JPH1126828A - Laminated piezo electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated piezo electric actuator which can prevent breaking of connecting projections or breaking of connections between the projections by soldering. SOLUTION: The actuator includes a plurality of laminated piezo electric plates 1 and thin metallic plates 3 each disposed between the piezo electric plates 1 and having connecting projections 7 joined to the respective plates 1 with use of conductive adhesive. In this case, the connecting projections 7 are alternately projected from the plates 1 in two directions so that the connecting projections 7 projected on one side and the connecting projections 7 projected on the other side are bent at their tip ends at a position spaced by 0.8-1.5 mm from outer peripheries of the plates 1, and their bent parts 11 are electrically connected each other by connecting materials 9. And gaps between the connecting members 9 and outer peripheries of the plates 1 are filled with silicone rubber 17 having an elastic modulus of 1×10<5> to 1×10<7> pa.

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 is used, for example, as 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 a multilayer piezoelectric actuator.

[0002]

2. Description of the Related Art Conventionally, a laminated piezoelectric actuator formed by laminating a plurality of piezoelectric plates on which electrodes are formed has been known. In such a laminated piezoelectric actuator,
A voltage is applied to the piezoelectric plate and the piezoelectric plate is extended by several tens of μm by the inverse piezoelectric effect to be used as a driving force source of the actuator.

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. was there.

Therefore, conventionally, a plurality of piezoelectric plates having metal electrodes formed on both sides are laminated, and a thin metal plate is arranged between the metal electrodes.
The connection projections of these thin metal plates are bent in the axial direction so as to leave a predetermined gap with respect to the outer peripheral edge of the piezoelectric plate, overlapped with the connection projections of the same polarity, joined and made conductive, and connected to each other. And the gap between the outer edge of the piezoelectric plate (interval 0.5m
m) is filled with an insulating coating material (silicone-based) having an elastic modulus of 0.3 to 10 kgf / mm ² , and a multilayer piezoelectric actuator in which the entire surface of the laminate is coated with the insulating coating material is disclosed (actual). Kaihei 3-503
No. 57).

[0005]

Since the laminated piezoelectric actuator is repeatedly driven at a high speed, a connecting projection or
Stress concentrates on the connection portion of the connection projections formed by the solder, and in order to alleviate this stress concentration, the above-described actual open flat 3-50 is used.
In the multilayer piezoelectric actuator disclosed in Japanese Patent No. 357, an insulating coating material (silicone) having an elastic modulus of 0.3 to 10 kgf / mm ² is used. There has been a problem that the protruding portions are disconnected at a connection portion by solder, and the displacement amount is reduced.

That is, in the multilayer piezoelectric actuator disclosed in Japanese Utility Model Laid-Open No. 50357/1991, the elasticity of the insulating coating material is low, so that the distortion of the connection projection cannot follow the distortion of the piezoelectric laminate, and There is a problem that stress concentrates on the root portion of the connection protrusion protruding from the laminate, and the connection protrusion is easily damaged. Further, there is a problem that it is difficult to maintain the shape of the insulating coating material, it is susceptible to external impact, and it is difficult to handle.

Further, since the distance between the connection protrusion and the outer peripheral edge of the piezoelectric plate is 0.5 mm, which is short, the stress transmitted to the connection by the solder between the connection protrusions via the connection protrusion. However, there is a problem that the connection is easily broken at this connection portion.

Further, since the distance between the connecting projection and the outer peripheral edge of the piezoelectric plate is 0.5 mm, which is short, there is a problem that electric discharge easily occurs during this period. In particular, in recent years, the tendency is higher because a high voltage is applied to obtain a larger displacement.

The present invention can prevent a disconnection of a connecting projection and a disconnection of a connecting portion due to solder between the connecting projections even when operating at a high speed, and can suppress discharge. The purpose is to provide.

[0010]

A laminated piezoelectric actuator according to the present invention has a plurality of laminated piezoelectric plates, each of which is interposed between the piezoelectric plates, and which is joined to the piezoelectric plates by a conductive adhesive. A metal thin plate having a connecting projection, wherein the connecting projections are alternately projected from the piezoelectric plate in two directions, a plurality of connecting projections projecting to one side and projecting to the other side. The distal ends of the plurality of connection protrusions are set at 0. 0 from the outer peripheral surface of the stacked piezoelectric plates.
It is bent at a position separated by 8 to 1.5 mm, and the bent portions are connected by connecting members, respectively, and the gap between the bent portion and the outer peripheral surface of the piezoelectric plate is 1 × 10 ⁵ to 1 × 1.
Silicone rubber having a modulus of elasticity of 0 ⁷ Pa is made by filling.

[0011]

According to the laminated piezoelectric actuator of the present invention, the tip of the connecting projection is bent and the bent portion is connected to the same-polarity connecting projection by soldering or the like. When connecting the bent portion of the connection projection to another connection member by soldering or the like, the gap between the bent portion of the connection projection and the outer peripheral surface of the piezoelectric plate is 0.8 to 1.5 mm. Yes,
Since the gap is wide, the distortion transmitted from the piezoelectric plate is reduced, and during repeated driving, the connection between the connection projections by solder or the like, or the connection between the bent portion of the connection projection and the connection member by solder or the like. The stress concentrated on the connection portion can be reduced, the disconnection at the connection portion can be prevented, and the connection portion can be operated for a long time with little deterioration of the connection portion even in high-speed continuous driving.

Further, since the gap between the bent portion of the connection projection and the outer peripheral surface of the piezoelectric plate is wide, for example, the bent portion of the connection projection of the positive electrode and the negative electrode thin plate interposed between the piezoelectric plates are provided. Intermittent discharge can be suppressed.

On the other hand, the larger the gap is, the more the stress concentrates on the root portion of the connecting projection, and the more easily it is deformed and disconnected.
In the present invention, since the gap between the bent portion of the connecting projection and the outer peripheral surface of the piezoelectric plate is filled with silicone rubber having a higher elastic modulus than that of Japanese Utility Model Application Laid-Open No. 3-50357, the deformation of the piezoelectric body is prevented. Accordingly, the concentration of stress at the root of the connection projection is suppressed, and the deformation and disconnection of the root of the connection projection are prevented.

Further, since it has an appropriate elastic modulus, it is easy to maintain the shape of the silicone rubber, is resistant to external impacts, and is easy to handle.

[0015]

1 and 2 are cross-sectional views of a laminated piezoelectric actuator according to the present invention, and reference numeral 1 denotes a disk-shaped piezoelectric plate. These piezoelectric plates 1 are made of Pb
It is a sintered body containing (Zr, Ti) O ₃ (hereinafter abbreviated as PZT) as a main component.

The piezoelectric material constituting the piezoelectric plate 1 is, for example,
A piezoelectric ceramic material containing lead zirconate titanate as a main component is used, but is not limited thereto, and any ceramic having piezoelectricity may be used.
As the piezoelectric material constituting the piezoelectric plate 1, those 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, and the molar ratio composition formula of these metal elements is represented by Pb _1-xy S
_{r x Ba y (Zn 1/3 Sb} 2/3) a (Ni 1/2 T
e _{1/2) b} Zr _c when expressed as _{Ti 1-abc O 3, x} ,
The molar ratio of y, a, b, and c is 0 ≦ x ≦ 0.12, 0 ≦ y
≦ 0.12, 0 <x + y, 0.05 ≦ a ≦ 0.12, 0
Pb having an equimolar ratio to 100 parts by weight of the basic component satisfying ≦ b ≦ 0.015 and 0.43 ≦ c ≦ 0.52
O and Nb ₂ O ₅ of the piezoelectric ceramic composition comprising adding 0.2 to 1.2 parts by weight in total is preferable.

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.

A plurality of piezoelectric plates 1 are stacked, two conductive adhesive layers 2 are formed between them, and a thin metal plate 3 is interposed between the conductive adhesive layers 2. . As shown in FIG. 3, these thin metal plates 3 include a disk portion 5 and a connection protrusion 7, and the connection protrusion 7 protrudes in a radial direction of the disk portion 5.

As shown in FIG. 2, the metal thin plate 3 is interposed between the piezoelectric plates 1 such that the connecting projections 7 are alternately turned 180 degrees. The connecting projections 7 may be alternately arranged at 90 degrees each other so as to face four directions. These metal thin plates 3 are made into a positive electrode metal thin plate 3a and a negative electrode metal thin plate 3b depending on the positions of the connection projections 7. The distal end of the connecting projection 7 of the positive electrode metal thin plate 3a is bent, the bent portion 11 is connected to the connecting member 9 by soldering, and the connecting projection 7 of the negative electrode metal thin plate 3b is connected. Is bent, and the bent portion 11 is connected to the connection member 9 by soldering.

The thin metal plate 3 and the connecting member 9 to be used have conductivity, and for example, metals such as silver, brass, copper, and stainless steel are preferable. The thicknesses of the metal sheet 3 and the connecting member 9 are as thin as possible because they do not contribute to the amount of displacement.
For example, those having a thickness of 20 to 100 μm are preferable. The metal plate 3 should be smaller than the piezoelectric plate 1 so that the disk portion 5 is not exposed to the outer peripheral surface of the laminated piezoelectric body in order to prevent a short circuit or discharge with another metal plate 3. desirable.

Bent portion 11 of connecting projection 7 of metal thin plate 3
The gap L between the outer peripheral surface of the piezoelectric plate 1 and the outer peripheral surface is set to 0.8 to 1.5 mm. The reason for providing such a clearance is that
When L is shorter than 0.8 mm, when continuous driving is performed, stress is concentrated on the connection portion 15 by soldering between the bent portion 11 and the connection member 9 due to repeated vibration, and connection failure such as disconnection at the connection portion 15 is caused. It is easy to occur, and for example, the bent portion 11 of the positive electrode
This is because the distance between the metal sheet 3b for the negative electrode and the end of the disk portion 5 of the negative electrode metal sheet 3b is shortened, and a discharge easily occurs during this time. When L is longer than 1.5 mm, a connection failure due to stress concentration at the connection portion 15 is unlikely to occur, but the laminated piezoelectric actuator itself becomes large or the connection projection 7 can follow the deformation of the piezoelectric plate 1. This is because the stress is concentrated on the root portion A of the connection projection 7 and the connection projection 7 may be damaged. The gap L is desirably 1.0 to 1.5 mm for the above reason. The connecting portion 15 may be joined not only by soldering but also by welding.

As described above, the conductive adhesive layer 2 is formed by applying a conductive adhesive layer paste to the piezoelectric plate 1 and drying the paste.
g, containing a metal powder and a glass component;
Those that melt at about ° C are desirable. This is because if the glass component contained in the conductive adhesive layer paste is melted by applying pressure and heating during lamination, the piezoelectric plates 1 are firmly joined to each other, and separation at the interface caused by repeated application of a high electric field is prevented. This is because the reliability of the multilayer piezoelectric body can be improved. Conductive adhesive layer paste, in particular, and 40 to 60 wt% of Ag powder, it is preferably made of 40-60 wt% glass component consisting _{PbO-SiO 2 -B 2 O 3} .

In the laminated piezoelectric actuator of the present invention, as shown in FIGS. 1 and 2, the entire laminated body is covered with silicone rubber 17 having an elastic modulus of 1 × 10 ⁵ to 1 × 10 ⁷ Pa. ing. That is, the gap L between the bent portion 11 and the outer peripheral surface of the piezoelectric plate 1 is filled with the silicone rubber 17, and the outer peripheral surface of the piezoelectric plate 1 is covered with the silicone rubber 17.

As a method of filling the silicone rubber 17 into the gap between the bent portion 11 and the outer peripheral surface of the piezoelectric plate 1, conditions such as viscosity are adjusted, and the silicone rubber 17 is filled in the gap under reduced pressure such as vacuum removal. It is necessary to fill it sufficiently. The silicone rubber 17 covering the outer surface and the like of the connection member 9 is coated so as not to restrict the stress relaxation of the connection portion 15.

In the present application, the elastic modulus of the silicone rubber 17 is set to 1 × 10 ⁵ to 1 × 10 ⁷ Pa because of 1 × 1
If the elastic modulus is greater than 0 ⁷ Pa, the connecting portion 15 is restrained by the silicone rubber 17 or the displacement of the piezoelectric body 1 itself is suppressed by the silicone rubber 17. If the elastic modulus is smaller than 1 × 10 ⁵ , the connecting projection 7 cannot follow the displacement of the piezoelectric body, and the stress concentrates on the root A of the connecting projection 7.

The elastic modulus of the silicone rubber 17 is preferably 1 × 10 ⁶ to 1 × 10 ⁷ Pa for the above reason. The elastic modulus of general silicone rubber is 5 × 10 ⁷ to 8 × 10 ⁷ Pa
However, the elastic modulus of the silicone rubber 17 of the present invention is such that, for example, a silicone-based chain polymer is chemically bonded to each other to reduce the crosslink density, thereby achieving a low elastic modulus. . In FIG. 2, a part of the silicone rubber 17 is removed so that the positive electrode metal sheet and the negative electrode metal sheet can be easily understood.

Incidentally, the laminated piezoelectric actuator of the present invention may have any polygonal shape such as a cylindrical shape, a quadrangular prism, a hexagonal prism, or the like. FIG. 1 illustrates an example in which the connection protrusion is bent and the bent portion is connected to the connection member.
In the present invention, the connecting projection may be bent, and the bent portion may be connected to the same-polarity connecting projection. In this case, the connecting member is constituted by a bent portion of the connecting protrusion and a connecting protrusion of the same polarity connecting the bent portion.

[0029]

[Example] _{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.
Both surfaces of a PZT sintered body containing O and Nb ₂ O ₅ added in a total amount of 0.5 parts by weight were polished to form a disc-shaped piezoelectric plate having a diameter of 20 mm and a thickness of 0.5 mm.

The print as on both major surfaces of the piezoelectric plate, comprising Ag powder 55 wt%, the glass 45 wt% of the electrically conductive paste mainly composed of PbO-SiO ₂ -B ₂ O ₃ in a thickness of 10μm After that, it was dried at 100 ° C and baked at 520 ° C. An Ag thin plate having a thickness of 25 μm was connected to a 2 mm × 2 mm connecting projection having a diameter of 1 mm as shown in FIG.
A 9 mm circle was punched into a metal thin plate, and this metal thin plate was sandwiched between piezoelectric plates, and 100 piezoelectric layers were stacked to form a laminate.

The connecting projections of the thin metal plates were alternately arranged so as to be at the same position every other layer. 10 piezo plates
The laminate having zero layers was lightly pressed so as not to cause displacement, and then a weight of about 3 kg was put on the top of the laminate and pressure-bonded at 600 ° C. for one hour.

Next, as shown in FIG. 1, the distal ends of the connecting projections projecting in the radial direction of the piezoelectric plate were each bent in the axial direction, and the bent portions were connected to the connecting members by soldering. At this time, the distance L between the bent portion of the connecting projection of the thin metal plate and the outer peripheral surface of the piezoelectric plate was 0.8 mm.

The exterior resin was covered with silicone rubber having an elastic modulus of 1 × 10 ⁷ Pa.

3 kv in a silicone oil at 80 ° C.
/ Mm DC voltage was applied for 30 minutes to perform polarization processing.

2K is applied to the obtained laminated piezoelectric actuator.
As a result of applying a load of N and applying a DC voltage of 500 V, a displacement amount of 44.2 μm was obtained. Further, a durability test was performed in which a DC electric field of 0 V to +500 V was applied to this actuator at a frequency of 10 Hz up to 1 × 10 ⁹ times, but the electrode portion (connection portion between the connection projection and the connection member) was tested. No disconnection and displacement after endurance test is 44.0μ
m.

The durability test was performed in the same manner as described above, while changing the type of the exterior resin, the elastic modulus of the exterior resin, and the distance L. Table 1 shows the results. The above example is described as Sample No. 3.

[0037]

[Table 1]

As shown in Table 1, the sample of the present invention has an elastic modulus of 1 × 10 ⁵ to 1 × 10 ⁷ and a distance L of 0.8 to 1.5 m.
In the case of m, it can be seen that even in the durability test, no disconnection of the electrode portion occurs and the displacement does not decrease. The displacement was measured by fixing the sample on an anti-vibration table, attaching aluminum foil to the upper surface of the sample, and evaluating the average value of the values measured at the central part and the peripheral part of the element using a laser displacement meter. did.

[0039]

As described above in detail, according to the present invention, the gap between the bent portion of the connecting projection and the outer peripheral surface of the piezoelectric plate is 0.8 to 0.8 mm.
Since the gap is 1.5 mm and the gap is wide, the distortion transmitted from the piezoelectric plate is reduced, and during repeated driving, a connection portion of the connection protrusions by solder or the like or a tip end of the connection protrusion of the same polarity. The stress concentrated on the connection part by solder etc. connected to the connection member which is another member can be reduced, disconnection at the connection part is prevented, and the deterioration of the connection part even at high speed continuous driving Small, long-time operation is possible.
In addition, since the gap between the bent portion of the connection protrusion and the outer peripheral surface of the piezoelectric plate is large, discharge between the positive electrode and the negative electrode can be suppressed. Furthermore, since the gap between the connecting member and the outer peripheral surface of the piezoelectric plate is filled with silicon rubber having a higher elastic modulus than that of Japanese Utility Model Application Laid-Open No. 50357/1991, it can follow the deformation of the piezoelectric body, and Stress concentration at
Deformation and disconnection of the root of the connection projection can be prevented.

Therefore, even when the humidity is high or the applied voltage is high, deterioration of the displacement amount due to repeated driving and disconnection of the electrode connection can be suppressed, and a highly reliable laminated piezoelectric actuator can be provided.

[Brief description of the drawings]

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

FIG. 2 is a plan view of FIG.

FIG. 3 is a plan view showing the metal sheet of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric plate 2 ... Conductive adhesive layer 3 ... Metal thin plate 7 ... Connection projecting part 9 ... Connection member 11 ... Bent part 15 ... Connection part 17 ... ·silicone rubber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koki Ashida 1-4-4 Yamashitacho, Kokubu-shi, Kagoshima Inside Kyocera Research Institute

Claims (1)

[Claims] A plurality of stacked piezoelectric plates, and a thin metal plate having connection projections interposed between the piezoelectric plates and joined to the piezoelectric plates by a conductive adhesive, The connection projections are alternately projected from the piezoelectric plate in two directions, and the tip ends of the plurality of connection projections projected to one side and the plurality of connection projections projected to the other side, 0.8 mm from the outer peripheral surface of the laminated piezoelectric plate
The piezoelectric element is bent at a distance of about 1.5 mm, the bent parts are connected by connecting members, and a gap between the bent part and the outer peripheral surface of the piezoelectric plate is 1 × 10 ⁵ to 1 × 10 ^5.
A laminated piezoelectric actuator characterized by being filled with silicone rubber having an elastic modulus of ⁷ Pa.