JPH02269481A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To prevent the characteristics of a motor from decreasing by cutting out a driving electrode of a second piezoelectric element and providing it at a symmetrical position with the cutout for a common electrode. CONSTITUTION:An ultrasonic motor 1 is composed of a base 2, a vibrator 6, first - second piezoelectric elements 7-8, a moving unit 9, a spring retainer 12, etc. Driving electrode patterns 14-17 are printed on front and rear of the elements 7-8. A cutout 18 for an arcuate common electrode is formed on the part of the outer peripheral edge of the element 8, and a driving electrode cutout 17a is provided symmetrically with respect to the center. As a result, the distortion of the standing wave of the element 8 can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic motor that generates traveling waves using two piezoelectric bodies that generate standing waves whose positions and phases are shifted.

[Summary of the Invention] In the present invention, drive electrodes are provided on the other surface of the vibrating body to which the movable body is pressed, and two first and second piezoelectric bodies are stacked and fixed, and the second piezoelectric body A notch for a common electrode is provided in the
In an ultrasonic motor that applies a voltage to these piezoelectric bodies and rotates a moving body using a traveling wave generated in the vibrating body,
By cutting out the driving electrode of the second piezoelectric body symmetrically with the common electrode notch with respect to its center, deterioration of motor characteristics due to distortion of standing waves of the second piezoelectric body can be prevented. be.

[Prior Art] Conventionally, an ultrasonic motor l as shown in FIG. 6 has been known.

This ultrasonic motor 1 includes a vibrating body 6, a movable body 9 pressed against one surface of the vibrating body 6, and first and second piezoelectric plates stacked and fixed on the other surface of the vibrating body 6. It is equipped with a body 7.8.

The vibrating body is made of a disk-shaped metal, and a plurality of comb-like protrusions 6a are formed on a predetermined radius of the negative side of the vibrating body. The movable body 9 is formed into a disk shape and is pressed against the upper surface of the protrusion 6a.

As shown in FIG. 4, the first and second piezoelectric bodies 7.8 are formed in a circular shape, and the regions in which the deflection directions are reversed, ie,
It is polarized into 2n regions so that when a voltage is applied, regions that expand (+) and regions that contract (-) are arranged alternately in the circumferential direction (
n is the vibration mode (n=4 in this conventional example).

The second piezoelectric body 8 is located at a wavelength that occurs when a voltage is applied to each of the first piezoelectric bodies 7. Driving electrode patterns 14.1516.17 are printed on both surfaces of the first and second piezoelectric bodies 7 and 8, respectively, and the second piezoelectric body 8 is provided with a common electrode cutout 18.

The first piezoelectric body 7 exposed from this common electrode notch 18
The drive electrode pattern 15 is connected to the first and second piezoelectric bodies 7°8
It is used as a common electrode. And a vibrating body 6 made of metal
Harnesses 21, 20, and 22 are connected to the drive electrode patterns 17 of the nine anti-transferring bodies of the second piezoelectric body 8, respectively.

Then, as shown in FIG. 4, a phase shifter (not shown) applies voltages whose phases are shifted by π, that is, an eO8 wave and a sine wave, to the first and second piezoelectric bodies 7.8. do.

Then, standing waves whose positions and phases are shifted are generated in the first and second piezoelectric bodies 7 and 8, and these two types of standing waves are synthesized,
A traveling wave is generated in the vibrating body 6.

Then, as shown in FIG. 5, the protrusion 6a of the vibrating body 6 repeats an elliptical motion, and the horizontal component of the elliptical motion acts on the movable body 9, which is pressed against the protrusion 61 with a predetermined pressing force, due to friction. and rotate.

[Problems to be Solved by the Invention] However, the second piezoelectric body 8 has a common electrode notch 18.
, the point symmetry with respect to the center of the second piezoelectric body 8 is lost and distortion occurs in the standing wave. As a result, there is a problem that the characteristics of the motor are deteriorated, such as uneven rotation and decreased sensitivity.

The present invention has been made to solve the above problems,
Should a cutout be provided for the common electrode? The purpose is to prevent this deterioration of motor characteristics.

[Means for Solving the Problems] The present invention includes a vibrating body, a movable body pressed against one surface of the vibrating body, and two pivoting electrodes stacked and fixed to the other surface of the vibrating body. a first and second piezoelectric body provided with a first and second piezoelectric bodies, a cutout for a common electrode is provided in the second piezoelectric body, a drive electrode exposed from the cutout is used as a common electrode, and In an ultrasonic motor that applies a voltage to a piezoelectric body and rotates the movable body by a traveling wave generated in the vibrating body, the drive electrode of the second piezoelectric body is arranged in a common electrode notch with respect to its center. The notch is symmetrical to
The structure shall be as follows.

[Function] The part where the pivoting electrode of the second piezoelectric body is notched does not contract due to the reverse piezo effect, and the part where the electrode is notched and the common electrode notch are provided symmetrically with respect to the center. , symmetry with respect to the center of deflection displacement of the second piezoelectric body is maintained, and standing wave distortion is eliminated.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 to 5.

1 and 2, a bracket fitting hole 2a is formed in the base 2 of the ultrasonic motor l, and a bracket 3 is fitted into this bracket fitting hole 2a. A rotating shaft 4 is rotatably inserted into the shaft insertion hole 3a of the bracket 3, and a bearing 5 is provided between the rotating shaft 4 and the bracket 3. Bracket fitting holes 6a, 7a, and 8a of a vibrating body 6 and first and second piezoelectric bodies 7.8 fixed to the lower surface of the vibrating body 6 are fitted into the outer periphery of the bracket 3. The vibrating body 6 is made of a disk-shaped metal, and a plurality of comb-like protrusions 6a are formed in the radial direction on a predetermined radius of the negative surface (upper surface in the figure). The outer circumferential portion 9a of a disk-shaped movable body 9 is in contact with the upper surface of this protrusion 6a, and the rotating shaft 4 is fitted into the shaft fitting hole 9c of the central portion 9b. A friction material 10 is provided on the lower surface of the outer peripheral portion 9a of the movable body 9. A spring seat storage recess 9d is formed in the intermediate portion between the center portion 9b and the outer peripheral portion 9a of the movable body 9. There is a spring seat in this spring seat storage recess 9d! l
is housed therein, and a spring retainer 12 fitted to the rotating shaft 4 is in contact with the upper surface of the spring seat 11. This spring presser 1
The upward movement of the upper surface of 2 is regulated by an E-ring 13 fixed to the rotating shaft 4, and the moving body 9 is pressed against the upper surface of the protrusion 6a of the vibrating body 6 with a predetermined pressure by the spring seat II. has been done.

As shown in FIGS. 1 and 4, two first and second piezoelectric bodies 7.8 are stacked on the other surface of the vibrating body 6 (lower surface in FIG. 1), and are bonded to each other with adhesive. It is glued. This first
- The second piezoelectric body 7.8 has a bracket fitting hole 7a in the center,
8a, and have 2n regions in which the direction of deflection is reversed, that is, regions that expand (+) and regions that contract (-) when a voltage is applied are arranged alternately at a predetermined angle - in the circumferential direction. (In this example, n=4, n=vibration mode). On one surface of the first and second piezoelectric bodies 7.8 on the vibrating body 6 side, driving electrode patterns 14.16 for energizing the first and second piezoelectric bodies 7.8 are provided for each of the polarized It is printed in a sector shape corresponding to the area (+, -). Further, on the other surface of the first and second piezoelectric bodies 7.8, an electrode pattern 15 for supplying current to these piezoelectric bodies 7.8 is provided.
17 is printed over almost the entire surface.

In FIGS. 1 and 3, a part of the outer peripheral edge of the second piezoelectric body 8 is provided with an arcuate common electrode notch I8. This common electrode notch 18 is a driving electrode pattern of the first piezoelectric body 7 exposed from the notch 18! By using 5 as a common electrode and energizing it, the first piezoelectric body 7
and the second piezoelectric body 8 via the driving electrode pattern 16.
This is for applying voltage to both.

As shown in FIG. 3, the drive electrode pattern 17 on the other surface of the second piezoelectric body 8 (the side opposite to the moving body 6) is aligned in shape and position with the common electrode notch 18 with respect to the center O. A symmetrically cut out drive electrode notch 17a is provided. The drive electrode pattern 17 is provided in this drive electrode notch 17a.
An arc-shaped sensor electrode pattern 19 is printed in a polarized state. A sensor (not shown) for detecting vibration displacement is electrically connected to this sensor electrode pattern 19.

Harnesses 20, 21, 22 are attached to the vibrating body 6, the driving electrode pattern 15 exposed from the common electrode notch 18, and the driving electrode pattern 17 on the side opposite to the moving body 6 of the second piezoelectric body 8, respectively. are electrically connected. The harness 20 is electrically connected to the vibrating body 6 because the vibrating body 6 is made of metal and is electrically connected to the driving electrode pattern 14 on the vibrating body 6 side of the first piezoelectric body 7. .

A power source is connected to these harnesses 20, 21, 22 as shown in FIG. 4, and a voltage is applied to the first piezoelectric body 7.

Next, the operation of the above embodiment will be explained based on FIGS. 4 and 5.

In general, the basic formula for a traveling wave is Z(θ, t)=a 5in(nθ+ωt)−・
-■ (n = 7 modes of vibration). If we transform this 2〇, Z(θ, t) = a sin nθ cos (1
) t −−−−−・■π +asinn(θ)sin (15t −■−n. In other words, the two standing waves, the COS wave expressed by the ■equation and the sine wave expressed by the 0 expression, are If they are combined, a traveling wave is obtained.This sine wave is shown by the equation 0.

Therefore, as shown in the principle diagram of FIG. 4, while shifting the above-mentioned position, the first piezoelectric body 7 has a cosine wave, and the second piezoelectric body 8 has a sine wave (the phase is changed to a cOI1 wave by L). ) is applied to the first piezoelectric body 7.
A standing wave of equation 0...a sin nθ cos ωt is generated, and a standing wave of 0 is generated in the second piezoelectric body.

Since the first and second piezoelectric bodies 7.8 are stacked and fixed on the lower surface of the vibrating body 6, the vibrating body 6 has a standing wave expressed by the above equations 0 and 2. are synthesized, and a traveling wave of formula (■) is generated. Then, as shown in FIG.
The upper surface of the protrusion 6a repeats an elliptical movement, and this protrusion 6a
The movable body 9, which is pressed with a predetermined pressure, is subjected to a horizontal component force F due to friction, causing it to rotate. Then, the rotating shaft 4 to which the movable body 9 is fitted rotates.

At this time, the drive electrode pattern of the second piezoelectric body 8 is symmetrical in shape and position with respect to the center O with respect to the common electrode notch I8! Since the driving electrode notch I7λ is provided by notching 7, the driving electrode notch 17a does not expand or contract due to the reverse piezo effect like the common electrode notch 18, so that the second piezoelectric material The symmetry with respect to the center 0 of 8 is not lost, and distortion of standing waves can be prevented.

Therefore, the provision of the common electrode notch 18 has the effect of preventing distortion of standing waves and preventing deterioration of motor characteristics such as uneven rotation and deterioration of sensitivity.

Further, a sensor electrode pattern 19 is printed on the drive electrode notch 17a in polarization with the drive electrode pattern 17, and vibration displacement can be detected by a sensor (not shown), so the motor can be easily controlled. There is also this effect.

In the above embodiment, it goes without saying that the sensor electrode pattern 19 may not be provided in the drive electrode cutout 17a of the second piezoelectric body 8. Further, the driving electrode pattern +4 on the vibrating body 6 side of the first and second piezoelectric bodies 7 and 8
・It is not necessary to provide 16.

Further, in the above embodiment, the circular moving plate, the diaphragm, and the first
1. Although the second piezoelectric body is used, it may be annular one. Furthermore, a structure may be adopted in which a diaphragm and an eleventh and second piezoelectric body are fitted in sequence inside a short cylindrical moving plate with a common center axis. In this case, the common electrode notch and the driving electrode notch are symmetrical about the central axis.

[Effects of the Invention] As is clear from the above description, according to the present invention, two first and second piezoelectric bodies each having a drive electrode are provided on the other surface of the vibrating body to which the movable body is pressed. In an ultrasonic motor in which two piezoelectric bodies are stacked and fixed, a common electrode notch is provided in this second piezoelectric body, a voltage is applied to these piezoelectric bodies, and a moving body is rotated by a traveling wave generated in the vibrating body. Since the driving electrode of the second piezoelectric body is cut out symmetrically with the common electrode notch with respect to its center, the standing wave of the second piezoelectric body due to the provision of the common electrode notch is reduced. Distortion (shi,
This has the effect of preventing deterioration of motor characteristics.

[Brief explanation of drawings]

Figures 1 to 3 show one embodiment of the present invention.
The figure is an exploded perspective view of the ultrasonic motor, FIG. 2 is a sectional view of FIG. 1, FIG. 3 is a perspective view showing the main parts, FIGS. FIG. 6 shows a conventional example, and is a perspective view of the main parts. 1... Ultrasonic motor, 6... Vibrating body, 7... First
piezoelectric body, 8... second piezoelectric body, 9... moving body, 1
4,15.16.17... Drive electrode (pattern),
17λ... Drive electrode notch, 18... Common electrode notch. Exit 1st figure 11" face cause (history) politics 4 dari) 2nd figure 1 Hi sound pθ) 41 to 8 D4 (Shirou Itari) 3rd figure 5 4g child H sign F" ＋ semi-glossy ria <sub'+ itali) Figure 6

Claims (1)

[Claims] (1) A vibrating body, a movable body pressed against one surface of the vibrating body, and first and second movable bodies that are stacked and fixed to the other surface of the vibrating body, and are each provided with a pivot electrode. a piezoelectric body, a common electrode cutout is provided in the second piezoelectric body, and a drive electrode exposed from the cutout is used as a common electrode;
In an ultrasonic motor that applies a voltage to these first and second piezoelectric bodies and rotates the movable body using a traveling wave generated in the vibrating body, the driving electrode of the second piezoelectric body is connected to the center of the ultrasonic motor. An ultrasonic motor characterized by having a notch symmetrical to a notch for a common electrode.