Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-06-26
2004-04-20
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S366000
Reexamination Certificate
active
06724129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to laminated piezoelectric elements and methods for manufacturing the same, and more particularly, to a laminated piezoelectric element used for manufacturing a piezoelectric actuator including a plurality of independently driven actuator units.
2. Description of the Related Art
In general, print heads mounted on inkjet-type printers are driven by piezoelectric actuators. An example of a known piezoelectric actuator is disclosed in Japanese Unexamined Patent Application Publication No. 11-320881, which includes a laminated piezoelectric element having an external shape illustrated in
FIGS. 12A and 12B
.
A laminated piezoelectric element
31
includes a monolithic piezoelectric body
37
, i.e., a sintered ceramic compact, which includes a driver
34
having a plurality of first driving internal electrodes
32
and a plurality of second driving internal electrodes
33
, the first and second driving internal electrodes being alternatively laminated with a piezoelectric layer interposed therebetween, and which includes a connector
36
having a plurality of laminated connecting internal electrodes
35
, with adjacent electrodes having a piezoelectric layer interposed therebetween. Since the piezoelectric layers in the driver
34
of the monolithic piezoelectric body
37
are polarized, the piezoelectric layers expand and contract in the laminating direction X indicated in
FIG. 12A
, i.e., in a so-called d-33 direction thereof when an alternating voltage is applied thereto.
As shown in
FIG. 12A
, ends of the first driving internal electrodes
32
are exposed at one of the mutually opposing side surfaces, i.e., only at a first side surface
37
a
, but the other ends are not exposed at the other side surface, i.e., at a second side surface
37
b
of the monolithic piezoelectric body
37
. Also, as shown in
FIG. 12B
, ends of the second driving internal electrode
33
are exposed at the second side surface
37
b
, but the other ends are not exposed at the first side surface
37
a
. Ends of the connecting internal electrodes
35
are exposed at both of the first and second side surfaces
37
a
and
37
b.
The monolithic piezoelectric body
37
includes a driving external electrode
38
and a connecting external electrode
39
, arranged in parallel on the first side surface
37
a
with a spacing
40
interposed therebetween. The driving external electrode
38
and the connecting external electrode
39
are electrically connected to each of the first driving internal electrodes
32
and each of the connecting internal electrodes
35
, respectively. The monolithic piezoelectric body
37
includes a common external electrode
41
provided on substantially the entire second side surface
37
b
and electrically connected to both the second driving internal electrodes
33
and the connecting internal electrodes
35
.
Although the common external electrode
41
is provided on substantially the entire second side surface
37
b
, the driving external electrode
38
and the connecting external electrode
39
are provided on the first side surface
37
a
, each having a spacing
42
having a desired width on the bottom of the first side surface
37
a
, that is, each having the spacing
42
so as to be spaced away from the edge of the lower surface of the monolithic piezoelectric body
37
. Thus, the driver
34
has a sectional structure illustrated in FIG.
13
.
A piezoelectric actuator
45
having an external shape illustrated in
FIGS. 14A and 14B
is made using the laminated piezoelectric element
31
. More particularly, the laminated piezoelectric element
31
is fixed on a support plate
46
with an adhesive or other suitable material, and the driver
34
includes a plurality of slits
47
formed by cutting from the upper surface toward the lower surface thereof in the laminating direction X.
As shown in
FIG. 14A
, the slits
47
divide each of the first and second driving internal electrodes
32
and
33
, and also divide the driving external electrode
38
, such that the driver
34
is divided into a plurality of portions. Thus, the divided driver
34
includes a plurality of independently driven actuator units
48
arranged therein.
In addition, a plurality of unit external electrodes
49
is provided by dividing the driving external electrode
38
, wherein the unit external electrodes
49
correspond to the respective actuator units
48
. The driver
34
and the connector
36
of the piezoelectric actuator
45
are divided by the slit
47
, and
FIG. 14B
illustrates the piezoelectric actuator
45
viewed from the other side of thereof.
Furthermore, although not shown, a flexible wiring substrate associated with a drive signal source disposed outside is connected to the piezoelectric actuator
45
having the actuator units
48
provided therein. When voltages having independent polarities are applied between the corresponding unit external electrodes
49
and the common external electrode
41
, that is, in practice, between the corresponding unit external electrodes
49
and the connecting external electrode
39
connected to the common external electrode
41
via the corresponding connecting internal electrodes
35
, each of the actuator units
48
is driven independently of each other.
When the piezoelectric actuator
45
is made from the laminated piezoelectric element
31
, the plurality of slits
47
is formed by cutting the driver
34
from the upper surface toward the lower surface of the monolithic piezoelectric body
37
in the laminating direction X so as to divide each of the first and second driving internal electrodes
32
and
33
, and also divide the driving external electrode
38
. In this case, the slits
47
are generally formed by making a deep cut close to the lower surface of the monolithic piezoelectric body
37
since the first and second driving internal electrodes
32
and
33
and also the driving external electrode
38
must be reliably divided.
On the other hand, since the top portion and the bottom portion of the monolithic piezoelectric body
37
, which extend perpendicular to the laminating direction X, that is, the top portion and the bottom portion located above and below the first and second driving internal electrodes
32
and
33
are piezoelectrically inactive, these upper and lower portions have thicknesses that are as small as possible to further reduce the size of the laminated piezoelectric element
31
. Accordingly, when the slits
47
are formed deeply, the common external electrode
41
provided on the second side surface
37
b
has a conducting path
41
a
which is sandwiched between the lower edges of the slits
47
and the lower surface of the monolithic piezoelectric body
37
and which is as narrow as, for example, about 0.1 mm to 0.2 mm.
The narrow conducting path
41
a
increases the electrical resistance between any two of the actuator units
48
, which decreases the conductivity of the overall piezoelectric actuator
45
. Further, the narrow conducting path
41
a
often has a disconnection because a driving current from the drive signal source flows in the conducting path
41
a
in a concentrated manner.
SUMMARY OF THE INVENTION
In order to overcome the above-described problems, preferred embodiments of the present invention provide a laminated piezoelectric element in which the electrical resistance of a conducting path of a piezoelectric actuator does not increase and in which the conductivity of the piezoelectric actuator increases even when the conducting path of the common external electrode is narrow, and a method for manufacturing such a novel laminated piezoelectric element.
In accordance with a first preferred embodiment of the present invention, a laminated piezoelectric element includes a monolithic piezoelectric body having at least one slit, and a plurality of independently driven actuator units. The monolithic piezoelectric body includes a driver, and a connector. The driver includes a plurality of first driving internal electrodes, an
Addison Karen Beth
Dougherty Thomas M.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
LandOfFree
Laminated piezoelectric element, method for manufacturing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laminated piezoelectric element, method for manufacturing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laminated piezoelectric element, method for manufacturing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3190071