JPH05226717A - Element for laminated piezoelectric actuator - Google Patents

Abstract

PURPOSE:To solve the problem of crack occurrence of a piezoelectric element and elevate durability, in an element for a laminated piezoelectric actuator which is constituted by stacking thin-plate-shaped piezoelectric elements, where electrodes are made at the centers on both sides, and metallic foils equipped with main body parts nearly in the same shapes as the electrodes and projections for extracting electrodes projected from the margins of the main body parts alternately. CONSTITUTION:The sections in contact with the projections of metallic foils, at margins on both sides of a piezoelectric element 10 are made electrode formed parts 11b and 12b. Other section is made a piezoelectric substance exposed face 13 where an electrode is not formed. Hereby, the projection of the metallic foil ceases to directly contact with the base of the piezoelectric substance, and the occurrence of cracks is prevented. Even in the driving under heavy weighting and high electric field, it shows remarkably high durability, and it can be used stably for a long term.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator element, and more particularly to a laminated piezoelectric element which is formed by alternately laminating thin plate-shaped piezoelectric elements and metal foils and expands and contracts in the laminating direction by applying a voltage. The present invention relates to an actuator element.

[0002]

2. Description of the Related Art A laminated piezoelectric actuator element in which thin plate-shaped piezoelectric elements having electrodes formed on both sides and metal foil are alternately laminated expands and contracts in the laminating direction by applying and releasing a voltage.

A piezoelectric element used for such a laminated piezoelectric actuator element is usually manufactured as follows. That is, a raw material powder containing oxides of Pb, Zr, and Ti as main components is formed by, for example, press forming, and then sintered at 1200 to 1300 ° C. (hereinafter, this sintered body is referred to as “PZT System piezoelectric ceramics.) Further, mechanical processing such as double-side polishing is performed to obtain a piezoelectric body. Then, for example, a paste silver ink including silver particles, an organic binder, a solvent and the like is applied to the surface of the piezoelectric body by a screen printing method or the like, and further dried and baked to form an electrode. After this, 50 to 100 ° C, 1 to 3 kV
A direct current voltage of / mm is applied for 5 to 30 minutes to perform polarization treatment to obtain a piezoelectric element.

As shown in FIG. 3 (plan view) and FIG. 4 (side view), in the conventional piezoelectric element 1, the electrodes 3 (3A, 3B) formed on both sides of the piezoelectric body 2 are both electrodes 3A. Three
In order to avoid electric discharge between Bs, it is usually formed at the center of both surfaces of the piezoelectric body 2. Further, on the peripheral edge, a portion (piezoelectric body exposed surface) 4 having a width in the radial direction of about 0.5 to 1 mm and not forming an electrode is provided.

As shown in FIG. 5 (plan view) and FIG. 6 (plan view), the metal foils 5A and 5B used for the laminated piezoelectric actuator element are made of, for example, a stainless foil having a thickness of several 10 μm. Usually, it is composed of a main body 5a having substantially the same shape as the electrode formed on the piezoelectric body, and a plurality of projections 5b protruding from the peripheral edge of the main body 5a.
The protrusions 5b are provided for taking out electrodes in order to apply a voltage from the outside, and usually two (example in FIG. 5) or three (example in FIG. 6) are provided.

However, as shown in FIG. 7 (plan view) and FIG. 8 (side view), the conventional laminated piezoelectric actuator element 6 is a thin plate-shaped piezoelectric element 1 obtained as described above. , So that they are electrically parallel to each other, and that the stretching directions in the thickness direction due to the application of voltage match.
Along with the metal foil 5, several tens to 100 sheets are alternately laminated. In FIGS. 7 and 8, 7 is an electrode lead-out portion, and 8 and 9 are lead wires.

When such a laminated piezoelectric actuator element 6 is made to act as a piezoelectric actuator, specifically, the following displacement, generated force, and high-speed response are obtained. That is, when, for example, a piezoelectric force of 1000 to 1500 V / mm is applied to the stacked piezoelectric elements 1 by about 1 μm, the piezoelectric element 1 is displaced by about 1 μm.
It is displaced by 0 μm. Moreover, the generating force is several hundred kg /
cm ² is very large, and moreover several tens to several hundreds μs
High-speed response of ec order can be obtained. Therefore, such a laminated piezoelectric actuator element is expected to be applied to a hydraulic switching valve, a high-speed printer, and the like.

[0008]

Due to its high generating force, the laminated piezoelectric actuator has a high load and a high load.
It is often required to be driven under a high electric field of 0 to 1500 V / mm. When used under such a high load and a high electric field, the internal piezoelectric element has a piezoelectric body exposed surface of the insulating portion (non-electrode forming portion) formed on the peripheral portions of both surfaces for electrode extraction. In many cases, a crack is generated and destroyed from a portion in contact with the protruding portion, which has been a big problem in durability of the element for laminated piezoelectric actuator. The cause of this is that the edge portion of the protrusion for taking out the electrode of the metal foil comes into direct contact with the electrode non-forming portion of the piezoelectric element, that is, the exposed surface of the voltage body during driving, so that the surface of the piezoelectric body base is scratched. It is considered that this scratch grows and becomes a crack.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a laminated piezoelectric actuator element having excellent durability without the risk of cracks in the piezoelectric body of the piezoelectric element.

[0010]

A laminated piezoelectric actuator element according to the present invention comprises a thin plate piezoelectric element having electrodes formed in the central portions of both surfaces, a main body portion having substantially the same shape as the electrodes, and the main body portion. In a laminated piezoelectric actuator element formed by alternately laminating a metal foil provided with a protruding portion for electrode extraction protruding from the peripheral edge of the piezoelectric element, the peripheral edge portions on both sides of the piezoelectric element have an electrode forming portion and an insulating electrode. Consisting of non-formed parts,
The electrode forming portion is arranged at a portion of the metal foil that comes into contact with the protrusion.

[0011]

In the laminated piezoelectric actuator element of the present invention, the electrode is formed on the peripheral portion of both surfaces of the piezoelectric element at a portion in contact with the electrode lead-out protruding portion of the metal foil. There is no direct contact with the body. Therefore, even when driven under a high load and a high electric field, cracks do not occur at the portions where the piezoelectric element and the metal foil electrode extraction protrusions come into contact, and therefore the durability of the element is significantly improved. It

In addition, except for the above-mentioned electrode forming portions on the peripheral portions of both sides of the piezoelectric element, the piezoelectric body exposed surface, that is, the insulating electrode non-forming portion, prevents discharge between the electrodes on both sides. To be done.

[0013]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view of a piezoelectric element 10 of a laminated piezoelectric actuator element according to a first embodiment of the present invention.

In the piezoelectric element 10 of this embodiment, electrodes 11 and 12 (reference numeral 12 is not shown) are formed on both surfaces of a disk-shaped piezoelectric body 2. The electrodes 11 and 12 have circular portions 11a and 12 having a diameter slightly smaller than that of the circular plate surface of the piezoelectric body 2.
a (12a is not shown) and the circular portions 11a and 12a
And extending portions 11b and 12b arranged on the outer peripheral portion of the. The extending portions 11b and 12b extend to the outer edge of the piezoelectric element 10.

The piezoelectric body exposed surface 13 in the arc-shaped region where the electrodes 11 and 12 are not formed is arranged at the edge of the piezoelectric element 10. By providing this region, discharge between the electrodes 11 and 12 is blocked. There is. The width of the region 13 in the radial direction of the piezoelectric element is preferably about 0.5 to 1 mm as in the conventional case.

In the embodiment shown in FIG. 1, the two extending portions 11b are diametrically opposed to each other, that is, 180 ° in the circumferential direction.
They are arranged at the pitch. The extension part 12b is also 1
They are arranged at a pitch of 80 °. Each extension 12b
Are arranged at intermediate positions in the circumferential direction of the extending portions 11b. That is, in FIG. 1, the extending portion 11b is located at the 3 o'clock and 9 o'clock positions with respect to the center of the piezoelectric element 10.
2b is at 0 o'clock and 6 o'clock. In this way, the extension 11
The positions of b and 12b are deviated so that the projections of the metal foil to be overlapped with the electrodes 11 and 12 can be arranged at the positions most distant from each other in the circumferential direction of the piezoelectric element.

In the embodiment shown in FIG. 2, electrodes 14 and 15 formed on both surfaces of the piezoelectric element 16 (reference numeral 15 is not shown).
Is a circular portion 14 having a diameter slightly smaller than the circular plate surface of the piezoelectric body 2.
a, 15a (15a is not shown), and the three-piece extension 1
4b and 15b. Each extension 14b, 15b
Extends from the circular portions 14a and 15a to the outer edge of the piezoelectric body 2. The extension portions 14b and 15b are arranged at positions equally divided into three in the circumferential direction of the piezoelectric element 16, and each extension portion 15b has the same circumference as the extension portion 14b, as in the embodiment of FIG. It is located in the middle position in the direction. No electrodes are formed in the arc-shaped regions between the respective extending portions 14b and between the extending portions 15b, which are the piezoelectric body exposed surfaces 13.

The piezoelectric element 10 shown in FIG. 1 is laminated with the metal foil 5A shown in FIG. 5, for example. Also,
The piezoelectric element 16 of FIG. 2 is laminated with the metal foil 5B shown in FIG.

Therefore, similarly to the laminated piezoelectric actuator element 6 shown in FIGS. 7 and 8, in the laminated piezoelectric actuator element of the present invention, one piezoelectric element is sandwiched between two metal foils. Are stacked. In this case, the piezoelectric element and the metal foil are laminated so that the protrusions of the metal foil are arranged on both sides of the extension of the electrode of the piezoelectric element.

In the element for a laminated piezoelectric actuator of the present invention, the protrusions on the peripheral portions on both sides of the piezoelectric body of the piezoelectric element, which are conventionally the entire electrode non-forming portion, that is, the exposed surface of the piezoelectric body. Except that electrodes are formed on the corresponding portions, the structure can be the same as that of the conventional laminated piezoelectric actuator element, and there is no particular limitation on the shape and material of the piezoelectric element and the metal foil.

The shape of the piezoelectric element used in the present invention may be a thin plate shape, and various shapes such as a circle, an ellipse, a square, a rectangle, and other polygons can be adopted depending on the application. As described above, such a piezoelectric element can be easily manufactured by forming electrodes at predetermined locations on both surfaces of a piezoelectric body made of PZT-based piezoelectric ceramic. As the electrode forming method, Ni plating, sputtering or the like can be adopted in addition to the above-described silver ink application.

On the other hand, examples of the metal foil include stainless steel foil, copper foil, brass foil, phosphor bronze foil, etc., which are appropriately selected according to the application, but stainless steel foil is not a problem such as corrosion. Is preferred.

Specific examples will be described below. Example 1 As a metal foil, a stainless steel foil having a thickness of 30 μm was used, and as shown in FIG. 5, projections with a width of 1.5 mm and a length of 3 mm for taking out electrodes were formed on the periphery of a circular main body having a diameter of 15 mm. Ones formed at two positions separated by 180 ° were manufactured.

On the other hand, a piezoelectric element having the shape shown in FIG. 1 was produced. The piezoelectric body used is 17 mm in diameter and 0.5 mm in thickness.
Made of PZT-based piezoelectric ceramics of d ₃₃ = 610 (pC
/ N). The electrodes were formed by printing a silver paste on both surfaces of this piezoelectric material, drying and baking at 600 ° C. As for the electrodes, as shown in FIG. 1, around the circular electrode having a diameter of 15 mm, the protrusion-shaped electrodes having a width of 3 mm and a length of 1 mm were separated by 180 ° at the protrusion corresponding portions, and the front and back electrode patterns were 90 each. Formed so as to be offset.

Fifty piezoelectric elements thus obtained and 51 metal foils are alternately laminated one by one, and a weight of 30 is applied.
While adding 0kg, as a durability test, voltage -200
A pulse wave (duty ratio 1) of ˜ + 600 V and 100 Hz was applied for 100 hours (1 × 10 ⁷ times as the driving frequency). Table 1 shows the amount of cracks generated.

Example 2 As the metal foil, a stainless steel foil having a thickness of 30 μm was used, and as shown in FIG. 6, a protrusion having a width of 1.5 mm and a length of 3 mm was formed on the periphery of a circular main body having a diameter of 15 mm for taking out electrodes. Was formed at three positions separated by 120 °.

On the other hand, a piezoelectric element having the shape shown in FIG. 2 was prepared using the same piezoelectric material as that used in Example 1. In addition, as shown in FIG. 2, as for the electrodes, a protrusion-shaped electrode having a width of 3 mm and a length of 1 mm was separated by 120 ° around a circular electrode having a diameter of 15 mm, and the electrode patterns on the front and back sides were It was formed so as to be shifted by 60 °.

Using the piezoelectric element thus obtained, a laminated piezoelectric actuator element was prepared in the same manner as in Example 1, and similarly subjected to a durability test. The results are shown in Table 1.

Comparative Example 1 A laminated piezoelectric actuator element was manufactured in the same manner as in Example 1 except that the electrodes on the piezoelectric element were circular with a diameter of 15 mm, and no electrode was formed at the portion in contact with the protrusion of the metal foil. Then, a durability test was conducted in the same manner, and the results are shown in Table 1.

[0030]

[Table 1]

It is apparent from Table 1 that the element for laminated piezoelectric actuator of the present invention has a significantly lower crack generation rate than the conventional element and is excellent in durability.

[0032]

As described above in detail, according to the laminated piezoelectric actuator element of the present invention, there is no problem of cracking of the piezoelectric body of the piezoelectric element, and even when driving under high load and high electric field, Provided is an element for a laminated piezoelectric actuator which exhibits remarkably high durability and can be stably used for a long period of time.

[Brief description of drawings]

FIG. 1 is a plan view showing a piezoelectric element of a laminated piezoelectric actuator element according to an embodiment of the present invention.

FIG. 2 is a plan view showing a piezoelectric element of a laminated piezoelectric actuator element according to an embodiment of the present invention.

FIG. 3 is a plan view of a conventional piezoelectric element.

FIG. 4 is a side view of the piezoelectric element shown in FIG.

FIG. 5 is a plan view of a metal foil.

FIG. 6 is a plan view of a metal foil.

FIG. 7 is a plan view of a laminated piezoelectric actuator element.

FIG. 8 is a side view of the element for laminated piezoelectric actuator shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Piezoelectric body 5A, 5B Metal foil 10, 16 Piezoelectric element 11, 14 Electrode 13 Piezoelectric body exposed surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuhiro Nagata 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Co., Ltd. (72) Inventor Satoshi 1060 Narita, Odawara-shi, Kanagawa Kasei Optonix (72) Inventor Hitoshi Aihara 1060 Narita, Odawara, Kanagawa Kasei Optonix Co., Ltd. (72) Inventor Eio Asakura 1060, Narita, Odawara, Kanagawa Kasei Optonix Co., Ltd.

Claims (1)

[Claims] 1. A metal foil comprising a thin plate-shaped piezoelectric element having electrodes formed on the central portions of both surfaces, a main body having substantially the same shape as the electrodes, and a protrusion for extracting an electrode protruding from the periphery of the main body. In an element for a laminated piezoelectric actuator formed by alternately stacking and, the peripheral edges of both surfaces of the piezoelectric element are composed of an electrode forming portion and an insulating electrode non-forming portion, and the electrode forming portion is a metal foil. The element for a laminated piezoelectric actuator, characterized in that it is arranged in a portion that comes into contact with the protrusion.