Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-02-19
2003-07-22
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06595628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a laminated piezoelectric element for use as a drive device in various apparatus, such as an ink-jet print head.
2. Description of Related Art
A piezoelectric element is used as a drive device (piezoelectric actuator) for various apparatus due to a characteristic of converting electric energy into mechanical displacement (deformation) by piezoelectric effects. In order to increase an amount of displacement by the deformation of a piezoelectric element, the piezoelectric element includes laminated piezoelectric sheets formed of ceramic material, such as lead zirconate titanate (PZT). The piezoelectric sheet has individual electrodes or common electrodes formed on a surface (larger face) thereof with electrical conductive material of, for example, paste. A plurality of the piezoelectric sheets having the individual electrodes formed thereon and a plurality of piezoelectric sheets having the common electrodes formed thereon are alternately stacked on top of each other in layers.
In the thus laminated piezoelectric element, to electrically connect between the individual electrodes or between the common electrodes adjacent in a sheet laminated direction, through holes are provided to which electrically conductive material is applied.
FIGS. 17 through 19
show an example of a known laminated piezoelectric element (piezoelectric actuator).
FIG. 17
is an exploded view of a piezoelectric actuator
100
.
FIG. 18
is a sectional view of the actuator
100
, taken along line
1005
—
1005
of FIG.
17
.
FIG. 19
is an explanatory view of the actuator
100
deformed by firing.
The conventional piezoelectric actuator
100
includes a piezoelectric sheet
103
a,
103
c,
103
e,
103
g
having individual electrodes
101
formed thereon, and a piezoelectric sheet
103
b,
103
d,
103
f,
103
h
having common electrodes
102
formed thereon, that are alternately laminated, and an insulating sheet
106
disposed on the top. The individual electrodes
101
are formed on the piezoelectric sheet
103
a
(
103
c,
103
e,
103
g
), which is odd-numbered when counted from the lower side of the actuator
100
. The individual electrodes
101
are provided so as to laterally extend along the shorter side of the piezoelectric sheet
103
a
(
103
c,
103
e,
103
g
) toward a central portion thereof. A row of the individual electrodes
101
is provided parallel to the longitudinal direction of the sheet
103
a
(
103
c,
103
e,
103
g
) along each longer side of the sheet
103
a
(
103
c,
103
e,
103
g
). The common electrodes
102
are formed on the piezoelectric sheet
103
b
(
103
d,
103
f,
103
h
), which is even-numbered when counted from the lower side of the actuator
100
. The common electrode
102
is provided in a substantially central portion of the piezoelectric sheet
103
b
(
103
d,
103
f,
103
h
). The common electrode
102
extends along the longitudinal direction of the piezoelectric sheet
103
b
(
103
d,
103
f,
103
h
), forming a substantially rectangular shape.
In the piezoelectric sheets
103
a
through
103
h,
piezoelectric active portions
107
that are deformed by the piezoelectric effects are provided at positions sandwiched between the individual electrodes
101
and the common electrodes
102
. Extending portions
102
a
are integrally formed with the common electrode
102
and extend laterally so as to cover a substantially entire length of each shorter side end of the even-numbered piezoelectric sheet
103
b
(
103
d,
103
f,
103
h
). Individual dummy electrodes
104
are formed so as to correspond to the individual electrodes
101
(in the vertically same positions), on the surfaces of the even-numbered piezoelectric sheet
103
b
(
103
d,
103
f,
103
h
) other than the piezoelectric active portions
107
.
Dummy common electrodes
105
are formed on each of the odd-numbered piezoelectric sheet
103
a
(
103
c,
103
e,
103
g
) at positions corresponding to the extending portions
102
a
(in the vertically same positions). The insulating sheet
106
has surface electrodes
108
associated with the individual electrodes
101
and surface electrodes
109
associated with the common electrodes
102
, along the longer sides of the sheet
106
. Except for the lowermost piezoelectric sheet
103
a,
through holes
110
are formed on the piezoelectric sheet
103
b
through
103
h
and the insulating sheet
106
, so as to communicate the surface electrodes
108
with the corresponding the individual electrodes
101
and individual dummy electrodes
104
. Similarly, through holes
111
are formed on the piezoelectric sheet
103
b
through
103
h
and the insulating sheet
106
, so as to communicate at least one surface electrode
109
with the corresponding extending portion
102
a.
The individual electrodes
101
formed on the photoelectric sheets
103
a,
103
c,
103
e,
103
g
and the associated surface electrodes
108
are electrically interconnected through electrically conductive material applied to the through holes
110
. Similarly, the common electrodes
102
formed on the piezoelectric sheet
103
b,
103
d,
103
f,
103
h
and the associated surface electrodes
109
are electrically interconnected through electrically conductive material applied to the through holes
111
. The through holes
110
,
111
are provided in a line parallel to an aligning direction of the individual electrodes
101
along the longitudinal direction of the piezoelectric sheet
103
b
through
103
g
and the insulating sheet
106
, as shown in FIG.
17
. The through holes
110
,
111
are not formed on the lowermost piezoelectric sheet
103
a
, to prevent electricity from being conducted to a driven member (e.g., a cavity plate in an ink-jet head) to which the piezoelectric actuator
100
is fixedly attached.
Another known piezoelectric actuator includes an insulating sheet disposed on a larger surface of the piezoelectric sheet laminate. The insulating sheet includes surface electrodes connected to a flexible printed cable to externally and selectively drive the piezoelectric actuator by applying a voltage. The surface electrodes are formed on the insulating sheet so as to be associated with individual electrodes or the common electrodes. Conventionally, the surface electrodes are formed mainly with the following three methods.
As a first method to form the surface electrodes on the insulating sheet, the common electrodes and the individual electrodes are formed on the surfaces of the piezoelectric sheets. A common electrode or individual electrode is extended so as to be exposed on a side face of the piezoelectric sheets. A plurality of the piezoelectric sheets are laminated with the insulating sheet (that has not yet had a surface electrode) placed on the top. Such laminate of the piezoelectric sheets and the insulating sheet is sintered or fired at a high temperature (e.g., approximately 1100° C.). Thereafter, electrically conductive Ag—Pd (silver-palladium)-based paste is applied to a side end face of the laminate such that side electrodes are formed to connect between the common electrodes or between the individual electrodes in the sheet laminated direction. Then, the surface electrodes are formed on a surface (larger face) of the insulating sheet, so as to be electrically connected to the side surfaces, by applying the same electrically conductive material (paste) as that used for the side electrodes. The surface electrodes are baked at a relatively low temperature (e.g., approximately 600° C.).
As a second method, the common electrodes and the individual electrodes are formed on the piezoelectric sheets and the insulating sheet. The through holes are formed on the piezoelectric sheets and the insulating sheet such that the adjacent individual electrodes or the common electrodes in the sheet laminated direction are connected to each other. The same electrically conductive material (paste) as that used for the common electrodes and the individual electrodes is applied to the through holes. Thereafter, the piez
Kitazima Akiyoshi
Takagi Atsuhiro
LandOfFree
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