Pumps – Motor driven – Magnetostrictive chamber
Reexamination Certificate
2001-07-06
2004-03-02
Tyler, Cheryl J. (Department: 3746)
Pumps
Motor driven
Magnetostrictive chamber
C417S413200
Reexamination Certificate
active
06699018
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART
The present invention relates to a cell-driving-type micro pump member based on the piezoelectric/electrostrictive effect, more specifically to a cell-driving-type micro pump member having a high response and providing a high pressurizing force, wherein the micro pump includes separate cells whose side walls are made of piezoelectric/electrostrictive elements, and each cell is used as a pressurizing chamber, so that a pressure can be produced in the pressurizing chamber by changing the volume of the cell with the aid of the displacement of the piezoelectric/electrostrictive elements.
Recently, mechanisms providing a change of volume in a pressurizing chamber by deforming a part of the walls forming the pressurizing chamber with the aid of the piezoelectric/electrostrictive effect are known, where the mechanism increases the pressure in a small pressurizing chamber formed in a base part. Such a micro pump member is used, for instance, as an ink pump member or the like in a print head used in an ink jet printer, wherein the pressure in the pressurizing chamber, to which ink is supplied and then stored therein, is increased by the displacement of the piezoelectric/electrostrictive elements, so that the ink particles (droplets) are ejected from nozzle holes connected to the pressurizing chamber, and thus the printing can be carried out.
For instance, in JP-A-6-40030, an example of an ink jet print head as shown in FIG.
16
and
FIG. 17
is described, wherein a micro pump member is used as an ink pump member. The ink jet print head
140
is formed by joining an ink nozzle element
142
, an ink pump member
144
and a piezoelectric/electrostrictive element
178
to each other, to form a unified body. The ink, which is supplied to ink pressurizing chambers
146
(hereafter simply referred to as pressurizing chambers), is ejected through nozzle holes
154
in the ink nozzle member
142
by the bending deformation of a closing plate
166
(vibration plate) forming the pressurizing chamber
146
in accordance with the deformation of the piezoelectric/electrostrictive element
178
, thus inducing a pressure in the pressurizing chamber
146
.
The ink pump member
144
is formed as a unified body, in detail, with such a construction that the closing plate
166
and a connecting plate
168
, each of which has a planar shape, are superimposed each other sandwiching a spacer blade
170
therebetween. In the connecting plate
168
, first connecting openings
172
and second connecting openings
174
are respectively formed at the positions corresponding to through-holes
156
and orifice holes
158
which are formed in an orifice plate
150
of the ink nozzle element
142
. Moreover, a plurality of rectangle-shaped window parts
176
is formed in the spacer plate
170
. The spacer plate
170
is superimposed on the connecting plate
168
in such a manner that each of the first connecting openings
172
and second connecting openings
174
, which are disposed in the connecting plate
168
is opened to the corresponding window parts
176
. In this spacer blade
170
, moreover, the closing plate
166
is superimposed on the surface opposite that on which the connecting plate
168
is superimposed, so that the openings of the window parts
176
are closed at the closing plate
166
. By so doing, the pressurizing chambers
146
, which are connected to the outside via the first and second connecting openings
172
,
174
, are formed in the inside of the ink pump member
144
.
In such an ink jet print head
140
, however, there are the following problems. In order to provide a greater displacement so as to be able to eject a greater number of droplets, it is effective to decrease the thickness of the closing plate
166
(vibrating plate) in the ink pump member
144
. However, this induces a decrease in the rigidity and reduces the high responsiveness. On the other hand, a significant enhancement in the high responsiveness requires an increase in the rigidity. For this purpose, it would be effective to increase the thickness of the closing plate
166
(vibrating plate), but this treatment provides a reduced displacement, thereby making it impossible to eject the required number of droplets. That is, in the ink pump member, it is difficult to attain both a greater displacement and a higher response property by the bending deformation of the vibrating plate due to the displacement of the piezoelectric/electrostrictive element. This is the first problem.
As for the second problem, it has been found that if one wants to make the adjacent ink pump members the same action, the displacement is reduced compared with the case where the piezoelectric/electrostrictive element is singly driven; this results in failure to display the intrinsic characteristics. That is, the vibrating plates of two adjacent ink pump members are bent simultaneously, so that a pulling force is applied to the walls between the ink pump members, thereby making it difficult to bend the vibrating plates.
Although not shown in the drawings, it has been proposed in JP-A-6-350155 that the interference due to the mutual displacement of the piezoelectric/electrostrictive elements is suppressed by disposing a groove between a concave part (ink pressurizing chamber) and the adjacent concave part, that is, by disposing a groove between adjacent ink pump members.
Moreover, as for a micro pump member based on the known piezoelectric/electrostrictive effect, for instance, a micro pump member, which is driven in shear mode and is similarly used in an ink jet head, is employed. This is a micro pump
271
having such a structure as shown in
FIG. 7
, wherein a plurality of piezoelectric/electrostrictive elements as comb teeth
276
, that is, driving parts
274
, are arranged like teeth of a comb on a base plate
272
, and cells
273
having substantially rectangular form are formed by a closing slit
275
between the comb teeth with a cover plate
277
. The openings at the front end of the micro pump member
271
are closed by a nozzle plate
9
having nozzles
8
, so that an ink jet head
270
is formed so as to use the cells
273
as pressurizing chambers. By applying a driving electric field in a direction vertical to the direction of polarizing field in the driving parts
274
, that is, comb teeth
276
, consisting of the piezoelectric/electrostrictive material, the comb teeth
276
are deformed and thus the volume of the cells
273
are changed, thereby enabling the ink stored in the cells
273
to be ejected. Furthermore, the method of driving where the displacement results from the driving electric field in the direction vertical to the direction of polarization in the piezoelectric/electrostrictive elements is called the shear mode method.
Such a micro pump member
271
is manufactured according to the steps shown in FIG.
8
(
a
)-FIG.
8
(
e
). Firstly, a piezoelectric/electrostrictive material
86
is provided as shown in FIG.
8
(
a
), and fired in FIG.
8
(
b
). In FIG.
8
(
c
), the polarization treatment is carried out and in FIG.
8
(
d
), fine slits are formed with a dicing saw or the like, and driving parts
274
are arranged like the teeth of a comb in a regular form by interposing therebetween a plurality of slits
275
corresponding to respective spaces for storing the ink, and then electrodes are formed on the wall surfaces in the slits
275
in FIG.
8
(
e
). After that, as shown in
FIG. 7
, the cover plate
277
comprising a glass plate or the like is mounted, and then the openings at the front end of the comb teeth are closed with the nozzle plate
9
having the nozzles
8
, so that the cells
273
used as the pressurizing chambers are formed.
In such a manufacturing method, however, there are the following problems due to machining rigid, fired piezoelectric/electrostrictive materials: The first problem is that it is time-consuming to machine the slits with the dicing saw or the like, and therefore it is unsuitable for mass production.
Furthermore, the second problem is the cost in
Kitamura Kazumasa
Takahashi Nobuo
Takeuchi Yukihisa
Tsuji Hiroyuki
Burr & Brown
NGK Insulators Ltd.
Tyler Cheryl J.
LandOfFree
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