BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to an ink jet print head which jets out ink from an
ink jet port to thereby form an image on a recording medium, an on-demand type of
ink jet printer including such ink jet print head, and a maintenance method for maintaining
such ink jet print head.
2. Description of the Related Art
[0002] Conventionally, as a typical ink jet printer, there are known an ink jet printer
using an ink jet print head of a piezoelectric type that a pressure chamber is mechanically
deformed by means of piezoelectric material and the resultant pressure is used to
jet out ink from its ink jet port, and an ink jet printer using a thermal ink jet
print head structured such that a heater disposed in an ink flow passage is electrically
energized to vaporize ink and the pressure of the vaporized ink is used to jet out
ink from its ink jet port.
[0003] The ink jet printers has been developed to increase the number of nozzles which are
used to jet out ink in order to improve the quality of a printed image and increase
the printing speed thereof. However, if the number of nozzles is increased, then there
is increased the pressure that is transmitted from a pressure generation source to
a common ink chamber with which a plurality of nozzles are in communication in common.
Such increased pressure causes an unstable ink jetting condition, or impedes the ink
supply to thereby make it impossible to jet out ink.
[0004] Now, Fig. 19 is a graphical representation which shows an example of pressure variations
in a common ink chamber used in a conventional ink jet printer. For example, if printing
a pattern having a high coverage is started, then pressure for jetting out ink is
generated in all of the nozzles. The pressures generated in the respective nozzles
are all transmitted to the common ink chamber and, therefore, as a whole, a large
pressure is temporarily applied from the nozzles to the common ink chamber. After
then, in order to carry out next printing, ink is supplied from the common ink chamber
to the nozzles. In such ink supply, due to the flow of the ink, pressure is applied
from the common ink chamber to the nozzles. In this manner, the pressure within the
common ink chamber, as shown in Fig. 19, is caused to vibrate or vary due to the inertia
of the ink. Such pressure variations reach as much as 400 mmH
2O (400x9.8Pa) under the worst condition. These pressure variations cause not only
the pressure within the nozzles at the respective printing timings but also the amount
of ink supplied to vary, which in turn causes the ink jetting condition to become
unstable.
[0005] Figs. 20A and 20B are explanatory views of a printed state of the conventional ink
jet printer obtained when the image quality thereof is poor. If printing is carried
out in such an unstable jetting condition as mentioned above, for example, when a
large pressure is applied in a direction to go from the common ink chamber to the
nozzles, as shown in Fig. 20A, not only dots are printed by normal ink droplets, but
also there occurs a phenomenon that small ink droplets are jetted at a timing different
from the normal print timing to thereby increase the density of the printed dots partially.
Especially, just as the negative pressure within the common ink chamber reaches its
peak, a shortage of ink supply occurs and, for this reason, no ink can be jetted out
from the nozzles, with the result that there is produced such an unprinted (missing)
portion as shown in Fig. 20B.
[0006] In order to solve such problem, for example, in Unexamined Japanese Patent Publication
(kokai) No. Sho. 63-128947, there is disclosed a structure in which a damper chamber
having an air layer is formed in an ink supply passage. That is, when the pressure
is transmitted to the common ink chamber, the pressure advances to the damper chamber
and is then relieved by the air layer of the damper chamber. This can reduce variations
in the pressure of the interior of the common ink chamber to thereby stabilize the
ink jetting condition. However, in this structure, since the opening of the damper
chamber is so formed as to face a position where the ink flows violently, the flow
of the ink is easy to be produced within the damper chamber, which causes the air
within the damper chamber to flow out gradually into the common ink chamber. Consequently,
the function of the damper chamber is lowered.
[0007] Also, for example, in Unexamined Japanese Patent Publication (kokai) No. Hei. 6-344558,
in the rear of a common ink chamber, there is provided an air chamber which is in
communication with the common ink chamber. In the structure disclosed in this publication,
because the communicating portion between the common ink chamber and air chamber is
narrow and the air chamber is wide, it is possible to prevent the outflow of the air
from the air chamber due to the inflow of the ink to the air chamber. This in turn
makes it possible to keep up a pressure relieving function. However, in this structure,
since the air chamber is provided in a second substrate in which the common ink chamber
is formed, a print head is increased in size by an amount corresponding thereto.
[0008] Further, Unexamined Japanese Patent Publication (kokai) No. Hei. 1-308644 discloses
that a pressure-volume converter is provided within an ink chamber. In this structure,
since no air is used, there can be obtained a stable pressure relieving function.
However, use of a new part, that is, the pressure-volume converter, increases not
only the number of steps to produce it but also the cost thereof.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide an ink jet printer and an ink
jet print head which can jet out ink always stably without increasing the size of
the print head or using a new part or the like, and also provide, in such ink jet
print head, a maintenance method for maintaining the ink jet print head in such a
manner that ink can be always jetted out stably.
[0010] In the present invention, an ink jet print head for jetting out ink from a plurality
of nozzles to thereby form an image, is comprised of: a plurality of energy generator
for causing the ink to be jetted out from the nozzles; a plurality of ink flow passages
respectively which is disposed to individually correspond to the energy generator
for supplying ink to the energy generator; an ink jet head including an ink reservoir
with which the plurality of ink flow passages communicate in common; and an ink supply
member including an ink supply passage for supplying ink to the ink reservoir of the
ink jet head, the ink supply member further including a plurality of gas hold portions
which are respectively in communication with only the ink reservoir and are respectively
capable of holding gas therein.
[0011] According to the present invention, due to the compression/expansion of gas to be
held within a plurality of gas hold portions, pressure transmission within an ink
tank and a common reservoir due to the flow of ink in printing can be controlled,
so that ink can be always jetted out stably, and thus high image quality can be realized
without producing unprinted area or density variations. Also, since the gas hold portions
are respectively in communication with the portions of the common reservoir where
ink flows only a little, there is eliminated the possibility that the gas within the
gas hold portions can be made to flow out therefrom due to the flow of the ink, which
can always realize a stable pressure adjust function. Further, because the gas hold
portions are formed in the ink supply member, no new parts are necessary and the ink
jet print head can be manufactured with no special process, while the size of the
print head remains unchanged.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In the accompanying drawings:
Fig. 1 is a perspective view of an embodiment of an ink jet print head according to
the invention;
Fig. 2 is a section view of the embodiment of an ink jet print head according to the
invention, taken along the line A-A' shown in Fig. 1;
Fig. 3 is a section view of the embodiment of an ink jet print head according to the
invention, taken along the line B-B' shown in Fig. 1;
Fig. 4 is a section view of the embodiment of an ink jet print head according to the
invention, taken along the line D-D' shown in Fig. 1;
Fig. 5 is a section view of the embodiment of an ink jet print head according to the
invention, taken along the line C-C' shown in Fig. 1;
Fig. 6 is a graphical representation of an example of pressure variations generated
in a common reservoir employed in the embodiment of an ink jet print head according
to the invention;
Fig. 7 is a section view of a first modification of the embodiment of an ink jet print
head according to the invention, taken along the line B-B' shown in Fig. 1;
Fig. 8 is a section view of the first modification of the embodiment of an ink jet
print head according to the invention, taken along the line D-D' shown in Fig. 1;
Fig. 9 is a section view of a second modification of the embodiment of an ink jet
print head according to the invention, taken along the line B-B' shown in Fig. 1;
Fig. 10 is a section view of the second modification of the embodiment of an ink jet
print head according to the invention, taken along the line D-D' shown in Fig. 1;
Fig. 11 is a section view of a third modification of the embodiment of an ink jet
print head according to the invention, taken along the line B-B' shown in Fig. 1;
Fig. 12 is a section view of the third modification of the embodiment of an ink jet
print head according to the invention, taken along the line D-D' shown in Fig. 1;
Fig. 13 is a section view of a fourth modification of the embodiment of an ink jet
print head according to the invention, taken along the line B-B' shown in Fig. 1;
Fig. 14 is a section view of the fourth modification of the embodiment of an ink jet
print head according to the invention, taken along the line D-D' shown in Fig. 1;
Fig. 15 is an explanatory view of a concrete experiment conducted in connection with
the embodiment of an ink jet print head according to the invention;
Fig. 16 is an explanatory view of the position and shape of gas hold portions formed
in an ink jet print head, that is, head No. 1 used in the experiment;
Fig. 17 is an explanatory view of the position and shape of gas hold portions formed
in an ink jet print head, that is, head No. 2 used in the experiment.
Fig. 18 is an explanatory view of the position and shape of gas hold portions formed
in an ink jet print head, that is, head No. 3 used in the experiment;
Fig. 19 is a graphical representation of an example of pressure variations generated
in a common reservoir in a conventional ink jet printer; and,
Figs. 20A and 20B are explanatory views of a printed condition of poor image quality
in the conventional in the conventional ink jet printer.
PREFERRED EMBODIMENTS OF THE INVENTION
[0013] Preferred embodiments of the present invention will be described as follows referring
to the accompanying drawings.
[0014] Now, in Figs. 1 to 5, there is shown an embodiment of an ink jet print head according
to the invention. In particular, Fig. 1 is a perspective view, Fig. 2 is a section
view taken along the line A-A', Fig. 3 is a section view taken along the line B-B',
Fig. 4 is a section view taken along the line D-D', and Fig. 5 is a section view taken
along the line C-C'. In the drawings, reference numeral 1 designates a heater substrate;
2, a channel substrate; 3, a nozzle; 4, a heating element; 5, an ink flow passage;
6, a common reservoir; 7, recessed portions; 11, an ink supply member; 12, an ink
supply passage; and 13, a gas hold portion.
[0015] The channel substrate 2 includes a plurality of ink flow passages 5 which are respectively
so formed as to correspond to a plurality of nozzles 3, and further includes the common
reservoir 6 which is so provided as to communicate in common with the ink flow passages
5. The common reservoir 6 is formed to extend through the channel plate 2. In the
present embodiment, a single common reservoir 6 is formed to communicate in common
with all of the ink flow passages 5. However, this is not limitative but, instead
of a single common reservoir 6, a plurality of common reservoirs may also be formed.
[0016] On the other hand, in the heater substrate 1, a plurality of heating elements 4 are
provided to respectively correspond to the ink flow passages 5, and as shown in Figs.
2 and 3, a plurality of recessed portions 7 are formed to respectively extend from
the upper portions of the heating elements 4 to communicate the ink flow passages
5 with common reservoir 6. Each of the recessed portions 7, as shown in Fig. 5, is
formed narrow in part and the wall surface of the recessed portion 7 on the common
reservoir 6 side thereof is formed in an arc shape. Such shape of the recessed portion
7 makes it difficult to transmit the pressure generated on the heating element 4 to
the common reservoir 6.
[0017] When the heater substrate 1 and channel substrate 2 are bonded to each other, a flow
passage for ink extending from the common reservoir 6 through the recessed portions
7 to the ink flow passages 5 is formed. Actually, the heater substrate 1 and channel
substrate 2 are respectively provided in large number on a wafer and are bonded to
each other and, thereafter, they are separated by dicing or the like. While they are
bonded, the end portions of the ink flow passages 5 and the through opening of the
common reservoir 6 are exposed. In this state, the end portions of the ink flow passages
5 respectively provide the nozzles 3.
[0018] The ink supply member 11 is mounted on the through opening of the common reservoir
6. In the ink supply member 11, an ink supply passage 12 and a plurality of gas hold
portion 13 are formed. The ink supply passage 12 is used to supply ink from an ink
tank (not shown) to the common reservoir 6, and a plurality of gas hold portions 13
are respectively capable of holding gas therein. Each of the gas hold portions 13,
as shown in Fig. 3, is formed in a substantially circular hole which is in communication
with only the common reservoir 6 but does not extend through the ink supply member
11. After ink is charged, variations in the pressure within the common reservoir 6
can be relieved by the gas retained within the gas hold portions 13. Actually, as
shown in Fig. 4, such gas hold portions 13 are arranged at almost equal intervals
together with the ink supply passage 12. Since the gas hold portions 13 can be formed
together with the ink supply passage 12 when the ink supply member 11 is molded, there
is no possibility that formation of the gas hold portions 13 can complicate the manufacturing
process of the ink jet print head.
[0019] Ink is guided from an ink tank (not shown) through the ink supply passages 12 in
the ink supply member 11 to the common reservoir 6. The ink that is guided to the
common reservoir 6 is charged into the common reservoir 6 as well as the respective
ink flow passages 5 are filled with the thus charged ink. In this state, since the
ink is pulled simultaneously by not only a negative pressure generated within the
ink tank but also a surface tension which is generated in the interfaces of the ink
in the respective ink flow passages 5, there is no possibility that the ink can leak
while printing is not in operation. Also, when the ink is fully loaded into the common
reservoir 6, gas is retained within the respective gas hold portions 13.
[0020] After then, a maintenance operation is carried out to stabilize the respective parts
of the ink jet print head. In particular, the maintenance operation is carried out
after the initial loading of the ink, or after ink is replaced, or after an ink suction
maintenance operation is executed when trouble occurs. As a concrete maintenance operation,
for example, after the ink jet print head is heated to, for example, about 60°C, ink
is sucked from the nozzle 3 side. In response to such ink suction, gas held within
the gas hold portions 13 is expanded as the temperature rises. Then, since the amount
of the gas that is expanded due to the temperature rising is discharged into the common
reservoir 6, the thus discharged gas is then discharged externally by means of suction
of the ink. After this maintenance operation is carried out, even if the temperature
of the ink jet print head rises in actual use, the gas held within the gas hold portions
13 is prevented from being discharged into the common reservoir 6, so that printing
can be always executed stably. That is, execution of such maintenance operation makes
it possible to keep an effect that the variations in the pressure within the common
reservoir can be restricted more positively.
[0021] While printing, the heating elements 4 which are respectively disposed in the ink
flow passages 5 corresponding to the respective nozzles 3 from which ink is jetted
out are electrically energized so as to be heated. As a result, due to the pressure
of the thus generated air bubbles, the ink is jetted out from the nozzles 3 and is
flown onto a recording medium to execute recording. During this operation, the pressure
of the air bubbles is also transmitted to the rear portion of the recessed portion
7 and is further transmitted to the common reservoir 6. The pressure is a force which
goes in a direction from the ink flow passages 5 to the common reservoir 6. After
then, the air bubbles are extinguished as well as the ink is in short supply on the
heating elements 4. Therefore, a force in a direction from the common reservoir 6
to the ink flow passages 5 is applied, so that ink is supplied from the common reservoir
6 to the ink flow passages 5.
[0022] As described above, during a short period of time from the growth to the extinction
of the air bubbles, two kinds of forces which their directions oppose to each other
are generated. For this reason, in the conventional ink jet print head having no air
bubbles (gas) hold portions 13, as described above, pressure variations shown in Fig.
13 occurs to thereby cause the poor ink jetting or the like. In the present invention,
the pressure which is transmitted to the common reservoir 6 when the air bubbles grow
is transmitted to the gas hold portion 13 to compress the gas in the gas hold portion
13. Accordingly, the transmitted pressure can be relieved. Also, when the air bubbles
are extinguished, the gas within the gas hold portions 13 is expanded to thereby be
able to relieve an increase in the negative pressure due to the sudden shortage of
ink. In this manner, the gas hold portions 13 function so as to reduce the pressure
variations within the common reservoir 6 as much as possible.
[0023] Also, when ink is supplied, the ink flows in a direction from the ink supply passages
12 to the recessed portions 7 corresponding to the respective ink flow passages 5.
Therefore, a position where the gas hold portion 13 communicates with the common reservoir
6 is a portion where ink flow a little. This makes it possible to restrict the outflow
of the gas within the gas hold-portions 13 due to the flow of the ink which occurs
in the conventional print head. Accordingly, the pressure variations within the common
reservoir 6 can be controlled stably.
[0024] Fig. 6 is a graphical representation to show an example of the pressure variations
produced in the common reservoir employed in the above embodiment of an ink jet print
head according to the present invention. As described above, according to the present
embodiment, since the pressure variations within the common reservoir 6 can be restricted
by the gas hold portions 13, even when printing is executed under the same condition
as the case shown in Fig. 13, as shown in Fig. 6, there cannot be found large pressure
variations and thus the printing can also be executed normally.
[0025] Now, in Figs. 7 and 8, there is shown a first modification of the above embodiment
of the ink jet print head according to the invention. In particular, Fig. 7 is a section
view taken along the line B-B' shown in Fig. 1, and Fig. 8 is a section view taken
along the line D-D' shown in Fig. 1. In the present modification, the section area
of the gas hold portion 13 is increased. If the section area of the gas hold portion
13 is increased in this manner, then the volume of the gas hold portion 13 can be
increased and thus the amount of gas to be held within the gas hold portion 13 can
be increased. This makes it possible to increase the function to restrict the variations
in the pressure within the common reservoir 6. Also, when a sufficient length cannot
be secured in the gas hold portion 13, if the section area of the gas hold portion
13 is increased in this manner, then the amount of the gas to be held within the gas
hold portion 13 can be secured.
[0026] Now, Figs. 9 and 10 show a second modification of the above embodiment of the ink
jet print head according to the invention. In particular, Fig. 9 is a section view
taken along the line B-B' shown in Fig. 1, and Fig. 10 is a section view taken along
the line D-D' shown in Fig. 1. In the present modification, the position of each of
the gas hold portions 13 is displaced. In this structure, since the section areas
of the communication portions between the respective gas hold portions 13 and the
common reservoir 6 are reduced, it is possible to further restrict the inflow of the
ink to the gas hold portions 13 as well as the outflow of the gas therefrom, which
in turn makes it possible to restrict the pressure variations within the common reservoir
6 more stably. Also, in the present modification, since the position of each gas hold
portion 13 is displaced on the opposite side to its corresponding nozzle 3, for example,
even in a ink jet printer of a type that the nozzle 3 faces downward and ink droplets
are flown downward, the gas within the gas hold portion 13 is prevented from flowing
out therefrom and the pressure variations within the common reservoir 6 can be restricted
properly.
[0027] Figs. 11 and 12 show a third modification of the above embodiment of the ink jet
print head of the invention. In particular, Fig. 11 is a section view taken along
the line B-B' shown in Fig. 1, and Fig. 12 is a section view taken along the line
D-D' shown in Fig. 1. In the present modification, each of the gas hold portions 13
is formed to extend obliquely backward. In the present modification, since the gas
is held within the gas hold portion 13 starting at the deepest portion of the gas
hold portion 13, even if the ink droplets are jetted in a horizontal direction, or
the ink droplets are jetted downward, it can be prevented that the gas within the
gas hold portion 13 is replaced by the ink.
[0028] Fig. 13 is a section view taken along the line B-B' shown in Fig. 1, and shows a
fourth modification of the above embodiment of the ink jet print head of the invention.
In the present modification, in the surface of the ink supply member 11, a groove
which serves as the gas hold portion 13 is formed and the ink supply member 11 is
bonded to the channel substrate 2. In this case, one surface of the gas hold portion
13 provides the surface of the channel substrate 2. The present modification is effective
especially when the ink droplets are jetted out downward. In the present modification,
since the surface of the channel substrate 2 is used as part of the gas hold portion
13, the channel substrate 2 requires a length which extends backwardly of the common
reservoir 6, and also the bonded portion must be airtight. As a further modification
of the fourth modification, if possible, the gas hold portion 13 can be formed to
be bent in the ink supply member 11.
[0029] Fig. 14 is a section view taken along the line D-D' shown in Fig. 1 and shows a fifth
modification of the above embodiment of the ink jet print head of the invention. In
the present modification, the gas hold portion 13 has a section shape which extends
along an opening formed in the common reservoir 6. That is, since the area of the
communication portion between the gas hold portion 13 and the common reservoir 6 is
increased, the pressure that is transmitted to the interior of the common reservoir
6 can be received in a wide range and can be thereby dampened. Also, since the capacity
of the gas hold portion 13 can be increased, the effect to restrict the pressure variations
within the common reservoir 6 can be enhanced. However, if the pressure receive area
is increased excessively, there is expected a possibility that such wide area cause
the flow of the ink and thus the air bubbles within the gas hold portion 13 can flow
out into the common reservoir 6. That is, it is necessary to set the pressure receive
area in a proper area.
[0030] According to the present invention, in addition to the above-mentioned embodiment
and the modifications thereof, there are also available other various modifications.
For example, although the section shape of the gas bold portion 13 is formed circular
or elliptic in the above embodiment and modifications thereof, the gas hold portion
13 can also be formed in other shape, for example, it may be formed in a rectangular
shape or in a triangular shape. Also, the shape and position of the gas hold portion
13 can be set freely, provided that they extend along the opening of the common reservoir
6. Further, it is also possible to combine together two or more of the above-mentioned
embodiment and modifications thereof.
[0031] Also, in the above-mentioned embodiment and modifications thereof, there is shown
an ink jet print head including a flow passage structure which communicates the ink
flow passages 5 with the common reservoir 6 by means of the recessed portions 7. However,
the invention is not limited to this flow passage structure but, for example, it is
also possible to employ other various flow passage structures such as a structure
including a common slit formed in part thereof or the like, provided that the ink
jet print head includes the common reservoir 6.
[0032] Further, if the above-mentioned type of ink jet print head is incorporated into a
printer, it is possible to structure an ink jet printer which can prevent unprinted
(missing) areas or density variations to thereby be able to obtain printed images
of high quality.
EXAMPLES
[0033] Fig. 15 is an explanatory view of Examples which was conducted in connection with
the above embodiment of an ink jet print head according to the invention. Also, Figs.
16 to 18 are explanatory views of the positions and shapes of gas hold portions provided
in the examples. In the Examples, an ink jet print head was used in which 125 pieces
of nozzles were arranged, and the capacity of the ink droplets to be jetted out from
each of the nozzles was 80 pl, while the ink jet print head was driven at a print
frequency of 7 KHz. The maximum flow amount of ink in rush print was 125 x 80 pl x
7 KHz = 0.07 cc/sec. = 70 mm
3/sec. Also, the through opening of the common reservoir 6 had a width of 0.5 mm and
a length of 10.4 mm. In Fig. 15, there are shown the amounts of gas per ink jet amount
which are respectively obtained when the total amounts of gas within a plurality of
gas hold portions 13 are divided by the maximum flow amount of ink. Also, head numbers
in Fig. 15 identify the ink jet print heads that are employed in the Examples.
[0034] An ink jet print head designated by the head No. 0 represents a conventional head
in which the gas hold portion 13 is not provided. In this head, as described above,
there were produced such density variations or unprinted area as shown in Fig. 20.
[0035] An ink jet print head, head No. 1, is an ink jet print head in which there are formed
four gas hold portions 13 each having a diameter of 0.4 mm and a depth of 2 mm. In
this ink jet print head, as shown in Fig. 16, the gas hold portions 13 are formed
two in the neighborhood of each of the two ends of the through opening of the common
reservoir 6. In this print head, although there were not found such density variations
or unprinted area as in the head No. 0, slight density variations were generated in
the neighborhood of the central portion of the present print head in which no gas
hold portion 13 is formed.
[0036] An ink jet print head, head No. 2, is an ink jet print head in which there are formed
eight gas hold portions 13 each having a diameter of 0.4 mm and a depth of 2 mm. In
this print head, as shown in Fig. 17, the eight gas hold portions 13 are arranged
almost uniformly in the through opening of the common reservoir 6. In this case, no
unprinted area or density variations were produced but excellent image quality could
be obtained.
[0037] As can be understood from comparison of the printed results of the ink jet print
heads, head Nos. 0 to 2, by forming the gas hold portion 13, it is possible to reduce
the unprinted area or density variations that have been generated in the prior art
print heads. Also, comparison between the print heads, head Nos. 1 and 2, shows that,
if the gas hold portions 13 are arranged almost uniformly in the through opening of
the common reservoir 6, then the unprinted area or density variations can be eliminated
over the whole head width and thus excellent image quality can be obtained.
[0038] An ink jet print head, head No. 3, is an ink jet print head in which six gas hold
portions are formed, each gas hold portion having a diameter of 0.7 mm and a depth
of 2 mm. The present ink jet print head corresponds to the above-mentioned first modification
of the embodiment of the invention and, as shown in Fig. 18, the six gas hold portions
13 each having a diameter larger than the width of the common reservoir 6 are arranged
almost uniformly in the through opening of the common reservoir 6. In this case as
well, no unprinted area or density variations were generated but fine image quality
could be obtained.
[0039] An ink jet print head, head No. 4, is an ink jet print head in which eight gas hold
portions each having a diameter of 0.5 mm and a depth of 2 mm are formed, while they
are inclined at an angle of 30°C. The present ink jet print head corresponds to the
above-mentioned third modification of the embodiment of the invention. In this case
as well, no unprinted area or density variations were generated but fine image quality
could be obtained.
[0040] That is, it can be understood that, according to the above-mentioned various modifications
of the embodimentof the invention as well, the unprinted area or density variations
can be eliminated but good image quality can be obtained.
[0041] Head Nos. 5 to 7 respectively show the results that were obtained when the amounts
of gas retained within the gas hold portions 13 of the ink jet print head, head No.
3, were adjusted and the variations thereof were then examined. In particular, in
the head No. 5, the interior of the print head No. 3 is made to produce a vacuum therein
and ink is then loaded into the vacuum print head, while the total amount of gas retained
in the respective gas hold portions 13 is 0.415 mm
3. In the head No. 6, after the gas within the print head is sucked a little, ink is
loaded into the print head, while the total amount of gas retained in the respective
gas hold portions 13 is 2.05 mm
3. In the head No. 7, after the gas within the print head is sucked slightly, ink is
loaded into the print head, while the total amount of gas retained in the respective
gas hold portions 13 is 3.39 mm
3. As the result of this experiment, in the head No. 5, there was generated slight
density variations, whereas in the heads No. 6 and 7, neither the unprinted area nor
density variations were produced but good image quality could be obtained. This shows
that, when gas is little present within the gas hold portions 13, similarly to the
conventional structure in which no gas hold portion 13 is formed, the density variations
or the like are generated, whereas, if a certain amount of gas is held within the
gas hold portions 13, the density variations or the like are not generated.
[0042] In the head No. 8, similarly to the head Nos. 5 to 7, after the ink jet print head
No. 2 is made to produce a vacuum therein, ink is loaded into the vacuous print head,
while the total amount of gas retained within the respective gas hold portions 13
is 0.0025 mm
3. In this case, that is, in a condition that gas is little present within the gas
hold portions 13, similarly to the conventional print head in which no gas hold portion
13 is formed, the density variations were generated.
[0043] From the results of the above experiment, it can be found that, if the gas hold portions
13 are formed within the print head and gas is held within the gas hold portions 13,
then generation of undesirable phenomena such as the unprinted area, density variations
and the like can be prevented and thus excellent image quality can be obtained. Also,
referring to the amount of gas to be held within the gas hold portions 13, in view
of the fact that, when it was 0.014 mm
3 per ink jet amount 1 mm
3/sec. for each unit time, there were produced slight density variations, if the gas
is held in an amount of 0.015 mm
3 or more, it can be expected that good image quality can be obtained.
1. An ink jet print head for jetting out ink from a plurality of nozzles to thereby form
an image, comprising:
a plurality of energy generating means for causing said ink to be jetted out from
said nozzles;
a plurality of ink flow passages respectively which is disposed to individually correspond
to said energy generating means for supplying ink to said energy generating means;
an ink jet head including an ink reservoir with which said plurality of ink flow passages
communicate in common; and
an ink supply member including an ink supply passage for supplying ink to said ink
reservoir of said ink jet head, said ink supply member further including a plurality
of gas hold portions which are respectively in communication with only said ink reservoir
and are respectively capable of holding gas therein.
2. An ink jet print head according to claim 1, wherein each of said gas hold portions
has a substantially circular section.
3. An ink jet print head according to claim 1, wherein said plurality of gas hold portions
are arranged at substantially equal intervals in a direction where said ink flow passages
are arranged.
4. An ink jet print head according to claim 1, wherein a total volume of said gas hold
portions is 0.015 mm3 or more per ink amount 1 mm3/sec. to be jetted out by said energy generating means.
5. An ink jet print head according to claim 1, wherein
an area of a communication portion where each of said gas hold portions is directly
connected with said ink reservoir is smaller than a section area of a surface of said
gas hold portion facing said ink reservoir.
6. An ink jet print head for jetting out ink from nozzles by means of the pressure of
thermally generated bubbles to thereby form an image, comprising:
a first substrate including a plurality of heating resistors for generating heat in
order to cause said bubbles;
a second substrate disposed opposed to said first substrate, said second substrate
including a plurality of channels for supplying ink onto said heating resistors and
a common ink reservoir communicating in common with said plurality of channels; and
an ink supply member including an ink supply passage for supplying ink to said common
ink reservoir and a plurality of air hold chambers respectively capable of holding
air therein and communicating with only said common ink reservoir.
7. An ink jet printer comprising an ink jet print head for jetting out ink from nozzles
by means of the pressure of thermally generated bubbles to thereby form an image,
said ink jet print head comprising:
a plurality of energy generating means for causing said ink to be jetted out from
said nozzles;
a plurality of ink flow passages respectively which is disposed to individually correspond
to said energy generating means for supplying ink to said energy generating means;
an ink jet head including an ink reservoir with which said plurality of ink flow passages
communicate in common; and
an ink supply member including an ink supply passage for supplying ink to said ink
reservoir of said ink jet head, said ink supply member further including a plurality
of gas hold portions which are respectively in communication with only said ink reservoir
and are respectively capable of holding gas therein.
8. An ink jet printer according to claim 7, wherein each of said gas hold portions has
a substantially circular section.
9. An ink jet printer according to claim 7, wherein said plurality of gas hold portions
are arranged at substantially equal intervals in a direction where said ink flow passages
are arranged.
10. An ink jet printer according to claim 7, wherein a total volume of said gas hold portions
is 0.015 mm3 or more per ink amount 1 mm3/sec. to be jetted out by said energy generating means.
11. An ink jet printer according to claim 7, wherein an area of a communication portion
where each of said gas hold portions is directly connected with said ink reservoir
is smaller than a section area of a surface of said gas hold portion facing said ink
reservoir.
12. An ink jet printer comprising an ink jet print head for jetting out ink from nozzles
by means of the pressure of thermally generated bubbles to thereby form an image,
said ink jet print head comprising:
a first substrate including a plurality of heating resistors for generating heat in
order to cause said bubbles;
a second substrate disposed opposed to said first substrate, said second substrate
including a plurality of channels for supplying ink onto said heating resistors and
a common ink reservoir communicating in common with said plurality of channels; and
an ink supply member including an ink supply passage for supplying ink to said common
ink reservoir and a plurality of air hold chambers respectively capable of holding
air therein and communicating with only said common ink reservoir.
13. A maintenance method for maintaining an ink jet print head, in which pressure is generated
by a pressure generating source, ink is jetted out from an ink jet port due to the
thus generated pressure, and pressure vibrations transmitted from said pressure generating
source are absorbed by air chambers, wherein:
after ink is filled initially, after ink is replaced, or after ink is sucked, the
temperature of said ink jet print head is raised and ink is then sucked from said
ink jet port.