Head chip

Details Head chip Head chip

2002-09-30

2004-05-25

Nguyen, Judy (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

Reexamination Certificate

active

06739702

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a head chip that is mounted on an ink jet recording device applied to, for example, a printer or a facsimile.
2. Description of the Related Art
Conventionally, there is known an ink jet recording device that records characters and images on a medium to be recorded using an ink jet head having a plurality of nozzles for discharging ink. In such an ink jet recording device, the nozzles of the ink jet head are provided in a head holder so as to oppose the medium to be recorded, and this head holder is mounted on a carriage to be scanned in a direction perpendicular to a conveying direction of the medium to be recorded.
A sectional view in the longitudinal direction of an example of a head chip of such an ink jet head is shown in
FIG. 16A and a
sectional view of a main portion of the same is shown in FIG.
16
B. As shown in
FIGS. 16A and 16B
, a plurality of grooves
102
are provided in parallel with each other in a piezoelectric ceramic plate
101
, and each groove
102
is separated by sidewalls
103
. An end portion in the longitudinal direction of each groove
102
is extended to an end surface of the piezoelectric ceramic plate
101
and the other end portion is not extended to the other end surface, making the groove
102
to be gradually shallow. In addition, electrodes
105
for applying a driving electric field are formed on surfaces on opening side of both sidewalls
103
in each groove
102
throughout its longitudinal direction.
In addition, a cover plate
107
is joined on the opening side of the grooves
102
of the piezoelectric ceramic plate
101
via a partitioning portion using an adhesive
109
. The cover plate
107
includes a common ink chamber
111
in the form of a recessed portion communicating with each groove
102
via communication holes provided in the partitioning portion in the longitudinal direction of the respective grooves
102
and an ink supply port
112
that is bored from the bottom portion of the common ink chamber
111
in the direction opposite to the grooves
102
.
In addition, a nozzle plate
115
is joined to an end surface of the joined body of the piezoelectric ceramic plate
101
, the partitioning portion and the cover plate
107
in which the grooves
102
are opened, and nozzle openings
117
are formed in the nozzle plate
115
at positions opposing the respective grooves
102
.
Further, a wiring substrate is fixed to the surface of the piezoelectric ceramic plate
101
on the opposite side of the nozzle plate
115
and on the opposite side of the cover plate
107
. Wiring connected to each electrode
105
via bonding wires
121
or the like is formed on the wiring substrate, and a driving voltage can be applied to the electrodes
105
via the wiring.
In a head chip configured in this way, when each groove
102
is filled with ink from the ink supply port
112
and a predetermined driving electric field is caused to act on the sidewalls
103
on both sides of the predetermined groove
102
via the electrode
105
, the sidewalls
103
are deformed to change the capacity inside the predetermined groove
102
, whereby the ink in the groove
102
is discharged from the nozzle opening
117
.
For example, as shown in
FIG. 17
, if ink is discharged from the nozzle opening
117
corresponding to a groove
102
a
, a positive driving voltage is applied to electrodes
105
a
and
105
b
in the groove
102
a
and, at the same time, opposing electrodes
105
c
and
105
d
to the respective electrodes are grounded. Consequently, a driving electric field in the direction toward the groove
102
a
acts on sidewalls
103
a
and
103
b
and, if the driving electric field is perpendicular to a direction of polarization of the piezoelectric ceramic plate
101
, the sidewalls
103
a
and
103
b
are deformed in the direction of the groove
102
a
by a piezoelectric thickness slip effect and the capacity inside the groove
102
a
decreases to increase pressure, whereby the ink is discharged from the nozzle opening
117
.
As a measure for solving a problem that it is difficult to achieve high speed consecutive discharging, that is, to achieve high speed printing in a head chip like this, the degree of sealing of a chamber is increased for the sake of shortening a time from the stoppage of vibration of the sidewalls caused by ink discharging to the obtainment of a situation where pressure of ink in the chamber corresponding to the groove becomes zero to perform the next ink discharging, although this time varies depending on the length of the chamber, the shape of the nozzle opening, and the like. However, if the opening area of the communicating hole is narrowed too much for the sake of enhancing the degree of sealing of the chamber, there occurs a problem that ink necessary for discharging is not sufficiently supplied from the common ink chamber to the chamber and printing is not normally performed.
SUMMARY OF THE INVENTION
In view of such circumstances, it is an object of the present invention is to provide a head chip in which the minimum size of the communicating hole, with which it is possible to sufficiently supply ink necessary for discharging and, at the same time, to enhance the degree of sealing of the chamber to a limit, is defined with reference to the length in the longitudinal direction of the chamber.
In order to solve the above-mentioned object, according to a first aspect of the present invention, a head chip includes: a chamber that is defined on a substrate and has an end portion in a longitudinal direction that communicates with a nozzle opening; and an electrode provided on a sidewall of the chamber, in which a driving voltage is applied to the electrode so that a capacity within the chamber is changed to discharge ink filled therein from the nozzle opening. The head chip is characterized in that: an ink chamber plate defining a common ink chamber communicating with the chamber is joined on the substrate; the common ink chamber is provided with a partitioning portion for partitioning the chamber and the common ink chamber; the partitioning portion is provided with a plurality of communicating holes that evenly divide a chamber longitudinal direction of the partitioning portion using a distance between the nozzle opening and a communicating hole establishing communication between the common ink chamber and the chamber and which is provided in the partitioning portion at a position close to the nozzle opening, and each of the plurality of communicating holes has the same opening ratio to an area of the partitioning portion; and if a length in the longitudinal direction of the chamber is referred to as Y (mm) and an opening ratio of each communicating hole to the area of the partitioning portion is referred to as X (%), when a size of the communicating hole satisfying a relation of “Y=−4.5X+15.8” is referred to as S
min
and a size of a communicating hole obtained by coupling the plurality of communicating holes to each other is referred to as S
max
, there is obtained a relation of S
min
size of communicating hole<S
max
.
According to a second aspect of the present invention, in the first aspect of the invention, a head chip is characterized in that the partitioning portion is formed of a separate member.
According to a third aspect of the present invention, in the first or the second aspect of the invention, a head chip is characterized in that the substrate is formed of a piezoelectric ceramic plate, and the chamber is defined by forming a groove in the piezoelectric ceramic plate.
According to a fourth aspect of the present invention, in the first or the second aspect of the invention, a head chip is characterized in that the sidewalls are made of piezoelectric ceramic and are arranged on the substrate at a predetermined interval, and the chamber is defined between the sidewalls.
According to a fifth aspect of the present invention, in the fourth aspect of the invention, a head chip is characterized in that the sidewalls

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