Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-05-23
2003-12-09
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06659600
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inkjet recording head cartridge and an inkjet recording apparatus.
2. Description of the Prior Art
An inkjet recording head cartridge (hereinafter referred to as cartridge) mounted in the carriage of conventional inkjet recording apparatuses is constructed to supply ink to a supply orifice of a head (head chip) through an ink supply passage from an ink tank.
The cartridge thus constructed has problems in (1) processing for bubbles generated in the ink supply passage and the head and (2) control of the fluctuation of ink supply pressure within the ink supply passage and the head. Various proposals are made to solve these problems. Hereinafter, a description will be made of several of these proposals.
The following four examples are proposed as measures against (1).
According to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 6-218945 (hereinafter referred to as conventional example 1), upon detecting bubbles generated in an ink supply passage, recording operation is stopped to prevent the bubbles from invading into a recording head.
Also, according to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 9-226142 (hereinafter referred to as a conventional example 2), an ink supply passage having a smaller cross-sectional area than that of a recording head opening part is provided to increase an ink flow velocity and thereby increase the ability to eliminate bubbles.
Furthermore, according to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 9-277552 (hereinafter referred to as a conventional example 3), a filter provided in an ink flow passage is provided with a bubble discharge part which discharges bubbles by pressuring the ink flow passage toward the outside.
According to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 9-131890 (hereinafter referred to as a conventional example 4), a wall outlined along a manifold is provided to discharge bubbles upward without depositing them on the wall face.
On the other hand, the following four example are proposed as measures against (2).
According to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 5-31904 (hereinafter referred to as a conventional example 5), bubbles are formed within a common liquid chamber by heating, and pressure waves are absorbed by transforming the bubbles to restrain pressure fluctuation caused by ink injection.
Also, according to the invention disclosed in Japanese Published Unexamined Patent Application No. Sho 55-128465 (hereinafter referred to as a conventional example 6), a minute hole for communication between the ink liquid passage and air is provided in part of the ink liquid passage to restrain pressure fluctuation.
Furthermore, according to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 7-125234 (hereinafter referred to as a conventional example 7), a gas holding part and a subheater for changing the volume of gas are provided to restrain pressure fluctuation caused by ink injection by changing the natural frequency of an ink supply system.
Furthermore, according to the invention disclosed in Japanese Published Unexamined Patent Application No. Hei 9-136415 (hereinafter referred to as a conventional example 8), plural gas holding parts for holding gas therein are provided in an ink supply passage to absorb pressure oscillation.
There are the following problems in the conventional examples 1 to 4.
In the conventional example 1, a bubble detection unit is required and it is questionable whether satisfactory bubble detection precision is obtained. Also, if a bubble is detected, recording must be temporarily halted.
In the conventional example 2, although it is possible to decrease the frequency of bubble-induced printing defects to some degree, it is impossible to completely eliminate printing defects.
In the conventional example 3, a pressurizing system for discharging bubbles is required, so that the apparatus becomes complicated.
In the conventional example 4, discharged bubbles accumulate under a filter and, if the accumulated bubbles spread throughout the manifold, printing would be disabled.
There are the following problems in the conventional examples 5 to 8.
In the conventional example 5, a heating unit in addition to an emission heater is required in the common liquid chamber, so that the mechanism becomes very complicated. Also, it is very difficult to control the size of bubbles generated by the heating unit.
In the conventional example 6, ink evaporation from the minute hole for communication with air and ink hardening in the minute hole are problematic.
In the conventional example 7, a heating unit is additionally required, so that the mechanism becomes complicated. Also, bubble size control is difficult.
In the conventional example 8, gas holding parts must be created, and therefore the construction of the ink supply passage becomes complicated. Also, gas in the gas holding parts may replace ink in the course of long-term preservation.
As described above, the conventional examples 1 to 8 have the problems that the structure of the mechanism is complicated or conventional problems cannot be completely solved.
SUMMARY OF THE INVENTION
Therefore, the present invention provides an inkjet recording head cartridge and an inkjet recording apparatus that have a simple structure and high reliability.
According to an aspect of the present invention, the inkjet recording head cartridge includes individual flow passages each having an ink emission orifice at one end thereof and an ink inflow orifice at another end thereof, an ink supply chamber communicating with the ink inflow orifices, and a heater face provided to be orthogonal to an ink emission face on which the ink emission orifices are formed, the heater face being part of the side of the ink supply chamber formed within an ink supplier. The ink supply chamber is formed to have a cross-sectional area allocated in an ink flow direction so that buoyancy acting on a bubble occurring in the ink supply chamber the size of which would cause a printing defect becomes larger than drag based on an ink flow velocity in the ink supply chamber when ink is emitted from all the ink emission orifices acting on the bubble, whereby the bubble moves away from the ink inflow orifices.
A bubble that occurring in the ink supply chamber due to printing operation or the like grows because of printing operation or the like and may hinder ink supply as a result of blocking the ink inflow orifices of the individual flow passages, causing a printing defect. In the present invention, the buoyancy that moves a bubble growing to such a size as to cause a printing defect away from the individual flow passages acts larger than drag based on the flow velocity of ink that flows toward the individual flow passages from the ink supply chamber. As a result, a bubble large enough to cause a printing defect is moved away from the individual flow passages (the ink inflow orifices) by the buoyancy, so that stable printing is achieved. Therefore, an ink suck mechanism or the like need not be used to discharge bubbles by sucking ink. In other words, highly reliable printing can be performed by preventing bubble-induced printing defects with a simple structure.
According to another aspect of the present invention, the following two expressions are satisfied for a given printing rate.
[(
Q/S
)
2
×Cd×&rgr;×&pgr;×d
2
]/8<(&rgr;×
g×&pgr;×d
3
)/6;
and
d≧
2
Np
where
Q: Average ink flow quantity during printing,
S: Minimum cross-sectional area in the ink flow direction within the ink supply chamber,
Cd: Resistance coefficient,
&rgr;: Ink density,
g: Gravitational constant,
Np: Individual flow passage (ink emission orifice) pitch, and
D: Bubble diameter.
A bubble within the ink supply chamber that has at least twice (=2Np) the diameter of
Funatsu Norikuni
Hamazaki Toshinobu
Hara Kohzo
Ikegami Koji
Kataoka Masaki
Morgan & Lewis & Bockius, LLP
Vo Anh T. N.
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