JPH08148731A - Lamination type piezoelectric actuator - Google Patents

Abstract

PURPOSE: To provide a lamination type piezoelectric actuator facilitating precisely positioned mounting with an even thickness. CONSTITUTION: In a lamination type piezoelectric actuator having a part of a different lamination number of an inner electrode, the thickness of the inner electrode of a part (part of 1a) having a small number of lamination of the inner electrode 1 is larger than the thickness of a part (part of 1b) having a large number of lamination of the inner electrode.

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, and more particularly to a laminated piezoelectric actuator used for precise positioning, or a laminated piezoelectric actuator used for an ink jet printer head or the like.

[0002]

2. Description of the Related Art Conventionally, when a stress is applied, an electric field corresponding to the stress is generated, and when an electric field is applied, a strain corresponding to the strength of the electric field is generated, or a mechanical stress is generated. The piezoelectric material having a is used for various applications such as a vibrator, a filter, and an actuator by utilizing its characteristics. Among them, laminated piezoelectric actuators that utilize mechanical strain depending on the strength of the applied electric field can control minute displacements, consume less power, generate less heat and generate less noise, etc. Since it has many excellent characteristics, it has been widely used in the fields of inkjet printer heads and the like, which require precise positioning.

FIG. 3 is a diagram schematically showing a cross section of an example of a conventional laminated piezoelectric actuator.
Piezoelectric ceramics 2 having a thickness of 0 to 200 μm and internal electrodes 1 having a thickness of 2 to 5 μm are laminated in about 20 to 300 layers, respectively. In the laminated piezoelectric actuator thus configured, the central piezoelectric active portion, the peripheral external electrode 3 and the internal electrode 1
Since the number of layers of internal electrodes is different from that near the connection part of the actuator and the thickness of the entire actuator is different between the central part and the peripheral part, the fixing surface when mounting is not a flat surface, and the position is precisely determined and fixed. There was a problem that it was difficult to do.

Further, FIG. 5 is a diagram schematically showing a cross section of the same conventional laminated piezoelectric actuator having an electrode structure different from that shown in FIG. In this laminated piezoelectric actuator, the internal electrodes 1 are arranged on the entire surface of the laminated surface, and external insulating layers 4 are provided at both ends of the internal electrodes 1 every other layer to connect to the external electrodes 3. In this case, since the internal electrode 1 is present not only in the central portion but on the entire surface, the thickness of the entire actuator is uniform, and the above-mentioned problem does not occur.
If the layer thickness is as thin as 10 μm or less, the outer insulating layer 4
Difficult to form. Therefore, one of the ceramics
When the layer thickness is thin, the electrode structure as shown in FIG. 3 is inevitably adopted, the thickness of the actuator is not uniform, and the position is precisely fixed and fixed during mounting. However, the problem of difficulty remained unsolved.

Further, Japanese Patent Laid-Open No. 334076/1992 discloses a laminated piezoelectric actuator having a structure in which a void layer or an insulating layer 5 is provided in a part of the internal electrode 1 as shown in FIG. This actuator is also shown in FIG.
As in the case of the actuator shown in FIG. 5, the overall thickness is uniform, but when the thickness of one layer of the piezoelectric ceramics 2 is thin, the strength in the vicinity of the void layer becomes extremely weak, or an insulating layer is formed. There are problems such as difficulty.

[0006]

As described above, in the conventional laminated piezoelectric actuator, the thickness of the actuator cannot be made uniform, especially when the layer thickness of the piezoelectric ceramics is thin, so that the actuator cannot be precisely formed. There was a problem that it was difficult to decide the position and implement.

An object of the present invention is to solve the above problems and to provide a laminated piezoelectric actuator having a uniform thickness so as to facilitate precise positioning and mounting.

[0008]

The gist of the present invention resides in the following laminated piezoelectric actuator.

In a laminated piezoelectric actuator having a portion in which the number of laminated internal electrodes is different, the thickness of the internal electrode in the portion in which the number of laminated internal electrodes is small is larger than the thickness of the internal electrode in the portion in which the number of laminated internal electrodes is large. A laminated piezoelectric actuator characterized by the following.

This actuator has a sectional structure as shown in FIG. 1, for example. In the figure, a portion 1a is a portion where the number of laminated internal electrodes 1 is small, and a portion 1b is a portion where the number of laminated internal electrodes 1 is large. It is thicker than the thickness of the internal electrode.

[0011]

Since the laminated piezoelectric actuator of the present invention has the structure as described above, it is possible to reduce the unevenness of the actuator thickness due to the difference in the number of layers of the internal electrodes. It is possible to fix and fix the position accurately while suppressing rattling.

For example, in the case where the number of layers of the internal electrodes is small and the number of layers of the layers is 1/2, the electrode thickness of the portion having a small number of internal electrodes is set to the number of layers of the internal electrodes. The thickness of the entire actuator can be made uniform by making the electrode thickness twice as large.

In the laminated piezoelectric actuator of the present invention, for example, as will be described later in Examples, the number of times the conductive paste is printed when forming the internal electrode layer is increased so that the thickness of the internal electrode in one layer is partially increased. It can be easily manufactured by adding a step of thickening (portion 1a in FIG. 1).

Examples and comparative examples of the laminated piezoelectric actuator according to the present invention will be described below.

[0015]

[Example] First, the composition of the piezoelectric ceramic is finally Pb.
{(Mg _1/3 Nb _2/3 ) _0.325 (Ni _1/3 Nb _2/3 ) _0.05 Zr _0.25 Ti
Lead oxide, magnesium oxide, niobium oxide, nickel oxide, zirconium oxide, and titanium oxide were weighed out and mixed so that the content would be _0.375 } O _3.
It was calcined at ℃ for about 2 hours and then pulverized to obtain a piezoelectric material powder. Polyvinyl butyral was added as a binder to the piezoelectric material thus obtained, and a green sheet having a thickness of about 25 μm was formed by the doctor blade method.

Next, a vehicle was added to a mixture of Ag 70 wt% and Pb 30 wt% and mixed sufficiently to prepare a conductive paste for forming internal electrodes, and this conductive paste was printed as an internal electrode layer on the green sheet. here,
Near the connection with the external electrode, which is piezoelectrically inactive (Fig. 1
Part 1a) was printed once, dried and then printed again so that the thickness of the electrode was about doubled.

Fifty layers of green sheets having such internal electrodes are laminated and the temperature is 120 ° C. and the pressure is 50 kg / cm ^2.
Thermocompression-bonded under the conditions of to form a molded body,
The binder was removed at 00 ° C. and further baked at 1120 ° C. for about 3 hours to produce a laminated piezoelectric actuator.

When the thickness of the internal electrode of the actuator thus obtained was measured by a microscope, it was 3 μm in the central piezoelectric active portion (portion 1b in FIG. 1), whereas it was It was 6 μm in the vicinity of the connection portion (portion 1a in FIG. 1). That is, it has a cross-sectional structure schematically shown in FIG.

Further, when the thickness distribution of the entire actuator in the width direction was measured, it was found to be almost uniform as shown in FIG.

[0020]

Comparative Example As a comparative example, the conventional laminated piezoelectric actuator shown in FIG. 3 was manufactured. The manufacturing method is the same as that of the example, but the conductive paste is printed only once, and the thickness of the internal electrodes is made uniform including the vicinity of the connection portion with the external electrodes (portion 1a in FIG. 1). I chose

When the thickness distribution in the width direction of the thus obtained laminated piezoelectric actuator was measured,
As shown in FIG. 4, the central part was thick and the peripheral part was thin, and it was confirmed that the thickness of the actuator was not uniform.

[0022]

As described in detail above, in the laminated piezoelectric actuator of the present invention, the unevenness of the overall thickness of the actuator caused by the difference in the number of layers of the internal electrodes is suppressed by the thickness of the internal electrodes in one layer. Since it is made uniform by changing it, it is easy to perform precise positioning without rattling the actuator when mounting and fixing.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cross section of a laminated piezoelectric actuator of the present invention.

FIG. 2 is a diagram showing a thickness distribution of the laminated piezoelectric actuator of the present invention.

FIG. 3 is a diagram schematically showing a cross section of an example of a conventional laminated piezoelectric actuator.

FIG. 4 is a diagram showing a thickness distribution of the conventional laminated piezoelectric actuator shown in FIG.

FIG. 5 is a diagram schematically showing a cross section of another example of a conventional laminated piezoelectric actuator.

FIG. 6 is a perspective view showing the configuration of still another example of the conventional laminated piezoelectric actuator.

[Explanation of symbols]

 1 ... internal electrode 1a ... part with a small number of laminated internal electrodes 1b ... part with a large number of laminated internal electrodes 2 ... piezoelectric ceramics 3 ... external electrode 4 ... external insulating layer 5 ... void layer or insulating layer

Claims (1)

[Claims] 1. In a laminated piezoelectric actuator having a portion in which the number of laminated internal electrodes is different, the thickness of the internal electrode in the portion in which the number of laminated internal electrodes is small is the thickness of the internal electrode in the portion in which the number of laminated internal electrodes is large. A laminated piezoelectric actuator characterized by being larger than the size.