JPH0491670A - Supersonic motor - Google Patents

Abstract

PURPOSE:To decrease the difference between the two flexural peculiar frequencies formed in a vibrator by providing a nonaxisymmetry means capable of mass adjustment at one part of a vibrator. CONSTITUTION:A screw hole is provided in the rear vibrating elastic body 2 of a pencil type vibrator A, and a screw 13 is provided to be screwed in it in, for example, diametrical direction. For the mounting position of the screw 13, it is provided, for example, in parallel with the center, which divides the element part of the piezoelectric element plate 3 in two, and has the slippage of 90 deg. with the center, which divides the element part of the one sheet out of the piezoelectric element plate 4. That is, by the screw 13 being added to the vibrator A, the axisymmetry of the vibrator collapses, and the two peculiar vibration frequencies 90 deg. different in phase are relieved of degeneracy, and are separated. Hereby, the peculiar frequency can be adjusted by mass adjustment, and the difference between the peculiar frequencies can be made very small.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a technique for clamping an electro-mechanical energy conversion element from both sides in the thickness direction by supplying electrical energy to the electro-mechanical energy conversion element such as a piezoelectric element. The present invention relates to an ultrasonic motor that bends and vibrates a fixed vibrating body, for example, a pencil type, and causes its mass point to move in a circular or elliptical manner, thereby frictionally driving a movable body pressed against the vibrating body.

[Prior Art] Conventional ultrasonic motors are of the type that generate progressive bending vibrations in a circular ring-shaped metallic vibrating elastic body and drive a moving body using frictional force, which is used for camera autofocus (
AF) mechanism, etc.

However, since this type of ultrasonic motor has a ring-shaped vibrating elastic body, it tends to be expensive as a unit that includes a pressurizing mechanism to obtain frictional force, and requires hollowness (ring shape). There was a disadvantage in terms of cost for applications that would never be used.

Therefore, a motor as shown in FIGS. 7 and 18 has been proposed as a rod-shaped ultrasonic motor such as a pencil type with a simple configuration of a pressurizing system.

A is a pencil-shaped vibrator, in which a donut-shaped piezoelectric element plate 3.4 is provided between a pencil-shaped front vibrating elastic body 1 and a cylindrical rear vibrating elastic body 2, and these piezoelectric element plates 3.
．． For example, an electrode plate (not shown) for applying an alternating voltage to the piezoelectric element plate 4 is inserted between the piezoelectric element plates 3 and 4, and the piezoelectric element plate is inserted between the front vibrating elastic body 1 and the rear vibrating elastic body 2 using bolts 6. 3.
4 and the electrode plate are clamped and fixed.

The piezoelectric element plate 3.4 is polarized symmetrically with different polarities in a cross section passing through the axis, and the piezoelectric elements 3 and 4 are arranged at an angle shifted by 90° in the θ direction.

Then, when an AC voltage V, V2 having a frequency close to the bending natural frequency of the vibrator is applied to each piezoelectric element, the piezoelectric element expands and contracts in the thickness direction, and the vibrator performs bending vibration. At this time, if the AC voltage v1 and the AC voltage ■2 have the same amplitude and frequency, but have a temporal phase difference of 90 degrees, the vibrator A will jump the rope around its axis. A circular motion like this (hereinafter referred to as pure vibration) will be performed. Also, AC voltage ■.

(2) By reversing the phase of step 2, forward and reverse rotation of the circular motion becomes possible.

On the other hand, R is a rotor that fits coaxially with the axis l of the vibrator A, and one end of the rotor is pressed against the sliding part B of the vibrator by the spring force of the spring 5, and is excited by the vibrator A. Rotates due to friction drive caused by vibration. The spring 5 is elastically mounted between the tip of the bolt 6 and a spring post 8 that fits into a flanged thrust bearing 7.

[Problems to be Solved by the Invention] By the way, in such an ultrasonic motor, is it required that the bending natural frequencies of the piezoelectric element plate 3 and the piezoelectric element plate 4 be equal? Due to processing errors of the plates 3, 4 and bolts 6, processing and assembly errors of the electrode plate, terminal parts for connection formed protruding from the electrode plate, solder for wiring fixed to the terminal parts, etc. There may be a difference between the two bending natural frequencies described above, and the influence of the eccentricity of the piezoelectric element plate 3.4 and the terminal portion of the electrode plate is particularly large.

When the natural frequencies of the drive modes are far apart, multiple bending modes are generated at frequencies near the natural frequencies, making it difficult to excite vibrations with the necessary amplitude and phase when obtaining circular or elliptical motion.

This has caused problems such as the required rotational speed and torque not being obtained or fluctuating, large losses, and poor efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic motor that can solve these conventional problems and reduce the difference between two natural bending frequencies formed in a vibrator.

[5! ! Means for Solving Problems l] A configuration for realizing the object of the present invention is to apply an alternating electric field to an electro-mechanical energy conversion element (hereinafter represented by PZT) arranged in a rod-shaped elastic body. By exciting the vibrations of the same-shaped bending moats in a plurality of different planes in a rod-shaped elastic body and giving them an appropriate phase difference in time, a vibrator that causes particles on the surface of the vibrator to perform circular or elliptical motion. , an ultrasonic motor having a movable body that is pressed by a vibrating body and driven by friction, characterized in that a part of the vibrator is provided with non-axisymmetric means capable of adjusting mass.

[Function] By adjusting the mass of the ultrasonic motor configured as described above, the natural frequency can be adjusted, and the difference in natural frequency can be made minute.

[Example] Example 1 FIG. 1 is a perspective view showing Example 1 of the ultrasonic motor according to the present invention.

In this embodiment, a screw hole is provided in the rear vibrating elastic body 2 of the pencil-type vibrator A similar to the conventional example, and a screw 13 is provided in the hole so as to be threadable, for example, along the radial direction.

In this embodiment, the mounting position of the screw 13 is, for example, provided in parallel to the central part that divides the element part of the piezoelectric element plate 3 into two,
The piezoelectric element plate 4 has a deviation of 90'' from the center portion that divides the element portion of one of the piezoelectric element plates 4 into two.

That is, by adding the screw 13 to the vibrator A, the axial symmetry of the vibrator is broken, and two natural frequencies with different phases of 90° are degenerated and separated.

Therefore, if you insert or remove this screw or change the length of the set screw, the natural frequency difference (△f) will change,
The natural frequency difference (△f) can be adjusted, and the electrode 10
This can be done by adjusting the effects of natural vibrations caused by machining errors in the terminal portion 11, soldering of the lead wires 12, etc.

In this embodiment, the screw 13 is designed to be able to be threaded toward the center, but it is not necessary, and the screw 13 may be provided at a plurality of locations.

Example 2 FIG. 2 shows a second embodiment.

In this embodiment, a slit 2a is provided in the bottom side circumferential wall of the post-vibration elastic body 2, and by adjusting the position of this slit 2a, the natural frequency difference (Δf) is adjusted. The post-vibration elastic body 2 can be fixed by slightly loosening the screw 6.

Example 3 FIG. 3 shows Example 3.

In the second embodiment described above, the natural frequency difference is adjusted by providing a slit in the rear vibrating elastic body 2 and adjusting the position of the slit by rotating the rear vibrating elastic body 2. However, in this embodiment In this case, a notch 14 is provided on the circumference of the rear vibrating elastic body 2 instead of a slit.

Example 4 FIG. 4 shows Example 4.

In Embodiment 1 shown in FIG. 1, a screw 13 is provided on the rear elastic body 2 so as to be screwable, but in this embodiment, a shaft 15 is protruded in place of the screw 13, and this shaft 15 is bent by the necessary amount. By removing it, the natural frequency difference is adjusted.

Example 5 FIG. 5 shows Example 5.

In this embodiment, an adjustment ring 16 having an adjustment protrusion 17 is fixed between an elastic body 1.2 coaxially with a piezoelectric element plate 3.4,
By bending the protrusion 17, the natural frequency difference is adjusted.

Example 6 FIG. 6 shows Example 6.

In this embodiment, an adjustment plate 18 for mass adjustment is provided at the rear end of the rear vibrating elastic body 2, and a bolt 6' having a hexagonal hole 6a is used to connect the elastic body 2, piezoelectric element plate, and electrode together with the adjustment plate 18. It is designed to clamp and fix plates, etc.

In this embodiment, the natural frequency difference is adjusted to 4 by changing the position of the adjusting plate 18, which has unequal radial length with respect to the fineness of the vibrator A, and is adjusted by loosening the bolt 6 degrees. Board 1
8, only the adjusting plate 18 can be rotated, and the clamping surface between the piezoelectric element plate and the rear vibrating elastic body can be prevented from moving.

Example 7 FIG. 9 shows Example 7.

In the embodiment described above, the natural frequency difference is adjusted by changing the position of the rear vibrating elastic body or adding mass, but the natural frequency difference can also be similarly adjusted by changing the position of the piezoelectric element plate 3.4. It is possible to adjust the frequency difference.

In this embodiment, the 6° head of the bolt for fixing the rear vibrating elastic body 2 to the front vibrating body 1 with the piezoelectric element plate 3.4 interposed is formed to have the same diameter as the rear vibrating elastic body 2, and the This makes it easier to loosen and tighten the screws.

In addition, as shown in FIG. 10, there is a notch 14 in the bolt 6'.
may be provided.

Further, as shown in FIG. 11, a hexagonal hole 6a may be provided in the head of the bolt 6 so that it can be loosened or tightened using a hexagonal wrench.

FIG. 12 shows an example of a configuration in which a motor according to the present invention is used to drive an optical lens barrel.

A gear 22 is coaxially connected to the movable body 8 and transmits rotational output to the gear 23 to rotate a lens barrel 24 having a gear that meshes with the gear 23.

In order to detect the rotational position and rotational speed of the moving body 8 and the lens barrel 24, an optical encoder slit plate 25 is connected to the gear 23.
The photocoupler 26 detects the position and speed.

Numeral 27 is a screw that can be screwed in the radial direction, and the same effect as in the first embodiment can be obtained.

[Effects of the Invention] As explained above, according to the present invention, it is possible to adjust the natural frequency of a vibration system excited in a plurality of planes by an electro-mechanical energy conversion element such as a piezoelectric element plate. , it is possible to make these natural motions the same or substantially equal, and the rotational speed and torque can be increased and stabilized, and efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a first embodiment of an ultrasonic motor according to the present invention, FIGS. 2(a) and (b) are a vertical cross-sectional view and a bottom perspective view showing a second embodiment, and FIG. 3(a), (b) is a perspective view and longitudinal sectional view showing Example 3, FIG. 4 is a perspective view showing Example 4, FIG. 5 is a perspective view showing Example 5, and FIGS.
) are a perspective view and a vertical sectional view showing the sixth embodiment, FIG. 7 is a perspective view showing a conventional ultrasonic motor, FIG. 8 is a vertical sectional view of FIG. 7, and FIG. 9 is a vertical sectional view of the seventh embodiment. Figure 10(a), (
b) is a vertical sectional view and a perspective view showing a modification of the seventh embodiment, and FIG. 11 is a perspective view showing a modification of the seventh embodiment. Figure 812 shows a cross-sectional view of a device using an ultrasonic motor. A... Vibrator 1... Front vibrating elastic body 2...
- Rear vibration elastic body 10... Electrode 11... Terminal portion 13... Screw 15 -... Shaft 17... Protrusion 12... Lead wire 14... Notch 16... Adjustment ring 18 ...Adjustment plate diagram 1

Claims (1)

[Claims] 1. By applying an alternating current electric field to an electro-mechanical energy conversion element (hereinafter represented by PZT) arranged on the rod-like elastic body, vibrations of the same bending mode are transmitted to a plurality of different planes in the rod-like elastic body. The vibrator has a vibrator that causes particles on the surface of the vibrator to perform circular or elliptical motion by excitation within the body and an appropriate temporal phase difference, and a moving body that is pressed by the vibrator and driven by friction. An ultrasonic motor, characterized in that a part of the vibrator is provided with non-axisymmetric means capable of adjusting mass. 2. An apparatus including the ultrasonic motor according to claim 1, further comprising an output member that obtains a driving force from a member that is pressed by a vibrator and driven by friction.