JPS59185177A - Supersonic motor - Google Patents

Abstract

PURPOSE:To obtain a supersonic motor having excellent drive efficiency by generating a traveling elastic wave by an electrostrictive element which is common to a plurality of elastic vibrators, thereby driving a movable element. CONSTITUTION:A member 1 of a driven side of a supersonic motor is, for example, the rear end of a lens holder, and a hard rubber portion 34 is bonded via an adhesive or the like to a driven side rotary member 1. Elastic vibrators 30-33 are radially divided and disposed in a ring shape so that the inside is formed thinner than the outside. An electrostrictive element 3 are bonded via an adhesive between the vibrators 30-33 and a vibration absorbing member 35 to construct a member of the drive side. The member 35 is made, for example, of a felt to absorb the vibration of reverse side. Thus, elastic surface wave is efficiently generated to the vibrators 30-33 via the element 3, to rotatably drive it, thereby providing the supersonic motor having excellent drive efficiency.

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. , one node of the electrostrictive element is connected to a driving power source, and the fixed body and the movable body are a device that converts a small amount on the surface of the vibrator into unidirectional movement of the movable body in order to transmit torque. De-sho,
This Maki device has already been disclosed in Japanese Patent Application Publication No. 52-2919.
This is disclosed in Publication No. 2, etc.

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 VC, and at this time, a standing wave is generated by the vibration of at least one electrostrictive element. We will describe a motor with a similar configuration.

FIG. 1 shows the driving principle of the motor of this building, where l is a moving body and 2 is an elastic vibrator. The X-axis indicates the traveling direction of the surface wave occurring on the surface of the vibrator 2, and the two axes are the normal directions 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 vibrator. This elastic wave Vi is a surface wave accompanied by a longitudinal wave and a transverse wave, and the motion of the mass point becomes a vibration that describes an elliptical orbit. Focusing on the mass point A, it performs an elliptical motion with a longitudinal width U and a lateral width W, resulting in υ
, if the traveling direction of the surface wave is the +X direction, the elliptical motion rotates counterclockwise. This surface wave has vertices A, A', . . . for each wavelength, and its apex velocity is only the X component, which is ■==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, it depends not only on the vertical oscillation width U but also on the lateral oscillation width W. That is, the moving speed of the moving body 1 is proportional to the size of the elliptical motion17, and the larger the elliptical motion, the higher the speed. Therefore, the speed of the moving body is proportional to the voltage applied to the n-strain element.

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

3a and 3b are electrostrictive elements such as PzT, which are attached to the elastic vibrator 2 at intervals of jij such that elastic waves can be obtained most efficiently from the resonance frequency of the elastic vibrator 2; 3b is connected to the wire A and the wire BK. 4 is the power supply for the body of this motor, and V = Vo
A voltage of sinωt is supplied, and as is clear from the figure, a spiral pressure of v = Vgain (, +t is applied to Wi A. V = Vgain (, +t) is applied to IB by the 90° phase shifter 5.
A voltage of Vosiri (, tt negative) is applied. 10 and - are switched from the moving direction V of the moving body. That is, when the phase is shifted by +900 by 90' phase shifter 5, and -90'
The moving direction of the moving body differs depending on the case where the phase is shifted.

(a) to (b) show the vibration state of the vibrator 2 depending on time.

The elastic wave is VC in the right direction in Figure 2,>! 4. However, any mass point on the driving surface of the perfect child 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.

FIG. 3 shows an example of a rotary drive type ultrasonic motor constructed based on the principle explained above, in which electrostrictive elements 3a and 3b are mounted on the outer peripheral surface of the elastic vibrator 2 and are determined by the material shape of the vibrator 2. They are pasted at the most efficient spacing.

Therefore, when this 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 movable body 1 is configured so that its outer circumferential surface is in pressure contact with the inner circumferential surface of the vibrator 2, when the vibrator 2 is fixed, the movable body 1 will be moved, and when the movable body 1 is fixed, the vibrator 2 will be is rotating. In the figure, the movable body 1 has a notch 1a and is configured to exert pressure contact force in the radial direction when incorporated into the vibrator 2, but this pressure contact mechanism can have various other configurations. .

FIG. 4 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, the lens group 8 involved in focus adjustment is stopped by a front lens holder 6 (/holding ring 7).A helicoid thread is cut in the rear end VC of the holder 6, and a fixed lens barrel 1
It is screwed into the helicoid screw near the front end of 1. Reference numeral 9 denotes an index ring fixed to the fixed lens barrel 11. A cam ring 19 is rotatably provided inside the fixed lens barrel 11, and on its inner peripheral surface, a variable power lens 17 and a correction lens 18 are moved in a predetermined relationship for zooming. A cam groove is cut for this purpose, and the holder 14 of the variable power lens 17 and the holders 15 of the correction lens 18 are engaged with this cam groove at their respective planting pins 20 and 21.

bar] 3 is a guide for the holder 14.15, and its front end and rear end are connected to the zoom front plate 1 fixed to the fixed lens barrel 11.
2 and the zoom rear plate 22, respectively. The zoom operation ring 10 has an external zoom operation knob 16, and is connected to a connecting mechanism V (not shown) so that the cam 13J19 can be rotated from the outside. Reference numeral 23 denotes a rear fixed lens barrel attached to the zoom rear plate 22, which holds an aperture 24 and an aperture drive meter 25 therebetween, and supports a holder 27 for a relay lens 28 inside. The relay lens holder 27 is fixed to the lens barrel 23 with a central screw 26 after assembly and adjustment.

The zoom lens assembly described above has a very general configuration, but here an ultrasonic motor of the type shown in FIG. 3 is disposed for driving the focusing lens group 8. That is,
An elastic vibrator 2 having an electrostrictive element 3 is fixed to the rear end of the front lens holder 6 (a portion below the indicator ring 9 that is not visible from the outside) by an appropriate means, and the entire inner circumferential surface of the elastic vibrator 2 is Fixed lens barrel 11
The parts 29 are pressed against each other. As a result, the front lens holder 7 is rotated relative to the fixed lens barrel 11 by the surface acoustic waves of the vibrator 2 according to the principle described above.

As the pressure contact mechanism, a rubber member or the like is arranged at the portion 29vC.

If this ultrasonic motor is linked with an automatic focus adjustment mechanism (not shown), it can be used as an AF (auto focus) 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 is no noise, and there is no need for a reduction gear or mechanism. - It is easy to understand that various benefits can be obtained.

However, today, low cost lightning power is being used for the purpose of energy saving in various devices such as video cameras and still cameras, and the ultrasonic motors mentioned above are also being used. Furthermore, it is desired to operate efficiently.

For example, the ultrasonic motor shown in FIGS. 5 and 6 differs from the ultrasonic motor shown in FIG.
As shown in the figure, radii rl and r with respect to the motor rotation center axis,
It is attached to the surface within the F[1 annular region defined between the two circles. Configure it like this.

Compared to the one shown in Figure 3, the adhesive surface of the electrostrictive element 3 is in contact with a flat surface, which makes it easier to process the electrostrictive element 3, and the overall thickness can be made thinner. This has advantages and can be used as a lens drive motor with a different configuration from that shown in FIG.

Here, the shape of the vibrator 2 that most efficiently drives the ring-shaped ultrasonic motor shown in FIG. 85 and FIG. 6 will be described.

As mentioned above, in this motor, the driving force changes depending on the vertical and horizontal waves generated at the mass point, in other words, the size of the elliptical locus that the mass point moves, so the vibrator 2
It is clear that resonance is a means of increasing efficiency.

Here, assuming that the longitudinal elastic modulus of the vibrator 2 is E, the density is ρ, the thickness is Z, and the wavelength of the given traveling wave is λ, the driving frequency f is expressed as follows. When calculating the value of λ, as shown in FIG. At other diameters, the resonance frequency will be exceeded.

Therefore, in order to generate resonance in the entire width of radii r1 to r1 and drive most efficiently, the plate thickness should be adjusted so that resonance occurs at the same resonant frequency at positions corresponding to each radius. It suffices if all z are equipped, and in this regard, if the distance in the radial direction is kr in FIG. (However, the circumference is assumed to be 0 times the wavelength.) However, it is not easy to process the vibrator 2 by changing the plate thickness in the radial direction according to the above calculation formula, and there is a problem in terms of productivity. .

(Purpose) The present invention has been made in view of the above-mentioned circumstances, and is particularly useful as a plane drive type ultrasonic motor (for example, the various motors shown in Figure 5) that is applied to rotational drive, and is effective in terms of cost. Another object of the present invention is to provide an ultrasonic motor for rotational drive that is more convenient in terms of manufacturing and has excellent drive efficiency.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

Figure 7 is based on the calculation formula shown in equation (2) above.
2 schematically shows a cross-sectional shape of a vibrator 2. FIG. On the other hand, FIG. 8 shows an example of the structure of a vibrator according to the present invention. The line S indicated by a two-dot chain line in FIG. 8 is a line based on equation (2) as in FIG. In the example of 3
0.31, 32, and 33) are arranged at different heights in two directions so as to approximate the cross-sectional shape according to equation (2). This makes it possible to drive the motor much more easily than with the vibrator having the ideal cross section shown in FIG. 7, and with almost the same high efficiency. In addition, in this figure, the vibrator is 4 of 30, 31, 32, and 33.
However, the number is not limited to this. Of course, it is clear that the more, the better.

FIG. 9 is an exploded perspective view of a specific example of the configuration of the ultrasonic motor of the present invention, and FIG. 10 is an assembled sectional view thereof.

In the figure, 1 is a member on the driven side, and in reality, it is, for example, the rear end of a lens holder. Reference numerals 3 and 34 are hard rubber parts fixed to the driven rotating member 1 with adhesive or the like. This is arranged to obtain a certain degree of friction between the driving side and the driven side, and can be omitted depending on the materials of the vibrators 30 to 33 and the rotating member 1. The portion constituted by the elements 1 and 34 described above is the driven side.

30 to 33 are the vibrators according to the present invention explained in FIG. 8, and as shown in FIG. 10, the inner side is thinner than the outside. 3 is an electrostrictive element, and 35 is a vibration absorbing member made of felt or the like to absorb vibrations on the opposite side. These elements indicated by 35 and 30 to 33 constitute the driving side, and these elements are also fixed with adhesive or the like.

As is clear from FIG. 10, since the vibrators 30 to 33 have a step-like shape, the rubber 34 on the driven side faces the vibrator so that it can efficiently receive the driving force from each vibrator. It is best to form the surface into a step-like shape.

FIG. 11 shows the electrostrictive element 3 with the vibrator surface of the rubber 34 being a flat surface.
' is made into a staircase shape.

In this case as well, in order to effectively absorb vibrations, it is preferable that the absorbing portion housing member 35 has a stepped shape according to the electrostrictive element 3' as shown in the figure.

By making the above-mentioned divided vibrators 30 to 33 the same material and changing the material thickness, high efficiency can be achieved at low cost. By making appropriate selections, it is also possible to improve efficiency by making the plate thicknesses the same.

FIG. 12 shows an example of such a case, in which the divided vibrators 30', 31', 32', and 33' are arranged so that the plate thicknesses are the same and each vibrator is in a resonant state. The material and diameter are selected.

(Effects) As explained above, according to the present invention, as a planar ultrasonic wave motor that rotationally drives a moving body by electrostriction, it is possible to manufacture an electrostrictive element and assemble the motor more easily than in the past. etc., which is advantageous in terms of cost and production, and driving efficiency is greatly improved.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the principle of an ultrasonic motor that uses surface acoustic waves of an elastic vibrator, Figure 2 is an explanatory diagram of the driving method of an ultrasonic motor, and Figure 3 is an exploded view of essential parts showing an example of an ultrasonic motor. FIG. 4 is a perspective view, FIG. 4 is a sectional view showing an example in which the ultrasonic motor of the type shown in FIG. 3 is incorporated into a zoom lens assembly for driving a focusing lens, and FIG. An exploded perspective view of essential parts of a vibrator and an electrostrictive element like a suitable ultrasonic motor, FIG. 6 is a sectional view of the vibrator in FIG. 5, and FIG. 7 is a vibrating element shown in FIG. Fig. 8 is an assembled sectional view of a similar cross-sectional shape, Fig. 11 is an assembled sectional view of a modified example of the embodiment shown in Figs. 9 and 10, and Fig. 12 is an assembled sectional view of another modified example. It is a diagram. 30, 31, 32, 33; 30', 31', 3
2'. 33'... Vibrator, 3; 3'... Electrostrictive element,
1... Mobile object. Patent applicant: Canon Co., Ltd.

Claims (1)

[Claims] A traveling elastic wave is generated in an elastic vibrator using an electrostrictive element,
An ultrasonic motor for driving a moving body thereby comprising a plurality of vibrators and an electrostrictive element common to these vibrators.