JPS5986484A - Supersonic motor - Google Patents

Abstract

PURPOSE:To simplify the manufacture of an electrostrictive element and the assembling of a motor and to improve the driving efficiency of a supersonic motor by flattening the electrostrictive element mounting surface of a vibrator. CONSTITUTION:An electrostrictive element 3 is bonded to the outer periphery of a cylindrical vibrator 2. A movable element 1 is rotatably driven by generating elastic traveling wave at the vibrator 2 by means of the element 3. The outer peripheral surface of the vibrator 2 is formed in a polygonal shape due to the array of a flat surface 2a, and the element 3 is bonded to the flat surface 2a. The profile of the polygonal shape of the vibrator 2 is decided by a resonance frequency determined by the shape of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an ultrasonic motor, and particularly to an ultrasonic motor that generates traveling elastic waves in an elastic vibrator using an electrostrictive element and drives a moving body using the traveling elastic waves.

(Prior Art) An ultrasonic motor includes, for example, a fixed body and a movable body, and at least one of the fixed body and the movable body includes at least one vibrator driven by a plurality of electrostrictive elements. , the extraction lead of the electrostrictive element is connected to a driving power source, the fixed body and the movable body press each other at at least one point on the surface of the vibrator to transmit torque, and ultrasonic electrical energy is applied to the electrostrictive element. It is a device that converts mechanical vibration energy into mechanical vibration energy and converts the mechanical vibration energy into unidirectional movement of a moving object. Regarding the science of this type of device,
This has already been disclosed in Japanese Unexamined Patent Publication No. 52-29192.

In particular, here, a surface acoustic wave is used as the mechanical vibration energy, and the moving body is frictionally driven by the elastic wave, and at the same time, a standing wave is generated by the vibration of at least one electrostrictive element. The motor rotation of the configuration will be described.

Figure 1 shows the driving principle of this type of motor.
Let be a moving body and 2 be an elastic vibrator. The X-axis indicates the traveling direction of a surface wave occurring on the surface of the vibrator 2, and the z-axis is the normal direction thereof.

When the elastic vibrator 2 is vibrated by an electrostrictive element (not shown), a surface acoustic wave is generated and propagates on the surface of the 4H oscillator.

This elastic wave is a surface wave with longitudinal waves and transverse waves, and the motion of the mass point is vibration that describes an elliptical orbit. Focusing on the mass point A, it performs an elliptical motion with a vertical oscillation width u1 and a lateral oscillation width W. If the traveling direction of the surface wave is the +X direction, the elliptical motion rotates counterclockwise. This surface wave has vertices A, A', etc. for each wavelength, and its apex velocity is only the X component, V=2πfu (where f is the frequency). Therefore, when the surface of the moving body 1 is brought into pressure contact with this surface, the surface of the moving body reaches the vertex A.

Since it contacts only A', the moving body 1 is driven in the direction of arrow N by the frictional force between it and the vibrator 2.

The moving speed of the moving body 1 in the direction of arrow N is proportional to the frequency f. In addition, since frictional drive is performed by pressurized contact, longitudinal vibration +lJ
It depends not only on u but also on lateral loss r11w. That is, the moving speed of the moving body 1 is proportional to the magnitude of the elliptical motion, and the larger the lateral motion, the higher the speed. Therefore, the moving object speed is city,
It is proportional to the voltage applied to the strain element.

FIG. 2 shows the principle for generating surface waves in the elastic vibrator 2 shown in FIG. 1.

3a and 3b are electrostrictive elements, such as PssT, attached to the elastic vibrator 2 at intervals such that elastic waves can be most efficiently obtained from the sum frequency; is connected to line A, and 3b is connected to line B. 4 is the power source for driving the motor, and V = Vosinω
t is supplied, and as is clear from the figure, 1. A voltage of t is applied to IJA.A voltage of t is applied to line B by 90° phase shifter 5.
A voltage of O81n (ωt±-) is applied. + and - are switched depending on the moving direction of the moving body. That is, 90° phase shifter 5
The traveling direction of the moving object differs depending on whether the phase is shifted by +90' or the phase is shifted by 190°.

(a) to (b) represent the vibration state of the vibrator 2 according to time t
=4−1, ni) is the state of t=−−4−−,−.

ω ω 2ω ω The elastic wave propagates rightward in FIG. 2, but any mass point on the driving surface of the perturber 2 performs an elliptical motion in the counterclockwise direction. Therefore, the moving body (not shown) that is pressed against the drive surface moves to the left.

Figure @3 shows an example of a one-layer rotation drive type ultrasonic motor based on the principle explained above, and includes electrostrictive elements 3a and 3b.
are attached to the outer peripheral surface of the elastic vibrator 2 at the most efficient intervals determined by the material shape of the vibrator 2. Therefore, when the vibrator 2 is driven according to the method described above, elastic traveling waves are generated on the outer and inner circumferential surfaces of the vibrator 2. Therefore, if the moving body 1 is configured so that its outer circumferential surface is in pressure contact with the inner circumferential surface of the perturber 2,
When the vibrator 2 is fixed, the movable body 1 rotates, and when the movable body 1 is fixed, the vibrator 2 rotates. In the figure, the movable body 1 has a notch 1a and is configured to have a pressure contact force in the radial direction when it is assembled into the vibrator 2, but this pressure contact mechanism can have various other configurations. .

FIG. PA4 shows an example in which the ultrasonic motor of the type shown in FIG. 3 is used, for example, to drive a focusing lens. In the figure, a lens group 8 involved in focus adjustment is secured to a front lens holder 6 with a presser ring 7. There is a helical screw cut near the rear end of the holder 6, which allows the lens barrel 1 to be fixed.
It is screwed into the helicoid screw near the front end of 1. 9 is an index Jx3 fixed to the fixed lens barrel 11. Fixed lens barrel 1
A cam ring 19 is rotatably provided inside the cam ring 1.
A variable power lens 17 and a correction lens 18 are provided on the inner peripheral surface of the lens.
The cam n for moving the lens to a predetermined relationship for zooming is cut, and the holder 14 of the variable power lens 17 and the holder 15 of the correction lens 18 are held at the respective planting pins 2° and 21. It engages with this cam groove.

The bar 13 is a guide for the holder 14.15, and its front and rear ends are connected to the zoom front plate 1 fixed to the fixed cylinder 11.
2 and the zoom rear plate 22, respectively. The zoom operation fJiNo has an external zoom operation knob 16, which is connected by a connection mechanism (not shown) so that the cam ring 19 can be externally rotated. Reference numeral 23 denotes a rear fixed lens barrel added to the zoom rear plate 22, which holds an aperture 24 and an aperture driving meter 25 therebetween, and supports a boulder 27 of a relay lens 28 inside.

The relay lens boulder 27 is fixed to the lens barrel 26 with a set screw 26 after assembly and adjustment.

The zoom l/lens assembly described above has a very general configuration, but here, the focal point 81 intersegmental lens l! For driving f-8? An ultrasonic motor of the type shown in Fig. 43 is arranged. That is, the elastic vibrator 2 having the electrostrictive element 3 is fixed to the rear end of the front ball boulder 60 (the part below the index ring 9 and is not visible from the outside) by an appropriate means, and the inside of the elastic vibrator 2 is fixed. The peripheral surface is brought into pressure contact with the fixed mirror 11 at a portion 29. As a result, the front lens holder 7 rotates relative to the fixed lens barrel 11 by the surface acoustic waves of the vibrator 20 according to the principle described above.

A rubber member or the like is disposed at the portion 29 as a pressure contact mechanism. AP (auto focus) can be achieved by linking automatic focus adjustment 'f11j (iJ, 4'N, not shown) with this ultrasonic motor.
Can be used as a motor.

As mentioned above, by using an ultrasonic motor as a lens drive motor, in addition to the advantage of being able to incorporate the motor without increasing the size of the lens, there are other advantages such as no noise and no need for a speed reduction mechanism. What you get is easy to understand.

However, in the case of the type of ultrasonic motor shown in Fig.
It is necessary to give an arcuate strain to the electrostrictive element before adhering it, which is disadvantageous in terms of molding and adhesion of the electrostrictive element, cost, and manufacturing.

(Purpose) The present invention has been made in view of the above-mentioned oil purifier, and is intended to be used as an ultra-hill wave motor applied to rotational drive in terms of cost and manufacturing department. It is an object of the present invention to provide an ultrasonic motor for rotational driving which is advantageous in terms of efficiency and is also excellent in terms of driving efficiency.

(Embodiment) Hereinafter, an embodiment of the present invention will be explained with reference to FIG. In order to attach the strain element 3 to a flat surface, the outer circumferential surface of the vibrator 2 has a polygonal shape formed by an arrangement of flat surfaces 2a, as shown in the figure. here,
As mentioned above, the shape of this polygon is determined by the resonance frequency determined by the shape of the material of the vibrator 2.

Of course, the electrostrictive element 3 is attached on this plane 2a.

Thus, according to the configuration of the embodiment, the electrostrictive element can be mounted on the cylindrical vibrator 2 because all the surfaces are flat.
It becomes possible to eliminate all the drawbacks of the conventional method. Of course, the surface 2a with the number of electrostrictive elements υ may be formed on the inner circumferential surface of the vibrator 2, and in that case, the movable body 1 will be engaged with the outer circumference thereof.

(Effects) As explained above, according to the present invention, as a rotary drive type ultrasonic motor that rotationally drives a υ moving body by generating elastic traveling waves in four radial elements using an electrostrictive element, The mounting surface of the IK electrostrictive element on the vibrator is flat, which makes manufacturing the electrostrictive element and assembling the motor easier than before, which is advantageous in terms of cost and production, and the drive efficiency is significantly improved. It will improve.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of an ultrasonic motor that utilizes surface acoustic waves of an elastic vibrator, Fig. 2 is an explanatory diagram of the driving method of an ultrasonic motor, and Fig. 2115 is an exploded perspective view of essential parts showing an example of an ultrasonic motor. Fig. 4 is a sectional view showing an example in which the ultrasonic motor of the type shown in Fig. 3 is incorporated into the zoom l/kuzu assembly for driving the focusing lens; Fig. 5 3 is an exploded perspective view of essential parts of an embodiment in which the present invention is applied to an ultrasonic motor having the configuration shown in FIG. 3. 1... Moving body 2... Elastic perturber 2a... Mounting the electrostrictive element is a practical matter 3...Electrostrictive element patent applicant Canon Corporation 840 汀小Goゝ3 2α 445- nof ノ2 σ

Claims (2)

[Claims] (1) In an ultrasonic motor that generates a traveling elastic wave in an elastic vibrator using an electrostrictive element and rotates a moving object, the ultrasonic motor is characterized in that the surface of the electrostrictive element is flat. sonic motor. (2) The vibrator is cylindrical, and one surface of the inner and outer circumferences of the cylindrical vibrator is circular, and the other surface is provided with at least two flat surfaces. The ultrasonic motor according to claim 1, wherein the electrostrictive element is attached to the ultrasonic motor.