Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2000-08-21
2002-06-11
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S065000
Reexamination Certificate
active
06402311
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording head in which a bubble is generated by heating ink by means of an electrothermal converting element and the ink is discharged by pressure upon generation of the bubble, an ink jet recording head cartridge in which such an ink jet recording head and a liquid container for supplying liquid to the ink jet recording head are integrally formed, and an ink jet recording apparatus to which such an ink jet recording head cartridge is mounted.
2. Related Background Art
Almost all of ink jet recording apparatuses have been used as a printing apparatus in an image forming apparatus such as a printer, a facsimile, a word processor, a copying machine and the like. Among them, an ink jet recording apparatus of type in which thermal energy is used as energy utilized for discharging the ink and the bubble is generated in the ink by the thermal energy and the ink is discharged by change in volume upon generation of the bubble has recently been spread.
Further, as another application of the ink jet recording apparatus of this kind, an ink jet print device for printing a predetermined pattern, a design or a composite image on cloth has recently been known. An ink jet recording head used in the above-mentioned ink jet recording heads utilizes electrothermal converting elements (referred to also as “heaters” hereinafter) as means for generating the energy, and, in many cases, one heater corresponds to one discharge port.
To the contrary, an ink jet recording head in which a plurality of heaters are provided with respect to each of discharge ports for the following reasons has also been known.
That is to say, firstly, in order to extend the service life of the ink jet recording head, the plurality of heaters are driven alternately or the heater to be driven is appropriately switched. Secondly, by changing an ink discharged amount by selecting the heater or heaters to be driven, the change in ink discharged amount is realized.
As a concrete construction of the latter, an arrangement in which a plurality of heaters are disposed in each ink flow path (nozzle) communicated with a corresponding ink discharge port of the ink jet recording head along an ink discharging direction so that the ink discharged amount is changed due to the difference in distance between the driven heater and the associated discharge port by selecting the heater to be driven (heated) or the ink discharged amount is changed by changing the number of heaters to be driven has been known.
Further, as another construction, for example, as disclosed in Japanese Patent Application Laid-open No. 55-132259, an arrangement in which a plurality of heaters having different surface areas are disposed in each ink flow path so that the ink discharged amount is changed by similarly changing the heater to be driven or changing the number of heaters to be driven is also known.
An example of such an ink jet recording head is shown in
FIG. 17
as a sectional view. As shown in
FIG. 17
, in this ink jet recording head, two heaters
6002
,
6003
having different dimensions and different distances from a discharge port
6004
are disposed in a nozzle
6001
for communicating the ink discharge port
6004
with a common liquid chamber
6005
for containing ink to be supplied to a plurality of nozzles
6001
so that the amount of ink to be discharged can be changed by driving one or both of the heaters
6002
,
6003
.
Although the above-mentioned ink jet recording head having the plurality of heaters disposed in the respective nozzle has a purpose for realizing high speed and high accurate printing in response to various images by changing the ink discharged amount, there arose the following problem to achieve this purpose.
Nowadays, high density arrangement of the nozzle has been requested to achieve high accurate and finer printing, and, to this end, a width of each nozzle must be narrower. On the other hand, the heaters having large sizes must be used in order to widen the variable range of the ink discharged amount. Accordingly, when the size of the heater tries to be increased in the narrow nozzle, a longitudinal dimension (length) of each heater must be increased along the longitudinal direction of the nozzle, with the result that a length of the nozzle must be increased. If the length of the nozzle is increased, flow resistance of the nozzle will be increased, with the result that a time (re-fill time) for restoring meniscus retarded within the nozzle after the ink discharging to the vicinity of the discharge port again is delayed, thereby reducing the recording speed.
As a method for shortening the ink re-fill time to hasten the recording speed, a method in which the length of the nozzle
6001
is shortened, and, as shown in
FIG. 18
, a method in which a cross-sectional area of the nozzle
6001
at the heater
6002
is selected to be smaller than a cross-sectional area thereof at the inlet of the common liquid chamber
6005
(as disclosed in U.S. Pat. No. 4,752,787) are already known.
However, if the length of the nozzle is smaller than a certain value with respect to the heater position, when the temperature of the recording head is increased, a bubbling volume on the heater is increased, and the bubble formed by the bubbling may protrude from a rear end of the nozzle.
That is to say, as shown in
FIG. 19A
, even in case of a recording head a bubble
6007
is generated within a nozzle
6001
when the ink is bubbled in a condition that the recording head has a room temperature (for example, 25° C.), when ink is generated in a condition that the temperature in the recording head is increased (for example, to about 60° C. or more) due to discharging of ink from all nozzles with high frequency, since the energy required for the bubbling is small, if the energy similar to that shown in
FIG. 19A
is given, as shown in
FIG. 19B
, the bubble will be grown greatly to protrude toward the common liquid chamber
6005
from the nozzle
6001
.
A state in which the ink is discharged in the condition that the temperature in the recording head is increased is shown in
FIGS. 20A
to FIG.
20
E.
FIG. 20A
shows a condition that film boiling is started by heating the heaters
6002
,
6003
. From this condition, when the energy is further applied to the heaters
6002
,
6003
, the bobbles
6007
are grown as shown in
FIG. 20B
, with the result that the ink is discharged from the discharge port
6004
by pressure generated by the growth of the bubbles
6007
.
FIG. 20C
shows a condition that the discharging of the ink is completed and the bubbles
6007
was grown to the maximum extent. In this condition, the bubble
6007
protrudes from the nozzle
6001
to reach the common liquid chamber
6005
. From this condition, when the heating of the heaters
6002
,
6003
is stopped to cool the bubbles
6007
, contraction of the bubbles
6007
is started, and the re-fill of ink from the common liquid chamber is started and the ink near the discharge port is shifted, with the result that the meniscus starts to be retarded within the nozzle
6001
. In the common liquid chamber communicated with the inlet of the nozzle, since the ink is flown into the nozzle at once around the bubble portion
6007
protruded in the common liquid chamber, eddy ink flow is created, with the result that, as shown in
FIG. 20D
, the bubble
6007
is separated. Thereafter, as shown in
FIG. 20E
, the bubbles
6007
on the heaters
6002
,
6003
are disappeared, and the meniscus is restored in the vicinity of the discharge port
6004
as the ink re-fill continues. At this stage, the separated bubble
6007
remains within the common liquid chamber
6005
.
Although the residual bubble
6010
remained within the common liquid chamber
6005
by single ink discharging in this way is small, when the ink is discharged from all of the nozzles with high frequency of about 10 kHz, a large amount of residual bubbles
6010
may be stored in the common liquid chamber for a short time. As shown in
Inoue Ryoji
Ishimatsu Shin
Saito Akio
Takenouchi Masanori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Vo Anh T. N.
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