Metal working – Piezoelectric device making
Reexamination Certificate
2002-04-19
2004-05-18
Arbes, Carl J. (Department: 3729)
Metal working
Piezoelectric device making
C029S830000, C029S831000, C029S832000, C029S846000, C029S854000
Reexamination Certificate
active
06735839
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multilayer piezoelectric components each including a plurality of internal electrodes stacked between ceramic layers. Particularly, the present invention relates to a multilayer piezoelectric actuator and a method of manufacturing the same, an ink jet head using the piezoelectric actuator, a multilayer piezoelectric resonator used as a resonator, a band pass filter, or other electronic component, and a method of manufacturing the same, a piezoelectric transformer and a method of manufacturing the same.
The present invention also relates to a piezoelectric actuator having an electrode structure which is improved so as to significantly decrease variations in displacement and a manufacturing method therefor, an ink jet head, a multilayer piezoelectric resonator including a sintered compact body having an electrode structure which is improved to significantly widen a difference &Dgr;F between the resonance frequency and antiresonance frequency, and to significantly decrease variations in resonance characteristics, and a manufacturing method therefor, a piezoelectric transformer having an electrode structure improved to significantly increase maximum efficiency and decrease variations in the maximum efficiency, and a manufacturing method therefor.
2. Description of the Related Art
An ink jet head of an ink jet printer uses a piezoelectric actuator for discharging a predetermined amount of ink. An example of conventional piezoelectric actuators will be described below with reference to FIG.
33
.
A piezoelectric actuator
71
includes a sintered ceramic compact body
72
. The sintered ceramic compact body
72
includes piezoelectric ceramic material such as lead titanate zirconate ceramic or the like.
In the sintered ceramic compact body
72
, a plurality of internal electrodes
73
a
to
73
l
are arranged to overlap each other in the thickness direction. The internal electrodes
73
a
,
73
c
,
73
e
,
73
g
,
73
i
, and
73
k
are extended to the first side
72
a
of the sintered ceramic compact body
72
. The other internal electrodes
73
b
,
73
d
,
73
f
,
73
h
,
73
j
, and
73
l
are extended to the second side
72
b
opposite to the first side
72
a.
First and second external electrodes
74
and
75
are disposed on the first side
72
a
and the second side
72
b
, respectively.
The ceramic layers disposed between the internal electrodes
73
a
to
73
l
are polarized in the thickness direction, as shown by arrows in FIG.
33
. Namely, the ceramic layers on both sides of each of the internal electrodes are polarized in opposite directions of the thickness direction.
Therefore, application of a voltage between the external electrodes
74
and
75
causes displacement in a polarized portion of the piezoelectric actuator
71
due to a piezoelectric effect.
In an ink jet head of a conventional ink jet printer, displacement is caused in the piezoelectric actuator
71
to press an ink chamber so that a predetermined amount of ink is discharged from the ink chamber. Therefore, in order to discharge ink with high precision, it is required to decrease variations in displacement of the piezoelectric actuator
71
.
However, the manufacture of many piezoelectric actuators
71
causes relatively large variations in displacement characteristics in the piezoelectric actuators. There is also the problem of causing variations in displacement in displacement portions when a plurality of notches are formed in the displacement portions of the piezoelectric actuator
71
in order to form a plurality of displacement portions.
Therefore, for example, an ink jet head of an ink jet printer including the above-described piezoelectric actuator is difficult to discharge a predetermined amount of ink with high precision.
FIG. 34
is a sectional view showing a conventional multilayer piezoelectric resonator.
A multilayer piezoelectric resonator
171
includes a sintered ceramic compact body
172
made of piezoelectric ceramic.
In the sintered ceramic compact body
172
, a plurality of internal electrodes
173
a
to
173
l
are provided. The stacking direction of the internal electrodes
173
a
to
173
l
is located in the thickness direction. The sintered ceramic compact body
172
includes ceramic layers which are held between the internal electrodes in the thickness direction, and polarized as shown by arrows in FIG.
34
. Namely, the adjacent ceramic layers are polarized in opposite directions in the thickness direction. The internal electrodes
173
a
to
173
l
are extended up to the opposite sides
712
a
and
172
b
of the sintered ceramic compact body
172
.
Insulating films
174
a
to
174
f
and insulating films
175
a
to
175
f
are disposed on the sides
192
a
and
172
b
, respectively, of the sintered ceramic compact body
172
. Each of the insulating films
174
a
to
174
f
and
175
a
to
175
f
is arranged to cover an exposed end of any one of the internal electrodes
173
a
to
173
l
on either of both sides
172
a
and
172
b
of the sintered ceramic compact body
172
. Therefore, an end of each of the internal electrodes
173
a
to
173
l
is coated with any one of the insulating films
174
a
to
175
f
, the other end being exposed from the side
172
a
or
172
b.
External electrodes
176
and
177
are arranged to cover both sides
172
a
and
172
b
, respectively.
In the multilayer piezoelectric resonator
171
, an alternating current electric field is applied between the external electrodes
176
and
177
to expand and contract the piezoelectric ceramic layers held between the respective internal electrodes
173
a
to
173
l
due to the piezoelectric effect, thereby obtaining resonance characteristics based on thickness longitudinal vibration.
However, in the piezoelectric resonator
171
, resonance characteristics cannot be necessarily obtained according to design values, and a difference &Dgr;F between the resonance frequency and antiresonance frequency tends to be lower than the desired value. A decrease in the frequency difference &Dgr;F narrows the pass band of the filter.
Furthermore, the manufacture of many multilayer piezoelectric resonators
171
produces the problem of relatively large variations in resonance characteristics.
Also a Rosen-type piezoelectric transformer using a rectangular plate-shaped piezoelectric ceramic layer is conventionally known.
An example of conventional Rosen-type piezoelectric transformers will be described below with reference to
FIGS. 35 and 36
. A piezoelectric transformer
251
includes a rectangular plate-shaped sintered ceramic compact body
252
made of piezoelectric ceramic. The sintered ceramic compact body
252
is obtained by stacking green sheets with internal electrodes disposed therebetween, and then firing the resultant layered product, as shown in FIG.
36
.
As shown in
FIG. 36
, green sheets
253
to
266
mainly composed of a piezoelectric ceramic powder are stacked in the direction shown in the drawing. First internal electrodes
267
are respectively disposed on the green sheets
253
,
259
, and
263
by screen printing conductive paste. Similarly, second internal electrodes
268
are respectively disposed on the green sheets
256
,
262
, and
266
by screen printing conductive paste.
Each of the first and second internal electrodes
267
and
268
contacts one end of a green sheet in the length direction. The first and second internal electrodes
267
and
268
are also arranged to overlap each other with ceramic layers held therebetween in the thickness direction. In the sintered ceramic compact body
252
(
FIG. 35
) as a final product, the internal electrodes
267
are exposed from the first side
252
a
along the longer side, and the second internal electrodes
268
are exposed from the second side
252
b
opposite to the first dies
252
a.
A first external electrode
269
is located in a portion of the first side
252
a
of the sintered ceramic compact body
252
in which the first internal electrodes
267
are exposed.
Kohno Yoshiaki
Sube Mitsuru
Arbes Carl J.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Tai V
LandOfFree
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