JPH07142779A - Multilayer piezoelectric device - Google Patents

Abstract

PURPOSE:To provide a multilayer piezoelectric device used for a reliable multilayer piezoelectric actuator, having excellent flatness of the upper and lower surfaces and stable adhesion between layers. CONSTITUTION:A thickness T1 between a piezoelectric part 1a at an upper position than an internal electrode 2a1 of the top layer of a laminated body 3 and a piezoelectric part 1b at a lower position than an internal electrode 2b1 of the lowest side is made larger so that the distance from inner electrodes of the top layer and the bottom, which are led to sides 3c and 3d of the laminated body 3 of the piezoelectric layers 1a and 1b and the inner electrodes 2a and 2b, to the top and the bottom ends of the sides 3c and increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element, and more particularly, to a side surface of a laminated body of a piezoelectric layer and an internal electrode, the external electrode being electrically connected to the internal electrode arranged between the piezoelectric layers. The present invention relates to a laminated piezoelectric element that is arranged in the.

[0002]

2. Description of the Related Art As a laminated piezoelectric actuator using a piezoelectric material, for example, as shown in FIG. 3, an internal electrode 52 having a partial electrode structure is arranged between a plurality of piezoelectric material layers 51, and a piezoelectric A plurality of laminated piezoelectric elements 55 each having an external electrode 54 disposed on the side surface of the laminated body 53 including the body layer 51 and the internal electrode 52 from which the internal electrode 52 is drawn out are stacked and bonded by an adhesive 56. A multilayer piezoelectric actuator having a structure in which the external electrodes 54 are connected by lead wires 57 has been proposed.

In the laminated piezoelectric element 55 constituting the above laminated piezoelectric actuator, the internal electrode 5 is used.
As shown in FIG. 4, the layers 2 are alternately drawn to the opposite end so that they are electrically connected to the external electrodes 54 (FIG. 3) on the opposite side every other layer.

As the external electrode 54, the internal electrode 5 is used.
The thick film electrode is used in consideration of the certainty of conduction with 2.

[0005]

However, in the above-mentioned laminated piezoelectric actuator, as shown in FIG. 5, the upper end portion 54a and the lower end portion 54b of the external electrode 54 of the laminated piezoelectric element 55 are the laminated body 53. Since it rises at the corners (edges) and projects from the upper and lower surfaces of the laminated body 53, the flatness of the upper and lower surfaces of the laminated piezoelectric element 55 is impaired. Therefore, the plurality of laminated piezoelectric elements 55 are attached to the adhesive 5
When stacked through 6, the stacked (joined) state becomes unstable and cannot be securely fixed, or when it is used as a laminated piezoelectric actuator, it may be broken by external force. There is a problem.

The present invention solves the above problems and is excellent in the flatness of the upper and lower surfaces, and is excellent in the stability of bonding when a laminated piezoelectric actuator is constructed by stacking and bonding a plurality of layers. An object of the present invention is to provide a laminated piezoelectric element capable of obtaining a highly reliable laminated piezoelectric actuator without causing breakage due to external force.

[0007]

In order to achieve the above object, a laminated piezoelectric element according to the present invention has a plurality of piezoelectric layers, internal electrodes arranged between the piezoelectric layers, and internal electrodes extended. In a laminated piezoelectric element including an external electrode formed on a side surface of the laminated body, the distance from the uppermost internal electrode drawn to the side surface of the laminated body of the piezoelectric layer and the internal electrode to the upper end of the side surface. , And the piezoelectric material portion above the internal electrode of the uppermost layer of the laminate and the internal electrode of the lowermost layer so that the distance from the internal electrode of the lowermost layer drawn to the side surface of the laminated body to the lower end of the side surface becomes large. The feature is that the thickness of the lower piezoelectric portion is increased.

[0008]

In the laminated piezoelectric element of the present invention, the piezoelectric body portion (piezoelectric layer) above the uppermost internal electrode of the laminated body and the piezoelectric body portion (piezoelectric body below the lowermost internal electrode). Layer), the distance from the uppermost internal electrode drawn to the side surface of the laminate to the upper end of the side surface and the lower internal electrode drawn to the side surface of the laminate to the side surface. The distance to the bottom edge of is increased. for that reason,
When the external electrode is formed on the side surface so as to be electrically connected to the internal electrode pulled out to the side surface of the laminate, the upper end and the lower end of the external electrode are prevented from reaching the upper and lower surfaces of the laminate, It is possible to secure the flatness of the upper and lower surfaces. Further, even if the external electrodes are displaced, the external electrodes do not reach the upper and lower surfaces of the laminated body, and the flatness of the upper and lower surfaces can be secured.

Therefore, by using the laminated piezoelectric element of the present invention, the stacking (bonding) is excellent in stability,
It becomes possible to construct a highly reliable laminated piezoelectric actuator.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a laminated piezoelectric element according to an embodiment of the present invention. The laminated piezoelectric element 5 of this embodiment is disposed between a plurality of laminated piezoelectric layers (for example, a piezoelectric layer made of lead zirconate titanate-based material) 1 and a plurality of piezoelectric layers 1. The internal electrodes 2a and 2b that are drawn out to two opposite side surfaces every other layer, and the same drawn to the two opposite side surfaces 3c and 3d of the laminated body 3 including the piezoelectric layer 1 and the internal electrodes 2a and 2b. Each internal electrode 2 of the pole
It is configured to include two external electrodes 4a and 4b that are electrically connected to a and 2b. As the external electrodes 4a and 4b, thick film electrodes are used in consideration of reliability of conduction with the internal electrodes 2a and 2b.

Then, the uppermost internal electrode 2a of the laminated body 3 is formed.
Piezoelectric part (piezoelectric layer) 1 above (2a ₁ ) 1 (1
a) and the piezoelectric portion (piezoelectric layer) 1 (1b) below the lowermost internal electrode 2b (2b ₁ ) have a thickness T ₁ of
Another piezoelectric layer 1 (1c) sandwiched between the internal electrodes 2a and 2b
Is considerably larger than the thickness T _{0 of the} .

In the laminated piezoelectric element 5 of this embodiment, as described above, the inner electrodes 2a ₁ and 2b _{1 of} the uppermost layer and the lowermost layer, which are drawn out to the side surfaces 3c and 3d of the laminated body 3, extend from the side surface 3c. , 3d distance to the upper and lower edges (ie,
Since T ₁ ) is large, when the external electrodes 4a and 4b are formed on both side surfaces 3c and 3d of the laminated body 3, the external electrodes 4a and 4b are not formed.
The upper end and the lower end of b exceed the upper end and the lower end of the side surfaces 3c, 3d of the laminated body 3, and the upper and lower surfaces 3a, 3 of the laminated body 3
It never reaches b. Therefore, it is possible to secure the flatness of the upper and lower surfaces 3a and 3b of the laminated piezoelectric element 5 without providing a lapping step or the like.

Then, a plurality of the laminated piezoelectric elements 5 thus obtained are stacked, and the laminated piezoelectric elements 5 are bonded to each other by using, for example, an organic adhesive, and the external electrodes 4a, 4b.
By connecting each other via lead wires,
It is possible to obtain a laminated piezoelectric actuator (not shown) having excellent stacking (bonding) stability and high reliability.

Next, a method of manufacturing the laminated piezoelectric element 5 of the above embodiment will be described.

In producing the laminated piezoelectric element 5, first, in order to produce a piezoelectric layer (green sheet), raw materials are weighed, pulverized, mixed with a binder, defoamed, and then the sheet. It is formed into a shape and punched into a predetermined shape. Then, the internal electrodes are printed on it.

On the other hand, piezoelectric layers (green sheets) on which internal electrodes are not printed are prepared as the piezoelectric layers on the upper and lower surfaces of the laminated piezoelectric element. Then, as shown in FIG. 2, the piezoelectric layers 1 (1c) on which the internal electrodes 2a and 2b are printed are laminated, and the upper and lower surfaces thereof have the same dimensions as the piezoelectric layer 1c, and The piezoelectric layers 1 (1a, 1b) on which the electrodes are not printed are laminated and pressure-bonded. And
By firing this, a laminated body 3 as shown in FIG. 1 is obtained.

Then, after wrapping the upper and lower surfaces 3a and 3b, the external electrodes 4a and 4 are provided on both side surfaces 3c and 3d of the laminated body 3.
By forming b, the laminated piezoelectric element 5 as shown in FIG. 1 can be obtained.

In this manufacturing method, there is no particular restriction on the number of laminated piezoelectric layers on which the internal electrodes are not printed,
The thickness of the piezoelectric portion above the inner electrode of the uppermost layer of the laminate and the thickness of the piezoelectric portion below the inner electrode of the lowermost layer are such that the external electrodes formed on the side surfaces of the laminate are above and below the laminate. It is necessary to stack so as to have a thickness sufficient to prevent the reaching.

The method of manufacturing the laminated piezoelectric element of the present invention is not limited to the above-mentioned manufacturing method, and other methods can be used.

The present invention is not limited to the above-mentioned embodiment in other respects, and the kind and composition of the material forming the piezoelectric layer, the specific shape and the number of laminated layers of the piezoelectric layer, Various applications and modifications can be made to the constituent materials of the internal electrodes and external electrodes within the scope of the invention.

[0021]

As described above, in the laminated piezoelectric element of the present invention, the distance from the uppermost internal electrode drawn to the side surface of the laminate of the piezoelectric layer and the internal electrode to the upper end of the side surface,
And a piezoelectric portion above the internal electrode of the uppermost layer of the laminate and an internal electrode of the lowermost layer so that the distance from the internal electrode of the lowermost layer drawn to the side surface of the laminated body to the lower end of the side surface becomes large. Since the thickness of the lower piezoelectric part is increased, it is possible to prevent the upper and lower ends of the external electrode from reaching the upper and lower surfaces of the laminate when forming the external electrode on the side surface of the laminate. Therefore, the flatness of the upper and lower surfaces can be ensured.

Therefore, by stacking a plurality of the laminated piezoelectric elements of the present invention and joining them, a highly reliable laminated piezoelectric actuator which has excellent joining stability and does not break due to an external force is obtained. Obtainable.

In the laminated piezoelectric element of the present invention, piezoelectric layers having a large thickness (piezoelectric inactive layers having no internal electrodes) are provided on the upper and lower surfaces,
Since the distance from the upper and lower surfaces to the piezoelectric active layer on which the internal electrodes are arranged is large, it is possible to obtain the effect of improving the moisture resistance.

[Brief description of drawings]

FIG. 1 is a sectional view showing a laminated piezoelectric element according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a method of manufacturing a laminated piezoelectric element according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a conventional laminated piezoelectric actuator.

FIG. 4 is an exploded perspective view showing a pattern of internal electrodes of a laminated piezoelectric element that constitutes a conventional laminated piezoelectric actuator.

FIG. 5 is a cross-sectional view showing a laminated piezoelectric element that constitutes a conventional laminated piezoelectric actuator.

[Explanation of symbols]

1 Piezoelectric layers 1a, 1b Piezoelectric parts (piezoelectric layers) on the upper and lower surfaces 2a, 2b Internal electrodes 2a ₁ Inner electrode of the uppermost layer of the laminated body 2b ₁ Inner electrode of the lowermost layer of the laminated body 3 Laminated body 3a, 3b Upper / lower surface of laminated body 3c, 3d Side surface of laminated body 4a, 4b External electrode 5 Multilayer piezoelectric element T ₁ Thickness of piezoelectric layer on upper / lower surface side of laminated body

Claims (1)

[Claims] 1. A multi-layer piezoelectric element comprising a plurality of piezoelectric layers, internal electrodes arranged between the piezoelectric layers, and external electrodes formed on side surfaces from which the internal electrodes are drawn out. Distance from the uppermost internal electrode drawn to the side surface of the laminate of the body layer and the internal electrode to the upper end of the side surface, and from the lowermost internal electrode drawn to the side surface of the laminate to the lower end of the side surface In order to increase the distance, the thickness of the piezoelectric body portion above the internal electrode of the uppermost layer of the laminate and the piezoelectric body portion below the internal electrode of the lowermost layer is increased, and the laminated piezoelectric element is characterized. .