JP2529233B2 - Ultrasonic rotary oscillator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic vibrator, and more particularly to improvement of an ultrasonic vibrator used for a stator of an ultrasonic motor or the like.

[Conventional technology]

A conventional ultrasonic motor is a device that utilizes the rotational torque received by a rotor that is crimped to an elliptical vibration stator. The stator consists of an ultrasonic elliptical oscillator, vibrates instead of rotating, and the rotor is constantly rotating in one direction. Even if the stator is stopped and the rotor is rotating, the static friction with no speed difference can be used for torque transmission between the two because the vertical vibration component of the elliptical vibration of the stator causes the buoyant force on the rotor. Is applied to the rotor for a half cycle of torsional vibration to transmit the rotational torque in one direction,
This is because the remaining half cycle leaves the rotor and returns in the direction opposite to the rotation, and when this principle is satisfied, wear can be avoided.

However, to satisfy this principle requires a complicated mechanism,
For example, it was impossible to make a thin flat motor. That is, the inability of the stator to rotate was the root of all problems.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the drawback of the conventional ultrasonic vibrator that it cannot rotate, and to provide an ultrasonic vibrator suitable for a stator of an ultrasonic motor.

[Means for solving problems]

In order to achieve the above object, the present invention provides, for example, a disc shape,
It consists of a circular oscillator such as an annular or cylindrical shape, and multiple pairs of regions of the oscillator that are polarized in the same direction in the thickness direction of the oscillator through multiple pairs of electrodes are It is characterized in that the center of gravity of the oscillator is rotated around the center of the oscillator by exciting the oscillator so that it is asymmetric and deformed in a plane perpendicular to the polarization direction. It realizes rotation similar to the movement of the body of a person who is turning a hula hoop at a rotation speed of several tens KHz.

Assuming a plurality of diameters that divide the circle into equal parts and a pair of radii that make up each diameter, and by contracting the radius by extending one radius, the circumference translates along the diameter.
At this time, in order to keep the shape of the circumference so as not to collapse from the original perfect circle, let the other radii also expand and contract in pairs.
Now suppose that a pair of radii that make up the adjacent diameters change to the same extent as the first diameter expands and contracts, and the other diameters expand and contract again so that the circumference does not deform. The center of the new circle moves to the center of the second diameter. In this way, the center of the circle moves on the circumference having the radius of the extension length of the first radius every time the adjacent diameters are expanded and contracted sequentially. That is, the center of the circle rotates.

When a disk is excited with its natural frequency, a resonance phenomenon appears,
A large amplitude vibration state is obtained. At this time, the deformation caused by the vibration of the disk is a uniform expansion / contraction deformation in the plane, which is also called a breathing mode. This state is called a basic resonance state or O-order resonance. Although the amplitude decreases drastically when the excitation frequency is changed, resonance states can be obtained even at frequencies twice or three times the fundamental frequency, which are called primary, secondary ... Resonance states. In the first-order resonance state, the center (or the center of gravity) of the circle revolves while the circle is almost a perfect circle.

〔Example〕

Hereinafter, the operating principle of the ultrasonic rotary oscillator according to the present invention will be specifically described based on Examples.

FIG. 1 is a schematic plan view showing an embodiment of an ultrasonic rotary oscillator according to the present invention, and FIG. 2 is a schematic side view thereof. Pb
A (Zr-Ti) O ₃ -based piezoelectric ceramic with a 40 mm outer diameter, a 15 mm inner diameter, and a pressure of 2 mm of a doughnut-shaped disk was coated with silver-baked electrodes on the upper and lower sides.

In this embodiment, it is divided into four equal parts, and the distance between adjacent electrodes is 0.5 mm.
An insulating groove 9 having a width is provided. Connect the top surface electrodes 1, 2, 3, 4 in common, and connect the back surface electrodes that face each other in common.
A direct current high voltage was applied between these four front electrodes and the four back electrodes facing each other to perform polarization treatment. The entire device could be polarized almost uniformly in the same direction.

Next, of these electrodes, the front of electrode 1 and the back of electrode 4,
Connect the back of electrode 1 to the front of electrode 4, the front of electrode 2 to the back of electrode 3, the back of electrode 2 to the front of electrode 3, and connect the lead wires 5, 6, 7, 8 to these 4 groups. did. An alternating voltage of 100 V and 40 KHz was applied between the lead wires 5 and 6, and the same voltage was applied between the lead wires 7 and 8 and the voltage of which phase was delayed by 90 ° at the same frequency. When the frequency of the applied voltage was changed slightly, strong resonance vibration occurred at 38.8 KHz.

An explanation of the deformation of the element due to this vibration is shown in FIG. FIGS. 3A to 3D show changes in the element during one cycle of the sine wave voltage. (A) shows the deformations 1'a, 3'a of the element at the moment when +100 V and -100 V are applied to the regions 1a and 3a, respectively, and 0 volt is applied to the regions 2a and 4a. (B) is + 100V, -100V in regions 2a and 4a,
Regions 1a and 3a represent the deformations 2'a, 4'a of the element at the moment when 0 volt is applied. Similarly, (c) and (d) show deformations 1 ″ a, 3 ″ a, 2 ″ a, 4 ″ a 1/2 cycle and 3/4 cycle after the time of (a), respectively. . With the progress from (a) to (d), the convex portion of the arc makes a full circle in the clockwise direction, and the center of gravity G of the element makes a circular movement in the clockwise direction as shown by 5,6,7,8. are doing.

Although the embodiment described above is a four-divided element, 6,10 ...
Needless to say, even division is possible, but if the number of divisions increases, the phase relationship becomes complicated and the driving voltage also becomes multiphase, so division of 2 to 6 is considered to be the most practical.

The circular vibrator of the present invention may be composed of a piezoelectric element and a disk-shaped, ring-shaped, or cylindrical elastic body fitted to the piezoelectric element.

〔The invention's effect〕

As described above, according to the present invention, in a disk, an annulus, or a cylindrical piezoelectric element having an even number of independently equally deformable regions that are radially equally divided, the regions that are arranged in central symmetry are mutually The regions adjacent to each other were excited by using electric signals in the ultrasonic band so that vibrations of opposite polarities and vibrations of mutually different phases would occur.

Therefore, in the ultrasonic rotary oscillator of the present invention, the deformation state due to vibration is sequentially propagated to the adjacent regions, and as a result, the center of gravity of the piezoelectric element whose center is fixed makes a clockwise or counterclockwise circular motion. The element that is fixed is effectively eccentrically rotated.

[Brief description of drawings]

1 and 2 are a plan view and a side view of an embodiment of an ultrasonic rotary oscillator according to the present invention, and FIG. 3 is a principle explanatory view of the ultrasonic rotary oscillator according to the present invention. 1,2,3,4, ... Electrodes, 1a, 2a, 3a, 4a ... Divided areas of piezoelectric element, 5,6,7,8 ... Lead wire, 9 ... Insulation groove, 10
……Piezoelectric element.

Claims (2)

(57) [Claims] 1. A plurality of pairs of regions, which are composed of circular vibrators and are polarized in the same direction in the thickness direction of the vibrators via a plurality of pairs of electrodes, are asymmetric with respect to the center of the vibrator. An ultrasonic rotary oscillator characterized in that the position of the center of gravity of the oscillator is rotated around the center of the oscillator by exciting the oscillator so as to deform in a plane perpendicular to the polarization direction. 2. The circular vibrator according to claim 1 is a disk, an annulus or a cylindrical piezoelectric element having an even number of independently radially deformable regions which are evenly divided. , An ultrasonic rotary oscillator characterized in that the centrally symmetric regions are excited asymmetrically so that they are excited in opposite phases.