Information
-
Patent Grant
-
6811247
-
Patent Number
6,811,247
-
Date Filed
Thursday, May 8, 200321 years ago
-
Date Issued
Tuesday, November 2, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 347 54
- 347 50
- 347 40
- 347 20
- 347 44
- 347 47
- 347 27
- 347 63
- 399 261
- 361 700
- 029 8901
-
International Classifications
-
Abstract
To provide an ink jet head and an ink jet recording apparatus in which it is possible to reliably prevent ink bubbles from staying in the ink sump and the interior of the head chip and in which it is relatively easy to remove the bubbles. The ink jet head includes: a plurality of grooves arranged side by side so as to communicate with nozzle openings; an ink chamber for supplying ink to each of the grooves; an ink sump provided so as to communicate with the ink chamber; and ink storage unit (50) communicating with the ink sump through ink supply passages, in which there is provided an air duct (100) establishing communication between a region in the ink sump which is substantially free from interference with an ink flow from the ink supply passages (33) to the ink chamber and in which bubbles easily gather and an air region of the ink storage unit (50). Therefore, the bubbles in the ink can be surely removed.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet head and an ink jet recording apparatus applicable, for example, to a printer or a facsimile machine.
2. Description of the Related Art
An ink jet recording apparatus has been known which records characters and images on a recording medium by using an ink jet head having a plurality of nozzles for ejecting ink. In such an ink jet recording apparatus, the nozzles of the ink jet head are provided in a head holder so as to be opposed to the recording medium, and the head holder is mounted on a carriage, with which scanning is performed in a direction perpendicular to the direction in which the recording medium is transported.
FIG. 11
is an exploded perspective view of an example of such an ink jet head. As shown in
FIG. 11
, a plurality of grooves
132
are arranged side by side in a piezoelectric ceramic plate
131
, and the grooves
132
are separated from each other by partition walls
133
. One longitudinal end portion of each groove
132
extends to one end surface of the piezoelectric ceramic plate
131
, whereas the other end portion thereof does not extend to the other end surface, and its depth gradually decreases. Further, on the opening side surfaces of the partition walls
133
on both sides of each groove
132
, electrodes
134
for applying a drive electric field are formed so as to extend in the longitudinal direction.
Further, attached to the opening side of the grooves
132
of the piezoelectric ceramic plate
131
is an ink chamber plate
136
defining a common ink chamber
135
communicating with the shallow end portions of the grooves
132
.
Further, fixed to the ink chamber plate
136
is a flow passage substrate
138
which seals one side of the common ink chamber
135
and which has a communication hole
137
communicating with an ink supply passage for supplying ink to the common ink chamber
135
.
Provided in the flow passage substrate
138
is an ink sump
139
constituting a part of the ink flow passage for supplying ink from the communication hole
137
to the common ink chamber
135
.
A nozzle plate
140
is attached to the end surface of the joint unit formed by the piezoelectric ceramic plate
131
and the ink chamber plate
136
where the grooves
132
are open, and nozzle openings
141
are formed at the positions of the nozzle plate
140
opposed to the grooves
132
.
In this ink jet head, constructed as described above, the grooves
132
are filled with ink from the communication hole
137
, and when a predetermined drive electric field is applied to the partition walls
133
on both sides of a predetermined groove
132
through the electrodes
134
, the partition walls
133
are deformed to change the volume of the predetermined groove
132
, whereby the ink in the groove
132
is ejected from the corresponding nozzle opening
141
.
In this ink jet head, the diameter of the nozzle openings
141
is very small, so that even if the volume of each groove
132
is varied, it is impossible to eject ink from the nozzle openings
141
in a satisfactory manner unless back pressure is generated in each groove
132
from the common ink chamber
135
side.
In view of this, in the conventional ink jet head, a mesh-like filter
142
formed, for example, of stainless steel (SUS), is provided between the ink sump
139
and the common ink chamber
135
. Due to this filter
142
, back pressure is generated in the grooves
132
to eject ink droplets from the nozzle openings
141
.
The ink sump of the conventional ink jet head, however, includes a region where ink does not flow easily. For example, in a region such as a corner of the ink sump, the ink supplied to the ink sump does not flow easily, with the result that bubbles stay in that region. When bubbles stay in such a region, the volume of the ink sump changes, resulting in a deficiency in the ink supply to the ink chamber. In particular, when, for example, an ink with poor bubble permeability such as a water-color ink is used, bubbles are likely to be generated in the ink, with the result that the deficiency in ink supply is gradually aggravated.
It is general practice to remove the bubbles thus accumulated in the ink sump through a so-called cleaning operation in which the bubbles are sucked from the nozzle opening side. However, even by this cleaning operation, it is difficult to substantially remove the bubbles staying in the portion of the ink sump on the upstream side of the filter, which do not pass through the filter.
In an ink jet head in which bubbles cannot be removed from a region where ink does not flow easily, bubbles staying in the ink sump may pass through the filter to be ejected together with ink during printing, thereby causing a printing failure. Thus, such an ink jet head is to be disposed of, resulting in a poor yield rate.
Further, when the size of the ink droplets is large or the number of nozzle openings is large, that is, when the amount of ink ejected per unit time is large, the amount of bubbles existing, in particular, in the ink sump, is large, so that the area of the ink flow passage is substantially reduced, resulting in the deficiency in the ink supply to the ink chamber being gradually aggravated.
It might be possible to accelerate the ink flow by narrowing the flow passage of the ink sump to thereby prevent the bubbles in the ink sump from staying. This, however, would involve a substantial reduction in the filter size, resulting in a deficiency in the ink supply to the common ink chamber. Further, even by adopting this method, it is impossible to completely remove the bubbles staying in the portion of the ink sump on the upstream side of the filter through the above-mentioned cleaning operation.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problem in the prior art. It is an object of the invention to provide an ink jet head and an ink jet recording apparatus in which it is possible to reliably prevent ink bubbles from staying in the ink sump and the interior of the head chip and in which it is relatively easy to remove the bubbles.
According to a first aspect of the present invention for solving the above-mentioned object, there is provided an ink jet head including: a plurality of grooves arranged side by side so as to communicate with nozzle openings; an ink chamber for supplying ink to each of the grooves; an ink sump provided so as to communicate with the ink chamber; and ink storage unit communicating with the ink sump through ink supply passages,
characterized in that there is provided an air duct establishing communication between a region in the ink sump which is substantially free from interference with an ink flow from the ink supply passages to the ink chamber and in which bubbles easily gather and an air region of the ink storage means.
According to a second aspect of the present invention, in the first aspect of the present invention, the ink jet head is characterized in that the ink chamber is provided so as to extend over the direction in which the grooves are arranged side by side, that the ink chamber and the ink sump communicate with each other over the direction in which the grooves are arranged side by side, that the ink supply passages are provided on both sides of the ink sump with respect to the direction in which the grooves are arranged side by side, and that the air duct is provided between the ink supply passages.
According to a third aspect of the present invention, in the first or second aspect of the present invention, the ink jet head is characterized in that the ink sump is equipped with a tapered portion gradually diverging from at least one of the openings of the ink supply passages and the air duct toward the ink chamber.
According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the ink jet head is characterized in that the ink sump is equipped with a filter situated in the vicinity of the border between the ink sump and the ink chamber.
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the ink jet head is characterized in that the air duct communicates with the portion of the ink flow passage which is on the upstream side of the filter of the ink sump.
According to a sixth aspect of the present invention, there is provided an ink jet recording apparatus equipped with an ink jet head according to any one of the first to fifth aspects.
According to the present invention, there is provided an air duct establishing communication between a region which is substantially free from interference with the ink flow in the ink sump from the ink supply passage to the ink chamber and in which bubbles gather easily and the air region of the ink storage unit, whereby it is possible to reliably prevent the bubbles in the ink from remaining in the ink sump and the interior of the head chip, and the bubbles can be removed relatively easily.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view of an ink jet head according to Embodiment 1 of the present invention;
FIGS. 2A and 2B
are an exploded perspective view and a perspective sectional view of a head chip according to Embodiment 1 of the present invention;
FIG. 3
is a sectional view of a main portion of the ink jet head of Embodiment 1 of the present invention;
FIG. 4
is a top plan view of a flow passage substrate of the ink jet head of Embodiment 1 of the present invention;
FIG. 5
is a schematic plan view of the flow passage substrate and air damper of the ink jet head of Embodiment 1 of the present invention;
FIG. 6
is a sectional view taken along the arrow line A-A′ of
FIG. 5
showing Embodiment 1 of the present invention;
FIG. 7
is a sectional view taken along the arrow line B-B′ of
FIG. 5
showing Embodiment 1 of the present invention;
FIG. 8
is a sectional view taken along the arrow line C-C′ of
FIG. 5
showing Embodiment 1 of the present invention;
FIG. 9
is a schematic sectional view of the flow passage substrate of the ink jet head of Embodiment 1 of the present invention;
FIG. 10
is a schematic perspective view of an ink jet recording apparatus according to Embodiment 1 of the present invention; and
FIG. 11
is a schematic exploded perspective view of a conventional ink jet head.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will now be described in detail.
Embodiment 1
FIG. 1
is a perspective view of an ink jet head according to Embodiment 1.
FIGS. 2A and 2B
are an exploded perspective view and a perspective sectional view of a head chip.
FIG. 3
is a sectional view of a main portion of the ink jet head.
FIG. 4
is a top plan view of a flow passage substrate.
As shown in the drawings, an ink jet head
10
according to this embodiment comprises a head chip
20
, a flow passage substrate
30
provided on one side thereof, a wiring board
40
on which a drive circuit for driving the head chip
20
, etc. are mounted, and an air damper
50
for mitigating the pressure variation in the head chip
20
. These components are fixed to a base plate
60
.
In a piezoelectric ceramic plate
21
constituting the head chip
20
, there are arranged side by side a plurality of grooves
23
communicating with nozzle openings
22
, and the grooves
23
are separated from each other by partition walls
24
. One longitudinal end portion of each groove
23
extends to one end surface of the piezoelectric ceramic plate
21
, whereas the other longitudinal end portion thereof does not extend to the other end surface, and its depth gradually decreases. Further, on the opening side of the partition walls
24
on both sides of each groove
23
with respect to the width direction thereof, electrodes
25
for applying a drive electric field are formed so as to extend in the longitudinal direction.
The grooves
23
arranged in the piezoelectric ceramic plate
21
are formed by, for example, a disc-shaped dice cutter, and the portions thereof whose depth gradually decreases are made in conformity with the configuration of the dice cutter. The electrodes
25
formed within the grooves
23
are formed, for example, by a well-known oblique deposition method.
Connected to the electrodes
25
provided on the opening side of the partition walls
24
on both sides of each groove
23
is one end of an external wiring
41
such as a flexible print cable (FPC), and the other end of the external wiring
41
is connected to a drive circuit (not shown) on the wiring board
40
, whereby the electrodes
25
are electrically connected to the drive circuit.
Further, an ink chamber plate
26
is joined to the opening side of the grooves
23
of the piezoelectric ceramic plate
21
. The ink chamber plate
26
is equipped with a common ink chamber
26
a
formed by cutting in the thickness direction and extending over the entire grooves
23
arranged side by side.
The ink chamber plate
26
can be formed of a ceramic plate, a metal plate or the like. Taking into account the deformation after it is joined to the piezoelectric ceramic plate
21
, however, it is desirable to use a ceramic plate whose coefficient of thermal expansion is close to that of the piezoelectric ceramic plate
21
.
Further, a nozzle plate
27
is attached to the end surface of the joint unit formed by the piezoelectric ceramic plate
21
and the ink chamber plate
26
where the grooves
23
are open, and nozzle openings
22
are formed in the nozzle plate
27
at positions opposed to the grooves
23
.
In this embodiment, the area of the nozzle plate
27
is larger than the area of the end surface of the joint unit of the piezoelectric ceramic plate
21
and the ink chamber plate
26
where the grooves
23
are open. The nozzle plate
27
consists of a polyimide film or the like, and the nozzle openings
22
are formed therein by using, for example, an excimer laser device. Further, although not shown, provided on the surface of the nozzle plate
27
opposed to the printing medium is a water-repellent film for preventing adhesion of ink or the like.
Further, joined to the outer peripheral surface of the end surface of the joint unit of the piezoelectric ceramic plate
21
and the ink chamber plate
26
on the side where the grooves
23
are open is a nozzle support plate
29
equipped with an engagement hole
28
to be engaged with the joint unit. This nozzle support plate
29
is joined to the outer side of the end surface of the joint unit of the nozzle plate
27
to hold the nozzle plate
27
in a stable manner.
The surface of the piezoelectric ceramic plate
21
of the above-described head chip
20
on the opposite side of the ink chamber plate
26
is fixed to the base plate
60
. The flow passage substrate
30
is attached to one surface of the ink chamber plate
26
.
The flow passage substrate
30
will be described in detail with reference to
FIGS. 3 and 4
.
FIG. 4
is a top plan view of the ink jet head flow passage substrate of Embodiment 1 of the present invention.
As shown in the drawings, the flow passage substrate
30
comprises a flow passage main body
32
having an ink sump
31
, connecting portions
34
which are provided on both longitudinal ends of the flow passage main body
32
and in which ink supply passages
33
are open, and a protruding portion
36
which is provided between the connecting portions
34
and in which a discharge hole
35
for discharging bubbles in the ink sump
31
is open.
The ink sump
31
communicates with the ink supply passages
33
and the discharge hole
35
, and ink from an air damper
50
described below is supplied thereto through the ink supply passages
33
.
Further, in the portion of the ink sump
31
opposed to the common ink chamber
26
a
, a filter A for removing dust or the like mixed in the ink is provided so as to extend in the direction in which the grooves
23
are arranged side by side. The filter A also serves to generate back pressure for each groove
23
when ink is ejected.
Further, the ink sump
31
is equipped with tapered portions
37
gradually increasing the ink flow passage from the ink supply passages
33
and the discharge hole
35
toward the common ink chamber
26
a
. In this embodiment, the tapered portions
37
are provided so as to extend to a position in front of the filter A and join together in front of it.
In the ink sump
31
of this embodiment, the inflow direction of the ink from the ink supply passages
33
and the inflow direction of the ink supplied to the common ink chamber
26
a
are substantially perpendicular to each other. Then, the ink supplied to the ink sump
31
from the ink supply passages
33
is supplied to the common ink chamber
26
a
through the filter A while being accelerated by the action of the above-mentioned tapered portions
37
.
Further, in this embodiment, the connecting portions
34
protrude along the base plate
60
from the upper portion on either side with respect to the width direction of the flow passage main body
32
. Then, in this embodiment, the flow passage substrate
30
and the air damper
50
are connected through the connecting portions
34
, and ink from the air damper
50
is supplied to the ink sump
31
through the ink supply passages
33
of the connecting portions
34
.
Further, in this embodiment, the protruding portion
36
protrudes from the upper portion substantially at the center of the flow passage substrate
30
so as to be substantially parallel to the connecting portions
34
. As will be described in detail below, the discharge hole
35
of this protruding portion
36
constitutes a part of an air duct for guiding bubbles staying in the ink sump
31
to the air damper
50
.
In this embodiment, the connecting portions
34
and the protruding portion
36
described above are formed integrally with the flow passage main body
32
by molding or the like. Of course, this should not be construed restrictively. They may also be formed as separate components joined together by screws.
Next, the air damper
50
for supplying ink to the ink sump
31
of the above-described flow passage substrate
30
will be described in detail with reference to
FIGS. 5 through 8
.
FIG. 5
is a schematic plan view of the flow passage substrate and the air damper.
FIG. 6
is a sectional view taken along the arrow line A-A′ of
FIG. 5
,
FIG. 7
is a sectional view taken along the arrow line B-B′ of
FIG. 5
, and
FIG. 8
is a sectional view taken along the line C-C′ of FIG.
5
.
FIG. 9
is a schematic sectional view of the flow passage substrate.
As shown in the drawings, the air damper
50
comprises a damper main body
52
having an ink storage portion
51
storing ink, a recess
53
provided in the end surface of the damper main body
52
on the opposite side of the base plate
60
, a film-like member
54
sealing the recess
53
, and a damper plate
55
retained in the ink storage portion
51
and formed as a thin plate.
The ink storage portion
51
is a space defined by closely attaching the film-like member
54
to the edge portion of the side of the damper main body
52
where the recess
53
is open. Due to this film-like member
54
, the air and ink inside the ink storage portion
51
are prevented from leaking out.
Inside the ink storage portion
51
, there is provided a damper plate
55
consisting of a plate-like member of stainless steel or the like. This damper plate
55
is held by the damper main body
52
so as to form a predetermined clearance with the bottom wall of the recess
53
.
Further, the damper plate
55
has a plurality of arm portions
55
a
protruding in the vertical direction as seen in the drawings so as to cover a wide range with respect to the face of the film-like member
54
, whereby it is possible to prevent the film-like member
54
from coming into contact with the bottom wall of the recess
53
, making it possible to maintain a fixed ink filling amount in the ink storage portion
51
.
Further, at the center of the upper portion of the damper main body
52
, there is provided a cylindrical joint member
56
to which an ink supply tube
120
consisting of a flexible tube of rubber, plastic or the like connected to an ink tank described below is to be connected (See FIG.
1
).
As shown in
FIG. 6
, this joint member
56
communicates with a filling passage
57
for filling the ink storage portion
51
with ink. More specifically, this filling passage
57
extends from the joint member
56
behind the recess
53
of the damper main body
52
to communicate with the bottom surface of the recess
53
on the flow passage substrate
30
side.
As shown in
FIG. 7
, on either side of the lower portion of the damper main body
52
, a supply pipe
58
having a supply passage
58
a
communicating with the ink storage portion
51
protrudes along the base plate
60
. In the boundary between the ink storage portion
51
and each supply passage
58
a
, there is provided a filter B for removing dust or the like mixed in the ink.
In this embodiment, the supply pipes
58
and the connecting portions
34
of the flow passage substrate
30
are connected through connecting tubes
200
(See
FIG. 1
) of rubber, plastic or the like, thereby forming ink flow passages for supplying the ink filling the ink storage portion
51
to the ink sump
31
.
Then, in the ink jet head
10
of this embodiment, ink from the ink tank is supplied through the filling passage
57
to fill the ink storage portion
51
at the time of initial filling, etc. Further, the ink in the ink storage portion
51
is supplied to the interior of the head chip
20
through the ink sump
31
, that is, to the grooves
23
by way of the common ink chamber
26
a.
After the grooves
23
have been thus filled with ink, there are formed in the ink storage portion
51
an ink region filled with ink and an air region filled with air.
Then, the ink storage portion
51
serves to adjust the pressure of the ink in the common ink chamber
26
a
and the grooves
23
of the head chip
20
. More specifically, when the ink jet head
10
moves in the main scanning direction, the pressure in the head chip
20
changes, which may destroy the meniscus formed in the nozzle openings
22
by the surface tension of the ink. In view of this, the change in the pressure in the head chip
20
is adjusted by the ink storage portion
51
, whereby ink can be ejected while maintaining a stable meniscus. This ink storage portion
51
stores a predetermined amount of ink and gas such as air therein to thereby contribute to bubble storage for preventing bubbles in the ink supply pipe
120
from entering the common ink chamber
26
a.
As shown in
FIG. 8
, in this embodiment, at the center of the damper main body
52
between the above-mentioned supply pipes
58
, there protrudes along the base plate
60
a protrusion
59
in which a communication passage
59
a
communicating with the air region of the ink storage portion
51
is open. This communication passage
59
a
extends behind the recess
53
of the damper main body
52
to communicate with the bottom surface of the recess
53
of the ink storage portion
51
on the opposite side of the filling passage
57
.
Then, in this embodiment, this protrusion
59
and the protruding portion
36
of the flow passage substrate
30
are connected through the connecting tube
200
(See FIG.
1
), whereby the communication passage
59
a
and the discharge hole
35
communicate with each other, forming an air duct
100
which is a piping for establishing communication between the ink sump
31
and the air region of the ink storage portion
51
.
In this embodiment, this air duct
100
establishes communication between a region in the ink sump
31
where there is substantially no interference with the ink flow to the common ink chamber
26
a
and where bubbles are likely to stay and the air region of the ink storage portion
51
.
More specifically, as described above, in the ink jet head
10
of this embodiment, the ink storage portion
51
and the ink sump
31
communicate with each other on either side of the lower portion of the damper main body
52
. Thus, as shown in
FIG. 9
, the ink X having flowed into the ink sump
31
from the ink storage portion
51
through the ink supply passages
33
flows toward the common ink chamber
26
a
along the tapered portions
37
of the ink sump
31
. Thus, upstream side of the ink flow passage positioned between the openings of the ink supply passages
33
of the ink sump
31
constitutes a region substantially free from interference with the ink flow, that is, a region where ink does not flow easily. This region where ink does not easily flow is the region where bubbles Y existing in the ink are easily allowed to stay.
In view of this, in this embodiment, there is provided the air duct
100
which is a piping connecting the region substantially free from interference with the ink flow and the air region of the ink storage portion
51
where the internal pressure is maintained at a fixed level, whereby for example, at the time of initial filling, or cleaning, etc., the bubbles Y in the ink sump
31
pass through the air duct
100
to reach the air region of the air damper
50
, thereby making it possible to efficiently remove the bubbles in the ink sump
31
. In this embodiment, an effect is to be expected which allows removal of bubbles generated in the ink sump
31
even during ink ejection.
Further, in this embodiment, the internal pressure of the air region is maintained at a predetermined value, so that there is no fear of the ink of the ink sump
31
flowing reversely to the ink storage portion
51
through the air duct
100
, and it is possible to selectively introduce the bubbles Y alone from the ink sump
31
to the air region.
Further, by applying a predetermined pressure to the ink from the air damper
50
side, the bubbles in the ink sump
31
are easily gathered substantially at the center of the ink sump
31
, so that it is also possible to introduce the bubbles in the ink sump
31
still more efficiently to the air region through the air duct
100
. As the bubbles in the ink sump
31
are thus introduced to the air region in the ink storage portion
51
, the air region substantially increases. Then, the film-like member
54
absorbs the internal stress inside the ink storage portion
51
, so that it swells outwardly. If it swells excessively, there is a fear of the film-like member
54
bursting to thereby cause the air and ink inside the ink storage portion
51
to leak out. In view of this, it is desirable to provide on the portion of the film-like member
54
on the side opposite to the damper main body
52
a reinforcing plate (not shown) for preventing the film-like member
54
from bursting which has a thickness, for example, of approximately 2 to 3 mm.
As described above, in the ink jet head
10
of this embodiment, it is possible to introduce exclusively the bubbles staying in the ink sump
31
to air region of the air damper
50
through the air duct
100
, so that it is possible to reliably prevent bubbles from staying in the ink sump
31
. As a result, it is possible to reliably prevent shortage in ink supply to the common ink chamber
26
a
and the grooves
23
due to variation in the volume of the ink sump
31
caused by remaining bubbles.
Further, in this embodiment, the air duct
100
communicates with the portion of the ink sump
31
on the upstream side of the ink flow passage of the filter A, whereby it is possible to remove relatively easily and reliably the bubbles which has been impossible to remove even by sucking from the nozzle openings
22
side, so-called cleaning operation.
In this embodiment, the bubbles in the portion of the ink flow passage on the upstream side of the filter A can be removed by the air duct
100
, and the bubbles in the portion of the ink flow passage on the downstream side of the filter A can be removed through cleaning operation, so that it is possible to completely remove the bubbles in the ink sump
31
and the head chip
20
communicating with the ink sump
31
.
In this way, it is possible to reliably prevent bubbles from remaining in the ink sump
31
, so that there is no danger of bubbles remaining in the ink sump at the time of printing passing through the filter A to be ejected together with the ink, thereby reliably preventing a printing failure or the like and achieving an improvement in yield.
Of course, in the ink jet head
10
of this embodiment, even if, for example, the amount of ink ejected per unit time is large or an ink of poor bubble permeability like a water-color ink is used, it is possible to reliably prevent shortage in ink supply to the common ink chamber
26
a
and the grooves
23
, thereby achieving an improvement in terms of stability in ink ejection and reliability.
Here, a serial type ink jet recording apparatus in which the above-described ink jet head
10
is mounted will be described.
FIG. 10
is a schematic perspective view of the ink jet recording apparatus.
As shown in
FIG. 10
, the ink jet recording apparatus is equipped with a plurality of ink jet heads
10
for different colors, a carriage
110
on which the plurality of ink jet heads
10
are arranged side by side in the main scanning direction, and ink cartridges
121
for supplying inks through ink supply tubes
120
consisting of flexible tubes. The carriage
110
is mounted so as to be axially movable on a pair of guide rails
122
a
and
122
b
. At one end of the guide rails
122
a
and
122
b
, there is provided a drive motor
123
, whose driving force is transmitted through a timing belt
125
stretched between a pulley
124
a
connected to the drive motor
123
and a pulley
124
b
provided at the other end of the guide rails
122
a
and
122
b.
Further, at the ends with respect to the direction perpendicular to the direction in which the carriage
110
is conveyed, there are respectively provided pairs of transport rollers
126
and
127
along the guide rails
122
a
and
122
b
, respectively. These transport rollers
126
and
127
serve to transport a recording medium S under the carriage
110
and in the direction perpendicular to the direction in which the carriage
110
is conveyed.
Then, while the recording medium S is transported by the transport rollers
126
and
127
, scanning is performed with the carriage
110
in the direction perpendicular to the transporting direction, whereby characters, images, etc. are recorded on the recording medium S by the ink jet head
10
.
As a result of the movement of the carriage
110
, the pressure of the ink in the head chip
20
of the ink jet head
10
is changed. However, due to the provision of the air damper
50
in the ink jet head
10
, pressure adjustment can be easily effected, thereby making it possible to execute a satisfactory ink ejection.
In this embodiment, four ink jet heads
10
, each of which ejects a monochrome ink, are arranged side by side on the carriage
110
corresponding to the four colors: black (B), yellow (Y), magenta (M), and cyan (C).
Similarly, four ink cartridges
121
for different colors are provided corresponding to the ink jet heads
10
. The ink cartridges
121
are provided at positions where they do not obstruct the movement of the carriage
110
in the main scanning direction and the movement of the recording medium S, and at positions lower than the nozzle openings
22
of the ink jet heads
10
by a predetermined distance so that negative pressure may be created in the ink jet heads
10
.
Although not shown, the ink jet recording apparatus is provided with a suction unit for use in a so-called cleaning operation, in which ink is sucked from the nozzle openings
22
. By this suction means, the ink in the common ink chamber
26
a
and the grooves
23
is sucked from the nozzle openings
22
side with a predetermined timing, whereby it is possible to reliably remove the bubbles existing in the ink in the common ink chamber
26
a
and the grooves
23
, thereby making it possible to consistently maintain a satisfactory print quality.
While this embodiment has been described as applied to an ink jet recording apparatus on which ink cartridges
121
for four colors are mounted, this should not be construed restrictively. It is also applicable to an ink jet recording apparatus on which ink cartridges for five to eight colors are mounted.
Other Embodiments
The ink jet head and the ink jet recording apparatus of the present invention are not restricted to Embodiment 1 described above.
For example, while the ink jet head
10
of Embodiment 1 has the air duct
100
for establishing communication between the ink sump
31
and the air region of the air damper
50
, there is no particular restriction regarding the air duct as long as it is provided so as to communicate with an air region existing in the ink flow passage between the ink storage unit such as the ink tank and air damper and the ink sump.
For example, in the case of a so-called line type ink jet recording apparatus in which the ink jet head is stationary, ink is directly supplied to the head chip from the ink tank, etc. Thus, a line type ink jet head has no air damper. Accordingly, in such a case, there is provided an air duct communicating with the air region of the ink tank. This construction provides the same effect as that of the above-described embodiment.
While the ink jet head
10
of Embodiment 1 has an ink supply passage
33
on either side of the flow passage substrate
30
with respect to the width direction, and the air duct
100
is provided between the ink supply passages
33
, this should not be construed restrictively. It is also possible to provide an air duct
100
on either side of the flow passage substrate
30
with respect to the width direction and to provide the ink supply passage
33
between the air ducts
100
. It is desirable for the air duct to be provided in a region substantially spaced apart from the opening of the ink supply passage of the ink sump. This is because a region spaced apart from the opening of the ink supply passage constitutes a region which is substantially free from interference with the ink flow in the ink sump and in which bubbles are easily gathered.
While in the above-mentioned Embodiment 1 the ink supply passages
33
and the discharge hole
35
are substantially parallel to each other, this should not be construed restrictively. It is only necessary for the discharge hole to be provided so as to communicate with a region substantially free from interference with the ink flow in the ink sump; its position is appropriately determined according to the positions of the ink supply passages.
Further, while in the above-mentioned Embodiment 1 the tapered portions
37
are respectively provided so as to extend from the openings of the ink supply passages
33
of the ink sump
31
and the air duct
100
toward the common ink chamber
26
a
, this should not be construed restrictively. It is also possible to provide a tapered portion in only either the ink supply passages or the air duct, or it is naturally also possible to provide none.
In any case, there is no particular restriction regarding the air duct as long as the ink jet head can be provided with an air duct for introducing exclusively bubbles to the air region, which is substantially free from interference with the ink flow in the ink sump and in which bubbles are easily gathered.
While the ink jet head of the present invention proves excellent when used with an ink with poor permeability, that is, an ink subject to generation of bubbles, it is naturally also applicable to inks of other kinds. Further, while the present invention is particularly effective for a large ink jet head ejecting a large amount of ink, it is naturally also applicable to a small ink jet head.
As described above, in accordance with the present invention, there is provided in the ink jet head an air duct establishing communication between a region which is substantially free from interference with the ink flow in the ink sump from the ink supply passage to the ink chamber and in which bubbles gather easily and the air region of the ink storage unit, whereby it is possible to reliably prevent the bubbles in the ink from remaining in the ink sump and the head chip, and the bubbles can be removed relatively easily.
Claims
- 1. An ink jet head comprising: a plurality of grooves arranged side by side so as to communicate with nozzle openings; an ink chamber for supplying ink to each of the grooves; an ink sump provided so as to communicate with the ink chamber; and ink storage means communicating with the ink sump through ink supply passages,wherein there is provided an air duct establishing communication between a region in the ink sump which is substantially free from interference with an ink flow from the ink supply passages to the ink chamber and in which bubbles easily gather and an air region of the ink storage means.
- 2. An ink jet head according to claim 1, wherein the ink chamber is provided so as to extend over the direction in which the grooves are arranged side by side, wherein the ink chamber and the ink sump communicate with each other over the direction in which the grooves are arranged side by side, wherein the ink supply passages are provided on both sides of the ink sump with respect to the direction in which the grooves are arranged side by side, and wherein the air duct is provided between the ink supply passages.
- 3. An ink jet head according to claim 1, wherein the ink sump is equipped with a tapered portion gradually diverging from at least one of the openings of the ink supply passages and the air duct toward the ink chamber.
- 4. An ink jet head according to claim 1, wherein the ink sump is equipped with a filter situated in the vicinity of the border between the ink sump and the ink chamber.
- 5. An ink jet head according to claim 4, wherein the air duct communicates with the portion of the ink flow passage which is on the upstream side of the filter of the ink sump.
- 6. An ink jet recording apparatus equipped with an ink jet head as claimed in claim 1.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2002-181955 |
Jun 2002 |
JP |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
404241949 |
Aug 1992 |
JP |