JPH07135347A - Multialyer piezoelectic actuator - Google Patents

Abstract

PURPOSE:To provide a multilayer piezoelectric actuator comprising a plurality of piezoelectric actuator elements, formed by laminating piezoelectric ceramic sheets and inner electrodes alternately, being arranged on a base at a constant interval in which the fluctuation is suppressed in the dimensions and characteristics while facilitating the manufacture. CONSTITUTION:Between an inactive ceramic part 4 forming a laminate base of piezoelectric ceramic sheet and an inactive ceramic part 3, an active ceramic part 1 is formed by firing and polarizing the laminate of inner electrode and the piezoelectric ceramic sheet of same material as the inactive ceramic part. It is then sintered and outer electrodes 6, 7 are formed, along with an insulating part 5, on the end face of an inner electrode 2 formed on the opposite end faces at the active ceramic part. Finally, the inactive ceramic part of base is left between the outer electrodes and a groove 8 intersecting the inner electrode perpendicularly is made at the active ceramic part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator for converting electric input energy into mechanical energy of displacement or force by utilizing a piezoelectric effect, and more specifically,
The present invention relates to a multi-layer piezoelectric actuator in which one multi-layer piezoelectric actuator is divided into a plurality of drive parts that can be individually driven and division driving is possible.

[0002]

2. Description of the Related Art Conventionally, a laminated piezoelectric actuator (hereinafter referred to as a piezoelectric actuator) capable of such a divisional drive has a ceramic sheet surface composed of a piezoelectric ceramic sheet made of a piezoelectric material such as zirconic acid / titanic acid / lead. Internal electrodes are formed on a plurality of layers to form a plurality of layers, and positive and negative internal potentials are applied to the internal electrodes adjacent to each other between the ceramic sheets, and the positive and negative internal electrodes are respectively connected to a pair of external electrodes. Since such a laminated piezoelectric actuator has a large strain induced in the piezoelectric material when an electric field is applied between the electrodes and has a high-speed displacement when a voltage is applied, it has a printer head, a positioner, a valve, a relay, etc. Is being used as a driving source for In particular, in the use of a printer head, a positioner, etc., generally, it is necessary to drive a plurality of positions individually, and therefore, using the laminated piezoelectric actuator at a required number of positions, in order to obtain a mechanical displacement. It is used as a driving source.

FIG. 2 shows a laminated piezoelectric actuator in which a plurality of conventional single-drive laminated piezoelectric actuator elements 20 are arranged side by side, and a device which requires fine positioning is mounted on the upper surface of the laminated piezoelectric actuator and used. To be done. The piezoelectric actuator elements that are the respective driving elements are
The piezoelectric ceramic sheet, the portion of the piezoelectrically active ceramics portion 1 in which the layers of the internal electrodes 2 are alternately laminated, and the piezoelectric material made of the same material as the active ceramics portion provided on both end surfaces of this portion are made of a piezoelectric material. However, the inactive ceramics portion 3 which is piezoelectrically inactive but is not polarized
1, 41. The layer of the internal electrode 2 made of a silver-palladium material is such that the end face of the internal electrode exposed on the surface by the insulating portion 5 covered with glass after firing is exposed so that the opposing internal electrodes are formed one by one with the active ceramics portion 1 interposed therebetween. Insulation is performed every other layer, and each inner electrode is connected to the outer electrodes 6 and 7 with one active ceramics portion therebetween.

Generally, when individually driving a plurality of piezoelectric actuators in a narrow and limited space, as shown in FIG. 2, individually formed piezoelectric actuator elements are used as bases (pedestals) made of metal or ceramics. ) 10 is adhered and fixed to the surface 10 by an adhesive 9 such as an epoxy resin with a gap 81 therebetween.

[0005]

However, in the structure of the laminated piezoelectric actuator in which a plurality of piezoelectric actuator elements of the related art shown in FIG. 2 are arranged, when a plurality of piezoelectric actuators are bonded to each other, the piezoelectric There is a drawback that the work of adhering the actuator is required and the work process becomes complicated.

In the case of bonding with an adhesive, the thickness of the bonding layer 9 and the pressure at the time of bonding cause variations in the dimensions of the end surface 11 of the piezoelectric actuator between the piezoelectric actuator and the base 10, There is a drawback that the amount of displacement on the end face 11 varies, and there is also a problem that it is necessary to further process the end face of the upper surface after bonding the piezoelectric actuator element to the base 10 in order to prevent the variation.

The present invention eliminates the above-mentioned drawbacks, reduces the dimensional variation of the end faces of a plurality of piezoelectric actuator elements in the height direction from the base, and eliminates the step of bonding the piezoelectric actuators. Laminated piezoelectric that can obtain uniform displacement when each element is driven independently, has little variation in displacement between each piezoelectric actuator element when the same voltage is applied between electrodes, and can significantly reduce the number of manufacturing steps. It is to provide an actuator.

[0008]

SUMMARY OF THE INVENTION A laminated piezoelectric actuator according to the present invention is a piezoelectric ceramic in which electrodes are not formed so as to form a piezoelectrically inactive ceramic portion on at least one end of a green sheet of piezoelectric ceramic material. After stacking a plurality of green sheets of material, subsequently forming internal electrodes on the green sheets and stacking them alternately, stacking green sheets without forming electrodes again, and sintering them on the side surface of the stacked body. , The exposed end surface of the internal electrode is formed by covering each exposed portion of the internal electrode on the piezoelectric ceramic sheet with an electrically insulating layer such as glass so as to form a counter electrode. By electrically connecting to the external electrodes, the piezoelectric ceramic sheet is made into a laminated piezoelectric actuator having a pair of external electrodes formed therebetween.

Then, the internal electrodes of the piezoelectric actuator, which are laminated in plural layers, are electrically or physically divided so that the piezoelectric actuators can be driven individually.
On the other hand, in order to remain integrally connected in the piezoelectrically inactive ceramics portion formed on at least one end of the piezoelectric actuator, the base from the upper surface in the direction perpendicular to the extending direction of the internal electrode layers of the piezoelectric actuator. A kerf that reaches the inactive ceramics portion on the side is formed and the active ceramics portion is divided to obtain the laminated piezoelectric actuator of the present invention.

That is, the present invention provides a laminated piezoelectric actuator in which a plurality of laminated piezoelectric actuator elements formed by alternately laminating a plurality of sheets of piezoelectric material and internal electrodes on a base are integrally mounted. A plurality of piezoelectric ceramic sheets having the width and the length of each piezoelectric actuator element laminated to form an inactive ceramics portion forming a base on the lower surface; a piezoelectric ceramics sheet formed on the upper surface of the inactive ceramics portion; and an internal electrode. The internal electrode end surface of the laminated body obtained by laminating and firing the active ceramics portion in which a plurality of layers are alternately laminated and the inactive ceramics portion laminated on the upper surface of the active ceramics portion in the same manner as the base on the lower surface Electrically insulating layers are alternately formed on the exposed front and back internal electrode end surfaces, and the alternately exposed internal electrodes are formed on the electrical insulating layer forming surface. External electrodes that apply positive voltage and negative voltage respectively are connected to each other, and reach the inert ceramic portion on the lower surface from the inert ceramic portion on the upper surface, leaving a part of the inert ceramic portion on the lower surface, and orthogonal to the internal electrode surface. A multilayer piezoelectric actuator comprising a plurality of piezoelectric actuator elements formed by forming a plurality of cut grooves for cutting the active ceramic portion so as to electrically divide the internal electrodes.

[0011]

According to the present invention, a plurality of laminated piezoelectric actuator elements forming the laminated piezoelectric actuator according to the present invention are preliminarily integrated with each other by laminating piezoelectric ceramic sheets with internal electrodes in between and sintering them, and then orthogonal to the internal electrode surfaces. Therefore, a piezoelectric actuator element is formed by providing a kerf for separating the internal electrode layer while leaving a part of the inactive layer as a base.
Piezoelectric ceramic materials that form a plurality of piezoelectric actuator elements are manufactured in the same process up to the sintering process, and the composition and the amount of binder added when making a piezoelectric ceramic sheet are uniform, and the piezoelectric ceramics in which each layer is laminated are laminated. The thickness distribution of the sheet is the same for each layer, the dimensional error in the height direction between the laminated piezoelectric actuator elements is small, and the dimensional accuracy between each piezoelectric actuator element is also high, so the load applied to each piezoelectric actuator element is uniform. And again
The variation in the amount of displacement when a voltage is applied to the electrodes is extremely small among the piezoelectric actuator elements, and therefore the operation of the piezoelectric actuator elements is also uniform. Further, since a plurality of laminated piezoelectric actuator elements are integrally manufactured in a sintering process, they are inexpensive, and since there is no adhesive layer, the strength of the piezoelectric actuator element is large.

[0012]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of a laminated piezoelectric actuator according to the present invention. In FIG. 1, there are piezoelectrically inactive ceramic parts 3 and 4 on the upper and lower surfaces of a plurality of piezoelectric actuator elements 20, and the inactive ceramic part 4 on the lower surface forms a base (pedestal). Between the inactive ceramic parts 3 and 4, the piezoelectrically active ceramic parts 1 form a layer of the internal electrode 2 in parallel with each other to form 100
Since more than one layer is formed and the counter electrode is formed for each layer, the insulating layer 5 is formed on each end face of the internal electrode with molten glass or the like, and the external electrode 6 is formed on the end face of the internal electrode on which the insulating layer is formed. 7 is formed to connect the internal electrode and the external electrode,
Polarization is applied between the internal electrodes at a temperature below the Curie point of the material to form the active ceramics portion 1.

In the laminated piezoelectric actuator according to the present invention, the plurality of piezoelectric actuator elements 20 are formed by laminating piezoelectric ceramic sheets of the same material as the active ceramic portion 1 in advance without forming internal electrode layers, and the inactive ceramic portion 4 is formed. Then, the layers of the piezoelectric ceramic sheets and the internal electrodes 2 are alternately laminated, and after firing at high temperature, they are polarized to form the active ceramic portion 1, and the same piezoelectric ceramic sheet as the active ceramic portion is formed again without the internal electrodes. Then, the inactive ceramics part 3 is formed. 1 block that laminated the piezoelectric ceramic sheet and the internal electrode 2
After firing at 100 ° C. for 2 hours in the air, the end surfaces of the internal electrodes 2 are covered with electric insulating materials such as glass every other surface opposite to each other and electrically insulated to form the insulating layer 5. The external electrodes 6 and 7 of the piezoelectric actuator element are formed on the end face of the internal electrode layer and the insulating layer 5, and the internal electrode 2 is cut by a cutting machine.
A kerf 8 is cut up to the inert ceramic portion 4 so that the cross-sectional area of the cross-section 11 of the piezoelectric actuator element is the same between the external electrodes in the direction perpendicular to the surface of the layer.

As an example of the laminated piezoelectric actuator of the present invention having such a structure, the total width is 21.5 mm and the width is 3 mm.
mm of piezoelectric ceramic block with a height of 25 mm
As shown in FIG. 1 (b), a width of 1 mm is formed on both surfaces of the surface where the insulating layer 5 is formed on the exposed portions of the internal electrodes.
Of the external electrode layers 6 and 7 are formed on the respective opposing surfaces, and the piezoelectrically inactive ceramics portion 4 serving as the base is left, and a 0.3 mm kerf 8 is formed by a cutting machine in the internal electrode layer forming portion. The active ceramics portion was cut off and both sides were cut to form six piezoelectric actuator elements each having a width of 2 mm to obtain a laminated piezoelectric actuator according to the present invention. Table 1 shows 100 manufacturing steps and dimensional errors in the extending direction between the 100 piezoelectric actuator elements at that time.

[0015]

[Table 1]

In the present invention, the time required to manufacture 100 pieces is the time from grooving, and in the comparative example, six piezoelectric actuators having a dimension of 2 mm on the insulating layer side (external electrode forming surface) in FIG. Was set at an interval 81 of 0.3 mm on the base 10 with the adhesive 9 and processed.

As can be seen from Table 1, the laminated piezoelectric actuator according to the present invention does not require a time for adhering the piezoelectric actuator element to the base 10, and therefore is manufactured as compared with the conventional case where individual piezoelectric actuator elements are adhered. The time is shortened to about 1/12, and the variation in dimension between piezoelectric actuators is 0.01 mm or less in the present invention until sintering, whereas in the conventional structure, even if the surface is ground, it is 0. It is about 0.05 mm and the mounting position accuracy has been greatly improved.

[0018]

As described above, according to the present invention,
The manufacturing process of a laminated piezoelectric actuator in which a plurality of piezoelectric actuator elements are integrally formed is shortened, and it becomes possible to provide a laminated piezoelectric actuator in which the dimensional variation and the piezoelectric characteristic variation among the piezoelectric actuator elements are uniform. It was

[Brief description of drawings]

1A and 1B are views showing an embodiment of a laminated piezoelectric actuator according to the present invention, FIG. 1A is a front view, and FIG. 1B is a side view.

2A and 2B are diagrams showing an example of a conventional laminated piezoelectric actuator, in which FIG. 2A is a front view and FIG. 2B is a side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Active ceramics part 2 Internal electrode 3,4,31,41 Inert ceramics part 5 Insulating layer 6,7 External electrode 8 Cut groove 9 Adhesive layer 10 Base (base) 11 End face 20 Piezoelectric actuator element 81 Gap A Lamination of the present invention Piezoelectric actuator B Conventional laminated piezoelectric actuator

Claims (1)

[Claims] 1. A laminated piezoelectric actuator in which a plurality of laminated piezoelectric actuator elements, which are formed by alternately laminating a plurality of sheets of piezoelectric material and internal electrodes, are integrally mounted on a base. A plurality of piezoelectric ceramic sheets having the width and length of the actuator element are laminated alternately to form a base on the lower surface, and a plurality of piezoelectric ceramic sheets and internal electrodes formed on the upper surface of the inert ceramic portion are alternately arranged. A layered active ceramics part and an inactive ceramics part laminated on the upper surface of the active ceramics part in the same manner as the base on the lower surface are stacked and fired, and the internal electrode end surface of the laminated body is exposed. Electrically insulating layers are alternately formed on the inner electrode end faces on the back surface, and the electrically insulating layer-forming faces are alternately connected to the exposed inner electrodes. An external electrode for applying a positive voltage or a negative voltage is provided, and the inner electrode reaches the inactive ceramics portion on the lower surface from the inactive ceramics portion on the upper surface to leave a part of the inactive ceramics portion on the lower surface. A laminated piezoelectric actuator comprising a plurality of piezoelectric actuator elements formed by forming a plurality of cut grooves for cutting an active ceramic portion so as to be electrically divided.