JP3100653B2 - Piezoelectric element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element used as a vibration source of a vibration wave motor or the like, and in particular, has an electrode pattern suitable for performing automatic assembly by recognizing the polarity of polarization by image processing or the like. The present invention relates to a piezoelectric element.

[0002]

2. Description of the Related Art Piezoelectric elements have been used for various purposes. Recently, piezoelectric elements have been used as a vibration source constituting a vibrator of a vibration wave motor . For example, the piezoelectric element is sandwiched between cylindrical metal blocks. As a vibration source of a vibrator of a pencil-type vibration wave motor that rotationally drives a rotor in contact with the metal block by a circular or elliptical motion of surface particles of the metal block caused by the vibration, or a ring-shaped vibrator. A ring-shaped vibration that is bonded and fixed to one surface of a metal vibrating body with an adhesive, for example, forms a traveling wave on the metal vibrating body by synthesizing two standing waves, and moves a member that is in contact with the vibrating body. It is used as a vibration source of a vibrator of a wave motor .

FIG. 6 shows a disk-shaped piezoelectric element used for a vibrator of a pencil type vibration wave motor . The surface shown in the drawing has a gap (hereinafter, referred to as a slit) having a constant width symmetrically on a diameter line. The electrode films 1A and 1B are formed by a known vapor deposition method or screen printing method, and the electrode films are formed on the entire back surface (not shown). The areas corresponding to the electrode films 1A and 1B on the front side are usually polarized in different polarization directions (+,-), and the same piezoelectric element is laminated via an electrode plate (not shown) and arranged before and after. A vibrator is formed by being sandwiched between metal blocks (not shown). In order to generate a motor driving force in, for example, the front metal block by combining vibrations, a positional phase difference is provided between the stacked piezoelectric elements. And it is often arranged with a phase of 90 degrees.

By the way, such a pencil type motor can be miniaturized as much as the little finger of a human hand, and the size of the piezoelectric element is inevitably reduced, so that the assembling workability is deteriorated, and automation is desired.

At this time, it is necessary to correctly recognize the polarization direction of the piezoelectric element and to assemble it. For this purpose, a non-electrode film forming portion is formed on one of the electrode films 1A and 1B (see Japanese Utility Model Application Laid-Open No. 63-187358). 7), a recognition index is obtained by forming one or a plurality of notches 2 on the outer peripheral portion of the piezoelectric element as shown in FIG.

However, in the former case, for example, a circular non-electrode film part is formed in a part of the electrode film and used as a recognition index, this part affects the expansion and contraction in the thickness direction when the piezoelectric element is driven. And there is a problem that the vibration is unbalanced.

Also, in the latter case where the notch 2 is formed in the piezoelectric element itself, there is a problem that the effect of the notch is not small and also affects the vibration of the vibrator.

[0008]

The problem to be solved by the present invention is that the recognition index for recognizing the polarization direction is present in the electrode film or the means for notching the piezoelectric element itself. May affect vibration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric element which can reduce the influence on the deformation at the time of expansion and contraction in the thickness direction and can recognize the polarization direction with high accuracy by a method such as a pattern recognition method. .

[0010]

The piezoelectric element of the present invention, in order to solve the problems], respectively the electrode portions are formed on the front and back surfaces, Li electrode portion on the surface side which is partitioned and formed in a plurality in the border a plurality of non-electrode portions
In the case of a piezoelectric element having a shaping shape, a plurality of
The non-electrode part is constant from the center of the piezoelectric element to the outer periphery
The width is linearly extended, and the width of one specific non-electrode portion is different from the width of another non-electrode portion .

[0011]

In the piezoelectric element having the above-described structure, a specific non-electrode portion can be specified from the difference in the width of the non-electrode portion by reading the width of the non-electrode portion on the front side with a camera or the like and performing image processing. In this case, the non-electrode portion is less deformed at the time of driving and the force due to voltage application is small. Even if the width of the non-electrode portion is slightly increased, there is almost no effect.

[0012]

FIG. 1 shows a first embodiment of a piezoelectric element according to the present invention.
(A) shows the front side, and (b) shows the back side.

In the piezoelectric element of this embodiment, the electrode films 1A and 1B formed on the surface side of the piezoelectric element are formed from the center to the outer periphery of the piezoelectric element by a vapor deposition method or a screen printing method.
It is formed symmetrically with respect to the diameter line with the slits S1 and S2 extending linearly with one width as a boundary . The width a1 of this slit S1
When, made different from the width a2 of the slit S2, widely the width of the slit S2 to the example a2> a1 and Do <br/> so that.

Therefore, when the slits S1 and S2 are read by an image pickup means such as a camera, the slits S1 and S2 can be accurately recognized by comparing the widths thereof, and the piezoelectric element is fixed to a predetermined position by an alignment device or the like. Positioning can be performed in the direction.

On the other hand, it seems at first glance that the width of the slit S2 is widened so as to affect the expansion and contraction of the piezoelectric element in the thickness direction. However, the vicinity of the slit is a portion which is a boundary between the extension direction and the contraction direction. And the slits S1 and S
It can be said that even if there is a difference in width between the two, there is almost no effect on expansion and contraction deformation.

When such a piezoelectric element is used in the vibrator of the above-described pencil type motor, the distortion due to the bending of the vibrator increases as it goes radially outward from the center of the piezoelectric element. That is, when a voltage is applied to the piezoelectric element, a large bending force is generated, and almost no force is generated at the center.
Even if the electrode is somewhat missing, the effect is small.

The same can be applied to the ring-shaped piezoelectric element shown in FIG.

The piezoelectric element shown in FIG. 4 is bonded to the bottom surface of a vibrating body (not shown) formed in a ring shape with an adhesive. is there. The electrode film has the same width as the other slits S5 except for one slit S4, and the width of the slit S4 is wider than the width of the other slits.

That is, as shown in FIG. 5, the vibrating body 3 of this piezoelectric element vibrates due to expansion and contraction of the element portions having different polarization directions in the length direction of the piezoelectric body ( PZT ) , but the slit S4 , S5 have a small displacement, so that even if the width of the slit S4 is widened as in the embodiment shown in FIG.

Second Embodiment FIGS. 2A and 2B show a second embodiment, in which FIG.
(B) shows the back side of the piezoelectric element.

In this embodiment, a slit S having the same width is formed on the front side.
1 and S2 are provided in the same manner as in the related art, except that a slit S3 is formed on the back side corresponding to the slit S1.

Therefore, by reading the slit S3 on the back side, the piezoelectric element can be positioned in a predetermined direction using the slit S3 as an index. In addition, the influence on the expansion / contraction in the thickness direction is almost the same as in the first embodiment described above, since it is at the boundary between the electrode films 1A and 1B corresponding to the slit S1.

Third Embodiment FIG. 3 shows a third embodiment, showing the front side of a piezoelectric element.

In this embodiment, slits S1 and S2 having the same width are formed on the diameter line, and a small cutout 4 is formed at the outer peripheral end of the slit S2 so that a part of the electrode film 1B is cut off. ,
The small missing part 4 is used as a recognition index.

In the present embodiment, the electrode films 1A and 1B are not formed in a symmetrical shape due to the small notch portion 4, but the small notch portion 4 is formed at a position where the expansion and contraction in the thickness direction is small, so that the vibration is reduced. The effect is negligible.

Similarly, a small notch 4 'may be provided by connecting the slit S2 to the end of the inner peripheral portion and partially removing the electrode film 1B (shown by a broken line in FIG. 3).

[0027]

As described above, according to the present invention, the function of the piezoelectric element is not affected by using the non-electrode portion as the recognition index, and the function of the ultra-small piezoelectric element is reduced. The effect of the present invention is that the formation of the recognition index can be performed at the same time without forming a special step of forming the recognition index by forming the electrode portion only by a vapor deposition method or a screen printing method. In particular, the non-electrode part
The shape extends from the center of the piezoelectric element to
In order to recognize the non-electrode part,
When the image sensor used for
Even if there is a deviation in the radial direction of the element,
Less susceptible to recognition degradation
It also has the effect of being suitable for

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of a piezoelectric element according to the present invention.

FIG. 2 is a diagram showing a second embodiment.

FIG. 3 is a diagram showing a third embodiment.

FIG. 4 is a view showing a modification of the embodiment shown in FIG. 1;

FIG. 5 is a diagram showing a sectional view of FIG. 4;

FIG. 6 is a view showing a conventional piezoelectric element.

FIG. 7 is a view showing a conventional piezoelectric element.

[Explanation of symbols]

1A, 1B ... Electrode film S1, S2, S3, S
4, S5 ... slit 2 ... notch 3 ... vibrator

Claims (6)

(57) [Claims] 1. A respective electrode portions are formed on the front and back surfaces, in the piezoelectric element of the ring-shaped electrode portion on the surface side which is partitioned and formed in a plurality in the boundary multiple non-electrode portions, a plurality of non-on surface The electrode is located at the center of the piezoelectric element.
A linear element extending in a constant width from the first to the outer periphery, wherein the width of one specific non-electrode portion is different from the width of another non-electrode portion . 2. The method according to claim 1, wherein the specific one non-electrode
The width of the non-electrode portion other than the electrode portion is equalized.
Electric element. 3. The method according to claim 1 or 2,
Piezoelectric characterized in that the polarization directions of the pole parts are opposite to each other
element. 4. A piezoelectric element in which an electrode portion is formed on each of the front and back surfaces, and the electrode portion on the front surface is partitioned and formed by a plurality of non-electrode portions. A piezoelectric element, wherein a non-electrode portion is formed corresponding to one of the non-electrode portions. 5. The piezoelectric element according to claim 4, wherein the piezoelectric element is formed in a disk shape having an inner diameter part, and the first non-electrode part and the second non-electrode part are arranged on the same diameter line on the surface side. A piezoelectric element, wherein a third non-electrode portion is formed on the back side corresponding to the first non-electrode portion. 6. A piezoelectric element in which an electrode portion is formed on each of the front and back surfaces, and the electrode portion on the front surface is partitioned and formed by a plurality of non-electrode portions. A piezoelectric element having a shape different from an end of a non-electrode portion.