JPH0362578A - Electrostriction effect element - Google Patents

Abstract

PURPOSE:To improve the reliability for the repletion life of an electrostriction effect element, by a method wherein a metal case and a metal stem composed of alloy, whose thermal expansion coefficient is small, is used and the difference of thermal expansion coefficient between said metal and electrostriction ceramic matrix is reduced. CONSTITUTION:Sheet type electrostriction members and inner electrode conductors are alternately laminated; protecting layers composed of only the electrostriction ceramic members are baked in a body on both ends; then outer electrode conductors and lead wires 6b are formed, and a lamination baked body 3 is formed. Said baked body 3 is surrounded with a case 7 and a stem 9 which are composed of super invar steal whose coefficient of linear thermal expansion is smaller than or equal to 10X10<-6>/ deg.C; the upper surface and the lower surface of the baked body 3 are fixed on the bottom part of the case 7 and on the single surface of the stem 9, respectively, via adhesive agent 11a, 11b. Finally the contact part 9a of the case 7 and the stem 9 is sealed, thereby reducing the stress acting on the interface between the protecting layer and the electrostriction effect layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostrictive effect element that utilizes the electrostrictive longitudinal effect.

[Conventional technology]

Conventionally, this type of electrostrictive effect element, as shown in FIG.
A laminated sintered body 3 in which sheet-shaped electrostrictive ceramic members and internal electrode conductors are alternately laminated, protective layers made only of electrostrictive ceramic members are laminated on both ends, and integrally fired to form external electrode conductors; 5US304 which surrounds the sintered body 3 and whose bottom part is fixed to one end of the laminated sintered body 3 with a thermosetting adhesive 11a and has a mechanism that expands and contracts in the polarization direction of the laminated sintered body 3.
．． A stainless steel case 17 made of 5US303 or the like,
One side is the other end of the laminated sintered body 3 and the thermosetting adhesive 11b
A lead wire 6a is fixed to the external electrode conductor of the laminated sintered body 3.
, 6b, and hermetically sealed terminal 8a.

8b, and the contact portion 9a of the stainless steel case 17.
The stainless steel stem 17 is made of plate-shaped 5US304, 5US303, etc., which are welded together.

[Problem to be solved by the invention]

The conventional electrostrictive effect element described above has a linear expansion coefficient of 0, I
10-67'C ceramic member and linear expansion coefficient 15
Since it has a structure in which a metal member of X10-6/'C or higher is fixed with a thermosetting adhesive, when the adhesive 11a that has been bonded at a temperature of 100°C or higher is cured and the temperature drops to room temperature, Due to the difference in linear expansion coefficient between the ceramic member and the metal member, stress is always present near the adhesive interface.

Furthermore, when a voltage is applied to the laminated sintered body 3 that is not enclosed in the metal case 17, as shown in FIG. Due to this, it expands by about 0.1% in the longitudinal direction of the figure, and contracts by about 0.03% in the direction parallel to the internal electrode conductor 2 due to the electrostrictive transverse effect.

At this time, since no electric field is applied to the protective layers 3a and 3b, neither expansion nor contraction occurs. As a result, the laminated sintered body 3 is deformed as shown by the dotted line in the figure, resulting in an electrostrictive effect 711 and a protective layer 3a.

Stress acts on the interface of 3b.

Further, the upper and lower surfaces of this laminated sintered body 3 are covered with metal plates 2 having a longitudinal elastic modulus E that is 5 to 6 times that of the ceramic base material.
0, the protective layers 3a, 3b are bonded as shown in FIG.
In order to forcibly restrain the spherical free deformation of , the stress acting on the interface between the protective layers 3a, 3b and the electrostrictive layer 1+1111-1 when voltage is applied becomes even larger.

When this electrostrictive effect element is repeatedly driven with a rectangular wave of 150 V and 30 Hz at room temperature, it enters the wear-out failure region after being driven 108 times or more and reaches the end of its life (see FIG. 3).

This is because the stress caused by the difference in thermal expansion coefficients of the protective layer 3a
, 3b and the electrostrictive layer 1, 1. This is because stress due to voltage application acts repeatedly on the potential acting on the interface with -1, and a phenomenon occurs in which the interface breaks after about 108 repetitions. In other words, this phenomenon has a disadvantage in that it limits the repeat life of the electrostrictive element to about 108 times.

The purpose of the present invention is to eliminate such drawbacks, use a metal case made of an alloy with a low coefficient of thermal expansion, reduce the difference in coefficient of thermal expansion with the electrostrictive ceramic base material, reduce stress strain, and improve element reliability. An object of the present invention is to provide an electrostrictive effect element with improved properties.

[Means to solve the problem]

The ellipse of the present invention is a laminated layer in which sheet-shaped electrostrictive ceramic members and internal electrode conductors are alternately laminated, and a protective layer made only of electrostrictive ceramic members is laminated on both ends, and after integral firing, external electrode conductors are formed. a sintered body, a metal case that surrounds the laminated sintered body, has a bottom portion fixed to one end of the laminated sintered body, and has elasticity in a direction in which displacement of the laminated sintered body occurs;
A terminal having one side fixed to the other end of the laminated sintered body, electrically connected to an external electrode conductor of the laminated sintered body via a lead wire, and hermetically sealed, and further in contact with the metal case. In the electrostrictive effect element, the material of the metal case or the metal stem has a linear expansion coefficient of 10XIO.
It is characterized by being made of a metal with a temperature of -6/'C or less.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view of the laminated sintered body before being attached to the case of the electrostrictive effect element of FIG. 1.

First, for example, nickel niobate 1QPb (Ni1/3
Nb2. /3) 03 and lead titanate P b -1'
A small amount of an organic binder is added to a pre-fired powder of an electrostrictive material whose main component is i03, etc., this mixture is dispersed in an organic solvent to prepare a slurry, and this slurry is used to form a film by slip casting, etc. An electrostrictive ceramic member having a layer thickness of 100 μm is formed. Next, a mixed powder of silver powder and palladium powder with a weight ratio of 7:3 was placed on one side of this electrostrictive ceramic member.
Alternatively, the internal electrode conductor 2 is formed by applying a conductor paste containing platinum powder as a main component to a thickness of approximately 10 μm by screen printing or the like, and approximately 150 sheets of this are laminated. Furthermore, the internal electrode conductor 2
A second electrostrictive ceramic member is formed by combining an electrostrictive ceramic member not printed with an electrostrictive ceramic member printed with
Electrostrictive layer 11.12.1n-2, 1n-1 (
(hereinafter referred to as a non-uniform layer) and protective layers 3a and 3b are laminated.

In the case of this embodiment, the electrostrictive effect Jtllx, 1fi-1 was three times thicker than the normal electrostrictive layers 13 to 1a-9, and the electrostrictive layer 12.1n-2 was twice as thick. This is an interface 21 between the protective layers 3a, 3b, which are electrostrictively inactive and do not spontaneously deform when a voltage is applied, and the electrostrictive layer 1, which contracts in the direction parallel to the internal electrode conductor 2 in FIG. 2 due to the electrostrictive transverse effect. .2. The purpose of this is to alleviate to some extent the stress exerted on the
See Publication No. 96>.

After stacking the sheets in this way, they are fired at approximately 1100°C for 2 hours, and then the sides are cut to form internal electrodes 21-
2. , into a prismatic shape with the end faces exposed to the outside. Next, glass powder is applied and sintered alternately on the side surfaces of the internal electrode conductors 21 to 2n exposed on a pair of opposing side surfaces of the prism by electrophoresis to form insulating layers 41 to 4fl. do. Subsequently, the internal electrode conductors 21~
In order to electrically connect every other layer 2n, a pair of external electrode conductors 5a and 5b is formed by printing and applying a conductive paste containing silver powder as a main component and baking it. Furthermore, lead wires 6a and 6b electrically connected to the external electrode conductors 5a and 5b are installed.

Next, super invar steel consisting of 30.5 to 32.5% Ni, 4 to 6% CO, and the remainder Fe, with a coefficient of linear expansion of 0.1 x 10-6/'C, was cold-rolled into a single-open cylindrical shape. In addition, a super invar steel case 7 with visible concavo-convex portions 7a formed on a part of the cylinder by the hydraulic pressing method, and a pair of hermetically sealed external parts made of iron alloy, copper alloy, nickel alloy, etc. A disk-shaped super invar steel stem 9 made of super invar steel having terminals 8a and 8b surrounds the laminated sintered body 3, and the upper and lower surfaces of this laminated sintered body 3 are heated at about 120°C for about 2 hours. They are fixed to the bottom of the Super Invar steel case 7 and one side of the Super Invar steel stem 9 through hardening epoxy resin adhesives 11a and llb, respectively. At this time, connect the lead wires 6a and 6b to the external terminal 8.
A and 8b are electrically connected to each other by soldering or welding.

Finally, the contact portion 9a between the Super Invar steel case 7 and the Super Invar S stem 9 is welded by laser beam welding, electro beam welding, resistance welding, TIG welding, or arc welding in vacuum, dry air, or inert gas. It will be sealed by law and completed.

The electrostrictive effect element created by this method was analyzed using a two-dimensional finite element method. The dimensions and physical properties of each member are shown below.
The cross-sectional shape of the laminated sintered body 3 is a square of 5 mm x 5 mm, the length of the laminated sintered body 20 mm, the thicknesses of the protective layers 3a and 3b are respectively 1.5 mm and 3°5 mm, and the electrostrictive layer 1! , 12
, II, -2, 1-t have a thickness of 0.3 mm, respectively.
0.2mm, 0°2mm, 0.3mm, electrostrictive effect R13
The thickness of ~1-x is 0.1 mm, and the longitudinal elastic modulus of the electrostrictive ceramic member is 4000 kgf/mn (bore ratio 0.34, thermal expansion coefficient 0, I x 10-6/'
It was set as C. Furthermore, the adhesive layer with the metal member has a thickness of 30 μm.
, longitudinal elastic modulus 400kgf/mni linear expansion coefficient 1゜0XI
The coefficient of linear expansion of the O-67"C1 metal member is 0 for Super Invar steel, I x 10-6/'C stainless steel)
SUS304) 17.3X10-6/'C, longitudinal elastic modulus is 15000kgf/mn? , 19700kgf
/-, and the dimensions of the metal member are 10mm x 10mm
It was made into a 5 mm rectangular parallelepiped.

According to this structure, after curing the adhesive at 120°C, 25°C
When heated to a high temperature, the maximum stress acting on the interface between the protective layer 3a (1.5 mm thick side), which has the lowest mechanical strength, and the electrostrictive layer 11 is 1.0 in tension when the metal member is stainless steel.
6kgf/mnt, 0.03kgf/mff1 in shear
, if the metal member is spar invar steel, the tension is 0.
．． 0.003kgf/-1 shear. OOO02kgf/
ml11. ! -It became.

Furthermore, when this electrostrictive effect element is driven by applying a voltage of 150 V, the protective layers 3a and 3b are restrained from spherical deformation as shown in FIG. 5 by the metal plate 20 as shown in FIG. The stress acting on the interface between 3a, 3b and the electrostrictive layer 1□, In-1 further increases.

When 150V is applied at room temperature after curing with a thermosetting adhesive, the stress due to the above two causes will reduce the strength of the interface between the protective layers 3a, 3b of the laminated sintered body and the electrostrictive layer 11.1n-1. pretty close to. Therefore, with conventional electrostrictive elements, the limit was that the deer could be driven repeatedly about 108 times. The tensile strength of the laminated sintered body is actually measured to be about 1.6 kgf/- on average, and in the electrostrictive element of this example, the stress at the interface can be drastically reduced by reducing the difference in thermal expansion coefficient. The effect was great in that it was possible.

As a second embodiment of the present invention, a laminated sintered body produced in exactly the same manner as the first embodiment was prepared with a linear expansion coefficient of 3.3X10-
A case using an Fe-42%Ni alloy of 6/°C was sealed in exactly the same manner, and a finite element analysis was performed on it under exactly the same conditions as in the first example 1. As a result, 1. The maximum value of the stress acting on the interface between the 5 mm thick protective FJ 3 a and the electrostrictive effect Nj 1 r is 0.0 in tension when no voltage is applied.
The resistance was 0.6 kgf/-, and the shear was 0.20 kgf/-. Furthermore, as in the first embodiment, the stress acting on the interface increases when a voltage of 150V is applied.

Therefore, the stress acting on the interface can be considerably reduced even when the Fe42%Ni alloy is used.

In this example, the material of the metal case or metal stem was explained as super invar steel or Fe-42 alloy, but invar steel (0°1~0.3%'C, 0
, 4%Mn, 35-36%Ni linear expansion coefficient α=1.2X
10-6/℃), etc. has a low coefficient of thermal expansion α of 10
An alloy of 6/'C or less may be used.

Figure 3 is a characteristic diagram explaining the details of the present invention, with a cross section of 5 mm.
These are the results of a repeated life test in which 150V was applied with a 30Hz rectangular wave to a conventional example (using SUS304), samples of Example 1, and 100P each of the samples of Example 2 of an electrostrictive effect element with a diameter of 5 mm and a laminated sintered body length of 20 mm. As described above, the present electrostrictive effect element did not produce any defects even after 109 pulses were applied, which is a remarkable result in that the device has a long service life.

〔Effect of the invention〕

As explained above, the present invention uses an alloy with a low coefficient of thermal expansion, such as super invar steel, invar steel, or Fe-42%Ni alloy, as the material of the case, so that suppress the difference in thermal expansion as much as possible,
Reducing the stress acting on the protective layer-electrostrictive layer interface has the effect of further improving the reliability of the electrostrictive element over its repeated life.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an electrostrictive effect element according to an embodiment of the present invention;
Fig. 2 is a vertical cross-sectional view showing the structure of only the laminated sintered body in Fig. 1, Fig. 3 is a characteristic diagram showing the repeated life test results of the elements of this example and the conventional example, and Fig. 4 is the characteristic diagram of the conventional example. A vertical cross-sectional view of an electrostrictive effect element, Fig. 5 is a schematic cross-sectional view showing deformation when a voltage is applied to a single laminated sintered body, and Fig. 6 is a longitudinal cross-sectional view of the laminated sintered body by gluing metal members. FIG. 2 is a schematic cross-sectional view showing deformation of a laminated sintered body when free deformation of a portion is restrained. 11-I n-1... Electrostrictive effect layer, 21-2n-1.
...Internal electrode conductor, 3a, 3b...Protective layer, 41-4
°-1... Insulating layer, 5a, 5b... External electrode conductor,
6a, 6b... Lead wire, 7... Super invar steel case, 7a... Uneven part, 8a, 8b... External terminal, 9... Super invar steel stem, 9a... Contact part, 10a. 10b...Solder, lla, llb...Adhesive, 17
...Stainless steel case, 19...Stainless steel stem, 20...Metal plate.

Claims (1)

[Claims] A laminated sintered body in which sheet-shaped electrostrictive ceramic members and internal electrode conductors are alternately laminated, protective layers made only of electrostrictive ceramic members are laminated on both ends, and after integral firing, external electrode conductors are formed, and this laminated body. A metal case surrounds the sintered body and has a bottom portion fixed to one end of the laminated sintered body and has elasticity in the direction of displacement of the laminated sintered body, and a metal case whose one side is fixed to the other end of the laminated sintered body. It includes a flat metal stem having a hermetically sealed terminal electrically connected to the external electrode conductor of the laminated sintered body via a lead wire, and further connected to a contact portion with the metal case. In the electrostrictive effect element constructed, the material of the metal case or the metal stem is made of a metal having a linear expansion coefficient of 10 x 10^-^6/°C or less.