JPH0387078A - Piezoelectric actuator and its manufacture - Google Patents

Abstract

PURPOSE:To prevent breaking at the bonding part of an element end surface, and easily control compressive force, by inserting an element into a metal case having expansion and contraction function, and performing hermetically sealing process in the state that compressive force is previously applied to the element. CONSTITUTION:An electrostrictive element 1 is bonded to the inner recessed surface of a metal member 3. Lead wires 4a, 4b of the element 1 are connected with the inner end portions of glass terminals 2a, 2b. The other end surface side 1b of the element 1 to which the metal member 3 is fixed is inserted from an aperture part of the fixing part 5a side of a metal case 5, and is bonded to the recessed surface of a metal member 6. The case 5 and the metal member 3 are seal-bonded in the manner in which a protrusion 3b of the metal member 3 comes into contact with the fixing part 5a. A fixing part 3a and the fixing part 5a are arranged so as to be brought into contact with each other from above and below. While, in this state, the fixing parts 3a, 5a are pressed via welding electrodes, a large current is applied. Thus seal-bonding is performed while the protrusion 3b is crushed by a specified dimension.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a piezoelectric actuator and a method for manufacturing the same;
In particular, we will focus on laminated piezoelectric actuators that utilize the longitudinal effect and their manufacturing methods.

[Conventional technology]

Piezoelectric actuators that utilize electrostrictive elements that convert electrical energy into mechanical energy are currently used in industrial fields such as mask flora controllers, XY table drives, and injection molding machines.

FIG. 4 is a longitudinal sectional view of an example of a conventional piezoelectric actuator enclosed in a metal case.

After half-IB connections are made to the lead wires 4a and 4b derived from the electrostrictive effect element 1 in which electrostrictive materials and internal electrodes are alternately laminated to the glass terminals 2a and 2b attached to the metal member 3, the metal member One end surface 1a of the electrostrictive element 1 is adhered to the recessed portion 3 using an adhesive such as epoxy resin. Next, after inserting the O-ring 10 made of python or the like into the ring edge 3c provided on the outer periphery of the metal member 3, the electrostrictive element 1 is inserted into the opening 9a of the bottomed cylindrical metal case 9. is inserted from the end 1b side, and the end 1b and the bottom 9b of the metal case 9 are adhesively fixed with an adhesive such as epoxy resin, thereby completing a piezoelectric actuator having an airtight sealing structure.

[Problem to be solved by the invention]

The conventional piezoelectric actuator described above has the following drawbacks because it has a structure in which the electrostrictive effect element is sealed by the contact pressure of the ring.

(1) Since the tensile strength of the electrostrictive element in the stacking direction is weak, if a tensile force is applied from the outside in the stacking direction during installation, the element will break.

(2) When an external force is applied through the metal member in a direction perpendicular to the stacking direction of the electrostrictive element, the element breaks.

The purpose of the present invention is to prevent the element from breaking when a tensile force is applied from the outside during installation, and to prevent the element from breaking at the element or the element end surface joint even when an external force is applied through a metal member in a direction perpendicular to the stacking direction of the electrostrictive element. It is an object of the present invention to provide a piezoelectric actuator that can prevent breakage and a method for manufacturing the piezoelectric actuator that has excellent productivity and allows easy control of compressive force.

[Means to solve the problem]

A piezoelectric actuator according to a first aspect of the present invention is a piezoelectric actuator in which an electrostrictive effect element formed by alternately laminating a plurality of electrostrictive materials and internal electrodes is hermetically sealed by a metal case, a metal member, and a glass terminal. In the above, either the metal case or the metal member is provided with an expandable part,
In order to apply the contractile force of the expandable part in the stacking direction of the electrostrictive element, a collar-shaped mounting part provided on the outer periphery of the metal case and a ring-shaped mounting part protruding by a certain dimension from the collar-shaped mounting part provided on the outer periphery of the metal member are attached. They are joined by abutting the protrusions provided on the sides and crushing the protrusions by a certain dimension.

A method for manufacturing a piezoelectric actuator according to a second aspect of the present invention includes hermetically sealing an electrostrictive effect element formed by alternately stacking a plurality of electrostrictive materials and internal electrodes with a metal case, a metal member, and a glass terminal. A method for manufacturing a piezoelectric actuator, comprising: a metal case having a collar-shaped attachment part provided for joining a telescopic part provided to apply a contractile force in the stacking direction of the sealed electrostrictive element and a metal member; , a step of preparing a metal member having a glass terminal and a brim-shaped attachment portion having an annular protrusion protruding by a certain dimension on the bonding surface for bonding to the metal case, and the electrostrictive effect. A step of housing the element in the metal case and the metal member and connecting it to a glass terminal, a step of holding the collar-shaped attachment portions of the metal case and the metal member against each other, and a step of holding the element in the annular projection portion by a certain size. The process includes the steps of crushing and sealing.

The present invention eliminates the drawbacks of conventional piezoelectric actuators because the element is inserted into a metal case with an expandable function and the element is sealed with compressive force applied to the element in advance.

〔Example〕

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

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

This piezoelectric actuator has an electrostrictive effect element 1 formed by alternately laminating a plurality of electrostrictive materials and internal electrodes, and has a circular attachment part 3a machined in advance on one end surface and a collar-shaped attachment part 3a on the outer periphery. A certain dimension from the part (e.g. 0.1 to 0.4 mm)
2(a).
A metal member 3 made of stainless steel having a triangular or trapezoidal cross-section as shown in ) to (d) and having a pair of glass terminals 2a and 2b sealed thereto is fixed, and its inner diameter is that of an electrostrictive element. The electrostrictive effect element 1 is inserted into a metal case 5, such as a bellows, which is larger than the outer dimensions of the case 1 and has a bell-shaped attachment part 5a on the outer periphery of one opening (upper part) and is made of stainless steel and has an elastic function. In this state, a metal member 6 made of stainless steel and having a U-shaped cross section and a circular shape is fixed to the other end face of the electrostrictive element 1, and the protrusion 3 of the metal member 3
b is crushed by a certain dimension and the expandable part of the metal case is expanded by a certain dimension, and the metal case 5 and the metal member 3,
6 are sealed together by welding and hermetically sealed so that the contraction force of the metal case is applied in the stacking direction of the electrostrictive effect element 1.

Next, a method for manufacturing the piezoelectric actuator of this example will be explained.

A multi-component solid solution ceramic powder with a perovskite crystal structure is mixed with an organic binder to form a green sheet with a thickness of about 100 μm, a paste-like pot internal electrode conductor is applied on top of the green sheet, and after drying, the number + Jif (for example, 64 layers) is formed.
First, a laminate is prepared by laminating and sintering. Since the end of the pot internal electrode conductor is exposed on the side of this laminate,
After selectively covering the ends with a glass insulating film, external electrode conductors are formed on the side surfaces, and the inner electrode conductors of the pan are alternately connected every other layer to form two comb-shaped electrodes. Then, the lead wires 4a and 4b are connected to external electrode conductors by soldering, and only the side surfaces are covered with resin.

The electrostrictive effect element 1 manufactured in this way is attached to a metal member 3.
The electrostrictive effect element 1 is fixed with an adhesive such as epoxy resin so that it is planted on the inner surface of the recess.

Next, the lead wires 4a, 4b of the electrostrictive element 1 and the inner ends of the glass terminals 2a, 2b are connected by soldering.

Next, the other end surface side 1b of the electrostrictive effect element 1 to which the metal member 3 is fixed is inserted through the opening (upper part) on the mounting part 5a side of the metal case 5, and the electrostrictive effect element is inserted into the concave surface of the metal member 6. 1. Fix with adhesive such as epoxy resin so that it is planted. Next, the protruding portion 3b of the metal member 3 and the mounting portion 5 of the metal case 5
The metal case 5 and the metal member 6 are held with a jig so that they are in contact with each other, and the metal case 5 and the metal member 6 are sealed and joined by welding or the like.

Next, a cylindrical metal case 5 made of NBR, beryllium copper, etc., in which a pair of upper and lower welding electrodes are brought into contact with each other, and the mounting parts 3a and 5a of the metal member 3 are placed in contact with each other so as to be sandwiched from above and below. .

In this state, pressure is applied to the mounting parts 3a and 5a via the welding electrode (
For example, apply a large current (for example, 10 to 20 KA) while holding 100 to 200 kg/Cm2 for a predetermined period of time (for example, 2 to 5 KA).
seconds), the protrusion 3b of the metal member 3 is crushed by a certain dimension (for example, 0.1 to 0.4 mm) and sealed by resistance welding to complete the sealing. At this time, the contractile force due to the elongation of the metal case 5 with respect to the collapsed dimension of the protrusion 3b is 20 to 100 times the maximum generated stress of the electrostrictive element 1.
% (for example, 20 to 50 kg-f), the electrostrictive element is pre-compressed with a force of about 20 to 100% of the maximum generated stress. A piezoelectric actuator enclosed in a hermetically sealed metal case can be formed.

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

This embodiment differs from the first embodiment in that a diaphragm 7 is attached instead of the lower metal member, a metal case 8 without an expansion and contraction function is used, and the concave surface of the diaphragm 7 is located below the electrostrictive element l. It is glued to the end face.

This embodiment has the advantage that the diaphragm and metal case can be manufactured at lower cost than the first embodiment.

〔Effect of the invention〕

As explained above, the present invention provides an expandable portion on either the metal case or the metal member, and a collar-shaped attachment portion provided on the outer periphery of the metal case and a collar-shaped attachment portion provided on the outer periphery of the metal member. After holding the annular protrusions that protrude by a certain dimension from each other, the protrusions are crushed by a certain dimension and sealed together, and the elastic part applies compressive force to the electrostrictive effect element in advance for sealing. Completing this will have the following effects:

(1) Element breakage can be prevented when tensile force is applied from the outside during installation.

(2> Even if an external force is applied to the electrostrictive element in a direction perpendicular to the stacking direction of the electrostrictive element through the metal member, breakage at the element or the element end surface joint can be prevented.

(3) Productivity is good because the work of applying compressive force and the sealing process can be performed at the same time.

(4) Compressive force can be controlled by the dimensions of the protrusion, so there is less variation.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a piezoelectric actuator showing a first embodiment of the present invention, and FIG. 2(a)
~(d) is a vertical cross-sectional view of a protrusion of the present invention, FIG. 3 is a vertical cross-sectional view of a piezoelectric actuator showing a second embodiment of the present invention,
FIG. 4 is a longitudinal sectional view of an example of a conventional piezoelectric actuator enclosed in a metal case. 1... Electrostrictive effect element, la, lb... End surface, 2a. 2b... Glass terminal, 3, 6... Metal member, 4a. 4b... Lead wire, 5, 8.9... Case, 9a.
...Opening, 3a, 5a...Mounting part, 7...Diaphragm, 3b...Protrusion, 9b...Bottom, 10...
・0 ring.

Claims (2)

[Claims] (1) In a piezoelectric actuator in which an electrostrictive effect element formed by alternately laminating a plurality of electrostrictive agents and internal electrodes is hermetically sealed by a metal case, a metal member, and a glass terminal, the metal case or metal one of the members is provided with an expandable portion, and a collar-shaped attachment portion provided on the outer periphery of the metal case so that the contractile force of the expandable portion is applied to the electrostrictive effect element in the stacking direction; A piezoelectric actuator characterized in that a ring-shaped protrusion projecting from a collar-shaped attachment part provided on the outer periphery by a predetermined dimension is brought into contact with the protrusion, and the protrusion is crushed and joined by a predetermined dimension. (2) In a method for manufacturing a piezoelectric actuator, in which an electrostrictive effect element formed by alternately laminating a plurality of electrostrictive materials and internal electrodes is hermetically sealed with a metal case, a metal member, and a glass terminal, the sealed electric a metal case having a collar-shaped attachment part provided for joining an expandable part provided to apply a contractile force in the stacking direction of the strain effect element and a metal member;
a step of preparing a metal member having a glass terminal and a brim-shaped attachment portion having an annular protrusion protruding by a certain dimension on its bonding surface for bonding to a metal case; and the electrostrictive effect element. a step of storing the metal case and the metal member in the metal case and connecting it to the glass terminal, a step of holding the collar-shaped attachment portions of the metal case and the metal member against each other, and crushing the annular protrusion by a certain dimension. A method of manufacturing a piezoelectric actuator, comprising the step of sealing the piezoelectric actuator.