Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-08-29
2004-01-27
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06682175
ABSTRACT:
The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2001-264452 filed on Aug. 31, 2001, which are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recording apparatus, and particularly relates to an ink jet recording head for ejecting ink droplets from a plurality of ejectors arrayed in a matrix, and an ink jet recording apparatus mounted with the ink jet recording is head.
2. Description of the Related Art
Non-impact recording systems have features of high speed, high image quality, low noise, and so on, and prevail in current printers. Of them, ink jet printers which fly ink droplets from a plurality of nozzles so as to perform printing of characters, drawings, pictures, and the like, on recording paper, are in widespread use because the ink jet printers have features in small size, low cost and capability of performing photorealistic printing.
An ink jet recording head is designed as follows. That is, while the head is moved in the main-scanning direction, ink droplets are ejected selectively from a plurality of nozzles, for example, 24-300 nozzles per color, in accordance with an electric signal based on print data. Thus, the ink droplets are made to adhere to the surface of a medium to be recorded on, such as recording paper. Further, in combination of the operation to feed the recording medium in the sub-scanning direction perpendicular to the main-scanning direction, the recording head can print characters or drawings on the medium to be recorded on.
In the ink jet recording head configured thus, ink is stored in an ink pool provided to be shared by the plurality of nozzles. The ink in this ink pool is introduced into pressure chambers via narrow inlets provided in the nozzles respectively. Further, in each of the pressure chambers, pressure exerting on the ink is generated by a pressure generating unit such as a piezoelectric element actuated in response to the electric signal. Thus, an ink droplet is ejected from the nozzle. The ink droplet ejecting mechanism constituted by the nozzle, the pressure chamber, the inlet and the pressure generating unit will be referred to as “ejector”.
An example of an ink jet recording head configured thus is disclosed in JP-A-8-58089.
FIGS. 16 and 17
are a sectional view and a plan view showing the ink jet recording head disclosed in the same publication respectively.
As shown in
FIGS. 16 and 17
, the ink jet recording head has a nozzle formation plate
61
, an ink pool plate
61
, a diaphragm formation plate
63
having ink supply diaphragms
63
a
(corresponding to the inlets), a sealing plate
64
, a pressure chamber formation plate
65
and a pressure plate
66
. These plates
61
to
66
are laminated in the order named. Each pressure generating unit is constituted by the pressure plate
66
and a piezoelectric element
67
. A pressure wave (acoustic wave) is generated for the ink in a pressure chamber
71
by applying a voltage control signal between an upper electrode
68
a
and a lower electrode
68
b
. By the plates
61
to
66
, an ink flow path is formed to reach-each nozzle
73
from the ink pool
69
through the ink supply diaphragm
63
a
, a communication-hole
70
, the pressure chamber
71
and an ink communication hole
72
.
In such an ink jet recording head, each ejector has the pressure generating unit constituted by the pressure plate
66
and the piezoelectric element
67
, the nozzle
73
, the pressure chamber
71
and the ink supply diagram
63
a
. Such ejectors are arrayed in a straight line as shown in
FIG. 17
, so as to form an ejector array
74
. The ink jet recording head having ejectors arrayed in a straight line will be referred to as “linear array head”.
Such a linear array head using piezoelectric elements as pressure generating units had a problem in realization of high-density arrangement of ejectors due to characteristic limits of the pressure generating units and restrictions on the manufacturing technology. In order to align the ejectors in high density in the linear array head, it is necessary to reduce the pressure chamber width. It is therefore necessary to arrange the ink jet recording head out of elongated ejectors having a large aspect ratio.
However, when the pressure chamber width is reduced to achieve the high-density arrangement of the ejectors, the width of a movable area of the pressure plate is also reduced so that the bending rigidity of the pressure plate increases. Thus, a sufficient deformation amount of the pressure plate cannot be obtained. As a result, there arises a problem that it becomes difficult to eject a desired quantity of ink droplets. In addition, the pressure chambers can be formed by etching, machining, resin molding, or the like, but there is also a limit in the reduction of the pressure chamber width due to the accuracy limit of machining.
Thus, in the linear array head using pressure generating units each constituted by a pressure plate and a piezoelectric element, there was a limit in high-density arrangement, substantially about 120-180 pieces/inch, due to the performance limit of the pressure generating units and the restrictions on the manufacturing technology. In the linear array head, ejectors can be indeed arrayed zigzag for doubling nozzle density. In that case, however, there arises a new problem that the head size increases while the head cost doubles.
As an ink jet recording head to solve the foregoing problems, there is known a recording head in which a large number of ejectors each having a pressure chamber with an aspect ratio close to 1 are arrayed in a matrix so as to place nozzles in high density. Recording heads configured thus are disclosed in Japanese Patent No. 2806386, JP-A-9-156095 and Japanese Translations of PCT publication No.10-508808, respectively.
FIGS. 18 and 19
show the main portion configuration of the ink jet recording head disclosed in Japanese Patent No. 2806386. This recording head will be referred to below as “matrix array head” because nozzles
75
are arrayed in a matrix.
The matrix array head has a nozzle plate
82
, a distribution plate
83
, a cavity plate
84
and a pressure plate
85
. The plates
82
to
85
are laminated in the order named. The nozzle plate
82
has the nozzles
75
. The distribution plate
83
has ink supply grooves
79
and ink passageways
77
. The cavity plate
84
has pressure chambers
76
and branch paths
81
. Piezoelectric elements
86
are fixed to the pressure plate
85
.
In the matrix array head, as shown in
FIG. 19
, a plurality of ink supply grooves
79
(corresponding to the branch flow paths) communicating with a not shown ink supply source (corresponding to the main flow path) are formed in parallel with one another between adjacent nozzles
75
and ink passageways
77
. Further, each communication hole
80
is coupled with a branch path
81
provided for each pressure chamber
76
, so that an ink flow path is formed. In such a matrix array head, there is an advantage that the nozzle density in the sub-scanning direction can be increased without reducing the width of each of the pressure chambers
76
.
To secure a sufficient acoustic capacitance in an ink pool is a very essential problem for the inkjet recording head.
In the ink jet recording head, by the propagation of a pressure wave applied to a certain pressure chamber, not only is an ink droplet ejected from a nozzle communicating with this pressure chamber, but so-called acoustic crosstalk is produced. The acoustic crosstalk is a phenomenon that the pressure wave is also propagated through an inlet to the ink pool communicating with the pressure chamber. When the pressure wave is propagated to an adjacent ejector through the ink pool, a bad influence may be given to the ejection condition of a nozzle other than a desired nozzle. When this influence is conspicuous, there arises a phenomenon that a small amount of ink is also ejected from the adjacent noz
Hayashi Kazuhiko
Ishiyama Toshinori
Okuda Masakazu
Otsuka Yasuhiro
Gordon Raquel Yvette
Morgan & Lewis & Bockius, LLP
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