Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-02-04
2001-04-03
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S367000
Reexamination Certificate
active
06211606
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a piezoelectric actuator and a method for manufacturing the same, and more in particular to a piezoelectric actuator employed in an ink jet type recording apparatus mounted in a printer, a facsimile, a copier and the like and having high strength and reliability, and a method for manufacturing the same.
(b) Description of the Related Art
In an ink jet printer (hereinafter referred to as an ink jet recording apparatus), a piezoelectric actuator is usually employed in an ink head for ejecting ink. A conventional piezoelectric actuator is disclosed in JP-A-8(1996)-156272 and JP-A-8(1996)-118623. The conventional piezoelectric actuator will be described referring to the annexed drawings and reciting JP-A-8(1996)-156272.
FIG.
1
A and
FIG. 1B
are perspective views showing the respective steps of a process of manufacturing a conventional piezoelectric actuator. In order to manufacture the conventional piezoelectric actuator, at first, a pair of piezoelectric element plates
28
are bonded to a substrate
14
along electrode patterns
26
,
27
(refer to FIG.
1
A).
Then, slits having a required pitch in the direction perpendicular to the longitudinal direction of the piezoelectric element plates
28
are formed on the piezoelectric element plate
28
and on the surface of the substrate
14
to make piezoelectric element rows
31
consisting of a plurality of piezoelectric elements (driving column)
29
,
30
for separating the electrode patterns
26
,
27
into individual electrodes
33
corresponding to each of the piezoelectric elements
29
(refer to FIG.
1
A).
Edge electrodes (external electrodes) made by connecting every other internal electrode are formed on the both edge surfaces of the piezoelectric elements
29
,
30
of the respective piezoelectric element rows
31
. One external electrode on the edge surface is connected to the common electrode which the internal electrode on the substrate through the electroconductive material, and the other edge electrode is connected to the individual electrode
33
on the substrate through the electroconductive material. A support member
34
is bonded of which a height is nearly the same as those of the piezoelectric elements
29
,
30
on the periphery of the piezoelectric elements
29
,
30
. The layered piezoelectric elements
29
,
30
outputs the displacement in the direction the same as that of the layers by means of the piezoelectric effect.
FIGS. 2A
,
2
B and
2
C are a perspective view, a plan view and a side elevation view showing the state of the above piezoelectric element plate
28
taken out with the substrate
14
, respectively. Conventionally, slit-like grooves
37
are formed in the direction perpendicular to the longitudinal direction of the piezoelectric element plate
28
to form a plurality of piezoelectric elements. Each piezoelectric element
29
,
30
is a long and narrow rectangle so that a pressure chamber formed thereby has a long and narrow shape. The displacement output surface
36
a
of each piezoelectric element
29
,
30
has the active region
36
b
formed by the crossing between the layers of the common electrode
32
and the individual electrode
33
which are the internal electrode and the inactive electrode extending to the side surface of the piezoelectric actuator connected to the external power and having either of the common electrode
32
or the individual electrode
33
.
The output displacement produced on the active region
36
b
has a problem such that the output displacement decreases or becomes unstable because the displacement is restricted by the inactive region
36
c.
Since the slit-like grooves are formed by a dicing process using a thin cutting blade, the sectional shape of the groove is nearly rectangular, and a crack or a cutting due to bending is likely to occur at the corners of the groove bottom surface or the bottom parts of each piezoelectric elements
29
,
30
. A further problem arises that the cost of manufacturing the piezoelectric actuator is high because the groove processing and the formation of the external electrode require a high cost.
It is necessary, in view of the above situation, to realize a piezoelectric actuator for an ink jet recording apparatus capable of generating an output displacement at high efficiency and stability by employing a shape having a narrowed part and a tapered part to elevate the strength and the reliability of a driving column in place of the rectangular displacement output surface and its rectangular section. It is also necessary to realize a piezoelectric actuator having excellent productivity by decreasing a processing cost of the slit-like groove separating and forming the piezoelectric actuator and of the external electrode.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a piezoelectric actuator having high strength and reliability and being capable of generating an output displacement at high efficiency and stability in order to elevate the productivity, and a method for manufacturing the same.
The present invention provides a piezoelectric actuator comprising a substrate and a plurality of driving columns extending parallel to one another and separated by grooves on the substrate, the driving column having an active region on the central part in the direction of the groove, which is formed by a layered electrode structure including common electrode layers and individual electrode layers alternately layered employing green sheets made of piezoelectric material, and a displacement output surface externally outputting the displacement produced by the piezoelectric effect of the active region on the upper surface of the driving column opposite to the substrate, the width of each driving column in the direction of the groove width widening from the displacement output surface to the substrate.
The present invention also provides a method for manufacturing a piezoelectric actuator having a substrate and a plurality of driving columns extending parallel to one another and separated by grooves on the substrate comprising: a step of applying electrode paste on one surface of a green sheet made of piezoelectric material to form an internal electrode, layering and pressing a plurality of green sheets having an internal electrode on the substrate and forming a layered electrode member on the substrate by sintering, a step of forming a mask having a plurality of slit-like empty patterns on the upper surface of the layered electrode member, forming slit-like grooves on the layered electrode member by blasting ground particles from the mask to the upper surface of the layered electrode member to form a plurality of driving columns having the layered electrode layer on the substrate separated with one another by means of the groove, and a step of forming on the side surface of the driving column an external electrode electrically connected with the internal electrode.
In accordance with the present invention, the strength of the bottom part of the driving column can be elevated compared with that of a conventional piezoelectric actuator having a rectangular driving column sectional shape, and the anti-cutting strength due to bending of the driving column can be also elevated. The scattering of the direction of generation of the displacement can be reduced to stabilize the output displacement.
REFERENCES:
patent: Re. 35011 (1995-08-01), Wersing et al.
patent: 5421071 (1995-06-01), Kanegae et al.
patent: 5942837 (1999-08-01), Reuter
patent: 0 402 171 (1990-12-01), None
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patent: 6-226974 (1994-08-01), None
patent: 8-80614 (1996-03-01), None
patent: 8-118623 (1996-05-01), None
patent: 8-156272 (1996-06-01), None
patent: 8-279631 (1996-10-01), None
patent: 9-11482 (1997-01-01), None
patent: 9-254385 (1997-09-01), None
Kagami Tsutomu
Kanda Torahiko
Nakamura Hirofumi
Dougherty Thomas M.
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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