JPH0529679A - Laminated piezoelectric element - Google Patents

Abstract

PURPOSE:To effectively utilize a side space by connecting leads to a terminal electrode plate at an inner peripheral surface side and leading it in an upper direction. CONSTITUTION:A spacer 60 is secured in a sandwich state interposed between an end face electrode plate 50 and an upper end face of a laminate 10. Further, a lateral movement is restricted by three pawls of the plate 50. Accordingly, parts such as the spacer 60, an insulating plate 40, etc., provided on the upper end face of the laminate 10, are integrally fixedly connected. A lead 71 is externally extended through central holes of the plate 50, a terminal electrode plate 32, the plate 40, and a lead 72 is externally extended through the central hole of the plate 50. Thus, since the leads and connectors of the leads to a electrode are not provided on the outer periphery of the laminate, a protrusion from the side in an outer circumferential direction is not provided. Accordingly, an inner diameter of a packing material for containing a laminated piezoelectric element can be reduced, and a space can be effectively utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric body formed by laminating a large number of plate-shaped piezoelectric elements that expand and contract according to an applied voltage, and is applied to, for example, a piezoelectric actuator for driving a fuel injection device. It

[0002]

2. Description of the Related Art Conventionally, a laminated piezoelectric body has a laminated body in which piezoelectric elements made of piezoelectric plates and metal electrode plates are alternately laminated, and every other electrode plate of the laminated body has a side surface on each side. It is electrically connected to form a pair of side electrodes. Lead wires are joined to the pair of side surface electrodes at the side surfaces. Then, a voltage is applied to the side surface electrode and the electrode plate through the lead wire, and the laminated piezoelectric material exhibits piezoelectric material characteristics.

The lead wire and the side surface electrode are usually joined by a joining technique such as soldering or caulking on the outer peripheral side surface of the laminated piezoelectric material. Therefore, on the outer peripheral surface of the laminated piezoelectric body, the lead wire and the joint portion thereof project from the outer peripheral surface, thereby increasing the outer diameter of the laminated body. For this reason, when packaging the laminated piezoelectric body (when assembled in a certain device), the accommodating container for the laminated piezoelectric body should have a large diameter space in consideration of the amount of lead wires that can be inserted.
Alternatively, it is necessary to make the relief groove portion for passing the lead wire into a bulged shape. Therefore, the conventional laminated piezoelectric body has a problem that the dead space increases.

Specifically, when the laminated piezoelectric material is used as an actuator, it is packaged as shown in FIG. The metal bellows 80 includes the laminated piezoelectric body 1, lead wires 73 and 74 protruding therefrom, and the joint portion 7.
It covers 6, 77. Therefore, the outer diameter is increased by the amount that covers the lead wires 73 and 74 and the joint portions 76 and 77. In FIG. 7, one end 1 a of the laminated piezoelectric body 1 is in contact with the disk-shaped cover 81, and the other end 1 b is in contact with the bottomed portion 82 a of the piston 82. The cover 81 and the piston 82 are connected by a metal bellows 80, and the tensile force acts on the metal bellows 80 as a preset load. Although the laminated piezoelectric body 1 is housed inside the metal bellows 80, the inner diameter of the bellows 80 needs to be larger than the outer diameter of the piezoelectric body due to the protrusion of the lead wire and the joint portion thereof, and as a result, the actuator. The volume of itself also becomes large.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a force generated per unit cross-sectional area of an assembled laminated piezoelectric body (when a voltage is applied to the laminated piezoelectric body). It is an object of the present invention to provide a laminated piezoelectric body in which the dead space on the side surface side is eliminated in order to improve the efficiency of the large load generated in (1).

[0006]

A laminated piezoelectric body of the present invention comprises a laminated body formed by alternately laminating piezoelectric elements made of piezoelectric plates and metal electrode plates, and a side surface of the laminated body. A pair of side surface electrodes that extend in the stacking direction and electrically connect each of the electrode plates of two sets of electrode plates that are alternately arranged on their side surfaces, and a voltage is externally applied to the side surface electrodes. A laminated piezoelectric body having a lead wire joined to the side surface electrode for stacking, is laminated on one end side of the laminated body, is electrically connected to one of the pair of side surface electrodes, and has an inner peripheral surface. And at least one terminal electrode plate connected to the lead wire on the side.

[0007]

In the laminated piezoelectric body of the present invention, the terminal electrode is laminated on one end side of the laminated body, electrically connected to one of the pair of side surface electrodes on the side surface, and connected to the lead wire on the inner peripheral surface side. It is equipped with a plate. Therefore, the outer peripheral surface of the laminated body has no lead wire or a joint portion between the lead wire and the side surface electrode, and therefore has no protruding portion from the side surface in the outer peripheral direction. Therefore,
In this laminated piezoelectric body, the outer peripheral side surface of the laminated body can be treated as the outer diameter, so that the inner diameter of the pack material for accommodating the laminated piezoelectric body can be reduced and the space can be effectively used. Therefore, the utilization efficiency of the space of the device is improved, the dead space is eliminated, and the actuator of the laminated piezoelectric body can be downsized as compared with the conventional case where the lead wire bonding portion has a protrusion.

Further, since the piezoelectric performance of the laminated piezoelectric body obtains a generated force based on the area of the piezoelectric element, if the laminated piezoelectric body has the same performance, it is apparent that the effective area ratio increases due to downsizing. This means improved performance.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples. (Embodiment 1) As shown in the front view of FIG. 1 and the sectional view of FIG. 2, the laminated piezoelectric body 1 includes a laminated body 10 and side surfaces formed along a side surface of the laminated body 10 in a laminating direction. Electrode 13,
14, the metal plate 20, the terminal electrode plates 31, 32, the insulating plate 40, the spacer 60, and the end face electrode plate 5 on the upper end surface of the laminated body 10.
0 is placed, and the lead wires 7 are attached to the terminal electrode plates 31 and 32.
1, 72 are connected.

As shown in the perspective view of FIG. 3, the laminated body 10 is a piezoelectric element 1 made of a ceramic piezoelectric plate having electrodes 15 formed on both sides by applying, for example, silver paste.
1 and an electrode plate 12 made of a disc-shaped metal and having three claws 121 provided on the end face and protruding outwardly are alternately laminated. Then, the electrode plates 12 of the two electrode plate sets consisting of every other electrode plate 12 are electrically welded by directly welding the claws 121 or by welding the side electrode plates (not shown) by welding or the like. To form a pair of side electrodes 13 and 14 (three pieces each). One side surface electrode 14 of the pair is joined by an engaging portion 52 that extends upward from the upper end surface of the laminated body 10 and engages with a claw 51 provided on the end surface electrode plate 50. The other side electrode 13 has the same length as the end surface of the laminated body 10 and
Is formed so as to be electrically connected to the metal plate 20 that abuts on the uppermost electrode plate 12.

On the upper end surface of the laminated body 10, as shown in the perspective view of the assembled state of the laminated piezoelectric body of FIG.
The terminal electrode plate 31, the insulating plate 40, the terminal electrode plate 32, the spacer 60, and the end surface electrode plate 50 are sequentially placed and fixed. The metal plate 20 is a relatively thick metal plate having an outer diameter smaller than the outer diameter of the electrode plate 12, and is placed on the end surface of the laminated body 10. The electrode plate 12 is laminated on the upper end surface of the laminated body 10 so that the metal plate 20 is formed by connecting three claws 121 protruding from the end surface of the electrode plate 12 to each other. Is electrically connected to the side surface electrode 13.

Since the metal plate 20 directly abuts on the end faces of the laminated body 10, the surface roughness and flatness of both end faces are finished with extremely high precision, and bending or concentrated load is applied to the piezoelectric element 11 of the laminated body 10. A material is used so that the piezoelectric element 11 does not have a defect such as cracking when (partial contact) is applied. The terminal electrode plate 31 is formed of a ring-shaped metal plate having the same outer diameter as the metal plate 20, is placed on the upper surface of the metal plate 20, and is electrically connected to the side surface electrode 13 via the metal plate 20. The inner peripheral surface of the ring is connected to the lead wire 71 by caulking or welding. The terminal electrode plate 31 may have a disc shape, not a ring shape, as long as the lead wire can be connected at the central portion.

The terminal electrode 31 is basically the electrode plate 1.
The same metal plate as that of No. 2 is formed by means of press working or the like, but if deburring of both end faces and surface finishing (flatness etc.) are made to the same degree as the metal plate 20, the metal plate 2
It is also possible to remove 0. The insulating plate 40 has a ring shape with the same outer diameter as the terminal electrode plate 31 and a thick thickness, and enables the lead wire 71 connected to the terminal electrode plate 31 in the hollow portion to be taken out to the outside. Placed. The insulating plate 40 is formed of an insulating material (resin, ceramics, etc.). As the insulating material, a material having a large Young's modulus and no plastic deformation is used in order to directly receive the pressure generated when a voltage is applied to the laminated piezoelectric body 1 and to reduce the loss of the generated force as much as possible. Is preferred.

The terminal electrode plate 32 is placed on the insulating plate 40 to insulate it from the terminal electrode plate 31. The terminal electrode plate 32 is made of the same material as the above-mentioned terminal electrode plate 31 and has a ring shape. The lead wire 71 can be taken out from the ring hole, and the lead wire 72 is connected by caulking or welding at the inner peripheral end surface of the ring. Has been done. The spacer 60 has a ring shape and is directly placed on the end surface of the laminated body 10 and has an outer diameter of the laminated body 1.
The same as 0 but the inner diameter is slightly larger than the outer diameter of the insulating plate 40, and the metal plate 20, the insulating plate 40, the terminal electrode plates 31, 32 are
Are arranged on the outer peripheral surface of the to constrain their lateral movement. The spacer 60 is made of the same insulating material as the insulating plate 40 in order to maintain the insulating property between the terminal electrodes 31 and 32.

The end face electrode plate 50 is a ring-shaped metal disc and is placed on the upper surface of the spacer 60 so as to cover the spacer 60 and the terminal electrode plate 32. The spacer 60 has three claws 51 provided at the end portions and extending in the stacking direction. At the outer periphery of the laminated body 10, the side surface electrode 14 extending upward of the laminated body 10 is engaged to form an engaging portion 52, which is connected by means of welding or the like and is locked to the laminated body 10. Therefore, the side surface electrode 14 is electrically connected to the terminal electrode plate 32 via the end surface electrode plate 50.

For this reason, the spacer 60 is used for the end face electrode plate 50.
It is sandwiched between the upper end faces of the laminated body 10 and fixed in a sandwich shape, and its lateral movement is restricted by the three claw portions of the end face electrode plate 50. Therefore, each part such as the spacer 60 and the insulating plate 40 provided on the upper end surface of the laminated body 10 is integrally fixed and locked. The lead wire 71 is taken out to the outside through the central hole of the end face electrode plate 50, the terminal electrode plate 32, and the insulating plate 40. The lead wire 72 is also taken out to the outside through the central hole of the end face electrode plate 50. Since the lead wires 71 and 72 are electrically connected to the side surface electrodes 13 and 14 via the terminal electrode plates 31 and 32, a voltage is applied to the lead wires 71 and 72 to apply a voltage to the laminated body 10. Piezoelectric properties are exhibited.

In addition, the thickness of the insulating plate 40 is made sufficiently large so that the joint portion between the terminal electrode plate 31 to which the lead wire 71 is joined and the terminal electrode plate 32 to which the lead wire 72 is joined does not come into contact with each other, or the insulating plate 40 has an insulating property. It is preferable to completely cover the joint between the lead wire and the terminal electrode plate by using a tube or the like. Next, a process of applying a voltage to the laminated piezoelectric body 1 will be described with reference to FIGS. 1 and 2. If the electric polarity of the electrode plate 12 on the upper end surface of the laminated body 10 is, for example, a negative electrode (the polarity of the terminal electrode plate 31 is a negative electrode and the lead wire 71 is also a negative electrode), the electrode on the upper end surface of the laminated body 10 will be described. Since the side surface electrode 14 not electrically connected to the plate 12 serves as a + pole, the polarity of the end surface electrode plate 50 connected to the side surface electrode 14 serves as a + pole (of the terminal electrode plate 32 and the lead wire 72). Polarity is + pole). However, since the electric polarity of the laminated piezoelectric material 1 is determined at the time of polarization, it does not matter which is the positive pole or the negative pole if the above is taken into consideration.

The laminated piezoelectric material 1 has a + voltage applied to the + electrode side.
It has the property of expanding when applied and contracting when applied with a voltage.
It At this time, a large generating force is generated as a feature of the laminated piezoelectric body 1.
This is a projection of the piezoelectric element 11 of the laminated piezoelectric body 1.
Proportional to the area. For example, the laminated piezoelectric material used here
The area of the piezoelectric element 11 of 1 is 78.5 mm ², The generating power is 3
000 N, but 38.2 MPa per unit area
It becomes the generating power of. However, in actual use, the conventional product
In the layered piezoelectric body, a voltage applying means such as a lead wire is arranged on the outer periphery.
Since it is necessary to place it, the area required for this portion becomes large. This
FIG. 6 schematically shows this as a plan view. Diagonal lines
The area of the piezoelectric element is within the range, and the lead wires are arranged on the side surface.
Then, the range of the dashed line is the actual area of the laminated piezoelectric body. versus
This area may vary depending on the position of the lead wire.
However, it does not become smaller than this. Therefore,
Place lead wires on the side surface compared to the area of the piezoelectric element only
Then, a dead space occurs as such an area. Fruit
When calculating the area required when using the piezoelectric element
It is 10% or more larger than the area required for. Because
Actually, the generated force per unit area is reduced by 10% or more.
Will be done.

On the other hand, in the present invention, since the lead wire and the like do not project to the side surface of the laminated body, the area projected on the lower surface of the laminated body is almost the same as that of the piezoelectric element. Therefore, the generated force of the piezoelectric body can be obtained only by the projected area of the piezoelectric body, and the space is effectively used, resulting in a structure of efficient generated force per unit area. In other words, even when the same laminated piezoelectric material is used, by using this structure, it is possible to supply a product that is 10% or more smaller than the conventional product. (Embodiment 2) In this embodiment, as shown in FIG. 5, one negative pole side of the voltage application lead wire of the laminated piezoelectric body 1 has a body ground structure. Therefore, the terminal electrode plate 31 provided on the upper end surface of the laminated body 10 is only the positive electrode and the lead wire 7
One can be taken out from only one side, and the structure can be simplified.

The laminated piezoelectric body 1 has a ring-shaped structure in which the upper end surface of the laminated body 10 is a piezoelectric element 11 on which a disc-shaped metal plate 20 is placed and a lead wire 71 is caulked thereto. The terminal electrode plate 31 is arranged, the spacer 60 is arranged around the metal plate 20 and the outer periphery of the terminal electrode plate 31, both are fixed, and the hollow end face electrode plate 50 is placed on the upper surface of the terminal electrode plate 31 and laminated. Side electrode 13 of body 10, claw 51 and engaging portion 5
2 is formed and joined to be integrally joined. In addition, when the uppermost end surface of the laminated body 10 is the electrode plate 12, the insulating plate 31 (a disk shape instead of a ring shape) is used instead of the metal plate 20.
By using, it is possible to prevent the side electrodes 13 and 14 from conducting.

The other side electrode 14 is body-grounded at the lower end surface. By arranging the lead wire 71 so as to be the positive electrode, the terminal electrode plate 32 and the insulating plate 40 or the metal plate 20 in FIG. 5 are not necessary, the structure is simplified, and the total length of the laminated piezoelectric body 1 is smaller. It becomes possible. At this time, the electrode plate 12 on the upper side of the laminated piezoelectric body 1
It is necessary that the lower electrode plate 12 and the lower electrode plate 12 have different polarities (the upper electrode plate has a positive polarity and the lower electrode plate has a negative polarity).

In this way, by connecting the lead wires on the upper surface of the laminate and arranging the terminal electrode plate through the insulating material and connecting to each of the side electrodes, the outer diameter is enlarged by the side joining of the lead wires of the laminate. Can be prevented.

[0023]

In this laminated piezoelectric body, the lead wire for applying a voltage is joined to the terminal electrode plate provided on the upper end surface of the piezoelectric body on the inner peripheral surface side, and the lead wire extends upward and is taken out. Has become. Therefore, there is no protrusion on the side surface of the laminated body and there is no dead space, so that the side surface space can be effectively used. For this reason, the mounting outer diameter when the laminated piezoelectric body is assembled to the device can be reduced.

Therefore, the generated force per unit area of the piezoelectric body can be efficiently obtained. Further, since the terminal electrode plate is joined to the electrode by a simple structure, it can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a front view of a multilayer piezoelectric body according to a first embodiment.

FIG. 2 is a cross-sectional view of the laminated piezoelectric body shown in FIG.

FIG. 3 is a perspective view illustrating a configuration of a laminated body.

FIG. 4 is a schematic diagram illustrating the configuration of the laminated piezoelectric body according to the first embodiment.

FIG. 5 is a schematic cross-sectional view of a laminated piezoelectric body of Example 2.

FIG. 6 is a schematic diagram showing a projected area of the degree of increase in area when a lead wire is joined to the area required for actual use of the conventional product and the area of the piezoelectric element.

FIG. 7 is a schematic cross-sectional view illustrating a state in which a conventional laminated piezoelectric body is assembled and used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 laminated piezoelectric body, 10 laminated body, 11 piezoelectric element, 12 electrode plate, 13, 14 side surface electrode, 20
Metal plate, 31, 32 terminal electrode plate, 40 insulating plate,
50 end face electrode plate, 60 spacer, 71, 72
Lead,

Front Page Continuation (72) Inventor Akira Fujii 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A laminated body in which piezoelectric elements made of piezoelectric plates and metal electrode plates are alternately laminated, and every other one extending in the laminating direction along the side surface of the laminated body. And a pair of side surface electrodes for electrically connecting each of the electrode plates of the two electrode plate sets consisting of the respective electrode plates at their side surfaces, and joined to the side surface electrodes for applying a voltage to the side surface electrodes from the outside. A laminated piezoelectric body having a lead wire formed on one end of the laminate, electrically connected to one of the pair of side electrodes, and connected to the lead wire on the inner peripheral surface side. Of at least one terminal electrode plate formed as described above.