JP3010835B2 - Piezo actuator - 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 actuator, and more particularly, to a structure of a fixing portion of an electrostrictive effect element of a laminated piezoelectric actuator utilizing a longitudinal effect.

[0002]

2. Description of the Related Art Piezoelectric actuators utilizing an electrostrictive effect element for converting electric energy into mechanical energy are currently used in industrial fields such as mass flow controllers, XY table drives, and injection molding machines.

FIG. 5 is a longitudinal sectional view of a conventional piezoelectric actuator in a metal case according to Japanese Patent Application No. 63-149158.

Conventionally, this piezoelectric actuator has an electrostrictive effect element 1 formed by alternately laminating a plurality of electrostrictive materials and internal electrodes, and an adhesive such as an epoxy resin on both ends of the electrostrictive effect element 1. A metal member 3 fixed at 9, 9 and including the hermetic seal terminal 2, a metal member 6, and a bellows-shaped metal case 5 sealed to the metal members 3 and 6 by welding or the like.

[0005]

Generally, displacement of an electrostrictive element utilizes the longitudinal strain of an electrostrictive material due to a voltage, but at the same time, a transverse strain is generated, the magnitude of which is proportional to the electric field strength. I do. For this reason, when a voltage is applied, the electric field strength of the electrostrictive material at the bonding portion is about several tenths to several hundredths as compared with the other electrostrictive material parts, and a similar difference occurs in the lateral strain. In the electrostrictive effect element, the electrostrictive material on the end face of the electrostrictive effect element is deformed in a convex shape to absorb the lateral strain. Therefore, when the electrostrictive effect element is bonded to a metal member, the adhesive surface tends to deform in a convex shape each time a voltage is applied to the electrostrictive effect element, and a large stress is present in the vicinity of the bonded portion. appear.

Further, temperature change (for example, normal temperature to 200 ° C.)
Even when used in an environment where there is, a large stress is generated in the vicinity of the bonding portion due to the difference in the thermal expansion coefficient between the metal member and the electrostrictive material.

[0007] For this reason, when used repeatedly to turn on and off the voltage or when used in a place where there is a temperature change, there is a disadvantage that cracks are generated in the electrostrictive material near the bonding portion. Further, depending on the material and thickness of the adhesive on the bonding surface, there is a disadvantage that the displacement is absorbed and the displacement is reduced by about several tens of percent.

[0008]

According to the present invention, there is provided a piezoelectric actuator in which an electrostrictive effect element is hermetically sealed by a metal case and a metal member. Is fixed without using an adhesive by a support member that fills a gap between them.

[0009]

According to the above construction, since the electrostrictive effect element is positioned and fixed to the metal member with the support member meeting without the adhesive, the stress in the vicinity of the bonded portion when the element is fixed by the adhesive is reduced. Even if it is used repeatedly, such as turning the voltage on and off, or using it in a place with a temperature change, it may peel off from the connection part or crack the electrostrictive material near the element in contact with the metal member It is possible to provide a piezoelectric actuator which does not have a small displacement amount.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a piezoelectric actuator showing a first embodiment of the present invention.

In this piezoelectric actuator, lead wires 4a and 4b are connected to both ends of an electrostrictive element 1 formed by alternately laminating a plurality of electrostrictive materials and internal electrodes, and hermetic seal terminals 2a and 2b are provided. The attached metal member 3 and the metal member 6 are fixed to both ends of the electrostrictive effect element 1 with support members 7a and 7b, and a metal case 5 such as a bellows having a stretching function is attached to the metal members 3 and 6. It is hermetically sealed by welding or the like.

Here, the shape of the support members 7a and 7b will be described. FIG. 2 is an exploded perspective view of the voltage actuator including the support member 7a. Support member 7a
Has a hollow hole having a hollow area slightly larger than the cross-sectional area of the end face 1a of the electrostrictive effect element, and an outer shape having a circular shape slightly smaller than the inner diameter φ of the metal member 3 or 6. Is made of an insulating material such as polyether sulfone which has a high processing accuracy and a heat resistance of 200 ° C. or more.

Next, a method of manufacturing the piezoelectric actuator of the present embodiment will be described. An organic binder is mixed with a multi-component solid solution ceramic powder having a perovskite crystal structure to form a green sheet having a thickness of about 100 μm, a paste-like silver internal electrode conductor is applied thereon, dried, laminated in several tens of layers, and fired. First, a tied laminate is prepared. The end portions of the silver internal electrode conductors exposed on a corresponding pair of side surfaces of the laminate are alternately coated with a glass insulating film every other layer, and further, external electrode conductors are formed on the side surfaces to form a silver internal electrode. An electrostrictive effect element 1 in which conductors and external electrode conductors are alternately connected every other layer is obtained. Then, the lead wires 4a and 4b are soldered to the external electrode conductors, and the end surface 1a of the electrostrictive effect element is inserted into the support member 7a.
a is fixed so that the electrostrictive effect element 1 is implanted. Next, the lead wires 4a, 4a connected to the electrostrictive effect element 1
b is soldered to the inner ends of the hermetic seal terminals 2a and 2b.

On the other hand, a case is prepared in which one opening 5b of the metal case 5 and the metal member 6 are previously sealed and joined by welding or the like. Next, another end face 1b of the electrostrictive effect element 1 to which the metal member 3 is fixed is inserted from the opening 5a of the metal case 5 so that the electrostrictive effect element 1 is planted at the center of the metal member 6. Is fixed with a support member 7b. Next, the metal member 3 and the opening 5a of the metal case 5 are sealed by welding or the like to be sealed to form a piezoelectric actuator in the metal case.

A temperature cycle test was performed using the piezoelectric actuator constructed in Example 1.

Conditions: −25 ° C. (30 minutes) → Normal temperature (30 minutes) → + 200
° C (30 minutes) 50 cycles, number of measurements n = 21p Result: There was no failure and no cracks or the like. The above effects were confirmed.

[0017]

Embodiment 2 FIG. 3 is a sectional view of a piezoelectric actuator showing a second embodiment of the present invention. This embodiment is the same as the first embodiment except that a material having a low thermal expansion coefficient, such as 42 alloy, which is surface-treated with an insulator (for example, fluorine coating) is used as the material of the support member of the first embodiment. , First
Therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted. In this embodiment, the processing accuracy can be easily obtained by using a metal material, the coefficient of thermal expansion is low, and it can be used at a high temperature of 300 ° C. or more.

[0018]

Third Embodiment FIGS. 4A and 4B are perspective views of a support member 7a for explaining a third embodiment of the present invention. This embodiment is the same as the first embodiment except that the hollow portion of the support member 7a is formed in a concave portion and the projection 7a is provided on the lower surface thereof. Therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted. In this embodiment, since the support members 7a and 7b and the metal members 3 and 6 are in point contact with each other, there is an advantage that no twisting force is applied to the element when the metal case is crimped and fixed by the spring pressure.

[0019]

As described above, according to the present invention, when the electrostrictive effect element is fixed, a voltage is applied to the laminated piezoelectric actuator by assembling the element into the support member and fixing the element by press-fitting with the spring pressure of the metal case. At this time, the deformation of the electrostrictive effect element connection caused by the difference in electric field strength between the electrostrictive material near the bonding portion and the electrostrictive material between the internal electrode conductor layers is not hindered, and even when the voltage is repeatedly turned on / off. This has the effect of preventing cracks from entering the electrostrictive material.

In addition, since no adhesive is used for the connection between the electrostrictive effect element and the metal member, the number of bonding steps can be greatly reduced, and the bonding interface can be prevented from being damaged by thermal stress at the time of curing the adhesive or in a high temperature environment. effective.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view of a main part when the electrostrictive element shown in FIG. 1 is connected.

FIG. 3 is a longitudinal sectional view of a piezoelectric actuator showing a second embodiment of the present invention.

FIG. 4 is a perspective view of a support member used in another embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a conventional piezoelectric actuator in a metal case.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrostriction effect element 1a, 1b End surface 2a, 2b Glass terminal 3, 6 Metal member 4a, 4b Lead wire 5 Metal case 5a, 5b Opening 7a, 7b Support member 8 Solder 9 Adhesive

Claims (2)

(57) [Claims] 1. A piezoelectric actuator in which an electrostrictive element is hermetically sealed by a metal case and a metal member, wherein an end of the electrostrictive element is fixed to a concave portion of the metal member so as to fill a gap therebetween. A piezoelectric actuator, which is performed by a support member without using an adhesive. 2. The support member according to claim 1, wherein the support member has a through hole through which an end of the electrostrictive effect element passes, or has a concave portion in which the end of the electrostrictive effect element is filled. Piezoelectric actuator.