JPH1154810A - Laminated piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable laminated piezoelectric actuator, capable of suppressing the decline in the displacement amount and the disconnection in the electrode connection parts due to repeated drives and being easily manufactured, even in the cases of high humidity and high impressed voltage. SOLUTION: A laminated piezoelectric actuator is provided with multiple laminated piezoelectric boards 1 and the metallic thin plates 3, respectively interposed between the piezoelectric boards 1 and having connecting protrusions 3a junctioned with the boards 1 by a conductive adhesive. At this time, the connecting protrusions 3a are protruded alternately in the two opposite directions, to be electrically connected to one another at positions which are releasable from the drive stress concentration from the outer periphery of the piezoelectric boards 1 which is laminated with plural connecting protrusions 3a protruded in the same direction using metallic tandem comb-teeth type spacers.

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, and more particularly to a laminated piezoelectric actuator used for a precision positioning device such as an optical device, a driving element for preventing vibration, a driving element for fuel injection of an automobile engine, and the like. Related to actuators.

[0002]

2. Description of the Related Art Conventionally, there has been a laminated piezoelectric actuator in which a plurality of piezoelectric plates on which electrodes are formed are laminated to form a piezoelectric body. In such a laminated piezoelectric actuator, a voltage is applied to the piezoelectric body to extend the piezoelectric body by several to several tens of μm by an inverse piezoelectric effect, and is used as a driving force source of the actuator.

As a method for manufacturing such a laminated piezoelectric actuator, there is a method based on simultaneous firing. According to this simultaneous firing method, it is relatively easy to manufacture the piezoelectric plate with a small thickness, and it is possible to obtain a high displacement at a low voltage because the applied electric field can be increased.
Pd is used as an internal electrode material for co-firing with a piezoelectric plate material made of ceramics such as (ZrTi) O _3.
It is necessary to use a noble metal such as Pt or Pt, and there is a problem that the cost increases as the number of layers increases.

In order to reduce the cost, conventionally, as shown in FIGS. 4 and 5, a plurality of piezoelectric plates 11 having metal electrodes 12 formed on the front and back surfaces are laminated, and a metal The thin plates 13 are arranged, and these metal thin plates 13
And a connecting projection 13a bent in the laminating direction of the piezoelectric body 11 so as to leave a predetermined gap with respect to the outer peripheral edge of the piezoelectric plate 11, and provided with the same polarity. The connection projections 13a are overlapped and electrically connected to each other, and a comb-tooth spacer 14 made of insulating synthetic resin or the like is inserted into a gap between the connection projection 13a and the outer peripheral edge of the piezoelectric plate 11, This was housed in a heat-shrinkable insulating tube 16 (for example, see Japanese Patent Application Laid-Open No. 4-370987).
Reference).

However, it is necessary to bend the connecting projections 13a of the soft and small thin metal plate 13 and overlap the connecting projections 13a of the same polarity to electrically connect them by soldering or the like. There was a problem that it took.

In recent years, in order to secure a large displacement with a small piezoelectric actuator, a higher voltage is applied. However, as described above, a comb made of an insulating synthetic resin or the like is used. In the laminated piezoelectric actuator in which the upper and lower connection protrusions 13a are connected via the tooth-like spacer 14, the upper and lower connection protrusions 13a are connected to each other by soldering or welding. 14, and when the piezoelectric plate 11 is repeatedly displaced at a high speed, the connection projection 1
3a may cause metal fatigue at the connection portion or the connection protrusion 1
There is a problem in that the friction between the comb-shaped spacer 3a and the comb-shaped spacer 14 and the insulating tube 16 breaks or breaks the connection between the connection protrusions 13a, thereby reducing the displacement of the piezoelectric plate 11.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional apparatus, and is easy to manufacture. Further, even when the apparatus operates at high speed, it is possible to connect a thin metal plate disposed between piezoelectric plates. It is an object of the present invention to provide a multilayer piezoelectric actuator that eliminates the occurrence of breakage or the like at a connection portion of a projection.

[0008]

In order to achieve the above object, in a laminated piezoelectric actuator according to the present invention, a thin metal plate is disposed between a plurality of laminated piezoelectric plates via a conductive adhesive. A laminated piezoelectric actuator in which a connecting projection protruding alternately in two opposite directions of the piezoelectric plate and bent in the laminating direction of the piezoelectric plate is provided on a thin metal plate, and a plurality of connecting projections protruding in the same direction are connected. In the above, a metal comb-shaped spacer is disposed on an opposing side of the laminated piezoelectric plate via an insulating resin, and the plurality of connection holes are provided on an outer peripheral portion of the piezoelectric plate through the metal comb-shaped spacer. The projections were connected and fixed.

In the laminated piezoelectric actuator according to the present invention, the metal comb-shaped spacer may be disposed at a position of 0.6 to 1.5 mm away from the piezoelectric plate via the insulating resin. desirable.

[0010]

As described above, the comb teeth of the comb-shaped spacer are inserted between the connection protrusions of the thin metal plate interposed between the plurality of piezoelectric plates, and the connection protrusion penetrating the comb teeth is inserted. By connecting and fixing to the metal comb-shaped spacer, the connection protruding portions of the thin metal plate can be electrically connected via the metal comb-shaped spacer, thereby facilitating the manufacture. Further, by providing the metal comb-shaped spacer and the laminated piezoelectric plate separately with an insulating resin interposed therebetween, it is possible to alleviate the concentration of stress on the connecting projections of the thin metal plate repeatedly, and to achieve high-speed continuous operation. Even when driving, the deterioration of the connection projection is small, and long-time operation is possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a main part of an embodiment of a laminated piezoelectric actuator according to the present invention, wherein 1 is a piezoelectric plate, 2 is a conductive adhesive, 3 is a thin metal plate, 3a is a connecting projection, Is a comb-shaped spacer.

The piezoelectric plate 1 is a sintered body containing Pb (ZrTi) O ₃ (hereinafter abbreviated as PZT) as a main component. Piezoelectric plate 1
The piezoelectric material constituting the is not limited thereto, but may be any ceramics having piezoelectricity, has high piezoelectric strain constant d ₃₃ is desirable. In particular, Pb, Zr, Ti, Zn, Sb, Ni, T
and e, a composite perovskite compound containing at least one of Sr and Ba, the composition formula by molar ratio of these metal _{elements, Pb 1-xy Sr x Ba} y (Zn
_{1/3 Sb 2/3) a (Ni 1/2} Te 1/2) b Zr c Ti
_When expressed as _1-abc O ₃ , the molar ratio of x, y, a, b, c is 0 ≦ x ≦ 0.12, 0 ≦ y ≦ 0.12, 0 <x +
y, 0.05 ≦ a ≦ 0.12, 0 ≦ b ≦ 0.015,
PbO and Nb ₂ O _{5 in} equimolar ratio with respect to 100 parts by weight of the basic component satisfying 0.43 ≦ c ≦ 0.52
Is preferably added in a total amount of 0.2 to 1.2 parts by weight. The thickness t of the piezoelectric plate is desirably 0.2 to 0.6 mm from the viewpoint of miniaturization and application of a high voltage. Such a piezoelectric plate 1 is used by laminating several tens to several hundred layers.

A conductive adhesive layer 2 is formed on both sides of the piezoelectric plate 1. This conductive adhesive layer 2 is made of silver or the like containing glass frit. This conductive adhesive layer 2
Is formed by applying a conductive paste to the piezoelectric plate 1, drying and baking. This conductive paste contains a metal powder such as Ag and a glass component, and
Those that melt at about 600 ° C. are desirable. This is because the glass component contained in the conductive paste melts when pressed and heated during lamination, and the piezoelectric plates 1 are firmly joined together to prevent separation at the interface caused by repeated application of a high electric field. This is because the reliability of the multilayer piezoelectric body can be improved. Such a conductive paste contains, for example, 40 to 60% by weight of Ag powder and PbO—SiO ₂ —
And the like made of a glass component 40 to 60% by weight consisting of B ₂ O _3.

A thin metal plate 3 is disposed between the piezoelectric plates 1 via a conductive adhesive layer 2. The thin metal plate 3 has conductivity, and is formed of a metal such as silver, brass, copper, and stainless steel. Since the metal sheet 3 does not contribute to the displacement, it is as thin as possible, for example, 20 to 100 μm.
m is preferred. Further, in order to prevent a short circuit or discharge with another thin metal plate 3, it is desirable that the size is smaller than the piezoelectric plate 1 so as not to be exposed on the outer peripheral surface of the piezoelectric body 1.

As shown in FIG. 2, the metal sheet 3 has
The connection projection 3a is formed, and protrudes in the radial direction of the piezoelectric plate 1. In addition, as shown in FIG. 1, the metal thin plate 3 is interposed between the piezoelectric plates 1 such that the connecting protrusions 3a face alternately. These metal thin plates 3 are made into a positive electrode metal thin plate and a negative electrode metal thin plate depending on the position of the connection projection 3a.

The connecting projection 3a of the thin metal plate 3 is electrically connected to and fixed to the metal comb-like spacer 4.
As shown in FIG. 3, the metal comb-like spacer 4 is formed in a comb-like shape so that the connecting projections 3a of the metal thin plate 3 are connected to each other. A clearance is provided so as to pass through the connection projection 3a. The metal comb-shaped spacers 4 are connected to the connecting projections 3 of the thin metal plate 3.
It is preferable that the tip of the comb tooth portion is tapered in order to facilitate the passage of a and improve workability. In addition, in order to reduce the stress generated in the comb teeth when the actuator is driven, it is preferable that the base of the comb teeth is formed in an R shape. This metal comb-shaped spacer 4 is also formed of a conductive metal such as silver, brass, copper, or stainless steel, and has a thickness of 20 to 100 μm.
m.

It is desirable that the metal comb-shaped spacer 4 is provided at a distance A of 0.6 to 1.5 mm from the outer peripheral portion of the piezoelectric plate 3. When the distance A is shorter than 0.6 mm, when continuous driving is performed, stress concentration due to repetition of displacement occurs at the connection portion between the metal comb-shaped spacer 4 and the connection protrusion 3a, and connection such as disconnection is caused. If the gap A is longer than 1.5 mm, the metal comb-shaped spacer 4
This is because a connection failure due to stress concentration at a connection portion between the piezoelectric actuator and the connection projection 3a is unlikely to occur, but the size of the multilayer piezoelectric actuator itself increases. The connecting projection 3a of the thin metal plate 3 is joined to the metal comb-like spacer 4 by soldering or welding.

The outer peripheral surface of the piezoelectric plate 1 is covered with an insulating resin 5,
In addition, the gap between the metal comb-shaped spacer 4 and the outer peripheral portion of the piezoelectric plate 1 is filled with the insulating resin 5 so that no gap is generated. The filling method is performed by adjusting conditions such as viscosity, and sufficiently filling the void with the insulating resin 5 by vacuum defoaming or the like under reduced pressure.

The laminated piezoelectric actuator may have any polygonal shape such as a cylindrical shape, a quadrangular prism, or a hexagonal prism.

[0020]

【Example】

Example _{1: Pb 1-xy Sr x} Ba y (Zn 1/3 S
_{b 2/3) a (Ni 1/2 Te} 1/2) b Zr c Ti 1-abc
When expressed as O ₃ , x = 0.04, y = 0.02, a =
Pb having an equimolar ratio with respect to 100 parts by weight of the basic component satisfying 0.075, b = 0.005, and c = 0.47.
PZ added with 0.5 parts by weight of O and Nb ₂ O ₅ in total
Both sides of the T sintered body are polished to a diameter of 20 mm and a thickness of 0.5
mm-shaped disc-shaped piezoelectric plate 1 was formed. On both main surfaces of the piezoelectric plate 1, Ag powder 55 wt%, PbO-SiO ₂ -B ₂
A conductive paste of 45% by weight of glass containing O ₃ as a main component was printed so as to have a thickness of 10 μm, dried at 100 ° C., and baked at 520 ° C. Ag 25μm thick
A thin plate made of 19 mm in diameter with a protrusion of 2 mm x 2 mm
And sandwiched between the piezoelectric plates 1 as the metal thin plate 3, and laminated 100 layers of the piezoelectric plates 1 to form a laminated piezoelectric body. The connecting projections 3a of the thin metal plate 3 were alternately arranged so as to be located in the same direction every other layer. The laminated piezoelectric body in which 100 layers of the piezoelectric plate 1 are laminated is lightly pressed so as not to cause displacement, and then a weight of about 3 kg is put on the upper part of the laminated body and pressed at 600 ° C. for 1 hour. Joined.

Next, the comb teeth of the metallic comb-like spacer 4 are inserted between the connecting projections 3a projecting in the radial direction of the piezoelectric plate 1, and thereafter, as shown in FIG. The tip of each connecting projection 3a protruding in the radial direction of the piezoelectric plate 1 is bent in the laminating direction of the piezoelectric plate 1, and the bent tip is connected to the metal comb tooth spacer 4 by soldering. The metallic comb-like spacer 4 was used as a positive electrode and a negative electrode. At this time, the distance A between the outer peripheral portion of the piezoelectric plate 1 and the metal comb tooth spacer 4
Was 1.0 mm. Further, the entire outer peripheral portion of the piezoelectric plate 1 was covered with an insulating silicon-based resin. This was polarized in a silicone oil at 80 ° C. by applying a DC voltage of 3 kv / mm for 30 minutes.

In the obtained laminated piezoelectric actuator, 30
As a result of applying a DC voltage of 0 V, a displacement of 25 μm was obtained. In addition, this actuator is applied from 0V to +300
As a result of applying a DC electric field of V at a frequency of 20 Hz, a displacement of 25 μm was maintained until the number of times of application was 1 × 10 ⁹ . Further, the laminated piezoelectric actuator of the present invention is moved from 0 V to +
Even when a DC electric field of 300 V was applied 1 × 10 ⁹ times at a frequency of 20 Hz, no discharge occurred and no breakage occurred.

For comparison, a piezoelectric actuator in which connection projections were continuously connected at a distance of 0.4 mm from the outer periphery of the piezoelectric plate without using a metal comb-like spacer was formed, and a DC voltage of 300 V was applied. When a voltage was applied, a displacement of 25 μm was obtained. However, when a DC electric field of 0 V to +300 V was further applied 2 × 10 ⁶ times at a frequency of 20 Hz, a disconnection occurred at the connection portion of the connection projection of the metal thin plate. It was observed.

The amount of displacement was measured by attaching an aluminum foil to the upper surface of the sample and fixing it on a vibration isolating table, and evaluating the average value of the values measured at the central part and three peripheral parts of the element by a laser displacement meter. did.

Embodiment 2: In the case of the piezoelectric actuator in which the connecting projections are connected to and fixed to the metal comb spacers at positions 0.6 mm and 1.5 mm away from the piezoelectric plate in the multilayer actuator of Example 1, respectively. , And a DC voltage of 300 V was applied to obtain a displacement of 25 μm. Further, a DC electric field of 0 V to +300 V is applied to this actuator for 2 hours.
When applied at a frequency of 0 Hz, the number of applications was 1 × 10
The displacement of 25 μm was maintained up to ⁹ times.

[0026]

As described above, according to the multilayer piezoelectric actuator of the present invention, the metal comb-like spacers are disposed on the opposite sides of the plurality of piezoelectric plates via the insulating resin.
The connection protruding portions of the metal thin plate, which are electrodes for applying voltage to the piezoelectric plate, are connected to the outer periphery of the metal comb-shaped spacer, so that the connection protruding portions of the soft and small metal thin plates overlap. There is no need to join them together, and they can be manufactured by inserting the comb teeth between the connecting projections and then bending and joining them, making production easy and making the connection projections and metal comb teeth The spacer can be firmly connected and fixed. Also. By disposing the metallic comb-tooth spacer and the laminated piezoelectric plate with an insulating resin interposed therebetween, peeling or disconnection of the connecting portion due to repeated driving can be prevented as much as possible, and even if a high voltage is applied to the piezoelectric plate. Thus, a multilayer piezoelectric actuator capable of ensuring a large displacement for a long period of time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of a laminated piezoelectric actuator according to the present invention.

FIG. 2 is a view showing a thin metal plate used for the laminated piezoelectric actuator according to the present invention.

FIG. 3 is a view showing a metal comb-like spacer used in the multilayer piezoelectric actuator according to the present invention.

FIG. 4 is a partially exploded perspective view showing a conventional laminated piezoelectric actuator.

FIG. 5 is a cross-sectional view showing a conventional laminated piezoelectric actuator.

[Explanation of symbols]

1 ... Piezoelectric plate, 2 ... Conductive adhesive layer, 3 ... Metal thin plate, 3a ... Connecting projection, 4 ... Metal comb spacer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuhiko Onizuka, Inventor 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima

Claims (2)

[Claims] 1. A thin metal plate is disposed between a plurality of stacked piezoelectric plates via a conductive adhesive, and the thin metal plates are alternately projected in two opposing directions of the piezoelectric plates so as to be stacked in the stacking direction of the piezoelectric plates. And a plurality of connection projections protruding in the same direction are connected to each other. A multi-layer piezoelectric actuator comprising: a plurality of connection protrusions connected to and fixed to an outer peripheral portion of a plurality of connection protrusions penetrating the metal comb spacers. 2. The laminate according to claim 1, wherein the metal comb-shaped spacer is disposed at a distance of 0.6 to 1.5 mm from the piezoelectric plate via the insulating resin. Type piezoelectric actuator.