode group A of the piezoelectric body 2.
(ωt), the phase of the electrode group BVCvO-CO8(ωt) is π/2, and if the entire voltage is applied, a traveling wave of bending vibration can be created in the circumferential direction of the driving body 3. Generally speaking, if the total amplitude of a traveling wave is ξ, then ξ=ξo −co
It can be expressed as s (ωt −kx) ・−(2). (
2) The formula is ξ=ξO・(cas(ωt)・ccs(kX)+5i
Rewritten as n(ωt) ・sj++(kX)'''e3), Equation (3) is expressed as follows: The traveling wave has a temporal phase shift of π/2 between the chamber (ωt) and 5in (ωt), and a positional cos (kX) and sin (k
It shows that it can be obtained by the sum of the products of n and x). From the above explanation, the piezoelectric bodies 2 are positioned at π/
Electrodes with a phase difference of 2 (=λ/4).

Since it has Bi, if all voltages with a phase difference of π/2 are applied to each of the electrode groups, a traveling wave of bending vibration will be produced in the driving body 3.

Figure 6 shows that the surface 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 V=ω·U in the opposite direction to the direction of wave propagation. In other words, the moving body 6 is pressed against the driving body 3 with an arbitrary static pressure and comes into contact with the surface of the driving body 3, and the shore force between the moving body 6 and the driving body 3 causes a velocity machining in the direction opposite to the direction of wave propagation. is driven by. When there is a slippage between the two, the velocity is also smaller than the above v and J.

Problem to be solved by the invention The speed V of the moving body 6 is v=ωuoCωξoh...-(
4), which is proportional to the prefectural width value ξ0 of the driving body 3 and the distance. The maximum amplitude value ξ0 is determined by the allowable strain limit of the piezoelectric ceramic, and the distance is determined once the materials and thicknesses of the piezoelectric body 2 and elastic body 1 that make up the entire drive body 3 are determined.
The maximum speed of the moving object 6 is determined, and it is difficult to obtain a larger value than that.

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 simple configuration and can move a moving object θ at a high speed.

Means for Solving the Problem Avoiding the antinode positions of the two elastic standing waves constituting the elastic traveling wave excited by the driving body, 4 integer projections are formed per wavelength of the elastic traveling wave. The body is placed on the contact surface side of the elastic body constituting the driving body 3 with the moving body, and the moving body is pressurized so as to come into contact with the tip of the protrusion.

The speed of the moving body can be increased by increasing the distance between the neutral surface and the contact surface without interfering with the excitation of the two standing waves that make up the elastic traveling wave excited by the action driving body. .

Example Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cutaway perspective view of an ultrasonic motor according to an embodiment of the present invention. In the figure, 7 is a protrusion provided on the contact surface side of the elastic body 1 constituting the drive body 3 with the moving body 6;
The moving body 6 is placed in pressure contact with the tip of the protrusion 7 through the entire slider 4 . When an alternating electric field near the resonant frequency of the driving body 3 is applied to the piezoelectric ceramic 2, a traveling wave of bending vibration is excited in the driving body 3, and the eliminating body 6 is moved to the protrusion 7.

FIG. 2 is a cross-sectional view of the driving body 3 in FIG. 1 when it is straightened for explanation. In the figure, a voltage of ASG is applied to the electrode group B, and a voltage of ASG is applied to the electrode group B.
M' and B'' in the same figure are standing waves of bending vibration in the driving body 3.
Make each one. These two standing waves M' and B' are superimposed to form a traveling wave.

The neutral surface when there is no protrusion 7 is located at the position indicated by L in the figure, and the distance between the neutral surface and the contact surface with the moving body 6 is h. When the projections 7 are provided on the surface of the elastic body 1, the change in the position of the neutral surface is smaller than the change in the distance to the contact surface.

The position of the neutral surface after the protrusion 7 is installed is indicated by L', and the total distance from the neutral surface to the contact surface is indicated by h'. In other words, as the distance from the neutral surface of the piezoelectric ceramic 2 increases, the amplitude ξ0 becomes smaller at a strain rate within the allowable limit of the piezoelectric ceramic 2, since the effect of increasing the distance is large, so (4)
It can be seen that a large speed can be obtained using the formula.

The bending rigidity at the protrusion 7 is high, and the bending rigidity at the location without the protrusion 7 is small. Therefore, if the protrusion 7 comes to the position of the antinode of the two standing waves A' and B/ that form the traveling wave of bending vibration, this position is actually difficult to bend, so the position of the antinode of the standing wave will be The bending becomes difficult, and efficient driving becomes impossible, which is different from the optimal standing limb position as seen from the electrode position. Therefore, as shown in Figure 2, the settled waves A', B
Efficient driving can be achieved by installing the protrusion 7 so that it does not come in the position of the clothes. In order to adjust this condition, it is possible to create one or two protrusions per wavelength, but in this case, the lateral component of the traveling wave of the bending vibration of the driving body 3 is constantly transmitted to the moving body 6. The information is no longer transmitted, and the moving speed of the moving body 6 actually decreases.

Although this embodiment has been described using an annular ultrasonic motor as an example, similar effects can be obtained with other ultrasonic motors that use elastic traveling waves.

Effects of the Invention According to the present invention, it is possible to provide an ultrasonic motor that can obtain a large speed with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a cutaway perspective view of an ultrasonic motor according to an embodiment of the present invention, Fig. 2 is a linear model diagram of a driving body in the embodiment of Fig. 1, and Fig. 3 is a conventional annular ultrasonic motor. 4 is a plan view showing the piezoelectric electrode structure used in the ultrasonic motor of FIG. 3, and FIG. 5 is a model diagram showing the vibration state of the driving body of the ultrasonic motor. FIG. 6 is a diagram explaining the principle of an ultrasonic motor. 1...Elastic body, 2...Piezoelectric body, 3°゛°°°driver, 4...Slider, 6...Elastic body, 6... ...Moving body, end...Protruding body. Name of agent: Patent attorney Toshio Nakao and one other name
1 Figure 2 Figure B' Figure 3 Figure 4 Figure 5 Figure 6

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 a driving body consisting of an elastic body and a piezoelectric body, the contact surface of the elastic body with the moving body is A protrusion is provided in the moving body, and the tip of the protrusion is arranged so as to be in contact with the moving object, and the number of protrusions is equal to 1 of the traveling wave.
An ultrasonic motor characterized in that the number of protrusions is an integer multiple of 4 per wavelength, and the protrusions are arranged at positions outside the antinode of two elastic standing waves constituting the elastic traveling wave.