JP2001168407A - Case-sealing type laminated piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a case-sealing type laminated piezoelectric actuator, which does not complicate a structure and a manufacturing step by an insulation process of a case terminal and a case or mounting of a lead line for applying a voltage to a case-sealing type laminated piezoelectric actuator. SOLUTION: In a case sealing type laminated piezoelectric actuator 10, respective laminated piezoelectric actuators 3 are put, in a case comprising first and second case parts 1, 2 which are individually connected directly to two end planes in a laminating direction, and the first and second case parts 1, 2 are respectively brought directly into contact with the two end planes in the laminating direction to be electrically connected, and also the first and second case parts 1, 2 are away from each other to be electrically insulated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer piezoelectric actuator which generates displacement or force by applying a voltage, and more particularly to a case-encapsulation type multi-layer piezoelectric actuator in which the external electrode structure of the multi-layer piezoelectric actuator and the multi-layer piezoelectric actuator are sealed in a case. The present invention relates to a case structure of a piezoelectric actuator.

[0002]

2. Description of the Related Art Conventionally, a multilayer piezoelectric actuator shown in FIG. 5 has been proposed. FIG. 5 is a perspective view showing the appearance of a conventional laminated actuator. Referring to FIG. 5, in the conventional multilayer piezoelectric actuator 3, the piezoelectric ceramic layers 56 and the internal electrode layers 55 are alternately arranged such that the ends of the internal electrode layers 55 are alternately exposed to the opposing side surfaces in the laminating direction. And external electrodes 4 are formed on the opposing side surfaces where the internal electrode layers are exposed. Each of the external electrodes 4 and 4 is formed with a soldered portion 53a which is soldered to connect the lead wire 14 for voltage application.

In the conventional laminated actuator 3 having such a configuration, when an external force is applied to the laminated piezoelectric actuator 3, breakage such as chipping may be caused, or the internal electrodes 55 of opposite polarity may be close to each other. If the exposed surface is flawed, the exposed internal electrode 55 may be stretched along the flaw and the interval between the internal electrodes 55 may be partially narrowed or even short-circuited.

Further, since there is a disadvantage that the laminated piezoelectric actuator 3 is short-circuited due to adhesion of moisture or a conductive material, a technique of sealing the piezoelectric actuator 3 in a case 51 has been used.

FIG. 6 is a view showing a conventional case-enclosed laminated piezoelectric actuator. FIG. 6 (a) is a top view and FIG.
(B) is a sectional view. As shown in FIGS. 6A and 6B, the case-enclosed multilayer piezoelectric actuator 50 includes:
External electrodes 4 and 4 are formed so as to face the side surfaces of the multilayer actuator, and are sealed in a case 51 provided with a spring mechanism 52 on the side surfaces so that both end surfaces contact the inner walls of the upper and lower ends of the case 51. Was. Further, the contact portion was fixed by the adhesive 61.

To the external electrodes 4 and 4 of the multilayer actuator 3, one ends of lead wires 60 and 60 are attached with solder 53a, and the other ends are connected to voltage application terminals 58 and 58 with solder 53b. Applying terminals 58 and 58 to case 5
1 had been pulled out. The case 51 is made of a conductive material, is integrated by welding or the like, and is electrically connected.
Insulation processing part 59 which performed insulation processing with 1 was formed and used. For this reason, the structure of the case 51 and the manufacturing process are complicated.

Further, in the case of such a structure, when the case-enclosed laminated piezoelectric actuator is attached to the device, the lead wire 14 is connected to the voltage application terminal 58 by the solder 53c.
Connection method was used. Therefore, when attaching the case-enclosed laminated piezoelectric actuator to the device, it is necessary to perform processing for passing the lead wire 14 on the device side, and further, the voltage application terminals 58 and 5 of the device are required.
8 had to be performed by connecting lead wires.

The electrical connection between the external electrode 4 of the multilayer piezoelectric ceramic 3 and the voltage application terminal 58 is made by a lead wire 60.
Are connected by forming soldering portions 53a and 53b by soldering, but when used in a soldering process and at a high temperature,
In some cases, the external electrode 4 is diffused into the soldering portions 53a and 53b, resulting in a decrease in strength and disconnection due to the removal of the soldering portions 53a and 53b.

Referring to FIG. 6 again, when enclosing the laminated piezoelectric actuator 3 in the case 51, the laminated piezoelectric actuator 3 is put in a case 51 made of a plurality of metal members, and the plurality of case members are integrated by welding or the like. Technology was used.

Therefore, since the entire case 51 is electrically conductive, the case terminal 58 and the case 51 are insulated 59 and the opposing external electrodes 4 of the multilayer piezoelectric actuator 3 are short-circuited by the case 51. Techniques to prevent things were being used.

In addition, a technique using a lead wire 60 by solder 53 connection has been used for the electrical connection between the case terminal 58 and the external electrode 4 of the multilayer piezoelectric actuator 3.

Further, in the structure in which the case 11 is not provided with the spring mechanism 12, the amount of displacement is reduced as compared with the laminated piezoelectric actuator 3 before enclosing in the case 11, since the binding force of the case 11 is large. Case 1
A technique of providing a retractable spring mechanism 12 in the first embodiment has been used.

Further, since there is a difference in thermal expansion between the case 51 and the multilayer piezoelectric actuator 3, when the operating environment temperature is increased, the case 51 and the multilayer piezoelectric actuator 3 are placed between the ends (displacement surfaces) in the stacking direction. Since a space is generated and the amount of displacement of the case-enclosed laminated piezoelectric actuator is reduced, a space is generated between the case 51 and the end (displacement surface) of the laminated piezoelectric actuator 3 in the laminating direction within the operating temperature range. To prevent this, a technique has been used in which the case is sealed in a state where a compressive force is applied in the stacking direction of the stacked piezoelectric actuator 3.

[0014]

As described above, in the prior art, the multilayer piezoelectric actuator 3 is liable to be damaged due to external force, such as chipping of the multilayer piezoelectric actuator 3, and furthermore, it is difficult for the multilayer piezoelectric actuator 3 to be damaged by moisture or water. In order to eliminate the disadvantage that the laminated piezoelectric actuator 3 is short-circuited due to the adhesion of a conductive material, a case-enclosed laminated piezoelectric actuator that is enclosed in a case 51 has been used.

However, in the case of the conventional case-enclosed laminated piezoelectric actuator 50, since the entire case 51 is electrically conductive, it is necessary to insulate the case terminal 58 of one or both polarities from the case 51. However, there is a disadvantage that the manufacturing process of the case-enclosed laminated piezoelectric actuator is complicated.

The electrical connection between the case terminal 58 and the external electrode 4 of the multilayer piezoelectric actuator 3 is determined by the case terminal 5
Since the electrical connection between the external electrode 8 and the external electrode 4 of the multilayer piezoelectric actuator 3 is made by the lead wire 60 by soldering 53, the structure becomes complicated, and further, the external electrode material 4 is placed in the solder 13. There is a disadvantage that it is diffused and lowers the strength.

Further, in the case of the structure in which the spring mechanism 12 is provided in the case 51, it is possible to reduce the decrease in the displacement amount.
There is a disadvantage that the case 51 is complicated.

Also, due to the difference in thermal expansion between the case 51 and the multi-layer piezoelectric actuator 3, a compression in the stacking direction of the multi-layer piezoelectric actuator 3 is performed in order to prevent a decrease in displacement of the case-enclosed multi-layer piezoelectric actuator 50 due to a rise in temperature. When enclosing the case in a state where a force is applied, there is a disadvantage that the process of enclosing the case is complicated.

Therefore, one technical problem of the present invention is that the structure and the manufacturing process are complicated by insulating the case terminals and the case and attaching the lead wires in order to apply a voltage to the case-enclosed laminated piezoelectric actuator. SUMMARY OF THE INVENTION It is an object of the present invention to provide a case-enclosed laminated piezoelectric actuator which does not need to be performed.

Further, another technical problem of the present invention is that
Provided is a case-enclosed laminated piezoelectric actuator that does not become complicated due to the addition of a spring mechanism for eliminating a conduction failure due to a decrease in strength between solder and an external electrode due to soldering and a decrease in displacement due to a case shape. It is in.

Still another technical problem of the present invention is that the case and the case enclosing process are complicated in order to eliminate the influence of the temperature change on the displacement amount due to the thermal expansion of the case and the multilayer piezoelectric actuator. It is an object of the present invention to provide a case-enclosed type laminated piezoelectric actuator without any problem.

[0022]

According to the present invention, at least one piezoelectric ceramic layer and at least two internal electrode layers are provided, and on one side thereof, the internal electrodes constitute one or more pairs of counter electrodes. In the laminated piezoelectric actuator having external electrodes formed thereon, the laminated piezoelectric actuator is placed in a case composed of first and second case portions which are directly connected to two end surfaces in the laminating direction, respectively. The case-encapsulated type laminate, wherein the first and second case portions are directly connected to two end surfaces, respectively, and the first and second case portions are separated from each other and are electrically insulated. A piezoelectric actuator is obtained.

Further, according to the present invention, in the case-enclosed laminated piezoelectric actuator, the first and second piezoelectric actuators may be provided.
Is made of a conductive material, and one of the first and second cases is connected to one of the external electrodes of the multilayer piezoelectric actuator in an electrically conductive state, and the first and second cases are connected to each other. The other of the case portions and an external electrode of the multilayer piezoelectric actuator having a different polarity from that connected to the one case portion of the multilayer piezoelectric actuator in an electrically conductive state; In addition, a case-enclosed laminated piezoelectric actuator characterized in that the second case portion is a voltage application terminal is obtained.

Further, according to the present invention, in any of the above-mentioned case-enclosed type laminated piezoelectric actuators, the external electrodes of the laminated piezoelectric actuator and the first and second case portions are each made of a conductive paint. A case-enclosed-type laminated piezoelectric actuator characterized by being connected is obtained.

Further, according to the present invention, in any of the above-mentioned case-enclosed laminated piezoelectric actuators, the external electrodes of the laminated piezoelectric actuator enclosed in the case are electrically connected to an end surface in the laminating direction. A case-enclosed laminated piezoelectric actuator characterized by having the above configuration is obtained.

Further, according to the present invention, in the case-enclosed laminated piezoelectric actuator, the surface of the laminated piezoelectric actuator in which the external electrodes are connected to the internal electrodes and the external electrodes extend to an end surface in the laminating direction. A case-enclosed laminated piezoelectric actuator characterized in that the corners between the formed surfaces are chamfered.

According to the present invention, in the case-enclosed laminated piezoelectric actuator according to any of the above,
Dimensional change of the case and the laminated piezoelectric actuator due to thermal expansion and external stress of the case and the laminated piezoelectric actuator in the use temperature range of the case-enclosed laminated piezoelectric actuator, and the laminated piezoelectric actuator Wherein the first and second case portions separately connected to the two end faces in the stacking direction are not in contact with each other even if a dimensional change occurs due to the driving of the case. A piezoelectric actuator is obtained.

Further, according to the present invention, in any one of the above-mentioned case-enclosed type laminated piezoelectric actuators, at least one elastic member is provided between the first and second case portions, and the inside and outside of the case are connected to each other. , A case-enclosed laminated piezoelectric actuator characterized in that the above-mentioned is cut off.

According to the present invention, in the case-enclosed laminated piezoelectric actuator, the elastic member may be
A case-enclosed laminated piezoelectric actuator characterized in that it is arranged so as not to move from the initial position between the first and second case portions even during vibration or long-term driving.

Further, according to the present invention, in any of the case-enclosed type laminated piezoelectric actuators, the elastic member is provided between the first and second case portions even when vibrating or driving for a long time. Not to move from the position of
A case-enclosed laminated piezoelectric actuator is characterized in that one or both of the first and second cases are subjected to an elastic member movement preventing process.

Further, according to the present invention, there is provided a case-enclosed laminated piezoelectric actuator according to any one of the above-mentioned case-enclosed laminated piezoelectric actuators, wherein the elastic member is an insulator.

Further, according to the present invention, in any one of the above-mentioned case-enclosed type laminated piezoelectric actuators, the heat of the pair of cases and the laminated type piezoelectric actuator within the operating temperature range of the case-inserted type laminated piezoelectric actuator. Even if a dimensional change of the pair of cases and the multi-layer piezoelectric actuator due to dimensional change due to expansion and an external stress or a dimensional change due to driving of the multi-layer piezoelectric actuator occurs, each of them is directly connected separately to the two end faces in the stacking direction. The case-enclosed laminated piezoelectric actuator is characterized in that the elastic member is compressed and manufactured to a state where no space is formed between each of the pair of cases and the elastic material 6.

Further, according to the present invention, in any of the above-mentioned case-enclosed laminated piezoelectric actuators, a voltage application terminal is provided on one or both of the first and second case portions. A case-enclosed laminated piezoelectric actuator is obtained.

Further, according to the present invention, in any one of the above-mentioned case-enclosed type laminated piezoelectric actuators, a part or all of the surface of the first and second case portions is subjected to an insulation treatment. Thus, a case-enclosed laminated piezoelectric actuator is obtained.

[0035]

Embodiments of the present invention will be further described below with reference to the drawings.

FIG. 1 is a view showing a case-enclosed laminated piezoelectric actuator according to a first embodiment of the present invention. FIG. 1 (a) is a perspective view, FIG. 1 (b) is a top view, and FIG. c) is a sectional view. As shown in FIGS. 1 (a), 1 (b) and 1 (c), a case for applying a voltage is set in the first and second case portions 1 and 2, and the first and second case portions 1 are used. , 2
The piezoelectric actuator 3 is inserted into the piezoelectric actuator 3.

The laminated piezoelectric actuator 3 enclosed in the first and second case portions 1 and 2 has substantially the same shape as that shown in FIG. 5, except that no lead wire and no soldering portion are provided. In addition, it is a rectangular parallelepiped having a cross-sectional shape of 5 × 5 mm and a displacement taking-out direction at the time of voltage application of 60 mm, and an internal electrode (reference numeral 5 in FIG.
5) and a piezoelectric ceramic layer (reference numeral 56 in FIG. 5) are laminated. Further, the laminated internal electrode layers are configured so as to serve as a counter electrode for each layer, and the external electrode 4 for ensuring electrical conduction with the internal electrode is provided on the opposing surface of 5 × 60 mm. Formed, and furthermore,
The opposing external electrodes 4 extend to opposing displacement surfaces, that is, upper and lower end surfaces. As described above, when manufacturing the case-enclosed laminated piezoelectric actuator, the two case portions 1 and 2 are encapsulated in a state where they are separately connected to the two end surfaces of the laminated piezoelectric actuator 3 in the laminating direction, respectively. The multilayer piezoelectric actuator 3 can be prevented from being damaged by an external force.

A chamfered portion 19 is formed between two surfaces of the laminated piezoelectric actuator 3 which straddle the external electrodes 4 in order to prevent the external electrodes 4 from being disconnected.

The material of the first case 1 and the second case 2 is SUS316. The first case part 1 and the second case part 2 include a multilayer piezoelectric actuator 3
Are connected by conductive adhesive (conductive paint) 5 to the end faces in the laminating direction, and are respectively electrically connected to the opposing external electrodes 4 separately.

As described above, the first and second case parts 1, 1
The first and second case portions 1 and 2 are made of a conductive material (SUS316) so that 2 serves as a voltage application terminal. Each of the external electrodes 4 of the piezoelectric actuator 3 is configured to be electrically conductive.

Accordingly, the case and the manufacturing process are simplified, and furthermore, by eliminating the solder, the configuration is made to prevent conduction failure due to a decrease in solder strength or the like.

Further, when viewed from above the end face in the stacking direction of the stacked piezoelectric actuator 3, the second case section 2 covers the first case section 1 with a width of 3 mm, and the cross section in the direction perpendicular to the stacking plane. Then, the outer diameter of the first case portion 1 is set to be larger than the inner diameter of the second case portion 2 by a distance of 0.9 mm so as to have a space of 0.9 mm in the laminating direction.
5 mm smaller, the first case 1 and the second case 2
Were manufactured so as not to contact each other. In the second case 2, two members are integrated by welding in the process of manufacturing the case-enclosed laminated actuator.

Further, in the case of the conventional multilayer piezoelectric actuator 3 shown in FIG. 5, when an external force is applied to the multilayer piezoelectric actuator 3, breakage such as chipping may be caused, or the internal electrodes of opposite polarity may be close to each other. If the exposed surface is scratched, the exposed internal electrodes are stretched along the scratches, causing a problem that the interval between the internal electrodes is partially narrowed or short-circuited. .

However, in the case of the case-enclosed multilayer piezoelectric actuator 10 according to the first embodiment of the present invention, the multilayer piezoelectric actuator 3 is protected by the two first and second case portions 1 and 2. Therefore, two case parts 1
It is possible to prevent the two or more gaps from directly contacting each other to prevent the laminated piezoelectric actuator 3 from being damaged or damaged.

Even when a case having a different cross-sectional shape from that of the first embodiment or a piezoelectric laminated actuator is used, the same effect can be obtained by enclosing the laminated piezoelectric actuator 3 in the case.

In the case of the conventional case-enclosed laminated piezoelectric actuator shown in FIG. 6, the case is made of a conductive material, is integrated by welding or the like, and is electrically connected. Was insulated from the case and used. For this reason, the case structure and the manufacturing process have been complicated. Furthermore, in the case of this conventional structure, a method of connecting a lead wire to a voltage applying terminal by soldering when a case-enclosed laminated piezoelectric actuator is attached to a device has been used. For this reason, when attaching the case-enclosed laminated piezoelectric actuator 50 to the device, it is necessary to perform processing for passing the lead wire on the device side, and furthermore, to connect the wiring with the voltage application terminal of the device to the connection of the lead wire. Had to be done.

In the prior art, the electrical connection between the external electrode of the laminated piezoelectric ceramic and the terminal for voltage application has been achieved by connecting the lead wires by soldering. May be diffused into the solder and the wire may be broken due to a decrease in strength and removal of the solder.

On the other hand, in the case of the first embodiment of the present invention shown in FIG. 1, the structure is simplified since the first and second case portions 1 and 2 are each a voltage application terminal. In addition, the appearance and structure can be made similar to that of a dry battery or a button battery, simplifying the structure of the device side for mounting a product having such a structure, and facilitating mounting and application of voltage. Can be.

Further, according to the first embodiment of the present invention, since the external electrode 4 of the laminated piezoelectric ceramic and the voltage application terminal 58 can be connected without using solder, the external electrode 4 made of solder can be connected. It is possible to prevent disconnection due to a decrease in the strength of the wire.

Even when a case having a shape different from that of the first embodiment is used, a conductive material is used for the case, and the two cases and the two external electrodes 4 of the multilayer piezoelectric actuator 3 are separately provided. The same effect can be obtained by connecting the two cases so as to be electrically conductive and further manufacturing the two cases so as not to be electrically conductive.

Furthermore, the electrical connection between the two cases and the external electrode 4 can be prevented by any method as long as the connection can be ensured without using solder even by a connection method other than the conductive paint. .

Further, in the multilayer piezoelectric actuator according to the embodiment of the present invention shown in FIG. 1, a normal temperature (25 ° C.) is provided between the first case 1 and the second case 2 in the stacking direction. Is manufactured to have a space of 0.9 mm, the reason for the limitation will be described.

The operating temperature range of the case-enclosed multilayer piezoelectric actuator according to the first embodiment of the present invention shown in FIG. 1 is -40 ° C. to 100 ° C., and the maximum displacement is 60 μm. went.

When the case-enclosed type laminated piezoelectric actuator is used while changing the temperature, and when no voltage is applied, the gap b in the laminating direction of the first case 1 and the second case 2 in FIG. This changes due to the thermal expansion of the second case portion 2 and the multilayer piezoelectric actuator 3 at the portion a. This is because, in the displacement direction, the parts other than the part a are made of the same material, so that the same amount of expansion or contraction occurs even when the temperature is changed. Here, the first and second case portions 1 and 2 have a thermal expansion coefficient of 16 × 10 ⁻⁶ / ° C., and the polarized piezoelectric actuator is −7.5 × 10 ^−6. Therefore, in the case of −40 ° C., the dimension of the second case part 2 at the part “a” shrinks by 0.0624 mm, and the multilayer piezoelectric actuator 3 expands by 0.02925 mm.
Therefore, when the temperature is changed from normal temperature (25 ° C.) to −40 ° C., the first
The gap b in the stacking direction of the case part 1 and the second case part 2 in the laminating direction is reduced by 0.09165 mm. When a voltage is applied to the multilayer piezoelectric actuator 3, the maximum is 60 μm.
(A dimension increase of 60 μm), the gap b in the stacking direction of the case 1 and the case 2 shrinks by 60 μm at the maximum in the displacement direction. Therefore, in a normal temperature (25 ° C.) atmosphere, the gap in the stacking direction of the first case 1 and the second case 2 is 0.09165 mm due to thermal expansion.
0.15165 obtained by adding the maximum displacement of 0.060 mm
In the first embodiment, it is necessary to keep various intervals (variations in manufacturing, thermal expansion, and actuator displacement dimensions for each product) in the first embodiment.
0.9 mm, which is larger than m. In addition, 0.15165m
When the distance is less than m, the first case part 1 and the second case part 2 come into contact with each other depending on the use conditions, and a short circuit occurs.
The displacement cannot be taken out from the case-enclosed laminated piezoelectric actuator 3. Even when the case is not used as a voltage application terminal, a predetermined displacement can be obtained because the first case portion 1 and the second case portion 2 come into contact with each other to apply a compressive force to the laminated piezoelectric actuator 3. Disappears.

In addition, in the case of the conventional case-enclosed type laminated piezoelectric actuator shown in FIG. 6, in order to obtain a predetermined displacement under any assumed use conditions,
A spring mechanism is attached to the case to prevent the displacement from being constrained.The displacement is reduced, and even if the dimensions change due to thermal expansion when the case is assembled, the end face in the displacement direction of the multilayer piezoelectric actuator and the case The case member is pre-tensioned so that no gap is created in the case (the laminated piezoelectric actuator contracts maximally,
The manufacturing is performed in a state where the tensile force applied to the case becomes zero when the case expands to the maximum.

On the other hand, in the case of the case-enclosed multilayer piezoelectric actuator 10 according to the first embodiment of the present invention shown in FIG. 1, the dimensions due to the temperature change of the use environment and the displacement of the multilayer piezoelectric actuator are described above. Even when a change occurs, it is possible to prevent a reduction in the amount of displacement due to the contact of the case and a short circuit between the voltage application terminals. Also, the first and second case portions 1 and 2 and the multilayer piezoelectric actuator 3
Even if any dimensional change occurs in the above, no compressive force is applied to the laminated piezoelectric actuator 3, so that it is possible to prevent a decrease in the amount of displacement. Further, the case structure can be simplified as compared with the conventional case-enclosed multilayer piezoelectric actuator 50, and the man-hour for assembling the case can be reduced.

Even in the case of the case-enclosed type laminated piezoelectric actuator having a shape or material different from that of the first embodiment, the dimension between cases is designed in consideration of the dimensional change shown in the first embodiment. By doing so, the same effect can be obtained in any use state within the range assumed at the time of design.

FIG. 2 shows a case-enclosed laminated piezoelectric actuator according to a second embodiment of the present invention.
(A) is a top view and (b) is a cross-sectional view.

As shown in FIG. 2, a case-enclosed laminated piezoelectric actuator 20 according to a second embodiment of the present invention
Has elasticity that does not restrict the displacement of the case-enclosed laminated piezoelectric actuator in the gap in the laminating direction of the first case part 1 and the second case part 2 of the case-enclosed laminated piezoelectric actuator 10 shown in FIG. An O (O) ring made of silicon is inserted as the elastic member 6, and the first and second case portions 1 and 2 are processed to prevent the elastic member from moving (the first case portion 1 and the second case portion). 2 in the laminating direction, respectively, to form a groove with a depth of 0.25 mm) to form the elastic member movement prevention processed portion 7. All other conditions are the same as those in the first embodiment of FIG. It is.

The size of the elastic member 6 in the stacking direction of the multilayer piezoelectric actuator 3 before the assembly into the case-enclosed multilayer piezoelectric actuator is 1.9 mm, but is reduced to 1.4 mm after the assembly. And the inside of the case is hermetically sealed.

As described above, the first and second case parts 1, 1
A short circuit due to adhesion of moisture or a conductive substance can be prevented by forming the elastic member 6 having elasticity which does not restrict displacement between the case 2 and the inside of the case and the outside of the case.

The elastic member 6 is made of an insulating material, and the first and second case portions 1 and 2 are made of an elastic material 6.
By configuring so that they do not directly contact each other, the case is used as a terminal for voltage application, and further, the first and second case portions 1 and 2 are prevented from contacting each other and short-circuiting.

Further, when the temperature of the use environment changes, the displacement of the multilayer piezoelectric actuator, or a compressive force is applied from the outside, the first and second case portions 1 and 2 and the multilayer piezoelectric actuator 3 undergo dimensional changes. However, by compressing the elastic member 6 so that no gap is generated between the elastic member 6 and the first and second case portions 1 and 2, under the assumed use condition, Since the inside of the case and the outside of the case are always interrupted and hermetically sealed, a short circuit due to adhesion of moisture or a conductive material can be similarly prevented.

In general, in the case of a laminated piezoelectric actuator, since silver or a material containing silver is used for the internal electrode and the external electrode, migration of silver occurs depending on the use environment (particularly humidity), and short-circuit occurs. There is a drawback to do.

However, by employing the structure according to the second embodiment shown in FIG. 2, the inside of the case and the outside of the case can be cut off, so that the multilayer piezoelectric actuator 3 is not affected by humidity. It becomes possible.

The reliability of the laminated piezoelectric actuator 3 shown in FIGS. 1, 2 and 6 is evaluated at 40 ° C., 90% and an applied voltage of 150 V in Table 1 below.
(TTF) shows the result of comparison.

As shown in Table 1 below, the structure shown in FIG. 2 can improve the reliability of the case-enclosed laminated type piezoelectric actuator of FIG. The same result as the piezoelectric actuator was obtained.

[0068]

[Table 1] Therefore, by using the case-enclosed type laminated piezoelectric actuator having the structure shown in FIG. 2, the same reliability as that of the conventional case-enclosed laminated piezoelectric actuator shown in FIG. 6 can be obtained at lower cost.

The same effect can be obtained by blocking the inside and the outside of the case with an elastic member (which does not restrict displacement) regardless of the shape and structure.

Further, in the case-enclosed laminated piezoelectric actuator according to the second embodiment of the present invention shown in FIG. 2, the first case 1 and the second case 2 are made of a conductive material, The first case portion 1 and the second case portion 2 are electrically connected to each of the opposing external electrodes 4 and the elastic member 6 is made of an insulating material.
The case 2 has no electrical continuity, and the first case 1 and the second case 2 can be used as voltage application terminals.

In any case shape and structure, the first case portion 1 and the second case portion 2 are electrically connected to the opposing external electrodes 4 of the multilayer piezoelectric actuator 3, respectively. Is a case-enclosed laminated piezoelectric actuator in which the first case part 1 and the second case part 2 are made of a conductive material, the elastic member 6 is made of an insulating material, and the case 1 and the case 2 are not electrically connected. The same effect can be obtained by manufacturing.

As shown in FIG. 2, the elastic member movement preventing processing 7 is performed on at least one of the first case portion 1 and the second case portion 2, and the elastic member By disposing the elastic member 6, the elastic member 6 can be used for a long period of time and when manufacturing a case-enclosed laminated piezoelectric actuator.
Can be prevented, and the inside and outside of the case can be more stably shut off, and further, the effect of preventing short circuit due to contact between the first and second case portions 1 and 2 can be obtained.

Further, the outer diameter of the elastic member 6 is set at a fixed position (for example, the outer diameter of the portion of the first case 1 where the elastic member 6 is disposed is equal to the inner diameter of the elastic member 6.
The inner diameter of the portion where the elastic member 6 is disposed is equal to the outer diameter of the elastic member 6. The same effect as in the case where the processing 7 for preventing the movement of the elastic member is performed can be obtained by configuring so as to fit in (1).

The elastic member 6 of the case-enclosed multilayer piezoelectric actuator shown in FIG. 2 has a length of 1.9 mm in the displacement direction of the case-enclosed laminated piezoelectric actuator. Is manufactured so as to be in a state of being compressed by 0.5 mm at room temperature (25 ° C.) between the case parts 2, which is determined under the following conditions.

The design was performed with the operating temperature range of the case-enclosed laminated piezoelectric actuator shown in FIG. When the case-enclosed multilayer piezoelectric actuator is used at different temperatures, the gap b in the stacking direction of the case 1 and the case 2 increases due to a dimensional change due to a temperature change in the portions a and b, and the gap b other than the portions a and b Does not affect the dimension of the part b because it is made of the same material in the displacement direction. Cases 1 and 2 have a thermal expansion coefficient of 16 × 10 ⁻⁶ / ° C. Further, the multilayer piezoelectric actuator has a thermal expansion coefficient of −7.5 × 10 ⁻⁶ / ° C. The gap b in the stacking direction of the case 1 and the case 2 increases. Therefore, at room temperature (2
When the operating environment temperature is increased from 5 ° C.) to 100 ° C., the gap between the case 1 and the case 2 in the stacking direction is
Increase by 0.10743 mm.

Therefore, the elastic member 6 is at room temperature (25 ° C.)
By manufacturing in a compressed state of 0.10743 mm or more, there is no gap between the elastic member 6 and the case 1 and the case 2 in any assumed use state, and the inside and the outside of the case can be always shut off. It is possible to prevent the reliability of the piezoelectric actuator from deteriorating due to the use environment (particularly humidity). In the second embodiment, the compression is 0.5 mm or more, which is 0.10743 mm or more.

Table 2 below shows that the elastic material is compressed by 0.5 mm, the elastic material is compressed by 0.01 mm, the laminated piezoelectric actuator not sealed in the case, and the conventional metal shown in FIG. A case-enclosed laminated actuator having a sealed structure is mounted at a temperature of 85 ° C.
%, The results of reliability evaluation performed at an applied voltage of 150 V, and comparison with the mean time to failure (MTTF) are shown.

[0078]

[Table 2] Incidentally, even in the case of a case-enclosed laminated piezoelectric actuator having a shape or material different from that of the embodiment, the compression amount of the elastic member 6 is designed in consideration of the dimensional change shown in the embodiment, so that the The same effect can be obtained in any usage state within the assumed range.

When a compressive force is applied from the displacement direction of the case-enclosed type laminated piezoelectric actuator, the compression amount of the first and second case portions 1 and 2 and the laminated piezoelectric actuator can be added to the design to achieve the same result. The effect of is obtained.

FIG. 3 shows a case-enclosed laminated piezoelectric actuator according to a third embodiment of the present invention.
(A) is a perspective view, (b) is a sectional view.

FIG. 3 shows a case-enclosed laminated piezoelectric actuator 30 according to a third embodiment of the present invention.
FIG. 3 shows a state in which an electrode application terminal 17 and a lead wire 14 are added to the case-enclosed laminated piezoelectric actuator 20 having the above structure, and the first and second case portions 1 and 2 are subjected to insulation treatment 18. .

Case-Enclosed Laminated Piezoelectric Actuator 3
The first case 1 and the second case 2 are provided with a voltage application terminal (in the case of the third embodiment, screws are attached), and the voltage application terminal 17 is connected to a lead wire 14. Are fixed by crimping to provide external voltage application terminals. This makes it easy to mount the case-enclosed laminated piezoelectric actuator 30 to a device when a voltage cannot be applied from a portion that directly contacts the case in the device.

It should be noted that even in the case of a case-enclosed laminated piezoelectric actuator having a shape or material different from that of the third embodiment, a voltage application terminal (for example, a convex pin,
A similar effect can be obtained by attaching a crimp terminal.

Further, the first and second case portions 1 and 2
By providing the voltage applying terminal 17 to the, the connection of the voltage applying conductor from the outside of the case-enclosed multilayer piezoelectric actuator is facilitated, and the attachment to the device for mounting the case-enclosed laminated piezoelectric actuator is simplified. I do.

Further, the case-embedded type laminated piezoelectric actuator mounting device is provided with first and second case portions 1 and 2.
In the case of a structure in which a short circuit occurs between them, a short circuit between the first and second case portions 1 and 2 is prevented by the insulating treatment 18.

In the case where the device and the case-enclosed type laminated piezoelectric actuator must not be electrically connected, a part or all of the externally exposed portion of the case is insulated 18 with an insulating material, so that the case-enclosed type piezoelectric actuator is insulated. The laminated piezoelectric actuator and the device can be electrically insulated.

The insulation treatment 18 is also applied to the inside of the cases 1 and 2 to prevent an electrical short circuit even when the cases 1 and 2 and the internal and external electrodes of the multilayer piezoelectric actuator 3 come into contact. Becomes possible.

FIG. 4 is a view showing a case-enclosed laminated piezoelectric actuator according to a fourth embodiment of the present invention.
(A) is a top view and (b) is a cross-sectional view.

As shown in FIG. 4, a case-enclosed laminated piezoelectric actuator 40 according to a fourth embodiment of the present invention.
Is different from that shown in FIGS. 1 and 2 in that the shape of the first and second case portions 1 ′ and 2 ′ has a shape in which cups having different diameters are inserted into openings. Is different. However, as shown in FIGS. 1 and 2, the first
And making the multi-layer piezoelectric actuator 3 a conductor in the second case portions 1 ', 2', connecting the cases 1 and 2 to the external electrodes 4 of the multi-layer piezoelectric actuator 3, inserting the elastic member 6, and insulating material. , First case 1 and second case
(In the case of the structure of FIG. 4, the thermal expansion in the cross-sectional direction perpendicular to the laminating direction is performed), and the distance between the cases 2 and the compression amount of the elastic member 6 are optimized. The same effects as those of the case-enclosed laminated piezoelectric actuators 10 and 20 can be obtained.

As shown in FIG. 3, a voltage applying terminal 17 is provided on the first and second case portions 1 'and 2', and the first and second case portions 1 'and 2' Insulation treatment 18
, The same effect as in the case of FIG. 3 can be obtained.

Also, in case-enclosed laminated piezoelectric actuators having different shapes and structures, insertion of the laminated piezoelectric actuator into the case, conversion of the two case members into conductors, and externalization of the two case members and the laminated piezoelectric actuator are also possible. Connection with electrodes, insertion of elastic members and use of insulating material, optimization of the distance between the two cases and the amount of compression of the elastic members, addition of terminals 17 for voltage application, insulation treatment of cases 18
The same effect can be obtained by performing.

[0092]

As described above, according to the present invention,
By enclosing it in a case, it is possible to prevent damage to the laminated piezoelectric actuator. In addition, by using the case as a conductor and electrically connecting it to external electrodes, the case can be directly used as a terminal for voltage application, simplifying installation of the device, and using a conductive paint for connection between the case and the external electrodes. This makes it possible to simplify the production and prevent disconnection due to soldering.

Further, according to the present invention, by optimizing the distance between the two cases, it is possible to prevent a decrease in the amount of displacement due to a compressive force due to an electrical short circuit between the cases and contact between the cases.

Further, according to the present invention, by inserting an elastic member having elasticity between the cases to shut off the inside and the outside of the case, and by optimizing the amount of compression of the elastic member, any usage conditions can be improved. However, the inside and the outside of the case can be cut off, so that a decrease in reliability due to the influence of the environment (particularly humidity) can be prevented.

Further, according to the present invention, the elastic member is made of an insulating material, so that the case is electrically connected to the external electrode of the laminated piezoelectric ceramic by the conductor, and the case is inserted even when the elastic member is inserted. Can be used as a voltage application terminal.

Further, according to the present invention, by preventing the elastic member from moving or by configuring the elastic member so as not to move, the inside and outside of the case can be more stably shut off, and furthermore, the electrical connection between the case members can be improved. Short circuits can also be prevented.

Further, according to the present invention, by providing the case with the voltage application terminal, it becomes easy to apply the voltage from a portion other than the contact portion between the device and the case-enclosed laminated piezoelectric actuator.

Further, according to the present invention, a part or the whole of the case is insulated with an insulating material to thereby electrically insulate the device from the case-enclosed type laminated piezoelectric actuator, and provide the case and the laminated type piezoelectric actuator. It is possible to secure electrical insulation.

Therefore, according to the present invention, it is possible to provide an inexpensive case-enclosed laminated piezoelectric actuator which can obtain a performance corresponding to the added item by performing any or all of the above. Was.

[Brief description of the drawings]

FIG. 1A is an external view showing a case-enclosed laminated piezoelectric actuator according to a first embodiment of the present invention. (B) is a top view of (a). (C) is a cross-sectional view of a plane perpendicular to the displacement plane of the multilayer piezoelectric actuator.

FIG. 2A is a top view showing a case-enclosed laminated piezoelectric actuator according to a second embodiment of the present invention. (B) is a cross-sectional view taken along a plane orthogonal to the displacement plane of the multilayer piezoelectric actuator of (a).

FIG. 3A is an external view showing a case-enclosed laminated piezoelectric actuator according to a third embodiment of the present invention. (B) is a cross-sectional view taken along a plane orthogonal to the displacement plane of the multilayer piezoelectric actuator of (a).

FIG. 4A is a top view showing a case-enclosed laminated piezoelectric actuator according to a fourth embodiment of the present invention. (B) is a cross-sectional view taken along a plane orthogonal to the displacement plane of the multilayer piezoelectric actuator of (a).

FIG. 5 is a perspective view showing the appearance of a conventional laminated piezoelectric actuator that is not enclosed in a case.

FIG. 6A is a top view of a conventional case-enclosed laminated piezoelectric actuator. (B) is a cross-sectional view taken along a plane orthogonal to the displacement plane of the multilayer piezoelectric actuator of (a).

[Explanation of symbols]

1, 1 'First case part 2, 2' Second case part 3 Laminated piezoelectric actuator 4 External electrode 5 Conductive paint 6 Elastic member 7 Elastic member movement preventing processed part 10, 20, 30, 40, 50 Case Encapsulation type laminated piezoelectric actuator 14 Lead wire 17 Voltage application terminal 18 Insulation processing part 19 Chamfered part 51 Case 52 Spring mechanism 53a, 53b, 53c Solder 55 Internal electrode layer 56 Piezoelectric ceramic layer 58 Voltage application terminal 59 Insulation processing 60 Lead Wire 61 adhesive

Claims (13)

[Claims] 1. A laminated piezoelectric actuator comprising at least one piezoelectric ceramic layer and at least two internal electrode layers, and external electrodes formed on side surfaces thereof such that the internal electrodes constitute one or more pairs of counter electrodes. In the above, the laminated piezoelectric actuator is separately and directly connected to two end faces in the laminating direction, respectively, and is put in a case composed of first and second case portions, and the first and second piezoelectric actuators are placed on the two end faces in the laminating direction. The case portions are directly connected to each other, and the first and second cases are connected.
Wherein the case portions are separated from each other and electrically insulated from each other. 2. The laminated piezoelectric actuator according to claim 1, wherein said first and second case portions are made of a conductive material, and one of said first and second cases is made of said laminated piezoelectric device. Connected to one of the external electrodes of the actuator in an electrically conductive state;
The other of the case portions and an external electrode of the multilayer piezoelectric actuator having a different polarity from that connected to the one case portion of the multilayer piezoelectric actuator in an electrically conductive state; And a case-enclosed laminated piezoelectric actuator characterized in that the second case part is a voltage application terminal. 3. The case-enclosed type multilayer piezoelectric actuator according to claim 1, wherein the external electrodes of the multilayer piezoelectric actuator and the first and second case portions are connected by a conductive paint, respectively. A case-enclosed laminated piezoelectric actuator characterized by the following characteristics. 4. The case-enclosed type laminated piezoelectric actuator according to claim 1, wherein an external electrode of the laminated piezoelectric actuator encapsulated in the case is electrically connected to an end face in a laminating direction. A case-enclosed laminated piezoelectric actuator characterized by being configured in a certain state. 5. The case-enclosed laminated piezoelectric actuator according to claim 4, wherein the surface of the laminated piezoelectric actuator, wherein the external electrodes are connected to the internal electrodes,
A case-enclosed laminated piezoelectric actuator characterized in that the corners between the surfaces where the external electrodes are formed up to the end surfaces in the laminating direction are chamfered. 6. The case-enclosed type laminated piezoelectric actuator according to claim 1, wherein the case and the laminated-type piezoelectric actuator are in a use temperature range of the case-enclosed type laminated piezoelectric actuator. Even if a dimensional change due to thermal expansion or external stress causes a dimensional change in the case and the multi-layer piezoelectric actuator, or a dimensional change due to driving of the multi-layer piezoelectric actuator, they are separately connected to the two end faces in the laminating direction. A case-enclosed laminated piezoelectric actuator, wherein the first and second case portions are configured not to contact each other. 7. The case-enclosed laminated piezoelectric actuator according to claim 1, wherein at least one elastic member is provided between the first and second case portions, and the inside of the case is provided. A case-enclosed laminated piezoelectric actuator characterized in that it is isolated from the outside. 8. The case-enclosed laminated piezoelectric actuator according to claim 7, wherein the elastic member does not move from an initial position between the first and second case portions even during vibration or long-term driving. A case-enclosed laminated piezoelectric actuator characterized by being arranged in the following manner. 9. The case-enclosed laminated piezoelectric actuator according to claim 7, wherein the elastic member is provided between the first and second case portions from an initial position even during vibration or long-term driving. A case-enclosed laminated piezoelectric actuator, characterized in that one or both of the first and second cases are processed to prevent movement of an elastic member so as not to move. 10. The case-enclosed multilayer piezoelectric actuator according to claim 7, wherein the elastic member is an insulator. 11. The case-enclosed laminated piezoelectric actuator according to claim 7, wherein:
The dimensional change of the pair of cases and the multilayer piezoelectric actuator due to thermal expansion and the dimensional change of the pair of cases and the multilayer piezoelectric actuator due to external stress in the operating temperature range of the case insertion type multilayer piezoelectric actuator, Even if a dimensional change occurs due to the driving of the laminated piezoelectric actuator, each of the pair of cases and the elastic material 6 which are separately connected directly to the two end faces in the laminating direction.
A case-enclosed laminated piezoelectric actuator characterized in that the elastic member is compressed and manufactured to a state where no space is created between the piezoelectric actuators. 12. The case-enclosed laminated piezoelectric actuator according to claim 1, wherein:
A case-enclosed laminated piezoelectric actuator, wherein a voltage application terminal is provided on one or both of the first and second case portions. 13. The case-enclosed laminated piezoelectric actuator according to claim 1, wherein:
A case-enclosed laminated piezoelectric actuator, wherein a part or all of the surface of the first and second case portions is subjected to insulation treatment.