JPH0491677A - Supersonic motor - Google Patents

Abstract

PURPOSE:To enable the agreement of each peculiar frequency by the flexural vibration of a piezoelectric element by forming electrodes in parts, respectively, on one side, corresponding to each region, and stacking piezoelectric elements so that the boundary regions of the electrodes corresponding to each polarizing region may agree with each other. CONSTITUTION:For electric-mechanical energy conversion elements (piezoelectric element plates) 3 and 4, polarizing regions, which are polarized in different directions, are made in pairs, and also electrodes a and b are formed in parts on one side each, respectively, corresponding to each region, and the piezoelectric element plates 3 and 4 are stacked so that the boundary regions of the electrodes a and b corresponding to each polarizing region may agree with each other. In the electrode part of the piezoelectric element plate 3 or 4, insulating parts d are provided in the directions of x axis and y axis, so the rigidities becomes equal regarding the flexure within the z-x face or within the z-y face. Hereby, the peculiar frequencies of each flexural vibration by both piezoelectric elements 3 and 4 can be agreed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a motor that generates mechanical power without relying on electromagnetic force;
That is, by supplying electrical energy to a piezoelectric element provided on an elastic body, mechanical vibrations are excited in the elastic body, causing circular or elliptical movement on the surface of the vibrator, thereby causing friction on the moving body pressed against the vibrator. This invention relates to an ultrasonic motor to be driven.

[Prior Art] Conventionally, ultrasonic motors include those that generate bending traveling waves in an annular vibrating elastic body and use frictional force to rotate a moving body that contacts the elastic body; A type that generates a flexural traveling wave and similarly drives rotation has been put into practical use.

On the other hand, a rod-shaped ultrasonic motor has also been proposed in which a rod-shaped vibrator causes bending vibration in two directions to drive a moving body that comes into contact with the vibrator.

FIG. 3 is an exploded perspective view of a conventional rod-shaped ultrasonic motor.

1 is a horn-shaped horn portion I whose diameter gradually decreases toward the tip between a small-diameter shaft portion 1a at the tip and a large-diameter shaft portion 1b at the rear end.
2 is a vibrating body made of a metal round bar formed with C; 2 is a presser body made of a metal round bar having an outer diameter the same as the large diameter shaft portion 1b of the vibrating body 1; and 3 has a bolt through hole at its axis; and 4 is an annular piezoelectric element plate formed to have the same outer diameter as the large diameter shaft portion 1b; 5 is an electrode plate of the piezoelectric element plates 3 and 4; , piezoelectric element plate 3 with electrode plate 5 sandwiched therebetween.
．． 4, and by fixing the presser body 2 to the vibrating body 1 with bolts 6, the piezoelectric element plate 3.4 is fixed between the vibrating body 1 and the presser body 2, thereby forming the vibrating body A. There is. The head of the bolt 6 is in contact with the presser body 2 via the annular insulator 7, and the shaft portion is held in a non-contact state with the piezoelectric element plate 3.4 and the electrode plate 5.

The piezoelectric element plates 3 and 4 have two electrodes (+ electrode layer, -
Electrodes b) are formed symmetrically on both sides of the insulating part d formed at the central axis position, and a common electrode C for the raw electrodes a and -electrodes is formed on the other side, and the axis of the vibrator A is They are arranged with a 90 degree angle shift in positional phase from each other. Note that the piezoelectric element plate 30 min & IE electrode (+ electrode layer, - electrode b) is in contact with the rear end surface of the vibrating body 1 which is a conductor, and the piezoelectric element plate 4 is in contact with the front wheel surface of the presser body 2 which is an electric conductor. ing.

Then, an AC voltage v1 is applied between the 1i8i plate 5 and the vibrator 1.
Also, by applying an AC voltage V between the electrode plate 5 and the presser body 2, vibrations due to expansion and contraction displacement in the thickness direction of the piezoelectric element plate 3 and vibrations due to expansion and contraction displacement in the thickness direction of the piezoelectric element plate 4 are generated. The oscillator A is made to vibrate by combining with .

As shown in FIG. 4, the AC voltage V and the AC voltage 2 have the same amplitude and frequency, but have a temporal phase shift of 90''.

Therefore, the vibrator A performs circular motion around the axis. Reference numeral 8 denotes a moving body that is pressed by the horn portion 1c of the vibrating body 1 and rotates under the frictional force from the vibrating body 7. The mechanism of this friction and drive is not essentially related to the present invention, so a description thereof will be omitted.

[Problems to be Solved by the Invention] Incidentally, such an ultrasonic motor has the following problems due to the structure of the piezoelectric element plate.

As shown in Fig. 5, the piezoelectric element plate 3.4 has electrode layers formed on both its front and rear surfaces (the outer peripheral surface is filled in black in the figure), and the front electrode layer has an electrode layer on its diameter. An insulating portion d that does not form a piezoelectric element plate 3 is provided in the y-axis direction, and an insulating portion d of the piezoelectric element plate 4 is provided in the x-axis direction. These insulating portions d become voids when the piezoelectric element plates 3.4 are stacked with the electrode plates 5 in between, so that stress becomes zero even when the vibrator undergoes bending vibration.

That is, regarding the bending vibration in the z-x plane caused by the piezoelectric element plate 3, the rigidity of the electrode part of the piezoelectric element plate 4 having a gap in the X direction is higher than that of the electrode part of the piezoelectric element plate 3 having a gap in the X direction. The stiffness is lower than that at the end. Conversely, regarding bending vibration in the z-y plane caused by the piezoelectric element plate 4, the rigidity at the electrode part of the piezoelectric element plate 3 with a gap in the X direction is higher than that of the piezoelectric element plate 4 with a gap in the X direction. The rigidity is lower than that of the electrode section.

Bending in the z-x plane and bending in the z-y plane each have a portion where the rigidity is reduced, but the positions on the two coordinates are different. Therefore, the modes of bending in the Z-X plane and bending in the Z-y plane are different, and the natural frequencies are also different.

No matter what frequency the AC voltages V, V2 are set in such a state, both the bending in the z-x plane and the bending in the zy plane will not result in resonant vibration. For this reason,
The vibrator A did not move in a circular motion, and was extremely inefficient in rotating the rotor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic motor that solves these conventional problems, eliminates the mismatch in natural frequencies caused by the insulation gap of the piezoelectric element plate, and improves motor efficiency.

[Means for Solving the Problem] A configuration for realizing the object of the present invention includes a rod-shaped elastic body,
Electricity that expands and contracts in the thickness direction with electrodes divided on one side.
By applying an alternating current electric field to the electro-mechanical energy converting elements in a vibrator formed by laminating mechanical energy converting elements, the vibrations of the bending motes of the same shape are adjusted to an appropriate phase difference in a plurality of different planes. In an ultrasonic motor, the electro-mechanical energy The conversion element has a pair of polarized regions polarized in different directions, and electrodes are formed separately on one side corresponding to each region, so that the boundary region of the electrode corresponding to each polarized region is The present invention provides an ultrasonic motor characterized in that electro-mechanical energy conversion elements are laminated so as to match each other.

[Function] The ultrasonic motor having the above configuration can make the mechanical shape and mechanical properties of the stacked electro-mechanical energy conversion elements such as piezoelectric elements, for example, 90 degrees rotationally symmetrical. The natural frequencies of each bending vibration caused by the piezoelectric element can be matched.

[Embodiment] FIGS. 1 and 2 also show an embodiment of an ultrasonic motor according to the present invention.

This embodiment differs from the conventional example only in the electrode structure provided on the front side of the piezoelectric element plates 3 and 4, and the other structures and the method of applying the driving voltages V, , V, are the same.

The piezoelectric element plates 3.4 of this embodiment both have the same structure,
An insulating part d having a planar cross shape is provided at orthogonal diameter parts, and a (+) polarized part and a (-) polarized part are provided in two adjacent regions in each of the four equally divided regions. ) and electrode a of (
-) electrodes are provided on the entire surface. The piezoelectric element plate 3 and the piezoelectric element plate 4 are arranged with a deviation of 90''.

That is, as shown in the assembled enlarged view of the piezoelectric element laminated portion in FIG. Since it is provided in the
The rigidity is also the same for bending in the zy plane, and the natural frequencies of each are the same.

FIG. 6 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 12 is coaxially connected to the moving body 8 and transmits rotational output to the gear 13 to rotate a lens barrel 14 having a gear that meshes with the gear 13.

In order to detect the rotational position and rotational speed of the moving body 8 and the lens barrel 14, an optical encoder slit plate 15 or a gear 13 is used.
The position and speed are detected by a photocoupler 16.

[Effects of the Invention] As described above, according to the present invention, it is possible to match each natural frequency due to bending vibration 1 of stacked drive electro-mechanical energy conversion elements, for example, piezoelectric elements. This results in the effect that the driving efficiency of the motor can be improved.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an embodiment of an ultrasonic motor according to the present invention, FIG. 2(a) is an enlarged perspective view showing a laminated state of piezoelectric element plates, and FIGS. A plan view of the element plate is shown. Fig. 3 is an exploded perspective view of a conventional ultrasonic motor, Fig. 4 is a voltage application waveform diagram, Fig. 5 is an enlarged perspective view showing the laminated state of the piezoelectric element plates, and Fig. 6 is an exploded perspective view of a conventional ultrasonic motor. FIG. 1... Vibration elastic body 2... Presser body 3.4...
Piezoelectric element plate 5... Electrode plate 6... Bolt
7...Insulator 8...Rotor a...Medium electrode b...-Electrode C...Common electrode d...Electrode insulator and 4 others Figure 2

Claims (1)

[Scope of Claims] 1. In a vibrator in which an electro-mechanical energy conversion element having an electrode divided on one side and expanding and contracting in the thickness direction is stacked on a rod-shaped elastic body, an alternating current is applied to the electro-mechanical energy conversion element. By applying an electric field, the vibration of the same bending mode is excited in the vibrator with an appropriate phase difference in a plurality of different planes, thereby causing the surface particles of the vibrator to perform circular or elliptical motion. In an ultrasonic motor that frictionally drives a movable body pressed against the sliding surface of the vibrator, the electro-mechanical energy conversion element forms a pair of polarized regions polarized in different directions, and An ultrasonic motor characterized in that electrodes are formed separately on one side corresponding to each of these regions, and electro-mechanical energy conversion elements are stacked so that the boundary regions of the electrodes corresponding to each polarization region match. 2. In claim 1, the stacked electro-mechanical energy conversion element is characterized in that the overlapping polarized regions are pairs of polarized regions in the same direction and polarized regions in different directions. sonic motor. 3. A device including the ultrasonic motor according to claim 1 or 2, further comprising an output member that obtains a driving force from a member that is pressed by a vibrator and driven by friction.