JPH1126829A - Piezo electric actuator device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated piezo electric actuator which can exhibit stable characteristics without causing any damage of an inactive part when operated at a high speed throughout for a long period of time under a constant stress. SOLUTION: The actuator device includes a piezo electric actuator having a laminate 11 of a plurality of piezo electric plates 10 laminated through an electrode and having inactive members 15 and 16 provided on upper and lower surfaces of the laminate 11, a cylindrical outer easing 25 for accommodating the piezo electric actuator, and a pair of metallic caps 29 and 31 for closing openings of the outer casing 25. In this case, the inactive members 15 and 16 are respectively formed on their outer surfaces in a laminated plate direction with a projection 21 having a spherical surface. The pair of metallic caps 29 and 31 are formed with spherical recesses 27 which mate with the projections 21 of the inactive members 15 and 16, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator device, for example, a precision positioning device such as an optical device, a drive element for preventing vibration, a drive element for fuel injection of an automobile engine, and the like. The present invention relates to an actuator device.

[0002]

2. Description of the Related Art Conventionally, there have been disclosed a number of methods of manufacturing a laminated actuator by laminating a plurality of piezoelectric plates (see, for example, Japanese Patent Publication No. 56-50434). In particular, various bonding methods have been suggested because the bonding state greatly changes depending on the bonding method of the piezoelectric plates, the characteristics after lamination greatly fluctuate, and the characteristics vary between elements.

As a method of manufacturing a laminated piezoelectric actuator, there is a method of simultaneous firing. According to the method of simultaneous firing, it is relatively easy to make the thickness of the piezoelectric plate thin, and it is possible to increase the applied electric field, thereby enabling low voltage and high displacement. However, the piezoelectric plate material (for example, Pb (Z
r, Ti) It is necessary to use a noble metal such as Pd or Pt as an internal electrode material for simultaneous firing with ceramics such as O ₃ , and the cost increases as the number of layers increases. There was a point.

Therefore, conventionally, in order to reduce the cost,
A plurality of piezoelectric plates having metal electrodes formed on both sides are laminated, a metal thin plate is arranged between the metal electrodes, and connection projections of these metal thin plates are pivoted so as to leave a predetermined gap with respect to the outer peripheral edge of the piezoelectric plate. In the direction, the connecting protrusions of the same polarity are overlapped to conduct electricity, and a comb-shaped insulating resin spacer made of synthetic resin is inserted into the gap between the connecting protrusion and the outer peripheral edge of the piezoelectric plate, and this is thermally shrunk. (Japanese Patent Laying-Open No. 4-37098) discloses a laminated piezoelectric actuator housed in an insulating tube for use.
No. 7).

[0005]

In recent years, a higher voltage has been applied to a small piezoelectric actuator in order to secure a large amount of displacement.
In the multilayer piezoelectric actuator disclosed in Japanese Patent Application Laid-Open No. 0987/2009, there is a fear that inactive bodies placed above and below are fatigued and damaged by repeated stress during driving in which displacement is repeated at high speed, and the displacement characteristics and load characteristics of the actuator are significantly deteriorated. there were.

Further, in the structure of the laminated actuator as described above, the parallelism of the inert body becomes important,
When the parallelism is poor, there is a problem that the reliability of the active portion, which is the driving portion, is reduced due to the concentrated load per piece.

[0007] The present invention provides a piezoelectric actuator device in which even when repeatedly displaced at a high speed, the inert body is not broken, a load acts on the inert body on average, and reliability can be improved over a long period of time. The purpose is to do.

[0008]

According to the present invention, there is provided a piezoelectric actuator device comprising: a plurality of piezoelectric plates laminated via electrodes; A piezoelectric actuator device comprising: a cylindrical outer case body for accommodating a piezoelectric actuator; and a pair of metal caps for closing an opening of the outer case body. A spherical projection is formed, and a spherical concave portion corresponding to the spherical projection of the inert body is formed in each of the pair of metal caps.

[0009]

In the piezoelectric actuator device of the present invention, an inert body having a spherical projection formed on the outer surface in the laminating direction is disposed on the upper and lower surfaces of the laminate, and the spherical projection is provided on the metal cap of the outer case body. The piezoelectric actuator is housed inside the outer case by abutting against the spherical concave part, so that the stress acting on the interface between the inactive body and the active portion (laminated body) becomes uniform, and the inactive body becomes inactive for a long period of high-speed driving. Breakage is prevented and reliability is improved. In addition, by receiving the stress on the spherical surface, the stress concentration due to one piece is reduced, and the reliability of the stacked body as the driving portion is also improved.

[0010]

FIG. 1 shows a piezoelectric actuator device of the present invention, FIG. 2 shows a piezoelectric actuator, and FIG.
2 shows an enlarged part of FIG. 2, FIG. 4 shows a thin metal plate, and FIG. 5 shows the metal cap of FIG. 1 to 3, reference numeral 10 denotes a disk-shaped piezoelectric plate. These piezoelectric plates 10 are made of Pb (Zr, Ti) O ₃ (hereinafter PZ).
(Abbreviated as T).

As the piezoelectric material constituting the piezoelectric plate, for example, a piezoelectric ceramic material containing lead zirconate titanate as a main component is used. However, the present invention is not limited to this. Any may be used. As the piezoelectric material constituting the piezoelectric plate, that the piezoelectric strain constant d ₃₃ is high is preferable.

In particular, Pb, Zr, Ti,
A composite perovskite compound containing Zn, Sb, Ni, Te, and at least one of Sr and Ba, wherein the composition formula based on the molar ratio of these metal elements is Pb
_{1-xy Sr x Ba y (} Zn 1/3 Sb 2/3) a (Ni 1/2
Te _1/2 ) _b Zr _c Ti _{1 -abc} O ₃ ,
When the molar ratio of x, y, a, b, c is 0 ≦ x ≦ 0.12, 0
≦ y ≦ 0.12, 0 <x + y, 0.05 ≦ a ≦ 0.1
2, with respect to 100 parts by weight of the basic component satisfying 0 ≦ b ≦ 0.015 and 0.43 ≦ c ≦ 0.52, PbO and Nb ₂ O ₅ having an equimolar ratio in a total amount of 0.2 to A piezoelectric ceramic composition containing 1.2 parts by weight is desirable. The thickness t of the piezoelectric plate 10 is desirably 0.2 to 0.6 mm from the viewpoint of miniaturization and application of a high voltage.

A laminate 11 is formed by laminating a plurality of piezoelectric plates 10, and two conductive adhesive layers 12 are formed between the piezoelectric plates 10.
A metal sheet 13 is interposed between the two. As shown in FIG. 4, connecting projections 14 are formed on the metal thin plates 13, and project in the radial direction of the piezoelectric plate 10. As shown in FIG. 6, the metal thin plates 13 are interposed between the piezoelectric plates 11 so as to alternately face 90 degrees,
These metal thin plates 13 become a positive electrode thin plate 13a and a negative electrode thin plate 13b depending on the position of the connecting projections 14.

The thin metal plate 13 used has conductivity, and is preferably, for example, a metal such as silver, brass, copper, or stainless steel. The thickness of the metal sheet 13 is preferably as thin as possible so as not to contribute to the displacement amount, for example, 20 to 50 μm. Further, it is desirable that the metal sheet 13 is smaller than the piezoelectric plate 10 so that the disk portion is not exposed on the outer peripheral surface of the laminated body 11 in order to prevent a short circuit or discharge with another metal sheet 13.

The conductive adhesive layer 12 is formed by applying a conductive adhesive paste to the piezoelectric plate 10 and drying it as described above. This conductive adhesive paste is made of a metal powder such as Ag and a glass component. It is desirable that the material has a melting point of about 400 to 600 ° C.

[0016] This is because if the glass component contained in the conductive adhesive paste is melted by applying pressure and heating during lamination, the piezoelectric plates 10 are firmly joined to each other, and peeling at the interface generated by repeated application of a high electric field. Can be prevented,
This is because the reliability of the laminate can be improved. In particular, the conductive bonding paste contains 40 to 60% by weight of Ag powder,
glass component consisting _{bO-SiO 2 -B 2 O 3} 40~6
Desirably, it is 0% by weight.

In the piezoelectric actuator device according to the present invention, the inert body 1 which does not expand and contract is provided on the upper and lower surfaces of the laminate 11.
5 and 16 are formed, and a spherical projection 21 is formed on the outer surface in the laminating direction, and a piezoelectric actuator 23 is formed. This piezoelectric actuator 23
Are housed in a cylindrical outer case body 25 as shown in FIG. In FIG. 1, the piezoelectric actuator is shown in a side view for easy understanding.

The outer case body 25 has a spherical concave portion 27 which abuts against the spherical projections 21 of the inert bodies 15 and 16 of the piezoelectric actuator 23 and which matches the spherical projections 21 of the inert bodies 15 and 16. The formed pair of metal caps 29, 3
1 is arranged. That is, the cylindrical outer case body 25
At the top and bottom of the metal cap 2
9, 31 are arranged. The material of the metal caps 29 and 31 is preferably a metal which is hardly corroded such as stainless steel and aluminum. The lower metal cap 31 is screwed so that it can be fixed to the outer case body 25.

The outer case body 25 is similarly screwed on the lower side, and is fixed to the lower metal cap 31 with screws. The outer case 25 is made of metal caps 29 and 31.
Similarly, metals that are not easily corroded, such as stainless steel and aluminum, are desirable. The inside of the outer case 25 is filled with an insulating resin 35.

The insulating resin 35 used has a high insulating property, can be used at a temperature from room temperature to 200 ° C., and does not crack due to repeated stress. desirable.

In order to fill the space with the insulating resin 35 so that there is no gap between the outer case 25 and the outer peripheral surface of the piezoelectric plate 11 and the gap between the outer peripheral portion of the piezoelectric plate 11 and the connecting projections 14, It is important to adjust the conditions such as viscosity and to completely remove air by vacuum degassing.

The multilayer piezoelectric actuator of the present invention may have any polygonal shape such as a columnar shape or a hexagonal prism other than a square prism.

[0023]

EXAMPLE A PZT sintered body was polished on both sides to a diameter of about 15 mm.
A disk-shaped piezoelectric plate having a thickness of 0.4 mm and a thickness of 0.4 mm was formed. 55% by weight of Ag powder, PbO-Si
An electrically conductive paste of 45% by weight of glass containing O ₂ —B ₂ O ₃ as a main component was printed to a thickness of 5 μm, dried at 100 ° C., and baked at 520 ° C. An Ag thin plate having a thickness of 25 μm was sandwiched between the piezoelectric plates, and 100 piezoelectric plates were laminated to form a laminate.

The connecting projections of the thin metal plates were alternately arranged so as to be located at the same position every other layer. 100 piezoelectric plates
An inert body that has been subjected to spherical processing on one side is laminated on the upper and lower surfaces of the laminated body, and set to a special spherical receiving jig and lightly apply pressure so that no displacement occurs. A weight of about 3 kg was placed on the upper part and pressure-bonded at 600 ° C. for one hour.

Next, as shown in FIG. 2, the radially protruding connecting projections of the piezoelectric plate were bent in the axial direction and electrically connected.

[0026] This is kept at 3 kV in silicon oil at 80 ° C.
/ Mm DC voltage was applied for 30 minutes to perform polarization processing. Thereafter, the laminated body is fixed by upper and lower metal caps and an outer case body, and is filled with a silicon-based outer resin.
The resultant was dried and hardened at 1 ° C. for 1 hour to produce a piezoelectric actuator device.

An AC electric field of 0 V to +500 V is applied for 100 H to 100 piezoelectric actuator devices of the present invention in the atmosphere.
Even when applied 1 × 10 ⁹ times at the frequency of z, the inert body was not damaged, and the displacement after application was 44 μm on average. The variation of the displacement amount of the piezoelectric actuator device manufactured in the experiment was ± 2% for 100 samples.

The load displacement characteristic of the test sample was 1
The measurement was performed 10 times at every 10 ⁸ driving, and the variation from the initial value was within ± 3%.

On the other hand, ten piezoelectric actuator devices were manufactured in which the inert bodies were not spherically processed, and the same test was carried out. As a result, three inert bodies were damaged in 2 × 10 ⁸ times. In addition, 5 out of 10 pieces had a bending point in the load displacement characteristics after driving 2 × 10 ⁸ times, and the variation from the initial value was about 50%.

The displacement was measured by fixing the sample to a jig for applying a load, applying a load of 2 kN and measuring with a laser displacement meter, and using a contact type laser holometer for the load displacement characteristics. The displacement during application of a load of ５5 kN was evaluated by an average value measured ten times.

[0031]

As described in detail above, according to the present invention, the stress acting on the interface between the inactive material and the active portion (laminated body) becomes uniform, and the inactive material is prevented from being damaged during long-term high-speed driving. And reliability can be improved. In addition, by receiving the stress on the spherical surface, the concentrated stress per piece is reduced, and the reliability of the stacked body as the driving portion can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a piezoelectric actuator device of the present invention.

FIG. 2 is a side view showing a laminate of the present invention.

FIG. 3 is an enlarged side view showing a part of FIG. 2;

FIG. 4 is a plan view showing the metal sheet of FIG. 1;

FIG. 5 is a side view showing the pair of metal caps of FIG. 1;

FIG. 6 is a plan view of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Piezoelectric plate 11 ... Laminated body 12 ... Conductive adhesive layer 13 ... Metal thin plate 14 ... Connection projection part 15, 16 ... Inactive body 21 ... Spherical projection Part 23 ... Piezoelectric actuator 25 ... Outer case body 27 ... Spherical recess 29, 31 ... Metal cap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Ogata 1-1-1, Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Corporation Kagoshima Kokubu Plant (72) Inventor Katsuhiko Onizuka 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Research Institute

Claims (1)

[Claims] 1. A piezoelectric actuator comprising: a plurality of piezoelectric plates laminated via electrodes; upper and lower surfaces of a laminated body provided with respective inactive members; and a cylindrical outer case body for accommodating the piezoelectric actuator. A piezoelectric actuator device comprising: a pair of metal caps for closing an opening of the outer case body, wherein a spherical projection is formed on an outer surface of the inactive body in a laminating direction, and the pair of metal caps is formed. A piezoelectric actuator device comprising: a metal cap; and a spherical concave portion corresponding to the spherical protrusion of the inert body.